Histogenesis, development and atresia of ovarian follicles in different developmental stages of Makuii ewe fetuses

ABSTRACT

This study was conducted to determine the histogenesis, growth and atresia of ovarian follicles in Makuii sheep fetuses at different developmental stages. Forty fetuses in four age groups of fetuses were collected and preserved in 10% neutral buffered formalin solution. After recognition and harvesting of ovaries from fetuses, they were processed through routine paraffin embedding. Serial 5-7 micro m thick sections were taken and stained with Hematoxylin-Eosin, Verhoeff, Van Gieson, Toluidine blue and PAS. Histologic and histomorphometric [point count] studies were adopted. In fetuses germ cells [PGCs] were identified by pyknotic, condensed or karyolytic nuclei. In these fetuses, the undifferentiated gonads were recognized at the caudal aspects of the developing metanephrous kidneys. The healthy PGCs, were large with euchromatic nuclei, without any somatic cell surrounding them. In 36-70 days old fetuses, the germ cells were observed in clusters, which were surrounded by simple squamous cells. The hilus cells were seen in mesovarium. In the 71-100 days old fetuses, primordial follicles were observed. In the 84 days old fetuses, primary follicles were seen for the first time. In the ovaries of 101-150 days old fetuses, the secondary follicles with zona pellucida and theca folliculi were seen. Tertiary follicles were not seen in any age groups. The mean number of germ cell population at 0.25 mm [2] surface area of ovary, was the highest in 36-70 days old and lowest in 101-150 days old age group fetuses. It was revealed that in all age groups, the population of healthy follicles and/or germ cells is higher than population of atretic follicles and that there was significant difference [P<0.001] between them. There were significant [P<0.001] differences in the mean distribution of healthy follicles and or germ cells among all age groups. There were significant [P< 0.001] differences in atretic follicles among all age groups, except between 36-70 days old and 71-100 days old fetuses. We concluded that by increasing age, a decrease in population of healthy as well as atretic follicles in fetuses takes place. However, in all age groups, the population of the healthy follicle is greater than the population of atretic follicles