Applications of computerized microscopic image analysis in infectious diseases.

Advances in computerized microscopy have resulted in image analysis systems that rapidly and precisely measure various aspects of cellular morphology and physiology. These systems-composed of a microscope and attached photomultiplier tube or camera, an image processor, and a computer-have been used to measure lysosomal enzymes, pH, and calcium within phagocytes; to detect viral nucleic acids in in situ hybridization preparations; and to quantitate rates of cellular movement. These experiments have shown that (1) the intracellular proliferation of virulent microorganisms is associated with reductions in acid phosphatase, beta-glucuronidase, and lysozyme activity; (2) virulent Toxoplasma gondii, Legionella pneumophila, and Nocardia asteroides inhibit phagosomal acidification; and (3) changes in intracellular calcium movement affect phagocytic function. These methods have also been used to detect the AIDS virus within cultured lymphocytes and to measure cellular chemotaxis and chemokinesis. Further advances in technology should produce improved microscopic image analysis systems with wider applications for the investigation of infectious diseases.