Biomedical subjects

R Tabrizchi

Publications and source records attributed to R Tabrizchi.

58 records · Page 4Linked to original sources

PubMed1986

Vascular role of vasopressin in the presence and absence of influence from angiotensin II or alpha-adrenergic system.

The effects of a vasopressin (AVP) pressor antagonist, d(CH2)5Tyr(Me)AVP, on mean arterial pressure (MAP), total peripheral resistance (TPR), cardiac output (CO), and the distribution of CO were investigated by the microsphere technique in three groups of pentobarbital anesthetized rats: intact (I), saralasin pretreated (II), and phentolamine pretreated (III). Saralasin and phentolamine were infused intravenously to inactivate the renin-angiotensin and alpha-adrenergic systems, respectively. The AVP antagonist decreased MAP and TPR in all groups and it caused a greater depressor effect in groups II and III than in group I. In group I, AVP antagonist increased blood flow (BF) to the stomach and skin. In group II, AVP antagonist increased BF to the muscle and skin. In group III, AVP antagonist markedly increased BF to the muscle. Therefore, the degree of vasoconstrictor influence exerted by AVP in different vascular beds varies depending on endogenous vasomotor tone from the renin-angiotensin and (or) sympathetic nervous systems.

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PubMedDate not supplied

Methods of blood flow measurement in the arterial circulatory system.

The most commonly employed techniques for the in vivo measurement of arterial blood flow to individual organs involve the use of flow probes or sensors. Commercially available systems for the measurement of in vivo blood flow can be divided into two categories: ultrasonic and electromagnetic. Two types of ultrasonic probes are used. The first type of flow probe measures blood flow-mediated Doppler shifts (Doppler flowmetry) in a vessel. The second type of flow probe measures the "transit time" required by an emitted ultrasound wave to traverse the vessel and are transit-time volume flow sensors. Measurement of blood flow in any vessel requires that the flow probe or sensor be highly accurate and exhibit signal linearity over the flow range in the vessel of interest. Moreover, additional desirable features include compact design, size, and weight. An additional important feature for flow probes is that they exhibit good biocompatability; it is imperative for the sensor to behave in an inert manner towards the biological system. A sensitive and reliable method to assess blood flow in individual organs in the body, other than by the use of probes/sensors, is the reference sample method that utilizes hematogeneously delivered microspheres. This method has been utilized to a large extend to assess regional blood flow in the entire body. Obviously, the purpose of measuring blood flow is to determine the amount of blood delivered to a given region per unit time (milliliters per minute) and it is desirable to achieve this goal by noninvasive methodologies. This, however, is not always possible. This review attempts to offer an overview of some of the techniques available for the assessment of regional blood flow in the arterial circulatory system and discusses advantages and disadvantages of these common techniques.

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PubMedDate not supplied

The vascular system. An overview of structure and function.

It is the function of the vascular system, through a complex network of arteries, capillaries and veins, to maintain cellular homeostasis. As research scientists it is necessary to understand not only some of the basic properties of the blood vessel itself but also how these vessels differ in cellular and physiological function. This review provides an overview of the basic physiological and pharmacological tenets of blood vessels. It also briefly describes in vivo and in vitro methods used in the measurement of blood flow and blood vessel function. It is hoped that this review will provide readers of this focussed issue of the Journal of Pharmacological & Toxicological Methods with an appreciation of the many mechanical, electrical and biochemical methodologies described within this issue.

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PubMedDate not supplied

Role of intracellular and extracellular calcium in alpha 1-adrenoceptor-mediated vasoconstriction in the rat perfused hindquarters.

The influence of the calcium channel antagonists, felodipine and cadmium, as well as of the putative phospholipase C inhibitor, 2-nitro-4-carboxyphenyl N,N-diphenylcarbamate (NCDC), on the vasoconstrictor actions of methoxamine in the rat perfused hindquarters was examined. Changes in perfusion pressure following bolus administration of methoxamine were monitored under constant flow. Methoxamine produced a dose-dependent increase in perfusion pressure of the hindquarters. Inclusion of cadmium (30 microM) in the physiological salt solution significantly reduced the maximum response, without significantly altering the ED50 or the Hill coefficient of the dose-response curve to methoxamine. Addition of felodipine (0.3 and 1 microM) in the physiological salt solution inhibited the vasoconstrictor actions of methoxamine. The dose-response curve to methoxamine was displaced to the right, with significant increases in ED50 and Hill coefficient, and the maximum response was significantly reduced. The vasoconstrictor action of methoxamine was also inhibited by NCDC (10 microM). The maximum response decreased and the Hill coefficient increased significantly, while the ED50 was not significantly altered. The presence of NCDC, together with either felodipine or cadmium, did not result in a further additive inhibition of the methoxamine-induced vasoconstriction. The inhibitory effects of felodipine and cadmium were partially reduced in the presence of NCDC. It is concluded that, in the rat perfused hindquarters, the vasoconstrictor actions of methoxamine depend on both intracellular and extracellular calcium ions. Calcium influx occurs, in part, via the felodipine-sensitive calcium channels. It is also apparent that NCDC interfered with the inhibitory actions of cadmium and felodipine.

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