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  • phosphorus  (43)
  • Drosophila  (42)
  • Springer  (85)
  • 1995-1999
  • 1990-1994  (85)
  • 1925-1929
  • 1992  (85)
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  • 1995-1999
  • 1990-1994  (85)
  • 1925-1929
  • 1980-1984  (55)
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  • 1
    Electronic Resource
    Electronic Resource
    Measurement of total dissolved phosphorus in small volumes of iron rich interstitial water (1992)
    Springer
    Aquatic sciences 54 (1992), S. 1-9 
    Details
    ISSN: 1420-9055
    Keywords: Sediment ; interstitial water ; phosphorus ; iron ; persulfate digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is shown that sorption of orthophosphate to iron compounds, formed during persulfate digestion, can cause a significant underestimation of total dissolved phosphorus in interstitial waters rich in iron and poor in phosphorus. Labelling the samples with carrier free32PO4 before digestion allows to correct for these losses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877261
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  • 2
    Electronic Resource
    Electronic Resource
    Unusual organizational features of the Drosophila Gart locus are not conserved within diptera (1992)
    Springer
    Journal of molecular evolution 35 (1992), S. 51-59 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila ; Gart locus ; Chironomus tentans ; Purine nucleotide biosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Drosophila Gart locus consists of two genes. One gene encodes three enzymes in the de novo purine nucleotide biosynthesis pathway [glycinamide ribonucleotide synthetase (GARS), aminoimidazole ribonucleotide synthetase (AIRS), and glycinamide ribonucleotide transformylase (GART)]. The second gene lies within an intron of the purine gene and encodes a cuticle protein. To investigate the evolution of the Gart locus, the Chironomus tentans homolog was cloned by screening a genomic DNA library with a polymerase chain reaction product. This study shows that the interesting structural features of this locus conserved in two distant Drosophila species are not found in the Chironomus homolog. These features include the cuticle protein gene nested within an intron and the existence of an alternative transcript to yield a monofunctional enzyme. In addition, the extremely rapid divergence of coding sequence seen for members of the tandemly duplicated AIRS domain in Drosophila is found to be much less rapid in Chironomus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160260
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  • 3
    Electronic Resource
    Electronic Resource
    Evolution of the threonine-glycine repeat region of the period gene in the melanogaster species subgroup of drosophila (1992)
    Springer
    Journal of molecular evolution 35 (1992), S. 411-419 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila ; per gene ; Threonine-Glycine ; repeat sequence ; melanogaster subgroup phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Threonine-Glycine (Thr-Gly) region of the period gene (per) in Drosophila was compared in the eight species of the D. melanogaster subgroup. This region can be divided into a diverged variable-length segment which is flanked by more conserved sequences. The number of amino acids encoded in the variable-length region ranges from 40 in D. teissieri to 69 in D. mauritiana. This is similar to the range found within natural populations of D. melanogaster. It was possible to derive a Thr-Gly “allele” of one species from that of another by invoking hypothetical Thr-Gly intermediates. A phylogeny based on the more conserved flanking sequences was produced. The results highlighted some of the problems which are encountered when highly polymorphic genes are used to infer phylogenies of closely related species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171819
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  • 4
    Electronic Resource
    Electronic Resource
    Complementary DNA-DNA hybridization in Drosophila (1992)
    Springer
    Journal of molecular evolution 34 (1992), S. 130-140 
    Details
    ISSN: 1432-1432
    Keywords: Drosophila ; Sophophora ; cDNA-DNA hybridization ; Phylogenetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have performed DNA-DNA hybridization experiments among several species of Drosophila using the evolutionarily conserved portion of the genome representing sequences coding for amino acids of proteins. This was done by using as tracer, radioactively labeled complementary DNA that was reverse transcribed from adult mRNA. We show that this procedure extends phylogenetically the distance over which the technique can be applied to fast-evolving groups such as Drosophila. The major phylogenetic conclusions are (1) the subgenus Sophophora is a monophyletic lineage; (2) within Sophophora the melanogaster subgroup is closer to the obscura group than either group is to the willistoni group; (3) the subgenus Drosophila is complex with most major lineages originating deep in the phylogeny; the subgenus may not be monophyletic; (4) as with most groups classically placed in Drosophila, the Hawaiian Drosophila originate early, supporting the notion that this lineage is older than the extant islands; and (5) the virilis/repleta lineage is monophyletic within Drosophila.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00182390
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  • 5
    Electronic Resource
    Electronic Resource
    The determination of phosphonate base scale inhibitors in brines by plasma spectrometry (1992)
    Springer
    Microchimica acta 109 (1992), S. 201-209 
    Details
    ISSN: 1436-5073
    Keywords: phosphonate base scale inhibitor ; brine ; direct current plasma ; inductively coupled plasma atomic emission spectrometry ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of phosphonate base scale inhibitors in brines by direct current plasma (DCP) and inductively coupled plasma atomic emission spectrometry (ICP-AES) is described. The first method is based on a direct nebulization of the brine samples and plasma using the phosphorus line at 213.618 nm. The second method involves extraction of phosphorus as phospho-antimonyl molybdate complex into methylisobutyl ketone (MIBK) phase and analysis of the extract for molybdenum using the Mo 313.260 nm line. Comparison between the proposed methods and an established recommended method [1] shows excellent agreement between the results in addition to the sensitivity and ease of automation provided by AES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01242475
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  • 6
    Electronic Resource
    Electronic Resource
    The interpretation of Olsen extractable P values in relation to recommendations for the fertilizer requirements of crops (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 223-227 
    Details
    ISSN: 1573-0867
    Keywords: Soil testing ; phosphorus ; relative yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A greenhouse experiment, with Okra (Abelmoschus esculentus L.) as the test crop, was conducted on twenty-one soils ranging in Olsen's extractable phosphorus from 1.8 to 15.5µg Pg−1 soil. The experiment was conducted at Punjab Agricultural University, Ludhiana, India. The soils were nonsaline with pH ranging from 7.7 to 8.6. A critical level of 2.55µg Pg−1 soil was predicted by Cate and Nelson's (1971) statistical procedure. Because of a wide range in relative yields, this value did not accurately predict response to applied P. An approach to compute minimum response to applied fertilizer, which is likely to be obtained at a particular Olsen P level, has been presented. It involves calculation of lower 60 percent confidence limits for relative yield and fitting loge-linear regression to the transformed data. The regression was tested on a published data set and was found to hold well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048784
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  • 7
    Electronic Resource
    Electronic Resource
    Two post thinning fertilizer trials inPinus radiata in New South Wales, Australia (1992)
    Springer
    Nutrient cycling in agroecosystems 32 (1992), S. 259-267 
    Details
    ISSN: 1573-0867
    Keywords: Nitrogen ; phosphorus ; timber increment ; fertilization ; Pinus radiata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two trials inPinus radiata growing on different sites in N.S.W. allowed consideration of fertilizer applications after 2nd or 3rd thinning. The trials included factorial applications of N and P at a single thinning intensity plus a further treatment which allowed assessment of different thinning intensities. The most significant growth responses were obtained by application of N and P in combination. The largest response (additional productivity compared with the unfertilized control) occurred 4 years after application and after 7 years there was no additional absolute response for either of the two sites. The largest fertilizer response was 70 m3 ha−1 over 7 years on one site and 36 m3 ha−1 on the other, indicating differences in absolute responses between sites. It was concluded that in planning treatments the most responsive sites near the end of the rotation should be selected to maximise economic returns. Foliage analyses indicated differences between sites at the commencement of the study. It was concluded that either a single year of foliage analyses at study commencement is of value, or sampling every year of the study should be used to analyse responses, but a single year of analysis during or at the end of the study would not be of value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01050363
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  • 8
    Electronic Resource
    Electronic Resource
    Insecticidal effects of essential oils. A study of the effects of essential oils extracted from eleven Greek aromatic plants onDrosophila auraria (1992)
    Springer
    Cellular and molecular life sciences 48 (1992), S. 616-619 
    Details
    ISSN: 1420-9071
    Keywords: Aromatic plants ; essential oils ; Drosophila ; insecticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Effects of the essential oils (EOs) extracted from eleven aromatic plants belonging to the Lamiaceae family (common in the Greek flora) were examined upon three different developmental stages ofDrosophila auraria. All of the EOs examined exhibited insecticidal effects, either by preventing egg hatching, or by causing the death of larvae and adult flies. In several cases, malformation and/or prohibition of puparium formation was also observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01920251
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  • 9
    Electronic Resource
    Electronic Resource
    Nutrient-chlorophyll trajectories across trophic gradients (1992)
    Springer
    Aquatic sciences 54 (1992), S. 58-76 
    Details
    ISSN: 1420-9055
    Keywords: Eutrophication ; lake management ; phosphorus ; nitrogen ; chlorophyll-a ; slope estimator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We estimate the response of chl-a (mg · m−3) to changes in concentrations of total phosphorus (TP) by calculating the slopeS = Δchl-a/ΔTP in chl-a =f(TP) graphs. Results show that in years where algae are P-limited oligotrophic lakes respond less (median slope 0.21) to changes in nutrient concentrations than eutrophic lakes, (median slope 0.31) and these again less than hypereutrophic lakes, (median slope 1.02). We find no saturation value for the slope within the TP range considered (6–480 mg · m−3). Chl-a in eutrophic lakes responds more frequently to non-nutrient factors than oligotrophic and hypereutrophic lakes. Results obtained by replacing TP with a new nutrient parameter, TP′ = 0.056 · TP · IN0.226, in which inorganic nitrogen, IN, is factored in, suggest that nitrogen has an influence on chl-a in oligotrophic lakes. Blue-green algae respond less to changes in TP than other algal species, e.g., diatoms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877264
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  • 10
    Electronic Resource
    Electronic Resource
    Possibilities and limitations of lake restoration: Conclusions for Lake Lugano (1992)
    Springer
    Aquatic sciences 54 (1992), S. 381-390 
    Details
    ISSN: 1420-9055
    Keywords: Eutrophication ; phosphorus ; lake restoration ; internal restoration measures for lakes ; Swiss lakes ; Lake Lugano (Lago di Lugano)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In most lakes eutrophication is linked to an excessive input of phosphorus. Lake restoration by reduction of P-input (external measure) has led to a considerable drop of the P-concentration in all major Swiss lakes as well as in many other lakes. Internal restoration measures such as artificial mixing, drainage of hypolimnetic water, flushing, aeration, biomanipulation and others serve to improve and accelerate the response of a lake to external measures. For the case of Lago di Lugano, a simple two-box model is employed to demonstrate that a reduction of the P-input to about 25% of the present values is necessary to reach the “P-criterion” (P-concentration below 30 µg/l). Internal measures could possibly accelerate the extremely slow response of the northern basin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00878149
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  • 11
    Electronic Resource
    Electronic Resource
    Mutations in a steroid hormone-regulated gene disrupt the metamorphosis of internal tissues in Drosophila: salivary glands, muscle, and gut (1992)
    Springer
    Development genes and evolution 201 (1992), S. 221-234 
    Details
    ISSN: 1432-041X
    Keywords: Muscle ; Salivary glands ; Gut ; Programmed cell death ; Steroid hormones ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In holometabolous insects, the steroid molting hormone 20-OH-ecdysone (ecdysterone) orchestrates the diverse developmental events of metamorphosis, in large part by regulating gene expression. In Drosophila, the Broad Complex (BR-C) is one of the first loci to be induced by ecdysterone at the end of larval life, and is essential for translating the hormonal signal into the behavioral and anatomical events which herald the onset of metamorphosis. BR-C products are believed to act by binding to and modifying the transcriptional activities of other hormone-sensitive genes. In addition to abnormalities of the epidermis, BR-C mutants dying during metamorphosis manifest a syndrome of multiple internal tissue defects which represent a failure of the larval-to-adult transition. We have reported features of central nervous system metamorphosis requiring BR-C function, notably morphogenetic movements and optic lobe organization. In this paper we describe defective development of salivary glands, flight muscles, and gut in BR-C mutants, including: persistence of larval salivary glands; failure of the adult salivary glands to extend into the thorax; abnormalities of midgut transition and of proventriculus structure and location; and absence of dorsal-ventral indirect flight muscles. Some of these abnormalities represent defects in programmed cell death. Distinct patterns of phenotypes were seen in mutants of each of the three lethal complementation groups comprising the BR-C. The patterns of phenotypes suggest overlapping but distinct functions encoded by this complex locus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188753
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  • 12
    Electronic Resource
    Electronic Resource
    The spatial expression ofDrosophila rotund gene reveals that the imaginal discs are organized in domains along the proximal-distal axis (1992)
    Springer
    Development genes and evolution 201 (1992), S. 284-295 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Imaginal discs ; Pattern formation ; rotund
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary InDrosophila imaginal discs, pattern formation requires the activity of three positional information systems, antero-posterior (A/P), dorso-ventral (D/V) and proximo-distal (P/D). Three genes,Decapentaplegic, Distal-less androtund (rn), involved in pattern formation along the P/D axis have been characterized. Thern gene is required in a sub-distal region, localized at a similar position along the P/D axis in all appendages; it encodes two major transcripts, m1.7 and m5.3, both expressed in the central region of all the major imaginal discs. The present study of these transcripts in severalrn mutant favours m5.3 as encodingrn morphogenetic function in the imaginal discs. The fine characterization of its distribution partitions all major imaginal discs in domains along the P/D axis. The ventral and dorsal discs appear to be similarly but not identically organized: two P/D domains are evident in the wing and haltere discs whilst the leg and antenna discs appear to be composed of at least three. We also show that m5.3 is sex-regulated in the genital disc and thatrn function is required for proper development of a sub-distal structure of the female genitalia. This suggests that the primordia of the female genitalia may be organized in a similar way to the other imaginal discs, and strongly supports the hypothesis thatrn function is specific to pattern formation along the P/D axis and that it may be involved in the establishment or maintenance of this pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592109
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  • 13
    Electronic Resource
    Electronic Resource
    Whole-embryo culture of Drosophila : development of embryonic tissues in vitro (1992)
    Springer
    Development genes and evolution 201 (1992), S. 364-375 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Tissue culture ; In vitro ; Invertebrate embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have devised techniques to culture whole, dissected embryos of Drosophila melanogaster. We examine multiple aspects of the morphological and physiological development of the epidermis, musculature, nervous system, and internal organs in this cultured preparation, and show that in vitro development closely parallels normal embryogenesis. These techniques permit a wide range of experimental manipulations during embryogenesis and allow us to extend observations through late embryonic stages, after cuticle deposition. Applications of this technique are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365124
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  • 14
    Electronic Resource
    Electronic Resource
    Gradual acquisition of the developmental capacity to differentiate adult structures by the genital disc of Drosophila melanogaster (1992)
    Springer
    Development genes and evolution 201 (1992), S. 105-112 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Genital disc ; tra-2 ts ; Differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Diplo-X flies homozygous for the transform-er-2 ts (tra-2 ts) mutation develop into females at 16° C, while they develop into males at 29° C (Belote and Baker 1982). By means of this conditional mutation, we have carried out a detailed analysis of the development of the genital disc. Temperature shifts between 16 and 29° C, in both directions, and temperature pulses at 29° C, have been applied during the larval growth of tra-2 ts homozygous diplo-X flies, and the external derivatives of the genital disc have been analysed. Genital discs shifted from 16 to 29° C rapidly lose their capacity to differentiate female genital structures, while they become able to differentiate male genital structures whose inventory is more complete the earlier in larval development the temperature shift is carried out; moreover, duplicated male genital structures were observed. In the shift from 29 to 16° C, the genital disc loses its capacity to differentiate male genital structures, while it becomes able to differentiate female genital structures. The inventory of male structures is smaller, and the inventory of the female structures is more complete, the earlier in larval development the temperature is shifted. No duplicated female or male genital structures were observed in the downshift experiment. With respect to the analia, the shift from 16 to 29° C resulted in the quick formation of pure male anal plates, while in the opposite shift the formation of pure female anal plates occurred gradually. Moreover, the time course for the dorsal and ventral anal plates to show normal female phenotype was different: when the dorsal anal plates were completely normal, it was still possible to find incomplete ventral anal plates. In the pulse experiment at 29° C, the genital disc is able to differentiate both female and male genital structures, although the inventory of the latter ones was not complete. In addition, the capacity of the genital disc to differentiate male genital structures depended on the duration of the temperature pulse. The anal plates were always female, although they showed a reduction in their size, the ventral female anal plate being more affected than the dorsal one. No male anal plates were observed. The results have revealed that the genital disc follows a sequence in its capacity to differentiate female or male adult structures. We suggest that this sequence reflects the sequence of determination events occurring in the genital disc during its larval growth. In addition, results shown here provide evidence for the existence in the female genital primordium of a set of cells capable of giving rise either to female genital structures (ventral vaginal plates) or to male genital structures (hypandrium and penis apparatus). We also present evidence supporting the previous idea of two primordia for the anal plates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420421
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  • 15
    Electronic Resource
    Electronic Resource
    Spatial and temporal expression of an Antennapedia/lac Z gene construct integrated into the endogenous Antennapedia gene of Drosophila melanogaster (1992)
    Springer
    Development genes and evolution 201 (1992), S. 65-80 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Homeotic gene regulation ; Antennapedia ; Development ; β-galactosidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to study the regulation of spatial and temporal expression of the homeotic gene Antennapedia (Antp) in Drosophila melanogaster, we have constructed fusion genes which contain Antp sequences linked to the reporter gene lac Z of Escherichia coli. In one case of P-element transformation, a fusion gene construct integrated into the endogenous Antp gene close to one of the two promoters (P1). The spatial expression from the reporter gene in this transformant line, as analysed by the detection of β-galactosidase activity, was found to exactly mimic the normal expression from the P1 promoter of the Antp gene. We have used this unique transformant as a tool for studying the expression of the P1 promoter in embryonic, larval and adult development. Parallel lines transformed with the same fusion gene construct did not confer a correct P1 pattern of expression. The position in the genome was, therefore, crucial for the expression pattern of the reporter gene. Experiments aiming at the detection of autoregulatory control of Antp gene expression were designed. The results did not, however, support models of positive or negative autoregulation of P1 expression by Amp protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420417
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  • 16
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    The expression of PS integrins in Drosophila melanogaster imaginal disc cell lines (1992)
    Springer
    Development genes and evolution 201 (1992), S. 120-123 
    Details
    ISSN: 1432-041X
    Keywords: Integrin ; Drosophila ; In vitro ; Imaginal disc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Drosophila imaginal disc cell lines show a characteristic pattern of aggregation in culture, which appears to be due to cell-cell rather than cell-substrate interactions. We have examined the distribution of PS integrins in wing and leg cell lines, and find that these integrin homologues are expressed preferentially in aggregates. Cell sheets, small cell clumps and chains of cells express antigen at points of cell-cell contact only.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420423
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  • 17
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    Expression of gooseberry-proximal in the Drosophila developing nervous system responds to cues provided by segment polarity genes (1992)
    Springer
    Development genes and evolution 201 (1992), S. 157-168 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Pattern formation ; Segment polarity genes ; gooseberry ; Cell interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Segment polarity genes define the cell states that are required for proper organization of each metameric unit of the Drosophila embryo. Among these, the gooseberry locus has been shown to be composed of two closely related genes which are expressed in an overlapping single-segment periodicity. We have used specific antibodies raised against the protein product of the gooseberry proximal (gsb-p) gene to determine the spatial distribution of this antigen in wild type embryos, and to monitor the effects of segment polarity mutants on the pattern of the gsb-p protein distribution. We find that the gsb-p protein accumulates beneath each posterior axonal commissure in the progeny of neuroblasts deriving from the epidermal compartments of wingless (wg) and engrailed (en) expression. The results of this analysis support the idea that gsb-p has a specific role in the control of cell fates during neurogenesis, and indicate that en and wg provide critical positional cues to define the domain in which gsbp will be activated. Furthermore, these data suggest that, in order to be expressed in the embryonic CNS, gsb-p may preliminarily require activity of the gooseberry-distal gene in the epidermis.
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    URL: http://dx.doi.org/10.1007/BF00188714
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  • 18
    Electronic Resource
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    Cell lineage of flight muscle fibers in Drosophila: a fate map of the induced shibire phenotype in mosaics (1992)
    Springer
    Development genes and evolution 201 (1992), S. 88-94 
    Details
    ISSN: 1432-041X
    Keywords: Fate map ; Drosophila ; Flight muscle ; Mosaics ; Cell lineage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A blastoderm fate map has been prepared for Drosophila, using mosaics of a temperature-sensitive mutation, shibire (shi). The mutation can cause abnormal flight muscle morphology, inducible only by a short heat pulse in early metamorphosis. Thus muscle lineage and development are unperturbed until the heat pulse in the early pupa. The developmental focus of the shi muscle phenotype maps to the ventral thorax at the expected site of thoracic mesoderm, and probably indicates the blastoderm progenitors of the adult flight muscle. The fate map provides greater detail than previously available for the dorsolongitudinal fibers (DLM) of flight muscle, showing wide separation of the fibers of flight muscle. DLM fibers a and b map close together, and far anterior to fibers e and f, which also map together. On a fate map, common developmental focus indicates a common blastoderm origin. Thus, the observed pattern for DLM fibers suggests that the blastoderm progenitors for each of these syncytial fiber pairs (a, b; e, f) include only one or two cells. It follows that there is usually a single genotype within each fiber pair (a, b; e, f), and that this genotype is directly reflected in the fiber phenotype. In a large number of cases, DLM fibers a and b differ in phenotype from other DLM fibers, in parallel with their other differences (e.g., timing of development in pupa, innervation, motor activity). The separation of fate map locations of the developmental focus for DLM fibers within mesoderm suggests that specific fibers of flight muscle may, in normal development, originate in all three thoracic mesodermal parasegments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420419
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  • 19
    Electronic Resource
    Electronic Resource
    The response of Drosophila imaginal disc cell lines to ecdysteroids (1992)
    Springer
    Development genes and evolution 202 (1992), S. 23-35 
    Details
    ISSN: 1432-041X
    Keywords: Ecdysteroid ; Imaginal disc ; Drosophila ; Cell line
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have investigated the action of the moulting hormone 20-hydroxy ecdysone (20-HOE) on our leg and wing imaginal disc cell lines. At the morphological level, cells stop dividing and there is some cell death. The remaining cells elongate and aggregate, often producing long processes which form connections between different aggregates. 20-HOE acts within the first one or two days of a passage, at an optimum concentration of 10 ng/ml, this being about 1/100 of the optimum for ecdysone. One cloned wing cell line, C9, has been found to be relatively insensitive to the action of 20-HOE. We have been able to select for resistance to 20-HOE by growing cells in gradually increasing concentrations of hormone followed by passages in hormone-free medium. This has enabled us to isolate a wing cell line C1.8R from its parent cloned line C1.8+. This shows no response to 20-HOE, and cell growth continues even at hormone concentrations as high as 150 ng/ml. We have measured chitin synthesis by the incorporation of radioactive glucosamine into a cell fraction resistant to extensive alkali hydrolysis. The residue was incubated with chitinase, which resulted in a 50% reduction in labelled product. Treatment with 10 ng/ml of 20-HOE dramatically increased chitin synthesis in line C1.8+, but had no effect in the line C1.8R, selected for resistance to hormone.
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    URL: http://dx.doi.org/10.1007/BF00364594
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  • 20
    Electronic Resource
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    Second-site modifiers of the Delta wing phenotype in Drosophila melanogaster (1992)
    Springer
    Development genes and evolution 202 (1992), S. 49-60 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Delta ; Enhancers ; Suppressors ; Neurogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have screened for dominant enhancers and suppressors of the wing phenotype associated with two Delta alleles: Dl 9P39, an amorphic allele, and Dl FE32, an antimorphic allele. The interactions of some of the modifiers with Delta are due to haplo-insufficient expression of the corresponding genes. Although not explicitly shown for the remaining cases, we assume that haploin-sufficiency is also the basis for the relationships of these genes to Delta, since no allele specific interactions were observed. The modifiers found define 22 genes with pleiotropic expression, which can be classified into two groups: genes required for wing vein pattern formation and for neurogenesis, and genes which are not required for neurogenesis. Among the genes of the first group, Hairless and Star were previously known to participate in neural development. One further modifier was found which may correspond to a new neurogenic gene. The second group of genes is larger and includes already known loci, e.g., Plexate, blistered, plexus, etc, as well as other previously unidentified genes, which function during wing morphogenesis.
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    URL: http://dx.doi.org/10.1007/BF00364596
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    Regulatory signals and signal molecules in early neurogenesis of Drosophila melanogaster (1992)
    Springer
    Development genes and evolution 201 (1992), S. 1-11 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Neurogenesis ; Signals ; Delta ; Notch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ectodermal germ layer of Drosophila melanogaster gives rise to two major cell lineages, the neural and the epidermal. Progenitor cells for each of these lineages arise from groups of cells, whose elements must decide between taking on either fate. Commitment of the progenitor cells to one of the developmental fates implies two factors. One is intrinsic to the ectodermal cells and determines a propensity to take on neural fate; this factor is probably represented by the products of the so-called proneural genes, which are differentially distributed throughout the ectoderm. The other factor in the cells' decision to adopt one of the two alternative fates is intercellular communication, which is mediated by the products of the so-called neurogenic genes. Two types of interactions, one inhibiting and the other stimulating neural development, have been inferred. We discuss here the assumed role of various neurogenic genes, in particular Notch and Delta, in these processes.
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    URL: http://dx.doi.org/10.1007/BF00188770
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    Studying Drosophila embryogenesis with P-lacZ enhancer trap lines (1992)
    Springer
    Development genes and evolution 201 (1992), S. 194-220 
    Details
    ISSN: 1432-041X
    Keywords: Drosophila ; Enhancer trap lines ; Embryogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Embryos of 171 Drosophila lines carrying a P-lacZ insertion on the second or third chromosome were analyzed regarding their pattern of lacZ expression. All lines were selected from a larger screen of about 4000 lines (Bier et al. 1989). Tissue specificity and time of onset of lacZ expression was documented for each line. Thereby, a comprehensive list of markers for the various tissue and cell types of the Drosophila embryo could be assembled. With the help of several P-lacZ lines the development of a number of structures was studied which so far had been described only insufficiently or not at all. In particular, the embryonic origin and early development of the oenocytes, imaginal discs, histoblasts, fat body, dorsal vessel, and perineurial cells was analyzed. Several previously unknown cell types associated with the dorsal vessel, trachea, and epidermis were discovered. By combining data regarding the origin of the different mesodermally derived organs it was possible to generate in some detail a fate map of the mesoderm of the stage 11 Drosophila embryo.
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    URL: http://dx.doi.org/10.1007/BF00188752
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    Heat shock response inDrosophila (1992)
    Springer
    Cellular and molecular life sciences 48 (1992), S. 623-629 
    Details
    ISSN: 1420-9071
    Keywords: Drosophila ; heat shock ; stress ; heat shock protein ; gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Major alterations in genetic activity have been observed in every organism after exposure to abnormally high temperatures. This phenomenon, called the heat shock response, was discovered in the fruit flyDrosophila. Studies with this organism led to the discovery of the heat shock proteins, whose genes were among the first eukaryotic genes to be cloned. Several of the most important aspects of the regulation of the heat shock response and of the functions of the heat shock proteins have been unraveled inDrosophila.
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    URL: http://dx.doi.org/10.1007/BF02118306
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    Attractiveness and exploitation of decaying herbage by Drosophila in temperate woodland (1992)
    Springer
    Oecologia 92 (1992), S. 183-187 
    Details
    ISSN: 1432-1939
    Keywords: Drosophila ; Resource exploitation ; Decaying-herbage breeding ; Host choice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Drosophila fauna of a deciduous flood plain forest rich in undergrowth near the river Isar, close to Munich, Germany, was surveyed in summer 1990. Decaying herbage baits (decay artificially induced) were set out to study the exploitation of that resource by Drosophila. Sixteen plant species belonging to several families dominant in the collecting area were tested. All attracted and produced drosophilid flies. Ten Drosophila species utilized decaying plant material as breeding sites; at least eight of the ten are polyphagous. Decaying stalks and leaves of Angelica sylvestris (Apiaceae) were examined in detail. In the case of the most frequent species of Drosophila attracted to A. sylvestris, the number of adults collected did not correlate with the number of flies emerging from the substrate. This was particularly true of D. limbata and D. phalerata. When oviposition and larval development of D. limbata and D. phalerata on A. sylvestris was tested in the laboratory, the number of offspring per female was the same in both species. The difference between these two species of the quinaria group in the exploitation of A. sylvestris in the field is therefore not due to differential suitability of the substrate.
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    URL: http://dx.doi.org/10.1007/BF00317362
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    Male sexual signaling is defective in mutants of theapterous gene ofDrosophila melanogaster (1992)
    Springer
    Behavior genetics 22 (1992), S. 469-487 
    Details
    ISSN: 1573-3297
    Keywords: courtship ; pheromones ; Drosophila ; apterous ; juvenile hormone ; reproductive development ; sexual behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract Theapterous (ap) gene ofDrosophila melanogaster exhibits extreme pleiotrophy: its functioning is essential for life, normal wing structure, juvenile hormone production, female fertility, and normal development of female sexual receptivity. Four mutantap alleles (ap 4,ap 56f,ap c, andap blt) were characterized for three additional phenotypes: male mating success, courtship behavior, and immature male sex appeal (the ability of males to stimulate homosexual cortship). Mating success with mature wild-type virgin females is reduced in males mutant for theap gene, the extreme case beingap 4/ap 4 males, which are behaviorally sterile. Inap mutants, nonwing courtship elements are qualitatively like those ofap +/ap + males. However, the mean rate of nonwing courtship directed toward virgin wild-type females (i.e., the mean temporal frequency of these displays) is reduced in males homozygous forap 4,ap 56f, orap c alleles. In contrast, theap blt allele makes for wild-type rates of nonwing courtship. Immature male sex appeal persists for at least 3 days in males homozygous forap c and, to a lesser extent, inap 56f orap 4 homozygotes;ap blt/ap blt and wild-type males lose immature male sex appeal after 1 day. All three male phenotypes map to theap locus, which is therefore essential for the development of normal levels of male courtship and male mating success and for the timely loss of immature male sex appeal. For each phenotype,ap + is dominant toap alleles making for behavioral abnormalities, with a single exception (for rate of nonwing courtship,ap +/ap c was low). For mating success and frequency of nonwing courtship, each allele pair exhibits at least partial complementation, except forap 4 andap 56f, which fail to complement. For immature male sex appeal,ap c,ap 4, andap 56f fall into the same complementation group. Juvenile hormone production is not correlated with effects on male reproductive behavior.
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    URL: http://dx.doi.org/10.1007/BF01066616
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    The homeotic genespineless-aristapedia affects geotaxis inDrosophila melanogaster (1992)
    Springer
    Behavior genetics 22 (1992), S. 557-573 
    Details
    ISSN: 1573-3297
    Keywords: Drosophila ; biometrical analysis ; behavior genetics ; genetic analysis ; ss a ; deletion mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Psychology
    Notes: Abstract The homeotic mutationspineless-aristapedia (ss a ) transforms the aristae into second tarsi. Flies with aSS a phenotype also show extremely positive geotaxis as measured in a Hirsch-type geotaxis maze. Other antennal mutants and flies with their aristae amputated do not show such extreme positive geotaxis. Deletion analysis has comapped the geotaxis effect withSS a in band 89C on the third chromosome. Finally, a biometrical analysis has detected additional genes on the X chromosome that also affects geotaxis.
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    URL: http://dx.doi.org/10.1007/BF01074308
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    Polymorphism in aDrosophila indirect flight muscle-specific tropomyosin isozyme does not affect flight ability (1992)
    Springer
    Biochemical genetics 30 (1992), S. 159-168 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; indirect flight muscle ; tropomyosin ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We describe polymorphism in aDrosophila indirect flight muscle-specific tropomyosin isozyme, named TnH-34. Three variants of this protein differ in their mobilities as determined by 1-D and 2-D SDS-PAGE. Meiotic mapping places the polymorphism close to, if not within, the structural gene encoding this tropomyosin isozyme. The most likely site of the mutations is within a single C-terminal exon. Flight-testing of different genotypes reveals that this variation in TnH-34 does not affect flight ability. These results suggest that some sequence variation may be tolerated in this section of the protein and correlate with the variability of this protein in different insect species.
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    URL: http://dx.doi.org/10.1007/BF02399706
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    Purification and characterization of diaphorases from someDrosophila species (1992)
    Springer
    Biochemical genetics 30 (1992), S. 305-315 
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    ISSN: 1573-4927
    Keywords: Drosophila ; diaphorase ; purification ; kinetics ; immunochemical characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Diaphorase-1 and diaphorase-2 were isolated from twoDrosophila species,D. virilis andD. melanogaster, and purified by gel filtration, affinity chromatography, immunoaffinity chromatography, and ion-exchange chromatography. The molecular weights of both enzymes were the same in each species. The molecular weight of diaphorase-1 was the same under both denaturating and nondenaturating conditions, close to 60,000, indicating a monomeric structure. Sodium dodecyl sulfate (SDS) electrophoresis of the purified diaphorase-2 revealed the presence of a single protein band of 55,000 Da, while the molecular weight of the native enzyme was found to be 67,000. The two diaphorases were further characterized by their pH optima, isoelectric points, and kinetic parameters, and antibodies were raised in rabbits against the purified enzymes fromD. virilis. The antibodies showed no cross-reactions but recognized the corresponding diaphorases inD. melanogaster andD. novamexicana as well asD. virilis. The data obtained confirmed the hypothesis of an independent genetic control of diaphorase-1 and diaphorase-2 inDrosophila.
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    Purification and characterization of diaphorases from someDrosophila species (1992)
    Springer
    Biochemical genetics 30 (1992), S. 305-315 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; diaphorase ; purification ; kinetics ; immunochemical characteristics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Diaphorase-1 and diaphorase-2 were isolated from twoDrosophila species,D. virilis andD. melanogaster, and purified by gel filtration, affinity chromatography, immunoaffinity chromatography, and ion-exchange chromatography. The molecular weights of both enzymes were the same in each species. The molecular weight of diaphorase-1 was the same under both denaturating and nondenaturating conditions, close to 60,000, indicating a monomeric structure. Sodium dodecyl sulfate (SDS) electrophoresis of the purified diaphorase-2 revealed the presence of a single protein band of 55,000 Da, while the molecular weight of the native enzyme was found to be 67,000. The two diaphorases were further characterized by their pH optima, isoelectric points, and kinetic parameters, and antibodies were raised in rabbits against the purified enzymes fromD. virilis. The antibodies showed no cross-reactions but recognized the corresponding diaphorases inD. melanogaster andD. novamexicana as well asD. virilis. The data obtained confirmed the hypothesis of an independent genetic control of diaphorase-1 and diaphorase-2 inDrosophila.
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    Drosophila acetylcholinesterase: Characterization of different mutants resistant to insecticides (1992)
    Springer
    Biochemical genetics 30 (1992), S. 77-83 
    Details
    ISSN: 1573-4927
    Keywords: acetylcholinesterase ; insecticide ; resistance ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Selection of field populations originating from several countries allowed us to isolate 13 strains ofDrosophila melanogaster resistant to parathion.In vitro studies of acetylcholinesterase inhibition by paraoxon have been carried out on purified enzymes: most of the resistant strains harbor an altered acetylcholinesterase. Enzymes with higher resistance levels have been characterized with respect to their cross-resistance toward several insecticides. The patterns obtained have permitted us to group them and to delineate four categories. The existence of four distinct types of protein suggests that several mutations of acetylcholinesterase are responsible for insecticide resistance inDrosophila.
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    Restriction site variation, gene duplication, and the activity ofsn-glycerol-3-phosphate dehydrogenase inDrosophila melanogaster (1992)
    Springer
    Biochemical genetics 30 (1992), S. 169-188 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; glycerol-3-phosphate dehydrogenase ; restriction map ; duplication ; enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Restriction site variation in a 25-kb region including thesn-glycerol-3-phosphate dehydrogenase (Gpdh) locus has been assessed in 29 single femaleD. melanogaster lines from the Cardwell (Australia, QLD) population. TheGpdh locus was duplicated in about one-third of the lines, although the duplication was incomplete and lacked exons 1 and 2. There was no restriction site variation in the duplicated region. Three insertions were found in the gene region but only one affected GPDH activity. The lines with the duplication had higher levels of GPDH activity and protein amount than did nonduplicated lines. This effect was also observed in lines extracted from two other Australian populations. The duplication is shown to have a similar structure in each population investigated and is also present in populations from China and Africa. It is suggested that the effect of the duplication on GPDH activity, which might be due to structural factors affecting transcription at theGpdh locus, could account for the worldwide distribution of the duplication.
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    URL: http://dx.doi.org/10.1007/BF02399707
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    Isolation of aDrosophila gene encoding glutathioneS-transferase (1992)
    Springer
    Biochemical genetics 30 (1992), S. 515-527 
    Details
    ISSN: 1573-4927
    Keywords: glutathioneS-transferase ; Drosophila ; cellular detoxification ; pesticide resistance ; insect metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We have isolated aDrosophila gene,DmGST-2, that encodes glutathioneS-transferase, a homo- or heterodimeric enzyme thought to be involved in detoxification of xenobiotics, including known carcinogens. The encoded protein has a primary sequence that is more similar to mammalian placental and nematode GSTs than that of a previously describedDrosophila GST gene, herein referred to asDmGST-1. We provide a physical map of the gene and show that it specifies at least two mRNAs, measuring 1.9 and 1.6 kb, which differ only in the lengths of their 3′ untranslated regions. Both of the mRNAs are present during all developmental stages.In situ hybridization of theDmGST-2 gene to larval polytene chromosomes places it within the 53F subdivision of chromosome 2, and Southern blotting to chromosomal DNA indicates that the gene has no close relatives within theDrosophila genome. Our results make possible molecular genetic approaches for further elaborating the function of glutathioneS-transferases in insect development and physiology, in the metabolism of plant toxins, and in conferring insecticide resistance.
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    Constructing balancer chromosomes for genetic screens in Drosophila hydei (1992)
    Springer
    Theoretical and applied genetics 83 (1992), S. 821-826 
    Details
    ISSN: 1432-2242
    Keywords: Drosophila ; Balancers ; Inversions ; Translocations ; Meiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We used a screen for maternally generated late embryonic lethals as a new method for the isolation of inversions that are suitable for the balancing of mutations in Drosophila hydei. The recovery of several inversions by this method demonstrates that female meiosis in D. hydei apparently differs from meiosis in female D. melanogaster, since in D. hydei the defective chromosomes which are generated by a single crossing-over within a paracentric inversion can be recovered via the egg nucleus. In addition, the classic method of crossingover suppression was used in order to isolate more inversions and to improve the balancing capacities of inversions. We succeeded in constructing chromosomes that allow the balancing of mutations on nearly the whole genome of D. hydei. We discuss here whether or not this method is suited for application to other organisms.
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    An EPR and molecular mechanics study of radical adducts of phosphonyl radicals with 2-hydroperfluoro-4-methyl-and 4,4-dimethyl-2-pentene (1992)
    Springer
    Russian chemical bulletin 41 (1992), S. 2008-2011 
    Details
    ISSN: 1573-9171
    Keywords: EPR ; radical ; fluorine ; conformation ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract EPR spectra of radical adducts of phosphonyl radicals with 2-hydroperfluoro-4-methyl- and 4,4-dimethyl-2-pentene have been studied. The molecular mechanics method has been used to determine the preferred conformation of the (CF3)2CF-CF-HCF3P(O)(OMe)2 radical. The eclipsed conformation of the C–P bond and 2p z -orbital of an unpaired electron is stabilized due to steric factor and hyperconjugation.
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    Selection, patches and genetic variation: A cellular automaton modellingDrosophila populations (1992)
    Springer
    Evolutionary ecology 6 (1992), S. 342-351 
    Details
    ISSN: 1573-8477
    Keywords: Drosophila ; polymorphism ; aggregation ; ephemeral patches ; soft selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Many models have been proposed in which environmental heterogeneity promotes genetic diversity. Such models describe the situation where different phenotypes have different fitness values in different types of patch and are the genetic equivalent of the traditional resource partitioning models in ecology which allow the coexistence of species. Here we construct a different type of cellular model in which polymorphisms in populations ofDrosophila can be maintained without traditional resource partitioning. Parameter values taken from laboratory and field observations represent fungal breedingDrosophila. Some stochasticity is used in the description of the migration between patches. In the model space is divided into a uniform matrix of cells each of which has the potential to contain an ephemeral resource item (fungal fruiting body). Square arenas of up to 400 cells were used. Genotypes arrive at a fresh site, breed (Hardy-Weinberg equilibrium) and lay eggs. The eggs hatch and the larvae compete using the Hassell-Comins competition equations, as if they were three different species. Adult emergents all migrate to an adjacent cell. The aggregation patterns observed in nature are produced using an ‘attraction probability’ where each fly has a chance of moving to the currently most densely populated adjacent patch. This ‘black box’ description of migration produces distribution patterns which are indistinguishable from those seen in wild populations of fungal breedingDrosophila. Results show that the ‘attraction probability’ is the key factor in the maintenance of polymorphism and that even when the competitive advantage of the superior genotype is very great, polymorphisms can be maintained.
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    Polymorphism in aDrosophila indirect flight muscle-specific tropomyosin isozyme does not affect flight ability (1992)
    Springer
    Biochemical genetics 30 (1992), S. 159-168 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; indirect flight muscle ; tropomyosin ; polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We describe polymorphism in aDrosophila indirect flight muscle-specific tropomyosin isozyme, named TnH-34. Three variants of this protein differ in their mobilities as determined by 1-D and 2-D SDS-PAGE. Meiotic mapping places the polymorphism close to, if not within, the structural gene encoding this tropomyosin isozyme. The most likely site of the mutations is within a single C-terminal exon. Flight-testing of different genotypes reveals that this variation in TnH-34 does not affect flight ability. These results suggest that some sequence variation may be tolerated in this section of the protein and correlate with the variability of this protein in different insect species.
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    Restriction site variation, gene duplication, and the activity ofsn-glycerol-3-phosphate dehydrogenase inDrosophila melanogaster (1992)
    Springer
    Biochemical genetics 30 (1992), S. 169-188 
    Details
    ISSN: 1573-4927
    Keywords: Drosophila ; glycerol-3-phosphate dehydrogenase ; restriction map ; duplication ; enzyme activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Restriction site variation in a 25-kb region including thesn-glycerol-3-phosphate dehydrogenase (Gpdh) locus has been assessed in 29 single femaleD. melanogaster lines from the Cardwell (Australia, QLD) population. TheGpdh locus was duplicated in about one-third of the lines, although the duplication was incomplete and lacked exons 1 and 2. There was no restriction site variation in the duplicated region. Three insertions were found in the gene region but only one affected GPDH activity. The lines with the duplication had higher levels of GPDH activity and protein amount than did nonduplicated lines. This effect was also observed in lines extracted from two other Australian populations. The duplication is shown to have a similar structure in each population investigated and is also present in populations from China and Africa. It is suggested that the effect of the duplication on GPDH activity, which might be due to structural factors affecting transcription at theGpdh locus, could account for the worldwide distribution of the duplication.
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    Drosophila melanogaster paramyosin : developmental pattern, mapping and properties deduced from its complete coding sequence (1992)
    Springer
    Molecular genetics and genomics 231 (1992), S. 385-394 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila ; Muscle proteins ; Paramyosin ; Leucine zippers ; Differential polyadenylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several cDNA clones encoding the complete Drosophila paramyosin sequence, including two potential polyadenylation sites, have been obtained. Southern analysis and in situ hybridization to polytene chromosomes indicate that in Drosophila the paramyosin gene is single copy, located on the left arm of the third chromosome at region 66D14. Northern analyses show predominantly two different RNAs which are the products of the choice between the two alternative polyadenylation sites. The two species begin to be synthesized around 10 h of development when embryonic muscles are formed, expression peaking at the end of embryogenesis. The protein is first expressed at germ band shortening in association with muscle precursor cells. A second maximum of paramyosin RNA expression occurs at late pupal stages when the higher molecular weight form becomes more abundant. In young adults this species becomes the main transcript detected. The 102 kDa polypeptide sequence is highly similar to that of Caenorhabditis elegans paramyosin. The protein has a central α-helical coiled-coil rod, organized in 29 groups of four typical seven-residue repeats and flanked by two short non-α-helical regions. Several leucine zippers are located on the hydrophobic face of the α-helix in paramyosin which, together with disulfide bonds between cysteines, are probably involved in the stabilization of the dimer. The structural and functional properties of Drosophila paramyosin deduced from the sequence are compared with those of known invertebrate myosins and paramyosins.
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    Two non-gypsy rudimentary mutations and their suppression by mutations of suppressor of Hairy-wing in Drosophila (1992)
    Springer
    Molecular genetics and genomics 235 (1992), S. 441-449 
    Details
    ISSN: 1617-4623
    Keywords: Drosophila ; Gene regulation ; Transcription ; Transposable element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two spontaneous mutations of rudimentary, the gene encoding the first steps of de novo pyrimidine biosynthesis in Drosophila, are suppressed by mutant alleles of the suppressor of Hairy-wing locus. This interaction differs from typical su(Hw) suppression in that neither rudimentary allele is associated with an insertion of the gypsy retrotransposon. One allele, r sP1, appears to be a point mutation. Adult r sP1 homozygous females accumulate substantially less 7.3 kb rudimentary transcript than do wild-type females. The other allele, r sP2, is an insertion of an mdg3 retrotransposon in the sixth exon of rudimentary and in the opposite transcriptional orientation. This insertion divides the rudimentary locus into two separate, yet functional, transcription units by truncating transcription from the rudimentary promoter and promoting transcription of downstream rudimentary sequences. Phenotypic suppression of both r sP1 and r sP2 by mutant alleles of the suppressor of Hairy-wing locus correlates with enhanced levels of the r sP1 and r sP2 transcripts.
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    Structure and expression of the phosphoglycerate kinase (Pgk) gene of Drosophila melanogaster (1992)
    Springer
    Molecular genetics and genomics 235 (1992), S. 213-220 
    Details
    ISSN: 1617-4623
    Keywords: Phosphoglycerate kinase ; Drosophila ; Nucleotide sequence ; Glycolysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gene that encodes phosphoglycerate kinase in Drosophila melanogaster (Pgk) has been isolated and characterized. There is a single copy of Pgk in the Drosophila genome located at cytogenetic position 23A1-2. Transcripts of Pgk are 1.6 kb long and are found during development with a profile similar to the expression pattern of other genes of the glycolytic pathway. There are substantial amounts of maternal transcript in early embryos which decline in abundance until mid-embryogenesis when transcript levels increase; levels remain high, during larval stages, fall during pupariation and rise again at emergence. The nucleotide sequence of the Pgk gene reveals two small introns, one of which is at a position identical to the site of an intron found in Pgk genes from other organisms. The Pgk gene has no TATA box in the region of transcription initiation and has multiple transcription initiation sites that are closely spaced within 110 nucleotides of the translation start site.
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    The non-dosage compensatedLSPI -α gene ofDrosophila melanogaster lies immediately downstream of the dosage compensatedL12 gene (1992)
    Springer
    Molecular genetics and genomics 233 (1992), S. 49-52 
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    ISSN: 1617-4623
    Keywords: Dosage compensation ; LSPI-α ; L12 ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The X-linked geneLSPI-α ofDrosophila melanogaster, expressed in the third larval instar, does not exhibit dosage compensation at its normal locus but does compensate when it is relocated to ectopic sites on the X chromosome. A transcription unit designatedL12, which is active in the second larval instar and capable of encoding a putative protein of 28.5 kDa, lies immediately downstream fromLSPI-α. We have determined thatL12 is dosage compensated by measuring the steady-state level of its transcript in male and female larvae. The difference in response of these two adjacent genes should be taken into consideration when models of the mechanism of dosage compensation are formulated.
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    The lysozyme locus in Drosophila melanogaster: different genes are expressed in midgut and salivary glands (1992)
    Springer
    Molecular genetics and genomics 232 (1992), S. 335-343 
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    ISSN: 1617-4623
    Keywords: Antibacterial ; Digestion ; Drosophila ; Gene family ; Lysozyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary As part of a study of the genes involved in antibacterial defense in Drosophila melanogaster, we have isolated genomic clones harboring a family of chicken-type lysozyme genes, using a lepidopteran lysozyme cDNA as probe. The locus was mapped to the cytological location 61F1-4 on the third chromosome and two of the genes at this locus, LysD and LysP, were analyzed in detail. In contrast to the bacteria-induced lysozymes in the hemolymph of many insects, the transcription levels of both Drosophila genes decrease after bacterial injections into the hemocoel. Apparently, these gene products, like the specifically adapted lysozymes in mammalian foregut fermenters, have been recruited for the digestion of bacteria present in fermenting food. The LysD gene is expressed in an anterior section of the midgut during all feeding stages of development in both larvae and adults. The LysP gene is only active in the adult where it is expressed in the salivary glands. The transcription units for both genes are very compact and they lack introns. Lysozyme D is unusual in that it is predicted to have an acidic isoelectric point whereas lysozyme P appears to be a typical basic lysozyme.
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    Nitrogen and phosphorus cycling in relation to stand age of Ecucalyptus regnans F. Muell (1992)
    Springer
    Plant and soil 142 (1992), S. 157-166 
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    ISSN: 1573-5036
    Keywords: Acacia ; Eucalyptus regnans ; decomposition ; litterfall ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The N and P contents of the litter layer and the return of these nutrients in litterfall were measured in seven stands of Mountain Ash (Eucalyptus regnans) ranging in age from 5 years to about 250 years. Both annual litterfall and nutrient return were correlated with stand basal area and were high compared with other productive eucalypt forests. In contrast, the fall of dead eucalypt leaves was constant with stand age, demonstrating that sites are fully occupied at an early age. Similarly, amounts of N and P in total leaf fall (overstorey plus understorey) were constant with stand age, except for low amounts in the stand aged 40 years where Acacia spp., important fixers of atmospheric N, were not prevalent. The decomposition constant (k) of organic matter in the litter layer decreased with stand age, from 0.31 year-1 at age 5 years to 0.23 year-1 at age 250 years. These constants also applied to N and P, indicating a tight coupling between organic matter decomposition and release of these nutrients from litter. The litter layer released about 30 kg ha-1 of N at age 5 years, and about 70 kg ha-1 at age 80 years. These results are discussed in relation to growth of Mountain Ash following fire, and the subsequent retention and accumulation of N during stand development.
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    Soil phosphorus status, pH and the manganese nutrition of wheat (1992)
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    Plant and soil 145 (1992), S. 45-50 
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    ISSN: 1573-5036
    Keywords: acidity ; manganese ; pH ; phosphorus ; soil solution wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was carried out in order to test the hypothesis that manganese nutrition of wheat was dependent on the phosphorus status of soil as well as on its pH and manganese status. An arable mineral soil whose lime and phosphorus status had been massively adjusted more than 18 years previously was compared with identical soil not so adjusted. Wheat plants were grown to maturity in these soils. Analyses were carried out on both soil and plant samples at intervals. Data for soil pH, soil solution concentrations of manganese and phosphorus, plant dry weight and tissue concentrations of manganese and phosphorus are presented. Concentrations of manganese were depressed in leaf tissue of plants from limed soils and also in high phosphorus soils. The depressed values for limed treatments were explained in terms of depressed soil solution manganese concentrations resulting from elevated pH. The results for high phosphorus soils could not be related to soil solution composition. It was suggested that high soil phosphorus resulted in elevated plant phosphorus which interfered in the uptake and/or translocation of manganese.
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    A review of phosphorus efficiency in wheat (1992)
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    Plant and soil 146 (1992), S. 163-168 
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    ISSN: 1573-5036
    Keywords: genetic variability ; NIR ; ploidy ; phosphorus ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract More efficient utilization of phosphorus by wheat plants is needed to extend the useful life of the phosphate reserves in the world, to reduce the cost of producing crops, and to improve the value of the grain and the straw produced. In this paper definitions of efficient use of phosphorus by wheat are reviewed, genotypic variation in phosphorus efficiency is reported, some consequences of breeding for greater efficiency are discussed, and ways to select more efficient genotypes are suggested.
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    Influence of plant nutrient concentration on growth rate: Use of a nutrient interruption technique to determine critical concentrations of N, P and K in young plants (1992)
    Springer
    Plant and soil 142 (1992), S. 221-233 
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    ISSN: 1573-5036
    Keywords: critical concentration ; deficiency ; diagnosis ; growth rate ; lettuce ; luxury consumption ; nitrogen ; nitrate ; nutrient requirement ; petiole sap ; phosphorus ; phosphate ; potassium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A method is described for determining the way in which growth rate varies with plant nutrient concentration using a simple nutrient interruption technique incorporating only 2 treatments. The method involves measuring the changes in growth and nutrient composition of otherwise well-nourished plants after the supply of one particular nutrient has been withheld. Critical concentrations are estimated from the relationship between the growth rate (expressed as a fraction of that for control plants of the same size which remained well-nourished throughout) and the concentration of the growth-limiting nutrient in the plants as deficiency developed. Trials of the method using young lettuce plants showed that shoot growth rate was directly proportional to total N (nitrate plus organic N) concentration, and linearly or near-linearly related to K and P concentration over a wide range; the corresponding relationship for nitrate was strongly curvi-linear. Critical concentrations (corresponding to a 10% reduction in growth rate) determined from these results were similar to critical values calculated from models derived from field data, but were generally higher than published estimates of critical concentration (based on reductions in shoot weight) for plants of a similar size. Reasons for these discrepancies are discussed. Nitrate, phosphate or potassium concentrations in sap from individual leaf petioles were highly sensitive to changes in shoot growth rate as deficiency developed, with the slope of the relationships varying with leaf position, due to differences both in their initial concentration and in the rates at which they were utilized in individual leaves. Each nutrient was always depleted more quickly in younger leaves than in older ones, providing earlier evidence of deficiency for diagnostic purposes. Although the plants were capable of accumulating nitrate, phosphate and potassium well in excess of that needed for optimum dry matter production during periods of adequate supply, the rate of mobilization of these reserves was insufficient to prevent reductions in growth rate as the plants became deficient. This brings into question the validity of the conventional concept that luxury consumption provides a store of nutrients which are freely available for use in times of shortage. The implications of these results for the use of plant analysis for assessing plant nutrient status are discussed.
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    Inability to solubilize phosphate in limestone soils—key factor controlling calcifuge habit of plants (1992)
    Springer
    Plant and soil 145 (1992), S. 65-70 
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    ISSN: 1573-5036
    Keywords: calcifuge plants ; phosphorus ; deficient absorption ; Deschampsia flexuosa ; Jasione montana ; Rumex acetosella ; Silene rupestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Germination, seedling establishment and growth of calcifuge plants in Swedish limestone soils of Archean and Ordovician age were studied. As previously demonstrated for Viscaria vulgaris, establishment of Rumex acetosella and Silene rupestris did not succeed unless CaHPO4 (at the rate of 10 mmol dm-3 of soil) was supplied. Growth of Deschampsia flexuosa was enhanced by phosphate addition, whereas establishment success of Jasione montana was poor, regardless of phosphate treatment. Establishment and growth in an acidic gneiss soil, used as a reference for the species studied, was good. Total, total inorganic, exchangeable, and soil solution P were considered in all soils and treatments. It is proposed that the calcifuge behaviour of plants is quite often caused by inability to solubilize the native phosphate of limestone soils.
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    Can maize cultivars with low mineral nutrient concentrations in the grains help to reduce the need for fertilizers in third world countries? (1992)
    Springer
    Plant and soil 146 (1992), S. 227-231 
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    ISSN: 1573-5036
    Keywords: cultivars ; grains ; maize ; nitrogen ; phosphorus ; potassium ; tropical climate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An earlier study revealed considerable genotypic variation in grain N, P and K concentrations (GNC, GPC and GKC, respectively) in tropical maize. The expression of varietal differences in GNC, GPC and GKC, however, may depend on environmental conditions such as the N status of the soil. Two tropical maize hybrids (Suwan 2301 and CP 1) with comparable yielding capacity, but contrasting GNCs, GPCs and GKCs, were therefore grown at four levels of N in a field experiment at Farm Suwan (Thailand, latitude 14.5°N). Suwan 2301 exhibited a higher GNC than did CP 1 at all rates of N, but large differences in GPC and GKC were found only at high N fertilization. This was obviously due to individual grain yield responses of the cultivars to increasing rates of N fertilizer, demonstrating that grain nutrient concentrations are, at least in part, functions of the amount of grain carbohydrates which dilute a genetically and environmentally fixed amount of grain P and K. As compared to Suwan 2301, CP 1 accumulated less N, P and K in the grains at almost all levels of N fertilization, confirming our hypothesis that the cultivation of maize genotypes with low grain mineral nutrient concentrations may help third-world cash-crop farmers to reduce the need for scarce and costly mineral fertilizers. This finding has to be verified at reduced availability of soil −P, −K, and water.
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    Effects of phytoplankton on the elemental composition (C, N, P) of suspended particulate material in the lower river Rhine (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 479-489 
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    ISSN: 1573-5117
    Keywords: River Rhine ; phytoplankton ; suspended material ; carbon ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spatial and temporal distribution of element concentrations were monitored together with chlorophyll a as an indicator of algal density to assess the effect of phytoplankton on the elemental composition (C, N, P) of suspended materials in the lower Rhine. The high concentrations of particulate C, N and P in the river were found to decrease in the delta and to increase again in the estuarine turbidity zone. Phytoplankton blooms increased the concentrations of particulate C, N, and P significantly in the upstream part of the river. In summer 1989, 15–65% of the particulate C and 20–75% of the particulate N were attributable to phytoplankton. Together with published data these observations indicate that in eutrophic rivers, the input of organic materials from the catchment is strongly modified and supplemented by in situ growth of phytoplankton. During seaward transport the phytoplankton and the particulate elements disappeared from the river water concomitantly with the suspended matter, indicating an increased retention of these elements due to sedimentation. In contrast, soluble ammonia, nitrite and phosphate increased in the tidal reaches of the river because of local input in the harbour and city of Rotterdam and because of mineralization. Therefore the total nutrient load of the Rhine estimated at the German/Dutch border does not reflect the actual input into the sea.
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    Iron:phosphorus ratio in surface sediment as an indicator of phosphate release from aerobic sediments in shallow lakes (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 731-743 
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    ISSN: 1573-5117
    Keywords: Lakes ; sediments ; iron ; phosphorus ; phosphate release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analysis of Danish lakes showed that both mean winter and mean summer concentrations of lake water total phosphorus in the trophogenic zone correlated negatively with the total iron to total phosphorus ratio (Fe:P) in surface sediments. No correlation was found between the water total phosphorus concentration and either the sediment phosphorus concentration alone or with sediment calcium concentration. The increase in total phosphorus from winter to summer, which is partly a function of net internal P-loading, was lowest in lakes with high Fe:P ratios in the surface sediment. A study of aerobic sediments from fifteen lakes, selected as representative of Danish lakes with respect to the sediment Fe and phosphorus content, showed that the release of soluble reactive phosphorus was negatively correlated with the surface sediment Fe:P ratio. Analysis of phosphate adsorption properties of surface sediment from 12 lakes revealed that the capability of aerobic sediments to buffer phosphate concentration correlated with the Fe:P ratio while the maximum adsorption capacity correlated with total iron. Thus, the Fe:P ratio may provide a measure of free sorption sites for orthophosphate ions on iron hydroxyoxide surfaces. The results indicate that provided the Fe:P ratio is above 15 (by weight) it may be possible to control internal P-loading by keeping the surface sediment oxidized. Since the Fe:P ratio is easy to measure, it may be a useful tool in the management of shallow lakes.
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    Biogeochemistry of manganese- and iron-rich sediments in Toolik Lake, Alaska (1992)
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    Hydrobiologia 240 (1992), S. 45-59 
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    ISSN: 1573-5117
    Keywords: arctic lakes ; trace metals ; lake sediments ; manganese ; iron ; phosphorus ; sediment-water flux ; diagenesis ; Toolik Lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sediments within Toolik Lake in arctic Alaska are characterized by extremely low rates of organic matter sedimentation and unusually high concentrations of iron and manganese. Pore water and solid phase measurements of iron, manganese, trace metals, carbon, nitrogen, phosphorus, and sulfur are consistent with the hypothesis that the reduction of organic matter by iron and manganese is the most important biogeochemical reaction within the sediment. Very low rates of dissolved oxygen consumption by the sediments result in an oxidizing environment at the sediment-water interface. This results in high retention of upwardly-diffusing iron and manganese and the formation of metal-enriched sediment. Phosphate in sediment pore waters is strongly adsorbed by the metal-enriched phases. Consequently, fluxes of phosphorus from the sediments to overlying waters are very small and contribute to the oligotrophic nature of the Toolik Lake aquatic system. Toolik Lake contains an unusual type of lacustrine sediment, and in many ways the sediments are similar to those found in oligotrophic oceanic environments.
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    Sources, concentrations and characteristics of organic matter in softwater lakes and streams of the Swedish forest region (1992)
    Springer
    Hydrobiologia 229 (1992), S. 23-41 
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    ISSN: 1573-5117
    Keywords: TOC ; COD ; humic ; colour ; Secchi ; phosphorus ; carbon ; permanganate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 18 Swedish forest lakes covering a wide range of dystrophy were studied in order to quantify and characterize the organic matter in the water with respect to origin (allochthonous or autochthonous), physical state (particulate or dissolved) and phosphorus content. Samples were collected repeatedly during a two-year period with unusually variable hydrological conditions. Water from three different depths and from tributaries was analysed with standard monitoring methods, including water colour, Secchi disk transparency, total organic carbon (TOC), CODCr, CODMn, total phosphorus and molybdate reactive phosphorus. Interrelationships were used to compare different methods and to assess the concentration and composition of organic matter. It is estimated that in remote softwater lakes of the Swedish forest region, autochthonous carbon is typically 〈 5 g m−3. Most lakes in this region receive significant amounts of humic matter originating from coniferous forest soils or peatland in the catchment area. In most humic lakes with a water colour of ≥ 50 g Pt m−3, more than half of the organic carbon in the surface water is of allochthonous origin, and in polyhumic lakes (〉 200 g Pt m−3) the proportion can exceed 90%. Secchi depth readings were related similarly to organic matter from both sources and provided good estimates of TOC with a single optical measurement. Water colour was used to distinguish allochthonous and autochthonous matter. High concentrations of phosphorus were found in humic waters, most of it being molybdate reactive, and probably associated with humic matter rather than as dissolved free inorganic forms. CODMn yielded only 25–60% of TOC and appears to include mainly truly dissolved substances of low molecular weight.
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    Nutrient loading and drainage channel response in a ricefield system (1992)
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    Hydrobiologia 230 (1992), S. 193-200 
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    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; ricefield system ; drainage channels ; mediterranean Deltas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen and phosphorus released into the water of a main drainage channel in the Ebro Delta was measured during a period of rice cultivation. An increase in total nitrogen and phosphorus in its different forms in accordance with the increase in cultivated area drained was observed. A significant correlation between the release of nutrients into the water and the nutrient load, for both nitrogen and phosphorus, if we consider the release of nutrients per unit of length of the channel and increased total phosphorus content of the water that flows through it during the period of rice cultivation. Physical and chemical changes in the water as a result of ricefield metabolism may explain the differences observed in nitrogen and phosphorus cycles between Ebro and Rhône Deltas, two mediterranean deltaic systems where a large area with similar drainage system is used for rice cultivation.
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    Changes in water quality in Lake Päijänne following decrease of effluent load from the pulp and paper industry in 1969–1989 (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 395-403 
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    ISSN: 1573-5117
    Keywords: Lake Päijänne ; pulp mills ; BOD ; phosphorus ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Päijänne, the second largest lake in Finland, has been seriously polluted since the 1960s due to the effluents from pulp and paper mills, notably the Äänekoski sulphate and sulphite pulp mills situated about 50 km north of the lake, and the sulphite pulp mill and paper mills of Jämsänkoski and Kaipola on Central Lake Päijänne. A sulphite lye evaporation and combustion plant installed at the Jämsänkoski sulphite pulp mill in 1969 reduced the organic pollution of Central Päijänne. Lignin concentration decreased and the oxygen balance improved. The sulphite pulp mill was closed in 1981 and replaced by a thermo-mechanical pulp mill. Eutrophication is the main threat to water quality in Central Lake Päijänne at present. A significant improvement in the water quality, especially in oxygen balance, was achieved in the watercourse of Äänekoski and in Northern Päijänne after replacement of the old sulphite and sulphate pulp mills at Äänekoski by a large sulphate pulp mill with a biological purification plant employing the activated sludge method. The BOD7-loading dropped from 46 to 3–4 t d−1, but the nutrient loading has not decreased sufficiently, and the Äänekoski watercourse and Northern Päijänne are still eutrophic.
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    Bioassay for phosphate demand in phytoplankton from acidified lakes: Lake Njupfatet, an example of phosphate deficiency induced by liming (1992)
    Springer
    Hydrobiologia 246 (1992), S. 99-110 
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    ISSN: 1573-5117
    Keywords: acid lakes ; ATP ; in situ enclosures ; liming ; phosphatases ; phosphorus ; phytoplankton community
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A bioassay was developed, involving steady-state ATP level determinations, for estimation of phosphate demand and deficiency in natural phytoplankton communities. The studies were performed on phytoplankton from the moderately acidified Lake Njupfatet in central Sweden before and after liming. Phytoplankton samples from in situ enclosure experiments with low-dose enrichments of nitrate and phosphate and removal of large (〉 100 µm) zooplankton and from the lake water were collected. The phytoplankton were concentrated by through-flow centrifugation and post-cultured in the laboratory with or without the addition of phosphate. A relative increase in the ATP:chlorophyll a ratio after the phosphate treatment as compared to samples without phosphate enrichment was found to be a highly reproducible indicator of phosphate deficiency in the natural phytoplankton population. In contrast, the absolute ATP:chlorophyll a ratio varied substantially between different sampling occasions. No phosphate deficiency was detected in phytoplankton from the acidic lake or from fertilized in situ enclosures. However, phytoplankton from in situ enclosures without added nutrients showed evidence of phosphate limitation after 21 days incubation. Also, the phytoplankton community developed a significant phosphate deficiency the summer after lake liming. The results from the ATP analyses are compared with chemical data of the lake water, phytoplankton community structure and phosphatase activities in the lake before and after liming. The average total biomass of phytoplankton and the average Tot-P measured during May to September decreased with appr. 30% after liming while Tot-N was essentially unaffected and the phosphatase activities increased by 1000–2000%.
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    Regeneration of inorganic phosphorus and nitrogen from decomposition of seston in a freshwater sediment (1992)
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    Hydrobiologia 228 (1992), S. 71-81 
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    ISSN: 1573-5117
    Keywords: nutrient regeneration ; phosphorus ; nitrogen ; sediment ; lakes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mineralization of phosphorus and nitrogen from seston was studied in consolidated sediment from the shallow Lake Arreskov (July and November) and in suspensions without sediment (July). In the suspension experiment, phosphorus and nitrogen were mineralized in the same proportions as they occurred in the seston. During the 30 days suspension experiment, 47 and 43% of the particulate phosphorus and nitrogen, respectively, was mineralized with constant rates. Addition of seston to the sediment had an immediate enhancing effect on oxygen uptake, phosphate and ammonia release, whereas nitrate release decreased due to denitrification. The enhanced rates lasted for 2–5 weeks, while the decrease in nitrate release persisted throughout the experiment. The increase in oxygen uptake (equivalent to 21% of the seston carbon) was, however, only observed in the July experiment. The release of phosphorus and nitrogen from seston decomposing on the sediment surface differed from the suspension experiments. Thus, between 91 and 111% of the phosphorus in the seston was released during the experiments. Due to opposite directed effects on ammonium and nitrate release, the resulting net release of nitrogen was relatively low. A comparison of C/N/P ratios in seston, sediment and flux rates indicated that nitrogen was mineralized faster than phosphorus and carbon. Some of this nitrogen was lost through denitrification and therefore not measurable in the flux of inorganic nitrogen ions. This investigation also suggests that decomposition of newly settled organic matter in sediments have indirect effects on sediment-water exchanges (e.g. by changing of redox potentials and stimulation of denitrification) that modifies the release of mineralized phosphate and nitrogen from the sediment.
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    The influence of flushing on nutrient dynamics, composition and densities of algae and transparency in Veluwemeer, The Netherlands (1992)
    Springer
    Hydrobiologia 233 (1992), S. 187-196 
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    ISSN: 1573-5117
    Keywords: eutrophication ; lake restoration ; flushing ; Veluwemeer ; algal species ; transparency ; phosphorus ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Total phosphorus and chlorophyll decreased significantly after reduction of the external phosphorus loading and the start of flushing Veluwemeer with polder water in 1979. Flushing of Veluwemeer has had a large impact on nutrient dynamics. Especially in the first winter, dilution was the main cause of changes in water quality. On a longer term the increase of the inactivation of phosphorus in sediments is important. Oscillatoria agardhii has been brought to the margins of its habitat. Three successive cold winters were an additional causal factor in the disappearance of Oscillatoria agardhii and the dominance of diatoms and green algae from 1985 onwards. Due to higher detritus and inorganic suspended matter concentrations transparency increased less than expected. Since 1985 chlorophyll only contributes for a small percentage to the transparency. In the present situation further improvement of the water quality of Veluwemeer is questionable, as the phosphorus concentration in the lake and the polder water is almost the same. Therefore it is recommanded to shift flushing operations, at least in the winter period, from Veluwemeer towards Wolderwijd.
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    Fixation of phosphorus in lake sediments using iron(III)chloride: experiences, expectations (1992)
    Springer
    Hydrobiologia 233 (1992), S. 211-212 
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    ISSN: 1573-5117
    Keywords: eutrophication ; lake restoration ; phosphorus ; sediments ; internal loading ; chemomanipulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract After a reduction of the external phosphorus loading to a lake, an internal loading from the sediments may delay the improvement of the water quality. The accepted method to combat internal loading is careful dredging of the upper sediment layers (Cooke et al., 1986), but this method is costly and time consuming. Addition of phosphorus binding agents to the sediments might offer an alternative. In the Netherlands the use of aluminum compounds, the most common phosphorus binding agent, for water quality improvement purposes is not favoured. Therefore a sediment treatment with a solution of iron(III)chloride was tested. Iron was chosen because it is considered to be a natural binder of phosphate. 100 g m−2 of Fe3+ were added to the sediments of the shallow (1.75 m average depth) and eutrophic Lake Groot Vogelenzang (The Netherlands) in October and November 1989. The iron(III)chloride solution was diluted 100 times with lake water and mixed with the surface sediments with a water jet. Following the addition the concentrations of total phosphorus (Fig. 1), chlorophyll-a and suspended solids decreased. This improvement of the water quality lasted for three months. After this time the total phosphorus concentration increased again, but remained at a lower level than in spring and summer of 1989. The phosphorus release rate from the sediments as measured from intact sediment cores decreased from 4 to 1.2 mg P m−2 d−1 (n = 5), and the bioavailability of the sediment phosphorus, as measured with bioassays, decreased from 34 to 23% (n = 5) shortly after the treatment. One year after the treatment the release rate was increased to 3 mg P m−2 d−1 (n = 5). Before treatment, the lake was thought to have a residence time of over one year. However, the chloride added to the lake disappeared according to a dilution rate of 0.03 d−1 or a retention time of about 35 days. A high external loading due to rapid flushing with phosphorus-rich water from surrounding lakes possibly prevented a more durable improvement in water quality. Another possibility is that the iron addition has lost its phosphate binding capacity due to reduction or binding with other anions like carbonate or sulphide. Therefore the suitability of the method to reduce internal loading and especially the long term availability of added iron to bind phosphorus needs additional proof. The treatment of the 18 ha area of Lake Groot Vogelenzang took three weeks. The operational costs were about US$ 125000. This is fast and cheap compared to dredging. Application of the technique is limited to those cases where the sediments are not polluted with micro-pollutants and the water depth need not be increased.
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    Phosphorus eutrophication in the SW Frisian lake district 1. Monitoring and assessment of a dynamic mass balance model (1992)
    Springer
    Hydrobiologia 233 (1992), S. 259-270 
    Details
    ISSN: 1573-5117
    Keywords: eutrophication ; lakes ; phosphorus ; chloride ; loading ; dynamic mass balance model ; sensitivity analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 1984 a frequent monitoring programme was started in the hypertrophic S.W. Frisian lake district, with emphasis on total phosphorus (TP) and chloride (Cl−). The main objectives of the project were: to quantify the phosphorus flows, to gain insight in the process of eutrophication, and to simulate management scenarios. The seasonal variability in the lakes is due mainly to the man-made hydrology: reception of humic-rich polder water in wet periods (winter) and inlet of chloride-rich Usselmeer water in dry periods (summer). The yearly means of TP concentrations in the lakes (Tjeukemeer, Groote Brekken and Slotermeer) ranged from 0.23 to 0.29 mg l−1. However, much higher concentrations (0.9 mg l−1) were found in periods with high inflow of polder water. The simulations with a mass balance showed an acceptable similarity between measured and simulated concentrations of TP as well as of Cl−. Chloride was modelled to verify the accuracy of a hydrodynamic model. A sensitivity analysis of the apparent settling rate in the P model showed that sensitivity was lowest in simulations of Groote Brekken and highest in simulations of Slotermeer, the difference being attributable to the influence of the water residence time. The model was found to be appropriate for simulating management scenarios.
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    A mathematical model of the phosphorus cycle in Lake Loosdrecht and simulation of additional measures (1992)
    Springer
    Hydrobiologia 233 (1992), S. 119-136 
    Details
    ISSN: 1573-5117
    Keywords: model ; simulation ; eutrophication ; phosphorus ; P/C ratio ; lake ecosystem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phosphorus cycle in the ecosystem of the shallow, hypertrophic Loosdrecht lakes (The Netherlands) was simulated by means of the dynamic eutrophication model PCLOOS. The model comprises three algal groups, zooplankton, fish, detritus, zoobenthos, sediment detritus and some inorganic phosphorus fractions. All organic compartments are modelled in two elements, carbon and phosphorus. Within the model system, the phosphorus cycle is considered as completely closed. Carbon and phosphorus are described independently, so that the dynamics of the P/C ratios can be modelled. The model has been partly calibrated by a method based on Bayesian statistics combined with a Range Check procedure. Simulations were carried out for Lake Loosdrecht for the periods before and after the restoration measures in 1984, which reduced the external phosphorus loading to the lake from ca. 2 mgP m−2 d−1 to 1 mgP m−2 d−1. The model outcome was largely comparable withthe measured data. Total phosphorus has slowly decreased from an average 130 µgP l−1 to ca. 80 µgP l−1, but chlorophyll-a (ca. 150 µg 1−1, summer-averaged) and seston concentrations (8–15 mgC 1−1) hardly changed since the restoration measures. About two-thirds of the seston consisted of detritus, while the phytoplankton remained dominated by filamentous cyanobacteria. The P/C ratio of the seston decreased from ca. 1.0% to 0.7%, while the P/C ratios of zooplankton, zoobenthos and fish have remained constant and are much higher. The system showed a delayed response to the decreased phosphorus loading until a new equilibrium was reached in ca. five years. Major reasons for the observed resilience of the lake in responding to the load reduction are the high phosphorus assimilation efficiency of the cyanobacteria and the high internal recycling of phosphorus. A further reduction of nutrient loading, perhaps in combination with additional measures like biomanipulation, will be the most fruitful additional restoration measure.
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    Coupling between benthic biomass of Microcystis and phosphorus release from the sediments of a highly eutrophic lake (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 375-385 
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    ISSN: 1573-5117
    Keywords: Microcystis ; microbial activity ; sediment ; phosphorus ; internal loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Variations in microbial biomass and activity in the sediments of hypereutrophic Lake Vallentunasjön were followed during a period of 5 years. The data were compared to the calculated release of phosphorus from the sediments during the same period. A strong co-variation was found between biomass of Microcystis, heterotrophic bacterial activity in the sediments and internal phosphorus loading. These parameters exhibited mainly a declining trend during the investigation period. A pronounced stability of the sediment chemistry, including the fractional composition of the sediment phosphorus, during the studied period indicates that microbial activity affected the phosphorus release from the sediments. Calculations of the percentage of sediment bacteria that was associated to the mucilage of Microcystis colonies imply, together with the specific bacterial production, that Microcystis in the sediment stimulates bacterial production. In the highly phosphorus-saturated sediments of Lake Vallentunasjön this would ultimately lead to an increased release of phosphorus from the sediment. Lake Vallentunasjön does not follow the common pattern of recovery after reduction of external phosphorus loading. The large biomasses and long survival of Microcystis in the sediment are probably important reasons for the delayed recovery of the lake.
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    The turnover of river-transported iron, phosphorus and organic carbon in the Öre estuary, northern Sweden (1992)
    Springer
    Hydrobiologia 235-236 (1992), S. 585-596 
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    ISSN: 1573-5117
    Keywords: estuary ; iron ; phosphorus ; organic carbon ; aggregation ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The turnover of iron, phosphorus and organic carbon was followed in the Öre Estuary, northern Sweden, during the spring flood periods of 1989 and 1990. River-supplied material rapidly sediments out of the water column and is primary deposited within the estuary. The removal of iron and phosphorus is complete, with the calculated sedimentation exceeding the total amounts of particulate and dissolved iron and phosphorus supplied by the river. Aggregation of dissolved or colloidal iron-phosphate complexes due to increasing salinity and pH in combination with adsorption on rapidly sedimentating inorganic particles is suggested to explain this estuarine filter effect. Organic carbon is only affected by aggregation and sedimentation to a minor extent.
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    Phosphorus transformations in the epilimnia of small humic forest lakes (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 105-111 
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    ISSN: 1573-5117
    Keywords: phosphorus ; transformations ; humic forest lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Research on epilimnetic phosphorus transformations in lakes had led to the establishment of a generalised picture which is promoted in reviews and textbooks. However, it would be wrong to believe that this established view can be applied to all lakes. Certainly the transformations of phosphorus in the summer epilimnia of small, coloured, humic forest lakes in southern Finland show features which deviate markedly from the generally accepted paradigm. (1) The plankton appears to be limited simultaneously by P and N rather than being strongly P limited. (2) Particulate P is typically a rather small fraction of the total P. (3) Molybdate reactive P may be a large part of the total P, although much of this MRP is not free orthophosphate, especially in highly humic lakes. (4) Turnover times for PO4-P are normally long (50–1000 minutes); turnover times appear to be longer in highly humic lakes. (5) Added 32 PO4 passes rapidly to macrozooplankton, apparently with rapid turnover of zooplankton phosphorus. (6) Sedimentation of phosphorus from the typically shallow epilimnion appears high, but may be partially compensated by biological retrieval of phosphorus from the phosphorus-rich hypolimnion.
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    Phytoplankton and zooplankton community structure after nutrient additions to the oligotrophic Lake Hecklan, Sweden (1992)
    Springer
    Hydrobiologia 243-244 (1992), S. 147-155 
    Details
    ISSN: 1573-5117
    Keywords: fertilization ; phosphorus ; nitrogen ; phytoplankton ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Lake Hecklan, in central Sweden, was fertilized with phosphorus and nitrogen during thermal stratification (late May-early Oct) 1984–1987. The nutrient additions were relatively small and raised the total phosphorus concentrations from 6 to 10 µg l−1. The working hypothesis was that this moderate increase in the phosphorus concentration could increase the phytoplankton biomass without adverse changes in the planktonic community structure. The fertilization increased the phytoplankton biomass from 0.1 to a maximum of 2 mm3 l−1. Chrysophyceae and Cryptophyceae dominated throughout the experimental period. Thus, the phytoplankton composition remained typical for a Swedish forest lake and provided a potential for increased zooplankton growth. An increased growth of zooplankton was indicated by increased biomass of Cladocera and Copepoda in 1984 and 1985, and by increased fecundity of herbivorous zooplankton.
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    Mass balance models for elongated lakes (1992)
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    Hydrobiologia 243-244 (1992), S. 341-349 
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    ISSN: 1573-5117
    Keywords: mass balance ; modelling ; phosphorus ; sedimentation ; CSTR ; PFR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mass balance models for elongated lakes have been developed. In these models particular attention is paid to the hydraulic description of the lake and to the description of net sedimentation. The hydraulic description is a linear combination of CSTR and PFR, with a coefficient regulating the degree of mixing. The PFR description was modified so that also additional input along the lake can be considered. Net sedimentation is described either as a first order or a second order reaction. Both voluminal and areal sedimentation is possible in the models. The models were tested against phosphorus balance data for two Finnish lakes. Lake Haukivesi and Lake Päijänne. In both lakes the PFR model with additional input together with second order net sedimentation gave the best fit to observations. The values of the sedimentation coefficients are not universal but vary from lake to lake. They are also dependent on the hydraulic description used in the model. There is a critical point for the monitoring of the lake at which measurements give the same sedimentation coefficient regardless of the hydraulic description.
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    Nutrient dynamics in the floodplain ponds of the Paraná River (Argentina) dominated by the water hyacinth Eichhornia crassipes. (1992)
    Springer
    Biogeochemistry 17 (1992), S. 85-121 
    Details
    ISSN: 1573-515X
    Keywords: nitrogen fixation ; phosphorus ; internal loading ; water hyacinth ; floodplain ; Paraná ; flood-pulse hypothesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Some aspects of nutrient status and dynamics prevailing during low and high water conditions in the fringing floodplain ponds of the Paraná River dominated by the floating macrophyte Eichhornia crassipes are described. During summertime low water conditions, low DIN:DRP ratios (0.16–1.0) and low DIN (0.5–4.8 μmol.liter−1) in the root-zone of the floating meadows suggest that macrophyte growth is limited by nitrogen. DRP concentrations appear to be controlled more by abiotic sorption-dissolution than by biological reactions. Preflood nutrient fluxes from the sediments, as estimated from porewater profiles, show that a minimum of 1.19 and 0.38 mmol.m−2.d−1 of DIN and DRP were regenerated from the sediments, respectively. Heterotrophic N2 fixation is primarily associated with decaying litter (0.4 to 3.2 μmolN2.g−1.d−1). Nutrient recycling from sediments and meadow-litter, and heterotrophic N2 fixation (1.4 mmolN.m−2.d−1) appear sufficient to sustain high floating macrophyte productivity for long periods of time, without invoking large inputs from the river. The high water and early isolation periods are characterized by a very dynamic behavior of DIN, reflecting marked imbalances between N supply and demand by the biota. After hydrologic isolation of the ponds, DIN rapidly decreases to undetectable levels and stays low for the following 3 weeks, presumably as a result of high demand by phytoplankton and sediment bacteria. DIN increases again to high values 3–8 weeks after the flood, following the re-establishment of NH4 + fluxes from the sediments. Compared to DIN, DRP concentrations remain relatively high and change little during and after the flood. Because of their small amplitude and short duration, floods do not appear to stimulate floating macrophyte production in the Paraná.
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    Effects of nitrogen: phosphorus supply ratios on nitrogen fixation in agricultural and pastoral ecosystems (1992)
    Springer
    Biogeochemistry 18 (1992), S. 19-35 
    Details
    ISSN: 1573-515X
    Keywords: Dinitrogen fixation ; nitrogen ; phosphorus ; competition ; legumes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract An analysis of data compiled from the literature confirms a strong inverse relationship between annual rates of nitrogen fixation and the soil nitrogen content in agricultural and pastoral ecosystems. However, this inverse relationship is strongly modified by the rate of application of phosphorus fertilizer, which strongly influences the activities of both symbiotic and non-symbiotic nitrogen fixing organisms. In the case of symbiotic legumes, the response of N-fixation to N and P is in part a result of changes in legume dominance within the plant community. These results, as well as supporting data presented from a review of experiments on nitrogen fixation in a variety of other terrestrial and aquatic ecosystems, provide important support for the hypothesis that phosphorus availability is a key regulator of nitrogen biogeochemistry.
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    Soil nutrient dynamics in response to irrigation of a Panamanian tropical moist forest (1992)
    Springer
    Biogeochemistry 19 (1992), S. 1-25 
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    ISSN: 1573-515X
    Keywords: nitrogen ; phosphorus ; soil fertility ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We measured concentrations of soil nutrients (0–15 and 30–35 cm depths) before and after the dry season in control and dry-season irrigated plots of mature tropical moist forest on Barro Colorado Island (BCI) in central Panama to determine how soil moisture affects availability of plant nutrients. Dry-season irrigation (January through April in 1986, 1987, and 1988) enhanced gravimetric soil water contents to wet-season levels (ca. 400 g kg−1 but did not cause leaching beyond 0.8 m depth in the soil. Irrigation increased concentrations of exchangeable base cations (Ca2+, Mg2+, K+, Na+), but it had little effect on concentrations of inorganic N (NH4 +C, NO3 − and S (SO4 2−). These BCI soils had particularly low concentrations of extractable P especially at the end of the dry season in April, and concentrations increased in response to irrigation and the onset of the rainy season. We also measured the response of soil processes (nitrification and S mineralization) to irrigation and found that they responded positively to increased soil moisture in laboratory incubations, but irrigation had little effect on rates in the field. Other processes (plant uptake, soil organic matter dynamics) must compensate in the field and keep soil nutrient concentrations at relatively low levels.
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    Genomic distribution of transposable elements among individuals of an inbred Drosophila line (1992)
    Springer
    Genetica 86 (1992), S. 1-11 
    Details
    ISSN: 1573-6857
    Keywords: Drosophila ; transposons ; mobility ; inbreeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The stability of the elements of eleven transposon families (412, B 104, blood, 297, 1731, G, copia, mdg 4, hobo, jockey and I) has been compared by the Southern technique among individuals of a Drosophila line that has been subjected to 30 generations of sister sib matings. The 412, B104, blood, 297, 1731 and G elements appear stable. Heterochromatic copia and hobo elements and euchromatic I elements appear highly polymorphic. In addition, copia, mdg 4, jockey and I elements undergo an instability resulting in significant variations in relative intensity among autoradiographic bands. The extent of the polymorphisms detected strongly suggests de novo rearrangements of transposable elements.
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    Evolution of the transposable element mariner in the Drosophila melanogaster species group (1992)
    Springer
    Genetica 86 (1992), S. 37-46 
    Details
    ISSN: 1573-6857
    Keywords: Mariner ; Drosophila ; molecular evolution ; transposable element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The population biology and molecular evolution of the transposable element mariner has been studied in the eight species of the melanogaster subgroup of the Drosophila subgenus Sophophora. The element occurs in D. simulans, D. mauritiana, D. sechellia, D. teissieri, and D. yakuba, but is not found in D. melanogaster, D. erecta, or D. orena. Sequence comparisons suggest that the mariner element was present in the ancestor of the species subgroup and was lost in some of the lineages. Most species contain both active and inactive mariner elements. A deletion of most of the 3′ end characterizes many elements in D. teissieri, but in other species the inactive elements differ from active ones only by simple nucleotide substitutions or small additions/deletions. Active mariner elements from all species are quite similar in nucleotide sequence, although there are some-species-specific differences. Many, but not all, of the inactive elements are also quite closely related. The genome of D. mauritiana contains 20–30 copies of mariner, that of D. simulans 0–10, and that of D. sechellia only two copies (at fixed positions in the genome). The mariner situation in D. sechellia may reflect a reduced effective population size owing to the restricted geographical range of this species and its ecological specialization to the fruit of Morinda citrifolia.
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    Evidence for De Novo rearrangements of Drosophila transposable elements induced by the passage to the cell culture (1992)
    Springer
    Genetica 87 (1992), S. 65-73 
    Details
    ISSN: 1573-6857
    Keywords: Drosophila ; transposons ; mobility ; cultured cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genomic distribution and the number of elements of eleven transposon families have been compared by the Southern technique between permanent cultured cells, larval salivary glands and the brains and whole flies of an inbred Drosophila line (inb-c) from which the cells were established. In cultured cells, changes in restriction patterns consistent with various types of rearrangements such as amplification, transposition and excision of the elements of copia, 1731, 412, 297 and mdg-4 transposon families are detected whereas B 104, G and blood elements appear stable. In previous reports these rearrangements were not detected among individuals of the inb-c line or among samples of somatic tissues, or in samples spanning years of maintenance of cultured cells. Hence, we believe that they have been induced de novo during the passage to the cell culture.
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    Population genetics of transposable DNA elements (1992)
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    Genetica 86 (1992), S. 67-84 
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    ISSN: 1573-6857
    Keywords: Drosophila ; population genetics ; transposable elements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper is an attempt to bring together the various, dispersed data published in the literature on insertion polymorphism of transposable elements from various kinds of populations (natural populations, laboratory strains, isofemale and inbred lines). Although the results deal mainly with Drosophila, data on other organisms have been incorporated when necessary to illustrate the discussion. The data pertinent to the regions of insertion, the rates of transposition and excision, the copy number regulation, and the degree of heterozygosity were analysed in order to be confronted with the speculations made with various theoretical models of population biology of transposable elements. The parameters of these models are very sensitive to the values of the transposable element characteristics estimated on populations, and according to the difficulties of these estimations (population not at equilibrium, particular mutations used to estimate the transposition and excision rates, trouble with the in situ technique used to localize the insertions, undesired mobilization of TEs in crosses, spontaneous genome resetting, environmental effects, etc.) it cannot be decided accurately which model better accounts for the population dynamics of these TEs. Tendencies, however, emerge in Drosophila: the copia element shows evidence for deficiency of insertions on the X chromosomes, a result consistent with selection against mutational effects of copia insertions; the P element repartition does not significantly deviate from the neutral assumption, in spite of a systematic copy number of insertions higher on the X than on the autosomes. Data on other elements support either the neutral model of TE containment, neither of the two models, or both. Prudence in conclusion should then be de rigueur when dealing with such kind of data. Finally the potential roles of TEs in population adaptation and evalution are discussed.
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    Putting the heat on sex determination (1992)
    Springer
    Genetica 87 (1992), S. 1-6 
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    ISSN: 1573-6857
    Keywords: Temperature ; splicing mechanism ; mammals ; Drosophila ; turtles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sex determination and differentiation are inherently fascinating to both layperson and geneticist. Major advances have accelerated interest in the molecular genetic events mediating these processes in nematodes, flies, mice and humans. Far less attention has been paid to those organisms, particularly reptiles, where sex is determined by environmental cues. However, recent experimental evidence suggests that the two modes of sex determination may not only share common genetic elements, but may also be regulated by similar mechanisms. We argue that the ability to manipulate sex by temperature provides a particularly suitable model for exploring the molecular basis of this fundamental biological process.
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    The influence of tillage and cropping-intensity on cereal response to nitrogen, sulfur, and phosphorus (1992)
    Springer
    Nutrient cycling in agroecosystems 31 (1992), S. 15-19 
    Details
    ISSN: 1573-0867
    Keywords: Tillage ; crop rotation ; cereal grain ; wheat ; nitrogen ; sulfur ; phosphorus ; no-till
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efficient fertilizer use is a prerequisite for achieving optimum crop yield while avoiding environmental contamination. Cereal response to nitrogen (N), sulfur (S), and phosphorus (P) were determined for 6 years under differing tillage [conventional-till (CT) vs. no-till (NT)] and intensity of cropping (cereal/fallow vs. cereal/cereal). Semidwarf white winter wheat (Triticum aestivum L.) alternated yearly with either fallow or spring cereal [barley (Hordeum vulgare L.) or spring wheat] on a Typic Haploxeroll soil in a 415 mm rainfall zone. Fertilizer treatments were no fertilizer (None), N only (N), N plus S (NS), and N plus S plus P (NSP). Average application rate, when applied, was 109 kg N, 18 kg S, and 11 kg P ha−1. Average cereal yield without fertilizer was 1.82 t ha−1. Nitrogen increased grain yield in 6 of 6, S in 4 of 6, and P in 3 of 6 years, with P and S response significant the remaining years at the 10% probability level. Average yield increases were 1.11 t ha−1 for N, 0.93 t ha−1 for S, and 0.47 t ha−1 for P. The NT/CT yield ratio was 0.60, 0.75, 0.93, and 0.95 with None, N, NS, and NSP addition, respectively, indicating that N and S deficiency were more severe in no-till. Limited increase in the NT/CT ratio with P addition indicated that P deficiency was less affected by tillage. Winter wheat always yielded less under NT than CT regardless of fertility, whereas spring cereals reached equality when fertilized with NSP. Annually-cropped wheat yielded 52, 67, 89, and 90% of wheat after fallow with None, N, NS, and NSP, respectively. Thus N and S, but not P, deficiency was more intense with increased frequency of cropping. Adequate fertility was a prime prerequisite for efficient yield in all systems.
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    An economic evaluation of a long-term experiment on phosphorus and manure amendments to sandy Sahelian soils: Using a stochastic dominance model (1992)
    Springer
    Nutrient cycling in agroecosystems 33 (1992), S. 193-202 
    Details
    ISSN: 1573-0867
    Keywords: manure ; Niger ; phosphorus ; Sahelian soils ; stochastic dominance framework
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Poor fertility status of sandy Sahelian soils represents a major constraint to cereal and legume production. Soil amendment options were evaluated, using a stochastic efficiency framework. Dominance analyses showed that in the presence of annual applications of 30 kg N ha−1 and 30 kg K ha−1, efficient soil amendment options comprise of either the annual application of 8.7 kg P ha−1 in the form of single superphosphates in combination with 5 tonnes manure ha−1 applied every three years or the annual application of 17.5 kg P ha−1 in the form of single superphosphates. Choice between these two efficient options depends on the availability of manure, deficiencies in sandy soils and farmer resource endowments.
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    The effects of dredging and fish stocking on the trophic status of shallow, peaty ditches (1992)
    Springer
    Hydrobiologia 233 (1992), S. 225-233 
    Details
    ISSN: 1573-5117
    Keywords: ditches ; fish stock ; dredging ; biomanipulation ; eutrophication ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the polder ‘Wormer, Jisp and Nek’, which forms part of a grossly eutrophicated region in the province North Holland, the effects of dredging and biomanipulation were studied in ditches. Four areas, including 5.7 ha surface water in total, were dammed up and dredged. It was feasible to remove the loose top-layer of sediments with a high content of phosphorus by modifications of the dredging machine. In two areas the fish stock was managed. The measures resulted in an improvement of the water quality: an increase of the transparency and a decrease of suspended solids, phosphorus, nitrogen and algae. The chlorophyll-a concentration decreased nearly to 100 µg l−1 (summer average). The relative densities of diatoms, green algae and cyanobacteria did not change. The zooplankton community was dominated by small rotifers and crustaceans both before and after restoration measures. Cladocerans were scarcely present. In the second year after the measures, submerged macrophytes developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016111
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    Phytoplankton and zooplankton population dynamics and production of a recently formed African reservoir (1992)
    Springer
    Hydrobiologia 237 (1992), S. 47-60 
    Details
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; underwater light ; primary production ; secondary production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The study provides a 2.5 year record of Rhenosterkop Dam (KwaNdebele, South Africa) plankton population dynamics and production in relation to physical and chemical changes which occurred during the trophic depression and stabilization phases of the reservoir. The mean volume of the reservoir was 4% of full storage capacity. Water temperatures ranged from 14 °C to 27 °C. Due to inorganic suspensoids, the euphotic zone averaged 2.6 m. An anaerobic zone developed each summer. The nitrogen, soluble reactive phosphorus (SRP) and silica concentrations did not displaya seasonal pattern, but the latter two nutrients declined over the study. The dominant phytoplankton group was the cryptophytes while the zooplankton population was dominated by crustaceans. Chlorophyll a concentrations ranged from 1.1 to 27 mg m−3 and were positively correlated to silica and SRP concentrations and inversely with NH4-N concentrations. Primary production ranged from 22.6 to 375 mgC m−2 h−1; changes in Amax were positively correlated to silica and SRP concentrations. Total zooplankton dry weight biomass varied from 〈0.5 to 〉4 mg l−1. Annual zooplankton (secondary) production was 8 to ∼ 15 gC m−3 a−1; both primary and secondary production were greatest in the first 12 months of study and remained at low levels for the remainder, similar to the trends for silica and SRP. The data indicate that the reservoir shifted from eutrophic to mesotrophic during the study, typical of events in new reservoirs, and that changes in the plankton populations were largely the result of changing nutrient concentrations.
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    URL: http://dx.doi.org/10.1007/BF00008427
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    Response of early and late semiarid seral species to nitrogen and phosphorus gradients (1992)
    Springer
    Plant and soil 140 (1992), S. 127-135 
    Details
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphorus ; root: shoot ratios ; secondary succession ; semiarid ; shrubland ; tissue nitrogen ; tissue phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Above- and below-ground biomass production, nitrogen (N) and phosphorus (P) tissue concentrations, and root: shoot ratios were examined for five species that are characteristic of a semiarid successional sequence under controlled greenhouse conditions. In two simultaneous experiments, seedlings of one forb, two grass, and two shrub species important in a sagebrush successional sere, were subjected to seven levels of N and P. Results of the experiments suggest distinct differences in nutrient response patterns between early and late seral species. Early seral species produced more biomass but had lower tissue nutrient concentrations than late seral species. As N and P availabilities decreased, late seral species displayed characteristics indicative of increasing competitive advantage over those of early seral species. Root: shoot ratios of the five species primarily reflected patterns related to lifeform, but with some early and late seral characteristics. Results from this study 1) confirm that nutrient use pattern, nutrient availability, and seral position relationships characteristic of mesic ecosystems hold equally true for semiarid systems, and 2) suggest that nutrients are important organizing factors in semiarid ecosystems.
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    URL: http://dx.doi.org/10.1007/BF00012814
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    Stoichiometric relationships among producers, consumers and nutrient cycling in pelagic ecosystems (1992)
    Springer
    Biogeochemistry 17 (1992), S. 49-67 
    Details
    ISSN: 1573-515X
    Keywords: algae ; nitrogen ; nutrient ; phosphorus ; regeneration ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Most ecosystem models consolidate members of food-webs, e.g. species, into a small number of functional components. Each of these is then described by a single state variable such as biomass. When a multivariate approach incorporating multiple substances within components is substituted for this univariate one, a ‘stoichiometric’ model is formed. Here we show that the Nitrogen:Phosphorus ratio within zooplankton herbivores varies substantially intraspecifically but not intraspecifically. By using stoichiometric theory and recent measurements of the N:P ratio within different zooplankton taxa, we calculate large differences in ratios of nutrients recycled by different zooplankton species. Finally, we demonstrate that N:P stoichiometry can successfully account for shifts in N- and P-limitation previously observed in whole-lake experiments. Species stoichiometry merges food-web dynamics with biogeochemical cycles to yield new insights.
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    URL: http://dx.doi.org/10.1007/BF00002759
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    Effects of deuterium oxide and temperature on heart rate in Drosophila melanogaster (1992)
    Springer
    Journal of comparative physiology 162 (1992), S. 278-283 
    Details
    ISSN: 1432-136X
    Keywords: Biological oscillator ; Deuterium ; Drosophila ; Heart rate ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A non-intrusive optical technique has been developed to monitor heartbeat in late third-instar Drosophila larvae. Heartbeat in this insect is an oscillation that is not temperature compensated. Deuterium oxide lengthens the period of a number of high and low frequency oscillators and clocks in a variety of organisms. To determine whether deuterium affects heart rate, flies were raised on proteated and deuterated media and their heartbeat was monitored at four temperatures ranging from 18 to 33°C. The rate of heartbeat increased linearly with increasing temperature, and decreased with increasing concentrations of deuterium. There was a significant interaction between temperature and deuterium: the higher the concentration of deuterium oxide the less temperature-sensitive was the heart rate. Raising temperatures also increased the amount of “noise” in the rhythm: signal-to-noise ratio, which characterizes the amount of power in a rhythmic signal, decreased with increasing temperatures. Deuterium oxide had no effect on signal-to-noise ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357535
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    Energy storage during reproductive diapause in the Drosophila melanogaster species group (1992)
    Springer
    Journal of comparative physiology 162 (1992), S. 203-208 
    Details
    ISSN: 1432-136X
    Keywords: Triacylglycerols ; Glycogen ; Reproductive diapause ; Overwintering ; Drosophila
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Temperate species of the Drosophila melanogaster group enter reproductive diapause for overwintering in response to short daylength. During the prediapause period they accumulate triacylglycerols, but not glycogen, as energy resources. The capacity for storing triacylglycerols differs between species, and appears to be closely correlated with diapause and cold-hardiness; cool-temperate species, such as those of the auraria species complex, which enter a deep diapause and are highly cold-hardy, accumulate larger quantities of triacylglycerols than warm-temperate species, such as D. rufa and D. lutescens, which enter a weak diapause and are less cold-hardy. Among the cool-temperate spcies, D. subauraria occurs at a higher latitude and has the greatest capacity for accumulating triacylglycerols. A subtropical species, D. takahashii, which has no diapause in nature and is not cold-hardy, is unable to store the same quantities of triacylglycerols as temperate species.
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    URL: http://dx.doi.org/10.1007/BF00357524
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    Nutrient and hydrologic budgets of a great lakes coastal freshwater wetland during a drought year (1992)
    Springer
    Wetlands ecology and management 1 (1992), S. 211-222 
    Details
    ISSN: 1572-9834
    Keywords: freshwater marsh ; freshwater wetland ; Great Lakes ; hydrology ; phosphorus ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A coastal wetland along Lake Erie (Ohio, U.S.A.) was studied to determine hydrologic and phosphorus budgets and spatial and temporal variation of phosphorus and related chemical parameters. The wetland was influenced by changing Lake Erie water levels, seiches, shifting shoreline sediments, and watershed inflow during a year of severe drought. The water budget for a 7-month period (March – September, 1988) had average inflow of 15 200 m3 day−1 from the watershed and 3.5 m3 day−1 from Lake Erie. The wetland increased in volume by 700 m3 day−1 despite a drought that resulted in 80% more evapotranspiration than rainfall as a barrier beach isolated the wetland from Lake Erie for 77% of the study period. Conductivity decreased by 34% as water flowed through the wetland and turbidity and total suspended solids were variable and statistically similar at inflow and outflow. Average total phosphorus concentrations in the inflow and outflow were also similar (247 and 248 µg P l−1 respectively) although total soluble phosphorus and soluble reactive phosphorus decreased significantly (α=0.05) from inflow to outflow (averages 94 to 45 µg P l−1 and 7.5 to 4.0 µg P l−1 respectively). Nutrient budgets from field data estimate a retention of 36% of the phosphorus, presumably in the sediments (0.8 mg P m−2 day−1). A general nutrient retention model, an estimated deposition rate from a sediment core and a simulation model predicted higher mass retention of phosphorus but similar percentage retention. Sommaire Un marecage qui côtoie le lac Erie (USA) a servi de site expérimental pour en déterminer les budgets d'eau et de phosphore, de même que pour la variation spatiale et temporelle du phosphore et d'autres facteurs chimiques. Le marécage a été influencé par: niveaux d'eau qui changeaient; seiches; sédiments mouvants du littoral; et afflux de la ligne de partage des eaux dans une année de grande sécheresse. Le budget d'eau dans une période de 7 mois (mars–septembre 1988) montre un afflux de 15 200 m3 jour−1 de la ligne de partage, et 3.5 m3 jour−1 du lac Erie. Le volume du marécage a augmenté par 700 m3 jour−1 malgré une sécheresse qui a produit plus d'évapotranspiration (80%) que de pluie pendant qu'une plage-obstacle a isolé le marecage du lac Erie pendant 77% de la période d'observation. La conductivité a diminué par 34% pendant que l'eau coulait, et la turbidité et les TSS ont varié, tout en démontrant des statistiques similaires à l'afflux et au déversement. Les moyennes pour les concentrations du total du phosphore à l'afflux et au déversement ont été similaires (247 and 248 µg P l−1), quoique le TSP et le SRP ont diminué (α=0.05) de l'afflux au déversement (donant des moyennes de 94 à 45 µg P l−1 et de 7.5 à 4.0 µg P l'−1). Les budgets de substances nutritives pour les données suggèrent une reténtion de 36% du phosphore, évidemment dans les sédiments (0.8 mg P m−2 jour−1). Un modèle pour la rétention des nutrients, un taux de déposition, estimé par un noyau de sédiments, et une simulation avaient prédit un plus grand taux de rétention de phosphore, mais un pourcentage similaire pour la rétention.
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    URL: http://dx.doi.org/10.1007/BF00244926
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    Rhizome dynamics and resource storage in Phragmites australis (1992)
    Springer
    Wetlands ecology and management 1 (1992), S. 239-247 
    Details
    ISSN: 1572-9834
    Keywords: biomass ; carbohydrates ; nitrogen ; phosphorus ; Phragmites australis ; potassium ; reed ; rhizome ; translocation ; wetland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands. Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (〈 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m−2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June. Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (〉 1000 g m−2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites. The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that “reloading” of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management. Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves.
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    URL: http://dx.doi.org/10.1007/BF00244929
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    Bio-availability of iron from spinach (Spanicia oleracea) cultivated in soil fortified with graded levels of iron (1992)
    Springer
    Plant foods for human nutrition 42 (1992), S. 313-318 
    Details
    ISSN: 1573-9104
    Keywords: Iron availability ; phosphorus ; soil iron level ; ascorbic acid ; oxalic acid ; spinach
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In vitro availability of iron along with ascorbic acid, oxalic acid and phosphorus content of two varieties of spinach (Pusa Jyoti and Allgreen) cultivated in soil with different levels of added iron was determined. Addition of graded levels of iron to soil markedly increased the total iron and phosphorus contents and significantly decreased the bio-availability of iron, ascorbic acid and oxalic acid contents of spinach. Ascorbic acid and oxalic acid contents markedly exerted a positive influence while phosphorus exerted a negative influence on the bio-availability of iron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02194092
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    Inhibition ofSchizachyrium scoparium (poaceae) by the allelochemical hydrocinnamic acid (1992)
    Springer
    Journal of chemical ecology 18 (1992), S. 2095-2105 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; Schizachyrium scoparium ; Ceratiola ericoides ; hydrocinnamic acid ; nitrogen ; phosphorus ; potassium ; fire ; sand pine scrub ; sandhill
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Bare zones around shrubs in the Florida scrub indicate the possibility of allelopathy by shrubs controlling the distribution of grasses invading from adjacent sandhills. The allelochemical, hydrocinnamic acid, has been identified as a breakdown product of ceratiolin, which is released from the shrubCeratiola ericoides. Here, hydrocinnamic acid (HCA) was shown to have a strongly inhibitory effect on shoot and root biomass of the grassSchizachyrium scoparium in greenhouse bioassays lasting 4.5 months. Linear increases in the concentration of HCA from 0 to 200 ppm, applied biweekly, resulted in exponential decreases in root and shoot biomass at harvest. Plants grown at 200 ppm HCA had root and shoot biomasses 13% and 17% of controls, respectively. Concurrent investigation of reduced nutrient levels indicated greater inhibition by HCA in a reduced nitrogen (N) treatment and in a reduced potassium (K) treatment relative to HCA inhibition in the full nutrient treatment. The negative slopes of the regressions of log of biomass on HCA concentration were steepest in the reduced N and reduced K treatments. Root and shoot biomasses in reduced N treatments were 20–43% and 24–34% less than the respective biomasses in the full nutrient treatment. Comparable reductions in the reduced K treatment were as much as 19% and 10% for root and shoot biomasses, respectively. The effects of HCA in a reduced phosphorus (P) treatment and in a reduced P and K treatment were not significantly different from the effects of HCA in the full nutrient treatment. Extraction of the soils at harvest indicated no buildup of HCA at the end of the experiment. The sensitivity ofSchizachyrium scoparium to HCA in general and increased sensitivity under low N and low K solutions may be important in the Florida scrub community where levels of N and K are known to be low.
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    URL: http://dx.doi.org/10.1007/BF00981930
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