PubMed · 9181248
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R Stiefel. Clinical engineering cannot do benchmarking.. https://pubmed.ncbi.nlm.nih.gov/9181248/
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Solar UVB initiates skin cancer mainly by generating highly premutagenic cyclobutane pyrimidine dimers (CPDs) and subsequent mutations in critical growth control genes. It is universally presumed that the upper epidermis in human skin blocks a significant portion of the incident UVB, thereby protecting the cancer-prone basal layer from CPD formation. Using two sensitive techniques for measuring CPD in cellular DNA, we confirmed that the multilayered organization of engineered human skin efficiently shields the basal layer against 254-nm UVC (which is not present in terrestrial sunlight) but, very unexpectedly, provides virtually no protection against environmentally relevant UVB. This underscores the importance of regular sunscreen use, which, in light of our data, may constitute a considerably more important first line of defense against photocarcinogenesis than previously believed.
The relationship between cell function and surface marker expression is a subject of active investigation in biology and medicine. These investigations require separating cells of a homogeneous subset into multiple fractions of varying marker expression. We have developed a novel cell sorter, the dipole magnet flow sorter (DMFS), which separates selected T lymphocyte subpopulations, targeted by immunomagnetic colloid, into multiple fractions according to cell surface marker expression, as determined by flow cytometry. A narrow stream of cells is introduced into a sheath of carrier fluid in a rectangular channel while subjected to a perpendicular magnetic force. The special design of the pole pieces ensures a constant magnetic force acting on the magnetically labeled cells in the separation area. Cells are spread across the flow in relation to their magnetophoretic mobility. Separation is achieved by control of the positions of the effluent stream boundaries, which separate fluid volumes with cells of different magnetophoretic mobility. CD4 and CD8 T lymphocytes labeled with primary antibody-fluorescein isothiocyanate (FITC) conjugate and anti-FITC-magnetic colloid are the chosen cell systems. Flow cytometry analysis shows that, for CD4 cells, a three-fold increase in total marker number per cell is observed when comparing the highest to the lowest fluorescence fractions. Similarly, a four-fold increase in total marker number is observed for CD8 cells. We also observed the separation of two dissimilar cell types that differed in expression of the CD4 marker, monocytes and T helper lymphocytes. We believe that this type of separation is applicable to any cells in suspension for which a suitable antibody exists and, due to the comparatively gentle nature of the process, is particularly suitable for the sorting of fragile cells.
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