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A Controlled Environment System for New Trace Element Deficiencies^{1 ,2}

Laboratory of Experimental Metabolic Diseases, Medical Research Programs, Veterans Administration Hospital, Long Beach, California and Department of Biological Chemistry, School of Medicine, University of California, Los Angeles, California

An all-plastic, controlled environment system is described for animals such as rats. The system, consisting of an air filter assembly, isolator, caging, and accessories, minimizes extraneous trace element contamination. The isolator, a modification of germfree isolator models, can hold 25 rats in groups of 5/cage. Weanling rats fed laboratory ration in the controlled, but not germfree, environment grew as well as control animals maintained outside of the isolator in metal cages under conventional conditions. A new trace element deficiency was observed in rats fed amino acid diets supplemented with the known required trace elements inside the controlled environment. Inhibition of growth, seborrhea, and pronounced alopecia developed within 1 to 3 weeks. Death occurred within 2 to 6 weeks. Conventional outside controls fed the same diet grew more rapidly and showed no deficiency symptoms. Supplementation of 0.4% yeast ash prevented the deficiency symptoms and improved growth. The results indicate that the amino acid diet lacks unidentified inorganic trace factors which are supplied by the environment under conventional conditions of animal experimentation. The described technique coupled with modern, sensitive methods of analysis permits rigorous and definitive experiments on the essentiality of specific trace elements.

² Some of these data were presented to the American Institute of Nutrition at the 50th annual meeting of the Federation of American Societies for Experimental Biology, Atlantic City, 1966, (Federation Proc., 25: 432, 1966, and to the VIIth International Congress of Nutrition at Hamburg, Germany (abstracts of papers, 1966, p. 297).

³ Present address: Laboratory of Nutrition Research, Veterans Administration Hospital, Washington, D. C.

Manuscript received 28 April 1967.

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