Fetal aberrations occurring at a greater incidence in the test than in the control groups make it difficult to estimate human safety from animal data. This is due to lack of agreement on the teratologic significance of aberrations and our ignorance of mechanisms governing their appearance. Quite often the aberrations are transitory and tend to disappear on further development. A requirement for specially designed studies exists in order to determine the true nature of aberrations and their effects on postnatal development. Only then will it be possible to establish a scientific basis for using animal data to estimate human safety. This review will illustrate the need with examples: changes in the ossification of sternum (which may be retarded by factors remotely related to a test chemical), presence of hydronephrosis (which cannot be diagnosed accurately owing to extreme physiological variations in size of the renal pelvis) and presence of supernumerary ribs (a fetal variation which has been inconsistently interpreted). Relatively little is known about the significance of bent or wavy ribs and undescended testes. Future research should be directed towards determining the teratologic significance, if any, of these and other embryological deviations occurring in experimental animals.

Abnormalities, Drug-Induced↗

PubMedDate not supplied

Cholinesterases and motor end-plates in developing duck skeletal muscle.

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Animals↗

PubMedDate not supplied

Evaluation of dimethoate (Cygon 4E) for teratogenic activity in the cat.

A commercial formulation (Cygon 4E), containing 47.3 percent dimethoate and 52.7 percent of unknown ingredients, was administered orally in single daily doses of time-mated cats between the 14th and 22nd day of pregnancy. The cats were necropsied on the 43rd day of pregnancy. Fetal values for survival, body weight, and skeletal and visceral anomalies were obtained following conventional methods. The highest dose, 12 mg/kg, was associated with polydactyl in eight of the 39 fetuses, whereas the 6 and 3 mg/kg doses produced no evidence of teratogenicity or embryotoxicity.

Abnormalities, Drug-Induced↗