['To determine whether testosterone-induced intra-testicular testosterone withdrawal and therefore spermatogenic impairment is associated with looser arrangement of spermatogenic cells in rats.', 'Adult male SD rats received intramuscular injection of testosterone undecanoate at 19 mg/(kg x 15 d) for 130 days, and then testicular tissue blocks were obtained for the preparation of methacrylate resin-embedded sections and observation of the changes in testicular histology.', 'Apart from such changes as impaired spermiogenesis and spermiation, apparently looser arrangement of spermatogenic cells was seen in 11.5% of the seminiferous tubule profiles, with radial cracks (empty spaces) running towards the tubule lumen being formed between lines, bundles or groups of spermatogenic cells (mainly spermatids and spermatocytes).'] Is [ Testosterone-induced spermatogenic impairment associated with looser arrangement of spermatogenic cells in rats ]?