Relationships between biotin and thymus morphology, and thymic and plasma peptides controlling DNA transcription

Biotin-deficient rats show a slower growth rate and thymus involution. The amount of the thymic peptides controlling DNA template, based on thymus weight, is higher in deficient than control rats. No significant difference was noticed in the content of active peptides when evaluated for the rat. This observation suggests that involution of the thymus does not involve those cells which produce active peptides. Inhibition of RNA synthesis is the same for peptides extracted from normal and from biotin-deficient rat thymus. The amount of plasma peptides controlling DNA template per milliliter of plasma is higher and inhibition of activity on RNA synthesis is lower in deficient as compared to control rats. These effects are reversible following biotin administration.