Ovulation

About: Ovulation is a research topic. Over the lifetime, 18900 publications have been published within this topic receiving 577209 citations. The topic is also known as: GO:0030728.

Dating the endometrial biopsy.

Abstract: It is asserted that examination of the endometrium during the secretory phase yields more information about the time of ovulation degree of progestational change and normality of the endometrium than any other test used in sterility studies. Attention to qualitative changes in 8 morphological factors is most useful in dating the endometrial biopsy. During the 1st week of luteal activity attention should be focused on changes occurring in gland epithelium: gland mitosis pseudostratification of nuclei basal vacuolation and secretion. During the 2nd week stromal changes (including edema) predecidual reaction stromal mitosis and leukocytic infiltration are the key criteria. Tissue from the fundus of the uterus gives the most reliable information. These critera were used in 300 sterility biopsies taken from normally menstruating women over a 3-year period. Absence of organic endometrial disease and availability of accurate menstrual history were the only selection criteria. 12 observers dated the biopsies. 42 of the 300 patients (14%) menstruated on the day predicted 36 (12%) menstruated later and 222 (74%) menstruated earlier. When a +or- 1 day error was allowed 112 patients (38%) were found to menstruate at the time predicted. When these same slides were reviewed by a single observer and the date for the most advanced area of the biopsy was used 179 patients (60%) menstruated within 1 day of prediction. To test the validity of the dating criteria change in basal body temperature was used to correlate endometrial dating with ovulation rather than onset of menstruation. Of the 40 patients who had adequate temperature records 31 (78%) ovulated as predicted allowing a +or- 1 day error indicating that dating is a better gauge of duration of progesterone effect than predictor of onset of menses. To determine whether biopsy caused early menstruation the secretory phases of the 25 patients who had recorded temperatures in at least 2 cycles in addition to that in which the biopsy was taken were examined. The secretory phase was definitely shorter in the biopsied than control cycle suggesting that biopsy does accelerate the onset of flow. However further analysis showed that biopsy does not interfere with length of flow or succeeding menstrual rhythm.

Initial and cyclic recruitment of ovarian follicles.

Abstract: Mammalian ovaries consist of follicles as basic functional units. The total number of ovarian follicles is determined early in life, and the depletion of this pool leads to reproductive senescence. Each follicle develops to either ovulate or, more likely, to undergo degeneration. The dynamics of ovarian follicle development have interested endocrinologists and developmental biologists for many years. With the advent of assisted reproductive techniques in humans, the possibility of regulating follicle development in vivo and in vitro has gained clinical relevance. In this review, we focus upon key branching points during the development of ovarian follicles as well as factors involved in determining the eventual destiny of individual follicles. We discuss inconsistencies in the literature regarding the definitions of follicle recruitment and selection and propose to name the two major steps of follicle development as initial and cyclic recruitment, respectively. Because some of these disparities have arisen due to differences in the animal systems studied, we also compare the development of the ovarian follicles of both humans and rats. We also review the status of knowledge of several puzzling clinical issues that may provide important clues toward unlocking the mechanisms of follicle development.

Synchronization of ovulation in dairy cows using PGF2α and GnRH

Abstract: This paper reports a new method for synchronizing the time of ovulation in cattle using GnRH and PGF(2alpha). In Experiments 1 and 2, lactating dairy cows (n=20) ranging from 36 to 280 d postpartum and dairy heifers (n=24) 14 to 16 mo old were treated with an intramuscular injection of 100 mug GnRH at a random stage of the estrous cycle. Seven d later the cattle received PGF(2alpha) to regress corpora lutea (CL). Lactating cows and heifers received a second injection of 100 mug GnRH 48 and 24 h later, respectively. Lactating cows were artificially inseminated 24 h after the second GnRH injection. Ovarian morphology was monitored daily by trans-rectal ultrasonography from 5 d prior to treatment until ovulation. In Experiment 3, the flexibility in the timing of hormonal injections with this synchronization protocol was evaluated by randomly assigning 66 lactating dairy cows to 3 different treatment groups. Lactating cows received the injection of PGF(2alpha) 48 (Group 1), 24 (Group 2), and 0 h (Group 3) prior to the second injection of GnRH, which was administered at the same time in each group to ensure the second injection of GnRH was given when follicles were at a similar stage of growth. In Experiments 1 and 2, the first injection of GnRH caused ovulation and formation of a new or accessory CL in 18 20 cows and 13 24 heifers. In addition, this injection of GnRH initiated or was coincident with initiation of a new follicular wave in 20 20 lactating cows and 18 24 heifers. Corpora lutea regressed after PGF(2alpha) in 20 20 cows and in 18 24 heifers. All cows and 18 24 heifers ovulated a newly formed dominant follicle between 24 and 32 h after the second injection of GnRH. Ten of 20 cows conceived to the timed artificial insemination. In Experiment 3, the conception rate in Groups 1 and 2 were greater than in Group 3, (55 and 46 % vs 11%, respectively). In summary, this protocol could have a major impact on managing reproduction in lactating dairy cows, because it allows for AI to occur at a known time of ovulation and eliminates the need for detection of estrus.

Endometriosis: pathogenesis and treatment

Abstract: Endometriosis is defined as the presence of endometrial-type mucosa outside the uterine cavity. Of the proposed pathogenic theories (retrograde menstruation, coelomic metaplasia and Mullerian remnants), none explain all the different types of endometriosis. According to the most convincing model, the retrograde menstruation hypothesis, endometrial fragments reaching the pelvis via transtubal retrograde flow, implant onto the peritoneum and abdominal organs, proliferate and cause chronic inflammation with formation of adhesions. The number and amount of menstrual flows together with genetic and environmental factors determines the degree of phenotypic expression of the disease. Endometriosis is estrogen-dependent, manifests during reproductive years and is associated with pain and infertility. Dysmenorrhoea, deep dyspareunia, dyschezia and dysuria are the most frequently reported symptoms. Standard diagnosis is carried out by direct visualization and histologic examination of lesions. Pain can be treated by excising peritoneal implants, deep nodules and ovarian cysts, or inducing lesion suppression by abolishing ovulation and menstruation through hormonal manipulation with progestins, oral contraceptives and gonadotropin-releasing hormone agonists. Medical therapy is symptomatic, not cytoreductive; surgery is associated with high recurrence rates. Although lesion eradication is considered a fertility-enhancing procedure, the benefit on reproductive performance is moderate. Assisted reproductive technologies constitute a valid alternative. Endometriosis is associated with a 50% increase in the risk of epithelial ovarian cancer, but preventive interventions are feasible.

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.