Comparative ultrastrucure of ventricular myocytes of dog and camel

ABSTRACT

The ultrastructure of dog and camel ventricular cardiocytes was compared with respect to the organization of the contractile material, the structure of the organelles and the cell junctions. The morphological changes during prolonged work, the myofilaments were associated in a single coherent bundle extending the fiber cross- section in the camel while in dog changes in the myofibrillar b and ing pattern were observed. The abundant mitochondria confirmed in clefts among the myofilaments often have slender prolongations in the camel possibly related to changes in their number or their distribution as energy source within the contractile mass. In the camel myocyte, the large T tubules that penetrate ventricular myocytes at successive I b and s are arranged in rows and are lined with a layer of protein- polysaccharide. Longitudinal connections between T tubules are common. The simple plexiform sarcoplasmic reticulum is continuous across the Z lines, and no circumferential "Z tubules" were identified. Specialized contacts between the reticulum and the sarcolemma are established on the T tubules and the cell periphery via subsarcolemmal saccules or cisterns. At cell junctions, a gap can be demonstrated between the apposed membranes