SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The concept of an internal pressure gradient in a rigid porous membrane has been proposed as the basis for osmotic flow. The origin of the pressure in terms of the theory of the chemical potential implies also the existence of states of negative pressure, that is, tension. These states have been observed experimentally by means of a Hepp-type osmometer.
Explore the source record for details and available documents.
Hardy, Paul H., Jr. (Johns Hopkins University, Baltimore, Md.) and E. Ellen Nell. Influence of osmotic pressure on the morphology of the Reiter treponeme. J. Bacteriol. 82: 967-978. 1961.-Spherical bodies similar to those that develop spontaneously in cultures of treponemes, and which have been considered by many investigators to represent one stage in a complex life cycle of these organisms, can be produced rapidly with the Reiter treponeme by merely altering the medium in which the organisms are suspended. Osmotic pressure appears to be the major factor responsible for this effect, as shown by the observation that treponemes suspended in NaCl solutions of 0.15 to 0.10 m retain their spirochetal morphology, whereas organisms suspended in more dilute salt solutions rapidly become spherical. Moreover, the concentration of salt appears to influence both the rate and extent of sphere formation. Further evidence that osmotic pressure is primarily involved is demonstrated by the selectivity of the conditions under which spheres form. Treponemes suspended in various 0.3 osmolal solutions either retain their spiral shape or form spheres, depending upon the nature of the solute. Viability studies of suspensions containing predominantly spherical forms, which have developed spontaneously or have been artificially induced, have failed to produce evidence that the resulting growth of treponemes came from the spheres. It is concluded, therefore, that the naturally occurring spheres probably arise as the result of an osmotic imbalance which develops between the cells and their environment, and that the spheres represent degenerative forms rather than an intermediate stage in a life cycle.
Sbarra, Anthony J. (St. Margaret's Hospital, Boston, Mass.), William Shirley, and John S. Baumstark. Effect of osmolarity on phagocytosis. J. Bacteriol. 85:306-313. 1963.-The effect of a number of different compounds on phagocytosis was studied. Phagocytosis was monitored by morphological and biochemical means. It was found that the addition of compounds such as KCl, NaCl, sodium or potassium malonate, and K(2)SO(4) to the phagocytic system inhibited phagocytosis. The increased salt concentration specifically inhibited the respiratory activity associated with phagocytosis. The endogenous respiration of the leukocytes was unaffected. Glycolysis and the increased flow of glucose through the hexose monophosphate pathway were also inhibited by the elevated concentration of salts. In addition, cells exposed to high salt concentrations appeared to be reduced in size as compared with normal cells. The inhibition can be reversed by lowering the salt concentration. It was suggested that the increased osmotic pressure of the system was responsible for the inhibition.
Sud, I. J. (University of Florida, Gainesville), and M. E. Tyler. Cell-wall composition and osmotic fragility of selected marine bacteria. J. Bacteriol. 87:696-700. 1964.-Cell-wall composition of three marine pseudomonads, selected to represent a spectrum of osmotic fragilities, was determined and compared with that of Pseudomonas aeruginosa. The walls of the marine bacteria were composed predominantly of lipoprotein. No sugars, except glucosamine, were detected, and the reducing values were similar to the respective hexosamine values. These varied from 0.9 to 1.8%, the most osmotically fragile marine bacterium possessing the lowest amount of hexosamine in the wall. Possible relationship between wall hexosamine content and osmotic fragility was indicated.
Harold, F. M. (National Jewish Hospital, Denver, Colo.). Stabilization of Streptococcus faecalis protoplasts by spermine. J. Bacteriol. 88:1416-1420. 1964.-Lysis of protoplasts of Streptococcus faecalis subjected to osmotic shock was prevented by the presence of 10(-3)m spermine and other divalent cations. Protein and nucleic acids were largely retained, but compounds of low molecular weight were discharged into the medium and the capacity for glycolysis was lost. Under these conditions, spermine was bound to the protoplasts. It could not be removed by washing with water or nonelectrolytes, but was displaced by salts, polyanions, and polycations. Removal of the spermine restored the osmotic fragility of the protoplasts, which could once again be protected from lysis by impermeant solutes. Protoplasts were also stabilized, in the absence of osmotic shock, by prolonged incubation with cations in 0.5 m sucrose. By either procedure, the protoplasts became resistant not only to osmotic lysis but also to sonic oscillation. It is concluded that the stabilization of protoplasts resulted from ionic binding of the cation to acidic sites on the external surface of the plasma membrane. This conferred upon the membrane additional mechanical strength, perhaps by the cross-linking of subunits, but did not alter its permeability to extracellular solutes.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
A single volume of 0.075 ml. of a 1 in 10 dilution of whole blood in isotonic NaCl solution is introduced into a container cell, two walls of which are made of a dialysing membrane. The container cell is introduced into a test tube of distilled water, placed in an instrument which is essentially a colorimeter with a recorder, between the source of light and the photoelectric cell. Dialysis through the membrane results in a continuous decrease in the salt concentration of the medium surrounding the erythrocytes. The measurement of the degree of haemolysis is based on the increasing transparency of the erythrocyte suspension while haemolysis takes place. Recording this increasing light transmission as a function of time, i.e., as a function of decreasing salt concentration, yields the osmotic fragility curve. The automatically recorded curve is obtained in less than 10 minutes.
Nine cases of the thalassaemia trait are described in an English family. The problem of distinguishing these cases from those of the common hypochromic anaemias by simple laboratory tests is discussed.Iron-resistant hypochromic anaemia in people of British ancestry may be caused by the thalassaemia trait. Such cases have been reported by Bywaters (1938), Israëls, Suderman, and Hoogstraten (1955), Israëls and Turner (1955), and Havard, Lehmann, and Bodley Scott (1958). Dacie (1960) mentions similar cases and Callender, Mallet, and Lehmann (1961) recently described the finding of 25 cases in three English families.
Five cases of thalassaemia minor and 11 symptomless trait carriers have been detected in four Scottish families, only one of which is known to have foreign ancestry. It is suggested that the condition is commoner than was once thought, and that the diagnosis should be considered in any patient with refractory hypochromic anaemia in which the red cells show increased osmotic resistance.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.