The influence of X-rays on human erythrocytes. Primary radicals

The effects on human erythrocytes of water-derived radicals generated by X-rays were studied under anaerobic conditions and in the presence of oxygen. Erythrocyte damage was estimated on the basis of the reduced GSH and MetHb content in the erythrocytes, the -SH group content in the membrane proteins and the amount of K(+)released from the erythrocytes. The results obtained show that the level of reduced GSH was the most sensitive indicator of erythrocyte damage by X-rays followed by the efflux of K(+). The processes of GSH oxidation took place most rapidly under air. At a dose of 100 Gy, the level of GSH fell to about 50%, whereas under argon and N(2)O to about 75% and 65%, respectively. A slight increase in the efflux of K(+)was observed in preparations irradiated under air. However, when erythrocytes were irradiated under argon and N(2)O, the loss of K(+)occurred at a dose 8-times higher. Changes in the remaining parameters occurred at considerably higher doses. On the basis of the results obtained one can say that oxygen is a factor increasing the toxicity of(.)OH radicals towards erythrocytes; however, e(-)(aq)present in the system can cause a decrease in damage to certain cellular components.     

The effect of ultrasound on the antigenic activity of human erythrocytes

The effect of ultrasound (frequency 0.88 MHz, intensity from 0.05 to 1 W/cm2) on alterations in antigenic activity has been investigated in vitro using ABO antigens of human erythrocytes. The existence of threshold doses of ultrasound influence has been found. These doses are shown to be independent of ultrasound intensity. The dependence of the effect on erythrocyte concentration has been established. Individual and group differences in the antigenic resistance to ultrasonic exposure in donors of groups A and B have been revealed. A drop in antigenic activity equal to 97% has been obtained.     

The influence of temperature and incubation time on deformability of human erythrocytes

Human erythrocytes have been heated and stressed in a novel and controlled manner using rectangular microcapillaries. Heated cells attached to the capillary wall were stressed by liquid flow. Under particular conditions of stress, temperature and incubation time the body of the cell could be pulled in the flow, retaining a connection with the glass by means of a narrow process or tether. The tethers appear as: regularly beaded, irregularly beaded or without beads depending upon the incubation conditions. We have outlined the incubation regimes necessary to achieve these different responses in the temperature range 48–55°C. The cells become less deformable as the incubation is continued beyond an optimum time. The behaviour of the tether is compared with that of a viscoelastic liquid. Circular dichroism studies of ghost membranes show that the denaturation of membrane proteins is partially reversible when incubation times are similar to those required to bring about a loss of deformability.     

The effect of the membrane skeleton of non-nucleated erythrocytes on the properties of transport ATPases]

Removal of spectrin and other proteins of membrane skeleton from rat erythrocyte membranes resulted in a significant loss of Na,K-ATPase and Ca-ATPase activities, and even more of respective phosphatase activities. At the same time the modulating influence of ATP and Ca2+ on the enzymes disappeared. These ATPase activities were reconstituted by addition of concentrated spectrin to spectrin-depleted membranes. The activating influence of Ca2+ on ouabain-resistant and ouabain-sensitive phosphatases in ghosts could be discovered only in the presence of ATP. The highest activities of both the phosphatases were revealed when both ATP (0.5 mM) and Ca2+ (10-30 mM) were present simultaneously in the incubation medium. These data show that the functioning of transport ATPases in non-nuclear erythrocyte membranes is related to the membrane skeleton: regulating influence of intracellular ATP and Ca2+ on enzymes seems to be realized through the proteins of the skeleton.     

The influence of cationic dendrimers on antibacterial activity of phage endolysin against P. aeruginosa cells

Nowadays, the researchers make a big effort to find new alternatives to overcome bacterial drug resistance. One option is the application of bacteriophage endolysins enable to degrade peptidoglycan (PG) what in consequence leads to bacterial cell lysis. In this study we examine phage KP27 endolysin mixed with poly(propyleneimine) dendrimers to evaluate an antimicrobial effect against Pseudomonas aeruginosa. Polycationic compounds destabilize bacterial outer membrane (OM) helping endolysins to gain access to PG. We found out that not only bacterial lipopolysaccharide (LPS) is the main hindrance for highly charged cationic dendrimers to disrupt OM and make endolysin reaching the target but also the dendrimer surface modification. The reduction of a positive charge and concentration in maltose poly(propyleneimine) dendrimers significantly increased an antibacterial effect of endolysin. The application of recombinant lysins against Gram-negative bacteria is one of the future therapy options, thus OM permeabilizers such as cationic dendrimers may be of high interest to be combined with PG-degrading enzymes.     

Transport ATPases in the erythrocytes of rats acclimatized to intermittent altitude hypoxia

The activity of Na+/K+- and Ca2+-ATPase and some allosteric properties of Na+/K+-ATPase were studied in whole erythrocytes and their membrane preparations (ghosts) from rats exposed to intermittent altitude hypoxia (10 and 24 exposures, 8 h/day in an altitude chamber, stepwise up to an altitude of 7,000 m). Ca2+-ATPase activity was increased both in whole erythrocytes and ghosts after the first phase of acclimatization (10 exposures). In a standard incubation medium (containing 3 mmol.l-1 MgCl2 ), Na+/K+-ATPase activity in the ghosts was also increased after the initial phase of acclimatization whereas in whole erythrocytes Na+/K+-ATPase was only decreased in the regression phase. At high MgCl2 concentrations (12 mmol.l-1) changes of Na+/K+-ATPase activity both in whole erythrocytes and in the ghosts followed similar time course with a pronounced increase in the first phase of acclimatization (10 exposures) followed by an abrupt drop (24 exposures) and then by a gradual normalization in the regression phase. Sensitivity of the enzyme to mounting MgCl2 concentrations was increased in the ghosts at the end of acclimatization and was decreased in whole erythrocytes during acclimatization and especially in the regression phase. It has been suggested that chronic altitude hypoxia leads to the alteration of cooperative interaction of the Na+/K+-ATPase subunits in the erythrocyte membrane and accumulation of some factor in the cells inhibiting this enzyme.     

The effects of lactose on human erythrocytes

Human erythrocytes suspended in isotonic lactose solution lost potassium and continued to lose potassium even when resuspended in isotonic sodium chloride. The same phenomenon was observed when the cells were suspended in an isotonic solution of the sodium salt of glutamate, a nonpenetrating anion. The presence of 5 mEq per liter of sodium chloride in the lactose or sodium glutamate suspensions greatly reduced the initial potassium loss and the potassium loss when the cells were resuspended in sodium chloride solution. Salts of nonpenetrating anions were less or not effective in blocking lactose damage. The results indicate that absence of penetrating anions in the suspending media is the initiating condition of lactose damage. Chloride and consequently potassium are lost from the erythrocyte. Changes in cellular ionic pattern and/or changes in the cell membrane result in a nontransient damage manifested by continued potassium loss by lactose-treated cells resuspended in isotonic NaCl.     

The mechanism of change in the rate of agglutination of human erythrocytes under the influence of adrenaline

The study of erythrocytes of 80 men showed that adrenaline (10^?10–10^?6 g/mL) and phenylephrine (10^?10–10^?6 g/mL) dose-dependently increase the rate of agglutination of erythrocytes, judging by the decrease in the start time of agglutination, whereas ginipral (10^?10–10^?7 g/mL), on the contrary, decreases it. The effect of adrenaline and phenylephrine is blocked by nicergoline (10^?6 g/mL), enhanced by obzidan (10^?6 g/mL), and is not changed by yohimbine (10^?6 g/mL) and atenolol (10^?6 g/mL). These data indicate that the rate of agglutination increases with the activation of α1-adrenergic receptor (AR) and decreases with the activation of β₂-AR, whereas the activation of α₂- and β₁-AR does not affect it. Trifluoperazine (10^?6 g/mL) as a calmodulin antagonist, barium chloride (10^?6 g/mL) as a Ca²⁺-dependent K⁺-channel blocker, and indomethacin (10^?6 g/mL) as an inhibitor of cyclooxygenase and phospholipase A₂ inhibit the ability of adrenaline to increase the rate of agglutination of erythrocytes. This suggests that this effect of adrenaline is caused by an increased Ca²⁺ entry into the erythrocyte, activation of calmodulin, cyclooxygenase, and phospholipase A₂, and subsequent K⁺ release from the erythrocytes through the Ca²⁺-dependent K⁺ channels, which is regarded as a manifestation of eryptosis. Indirectly, this means that the potentiation of activation of α₁-AR and β₂-AR, respectively, increases and, conversely, decreases the rate of eryptosis.     

The influence of unipolar air ions on the electrophoretic mobility of erythrocytes

Positive air ions decreased the electrophoretic mobility of erythrocytes of cats while negative air ions increased it. Inhalation of normal air supplied by a fan did not affect the electrophoretic mobility of erythrocytes.

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Zusammenfassung Positive Luftionen setzten die elektrophoretische Beweglichkeit der Erythrocyten von Katzen herab, während negative Luftionen sie steigerten. Die Inhalation normaler Luft, die von einem Ventilator unterstüzt wurde,beeinflusste die elektrophoretische Beweglichkeit von Erythrocyten nicht.

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Resume Les ions positifs diminuent la mobilité électrophorétique des érythrocytes des chats, alors que les ions négatifs l'augmentent. L'inhalation d'air normal,même activée par un ventilateur, ne l'influence par contre pas.

     

Oxidative stresses induced the cystine transport activity in human erythrocytes

Cystine was transported into human erythrocytes in the presence of tertiary-butyl hydroperoxide (t-BH) or 1-chloro-2,4-dinitrobenzene (CDNB). The transport rate of cystine was dependent on the extracellular concentration of t-BH or CDNB, and on the incubation time. According to Dowex-1 column chromatography, the transported cystine was incorporated into fractions of glutathione disulfide (GSSG) and glutathione-S (GSH-S) conjugate. The transport of cystine was competitively inhibited by DL-homocystine and alanine. The inhibition rates by DL-homocystine and alanine were 75% and 68%, with similar Ki values of 0.7 mM and 0.6 mM, respectively. It is suggested that cystine transport is induced for glutathione synthesis when human erythrocytes are exposed to oxidative stresses. This transport system of cystine may serve as an emergency function in human erythrocytes.