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61.
Bioremediation of contaminated soils and aquifers is subject to spatial and temporal temperature changes that can alter the kinetics of key microbial processes. This study quantifies temperature effects on the kinetics of an ethanol-fed sulfate-reducing mixed culture derived from a uranium-contaminated aquifer subject to seasonal temperature fluctuations. The mixed culture contains Desulfovibrio sp. and a Clostridia-like organism. Rates of growth, ethanol utilization, decay, and uranium reduction decreased with decreasing temperature. No significant uranium reduction was observed at 10 degrees C. While both Monod saturation kinetics and pseudo second-order kinetics adequately described the rates of growth and utilization of electron donor (ethanol), model parameters for the pseudo second-order expression had smaller uncertainties. Uranium reduction kinetics were best described by pseudo second-order kinetics modified to include a term for inactivation/death of cells. 相似文献
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Shinozawa T Mizutani E Tomioka I Kawahara M Sasada H Matsumoto H Sato E 《Molecular reproduction and development》2004,68(3):313-318
In the present study, we examined the developmental ability of enucleated zygotes, MII oocytes, and parthenogenetically activated oocytes at pronuclear stages (parthenogenetic PNs) as recipient cytoplasm for rat embryonic cell nuclear transfer. Enucleated zygotes as recipient cytoplasm receiving two-cell nuclei allowed development to blastocysts, whereas the development of embryos reconstituted with MII oocytes and parthenogenetic PNs was arrested at the two-cell stage. Previous observations in rat two-cell embryos suggested that the distribution of microtubules is involved in two-cell arrest. Therefore, we also examined the distribution of microtubules using immunofluorescence. At the two-cell stage after nuclear transfer into enucleated zygotes, microtubules were distributed homogeneously in the cytoplasm during interphase, and normal mitotic spindles were observed in cleaving embryos from the two- to four-cell stage. In contrast, embryos reconstituted with MII oocytes and parthenogenetic PNs showed aberrant microtubule organization. In enucleated zygotes, fibrous microtubules were distributed homogeneously in the cytoplasm. In contrast, dense microtubules were localized at the subcortical area in the cytoplasm and strong immunofluorescence intensity was observed at the plasma membrane, while very weak intensity was detected in the central part of enucleated MII oocytes. In enucleated parthenogenetic PNs, high-density and fibrous microtubules were distributed in the subcortical and central areas, respectively. Pre-enucleated parthenogenetic PNs also showed lower intensity of microtubule immunofluorescence in the central cytoplasm than zygotes. In conclusion, the results of the present study showed that zygote cytoplasm is better as recipient than MII oocyte and parthenogenetic PNs for rat two-cell embryonic cell nuclear transfer to develop beyond four-cell stage. Furthermore, microtubule organization is involved in the development of reconstituted embryos to overcome the two-cell arrest. 相似文献
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Karreman MA Agronskaia AV Verkleij AJ Cremers FF Gerritsen HC Humbel BM 《Biology of the cell / under the auspices of the European Cell Biology Organization》2009,101(5):287-299
Background information. Treatment of cells with UVC radiation leads to the formation of DNA cross‐links which, if not repaired, can lead to apoptosis. γ‐H2AX and cleaved caspase 3 are proteins formed during UVC‐induced DNA damage and apoptosis respectively. The present study sets out to identify early morphological markers of apoptosis using a new method of correlative microscopy, ILEM (integrated laser electron microscopy). Cleaved caspase 3 and γ‐H2AX were immunofluorescently labelled to mark the cells of interest. These cells were subsequently searched in the fluorescence mode of the ILEM and further analysed at high resolution with TEM (transmission electron microscopy). Results. Following the treatment of HUVECs (human umbilical vein endothelial cells) with UVC radiation, in the majority of the cells γ‐H2AX was formed, whereas only in a subset of cells caspase 3 was activated. In severely damaged cells with high levels of γ‐H2AX a round, electron‐dense nuclear structure was found, which was hitherto not identified in UV‐stressed cells. This structure exists only in nuclei of cells containing cleaved caspase 3 and is present during all stages of the apoptotic process. Energy‐loss imaging showed that the nuclear structure accumulates phosphorus, indicating that it is rich in nucleic acids. Because the nuclear structure did not label for DNA and was not affected by regressive EDTA treatment, it is suggested that the UV‐induced nuclear structure contains a high amount of RNA. Conclusions. Because the UV‐induced nuclear structure was only found in cells labelled for cleaved caspase 3 it is proposed as an electron microscopic marker for all stages of apoptosis. Such a marker will especially facilitate the screening for early apoptotic cells, which lack the well‐known hallmarks of apoptosis within a cell population. It also raises new questions on the mechanisms involved in the UV‐induced apoptotic pathway. 相似文献
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The evolution of floral display is thought to be constrained by trade‐offs between the size and number of flowers and inflorescences. We grew in the glasshouse 60 maternal families from each of two Brazilian populations of the annual herb, Eichhornia paniculata. We measured flower size, daily flower number, and total flower number per inflorescence, and two indices of module size, leaf area and age at flowering. We also assessed the size and number of inflorescences produced over 6 weeks. All floral traits exhibited significant heritable variation, some of which was due to genetic variation in module size. Genetic (maternal family) correlations between daily and total flower number did not differ from 1.0, indicating that display size (daily flower number) cannot evolve independently from total flower number per inflorescence. Genetic correlations between flower size and daily flower number ranged from negative to positive (r=–0.78 to +0.84), depending on population and inflorescence. Positive correlations occurred when variation in investment per inflorescence was high so that some families produced both larger and more flowers. These correlations became zero when we controlled for variation in module size. Families that flowered later produced fewer, larger inflorescences (r=–0.33, –0.85). These data support theoretical predictions regarding the combined effects of variation in resource acquisition and allocation on traits involved in trade‐offs, and they emphasize the hierarchical organization of floral displays. Our results imply that patterns of resource allocation among inflorescences influence evolutionary changes in flower size and number per inflorescence. 相似文献
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