The Neck Venous Hum in Adults

In a survey of 200 persons, ages 18 to 76, the incidence of normal cervical venous hum was 47 per cent in young adults and 21 per cent in persons of middle and older age, a group in whom it once was thought to be rare. The importance of the hum is that it may be misinterpreted as caused by a pathologic state such as an arteriovenous aneurysm, aortic insufficiency, carotid artery stenosis, patent ductus arteriosus or thyrotoxicosis.The normal cervical venous hum may be distinguished clinically from murmurs associated with disease states by the fact that it can be silenced by light pressure over the jugular vein.     

Pulse radiolysis of lactate dehydrogenase.

Pulse radiolysis has been used to investigate the rates and transient spectra for the reactions of free radicals with beef heart lactate dehydrogenase at pH 7. Analysis of the results leads to second-order rate-constants for eaq-, .OH, .I, .Br2-, .I2- and .(CNS)2- which are, respectively, 24, 21, 10, 0.55, 0.43 and 0.15 in units of 10(10) M-1 s-1 with uncertainties of +/- 20 per cent. Those for .I and .I2- are similar to the corresponding rate-constants for the related enzyme alcohol dehydrogenase. The spectra of the transient species produced by .OH, .Br2- and .(CNS)2- all showed evidence for reactions with tyrosine and tryptophan residues, and in general terms the magnitudes of the rate-constants appeared to increase with the oxidizing abilities of the radicals. The implication of the results for understanding the mechanism of deactivation by free radicals is discussed.