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Biomedical subjects

G Tóth

Publications and source records attributed to G Tóth.

At least 19 recordsLinked to original sources

[Vascular diseases, spina bifida and schizophrenia in a single family associated with the heterozygote mutation of the heat-sensitive variant of methylenetetrahydrofolate reductase].

Homozygous mutation of the thermolabile variant of methylene tetrahydrofolate reductase (MTHFR) may result in hyperhomocystinemia, leading to an increased risk for early cardiovascular disease, neural tube defects, and possibly major depression, schizophrenia. According to recent studies heterozygosity for the thermolabile variant of the MTHFR gene mutation is also more frequent in patients with thrombotic disease compared to that in the average population. We report on a family with different types of early vascular disease. In four consecutive generations MTHFR heterozygosity was detected: in the proband and in her mother, grandfather and daughter. Further conditions of the family members, possibly due to carrying the mutation, came to light by the pedigree analysis and examinations. The patient had pulmonary emboli at young age, her aunt died of spina bifida shortly after birth. The patient's mother suffers from schizophrenia and depression. The grandfather had pulmonary emboli, her sister with spina bifida occulta also carries the same mutation, as does her daughter who is sofar asymptomatic. In other asymptomatic members of the family no mutations were found. Unexpectedly, hyperhomocystinemia was detected in all heterozygote individuals. Our study demonstrates the necessity for folic acid therapy in mutation carriers to prevent early vascular events, depression and schizophrenia, and also to reduce the risk for neural tube defects in a preconception setting.

Adult↗

Superelastic scattering of electrons from highly charged ions with inner shell vacancies.

We report the measurement of electrons scattered superelastically from highly charged ions having an initial K-shell vacancy. In this process, the scattered electron gains approximately 725 eV of energy from the deexcitation of an excited He-like F7+(1s2s 3S) metastable ion to its ground state. Theoretical calculations based on an R-matrix approach agree well in position, shape, and magnitude with the experimental data.

Journal Article↗

Influence of degradation on binding properties and biological activity of endomorphin 1.

The recently-isolated endogenous peptide endomorphin 1 has high affinity for the mu opioid receptor and plays an important role in analgesia. Several of its degradation products have been isolated from the central nervous system. Degradation products present structural similarities and may influence the receptor binding properties and biological activity of the parent compound. Therefore, we investigated how degradation of endomorphin 1 might influence ligand binding to the mu opioid receptor, the consequent activation of G proteins and its antinociceptive effect. Both N- and C-terminal truncation of endomorphin 1 resulted in peptides presenting considerably lower opioid receptor binding potency. None of these peptides had an effect on GTP binding, nor was able to produce analgesia, suggesting that degradation destroys the biological activity of endomorphin 1.

Analgesia↗

Significance of aromatic-backbone amide interactions in protein structure.

Weakly polar interactions between aromatic rings of amino acids and hydrogens of backbone amides (Ar-HN) have been shown to support local structures in proteins. Their role in secondary structures, however, has not been elucidated. To investigate the relationship between Ar-HN interaction and the stability of local and secondary structures of polypeptides and to improve the prediction of this interaction based on amino acid sequence, the structures of 560 nonhomologous proteins, from the Protein Data Bank, were searched for Ar-HN interactions between the aromatic ring of each Phe, Tyr, and Trp residue at position i and the backbone amide group of any residue, except Pro, at the positions i, i - 1, i - 2, i - 3, i + 1, i + 2, and i + 3. Ar-HN interactions were identified by calculating the chemical shift of the amide hydrogen caused by the proximal aromatic ring. Ar(i)-HN(i + 1, i + 2 and i + 3) interactions were more common (7.10%, 2.08%, and 0.54%, respectively) than were Ar(i)-HN(i - 1, i - 2, and i - 3) interactions (0.66%, <0.1%, and 0.18%, respectively). The value of the chi(1) torsion angle of the aromatic residue in position i depended on the direction of the Ar-HN interaction. The position of the aromatic ring in Ar(i)-HN(i + 1, i + 2, and i + 3) interactions was mostly trans, in Ar(i)-HN(i - 1, i - 2, and i - 3) interactions mainly gauche(-), and in Ar(i)-HN(i) interactions mostly gauche(+). The analyses of the secondary structures of the protein fragments containing Ar-HN interactions showed that Ar-HN interactions were in all types of secondary structures. Search results suggest that Ar-HN interactions have a stabilizing effect on all types of secondary structures.

Amides↗

Quercetin 3,3',4'-tri-O-beta-D-glucopyranosides from leaves of Eruca sativa (Mill.).

Three new quercetin 3,3',4'-tri-O-beta-D-glucopyranosides isolated from leaves of Eruca sativa (Mill.) were identified as quercetin 3,3',4'-tri-O-beta-D-glucopyranoside, quercetin 3'-(6-sinapoyl-O-beta-D-glucopyranosyl)-3,4'-di-O-beta-D-glucopyranoside and quercetin 3-(2-sinapoyl-O-beta-D-glucopyranosyl)-3'-(6-sinapoyl-O-beta-D-glucopyranosyl)-4'-O-beta-D-glucopyranoside. The structures were established by one- and two-dimensional 1H and 13C NMR spectra as well as b

Brassicaceae↗

Behavioral and neuroendocrine actions of endomorphin-2.

The effects of intracerebroventricularly administered endomorphin-2 (EM2) on open-field activity and the hypothalamo-pituitary-adrenal (HPA) system were investigated. EM2 (0.25-1 microg) significantly increased both the locomotor and the rearing activity, resulting in a bell-shaped dose-response curve. EM2 also enhanced corticosterone release, with an even more profound downturn phase at higher concentrations. The corticotropin-releasing hormone (CRH) antagonist alpha-helical CRH9-41 completely abolished the EM2-evoked endocrine and behavioral responses. These findings reinforce the hypothesis that the endomorphins may play a significant role in the regulation of locomotion, rearing activity and the HPA system through the release of CRH.

Analgesics, Opioid↗

Biochemical basis of color as an aesthetic quality in Citrus sinensis.

The biochemical basis of color as an aesthetic quality in mature fruit of navel and Valencia orange (Citrus sinensis) was determined. Saponification of the two major color-imparting components resolved by thin-layer chromatography, followed by reversed-phase high-performance liquid chromatography, revealed that these comprised acyl esters of (9Z)-violaxanthin and beta-citraurin. Identification of the chromophores was based on cochromatography and online spectral analysis. The color quality of flavedo of mature fruit was dependent on the content and relative amounts of (9Z)-violaxanthin and beta-citraurin. Quantitative results revealed that increased color intensity was associated with a decline in the (9Z)-violaxanthin:beta-citraurin ratio from greater than 50 to below 10, an increase in flavedo (9Z)-violaxanthin and beta-citraurin content, and that measurement of the mass and ratio of these carotenoids can be used to accurately color-grade orange fruit for local and export markets.

Carotenoids↗

Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprika.

The changes in the carotenoid pigments of the Capsicum annuum var. lycopersiciforme rubrum during maturation have been investigated quantitatively by means of a HPLC technique. In all of the chromatograms, 40 peaks were detected; 34 carotenoids were identified. The total carotenoid content of the ripe fruits was about 1.3 g/100 g of dry weight, of which capsanthin constituted 37%, zeaxanthin was 8%, cucurbitaxanthin A was 7%, capsorubin constituted 3.2%, and beta-carotene accounted for 9%. The remainder was composed of capsanthin 5,6-epoxide, capsanthin 3,6-epoxide, 5,6-diepikarpoxanthin, violaxanthin, antheraxanthin, beta-cryptoxanthin, and several cis isomers and furanoid oxides. The possible biosynthetic routes for the formation of minor carotenoids containing 3,5,6-trihydroxy-beta-, 3,6-epoxy-beta-, and 6-hydroxy-gamma-end groups are described.

Capsicum↗

(9Z)-capsanthin-5,6-epoxide, a new carotenoid from the fruits of Asparagus falcatus.

From the fruits of Asparagus falcatus a novel minor (Z)-carotenoid has been isolated and, on the basis of spectral data interpretation, characterized as (9Z)-capsanthin-5,6-epoxide [(9Z,3S,5R,6S,3'S,5'R)-5,6-epoxy-3,3'-dihydroxy-5,6-dihydro-beta,kappa-caroten-6'-one, (1)]. In addition, seven other (Z)-carotenoids [namely, (9Z)-, (9'Z)-, (13Z)-, and (13'Z)-capsanthins, (9Z)- and (13Z)-capsorubins, and (9Z)-violaxanthin], which have been previously described from other plants, were isolated and identified.

Asparagus Plant↗

Auto-inhibition of Ca(2+)/calmodulin-dependent protein kinase II by its ATP-binding domain.

Ca(2+)/calmodulin dependent protein kinase (CaMPK) II is a key enzyme in many physiological processes. The enzyme is inactive unless Ca(2+)/CaM binds to it. In this inactive form CaMPK-II does not bind ATP suggesting that the ATP-binding domain is involved in an intramolecular interaction. We show here that F12, a 12 amino acid long peptide fragment of the ATP-binding domain (CaMPK-II(23-34), GAFSVVRRCVKV) can inhibit the Ca(2+)/CaM-dependent activity (IC(50) of 3 microM) but has no effect on the Ca(2+)/CaM-independent activity of CaMPK-II. Kinetic analysis exhibited mixed inhibition with respect to autocamtide-2 and ATP. The inhibition by F12 showed specificity towards CaMPK-II, but also inhibited CaMPK-I (IC(50) = 12.5 microM), while CaMPK-IV (IC(50) = 85 microM) was inhibited poorly and cAMP-dependent protein kinase (PKA) was not inhibited. Substitution of phenylalanine at position 25 to alanine (A12), had little effect on the inhibition of different Ca(2+)/CaM-dependent protein kinases, suggesting that phenylalanine 25 does not play a crucial role in the interactions involving F12. Thus the molecular interactions involving the ATP-binding domain appears to play a role in the regulation of nonphosphorylated CaMPK-II activity.

Adenosine Triphosphate↗

Stabilization of local structures by pi-CH and aromatic-backbone amide interactions involving prolyl and aromatic residues.

Weakly polar interactions between the side-chain aromatic rings and hydrogens of backbone amides (Ar-HN) and CHn of aliphatic groups (pi-CH) are known to form local structures and to stabilize secondary structure in peptides and proteins. To investigate the existence of these interactions and to explore their possible role in constraining the structures of Pro-Xaa and Xaa-Pro fragments in proteins, a database search was performed in a non-redundant set of proteins from the Brookheaven Protein Data Bank for pi-CH and Ar-HN interactions in Pro-Xaa and Xaa-Pro fragments (where Xaa is either Phe, Tyr or Trp). In Xaa-Pro fragments, the percentage of pi-CH interactions and Ar-HN interactions, respectively, was 20.6 and 3.2%, in Pro-Xaa fragments 26.8, 8.6 and 4.0% of the Pro-Xaa fragments contained both interactions, while no Xaa-Pro fragments had both. The protein fragments containing Ar-HN and/or pi-CH interactions were clustered on the basis of similarity of selected torsion angles. The clustering resulted in well defined clusters. Thus, pi-CH and Ar(i)-HN(i) interactions were able to constrain individual conformations of the Pro-Xaa and Xaa-Pro fragments. These local structures were found to be independent of the secondary structure of the polypeptide chains in which the fragments were found.

Amides↗

Effects of endomorphin-1 on open-field behavior and on the hypothalamic-pituitary-adrenal system.

The effects of endomorphin-1 (EM1) on behavioral responses and on the hypothalamic-pituitary-adrenal system were investigated in mice. Locomotor activity was measured in an "open-field" apparatus, with parallel recording of the numbers of rearings and groomings. Different doses of the peptide (250 ng to 5 microg) were administered to the animals intracerebroventricularly 30 min before the tests. EM1 caused significant increases in the locomotor activity and the number of rearings. The effect of EM1 on the basal corticosterone secretion was also investigated. At a dose of 5 microg, the peptide significantly increased plasma corticosterone level. The corticotropin-releasing hormone (CRH) antagonist alpha-helical CRH9-41, applied 30 min prior to EM1 administration, completely abolished the increases in both locomotion and the number of rearings and attenuated the corticosterone release evoked by EM1. These results suggest that the EM1 -induced increases in locomotion and rearing activity as well as the pituitary-adrenal activation are mediated by CRH.

Adrenal Glands↗

High-performance liquid chromatographic separation of enantiomers of synthetic amino acids on a ristocetin A chiral stationary phase.

A macrocyclic glycopeptide, ristocetin A, was used as chiral stationary phase for the high-performance liquid chromatographic separation of enantiomers of 28 unnatural amino acids, such as analogues of phenylalanine, tyrosine and tryptophan, and analogues containing 1,2,3,4-tetrahydroisoquinoline, tetraline or 1,2,3,4-tetrahydro-2-carboline skeletons. Excellent resolutions were achieved for most of the investigated compounds by using reversed-phase or a new polar-organic mobile phase system. The conditions of separation were optimized by variation of the mobile phase composition, temperature and flow-rate.

Amino Acids↗

Convenient synthesis of 3,4-methano-1,2,3, 4-tetrahydroisoquinoline-3-carboxylic acid and its derivatives as doubly constrained nonproteinogenic amino acid derivatives.

Three strategies for the synthesis of the novel, doubly constrained, 3,4-methano-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid and its derivatives were evaluated. Only cyclocondensation of the mono(triphenyl)phosphonium salt derived from 1, 2-bis(bromomethyl)benzene with N-alkoxycarbonyloxamates in 1, 2-dimethoxyethane in the presence of potassium carbonate and subsequent cyclopropanation with dimethylsulfoxonium methylide in dimethyl sulfoxide furnished suitable O- and N-protected derivatives of 3,4-methano-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid in a convenient way. A detailed 2D DQF-COSY and 2D NOESY NMR analysis of the rotational isomerism of the latter bicyclic amino acid derivatives was performed. Various O- and N-protection protocols were worked out to afford access to a whole range of new derivatives of the title amino acid, suitable for peptide synthesis.

Amino Acids↗

[22q11.2 chromosome deletion and velo-cardio-facial syndrome in a patient with tetralogy of Fallot].

Velo-cardio-facial syndrome includes the following clinical features: congenital heart anomaly, velo-pharyngeal malformations and dysmorphic facial features. In 80% of the patients microdeletion of the long arm of chromosome 22 can be detected. Many patients with DiGeorge syndrome have the same underlying chromosomal etiology, however the same deletion results in severe dysmorphic features, immune defect, hypocalcaemia and in severe mental retardation. In isolated heart defects deletion can be detected in about 15% of the patients. We report the detection of the microdeletion in a patient with tetralogy of Fallot, minimal dysmorphic facial features and normal psychomotor development. Early diagnosis of 22q11.2 chromosomal deletion is important for genetic counseling and further rehabilitation. We emphasize the importance of genetic screening in patients with isolated congenital heart defects.

Child, Preschool↗