Increases in apoptosis and declines in Bcl-XL protein characterise testicular regression in American crows (Corvus brachyrhynchos).

The present study investigated the cellular changes observed during testicular regression in American crows. Testes from adults caught during the early (March), progressing (April), peak (early May), transitional (late May), and post- (June) breeding season were examined. Apoptosis was assessed by in situ terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) and Bcl-X(L) protein immunolabelling.