D. K. Bosshardt

A Nutritional Requirement for Bromine

Summary Addition of an iodinated casein with thyroid activity to a purified diet adequate in all known essential nutrients produced a growth retardation in mice. Growth inhibition was reversed by fractions of whey and by whey ash. The active inorganic component was found to be bromine.

THE EVALUATION OF PROTEIN QUALITY IN THE NORMAL ANIMAL

There are available to the investigator several methods of measuring the nutritive adequacy of protein foods. These methods provide a good classification of dietary proteins, and their wide application has resulted in a rather coinprehensivc knowledge of many single protcin sources and protein mixtures. The methods are more or less empirical, and occasionally values are obtained that are sufficiently out of line to lead one to suspect that a lack of adequate control was employed. It must be emphasized that these methods, empirical as they may be, have proven t o be of considerable practical value. It is seldom that one observes a serious reversal in the relative classification of proteins, although variations in the absolute values obtained by any one method may be large. The practical usefulness of these methods, in their present form, should not cause a stagnation of effort toward improvements and a more thorough understanding of metabolic phenomena that are involved, for these are pathways that will lead to a more complete knowledge of protein nutrition. In this discussion, i t is intended to present a few of the more or less controversial factors that are evident in the measurements of protein quality, for growth or maintenance in the normal animal. The factors that will be discussed are the following:

Effect of Bromine on Chick Growth

Summary A growth response to trace addition of bromine to a semi-synthetic diet has been observed in chicks. The conditions required in order to obtain this effect are discussed.

Interrelation of Cholesterol, Palmitic Acid, and Unsaturated Fatty Acids in the Growing Mouse and Rat

During the course of a study of the nu tritional effects of various fats and fatty acids it was observed that the feeding to weanling mice of a purified type of diet containing 10% of a hydrogenated coco nut oil,8 20% of palmitic acid, and 1% of cholesterol caused a complete cessation of growth with all animals dying within a period of 5 days. No abnormalities were noted in the mice except for extremely small spleens and lymph nodes and these showed no histological defects. The liter ature on atherosclerosis, lipid metabolism and related topics is very ex tensive and mentions many interesting interrelationships of factors such as satu rated and unsaturated fatty acids, choles terol, pyridoxine and still other substances. None of these interrelationships, to the best of our knowledge, is associated with the phenomenon we observed. This paper is a report of the observations made in the course of experiments designed to throw some light on this peculiar phenomen.

The hypolipemic properties of 5β-cholanic acid in the mouse and rat

Abstract Dietary 5β-cholanic acid in the mouse caused a marked reduction of plasma cholesterol, an increase in rate of excretion of intraperitoneally administered 14 C-labeled cholic and chenodeoxycholic acids and an increase in rate of excretion of orally administered 14 C-labeled cholesterol. In this species it also caused a reduction in plasma triglycerides and an increase in liver size. Dietary 5β-cholanic acid did not greatly influence the rate of synthesis of cholesterol by liver homogenates of normally fed mice, but did cause a striking increase in this parameter in mice in which liver cholesterol synthesis had been suppressed by feeding cholesterol. In the rat 5β-cholanic acid caused a striking reduction in plasma triglycerides, but in sharp contrast to the effect observed in the mouse, a mild elevation of plasma cholesterol. In in vitro and in vivo experiments, in the presence and absence of depressed cholesterol synthesis by dietary cholesterol, 5β-cholanic acid caused a marked increase in rate of cholesterol synthesis by rat liver homogenates. Finally, in the rat, 5β-cholanic acid caused a sharp increase in plasma post heparin lipoprotein lipase activity.