Tamás Tábi - Academia.edu (original) (raw)
Papers by Tamás Tábi
Objective: A challenge to periodontal disease control is the elimination of bacterial agents resp... more Objective: A challenge to periodontal disease control is the elimination of bacterial agents responsible for gingival inflammation. The bacterial enzyme lysine decarboxylase (LDC) converts lysine to cadaverine in dental biofilms (plaques) that extend into gingival sulci after oral hygiene restriction (OHR). Yet measures of gingival inflammation such as gingival crevicular fluid (GCF) or gingival index are reduced if lysine remains above minimal blood plasma levels, or if LDC is inhibited by vaccination in beagle dogs (J Periodontol, 83:1048-1056, 2012; Vaccine, 30:6706-6712, 2012). Tranexamic acid (TA) is a lysine analog which inhibits plasminogen activated dissolution of fibrin blood clots (fibrinolysis). TA is routinely prescribed for tooth extractions in patients with blood clotting problems. The aim of this study was to determine whether TA inhibits LDC from E. corrodens in vitro and affects LDC activity and gingivitis development in vivo. Method: We determined presence of E. co...
Croatian medical journal, Jan 20, 2015
To study the effect of resveratrol on survival and caspase 3 activation in non-transformed cells ... more To study the effect of resveratrol on survival and caspase 3 activation in non-transformed cells after serum deprivation. Apoptosis was induced by serum deprivation in primary mouse embryonic fibroblasts. Caspase 3 activation and lactate dehydrogenase release were assayed as cell viability measure by using their fluorogenic substrates. The involvement of PI3K, ERK, JNK, p38, and SIRT1 signaling pathways was also examined. Serum deprivation of primary fibroblasts induced significant activation of caspase 3 within 3 hours and reduced cell viability after 24 hours. Resveratrol dose-dependently prevented caspase activation and improved cell viability with 50% inhibitory concentration (IC50)=66.3±13.81 μM. It also reduced the already up-regulated caspase 3 activity when it was added to the cell culture medium after 3 hour serum deprivation, suggesting its rescue effect. Among the major signaling pathways, p38 kinase was critical for the protective effect of resveratrol which was abolishe...
Salivary bacteria produce the enzyme lysine decarboxylase which converts lysine to cadaverine. In... more Salivary bacteria produce the enzyme lysine decarboxylase which converts lysine to cadaverine. In the absence of appropriate oral hygiene, overgrowth of these bacteria depletes lysine. This may contribute to gingival inflammation, while cadaverine contributes to oral malodor. A selective and sensitive capillary electrophoresis method with laser-induced fluorescence detection has been developed for the determination of cadaverine and lysine in saliva, as an indicator of lysine decarboxylase enzyme activity. The diamino compounds were separated in acidic background electrolyte in their mono-labeled form after derivatization with 4-fluoro-7-nitrobenz-2-oxa-1,3-diazole (NBD-F). Linearity and reproducibility of the method in the range 1-50 μmol L(-1) have been demonstrated using saliva samples. The method was applied for the measurement of cadaverine and lysine in the saliva of healthy volunteers with or without proper oral hygiene. In the absence of oral hygiene, the mol fraction of cadaverine to cadaverine plus lysine in saliva increased significantly (0.65 ± 0.13 vs. 0.39 ± 0.18, P < 0.001), indicating the presence of higher amount of bacterial lysine decarboxylase, that may contribute to periodontal diseases.
A rapid and sensitive high-performance liquid chromatography method has been developed for the me... more A rapid and sensitive high-performance liquid chromatography method has been developed for the measurement of oxidized pyridine dinucleotides (NAD þ , NADP þ ) in biological samples following fluorescence derivatization. Under strongly alkaline conditions the pyridinium ring of the nicotinamide moiety reacts with carbonyl compounds, resulting in stable fluorescent products. Upon subsequent addition of concentrated formic acid and treatment with heat, this fluorescence is further amplified and is shifted to higher-wavelength regions. From among the ketones assayed (acetone, ethylmethyl ketone, acetophenone) the condensation product with acetophenone possesses the highest molar relative fluorescence, thus allowing the most sensitive detection in our experimental setup (limit of detection: 0.02 pmol/50 ll injected volume). The fluorescent products have been separated on a reversephase C-18 column using 0.1 M citric acid (pH 3.2)/acetonitrile (92/8, v/v) as mobile phase. Our method is suitable for assaying NADH-and NADPH-dependent enzyme reactions by quantifying oxidized coenzyme products. As an example, the activity of neuronal nitric oxide synthase (nNOS), a NADPH-requiring enzyme, has been assessed by measuring the products NADP þ and L L -citrulline at various substrate (L L -arginine) concentrations. The rate of the uncoupled NADPH oxidation by nNOS can be estimated from the ratio of NADP þ /L L -citrulline produced.
Decreased biological action of nitric oxide (NO) and increased oxidative stress are established t... more Decreased biological action of nitric oxide (NO) and increased oxidative stress are established to be involved in the development of endothelium dysfunction, early sign of diabetic angiopathy. In the present study, increased nitric oxide synthase (NOS) enzyme activity in the aorta and decreased activity in the kidney tissue of streptozotocin-induced diabetic rats has been found in the early phase of the disease. Augmentation of oxidative transformation of NO in the kidney and heart of the diabetic animals has been demonstrated by the measurement of the stable end-products of NO and other reactive nitrogen species. Insulin treatment was found effective to reduce the intensified oxidative metabolism of NO without increasing its production. Reduced biological effects of NO observed in endothelial dysfunction, is thus probably the consequence of its increased oxidative inactivation.
ABSTRACT Objectives: This study was aimed at examining lysine content and bacterial lysine decarb... more ABSTRACT Objectives: This study was aimed at examining lysine content and bacterial lysine decarboxylase activity in the oral cavity, and at determining whether exogenous lysine depletion affects dental biofilm (plaque) accumulation. Lysine decarboxylase removes free lysine by converting it irreversibly to cadaverine, a contributor to oral malodor. After oral hygiene restriction (OHR) for a week, lysine decarboxylase activity of plaque had increased in all gingivally healthy young adults (IADR 2007 New Orleans, #2363). Methods: Following consent saliva, tongue biofilm and plaque samples were collected from 16 healthy volunteers after no overnight tooth-cleaning. Volunteers then received a prophylaxis and maintained oral hygiene while a bioguard was constructed. After another tooth-cleaning, the bioguard protected a quadrant from oral hygiene (1 week). Plaque index (PlI) and gingival crevicular fluid (GCF) exudation were measured and plaque samples were collected from the bioguarded quadrant. Lysine and cadaverine were measured from samples by laser-induced fluorescence after capillary electrophoresis (Anal Bioanal Chem, 391;647-651, 2008). Results: Before OHR, plaque cadaverine and lysine contents (0.210.13, 0.170.05μmol/g) were each ~10-fold greater than in saliva or tongue biofilm. Cadaverine fraction (0.520.14) was ~60% greater. After OHR, plaque cadaverine content was increased (0.340.25μmol/g). Plaque lysine was reduced (0.070.07μmol/g) and correlated positively with PlI (R2=0.58, p<0.001) and GCF (R2=0.46, p<0.01). Collinearity indicated that plaque lysine content underlay the PlI-GCF relationship (R2=0.34, p<0.03) except for two influential outliers exhibiting reduced GCF exudation despite high lysine content and PlI. Conclusion: Lysine decarboxylase limits lysine availability for the initial growth of plaque to induce inflammation. The reduced GCF in outliers may be due to high lysine content maintaining the epithelial barrier to bacterial products. Plaque lysine and cadaverine contents may be biomarkers for diagnosing or examining therapeutic response and lysine decarboxylase inhibitors may be new agents for controlling periodontal disease. Support: Hungarian NKTH ALAP2-9/2006 and OTKA T049708.
Background-Dental biofilms contain a protein that inhibits mammalian cell growth, possibly lysine... more Background-Dental biofilms contain a protein that inhibits mammalian cell growth, possibly lysine decarboxylase from Eikenella corrodens. This enzyme decarboxylates lysine, an essential amino acid for dentally attached cell turnover in gingival sulci. Lysine depletion may stop this turnover, impairing the barrier to bacterial compounds. The aims of this study were to determine biofilm lysine and cadaverine contents before oral hygiene restriction (OHR), and their association with plaque index (PI) and gingival crevicular fluid (GCF) after OHR for a week.
Chiral CE method has been developed for quantitative determination of d-amino acid modulators of ... more Chiral CE method has been developed for quantitative determination of d-amino acid modulators of NMDA glutamate receptor; d-serine and d-aspartate along with l-glutamate and l-aspartate in biological samples. These ligands are suggested to be involved in regulation of NMDA receptor related brain functions, such as neurogenesis, neuronal plasticity, and memory formation. For sensitive determination of the amino acids LIF detection was chosen, and a fluorogenic reagent, 7-fluoro-4-nitro-2,1,3-benzoxadiazole was used for derivatization. An amino-modified β-CD, 6-monodeoxy-6-mono(3-hydroxy)propylamino-β-CD (HPA-β-CD) was applied as chiral selector. Determinations were accomplished in a polyacrylamide coated capillary and reverse polarity was used for the analysis of the negatively charged analytes. The method was optimized and validated; 6 mM HPA-β-CD in 50 mM HEPES buffer, pH 7 was appropriate to achieve baseline separation of the analytes. The limit of quantification with acceptable accuracy is 0.05 μM for both d-amino acids. The method was used for the determination of d-aspartate and d-serine content in various brain regions of adult mice.
Cyclization of tert-anilines with a properly substituted vinyl moiety by the tert-amino effect af... more Cyclization of tert-anilines with a properly substituted vinyl moiety by the tert-amino effect affords fused pyridines. This type of ring closure reaction of 5-morpholino-4-vinylpyridazinones and a benzene analogue was investigated by differential scanning calorimetry (DSC) measurements. The structure of products was confirmed by spectroscopic and microanalytical methods. The enthalpy values and heats of reactions were obtained from the thermograms by
Several studies have demonstrated the involvement of reactive nitrogen and oxygen species (RNOS) ... more Several studies have demonstrated the involvement of reactive nitrogen and oxygen species (RNOS) in the neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridin (MPTP) and methamphetamine (METH), so the contribution of altered nitric oxide synthase (NOS) enzyme function can be suspected. In this study, about 50% increase in nitric oxide (NO) production in the mouse striatum was found between 4 and 12 h after a single MPTP injection, allowing an increased peroxynitrite (ONOO-) formation in the target brain region. However, METH injection induced a rapid decrease of NO formation both in mouse striatum and hippocampus, reaching its minimum level at 2 h, and restored to the control value after 6 h in the striatum and 12 h in the hippocampus. The uncoupled function of NOS with increased superoxide (O2*-) production after METH injection is suggested.
Tissue level of nitrate and nitrite are established indicators of altered nitric oxide metabolism... more Tissue level of nitrate and nitrite are established indicators of altered nitric oxide metabolism under various pathological conditions. Determination of these anions in biological samples, in the presence of high chloride concentration, using capillary zone electrophoresis suffers from poor detection sensitivity. Separation conditions providing excellent resolution and submicromolar detection sensitivity of nitrate and nitrite have been developed and validated. Simple sample preparation was applied that maintains nitrite stability in tissue extracts and at the same time allows transient isotachophoresis stacking of the analytes. Nitrate and nitrite concentrations in rat brain and liver tissue samples were determined in control and lipopolysaccharide treated animals.
In this paper an overview is provided on practical difficulties as well as applications of capill... more In this paper an overview is provided on practical difficulties as well as applications of capillary electrophoresis coupled to laser induced fluorescence detection methods in the field of analysis of biological samples. Various methodological approaches elaborated for determination of small molecules, peptides and proteins are outlined. Besides giving an overview on detection based on native fluorescence, immune and enzyme assays, the main focus is the problematics of sample derivatization and achievable detection sensitivities in the analysis of real biological samples. The characteristics and applicability of the most commonly used labeling reagents are discussed in details.
Journal of Molecular Structure: THEOCHEM, 2003
... István Bágyi E-mail The Corresponding Author , a , Balázs Balogh E-mail The Corresponding Aut... more ... István Bágyi E-mail The Corresponding Author , a , Balázs Balogh E-mail The Corresponding Author , b , András Czajlik E-mail The Corresponding Author , c , Olivér Éliás E-mail The Corresponding Author , b , Zoltán Gáspári E-mail The Corresponding Author , c , Viktor Gergely ...
Acta pharmaceutica Hungarica, 2006
The possible contribution of reactive oxygen and nitrogen species (RONS) to the development of th... more The possible contribution of reactive oxygen and nitrogen species (RONS) to the development of the neurode-generation came up after the investigations with neurotoxic compounds. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and methamphetamine (METH) have detrimental effect on the dopaminergic neurons. The aim of our study was to examine whether altered nitric oxide synthase (NOS) enzyme activity can be involved in the damage induced by these neurotoxins. The other goal of the study was to investigate the applicability of the measurement of the ratio of NADP+/L-citrulline formed by the enzyme to assess the coupled state of the NOS. Elevated NOS activity in mouse striatum and declined enzyme activity in mouse hippocampus have been found after administration of MPTP Decreased NOS activity in mouse striatum and hippocampus was observed after administration of METH. The ratio of the NADP+/L-citrulline produced by the enzyme provides useful information about the coupling state of t...
Neurochemistry International, 2008
Neurochemical Research, 2010
Deprenyl has been discovered by Knoll and co-workers. The R-enantiomer of deprenyl (selegiline) i... more Deprenyl has been discovered by Knoll and co-workers. The R-enantiomer of deprenyl (selegiline) is a selective and irreversible inhibitor of the B-isoform of monoamine oxidase (MAO-B) enzyme. Due to its dopamine potentiating and possible neuroprotective properties it has an established role in the treatment of parkinsonian patients. By inhibiting MAO-B enzyme, R-deprenyl decreases the formation of hydrogen peroxide, alleviating the oxidative stress also reduced by increased expression of antioxidant enzymes (superoxide dismutases and catalase) reported during chronic treatment. It was shown to prevent the detrimental effects of neurotoxins like MPTP and DSP-4. R-Deprenyl elicits neuroprotective and neuronal rescue activities in concentrations too low to inhibit MAO-B. It is extensively metabolized and some of the metabolites possess pharmacological activities, thus their contribution to neuroprotective properties was also suggested. The recently identified deprenyl-N-oxide is extensively studied in our laboratory. Effects other than neuroprotection, like influencing cell adhesion and proliferation cannot be neglected.
Neurochemical Research, 2012
It has long been proposed that L-aspartate (Asp) is an excitatory neurotransmitter similar to L-g... more It has long been proposed that L-aspartate (Asp) is an excitatory neurotransmitter similar to L-glutamate (Glu) but with distinct signaling properties. The presence of Asp in excitatory synapses of the medial striatum/nucleus accumbens of domestic chicks suggests that Asp plays a role of neurotransmitter also in the avian brain. Neurotransmitters are released from the presynaptic bouton mostly by Ca 2? dependent exocytosis. We used in vivo microdialysis to monitor the simultaneous changes of the extracellular levels of Asp and Glu in the medial striatum of young post-hatch domestic chicks. Microdialysis samples were collected from freely moving birds at 5 min intervals and analysed off-line using capillary electrophoresis. Event-related elevations of extracellular Glu and Asp concentrations in response to handling stress and to high KCl (50 mM) were observed. Increase of Glu and Asp on handling stress was 200 and 250 %, whereas on KCl stimulation the values were 300 and 1,000 %, respectively, if stress was applied before high KCl, and 150 and 200 %, respectively, in the absence of stress. In most cases, the amino acids showed correlated changes, Asp concentrations being consistently smaller at resting but exceeding Glu during stimulation. Using Ca 2? free medium, the KCl triggered elevation of Glu was reduced. When KCl stimulation was combined with tetrodotoxin infusion, there was no significant elevation in Asp or in Glu suggesting that most of the extracellular excitatory amino acids were released by synaptic mechanisms. The results support the suggestion that Asp is co-released with Glu and may play a signaling role (as distinct from that of glutamate) in the striatum of birds.
Objective: A challenge to periodontal disease control is the elimination of bacterial agents resp... more Objective: A challenge to periodontal disease control is the elimination of bacterial agents responsible for gingival inflammation. The bacterial enzyme lysine decarboxylase (LDC) converts lysine to cadaverine in dental biofilms (plaques) that extend into gingival sulci after oral hygiene restriction (OHR). Yet measures of gingival inflammation such as gingival crevicular fluid (GCF) or gingival index are reduced if lysine remains above minimal blood plasma levels, or if LDC is inhibited by vaccination in beagle dogs (J Periodontol, 83:1048-1056, 2012; Vaccine, 30:6706-6712, 2012). Tranexamic acid (TA) is a lysine analog which inhibits plasminogen activated dissolution of fibrin blood clots (fibrinolysis). TA is routinely prescribed for tooth extractions in patients with blood clotting problems. The aim of this study was to determine whether TA inhibits LDC from E. corrodens in vitro and affects LDC activity and gingivitis development in vivo. Method: We determined presence of E. co...
Croatian medical journal, Jan 20, 2015
To study the effect of resveratrol on survival and caspase 3 activation in non-transformed cells ... more To study the effect of resveratrol on survival and caspase 3 activation in non-transformed cells after serum deprivation. Apoptosis was induced by serum deprivation in primary mouse embryonic fibroblasts. Caspase 3 activation and lactate dehydrogenase release were assayed as cell viability measure by using their fluorogenic substrates. The involvement of PI3K, ERK, JNK, p38, and SIRT1 signaling pathways was also examined. Serum deprivation of primary fibroblasts induced significant activation of caspase 3 within 3 hours and reduced cell viability after 24 hours. Resveratrol dose-dependently prevented caspase activation and improved cell viability with 50% inhibitory concentration (IC50)=66.3±13.81 μM. It also reduced the already up-regulated caspase 3 activity when it was added to the cell culture medium after 3 hour serum deprivation, suggesting its rescue effect. Among the major signaling pathways, p38 kinase was critical for the protective effect of resveratrol which was abolishe...
Salivary bacteria produce the enzyme lysine decarboxylase which converts lysine to cadaverine. In... more Salivary bacteria produce the enzyme lysine decarboxylase which converts lysine to cadaverine. In the absence of appropriate oral hygiene, overgrowth of these bacteria depletes lysine. This may contribute to gingival inflammation, while cadaverine contributes to oral malodor. A selective and sensitive capillary electrophoresis method with laser-induced fluorescence detection has been developed for the determination of cadaverine and lysine in saliva, as an indicator of lysine decarboxylase enzyme activity. The diamino compounds were separated in acidic background electrolyte in their mono-labeled form after derivatization with 4-fluoro-7-nitrobenz-2-oxa-1,3-diazole (NBD-F). Linearity and reproducibility of the method in the range 1-50 μmol L(-1) have been demonstrated using saliva samples. The method was applied for the measurement of cadaverine and lysine in the saliva of healthy volunteers with or without proper oral hygiene. In the absence of oral hygiene, the mol fraction of cadaverine to cadaverine plus lysine in saliva increased significantly (0.65 ± 0.13 vs. 0.39 ± 0.18, P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), indicating the presence of higher amount of bacterial lysine decarboxylase, that may contribute to periodontal diseases.
A rapid and sensitive high-performance liquid chromatography method has been developed for the me... more A rapid and sensitive high-performance liquid chromatography method has been developed for the measurement of oxidized pyridine dinucleotides (NAD þ , NADP þ ) in biological samples following fluorescence derivatization. Under strongly alkaline conditions the pyridinium ring of the nicotinamide moiety reacts with carbonyl compounds, resulting in stable fluorescent products. Upon subsequent addition of concentrated formic acid and treatment with heat, this fluorescence is further amplified and is shifted to higher-wavelength regions. From among the ketones assayed (acetone, ethylmethyl ketone, acetophenone) the condensation product with acetophenone possesses the highest molar relative fluorescence, thus allowing the most sensitive detection in our experimental setup (limit of detection: 0.02 pmol/50 ll injected volume). The fluorescent products have been separated on a reversephase C-18 column using 0.1 M citric acid (pH 3.2)/acetonitrile (92/8, v/v) as mobile phase. Our method is suitable for assaying NADH-and NADPH-dependent enzyme reactions by quantifying oxidized coenzyme products. As an example, the activity of neuronal nitric oxide synthase (nNOS), a NADPH-requiring enzyme, has been assessed by measuring the products NADP þ and L L -citrulline at various substrate (L L -arginine) concentrations. The rate of the uncoupled NADPH oxidation by nNOS can be estimated from the ratio of NADP þ /L L -citrulline produced.
Decreased biological action of nitric oxide (NO) and increased oxidative stress are established t... more Decreased biological action of nitric oxide (NO) and increased oxidative stress are established to be involved in the development of endothelium dysfunction, early sign of diabetic angiopathy. In the present study, increased nitric oxide synthase (NOS) enzyme activity in the aorta and decreased activity in the kidney tissue of streptozotocin-induced diabetic rats has been found in the early phase of the disease. Augmentation of oxidative transformation of NO in the kidney and heart of the diabetic animals has been demonstrated by the measurement of the stable end-products of NO and other reactive nitrogen species. Insulin treatment was found effective to reduce the intensified oxidative metabolism of NO without increasing its production. Reduced biological effects of NO observed in endothelial dysfunction, is thus probably the consequence of its increased oxidative inactivation.
ABSTRACT Objectives: This study was aimed at examining lysine content and bacterial lysine decarb... more ABSTRACT Objectives: This study was aimed at examining lysine content and bacterial lysine decarboxylase activity in the oral cavity, and at determining whether exogenous lysine depletion affects dental biofilm (plaque) accumulation. Lysine decarboxylase removes free lysine by converting it irreversibly to cadaverine, a contributor to oral malodor. After oral hygiene restriction (OHR) for a week, lysine decarboxylase activity of plaque had increased in all gingivally healthy young adults (IADR 2007 New Orleans, #2363). Methods: Following consent saliva, tongue biofilm and plaque samples were collected from 16 healthy volunteers after no overnight tooth-cleaning. Volunteers then received a prophylaxis and maintained oral hygiene while a bioguard was constructed. After another tooth-cleaning, the bioguard protected a quadrant from oral hygiene (1 week). Plaque index (PlI) and gingival crevicular fluid (GCF) exudation were measured and plaque samples were collected from the bioguarded quadrant. Lysine and cadaverine were measured from samples by laser-induced fluorescence after capillary electrophoresis (Anal Bioanal Chem, 391;647-651, 2008). Results: Before OHR, plaque cadaverine and lysine contents (0.210.13, 0.170.05μmol/g) were each ~10-fold greater than in saliva or tongue biofilm. Cadaverine fraction (0.520.14) was ~60% greater. After OHR, plaque cadaverine content was increased (0.340.25μmol/g). Plaque lysine was reduced (0.070.07μmol/g) and correlated positively with PlI (R2=0.58, p<0.001) and GCF (R2=0.46, p<0.01). Collinearity indicated that plaque lysine content underlay the PlI-GCF relationship (R2=0.34, p<0.03) except for two influential outliers exhibiting reduced GCF exudation despite high lysine content and PlI. Conclusion: Lysine decarboxylase limits lysine availability for the initial growth of plaque to induce inflammation. The reduced GCF in outliers may be due to high lysine content maintaining the epithelial barrier to bacterial products. Plaque lysine and cadaverine contents may be biomarkers for diagnosing or examining therapeutic response and lysine decarboxylase inhibitors may be new agents for controlling periodontal disease. Support: Hungarian NKTH ALAP2-9/2006 and OTKA T049708.
Background-Dental biofilms contain a protein that inhibits mammalian cell growth, possibly lysine... more Background-Dental biofilms contain a protein that inhibits mammalian cell growth, possibly lysine decarboxylase from Eikenella corrodens. This enzyme decarboxylates lysine, an essential amino acid for dentally attached cell turnover in gingival sulci. Lysine depletion may stop this turnover, impairing the barrier to bacterial compounds. The aims of this study were to determine biofilm lysine and cadaverine contents before oral hygiene restriction (OHR), and their association with plaque index (PI) and gingival crevicular fluid (GCF) after OHR for a week.
Chiral CE method has been developed for quantitative determination of d-amino acid modulators of ... more Chiral CE method has been developed for quantitative determination of d-amino acid modulators of NMDA glutamate receptor; d-serine and d-aspartate along with l-glutamate and l-aspartate in biological samples. These ligands are suggested to be involved in regulation of NMDA receptor related brain functions, such as neurogenesis, neuronal plasticity, and memory formation. For sensitive determination of the amino acids LIF detection was chosen, and a fluorogenic reagent, 7-fluoro-4-nitro-2,1,3-benzoxadiazole was used for derivatization. An amino-modified β-CD, 6-monodeoxy-6-mono(3-hydroxy)propylamino-β-CD (HPA-β-CD) was applied as chiral selector. Determinations were accomplished in a polyacrylamide coated capillary and reverse polarity was used for the analysis of the negatively charged analytes. The method was optimized and validated; 6 mM HPA-β-CD in 50 mM HEPES buffer, pH 7 was appropriate to achieve baseline separation of the analytes. The limit of quantification with acceptable accuracy is 0.05 μM for both d-amino acids. The method was used for the determination of d-aspartate and d-serine content in various brain regions of adult mice.
Cyclization of tert-anilines with a properly substituted vinyl moiety by the tert-amino effect af... more Cyclization of tert-anilines with a properly substituted vinyl moiety by the tert-amino effect affords fused pyridines. This type of ring closure reaction of 5-morpholino-4-vinylpyridazinones and a benzene analogue was investigated by differential scanning calorimetry (DSC) measurements. The structure of products was confirmed by spectroscopic and microanalytical methods. The enthalpy values and heats of reactions were obtained from the thermograms by
Several studies have demonstrated the involvement of reactive nitrogen and oxygen species (RNOS) ... more Several studies have demonstrated the involvement of reactive nitrogen and oxygen species (RNOS) in the neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridin (MPTP) and methamphetamine (METH), so the contribution of altered nitric oxide synthase (NOS) enzyme function can be suspected. In this study, about 50% increase in nitric oxide (NO) production in the mouse striatum was found between 4 and 12 h after a single MPTP injection, allowing an increased peroxynitrite (ONOO-) formation in the target brain region. However, METH injection induced a rapid decrease of NO formation both in mouse striatum and hippocampus, reaching its minimum level at 2 h, and restored to the control value after 6 h in the striatum and 12 h in the hippocampus. The uncoupled function of NOS with increased superoxide (O2*-) production after METH injection is suggested.
Tissue level of nitrate and nitrite are established indicators of altered nitric oxide metabolism... more Tissue level of nitrate and nitrite are established indicators of altered nitric oxide metabolism under various pathological conditions. Determination of these anions in biological samples, in the presence of high chloride concentration, using capillary zone electrophoresis suffers from poor detection sensitivity. Separation conditions providing excellent resolution and submicromolar detection sensitivity of nitrate and nitrite have been developed and validated. Simple sample preparation was applied that maintains nitrite stability in tissue extracts and at the same time allows transient isotachophoresis stacking of the analytes. Nitrate and nitrite concentrations in rat brain and liver tissue samples were determined in control and lipopolysaccharide treated animals.
In this paper an overview is provided on practical difficulties as well as applications of capill... more In this paper an overview is provided on practical difficulties as well as applications of capillary electrophoresis coupled to laser induced fluorescence detection methods in the field of analysis of biological samples. Various methodological approaches elaborated for determination of small molecules, peptides and proteins are outlined. Besides giving an overview on detection based on native fluorescence, immune and enzyme assays, the main focus is the problematics of sample derivatization and achievable detection sensitivities in the analysis of real biological samples. The characteristics and applicability of the most commonly used labeling reagents are discussed in details.
Journal of Molecular Structure: THEOCHEM, 2003
... István Bágyi E-mail The Corresponding Author , a , Balázs Balogh E-mail The Corresponding Aut... more ... István Bágyi E-mail The Corresponding Author , a , Balázs Balogh E-mail The Corresponding Author , b , András Czajlik E-mail The Corresponding Author , c , Olivér Éliás E-mail The Corresponding Author , b , Zoltán Gáspári E-mail The Corresponding Author , c , Viktor Gergely ...
Acta pharmaceutica Hungarica, 2006
The possible contribution of reactive oxygen and nitrogen species (RONS) to the development of th... more The possible contribution of reactive oxygen and nitrogen species (RONS) to the development of the neurode-generation came up after the investigations with neurotoxic compounds. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and methamphetamine (METH) have detrimental effect on the dopaminergic neurons. The aim of our study was to examine whether altered nitric oxide synthase (NOS) enzyme activity can be involved in the damage induced by these neurotoxins. The other goal of the study was to investigate the applicability of the measurement of the ratio of NADP+/L-citrulline formed by the enzyme to assess the coupled state of the NOS. Elevated NOS activity in mouse striatum and declined enzyme activity in mouse hippocampus have been found after administration of MPTP Decreased NOS activity in mouse striatum and hippocampus was observed after administration of METH. The ratio of the NADP+/L-citrulline produced by the enzyme provides useful information about the coupling state of t...
Neurochemistry International, 2008
Neurochemical Research, 2010
Deprenyl has been discovered by Knoll and co-workers. The R-enantiomer of deprenyl (selegiline) i... more Deprenyl has been discovered by Knoll and co-workers. The R-enantiomer of deprenyl (selegiline) is a selective and irreversible inhibitor of the B-isoform of monoamine oxidase (MAO-B) enzyme. Due to its dopamine potentiating and possible neuroprotective properties it has an established role in the treatment of parkinsonian patients. By inhibiting MAO-B enzyme, R-deprenyl decreases the formation of hydrogen peroxide, alleviating the oxidative stress also reduced by increased expression of antioxidant enzymes (superoxide dismutases and catalase) reported during chronic treatment. It was shown to prevent the detrimental effects of neurotoxins like MPTP and DSP-4. R-Deprenyl elicits neuroprotective and neuronal rescue activities in concentrations too low to inhibit MAO-B. It is extensively metabolized and some of the metabolites possess pharmacological activities, thus their contribution to neuroprotective properties was also suggested. The recently identified deprenyl-N-oxide is extensively studied in our laboratory. Effects other than neuroprotection, like influencing cell adhesion and proliferation cannot be neglected.
Neurochemical Research, 2012
It has long been proposed that L-aspartate (Asp) is an excitatory neurotransmitter similar to L-g... more It has long been proposed that L-aspartate (Asp) is an excitatory neurotransmitter similar to L-glutamate (Glu) but with distinct signaling properties. The presence of Asp in excitatory synapses of the medial striatum/nucleus accumbens of domestic chicks suggests that Asp plays a role of neurotransmitter also in the avian brain. Neurotransmitters are released from the presynaptic bouton mostly by Ca 2? dependent exocytosis. We used in vivo microdialysis to monitor the simultaneous changes of the extracellular levels of Asp and Glu in the medial striatum of young post-hatch domestic chicks. Microdialysis samples were collected from freely moving birds at 5 min intervals and analysed off-line using capillary electrophoresis. Event-related elevations of extracellular Glu and Asp concentrations in response to handling stress and to high KCl (50 mM) were observed. Increase of Glu and Asp on handling stress was 200 and 250 %, whereas on KCl stimulation the values were 300 and 1,000 %, respectively, if stress was applied before high KCl, and 150 and 200 %, respectively, in the absence of stress. In most cases, the amino acids showed correlated changes, Asp concentrations being consistently smaller at resting but exceeding Glu during stimulation. Using Ca 2? free medium, the KCl triggered elevation of Glu was reduced. When KCl stimulation was combined with tetrodotoxin infusion, there was no significant elevation in Asp or in Glu suggesting that most of the extracellular excitatory amino acids were released by synaptic mechanisms. The results support the suggestion that Asp is co-released with Glu and may play a signaling role (as distinct from that of glutamate) in the striatum of birds.