The objectives were to determine hypothalamic regulation of pulsatile luteinizing hormone (LH) secretion in female pigs and the biphasic feedback actions of estradiol-17beta (E(2)-17beta). In the first study, the minimum effective dosage of E(2)-17beta that would induce estrus in ovariectomized gilts was determined to be 20microg/kg body weight. In the second study, ovariectomized gilts were as...

The functional consequences of luteinizing hormone/human chorionic gonadotropin signaling via neuronal luteinizing hormone/human chorionic gonadotropin receptors expressed throughout the brain remain unclear. A primary function of luteinizing hormone (LH) in the gonads is the stimulation of sex steroid production. As LH can cross the blood-brain barrier, present in cerebrospinal fluid and is ex...

Mean serum testosterone concentration in the 27-day-old prepubertal Holtzman rat was 0\m=.\25ng/ml, much lower than that observed in the adult male, 5\m=.\5ng/ml. Within 15 min after the intravenous injection of rat LH (in a dose of 400 ng-equiv. NIH-LH-S1/100 g body weight) serum testosterone concentration in the prepubertal rat increased approximately fivefold. Maximal elevation of serum test...

We have investigated the effects of ovariectomy (OVX) and photostimulation (PS) on anterior pituitary LH beta mRNA abundance and circulating levels of LH in the domestic turkey. The birds were divided into the following four treatment groups: non-PS SHAM, PS SHAM, non-PS OVX, and PS OVX. Photostimulation was initiated 7 days after OVX. Anterior pituitaries and blood samples were collected on Da...

The objective of this study was to examine the influence of 17 beta-estradiol (E2) on distribution of LH and FSH isoforms during the follicular phase of the bovine estrous cycle prior to the preovulatory surges of LH and FSH. On Day 16 of the estrous cycle (Day 0 = estrus), intact controls (CONT; n = 4) were treated with prostaglandin F2 alpha (PGF2 alpha) to induce luteal regression and initia...

BACKGROUND AND OBJECTIVE Kisspeptin stimulates hypothalamic GnRH secretion resulting in gonadotrophin release and has potential as a future therapeutic. Chronic subcutaneous infusion of kisspeptin via a pump (similar to an insulin pump) may provide an alternative route of administration in the future. We investigated for the first time in humans, the gonadotrophin response to subcutaneous (SC) ...

Concentrations of progesterone have been reported to influence GnRH-induced LH surges. At the beginning of many synchronization protocols, GnRH is used to synchronize follicular growth. Therefore, the objective of this study was to determine the effect of elevated concentrations of progesterone from a controlled internal drug-releasing device (CIDR) on the GnRH-induced LH surge and ovulatory re...

Peripubertal beef heifers (n = 57) and postpartum multiparous cows (n = 52) were used to determine the optimal dose of estradiol benzoate (EB) to induce and synchronize estrus after treatment with intravaginal progesterone inserts (IVP4, EAZI-BREED CIDR) . All females received an IVP4 for 7 d (d 0 = insertion day) with a 25-mg injection of PGF2a (Lutalyse) on d 6. At 24 to 30 h after IVP4 re...

To investigate the postreceptor mechanism, especially the role of protein kinase C (C-kinase), in luteinizing hormone (LH) release from anterior pituitary cells, dispersed rat anterior pituitary cells were stimulated with luteinizing hormone-releasing hormone (LH-RH), [D-Ser(tBu)]6 des-Gly-NH2(10) ethylamide (Buserelin), 12-0-tetradecanoyl phorbol-13-acetate (TPA) and trifluoperazine (TFP) and ...

The experiment was conducted on 14 postpartum mithun (Bos frontalis) cows to establish the preovulatory LH and FSH surge patterns during estrus in peripheral circulation. Blood samples from jugular vein were collected every 2 h until 72 h and on alternate days till day 22 (day 0 = day of estrus) following the day of estrus onset. Plasma progesterone (P4), LH and FSH levels were estimated. Plasm...