Histogenesis of the tibiotarsus in Malathion-treated chick embryos

Abstract

Chick eggs were injected with 0.1 ml of 2% Malathion in corn oil on the 5th day of incubation, and its effect on skeletogenesis, particularly the development of the tibiotarsus, was studied throughout the incubation period. Anatomically, the treated embryos showed a generalized reduction in body size, delayed patterns of mineralization in certain of the endochondral bones, and micromelia. The treated tibiotarsi consistently exhibited a reduced growth rate and an angulation at the junction of the diaphysis and distal epiphysis. The rate of periosteal ossification, cartilage resorption, and marrow cavity formation progressed more rapidly in the tibiotarsi of the treated embryos. The striking feature of the treated tibiotarsi was degenerative necrosis of the cartilage within both proximal and distal epiphyses. This necrotic zone exhibited a reduced matrix and progressive degeneration of the chondrocytes.