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Biomedical subjects

R Volpi

Publications and source records attributed to R Volpi.

At least 163 records · Page 9Linked to original sources
PubMed1984

The growth hormone response to thyrotropin-releasing hormone in insulin-dependent diabetics involves a cholinergic mechanism.

In order to establish whether cholinergic receptors mediate GH secretion induced by TRH in insulin-dependent diabetes, 10 patients were treated with pirenzepine, an anticholinergic agent, and tested with TRH. Basal concentrations of GH were elevated in these patients and 8 of 10 patients responded to TRH with a significant rise in GH levels. Pretreatment with pirenzepine (40 mg given iv 10 min before TRH) suppressed the TRH-induced GH rise. Pirenzepine had no effect on TRH-induced TSH release. This finding suggests that a cholinergic mechanism is involved in the paradoxical response of GH to TRH in diabetic patients.

Adult↗
PubMed1984

Histaminergic H1 and H2 receptors do not mediate cortisol release in response to naloxone in normal men.

In order to evaluate the role of histamine as a possible mediator of the ACTH-cortisol response to naloxone, a specific opioid receptor antagonist, 12 normal men were treated with naloxone before and after the administration of dexchlorpheniramine and cimetidine, respectively H1 and H2 histamine receptor antagonists. Cortisol levels in the plasma were measured before and after drug injections. Naloxone significantly stimulated the secretion of cortisol in all subjects; the administration of dexclorpheniramine or cimetidine failed to modify this response. These data confirm the stimulatory effect of naloxone on cortisol secretion, but do not support the hypothesis that a histaminergic pathway mediates this response.

Adrenocorticotropic Hormone↗
PubMed1983

Naloxone does not alter the effect of gamma aminobutyric acid derivative, baclofen, on GH release in man.

To evaluate the interaction between opioid peptides and GABAergic system in regulating GH secretion we administered 5 mg of baclofen, a GABA derivative, to eight normal male subjects. The results were compared to those obtained in the same subjects treated with naloxone (10 mg/2 h) plus baclofen. GH levels increased significantly above basal value either after baclofen and naloxone plus baclofen without any significant difference between GH responses during the two tests. It is suggested that the two substances do not act at the level of the same receptor site. The evaluation of a possible interaction between opioid peptides and GABAergic system on GH release requires further investigation.

Adult↗
PubMed1983

Effect of metoclopramide on serum growth hormone levels in cirrhotic men.

Growth hormone (GH) secretory response to metoclopramide (MCP) administration was evaluated in 9 male patients with liver cirrhosis and in 6 normal controls. As expected, MCP did not modify serum GH concentrations in normal subjects. In contrast, a striking GH secretory response to MCP was observed in 5 out of 9 cirrhotics. In the other four patients serum GH levels did not show any variation after MCP. The different behavior between cirrhotic "responders" and "non responders" can not be interpreted on the basis of the medical history or the clinical and laboratory data. Three hypothesis are proposed: i) The effect of MCP could be promoted by estrogens and inhibited by androgens. ii) False neurochemical transmitters could affect dopaminergic system of some cirrhotics, allowing or inhibiting the GH response to MCP. iii) MCP could stimulate GH secretion by a serotonergic mechanism. These findings provide further evidence of a modification of the GH secretory pattern in patients with cirrhosis of the liver.

Adult↗
PubMed1981

[Urinary levels of dehydroepiandrosterone in a group of male patients with functional hyperprolactinemia].

On 22 male patients diagnosed as "functional hyperprolactinemia" (the Prolactin (PRL) basal value, was higher than the basal PRL means +/- 2 DS of a control group) we have measured the urinary excretion of Dehydroepiandrosterone (DHEA) mainly produced by adrenal cortex. Our results haven't shown no difference in the urinary excretion of DHEA values in hyperprolactinemic patients has been documented.

Adult↗
PubMed1980

[Study of GH in patients suffering from sexual impotence and abnormal glucose tolerance test (author's transl)].

The correlation between dopamine-serotonin systems and sexual behaviour and the influence of these two amines on GH secretion is well known. We evaluated GH responses (maximum increase (delta) after OGTT and mean increase (delta M) after insulin test) in a group of 32 males suffering from erective impotence with impotence with abnormal reaction to a glucose tolerance test. Results were compared with those obtained in a group of 13 normal controls. No significant difference in basal values and dynamic responses between the two groups was present. Our data suggest that GH doesn't decrease the tolerance to glucose in these patients. The abnormal values observed during a glucose tolerance test may be due to some agent involved in the interactions between limbic system, ventral lateral and ventral medial hypothalamic nuclei and dopamine-serotonin systems. No influence by this system on GH secretion is evident.

Adult↗
PubMed1979

Gonadotropin-releasing hormone test for hypogonadic men.

Gonadotropin patterns before and after stimulation with gonadotropin-releasing hormone (GnRH) have been studied in 69 hypogonadic men of various types: patients with expansive hypothalamus--pituitary disorders before and after surgery, patients with hypogonadotropic hypogonadism, and patients with oligozoospermia or azoospermia who have primary partial or total testicular deficiency. Three characteristic gonadotropin patterns were found: (a) low basal values of LH and FSH with either absent or decreased and delayed responses; (b) normal basal values and pituitary responses above the normal range; or (c) high basal values and pituitary responses above the normal range. These gonadotropin patterns were correlated with disorders of the hypothalamus--pituitary--testis axis. The advantages and disadvantages of the GnRH test for the clinical evaluation of male hypogonadism are discussed.

Adolescent↗
PubMedDate not supplied

The GABAergic control of prolactin release is not affected by insulin-dependent diabetes mellitus: evidence from studies with sodium valproate.

In order to evaluate the influence of the GABAergic system in the regulation of PRL secretion in patients with IDDM, serum PRL levels were measured in 7 diabetics and in 7 normal men with sodium valproate (400 mg per os), a drug capable of increasing cerebral GABA concentrations. A significant decrease of serum PRL concentrations was observed between 30 and 120 min after sodium valproate administration in both control and diabetic subjects. The time course and magnitude of the sodium valproate effect were similar in all subjects. These data confirm the inhibitory control of the GABAergic system on PRL secretion in man as evidenced by the GABAergic drug sodium valproate. It is suggested that this system is not altered in diabetic patients.

Adult↗
PubMedDate not supplied

Prolactin secretion and nodular goiter. (Hypothetical correlations).

In a group of 129 female patients with nodular goiter, Graves' disease and primary hypothyroidism, the PRL and TSH secretions were studied in parallel. Concurrent changes in the two hormones were evident only in conditions of marked hyper- or hypothyroidism. In the patients with non-toxic nodular (single or multiple) goiter the TSH showed low or normal values, while the PRL appeared normal or elevated. From these results two important conclusions can be drawn: 1. the T3 and T4 levels interact with PRL secretion concomitantly with TSH only when they undergo a huge deviation from the normal range; 2. the goitrogenic action of PRL that has been reported in experimental animals cannot be excluded in man.

Adolescent↗
PubMedDate not supplied

Thyrotropin and prolactin in patients with hypothalamus-pituitary diseases.

Seventy patients with hypothalamus-pituitary diseases were studied. 13 of them were studied before surgical treatment and then 15-20 days and 6 months later. A comparison was made with 59 controls. In all these subjects PRL and TSH were studied under basal conditions and after TRH stimulation. As for TSH the highest percentage of abnormal responses was found in the group of patients with chromophobe adenoma and parasellar dysplasias. This area of the pituitary appears relatively undamaged in acromegalic patients. In clinically hypothyroid patients, normal or high TSH responses to TRH were often found. As for PRL, a hyperprolactinaemia was mostly found in the group of patients with chromophobe adenoma, parasellar dysplasias and craniopharyngioma, although there was a different pattern in the TSH responses. No correlation was found between the basal PRL levels and the TSH responses to TRH. There was no significant difference in the TSH responses of the patients with PRL secreting and non-secreting chromophobe adenomas. The hypothesis of two autonomous systems is supported by the finding of differences in the functional recovery of the two pituitary areas studied at different times after surgical treatment.

Acromegaly↗
PubMedDate not supplied

Effect of lysine vasopressin on basal and TRH stimulated TSH and PRL release in normal men.

In order to test the possible effects of lysine vasopressin (LVP) on basal and TRH stimulated TSH and PRL release, an iv bolus of LVP (0.06 IU/kg bw) was injected alone or just before TRH (20 or 400 micrograms iv) in 18 normal male subjects. The administration of LVP modified neither the basal secretion of TSH and PRL nor the TSH and PRL release induced by 20 or 400 micrograms TRH. These data suggest that in humans, vasopressin is not involved in the control of TSH and PRL release at the anterior pituitary level.

Adult↗
PubMedDate not supplied

Intravenously infused substance P enhances basal and growth hormone (GH) releasing hormone-stimulated GH secretion in normal men.

The effect of synthetic substance P (SP), infused intravenously (IV) in doses of 0.5, 1, or 1.5 pmol/kg-1/min-1 over 60 min, on GH secretion was evaluated in seven healthy men. Substance P tests and a control test with normal saline were randomly performed at weekly intervals. No untoward side effects or changes in blood pressure were observed during SP infusions. Serum GH concentrations did not change when normal saline, the lowest dose, or the middle dose of SP were infused. In contrast, GH levels rose significantly when the highest dose of SP was given, with a mean peak two times higher than baseline. Further studies were performed to test the possible influence of SP on the GH response to GH-RH. For this purpose, seven other healthy men were tested with GH-RH (1 micrograms/kg body weight in an IV bolus) during saline or SP (1.5 pmol/Kg-1/min-1 x 60 min) infusion. The GH-RH induced a significant GH rise, with a mean peak seven times higher than baseline. When subjects were infused with SP, the GH response to GH-RH was greatly enhanced, with a mean peak 12 times higher than baseline. These results demonstrate for the first time in humans that the systemic infusion of SP stimulates GH secretion, and suggest that SP might interact with GH-RH in the stimulation of GH secretion.

Adult↗
PubMedDate not supplied

Peripheral blood abnormalities in Alzheimer disease: evidence for early endothelial dysfunction.

Clinical and epidemiologic studies demonstrate that vascular risk factors may be involved in Alzheimer disease (AD). To evaluate whether vascular abnormalities are an early feature of AD, several parameters of coagulation and fibrinolysis were assessed. Thirty patients with mild AD and 30 age-matched control subjects entered the study. All subjects performed a standardized clinical and laboratory protocol. Persons with vascular risk factors and systemic diseases were excluded. AD patients present significant increased levels of thrombomodulin (p < 0.0001) and sE-selectin (p < 0.03). In contrast, no difference was found between the two diagnostic groups in the levels of beta-thromboglobulin, prothrombin fragment 1+2, fibrinogen, and von Willebrand factor. No other association but diagnosis was found with thrombomodulin and sE-selectin. These findings suggest that endothelial dysfunction is an early event in AD patients.

Aged↗