Abstract
Apoptosis was studied in chickens with reference to bursal involution. Morphological and biochemical apoptosis occurred first on day 18 of incubation in bursa of normal embryos. Such phenomena were never detected before 18 th day of embryonic life. Therefore, apoptotic induction was stage specific in chicken bursa. Embryos treated with testosterone propionate (TP) showed DNA fragmentation on day 18, 8 days after the TP injection; these apoptotic responses were negligible on other experimental days. Furthermore, apoptotic cells were occasionally seen among the bursal lymphocytes or epithelial cells in the TPtreated embryos. Embryos injected with half dose of TP showed lower levels of DNA fragmentation than the normals, and the cells undergoing apoptosis were low in number. After hatching, apoptosis was detected morphologically and biochemically in normal bursa, especially after the stage of sexual maturation. These findings demonstrate an apparent correlation between apoptosis and normal involution of bursa after maximal stage of tissue maturation and are suggesting for an apoptosis-independent process of bursal involution introduced by TP treatment.
