Closed-loop baroreflex model with biophysically detailed afferent pathway.

In this work, we couple a lumped-parameter closed-loop model of the cardiovascular system with a physiologically-detailed mathematical description of the baroreflex afferent pathway. The model features a classical Hodgkin-Huxley current-type model for the baroreflex afferent limb (primary neuron) and for the second-order neuron in the central nervous system. The pulsatile arterial wall distension triggers a frequency-modulated sequence of action potentials at the afferent neuron.

Heart rate variability for small animal veterinarians - A concise debate.

This manuscript aims to provide a simple and concise discussion on heart rate variability (HRV) for small animal veterinarians. Despite the fact that heart rate variability analysis techniques have been used for quite a long time in medical sciences, it seems to be not completely understood by a large fraction of veterinarian professionals, thereby, reducing the possible benefits to patients that could arise from such information. The analysis of the R-R intervals enables the veterinarian to evaluate autonomic sympathetic and parasympathetic modulation of the heart, composing the so-called cardiac autonomic balance.

Integrated cardiorespiratory system model with short timescale control mechanisms.

A compartmental model of the cardiorespiratory system featuring pulsatile blood flow and gas transport, as well as closed loop mechanisms of cardiorespiratory regulation is presented. Short timescale regulatory action includes baroreflex, peripheral and central chemoreflex feedback. The cardiorespiratory model is composed by compartments to describe blood flow and gas exchange in the major systemic and pulmonic regions.

An integrated mathematical model of the cardiovascular and respiratory systems.

This study presents a lumped model for the human cardiorespiratory system. Specifically, we incorporate a sophisticated gas dissociation and transport system to a fully integrated cardiovascular and pulmonary model. The model provides physiologically consistent predictions in terms of hemodynamic variables such as pressure, flow rate, gas partial pressures, and pH.

Malnutrition alters the cardiovascular responses induced by central injection of tityustoxin in Fischer rats.

Scorpion envenoming and malnutrition are considered two important public health problems in Brazil, involving mainly children. Both these conditions are more common among the economically stratified lower income portion of the population, thus suggesting that these factors should be analyzed concomitantly. It is known that cardiorespiratory manifestations, as cardiac arrhythmias, arterial hypertension and hypotension, pulmonary edema and circulatory failure are the main "causa mortis" of scorpion envenomation.

Increased activity of the renin-angiotensin and sympathetic nervous systems is required for regulation of the blood pressure in rats fed a low-protein diet.

Previous studies have shown that postweaning protein restriction induces changes in the sympathetic nervous system in rats, leading to alterations in cardiovascular parameters. In addition, the renin-angiotensin system is also affected in these animals. Here, we hypothesized that adjustments in the interaction between the RAS and SNS underlie the cardiovascular adaptations observed in rats fed a low-protein diet.

Bezold-Jarisch reflex in sino-aortic denervated malnourished rats.

In this study we assessed the role of Bezold-Jarisch reflex (BJR) in the regulation of blood pressure (BP) of malnourished (MN) and control rats (CN) with sino-aortic denervation (SAD). Fischer rats were fed diets containing either 6% (MN) or 15% (CN) protein for 35 days after weaning. These rats underwent sham or SAD and catheterization of femoral artery and vein for BP measurements and drug injection.

Cardiac autonomic balance in rats submitted to protein restriction after weaning.

1. In the present study, we evaluated the autonomic balance of the heart in protein/energy-undernourished rats. 2.

Sympathoinhibition to Bezold-Jarisch reflex is attenuated in protein malnourished rats.

Malnutrition affects cardiovascular reflexes, including chemoreflex and baroreflex. In this study we assessed the hypothesis that malnourishment changes the responses in mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA) evoked from Bezold-Jarisch reflex (BJR). Fischer rats were fed diets containing either (6% malnourished or 14% control) protein for 35 days after weaning.

Cardiopulmonary reflex is attenuated in iron overload conscious rats.

Increased iron intake can lead to iron accumulation in serum and tissues. Its has been described that serum and tissue iron overload increase reactive oxygen species (ROS) levels and reduce the effectiveness of the cardiovascular neural mechanisms involved in the maintenance of the arterial blood pressure whithin a narrow range of variation, therefore, iron overload may disrupt cardiovascular homeostasis contributing to physiopathological status development. In the present study we evaluated whether iron accumulated in serum or tissue of awake animals affect the cardiovascular homeostasis through changes in the cardiopulmonary reflex (CPR).

Baroreflex dysfunction in rats submitted to protein restriction.

Earlier studies from the authors' laboratory showed that malnourishment induces alterations in the cardiovascular homeostasis increasing the basal mean arterial pressure and heart rate. In this study, the authors evaluated whether the sympathetic and parasympathetic efferent activities contribute to changes in the cardiovascular homeostasis through altered modulation of the arterial baroreflex of malnourished rats. After weaning, male Fischer rats were given 15% (Normal Protein--NP) or 6% (Low Protein--LP) protein diet for 35 d.

Malnutrition enhances cardiovascular responses to chemoreflex activation in awake rats.

Several studies in the literature suggest that low-protein intake is associated with increases in sympathetic efferent activity and cardiovascular disease. Among the possible mechanisms, changes in the neurotransmission of cardiovascular reflexes have been implicated. Therefore, the present study comprised the evaluation of chemoreflex responsiveness in rats subjected to a low-protein diet during the 35 days after weaning.

Pressor response to chemoreflex activation in awake rats: role of vasopressin and adrenal medulla.

The possible role of the peptide vasopressin and adrenal catecholamine in the pressor response to chemoreflex activation was evaluated in awake rats. Data show that the peripheral blockade of the V1 vasopressin receptor produced no change in the cardiovascular responses to chemoreflex activation, indicating that vasopressin plays no role on the pressor response to chemoreflex activation. We also have shown that the pressor response to chemoreflex activation is dependent on the sympathetic efferent activity since the antagonism of the alpha1-adrenoceptor with prazosin almost abolished the pressor response to chemoreflex activation.