The differential scattered light intensity patterns of spherical mammalian cells were measured with a new photometer which uses high-speed film as the light detector. The scattering objects, interphase and mitotic Chinese hamster ovary cells and HeLa cells, were modeled as (a) a coated sphere, accounting for nucleus and cytoplasm, and (b) a homogeneous sphere when no cellular nucleus was present. The refractive indices and size distribution of the cells were measured for an accurate comparison of the theoretical model with the light-scattering measurements. The light scattered beyond the forward direction is found to contain information about internal cellular morphology, provided the size distribution of the cells is not too broad.

A high-speed flow system for quantitative determination of fluoresence of cells containing fluorochrome has been developed. Feulgen-DNA distributions in populations of tissue culture cells and human leukocytes havebeen measured at a rate of 10(4) to 10(5) cells per minute and compare well with results of other independent methods.

A new flow-system instrument for quantitative analysis and sorting of microscopic particles, particularly biological cells, based on multiple measurements of physical and biochemical properties has been developed. Cells stained with fluorescent dyes in liquid suspension enter a unique flow chamber where electrical and optical sensors measure cell volume, single- or two-color fluorescence, and light scatter, and emerge in a liquid jet that is broken into uniform droplets. Sensor signals are electronically processed several ways for optimum cell discrimination and are displayed as pulse-amplitude distributions using a pulse-height analyzer. Processed signals trigger cell sorting according to preselected parametric criteria. Sorting is accomplished by electrically charging droplets containing the cells and electrostatically deflecting them into collection vessels. This instrument is described in detail with illustrative examples of experiments using polystyrene fluorescent microspheres, cultured human cells, and human leukocytes.

Theory predicts that small angle light scattering by spherical particles of 5 to 20 p. diam is nearly proportional to volume and insensitive to particle refractive index. A flow system photometer with helium-neon laser light source measures the scattering between 0.5 and 2.0 0 from individual particles at 10 4 to 10 5 /min. Volume distributions of mammalian cells and plastic microspheres agree with other independent determinations.A large desorption cryostat with a heat leak of about 150 mW is described. With the help of an electronic temperature regulator it is capable of maintaining any temperature between 4.2 and 19.0 K to an accuracy of better than 0.5%, using only 200 g of activated charcoal.

No abstract