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.

We have found a defect in the ouabain-sensitive Na+,K+-ATPase (Na+ pump, EC 3.6.1.37) oferythrocytes from streptozotocin diabetic rats. This defect was accompanied by an increase in cell volume and osmotic fragility and a decrease in the cytosolic K+/Na+ ratio. There was also a doubling in the time needed for diabetic erythrocytes to pass through 4.7-jim channels in a polycarbonate filter. Our data are consistent with a primary defect in the erythrocyte Na+ pump and secondary changes in cell volume, osmotic fragility, K+/Na+ ratio, and cell ifiterability. All were reversed or prevented in vivo by insulin or the aldose reductase inhibitor Sorbinil. Protein kinase C agonists (phorbol ester and diacylglycerol) and agonist precursor (myoinositol) reversed the Na+ pump lesion, suggesting that protein kinase C-dependent phosphorylation of the 100-kDa subunit regulates Na+ pump activity and that insulin can influence erythrocyte protein kinase C activity. Ouabain inhibition of the erythrocyte Na+ pump also produced increases in cell size and reductions in rates of ifitration. Theoretical treatment of the volume changes also predicts reduction in ifiterability as a consequence of cell swelling. We suggest that enlarged erythrocytes could play a role in the evolution of the microvascular changes of diabetes mellitus.A decrease in ouabain-sensitive Na',K+-ATPase (Na' pump, EC 3.6.1.37) activity has been found in diabetic lens, nerve, and glomerulus (1-3). This Na' pump impairment was corrected by aldose reductase inhibitors or by normalization of blood sugar with insulin. In contrast, Na' pump activity in diabetic erythrocytes (RBCs) is a subject of controversy, with reports of increases (4, 5) and decreases (6, 7). We therefore initiated a study of the Na' pump in erythrocytes of rats rendered diabetic with streptozotocin. The streptozotocin diabetic rat provided a reliable source ofRBCs whose time-integrated exposure to hyperglycemia was determined by measurement of glycated albumin. Since nondiabetic RBCs must deform considerably to pass through small capillaries, we were especially interested in learning whether such a putative Na' pump lesion would influence the volume and hence filterability of affected RBCs. MATERIALS

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A new type of analytical and preparative cytometric instrument was developed. fie instrument ccxnbines image analysis and machine vision with single cell and chromosome manipulation by means of optical trapping. A proof-of-@nciplc instrument, OCAM, has the ability to locate and analyze biological particles inside an exlosed manipulation chamber, as well as the ability to move and position particIes =card.ing to prcprogmmm ed pocols.Prelimirlfu-y results and potential biologicaJ applications of such a microrobcx are discussed.

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