Experimental production of "septa" and apparent subdivision of muscle mitochondria

The rapid formation (in less than 45 min) of internal septa and the apparent subdivision in situ of mitochondria for cardiac and skeletal muscle are described following a variety of experimental treatments. For example, the ionophore A23187, caffeine, DNP, ruthenium red, and the insecticide lindane have been applied to intact, glycerinated, and chemically skinned skeletal muscle fibers and to cardiac muscle strips from both amphibians and mammals. In some mitochondria, the two compartments are in the same configurations; in others they are different. The significance of these mitochondrial septa is discussed, and it is suggested that the findings are consistent with the hypothesis that a variety of experimental procedures can promote rapid mitochondrial division.