Follicular phase

About: Follicular phase is a research topic. Over the lifetime, 15339 publications have been published within this topic receiving 530997 citations.

Regulation of ovarian follicular development in primates: facts and hypotheses.

Abstract: I. Introduction IN THE adult ovary, folliculogenesis starts when follicles leave the pool of resting follicles (RF) to enter the growth phase. From there, the early growing follicle undergoes a developmental process including a dramatic course of cellular proliferation and differentiation. In primates, only one follicle commonly reaches the preovulatory stage every cycle; most follicles fail to complete this maturation scheme, dying in the process termed atresia. In recent years, a picture has emerged depicting the classic endocrine control of ovarian function by LH and FSH, entangled in a maze of regulatory systems hinging on cell-cell interactions between follicular cells, via action of a variety of molecules (1–3). Different types of cell-cell interactions have been described. In paracrine regulations, a molecule synthesized by one cellular type is released into the interstitial milieu to act directly on another cellular type. In autocrine regulations, molecules synthesized by one cellular type are rel...

The neuroendocrine control of the menstrual cycle.

Abstract: Publisher Summary This chapter discusses the construction of a model of the neuroendocrine control system that governs the 28-day ovarian cycle of the rhesus monkey. This model has three basic components: the arcuate nucleus of the hypothalamus, the gonadotrophs of the pituitary gland, and the ovary. The arcuate nucleus is the central component of the control system. The gonadotrophs respond to this unvarying pulsatile gonadotropin releasing hormone (GnRH) stimulation by releasing pulses of follicle stimulating hormone (FSH) and luteinizing hormone (LH). Immature follicles respond to this unvarying gonadotropic stimulus by increasing in size and secreting increasing quantities of estradiol, which achieve maxima near mid-cycle. This process occupies approximately 14 days. The magnitude of the response to each GnRH pulse is modulated by estradiol acting directly on the gonadotrophs. The characteristic duration of the rhesus monkey ovarian cycle is thus determined by the duration of follicular development. This can occur in the presence of an absolutely unvarying pattern of hypophysiotropic stimulation.

Interrelationships between energy balance and postpartum reproductive function in dairy cattle.

Abstract: Genetic improvement of dairy cows has markedly increased milk yield over the last three decades. Increased production has been associated with reduced conception rates (66% in 1951 versus 40 to 50% since 1975). Because conception rate in dairy heifers has remained higher, the metabolic demands of higher production may be related to the decline in reproductive performance in cows. During early lactation, increasing dietary intake fails to keep pace with rising milk production. The resultant negative energy balance and rate of mobilization of body reserves appear directly related to the postpartum interval to first ovulation and lower conception rate. Delays in the onset of normal ovarian activity, thus limiting the number of estrous cycles before breeding, may account for the observed decrease in fertility. Negative energy balance probably acts similarly to undernutrition and may manifest in delayed ovarian activity by impinging on pulsatile secretion of LH. Lower availability of glucose and insulin may also decrease LH pulsatility or limit ovarian responsiveness to gonadotropins. Alternatively, release of endogenous opioids in association with increasing feed intake or other lactational hormone responses may provide neural or pituitary inhibition of the pulsatile LH production that is requisite for ovarian follicular development.

The comparative behavior of mammalian eggs in vivo and in vitro : i. the activation of ovarian eggs.

Abstract: 1 A definite chronological sequence of events occurs in the eggs and follicles of rabbits after mating or after the injection of ovulation-inducing substances The follicle secretes secondary liquor folliculi, and there occurs a separation of the corona radiata from strands connecting it to the follicle cells The ovum goes through nuclear maturation with as climax the production of the first polar body by the 8th hour after copulation 2 Thyroxin injections cause indirectly the same effects as mating or pituitary injections but no ovulation occurs The thyroxin effect occurs later than the pituitary effect and is due to an initiation of atresia in the follicles 3 Explantation of ova results in typical maturation phenomena which are apparently unaffected by the presence of pituitary hormones or of thyroxin in the culture medium 4 It is concluded that maturation of the ovum can be obtained simply by isolating it from the normal follicular environment 5 Normal fertilization can be secured with eggs removed from the follicles

Oocyte control of ovarian follicular development and function in mammals.

Abstract: A new perspective on ovarian follicular development has emerged over the last decade. Whereas the oocyte was previously considered only a passive recipient of developmental signals from oocyte-associated granulosa cells, it is now clear that communication between oocytes and granulosa cells is bidirectional. A complex interplay of regulatory factors governs the development of both types of cell. This interplay is essential not only for oocyte development but also for follicular development, beginning with the initial assembly of the primordial follicle and continuing throughout ovulation. The existence of an oocyte-granulosa cell regulatory loop, essential for normal follicular differentiation as well as for the production of an oocyte competent to undergo fertilization and embryogenesis, is proposed. Although gonadotrophins are essential for driving the differentiation of granulosa cell phenotypes, within its sphere of influence, the oocyte is probably the dominant factor determining the direction of differentiation and the function of the granulosa cells associated with it.