Distinct vesicle populations are impacted by TNF. Electron micrographs of aldehyde-fixed, plastic-embedded jejunum from control and TNF-treated wild-type mice are shown. (A) Low magnification view of jejunal enterocytes showing the relationship between the intestinal lumen (L), microvillus brush border (Mv), tight junction (TJ), adherens junction (AJ), and desmosomes (D). Note the exclusion of mitochondria (M) from the most apical cytoplasm by the dense perijunctional actomyosin ring (PAMR). Bar, 2 µm. (B) Jejunal enterocytes of untreated mice (0 min) and mice sacrificed at the indicated times after TNF treatment were examined. Representative electron micrographs are shown. At least 1,000 µm² apical cytoplasm was examined per condition. Incremental fits show that the data can be modeled as the sum of four Gaussian distributions (solid lines). Mean diameters of 80, 125, 170, and 240 nm (dashed lines) are shown. The number of vesicles in each population (per 1,000 µm² cytoplasm) is indicated above each curve. The actual number of vesicles observed (per 1,000 µm² cytoplasm) is shown in the top right corner of each graph. Bar, 500 nm.