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  • Articles  (198)
  • Mitochondria  (198)
  • Springer  (198)
  • National Academy of Sciences
  • 1995-1999  (140)
  • 1975-1979  (55)
  • 1965-1969  (3)
  • Biology  (198)
  • Architecture, Civil Engineering, Surveying
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  • Articles  (198)
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  • 1
    Electronic Resource
    Electronic Resource
    Regulated protein degradation in mitochondria (1996)
    Springer
    Cellular and molecular life sciences 52 (1996), S. 1069-1076 
    Details
    ISSN: 1420-9071
    Keywords: Mitochondria ; proteolysis ; PIM1 protease ; AAA protease ; chaperone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Various adenosine triphosphate (ATP)-dependent proteases were identified within mitochondria which mediate selective mitochondrial protein degradation and fulfill crucial functions in mitochondrial biogenesis. The matrix-localized PIM1 protease, a homologue of theEscherichia coli Lon protease, is required for respiration and maintenance of mitochondrial genome integrity. Degradation of non-native polypeptides by PIM1 protease depends on the chaperone activity of the mitochondrial Hsp70 system, posing intriguing questions about the relation between the proteolytic system and the folding machinery in mitochondria. The mitochondrial inner membrane harbors two ATP-dependent metallopeptidases, them- and thei-AAA protease, which expose their catalytic sites to opposite membrane surfaces and cooperate in the degradation of inner membrane proteins. In addition to its proteolytic activity, them-AAA protease has chaperone-like activity during the assembly of respiratory and ATP-synthase complexes. It constitutes a quality control system in the inner membrane for membrane-embedded protein complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01952104
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  • 2
    Electronic Resource
    Electronic Resource
    Mitochondrial distribution and inheritance (1996)
    Springer
    Cellular and molecular life sciences 52 (1996), S. 1111-1116 
    Details
    ISSN: 1420-9071
    Keywords: Mitochondria ; mitochondrial inheritance ; cytoskeleton ; Saccharomyces cerevisiae ; Schizosaccharomyces pombe ; membrane proteins ; organelle movement ; mitochondrial morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Mechanisms mediating the inheritance of mitochondria are poorly understood, but recent studies with the yeastsSaccharomyces cerevisiae andSchizosaccharomyces pombe have begun to identify components that facilitate this essential process. These components have been identified through the analysis of conditional yeast mutants that display aberrant mitochondrial distribution at restrictive conditions. The analysis of these mutants has uncovered several novel proteins that are localized either to cytoskeletal structures or to the mitochondria themselves. Many mitochondrial inheritance mutants also show altered mitochondrial morphology and defects in maintenance of the mitochondrial genome. Although some inheritance components and mechanisms appear to function specifically in certain types of cells, other conserved proteins are likely to mediate mitochondrial behavior in all eukaryotic cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01952109
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  • 3
    Electronic Resource
    Electronic Resource
    Stabilization of amorphous calcium phosphate by Mg and ATP (1977)
    Springer
    Calcified tissue international 23 (1977), S. 245-250 
    Details
    ISSN: 1432-0827
    Keywords: Stabilization ; Amorphous calcium phosphate ; Mitochondria ; Mg and ATP ; Nucleation poisoning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary A synergistic effect has been demonstrated when magnesium and adenosine triphosphate (ATP) are used together in solution to delay the conversion of a slurry of amorphous calcium phosphate (ACP) to crystalline hydroxyapatite (HA). Conversion is delayed in some instances more than 10 times as long as with either ATP or Mg alone. In all experiments conversion did not begin until ATP in solution had decreased through hydrolysis to an undetectable level. The effect of Mg is to decrease substantially the rate at which ATP hydrolysis occurs. Once conversion began it proceeded more slowly in the presence of both Mg and ATP than with Mg or ATP alone. ATP was also found to prevent the formation of HA from metastable solutions of calcium and phosphate which did not contain any solid phase. Over the time period of these experiments, ATP hydrolyzed to a negligible extent in Tris-HCl buffer and in solutions containing Ca, PO4, and Ca plus PO4 ions. Hydrolysis of ATP does occur in the presence of ACP or HA, presumably by transphosphorylation on the surface of the solid calcium phosphate phase. It was concluded that ATP stabilized ACP, not by affecting its dissolution, but either by poisoning heteronuclear growth sites, or by poisoning the growth of embryonic HA nuclei (formed heterogeneously or homogeneously) before their critical size is reached, or by poisoning both. In the case of embryonic HA nuclei, the poisoned nuclei would go back into solution preventing HA crystal formation. In addition, it was found that the neutral Ca9(PO4)6 clusters, which are believed to be the basic structural unit of ACP, break down into individual Ca and PO4 ions when ACP dissolves in aqueous medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02012793
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  • 4
    Electronic Resource
    Electronic Resource
    The origin of mitochondria (1975)
    Springer
    Journal of molecular evolution 5 (1975), S. 167-176 
    Details
    ISSN: 1432-1432
    Keywords: Mitochondria ; Endosymbiont Hypothesis ; Episome Hypothesis ; Duplication ; Compartimentalisation ; Enslavement Hypothesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The endosymbiont and episome theories about the origin of mitochondria are reviewed. Biochemical and genetic data, relevant to these theories are discussed. An alternative theory is also proposed; this theory is that nuclear and mitochondrial DNAs developed from compartmentalized duplicate prokaryote DNAs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01741239
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  • 5
    Electronic Resource
    Electronic Resource
    The evolution of the RNase P- and RNase MRP-associated RNAs: Phylogenetic analysis and nucleotide substitution rate (1996)
    Springer
    Journal of molecular evolution 43 (1996), S. 46-57 
    Details
    ISSN: 1432-1432
    Keywords: RNase P ; RNase MRP ; Ribonucleoproteins ; Multialignment ; Molecular clock ; Phylogenetic tree ; Quantitative evolutionary rate ; Yeasts ; Vertebrates ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report a detailed evolutionary study of the RNase P- and RNase MRP- associated RNAs. The analyses were performed on all the available complete sequences of RNase MRP (vertebrates, yeast, plant), nuclear RNase P (vertebrates, yeast), and mitochondrial RNase P (yeast) RNAs. For the first time the phylogenetic distance between these sequences and the nucleotide substitution rates have been quantitatively measured. The analyses were performed by considering the optimal multiple alignments obtained mostly by maximizing similarity between primary sequences. RNase P RNA and MRP RNA display evolutionary dynamics following the molecular clock. Both have similar rates and evolve about one order of magnitude faster than the corresponding small rRNA sequences which have been, so far, the most common gene markers used for phylogeny. However, small rRNAs evolve too slowly to solve close phylogenetic relationships such as those between mammals. The quicker rate of RNase P and MRP RNA allowed us to assess phylogenetic relationships between mammals and other vertebrate species and yeast strains. The phylogenetic data obtained with yeasts perfectly agree with those obtained by functional assays, thus demonstrating the potential offered by this approach for laboratory experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02352299
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  • 6
    Electronic Resource
    Electronic Resource
    Organization and evolution of the mitochondrial genome of yeast (1976)
    Springer
    Journal of molecular evolution 9 (1976), S. 25-35 
    Details
    ISSN: 1432-1432
    Keywords: Genome organization ; Evolution ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial genome of yeast (S. cerevisiae orS. carlsbergensis) appears to be formed by 60–70 genetic units, each one of which is formed by (1) a GC-rich sequence, possibly having a regulatory role; (2) a gene, and (3) an AT-rich spacer, which probably is not transcribed. Recombination in this genome appears to underlie a number of important phenomena. The organization of the mitochondrial genome of yeast and these recombinational events are discussed in relationship with the organization and evolution of the nuclear genome of eukaryotes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01796120
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  • 7
    Electronic Resource
    Electronic Resource
    A comparison of mitochondrial tRNAs in five vertebrates (1995)
    Springer
    Journal of molecular evolution 40 (1995), S. 537-540 
    Details
    ISSN: 1432-1432
    Keywords: Transfer RNA ; Mitochondria ; Neutral changes ; Evolutionary divergence ; Vertebrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sequences of several vertebrate mitochondrial tRNAs were aligned and compared. The comparisons were made in pairs of the tRNAs for an identical amino acid. There are 22 genes for different tRNAs in each vertebrate mitochondrial DNA. The closest similarities were between rat and mouse, the next were between mammals, and the widest difference was between human or rat and Xenopus laevis. However, there were very wide variations between different amino acids in each set of comparisons. The time lapse for each percent of difference greatly increased with evolutionary separation. Most of the nucleotide substitutions appeared to be neutral in character.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00166622
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  • 8
    Electronic Resource
    Electronic Resource
    Evolution according to large ribosomal subunit RNA (1995)
    Springer
    Journal of molecular evolution 41 (1995), S. 366-375 
    Details
    ISSN: 1432-1432
    Keywords: Large ribosomal subunit RNA ; Small ribosomal subunit RNA ; Archaea ; Bacteria ; Eucarya ; Plastids ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Evolutionary trees were constructed, by distance methods, from an alignment of 225 complete large subunit (LSU) rRNA sequences, representing Eucarya, Archaea, Bacteria, plastids, and mitochondria. A comparison was made with trees based on sets of small subunit (SSU) rRNA sequences. Trees constructed on the set of 172 species and organelles for which the sequences of both molecules are known had a very similar topology, at least with respect to the divergence order of large taxa such as the eukaryotic kingdoms and the bacterial divisions. However, since there are more than ten times as many SSU as LSU rRNA sequences, it is possible to select many SSU rRNA sequence sets of equivalent size but different species composition. The topologies of these trees showed considerable differences according to the particular species set selected. The effect of the dataset and of different distance correction methods on tree topology was tested for both LSU and SSU rRNA by repetitive random sampling of a single species from each large taxon. The impact of the species set on the topology of the resulting consensus trees is much lower using LSU than using SSU rRNA. This might imply that LSU rRNA is a better molecule for studying wide-range relationships. The mitochondria behave clearly as a monophyletic group, clustering with the Proteobacteria. Gram-positive bacteria appear as two distinct groups, which are found clustered together in very few cases. Archaea behave as if monophyletic in most cases, but with a low confidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01215184
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular phylogeny of Allomyces macrogynus: Congruency between nuclear ribosomal RNA- and mitochondrial protein-based trees (1995)
    Springer
    Journal of molecular evolution 41 (1995), S. 657-665 
    Details
    ISSN: 1432-1432
    Keywords: Ribosomal RNA ; Protein ; Phylogeny ; Mitochondria ; Nuclear ; Lower fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have sequenced the nuclear and mitochondrial small subunit rRNA genes (rns) and the mitochondrial genes coding for subunits 1 and 3 of the cytochrome oxidase (cox1 and cox3, respectively) of the chytridiomycete Allomyces macrogynus. Phylogenetic trees inferred from the derived COX1 and COX3 proteins and the nuclear rns sequences show with good bootstrap support that A. macrogynus is an early diverging fungus. The trees inferred from mitochondrial rns sequences do not yield a topology that is supported by bootstrap analysis. The similarity and the relative robustness of the nuclear rns and the mitochondrial protein-derived phylogenetic trees suggest that protein sequences are of higher value than rRNA sequences for reconstructing mitochondrial evolution. In addition, our trees support a monophyletic origin of mitochondria for the range of analyzed eukaryotes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175824
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  • 10
    Electronic Resource
    Electronic Resource
    Evolution of thenad3-rps12 gene cluster in angiosperm mitochondria: Comparison of edited and unedited sequences (1996)
    Springer
    Journal of molecular evolution 43 (1996), S. 447-452 
    Details
    ISSN: 1432-1432
    Keywords: Angiosperm ; Mitochondria ; Gene cluster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have analyzed thenad3-rps12 locus for eight angiosperms in order to compare the utility of mitochondrial DNA and edited mRNA sequences in phylogenetic reconstruction. The two coding regions, containing from 25 to 35 editing sites in the various plants, have been concatenated in order to increase the significance of the analysis. Differing from the corresponding chloroplast sequences, unedited mitochondrial DNA sequences seem to evolve under a quasi-neutral substitution process which undifferentiates the nucleotide substitution rates for the three codon positions. By using complete gene sequences (all codon positions) we found that genomic sequences provide a classical angiosperm phylogenetic tree with a clear-cut grouping of monocotyledons and dicotyledons with Magnoliidae at the basal branch of the tree. Conversely, owing to their low nucleotide substitution rates, edited mRNA sequences were found not to be suitable for studying phylogenetic relationships among angiosperms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02337516
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  • 11
    Electronic Resource
    Electronic Resource
    Evolution according to large tribosomal subunit RNA (1995)
    Springer
    Journal of molecular evolution 41 (1995), S. 366-375 
    Details
    ISSN: 1432-1432
    Keywords: Large ribosomal subunit RNA ; Small ribosomal subunit RNA ; Archaea ; Bacteria ; Eucarya ; Plastids ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Evolutionary trees were constructed, by distance methods, from an alignment of 225 complete large subunit (LSU) rRNA sequences, representing Eucarya, Archaea, Bacteria, plastids, and mitochondria. A comparison was made with trees based on sets of small subunit (SSU) rRNA sequences. Trees constructed on the set of 172 species and organelles for which the sequences of both molecules are known had a very similar topology, at least with respect to the divergence order of large taxa such as the eukaryotic kingdoms and the bacterial divisions. However, since there are more than ten times as many SSU as LSU rRNA sequences, it is possible to select many SSU rRNA sequence sets of equivalent size but different species composition. The topologies of these trees showed considerable differences according to the particular species set selected. The effect of the dataset and of different distance correction methods on tree topology was tested for both LSU and SSU rRNA by repetitive random sampling of a single species from each large taxon. The impact of the species set on the topology of the resulting consensus trees is much lower using LSU than using SSU rRNA. This might imply that LSU rRNA is a better molecule for studying wide-range relationships. The mitochondria behave clearly as a monophyletic group, clustering with the Proteobacteria. Gram-positive bacteria appear as two distinct groups, which are found clustered together in very few cases. Archaea behave as if monophyletic in most cases, but with a low confidence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186549
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  • 12
    Electronic Resource
    Electronic Resource
    Free-radical-induced mutation vs redox regulation: Costs and benefits of genes in organelles (1996)
    Springer
    Journal of molecular evolution 42 (1996), S. 482-492 
    Details
    ISSN: 1432-1432
    Keywords: Aging ; Chloroplasts ; Mitochondria ; Cell evolution ; Cytoplasmic genomes ; Gene transfer ; Redox regulation ; Free radical mutagenesis ; Nitrogen fixation ; Endosymbiosis ; Mutation frequency ; Uniparental inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The prokaryotic endosymbionts that became plastids and mitochondria contained genes destined for one of three fates. Genes required for free-living existence were lost. Most genes useful to the symbiosis were transferred to the nucleus of the host. Some genes, a small minority, were retained within the organelle. Here we suggest that a selective advantage of movement of genes to the nucleus is decreased mutation: plastids and mitochondria have high volume-specific rates of redox reactions, producing oxygen free radicals that chemically modify DNA. These mutations lead to synthesis of modified electron carriers that in turn generate more mutagenic free radicals—the “vicious circle” theory of aging. Transfer of genes to the nucleus is also advantageous in facilitating sexual recombination and DNA repair. For genes encoding certain key components of photosynthesis and respiration, direct control of gene expression by redox state of electron carriers may be required to minimize free radical production, providing a selective advantage of organelle location which outweighs that of location in the nucleus. A previous proposal for transfer of genes to the nucleus is an economy of resources in having a single genome and a single apparatus for gene expression, but this argument fails if any organellar gene is retained. A previous proposal for the retention of genes within organelles is that certain proteins are organelle-encoded because they cannot be imported, but there is now evidence against this view. Decreased free radical mutagenesis and increased sexual recombination upon transfer to the nucleus together with redox control of gene expression in organelles may now account for the slightly different gene distributions among nuclei, plastids, and mitochondria found in major eukaryote taxa. This analysis suggests a novel reason for uniparental inheritance of organelles and the evolution of anisogametic sex, and may also account for the occurrence of nitrogen fixation in symbionts rather than in nitrogen-fixing organelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02352278
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  • 13
    Electronic Resource
    Electronic Resource
    Action de la rubratoxine B sur la respiration des mitochondries hépatiques de rat (1975)
    Springer
    Mycopathologia 55 (1975), S. 53-55 
    Details
    ISSN: 1573-0832
    Keywords: Rubratoxine B ; Mitochondria ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The in vitro effect of rubratoxin B on the electron transport system of rat liver mitochondria was investigated. This mycotoxin depressed oxygen consumption in ADP-lacking mitochondria and in ADP-coupled mitochondria, using succinate or β-hydroxybutyrate as substrats. Rubratoxin B is neither an oxidative-phosphorylation inhibitor nor uncoupling agent. Its effect is compared with aflatoxin B1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00467092
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  • 14
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02258357
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  • 15
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00898-998-0012-4
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  • 16
    Electronic Resource
    Electronic Resource
    Mitochondrial granules in chondrocytes (1969)
    Springer
    Calcified tissue international 3 (1969), S. 184-193 
    Details
    ISSN: 1432-0827
    Keywords: Mitochondria ; Calcification ; Calcium ; Chondrocytes ; Growth plate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Description / Table of Contents: Résumé Des cultures d'épiphyse prélevées sur des rats et des souris ont été étudiées sous le microscope électronique. Un profile de granules mitochondriques de densité électronique a été trouvé. Les chondrocytes dans la zone proliférative avaint peu de granules, alors que ceux des zones successives ont montré une augmentation progressive de leur nombre et densité jusqu'à ce que la zone de calcification provisoire ait été atteinte. Cette zone a montré une distribution périphérique de mitochondries et une réduction du nombre et de la densité des granules mitochondriques. Du calcium isotopique 47 a été utilisé autoradiographiquement pour déterminer la location de calcium dans ces cellules. Des grains ont été trouvés sur les membranes R.E. et sur la plupart des mitochondries. La preuve d'un profile de ces granules et de leur rapport spatial avec la face de minéralisation indique une action éventuelle de mitochondries dès le début de la calcification de la matrice.
    Abstract: Zusammenfassung Epiphysekulturen von Ratten und Mäusen wurden unter dem Elektronenmikroskop untersucht. Ein Profil von mitochondrischen Körnchen mit elektronischer Dichte wurde gefunden. Chondrozyten in der Proliferationszone wiesen wenig Körnchen auf, während die der nachfolgenden Zonen allmählich an Zahl und Dichte zunahmen, bis die Zone der provisorischen Verkalkung erreicht wurde. Diese Zone zeigte eine periphere Verteilung der Mitochondrien und eine Abnahme in Zahl und Dichte der mitochondrischen Körnchen. Isotopes Kalzium 47 wurde autoradiographisch verwendet, um die Lage des Kalziums in diesen Zellen zu bestimmen. Körnchen wurden auf den E.R.-Membranen und auf einem Großteil der Mitochondrien gefunden. Der Nachweis eines Profils dieser Körnchen und ihres räumlichen Verhältnisses zur Mineralisierungsfläche weist auf einen möglich Einfluß der Mitochondrien mit Beginn der Matrixverkalkung hin.
    Notes: Abstract Rat and mice epiphyseal growth plates were studied with the electron microscope. A gradient of mitochondrial electron-dense granules was found. Chondrocytes in the proliferative zone had few granules, while those of the succeeding zones showed a gradual increase in number and density until the zone of provisional calcification was reached. This zone showed a peripheral distribution of mitochondria and a decrease in the number and density of mitochondrial granules. Isotopic47calcium was used autoradiographically to determine the location of calcium in these cells. Grains were found over the endoplasmic reticulum membranes and over most mitochondria. The demonstration of a gradient of these granules and their spatial relation to the mineralization front suggests a possible involvement of mitochondria in the onset of matrix calcification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02058661
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  • 17
    Electronic Resource
    Electronic Resource
    Absence of mitochondrial terminal respiratory enzymes in cartilage matrix vesicles (1977)
    Springer
    Calcified tissue international 24 (1977), S. 37-39 
    Details
    ISSN: 1432-0827
    Keywords: Cartilage ; Matrix vesicles ; Mitochondria ; Respiratory enzymes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary This study attempted to detect evidence of mitochondrial terminal respiratory components in matrix vesicles isolated from rachitic rat tibial epiphyseal plates. Biochemical assays for cytochrome c oxidase, NAD isocitrate dehydrogenase, NADP isocitrate dehydrogenase and succinate-cytochrome c reductase were negative. Polarimetric determinations revealed that the addition of succinate to matrix vesicles in suspension did not cause any increase in oxygen utilization. Spectrophotometric tracings of deoxycholate-solubilized matrix vesicles showed no characteristic absorption peaks or maxima belonging to any of the cytochrome complex components. Attempts to prepare pyridine hemochromes of cytochrome prosthetic groups from the matrix vesicles were also unsuccessful. The above results indicate that key components of mitochondrial respiratory systems are not detectable in rachitic matrix vesicles. The results are compatible with the interpretation that such vesicles are not derived from mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02223294
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  • 18
    Electronic Resource
    Electronic Resource
    Are mitochondria directly involved in biological mineralisation? (1969)
    Springer
    Calcified tissue international 3 (1969), S. 100-102 
    Details
    ISSN: 1432-0827
    Keywords: Mitochondria ; Calcium ; Mineralisation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02058651
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  • 19
    Electronic Resource
    Electronic Resource
    A proposed cellular mechanism for calcium transport in the intestinal epithelial cell (1978)
    Springer
    Calcified tissue international 26 (1978), S. 71-79 
    Details
    ISSN: 1432-0827
    Keywords: Absorption ; Calcium ; Mitochondria ; Intestinal epithelium ; Potassium-pyroantimonate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Intracellular transport of calcium from the apical to the basal-lateral region of the intestinal epithelial cell was invetigated in duodenum from normal fed, fasted, and calcium-loaded rats. The process was followed with time using electron microscopy with potassium pyroantimonate to precipitate calcium. The observations made were subjected to morphometric analysis. The specificity of the method was demonstrated in the villus cell by resistance to micro-incineration and by absence of deposits following exposure to EGTA. Using this method calcium was seen in cells from calcium-fed rats at the microvillus border, in the Golgi zone, and within the internal compartments of the mitochondria. In cells from fasted rats calcium was not seen. Mitochondria were found largely at the apex of the cell and were free of detectable calcium. By 5 min, in the cells of fasted rats given a calcium load, the calcium had reached the Golgi apparatus and the inner mitochondrial compartment. After 15 min mitochondria were heavily loaded with calcium and had moved to the basal region of the cell. These observations suggest that mitochondria play an important role in absorption of calcium and appear to transport this ion from the apex to the basal region of the cell where entry into the capillaries takes place.
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    URL: http://dx.doi.org/10.1007/BF02013237
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    Mitochondria, calcification and waste disposal (1969)
    Springer
    Calcified tissue international 3 (1969), S. 363-365 
    Details
    ISSN: 1432-0827
    Keywords: Calcification ; Mitochondria ; Protozoa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02058679
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    Glyoxysomal and mitochondrial malate dehydrogenase of watermelon (Citrullus vulgaris) cotyledons (1977)
    Springer
    Planta 136 (1977), S. 211-220 
    Details
    ISSN: 1432-2048
    Keywords: Citrullus ; Isoenzymes ; Malate dehydrogenase ; Enzyme subunits ; Mitochondria ; Glyoxysomes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Molecular properties of the glyoxysomal and mitochondrial isoenzyme of malate dehydrogenase (EC 1.1.1.37; L-malate: NAD+ oxidoreductase) from watermelon cotyledons (Citrullus vulgaris Schrad.) were investigated, using completely purified enzyme preparations. The apparent molecular weights of the glyoxysomal and mitochondrial isoenzymes were found to be 67,000 and 74,000 respectively. Aggregation at high enzyme concentrations was observed with the glyoxysomal but not with the mitochondrial isoenzyme. Using sodium dodecyl sulfate electrophoresis each isoenzyme was found to be composed of two polypeptide chains of identical size (33,500 and 37,000, respectively). The isoenzymes differed in their isoelectric points (gMDH: 8,92, mMDH: 5.39), rate of heat inactivation (gMDH: τ1/2 at 40°C=3.0 min; mMDH: stable at 40°C; τ1/2 at 60°C=4.5 min), adsorption to dextran gels at low ionic strenght, stability against alkaline conditions and their pH optima for oxaloacetate reduction (gMDH: pH 6.6, mMDH: pH 7.5). Very similar pH optima, however, were observed for L-malate oxidation (pH 9.3–9.5). The results indicate that the glyoxysomal and mitochondrial MDH of watermelon cotyledons are distinct proteins of different structural composition.
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    Destruction and possible de novo synthesis of phytochrome in subcellular fractions of laminae from Avena sativa L. (1978)
    Springer
    Planta 141 (1978), S. 273-277 
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    ISSN: 1432-2048
    Keywords: Avena ; Etioplasts ; Mitochondria ; Phytochrome
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytochrome was determined in etiolated laminae of Avena sativaL. either without pretreatment or after 5 min of red irradiation followed by different periods of darkness (0–24 h). At given intervals laminae were homogenized and phytochrome was determined spectrophotometrically in the total homogenate and in purified etioplasts and mitochondria. Enhanced specific activity of phytochrome was found in all fractions after the irradiation in comparison to dark controls. Phytochrome destruction was observed in all fractions at the beginning of the subsequent dark period. Whereas the homogenate and the mitochondrial fraction showed a continuous destruction so that phytochrome reached a level far below that in etiolated plants, the phytochrome level in the plastid fraction reacheda minimum at 2 h with a subsequent increase beyond the dark level. This increase was most pronounced between 4 and 8 h after the red irradiation. The results are discussed in terms of the destruction and possible de novo synthesis of phytochrome that may be different in mitochondria and plastids.
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    Influence of bovine serum albumine on the proton conductance of potato mitochondria membranes (1979)
    Springer
    Planta 147 (1979), S. 122-126 
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    ISSN: 1432-2048
    Keywords: Mitochondria ; Proton conductance ; Serum albumin ; Solanum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pulsed acid base titrations, according to the procedure of Mitchell and Moyle, have been carried out on potato mitochondria in the presence and absence of Bovine Serum Albumine (BSA). The rate of the pH decay is slower when BSA is present. The buffering capacities of the outer and inner phases, the t1/2 of the pH decay after an acid pulse and the proton conductance of the inner membrane have been measured. The results show that plant mitochondria are relatively impermeable to H+ and OH−, but leakier than animal mitochondria. This may be related to the lower respiratory control ratios generally found with plant mitochondria.
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    Control of mitochondrial activities by phytochrome during greening (1979)
    Springer
    Planta 147 (1979), S. 229-235 
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    ISSN: 1432-2048
    Keywords: Avena ; Greening ; Mitochondria ; Oxidative Phosphorylation ; Phytochrome ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria isolated from 7-day old darkgrown Avena sativa L. (var. Arnold) laminae given 5 min illumination of red light, followed by varying lengths of darkness up to 3 h, showed at least a twofold increase in the rates of both NADH-dependent oxygen consumption and respiratory chain phosphorylation over those of mitochondria isolated from unilluminated tissue. Similar organelles, isolated from tissue given either far-red or red followed by far-red pretreatment, exhibited rates of both functions of between 25% and 75% below those of the mitochondria from unilluminated tissue. The induction-reversion criteria for phytochrome control of respiration and oxidative phosphorylation were satisfied under all experimental conditions during the greening process. Treatment with continuous far-red light, acting presumably through the ‘high irradiance’ reaction of phytochrome, served to disengage phytochrome activity from photosynthesis. The stimulation of oxidative phosphorylation still occurred under these conditions, slightly slower but much more prolonged in the absence of ATP from photophosphorylation.
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    Effect of temperature on the pathways of NADH-oxidation in broad-bean mitochondria (1979)
    Springer
    Planta 144 (1979), S. 359-365 
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    ISSN: 1432-2048
    Keywords: Mitochondria ; NADH oxidation ; Respiration (rotenone-resistant) ; Temperature activation ; Vicia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. Respiration rates of broad-bean (Vicia faba) mitochondria were studied as a function of temperature. Arrhenius plots of all membrane-bound enzymes, as obtained with saturating substrate concentrations, revealed a break in the lower temperature range. That break was considered to indicate a phase transition of membrane phospholipids, characteristic for chilling-sensitive plants. A second discontinuity at 30°C occurred only with activities linked to energy conservation. — 2. The activation energies for the oxidation of NAD+-linked substrates differ between states 3 and 4. State 3 respiration of NAD+-linked substrates is the result a superimposition of two branches of electron transport, which can be separated by different sensibilities to rotenone. A characteristic temperature dependency of the respiratory control, as well as a shift of the low temperature break in the Arrhenius plot toward a higher temperature after state 4 to state 3 transition, are calculated to be caused by the superimposition of the two branches. — 3. The temperature dependency of the oxidation of extra-mitochondrial NADH and of succinate differs remarkably from that of the oxidation of matrix-NADH. It has been concluded that the rotenone-resistant oxidation of matrix-NADH and the oxidation of external NADH are mediated via different pathways with individual regulation sites.
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    Post-meiotic nucleo-cytoplasmic interaction in Cosmos bipinnatus (1979)
    Springer
    Planta 145 (1979), S. 449-457 
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    ISSN: 1432-2048
    Keywords: Alternation of generation ; Cosmos ; Gametogenesis ; Mitochondria ; Nuclear envelope ; Organelle autonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An interaction involving the nuclear envelope and spherical double-membrane bound inclusions takes place in the cytoplasm of post-meiotic male microspores of Cosmos (tribe Heliantheae, sub-tribe Coreopsidinae). The identity of the spherical inclusions has yet to be fully established, but they closely resemble profiles elsewhere in the cytoplasm, themselves presumably derived from the mitochondrial population of the premeiotic pollen mother cells. Both the cytoplasmic and nucleaar-associated inclusions regularly contain a central ‘vesicle’, formed by an ingagination of their bounding membranes. The interaction, which occurs immediately prior to the deposition of the primexine of the pollen wall, involves the adhesion of the inclusions to the nuclear surface. Experiments with osmotically disrupted cells reveal that the inclusions are firmly bound to the envelope and, at the points of contact, electron opaque granules are regularly present. Frequently elements of the chromatin may be observed in juxtapostion to these points of contact, but on the inner face of the envelope. The interaction in Cosmos is proposed to constitute part of the process by which the cytoplasm and its content are realigned to the new “gametophylic” style of growth.
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    Kinetics of mitochondrial phosphate transport and rates of respiration and phosphorylation during greening of etiolated Avena leaves (1979)
    Springer
    Planta 144 (1979), S. 325-332 
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    ISSN: 1432-2048
    Keywords: Avena ; Greening ; Mitochondria ; Phosphate transport ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using the technique of silicone oil filtration of organelles and the inhibitor stop method, the kinetics of transport of inorganic phosphate across the inner mitochondrial membrane were tested in relation to different stages of greening (0 to 24 h) of etiolated laminae of Avena sativa L., and compared to the rates of oxygen consumption and ATP formation. The results demonstrate that there is a pronounced increase in phosphate transport after 3 h of greening, reaching values for Vmax (about 17 μmol mg protein-1 h-1) that are three times as high as those measured with mitochondria from etiolated tissue. This is also mirrored by the rates of respiration and oxidative phosphorylation. After 24 h of light treatment (4 Klx), respiration and ATP formation, as well as V decreased again to levels below those of the etiolated stage. In contrast to V, there was no change in the affinity between inorganic phosphate and the binding sites of the transporting systems involved, as indicated by a rather constant Km (0.23 mM) for phosphate transport. Of the inhibitors of phosphate transport tested, mersalyl and methyl mercuric iodide were most efficient with identical characteristics of inhibition; but compared to animal mitochondria, the concentrations needed to result in similar amounts of inhibition, were more than ten times higher. The results are discussed with respect to plastid development.
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    Conjoined mitochondria and plastids in the barley mutant ‘albostrians’ (1979)
    Springer
    Planta 147 (1979), S. 178-179 
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    ISSN: 1432-2048
    Keywords: Hordeum ; Mitochondria ; Plastids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The intercalary meristem and surrounding tissues of the gene induced plastome mutant ‘albostrians’ of Hordeum vulgare L. were examined in the electron microscope for ultrastructural evidence of membrane continuities between plastids and mitochondria. In well developed tissues the ribosome-deficient plastids were usually in close proximity or appressed to mitochondria of normal appearance. In some sections through the meristemmatic region however the relationship between the two organelles was observed to be of a fused nature. These conjoinings are thought to be similar to those reported in normal living cells using cinephotomicrography but never before observed by transmission electron microscopy.
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    Characteristics of rotenone-insensitive oxidation of matrix-NADH by broad bean mitochondria (1978)
    Springer
    Planta 142 (1978), S. 83-90 
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    ISSN: 1432-2048
    Keywords: Mitochondria ; NADH oxidation ; Rotenone-resistant respiration ; Vicia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria from Vicia faba L. exhibit two pathways for the oxidation of endogenous NADH. One pathway is rotenone-sensitive and includes three phosphorylation sites, the other one is rotenone-insensitive and by-passes site I. This by-pass is located in the area of flavoproteins, but several lines of evidence suggest that the rotenone-insensitive oxidation of matrix-NADH is not mediated by the external NADH dehydrogenase. With saturating substrate concentrations the two pathways are superimposed in state 3 while in state 4 the electrons are transferred only via the by-pass. The rotenone-resistant electron flux is obviously regulated from the substrate side. We suggest that the function of the by-pass is to regulate the NADH/NAD+ ratio of the matrix space.
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    Cytokinin inhibition of respiration by cells and mitochondria of soybean, Glycine max (L.) Merrill (1979)
    Springer
    Planta 146 (1979), S. 503-511 
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    ISSN: 1432-2048
    Keywords: Coumarate ; Cytokinin ; Glycine ; Respiration ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cells of a soybean tissue strain, suspended in an aerated liquid medium, caused disappearance of p-coumaric acid from the medium and oxidation of guaiacol, benzidine, pyrogallol, L-dihydroxyphenylalanine and L-epinephrine. Both the disappearance and the oxidations were inhibited by 6-benzylaminopurine (BAP) at a concentration of 0.5 mM. BAP at other concentrations either promoted or inhibited oxidation of epinephrine in precisely the pattern reported earlier for the disappearance of coumarate; therefore, the disappearance of coumarate probably involves its oxidation. The effectiveness of other cytokinins in inhibiting the oxidation was studied. At 0.5 mM, and perhaps even at 0.5 μM, some of the several cytokinins tested inhibited oxygen consumption by the soybean cells. This inhibition, which did not require any of the above metabolizable compounds, was especially marked in the presence of cyanide, azide or Antimycin A, and was detectable in 10 min or less. Either Antimycin A or salicylhydroxamic acid alone promoted O2 consumption but together they were quite inhibitory. The soybean cells apparently have an alternate respiratory pathway and cytokinins may influence its operation. Several cytokinins at 0.5 mM, and perhaps at 0.5 μM, also inhibited oxygen consumption by mitochondrial preparations from the soybean cells, the inhibition being evident in about 20 s. The consumption required a substrate such as malate, succinate or NADH. Cytokinins and related compounds varied in effectiveness as follows: BAP and 6-isopentenyla-minopurine ≥ 9-tetrahydropyranyl-BAP 〉 kinetin, ribosyl-isopentenylaminopurine, 9-methyl-BAP and 9-methoxymethyl-BAP 〉 6,6-dimethylaminopurine and zeatin (slight activity) 〉 6-methylaminopurine, nicotinamide and adenine (ineffective). To a great extent this order parallels the order of effectiveness of the compounds in causing cell division. Mitochondria, therefore, may contain a site for an important cytokinin action.
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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 
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    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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    The suv3 nuclear gene product is required for the in vivo processing of the yeast mitochondrial 21s rRNA transcripts containing the r1 intron (1995)
    Springer
    Current genetics 27 (1995), S. 234-238 
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    ISSN: 1432-0983
    Keywords: Mitochondria ; Introns ; Saccharomyces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have constructed a yeast mitochondrial genome containing only one group-I intron, r1, from the 21s rRNA gene and introduced this genome into a strain bearring a disruption of the suv3 gene. The presence of the r1 intron alone causes a block in respiration, while the isogenic strain containing the intronless genome is respiratory competent. Northern analysis indicates that the functional suv3 protein is necessary for the yeast cell in order to process the r1-containing transcripts: in the absence of the suv3 protein the hybridization pattern of the excised r1 intron is altered and the amount of mature 21s rRNA is 50-fold lower. We suggest that the multifunctional suv3 protein, which displays motifs of ATP-dependent RNA helicases, is necessary for the in vivo pathway leading to formation of mature 21s rRNA from the transcripts containing the r1 intron in mitochondria of Saccharomyces cerevisiae.
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    Genetic and biochemical dissection of the mitochondrial protein-import machinery (1995)
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    Current genetics 27 (1995), S. 393-403 
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    ISSN: 1432-0983
    Keywords: Mitochondria ; Protein sorting ; MOM proteins ; MIM proteins ; Heat-shock proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria import most of their proteins from the cytosol. A multi-subunit machinery accomplishes the translocation of precursor polypeptides into across the two mitochondrial membranes. Within recent years more than 20 different proteins have been identified which are involved in mitochondrial protein import. This review summarizes the successful genetic and biochemical approaches that led to the identification of these transport and folding components. The identification and functional characterization of the components can be seen as a paradigm for the molecular analysis of a complex biological process by a combination of biochemical and genetic procedures.
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    Analysis of the transcription products of the rainbow trout (Oncorynchus mykiss) liver mitochondrial genome: detection of novel mitochondrial transcripts (1995)
    Springer
    Current genetics 28 (1995), S. 67-70 
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    ISSN: 1432-0983
    Keywords: RNA ; Mitochondria ; Rainbow trout ; Liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated and, by electrophoresis, using agarose slab gels in the presence of methylmercury hydroxide, analyzed the mitochondrial RNA content of the liver of rainbow trout. The RNAs corresponding to most of the mitochondrial DNA-encoded genes have been identified. Furthermore, among the transcription products we have also identified the nature of the RNA 8 previously described in human mitochondria, and detected a novel transcript that may represent the mRNA for ND6.
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    A point mutation in the 5′-untranslated leader that affects translational activation of the mitochondrial COX 3 mRNA (1995)
    Springer
    Current genetics 28 (1995), S. 60-66 
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    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Translation ; mRNA 5′-leader
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 613-base 5′-untranslated leader (5′-UTL) of the Saccharomyces cerevisiae mitochondrial COX 3 mRNA contains the target of an mRNA-specific translational activator complex composed of at least three nuclearly encoded proteins. We have genetically mapped a collection of cox 3 point mutations, using a set of defined COX 3 deletions, and found one to be located in the region coding the 5′-UTL. The strain carrying this allele was specifically defective in translation of the COX 3 mRNA. Nucleotide-sequence analysis showed that the allele was in fact a double mutation comprised of a single-base insertion in the 5′-UTL (T inserted between bases-428 and-427 with respect to the start of translation) and a G to A substitution at+3 that changed the ATG initiation codon to ATA. Both mutations were required to block translation completely. The effects of the ATG to ATA mutation alone (cox 3-1) had previously been analyzed in this laboratory: it reduces, but does not eliminate, translation, causing a slow respiratory growth phenotype. The T insertion in the 5′-UTL had no detectable respiratory growth phenotype as a single mutation. However, the 5′-UTL insertion mutation enhanced the respiratory defective phenotype of missense mutations in pet 54, one of the COX 3-specific translational-activator genes. This phenotypic enhancement suggests that the-400 region of the 5′-UTL, where the mutation is located, is important for Pet54p-COX 3 mRNA interaction.
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    Functional mitochondria are essential for Saccharomyces cerevisiae cellular resistance to bleomycin (1996)
    Springer
    Current genetics 30 (1996), S. 279-283 
    Details
    ISSN: 1432-0983
    Keywords: Key words Yeast ; Mitochondria ; Bleomycin ; OXA1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The antitumor activity of bleomycin is associated with its ability to produce DNA lesions. The cellular process that repairs bleomycin-induced DNA lesions is not entirely clear. To understand how these DNA lesions are repaired in eukaryotic cells, we used mini Tn3 : : LEU2 :: LacZ transposon mutagenesis to isolate yeast mutants that were hypersensitive to bleomycin. One of the mutants, HCY69, was characterized further and found to be 4- and 3-fold more sensitive, respectively, to bleomycin and hydrogen peroxide, as compared to the parent. The mutant displayed parental resistance to a variety of other DNA-damaging agents. Plasmid rescue and DNA sequence analysis revealed that the transposon interrupted the OXA1 gene, which encodes a protein required to process one of the subunits, cox II, of the cytochrome oxidase complex in mitochondria. A plasmid carrying the native OXA1 gene fully restored drug resistance to strain HCY69. Our data strongly suggest that functional mitochondria are required for cellular protection against the toxic effects of bleomycin.
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    Preferential RNA editing at specific sites within transcripts of two plant mitochondrial genes does not depend on transcriptional context or nuclear genotype (1996)
    Springer
    Current genetics 30 (1996), S. 502-508 
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    ISSN: 1432-0983
    Keywords: Key words RNA editing ; Mitochondria ; Plant ; NADH dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcripts of most plant mitochondrial protein-coding genes exhibit C-to-U RNA editing events. In Petunia, two co-transcribed genes, nad3 and rps12, exhibit transcripts which are not fully edited at all potential editing sites. We investigated the nad3/rps12 transcript population in four different genotypes. In one pair of genotypes, the nuclear genome is identical but the nad3/rps12 genes are in different transcriptional contexts. Both the nad3/ rps12 genes and the plant mitochondrial genomes are identical in a second pair of genotypes, but the nuclear background is derived from two different Petunia species. We found that the overall extent of editing varied greatly between genotypes and is affected by nuclear genotype but not by the global transcriptional context. Local sequence context around a particular site does affect editing frequency. In all genotypes, certain sites exhibit high editing frequency, but these sites do not share obvious primary sequence characteristics. In all genotypes examined, editing sites which do not affect the encoded amino acid are less frequently edited than sites which alter codons to non-synonymous forms. All these data indicate that an unidentified property of the sequences immediately surrounding a cytosine affect its selection as a target in the editing process.
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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 
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    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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    Structure of aGelasinospora linear plasmid closely related to the kalilo plasmid ofNeurospora intermedia (1996)
    Springer
    Current genetics 29 (1996), S. 150-158 
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    ISSN: 1432-0983
    Keywords: Gelasinospora ; Neurospora ; Plasmid ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have determined the complete nucleotide sequence of a linear mitochondrial plasmid from a natural isolate of a homothallic species ofGelasinospora. The plasmid genome is 8231 by long. It carries terminal inverted repeats of 1137 bp. Extending inwards from the terminal repeats are two long open reading frames coding for putative proteins with similarity to DNA and RNA polymerases. These are separated by a short intergenic region. The plasmid sequence shows remarkable similarity to that of theNeurospora intermedia senescence-plasmid kalilo. Overall the two plasmids have a similar genetic organization and are clearly homologous at the sequence level. The main differences are in the intergenic region and in the terminal repeats.
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    URL: http://dx.doi.org/10.1007/BF02221579
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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 
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    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 
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    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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    The fungal mitochondrial genome project: evolution of fungal mitochondrial genomes and their gene expression (1997)
    Springer
    Current genetics 31 (1997), S. 380-395 
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    ISSN: 1432-0983
    Keywords: Key words Chytridiomycetes ; Mitochondria ; Comparative genomics ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The goal of the fungal mitochondrial genome project (FMGP) is to sequence complete mitochondrial genomes for a representative sample of the major fungal lineages; to analyze the genome structure, gene content, and conserved sequence elements of these sequences; and to study the evolution of gene expression in fungal mitochondria. By using our new sequence data for evolutionary studies, we were able to construct phylogenetic trees that provide further solid evidence that animals and fungi share a common ancestor to the exclusion of chlorophytes and protists. With a database comprising multiple mitochondrial gene sequences, the level of support for our mitochondrial phylogenies is unprecedented, in comparison to trees inferred with nuclear ribosomal RNA sequences. We also found several new molecular features in the mitochondrial genomes of lower fungi, including: (1) tRNA editing, which is the same type as that found in the mitochondria of the amoeboid protozoan Acanthamoeba castellanii; (2) two novel types of putative mobile DNA elements, one encoding a site-specific endonuclease that confers mobility on the element, and the other constituting a class of highly compact, structured elements; and (3) a large number of introns, which provide insights into intron origins and evolution. Here, we present an overview of these results, and discuss examples of the diversity of structures found in the fungal mitochondrial genome.
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    The novel nuclear gene DSS-1 of Saccharomyces cerevisiae is necessary for mitochondrial biogenesis (1995)
    Springer
    Current genetics 28 (1995), S. 108-112 
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    ISSN: 1432-0983
    Keywords: Mitochondria ; Saccharomyces ; RNA metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A previously unknown nuclear gene DSS-1 from Saccharomyces cerevisiae was cloned and sequenced. The gene was isolated as a multicopy suppressor of a disruption of the SUV-3 gene coding for a DEAD/H box protein involved in processing and turnover of mitochondrial transcripts. The DSS-1 gene codes for a 970 amino-acid protein of molecular weight 111 kDa and is necessary for mitochondrial biogenesis. Amino-acid sequence analysis indicates the presence of motifs characteristic for Escherichia coli RNase II, the dis3 protein from Schizosaccharomyces pombe, the cyt4 protein participating in RNA processing and turnover in Neurospora crassa mitochondria, and the vacB protein from Shigella flexneri. We suggest that the DSS-1 protein may be a component of the mitochondrial 3′–5′ exoribonuclease complex.
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    Selective DNA amplification regulates transcript levels in plant mitochondria (1995)
    Springer
    Current genetics 28 (1995), S. 113-121 
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    ISSN: 1432-0983
    Keywords: Transcription ; Plant ; Mitochondria ; Copy number ; Gene regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Most plant mitochondrial genomes exist as subgenomic-size fragments apparently due to recombination between repetitive sequences. This leads to the possibility that independently replicating subgenomic domains could result in mitochondrial gene copy number variation. We show, through Southern-blot analysis of both restricted and intact mtDNA, that there are gene-specific copy number differences in the monocot Zea mays. Comparison of two different maize genotypes, B37(N) and B37(T), a cytoplasmic male-sterile strain, reveal fewer gene copy number differences for B37(T) than for B37(N). In contrast to maize, significant gene copy number differences are not detected in the dicot Brassica hirta. We also demonstrate that mitochondrial transcriptional rates in both species are apparently dependent on gene copy number since relative rates determined by run-on analysis are proportional to relative gene copy numbers. Thus a direct relationship exists between plant mitochondrial gene copy number and transcriptional rate.
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    Disruption of the gene encoding the 78-kilodalton subunit of the peripheral arm of complex I in Neurospora crassa by repeat induced point mutation (RIP) (1995)
    Springer
    Current genetics 27 (1995), S. 339-350 
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    ISSN: 1432-0983
    Keywords: Neurospora ; Complex I ; RIP ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have used the procedure of sheltered RIP to generate mutants of the 78-kDa protein of the peripheral arm of Neurospora crassa complex I. The nuclei containing the mutations were initially isolated as one component of a heterokaryon but subsequent analysis showed that nuclei containing null alleles of the gene could be propagated as homokaryons. This demonstrates that the gene does not serve an essential function. Sequence analysis of one allele shows that 61 transition mutations were created resulting in 39 amino-acid changes including the introduction of four stop codons. Mutant strains grow at a slower rate than wild-type and exhibit a decrease in the production of conidia. Electron paramagnetic spectroscopy of mutant mitochondria suggest that they are deficient in Fe−S clusters N-1, N-3, and N-4.
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    The Neurospora crassa cya-5 nuclear gene encodes a protein with a region of homology to the Saccharomyces cerevisiae PET309 protein and is required in a post-transcriptional step for the expression of the mitochondrially encoded COXI protein (1997)
    Springer
    Current genetics 32 (1997), S. 273-280 
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    ISSN: 1432-0983
    Keywords: Key words Neurospora ; Cytochrome c oxidase ; Mitochondria ; COXI translation ; cya-5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cya-5 nuclear mutant of Neurosopora crassa was previously shown to be deficient in cytochrome aa 3, cytochrome c oxidase activity, and the immunologically detectable COXI protein. We have now demonstrated that the mitochondria of this mutant contain mRNA for the COXI protein and that COXI cannot be detected during pulse-chase labeling experiments of mitochondrial translation products. Cloning and analysis of the cya-5 gene reveal a long open reading frame capable of encoding a 1136 amino-acid protein. Sequence analysis suggests that the potential CYA-5 protein contains a mitochondrial targeting sequence at its amino-terminus. The long open reading frame also contains a 200 amino-acid region with homology to the PET309 protein, which is required for the production or stability of intron-containing coxI mRNAs, as well as the translation of mature coxI mRNAs, in the yeast Saccharomyces cerevisiae. These data suggest that the CYA-5 protein of N. crassa is required in a post-transcriptional step for COXI expression, most probably for the efficient translation of coxI mRNA.
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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 
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    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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    A probable cis-regulatory element on yeast mitochondrial DNA responsible for cAMP-mediated transcription (1996)
    Springer
    Current genetics 30 (1996), S. 493-501 
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    ISSN: 1432-0983
    Keywords: Key wordsSaccharomyces cerevisiae ; Transcription ; Mitochondria ; cis element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies from this laboratory have suggested that mitochondrial (mt) transcription in yeast (Saccharomyces cerevisiae) is governed by changing cellular cAMP levels, and that the mechanism of such transcriptional regulation requires cAMP-dependent protein kinase (PKA) activity; these observations, in turn, suggest a trans-activation process for nucleotide-dependent mt transcriptional control. Here we demonstrate a sequence-specific mtDNA-phosphorylated protein interaction, a requisite part of such a control mechanism, using filter-binding and gel mobility shift assays with mt protein extracts and mtDNA from ρ – strains whose retained mt genes show cAMP-sensitive expression. We demonstrate that the protein-mt DNA interaction depends on PKA activity, that it specifically involves a tripartite GC-rich sequence element on yeast mtDNA, and that it does not involve mt coding or promoter sequences. Sequence analysis indicates that the GC-rich element undergoing protein interaction is present in ten copies on the yeast mt genome, and that each copy is located 5′ to a strong mt promoter; the elements appear in both orientations relative to, and at varying distances upstream from, the putatively associated mt promoter elements. The mt element shows no sequence homology to relevant nuclear cis-elements examined and is unrelated to published vertebrate mt cis-elements. Several lines of evidence and argument strongly suggest that this GC-rich element functions as the cis-regulatory sequence involved in cAMP-mediated transcriptional control in yeast mitochondria.
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    The yeast ORF YDL202w codes for the mitochondrial ribosomal protein YmL11 (1997)
    Springer
    Current genetics 31 (1997), S. 396-400 
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    ISSN: 1432-0983
    Keywords: Key wordsSaccharomyces cerevisiae ; Mitochondria ; Ribosomal protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Saccharomyces cerevisiae open reading frame YDL202w has been characterised in the course of the EUROFAN yeast genome analysis program. Disruption of YDL202w causes a respiratory deficient phenotype accompanied by a loss of mitochondrial DNA. This phenotype is usually found in mutants defective in mitochondrial replication or gene expression. YDL202w has the potential to encode a soluble protein of 249 amino acids. It shows significant similarities to the ribosomal protein L10 from various bacteria and to a previously determined amino-terminal peptide sequence of the yeast mitochondrial ribosomal protein L11. The predicted amino-acid sequence of YDL202w starts with a stretch which has neither any correspondence in the bacterial sequences nor in the protein isolated from mitochondrial ribosomes. Furthermore, this stretch matches the requirements for a signal sequence for mitochondrial protein import. A mitochondrial location of the YDL202w gene product was proven by use of a carboxy terminally HA-tagged version. These findings clearly indicate that YDL202w encodes this mitochondrial ribosomal protein (YmL11).
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    The evolution of the Calvin cycle from prokaryotic to eukaryotic chromosomes: a case study of functional redundancy in ancient pathways through endosymbiosis (1997)
    Springer
    Current genetics 32 (1997), S. 1-18 
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    ISSN: 1432-0983
    Keywords: Key words Chloroplast ; Mitochondria ; Endosymbiosis ; Endosymbiotic gene transfer ; Calvin cycle ; Glycolysis ; Evolution ; Amitochondriate ; Metabolism ; Compartmentation ; Hydrogenosome ; Eukaryote ; Origin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The evolutionary histories of the 12 enzymes that catalyze the reactions of the Calvin cycle in higher-plant chloroplasts are summarized. They are shown to be encoded by a mixture of nuclear genes of cyanobacterial and proteobacterial origin. Moreover, where cytosolic isoforms of these enzymes are found they are almost invariably encoded by genes of clearly endosymbiont origin. We infer that endosymbiosis resulted in functional redundancy that was eliminated through differential gene loss, with intruding eubacterial genes repeatedly replacing pre-existing nuclear counterparts to which they were either functionally or structurally homologous. Our findings fail to support the `product-specificity corollary', which predicts re-targeting of nuclear-encoded gene products to the organelle from whose genome they originated. Rather it would appear that the enzymes of central carbohydrate metabolism have evolved novel targeting possibilities regardless of their origins. Our findings suggest a new hypothesis to explain organelle genome persistence, based on the testable idea that some organelle-encoded gene products might be toxic when present in the cytosol or other inappropriate cellular compartments.
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    Evidence for giant linear plasmids in the ascomycete Podospora anserina (1995)
    Springer
    Current genetics 27 (1995), S. 379-386 
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    ISSN: 1432-0983
    Keywords: Podospora anserina ; Linear plasmid ; Mitochondria ; Plasmid integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the extrachromosomal mutant AL2 of the ascomycete Podospora anserina longevity is correlated with the presence of the linear mitochondrial plasmid pAL2-1. In addition to this autonomous genetic element, two types of closely related pAL2-1-homologous molecules were detected in the high-molecular-weight mitochondrial DNA (mtDNA). One of these molecules is of linear and the other of circular structure. Both molecules contain pAL2-1 sequences which appear to be integrated at the same site in the mtDNA. Sequence analysis of a DNA fragment cloned from one of these molecules revealed that it contains an almost full-length copy of pAL2-1. At the site of plasmid integration a 15-nucleotide AT-spacer and long inverted mtDNA sequences were identified. Finally, two giant linear plasmid-like DNAs of about 50 kbp and 70 kbp were detected in pulsed-field gels of mutant AL2. These molecules are composed of mtDNA and pAL2-1-specific sequences and may result from the integration of mtDNA sequences into linear plasmid pAL2-1.
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    New alleles of mgm1: a gene encoding a protein with a GTP-binding domain realted to dynamin (1995)
    Springer
    Current genetics 28 (1995), S. 499-501 
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    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; mgm ; Dynamin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three previously described genes that affect baker's yeast (Saccharomyces cerevisiae) mitochondrial DNA (mtDNA) or mitochondrial RNA, tpm2-1, mnal-1, and mgml-1, are shown to be alleles of the same gene. This report demonstrates that tpm2-1 does not affect recombination of mtDNA. Therefore, there is no evidence that this dynamin-like protein is involved in movement of mtDNA within a cell.
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    The cox1 gene from Euglena gracilis: a protist mitochondrial gene without introns and genetic code modifications Received: 10 October / 22 November 1996 (1997)
    Springer
    Current genetics 31 (1997), S. 208-213 
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    ISSN: 1432-0983
    Keywords: Key wordsEuglena ; Mitochondria ; cox1 ; Evolution ; RNA editing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present the nucleotide sequence of the cox 1 gene encoding subunit 1 of cytochrome c oxidase in Euglena gracilis, the first report on a mitochondrial gene from this protist. Its study reveals that the Euglena mitochondrial genome does not appear as a compact and homogeneous structure and that its A+T content is high (about 76%) whereas this value is less than 50% in nuclear DNA. The Euglena cox1 gene does not exhibit any intron, and an amino-acid alignment of Euglena COX1 with homologous proteins shows that the universal genetic code is used. Comparisons of the genomic and cDNA sequences of Euglena cox1 indicate that the transcript does not undergo RNA editing as found in trypanosomes and in higher plants. The phylogeny obtained with COX1 protein sequences is in agreement with that obtained with nuclear rRNA sequences and places Euglena and Trypanosoma far apart from other eukaryotes. This result strengthens the hypothesis that these protists represent the earliest mitochondrion-containing organisms.
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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 
    Details
    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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    URL: http://dx.doi.org/10.1007/s002940050446
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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 
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    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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    Isolation and molecular analysis of the gene for cytochrome c1 from Kluyveromyces lactis (1996)
    Springer
    Current genetics 30 (1996), S. 145-150 
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    ISSN: 1432-0983
    Keywords: Key words  Kluyveromyces lactis ; Cytochrome c1 ; Mitochondria ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   By ethyl methanesulphonate mutagenesis of the yeast Kluyveromyces lactis we have isolated five nuclear mutants that were unable to grow on non-fermentable carbon sources. The mutations were found to belong to three complementation groups. After functional complementation of the mutation in one of these mutants we have cloned the structural gene for cytochrome c 1, named KlCYT1. This gene has been assigned to chromosome VI and its nucleotide sequence exhibited 74.3% identity to the homologous gene of S. cerevisiae.
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    Analysis of exon and intron mutants in the cytochrome b mitochondrial gene of Saccharomyces cerevisiae (1996)
    Springer
    Current genetics 30 (1996), S. 200-205 
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    ISSN: 1432-0983
    Keywords: Key words Cytochrome b ; Mutants ; Mitochondria ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nucleotide changes present in a group of five cytochrome b mit– mutants were analyzed at the sequence level. Two single-base changes were found: one (M10-152) generated a nonsense codon in the first exon while the other (M8-181) created a missense substitution in the second exon. The other mutants all have multiple (three) substitutions that either resulted in a missense mutation in a coding region (M17-162) or else changed nucleotides in the last intron of the gene, so blocking its excision (M6-200 and M8-53). The synthesis of mitochondrial polypeptides and the steady state concentration of the complex-III subunits were examined. The Rieske protein and the core-4 and core-5 subunits were much reduced in all mutants. Consequently the overall stability of complex III is very sensitive even to amino-acid substitutions in the cytochrome b protein. Mutant M8-53 provides direct evidence for the proposed role of the P9.1 stem in the core structure of the group-I type last intron of this gene.
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    Structure of a Gelasinospora linear plasmid closely related to the kalilo plasmid of Neurospora intermedia (1996)
    Springer
    Current genetics 29 (1996), S. 150-158 
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    ISSN: 1432-0983
    Keywords: Key words  Gelasinospora ; Neurospora ; Plasmid ; Mitochondria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   We have determined the complete nucleotide sequence of a linear mitochondrial plasmid from a natural isolate of a homothallic species of Gelasinospora. The plasmid genome is 8231 bp long. It carries terminal inverted repeats of 1137 bp. Extending inwards from the terminal repeats are two long open reading frames coding for putative proteins with similarity to DNA and RNA polymerases. These are separated by a short intergenic region. The plasmid sequence shows remarkable similarity to that of the Neurospora intermedia senescence-plasmid kalilo. Overall the two plasmids have a similar genetic organization and are clearly homologous at the sequence level. The main differences are in the intergenic region and in the terminal repeats.
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    Association of transcripts from a group-I intron-containing gene with high sedimentation coefficient particles (1997)
    Springer
    Current genetics 32 (1997), S. 175-181 
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    ISSN: 1432-0983
    Keywords: Key words Yeast ; Mitochondria ; Group-I intron ; Sedimentation coefficient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mitochondrial gene coding for the large rRNA contains a self-splicing optional group-I intron (Sc-LSU ⋅ 1) in some Saccharomyces cerevisiae strains. Although the mechanisms of splicing have been extensively studied, little is known about the possible interactions of this intron with other mitochondrial molecules such as proteins. Using glycerol gradients, we have compared the sedimentation coefficients of mitochondrial transcripts containing the Sc-LSU ⋅ 1 intron in native yeast extracts and in purified RNA preparations. By comparing extracts from ρ + and ρ – cells we have found that at least three RNA species containing the Sc-LSU ⋅ 1 intron (4.5 kb, 2.7 kb and 1.2 kb respectively) are associated in vivo with a multi-molecular complex of sedimentation coefficient 50S made up of nuclearly encoded proteins. Another RNA species of 2.7 kb, which may correspond to a cleavage at the dodecamer sequence of the intron, is not associated with the same particle. The possibility that the 50S particle corresponds to the mitochondrial ribosome or its precursor form(s) is discussed.
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    Cloning and characterization of KlCOX18, a gene required for activity of cytochrome oxidase in Kluyveromyces lactis (1997)
    Springer
    Current genetics 32 (1997), S. 267-272 
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    ISSN: 1432-0983
    Keywords: Key wordsKluyveromyces lactis ; Cytochrome c oxidase ; Mitochondria ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We describe the isolation and initial characterization of KlCOX18, a gene that is essential for the assembly of a functional cytochrome oxidase in the yeast Kluyveromyces lactis. Cells carrying a recessive nuclear mutation in this gene are respiratory deficient and contain reduced levels of cytochromes a and a 3 . The KlCOX18 gene has been cloned by complementation of the respective nuclear mutation, sequenced, and disrupted. KlCOX18 is located on chromosome II and contains an open reading frame of 939 base pairs. The corresponding protein exhibits 70.4% similarity to the Cox18p of Saccharomyces cerevisiae. It contains three possible membrane-spanning domains and a putative amino-terminal mitochondrial import sequence. The strain carrying a null mutation in KlCOX18 does not grow on non-fermentable carbon sources and is deficient in both cytochrome c oxidase and respiratory activity. It is proposed that KlCox18p, like its S. cerevisiae counterpart, provides an important function at a later step of the cytochrome oxidase assembly pathway.
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    Transcriptional initiation sites in sorghum mitochondrial DNA indicate conserved and variable features (1997)
    Springer
    Current genetics 32 (1997), S. 287-295 
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    ISSN: 1432-0983
    Keywords: Key words Sorghum ; Mitochondria ; Transcription promoters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transcriptional initiation and processing was examined for three sorghum mitochondrial DNA genes (atp6-1, atp6-2, urf209) and two open reading frames (orf265/130, orf107) to characterize sequences associated with initiation and other transcriptional strategies for this species. The 5′ termini of ten transcripts were determined by primer extension, and mtRNA was capped with guanylyl transferase and annealed to anti-sense riboprobes to identify transcriptional initiation regions. Eight transcript termini were suitable substrates for guanylyl transferase, indicating the presence of one (atp6-1, atp6-2, urf209), two (orf265/130), or three (orf107) promoters for the five examples. The majority of the putative promoters were associated with single primer-extension termini, while two examples exhibited two transcript-initiation sites within the promoter. Four examples were characterized by initiated transcripts without subsequent processing, indicating that processing is not obligatory. Each of the putative promoter regions included significant A/T-rich 5′ regions, consistent with previous examples, but four exceptions to a consensus core YRTA sequence were identified. The anomalies (AATA, CTTA) suggest plasticity in the primary structure of the core region of higher-plant mitochondrial DNA promoters.
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    Organisation of the mitochondrial genome of Trichophyton rubrum. DNA sequence analysis of the ND4 gene, the ATPase subunit-6 gene, the ribosomal RNA small-subunit gene, the ND6 gene, the COXIII gene, the ATPase subunit-8 gene and six tRNA genes that correspond respectively to the tyrosine, lysine, glutamine, asparagine, isoleucine and tryptophan isoacceptors (1995)
    Springer
    Current genetics 28 (1995), S. 553-559 
    Details
    ISSN: 1432-0983
    Keywords: ATPase 6 ; ATPase 8 ; Cytochrome oxidase ; DNA nucleotide sequence ; NADH deshydrogenase ; tRNA ; Mitochondria ; Small ribosomal RNA subunit ; Trichophyton rubrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present the nucleotide sequence of a 5207-bp-long region of the mitochondrial genome of the dermat-ophyte Trichophyton rubrum. This represents about 1/5th of the total genome and extends a previous study. From the 5′ end of the present sequence, the order of genes is as follows: the end of the ND4 gene, the gene coding for subunit 6 of ATPase, the gene coding for the small ribosomal RNA (SSU rRNA), the tyrosyl tRNA gene, the ND6 gene, the COXIII gene, the ATPase 8 subunit gene and a cluster of tRNAs genes corresponding respectively to the lysine, glutamine, asparagine, isoleucine and tryptophan isoacceptors. The interesting features of this region are its compact organisation, the presence of subunit 8 of the ATPase gene and the secondary structure of SSU rRNA which is close to that of Aspergillus nidulans. On the basis of the order of the genes, which is essentially similar to that of A. nidulans, we can also assume that the LSU rRNA subunit gene should be just upstream of this sequenced region.
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    Interspecies transplacement of mitochondria in yeasts (1997)
    Springer
    Current genetics 32 (1997), S. 24-26 
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    ISSN: 1432-0983
    Keywords: Key words Cybrids ; Mitochondria ; Transplacement ; Yeasts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts of a respiration-deficient rho0 strain of Saccharomyces cerevisiae were incubated with mitochondria isolated from various respiration-competent yeast species under conditions enabling transplacement of mitochondria. Respiration-competent cybrids were selected by plating the protoplasts on agar media containing a non-fermentable energy source. The resulting cybrids contained nuclear DNA of the acceptor S. cerevisiae and mitochondrial DNA of the donor species, as detected by pulsed-field gel electrophoresis of chromosomes and restriction analysis of mitochondrial DNA, respectively. Successful restoration of respiration in the S. cerevisiae mutant was achieved by transplacement of mitochondria isolated from the following Saccharomyces species: S. bayanus, S. capensis, S. delbrueckii, S. exiguus, S. italicus and S. oviformis.
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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 
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    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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    Comments on the translational and transcriptional origin of Euglena chloroplastic aminoacyl-tRNA synthetases (1976)
    Springer
    Archives of microbiology 109 (1976), S. 201-203 
    Details
    ISSN: 1432-072X
    Keywords: Euglena gracilis ; W3BUL ; Chloroplast ; Mitochondria ; Phenylalanyl-tRNA ; Synthetase ; Streptomycin ; Cycloheximide ; tRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A response to: “A consideration of Euglena gracilis W3BUL as a cytoplasmic control for the wild-type phenylalanyl-tRNA synthetase system” and “A reinvestigation of the sites of transcription and translation of Euglena chloroplastic phenylalanyl-tRNA synthetase” by J. L. Lesiewicz and D. S. Herson.
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    Non electrogenic function of the mitochondrial, alternative, cyanide-insensitive respiration in the yeast Saccharomycopsis lipolytica (1978)
    Springer
    Archives of microbiology 116 (1978), S. 297-302 
    Details
    ISSN: 1432-072X
    Keywords: Cyanide-insensitive respiration ; Mitochondria ; ATP synthesis ; Proton translocation ; Exogenous NADH dehydrogenase ; Yeast ; Saccharomycopsis lipolytica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyanide-insensitive mitochondria from Saccharomycopsis lipolytica possess an exogenous NADH dehydrogenase, located outside the inner mitochondrial membrane, and linked to coupling site II. These mitochondria are able to oxidize exogenous NADH via two pathways: (1) a cyanide- and antimycin-sensitive pathway, or cytochrome pathway, and (2) a cyanide- and antimycin-insensitive pathway, or alternative pathway. Although the oxidation of exogenous NADH through the cytochrome pathway occurs with an ATP/0 ratio tending to 2, it proceeds, per molecule of NADH oxidized, with the apparent ejection in the outer medium of only 3 protons instead of 4 protons, as is the case with glycerol 3-phosphate as control substrate, but leaves 1 hydroxyl ion in the outer medium after decay of the protonmotive force. These properties were used to demonstrate the non electrogenic function of the alternative pathway. Indeed, the oxidation of exogenous NADH via the alternative pathway proceeds without apparent ejection of protons, although this oxidation generates an electron flux in the alternative pathway as demonstrated by the net appearance in the outer medium of 1 hydroxyl ion per atom of oxygen reduced, appearance which proves sensitive to benhydroxamic acid, a specific inhibitor of the alternative pathway. The non electrogenicity of the alternative pathway is accompanied by the absence of ATP synthesis as expected from Mitchell's chemiosmotic model. The absence of energy conservation when the electron transfer proceeds via the alternative pathway is not the result of an uncoupling property of an active alternative pathway, as the oxidation of malate plus pyruvate via coupling site I and the alternative pathway occurs with an ATP/0 ratio tending to 1.
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    Novel NADP-linked isocitrate dehydrogenase present in peroxisomes of n-alkane-utilizing yeast, Candida tropicalis: comparison with mitochondrial NAD-linked isocitrate dehydrogenase (1995)
    Springer
    Archives of microbiology 163 (1995), S. 104-111 
    Details
    ISSN: 1432-072X
    Keywords: Peroxisomal NADP-linked isocitrate dehydrogenase ; NAD-linked isocitrate dehydrogenase ; Candida tropicalis ; Peroxisomes ; Mitochondria ; Cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Peroxisomal NADP-linked isocitrate dehydrogenase (Ps-NADP-IDH) was purified for the first time from Candida tropicalis cells grown on n-alkane as a carbon source, which was effective in proliferation of peroxisomes. The properties of Ps-NADP-IDH were compared with those of mitochondrial NAD-linked isocitrate dehydrogenase (Mt-NAD-IDH) purified from the cells grown on acetate, in which peroxisomes did not proliferate. Ps-NADP-IDH was a homodimer of identical subunits (45 kDa), while Mt-NAD-IDH was suggested to be a heterooctamer composed of two types of subunits with different molecular masses (41 and 38 kDa). Kinetic studies revealed that Ps-NADP-IDH gave Michaelis-Menten saturation curves against isocitrate and NADP concentrations, whereas Mt-NAD-IDH was an allosteric enzyme regulated by ATP, AMP, and citrate. Inhibition by 2-oxoglutarate, a precursor of glutamate, was observed only for Ps-NADP-IDH. Both enzymes were inhibited by concomitant addition of oxalacetate and glyoxylate. The function of Ps-NADP-IDH seems to be completely discriminated from that of Mt-NAD-IDH as reflected by their distinct subcellular localizations. Furthermore, the properties of Ps-NADP-IDH were also compared with those of other mitochondrial and cytosolic IDHs from sources reported previously.
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    Influence of specific growth limitation and dilution rate on the phosphorylation efficiency and cytochrome content of mitochondria of Candida utilis NCYC 321 (1977)
    Springer
    Archives of microbiology 113 (1977), S. 65-72 
    Details
    ISSN: 1432-072X
    Keywords: Candida utilis ; Continuous culture ; Mitochondria ; Oxidative phosphorylation ; Cytochromes ; Respiratory chain ; Potassium-limitation ; Sulphate-limitation ; Phosphate-limitation ; Magnesium-limitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract With Candida utilis cells that had been removed directly from a 61 chemostat culture, in steady state, well-coupled mitochondria generally could be isolated. This required a modified snail-gut enzyme procedure that allowed the total processing time to be decreased to 3 h, or less. Examination of these mitochondria in an oxygraph showed the presence of 3 sites of energy conservation when the cells were grown at various dilution rates between 0.1 and 0.45 h-1 in environments that were, successively, glucose-, ammonia-, magnesium-, phosphate- and sulphate-limited. Potassium-limited cells also apparently possessed 3 sites of oxidative phosphorylation when growing at dilution rates greater than 0.2 h-1, but only 2 sites when growing at lower dilution rates. Analysis of cytochrome spectra obtained with these intact mitochondria revealed large quantitative (but not qualitative) differences, depending on the environmental conditions under which the yeast had been cultured. In particular, comparison of the ratio of cytochrome b to cytochrome a showed a pattern of change with dilution rate in mitochondria from potassium-limited cells that was distinctly different from those evident in mitochondria from cells that had been limited in their growth by the availability of other nutrients.
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    Changes in mitochondrial density and succinic dehydrogenase activity in Euglena gracilis as a function of the dependency on light for growth (1975)
    Springer
    Archives of microbiology 104 (1975), S. 233-236 
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    ISSN: 1432-072X
    Keywords: Euglena gracilis ; Mitochondria ; Repression ; Succinate Dehydrogenase ; Equilibrium Density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondria from Euglena gracilis strain z grown under strictly heterotrophic conditions have higher equilibrium densities and higher succinate dehydrogenase activities than those grown in the presence of light. There is a consistent trend toward lower mitochondrial density with increasing time of exposure to light. Experiments reported here indicate that the development of dependency upon light for the provision of energy results in the repression of mitochondrial development with respect to both density and enzymatic activity.
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    Novel NADP-linked isocitrate dehydrogenase present in peroxisomes of n-alkane-utilizing yeast, Candida tropicalis: comparison with mitochondrial NAD-linked isocitrate dehydrogenase (1995)
    Springer
    Archives of microbiology 163 (1995), S. 104-111 
    Details
    ISSN: 1432-072X
    Keywords: Key words Peroxisomal NADP-linked isocitrate ; dehydrogenase ; NAD-linked isocitrate dehydrogenase ; Candida tropicalis ; Peroxisomes ; Mitochondria ; Cytosol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Peroxisomal NADP-linked isocitrate dehydrogenase (Ps-NADP-IDH) was purified for the first time from Candida tropicalis cells grown on n-alkane as a carbon source, which was effective in proliferation of peroxisomes. The properties of Ps-NADP-IDH were compared with those of mitochondrial NAD-linked isocitrate dehydrogenase (Mt-NAD-IDH) purified from the cells grown on acetate, in which peroxisomes did not proliferate. Ps-NADP-IDH was a homod imer of identical subunits (45 kDa), while Mt-NAD-IDH was suggested to be a heterooctamer composed of two types of subunits with different molecular masses (41 and 38 kDa). Kinetic studies revealed that Ps-NADP-IDH gave Michaelis-Menten saturation curves against isocitrate and NADP concentrations, whereas Mt-NAD-IDH was an allosteric enzyme regulated by ATP, AMP, and citrate. Inhibition by 2-oxoglutarate, a precursor of glutamate, was observed only for Ps-NADP-IDH. Both enzymes were inhibited by concomitant addition of oxalacetate and glyoxylate. The function of Ps-NADP-IDH seems to be completely discriminated from that of Mt-NAD-IDH as reflected by their distinct subcellular localizations. Furthermore, the properties of Ps-NADP-IDH were also compared with those of other mitochondrial and cytosolic IDHs from sources reported previously.
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    Immunochemically distinct NADP-linked isocitrate dehydrogenase isozymes in mitochondria and peroxisomes of Candida tropicalis (1997)
    Springer
    Archives of microbiology 168 (1997), S. 389-395 
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    ISSN: 1432-072X
    Keywords: Key wordsCandida tropicalis ; NADP-linked isocitrate dehydrogenase ; Mitochondria ; Peroxisomes ; Isozyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Although peroxisomal localization of NADP-linked isocitrate dehydrogenase (Idp) was first demonstrated in Candida tropicalis, the mitochondrial isozyme has not been found in this yeast. Here we report that the presence of mitochondrial Idp in the yeast was demonstrated by screening for its gene with a DNA probe containing conserved sequences of Idps from various organisms. The nucleotide sequence of the gene (CtIDP1) revealed a 1,290-bp open reading frame corresponding to a 430-amino-acid protein with a high similarity to previously reported Idps. Overexpression of CtIDP1 in Saccharomyces cerevisiae gave a high intracellular Idp activity, and the purified recombinant Idp was shown to be a homodimer with a subunit molecular mass of approximately 44 kDa, different from that of peroxisomal Idp (45 kDa) previously purified from C. tropicalis. Western blot analysis of the subcellular fractions from acetate-grown C. tropicalis with polyclonal antibodies raised against the recombinant CtIdp1 showed that the CtIdp1 in C. tropicalis was localized in mitochondria but not in peroxisomes. Similar levels of CtIDP1 mRNA and its protein product were detected in cells grown on glucose, acetate, and n-alkane, although a slight decrease was observed in n-alkane-grown cells. From these results, CtIdp1 was demonstrated to be mitochondrial Idp. The properties of mitochondrial Idp and peroxisomal Idp isozymes were proven to be similar, but they were immunochemically distinct, suggesting the presence of another gene responsible for peroxisomal Idp in C. tropicalis.
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    Characterization of the intron-containing citrate synthase gene from the alkanotrophic yeast Candida tropicalis: cloning and expression in Saccharomyces cerevisiae (1997)
    Springer
    Archives of microbiology 168 (1997), S. 8-15 
    Details
    ISSN: 1432-072X
    Keywords: Key wordsCandida tropicalis ; Citrate synthase ; Intron ; Mitochondria ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Citrate synthase, an essential enzyme of the tricarboxylic acid cycle in mitochondria, was purified from acetate-grown Candida tropicalis. Results from SDS-PAGE and gel filtration showed that this enzyme was a dimer composed of 45-kDa subunits. A citrate synthase cDNA fragment was amplified by the 5′-RACE method. Nucleotide sequence analysis of this cDNA fragment revealed that the deduced amino acid sequence contained an extended leader sequence which is suggested to be a mitochondrial targeting signal, as judged from helical wheel analysis. Using this cDNA probe, one genomic citrate synthase clone was isolated from a yeast λEMBL3 library. The nucleotide sequence of the gene encoding C. tropicalis citrate synthase, CtCIT, revealed the presence of a 79-bp intron in the N-terminal region. Sequences essential as yeast splicing motifs were present in this intron. When the CtCIT gene including its intron was introduced into Saccharomyces cerevisiae using the promoter UPR-ICL, citrate synthase activity was highly induced, which strongly indicated that this intron was correctly spliced in S. cerevisiae.
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    Gametangial development in Allomyces macrogynus (1977)
    Springer
    Archives of microbiology 113 (1977), S. 173-179 
    Details
    ISSN: 1432-072X
    Keywords: Phycomycete ; Allomyces ; Mitochondria ; Gametangial differentiation ; Sex ; Diaminobenzidine ; Cytochrome oxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The possible role of mitochondria in determining the sex of the gametangia of Allomyces macrogynus was investigated. Quantitative studies of mitochondrial distribution in vegetative hyphae confirmed previous reports of apical mitochondrial clustering. However, by the time the male and female gametangia were partitioned off, no significant difference in mitochondrial distribution between the two sexes was present. Possible mechanisms for the redistribution of mitochondria during early differentiation are discussed. In addition, cytochrome oxidase activity was demonstrated in all mitochondria of both male and female gametangia by the use of diaminobenzidine. It is concluded that neither mitochondrial distribution nor differential mitochondrial activity plays a determining role in the differentiation of the sexual cells in Euallomyces.
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    URL: http://dx.doi.org/10.1007/BF00492021
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    Superoxide Production by the Mitochondrial Respiratory Chain (1997)
    Springer
    Bioscience reports 17 (1997), S. 3-8 
    Details
    ISSN: 1573-4935
    Keywords: Mitochondria ; reactive oxygen species ; superoxide ; hydrogen peroxide ; superoxide dismutase ; catalase ; lipid peroxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract This mini-review describes the role of different mitochondrial components in the formation of reactive oxygen species under normal and pathological conditions and the effect of inhibitors and uncouplers on superoxide formation.
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    URL: http://dx.doi.org/10.1023/A:1027374931887
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    The Physiological Significance of Mitochondrial Proton Leak in Animal Cells and Tissues (1997)
    Springer
    Bioscience reports 17 (1997), S. 9-16 
    Details
    ISSN: 1573-4935
    Keywords: Mitochondria ; proton leak ; Standard Metabolic Rate ; thermogenesis ; metabolic sensitivity ; reactive oxygen species ; carbon flux control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Mitochondrial proton leak is an important component of cellular metabolism in animals and may account for as much as one quarter to one third of the Standard Metabolic Rate of the rat. The activity of the proton leak pathway is different in a wide range of animal species and in different thyroid states. Such differences imply some function for proton leak and candidates for this function include thermogenesis, protection against reactive oxygen species, endowment of metabolic sensitivity and maintenance of carbon fluxes.
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    URL: http://dx.doi.org/10.1023/A:1027327015957
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    The general mitochondrial processing peptidase from wheat is integrated into the cytochrome bc 1-complex of the respiratory chain (1995)
    Springer
    Planta 195 (1995), S. 396-402 
    Details
    ISSN: 1432-2048
    Keywords: bc 1-Complex ; Mitochondria ; Mitochondrial processing peptidase ; Protein import ; Respiratory chain ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The bc 1-complex (EC 1.10.2.2.) from Triticum aestivum L. was purified by cytochrome-c affinity chromatography and gel filtration using either etiolated seedlings or wheat-germ extract as starting material. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the isolated enzyme revealed ten bands, which were analysed by immunoblotting and direct amino-acid sequencing. The enzyme from wheat is the first bc 1-complex that is reported to contain four core proteins (55.5, 55.0, 51.5 and 51.0 kDa). In addition, the wheat bc 1-complex comprises cytochrome b (35 kDa), cytochrome c 1 (33 kDa) the “Rieske” iron-sulphur protein (25 kDa) and three small subunits 〈 15 kDa. This composition differs from the one reported in fungi, mammals and potato. Partial sequence determination of the large subunits suggests that the 55.5 and 55.0-kDa-proteins represent the β-subunit of the general mitochondrial processing peptidase, and the 51.5 and 51.0-kDa proteins the α-subunit of this enzyme. The bc 1-complex from wheat efficiently processes mitochondrial precursor proteins as shown in an in-vitro processing assay. In control experiments the isolated bc 1-complexes from potato, yeast, Neurospora and beef, all purified by the same isolation procedure, were also tested for processing activity. Only the protein complexes from plants contain the general mitochondrial processing peptidase. The composition of the wheat bc 1-complex sheds new light on the co-evolution of the processing peptidase and the middle segment of the respiratory chain.
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    URL: http://dx.doi.org/10.1007/BF00202597
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    Analysis of wheat mitochondrially encoded polypeptides by in organello labelling (1999)
    Springer
    Plant cell reports 19 (1999), S. 161-165 
    Details
    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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    URL: http://dx.doi.org/10.1007/s002990050727
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    Import of phosphatidylethanolamine for the assembly of rat brain mitochondrial membranes (1995)
    Springer
    The journal of membrane biology 148 (1995), S. 169-176 
    Details
    ISSN: 1432-1424
    Keywords: Phosphatidylethanolamine ; Phospholipid transport ; Mitochondria ; Phosphatidylserine decarboxylase ; Brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Mitochondria can synthesize phosphatidyl-ethanolamine (PE) through phosphatidylserine decarboxylase (PS decarboxylase) activity or can import this lipid from the endoplasmic reticulum. In this work, we studied the factors influencing the import of PE in brain mitochondria and its utilization for the assembly of mitochondrial membranes. Incubation of rat brain homogenate with [1-3H]ethanolamine resulted in the synthesis and distribution of 3H-PE to subcellular fractions. T-wenty-one percent of labeled PE was recovered in purified mitochondria. The import of PE in mitochondria was studied in a reconstituted system made of microsomes (donor particles) and purified mitochondria (acceptor particles). Ca+2 and nonspecific lipid transfer protein purified from liver tissue (nsL-TP) enhanced the translocation process. 3H-PE synthesized in membrane associated to mitochondria (MAM) could also translocate to mitochondria in the reconstituted system. Exposure of mitochondria to trinitrobenzensulfonic acid (TNBS) resulted in the reaction of more than 60% of 3H-PE imported from endoplasmic reticulum and of about 25% of 14C-PE produced in mitochondria by decarboxylation of 14C-PS. Moreover, the removal of the outer mitochondrial membrane by digitonin treatment, resulted in the loss of 3H-PE, but not 14C-PE. These results indicate that labeled PE imported in mitochondria is mainly localized in the outer mitochondrial membrane, whereas PE produced by PS decarboxylase activity is confined to the inner mitochondrial membrane. Phospholipase C hydrolyzed 25–30% of both PE radioactivity and mass of the outer mitochondrial membrane indicating an asymmetrical distribution of this lipid across the membrane.
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    URL: http://dx.doi.org/10.1007/BF00207272
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    Organization of the mitochondrial Cob 2 pseudogene in different lines of rice (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 1087-1093 
    Details
    ISSN: 1432-2242
    Keywords: Apocytochrome b ; Mitochondria ; Pseudogene ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the fertile rice line IR 36 there are two copies of the apocytochrome b (cob) gene: a functional copy, cob 1, and a pseudogene, cob 2 (Kaleikau et al. 1992). In a survey of diverse rice lines, we found that cob 2 was absent in the wild abortive(WA)-type cytoplasmic male-sterile cytoplasm, but was present in the fertile lines. While cob 1 was conserved among all the lines, fertile and sterile, the cob 2 region was different in the fertile lines tested. The 5′ regions of most cob 2 loci were similar to cob 1 (about 4 kb of the flanking region and most of the coding region), but the 3′ region varied among different fertile lines. The point of divergence, the break-point, from the cob 1 sequence was conserved in all the cob 2 regions tested. In all the cob 2 regions, this break-point seems to be linked to the variable region of cob 2 through a conserved 192-bp segment, which is not a part of cob 1. It is proposed that the cob 2 regions could have been produced by recombination or insertion events involving cob 1 and the 192-bp segment which is present at different locations in the mitochondrial genomes of the various rice lines.
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    URL: http://dx.doi.org/10.1007/BF00222926
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    RFLP mapping of the maize gametophytic restorer-of-fertility locus (rf3) and aberrant pollen transmission of the nonrestoring rf3 allele (1997)
    Springer
    Theoretical and applied genetics 95 (1997), S. 525-531 
    Details
    ISSN: 1432-2242
    Keywords: Key words Cytoplasmic male sterility ; Mitochondria ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Cytoplasmic male sterility (CMS) is the maternally inherited inability to produce functional pollen. The Rf3 allele of the nuclear gene rf3 gametophytically restores male fertility to maize plants with the S-type of CMS. The rf3 locus is on the long arm of maize chromosome two (2L). Using 2L RFLPs and three-point mapping analysis we showed that the rf3 locus is located an estimated 4.3 cM distal to the whp locus and 6.4 cM proximal to the bnl17.14 locus. This information was used in combination with RFLPs on two additional maize chromosomes to show that Rf3/rf3 CMS-S plants may aberrantly transmit the nonrestoring allele, rf3, through the male gametophyte.
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    URL: http://dx.doi.org/10.1007/s001220050593
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    Variation in protein and RNA synthesis activity in isolated mitochondria of the developing rice (Oryza sativa L.) panicle (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 1112-1118 
    Details
    ISSN: 1432-2242
    Keywords: Mitochondria ; Protein and RNA synthesis ; Oryza sativa L ; Panicle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have studied variation in mitochondrial protein and RNA synthesis during the development of a specialized rice (Oryza sativa L.) reproductive organ in a bacteria-free environment. Mitochondria were prepared from the maturing panicle during microsporogenesis when meiosis occurred and from etiolated seedlings at two growth stages. We found (1) that there was no discernible qualitative difference among the polypeptides synthesized by these three mitochondrial samples; (2) that the quantity of proteins synthesized by panicle mitochondria was approximately 3 times that of the seedling mitochondria, while the two seedling samples exhibited only a minor quantitative difference; (3) that panicle and seedling mitochondria samples synthesized qualitatively the same RNA but at distinctly different rates and that more RNA products were synthesized by panicle than by seedling mitochondria. These results, taken together, suggest that either the regulation of mitochondrial transcription and translation or the copy number of mitochondrial DNA per mitochondrion change discretely in the developing panicle and consequently that the level of mitochondrial gene expression increases considerably during the development of the reproductive structure in rice.
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    URL: http://dx.doi.org/10.1007/BF00222930
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    A chimeric and truncated mitochondrial atpA gene is transcribed in alloplasmic cytoplasmic male-sterile tobacco with Nicotiana bigelovii mitochondria (1995)
    Springer
    Theoretical and applied genetics 91 (1995), S. 603-610 
    Details
    ISSN: 1432-2242
    Keywords: CMS ; Cybrids ; Chimeric atpA ; Gene ; Mitochondria ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplast fusions were performed between two sexually produced alloplasmic male-sterile tobacco cultivars, with cytoplasms from Nicotiana bigelovii [Nta (big)S] and N. undulata[Nta(und)S], both of which exhibit homeotic-like phenotypes affecting the petal and stamen whorls. Among the fusion products obtained, both novel male-sterile and pollen-producing cybrid plants were identified. Of the pollen-producing cybrid plants, all of which were indehiscent, some had flowers with stamens that appeared normal when compared to male-fertile tobacco plants. Other hybrid plants were incompletely restored as they exhibited petaloid structures on the anther-bearing pollen-producing stamens. In this study, gel-blot analyses with mitochondrial geneprobes were conducted comparing the mitochondrial DNA of cybrids and male-sterile parents. It was found that the flower morphology typical of the Nta(big)S parental plants, as well as of the novel male-sterile cybrids, coincided with the presence of a chimeric atpA gene copy where an open reading frame of unknown origin was found to be linked in-frame to the 3′-end of a truncated atpA gene. RNA gel-blot hybridizations revealed the presence of atpA transcripts in the malesterile parent Nta(big)S and novel male-sterile cybrids, but which were absent in cybrids capable of pollen production.
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    URL: http://dx.doi.org/10.1007/BF00223286
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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 
    Details
    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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    URL: http://dx.doi.org/10.1007/s001220051301
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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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    An association between mitochondria and vesicles in smooth muscle (1975)
    Springer
    Cell & tissue research 161 (1975), S. 119-132 
    Details
    ISSN: 1432-0878
    Keywords: Muscle, smooth ; Mitochondria ; Cell membrane, vesicles ; Electron microscopy ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Two methods are described for measuring the mitochondrion-vesicle association seen by electron-microscopy in thin sections of the guinea-pig taenia coli. Both methods are based on comparisons of the observed distributions with predicted random distributions. It was found in control muscles that mitochondria were consistently nearer to vesicles than corresponding random points. 1 mM ouabain treatment reduced the mitochondrion-vesicle association for mitochondria which were closer to the membrane surface than 130 nm. Quantitative investigation of the freeze-etch structure of the membrane fracture faces is also reported, confirming the observation that membrane particles are more numerous in vesiculated membrane regions of smooth muscle.
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    URL: http://dx.doi.org/10.1007/BF00222118
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    Glucose dependent alterations of mitochondrial ultrastructure and enzyme content in mouse pancreatic islets maintained in tissue culture (1975)
    Springer
    Cell & tissue research 162 (1975), S. 313-321 
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    ISSN: 1432-0878
    Keywords: Islands of Langerhans ; Mitochondria ; Enzymes ; Tissue Culture ; Electron Microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Isolated islets of Langerhans from mice were maintained in tissue culture for one week at either a high (28 mM) or a low (3.3 mM) extracellular glucose concentration. Electron microscopic morphometry by means of stereological methods revealed a much greater volume of mitochondria in islet cells cultured at low glucose than in those cultured at high glucose. The former islets also showed a higher activity of the mitochondrial marker enzyme, L-3-hydroxyacyl-CoA-dehydrogenase (E.C.1.1.1.35). These results indicate a true mitochondrial hypertrophy at the low glucose concentration. Although it is known from previous studies that the islet cell metabolism is diminished after low-glucose culture, the present observations of an increased mitochondrial volume probably do not reflect a degenerative process, but rather adaptive changes towards oxidation of energy yielding substrates other than glucose.
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    URL: http://dx.doi.org/10.1007/BF00220177
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    Investigations on the turnover of adrenocortical mitochondria (1976)
    Springer
    Cell & tissue research 168 (1976), S. 1-9 
    Details
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Mitochondria ; ACTH ; Stereology ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of chronic administration of ACTH (up to 36 consecutive days) on the mitochondria of the zona reticularis of the rat adrenal cortex were investigated by stereologic techniques. It was found that ACTH induces two phases of hypertrophy of mitochondria alternating with two proliferative stages, which are associated with a significant decrease in the average volume of the organelles. It is suggested that, as in the zona fasciculata, ACTH controls the processes of growth and division of mitochondria in the zona reticularis. The mechanism underlying this action of ACTH as well as the differences between the responses to ACTH of the mitochondrial population of the two adrenal zones are discussed in the light of evidence indicating that mitochondria contain a complete genetic apparatus largely independent of nuclear control.
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    URL: http://dx.doi.org/10.1007/BF00219719
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    Investigations on the turnover of adrenocortical mitochondria (1975)
    Springer
    Cell & tissue research 163 (1975), S. 273-290 
    Details
    ISSN: 1432-0878
    Keywords: Adrenal cortex ; Mitochondria ; Dexamethasone ; DNA-synthesis ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The effects of chronic administration of dexamethasone (for up to 15 consecutive days) on both the morphology and DNA-synthesis of the mitochondria of the rat adrenal zona fasciculata were investigated by stereologic and autoradiographic techniques. Up to the 3rd day of continuous dexamethasone treatment, the average volume of mitochondria did not change, whereas the number of mitochondria per cell was significantly decreased. From the 3rd to the 15th day of hormonal administration both the volume and number of mitochondria were found to decrease in proportion to the duration of treatment. Autoradiography showed that after the 3rd day of dexamethasone administration there is virtually no incorporation of 3H-thymidine into the mitochondrial compartment. These findings are discussed in the light of evidence indicating that dexamethasone blocks ACTH-release by inhibiting the hypothalamo-hypophyseal axis. The results confirm the view that ACTH controls the maintenance of growth and proliferation of rat adrenocortical mitochondria.
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    URL: http://dx.doi.org/10.1007/BF00219464
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    A light and electron microscope study of changes occurring at the cut ends following section of the dorsal roots of rat spinal nerves (1976)
    Springer
    Cell & tissue research 170 (1976), S. 491-505 
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    ISSN: 1432-0878
    Keywords: Axoplasmic flow ; Mitochondria ; Neurones, dorsal root ganglia ; Spinal nerve roots ; Synaptic vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rat dorsal spinal nerve roots were cut; 20 h later the axons in the vicinity of the cut were examined by light and electron microscopy. The changes in the cut tip distant from the ganglion were largely degenerative. On the ganglionic side of the cut a cap of free unmyelinated sprouts was formed. These sprouts contained clear and dense-core vesicles 40–150 nm in diameter, smooth endoplasmic reticulum and mitochondria. Some of the unmyelinated sprouts were extensions of myelinated axons, others arose from myelinated axons by lateral budding. In both myelinated and non-myelinated axons there was an accumulation of mitochondria, tubulo-vesicular smooth endoplasmic reticulum and large and small dense-core vesicles for a distance of approximately 500 μm behind the tip. Dense-core vesicles were more common in nonmyelinated axons than in their myelinated counterparts. In areas of intense accumulation the non-myelinated fibres were grossly swollen and distorted. The myelinated axons and some of the sprouts contained an unusual type of mitochondrion. The similarity between these sprouts and pre-synaptic terminals is discussed.
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    URL: http://dx.doi.org/10.1007/BF00361707
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    Synaptology of the rat suprachiasmatic nucleus (1976)
    Springer
    Cell & tissue research 165 (1976), S. 509-544 
    Details
    ISSN: 1432-0878
    Keywords: Hypothalamus ; Suprachiasmatic nucleus ; Synapses ; Mitochondria ; Endoplasmic reticulum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Within the suprachiasmatic nucleus (SCN) of the rat the fine structure of the synapses and some features of their topological arrangement were studied. Five types of synapses could be distinguished with certainty: A. Two types of Gray-type-I (GTI) or asymmetrical synapses (∼33%). The presynaptic elements contain strikingly different types of mitochondria. Size of clear vesicles: ∼ 450 Å. Synapses with subjunctional bodies often occur, among these also “crest synapses”. Localization: dendritic shafts and spines, rarely somata. B. Three types of Gray-type-2 (GTII) or symmetrical synapses (∼66%)∶:1) Axo-dendritic and -somatic (=AD) synapses. Size of clear vesicles: ∼500 Å. 2) Invaginated axo-dendritic and -somatic (=IAD) synapses with club-like postsynaptic protrusions within the presynaptic elements (PreEl). Size of clear vesicles is very variable: ∼ 400–1,000 Å. 3) Dendro-dendritic, -somatic and somato-dendritic (=DD) synapses occurring at least partly in reciprocal arrangements. They represent an intrinsic system. Shape of clear vesicles: often oval; sucrose treatment partly produces flattening. Dense core-vesicles (dcv) are found in all GTII- and most of the GTI-synapses after three-dimensional reconstruction. All types of synapses (mostly GTII-synapses) can be enclosed by multilamellar astroglial formations. The synapses often occur in complex synaptic arrangements. Dendrites and somata of females show significantly more multivesiculated bodies than those of males. Further pecularities of presynaptic (PreEls) and postsynaptic elements (PostEls) within the SCN are described and discussed.
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    URL: http://dx.doi.org/10.1007/BF00224478
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    Silicon-containing granules of rat liver, kidney and spleen mitochondria (1976)
    Springer
    Cell & tissue research 174 (1976), S. 315-327 
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    ISSN: 1432-0878
    Keywords: Silicon granules ; Mitochondria ; Rat liver ; Electron probe ; X-ray microanalysis ; 68Ge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Isolated rat liver mitochondria containing granule aggregates (25–75 nm in diameter) and small (5–10 nm) electron opaque granules were examined by electron probe X-ray microanalysis. The granule aggregates gave an intense Si signal, while the small granules gave both Si and P signals. Isolated mitochondria of rat liver, spleen and kidney, subjected to detergent solubilization and differential centrifugation, produced two granule fractions: (1) a 10,000g fraction consisting predominantly of granule aggregates (25–75 nm) composed of smaller granules (5–10 nm in diameter), and (2) a 10,000–30,000 g fraction of non-aggregated small granules (5–10 nm). Thin sections of isolated granule aggregates gave Si X-ray signals similar to those obtained from in situ granules. In addition S, Cl, Mg, Cr and Fe X-ray signals were observed. Cr occurred only in the large kidney granules, while Fe occurred in both fractions of the spleen and kidney granules. The presence of Si in the granules was confirmed by chemical analysis of the isolated granules and in vivo radiolabeling of the granules with 31Si and 68Ge. Contamination within the electron microscope was eliminated by a liquid nitrogen anticontamination device.
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    URL: http://dx.doi.org/10.1007/BF00220678
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    Mitochondrial degeneration after organic phosphate poisoning in prosimian primates (1977)
    Springer
    Cell & tissue research 175 (1977), S. 459-465 
    Details
    ISSN: 1432-0878
    Keywords: Mitochondria ; Degeneration ; Tricresylphosphate ; Lipofuscin ; Slow Loris (Nycticebus coucang coucang)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The degenerative reaction of mitochondria to tricresylphosphate (TCP) poisoning in spinal ganglion cells of Slow Loris (Nycticebus coucang coucang) were studied with the electron microscope. In neurones of animals treated with TCP, mitochondria display various stages of alterations which confirm mitochondrial involvement in TCP poisoning. The role of degenerated mitochondria in the formation of neuronal lipofuscin is discussed. It is suggested that the lipofuscin granule is a metabolic product inherently related to mitochondrial degeneration, irrespective of the primary cause: ageing or intoxication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222412
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  • 98
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    Electronic Resource
    Giant nerve fibers in the ciliary muscle and iris sphincter of Macaca mulatta (1976)
    Springer
    Cell & tissue research 169 (1976), S. 33-40 
    Details
    ISSN: 1432-0878
    Keywords: Nerve fibers ; Ciliary muscle ; Sphincter of the iris ; Mitochondria ; Glycogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Unusually large nerve processes, containing numerous mitochondria, glycogen particles, and synaptic vesicles are described in both the ciliary muscle and the iris sphincter muscle of the rhesus monkey. The striking similarity of these axonal profiles to the dendritic enlargements observed by Sotelo and Palay (1968) is noted and the possibility that they represent growing ends of peripheral nerve fibers is suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00219305
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  • 99
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    Electronic Resource
    The subcellular localization of calcium in vertebrate smooth muscle: Calcium-containing and calcium-accumulating structures in muscle cells of mouse intestine (1976)
    Springer
    Cell & tissue research 169 (1976), S. 221-231 
    Details
    ISSN: 1432-0878
    Keywords: Smooth muscle ; Calcium ; Sarcoplasmic reticulum ; Mitochondria ; Microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The intracellular localization of calcium by means of cytochemical techniques was studied in smooth muscle cells of mouse intestine. When the lead acetate method according to Carasso and Favard (1966) was used calcium was found in mitochondria and sarcoplasmic reticulum and occasionally between the myofilaments. The active ATP-dependent accumulation of calcium into cell structures was investigated by the oxalate method (Heumann and Zebe, 1967). After appropriate treatment the only structures of smooth muscle cells which contained calcium oxalate (identified by microprobe analysis) were elements of the sarcoplasmic reticulum. The results are discussed in relation to the role of calcium in the control of muscle activity during the contraction-relaxation cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214210
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  • 100
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    Electronic Resource
    Variations in mitochondrial size and ultrastructure during germ cell development (1976)
    Springer
    Cell & tissue research 169 (1976), S. 531-550 
    Details
    ISSN: 1432-0878
    Keywords: Germ cells ; Oogenesis ; Mitochondria ; Organelle differentiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Size variations and ultrastructural changes in mitochondria of developing germ cells of the female hamster were analyzed. Mitochondria in oogonia of foetus and newborn were elongate with transverse cristae. During pre-dictyate meiotic prophase they became small, rounded, and electron-dense with pleomorphic cristae. These changes were largely reversed when dictyate was reached. Maximum mitochondrial size and complexity of cristae were reached just at the beginning of the phase of rapid oocyte growth, and thereafter declined. As mitochondrial size and number of cristae decreased in the rapidly enlarging oocyte, the ratio of length to width increased, as did electron density of the matrix, until the formation of an antrum within the follicle. After antrum formation, the mitochondria again became more rounded and cristae were seldom seen. An attempt is made to correlate changes of mitochondrial morphology with other events occurring during oogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218151
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