Figure 4: Photomicrographs of seminiferous tubules of animals from CMT/ B12G and B12G, at stages I-VI, stained by H.E. (a - d) and subjected to TUNEL method (e and f). In 4a and 4d , numerous spermatogonia (Sg) and spermatocytes (white arrowheads) are observed. Some spermatogonia are in mitosis (4b ; arrows). In 4c , types A (white arrows) and In/B (black arrowheads) spermatogonia and spermatocytes (white arrowheads). In 4e and 4f , TUNEL-positive spermatogonia and spermatocytes (arrows). Bars: 30 μm (4a); 15 μm (4d); 6 μm (b , c , e , f). CMT/B12G: cimetidine/vitamin B12 group; B12G: vitamin B12 group; TUNEL: terminal deoxynucleotidyl-transferase mediated dUTP nick end labeling.