Effects of modifying olfactory and pineal gland function on the seasonality of semen production and plasma luteinizing hormone,testosterone and prolactin levels in rams

In an experiment designed to evaluate neuroendocrine mechanisms which could mediate seasonality of reproduction in Romney rams, the effects on semen production and plasma hormone levels of olfactory bulbectomy, cranial cervical ganglionectomy, or both operations, were studied over a period of 16 months.Concentrations and total numbers of spermatozoa in ejaculates from surgically treated rams were higher than in those from unoperated controls. Although mean fructose concentrations were lower in semen from treated animals, the pattern of seasonal changes in seminal fructose was similar in all groups of rams. Olfactory bulbectomy disrupted the regular seasonal changes in plasma luteinizing hormone (LH) levels, while cranial cervical ganglionectomy abolished the seasonality of secretion of both LH and prolactin. The annual pattern of testosterone secretion was not affected by any surgical treatment. Ganglionectomy reduced hydroxyindole-O-methyl transferase activity and cell volumes in pineal glands, so it was concluded that this treatment produced its effects by reducing the capacity of the pineal gland to respond to seasonal variations in daily photoperiod. No conclusions could be drawn about the role of olfactory function in regulating seasonality of reproduction in rams.     

An enzyme linked immunosorbent assay (ELISA) for plasma medroxyprogesterone acetate (MPA).

A single extraction fixed antigen enzyme-linked immunosorbent assay (ELISA) that can be completed in less than 24 h is described for the measurement of medroxyprogesterone acetate (MPA) in plasma. MPA is covalently coupled to bovine thyroglobulin and passively adsorbed in guanidine hydrochloride to a standard 96-well microtitre plate where it competes with MPA in the extracted plasma sample for goat anti-MPA. Antibody binding to the solid phase is determined via binding of a horse-radish peroxidase second antibody which reacts colorimetrically with its substrate. The reaction is stopped by addition of 1.25 M H2SO4 and absorbance read at 492 nm. All steps except for sample addition and extraction can be performed on an automatic ELISA processing machine. The assay is sensitive, specific and precise, with intra- and inter-assay coefficients of variation of less than 10 and 15%, respectively. Assay sensitivity is 0.08 ng/ml. The assay follows established methodology for other assays in this laboratory which assists standardization, cost structure and sample throughput and thus is a useful alternative to radioimmunoassays for the determination of MPA in plasma.     

Effects of subcutaneous melatonin implants on reproductive seasonality of farmed fallow deer (Dama dama)

A total of 18 fallow does, including pubertal, non-pregnant and pregnant adult does (6 per class), each received a single subcutaneous implant containing 18 mg melatonin on 4 occasions at 29-30-day intervals from 10 November 1986 (approximately 120-day treatment period). A further 18 contemporary does served as herd-mate controls. Two adult fallow bucks were treated the same and were run with the does until 16 March. Thereafter, 1 of 4 control bucks was run with the does until 1 June. Of the 6 pregnant does receiving implants within the last 40 days of their gestation, 4 failed to lactate after parturition in December 1986. The remaining 2 does successfully reared their fawns, as did the 6 contemporary controls. Mean (+/- s.e.m.) dates of first oestrus in 1987 were 27.6 February (+/- 3.0 days) and 22.9 April (+/- 0.8 days) for all treated and all control does respectively (P less than 0.001). Pubertal does were generally later to exhibit first oestrus than were older does within their respective treatment groups. Return oestrus occurred only in 2 pubertal does (1 treated and 1 control) with remaining does conceiving to their first oestrus, as verified by plasma progesterone profiles. However, 5 (28%) of the treated does and 3 (17%) of the control does failed to maintain pregnancy and fawn in 1987. The mean (+/- s.e.m.) 1987 fawning date of the remaining does was 22.4 October (+/- 2.7 days) for the treated group (N = 13) and 13.1 December (+/- 0.8 days) for the control group (N = 15; P less than 0.001). Mean (+/- s.e.m.) gestation length of treated does (238.9 +/- 0.6 days) was significantly longer than that of control does (234.5 +/- 0.4 days; P less than 0.001). Of 13 fawns born to treated does, 4 (31%) died within 24 h of birth (mainly due to hypothermia) whereas all 15 fawns born to control does survived to weaning. Melatonin-treated bucks exhibited a marked advancement of neck muscle hypertrophy during the treatment period and displayed normal rutting activity (e.g. vocalization) in response to early oestrus in the treated does.