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Biomedical subjects

B T Donovan

Publications and source records attributed to B T Donovan.

At least 19 recordsLinked to original sources
PubMed1986

Acute effects of GnRF-induced gonadotrophin secretion upon ovarian steroid secretion in the ferret.

The effects of an increase in endogenous gonadotrophin secretion on the production of oestradiol, progesterone, androstenedione and testosterone by the ovaries of anaesthetized anoestrous and oestrous ferrets were followed. Gonadotrophin secretion was enhanced by the injection of gonadotrophin releasing factor (GnRF), and serial blood samples were collected over 9 h for hormone assay. Thyrotrophic hormone releasing factor (TRF) or acetic acid were injected for control purposes. The plasma content of oestradiol in oestrous females was significantly higher than during anoestrus, but secretion of this steroid was not increased by any means. The plasma concentration of progesterone in anoestrous females was significantly higher than during oestrus. It was increased by GnRF in anoestrous ferrets and less markedly in oestrous females. The plasma concentration of androstenedione was raised by GnRF to a greater extent during anoestrus than during oestrus. Testosterone was present in higher concentration in the plasma during anoestrus than during oestrus, and the level was increased by GnRF administration. These findings indicate that the ovaries of the anoestrous ferret secrete significant quantities of steroid hormones, and that they respond readily to gonadotrophic hormone.

Androstenedione↗
PubMed1978

The behavioural actions of the hypothalamic peptides: a review.

Recent work has shown that the hypothalamic peptides commonly associated with the control of pituitary function have important behavioural actions of possible psychiatric significance. Thus, vasopressin, ACTH and like peptides may influence memory processes, and ACTH and MSH given intracranially induce a peculiar stretching and yawning syndrome accompanied by penile erection and ejaculation. Thyrotrophic hormone-releasing factor potentiates behavioural excitation, somatostatin is depressive, while luteinizing hormone-releasing hormone facilitates sexual behaviour and the newly identified endorphins are markedly opioid in character. These and other activities of the hypothalamic peptides are reviewed and assessed alongside the clinical information available.

Adrenocorticotropic Hormone↗
PubMed1977

Gonadotrophin secretion in the ovariectomized guinea-pig: effects of electrical stimulation of the hypothalamus and of LH-RH.

1. Serial blood samples were collected from anaesthetized spayed guinea-pigs subjected to anterior hypothalamic stimulation or injected with luteinizing hormone-releasing hormone (LH-RH), and the effect on the secretion of follicle-stimulating hormone (FSH) and LH followed. 2. Hypothalamic stimulation enhanced LH secretion, although the response waned during the course of the 1 hr period of stimulation; the secretion of FSH was not increased. After stimulation, FSH and LH levels fell below control values. 3. The response to stimulation of the hypothalamus was greater 2 weeks after spaying than after 1 week. 4. Since repeated periods of hypothalamic stimulation induced repeated surges of LH secretion, the decline in LH secretion during stimulation was not likely to have resulted from hypothalamic damage, while the observation that the plasma concentration of FSH and LH declined below control values after brain stimulation implies the operation of inhibitory mechanisms. 5. Pre-treatment of spayed guinea-pigs with progesterone depressed the resting plasma concentration of LH but did not affect the immediate response to hypothalamic stimulation. After hypothalamic stimulation the plasma gonadotrophin levels did not fall below control values. 6. Pre-treatment with oestradiol benzoate depressed the resting plasma level of LH and slightly reduced the size of the LH surge produced by hypothalamic stimulation. However, the raised plasma LH concentration was sustained after stimulation ended. 7. The response to hypothalamic stimulation after pre-treatment with progesterone and oestradiol benzoate showed features of the reaction to each steroid given singly. 8. The I.V. injection of 0-5 microng LH-RH induced a surge of LH secretions without affecting FSH discharge. 9. Pre-treatment with progesterone did not greatly modify the response to LH-RH but after an injection of oestradiol the high level of LH produced by the releasing factor was sustained for about 2 hr. 10. Injections of LH-RH during the phase of depressed LH release after hypothalamic stimulation produced a surge of LH secretion which matched that seen in non-stimulated animals.

Animals↗
PubMed1977

Stimulation of the Hypothalamus and FSH and LH secretion in the ferret.

The acute effects of hypothalamic electrical stimulation on the secretion of FSH and LH have been examined in anestrous and estrous ferrets. Basal levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were higher in the anestrous than in the estrous animals; the anestrous animals showed a more marked increase in gonadotropin levels following hypothalamic stimulation than did the estrous animals whether the stimulation current was constant or increased in the course of the experiment. It is concluded that the physiological difference in the control of gonadotropin secretion in the estrous (vs the anestrous) ferret is not reflected in an increased sensitivity of the hypothalamo-hypophysial axis to stimulation.

Anestrus↗
PubMed1977

Effects of luteinizing hormone releasing hormone on plasma follicle-stimulating hormone and luteinizing hormone levels in the ferret.

Heterologous radioimmunoassays for FSH and LH were employed to examine the effect of synthetic LH-RH upon gonadotrophin secretion in the ferret. Intravenous injection of 4 microng LH-RH induced a surge of FSH and of LH secretion in male and in female animals. In intact and in castrated males, the rise of LH was much more marked than that of FSH. The gonadotrophin response to LH-RH was greater in anoestrous than in oestrous females; FSH secretion was not enhanced during oestrus. Ovariectomized females behaved as anoestrous females with respect to LH secretion, while FSH secretion remained unchanged. Treatment of ovariectomized females with progesterone did not alter the pattern of response to LH-RH, but oestradiol treatment depressed the reaction to match that seen in oestrous females. Repetitive injections of LH-RH induced repetitive surges of FSH and LH in anoestrous females, but only of LH during oestrus: slow i.v. infusion of LH-RH induced a sustained elevation of plasma LH levels both in oestrous and in anoestrous females; again FSH levels rose only in anoestrous females. Injection of synthetic TRH did not alter gonadotrophin secretion in corresponding groups of male or female ferrets.

Animals↗
PubMed1976

Effect of intra-uterine beads alone, or combined with oestrogen treatment, on utero-ovarian venous plasma prostaglandin F2alpha and progesterone levels in the guinea-pig.

The presence of beads in the guinea-pig uterus caused premature regression of the corpora lutea, and a corresponding decrease in utero-ovarian venous plasma levels of progesterone, by days 9-10 of the oestrous cycle. If the beads were placed in one horn only, premature luteal regression occurred only in the adjacent ovary. Induced luteal regression was preceded by an increased release of prostaglandin F2alpha (PGF2alpha) from the uterine horns which contained the beads. Oestradiol benzoate treatment of guinea-pigs carrying beads in one uterine horn overcame the unilateral effect and resulted in premature luteal regression in both ovaries. This was also associated with the early release of PGF2alpha from both uterine horns, though a difference in the timing of the release was apparent between the bead-containing (experimental) and control horns.

Animals↗
PubMed1976

Effect of intra-uterine foreign bodies and of prostaglandin administration on progesterone secretion during the oestrous cycle of the guinea-pig.

The response of the guinea-pig corpus luteum to the luteolytic influence of glass beads placed in the uterus, or to prostaglandin administration, was followed by assay of the progesterone content of blood samples collected daily. Following the introduction of glass beads into the uterus early in the cycle, the secretion of progesterone was curtailed. Treatment with prostaglandin F2alpha over days 4-6 or 6-8 of the cycle temporarily depressed progesterone release without shortening the life of the corpora lutea. When the drug was administered over days 8-10, 10-12 or 12-14 the depression in progesterone was not followed by any recovery. These observations indicate that the response of the corpora lutea to a luteolytic influence changes during the oestrous cycle.

Animals↗
PubMed1976

Puberty.

Explore the source record for details and available documents.

Adolescent↗
PubMed1975

Indomethacin, ketoprofen and corpus luteum regression in the guinea-pig.

1 The accelerated regression of the corpora lutea normally produced by glass beads inserted unilaterally into the uterus of the guinea-pig early in the oestrous cycle was prevented when the beads were filled with indomethacin or ketoprofen. 2 Luteal regression was enhanced by the placement of beads in both horns of the uterus. When empty beads were placed in one horn of the uterus and drug-filled beads in the other, indomethacin blocked regression in both ovaries whereas ketoprofen was ineffective. 3 Indomethacin probably blocks luteal regression by inhibition of prostaglandin syntheses in the uterus.

Animals↗
PubMed1975

Changes in the concentration of luteinizing hormone in plasma during development in the guinea-pig.

The concentration of LH in the plasma of guinea-pigs from day 50 of gestation to day 45 of postnatal life was assayed by radioimmunoassay utilizing a cross-reaction with anti-ovine LH antiserum. The effect of gonadectomy in infancy and in the adult upon the plasma concentration of LH was also studied. The LH concentration in the plasma of male or female foetuses was high immediately prenatally and fell at birth. High levels of LH were again detected in male, with a lesser increase in female, guinea-pigs over the first 10 days postnatally. Maternal plasma concentrations of LH remained consistently low. Removal of the gonads on days 0, 5, 10, 15, 25 or 35 of postnatal life, followed by blood collection at autopsy 10 days later, caused a significant rise in plasma LH content at all ages. The rise in plasma LH after gonadectomy in adults was less marked in male than in female guinea-pigs.

Age Factors↗
PubMed1975

Changes in the concentration of follicle-stimulating hormone in plasma during development in the guinea-pig.

The concentration of FSH in the plasma of guinea-pigs from day 50 of gestation to day 45 of postnatal life was assayed by a radioimmunological procedure utilizing a cross-reaction with the NIAMDD S6 antiserum to rat FSH. At 68 days of gestation the mean plasma FSH concentration of female foetuses was greater than that of the males, although the concentrations in the two sexes were similar on day 50 of gestation. Maternal levels remained consistently low throughout gestation. Postnatally there were no marked changes in plasma FSH levels through to maturity, although a transient rise in the male occurred over the first 3 days after birth. Gonadectomy on days 0, 5, 10, 15, 25 or 35 of postnatal life, or when adult, resulted in a significant increase in plasma levels of FSH within 10 days. The rise in plasma FSH concentration was greater in males than in females at all ages, although, a larger increase was observed in females spayed at 5 or 10 days of age than at other times.

Age Factors↗