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I have recently been involved in a project where direct comparisons were made
between changes in FSC and changes in cell volume as measured by Coulter volume.
My (in preparation) data involved changes in cell volume induced by hypotonic
stress. In lymphoid cell lines the FSC signal DECREASES in response to hypotonic
stress. Coulter volume measurements show that cell volume INCREASES. The
explanation is that lymphoid cells have a very heavily 'digitated' cell surface,
when the cells swell the rough surface becomes smoother as the 'fingers' become
shorter and is therefore less effective at low angle light scatter. We also
looked at two non-lymphoid cell lines and changes in cell volume of 20-30% were
not detectable by FSC. The relationship between FSC and particle size holds well
for beads but is not reliable for such optically complex partcles as cells.
I realize that this does not help answer the original question but FSC
is not a reliable indicator of cell size. If the cells are larger than the beam
than perhaps a revised focusing optic with a wider beam would allow standard
methods to be used. Good Luck.
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James L. Weaver Email: WEAVER@FDACD.CDER.FDA.GOV
Molecular Pharmacology Phone: 301-594-5879
Division of Research & Testing FAX: 301-594-3037
ORR, CDER, Food & Drug Admin. Voice: 'Hey you'
Laurel, MD
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