The chick embryo test as used in the study of the toxicity of certain dithiocarbamates

Abstract

The Chick Embryo Test As Used in the Study of the Toxicity of Certain Dithiocarbamates. GEBHARDT, D. 0. E., and VAN LOGTEN, M. J. (1968). Toxicol. Appl. Pharmacol. 13, 316-324. The toxicities of six dithiocarbamates: bis(dimethy1 thiocarbamoyl) disulfide (thiram), zinc dimethyldithiocarbamate (ziram), ferric dimethyldithiocarbamate (ferbam), bis(dimethyl thiocarbamoyl) ethylene bis(dithiocarbamate) (triaram), sodium diethyl dithiocarbamate (NaDEDC), and sodium ethylene bis(dithiocarbamate) (nabam) were determined in the chick embryo. The substances were dissolved in propylene glycol and injected in the air chamber prior to incubation. Injection in the yolk sac on any day of development or in the air chamber after the first day was unsuitable for the assessment of an LD50. With the exception of nabam, the dithiocarbamates were extremely toxic for the early chick embryo. Cysteine injected simultaneously in the air chamber protected the embryos from the toxic effect of thiram or ziram but not from the action of triaram. It is suggested that the former two dithiocarbamates are reduced by cysteine to less toxic compounds.In recent years more attention has been paid to the methodology of testing the toxicity of chemical substances in the developing chick. Ridgway and Karnofsky (1952) studied the effect of various metals on the chick embryo. They injected these substances in the yolk on the day 4 or 8 or on the chorioallantois on day 8 and discovered that the place and time of injection were important factors in determining the responsiveness of the embryo. A difference in sensitivity depending on the site of injection was also found by Verrett et al. (1964), who showed that the toxicity of aflatoxin when injected into the air chamber was twice as high as when injected into the yolk.Other comprehensive studies on the injection of chemicals into eggs were performed by McLaughlin and co-workers (McLaughlin et al

An Early–Life Stage Alternative Testing Strategy for Assessing the Impacts of Environmental Chemicals in Birds

“…The relationship between injection location and toxicity is unclear and inconsistent among chemicals. For example, 2,3,7,8‐tetrachloro‐ p ‐dibenzodioxin administered through the yolk in chicken eggs was more toxic relative to an air cell injection (LD50 = 122 vs 297 pg/g; Henshel et al ), but thiram exposure through the air cell was more toxic than through the yolk (LD50 = 1.1 vs 18 µg; Gebhardt and van Logten ). These results reiterate the importance of a standardized method for egg injections.…”

“…Eggs are most commonly injected prior to incubation (ED0) or on ED3 to 4. Gebhardt and Van Logten (1968) showed that the early embryo was sensitive to mechanical manipulations into the yolk; needle insertion alone caused 55% mortality on ED0 but only 5% mortality when performed on ED4. Air cell injection, on the other hand, had minimal effects on survival from ED0 to 4 (Gebhardt and Van Logten 1968).…”

The relative sensitivity of chicken embryos to yolk‐ or air‐cell‐injected 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin

“…Our observation that the chick embryos were more sensitive to TCDD injected into the yolk rather than into the air cell is especially interesting in view of conclusions about the relative behavior and toxicity of yolk‐ versus air‐cell‐injected compounds made by Gebhardt and van Logten [22] and Gebhardt [23] and Walker [24]. Walker injected a number of dye‐labeled chemicals into the yolks of fertile chicken eggs and observed the behavior of the chemicals in the yolks.…”

“…Gebhardt and van Logten [22] applied thiram, a dithiocar‐bamate, dissolved in propylene glycol into the yolk and into the air cell of embryonic day one chicks. He reported that for these toxicants, the embryos were more sensitive to the thiram injected into the air cell (LD50 =1.1 μg), rather than into the yolk (LD50 = 18 μg).…”

Neurotoxic effect of the dithiocarbamate tecoram on the chick embryo

“…In addition to the yolk sac, tecoram was also injected into the air chamber, as it was shown by Gebhardt and van Logten (1968), that certain dithiocarbamates were more effective, at least in the very young chick embryo, when this method of inoculation was used.…”