Populations of granulosa cells in small follicles of the sheep ovary

Abstract

The aim of this study in sheep ovaries was to determine the total number of granulosa cells in primordial follicles and at subsequent stages of growth to early antrum formation. The second aim was to examine the interrelationships among the total number of granulosa cells in the follicles, the number of granulosa cells in the section through the oocyte nucleolus, and the diameter of the oocyte. A third aim was to examine whether proliferating cell nuclear antigen labelling occurred in flattened granulosa cells in primordial follicles or was confined to follicles containing cuboidal granulosa cells. The follicles were classified using the section through the oocyte nucleolus by the configuration of granulosa cells around the oocyte as type 1 (primordial), type 1a (transitory), type 2 (primary), type 3 (small preantral), type 4 (large preantral), and type 5 (small antral). In type 1 follicles, the number of granulosa cells and oocyte diameter were highly variable in both fetal and adult ovaries. Each type of follicle was significantly different from the others (all P < 0.05) with respect to oocyte diameter, number of granulosa cells in the section through the oocyte nucleolus and total number of granulosa cells. Follicles classified as type 2, 3, 4 or 5 each corresponded to two doublings of the total granulosa cell population. The relationships between oocyte diameter and the number of granulosa cells (that is, in the section through the oocyte nucleous or total population per follicle) could all be described by the regression equation loge chi = a + b loge gamma with the correlation coefficients R always > 0.93. For each pair of variables the slopes (b) for each type of follicle were not different from the overall slope for all types of follicle pooled. Immunostaining for proliferating cell nuclear antigen was observed in granulosa cells in type 1 follicles, as well as in the other types of follicle. These findings indicate that 'flattened' granulosa cells in type 1 follicles express an essential nuclear protein involved in cell proliferation before assuming the cuboidal shape. Thus, when considering factors that regulate specific phases of early follicular growth, it is important to consider: (i) the follicle classification system used; (ii) the animal model studied; (iii) whether type 1 follicles are all quiescent; and (iv) the likelihood that each follicle type represents more than one doubling of the population of 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).…”

“…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. These differences may be species-specific or due to differences in measurement techniques.…”

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).…”

“…Measurements were taken of 30 type 1 primordial follicles per ovary of each animal and all observable healthy follicles of the remaining follicular categories (type 2/primary to type 5/large antral), because of the few number present in all the sections studied. Ovarian follicular structure was described previously in SAFS pups (Katz et al, 2009) as follows and was based on the classification proposed by Lundy et al (1999):…”

“…The following variables were recorded according to the histological classification proposed by Lundy et al (1999): oocyte diameter, nuclei diameter, follicular diameter, thickness of the granulosa and theca layers, classification of preantral and antral follicles with normal development or different degree of atresia, average depth of location of different follicles within the ovarian cortex. Follicles were measured from the outer wall of the theca cells (if present) or from the outer layer of the granulosa cells (when theca cells were absent).…”