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Biomedical subjects

K E Turnbull

Publications and source records attributed to K E Turnbull.

8 recordsLinked to original sources
PubMed1987

Effect of mouse epidermal growth factor on plasma concentrations of FSH, LH and progesterone and on oestrus, ovulation and ovulation rate in merino ewes.

The 24 h i.v. infusion of Merino ewes with 60 or 100 microgram mouse epidermal growth factor (EGF)/kg body weight on Days 4, 9 or 14 of the oestrous cycle decreased the strength of wool attachment and caused marked changes in subsequent reproductive performance. In ovaries removed 2 days after EGF treatment all follicles greater than or equal to 0.6 mm diameter were atretic. After 7 days either a normal pattern of atresia or no atresia was evident while after 12 days the pattern of follicular atresia was similar to that in controls. Irrespective of stage of cycle EGF caused dose-dependent increases in plasma FSH concentrations that persisted for up to 14 days. Changes in plasma LH concentrations were generally similar after infusion on Days 4 and 14, but were smaller and shorter-lived after infusion on Day 9. Irrespective of dose, the infusion of EGF on Days 4 and 14 caused immediate luteolysis then the formation of a luteinized follicle in many ewes. Most ewes treated on Day 4 returned to oestrus between Days 17 and 21 with the same ovulation rate (1.3) as the controls. Of those infused on Day 14 oestrus occurred about a cycle length later than expected and their ovulation rate then (1.9) was also similar to that of the controls (1.7). Luteal function was not affected in ewes infused on Day 9, and most returned to oestrus between Days 17 and 20 with an ovulation rate of 3.2. Fertile rams were not placed with the ewes until after the differences in ovulation rate had been observed. Mating occurred generally 2-4 weeks after treatment, and there were no differences between EGF-treated and control ewes in fertility or fecundity. The results are interpreted as indicating that mouse EGF induces ovarian follicular atresia but has differential effects on luteal function according to the stage of the oestrous cycle at which it is given. As a consequence of these two effects, which lead to differential changes in gonadotrophin secretion, ovarian function may be temporarily impaired, little affected or improved.

Animals↗
PubMed1981

Ovarian function in the ewe after active immunization against testosterone.

The secretion rates of testosterone measured during the last half of the oestrous cycle in 2 Merino crossbred ewes with utero-ovarian autotransplants were 1.95 +/- 0.34 ng/min and 2.48 +/- 0.63 ng/min. The secretion rate of testosterone was not correlated with the secretion rate of oestradiol or androstenedione in either ewe. Welsh Mountain ewes were actively immunized against testosterone-3-(O-carboxymethyl)-oxime-bovine serum albumin (testosterone-3-BSA) or BSA alone (controls). Immunization against testosterone-3-BSA (5 ewes) resulted in anovulation (2 ewes) and the disruption of oestrous cycles and irregular ovulations (2 ewes). The ovaries showed morphological and endocrinological evidence of over-stimulation. Numerous large non-atretic follicles were present and in those ewes still ovulating the numbers of corpora lutea (ovulation rate) were increased. The concentrations of androstenedione and of oestradiol in the ovarian venous plasma were also markedly increased when compared to those in control ewes. The plasma binding capacity for steroids and the jugular venous concentrations of steroids were higher in immunized ewes. The binding capacity of follicular fluid for testosterone was similar to that of jugular venous plasma from the same ewe. These results show that immunization against testosterone-3-BSA leads to a disruption of ovarian cycles and ovarian over-stimulation.

Androstenedione↗
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 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 relation between patterns of ovarian follicle growth and ovulation rate in sheep.

The number and growth rate of follicles within classes based on granulosa volume were determined for ovaries taken from groups of 4-5-year-old, fine-wool Merino ewes drawn at different times of the year from a single strain flock maintained at Armidale, N.S.W. The breeding season of the flock normally extends from February to October and the mean ovulation rate rises from about 0.5 in February to about 1.8-1.9 during April-May. Ewes sampled when they were anoestrous or had one (single-ovulatory) or two (twin-ovulatory) recent corpora lutea did not differ in respect to the mean total number of ovarian follicles, the mean number of follicles in individual classes, the time for follicles to complete their rapid growth stage, or the incidence of follicle atresia. However, the ovaries of twin-ovulatory ewes contained significantly more follicles in the two terminal classes within the rapid growth stage than did the ovaries of single-ovulatory or anoestrous ewes (2.2 v. 0.9 and 1.0). This difference was attributed to the differing numbers of follicles per day entering into the rapid growth stage (5.2, 4.5 and 3.7 respectively in twin-ovulatory, single-ovulatory and anoestrous ewes).

Animals↗