Volume 7, Issue 2
March 1985, pages 75-255
pp 75-75 March 1985
pp 77-94 March 1985
The hormonal modulation of thiamin carrier protein in the plasma and uterine luminal secretion during the normal reproductive phases of the animal (estrous cycle and pregnancy) as well as during experimental estrogenisation was investigated in the rat using a specific and sensitive homologous radioimmunoassay procedure developed for this purpose. Following a single injection of estrogen to immature male rats, thiamin carrier protein rapidly accumulated in plasma attaining peak concentration at 48 h and declining thereafter. A 1.5-fold amplification of the inductive response was observed on secondary stimulation with the hormone. The magnitude of the response exhibited a clear dependency on the dose of the steroid hormone, whereas the time at which peak levels of thiamin carrier protein production was remained unaltered in the concentration range of the steroid tested. The inductive effect of estrogen was severely curtailed by the antiestrogens,viz., En- and Zu-clomiphene citrates, while progesterone was incapable of either modulating the estrogen-induced response or eliciting an induction by itself. Cycloheximide drastically blocked the response to estrogen. Evidence for the ability of uterus to serve as yet another independent site of thiamin carrier protein synthesis was obtained byin vitro incorporation of radioactive amino acids into immunoprecipitable thiamin carrier protein in the tissue explants of estrogenised female rats. The levels of thiamin carrier protein in uterine luminal fluid measured during estrous cycle, pregnancy and experimental estrogenisation exhibited remarkable similarity to the plasma thiamin carrier protein profiles.
pp 95-103 March 1985
Lactating bonnet monkeys were used as a model to understand the mechanism of ovarian quiescence during lactation. The ovary of the bonnet monkey in the 3rd month of lactation responds well to exogenous pregnant mare serum gonadotropin stimulation with serum estrogen values reaching maximal levels by day 3 of the gonadotropin injection. The adminstration of ovine prolactin to such monkeys significantly inhibited the ovarian responsiveness to exogenous gonadotropin. The responsiveness of the pituitary of the lactating monkey (in the 3rd month of lactation) to luteinizing hormone releasing hormone injection was suppressed and supplementation with exogenous prolactin further accentuating this effect. The relative ability of chlorpromazine given intravenously/intramuscularly/intranasally to enhance endogenous prolactin levels was assessed. During the first 5 months of lactation when the basal prolactin levels were high, the luteinizing hormone levels were low. As the suckling stimulus reduces and prolactin levels fall, luteinizing hormone levels increase, the first post-parturient mensus occurring by 218 ± 4 days. This event was postponed by 3 months on increasing endogenous prolactin levels by administering chlorpromazine (250 μg/day by intranasal mode) over a 5 day period every month starting from the 3rd month of lactation.
pp 105-113 March 1985
Monoclonal antibodies derived from ten hybrid cell clones, generated against porcine zona pellucida gave strong immunofluorescence with zona but the pattern varied from patchy, thin rim to heavy precipitation type of rim. Five of the 6 monoclonals studied prevented the binding of the porcine epididymal sperm to homologous oocytesin vitro, whereas the sixth one was partially effective. All of the 6 monoclonale of this batch inhibited the lysis of zonae by proteolytic enzymes even at dilutions up to 1 × 10−3. Three of the four monoclonals prepared in a subsequent batch gave strong immunofluorescent reactions and had high titres as determined by enzyme immunoassay. These monoclonals did not, however, protect the zonae against lysis by proteolytic enzymes. These properties are suggestive of the heterogeneity of the antigenic determinants in zona and emphasize the employment of appropriate bioassays for screening and selection of bioeffective antibodies.
pp 115-122 March 1985
Acetone powder preparations of ventral prostates of adult albino rat exhibit an inhibin-like activity.In vitro cultured ventral prostate explants secrete a substance possessing similar activity which appears to be independent of testicular androgens for its elaboration.
pp 123-133 March 1985
Kinetic studies of the binding and dissociation of [125I]-human growth hormone to rabbit liver and mammary gland membrane receptors have showed that the binding of [125I]-human growth hormone was largely irreversible to liver membrane receptors and completely to the solubilised mammary gland receptor. As Scatchard analysis assumes complete reversibility of the hormone-receptor interaction the validity of estimates of affinity and capacity of receptors derived by this analysis may be questionable.
Theoretical considerations show that in unimolecular irreversible interactions of hormone and receptor, a nonlinear (concave) or a linear Scatchard plot can be obtained. In linear Scatchard plots the capacity of the receptor obtained by extrapolation represents an overestimation of true capacity. This overestimation correlates with the value of the intercept in the Scatchard plot.
pp 135-144 March 1985
The Scatchard plot in a radioreceptor assay depends upon the definition of specific binding and the quality of the iodinated hormone used. Iodination of protein hormones may alter it so that it no longer binds to the receptor and methods are available to measure the extent of this inactivation. When appropriate corrections are made for specific binding and the amount of inactive iodinated hormone in an assay, both qualitative and quantitative differences were observed in estimates of binding capacity and affinity in some well characterised hormone receptor systems.
Theoretical predictions derived from Scatchard analysis of irreversible unimolecular hormone-receptor interactions were applicable, both qualitatively and quantitatively to two irreversible hormone-receptor systems. A method described permits a more accurate estimate of capacity from radioreceptor assay data.
pp 145-152 March 1985
Using an antibody raised in the rabbit to ovine leutenizing hormone β subunit coupled to activated cellulose, a solid phase radioimmunoassay to detect early pregnancy in the South Indian bonnet monkey has been developed. Non-specific inhibition due to serum was eliminated by inclusion of new born calf serum in the assay tubes. The assay is simple, needs only one centrifugation and can be completed in 6 h at room temperature with no false positive results.
pp 153-159 March 1985
Estradiol-induced incorporation of radioactive uridine and leucine into the uterus of rat was inhibited by simultaneous treatment with an analogue of gonadotropin releasing hormone. The inhibitory action of gonadotropin releasing hormone was not mediated through modulation of estradiol receptor content. However, estradiol-induced increase in the level of poly(A) polymerase was inhibited by gonadotropin releasing hormone analogue, indicating that the inhibitory effect might involve post-transcriptional phenomenon.
pp 161-173 March 1985
Estrogens secreted by the ovary during the pre/periimplantation period and/or by the blastocyst and acting locally on the endometrium are involved in the initiation of implantation. Estrogens induce a cascade of metabolic changes in the uterus and blastocyst prior to and soon after the attachment and implantation of the blastocysts. Antiestrogens either administered intraluminally into the uterus prior to implantation or washing free blastocysts with antiestrogens prior to transfer to uteri of progesterone treated hamsters leads to failure of implantation. A number of antiestrogens which inhibit fertility in the rats do not interfere with implantation in the hamster and monkey when administered post-coitally. However, Zuclomiphene administered during days 5–11 of the menstrual cycle inhibits implantation in the rhesus monkey. Antiestrogens are being evaluated in other non-human primates to confirm the above results and to determine the time in the menstrual cycle susceptible to modification and inhibition of implantation. Tamoxifen administered from days 18–30 of the cycle to mated bonnet monkeys inhibited implantation despite maintenance of high levels of circulating progesterone. Neutralization of the vitamin carrier proteins (by active immunization against these proteins) interferes with established pregnancy in the rat and perhaps in the bonnet monkey. Whether antiestrogens can reduce the levels of vitamin carrier proteins to a level which is not adequate for maintenance of early pregnancy is not clear. Compounds which show antiestrogenic and antiprogestational properties may have advantages in inhibiting implantation or disruption of early pregnancy. Critical experiments need to be carried out in non-human primates to delineate the effectiveness of antiestrogens, with particular emphasis on time, dose, duration and route of administration in inhibition of implantation. Centchroman, an antiestrogen with antiprogestational properties, has been found to provide pregnancy protection with minimal side effects. However, several concerns relating to safety in toxicological studies in monkeys and a dose which would provide acceptable rate of contraceptive efficacy without major effects on the menstrual cycle need to be clarified before considering the potential of centchroman as a possible oral contraceptive administered either post-coitally or once a week. Inhibition of implantation by administration of tamoxifen opens up new possibilities of use of antiestrogens for fertility regulation.
pp 175-190 March 1985
Two moieties of inhibin could be obtained by chromatography of partially purified preparations of inhibin from human placenta on Sephadex G-100, G-25 and ion exchange chromatography on diethylaminoethyl Sephadex A-50. The higher molecular weight moiety (14,000) designated as HPI-H appears to be similar to inhibin from human seminal plasma. While the lower molecular weight moiety (1500) designated as HPI-L appears to be similar to that of sheep testicular inhibin.
The preparations from both human term placenta and human seminal plasma inhibited the binding of [125I] human follicle stimulating hormone to rat testicular receptors. This effect of inhibins could be neutralized by antisera raised against corresponding polypeptide. Further these antibodies could neutralize endogenous inhibin resulting in 2 to 3 fold increase in serum follicle stimulating harmone levels, which could then be reversed by exogenous administration of the isolated inhibin preparations.
pp 191-195 March 1985
The epididymis is an ideal extragonadal target site to inhibit fertility in the male. Synthesis and secretion of constituents like sialic acids, protein and glycerylphosphoryl choline by the epididymal epithelium under androgen control provide an ideal fluid environment for sperm maturation. An optimal level of sialic acid secretion by the epididymal epithelium is needed to maintain functional integrity of sperm. The existence of specific androgen receptors in the epididymis and spermatozoa are related to their ability to metabolise androgens.
pp 197-201 March 1985
The study of possible adverse effects of vasectomy have been mainly focussed on hormonal balance, spermatogenesis, the induction. of auto-immune reactions and cardiovascular changes including the non-fatal myocardial infarction. The review of literature, including our own work on the immunological sequelae of vasectomy, indicates that there is no health hazard following vasectomy. The presence of antibodies to spermatozoa in some individuals, however, may effect future fertility, if reversal is requested.
pp 203-206 March 1985
Chronic administration of a potent gonadotropin releasing hormone inhibits ovulation in women. The suppression of gonadal function during long term treatment with the GnRH analogues is ascribable to inhibition of gonadotropin secretion caused by the down regulatory action of the decapeptide at the pituitary level. Reduced progesterone production with premature onset of menstruation has been observed in women injected with the agonist during the midluteal phase. The decapeptide however, has no effect onin vitro human ovarian steroidogenesis. Specific receptors for GnRH have been located on rodent ovarian cells, but corpora lutea of rhesus monkey and human ovaries seem to lack these receptors. The luteolytic effect in women thus appears to be central in origin and not a direct effect on the corpus luteum. Recently, a superactive agonist of GnRH given around the peri-implantation period has been shown to terminate pregnancy in baboons. Monoclonal antibodies against GnRH administered during the same period in a fertile cycle also abrogated pregnancy in these animals. Using immuno-enzymatic techniques GnRH has been localized on the placenta. GnRH also exerts a stimulatory effect on hCG production by the placental villi maintained in culture. Addition of anti-luteinizing hormone releasing hormone antibodies blocks this effect completely. It seems that placenta is the only other tissue besides the pituitary where GnRH has probably a regulatory role in the human female.
pp 207-213 March 1985
Rapid progress has been recorded recently in the understanding of the role of neuro-transmitters and neuropeptides in the control of reproduction and on their apparent potential in the regulation of fertility. Peptides, as well as monoamines, are important in the control of lutinizing hormone releasing hormone and gonadotropin release. The input from brainstem noradrenergic neurons as well as dopamine mediated stimulated release of lutinizing hormone. In addition considerable evidence exist for the occurrence of a specific follicle stimulating hormone-releasing factor. A large number of brain peptides affect the secretion of lutinizing hormone releasing hormone and the endogenous opioid peptides appear to have a physiologically important function in restraining the influence on lutinizing hormone releasing hormone release under most circumstances. Vasoactive intestinal peptide and substanceP stimulate whereas cholecystokinin, neurotensin, gastrin, secretin, somatostatin α-melanosite stimulating hormone and vasotocin inhibit lutinizing hormone release. Of the inhibitory peptides, cholecystokinin and arg-vasotocin are the most potent. Inhibin injected into the ventricle selectively suppresses follicle stimulating hormone release by a hypothalamic action. Thus the control of gonadotropin release is complex and a number of aminergic and peptidergic transmitters are involved.
pp 215-221 March 1985
The structural and functional integrity of the vas deferens and its role in ensuring the fertilizing ability, viability of spermatozoa and their survival in the vas deferens, are elucidated. The regulation of the function of the vas deferens and the differential androgen dependency of its two regions have been discussed in relation to its secretory and absorptive activities as well as its contractility. The importance of ascorbic acid in maintaining its functions has also been investigated.
The potentiality of the use of an androgen antagonist, steroids (testosterone, estradiol benzoate), prostaglandins, copper devices, vasectomy, vasocclusive agents, effects of nutr itional deficiencies, human chorionic gonadotropin-antiserum and plant products as antifertility agents have been discussed.
pp 223-227 March 1985
Polyadenylation of mRNA is a post-transcriptional phenomenon and is catalysed by both nuclear and cytoplasmic poly(A) polymerases. In rat testis the specific activity of cytoplasmic poly(A) polymerase increased with age reaching a peak value in 80 days. After this time the activity was maintained at a slightly lower level for the next 280 days. Follicle stimulating hormone, luteinizing hormone, human chorionic gonadotropin, pregnant mare serum gonadotropin and a gonadotropin releasing hormone analogue significantly increased the enzyme activity in immature rat testis. These results show that testicular poly(A) polymerase was probably under the influence of gonadotropic hormones.
pp 229-243 March 1985
Biological and clinical research on male reproduction and fertility regulation carried at the National Institute of Health and Family Welfare over the past 17 years has been highlighted in this review. Areas of research covered pertains to hormones in relation to sperm maturation and transport; fertilizing ability of spermatozoa under different experimental conditions; agents producing functional sterility; seasonal variations in primate reproduction; male infertility including semen biochemistry, differential diagnosis between obstructive and non-obstructive azoospermia and hormone therapy; vasectomy, reversible vasocclusion and vasanastomosis; and the use of cyproterone acetate and testosterone enanthate in male rhesus monkey and human volunteers for reversible contraception.
pp 245-255 March 1985
Different procedures have been developed to assess the functions of spermatozoa in terms of their motility as well as their fertilizing potential. The procedures for assessment of motility are either qualitative or quantitative, subjective or objective, while the procedures for assessment of fertilizing potential are either direct or indirect. In this review, the information available on the procedures are compiled and analysed including the procedures forin vitro penetration of zona-free hamster eggs by human or non-human primate spermatozoa.