Search PubMed⌕ Search

Biomedical subjects

N R Moudgal

Publications and source records attributed to N R Moudgal.

At least 73 records · Page 4Linked to original sources
PubMed1978

Effect of human chorionic gonadotrophin and ovine luteinizing hormone on rat ovarian macromolecular metabolism.

Administration of human chorionic gonadotrophin (HCG) or ovine LH to immature rats primed with pregnant mare serum gonadotrophin (PMSG) stimulated the rate of synthesis of polyadenylic acid (poly A)-rich RNA in the ovaries. The rate of total RNA synthesis was not affected significantly by hormone treatment, whereas protein synthesis was enhanced. The increase in the rate of synthesis of poly(A)-rich RNA in the ovaries could be inferred as induction of messenger RNA synthesis after the hormone treatment. The poly(A)-rich nature of the isolated RNA was established by oligo(dT)-cellulose chromatography, binding the Millipore filter disks and hydridization with [3H]polyuridylic acid. The level of cyclic AMP in the ovaries of such rats was also raised after administration of LH, the increase coincided with the increase in the rate of synthesis of poly(A)-rich RNA. The implications of these results are discussed in the light of the biochemical basis of luteinization and the action of LH.

Animals↗
PubMed1977

Inhibition of in vivo pituitary release of luteinizing hormone in lactating rats by exogenous prolactin.

The mechanism whereby the reciprocal relationship between the plasma levels of prolactin and HL is maintained in lactating rats under different degrees of suckling stimulus has been investigated in the present study. Plasma levels of luteinizing hormone (LH) in lactating rats suckling two pups could be reduced significantly by injecting prolactin (PRL). This reduction was also evident in ovariectomized and ovariectomized-adrenalectomized lactating rats, thus excluding mediation of the inhibitory effect by steroids from end-organs. The in vivo response of the pituitary to exogenous LHRH was lower in rats suckling eight pups than those suckling two pups. Prolactin administered prior to LHRH caused an inhibition of the response of the pituitary to exogenous LHRH in rats suckling two pups. These data provide evidence for the hypothesis that in the lactating rat, in the presence of minimal suckling stimulus, the causative factor for reducing serum LH levels is prolactin, which acts by altering the pituitary responsiveness to LHRH.

Adrenalectomy↗
PubMed1977

Examination of the role of FSH in periovulatory events in the hamster.

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 FHS 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.

Animals↗
PubMed1977

Enzymic changes in the cervix of the rat and hamster during the oestrous cycle and the effect of steroids.

Changes in four hydrolytic enzymes, namely acid phosphatase, alkaline phosphatase, arylsulphatase A and B, of the cervix of the rat and hamster have been studied during the 4-day oestrous cycle. All four enzymes showed maximal activity on the day of oestrus and least activity on day 2 of dioestrus. All the enzymes showed significant reduction of activity after ovariectomy, arylsulphatase A and B showing the earliest changes in specific activity. A single subcutaneous injection of 0-02 microng oestradiol-17beta/rat increased the especific activity of arylsulphatase A and B from the low ovariectomized level to that observed in control oestrous animals within 18 and 6 h respectively. A higher concentration of oestradiol 17beta (2-0 microng) had an inhibitory effect. Progesterone was without effect on arylsulphatase B activity, but when given (2-0 mg) with 0-02 microng oestradiol-17beta, it inhibited the response to oestrogen. Cycloheximide prevented the rise in arylsulphatase B activity occurring after oestrogen injection, suggesting a regulation of cervical arylsulphatase B at the level of protein biosynthesis. These results suggest that arylsulphatase B activity may be induced by oestrogen in the cervix of the rat.

Acid Phosphatase↗
PubMed1976

Studies on rat ovarian receptors for lutropin (luteinizing hormone). Applicability of radioimmunoassay to measure lutropin bound to receptors.

Measurement of receptor-bound unlabelled physiologically active lutropin (luteinizing hormone, LH) was possible by a modified radioimmunoassay. The conventional radioimmunoassay conducted at 4 degrees C was inadequate, whereas the modified assay performed at 37 degrees C could measure receptor-bound lutropin. The radioimmunoassay at 37 degrees C takes only 36h for completion compared with 5-7 days at 4 degreesC. The sensitivity and range of dose-response curves are, however, unaltered. The validity of the technique was established by a number of criteria.

Animals↗
PubMed1976

Studies on rat ovarian receptors for lutropin (luteinizing hormone). Factors influencing binding and response.

The interaction of rat ovarian receptors with lutropin (luteinizing hormone, LH) in vitro was rapid and reversible. The degree of binding was saturable and susceptible to changes in the concentration of lutropin in the medium. The concentration of lutropin receptors in the ovary increases during the natural pubertal period and also in immature rats given pregnant-mare-serum gonadotropin and human choriogonadotropin. In the latter case, the increase in lutropin receptor, after injection of pregnant-mare-serum gonadotropin alone, could be detected only if the ovaries are freed of the bound gonadotropin before exposure to lutropin. The concentration of lutropin receptors was higher in the luteal compartment of the ovary than in the non-luteal parts and increased slightly in aged corpora lutea. Correlation between binding of lutropin to the ovary and the ovarian response to lutropin in terms of cyclic AMP production was found only in prepubertal rat ovaries and in young corpora lutea and not in aged corpora lutea, suggesting the non-equivalence of binding in vitro and ovarian response.

Age Factors↗
PubMed1976

Studies on rat ovarian receptors for lutropin (luteinizing hormone). Interaction with beta-subunit of sheep lutropin.

By using radioimmunoassay, the interaction of sheep lutropin (luteinizing hormone, LH) beta-subunit with rat ovarian receptors was investigated. The binding of beta-subunit was specific, although of much lower order than that of lutropin. Sheep lutropin beta-subunit effectively inhibited the binding of human choriogonadotropin (chorionic gonadotropin, gCG) to the ovary, showing that both occupy the same sites. The binding of sheep lutropin beta-subunit to ovary was not followed by any detectable increase in cyclic AMP. The ovarian response to lutropin in terms of cyclic AMP production was inhibited in the presence of free beta-subunit. The alpha-subunit of lutropin, when used at concentrations where contamination with whole lutropin was negligible, enhanced the degree of binding of beta-subunit; this did not lead to increased cyclic AMP in the tissue. Surprisingly, the binding of beta-subunit in vitro was drastically decreased by the prior removal of all endogenous rat lutropin bound to receptors. The implications of these data are discussed in the light of the reported biological activity of the beta-subunit.

Animals↗
PubMed1976

Relative sensitivity of the corpus luteum of different days of pregnancy to LH-deprivation in the rat and hamster.

Deprivation of endogenous LH by LH antiserum (LH A/S) in 6-day pregnant rats did not affect the luteal or serum progesterone within 24 h. LH A/S treatment on day 7 or 8 of pregnancy, however, caused a 70 and 92% reduction in luteal progesterone, respectively, within 24 h. Serum levels of progesterone showed a similar reduction. In the case of pregnant hamster, unlike the rat, there was a significant decrease in progesterone in the serum, luteal and non-luteal compartments whether the A/S was administered on day 4, 5 or 6. There was more than a 10-fold increase in the luteal cholesterol esters within 24 h whether the A/S was given on day 6, 7 or 8 of pregnancy in the rat. Rat corpora lutea of days 6 and 8 of pregnancy reacted in a like manner to LH-deprivation, showing an increased utilization of [U-14C]glucose to form 14CO2 in vitro. In the rat, LH (25 mug NIH-S19) administration in vivo either on day 6 or day 8 of pregnancy, caused within 2 h an increase in serum and non-luteal progesterone, but luteal progesterone was unchanged. On the other hand, LH administration to hamsters on day 8 of pregnancy caused an increase in progesterone levels in serum, luteal and non-luteal tissue. Incubation of corpora lutea isolated from untreated 6- and 8-day pregnant rats with LH brought about an increase in progesterone secretion into the medium in both cases. The results show that, even though LH-deprivation does not apparently affect progesterone concentration in the corpus luteum of 6-day pregnant rats, it does affect other metabolic parameters such as glucose utilization and cholesterol turnover, suggesting that the corpus luteum of early pregnancy exhibits a continuous dependency on LH for the maintainence of metabolic functions.

Animals↗
PubMed1976

A model system for studying inhibin.

We report here a sensitive model for studying inhibin-like activity in crude ovine testicular extracts (CoTE). The administration of CoTE in 25-100 mg amounts to 35-day-old immature male rats, orchidectomized just prior to use, resulted in the prevention of a rise in plasma FSH levels, seen 10 h post-treatment. In a second model, CoTE was injected at 1000 h of day 35 to a group of rats that was castrated 12-24 h prior to injection, and the animals were sacrificed 6 h later; plasma FSH levels were found to be significantly suppressed. CoTE, administered subcutaneously, both in multiple doses and as a single injection, was found to be equally effective. A single injection suppressed FSH levels within 3-6 h while LH levels were unaffected. The suppressive effect was dose-dependent, reaching a maximum value at doses of 100 mg CoTE and above. FSH levels could not be suppressed below the tonic level, either by the administration of a single large dose of CoTE, or by repetitive injections of maximal doses of CoTE at 3 h intervals. The suppression in FSH levels caused by a single injection of CoTE waned with time and totally disappeared by 36h. CoTE was prepared by the heat treatment (55 C for 30 min) of an aqueous extract of ovine testis, followed by centrifugation and ether extraction of the supernatant. The aqueous layer was then dialyzed and lyophilized. The lyophilized material was found to be free of testosterone, as measured by a specific radioimmunoassay, indicating that the active factor is a heat-stable, lyophilizable, nondialyzable material, free of contamination by testosterone and probably by other steroids.

Animals↗
PubMed1976

Physiology of the epididymis and induction of functional sterility in the male.

The factors regulating the physiology of the epididymis and the induction of functional sterility by alteration of epididymal function are discussed. The threshold requirement of androgens to maintain the structural and functional integrity of the epididymis in the rat, hamster and monkey is much higher than that needed by the accessory glands. Further, the cauda epididymidis has a higher threshold requirement of androgens than the caput epididymidis and may reflect the differences in the availability and metabolism of androgens to these two segments. An inverse relationship exists between the levels of sialic acid (sialoproteins) in the epididymal luminal plasma and that bound to the spermatozoa in the cauda epididymidis. Androgen deprivation and consequent alteration of the secretory activity of the epididymis either by castration or by treatment with antiserum to LH or by the antiandrogen, cyproterone acetate, caused concurrent decrease in the levels of sialic acid in the luminal plasma and in the spermatozoa of the different regions of the epididymis. These changing patterns of sialic acid in the spermatozoa and luminal plasma may be associated with changes in the surface charge of the spermatozoa and the stabilization of the acrosome and its membranes during sperm maturation.

Androgens↗