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Biomedical subjects

B M Bindon

Publications and source records attributed to B M Bindon.

At least 37 records · Page 2Linked to original sources
PubMed1985

Ovarian follicular populations and preovulatory enlargement in Booroola and control Merino ewes.

To investigate the factors contributing to the different ovulation rates observed in two strains of sheep (Booroola 5.2, Merino 1.2), in-vivo monitoring of follicular kinetics followed by histological examination of both ovaries was performed during the late luteal and follicular phases. Ewes of both strains were either ovariectomized at Day 13, or had the 3 largest follicles of each ovary ink-labelled at Day 13 and were ovariectomized at Day 15, or had the 3 largest follicles of each ovary ink-labelled at Days 13 and 15 and were ovariectomized 16 h after the beginning of oestrus (N = 6 per time per strain). In another experiment, the age effects on the follicular populations of these two strains were also studied. There were 2-4 times more primordial follicles and 1.5-2 times more preantral follicles in the ovaries of Booroola than in control Merino ewes, although the number of antral follicles was the same. The percentage of normal follicles in this population was higher in Merino than Booroola ovaries. In Booroola ewes, there was no correlation between the number of antral follicles per ovary and the ovulation rate at the previous cycle (r = 0.22). This suggests that follicle numbers do not play a key role in the high ovulation rate of the Booroola strain. The number of follicles initiating growth from the primordial pool, the number of growing follicles disappearing at the preantral stage, the pattern of antrum development, granulosa cell multiplication and appearance of atresia differed between strains. The reasons for the high ovulation rate of the Booroola strain became clear when preovulatory enlargement was followed by ink labelling. An extended period of time during which recruitment of ovulatory follicles takes place, together with a low incidence of selection and the ability of the follicles to wait for ovulation are the features involved in this high ovulation rate.

Animals↗
PubMed1985

Plasma FSH and LH in prepubertal Booroola ewe lambs.

Basal plasma concentrations (four 30-min samples) and GnRH-induced release of gonadotrophins were measured every 15 days between 30 and 90 days and at 110 days of age in Merino ewe lambs from the prolific Booroola ('B') flock (n = 18-23), the medium prolificacy ('T') flock (n = 14-20), and the 'O' flock (n = 4-8) of low prolificacy. At ages of 30 and 45 days B ewe lambs had mean basal plasma FSH concentrations of 145 and 122 ng/ml which were significantly higher (P less than 0.01) than those seen in T (45 and 53 ng/ml), and O (39 and 38 ng/ml) flock ewes. Between 60 and 110 days of age there were no significant differences between genotypes. The increment in FSH concentrations above basal levels induced by the subcutaneous injection of 100 micrograms synthetic GnRH was only significantly (P less than 0.05) greater in B than T and O genotype ewe lambs at 110 days of age but not at other ages. The basal plasma FSH differences between the B, T and O genotypes at 30 and 45 days of age were not consistently related to the size of litter in which lambs were born. At 30 days of age the mean plasma LH concentration of B, T, and O flock lambs were 2.6 +/- 0.5, 1.2 +/- 0.6 and 0.7 +/- 0.8 ng/ml respectively. These differences were not significant. At later ages there were also no significant differences between the genotypes with respect to basal LH, and the increase in LH induced by exogenous GnRH was always similar for the three genotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1984

Effect of litter size on blood haematocrit and liveweight in Booroola Merino and Merino ewes during pregnancy and the post-partum period.

Blood haematocrit and liveweight were determined throughout pregnancy and the post-partum period in 217 Booroola Merino and Merino ewes in order to relate these parameters to litter size at birth. In pregnant ewes, haematocrit declined from three until five months gestation, rose immediately after parturition then declined until two months post-partum. During the third to fifth month of gestation, haematocrit decreased in proportion to litter size. Nonpregnant ewes, measured at similar intervals, did not show the same pattern. Haematocrit of nonpregnant animals was higher than that of triplet-bearing ewes at three, four and five months gestation, but was only significantly different to single- and twin-bearing ewes at five months. The liveweight of pregnant ewes increased up to parturition and then declined until two months post-partum. The liveweight of nonpregnant ewes increased over the experimental period. It was concluded that the number of foetuses a ewe carried had significant effects on the decline in haematocrit during pregnancy. Haematocrit was not a precise indicator of litter size in sheep. Haematocrit, ewe liveweight and ovulation rate together in a multiple regression only accounted for 37% of the variation in litter size.

Journal Article↗
PubMed1984

Reproductive biology of the Booroola Merino sheep.

This paper reviews the genetic and physiological characteristics of the Booroola Merino, one of the four most prolific sheep breeds in the world, and which was acquired by CSIRO in 1958 from a commercial sheep property, 'Booroola', Cooma, N.S.W. The exceptional prolificacy of this genotype--e.g. mean flock ovulation rate in 1982 of 4.2 (range 1-10) and mean litter size of 2.5 (range 1-7)--is largely attributable to a single gene (F) of uncertain origin which increases ovulation rate. Crosses of the Booroola with other Merinos produce progeny which have a 47-87% increase in ovulation rate, a 45-56% increase in litter size at birth, and a 1-33% reduction in lamb survival relative to control Merinos. This represents a 16-37% increase in the number of lambs weaned per ewe joined in favour of the Booroola crosses. The exact site of action of the F gene is not well established, although it is expressed primarily at the ovary, where more than the normal number of follicles mature and ovulate each oestrous cycle. This may result from some abnormality of the Booroola follicle itself or it may reflect differences in Booroola gonadotrophin secretion. There is some evidence that Booroola ewes have elevated plasma concentrations of follicle stimulating hormone (FSH) early in life and during the oestrous cycle, and that FSH concentrations in the pituitary gland and urine of the adult ewe are also high. These elevated FSH levels in the adult are attributed to an ovarian feedback deficiency, probably because the inhibin content of the Booroola ovary is only one-third that of normal Merino ovaries. The low inhibin content appears to be due to Booroola follicles having significantly fewer granulosa cells than control Merinos. Analogous studies of the prolific D'man sheep of Morocco point to FSH as the main correlate of prolificacy. The testis growth rate, testis size and total daily production of spermatozoa of the Booroola ram are similar to those of normal Merinos, as also are the endocrine characteristics of adult rams. The Booroola gene's expression is evidently sex-limited. Several theories concerning the mode of action of the F gene are being tested.

Androgens↗
PubMed1984

Pituitary gonadotrophins in Booroola and control Merino sheep.

Pituitary content of FSH and LH, using radioreceptor assay methods, was determined in control and Booroola Merino ewes on the 3rd day of the oestrous cycle and in adult rams slaughtered in winter. Significantly more pituitary FSH (as per gland or per g wet wt) was found in the Booroola than in the control ewe. No significant differences were found in LH content although the difference in FSH/LH ratio between Booroola and control ewes was significant (P less than 0.001). Pituitary FSH content was similar in the rams of the two genotypes. A good correspondence between FSH values by the radioreceptor assay and by radioimmunoassays using anti-ovine and anti-human serum was observed for the Booroola ewes. However, radioimmunological estimates of FSH activity were significantly higher than radioreceptor estimates in control ewes and in Booroola and control rams in which the pituitary FSH values were 5-6% of that of the ewe. This over-estimation is attributed to differences in specificity between methods. Fractionation of pituitary extracts by electrofocussing indicated a similar pI profile of FSH for ewes and rams of both genotypes. It is concluded that quantitative rather than qualitative differences in pituitary FSH occur in Booroola and control Merino ewes. It is suggested that increased FSH levels contribute to the hormonal basis for the increased ovulation rate of the Booroola Merino.

Animals↗
PubMed1984

Preovulatory LH characteristics and time of ovulation in the prolific Booroola Merino ewe.

In 4 separate experiments involving 133 ewes the timing of the onset of the LH discharge relative to the onset of oestrus was compared in prolific Booroola Merinos and in other Merinos of low ('C' and 'O' genotypes) and medium ('T' genotype) prolificacy. Despite different average ovulation rates of 3.05, 1.85, 1.18 and 1.37 for Booroola, 'T', 'O' and 'C' ewes, respectively, there were no consistent differences in the time of the LH discharge which occurred on average 4.5 h after the onset of oestrus. Time of ovulation was studied, in two experiments involving 430 Booroola, 'T', 'O' and 'C' ewes, by laparoscopic ovarian examination of subsamples of ewes at 20, 24, 28 or 32 h after onset of oestrus. Ovulation occurred significantly (P less than 0.001) earlier (7.5 h) in Booroola ewes than in those of the other genotypes.

Animals↗
PubMed1983

Ovarian follicles of new-born Merino lambs from genetic lines which differ in fecundity.

Ovaries were obtained from 78 new-born lambs (12 singletons, 25 twins, 28 triplets, 10 quadruplets and 3 quintuplets) from flocks selected for (T902, T903 and Booroola) or against (O) multiple births. Sections of the ovaries were examined with a projection microscope and the numbers of all types of follicles were estimated. There were no differences between genetic lines in the number of primordial follicles, after adjustment for litter size and sire; however, there were significantly more of these follicles in single-born lambs than in lambs born in litters of two or more within genetic lines. The number of vesicular follicles was lower in Booroola than in O lambs.

Animals↗
PubMed1983

Plasma luteinizing hormone and testosterone concentrations in different breeds of young beef bulls in the tropics.

Plasma concentrations of luteinizing hormone (LH) and testosterone were measured at 3, 8, and 11 months of age in 48 Africander cross (AX), 24 Brahman cross (BX), 21 Hereford-Shorthorn, selected (HSS) and 14 Hereford-Shorthorn, random-bred (HSR) bulls. In all breeds plasma LH was lower (P less than 0.01) at 8 months (1.7 ng/ml) than at 3 months (2.6 ng/ml) or at 11 months (2.6 ng/ml). Over all ages there were no differences among breeds in mean plasma LH (AX 2.4, BX 2.4, HSS 1.8, HSR 2.2 ng/ml) and no breed X age interactions. In contrast, plasma testosterone increased significantly (P less than 0.01) with age at a faster rate in the AX breed, resulting in a significant (P less than 0.05) breed X age interaction. Testosterone concentrations, though similar among breeds at 3 months of age (0.45 ng/ml), were much higher (P less than 0.01) by 11 months in AX (2.56 ng/ml) than in BX (1.30 ng/ml), HSS (0.78 ng/ml) or HSR (0.66 ng/ml) bulls. Although LH did not differ among the breeds studied, the more pronounced increase in testosterone with age in the Africander cross bulls is consistent with the higher level of fertility commonly observed in this breed when compared to Brahman cross and Hereford-Shorthorn breeds during natural mating in Queensland.

Aging↗
PubMed1983

Ovarian inhibin content and sensitivity to inhibin in Booroola and control strain Merino ewes.

The inhibin content of ovaries collected from highly fecund Booroola Merino ewes was only one third that of control Merino ewes. Ovariectomized ewes of both strains were treated with charcoal-treated ovine follicular fluid for 2 days. A dose-dependent effect on plasma FSH was observed: maximum FSH suppression was observed on the day after the last injection of follicular fluid. Ewes receiving the highest dose of follicular fluid (total dose 72000 units of inhibin) had FSH levels depressed to only 8% of pre-treatment levels. Booroola ewes showed FSH suppression 1 day earlier than control ewes but otherwise the responses of the two strains to follicular fluid were similar. Plasma LH levels were only slightly depressed with the highest dose of follicular fluid. These results suggest that the feedback relationship of inhibin and FSH in Booroola ewes may be set differently from that in control ewes and this may contribute to the difference in ovulation rate between ewes of the two genotypes.

Animals↗
PubMed1979

Periovulatory gonadotrophin and ovarian steroid patterns in sheep of breeds with differing fecundity.

Plasma hormone concentrations before and during luteolysis (induced by injection of a prostaglandin analogue on Day 10 or 11 of the cycle), during the period of preovulatory follicle growth and ovulation were examined in sheep with known differences in ovulation rate (Romanov, Préalpes, Romanov x Préalpes cross, Ile de France). The number of CL at the time of treatment and the ovulation rate in the ensuing cycle were established by endoscopy. Plasma concentrations of FSH, LH, progesterone and total oestrogen were measured by radioimmunoassays in the 3 days before PG injection, then hourly for the 24 h after PG injection and 2-hourly for a further period up to about 100 h after PG injection. The onset and duration of oestrus were also recorded. Although breed differences were observed for many of the features studied, only the intervals between oestrus and the LH peak and between PG injection and the LH peak were significantly correlated with ovulation rate.

Animals↗
PubMed1976

Solid-phase assay for luteinizing hormone in mouse plasma.

A solid-phase tube assay for measuring LH levels in mouse plasma is described. The assay utilizes an antiserum to ovine LH and ovine LH standards and it measures LH levels in 20 mul of plasma with a sensitivity of less than 0.6 ng/ml. Various parameters affecting the sensitivity and specificity of the assay were investigated. Serial dilutions of plasma from pregnant mice, a pituitary homogenate from mice and plasma from hypophysectomized mice, injected subcutaneously with ovine LH, ran parallel with ovine LH standards in plasma from hypophysectomized mice and plasma with low LH levels from intact mice. Ovine TSH showed about 12% cross reaction in the assay system, whilst rat FSH and prolactin and also ovine FSH, prolactin and GH showed practically no cross reaction. Measurements of plasma LH levels have been made in hypophysectomzied mice after injection with different vehicles containing 10 or 50 mug LH or 50 mug FSH per animal. Daily measurements of LH levels throughout pregnancy in the mouse show a rise in LH level prior to implantationand a further rise around mid-pregnancy which drops off sharply to levels which remain fairly constant until parturition when there is another rise.

Animals↗