Real-time dynamics of label-free single mast cell granules revealed by differential interference contrast microscopy

We demonstrate the capability of differential interference contrast (DIC) microscopy as a simple and useful tool for studying cellular events without fluorescence labeling. By coupling an advanced DIC microscope to a computer-controlled motorized vertical stage and a high-speed, high-resolution CCD camera, real-time three-dimensional monitoring is possible in a high-throughput manner. The performance among three modes of microscopy, bright-field, dark-field and DIC, in terms of horizontal resolving power and vertical sectioning was investigated. As a model, exocytosis of rat peritoneal mast cells was recorded on the subsecond time scale. Three-dimensional tracking of granules during degranulation was achieved and granule-granule fusion before plasma membrane fusion was recorded.