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G Tóth

Publications and source records attributed to G Tóth.

At least 109 records · Page 6Linked to original sources
PubMed1996

Regional glucose metabolic rates in the human brain: a PET study.

With the purpose of determining the regional cerebral glucose metabolic rates (rCMRglu) in the normal human brain in resting state, we measured with PET and FOG, as the tracer, the distribution of regional radioactivity levels in the brains of seven young healthy volunteers. The individual brain images were stereotactically standardised with the help of a computerised brain atlas. In the next steps, the global cerebral glucose metabolic rate (gCMRglu) in the individual subjects was normalised to 34 mumol/ 100 g/min, followed by the averaging of the stereotactically standardised and metabolically normalised brain images across the subject population. In the final step, on the basis of high precision anatomical information, three-dimensional (3-D) volumes-of-interest (VOI's), covering over thirty anatomical structures in the brain, were created and the rCMRglu values inside the VOI's were determined in the averaged image. The present measurements of the rCMRglu values are in outstanding agreement with those determined in earlier quantitative PET-FDG studies, demonstrating that stereotactically standardised and metabolically normalised images of regional radioactivity distributions in the brain can be used for quantitative determination of rCMRglu values.

Adult↗
PubMed1996

Synthesis of GnRH analogs having direct antitumor and low LH-releasing activity.

New chicken I GnRH agonists and antagonists have been synthesized and tested for their biological activities. The common feature of these analogs was that the molecules had a beta-L-aspartyl residue inserted in position 6. The agonist bound to the pituitary still had low endocrinological activity. On the other hand, it exhibited direct antitumor effect in in vitro assays. The endocrinological activity of the antagonist was low; however, it showed potent, direct antitumor activity. These observations might lead to the development of new GnRH analogs with selective antitumor effect.

Animals↗
PubMed1995

Chromatographic behaviour of opioid peptides containing beta-methylphenylalanine isomers.

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method was developed to obtain pure erythro[2S3S, 2R3R]- and threo[2S3R, 2R3S]-beta-methylphenylalanine. These amino acids were incorporated into an enkephalin, H-Tyr-D-Ala-Gly-beta-MePhe-Val-Val-Gly-NH2, and into a deltorphin C, H-Tyr-D-Ala-beta-MePhe-Asp-Val-Val-Gly-NH2, analogue, which yielded four diastereoisomers of the peptides. The diastereoisomers were separated on different columns and with different eluent systems. The sequence of elution of the peptide diastereoisomers was determined after hydrolysis of the peptides. For identification of the beta-methylphenylalanine enantiomers, enzymatic degradation and an RP-HPLC method were used, with application of 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide as derivatizing reagent.

Amino Acid Sequence↗
PubMed1995

Ancestral, mammalian-wide subfamilies of LINE-1 repetitive sequences.

Analysis of the 3'-ends of approximately 900 separate human LINE-1 (L1) elements from primates revealed 47 contiguous but distinct subfamilies with the L1 family. Eight previously described medium reiteration frequency sequences (MERs) were found to be parts of ancient L1 untranslated 3'-regions which show little or no sequence similarity to the presently active L1 3'-end. Some of the major changes in 3'-end sequence can be explained by recombination events between different L1 repeats as well as between L1 and unrelated repetitive sequences. One of these sequences, MER42, is reported in this paper. With the set of consensus sequences for different subfamilies and their diagnostic features, it is possible to estimate the age of individual LINE-1 elements. Contrary to earlier suggestions, the majority of L1 copies in the human genome is very old; more than half of the identifiable elements were inserted into the genome before the mammalian radiation, as evidenced by elements at orthologous sites in human and other mammalian genomes. Multiple distinct L1 source genes seem to have been active simultaneously over long periods of time.

Amino Acid Sequence↗
PubMed1995

Synthesis and binding characteristics of tritiated TIPP[psi], a highly specific and stable delta opioid antagonist.

The pseudopeptide H-Tyr-Tic psi [CH2-NH]Phe-Phe-OH (TIPP[psi]) is a delta opioid antagonist with high delta receptor affinity and unprecedented delta selectivity. TIPP[psi] was radiolabelled by catalytic tritiation of its precursor [Tyr(3',5'-I2)1]TIPP[psi]. The resulting radioligand, [3H]TIPP[psi], had a specific activity of 1.77 TBq/mmol (47.9 Ci/mmol) and showed high stability against enzymatic degradation. [3H]TIPP[psi] binding to rat brain membranes was saturable and Scatchard analysis indicated a single binding site with a Kd of 0.98 nM and a Bmax of 105.4 fmol/mg. A study of [3H]TIPP[psi] binding displacement by various receptor-selective opioids showed the expected rank order of potency (delta >> mu > kappa). [3H]TIPP[psi] represents an excellent new radioligand for delta receptor labelling studies in vitro and in vivo.

Animals↗
PubMed1995

C-type natriuretic peptide can modify the acute and chronic effects of morphine.

Different doses (0.2-200 ng) of C-type natriuretic peptide (CNP) were administered into the lateral brain ventricle, and morphine (5 mg/kg) was injected subcutaneously. The analgesic effect was measured in a tail-flick test, in CFLP mice. CNP administered centrally did not itself affect pain sensitivity, but it depressed the acute antinociceptive effect of morphine 30 min after icv (0.2, 2 or 20 ng) CNP administration and the 2 and 20 ng doses also decreased this action after 60 min. CNP in a 0.2 or 200 ng dose blocked the development of acute tolerance to morphine after 30 min, as did the 200 ng dose at 60 min. CNP in a 0.2 ng dose blocked the development of chronic tolerance to morphine after 30 min, but there was no effect at 60 min. Morphine withdrawal signs were studied by injecting naloxone (1 mg/kg sc). There was no significant difference in symptoms between the tolerant group and the animals treated with CNP.

Animals↗
PubMed1995

Involvement of neurotransmitters in the 'anxiolytic-like' action of atrial natriuretic peptide in rats.

Effects of centrally administered rat atrial natriuretic peptide (ANP1-28) in different doses (50, 100, 150, 200, 500 or 1000 ng) were examined in rats with respect to anxiolytic properties in an elevated plus-maze model. In doses of 100, 150 and 200 ng, ANP1-28 abolished the normal preference for the closed arms of the maze, and increased the percentage of time spent on the open arms; this is consistent with an 'anxiolytic-like' effect. Doses of 50, 500 and 1000 ng of rANP1-28 produced no behavioral effects in the elevated plus-maze model. Pretreatment with a dopaminergic blocker, an alpha-adrenoreceptor or a beta-adrenoreceptor antagonist antagonized the effect of 200 ng ANP1-28 in the elevated plus-maze test. A muscarinergic cholinergic blocker, a GABA receptor antagonist, a 5-HT receptor antagonist and an opiate antagonist were not able to modulate the 'anxiolytic-like' effects of ANP1-28. These results suggest that a multiple neurotransmitter system activation might be responsible for the ANP1-28-induced 'anxiolytic-like' activity.

Animals↗
PubMed1994

DNA uptake stimulating protein from Neurospora crassa enhances DNA and oligonucleotide uptake also in mammalian cells.

The presence of the DNA uptake stimulating protein (designated earlier as DUSF by Schablik and Szabó (1981) FEMS Microbiol. Lett. 10, 395-397) was demonstrated on the surface of Neurospora crassa (FGSC 1118, slime) fungal cells as well as on HEp-2 and K562 human and F4N mouse tumor cells by immunofluorescence microscopy. DUSF markedly enhanced the uptake of both macromolecular [3H]DNA and of [3H]oligonucleotides by K562, HL-60 and also by DD human leukemia cells. Polyclonal anti-DUSF antibodies inhibited both the basal and stimulated [3H]oligonucleotide uptake by K562 cells. DNA-DNA hybridization has shown that the uptake of linearized pBR322 plasmid DNA into N. crassa and K562 cells was stimulated by DUSF, increasing proportionally with the length of incubation time. Unfragmented plasmid molecules were recovered from the cells. It is assumed that DUSF (or related proteins) may play a role in the physiological uptake of oligonucleotides and DNA not only in N. crassa but also in--at least some--mammalian cells.

Biological Transport↗
PubMed1994

Repetitive DNA in and around translocation breakpoints of the Philadelphia chromosome.

This paper describes systematic sequence studies of repetitive DNA in and around translocation breakpoints on chromosomes 9 and 22, which are involved in the formation of the Philadelphia chromosome in acute leukemias. In addition to Alu repeats described in previous studies, the breakpoint regions appear to contain many other repetitive elements, including a member of a new repetitive family (MER34) reported in this paper. Identification of these repeats broadens current studies on the possible involvement of repetitive DNA in this intensely studied chromosomal translocation.

Base Sequence↗
PubMed1994

Characterization of [3H]Met-enkephalin-Arg6-Phe7 binding to opioid receptors in frog brain membrane preparations.

A tritiated heptapeptide, [3H]Tyr-Gly-Gly-Phe-Met-Arg-Phe ([3H]Met-enkephalin-Arg6-Phe7), with high specific radioactivity has been synthesized in order to characterize its opioid binding activity to frog brain membrane fractions. The apparent KD value of the radioligand calculated from homologous displacement experiments was 3.4 nM, and the maximal number of specific binding sites was 630 fmol/mg of protein. The KD determined from equilibrium saturation binding studies was found to be 3.6 nM. However, the Hill coefficient was far below unity (nH = 0.43), which suggests the presence of a second, lower affinity binding site. The presence of this binding component is strengthened by the displacement experiments performed with levorphanol and some other ligands. It is assumed that the lower affinity site has no opiate character. The rank order of potency of the applied ligands in competing reversibly with [3H]Met-enkephalin-Arg6-Phe7 binding reflects a kappa 2- and/or delta-subtype specificity of the heptapeptide. Binding to a kappa 1 and/or mu site of opioid receptors is excluded, but the existence of a novel endogenous opiate receptor subtype for Met-enkephalin-Arg6-Phe7 in frogs cannot be ruled out. The [3H]-Met-enkephalin-Arg6-Phe7 binding was inhibited by both sodium ions and GppNHp, which suggests the opioid agonist character of the heptapeptide.

Analgesics↗
PubMed1994

[Water absorption and water solubility of prosthetic materials].

Denture base materials investigated with using surface coating polymers fulfilled requirements of ISO Standards 1567 for water sorption and water solubility. The heat-cured polymer gave up water in a greater extent comparing to the cold-cured one. Further amount of water was retained by the surface treatment of coating. A five times increase of water solubility in samples of cold-cured resin was found comparing to the heat-cured ones. A significant decrease of water sorption was measured by using the surface coating.

Absorption↗
PubMed1993

ANP(1-28), BNP(1-32) and CNP(1-22) increase the severity of picrotoxin-kindled seizure syndrome in rats.

The administration of rANP(1-28) in doses of 1.0 and 2.0 nmol (but not 0.2 nmol) into the lateral cerebral ventricle (i.c.v) of rats preliminarily kindled with picrotoxin resulted in an increase of the severity of picrotoxin-kindled convulsions 24 hrs after injection of the peptide. I.c.v. injection of pBNP(1-32) also resulted in a proepileptic effect when it was applied in the same doses with a similar time course; the increased seizure severity was observed 48 hrs after injection of pBNP in a dose of 2 nmol. I.c.v. administration of CNP(1-22) in a dose of 2 nmol induced an increase in the severity of picrotoxin-kindled convulsions 24 and 48 hrs after application of the peptide. None of the peptides influenced the seizure syndrome immediately after the injections. It is presumed that the delayed proepileptic properties of the three natriuretic peptides could be caused by some of their stable fragments which accumulate during their metabolism.

Animals↗
PubMed1993

The effects of atrial natriuretic peptide on food-reinforced conditioning in rats. Interactions with neurotransmitters.

The effects of two doses of rat atrial natriuretic peptide (TANP-1-28), 200 and 500 ng, on 6-day acquisition and extinction of food-reinforced conditional learning (conditional stimulus: light) were studied in rats following administration into the lateral cerebroventricle. With the higher dose, there was a tendency for facilitated acquisition and significantly delayed extinction of the positively reinforced learning task. In order to clarify whether the effect of the peptide is obtained through the involvement of neurotransmitters, the experimental animals were pretreated with different receptor blockers in selected doses that did not influence the behavioral test. Haloperidol, atropine, phenoxybenzamine, and propranolol blocked the action of ANP on extinction of the food-reinforced conditioning, whereas naloxone, bicuculline, and methysergide were ineffective. The results suggest that ANP might be considered a modulating agent in a positively reinforced conditional learning task, and that its action might involve dopaminergic, cholinergic, and alpha- and beta-adrenergic mechanisms.

Animals↗
PubMed1993

Vagal nerve and the gastric mucosal defense.

An essential role for an intact vagal nerve has been proven in the development of gastric mucosal cyto- and general protection. On the other hand, chemically-induced (ethanol, HCl, indomethacin) gastric mucosal damage is enhanced after acute surgical vagotomy. The aims of this paper were to study the possible mechanisms of the vagal nerve in the development of gastric mucosal defense. The following questions were addressed: 1) effect of surgical vagotomy on the development of ethanol- (ETOH), HCl-, and indomethacin (IND)-induced gastric mucosal damage: 2) changes in the gastric mucosal defense by scavengers, prostacyclin and other compounds (small doses of atropine and cimetidine; 3) changes in the gastric mucosal vascular permeability due to chemicals; 4) effect of indomethacin in the ETOH and HCl models with and without surgical vagotomy; 5) changes in the gastric mucosal content of prostacyclin and PGE2 in the ETOH and HCl models after surgical vagotomy; and 6) changes in the role of SH-groups in gastric mucosal defense after surgical vagotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Binding properties of the pure opioid antagonist [3H](N-propyl)-noroxymorphone in rat brain membranes.

(-)[N-(propyl)-14-OH-dihydromorphinan-6-one] = (N-propyl)-noroxymorphone and its multiple tritiated form (molar activity: 126 Ci/mmol; 1 Ci = 37 GBq) was synthesized. According to our knowledge this specific radioactivity exceeds all of the commercially available [3H]opioid ligands. The ligand was found to be a pure opioid antagonist in receptor binding assays performed with rat brain membranes. Scatchard analysis of equilibrium binding isotherms revealed one high affinity (Kd approximately 4 nM) binding site. Reversibility, stereospecificity and opioid nature of the binding was confirmed by ligand binding experiments. Because of its antagonist character combined with high specific radioactivity the ligand might be a useful tool in characterizing and purifying opioid receptors.

Animals↗
PubMed1992

Effect of atrial natriuretic peptide on apomorphine-induced stereotyped cage-climbing behavior in mice.

In previous experiments, it was observed that rat atrial natriuretic peptide-(1-28) (ANP-(1-28)) participated in fear-induced learning and memory processes via dopaminergic and cholinergic mediation. Since cage-climbing behavior is described as a simple test for studying dopaminergic activity in the central nervous system, a systemic study was carried out with ANP-(1-28) in order to confirm or to exclude the possible involvement of dopamine in the ANP-induced action in the brain. The present study demonstrate that ANP-(1-28) facilitated cage-climbing behavior in mice in a dose-dependent manner. When combined with apomorphine, the peptide potentiated the effect of the dopamine agonist. The effect of ANP-(1-28) in combination with apomorphine could be antagonized by a selected dose of haloperidol. These data suggest that ANP might be regarded as a dopamine agonist-modulating agent and that a dopaminergic mechanism is a possible mode of action of ANP in the fear-induced learning studied earlier.

Animals↗