1. Transcranial Doppler measurements of the mean blood flow velocity and the resistance index in the middle cerebral artery are used to assess cerebral haemodynamics. The prerequisite for the use of these parameters in clinical pharmacology studies is an evaluation of their repeatability and spontaneous variation with time. 2. Repeatability of transcranial Doppler measurements of mean blood flo...

We report the hemodynamic parameters of stage 18, 21, 24, and 27 chick embryos (from 3 to 5 days of incubation). Dorsal aortic blood velocity and mean vitelline artery blood pressure are measured with a 20 MHz pulsed-Doppler meter and servo-null pressure system respectively. We also measure heart rate, dorsal aortic diameter and embryo weight of each developmental stage. From these data, we cal...

Insulin resistance confers risk for diabetes mellitus and associates with a reduced capacity of the arterial baroreflex to regulate blood pressure. Importantly, several brain regions that comprise the central autonomic network, which controls the baroreflex, are also sensitive to the neuromodulatory effects of insulin. However, it is unknown whether peripheral insulin resistance relates to acti...

The objective of this present numerical model is to investigate the effect of shape of stenosis on blood flow through an artery using power-law fluid model. Blood is modeled as power-law fluid in a uniform circular tube with an axially non-symmetric but radially symmetric stenosis. The expressions for dimensionless resistance to flow, wall shear stress and apparent viscosity have been obtained....

Systole causes a redistribution of coronary blood flow away from the subendocardium. In the present study the relative contribution of shortening of the myocardial fibers (wall strains) and of pressure development in the ventricular lumen to redistribution were determined. The distribution of coronary blood flow during systole in hearts ejecting into a severed aorta (large wall strains and near...

We report the hemodynamic parameters of stage 18, 21, 24, and 27 chick embryos (from 3 to 5 days of incubation). Dorsal aortic blood velocity and mean vitelline artery blood pressure are measured with a 20 MHz pulsed-Doppler meter and servo-null pressure system respectively. We also measure heart rate, dorsal aortic diameter and embryo weight of each developmental stage. From these data, we cal...

The mechanisms underlying cerebral vasodilatation during hypercapnia are not fully understood. To examine the role of nerves and prostaglandins in the regulation of basal blood flow and in hypercapnia-induced vasodilatation in the cerebral blood vessels of rabbit.Cerebral blood flow was measured by laser Doppler flow-meter in 18 NZW rabbits anesthetized with sodium pentobarbital.  Tetrodetoxin ...

The present article concerns the problem of blood flow through an artery with an axially asymmetric stenosis (constriction). The two-layered macroscopic model consisting of a cell-rich core of suspension of all the erythrocytes described as a particle-fluid suspension (Jeffrey fluid) and a peripheral zone of cell-free plasma (Newtonian fluid). The analytical expressions for flow characteristics...

OBJECTIVE Endothelin-1 concentrations are increased in patients with increased mean pulmonary arterial pressure, pulmonary blood flow, and pulmonary vascular resistance. However, endothelin-1 concentrations have not been well characterized in patients with congenital heart disease and normal pulmonary vascular resistance. In particular, it is unclear whether pressure or flow is the key regulato...

Blood flow through a vascular bed is usually determined by the pressure gradient across it and the diameter of the precapillary resistance vessels. Special circulations have additional specific features of blood flow control. Several organs control their blood supply by autoregulation. Coronary blood flow is linked to myocardial oxygen consumption, primarily by a metabolic mechanism, thus incre...