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Biomedical subjects

G Mazzocchi

Publications and source records attributed to G Mazzocchi.

At least 145 records · Page 8Linked to original sources
PubMed1987

The human adrenal cortex: ultrastructure and base-line morphometric data.

The morphology of the human adult female adrenal cortex was studied by electron microscopy and morphometry. Zona glomerulosa contains outer undifferentiated small cells and inner well-differentiated larger elements, which display mitochondria with tubulo-laminar cristae, abundant smooth endoplasmic reticulum (SER) and sparse lipid droplets. Zona fasciculata cells possess typical mitochondria with vesicular cristae, a well-developed SER, lipid droplets and some lipofuscin-pigment granules, which increase in number in the cells of the inner portion of the zone. Sometimes lipid-laden cells can be observed in the zona fasciculata. Zona reticularis cells have the same morphological features as the zona fasciculata elements, but display a striking rise in the number of lipofuscin-pigment granules.

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↗
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

Effects of chronic administration of a methionine-enkephalin analogue on the zona glomerulosa of the rat adrenal cortex.

The effects of D-ala2-met-enkephalinamide (DALA) on the zona glomerulosa of dexamethasone-ACTH-treated rats were investigated by coupled radioimmunologic and morphometric techniques. Short-term DALA administration provoked a significant increase in the aldosterone plasma level along with a notable lipid droplet depletion in zona glomerulosa cells. Long-term DALA treatment induced a striking hypertrophy of zona glomerulosa cells and a further rise in the blood concentration of aldosterone. These findings seem to indicate that DALA is involved not only in the acute enhancement of aldosterone output but also in the stimulation of the growth and steroidogenic capacity of rat adrenal zona glomerulosa.

Adrenal Cortex↗
PubMed1986

Further studies on the effects of prolonged prolactin administration on the zona glomerulosa of the rat adrenal cortex.

The effects of a prolonged treatment with prolactin on the morphology and hormone secretion of adrenal zona glomerulosa of gonadectomized testosterone-replaced rats were investigated by coupled morphometric and radioimmunologic techniques. The dexamethasone/captopril-induced atrophy of zona glomerulosa cells (-42%) and fall in the blood level of aldosterone (-37%) were partially counteracted by chronic prolactin administration: the values had increased by about 15% and 17%, respectively, but remained lower than in the control animals. The prolonged treatment with prolactin of dexamethasone/captopril-administered ACTH/angiotensin II-replaced rats provoked a striking increase in the zona glomerulosa cell volume (24%) and in the blood level of aldosterone (33%) above the control values. The possibility is discussed whether prolactin may be directly involved in the stimulation of the growth and steroidogenic capacity of rat zona glomerulosa, without interacting with the gonads and interfering with the hypothalamo-hypophyseal axis and the renin-angiotensin system.

Adrenal Cortex↗
PubMed1986

Effect of simultaneous administration of GHRH (1-40) and TRH on GH, PRL and TSH secretion in normal man.

The GHRH test represents a new tool in the study of secretion in man. Nine normal fasting males received on separate occasions in random order 1) GHRH 1-40 (1 microgram/Kg bw) iv at time 0; 2) TRH (6 micrograms/min) infusion between -30 and +120 min; 3) GHRH 1-40 (1 microgram/Kg bw) iv at time 0 plus TRH (6 micrograms/min) infusion between -30 and +120 min. Blood samples were drawn for GH, PRL and TSH at -90, -60, -30, 0 min and then every 15 min for 2 h. GHRH significantly increased GH in all subjects. The same GH response was found during GHRH plus TRH test. No effect was found either on PRL and TSH secretion after GHRH administration, or on GH pattern after TRH administration. A significant decrease of TSH, but not of PRL response was observed after GHRH plus TRH administration in comparison to TRH alone. These results underline that the inhibitory effect exerted by TRH on GH secretion during some experimental conditions is not linked to a pituitary interference between GHRH and TRH. The difference in TSH secretion, following GHRH plus TRH in comparison with TRH alone, could be due to a GHRH-induced central inhibitory mechanism, probably GHRH-related.

Adolescent↗
PubMed1986

Investigations on the effects of long-term administration of a methionine-enkephalin analogue on the adrenal zona fasciculata of rats treated with dexamethasone or dexamethasone and ACTH.

Prolonged (7 days) methionine-enkephalin (DALA) treatment provoked a dose-dependent increase in the volume of zona fasciculata cells of dexamethasone-administered rats, along with a notable rise in the plasma concentration of corticosterone and the activity of 11 beta-hydroxylase. Comparable dose-dependent effects were observed after chronic administration of ACTH to dexamethasone-suppressed rats. The chronic administration of the maximum dose of DALA (500 micrograms/kg/day) was found to significantly further the trophic action of ACTH on the zona fasciculata of dexamethasone-treated animals. It is suggested that enkephalins act independently of and synergistically with ACTH in stimulating the growth and steroidogenic capacity of the rat adrenal zona fasciculata.

Adrenal Cortex↗
PubMed1986

Evidence that long-term methionine-enkephalin administration stimulates rat adrenal zona fasciculata.

Short-term methionine-enkephalin (DALA) treatment did not induce evident changes in the adrenal zona fasciculata and in the basal corticosterone output of dexamethasone-treated rats administered with maintenance doses of ACTH. Conversely, prolonged (5 days) DALA treatment caused a notable hypertrophy of zona fasciculata cells, along with a significant increase in the plasma concentration of corticosterone. It is suggested that enkephalins exert a trophic action on the rat zona fasciculata.

Adrenal Cortex↗
PubMed1986

Further studies on the inhibitory effects of somatostatin on the growth and steroidogenic capacity of rat adrenal zona glomerulosa.

Chronic somatostatin administration was found to partially reverse the ACTH-enhanced growth of the rat zona glomerulosa. The effect of somatostatin was completely superposable to that of captopril, a specific inhibitor of the angiotensin-converting enzyme, and the inhibitory actions of these two agents did not cumulate. Neither somatostatin nor captopril counteracted the ACTH-induced stimulation of the growth and steroidogenic capacity of the rat zona fasciculata. These findings support the view that somatostatin acts as an exclusive and specific modulator of the adrenoglomerulotrophic action of the renin-angiotensin system.

Adrenal Glands↗
PubMed1986

Chronic angiotensin treatment stimulates the growth and the 11 beta-hydroxylase activity of rat zona fasciculata cells.

Long-term angiotensin-II (AII) administration provokes a time-dependent rise in the volume of zona fasciculata cells and in the plasma concentration of corticosterone in rats treated with dexamethasone and maintenance doses of ACTH. The AII-induced zona fasciculata cell hypertrophy is coupled with comparable increases in the surface area per cell of the mitochondrial cristae and in the activity per cell of 11 beta-hydroxylase. These findings suggest that AII enhances the growth and the steroidogenic capacity of rat adrenal zona fasciculata.

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

Effects of prolactin administration on the zona glomerulosa of the rat adrenal cortex: stereology and plasma hormone concentrations.

The effects of short and prolonged treatments with prolactin on the morphology and hormone secretion of the rat adrenal zona glomerulosa were investigated by coupled morphometric and radioimmunological techniques. Short-term prolactin administration did not alter plasma aldosterone concentration or zona glomerulosa morphology. Conversely, chronic prolactin treatment caused both a notable hypertrophy of zona glomerulosa cells and a significant rise in the blood level of aldosterone. The possibility is discussed that prolactin may be involved in the control of the growth and steroidogenic capacity of the rat adrenal zona glomerulosa.

Adrenal Cortex↗
PubMed1986

Long-term trophic action of alpha-melanocyte-stimulating hormone on the zona glomerulosa of the rat adrenal cortex.

The effects of alpha-melanocyte-stimulating hormone (alpha-MSH) on the rat adrenal cortex were investigated by coupled morphometric and radioimmunological techniques. Short-term alpha-MSH administration provoked a significant increase in the aldosterone plasma level along with a notable lipid droplet depletion in zona glomerulosa cells. Long-term alpha-MSH treatment induced a notable hypertrophy of zona glomerulosa cells and a further rise in the blood concentration of aldosterone. alpha-MSH did not affect zona fasciculata morphology and corticosterone plasma level. The possibility is discussed that alpha-MSH may be specifically involved in the control of the growth and steroidogenic capacity of rat adrenal zona glomerulosa.

Adrenal Cortex↗
PubMed1986

Effects of the hypolipidemic drug nafenopin on the zona glomerulosa of the rat adrenal cortex: morphological counterparts of functional alterations.

The effects of nafenopin, a hypolipidemic drug, on the zona glomerulosa of the rat adrenal cortex were investigated. Chronic nafenopin treatment significantly lowered serum cholesterol level, but did not alter blood aldosterone concentration, though the biosynthesis of adrenal cortico-steroid hormones seems to be largely dependent upon a continuous uptake of cholesterol from plasma lipoproteins. Stereology showed that the treatment provoked a notable lipid droplet depletion, coupled with a significant proliferation of smooth endoplasmic reticulum (SER) profiles. Since SER is known to be involved in the endogenous synthesis of cholesterol, the hypothesis is advanced that SER hypertrophy is a compensatory response enabling zona glomerulosa cells to maintain an adequate level of aldosterone output even in the absence of a normal supply of exogenous cholesterol.

Adrenal Cortex↗
PubMed1986

Long term effects of the hypocholesterolaemic drug 4-aminopyrazolo-pyrimidine on the zona fasciculata of the rat adrenal cortex.

Prolonged 4-APP administration to dexamethasone/ACTH-treated rats was found to lower both plasma and intra-adrenal gland cholesterol concentrations. Morphological examination showed that zona fasciculata cells underwent a severe lipid droplet depletion, and a conspicuous increase of agranular endoplasmic reticulum and peroxisomes. The blood level of corticosterone remained unchanged. A high cholesterol diet completely reversed the effects of 4-APP treatment. The hypothesis is discussed that these morphological changes are the expression of a compensatory response enabling rat adrenocortical cells to maintain an adequate level of hormone output even in the absence of a normal supply of exogenous cholesterol.

Adenine↗
PubMed1985

The effects of growth hormone-releasing factor (GRF) and dopamine on growth hormone (GH) secretion in acromegaly.

GRF (1-40), dopamine (DA), DA plus GRF and placebo were administered to 6 acromegalic patients. The GRF administration induced a highly variable GH release (GH delta % 167.3 +/- 21.4; mean +/- SE). GRF did not provoke any change in PRL serum levels. During simultaneous GRF and DA administration GH release was found to be reduced (GH delta % 80.2 +/- 17.8) compared to that observed for a corresponding period of time after GRF alone (p less than 0.05). Our data underscore that in acromegaly the DA tonus inhibits GH secretion after GRF by acting directly at the pituitary level.

Acromegaly↗
PubMed1985

Effect of somatostatin on the zona glomerulosa of rats treated with angiotensin II or captopril: stereology and plasma hormone concentrations.

Chronic somatostatin (SRIF) administration induced atrophy of zona glomerulosa cells of the rat adrenal cortex and a noticeable fall in the plasma concentration of aldosterone. The effects of SRIF were comparable with those of captopril, a specific inhibitor of the angiotensin-converting enzyme. SRIF completely abrogated the adrenoglomerulotrophic effects of angiotensin II (AII); the inhibitory actions of SRIF and captopril were not additive. The slight but significant enhancement of zona fasciculata cell growth and plasma corticosterone levels caused by chronic AII administration were ot reversed by SRIF. We interpret these data to indicate that SRIF specifically modulates the stimulatory effects of AII on the growth and steroidogenic capacity of rat zona glomerulosa.

Adrenal Cortex↗