In vitro studies of meiotic maturation of mouse oocytes have been carried out in the presence of several drugs. The individual steps of nuclear progression, including dissolution of the nuclear (germinal vesicle) membrane, condensation of dictyate chromatin into compact bivalents, formation of the first metaphase spindle, and extrusion of the first polar body, are each susceptible to one or mor...

Germinal vesicle breakdown in mouse oocytes in vivo and in vitro has been examined by electron microscopy. In vitro oocytes were studied immediately after release from follicles and at various times (05-11 h) in culture. Approximately 30 min after oocyte release, chromatin condensation begins along the convoluted nuclear envelope (NE). Chromatin granules are common in all condensing chromosomes...

Histological examination of gonadotrophin stimulated Macaca fascicularis ovaries removed at mid-follicular phase showed that germinal vesicles (GV) could exhibit different configurations in follicles greater than 1000 microns in diameter. We describe 3 types of nuclear organization called GV1 (dispersed and filamentous chromatin), GV2 (clumped and filamentous chromatin) and GV3 (perinucleolar c...

background: in vitro maturation (ivm) of oocytes reduces the costs and averts the side-effects of gonadotropin stimulation for in vitro fertilization (ivf). reliable ivm is an intellectual, scientific and clinical challenge with a number of potential applications. objective: the effect of hcg was evaluated on the timing and regulation of in vitro ovulation for the syrian mice oocytes in the pre...

During the first meiotic cell division of the Xenopus oocyte, a transient microtubule network appears at the basal part of the disintegrating nucleus. In order to know if this structure plays a role in the formation of the first meiotic spindle, we have studied the actions of Ca2+ ions and taxol during the whole maturation process. We now report that when the free cytosolic Ca2+ concentration i...

the changes of total calcium content of persian sturgeon, acipenser persicus follicles were investigated during different stages of germinal vesicle migration. total calcium content increased during maturation and ripening of the oocytes i.e. migration of nucleus toward the animal pole. according to data, the total calcium of follicles with polarization index (pi: the ratio of the distance of t...

The present study was undertaken to explore the regulatory mechanisms for meiotic resumption of pig cumulus-oocyte complexes (COCs) by assessing the nuclear status of oocytes, the degree of gap junction cell-to-cell communication and cumulus expansion after culture of various numbers of COCs in 10 microl droplets of medium for 24 h. Gap junction communication was examined by confocal laser scan...

The major objective of the present study was to demonstrate the actions of exogenous melatonin on ovaprim (synthetic GnRH and domperidone)-induced final oocyte maturation focusing on the oxidative status of pre-ovulatory follicles in the carp Catla catla. Accordingly, gravid carp during the early spawning phase of the reproductive cycle were injected with melatonin and/or ovaprim at different t...

Meiotic cell cycles differ from mitotic cell cycles in that the former lack S-phase in the interphase between meiosis I and meiosis II. To obtain clues for mechanisms involved in the cell cycle regulation unique to meiosis, we have examined changes in chromosomal morphology and H1 kinase activity during a meiotic period from metaphase I (MI) to metaphase II (MII) in Xenopus oocytes. Using popul...

Although oocytes of many teleost fish, especially marine species, are subjected to a hydration process during meiotic maturation, which leads to an important volume increase, no noticeable hydration of the preovulatory oocyte has ever been reported in rainbow trout (Oncorhynchus mykiss). In the present study, oocyte water content and dry mass were monitored using consecutive samples taken in vi...