Cell death and abnormalities in limb morphogenesis ofPleurodeles waltlii Michah. (urodela, amphibia) after nitrogen mustard treatment.

The effects of nitrogen mustard (methylbis-chlorethylamine) on limb organogenesis were studied inPleurodeles waltlii at different stages of fore and hind limb development.The effects of four different doses of nitrogen mustard (1.25; 2.5; 5 and 10 μg/ml) on the limb bud mesoderm and epidermis were studied histologically. This analysis was carried out on cylindrical unchondrified hind limb buds treated at stage 45.The effects of these doses on all stages of fore and hind limb development were investigated. This included the effect on the establishment of the proximo-distal sequence (segment chondrification) and the antero-posterior sequence (pre-postaxial zeugopod, basipod chondrification and progressive pre-postaxial organization of fingers and toes.Correlations were established between the mesodermal necrosis observed in hind limb buds treated at stage 45 and the skeletal abnormalities occurring in fore and hind limbs after treatment at all stages of their development.Thus, it appears that the effects of nitrogen mustard on organogenesis demonstrates the existence of a state in the differentiation of the mesoderm that is not revealed by morphological studies.