FIG. 5.

Ultrastructural appearance of Leydig cells in Bclw-mutants. A) At 34 days of age, Leydig cells (darker cells in the lower left) appeared normal. Often, a mononuclear infiltrate was seen in the interstitium (lighter cells in the upper right). A macrophage is also indicated (Ma). ×4500. B) Beginning around 8 mo of age, Leydig cells in mutants were observed undergoing apoptosis, as evidenced by the fragmented nuclei (n) and accumulation of associated peripheral heterochromatin (arrowheads). The Leydig cell could be recognized as such by the abundant smooth endoplasmic reticulum and mitochondria possessing tubular cristae and by comparison with relatively normal-appearing, adjacent Leydig cells (top right). ×7200. C) Phagocytosis of degenerating Leydig cell (asterisk) by an interstitial macrophage (M). The phagocytosed cell appears dense and contains mitochondria characteristic of those found in Leydig cells. ×14 000.