UC Irvine

A correlation is made between individual laser microbeam lesions (0.25-1 μm in diameter) in single mitochondria of myocardial cells and alterations in cellular contractility. A moderate lesion is described ultrastructurally that has three concentric zones of damage. In addition, the outer mitochondrial membrane is broken, and the intercristae matrix outside the lesion may be affected. Two kinds of weak lesions are described. No concentric zones of damage are observed, and the cristae and mitochondrial membranes outside the lesion area are not grossly affected. All cells that exhibited an alteration in contractile patterns had moderate lesions. A correlation between laser energy density and type of lesion was observed. The nature of the lesions and explanations of the contractile responses are discussed. © 1976.