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31.
Clinical and biochemical studies in three patients with severe early infantile Cockayne syndrome 总被引:2,自引:0,他引:2
Jaak Jacken Helmut Klocker Helga Schwaiger Romuald Bellmann Monica Hirsch-Kauffmann Manfred Schweiger 《Human genetics》1989,83(4):339-346
Summary We present clinical and biochemical data from three patients with severe Cockayne syndrome (CS) of very early onset. Unlike in classic CS, signs became evident in the first weeks of life and led to unusually early death. Fibroblasts from two of the patients showed a complete defect of the repair of UV-induced thymine dimer lesions. They were unable to remove thymine dimer lesions from their DNA, had a severe reduction of the RNA synthesis rates after UV irradiation, and showed no reactivation of an UV-inactivated indicator gene and no DNA recondensation after UV irradiation. DNA repair investigated in these two fibroblast cell strains resembled that of xeroderma pigmentosum cells of complementation group A. In contrast, fibroblasts from the third patient showed the same in vitro repair characteristics as classic CS cells. 相似文献
32.
Jorge Florin-Christensen Monica Florin-Christensen Arno Tiedtke Leif Rasmussen 《Microbial ecology》1990,19(3):311-316
In an attempt to extend our knowledge of the biology of feeding of the ciliateTetrahymena thermophila, this organism was grown axenically on complex organic material. The nutrient substrate was based on autoclaved wheat grains and adjusted to either pH 5.5 or 7.5. In wild type cultures the cells grew and multiplied only under acidic conditions. In cultures of a mutant cell line blocked in the secretion of acid hydrolases the cells did not grow at either pH value. Thus released acid hydrolases may play a key role in the utilization of complex nutrients in combination with uptake of small organic molecules. Mechanisms in the feeding biology ofTetrahymena thermophila andParamecium tetraurelia are compared. 相似文献
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Abstract. The phenological changes in populations of Festuca pallescens (St. Yves) Parodi at different topographic positions and exposure along an altitudinal gradient (600 - 1100 m) were investigated during two growing seasons in northwestern Patagonia. Stepwise multiple regression analysis was used to describe the relationship between phenology and environment during the entire growing season. Analysis of variance was also performed at each sample date to detect significant environmental factors influencing phenology at different sites. The sum of maximum air temperatures was identified as the environmental variable best correlated with the seasonal variation of phenological events of Festuca pallescens over the period of two growing seasons, explaining 93.2 % of the total variance. Significant differences between sites were observed at each sample date. Main effects of altitude and topographic position and two-way interactions between altitude and topographic position, and topographic position and exposure were also detected as significant. Phenology was delayed at increased altitude. Differences in phenology between topographic sites at the same altitude were not detected during the entire growing season and were only observed in the reproductive phase. At this time, the phenology was significantly delayed at high topographic positions on the slopes as compared with low and mid positions. At high altitudes in the valley (950 m a. s. 1.), where steep slopes and humid conditions prevail, phenology was delayed on western exposures and low positions. The results adequately summarize and quantify the effect of spatial and temporal environmental variation on the phenological development of Festuca pallescens in northwestern Patagonia. 相似文献
35.
The molecular biology of plant acclimation to low temperature 总被引:51,自引:8,他引:43
36.
Summary Two plasmids isolated from Lactobacillus helveticus strain ILC 54 were analysed by restriction digestion. A restriction map of the 14.3 and 5.6 kb plasmids is presented. Plasmid-curing studies suggest that these plasmids are involved in lactose metabolism and peptidase activity. 相似文献
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39.
Flemming S. Vassbotn Arne
stman Nina Langeland Holm Holmsen Bengt Westermark Carl-Henrik Heldin Monica Nistr 《Journal of cellular physiology》1994,158(2):381-389
Human glioblastoma cells (A172) were found to concomitantly express PDGF-BB and PDGF β-receptors. The receptors were constitutively autophosphorylated in the absence of exogenous ligand, suggesting the presence of an autocrine PDGF pathway. Neutralizing PDGF antibodies as well as suramin inhibited the autonomous PDGF receptor tyrosine kinase activity and resulted in up-regulation of receptor protein. The interruption of the autocrine loop by the PDGF antibodies reversed the transformed phenotype of the glioblastoma cell, as determined by (1) diminished DNA synthesis, (2) inhibition of tumor colony growth, and (3) reversion of the transformed morphology of the tumor cells. The PDGF antibodies showed no effect on the DNA synthesis of another glioblastoma cells line (U343MGa 31L) or on Ki-ras-transformed fibroblasts. The present study demonstrates an endogenously activated PDGF pathway in a spontaneous human glioblastoma cell line. Furthermore, we provide evidence that the autocrine PDGF pathway drives the transtormed phenotype of the tumor cells, a process that can be blocked by extracellular antagonists. © 1994 Wiley-Liss, Inc. 相似文献
40.
Expression of the hepatitis delta virus large and small antigens in transgenic mice. 总被引:5,自引:3,他引:2 下载免费PDF全文
S Guilhot S N Huang Y P Xia N La Monica M M Lai F V Chisari 《Journal of virology》1994,68(2):1052-1058
Simultaneous infection with hepatitis delta virus (HDV) and hepatitis B virus (HBV) in humans is often associated with severe viral liver disease including fulminant hepatitis. Since HBV is thought to be noncytopathic to the hepatocyte, the enhanced disease severity observed during dual infection has been attributed to either simultaneous immune responses against the two viruses or direct cytotoxic effects of HDV products on the hepatocyte or both. To examine these alternate possibilities, we produced transgenic mice that express the small and large delta antigens (HDAg) in hepatocyte nuclei at levels equal to those observed during natural HDV infection. No biological or histopathological evidence of liver disease was detectable during 18 months of observation, suggesting that neither the large nor small form of HDAg is directly cytopathic to the hepatocyte in vivo. 相似文献