A study of teratogenic effects of particulate compounds in the amniotic cavity of chick embryos.

Abstract

Silica, which is known to have certain toxic properties, was injected in colloidal suspension of minute particle size into the amniotic cavity of chick embryos. It produced defects very similar to those previously observed with the highly nontoxic colloidal alumina. Carbon particles also produced striking defects of the same types as those produced by thalidomide and other noncolloidal but insoluble compounds which have been studied previously. Microscopic studies of tissues from chick embryos inoculated with carbon particles indicated that the particles entered the integumental ectoderm where they caused severe necrosis and sloughing of cells as well as marked localized hyperplasia. Following this the carbon entered the mesoderm, either through the denuded areas or, as observed in many instances, by passing through the ectoderm into the subjacent mesoderm. In the meso-derm the particles became located at progressively deeper levels, in some cases penetrating cartilagenous structures. Studies of the distribution of the carbon within the embryonic tissues indicated that defects occurred in structures developing in or near tissues in which the particles were located. Continual destruction of surface epithelium of the cephalic region which plays an important role in the development of skin, feather follicles, eyelids, nictitating membrane and cornea, resulted in defective development of these structures. When carbon was present in areas of the mesoderm from which bone or cartilage developed these structures were retarded or abnormal. Since the greater amount of carbon accumulated in the cephalic region (due to the tendency of carbon aggregates to gravitate toward this region) the frontal and squamosal bones and the sclerotic cartilages were chiefly affected.