4 research outputs found
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Comparison of protein patterns of xrs-5, a radiosensitive Chinese hamster ovary cell line, and CHO-K1, its radioresistant parent, using two-dimensional gel-electrophoresis
X-ray sensitive strains of Chinese hamster ovary cell lines have been used to analyze radiation repair mechanisms. One cell line, xrs-5, has been shown to be very sensitive to ionizing radiation and radical forming chemical mutagens. This sensitivity is thought to be a result a mutation in the DNA double strand break (DSB) repair mechanism, and its characterization has been a goal of several repair mechanism studies. Using two-dimensional gel electrophoresis, we have detected a protein (MW approximately 55KD) in the DNA/Nuclear Matrix (nucleoid) cell fraction of CHO-Kl cells that is absent in the nucleoid fraction of xrs-5. This protein is present, however, in both CHO-Kl and xrs-5 whole cell protein maps. To determine whether the 55KD protein is responsible for the radiosensitive and defective DSB repair phenotype of xrs-5 cells, studies are now underway to analyze revertants of xrs-5 that are proficient in DSB repair. Furthermore, an effort to sequence the protein in question is planned. 23 refs., 2 figs
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Regional effects of ovariectomy and cadmium on bone mineral in ribs from aged female beagles
The purpose of this study was to evaluate effects of estrogen depletion and cadmium (Cd) on bone calcium and to determine if these effects were localized in specific regions of ribs. Fourteen female beagles with {sup 45}Ca labeled skeletons were divided into four groups: sham controls (SO{minus}); ovariectomized (OV{minus}); shams exposed to Cd (SO+); ovariecomized exposed to Cd (OV+). Total Cd exposure period was 7 months, including 1 month by capsules and 6 months by drinking H{sub 2}O. Ribs were taken at necropsy from 12 of the 14 dogs, and each rib was quartered. Wet, dry, and ash weights, as well as total Ca and {sup 45}Ca content, were determined for each quarter. Analysis of ribs from control animals demonstrated that a given rib is heterogeneous in composition. One end appears to be less mineralized and more metabolically active than other regions. The OV{minus} and OV+ mid-rib regions had significantly lower dry and ash weights than SO{minus}. Total Ca contents of these same regions were also decreased in the OV{minus} and OV+. The only significant change in Ca/dry and Ca/ash was observed when comparing OV+ to SO{minus}. Analysis of treatment suggests that there are regional effects following ovariectomy increased the loss of bone mineral occurring as a result of ovariectomy. 30 refs., 1 fig
Data from: Plant controls on Late Quaternary whole ecosystem structure and function
Plants and animals influence biomass production and nutrient cycling in terrestrial ecosystems; however their relative importance remains unclear. We assessed the extent to which mega-herbivore species controlled plant community composition and nutrient cycling, relative to other factors during and after the Late Quaternary extinction event in Britain and Ireland, when two-thirds of the region’s mega-herbivore species went extinct. Warmer temperatures, plant-soil and plant-plant interactions, and reduced burning contributed to the expansion of woody plants and declining nitrogen availability in our five study ecosystems. Shrub biomass in particular was consistently one of the strongest predictors of ecosystem change, equaling or exceeding the effects of other biotic and abiotic factors. In contrast, there was relatively little evidence for mega-herbivore control on plant community composition and nitrogen availability. The ability of plants to determine the fate of terrestrial ecosystems during periods of global environmental change may therefore be greater than previously thought