Figure 10. Digitally colored TEM image showing the ultrastructural changes in the interstitial tissues of young and aged mice. (A) In the control group, the Leydig cells (violet) contained lipid droplets (arrowhead), sER, lysosomes (L). Telocytes (TCs, red) contained secretory vesicles (V) and mitochondria (M). (B) In the young mutant mice, the Leydig cells (violet) characterized by an increase the number of lipid droplets (arrowhead) and lysosomes (arrows). (C) In aged mice, Leydig cell showed few mitochondria (M) and pyknotic nucleus (N). Note, the presence of TC (red) that contained many secretory vesicles (arrowhead) and the special type of blood vessel that characterized by the presence of large glomus cells (G). (D, E) Leydig cell (violet) contained many lipid droplets (arrowheads), and residual bodies (arrows). The glomus cell (G) was characterized by a high number of mitochondria (asterisk). The telocytes (red, TC) extended their telopodes (Tp) to establish close contact with Leydig cells, myoid cells (MC) and glomus cell (G). (F, G) In melatonin group, Leydig cells (violet) showed many mitochondria (M), secretory granules (arrows), rER, well-developed microvilli (arrowheads) that extended to the blood capillaries (BC). TCs (red) showed mitochondria (M), secretory vesicles (arrow) and rER.