ABSTRACT
Current cell sorting machines do not preserve the individual identity of processed cells; after analysis, the cells are assigned to a subpopulation where they are pooled with other similar cells. This paper reports progress on a system that sorts cells individually to precise locations on a microscope slide and preserves them for further observation with a light microscope while recording flow measurement data for each cell. Various electronic and mechanical modifications to an existing sorting machine are described that increase drop placement accuracy and permit individual cell sorting.
Subject(s)
Cytological Techniques , Lymphocytes/cytology , Animals , Cell Separation , Cytological Techniques/instrumentation , Humans , Mice , Microscopy, Fluorescence , Microspheres , Models, BiologicalABSTRACT
Flattened cells, such as red blood cells, epithelial cells, and sperm of many species, cause problems for fluorescence-activated cell analysis and sorting machines because the flow systems of such devices are unable to control the orientation of these cells as they flow past the detectors. For this reason, the fluorescence or scattered light measurements for identical cells may vary greatly. A flow geometry is here described that orients flat cells in a coaxial flow system so that each cell presents the same aspect to the observation device. A wedge-shaped exit on the sample injection tube in a coaxial flow system is sufficient to produce the desired orientation effect when used with low sample flow rates. Data is presented showing the effect of orientation of fixed chicken erythrocytes on histograms of small forward-angle light-scattering measurements.
Subject(s)
Cytological Techniques , Fluorescence , Light , Mathematics , Rheology , Scattering, RadiationABSTRACT
Today, one out of five practicing physicians in the U.S. is a graduate of a foreign medical school. The sixfold growth in their number over the past two decades results from national policy; but the place and conditions of practice have been controlled by state governments. The several states have used their jurisdiction over licensure in ways that have often been unfair and irrational. Recent trends toward uniform standards, however, may lead to more equitable assurance of professional competence, and to interstate mobility related to local and national needs.
Subject(s)
Foreign Medical Graduates , Licensure, Medical , Certification , Educational Measurement , Emigration and Immigration/history , Foreign Medical Graduates/history , History, 20th Century , Humans , Licensure, Medical/history , United StatesABSTRACT
Measurement of the light scattered by biological cells as a function of scattering angle provides information that can be correlated with cell type. Two flow systems that provide multiangle scattering data from cells have been constructed and tested. The first utilizes two narrow-aperture detectors positioned at different angles; the second utilizes the motion of the cell to generate complete scatter patterns of individual cells over a 67 degrees range of scattering angle.
