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1.
Hepatocytes from male rats were incubated with [32P]Pi for 40 min at 37 degrees C, thereby equilibrating the cellular ATP pool with 32P. Subsequent exposure to bovine growth hormone for 10 additional min did not change the specific activity of cellular [gamma-32P]ATP. Two-dimensional gel electrophoresis or chromatofocusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to fractionate phosphoproteins solubilized from control or hormone-stimulated cells. Stimulation of hepatocytes with 5 nM growth hormone for 10 min at 37 degrees C affected the phosphorylation of a number of proteins including an Mr 46,000 species of pI 4.7 whose phosphorylation was augmented (2.65 +/- 0.50)-fold. A significant fraction of the maximal effect of growth hormone on phosphorylation of the Mr 46,000 species was elicited by 1-5% receptor occupancy. Bovine growth hormone, which binds to somatogenic receptors with great specificity, or recombinant human growth hormone, which is not contaminated with other hormones, affected phosphorylation of hepatic proteins similarly. The Mr 46,000 phosphoprotein was isolated in a fraction enriched in cytosol after centrifugation of cellular homogenates. Phosphorylation of the Mr 46,000 phosphoprotein was also increased (1.75 +/- 0.35)-fold and (2.15 +/- 0.50)-fold by insulin and glucagon, respectively. These observations are consistent with the possibility that selective changes in the phosphorylation state of cellular proteins may mediate growth hormone actions in cells. 相似文献
2.
Insulin binding to rat liver plasma membranes promotes proteolysis of the Mr 135,000 alpha subunit of the insulin receptor to a fragment of Mr 120,000 (Lipson, K. E., Yamada, K., Kolhatkar, A. A., and Donner, D. B. (1986) J. Biol. Chem. 261, 10833-10838). The enzyme that catalyzes this degradation copurifies with plasma membranes and cannot be identified in any other cellular organelle or in cytosol. The proteinase has optimal activity above pH 7 and is an integral protein based upon its resistance to extraction with 2 M NaCl. After affinity labeling, degraded insulin receptors were identified in plasma membranes isolated from a liver perfused with 1 nM 125I-insulin for 10 min at 37 degrees C, indicating that proteolysis occurs in the hepatocyte cell membrane under physiological conditions. Microsomes do not contain the receptor degrading activity or a detectable amount of degraded receptors under basal conditions. After perfusion of a liver with 125I-insulin, Mr 135,000 and Mr 120,000 complexes were detected in microsomes, suggesting that both intact and degraded receptors can be internalized. The initial absence of degraded receptors in plasma membranes suggests that, following internalization, such sites do not recycle. Thus, hormone-induced proteolysis of the insulin receptor begins at the surface of the rat hepatocyte and can lead to loss of receptors from the plasma membrane. 相似文献
3.
The plasminogen activator family from the salivary gland of the vampire bat Desmodus rotundus: cloning and expression 总被引:4,自引:0,他引:4
J Kr?tzschmar B Haendler G Langer W Boidol P Bringmann A Alagon P Donner W D Schleuning 《Gene》1991,105(2):229-237
Complementary DNAs coding for four Desmodus rotundus salivary plasminogen activators (DSPAs) were isolated and characterized. The predicted amino acid sequences display structural features also found in tissue-type plasminogen activator. The largest forms (DSPA alpha 1 and -alpha 2) contain a signal peptide, a finger (F), an epidermal growth factor (EGF), a kringle, and a serine protease domain, whereas DSPA beta and -gamma lack the F and F-EGF domains, respectively. Additional differences between the four forms suggest that distinct genes code for the members of the DSPA family. Transfection of DSPA-encoding cDNAs, placed under the control of the simian virus 40 late promoter, into COS-1 cells resulted in the secretion of highly fibrin-dependent PAs. 相似文献
4.
Loren C. Skow Maria E. Donner Shu-Mei Huang John M. Gardner Benjamin A. Taylor Wesley G. Beamer Peter A. Lalley 《Biochemical genetics》1988,26(9-10):557-570
Restriction fragments analysis of DNA from mouse-hamster somatic-cell hybrid clones revealed that a mouse gamma crystallin cDNA hybridized to genomic sequences located on mouse chromosome 1. Identification of restriction fragment length polymorphisms (RFLPs) in the gamma crystallin sequences of inbred strains of mice permitted the further localization of the gamma crystallin genes (Cryg) to the proximal region of chromosome 1 closely linked to the loci encoding isocitrate dehydrogenase (Idh-1), a low molecular weight (LM) crystallin protein polymorphism (Len-1), and fibronectin (Fn-1). A single recombinant was observed betweenLen-1 and an RFLP in the gamma crystallin gene family, consistent with the hypothesis thatLen-1 is one of the several structural loci encoding gamma crystallin genes.Len-1 is probably located on the centromeric end of theCryg gene family. Linkage ofIdh-1, Cryg, andFn-1 in mice extends the syntenic relationship of those loci to the human, bovine, and rodent genomes and may define a chromosomal region that is generally conserved among mammals. The map position ofCryg, near the eye lens obsolescence (Elo) locus, was confirmed by the discovery that the restriction fragment patterns of gamma crystallin sequences differed between strain C3H/HeJ and the congenic anophthalmic mutant strain, C3H.Elo. Therefore, the gamma crystallin genes were contransferred with the mutantElo gene in the derivation of C3H.Elo. The results establish that LEN-1 is a marker for the gamma crystallin gene family, position the gamma crystallin gene family relative to other markers on mouse chromosome 1, and provide additional evidence that theElo mutation is encoded at a locus closely linked to the gamma crystallin gene cluster. This study found no evidence of recombination hot spots within the gamma crystallin gene cluster. 相似文献
5.
A new estimator of a common odds ratio is proposed for case-control studies of familial aggregation. The proposed estimator is a modification to the usual Mantel-Haenszel estimator that relies on an empirical adjustment for the within-family clustering which is typical of such designs. A simulation study shows that the estimator tends to have smaller mean squared error than the unmodified Mantel-Haenszel estimator under conditions likely to arise in practice. The construction of confidence intervals is also discussed. 相似文献
6.
A comparison of confidence interval methods for the intraclass correlation coefficient 总被引:2,自引:0,他引:2
Different methods of obtaining confidence intervals for the intraclass correlation coefficient rho in the unbalanced one-way random-effects model are investigated, focusing on applications to family studies. Methods based on simple modifications of formulas for the case of equal group sizes are found to provide adequate coverage at small to moderate values of rho. A method based on the large-sample standard error of the sample intraclass correlation, as derived by Smith (1956, Annals of Human Genetics 21, 363-373), is shown to provide consistently good coverage at all values of rho. A method proposed by Thomas and Hultquist (1978, Annals of Statistics 6, 582-587) also provides consistently good coverage, but generates mean interval widths substantially greater than those generated by Smith's method at values of rho likely to arise in practice. 相似文献
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9.
蚕豆叶片发育与衰老过程中超氧物歧化酶活性与丙二醛含量变化 总被引:2,自引:0,他引:2
蚕豆植株叶片随茎节自上而下表现出明显的发育与衰老顺序,可作为衰老特征的是叶绿素和蛋白质含量明显下降。蚕豆叶中SOD活性主要定位于12 000× g离心后所得的上清液和叶绿体组分。衰老叶片的SOD总活性和叶绿体组分的相对活性都有所下降,SOD同工酶谱也发生了改变。O_2~ 产生速率随叶龄增大而稍上升;而MDA含量在叶片外观表现枯黄衰老征兆前就急剧上升。可能因为衰老叶片过氧化氢酶活性大幅度下降与SOD之间的不平衡,致使O_2~ 代谢中间产物累积而引起膜的损伤. 相似文献
10.
Visual performance of the toad (Bufo bufo) at low light levels: retinal ganglion cell responses and prey-catching accuracy 总被引:3,自引:0,他引:3
A. -C. Aho K. Donner S. Helenius L. Olesen Larsen T. Reuter 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,172(6):671-682
The accuracy of toad snapping towards moving worm dummies under various levels of dim illumination (from absolute threshold to moonlight) was videorecorded and related to spike responses of retinal ganglion cells exposed to equivalent stimuli. Some toads (at ca. 16 °C) successfully snapped at dummies that produced only one photoisomerization per 50 rods per second in the retina, in good agreement with thresholds of sensitive retinal ganglion cells. One factor underlying such high sensitivity is extensive temporal summation by the ganglion cells. This, however, is inevitably accompanied by very long response latencies (around 3 s near threshold), whereby the information reaching the brain shows the dummy in a position where it was several seconds earlier. Indeed, as the light was dimmed, snaps were displaced successively further to the rear of the dummy, finally missing it. The results in weak but clearly supra-threshold illumination indicate that snaps were aimed at the advancing head as seen by the brain, but landed further backwards in proportion to the retinal latency. Near absolute threshold, however, accuracy was too good, suggesting that the animal had recourse to a neural representation of the regularly moving dummies to correct for the slowness of vision. 相似文献