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Guest Editor's Introduction: This paper was presented at the 26th ASAIO Congress held in April 1980. It was printed in Trans. Am. Soc. Artif. Intern Organs, Volume 26, page 406–411, 1980, and reprinted here with permission. This is the first clinical paper dealing with double filtration plasmapheresis. The plasma separator was made using Kuraray's polyvinyl alcohol hollow fiber, and Kuraray's plasma fractionator was made of ethylene vinyl alcohol hollow fibers. Seven patients afflicted with various diseases were treated by this method for 2 to 10 sessions. This procedure required supplemental infusion of albumin solution.

The cellular concentrations of Na, K, and C1 have been measured in kidney slices of the amphibian, Necturus maculosus. Permeability coefficients have been determined for Na, K, C1, Rb, Cs, and choline, from studies both of the uptake of radioactive isotopes and the rate of cell swelling in anisotonic solutions. The results of both methods were found to agree well. Measurements were also made of electrical potential differences across the peritubular face of the kidney cells using bathing solutions in which the electrolyte composition and concentrations could be varied. The data obtained are consistent with a model cell in which the potential difference arises as a result of differences in Na permeability relative to K on the two faces of the cell. The intracellular Na concentration is considered to be regulated by a Na-K coupled pump located at the peritubular face of the cell.Electrical potential gradients have been demonstrated between the interstitial fluid and the lumen of the proximal tubule of the kidney of the amphibian, Necturus rnaculosus, by Giebisch (1, 2), Whittembury (3), and Whittembury and Windhager (4). These authors have also shown that the electrical potential difference across the peritubular face of the cell is larger than that across the luminal face. The relationship between electrical potential differences and ionic permeabilities has been studied in nerve by Hodgkin and Katz (5). The present studies are concerned with similar relationships in Necturus proximal tubule cells.For this purpose we have used kidney slices. The permeability of kidney slices to a variety of small ions and molecules has been studied using a combination of radioactive techniques and studies of cell swelling. It is possible to make chemical analyses of the slices before and after exposure to permeant molecules and to measure potential differences in the slices under the same conditions. The combination of the present results with those obtained in situ has enabled us to put forward a hypothetical model kidney cell which 689

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We believe that this procedure for isolating kidney lysosome will be useful in the study of the mechanisms of specific modification, processing and catabolism of proteins.

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