Selection of a single follicle per day into the preovulatory hierarchy, in vivo, occurs from a small pool of 6- to 8-mm follicles; and although the fate of follicles not selected on any given day has yet to be determined, it is thought that the majority are destined to undergo atresia and are continually replaced by smaller, growing follicles. Moreover, it has not been established in this or any mammalian species what factors predispose a follicle for recruitment into the final stages of growth and differentiation prior to ovulation. buy ortho tri-cyclen online
Given that granulosa cells from 6- to 8mm (prehierarchal) follicles are highly susceptible to undergoing apoptosis , it is possible that one prerequisite for follicle selection is the appropriate expression of “death-suppressing” genes, including bcl-x^g and possibly ita. We have previously reported that, similar to findings for ita, bcl-x mRNA levels first increase in granulosa cells at the stage of development corresponding to those follicles that have most recently been recruited into the follicle hierarchy (9- to 12-mm-diameter follicles ).