Search PubMed⌕ Search

Biomedical subjects

S Valenti

Publications and source records attributed to S Valenti.

86 records · Page 5Linked to original sources
PubMedDate not supplied

Immunoreactive and bioactive LH release from pituitaries of intact or castrated male rats: effect of in vitro GnRH and KCl administration.

The in vitro immunoreactive (i-LH) and bioactive (b-LH) LH release from hemipituitaries of intact adult male rats (INT) or rats castrated 7 days earlier (CAS) was studied. Hemipituitaries were incubated for 30 min (time 1) plus an additional 30 min (time 2) with GnRH (10 nM) and/or KCl (50 mM), according to one of the following protocols: media alone (C), KCl+KCl (K/K), GnRH+GnRH (G/G), KCl+GnRH (K/G), GnRH+KCl (G/K). All of the hemipituitaries were further incubated in media alone for 120 min (time 3). I-LH, b-LH and i-FSH were assayed on the media. In both models, the highest bioactive:immunoactive (b/i) ratio was noted during time 1; however, CAS always secreted more b-LH than INT at any given time of the study. In INT, GnRH--but not KCl--administration during time 2 resulted in blunted i-LH. During the same time, the b/i ratios decreased in all groups but G/K. LH secretion recovered during time 3 in all groups. In CAS, i-LH levels comparable to those of time 1 were sustained by either stimulus during time 2, while the b/i ratios were markedly decreased. LH secretion recovered in the K/K group during time 3. These results suggest that: 1) promptly releasable pools of b-LH are available in both models; 2) CAS always secrete more b-LH; 3) in INT, desensitization occurs involving parallel changes in both i-LH and b-LH, while changes in b-LH rather than i-LH are noted in CAS; 4) prolonged KCl administration might play a role in new gonadotropin synthesis and/or release.

Animals↗
PubMedDate not supplied

Nitric oxide biphasically modulates GH secretion in cultured cells of GH-secreting human pituitary adenomas.

BACKGROUND: Nitric oxide (NO) biphasically modulates osteoclast function, sperm motility and testosterone production by exerting a positive effect at low concentrations and a negative effect at high concentrations. In this study the effect due to administration of four NO-donors, each releasing an individual amount of NO, was studied on GH secretion from human adenomatous GH-secreting cells. METHODS: Sodium nitroprusside (SNP), diethylenetriamine NO adduct (DETA/NO), diethylamine/NO complex sodium salt (DEA/NO), and S-nitroso-N-acetylpenicillamine (SNAP) were administered at a concentration of 10-4 M to cells isolated after transsphenoidal adenomectomy from five acromegalic patients. RESULTS: SNP significantly (p < 0.01) increased GH secretion, while the other NO donors inhibited GH secretion in comparision with the amount of GH spontaneously released by unstimulated cells. Each drug showed an individual degree of inhibitory potency: DEA/NO > DETA/NO > SNAP. Nitrite accumulation in the media was measured as a marker of NO released by each individual drug and was found to be different for each drug (DEA/NO > DETA/NO > SNAP > SNP). A negative correlation (R = -0.93; p < 0.05) was found between nitrite release and GH secretion induced by each drug. CONCLUSIONS: These data show that low and quasi-physiological levels of NO, such as those released by SNP, stimulate GH secretion, while high NO levels, such as those released by the other NO-donors, inhibit GH secretion. Thus, NO is shown to be able to modulate GH secretion in a dose-dependent manner in GH adenomatous cells from human pituitary adenomas.

Adenoma↗
PubMedDate not supplied

[Spinal anesthesia in cesarean section: 1% versus 0.5% hyperbaric bupivacaine].

AIM: To compare the quality of anesthesia produced by the intrathecal administration of equivalent doses of 0.5% and 1% hyperbaric bupivacaine in patients undergoing cesarian section. EXPERIMENTAL DESIGN: A prospective, comparative and randomised clinical study. SETTING: Anesthesia Unit-Non-university civil hospital. PATIENTS: 50 patients undergoing elective or emergency cesarian section randomly assigned to two groups of 25 patients each. SURGERY: After prehydration, subarachnoid access was achieved through space L2-L3 or L3-L4 using a 24G Sprotte's needle with patients in right hand lateral decubitus. Patients in group A were injected with 1.25 ml of 1% hyperbaric bupivacaine and those in group B with 2.5 ml of 0.5% hyperbaric bupivacaine (12.5 mg). Patients were positioned immediately in partial decubitus on their left hand sides and ephedrine infusion, or if required i.v. bolus, was commenced to counter hypotension (SAP < 80% basal). MEASUREMENTS: ECG, pulse measurement, arterial pressure with non-invasive method, metameric level of analgesia (pin prick), motor block of lower limbs (Bromage's scale), time lapsed between induction of anesthesia and extraction of neonate, Apgar score, quantity of ephedrine used, duration of surgery, respiratory complications, insufficient analgesia, resolution of motor block, any postspinal cephalea. STATISTICAL ANALYSIS: Variance analysis, Student's t-test, chi 2. RESULTS: Both solutions guaranteed satisfactory intraoperative analgesia in 96% of cases. No statistically significant differences were noted between the two groups relating to the maximum duration of analgesia, the extent of motor block, induction times and regression, incidence of complications. CONCLUSIONS: No important difference was observed in the quality of the anesthesia obtained using the intrathecal administration of equivalent doses of 1% and 0.5% solutions of hyperbaric bupivacaine in patients undergoing cesarian section. In view of the possible relationship between the neurotoxicity of local anesthetics and the concentration of the solution used for spinal anesthesia, it is to be hoped that less concentrated solutions of hyperbaric bupivacaine will be introduced in Italy compared to the 1% solution currently available.

Adult↗