THE DETERMINATION OF VITAMIN B₁₂‐ACTIVITY IN THE ORGANS AND EXCRETA OF SHEEP

Abstract

It seems probable from available evidence that vitamin B12 and the closely analogous vitamin Bv2a (or Bi2b) and vitamin Biac all originate in nature only as products of the metabolic activity of certain micro-organisms. The chemical differences between these analogues are minor ones-the cyanogen group, which is attached rather loosely to the cobalt atom in the complex molecule of vitamin B12, is replaced in vitamin Bjoa (or Bjab) by a hydroxyl group, and in vitamin Bi2« by a nitrite radicle; and there is little if any difference between their capacities to provide the nutritional requirements of higher animals and of exacting micro-organisms. These cobalamins (vitamin B12 and its analogues) are readily interconvertible-vitamins Bi2a (Bi2b) and Biac, for example, are converted into vitamin B12 in dilute cyanide solution (Kaczka, Wolf, Kuehl and

Methylmalonic acid and coenzyme A concentrations in the livers of pair-fed vitamin B12-deficient and vitamin B12-treated sheep

“…As8ay of vitamin B12. Vitamin B12 activity in liver and blood serum was determined by microbiological assay with Lactobacillus leichmanii (Dawbarn & Hine, 1954; Hine & Smith, 1957).…”

Reduction of Heliotrine by A Rumen Microorganism

“…A medium low in vitamin B12 was prepared from medium 3 by the method of Davis and Chow (1952), after it was found that all of several preparations of yeast extract available contained about 10-3 ng vitamin B,. activity/mg dry solids, as estimated by the Lactobacillusleichmannii procedure (Dawbarn and Hine 1954). This vitamin B12 activity was probably due to deoxyribonucleosides in the yeast extracts (Smith 1960).…”

“…and Factor B Medium 3 contained sufficient yeast extract to give an apparent vitamin B12 content of 10-6 ng/ml, but this was reduced by the method of Davis and Ohow (1952) to a point where the L. leichmannii assay (Dawbarn and Hine 1954) was insufficiently sensitive to detect any residual vitamin B 12 • An initial inoculum containing 10-6 ng/ml of vitamin B12 activity was serially subcultured seven times at the 1 % level in the vitamin B 12 -low medium. In all these cultures the organism grew normally and reduced heliotrine as rapidly as in the presence of 5 fLg/ml of vitamin B 12 .…”