Metabolic and Ultrastructural Changes in the Frog Ovarian Follicle in Response to Pituitary Stimulation

Abstract

Frog ovarian fragments were prevented from ovulating in vitro by the addition of actinomycin D up to 3 hr following pituitary stimulation ; but addition of Actinomycin D 6 hr after stimulation was far less effective . Puromycin, on the other hand, effectively inhibited ovulation when added as late as 6 hr after pituitary stimulation . Although actinomycin D reduced uptake of uridine-3H, and puromycin reduced uptake of leucine 8H and lysine-14C by pituitary-stimulated ovarian tissue minus oocytes (OTMO) in vitro, it was found that pituitary stimulation did not significantly increase uptake of these compounds by OTMO . Radioautographs of ovarian follicles fixed 6 hr after the addition of pituitary extract and uridine sH in vitro revealed increased RNA synthesis in the peritoneal surface epithelium, compared with unstimulated controls, while the ovarian sac epithelium showed no increase . Gross ultrastructural changes occurred in the peritoneal area of ovarian follicles following pituitary stimulation in vivo, including loss of collagen fibrils, and general disorganization of the connective tissue theca . Changes in the rough endoplasmic reticulum of the peritoneal epithelial cells, while frequently encountered, were less pronounced . None of these changes was observed in the ovarian sac area, or in the interfollicular region . The above data are consistent with the hypothesis that pituitary stimulation of the frog ovary results in increased synthesis of RNA and protein by the peritoneal epithelial cells, and that the protein may be collagenase .

Localization of smooth‐muscle markers in the ovaries of some ectothermic vertebrates

“…She has demonstrated a sparse supply of smooth-muscle cells in the theca of ovarian follicles, and the presence of smooth-muscle fibres in the mesovarium. Anderson and Yatvin (1970) were unable to detect smooth-muscle cells in the follicle wall of the frog ovary. In the Pacific treefrog, Larsen et al (1977) have reported a non-muscular contractile system, constructed by inner ovarian epithelium cells, and they have shown that smooth-muscle cells are present in the theca of interfollicular regions, but never in the follicle itself.…”

The ultrastructure of the thecal cell of the teleost, Oryzias latipes, during ovulation in vitro

“…Direct observation of electronmicrographs of follicles does not reveal any smooth muscle fibres. Anderson & Yatvin (1970) pointed out that the absence of smooth muscle in a variety of amphibians raised the question of the source of the squeezing phenomenon accompany¬ ing ovulation.…”

Evidence for Follicle Wall Involvement in Ovulation and Progesterone Production by Frog (Rana pipiens) Follicles in vitro

“…A pool of large uniformly sized ovarian follicles from each animal were manually removed from ovaries under magnification (Wild MJ-dissecting microscope) with watchmakers forceps. By varying the technique of manual dissection, oocytes were either stripped of (1) surface epithelium, or (2) both the surface epithelium and theca layer. The normal defolliculation process typically removes both of these outer layers leaving the oocyte encased by a single layer of follicle cells which remain attached to the outer surface of the vitelline membrane [lo, 24, 261.…”