[Low levels of testosterone in patients with pancreatic carcinoma].
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
C Scandellari
Publications and source records attributed to C Scandellari.
Alpha human atrial natriuretic peptide and anterior pituitary hormones secretion in men.
Explore the source record for details and available documents.
Adult↗
Evidence of immunoreactive human atrial natriuretic peptides in human anterior pituitary cells.
Explore the source record for details and available documents.
Adult↗
Angiotensin-converting enzyme content of human spermatozoa and its release during capacitation.
In this study, we demonstrated, by using known detergents, the presence of angiotensin-converting enzyme (ACE) within human spermatozoa. We determined that maximal angiotensin-converting activity is expressed by sperm incubated in capacitating conditions, whereas this activity is negligible in saline-incubated spermatozoa. We further demonstrated that not acrosomes but cytoplasmic residues contain ACE. Because follicular fluid provides the necessary conditions for a maximal angiotensin-converting activity and for capacitations' metabolic activation, we hypothesize that ACE may play its physiologic role within the female reproductive tract.
Adult↗
Reduced calcitonin reserve in young hypogonadic osteoporotic men.
Calcitonin is a potent inhibitor of bone resorption and in both sexes, plasma levels progressively decrease with age: therefore, a relative deficiency of calcitonin may be involved in the pathogenesis of osteoporosis in the elderly. Calcitonin plasma levels of young hypogonadic men with osteoporosis are significantly lower than controls: the hypothesis that the decreased calcitonin plasma levels in the elderly are due to a reduced secretory capacity of the "C" cells of the thyroid gland, related to age, does not explain the low calcitonin plasma levels found in young hypogonadic osteoporotic men. Our hypothesis is that gonadal steroid deficiency may participate in the mechanisms regulating calcitonin secretion. Therefore, we studied ten males affected by hypogonadotropic hypogonadism and ten normal men, of comparable age, as controls: we measured plasma levels of testosterone, 17 beta estradiol, androstenedione and calcitonin, and the response of calcitonin to an i.v. bolus of pentagastrin, a well known "C" cells stimulatory drug. Testosterone and calcitonin plasma levels and the response of calcitonin to pentagastrin were also evaluated after 6 months of replacement therapy with testosterone. Basal levels of testosterone, 17 beta estradiol, androstenedione and calcitonin, and the response of calcitonin to pentagastrin, are significantly lower in our patients than in controls, demonstrating that hypogonadotropic hypogonadic subjects have a lower secretory reserve of calcitonin. After testosterone therapy the basal calcitonin plasma levels and its response to pentagastrin stimulus did not differ from controls, suggesting that gonadal steroids influence the calcitonin secretion and reserve. Our data cannot clarify whether osteoporosis of hypogonadotropic hypogonadic patients is related to androgen or estrogen deficiency; however, they suggest that the mechanisms by which gonadal steroid influence bone metabolism may involve calcitonin secretion.
Adult↗
Role of gonadal steroids in the serotoninergic control of prolactin secretion in men.
The physiological regulation of PRL secretion seems to involve the central serotonin system, since plasma PRL levels are enhanced by serotoninergic agonists and serotonin re-uptake blockers. The aim of this study was to evaluate whether the influence of oestrogens on PRL is mediated by the hypothalamic serotonin system. The PRL response to fenfluramine, a serotonin agonist that releases the amine and inhibits its re-uptake, was assessed in 10 normal men (aged 18-25 years) and in six castrated men (aged 18-24 years). In both groups, the effect of fenfluramine on PRL secretion was also evaluated on the sixth day after receiving clomiphene citrate, an oestrogen antagonist and partial agonist. In castrated men, fenfluramine administration was also performed on the seventh day after the last dose of testosterone enanthate (200 mg i.m. every 3 weeks for 4 months). Our results demonstrate that in normal men fenfluramine treatment significantly enhances plasma PRL levels, and clomiphene citrate treatment significantly reduces this effect. In castrated men, fenfluramine is also able to enhance PRL secretion but to a lesser extent; after clomiphene citrate treatment the increase of plasma PRL levels induced by fenfluramine rises to the normal range. We therefore suggest that in man oestrogens and aromatizable androgens influence PRL secretion at least in part by involving the activation of the hypothalamic serotonin system.
Adolescent↗
Plasma carnitine and acetyl-carnitine levels at different times of the day.
An interest in both biochemical and clinical carnitine investigation has recently developed. A more complete and extensive study is obtained if acetyl-carnitine as well as carnitine are investigated. This research, using an improved and simplified method for carnitine and acetyl-carnitine determination in the same sample (1 ml) without radioisotopic tracer use, investigates if there are the same differences in their plasma levels at different times of the day. The sample was eluted in a chromatographic column (55 X 15 mm) containing Sephadex G-25M with phosphate buffer (25 mmol/l, pH 7.4). The fraction containing acetyl and free carnitine was divided and employed separately for two assays. The carnitine assay uses an enzymatic reaction catalyzed by carnitine acetyl-transferase (CAT) and measurements are carried out spectrophotometrically. The calibration curve shows r = 0.987 and sensitivity at 5 mumol/l (reference plasma values: 38 +/- 3 mumol/l in 9 subjects). The acetyl-carnitine assay is carried out concentrating the sample by lyophilization and then measuring the enzymatic coupled reactions catalyzed by CAT, malate dehydrogenase and citrate synthase fluorimetrically. The calibration curve gives r = 0.991 and sensitivity at 1.4 mumol/l (reference plasma values: 2.8 +/- 0.3 mumol/l in 9 subjects). Both assay methods are measured at the end point. The carnitine and acetyl-carnitine measured in the plasma of 6 normal subjects at different times of the day vary respectively from 28 to 37 mumol/l and from 1.1 to 5.2 mumol/l in agreement with plasma free fatty acid (FFA) variation from 230 to 779 microEq/l.(ABSTRACT TRUNCATED AT 250 WORDS)
Acetylcarnitine↗
Evidence for serotoninergic system involvement in opioid control of luteinizing hormone secretion in man.
Endogenous opioid peptides tonically inhibit LH by acting on hypothalamic mechanisms which regulate LHRH secretion. Opiates increase hypothalamic serotonin turnover but the involvement of the serotoninergic system in the opioid mechanisms regulating LH secretion in man is not clear at present. This study was designed to evaluate whether the tonic inhibitory effect on LH secretion induced by opiates involves the serotoninergic system. We have studied 10 healthy young men (aged 20-28 years). Five subjects were infused with naloxone (10 mg/h for 3 h) before and 120 min after fenfluramine administration (60 mg orally) on two different occasions. In five other subjects naloxone was infused before and after metergoline pretreatment (8 mg on first and second day and 4 mg on the third day, orally, at 0 time of naloxone infusion). After fenfluramine, naloxone infusion failed to induce any increase in LH plasma levels; metergoline pretreatment significantly enhanced the naloxone-induced LH increase. These data suggest that in man a hypothalamic serotoninergic system may be involved in the opioid mechanisms regulating LH secretion.
Adult↗
Localization of met-enkephalin on human spermatozoa and evidence for its physiological role.
Pro-opio-melano-cortino-derived peptides have been identified in rat testicular extracts and in human seminal plasma, but their physiological role is still unknown. We report that met-enkephalin is localized on human spermatozoa, by means of an indirect immunofluorescent technique. Furthermore, we demonstrate that a met-enkephalin analog (D-Ala2-Mephe4-Met-(o)-ol-enkephalin, FK 33-824, Sandoz, Basel, Switzerland: DAMME) inhibits in a dose-dependent manner the acrosome reaction induction. The hypothesis of a physiological role of seminal met-enkephalin on human spermatozoa fertilizing ability is briefly discussed.
Acrosome↗
Effects of pirenzepine on plasma insulin, glucagon and pancreatic polypeptide levels in normal man.
The secretion of various pancreatic hormones (insulin, glucagon and pancreatic polypeptide) is affected to a different extent by the cholinergic system. In 7 healthy subjects the effects of treatment for 1 week with pirenzepine, an anticholinergic drug selective for muscarinic receptors, on basal secretion of these hormones and on that induced by i.v. glucose (IVGTT) and arginine were evaluated. The drug did not reduce basal levels of insulin and glucagon whereas it caused an appreciable reduction in basal pancreatic polypeptide (PP). The responses of insulin and blood glucose to IVGTT and to arginine were not changed by treatment, nor was that of plasma glucagon to arginine. The infusion of arginine did induce an increase in PP level, which reached a statistically significant maximum at 90 min. This response was not particularly different after administration of pirenzepine. Thus, the results confirm the finding that arginine stimulates PP secretion in vivo and that pirenzepine reduces the basal level of the hormone, whereas it did not appear to affect the response to arginine. The findings exclude any direct action of the drug on insulin or glucagon secretion or on glucose metabolism in general.
Adult↗
Testosterone and calcitonin plasma levels in hypogonadal osteoporotic young men.
The aim of this study was to ascertain whether there was an interrelationship between male osteoporosis, calcitonin and androgens. Ten young hypogonadal osteoporotic men were studied: testosterone and calcitonin plasma levels were measured before and after therapy with testosterone enanthate (200 mg im every three weeks for four months). In these patients testosterone and calcitonin plasma levels were significantly lower than controls, before therapy (p less than 0.001 and p less than 0.01 respectively). Testosterone treatment significantly increased (p less than 0.05) serum calcitonin. The conclusion was that androgen deficiency may cause osteoporosis also by decreasing calcitonin secretion.
Adult↗
Lack of effect of im diazepam administration on hGH and hPRL secretion in normal and acromegalic subjects.
The usefulness of diazepam as a provocative stimulus for hGH secretion has been suggested as a simple, reliable test in clinical hGH assessment of pituitary disorders. We have investigated the effects of diazepam (10 mg im) on plasma hGH and hPRL in 5 normal and 7 acromegalic subjects. No significant variations in hGH and hPRL levels have been observed in any of the studied subjects. These findings indicate that the drug is ineffective on hGH and hPRL release and that it cannot be considered a valid provocative test either in normal or acromegalic subjects.
Acromegaly↗
Serotonin but not dopamine is involved in the naloxone-induced luteinizing hormone release in man.
Endogenous opioid peptides exert a tonic inhibition on gonadotropin secretion at the hypothalamic level, but the mechanisms by which they act are still unknown. Previous experimental studies suggest that the endogenous opioid peptides change dopaminergic and serotoninergic tones at the hypothalamic level. We have investigated whether the stimulatory effect of naloxone on luteinizing hormone (LH) secretion is due to its influence on these neurotransmitters. Two experimental models were studied, and two sets of effects on LH secretion induced by intravenous naloxone infusion (20 mg over 2 hours) in 14 normal men 20 to 25 years of age were evaluated: the effect of oral sulpiride (150 mg), a potent dopaminergic antagonist, and the effect of oral fenfluramine (60 mg), a drug that stimulates the serotoninergic receptors by releasing serotonin and inhibiting its reuptake. The study demonstrated that naloxone infusion significantly stimulated the LH secretion throughout the period of observation (P less than 0.01 versus saline). The pretreatment with sulpiride did not change the LH response to naloxone. After fenfluramine pretreatment, naloxone failed to induce any rise in LH secretion. Follicle-stimulating hormone did not show any important variation in either test. The data suggest that in man the stimulatory ability of the opiate receptor antagonist naloxone to elicit a rise in LH plasma levels may involve the serotoninergic, but not the dopaminergic, hypothalamic system. This hypothesis, however, does not exclude the involvement of other hypothalamic neurotransmitters.
Adult↗
Dopamine is not involved in the opioid control of luteinizing hormone secretion in man.
The aim of this study was to examine the role of the central dopaminergic system in the mechanisms by which opioid peptides exert their influence on luteinizing hormone (LH) secretion in man. The effects of sulpiride and naloxone on the changes in LH secretion induced by a metenkephalin analog (D-Ala2-MePhe4-Met-(o)-ol-Enkephalin, FK 33824, Sandoz, Basel, Switzerland) (DAMME) and dopamine infusion in four castrated men (21 to 25 years of age) were studied. In these patients, sulpiride pretreatment counteracted the inhibitory effect of dopamine but did not alter the fall of LH plasma levels that DAMME induced. Moreover, in these subjects naloxone reduced the inhibitory effects induced by DAMME but did not change the inhibitory effect of dopamine on LH secretion. These findings confirm that central dopaminergic and opiatergic systems play a role in the control of LH secretion; the data also exclude any interaction between these systems in regulating LH secretion.
Adult↗
Gonadal steroids deficiency and prolactin response to a met-enkephalin analog in man.
The aim of this study was to ascertain whether there is a correlation between gonadal steroids and opioid control of prolactin (PRL) secretion. Four castrated men, aged 18 to 24 years were submitted to intravenous injection of 250 ug of a met-enkephalin analog (D-Ala2-Mephe4-Met-(o)-ol-Enkephalin, FK 33824) (DAMME). In normal men DAMME injection was also performed on the 6th day after treatment with clomiphene citrate (CC) (200 mg/day for 5 days), a specific nonsteroidal estrogen receptor blocker. In castrated men and in normal men after CC treatment, there was a lower PRL response to DAMME than in controls (P less than 0.0005). These results suggest that gonadal steroid deficiency seems to cause a change in the opioid system and/or dopaminergic control of prolactin secretion.
Adolescent↗
Naloxone reduces the fenfluramine-induced prolactin release in man.
In order to ascertain whether there is a relation between opioids and the serotoninergic system in prolactin (PRL) secretion increase, we investigated in seven healthy men (21 to 26 years of age) the effect of naloxone, a specific opioid antagonist, on PRL secretion induced by fenfluramine, a drug that stimulates serotonin release and inhibits its re-uptake. We observed that subjects receiving fenfluramine (60 mg orally) had a significantly (P less than 0.001) higher increase in PRL plasma levels than the controls receiving placebo. In all subjects naloxone infusion at a dose of 15 mg caused a significant reduction (P less than 0.0005) in the PRL response to fenfluramine. Higher doses of naloxone (30 mg) do not further inhibit the PRL secretion induced by fenfluramine. These results suggest that naloxone may interact with opiate receptors on serotonin neurons thereby reducing the synthesis and release of serotonin. It seems that in man, therefore, there is an interplay between opiates and the serotoninergic system in the facilitatory influence on PRL release.
Adult↗
Effects of a met-enkephalin analogue on motility, O2 consumption, and ATP content of human spermatozoa.
Opioid narcotics are present in seminal plasma, although their physiological effect on spermatozoa is still unknown. This study reports data on metabolic parameters of human spermatozoa in the presence of a met-enkephalin analogue: D-Ala2-Mephe4-Met-(o)-ol-Enkephalin, FK 33824, Sandoz, Basel, Switzerland (DAMME), and its receptor antagonist naloxone hydrochloride, Endo Laboratories, Garden City, New York. Our findings indicate that the metenkephalin analogue reduces sperm motility and cellular O2 consumption without affecting cellular ATP content and viability. The hypothesis that DAMME acts on adenylate-cyclase is briefly discussed.
Adenosine Triphosphate↗
The influence of gonadal steroids on the dopamine inhibitory effect on gonadotropin release in men.
The aim of this study was to ascertain whether an interrelationship exists between gonadal steroids and the inhibition of gonadotropin secretion by dopamine. The effect of dopamine infusion (4 micrograms/kg/minute intravenously) on gonadotropin plasma levels in four castrated men (18 to 23 years of age) and in four age-matched normal men was studied. Normal subjects were studied before and after treatment with a specific nonsteroidal estrogen receptor antagonist, CC. LH plasma levels in normal subjects receiving CC had a maximum decrease percentage and a net decrease significantly greater (P less than 0.005 and P less than 0.012, respectively) than those before CC treatment. In castrated subjects the maximum decrease percentage was significantly greater (P less than 0.005) than in control subjects, but it did not show any difference from that of normal subjects receiving CC. In none of the group were significant changes in FSH concentration observed. The findings suggest that whenever there is a gonadal steroid deficiency, dopamine infusion causes an increased sensitivity to LH inhibition. This may be due to a lower endogenous dopaminergic influence on LH secretion.
Adolescent↗