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Biomedical subjects

G Valenti

Publications and source records attributed to G Valenti.

At least 163 records · Page 9Linked to original sources
PubMed1982

[The nature of urea transport across the skin of of Rana esculenta].

In several epithelial tissues such as toad bladder, gallbladder and human red cells, it has been established that urea movement implies a phloretin sensitive mediated transport. In the skin of the toad Bufo viridis also it has been described an active transport of urea. Our data, obtained on the frog skin seem to demonstrate the existence of some specific mechanism for urea transport towards the inside solution. In fact, two molecules having the some molecular diameter, such as urea and thiourea, show a large difference in permeability at low concentration. In addition 0.1 mM urea influxes and outfluxes, measured on paired skin halves in the absence of concentration gradient, exhibit an evident asymmetry. Further approaches with phloretin experiments were made in order to characterize the urea transport system. Phloretin (5.10(-4)M) added to the external solution significantly inhibits the urea influx. Little can be said at this time about the composition or kinetics of the carrier involved in the transport.

Animals↗
PubMed1982

Phloretin sensitive active urea absorption in frog skin.

This report presents evidence for urea active absorption by isolated skin of Rana esculenta. One of the supporting factors of such evidence is that at a low concentration the urea influx is five times greater than the outflux, in the absence of a chemical gradient. The transport shows a saturation kinetics with an apparent Km = 1.33 mM and is inhibited by un uncoupling agent (FCCP). 5 x 10(-4) M Phloretin, added to the external side, markedly inhibits inward urea transport, whereas it is ineffective when added to the serosal fluid. This provides evidence for a phloretin-sensitive mechanism located at the external side of the epithelium. Phloretin stimulates the sodium active transport; the possible coupling of urea and sodium movement is analysed.

Animals↗
PubMed1982

Nonspecific growth hormone responses to thyrotropin-releasing hormone in insulin-dependent diabetes: sex- and age-related pituitary responsiveness.

To evaluate GH pituitary responsivity to nonphysiological stimuli in insulin-dependent (type I) diabetes, a TRH test (200-micrograms iv bolus) was carried out in 31 type I diabetics (16 females and 15 males). TRH was capable of inducing GH responses in most of the studied patients, with a striking difference between the sexes; responses were documented in 7 of 15 males and in 13 of 16 females. Linear regression analyses of the results showed a positive correlation between basal values and peak levels of GH and a negative correlation between GH peaks and the ages of the patients. No correlation was found between GH values (basal and peak levels) and blood glucose levels or duration of disease. In conclusion, our results support the observation that GH secretion in diabetes is abnormal. TRH induces GH secretory responses, especially when GH basal values are elevated and in female patients. Pituitary GH responsiveness to TRH shows a progressive decline with advancing age unrelated to the duration of the disease or the presence of retinopathy.

Adolescent↗
PubMed1982

Pituitary-thyroid axis after bilateral orchiectomy in men.

The functional interaction between the testis and thyroid was evaluated in 13 patients affected by prostatic carcinoma before and after bilateral orchiectomy. Two different patterns of thyroid hormones were noted. Immediately after surgery, free thyroxine (T4) increased and total triiodothyronine (T3) decreased probably as a result of surgical stress at anesthesia. Later, free T4 levels decreased while total T4 and thyroxine binding globulin (TBG) were unchanged. Such changes may be due to qualitative changes in binding proteins.

Aged↗
PubMed1982

Beta-thromboglobulin and platelet factor 4 plasma levels during haemodialysis: effect of indobufen.

The effect of a single dose of indobufen (100 mg i.v.) on the release of beta-thromboglobulin and of the platelet factor 4 was investigated during dialysis in 20 uraemic subjects by a within-subjects, single-blind, indobufen versus placebo study. Plasma levels were measured in baseline conditions and 15, 30, 60, 120 and 240 minutes after the beginning of dialysis. Pre-treatment with indobufen clearly inhibited beta-TG and PF 4 output. The difference from placebo was highly significant (p less than 0.01) from the 30-minute control up to the end of dialysis. No changes in platelet count before and after dialysis were observed.

Adult↗
PubMed1982

Reduction of plasma levels of betathromboglobulin and platelet factor 4 during hemodialysis: a possible role for a short acting inhibitor of platelet aggregation.

Plasma levels of the platelet markers betathromboglobulin and platelet factor 4 are elevated in patients with chronic renal failure, and their levels in hemodialysis patients increase further during exposure to the dialysis membrane. The effectiveness of a short acting inhibitor of platelet aggregation in reducing the blood levels of betathromboglobulin and platelet factor 4 was assessed by means of a double blind cross over study. A statistically significant reduction of betathromboglobulin and platelet factor 4 levels was observed during treatment with the platelet inhibitor.

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↗
PubMed1981

Failure of drugs acting on H2-receptors to modify plasma prolactin levels in pituitary adenomas: evidence for a suprapituitary locus of action.

Cimetidine, which strongly stimulates prolactin release in healthy man, was unable to modify prolactin levels in prolactin-secreting pituitary adenomas. Furthermore, the infusion of 5-methylhistamine, an H2-receptor selective agonist, was equally ineffective. The results of these experiments together with the data reported in the literature suggest that H2-receptors modulate prolactin secretion at a hypothalamic level.

Adenoma↗
PubMed1979

Effects of cimetidine on the secretion of some pituitary hormones.

Cimetidine infused intravenously into 6 healthy volunteers did not induce significant changes in plasma levels of prolactin (hPRL), thyreotropin (hTSH), gonadotropin (hLH and hFSH) and growth hormone (hGH). Conversely it caused a significant increase in prolactin response to TRH without modifying the hTSH response to thyreotropin-releasing hormone (TRH) and gonadotropin response to gonadotropin-releasing hormone (GnRH). Data obtained in these experiments, together with data reported in the literature, suggest that the amplified prolactin response to TRH observed during cimetidine infusion, is likely to be connected with a blockade of H2-receptors rather than to unspecific actions of cimetidine.

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↗
PubMed1979

Prolactin response to TRH after intravenous cimetidine.

Cimetidine administered intravenously to six healthy volunteers caused a significant increase in plasma prolactin response to TRH. The meaning of these results and their relation with the physiological role of histamine H2-receptors in the control of prolactin secretion is discussed.

Blood-Brain Barrier↗
PubMed1979

[Evaluation of the pituitary reserve of gonadotropins and seminal function of the testis in subjects operated for cryptorchism].

76 patients (prepuberal, puberal and adults) who had undergone surgery for monolateral (35) or bilateral (41) cryptorchidism in childhood were studied. Testicular volume (76 cases), seminiferal function (18 cases) and pituitary gonadotropin reserve (51 cases) were evaluated. We obtained the following results: 1) the prepuberal patients had a normal testicular volume, while 70% of the puberal and adult patients had a mean testicular volume below normal levels. 2) 55.6% of the adults who underwent spermiogram had a pathological seminiferal function. 3) The number of patients whith exagerated gonadotropin response to GnRH-test increases with increasing puberal stage and reaches its highest significance after complete puberal development. These data confirm that: 1) the long permanence of one or both testis out of their natural position has a negative influence on their trophism; 2) the long-term prognosis of the tubular function of the testis after orchidopessis is poor in a high percentage of cases. 3) the endocrine anomalies which follow the early morphologic and functional changes of the cryptorchid testis are more easily detected during puberty as a reduced hypothalamic feedback of the gonadotropin secretion.

Adolescent↗