Investigations on myelination in vitro. Regulation by thyroid hormone in cultures of dissociated brain cells from embryonic mice.

Cultures of dissociated brain cells from embryonic mice were used to study the influence of thyroid hormone on myelination in vitro. Synthesis of myelin-associated lipids such as cerebrosides and sulfatides was used as an index for myelination. An experimental design, in which the cells were grown on medium containing serum from a thyroidectomized calf, was employed to demonstrate the direct effect of L-3,5,3'-triiodothyronine (T3Y on the biosynthesis of myelin lipids. The cells grown in the presence of hypothyroid calf serum which contained very low levels of thyroid hormones (T4 (thyroxine), 1.2 microgram/ml; T3, less than 25 ng/100 ml) compared to normal serum (T4, 5.8 microgram/ml; T3, 110 ng/100 ml) showed a diminished synthesis of myelin-associated glycolipids. This reduced activity could be restored to normal by including T3 (13 ng/ml) in the medium.