SELECTIVE ISOLATION OF HUMAN X-BEARING SPERM BY DIFFERENTIAL VELOCITY SEDIMENTATION IN PERCOLL DENSITY GRADIENTS

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Abstract
Examinations of [human] sperm sedimentation in Percoll density gradients suggested that the sedimentation velocity of X-bearing sperm was faster than that of Y-bearing sperm, despite the fact that the apparent densities of the 2 types of cells, obtained by equilibrium sedimentation, were similar. From this, it seems difficult to obtain both types of cells simultaneously by only 1 procedure. Assuming that the ease with which the cells pass through the density interfaces influences their sedimentation velocity, a discontinuous density gradient with 12 steps (25-80% percoll) was adopted for the selective isolation of X-bearing sperm. Among the conditions examined, centrifugation at 250 g for 30 min gave the optimum result: 23.3 .+-. 6.3% of sperm was recovered in the sediment, of which the percentage of Y-bearing sperm was only 6.4 .+-. 1.8%; thus the purity of X-bearing sperm was .apprx. 94%. Almost all the sperm in the sediment were active and forward motile.