Effects of vanadyl sulphate on ornithine decarboxylase and progesterone levels in the ovary of rat

The effects of vanadyl sulphate in vitro on the levels of ODC activity and progesterone synthesis in ovaries were studied. The levels of ODC in the ovaries were stimulated with high concentration of vanadyl sulphate and at low concentrations there was no change in the levels of ODC activity. On the contrary progesterone levels were stimulated with low concentrations of vanadyl sulphate and were inhibited at higher concentrations. Vanadyl sulphate showed additional stimulation of ODC activity, when it was added with hCG and caused inhibition of hCG induced progesterone biosynthesis. These results show that the effects of vanadyl sulphate on ODC and progesterone are different.

Regulation of DNA methyltransferase in the testis of rat

In mammalian DNA, the base 5-methylcytosine is generated by post-replicational methylation of cytosine residue by DNA methyltransferase. In this study the levels of DNA methyltransferase of testis during various ages and the effects of gonadotropic hormones on immature rat testis were studied. It was observed that the specific activity of DNA methyltransferase was high in the testis at the age of 20 and 30 days. After this age, the activity of DNA methyltransferase declined significantly and was maintained at lower level from days 120 to 240. Treatment with follicle stimulating hormone significantly decreased the enzyme activity in the testis while luteinizing hormone did not cause any effect. These results indicate that DNA methyltransferase of certain cells in the testis is under the influence of follicle stimulating hormone.

Desensitization of immature rat testicular ornithine decarboxylase to arginine vasopressin

Prior exposure of immature rat testis to arginine vasopressin caused the testis refractory at 24 h in terms of ornithine decarboxylase activity. Arginine vasopressin caused desensitization both in Leydig cells and seminiferous tubules. Arginine vasopressin induced desensitization was found to be both time and dose-dependent. Arginine vasopressin desensitized testis was refractory to luteinizing hormone, follicle stimulating hormone, norepinephrine, dibutyryl cAMP, phorbol-myristate acetate and cholera toxin at 24 h. Arginine vasopressin desensitized testis showed recovery of response to norepinephrine at 48 h after the first injection. On the contrary arginine vasopressin could stimulate ornithine decarboxylase in luteinizing hormone desensitized testis. These results indicate that in arginine vasopressin desensitized testis the block is at post cAMP step which is common to both cAMP dependent and protein kinase C-diacylglycerol system in stimulating testicular ornithine decarboxylase.

Conjunctival goblet cells and mitotic rate in children with retinol deficiency and measles

To study the effect of retinol deficiency and measles on the conjunctival epithelium, we determined the epithelial mitotic rate (MR) and goblet cell frequency (GCF) in conjunctival biopsy specimens from preschool children in Hyderabad, India. We studied three groups of children: normal appearing, clinically retinol deficient (defined by the presence of superficial fine punctate keratitis), and clinically retinol deficient with measles. The last group was subdivided into those with low serum retinol levels (less than or equal to 20 micrograms/dL [less than or equal to mumol/L]) and those with normal serum retinol levels (greater than 20 micrograms/dL [greater than 0.70 mumol/L]). In the control group of seven normal-appearing children with a mean age of 4.6 years, the mean MR was 1.3% +/- 0.4%, and the mean GCF was 8.0% +/- 3.6% of the basal epithelial cells. In seven children with clinical retinol deficiency, the mean MR was 15.4% +/- 1.2%, and the mean GCF was 1.0% +/- 0.5%, values significantly different from normal ones. Among 11 children with clinical retinol deficiency, measles, and low serum retinol levels, the mean MR was 9.0% +/- 1.9%, and the mean GCF was 3.1% +/- 1.1%, values not statistically different from those in children with clinical retinol deficiency alone. Five children with clinical retinol deficiency, measles, and normal serum retinol levels had a mean MR of 10.2% +/- 3.7% and a mean GCF of 1.9% +/- 1.7%, values similar to those in the other disease groups. This indicates that retinol deficiency sufficient to cause clinical signs without subepithelial scarring or keratinization is associated with hyperproliferation of the conjunctiva whether or not there is a superimposed measles infection.

Regulation of cytoplasmic poly(A) polymerase activity by dihydrotestosterone in the kidney of rat

Polyadenylation of mRNA, a post-transcriptional phenomenon, is catalysed by cytoplasmic and nuclear poly(A) polymerases. During normal growth and development cytoplasmic poly(A) polymerase activity in the kidney of rat increased from day 20 reaching to a peak at 35 days. Dihydrotestosterone at a dose of 500 micrograms and above significantly stimulated the enzyme activity in the cortex of kidney in the castrated animals. A single dose of dihydrotestosterone caused significant increase in the enzyme activity at 12 h after treatment and was maintained till 24 h. Antiandrogen cyproterone acetate inhibited dihydrotestosterone-induced enzyme activity in kidney cortex. These results show that cytoplasmic poly(A) polymerase of rat kidney is regulated by dihydrotestosterone.

Stimulation of testicular ornithine decarboxylase activity by arginine vasopressin

Intratesticular injection with arginine vasopressin caused stimulation of ornithine decarboxylase activity in the testes of immature rats. The increase in ornithine decarboxylase activity in response to arginine vasopressin was dose and time dependent. Maximal stimulation of ornithine decarboxylase activity occurred at 2 h after injection with 0.1 micrograms of arginine vasopressin. It was observed that stimulation of ornithine decarboxylase activity occurred in seminiferous tubules and in Leydig cells of the testis in response to arginine vasopressin.

Direct inhibitory actions of GnRH on accessory reproductive organs of rat

Recently gonadotropin releasing hormone (GnRH) and its agonistic analogs were demonstrated to have some direct actions in accessory reproductive organs. In our study the effects of GnRH and its analogs on some steroid hormone induced responses were investigated. GnRH and its analogs inhibited estradiol induced ornithine decarboxylase (ODC) and glucosamine-6-phosphate synthase activities in the uterus of rat. These enzymes which are markers for cell proliferation are regulatory enzymes in the biosynthetic pathways of polyamines and glycoproteins, respectively. Similarly, GnRH and its analogs also inhibited testosterone stimulated ODC activity in ventral prostate of rat. In addition, GnRH analog inhibited incorporation of radioactive precursors into RNA and protein induced by estradiol in uterus or dihydrotestosterone (DHT) in ventral prostate. In an effort to elucidate the mechanism of action of GnRH in uterus, it was found that GnRH analog treatment does not alter the estradiol receptor content in vivo. Also, GnRH does not show any effect on radioactive estradiol binding to its receptor in vitro. Hence, the inhibitory actions of GnRH in uterus may not involve estradiol receptors. However, GnRH analogs were found to have post-transcriptional effects. It was observed that DHT induced poly(A) polymerase activity in ventral prostate and estradiol induced poly(A) polymerase activity in uterus were inhibited by GnRH analog treatment. It was further observed that GnRH inhibited incorporation of [3H]uridine into poly(A)+ RNA of ventral prostate. This indicates that the inhibitory effects of GnRH involve post-transcriptional mechanisms.

Inhibition of sex-steroid hormone induced ornithine decarboxylase and poly(A)-polymerase activities by a GnRH agonist in the rat kidney

Recently GnRH and its synthetic agonists were shown to exert extrapituitary actions and inhibit the growth-promoting effects of testosterone and estradiol. In the present study, the long-term effect of GnRH agonist [des-Gly10, D-Ala6-GnRH ethylamide GnRHa] on the steroid-induced renotropic effect was investigated. Gonadectomy of 30-day old male and female rats resulted in the drastic reduction of kidney ornithine decarboxylase (ODC) activity. Injection of testosterone (75 micrograms/rat) or estradiol (1 microgram/rat) to castrated rats significantly increased the enzyme activity at 24 h. Treatment with the GnRH agonist, two doses of 100 micrograms each, caused significant inhibition of the hormone induced ODC activity. Similarly injection of dihydrotestosterone to castrated adult male rats significantly increased poly(A)-polymerase activity at 24 h. Two doses of 100 micrograms of GnRHa caused significant inhibition of DHT induced poly(A)-polymerase activity. These results show that chronic exposure to potent GnRH analogs may have anti-steroidal activity in the kidney.

Desensitization of testicular ornithine decarboxylase to gonadotropin releasing hormone and gonadotropic hormones

Prior exposure of the testis to gonadotropin releasing hormone, luteinizing hormone or follicle stimulating hormone caused the testis refractory to these hormones in terms of ornithine decarboxylase activity at 24 h. Luteinizing hormone caused desensitization in the Leydig cells while the levels of ornithine decarboxylase in the seminiferous tubules were unaltered. In gonadotropin releasing hormone desensitized testis all the other treated compounds namely, luteinizing hormone, follicle stimulating hormone, prostaglandin F2 alpha, norepinephrine and cyclic AMP caused stimulation of ornithine decarboxylase activity. The testis desensitized with LH responded to cyclic AMP and norepinephrine whereas prostaglandin E2 or gonadotropin releasing hormone caused less stimulation of ornithine decarboxylase activity. These results indicate that testicular desensitization to gonadotropin releasing hormone and luteinizing hormone is not due to a post cyclic AMP block.

Effect of gonadotropin releasing hormone on ventral prostate of rat

Testosterone induced increase in ornithine decarboxylase (ODC) activity was inhibited by simultaneous treatment with gonadotropin releasing hormone (GnRH) and its analogue in the ventral prostate of rat. Inhibition of 3H-uridine, 3H-phenylalanine and 3H-leucine incorporation into TCA precipitable material was also inhibited by GnRH in the dihydrotestosterone (DHT) treated animals. These studies further confirm that GnRH acts directly on ventral prostate and causes inhibitory effects.

Quantitative aspects of metal ion binding to certain transfer RNA anticodon loop modified nucleosides

Magnesium and manganese ions bind strongly to the unusual transfer RNA anticodon loop nucleotides, N-[(9-beta-D-ribofuranosyl-9H-purin-6-yl)carbamoyl]-L-threonine 5'-monophosphate (pt6A) and uridine-5-oxyacetic acid 5'-monophosphate (pV). Potentiometric measurements have shown that the delta G for metal ion-pt6A complex formation is 2-3-times more exothermic than for AMP. Electron-nuclear longitudinal dipolar relaxation data yielded manganese-ligand atom distances which permit a three-dimensional construct of the complex in which metal is coordinated to the phosphate, carboxylate of the threonine side-chain (with the nucleotide in the anti glycosidic conformation) and N7 of the adenine ring. Similarly, manganese binds strongly to pV, involving phosphate and carboxylate functions. It is possible that a facet of the functional role of these unusual residues is to chelate magnesium ions and in so doing permit optimum anticodon loop conformational stability and stability of tRNA-mRNA-ribosome complexes.

Direct inhibitory effect of gonadotropin releasing hormone in the uterus of rat

Estradiol induced increase in ornithine decarboxylase (ODC) and glucosamine-6-phosphate synthase activities of rat uterus were inhibited by simultaneous treatment with gonadotropin releasing hormone (GnRH) or its agonists. The direct inhibitory effect of GnRH analogs was found to be dose dependent. It was observed that a higher dose of GnRH analog was needed to cause inhibition of glucosamine-6-phosphate synthase when compared to ODC activity. The inhibitory effect of GnRH was not observed if its injection was delayed following estradiol treatment. These results show that the extra-pituitary inhibitory effects of GnRH involves enzymes associated with cell proliferation.

Androgen regulation of poly(A) polymerase in the ventral prostate of rat

The effect of various hormones on the levels of poly(A) polymerase in the ventral prostate of castrated rats was investigated. It was observed that this enzyme is specifically induced by androgens; progesterone and estradiol-17 beta did not cause stimulation of poly(A) polymerase activity. Dihydrotestosterone-induced poly(A) polymerase was inhibited by cordycepin, actinomycin-D and cycloheximide, which indicates that the genetic transcription leading to the enzyme poly(A) polymerase is regulated by androgens in the ventral prostate.

Desensitization of ornithine decarboxylase activity to norepinephrine in the testis of rat

Injection of norepinephrine (NE) at a dose of 10 micrograms per testis caused the testis refractory in terms of ornithine decarboxylase (ODC) activity at 24 h. This desensitization was found to be both time and dose dependent. Injection with follicle stimulating hormone, luteinizing hormone, prostaglandin F2 alpha, cyclic AMP or epinephrine to norepinephrine desensitized testis caused stimulation of ODC activity. This indicates that the refractoriness caused by norepinephrine is specific to this agent alone.

Desensitization of testicular ornithine decarboxylase to prostaglandin E2

Intratesticular injection of prostaglandin E2 at a dose of 10 or 25 micrograms per testis caused desensitization of the testis to ornithine decarboxylase activity at 24 h after the injection. PGE2 caused desensitization in both Leydig cells and seminiferous tubules. The desensitized testis was refractory to follicle stimulating hormone, luteinizing hormone and cAMP in addition to PGE2. These results indicate that testicular desensitization to PGE2 is at a step beyond cAMP formation.

Inhibition of polyadenylation of mRNA by gonadotropin releasing hormone

The mechanism of extra pituitary inhibitory action of gonadotropin releasing hormone (GnRH) was investigated. Simultaneous injection of GnRH caused dose dependent inhibition of dihydrotestosterone (DHT) induced poly(A) polymerase in the ventral prostate of rat. In addition injection of GnRH to DHT treated animals caused reduced incorporation of 3H-uridine into poly(A)+ mRNA. Since poly(A) segment is known to help in translation of mRNA, it is possible that the inhibitory effect of GnRH is due to the inhibition of polyadenylation of mRNA.

Androgen influences on glucosamine 6-phosphate synthase in the epididymis of the rat

Glucosamine 6-phosphate synthase activity in the total, caput, and cauda epididymis was estimated. Efferent duct ligation for 7 or 16 days caused significant reduction in the enzyme activity of caput epididymidis only and had no effect on the cauda epididymidis. Treatment with dihydrotestosterone (DHT) at a dose of 100 micrograms per day restored the enzyme activity in the caput epididymidis.

Early menopause and its determinants

In rural women in Andhra Pradesh, major determinants of early menopause are poor health status, particularly low haemoglobin and protein levels, increased parity, and pathological conditions including infection by bacteria, fungi and viruses. Early menopause leads to increased likelihood of extramarital sexual relations by husbands, resulting in family disharmony. As remedial measures, a greater age difference between prospective spouses, education in sexual hygiene, improvement of health and nutritional status, and limitation of conception are indicated.