Accurate analysis of female reproductive toxicity requires a thorough understanding the differences in and specifics of estrous or menstrual cycles between laboratory animals. There are some species differences such as the time of sex maturation, the length of the estrous or menstrual cycle, the length of the luteal phase, the number of dominant follicles or corpora lutea, the size of follicles...

In a normal menstrual cycle the hypothalamus in the brain signals the release of gonadotropin releasing hormone (GnRH) which, in turn stimulates the anterior pituitary gland to release FSH followed by LH. These hormones target the granulosa and theca cells respectively within the ovary. The dual action of these hormones causes the follicle to mature, and during its maturation oestrogen is incre...

Cattle genetically selected for twin ovulations and births (Twinner) exhibit increased ovarian follicular development, increased ovulation rate, and greater blood and follicular fl uid IGF-1 concentrations compared with contemporary cattle not selected for twins (Control). Experimental objectives were to 1) assess relationships among aromatase (CYP19A1), IGF-1 (IGF1), IGF-2 receptor (IGF2R), an...

The ultrastructure of the follicular wall in primordial, previtellogenic and vitellogenic follicles of the sexually immature ostrich is described in the present study. The follicular wall consists of a zona radiata, granulosa cell layer, basal lamina and thecal layer. Cytoplasmic processes from the plasma membranes of the granulosa cell layer and the ovocyte form the zona radiata in previtellog...