PubMed Health⌕ Search

Biomedical subjects

G Tóth

Publications and source records attributed to G Tóth.

At least 145 records · Page 8Linked to original sources
PubMed1989

Cellular energy status of the gastric mucosa and gastric mucosal prevention by vitamin A in indomethacin-treated rats.

To evaluate the cellular energy status of gastric mucosa during the development of gastric mucosal damage and its prevention by application of a cytoprotective scavenger (vitamin A) in rats treated with indomethacin, the tissue levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and lactate were measured enzymatically, while the concentration of cyclic adenosine monophosphate (cAMP) was measured by radioimmunoassay, 4 h after the treatment with indomethacin and vitamin A simultaneously. It was found that a) the tissue levels of ATP, cAMP, AMP and the ratio of ATP/ADP were increased dose-dependently in the gastric mucosa in connection with the development of gastric mucosal prevention produced by vitamin A, b) the tissue level of ADP was decreased dose-dependently by vitamin A in indomethacin-treated rats, and c) the value of "energy charge" and the ratio of the ATP-ADP was unchanged during the vitamin A treatment in indomethacin-treated rats. The presence of tissue hypoxia could not be proved either in the development of indomethacin-induced gastric mucosal damage nor in the prevention of gastric mucosal damage by vitamin A.

Adenosine Diphosphate↗
PubMed1989

Effect of atropine, PGF2 alpha and cimetidine on the beta-carotene induced cytoprotection in ethanol-treated rats.

The aim of the study was to evaluate the influence of atropine, PGF2 alpha and cimetidine on the gastric cytoprotective effect of beta-carotene. Mucosal damage was produced by intragastric (i.g.) addition of 96% ethanol in CFY-strain rats of both sexes weighing 180-220 g. Gastric cytoprotection caused by i. g. pretreatment with 1.0 mg/kg beta-carotene 30 minutes before ethanol administration, was observed after 1 hour. Atropine (0.5 mg/kg), cimetidine (50 mg/kg) and PGF2 alpha (200 micrograms/kg) were given intraperitoneally (i.p.) 30 minutes before ethanol administration with and without beta-carotene and the changes in the number and severity of the gastric ulcers were detected. PGF2 alpha did not influence the gastric cytoprotective effect of beta-carotene meanwhile it was inhibited by atropine and markedly by cimetidine. Deleterious effect of cimetidine on the beta-carotene-induced cytoprotection may be explained perhaps by the adverse effect of the two compounds on ATP-cAMP transformation hereby counteracting one another, but more data are needed to the better understanding of drug interactions relating to mucosal cytoprotection.

Animals↗
PubMed1989

The free radical mechanisms in beta-carotene induced gastric cytoprotection in HCl model.

The aims of our experiments were to clear up the possible correlations between the free radical mechanisms and the gastric cytoprotection of beta-carotene on HCl-induced gastric mucosal lesions. The beta-carotene was intragastrically given in doses of 1 and 10 mg/kg and 30 min. later 1 ml 0.6 N HCl was given to provoke the mucosal damage. After 1, 5, 15, 30 and 60 min. the animals were sacrificed. The number and severity of gastric mucosal lesions were calculated. The superoxide dismutase (SOD), glutathion peroxidase (GPX), catalase (CAT) activity and the malondialdehyde (MDA) and reduced glutathion (GSH) contents were determined from the gastric mucosa of rats. It was found that 1. beta-carotene was able to reduce the number and severity of ulcers only after 30 min.; 2. the CAT activity was decreased at 60 min. by carotene; 3. the GPX activity became dissimilar in the different groups after 15 min; 4. the changes of GSH were found to be similar ones; 5. the SOD activity was lower during the cyto-protection; 6. the MDA level remained practically unchanged. It has been concluded that 1. the free radicals are the consequences of the development of gastric ulcer and cytoprotection; 2. the scavenger character of beta-carotene is involved in its cytoprotective effect.

Animals↗
PubMed1988

Synthesis of 3H-Tyr-D-Ala-Gly-N(Me)Phe chloromethyl ketone--an opioid affinity label.

A radioactive enkephalin affinity reagent, selective for the mu opioid receptor subtype, was synthesized by a fragment condensation method. 3H-BOC-Tyr-D-Ala-Gly-OH was prepared by catalytic tritiation of the protected iodinated tripeptide. The protected tritiated tripeptide and N(Me)Phe-CH2Cl were condensed by the mixed anhydride method. The protecting group was removed by HCl/acetic acid. The tritiated tetrapeptide has a specific radioactivity of 56.8 Ci/mmole (2.1 TBq/mmole).

Affinity Labels↗
PubMed1987

Covalent labeling of opioid receptors with 3H-D-Ala2-Leu5-enkephalin chloromethyl ketone. I. Binding characteristics in rat brain membranes.

The chloromethyl ketone derivative of D-Ala2-Leu5-enkephalin was synthesized in a radioactive form, and the resulting compound (3H-DALECK) was used to label opioid receptors. 3H-DALECK binds with high affinity, specificity and saturability to rat brain membranes. The number of sites labeled is 130 fmoles/mg protein. Unlabeled opioids inhibited the binding of 3H-DALECK; etorphine and DAGO being most potent. A 10-fold preference for mu sites over delta was seen in site-specific competition experiments; while DALECK displayed low affinity for kappa sites of rat brain. DALECK irreversibly blocked a certain population of sites. Approximately 40% of 3H-DALECK binding at 15 min, and 60% at 60 min association time did not dissociate in the presence of a large excess of unlabeled DALECK and was resistant to washing. Autoradiography performed after SDS-PAGE revealed specific alkylation of proteins with molecular weight of 74, 65, 56, 43 and 34 kD. These results demonstrate the applicability of using 3H-DALECK to covalently label opioid receptors.

Amino Acid Chloromethyl Ketones↗
PubMed1987

Covalent labeling of opioid receptors with 3H-D-Ala2-Leu5-enkephalin chloromethyl ketone. II. Binding characteristics in frog brain membranes.

3H-D-Ala2-Leu5-enkephalin chloromethyl ketone (3H-DALECK) was used to label opioid receptors of frog brain membranes. We have previously shown (15) that 70% of the opioid receptors are of kappa type in this preparation. The binding of 3H-DALECK was of high affinity, half maximal binding being achieved by 0.9 nM of the radioligand. The number of sites labeled was calculated to be 108 fmol/mg protein. Opioid ligands, incubated with the membranes prior to the label, inhibited 3H-DALECK binding with the following rank order:etorphine greater than EKC greater than DAGO greater than DALECK greater than DADLE. Dissociation experiments showed that 70% of the binding is irreversible. Fluorography performed after SDS-PAGE revealed specific covalent labeling of protein subunits of 90, 58 and 20 kD molecular weights. Results will be compared to those obtained in rat brain (13). Our two studies demonstrate that 3H-DALECK is a useful probe for investigation the subunit structure of opioid receptors.

Amino Acid Chloromethyl Ketones↗
PubMed1987

Separation of serum carotenoids and vitamin A on chromsil-amino and -cyano phases by a bi-directional gradient elution technique.

Vitamin A, beta-carotene, lycopene, beta-cryptoxanthin, lutein and zeaxanthin can be simultaneously separated in human serum extracts by normal-phase liquid chromatography. Two stationary phases (containing amino and cyano groups, respectively) were investigated. With a bi-directional (up-down) gradient-elution technique both packings are useful for the determination of serum levels of carotenoids and retinol in serum extracts. The small sample size, the simplicity of extraction, and a good reproducibility render these procedures ideal for clinical use.

Carotenoids↗
PubMed1987

Isolation and characterization of a DNA-uptake-stimulating protein from the culture medium of Neurospora crassa slime strain.

A protein fraction was purified to homogeneity from the culture medium of the wall-less (slime) strain of Neurospora crassa (FGSC 1118), which proved to be identical with DNA-uptake-stimulating factor (designated DUSF), which has been described earlier [Schablik, M. and Szabó, G. (1981) FEMS Microbiol. Lett. 10, 395-397]. The quantity of DUSF is measured by the amount of [3H]DNA uptake by Neurospora cells at standard conditions. Its relative molecular mass was 230,000. It has an isoelectric point of pH 5.5. This protein consists of two identical subunits, relative molecular mass 110,000.

Chromatography, DEAE-Cellulose↗
PubMed1987

Detailed analysis of heterogeneity of [3H]naloxone binding sites in rat brain synaptosomes.

The experiments reported in this paper address the question of heterogeneity of [3H]naloxone binding sites in rat brainstem synaptosomal preparations at 23 degrees C in the presence of 100 mM sodium chloride. Kinetic analysis in the presence of 0.4, 4 and 10 nM [3H]naloxone gave pseudo-first order association rate of 0.9 +/- 0.04, 1.23 +/- 0.08 and 1.06 +/- 0.08 min-1, respectively. The dissociation of a 1 nM [3H]naloxone receptor complex was biphasic with dissociation rate constants of 1.8 and 0.4 min-1. On the other hand, dissociation of 10 nM [3H]naloxone was monophasic with a kd of 1.1 min-1. Two subpopulations of binding sites were also observed by steady state binding studies, with Kd values of 0.5 and 3.4 nM and a ratio of high to low affinity sites of 1:9. Heterogeneity of [3H]naloxone binding sites could be seen by displacement studies performed with opioid peptides and alkaloids. We suggest that our data best fits a model with two independent naloxone binding sites wherein either one or both undergo a multi-step interaction with ligand.

Animals↗
PubMed1987

Thermodynamic analysis of rat brain opioid mu-receptor-ligand interaction.

Opioid mu-receptors are membrane bound receptors. The mechanism by which they transduce their biological effect into the inner compartment of the postsynaptic cell is still not fully understood. The present study was attempted to the measurement of changes of the thermodynamic parameters of the receptor--agonist/antagonist interaction. We have set up the binding assays of a mu-receptor agonist (3H-dihydromorphine) as well as an antagonist (3H-naloxone). The saturation isotherms of both ligands have been assayed at various temperatures and from the resulting KD values the standard changes of Gibbs energy, enthalpy and entropy have been calculated. While the binding of the mu-receptor agonist 3H-dihydromorphine appears to be entropy driven (delta S0 = 230 J mol-1 K-1) and endothermic (delta H0 = 19 kJ mol-1), the binding of the mu-receptor antagonist 3H-naloxone is apparently driven by a decrease of standard enthalpy (delta H0 = -27 kJ mol-1; i.e. the reaction is exothermic) and is also characterized by an increase of standard entropy (delta S0 = 76 J mol-1 K-1). The maximal number of 3H-naloxone binding sites has to be determined by incubation at 0-4 degrees C. The present data to not support the view that opioid mu-receptors transduce their biological signal through the adenylatecyclase system by a mechanism similar to beta-adrenergically stimulated adenylatecyclase.

Adenylyl Cyclases↗
PubMed1986

Interaction of casein with human polymorphonuclear cells.

Attachment of 125I-casein to PMN cells was investigated. Iodination did not decrease the chemotactic effect of casein. 125I-casein binding was increasing toward a maximum reached at about 45 min at 24, and 37 degrees C. At 4 degrees C the binding was proportional to time for 45 min. No saturation was achieved even at 15 mg/ml casein. About 40% of casein remained attached to PMN in a casein-free medium after 60 min, at 37 degrees C. Pretreatment of the cells with trypsin or butanol, or the presence of indomethacin, azide, and PMSF did not affect the binding of casein. The hydrophobic amino acid, leucin counteracted the attachment of casein. Our data show that at chemotactic doses casein is bound specifically to cell membranes by hydrophobic forces. The induction of chemotaxis may be due to micellar casein-membrane lipid complexes.

Adult↗
PubMed1986

Kinetics and physical parameters of rat brain opioid receptors solubilized by digitonin and CHAPS.

Rat brain opioid receptors were solubilized with digitonin and a zwitterionic detergent, 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS). The yield of solubilization was 70-75% with digitonin and 30-35% with CHAPS. Kinetic and equilibrium studies performed from digitonin extracts resulted in KD values comparable with those of the membrane fractions. Two [3H]naloxone binding sites were obtained in the extracts similarly to membrane fractions. The rank order potency of drugs used in the competition experiments did not change during solubilization. The distributions of mu, delta, and kappa opioid receptor binding sites were similar in membrane and digitonin-solubilized fractions (48-50% mu, 35-37% kappa, and 13-17% delta subtypes). The hydrodynamic properties of digitonin- and CHAPS-solubilized preparations were studied by sucrose density gradient centrifugation and Sepharose-6B chromatography. In all cases, two receptor populations were identified with the following parameters: sedimentation coefficients for the digitonin extracts were 9.2S and 13.2S and for CHAPS extract 8S and 15.6S; the Stokes radii were 45 A and 65A for the digitonin extract and 31A and 76A for the CHAPS-solubilized preparation.

Animals↗
PubMed1986

5-Hydroxyindole acetic excretion in newborns, infants and children.

The 5-hydroxyindole acetic acid excretion of healthy prematures, term newborns, infants, and children up to 15 years of age was investigated. Comparison of the results with healthy adult values suggests that more exact information can be obtained on excretion values of children if they are calculated for bodyweight. The results obtained in the different age groups point to an increased activity of serotonin metabolism in newborns, infants and children. During the important phases of somatic and psychomotor development an increased urinary output of 5-hydroxyindole acetic acid was found as compared with adult values.

Adolescent↗