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Biomedical subjects

F R Calaresu

Publications and source records attributed to F R Calaresu.

At least 109 records · Page 6Linked to original sources
PubMed1976

Haemodynamic responses and renin release during stimulation of afferent renal nerves in the cat.

1. Experiments were done on anaesthetized cats to study the effect of electrical stimulation of afferent renal nerves on the circulatory system and on the release of renin from the kidney. 2. Stimulation of afferent renal nerves over a wide range of parameters consistently elicited an increase in arterial pressure and heart rate. This response was still present in paralysed animals and was not accompanied by changes in respiration or in sympathetic autonomic activity usually associated with painful stimulation. Mesenteric and iliac vasoconstriction was observed concomitantly with the increase in arterial pressure. 3. Release of renin from the contralateral innervated kidney was not significantly changed by stimulation of afferent renal nerves. 4. The existence of renal vascular mechanoreceptors was investigated by altering renal circulation. Stenosis of the renal artery or a marked reduction in renal perfusion pressure elicited an increase in arterial pressure while stenosis of the renal vein elicited a decrease in arterial pressure. These responses, however, were not affected by denervation of the kidney and were therefore interpreted as not being due to neural mechanisms. 5. The precise nature, location and physiological role of renal receptors involved in the cardiovascular responses observed during electrical stimulation of afferent renal nerves remain to be determined.

Animals↗
PubMed1976

Identification of pathways mediating cardiovascular responses elicited by stimulation of the septum in the rat.

1. Experiments were done in rats anaesthetized with sodium pentobarbitone to localize pathways mediating the cardiovascular responses elicited by electrical stimulation of the septum. The major efferent projections from the septum were first identified anatomically by the Fink-Heimer II technique and these pathways were subsequently lesioned in acute experiments to establish their role in the mediation of the cardiovascular responses elicited by septal stimulation. 2. Electrical stimulation of histologically localized sites in the lateral septum elicited hypotension and bradycardia whereas stimulation of sites in the medial septum elicited hypertension and bradycardia. 3. Selective lesions of cardiovascular responsive sites in either the lateral or medial septum produced a pattern of degeneration essentially similar to that of previous anatomical studies, i.e. the main efferent projections were localized to the fornix, stria medullaris and the medial forebrain bundle. 4. Stimulation of the fornix did not elicit cardiovascular changes and lesions of this pathway did not alter cardiovascular responses to septal stimulation. 5. Stimulation of the stria medullaris elicited hypotension and bradycardia whereas stimulation of the medial forebrain bundle elicited hypertension and bradycardia. Ipsilateral lesions of the stria medullaris, signicicantly attenuated the hypotension and bradycardia elicited by stimulation of the lateral septum but did not affect the responses to stimulation of the medial septum. Bilateral lesions of the medial forebrain bundle in the region of the lateral hypothalamus abolished the hypertension but did not affect the bradycardia elicited by medial septum stimulation. Cardiovascular, reponses elicited by stimulation of the lateral septum were not affected by medial forebrain bundle lesions. 6. It is suggested that the cardiovascular responses elicited by stimulation of the lateral septum are mediated via the stria medullaris and that the hypertension elicited by stimulation of the medial septum is mediated via the medial forebrain bundle. On the other hand, the bradycardia elicited by stimulation of the medial septum is probably mediated by a pathway presently unknown.

Animals↗
PubMed1975

Projections from the nucleus and tractus solitarius in the cat.

After lesions in the nucleus of the tractus solitarius (NTS) in cats and kittens, the termination of degenerating fibers was localized using the Nauta and the Fink-Heimer techniques. The distribution of degenerating fibers was compared with that seen after lesions of the dorsal nucleus of the vagus (DNV) and after section of the ninth and tenth cranial nerves. The projection from the NTS is to the nucleus ambiguus (A), the other divisions of the NTS including the medial NTS and the ventrolateral NTS, and DNV, the medial reticular formation ventral to the NTS (probably the paramedian reticular nucleus), the nucleus intercalatus (INC), and the intermediate nucleus (INT). The probable functional significance of projections from the NTS to these medullary nuclei is discussed in relation to pathways of cardiovascular reflexes. Of particular note is the projection to the INT which may be part of a descending pathway to spinal cardiovascular neurons in the intermediolateral horn.

Age Factors↗
PubMed1975

Spectral analysis as a diagnostic aid in the management of high-risk pregnancy.

Spectral analysis of the fetal heart rate and intrauterine pressure was done with data obtained during labor for 24 patients delivered of their infants in an obstetric intensive care unit. The patients were grouped according to clinical assessment of labor and neonatal outcome as normal (11), abnormal/premature (4), and prolonged labor/cesarean section (9). A comparison among groups of spectral density functions and of coherence functions and phase angles failed to reveal consistent features that could be used to distinguish between groups. However, an analysis of the variance (integrated spectrum) and the mean of the base-line component of the fetal heart rate showed that the values for the normal and abnormal/premature groups could be distinguished from the background population. It is suggested that a study of the joint statistics of the variance and the mean may lead to the development of a diagnostic aid to the early detection of incipient fetal distress.

Analysis of Variance↗
PubMed1975

Central neural regulation of heart and blood vessels in mammals.

The study of the central regulation of the circulation in the past has been directed primarily at observing reflex responses to stimulation of peripheral receptors and at producing changes in cardiovascular parameters during electrical stimulation of central sites. These studies have demonstrated that the nervous system can regulate the circulation to different vascular beds with a high degree of specificity and that it has the ability to provide a range of coordinated responses which are appropriate to the metabolic needs of a particular behavioural pattern. In addition, it has become firmly established that the nervous system is capable of coupling cardiovascular changes with other autonomic and somatic activities to produce an integrated response. In the last decade it has become apparent that although the mode of operation of central cardiovascular regulation has been described in general terms, very little is known about the accurate anatomical localization of neuronal circuits and pathways and of impulse traffic corresponding to the changes in cardiovascular parameters that have been observed. This essay reviews recent information on discrete neuronal circuits and pathways and their mode of operation in electrophysiological terms. One of the most serious difficulties in this endeavour is the problem of demonstrating specificity of pathways and circuits because patterns of firing of afferent and efferent peripheral nerves can be usually identified, but the demonstration of specificity of central structures is a conceptual and technical challenge to the most skilled investigator. Several studies have been made in the last decade in an attempt to trace anatomically and functionally pathways involved in central cardiovascular regulation. Progress has been made especially with regard to the precise sites of termination of cardiovascular afferent fibres and the pattern of discharge of efferent cardiovascular neurons; some work has also been done to trace discrete pathways between the hypothalamus and the medulla and the medulla and the spinal cord. However, in view of the difficulties of establishing the specificity of cardiovascular pathways, progress will depend on the acquisition of a wiring diagram of simple cardiovascular reflex arcs before attempts are made to study the functional interactions of regions in the brain that have been traditionally associated with central regulation of the circulation. Future experiments should concentrate less on the demonstration of cardiovascular responses to stimulation or lesions in the central nervous system and more on the connections of discrete regions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1975

Influence of cardiac neural inputs on rhythmic variations of heart period in the cat.

Spectral analysis was used to investigate variations of heart period in 13 decerebrate cats under different conditions of neural input to the heart. Spectral density plots in intact animals showed three well-defined peaks: P1 (1.5-2.5 cycles/min), P2 (6-10 cycles/min), and P2 (respiratory frequency). In the presence of sympathetic input only the amplitudes of all peaks were decreased; when only vagal input was present the amplitudes of P1 and P2 were increased and there was no change in P3; when neither sympathetic nor vagal input was present the amplitudes of all peaks were decreased. In addition, the amplitudes of P1 and P2 were increased and there was no change in P3; when neither sympathetic nor vagal input was present the amplitudes of all peaks were decreased. In addition, the amplitudes of P1 and P2 were found to be significantly correlated with the mean heart period under the condition of vagal control only. It is concluded that P3 is related to sinus arrhythmia and that P1 and P2 may be related to spontaneous rhythms that are an intrinsic feature of the dynamic regulation of heart period by the vagus system. Sympathetic activity plays no role in the genesis of these rhythms.

Analysis of Variance↗
PubMed1975

Pathway mediating hypotension elicited by stimulation of the amygdala in the rat.

Cardiovascular responses were elicited from 372 histologically verified sites in the amygdala and closely adjacent structures in 82 rats under urethan or chloralose anesthesia. Arterial hypotension was elicited at low current intensities from the medial, central, lateral, and basal nuclei of rats under either anesthetic; the hypotension was still elicited in artificially respired paralyzed rats. Stimulation of the cortical nucleus produced variable changes in arterial pressure. The hypotension elicited under urethan was not found to be correlated with changes in the frequency of electrical activity of hippocampus, amygdala, or septum or to be associated with electrical seizures. Hypertension was usually elicited from the medial nucleus at high current intensities and was attributed to current spread to the cortex ventral to the medial nucleus from which hypertension was elicited at low current intensities. Stimulation of the central, basal, and lateral nuclei under chloralose elicited bradycardia. Lesions of the stria terminalis had no effect on the hypotension, whereas lesions of the ipsilateral medial forebrain bundle abolished this response.

Amygdala↗