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Biomedical subjects

F J Cunningham

Publications and source records attributed to F J Cunningham.

At least 55 records · Page 3Linked to original sources
PubMed1980

Concentrations of corticosterone and luteinizing hormone in plasma during the ovulatory cycle of the domestic hen and after the administration of gonadal steroids.

Plasma concentrations of corticosterone and LH were measured in hens in relation to the ovulation of an egg either early or late in a sequence and also in hens injected with gonadal steroids. In hens about to ovulate an egg early in the sequence, the plasma concentration of LH rose at the onset of darkness while levels of corticosterone remained low. As levels of LH fell during the 4 h preceding ovulation, those of corticosterone increased steeply to reach a maximum at about the time of ovulation, which is shortly after dawn. In contrast, in hens about to ovulate an egg late in a sequence, the concentration of LH in plasma fell and that of corticosterone tended to increase during the hours of darkness. During the 7 h preceding ovulation the temporal relationship of LH to corticosterone was similar to that observed before an early ovulation such that levels of corticosterone increased rapidly on the descending slope of the preovulatory LH surge and reached maximum values at the time of oviposition and ovulation. Infections of oestradiol benzoate and testosterone propionate did not alter plasma concentrations of either corticosterone or LH. On the other hand, the injection of progesterone was associated with a rapid fall in levels of corticosterone. It is suggested that progesterone may suppress the pituitary-adrenal system and thus modulate the pattern of corticosterone secretion during the ovulatory cycle.

Animals↗
PubMed1978

Effects of an essential fatty acid deficiency, pair-feeding and level of dietary corn oil on the hypothalamic-pituitary-gonadal axis and other physiological parameters in the male chicken.

Two studies were conducted to observe the effects of an essential fatty acid (EFA) deficiency, added dietary corn oil and pair-feeding on growth, reproduction and other physiological parameters in the mature cockerel. A purified, linoleic acid (LA)-deficient diet (0.01% LA), or additions of 5% (3.01% LA) or 15% (9.04% LA) corn oil, were fed ad libitum from hatching through 24 weeks of age. Reductions in growth, feed consumption, and comb, and testes size, incomplete spermatogenesis, increased tissue eicosatrienoic acid (20: 3 omega 9) and changes in weights of selected internal organs were observed in deficient cockerels. Total pituitary gonadotropic activity was measured by two bioassay procedures and blood luteinizing hormone was measured by radioimmunoassay. By maturity both of these parameters were significantly reduced in deficient chickens. When these chickens were fed diets with 5% or 15% corn oil under pair-feeding or ad libitum conditions from 20 to 24 weeks, the reduced growth, comb and testes size and gonadotropin metabolism appeared to be caused by depressions in appetite and energy intake rather than EFA per se. The degenerate testicular histology of the 20-week old deficient cockerels, while responding fully to the ad libitum intake of the diets containing corn oil, showed only partial rehabilitation of spermatogenesis when diets with either 5% or 15% corn oil were pair-fed. In general, increasing the level of dietary fat from 5% to 15% did not cause many physiological changes.

Animals↗
PubMed1977

The plasma concentrations of testosterone and LH during the ovulation cycle of the hen (Gallus domesticus).

The plasma concentrations of testosterone and luteinizing hormone (LH) were measured by radioimmunoassay during the ovulation cycle of the hen. The baseline concentrations of testosterone were 100 to 250 pg/ml and the maximum concentration of 904 pg/ml was observed 6 h before ovulation. The possibility that testosterone is the ovarian excitation hormone which initiates the ovulation-inducing surge of LH is discussed.

Animals↗
PubMed1976

The effect of pregnenolone, progesterone, deoxycorticosterone or corticosterone on the time of ovulation and oviposition in the hen.

Pregnenolone, progesterone, deoxycorticosterone and corticosterone were injected into hens between 16.30 and 17.00 h on the day of oviposition of the last egg of a sequence. 2. Pregnenolone did not affect ovulation, but all of the other steroids induced ovulation prematurely. 3. To induce premature ovulation in 50% of the hens, 82-31 mug+/-0-06 mug, 23-86 mug+/-0-07 mug and 659-26 mug+/-0-05 mug of progesterone, deoxycorticosterone and corticosterone, respectively were required for injection. 4. Differences were observed in the times of oviposition of eggs which ovulated in response to injections of either progesterone or a corticosteroid and it was suggested that the mechanism of action of progesterone and corticosteroids operates through different endocrine pathways.

Animals↗
PubMed1976

Development and application of a heterologous radioimmunoassay for ovine follicle-stimulating hormone.

A highly specific and sensitive heterologous double antibody radioimmunoassay for ovine follicle-stimulating hormone (oFSH) is described in detail. The assay using a rabbit antiserum to human FSH and either 125I-labelled rat FSH or 125I-labelled oFSH as tracer is specific for FSH. A maximum cross-reaction (B/Bo = 50%) of 0-1% was observed with other ovine, rat or human pituitary hormones or human chorionic gonadotrophin. Serum levels of oFSH in samples collected daily throughout the oestrous cycle showed large individual variations. In five out of nine animals a peak of FSH was observed on the day of oestrus.

Animals↗
PubMed1976

The interrelationship between progesterone and luteinizing hormone during the ovulation cycle of the hen (Gallus domesticus).

The existence of a circadian rhythm in the sensitivity of the hypothalamus of the laying hen to stimulation by progesterone was investigated by injecting 0.5 mg progesterone subcutaneously during the proposed period of maximum insensitivity. Following this treatment increases in plasma concentrations of both LH and progesterone were observed which were comparable to the spontaneous preovulatory rises in the plasma levels of the hormones. The ability of either progesterone or luteinizing hormone releasing hormone (LH-RH) to induce premature ovulation varied according to the stage of follicular development. Neither hormone was more than 28% effective when injected within 6.5 h of the previous ovulation, whereas both hormones were 100% effective approximately 27 h after the terminal ovulation of a clutch sequence. Failure to ovulate in response to LH-RH given 6.5 h after ovulation was associated with a lack of progesterone secretion. Both LH and progesterone were secreted when ovulation was induced by injections of either LH-RH or progesterone, and LH was secreted in response to progesterone given 6.5 h after ovulation. These results demonstrate that progesterone stimulates the secretion of LH and LH stimulates the secretion of progesterone. The precise physiological role of these two hormones, however, was not established.

Animals↗
PubMed1975

Obesity induced by force-feeding and accompanying changes in body temperature and fertility in the male domestic fowl.

1. Excessive amounts of food (two-fold more than the ad libitum intake) introduced into the gastro-intestinal tract of three adult male fowls, for 5 weeks, caused a marked increase in body weight resulting mainly from fat deposition. 2. The induced obesity was accompanied by an increase of the rectal temperature (0-2 to 0-3 degrees C) and a decrease of the skin and comb temperatures, a cessation in the growth of the comb, a reduction in the blood packed cell volume, an eight-fold reduction in the number of spermatozoa in the vasa deferentia and a concomitant depression in their motility. 3. A decrease of the testosterone and an increase of luteinising hormone concentrations in the blood plasma was obtained in two of the three treated birds.

Animal Feed↗
PubMed1975

Luteinizing hormone concentrations in the plasma of laying hens exposed to a 27-hr cycle of light and darkness.

The time of peak concentration of LH in the peripheral plasma of ten laying hens kept on a 14 hr light/13 hr dark cycle was determined by radioimmunoassay. A single peak of LH occurred in each hen 3 1/2 hr before oviposition or 4 hr before ovulation. These are similar intervals to those reported for laying hens kept on a 14 hr light/10 hr dark cycle. The mean time of the observed peak in plasma LH was 2 hr 9 min after the beginning of the dark period. This is about 3 hr earlier than corresponding LH peaks reported for hens under normal lighting.

Animals↗