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Biomedical subjects

L K Malendowicz

Publications and source records attributed to L K Malendowicz.

At least 235 records · Page 13Linked to original sources
PubMed1980

Sex differences in adrenocortical structure and function. VI. Long-term effect of gonadectomy and testosterone or estradiol replacement on rat adrenal cortex.

Gonadectomy or sham operations were performed on rats of Wistar strain weighing 150--170 g. Animals were sacrificed in groups, males 397 days and females 395 days after surgery. 14 days before autopsy some of the gonadectomized rats were injected with a single dose of depo-testosterone or depo-estradiol respectively. Absolute as well as relative adrenal weights were larger in female than in male rats. Long-term orchiectomy did not change these weights while testosterone, if compared with control, lowers the weights of the adrenals. Long-term ovariectomy lowers the weights of the glands and estradiol reversed them to the control level. Adrenal cortex of rats studied show irregular zonation. Within the zona fasciculata two types of cells were observed--with strongly eosinophilic and pale cytoplasm. In some cases groups of hypertrophied cells surrounded by spindle-shaped cells were observed. Neither long-term gonadectomy nor gonadal hormone replacement has a marked effect on the structure of the adrenal cortex. In male and female rats there was no difference in the volume of single zona fasciculata and reticularis cells. Long-term orchiectomy has no effect on this volume while testosterone resulted in a lowering of volume of zona fasiculata cells. Neither long-term ovariectomy nor estradiol has an effect on morphometric parameters studied in the fasciculata and reticularis zones. Distinct sex differences and dependence on sex hormones were found in reactions for alpha-glycerophosphate dehydrogenase and nonspecific esterases activity.

Adrenal Cortex↗
PubMed1980

Progesterone effects on adrenal cortex of intact and ovariectomized rat.

Studies on the effects of progesterone on rat adrenal cortex were performed on two age groups of intact or ovariectomized female rats. Ovariectomy was performed on animals weighing 150-170 g and autopsies were carried out 6 weeks and 8.5 months after surgery (4- and 11-month-old animals). 12 days before autopsy part of the animals were treated with progesterone at a daily dose of 5 mg per rat, the others received a single injection of depot-estradiol or jointly with progesterone and estradiol. Intact female rats of a corresponding age were treated with progesterone or vehicle only. In younger intact female rats progesterone lowers the relative adrenal weight and corticosterone output by whole adrenal homogenates. In older rats despite the lowering in absolute and relative adrenal weights there were no changes in corticosterone output. In ovariectomized rats of both age groups progesterone had no marked effects on studied parameters while estradiol resulted in an increase in adrenal weights and corticosterone output. Part of the changes evoked by estradiol were prevented by concomitant progesterone administration. The above described changes were accompanied by morphologic alterations. Performed studies show that progesterone effects on the rat adrenal cortex are modified by the ovaries and depend on the age of animals.

Adrenal Cortex↗
PubMed1979

Sex differences in adrenocortical structure and function. V. The effects of postpubertal gonadectomy and gonadal hormone replacement on nuclear-cytoplasmic ratio, morphology and histochemistry of rat adrenal cortex.

Studies were carried out on adult rats of Wistar strain. Six weeks after postpubertal gonadectomy some of the orchiectomized rats were injected with a single dose of testosterone cypionate and ovari-ctomized rats with estradiol cypionate (17 beta-cyclopentyloproprionate esters of testosterone or estradiol). The control rats were sham operated. Investigations were carried out 8 weeks after surgery. Absolute and relative adrenal weight is lower in the male than in the female rat. Orchiectomy increases these weights while testosterone restores them to their normal level. Ovariectomy has no effect on the weight of adrenal, estradiol, however, increases the relative weight of the gland. The adrenal cortex of the adult female is wider than in the adult male rat and in female gland sudanophobic zone is lacking. Orchiectomy leads to the broadening of the adrenal cortex and testosterone replacement has an opposite effect. Ovariectomy has no effect on the structure of adrenal cortex and estradiol replacement resulted in the narrowing of zona glomerulosa. There were no differences in the nuclear-cytoplasmic ratio of zona glomerulosa cells in male and Female rats and neither gonadectomy nor gonadal hormone replacement has no effect on this parameter. The nuclear-cytoplasmic ratio of zona fasciculata cells in the male is markedly higher than in female. Orchiectomy lowers this ratio and testosterone restores it to the normal level. Neither ovariectomy nor estradiol replacement has effect on the nuclear-cytoplasmic ratio of zona fasciculata cells. Similar changes as those in the zona fasciculata were observed in zona reticularis cells. Among the oxidoreductases studied, the most marked sex differences were found in alpha-glycerophosphate dehydrogenase activity. In control female rats an intense reaction for this enzyme is observed in broad band of cells of the zona fasciculata interna, while in male rats only individual cells showed this reaction. In orchiectomized rats the reaction for this enzyme is similar as in control female rats and testosterone restores it to normal. Ovariectomy has no effect on localisation of reaction while after estradiol replacement reaction was more intense. Regarding the remaining oxidoreductases studied, in the adrenal cortex of rats of both sexes no marked differences were observed in localization, however, intensity of reaction depended upon applied experimental conditions. More distinct sex differences were observed in topochemistry of some hydrolases and intensity of reaction depended upon the applied experimental conditions.

Adrenal Cortex↗
PubMed1978

Sex differences in adrenocortical structure and function. IV. Effects of postpubertal gonadectomy and sex hormones on adrenal steroid 5alpha-reductase activity in the rat.

Studies on the effects of gonadectomy and gonadal hormones on adrenal 5alpha-reductase activity in the rat were performed. In rats of both sexes postpubertal gonadectomy is followed by an increase in adrenal 5alpha-reductase activity. The enzyme activity gradually increases during 6 postoperative weeks. Replacement of testosterone or estradiol to gonadectomized rats within 5 days lowers the enzyme activity to the level observed in intact control rats. Likewise, testosterone injected to ovariectomized rats and estradiol administered to orchiectomized animals within 5 days reversed the effect of gonadectomy on 5alpha-reductase. In all experiments the temporal changes in 5alpha-reductase activity were similar. By contrast, the weight of seminal vesicles of gonadectomized rats was normalized after 7 days of testosterone action whereas the highest uterine weight was found 3 days post depot-estradiol injection. Regarding temporal changes in 5alpha-reductase activity the experiments revealed similar inhibitory action of testosterone and estradiol. This action probably depends on the inhibition of enzyme synthesis by gonadal hormones. Moreover, greater sensitivity of adrenals of gonadectomized rats to testosterone, if compared with seminal vesicles, was observed.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1977

Sex dimorphism in the thyroid gland. I. Morphometric studies on the thyroid gland of intact adult male and female rats.

Morphometric studies were performed on thyroid glands of intact adult male and female rats. Thyroid follicular cells are markedly higher in the male rats than in the females during estrus. The volume fraction of the epithelium is larger but the fraction of colloid is less in males than in females. Also epithelium/colloid ratio is higher in male than in female rats.

Animals↗
PubMed1976

Studies on the toxic effect of cadmium in the rat. I. Testicular changes induced by a single subcutaneous injection of cadmium chloride.

Adult male rats of Wistar strain were subcutaneously injected with a single dose of 0.025 mM CdCl2/kg body weight. The autopsies were performed 2 and 12 weeks post cadmium injection. Experimental animals showed a normal gain of body weight while a marked lowering of the testes weight was observed. The lowering of testes weight of cadmium treated rats occured mainly due to the necrosis of seminiferous tubules, volume of which is markedly lower if compared to intact control rats. After 2 weeks of experiment a marked enlargement of the interstitial gland of the testis occured while after 12 weeks the gland is markedly lower if compared to control rats and to rats studied 2 weeks post cadmium injection. Histochemical reactions for lactic, succinic, alpha-glycerophosphate and 3beta-hydroxy steroid dehydrogenases, NADH tetrazolium reductase, acid phosphatase and nonspecific esterases showed for irreversible necrotic changes of seminiferous tubules of cadmium treated rats while the damage to interstitial gland is only temporary.

Animals↗
PubMed1976

Sex differences in adrenocortical structure and function. III. The effects of postpubertal gonadectomy and gonadal hormone replacement on adrenal cholesterol sidechain cleavage activity and on steroids biosynthesis by rat adrenal homogenates.

In rats postpubertal orchiectomy results in an increase in the adrenal weight, testosterone replacement restores the adrenal weight to the normal level. Neither ovariectomy (8 weeks of duration) nor estradiol replacement has an effect on adrenal weight in female rats. Pregnenolone synthesis as well as corticosterone and blue tetrazolium-positive steroids secretion is significantly higher in homogenates of adrenals from female rats than from males. Orchiectomy results in a marked increase in pregnenolone biosynthesis, testosterone replacement restores the value to the normal levels. Neither ovariectomy nor estradiol replacement has an effect on pregnenolone synthesis in v i t r o. In both sexes gonadectomy causes a marked decrease in corticosterone output by adrenal homogenates, concomitantly the increase in the adrenal 5alpha-reductase activity is observed. The ratio of secreted corticosterone to pregnenolone is significantly lower in gonadectomized rats of both sexes than in control animals. Estradiol or testosterone replacement inhibits the adrenal 5alpha-reductase activity and restores the corticosterone output as well as corticosterone/pregnenolone ratio to the normal values. The above described findings show that the sex differences in steroids secretion by the rat adrenal are partially conditioned by a cholesterol sidechain cleavage activity. Testosterone inhibits this activity while estradiol under applied experimental conditions has no effect on the cholesterol sidechain cleavage activity.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1975

A karyometric and stereologic study of the effects of gonadotrophin and testosterone on the interstitial gland of the testis of intact and endoxan treated rats.

Adult male rats were treated daily for 18 days with endoxan in doses of 4 mg/kg of body weight or testosterone in doses 2.5 mg per rat. For the last 5 days of the experiment some of the rats received gonadotrophin injections in doses of 50 I.U. Karyometric and stereologic studies were undertaken on paraffin sections of the testes stained with haematoxylin and eosin. Endoxan treatment decrease the nuclear volume of the Leydig cells and lowers the volume fraction occupied by the interstitial gland in the testis. These changes were accompanied by a decrease in the intensity of reaction for acid phosphatase, non-specific esterases and 3-beta-hydroxy-steroid dehydrogenase. Testosterone injected alone or jointly with endoxan resulted in more pronounced changes than following treatment with endoxan alone. As expected, gonadotrophin injections into intact rats resulted in a marked increase in nuclear volume of the Leydig cells and in the volume fraction of the interstitial gland. This effect of gonadotrophin on the interstitial gland of the rat testis was partially inhibited by endoxan treatment. It follows from these experiments that endoxan impairs the functional activity of the interstitial gland of the rat testes by lowering the endogenous gonadotrophin levels, as well as by direct action on the Leydig cells.

Acid Phosphatase↗
PubMed1975

Role of adrenal 5alpha-reductase activity in determining the responsiveness of hypophysectomized rats to ACTH.

Studies were conducted to examine the contribution of adrenal 5alpha-reductase to the phenomenon of diminished adrenal "responsiveness" to ACTH after hypophysectomy in rats. Rats hypophysectomized for 1 week secreted small amounts of corticosterone (B), 5alpha-dihydrocorticosterone (DHB) and 3beta,5alpha-tetrahydrocorticosterone (R) acutely after ACTH. Adrenal reductase activity in vitro at that time was high. After replacement with ACTH for 24 h, B,DBH, and R secretion increased slightly. Reductase activity remained high. Treatment with ACTH for 2 days further stimulated secretion of DHB and R but not B. Reductase activity was unaffected. Enzyme activity declined at 3 days concomitant with a proportionately greater increase in B than DHB and R secretion. Only after 7 days of ACTH did B secretion exceed DHB and R output. At that time, reductase activity was still lower. The results establish the functional significance of 5alpha-reductase activity as a regulatory site for the action of ACTH in determining the composition of adrenocortical secretory products in hypophysectomized rats.

Adrenal Glands↗
PubMed1975

The effects of adrenalectomy and hydrocortisone replacement on the thyriod of the adult male rat I. Morphometrical data and histochemistry of some oxidative enzymes.

Morphometrical and histochemical studies were performed to determine the effects of adrenalectomy and hydrocortisone replacement on the rat thyroid. It follows from the performed studies that morphometrical and histochemical changes in the rat thyroid induced by adrenalectomy or hydrocortisone replacement depend upon the duration of the experiment. From the 4th day of the experiment adrenalectomy results in an increase in the volume fraction of the epithelium of the thyroid vesicles with a concomitant decrease of the colloid fraction. As compared to sham operated animals on the 10th day of the experiment the increase in the height of the epithelial cells was seen. Hydrocortisone replacement partially prevents the thyroid changes induced by adrenalectomy, however, this hormone markedly increases the volume fraction of the thyroid stroma and the height of the epithelial cells. On the other hand, histochemical reactions for various oxido-reductases do not provide helpful information for evaluation of the secretory activity of the rat thyroid. It follows from our results that adrenalectomy enhances thyroid stimulation by TSH and enhances the secretory activity of this gland, effects partially prevented by hydrocortisone replacement.

Adrenal Glands↗