C. A. Elvehjem

GROWTH-RETARDING EFFECT OF CORN IN NICOTINIC ACID-LOW RATIONS AND ITS COUNTERACTION BY TRYPTOPHANE

Either 50 mg 1(-)tryptophane or 1.0 mg nicotinic acid per 100 gms of ration completely counteracts the growth retardation caused by the inclusion of 40 per cent. corn grits in a low protein ration. A possible explanation of this observation is discussed.

L-Leucine, an isoleucine antagonist in the rat.

Abstract An excess of dietary l -leucine has been shown to retard the growth of rats fed low-protein diets or diets deficient in isoleucine. The addition of isoleucine to such diets overcame, to a large extent, the growth-retarding action of an excess of l -leucine. These observations suggest that an excess of dietary l -leucine can act as an antimetabolite of isoleucine in the rat and can thereby increase the requirement of the rat for isoleucine.

Leucine, isoleucine and valine relationships in the rat.

Abstract Previous work had demonstrated that leucine fed to rats increased the requirement for isoleucine but, when 3% of l -leucine was fed, isoleucine only partially overcame the growth depression. It has now been shown that a supplement of valine was necessary to restore the rate of growth. Valine, isoleucine, and phenylalanine have been shown to reduce the utilization of leucine for the growth of rats fed a 9% casein diet supplemented with a number of amino acids. By using this diet and varying the levels of leucine, valine, isoleucine, and phenylalanine, evidence has been obtained for antagonisms between isoleucine and valine, between phenylalanine and isoleucine, and between phenylalanine and valine. It is suggested that antagonisms between each of these pairs of amino acids may be found under the proper dietary conditions.

Use of Sulfaguanidine in Nutrition Experiments.

Summary It has been shown that on a purified basal ration 0.5% sulfaguanidine greatly reduces the growth rate of young rats. When liver extract is fed with 0.5% sulfaguanidine, optimum growth is obtained. p-amino benzoic acid fed with 0.5% sulfaguanidine from the beginning of an experiment gives a definite growth response, but gives no response during the first week when fed to rats which have received sulfaguanidine alone for several weeks. The bearing of these results upon the possible synthesis of unidentified rat growth factors by intestinal bacteria is discussed.

Intestinal Flora of Rats on Purified Diets Containing Sulfonamides.

Summary Rats receiving purified diets plus sulfaguanidine and succinylsulfathiazole showed a decrease in the number of E. coli in the feces and cecum within three days after the drug was given. The number remained low for 10 days and then began to increase and at the end of the five weeks approached the normal level. The “total” counts remained constant throughout the test period. Enterococci replaced the coliforms during the time of repressed E. coli growth. On a succinylsulfathiazole-containing diet supplemented with either liver extract or a crude folic acid concentrate normal growth was maintained in spite of a marked reduction in the number of E. coli in the cecum.

Effect of isoleucine supplementation on the growth of rats fed zein or corn diets.

Abstract Isoleucine was found to be limiting for the growth of rats fed corn diets supplemented with lysine, tryptophan, valine, and threonine or 24% zein diets supplemented with most of the essential amino acids. Since phenylalanine, which is known to be present in zein at quite a high level, was also found to be limiting for the growth of rats fed 21% of zein, it was suggested that all of the essential amino acids in zein were utilized poorly. This was further substantiated when rats fed diets containing alcohol-extracted corn showed a much greater growth response to a level of isoleucine equivalent to that supplied by the zein extracted than to the zein itself. When the level of leucine supplied by the zein was also added, no growth depression was obtained.

“Folic Acid” Active Compounds in the Nutrition of the Monkey.

Summary Vitamin B10 and B11 concentrates were inactive as a source of folic acid for the monkey. Crystalline vitamin Bc and the synthetic Lactobacillus casei factor were active as a source of folic acid for the monkey when fed at a level of 100 γ per day. The Bc conjugate had less activity when fed at levels of 200 and 300 γ per clay. Folic acid deficiency precipitates a deficiency for the monkey anti-anemia factor which is characterized by lack of growth, sub-optimal hemoglobin levels and a reversal in the lymphocyte-neutrophile ratio.

Biological availability of isoleucine.

Abstract Biological availability of isoleucine in eight different proteins was determined using a blood meal diet low in isoleucine. Isoleucine in zein was available to the extent of 30%; in casein and gelatin, around 60–70%; and in fibrin, beef, egg albumin, and Drackett, over 90% of the isoleucine was available to the rat. In the case of zein, there was an increase of from 30 to 60% in the availability of isoleucine, when the acid-hydrolyzed zein was fed. No such effect was observed with the hydrolyzates of casein and fibrin.

Activity of Pyridoxine Derivatives in Chick Nutrition.

Summary Pyridoxal, pyridoxamine and pyracin-5 were found to be inactive singly in replacing vitamin B10 or vitamin B11 in chick nutrition. The biological vitamin Be activity of these three compounds is approximately > 1/2, 4/5, and 0 respectively. Vitamin B6 deficiency symptoms in the chick were found to include a decreased clotting time, hyperprothrombinemia, small spleens and anemia.

Rumen Synthesis of the Vitamin B Complex on Natural Rations.

Summary Six members of the vitamin B complex in the rumen ingesta of a heifer fed a ration composed of natural feeds were determined. In most cases higher values were found in the rumen ingesta than in the ration fed. With the exception of flavin, variation of the amount of urea or protein in the grain mixture of the ration had little if any effect on the vitamin content of the ingesta.