Abstract
Laser irradiated mitochondria in rat myocardial cells were analysed cytochemically for succinic dehydrogenase and with the electron microscope for ultrastructure. The least severe lesion type did not alter the SDH activity of the mitochondria. The major ultrastructural alteration observed was an electron-dense region corresponding to a phase-dark spot in the light micrographs. This lesion appeared to be restricted in depth and width within the irradiated structure. The damage was primarily localized to the intercristae matrix. The cristae appeared normal.
Highlights
In previous reports in this series we described various alterations in morphology and contractility of cultured myocardial cells following selective argon laser microirradiation (0.5-l pm spot) of single mitochondria [I, 3, 41
SDH analysis of the cell demonstrates that even though the irradiation resulted in a substantial light microscope morphological effect to the mitochondria, the enzyme activity was not affected (Plate 3)
The most frequently observed ultrastructural change was the production of an electron dense area in a localized region of the irradiated organelle
Summary
In previous reports in this series we described various alterations in morphology and contractility of cultured myocardial cells following selective argon laser microirradiation (0.5-l pm spot) of single mitochondria [I, 3, 41. It was demonstrated that three different types of light-microscope lesions could be produced in the mitochondria, and that these lesions could be correlated with the amount of laser energy and/or the optical density of the target mitochondrion [3]. The “least severe” lesions appeared as a general phase “paling” or blanching of the entire irradiated structure, often with a small phase-dark spot at the center. The “moderate” lesion-type resembled a hole with a dark border, and the “severe” lesion appeared to be destruction of the entire organelle with only a vacuole remaining [I]. Specific changes in the contractile state of the cell were associated with the moderate and severe lesions. These responses varied from a slight increase in beat rate to the precipitation of a violent, uncoordinated contractile state termed
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