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A K Solomon

Publications and source records attributed to A K Solomon.

99 records · Page 6Linked to original sources
PubMed1967

Permeability studies on red cell membranes of dog, cat, and beef.

Water permeability coefficients of dog, cat, and beef red cell membranes have been measured under an osmotic pressure gradient. The measurements employed a rapid reaction stop flow apparatus with which cell shrinking was measured under a relative osmotic pressure gradient of 1.25 to 1.64 times the isosmolar concentration. For the dog red cell the osmotic permeability coefficient is 0.36 cm(4)/(sec, osmol). The water permeability coefficient for the dog red cell under a diffusion gradient was also measured (rate constant = 0.10/msec). The ratio between the two permeabilities was used to calculate an equivalent pore radius of 5.9 A. This value agrees welt with an equivalent pore radius of 6.2 A obtained from reflection coefficients of nonelectrolyte water-soluble molecules, and is consistent with data on the permeability of the dog red cell membrane to glucose. These data provide evidence supporting the existence of equivalent pores in single biological membranes.

Animals↗
PubMed1967

The effect of the unstirred layer on human red cell water permeability.

A study has been made of water entry into human red blood cells under an osmotic pressure gradient. The measurements were made using a rapid reaction stop flow apparatus, whose construction, calibration, and performance are described in detail. Red cell volume changes were determined from 90 degrees scattered light. The permeability coefficient for water entry under a relative isosmolar concentration of 1 to 1.5 was found to be 0.22 +/- 0.01 cm(4)/sec osmol, which agrees well with our previously published value. The experiments were also designed to measure the thickness of the unstirred layer around the6 red cells. This was found to be 5.5 +/- 0.8 micro under the present experimental conditions. It is concluded that our previously measured permeability coefficient for water entrance under a diffusion gradient does not require correction on account of the unstirred layer.

Biological Transport↗
PubMed1967

Osmotic properties of mitochondria.

The osmotic behavior of rat liver mitochondria has been studied in a sucrose medium. The mitochondria behave like a two compartment system. One compartment is permeable to sucrose and has a volume of 1.22 microl/(mg mitochondrial dry weight) in a 272 milliosmol sucrose medium; the second, inaccessible to sucrose, has a volume of 0.555 microl/mg dry weight) under the same conditions. Part of the water in the sucrose inaccessible space is apparently not free to participate in osmotic phenomena. This volume is 0.272 microl/(mg dry weight) under the same conditions. It is suggested that the osmotically inactive water corresponds to the water of hydration of the mitochondrial macromolecules. The volume of the remainder of the water in the sucrose inaccessible space depends inversely on the osmolality of the medium, as is to be expected. The volume of water in the sucrose accessible space is constant, independent of the osmolality of the medium, as is the volume of the mitochondrial framework plus the nonvolatile solutes.

Animals↗
PubMed1956

Water flow through frog gastric mucosa.

The transport of water through biological membranes can be attributed to several causes. Gradients of chemical activity caused by the application of hydrostatic pressure or differences in solute concentration across the membrane may produce a net water flow, called passive transport (1). In the absence of such gradients a net flow may also occur which is defined as active transport, and is presumed to arise from metabolic processes occurring in the membrane. Pappenhehner, Renkin, and Borrero (2) and Koefoed-Johnsen and Ussing (3) have independently shown that passive flows can be interpreted to give a model of the membrane in terms of pore structure. In the present study two types of experiments have been performed on passive water transport across the isolated gastric mucosa of the frog. First, the unidirectional diffusion flow of water in either direction has been measured using tritiated water as a tracer. Second, an osmotic gradient has been applied across the membrane and a passive net flow has been measured. At the same time an active net flow in the same direction as HC1 secretion has also been observed. In addition to the water transport studies, separate measurements have been made of the restriction offered by the membrane to diffusion of various sized molecules. The combined results of these experiments are interpreted in terms of a polydisperse population of pores in the membrane.

Animals↗