FIGURE 2.
(A) Histogram of intensity distribution on entire images of a cell in the initial (before addition of fMLF), intermediate (before tight contact formation), and late (after tight contact formation) stages of spreading. The inset shows the entire histogram, and the main image is a zoom in on the low intensity part. The total number of pixels remains constant from image to image; however, the distribution of intensity changes. The large peak at intermediate intensities in the inset corresponds to the intensity of the background since most of the pixels in the image have that intensity. When “tight contact” forms, pixels that were previously bright (or intermediate) become considerably darker, resulting in the appearance of a small peak at low intensities which is apparent in the main image. (B) A spreading cell; (from left to right) raw RICM image, average-image, width-image, binary image, and trinary image. See text for explanation.