[Ultrastructure of small granular cells in cardiac ganglia]

Ultrastructure of small granular cells (SG cells) has been studied in intramural ganglia of the white rat and guinea-pig hearts. No ultrastructural organizational differences have been revealed in SG-cells of these two species. Large granular vesicles in SG-cell cytoplasm make their peculiar sign, three main types among them differing by their form and structure can be mentioned. In SG-cells of the first type, round vesicles 100 nm in the diameter with a central electronopaque core predominate. In SG-cells of the second type, oval vesicles 100--200 nm in the diameter with an eccentric core occur more often. In both cell types, a small amount of round vesicles filled with electronopaque material of moderate density is present. A glomerule consisting of intertangled filaments with large granular vesicles and single mitochondria is described for the first time. Its diameter is about 2 mkm, its preferable position--near the nucleus. On the SG-cell bodies and processes there are synapses formed by terminals with small light vesicles. SG-cell processes form synaptic contacts on neuronal processes.