Ultrastructural cytochemistry of atrial muscle cells. V. Characterization of specific granules in the human left atrium

The carbohydrate content of specific granules in human left atrial appendages was assessed by cytochemical methods. The specific granules were found to be argentaphobic when ultrathin sections of Araldite-embedded atrial appendages were stained according to the periodic acid-thiocarbohydrazide-silver proteinate technique of Thiery. The entire core of these granules was moderately positive after ultrathin sections of glutaraldehyde-fixed, glycol methacrylateembedded auricles were stained with phosphotungstic acid at a low pH. An analogous reaction was shown by the cell coat, residual bodies (C-granules), lysosomes, multivesicular bodies (mvb), and Z-disks as well as by a small portion of the Golgi complex. Cardiocytes of human left atrial appendages contain mvb with a dense core similar to those already noted in hypothalamic neurosecretory cells, mammotrophs, and adrenal medullary cells and are thought to be crinophagic.