No abstract

Evidence is presented to indicate that the level of serum cholesterol in certain individuals may vary widely within a matter of hours. The data suggest also that a rapid fluctuation of the serum cholesterol level may be induced in some persons by modifying certain aspects of their environment. Varying lability of the level of serum cholesterol and the differing response of individuals to certain environmental factors require that careful attention be given to the sampling methods used in research.

Further evidence has been obtained to indicate that the concentration of serum cholesterol can vary widely during the course of a few hours in certain individuals. The data are consistent with a hypothesis that changes in the concentration of serum cholesterol may relate to the anticipation of an event as well as to the event itself. Similarity in the hourly variation in serum cholesterol concentration occurring among eight carefully selected subjects, during control as well as during test periods, is note-worthy.

A method is presented for the automated determination of urea nitrogen using the Berthelot reaction for measuring the ammonia released by the enzymatic action of urease. The method compares favorably with the automated diacetyl monoxime method and employs less dangerous and less expensive reagents.