At 08:16 AM 12/20/99 -0600, I wrote: > ><musing quietly> >If your hardware supports it integral versus peak is much more useful than >width v. area. Wide beams don't help either (grateful for his 5 micron >beam). Saving these options sometimes an extra marker (appropriate cyclins) >can help. (Putting hornets back in nest - returning worms to can). Lots of mail on this one. Sorry I should have been more specific. Peak signals can be very helpful in doublet discrimination but only if you have narrow beam excitation optics. IMHO adequate DNA measurements can only be made if the cross section of your interogating beam is substantially narrower than the diameter of the objects that you are measuring. (Waiting for flames.) Under these conditions 2 G1 cells stuck together will have a very similar integral (yes - mostly the same as area) signal as a true single G2/M cell. The peak signal from a G2/M cell will however be significantly greater than that from a G1 cell and from the sequential peak signals from a G1G1 doublet. But, the latter is only visible if the exciting beam is narrow. In comparisons between area/width and integral (area)/peak discriminating ability on an instrument with 5 micron excitation optics the integral peak analysis gave the best discrimination. It is even possible to recognize doublets that are not progressing linearly through the beam due to turbulence or other factors. How anyone manages to discriminate doublets from true G2 cells with a 40 micron beam, or nuclei with a 15-20 micron beam is beyond me. (tactfully). (Pondering the likelihood that there is a greater proportion of tetraploid tumors in the literature than in reality.) Happy Christmas/holidays and New Year to all! Nick Nicholas Terry, M.A., Ph.D., Experimental Radiation Oncology - 066, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, Texas 77030. 'Phone: 713-792-3424, 'Fax: 713-794-5369. http://drad52.mdacc.tmc.edu. ntflow@odin.mdacc.tmc.edu. Nicholas Terry, M.A., Ph.D., Experimental Radiation Oncology - 066, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, Texas 77030. 'Phone: 713-792-3424, 'Fax: 713-794-5369. http://drad52.mdacc.tmc.edu. ntflow@odin.mdacc.tmc.edu.
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