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Biomedical subjects

J K Findlay

Publications and source records attributed to J K Findlay.

At least 199 records · Page 11Linked to original sources
PubMed1978

The importance of prolactin and the milking stimulus in the artificial induction of lactation in cows.

Lactations were successfully induced in 15 out of 18 non-pregnant cows treated with oestradiol-17beta (0.1 mg/kg body weight) and progesterone (0.25 mg/kg body weight) on days 1-7 (where day 1 is the first day of treatment). A further 23 out of 26 cows were successfully treated with oestradiol-17beta and progesterone standardized at 40 and 100 mg/day respectively. No significant differences in milk yields were obtained by the additional treatments of twice daily milking from day 10, sustained elevation or suppression of plasma prolactin during the induction phase by reserpine and bromo-cryptine respectively, or by continuing oestradiol-17beta injections alone on days 8-11. Levels of plasma prolactin less than 20 ng/ml were adequate for the preparation of the mammary gland for lactation to occur. The induced lactation of 24 monozygotic twin cows ranged from 20 to 87% of their respective siblings which had normal parturient lactations. All 11 cows treated with the standard oestrogen-progesterone treatment plus reserpine had successfully induced lactations. In the absence of oestrogen and progesterone treatment, a short period of resperpine treatment followed by dexamethasone trimethylacetate failed to induce lactation in five cows. Ninety per cent of induced cows (n = 39) and 91% of parturient cows (n = 22) conceived and subsequently calved following natural mating.

Animals↗
PubMed1978

Effect of anaesthesia on ovarian follicular development and ovulation in the sheep subsequent to prostaglandin-induced luteolysis.

Prostaglandin analogues were used to induce luteal regression simultaneously in a number of ewes, thereby synchronizing the final stages of follicular maturation in these animals. Some of the ewes were anaesthetized for 24 h immediately after the injection of prostaglandin (experiment 1), and others for 15 h, starting 24 h after the injection of prostaglandin (experiment 2). In both experiments administration of anaesthetic significantly delayed the onset of oestrus and the time of ovulation relative to prostaglandin-treated control animals. The results from assays of blood samples collected at regular intervals in experiment 1 indicated that the preovulatory peak in the concentration of LH and the periovulatory changes in the concentration of FSH were similarly delayed and that during anaesthesia the level of LH was significantly reduced. It is suggested that the reduced level of LH, which probably resulted from a reduction in the secretion of releasing factor due to anaesthesia, failed to support oestrogen production by the Graafian follicle(s), thereby delaying the occurrence of oestrus and ovulation.

Anesthesia↗
PubMed1978

The importance of prolactin for lactation in the ewe.

The effect of 2-bromo-alpha-ergocryptine (bromocriptine) on the induction, initiation and maintenance of milk secretion was studied in post-parturient ewes and in ovariectomized ewes artificially induced to lactate by treatment with oestrogen plus progesterone and then dexamethasone. Treatment with bromocriptine (about 0.4 mg/kg every 3 days) lowered and maintained the plasma concentration of prolactin at less than 12 ng/ml. Ewes receiving bromocriptine concurrently with oestrogen plus progesterone during the priming phase had a significantly lower (P less than 0.05) mean cumulative milk yield than control ewes, although the milk of the treated ewes contained normal amounts of fat, protein and lactose. Administration of bromocriptine during dexamethasone-induced lactogenesis had no significant effect on the mean cumulative milk yield but significantly (P less than 0.05) increased the milk fat and protein content. In established lactation, bromocriptine markedly reduced the milk yield in both intact and ovariectomized ewes. The concentration of protein was not significantly affected although the milk fat content was higher in the bromocriptine-treated than in the control ewes. The effects of bromocriptine on milk yield and composition during galactopoiesis could be reversed by concurrent infusion of prolactin and the results suggest that prolatin is an important hormone during mammogenesis and galactopoiesis in the sheep.

Animals↗
PubMed1977

The effects of prostaglandin F2alpha on sperm output in boars.

The effect of prostaglandin F2alpha (PGF2alpha) on the sperm output of six boars was investigated in two studies. Although PGF2alpha did not significantly affect sperm numbers in the ejaculate, a significantly longer (P less than 0.05) ejaculation of the sperm rich fraction occurred following injection of PGF2alpha. In the second study it was found that PGF2alpha produced a 49% increase (P less than 0.05) in the number of sperm in the sperm rich fraction of the ejaculate. The implications of these results on artificial breeding are discussed.

Animals↗
PubMed1977

The effect of 2-bromo-alpha-ergocryptine and 2-chloro-alpha-methylergoline-8beta-acetonitrile (lergotrile mesylate) on the prolactin secretion of the ewe.

The effects of two ergot alkaloids, 2-bromo-alpha-ergocryptine methane-sulphonate (CB154, Sandoz) and lergotrile mesylate (LM, E. Lilly & Co.), on the basal secretion of prolactin and on the prolactin response to TRH or the milking stimulus was investigated in the sheep. Both CB154 (c. 0.5 mg/kg) and LM (c. 0.75 mg/kg) markedly reduced basal levels of prolactin and inhibited the TRH-induced prolactin release in ewes in the mid-luteal phase of the oestrous cycle. Both compounds also suppressed basal levels of prolactin in lactating ewes and inhibited the prolactin response to the milking stimulus in lactating ewes.

Acetonitriles↗
PubMed1976

The use of synthetic prostaglandin analogue to induce oestrus in mares.

A clinical trial involving 359 mares was conducted to ascertain the clinical value of a synthetic prostaglandin analogue (fluprostenol, ICI-81,008) structurally related to PGF2oc for treating mares in prolonged dioestrus. Some 263 mares (73.3%) displayed oestrus within 5 days of a first intramuscular injection of 250 mug fluprostenol and, of those mares later examined for pregnancy, 108 (40%) were found to have conceived during the first induced oestrus. A further 21 mares (8%) cycled normally and conceived to services during the second oestrus. Most (80.3%) of the plasma samples obtained from 242 mares prior to treatment showed a progesterone concentration greater than 1 ng/ml, thereby indicating the presence of functional luteal tissue in the ovaries. The results support earlier observations that most non-pregnant mares which fail to cycle during the breeding season are in a state of prolonged dioestrus rather than anoesturs.

Animals↗
PubMed1976

Regulation of gonadotrophin secretion in rams from birth to sexual maturity. I. Plasma LH, FSH and testosterone levels.

Plasma LH, FSH and testosterone concentrations were measured by radioimmunoassays in male crossbred Merino/Corriedale sheep from birth to 45 weeks of age. FSH levels were 11 and 22 ng/ml at birth, increased to peak levels (mean value of 47 ng/ml) at 5 weeks and fluctuated between 25 and 35 ng/ml for the next 40 weeks. Similarly, LH (less than 0-5 ng/ml) and testosterone (less than 38 ng/100 ml) levels were low at birth and were significantly elevated by 5 weeks of age. LH values varied betwen 0-9 and 3-0 ng/ml for the next 30 weeks and then a secondary rise occurred reaching levels of 2-4 ng/ml by the 41st week after birth. Concentrations of LH subsequently fell to levels observed in adult rams. Testosterone levels rose gradually between the 5th and the 25th week, and then increased rapidly to values of 270-517 ng/100 ml by the 41st week after birth, a time coincident with the peak LH levels. Histological examination of testicular biopsies demonstrated that Sertoli cell maturation occurred 17-21 weeks after birth and was followed by activation of spermatogenesis leading to the presence of spermatozoa in the seminiferous epithelium by 39-42 weeks of age.

Age Factors↗
PubMed1976

Regulation of gonadotrophin secretion in rams from birth to sexual maturity. II. Response of the pituitary-testicular axis to LH-RH infusion.

The response of the pituitary-testicular axis to LH-RH infusion was investigated in rams from birth to sexual maturity. During early postnatal life ram lambs were responsive to LH-RH stimulation and heightened pituitary sensitivity was observed in rams aged 2-3 months. It is suggested that a change in sensitivity of the pituitary-testicular axis occurs at this time and perhaps represents the time of initiation of the pubertal process.

Age Factors↗
PubMed1976

Pregnancy-specific antigens in the sheep: application to the diagnosis of pregnancy.

Antisera to 14-day-old sheep embryos were raised in rabbits and used to detect antigens specific to pregnancy by immunofluorescent staining and haemagglutination. Non-specific antibodies were removed by repeated absorptions of the antisera with homogenates of liver and kidney from non-pregnant ewes. The pregnancy-specific antigens were detected using immunofluorescence in the embryo, myometrium, maternal blood and CL as early as Day 8. No fluorescence was detected in pituitary, hypothalamus, liver, kidney, skeletal muscle or endometrium of pregnant ewes, or in any tissues of non-pregnant ewes. Haemagglutination occurred when a 1:8 dilution of rabbit anti-sheep embryo sera was added to blood obtained from ewes between Days 6 and 50 of pregnancy, but not when added to blood from non-pregnant ewes, rams and wethers or from pregnant mares, sows and cows. The immunological activity was removed from the anti-sheep embryo sera by absorption with homogenates of 14-day-old sheep embryo or pregnant uterus, or erythrocytes from Day 14 pregnant ewes, confirming that the antigens were specific to pregnancy. The presence of these antigens provides a basis for a haemagglutination test for pregnancy from Day 6 after mating and may be involved in the maternal recognition of pregnancy in the ewe.

Animals↗