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Biomedical subjects

A R Sheth

Publications and source records attributed to A R Sheth.

At least 109 records · Page 6Linked to original sources
PubMed1984

Effect of pregnancy plasma, neuraminidase and sialic acid on phytohemagglutinin-induced human lymphocyte response.

The effect of human pregnancy plasma on phytohemagglutinin-(PHA-)induced blastogenesis of lymphocytes from unrelated donors was studied in relation to the sialic acid (N-acetyl-neuraminic acid) content of the plasma. The total sialic acid levels in plasma were found to be elevated during pregnancy as compared with plasma from non-pregnant, normally menstruating control groups (p less than 0.001) and to increase with advancing gestation, reaching peak values in the post-partum period (1-14 days). On the other hand, pregnancy plasma at a concentration of 15% caused a significant suppression of lymphocyte proliferation (p less than 0.05 to p less than 0.001, depending on the stage of gestation). The maximum effect was observed with plasma obtained during the third trimester of pregnancy. The immunosuppressive activity was not detectable after parturition. It was further observed that desialation of both pregnancy and control plasma with neuraminidase diminished lymphocyte response to PHA (p less than 0.05). Addition of free sialic acid (0.1-1.0 mumol/ml) or treatment of the cells with neuraminidase (0.06-1.0 IU/ml) had no effect on lymphocyte transformation under assay conditions. These findings support the hypothesis that an immunosuppressive environment provided by pregnancy plasma could be one of the mechanisms protecting the antigenically alien fetus from maternal immunologic attack. The sialic acid content of maternal plasma did not appear to play a role in the immunosuppressive property of maternal plasma. On the contrary, the presence of plasma-bound sialic acid in the culture medium was found to be necessary for normal lymphocyte reactivity.

Blood Physiological Phenomena↗
PubMed1983

Levels of immunoreactive inhibin-like material in urine during the menstrual cycle.

Using a specific and sensitive radioimmunoassay, the authors determined levels of inhibin-like material in the urine of eight healthy women with normal menstrual cycle length of 28 +/- 4 days. The results revealed a cyclic variation in urinary immunoreactive inhibin levels during the menstrual cycles, with a sharp rise in levels three to four days prior to luteinizing hormone (LH) and follicle-stimulating hormone (FSH) peaks. These levels of immunoreactive inhibin may thus serve as a parameter to detect impending LH surge.

Animals↗
PubMed1983

Sialic acid, sialyltransferase and neuraminidase levels in maternal plasma, urine and lymphocytes during pregnancy and post-partum period--a longitudinal study in women.

The total sialic (N-acetylneuraminic acid) levels were serially determined in maternal plasma, urine and lymphocytes during human pregnancy and post-partum period. The enzymes, sialyltransferase and neuraminidase, were also examined in the plasma samples. The sialic acid content of plasma and urine (expressed in terms of the creatinine content in urine) was elevated during pregnancy and increased with advancing gestation (P less than 0.001). A few days (0-6) prior to parturition there was a significant (P less than 0.01) fall in the plasma sialic acid levels, which subsequently increased again in the post-partum period (1-14 days), reaching values even greater than that observed during pregnancy. On the other hand, there was no decrease in the urinary sialic acid levels before delivery, and the post-partum values in urine, though higher than the values obtained in non-pregnant women, were not significantly greater than the levels observed during pregnancy. The sialic acid levels in lymphocytes were not altered during pregnancy. There was also no statistically significant change in serum sialyltransferase activity at any stage of pregnancy or post-partum period, while neuraminidase was not detectable in any of the plasma samples. The results are discussed with reference to the role of circulating sialic acid during pregnancy.

Adult↗
PubMed1983

Interaction of thyrotrophin releasing hormone with inhibin in male rats.

Inhibin administered to adult male rats delayed the in-vivo pituitary responsiveness to thyrotrophin releasing hormone (TRH) as observed in terms of prolactin release in the serum. It also decreased the sensitivity of the pituitary gland to TRH, in terms of TSH release. However, inhibin alone did not alter the serum levels of prolactin and TSH, although it significantly suppressed serum FSH levels. In addition, the inhibin effect on FSH release was blocked by TRH.

Animals↗
PubMed1983

Shift of glycolysis as a marker of sperm maturation.

The presence of glycogen-phosphorylase (A and B forms), glucose-6-phosphatase and fructose-1, 6-diphosphatase in bonnet monkey spermatozoa was determined. The process of glycolysis gradually decreased and the process of reversal of glycolysis steadily increased in monkey spermatozoa as they move from testis to caput to corpus to cauda to vas deferens and finally in ejaculate. Hence in bonnet monkeys, the functional maturity of spermatozoa and the shift in glycolysis are closely related.

Animals↗
PubMed1983

Effect of chronic administration of inhibin and testosterone on spermatogenesis in adult male rats.

Inhibin (Inh) and testosterone (T) were administered to adult male rats for 32 days to evaluate their effect on spermatogenesis. Fifty micrograms of Inh was injected subcutaneously twice daily, and T was administered as Silastic implants 2.5 cm in length. Weights of testes and epididymides were significantly decreased in (Inh + T)- and T-treated groups, but not in Inh-treated rats. Although Inh alone could suppress both the testicular and the epididymal sperm count, maximum suppression was observed in the (Inh + T)-treated group. The effect on the epididymal sperm count, however, was pronounced. The accessory organ weights remained unaffected in all treated groups. Chronic administration of Inh and T results in partial impairment of spermatogenesis.

Animals↗
PubMed1982

Can vasectomy reduce the incidence of prostatic tumor?

Results from our laboratory have revealed that seminal plasma concentration of acid phosphatase, maltase, prolactin, citric acid, zinc and magnesium which are the secretory products of the prostate gland, decreased significantly in vasectomized men compared to those in controls namely normal fertile men. Further, it was observed that the decrease in prostatic function was not related to the time since vasectomy. Considering these two facts together, we propose that vasectomy may lead to decrease in the incidence of prostatic tumors - a disease that claims nearly 22,000 lives each year in the United States alone.

Acid Phosphatase↗
PubMed1982

A peptide in gastric secretion with inhibin-like properties.

The presence of inhibin like peptide which is biologically active in reducing FSH secretion in castrated rats and suppressing hCG-induced increase in ovarian weights of immature mice, is reported for the first time in gastric aspirates of normal men. Immunological characteristics of this peptide were similar to inhibin extracted from human seminal plasma. The concentration of inhibin-like peptide measured by RIA developed for seminal inhibin is more than thirty-fold higher in gastric aspirates compared with serum.

Animals↗
PubMed1982

An assessment of inhibin-like activity secreted by Sertoli cells in culture using castrated adult male rats.

Sertoli cells isolated from testes of 16-18 days old male rats were maintained in culture. Incubation media from these culture were pooled on day 7 and tested for its inhibin-like activity either with (SCCM) or after charcoal treatment (CSCCM) in castrated adult male rats. The assay was based on the tacit assumption that SCCM or CSCCM would specifically lower circulating blood serum levels of FSH. Subcutaneous (sc)injections of CSCCM at a dose level of 1 mg protein per rat, per day, x 3 days caused a specific suppression of FSH levels, while lower dosages of CSCCM (Protein content of 300 micrograms or 600 micrograms/rat/day, x 3 days) were without any affect on basal levels of FSH and LH. SCCM was ineffective at all dose levels tested. Intracardiac injections of varying doses of LHRH (25 to 400 ng/rat) to CSCCM pre-treated rats (200 micrograms/rat/day, x 3 days) failed to increase the levels of LH and FSH. These results support the presence of inhibin like activity in SCCM by a bioassay procedure alternate to in vitro pituitary cell culture system used by other investigators.

Animals↗
PubMed1982

Delta-9-tetrahydrocannabinol: its effect on hypothalamo-pituitary system in male rats.

Subcutaneous administration of delta-9-tetrahydrocannabinol (delta 9-THC) in adult male rats caused a decrease in serum luteinizing hormone (LH) levels with unchanged serum prolactin, pituitary LH and pituitary prolactin content. Response of pituitary to in vitro gonadotropin releasing hormone (GnRH) remained unaltered while the response to in vivo GnRH treatment was markedly increased with the drug indicating the pituitary to be functionally normal. Differences in the in vitro and in vivo response could be due to the endogenous steroid levels. The hypothalamic LH-RH content concommitantly increased. Delta-9-tetrahydrocannabinol may inhibit the release of luteinizing hormone releasing hormone (LHRH).

Animals↗
PubMed1982

Inhibin interaction with LHRH receptors at the pituitary level.

In order to investigate whether inhibin could modulate the action of luteinizing hormone releasing hormone (LHRH), the in vitro effect of inhibin of LHRH bindings to the pituitaries from intact adult male rats was studied. The inhibin preparations suppressed the binding of labeled LHRH to pituitary receptors in a dose-related manner. In vivo administration of inhibin decreased the pituitary LHRH receptor concentration, with an apparent increase in the affinity of these receptors. A dose-related decrease was observed in serum follicle stimulating hormone (FSH) levels in the same group whereas the serum luteinizing hormone (LH) levels remained unaltered. There may be a direct action of inhibin at the pituitary level to suppress FSH levels specifically.

Animals↗
PubMed1982

Effect of FSH deprivation on spermatogenesis in prepubertal mice.

A specific antiserum to ovine follicle stimulating hormone (AS/FSH) raised in rabbits and administered to prepubertal mice from days 5 to 35 of age, inhibited intermediate and type B spermatogonia. Development of spermatocytes, spermatids, and spermatozoa was affected, indicating a role for FSH in the initiation of spermatogenesis. Decrease in the testicular and epididymal weights, but not that of seminal vesicles and ventral prostate, demonstrated the specific action of AS/FSH. Reduction in the weights of the epididymis in AS/FSH-injected mice accompanied by the absence of spermatozoa in the lumen suggests a possible role for FSH in spermiation.

Animals↗