Figure 3.

Electron micrographs of control and infected islets 30 days postinfection. Correlation of histopathological studies of the pancreas with ultrastructural studies. Electron micrographs (EM) of T. cruzi-infected or uninfected islets were analyzed for changes in granule number or distribution. Representative images and the quantitative evaluations using ImageJ version 1.46 are shown. Granule numbers (A–D): The unique morphology of insulin granules, electron-dense core surrounded by a halo and membrane, remained unchanged in both normal (A and C) and infected mice (B and D). C and D are magnified from the insets (A and B, respectively). Secretory granule density per unit area was used as a measure of total insulin content and appeared minimally reduced with T. cruzi infection (EM, A and B; quantitation, G). Controls 3.98 ± 0.32 (SEM) (n = 8); infected 2.56 ± 0.45 (SEM) (n = 14). (P < 0.05). Granule distribution (E and F): Arrowheads pinpoint the plasma membrane. The cortical region was defined as a distance from the plasma membrane corresponding to 1 granule diameter (1 D), or ∼350 nmol/L (EM, E and F; quantitation, H). One granule diameter, 0.80 ± 0.16 (SEM), n = 14; infected 2.00 ± 0.18 (SEM), (n = 20); P < 0.05. Two granule diameters, control 1.46 ± 0.20 (SEM), n = 14; infected = 1.15 ± 0.15 (SEM) n = 20. Increased secretory granule association with the cortical region (ie, docked granule pool) is observed in infected β cells (EM, E and F; quantitation, H). Nests of parasites were observed in β-cells (I, white arrows, T. cruzi). Morphological appearance of insulin β-granules (I, black arrows) and glucagon containing α-granules (I, arrowheads) seemed normal.