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Biomedical subjects

P Valensi

Publications and source records attributed to P Valensi.

At least 127 records · Page 7Linked to original sources
PubMed1991

Stimulating effect of forskolin on thyroxine secretion. Influence of calcium.

The aim of this study was to determine, with a rat thyroid fragment perifusion system, the short-term (20 min) effect of forskolin (FK), an adenylate cyclase activator, on T4 secretion, the effect of forskolin on T4 secretion stimulated by theophylline and TSH, and the role played by calcium in the forskolin effect. A dose-dependent effect on T4 secretion was obtained with forskolin, from 10(-8) to 10(-4) mol/l, with a maximal effect between 10(-6) and 10(-5) mol/l. The effect of forskolin was not increased by theophylline. The combined stimulation with forskolin and theophylline induced a T4 release which remained significantly lower than the effect of 22 or 65 mIU/ml TSH. Forskolin slightly increased the stimulating effect of 22 mIU/ml TSH but significantly decreased the effect of 65 mIU/ml TSH. A reduction in the buffer calcium concentration slightly decreased the effect of the forskolin and theophylline stimulations and the effect of the combined stimulation with forskolin and theophylline without suppressing completely the effect of these stimulations. This study demonstrates that 1) low concentrations of forskolin are able to induce a significant T4 release during short-term stimulations; 2) calcium is necessary in order to obtain a maximum effect of adenylate cyclase activation on T4 release; 3) the part of the thyroid hormone response to TSH which is mediated by adenylate cyclase activation is relatively small.

Animals↗
PubMed1990

Effect of beta adrenoceptors and thyroid hormones on velocity and acceleration of peripheral arterial flow in hyperthyroidism.

Brachial artery flow patterns were studied in 10 hyperthyroid and 10 normal subjects. Mean blood velocity and flow were evaluated by pulsed Doppler, and peak systolic acceleration was calculated by computer-assisted digitization of the instantaneous velocity curve. Compared to control subjects, hyperthyroid patients had higher velocity and flow (p less than 0.01, p less than 0.02) and higher peak systolic acceleration (p less than 0.01). In hyperthyroid patients, measurements were repeated after (1) mechanical exclusion of the hand from brachial circulation, (2) short-term beta-blocker treatment and (3) inducement of the euthyroid state. Exclusion of the hand reduced velocity and flow (p less than 0.001) but did not change peak systolic acceleration. Beta blockade induced disparate changes of velocity and flow but reduced peak systolic acceleration (p less than 0.05). In the euthyroid state, decreased blood velocity (p less than 0.01), flow (p less than 0.02) and acceleration (p less than 0.02) were observed. A hyperkinetic arterial circulation consisting of an increase in both velocity and acceleration is thus observable in hyperthyroidism. Hand exclusion showed that velocity seems to be influenced by peripheral factors while beta blockade suggests that acceleration is dependent of beta 1 adrenoceptors. Comparison between euthyroidism and hyperthyroidism indicates that both mean blood velocity and peak systolic acceleration are influenced by thyroid hormones.

Adrenergic beta-Antagonists↗
PubMed1990

Erythrocyte deformability in diabetes and erythrocyte membrane lipid composition.

Erythrocyte deformability was assessed in 40 diabetic patients, 24 insulin-dependent (IDD) and 16 non-insulin-dependent (NIDD), by measuring the initial filtration flow rate of whole blood, isolated red blood cells (RBC), and isolated RBC membranes with the Hanss hemorheometer, and its relationship to the plasma and ghost membrane lipid composition was investigated. RBC deformability was significantly reduced, whereas the deformability of the isolated RBC membranes did not differ significantly from the controls. In the plasma, the triglycerides were high, the high-density lipoprotein (HDL) cholesterol was reduced, and the ratio of total cholesterol over HDL cholesterol was high as compared with the controls. The RBC lipid composition expressed in mumol lipids/10(10) RBC showed significantly lower levels of free cholesterol, sphingomyelines, and phosphatidylcholine, which are the lipids principally located on the outer layer of the RBC membranes. These data suggest that in both IDD and NIDD patients, there may be a relation between these modifications in the RBC lipid composition and rheological impairment of the RBC.

Cholesterol↗
PubMed1990

Transport of thyroid hormones by human erythrocytes: kinetic characterization in adults and newborns.

The uptake of [125I]T3 and [125I]T4 by human erythrocytes was studied. The erythrocytes were obtained from adult subjects (28-41 yr old) and suspended in a protein-free medium. The half-times of equilibration for both T3 and T4 were 6 min. At equilibrium, T3 was concentrated 55-fold inside the cells, while T4 was concentrated 40 times, but these accumulations were not dependent on either cellular ATP or the transmembrane Na+ gradient. The amounts of cell-associated thyroid hormones were 20 times (T3) and 17 times (T4) higher than the amounts of free extracellular hormones at 5 X 10(9) erythrocytes/mL (the blood concentration). Oligomycin and phloretin inhibited T3-saturable transport (but not T4 transport) independently of cellular energy. We suggest that thyroid hormones are concentrated by intracellular trapping. The rates of T3 and T4 efflux from preloaded erythrocytes were similar to the influx rates. The initial velocities of T3 (but not T4) uptake and efflux were 70% saturable. The uptake was specific because the unlabeled analogs T4, triiodothyroacetic acid, rT3, D-T3, and D,L-thyronine inhibited [125I]T3 uptake 60, 125, 160, 190, and 1600 times less, respectively, than did unlabeled T3. The kinetic parameters of T3-saturable uptake, Km, and maximum velocity were determined for three groups of subjects: newborns, 28 to 41-yr-old adults, and 76 to 90-yr-old adults. The Km (67 nmol/L in 28 to 41-yr-old adults) was not age dependent, BUT the maximum velocity was significantly higher in newborns than in adults. We conclude that T3 transport across the human erythrocyte membrane is mediated mainly by facilitated diffusion, whereas T4 transport results from free diffusion. Human erythrocytes might act as a circulating pool of thyroid hormones, especially T3 in newborns.

Adenosine Triphosphate↗
PubMed1989

Effect of nifedipine on thyrotropin, prolactin, and thyroid hormone release in man: a placebo-controlled study.

Nifedipine (10 mg tid) or placebo was administered in a randomized double-blind trial for 1 wk to 2 groups of 10 mildly hypertensive euthyroid patients. Hormonal concentrations (thyrotropin [TSH], prolactin [PRL], thyroxin, triiodothyronine, and reverse triiodothyronine) before and during a TRH test were assessed in the 2 groups before (D0) and after (D7) each treatment. Parameters of the TRH test were determined (peak values, area under the curve [AUC], release [Kr], and elimination [Ke] rate constants) and their D7:D0 ratios were compared in the 2 groups. The TSH (peak values and Kr) and PRL (peak values and AUC) responses to TRH were significantly decreased in the nifedipine group compared to the placebo group. Neither basal nor TRH-stimulated thyroid hormone levels were modified. These results confirm experimental data but seem to be clinically irrelevant.

Adult↗
PubMed1989

Ultradian, circadian and seasonal variations of plasma progesterone and LH concentrations during the luteal phase.

The circadian variations in plasma progesterone (P) and LH concentrations were investigated in six women, aged 23-40 years. All were studied in the mid-luteal phase (7 +/- 2 days after LH mid-cycle surge). Experiments were conducted in autumn and in spring. Blood samples were obtained every 15 min for 24 hr. Plasma P and LH concentrations were measured by RIA. Each subject's time-series was analysed using three methods; visual inspection (chronogram), spectral analysis to estimate component periods of rhythms (tau) and cosinor analysis to quantify the rhythms parameters. Marked temporal variations in plasma P concentration were observed in each subject. The maximal variations over a 24-hr period, ranged between 13-58.5 mmol/l. Differences related to sampling time were statistically validated by ANOVA (p less than 0.00001). Significant harmonic periods were detected by spectral analysis but differed among subjects. In all subjects but one, a circadian rhythm was detected. The acrophase location was similar (about 0700 hr) in the four subjects studied in autumn, but ranged from 1940 to 0320 hr in those studied in spring. An ultradian rhythm with tau = 8 hr was also validated in six time-series with similar acrophases (about 0200, 1000, and 1800 hr). Cosinor analysis of pooled data revealed that the 24-hr, 12-hr, and 8-hr rhythms were statistically significant (p = 0.001) in autumn. algebraic sum of these three cosine functions yielded a circadian waveform with peak-times occurring near 0300 and 1130 hr and a trough-time about 2200 hr. In spring, the circadian pattern appeared quite different, and peak-times were found near 0700 and 2000 hr, and trough-times near 0300 and 1500 hr. Furthermore, the 24-hr mean of P was higher in autumn (28.9 +/- 0.4 nmol/l) than in spring (17.2 +/- 0.4 nmol/l), p from ANOVA less than 0.00001. The evidence for a similar circadian LH pattern is not as strong. Seasonal, circadian and ultradian rhythms characterize the physiologic time structure of plasma P concentration in mid-luteal phase.

Activity Cycles↗
PubMed1989

[Value of endomyocardial biopsy in congestive heart failure in diabetics without coronary disease].

Two cases of congestive heart failure in diabetic females are reported. One patient had moderate hypertension. Echography and angiography revealed a low-output dilated cardiopathy and ruled out the possibility of coronary artery stenosis and thin amyloid deposits were found in one patient. The evolution was favorable with a low-salt diet, associated with diuretic and vasodilator treatments. These case reports confirm the existence of a diabetic myocardiopathy, which may lead to congestive heart failure. They justify a complete hemodynamic analysis and a histopathological evaluation of the myocardium when this complication occurs.

Aged↗
PubMed1989

[Preoperative localization of parathyroid adenoma with technetium and thallium double-labeling scintigraphy. Difficulties related to associated thyroid lesions].

Technetium and thallium double-labeling scintigraphy with image subtraction was carried out on 63 patients suspected of having primary hyperparathyroidism, with or without thyroid involvement. Forty-four patients had a normal thyroid image with technetium. The positive foci located by double-labeling in patients who were to undergo surgery always coincided with parathyroid adenoma. In the 16 cases where the initial diagnosis of hyperparathyroidism was not substantiated, the double-labeling test was normal. Thus for these 44 patients, scintigraphy sensitivity was 75% and specificity was 100%. Nineteen patients had an abnormal thyroid image with technetium. In 7 cases, image subtraction following double-labeling yielded uninterpretable data. In 12 other patients, the positive foci located outside the thyroid by double-labeling coincided with a parathyroid adenoma, whereas this was true for only one patient whose positive foci were located inside the thyroid; a parathyroid adenoma was not detected preoperatively in 4 patients. This double-labeling test is thus useful in locating parathyroid adenomas when technetium scintigraphy of the thyroid is normal; when it is abnormal, double-labeling is advantageous only in cases of extra-thyroid foci.

Adenoma↗
PubMed1989

[Uncommon collapse].

Explore the source record for details and available documents.

Adrenal Gland Neoplasms↗
PubMed1988

Asymptomatic diabetic cardiomyopathy: a noninvasive study.

Forty-nine diabetic patients (26 type I and 23 type II), free of cardiovascular disease symptoms, were compared with 32 controls in a noninvasive study of left ventricular (LV) function. Absence of ischemic cardiopathy was confirmed by routine investigations and an exercise electrocardiogram using 12 leads with a thallium-201 myocardial scintigraphy. Diabetic patients had (1) a significantly prolonged mean isovolumetric relaxation time (IVRT) assessed by M-mode echocardiography and phonomechanography; (2) a significantly reduced E-F slope; (3) an increased mean Weissler index (pre-ejection period/LV ejection time). The IVRT and E-F slope abnormalities reflect increased myocardial stiffness and impaired LV compliance. The increased Weissler index reflects impaired myocardial contractility. These abnormalities were not related to sex, age, duration of diabetes or to the presence or extent of complications. No significant difference was found between diabetic patients and controls for mean diastolic and systolic LV diameters, thickness of the posterior wall or of the interventricular septum, assessed by echocardiography, or for the ejection fraction, determined by radionuclide angiocardiography. Finally, more than half of the patients with a frankly abnormal IVRT, Weissler index and E-F slope had had diabetes for less than 5 years, some even less than 2 years, without complications. These data show: (1) evidence of LV dysfunction specific to diabetes and unrelated to ischemic cardiopathy and hypertension; (2) the possible involvement of a metabolic factor in this early asymptomatic LV abnormality rather than microangiopathy.

Adult↗
PubMed1988

Use of a pharmacokinetic model to characterize the thyrotropin (TSH) and prolactin (PRL) response to thyrotropin-releasing hormone (THR) in man.

On the basis of a pharmacokinetic model using the data of a TRH test and without the use of radio-isotope tracers, a simple procedure of estimation of PRL and TSH TRH-stimulated release and elimination half-lives is presented. TRH tests were performed in 33 healthy subjects and their data were used to calculate the kinetic parameters of each subject. Elimination half-lives of TSH and PRL were found to be respectively (mean +/- SD in min) 63 +/- 7.4 and 35 +/- 2.8. Release half-lives were 8.2 +/- 1.3 for TSH and 5 +/- 0.4 for PRL. The usefulness of the procedure in the evaluation of drug effects on pituitary secretion in man and the comparison with the literature data are discussed.

Adult↗
PubMed1987

Detection of thyroid-stimulating antibodies in thyroid diseases, employing rat thyroid fragment perifusion.

The technique of perifusing rat thyroid fragments was used to investigate the presence of thyroid-stimulating antibodies (TSAb) in the sera of 48 patients. Response to IgG was measured by determining the mean rate of release of T4 (R) during a 30-min perifusion and the secretion peak (Imax) by means of samples taken every 5 min. Values found to be above the mean + 2 SD of the control values of R or Imax were considered to be positive. TSAb were found in all the 17 patients with untreated Graves' disease (GD) and in the 2 treated with antithyroid drugs, but not in the 3 who had undergone surgery or 131I treatment or in the 2 on corticosteroid treatment. TSAb were also found in 2 out of 3 patients with untreated nodular toxic goiter (UNTG) and in 6 out of 8 with diffuse nontoxic goiter (DNG) but at lower levels. In the untreated GD group, R and Imax correlated significantly with the corresponding IgG concentrations (from 90 to 800 micrograms/ml), suggesting TSAb activity which can be compared from one patient to another. TSAb activity did not correlate with thyroid function tests in any group. In all the groups it induced an early secretion peak followed by a decreasing response throughout the stimulation period, as was previously found with 65 mIU/ml TSH. The specificity of this technique was verified by five different control methods: the perifusion technique was checked by using KRBG buffer alone; sera were studied from a group of healthy controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Feminizing Leydig cell tumor: endocrine and incubation studies.

A 32-year-old patient with a history of surgery for left gynecomastia four years previously presented with right gynecomastia; a tumor in the left testis proved to be a Leydig cell tumor. Preoperative investigations showed elevated but variable levels of plasma estradiol (E2) and estrone (E1), and reduced serum LH and FSH and plasma testosterone (T). After hCG stimulation, E2 response was increased and abnormally prolonged; T reached normal values, which has predictive value for a return to normal of post-operative T level. After left orchiectomy, gynecomastia regressed within a few days, gonadotropins increased by day 2, estrogens dropped by day 2 and were normal at day 7, T and 5 alpha-dihydrotestosterone dropped at day 2 but reached normal levels at day 16. Pathophysiology of these hormonal data are discussed. An incubation procedure with 3H testosterone showed an aromatase activity 21 times greater in the tumor than in normal peritumoral tissue, while the percentage of the volume occupied by Leydig cells was 34 times higher. This suggests that the aromatase activity of a single tumor cell is very similar to that of a normal Leydig cell. Furthermore, evidence of juxtatumoral Leydig cell hyperplasia in areas where the tumor was well encapsulated suggests the existence of a factor stimulating Leydig cell multiplication.

Adult↗