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121.
The repertoire of mature class II-restricted T cells is generated through a complex process of selection whereby early T cells confront class II molecules in the thymus, especially on epithelial cells. Expression of class II molecules on such cells is prominent both in the cortex and in the medulla. We have identified a novel class II molecule, H-20, which is expressed only in epithelial cells of the thymic medulla and in B cells. The unusual tissue distribution and the nonpolymorphic nature of H-20 suggest that its function is different from that of classical class II molecules. 相似文献
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P. A. Sedmak D. Sedmak H. I. Fritz G. R. Peterson 《Cellular and molecular life sciences : CMLS》1978,34(8):1059-1060
Summary Chronically-administered ethanol, not impaired nutrition, exerts a specific effect to decrease myelination as measured by the activity of the marker enzyme for myelin, 2, 3-cyclic nucleotide 3-phosphohydrolase.Acknowledgment. This work was supported in part by N.I.H. Biomedical Research Support Grant Program, Grant No. 1-507-RR07155-01. To whom reprint requests should be addressed. 相似文献
124.
R. M. Weppelman R. L. Tolman A. Ann Van Iderstine L. Peterson G. Olson 《Cellular and molecular life sciences : CMLS》1981,37(9):995-997
Summary Clonidine was anovulatory and markedly antigonadal in laying hens when infused for 1 week from minipump implants at daily rates of 1.08 mg per hen or greater. The ovaries of hens treated with clonidine responded to FSH injections which suggests that the antigonadal effect of clonidine resulted from a reduction in the output of gonadotropin by the pituitary. These data suggest that 2 receptors may be important in regulating avian fertility. 相似文献
125.
Evidence for extraterrestrial amino-acids and hydrocarbons in the Murchison meteorite 总被引:13,自引:0,他引:13
K Kvenvolden J Lawless K Pering E Peterson J Flores C Ponnamperuma I R Kaplan C Moore 《Nature》1970,228(5275):923-926
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Extinction risk from climate change 总被引:20,自引:0,他引:20
Thomas CD Cameron A Green RE Bakkenes M Beaumont LJ Collingham YC Erasmus BF De Siqueira MF Grainger A Hannah L Hughes L Huntley B Van Jaarsveld AS Midgley GF Miles L Ortega-Huerta MA Peterson AT Phillips OL Williams SE 《Nature》2004,427(6970):145-148
Climate change over the past approximately 30 years has produced numerous shifts in the distributions and abundances of species and has been implicated in one species-level extinction. Using projections of species' distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth's terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15-37% of species in our sample of regions and taxa will be 'committed to extinction'. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction ( approximately 18%) than mid-range ( approximately 24%) and maximum-change ( approximately 35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions and strategies for carbon sequestration. 相似文献
130.
M G Peterson J Inostroza M E Maxon O Flores A Admon D Reinberg R Tjian 《Nature》1991,354(6352):369-373