Biomedical subjects

L K Malendowicz

Publications and source records attributed to L K Malendowicz.

At least 181 records · Page 10Linked to original sources

PubMed1989

Effects of unilateral adrenalectomy on the remaining adrenal cortex of adrenocorticotropic hormone-treated male and female hamsters.

Sham-operated and unilaterally adrenalectomized male and female hamsters were administered 25 micrograms adrenocorticotropic hormone (ACTH) for 5 days after the operation in order to examine the effects of ACTH on compensatory adrenal growth. In ACTH-treated male and female hamsters, unilateral adrenalectomy did not change the relative weight of the remaining adrenal. There were no significant differences in the volumes of the adrenocortical zones and their parenchymal cells, as well as in the number of adrenocortical cells per gland if compared with unilaterally adrenalectomized and sham-operated ACTH-treated male hamsters, while 3H-thymidine incorporation per gland was lower in monoadrenalectomized animals. On the contrary, in ACTH-treated females, unilateral adrenalectomy resulted in a significant hypertrophy of zona fasciculata cells and in an enhanced 3H-thymidine uptake by the remaining gland. These findings stress the existence of notable sex-related differences in the compensatory adrenal growth in hamsters.

Adrenal Cortex↗

PubMed1989

Compensatory adrenal growth in aldosterone-treated male and female hamsters.

The aim of the study was to investigate the compensatory adrenal growth in aldosterone-treated male and female hamsters. Hemiadrenalectomised and sham-operated animals were treated for 5 days with a daily d-aldosterone dose of 25 micrograms/animal. In both male and female aldosterone-treated hamsters monoadrenalectomy did not change the relative adrenal weight if compared with sham-operated groups. The fasciculata zonae of monoadrenalectomised aldosterone-treated males was larger and contained more parenchymal cells than in appropriate control group. There was no difference in the volume of adrenocortical zones, average cell volume and in cell number between sham-operated and unilaterally adrenalectomised females. In vitro 3H-thymidine incorporation per adrenal was markedly higher in monoadrenalectomised than in sham-operated aldosterone-treated males while the opposite was true for female hamsters. Thus, the action of aldosterone on CAG in the hamster seems to depend on sex, with no effect in males and inhibitory action in females.

Adrenal Glands↗

PubMed1989

Long-term studies on compensatory adrenal growth in the female hamster induced by unilateral adrenalectomy.

The study was designed to explain the cellular aspects of compensatory adrenal growth in the female hamster in the course of long-term unilateral adrenalectomy. Animals were autopsied 3, 6, 9, 18 and 36 days after unilateral adrenalectomy. Removal of the left adrenal gland within 36 days did not change both the absolute and relative adrenal gland weight of the female hamster. Also the volume of particular adrenocortical zones and the number of parenchymal cells in the zones and in the entire cortex were unchanged in unilaterally adrenalectomised hamsters. Moreover, in the course of experiments the volumes of the glomerulosa and fasciculata cells were unchanged in relation to the control group. On the contrary, a marked increase in the volume of the zona reticularis cells was observed, with the highest rate of increase within the first 9 days after unilateral adrenalectomy.

Adrenal Glands↗

PubMed1989

Morphological and functional responses of rat Leydig cells to a prolonged treatment with human chorionic gonadotropins.

The morphological and functional responses of rat Leydig cells to a 3- and 6-day treatment with human chorionic gonadotropins (hCG) (10 IU/kg/day) were investigated by morphometric and radioimmunological techniques. hCG-administration induced a notable time-dependent enhancement in the steroidogenic capacity and growth of Leydig cells; this last was almost exclusively due to hypertrophy (and not to hyperplasia). The volume of mitochondrial and peroxisome compartments, as well as the surface area per cell of mitochondrial cristae and smooth endoplasmic reticulum (SER) were significantly increased after hCG treatment, and showed a highly significant positive linear correlation with both basal and stimulated testosterone production by isolated Leydig cells of the contralateral testis. Also the volume of nuclei and lipid-droplet compartment and the surface area per cell of Golgi apparatus displayed a notable hCG-induced rise, but they did not correlate with testosterone secretion. These findings suggest that, in addition to mitochondria and SER, in which the enzymes of steroid synthesis are located, peroxisomes are also specifically involved in the secretory activity of rat Leydig cells.

Animals↗

PubMed1988

Effects of prolonged dopamine infusion on the zona glomerulosa of sodium-restricted rats treated or not with prolactin: stereology and plasma hormone concentrations.

Prolonged sodium restriction was found to induce a notable hypertrophy of rat zona glomerulosa (ZG) cells and a significant rise in the basal plasma aldosterone concentration. Chronic prolactin administration significantly furthered the effects of sodium restriction. Dopamine infusion (3 mg/kg day for 7 days) did not apparently affect ZG morphology and function in the control rats, while it significantly counteracted the effects of sodium deprivation combined or not with prolactin administration. However, the action of dopamine was less intense in sodium-deprived rats treated with prolactin. These findings confirm the view that the dopaminergic system exerts a tonic inhibitory effect, modulated by the sodium balance, on the growth and secretory activity or rat ZG. Moreover, they suggest that the mechanism(s) underlying the antiadrenoglomerulotrophic action of dopamine in rats only partially involve(s) the well-known suppression of the hypophyseal release of prolactin.

Adrenal Cortex↗

PubMed1988

Effects of streptozotocin-induced experimental diabetes on the morphology and function of the zona fasciculata of rat adrenal cortex.

The effects of a severe streptozotocin (STZ)-induced diabetes on the morphology and function of the adrenal zona fasciculata were examined in rats with intact or pharmacologically interrupted hypothalamic-hypophyseal-adrenal axis. In animals with an intact hypothalamic-hypophyseal axis, STZ-diabetes induced hypertrophy of the cells of the zona fasciculata and a rise in the plasma corticosterone concentration. Conversely, in rats in which the hypothalamic-hypophyseal axis had been interrupted, experimental diabetes provoked atrophy of the zona fasciculata cells, and a lowering in the plasma corticosterone level. The effects of STZ-diabetes were completely reversed by insulin infusion in both groups of rats. The hypothesis is discussed that the chronic lack of insulin may directly inhibit the growth and steroidogenic capacity of the rat zona fasciculata and that this effect of experimental diabetes may be masked in rats with an intact hypothalamic-hypophyseal axis by the concurrent enhancement of ACTH release due to chronic stress resulting from the metabolic consequences of prolonged diabetes.

Animals↗

PubMed1988

Evidence that prolonged alpha-MSH infusion enhances the steroidogenic capacity of rat adrenal zona glomerulosa in vivo.

Prolonged infusion with 120 micrograms/kg/day alpha-MSH significantly increased basal plasma level of aldosterone in the rat, as well as raised the acute aldosterone response to a bolus administration of a high dose of ACTH or angiotensin II. These findings suggest that chronic alpha-MSH treatment stimulates the steroidogenic capacity of rat zona glomerulosa.

Adrenal Glands↗

PubMed1988

Long-term stimulatory effect of neuropeptide-Y on the growth and steroidogenic capacity of rat adrenal zona glomerulosa.

A prolonged infusion with neuropeptide-Y (NPY) caused a notable hypertrophy of the adrenal zona glomerulosa and its parenchymal cells in rats whose hypothalamo-hypophyseal axis and renin-angiotensin system were pharmacologically interrupted. Zona glomerulosa hypertrophy was associated with a significant rise in both basal and stimulated plasma levels of aldosterone. Zona fasciculata cells and the blood concentration of corticosterone were not affected. These findings suggest that NPY is specifically involved in the stimulation of the growth and steroidogenic capacity of rat adrenal zona glomerulosa.

Adrenal Cortex↗

PubMed1988

Studies on hypothalamo-pituitary corticoliberin system. V. The effects of gonadectomy and sex hormones on plasma ACTH and on the reactivity of the anterior pituitary gland to CRF.

The aim of the study was to investigate the effects of gonadectomy and sex hormones on responsiveness of anterior pituitary slices to synthetic CRF and on plasma ACTH level in male and female control, gonadectomised and testosterone or estradiol replaced rats. In animals of both sexes neither gonadectomy nor sex hormone replacement had an effect on plasma level of radioimmunoassayable ACTH. Adenohypophyseal ACTH output in vitro in response to CRF was unchanged by orchiectomy and lowered after testosterone replacement. Moreover, neither ovariectomy nor estradiol replacement had an effect on ACTH output by the entire adenohypophysis. Thus, since there were no apparent changes in plasma ACTH concentration among intact, gonadectomised and testosterone or estradiol replaced male and female rats as well as in responsiveness of the gland to CRF it seems that sex difference in the adrenocortical structure and function depends on action of sex hormones on adrenal and/or liver than on ACTH release on hypothalamic or pituitary level.

Adrenocorticotropic Hormone↗

PubMed1988

Zona glomerulosa morphology and function in streptozotocin-induced diabetic rats.

Streptozotocin-induced diabetic rats showed a significant lowering in both PRA (-31%) and basal plasma aldosterone concentration (-59%), coupled with a notable atrophy of the zona glomerulosa (-30%) and its parenchymal cells (-36%). Kalaemia and the blood level of ACTH were not affected. Insulin infusion reversed all the streptozotocin-evoked effects. Analogous, though less conspicuous, changes were induced by experimental diabetes also in rats whose hypothalamo-hypophyseal-adrenal axis and renin-angiotensin system had been pharmacologically interrupted by the simultaneous administration of dexamethasone-captopril and maintenance doses of ACTH-angiotensin II: the drops in the basal plasma aldosterone concentration and in the volume of zona glomerulosa and its cells ranged from -20% to -22%. In these animals, experimental diabetes significantly depressed the aldosterone response to the acute stimulation with angiotensin II (-55%), potassium (-50%), and ACTH (-43%). These findings indicate that the well known impairment of renin release may only partially account for the antiadrenoglomerulotrophic effect of experimental diabetes in rats. The hypothesis is advanced that the chronic lack of insulin may directly depress both the growth of the zona glomerulosa and the newly synthesis of some enzymes of aldosterone synthesis.

Adrenal Glands↗

PubMed1987

Sex differences in adrenocortical structure and function. XXIV. Comparative morphometric studies on adrenal cortex of intact mature male and female rats of different strains.

The zonation and cellular composition of the adrenal cortex of intact mature male and female rats of different strains (Chbb Thomm, CFY) and three strains of Wistar rats (W1, W2 and W3) at the age of 84-90 days were compared using morphometry. Both absolute and relative adrenal gland weights were higher in female than male rats. Rats of W3 and Chbb Thomm strains had the largest adrenals. These differences depended upon the higher volume of the zona fasciculata (ZF) and zona reticularis (ZR) in the W3 and Chbb Thomm strains than in the remaining animals. Females had larger adrenocortical zones than corresponding males. The average volume of the ZF cell ranged in males from 1589 micron 3 (W1 strain) to 2111 micron 3 (Chbb Thomm) and in females from 2249 micron 3 (W1 strain) to 2894 micron 3 (W3 strain). The average nuclear volume of the ZF cells was higher in female rats whereas there were no strain- and sex-differences in the size of zona glomerulosa (ZG) and ZR cells. The total number of parenchymal cells per pair of adrenals varied markedly among the studied strains, with the highest number in W3 and Chbb Thomm females. W3, Chbb Thomm and CFY females had larger number of parenchymal cells than males; the reverse was true for W1 strain whereas no differences were found among W2 male and female rats.

Adrenal Cortex↗

PubMed1987

Adrenocortical function in 4-APP treated rats: a coupled stereological and biochemical study.

Adrenocortical function in 4-APP-induced (4-aminopyrazolo[3,4-d]pyrymidine) lipoprotein-deficient rats was studied in relation to quantitative morphologic changes in the gland. 4-APP treatment results in enlargement of the adrenal cortex and its zona fasciculata and reticularis cells. In enlarged livers, cholesterol and free fatty acid concentrations were similar to that of control rats, however a marked accumulation of triglycerides with a concomitant drop in hepatic delta 4-steroid hydrogenase activity was found. A profound drop in serum cholesterol in both, high and low density lipoproteins, as well as triglycerides and plasma corticosterone concentrations was accompanied by a marked lowering of cholesterol and corticosterone concentration in the adrenal gland. Corticosterone output by adrenal homogenates was higher in 4-APP treated rats than in control animals. Such a treatment did not change cholesterol side-chain cleavage, 11 beta-hydroxylase, 3 beta-ol dehydrogenase-isomerase, steroid 5 alpha-reductase and neutral lipase activities when expressing results per unit weight of tissue or protein. However, when calculating per adrenocortical cell, adenine analogue applied increased 11 beta-hydroxylase, steroid 5 alpha-reductase and neutral lipase activities. Thus, coupled biochemical and stereologic studies revealed a complex and multidirectional effect of 4-APP on the rat adrenal cortex. This effect may be caused by serum lipoprotein deficiency and by toxic and stressful action of the adenine analogue on the rat. Also a direct effect of 4-APP on rat adrenal cortex may not be excluded.

Adenine↗

PubMed1987

Stereologic studies on the adrenal cortex of 4-APP (4-amino-pyrazolopyrimidine)-induced lipoprotein-deficient rats.

The effect of 4-APP (4-aminopyrazolopyrimidine), the compound reducing hepatic release of lipoproteins, on the rat adrenal cortex was studied by means of stereological methods. Within 3 days 4-APP resulted in a marked increase in the absolute and relative adrenal weights and markedly lowered plasma and adrenal total cholesterol concentration. 4-APP did not change the relative volume of individual adrenocortical zones, however significantly increased the volume in mm3 of the zona fasciculata (ZF) and reticularis (ZR) and of the entire cortex. The average volume of the ZF and ZR cells of 4-APP treated rats was markedly higher than in control rats while no difference was found in the zona glomerulosa (ZG) cell. In lipoprotein-deficient rats the number of adrenocortical cells within the entire cortex was similar to that observed in control rats. A marked increase in the number of mitoses in both, adrenocortical and endothelial cells suggests inhibitory action of 4-APP on the proliferative activity of these cells. The present study shows that 4-APP-induced changes in the rat adrenal cortex mainly depends upon the stimulatory action of that compound on ACTH secretion, however this adenine analogue also exerts a direct action on the adrenocortical cells.

Adenine↗

PubMed1987

Sex differences in adrenocortical structure and function. XXV. Quantitative analysis of ACTH-immunoreactive cells in the anterior pituitary of gonadectomized and gonadal hormone replaced male and female rats.

Coupled immunocytochemical and stereologic studies of ACTH-immunoreactive cells were performed on anterior pituitaries of control male and female rats and on gonadectomized and testosterone or estradiol replaced animals. The average area and average volume of studied cells as well as their number were similar in anterior pituitary glands of control male and female rats. Orchiectomy increased average area of ACTH-immunoreactive cells, an effect reversed by testosterone while neither ovariectomy nor estradiol replacement had an effect on the area of studied cells. Average volume of these cells was similar in all experimental groups studied. Orchiectomy lowered the total number of ACTH-immunoreactive cells in the gland, an effect reversed by testosterone. Also ovariectomy lowered their number while after estradiol they were more numerous, even in comparison with control females. There is no significant correlation between the size and total number of ACTH-immunoreactive cells of the rat anterior pituitary gland and the size of the adrenal gland in both, male and female control, gonadectomized and testosterone or estradiol replaced rats.

Adrenocorticotropic Hormone↗

PubMed1987

Studies on hypothalamo-pituitary corticoliberin system. IV. Quantitative changes in ACTH-immunoreactive anterior pituitary cells evoked by long-term intraventricular CRF administration and adrenalectomy.

The aim of the study was to investigate, by coupled immunocytochemical and stereologic methods, the effects of long-term intraventricular administration of ovine CRF (oCRF) on ACTH-immunoreactive cells of the rat anterior pituitary and to compare this effect with that of adrenalectomy. CRF-treated rats received 100 ng of oCRF daily for 8 days while control rats were administered with bovine serum albumin (BSA). After BSA administration number of ACTH-immunoreactive cells/mm2 was greater than in intact rats and CRF lowered their number, however, they were still more numerous than in intact rats. Neither average area nor average volume of studied cells were changed in control and CRF-treated animals if compared with intact ones. The total number of ACTH-immunoreactive cells was higher in the glands of BSA and CRF-treated rats than in intact animals. On the other hand, 60 h after bilateral adrenalectomy a marked increase in both, average area and average volume of ACTH-immunoreactive cells was found. The different response of rat corticotropes to intraventricular CRF administration and adrenalectomy may depend on the presence of operating negative corticosterone feedback in animals with adrenal glands intact. Moreover, the present study revealed the lack of correlation between the average area and average volume of ACTH-immunoreactive cells and the weight of the adrenal gland.

Adrenal Glands↗

PubMed1987

Hyperresponsiveness of residual thyroid lobe of hemithyroidectomised rat to thyrotropin.

The effects of hemithyroidectomy and thyrotropin administration on rat thyroid gland function were studied in adult male rats. Immediately after surgery or sham operation rats were treated daily with 0.12 IU of bovine thyrotropin (TSH) for 3 or 5 days. In control rats TSH dose applied resulted in an increase in serum T4 level at day 5 of experiment. Serum thyroxine concentration markedly decreased in sham operated and hemithyroidectomised rats, an effect observed at days 3 and 5 of experiment. TSH administration had no effect on serum T4 concentration in sham operated rats while in hemithyroidectomised animals such a treatment resulted in a marked increase in serum T4 level, a phenomenon observed in both time intervals studied. The reasons for hemithyroidectomy-induced hyperresponsiveness of rat thyroid residual lobe to thyrotropin are unknown.

Adaptation, Physiological↗

PubMed1987

Cytochemical and functional evaluation of ACTH responsive isolated rat adrenocortical cells. The maintenance of sex differences.

The critical evaluation of isolation methods for obtaining the adrenocortical cell suspension due to trypsin or collagenase digestion was done. Some collagenase advantages were indicated by morphological observations on the staining smears as well as by ACTH stimulation test. The cytochemical reactions for enzyme activities had the limited applications for those purposes. It also appeared that commonly applied dye exclusion tests were inadequate for characterization of cell suspension. The possible role of the adrenocortical cell debris in the basal corticosterone production was pointed out. The maintenance of the sex dimorphism and the functional differences in the adrenocortical cells isolated from male and female rats have been observed.

Adrenal Cortex↗

PubMed1986

Acute effects of alpha-MSH on the rat zona glomerulosa in vivo.

alpha-MSH acutely enhanced the plasma concentration of aldosterone (but not that of corticosterone) in the rat, with a maximal response at a dose of 100 micrograms/kg. This dose of alpha-MSH increased the blood level o aldosterone and the activity of 11 beta-hydroxylase and 18-hydroxylase of capsular adrenals in rats infused for 24 h with dexamethasone, dexamethasone plus ACTH, or captopril plus angiotensin II, but not in animals treated with captopril alone. The plasma concentration of corticosterone and the activity of 11 beta-hydroxylase in the inner adrenal layers were not changed. These findings indicate that alpha-MSH is specifically involved in the acute stimulation of the late steps of the secretory activity of the rat zona glomerulosa, and that this action of alpha-MSH requires a normal level of circulating angiotensin II.

Adrenal Glands↗