A computer electron microscope plotter for mapping spatial distributions in biological tissues.

We have designed a computer-based electron microscope plotting system which maps the locations of organelles in tissue specimens and analyzes their distribution. The system includes: (1) two optical incremental shaft encoders which translate stage drive rotation to electrical pulses; (2) a Display/Control unit used to convert encoder pulses to binary code for computer input; (3) two 16-bit parallel interfaces for transferring data to the computer; (4) a Hewlett-Packard 9845T microcomputer, used to control data input and to store, graph, and analyze the plots. The software for the plotter is written in enhanced BASIC. The plotter system is driven by 4 programs called Trace, Plot, Analyze, and Density. The Trace program "draws" an outline of the edges of the tissue. The Plot program maps the positions of profiles within the tissue. The Analyze program compares trace and plot data and calculates the depth and medial-lateral distance of each plotted profile from the surfaces of the tissue. The Density program sorts and counts profile types, measures surface areas, and calculates profile densities. Commercial statistical software is used to analyze the data. Our laboratory uses the system to map the spatial distribution of synapses and neurons in the central nervous system. The plotting system will also be of value in other areas of neurobiology research.