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1.
In vitro stimulation of intact rat posterior pituitary by either veratridine or K+ depolarization results in the concomitant release of neurophysins and in a decrease (70-80%) in their carboxyl methylation as measured either with L-[methyl-3H]methionine in the intact lobes after stimulation or in their homogenates with [methyl-3H]S-adenosyl-L-methionine and purified protein carboxyl methyltransferase. A similar reduction in neurophysin methylation (60%) was observed when the arrival of newly synthesized neurophysins at the posterior pituitary was blocked by colchicine. Experimental data indicate that the reduction in neurophysin content of the lobes after 12 h of colchicine treatment (less than 7%) or after in vitro stimulation (about 10%) cannot account for the marked reduction in neurophysin methylation. The results suggest that the granule pool characterized by rapid turnover of neurophysins probably represents the major source of methyl acceptor proteins in the lobe. In spite of the marked reduction in neurophysin methyl accepting capacity observed after stimulation, there was no parallel increase in methyl accepting capacity of the released neurophysins. We propose that a neurophysin subfraction that might be associated with the membrane of releasable granules participates in the methylation reaction in situ.  相似文献   
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Summary Dysgenic hybrids of Drosophila melanogaster were screened for the induction of mutations in the Y chromosomal fertility genes. Out of 2,417 Y chromosomes analysed 13 male steriles (ms (Y)) were isolated. This high rate of mutation is most probably due to the unusually large physical size of the fertility genes.  相似文献   
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Female reproductive capacity declines dramatically in the fourth decade of life as a result of an age‐related decrease in oocyte quality and quantity. The primary causes of reproductive aging and the molecular factors responsible for decreased oocyte quality remain elusive. Here, we show that aging of the female germ line is accompanied by mitochondrial dysfunction associated with decreased oxidative phosphorylation and reduced Adenosine tri‐phosphate (ATP) level. Diminished expression of the enzymes responsible for CoQ production, Pdss2 and Coq6, was observed in oocytes of older females in both mouse and human. The age‐related decline in oocyte quality and quantity could be reversed by the administration of CoQ10. Oocyte‐specific disruption of Pdss2 recapitulated many of the mitochondrial and reproductive phenotypes observed in the old females including reduced ATP production and increased meiotic spindle abnormalities, resulting in infertility. Ovarian reserve in the oocyte‐specific Pdss2‐deficient animals was diminished, leading to premature ovarian failure which could be prevented by maternal dietary administration of CoQ10. We conclude that impaired mitochondrial performance created by suboptimal CoQ10 availability can drive age‐associated oocyte deficits causing infertility.  相似文献   
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Yaakov B  Kashkush K 《Génome》2011,54(1):42-49
Rapid and reproducible genomic changes can be induced during the early stages of the life of nascent allopolyploid species. In a previous study, it was shown that following allopolyploidization, cytosine methylation changes can affect up to 11% of the wheat genome. However, the methylation patterns around transposable elements (TEs) were never studied in detail. We used transposon methylation display (TMD) to assess the methylation patterns of CCGG sites flanking three TE families (Balduin, Apollo, and Thalos) in the first four generations of a newly formed wheat allohexaploid. In addition, transposon display (TD), using a methylation-insensitive restriction enzyme, was applied to search for genomic rearrangements at the TE insertion sites. We observed that up to 54% of CCGG sites flanking the three TE families showed changes in methylation patterns in the first four generations of a newly formed wheat allohexaploid, where hypermethylation was predominant. Over 70% of the changes in TMD patterns occurred in the first two generations of the newly formed allohexaploid. Furthermore, analysis of 555 TE insertion sites by TD and 18 cases by site-specific PCR revealed a full additive pattern in the allohexaploid, an indication for lack of massive rearrangements. These data indicate that following allopolyplodization, DNA-TE insertion sites can undergo a significantly high level of methylation changes compared with methylation changes of other genomic sequences.  相似文献   
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The prevalence of domain-swapping in nature is a manifestation of the principle of minimal frustration in that the interactions designed by evolution to stabilize the protein are also involved in this mode of binding. We previously demonstrated that the Symmetrized-Go potential accurately predicts the experimentally observed domain-swapped structure of Eps8 based solely on the structure of the monomer. There can be, however, multiple modes of domain-swapping, reflecting a higher level of frustration, which is a consequence of symmetry. The human prion and cyanovirin-N are too frustrated to form unique domain-swapped structures on the basis of the Symmetrized-Go potential. However, supplementing the completely symmetric model with intermolecular and intramolecular disulfide bonds in the prion and cyanovirin-N proteins, respectively, yielded unique domain-swapped structures with a remarkable similarity to the experimentally observed ones. These results suggest that the disulfide bonds may sometimes be critical in overcoming the intrinsic frustration of the symmetrized energy landscapes for domain-swapping. We also discuss the implications of intermolecular disulfide bonds in the formation of mammalian prion aggregates.  相似文献   
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