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K Tóth

Publications and source records attributed to K Tóth.

At least 19 recordsLinked to original sources
PubMed2006

Morphology and synaptic input of substance P receptor-immunoreactive interneurons in control and epileptic human hippocampus.

Substance P (SP) is known to be a peptide that facilitates epileptic activity of principal cells in the hippocampus. Paradoxically, in other models, it was found to be protective against seizures by activating substance P receptor (SPR)-expressing interneurons. Thus, these cells appear to play an important role in the generation and regulation of epileptic seizures. The number, distribution, morphological features and input characteristics of SPR-immunoreactive cells were analyzed in surgically removed hippocampi of 28 temporal lobe epileptic patients and eight control hippocampi in order to examine their changes in epileptic tissues. SPR is expressed in a subset of inhibitory cells in the control human hippocampus, they are multipolar interneurons with smooth dendrites, present in all hippocampal subfields. This cell population is considerably different from SPR-positive cells of the rat hippocampus. The CA1 (cornu Ammonis subfield 1) region was chosen for the detailed morphological analysis of the SPR-immunoreactive cells because of its extreme vulnerability in epilepsy. The presence of various neurochemical markers identifies functionally distinct interneuron types, such as those responsible for perisomatic, dendritic or interneuron-selective inhibition. We found considerable colocalization of SPR with calbindin but not with parvalbumin, calretinin, cholecystokinin and somatostatin, therefore we suppose that SPR-positive cells participate mainly in dendritic inhibition. In the non-sclerotic CA1 region they are mainly preserved, whereas their number is decreased in the sclerotic cases. In the epileptic samples their morphology is considerably altered, they possessed more dendritic branches, which often became beaded. Analyses of synaptic coverage revealed that the ratio of symmetric synaptic input of SPR-immunoreactive cells has increased in epileptic samples. Our results suggest that SPR-positive cells are preserved while principal cells are present in the CA1 region, but show reactive changes in epilepsy including intense branching and growth of their dendritic arborization.

Adult↗
PubMed2006

Potentiation of irinotecan sensitivity by Se-methylselenocysteine in an in vivo tumor model is associated with downregulation of cyclooxygenase-2, inducible nitric oxide synthase, and hypoxia-inducible factor 1alpha expression, resulting in reduced angiogenesis.

Until recently, the use of Se-methylselenocysteine (MSC) as selective modulator of the antitumor activity and selectivity of anticancer drugs including irinotecan, a topoisomerase I poison, had not been evaluated. Therapeutic synergy between MSC and irinotecan was demonstrated by our laboratory in mice bearing human squamous cell carcinoma of the head and neck tumors. In FaDu xenografts, a poorly differentiated tumor-expressing mutant p53, the cure rate was increased from 30% with irinotecan alone to 100% with the combination of irinotecan and MSC. Cellular exposure to cytotoxic concentration of SN-38, the active metabolite of irinotecan (0.1 microM) alone and in combination with noncytotoxic concentration of MSC (10 microM) did not result in additional enhancement of chk2 phosphorylation and downregulation of specific DNA replication-associated proteins, cdc6, MCM2, cdc25A, nor increase in PARP cleavage, caspase activation and the 30-300 kb DNA fragmentation induced by SN-38 treatment. MSC did not alter significantly markers associated with apoptosis, nor potentiate irinotecan-induced apoptosis. These results indicate that apoptosis is unlikely to be one of the main mechanism associated with the observed in vivo therapeutic synergy. In contrast, significant downregulation of cyclooxygenase-2 (COX-2) expression and activity was observed in the cells exposed to SN-38 in combination with MSC compared to SN-38 alone. Moreover, the inhibition of PGE(2) production was also observed in the cells treated with the combination as compared with SN-38 alone. Analysis of tumor tissues at 24 h after treatment with synergistic modality of irinotecan and MSC revealed significant downregulation of COX-2, inducible nitric oxide synthase (iNOS) and hypoxia-induced factor-1alpha expression (HIF 1alpha). Moreover, decreased microvessel density was observed after irinotecan treatment with the addition of MSC. These results suggest that observed therapeutic synergy correlates with the inhibition of neoangiogenesis through the downregulation of COX-2, iNOS and HIF-1alpha expression.

Animals↗
PubMed2006

DNA damaging capability of hematoporphyrin towards DNAs of various accessibilities.

In this work we wanted to verify that photoactivation of DNA-non-binding porphyrin derivative hematoporphyrin IX (Hp) is able to induce damages in DNAs of various accessibilities such as B-conformation and superhelical isolated DNA, nucleoprotein complex and intracellular DNAs. It was found that photodynamic reaction of Hp results significant changes in thermal stability of isolated T7 DNA and induces single strand breaks in supercoiled Bluescript plasmid isolated from Escherichia coli cells. As optical melting measurements revealed, the irradiation of photosensitized T7 nucleoprotein complex leads to a destabilization of the protein capsid. The photodynamic reaction affected both the protein structure and DNA-protein interaction, however, the parameters corresponding to the DNA denaturation are not influenced. The accumulation of Hp in HeLa cells was followed by laser scanning confocal microscopy. The picture received is typical for lipophilic dyes. When Hp loaded cells were irradiated, a reduction of viability could be observed in a concentration and a light dose dependent manner; 12microM porphyrin induced almost complete cell killing after 30min irradiation. After similar treatment, alkaline agarose gel electrophoresis of isolated nuclear DNA did not show the presence of single strand breaks. The alkaline comet assay also failed to demonstrate any DNA damage in HeLa cells. We also considered the possibility of the generation of damages in intracellular SV40 DNA. According to the electropherograms there was no difference between the patterns of DNAs from treated and control samples.

DNA↗
PubMed2006

[Initial experience with transpalpebral orbital lipectomy].

PURPOSE: The aim of this study was to evaluate the short-term effectiveness of transpalpebral orbital lipectomy. METHOD: Using a transpalpebral approach, 2.0-6.5 ml connective tissue was removed from 50 orbits of 33 patients with mild to severe Graves' orbitopathy (25 females, 8 males) over a 5-year period. Indications for surgery comprised cosmetic correction of exophthalmos (27/33 patients), corneal damage (5/33), and rapid bilateral deterioration of visual acuity in 1 patient. RESULTS: In 27 patients undergoing correction for aesthetic purposes no change in visual acuity ensued; in 4 of 5 keratopathy patients an improvement in visual acuity was detected. Diplopia ceased in 4 of 13 patients, diminished in 3 of 13 cases, and constantly increased in 2 of 13 cases. The high intraocular pressure returned to normal in 8 of 13 patients. The proptosis was reduced at 3.2+/-1.3 mm. CONCLUSION: Transpalpebral orbital lipectomy is a low-risk, highly effective technique for orbital decompression in both acute and chronic cases of Graves' orbitopathy.

Adolescent↗
PubMed2004

Properties of mixed alkanethiol-dendrimer layers and their applications in biosensing.

We studied the properties of mixed alkanethiol-dendrimer layers on a gold support and their application in biosensing. We showed that properties of glucose sensor can be modified using a different ratio of 1-hexadecanethiol (HDT) and poly(amidoamine) dendrimer of first generation (G1). The cyclic voltammetry in the presence of the redox couple, Fe(CN)(6)(3-)/Fe(CN)(6)(4-), was used for estimating how effectively the layer blocks the redox probe's access to the electrode surface. A scanning electrochemical microscope (SECM) was used to image the resulting distribution of the organic compounds. We found that with increasing content of dendrimers, the integrity of the layers was improved.

Biosensing Techniques↗
PubMed2003

Photosensitized inactivation of T7 phage as surrogate of non-enveloped DNA viruses: efficiency and mechanism of action.

We investigated the efficiency and the mechanism of action of a tetraphenyl porphyrin derivative in its photoreaction with T7 phage as surrogate of non-enveloped DNA viruses. TPFP was able to sensitize the photoinactivation of T7 phage in spite of the lack of its binding to the nucleoprotein complex. The efficiency of TPFP photosensitization was limited by the aggregation and by the photobleaching of porphyrin molecules. Addition of sodium azide or 1,3-dimethyl-2-thiourea (DMTU) to the reaction mixture moderated T7 inactivation, however, neither of them inhibited T7 inactivation completely. This result suggests that both Type I and Type II reaction play a role in the virus inactivation. Optical melting studies revealed structural changes in the protein part but not in the DNA of the photochemically treated nucleoprotein complex. Polymerase chain reaction (PCR) also failed to demonstrate any DNA damage. Circular dichroism (CD) spectra of photosensitized nucleoprotein complex indicated changes in the secondary structure of both the DNA and proteins. We suggest that damages in the protein capsid and/or loosening of protein-DNA interaction can be responsible for the photodynamic inactivation of T7 phage. The alterations in DNA secondary structure might be the result of photochemical damage in phage capsid proteins.

Bacteriophage T7↗
PubMed2001

Enzyme-linked immunosorbent assay for the determination of blood coagulation factor XIII A-subunit in plasma and in cell lysates.

A new one-step ELISA was developed for the determination of the concentration of blood coagulation factor XIII subunit A (FXIII-A) in plasma and in cell lysates. Monoclonal antibodies directed against different epitopes on FXIII-A were used for the assay. The capture antibody was biotinylated on its carbohydrate moiety and the detection antibody was labelled with horseradish peroxidase. The antigen-antibody reaction was carried out in the well of a streptavidin-coated microplate. Complex formation with FXIII subunit B (FXIII-B) and association to fibrinogen did not influence the accessibility of the antibodies to FXIII-A. The method could be performed within 2 h and demonstrated good reproducibility, recovery and sensitivity. Plasma samples could be assayed after storage at -20 degrees C for at least 6 months. However, in the case of platelet lysates freezing and rethawing resulted in a significant loss of FXIII-A. FXIII-A concentrations measured in the plasma samples of healthy individuals and patients correlated well with the concentrations of complexed plasma FXIII (A2B2) and with the results of FXIII activity measurements. A reference range of 46-82 fg/platelet was established for platelet FXIII-A.

Antibodies, Monoclonal↗
PubMed2001

Picomolar detection limits with current-polarized Pb2+ ion-selective membranes.

Minor ion fluxes across ion-selective membranes bias submicromolar activity measurements with conventional ion-selective electrodes. When ion fluxes are balanced, the lower limit of detection is expected to be dramatically improved. As proof of principle, the flux of lead ions across an ETH 5435 ionophore-based lead-selective membrane was gradually compensated by applying a few nanoamperes of galvanostatic current. When the opposite ion fluxes were matched, and the undesirable leaching of primary ions was eliminated, Nernstian response down to 3 x 10(-12) M was achieved.

Journal Article↗
PubMed2001

Trajectory of nucleosomal linker DNA studied by fluorescence resonance energy transfer.

While the structure of the nucleosome core is known in atomic detail, the precise geometry of the DNA beyond the core particle is still unknown. We have used fluorescence resonance energy transfer (FRET) for determining the end-to-end distance of DNA fragments assembled with histones into nucleosomes. The DNA of a length of 150-220 bp was labeled with rhodamine-X on one end and fluorescein or Alexa 488 on the other. Assembling nucleosomes on these DNA fragments leads to a measurable energy transfer. The end-to-end distance computed from the FRET increases from 60 +/- 5 A at 150 bp to 75 +/- 5 A at 170 bp without measurable change above it. These distances are compatible with different geometries of the linker DNA, all having in common that no crossing can be observed up to 220 bp. Addition of H1 histone leads to an increase in energy transfer, indicating a compaction of the linker DNA toward the nucleosome.

Animals↗
PubMed2001

Direct evidence of ionic fluxes across ion-selective membranes: a scanning electrochemical microscopic and potentiometric study.

Scanning electrochemical microscopy (SECM) supplemented with potentiometric measurements was used to follow the time-dependent buildup of a steady-state diffusion layer at the aqueous-phase boundary of lead ion-selective electrodes (ISEs). Differential pulse voltammetry is adapted to SECM for probing the local concentration profiles at the sample side of solvent polymeric membranes. Major factors affecting the membrane transport-related surface concentrations were identified from SECM data and the potentiometric transients obtained under different experimental conditions (inner filling solution composition, membrane thickness, surface pretreatment). The amperometrically determined surface concentrations correlated well with the lower detection limits of the lead ion-selective electrodes.

Ion-Selective Electrodes↗
PubMed2001

Effect of vasoactive peptides on Tetrahymena. chemotactic properties of endothelins (ET-1, ET-2, ET-3, fragment 11-21 of ET-1 and big endothelin-1): a short-term inducible signalling mechanism of chemotaxis.

The unicellular Tetrahymena is a sensitive model for the study of chemotaxis induced by endothelins. In short-term chemotactic responses, ET-2 and ET-3 were chemorepellent, compared to the referent control (culture medium) and chemoattractant, ET-1. These differences suggest that the change of some aromatic residues in the loop region (residues 5-9) of the ET-1 abrogates its chemoattractant character. The response of Tetrahymena is highly selective, since substitution of two amino acids are enough to cause this alteration in (behavioural) response. Such a change seems to be more important than the loss of the entire first 10 amino acids (in ET-1 fragment 11-21), since after this it acquires some chemoattractive effect of ET-1. Selection with ET-3 rigorously stimulated the cell's responsiveness to the medium, this ability was abolished by the repeated ET-3 treatment. Big endothelin-1 was repellent in all concentrations. These experiments demonstrate the very sensitive discriminating capacity of chemotactic responsiveness at a low level of phylogeny. Chemotactic selection with endothelins underlines the possibility that there may be separate mechanisms responsible for the short-term chemotactic responses and the long-lasting effects of chemotactic selection.

Animals↗
PubMed2001

Rotational dynamics of curved DNA fragments studied by fluorescence polarization anisotropy.

The rotational dynamics of short DNA fragments with or without intrinsic curvature were studied using time-resolved phase fluorimetry of intercalated ethidium with detection of the anisotropy. Parameters determined were the spinning diffusion coefficient of the DNA fragments about the long axis and the zero-time ethidium fluorescence anisotropy. We find a significant decrease in the spinning diffusion coefficient for all curved fragments compared to the straight controls. This decrease is likewise evident in rotational diffusion coefficients computed from DNA structures obtained by a curvature prediction program for these sequences. Using a hinged-cylinder model, we can identify the change in rotational diffusion coefficient with a permanent bend of 13-16 degrees per helix turn for the sequences studied. Moreover, for some of the curved fragments an increased flexibility has to be assumed in addition to the permanent bend in order to explain the data.

Algorithms↗
PubMed2001

Photoinduced inactivation of T7 phage sensitized by symmetrically and asymmetrically substituted tetraphenyl porphyrin: comparison of efficiency and mechanism of action.

We investigated the efficiency and the mechanism of action of two--one symmetrically and one asymmetrically substituted--glycoconjugated tetraphenyl porphyrins in their photoreaction with T7 phage as a model of nucleoprotein (NP) complexes. A correlation was found between the dark inactivation of T7 and the binding of porphyrins determined by fluorescence spectroscopy. Both types of porphyrin sensitized the photoinactivation of T7, but the slopes of inactivation kinetics were markedly different. There was no correlation between the dark binding and the photosensitizing efficacy of the two derivatives. Inactivation was moderated by 1,3-diphenylisobenzofuran and 1,3-dimethyl-2-thiourea; however, neither of them inhibited T7 inactivation completely. This result suggests that both Type-I and Type-II reactions play a role in the virus inactivation. Optical melting studies revealed structural changes in the protein part but not in the DNA of the photochemically treated NP complex. Polymerase chain reaction analysis of a 555 bp segment of gene 1 and a 3826 bp segment of genes 3 and 4 failed to demonstrate any DNA damage.

Bacteriophage T7↗
PubMed2001

Computerized comparison of the protein compositions of Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum strains.

Protein profiles of six Erysipelothrix rhusiopathiae strains, five Erysipelothrix tonsillarum strains and three Erysipelothrix strains of uncertain taxonomic position were studied by sodium dodecyl sulphate-polyactylamide gel electrophoresis (SDS-PAGE). In a computerized comparison of the protein patterns of the strains, the level of similarity between the strains was determined. The SDS-PAGE protein bands were divided into 14 groups based on molecular weight. The relative distribution of proteins within these groups was used to characterize the strains. These distribution patterns were analysed by computing Pearson's correlation coefficient between strains, and by cluster analysis based on Euclidean distances and the unweighted pair-group method of arithmetic averages (UPGMA). The geometric mean of the similarities calculated by Pearson's correlation coefficient was 0.980 +/- 0.018 between the E. rhusiopathiae strains and 0.979 +/- 0.013 for E. tonsillarum strains. The value was 0.932 +/- 0.036 between the strains belonging to different species. However, a threshold value applicable for identification of a given strain to a species could not be established. Of the three strains of uncertain taxonomic position, the strains designated Rotzunge and Iszap 4 had a protein composition more similar to that of E. tonsillarum than to that of the E. rhusiopathiae type strain. The strain designated Pécs 56, which may be a member of a new species according to literature data, gave inconsistent results by the two methods used. The computerized evaluation method developed here is suitable for the comparison of the protein composition of the strains and for the construction of the protein similarity tree by cluster analysis.

Animals↗
PubMed2001

Hemorheological and oxygen free radical associated alterations during and after percutaneous transluminal coronary angioplasty.

Percutaneous transluminal coronary angioplasty (PTCA) is a frequently used method in the treatment of coronary artery disease. Coronary stenosis, endothelial injury, and ischemia-reperfusion caused by the balloon inflation and deflation during this procedure can cause several changes in blood flow. In our study 19 patients (mean age: 58 +/- 9 years) undergoing PTCA were examined. For the laboratory measurements several blood samples were taken from the femoral vein and the coronary sinus before and 30 minutes after PTCA, and from the cubital vein 1, 2, 5 days and 1, 6 months after PTCA. Among hemorheologic parameters hematocrit, plasma fibrinogen level, plasma and whole blood viscosities were measured and corrected blood viscosity value was calculated. To characterize the oxidative stress, samples were analyzed for thiobarbituric acid reactive substances (TBARS) of blood as a marker of lipidperoxidation and changes in the antioxidant system were investigated by measuring the activity of superoxide dismutase, catalase and the concentration of glutathione; superoxide generating capacity of isolated leukocytes and platelet aggregation were examined as markers of cellular activation. Plasma fibrinogen concentration increased markedly during the first and second day after PTCA (p < 0.001), which was accompanied by the elevation of plasma viscosity (p < 0.05). Plasma fibrinogen returned to the baseline at the one-month check-up visit, but there was a significant increase in its concentration by the end of the sixth month follow-up. Apparent whole blood viscosity at 90 s (-1) showed gradually increasing values up to the one- and six-month check-up visits (p < 0.01), which can partially be explained by the elevation of hematocrit. Corrected blood viscosity was significantly elevated on the fifth day already (p < 0.01), and one month later also. Superoxide production of leukocytes showed an increasing tendency (p = 0.05), and blood TBARS was elevated after one day (p < 0.05) and remained higher during the following days. Catalase activity showed significantly increasing values (p < 0.01) during the hospital phase, then at the end of the first month. SOD activity and spontaneous platelet aggregation were higher in the samples from the coronary sinus than in those from the peripheral vein before the procedure; 30 minutes after PTCA increased levels in the peripheral sample were found (p < 0.01). Our findings indicate that PTCA may cause significant changes in the hemorheologic and free radical associated parameters, which can affect the final outcome of this intervention.

Angioplasty, Balloon, Coronary↗
PubMed2001

Ectopic alphaIIbbeta3 integrin signaling involves 12-lipoxygenase- and PKC-mediated serine phosphorylation events in melanoma cells.

Megakaryocytic genes such as alphaIIbbeta3 can be expressed by malignant cells as part of the disturbances in their gene regulation. However, the function of the gene product greatly depends on the interaction of the ectopic protein with the new environment. The outside-in signaling of the ectopically expressed alphaIIbbeta3 integrin was studied in B16a murine melanoma cells using a monoclonal antibody, specifically directed to the activated conformation of alphaIIbbeta3, PAC-1 and the physiological ligand, fibrinogen. Ligation of alphaIIbbeta3 induced down-regulation of FAK but serine phosphorylation of three protein bands, 20/21, 85 and 140 kDa within 1-15 min. Flow cytometry indicated that the ligation of the receptor in B16a cells induces approximately 50% increase in phosphoserine positive cells within 5-15 min. 12-lipoxygenase is placed downstream in the signaling pathway, since ligation of alphaIIbbeta3 induces 12-HETE production within 5 min and pretreatment of tumor cells with select lipoxygenase inhibitior, Baicalein, prevents the increase in serine phosphorylation. Confocal microscopy of adherent tumor cells demonstrated rearrangement of actin filaments upon alphaIIbbeta3 ligation paralleled by downregulation of p125FAK and phoshotyrosine+ adhesion plaques and translocation of PKCalpha to stress fibers and cortical actin. PKC appears to be the major effector serine kinase of the alphaIIbbeta3-coupled signaling pathway, since pretreatment of tumor cells with a select PKC inhibitor, Calphostin C, prevents the ligation-induced serine phosphorylation. Previous studies have indicated a role for the 12-lipoxygenase-PKC signaling pathway in platelet aggregation as well as tumor invasion, therefore the involvement of this cascade in the signaling of the ectopic alphaIIbbeta3 integrin may partially explain its role in tumor progression.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2001

[The effect of carvedilol on enhanced adp-ribosylation and red blood cell membrane damage caused by free radicals].

OBJECTIVE: Previous studies have reported that the beta and alpha adrenoceptor blocker carvedilol had unique protective effect on free radical induced myocardial injury. The aim of this study was to examine how carvedilol regulates ROI-mediated signaling and decreases RBC membrane damage in heart perfusion and rheological model. METHODS: The ischemia-reperfusion induced oxidative cell damages, and changes in the intracellular signaling mediated by reactive oxygen species and peroxynitrite were studied on rats, in Langendorff heart perfusion system (n = 15). The effect of carvedilol on red blood cell suspension viscosity (hematocrit: 60%) incubated with free radical generator (phenazine methosulphate) was also investigated (n = 10). The measurements were performed on a capillary viscosimeter. RESULTS: In both studies a protective effect of carvedilol was found, as the decrease of red blood cell suspension viscosity and K+ concentration in the supernatant indicated. Carvedilol significantly decreased the ischemia-reperfusion induced free radical production and the NAD+ catabolism and reversed the poly- and mono-ADP-ribosylation. Carvedilol also decreased the lipid peroxidation and membrane damages as determined by free malondialdehyde production and the release of intracellular enzymes. The self ADP-ribosylation of isolated PARP was also significantly inhibited by carvedilol. CONCLUSION: Our results show that carvedilol can modulate the ROI-induced signaling through poly- and mono-ADP-ribosylation reactions, the NAD+ catabolism in postischemic perfused hearts and has a marked scavenger effect on free radical generator induced red blood cell membrane damage. All these findings may play an important role in the beneficial effects of carvedilol treatment in different cardiovascular diseases.

Adenosine Diphosphate Ribose↗