Harry F. Zinsser

Use of in vivo Magnification Renal Arteriography to Study Cadmium Effects on Vasoactive Responses

Abstract Antiotensin, norepinephrine, and epinephrine administered into the renal artery produced mild to marked renal vasoconstriction in 15 dogs. Cadmium acetate administered in association with the vasoactive drugs (agonists) resulted in mild to complete inhibition of the agonist-induced renal vasoconstriction; this effect was reversible, reproducible, and dose-related. Decreased intrarenal vascular resistance secondary to the inhibition of vasoactive responses by cadmium may play a role in the pathophysiology of cadmium hypertension.

Dispersion of Blood Pressure and Heart Rate in Essential Hypertension

The dispersion of the cardiovascular control system variables of heart period, systolic and diastolic blood pressure in a group of resting essential hypertensives has been compared with a group of normotensive subjects. Controlled variable dispersion in the absence of external perturbation was considered to be a measure of short term cardiovascular control system offset (error) from reference values (setpoint). The high blood pressure group demonstrated a greatly decreased controlled variable dispersion compared with the normal, implying the operation of a control system having a high closed loop gain, low system error and poor stability secondary to perturbation or stress. The extent of the changes in control system performance in essential hypertension was reduced by the adrenergic neuron blocking agent, guanethidine. These conclusions are consistent with and are discussed in relation to the known dynamic responses of heart rate and blood pressure to stress, together with the pathophysiology of the forward and feedback pathways of the cardiovascular control system, in essential hypertension.

Radiopotassium Indicator-Dilution Studies During Angiocardiography

In an attempt to learn more about the physiologic changes in the cardiovascular system during angiocardiography and the nature of mixing of radio-opaque dyes with blood, radiopotassium and Diodrast I131 dilution curves were obtained before and during angiocardiography. Studies in patients without vulvuar disease and with mitral valvular disease indicated an increased cardiac output during angiocardiography, but the increases were not statistically greater than those following control injections. No difference in indicator-dilution patterns of potassium and Diodrast was demonstrable, suggesting identical circulatory mixing pattterns.