Studies in vivo and in vitro on the initiation of follicle growth in the bovine ovary

Abstract

Histological sections prepared from cortical parts of 25 bovine ovaries were used to study initiation of follicle growth in vivo. Small follicles were measured and characterized. Initiation of follicle growth consisted of two distinct consecutive phases. The first phase was characterized by transformation of granulosa cells from a flattened to a cuboidal shape and by their proliferation. In the second phase an increase in the number of granulosa cells was accompanied by a rapid increase in the size of the oocyte. Oocytes commenced growth when there were at least 40 granulosa cells in the largest cross-section (fourth generation of follicle cells). The oocyte diameter increased from 29.74 +/- 0.30 microns (mean +/- SEM) in primordial follicles to 92.90 +/- 4.50 microns in small antral follicles. The zona pellucida first appeared as an island of periodic acid-Schiff positive material in small preantral follicles, but formed a complete ring around the oocyte when the late preantral stage was reached. Organ culture of ovarian cortical explants was used to study initiation of follicle growth in vitro. Within 2 days of culture most of the primordial follicles entered the growth phase: granulosa cells changed from a flattened to a cuboidal shape and entered S-phase as demonstrated by autoradiography after [3H]thymidine incorporation. On day 2, 48.6% of follicles were labelled compared with 3% on day 0. Follicle growth started in the absence of gonadotrophins, in the serum-free medium, confirming the notion that gonadotrophins are not essential for this process. The culture system used here will be helpful in the study of the involvement of putative factor(s) in the initiation of follicle growth in large domestic animals.

Effect of Braun-Collins and Saline solutions at different temperatures and incubation times on the quality of goat preantral follicles preserved in situ

“…The histological analysis of preantral follicles present in the controls as well as in fragments stored at 4 or 20°C showed that changes at the oocyte level constitute the first observed degenerative sign. Similar results were also observed with fresh ovine (Jorio et al, 1991) and caprine (Lucci et al, 1999b) preantral follicles, cold stored at 4°C feline preantral follicles (Wood et al, 1997) and cultured bovine preantral follicles in vitro Braw-Tal andYossefi, 1997). These results show that the oocyte is much more sensitive to degeneration than granulosa cells.…”

Light microscopical and ultrastructural characterization of goat preantral follicles

“…In the present study, the ontogeny of formation of the ZP was similar to that in cows (Braw-Tal andYossefi, 1997 andFair et al, 1997b) and ewes (Lundy et al, 1999), in which it appeared as islands of zonal material in secondary follicles with two to three layers of granulosa cells and as a complete PAS-positive ring in follicles with more than three layers of granulosa cells (Fig. 7).…”

“…Progressive accumulation of fluid will induce distension and coalescence of the lacunae and result in formation of the antrum in antral follicles. In addition, in goat, the formation of the theca appears to be similar to that in cattle (Braw-Tal and Yossefi, 1997) and sheep (Lundy et al, 1999).…”

“…Concerning the histological aspects, the mean diameter of oocytes and follicles, in all the three developmental stages (i.e. primordial, primary and secondary), was smaller than those observed in ewes (Lundy et al, 1999) and cows (Van Wezel and Rodgers, 1996, Braw-Tal and Yossefi, 1997, but was similar to those observed in humans (Lintern-Moore et al, 1974). However, the mean and range in the number of granulosa cells at the equatorial section were compatible to those described for ewes (Lundy et al, 1999), cows (Braw-Tal and Yossefi, 1997) and humans (Lintern-Moore et al, 1974), even when the diameter of oocytes and follicles was smaller.…”

Ovarian Follicular Morphometry of South American Fur Seal Pups (Arctophoca australis)

“…. 1997Braw-Tal and Yossefi, 1997;Sanchez and Ocampo, 1998;Felipe et al, 1999;Zitny et al, 2004;Reynaud et al, 2009;Songsasen et al, 2009). This also showed that folliculogenesis occurs in prepuberal females as reported by Lundy et al (1999) probably mediated by independient gonadotrophin stimuli or by basal levels (Van Vooris, 1999;Evans, 2003).…”