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Biomedical subjects

G Raimondi

Publications and source records attributed to G Raimondi.

At least 55 records · Page 3Linked to original sources
PubMed1990

[Integrated cardiorespiratory changes induced by chemical stimulation of muscular receptors].

Muscular exercise is accompanied by evident and perfectly matched cardiovascular and respiratory adjustments to avoid changes in arterial blood gases. The mechanisms responsible for this perfect regulation have not yet been defined. Our previous experimental investigations have shown that a consistent rate of cardiorespiratory reflex responses to exercise is caused by chemosensitive muscular receptors activation. The 2 different types of classical muscular exercise (rhythmic and isometric exercise) are joined with the 2 different patterns of cardiorespiratory reflex responses attributed in our opinion to the activation of 2 different kinds of muscle receptors (K and P). It has been observed that the increase in ventilation (VE), elicited by activation of both types of chemoreceptors during muscular experimental exercise is not accompanied by significant variations of partial pressure of CO2 (PaCO2) in the arterial blood (isocapnic hyperpnea). This suggest that muscular chemoreceptor activation during physical exercise determines an adequate cardiopulmonary matching. The main purpose of the present study has been to verify, in anesthetized rabbits, if also the chemical activation of muscular receptors was able to evoke reflexly an adequate degree of cardiopulmonary matching. The ventilation reflex changes and the concomitant variations of PaCO2 induced by injection of bradikinin (BK 250 ng) and hypertonic solutions (NaCl 10% 1 ml) in femoral artery have been evaluated in 10 anesthetized rabbits. The PaCO2 modifications observed during reflex hyperpnea have been compared with those recorded during hyperpnea induced by artificial ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1989

[Study of the interactions of atrial natriuretic peptides with the autonomic nervous system. Effects on cardiocirculatory and respiratory reflexes caused by activation of chemosensitive muscle receptors].

In order to verify the hypothesis that possible interactions with the autonomic nervous system may contribute to the cardiovascular effects of atrial natriuretic factor (ANF), 9 rabbits were anesthetized to study the effect of the infusion of synthetic human ANP (2 mcg/kg in bolus followed by 0.2 mcg/kg/min for 20 min iv) on the reflex responses induced by intra-arterially injected BK (250 ng) and hypertonic NaCl (10%) or glucose (40%). The infusion of ANP provoked a decrease in systolic (SBP, 14%) and diastolic (DBP, 8%) pressure without any significant changes in heart rate (HR). The injection of BK and hypertonic NaCl into femoral arteries carried out during ANP infusion produced cardiorespiratory response patterns similar to those observed in control conditions. After injecting BK, a fall in SBP (25%), DBP (50%) and HR (16%), and an increase in breathing frequency were observed. After injecting NaCl, an increase occurred in SBP (20%), DBP (25%), HR (10%) and in depth of breathing. In the present experimental conditions, ANP has not been found to be capable of significantly interfering with the reflex pattern of cardiorespiratory responses either from the inhibition or activation of the sympathetic nervous system induced by chemical stimulation of muscle receptors.

Animals↗
PubMed1989

[Cardiocirculatory and respiratory reflexes of muscular origin during prolonged experimental dynamic exercise. Effects of sectioning of the sino-carotid and aortic nerves and bilateral vagotomy].

In anesthetized rabbits we have evaluated the effects of denervation of sino-aortic areas and vagotomy on the reflex cardiorespiratory responses during 2 min of contractions of gastrocnemius muscle induced by electrical stimulation of tibial nerve. The following parameters were examined: blood pressure (BP), heart rate (HR), respiratory frequency (f), tidal volume (Vt) and pulmonary ventilation (Ve) while arterial pH, pCO2 and pO2 and end-tidal CO2 (petCO2) were monitored. During steady state of rhythmic contractions we observed a decrease of BP, a slight decrease in HR and marked rise of Ve due to an increase of f with a slight increase of Vt. The sectioning of carotid-sinus, aortic and vagus nerves does not substantially modify the cardiorespiratory responses to muscular exercise; all the responses are abolished from the sectioning of somatic nerves in exercising limbs. The importance of the role of the peripheral nervous control by muscles (peripheral drive) is confirmed in the regulation of cardiorespiratory participation in motory activity, also in the steady state phase of muscular exercise in which components of a chemometabolic or hemodynamic nature could be more effective.

Animals↗
PubMed1987

[Early angio-computer tomography of ruptured cerebral aneurysms in subarachnoid hemorrhage].

In acute subarachnoid hemorrhage a ruptured cerebral aneurysm can be detected by Computed Angiotomography (Angio-CT). In a hyperdense cistern by extravasal blood, a round low-density defect on plain CT which turns into high-density nodular mass with afferent and efferent arteries, is an important finding of ruptured aneurysm. The inverting-density cisternal defect in connection with cerebral arteries is essential for the direct and early Angio-CT diagnosis of ruptured aneurysm.

Adult↗
PubMed1985

Cardiorespiratory reflexes from muscles during dynamic and static exercise in the dog.

Cardiorespiratory reflex responses during the initial phase of dynamic and static contraction of hindlimb muscles were studied in anesthetized dogs. Muscle contractions were elicited by stimulating the femoral and gastrocnemius nerves at 3 and 100 Hz with the intensity of 2.0-2.5 times the motor threshold for a 20-s period. Rhythmic contractions caused a decrease in arterial pressure (Pa) and heart rate (HR) and increased pulmonary ventilation (VE) by increasing frequency (f) without significantly changing VT. Tetanic contractions provoked an increase in Pa and HR and a hyperpnea resulting from a rise in both f and VT. Similar responses were also obtained in anesthetized dogs with carotid sinuses denervated and cervical vagi cut. The abrupt increase in VE at the start of both types of exercise was not associated with immediate significant decreases in end-tidal CO2 values. These two patterns of cardiocirculatory and respiratory responses were closely similar to those reported in anesthetized rabbits in previous studies. Both patterns of responses were reflexes initiated by activation of muscle receptors verified by interrupting the afferents from the contracting muscles. It is concluded that, during dynamic and static work, two distinct muscular reflex mechanisms might exert their drives, related to the muscular metabolic rate, on the circulatory and respiratory function.

Animals↗
PubMed1983

Different patterns of respiratory reflexes originating in exercising muscle.

In anesthetized rabbits, rhythmic contractions of the gastrocnemius muscle elicited by stimulating the gastrocnemius nerves (40 trains/min of 0.5-ms rectangular pulses at 2.0-2.5 mult of motor threshold), increased pulmonary ventilation by increasing frequency (f). Expiratory duration (TE) was greatly reduced, while inspiratory time (TI) was much less changed. Mean expiratory flow (VT/TE) was increased consistently more than mean inspiratory flow (VT/TI). Arterial pressure (Pa) and heart rate (HR) were decreased. During tetanic contractions (100 Hz, 2.0-2.5 X T) tidal volume (VT) increased considerably more and f considerably less than during rhythmic exercise, TE was shortened, and TI was only slightly affected. Pa and HR, after a transitory reduction, increased over the resting levels. Similar responses were also obtained in deafferented rabbits with carotid sinus, aortic, and cervical vagus nerves cut. These two patterns of cardiorespiratory changes were initiated by activation of muscle receptors verified by interrupting the afferents from the contracting muscles. It is concluded that, in the anesthetized rabbit, two different muscular reflex mechanisms are involved in controlling the pattern of breathing and ventilation during muscular exercise. One mechanism, predominantly activated during dynamic exercise, decreases TE and increases f, the other mechanism, mainly activated during static exercise, increases the inspiratory drive, thus increasing the depth of breathing.

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