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Biomedical subjects

L K Malendowicz

Publications and source records attributed to L K Malendowicz.

At least 199 records · Page 11Linked to original sources
PubMed1986

Sex differences in adrenocortical structure and function. XXII. Light- and electron-microscopic morphometric studies on the effects of gonadectomy and gonadal hormone replacement on the rat adrenal cortex.

The cytological aspects of sexual dimorphism in the rat adrenal cortex and its relationship to the gonads have been investigated. The adrenal glands of mature female rats were heavier than those of males, and morphometry showed that this was almost exclusively due to conspicuous differences in the volume of cells of the zona fasciculata (ZF) and zona reticularis (ZR). Stereology demonstrated that the volume of the mitochondrial and lipid droplet compartments, as well as the surface area per cell of mitochondrial cristae and smooth endoplasmic reticulum tubules, were markedly higher in the ZF and ZR cells of female animals. Orchiectomy increased and ovariectomy decreased the adrenal weight, by eliciting hypertrophy and atrophy, respectively, of ZF and ZR cells; these effects of gonadectomy were reversed by the appropriate gonadal hormone replacement. It is suggested that the sexual dimorphism of the rat adrenal cortex may depend upon the inhibitory action of testosterone and the stimulatory effect of estradiol on the hypothalamo-hypophyseal-adrenal axis.

Adrenal Cortex↗
PubMed1986

Short- and long-term effects of ACTH on the adrenal zona glomerulosa of the rat. A coupled stereological and enzymological study.

Short-term ACTH treatment provoked a decrease in volume of the lipid-droplet compartment in rat zona glomerulosa cells, and a rise in plasma and intracellular concentrations of corticosterone and aldosterone. It enhanced activities of 3 beta-hydroxysteroid dehydrogenase (3 beta HSD), 11 beta-hydroxylase (11 beta OH) and 18-hydroxylase (18OH). Long-term ACTH administration produced a hypertrophy of the zona glomerulosa and its parenchymal cells, a result of the increase in volume of the smooth endoplasmic reticulum and the mitochondrial compartment. The surface area per cell of mitochondrial inner membranes increased; the tubular cristae were transformed into a homogeneous population of vesicles. The plasma and intracellular concentrations of corticosterone further increased, whereas those of aldosterone fell below basal levels (the "aldosterone-escape" phenomenon). The activities of 3 beta HSD and 11 beta OH were enhanced, that of 180H decreased. Therefore, ACTH stimulates zona glomerulosa growth and transforms parenchymal elements into zona fasciculata cell-types. Cyanoketone nullified acute ACTH effects on plasma and intracellular concentrations of corticosterone and aldosterone, but did not affect the activities of 11 beta OH and 18OH. Chronic ACTH treatment produced similar results, although 18OH activity was not suppressed. The mechanism underlying the "aldosterone-escape" phenomenon may thus involve a rise in the intracellular concentration of corticosterone, caused by the enhanced synthesis and activation of 3 beta HSD and 11 beta OH.

3-Hydroxysteroid Dehydrogenases↗
PubMed1986

Sex differences in adrenocortical structure and function. XXI. The effects of gonadectomy and testosterone or estradiol replacement on mitotic activity of the rat adrenal cortex.

The study was designed to investigate the mitotic activity of adrenal cortex in the adult male and female rats and to explain the effects of gonadal hormones on proliferation of rat adrenocortical cells. Mitotic index in individual zones of the adrenal cortex as well as a total number of mitoses on the "equatorial" sections of the gland were estimated in dexamethasone and colchicine pretreated control, gonadectomized and gonadectomized-gonadal hormone replaced rats. If compared with males, mitotic index of the zona reticularis (ZR) cells was higher in females, however, there was no difference in the remaining zones of the cortex. Neither orchiectomy nor testosterone had an effect on mitotic index of the zona glomerulosa (ZG) and zona fasciculata (ZF) cells. In the ZR, orchiectomy increased this index, an effect reversed by testosterone. Neither ovariectomy nor estradiol administration had an effect on mitotic index of the ZG and ZF, while in the ZR estradiol lowered this index if compared with control and gonadectomized rats. Total number of mitoses per "equatorial" section of the gland was similar in male and female rats. Orchiectomy increased this value, an effect reversed by testosterone. On the other hand, neither ovariectomy nor estradiol had an effect on the total number of mitoses per section of the adrenal gland.

Adrenal Cortex↗
PubMed1986

Short- and long-term effects of angiotensin II on the rat adrenal zona glomerulosa. A coupled stereological and enzymological study.

Long-term angiotensin II administration induced a time-dependent increase in the volume of rat zona glomerulosa cells and in the plasma concentration of aldosterone. Cell hypertrophy is coupled with comparable increases in the surface area per cell of mitochondrial cristae and in the activity per cell of 18-hydroxylase. 11 beta-hydroxylase activity was not affected. These findings allow to suggest that the angiotensin-II-enhanced growth of rat zona glomerulosa is associated with the de novo synthesis of 18-hydroxylase.

Adrenal Cortex↗
PubMed1986

Sex dimorphism in the thyroid gland. IV. Cytologic aspects of sex dimorphism in the rat thyroid gland.

This study was designed to explain whether the sex-dependent differences in the structure of the thyroid gland of adult male and female rats depend on quantitative or qualitative changes in the thyroid follicular cells. Absolute thyroid gland weight was similar in male and female rats, but its relative weight was markedly higher in females however. Volume fractions of epithelium and stroma were higher and that of colloid lower in male than in female rats and the epithelium/colloid ratio was higher in the males. Also absolute the volumes (in mm3) of epithelium and stroma were higher in the males; the thyroid gland of females contained more colloid. The average volume of a thyroid follicular cell, estimated by stereology, was higher in males than in females, although the thyroid gland contained similar numbers of follicular cells in both sexes. Also, thyroid glands from both male and female rats contained a similar DNA quantity. Results of the present study show that the sex dimorphism in the rat thyroid depends upon a difference in the mean volume of thyroid follicular cells, with males having larger cells than females. However, in both sexes the thyroid gland contains a similar quantity of these cells.

Animals↗
PubMed1986

Comparative stereological studies on the effects of long term CRF and ACTH treatment on the cortex of the suprarenal gland.

The aim of the study was to investigate by means of stereological and biochemical methods the effects of long-term CRF administration on the cortex of the suprarenal gland of adult male rats and to compare these effects with those of ACTH. Both CRF (administered into the lateral ventricle of the brain) and ACTH resulted after 8 days in an increase in weight of the suprarenal gland. Both treatments increased the volume of individual adrenocortical zones and the average volume of adrenocortical cells as well as enhancing the total number of parenchymal cells in the paired glands. There was also no significant difference in those functional parameters studied of the adrenocortical cells of CRF- and ACTH-treated rats. Thus, long term treatment of adult male rats with CRF evoked adrenocortical changes similar to those observed after ACTH administration.

Adrenal Cortex↗
PubMed1986

Stereologic investigations on the effects of pinealectomy, melatonin and sex hormones on the rat thyroid gland.

The aim of the study was to investigate, by means of stereology, the effects of pinealectomy (PX) and melatonin on the rat thyroid gland and to explain whether sex hormone effects on the gland are related to the presence of pineal gland. Gonadectomized rats of both sexes were employed, some of them were PX and on remaining sham surgery was performed. In appropriate groups rats were treated with melatonin, testosterone and estradiol. The volume of thyroid colloid, epithelium and stroma and the epithelium/colloid ratios were estimated by stereologic methods. Neither PX nor melatonin had a significant effect on the volume of principal histologic components of the thyroid gland and did not change epithelium/colloid ratio. Obtained data suggest that exogenous melatonin partially prevented stimulatory action of testosterone on the gland while neither PX nor melatonin modified estradiol effect on the gland.

Animals↗
PubMed1986

Sex differences in adrenocortical structure and function. XXIII. Time-studies on the long-term effects of gonadectomy on rat adrenal cortex.

The aim of the study was to investigate the changes in the size and function of the rat adrenal gland in relation to time-intervals elapsed from postpubertal gonadectomy. Eight weeks after testectomy absolute adrenal gland weights were higher than in intact rats. After that time gradual decrease in the weight was observed and at week 32 the weights were similar to that in intact rats. At weeks 8 and 12 after ovariectomy there was no change in the weight of the gland, however from week 16 onward a gradual decrease occurred. Corticosterone output by adrenal homogenate of orchiectomized rats was lower than in control male rats from week 24 of experiment while in ovariectomized rats such a drop was observed from week 12 of experiment. Activity of adrenal 5 alpha-reductase was markedly higher in either orchiectomized or ovariectomized rats as compared to intact rats at week 8 of experiment. After that time enzyme activity decreased reaching at weeks 24 and 32 control levels. This suggests that 5 alpha-reductase plays only transitional role in adaptation of adrenals to gonadectomy. Neither orchiectomy nor ovariectomy had significant effect on mitochondrial 11 beta-hydroxylase activity. Obtained results clearly show that gonadectomy-induced changes in rat adrenal depend upon time-interval elapsed from surgery. Moreover, they suggest that additionally to 5 alpha-reductase activity, also other factors induced by gonadectomy are responsible for the drop in corticosterone output by adrenals of gonad-deprived rats.

Adrenal Cortex↗
PubMed1985

Sex differences in adrenocortical structure and function. XX. The effects of gonadectomy and testosterone or estradiol replacement on cholesterol content and distribution in the gland.

Sex differences in the distribution of free and esterified cholesterol in the mitochondria and lipid droplets of the rat adrenal glands, as well as their dependence on gonadal hormones were studied. For these purposes intact, gonadectomized and gonadectomized-testosterone or estradiol replaced rats were employed. The concentration of free cholesterol [FC] as well as esterified cholesterol [EC] in full homogenates of decapsulated glands was higher in male than in female rats. Neither orchiectomy nor testosterone replacement had an effect on FC and EC concentration. Ovariectomy increased FC and EC concentration in full adrenal homogenates, an effect reversed by estradiol replacement. Similar changes were found in the lipid droplets. The concentration of FC and EC in the adrenal mitochondria was higher in male than in female rats. Orchiectomy increased the concentration of FC and decreased the concentration of EC. Testosterone administration resulted in further increase in FC concentration and restored EC concentration to the level of the control group. On the other hand ovariectomy increased FC and EC concentration, an effect reversed by estradiol replacement. Results obtained clearly showed that sex differences in FC and EC concentration in rat adrenal gland depend mainly on estradiol which lowers FC and EC concentration in the adrenal lipid droplets and mitochondria.

Adrenal Cortex↗
PubMed1985

Estradiol and melatonin effects on adrenal cortex of ovariectomized and pinealectomized rats.

Studies on the effect of pinealectomy (PX) and melatonin on adrenal cortex of ovariectomized and estradiol replaced rats were performed. Neither PX nor melatonin replacement changed corticosterone output by adrenal homogenate, 11 beta-hydroxylase activity, liver corticosterone metabolism or serum corticosterone level, however, melatonin increased adrenal 5 alpha-reductase activity. On the other hand, PX of 14 months duration resulted in an increase in intraadrenal 5 alpha-reductase activity. PX did not modify estradiol effect on rat adrenal cortex, while concomitant estradiol-melatonin administration increased corticosterone output by adrenal homogenate. Stimulatory effect of estradiol on liver corticosterone metabolism was observed only in the presence of pineal gland or exogenous melatonin. In non of experiments, 45 nmole/ml of melatonin added into incubation medium stimulated adrenal 5 alpha-reductase activity. Obtained results cast doubt on a physiological role of melatonin in regulation of adrenocortical secretory activity in ovariectomized rats and suggest that estradiol effect on the adrenal cortex is not mediated by the pineal gland.

Adrenal Cortex↗
PubMed1985

Testosterone and melatonin effects on adrenal cortex of orchiectomized and pinealectomized rats.

The study aimed to examine the effects of pinealectomy (PX) and melatonin on adrenal cortex of orchiectomized rats and to explain whether the testosterone action on adrenal cortex is modified by the pineal gland. Neither PX (53 days) nor melatonin administration (10 days) had an effect on the structure as well as on the studied functional parameters of the adrenal gland--corticosterone output by homogenates, 11 beta-hydroxylase and 5 alpha-reductase activities, liver corticosterone metabolism and serum corticosterone level. On the contrary, PX of 14 months duration resulted in an increase in 5 alpha-reductase activity. Testosterone administration into orchiectomized rats lowered corticosterone output and liver corticosterone metabolism and these effects were unaffected by PX or melatonin. Testosterone lowered 5 alpha-reductase and 11 beta-hydroxylase activities, the effects not modified by PX, however, after melatonin administration activities of these enzymes were similar as in orchiectomized rats. Obtained results cast doubts on a physiological role of the pineal gland and its principal hormone--melatonin--in regulation of adrenocortical structure and secretory activity and suggest that testosterone action on the rat adrenal cortex is not modified by the pineal gland.

Adrenal Cortex↗
PubMed1985

Trophic effects of potassium loading on the rat zona glomerulosa: permissive role of ACTH and angiotensin II.

The trophic effects of chronic potassium loading on the rat zona glomerulosa were investigated by morphometric and radioimmunological methods. Potassium loading exerted a potent adrenoglomerulotrophic effect in saline treated control rats, but it was not able to reverse the captopril- and dexamethasone-induced atrophy of the zona glomerulosa. However, if the captopril/dexamethasone administered rats were given maintenance doses of angiotensin II and ACTH, potassium loading was found to exert a strong trophic action. The hypothesis is advanced that potassium loading requires the integrity of both the renin-angiotensin system and the hypothalamo-hypophyseal axis to exert its powerful direct stimulating effect on the growth and steroidogenic capacity of the rat zona glomerulosa.

Adrenal Glands↗
PubMed1985

Sex differences in adrenocortical structure and function. XIX. Differences in the compensatory hypertrophy of the adrenal cortex of the male and female hamster after unilateral adrenalectomy.

Stereological studies on the adrenal cortex of unilaterally adrenalectomised hamsters have revealed differences in adrenal compensatory hypertrophy in male and female animals. The operation evokes an increase in the average volume of the zona fasciculata cells in the male and of the zona reticularis cells in the female.

Adrenal Cortex↗
PubMed1985

Stereological studies on the effects of pinealectomy, melatonin and oestradiol on the adrenal cortex of ovariectomised rats.

The aim of the study was to examine by means of stereology the effects of pinealectomy and melatonin on the structure of the adrenal cortex of ovariectomised rats and to check whether the effect of oestradiol on the rat adrenal cortex is modified by the pineal gland. Neither pinealectomy (73 days) nor melatonin treatment (10 micrograms/day for 17 days) changed the absolute and relative weights of adrenal glands of ovariectomised rats or the volumes of individual adrenocortical zones. The average volume of the zona fasiculata cell was higher in pinealectomised than in control rats; adrenal glands of all groups studied contained a similar number of adrenocortical cells. Oestradiol (two injections of estradiol cypionate) resulted within 22 days in a marked increase in adrenal weight, associated with an increase in the total number of parenchymal cells in the cortex of the gland; however, the average volume of adrenocortical cells was unchanged. Neither pinealectomy nor melatonin replacement treatment modified oestradiol effects on the gland. The results cast doubt on the role of the pineal gland and of its principal hormone, melatonin, in influencing adrenocortical structure in the rat and reveal that the pineal gland does not modify oestradiol effects on the gland.

Adrenal Cortex↗
PubMed1984

Sex differences in adrenocortical structure and function. XIII. Stereologic studies on adrenal cortex of maturing male and female hamsters.

Adrenal glands of adult male hamsters are larger and secrete more cortisol than those of females. Stereology was therefore used to study zonal and cellular aspects of development of the adrenal cortex of male and female hamsters. Adrenal glands were studied at weekly intervals from day 21 to day 77 of postnatal ontogenesis. Within this period, body weight did not differ significantly between the sexes. During development, absolute and relative adrenal weights were higher in males; their zona glomerulosa (ZG), zona fasciculata (ZF) and zona reticularis (ZR) become markedly larger than those in females. No marked changes in the volume of individual ZG cells occurred although ZF cells and ZR cells become larger in male than female animals. The total number of adrenocortical cells increased within the period studied, a greater increase being observed in ZG and ZF in males. No distinct sex difference was observed in the number of ZR cells throughout development. From day 56 of postnatal life the adrenal cortex of male hamster contained more parenchymal cells than the female gland. These results thus indicate that sex differences in hamster adrenal cortex depend upon changes in number and size of parenchymal cells.

Adrenal Cortex↗
PubMed1984

Gonadal hormones and thyroxine effects on adrenocortical function in thyroparathyroidectomized rats.

The purpose of the study was to investigate whether testosterone and estradiol effects on rat adrenal cortex are mediated by the thyroid gland. Experiments were performed on gonadectomized rats, some of them underwent also surgical thyroparathyroidectomy (TPX). In appropriate groups animals were treated with testosterone or estradiol and thyroxine. The following parameters of the adronocortical function were estimated: weight of the adrenal gland, corticosterone production by adrenal homogenate and slices, sensitivity of slices to ACTH, adrenal 5 alpha-reductase and 11 beta-hydroxylase activities and serum corticosterone level. Obtained results suggest that estradiol effects on adrenal glands weight and their responsiveness to ACTH were partially mediated by the thyroid gland. On the contrary, thyroid gland was not involved in testosterone evoked changes in function of the rat adrenal cortex.

Adrenal Cortex↗
PubMed1984

Sex differences in adrenocortical structure and function. XIV. Heparin-releasable liver-lipase like activity in rat adrenals as affected by gonadectomy and testosterone or estradiol replacement.

Heparin-releasable liver-lipase like activity was studied in adrenals of intact, gonadectomized and gonadectomized-testosterone or estradiol replaced rats. Besides acid lipase, rat adrenals contain a neutral lipase activity. From both male and female adrenals about 70% of this activity is extractable by heparin containing medium. Activity of this lipase in 8000 g supernatant was higher in female than male adrenals. Orchiectomy of 12 weeks duration increased neutral lipase activity in rat adrenal, an effect reversed to normal level by testosterone replacement. On the other hand ovariectomy had no effect while estradiol replacement resulted in an increased activity of the neutral lipase of rat adrenal gland. The results showed a distinct sex-difference in heparin-releasable liver-lipase like activity of rat adrenals which depends on the inhibitory action of testosterone on the enzyme activity.

Adrenal Glands↗