Isopynic separation of ram spermatids in colloidal silica gradients

Abstract

By a two-step separation procedure, round and elongated spermatid populations were obtained with purities of 90–97% and an intermediate spermatid population with a purity of 85%. Cells of ram testes were first separated at unit gravity and 5 spermatid fractions were collected. They were centrifuged for 23 min at 4 000 g in linear and non-linear isotonic polymer-free colloidal silica gradients. Improvements were made in centrifuge tubes and in gradient collection for optimum results. Fractions were analysed using a phase contrast microscope for cell counting and determination of cell viability. True cell density was measured and found to increase during late spermiogenesis from 1.045 g/cm 3 for round spermatids to 1.152 g/cm 3 for testicular spermatozoa, thus reflecting an increase in the nuclear density.