Thomas A. Bramley

Specific binding of luteinizing hormone releasing hormone to human luteal tissue

Abstract Homogenates of human luteal tissue bound radioiodinated luteinizing hormone releasing hormone agonist. Specific binding was both time- and temperature- dependent. Native LHRH and two LHRH agonists competed for binding, whereas TRH, somatostatin and oxytocin did not, indicating that the binding sites were specific. The apparent Ka values were 2 × 107M−1 for both LHRH agonists and 106M−1 for native LHRH. This is the first demonstration of specific binding of LHRH to human ovarian tissue. No binding could be detected to ovarian tissue from postmenopausal women.

Specific, high-affinity binding sites for human luteinizing hormone (hLH) and human chorionic gonadotrophin (hCG) in Candida species

The presence of specific binding sites for [125I]-labelled hLH and hCG is described in Candida species. Binding was present in three strains of Candida albicans, and in Candida tropicalis, and was greatest in microsomes, though binding was also present in cytosol fractions. hLH and hCG mutually competed for these binding sites. Other hormones did not bind and did not compete for hLH binding sites. Scatchard plots showed two classes of binding sites, one with high affinity, low capacity and the other with lower affinity, high capacity binding in both microsomes and cytosol. This is the first report of specific binding sites for mammalian peptide hormones in a yeast.

Subcellular distribution of a gonadotropin-induced form of mouse ovarian arian alkaline phosphate

Abstract The subcellular distributions of alkaline phosphatase I (the major activity of prepubertal mouse ovaries) and alkaline phosphatase Ib (a kinetically distinct isoenzyme induced in large amounts by injection of human chorionic gonadotropin and discontinous density gradient centrifugation of ovarin homogenates from control and gonadotropin-treated mice. The distributions of the two alkaline phosphatases were alike and were similar to those of nucleotidase, Mg 2+ -dependent ATPase and Co 2+ -stimulated naphthylamidase activities, suggesting that they were associated with plasma-membrane vesicles.

Effects of infusion of GnRH pulses and level of body condition on ovarian function in postpartum beef cows

An experiment was conducted to test the hypothesis that postpartum anoestrus in beef cows is prolonged in cows in low body condition (BC) because they have a reduced LH pulse frequency compared with cows in high BC. Thirty-six multiparous Blue-Grey (White Shorthorn × Galloway) cows were fed so that they calved in either low (L) (BC score 2.07; SE 0.05; n = 24) or high (H) (BC score 2.81; SE 0.08; n = 12) body condition. They were then fed to maintain BC after calving. Twelve L cows were infused (i.v.) with 2 μg GnRH in 2 ml saline every 2 h from 5 to 7 weeks postpartum (LG) while the remaining L cows and all H cows were infused with saline only (LS and HS). Ovulations, as indicated by the presence of a morphologically normal corpus luteum, were recorded in one, one and ten of the cows of the LS, HS and LG groups, respectively. Mean LH concentrations and pulse frequencies were not affected by either GnRH treatment or BC but mean LH pulse amplitudes were lower (P < 0.05) in LG and LS cows than in HS cows at Week 5 and in LG cows at Week 6. At Week 7 postpartum, the numbers of small (3–7.9 mm diameter) and large (≥ 8 mm diameter) ovarian follicles, mean granulosa cell numbers per follicle and mean concentrations of LH receptors (pg per mg thecal and granulosa tissue) were not affected by GnRH treatment or BC. Granulosa cells from oestrogen active follicles of HS and LG cows secreted more oestradiol in vitro (P < 0.01) than cells from LS cows. However, there were no significant differences with treatment in the intrafollicular concentrations of oestradiol, testosterone or insulin-like growth factor-1. It was concluded that, since infusion of GnRH pulses enhanced both follicular steroidogenesis and the incidence of ovulation in low BC cows, the frequency of GnRH pulses is one determinant of follicle development in the postpartum cow. While H cows also exhibited a degree of enhancement of oestradiol synthesis by the granulosa cells of oestrogenic follicles, compared with L cows there was no difference in the LH pulse frequency or in the incidence of ovulation. It is concluded that there may be a threshold level of oestrogen synthesis by granulosa cells below which the final stages of follicle maturation and ovulation cannot be initiated, or that a high rate of oestradiol synthesis by this tissue is not the only factor mediating the effects of body condition on follicle development in the postpartum cow.

Specific binding sites for human luteinizing hormone in Neurospora crassa and Saccharomyces cerevisiae

Specific binding sites for 125 I-labelled human luteinizing hormone (hLH) were detected in microsomal and cytosolic fractions from Saccharomyces cerevisiae, Neurospora crassa and a wall-less (‘slime’) mutant of N. crassa . Scatchard analysis of hLH-binding to microscomes revealed the presence of both high affinity ( K a of 60–70 × 10 10 m −1 ) and lower affinity ( K a of 1·3–1·9 × 10 10 m −1 ) binding sites in each organism. 125 I-hLH binding to both S. cerevisiae and N. crassa (wild type) microsomes was inhibited by low concentrations of Ca 2+ and Mg 2+ (30 μ m ), and by higher concentrations of Na + and K + (40 m m ). Binding was also inhibited, in dose-dependent fashion, by partially-purified preparations of hLH and hCG. In contrast, highly purified hCG preparations were much less potent, though they strongly inhibited hLH binding to sheep corpus luteum LH-receptors. Moreover, high-purified hCG β-core protein inhibited hLH binding to S. cerevisiae and N. crassa microsomes in a dose-dependent manner, but had no effect on hLH binding to sheep luteal receptors. The properties of the S. cerevisiae and N. crassa LH-binding sites are similar to those of binders detected previously in Candida albicans . Thus, interactions between hLH-like molecules and their receptors may have a widespread distribution in the Ascomycotina and Deuteromycotina.

Inactivation of porcine corpus luteum lutropin receptors by a microsomal enzyme: Activation in ageing and regressing corpora lutea

The binding of 125I-labelled human choriogonadotropin (hCG) to homogenates of porcine corpora lutea showed a marked departure from ideal behaviour, due to a time- and temperature-dependent inactivation of both free hormone and unoccupied receptors. Occupied receptors were not affected. Lutropin (LH)-receptor-inactivating activity was detected after preincubation of homogenates, particulate fractions and microsomes, but little activity could be demonstrated in cytosol fractions. Inactivation was dependent on the temperature and pH of preincubation, and on tissue concentration: LH-receptor inactivation was first-order with respect to preincubation time. Lutropin-receptor-inactivating activity was low in early-luteal and mid-luteal phase in pig corpora lutea, but was increased significantly in late-luteal and regressing corpora lutea.

Specific Binding of Luteinizing Hormone Releasing Hormone to Human Luteal Tissue

Homogenates of human luteal tissue bound radioiodinated luteinizing hormone releasing hormone agonist. Specific binding was both time- and temperature-dependent. Native LHRH and two LHRH agonists competed for binding, whereas TRH, somatostatin and oxytocin did not, indicating that the binding sites were specific. The apparent Ka values were 2 X 10(7)M-1 for both LHRH agonists and 10(6)M-1 for native LHRH. This is the first demonstration of specific binding of LHRH to human ovarian tissue. No binding could be detected to ovarian tissue from postmenopausal women.