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Biomedical subjects

P Seeman

Publications and source records attributed to P Seeman.

At least 307 records · Page 17Linked to original sources
PubMed1970

The erythrocyte ghost is a perfect osmometer.

The osmotic swelling of intact erythrocytes in hypotonic solutions was measured using microhematocrit tubes, Van Allen tubes, and a calibrated Coulter counter. In agreement with earlier workers the intact cells did not behave as perfect osmometers, the cells swelling less than predicted by the Boyle-van't Hoff law. Erythrocyte ghosts were prepared from fresh intact erythrocytes by one-step hemolysis in 0.25% NaCl at an extremely dilute concentration of cells and the membranes were sealed at 37 degrees . The ghosts were mixed with NaCl solutions of different osmolarities and the MCV (mean cell volume) of the shrunken cells immediately monitored by a calibrated Coulter counter. It was found that the MCV values of the shrunken ghosts were accurately predicted by the Boyle-van't Hoff law. These results indicate that these erythrocyte ghosts behaved as perfect osmometers.

Cell Membrane Permeability↗
PubMed1967

Transient holes in the erythrocyte membrane during hypotonic hemolysis and stable holes in the membrane after lysis by saponin and lysolecithin.

Ferritin and colloidal gold were found to permeate human erythrocytes during rapid or gradual hypotonic hemolysis. Only hemolysed cells contained these particles; adjacent intact cells did not contain the tracers. Ferritin or gold added 3 min after the onset of hypotonic hemolysis did not permeate the ghost cells which had, therefore, become transiently permeable. By adding ferritin at various times after the onset of hemolysis, it was determined that for the majority of the cells the permeable state (or interval between the time of development and closure of membrane holes) existed only from about 15 to 25 sec after the onset of hemolysis. It was possible to fix the transient "holes" in the open position by adding glutaraldehyde only between 10 and 20 sec after the onset of hemolysis. The existence of such fixed holes was shown by the cell entry of ferritin and gold which were added to these prefixed cells. Membrane defects or discontinuities (of the order of 200-500 A wide) were observed only in prefixed cells which were permeated by ferritin subsequently added. Adjacent prefixed cells which did not become permeated by added ferritin did not reveal any membrane discontinuities. Glutaraldehyde does not per se induce or create such membrane defects since cells which had been fixed by glutaraldehyde before the 10-sec time point or after the 180-sec time point were never permeable to added ferritin, and the cell membranes never contained any defects. It was also observed that early in hemolysis (7-12 sec) a small bulge in one zone of the membrane often occurred. Ghost cells produced by holothurin A (a saponin) and fixed by glutaraldehyde became permeated by ferritin subsequently added, but no membrane discontinuities were seen. Ghosts produced by lysolecithin and fixed by glutaraldehyde also became permeated by subsequently added ferritin, and many membrane defects were seen here (about 300 A wide).

Biological Transport↗