The aim of this review is to provide a critical and concise discussion of present knowledge on the role of atrial natriuretic factor (ANF) in physiological as well as pathological pulmonary conditions. The lung contributes only to a small extent to the production of circulating ANF; on the other hand, the lung represents the major degrading site of the protein. Plasmatic ANF concentration increment during lung disease may therefore be due to a reduction in ANF plasma removal enzyme rather than to increased ANF production. Lung tissue shows more ANF receptor sites than any other organ. The effect of ANF on bronchial and pulmonary artery muscle lining is particularly evident. In fact ANF administration in asthmatic patients leads to bronchodilation comparable to dilation induced by salbutamol. Furthermore, elevated levels of circulating ANF seem to influence fluid redistribution through alveolar-capillary membrane leading to protein mobilization through the alveolar space. On the contrary, in the cardiomyopathic hamster ANF induces relevant guanylate cyclase activation before the animal has developed hemodynamic changes. Guanylate-cyclase activation may protect the lung through counteracting pulmonary edema formation, as shown by fluid reduction in alveolar spaces following pneumotoxic agents administration. This effect seems independent of natriuretic and hypotensive ANF effects.

Animals↗

PubMedDate not supplied

Cardiorespiratory effects evoked by electrical stimulation of somatic afferent fibers.

Several neurophysiological studies have shown that electrical activation of afferent fibers of somatic nerves can evoke inhibitory or excitatory cardiovascular responses. The present investigation was undertaken to examine the effects induced by electrical stimulation of somatic nerves on cardiocirculatory and respiratory functions in anesthetized rabbits. Both low frequency stimulation and high frequency stimulation of afferent fibers of somatic nerves caused two distinct patterns of cardiocirculatory and respiratory reflex responses absolutely similar to those observed in our previous experiments on rabbits with dynamic and static exercise. The present findings do not support the existence in the somatic nerves of afferent fibers with cardiorespiratory effect having physiological functions different from that of producing cardiopulmonary adjustments to muscular activity.

Afferent Pathways↗

PubMedDate not supplied

[Biology and space medicine. New prospects for internal medicine].

Most of the functional problems astronauts may suffer during and after long-term space missions are mainly associated with the reduction of the gravity force which causes a central fluid shift and a redistribution of the blood flow. Blood volume centralization induces a rapid increase in diuresis with elimination of consistent amounts of water and electrolytes which leads to a reduction of cardiac output, body fluid and to a hypodynamic state of the cardiovascular system. The effects of micro-gravity on skeletal and muscular systems are quite severe causing rapid bone demineralization, especially in the spine and lower extremities, and hypotrophy of the muscular masses. Micro-g also appears to determine cellular and molecular modifications with inhibition of the immune system, hematopoiesis and resistance to infections. Orthostatic intolerance, with feeling sick, instability and sometimes syncope, is characteristically observed after the return to earth due to a remarkable fluid shift in the lower part of the body and an acute reduction in blood flow to the brain. Physical exercise may play an important role among the countermeasures proposed to reduce most of the cardiovascular and musculo-skeletal effects of micro-g. Furthermore, micro-g offers many interesting prospects for the development of new technologies for the synthesis of biologically active substances for pharmacological use. Further severe limiting factors, for more prolonged manned space missions, are the so called "human factors" including psycho-emotional and social behaviour, especially regarding the future of astronauts after their return to earth.

Aerospace Medicine↗

PubMedDate not supplied

[Cardiovascular and respiratory reflex responses due to stimulation of muscle nerve receptors and experimental physical exercise].

The cardiovascular and respiratory reflex effects brought on by the infection into the femoral artery of bradyquinine and of hypertonic sodium chloride solutions and by rhythmic muscular work and muscular work of tetanic type induced by low and high frequency electrostimulation in the muscles have been investigated in the rear extremity anaesthetized rabbits. Intra-arterial injection of bradyquinine and rhythmic muscular contractions trigger off cardiovascular reflux effects of inhibitory type represented by a reduction in arterial pressure, heart frequency and vascular resistances of the rear extremity controlateral to the one stimulated. Intra-arterial injection of hypertonic NaCl and tetanic contractions cause opposite effects, namely of decidedly excitatory type. Such responses are not substantially altered by complete removal of the skin layer of the stimulated extremity. The neuromuscular block obtained with curare-like substances does not affect chemical stimulation responses, whereas it eliminates similar effects caused by experimental muscular work. The experiments carried out show that injection into the muscular arteries of chemical agents of various type produces varying cardiovascular reflex effects as a result of activation of chemosensitive nervous receptors located in the muscular tissue, and also that during physical exercise similar reflex modifications are produced, very probably caused by stimulation of receptors present in the contracting muscles.

Animals↗

PubMedDate not supplied

[Observations on the course of acute viral hepatitis in a group of cases treated with bioflavonoids].

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Adolescent↗