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Biomedical subjects

C D Nancarrow

Publications and source records attributed to C D Nancarrow.

At least 55 records · Page 3Linked to original sources
PubMed1981

Termination of early pregnancy in ewes by use of a prostaglandin analogue and subsequent fertility.

Of 87 Dorset ewes injected at 20 to 60 days of pregnancy with either 125 micrograms or 250 micrograms of the prostaglandin F2 alpha analogue, cloprostenol, 72 (83%) were detected in oestrus by teaser rams within 7 days. A total of 60 ewes mated with fertile rams 14 to 28 days after treatment and 36 of these (60%) subsequently lambed. Thirty-eight ewes mated with fertile rams 29 to 56 days after treatment and 30 of these (79%) subsequently lambed. The difference in fertility between the 2 periods was not significant. Six additional ewes which did not respond to the cloprostenol lambed normally within 6 weeks. They were more than 100 days pregnant when treated. In ewes which first exhibited oestrus by 7 days of treatment, plasma progesterone concentrations fell from near 4 ng/ml to 0.6 ng/ml within 48 h of treatment. In ewes not detected in oestrus progesterone concentrations did not decrease to similar low levels (1.4 ng/ml; t-test p less than 0.005). Concentrations in the 6 ewes treated near 100 days of pregnancy dropped from 7.4 to 4.4 ng/ml over 48 h. Overall, the progesterone concentrations indicated that 92% of ewes treated at 20 to 60 days of pregnancy experienced rapid luteolysis in response to the cloprostenol. There were no differences between the 2 doses of cloprostenol in the responses or subsequent fertility of the ewes.

Abortifacient Agents↗
PubMed1980

Growth of Graafian follicles in cows following luteolysis induced by the prostaglandin F2 alpha analogue, cloprostenol.

The ovaries of six multiparous cows 6-8 years old were collected 49-71 h after injection of a synthetic prostaglandin F analogue (cloprostenol) and serially sectioned. All follicles greater than 0.4 mm in diameter were counted and measured. The number of normal follicles ranged from 46 to 360 per cow. Atresia was not seen in follicles of less than 1.7 mm diameter. The number of early atretic follicles ranged from 4 to 20 per cow. The volume and mitotic index of the granulosa tissue was calculated for all follicles. Follicles were then grouped into classes according to granulosa volume, each class having twice the volume of granulosa of the preceding class. In all cows the rate of growth of follicles was slow up to 0.5 mm diameter (class 4). Above this size growth accelerated to a maximum in follicles of 1.2-1.7 mm diameter (class 8) and declined thereafter to a minimum in follicles 8-10 mm in diameter (class 13). Follicles beyond class 13 were not present in any of the ovaries. It was estimated that 22.1 days were required for a follicle to grow from 0.4 mm to 10 mm in diameter (classes 4 through to 13). The present data suggest that the pattern of synchronization of oestrus in cattle treated with cloprostenol may be related to the size of the largest non-atretic follicle present at the time of treatment because of the time required for such a follicle to complete its development.

Animals↗
PubMed1979

Detection of early pregnancy in sheep by the rosette inhibition test.

The rossette inhibition test, an established test for determining the immunosuppressive potential of antilymphocyte serum, has been applied to the serum of sheep after mating. The rosette inhibition titre was much higher (12--26) in 7 sheep which were fertilized and remained pregnant for up to 21 days than in 5 sterile ewes mated with intact rams (8--10). The difference was apparent by 24 h after mating. One ewe had high titres for 6 days after mating but these then dropped and she returned to oestrus; early embryonic loss was suspected. Another ewe which returned to oestrus had consistently low titres. The results indicate that the rosette inhibition test can be used to detect fertilization, early embryonic death and continued pregnancy in sheep.

Animals↗
PubMed1979

Detection of induced death of embryos in sheep by the rosette inhibition test.

The rosette inhibition test has been used to monitor the decrease of an 'early pregnancy factor' in 2 groups of pregnant sheep (19-21 days) in which embryos were removed surgically or by induction of luteolysis with cloprostenol. The rosette inhibition titres of sera taken from sheep of each group declined from high (16-18) to low (8-10) levels within 48 h of treatment. Surgical removal of embryos caused little change in serum progesterone concentration whereas cloprostenol prompted a rapid decrease over the same period. Death of the embryo can therefore be detected by the rosette inhibition test within 48 h of occurrence, but not necessarily by the measurement of progesterone in blood within this period.

Animals↗
PubMed1978

The effect of 2-deoxy-D-glucose on ovarian function of cattle.

The administration of the metabolic inhibitor, 2-deoxy-D-glucose (2DG), to four well fed heifers just before and during the time of expected oestrus, and to another heifer following the removal of the corpus luteum, prevented both the occurrence of oestrus and the formation of corpora lutea in all animals. Plasma progesterone concentrations remained low for at least 10-21 days after the last dose of 2DG. The results suggest that the inhibition of glycolysis is associated with the failure of both oestrus and formation of functional corpora lutea, and they support the hypothesis that hypoglycaemia is the primary biochemical change responsible for infertility induced by acute energy deficiency in lactating cattle.

Animals↗
PubMed1978

Ovarian function in suckling and non-suckling beef cows post partum.

Two groups, each of 7 crossbred beef cows, which were suckling or not suckling calves, were fed a high quality food ad libitum for 3 months post partum. The non-suckling cows experienced regular ovarian cycles from 10--33 days post partum while the suckling cows did not do so until at least 14 weeks post partum. There was little difference between the groups in growth rate or in plasma glucose concentration. The plasma prolactin concentrations in the non-suckling cows showed a seasonal trend which paralleled ambient temperature and daylight hours; in the suckling cows this trend was less evident. Plasma LH concentrations were lower in suckling cows before Day 30 post partum but were similar thereafter. Most suckling cows also failed to experience oestrus or to exhibit LH release in response to an injection of oestradiol benzoate at about 6 weeks post partum. This failure, together with the earlier lower levels of LH in the suckling cows, is considered to be indicative of malfunction of the hypothalamic mechanism normally responsible for the establishment and maintenance of cyclic ovarian function.

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↗
PubMed1977

Secretion of granules by the luteal cells of the sheep and the goat during the estrous cycle and pregnancy.

The fine structure of luteal tissue from sheep and goats at the mid-stage of the estrous cycle and during pregnancy was examined. At the mid-stage of the estrous cycle, when the corpus luteum of both species is secreting progesterone, the ultrastructure of the luteal cells is similar in that granule secretion is prevalent. In late pregnancy, the corpus luteum of the sheep produces very little progesterone and there is an absence of granule secretion. In the pregnant goat, the production of progesterone from the corpus luteum is high and there is plentiful evidence of granule formation and secretion.

Animals↗