Biomedical subjects
Publications and source records attributed to A Knifton.
Daily oral doses of 500 mg meclofenamic acid, a potent inhibitor of prostaglandin biosynthesis, had no observable effects on parturition in goats. These findings are contrary to previous studies in the goat and other animals, but may be a result of the route of meclofenamate administration.
Aortic infusions of PGF-2 alpha to goats during late pregnancy had no dramatic effects on uterine motility. Only when plasma progesterone concentrations had decreased by 50% due to the luteolytic action of PGF-2 alpha did uterine activity increase. No cervical softening was detected during the infusion periods. Cervical softening was detected after the decline in progesterone concentraton and the increases in endogenous PGF and uterine motility. It is suggested that the corpus luteum, presumably by secretion of progesterone, has an inhibitory action on the cervix, preventing other hormones from inducing dilatation.
Removal of corpora lutea from seven goats during late pregnancy (122 to 129 days) resulted in an abrupt decline in uterine venous plasma progesterone concentrations within 10 min and abortion after a mean interval of 29.88 +/- 1.64 (SD) h. Abortion was preceded by a significant increase in uterine venous plasma PGF concentration either before or coincident with palpable cervical softening. Intrauterine, extra-fetal administration of indomethacin, as a single dose, in a further five lutectomised goats significantly prolonged the interval to abortion and delayed both cervical ripening and the increase in plasma PGF.
Spontaneous uterine motility and reactivity to intravenous oxytocin were recorded in eight ovariectomised, oestrogen-primed goats before and after oral meclofenamic acid treatment. Spontaneous motility was completely abolished within 50 to 100 min of meclofenamate administration. However, although uterine reactivity to oxytocin was significantly reduced, the sensitivity was not altered. It is suggested that, in the goat, oxytocin has two effects on the uterus: it increases myometrial activity and also stimulates prostaglandin synthesis.
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Further changes to the medicine labelling regulations have important implications for practising veterinary surgeons. They amend the regulations made recently by specifying warning labels and other special labelling requirements for certain types of veterinary medical products.
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Uterine motility was recorded for several weeks in 10 ovariectomised goats, using small intra-uterine balloons, to study the effects of female sex hormones on uterine activity and reactivity to oxytocin. Oestradiol stimulated uterine contractions and increased both the sensitivity and intra-uterine pressure response to oxytocin. When progesterone was administered in addition to oestradiol, spontaneous uterine motility became irregular with low amplitude contrations; the sensitivity and reactivity to oxytocin was significantly depressed.
Spontaneous uterine motility and reactivity to intravenously administered oxytocin were recorded through the oestrous cycle in a group of goats. Contractions during oestrus were of significantly greater amplitude than in dioestrus and both the sensitivity and degree of response to oxytocin were greater in the oestrous phase. Evidence from a previous study suggests that the depressed spontaneous and oxytocin-induced motility in dioestrus is due to the predominating influence of progesterone during this stage of the cycle.
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