Effect of middle-intensity exercise on carnitine and beta-hydroxybutyrate plasmatic concentration in men and women.

The purpose of this study is to describe the dynamics of carnitine, its esters and beta-hydroxybutyrate, during a prolonged moderate-intensity physical exercise, as the literature data (Angelini 1986, Carlin 1986, Lennon 1984) up to date reported were not uniform. In our study twenty-two untrained subjects (11 males, 11 females) performed a test exercise on a motor-driven treadmill for 90 min at 50-60% of VO2 max. Blood samples were obtained at rest, at 20, 40, 60 and 90 min during the exercise and after 30 min of recovery. Men show an increase over rest values in short chain acyl carnitine after 90 min of exercise higher than women (M 157%, F 80%), while women have a more elevated relative increase in beta-hydroxybutyrate (M 201%, F 233%); Total carnitine in both sexes is not significantly modified.

Vagal stimulation and exogenous acetylcholine in isolated rat stomach: calcitonin effect on contractile activity.

Calcitonin induces contraction in the vascular and extravascular smooth muscle and facilitates the transmission of the excitation in somatic motor nerve endings. These actions are Ca2(+)-dependent. The calcitonin effect on autonomic nerve endings has been studied here by testing influence of calcitonin on the contractile responses of the isolated rat stomach. The organ was submitted to electrical vagal stimulation or, after denervation, to exogenous acetylcholine. Calcitonin invariably increased the muscular tone and reduced the contractile responses to vagal stimulation. Opposite effects were noted after a serotoninergic block with nicergoline. Calcitonin also increased the contractile response evoked by exogenous acetylcholine and the Ca(2)-antagonist nicardipine counteracted the facilitatory effects. We suggest that the inhibitory action of calcitonin is serotonine-dependent while the facilitatory one is Ca2(+)-dependent.

[Mechanical responses on isolated frog neuromuscular preparations in the presence of calcitonin]. / Risposte meccaniche di preparati neuromuscolari isolati di rana in presenza di calcitonina.

Previous observations had shown that, in the isolated rat preparations, calcitonin facilitates the excitement transmission from autonomic nerve-endings to smooth muscle. The present research, was designed to verify whether this facilitation effect could be present in somatic nerve-endings too. For this reason, we used the isolated frog "sciatic nerve-gastrocnemius muscle" preparation where the calcitonin influence on the beginning of a complete tetanic response was studied. The motor nerve-endings were stimulated at different frequencies. It was observed that the added calcitonin and/or an increased [Ca++] medium induced a complete tetanic response also at stimulating frequencies that, in the controls, provoked only a clonic response. Moreover, both the calcitonin and the increased [Ca++] medium frequently induced an increase in the mechanical muscle tension developed. These facilitating effects were reduced or even abolished with inhibition of Ca++-passage through the cell membrane by nifedipine. Therefore, we could hypothesize that the added calcitonin causes increased Ach-release from the somatic nerve-endings and that this action depends on facilitated Ca++-passage through the cell membrane of the nerve-endings and of the muscle fibres too.

[Contraction of the isolated stomach of the rat as a result of stimulation of postganglionic fibers in the presence of 4-methylesculetol]. / Contrazione dello stomaco isolato di ratto per stimolazione di fibre post-gangliari, in presenza di 4-metilesculetolo.

It is known that the bioflavonoids as the Ca++ have an enhancing effect on the transmitter release in different cholinergic nerve-endings. For this reason, it is seemed interesting to study the influence of the separately tested 4-methylesculetin or associated with the ascorbic acid and comparatively the Ca++ concentration increase on the isolated rat stomach response by electrical transmural stimulation achieved in presence or absence of hexamethonium. Both the 4-methylesculetin and the ascorbic acid have always increased the response of the preparation submitted to electrical transmural stimulation. The 4-methylesculetin effect resulted particularly strong if the substance was employed with the ascorbic acid. The enhancing effect of the 4-methylesculetin, obtained with or without the ascorbic acid, is resulted comparatively lesser in presence of hexamethonium. On the basis of the evident analogy between the 4-methylesculetin effects and the ones determined by the increased Ca++ concentration, it can be supposed that the bioflavonoid facilitates the transmitter release in the pre- and postganglionic nerve-endings. The results here reported, confirm other previous observations accomplished on different cholinergic nerve-endings and could substain the hypothesis according to which the 4-methylesculetin increase the Ca++ transport through the biological membranes.

[Facilitation of the onset of tetanic responses induced by 4-methylesculetol in amphibian isolated neuromuscular preparations]. / Facilitazioni sull'insorgenza delle risposte tetaniche indotte dal 4-metilesculetolo in preparati neuromuscolari isolati di anfibio.

Previous observations have shown that the 4-Methylesculetin (4ME) and the calcium provoke an increased response when the motor somatic and autonomic nerve-endings are stimolated. In the present research, we have studied the influence of the bioflavonoid and of an increased medium [Ca++] on the tetanic responses obtained from the isolated frog "sciatic nerve-gastrocnemius muscle" preparation. The 4ME has always facilitated the beginning of a complete tetanic response and has also frequently increased the developed mechanical tension. These effects appeared more evident when the bioflavonoid was employed together with the ascorbic acid. Moreover, an increased medium [Ca++] has induced similar effects. The nifedipine and the flunarizine, well-known Ca++ -antagonists, have constantly reduced or even abolished the facilitating effect induced by the bioflavonoid. On the basis of these results, we could hypothize that these observed facilitating effects are dependent on both an increased Ach-release and an increased muscle mechanical efficiency. Our previous results and also some literature data suggest that these effects could be due to an increased Ca++-passage through the cell membrane of the motor nervendings and of the muscle fibres too.

[Influence of hydrocortisone on the response to noradrenaline of segments of isolated coronary arteries in the presence of a beta-adrenergic blocking agent]. / Influenza dell'idrocortisone sulle risposte alla noradrenalina di segmenti di arterie coronarie isolate in presenza di un bloccante beta-adrenergico.

The effect of hydrocortisone on the noradrenaline-induces contraction, after propranolol, was studied in vitro. Contraction of response to noradrenaline were increased by hydrocortisone. We suggest that the hydrocortisone influence depends on inhibition of catecol-O-metiltransferase (COMT).