Oocyte during

The first cell cycle of the mouse embryo differs in many respects from the second and the following cell cycles. It is characterized by a long Gl phase that starts after the penetration of the spermatozoon or artificial activation of the oocyte. During this period the chromatin of the oocyte completes the second meiotic division and forms the female pronucleus. At the same time, in the fertilized egg, the highly condensed chromatin of the sperm nucleus decondenses and sperm-specific proteins, protamines, are replaced by histones. After the initial sperm chromatin... 

Bik release also occurs when Ial heavy chains are covalently transferred to hyaluronan in the extracellular matrix [23], This is a major component of cumulus cell-oocyte during fertilization and fibroblasts and mesothelial cells during inflammation. The heavy chains coupled to hyaluronan molecules bind to the cell surface through association with the hyaluronan receptor (CD44). The tumor necrosis factor-stimulated gene 6 (TSG-6) enhances the association of hyaluronan-linked heavy chains with CD44 and increases the release of free Bik [24, 25]. 

Activity of the inhibitors in vivo was assayed as described in Feyereisen et al. (30). The compounds were topically applied to the ventral surface of the thorax in 2 pi of acetone. Adult mated females were treated on day 2 and the length of the terminal oocytes was measured on day 5. Seven to 20 insects were used for each dose of inhibitor. Growth of the oocytes during that period was compared to the growth of oocytes from control insects treated with acetone alone. In some experiments the insects were treated sequentially with inhibitor and 200 pg hydroprene (ZR512) on day 2. 

Bleil, J.D. and Wassarman, P.M. (1980b). Synthesis of zona pellucida proteins by denuded and follicle-enclosed mouse oocytes during culture in vitro. Proc. Natl. Acad. Sci. 77 1029- 1033. 

Displays several properties of a myb-like transcription factor (Lederer et al. 2005) Belongs to the hnRNP family, binds to mRNAs that localize to the vegetal cortex of Xenopus oocytes during oogenesis (Zhao et al. 2001) Binds to Ena/VASP and to the GTPase RAPl (Lafuente et al. 2004) Interacts with many different members of the presynaptic cytomatrix at active zones of nerve terminals (Gamer et al. 2000)... 

Liu L, Rajareddy S, Reddy P, Jaj lamudi K, Du C, Shen Y, Guo Y, Boman K, Lundin E, Ottander U, Selstam G, Liu K 2007. Phosphorylation and inactivation of glycogen synthase kinase-3 by soluble kit ligand in mouse oocytes during early follicular development. J Mol Endocrinol 38(1-2) 137-146. 

Fan HY, Sun QY, Zou H. 2006. Regulation of Separase in meiosis Separase is activated at the metaphase I-II transition in Xenopnis oocytes during meiosis. Cell Cycle 5(2) 198-204. 

Some of the extra rDNA copies remained in the nucleus of oocytes during mitosis and one or more copies remained in the embryonic cells and were incorporated into the germinal cells. In regard to this hypothesis all extra rDNA copies are originated from one (or some) stored copies. This is a mechanism of episomic heredity. 

Fig. 88. Changes in oocytes during maturation revised tentative scheme, thick line puromy-cin sensitive processes dotted line, the supposed part of the process. (After Detlaff and Skob-lina, 1969)...

Another unusual hyaluronan-binding protein is inter-a-trypsin inhibitor [30]. This serum protein is composed of a light ehain, also known as bikunin, and two heavy chains which are covalently cross-bridged by chondroitin sulfate. Hyaluronan can replace chondroitin sulfate by trans-esterification or bind non-covalently to the heavy chains. This interaction has been shown to bind hyaluronan to cell surfaces [30] and to participate in forming a matrix around the oocyte during ovulation [31, 32). 

Another interesting system in which hyaluronan plays an important role is expansion of the cumulus oophorus during ovulation. In response to follicle stimulating hormone and a factor produced by the oocyte, hyaluronan synthesis by the cumulus cells surrounding the oocyte increases dramatically [32], A stable, gel-like matrix is formed between the cumulus cells due to crosslinking of hyaluronan by inter-a-trypsin inhibitor and TSG-6 [31, 32]. This matrix is responsible for the integrity of the cumulus cell-oocyte complex which is required for protection and transport of the oocyte during ovulation, entry into the oviduct and fertilization. Sperm-associated hyaluronidases allow penetration of this matrix at fertilization. 

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