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Biomedical subjects

R Minelli

Publications and source records attributed to R Minelli.

At least 55 records · Page 3Linked to original sources
PubMed1988

Metergoline, naloxone, and sodium valproate did not modify arginine vasopressin response to insulin-induced hypoglycemia in man.

The present study was carried out in order to determine whether insulin-induced hypoglycemia exerts its stimulatory effect on plasma concentrations of arginine vasopressin (AVP) by interacting with a serotonergic, a GABA-ergic or an opioid pathway. For this purpose, the effect of the serotonergic antagonist metergoline (10 mg/day for 4 days po), the GABA-ergic agonist sodium valproate (600 mg in three divided doses po) and the opioid-receptor blocker naloxone (10 mg in a iv bolus) on the AVP response during an insulin (0.15 IU/kg bw) tolerance test (ITT) was evaluated in three groups of 6 normal men each. In all men, control ITTs were performed without drug treatments. Basal and ITT-stimulated AVP secretion was not modified by drug administration, suggesting that serotonergic, GABAergic and naloxone-sensitive opioid receptors are not involved in the regulation of AVP secretion in response to insulin-induced hypoglycemia.

Adrenocorticotropic Hormone↗
PubMed1988

Dopaminergic control of TSH secretion in endogenous depression.

To evaluate whether the inhibitory control exerted by endogenous dopamine on thyroid-stimulating hormone (TSH) secretion is altered in patients with major depressive disorder, 11 depressed patients and 9 normal controls were tested with the dopaminergic receptor antagonist domperidone (10 or 20 mg i.v.). The administration of domperidone induced a significant increase in circulating TSH levels in the normal controls, but not in the depressed patients. These data excluded the possibility that the dopaminergic inhibition of TSH secretion is enhanced in depression. To establish whether domperidone failure was due to a reduced dopaminergic tone, domperidone was administered before stimulation of TSH secretion with thyrotropin-releasing hormone (TRH) (200 micrograms i.v.). The TSH response to TRH was significantly lower in the depressed than in the control subjects, regardless of domperidone priming. However, in both groups domperidone enhanced the TRH-induced TSH release by 50%. These data suggest that the dopaminergic control of TSH secretion is not altered in patients with endogenous depression and that a reduced capacity of the pituitary to secrete TSH might be responsible for the reduced TSH responsiveness to TRH and domperidone.

Adult↗
PubMed1988

The effect of diltiazem, a calcium channel-blocking drug, on cardiac rate and rhythm in hyperthyroid patients.

Tachycardia and tachyarrhythmias are frequent in patients with thyrotoxicosis, especially in the elderly. Since myocardial calcium uptake is increased in thyrotoxic rats, the efficacy of the calcium channel-blocking drug diltiazem in decreasing heart rate and the incidence of arrhythmias was evaluated in 11 hyperthyroid patients. All patients were studied with a 24-hour Holter monitor prior to the beginning of sole diltiazem therapy (120 mg given every eight hours), on the tenth day of therapy, and five days after therapy was discontinued. Heart rate significantly decreased by 17% during diltiazem treatment (96.5 +/- 3.7 systoles/min vs 79.9 +/- 3.2 systoles/min [mean +/- SE]) and returned to baseline values five days after the therapy was discontinued (100.7 +/- 3.4 systoles/min). Similarly, the number of premature ventricular extrasystoles per hour was significantly decreased (18 +/- 7 vs 2 +/- 1). In three patients, asymptomatic bouts of supraventricular tachycardia, paroxysmal atrial fibrillation, or ventricular tachycardia disappeared during diltiazem therapy. These findings suggest that calcium-blocking drugs may be extremely useful as adjunctive therapy for thyrotoxicosis in the presence of angina, congestive failure, and tachyarrhythmias.

Adult↗
PubMed1988

Graves' disease and thyroxine-binding globulin deficiency.

Thyroxine-binding globulin (TBG) deficiency has been frequently described in single patients and in many families. Most people with abnormal TBG concentrations are euthyroid. Cases of Graves' disease and TBG deficit have rarely been reported. We describe the case of a person with Graves' disease and TBG deficiency. Because of this condition, the patient had a misdiagnosis during part of his clinical history, and therefore underwent unnecessary therapy.

Diagnostic Errors↗
PubMed1987

Nicotinic and M1-, M2-muscarinic cholinergic control of ACTH response to insulin-induced hypoglycaemia in man.

The possible mediation of muscarinic and/or nicotinic-cholinergic receptors in the response of ACTH to insulin-induced hypoglycaemia was evaluated in 18 normal men. Subjects were tested with the insulin (0.15 U/kg) tolerance test (ITT) in basal conditions and in the presence of the M1- and M2-muscarinic antagonist atropine (600 micrograms iv just before insulin injection (time 0) plus 600 micrograms 20 min later in 6 subjects) or the M1-muscarinic receptor blocker pirenzepine (40 mg iv 10 min before ITT or 20 mg at time 0 plus 30 mg at time 20 in 6 subjects). The remaining 6 men were treated with the nicotinic receptor antagonist trimethaphan (0.3 mg/min x 30 min before ITT). ACTH rose 4.7 times in response to hypoglycaemia. The ACTH response to hypoglycaemia did not change after pirenzepine administration, whereas it was significantly increased by atropine and decreased by trimethaphan treatment. These data indicate that nicotinic and muscarinic (M2 but not M1) receptors participate in a different manner in the regulation of the hypoglycaemia-induced ACTH release.

Adrenocorticotropic Hormone↗
PubMed1984

[The cost of energy and cardiovascular expenditure in basketball players during a game].

Energy expenditure was evaluated for 6 Basket players while exercising on a cyclergometer. Oxygen consumption (VO2), pulmonary ventilation (VE), heart rate (HR), respiratory quotient (QR) and other parameters were estimated at various levels of load (25 Watt each step of 3 minutes duration), till to submaximal load of 175 Watt. The same subjects participate to a regular Basket game and their heart rate was continuously stored on a tape recorder (Holter). Arterial blood pressure was also taken whenever possible (timeout, etc). From the laboratory and field data, estimates were made for the oxygen consumption together with energy cost of the game. This can be assume a net value of 0.1339 Kcal X Kg-1 X min-1.

Blood Pressure↗
PubMed1983

[Readjustment of peripheral factors during the unsteady-state phase of dynamic muscular exercise].

The behaviour of the ratio: oxygen extraction (total peripheral resistance (DAV/TPR) in a group of untrained healthy young male students has been bloodless investigated during the unsteady-state phase of the dynamic muscular exercise (2.5 watt/Kg). The results obtained have shown that the kinetics of the ratio, from a resting value of 3.40 ml O2 . min-1 . mmHg-1 to a figure of 17.62 (steady-state) doesn't follow a step function. During the first 30 seconds the percentual increase of the ratio falls to 0.45, becomes 1.5 thirty seconds later and there this exponentially drops down to a value of 1. The observed behaviour agrees with experimental findings of other authors.

Adolescent↗
PubMed1982

Factors modulating the sensitivity of the relaxation to the loading conditions in rat cardiac muscle.

The load sensitivity of the relaxation phase was studied in rat papillary muscle, with isotonic afterloaded contractions and stretches applied after the peak of isometric twitches. The tension decay occurred earlier in isotonic than in isometric contractions. When a central region of the preparation was marked with small stainless steel pins, a lengthening of this region could be shown during relaxation of isometric (fixed end) contractions. This lengthening was earlier and faster in isotonic afterloaded contractions. Therefore the sensitivity of relaxation to load or length changes could be described in the context of the general mechanism of relaxation which takes into account the non uniform behaviour of the muscle and the internal movement during contractions. Interventions which decelerate the activation decay rate had different effects on the load dependence of relaxation. Caffeine addition and substitution of strontium for calcium abolished the load sensitivity while a temperature reduction had no influence on it.

Animals↗
PubMed1982

[The "peripheral factor" in muscular exertion].

On the basis of their own experimental results and of those from the literature, the Authors have studied the possibility of bloodless evaluation of the ratio: oxygen extraction (DAV) to total peripheral resistances (TPR). The so called "peripheral factor" which can be thus obtained (units: m10(2) X min-1 X mmHg-1), appears to be a sensitive index of the metabolic-functional behaviour of skeletal musculature and of the degree of left ventricular involvement during various types of muscular exercise. From resting value of 3-5, the "peripheral factor" can increase up to 40 m10(2) X min-1 X mmHg-1 in well trained athletes, and it appears to be influenced not only by the amount of work performed but also by the "type" of muscle group involved.

Blood Pressure↗
PubMed1982

[Changes in hemodynamic and metabolic parameters during controlled muscular exertion in a group of international-level professional cyclists].

The behaviour of some cardiovascular and metabolic parameters have been studied in 11 competitive road-cyclists under controlled submaximal work load. The test used was intermittent with load increasing from 100 to 250 watt, independent from age and body weight of the athletes. The results obtained have shown that whereas the estimated VO2 was 4,76 LO2/min, the extrapolated VO2max goes up to 6,08 LO2/min, corresponding to 84,55 m102/Kg X min. Particularly interesting seems to be the way through which the high VO2 levels can be obtained in these subjects: small increment of the mean arterial blood pressure together with large oxygen extraction and high vasodilatation.

Adult↗
PubMed1982

[Dynamics of respiratory function during muscular exertion: a study in a group of international-level road cyclists].

The behaviour of some respiratory parameters have been studied in a group of road-cyclists with high standard of competitive performance. The results obtained have shown that the respiratory pattern seems to be marked to a great efficiency in the alveolo-capillary gas exchange. High levels of pulmonary ventilation are obtained through low respiratory rate and high tidal volumes. This determines a more pronounced increase in the alveolar ventilation and a better ratio VA/VE during muscular effort. It seems interesting the behaviour of the pulmonary oxygen extraction (FIO2-FEO2); this parameter in fact reach its maximal level already at the low levels of load imposed.

Adult↗
PubMed1980

[Modifications of some cardiorespiratory parameters under a controlled work-load in a group of football players, winners of Italian championship football].

The modifications of some cardiorespiratory and metabolic parameters in 18 football players under controlled work-load has been investigated. The results obtained show that by increasing work-load VO2, HR, VE, RR, TV and VA also linearly increase; FiO2-FeO2 steeply increases at he reduced work-load (50 Watt) while at the higher loads (from 100 to 200 Watt) grows with less steep slope. The oxygen consumption evaluated at 200 Watt shows a figure of 50 ml O2/min/Kg, whereas the maxim calculated VO2 goes up to 75,56 ml/min/Kg body weight.

Adult↗
PubMed1980

Time course and duration of the depressant effect of active shortening in cardiac muscle.

Shortening deactivation is studied in isolated preparations of rat cardiac muscle by comparing tension redevelopment in partially fused isometric contractions with quick releases of different extent ("control" and "test" displacements). The active shortening takes place during the ascending phase of the 1st contraction of the couple and the comparison of redeveloped tension is carried out at the peaks of both 1st and 2nd contractions. The depressant effect of active shortening can be demonstrated at the 1st peak and also at the 2nd one, after the restimulation of the muscle. This effect slowly decreases with time and disappears within approximately one second after active shortening took place. By keeping constant the control shortening and changing the test shortening, a clear dependence of depressant effect on the amount of displacement can be shown in the 1st and in the 2nd contraction.

Animals↗
PubMed1980

The variation in tension output with active shortening in rat myocardium.

The effect of active shortening on tension development has been studied in rat papillary muscle preparations at 20 degrees C. Total tension at the peak of a contraction with a shortening phase is reduced below the value predicted by the isometric length-tension relationship. At the same instantaneous length, total tension is less in contractions with an isotonic phase than in isometric responses and the amount of the tension deficit increases with the extent of shortening. The influence of the time at which shortening takes place, on the amount of tension deficit, has been explored. The increase in [Ca2+]o does not affect the tension deficit. Conversely an increase in [Ca2+]o associated to addition of caffeine to the bathing solution almost abolished the effect of active shortening on tension development. Several possible explanations of the reduction of tension development by shortening are discussed.

Animals↗
PubMed1979

[Visco-elastic characteristics of the rat aorta].

In order to estimate wave propagation "in vitro", aortic compliance has been studied by means of rings and stripes from 6 adult male Wistar rats. Lengthening and shortening maneuvres have been performed; the pulse transmission rate was evaluated by calculating the elastic modulus during the maneuvres. A Norepinephrine infusion has been done. Results obtained show that transmission rate is higher in shortening than in lengthening phases. Norepinephrine did not significantly affect the values. The rate values were not greatly different whether "in vitro" or "in vivo". By increasing specimen stress, the rate too was increased, but the amount was lower than "in vivo" values. Hence it was assumable that rate variations "in vivo", should be partially influenced by elastic modulus, and a vegetative intervention should be implied.

Animals↗