A Modified Warthin-Starry Silver Impregnation Method to Detect Programmed Cell Death in the Interdigital Tissue of the Fetal Rat Limb

Previously we have shown that a modified Warthin-Starry (mWS) method, to which was added a minor change to prevent fading, is useful and convenient to detect chemically induced chromatin condensation during thymic apoptosis in rats treated with dexamethasone. In this study, we investigated the relationship between mWS-positive cells and programmed cell death in the interdigital spaces of the developing limb in fetal SD rats. The limbs were removed from fetuses at day 15 of gestation, and routinely processed for both hematoxylin and eosin (H&E) staining and the mWS method. The results clearly showed that the distribution pattern of mWS-positive cells coincided well with that for the programmed cell death observed by H&E staining in the mesenchyme of interdigital notches and at the areas corresponding to the interphalangeal joints. These results confirm that the mWS method might be useful and convenient to detect condensed chromatin during apoptosis in embryonic organogenesis as well as by chemical induction.