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Biomedical subjects

G Valenti

Publications and source records attributed to G Valenti.

At least 145 records · Page 8Linked to original sources
PubMed1986

Diminished pituitary responsiveness to growth hormone-releasing factor in aging male rats.

The pattern of GH secretion undergoes substantial changes in the aging rat, resulting in decreased daily secretion of GH. In this study, the pituitary responsiveness to GH-releasing factor (GRF) was examined in young (2- to 5-month old) and aging (14- to 18-month old) male rats. In vivo studies were performed under sodium pentobarbital anesthesia. After injection of 250 ng GRF/100 g BW, young rats experienced more GH secretion [peak level, 544.5 +/- 209.5 (+/- SEM) ng/ml] than did 18-month-old rats (89.3 +/- 13.7 ng/ml). To investigate the locus of this insensitivity to GRF, anterior pituitary cells from young and aging rats were dispersed and placed in primary culture. While basal GH secretion from the cultured pituitary cells was similar in the two groups (49.7 +/- 3.5 vs. 47.8 +/- 2.7 ng/ml X 4 h for the 2- and 18-month old rats, respectively), the GH-releasing ability of GRF was partially but significantly impaired in cells derived from both 14- and 18-month old rats; 100 nM GRF stimulated the release of 96.7 +/- 1.8 ng/ml X 4 h in the 18-month old rats as opposed to 115.0 +/- 6.0 (P less than 0.05) ng/ml X 4 h in the 2-month-old rats. Since GRF stimulates GH release through the activation of adenylate cyclase, intracellular cAMP levels were measured in the cultured pituitary cells. GRF stimulated 65% less intracellular cAMP accumulation in the 18-month-old rats. In 14-month-old rats, the ability of forskolin and (Bu)2 cAMP to release GH was impaired, while phorbol ester-elicited GH secretion was unchanged. In conclusion, the GH response to GRF is blunted in aging rats. While much of the insensitivity to GRF may be mediated by the increased somatostatin tone reported in aging rats, a diminished pituitary cAMP response to GRF may also be an important etiological factor in the hyposomatotropinemia of the aging male rat.

Aging↗
PubMed1986

Biofiltration and calcium-phosphate metabolism.

We evaluated the effect of one session of biofiltration on calcium-phosphate metabolism in four uremic patients and compared the results with those of a previous traditional hemodialysis (Cuprophane membrane) session, on the same subjects. The most noteworthy results were: both total and ionized plasma calcium rose less in biofiltration; phosphate clearance and parathyroid hormone clearance were higher in biofiltration; plasma 25-OH D did not change in either dialysis technique.

Adult↗
PubMed1985

Activation of PRL secretion by combined treatment with cyproterone acetate and ethinylestradiol.

Two groups of patients affected by idiopathic androgenization have been treated with ethinylestradiol (EE) associated with two different (high and low) dosages of cyproterone acetate (CA); the aim of this study was to evaluate the possible endocrine side effects at the pituitary level. After three and six months of treatment gonadotropins secretion appeared significantly inhibited with higher evidence for LH than for FSH and especially in the patients on high dose of CA. Nevertheless the most impressive finding was represented by the increase in PRL responses to TRH documented when higher doses of CA were employed without significant change in TSH secretion. The Authors suggest that such PRL hyperresponsiveness cannot be completely disregarded in the management of idiopathic androgenization.

Adult↗
PubMed1985

Effects of dopamine receptor stimulation on opiate-induced modifications of pituitary-gonadal function.

We evaluated the effects of the dopaminergic drug bromocriptine (Br) on prolactin (PRL), luteinizing hormone (LH) and testosterone (Te) levels in a homogeneous group of opiate addicts in a methadone maintenance program (20 mg twice daily). Basal blood levels of PRL, LH and Te were determined in 15 adult male drug addicts, before 30 and 60 days after Br administration (7.5 mg/day) was started. 15 healthy volunteers served as controls for the evaluation of basal values of the hormones. Before treatment PRL values were high, while LH and Te levels were lower than normal. 30 days later, PRL lowered significantly while LH and Te increased significantly. 60 days later, the blood hormone values were still significantly different from pretreatment values, and close to the normal range. This observation shows that Br, probably through an increase of dopaminergic tone, may counteract some effects of opiates on the hypothalamic-pituitary-gonadal axis.

Adolescent↗
PubMed1984

Effects of gangliosides on the functional recovery of damaged brain.

The effect of GM1 ganglioside on the recovery of dopaminergic nigro-striatal neurons was studied in rats after unilateral hemitransection. GM1 treatment favoured the collateral sprouting of dopaminergic axons in the striatum as indicated by the induced increase of tyrosine hydroxylase (TH) activity and immunofluorescence. Concomitantly GM1 partially prevented the decrease of TH activity caused by the hemitransection in the substantia nigra ipsilateral to the lesion. A significant increase of TH immunoreactivity was also detected in the substantia nigra: GM1 prevented the disappearance of TH-positive cell bodies and increased the formation of TH-positive collaterals and dendrites with respect to the saline treatment. The addition of GM1 to embryonic dissociated mesencephalic cell cultures stimulates the expression of dopaminergic characteristics as suggested by the increase of 3H-DA uptake.

Animals↗
PubMed1984

Effect of methadone on TSH and thyroid hormone secretion.

The hypothalamus-pituitary-thyroid function was studied in 15 male patients on chronic methadone treatment (40 mg/day). No significant variations of TSH, T4, T3 and rT3 levels were documented, either in basal conditions or after TRH stimulation; however a reduced TSH pituitary response was recorded in some patients (6 out of 15).

Adult↗
PubMed1984

Effect of GM1 ganglioside treatment on the recovery of dopaminergic nigro-striatal neurons after different types of lesion.

The effect of GM1 ganglioside treatment on the recovery of biochemical and behavioral parameters which define the activity of nigro-striatal dopaminergic systems has been investigated in rats after different types of lesion. GM1 favours the recovery of tyrosine-hydroxylase activity, of the number and affinity of 3H-N-n-propyl-norapomorphine binding sites in the striatum of the lesioned side and reduces the apomorphine-induced rotational behavior after mechanical (i.e. unilateral hemitransection) but not after chemical (i.e. 6-OHDA injected in the substantia nigra) lesion. The source of regrowing dopaminergic nerve terminals in the striatum after hemitransection is mainly a response of intact remaining axons of the ipsilateral side. Moreover the contralateral nigro-striatal systems seems to play, through intrathalamic connections, an important role in regulating the GM1-induced increase of the tyrosine-hydroxylase activity.

Animals↗
PubMed1984

Acute infusion of hCG and thyroid hormone pattern before and after bilateral orchiectomy.

An acute infusion of 5000 IU of hCG was given to a group of 10 elderly men affected by prostatic carcinoma prior to and 1 month after castration to evaluate the possibility of any aspecific effect on thyroid hormones. No significant change was documented for TT4 and TT3, and a significant increase in fT4 occurred only in the presurgical experiment. From these results the authors conclude that the thyroid movement documented may be correlated to the decreased binding capacity of thyroxine-binding globulins promoted by the increase in Te levels.

Aged↗
PubMed1984

Neuroendocrine effects of styrene on occupationally exposed workers.

The serum levels of prolactin (PRL), human growth hormone (HGH), thyroid-stimulating hormone (TSH), and the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured in 30 females exposed to about 130 (range 65-300) ppm of styrene in the air and in 30 age-matched referents to show whether styrene exposure influences the dopaminergic tuberoinfundibular system (TIDA). The exposed subjects' serum levels of PRL were more than double the reference values and were significantly related to the urinary excretion of styrene metabolites, ie, to the sum of mandelic acid (MA) and phenylglyoxylic acid (PGA) in the "next-morning" urine spot sample. Such a relationship still proved to be statistically significant after the removal of the effects of age and duration of exposure with the method of partial correlation. The serum concentrations of HGH in the exposed workers were also higher than in the reference group. Though within the reference levels, the TSH values of the exposed subjects were significantly related to the urinary excretion of MA and PGA. These results are consistent with the dose-dependent depletion in tuberoinfundibular dopamine after experimental styrene exposure of rabbits.

Adult↗
PubMed1984

Progress of renal osteodystrophy during continuous ambulatory peritoneal dialysis.

At present, only a few data are available on the effects of continuous ambulatory peritoneal dialysis (CAPD) on renal osteodystrophy. Twelve patients on CAPD were studied for one year, in order to evaluate the progress of renal osteodystrophy. Our results showed a downward trend of plasma calcium, a good control of phosphatemia, a significant increase of alkaline phosphatase and parathyroid hormone. We also found an important decrease of plasma vitamin D metabolites (25(OH)D3 and 1,25 (OH)2D3) and bone mineral content. Bone biopsy showed a general worsening of both secondary hyperparathyroidism and osteomalacia. Thus, we can conclude that CAPD alone is not able to control the evolution of renal osteodystrophy.

Alkaline Phosphatase↗
PubMed1984

In vitro evaluation of the antimycotic activity of a thiophene derivative.

The antifungal activity of the protiofate, a molecule derived from thiophene, was determined in vitro. For the testing, we determined the MIC values of 63 fungal strains (27 yeasts, 36 filamentous fungi, 14 of which were dermatophytes) at different pH values and different inoculum sizes. The comparison was made with econazole and clotrimazole. The results indicate that protiofate has good inhibitory activity vs yeasts at pH 7 and that it is active on filamentous fungi at pH 6.5 and 7.

Antifungal Agents↗
PubMed1983

Impaired TSH response to TRH after intravenous ranitidine in man.

Ranitidine, given by i.v. infusion, decreased TSH response to TRH in 7 subjects. This effect, completely different from that obtained with cimetidine, suggests that the action of ranitidine is likely to be independent of H2-receptor blockade and rather may be related to the cholinergic-like effect of this drug.

Adult↗
PubMed1983

cAMP levels and alpha and beta receptors stimulation by noradrenaline in frog skin.

The effect of noradrenaline on intracellular levels of cAMP in epithelial cells isolated from frog skin, has been studied both in the presence and in the absence of alpha (phentolamine) or beta (propranolol) adrenergic blocking agents. Such levels are increased by hormonal treatment and are linked to the stimulation of beta-adrenergic receptors, while alpha-stimulation has an inhibitory effect. Higher levels of cAMP are reached in the presence of both Ca2+ and Mg2+, confirming the existence of a Ca2+ and Mg2+-dependent adenyl-cyclase, stimulated by noradrenaline. The experimental conditions necessary to induce the highest intracellular cAMP levels, are those in which the permeabilizing effect reaches its maximum.

Animals↗