Ovarian cyclicity and follicular recruitment in unilaterally ovariectomized mice

Abstract

Summary. Halving the numbers of follicles in young adult mice by unilateral ovariectomy resulted in compensatory Graafian follicle growth with a reduction by about 25% of the expected number of oestrous cycles. The impact of the operation on the numbers and dynamics of preantral follicles during the first 2 months after ovariectomy was studied using a compartmental mathematical model to analyse differential follicle counts. There were changes in growth and/or death rates at all stages of follicle development, and the patterns emerging were time-dependent. The rate of follicle survival from the pool of unilaminar stages was paradoxically reduced, but those forming two granulosa cell layers continued to develop towards Graafian size. As the frequency of follicle death declined, the numbers of healthy large preantral and antral stages in unpaired ovaries rose to approach those in pairs of age-matched control ovaries, suggesting that follicles otherwise undergoing atresia were being rescued. In the long-term, follicle dynamics after unilateral ovariectomy at young ages did not appear to compromise fecundity seriously.

Ovarian control of growth and sexual size dimorphism in a male-larger gecko

“…Vertebrates possessing variable numbers of progeny in a clutch or litter react to unilateral ovariectomy by compensatory recruitment of additional follicles in the remaining ovary (lizard: Jones et al, 1977;fish: Tyler et al, 1994;mammal: Greenwald, 1961;Gosden et al, 1989). However, animals such as anoles and geckos, with an invariant clutch size typified by a more or less fixed number of offspring per clutch and ovulating just a single egg per ovary at time (Jones et al, 1976;Kratochvíl and Frynta, 2006;Kratochvíl and Kubicǩa, 2007;Weiser et al, 2012;Meiri et al, 2015), do not have this possibility and can only compensate for unilateral ovariectomy by increasing the rate of clutch laying or by increasing egg size.…”

Initial and Cyclic Recruitment of Ovarian Follicles*

“…In rodent studies, removal of one ovary accelerates follicle loss in the remaining ovary (30), but halving the total follicle number only results in the loss of a quarter of expected cycles (157). Furthermore, unilateral oophorectomy increases the loss of remaining primordial follicles in middle-aged rats but not in young rats operated on at 30 days of age (158).…”

Morphometry and immunohistochemistry of follicles growth and steroidogenesis in saharian wild sand rat, Psammomys obesus, ovary.

“…After dewaxed and re-hydrated through a graded ethanol series (100%, 95% & 70%) and washed in distilled water, topographical colorations were carried out by Heindenhain's azan or Masson's trichroma. The follicles were classified in healthy or atretic ones, according to their morphological and histological evolutional aspect [37][38][39][40][41]. Primary follicle has one layer of cuboidal granulosa cells, including those follicles containing a mixed layer of flattened and cuboidal granulosa cells because these belong to the growing pool of follicles in rodents; in secondary follicle, the oocyte is surrounded with two layers of granulosa cells; preantral follicle was distinguished by the presence of more than two layers of granulosa cells, without any cavity; and the antral follicles were the larger ones with a fluid-filling the unique cavity.…”

“…The ovarian sections were viewed and examined by light microscopy, at different magnifications, microphotographs were taken at the same time using a Carl Zeiss (Germany) photomicroscope. Morphometric studies were performed according to [39,40], follicle diameter was measured in the largest cross-section that showed the nucleolus by taking the average of both the two perpendicular diameters of each follicle. Values are presented as the minimum-maximum or as the means ±SEM.…”