Oocyte production

Fig. 2. Methods for production of identical catde. (a) Embryo spHtting. A microdissection knife is used to cut an early embryo into two identical halves, (b) Embryo cloning. A cell from a morula stage embryo is removed and then inserted into an oocyte that has had its nucleus removed. EoUowing fusion of the two cells the newly produced one-ceU embryo is identical to the original morula. The procedure can be repeated to give multiple copies of the original...

Xenobiotic induced disruption of female fertility follows essentially the same pattern as that of the male and can be caused by changes in pituitary-hypothalamic function, primary disruption of ovarian structure or hormone secretion, or changes in the rate of hormone deactivation. In addition, there may be changes in the synthesis of estrogen induced production of the yolk protein by the liver (vitellogenesis), which in turn can lead to failure to lay down sufficient yolk in the developing oocytes. Vitellogenesis provides a valuable biomarker for endocrine dysfunction in both sexes,but is more properly considered as part of the liver function. 

Sagata, N., Oskarsson, M., Copeland, T Brumbaugh, J and Vande Woude, G. F. (1988). Function of c-mos proto-oncogene product in meiotic maturation in Xenopus oocytes. Nature 335 519-525. 

Winston N J 1997 Stability of cyclin B protein during meiotic maturation and the first mitotic cell division in mouse oocytes. Biol Cell 89 211-219 Winston NJ, Maro B 1995 Calmodulin-dependent protein kinase II is activated transiently in ethanol-stimulated mouse oocytes. Dev Biol 170 350-352 Winston NJ, Bourgain-Guglielmetti F, Ciemerych MA et al 2000 Early development of mouse embryos null mutant for the cyclin A2 gene occurs in the absence of maternally derived cyclin A2 gene products. Dev Biol 223 139-153... 

Kaneko S, Nakamura S, Adachi K, Akaike A, Satoh M. Mobilization of intracellular Ca++ and stimulation of cAM P production by kappa opioid receptors in Xenopus oocytes. Mol Brain Res 1994 27 258-264. 

R-HETE is a very potent and selective inducer of oocyte maturation [196, 199]. 8S-HETE does not show this activity. The allene oxide hydrolysis products and the hydroperoxide lyase products were not active in promoting oocyte maturation [200]. 

Pivotal pre-approval safety and efficacy was assessed in a randomized, open label, multicentre study of infertile females undergoing in vitro fertilization and embryo transfer. The primary efficacy parameter was the mean number of oocytes retrieved, which (at 13.6) was similar to the number retrieved when urinary-derived hCG was used. Serious potential side effects can include ovarian over/hyper-stimulation, sometimes with pulmonary or vascular complications. The product is marketed by Serono Inc. 

Egg production constitutes a major loss of zinc and other trace metals by the laying hen. Vitellogenin mediates the transfer of zinc from liver to the maturing oocyte, ultimately resulting in deposition into yolk of the newly formed egg (Richards 1989). More research seems needed on the role of zinc in avian reproduction. 

Increased respiration rate in 4 days, growth reduction and liver damage in 9 days, abnormal oocyte development and reduced spermatogonia production in 18-20 days 2... 

Egg production reduced in all treated groups females in the 8 and 400 pg/kg groups had a reduced number of mature oocytes. Median survival time of larvae in high-dose group was 7.7 days vs. 14 days in controls... 

Some end-points that detect endocrine-related effects in exposed adults are part of routine testing. These include some measures of fertility, reproductive organ appearance and weight, histopathology, oocyte number, cycle patterns and mating behaviour. Uterine protein production has also been used in toxicological assessment (Maier et al.,... 

In the humans, the primordial germ cells are differentiated from about the sixth week of gestation and are consequently susceptible from then onward. In the female, production of the primary oocytes, which involves the first meiotic division, occurs in fetal life. These primary oocytes do not mature into ova until puberty, with the second meiotic division yielding one ovum from each primary oocyte (Fig. 6.48). 

Allene oxides are unusual biological products. However, they are formed from arachidonic acid by some corals and are evidently precursors to prostaglandin esters, which may be present in high concentrations 327 Allene oxides are also present in starfish oocytes.321,328... 

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