Archive for the 'Cells' Category

03 Sep

Formation of Ovarian Follicles During Fetal Development in Sheep: DISCUSSION(7)

This study does not address the issue of where the precursor cells for the theca interna originate. Recently, Quirke et al. have demonstrated that the developing fetal ovary is steroidogenically active from Day 30 to Day 75. It was established that the steroidogenically active cells were initially located at the boundary of the ovarian cortex […]

27 Aug

Formation of Ovarian Follicles During Fetal Development in Sheep: DISCUSSION(6)

The results of the present study are consistent with the concept that granulosal cells arise from at least two sources, namely the mesonephros (or blastema) until Day 38 and, thereafter, from the ovarian surface epithelium. The notion of heterogeneity of granulosal cells in primordial follicles has been reported by many authors (for reviews, see Peters […]

23 Aug

Formation of Ovarian Follicles During Fetal Development in Sheep: DISCUSSION(5)

The results support the notion that, as discrete primordial follicles emerged, the associated granulosal cells could be present either as a concentric layer of squamous cells giving rise to type 1 primordial follicles or as a mixture of squamous and cuboidal cells giving rise to type 1a primordial follicles. The presence of cuboidal cells was […]

16 Aug

Formation of Ovarian Follicles During Fetal Development in Sheep: DISCUSSION(4)

What is known is that the first follicles form at the base (i.e., that portion of a cord closest to the medulla) of ovigerous cords, and that somatic cells within the cords do not appear to divide. Therefore, it seems reasonable to hypothesize that, as germ cells die, the surviving somatic cells may form associations […]

11 Aug

Formation of Ovarian Follicles During Fetal Development in Sheep: DISCUSSION(3)

Between Day 75 and Day 90, >75% of germ cells die, presumably by apoptosis. The substantial loss of germ cells is not accompanied by any evidence for pyk-nosis of the pregranulosal cells. This phenomenon of germ cell apoptosis without concomitant loss of somatic cells by apoptosis has been reported for other species (e.g., human ). […]

05 Aug

Formation of Ovarian Follicles During Fetal Development in Sheep: DISCUSSION(2)

The proliferation of oogonia occurs despite the close physical association of this cell with a pregranulosa cell. Moreover, the associations of pregranulosal cells with oogonia at Day 38 preceded ovigerous cord formation. From Day 38 onward, ovigerous cords appeared to arise from a progressive fusion of pregranulosa cell-oogonium complexes and with the arrangement of these […]

01 Aug

Formation of Ovarian Follicles During Fetal Development in Sheep: DISCUSSION(1)

The questions addressed in the present study relate to the origins of the granulosal cells and how primordial follicles are formed. The results from the present studies, when considered together with those from previous studies, support the following hypotheses: 1) that most (i.e., >95%) of the granulosal cells in newly formed primordial follicles originate from […]

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