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  • Evolution  (689)
  • phosphorus  (681)
  • Springer  (1,366)
  • Oxford University Press  (4)
  • American Association of Petroleum Geologists (AAPG)
  • Blackwell Publishing Ltd
  • 1
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    Adaptive proteome diversification by nonsynonymous A-to-I RNA editing in coleoid cephalopods (2022)
    Oxford University Press
    Details
    Publication Date: 2022-10-27
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Shoshan, Y., Liscovitch-Brauer, N., Rosenthal, J. J. C., & Eisenberg, E. Adaptive proteome diversification by nonsynonymous A-to-I RNA editing in coleoid cephalopods. Molecular Biology and Evolution, 38(9), (2021): 3775–3788, https://doi.org/10.1093/molbev/msab154.
    Description: RNA editing by the ADAR enzymes converts selected adenosines into inosines, biological mimics for guanosines. By doing so, it alters protein-coding sequences, resulting in novel protein products that diversify the proteome beyond its genomic blueprint. Recoding is exceptionally abundant in the neural tissues of coleoid cephalopods (octopuses, squids, and cuttlefishes), with an over-representation of nonsynonymous edits suggesting positive selection. However, the extent to which proteome diversification by recoding provides an adaptive advantage is not known. It was recently suggested that the role of evolutionarily conserved edits is to compensate for harmful genomic substitutions, and that there is no added value in having an editable codon as compared with a restoration of the preferred genomic allele. Here, we show that this hypothesis fails to explain the evolutionary dynamics of recoding sites in coleoids. Instead, our results indicate that a large fraction of the shared, strongly recoded, sites in coleoids have been selected for proteome diversification, meaning that the fitness of an editable A is higher than an uneditable A or a genomically encoded G.
    Description: This research was supported by a grants from the United States–Israel Binational Science Foundation (BSF), Jerusalem, Israel (BSF2017262 to J.J.C.R. and E.E.), the Israel Science Foundation (3371/20 to E.E.) and the National Science Foundation (IOS 1827509 and 1557748 to J.J.C.R).
    Keywords: RNA editing ; Adaptation ; Evolution
    Repository Name: Woods Hole Open Access Server
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  • 2
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    The Pangenome (2021)
    Springer Nature | Springer
    Details
    Publication Date: 2024-04-05
    Description: This open access book offers the first comprehensive account of the pan-genome concept and its manifold implications. The realization that the genetic repertoire of a biological species always encompasses more than the genome of each individual is one of the earliest examples of big data in biology that opened biology to the unbounded. The study of genetic variation observed within a species challenges existing views and has profound consequences for our understanding of the fundamental mechanisms underpinning bacterial biology and evolution. The underlying rationale extends well beyond the initial prokaryotic focus to all kingdoms of life and evolves into similar concepts for metagenomes, phenomes and epigenomes. The book’s respective chapters address a range of topics, from the serendipitous emergence of the pan-genome concept and its impacts on the fields of microbiology, vaccinology and antimicrobial resistance, to the study of microbial communities, bioinformatic applications and mathematical models that tie in with complex systems and economic theory. Given its scope, the book will appeal to a broad readership interested in population dynamics, evolutionary biology and genomics.
    Keywords: Microbial Genetics and Genomics ; Evolutionary Biology ; Genetics and Population Dynamics ; Microbial Ecology ; Human Genetics ; Genetics and Genomics ; Comparative genomics ; Metagenomics ; Microbial Population Analysis ; Pangenome Profile ; Supra-Genome Analysis ; Adaptive Evolution ; Computational Tools ; Bioinformatic Genomics ; Core Dispensable Genome ; Selection, Recombination, Composition ; Acquired Resistance ; Bacterial Species Concept ; Genomic Diversity ; Bacterial Ecology, Microevolution ; Open Access ; Pan-metagenomics ; Pan-microbiomics ; Pan-epigenome ; Gene Transfer ; Pan-phenomes ; Microbiology (non-medical) ; Genetics (non-medical) ; Evolution ; Applied mathematics ; Ecological science, the Biosphere ; Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSG Microbiology (non-medical) ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAJ Evolution ; thema EDItEUR::P Mathematics and Science::PB Mathematics::PBW Applied mathematics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFN Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAK Genetics (non-medical)
    Language: English
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  • 3
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    Everything Flows (2021)
    Oxford University Press
    Details
    Publication Date: 2024-04-05
    Description: This collection of essays explores the metaphysical thesis that the living world is not ontologically made up of substantial particles or things, as has often been assumed, but is rather constituted by processes. The biological domain is organized as an interdependent hierarchy of processes, which are stabilized and actively maintained at different timescales. Even entities that intuitively appear to be paradigms of things, such as organisms, are actually better understood as processes. Unlike previous attempts to articulate processual views of biology, which have tended to use Alfred North Whitehead’s panpsychist metaphysics as a foundation, this book takes a naturalistic approach to metaphysics. It submits that the main motivations for replacing an ontology of substances with one of processes are to be looked for in the empirical findings of science. Biology provides compelling reasons for thinking that the living realm is fundamentally dynamic and that the existence of things is always conditional on the existence of processes. The phenomenon of life cries out for theories that prioritize processes over things, and it suggests that the central explanandum of biology is not change but rather stability—or, more precisely, stability attained through constant change. This multicontributor volume brings together philosophers of science and metaphysicians interested in exploring the consequences of a processual philosophy of biology. The contributors draw on an extremely wide range of biological case studies and employ a process perspective to cast new light on a number of traditional philosophical problems such as identity, persistence, and individuality.
    Keywords: explanation ; identity ; individuality ; metaphysics of science ; organism ; persistence ; philosophy of biology ; process ontology ; substance ontology ; symbiosis ; Evolution ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences
    Language: English
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  • 4
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    A-to-I RNA editing in the earliest-diverging Eumetazoan phyla (2017)
    Oxford University Press
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Molecular Biology and Evolution 34 (2017): 1890-1901, doi:10.1093/molbev/msx125.
    Description: The highly conserved ADAR enzymes, found in all multicellular metazoans, catalyze the editing of mRNA transcripts by the deamination of adenosines to inosines. This type of editing has two general outcomes: site specific editing, which frequently leads to recoding, and clustered editing, which is usually found in transcribed genomic repeats. Here, for the first time, we looked for both editing of isolated sites and clustered, non-specific sites in a basal metazoan, the coral Acropora millepora during spawning event, in order to reveal its editing pattern. We found that the coral editome resembles the mammalian one: it contains more than 500,000 sites, virtually all of which are clustered in non-coding regions that are enriched for predicted dsRNA structures. RNA editing levels were increased during spawning and increased further still in newly released gametes. This may suggest that editing plays a role in introducing variability in coral gametes.
    Description: This work was supported by the Australian Research Council (to PK), the European Research Council (grant 311257), the I-CORE Program of the Planning and Budgeting Committee in Israel (grants 41/11 and 1796/12), and the Israel Science Foundation (1380/14).
    Keywords: RNA editing ; ADAR ; Evolution ; Coral
    Repository Name: Woods Hole Open Access Server
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  • 5
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    The reduced genome of the parasitic microsporidian Enterocytozoon bieneusi lacks genes for core carbon metabolism (2010)
    Oxford University Press
    Details
    Publication Date: 2022-05-25
    Description: © The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution-Noncommercial 2.5 License. The definitive version was published in Genome Biology and Evolution 2 (2010): 304, doi:10.1093/gbe/evq022.
    Description: Reduction of various biological processes is a hallmark of the parasitic lifestyle. Generally, the more intimate the association between parasites and hosts the stronger the parasite relies on its host's physiology for survival and reproduction. However, some systems have been held to be indispensable, for example, the core pathways of carbon metabolism that produce energy from sugars. Even the most hardened anaerobes that lack oxidative phosphorylation and the tricarboxylic acid cycle have retained glycolysis and some downstream means to generate ATP. Here we describe the deep-coverage genome resequencing of the pathogenic microsporidiian, Enterocytozoon bieneusi, which shows that this parasite has crossed this line and abandoned complete pathways for the most basic carbon metabolism. Comparing two genome sequence surveys of E. bieneusi to genomic data from four other microsporidia reveals a normal complement of 353 genes representing 30 functional pathways in E. bieneusi, except that only 2 out of 21 genes collectively involved in glycolysis, pentose phosphate, and trehalose metabolism are present. Similarly, no genes encoding proteins involved in the processing of spliceosomal introns were found. Altogether, E. bieneusi appears to have no fully functional pathway to generate ATP from glucose. Therefore, this intracellular parasite relies on transporters to import ATP from its host.
    Description: This work was supported by grants from the Canadian Institutes for Health Research (MOP-84265), the National Institutes of Health (NIH AI31788, R21 AI52792, and R21 AI064118), and the National Science Foundation (MCB- 0135272). N.C. is a Scholar of the Canadian Institute for Advanced Research and is supported by a fellowship from the Swiss National Science Foundation (NSF) (PA00P3- 124166). D.E. is supported by the Swiss NSF. P.J.K. is a Fellow of the Canadian Institute for Advanced Research and a Senior Scholar of the Michael Smith Foundation for Health Research.
    Keywords: Microsporidia ; Parasite ; Glycolysis ; Carbon metabolism ; Reduction ; Evolution
    Repository Name: Woods Hole Open Access Server
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  • 6
    Electronic Resource
    Electronic Resource
    Class I and class II MHC bind self peptide sets that are strikingly different in their evolutionary characteristics (2000)
    Springer
    Immunogenetics 51 (2000), S. 8-15 
    Details
    ISSN: 1432-1211
    Keywords: Key words Antigen presentation ; Autoimmune disease ; Evolution ; MHC ; Self peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Comparison of peptides eluted from human class I and class II major histocompatibility complex (MHC) molecules and the proteins from which they are derived (source proteins) revealed that class I MHC bind peptides derived from proteins that are highly conserved, hydrophilic, and universally expressed, while the peptides themselves are hydrophobic and even more conserved than their source proteins. In contrast, source proteins for class II-bound peptides were not significantly more conserved than a random sample of proteins. Class II-bound peptides were generally more conserved than their source proteins but were significantly less conserved than class I-bound peptides. The characteristics of class I-bound peptides can probably be explained by the selectivity of processing and transport of peptides for binding by class I, while the relative lack of selectivity of peptide binding for class II may explain the high incidence of autoimmune diseases associated with alleles of these molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050002
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular and functional characterization of a fish inducible-type nitric oxide synthase (2000)
    Springer
    Immunogenetics 51 (2000), S. 339-346 
    Details
    ISSN: 1432-1211
    Keywords: Key words iNOS ; Fish ; Parasite ; Evolution ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Using an oligonucleotide primer based on a partial goldfish inducible nitric oxide synthase (iNOS) sequence, a complete carp iNOS cDNA was isolated from an activated carp phagocyte cDNA library. Nucleotide and predicted amino acid sequence analysis indicate that carp iNOS encodes a 1127-amino acid protein with 57% sequence identity to human iNOS. Like mammalian NOSs, carp iNOS protein contains putative binding sites for heme, tetrahydrobiopterin, calmodulin, flavine mononucleotide, flavine adenine dinucleotide, and NADPH. Phylogenetic analysis, using neighbor joining, showed that the carp iNOS protein clustered together with the other vertebrate iNOS proteins. Inducibility of carp iNOS was confirmed by reverse transcription-polymerase chain reaction after stimulation of carp phagocytes with lipopolysaccharide or the protozoan blood flagellate Trypanoplasma borreli. These stimulators produced high amounts of nitric oxide that were toxic for T. borreli in vitro. The nuclear transciption factor NF-κB was shown to play a role in the induction of iNOS transcription.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050628
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  • 8
    Electronic Resource
    Electronic Resource
    Major histocompatibility complex class I diversity in a West African chimpanzee population: implications for HIV research (2000)
    Springer
    Immunogenetics 51 (2000), S. 398-409 
    Details
    ISSN: 1432-1211
    Keywords: Key words HLA ; Patr class I molecules ; Evolution ; Polymorphism ; AIDS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Human immunodefiency virus (HIV) poses a major threat to humankind. And though, like humans, chimpanzees are susceptible to HIV infection, they are considered to be resistant to the development of the acquired immune deficiency syndrome (AIDS). Little is known about major histocompatibility complex (MHC) class I diversity in chimpanzee populations and, moreover, whether qualitative aspects of Patr class I molecules may control resistance to AIDS. To address these questions, we assayed MHC class I diversity in a West African chimpanzee population and in some animals from other subspecies of chimpanzee. Application of different techniques allowed the detection of 17 full-length Patr-A, 19 Patr-B, and 10 Patr-C alleles. All Patr-A alleles cluster only into the HLA-A1/A3/A11 family, which supports the idea that chimpanzees have experienced a reduction in their repertoire of A locus alleles. The Patr-B alleles do not cluster in the same lineages as their human equivalents, due to frequent exchange of polymorphic sequence motifs. Furthermore, polymorphic motifs may have been exchanged between Patr-A and Patr-B loci, resulting in convergence. With regard to evolutionary stability, the Patr-C locus is more similar to the Patr-A locus than it is to the Patr-B locus. Despite the relatively low number of animals analyzed, humans and chimpanzees were ascertained as sharing similar degrees of diversity at the contact residues constituting the B and F pockets in the peptide-binding side of MHC class I molecules. Our results indicate that within a small sample of a West African chimpanzee population, a high degree of Patr class I diversity is encountered. This is in agreement with the fact that chimpanzees display more mitochondrial DNA variation than humans. In addition, population analyses demonstrated that particular Patr-B molecules, with the capacity to bind conserved HIV-1 epitopes, are characterized by high gene frequencies. These findings have important implications for evaluating immune responses in HIV vaccine studies and, more importantly, may help in understanding the relative resistance of chimpanzees to AIDS.
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    URL: http://dx.doi.org/10.1007/s002510050638
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  • 9
    Electronic Resource
    Electronic Resource
    Is a mutator analogous to the Ig hypermutator of the sheep ileal Peyer's patch active on MHC class I genes in the germ line? (2000)
    Springer
    Immunogenetics 51 (2000), S. 462-472 
    Details
    ISSN: 1432-1211
    Keywords: Key words HLA genes ; IgV genes ; Evolution ; Gene conversion ; Sheep ileal Peyer's patch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Polymorphic sequence variation in the peptide-binding domains of MHC class I molecules appears to have been driven largely by the constructive action of natural selection on the specificity of the peptide-binding groove. Similar features are displayed by the variable domains of immunoglobulins generated in the sheep ileal Peyer's patch, but in this case there is evidence that the action of a targeted hypermutator acting on a selected substrate rather than antigen-driven selection is responsible for the pattern of variation in the system. Such a hypermutator acting in the germ line would not only mimic the action of natural selection but also, by convergent mutation, generate similar patterns of variation in unrelated alleles that could be interpreted as evidence for short-tract gene conversion. We analyzed human class I MHC alleles in the light of these data, but failed to find evidence of the action of a similar hypermutator. A search for other mutationally driven patterns of variation also failed, even in hypervariable residues from parsimonious phylogenies. Single-nucleotide variation at these residues is also frequent in recent allelic variants, but the data are as consistent with short-tract gene conversion as with base mutation. We conclude that the patterns of allelic variation in MHC molecules are not driven by mutational pressure, but rather by conventional mutational processes, accompanied by short-tract gene conversion and intense natural selection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050645
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  • 10
    Electronic Resource
    Electronic Resource
    The sequence of J chain in an amphibian, Rana catesbeiana (2000)
    Springer
    Immunogenetics 51 (2000), S. 587-590 
    Details
    ISSN: 1432-1211
    Keywords: Key words J chain ; Immunoglobulin ; Amphibian ; Evolution ; Comparative immunology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510000169
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  • 11
    Electronic Resource
    Electronic Resource
    A novel Mhc-B-related processed pseudogene in two species of New World primates (2000)
    Springer
    Immunogenetics 51 (2000), S. 606-609 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC ; Evolution ; Primate ; Callithrix ; Callicebus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002519900143
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  • 12
    Electronic Resource
    Electronic Resource
    The arbuscular mycorrhizas of pteridophytes in Yunnan, southwest China: evolutionary interpretations (2000)
    Springer
    Mycorrhiza 10 (2000), S. 145-149 
    Details
    ISSN: 1432-1890
    Keywords: Keywords Arbuscular mycorrhiza ; Pteridophyte ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The percentage of arbuscular mycorrhizal pteridophytes among 256 pteridophyte species distributed in Yunnan (southwest China) was found to be lower than that in angiosperms. In the pteridophytes, the occurrence of arbuscular mycorrhizas was low in sporophytes of fern-allies and leptosporangiates, whereas in the eusporangiates it was relatively high. From the standpoint of mycotrophism, the evolutionary trend in the Filicineae may be from constantly mycorrhizal to facultative mycorrhizal and finally to nonmycorrhizal plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720000076
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  • 13
    Electronic Resource
    Electronic Resource
    Multiple motor patterns in the stomatogastric ganglion of the shrimp Penaeus japonicus (2000)
    Springer
    Journal of comparative physiology 186 (2000), S. 105-118 
    Details
    ISSN: 1432-1351
    Keywords: Key words Stomatogastric nervous system ; Penaeus ; Motor pattern ; Neural network ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Motor patterns of the cardiac sac, the gastric and the pyloric network in the stomatogastric nervous system of the shrimp Penaeus japonicus, the most primitive decapod species, were studied. Single neurons can switch from the gastric or the pyloric pattern to the cardiac sac pattern. Some of the pyloric neurons fire with the gastric pattern. All of the gastric neurons fire with the pyloric pattern, unlike those in reptantians. Proctolin activates and modulates the cardiac sac and the pyloric rhythm, and promotes reconfiguration of the networks. Neurons of the three networks have so many interconnections that they construct a multifunctional neural network like those in Cancer. This network may function in different configurations under the appropriate conditions. Several modes of interactions between the networks found in different reptantian species can apply to the penaeidean shrimp. Such interactions are general features of the stomatogastric nervous system in decapods. Phylogenetic differences among the decapod infraorders are seen in the number and orientation of muscles and the innervation pattern of muscles. The multifunctional networks have existed in the most primitive decapod species, and types of configurations of the networks would have evolved to produce a wide range of motor patterns as the foregut structure has become complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050011
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  • 14
    Electronic Resource
    Electronic Resource
    Nutrient flows and land use change in a rural catchment: a modelling approach (2000)
    Springer
    Landscape ecology 15 (2000), S. 187-199 
    Details
    ISSN: 1572-9761
    Keywords: BOD5 ; catchment ; empirical model ; land use change ; land use scenarios ; nitrogen ; phosphorus ; runoff ; SO4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO4 and organic matter (after BOD5) decreased from 25.9 to 5.1, 0.32 to 0.13, 78 to 48, and 7.4 to 3.5 kg ha−1 yr−1, respectively. The most significant decreases occurred in agricultural subcatchments while the changes were insignificant in the forested upper course catchment. A simple empirical model which incorporates land-use pattern, fertilization intensity, soil parameters and water discharge accurately described the variations of total-N and total-P runoff in both the whole catchment and its agricultural subcatchments (R 2 varies from 0.95–0.99 for N to 0.49–0.93 for P). In small agricultural subcatchments the rate of fertilization is found the most important factor for nitrogen runoff, whereas in larger mosaic watersheds land use pattern plays the main role. Seven alternative scenarios compiled on the base of the empirical model allow to forecast potential nitrogen and phosphorus losses from the catchment. This information can be used in further landscape and regional planning of the whole region.
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    URL: http://dx.doi.org/10.1023/A:1008181811552
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  • 15
    Electronic Resource
    Electronic Resource
    Origin of the paired domain (2000)
    Springer
    Development genes and evolution 210 (2000), S. 644-650 
    Details
    ISSN: 1432-041X
    Keywords: Keywords Pax protein ; Paired domain ; Homeobox ; Transposase ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Pax proteins play a diverse role in early animal development and contain the characteristic paired domain, consisting of two conserved helix-turn-helix motifs. In many Pax proteins the paired domain is fused to a second DNA binding domain of the paired-like homeobox family. By amino acid sequence alignments, secondary structure prediction, 3D-structure comparison, and phylogenetic reconstruction, we analyzed the relationship between Pax proteins and members of the Tc1 family of transposases, which possibly share a common ancestor with Pax proteins. We suggest that the DNA binding domain of an ancestral transposase (proto-Pax transposase) was fused to a homeodomain shortly after the emergence of metazoans about one billion years ago. Using the transposase sequences as an outgroup we reexamined the early evolution of the Pax proteins. Our novel evolutionary scenario features a single homeobox capturing event and an early duplication of Pax genes before the divergence of porifera, indicating a more diverse role of Pax proteins in primitive animals than previously expected.
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    URL: http://dx.doi.org/10.1007/s004270000106
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  • 16
    Electronic Resource
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    The evolution of paired appendages in vertebrates: T-box genes in the zebrafish (2000)
    Springer
    Development genes and evolution 210 (2000), S. 82-91 
    Details
    ISSN: 1432-041X
    Keywords: Key words T-box genes ; Zebrafish ; Fins ; Evolution ; Gene duplication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The presence of two sets of paired appendages is one of the defining features of jawed vertebrates. We are interested in identifying genetic systems that could have been responsible for the origin of the first set of such appendages, for their subsequent duplication at a different axial level, and/or for the generation of their distinct identities. It has been hypothesized that four genes of the T-box gene family (Tbx2–Tbx5) played important roles in the course of vertebrate limb evolution. To test this idea, we characterized the orthologs of tetrapod limb-expressed T-box genes from a teleost, Danio rerio. Here we report isolation of three of these genes, tbx2, tbx4, and tbx5. We found that their expression patterns are remarkably similar to those of their tetrapod counterparts. In particular, expression of tbx5 and tbx4 is restricted to pectoral and pelvic fin buds, respectively, while tbx2 can be detected at the anterior and posterior margins of the outgrowing fin buds. This, in combination with conserved expression patterns in other tissues, suggests that the last common ancestor of teleosts and tetrapods possessed all four of these limb-expressed T-box genes (Tbx2–Tbx5), and that these genes had already acquired, and have subsequently maintained, their gene-specific functions. Furthermore, this evidence provides molecular support for the notion that teleost pectoral and pelvic fins and tetrapod fore- and hindlimbs, respectively, are homologous structures, as suggested by comparative morphological analyses.
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    URL: http://dx.doi.org/10.1007/s004270050014
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  • 17
    Electronic Resource
    Electronic Resource
    A role for Fringe in segment morphogenesis but not segment formation in the grasshopper, Schistocerca gregaria (2000)
    Springer
    Development genes and evolution 210 (2000), S. 329-336 
    Details
    ISSN: 1432-041X
    Keywords: Key words Development ; Evolution ; Notch ; Insect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Studies of somitogenesis in vertebrates have identified a number of genes that are regulated by a periodic oscillator that patterns the pre-somitic mesoderm. One of these genes, hairy, is homologous to a Drosophila segmentation gene that also shows periodic spatial expression. This, and the periodic expression of a zebrafish homologue of hairy during somitogenesis, has suggested that insect segmentation and vertebrate somitogenesis may use similar molecular mechanisms and possibly share a common origin. In chicks and mice expression of the lunatic fringe gene also oscillates in the presomitic mesoderm. Fringe encodes an extracellular protein that regulates Notch signalling. This, and the finding that mutations in Notch or its ligands disrupt somite patterning, suggests that Notch signalling plays an important role in vertebrate somitogenesis. Although Notch signalling is not known to play a role in the formation of segments in Drosophila, we reasoned that it might do so in other insects such as the grasshopper, where segment boundaries form between cells, not between syncytial nuclei as they do in Drosophila. Here we report the cloning of a single fringe gene from the grasshopper Schistocerca. We show that it is not detectably expressed in the forming trunk segments of the embryo until after segment boundaries have formed. We conclude that fringe is not part of the mechanism that makes segments in Schistocerca. Thereafter it is expressed in a pattern which shows that it is a downstream target of the segmentation machinery and suggests that it may play a role in segment morphogenesis. Like its Drosophila counterpart, Schistocerca fringe is also expressed in the eye, in rings in the legs, and during oogenesis, in follicle cells.
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    URL: http://dx.doi.org/10.1007/s004270000072
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  • 18
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    Volcanic history of El Chichón Volcano (Chiapas, Mexico) during the Holocene, and its impact on human activity (2000)
    Springer
    Bulletin of volcanology 62 (2000), S. 90-104 
    Details
    ISSN: 1432-0819
    Keywords: Stratigraphy ; Evolution ; El Chichón ; México
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 abundance and depletion in MgO, CaO, TiO2, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichón also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization.
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    URL: http://dx.doi.org/10.1007/s004459900064
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    The genomic organization and evolution of the natural killer immunoglobulin-like receptor (KIR) gene cluster (2000)
    Springer
    Immunogenetics 51 (2000), S. 268-280 
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    ISSN: 1432-1211
    Keywords: Key words KIR ; Multigene family ; Gene duplication ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Natural killer (NK) immunoglobulin-like receptors (KIRs) are a family of polymorphic receptors which interact with specific motifs on HLA class I molecules and modulate NK cytolytic activity. In this study, we analyzed a recently sequenced subgenomic region on chromosome 19q13.4 containing eight members of the KIR receptor repertoire. Six members are clustered within a 100-kb continuous sequence. These genes include a previously unpublished member of the KIR gene family 2DS6, as well as 2DL1, 2DL4, 3DL1, 2DS4, 3DL2, from centromere to telomere. Two additional KIR genes, KIRCI and 2DL3, which may be located centromeric of this cluster were also analyzed. We show that the KIR genes have undergone repeated gene duplications. Diversification between the genes has occurred postduplication primarily as a result of retroelement indels and gene truncation. Using pre- and postduplication Alu sequences identified within these genes as evolutionary molecular clocks, the evolution and duplication of this gene cluster is estimated to have occurred 30–45 million years ago, during primate evolution. A proposed model of the duplication history of the KIR gene family leading to their present organization is presented.
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    URL: http://dx.doi.org/10.1007/s002510050620
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    Isolation of the HLA-H orthologue in gorillas and chimpanzees (2000)
    Springer
    Immunogenetics 51 (2000), S. 69-74 
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    ISSN: 1432-1211
    Keywords: Key words MHC class I ; Pseudogene ; Evolution ; Gorilla ; Chimpanzee
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050011
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    Characterization of approximately 50 kb of the immunoglobulin VH locus of the Japanese pufferfish, Fugu rubripes (2000)
    Springer
    Immunogenetics 51 (2000), S. 443-451 
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    ISSN: 1432-1211
    Keywords: Key words Immunoglobulin ; Fugu ; VH family ; Teleosts ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The variable region of the immunoglobulin heavy chain is created by a somatic rearrangement of a limited number of germline genes. This mechanism of gene assembly [V(D)J recombination] has been found to take place only in jawed vertebrates (gnathostomes). To understand how this mechanism evolved and diversified it is necessary to study the genomic organization of the heavy-chain gene in different vertebrate lineages. Since there is scant sequence information on the VH locus in fish, shotgun sequencing of a cosmid clone containing part of the VH genomic region of the Japanese pufferfish, Fugu rubripes, was undertaken. Eight full-length VH genes were isolated and characterized. They have higher homology to trout genes, but show the same structural features as VHs found in other vertebrates. Two VH subgroups have been identified whose members are interspersed. The frequency of synonymous and nonsynonymous substitution for VH comparisons between family members was found to be higher in the complementarity-determining regions than in the framework regions. Finally, there are four other genes interspersed with the VH genes, one of which is the first full-length retrotransposon element characterized in vertebrates.
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    URL: http://dx.doi.org/10.1007/s002510050643
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    Cloning and expression of the chicken immunoglobulin joining (J)-chain cDNA (2000)
    Springer
    Immunogenetics 51 (2000), S. 85-91 
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    ISSN: 1432-1211
    Keywords: Key words J chain ; Polymeric immunoglobulin ; Ontogeny ; Evolution ; Comparative immunology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The J chain is a component of polymeric immunoglobulin (Ig) molecules and may play an important role in their polymerization and the transport of polymeric Ig across epithelial cells. In this study, the primary structure of the chicken J chain was determined by sequencing cDNA clones. The cDNA had an open reading frame of 476 nucleotides encoding a putative protein of 158 amino acid residues including the signal sequence. The 3′ untranslated region consisted of 1216 nucleotides and a poly(A) tail. The deduced amino acid sequence of the chicken J chain had a high degree of homology to that of human, cow, rabbit, mouse, frog, and earthworm, with eight conserved Cys residues identical to the mammalian J chains. Northern blot hybridization performed with total RNA from various chicken tissues revealed high levels of J-chain mRNA expression in spleen, intestine, Harderian gland, and bursa of Fabricius, and low levels in the thymus. The J chain was expressed in the bursa as early as day 15 of embryogenesis. These data indicated that the chicken J-chain gene displays a high degree of homology with that of other species, and is expressed at an early stage of development of the chicken immune system.
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    URL: http://dx.doi.org/10.1007/s002510050016
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    Is atmospheric CO2 a selective agent on model C3 annuals? (2000)
    Springer
    Oecologia 123 (2000), S. 330-341 
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    ISSN: 1432-1939
    Keywords: Key words  Arabidopsis thaliana ; Carbon dioxide ; Evolution ; Reproduction ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Atmospheric CO2 partial pressure (pCO2) was as low as 18 Pa during the Pleistocene and is projected to increase from 36 to 70 Pa CO2 before the end of the 21st century. High pCO2 often increases the growth and reproduction of C3 annuals, whereas low pCO2 decreases growth and may reduce or prevent reproduction. Previous predictions regarding the effects of high and low pCO2 on C3 plants have rarely considered the effects of evolution. Knowledge of the potential for evolution of C3 plants in response to CO2 is important for predicting the degree to which plants may sequester atmospheric CO2 in the future, and for understanding how plants may have functioned in response to low pCO2 during the Pleistocene. Therefore, three studies using Arabidopsis thaliana as a model system for C3 annuals were conducted: (1) a selection experiment to measure responses to selection for high seed number (a major component of fitness) at Pleistocene (20 Pa) and future (70 Pa) pCO2 and to determine changes in development rate and biomass production during selection, (2) a growth experiment to determine if the effects of selection on final biomass were evident prior to reproduction, and (3) a reciprocal transplant experiment to test if pCO2 was a selective agent on Arabidopsis. Arabidopsis showed significant positive responses to selection for high seed number at both 20 and 70 Pa CO2 during the selection process. Furthermore, plants selected at 20 Pa CO2 performed better than plants selected at 70 Pa CO2 under low CO2 conditions, indicating that low CO2 acted as a selective agent on these annuals. However, plants selected at 70 Pa CO2 did not have significantly higher seed production than plants selected at 20 Pa CO2 when grown at high pCO2. Nevertheless, there was some evidence that high CO2 may also be a selective agent because changes in development rate and biomass production during selection occurred in opposite directions at low and high pCO2. Plants selected at high pCO2 showed no change or reductions in biomass relative to control plants due to a decrease in the length of the life cycle, as indicated by earlier initiation of flowering and senescence. In contrast, selection at low CO2 resulted in an average 35% increase in biomass production, due to an increase in the length of the life cycle that resulted in a longer period for biomass accumulation before senescence. From the Arabidopsis model system we conclude that some C3 annuals may have produced greater biomass in response to low pCO2 during the Pleistocene relative to what has been predicted from studies exposing a single generation of C3 plants to low pCO2. Furthermore, C3 annuals may exhibit evolutionary responses to high pCO2 in the future that may result in developmental changes, but these are unlikely to increase biomass production. This series of studies shows that CO2 may potentially act as a selective agent on C3 annuals, producing changes in development rate and carbon accumulation that could not have been predicted from single-generation studies.
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    URL: http://dx.doi.org/10.1007/s004420051019
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    The plasma membrane H+-ATPase gene family in the arbuscular mycorrhizal fungus Glomus mosseae (2000)
    Springer
    Current genetics 37 (2000), S. 112-118 
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    ISSN: 1432-0983
    Keywords: Key words Arbuscular mycorrhizas ; Evolution ; Glomus mosseae ; Plasma membrane H+-ATPase genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To identify genes that encode plasma membrane H+-ATPases in the arbuscular mycorrhizal fungus Glomus mosseae two sets of degenerate primers matching highly conserved motifs present in all plant and fungal ATPases were designed. Nested PCR-amplification of G. mosseae genomic DNA using the designed degenerate primers was carried out. Sequence analysis of the cloned PCR products identified five different clones (GmHA1, GmHA2, GmHA3, GmHA4 and GmHA5) encoding putative plasma membrane H+-ATPases. Comparison of the deduced amino-acid sequences of GmHA1–GmHA5 indicate that GmHA1, GmHA3 and GmHA4 are highly identical, while GmHA2 and GmHA5 are more divergent. The evolutionary and functional significance of the divergence found among the different members of the H+-ATPase gene family in G. mosseae is discussed.
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    Conservation and variability of sequence-tagged microsatellite sites (STMSs) from chickpea (Cicer aerietinum L.) within the genus Cicer (2000)
    Springer
    Theoretical and applied genetics 101 (2000), S. 269-278 
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    ISSN: 1432-2242
    Keywords: Key words Cicer species ; Microsatellites ; Zero-allele ; Phylogenetic tree ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The conservation of 90 microsatellite-flanking sequences from chickpea in 39 accessions of eight annual and 1 accession of a perennial species of the genus Cicer was investigated. All of the primer sequences successfully amplified microsatellites in related species, indicating the conservation of microsatellite-flanking sequences in chickpea’s relatives. However, the degree of conservation of the primer sites varied between species depending on their known phylogenetic relationship to chickpea, ranging from 92.2% in C. reticulatum, chickpea’s closest relative and potential ancestor, down to 50% for C. cuneatum. A phylogenetic tree revealed that chickpea and the other members of its crossability group were more closely related to the perennial C. anatolicum than to other annual species of the genus. Considerable variation in size and number of amplification products between and within species was observed. Sequence analysis of highly divergent amplification products proved that variation is either due to large differences in the number of microsatellite repeats or to the amplification of a locus unrelated to the one amplified from chickpea. Sequence information and bootstrapping using PAUP suggested that STMSs derived from chickpea may be efficiently and reliably used for synteny studies in chickpea’s crossability group, including C. anatolicum. However, care should be taken when applying these markers to other species of the genus. Considering the data presented here and the known historical record, the age of section Monocicer, including chickpea, is estimated to be about 100,000 years.
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    The genetic basis of seed-weight variation: tomato as a model system (2000)
    Springer
    Theoretical and applied genetics 100 (2000), S. 1267-1273 
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    ISSN: 1432-2242
    Keywords: Keywords Domestication ; Evolution ; QTL ; Map-based cloning ; Lycopersicon esculentum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The seeds of domesticated plants are normally much larger than those of their wild counterparts. This change in seed weight was most likely in response to the selection pressure for yield, uniform germination and seedling vigor which was exerted by humans during domestication. However, despite the evolutionary and agronomic significance of seed weight, very little is know about the genetic and developmental controls of this trait; and, thus far, none of the genes in this pathway have been isolated from any plant species. QTL mapping experiments conducted in tomato during the past decade have allowed the identification of many seed-weight QTLs and have also revealed that only a few loci are responsible for the majority of the seed-weight changes that accompanied the domestication of tomato. This review presents a consensus map for seed weight QTL identified in previously published reports and in unpublished results from our laboratory. This summary of seed-weight QTL data allows for the identification of the major loci controlling this trait in the genus Lycopersicon. It is hoped that this work will allow the elucidation of this important phenotypic transition that occurred during crop-plant domestication and will also provide the starting point for the cloning of a gene responsible for seed-weight variation.
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    URL: http://dx.doi.org/10.1007/s001220051433
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    Geographic distribution and multilocus organization of isozyme variation of rice (Oryza sativa L.) (2000)
    Springer
    Theoretical and applied genetics 101 (2000), S. 379-387 
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    ISSN: 1432-2242
    Keywords: Key words Rice ; Isozyme variation ; Multilocus organization ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic organization of isozyme variation in rice (Oryza sativa L.) was investigated based on 17 polymorphic isozyme loci using a sample of 511 accessions of worldwide origin. The genetic diversity within the species was very high (H=0.36 with 4.82 alleles per locus), as compared with most selfing plant species. Three diversity centers were detected for isozyme variation including South Asia, China and Southeast Asia. The accessions were classified into three well-differentiated cultivar groups corresponding to the indica and japonica subspecies, and a new unnamed group. Variation within the cultivar groups accounted for 80% of the total isozyme variation. Within-country variation accounted for 58% of the total variation while among-region and among-country variation within the cultivar groups accounted for only 14% and 8% of the total variation. Analyses using log-linear models revealed that pronounced non-random associations between and among alleles at many unlinked isozyme loci were organized in a non-hierarchical pattern, and subspecific and macro-geographic differentiation was much more pronounced in multilocus phenotype frequencies than in allelic frequencies at individual loci. These results suggest that selection on multilocus gene complexes was largely responsible for the maintenance of the extensive isozyme variation within the species and the indica-japonica differentiation. Our results further suggest the independent domestication of indica and japonica, the dual origins of the indica rice from China and South Asia (India), and the differentiation of the ecotypes ’javanica’ and the ’temperate japonica’ within the japonica subspecies.
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    URL: http://dx.doi.org/10.1007/s001220051494
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    The development of oat microsatellite markers and their use in identifying relationships among Avena species and oat cultivars (2000)
    Springer
    Theoretical and applied genetics 101 (2000), S. 1259-1268 
    Details
    ISSN: 1432-2242
    Keywords: Key words Enriched-library ; SSR ; Repetitive elements ; Allelic diversity ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Microsatellites have many desirable marker properties. There has been no report of the development and utilization of microsatellite markers in oat. The objectives of the present study were to construct oat microsatellite-enriched libraries, to isolate microsatellite sequences and evaluate their level of polymorphism in Avena species and oat cultivars. One hundred clones were isolated and sequenced from three oat microsatellite-libraries enriched for either (AC/TG) n , (AG/TC) n or (AAG/TTC) n repeats. Seventy eight clones contained microsatellites. A database search showed that 42% of the microsatellite flanking sequences shared significant homology with various repetitive elements. Alu and retrotransposon sequences were the two largest groups associated with the microsatellites. Forty four primer sets were used to amplify the DNA from 12 Avena species and 20 Avena sativa cultivars. Sixty two percent of the primers revealed polymorphism among the Avena species, but only 36% among the cultivars. In the cultivars, the microsatellites associated with repetitive elements were less polymorphic than those not associated with repetitive elements. Only 25% of the microsatellites associated with repetitive elements were polymorphic, while 46% of the microsatellites not associated with repetitive elements showed polymorphism in the cultivars. An average of four alleles with a polymorphism information content (PIC) of 0.57 per primer set was detected among the Avena species, and 3.8 alleles with a PIC of 0.55 among the cultivars. In addition, 54 barley microsatellite primers were tested in Avena species and 26% of the primers amplified microsatellites from oat. Using microsatellite polymorphisms, dendrograms were constructed showing phylogenetic relationships among Avena species and genetic relationships among oat cultivars.
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    URL: http://dx.doi.org/10.1007/s001220051605
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    Thermal Destruction of Polydimethyl-Siloxane on a Phosphorus-containing Silica Surface (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 335-344 
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    ISSN: 1572-8943
    Keywords: phosphorus ; polydimethylsiloxane ; silica ; surface ; thermogravimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermogravimetry, differential thermal analysis, and IR spectroscopy were used to investigate the process of thermal destruction of adsorbed polydimethylsiloxane (PDMS) in air. The disperse adsorbents were pristine fumed silica and modified fumed silica whose surface contained oxygen compounds of phosphorus. It was shown that under the given experimental conditions the thermal destruction of PDMS on the fumed silica surface was accompanied by the complete transformation of the adsorbed PDMS to SiO2. In the case of phosphorus-containing silica, the thermal destruction proceeded in a different way. It was found that at 140–300°C depolymerization of the siloxane chains of a certain part of the adsorbed polymer took place with the concurrent removal of volatile products of the reaction. However, the remaining part of the adsorbed PDMS interacted with the modified silica surface to form chemisorbed dimethylsilyl structures. The thermal destruction of the chemisorbed fragments of PDMS in air was initiated at 400°C or above for both types of silica investigated.
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    URL: http://dx.doi.org/10.1023/A:1010184519492
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    XRD Investigations of the Phosphorus Effect on the Oxidation of TiAl Alloys by High-Resolution Methods (2000)
    Springer
    Oxidation of metals 54 (2000), S. 317-337 
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    ISSN: 1573-4889
    Keywords: TiAl ; oxidation ; phosphorus ; microdiffraction ; doping ; rutile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Recently it has been found that very small amounts (a few 100 ppm) of Padded to γ -titanium aluminide can significantly alter the oxidationbehavior between 973 and 1273 K. The mechanism responsible for this changeis, however, still not clear. In the present study, phosphorus wasincorporated into the surface of TiAl (containing 50 at.% Al) by ionimplantation and oxidation tests were carried out at 1173 K inair. Improvement of oxidation resistance is only temporary up to 100 hr forphosphorus-implanted TiAl. After 100 hr, the oxidation rate increases andbreakaway oxidation follows. XRD and EPMA showed that the breakawayoxidation is connected with massive nitride formation. Two different modelsare proposed which can explain the effect of phosphorus additions on theoxidation kinetics of TiAl during the protective stage within the first100 hr. The breakaway effect can be explained by penetration of air to themetal–oxide interface zone because of microcrack formation in theoxide scale, which was experimentally proved by acoustic-emission analysis.
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    Vanadium–molybdenum phosphates supported by TiO2 for ethane oxidation to acetic acid: a correlation between the local environment of vanadium and the reactivity (2000)
    Springer
    Topics in catalysis 11-12 (2000), S. 101-109 
    Details
    ISSN: 1572-9028
    Keywords: ethane ; vanadium ; molybdenum ; phosphorus ; titanium oxide ; acetic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Different complementary physicochemical tools have been used to explain the improvement of the catalytic performances for ethane oxidation into acetic acid induced by the addition of molybdenum as phosphate to vanadium phosphate deposited on TiO2-anatase, at a coverage below the monolayer. Electron microscopy techniques have shown that the elements are dispersed on the support. Electron spin resonance, laser Raman and UV-visible spectroscopies have evidenced that the short range order around vanadium is modified by the presence of molybdenum. 51V NMR has shown that molybdenum favours the octahedral symmetry of vanadium. The acidic properties of the catalyst are improved by the adding effect of molybdenum and by the addition of water. This should explain a better desorption of acetic acid and the improvement of the corresponding yield. This confirms the importance of the atomic environment of vanadium-based oxides to control the mild oxidation of light alkanes.
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    Does phylogenetic inertia explain the evolution of ineffective antipredator behavior in a sunfish-salamander system? (2000)
    Springer
    Behavioral ecology and sociobiology 49 (2000), S. 48-56 
    Details
    ISSN: 1432-0762
    Keywords: Keywords Antipredator behavior ; Phylogenetic inertia ; Conflicting selection pressures ; Evolution ; Salamanders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The streamside salamander, Ambystoma barbouri, exhibits ineffective antipredator behavior (high emergence rate from refuge, and high activity while out of refuge) and thus suffers heavy predation in stream pools with sunfish. A. barbouri evolved relatively recently from an ancestor that closely resembled a sister species, A. texanum, which breeds in fishless, ephemeral ponds. Sunfish thus represent a relatively new selection pressure for A. barbouri. Phylogenetic inertia predicts that (1) A. texanum should be very poor at coping with fish and (2) because it has only recently been exposed to fish, A. barbouri should still be poor at avoiding fish, but due to its recent exposure to fish, A. barbouri should be better than A. texanum at coping with sunfish. Experimental results provided mixed support for these predictions. As predicted, A. texanum suffered heavy sunfish predation. Compared to A. texanum, A. barbouri showed a greater tendency to initiate alarm moves that enhanced escape success from fish. However, in both the presence and absence of fish, A. barbouri showed higher emergence rates from refuge and higher movement while out of refuge than A. texanum. These behaviors tend to increase exposure to sunfish, i.e., for these key behaviors, A. barbouri apparently evolved in the wrong direction as far as fish predation is concerned. Due to these offsetting effects (increased exposure to fish, increased escape success), A. barbouri is no better at surviving with sunfish than A. texanum. A possible explanation for the high activity of A. barbouri is its use of highly ephemeral habitats (relative to A. texanum) that favor the evolution of higher activity, feeding, and developmental rates for A. barbouri relative to A. texanum.
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    Acquisition of a potential marker for insect transformation: isolation of a novel alcohol dehydrogenase gene from Bactrocera oleae by functional complementation in yeast (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 90-95 
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    ISSN: 1617-4623
    Keywords: Key wordsDrosophila melanogaster ; Ceratitis capitata ; Tephritids ; Evolution ; Dacus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The alcohol dehydrogenase genes make up one of the best studied gene families in Drosophila, both in terms of expression and evolution. Moreover, alcohol dehydrogenase genes constitute potential versatile markers in insect transformation experiments. However, due to their rapid evolution, these genes cannot be cloned from other insect genera by DNA hybridization or PCR-based strategies. We have therefore explored an alternative strategy: cloning by functional complementation of appropriate yeast mutants. Here we report that two alcohol dehydrogenase genes from the medfly Ceratitis capitata can functionally replace the yeast enzymes, even though the medfly and yeast genes have evolved independently, acquiring their enzymatic function convergently. Using this method, we have cloned an alcohol dehydrogenase gene from the olive pest Bactrocera oleae. We conclude that functional complementation in yeast can be used to clone alcohol dehydrogenase genes that are unrelated in sequence to those of yeast, thus providing a powerful tool for isolation of dominant insect transformation marker genes.
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    The mitochondrial DNA of Dictyostelium discoideum: complete sequence, gene content and genome organization (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 514-519 
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    ISSN: 1617-4623
    Keywords: Key wordsDictyostelium discoideum ; Mitochondrial DNA ; Genome sequencing ; Genetic map ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present an overview of the gene content and organization of the mitochondrial genome of Dictyostelium discoideum. The mitochondria genome consists of 55,564 bp with an A + T content of 72.6%. The identified genes include those for two ribosomal RNAs (rnl and rns), 18 tRNAs, ten subunits of the NADH dehydrogenase complex (nad1, 2, 3, 4, 4L, 5, 6, 7, 9 and 11), apocytochrome b (cytb), three subunits of the cytochrome oxidase (cox1/2 and 3), four subunits of the ATP synthase complex (atp1, 6, 8 and 9), 15 ribosomal proteins, and five other ORFs, excluding intronic ORFs. Notable features of D. discoideum mtDNA include the following. (1) All genes are encoded on the same strand of the DNA and a universal genetic code is used. (2) The cox1 gene has no termination codon and is fused to the downstream cox2 gene. The 13 genes for ribosomal proteins and four ORF genes form a cluster 15.4 kb long with several gene overlaps. (3) The number of tRNAs encoded in the genome is not sufficient to support the synthesis of mitochondrial protein. (4) In total, five group I introns reside in rnl and cox1/2, and three of those in cox1/2 contain four free-standing ORFs. We compare the genome to other sequenced mitochondrial genomes, particularly that of Acanthamoeba castellanii.
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    Cooperative exploration of distributed worlds in WAVE (2000)
    Springer
    Artificial life and robotics 4 (2000), S. 109-118 
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    ISSN: 1614-7456
    Keywords: Parallel and distributed processing ; Space navigation ; Evolution ; WAVE model ; Cooperative behavior ; Mobile robots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper modifies the WAVE model for parallel processing in virtual networks to explore and process continuous physical worlds. Expressing distributed activity by cooperative jobs spreading in space and “seeing” each other, rather than as vehicles exchanging messages, the model allows complex missions to be planned in a very flexible manner, with mobile hardware being assigned to the evolving space-conquering programs (waves) dynamically, when required or available. A number of cooperative scenarios in a physical world demonstrate the simplicity and compactness of the wave code. The execution of waves by mobile hardware is discussed, including run-time mapping of waves to vehicles, and supporting multiple distributed jobs in cases of hardware shortages. WAVE can be used efficiently for solving complex problems in space by organized groups of cheap specialized mobile robots, where intelligent behavior is provided by very high level of system organization rather than by the smartness of individual units. In a broader sense, it may also serve as a basic technology for parallel and distributed simulation, and the management of evolution and self-organization of large open systems of different natures.
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    Sources, sinks, and fluxes of nutrients (N + P) in a small highly modified urban estuary in southern California (2000)
    Springer
    Urban ecosystems 4 (2000), S. 125-144 
    Details
    ISSN: 1573-1642
    Keywords: nitrogen ; phosphorus ; macroalgae ; estuary ; anthropogenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Our objective was to begin to investigate sources, sinks, and flux rates of nitrogen (N) and phosphorus (P) in Famosa Slough, a small (12 ha) highly modified urban estuary in San Diego, California, U.S.A. The hydrology of Famosa Slough has been modified by culverts that dampen tidal influence and seasonal runoff from two urban watersheds, each of which has been implicated as a nutrient source that generates nuisance algal blooms. In 1995 and 1996, the ranges of nutrients measured in the water column were extremely wide; upper values exceeded those in other estuaries identified as eutrophic. Average dissolved inorganic nitrogen ranged from 2 to 250 μM, while dissolved inorganic phosphorus ranged from 〈1 to 15 μM. Nutrient content of the water changed rapidly both spatially and temporally depending on the tides and rainfall. While tidal water dominated this system, especially in the dry season, our results indicate that Famosa Slough's small watershed, not the larger watershed of the San Diego River, was the major source of nutrients during rainfall. Sediment nutrients were also high (∼3 mg N g dry wt−1 and 0.600 mg P g dry wt−1). Short-term flux studies suggest that the large accumulations of opportunistic green macroalgae commonly found in this estuary, and possibly the sediments, may act as a large and rapid sink for nutrients during times of high nutrient supply. We suggest that small, shallow estuaries in urban settings may have more complex and rapid nutrient dynamics than those found in larger systems.
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    Co-development of wetland soils and benthic invertebrate communities following salt marsh creation (2000)
    Springer
    Wetlands ecology and management 8 (2000), S. 197-207 
    Details
    ISSN: 1572-9834
    Keywords: benthic invertebrates ; mitigation ; nitrogen ; organic matter ; pedogenesis ; phosphorus ; plant productivity ; restoration and rehabilitation ; salt marsh ; wetland creation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of wetland soil characteristics andbenthic invertebrate communities were evaluated increated Spartina alterniflorasalt marshes inNorth Carolina ranging in age from 1 to 25 years-old.A combination of measurements from different-agecreated marshes as well as periodic measurements overtime on two marshes were used to (1) document rates ofwetland pedogenesis, especially soil organic matter,and, (2) explore relationships between soil andbenthic invertebrate community development. Soilmacro-organic matter (MOM, the living and dead rootand rhizome mat), organic C and N increased and bulkdensity decreased during the 25 years following marshestablishment. The most dramatic changes in bulkdensity, MOM, C and N occurred within the upper 10 cmof the soil with lesser changes below this depth.Created marshes were sinks for organic C (90–140g·m-2·yr-1) and N (7–11g·m-2·yr-1) but not for P (0–1g·m-2·yr-1). The density of benthicinvertebrates (〉250 μm) and subsurface-depositfeeding oligochaetes also increased over time oncreated salt marshes. Invertebrate and oligochaetedensity were strongly related to MOM content(r2= 0.83–0.87) and soil organic C(r2= 0.52–0.82) and N (r2= 0.62–0.84). Thesefindings suggest that, in created salt marshes,development of the benthic invertebrate community istied to marsh soil formation, especially accumulationof organic matter as MOM and soil. Field studies thatmanipulate the quantity and quality of soil organicmatter are needed to elucidate the relationshipbetween salt marsh pedogenesis and benthicinvertebrate community development.
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    Growth analysis of maize field crops under phosphorus deficiency (2000)
    Springer
    Plant and soil 223 (2000), S. 119-132 
    Details
    ISSN: 1573-5036
    Keywords: leaf area index ; leaf elongation rate ; phosphorus ; phyllochron ; Zea mays L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Biomass accumulation by crops depends both on light interception by leaves and on the efficiency with which the intercepted light is used to produce dry matter. Our aim was to identify which of these processes were affected for maize (Zea Mays L., cv Volga) field crops grown under phosphorus (P) deficiency, and assess their relative importance. In this paper, the effects of P deficiency on leaf appearance, leaf elongation rate, final individual leaf area and leaf senescence were studied. The experimental work was carried out in 1995–1977 on a long-term P fertilisation trial located on a sandy soil in the south-west of France. Three P fertilisation regimes have been applied since 1972: no-P (P0 treatment) and different rates of P fertiliser (P1.5:1.5 times the grain P export and P3:3 times the grain P export). These fertilisation regimes have led to contrasted levels of soil P supply, with the P0 treatment being limiting for growth. Very few differences were observed about leaf growth between the P1.5 and P3 treatments. Conversely, the leaf area index (LAI) was significantly reduced in the P0 treatment, especially during the first phases of the crop cycle (up to −60% between the 7- and 14-visible leaves). This effect gradually decreased over time. The lower LAI in P0 treatment was due to two main processes affecting the leaf growth. The final number of leaves per plant and leaf senescence were only slightly modified by P deficiency. Conversely, leaf appearance was delayed during the period between leaf 4 and leaf 9. The value of the phyllochron increased from 47 °C days in the P1.5 treatment to 65 °C days in the P0 treatment. Leaf elongation rates during the quasi-linear phase of leaf expansion were significantly reduced for lower leaves of P0 plants. The final size of leaves L2–L12 was reduced. On the opposite, leaf elongation duration was not greatly affected by P treatments. Before the emergence of leaf 9, the reduction of individual leaf size was the main factor responsible for the reduced LAI in the P0 treatment. After this stage, the delayed leaf appearance accounted for a great part of the reduced LAI in the P0 treatment.
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    Leaf endophyte Neotyphodium coenophialum modifies mineral uptake in tall fescue (2000)
    Springer
    Plant and soil 227 (2000), S. 115-126 
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    ISSN: 1573-5036
    Keywords: endophyte ; mineral nutrition ; Neotyphodium coenophialum ; phosphorus ; tall fescue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte found primarily in shoots of tall fescue (Festuca arundinacea Shreb.), can modify rhizosphere activity in response to phosphorus (P) deficiency. In a controlled environment experiment, two cloned tall fescue genotypes (DN2 and DN4) free (E-) and infected (E+) with their naturally occurring endophyte strains were grown in nutrient solutions at low P (3.1 ppm) or high P (31 ppm) concentrations for 21 d. Endophyte infection increased root dry matter (DM) of DN4 by 21% but did not affect root DM of DN2. Under P deficiency, shoot and total DM were not affected by endophyte but relative growth rate was greater in E+ than E- plants. In high P nutrient solution, E+ plants produced 13% less (DN2) or 29% more (DN4) shoot DM than E- plants. Endophyte affected mineral concentrations in roots more than in shoots. Regardless of P concentration in nutrient solution, E+ DN2 accumulated more P, Ca, Zn and Cu but less K in roots than E- plants. When grown in high P nutrient solution, concentrations of Fe and B in roots of E+ DN2 plants were reduced compared with those of E- plants. Concentrations of P, Ca and Cu in roots of DN4 were less, but K was greater in E+ than E- plants. In shoots, E+ DN2 had greater concentrations of Fe and Cu than E- DN2, regardless of P concentration in nutrient solution. Genotype DN4 responded to endophyte infection by reducing B concentration in shoots. Nutrient uptake rates were affected by endophyte infection in plants grown in low P nutrient solution. A greater uptake rate of most nutrients and their transport to shoots was observed in DN2, but responses of DN4 were not consistent. Results suggest that endophyte may elicit different modes of tall fescue adaptation to P deficiency.
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    The effects of slash burning on ecosystem nutrients during the land preparation phase of shifting cultivation (2000)
    Springer
    Plant and soil 220 (2000), S. 247-260 
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    ISSN: 1573-5036
    Keywords: cations ; fire ; nitrogen ; nutrients ; phosphorus ; slash-and-burn ; soil ; tropical forests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The most commonly observed change in soil following slash-and-burn clearing of tropical forest is a short-term increase in nutrient availability. Studies of shifting cultivation commonly cite the incorporation of nutrient-rich ash from consumed aboveground biomass into soil as the reason for this change. The effects of soil heating on nutrient availability have been examined only rarely in field studies of slash-and-burn, and soil heating as a mechanism of nutrient release is most often assumed to be of minor importance in the field. Few budgets for above and belowground nutrient flux have been developed in the tropics, and a survey of results from field and laboratory studies indicates that soils are sufficiently heated during most slash-and-burn events, particularly in dry and monsoonal climates, to cause significant, even substantial release of nutrients from non-plant-available into plant-available forms in soil. Conversely, large aboveground losses of nutrients during and after burning often result in low quantities of nutrients that are released to soil. Assessing the biophysical sustainability of an agricultural practice requires detailed information about nutrient flux and loss incurred during management. To this end, current conceptual models of shifting cultivation should be revised to more accurately describe these fluxes and losses.
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    The importance of root gravitropism for inter-root competition and phosphorus acquisition efficiency: results from a geometric simulation model (2000)
    Springer
    Plant and soil 218 (2000), S. 159-171 
    Details
    ISSN: 1573-5036
    Keywords: competition ; roots ; common bean ; mineral nutrition ; models ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We have observed that low soil phosphorus availability alters the gravitropic response of basal roots in common bean (Phaseolus vulgaris L.), resulting in a shallower root system. In this study we use a geometric model to test the hypotheses that a shallower root system is a positive adaptive response to low soil P availability by (1) concentrating root foraging in surface soil horizons, which generally have the highest P availability, and (2) reducing spatial competition for P among roots of the same plant. The growth of nine root systems contrasting in gravitropic response over 320 h was simulated in SimRoot, a dynamic three-dimensional geometric model of root growth and architecture. Phosphorus acquisition and inter-root competition were estimated with Depzone, a program that dynamically models nutrient diffusion to roots. Shallower root systems had greater P acquisition per unit carbon cost than deeper root systems, especially in older root systems. This was due to greater inter-root competition in deeper root systems, as measured by the volume of overlapping P depletion zones. Inter-root competition for P was a significant fraction of total soil P depletion, and increased with increasing values of the P diffusion coefficient (De), with root age, and with increasing root gravitropism. In heterogenous soil having greater P availability in surface horizons, shallower root systems had greater P acquisition than deeper root systems, because of less inter-root competition as well as increased root foraging in the topsoil. Root P acquisition predicted by SimRoot was validated against values for bean P uptake in the field, with an r 2 between observed and predicted values of 0.75. Our results support the hypothesis that altered gravitropic sensitivity in P-stressed roots, resulting in a shallower root system, is a positive adaptive response to low P availability by reducing inter-root competition within the same plant and by concentrating root activity in soil domains with the greatest P availability.
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    URL: http://dx.doi.org/10.1023/A:1014987710937
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    Uptake of P from apatite by Pinus sylvestris seedlings colonised by different ectomycorrhizal fungi (2000)
    Springer
    Plant and soil 218 (2000), S. 249-256 
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    ISSN: 1573-5036
    Keywords: ectomycorrhiza ; phosphorus ; Paxillus ; Suillus ; weathering ; ergosterol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The role of ectomycorrhizal (EM) fungi in increasing apatite dissolution was tested in a pot system with Pinus sylvestris (L.) seedlings growing in a sand/peat mixture. Non-mycorrhizal seedlings and seedlings inoculated with one of three different isolates of EM fungi were grown for 210 days in pots divided into a root-containing and a root-free compartment. The EM mycelium was allowed to colonise the root-free compartment, to which apatite had been added as a P source in half of the pots. All mineral nutrients except P were supplied in the form of a balanced nutrient solution. Seedlings grown with apatite as their P source grew significantly better and had higher P concentrations (1.1–1.5 mg/g) compared with seedlings growing without any P source (0.6–1.0 mg/g), indicating that they were able to use apatite-P. A weathering budget based on P uptake indicated that 6.7–18.9 mg apatite was weathered per pot which corresponds to 0.3–0.9% of the added apatite. A similar budget based on Sr uptake indicated that the apatite weathering rate was lower (0.13-0.3%). One Suillus variegatus isolate and an unidentified fungus had a significant positive influence on the dissolution of apatite, while another S. variegatus isolate had colonised roots poorly and did not influence weathering significantly. Oxalic acid was detected in root-free soil and was especially abundant in compartments colonised by S. variegatus. The concentration of oxalic acid was correlated to the concentration of phosphate in the soil solution of root-free soil, indicating that oxalic acid influences apatite dissolution.
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    URL: http://dx.doi.org/10.1023/A:1014936217105
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    On variation in forest floor thickness across four red pine plantations in Pennsylvania, USA (2000)
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    Plant and soil 219 (2000), S. 57-69 
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    ISSN: 1573-5036
    Keywords: decomposition ; litter quality ; mycorrhiza ; nitrogen ; phosphorus ; saprotrophic microorganisms ; tannins ; forest soils ; acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We studied variation in forest floor thickness in four plantations of red pine (Pinus resinosa Ait.) which were similar in age, soil type and associated vegetation. The plantations were located (west to east) in the Clear Creek, Moshannon, Sproul and Tiadaghton State Forests of Pennsylvania, USA. A gradient in forest floor thickness exists across these plantations; the forest floor is thickest in the west and it becomes progressively thinner toward the east. Decomposition of imported litter increased from west to east, suggesting that the variation in forest floor thickness is related to variation in the rate of decomposition. Decomposition rates were related to saprotroph abundance. Variation in forest floor N and phenolic concentrations, in overall mycorrhiza density and in the relative proportions of three common mycorrhiza morphotypes could not explain the variation in decomposition rate. The P concentrations and pH of the forest floor were significantly lower at Clear Creek and Moshannon, where decomposition rates were lowest, compared to Sproul and Tiadaghton, where decomposition rates were most rapid. This suggests that P concentration and pH may have exerted some control on decomposition.
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    URL: http://dx.doi.org/10.1023/A:1004748220856
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    Growth analysis of maize field crops under phosphorus deficiency. II. Radiation-use efficiency, biomass accumulation and yield components (2000)
    Springer
    Plant and soil 224 (2000), S. 259-272 
    Details
    ISSN: 1573-5036
    Keywords: light interception ; phosphorus ; radiation-use efficiency ; yield components ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Biomass accumulation by crops depends on both light interception by leaves and on the efficiency with which the intercepted light is used to produce dry matter. Our aim was to identify which of these processes were affected for maize (Zea mays L., cv Volga) field crops grown under phosphorus (P) deficiency. In the preceding paper (Plénet et al., 2000), it was shown that P deficiency severely reduced leaf growth. In this paper, the effect of P deficiency on the radiation-use efficiency (RUE) was investigated. The experimental work was carried out in 1995, 1996 and 1997 on a long-term P fertilisation trial located on a sandy soil in the south-west of France. Three P fertilisation regimes have been applied since 1972: no- P (P0 treatment) and different rates of P fertiliser (P1.5: 1.5 times the grain P export and P3: 3 times the grain P export). These fertilisation regimes have led to contrasted levels of soil P supply. Only slight differences were observed between the P1.5 and P3 treatment for above-ground biomass accumulation and grain yield. Conversely the grain yield was significantly reduced in P0 (−11%). Above-ground biomass production was severely reduced, with the maximum difference between treatment (−60% in P0) occurring between 400 and 600 °C days after sowing. The lower biomass production in P0 was accounted for by the reduced amount of photosynthetically active radiation (PAR) absorbed by the canopy, which was itself the consequence of the reduced leaf area index (see Plénet et al., 2000). The calculated RUE were found to depend on the plant stage, especially during the pre-flowering period, and on the average air temperature. No effect of P deficiency was observed on the calculated RUE, even during the period when above-ground biomass accumulation was the most severely reduced. These results obtained in field crop conditions strengthen the idea that P deficiency affects plant growth, especially leaf growth, earlier and to a greater extent than photosynthesis per unit leaf area.
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    Autumn leaf colours as indicators of decomposition rate in sycamore (Acer pseudoplatanus L.) (2000)
    Springer
    Plant and soil 225 (2000), S. 33-38 
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    ISSN: 1573-5036
    Keywords: deciduous tree ; foliar pigmentation ; fungus ; litter mass loss ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We tested the hypothesis that there is a causal connection between autumn colour, nutrient concentration and decomposibility of fresh leaf litter. Samples from patches of different autumn colours within the leaves of the deciduous tree sycamore (Acer pseudoplatanus) were sealed into litter bags and incubated for one winter in an outdoor leaf mould bed. Green leaf patches were decomposed faster than yellow or brown patches and this corresponded with the higher N and P concentrations in the former. Black patches, indicating colonisation by the tar spot fungus Rhytisma acerinum, were particularly high in P, but were decomposed very slowly, owing probably to resource immobilisation by the fungus. The results supported the hypothesis and were consistent with a previous study reporting an interspecific link between autumn coloration and decomposition rate. Autumn leaf colour of deciduous woody plants may serve as a useful predictor of litter decomposibility in ecosystem or biome scale studies where extensive direct measurements of litter chemistry and decomposition are not feasible.
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    Phosphatase activity of extra-radical arbuscular mycorrhizal hyphae: A review (2000)
    Springer
    Plant and soil 226 (2000), S. 199-210 
    Details
    ISSN: 1573-5036
    Keywords: Histochemical staining ; mineral nutrition ; phosphorus ; stress ; vital staining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphatase activity of arbuscular mycorrhizal (AM) fungi has attracted attention in three fairly distinct domains: intracellular enzymes with defined metabolic functions that have been studied in intraradical hyphae, histochemical staining of alkaline phosphatase as an indicator of fungal activity measured both intra- and extraradically, and extracellular activity related to mineralization of organic P (Po) compounds that may enhance mycorrhizal utilization of an important nutrient pool in soil. This review focuses on the latter subjects with emphasis on extraradical mycelium (ERM), while it draws on selected data from the vast material available concerning phosphatases of other organisms. We conclude that histochemical staining of alkaline phosphatase is a sensitive and suitable method for monitoring the effect of adverse conditions encountered by ERM both as a symbiotically functional entity in soil, and in vitro without modifying interference of soil or other solid substrates. Furthermore, the quantitative importance of extracellular enzymes for P nutrition of AM plants is estimated to be insignificant. This is concluded from the low quantitative contribution extracellular hyphae of AM fungi give to the total phosphatase activity in soil, and from estimations of which processes that may be rate limiting in organic P mineralization. Maximum values for the former is in the order of a few percent. As for the latter, solubilization of Po seems to be far more important than Po hydrolysis for utilization of Po by AM fungi and plants, as both endogenous soil phosphatase activity and phosphatases of other soil organisms are ubiquitous and abundant. Our discussion of mycorrhizal phosphatases supports the view that extracellular phosphatases of roots and micro-organisms are to a large extent released incidentally into soil, and that the source has limited benefit from its activity.
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    Response of tomato plants to chilling stress in association with nutrient or phosphorus starvation (2000)
    Springer
    Plant and soil 226 (2000), S. 99-106 
    Details
    ISSN: 1573-5036
    Keywords: chilling ; chlorophyll fluorescence ; nutrient ; phosphorus ; photosynthesis ; starvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The experiments were conducted on two tomato cultivars: Garbo and Robin. Mineral starvation due to plant growth in 20-fold diluted nutrient solution (DNS) combined with chilling reduced the rate of photosynthesis (P N) and stomatal conductance (g) to a greater extent than in plants grown in full nutrient solution (FNS). In phosphate-starved tomato plants the P N rate and stomatal conductance decreased more after chilling than in plants grown on FNS. In low-P plants even 2 days after chilling the recovery of CO2 assimilation rate and stomatal conductance was low. A resupply of phosphorus to low-P plants (low P + P) did not improve the rate of photosynthesis in non-chilled plants (NCh) but prevented PN inhibition in chilled (Ch) plants. The greatest effect of P resupply was expressed as a better recovery of photosynthesis and stomatal conductance, especially in non-chilled low P + P plants. The F v/F m (ratio of variable to maximal chlorophyll fluorescence) decreased more during P starvation than as an effect of chilling. Supplying phosphorus to low-P plants caused the slight increase in the F v/F mratio. In conclusion, after a short-term chilling in darkness a much more drastic inhibition of photosynthesis was observed in nutrient-starved or P-insufficient tomato plants than in plants from FNS. This inhibition was caused by the decrease in both photochemical efficiency of photosystems and the reduction of stomatal conductance. The presented results support the hypothesis that tomato plants with limited supply of mineral nutrients or phosphorus are more susceptible to chilling.
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    A function of cyanobacterial mats in phosphorus-limited tropical wetlands (2000)
    Springer
    Hydrobiologia 431 (2000), S. 135-153 
    Details
    ISSN: 1573-5117
    Keywords: cyanobacteria ; wetlands ; biomass ; phosphorus ; nitrogen fixation ; alkaline phosphatase ; Belize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyanobacterial mats are important components of oligotrophic wetland ecosystems in the limestone-based regions of the Caribbean. Our goals were to: (1) Estimate the biomass and primary production of cyanobacterial mats, quantify the extent of nitrogen fixation and measure the activity of alkaline phosphatase (APA) in representative marshes of northern Belize; (2) Record changes in these variables following nutrient additions. The mat biomass ranged from 200 to 700 g m−2 AFDM, with the epipelon contributing up to 87% of the total. Tissue nitrogen was similar in all marshes (1.1–1.5%), while tissue phosphorus was extremely low (0.0055–0.0129%) and well correlated with the N:P ratio in water. Nitrogen fixation expressed as nitrogenase activity was high in some marshes (17.5 nmol C2H4 cm−2 h−1) and low (〈 5 nmol C2H4 cm−2 h−1) in others depending mainly on the proportion of heterocyst-forming cyanobacteria (Nostocales, Stigonematales) in the mat. Alkaline phosphatase activity was positively correlated with the N:P ratio of the mat. Experimental addition of phosphorus resulted in significant increase in primary production and nitrogen fixation while it suppressed the APA activity. The presented data clearly showed that oligotrophic marshes of northern Belize are strongly P limited. Increased input of phosphorus would profoundly change their structure and functions.
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    Nitrogen limitation of production in a Californianannual grassland: The contribution of arbuscularmycorrhizae (2000)
    Springer
    Biogeochemistry 49 (2000), S. 37-51 
    Details
    ISSN: 1573-515X
    Keywords: Arbuscular mycorrhizae/Vesicular-arbuscular mycorrhizae (AM/VAM) ; annual grasslands ; benomyl ; nitrogen limitation ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nutrient availability limits plant production acrossa wide range of terrestrial ecosystems. In this studyof a Californian annual grassland community, theinfluence of arbuscular mycorrhizal (AM) associationson plant nutrient acquisition was investigated usingfactorial combinations of nitrogen (N), phosphorus (P)and benomyl fungicide. N additions resulted in asignificant increase in shoot biomass demonstratingthat plant productivity in these soils was N-limited. The effect of P additions consistently depended onfungicide treatment. In the absence of benomyl, shootP accumulation was unaltered by P addition. In thepresence of benomyl, P addition significantlyincreased shoot P accumulation and was associated witha consistent trend towards enhanced shoot biomass.The induction of P-deficiency with benomylapplication suggests that effective P acquisition byAM may contribute to the strong N-limitation ofproduction observed in many terrestrial ecosystems.
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    Nutrient losses in runoff from grasslandand shrubland habitats in southern New Mexico: II. Field plots (2000)
    Springer
    Biogeochemistry 49 (2000), S. 69-86 
    Details
    ISSN: 1573-515X
    Keywords: Bouteloua eriopoda ; Chihuahuan Desert ; desertification ; hydrology ; Larrea tridentata ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Losses of dissolved nutrients (N, P, K, Ca, Mg, Na,Cl, and SO4) in runoff were measured on grasslandand shrubland plots in the Chihuahuan desert ofsouthern New Mexico. Runoff began at a lowerthreshold of rainfall in shrublands than ingrasslands, and the runoff coefficient averaged 18.6%in shrubland plots over a 7-year period. In contrast,grassland plots lost 5.0 to 6.3% of incidentprecipitation in runoff during a 5.5-year period. Nutrient losses from shrubland plots were greater thanfrom grassland plots, with nitrogen losses averaging0.33 kg ha−1 yr−1 vs0.15 kg ha−1 yr−1, respectively, during a 3-year period. Thegreater nutrient losses in shrublands were due tohigher runoff, rather than higher nutrientconcentrations in runoff. In spite of these nutrientlosses in runoff, all plots showed net accumulationsof most elements due to inputs from atmosphericdeposition. Therefore, loss of soil nutrients byhillslope runoff cannot, by itself, account for thedepletion of soil fertility associated withdesertification in the Chihuahuan desert.
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    URL: http://dx.doi.org/10.1023/A:1006246126915
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    Sampling Strategies for Mapping Soil Phosphorus and Soil Potassium Distributions in Cool Temperate Grassland (2000)
    Springer
    Precision agriculture 2 (2000), S. 347-357 
    Details
    ISSN: 1573-1618
    Keywords: grassland soils ; mapping ; phosphorus ; potassium ; sampling strategies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Unlike the situation for arable soils, virtually nothing is known about the spatial dependencies of soil properties in cool temperate grassland or about what the optimal sampling strategies ought to be for mapping soil nutrient distributions in such situations. The aim of this study was to investigate the spatial variability in ‘plant-available’ (soil) phosphorus and potassium in a grass silage field in Northern Ireland and devise ‘optimal’ sampling strategies for mapping their distributions. Soil samples were collected from the field at 25 m intervals in a regular rectangular grid to provide a database of soil properties. Different data combinations were subsequently abstracted from this database for comparison purposes, and ordinary kriging used to produce interpolated soil maps. Soil potassium displayed greater spatial variability than soil phosphorus. In keeping with this observation, the results of three separate statistical procedures demonstrated that the optimal sample size for estimating the ‘true’ population means was about twice as large for soil potassium as for soil phosphorus. Optimal sampling strategies, however, related not just to sample size but to sample combination and field shape as well.
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    URL: http://dx.doi.org/10.1023/A:1012399915193
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    Phosphorus (P) management in the ‘De Marke’ dairy farming system (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 219-229 
    Details
    ISSN: 1573-0867
    Keywords: phosphorus ; P ; dairy farming ; systems research ; environment ; pollution ; soil fertility ; sandy soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the sandy regions of the Netherlands water quality is threatened by high losses of nutrients from intensive dairy farms. About 67% (32 kg ha-1yr-1) of farm inputs of P in purchased feeds and fertilisers do not leave in milk or cattle. The Dutch government defined decreasing maximum permitted nutrient surplusses for the period 1998–2008, at 9 kg ha-1yr-1 for P. Farmers suppose that reducing the surplusses will be costly, because it limits application of slurry, which then has to be either exported or additional land has to be purchased. Moreover, farmers are worried about the impact on soil fertility and crop growth. To explore the possibilities of reducing surplusses by improved management, farming systems research is carried out at prototype farm ‘De Marke’. Results indicate that average intensive dairy farms can reduce P surplus sufficiently, without the need to buy land or to export slurry. Key factors are reductions in purchased feeds (by reduced needs per kg milk as a result of a higher milk yield per cow, less young stock and judicious feeding) and fertilisers (by improved management of ‘home-made’ manure and an increased maize area). Initially, P fertility status of the fields of ‘De Marke’ decreased, but stabilised in the seventh year at a level not restrictive to crop production.
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    Tithonia diversifolia as a green manure for soil fertility improvement in western Kenya: A review (2000)
    Springer
    Agroforestry systems 49 (2000), S. 201-221 
    Details
    ISSN: 1572-9680
    Keywords: biomass transfer ; integrated nutrient management ; nitrogen ; nutrient cycling ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tithonia diversifolia, a shrub in the family Asteraceae, is widely distributed along farm boundaries in the humid and subhumid tropics of Africa. Green biomass of tithonia has been recognized as an effective source of nutrients for lowland rice (Oryza sativa) in Asia and more recently for maize (Zea mays) and vegetables in eastern and southern Africa. This paper reviews the potential of tithonia green biomass for soil fertility improvement based on recent research in western Kenya. Green leaf biomass of tithonia is high in nutrients, averaging about 3.5% N, 0.37% P and 4.1% K on a dry matter basis. Boundary hedges of sole tithonia can produce about 1 kg biomass (tender stems + leaves) m−1 yr−1 on a dry weight basis. Tithonia biomass decomposes rapidly after application to soil, and incorporated biomass can be an effective source of N, P and K for crops. In some cases, maize yields were even higher with incorporation of tithonia biomass than with commercial mineral fertilizer at equivalent rates of N, P and K. In addition to providing nutrients, tithonia incorporated at 5 t dry matter ha−1 can reduce P sorption and increase soil microbial biomass. Because of high labor requirements for cutting and carrying the biomass to fields, the use of tithonia biomass as a nutrient source is more profitable with high-value crops such as vegetables than with relatively low-valued maize. The transfer of tithonia biomass to fields constitutes the redistribution of nutrients within the landscape rather than a net input of nutrients. External inputs of nutrients would eventually be required to sustain production of tithonia when biomass is continually cut and transferred to agricultural land.
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    URL: http://dx.doi.org/10.1023/A:1006339025728
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    Stock-type patterns of phosphorus uptake, retranslocation, net photosynthesis and morphological development in interior spruce seedlings (2000)
    Springer
    New forests 19 (2000), S. 27-49 
    Details
    ISSN: 1573-5095
    Keywords: Picea glauca (Moench) Voss × Picea engelmannii Parry ; phosphorus ; phosphorus-use efficiency ; retranslocation ; specific absorption rate ; spring-stock ; stock-type ; summer-stock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract One-year-old interior spruce (Picea glauca (Moench) Voss × Picea engelmannii Parry) spring-stock and summer-stock were grown under two phosphorus (P) fertility regimes, with (+P) or without (−P), followed by a simulated winter, and a second growing period under an adequate fertility regime in a controlled environment room. The two stock-types differed in their response to low P availability. For spring-stock, morphological development, phosphorus-use efficiency (PUE) and P specific absorption rate (SAR) were similar between −P and +P seedlings. For summer-stock, −P seedlings compared to +P seedlings had lower (p ≤ 0.05) morphological development, but greater PUE and SAR. For both stock-types, P content increased in +P seedlings, remained low in −P seedlings, and P concentration decreased in nursery-needles (i.e., formed in the nursery) of −P seedlings. The difference in stock-type response to low phosphorus availability (−P) was attributed to internal supply of P and it's retranslocation. Assimilation (A) of CO2 in nursery-needles was similar between −P and +P seedlings for both stock-types. For spring-stock, +P seedlings had greater A in new-needles (i.e., needles formed during the trial) than −P seedlings. It was recommended that the spring-stock be selected over summer-stock for sites low in P availability.
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    URL: http://dx.doi.org/10.1023/A:1006618312161
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    Traits associated with improved P-uptake efficiency in CIMMYT's semidwarf spring bread wheat grown on an acid Andisol in Mexico (2000)
    Springer
    Plant and soil 221 (2000), S. 189-204 
    Details
    ISSN: 1573-5036
    Keywords: Andisol ; phosphatases ; phosphorus ; roots ; VA mycorrhiza ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus deficiency is a major yield limiting constraint in wheat cultivation on acid soils. The plant factors that influence P uptake efficiency (PUPE) are mainly associated with root characteristics. This study was conducted to analyze the genotypic differences and relationships between PUPE, root length density (RLD), colonization by vesicular arbuscular and arbuscular mycorrhizal (V)AM fungi and root excretion of phosphatases in a P-deficient Andisol in the Central Mexican Highlands. Forty-two semidwarf spring-bread-wheat (Triticum aestivumL.) genotypes from CIMMYT were grown without (−P) and with P fertilization (+P), and subsequently in subsets of 30 and 22 genotypes in replicated field trials over 2 and 3 years, respectively. Acid phosphatase activity at the root surface (APASE) was analyzed in accompanying greenhouse experiments in nutrient solution. In this environment, PUPE contributed more than P utilization efficiency, in one experiment almost completely, to the variation of grain yield among genotypes. Late-flowering genotypes were higher yielding, because the postanthesis period of wheat was extended due to the cold weather at the end of the crop cycles, and postanthesis P uptake accounted for 40–45% of total P uptake. PUPE was positively correlated with the numbers of days to anthesis (at −P r=0.57 and at +P r=0.73). The RLD in the upper soil layer (0–20 cm) of the wheat germplasm tested ranged from 0.5 to 2.4 cm cm-3 at –P and 0.7 to 7.7 at +P. RLD was the most important root trait for improved P absorption, and it was positively genetically correlated with PUPE (at –P r=0.42 and at +P r=0.63) and the number of spikes m-2 (at –P r=0.58 and at +P r=0.36). RLD in the upper soil layer was more important with P fertilizer application. Without P fertilization, root proliferation in the deeper soil profile secured access to residual, native P in the deeper soil layer. (V)AM-colonisation and APASE were to a lesser degree correlated with PUPE. Among genoptypes, the level of (V)AM-colonisation ranged from 14 to 32% of the RLD in the upper soil layer, and APASE from 0.5 to 1.1 nmol s-1 plant-1 10-2.
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    Temporal changes in C, P and N concentrations in soil solution following application of synthetic sheep urine to a soil under grass (2000)
    Springer
    Plant and soil 222 (2000), S. 1-13 
    Details
    ISSN: 1573-5036
    Keywords: carbon ; defoliation ; nitrogen ; phosphorus ; sheep urine ; soil solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We have determined the temporal changes in the concentration of dissolved organic carbon (DOC) and P and N components in soil solution following application of synthetic sheep urine (500 kg N ha-1) to a brown forest soil in boxes sown with Agrostis capillaris. Three contrasting defoliation treatments (no cutting, single cut before urine application and regular cutting twice per week) plus a fallow soil were studied. The synthetic urine contained 15N labelled urea and was P-free. Intact soil cores were taken after 2, 7, 14, 21 and 56 d and centrifuged to obtain soil solution. The urea in the synthetic urine was rapidly hydrolysed in the soil, increasing soil solution pH, DOC and total dissolved phosphorus (TDP) concentrations. For the regularly defoliated sward, DOC and P reached maximum concentrations (4000 mg DOC L-1 and 59 mg TDP L-1) on day 7. From their peak values, pH and DOC and P concentrations generally decreased with time and at day 56 were near those of the control. Concentrations of NH4 + and NO3 - in the no-urine treatments fluctuated and the greatest treatment differences were between the fallow soil and the soil sown with grass. Adding synthetic urine increased NH4 + concentrations during the first week, but NO3 - concentrations decreased. This was consistent with the 15N labelling of the NO3 - pool which required 3 weeks to reach that of 15NH4 +. Dissolved organic nitrogen (DON) reached a maximum value at day 7 with a concentration of 409 mg N L-1. The DON in soil solution contained no detectable amounts of 15N label indicating that it was derived from sources in the soil. Differences in soil solution composition related to the effect of the other cutting treatments and the fallow treatment were small compared to the effect of synthetic urine addition.
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    URL: http://dx.doi.org/10.1023/A:1004799323646
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    Root-induced increases in soil pH and nutrient availability to field-grown cereals and legumes on acid sandy soils of Sudano-Sahelian West Africa (2000)
    Springer
    Plant and soil 225 (2000), S. 117-127 
    Details
    ISSN: 1573-5036
    Keywords: anion/cation uptake ; cowpea ; millet ; phosphorus ; rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment with millet (Pennisetum glaucum L.), sorghum [Sorghum bicolor (L.) Moench], cowpea (Vigna unguiculata L.) and groundnut (Arachnis hypogeae L.) was conducted on severely P-deficient acid sandy soils of Niger, Mali and Burkina Faso to measure changes in pH and nutrient availability as affected by distance from the root surface and by mineral fertiliser application. Treatments included three rates of phosphorus (P) and four levels of nitrogen (N) application. Bulk, rhizosphere and rhizoplane soils were sampled at 35, 45 and 75 DAS in 1997 and at 55 and 65 DAS in 1998. Regardless of the cropping system and level of mineral fertiliser applied, soil pH consistently increased between 0.7 and two units from the bulk soil to the rhizoplane of millet. Similar pH gradients were observed in cowpea, but pH changes were much smaller in sorghum with a difference of only 0.3 units. Shifts in pH led to large increases in nutrient availability close to the roots. Compared with the bulk soil, available P in the rhizoplane was between 190 and 270% higher for P-Bray and between 360 and 600% higher for P-water. Exchangeable calcium (Ca) and magnesium (Mg) levels were also higher in the millet rhizoplane than in the bulk soil, whereas exchangeable aluminium (Al) levels decreased with increasing pH close to the root surface. The results suggest an important role of root-induced pH increases for crops to cope with acidity-induced nutrient deficiency and Al stress of soils in the Sudano-Sahelian zone of West Africa.
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    URL: http://dx.doi.org/10.1023/A:1026570406777
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    Nutrient enrichment of northern rivers in response to pulp mill and municipal discharges (2000)
    Springer
    Journal of aquatic ecosystem stress and recovery 8 (2000), S. 53-66 
    Details
    ISSN: 1573-5141
    Keywords: Canada ; nitrogen ; periphyton ; phosphorus ; pulp mill effluent ; rivers ; sewage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To evaluate the effects of pulp mill and municipal sewageeffluents on the nitrogen (N) and phosphorus (P) status of northernCanadian rivers, the Northern River Basins Study required an integratedresearch and assessment program consisting of field observation andexperimentation. Analysis of monitoring data collected over 3–13 yshowed that on an annual basis, pulp mills contributed 22% of theP and 20% of the N load discharged from the Wapiti to the Smokyriver, and 6 to 16% of the P load and 4 to 10% of the Nload in the Athabasca River. Despite these low contributions, N and Pconcentrations were elevated below pulp mill discharges on all threerivers during the low discharge period of September to April. Insitu experiments conducted with nutrient diffusing substrata showedthat periphyton biomass was maintained at low levels by insufficient Pin the upper reaches of the Athabasca River and insufficient N+P inthe Wapiti River upstream of point-source discharges. In contrast,effluent loading from pulp mill and sewage inputs alleviated nutrientlimitation downstream of major discharges on both rivers. Experimentsconducted in artificial streams located beside the Athabasca Riverupstream of the first pulp mill showed that P addition increasedperiphyton biomass (expressed as chlorophyll a content) suchthat biomass increased sharply at low P concentrations (2–5µg/L soluble reactive P) and approached saturation at 35µg/L soluble reactive P. As a result of recommendations fromthis integrated program of river monitoring and experimentation,nutrient loading has been reduced to the most affected river(Wapiti-Smoky) and federal and provincial departments of environment arereviewing loading limits for other river reaches.
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    URL: http://dx.doi.org/10.1023/A:1011447907574
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    Light- and nutrient-limited periphyton in low order streams of Oahu, Hawaii (2000)
    Springer
    Hydrobiologia 432 (2000), S. 101-111 
    Details
    ISSN: 1573-5117
    Keywords: Hawaii ; light ; nitrogen ; nutrients ; periphyton ; phosphorus ; spate ; stream
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To date, most studies of light- and nutrient-limited primary productivity in forested streams have been carried out in deciduous forests of temperate, continental regions. Conceptual models of light and nutrient limitation have been developed from these studies, but their restricted geographic range reduces the generality of such models. Unlike temperate continental streams, streams on tropical high islands are characterized by flashy, unpredictable discharge and riparian canopies that do not vary seasonally. These contrasting conditions suggest that patterns of light and nutrient limitation in tropical streams may differ from those in temperate streams. The effects of light, and nitrogen and phosphorus availability on periphyton accrual (measured as chlorophyll a per unit area) were investigated using field experiments in 4 low-order streams on the island of Oahu, Hawaii. Levels of chlorophyll a in partially-shaded stream pools were significantly greater than in heavily-shaded pools, and nutrient-enrichment increased the level of chlorophyll a in partially-shaded pools but not in heavily-shaded pools. In each stream, phosphate enrichment resulted in an increase in the level of chlorophyll a, but nitrate enrichment had no effect. Spates following rainstorms occur frequently in these streams, and may increase periphyton productivity by increasing the flux of nutrients to algal cells. However, differences in inorganic nitrogen and phosphorus concentrations measured during spates and baseflow were small, and during some spates, concentrations of these two nutrients declined relative to baseflow concentrations. These observations suggest that phosphorus limitation was not alleviated by spates.
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    URL: http://dx.doi.org/10.1023/A:1004074004416
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    Effects of the emergent macrophyte Juncus effusus L. on the chemical composition of interstitial water and bacterial productivity (2000)
    Springer
    Biogeochemistry 48 (2000), S. 307-322 
    Details
    ISSN: 1573-515X
    Keywords: aquatic plants ; dissolved organic carbon ; nutrient cycling ; phosphorus ; sediments ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Release of oxygen from the roots ofaquatic macrophytes into anaerobic sediments canaffect the quantity of interstitial dissolved organicmatter and nutrients that are available to bacteria. Nutrient and dissolved organic carbon (DOC)concentrations were compared between subsurface(interstitial) waters of unvegetated sediments andsediments among stands of the emergent herbaceousmacrophyte Juncus effusus L. in a lotic wetlandecosystem. Concentrations of inorganic nitrogen(NH4 +, NO3 -, and NO2 -)were greater from sediments of the unvegetatedcompared to the vegetated zone. DOC concentrations ofinterstitial waters were greater in sediments of theunvegetated zone both in the winter and springcompared to those from the vegetated zone. AlthoughDOC concentrations in hydrosoils collected from bothzones increased from winter to spring, bacterialproductivity per mg DOC in spring decreased comparedto winter. Greater initial bacterial productivityoccurred on DOM collected from the vegetated comparedto the unvegetated zone in winter samples (days 1 and4), with increased bacterial productivity on samplescollected from the unvegetated zone at the end of thestudy (day 20). Bacterial productivity wassignificantly greater on all sampling days on DOM fromvegetated samples compared to unvegetated samples. In nutrient enrichment experiments, bacterialproductivity was significantly increased (p 〈 0.05)with phosphorus but not nitrogen only amendments.
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    Carbon, nitrogen and phosphorus cycling in rivermarginal wetlands; a model examination of landscapegeochemical flows (2000)
    Springer
    Biogeochemistry 50 (2000), S. 45-71 
    Details
    ISSN: 1573-515X
    Keywords: carbon ; landscape geochemical flows ; model ; nitrogen ; phosphorus ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The importance of landscape geochemical flows wasinvestigated using a dynamic model simulating carbon,nitrogen and phosphorus cycling in riverine wetlands,which has been described in a previous paper. Thehydro-geomorphic unit (HGMU) concept was incorporatedin the model by defining a separate, completeunit-model for each unit (HGMU) within the wetland.These unit-models were connected by defining the flowsof nitrogen and phosphorus between them. These flows,also called landscape geochemical flows, usuallyconsist of flows of water containing N and P. The model was applied to a site at Kismeldon Meadows,in south-western England. This site consists of twounits, a slope and a floodplain, separated by a ditch,which catches most of the run off and shallowgroundwater flows from the slope. Only an estimated1% of the N and P that leaves the slope unit in thewater outflow reaches the floodplain unit; the rest iscaught in the system of ditches, which prevent thegeochemical flows taking their natural course. Toexamine the influence of this system of ditches, themodel was run for the same site, but without theditches. This is comparable to a situation of arestored site, where run off and shallow groundwaterflows containing nutrients, can freely get from theslope to the floodplain. The computer simulation experiment reconnecting theslope and floodplain showed that this (1) increasedthe nutrient input into the floodplain, causing ahigher biomass production, and (2) increased thewetness of the floodplain, causing slowerdecomposition, which together (3) led to a faster soilorganic matter accumulation in the floodplain.Nutrient inflows became relatively more importantcompared to atmospheric deposition, especially forphosphorus. By connecting the slope and the floodplainmore nitrogen and less phosphorus flowed into theriver.
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    Internal eutrophication in peat soils through competition between chloride and sulphate with phosphate for binding sites (2000)
    Springer
    Biogeochemistry 50 (2000), S. 183-194 
    Details
    ISSN: 1573-515X
    Keywords: chloride ; internal eutrophication ; nitrogen ; peat soil ; phosphorus ; phytometer ; sulphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Inputs of surface waters high in chloride and sulphateincreased the availability of nutrients in fenpeatlands. This `internal eutrophication' wasdemonstrated with test plants (`phytometers') andthrough water and soil analysis. Three experiments arepresented in which the level of chloride and/orsulphate was increased to 3 mmolc l−1. Inexperiment 1 chloride levels were increased from 0.5to 3 mmolc l−1 as CaCl2 or NaCl. Inexperiment 2 and 3 similar increased levels forchloride and sulphate (3 mmolc l−1; as NaCland Na2SO4) were used. The following resultswere found: (i) No differences in soil total-N and total-P werefound before and after the treatments in any of thethree experiments. (ii) Experiment 1 showed a significant increase inBio-Available P (BAP) in pots planted with Anthoxanthum odoratum as well as in bare pots for theNaCl and CaCl2 treatments. The plants in thesetreatments had taken up much more P. (iii) Experiment 2 showed an increase in soil BAPafter treatment with chloride and sulphate in potsplanted with Anthoxanthum odoratum. The chloridetreatment had no effect on plant biomass, whereas thesulphate treatment resulted in a reduction in rootbiomass and root N and P content. The shoots showedan increase in P content in the sulphate and chloridetreatments, while N content remained the same. (iv) In experiment 3, treatments with chloride andsulphate led to significantly increased biomass and Puptake of Anthoxanthum odoratum. Again, noeffects on N uptake were found. These experiments provide evidence for distinctlyincreased availability of phosphate in peat soils whenthese come into contact with water with evenmoderately increased sulphate or chloride levels.Surface water originating from the Rhine river, whichis enriched in chloride and sulphate, is oftensupplied to fen reserves in The Netherlands, tocompensate for water losses due to agriculturaldrainage in the region. The results of this study showthat phosphate availability to the vegetation may risedrastically, with detrimental effects on the speciesdensity and the occurrence of rare species in thevegetation. Hence, supply of this water should beavoided.
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    Al and Fe Biogeochemistry in a floodplain forest: Implications for P retention (2000)
    Springer
    Biogeochemistry 51 (2000), S. 1-32 
    Details
    ISSN: 1573-515X
    Keywords: aluminum ; floodplain forests ; iron ; organic matter ; P sorption capacity ; phosphorus ; soil ; wetlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We examined spatial and temporal variationsin soil chemistry in a floodplain forest landscape todetermine the effects of flooding on aluminum (Al) andiron (Fe) oxide biogeochemistry and inorganicphosphorus (Pi) sorption capacity. Whenpreviously sorbed Pi was considered, the sorptioncapacities of floodplain and adjacent upland soilswere comparable, suggesting that floodplain soilsrepresent a second line of defense protectingdownstream aquatic ecosystems from agriculturalrun-off. Pi sorption capacity was highlycorrelated with oxalate-extractable Al (Alo)(rs = 0.78); Alo and percent organic matter(OM) were also highly correlated (rs = 0.72),suggesting the importance of OM-Al complexes in thesesoils. The correlation of oxalate-extractable Fe(Feo) with OM (rs = 0.64) was improved(rs = 0.80) by removing lower elevation (swale)soils, suggesting that flooding inhibits theassociation of Feo with OM. Fe oxidecrystallinity decreased during seasonal flooding, buttotal extractable Fe did not change significantly. Fesolubilized during flooding was either replaced bysediment deposition (252 ± 3 mmol kg−1yr−1), and/or reprecipitated locally. Al oxidecrystallinity also decreased during flooding due to asignificant decline in NaOH-extractable Al (AlN). AlN concentrations subsequently returned topre-flooding levels, but sediment Al inputs (57 ±3 mmol kg−1 yr−1), were insufficient to account for this recovery. Observed Fetransformations suggest the importance offlooding-induced declines in soil redox potential toFe biogeochemistry; observed Al transformationssuggest the importance of complexation reactions withsoil OM to Al biogeochemistry in this floodplainforest.
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    URL: http://dx.doi.org/10.1023/A:1006302600347
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    Using Bacterial Growth on Insects to Assess Nutrient Impacts in Streams (2000)
    Springer
    Environmental monitoring and assessment 63 (2000), S. 431-446 
    Details
    ISSN: 1573-2959
    Keywords: aquatic bacteria ; benthic macroinvertebrates ; bioindicator ; eutrophication ; nitrogen ; phosphorus ; stream pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A combination field and laboratorystudy was conducted to evaluate the ability of arecently developed bioindicator to detect detrimentalnutrient conditions in streams. The method utilizesbacterial growth on aquatic insects to determinenutrient impacts. Field investigations indicated thatelevated concentrations of nitrate and phosphate wereassociated with growth of filamentous bacteria oninsect body surfaces, and that there was a significantreduction in the density of major insect taxa in thenutrient-enriched stream reaches. Laboratoryinvestigations confirmed a strong linkage betweenbacterial growth and reduced survival of insects. Survival was examined for insects with bacterialinfestation ranging from 0% to greater than 50%coverage of the body surface. A threshold forcatastrophic mortality occurred at about 25% bodycoverage; there were few survivors above that amount. Based on these findings, the diagnostic endpoint forthe bioindicator is 25% body coverage by bacterialgrowth, a level that signifies major impacts and isalso easy to detect visually. This study providesadditional evidence that the insect-bacteriabioindicator is a reliable tool for assessing nutrientimpacts on stream macroinvertebrate communities. Thebioindicator should prove useful for identifyingnutrient-impacted sites as well as monitoring thesuccess of management actions to improve water quality.
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    URL: http://dx.doi.org/10.1023/A:1006211929599
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    Transfer RNA Identity Change in Anticodon Variants of E. coli tRNAPhe in Vivo (2000)
    Springer
    Molecules and cells 10 (2000), S. 76-82 
    Details
    ISSN: 0219-1032
    Keywords: Anticodon ; Evolution ; Identity ; tRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The anticodon sequence is a major recognition element for most aminoacyl-tRNA synthetases. We investigated the in vivo effects of changing the anticodon on the aminoacylation specificity in the example of E. coli tRNAPhe. Constructing different anticodon mutants of E. coli tRNAPhe by site-directed mutagenesis, we isolated 22 anticodon mutant tRNAPhe; the anticodons corresponded to 16 amino acids and an opal stop codon. To examine whether the mutant tRNAs had changed their amino acid acceptor specificity in vivo, we tested the viability of E. coli strains containing these tRNAPhe genes in a medium which permitted tRNA induction. Fourteen mutant tRNA genes did not affect host viability. However, eight mutant tRNA genes were toxic to the host and prevented growth, presumably because the anticodon mutants led to translational errors. Many mutant tRNAs which did not affect host viability were not aminoacylated in vivo. Three mutant tRNAs containing anticodon sequences corresponding to lysine (UUU), methionine (CAU) and threonine (UGU) were charged with the amino acid corresponding to their anticodon, but not with phenylalanine. These three tRNAs and tRNAPhe are located in the same cluster in a sequence similarity dendrogram of total E. coli tRNAs. The results support the idea that such tRNAs arising from in vivo evolution are derived by anticodon change from the same ancestor tRNA.
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    URL: http://dx.doi.org/10.1007/s10059-000-0076-7
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    Nitrogen and Phosphorus Levels in Sediments from Tropical Catatumbo River (Venezuela) (2000)
    Springer
    Water, air & soil pollution 117 (2000), S. 27-37 
    Details
    ISSN: 1573-2932
    Keywords: eutrophication ; nitrogen ; phosphorus ; river ; sediment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Nitrogen (N) and phosphorus (P) concentrations were determined in sediment samples along the bed of Catatumbo river in both Colombian and Venezuelan territories until the river outlet in Maracaibo lake. Total phosphorus was determined by digestion with HCl followed by analysis using the ascorbic acid method and total nitrogen was done using the standard microkjeldahl method plus nitrate-nitrite. Ammonium, orthophosphate and nitrate were determined using standard methods after extraction steps. The mean concentrations along the river bed were found in an interval of 0.035 and 1.492 mg g-1 dry sed. for nitrogen and 0.027 and 1.039 mg g-1 dry sed. for phosphorus at 95% confidence level. The mean molar ratio N/P in the river bed was 4.42 and 3.46 for river outlet zones in the lake, which indicates that nitrogen is the limiting nutrient. For comparison with previous results of lake sediments from sites near the river outlet it was concluded that Catatumbo river is a significant source of nutrients to the Maracaibo Lake system because sediment nutrients concentrations from Catatumbo river were higher than the ones in Maracaibo Lake. Statistic studies showed significant differences between countries, zones and similar behaviour in the river bed as related to the affluent rivers.
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    External Phosphorus Load Estimates and P-Budget for the Hydroelectric Reservoir of Bort-les-Orgues, France (2000)
    Springer
    Water, air & soil pollution 119 (2000), S. 91-103 
    Details
    ISSN: 1573-2932
    Keywords: eutrophication ; external load ; mass balance ; P-export coefficient ; phosphorus ; reservoir
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper presents two methods used to estimate the externalphosphorus load for the hydroelectric reservoir ofBort-Les-Orgues (in France's `Massif Central' region). The Pload calculated from export coefficients (150 t yr-1) agreedwith field measurements taken during a one-year survey carriedout from March 1996 to February 1997 (121 t yr-1). Exportcoefficients represent a good option for estimating phosphorusloads of other reservoirs in the region of Bort-Les-Orgues,provided that they display similar characteristics. Theseexternal load estimates are greater than the maximum permissibleload for a mesotrophic lake calculated from the OECD equations(40 t yr-1); thus, a yearly reduction of about 60 t shouldideally be achieved. This target, however, is probably tooambitious, and measures to reduce both point and non-pointsources must be implemented for the reservoir to tbe mesotrophic.Moreover, Bort-Les-Orgues is a tourist area. As such, thepresence of algal blooms (a regular occurrence on the lake) dueto an excess of P in the lake's water inflow could actuallyexert a negative impact on regional economy.
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    URL: http://dx.doi.org/10.1023/A:1005186122618
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    Distributions of Mercury and Phosphorous in Everglades Soils From Water Conservation Area 3A, Florida, U.S.A. (2000)
    Springer
    Water, air & soil pollution 121 (2000), S. 133-159 
    Details
    ISSN: 1573-2932
    Keywords: Everglades ; mercury ; mobility ; peat ; phosphorus ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Soils in the southern half of Water Conservation Area3A are mostly peats with some organic-rich marls. Mercury contents of 64 surface samples over a500 km2 area average 28.7 ng cc-1 (209 ppb drysediment), which is typical of organic-rich soils. High Hg contents in Everglades fish are therefore notcaused by anomalously high soil Hg. Hg contents showno systematic lateral variation, consistent withdeposition from well-mixed atmospheric sources ratherthan nearby point sources or runoff from canals.Cores from 9 sites contain more Hg and P at or nearthe surface than at 20–30 cm depth. Hg and P contentsof individual cores correlate well and define separatebackground and anomalous populations. The subsurfacedistribution of P is determined largely by uptake bysawgrass and other plants. The correlation between Pand Hg suggests that, although atmospheric Hgdeposition has undoubtedly increased in recentdecades, postdepositional mobilization of Hg may beimportant in Everglades soils. This finding, togetherwith recent direct measurements of atmospheric Hgdeposition, indicates that previous estimates of Hgdeposition rates based on Everglades peat cores, whichassumed that Hg is immobile in peat after deposition,have yielded large overestimates.
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    URL: http://dx.doi.org/10.1023/A:1005214908516
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    The Role of Plant Size and Nutrient Concentrations in Associations between Medicago, and Rhizobium and/or Glomus (2000)
    Springer
    Biologia plantarum 43 (2000), S. 221-226 
    Details
    ISSN: 1573-8264
    Keywords: alfalfa ; arbuscular mycorrhizal fungi ; nitrogen ; nitrogen-fixing bacteria ; phosphorus ; plant growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this research was to carry out a critical study of the method of obtaining size equivalence between non-symbiotic alfalfa and alfalfa associated with Glomus and/or Rhizobium by applying fixed addition rates of nutrients to the non-symbiotic controls. The experimental design included three nutrient response curves in which the levels of added phosphorus and/or nitrogen were constant during the whole plant growth process: 1) a phosphorus response curve, in order to compare the growth of double symbiotic plants with that of only-Rhizobium inoculated ones; 2) a nitrogen response curve, that consisted of a comparison between the growth of double symbiotic alfalfa and four treatments associated only with Glomus; 3) a phosphorus and nitrogen response curve, to compare the growth of non-inoculated alfalfa with that of double symbiotic plants. Although similar size was achieved among some treatments at harvest, shoot growth over time and nutrient concentrations in tissues differed, indicating that growth equivalence did not mean functional equivalence. A second experimental design was performed taking into account the establishment of microsymbionts for determining the adequate moment to add supplemental phosphorus and/or nitrogen. It included four treatments: a) double symbiotic plants (MR); b) plants inoculated with Rhizobium only (R); c) plants inoculated with Glomus only (M), and d) non-inoculated plants (N). Great similarity in terms of plant growth and nutrient contents in tissues were obtained. Moreover, symbiotic plants were able to produce similar dry matter than non-symbiotic ones under P and N limitations.
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    Ni–Zn–P alloy deposition from sulfate bath: inhibitory effect of zinc (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 1171-1176 
    Details
    ISSN: 1572-8838
    Keywords: alloys ; cyclic voltammetry ; electrodeposition ; electroless deposition ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy deposition from a sulphate bath, containing sodium hypophosphite as reducer, was investigated. To increase the plating rate, the deposition parameters were optimized. The effect of process parameters (T, pH and [Zn2+]) on the plating rate and deposit composition was examined and it was found that the presence of zinc in the bath has an inhibitory effect on the alloy deposition. As a consequence, the percentage of zinc in the electroless Ni–Zn–P alloys never reaches high values. Using cyclic voltammetry the electrodeposition mechanism of Ni–Zn–P alloys was investigated. It was observed that the zinc deposition inhibits the nickel discharge and, as a consequence, its catalytic activity on hypophosphite oxidation. It was also found that increase in temperature or pH leads to the deposition of nickel rich alloys.
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    URL: http://dx.doi.org/10.1023/A:1003426904395
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    Microstructural characterization and corrosion resistance of Ni–Zn–P alloys electrolessly deposited from a sulphate bath (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 637-645 
    Details
    ISSN: 1572-8838
    Keywords: alloys ; electroless ; microstructure ; morphology ; nickel ; phosphorus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Electroless Ni–Zn–P alloy coatings were obtained on an iron substrate from a sulfate bath at various pH values. The effects of changes in bath pH on alloy composition, morphology, microstructure and corrosion resistance were studied. Scanning electron microscopy was performed to observe the morphological change of the deposits with bath pH. Coating crystallinity was investigated by grazing incidence asymmetric Bragg X-ray diffraction and transmission electron microscopy. A transition from an amorphous to polycrystalline structure was observed on increasing the bath alkalinity, and thus decreasing the phosphorus content of the alloys. A single crystalline phase corresponding to face-centred-cubic nickel was identified in the alloys obtained from a strong alkaline solution. An increase in zinc percentage up to 23% in the deposits does not change the f.c.c. nickel crystalline structure. Corrosion potential and polarization resistance measurements indicated that the corrosion resistance of electroless Ni–Zn–P alloys depends strongly on the microstructure and chemical composition. The deposits obtained at pH 9.0–9.5 and with 11.4–12.5% zinc and 11.8–11.2% phosphorous exhibited the best corrosion resistance.
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    URL: http://dx.doi.org/10.1023/A:1026441403282
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    Purification and characterization of an ADP-dependent phosphofructokinase from Thermococcus zilligii (1999)
    Springer
    Extremophiles 3 (1999), S. 121-129 
    Details
    ISSN: 1433-4909
    Keywords: Key words Thermococcus ; Pyrococcus ; Thermophilic ; Phosphofructokinase ; Evolution ; ADP ; Glycolysis ; ATP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The ADP-dependent phosphofructokinase (PFK) from Thermococcus zilligii has been purified 950 fold; it had a specific activity of 190 U mg−1. The enzyme required Mg2+ ions for optimal activity and was specific for ADP. The forward reaction kinetics were hyperbolic for both cosubstrates (pH optimum of 6.4), and the apparent K m values for ADP and fructose-6-phosphate were 0.6 mM (apparent V max of 243 U mg−1) and 1.47 mM (apparent V max of 197 U mg−1), respectively. Significantly, the enzyme is indicated to be nonallosteric but was slightly activated by some monovalent cations including Na+ and K+. The protein had a subunit size of 42.2 kDa and an estimated native molecular weight of 66 kDa (gel filtration). Maximal reaction rates for the reverse reaction were attained at pH 7.5–8.0, and the apparent K m values for fructose-1,6-bisphosphate and AMP were 0.56 mM (apparent V max of 2.9 U mg−1) and 12.5 mM, respectively. The biochemical characteristics of this unique ADP-dependent enzymatic activity are compared to ATP and pyrophosphate-dependent phosphofructokinases.
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    URL: http://dx.doi.org/10.1007/s007920050107
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    Isolation of a chymotrypsinogen B-like enzyme from the archaeon Natronomonas pharaonis and other halobacteria (1999)
    Springer
    Extremophiles 3 (1999), S. 153-161 
    Details
    ISSN: 1433-4909
    Keywords: Key wordsNatronomonas pharaonis ; Natronobacteria ; Archaea ; Serine protease ; Chymotrypsinogen ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A protease of a molecular mass of approximately 30 kDa was isolated and purified from the haloalkaliphilic archaeon Natronomonas (formerly Natronobacterium) pharaonis. The enzyme hydrolyzed synthetic peptides, preferentially at the carboxyl terminus of phenylalanine or leucine, as well as large proteins. Hydrolysis occurred over the range of pH from 6 to 12, with an optimum at pH 10. The temperature optimum was 61°C. The enzyme was nearly equally active over the range of salt concentration from 0.5 to 4 M (NaCl or KCl). A strong cross-reaction with a polyclonal antiserum against human chymotrypsin was observed. Enzymatic activity was inhibited by typical serine protease inhibitors. There was significant homology between N-terminal and internal sequences from autolytic fragments and the sequence of bovine chymotrypsinogen B; the overall amino acid composition was similar to that of vertebrate chymotrypsinogens. Evidence for a zymogen-like processing of the protease was obtained. Cell extracts from other halobacteria exhibited similar proteolytic activity and immunoreactivity. The data suggested a widespread distribution of a chymotrypsinogen B-like protease among halo- and haloalkaliphilic Archaea.
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    Multiple class I loci expressed by the quail Mhc (1999)
    Springer
    Immunogenetics 49 (1999), S. 456-460 
    Details
    ISSN: 1432-1211
    Keywords: Key words Antigen processing ; Evolution ; Cell surface molecules ; Mhc ; Class I antigens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/s002510050519
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    Identification and characterization of a fish natural resistance-associated macrophage protein (NRAMP) cDNA (1999)
    Springer
    Immunogenetics 50 (1999), S. 60-66 
    Details
    ISSN: 1432-1211
    Keywords: Key words NRAMP ; Fish ; Carp ; Evolution ; Expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The mouse Lsh/Ity/Bcg locus regulates natural resistance to intracellular pathogens, and the Nramp1 gene was isolated as its candidate. Nramp is part of a small family of at least two genes, Nramp1 and Nramp2. In the present study, a full-length cDNA for carp NRAMP has been isolated and characterized. Nucleotide and predicted amino acid sequence analysis indicate that the carp NRAMP encodes a 548 amino acid membrane protein with 12 putative transmembrane domains, two N-linked glycosylation sites, and an evolutionarily conserved consensus transport motif. The peptide sequence identity among carp and human NRAMP2 is 78%, and 65% with human NRAMP1. Reverse transcription-polymerase chain reaction revealed that carp NRAMP is ubiquitously expressed. Phylogenetic analysis, using neigbor-joining, showed that the carp NRAMP protein clustered together with mammalian NRAMP2 proteins.
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    Diversity and evolution of T-cell receptor variable region genes in mammals and birds (1999)
    Springer
    Immunogenetics 50 (1999), S. 301-308 
    Details
    ISSN: 1432-1211
    Keywords: Key words T-cell receptors ; Variable region genes ; Evolution ; Phylogeny ; Diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The receptor of a T lymphocyte (TCR) recognizes nonself antigens in the company of major histocompatibility complex (MHC) molecules presented to it by the antigen-presenting cell. The variable region of TCR is encoded by either a concatenation of variable region (TCR-V), diversity region (TCR-D), and joining region (TCR-J) genes, or a concatenation of TCR-V and TCR-J genes. The TCR-V genes exist as a multigene family in vertebrate species. Here we study the evolutionary relationships of TCR-V genes from humans, sheep, cattle, rabbits, mice, and chicken. These six species can be classified into two groups according to the frequency of γδ T-cells in their peripheral T-cell populations. The "γδ low" group of species includes humans and mice, in which γδ T-cells constitute very limited portion of the T-cell population. The "γδ high" group includes sheep, cattle, rabbits, and chicken, in which γδ T-cells comprise up to 60% of the T-cell population. Here, we compiled TCR-V sequences from the six species and conducted a phylogenetic analysis. We identified various TCR-V gene subgroups based on the analysis. We found that humans and mice have representatives from nearly all of the subgroups identified, while other species have lost subgroups to different extent. Therefore, the γδ low species have a high degree of diversity of TCR-V genes, while γδ high species all have limited diversity of TCR-V genes. This pattern is similar to that found for immunoglobulin variable region (IGV) genes.
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    Marsupial light chains: IGK with four V families in the opossum Monodelphis domestica (1999)
    Springer
    Immunogenetics 50 (1999), S. 329-335 
    Details
    ISSN: 1432-1211
    Keywords: Key words Marsupials ; Light chains ; Variable regions ; IGK ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  A full-length and several partial cDNAs encoding IGK light chains from the marsupial South American opossum, Monodelphis domestica, were isolated and characterized. Using these clones as a starting point, the expressed IGKV repertoire was sampled by anchored polymerase chain reaction using an IGKC-specific primer. Based on nucleotide sequences of twenty unique, expressed IGKV-J combinations, there are at least four IGKV families and two J segments. Southern blot analysis revealed each IGK-V family contains multiple gene segments totaling at least thirty-five IGKV in the opossum genome. No evidence for particular, recurrent IGKV-J combinations in the opossum IGK repertoire was seen, rather the V-J combinations appeared random and diverse. Each of the four IGKV families appear more closely related to V segments from placental mammals than to each other, suggesting the duplication of the IGKV families prior to the separation of marsupials and placental mammals more than one-hundred-million years ago. Overall, the complexity of opossum light chain V segments appears greater than that found in the heavy chain, and light chains are likely to contribute significantly to Ig diversity in this species.With this report, the homologues encoding all three classes of eutherian Ig chains, IGH, IGL, and IGK, have been described in a non-placental mammal.
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    Major histocompatibility complex-linked MIC genes in rhesus macaques and other primates (1999)
    Springer
    Immunogenetics 50 (1999), S. 358-362 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC ; MIC ; Nonhuman primates ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/s002510050614
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    Isolation and mapping of the rabbit DM genes (1999)
    Springer
    Immunogenetics 49 (1999), S. 295-302 
    Details
    ISSN: 1432-1211
    Keywords: Key words Major histocompatibility complex ; Class II ; Antigen processing ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Proper peptide presentation by major histocompatibility complex (MHC)-encoded class II antigens is dependent on the products of the MHC DM loci. We identified the rabbit orthologues (RLA-DMA and -DMB) of human HLA-DMA and -DMB and found that they have 76.9% and 78.8% identity with HLA-DMA and -DMB, respectively. Like classical class II MHC genes, RLA-DM genes are more closely related to human HLA-DM genes than to mouse H2-DM. Among the DM family, there is a high degree of variability at the amino terminus of the DMa chains, and length variability in the cytoplasmic tails of both DMα and DMβ. The rabbit DM genes are coexpressed with class II genes in lymphoid tissues, as are the DM genes of other mammals. The RLA-DM locus maps to the class II region of the rabbit MHC, and is flanked by the DP and DOB loci. Despite having some similarities to class II genes of bony fishes, the DM family represents a separate branch of the MHC class II family.
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    New family of Mhc class II A genes identified from cDNA sequences in the cichlid fish Aulonocara hansbaenschi (1999)
    Springer
    Immunogenetics 49 (1999), S. 544-548 
    Details
    ISSN: 1432-1211
    Keywords: Key words Mhc ; Class II A ; Cichlid ; Fish ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/s002510050533
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    Characterization of beta2-microglobulin in a primitive fish, the Siberian sturgeon (Acipenser baeri) (1999)
    Springer
    Immunogenetics 50 (1999), S. 79-83 
    Details
    ISSN: 1432-1211
    Keywords: Key words Beta2-microglobulin ; Evolution ; Sturgeon ; cDNA ; Genomic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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    URL: http://dx.doi.org/10.1007/s002510050690
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    Effects of repeated manure and fertilizer phosphorus additions on soil phosphorus dynamics under a soybean-wheat rotation (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 150-155 
    Details
    ISSN: 1432-0789
    Keywords: Key words Phosphorus dynamics ; Olsen ; phosphorus ; Soil phosphorus fractions ; Manure ; Soybean-wheat rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Soil P availability and efficiency of applied P may be improved through an understanding of soil P dynamics in relation to management practices in a cropping system. Our objectives in this study were to evaluate changes in plant-available (Olsen) P and in different inorganic P (Pi) and organic P (P0) fractions in soil as related to repeated additions of manure and fertilizer P under a soybean-wheat rotation. A field experiment on a Typic Haplustert was conducted from 1992 to 1995 wherein the annual treatments included four rates of fertilizer P (0, 11, 22 and 44 kg ha–1 applied to both soybean and wheat) in the absence and presence of 16 t ha–1 of manure (applied to soybean only). With regular application of fertilizer P to each crop the level of Olsen P increased significantly and linearly through the years in both manured and unmanured plots. The mean P balance required to raise Olsen P by 1 mg kg–1 was 17.9 kg ha–1 of fertilizer P in unmanured plots and 5.6 kg ha–1 of manure plus fertilizer P in manured plots. The relative sizes of labile [NaHCO3-extractable Pi (NaHCO3-Pi) and NaHCO3-extractable P0 (NaHCO3-P0)], moderately labile [NaOH-extractable Pi (NaOH-Pi) and NaOH-extractable P0 (NaOH-P0)] and stable [HCl-extractable P (HCl-P) and H2SO4/H2O2-extractable P (resisual-P)] P pools were in a 1 : 2.9 : 7.6 ratio. Application of fertilizer P and manure significantly increased NaHCO3-Pi and -P0 and NaOH-Pi, and -P0 fractions and also total P. However, HCl-P and residual-P were not affected. The changes in NaHCO3-Pi, NaOH-Pi and NaOH-P0 fractions were significantly correlated with the apparent P balance and were thought to represent biologically dynamic soil P and act as major sources and sinks of plant-available P.
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    A nose that looks like a hand and acts like an eye: the unusual mechanosensory system of the star-nosed mole (1999)
    Springer
    Journal of comparative physiology 185 (1999), S. 367-372 
    Details
    ISSN: 1432-1351
    Keywords: Key words Cortical magnification ; Somatosensory cortex ; Development ; Evolution ; Behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The star-nosed mole (Condylura cristata) has a snout surrounded by 22 fleshy and mobile appendages. This unusual structure is not an olfactory organ, as might be assumed from its location, nor is it used to manipulate objects as might be guessed from its appearance. Rather, the star is devoted to the sense of touch, and for this purpose the appendages are covered with thousands of small mechanoreceptive Eimer's organs. Recent behavioral studies find that the star acts much like a tactile eye, having a small behavioral focus, or “fovea” at the center – used for detailed explorations of objects of interest. The peripheral and central nervous systems of the mole reflect these behavioral specializations, such that the small behavioral focus on the nose is more densely innervated in the periphery, and has a greatly enlarged representation in the somatosensory cortex. This somatosensory representation of the tactile fovea is not correlated with anatomical parameters (innervation density) as found in other species, but rather is highly correlated with patterns of behavior. The many surprising parallels between the somatosensory system of the mole, and the visual systems of other mammals, suggest a convergent and perhaps common organization for highly developed sensory systems.
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    URL: http://dx.doi.org/10.1007/s003590050396
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    Peripheral frequency mis-match in the primitive ensiferan Cyphoderris monstrosa (Orthoptera: Haglidae) (1999)
    Springer
    Journal of comparative physiology 184 (1999), S. 543-551 
    Details
    ISSN: 1432-1351
    Keywords: Key words Auditory physiology ; Insect ; Frequency discrimination ; Evolution ; Song recognition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Peripheral auditory frequency tuning in the ensiferan insect Cyphoderris monstrosa (Orthoptera: Haglidae) was examined by comparing tympanal vibrations and primary auditory receptor responses. In this species there is a mis-match between the frequency of maximal auditory sensitivity and the frequency content of the species' acoustic signals. The mis-match is not a function of the mechanical properties of the tympanum, but is evident at the level of primary receptors. There are two classes of primary receptors: low-tuned and broadly tuned. Differences in the absolute sensitivity of the two receptor types at the male song frequency would allow the auditory system to discriminate intraspecific signals from sounds containing lower frequencies. Comparisons of tympanal and receptor tuning indicated that the sensitivity of the broadly tuned receptors did not differ from that of the tympanum, while low-tuned receptors had significantly narrower frequency tuning. The results suggest that the limited specialization for the encoding of intraspecific signals in the auditory system of C. monstrosa is a primitive rather than a degenerate condition. The limited specialization of C. monstrosa may reflect the evolutionary origin of communication-related hearing from a generalized precursor through the addition of peripheral adaptations (tympana, additional receptors) to enhance frequency sensitivity and discrimination.
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    URL: http://dx.doi.org/10.1007/s003590050354
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    Comparison of morphology and physiology of two plurisegmental sound-activated interneurones in a bushcricket (1999)
    Springer
    Journal of comparative physiology 185 (1999), S. 199-205 
    Details
    ISSN: 1432-1351
    Keywords: Key words Hearing ; Orthoptera ; Phaneropteridae ; Cercal system ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The unusual morphology of a sound-activated plurisegmental ascending interneurone (AN5-AG7) in an insect (Ancistrura nigrovittata, Ensifera, Phaneropteridae) is described. This neurone's soma is located in the penultimate abdominal ganglion. The most prominent arborisations with smooth endings are found in the prothoracic ganglion. The neurone terminates with numerous beaded endings in the brain (protocerebrum). All abdominal ganglia including the penultimate contain only tiny side branches of beaded appearance. The neurone's morphology is compared to the morphology of a `typical' sound-activated plurisegmental neurone of bushcrickets with its soma in the prothorax. In the prothoracic ganglion and in the brain the arborisations of the two cells are very similar. Graded potentials and action potentials are generated in the prothoracic portion of both neurones. Both receive excitation mainly by ultrasound, and inhibition by soma-ipsilateral stimuli. Neither wind, substrate vibration nor touch of the abdomen evoke responses in AN5-AG7. It is assumed that early in evolution this neurone had its dendrites in the ganglion which houses the cell body (like cercal interneurones of this neuromere). Profound evolutionary changes probably have taken place to bring about this neuron's modern morphology.
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    URL: http://dx.doi.org/10.1007/s003590050378
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    Spatial discrimination of pheromones and behavioural antagonists by the tortricid moths Cydia pomonella and Adoxophyes orana (1999)
    Springer
    Journal of comparative physiology 185 (1999), S. 419-425 
    Details
    ISSN: 1432-1351
    Keywords: Key wordsCydia pomonella ; Adoxophyes orana ; Sex pheromone ; Interspecific interruption ; Evolution ; AbbreviationsZ9-14:Ac (Z9)-tetradecenylacetate Z11-14:Ac (Z11)-tetradecenylacetate ; E8, E10-12:OH (E8, E10)-dodecadienol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Male moths responding to their species-specific sex pheromone, may cease their upwind flight when pheromone components of sympatric species are added to the mixture. The interspecific interaction between the pheromone response of the tortricid moths Cydia pomonella and Adoxophyes orana was investigated in field-trapping and wind-tunnel studies. Addition of the A. orana pheromone [(Z9)-tetradecenylacetate and (Z11)-tetradecenylacetate] to a source containing the C. pomonella pheromone [(E8, E10)-dodecadienol] resulted in a significant inhibition of attraction by male C. pomonella. It is demonstrated that this behavioural antagonist for C. pomonella must be emitted from the same point source to induce this inhibitory effect. A spatial separation of the two interspecific pheromones (at 14 cm, 5 cm and 0.5 cm crosswind) restored the attraction of the conspecific pheromone for male C. pomonella. In contrast to C. pomonella, male A. orana were not inhibited by point sources releasing both the C. pomonella and A. orana pheromone. We suggest that the discrepancy in the interspecific pheromone interaction between these two tortricids can be explained if we consider the evolutionary ecology of interspecific pheromone communication in C. pomonella and A. orana.
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    URL: http://dx.doi.org/10.1007/s003590050402
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    Stable isotope (δ13C and δ15N) signatures of sedimented organic matter as indicators of historic lake trophic state (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 205-221 
    Details
    ISSN: 1573-0417
    Keywords: carbon isotopes ; diatoms ; lake management ; nitrogen isotopes ; phosphorus ; radium-226 ; sediments ; trophic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract We explored the use of carbon and nitrogen isotopes (δ13C and δ15N) in sedimented organic matter (OM) as proxy indicators of trophic state change in Florida lakes. Stable isotope data from four 210Pb-dated sediment cores were compared stratigraphically with established proxies for historical trophic state (diatom-inferred limnetic total phosphorus, sediment C/N ratio) and indicators of cultural disturbance (sediment total P and 226Ra activity). Diatom-based limnetic total P inferences indicate a transition from oligo-mesotrophy to meso-eutrophy in Clear Lake, and from eutrophy to hypereutrophy in Lakes Parker, Hollingsworth and Griffin. In cores from all four lakes, the carbon isotopic signature of accumulated OM generally tracks trophic state inferences and cultural impact assessments based on other variables. Oldest sediments in the records yield lower diatom-inferred total limnetic P concentrations and display relatively low δ13C values. In the Clear, Hollingsworth and Parker records, diatom-inferred nutrient concentrations increase after ca. AD 1900, and are associated stratigraphically with higher δ13C values in sediment OM. In the Lake Griffin core, both proxies display slight increases before ~1900, but highest values occur over the last ~100 years. As Lakes Clear, Hollingsworth and Parker became increasingly nutrient-enriched over the past century, the δ15N of sedimented organic matter decreased. This reflects, in part, the increasing relative contribution of nitrogen-fixing cyanobacteria to sedimented organic matter as primary productivity increased in these waterbodies. The Lake Griffin core displays a narrow range of both δ13C and δ15N values. Despite the complexity of carbon and nitrogen cycles in lakes, stratigraphic agreement between diatom-inferred changes in limnetic total P and the stable isotope signatures of sedimented OM suggests that δ13C and δ15N reflect shifts in historic lake trophic state.
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    URL: http://dx.doi.org/10.1023/A:1008078222806
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    Calibration of diatoms along a nutrient gradient in Florida Everglades Water Conservation Area-2A, USA (1999)
    Springer
    Journal of paleolimnology 22 (1999), S. 413-437 
    Details
    ISSN: 1573-0417
    Keywords: diatoms ; Everglades ; phosphorus ; wetland ; calibration ; multivariate ; Florida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract The relationship between diatom taxa preserved in surface soils and environmental variables at 31 sites in Water Conservation Area 2A (WCA-2A) of the Florida Everglades was explored using multivariate analyses. Surface soils were collected along a phosphorus (P) gradient and analyzed for diatoms, total P, % nitrogen (N), %carbon (C), calcium (Ca), and biogenic silica (BSi). Phosphorus varied from 315-1781 μg g-1, and was not found to be correlated with the other geochemical variables. Canonical correspondence analysis (CCA) was used to examine which environmental variables correlated most closely with the distributions in diatom taxa. Canonical correspondence analysis with forward selection, constrained and partial CCA, and Monte Carlo permutation tests of significance show the most significant changes in diatom assemblages along the P gradient (p 〈 0.01), with additional species differences correlated with soil C, N, Ca, and BSi. Weighted-averaging (WA) regression and calibration models of diatom assemblages to P and BSi were developed. The diatom-based inference model for soil [P] had a high apparent r2 (0.86) with RMSEboot = 218 μg g-1. Indicator diatom species identified by assessing species WA optima and WA tolerance to [P], such as Nitzschia amphibia and N. palea for high [P] (~1300-1400 μ g-1) and Achnanthes minutissima var. scotica and Mastogloia smithii for low [P] (~400-600 μg g-1), may be useful as monitoring tools for eutrophication in WCA-2A as well as other areas of the Everglades. Diatom assemblages analyzed by cluster analysis were related to location within WCA-2A, and dominant taxa within clusters are discussed in relation to the geochemical variables measured as well as hydrology and pH. Diversity of diatom assemblages and a ‘Disturbance Index’ based on diatom data are discussed in relation to the historically P-limited Everglades ecosystem. Diatom assemblages should be very useful for reconstructions of [P] through time in the Florida Everglades, provided diatoms are well preserved in soil cores.
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    URL: http://dx.doi.org/10.1023/A:1008049224045
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    Controlling soil water content in fertiliser dissolution experiments (1999)
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    Nutrient cycling in agroecosystems 55 (1999), S. 7-14 
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    ISSN: 1573-0867
    Keywords: fertiliser formulation ; nutrients ; phosphorus ; relative humidity ; soil moisture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and contributes to algal blooms. Fertilisers are one source of this P. To compare the water available P of different fertiliser formulations in the laboratory it is necessary to control environmental conditions, temperature, relative humidity and soil water content, prior to simulating rainfall. Two chambers were designed in which relative humidity and soil water content were controlled using salt solutions. An initial design comprising a sealed chamber with three layers of soil samples over a salt bath was found to be inferior to a single layer design. The changes in water content of soil samples were used to test the single layer chamber in a constant temperature environment (15 °C) using a saturated KCl solution (90% relative humidity). Based on the final soil water content of the samples, the spatial variation within the chamber was within tolerable limits. The single layer chamber was used for a simulation experiment comparing the water available P of two commercial fertilisers. Using a saturated resorcinol solution (95% relative humidity) soil samples were equilibrated at 15 °C for 21 days, fertiliser added, and the water available P measured up to 600 h after fertiliser application. The results indicate that the amount of water available P was related to the fertiliser compound and exponentially related to the time since fertiliser application. It was concluded that the single layer chamber is suitable for controlling relative humidity and soil water content in trials such as these where the water available P of fertilisers are being compared.
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    URL: http://dx.doi.org/10.1023/A:1009816716466
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    Transfers of phosphorus within three dairy farming systems receiving varying inputs in feeds and fertilizers (1999)
    Springer
    Nutrient cycling in agroecosystems 55 (1999), S. 63-75 
    Details
    ISSN: 1573-0867
    Keywords: dairy systems ; feeds ; fertilizers ; phosphorus ; P surplus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Inputs of phosphorus (P) above requirements for production on dairy farms lead to surplus P with increased risk of P transfer in land run-off to surface waters causing eutrophication. The impact of reducing surplus P inputs in purchased feeds and fertilizers on milk and forage production was investigated in a comparison of three dairy farm systems on chalkland soils in southern England over a 3-year period. In accordance with current commercial practice, no attempt was made to regulate P inputs in system 1, which accumulated an average annual surplus of 23 kg P ha-1. Progressive reductions in purchased feed and/or fertilizer inputs into systems 2 and 3 decreased surplus P to 17 and 3 kg ha-1, respectively, without apparently limiting either milk or herbage dry matter production. The estimated reduction in faecal P output from system 3 cows fed a low P diet compared to system 1 cows fed a high P diet was 26%. Milk P concentrations significantly (P 〈0.001) increased in systems 2 and 3 which included maize in the diet. Output of P in milk and meat products, as a proportion of the total dietary P inputs, increased from 28% in system 1 to 36% in system 3. Surplus P was greatest in continuous maize fields receiving both dairy manure and starter P fertilizer. Withholding P fertilizer in system 3 did not reduce P offtake in cut herbage on soils of moderate P fertility. Total annual losses of P in storm run-off and leaching were no greater than annual inputs of P from the atmosphere (0.5 kg ha-1). The results indicate there is scope to reduce surplus P on commercial dairy farms without sacrificing production targets at least in the short term. Purchased feeds are the largest of the P inputs on intensive dairy farms, yet these are rarely quantified on commercial holdings.
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    URL: http://dx.doi.org/10.1023/A:1009860915462
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    Applications of poultry litter and triple superphosphate fertilizer to a sandy soil: effects on soil phosphorus status and profile distribution (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 233-242 
    Details
    ISSN: 1573-0867
    Keywords: leaching ; phosphorus ; poultry litter ; soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To determine P loadings, added through poultry litter, sufficient to cause downward movement of P from the cultivated layer of a sandy soil, six rates of poultry litter were applied annually for four years to a site in central England. (total loading 0 – 1119 kg P ha-1). A single extra plot also received an extra 1000 kg ha-1 as triple superphosphate (TSP; total loading 2119 kg P ha-1) and three other treatments received 200 – 800 kg ha-1 P as TSP only. Annual soil sampling in 30-cm increments to 1.5-m depth provided information on P build-up in the topsoil and P movement to depth. There were strong linear trends between P balance (P applied – P removed in crops) and total P, Olsen bicarbonate extractable P and water-soluble P in the topsoil. Phosphorus from TSP and poultry litter fell on the same regression lines, suggesting that both would be equally effective as fertilizer sources. We calculated that 100 kg ha-1 surplus total P would increase the Olsen extractable P content by c. 6 mg kg-1 and the water-soluble P by c. 5 mg kg-1. Thus, relatively large amounts of P would need to be applied to raise soil P status. We found some evidence of P movement into the soil layers immediately below cultivation depth. However, neither soil sampling nor soil solution extracted through Teflon water samplers showed evidence of movement into the deep subsoil (1 m) despite large P loadings.
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    URL: http://dx.doi.org/10.1023/A:1009744706679
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    Inorganic phosphorus and manure effects on bahiagrass production on a Spodosol (1999)
    Springer
    Nutrient cycling in agroecosystems 54 (1999), S. 259-266 
    Details
    ISSN: 1573-0867
    Keywords: bahiagrass ; manure ; pasture fertilization ; phosphorus ; phosphorus cycling ; Spodosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bahiagrass (Paspalum notatum Flugge) pasture fertilization recommendations have traditionally been based upon clipping studies. Inclusion of P from manure, not originally considered when P recommendations were developed for pastures, may minimize the need for P fertilization without reducing bahiagrass production or P uptake. The objective of this research was to determine if manure contributes greatly to the P crop nutrient requirement. A 2-year field study utilized a factorial arrangement of 0 and 6.9 Mg air-dried manure ha-1 with 0, 17, 34, 51, and 68 kg inorganic P ha-1 from triple superphosphate to evaluate bahiagrass yield, root distribution, and P uptake response on a Myakka fine sand (sandy, siliceous, hyperthermic Aeric Alaquod). Because air-dried manure was used in the field study, a greenhouse study was employed to confirm that there were no differences in bahiagrass yield or P uptake from either air-dried or fresh cattle (Bos spp.) manure sources. There were no manure or manure by P interaction effects on yield or P uptake of bahiagrass indicating that manure source did not effect grass production in the greenhouse. In the field study, bahiagrass roots were distributed into the Bh horizon, and the Bh horizon had at least four times more Mehlich-1 extractable P than that of the Ap horizon. This horizon was most likely acting as a main source for P-uptake by the grass. This observation was further confirmed by no yield response to levels of inorganic P application in 1989. A linear-response-and-plateau (R2=0.196) relationship with a critical point of 15.4 kg P ha-1 was found in 1990. Bahiagrass yield and P uptake were not dependent on P fertilization, either from manure or inorganic P, due to the availability of P from the Bh horizon.
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    URL: http://dx.doi.org/10.1023/A:1009831011649
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    Risk and evolution (1999)
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    Economic theory 13 (1999), S. 329-343 
    Details
    ISSN: 1432-0479
    Keywords: Keywords and Phrases: Risk ; Evolution ; Entrepreneur. ; JEL Classification Numbers: C72 ; D81.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Summary. I examine a Knightian (1921) model of risk using a general equilibrium model of investment and trade. A population of agents with various preference types can choose between a safe production technology and a risky production technology. In addition, the distribution of types of agents changes through a standard evolutionary dynamic. For a given population distribution, the equilibrium is in general inefficient, however, by allowing the population distribution to change in response to market generated rewards, the population will converge to one where the equilibrium is efficient and where the population as a whole behaves as if all agents were risk neutral.
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    URL: http://dx.doi.org/10.1007/s001990050257
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    Evolution of groundwater chemical composition under human activity in an oilfield (1999)
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    Environmental geology 38 (1999), S. 34-46 
    Details
    ISSN: 1432-0495
    Keywords: Key words Alkaline/acid/neutral water ; Acid rain ; Geochemical modeling ; Brine ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Analysis and hydrogeochemical modeling of hydrocarbonate groundwater, including its buffering geochemical properties, have demonstrated that this water has undergone a geochemical transformation almost throughout the whole of one industrial region. It is known that hydrocarbonate groundwater possesses a high protective natural geochemical potential, supporting neutralization of acid atmospheric precipitation. Natural hydrocarbonate water undergoes three stages of anthropogenic transformation caused by acid atmospheric precipitation over more than 50 years. The first stage is transformation of neutral hydrocarbonate water into alkaline water, accompanied by calcite precipitation and sodium carbonate dissolution from the unsaturated zone. The second stage is transformation of alkaline water into neutral hydrocarbonate water; the hydrocarbonate content, being less than the lower limit for background concentrations, showed reduced water buffering properties or protective potential relative to acid precipitation. The third stage is transformation of neutral hydrocarbonate water into acidic water, with a complete loss of protective geochemical potential. This unfavorable ecological situation with natural geochemically hydrocarbonate groundwater shows that natural groundwater less protected from the impact of acid atmospheric precipitation is in a worse ecological condition, which is confirmed by observations in northern and Western Europe and other regions of the world.
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    Evolution of homeobox genes: Q50 Paired-like genes founded the Paired class (1999)
    Springer
    Development genes and evolution 209 (1999), S. 186-197 
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    ISSN: 1432-041X
    Keywords: Key words Cnidaria ; Paired class ; Paired-like ; Homeobox gene ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The genes belonging to the Paired class exert primary developmental functions. They are characterized by six invariant amino acid residues in the homeodomain, while the residue at position 50 can be a serine, glutamine or lysine as in the Pax-type, Q50 Paired-like or the K50 Paired-like homeodomains respectively. Genes in this class emerged early in animal evolution: three distinct Pax genes and two Q50 Paired-like genes have recently been characterised from cnidarians. Phylogenetic molecular reconstructions taking into account homeodomain and paired-domain sequences provide some new perspectives on the evolution of the Paired-class genes. Analysis of 146 Paired-class homeodomains from a wide range of metazoan taxa allowed us to identify 18 families among the three sub-classes from which the aristaless family displays the least diverged position. Both Pax-type and K50 families branch within the Q50 Paired-like sequences implying that these are the most ancestral. Consequently, most Pax genes arose from a Paired-like ancestor, via fusion of a Paired-like homebox gene with a gene encoding only a paired domain; the Cnidaria appear to contain genes representing the ’before’ and ’after’ fusion events.
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    Rapid divergence in the course of Drosophila evolution reveals structural important domains of the Notch antagonist Hairless (1999)
    Springer
    Development genes and evolution 209 (1999), S. 155-164 
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    ISSN: 1432-041X
    Keywords: Key words Notch pathway ; Antagonist ; Hairless ; Orthologue ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Hairless is a member of the Notch signalling pathway, where it acts as antagonist by binding to Suppressor of Hairless [Su(H)], thereby inhibiting Notch target gene activation. The pathway and its members are highly conserved in metazoans from worms to humans. However, a Hairless orthologue from another species has not yet been identified. The identification of Hairless in largely diverged species by cross-hybridization has failed so far probably due to a low degree of conservation. Therefore, we turned to D. hydei where a Hairless mutation has been described before. The D. hydei Hairless orthologue is reasonably well conserved with regard to gene structure and expression. The prospective Hairless protein orthologues share several highly conserved regions which are separated by quite diverged stretches. As to be expected, the largest region of high conservation corresponds to the Su(H) binding domain. This region is also functionally conserved, since this D. hydei protein domain binds very strongly to the D. melanogaster Su(H) protein. The other conserved regions support our earlier structure-function analysis since they nicely correspond to previously defined, functionally important protein domains. Most notably, the very C-terminal domain which is very sensitive to structural alterations, is nearly identical between the two species. In summary, this evolutionary study improves the knowledge on functionally significant domains of the Hairless protein, and may be helpful for the future identification of homologues in other animals, especially in vertebrates.
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    Maternal factors and the evolution of developmental mode: Evolution of oogenesis in Heliocidaris erythrogramma (1999)
    Springer
    Development genes and evolution 209 (1999), S. 275-283 
    Details
    ISSN: 1432-041X
    Keywords: Key words Echinoid ; Oogenesis ; Development ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Evolutionary change in developmental mode in sea urchins is closely tied to an increase in maternal provisioning. We examined the oogenic modifications involved in production of a large egg by comparison of oogenesis in congeneric sea urchins with markedly different sized oocytes and divergent modes of development. Heliocidaris tuberculata has small eggs (95 µm diameter) and the ancestral mode of development through feeding larvae, whereas H. erythrogramma has large eggs (430 µm diameter) and highly modified non-feeding lecithotrophic larvae. Production of a large egg in H. erythrogramma involved both conserved and divergent mechanisms. The pattern and level of vitellogenin gene expression is similar in the two species. Vitellogenin processing is also similar with the gonads of both species incorporating yolk protein from coelomic and hemal stores into nutritive cells with subsequent transfer of this protein into yolk granules in the developing vitellogenic oocyte. Immunocytology of the eggs of both Heliocidaris species indicates they incorporate similar levels of yolk protein. However, H. erythrogramma has evolved a highly divergent second phase of oogenesis characterised by massive deposition of non-vitellogenic material including additional maternal protein and lipid. Maternal provisioning in H. erythrogramma exhibits recapitulation of the ancestral vitellogenic program followed by a novel oogenic phase with hypertrophy of the lipogenic program being a major contributor to the increase in egg size.
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    Identification and genetic mapping of Xenopus TAP2 genes (1999)
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    Immunogenetics 49 (1999), S. 171-182 
    Details
    ISSN: 1432-1211
    Keywords: Key words MHC ; Transporter ; Evolution ; PCR cloning ; Allelic lineage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The amphibian Xenopus laevis is one non-mammalian vertebrate in which the major histocompatibility complex (MHC) has been analyzed extensively. Class IIβ, class Ia, LMP2, LMP7, HSP70, C4, Factor B, and Ring3 genes have been identified and mapped to the MHC. Here, we report the isolation of a transporter associated with antigen processing (TAP) gene, TAP2, and demonstrate its linkage to the MHC. While the ATP-binding region of Xenopus TAP2 is highly conserved in evolution, amino acid identity to other vertebrate TAP proteins was not detected in the N-terminal region. Segregation analysis of 34 individuals from two families showed exact restriction fragment length polymorphism matching between the MHC class Ia gene and the one TAP2 gene demonstrating linkage conservation since the mammalian/amphibian divergence ∼350 million years ago. In addition, one non-MHC-linked TAP2–hybridizing fragment was detected in approximately half of the individuals tested. Interestingly, TAP2 allelic lineages appear to match those of LMP7 and classical class I, which previously were categorized into two highly divergent groups that emerged at least 60 million years ago. Similar to LMP7 and class Ia,TAP2 is expressed ubiquitously with highest levels in intestine and spleen.
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    Organization of the genes encoding the human proteasome activators PA28α and β (1999)
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    Immunogenetics 49 (1999), S. 438-445 
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    ISSN: 1432-1211
    Keywords: Key words PA28 ; Proteasome ; Gene structure ; Evolution ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Two proteasome activators PA28α and β, which have been implicated in antigen processing for loading class I MHC molecules, are synthesized in response to Ifn-γ. The human genes encoding these activators (PSME1 and PSME2, respectively) were analyzed by sequencing. Each gene comprised 11 exons, consistent with gene duplication during vertebrate evolution. The intron/exon organization of both genes was highly conserved, the major difference being the absence of the exon encoding the lysine and glutamic acid-rich 'KEKE' motif in PA28β. Two other genes of relevance to the immune system were located close to those for PA28 at 14q11.2 including ISGF3G, a protein involved in transcription after IFNα signalling. These sequences were also characterized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050517
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    Variation in the number of expressed MHC genes in different cattle class I haplotypes (1999)
    Springer
    Immunogenetics 50 (1999), S. 319-328 
    Details
    ISSN: 1432-1211
    Keywords: Key words Cattle ; MHC class I ; Haplotypes ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Analysis of cattle major histocompatibility complex (MHC) (BoLA) class I gene expression using serological and biochemical methods has demonstrated a high level of polymorphism. However, analysis of class I cDNA sequences has failed to produce conclusive evidence concerning the number and nature of expressed genes. Such information is essential for detailed studies of cattle immune responses, and to increase our understanding of the mechanisms of MHC evolution. In this study a selective breeding programme has been used to generate a number of MHC homozygous cattle expressing common serologically defined class I specificities. Detailed analysis of five class I haplotypes was carried out, with transcribed class I genes identified and characterized by cDNA cloning, sequence analysis, and transfection/expression studies. Surface expression of the gene products (on lymphocytes) was confirmed using monoclonal antibodies of defined BoLA specificity. Phylogenetic analysis of available transcribed cattle MHC class I sequences revealed complex evolutionary relationships including possible evidence for recombination. The study of individual haplotypes suggests that certain groupings of related sequences may correlate with loci, but overall it was not possible to define the origin of individual alleles using this approach. The most striking finding of this study is that none of the cattle class I genes is consistently expressed, and that in contrast to human, haplotypes differ from one another in both the number and composition of expressed classical class I genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002510050608
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