Biomedical subjects
Publications and source records attributed to J G Szelényi.
We demonstrated that thymocytes have significantly lower AChE activity, no mAChR binding capacity and the same nAChR binding value, that we can measure on PBLs. The expression of all these structures was changed due to mitogenic stimulation. There is a strong evidence that cholinergic modulation may play a role in T-cell differentiation.
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The alteration of acetylcholinesterase (ACHE) activity, a marker enzyme of erythroid differentiation, was studied during the hemin-induced erythroid differentiation of K562 human leukemia cells in suspension culture. The kinetics of postinduction differentiation was followed by determining the hemoglobin (Hb) content and the ACHE activity of cells. Embryonic hemoglobins as well as small quantities of fetal Hb (HbF) were synthetized by stimulated cells. The peaks of ACHE activity preceded the highest level of Hb content and, following induction, reached their pinnacles at 72 and 120 hours, respectively. These data indicate that ACHE activity is an earlier and more sensitive marker for hemin-induced erythroid differentiation of K562 cells than is elevated Hb content. Electrophoretic mobility of ACHE from hemin-treated cells proved to be the fetal type, but after incubation with neuraminidase, the rate of migration decreased to the level of the adult type enzyme.
Blood sample from a 52 year old woman of mild anaemia was investigated for thalassaemia. Based on the haematological data and the results of the restriction enzyme analysis we concluded that the patient was heterozygote for alpha-thal-1 and alpha-thal-2.
Chromatographic and electrophoretic quantitation of the two different kinds of abnormal alpha-chain variations, present in the double heterozygote for Hb J Buda/Hb A/Hb G Pest, revealed a relative abundance of Hb J Buda in the young red cells in comparison to the old and total erythrocyte populations of the same individual. This result is in good agreement with the literary data on the unequal mRNA production of the two alpha-globin genes, providing the supposition that unequal alpha-gene expression is manifested at the protein level in humans too.
The specific AchE (EC 3.1.1.7) activity of lymphocytes from the peripheral blood of normal donors was determined. On Leukopak filter the isolated T lymphocytes showed activity, whereas in stepwise Percoll gradient, population TLD displayed enzyme activity. The THD and B cells were inactive. [Szelényi J. G., Bartha E. & Hollán S. R. (1982) Br. J. Haemat. 50, 241]. A mixed cell population derived from CLL patients had significantly lower enzyme activity than normal. With the progress of B-cell proliferation AchE activity decreased in parallel with the number of T cells. The sp. act. of TLD population isolated from CLL patients was the same as that of normal donors whereas their B cells were inactive.
Acetylcholinesterase (AchE) activity of normal human peripheral blood lymphocytes was determined by an adaptation of the colorimetric and radiometric techniques described for other cells. The enzyme activity seemed to be correlated to the number of T-lymphocytes in the blood. To decide whether only the T-cells possess AchE activity the lymphocytes were separated on Leucopac filter and on Percoll density gradient. B-lymphocytes had no detectable enzyme activity, while the T-lymphocyte fraction represented the total activity measured in the unseparated sample. The majority of AchE activity could be demonstrated in T-lymphocytes of lower density (TLD). The role of AchE in the plasma membrane of various blood cells is not known. Nevertheless, the enzyme is a good marker of the integrity and functional state of the membrane. The difference observed in AchE activity of the lymphocyte populations seems to be suitable for using it to characterize T-lymphocytes.
The total amount of haemoglobin-bound glucose is determined by the chemical method for quantification of glycosylated haemoglobin, used in the control of diabetic patients. About 40 per cent of the measured amount of glucose is bound by the alpha chains of haemoglobin. The effect of substitution of alpha chains on the glycosylation of the abnormal and normal chains was investigated in a J Buda and G Pest heterozygote. Intact red blood cells were incubated in the presence of labelled glucose of 0.20 MBq/mumol specific activity and 35 mM concentration, and nonenzymatic glucose incorporation into normal and abnormal alpha chains was followed. By the help of fingerprinting and autoradiography of separated chains the distribution of the incorporated radioactivity was investigated. Based on the results we may conclude that (i) 65 per cent of incorporated glucose is bound to five peptides; (ii) the abnormal chain does not affect the glycosylation of the normal alpha chain; (iii) the substitution of a potent glucose binding site (alpha 61) does not affect the glycosylation of the other residues in the abnormal chain; (iv) the presence of the abnormal chain does not interfere with the diagnostic use of the chemical method for quantification of glycosylated haemoglobin.
This study on erythrocytes in hemoglobin H (Hb H) disease reveals that unstable Hb H is bound to membranes to a greater extent, especially when it forms methemoglobin or is precipitated as inclusion body. The methemoglobin content of these erythrocytes is elevated in spite of a higher activity of NADH-methemoglobin reductase. The ATPase activity is doubled, and the ATP is presumably used for phosphorylation of membrane proteins, which leads to cross-linking of membrane proteins. This assumption could be supported by the observed decrease in non-electrolyte permeability, by increased binding of hemoglobin to the membrane and by polymerisation of membrane proteins detected by SDS-polyacrylamide gel electrophoresis. By means of electron microscopy, it could also be shown that the inclusion bodies are bound to the inner surface of membrane and cause its protrusion. This linkage might be responsible for the observed inhibition of the lateral movement of intramembrane particles.
A method based on measuring the tryptic digestibility of haemoglobin has been elaborated for the detection of mutations affecting the conformation of the haemoglobin molecule. By the aid of this technique not only haemoglobins that prove labile by other procedures can be detected, but such mutants can also be discovered which confer no decreased stability as reflected by clinical and conventional laboratory examinations. The method is suitable for tackling questions of theoretical or basic research interest, whilst in a simplified form it can be applied as a routine laboratory test.
The role of red cell membrane lipids in the membrane-haemoglobin interaction was studied by measuring the surface potential and surface pressure of monomolecular lipid layers interacting with haemoglobin. Lipids of the outer and inner half of the red cell membrane were compared in respect to their haemoglobin-binding capacity. It was shown, that haemoglobin molecules interacted readily with the inner layer lipid film in acidic pH regions. This interaction is reduced as pH is increasing but still exists in the physiological pH range. It is in contrast with the increasing but still exists in the physiological pH range. It is in contrast with the findings for the outer layer lipid film, where only a partial interaction could be shown at pH 4, which was reduced to zero reaching the physiological pH range. It can be concluded from titration experiments that the process of haemoglobin binding as reflected in the measured parameters is irreversible. The result of this model experiments support the hypothesis on phosphatidylserine binding sites for haemoglobin in the inner side of red cell membrane.
A hemoglobin variant of slow electrophoretic mobility has been demonstrated in a Hungarian female patient. The abnormal component amounted to about 30% and proved to be a new hemoglobin variant, alpha 49 (CE7) Ser replaced by Arg, which has been named Hb Savaria.
The results presented here indicate that haemoglobin is an integral part of the red cell membrane. The haemoglobin content of the membrane is highly dependent on the Ca++ content of the membrane in health and disease. Changes in the red cell interior alter the whole organization of the membrane and are even reflected in the binding of immunoglobulins to the red cell surface. The preferential binding of Hb-s A2 and S to the membrane has been confirmed. This phenomenon cannot be explained by differences in the charge between these haemoglobins and Hb A.
Gene duplication is one of the basic processes underlying evolutionary changes. The gamma-chains of human foetal haemoglobin is coded by multiple structural genes. The delta-chains of Hb A2 can be regarded as a duplication of the beta-locus. We have presented the first evidence for the presence of two major alpha-chain loci in man. The alpha-gene appears to have duplicated recently, since apart of the single point mutations characterizing Hb J-Buda and Hb G-Pest, the two alpha-gene products seem to be identical. Sensitive immunochemical measurement techniques may reveal structural differences which might escape detection by chemical methods based on differences in charge and/or chromatographic behaviour. Anti-alpha-chain sera recognizing the single amino acid substitution in alphaJ-Buda could be raised in rabbits. The anti-alpha-chain sera were found to be more powerful tools for detecting differences in the primary structure of the chain than the immune sera raised against the whole tetramer. None of the immune sera could reliably differentiate Hb G-Pest from Hb A1. The relative strength of complement fixation of the alpha-chains from haemoglobin A1 F and A2 was compared by hybridizing these human haemoglobins with caninehaemoglobin and measuring the quantitative complement fixation of the different hybrids with anti-Hb A1 and anti-alphaA1 rabbit immune sera. No antigenic difference among the alpha-chains from haemoglobins A1, A2 and F could be detected by this method either with anti-A1 or with anti-alphaA1 sera. These results do not exclude the possibility of conformational differences between the alpha-chains in native Hb A and Hb F. The antigenic activity of the alpha-chains of Hb A from normal subjects (alphaA1) and of the alpha-chains of Hb A from a double heterozygote for alphaJ-Buda and alphaG-Pest (alphaA1) were compared by the complement fixation technique. Definite differences could be detected in the relative strength of complement fixation by alphaA1 and alphaA1 with anti-alphaA1 serum. Final decision as to whether alpha-chain duplication is a universal phenomenon or whether it is restricted to only a part of mankind cannot be drawn until the presence of a silent alpha-thalassaemia gene is not excluded in some debated cases by reliable chemical methods. Measurement of alpha-globin genes in Hb H disease with cDNA enriched in alpha-globin sequences provided direct evidence that a non-thalassaemic subject has to have at least four alpha-globin genes per diploid cell.
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Explore the source record for details and available documents.