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Biomedical subjects

J K Findlay

Publications and source records attributed to J K Findlay.

At least 163 records · Page 9Linked to original sources
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

Relationships between aromatase activity, follicular fluid oestradiol-17 beta and testosterone concentrations, and diameter and atresia of individual ovine follicles.

Aromatase activity was measured in granulosa cells using a 1-h in-vitro assay. This activity correlated with the concentration of oestradiol-17 beta and the ratio of oestradiol-17 beta to testosterone in follicular fluid of individual follicles ranging from 1.5 to 7.0 mm diameter. These data show an 8-10-fold difference in aromatase activity between small and large follicles and that aromatase activity per cell increased in small non-atretic follicles (less than 3.5 mm) whereas it remained relatively constant in large nonatretic follicles (greater than or equal to 3.5 mm). Aromatase activity was much lower in follicles at more advanced stages of atresia. Atresia was assessed using the morphological and the morphometric methods (% of maximum number of granulosa cells/follicle). Although the morphological method of assessment was preferable to the morphometric method, it did not differentiate a decrease in aromatase activity as a very early event in the atretic process. We believe this is due to the inability of these methods to detect follicles in the initial stages of atresia.

Animals↗
PubMed1983

Large luteal cells the source of luteal oxytocin in the sheep.

To determine the cellular origin of oxytocin produced by the cyclical corpus luteum (CL) of the sheep, enriched fractions of enzymatically dispersed small and large luteal cells from 12 CL were prepared on a Ficoll 400 gradient. Oxytocin was measured by RIA. Large luteal cells contained 1.08 +/- (SD) 0.70 fg/cell oxytocin, which was congruent to 30 X the content of small luteal cells. Endothelial cells contained little if any oxytocin. During a 12-h incubation, large luteal cells produced 0.28 fg/cell.h oxytocin: small luteal cells did not produce measurable amounts of oxytocin. It is concluded that the large luteal cells are the source of the oxytocin produced by the CL of the sheep.

Animals↗
PubMed1983

Blood flow in the ovary and adjacent structures of the non-pregnant sheep.

Blood flow of the ovary, vascular pedicle and oviduct was measured in anaesthetized non-cycling and cycling ewes by timed collection of ovarian venous blood. The degree of arterio-venous shunting across the ovary and pedicle was estimated both in vivo and in vitro by perfusing the tissues with 15 +/- 5 micrometers radioactive microspheres. The mean ovarian blood flow in non-cycling animals was 1.9 ml/min, which was 51% of blood flow in the ovarian vein. In cycling animals ovarian blood flow at midcycle was 2.9 ml/min (66% of ovarian venous flow) in non-luteal ovaries and 4.3 ml/min (79% of venous flow) in luteal ovaries. The degree of arterio-venous shunting was low in all stages of the cycle (1.0-2.6% across ovary + pedicle). The degree of shunting was also found to be very small in vitro (0.007-1.38%) in both non-luteal and luteal ovaries. A considerable number of microspheres was entrapped in the vascular pedicle of the ovary indicating the presence of an extensive capillary bed. There was an inverse relationship between blood flow in the ovary and flow in the vascular pedicle. Alterations in distribution of blood flow between the ovary and adjacent structures supplied by the ovarian artery may be of functional significance in allowing rapid changes in ovarian blood flow. The results of the present study indicate that changes in ovarian blood flow during the oestrus cycle are not caused by an action on arterio-venous shunt vessels.

Animals↗
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↗
PubMed1983

Inhibin in individual ovine follicles in relation to diameter and atresia.

Inhibin activity was measured by bioassay in follicular fluid of 99 individual ovine follicles ranging from 1 . 4 to 6 . 8 mm diameter (used to calculate volume) and in various stages of atresia. Treatment of samples before assay with charcoal concentrations of greater than 1 mg/ml resulted in significant loss of inhibin activity. The inhibin content of follicular fluid from individual follicles varied with follicular fluid volume but not with the degree of atresia, as assessed by morphological criteria. Inhibin concentration was not related to atresia, but was correlated with follicular fluid volume. However, aromatase activity in granulosa cells and oestradiol-17 beta concentration of follicular fluid, considered to be good indices of atresia, were highly correlated with both inhibin content and concentration in follicles greater than or equal to 3 . 5 mm diameter. Inhibin in ovine follicular fluid shows marked variation between follicles and it is suggested that this reflects a combination of the number and activity of granulosa cells within the follicle and the exit rate of inhibin from the follicle.

Animals↗
PubMed1983

LH release and luteal function in post-partum acyclic ewes after the pulsatile administration of LH-RH.

The administration of LH-RH in a pulsatile regimen (100 ng i.v./h for 48 h) to acyclic ewes 26-30 days post partum increased plasma LH concentrations, and both the frequency and amplitude of plasma LH pulses. In 12/14 ewes these increases were followed by plasma LH surges similar to the preovulatory surges observed in 10 control cyclic ewes. Subsequent luteal function in the post-partum ewes was deficient. Plasma progesterone was detected in 7/12 post-partum ewes showing plasma LH surges. The concentrations were lower (1.3 +/- 0.2 ng/ml) and detected for shorter periods (3-10 days) than in cyclic ewes (2.4 +/- 0.2 ng/ml, 12/15 days). In the post-partum ewes the increases in plasma LH concentrations before the LH surge were higher but of shorter duration than in the cyclic ewes. The inadequate luteal function in the post-partum ewes could therefore have been due to inappropriate LH stimulation of the ovary before the LH surge.

Animals↗
PubMed1983

Prostaglandin F and 13,14-dihydro-15-keto prostaglandin F in the endometrium and uterine flushings of sheep before implantation.

The concentrations of prostaglandin F (PGF) and its major metabolite, 13,14-dihydro-15-keto prostaglandin F-2 alpha (PGFM), were measured in caruncular and intercaruncular endometrium of pregnant and non-pregnant ewes on Days 9, 11, 13 and 15 after mating (Day 0) and related to the content of PGF and PGFM in the uterine flushings. The tissue concentrations of PGF and PGFM increased with time after mating particularly on Days 13 and 15 and to a greater extent in pregnancy. However, the ratio of PGF to PGFM remained constant at 0.7, except on Day 15 in non-pregnant endometrium when it fell to 0.3 (P less than 0.05), suggesting that synthesis rather than metabolism was limiting tissue concentrations of PGs. The changes in tissue concentrations of PGF and PGFM were reflected in the contents of PGF and PGFM in the uterine flushings of non-pregnant, but not pregnant ewes. Pregnant ewes had relatively more PGF and less PGFM than did non-pregnant ewes on Day 15. Moreover, there was always 5-10-fold less PGFM than PGF in the uterine flushings. It is concluded that the increase in PG in the uterine lumen in pregnancy has its origin in the blastocyst, and that pregnancy may be associated with an increase in the synthesis and retention of PGs in the endometrium, rather than a redistribution towards the uterine lumen away from the uterine venous drainage.

Animals↗
PubMed1983

Progesterone production in vitro by small and large ovine luteal cells.

Corpora lutea from cyclic ewes were dissociated by collagenase digestion and trypsin/EGTA treatment. Enriched fractions of endothelial cells, small luteal cells and large luteal cells were prepared on a stepped gradient of Ficoll 400. Progesterone was measured by radioimmunoassay and the results corrected so that progesterone production by each cell type could be determined. Endothelial cells did not produce significant amounts of progesterone, with or without LH stimulation, and endothelial cell contamination of small and large luteal cell fractions did not influence progesterone production by these fractions. Mean +/- s.e.m. basal progesterone production (n = 10) by large luteal cells was greater (P less than 0.001) on a per cell basis than that by small luteal cells (1.16 +/- 0.16 compared with 0.25 +/- 0.06 pg/h/cell). However LH, which stimulated a maximal 3-4-fold increase in progesterone production by small luteal cells (LH ED50 = 0.14 ng/ml), had no significant effect on production by large luteal cells, when contamination by small luteal cells was taken into account. The response of small luteal cells was specific to LH, other hormones having had no significant effect. Basal progesterone production by small luteal cells (0.12 +/- 0.03 fg/h/micron3) calculated per unit volume of cell was not significantly different from that of large luteal cells (0.17 +/- 0.02 fg/h/micron3). After LH stimulation, small luteal cells produced more progesterone than did large luteal cells (0.40 +/- 0.09 compared with 0.18 +/- 0.03 fg/h/micron3) (P less than 0.05). When the amounts of progesterone produced per cell were multiplied by the absolute numbers of large luteal (1 X 10(7] and small luteal (5 X 10(7] cells in the intact corpus luteum, basal progesterone production by large luteal cells (11.6 +/- 1.6 micrograms/h) was similar to that by small luteal cells (12.3 +/- 3.0 micrograms/h). However, under LH stimulation, progesterone production by the small luteal cell type (39.9 +/- 9.5 micrograms/h) was approximately 3 times greater than that by the large luteal cell type (12.3 +/- 1.6 micrograms/h) (P less than 0.05). We therefore conclude that small luteal cells may be the principal source of luteal progesterone production in the sheep.

Animals↗
PubMed1982

Glucocorticoid receptors in epithelial cells isolated from the mammary glands of pregnant and lactating rats.

We have isolated epithelial cell clusters from mammary glands of pregnant and lactating rats by collagenase-hyaluronidase-deoxyribonuclease digestion, followed by Ficoll density-gradient centrifugation. Clusters of greater than 90% viable cells were identified by light microscopy as essentially devoid of other cell types; the integrity of their subcellular organelles verified by electron microscopy. Binding characteristics of the synthetic glucocorticoid [3H]dexamethasone were studied in cytosols prepared from isolated cell clusters. Cytosols from both pregnant and lactating rats bound [3H]dexamethasone with high affinity to a single class of low capacity binding sites. In both types of cytosol the dissociation constant (Kd 4 degrees C approximately/nM) of the binding was similar; the number of sites per cell in lactating rats was approximately double that in pregnant rats. The specificity of binding was typical of a classical glucocorticoid receptor, with a hierarchy of affinity by competition studies dexamethasone greater than progesterone greater than aldosterone much much greater than testosterone = estradiol. In particular, no difference in progesterone affinity for these glucocorticoid receptors was seen between pregnancy and lactation. This suggests that reported differences in inhibitory action of progesterone, pregnancy versus post-partum, are not glucocorticoid-receptor mediated.

Aldosterone↗
PubMed1982

Analysis of androgen action on pituitary gonadotropin and prolactin secretion in ewes.

To study the role of androgens in the control of gonadotropin and prolactin secretion in ther ewe, we have characterized androgen receptors in pituitary cytosol, and investigated the effect of androgens on pituitary hormone release in vivo and in vitro. High affinity, low capacity receptors, with an affinity for methyltrienolone (R1881) greater than 5 alpha-dihydrotestosterone (5 alpha-DHT) greater than testosterone (T) much greater than androstenedione (A4), estradiol-17 beta (E2) and progesterone (P), were identified in pituitary cytosol. Addition of 1 nM 5 alpha-DHT, but not A4, inhibited luteinizing hormone (LH) release from pituitary cells in vitro, induced by 10(10) to 10(-7) M luteinizing hormone releasing hormone (LHRH). The release of follicle-stimulating hormone (FSH) with 10(-9) M LHRH was inhibited when cells were incubated with 1 nM 5 alpha-DHT. 5 alpha-DHT had no effect when higher or lower doses of LHRH were used. In ovariectomized ewes, neither an i.v. injection of 1 mg, nor intracarotid injections of up to 1 mg, 5 alpha-DHT affected plasma LH, FSH or prolactin levels, despite dose-related increases in plasma 5 alpha-DHT levels. Daily or twice daily i.m. injections of 5 mg 5 alpha-DHT in oil did not affect LH or FSH levels, but daily injections of 20 mg significantly reduced plasma LH levels within 4 days and plasma FSH levels within 6 days. Thus, despite the presence of androgen receptors in the ewe pituitary, we conclude that androgens per se are of minimal importance in the regulation of pituitary LH, FSH and prolactin secretion in the ewe. The low binding affinity of A4 and the lack of its effect on hormone secretion in vitro suggests that A4 may act as an estrogen precursor rather than an androgenic hormone. The function of the pituitary androgen receptor remains to be established.

Androgens↗
PubMed1982

Successful fertilisation of human oocytes in vitro: concentration of estradiol-17 beta, progesterone and androstenedione in the antral fluid of donor follicles.

Oocytes and matched samples of follicular fluid were obtained from 156 pre-ovulatory follicles in 125 women 26--36 h after either administration of hCG or the onset of an endogenous LR surge. Concentrations of estradiol-17 beta (E2), progesterone (P) and androstenedione (A4) in the fluid of individual donor follicles were measured and related to the success of fertilisation of oocytes in vitro and the incidence of pregnancies after embryo transfer. Oocytes which gave rise to successful pregnancies were obtained from follicles which contained greater concentrations of E2 and a higher ratio of E2:P than did oocytes from which pregnancy did not result. These data provide direct evidence in support of the hypothesis that estrogenic follicles are the sole source of ova which undergo fertilisation and subsequently give rise to pregnancy in women.

Androstenedione↗
PubMed1982

Oestrogen receptors and protein synthesis in caruncular and intercaruncular endometrium of sheep before implantation.

The rate of protein synthesis was higher in caruncular (P less than 0.05) and intercaruncular endometrium (P less than 0.01) of pregnant compared to non-pregnant ewes on Day 11 (Day 0 = day of oestrus), but not on Days 9, 13 and 15. Cytosolic oestrogen receptor concentrations (nmol/mg protein) were lower in caruncular endometrium of pregnant ewes than in non-pregnant ewes on Days 9 (P less than 0.02), 13 (P less than 0.05) and 15 (P less than 0.001) but not on Day 11. In intercaruncular endometrium, the receptor values were lower on Day 15 (P less than 0.02) of pregnancy compared to non-pregnancy, but not on the other days. The dissociation constant (0.75-2.55 x 10(-10) M) of oestradiol-17 beta for cytosolic receptors was similar in both tissues, regardless of pregnancy status or day of sampling. The rate of protein synthesis was generally higher in intercaruncular endometrium whereas cytosol receptor concentrations were higher in caruncular endometrium. When the blastocyst was confined to one uterine horn on Day 2 in another group of ewes, there was a decrease in nuclear (P less than 0.05), cytosolic (P less than 0.05) and total (P less than 0.05) oestrogen receptors only in caruncular endometrium in the pregnant horn on Day 15. There were no difference in the proportions of receptors localized in nuclear fractions or in the rate of protein synthesis in either endometrial tissue from the pregnant or the non-pregnant horn. We conclude that the ovine blastocyst is capable of influencing oestrogen receptors levels in caruncular and intercaruncular endometrium by a local action as early as Day 9, well before endocrine recognition of pregnancy on Day 12 and attachment on Day 15.

Animals↗
PubMed1982

Relationship between pituitary nuclear oestrogen receptors and the release of LH, FSH and prolactin in the ewe.

Ovariectomized ewes were given a single injection (i.v.) of 100 micrograms oestradiol-17 beta. Nuclear oestrogen receptor values in the pituitary, as a function of total receptor concentrations, were 3.0 +/- 1.0% in controls, 56.0 +/- 5.4% at 1 h (P less than 0.001) and 6.5 +/- 2.1% at 6 h (P less than 0.05) after oestradiol injection. There was a fall in plasma LH values from 5.7 +/- 1.0 (preinjection) to 2.1 +/- 0.3 ng/ml (P less than 0.01) 4-6 h after oestradiol. At 13-21 h after injection plasma levels increased to 37 +/- 8 ng/ml (P less than 0.001). Plasma FSH levels declined from 840 +/- 18 to 506 +/- 48 ng/ml after 20-22 h (P less than 0.001). Plasma prolactin concentrations fell from 90 +/- 16 ng/ml before injection to 29 +/- 9 ng/ml at 1 h (P less than 0.05), and then rose to a maximum of nuclear compartmentalization of oestrogen receptors after a bolus injection of oestradiol was associated with the feedback effects of oestradiol on LH, FSH and prolactin release.

Animals↗
PubMed1982

Effects of 2-hydroxyoestradiol-17 beta on plasma luteinizing hormone, follicle-stimulating hormone and prolactin, and nuclear translocation of pituitary oestrogen receptors in ovariectomized ewes.

The ability of oestradiol-17 beta (OE2) and 2-hydroxyoestradiol (2OH-OE2) to translocate pituitary oestrogen receptors to the nuclear compartment and to affect plasma concentrations of LH, FSH and prolactin was studied in ovariectomized ewes. Mean (+/- S.E.M.) nuclear oestrogen receptor levels (% of total pituitary oestrogen receptors) after intracarotid injections of 1.25 micrograms OE2, 400 micrograms 2OH-OE2 or vehicle were 8.7 +/- 2.3, 16.9 +/- 3.2 and 0.8 +/- 0.1% respectively. Whereas 1.25 or 12.5 micrograms OE2 significantly lowered plasma LH and FSH, 400 micrograms 2OH-OE2 did not affect plasma LH or FSH levels. Injection of 4000 micrograms 2OH-OE2 however, significantly affected plasma LH and FSH. Plasma prolactin levels were not significantly affected by the treatments. These data indicate a discrepancy between oestrogen receptor occupancy and effects on gonadotrophin and prolactin secretion after injection of catechol oestrogen.

Animals↗