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N. Ravindranath and N. R. Moudgal

Summary. Female bonnet monkeys were injected i.v. with 25 μl antiserum to FSH on Days 5, 6 or 7 of the cycle: the length of the luteal phase was shortened but there was no alteration in cycle length. Proven fertile females (N = 6) were caged throughout the period of the experiment (6 cycles) with proven fertile males and treated with 25 μl FSH antiserum on Day 7 of each of 3 successive cycles. Out of 18 cycle exposures during the treatment phase, 17 were ovulatory, but no pregnancies occurred. In the post-treatment phase, 5 monkeys became pregnant within 3 cycle exposures. These results show that it is possible to render female monkeys infertile by creating luteal insufficiency and this can be achieved repeatedly in a reproducible manner by depriving the cyclic females of FSH support on Day 7 of consecutive cycles.

Keywords: monkey; ovary; follicular phase; luteal phase defect; pregnancy

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N. Ravindranath and N. R. Moudgal

Summary. Administration of tamoxifen orally (3 mg/kg/day) during the post-ovulatory period from Days 16 to 20 or from Days 18 to 30 of female bonnet monkeys mated between Days 9 and 14 of the cycle resulted in inhibition of pregnancy establishment in 90–100% of monkeys tested. The pregnancy establishment in control female monkeys after exposure to the male during one ovulatory cycle was 66%. The effect of tamoxifen was not due to interference with luteal function because there was no reduction in serum progesterone concentrations after drug treatment. Exogenously administered progesterone could not reverse the inhibitory effect of tamoxifen on pregnancy establishment. The effect of tamoxifen was dose-dependent. We suggest that tamoxifen could be developed as an effective post-ovulatory contraceptive for regulation of female fertility.

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N. Selvaraj and N. R. Moudgal

The development of a radioreceptor assay (RRA) that can measure serum LH in a variety of species and CG in sera and urine of pregnant women and monkeys is reported. Using sheep luteal membrane as the receptor source and 125I-labelled hLH/hCG as the tracer, dose–response (displacement) curves were obtained using hLH or hCG as standard. The addition of LH-free serum (200 μl per tube) had no affect on the standard displacement curve. The assay is simple, requires less than 90 min to complete and provides reproducible results. The sensitivity of the assay was 0.6 ng hLH per tube and the intra- and interassay variations were 9.6 and 9.8, respectively. Sera obtained from male and female bonnet monkeys (Macaca radiata) and monkey pituitary extract showed parallelism to the standard curve. The concentrations of LH measured correlated with the physiological status of the animals. Sera of rats, rabbits, hamsters, guinea-pigs, sheep and humans showed parallelism to the hLH standard curve indicating the viability of the RRA to measure serum LH of different species. Since the receptors recognize LH and CG, detection of pregnancy in monkeys and women was possible using this assay. The sensitivity of the assay for hCG was 8.7 miu per tube. This RRA could be a convenient alternative to the Leydig cell bioassay for obtaining the LH bioactivity profile of sera and biological fluids.

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RHODA MANECKJEE and N. R. MOUDGAL

Laboratory of Endocrine Biochemistry, Department of Biochemistry, Indian Institute of Science, Bangalore-560012, India

(Received 2nd January 1975)

Lactation delays the re-initiation of oestrous cyclicity in rats, resulting in physiological sterility for the duration of suckling. During this phase, the secretion of pituitary gonadotrophins is suppressed by an unknown mechanism. Continued application of the suckling stimulus by litter replacement (Bruce, 1958; Nicoll & Meites, 1959), or injections of prolactin (Meites & Nicoll, 1959), have been shown to prolong lactation considerably beyond the usual period.

The present study aimed to demonstrate the role of prolactin in inhibiting the gonadotrophin secretion necessary for the re-establishment of oestrous cyclicity during lactation.

Pregnant rats weighing approximately 300 g were obtained from the Institute colony and housed in individual cages. At parturition, the number of young in the litter was adjusted to eight, two or one as required. The day following the post-partum oestrus was regarded

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RHODA MANECKJEE and N. R. MOUDGAL

Summary.

The interrelationship between prolactin and LH in the maintenance of pregnancy during lactation was studied. The reduction of suckled young from eight to two or less, as late as on the morning of Day 4 of pregnancy, resulted in normal implantation. Reintroduction of eight young on Day 4 to lactating pregnant rats deprived of their litters on Day 1 resulted in an inhibition of implantation, but reintroduction on Days 5 or 6 did not inhibit implantation. If oestrogen, HCG or PMSG was given on Day 4 of pregnancy, implantation was induced at the normal time in rats suckling large litters. When LH antiserum was given on the morning of Day 4 or Day 8 to pregnant rats suckling two young each, it blocked implantation and postimplantation survival of blastocysts, respectively. When the number of suckling young was increased from two to eight on Day 6, however, LH antiserum blocked pregnancy only to the extent of 70%. Prolactin administered during the preimplantation phase inhibited implantation in pregnant rats suckling a minimum number of young, but had no effect when given during the postimplantation phase. Progesterone failed to block implantation. Prolactin had no inhibitory effect on implantation in the absence of the suckling stimulus or in non-lactating pregnant rats. The inhibition of implantation by prolactin in rats suckling two young could be effectively reversed by the administration of oestrogen, PMSG or HCG on Day 4 of pregnancy.

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C. S. Sheela Rani and N. R. Moudgal

Summary. The need for endogenous FSH in the periovulatory events such as oocyte maturation, ovulation, luteinization, maintenance of luteal function and follicular maturation was examined in the cyclic hamster. A specific antiserum to ovine FSH, shown to be free of antibodies to LH and to cross-react with FSH of the hamster, was used to neutralize endogenous FSH at various times. Administration of this antiserum during pro-oestrus did not affect oocyte maturation and ovulation, as judged by the normality of the ova to undergo fertilization and normal implantation. It also had no effect on the process of luteinization or on the maintenance of luteal function, as indicated by the normal levels of plasma and luteal progesterone during pro-oestrus and oestrus during the cycle and in pregnancy. All these processes were, however, disrupted by administration of an antiserum to ovine LH, thereby demonstrating their dependence on endogenous LH.

Although FSH antiserum given at pro-oestrus did not prevent the imminent ovulation, it blocked the ovulation occurring at oestrus of the next cycle. This antiserum was effective in preventing the ensuing ovulation when given at any other time of the cycle until the morning of pro-oestrus. It is concluded that, in the hamster, high levels of FSH during pro-oestrus and oestrus are required for initiating maturation of a new set of follicles which are dependent on the trophic support of FSH throughout the cycle until the morning of pro-oestrus. Such follicles then appear to need only LH for subsequent ovulatory and associated processes.

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G. R. Aravindan, N. Ravindranath, K. Gopalakrishnan and N. R. Moudgal

Summary. Testicular germ cell populations of biopsies from 32 male bonnet monkeys in 5 different age groups were quantitated in a flow cytometer after labelling of germ cell DNA with the specific fluorochrome, 4,6-diamidino phenyl indole. The 5 quantifiable populations were spermatogonia (2C), preleptotene spermatocytes (S phase), primary spermatocytes (4C), round spermatids (1C) and elongate spermatids (HC). The seminiferous tubules of immature 3–4-year-old monkey had only Sertoli cells and spermatogonia (2C).

At 5–6 years, germ cells in S-phase (9·5%), 4C (11·1%), 1C (41·8%) and HC (17·1%) stages of maturation appeared for the first time but at 7–8 years of age and beyond all cell types except HC decreased while IC remained relatively constant. Histometric analysis correlated well with the flow-cytometric data. The decrease in cells of 2C, S-phase and 4C stages was associated with an increase in mitotic index, signifying acceleration in the kinetics of germ cell transformation into subsequent cell types. The total turnover in cell transformation (1C:2C) was significantly (P < 0·01) increased at and beyond 7–8 years. Maximum transition from 2C to 4C occurred at 5–6 years (4C: 2C ratio 0·8 at 5–6 years and 0·6 at 7–8 years). The ratio HC:1C (kinetics of cell transformation during spermiogenesis) attained near total efficiency only by 10 years of age (1·08 at 10–14 years; 0·9 at 18–20 years). Also, the cell associations within the seminiferous tubules of monkeys ≥ 10 years of age were better defined than those of younger animals.

The changes in germ cell ratios correlated well with alterations in testicular volume, sperm numbers in the ejaculate and surges of testosterone and increments in FSH in the serum, characteristic of development of sexual maturity. It is apparent from this study that DNA flow cytometry of testicular germ cell populations reveals subtle changes in spermatogenic status of bonnet monkeys with a high degree of sensitivity.

Keywords: spermatogenesis; DNA flowcytometry; germ cells; testosterone; FSH; puberty; primate

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H. G. MADHWA RAJ, M. R. SAIRAM and N. R. MOUDGAL

Summary.

The use of specific anti-fsh and anti-lh substances has shown that lh is the only pituitary gonadotrophin involved in the implantation process. Using different dosages of lh antiserum at different time intervals, it has been possible to arrive at a minimum effective dose (0·05 ml) which, when given on the 4th day at 10.00 hours, results in inhibition of implantation on the 8th day. We have shown that, at this dose, the antiserum is mainly inhibiting the oestrogen surge. It is proposed that an lh surge precedes an oestrogen surge on Day 4 of pregnancy.

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A. JAGGANNADHA RAO, H. G. MADHWA RAJ and N. R. MOUDGAL

Summary.

Administration of lh antiserum to intact pregnant hamsters on any day from Days 6 to 11 of pregnancy resulted in termination of gestation. Following lh antiserum injection, the ovarian weights were markedly reduced.

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A. Jagannadha Rao, S. G. Kotagi and N. R. Moudgal

Summary. Serum concentrations of chorionic gonadotrophin (CG) during early pregnancy in the bonnet monkey (Macaca radiata), were determined by a radioimmunoassay validated for measuring monkey chorionic gonadotrophin. The earliest time at which CG could be detected was on the 28th day of a fertile cycle and it could not be detected beyond the 50th day. During a fertile cycle, mean values of oestradiol-17β in addition to exhibiting a preovulatory peak around Days 9–10 of cycle, exhibited a secondary peak around Day 30 of the cycle. Serum progesterone levels remained elevated throughout the period of study from Day 18 to Day 50 and at no time did the levels fall below 2 ng/ml.