Mark A. KuKuruga said: >Thomas,What are you taking about? What fo you mean by "measure?" Do you >dispute >the relative change that occurs in a quiescent population upon stimulation to >proliferate, as detected by AO? Have you looked at the supporting >literature that >validates this phenomenon? Have you done these experiments, and observed >these >changes first hand? I think it's time you showed us some "independent >assays and >data" to support your opinion that AO does not do what that extensive body of >literature suggests. >MAK. On the contrary, the lack of data from assays independent of flow cytometry in the "extensive body of literature" is one of the problems I was attempting to point out. But even if AO can quantitatively differentiate RNA from DNA in intact cells how is this a reliable measure of G0? The AO assay relies on G0 cells having low RNA content relative to G1 cells. What about fully differentiated cells? For example, a terminally differentiated epithelial cell in a secretory gland, let's say a mammary gland of an actively lactating new mother. These cells have large quantities of mRNA and rRNA for producing proteins unrelated to G1 entry or DNA synthesis. Smaller, cycling cells in the basal layer could have less total RNA than the differentiated secretory cells. The bigger problem is defining G0 cells. It's like Time; everybody knows what it is but can't define it. Consequently, people use the term G0 to describe any cells not in log-phase growth. The current habit of referring to "resting" lymphocytes, serum-starved cell lines and terminally differentiated cells in-vivo as being in G0 implies these cells are in the same, defined state of growth and growth potential. We need definitions based on molecular markers known to be involved in cell cycle regulation. td Nothing really worth having ever comes without a fight you've got to kick at the darkness 'til it bleeds daylight - Bruce Cockburn -- ============================================================================== Thomas M. Delohery |Internet: t-delohery@ski.mskcc.org Supervisor, Flow Cytometry Core Facility | Phone: (212) 639-8729 Memorial Sloan-Kettering Cancer Center | Fax: (917) 432-2333 1275 York Ave. Box 98 | New York, NY 10021 | ==============================================================================
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