Quantitative methods of measuring the sensitivity of the mouse sperm morphology assay

In this study murine sperm were subjected to graded doses of X irradiation (0 to 120 rad) to determine whether quantitative measurements made on enlarged photographs of the sperm heads are related to radiation dose. We found that the Mahalanobis distance statistic, when used to measure distance in a multivariate space from a control group of measurements, could be used to classify sperm as normal or abnormal. The percent classified as abnormal by this method was found to be linearly related to dose. The results suggest that sensitivity of the murine sperm assay can be improved by selecting an optimal set of measurements. This improvement can reduce the doubling dose from approximately 70 rad to 10 to 15 rad while keeping the percentage of abnormal sperm in control mice at 3%, equal to the current visual method.