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91.
At the moment of insemination millions of mammalian sperm cells are released into the female reproductive tract in order to
find a single cell – the oocyte. The spermatozoa subsequently ignore the thousands of cells they make contact with during
their journey to the site of fertilisation, until they reach the surface of the oocyte. At this point, they bind tenaciously
to the acellular coat, known as the zona pellucida, that surrounds the oocyte and initiate the chain of cellular interactions
that will culminate in fertilization. These exquisitely cell- and species-specific recognition events are among the most strategically
important cellular interactions in biology. Understanding the cellular and molecular mechanisms that underpin them has implications
for diagnosis of the aetiology of human infertility and the development of novel targets for fertility regulation. Herein,
we describe two models indicating the plethora of highly orchestrated molecular interactions underlying successful sperm zona
binding and sperm oocyte fusion.
Received 17 December 2006; received after revision 31 January 2007; accepted 16 March 2007 相似文献
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根据不同的岩浆侵入地层方式以及围岩内孔隙水是否发生气化建立了四种热传导模型,以苏格兰西北部Skye岛的辉绿岩岩墙为实例分别采用这四种热传导模型数值模拟了侵入体相邻泥质烃源岩有机质的成熟度。模拟结果显示:(1)岩浆的侵入方式能显著地影响热传导模型对侵入体围岩成熟度的预测,岩浆有限时间侵入方式的假设下热传导模型所预测的镜质体反射率(Ro)与假设岩浆瞬间侵入方式的模型相比,最大偏差处低2.13%~2.59%;(2)当岩浆侵入方式相同时,考虑孔隙水气化的模型预测的Ro普遍低于不考虑孔隙水气化的模型。孔隙水气化引起Ro的最大偏差达0.71%~0.91%,明显低于岩浆的侵入方式对围岩成熟度预测结果的影响;(3)不考虑围岩内孔隙水的气化且假设岩浆有限时间侵入地层的热传导模型所预测的Ro与实测值十分吻合,说明岩浆侵入方式应为有限时间侵入且围岩孔隙水的气化作用不显著,该模型是否适用于其他地区,还有待于进一步研究。 相似文献
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生长因子对牛体外受精卵体外发育的影响 总被引:2,自引:0,他引:2
本研究探讨了在成熟培养液和发育培养液内添加EGF和TGF-α对牛体外受精卵发育的影响,在成熟培养液内分别添加EGF和TGF-α,经体外受精处理后卵裂率分别为78.3%和82.6%,显著高于对照组60.2%的卵裂率;三个处理组囊胚发育率分别为19.6%、24.5%和18.7%,三者间无显著差异.在发育培养液内分别添加EGF和TGF-α,其囊胚发育率分别为30.0%和23.4%,与对照组21.0%的囊胚发育率相比差异不显著.在成熟培养液内添加TGF-α,在发育培养液内添加EGF,经这两种生长因子分别作用后,体外受精卵翼胚发育率为21.0%,与单独使用其中一种生长因子相比囊胚发育率无明显提高. 相似文献
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A. Hasilik 《Cellular and molecular life sciences : CMLS》1992,48(2):130-151
Lysosomal enzymes are subjected to a number of modifications including carbohydrate restructuring and proteolytic maturation. Some of these reactions support lysosomal targeting, others are necessary for activation or keeping the enzyme inactive before being segregated, while still others may be adventitious. The non-segregated fraction of the enzyme is secreted and can be isolated from the medium. It is considered that the secreted lysosomal enzymes fulfill certain physiological and pathophysiological roles. By comparing the secreted and the intracellular enzymes it is possible to distinguish between the reactions that occur before and after the segregation. In this review the reactions that may influence the segregation are referred to as the early processing and those characteristic for the enzymes isolated from lysosomal compartments as the late processing. The early processing is characterized mainly by modifications of carbohydrate side chains. In the late processing, proteolytic fragmentation represents the most conspicuous changes. The review focuses on the compartmentation of the reactions and the proteolytic fragmentation of lysosomal enzyme precursors. While a plethora of proteolytic reactions are involved, our knowledge of the proteinases responsible for the particular maturation reactions remains very limited. The review points also to work with cells from patients affected with lysosomal storage disorders, which contributed to our understanding of the lysosomal apparatus. 相似文献
100.
《科学通报(英文版)》1999,44(17):1600-1600
The low-temperature and low-pressure artificial hydropyrolysis experiment proves that at the immature-low mature thermal evolution stage of source rock, the condensation reaction and the thermal degradation reaction occur continuously and simultaneously in both soluble organic matter and insoluble organic matter. This process was called "antipole evolution", which means transformation into two opposing extremes. The soluble organic matter and insoluble organic matter constitute an organic related integrity, transforming mutually in a dynamic equilibrium. Non-hydrocarbon and asphaltene are key intermediates between kerogen and hydrocarbon . Asphaltene is one of the major sources of immature hydrocarbons. 相似文献