Cell Osmotic Fragility Research Articles

Sodium Nitrate Induces Reactive Oxygen Species That Lower the Antioxidant Power, Damage the Membrane, and Alter Pathways of Glucose Metabolism in Human Erythrocytes.

Nitrate salts are widely used as food additives and nitrogenous fertilizers and are present as contaminants in drinking water supplies. The effect of different concentrations (1-15 mM) of sodium nitrate (NaNO3) on human erythrocytes was studied under in vitro conditions. Treatment of erythrocytes with NaNO3 resulted in increases in methemoglobin levels, lipid peroxidation, and protein oxidation and a decrease in glutathione content. There were changes in the activities of all major antioxidant defense enzymes, and the pathways of glucose metabolism were also affected. Increased generation of reactive oxygen species (ROS) took place while the antioxidant power was impaired. The osmotic fragility of cells was increased, and membrane-bound enzymes were greatly inhibited. All changes were statistically significant at a probability level of P < 0.05 at all concentrations of NaNO3 except the lowest (1 mM). Thus, NaNO3 generates ROS that cause significant damage to human erythrocytes and interfere in normal cellular pathways.

Human amniotic epithelial cells: Proliferation and apoptosis during their hepatic differentiation

Human amniotic epithelial cells: Proliferation and apoptosis during their hepatic differentiation

Alterations in osmotic fragility of the red blood cells in hypo- and hyperthyroid patients

Changes in concentration of thyroid hormones can affect Na+-K+-ATPase number and activity and phospholipid composition of the cell membranes leading to changes in the surface to volume ratio and strength of membrane. In this study, the osmotic fragility of the red blood cells from non-treated hypo- and hyperthyroid patients was compared to that of control subjects. After 3 washings with normal saline, red blood cells were placed in varying concentrations of sodium chloride (Na- Cl) (0-0.9%) and fragility was assessed with colorimetric method; to do this, after the incubation period, tubes were centrifuged and the optical density of the tubes was measured. Hemolysis percentage in tubes was calculated based on 100% hemolysis in the tubes containing no NaCl (0%). Osmotic fragility of the cells from hyperthyroid patients in 0.45% NaCl was significantly lower than control subjects (74.6%+/-30.2 vs 93.8%+/-9.1, p<0.01). The osmotic fragility of red blood cells in 0.5% concentration of sodium chloride in hyperthyroid patients was significantly lower compared to that of controls (27.8%+/-26.0 vs 63.5%+/-27.5, p<0.001). No significant difference was observed between the osmotic fragility of the hypothyroid patients compared with control subjects. Alteration in osmotic fragility is seen in patients with hyperthyroidism; however, anemia reported in hypo- or hyperthyroid patients is not due to high osmotic fragility of red blood cells and other causes need to be investigated.

The Effects of S-Adenosylmethionine on Clinical Pathology and Redox Potential in the Red Blood Cell, Liver, and Bile of Clinically Normal Cats

S-adenosylmethionine (SAMe), an important hepatic metabolite and glutathione (GSH) donor, has been studied mechanistically in vitro, in humans with clinical liver disease, and in experimental animal models of liver disease. Collective findings encourage its therapeutic use in necroinflammatory and cholestatic liver disorders. A chronic longitudinal study (pre- and posttreatment parameters compared) was undertaken with 15 clinically healthy cats given a stable 1,4-butanedisulfonate (S'S isomer) SAMe salt (enteric coated tablets providing 180 mg SAMe), dosage 48 mg/kg PO q24h, on an empty stomach for 113 days. Routine physical and clinicopathologic assessments, red blood cell (RBC) osmotic fragility, liver function and histology, hepatic concentrations of reduced GSH (RGSH) and its oxidized disulfide form (GSSG), protein, glycogen, and deoxyribonucleic acid, GSH concentrations in RBCs, total bile acids in serum and bile, oxidative membrane products (TBARS) in RBCs and liver, and plasma SAMe concentrations were evaluated. SAMe administered PO significantly increased plasma SAMe concentrations, and peak concentrations usually occurred 2-4 hours after dosing. Chronic SAMe administration did not change peak or cumulative plasma SAMe concentrations and did not [corrected] cause overt signs of toxicity. A positive influence on RBC and hepatic redox status (RBC TBARS reduced 21.1% [P < .002], liver GSH increased 35% [P < .002], liver RGSH: GSSG ratio increased 69% [P < .03]) and improved RBC resilience to osmotic challenge (P < .03) were observed. Results prove that this SAMe PO product is enterically available and suggest that it imparts biologic effects that might be useful for attenuating systemic or hepatic oxidant challenge.

Hypochlorous acid-induced membrane pore formation in red blood cells

The hyperproduction of hypochlorous acid (HOCl), an extremely toxic biological oxidant generated by neutrophils and monocytes, is involved in the pathogenesis of many diseases. In these studies, we attempted to determine the membrane and cellular events associated with HOCl-induced erythrocyte impairment and haemolysis. In vitro human erythrocyte exposure to HOCl (0.1–1.0 mM) resulted in rapid oxidation of reduced glutathione, an increase in cell osmotic fragility and the formation of transient membrane pores. The process of glutathione oxidation depended on the [oxidant]/[cell number] ratio. The HOCl-induced haemolysis observed was apparently mediated by pore formation and altered membrane electrolyte permeability. The estimated pore radius was approximately 0.7 nm and the average number per cell was 0.01. The rate constant of HOCl-produced haemolysis depended on pH. There were significant differences in haemolysis of HOCl-treated erythrocytes which had maximal stability at pH 7.2–7.3.

Fostriecin, an inhibitor of protein phosphatase 2A, limits myocardial infarct size even when administered after onset of ischemia.

The role of protein phosphatases (PPs) during ischemic preconditioning in the rabbit heart was examined. Fostriecin, a potent inhibitor of PP2A, was administered to isolated rabbit hearts starting either 15 minutes before or 10 minutes after the onset of a 30-minute period of regional ischemia and continuing until the onset of reperfusion. After 2 hours of reperfusion, infarct size was measured with triphenyltetrazolium chloride. In a second study with isolated rabbit cardiomyocytes, the effect of fostriecin pretreatment was assessed by measuring changes in cell osmotic fragility during simulated ischemia. PP1 and PP2A activities of isolated control and ischemically preconditioned cells were also measured. In a third series of experiments, left ventricular biopsies of isolated rabbit hearts were obtained before and at selected times during 60 minutes of global ischemia, and the tissue was assayed for PP1 and PP2A activities. In isolated hearts pretreated with fostriecin, only 8% of the ischemic zone infarcted, significantly less than that in untreated control hearts (33%; P<0.001) but comparable to that in ischemically preconditioned hearts (9%; P<0.001 versus control). Significant protection was also observed in the hearts treated only after the onset of ischemia (18% infarction; P<0.05 versus control). In isolated myocytes, fostriecin also provided protection comparable to that produced by metabolic preconditioning. Preconditioning had no apparent effect on the activity of either PP1 or PP2A in isolated ventricular myocytes or ventricular tissue obtained from heart biopsies. Fostriecin, a potent inhibitor of PP2A, can protect the rabbit heart from infarction even when administered after the onset of ischemia. But inhibition of either PP1 or PP2A does not appear to be the mechanism of protection from ischemic preconditioning.

Engineered human erythrocytes as carriers for ciprofloxacin

AbstractCiprofloxacin (CFX), a broad-spectrum antibacterial agent, was loaded into human erythrocytes by a method based on hypotonic preswelling, hemolysis, isotonic resealing, and reannealing. Various parameters such as volume of aqueous drug solution added, drug concentration, and temperature were optimized to obtain maximum loading of drug into erythrocytes. The loaded cells were characterized for drug content, hemoglobin content, percent cell recovery, morphology, osmotic fragility, turbulence shock, and in vitro drug as well as hemoglobin efflux. No appreciable detrimental effects on cell morphology, osmotic fragility, and turbulence shock in comparison with normal cells were noted. Osmotic fragility and turbulence shock studies indicated that the loaded erythrocytes are less resistant than the normal erythrocytes. Glutaraldehyde treatment stabilized both types of cells with respect to drug and hemoglobin release, osmotic fragility, and turbulence fragility. The studies suggest the potential of CFX-l...

Preparation and in vitro characterization of a magnetically responsive ibuprofen-loaded erythrocytes carrier.

The erythrocytes were loaded with ibuprofen and magnetite (ferrofluids) using the pre-swell technique. Various process variables including drug concentration, magnetite concentration, sonication of ferrofluids that could affect the loading of drug and magnetite were optimized. The loaded erythrocytes were characterized for in vitro drug efflux, haemoglobin release, morphology, osmotic fragility, turbulence shock, in vitro magnetic responsiveness and percentage cell recovery. In optimum concentration erythrocytes could tolerate ibuprofen as no appreciable detrimental effects were noticed on cell morphology, osmotic fragility, and turbulence shock, when compared with normal erythrocytes. However, magnetite showed some detrimental effect on erythrocytes. A drug release profile from the cellular system was observed to follow approximate zero-order kinetics. The loaded cells effectively responded for an external magnetic field of 8.0 KOe.

Effect of 2-Deoxyglucose on Cell Wall Formation in Saccharomyces cerevisiae and Its Relation to Cell Growth Inhibition

The growth inhibition and the lysis of Saccharomyces cerevisiae caused by 2-deoxy-d-glucose (2-DG) were shown to be a consequence of unbalanced cellular growth and division. The lysis, but not the repression of growth and osmotic fragility of cells, could be suppressed by the addition of mannitol as an osmotic stabilizer. This result, as well as the morphological changes observed in the cells and changes in the chemical composition of the cell walls, showed that S. cerevisiae grown in the presence of 2-DG formed weakened cell walls responsible for the osmotic fragility. Evidence is presented for the first time demonstrating the incorporation of 2-DG into yeast cell wall material. Other data suggest that the inhibition of yeast growth by 2-DG results from an interference of phosphorylated metabolites of 2-DG with metabolic processes of glucose and mannose involved in the synthesis of structural cell wall polysaccharides.

Influence of lipid components of Mycoplasma laidlawii membranes on osmotic fragility of cells.

Razin, S. (University of Connecticut, Storrs), M. E. Tourtellotte, R. N. McElhaney, and J. D. Pollack. Influence of lipid components of Mycoplasma laidlawii membranes on osmotic fragility of cells. J. Bacteriol. 91:609-616. 1966.-Lipid composition of Mycoplasma laidlawii membranes could be significantly changed by variations in the growth medium. The effect of these changes on the osmotic fragility of the cells was studied. Cholesterol, incorporated into the membrane from the growth medium, had no significant effect on osmotic fragility. Carotenoids, synthesized by the cells from acetate, were likewise without effect. Unsaturated long-chain fatty acids increased markedly the resistance of M. laidlawii to osmotic lysis and promoted growth. The fatty acids of the growth medium were incorporated mainly into membrane phospholipids. The ratio between saturated and unsaturated fatty acids in membrane lipids depended on that of the growth medium.