This article has an accompanying continuing medical education activity, also eligible for MOC credit, on page e23. Learning Objective: Upon completion of this evaluation, successful learners will be able to manage patients with ulcerative colitis who are at high risk for the development of colorectal cancer.
A sensitive radioimmunoassay (RIA) for the determination of inhibin in peripheral plasma and tissue homogenates of different species has been developed using antisera to partially purified bovine follicular fluid (bFF) inhibin and 125I-labelled bFF 32 kDa inhibin. Antisera were produced by immunization of rabbits with partially purified bFF inhibin prepared by immunoaffinity chromatography. Increasing doses of a high titre antiserum could neutralize the suppressing effect of bFF, porcine follicular fluid and rat ovarian homogenate on FSH secretion from rat anterior pituitary cells in culture. Sensitivity of the assay was 3.1 ng International Research Standard of porcine inhibin per tube. Parallel inhibition curves were obtained for inhibin preparations from female and male animals of ten species, i.e. cattle, goats, sheep, cats, dogs, monkeys, pigs, horses, rats and man. Inhibin subunits and related proteins cross-reacted minimally with the antiserum used in the study. Plasma concentrations of inhibin in adult male and female rats were measured by the RIA before and at various times after gonadectomy. Inhibin levels in peripheral plasma before gonadectomy were significantly higher in adult female than in adult male rats. Inhibin levels decreased abruptly after gonadectomy in both sexes and they correlated negatively with plasma concentrations of FSH. This inhibin RIA will facilitate studies of the physiology of inhibin in various species of animals.
Ovarian changes determined by daily transrectal ultrasound and its relationship with FSH, LH, estradiol-17beta, progesterone, and inhibin were investigated in six goats for three consecutive interovulatory intervals. Estrous cycles were synchronized using two injections of prostaglandin F2alpha analogue 11 days apart. All follicles 3 mm or greater in diameter and corpora lutea were measured daily. A follicular wave was defined as one or more follicles growing to 5 mm or greater in diameter. The day that the follicles reached 3 mm in diameter was defined as the day of wave emergence, and the first wave after ovulation was defined as wave 1. During the interovulatory interval (mean +/- SEM, 21.3 +/- 0.4 days; n = 18), follicular waves emerged at 0.3 +/- 0.5, 6.5 +/- 0.2, and 12.1 +/- 0.4 days for wave 1, wave 2, and wave 3, respectively, in goats with three waves of follicular development and at -0.6 +/- 0.3, 4.7 +/- 0.2, 9.4 +/- 0.5, and 13.4 +/- 0.5 days for wave 1, wave 2, wave 3, and wave 4, respectively, in goats with four waves of follicular development (Day 0 = the day of ovulation). The mean diameter of the largest follicle of the ovulatory wave was significantly larger than those of the largest follicles of the other waves. Corpora lutea could be identified ultrasonically at Day 3 postovulation and attained 12.1 +/- 0.3 mm in diameter on Day 8. Transient increases in plasma concentrations of FSH were detected around the day of follicular wave emergence. The level of FSH was negatively correlated with that of inhibin. These results demonstrated that follicular waves occurred in goats and that the predominant follicular wave pattern was four waves with ovulation from wave 4. These results also suggested that the emergence of follicular waves was closely associated with increased secretion of FSH.
To determine the regulatory mechanism of the LHRH release associated with puberty, episodic release of LHRH from the stalk-median eminence was measured using a push-pull perfusion technique in conscious prepubertal and peripubertal female monkeys. After insertion of a push-pull cannula into the stalk-median eminence, a modified Krebs-Ringer phosphate buffer solution was infused through the push-cannula, and perfusates were collected through the pull-cannula at 200 microliters/10 min. LHRH in perfusates was determined by RIA. Two 6-h sampling sessions, in the morning (0600-1200 h; lights on 0600 h) and in the evening (1800-2400 h; lights off 1800 h) were performed in each animal. LHRH release patterns were analyzed in prepubertal (15.7 +/- 0.7 months of age; mean +/- SEM, n = 6) early pubertal (premenarcheal; 26.1 +/- 1.0 months, n = 7), and midpubertal (40.0 +/- 1.4 months, n = 6) monkeys. Results were as follows: 1) LHRH release was pulsatile in all age groups. While LHRH release in five of six prepubertal animals consisted of small (amplitude less than 2.5 pg/ml) pulses, in all peripubertal animals LHRH release was a mixture of small and large (amplitude greater than 2.5 pg/ml) pulses. 2) There was a significant developmental increase in mean LHRH release (P less than 0.02), and this was particularly apparent in the evening. Mean LHRH release in the early and midpubertal groups was higher than that in the prepubertal group (P less than 0.05 for morning and P less than 0.01 for evening). The mean release in the evening of the midpubertal group further increased over that of the early pubertal group (P less than 0.05). 3) Similarly, LHRH pulse amplitude increased developmentally (P less than 0.01). Pulse amplitudes in early and midpubertal groups were higher than those in the prepubertal group (P less than 0.05 for morning and P less than 0.02 for evening). Again the amplitude in the evening further increased from the early pubertal to the midpubertal period (P less than 0.05). 4) There was also a developmental increase in basal LHRH release (P less than 0.01). The evening values in the early pubertal and midpubertal groups were higher than those in the prepubertal group (P less than 0.05). 5) The interpulse interval decreased developmentally (P less than 0.001). Interpulse intervals in early and midpubertal groups were shorter than those in the prepubertal group (P less than 0.01 for morning and P less than 0.025 for evening).(ABSTRACT TRUNCATED AT 400 WORDS)
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