A technique for improved resolution of [3H]thymidine autoradiography in the avian embryo: a preliminary report.

A technique is described for producing pulse-like effects in [3H]thymidine autoradiography in chick embryos. This procedure involves combining thymidine with reserpine, which temporarily inhibits thymidine incorporation. The concept is to introduce thymidine, allow time for its incorporation, then introduce reserpine, so that subsequent uptake is inhibited, and a relatively discrete label will appear in cells generated at the time of thymidine administration. The best results occurred when thymidine was administered 12 h prior to reserpine, or when the two were introduced simultaneously. A dose of 0.004 mg of reserpine produced the suppression, but had no deleterious effects, in terms of embryonic survival or in long-lasting changes in cell numbers, as reflected by cell counts in the trochlear nucleus, a population which was undergoing proliferation at the time of reserpine injection. Thus, this technique appears to hold considerable promise for improving the precision of the autoradiography procedure in avian embryos.