Effects of monosodium glutamate on food acceptance and toxicity of selenium in rats.

Food acceptance and toxic effects of feeding sodium selenite (Se) alone and in combination with monosodium glutamate (MSG), a taste enhancer were studied in the laboratory rat. Dose-dependent stimulation of daily food intake was observed with MSG offered in no-choice or bi-choice with the plain food. Consumption of pellets containing 0.05, 0.5 and 1.0% Se was significantly low than the plain or MSG containing pellets but their active ingredient was sufficient to cause mortality of rats. Food pellets containing both MSG and Se in no-choice feeding trial were not preferred by the rats, as their consumption remained low as compared to pellets containing only MSG. However, prior feeding on MSG containing pellets for two days increased the amount of intake of Se-containing pellets. No mortality of rats feeding on pellets containing different concentrations of MSG was recorded. Feeding on Se-containing pellets caused dose-dependent mortality on the third day of the trial. As compared to rats feeding on Se-containing pellets, the mortality rate was reduced in those provided Se in combination with MSG but the intake of active ingredient of Se in both these trials did not differ significantly. Decrease in death rate of rats feeding on Se in combination with MSG containing pellets suggested that addition of MSG to seleniferous food probably provide protection to some extent from the toxic effects of selenium. However, combination of excess doses of MSG and Se in food pellets caused mortality of all experimental animals.

Cystogenesis of antral follicles induced by dehydroepiandrosterone (DHEA) stimulates mast cell proliferation and maturation in the house rat (Rattus rattus) ovary.

Mast cell dynamics has been studied in relation to cystogenesis of ovarian follicles in the house rat. Immature rats were injected (s.c.) daily with DHEA (6.0 mg/100 g body weight) and were sacrificed on the day 8, 16 and 24 of the start of treatment. Ovarian sections of the treated rats had majority of the antral follicles undergoing atresia or in early stages of cystogenesis. Completely developed cysts were evident from the ovarian surface after 24 days of daily treatment. Treatment for 8 days resulted in significant increase in the number of alcian blue-positive ovarian mast cells. Ovaries after 16 days of DHEA treatment showed no marked change with regard to the number of total mast cells per unit area and staining characteristics. However, a significant rise in ovarian mast cell counts was recorded after 24 days of treatment and most of the cells contained safranin-positive red granules. This increase was attributed due to the increase in their number in medulla and stroma around the cystic follicles.

Effects of selenium toxicity on oestrous cyclicity, ovarian follicles, ovulation and foetal survival in rats.

Effects of intraperitoneal injections of sodium selenite (2.0 and 4.0 mg/kg body weight) to normally cycling female albino Wistar rats daily for 30 days, and of single injection either during proestrous or oestrous and at each stage of the 4-day oestrous cycle were determined on oestrous cyclicity, ovarian follicles, ovulation, implantation and pregnancy outcome on day 14 of gestation. Administration of selenite for 30 days had no effect on the duration of first two oestrous cycles but afterwards the rats remained at the dioestrus stage. Their ovaries developed cystic follicles. Selenite treatments during the oestrous cycle preceding mating affects the implantation and pregnancy outcome in a dose-related manner. Its single dose containing 2.0 mg/kg body weight administered either at proestrous or oestrous, though had no effect on different reproductive parameters investigated in this study but its daily dose during the 4 day oestrous cycle reduced the number of corpora lutea and implantations as compared to saline injected control female rats. Similar effects of a single dose of selenite (4.0 mg/kg body weight) when injected at proestrous were recorded. Higher dose of selenite at oestrous or throughout the cycle decreased the number of implantations, but in addition, also increased the resorption rate/litter on day 14 of gestation. The present studies clearly show that high selenium levels in the body during the oestrous cycle preceding mating affects the number of ovulations, implantations and live embryos depending upon its dose and stage of administration.

Quantitative assessment of changes and maturation of mast cells in the ovary of postnatal and adult rats, Rattus rattus.

Numerical changes in the distribution of immature mast cells in the different ovarian compartments of the immature and adult ovary of rats Rattus rattus have been studied using alcian blue-safranine staining method. Maturational changes of mast cells from the first day of birth to maturity of animal and during the oestrous cycle have also been determined. Immature animals were divided into five groups on the basis of their increasing body weights. All the mast cells in the ovary group of I and II were immature as they showed positive staining with alcian blue and appear to possess the proliferative capacity. Cells containing safranine-stained red granules were first observed in group III rats and they appeared simultaneously in hilus, medulla and cortical regions of the ovary. Total counts of immature mast cells per ovary increased significantly from group I to II, decreased in group III and thereafter no change was recorded in group IV and V. Mast cells in the ovary of rats of group I and II were mainly localized in the stroma, followed by medulla and hilus. In mature rats major part of cell population was concentrated in the hilar region. Alcian blue-positive mast cells were observed at all stages of oestrous cycle, their number per ovary was found to be highest at oestrus, intermediary at dioestrus and metoestrus, and lowest at pro-oestrus which suggested that new population of mast cells continue to differentiate in the cycling rat ovary.

Failure of hCG to reverse incipient atretic changes induced in granulosa cells of rat ovarian follicles.

Surface membrane changes in the granulosa cells from follicles at different times following a single dose of PMSG have been investigated after the incubation of cells in media with and without hCG by spectrophotometric measure of concanavalin A-induced cellular agglutination rate. Agglutination rate and final level of agglutination of cells do not change from 24 to 48 hr but significantly rise at 72, 96 and 120 hr after PMSG administration. Incubation of cells in presence of hCG for 20 min decrease the agglutination level of cells at 24, 48 and 72 hr and no significant change was observed at 96 and 120 hr. The results, thus suggest that atretic changes when induced in the surface membrane of granulosa cells (after 72 hr of PMSG administration) cannot be reversed with hCG.

Effect of restricted feeding of prepubertal and adult male rats on fertility and sex ratio.

Food consumption per day per rat decreased in animals kept on restricted feeding schedules (2, 4, 8 and 12 hr) during adulthood but it remained unchanged in immature rats except in a group which was restricted to feed for 2 hr. The body weight gain decreased significantly in both the age groups. Epididymal sperm concentration did not change with feeding restriction in adult rats but decreased significantly in rats which attained puberty during the study period. Conception rate in females after mating with males under study decreased considerably. Percentage of female pups was greater in litters obtained after mating with males kept on 2, 4 and 8 hr per day feeding schedules during prepubertal period. The results, thus reveal that restricted feeding during prepubertal period decreases fertility and affects sex ratios in rats.

Changes in catalase activity during follicular growth, atresia and luteinization in rat ovary.

Quantitative changes have been observed in the catalase activity during follicular growth, induced atresia and in corpora lutea of cycle and pregnancy. Large growing and preovulatory follicles showed higher enzyme activity as compared to the smaller follicles; the activity was mainly present in the thecal layer of the preovulatory follicle. After the blockade of ovulation with barbiturate, the activity increases significantly in the whole follicle and also in the thecal layers till third day of ovulation and afterward it declines on 5th day, suggesting that rise in catalase activity may exert a protective function against lytic actions of peroxide which is known to be produced in the ovary during several metabolic and steroidogenic events. The corpora lutea of the cycle showed significantly less enzyme activity than the corpora lutea of pregnancy. The significance of catalase activity during follicular and corpus luteum degeneration is discussed.

Chemotactic detection of incipient ovarian follicular atresia.

Chemotactic activity was measured in the follicular fluid collected from normal and atretic Graafian follicles isolated from the rat ovaries. The atresia of Graafian follicles was induced by pentobarbitone injections for 3 days beginning the day of proestrous. The chemotactic activity, as measured by direct morphological evaluation of cellular locomotion of individual cells and Boyden leading front assay, was significantly higher in follicular fluid from atretic follicles and it showed a progressive increase from day 1 to day 3 of blockade of ovulation. In vitro exposure of blocked follicles to PMSG and hCG on day 1, 2 and 3 failed to alter the chemotactic response of leukocytes towards follicular fluid of atretic follicles. Increased chemotaxis in the follicular fluid after 24 hr of blockade of ovulation appears to form an important criterion to identify atretic follicles well in advance, before the morphological symptoms of degeneration become apparent and the incipient change once induced in follicles is not reversed by gonadotropins.

Comparison of glucose-6-phosphate dehydrogenase activity in healthy and atretic follicles in rat ovary.

Changes in the glucose-6-phosphate dehydrogenase activity have been determined in relation to atresia of Graafian follicles in the rat ovary. Induction of atresia in follicles either due to absence of hCG in the hormonally stimulated immature ovaries or by repeated injections of pentobarbitone sodium to proestrous rats caused significant rise in the enzyme activity. Measurement of enzyme activity in isolated follicular compartments of healthy and atretic follicles revealed that it is significantly higher in the thecal tissue than the granulosa. Increase in enzyme activity in the atretic follicles than the healthy ones occurs due to its rise both in theca and granulosa cells. The significance of these changes in the enzyme activity in healthy and atretic follicles are discussed in relation to the precocious luteinization of cells in the follicular envelope with the onset of atresia.

Mast cell dynamics in relation to ovulation in rat ovary.

Quantitative changes in the total number and distribution of ovarian mast cells have been studied after administration of histamine and pentobarbitone sodium to rats at pro-oestrous stage. No significant differences in the total cell counts per section and percentage distribution in the hilar and stromal regions of the ovary were observed after blockade of ovulation with pentobarbitone as compared to control. However, after 24 hr of histamine treatment the number of cells was significantly less than that of oestrous stage but no change was seen relative to the pro-oestrous stage. The results suggest that the number of cells increases late in the pro-oestrous stage by invasion or differentiation in the stroma to maintain the requisite levels of histamine during ovulation.