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  • Articles  (781)
  • Mitochondria  (539)
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  • 1
    Electronic Resource
    Electronic Resource
    The Dynamics of a Fish Stock Exploited in Two Fishing Zones (2000)
    Springer
    Acta biotheoretica 48 (2000), S. 207-218 
    Details
    ISSN: 1572-8358
    Keywords: Dynamical population ; fishing efforts ; metapopulation ; time scales ; aggregation method ; equilibrium ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010208910738
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  • 2
    Electronic Resource
    Electronic Resource
    Mitochondrial role in life and death of the cell (2000)
    Springer
    Journal of biomedical science 7 (2000), S. 2-15 
    Details
    ISSN: 1423-0127
    Keywords: Apoptosis ; Mitochondria ; Necrosis ; Oxidative stress ; Reactive oxygen species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mitochondria are the major ATP producer of the mammalian cell. Moreover, mitochondria are also the main intracellular source and target of reactive oxygen species (ROS) that are continually generated as by-products of aerobic metabolism in human cells. A low level of ROS generated from the respiratory chain was recently proposed to take part in the signaling from mitochondria to the nucleus. Several structural characteristics of mitochondria and the mitochondrial genome enable them to sense and respond to extracellular and intracellular signals or stresses in order to sustain the life of the cell. It has been established that mitochondrial respiratory function declines with age, and that defects in the respiratory chain increase the production of ROS and free radicals in mitochondria. Within a certain concentration range, ROS may induce stress responses of the cell by altering the expression of a number of genes in order to uphold energy metabolism to rescue the cell. However, beyond this threshold, ROS may elicit apoptosis by induction of mitochondrial membrane permeability transition and release of cytochrome c. Intensive research in the past few years has established that mitochondria play a pivotal role in the early phase of apoptosis in mammalian cells. In this article, the role of mitochondria in the determination of life and death of the cell is reviewed on the basis of recent findings gathered from this and other laboratories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02255913
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  • 3
    Electronic Resource
    Electronic Resource
    Kalilo plasmids are a family of four distinct members with individual global distributions across species (2000)
    Springer
    Current genetics 37 (2000), S. 39-44 
    Details
    ISSN: 1432-0983
    Keywords: Key words Kalilo ; Plasmid ; Neurospora ; Mitochondria ; Senescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Kalilo is a linear 9-kb plasmid, isolated originally from Hawaiian strains of the heterothallic fungus Neurospora intermedia. Its properties include terminal inverted repeats, two ORFs coding for a presumptive DNA and an RNA polymerase, and the ability to cause senescence in its original host and in the closely related species Neurospora crassa. We have examined natural isolates alleged to contain plasmids homologous to kalilo. Most of these isolates do in fact contain plasmids with so close an identity to kalilo as to be certain relatives. We found a new case of kalilo in Neurospora tetrasperma from Moorea-Tahiti, and a new case of LA-kalilo (previously found only in N. tetrasperma) in N. crassa from Haiti. A previously unreported, substantially shorter, kalilo variant has been found in three geographically separate isolates of the heterothallic species Neurospora discreta. Therefore, if the previously reported kalilo variant from the genus Gelasinospora is included, in all there are four members of the kalilo plasmid family. The main differences between these plasmids are in the terminal inverted repeats (TIRs). The phylogeny of the TIR sequences is largely congruent with that of nuclear DNA in the species in which they are found, suggesting that the plasmids are related by vertical descent throughout the evolution of these species. However, there are two cases of a plasmid found in a heterothallic and a pseudohomothallic species in the same global area; these cases might have arisen from more recent horizontal transmission or introgression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050006
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of the plastome and chondriome origin in plants regenerated after asymmetric Solanum ssp. protoplast fusions (2000)
    Springer
    Theoretical and applied genetics 101 (2000), S. 336-343 
    Details
    ISSN: 1432-2242
    Keywords: Key words Potato ; Mitochondria ; Chloroplast ; Asymmetric hybrids ; Cybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Protoplasts from potato cultivars used as recipient parents were fused with irradiated protoplasts from wild Solanum donor species. Regenerated plants were analysed by RAPDs to identify hybrids. Irradiation of donor protoplasts with ionizing irradiation induced a broad range of donor nuclear DNA elimination in the asymmetric hybrids. Usage of chloroplast (cp)- and mitochondrial (mt)-specific PCR markers made it possible to trace the different origins of the cp genome in seven fusion combinations, as well as the mt genomes in two fusion combinations. Regenerated plants with recipient nucleus and plastome markers from the donors were found in six of the seven analysed fusion combinations. Protoplast fusion has generated novel mt genome combinations consisting of different portions of the mt genomes from the fusion partners. Selection of heterofusion products based on fluorescence markers is an efficient method to obtain asymmetric Solanum hybrids and cy- brids from most fusion combinations. Possible models for cybrid formation are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051488
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic analysis of fertility restoration and accumulation of ORF125 mitochondrial protein in the kosena radish (Raphanus sativus cv. Kosena) and a Brassica napus restorer line (2000)
    Springer
    Theoretical and applied genetics 100 (2000), S. 949-955 
    Details
    ISSN: 1432-2242
    Keywords: Key words. Fertility Restoration (Rf) ; Cytoplasmic male sterility (CMS) ; Raphanus sativus L. ; Brassica napus ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The genetics of fertility restoration (Rf) of kosena radish CMS has been characterized. The kosena CMS-Rf system is genetically the same as that of the ogura CMS-Rf system. Two dominant genes that act complementary to the restoration of fertility control fertility restoration in kosena CMS. One allele (Rf1) is associated with accumulation of the CMS-associated protein, ORF125. The interaction of Rf1 and another allele (Rf2) was essential for the restoration of fertility in radish, whereas Rf1 alone was sufficient for the complete restoration of fertility in the B. napus kosena CMS cybrid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051375
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  • 6
    Electronic Resource
    Electronic Resource
    The nad4L-orf25 gene cluster is conserved and expressed in sugar beet mitochondria (2000)
    Springer
    Theoretical and applied genetics 100 (2000), S. 214-220 
    Details
    ISSN: 1432-2242
    Keywords: Key words Nad4L-orf25 linkage ; RNA editing ; Sugar beet ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We have found that a gene coding for NADH dehydrogenase subunit 4L and a presumed gene, orf25, are linked and co-transcribed with each other in sugar beet mitochondria. Ten and twelve C-to-U editing events were observed in the mRNAs of nad4L and orf25, respectively; the amino-acid sequence specified after editing is better-conserved in comparison with the homologues of other organisms. It is interesting to note that the translation initiation codon of nad4L is created by editing. The conservation of the nad4L-orf25 linkage was examined by PCR-amplification of the intergenic region. We obtained successful PCR products from five dicots (spinach, apple, snapdragon, petunia and tobacco) and two monocots (tulip and pineapple), but not in two poaceous plants, rice and maize. The intergenic region, when present, was found to be well-conserved in its sequence, suggesting a monophyletic origin of this linkage. Our result, together with previous reports of Arabidopsis and four poaceous species, favour the argument that the nad4L-orf25 linkage is conserved throughout angiosperms except in the Poaceae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050029
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  • 7
    Electronic Resource
    Electronic Resource
    Long-term monitoring of benthic macroinvertebrate community structure: a perspective from a Colorado river* (2000)
    Springer
    Aquatic ecology 34 (2000), S. 261-278 
    Details
    ISSN: 1573-5125
    Keywords: discharge effects on lotic invertebrates ; disturbance ; persistence ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites indicated that several chemical parameters, including conductivity, un-ionized NH3-N and NO2-N have increased since the beginning of the study within most sites. Levels of some parameters (e.g., dissolved oxygen, un-ionized NH3-N) violated aquatic life standards a few times during the study. Over 175 taxa of macroinvertebrates (primarily insects) were collected in the study reach from 1981–1996. Results from detrended correspondence analyses (DCA) on macroinvertebrate data indicated that this stretch of the river exhibited little longitudinal change beyond the two farthest upstream sites. There was a decline in macroinvertebrate density and total number of taxa within most individual sites during 1983–1984, corresponding with the highest recorded discharge in 75 years (1983) and a prolonged, heavy spring runoff in 1984. Taxa richness and density recovered to pre-1983 levels within a few months to a year following the high flows at most sites. These findings suggested that the macroinvertebrate assemblages had low resistance to disturbance, but high resilience. However, the results from DCAs and Kendall's Coefficient of Concordance (W) on individual sites for the entire study period suggested a similar macroinvertebrate community structure through time. It would appear that the composition and abundance of the lotic macroinvertebrate assemblages in the Poudre River has remained relatively constant over the long-term. This has occurred even with some potentially negative changes in water chemistry and increased urban development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009989510721
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  • 8
    Electronic Resource
    Electronic Resource
    Som1, a third component of the yeast mitochondrial inner membrane peptidase complex that contains Imp1 and Imp2 (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 483-491 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; Mitochondria ; Protein export ; Inner membrane peptidase Imp ; SOM1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mitochondrial inner membrane peptidase Imp is required for proteolytic processing of the mitochondrially encoded protein Cox2, the nucleus-encoded Cyt b2, Mcr1, and Cyt c1, and possibly other proteins, during their transport across the mitochondrial membranes. The peptidase contains two catalytic subunits, Imp1 and Imp2. The small protein Som1 was previously shown to affect the function of Imp1, but the precise role of Som1 remained unknown. Using mutants deleted for IMP1, IMP2 and SOM1, we show here that the Som1 protein is absent in the imp1Δ mutant, whereas the level of the Imp1 subunit of the peptidase is only slightly reduced in the som1 null mutant. The Som1 protein is not essential for proteolytic processing of Cyt b2, while the two other known Imp1 substrates, Cox2 and Mcr1, are not processed in the absence of Som1. Proteolytic processing of Cyt c1 by the Imp2 subunit, and of Ccp by an as yet unidentified peptidase, is not impaired in the som1 deletion mutant. By crosslinking and co-immunoprecipitation assays we demonstrate that the Imp1 and Som1 proteins physically interact. We conclude from our results that stabilisation of Som1 and correct Imp1 function is mediated by a direct interaction between the Imp1 and Som1 proteins, suggesting that Som1 represents a third subunit of the Imp peptidase complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380051192
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  • 9
    Electronic Resource
    Electronic Resource
    The Holliday junction resolvase SpCCE1 prevents mitochondrial DNA aggregation in Schizosaccharomyces pombe (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 889-897 
    Details
    ISSN: 1617-4623
    Keywords: Key words DNA repair ; Endonuclease ; Holliday junction ; Mitochondria ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract SpCCE1 (YDC2) from Schizosaccharomyces pombe is a DNA structure-specific endonuclease that resolves Holliday junctions in vitro. To investigate the in vivo function of SpCCE1 we made an Spcce1::ura4 + insertion mutant strain. This strain is viable and, despite being devoid of the Holliday junction resolvase activity that is readily detected in fractionated extracts from wild-type cells, exhibits normal levels of UV sensitivity and spontaneous or UV-induced mitotic recombination. In accordance with the absence of a nuclear phenotype, we show by fluorescence microscopy that a SpCCE1-GFP fusion localises exclusively to the mitochondria of S. pombe. In Saccharomyces cerevisiae the homologue of SpCCE1, CCE1, is known to function in the mitochondria where its role appears to be to remove recombination junctions and thus facilitate mitochondrial DNA segregation. A similar function can probably be attributed to SpCCE1 in S. pombe, since the majority of mitochondrial DNA from the Spcce1::ura4 + strain is in an aggregated form apparently due to extensive interlinking of DNA molecules by recombination junctions. Surprisingly, this marked effect on the conformation of mitochondrial DNA results in little or no effect on proliferation or viability of the Spcce1::ura4 + strain. Possible explanations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380000256
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  • 10
    Electronic Resource
    Electronic Resource
    Rna14p, a component of the yeast nuclear Cleavage / Polyadenylation Factor I, is also localised in mitochondria (2000)
    Springer
    Molecular genetics and genomics 262 (2000), S. 1103-1112 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; 3′-End mRNA processing ; Mitochondria ; Bi-functional protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract RNA14 was identified as a gene involved in premessenger RNA cleavage and polyadenylation. These processing steps take place in the nucleus, but the Rna14p protein is distributed in both the nucleus and the cytoplasm. By subcellular fractionation, we show here that the cytoplasmic fraction is localised in the mitochondria. In order to understand the role played by Rna14p in mitochondria, we have searched for new thermosensitive alleles of RNA14. We isolated thirteen new mutants. Some of them are deficient in mRNA cleavage and polyadenylation at the restrictive temperature – like the first mutant identified (rna14-1). However, others do not appear to be impaired in any of the steps in RNA metabolism investigated, nor do they appear to be involved in the replication or expression of mitochondrial DNA or in respiration. The localisation data strongly suggest that, besides an essential function in mRNA polyadenylation, the Rna14p protein has a non essential function in mitochondrial metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00008653
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  • 11
    Electronic Resource
    Electronic Resource
    Unique positioning of mitochondria in developing microspores and pollen grains inPharbitis nil: mitochondria cover the nuclear surface at specific developmental stages (2000)
    Springer
    Protoplasma 213 (2000), S. 74-82 
    Details
    ISSN: 1615-6102
    Keywords: 3,3′-dihexyloxacarbocyanine iodide ; Male gametogenesis ; Mitochondria ; Nuclear envelope ; Pollen ; Pharbitis nil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Changes in the number and distribution of mitochondria in microspores and pollen grains during male gametogenesis inPharbitis nil were examined with Technovit sections stained with 3,3′-dihexyloxacarbocyanine iodide. The number of mitochondria per microspore or pollen grain ofP. nil increased constantly and dramatically during male gametogenesis. During this process, mitochondria exhibited characteristic localizations: subpopulations of mitochondria covered the surface of the microspore and vegetative nuclei before and again just after postmeiotic mitosis I (9 and 5 days before flowering, respectively). The mitochondria also surrounded the generative nucleus 2 days after postmeiotic mitosis I (5 days before flowering), although the density of mitochondria on the nuclear surface was lower. Electron microscopy showed that the mitochondria were about 30 nm from the nuclear envelope and that each mitochondrion was located near a nuclear pore. The characteristic localization of mitochondria inP. nil pollen may serve as a model to analyze the mechanisms that control mitochondrial positioning within a cell and interactions between mitochondria and nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280507
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  • 12
    Electronic Resource
    Electronic Resource
    Isolation and characterization of the wheat prolyl isomerase FK506-binding protein (FKBP) 73 promoter (2000)
    Springer
    Plant molecular biology 42 (2000), S. 489-497 
    Details
    ISSN: 1573-5028
    Keywords: ABA-responsive ; FKBP73 ; promoter ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The wheat FK506-binding protein (FKBP) 73 is a member of the peptidyl prolyl cis-trans isomerase gene family, which catalyses the interconversion between the cis and trans forms of the peptide bond preceding proline residues in proteins. A 3.5 kb sequence 5′ upstream of the ATG codon of the wheat FKBP73 was isolated from a wheat genomic library, and characterized by deletion analysis and transient expression in wheat embryos. The 1517 bp fragment is referred to as the full promoter due to the maximal activity of the fused luciferase reporter gene. Sequence analysis revealed the presence of three abscisic acid (ABA)-responsive elements (ABREs) proximal to coupling elements (CE1-like), a putative lectin box, two putative binding sites for the myb transcription factor and a 36 bp fragment which exhibits 100% identity to the pSau3A9 clone located in the centromeric region of wheat chromosomes. In a transient expression assay the promoter preserved the tissue specificity described in vivo, namely it is expressed only in germinating embryos and young shoots. The promoter was induced 1.9-fold by ABA, the minimal promoter was designated at −221 and the TATA box located at −137. The inducibility by ABA and the expression during germination may indicate that FKBP73 belongs to the group of genes induced by ABA upon germination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006345411056
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  • 13
    Electronic Resource
    Electronic Resource
    Intron-mediated gusA expression in tritordeum and wheat resulting from particle bombardment (2000)
    Springer
    Plant molecular biology 42 (2000), S. 615-622 
    Details
    ISSN: 1573-5028
    Keywords: introns ; maize ubiquitin promoter ; tritordeum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The promoterless maize ubiquitin first exon and intron fragment can drive gusA expression in immature tritordeum inflorescences and immature wheat scutella. In fluorescence assays, this fragment induces gusA expression in tritordeum inflorescences to 50 times higher than background. The activity of the complete promoter, exon and intron cassette was up to 20 000-fold higher than background but the maize ubiquitin promoter in isolation had very low activity. A construct with the maize alcohol dehydrogenase first exon and intron had low activity, visible in histochemical assays. Both intron sequences have promoter-like features and in the ubiquitin intron there is a sequence homologous to the opaque-2-binding box. We suggest that the combination of these elements may explain the promoter activity detected in these introns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006331831858
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  • 14
    Electronic Resource
    Electronic Resource
    A rapid induction by elicitors of the mRNA encoding CCD-1, a 14 kDa Ca2+-binding protein in wheat cultured cells (2000)
    Springer
    Plant molecular biology 42 (2000), S. 807-817 
    Details
    ISSN: 1573-5028
    Keywords: Ca2+-binding protein ; EF-hand ; elicitor ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intracellular Ca2+ has been implicated in the signal transduction processes during the development of the plant defense system against fungal pathogens. From wheat cultured cells that had been treated with the elicitor derived from Typhula ishikariensis, the ccd-1 gene encoding a 14 kDa Ca2+-binding protein with an acidic amphiphilic feature was isolated. The ccd-1-encoded protein (CCD-1) shares homology to the C-terminal half domain of centrin, a Ca2+-binding protein conserved in eukaryotes. Unlike typical eukaryotic centrins, CCD-1 contains only one Ca2+-binding loop, which corresponds to the one in the fourth EF-hand from the N-terminus of centrin. The recombinant CCD protein expressed in Escherichia coli bound to a phenyl-Sepharose column in the presence of Ca2+ and was eluted out by EGTA. It also showed a Ca2+-dependent electrophoretic mobility shift on the non-denaturing polyacrylamide gel. The ccd-1 mRNA expression was rapidly induced by treatment with fungal and chitosan oligosaccharide elicitors, implying that it might have a role in transducing Ca2+ signals provoked by the elicitors. The expression of the ccd-1 mRNA was induced by treatment with A23187, and the induction was suppressed by La3+ or 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). This study suggests the involvement of intracellular Ca2+ in the elicitor-induced mRNA expression of a novel class of Ca2+-binding proteins conserved in higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006431724090
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  • 15
    Electronic Resource
    Electronic Resource
    Determination of primary structure of amberjack myosin heavy chain and its relationship with structural stability of various fish myosin rods (2000)
    Springer
    Fish physiology and biochemistry 23 (2000), S. 283-294 
    Details
    ISSN: 1573-5168
    Keywords: amberjack ; myosin heavy chain ; cDNA ; α-helix ; coiled coils ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural stability of fish myosin depends upon species and temperatures of water in which fish live. Primary, secondary, and quaternary structures of myosin heavy chain (MyHC) from three species of fish living at different temperature ranges have been compared with those of rabbit MyHC in order to investigate the differences in stability. Primary structure of MyHC, although being accessible for warm-water and cold-water fish (carp and walleye pollack), was not available in previous for tropical-water fish literature; so in this study primary structure of MyHC of the tropical-water fish amberjack has been determined by cloning and sequencing its cDNA. The MyHC has 1938 amino acid residues (AA), which are almost as much as as those of carp and walleye pollack. The amberjack MyHC is 91–95% homologous with other fish and rabbit MyHCs. There is a discernible difference between animal species with stable myosin rod (amberjack, carp, and rabbit) and walleye pollack with unstable rod. Stable rod species have a high probability of forming coiled-coil around the COOH-terminal end of the rod, while the pollack has a low coiled-coil formation probability. In addition, the average scores of the coiled-coil for myosin rod were rabbit (1.738) 〉 amberjack (1.691) 〉 carp (1.680) 〉 walleye pollack (1.674) which correlated exactly with the observed stability. The results suggest that coiled-coil forming ability, particularly around the COOH-terminal end, directs structural stability of fish myosin rod.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011176105285
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  • 16
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    Mitochondrial Calcium Signaling Driven by the IP3 Receptor (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 15-25 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; endoplasmic reticulum ; Ca2+ ; IP3 ; local signaling ; energy metabolism ; apoptosis ; necrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Many agonists bring about their effects on cellular functions through a rise incytosolic [Ca2+]([Ca2+]c) mediated by the second messenger inositol 1,4,5-trisphosphate (IP3). Imaging studiesof single cells have demonstrated that [Ca2+]c signals display cell specific spatiotemporalorganization that is established by coordinated activation of IP3 receptor Ca2+ channels.Evidence emerges that cytosolic calcium signals elicited by activation of the IP3 receptors areefficiently transmitted to the mitochondria. An important function of mitochondrial calciumsignals is to activate the Ca2+-sensitive mitochondrial dehydrogenases, and thereby to meetdemands for increased energy in stimulated cells. Activation of the permeability transitionpore (PTP) by mitochondrial calcium signals may also be involved in the control of cell death.Furthermore, mitochondrial Ca2+ transport appears to modulate the spatiotemporal organizationof [Ca2+]c responses evoked by IP3 and so mitochondria may be important in cytosolic calciumsignaling as well. This paper summarizes recent research to elucidate the mechanisms andsignificance of IP3-dependent mitochondrial calcium signaling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005504210587
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  • 17
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    Localization of the Site of Oxygen Radical Generation inside the Complex I of Heart and Nonsynaptic Brain Mammalian Mitochondria (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 609-615 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; free radicals ; complex I ; superoxide ; iron—sulfur centers ; submitochondrial particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Mitochondrial production of oxygen radicals seems to be involved in many diseases and aging. Recent studies clearly showed that a substantial part of the free radical generation of rodent mitochondria comes from complex I. It is thus important to further localize the free radical generator site within this respiratory complex. In this study, superoxide production by heart and nonsynaptic brain submitochondrial particles from up to seven mammalian species, showing different longevities, were studied under different conditions. The results, taking together, show that rotenone stimulates NADH-supported superoxide generation, confirming that complex I is a source of oxygen radicals in mammals, in general. The rotenone-stimulated NADH-supported superoxide production of the heart and nonsynaptic brain mammalian submitochondrial particles was inhibited both by p-chloromercuribenzoate and by ethoxyformic anhydride. These results localize the complex I oxygen radical generator between the ferricyanide and the ubiquinone reduction site, making iron—sulfur centers possible candidates, although unstable semiquinones can not be discarded. The results also indicate that the previously described inverse correlation between rates of mitochondrial oxygen radical generation and mammalian longevity operates through mechanisms dependent on the presence of intact functional mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005626712319
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  • 18
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    Yeast Mitochondrial Carriers: Bacterial Expression, Biochemical Identification and Metabolic Significance (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 67-77 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; transport ; overexpression ; dicarboxylate carrier ; ACR1 gene ; succinate-fumarate exchange ; ARG11 gene; ornithine carrier ; arginine biosynthesis ; yeast ; metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The genome of Saccharomyces cerevisiae encodes 35 members of a family proteins thattransport metabolites and substrates across the inner membranes of mitochondria. They includethree isoforms of the ADP/ATP translocase and the phosphate and citrate carriers. At the startof our work, the functions of the remaining 30 members of the family were unknown. We areattempting to identify these 30 proteins by overexpression of the proteins in specially selectedhost strains of Escherichia coli that allow the carriers to accumulate at high levels in the formof inclusion bodies. The purified proteins are then reconstituted into proteoliposomes wheretheir transport properties are studied. Thus far, we have identified the dicarboxylate,succinate-fumarate and ornithine carriers. Bacterial overexpression and functional identification, togetherwith characterization of yeast knockout strains, has brought insight into the physiologicalsignificance of these transporters. The yeast dicarboxylate carrier sequence has been used toidentify the orthologous protein in Caenorhabditis elegans and, in turn, this latter sequencehas been used to establish the sequence of the human ortholog.
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    Transport of Ca2+ from Sarcoplasmic Reticulum to Mitochondria in Rat Ventricular Myocytes (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 97-104 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; sarcoplasmic reticulum ; calcium ; caffeine ; myocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Studies with electron microscopy have shown that sarcoplasmic reticulum (SR) andmitochondria locate close to each other in cardiac muscle cells. We investigated the hypothesis thatthis proximity results in a transient exposure of mitochondrial Ca2+ uniporter (CaUP) to highconcentrations of Ca2+ following Ca2+ release from the SR and thus an influx of Ca2+into mitochondria. Single ventricular myocytes of rat were skinned by exposing them to aphysiological solution containing saponin (0.2 mg/ml). Cytosolic Ca2+ concentration ([Ca2+]c)and mitochondrial Ca2+ concentration ([Ca2+]m) were measured with fura-2 and rhod2,respectively. Application of caffeine (10 mM) induced a concomitant increase in[Ca2+]c and [Ca2+]m.Ruthenium red, at concentrations that block CaUP but not SR release, diminished thecaffeine-induced increase in [Ca2+]m but not[Ca2+]c. In the presence of 1 mM BAPTA, a Ca2+ chelator,the caffeine-induced increase in [Ca2+]m was reduced substantially less than [Ca2+]c. Moreover,inhibition of SR Ca2+ pump with two different concentrations of thapsigargin caused anincrease in [Ca2+]m, which was related to the rate of [Ca2+]c increase. Finally, electronmicroscopy showed that sites of junctions between SR and T tubules from which Ca2+ is released,or Ca2+ release units, CRUs, are preferentially located in close proximity to mitochondria.The distance between individual SR Ca2+ release channels (feet or ryanodine receptors) isvery short, ranging between approximately 37 and 270 nm. These results are consistent withthe idea that there is a preferential coupling of Ca2+ transport from SR to mitochondria incardiac muscle cells, because of their structural proximity.
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    URL: http://dx.doi.org/10.1023/A:1005520714221
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    Neocentric activity of rye 5RL chromosome in wheat (2000)
    Springer
    Chromosome research 8 (2000), S. 543-554 
    Details
    ISSN: 1573-6849
    Keywords: genomic in-situ hybridization ; meiosis ; neocentromere ; rye ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The neocentric activity of a constriction located on the long arm of rye 5R chromosome (5RL) was analysed. It is not observed in normal rye but it is unusually stretched in bivalents involving 5RL telosomes in wheat–ditelosomic 5RL addition lines. In 20% of metaphase I cells, the 5RL bivalent presents the centromeres oriented to one pole and the constrictions oriented towards the opposite pole with a strong tension. In 5% of the cells, the constriction was able to orient the bivalent to the poles without tension in the centromeres. Sister chromatid cohesion, which is one of the distinct features of centromeric function, is persistent at the constriction in delayed 5RL chromosomes at anaphase I. Neither the elongation of the constriction nor the neocentric activity was observed at second meiotic division or mitosis. FISH studies showed that the 5RL constriction lacked detectable quantities of two repetitive DNA sequences, CCS1 and the 180-bp knob repeat, present at cereal centromeres and neocentromeres, respectively. We propose that, under special conditions, such as the wheat background, the normally non-centromeric DNA present at this region of 5RL acquires a specific chromatin structure, differentiated as an elongated constriction, which is able to function as a centromere.
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    URL: http://dx.doi.org/10.1023/A:1009275807397
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    Cloning and Characterization of a 35-kDa Mouse Mitochondrial Outer Membrane Protein MOM35 with High Homology to Tom40 (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 111-121 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; protein import ; Tom40 ; mammalian Tom complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract We have cloned a 35-kDa protein from a mouse cDNA library with a 25% overall amino acididentity to yTom40 and 27% identity to nTom40. This homolog to Tom40 was named MOM35.It contains two possible start codons 36 amino acids apart from each other. Both the long andthe short version of MOM35 can be imported in vitro into mouse mitochondria. The identifiedprotein is imported into the outer mitochondrial membrane and comprises a trypsin-resistancepattern similar to that of nTom40. Tom40 of N. crassa, S. cerevisiae, and the protein identifiedherein contains a highly conserved region with possible physiological importance. Subsequentinvestigation has revealed that this region interacts specifically in vitro with preproteinsproposed to be imported by a Tom40-dependent pathway.
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    Inactivation of Mitochondrial Permeability Transition Pore by Octylguanidine and Octylamine (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 193-198 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; octylguanidine ; octylamine ; carboxyatractyloside ; permeability transition ; kidney mitochondria ; nonspecific pore ; calcium ; mitochondrial calcium ; mitochondrial membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Mitochondrial permeability transition occurs through a Ca2+-dependent opening of atransmembrane pore, whose identity has been attributed to that of the adenine nucleotide translocase(ANT). In this work, we induced permeability transition by adding 0.5 μM carboxyatractyloside.The process was evaluated analyzing Ca2+ efflux, a drop in transmembrane electric gradient,and swelling. We found that the amphiphyllic cations octylguanidine and octylamine, at theconcentration of 100 μM, inhibited, almost completely, nonspecific membrane permeability.Hexylguanidine, hexylamine, as well as guanidine chloride and hydroxylamine failed to doso. The inhibition was reversed after the addition of 40 mM Li+, Na+ K+,Rb+, or Cs+; K+ wasthe most effective. We propose that the positive charge of the amines interact with negativecharges of membrane proteins, more likely the ADP/ATP carrier, while the alkyl chain penetratesinto the hydrophobic milieu of the inner membrane, fixing the reagent.
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    URL: http://dx.doi.org/10.1023/A:1005516115189
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    Distribution and Exudation of Allelochemicals in Wheat Triticum aestivum (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 2141-2154 
    Details
    ISSN: 1573-1561
    Keywords: Allelopathy ; phenolic acids ; 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one ; DIMBOA ; GC-MS-MS ; wheat ; Triticum aestivum ; weed suppression ; annual ryegrass ; Lolium rigidum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Wheat allelopathy has potential for weed suppression. Allelochemicals were identified in wheat seedlings, and they were exuded from seedlings into agar growth medium. p-Hydroxybenzoic, trans-p-coumaric, cis-p-coumaric, syringic, vanillic, trans-ferulic, and cis-ferulic acids and 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) were identified in both the shoots and roots of 17-day-old wheat seedlings and their associated agar growth medium. Wheat accessions with previously identified allelopathic activity tended to contain higher levels of allelochemicals than poorly allelopathic ones. The allelopathic compounds present in the shoots generally also were identified in the roots and in the agar medium. Allelochemicals were distributed differentially in wheat, with roots normally containing higher levels of allelochemicals than the shoots. When the eight allelochemicals were grouped into benzoic acid and cinnamic acid derivatives, DIMBOA, total coumaric, and total ferulic acids, the amount of each group of allelochemicals was correlated between the roots and the shoots. Most of the allelochemicals identified in the shoots and roots could be exuded by the living roots of wheat seedling into the agar growth medium. However, the amounts of allelochemicals in the agar growth medium were not proportional to those in the roots. Results suggest that wheat plants may retain allelochemicals once synthesized. The presence of allelochemicals in the agar growth medium demonstrated that wheat seedlings were able to synthesize and to exude phytotoxic compounds through their root system that could inhibit the root growth of annual ryegrass.
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    Mitochondrial DNA mutations in Leigh syndrome and their phylogenetic implications (2000)
    Springer
    Journal of human genetics 45 (2000), S. 69-75 
    Details
    ISSN: 1435-232X
    Keywords: Key words Leigh ; Mitochondria ; ATPase ; Phylogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Of 100 patients with the clinical diagnosis of Leigh syndrome, 21 were found to have specific enzyme defects: 15 involving cytochrome c oxidase (COX); 4, pyruvate dehydrogenase complex (PDHC); one, complex I (reduced nicotinamide adenine dinucleotide [NADH]-coenzyme Q reductase) and one, complex II (succinate-ubiquinone reductase) deficiencies. In addition to the most common form of COX deficiency, mtDNA mutations in the adenosine triphosphatase (ATPase) 6 coding region were also commonly seen. Eighteen patients (18%) had mtDNA mutations at nucleotide position (np) 8993 or 9176. The mutated DNAs were present in a heteroplasmic state, comprising more than 90% of the DNA in muscle and/or blood samples from all patients. Patients with the T-to-G mutation at np 8993 usually had early onset of the disease with rapid progression, showing the typical clinical features of Leigh syndrome. On the other hand, those with the T-to-C 8993 mutation showed a milder and more chronic course. Patients with the mutation at np 9176 showed variable courses. Phylogenetic analysis of mtDNA D-loop sequences for the patients with the ATPase 6 mutations and normal Japanese subjects revealed that a T-to-G/C mutation at np 8993 and a T-to-C mutation at np 9176 occurred many times independently in the Japanese population.
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    The gel microdrop secretion assay: Identification of a low productivity subpopulation arising during the production of human antibody in CHO cells (2000)
    Springer
    Cytotechnology 34 (2000), S. 27-37 
    Details
    ISSN: 1573-0778
    Keywords: CHO cells ; gel microdrops ; human antibody ; population parameters ; productivity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The long-term stability of high-level expression is the mostimportant factor to consider when choosing cell lines for the expression of recombinant proteins. Declining volumetricyields in large-scale fermentation can be caused by changes affecting the cell population as a whole such as loss in viability, depletion of nutrients or accumulation of metabolites affecting cell growth. Alternatively, geneticinstability may lead to the outgrowth of a less productive,metabolically favored sub-population. Currently a variety ofparameters are measured to monitor the condition of cells infermenters including glucose uptake, lactate accumulation andoxygen consumption; in addition, periodic viable cell countsallow the determination of the growth rate and viability of the population. All of these methods measure the condition ofthe cell population as a whole and changes must involve a significantly large proportion of the total culture in orderto be detectable. Here we report on a method that allows theevaluation of the productivity of individual cells. Using the gel microdrop secretion assay, we detected the appearance ofa sub-population of cells with lower productivity. Subsequentanalysis of the culture confirmed the existence of lower productivity cells with a lower vector copy number. Therefore,the single cell secretion assay proved to be a rapid method todetect and isolate a low productivity variant of the producer cell line.
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    Isolation and characterization of a human cDNA encoding a protein homologous to the 7.2-kDa protein (subunit X) of bovine ubiquinol-cytochrome C reductase (2000)
    Springer
    Journal of human genetics 45 (2000), S. 43-46 
    Details
    ISSN: 1435-232X
    Keywords: Key words Ubiquinol-cytochrome C reductase ; Subunit X ; cDNA library screening ; Mitochondria ; Respiratory chain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Through large-scale sequencing of clones randomly selected from a library of human cDNAs, we have isolated a novel human gene termed hUQCR10. Its open reading frame encodes 63 amino acids that share 88.5% identity with the sequence of bovine ubiquinol-cytochrome C reductase 7.2-kDa protein (subunit X). A single 0.6-kb transcript was expressed in all human tissues examined, but was particularly abundant in heart and skeletal muscle, tissues that consume a large amount of oxygen. The gene product therefore may play a significant role in the cellular respiratory system. In support of this hypothesis, our immunohistochemical analysis revealed that the hUQCR10 protein is located in mitochondria. A homology search using computer programs determined the chromosomal localization of the gene at 22q12.
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    Relationship between Carbon and Nitrogen Metabolisms in Photosynthesis. The Role of Photooxidation Processes (2000)
    Springer
    Photosynthetica 37 (2000), S. 519-527 
    Details
    ISSN: 1573-9058
    Keywords: alanine ; aspartate ; glycine ; glycollate ; malate ; nitrate ; serine ; sugars ; Triticum aestivum ; urea ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 14CO2 uptake in leaves of wheat plants (Triticum aestivum L.) fertilized by urea or Ca(NO3)2 (25 mol m-3) was investigated. The Warburg effect (inhibition of 14CO2 uptake by oxygen) under 0.03 vol. % CO2 concentration was observed only in non-fertilized plants. Under 0.03 vol. % CO2, the Warburg antieffect (stimulation of 14CO2 uptake by oxygen) was detected only in plants fertilized by Ca(NO3)2. Under saturating CO2 concentration (0.30 vol. %), the Warburg antieffect was observed in all variants. Under limitation of ribulose-1,5-bisphosphate carboxylase/oxygenase activity (0.30 vol. % CO2 + 1 vol. % O2), the rate of synthesis of glycollate metabolism products decreased in control and urea-fertilized plants but was enhanced in nitrate-fed plants. Hence, there was an activation of glycollate formation via transketolase reaction in fertilized plants, and the products of nitrate reduction function were oxidants in nitrate-fertilized plants whereas the superoxide radical played this role in urea-fertilized plants.
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    Interactive Effects of Sulphur Dioxide and Mineral Nutrient Supply on Photosynthetic Characteristics and Yield in Four Wheat Cultivars (2000)
    Springer
    Photosynthetica 38 (2000), S. 91-96 
    Details
    ISSN: 1573-9058
    Keywords: biomass ; carotenoids ; chlorophyll ; nutrients ; sulphur dioxide ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Field experiments were conducted on four cultivars of wheat (Triticum aestivum L.) to examine the variability in cultivar response to sulphur dioxide (SO2) under different concentrations of mineral nutrients. Thirty-days-old plants were exposed for 8 weeks to 390±20 µg m−3 (0.15 ppm) SO2 for 4 h per day, 5 d per week. Decline in net photosynthetic rate, contents of pigments and nitrogen, biomass and grain yield of each cultivars were due to SO2 at all the nutrient concentrations studied. However, the magnitude of reduction was higher in plants grown without nutrient application. On the basis of the reductions in photosynthesis and yield, the susceptibility of wheat cultivars to SO2 was in the order of Malviya 213 〉 Malviya 37 〉 Malviya 206 〉 Malviya 234 at recommended dose of NPK, whereas the same without the nutrients was Malviya 206 〉 Malviya 234 〉 Malviya 213 〉 Malviya 37.
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    Within-plant distribution of Rhopalosiphum padi on wheat seedlings is affected by induced responses (1999)
    Springer
    Entomologia experimentalis et applicata 93 (1999), S. 227-230 
    Details
    ISSN: 1570-7458
    Keywords: Rhopalosiphum padi ; cereal aphids ; wheat ; induced responses ; feeding site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003874225681
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    Comparison of Diuraphis noxia resistance in wheat isolines and plant introduction lines (1999)
    Springer
    Entomologia experimentalis et applicata 92 (1999), S. 157-164 
    Details
    ISSN: 1570-7458
    Keywords: plant resistance ; antibiosis ; tolerance ; antixenosis ; Russian wheat aphid ; wheat ; Homoptera ; Aphididae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Russian wheat aphid, Diuraphis noxia (Mordvilko), is one of the most important aphid pests of wheat, Triticum aestivum L., worldwide. Among the various pest management options, plant resistance is an economical management tactic to control D. noxia in cereal crops such as wheat. Researchers have identified D. noxia resistant germplasm and it has been incorporated into wheat. This study compared D. noxia resistance between the ‘Betta’ wheat isolines Betta-Dn1, Betta-Dn2, and Betta-Dn5 and their corresponding donor gene plant introduction (PI) lines PI 137739 (Dn1), PI 262660 (Dn2), and PI 294994 (Dn5). Although the Betta isolines and PI lines showed D. noxia resistance when compared with Betta wheat, the degree of resistance in the isolines to D. noxia was different from their corresponding PI donors. Aphid number, aphid fecundity, and biomass per aphid were not different between Betta-Dn1 and PI 137739 or Betta-Dn2 and PI 262660; however, the same parameters were significantly lower on PI 294994 compared with Betta-Dn5. This indicated that aphid resistance in PI 137739 and PI 262660 was probably governed by a single dominant gene, while the resistance in PI 294994 was controlled by more than one gene. Additionally, plant biomass reduction was aphid density dependent, which suggested that use of appropriate aphid infestation level is important when using plant biomass reduction as an indicator of resistance. Plant resistance categorization showed that there was no detectable difference in antixenosis among the seven lines evaluated. However, the higher aphid fecundity observed on PI 262660 compared with PI 137739 and PI 294994, in addition to no significant differences among the three PIs in plant biomass reduction, suggested PI 262660 was a tolerant line, while PI 137739 and PI 294994 were antibiotic lines. Plant tolerance could not be elucidated among the three Betta isolines using aphid fecundity and plant biomass reduction as indicators.
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    Salivation into sieve elements in relation to plant chemistry: the case of the aphid Sitobion fragariae and the wheat, Triticum aestivum (1999)
    Springer
    Entomologia experimentalis et applicata 91 (1999), S. 111-114 
    Details
    ISSN: 1570-7458
    Keywords: sieve element ; salivation ; aphid ; plant resistance ; wheat ; Sitobion fragariae ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Extended sieve element salivation (E1 waveform in the electrical penetration graph) is a characteristic activity during early sieve element punctures, particularly in resistant plants. In order to explore a chemically-mediated mechanism of resistance associated with sieve element salivation, we compared the pattern of feeding behaviour of the aphid, Sitobion fragariae (Walker), on two cultivars of the wheat Triticum aestivum L., with different concentrations of hydroxamic acids (Hx). During 24 h of electronic monitoring, aphids dedicated over 50% of the total time to phloem ingestion from the sieve elements. Total time allocated to E1 in the experiment, time to first E1 within the experiment, time allocated to E1 before a sustained phloem ingestion (E2) and the contribution of sieve element salivation to the phloem phase (E1/[E1+E2]) were significantly higher in the high-Hx cultivar. The increased salivation in plants with higher contents of Hx suggests the existence, at least in this system, of a chemically-mediated sieve element constraint.
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    A Modular Vector for Agrobacterium Mediated Transformation of Wheat (1999)
    Springer
    Plant molecular biology reporter 17 (1999), S. 323-331 
    Details
    ISSN: 1572-9818
    Keywords: Agrobacterium ; modular vector ; transformation ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wheat (cv Chinese Spring) tissues were transformed using Agrobacterium tumefasciens and a new plasmid modular vector, pMVTBP. We constructed pMVTBP with unique restriction sites connecting (1) the CaMV 35S promoter, (2) a Kozak sequence, (3) the FLAG epitope, (4) the (His)6 epitope, (5) a coding region (for wheat TATA Binding Protein, wTBP) and (6) the CaMV 35S 3′UTR. This vector thus allows easy exchange of different regulatory or coding sequences. Explants of either germinating mature seeds, or immature embryos, were induced to callus for up to two weeks, treated with virulence-induced bacteria for one hour, then regenerated into plantlets. Transient expression of a GUS reporter gene, assayed at about one week, occurred in 10–12% of calluses. Expression of the FLAG-tagged wTBP was also detected, by immunostaining. Stable expression, by selective growth on geneticin, and by GUS expression at about six weeks, occurred in 1–2% of calluses, quite comparable to that achieved by other methods.
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    Influence of within-field and landscape factors on aphid predator populations in wheat (1999)
    Springer
    Landscape ecology 14 (1999), S. 239-252 
    Details
    ISSN: 1572-9761
    Keywords: Coccinellidae ; Aphididae ; wheat ; spatial scale ; species diversity ; numerical response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of prey density, within-field vegetation, and the composition and patchiness of the surrounding landscape on the abundance of insect predators of cereal aphids was studied in wheat fields in eastern South Dakota, USA. Cereal aphids, aphid predators, and within-field vegetation were sampled in 104 fields over a three year period (1988–1990). The composition and patchiness of the landscape surrounding each field were determined from high altitude aerial photographs. Five landscape variables, aggregated at three spatial scales ranging from 2.6 km2 to 581 km2, were measured from aerial photographs. Regression models incorporating within-field and landscape variables accounted for 27–49% of the variance in aphid predator abundance in wheat fields. Aphid predator species richness and species diversity were also related to within-field and landscape variables. Some predators were strongly influenced by variability in the composition and patchiness of the landscape surrounding a field at a particular spatial scale while others responded to variability at all scales. Overall, predator abundance, species richness, and species diversity increased with increasing vegetational diversity in wheat fields and with increasing amounts of non-cultivated lands and increasing patchiness in the surrounding landscape.
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    Mitochondrial orf107 transcription, editing, and nucleolytic cleavage conferred by the gene Rf3 are expressed in sorghum pollen (1999)
    Springer
    Sexual plant reproduction 12 (1999), S. 53-59 
    Details
    ISSN: 1432-2145
    Keywords: Key words Cytoplasmic male sterility ; Mitochondria ; Sorghum ; RNA editing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Restoration of male fertility in the A3, IS1112C source of cytoplasmic male sterility (cms) in sorghum is exacted in a gametophytic manner. One required nuclear gene, Rf3, regulates a nucleolytic transcript processing activity, cleaving sequences internal to the chimeric mitochondrial open reading frame orf107. We examined mitochondrial transcription, RNA editing, and action of Rf3 in developing pollen from a male-sterile line, the progenitor, a male-fertile line, and the fertile F1 to determine if these expression processes were manifested at the haploid pollen stage. Steady-state levels of orf107 transcripts and nucleolytic processing conferred by Rf3 were similar to observations from leaves, indicating comparable expression in pollen. RNA editing frequency at two of three sites in orf107 was differentially suppressed compared to leaves, but editing was higher in male-sterile plants than in fertile plants, consistent with the possibility that nucleolytic cleavage is enhanced by editing. The differential suppression of editing frequency at two sites in orf107 contrasts with near-complete editing of a third site in orf107, shared with atp9, indicating that factors influencing editing frequency of the chimeric transcript are temporally regulated and sequence-specific. Since action of the nuclear gene Rf3 is manifested at the diploid and haploid stages, pollen-specific expression of this fertility restoration gene is not required in the A3 gametophytic cms system.
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    Cloning and expression of the cDNA encoding an alternative oxidase gene from Aspergillus niger WU-2223L (1999)
    Springer
    Current genetics 34 (1999), S. 472-477 
    Details
    ISSN: 1432-0983
    Keywords: Key words Alternative oxidase ; Aspergillus niger ; Cyanide-insensitive respiration ; Mitochondria ; Salicylhydroxamic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A cDNA fragment encoding the mitochondrial alternative oxidase, the enzyme responsible for cyanide-insensitive and salicylhydroxamic acid (SHAM)-sensitive respiration, from the citric acid-producing fungus Aspergillus niger WU-2223L was cloned and expressed in Escherichia coli as a host strain. Synthetic primers were designed from the conserved nucleotide sequences of the alternative oxidase genes from higher plants and a yeast. The 210-bp DNA fragment was amplified by PCR with these primers using chromosomal DNA of WU-2223L as a template, and was employed to screen a cDNA library of A. niger. One full-length cDNA clone of 1.2 kb was obtained, and was sequenced to reveal that the clone contained an open reading frame (ORF-AOX1) encoding a polypeptide of 351 amino acids. The predicted amino-acid sequence exhibited 50%, 55%, and 52% homology to the alternative oxidases of Hansenula anomala, Neurospora crassa and Sauromatum guttatum, respectively. In the 5′-terminus region of the ORF-AOX1, a mitochondrial targeting motif was found. The whole open reading frame of ORF-AOX1 was ligated to plasmid pKK223-3 to construct the expression vector pKAOX1. The E. coli transformant harboring pKAOX1 showed cyanide-insensitive and SHAM-sensitive respiration, and expression was increased approximately two-fold by the addition of IPTG. These results indicated that the ORF-AOX1 encodes an alternative oxidase of A. niger.
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    Confirmation of predicted edits and demonstration of unpredicted edits in Acanthamoeba castellanii mitochondrial tRNAs (1999)
    Springer
    Current genetics 35 (1999), S. 23-29 
    Details
    ISSN: 1432-0983
    Keywords: Key words RNA editing ; Mitochondria ; Acanthamoeba castellanii ; Transfer RNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the amoeboid protozoon Acanthamoeba castellanii 13 of the 16 mtDNA-encoded tRNA sequences have mis-matches at one or more of the first three positions in the acceptor stem. A previous study had indicated that these mis-matches are corrected by a form of RNA editing. In the present study, the pattern of editing was further investigated by sequence analysis of both halves of the acceptor stem of 11 mtDNA-encoded tRNAs. The results confirm all of the remaining editing sites predicted on the basis of the secondary structure modelling of A. castellanii mitochondrial tRNAs, and identify two unexpected edits. We also investigated the expression and editing of transcripts of an unusual trnX gene specifying an eight-nucleotide anticodon loop sequence. Although no mature 3′-CCAOH-containing tRNAX products were detected, editing was observed in some circularized tRNAX clones. The implications of these results with respect to the mechanism of editing and the evolutionary origin of this process are discussed.
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    A novel group-II intron in the cox1 gene of the fission yeast Schizosaccharomyces pombe is inserted in the same codon as the mobile group-II intron aI2 in the Saccharomyces cerevisiae cox1 homologue (1999)
    Springer
    Current genetics 35 (1999), S. 602-608 
    Details
    ISSN: 1432-0983
    Keywords: Key wordsSchizosaccharomyces pombe ; Fission yeast ; Mitochondria ; Group-II intron ; Secondary structure ; Intron maturase ; Reverse transcriptase motif ; cox1 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We describe herein a large group-II intron which is inserted in the mitochondrial cox1 gene of the Schizosaccharomyces pombe strain EF2. The intron RNA consists of 2492 nucleotides which can be folded into a secondary structure with all the expected sequence motifs of subgroup-IIA1 introns (Michel et al. 1989). Determination of the exact splice point revealed that the intron is inserted in the same codon, but 1 bp downstream, as the mobile intron aI2 in the Saccharomyces cerevisiae cox1 homologue. A total of nine nucleotide changes was observed around the insertion site of the intron in the cox1 gene of strain EF2 compared with the reference strain ade7-50h – . Seven of these changes are clustered within the 51 bp upstream of the splice point. Only one sequence deviation was found in the downstream exon. The intron is capable of splicing despite the fact that both the EBS1/IBS1 and the EBS2/IBS2 sequence motifs, thought to be necessary for correct splicing, extend over 5 instead of 6 bp. The maturase, endonuclease and reverse transcriptase domains of the putative protein encoded by the newly described S. pombe group-II intron were not closer to those encoded by the other two, cobI and cox2I, S. pombe group-II introns than to the group-II intron-encoded proteins in Allomyces, Marchantia, Podospora and Saccharomyces.
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    Mitochondrial copper metabolism in yeast: mutational analysis of Sco1p involved in the biogenesis of cytochrome c oxidase (1999)
    Springer
    Current genetics 35 (1999), S. 103-108 
    Details
    ISSN: 1432-0983
    Keywords: Key words Yeast Sco1p ; Copper ; Cytochrome c oxidase ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Saccharomyces cerevisiae Sco1p is believed to be involved in the transfer of copper from the carrier Cox17p to the mitochondrial cytochrome c oxidase subunits 1 and 2. We here report on the results of a mutational analysis of Sco1p. The two cysteine residues of a potential metal-binding motif (CxxxC) are essential for protein function as shown by their substitution by alanines. Chimeras consisting of Sco1p and its homolog S. cerevisiae Sco2p restrict the specificity of Sco1p function to the N-terminal half of the protein. A candidate region for conferring specificity on Sco1p is a stretch of hydrophobic amino acids, which act as a membrane anchor. In line with this suggestion is the result that alterations of individual amino acids within this region impair Sco1p function.
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    Inactivation of the Neurospora crassa mitochondrial outer membrane protein TOM70 by repeat-induced point mutation (RIP) causes defects in mitochondrial protein import and morphology (1999)
    Springer
    Current genetics 36 (1999), S. 137-146 
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    ISSN: 1432-0983
    Keywords: Key wordsNeurospora ; TOM70 ; Mitochondria ; Protein import
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial biogenesis requires the efficient import of hundreds of different cytosolically translated preproteins into existing organelles. Recognition and translocation of preproteins at the mitochondrial outer membrane is achieved by the TOM complex (translocase of the outer mitochondrial membrane). The largest component of this complex is TOM70, an integral outer membrane protein with a large cytosolic domain thought to serve as a receptor for a specific group of preproteins. To investigate the functional role of TOM70 in Neurospora crassa the tom70 gene was inactivated using the natural phenomenon of repeat-induced point mutation (RIP). Mutant strains were identified that harbored RIPed tom70 alleles and contained no immunologically detectable TOM70. Strains that lack TOM70 grow more slowly than wild-type strains, conidiate poorly, and contain enlarged mitochondria. In vitro preprotein import studies using TOM70-deficient mitochondria revealed a defect in the uptake of the ADP/ATP carrier. Other preproteins tested were imported at wild-type rates with the exception of the precursor of the mitochondrial-processing peptidase (MPP) which was imported more efficiently by TOM70-deficient mitochondria. These data support the view that TOM70 plays a role as a specific receptor for carrier proteins in mitochondrial-preprotein import. The presence of tetratricopeptide repeats (TPRs) in the TOM70 sequence and the enlarged shape of mitochondria lacking TOM70 raise the possibility that the protein also plays a role in the maintenance of mitochondrial morphology.
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    Mutational analysis of yeast mitochondrial translational activator Cbs2p and of YHR063Cp, a protein with similarity to Cbs2p (1999)
    Springer
    Current genetics 36 (1999), S. 201-207 
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    ISSN: 1432-0983
    Keywords: Key words Yeast Cbs2p ; YHR063C ; Mitochondria ; Translational activator ; Mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Translation of mitochondrial cytochrome b in Saccharomyces cerevisiae requires the nuclearly encoded proteins Cbs1p, Cbs2p and Cbp6p. So far no homologs have been identified, except for the product of the S. cerevisiae orf YHR063C, which has some similarity to Cbs2p. Here we analyze the effect of a null mutation of YHR063C and show that it is not required for mitochondrial respiration. In addition, we report on the importance of the carboxyl-terminus of Cbs2p for its function. We show that truncations and some directed mutations in the carboxyl-terminal region of Cbs2p render the protein non-functional. The importance of the COOH-terminus is further underscored by the finding that mutational alteration of the cbs2-1 allele results in the substitution of Ile372 by Lys.
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    Emergence of symmetric, modular, and reciprocal connections in recurrent networks with Hebbian learning (1999)
    Springer
    Biological cybernetics 81 (1999), S. 211-225 
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    ISSN: 1432-0770
    Keywords: Key words: Hebbian learning rule ; attractor dynamics ; symmetric connections ; multiplicative normalization ; self-organization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. While learning and development are well characterized in feedforward networks, these features are more difficult to analyze in recurrent networks due to the increased complexity of dual dynamics – the rapid dynamics arising from activation states and the slow dynamics arising from learning or developmental plasticity. We present analytical and numerical results that consider dual dynamics in a recurrent network undergoing Hebbian learning with either constant weight decay or weight normalization. Starting from initially random connections, the recurrent network develops symmetric or near-symmetric connections through Hebbian learning. Reciprocity and modularity arise naturally through correlations in the activation states. Additionally, weight normalization may be better than constant weight decay for the development of multiple attractor states that allow a diverse representation of the inputs. These results suggest a natural mechanism by which synaptic plasticity in recurrent networks such as cortical and brainstem premotor circuits could enhance neural computation and the generation of motor programs.
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    Mechanisms of mitochondrial DNA escape to the nucleus in the yeast Saccharomyces cerevisiae (1999)
    Springer
    Current genetics 36 (1999), S. 183-194 
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    ISSN: 1432-0983
    Keywords: Key words Mitochondrial DNA escape ; Mitochondria ; Yeast ; Plasmids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The transfer of organelle nucleic acid to the nucleus has been observed in both plants and animals. Using a unique assay to monitor mitochondrial DNA escape to the nucleus in the yeast Saccharomyces cerevisiae, we previously showed that mutations in several nuclear genes, collectively called yme mutants, cause a high rate of mitochondrial DNA escape to the nucleus. Here we demonstrate that mtDNA escape occurs via an intracellular mechanism that is dependent on the composition of the growth medium and the genetic state of the mitochondrial genome, and is independent of an RNA intermediate. Isolation of several unique second-site suppressors of the high rate of mitochondrial DNA-escape phenotype of yme mutants suggests that there are multiple independent pathways by which this nucleic acid transfer occurs. We also demonstrate that the presence of centromeric plasmids in the nucleus can reduce the perceived rate of DNA escape from the mitochondria. We propose that mitochondrial DNA-escape events are manifested as unstable nuclear plasmids that can interact with centromeric plasmids resulting in a decrease in the number of observed events.
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    YNT20, a bypass suppressor of yme1 yme2, encodes a putative 3′-5′ exonuclease localized in mitochondria of Saccharomyces cerevisiae (1999)
    Springer
    Current genetics 34 (1999), S. 438-448 
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    ISSN: 1432-0983
    Keywords: Key words Mitochondrial DNA escape ; Mitochondria ; 3′-5′ exonuclease ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutation of YME genes in yeast results in a high rate of mitochondrial DNA escape to the nucleus. The synthetic respiratory growth defect of yme1 yme2 yeast strains is suppressed by recessive mutations in YNT20. Inactivation of YNT20 creates a cold-sensitive respiratory growth defect that is more pronounced in a yme1 background and which is suppressed by yme2. Inactivation of YNT20 causes a qualitative reduction in the rate of mitochondrial DNA escape in yme1, but not yme2, strains, suggesting that YNT20 plays a role in the yme1-mediated mitochondrial DNA escape pathway. YNT20p is a soluble mitochondrial protein that belongs to a subfamily of putative 3′-5′ exonucleases. Furthermore, conserved sequence elements in Yme2p suggest that this protein may also function as an exonuclease.
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    DNA-binding factors assemble in a sequence-specific manner on the maize mitochondrial atpA promoter (1999)
    Springer
    Current genetics 35 (1999), S. 506-511 
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    ISSN: 1432-0983
    Keywords: Key words Toeprinting ; Maize ; Mitochondria ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maize mitochondrial atpA promoter has been well-characterized using in vitro transcription. The functional elements of this promoter comprise a central domain extending from –7 to +5 relative to the transcription start site, and an upstream domain of 1–3 bp that is purine-rich and centered around positions –11 to –12. As a first step in characterizing the transcriptional machinery, exonuclease-III mapping (toeprinting) was used to map the borders of DNA-protein interactions using either a 107-bp wild-type template or transcriptionally-inactive templates containing linker-scanning mutations. These experiments revealed that, with a wild-type promoter, protein factors occupy as much as 36 bp, from positions –20 to +16 relative to the transcription initiation site. Protein-binding patterns were altered when the linker-scanning mutants were used, suggesting that either the number or conformation of DNA-binding proteins could account for their inability to promote transcription initiation.
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    Bicelle-based liquid crystals for NMR-measurement of dipolar couplings at acidic and basic pH values (1999)
    Springer
    Journal of biomolecular NMR 13 (1999), S. 187-191 
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    ISSN: 1573-5001
    Keywords: alignment ; bicelle ; dipolar coupling ; liquid crystal ; pH ; stability ; ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract It is demonstrated that mixtures of ditetradecyl- phosphatidylcholine or didodecyl-phoshatidylcholine and dihexyl- phosphatidylcholine in water form lyotropic liquid crystalline phases under similar conditions as previously reported for bicelles consisting of dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl- phosphatidylcholine (DHPC). The carboxy-ester bonds present in DMPC and DHPC are replaced by ether linkages in their alkyl analogs, which prevents acid- or base-catalyzed hydrolysis of these compounds. 15N-1H dipolar couplings measured for ubiquitin over the 2.3–10.4pH range indicate that this protein retains a backbone conformation which is very similar to its structure at pH 6.5 over this entire range.
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    Analysis of wheat mitochondrially encoded polypeptides by in organello labelling (1999)
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    Plant cell reports 19 (1999), S. 161-165 
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    ISSN: 1432-203X
    Keywords: Key words In organello labelling ; Mitochondria ; Respiratory chain ; Wheat ; Embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The in organello labeling pattern in wheat (Triticum aestivum) mitochondria isolated from imbibed embryos were compared with those from the commonly used starting material, etiolated seedlings. Mitochondria from imbibed embryos proved to be metabolically more active than those from etiolated seedlings and produced a large number of strongly in organello-labeled polypeptides. Immunoprecipitation of the labeled proteins enabled the identification of mitochondrially encoded subunits of the respiratory chain complex I, some of which could not be detected by conventional Western blotting due to their high hydrophobicity. A method for mass isolation of wheat embryos is also presented which allows easy preparation of large amounts of intact and highly active mitochondria suitable for biochemical studies.
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    Organelle DNA and male fertility variation in Solanum spp. and interspecific somatic hybrids (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 819-828 
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    ISSN: 1432-2242
    Keywords: Key words Interspecific hybridization ; Solanum ; Male fertility ; Chloroplasts ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Novel and potentially useful genetic variation in cytoplasmic genomes can be induced by interspecific somatic hybridization in plants. To evaluate such variability and correlate it with nuclear-cytoplasmic interactions leading to male sterility in Solanum spp., we examined progeny of male-sterile and male-fertile somatic hybrids between Solanum tuberosum (tbr), the common potato, and S. commersonii (cmm), a wild species showing sexual incongruity with tbr, for fertility and organelle DNA composition. Uniform male-fertile and male-sterile progenies were obtained by selfing the male-fertile hybrid and crossing the male-sterile ones, indicating maternal inheritance of the fertility phenotype. The two fusion partners were only slightly differentiated in the plastidial genome. MtDNA polymorphism between the species was greater, although its extent varied with the genomic region investigated. All somatic hybrids had non-parental organelle genomes, with reassorted organelles and/or rearranged mitochondria (i.e., cmm-specific bands for some regions and tbr-specific bands for others). Mitochondria reassorted independently from chloroplasts. Most hybrids showed the cmm cpDNA hybridization pattern, indicating non-random transmission of chloroplasts. Most male-sterile hybrids showed preferential inheritance of tbr mtDNA fragments. The male-fertile somatic hybrid clone had predominantly cmm mtDNA fragments. This result suggests that a tbr-derived region involved in nuclear-cytoplasmic incompatibility and male sterility has been lost by rearrangement; however, no clear correlation between a specific mitochondrial region and male sterility has been found so far.
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    A molecular phylogeny of bryophytes based on nucleotide sequences of the mitochondrialnad5 gene (1999)
    Springer
    Plant systematics and evolution 218 (1999), S. 179-192 
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    ISSN: 1615-6110
    Keywords: Bryophyta ; Mitochondria ; nad5 gene ; group I intron ; molecular phylogeny ; taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In contrast to animals, the slowly evolving mitochondrial nucleotide sequences of plants appear well suited to investigate phylogenetic relations between old taxonomic groups. Analysis ofnad5 gene sequences in 47 bryophytes, the living representatives of very early land plants, confirm this assessment. Statistically reliable phylogenetic trees are obtained with different mathematical approaches. A group I intron sequence conserved in thenad5 gene of all 30 mosses and 15 liverworts investigated supports a sister group relationship of the two classes. The intron sequence adds phylogenetic information for fine resolution on top of the conserved exon sequences down to the level of classically defined orders or families, respectively. This intron is not present in the hornwortsAnthoceros husnotii andA. punctatus. The results allow statements on diverging taxonomic interpretations and support the monophyly of the liverworts, mosses, Jungermanniidae, Marchantiidae and Bryidae, and allow recognition of subclasses like Hypnanae and Dicrananae. Among the mosses, the derived orders (subclass Bryidae) are confidently set apart from the Sphagnales, Andreaeales, Polytrichales and Tetraphidales with Buxbaumiales occupying a mediating position. Among the liverworts, full support is found for the classic separation of simple (jungermanniid) and complex thalloid (marchantiid) species with a strikingly low mitochondrial sequence divergence among the latter.
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    The role of competition in invertebrate community development in a recently formed stream in Glacier Bay National Park, Alaska (1999)
    Springer
    Aquatic ecology 33 (1999), S. 175-184 
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    ISSN: 1573-5125
    Keywords: Chironomidae ; interspecific competition ; streams ; stability ; succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract New streams formed following ice recession in Glacier Bay National Park, southeastern Alaska allow insights into the role of abiotic and biotic interactions in the assemblage of benthic communities. Reductions in abundance of a pioneer chironomid colonizer, Diamesa alpina/lupus, in one new stream, Wolf Point Creek, is considered to be a result of competitive interactions with subsequent colonizers, as opposed to intolerance of warmer water temperature as previously suggested. Reduced densities of potential competitors (25–50 larvae per 500 cm2) in a cobble transplant experiment between streams, allowed persistence of D. alpina/lupus at low densities. In addition, significantly more D. alpina/lupus larvae emigrated from artificial stream channels containing other chironomid taxa than channels without potential competitors while there was no significant correlation of emigration with water temperature. A small number of D. alpina/lupus transplanted from a cold stream (4–6 °C) survived at water temperatures of 10–15 °C for 1 week. These results infer that interference competition is the causal mechanism in the decline of D. alpina/lupus. Complete exclusion of D. alpina/lupus from the stream has not occurred and water temperature may play a role in partitioning D. alpina/lupus from other taxa on a temporal or a spatial basis.
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    Chloroplast suppressors that act on a mitochondrial mutation in Chlamydomonas reinhardtii (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 85-89 
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    ISSN: 1617-4623
    Keywords: Key wordsChlamydomonas reinhardtii ; Chloroplast ; Mitochondria ; Suppressor mutation ; tRNA import
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report genetic evidence supporting the existence of suppressor genes in the chloroplast that act on a mitochondrial mutation that impairs heterotrophic growth in the green alga Chlamydomonas reinhardtii. One of these suppressors also acts on a point mutation in the rbcL gene in the chloroplast. These results are consistent with previous data showing that mitochondrial protein synthesis depends on chloroplast protein synthesis in C. reinhardtii. The nature of the interaction between chloroplasts and mitochondria is discussed in light of the requirement for import of tRNAs by plant mitochondria.
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    The mitochondrial cytochrome c peroxidase Ccp1 of Saccharomyces cerevisiae is involved in conveying an oxidative stress signal to the transcription factor Pos9 (Skn7) (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 437-447 
    Details
    ISSN: 1617-4623
    Keywords: Key words Oxidative stress signalling ; Mitochondria ; Pos9 (Skn7) ; Ccp1 ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Saccharomyces cerevisiae two transcription factors, Pos9 (Skn7) and Yap1, are involved in the response to oxidative stress. Fusion of the Pos9 response-regulator domain to the Gal4 DNA-binding domain results in a transcription factor which renders the expression of a GAL1-lacZ reporter gene dependent on oxidative stress. To identify genes which are involved in the oxygen-dependent activation of the Gal4-Pos9 hybrid protein we screened for mutants that failed to induce the heterologous test system upon oxidative stress (fap mutants for factors activating Pos9). We isolated several respiration-deficient and some respiration-competent mutants by this means. We selected for further characterization only those mutants which also displayed an oxidative-stress-sensitive phenotype. One of the respiration-deficient mutants (complementation group fap6) could be complemented by the ISM1 gene, which encodes mitochondrial isoleucyl tRNA synthetase, suggesting that respiration competence was important for signalling of oxidative stress. In accordance with this notion a rho0 strain and a wild-type strain in which respiration had been blocked (by treatment with antimycin A or with cyanide) also failed to activate Gal4-Pos9 upon imposition of oxidative stress. Another mutant, fap24, which was respiration-competent, could be complemented by CCP1, which encodes the mitochondrial cytochrome c peroxidase. Mitochondrial cytochrome c peroxidase degrades reactive oxygen species within the mitochondria. This suggested a possible sensor function for the enzyme in the oxidative stress response. To test this we used the previously described point mutant ccp1 W191F , which is characterized by a 104-fold decrease in electron flux between cytochrome c and cytochrome c peroxidase. The Ccp1W191F mutant was still capable of activating the Pos9 transcriptional activation domain, suggesting that the signalling function of Ccp1 is independent of electron flux rates.
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    Analysis of programmed cell death in wheat endosperm reveals differences in endosperm development between cereals (1999)
    Springer
    Plant molecular biology 39 (1999), S. 915-926 
    Details
    ISSN: 1573-5028
    Keywords: programmed cell death ; wheat ; endosperm ; ethylene ; nucleases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although maize endosperm undergoes programmed cell death during its development, it is not known whether this developmental feature is common to cereals or whether it arose inadvertently from the selection process that resulted in the enlarged endosperm of modern maize. Examination of wheat endosperm during its development revealed that this tissue undergoes a programmed cell death that shares features with the maize program but differs in some aspects of its execution. Cell death initiated and progressed stochastically in wheat endosperm in contrast to maize where cell death initiates within the upper central endosperm and expands outward. After a peak of ethylene production during early development, wheat endosperm DNA underwent internucleosomal fragmentation that was detectable from mid to late development. The developmental onset and progression of DNA degradation was regulated by the level of ethylene production and perception. These observations suggest that programmed cell death of the endosperm and regulation of this program by ethylene is not unique to maize but that differences in the execution of the program appear to exist among cereals.
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    Elicitor- and A23187-induced expression of WCK-1, a gene encoding mitogen-activated protein kinase in wheat (1999)
    Springer
    Plant molecular biology 40 (1999), S. 921-933 
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    ISSN: 1573-5028
    Keywords: A23187 ; calcium ; elicitor ; MAP kinase ; Typhula ishikariensis ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wheat cultured cells were used to study the role of Ca2+ in regulating protein kinases during the induction of defense-related genes by fungal elicitor treatments. Manipulation of intracellular Ca2+ concentrations by treatment with calcium ionophore A23187 in the presence of high extracellular Ca2+ resulted in the induction of mRNA expression of WCK-1, a gene encoding mitogen-activated protein (MAP) kinase. The induction of WCK-1 mRNA by A23187 did not occur when extracellular Ca2+ was chelated by 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA). The WCK-1 mRNA was also induced by Typhula ishikariensis-derived elicitors, suggesting a possible involvement of WCK-1 in the plant defense response against pathogens. BAPTA and a calcium channel blocker, La3+, inhibited the elicitor-induced expression of the WCK-1 mRNA. A recombinant fusion protein of WCK-1 (GST-WCK-1) autophosphorylated at the Tyr residue and exhibited an autophosphorylation-dependent protein kinase activity towards myelin basic protein. Alteration of Tyr-196 in the conserved ‘TEY’ motif in GST-WCK-1 to Phe by site-directed mutagenesis abolished the autophosphorylation. The GST-WCK-1 protein was activated by elicitor-treated wheat cell extracts but not by the control extract. These results suggest that fungal elicitors activate WCK-1, a specific MAP kinase in wheat. Furthermore, the results suggest a possible involvement of Ca2+ in enhancing the MAP kinase signaling cascade in plants by controlling the levels of the MAP kinase transcripts.
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    URL: http://dx.doi.org/10.1023/A:1006263607135
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    A starch-branching enzyme gene in wheat produces alternatively spliced transcripts (1999)
    Springer
    Plant molecular biology 40 (1999), S. 1019-1030 
    Details
    ISSN: 1573-5028
    Keywords: alternative splicing ; starch biosynthesis ; starch-branching enzyme ; transit peptide ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A wheat gene, denoted Sbe1, encoding a type I starch-branching enzyme (SBEI) was isolated from a genomic library and shown to comprise 14 exons distributed over a 5.7 kb DNA region. Analyses of kernel RNA by 5′ rapid amplification of cDNA ends (5′-RACE) and reverse transcription-polymerase chain reaction (RT-PCR) demonstrated a considerable sequence variation at the 5′ ends of SBEI gene transcripts. DNA sequence alignments between the 5′-RACE products and the Sbe1 genomic DNA indicated that the first two exons and first intron were differentially processed to generate three classes of the mature transcript. One form of the SBEI gene transcript in 12-day old kernels contained the exon I+II+III combination at the 5′ end, whereas other forms differed by inclusion of intron 1 or exclusion of exon II sequences. RT-PCR analysis of Sbe1-uidA::nptII chimeric mRNA produced in transgenic wheat cultured cells confirmed that the isolated Sbe1 was able to produce all three forms of SBEI gene transcripts by alternative splicing of the primary mRNA. The variants of processed Sbe1 mRNA were potentially translated into N-terminal variants of the SBEI precursor with different transit peptide sequences.
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    URL: http://dx.doi.org/10.1023/A:1006286807176
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    Identification and characterization of T3/T7 bacteriophage-like RNA polymerase sequences in wheat (1999)
    Springer
    Plant molecular biology 40 (1999), S. 567-578 
    Details
    ISSN: 1573-5028
    Keywords: wheat ; mitochondria ; RNA polymerase ; transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using PCR-based methods, we assembled two wheat cDNA sequences, wheat-G and wheat-C, that encode T3/T7 bacteriophage-like RNA polymerases (RNAPs) sharing 45% amino acid identity. In phylogenetic analyses using maximum likelihood, parsimony and distance methods, the predicted protein sequence of wheat-G (1005 amino acids, 113 kDa) clusters with sequences of previously assigned mitochondrial RNAPs from dicotyledonous plants (Arabidopsis thaliana, Chenopodium album); likewise, in such analyses, the wheat-C sequence (949 amino acids, 107 kDa) affiliates specifically with the Arabidopsis sequence that encodes a phage-like RNAP thought to function in chloroplasts. To confirm biochemically the assignment of the gene encoding the putative wheat mitochondrial RNAP, we isolated a ca. 100 kDa wheat mitochondrial protein that is enriched in fractions displaying specific in vitro transcription activity and that reacts with an antibody raised against a recombinant maize phage-type RNAP. Internal peptide sequence information obtained from the 100-kDa polypeptide revealed that it corresponds to the predicted wheat-G cDNA sequence, providing direct evidence that the wheat-G gene (which we propose to call RpoTm) encodes the wheat mitochondrial RNAP.
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    URL: http://dx.doi.org/10.1023/A:1006203928189
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    Mitochondria at the Crossroad of Apoptotic Cell Death (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 321-326 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; apoptosis ; caspases ; cytochrome c ; Fas ; bcl-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract In the past few years, it has become widely appreciated that apoptotic cell death generallyinvolves activation of a family of proteases, the caspases, which undermine the integrity ofthe cell by cleavage of critical intracellular substrates. Caspases, which are synthesized asinactive zymogens, are themselves caspase substrates and this cleavage leads to their activation.Hence, the potential exists for cascades of caspases leading to cell death. However, it has beenrecently recognized that another, perhaps more prominent route to caspase activation, involvesthe mitochondria. Upon receipt of apoptotic stimuli, either externally or internally generated,cells initiate signaling pathways which converge upon the mitochondria to promote release ofcytochrome C to the cytoplasm; cytochrome c, thus released, acts as a potent cofactor incaspase activation. Even cell surface “death receptors” such as Fas, which can trigger directcaspase activation (and potentially a caspase cascade), appear to utilize mitochondria as partof an amplification mechanism; it has been recently demonstrated that activated caspases cancleave key substrates to trigger mitochondrial release of cytochrome c, thereby inducing furthercaspase activation and amplifying the apoptotic signal. Therefore, mitochondria play a centralrole in apoptotic cell death, serving as a repository for cytochrome c.
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    Mitochondrial Effects of Triarylmethane Dyes (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 581-590 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; triarylmethane dyes ; photodynamic therapy ; respiration ; mitochondrial permeability transition ; cyclosporin A ; calcium ; proton transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The mitochondrial effects of submicromolar concentrations of six triarylmethane dyes, withpotential applications in antioncotic photodynamic therapy, were studied. All dyes promotedan inhibition of glutamate or succinate-supported respiration in uncoupled mitochondria, in amanner stimulated photodynamically. No inhibition of N,N,N′,N′-tetramethyl-p-phenylenediamine(TMPD) supported respiration was observed, indicating that these dyes do not affectmitochondrial complex IV. When mitochondria were energized with TMPD in the absence ofan uncoupler, treatment with victoria blue R, B, or BO, promoted a dissipation of mitochondrialmembrane potential and increase of respiratory rates, compatible with mitochondrialuncoupling. This effect was observed even in the dark, and was not prevented by EGTA, Mg2+ orcyclosporin A, suggesting that it is promoted by a direct effect of the dye on inner mitochondrialmembrane permeability to protons. Indeed, victoria blue R, B, and BO promoted swellingof valinomycin-treated mitochondria incubated in a hyposmotic K+-acetate-based medium,confirming that these dyes act as classic protonophores such as FCCP. On the other hand, ethylviolet, crystal violet, and malachite green promoted a dissipation of mitochondrial membranepotential, accompanied by mitochondrial swelling, which was prevented by EGTA, Mg2+, andcyclosporin A, demonstrating that these drugs induce mitochondrial permeability transition.This mitochondrial permeabilization was followed by respiratory inhibition, attributable tocytochrome c release, and was caused by the oxidation of NAD(P)H promoted by these drugs.
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    Contribution to the Identification and Analysis of the Mitochondrial Uncoupling Proteins (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 407-418 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; uncoupling ; UCP ; thermogenesis ; brown adipose tissue ; fatty acid oxidation ; mitochondrial carrier ; membrane ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract This review is primarily focused on the contribution of our laboratory to study of themitochondrial uncoupling UCPs. The initial stage was the description of a 32-kDamembranous protein specifically induced in brown adipose tissue mitochondria of cold-adaptedrats. This protein was then shown by others to be responsible for brown fat thermogenesisand was referred to as the uncoupling protein-UCP (recently renamed UCP1). cDNA andgenomic clones of UCP1 were isolated and used to investigate the topology and functionalorganization of the protein in the membrane and the mechanisms of control of UCP1 genetranscription. Orientation of the transmembrane fragments was proposed and specificamino acid residues involved in the inhibition of UCP1 by purine nucleotides wereidentified in recombinant yeast. A potent enhancer mediating the response of the UCP1gene to retinoids and controlling the specific transcription in brown adipocytes wasidentified using transgenic mice. More recently, we identified UCP2, an UCP homologwidely expressed in human and rodent tissues we also collaborated to characterize theplant UCP. Although the biochemical activities and physiological roles of the novel UCPsare not well understood, these recent data stimulate research on mitochondrial carriers,mitochondrial bioenergetics, and energy expenditure.
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    Oligomeric State of Wild-Type and Cysteine-Less Yeast Mitochondrial Citrate Transport Proteins (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 543-549 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; transporter ; dimer ; overexpression ; membrane protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Experiments have been conducted to determine the oligomeric state of the mitochondrial citratetransport protein (CTP) from the yeast Saccharomyces cerevisiae. Both wild-type andcysteine-less (Cys-less) CTPs were overexpressed in E. coli and solubilized with sarkosyl. The purity ofthe solubilized material is approximately 75%. Upon incorporation into phospholipid vesicles, ahigh specific transport activity is obtained with both the wild-type and Cys-less CTPs, therebydemonstrating the structural and functional integrity of the preparations. Two independentapproaches were utilized to determine native molecular weight. First, CTP molecular weightwas determined via nondenaturing size-exclusion chromatography. With this methodology weobtained molecular weight values of 70,961 and 70,118 for the wild-type and Cys-less CTPs,respectively. Second, charge-shift native gel electrophoresis was carried out utilizing a lowconcentration of the negatively charged detergent sarkosyl, which served to both impart acharge shift to the CTP and the protein standards, as well as to promote protein solubility.Via the second method, we obtained molecular weight values of 69,122 and 74,911 forthe wild-type and Cys-less CTPs, respectively. Both methods clearly indicate that followingsolubilization, the wild-type and the Cys-less CTPs exist exclusively as dimers. Furthermore,disulfide bonds are not required for either dimer formation or stabilization. The dimericstate of the CTP has important implications for the structural basis underlying the CTPtranslocation mechanism.
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    Cloning of a wheat puroindoline gene promoter by IPCR and analysis of promoter regions required for tissue-specific expression in transgenic rice seeds (1999)
    Springer
    Plant molecular biology 39 (1999), S. 1101-1112 
    Details
    ISSN: 1573-5028
    Keywords: promoter analysis ; puroindoline gene ; seed ; tissue-specific expression ; transgenic rice ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A genomic DNA fragment containing the 5′-upstream sequence and part of the open reading frame corresponding to Triticum aestivum puroindoline-b cDNA, was isolated by inverse PCR. Promoter fragments extending to −1068, −388, −210 or −124 upstream of the translation initiation ATG codon and the sequence coding for the first 13 amino acids of the puroindoline-b, were translationally fused to the uidA reporter gene encoding β-glucuronidase and transferred to rice calli via particle bombardment-mediated transformation. The 1068 bp and 124 bp promoters were also transcriptionally fused to the uidA reporter gene. Out of the 196 plants regenerated from transformed rice calli, 118 plants set seeds. No GUS activity was detectable in the stems, roots, leaves or pollen of the transgenic rice which had integrated the puroindoline-b promoter or its deletions; GUS activity was detected only in seeds, except in those having integrated the 124 bp promoter. Within seeds, histological localisation showed GUS activity as being restricted to the endosperm, aleurone cells and pericarp cell layers; no GUS activity was detected in the embryonic axis. Analysis of 5′ promoter deletions identified the region between −388 and −210 as essential for endosperm expression, and the region between −210 and −124 as essential for expression in the epithelium of the scutellum. No difference of expression was observed between the translational and transcriptional fusion genes.
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    Plant regeneration from protoplasts of Triticum aestivum L. cv. Nakasoushu (1999)
    Springer
    Plant cell, tissue and organ culture 58 (1999), S. 119-125 
    Details
    ISSN: 1573-5044
    Keywords: plant regeneration ; protoplast ; suspension culture ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A fast-growing, small, granular, embryogenic callus was selected from primary calli induced from the Japanese wheat cultivar Nakasoushu and the Australian wheat cultivar Bodallin. Regenerable and fine suspension cultures were induced three to six months after liquid culture was initiated and were characterized by dense cytoplasm and active division. These suspension cultures routinely provided high yields of protoplasts with about 90% viability when incubated in a modified KMP (Kao and Michayluk, 1975) medium containing 1 mg l-1 2,4-D (2,4-dichlorophenoxyacetic acid), and 1 mg l-1 zeatin. Nakasoushu and Bodallin protoplasts divided at frequencies of 8.6% and 11.1%, respectively, in agarose-solidified media. When Nakasoushu protoplasts were cultured with effective nurse cells of sorghum and wheat, protoplast division increased to 16.9% and 12.6%, respectively. Plating efficiencies varied from 0.03% to 2.5%. After subculture, protocolonies yielded embryogenic calli and somatic embryos, from which green plants were eventually regenerated. Whole plants obtained from Nakasoushu protoplasts were fertile, demonstrating the first report of Japanese cultivars in wheat protoplast cultures.
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    Stability and resilience in benthic macroinvertebrate assemblages (1999)
    Springer
    Hydrobiologia 403 (1999), S. 123-133 
    Details
    ISSN: 1573-5117
    Keywords: disturbance ; stability ; resilience ; Trichoptera ; Ephemeroptera ; Psychomyia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Benthic macroinvertebrate assemblages of Bushkill Creek, Northampton County, PA were studied at the same site during the 1970s (11 dates) and 1990s (8 dates) to evaluate stability and resilience. In the 1970s, a Surber sampler was used, and in the 1990s, a Hess sampler. Assemblages appeared stable over a wide range of environmental stresses with the exception of 1994–1995 when total numbers and total Trichoptera decreased. Taxa richness and EPT indices varied little in 1994–1995 from other sampled years. By July 1996, all metrics (Trichoptera numbers, total numbers, taxa richness, EPT index, Bray-Curtis Index) resembled the 1970s exception for lower wet weight. Bray-Curtis indices and taxa composition were similar in July 1972 and July 1996, suggesting assemblage stability over 25 years. The Trichoptera, Psychomyia (Psychomiidae) and Leucotrichia (Hydroptilidae), decreased during the 1990s and never rebounded to 1970s numbers. During winter 1994, the coldest temperatures and greatest cumulative snowfall occurred in the region. These conditions probably stressed the assemblage with low temperatures, anchor/frazil ice and ice break-up. The assemblage was then exposed to four bankful floods in winter/spring 1994 and five bankful floods in winter/spring 1996. Recovery time following these multiple disturbances was 27 months. Previous recovery times from winter and flood disturbances were considerably shorter (2–5 months). The 1990s recovery time (5–9 times previusly recorded) for this assemblage was apparently extended by multiple physical disturbances, outside the predicted range. The assemblages had not been previously exposed to such severe conditions and, therefore, recovery time was extended. Despite severe weather conditions, the assemblage recovered and exhibited both stability and resilience in its return to an assemblage similar to the 1970s.
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    Procedures for the characterisation of bioaerosol particles. Part I: aerosolisation and recovery agent effects (1999)
    Springer
    Aerobiologia 15 (1999), S. 267-280 
    Details
    ISSN: 1573-3025
    Keywords: aerosolisation effects ; bioaerosol ; bioaerosol sampling ; effects of recovery agents ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sampling and assay of bioaerosols are important ina number of industrial and health-care applications. Airborne microorganisms are notoriously difficult toenumerate accurately under such conditions and nosingle procedure is suitable for all applications. Problems are compounded by the differences in assaymethod or sampler type selected, making theinterpretation of results difficult.Understanding the airborne behaviour of microorganismsover a range of environmental conditions is vital ifprocedures are to be defined and recommended for theassessment of bioaerosols. Microorganisms that arerobust over a wide range of conditions are ideal astracer particles. Unfortunately, the large majorityof non-fungal bioaerosols are susceptible to damage. A predictable assessment procedure is required whichwill not affect the viability of the collectedsample. This paper examines how aerosolisation may affect the characteristics of two speciesof microorganism (Pseudomonas fluorescens andMS2 coliphage). It forms part of a larger programmeto develop standards for the assessment of biologicalparticles. The aim of the work was to develop procedures toexamine the effects of aerosolisation onmicroorganisms, with particular reference topre-aerosolisation protocol (spray suspension age) andpost-sampling handling protocol (aerosol age incollection solution). These procedures were then usedto examine the effect of recovery agents, addedto the spray suspension prior to aerosolisation, onthe culturability of E.coli. Aerosolisation reduces the culturability of P. fluorescensand the viability of viability of MS2coliphage. Pre-sampling and post-collection handlingand storage of these aerosolised microorganisms werealso found to have an effect. This and earlierstudies have shown that the culturable fraction ofmicroorganisms can be affected by the same factorsdescribed above. Of five microorganisms tested so farin the main programme, only Penicillium expansumspores were shown to be robust and stable with aconstant culturable fraction. Therefore, recommendinga particular microorganism (apart from P. expansum) as an airborne biological standard foraerosol studies is not advised. It is recommendedthat a microorganism, representative of the envisagedapplication, be characterised it in terms of theaerosolisation parameters, storage time and conditionsin the manner reported in this study. This can beachieved using the experimental equipment described.The addition of 0.1 mM concentrations of the sugarsinositol, trehalose and raffinose to spray suspensionsof Escherichia coli, prior to aerosolisation,made no significant difference to the culturablefraction of the aerosol.
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    Effects of temperature and photoperiod on thermogenesis in plateau pikas (Ochotona curzoniae) and root voles (Microtus oeconomus) (1999)
    Springer
    Journal of comparative physiology 169 (1999), S. 77-83 
    Details
    ISSN: 1432-136X
    Keywords: Key words Acclimation ; Mitochondria ; Plateau pika ; Root vole ; Thermogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We examined the effects of temperature and photoperiod on metabolic thermogenesis and the thermogenic characteristics of brown adipose tissue in plateau pikas (Ochotona curzoniae) and root voles (Microtus oeconomus), the dominant species of small mammals in the alpine meadow ecosystems on the Qinghai-Tibetan Plateau. Pikas and voles were acclimated in the following groups: (1) Long day – warm temperature (16L:8D, 23 °C), (2) Long day – cold temperature (16L:8D, 5 °C), (3) short day – warm temperature (8L:16D, 23 °C), and (4) short day – cold temperature (8L:16D, 5 °C). Both temperature and photoperiod were important environmental cues for changes in thermogenesis for both species. Low temperature and short photoperiod induced increases in metabolic rate, nonshivering thermogenesis (NST), mitochondrial protein contents of brown adipose tissue, and cytochrome C oxidase activity of brown adipose tissue mitochondria in both species. Plateau pikas were more sensitive to cold (79% of the total NST response) than to short photoperiod (21%), while root voles were more sensitive to short photoperiod (60% of the total NST response) than to cold (40%), although cold clearly enhanced thermogenesis. Their thermogenic characteristics correlated with their preferred habitats: plateau pikas are found mainly in more exposed microhabitats in open sunny meadow, while root voles live in more sheltered microhabitats in relatively closed shrub. Our results also showed that temperature and photoperiod combined induce thermogenic adjustments in both species in seasonal acclimatization in their alpine meadow macrohabitat.
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    Formation of cross-linking between photosystem 2 proteins during irradiation of thylakoid membranes at high temperature (1999)
    Springer
    Photosynthetica 36 (1999), S. 213-223 
    Details
    ISSN: 1573-9058
    Keywords: D1 protein ; diphenylcarbazide ; oxygen evolving complex ; scavengers ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Irradiation of thylakoid membranes at 40 °C resulted in complete inhibition of photosystem (PS) 2 activity measured as 2,6-dichlorophenol indophenol (DCIP) photoreduction either in the absence or presence of 1,5-diphenylcarbazide (DPC). Concomitant with the inactivation of PS2 activity, several thylakoid proteins were lost and high molecular mass cross-linking products appeared that cross-reacted with antibodies against proteins of PS2 but not with antibodies against proteins of other three complexes PS1, ATP synthase, and cytochrome b6f. Irradiation of thylakoid membranes suspended in buffer of basic pH or high concentration of Tris at 25 °C resulted in the formation of cross-linking products similar to those in thylakoid membranes irradiated at 40 °C. Presence of radical scavengers and DPC during the high temperature treatment prevented the formation of cross-linking products. These results suggest the involvement of oxygen evolving co mplex (OEC) in the formation of cross-linking between PS2 proteins in thylakoid membrane irradiated at high temperature.
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    Specific Degradation of D1 Protein during Exposure of Thylakoid Membranes to High Temperature in the Dark (1999)
    Springer
    Photosynthetica 36 (1999), S. 433-440 
    Details
    ISSN: 1573-9058
    Keywords: antibody ; polyacrylamide gel electrophoresis ; protease ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exposure of thylakoid membranes to high temperature in dark leads to the degradation of D1 protein. Maximum degradation of D1 protein occurred at 45 °C. Using N-terminal specific D1 antibody, a 23 kDa fragment of D1 protein was detected. The degradation of D1 protein could be prevented both by radical scavengers and inhibitors of serine protease and metallo-protease. These results suggest that degradation of D1 protein during exposure of thylakoid membranes to high temperature in dark is catalyzed by protease.
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    A Two-Patch Model of Gambian Sleeping Sickness: Application to Vector Control Strategies in a Village and Plantations (1998)
    Springer
    Acta biotheoretica 46 (1998), S. 207-222 
    Details
    ISSN: 1572-8358
    Keywords: Epidemiology ; sleeping sickness ; vector controls ; differential equations ; spacialization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A compartmental model is described for the spread of Gambian sleeping sickness in a spatially heterogeneous environment in which vector and human populations migrate between two "patches": the village and the plantations. The number of equilibrium points depends on two "summary parameters": gr the proportion removed among human infectives, and R0, the basic reproduction number. The origin is stable for R0 〈1 and unstable for R0 〉1. Control strategies are assessed by studying the mix of vector control between the two patches that bring R0 below 1. The results demonstrate the importance of vector control in the plantations. For example if 20 percent of flies are in the village and the blood meal rate in the village is 10 percent, then a 20 percent added vector mortality in the village must be combined with a 9 percent added mortality in the plantations in order to bring R0 below 1. The results are quite insentive to the blood meal rate in the village. Optimal strategies (that minimize the total number of flies trapped in both patches) are briefly discussed.
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    Influence of cereal leaf epicuticular wax on Diuraphis noxia probing behavior and nymphoposition (1998)
    Springer
    Entomologia experimentalis et applicata 89 (1998), S. 111-118 
    Details
    ISSN: 1570-7458
    Keywords: leaf surface wax ; probing behavior ; nymphoposition ; Russian wheat aphid ; wheat ; barley ; oat ; Homoptera ; Aphididae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of cereal leaf surface wax on Diuraphis noxia (Mordvilko), the Russian wheat aphid, probing behavior and nymphoposition was evaluated. Ultrastructure of leaf epicuticular wax from wheat (Triticum aestivum L.) c.v. ‘Arapahoe’ and ‘Halt’ was different from barley (Hordeum vulgare L.) c.v. ‘Morex’, and oat (Avena sativa L.) c.v. ‘Border’. Both wheat cultivars had similar rod-shaped epicuticular wax, while barley and oat plants had flakes. The chemical composition comparison of gas chromatograms also indicated that the extract of the two wheat cultivars had similar pattern of peaks, while the barley and oat leaves had similar peaks. Cereal variety significantly affected aphid probing behavior (P 〈 0.05), but wax removal using ethyl ether swab did not (P 〈 0.05). Aphids initiated significantly more probes on Border oat leaves than on Morex barley irrespective of wax removal, although total probing duration per aphid was not significantly different among the four cereals examined. Accumulative salivation duration per aphid on oat leaves with wax was significantly longer than other cereal leaves with wax, while accumulative ingestion duration per aphid on Arapahoe wheat and Morex barley was significantly longer than on oat. Nymphoposition of D. noxia on cereal leaves maintained on the benzimidazole-agar medium showed that aphids produced a greater number of nymphs on Morex barley and less on Border oat leaves, although wax removal did not affect aphid nymphoposition. Removal of leaf epicuticular waxes from the 4 cereal genotypes using ethyl ether swab indicated that the influence of wax on plant resistance to D. noxia probing and reproduction was limited. Morex barley was the most favorable, while Border oat was the least favorable cereal host of D. noxia.
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    A survey on the occurrence of mycotoxins in wheat and maize from western Romania (1998)
    Springer
    Mycopathologia 143 (1998), S. 97-103 
    Details
    ISSN: 1573-0832
    Keywords: deoxynivalenol ; enzyme immunoassay ; feed ; maize ; mycotoxins ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Samples of wheat (n = 25) and maize (n = 30) for animal consumption, collected in 1997 after harvest from western Romania, were analyzed by enzyme immunoassays for mycotoxin contamination. Toxins analyses included deoxynivalenol (DON), 3-acetylDON, 15- acetylDON, fusarenone X (FX), T-2 Toxin (T-2), diacetoxyscirpenol (DAS), zearalenone (ZEA), fumonisin B1 (FB1), aflatoxin B1 (AFB1), ochratoxin A (OA), and citrinin (CT). DON and acetylDONs were the major contaminants in wheat (100%) and maize (46%). Median values for DON, 3-acetylDON, and 15-acetylDON were 880 μg kg-1, 66 μg kg- 1, and 150 μg kg-1 in wheat, and 890 μg kg-1, 180 μg kg-1, and 620 μg kg- 1 in maize, respectively. Additionally, 3,15-diacetylDON was detected in some samples by HPLC-EIA analysis. All samples were negative for FX (〈150 μg kg-1). T-2 was found in wheat (n = 6) and maize (n = 1) at levels between 13 and 63 μg kg- 1. DAS (2.6 μg kg-1) was found in one maize sample. ZEA occurred in all wheat and in four maize samples, median values were 10 μg kg-1 and 250 μg kg-1, respectively. One maize sample contained FB1 (140 μg kg-1). All samples were AFB1-negative (〈4 μg kg-1). OA was found in one wheat sample (37 μg kg- 1), CT was found in one maize sample (580 μg kg- 1). This first reported natural occurrence of a range of mycotoxins in Romanian feeding stuff shows that DON and acetyl DONs may be present at levels which may affect animal production.
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    URL: http://dx.doi.org/10.1023/A:1006987205986
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    Do single mitochondria contain zones with different membrane potential? (1998)
    Springer
    Experimental biology online 3 (1998), S. 1-13 
    Details
    ISSN: 1430-3418
    Keywords: Cell cultures ; DASPMI ; Fluorescence ; JC-1 ; Membrane potential ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Observations of Lan Bo Chen’s group using a mitochondria-selective fluorochrome 5,5’,6,6’- tetrachloro- 1,1’,3,3’- tetraethylbenzimidazolocarbocyanine iodide (JC-1) indicate that mitochondria in situ may have zones of different electrochemical potential along their length. This was indicated by the formation of J-aggregates of this dye at distinct sites along a single mitochondrion. Also, intensity variations along single mitochondria were found with diamino-styryl-pyridinium methiodide (DASPMI), another fluorochrome that selectively stains mitochondria depending on their electrochemical potential. DASPMI exchanges easily with the cytoplasm and changes its quantum yield when bound to mitochondrial membranes. Therefore, fluorescence intensity is primarily controlled by the membrane environment rather than by mass accumulation. Two possible explanations of intramitochondrial fluorescence intensity variations have to be discussed: variations in the amount of mitochondrial inner membrane per unit of projection area (or voxel), and differences in the electrochemical gradient. This problem has been approached by comparing fluoro-micrographs of mitochondria in endothelial cells stained with either JC-1 or DASPMI with electron micrographs of the same mitochondria after fixation with glutardialdehyde and osmium tetroxide and ultrathin sectioning. JC-1 red fluorescence (revealing J-aggregate formation) as well as high-intensity staining with DASPMI correlate roughly with the local thickness of mitochondria; no differences in the crista organization are revealed for those areas or mitochondria exhibiting red JC-1 fluorescence and those with green fluorescence. The distance between red fluorescing areas in a single mitochondrion seem to be caused by competition for dye molecules placed in between centres of JC-1 aggregation. Isolated mitochondria are of uniform small size and spherical shape; therefore, no differences in shape interfere with JC-1 staining. Thus JC-1 may be an appropriate indicator of membrane potential in isolated mitochondria. In living cells mitochondria often are large and elongated, and thus the situation is not straightforward to interpret. However, evidence is provided that there are submitochondrial zones, which differ in membrane potential from one adjacent area to another, because DASPMI staining of intramitochondrial zones reveals differences in fluorescence intensity and preferred photodamage of these areas. In some cases separation of the zones of higher membrane potential by cristae traversing the whole diameter of a mitochondrion has been observed. Local photobleaching of stained mitochondria results in a loss of fluorescence along the total length of a mitochondrion. However, this type of bleaching develops over tens of seconds, not in the very short time range (e.g. ms) expected from the discharge of all the membranes if they were electrically coupled.
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    URL: http://dx.doi.org/10.1007/s00898-998-0012-4
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    In situ determination of intracellular membrane physical state heterogeneity in renal epithelial cells using fluorescence ratio microscopy (1998)
    Springer
    European biophysics journal 27 (1998), S. 341-351 
    Details
    ISSN: 1432-1017
    Keywords: Key words Living MDCK cells ; Laurdan ; Generalized polarization ; Endosomes ; Golgi ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract 6-Lauroyl-2-dimethylaminonaphtalene (laurdan) shows a spectral sensitivity to the lipid phase state with a 50 nm red shift of the emission maximum when passing from the gel to the liquid crystalline phase. This spectral sensitivity allows one to determine the membrane physical state using Generalized Polarization (GP). In the present experiments, we used fluorescence ratio imaging microscopy to determine the laurdan GP in living kidney cells. Two renal epithelial cells lines, MDCK and LLC-PK1 cells, and CV-1 cells, a fibroblast-like renal cell line were investigated. In these cells, laurdan labels both the plasma membrane and intracellular membranes. Comparison of spectrofluorimetry and fluorescence ratio imaging data obtained from liposomes and cells suspensions labeled with laurdan demonstrates that the GP can be accurately determined using common fluorescence microscopy equipment. The GP mean values determined from individual cells varied from 0.2 to 0.4 for the epithelial cells as compared to 0.0 – 0.1 for CV1 cells. Using living MDCK cells grown as a monolayer, the GP maps indicated that, within a single cell, the intracellular GP values varied from 0.0 to 0.6, i. e., from the equivalent of a liquid-crystalline state to a gel or a lipid-ordered state, and that there was a marked heterogeneity in the spatial distribution of the GP values. To further characterize this intracellular heterogeneity, co-localization experiments with specific organelle markers were undertaken. The results strongly suggest that in intact cells at physiological temperature, GP values decrease in the following order: plasma membranes 〉 endosomes 〉 mitochondria 〉 Golgi apparatus.
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    URL: http://dx.doi.org/10.1007/s002490050141
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    Ts mutations in mitochondrial tRNA genes: characterization and effects of two point mutations in the mitochondrial gene for tRNAphe in Saccharomyces cerevisiae (1998)
    Springer
    Current genetics 33 (1998), S. 110-116 
    Details
    ISSN: 1432-0983
    Keywords: Key wordsSaccharomyces cerevisiae ; Mitochondria ; tRNA ; Mutations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two new mitochondrial mutations conferring heat sensitivity on glycerol medium to the cells that carry them and affecting mitochondrial protein synthesis were investigated. Both map in the mitochondrial tRNAphe gene and have C-to-U transitions, one at position 2 (ts22b16) and the other at 62 (ts1345). The latter mutation clearly affects the 3′ end-maturation of tRNAphe, while the former presents normal patterns of both tRNA processing and amino-acylation. The defective phenotype resulting from the ts22b16 mutation can be corrected by over-expressing either the mitochondrial elongation factor EF-Tu or the mutated form of the tRNA. These results suggest that this mutation's primary effect might involve modified interactions during the ternary complex formation.
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    URL: http://dx.doi.org/10.1007/s002940050315
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    Differential transmission of the Cucumis organellar genomes (1998)
    Springer
    Theoretical and applied genetics 97 (1998), S. 122-128 
    Details
    ISSN: 1432-2242
    Keywords: Key words Cucumber ; Melon ; Mitochondria ; Chloroplast ; DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Although plants generally show maternal transmission of the organellar genomes, previous research has demonstrated that the mitochondrial (mt) genome of cucumber is paternally transmitted. In this study, we identified RFLPs in the organellar genomes of melon, squash, and watermelon to establish organellar DNA transmission. Serial dilutions of DNA demonstrated that our hybridizations revealed the presence of a polymorphic cytoplasm when it represented at least 1% of the DNA sample. At this level of sensitivity, the chloroplast genomes of melon, squash, and watermelon were maternally transmitted. The mitochondrial genomes of squash and watermelon were maternally transmitted; however, melon, like cucumber, showed paternal transmission of the mitochondrial genome. Because most angiosperms and the related genera Cucurbita and Citrullus show maternal transmission of the mtDNA, paternal transmission in Cucumis is likely the derived state. The Cucumis mitochondrial genomes are several-fold larger than those of other cucurbits. Based on 55 probe-enzyme combinations, mtDNA size differences could not be explained by duplication of the entire genome or partial duplication of regions hybridizing with the mitochondrial probes. Because the chloroplast, mitochondrial, and nuclear genomes of Cucumis are differentially transmitted, this genus is an excellent system to study the role of intergenomic transfer in the evolution of extremely large mitochondrial genomes.
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    URL: http://dx.doi.org/10.1007/s001220050875
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    Immunolocalization of a putative unconventional myosin on the surface of motile mitochondria in locust photoreceptors (1998)
    Springer
    Cell & tissue research 292 (1998), S. 219-227 
    Details
    ISSN: 1432-0878
    Keywords: Key words Photoreceptor cells ; Transport ; intracellular ; Cytoskeleton ; Myosin ; Actin filaments ; Mitochondria ; Schistocerca gregaria (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Light stimulation of locust (Schistocerca gregaria) photoreceptors results in an actin-dependent translocation of mitochondria towards the photoreceptive microvilli and an antagonistic movement of endoplasmic reticulum towards the cell body. Using immunocytochemical techniques, we have tried to identify myosin-like motors that may drive the light-induced organelle motility. A monoclonal antibody against the motor domain of Acanthamoeba myosin identifies a prominent 110-kDa protein on Western blots of locust retina. Cross-reactivity with two polyclonal anti-myosin antibodies and a monoclonal anti-myosin-I-antibody, together with ATP-dependent binding to actin filaments, provides evidence that the 110-kDa protein is an unconventional myosin. By indirect immunofluorescence, the 110-kDa protein has been localized to both photoreceptors and pigment cells within the retina. In the photoreceptor cells, the 110-kDa protein is bound to the surface of mitochondria. This putative unconventional myosin may thus be a motor protein involved in the light-induced translocation of mitochondria in photoreceptors.
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    URL: http://dx.doi.org/10.1007/s004410051053
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    Chloral hydrate alters the organization of the ciliary basal apparatus and cell organelles in sea urchin embryos (1998)
    Springer
    Cell & tissue research 293 (1998), S. 453-462 
    Details
    ISSN: 1432-0878
    Keywords: Key words Tranquilizers ; Cytoskeleton ; Deciliation ; Golgi ; Mitochondria ; Cell motility ; Sea urchin ; Lytechinus pictus (Echinodermata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The mitotic inhibitor, chloral hydrate, induces ciliary loss in the early embryo phase of Lytechinus pictus. It causes a breakdown of cilia at the junction of the cilium and the basal body known as the basal plate. This leaves the plasma membrane temporarily unsealed. The basal apparatus accessory structures, consisting of the basal body, basal foot, basal foot cap, striated side arm, and striated rootlet, are either misaligned or disintegrated by treatment with chloral hydrate. Furthermore, microtubules which are associated with the basal apparatus are disassembled. Mitochondria accumulate at the base of cilia – underneath the plasma membrane – and show alterations in their structural organization. The accumulation of mitochondria is observed in 40% of all electron micrograph sections while 60% show the areas mostly devoid of mitochondria. The microvilli surrounding a cilium and striated rootlet remain intact in the presence of chloral hydrate. These results suggest that deciliation in early sea urchin embryos by chloral hydrate is caused by combined effects on the ciliary membrane and on microtubules in the cilia. Furthermore, it is suggested that chloral hydrate can serve as a tool to explore the cytoskeletal mechanisms that are involved in cilia motility in the developing sea urchin embryo.
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    URL: http://dx.doi.org/10.1007/s004410051137
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    The cytoskeleton of Drosophila-derived Schneider line-1 and Kc23 cells undergoes significant changes during long-term culture (1998)
    Springer
    Cell & tissue research 294 (1998), S. 525-535 
    Details
    ISSN: 1432-0878
    Keywords: Key words Microfilaments ; Cell surface ; Cell division ; Mitochondria ; Organelle transport ; Drosophila melanogaster (Insecta)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Insect cell cultures derived from Drosophila melanogaster are increasingly being used as an alternative system to mammalian cell cultures, as they are amenable to genetic manipulation. Although Drosophila cells are an excellent tool for the study of genes and expression of proteins, culture conditions have to be considered in the interpretation of biochemical results. Our studies indicate that significant differences occur in cytoskeletal structure during the long-term culture of the Drosophila-derived cell lines Schneider Line-1 (S1) and Kc23. Scanning, transmission-electron, and immunofluorescence microscopy studies reveal that microfilaments, microtubules, and centrosomes become increasingly different during the culture of these cells from 24 h to 7–14 days. Significant cytoskeletal changes are observed at the cell surface where actin polymerizes into microfilaments, during the elongation of long microvilli. Additionally, long protrusions develop from the cell surface; these protrusions are microtubule-based and establish contact with neighboring cells. In contrast, the microtubule network in the interior of the cells becomes disrupted after four days of culture, resulting in altered transport of mitochondria. Microtubules and centrosomes are also affected in a small percent of cells during cell division, indicating an instability of centrosomes. Thus, the cytoskeletal network of microfilaments, microtubules, and centrosomes is affected in Drosophila cells during long-term culture. This implies that gene regulation and post-translational modifications are probably different under different culture conditions.
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    URL: http://dx.doi.org/10.1007/s004410051203
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    The yeast nuclear gene DSS1, which codes for a putative RNase II, is necessary for the function of the mitochondrial degradosome in processing and turnover of RNA (1998)
    Springer
    Molecular genetics and genomics 260 (1998), S. 108-114 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; RNase II ; RNA helicase ; RNA turnover ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The yeast nuclear gene DSS1 codes for a mitochondrial protein containing regions of homology to bacterial RNase II and can act as a multicopy suppressor of a deletion of the SUV3 gene, which encodes an RNA helicase. In order to establish the function of the DSS1 gene in mitochondrial biogenesis we studied RNA metabolism in yeast strains disrupted for SUV3 or DSS1. The results indicate that in the absence of DSS1 the in vitro activity of 3′-5′ exoribonuclease is abolished and mitochondrial translation is blocked. In disruption strains harboring intronless mitochondrial genomes steady-state levels of COB mRNA and 16S rRNA were very low, while in the presence of a mitochondrial genome containing the omega intron in the 21S rRNA gene the excised intron accumulates. Moreover we observed an accumulation of precursors of 21S rRNA and the VAR1 mRNA. All these phenotypes are virtually identical to those of strains in which SUV3 is disrupted. We suggest that the DSS1 gene product, like the SUV3 gene product, is a subunit of the yeast mitochondrial degradosome (mtEXO), and that this protein complex participates in intron-independent turnover and processing of mitochondrial transcripts. In addition our studies exclude any role for the NUC1 nuclease in the these phenomena.
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    Apoptosis and redox homostasis: On a possible mechanism of action of Bcl-2 (1998)
    Springer
    Protoplasma 205 (1998), S. 10-20 
    Details
    ISSN: 1615-6102
    Keywords: Proto-oncogene product Bcl-2 ; Calcium ; Mitochondria ; Plasma membrane NADH oxidoreductase ; Transcription factor NF-κB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We discuss the involvement of several mammalian redox systems in the regulation of apoptosis. We focus especially on the role that mitochondria and the still ill-characterized plasma membrane NADH-oxidoreductase system play in apoptosis. The latter system was shown to respond to downregulation of mitochondrial function; inhibition of either system induces apoptosis. Apoptosis induced by inhibitors of the oxidase involves both Bcl-2 and calcineurin, two proteins recently shown to be capable of forming a tight complex. We suggest that Bcl-2 acts as an antioxidant, but in an electron sense rather than in an oxygen sense.
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    URL: http://dx.doi.org/10.1007/BF01279288
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    A mitochondrion as the structural basis of the formation of a cell-type-specific organelle inDictyostelium development (1998)
    Springer
    Protoplasma 201 (1998), S. 172-179 
    Details
    ISSN: 1615-6102
    Keywords: Mitochondria ; Golgi complex ; Prespore-specific vacuole ; Prespore differentiation ; Immuno-electron microscopy ; Dictyostelium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrion has been mainly given attention as a self-reproductive and respiratory organelle. We report here that the mitochondrion may participate in the formation of a cell-type-specific organelle, coupling with the Golgi complex. During the development ofDictyostelium discoideum, the two types of cells, i.e., the anterior prestalk cells and the posterior prespore cells form a polarized cell mass. Prespore differentiation is characterized by the presence of unique vacuoles named PSVs (prespore-specific vacuoles) in the cytoplasm. Thus the PSV is the most essential organelle to understand the structural basis of cell differention in this organism. In differentiating prespore cells, the mitochondrion exerts a remarkable transformation to form a sort of vacuole (M-vacuole). Using a PSV specific antibody, it was immunocytochemically shown that a PSV antigen (C-10) is localized in the M-vacuole as well as in the lining membrane of PSV. Interestingly, the C-10 antigen was also noticed in the Golgi cisternae that had fused with M-vacuole. Based on these findings, we propose here a promising model which suggests how both mitochondria and Golgi cisternae may be coordinately involved in the PSV formation. This model will provide a new aspect of mitochondrial functions in cell differentiation.
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    URL: http://dx.doi.org/10.1007/BF01287413
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    Behavior of mitochondria during eupyrene and apyrene spermatogenesis in the silkworm,Bombyx mori (Lepidoptera), investigated by fluorescence in situ hybridization and electron microscopy (1998)
    Springer
    Protoplasma 202 (1998), S. 223-231 
    Details
    ISSN: 1615-6102
    Keywords: Apyrene ; Eupyrene ; Mitochondria ; Silkworm ; Spermatogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Changes in the morphology and quantity of mitochondria and mitochondrial DNA during eupyrene and apyrene spermatogenesis in the silkworm were examined by electron microscopy and by fluorescence in situ hybridization with a 2 kb silkworm mitochondrial DNA clone (pBmMtE2). In the eupyrene spermatogenesis, the spermatocytes at early prophase I contained only a small amount of cytoplasm and showed a rather faint signal. As the cells grew larger in the later prophase I, the signal grew stronger. In the eupyrene spermatids, an especially strong signal was evident in the nebenkerns, in which all the cell's mitochondria were aggregated, and the strong fluorescence was maintained in mitochondrial derivatives. On the other hand, the apyrene cells were markedly smaller throughout spermatogenesis, showing much fainter signals for mitochondrial DNA than the eupyrene. Electron microscopy disclosed considerable differences in the behavior of mitochondria between the apýrene and the eupyrene cells. The observed qualitative and/or quantitative differences in the mitochondria may have some physiological bearing on the spermatogenesis of the two types of sperm.
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    URL: http://dx.doi.org/10.1007/BF01282550
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    Competing Models of Stability in Complex, Evolving Systems: Kauffman vs. Simon (1998)
    Springer
    Biology and philosophy 13 (1998), S. 541-554 
    Details
    ISSN: 1572-8404
    Keywords: complex natural system ; stability ; evolvability ; decomposable hierarchy ; genetic network ; Random NK Boolean Network
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Philosophy
    Notes: Abstract I criticize Herbert Simon's argument for the claim that complex natural systems must constitute decomposable, mereological or functional hierarchies. The argument depends on certain assumptions about the requirements for the successful evolution of complex systems, most importantly, the existence of stable, intermediate stages in evolution. Simon offers an abstract model of any process that succeeds in meeting these requirements. This model necessarily involves construction through a decomposable hierarchy, and thus suggests that any complex, natural, i.e., evolved, system is constituted by a decomposable hierarchy. I argue that Stuart Kauffman's recent models of genetic regulatory networks succeed in specifying processes that could meet Simon's requirements for evolvability without requiring construction through a decomposable hierarchy. Since Kauffman's models are at least as plausible as Simon's model, Simon's argument that complex natural systems must constitute decomposable, mereological or functional hierarchies does not succeed.
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    Meiosis of Wheat × Lymegrass Hybrids (1998)
    Springer
    Chromosome research 6 (1998), S. 339-344 
    Details
    ISSN: 1573-6849
    Keywords: Leymus ; meiosis ; molecular cytogenetics ; wheat ; wide-hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Meiosis was examined in pollen mother cells of F1 hybrids made from crosses between wheat (Triticum aestivum) and lymegrass (Leymus arenarius and L. mollis). Fluorescence genomic in situ hybridization detected pairing between wheat and lymegrass chromosomes during prophase I and metaphase I. Such pairing, when resulting in bivalent formation, was likely to yield correct disjunction, and hence intergenomic recombination could be incorporated into the gametes. Bivalents in these hybrids, however, were more frequently formed between chromosomes of the same parental origin. Univalents were common, whereas multivalents were not clearly detected. Meiotic behaviour in some cells was not totally aberrant, and this may have accounted for the presence of normal pollen. The results are discussed in relation to intergenomic pairing, meiotic behaviour in wide-hybrids and genome relationships, including the Leymus genome origin.
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    Molecular characterization of a new type of receptor-like kinase (wlrk) gene family in wheat (1998)
    Springer
    Plant molecular biology 37 (1998), S. 943-953 
    Details
    ISSN: 1573-5028
    Keywords: barley ; kinase ; leaf rust ; receptor-like kinase ; resistance ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In plants, several types of receptor-like kinases (RLK) have been isolated and characterized based on the sequence of their extracellular domains. Some of these RLKs have been demonstrated to be involved in plant development or in the reaction to environmental signals. Here, we describe a RLK gene family in wheat (wlrk, wheat leaf rust kinase) with a new type of extracellular domain. A member of this new gene family has previously been shown to cosegregate with the leaf rust resistance gene Lr10. The diversity of the wlrk gene family was studied by cloning the extracellular domain of different members of the family. Sequence comparisons demonstrated that the extracellular domain consists of three very conserved regions interrupted by three variable regions. Linkage analysis indicated that the wlrk genes are specifically located on chromosome group 1 in wheat and on the corresponding chromosomes of other members of the Triticeae family. The wlrk genes are constitutively expressed in the aerial parts of the plant whereas no expression was detected in roots. Protein immunoblots demonstrated that the WLRK protein coded by the Lrk10 gene is an intrinsic plasma membrane protein. This is consistent with the hypothesis that WLRK proteins are receptor protein kinases localized to the cell surface. In addition, we present preliminary evidence that other disease resistance loci in wheat contain genes which are related to wlrk.
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    Characterization of a gene encoding a single-subunit bacteriophage-type RNA polymerase from maize which is alternatively spliced (1998)
    Springer
    Molecular genetics and genomics 260 (1998), S. 30-37 
    Details
    ISSN: 1617-4623
    Keywords: Key words Maize ; Mitochondria ; RNA polymerase ; Alternative splicing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Single-subunit RNA polymerases belonging to the T3/T7 bacteriophage family are thought to be common throughout eukaryotes. We report the isolation and characterization of a nucleus-encoded single-subunit RNA polymerase gene from maize. This gene is highly homologous to other single-subunit RNA polymerase genes from Arabidopsis, Chenopodium, yeast and Neurospora crassa involved in organellar transcription. Genomic Southern analysis reveals 10 to 15 hybridising fragments, suggesting that maize contains a small gene family. The isolated gene contains 19 exons and its genomic structure is highly conserved when compared to the three Arabidopsis homologues. Unlike the case in Arabidopsis, intron-12 of the maize bacteriophage-type RNA polymerase gene is alternatively spliced. Quantitative RT-PCR revealed that the resultant alternatively spliced transcript represents approximately 21 to 26% of the total polymerase mRNA in maize coleoptiles. The orthologous wheat bacteriophage-type RNA polymerase is also alternatively spliced and the intron exhibits 78% identity to maize intron-12. The conservation in alternative splicing between wheat and maize and its absence from Arabidopsis suggest a functional requirement for the alternatively spliced product.
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    The Des-1 protein, required for central spindle assembly and cytokinesis, is associated with mitochondria along the meiotic spindle apparatus and with the contractile ring during male meiosis in Drosophila melanogaster (1998)
    Springer
    Molecular genetics and genomics 259 (1998), S. 664-673 
    Details
    ISSN: 1617-4623
    Keywords: Key words Spermatogenesis ; Central spindle ; Mitochondria ; Contractile ring ; Cytokinesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spermatogenesis in Drosophila melanogaster serves as an excellent model system for the isolation and analysis of genes required in the control of chromosome segregation and cytokinesis. We report here the isolation and molecular characterization of a novel P-element induced allele of the des-1 gene, which leads to male sterility as a consequence of the failure of central spindle assembly in meiotic spermatocytes and the formation of aberrant meiotic end products characteristic of cytokinesis failure. We have raised affinity-purified antibodies against a Des-1 fusion protein, and localized the Des-1 protein in Drosophila spermatocytes. We show that the Des-1 protein is colocalized with mitochondria throughout male meiosis, becoming intimately associated with mitochondria along the spindle apparatus during anaphase and telophase, and with the Nebenkern, or mitochondrial derivative, of the meiotic end products. In addition, a significant association of Des-1 with the contractile ring is observed during anaphase and telophase of meiosis. These observations, together with the presence of six potential transmembrane domains in the Des-1 protein, raise the possibility that Des-1 may act as part of an anchoring mechanism that links membrane-bounded cellular compartments to components of the cytoskeleton.
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    URL: http://dx.doi.org/10.1007/s004380050861
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    Behavior of mitochondria, microtubules, and actin in the triangular yeastTrigonopsis variabilis (1998)
    Springer
    Protoplasma 204 (1998), S. 47-60 
    Details
    ISSN: 1615-6102
    Keywords: Yeast ; Trigonopsis variabilis ; Mitochondria ; Actin ; Microtubules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dimorphic yeastTrigonopsis variabilis is a unique species that can form either an ellipsoidal or a triangular cell depending upon nutritional conditions. This fluorescence microscopic study was intended to correlate morphological changes of mitochondria in the triangular cells with the distribution of the cytoskeleton. In addition, unique features in the behavior of the cytoskeleton were also examined during triangular cell formation. In log-phase cells stained with 4′,6-diamidino-2-phenylindole, mitochondrial nucleoids appeared as a string of beads throughout the vegetative growth. The profile of mitochondria stained by 3,3′-dihexyloxacarbocyanine iodide showed a network corresponding to the fluorescence images of mitochondrial nucleoids in both mother and daughter cells. Cell-cycle-dependent fragmentation of mitochondria was not discerned. As the culture reached stationary phase, a network of mitochondria gradually changed to form unique rings that were located near the angles of triangular cells. When examined by immunofluorescence microscopy with anti-tubulin antibody, microtubules were found to be well developed along the sides of cells in the cytoplasm ofT. variabilis interphase cells. Although distributions of microtubules and mitochondria are different during cell cycle as a whole, cytoplasmic microtubules frequently extended along a part of the mitochondria in budded cells, suggesting correlation of microtubules and mitochondria. Rhodamine-phalloidin staining revealed both actin patches and cables. Actin cables elongated from mother cells into the buds and showed close proximity to mitochondria, although complete overlapping of both structures was rare. Moreover, actin patches localized on the mitochondrial network at a frequency of 65%. These results suggested that actin cables and patches, as well as microtubules, participated in the distribution of mitochondria. The localization of actin patches separated towards opposite ends at a bud tip when the bud grew to medium size. The unique localization of actin patches is responsible for bi-directional growth of the bud, forming triangular cells.
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    URL: http://dx.doi.org/10.1007/BF01282293
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    Do body and fin form affect the abilities of fish to stabilize swimming during maneuvers through vertical and horizontal tubes? (1998)
    Springer
    Environmental biology of fishes 53 (1998), S. 365-371 
    Details
    ISSN: 1573-5133
    Keywords: Carassius auratus ; Metynnis hypsauchen ; Pterophyllum scalare ; goldfish ; angelfish ; silver dollar ; swimming ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Goldfish, Carassius auratus, silver dollar, Metynnis hypsauchen, and angelfish, Pterophyllum scalare were induced to swim through narrow vertical and horizontal tubes ranging in length from 0 to 20 cm (approximately 0 to 3 times total fish length, FL). The ability to stabilize the body while negotiating these confined spaces was quantified as (1) the minimum width of vertical (wv) and horizontal (wh) tubes traversed, where width is the smaller cross-sectional dimension of the tube, (2) the ratio wv/wh, and (3) transit speed through the tubes. Tube width was expressed as relative width, obtained by dividing tube width by fish length. Minimum relative widths traversed increased from 0.15 to 0.19 in the order silver dollar 〉 angelfish 〉 goldfish for vertical tubes and from 0.17 to 0.18 in the order goldfish=silver dollar 〉 angelfish for horizontal tubes. wv/wh increased from 0.91 to 1.10 in the order silver dollar=angelfish 〉 goldfish. Minimum tube widths generally increased with tube length for vertical tubes. Although significant differences in relative minimum widths among species were found, these were small. In contrast, for horizontal tubes, there was no significant effect of tube length on minimum tube width for any species. Large differences were found in transit speed. Transit speed generally decreased as the tube length increased. The slope of the relationship between transit speed and tube length varied among species generally increasing from − 0.41 to − 1.16 for horizontal tubes in the order goldfish 〉 silver dollar 〉 angelfish and from − 0.42 to − 1.07 in the order silver dollar 〉 goldfish 〉 angelfish for vertical tubes. As a result, goldfish usually took longest to traverse tubes of zero length but the shortest time to traverse the longest tubes. In contrast, angelfish traversed short tubes in the least time and long tubes in the greatest time. Deeper bodied angelfish swam slowly and traversed tubes with difficulty because they required experience during each trial to replace median and paired fin with body and caudal fin swimming. According to our data, goldfish were best able to swim in confined spaces.
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    URL: http://dx.doi.org/10.1023/A:1007414911734
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    Advances in the Purification of the Mitochondrial Ca2+ Uniporter Using the Labeled Inhibitor 103Ru360 (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 489-498 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; Ca2+ uniporter ; calcium transport inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract For many years the calcium uniporter has eluded attempts of purification, partly because of the difficulties inherent in the purification of low-abundance hydrophobic proteins (Reed and Bygrave, 1974). Liquid-phase preparative isoelectric focusing improved the fractionation of mitochondrial membrane proteins. A single 6-h run resulted in a 90-fold increase in specific activity of pooled active fractions over a semipurified fraction, allowing for enrichment of the calcium transport function in cytochrome oxidase vesicles. An additional powerful tool in the isolation of the uniporter was the use of the labeled inhibitor 103Ru360 as an affinity ligand; by following this procedure a protein of 18 kDa was purified in nondenatured, but rather inactive, form. The labeled protein corresponds to the protein that showed Ca2+ transport activity.
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    URL: http://dx.doi.org/10.1023/A:1020546331217
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  • 89
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    Minireview: Cardiolipins and Mitochondrial Proton-Selective Leakage (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 511-532 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; proton-leak ; cardiolipins ; membrane sidedness ; phospholipids ; fatty acyls ; thyroid hormone actions ; uncoupling proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The proton-selective leak (State 4 respiratory rate) but not Δψ, in mitochondria from thyroid-sensitive tissues, responds to in vivo stimuli in unique correlation with changes in cardiolipins, saturated and mono-unsaturated (extended) fatty acyl contents, cardiolipins/phospholipids ratios, and/or membrane outer-sidedness. Liver mitochondrial State 4 respiration, basal in fasted rats, contributes little to resting metabolic rate in fed rats, where State 3 depresses Δψ. In a proposed model, an essential inner-membrane outer-surface proton antenna collects protons and donates them, via a water-shuttle, to transmembrane porters: transient water-molecule-chains between extended phospholipid acyls; protonophores, and uncoupling proteins. Only cardiolipin microdomains can donate, from an anomalously-dissociating phosphate group in each headgroup; unadapted cardiolipins have few conducting water chains. Thyroid states regulate each cardiolipin property, and are permissive, via the proton antenna, for proton leaks, including those through adapted and possibly constitutive BAT and ectopic uncoupling proteins. Slow leakage in liposomes may reflect insufficient cardiolipin proton antennas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020576315771
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  • 90
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    Binding of Rat Brain Hexokinase to Recombinant Yeast Mitochondria: Effect of Environmental Factors and the Source of Porin (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 245-255 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; rat brain hexokinase ; porin ; VDAC ; yeast ; cooperative binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Heterologous binding of rat brain hexokinase to wild type, porinless, and recombinant yeast mitochondria expressing human porin was assessed, partially characterized, and compared to that in the homologous system (rat liver mitochondria). With porin-containing yeast mitochondria it is shown that (i) a significant, saturatable association occurs; (ii) its extent and apparent affinity, correlated with the origin of porin, are enhanced in the presence of dextran; (iii) the binding requires Mg ions and apparently follows a complex cooperative mechanism. This heterologous association does not seem to differ fundamentally from that in the homologous system and represents a good basis for molecular studies in yeast. With porinless yeast mitochondria, binding occurs at much lower affinity, but to many more sites per mitochondrion. The results indicating a major but not exclusive role for porin in the binding are discussed in terms of (i) the mode and mechanism of binding, and (ii) the suitability of the rat hexokinase–yeast mitochondria couple for the study of heterogeneous catalysis in reconstituted cellular model systems.
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    URL: http://dx.doi.org/10.1023/A:1020544803475
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  • 91
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    Exogenous Ubiquinol Analogues Affect the Fluorescence of NCD-4 Bound to Aspartate-160 of Yeast Cytochrome b (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 455-464 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; conformation ; proton translocation ; cytochrome bc 1 complex ; fluorescence quenching ; ubiquinol–cytochrome-c reductase ; NCD-4 ; DCCD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract Previously, we reported that the carboxyl-reacting reagent DCCD, and its fluorescent derivative NCD-4 binds covalently to aspartate-160 localized in amphipathic helix cd of the CD loop connecting membrane-spanning helices C and D of cytochrome b (Wang et al., 1995). We have investigated the fluorescent properties of NCD-4 to probe possible changes in the cd helix resulting from the binding of exogenous ubiquinol analogues to the bc 1 complex. Preincubation of the bc 1 complex with the reduced substrate analogues, DQH2, DBH2, and Q6H2 resulted in 20–40% increase in the fluorescence emission intensity of NCD-4 and a 10–20% increase in the binding of [14C]DCCD to the bc 1 complex. By contrast, preincubation with the oxidized analogues DQ, DB, and Q6 resulted in a 20–40% decrease in the fluorescence emission intensity of NCD-4 and a 20–40% decrease in the binding of [14C]DCCD to the bc 1 complex. Moreover, addition of the reduced ubiquinols to the bc 1 complex preincubated with NCD-4 resulted in a blue shift in the fluorescence emission spectrum. In addition, incubation of the cytochrome bc 1 complex reconstituted into proteoliposomes with both reduced and oxidized ubiquinol analogues resulted in changes in the quenching of NCD-4 fluorescence by CAT-16, the spin-label probe that intercalates at the membrane surface. These results indicate that the addition of exogenous ubiquinol to the bc 1 complex may result in changes in the cd helix leading to a more hydrophobic environment surrounding the NCD-4 binding site. By contrast, preincubation with the inhibitors of electron transfer through the bc 1 complex had no effect on the binding of NCD-4 to the bc 1 complex or on the fluorescent emission spectra, which suggests that the binding of the inhibitors does not result in changes in the environment of the NCD-4 binding site.
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    URL: http://dx.doi.org/10.1023/A:1020590113470
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  • 92
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    Dissolved oxygen and thermal regimes of a Ugandan crater lake (1998)
    Springer
    Hydrobiologia 385 (1998), S. 201-211 
    Details
    ISSN: 1573-5117
    Keywords: hypoxia ; anoxic hypolimnion ; volcanic crater lake ; stratification ; productivity ; heat budget ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper quantifies the temporal pattern of thermal stratification and deoxygenation in Lake Nkuruba, a small (3 ha), deep (maximum depth = 38 m) crater lake in western Uganda. Dissolved oxygen penetrated to an average depth of 9 m and a maximum depth of 15 m below which the lake was permanently anoxic over the 2 years of study. Although surface oxygen levels were correlated with both surface water temperature and rainfall, seasonal cycles of dissolved oxygen were not well-defined and may have been obscured by the high frequency of short-term fluctuations and by inter-annual variations caused by shifts in rainfall. Surface water temperature averaged 23.3±0.7 °C (S.D.) and varied directly with air temperature. Both diurnal changes and top-bottom temperature differentials were small averaging 1.7±0.7 °C and 1.6±0.8 °C, respectively. Thermal stability ranged from 101.3 to 499.9 g-cm cm-2 and was positively related to surface water temperature suggesting that this small protected lake responds rapidly to short-term meteorological changes. Because contribution to the annual heat exchange cycle was confined to upper waters, the lake's annual heat budget was low, 1,073.8 cal cm-2 yr-1. However, net primary productivity was relatively high averaging 1.3 g C m-2d-1. The region where Lake Nkuruba is situated experienced a very strong earthquake (6.2 on the Richter scale) on 4 February, 1994. Subsequently, water levels dropped markedly in the lake, falling 3.14 m over a 5-month period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003527016384
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    Dissolved oxygen and thermal regimes of a Ugandan crater lake (1998)
    Springer
    Hydrobiologia 385 (1998), S. 201-211 
    Details
    ISSN: 1573-5117
    Keywords: hypoxia ; anoxic hypolimnion ; volcanic crater lake ; stratification ; productivity ; heat budget ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper quantifies the temporal pattern of thermal stratification and deoxygenation in Lake Nkuruba, a small (3 ha), deep (maximum depth = 38 m) crater lake in western Uganda. Dissolved oxygen penetrated to an average depth of 9 m and a maximum depth of 15 m below which the lake was permanently anoxic over the 2 years of study. Although surface oxygen levels were correlated with both surface water temperature and rainfall, seasonal cycles of dissolved oxygen were not well-defined and may have been obscured by the high frequency of short-term fluctuations and by inter-annual variations caused by shifts in rainfall. Surface water temperature averaged 23.3±0.7 °C (S.D.) and varied directly with air temperature. Both diurnal changes and top-bottom temperature differentials were small averaging 1.7±0.7 °C and 1.6±0.8 °C, respectively. Thermal stability ranged from 101.3 to 499.9 g-cm cm-2 and was positively related to surface water temperature suggesting that this small protected lake responds rapidly to short-term meteorological changes. Because contribution to the annual heat exchange cycle was confined to upper waters, the lake's annual heat budget was low, 1,073.8 cal cm-2 yr-1. However, net primary productivity was relatively high averaging 1.3 g C m-2d-1. The region where Lake Nkuruba is situated experienced a very strong earthquake (6.2 on the Richter scale) on 4 February, 1994. Subsequently, water levels dropped markedly in the lake, falling 3.14 m over a 5-month period.
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    URL: http://dx.doi.org/10.1023/A:1003527016384
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    The rate of free radical production as a determinant of the rate of aging: evidence from the comparative approach (1998)
    Springer
    Journal of comparative physiology 168 (1998), S. 149-158 
    Details
    ISSN: 1432-136X
    Keywords: Key words Aging ; Maximum longevity ; Mitochondria ; Free radical production ; Antioxidants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The relationship of oxidative stress with maximum life span (MLSP) in different vertebrate species is reviewed. In all animal groups the endogenous levels of enzymatic and non-enzymatic antioxidants in tissues negatively correlate with MLSP and the most longevous animals studied in each group, pigeon or man, show the minimum levels of antioxidants. A possible evolutionary reason for this is that longevous animals produce oxygen radicals at a low rate. This has been analysed at the place where more than 90% of oxygen is consumed in the cell, the mitochondria. All available work agrees that, across species, the longer the life span, the lower the rate of mitochondrial oxygen radical production. This is true even in animal groups that do not conform to the rate of living theory of aging, such as birds. Birds have low rates of mitochondrial oxygen radical production, frequently due to a low free radical leak in their respiratory chain. Possibly the low rate of mitochondrial oxygen radical production of longevous species can decrease oxidative damage at targets important for aging (like mitochondrial DNA) that are situated near the places of free radical generation. A low rate of free radical production can contribute to a low aging rate both in animals that conform to the rate of living (metabolic) theory of aging and in animals with exceptional longevities, like birds and primates. Available research indicates there are at least two main characteristics of longevous species: a high rate of DNA repair together with a low rate of free radical production near DNA. Simultaneous consideration of these two characteristics can explain part of the quantitative differences in longevity between animal species.
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    URL: http://dx.doi.org/10.1007/s003600050131
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    Effects of temperature on mitochondrial function in the Antarctic fish Trematomus bernacchii (1998)
    Springer
    Journal of comparative physiology 168 (1998), S. 190-196 
    Details
    ISSN: 1432-136X
    Keywords: Key words Cold adaptation ; Mitochondria ; Stenothermy ; Temperature ; Trematomus bernacchii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Effects of temperature on O2 consumption by mitochondria of the Antarctic fish Trematomus bernacchii were compared with effects obtained with mitochondria from tropical (Sarotheridon mossambica) and temperate zone fishes (Sebastes carnatus and Sebastes mystinus). Arrhenius plots of O2 consumption versus temperature exhibited slope discontinuities (“breaks”) at temperatures (Arrhenius break temperatures: ABTs) reflective of the species' adaptation temperatures. The ABT for mitochondria of T. bernacchii is the lowest reported for any animal and is ∼12 °C below the value predicted by a regression equation based on ABT data for several invertebrates and fishes. The temperature at which the acceptor control ratio (ACR), an index of efficiency of coupling of electron transport to synthesis of ATP, began to decrease with rising temperature also reflected adaptation temperature. The decrease in ACR with rising temperature began at ∼18 °C for mitochondria of T. bernacchii, in contrast to ∼35 °C for mitochondria of Sarotheridon mossambica. Maintaining T. bernacchii at 4 °C for 2 weeks led to no changes in ABT or in the response of ACR to temperature. The thermal sensitivities of mitochondria of T. bernacchii reflect the high level of cold adaptation and stenothermy that is characteristic of Antarctic Notothenioid fishes.
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    URL: http://dx.doi.org/10.1007/s003600050136
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    Cloning and chromosomal mapping of a novel ABC transporter gene (hABC7), a candidate for X-linked sideroblastic anemia with spinocerebellar ataxia (1998)
    Springer
    Journal of human genetics 43 (1998), S. 115-122 
    Details
    ISSN: 1435-232X
    Keywords: Key words ABC transporter ; Mitochondria ; Heme ; Xq13 ; X-linked sideroblastic anemia with spinocerebellar ataxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We isolated a novel human ATP-binding cassette (ABC) transporter cDNA, determined its nucleotide sequence, and designated it human ABC7 (hABC7). The nucleotide sequence was highly homologous to the ATM1 gene in yeast, which encodes an ABC transporter (yAtm1p) located in the mitochondrial inner membrane. The deduced human product, a putative half-type transporter, consists of 752 amino acids that are 48.9% identical to those of yAtm1p. A computer-assisted protein structural and localization analysis revealed that the mitochondrial targeting signal of yAtm1p is conserved in the N-terminal region of the primary sequence of the hABC7 protein, and therefore this product is also likely to be located in the mitochondrial inner membrane. The evidence strongly suggests that the hABC7 gene is a counterpart of ATM1 and that its product is probably involved in heme transport. We mapped the hABC7 gene to chromosome Xq13.1–q13.3 by fluorescence in-situ hybridization. As band Xq13 has been implicated in X-linked sideroblastic anemia with spinocerebellar ataxia, hABC7 becomes a candidate gene for this heritable disorder.
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    URL: http://dx.doi.org/10.1007/s100380050051
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  • 97
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    Statistical properties of chlorophyll fluorescence induction parameters (1998)
    Springer
    Photosynthetica 35 (1998), S. 121-127 
    Details
    ISSN: 1573-9058
    Keywords: Gaussian distribution ; leaf age ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Parameters of the fast chlorophyll (Chl) fluorescence induction (the O-J-I-P curve) of plants of winter wheat grown in the field canopy were statistically tested for Gaussian distribution. Five different statistical methods showed that the obtained values did not obey the Gaussian distribution law. The presentation of the parameters with the help of the mean and standard deviation masks the information about statistical properties of the values. Thus, we recommend to present the parameters by means of median, quartiles, and minimum and maximum values rather than by means of the mean and standard deviation.
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    URL: http://dx.doi.org/10.1023/A:1006886202444
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    Use of a lux-based procedure to rapidly visualize root colonisation by Pseudomonas fluorescens in the wheat rhizosphere (1997)
    Springer
    Antonie van Leeuwenhoek 72 (1997), S. 365-372 
    Details
    ISSN: 1572-9699
    Keywords: bioluminescence ; Pseudomonas ; root colonization ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bioluminescently marked Pseudomonas fluorescens strain 5RL, has been used previously to follow colonisation of soy bean roots (De Weger et al. [1991] Appl. Environ. Microbiol. 57:36-41). In the present paper the method has been further developed and optimized for wheat roots and it is used to get a quick overview of the colonisation patterns of many different root systems at the same time. Colonisation was followed on wheat plants grown in our gnotobiotic sand system (Simons et al., 1996. Mol Plant Microbe Interact 9: 600–607) and the following results were obtained. (i) A spatio-temporal analysis of the colonisation of wheat roots showed that 4 days after planting the highest bacterial activity was observed at the upper part of the root. After 6 days the high bacterial activity at the upper part was further increased, whereas spot-like activities were observed on the lower root parts, possibly due to micro-colonies. (ii) Bacterial mutations causing lack of motility or auxotrophy for amino acids resulted in impaired colonisation of the lower root parts, indicating that motility and prototrophy for the involved amino acid(s) are important factors for wheat root colonisation by strain 5RL. (iii) Coinoculation of strain 5RL with other wild type Pseudomonas strains on the root influenced the colonisation pattern observed for strain 5RL. Colonisation was not visually affected when the competing strain was a poor root coloniser, but was severely reduced when the competing strain was a good root coloniser. The results show that the spatio-temporal colonisation of wheat root by P. fluorescens strain 5RL and derivatives is similar to that of strain WCS365 on tomato. The advantage of the use of lux-marked strains is that the results are obtained much quicker than when conventional methods are used and that the result is supplied as an image of the colonisation pattern of many different roots.
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    URL: http://dx.doi.org/10.1023/A:1000565413024
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    Role of mitochondria in human aging (1997)
    Springer
    Journal of biomedical science 4 (1997), S. 319-326 
    Details
    ISSN: 1423-0127
    Keywords: Oxidative damage ; Reactive oxygen species ; Mitochondria ; Mitochondrial DNA ; Mutation ; Aging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mitochondria are the major intracellular source and target sites of reactive oxygen species (ROS) that are continually generated as by-products of aerobic metabolism in animal and human cells. It has been demonstrated that mitochondrial respiratory function declines with age in various human tissues and that a defective respiratory chain results in enhanced production of ROS and free radicals in mitochondria. On the other hand, accumulating evidence now indicates that lipid peroxidation, protein modification and mitochondrial DNA (mtDNA) muutation are concurrently increased during aging. On the basis of these observations and the fact that the rate of cellular production of superoxide anions and hydrogen peroxide increases with age, it has recently been postulated that oxidative stress is a major contributory factor in the aging process. A causal relationship between oxidative modification and mutation of mtDNA, mitochondrial dysfunction and aging has emerged, although some details have remained unsolved. In this article, the role of mitochondria in the human aging process is reviewed on the basis of recent findings gathered from our and other laboratories.
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    URL: http://dx.doi.org/10.1007/BF02258357
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    Cloning and characterization of MRP10, a yeast gene coding for a mitochondrial ribosomal protein (1997)
    Springer
    Current genetics 31 (1997), S. 228-234 
    Details
    ISSN: 1432-0983
    Keywords: Key wordsSaccharomyces cerevisiae ; MRP10 ; Mitochondria ; Mitochondrial ribosomal protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear gene MRP10 of Saccharomyces cerevisiae was cloned by complementation of a respiratory deficient mutant N518/L1. This mutant is defective in mitochondrial translation and shows a tendency to accumulate deletions in mitochondrial DNA (ρ –). Analysis revealed Mrp10p to be a component of the 37 S subunit of the mitochondrial ribosomes. Disruption of MRP10 in a haploid strain of yeast elicits a phenotype identical to that of the original mutant. The respiratory defect of the null mutant is rescued by re-introducing the MRP10 gene in a wild-type mitochondrial DNA background. These results indicate that Mrp10p belongs to the class of yeast mitochondrial ribosomal proteins that are essential for translation. Searches of current databases failed to reveal any homologs among known bacterial or eucaryotic cytoplasmic ribosomal proteins. Some sequence similarity, however, was detected between Mrp10p and Yml37p, previously identified as a component of the yeast mitochondrial 50 S ribosomal subunit.
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    URL: http://dx.doi.org/10.1007/s002940050199
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