Figure 3.

Ultrastructure of IGMs in the mouse colon. Low magnification image of a myenteric ganglion (A) shows electron-dense IGM, displaying distinct morphology from enteric glial cells (EGC) and enteric neurons (EN). Dashed line labels EN with condensed cytoplasm. IGM (∗ marks IGM nucleus) shows active phagocytosis, with multiple pseudopodia around glial cell processes (A–A’, arrows). IGM is situated internal to the basement membrane of the enteric ganglion (A, blue line; A’, arrowheads). Periganglionic MyM exhibits a high nucleus/cytoplasm ratio, in contrast to IGM, which is characterized by hypertrophic cytoplasm, abundant mitochondria, extensive vacuolization, and well-developed Golgi apparatus (B, encircled area). A phagocytic vesicle is seen (B, asterisk). The ganglionic basement membrane is continuous and uninterrupted on external surface of IGM (B, arrowheads, with basement membrane located under dashed blue line). IGMs exhibit mostly empty vacuoles (C, dotted line; enlarged in D, where vacuoles are marked by asterisks), with lined-up ribosomes on their borders (E, arrows) and occasional membranous whorls are present (C, dashed line; enlarged in E, asterisk). Evidence of phagocytic activity is seen in IGM (C, inset and arrow), but autophagosomes are rarely seen (E, arrowhead). EGC, enteric glial cell; EN, enteric neuron.