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Biomedical subjects

A Stella

Publications and source records attributed to A Stella.

At least 145 records · Page 8Linked to original sources
PubMed1987

Sympatho-renal interactions.

The renal nerves appear to be involved in the control of cardiovascular homeostasis and volume balance both in physiological and in pathological conditions such as experimental hypertension. Anatomical and electrophysiological evidence suggests that the kidney has a diffuse sensory innervation connected with areas in the brain and spinal cord that are known to regulate cardiovascular functions by both neural and humoral mechanisms. The demonstration of the existence of neural reno-renal reflexes controlling several renal functions indicates that a functional balance between the two kidneys exists and may play an important role in the moment-to-moment control of kidney functions.

Animals↗
PubMed1987

Renal reflexes in the regulation of blood pressure and sodium excretion.

The rich innervation of the kidney is distributed to all structures of renal parenchyma thus providing important anatomical support to the functional evidence that the renal nerves can control kidney functions and send signals on the kidney environment to the central nervous system. Efferent renal nerve fibres are known to influence renal haemodynamics by modifying arteriolar vascular tone, renin release by a direct action on juxtaglomerular cells, and the excretion of sodium and water by changing tubular reabsorption of sodium and water at the different tubular levels. Mechano- and chemo-receptors have been shown in the kidney. Afferent fibres connected with renal receptors convey signals to the central nervous system both at spinal and supraspinal levels. The central areas receiving inputs from the kidney are those involved in the control of cardiovascular homeostasis and fluid balance. Activation of renal receptors by the electrical stimulation of renal afferent fibres were found to elicit both excitatory and inhibitory sympathetic responses. Although the existence of excitatory renorenal reflexes has been suggested, electrophysiological and functional data demonstrate that neural renorenal reflexes exert a tonic inhibitory influence on the tubular sodium and water reabsorption and on the secretion of renin from the juxtaglomerular cells.

Afferent Pathways↗
PubMed1987

Neural, hemodynamic, and renal responses to stimulation of intestinal receptors.

Stimulation of visceral receptors with bradykinin has been shown to cause reflex increases in sympathetic nerve activity and systemic arterial pressure. In this investigation, serosal receptors of the intestine were stimulated by bradykinin in anesthetized cats to 1) compare mesenteric and renal sympathetic responses, 2) compare hemodynamic responses in mesenteric and renal beds, and 3) determine changes in renal function. This stimulation in intact animals caused pressor responses, significantly greater excitation of mesenteric than renal nerves, significantly greater mesenteric than renal vasoconstriction, diuresis, natriuresis, and, in denervated kidneys, increases in fractional sodium excretion. In vagotomized, sinoaortic-denervated cats, stimulation of intestinal receptors caused excitation of mesenteric nerve activity greater than renal for only 30 s. This sympathetic reflex response led to pressor responses, equal mesenteric and renal vasoconstriction, diuresis, natriuresis, and increased fractional excretion of sodium only in denervated kidneys. When abdominal perfusion pressure was held constant with an aortic snare in these same animals, the sympathetic reflexes initially caused greater mesenteric than renal vasoconstriction and antidiuresis and antinatriuresis only in innervated kidneys. These findings demonstrate that the intensity of hemodynamic and renal responses to stimulation of visceral receptors correlates well with the magnitude of sympathetic nerve responses.

Animals↗
PubMed1987

Cardiovascular effects of afferent renal nerve stimulation.

Electrical stimulation of afferent renal nerves elicits an increase in arterial pressure and heart rate. The hypertensive response is presumably due to the widespread activation of the sympathetic nervous system leading to peripheral vasoconstriction. Interestingly, the kidney does not appear involved in this reflex excitatory response to afferent renal nerve stimulation since changes in vascular conductances and excretory functions are equal in both the innervated and denervated kidney, and secondary to changes in renal perfusion pressure. In addition, no changes in renin release from either kidneys are observed during afferent renal nerve stimulation. It is likely that the electrical stimulation of afferent renal nerves activates other reflexes exerting an inhibitory influence on efferent renal nerve activity. Indeed, neural renorenal reflexes which tonically inhibit renal functions have clearly been demonstrated. Furthermore, preferential inhibition of efferent renal nerve activity by cardiopulmonary and sinoaortic receptors has recently been shown during activation of other visceral afferents.

Afferent Pathways↗
PubMed1987

Complications following the treatment of abdominal aortic aneurysms.

The complications following the surgical treatment of 328 cases of abdominal aortic aneurysm are reported. In some cases such complications are predictable and their knowledge is useful to reduce the operative mortality. Cardiac and renal complications were more frequent in emergency, while surgical complications were mostly observed in patients with large aneurysms involving the iliac arteries. Duodenal lesions were caused in patients affected by inflammatory aneurysms. The late complications observed were: ureteral stenosis, infections, pseudoaneurysms and occlusion of a branch of the bifurcated graft.

Acute Kidney Injury↗
PubMed1987

Afferent pathways of neural reno-renal reflexes controlling sodium and water excretion in the cat.

We have studied the role of afferent renal nerve fibres in anaesthetized cats in mediating the decrease in sodium and water excretion from the contralateral kidney caused by unilateral renal denervation. Transient denervation of one kidney obtained by cooling of the left renal nerves increases contralateral efferent renal nerve activity and decreased sodium and water excretion from the opposite kidney. The results observed in animals with intact neural pathways were compared with those obtained after the left kidney had been selectively deafferentated by cutting the dorsal roots from T9 to L4. Bilateral section of dorsal roots did not affect the increase in sodium and water excretion from the transiently denervated left kidney, but entirely abolished the decrease in sodium and water excretion from the contralateral kidney. Neither the left nor the right dorsal root section alone, affected the response of the contralateral right kidney. Our data demonstrate that afferent renal nerve fibres project bilaterally to the spinal cord and form the afferent branch of the reno-renal reflex by which one kidney can control the function of the opposite one.

Afferent Pathways↗
PubMed1986

Effects of reversible renal denervation on haemodynamic and excretory functions of the ipsilateral and contralateral kidney in the cat.

In anaesthetized cats reversible denervation of one kidney was performed by cooling of the left renal nerves to 3 degrees C for 16 min. The response of the left (ipsilateral) kidney was compared with the response of the right (contralateral) kidney twice in the same animal: (1) when the right kidney was still innervated, and (2) after it had been surgically denervated. Left renal nerve cooling did not cause any changes in arterial pressure. In the left kidney, blood flow, vascular conductance, sodium and water excretions increased, and renin release decreased. Simultaneously in the contralateral kidney, no haemodynamic changes were observed, glomerular filtration was only transiently decreased, whereas sodium and water excretion significantly decreased and renin release increased. When left renal nerve cooling was repeated after surgical denervation of the right kidney, similar changes were observed in the left (ipsilateral) kidney, whereas all contralateral effects were abolished. These experiments suggest that tonically active afferent fibres from one kidney exert a reflex inhibitory action on sympathetic activity directed to the contralateral kidney controlling tubular sodium reabsorption and renin release.

Animals↗
PubMed1985

An anomalous vagorenal reflex pathway in the cat.

Although physiological investigations support the view that the innervation to the kidney is primarily sympathetic in origin, there is anatomic evidence suggesting direct vagal projections to the kidney. We examined electrophysiologically the possibility that neural connections exist between the cervical vagus and renal nerves. Electrical stimulation of the peripheral segment of the cut cervical vagus evoked electrical activity in the central segment of cut renal nerve of chloralose-anesthetized, paralyzed cats. The evoked potentials (vagorenal responses) displayed components with peak latencies of about 50, 120, and 500 ms. Another peak at about 175 ms was also seen in some cases. In addition, a period of postexcitatory depression occurred between approximately 180 and 400 ms after delivery of the stimulus. Evoked responses were recorded in the contralateral as well as the ipsilateral renal nerves. In contrast, stimulation of the central cut end of renal nerves did not elicit responses in the cervical vagus. Vagorenal responses were not altered by cutting the subdiaphragmatic vagus indicating that the abdominal vagus was not involved in this response. Electrical activity in renal nerves elicited by vagal stimulation could be eliminated by either ganglionic blockade or by cutting or cooling the splanchnic nerves. Finally, supraspinal ischemia abolished the vagorenal response. These data suggest that a vagorenal reflex pathway exists and that the potentials recorded in renal nerves are due to activation of aberrant sensory fibers traveling from the peripheral segment of the cut cervical vagus to the central nervous system, where they excite a sympathetic efferent pathway to the kidney.

Animals↗
PubMed1985

Adrenergic sodium handling and the natriuretic action of calcium antagonists.

Stimulation and denervation experiments have provided evidence that adrenergic mechanisms can enhance sodium and water reabsorption from the renal tubule, and that this influence is probably exerted on the entire tubular extent. Reflexes originating from cardiopulmonary and renal receptors can control adrenergic renal sodium handling, and evidence has recently been presented that a reno-renal reflex tonically inhibits the contralateral sympathetic control of tubular reabsorption of sodium and water. Other investigations indicate that adrenergic renal sodium handling is mediated through alpha-rather than beta-receptors, and that the alpha-receptors are of the alpha 1-subtype. The question of whether the natriuretic action of calcium antagonists is, at least in part, mediated by interference with adrenergic control of tubular reabsorption cannot yet be definitely answered. Although available data are only preliminary, they do not support an important action of calcium antagonists on adrenergic renal sodium handling, but a separate contribution of impaired adrenergic control and of a direct tubular effect of calcium antagonists cannot be excluded.

Adrenergic Fibers↗
PubMed1985

Interactions between the sympathetic nervous system and the kidney: experimental observations.

Increasing evidence suggests that the renal nerves may contribute to the pathogenesis of several types of experimental hypertension. It has been demonstrated that renal denervation can either attenuate the severity or delay the development of hypertension in spontaneously hypertensive rats (SHR), in DOCA-salt treated rats and in renovascular hypertensive rats. On the other hand, intrarenal administration of catecholamines has been shown to elicit an increase in systemic arterial pressure as long as the infusion is continued. The underlying mechanisms by which renal nerves might participate in the regulation of cardiovascular homeostasis have not been entirely clarified. It is known that efferent renal nerve activity, by exerting a direct influence on renal arteriolar tone, renin release and sodium and water excretion, can interfere with the control of arterial pressure by modifying peripheral resistances, circulating angiotensin II and volume balance. In addition, a role of afferent renal nerve activity in cardiovascular control and, possibly, in the pathogenesis of renovascular hypertension, has recently been proposed after the demonstration of mechano- and chemoreceptors inside the kidney. Indeed, blood pressure is reflexly influenced either by several manoeuvres applied to the kidney or by the electrical stimulation of afferent renal nerve fibres. Afferent and efferent renal nerve activity appear to be closely related since recent experiments by our group have provided further evidence of the existence of neural renorenal reflexes by which one kidney exerts a tonic inhibitory effect on the release of renin from juxtaglomerular cells and on tubular sodium and water reabsorption of the contralateral kidney.

Afferent Pathways↗
PubMed1984

A placebo-controlled trial of thymic hormone treatment of recurrent herpes simplex labialis infection in immunodeficient host: results after a 1-year follow-up.

Twenty-one immunodeficient patients with recurrent herpes simplex labialis (HSL) were randomly allocated to either the saline or the bovine thymus extract Thymostimulin (TS) group and treated for a period of 6 months. A total of 17 recurrences with a mean severity index of 266.2 +/- 192 in the TS-treated group versus a total of 62 recurrences in the placebo group (score 458.8 +/- 299.6) were observed after 12 months of follow-up. A significant increase of total WBC (P less than 0.05 versus control group), lymphocyte count, and T-cell number (P less than 0.001) were detected in the TS group after 6 months as well as after 12 months. In vitro lymphoproliferative responses to herpes simplex virus antigen and natural killer cell activity were also significantly higher (P less than 0.05) in the TS group, whereas no significant difference in antibody titers to herpes simplex could be detected between the two groups. TS may be potentially useful in preventing viral reactivation in immunocompromised hosts by potentiating cell-mediated immune responses. Further studies evaluating TS for prophylaxis of infection in patients at risk should be considered.

Adolescent↗