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At least 55 records · Page 3Linked to original sources
PubMed2000

Vitamin B(1) status assessed by direct measurement of thiamin pyrophosphate in erythrocytes or whole blood by HPLC: comparison with erythrocyte transketolase activation assay.

BACKGROUND: The concentration of thiamin diphosphate (TDP) in erythrocytes is a useful index of thiamin status. We describe an HPLC method for TDP and its results in patients at risk of thiamin deficiency. METHODS: We used reversed-phase HPLC with postcolumn derivatization with alkaline potassium ferricyanide and fluorescence detection. Samples were deproteinized and injected directly onto a C(18) column. TDP concentrations in erythrocytes were compared with those in whole blood. Reference intervals for erythrocyte TDP (n = 147; 79 males and 68 females; mean age, 54 years) and whole blood TDP (n = 124; 68 males and 56 females; mean age, 54 years) were determined in an apparently healthy population. We compared erythrocyte TDP with results of the erythrocyte transketolase activation test in 63 patients who were considered at risk of thiamin deficiency. RESULTS: The method was linear to at least 200 microgram/L. The between-run CV was <8%. The lower limit of quantification for both whole blood and packed erythrocytes was 300 pg on column with a detection limit of 130 pg on column. Recovery of TDP from blood samples was >90%. TDP in erythrocytes correlated strongly with that in whole blood (r = 0.97). Reference intervals for erythrocyte and whole blood TDP were 280-590 ng/g hemoglobin and 275-675 ng/g hemoglobin, respectively. Of the 63 patients suspected of thiamin deficiency, 46 were normal by both TDP and activation tests, 13 were deficient by both tests, 1 was deficient by the activation test but had normal erythrocyte TDP concentrations, and 4 were normal by the activation test but had low TDP. CONCLUSIONS: The HPLC method is precise and yields results similar to the erythrocyte activation assay.

Chromatography, High Pressure Liquid↗
PubMed1980

Anti-erythrocyte autoantibody production in mice associated with the injection of rat erythrocytes.

Mice injected with rat erythrocytes developed anti-erythrocyte autoantibodies which reached a plateau at 4-12 weeks, then gradually declined until at about 24 weeks the majority of mice were negative. In such recovered mice re-challenge with rat erythrocytes produced an accelerated peak of autoantibody and a much more rapid return to a Coombs' negative state. The auto-antibody response was distinguished from the anti-rat response in being more radio-sensitive. Purified autoantibody reacted to higher titre with rat than with syngeneic erythrocytes. Lymphoid cells, from mice given rat erythrocytes (but not sheep, rabbit or guinea-pig erythrocytes) transferred to normal syngeneic recipients given rat erythrocytes suppressed autoantibody production in the recipients. This suppression was much more effective against the autoantibody response than against the response to the inducing cross-reactive antigen; and the degree of suppression was related to the number of cells transferred and to their time of administration relative to the injection of rat erythrocytes. The induction of autoantibody and the generation of suppressor cells in donor animals was unaffected by adult thymectomy. A comparison of the effect of anti-rat erythrocyte antibodies and spleen cells from rat-immunized donors on recipients responses to rat erythrocytes revealed that whereas anti-rat antibodies suppressed both the autoantibody and the anti-rat responses, the spleen cells suppressed only the autoantibody response. Populations of spleen cells, from rat immunized donors, depleted of B cells retained their suppressive activity, whereas the suppressive efficacy of T-cell depleted populations was reduced but not abolished. It is suggested that T cells can specifically interfere with thesponse of autoreactive B cells, although non-T cells (possibly B cells acting by an antibody-feedback mechanism) can also suppress their response.

Animals↗
PubMed1998

An enzymatic assay for erythrocyte creatine as an index of the erythrocyte life time.

OBJECTIVES: To establish and estimate an enzymatic measurement of creatine in erythrocytes as an index of the erythrocyte life time. DESIGN AND METHOD: The measurement of creatine in erythrocytes was performed using an enzymatic assay kit that was developed for serum and urine creatine. An erythrocyte sample was subjected to creatine measurement after hemolysis and deproteinization. Performance of the method for creatine measurement in erythrocytes was estimated. Effects of age and gender on the creatine content of erythrocytes were also estimated in 305 normal subjects. RESULTS: The method showed within-run CVs varying from 0.7 to 1.0% (n = 20), and between-day CVs from 1.3 to 1.7% (15 days). Good linearity was observed at least up to 1000 mumol/L as creatine value in hemolyzed sample. The analytical recovery was calculated to be 98.1 +/- 1.3% on average. No considerable interference by various substances, including guanidino compounds and amino acids, with the assay was observed. Excellent correlation was observed between the present method and high performance liquid chromatography. With the unit of mumol/g Hb: slope, 1.034 +/- 0.003 (mean +/- SD); intercept, -0.059 +/- 0.012 (mean +/- SD); correlation coefficient, 0.9996; and Sy.x, 0.069. With the unit of mumol/L RBC: slope, 1.033 +/- 0.003 (mean +/- SD); intercept, -18.23 +/- 3.55 (mean +/- SD); correlation coefficient 0.9996; and Sy.x, 20.40. A significant increase in erythrocyte creatine was observed in females aged 11- to 50 years old as compared with males in the corresponding age bracket, however, a gender difference was not observed in other age bracket. This finding suggests the possibility of a slight decrease in the erythrocyte life time due to menstruation in females. CONCLUSION: This study showed that the present method is favorable for quantifying erythrocyte creatine, and has analytical characteristics suitable for routine work in clinical laboratories.

Adolescent↗
PubMed1997

Interactions between Fusobacterium necrophorum hemolysin, erythrocytes and erythrocyte membranes.

The interactions between the hemolysin of Fusobacterium necrophorum subsp. necrophorum, erythrocytes and erythrocyte membranes were studied as an attempt to determine the initial characteristics leading to hemolysis. The spectrum of erythrocyte sensitivity indicated that horse, dog and mouse erythrocytes were highly sensitive whereas those of cattle, sheep, goat and chicken were insensitive to the hemolysin. Binding of hemolysin to horse and dog erythrocytes or their ghosts was more pronounced than to those of cattle and sheep as detected by a decrease of hemolytic activity from hemolysin preparations. The kinetics of hemolysis revealed that lysis is preceded by a prelytic phase characterized by binding of hemolysin to erythrocytes. Treatment of horse erythrocytes with hemolysin at various temperatures prior to incubation at 37 degrees C also revealed that this binding prelytic phase is temperature independent. This was followed by a temperature dependent lytic stage since erythrocytes pretreated with hemolysin and incubated at 4 degrees C showed no hemolysis. An inverse relation was found between erythrocyte concentration and hemolytic activity suggesting a multiple-hit mechanism of hemolysis.

Animals↗
PubMed1992

[A study on creatine uptake into human erythrocytes: relation to erythrocyte aging].

In order to assess the relation between creatine uptake into human erythrocytes and erythrocyte aging, actual influx of creatine into erythrocytes and creatine contents in erythrocytes were measured by using method of high performance liquid chromatography and isotopic estimation of 14C-creatine concentration. Actual influx of creatine into erythrocytes was showed rapidly, in spite of constant contents of erythrocyte creatine under the condition to be incubated at 37 degrees C for approximate 4 hours in isotonic saline containing high concentration of creatine. Km values of the creatine uptake into young erythrocytes were evidently smaller than that into old erythrocytes. On the other hand, no significant difference of Vmax values was observed to be dependent on erythrocyte aging.

Creatine↗
PubMed1993

Erythrocyte uptake and protein binding of cyclosporin A (CyA) in human blood: factors affecting CyA concentration in erythrocytes.

To further the understanding of the complexity of cyclosporin A (CyA) pharmacokinetics, we conducted an erythrocyte uptake and efflux study, and a protein binding study in human blood. The uptake study showed that the transport of CyA from the extracellular fraction to erythrocytes was retarded by increased human serum albumin (HSA) and lipid levels in this fraction. In addition, the concentration of CyA in erythrocytes increased with increases in CyA concentration in blood and reductions in hematocrit. The efflux study showed that the transport of CyA from erythrocytes to the extracellular fraction was essentially enhanced by increases of HSA and lipid levels in that fraction, but that these effects were relatively small. There were two affinity binding sites for CyA in ghost-free erythrocyte hemolysate, but not in the plasma fraction. The affinity binding constants for these binding sites were reduced by elevations in temperature, and under physiological conditions, 37 degrees C, almost all the CyA in erythrocytes was bound to a CyA binding protein, namely, cyclophillin. These findings suggest that CyA distribution in blood is of two different types which are present in the erythrocyte and plasma fractions, respectively. Monitoring of blood biochemistry variables showed that the concentration of CyA in erythrocytes had an interlocking relationship with these physiological factors, which were related to patient disease state, i.e., hematocrit, lipids, albumin, and total protein; the concentration of CyA in erythrocytes could be predicted from these physiological factors.

Amino Acid Isomerases↗
PubMed1994

Simultaneous influence of erythrocyte deformability and macromolecules in the medium on erythrocyte aggregation: a kinetic study by a laser scattering technique.

The aggregation and sedimentation kinetics of human erythrocytes was studied by modifying the cellular properties and medium compositions simultaneously. Dextrans of average molecular weight 70400 and 494000 were used to provide suspending medium modifications, while diamide (diazene dicarboxylic acid bis(N,N-dimethylamide)) was used to alter the membrane structural properties. Laser scattering method was employed for this study, and it was compared with a kinetic method combined with a low-shear rheoscope and an image analyzer. From scattered light intensity profiles continuously obtained during aggregation of erythrocytes and sedimentation of the aggregates, characteristic kinetic parameters were computed. Kinetic parameters obtained from a phase of the one-dimensional aggregate formation and sedimentation corresponded well to the velocity of rouleaux formation obtained by the low-shear rheoscope technique. Dextrans accelerated the erythrocyte aggregation and the sedimentation, and diamide treatment suppressed the process by decreasing the erythrocyte deformability. The aggregating force by dextrans overcame the disaggregating force by the decreased deformability. However, the arrangement of erythrocytes as expressed in specific units for aggregates (i.e., rouleaux) became irregular by decreasing the erythrocyte deformability. In conclusion, the progression of erythrocyte aggregation and the structure of the aggregates were dependent on both erythrocyte properties and macromolecules in the medium.

Blood Sedimentation↗
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↗
PubMed2001

Vesicle-mediated trafficking of parasite proteins to the host cell cytosol and erythrocyte surface membrane in Plasmodium falciparum infected erythrocytes.

During the development of the asexual stage of the malaria parasite, Plasmodium falciparum, the composition, structure and function of the host cell membrane is dramatically altered, including the ability to adhere to vascular endothelium. Crucial to these changes is the transport of parasite proteins, which become associated with or inserted into the erythrocyte membrane. Protein and membrane targeting beyond the parasite plasma membrane must require unique pathways, given the parasites intracellular location within a parasitophorous vacuolar membrane and the lack of organelles and biosynthetic machinery in the host cell necessary to support a secretory system. It is not clear how these proteins cross the parasitophorous vacuolar membrane or how they traverse the erythrocyte cytosol to reach their final destinations. The identification of: (1) a P. falciparum homologue of the protein Sar1p, which is an essential component of the COPII-based secretory system in mammalian cells and yeast and (2) electron-dense, possibly coated, secretory vesicles bearing P. falciparum erythrocyte membrane protein 1 and P. falciparum erythrocyte membrane protein 3 in the host cell cytosol of P. falciparum infected erythrocytes recently provided the first direct evidence of a vesicle-mediated pathway for the trafficking of some parasite proteins to the erythrocyte membrane. The major advance in uncovering the parasite-induced secretory pathway was made by incubating infected erythrocytes with aluminium tetrafluoride, an activator of guanidine triphosphate-binding proteins, which resulted in the accumulation of the vesicles into multiple vesicle strings. These vesicle complexes were often associated with and closely abutted the erythrocyte membrane, but were apparently prevented from fusing by the aluminium fluoride treatment, making their capture by electron microscopy possible. It appears that malaria parasites export proteins into the host cell cytosol to support a vesicle-mediated protein trafficking pathway.

Animals↗