Two‐parameter data acquisition system for rapid slit‐scan analysis of mammalian chromosomes

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Abstract
A data acquisition system is described for recording two independent signals simultaneously from a laser‐based flow cytometer for rapid slit‐scan chromosome analysis. High‐aperture microscope optics allow recording of fluorescence distributions along the longest axis of metaphase chromosomes with a spatial resolution better than 1 μm. Fluorescence and small angle forward light scatter as well as dual‐wavelength fluorescence signals from Indian muntjac chromosomes stained with propidium iodide (PI) or acridine orange (AO) have been recorded simultaneously. While maintaining the multi‐user operation of the computer, photomultiplier signals are digitized at a rate of 400 signals per second, stored temporarily in high‐speed cache memories, and transferred subsequently to a minicomputer for further storage. Extensive software packages for data acquisition, analysis, and display of the results are described. Data acquisition is generally done in list mode, allowing complete reconstruction of individual signals (profiles) at any time. The distribution of stained constituents along the chromosomes can be displayed. Furthermore, histograms of various parameters of the input signals may be generated.