Figure 2. Histological pattern of spermatogenesis in young and aged mice stained with HE except for C, G, J are stained with Crossmon's trichrome. (A, B) Seminiferous tubules of the control group characterized by normal spermatogenesis (S). Note, a narrow interstitium contained interstitial cells (arrowhead). (C) Seminiferous tubules in young mutant mice characterized by pyknosis (asterisk) in the spermatogenic epithelium with spermatids aggregation (arrowhead). (D) In aged mice, a mosaic pattern of seminiferous tubules ranged from tubules with complete, reduced spermatogenesis to degenerated tubules. (E) Clusters of vacuoles and absence of mitotic cells among the epithelium of seminiferous tubules with apparent degeneration, and absence of sperms in many tubules of aged mice (arrowhead). (F) The lumen of seminiferous tubules contained spermatids and spermatocytes (arrowhead). (G) The volume of interstitial tissue increased with an abundance of collagen fibers (arrowhead). Note sclerosed tubule (asterisk) that showed loss of spermatids. (H–J) In melatonin group, enhanced spermatogenesis, presence of many sperms (asterisk) and normal interstitial tissues (arrowhead) demonstrated.