Search PubMed⌕ Search

Biomedical subjects

N R Moudgal

Publications and source records attributed to N R Moudgal.

At least 55 records · Page 3Linked to original sources
PubMed1985

Differences in the behavior of luteinizing hormones of various species at the rat gonadal cell receptor site.

The ability of different LH-like hormones, such as hCG, PMSG/equine (e) CG, ovine (o) LH, eLH, and rat (r) LH, to bind to and stimulate steroidogenesis in two types of rat gonadal cells was studied under the same experimental conditions. In both Leydig and granulosa cells, the maximal steroidogenic responses elicited by optimal doses of different LHs present during a 2-h incubation were comparable. However, if the cells were exposed to the different LHs for a brief period and then subjected to interference with hormone action by removing the unbound hormone from the medium by washing or adding specific antisera, differences were observed in the amount of steroid produced during subsequent incubation in hormone-free medium. Thus, in the case of hCG, either of these procedures carried out at 15 or 30 min of incubation had little inhibitory effect on the amount of steroid produced at 2 h, the latter being similar to that produced by cells incubated in the continued presence of hCG for 2 h. With eCG and rLH, the effect was dramatic, in that there was a total inhibition of subsequent steroidogenic response. In cells exposed to eLH and oLH, inhibition of subsequent steroidogenesis due to either removal of the free-hormone or addition of specific antisera at 15 or 30 min was only partial. Although all of the antisera used were equally effective in inhibiting the steroidogenic response to respective gonadotropins when added along with hormones at the beginning of incubation, differences were observed in the degree of inhibition of this response when the same antisera were added at later times of incubation. Thus, when antisera were added 60 min after the hormone, the inhibition of steroidogenesis was total (100%) for eCG, partial (10-40%) for eLH and oLH, and totally lacking in cells treated with hCG. From this, it appears that hCG bound to the receptor probably becomes unavailable for binding to its antibody with time, while in the case of eCG and other LHs used, the antibody can still inhibit the biological activity of the hormone. Studies with 125I-labeled hormones further supported the conclusion that hCG differs from all other LHs in being most tightly bound and, hence, least dissociable, while eCG and rLH dissociate most readily; oLH and eLH can be placed in between these hormones in the extent of their dissociability.

Animals↗
PubMed1984

Effect of pregnant mare serum gonadotropin on the induction and degradation of FSH and LH receptors in the granulosa cell of the immature rat.

The relative induction of FSH and LH receptors in the granulosa cells of immature rat ovary by pregnant mare serum gonadotropin (PMSG) has been studied. A single injection of PMSG (15 IU) brought about a 3- and 12-fold increase in FSH and LH receptor concentration, respectively, in the granulosa cells. Maximal concentration was reached by 72 h but the receptor levels showed a sharp decline during the next 24-48 h. The kinetic properties of the newly formed FSH receptors were indistinguishable from the pre-existing ones. The induced FSH receptors were functional as demonstrated by an increase in the in vitro responsiveness of the cells to exogenous FSH in terms of progesterone production. Treatment of immature rats with cyanoketone, an inhibitor of delta 5,3 beta-hydroxysteroid dehydrogenase, prior to PMSG injection effectively reduced the PMSG-stimulated increase in the serum estradiol, uterine weight and LH receptors but had no effect on the FSH receptor induction. The ability of PMSG to induce gonadotropin receptors can be arrested at any given time by injecting its antibody, thereby suggesting a continuous need for the hormonal inducer. Estrogen in the absence of the primary inducer was unable to maintain the induced LH and FSH receptor concentration. Inhibition of prostaglandin synthesis using indomethacin aslo had no effect on either the induction or degradation of gonadotropin receptors. Administration of PMSG antiserum, 48 h after PMSG injection, brought about a rapid decline in the induced receptors over the next 24 h, with a rate constant and t 1/2 of 0.078 h-1 and 8.9 h for FSH receptors and 0.086 h-1 and 8.0 h for the LH receptors, respectively.

Animals↗
PubMed1984

Serum concentrations of chorionic gonadotrophin, oestradiol-17 beta and progesterone during early pregnancy in the south Indian bonnet monkey (Macaca radiata).

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-17 beta, 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.

Animals↗
PubMed1983

Use of alpha- and beta-subunit specific antibodies in studying interaction of hCG with Leydig cell receptors.

Antisera (a/s) raised to individual alpha- and beta-subunits of human chorionic gonadotropin (hCG) have been characterized for specificity using immunoaffinity procedures and used to study the disposition of the two subunits when intact hCG is complexed with luteinizing hormone (LH) receptor of the Leydig cells. Three kinds of experiments were done. (a) The ability of the preformed hormone-antibody (H-Ab) complex to bind to receptor and stimulate a response; (b) the ability of the a/s to dissociate hCG from its complex with the receptor and thereby terminate response; and (c) the ability of the premixed antibody and receptor to compete for binding of labeled hCG. Although the subunit specific a/s used here were equipotent in binding hCG (capacity to bind and Ka being very similar), their behavior once the receptor preparation or Leydig cell is introduced into the system was drastically different. The beta-subunit antibody relative to the alpha-subunit antibody, appeared to be poorly effective in preventing hCG from either binding to the receptor or inhibiting the continuation of response. The results suggest that hCG upon interaction with the receptor loses the determinants specific to the beta-region more rapidly compared to those specific to the alpha-region suggesting thereby that the initial interaction of hCG with the receptor should be occurring through sites in the beta-subunit. Although the alpha-subunit portion of the hCG molecule is available for binding to the antibody for a relatively longer time, the biological response of the cell seems very sensitive to such binding with the antibody as it invariably results in loss of response.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Studies on follicular atresia: lysosomal enzyme activity and gonadotropin receptors of granulosa cells following administration or withdrawal of gonadotropins in the rat.

The changes that occur during follicular growth and atresia in the lysosomal enzyme activities and in gonadotropin receptors of isolated granulosa cells were studied. At different intervals after an injection of PMSG to 21-day-old female rats, the granulosa cells (GC) were isolated and the total activity of cathepsin-D, a representative lysosomal enzyme, and FSH receptor activity in terms of binding of [125I]oFSH to GC and the steroidogenic response of GC to FSH in vitro were determined. During the period of both follicular growth and atresia there was an inverse correlation between the lysosomal enzyme activity and FSH receptor activity of granulosa cells, the former being low during follicular growth or tropic phase when the levels of FSH receptors were increasing. During the atretic phase, beyond 48 h of PMSG treatment (perhaps due to the normal metabolic clearance of the injected PMSG), the cathepsin-D activity showed a significant increase while the FSH receptors were on the decline. That lack of the hormone was responsible for atresia was confirmed when an antiserum to PMSG was injected during the tropic phase (24 h after PMSG); this resulted in a sharp increase in cathepsin-D activity. Injection of excess amounts of either FSH or LH, along with or soon after PMSG antiserum, was found to prevent the increase in cathepsin-D activity, and also resulted in the maintenance of gonadotropin receptors. This suggested that gonadotropins can 'rescue' follicles from undergoing atresia. In the unprimed immature rat FSH, but not LH or hCG, mimicked the effects of PMSG, in terms of bringing about a reduction in cathepsin-D activity of GC. Also in such rats, neutralization of endogenous FSH with an antiserum to FSH resulted in an increase in the cathepsin-D activity of GC, suggesting that even the prepubertal rat ovary is dependent on the tropic support of FSH for prevention of atresia.

Animals↗
PubMed1982

Equine luteinizing hormone possesses follicle-stimulating hormone activity in hypophysectomized female rats.

The ability of equine luteinizing hormone (eLH) to promote follicular growth and maturation in hypophysectomized rats has been assessed. A single injection of equine LH has been shown to promote the growth of a large number of antral and preovulatory follicles. In addition, equine LH markedly increased serum estrogen levels and uterine weight. Furthermore, equine LH, like equine chorionic gonadotropin (eCG; PMSG) was able to significantly enhance the incorporation of [3H]thymidine into ovarian DNA, an activity shown to be specific to hormones having follicle-stimulating hormone (FSH) activity. Equine LH treated with an FSH antibody immunoaffinity column to remove any possible contamination still exhibited the above activity, demonstrating that the FSH activity is intrinsic to the eLH molecule. Equine LH has also been shown to be capable of inducing LH receptors in granulosa cells of ovaries of hypophysectomized rats, an activity specific to FSH-like hormones. From the doses required of eLH and the degree of response observed, it is concluded, however, that eLH in the hypophysectomized rat is less active than eCG as an FSH.

Animals↗
PubMed1979

Ability of human chorionic gonadotropin beta-subunit to inhibit the steroidogenic response to lutropin.

Ability of the beta-subunit of human chorionic gonadotropin to inhibit the response to lutropin (luteinizing hormone, LH) was tested in the immature rat ovarian system and pregnant-mare-serum-gonadotropin-primed rat ovarian system with progesterone production being used as the response. Human chorionic gonadotropin beta-subunit was found to inhibit human and ovine lutropin-stimulated progesterone production. At a constant dose of lutropin, inhibition was dependent on the concentration of beta-subunit. When concentration of the beta-subunit was kept constant at 5.0 microgram/ml and the concentration of lutropin was varied, the inhibition was maximum at the saturating concentration of the native hormone. The alpha-subunit of the human chorionic gonadotropin did not inhibit the response to lutropin. The lutropin/beta-subunit ratio required to produce an inhibition of response was much lower than that required to bring about an observable inhibition of binding.

Animals↗
PubMed1979

Effect of follicle-stimulating hormone and its antiserum on the activity of ornithine decarboxylase in the ovary of rat and hamster.

The ability of FSH to stimulate the activity of ornithine decarboxylase (ODC) in the ovary of the immature rat and cycling hamster has been examined using specific antisera to gonadotropins. The stimulatory effect of FSH on ODC activity in the ovary of the immature rat was abolished when LH antiserum was administered along with FSH, while similar administration of FSH antiserum had no effect on LH action in stimulating ODC activity, thereby demonstrating the specificity of the LH effect. During the estrus cycle of the hamster, ODC activity in the ovary could be detected only on the evening of proestrus, the maximal activity seen at 1700 h being associated with both the Graafian follicles and the rest of the ovarian tissue. Neutralization of the proestrous FSH surge had no effect on the activity of ODC in either of these tissues, while similar administration of LH antiserum at 1300 h of proestrus completely inhibited the ODC activity in both large follicles and the rest of the ovarian tissue. Thus, the surge of LH, but not of FSH, appears to be responsible for regulating the ODC activity in the ovary of the cycling hamster.

Animals↗
PubMed1978

Examination of the role of follicle stimulating hormone in estrogen biosynthesis in vivo and in vitro in the ovary of the cyclic hamster.

The effect of neutralizing endogenous follicle stimulating hormone (FSH) or luteinizing hormone (LH) with specific antisera on the in vivo and in vitro synthesis of estrogen in the ovary of cycling hamster was studied. Neutralization of FSH or LH on proestrus resulted in a reduction in the estradiol concentration of the ovary on diestrus-2 and next proestrus, suggesting an impairment in follicular development. Injection of FSH antiserum at 0900 h of diestrus-2 significantly reduced the ovarian estradiol concentration within 6--7 h. Further, these ovaries on incubation with testosterone (T) in vitro at 1600 h of the same day or the next day synthesized significantly lower amounts of estradiol, compared to corresponding control ovaries. Although testosterone itself, in the absence of endogenous FSH, could stimulate estrogen synthesis to some extent, FSH had to be supplemented with T to restore estrogen synthesis to the level seen in control ovaries incubated with T. Lack of FSH thus appeared to affect the aromatization step in the estrogen biosynthetic pathway in the ovary of hamster on diestrus-2. In contrast to this, FSH antiserum given on the morning of proestrus had no effect on the in vivo and in vitro synthesis of estrogen, when examined 6--7 h later. The results suggest that there could be a difference in the need for FSH at different times of the cycle. Neutralization of LH either on diestrus-2 or proestrus resulted in a drastic reduction in estradiol concentration of the ovary. This block was at the level of androgen synthesis, since supplementing testerone alone in vitro could stimulate estrogen synthesis to a more or less similar extent as in the ovaries of control hamsters.

Animals↗