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M Horányi

Publications and source records attributed to M Horányi.

At least 19 recordsLinked to original sources
PubMed2006

Saturn's spokes: lost and found.

The spokes are intermittently appearing radial markings in Saturn's B ring that are believed to form when micrometer-sized dust particles are levitated above the ring by electrostatic forces. First observed by the Voyagers, the spokes disappeared from October 1998 until September 2005, when the Cassini spacecraft saw them reappear. The trajectories of the charged dust particles comprising the spokes depend critically on the background plasma density above the rings, which is a function of the solar elevation angle. Because the rings are more open to the Sun now than when Voyager flew by, the charging environment above the rings has prevented the formation of spokes until very recently. We show that this notable effect is capable of stopping spoke formation entirely and restricting the size of the particles in the spokes.

Journal Article↗
PubMed2001

Distinct behavior of mutant triosephosphate isomerase in hemolysate and in isolated form: molecular basis of enzyme deficiency.

In a Hungarian family with severe decrease in triosephosphate isomerase (TPI) activity, 2 germ line-identical but phenotypically differing compound heterozygote brothers inherited 2 independent (Phe240Leu and Glu145stop codon) mutations. The kinetic, thermodynamic, and associative properties of the recombinant human wild-type and Phe240Leu mutant enzymes were compared with those of TPIs in normal and deficient erythrocyte hemolysates. The specific activity of the recombinant mutant enzyme relative to the wild type was much higher (30%) than expected from the activity (3%) measured in hemolysates. Enhanced attachment of mutant TPI to erythrocyte inside-out vesicles and to microtubules of brain cells was found when the binding was measured with TPIs in hemolysate. In contrast, there was no difference between the binding of the recombinant wild-type and Phe240Leu mutant enzymes. These findings suggest that the missense mutation by itself is not enough to explain the low catalytic activity and "stickiness" of mutant TPI observed in hemolysate. The activity of the mutant TPI is further reduced by its attachment to inside-out vesicles or microtubules. Comparative studies of the hemolysate from a British patient with Glu104Asp homozygosity and with the platelet lysates from the Hungarian family suggest that the microcompartmentation of TPI is not unique for the hemolysates from the Hungarian TPI-deficient brothers. The possible role of cellular components, other than the mutant enzymes, in the distinct behavior of TPI in isolated form versus in hemolysates from the compound heterozygotes and the simple heterozygote family members is discussed.

Adult↗
PubMed2001

Study of hepatitis C virus infection in 213 Hungarian patients with Sjögren's syndrome.

In the current study we investigated 213 randomly selected Hungarian patients diagnosed with primary Sjögren's syndrome (SS). All patients were monitored for hepatitis C virus (HCV) infection and 13 were positive. We compared HCV-negative and -positive patients and made observations on how HCV infection alters the clinical and laboratory features of Sjögren's syndrome. On the basis of these findings, we conclude that HCV infection is more frequent in Hungarian SS patients than in the normal population and that the presence of this virus has a disease-modifying effect on SS.

Adult↗
PubMed2001

The detection of hepatitis C virus in South Hungary.

BACKGROUND: More than 100 million people are infected with hepatitis C virus (HCV) worldwide. The prevalence of HCV infection varies from country to country and the natural history of hepatitis C infection is not well understood. OBJECTIVES: The prevalence of anti-HCV positive blood donors in South Hungary was determined. Potential risk factors of HCV transmission were investigated and compared to anti-HCV-negative blood donors. Furthermore, the rate of anti-HCV positivity in children who had received one or more blood transfusions prior to the implementation of anti-HCV blood donor screening was evaluated. STUDY DESIGN: A total of 45719 blood donors and 120 children were tested for the presence of anti-HCV antibodies by second- and third-generation enzyme immunoassays. Positive results were confirmed by a recombinant immunoblot assay. Data on potential sources of HCV transmission were obtained by interviews. RESULTS: Among blood donors, the rate of confirmed HCV antibody-positives was 0.4% (195 of 45719 donors). Previous surgery, transfusion, more than three pregnancies, and tattoos were significantly correlated with confirmed anti-HCV positivity. Two of 120 children (1.7%) were confirmed anti-HCV positives. In both of them, serum HCV RNA could be detected. CONCLUSIONS: The prevalence of anti-HCV positive blood donors in South Hungary is low. Nosocomial infections and tattooing were found to be the most important risk factors for transmission of HCV. Because of the low prevalence of anti-HCV positive blood donors, only a small number of children, who received blood transfusions prior to the implementation of anti-HCV blood donor screening, are infected with HCV.

Adolescent↗
PubMed2000

[Are the hemochromatosis (HFE) gene mutation and hepatitis C virus (HCV) infection risk factors for porphyria cutanea tarda?].

As it is not clear whether mutations in hemochromatosis gene (HFE) and hepatitis C virus (HCV) act independently in the pathogenesis of porphyria cutanea tarda (PCT), and prevalence of both risk factors reveals a great variety in different parts of the world, PCT patients from our Central East European country were investigated for this aspect. The occurrence of the C282Y and H63D mutations in HFE gene were determined in 19 PCT patients and compared with the reported control frequencies. Furthermore, the presence of HCV infection was determined and related to the patients' HFE status. The C282Y mutation was found in 3/19 cases (one patient was homozygous and two heterozygous), with an 10.5% allele frequency (vs. 3.8% control) (p < 0.05). Five patients were heterozygous for the H63D mutation, allele frequency 13.1%, which did not differ from the reported control prevalence of 12.3%. Six patients (31.7%) were HCV-RNA positive, out of the six one was heterozygous for H63D mutation and one was compound heterozygous. HCV infection and HFE C282Y mutations may probably be independent predisposing factors for development of PCT in Hungarian patients.

Adult↗
PubMed2000

Photoelectric charging of dust particles in vacuum.

Photoelectric charging measurements are presented of dust grains in vacuum for isolated grains and for grains near a photoemissive surface. Isolated grains reach a positive-equilibrium floating potential, dependent upon the work function of the particle, which causes the emitted electrons to be returned. Grains dropped past a photoemitting surface reach a negative floating potential for which the sum of the emitted and collected currents is zero. The particles tested are 90-106 microm in diameter and are composed of Zn, Cu, graphite, and glass.

Journal Article↗
PubMed2000

Changes in the acute phase complement component and IL-6 levels in patients with chronic hepatitis C receiving interferon alpha-2b.

In order to study the effect of interferon alpha on the levels of acute phase complement proteins in vivo, serum concentrations of C9 and C1-inhibitor (C1-INH) were measured in patients with chronic hepatitis C before and 3 months after the beginning of interferon alpha2b therapy. Serum levels of the activation product of terminal complement pathway, C5b-9, HCV RNA and IL-6 were also determined. IFN alpha treatment significantly (P<0.0001) increased the serum concentrations of both complement proteins. C5b-9 levels were found to significantly decrease during the same period of time. When the patients were divided into responders or non-responders (more or less than 50% decrease in plasma HCV RNA concentrations) C9 and C1-INH levels were elevated only in the responder patients. There was no correlation between the changes of IL-6 levels or the amounts of IFN alpha administrated on one hand, and the changes in the complement protein levels on the other. These findings suggest that the marked increase in the serum concentrations of the acute phase complement proteins is a secondary phenomenon due to the IFN alpha-caused diminution of the viral load and the resulting immune complex-induced complement activation.

Acute-Phase Proteins↗
PubMed2000

Stability of halo orbits.

We predict new populations of trapped nonequatorial ("halo") orbits of charged dust grains about an arbitrary axisymmetric planet. Simple equilibrium and stability conditions are derived, revealing dramatic differences between positively and negatively charged grains in prograde or retrograde orbits. Implications for the Cassini mission to Saturn are discussed.

Dust↗
PubMed2000

Enhanced association of mutant triosephosphate isomerase to red cell membranes and to brain microtubules.

In a Hungarian family with triosephosphate isomerase (TPI; D-glyceraldehyde-3-phosphate keto-isomerase, EC 5.3.1.1) deficiency, two germ-line identical, but phenotypically differing compound heterozygote brothers (one of them with neurological disorder) have been identified with the same very low (<5%) TPI activity and 20- or 40-fold higher erythrocyte dihydroxyacetone phosphate levels as compared with normal controls. Our present studies with purified TPI and hemolysates revealed the binding of TPI, and the binding of human wild-type and mutant TPIs in hemolysate, to the red cell membrane, and the interference of binding with other hemolysate proteins. The binding of the mutant TPI is enhanced as compared with the wild-type enzyme. The increased binding is influenced by both the altered structure of the mutant and the changes in the red cell membrane. Compared with binding of glyceraldehyde-3-phosphate dehydrogenase, the isomerase binding is much less sensitive to ionic strength or blocking of the N-terminal tail of the band-3 transmembrane protein. The binding of TPIs to the membrane decreases the isomerase activity, resulting in extremely high dihydroxyacetone phosphate levels in deficient cells. In cell-free brain extract, tubulin copolymerizes with TPI and with other cytosolic proteins forming highly decorated microtubules as shown by immunoblot analysis with anti-TPI antibody and by electron microscopic images. The efficacy order of TPI binding to microtubules is propositus > brother without neurological disorder > normal control. This distinct microcompartmentation of mutant proteins may be relevant in the development of the neurodegenerative process in TPI deficiency and in other, more common neurological diseases.

Anemia, Hemolytic, Congenital↗
PubMed2000

Diminished blood levels of reduced glutathione and alpha-tocopherol in two triosephosphate isomerase-deficient brothers.

The glutathione redox system and alpha-tocopherol, both of which are essential for maintaining the normal structure of biological membranes, some other lipid-soluble antioxidants (lycopene, beta-carotene, retinol), and lipid peroxidation, were investigated in the blood from two triosephosphate isomerase (TPI)-deficient brothers. Both of the genetically identical compound heterozygote brothers have congenital hemolytic anemia, but only one of them has a neurological defect, the second cardinal symptom of TPI deficiency. Whole blood reduced glutathione levels were markedly decreased in both brothers. The glutathione reductase activities as well as the NADPH contents of their erythrocytes were in the normal range or slightly enhanced. Increased ratio of oxidized/reduced glutathione, elevated glutathione S-transferase activity, and increased d-lactate level, a metabolite of the glyoxalase pathway, were detected only in the neurologically affected propositus. The plasma carotenoids (lycopene + beta-carotene), alpha-tocopherol/cholesterol + triglyceride ratios, and the erythrocyte alpha-tocopherol levels were significantly decreased in both patients. It seems conceivable that membrane alterations due to the low level of these reducing agents may contribute to the shortened life span of erythrocytes. The imbalance of the prooxidant/antioxidant homeostasis as well as the increased rate of methylglyoxal formation may also have been involved in the development of the neurological manifestations in the propositus.

Adult↗
PubMed2000

Identical germ-line mutations in the triosephosphate isomerase alleles of two brothers are associated with distinct clinical phenotypes.

We describe here a new stop mutation at triosephosphate isomerase (TPI) position 145 in a Hungarian family for which the first mutation (240 Phe-->Leu) was published earlier. The entire genomic TPI locus (exons, introns and promoter) was sequenced and found to be identical in the two compound-heterozygote brothers. Both brothers have the same well-compensated level of non-spherocytic hemolytic anemia and very high levels of the TPI substrate dihydroxyacetonephosphate (DHAP), but only one brother manifests neurologic disorders. Differences in nonsense-mediated mRNA decay may be at the basis of the differences in phenotype expression although it cannot be excluded the interaction with a modifier gene. Based on our earlier results, the development of neurodegeneration may be decisively modulated by the cellular environment of the mutant proteins initiating the process of focal apoptosis of neurons in glycolytic, peroxisomal and prion-induced neurological diseases.

Alleles↗
PubMed2000

C5b-9 and interleukin-6 in chronic hepatitis C. Surrogate markers predicting short-term response to interferon alpha-2b.

BACKGROUND: Available data and our observations suggest that elevated levels of interleukin (IL)-6 and -10 and some complement parameters may be associated with a poor response to IFN alpha. We evaluated how baseline levels of C5b-9, IL-6, and IL-10 influence the outcome of IFN alpha treatment. METHODS: Fifty-one patients with established chronic hepatitis C were enrolled and treated with IFN alpha-2b. Before and after a 12-week-IFN-treatment (3 MU or 5 MU tiw) serum levels of IL-6, IL-10, C5b-9 and RNA of hepatitis C virus (HCV) were assessed. Sera of 46 sex- and age-matched, healthy blood donors served as control. RESULTS: While two-thirds of patients was considered 'responder', 14 patients had no significant decrease either in HCV RNA or in ALT levels. In the responder's group lower baseline levels of IL-6 and C5b-9 were found than those in the 'non-responder' group. As a result of IFN therapy HCV RNA and C5b-9 levels significantly decreased. While the serum concentration of IL-6 increased during the follow-up period, regarding IL-10, no change was observed. In patients with 'low' baseline levels of C5b-9 (<2053 ng/ml) IFN alpha resulted in a significantly (P = 0.0005) higher decrease in HCV RNA level. Regarding 'low' IL-6 values (< 1.47 pg/ml) similar but somewhat less significant (P = 0.0039) difference was found if the change of HCV RNA was investigated. The odds ratio of patients with low IL-6 and/or C5b-9 to responding to IFN alpha treatment was almost 10 times (CI: 9.1 (1.8-50.9)) higher as compared with patients without 'low' levels of these parameters. CONCLUSION: Our data suggest that serum level(s) of IL-6 and/or C5b-9 taken prior to the initiation of IFN treatment may serve as surrogate marker(s) in evaluating patients with chronic hepatitis C whether to get IFN alpha in monotherapy or to consider having combination therapy in the form of IFN alpha-ribavirin.

Adult↗
PubMed1999

[Severe relapse of hepatitis C following liver transplantation. Successful treatment with a combination of interferon-alpha and ribavirin].

A 38-year-old, male patient, with end-stage HCV cirrhosis, underwent liver transplantation (OLT). After a sufficient recovery a rapid elevation of ALT and profound jaundice developed 3 months after OLT, together with a 15-fold rise of pre-transplant HCV RNS level. Liver biopsy was carried out, histology excluded rejection and signs of acute hepatitis were observed. Interferon alpha 2b 3 MU TIW and ribavirin 800 mg/day resulted in normalization of ALT, se. bilirubin and decrease of viral load by 90 per cent at the 3rd month of treatment. Improvement of hepatitis and no rejection was shown by control histology. A 6-month combination therapy followed by continuous ribavirin monotherapy maintains a permanent good condition with normal ALT, no icterus, a continuously low HCV RNA level and a mild chronic hepatitis with fibrosis in the liver histology 18 months after OLT. Danger of HCV reactivation after OLT, difficulties of diagnosis, interactions of immunostimulant and immunosuppressive drugs, advantages of combination therapy are discussed.

Adult↗
PubMed1998

Capture of interplanetary and interstellar dust by the jovian magnetosphere.

Interplanetary and interstellar dust grains entering Jupiter's magnetosphere form a detectable diffuse faint ring of exogenic material. This ring is composed of particles in the size range of 0. 5 to 1.5 micrometers on retrograde and prograde orbits in a 4:1 ratio, with semimajor axes 3 < a < 20 jovian radii, eccentricities 0. 1 < e < 0.3, and inclinations i less, similar 20 degrees or i greater, similar 160 degrees. The size range and the orbital characteristics are consistent with in situ detections of micrometer-sized grains by the Galileo dust detector, and the measured rates match the number densities predicted from numerical trajectory integrations.

Cosmic Dust↗
PubMed1997

Search for the pathogenesis of the differing phenotype in two compound heterozygote Hungarian brothers with the same genotypic triosephosphate isomerase deficiency.

In a Hungarian family with triosephosphate isomerase (TPI) deficiency, two compound heterozygote brothers were found with the same severe decrease in TPI activity, but only one of them had the classical symptoms. In search for the pathogenesis of the differing phenotype of the same genotypic TPI deficiency, an increase in red cell membrane fluidity was found. There were roughly 100% and 30% more 16:0/20:4 and 18:0/20:4 diacyl-phosphatidylcholine species in erythrocytes from the two TPI-deficient brothers than in the probes from healthy controls. The activities of acethylcholinesterase and calmodulin induced Ca2+ ATPase were significantly enhanced in erythrocytes from the propositus as compared with those of the neurologically symptom-free brother and other members of the TPI-deficient family as well as to those from healthy controls. Both enzymes are crucially involved in the function of nerve cells. The observed differences in membrane fluidity and enzyme activities between the erythrocytes from the phenotypically differing TPI-deficient brothers underline the importance of investigations into the effect of biophysical changes in the lipid environment of the membrane proteins on the development of disseminated focal neurological disorders of unknown pathogenic origin.

Acetylcholinesterase↗
PubMed1996

Triosephosphate isomerase deficiency: predictions and facts.

Deficiencies in around 20 enzymes, associated with widely different degrees of severity and complexity, have been identified for human erythrocytes. The fact that glycolysis is crucial for erythrocyte function is reflected by the large number of inherited glycolytic enzymopathies. Triosephosphate isomerase (TPI) deficiency, a rare autosomal disease, is usually associated with nonspherocytic hemolytic anemia, progressive neurologic dysfunction, and death in childhood. The two affected Hungarian brothers studied by us have less than 3% TPI activity and enormously (30-50-fold) increased dihydroxyacetone phosphate (DHAP) concentration in their erythrocytes. The well-established concept of the metabolic control theory was used to test the contribution of TPI and some related enzymes to the control of a relevant segment of the glycolytic pathway in normal and deficient cells. Deviation indices, DEJ = (delta J/delta E) E(r)/J(r), which give a good estimation of flux control coefficients using a single large change in enzyme activity, were determined from the fluxes in the absence and presence of exogeneous enzymes. We found that PFK and aldolase are the enzymes that predominantly control the flux, however, the quantitative values depend extensively on the pH: DEJ values are 0.85 and 0.14 at pH 8.0 and 0.33 and 0.67 at pH 7.2 for aldolase and PFK, respectively. Neither the flux rates nor the capacities of the enzymes seem to be significantly different in normal and TPI deficient cells. There is a discrepancy between DHAP levels and TPI activities in the deficient cells. In contrast to the experimental data the theoretical calculations predict elevation in DHAP level at lower than 0.1% of the normal value of TPI activity. Several possibilities suggested fail to explain this discrepancy. Specific associations of glycolytic enzymes to band-3 membrane proteins with their concomitant inactivation have been demonstrated. We propose that the microcompartmentation of TPI that could further decrease the reduced isomerase activity of the deficient cells, is responsible for the high DHAP level.

Anemia, Hemolytic, Congenital Nonspherocytic↗