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Biomedical subjects

N Meyerstein

Publications and source records attributed to N Meyerstein.

At least 37 records · Page 2Linked to original sources
PubMed1995

Conductometric study of erythrocytes during centrifugation. II. Erythrocyte deformability.

Erythrocyte deformability was studied by continuous reading of sediment conductance during centrifugation. The decrease in sediment conductivity during centrifugation reflects erythrocyte deformation in the pellet. The degree of erythrocyte deformation depends on the duration of centrifugation and the magnitude of centripetal acceleration. When constant centrifugal force is applied over an extended period of time, a gradual decrease in pellet conductivity occurs. Stepwise enhancement of centripetal acceleration during centrifugation induces a rapid increase in erythrocyte deformation. After centrifugation, the relaxation of erythrocyte deformation is observed. However, the relaxation and the recovery of cell shape are incomplete. The difference in compressibility of previously centrifuged and noncentrifuged cells demonstrates that centrifugation causes irreversible alteration in erythrocyte deformability. The results show that the time-dependent resistance of erythrocyte sediment during centrifugation may serve as a useful index for the kinetics of erythrocyte deformation.

Blood Sedimentation↗
PubMed1994

Prolonged storage of red cells: the effect of pH, adenine and phosphate.

Prolonged storage of red blood cells (RBCs) at 4 degrees C results in decreased intracellular ATP levels with diminished posttransfusion survival. Meryman described a preservative medium, exceptional in its capacity to increase these intracellular levels during the first weeks of storage and later in maintaining adequate levels, for extended storage periods. We modified this medium, investigated its constituents, and found that its ATP-preserving effect was unrelated to its tonicity or to the presence of mannitol. Throughout storage, RBC potassium leakage and lactate production were moderate. No evidence of osmotic swelling was detected. In spite of high ATP levels, the cells became echinocytes, thus discounting a direct correlation between shape and metabolic status. The most striking finding in this study was that the prestorage pH of the blood unit (pH 7.0), has a crucial contribution in elevating nucleotide levels in a medium containing high levels of phosphate (18-40 mM) and adenine. We suggest that a combined effect of optimal pH, adenine, glucose and phosphate in the medium contributes to the ability of the RBCs to synthesize the necessary purine nucleotides by the 'salvage pathway'.

Adenine↗
PubMed1994

Radiation damage to the erythrocyte membrane: the effects of medium and cell concentrations.

Human erythrocytes suspended in plasma, or in phosphate buffered saline (PBS), were exposed to ionizing radiation. Potassium leakage from irradiated erythrocytes is significantly higher in PBS than in plasma. The potassium leakage decreases when PBS is gradually replaced by plasma. These findings suggest that some of the plasma constituents have radioprotective properties. The potassium leakage per cell is independent of the hematocrit, Hct. The potassium leakage is attributed to the formation of radiation defects in the membrane. Analysis of the effect of radiation dose, plasma and cell concentrations on the product of the number and surface area of the radiation defects indicates that the radiation damage is mainly due to the direct formation of free radicals in the cell membrane. The radioprotective effect of plasma is attributed to surface reactions of these free radicals with plasma constituents adsorbed on the membrane.

Blood Banks↗
PubMed1993

Iron deficiency anemia: recovery from in vitro oxidative stress.

Red blood cells in iron deficiency anemia (IDA) have a decreased activity of essential antioxidant enzymes. The present study examined the effect of in vitro exposure to oxidative agents in IDA cells and their recovery capacity. Red cells of 26 IDA patients and 10 healthy subjects were examined. Cells of IDA patients had higher levels of reduced glutathione (GSH), and normal methemoglobin and malonyldialdehyde (MDA) levels. Exposure to butyl hydroperoxide revealed a dose-dependent sensitivity in IDA cells, with extensive GSH depletion and increased MDA levels. These changes were partially reversible by incubation with dithiothreitol. Exposure to phenazine methosulfate, to produce intracellular superoxide ions, resulted in moderate GSH depletion and methemoglobin production. IDA cells were more sensitive than control cells to high concentrations of this substance. This effect was further augmented by preincubation with a superoxide dismutase inhibitor. Our data demonstrate that IDA cells are more susceptible to oxidation but have good capacity for recovery.

Adolescent↗
PubMed1992

Effect of vitamin K on neonatal erythrocytes.

This study investigated the possible oxidative effect of vitamin K3 (menadione) and Vitamin K1 (Konakion) on neonatal erythrocytes by controlled in vitro exposure. Menadione caused only mild morphological changes and did not decrease ATP levels. However, it oxidized intracellular hemoglobin to methemoglobin in neonatal cells more than in adult cells. Reduced glutathione contents were higher in neonatal cells, but less available for antioxidant protection. Konakion did not increase methemoglobin levels in newborn infants after a prophylactic injection. In vitro exposure to Konakion did not affect reduced glutathione and ATP levels, nor did it oxidize hemoglobin. However, extensive morphological changes were observed, attributed to the effect of its solvent. Therefore, it seems that menadione, which is no longer administered to newborns, causes oxidative stress in neonatal cells whereas Konakion, the current vitamin K1, does not, either in in vitro studies or by therapeutic administration.

Adenosine Triphosphate↗
PubMed1991

Kinetics of hemolysis of normal and abnormal red blood cells in glycerol-containing media.

The kinetics of hemolysis of erythrocytes in glycerol-containing media was studied spectrophotometrically. The hemolytic process starts by a rapid process, obeying a first order rate law, which is followed by a slow change in absorbance. The kinetics of hemolysis may be described by (a) the maximum absorption, Emax, due to cellular expansion, (b) the rate constant, k, of the fast process and (c) the final absorption at its end, Einf and the ratio Einf/Emax. At pH 6.85 in normal human cells, k = 0.72 min-1 while in hereditary spherocytosis cells, k = 1.06 min-1, iron deficiency k = 0.52 and beta-thalassemia minor k = 0.36 min-1. The percentages of Einf/Emax were 35.3 in control cells, while they were 9.8, 50.0 and 88.3 in spherocytosis, iron deficiency and thalassemia, respectively. Thus these kinetic parameters may help to distinguish and understand the above mentioned erythrocyte disorders. At physiological pH (7.4-7.2), no hemolysis was detected in the medium used. When the pH decreased, hemolysis occurred, its rate increasing gradually until pH 6.3. On further acidosis, the hemolytic rate slowed down again. Addition of DIDS to the whole blood prior to the test inhibits hemolysis. Similar effect of DIDS was noted in washed cells; this effect was partially reversed by albumin. These results suggest that a process involving band 3 affects the rate and degree of glycerol-induced hemolysis of normal red blood cells.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1991

Erythrocyte acetylcholinesterase activity in Hirschsprung's disease in Israel.

Hirschsprung's disease is a relatively prevalent disorder in newborn babies and young children. Acetylcholinesterase (AChE) activity is augmented locally, in the neural plexus of the affected gut segment. It has been suggested that this enzyme will also be increased in red blood cells (RBCs) of affected children. Thus, we studied AChE activity in newborn babies and children, as well as age-adjusted data. This Israeli study consisted of healthy and affected Bedouins as well as Ashkenazi and Sephardic Jews. This study supports the Japanese study in that the RBC AChE is not augmented in Hirschsprung's disease. However, final conclusions cannot yet be drawn, because of the small sample.

Acetylcholinesterase↗
PubMed1991

Oxidative stress in newborn erythrocytes.

Phenylhydrazine (PHZ) exposure is used to study in vitro red cell aging mechanisms dependent on Hb oxidation. The effect of PHZ on normal neonatal red blood cells was studied in unseparated blood and after separation into light and heavy cells. PHZ caused more extensive morphologic changes in neonatal than in adult red blood cells. PHZ exposure of neonatal cells caused less reduced glutathione depletion than in adult cells. Although we found the same total amount of oxidized Hb in both cells, a well-defined oxidation product of Hb was demonstrated by Mössbauer spectra only in neonatal cells. This oxidation product was not methemoglobin but a trivalent, high-spin iron compound. All neonatal cell populations were more sensitive to PHZ than were adult ones, as demonstrated by the presence of Heinz bodies at low PHZ concentration, which did not affect adult cells. These studies demonstrate greater sensitivity of neonatal cells to PHZ in all density-separated populations.

Adult↗
PubMed1990

Prolonged storage of red cells with ammonium chloride and mannitol.

Recently, a new preservation medium consisting of ammonium chloride added to adenine, glucose, mannitol, citrate, and potassium phosphate, was described. Unexpectedly, the predominant effect on red cell storage was an initial elevation of ATP levels, followed by remarkable maintenance of these levels at 12 to 18 weeks with acceptable 24-hour survival. The aim of the study reported here was to investigate the reasons for the advantageous effects of the different constituents. With the new preservation medium, ATP content was maintained at acceptable levels for at least 8 weeks with low spontaneous hemolysis. However, similarly high ATP levels were also maintained in the absence of ammonium chloride. Comparable results were obtained on substituting sodium for potassium salts in the new medium. When the main cation in the preservation medium was replaced by sodium, the addition of ammonium or rubidium chloride did not provide an advantage. Therefore, ammonium chloride was not essential for this medium, whereas mannitol does seem to be essential in a solution whose content of nonpermeant solutes is hypotonic.

2,3-Diphosphoglycerate↗
PubMed1989

Acidified glycerol lysis test (AGLT) studies in Japan.

We investigated the usefulness of the acidified glycerol lysis test (AGLT) as a diagnostic tool for anemic patients in Japan. The results of the AGLT were found to be useful indicators of autoimmune processes and red cell membrane defects. When glycerol permeability was low and AGLT50 could not be determined, the reduction in optical density could be measured accurately by calculating the value during the first two minutes.

Anemia↗
PubMed1986

Physical activity and blood pressure in normotensive young women.

Blood pressure and heart rate were measured in 22 physically active normotensive women, 20 +/- 1.7 years old (mean +/- SD) and in 25 physically non-active normotensive women 20.9 +/- 1.7 years old in supine, sitting and standing positions. Diastolic and mean blood pressures were found to be significantly lower in active women than non-active women. A significant negative correlation was found between maximal oxygen consumption and blood pressure, and it is suggested that aerobic physical activity could be used as non-pharmacological therapy in cases of moderate and borderline hypertension in young women.

Adult↗
PubMed1986

Erythrocyte involvement in chronic lymphocytic leukaemia.

Chronic lymphocytic leukaemia (CLL) is a lymphoproliferative disorder which sometimes also affects the erythrocytes. In this study we investigated erythrocyte involvement in 23 CLL patients. We found increased erythrocyte osmotic fragility in 15 CLL patients, but this finding was not accompanied by increased permeability to acidified glycerol (decreased AGLT50). Only those CLL patient who had positive direct antiglobulin test (DAT) had significantly decreased AGLT50. AGLT cannot serve as a predictor test for the future development of autoimmune haemolytic anaemia in CLL patients. ATP content was unaffected by the lymphoproliferative disease, but whole blood filterability was markedly decreased in CLL patients. Our study supports the hypothesis that erythrocytes are indeed affected by the lymphoproliferative disorder, even in the absence of overt autoimmune haemolytic processes.

Adenosine Triphosphate↗
PubMed1984

Lateral mobility of phospholipids in the external and internal leaflets of normal and hereditary spherocytic human erythrocytes.

The lateral diffusion coefficients (D) and the mobile fractions of the fluorescent phospholipid N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanolamine (NBD-PE) and of membrane proteins labelled with fluorescein isothiocyanate, were measured by fluorescence photobleaching recovery on erythrocytes from healthy persons and from a hereditary spherocytosis patient. Measurements of lipid probe mobility were performed on ghosts labelled by NBD-PE exclusively at the external monolayer, or at both sides of the membrane. Our results indicate the following: (1) The mean values and the temperature dependence of D are different at the external and internal membrane leaflets. (2) In both normal and HS ghosts the mobile fraction of NBD-PE in the external monolayer does not depend significantly on temperature. On the other hand, the mobile fraction in the internal monolayer is reduced as the temperature is decreased. (3) At low temperatures, the mobile fraction of NBD-PE in the internal monolayer of spherocytic ghosts is significantly lower than the mobile fraction in the internal monolayer of normal ghosts. (4) No differences were observed between the mobilities of membrane proteins in normal and in spherocytic ghosts. However, differences were observed between the two cell populations in the temperature-dependence of the intrinsic fluorescence of unlabelled membrane proteins. The implications of these results for membrane phospholipid asymmetry and for cytoskeletal interactions with the internal lipid monolayer are discussed.

Erythrocyte Membrane↗
PubMed1984

Tritiated water metabolism during dehydration and rehydration in the camel.

The metabolism of tritiated water in the camel was compared in two 10-day periods, one when water was readily available and the second during dehydration. There was a radically depressed metabolism after 2 days of dehydration. Two other experiments examined the absorption rate of drinking water. In one experiment drinking water was labeled with tritium, and in the second experiment dilution of tritium-labeled blood was examined. In both experiments there was a rapid uptake and dilution of the blood, which continued for 4 h. Following this only slight changes were observed up to 24 h after drinking. The results are in accord with other data showing changes in erythrocyte shape 4 h after rapid rehydration. It is concluded that there is a rapid absorption of water in the rehydrating camel.

Absorption↗