From: Bob Leif To: cyto-inbox You are absolutely correct! The technology to perform electro-optical analysis of cells has been developed. In fact, it is in the high-end Coulter hematology analyzers. The two Coulter impedance parameters, AC (opacity) and DC (volume)are extremely useful parameters. I might add that even in the case of light-scatter, the commercial instruments should be set to 45 rather than 90 degrees. Unfortunately, I have learned that solving technical problems is certainly more fun and usually much easier than solving people problems. In any case, my monolithic spherical transducers and other innovations are now off-patent. If anyone is interested in improving the bread of flow cytometers and digital microscopes, I suggest attending the SPIE BiOS meeting (www.spie.org, 20-26 January, 2001) including the session on Advanced Techniques in Analytical Cytology (Thursday 25 January, 2001), which I have the privilege to chair. If there is any interest in a means to implement or encourage the development of modern analytical cytology instrumentation, I will gladly organize a bull-session at the end of the meeting. I might note that I have been honored to have as CoChairs individuals, who have made major contributions to this field. 1. Orifice Inside Optical Elements, Coulter Electronics, R. C. Leif, 4,348,107 (1982). 2. Monitoring of a Detection Zone Utilizing Zero Order Radiation From a Concave Reflecting Grating, Coulter Electronics, R. C. Leif, 4,351.611 (1982). 3. R. C. Leif, R. A. Thomas, T. A. Yopp, B. D. Watson, V. R. Guarino D. H. K. Hindman, N. Lefkove and L. M. Vallarino; “Development of Instrumentation and Fluorochromes for Automated Multiparameter Analysis of Cells”. Clin. Chem. 23, 1492-1498 (1977). 4. R. C. Leif, S. Schwartz, C. M. Rodriguez, L. Pell-Fernandez, M. Groves, S. B. Leif, M. Cayer, H. Crews; “Two Dimensional Impedance Studies of BSA Buoyant Density Separated Human Erythrocytes”. Cytometry 6 pp. 13-21 (1985). 5. R. C. Leif, M. L. Cayer, W. Dailey, T. Stribling, and K. Gordon, “The use of a Spherical Multiparameter Transducer for Flow Cytometry”. Cytometry 20, pp 185-190 (1995). -----Original Message----- From: James Weaver 301-594-5879 FAX 301-594-3037 [mailto:WEAVER@CDER.FDA.GOV] Sent: Thursday, October 12, 2000 10:55 AM To: cyto-inbox Subject: Re: Cell Volume Revisited Sensitivity: Confidential Despite what is written in various places, flow cytometry can only be used for size measurement on homogenous particles such as plastic beads. It does not work for particles with complex optics such as cells. With beads, increasing size leads to increased light scatter. With cells the situation is quite different, a treatment that resulted in a 30% change in cell volume caused a light scatter decrease in a lymphoid cell line and no change in light scatter from NIH3T3 cells. Coulter volume measurements are regarded as the gold standard of cell volume measurements. I have done cell volume measurements on nucleated cells in the past with no problems. If you are not seeing changes in cell volume, than either the treatment is not causing a change or the instrument needs repair. -Jim Weaver ************************************************* * * * James L. Weaver Ph.D. * * Division of Applied Pharmacology Research * * Office of Testing & Research * * CDER MOD-1, FDA * * 8301 Muirkirk Rd, Laurel MD 20708 * * * * Phone: 301-594-5879 * * Fax: 301-594-3037 * * Email:WEAVER@CDER.FDA.GOV * * * *************************************************
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