[Chronology and dynamics of the development of female genital organs of cattle fetuses].
The chronology and dynamics of the female germ cell development, of the mitotic activity of oogonia, and of the chromosome rearrangements at prophase I of meiosis have been quantitatively estimated in 30 cow embryos and foetuses at the age of 1.5 to 9 months. The sexual differentiation of the gonads was shown in a 1.5 month old embryo. The oocytes at the stages of preleptotene chromosome condensation and decondensation occurred in the 1.5 month old embryos and their maximum number was observed in the 2-5 month old foetuses. The leptotene oocytes were found in the 2-2.5 month old foetuses. The transition to zygotene and pachytene was also recorded in the 2-2.5 month old foetuses but their maximum number was observed in the 4-6 month old foetuses; their number was reduced to single oocytes thereafter. The first diplotene oocytes appeared in the 3 month old foetuses but the active transition of the oocytes to diplotene was observed after four months of development. The formation of a layer of follicle cells takes place around the diplotene oocytes. The vast majority of degenerating germ cells are the oocytes in zygotene-pachytene and in diplotene. The population of germ cells is formed by the mitotic division of oogonia in the cow foetuses, mainly at the age of 1.5 to 4 months of development.
L F
LF
Kurilo
N P
NP
Tepliakova
D000818:Animals; D002417:Cattle / Q000196:embryology*; D005260:Female; D005865:Gestational Age; D008540:Meiosis; D010053:Ovary / Q000166:cytology / Q000196:embryology*; D011247:Pregnancy
Khronologiia i dinamika razvitiia zhenskikh polovykh organov u krupnogo rogatogo skota.