Effects of minute doses of ethylenebisdithiocarbamate disodium salt (nabam) and its degradative products on connective tissue envelopes of the notochord in Xenopus: an ultrastructural study.

The fungicide ethylenebisdithiocarbamate disodium salt (nabam) at 40 or 100 micrograms/l has deleterious effects on the survival of Xenopus laevis embryos. The tissues of the notochordal enveloping layer show definite alterations at the ultrastructural level. There is a significant reduction or absence of the collagen fibres of the outer connective tissue cells. Embryos treated with 100 micrograms/l nabam stored for 3 weeks developed more severe malformations of the enveloping connective tissue layers of the notochord similar to the embryos immersed in combinations of ethylene thiourea and methyl isothiocyanate. In these animals the arrangement of collagen fibres of the notochordal sheath showed complete disarray. Furthermore, the elastica externa was reduced and fragmented. These fine structural observations clearly demonstrate the deleterious effects of this pesticide on cells and tissues of developing systems.