Experimental verification is provided for the theoretical expressions (see preceding article, I. Theory) describing the electrical processes that take place during the passage of an aqueous suspension of rigid, nonconducting spheres (ragweed pollen) through an orifice across which there exists an electrical field, for a large range of orifice dimensions; the instrumentation developed is considered in some detail. The effective length of an orifice as deduced from conductivity measurements is shown to be essentially the same as that predicted theoretically. Absolute volume distributions are presented of a suspension of polystyrene latex spheres as determined electrically (mean 11.17 mu(3), c. v. 4.2%) and with an electron microscope (mean 11.01 mu(3), c. v. 4.1%). Conflicting experimental results reported in the literature are discussed.

The processes involved during the passage of a suspended particle through a small cylindrical orifice across which exists an electric field are considered in detail. Expressions are derived for the resulting change in current in terms of the ratios of particle to orifice volume and particle to suspending fluid resistivity, and particle shape. Graphs are presented of the electric field and of the fluid velocity as functions of position within the orifice, and of the shape factor of spheroids as a function of their axial ratio and orientation in the electric field. The effects of the electric and hydrodynamic fields on the orientation of nonspherical particles and on the deformation of nonrigid spheres is treated, and the migration of particles towards the orifice axis is discussed. Oscillograms of current pulses produced by rigid, nonconducting spheres in various orifices are shown and compared with the theoretical predictions.

Spleen cells from random-bred chickens bearing Rous sarcomas were commonly more reactive against the neoplastic target cells'in autochthonous than in allogeneic interactions in vitro. This difference was observed both in cytotoxic assays (hCr release from labeled target cells) and in an immunoadherence test measuring attachment of $"Cr-labeled splenocytes to Rous sarcoma cells. Specific splenocyte reactivity was not observed with normal embryonic chicken fibroblasts, 3T3 cells, or embryonic mouse C3H fibro'blasts. The immunoadherence technique required only 2 hr to perform, and revealed a more consistent superiority of autochthonous recognition of Rous sarcoma cells than the cytotoxicity assay. Experiments in which both procedures were used simultaneously with identical cell populations yielded similar resiilts, indicating that splenocyte adherence may be a precursor of and/or concomitant to target cell damage and that individual-specific tumor antigencity may play a part in cellular immunity against Rouis sarcomas.The host-tumor relationship of chickens bearing Rous sarcomas has a number of advantages as a model pertinent to neoplasia in man. The tumor host is an outbred, nonlaboratory adapted animal, and the virus that induces the neoplastic transformation is one of a family of agents whose members are oncogenic in nature as well as in the laboratory, and active in a broad range of species in addition to the chicken (1). Cellular and humoral immunity in this system is well established both in vito and in vitro (2,3), and the chicken lends itself uniquely to the separation of lymphoid cell populations of diverse origin, and thereby to a differential definition of immunological capacity (4).The purpose of the present investigation was to compare splenocyte-target cell interaction in both autochthonous and allogeneic confrontations between Rous sarcoma cells and effector cells, by use of splenocytes sensitized during the course of the host's experience with a primary, actively growing tumor-a situation reflecting the only type of interaction that can be studied in man.This interaction was evaluated by a newly developed quantitative immunoadherence test, and by the cytotoxicity assay based on the liberation of labeled chromium from target cells.The [Medium 199 (Grand Island Biological Co., Grand Island, N.Y.) supplemented, with 5-10% inactivated calf serum (In Vitro, Jerusalem), 10% tryptose phosphate broth (Difco Laboratories), 200 units/ml of penicillin, 200 jg/ml of streptomycin, and 15-25 ml/liter of 5% NaHCOs]. The cells were washed by centrifugation, pooled, counted, and seeded.Other Cell Types. Normal chicken embryo cells (CEC) were secondary cultures (2-to 3-days-old) derived from 9-to 11-

Cells of multicellular organisms are semi-fluid creatures. Even when they form specific cell-cell adhesions, they cannot create a defined shape or a tissue-specific architecture. Cartilaginous organs, such as ears and noses, exemplify the fact that form is imprinted in the extracellular matrix (ECM), which leads to the conclusion that cells must have the ability to shape the ECM in which they reside. This seems to be true for most tissues. The role of the ECM as an integrator of cells into functional assemblies with defined architecture is unique to multicellular organisms. The evolution of multicellularity became possible as a consequence of cells acquiring two new properties: first, cell surface macromolecular complexes that function in cell-cell binding; and, second, an ECM that integrates cells into three-dimensional structures. These two new properties allowed the evolution of the two basic types of cells—epithelial and mesenchymal. The appearance of the latter, a fibroblast-like cell with abundant filopodia, enabled the sculpturing of the ECM and the formation of complex tissue-specific architectures.

The dynamic response of chick blood lymphocytes to hypotonic shock is investigated using electrical sizing techniques, and an attempt is made to characterize the mechanisms involved. The cells first swell rapidly, as expected, but then gradually return to their initial volume. Maximum volume is attained in 2 minutes and the return is complete within about 15 minutes at room temperature. This cycle is studied under different osmotic strengths, temperatures, and cation compositions; behavior following successive hypotonic and hypertonic shocks is also described. Metabolic inhibitors are shown to have no effect, even at relatively high concentrations, while ouabain (10-3 M) affects only the much slower second-order return process that sets in when the main one is blocked by appropriate external cation concentration.It is proposed that a large increase in membrane permeability to K+ occurs as the cell swells beyond its iso-osmotic volume, but none to Na+. The experimental results are then explained by ascribing the swelling to water entering the cell until the osmotic pressure inside equals that outside, and the return phase to the electrochemical potential gradient for K+ forcing it out of the swollen cell together with the associated anion and water in proportions that preserve osmotic equilibrium. This latter is a non-active process independent of Na+ whose direction can be reversed by using K+ as the cation in the external medium.The existence in the literature of several related observations is pointed out and some of the implications of our findings are discussed briefly in terms of a corrugated membrane structure.