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Effect of Reserpine on Vascular Responses of Forearm to Tyramine and Norepinephrine in Man. FRANCOIS M. ABBOUD AND JOHN W. ECKSTEIN, Iowa City, Iowa (introduced by Willis M. Fowler). The vasoconstrictor response to tyramine is reduced, and that to norepinephrine is enhanced, in animals treated with reserpine. These effects have not been demonstrated in man. Observations on blood pressure (cuff) and forearm blood flow (plethysmograph) were made in 7 healthy men before and after intravenous injection of tyramine (0.1 mg/kg) and before and during 6-minute infusions of norepinephrine in doses of 0.032, 0.064, and 0.15 jug per kg per minute. Each subject was studied 3 times. Session A served as the control. Session B followed 2 weeks of treatment with reserpine, 1 mg daily. Session C was held 3 to 6 weeks after reserpine was discontinued. Analysis of variance of the data revealed no significant differences in the levels of blood pressure, blood flow, or resistance to flow during norepinephrine infusions in the 3 sessions. The values for pressure, flow, and resistance obtained with all 3 doses of norepinephrine averaged 109 mm Hg, 3.39 ml per minute per 100 ml of forearm, and 33.5 U, respectively, during session A. The corresponding values during session B were 107 mm Hg, 3.26 ml, and 38.7 U. During session C these values were 111 mmHg, 2.69 ml, and 44.2 U. Resting levels of blood pressure and heart rate were slightly reduced in session B while resistance was unchanged. Tlhe pressor response to tyramine during session B (4.3 + 0.9 mmHg) was significantly lower than during session A (13.7 + 4.1 mmHg) or session C (21.0 + 3.77 mm Hg). The responses to norepinephrine were similar in 5 additional subjects who received reserpine, 3 mg daily for 5 days. Conclusion: In these experiments reserpine failed to cause vascular supersensitivity to norepinephrine even though the pressor response to tyramine was reduced. Effect of Hypertension on Cholesterol Synthesis in Rats. HAROLDADEL, MARIE M. DALY, QUENTIN B. DEMING,* Lim BRUN AND VICTORIA RAEFF, New York, N. Y. The development of atherosclerosis in animals and man is accelerated by hypertension. Increased concentrations of cholesterol in serum and tissues have been observed in hypertensive rats. In order to determine whether these observations might be related to an effect of hypertension on cholesterol synthesis, the incorporation of labeled precursors into cholesterol by tissues of normotensive and Goldblatt-hypertensive rats was measured in vivo and in vitro. After intraperitoneal iniec* Member. tion of acetate-i-C'4 into hypertensive rats and paired normotensive controls, the cholesterol isolated from liver, serum, and residual carcass showed higher specific activity in the hypertensives. The mean increase was, in liver 58%, in serum 57%, in carcass 35%; p, respectively, less than 0.01, 0.05, 0.05. The incorporation of acetate-i-C1' into cholesterol by liver slices was greater in slices from hypertensive animals than in those from paired normotensive controls. The mean difference in specific activity was 135% (p less than 0.005). No difference was shown when mevalonate-2-C1' was used as precursor. The incorporation of acetate or mevalonate into cholesterol by 6 pools of aortas isolated from hypertensive rats and pools of paired normotensive controls was measured. With either precursor the incorporation of label into cholesterol (purified by repeated bromination) was higher in the aortas of the hypertensives (p less than 0.025). Synthesis of cholesterol, whether measured in the living rat or in isolated liver or aorta, is accelerated by hypertension. The Mechanism of Puromycin Inhibition of Hemoglobin Synthesis by Rabbit Reticulocyte Ribosomes. DAVID W. ALLEN AND PAUL C. ZAMECNIK,* Boston, Mass. Reticulocyte ribosomes contain the partially formed polypeptide chains of hemoglobin, of varying chain lengths but each having the same N-terminal group, valine. These incomplete polypeptide chains are considered bound to the ribosome by soluble RNA residues attached to the peptide chain at its growing C-terminal end. Puromycin, a potent inhibitor of protein synthesis, is an analog of aminoacyl-soluble RNA. The effect of this drug on reticulocyte ribosomes, labeled with C14amino acids by prior incubation of the intact reticulocytes, has been studied in a cell-free system capable of hemoglobin synthesis. Puromycin is found to release the polypeptide intermediates of hemoglobin synthesis from the ribosome. Unlike the more naturally occurring release of the completed hemoglobin molecule, the puromycin-produced release of polypeptide from the ribosome does* not require an ATP-generating system or the supernatant fraction and occurs maximally in 1 or 2 minutes. The polypeptides released by puromycin do not appear as hemoglobin chromatographically or electrophoretically but, like the completed molecule, have only N-terminal valine. C'4-puromycin synthesized by methylating its tyrosyl analog with C!-diazomethane is bound to the soluble polypeptide it releases. Saturation of the binding site of the puromycin-released polypeptide occurs at a puromycin concentration (200 m/Amoles/ml) equivalent to that producing maximal inhibition of C1'-amino acid incorporation in a cell-free system and maximal release of C'4-polypeptide from the ribosomes. One residue of puromycin is bound to the

the journal of clinical investigation/the journal of clinical investigation

PROCEEDINGS OF THE FIFTY-FOURTH ANNUAL MEETING OF THE AMERICAN SOCIETY FOR CLINICAL INVESTIGATION, INC., HELD IN ATLANTIC CITY, N. J., APRIL 30, 1962. . THE TRAINING OF THE CLINICAL INVESTIGATOR