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Biomedical subjects

G Tóth

Publications and source records attributed to G Tóth.

At least 37 records · Page 2Linked to original sources
PubMed2001

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↗
PubMed2001

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↗
PubMed2001

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↗
PubMed2001

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↗
PubMed2001

(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↗
PubMed2001

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↗
PubMed2001

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↗
PubMed2001

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↗
PubMed2001

Relative deficiency in CpG dinucleotides is a widespread but not unique feature of Gammaherpesvirinae genomes.

Since methylcytosine is relatively unstable, a deficiency of CpG dinucleotides and accumulation of mutations that manifest as TpG (and its complement CpA) is a diagnostic feature of higher eukaryotic DNA sequences subjected to methylation by DNA (cytosine-5) methyltransferases. Latent viral genomes may also be affected by DNA methylation in their host cells. We calculated, therefore, frequencies of dinucleotides in 20 completely sequenced herpesvirus genomes. We found a relative deficiency of CpG dinucleotides and a surplus of TpG + CpA dinucleotides in all lymphotropic gammaherpesvirus genomes except for two strains of rhesus rhadinovirus. DNAs of two strains of human herpesvirus 7, a betaherpesvirus targeting helper T cells, and equine herpesvirus 4, an alphaherpesvirus residing in the lymphoreticular system, also had a moderate CpG deficiency and TpG + CpA surplus. In contrast, most members of Alpha-, and Betaherpesvirinae subfamilies contained a relative surplus of CpG dinucleotides in their DNAs. Our data are consistent with the idea that methylated latent genomes are involved, after reactivation and productive replication, in the natural transmission cycle of most members of Gammaherpesvirinae and certain lymphotropic members of Alpha- and Betaherpesvirinae.

Alphaherpesvirinae↗
PubMed2001

[Carotenoid contents of herbal teas].

Carotenoid composition of 14 herbal tea consumed by Herbaria was investigated by HPLC method. The main components were lutein (36-49%) cis-luteins (2-20%) and beta-carotene (3-25%). alpha- and beta-cryptoxanthin, alpha-carotene and some 5,6-epoxy-carotenoids (neoxanthin, violaxanthin, antheraxanthin) were detected. The chlorophyll content was also measured.

Beverages↗
PubMed2000

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↗
PubMed2000

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↗
PubMed2000

[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↗
PubMed2000

Characterization of N,N(Me)2-Dmt-Tic-OH, a delta selective opioid dipeptide antagonist.

N,N(Me)2-Dimethyl-tyrosine-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid-OH (N,N(Me)2-Dmt-Tic-OH) is a very selective delta opioid dipeptide with elevated antagonist activity. We have radiolabelled this compound by catalytic tritiation of the N,N(Me)2-Dmt(3',5'-I2)-Tic-OH precursor. The ligand labelled rat brain membranes with a Kd value of 0.42 nM and a Bmax of 63.12 fmol/mg protein. The new tritiated ligand showed high affinity for the delta opioid receptor whereas its binding at mu and kappa opioid receptors was weak. N,N(Me)2-Dmt-Tic-OH was able to inhibit the agonist-stimulated binding of the non-hydrolysable GTP analogue ¿35SGTPgammaS, thus attenuating the activation of G proteins via opioid receptors. This simple opioid dipeptide in both normal and labelled form may serve as a useful tool to study delta opioid receptors in vitro and in vivo.

Animals↗
PubMed2000

Genetic subtypes of HIV type 1 in Hungary.

We examined the diversity of HIV-1 subtypes in 11 adults from Hungary, using the heteroduplex mobility assay (HMA) and DNA sequencing. HMA results showed that HIV-1 gp120 sequences from 10 patients were of subtype B, whereas 1 patient, infected in Africa, carried a subtype C strain. DNA sequencing confirmed the HMA results and revealed a high intrasubtype diversity in the C2V3 region of env in different clade B isolates, which suggests multiple introduction of subtype B to Hungary. This study shows that subtype B is the predominant HIV-1 clade in Hungary.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Deltorphin II analogues with 6-hydroxy-2-aminotetralin-2-carboxylic acid in position 1.

Two approaches to the design of very active and highly selective delta opioid peptides were used to obtain new deltorphin analogues with altered hydrophobic and stereoelectronic properties. Deltorphin II analogues were synthesized with the substitution of Ile instead of Val at positions 5 and 6 in the address domain and 6-hydroxy-2-aminotetralin-2-carboxylic acid (Hat) instead of Tyr(1) in the message domain. In the radioreceptor-binding studies, in which type-specific tritiated opioid ligands were used, (R)- and (S)-Hat-deltorphins exhibited similar K(i) values, revealing high delta selectivity. The peptides displayed agonist properties in the in vitro bioassay, with IC(50) values in the subnanomolar range in the mouse vas deferens assay and in the micromolar or higher range in the guinea pig ileum assay, again demonstrating a high selectivity toward delta receptors. The agonist property of the new ligands was confirmed by means of [(35)S]GTPgammaS-binding experiments in membranes of the rat frontal cortex.

2-Naphthylamine↗