The study by Johnson, Walsh, and Chen demonstrates the use of rhodamine 123 as a specific probe for localizing mitochondria in living cells. Rhodamine 123, a laser dye, is shown to be highly effective in staining mitochondria due to its selectivity and fluorescent properties, providing better detectability compared to conventional fluorescence microscopy techniques. The dye stains mitochondria directly without passing through endocytic vesicles or lysosomes, and it does not cause significant cytotoxic effects. The authors tested various concentrations and conditions to optimize staining, finding that 10 μg/ml was sufficient and non-toxic. Rhodamine 123 was successfully used to visualize mitochondria in a variety of cell types, including gerbil fibroma cells, rat cardiac muscle cells, and human erythrocytes. The dye's ability to stain mitochondria was confirmed by comparing fluorescent images with phase-contrast micrographs. Additionally, the authors observed changes in mitochondrial distribution and shape following transformation by Bous sarcoma virus and treatment with colchicine, highlighting the utility of rhodamine 123 in studying these processes. The molecular basis for the specific interaction between rhodamine 123 and mitochondria remains to be determined, but the positive charge of the dye at physiological pH suggests a potential role in binding to the mitochondrial membrane.The study by Johnson, Walsh, and Chen demonstrates the use of rhodamine 123 as a specific probe for localizing mitochondria in living cells. Rhodamine 123, a laser dye, is shown to be highly effective in staining mitochondria due to its selectivity and fluorescent properties, providing better detectability compared to conventional fluorescence microscopy techniques. The dye stains mitochondria directly without passing through endocytic vesicles or lysosomes, and it does not cause significant cytotoxic effects. The authors tested various concentrations and conditions to optimize staining, finding that 10 μg/ml was sufficient and non-toxic. Rhodamine 123 was successfully used to visualize mitochondria in a variety of cell types, including gerbil fibroma cells, rat cardiac muscle cells, and human erythrocytes. The dye's ability to stain mitochondria was confirmed by comparing fluorescent images with phase-contrast micrographs. Additionally, the authors observed changes in mitochondrial distribution and shape following transformation by Bous sarcoma virus and treatment with colchicine, highlighting the utility of rhodamine 123 in studying these processes. The molecular basis for the specific interaction between rhodamine 123 and mitochondria remains to be determined, but the positive charge of the dye at physiological pH suggests a potential role in binding to the mitochondrial membrane.