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Biomedical subjects

N B Haynes

Publications and source records attributed to N B Haynes.

At least 37 records · Page 2Linked to original sources
PubMed1977

Response of cyclic and post-partum suckled cows to injections of synthetic LH-RH.

Doses of 125, 250 or 500 micrograms LH-RH were injected i.m. into suckled beef cows on approximately Day 11 of an oestrous cycle synchronized by prostaglandin treatment. There was a positive linear relationship between dose of LH-RH and the area under the measured LH peak. Administration of 500 micrograms LH-RH as a single injection to suckled cows 13-32 days post partum resulted in LH release but failed to induce normal ovarian activity. A small transient rise in plasma progesterone for 6--9 days occurred at the expected time after injection in 50% of animals. Administration of 500 micrograms LH-RH to suckled beef cows approximately 20--30 days post partum and a second injection approximately 10 days later at the time when the resulting transient rise in plasma progesterone had returned to basal values induced normal cyclic activity (as shown by progesterone concentrations and observed oestrus) at 35 days compared with 70 days for untreated controls. Pituitary responsiveness to LH-RH, as assessed by LH levels, was found to increase up to 20 days post partum.

Animals↗
PubMed1976

Plasma concentrations of testosterone in the developing ram in different social environments.

Plasma testosterone profiles were determined by taking frequent blood samples at intervals from birth to 21 months of age from rams reared in isolation, in an all-male group and in a mixed-sex group. The testosterone pattern was not modified by these different social environments. The ability of the ram to copulate when first exposed to an oestrous ewe, apparently a maturational process, was also independent of social rearing. At birth plasma testosterone levels were detectable but low, they were higher at 10 and 16 weeks of age and showed a marked rise by 26 weeks, coincident with the time of puberty. Depressive effects of season on testosterone profiles occurred during the 2nd year of life but not the 1st year.

Age Factors↗
PubMed1976

Effects of ewe proximity on peripheral plasma testosterone levels and behaviour in the ram.

Groups of yearling and immature rams were kept for 6 months during the breeding season either adjacent to or apart from ovariectomized ewes in which oestrus was induced by hormone therapy. The older rams kept near ewes were found to have larger testes, higher plasma testosterone levels and greater sexual and aggressive activity, although the immature animals showed no response. Plasma testosterone concentration was also found to increase after copulation in some animals.

Age Factors↗
PubMed1975

Progesterone levels following treatment of seasonally anoestrous ewes with synthetic LH-releasing hormone.

Plasma progesterone determinations were carried out on blood samples collected daily from Clun Forest ewes during the normal oestrous cycle and also after administration of LH-releasing hormone (LH-RH) during seasonal anoestrus. Levels of plasma progesterone at oestrus ranged from 0.1 to 0.5 ng/ml and luteal phase levels from 3 to 6 ng/ml. Levels found during seasonal anoestrus were within the range of those observed as oestrus. Following treatment with LH-RH, there was in increase in the plasma LH level in a-l cases and ovulation occurred in twenty-three out of twenty-seven treated ewes. In the animals which ovulated, the plasma progesterone concentration either remained basal (eighteen animals) or rose to a lower level (2 ng/ml is greater than) than that found during the luteal phase of the cycle.

Animals↗
PubMed1975

Stimulation effect of prostaglandin F2ALPHA on the plasma concentration of testosterone in bulls.

The concentrations of peripheral plasma testosterone were measured by radioimmunoassay in samples collected from five bulls, each given i.m. injections of 0, 5. 15, 30 and 60 mg prostaglandin F2alpha (PGF2alpha). Synchronized peaks in testosterone concentration occurred with maximum values 1.2h after treatment. These increases of testosterone persisted significantly longer than those observed to occur as natural episodic peaks during two 24 h periods in the same bulls. The mean peak testosterone concentration after PGF2alpha injection was related to the dose of PGF2alpha, values after 60 and 30 mg doses being significantly greater than after 15 mg. The response produced by a 5 mg dose was not significant. The results indicate that intramuscular injection of PGF2alpha, acutely stimulates synthesis and release of testosterone in fulls.

Animals↗