Induced thiamin deficiency in lambs.

By following a feeding regimen which consistently induced polioencephalomalacia in pre-ruminant lambs it was possible to study certain characteristics just before the terminal stage in polioencephalomalacia. There was always a marked deficit in erythrocyte precursors in bone marrow and this preceded any pathological changes in the brain. Erythrocyte transketolase activity decreased in control lambs, and decreased to an even greater extent in thiamin-deficient lambs. Glucose was the only substrate of those measured which was used by the brain, and its rate of use was not affected by thiamin deficiency. After a single intravenous injection of 35S-thiamin, the decrease of 35S in the plasma was consistent with its dispersal into two pools: the half-time of disappearance of 35S into the slowly equilibrating pool was less in thiamin-deficient lambs than in their controls. Characteristics which were not altered in thiamin deficiency were concentrations of calcium and magnesium in various regions of brain and concentrations of calcium, magnesium, sodium and potassium in plasma.