Changes in mammalian sperm morphology after X-ray and chemical exposures

Sperm head morphology in mammals provides a unique approach to quantiating the effects of environmental agents on the germ cells. In unperturbed male mice, the sperm of each genotype can be reproducibly characterized by the shape of the head, the overall percent of sperm with head-shape abnormalities and the types of shape abnormalities seen. Genetic studies show that sperm shape is highly heritable, and that the fraction of abnormal sperm is controlled by a multitude of autosomal factors plus probably involvement of the sex chromosomes.--Exposure to ionizing radiation or certain chemical agents in vivo leads to dosage-dependent increase in the fraction of sperm with head-shape abnormalities. These results are documented in numerous mammalian species, including man. Evidence from mouse studies suggests that in general sperm shape is affected by those agents considered to be mutagenic. Since sperm samples are easily obtained and sperm morphology is rapidly quantitated, these observations suggest that sperm morphology in the mouse may be an applicable screen for environmental effects on germ cells. Changes in sperm are also seen in the offspring of male mice exposed to irradiation or a chemical alkylating agent. Preliminary evidence suggests that these changes represent heritable sperm shape abnormalities that can be further transmitted to subsequent generations.--The problems of determining the genetic implications of induced sperm abnormalities in exposed males are discussed. It is suggested that sperm morphology testing may have a direct application in man.