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211.
Sequence of an unusually large protein implicated in regulation of myosin activity in C. elegans 总被引:36,自引:0,他引:36
The Caenorhabditis elegans gene unc-22 encodes a very large muscle protein, called twitchin, which consists of a protein kinase domain and several copies of two short motifs. The sequence of twitchin has unexpected similarities to the sequences of proteins of the immunoglobulin superfamily, cell adhesion molecules and vertebrate muscle proteins, including myosin light-chain kinase. These homologies, together with results from earlier genetic and molecular analyses, indicate that twitchin is involved in a novel mechanism of myosin regulation. 相似文献
212.
J. N. D. Wurpel 《Cellular and molecular life sciences : CMLS》1994,50(5):475-478
This study investigates the effect of the gamma-aminobutyric acid (GABAB) agonist, baclofen, on amygdala kindling in adult rats. Baclofen has been reported to be anticonvulsant in a variety of seizure models and prevents kindling in immature rats. These experiments describe the effects of baclofen (2, 5 and 10 mg/kg, i.p.) on the afterdischarge threshold and kindling rate. Baclofen, 10 mg/kg, significantly increased the afterdischarge threshold in the amygdala. Baclofen at 5 and 10 mg/kg, retarded the rate of kindling as measured by the number of stimuli required to advance to subsequent seizure stages. These results suggest that baclofen may decrease the local excitability of the amygdala and retard the rate of seizure spread (or generalization) throughout the brain. Baclofen, acting at GABAB receptors exerts an anticonvulsant effect on amygdala kindling in these experiments. 相似文献
213.
H. Miyamoto N. Manabe Y. Akiyama T. Watanabe M. Sugimoto E. Sato 《Cellular and molecular life sciences : CMLS》1994,50(9):808-811
The morphometric parameters of spermatogenic cells in a mouse strain prone to accelerated senescence (SAM-P), a novel murine model of spontaneously promoted aging, were compared with those of a SAM resistant strain (SAM-R) after birth until 40 weeks (mean life span of SAM-P). A mixture of gonocytes and spermatogonia were present in the testis in 1-week-old mice, and no gonocytes were observed in 2-week-old mice. At 6 weeks of age, the absolute number of spermatogonia in SAM-P was 27% greater than that in SAM-R, whereas the cell number in 40-week-old SAM-P was 17% less than in SAM-R. Primary spermatocytes were first observed in 3-week-old animals, and the cell numbers in SAM-P at 3, 5 and 6 weeks were 78%, 31% and 25%, respectively, greater than in SAM-R, whereas the cell number in SAM-P at 40 weeks was 30% less than SAM-R. Round spermatids were first observed in all SAM-P at 4 weeks old, but 20% of SAM-r had no spermatids and the rest had only a few. At 5 and 6 weeks old, the absolute numbers of round spermatids in SAM-P was about 34% and 41%, respectively, greater than in SAM-R, whereas the cell number in 40-week-old SAM-P was about 34% less than SAM-R. These results indicate that testicular maturation begins at an earlier age in SAM-P than SAM-R. Furthermore, at the age of 40 weeks signs of testicular deterioration are evident in SAM-P mice only 相似文献
214.
人工引入核电站排放的关键核素 ̄(131)I,采用γ能谱和总β计数两种方法确定核素在土壤-蔬菜系统中的转移系数。测得核素不同迁移时间、不同生长期的蔬菜、以及土壤中不同核素浓度等各种情况下的转移系数。给出转移系数的频数分布及变异性。γ能谱法测得的 ̄(131)I在广东土壤-蔬菜系统中转移系数的观察值范围为1.28×10 ̄(-2)~2.10×10 ̄(-1),几何平均值为5.05×10 ̄(-2),几何标准偏差为1.96.实验中观察到蔬菜棵株大小、不同气候条件等因素对转移系数的影响。 相似文献
215.
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218.
Acute leukaemia in bcr/abl transgenic mice 总被引:38,自引:0,他引:38
N Heisterkamp G Jenster J ten Hoeve D Zovich P K Pattengale J Groffen 《Nature》1990,344(6263):251-253
219.
Structure of Arc repressor in solution: evidence for a family of beta-sheet DNA-binding proteins 总被引:15,自引:0,他引:15
The Arc repressor, which is involved in the switch between lysis and lysogeny of Salmonella bacteriophage P22, does not belong to any of the known classes of DNA-binding proteins. Mutagenesis studies show that the DNA-binding region is located in the 15 N-terminal amino-acid residues. We have now determined the three-dimensional structure of the Arc dimer from an extensive set of interproton-distance data obtained from 1H NMR spectroscopy. A priori, intra- and inter-monomer nuclear Overhauser effects (NOEs) cannot be distinguished for a symmetric dimer. But by using the homology with the Escherichia coli Met repressor we could interpret the NOEs unambiguously in an iterative structure refinement procedure. The final structure satisfies a large set of NOE constraints (1,352 for the dimer). It shows a strongly intertwined dimer, in which residues 8-14 of different monomers form an antiparallel beta-sheet. A model for the Arc repressor-operator complex can account for all available biochemical and genetic data. In this model two Arc dimers bind with their beta-sheet regions in successive major grooves on one side of the DNA helix, similar to the Met repressor interaction. Thus, Arc and Met repressors are members of the same family of proteins, which contain an antiparallel beta-sheet as the DNA-binding motif. 相似文献
220.