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排序方式: 共有81条查询结果,搜索用时 31 毫秒
31.
Summary Oogenesis ceases in virgin Monarch butterflies at about 10 days posteclosion, but an enhanced production of mature oocytes occurs after mating. Juvenile hormone injections into virgins, and allatectomies of mated females, indicate that the observed fluctuations in oogenesis are due to periods of corpora allata activity and inactivity.Supported by USPHS, grant HD-07336.The assistance of T. F. Scirwudo is very much appreciated. 相似文献
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Z. S. Herman Z. Stachura Ł. Opiełka I. Z. Siemion E. Nawrocka 《Cellular and molecular life sciences : CMLS》1981,37(1):76-77
Summary Tuftsin has marked analgesic activity but is less potent than D-Arg3-tuftsin. The absence of an antagonistic effect of naloxone on tuftsin and its analogue suggests that these substances do not act on opiate receptors. Tuftsin and its analogues may represent a new class of substances of interest in the search for new analgesics. 相似文献
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Nicastro F Mathur S Elvis M Drake J Fang T Fruscione A Krongold Y Marshall H Williams R Zezas A 《Nature》2005,433(7025):495-498
Recent cosmological measurements indicate that baryons comprise about four per cent of the total mass-energy density of the Universe, which is in accord with the predictions arising from studies of the production of the lightest elements. It is also in agreement with the actual number of baryons detected at early times (redshifts z > 2). Close to our own epoch (z < 2), however, the number of baryons detected add up to just over half (approximately 55 per cent) of the number seen at z > 2 (refs 6-11), meaning that about approximately 45 per cent are 'missing'. Here we report a determination of the mass-density of a previously undetected population of baryons, in the warm-hot phase of the intergalactic medium. We show that this mass density is consistent, within the uncertainties, with the mass density of the missing baryons. 相似文献
35.
Bong June Yoon Herry Herman Aimee Sikora Laura T Smith Christoph Plass Paul D Soloway 《Nature genetics》2002,30(1):92-96
In mammals, DNA is methylated at cytosines within CpG dinucleotides. Properly regulated methylation is crucial for normal development. Inappropriate methylation may contribute to tumorigenesis by silencing tumor-suppressor genes or by activating growth-stimulating genes. Although many genes have been identified that acquire methylation and whose expression is methylation-sensitive, little is known about how DNA methylation is controlled. We have identified a DNA sequence that regulates establishment of DNA methylation in the male germ line at Rasgrf1. In mice, the imprinted Rasgrf1 locus is methylated on the paternal allele within a differentially methylated domain (DMD) 30 kbp 5' of the promoter. Expression is exclusively from the paternal allele in neonatal brain. Methylation is regulated by a repeated sequence, consisting of a 41-mer repeated 40 times, found immediately 3' of the DMD. This sequence is present in organisms in which Rasgrf1 is imprinted. In addition, DMD methylation is required for imprinted Rasgrf1 expression. Together the DMD and repeat element constitute a binary switch that regulates imprinting at the locus. 相似文献
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Temporal dynamics and genetic control of transcription in the human prefrontal cortex 总被引:1,自引:0,他引:1
Colantuoni C Lipska BK Ye T Hyde TM Tao R Leek JT Colantuoni EA Elkahloun AG Herman MM Weinberger DR Kleinman JE 《Nature》2011,478(7370):519-523
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Herman MA Peroni OD Villoria J Schön MR Abumrad NA Blüher M Klein S Kahn BB 《Nature》2012,484(7394):333-338
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C. A. Wallace R. Jenness R. J. Mullin W. S. Herman 《Cellular and molecular life sciences : CMLS》1985,41(4):485-486
Summary L-Gulonolactone oxidase (EC 1.1.3.8) which catalyzes oxidation of L-gulonolactone to L-ascorbic acid was detected in tissues ofLimulus polyphemus. 相似文献