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Biomedical subjects

M Condorelli

Publications and source records attributed to M Condorelli.

At least 325 records · Page 18Linked to original sources
PubMed1978

[Programmed electrical stimulation in the treatment of reciprocating arrhythmias. Use of radiofrequency as a stimulating and synchronising means (author's transl)].

A new model of radiofrequency stimulator is presented, which can be programmed for the transmission of one or two impulses synchronised and delayed on the endocardial electrogram. This pacemaker was successfully used in jounctional reciprocating tachycardias and in a case of recurrent ventricular tachycardia. The implanted device, connected to the electrode catheter in right ventricle, does not contain energy sources. This lets a little size and allows having outside the body all the program controls, which in the time can have to change, due to variations of the parameters of tachycardias interruption. The implanted receiver is designed to induce in the resonant coil of external transmitter a frequency modulation proportional to the endocavitary signal. A slope detector receives this signal and programs on them the stimulating impulses, transmitted to stop the tachycardia. It is possible to manufacture such a simple device that the same patient can use it. Of course, periodic controls on the patient must be made to assess the cause of the tachycardia.

Cardiac Pacing, Artificial↗
PubMed1977

Effects of guanethidine on histamine release during reflex vasodilatation in the dog.

1 The effects of guanethidine pretreatment on the release of [14C]-histamine during the reflex vasodilatation induced in the atropinized gracilis muscle by rapid intravenous administration of noradrenaline, were studied in dogs. 2 After guanethidine treatment the haemodynamic reflex response was completely abolished and no appreciable modification of [14C]-histamine release from the gracilis muscle following intravenous noradrenaline was observed. 3 These results suggest the hypothesis that the withdrawal of the sympathetic discharge represents the mechanism of histamine release during the reflex vasodilatation. Therefore, guanethidine would suppress both the passive and the histaminergic component of the baroreceptor reflex through the abolition of the sympathetic tone.

Animals↗
PubMed1977

Reduction of blood flow following ischemia in arteriopathic patients: reversion of the phenomenon induced by propranolol.

In most arteriopathic patients, the release of a transitory ischemia in the affected limb reduces blood flow, instead of increasing it as in normal subjects. In this study the effects of propranolol administration on this paradoxical response have been investigated. After rheographic tracings were recorded in 14 arteriopathic patients in the basal condition and in the postischemic period, 10 mg of propranolol was administered IV and the protocol was then repeated. The blood flow in the affected area, measured as Jantsch's index of the rheographic tracings, was 0.63 +/- 0.04 in the basal condition and was reduced to 0.51 +/- 0.05 (P less than 0.001) in the postischemic period. When the ischemia was repeated after propranolol administration, Jantsch's index rose from 0.57 +/- 0.04 to 0.85 +/- 0.09 (P less than 0.01). The reversion of the paradoxical response to the ischemia induced by propranolol administration suggests that the beta-adrenergic blockade can increase blood flow to the ischemic area, probably through a constrictive action on arterovenous connections.

Arteriosclerosis↗
PubMed1977

Myocardial contractility after injection of prolonged infusion of magnesium sulphate.

The effect of magnesium sulphate administration on myocardial inotropism has been evaluated by means of the noninvasive indexes of myocardium contractility in 18 patients affected by myocardiosclerosis associated with signs of cardiac impairment of different degree. Magnesium has been administered via either a prolonged infusion (30-50 mg/min) or a single injection (2.5 g/30 sec). It is emphasized that the influence of this agent on systolic time intervals (STI) is dependent upon its route of administration. Thus, prolonged infusion does not modify significantly these parameters, whereas a single injection induces marked variations, i.e., decrease of LVET, increase of PEP, ICT and PEP/LVET ratio, which are all more marked in cases of severe cardiac impairment. In view of the strict correlation established between the STI and the invasive indexes of myocardial contractility, it is suggested that administration of magnesium sulphate via prolonged infusion does not induce a decrease of cardiac performance, while a single injection of this agent leads to this effect.

Arrhythmias, Cardiac↗
PubMed1976

Theophylline stimulation of gluconeogenesis from alanine in normal and sympathectomized rats.

The influence of theophylline ethylenediamine (100 mg/kg i.p.) on gluconeogenesis was studied in normal and in adrenodemedullated and reserpinized rats after overnight fasting by measuring the time-course of Alanine-14C incorporation into Glucose-14C. In the normal rat, theophylline produced a moderate hyperglycemia associated with an increased conversion of alanine to glucose at all time intervals. In addition, a marked rise of plasma levels of insulin and glucagon was observed. In sympathetctomized rats, plasma glucose and gluconeogenesis were again enhanced by theophylline, but the pattern of these modifications differed from that of normal rats since the peak values occurred earlier. Subsequently, both parameters rapidly declined reaching values lower than controls at the end of the experiment. Insulin response to theophylline was higher in sympathectomized animals in comparison to normal rats, while glucagon response was approximately of the same magnitude in the two groups. From these findings it was concluded that theophylline is able to stimulate gluconeogenesis from alanine both in the normal and sympathectomized rat. The different pattern of alanine conversion to glucose seems to depend on the different participation of insulin and catecholamines in the two groups.

Alanine↗
PubMed1976

Hepatic erythropoietin: enhanced production in anephric rats with hyperplasia of Kupffer cells.

Erythropoietin (Ep) levels were assayed in serum of adult male rats subjected sequentially to (1) administration of colloidal carbon, Zymosan or their vehicles (2) sham operation or bilateral nephrectomy with and without subtotal hepatictomy, and (3) hypoxia (0.45-0.40 atmospheres of air for 6 h starting 1 h after the operation). In anephric rats these agents induced a significant potentiation of hypoxic Ep activity. Since they did not apparently modify the kinetics of exogenous Ep, it is postulated that this phenomenon is mediated by enhanced extrarenal Ep production. Both colloidal carbon and Zymosan induced hyperplasia of the reticuloendothelial system (RES). Moreover, subtotal hepatectomy almost abolished the Ep response to hypoxia evoked by Zymosan. The correlation between hyperplasia of hepatic RES and enhanced Ep production in anephric rats primed with these agents suggests that Kupffer cells constitute a major source for extrarenal Ep. Additionally, it is of interest that colloidal carbon and Zymosan did not significantly modify the renal production of Ep.

Animals↗
PubMed1976

The cholinergic component in the reflex vasodilatation elicited by stimulation of the depressor nerves in the rabbit.

1 The effects of the stimulation of the cephalic endings of the depressor nerve on the resistance in the perfused hindlimb were studied in the rabbit. 2 The vasodilatation thus elicited in the perfused hindlimb was reduced either by administration of guanethidine or by sympathectomy and abolished by subsequent treatment with atropine. 3 These data confirm the existence of two components in the genesis of the reflex vasodilatation: a passive component, due to the inhibition of sympathetic discharge, and an active component which in the rabbit is cholinergic in nature.

Animals↗
PubMed1976

Erythropoietin production in the rat: additive role of kidney and liver.

Erythropoietin (Ep) levels were evaluated in serum of neonate, weanling, or adult rats subjected to 1) sham operation, nephrectomy, and/or subtotal hepatectomy and 2) a standard bout of hypoxia (0.45 atm air/6 h, starting 1 h after the operation). Ep activity was quantitated by means of strictly controlled assays in exhypoxic polycythemic mice. The sum of Ep titers in the serum of nephrectomized or hepatectomized rats was compared to Ep levels in sham-operated animals of corresponding age levels, with the exception of 1-wk-old rats: it is relevance that no significant difference is apparent between these Ep production curves. Thus, evidence is presented indicating for the first time that Ep derives from two functionally distinct and additive sources, i.e., the kidney and the liver. Liver Ep, although prevalent in neonatal animals, is obscured in the weanling adult rat by both gradual initiation of massive renal Ep production and progressive decrease of hepatic Ep activity.

Age Factors↗
PubMed1976

Participation of beta receptors in reflex vasodilatation in the dog.

The effects of propranolol, given by direct intraarterial injection, on the reflex vasodilatation induced in the atropinized isolated gracilis muscle by rapid intravenous administration of norepinephrine, were studied in dogs. In these studies, both atropine and atropine plus propranolol did not significantly alter the maximum fall in vascular resistance in the perfused gracilis muscle following intravenous norepinephrine; however, if the reflex responses were evaluated as integrated areas of vasodilatation, atropine attenuated the vasodilatation and the administration of propranolol further attenuated the reflex. In fact, the value of the integrated areas of vasodilatation was 52.8 +/- 9 mmHg/min in the basal state, 39 +/- 6 mmHg/min after administration of atropine, and 24 +/- 7 mmHg/min after propranolol, whereas the integrated areas of the systemic hypertension did not show any modification. These results prompt us to conclude that the adrenergic beta receptors participate in the reflex vasodilatation, although the mechanism of their action needs further elucidation.

Animals↗
PubMed1976

[Importance of coronarographic evaluation in valvular diseases for correct surgical indication (author's transl)].

Among 100 patients who underwent cardiac catheterization for acquired valvular disease, selective coronaryangiography showed in 25 cases obstructive changes of coronary arteries, in many instances of such severity to modify the therapeutic program (myocardial revascularization associated with valvular repair, counter-indication to surgical therapy). Coronary artery alterations were discovered in patients without clinical and electrocardiographic signs of coronary insufficiency, and, on the contrary, normal coronary tree was found in patients with positive clinical and electrocardiographic findings. The importance of coronarography in the haemodynamic study of valvular patients is stressed, even in absence of evident clinical signs of coronary insufficiency. The preoperative evaluation of the coronary arteries is fundamental for a correct surgical indication and for the results of surgical therapy.

Coronary Angiography↗
PubMed1976

[The participation of the cholinergic system in the genesis of the reflex vasodilatation in the gracilis muscle of the dog (author's transl)].

These experiments were undertaken to demonstrate the participation of the cholinergic system in the reflex vasodilatation in the gracilis muscle of the dog evoked by rapid i.v. injection of norepinephrine. The analysis of the integrated areas of vasodilatation curves after pretreatment with atropine showed a significant decrease of the reflex vasodilatation suggesting the participation of the cholinergic system to the mechanism underlying the phenomenon. The residue vasodilatation was completely abolished by the subsequent i.a. administration of phentolamine. On the other hand, guanethidine too could, also without pretreatment with atropine, nullify the reflex vasodilatation. This effect, therefore, does not permit the ruling out of the existence of a cholinergic component in the reflex vasodilatation since the actions of these drugs are not yet completely known.

Animals↗