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Biomedical subjects

F Rengo

Publications and source records attributed to F Rengo.

At least 235 records · Page 13Linked to original sources
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

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↗
PubMed1976

[Participation of the beta-receptor system in the genesis of the carotid aortic baroreceptor reflex in the dog (author's transl)].

The effects of propranolol, given by close arterial injection, on the reflex vasodilatation induced in the atropinized isolated gracilis muscle by rapid i.v. administration of norepinephrine were studied in dogs. The integrated areas of vasodilatation were significantly reduced after treatment with propranolol. Thus the conclusion was that adrenergic beta-receptors participate in the reflex vasodilatation, although how they act needs further elucidation.

Animals↗
PubMed1975

Studies on the nature of the vasodilator fibers running in the lumbar sympathetic chain of the dog.

These experiments were performed to further elucidate the nature of the vasodilator fibers running in the sympathetic chain in the dog. The electrostimulation of the lumbar sympathetic trunk caused vasoconstriction in the perfused hind limb which inverted to vasodilatation after guanethidine was administered. This vasodilator response is mediated by cholinergic fibers since it was completely abolished by atropine. The observation, furthermore, that hexamethonium completely nullified both vasodilator and vasoconstrictor responses to the electrostimulation of the sympathetic chain indicates that both vasoconstrictor and vasodilator fibers, which are activated during the stimulation of the sympathetic chain, are preganglionic in nature.

Animals↗
PubMed1975

Studies on the hemodynamic changes induced by electrical stimulation of the vagosympathetic trunks in the dog.

The effects of electrostimulation of the cephalic endings of the vago-sympathetic trunks on the systemic and perfusion pressure of the hind limb of the dog depend upon frequency, intensity and duration of the stimulus. The electrostimulation performed with stimuli of high frequency, low intensity and moderately long duration (rectangular waves of 1.5 V, 0.7 msec, 100 Hz) consistently elicited systemic hypertension and vasoconstriction. This response was completely abolished by pretreatment with guanethidine or hexamethonium. On the other hand, electrostimulation with stimuli of low frequency, high intensity and long duration (5 V, 1 msec, 10 Hz) produced systemic hypotension and vasodilatation in the perfused hind limb. These effects were completely blocked by atropine or hexamethonium, while guanethidine was unable to induce any modification. These findings suggest that electrostimulation of vagosympathetic trunks can evoke different hemodynamic responses depending upon the characteristics of the stimulus. The occurrence of a vasodilatation specifically blocked by atropine demonstrates that a purely cholinergic mechanism underlies such a reflex response.

Animals↗