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  • 1
    ISSN: 1432-1076
    Keywords: Lacticacidosis ; Neurological deterioration ; Redox disequilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two patients, one dying at 25 days and one at 20 months had ‘chronic’ lactic acidaemia with a high lactate to pyruvate ratio. Both showed EEG abnormalities and seizure activity and both died of respiratory failure. Investigation of cultured skin fibroblasts from these patients revealed normal pyruyate dehydrogenase and pyruvate carboxylase activities but the cells showed a decreased ability to oxidise pyruvate which was returned to normal on the addition of methylene blue. Subsequent investigations revealed that the mitochondria from the patients' cells could oxidise pyruvate normally but that the cells had an abnormal NAD to NADH ratio under standard conditions of incubation. It was concluded that both children had a redox disequilibrium in the cytoplasmic compartment due to a problem in transporting reducing equivalents from the cytoplasmic to the mitochondrial compartments.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1076
    Keywords: Lactic acidosis ; Pyruvate dehydrogenase ; Dihydrolipoyl dehydrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A girl with failure to thrive in the neonatal period was brought to the hospital at 10 weeks of age following a respiratory arrest, preceded by 12 h of vomiting and diarrhea. There was significant acidosis with a blood lactate of 8.8 mM. A high carbohydrate diet decreased her acidosis. Episodes of acidosis, often associated with infections, and accompanied by progressive neurological deterioration, have continued for 18 months. The activity of pyruvate dehydrogenase from cultured skin fibroblasts was 24% of that from normal fibroblasts. The activities of α-ketoglutarate dehydrogenase and branched-chain keto acid dehydrogenase were also deficient. The activity of the dihydrolipoyl dehydrogenase component (E3) of PDH in skin fibroblasts was 5% of that in control cell lines. Limited studies performed on liver and muscle biopsy specimens showed E3 activity in liver and muscle to be undetectable in both tissues. We conclude that the enzyme defect present in dihydrolipoyl dehydrogenase is responsible for the reduced activity of all three α-keto-acid dehydrogenase complexes and the patient's symptoms. Our results provide further evidence that the E3 component of these complexes is genetically and biochemically the same protein.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 440 (2006), S. 1005-1005 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Like their aquatic counterparts, terrestrial crabs repeatedly shed their rigid exoskeleton during moulting. But in the case of land crabs, little water is available to provide a temporary hydrostatic skeleton before the new skeleton hardens, and air does not provide the buoyancy necessary to ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 42 (1999), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Zooplankton exist in environments where food availability varies greatly over time, and success depends in part on the ability to store resources when food is abundant and to conserve them when food is scarce. This paper reports on interspecific differences in the size of stored reserves, and in respiration rate during food deprivation, of four species of planktonic rotifers.2. The size of reserves varied from 42 to 71% of initial (well-fed) body mass. Interspecific differences in reserve size explained some of the previously observed differences in starvation time.3. The initial response of respiration rate to food deprivation was quite variable between species. Brachionus calyciflorus was the only species to conserve energy by decreasing respiration rate in response to food deprivation. In contrast, the respiration rate of starved Asplanchna priodonta increased, while that of A. silvestrii and Synchaeta pectinata did not change, during food deprivation.4. Theory predicts that temporal variation in resource level may facilitate the coexistence of competing species. This theory depends upon trade-offs between traits that confer competitive success in different environments. Although rotifers show a trade-off between competitive ability and maximum population growth rate, we found no evidence for trade-offs between either of those two traits and the size of reserves.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Melbourne, Australia : Blackwell Science Pty
    Austral ecology 30 (2005), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  The distributions of lizards across habitat edges delimiting open-forest and regenerating sand-mined areas as a function of distance from the edge were studied at Tomago, New South Wales, Australia. Pitfall-trapping was used to survey lizards across the northern edges of four forest fragments, to determine if lizards displayed characteristic responses across the edge, and whether these could be explained by the different habitat conditions. At each site, 11 equally spaced drift fences (each parallel to the edge) were arranged in a transect running perpendicular to the edge, and stretching 50 m into each habitat type. Captures of Amphibolurus muricatus (Agamidae) decreased substantially across the edge from the mine-path to the forest so that it was identified as a mine-path specialist lizard species. Captures of two skink species decreased across the mine-path before reaching the edge, and were not caught (Ctenotus taeniolatus) or were seldom caught (Ctenotus robustus) in the forest, so they were identified as mine-path specialist, edge avoiding, lizard species. Captures of Lampropholis delicata (Scincidae) increased across edges into the forest, consistent with the expectation for a forest specialist. Regression analyses indicated the responses to edges of three lizard species (A. muricatus, C. robustus and C. taeniolatus) were negatively correlated with canopy cover (probably due to its influence on temperature, as captures of A. muricatus and C. robustus were also correlated positively with mean daily temperature). In addition, the response of C. robustus correlated negatively with a vegetation factor (dense, even vegetation in the first 50 cm from ground level). The response of L. delicata correlated positively with understorey height. We have identified edge response strategies for four species of lizards across edges delimiting temperate open-forest and mined areas, and identified habitat and microclimate variables that may have driven these responses.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract  Multiple disturbance regimes are increasingly common as novel anthropogenic disturbances are added to existing natural disturbances. However, it is generally unknown whether simultaneous or sequential effects of different forms of disturbance are predictable from the independent effects of each disturbance. This study examines the short-term effects of sequential disturbance by mineral sand-mining followed by fire in a forest community in south-eastern Australia. Four combinations of disturbance were sampled: unburned mined, burned mined, unburned forest (unmined) and burned forest (unmined, with between-fire interval matching the disturbance interval between mining and fire of the burned mined treatment). All combinations were sampled approximately 12 months following fire on the burned sites. The impact of fire after mining depended on disturbance interval. Sites burned 0.5–2.4 years since mining had fewer native vascular plant species than unburned mined sites of the same mined age, whereas sites with 10–16 years or 20–26 years between mining and fire had greater native species richness than unburned mined sites of the same age. Burning 20–26 years after mining brought native species richness within the range of burned forest. For both unmined and mined sites native seedling densities increased with burning, and with longer disturbance intervals. Weed species richness and weed seedling densities were greater on mined sites than in forest, and burning mined sites elevated weed seedling densities further, particularly for short intervals. Both disturbance interval and fire intensity are likely to have contributed to these results, as intensity on mined areas increased with interval, and at 20–26 years post-mining was equivalent to unmined forest. These results suggest that fire could be used to promote rehabilitation of these mined areas after at least 10 years, but should be excluded from earlier stages of post-mining regeneration. However, other sources of spatial and temporal variability should be considered in addition to interval and intensity, as variation among mined areas was correlated with post-fire weather conditions and available weed sources. Finally, the combined effects of mining and fire could not be predicted from knowledge of the disturbances operating separately, indicating that effects of multiple disturbance may be synergistic rather than additive.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Melbourne, Australia : Blackwell Science Asia Pty. Ltd.
    Austral ecology 26 (2001), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The lizard fauna of sand-mined dunes of the central coast of New South Wales, Australia has been shown to be dominated by Ctenotus robustus and Ctenotus taeniolatus (Scincidae), with relative abundance changing with time since mining. However, there is little published information on how this lizard fauna compares to that of the undisturbed open forest that previously grew on these sites. Here, existing data are added to in order to produce a longer chronosequence of times since sand-mining (4, 8, 14 and 20 years) than has been examined previously. The new data are compared to those from unmined forests. Ctenotus robustus and C. taeniolatus dominated lizard captures on mined areas, with peak abundances at 8 and 14 years, respectively. Lampropholis guichenoti (Scincidae) was at low abundance until 20 years post-mining and L. delicata was present only at 20 years post-mining. Unmined forest burned 4, 8 or 14 years ago had a significantly different lizard community from that of sand-mined areas. Ctenotus robustus and C. taeniolatus were absent from unmined forest at all post-fire periods. Lampropholis guichenoti and Lampropholis delicata were numerically dominant in forest, with increasing abundance of L. guichenoti with time since fire. Thus the composition of the lizard community on these coastal dunes is not solely determined by time since disturbance per se. Comparisons of sites on the basis of accumulated leaf litter showed a significant relationship between Lampropholis abundance and litter density. On sand-mined sites and forested sites with similar leaf litter densities, the abundances of L. guichenoti were similar. As Ctenotus were absent from unmined forest, we could not compare their distribution in unmined and mined areas. However, negative correlations of Ctenotus abundance with canopy cover and understorey vegetation density offer a possible explanation for the absence of these species from forest.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Austral ecology 25 (2000), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The jacky dragon, Amphibolurus muricatus (White, ex Shaw 1790) is a medium sized agamid lizard from the southeast of Australia. Laboratory incubation trials show that this species possesses temperature-dependent sex determination. Both high and low incubation temperatures produced all female offspring, while varying proportions of males hatched at intermediate temperatures. Females may lay several clutches containing from three to nine eggs during the spring and summer. We report the first field nest temperature recordings for a squamate reptile with temperature-dependent sex determination. Hatchling sex is determined by nest temperatures that are due to the combination of daily and seasonal weather conditions, together with maternal nest site selection. Over the prolonged egg-laying season, mean nest temperatures steadily increase. This suggests that hatchling sex is best predicted by the date of egg laying, and that sex ratios from field nests will vary over the course of the breeding season. Lizards hatching from eggs laid in the spring (October) experience a longer growing season and should reach a larger body size by the beginning of their first reproductive season, compared to lizards from eggs laid in late summer (February). Adult male A. muricatus attain a greater maximum body size and have relatively larger heads than females, possibly as a consequence of sexual selection due to male-male competition for territories and mates. If reproductive success in males increases with larger body size, then early hatching males may obtain a greater fitness benefit as adults, compared to males that hatch in late summer. We hypothesize that early season nests should produce male-biased sex ratios, and that this provides an adaptive explanation for temperature-dependent sex determination in A. muricatus.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Melbourne, Australia : Blackwell Science Asia Pty. Ltd.
    Austral ecology 26 (2001), S. 0 
    ISSN: 1442-9993
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of atmospheric fluoride pollution on the lizard fauna of the open forest of coastal dunes in New South Wales, Australia were examined. Lizards were pitfall-trapped at sites with background fluoride levels (〈 0.25 μmol F.g–1), or subject to low (1.85–3.4 μmol F.g–1) or high (8.00–13.2 μmol F.g–1) levels of fluoride pollution. Sites had been disturbed by fire or mineral sand-mining 4 or 8 years prior to the study. Fluoride pollution resulted in significant changes to canopy cover, understorey vegetation density and ground cover. Where fluoride levels were low in unmined forest, there was significantly higher species richness, total lizard abundance and abundance of the most common species, Lampropholis guichenoti and Lampropholis delicata (Scincidae), compared with areas of high or background fluoride levels. Both the present and previous studies show that fluoride pollution is significantly correlated with increased abundance of the most common lizard species in sand-mined areas, Ctenotus robustus, Ctenotus taeniolatus (Scincidae) and Amphibolurus muricatus (Agamidae). A discriminant function model of background-fluoride mined sites was used to predict lizard abundances based on vegetation density, leaf litter density and soil hardness. The model was verified by using it to predict similarities between background-fluoride sites and fluoride-affected sites. The sites within each predicted group were more similar in lizard species composition than when grouping of sites was done by time since mining or fire. With this analysis, a close relationship between vegetation variables and the lizard fauna, irrespective of the type of disturbance or time since disturbance, is demonstrated. Discriminant function analysis suggested that Ctenotus would be unlikely to use unmined forest sites that had been burned within 12 months previously. Thus it seems unlikely that the original open forest of these coastal dunes would have supported populations of either C. robustus or C. taeniolatus. In conclusion, the original source of Ctenotus that colonized sand-mined areas is more likely to have been the relatively small areas of heath vegetation in the area. Therefore, sand-mining and atmospheric fluoride pollution result in landscape-scale changes to the relative abundance of lizard species, with forest species becoming less common and lizard species from open areas becoming more common.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] Resistance to apoptosis, which plays an important role in tumors that are refractory to chemotherapy, is regulated by the ratio of antiapoptotic to proapoptotic proteins. By manipulating levels of these proteins, cells can become sensitized to undergo apoptosis in response to chemotherapeutic ...
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