Effect of hydration on the water content of human erythrocytes.

An ideal, hydrated, nondilute pseudobinary salt-protein-water solution model of the RBC intracellular solution has been developed to describe the osmotic behavior of human erythrocytes during freezing and thawing. Because of the hydration of intracellular solutes (mostly cell proteins), our analytical results predict that at least 16.65% of the isotonic cell water content will be retained within RBCs placed in hypertonic solutions. These findings are consistent not only with the experimental measurements of the amount of isotonic cell water retained within RBCs subjected to nonisotonic extracellular solutions (20-32%) but also with the experimental evidence that all of the water within RBCs is solvent water. By modeling the RBC intracellular solution as a hydrated salt-protein-water solution, no anomalous osmotic behavior is apparent.     

The point of maximum cell water volume excursion in case of presence of an impermeable solute

A relativistic permeability model of cell osmotic response (Cryobiology 40:64-83; 41:366-367) is applied to a two-solute system with one impermeable solute. The use of the normalized water volume (w), and the amount of intracellular permeable solute (x), which is the product of the water volume and intracellular osmolality (y), as the main variables allowed us to obtain a homogeneous differential equation dx(Delta)/dw(Delta)=f(x(Delta)/w(Delta)), where w(Delta)=w-w(f), x(Delta)=x-x(f), and f refers to the final (equilibrium) values. The solution of this equation is an explicit function, w(Delta)=g(x(Delta)), which is given in the text. This approach allows us to obtain an analytical (exact) expression of the water volume at the moment of the maximum excursion (water extremum w(m)). Results are compared with numeration of basic osmotic equations and with approximation given in (Cryobiology 40:64-83). Assumption that, dw/dt approximately 0 gives good approximations of the kinetics of water and permeable CPA after the point of maximum volume excursion (the slow phase of osmotic response). Practical aspects of the relativistic permeability approach are also discussed.     

Nonsolvent water in human erythrocytes

From the ability of a concentrated suspension of human erythrocytes to regulate the pH of unbuffered, anisotonic, external media it is possible to calculate the fractional cell volume in which chloride is dissolved. The difference between this volume and the total cell water gives the nonsolvent water (for chloride) of the cell. Nonsolvent water is less than 3% of the isotonic cell volume. The quantity of nonsolvent water per cell may increase as the cells shrink in hypertonic solutions.     

Constancy of cell volume during shape change of erythrocytes induced by increasing ATP content

Erythrocytes in long-preserved blood are spherical, but when the cells are incubated with inosine and adenine, the resulting increase in ATP content is accompanied by a shape change of the cells to discoidal form via a crenated form. The cells incubated with adenine alone or with no addition remain almost unchanged in shape. When incubated with inosine alone, the elevation in ATP level is less than that with both inosine and adenine, and the cell shape remains unchanged or changes partially into a crenated form. These phenomena occur in the presence of EDTA as well as in the absence of serum protein in the media. The cell volumes are measured as packed cell volume after centrifugation, by means of a Coulter counter (model S), and by determination of the intercellular space by the use of¹³¹I-labeled bovine serum albumin. The results show that no alteration in cell volume occurs during the shape changes. Accordingly, the surface area of the cell must increase with increase in the ATP content. This suggests that both the lipid bimolecular layer and the undermembrane structure are altered during the shape change.     

Effects of reduced cell volume and water content on glycolysis in L-929 cells

Mouse L-929 cells were subjected to increasing concentrations of sorbitol, which remove cell water and reduce volume osmotically. The rate of lactate production from glucose was significantly higher in osmotically perturbed cells than in controls, both in monolayers and in suspensions. L cells can apparently use sorbitol as a glycolytic substrate; however, studies using other solutes (trehalose and sucrose) and permeabilized cells showed that the major effect of sorbitol on glycolysis in intact cells is mediated through a reduction in cell water content and volume. It is possible to explain some of these results by an increase in the chemical potentials of dissolved components of the glycolytic pathway caused by water loss; however, the relationship between water loss and glycolytic rate increase in not a simple linear one, suggesting that the situation is more complex than would result merely from increased concentrations of pathway components. Whatever the complete explanation might be, these studies show that glycolysis continues in an orderly fashion in cells that have lost about 85% of their original water content, suggesting that the operation of this pathway is not unduly sensitive to events taking place in the bulk aqueous phase.     

Critical cell volume and shape of bovine erythrocytes.

The relationship between erythrocyte shape and the critical cell volume was investigated. Agents able to increase the critical cell volume induced three main stable shapes of erythrocytes: discocytic, stomatocytic, and echinocytic. The absence of correlation between shape and critical cell volume under isoosmotic conditions suggests that relative differences between the surface areas of the inner and the outer leaflet of the cell membrane do not influence the critical volume of a cell.     

Augmented water binding and low cellular water content in erythrocytes of camel and camelids.

We investigated a link between hemoglobin primary structure, hemoglobin hydrophobicity-hydrophilicity, and erythrocyte water content in various mammalian species. Some hemoglobin molecules, particularly those of the camel and camelids, contain more charged amino acid residues and are more hydrophilic than the hemoglobins of human and a number of other mammalian species. To test the in vivo significance of these alterations of hemoglobin primary structure, we determined the osmotically unresponsive erythrocyte water fractions in mannit solutions of various osmolarities at 4 degreesC. Among the species investigated, the size of the osmotically unresponsive erythrocyte water fraction relates in a positive linear way to hemoglobin hydrophilicity. The extreme low total erythrocyte water content of camel erythrocytes (1.1-1.3 g water/g dry mass) may be explained by a comparatively high osmotically unresponsive erythrocyte water fraction. It is proposed that alterations of hemoglobin sequences of camel and camelids may be the part of a natural selection process aimed at protecting these animals against osmotic dehydration in arid environments.     

The relationship between RNA content, cell volume and growth potential in ageing human embryonic mesenchymal cells

Modal cell volume and cellular RNA content were meaume was found to correlate with both culture replication rate and cellular RNA content. This observation suggests that cell volume changes may be related to the rate of cell division during ageing in vitro, and that both cell volume and RNA content may be closely controlled. There was no change in the relative proportions of the major rRNA species during the cultures' lifespan.     

Measurement of DNA content and cell volume in senescent human fibroblasts utilizing flow multiparameter single cell analysis

Cell cycle analysis of senescent cultured human fibroblasts by flow cytofluorometry reveals an increased proportion of cells in the G 1 period. An increased variation as well as a slight decrease in cellular DNA contents were observed in both G 1 and G 2 + M senescent cells. Utilizing gated single parameter analysis, the increased cell volumes observed in these senescent fibroblasts were demonstrated to be present in G 1 as well as G2 + M cells.     

Osmotic water permeability of the human red cell. Dependence on direction of water flow and cell volume

The osmotic permeability coefficient (Pf) was measured with a stopped- flow light-scattering technique. There is an artifactual light- scattering signal produced by the initial mixing that decays with a half-time of approximately 0.2 s. This seriously interferes with the measurement of the osmotically induced change in cell volume, which has a similar half-time. This "injection artifact" is associated with the biconcave shape of the cells. It is negligible for cells that have been made nearly spherical by swelling them in 160 mosmol. The dependence of this artifact on the cell volume may explain the previously observed dependence of Pf on the cell volume. When cells are made echinocytic (and therefore spherically symmetric), this injection artifact becomes negligible at all cell volumes and Pf can be accurately measured. The Pf of echinocytic cells was nearly constant, varying by less than 10% with the direction of flow and the medium osmolarity (160-360 mosmol). The average value of Pf was 2.0 X 10(-2) cm/s (T = 23 degrees C).     

Characteristic moisture curves and maximum water content of two crop residues

Limited data are available relating water potential () to crop residue water content (), although this relationship is important to study decomposition and moisture retention of the residue layer in no-till systems and other agricultural situations where residues are used. The objectives of this study were (i) to determine the characteristic moisture curves of rye (Secale cereale L.) and clover residues (Trifolium incarnatum L.), and (ii) to determine residue characteristics that can predict maximum water content of crop residues. Air-dried residues were separated into leaves and stems, cut into 0.5 cm length pieces and saturated with distilled water. Pieces of the drained residues were dried to various water contents in the laboratory and then transferred into thermocouple psychrometer chambers. Characteristic moisture functions of the type = a ^–b, where a and b are empirical constants, were fitted to the data. The characteristic moisture curves had a similar shape to that of a Cecil sandy loam soil used as an example; however, while plant residues were able to retain up to 4.3 g H₂O g^–1, the mineral soil retained only 0.22 g H₂O g^–1. Soluble carbohydrate concentration can be used as a practical index to estimate maximum water content of residues, given the good relationship between both variables (R ² = 0.92).     

The effect of thyroxine on the 2,3-diphosphoglycerate content of erythrocytes in vivo and in vitro]

After ending a continous treatment with thyroxine the average dropping of the 2,3 DPG level was 0.4 mumol/ml. T4 decreased on the average by 7.6 microgram/ml. One time application of 1 mg thyroxine p.o. led within 24 hours to an increase of the 2,3 DPG level of -chi = 0.2 mumol/ml, the pH in the erythrocytes increased by 0.02 on the average. Blood incubation with thyroxine added in a concentration of -chi = 24 microgram/100 ml showed no increase of 2,3 DPG, pH and phosphate, while there was a significant acidosis and increase of phosphate in the control blood. The lactate production was significantly lower and glucose consumption was significantly higher in the blood with thyroxine.     

Changes in water content and volume accompanying exsheathment of Haemonchus contortus

Davey K. G. and Rogers W. P. 1982. Changes in water content and volume accompanying exsheathment of Haemonchus contortus, International Journal for Parasitology12: 93–96. The exchange water volume was determined for ensheathed larvae, for larvae exsheathed by exposure to CO₂ and for larvae desheathed by exposure to a solution of NaOCl. Larvae exsheathed by exposure to CO₂ lose approx. 66 pl. of water while those desheathed by exposure to NaOCl lose approx. 50 pl. Larvae first desheathed by exposure to NaOCl lose a further 20 pl of water when subsequently exposed to CO₂. Volumes calculated from linear measurements of larvae demonstrate that larvae exsheathed by exposure to CO₂ lose about 69 pl of their total volume, while those desheathed by NaOCl lose about 54 pl. It is concluded that exsheathment may involve at least two parallel processes. Both processes are initiated by CO₂, while one is mimicked by exposure to NaOCl.