Quantitative analysis of fluorescent micrographs. A, fluorescent micrograph of rhodamine labeled AChRs at the meridian of the cell, showing six aggregates labeled 1–6. For each aggregate there is an associated nearest neighbor distance – the lesser of the distances to its two flanking neighbors. Aggregates #1 and #2 happen to have the same nearest neighbor distance, indicated by the white arc. B, the same cell as in A overlain to illustrate sector analysis. The software identifies the cell perimeter and represents it as a series of 256 sectors, starting at the left and proceeding counter-clockwise. In B every fourth sector is marked in white to illustrate its size and position. C, plots of sequential sector analysis. Raw Data is simply a plot of sector intensity vs. position in degrees, where the arrows indicate the corresponding aggregates identified in A. The data are processed to produce the High Frequency components, which can be thought of as the original data with the Low Frequency (gradually changing) components removed. A threshold is applied to the high frequency components (dashed line) to identify the Above Threshold aggregates, where again the arrows indicate aggregates corresponding to A.