Measuring regional blood flow by fluorescence or absorbance of dissolved microspheres isolated from tissue homogenate is a labor intensive procedure. We have developed a fluorescent microsphere counting system that directly counts individual microspheres in tissue hydrolysates. The instrument uses an argon-ion laser to induce fluorescence in microspheres as they pass through a flow cell. Photomultipliers (with appropriate cut off filters) at right angles to the laser excitation permit simultaneous counting of more than one color of microsphere in each solution. Instrument characteristics such as fluorescence intensity of individual microspheres, instrument signal-to-noise and microsphere color discrimination are discussed. Results of microsphere counts from solutions and tissue hydrolysates are presented. The instrument design is amenable to development of full automation for counting microspheres in tissue hydrolysates.
Research supported by grant HL53880-01 from the National Institutes of Health.
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