Following the recently reported trapping of biological particles by finely focused laser beams, we report on the automated micromanipulation of cells and other microscopic particles by purely optical means as well as on a newly observed interaction between particles in the trapping beam. A simple instrument is described which allows single cells to be positioned with high accuracy, transported over several millimeters, and automatically sorted on the basis of their optical properties. These operations are performed inside a small enclosed chamber without mechanical contact or significant fluid flow. Potential applications of this technique in experimental cell biology are discussed.

In 1984, the first flow cytometry data file format was proposed as Flow Cytometry Standard 1.0 (FCS1.0). FCS 1.0 provided a uniform file format allowing data acquired on one computer to be correctly read and interpreted on other computers running a variety of operating systems. That standard was modified in 1990 and adopted by the Society of Analytical Cytology as FCS 2.0. Here, we report on an update of the FCS 2.0 standard which we propose to designate FCS 3.0. We have retained the basic four segment structure of earlier versions (HEADER, TEXT, DATA and ANALYSIS) in order to maintain analysis software compatibility, where possible. The changes described in this proposal include a method to collect files larger than 100 megabytes (not possible in earlier versions of the standard), the inclusion of international characters in the TEXT portions of the file, a method of verifying data integrity using a 16-bit cyclic redundancy check, and increased keyword support for cluster analysis and time acquisition. This report summarizes the work of the ISAC Data File Standards Committee. The complete and detailed FCS 3.0 standard is available through the ISAC office [Sherwood Group,

A differential light scattering photometer has been developed for rapid size analysis of single particles in flow. A fluid stream carrying individual particles in single file intersects a focused laser beam at the primary focal point of an annular strip of an ellipsoidal reflector situated in a scattering chamber. The light scattered from polar angles theta = 2.5-177.5 degrees at azimuthal angles phi = 0 and 180 degrees , spanning a circle of 355 degrees , is reflected onto a circular array of 60 photodiodes. The signal processing electronics and computer storage can accept 32 signals/particle at rates up to 1000 particles/sec. Photometer performance is tested by comparing measured responses from individual spherical particles with angular scattering patterns calculated for the particular detector geometry. These patterns exhibit the required symmetry in the two half scattering planes. Response measurements for eight samples with particle diameters of 1.1, 2.7, 5.0, 7.9, 10.0, 12.5, 15.6, and 19.5 microm are consistent with calculated size-response curves. The composition of a mixture of five components with particle diameters of 1.1, 5.0, 10.0, 15.6, and 19.5 Am is determined from an analysis of light scattering measurements at various forward-scattering angles.

No abstract

A flow-system cell-analysis instrument is described in which cells from a heterogeneous population are characterized by their light-scatter patterns alone. As the cells pass at high speed through a focused helium/neon laser beam, the scatter pattern from each cell is sampled simultaneously at up to 32 angles between 0° and 30° with respect to the laser beam axis, and the scatter pattern for each cell is transferred to a computer. A mathematical clustering algorithm is used to determine the number of classes into which the cells can be divided, and a linear separation algorithm is used to find the boundaries between the classes. Preliminary results on exfoliated cells from gynecological specimens are presented. This technique may be useful for automated prescreening of gynecological specimens.