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Biomedical subjects

M Abrahám

Publications and source records attributed to M Abrahám.

11 recordsLinked to original sources
PubMed2001

Tissue-specific expression of two metallothionein genes in common carp during cadmium exposure and temperature shock.

Two metallothionein cDNA isoforms (MT-1 and MT-2) were isolated from carp (Cyprinus carpio) by RT-PCR. Sequence analysis of the cDNAs revealed two amino acid differences between the coding regions and markedly different 3'-untranslated ends. Gene-specific primers were selected and used in RT-PCR reactions to measure the basal MT-1 and MT-2 mRNA levels and to follow the inducer-specific expression of MT genes in different tissues during in vivo studies. In the brain and muscle, the uninduced levels of the two MT mRNAs were similar. In the kidney and liver, the MT-1 gene product predominated, while in the heart the relative expression levels of the two genes were opposite. Both the MT-1 and MT-2 mRNA levels increased with Cd concentration in a time- and dose-dependent manner. The expression of MT-2, however, was more responsive to a high Cd concentration. In parallel with the induction of the MTs by Cd, we followed the accumulation of this metal in the kidney and liver. Although the Cd level was always higher in the kidney during treatment, the rate of accumulation was higher in the liver. Cold stress resulted in a significantly higher induction of MT-1 than of MT-2, while heat shock had no effect on the expression of either gene.

Animals↗
PubMed2001

Biochemical and morphological changes in carp (Cyprinus carpio L.) liver following exposure to copper sulfate and tannic acid.

As a consequence of human activity various toxicants reach the aquatic ecosystems; humics may interact with them and may change their toxicity. Many fish are exposed to a considerable concentration of humics and pollutants. Because of paucity of data on the biochemical action of tannins in the presence of the fungicide CuSO4 a comparative study was undertaken. The alterations of redox-parameters in carp liver were monitored and tissue necrosis was followed by measuring the plasma transaminase activities and by electron microscopy. Tannic acid, a representative phenolic/humic compound, exerted prooxidant effects in carp, which may be partially due to formation of prooxidant intermediates/end-products via its biotransformation. Alternatively, tannic acid may partially inhibit the antioxidant enzymes of fish. The response to CuSO4 was more severe. Although tannic acid alone acted as a prooxidant in fish, electron micrographs demonstrated that it reduced the necrotizing effect of copper, which may be due to the complexing activity of tannic acid with the biomolecules of the hepatocytes and to the H2O2-degrading activity of tannin-CuSO4 combination. Our results indicate that the heavy metal-detoxifying capacity of tannin may be significant; however, tannin-exposure alone or combined with metals may be toxic for fish due to enzyme inhibition and oxidative stress induction.

Alanine Transaminase↗
PubMed2001

Identification of two hsp90 genes in carp.

Two hsp90 cDNA isoforms (hsp90alpha and hsp90beta) were isolated from the common carp (Cyprinus carpio). Gene-specific probes and primers were selected and used in Northern blot hybridization and RT-PCR reactions to measure the basal hsp90 mRNA levels and to follow the inducer-specific expression of the hsp90 genes in different tissues during in vivo studies. The hsp90beta gene is largely constitutively expressed at a fairly high level in all the examined tissues (brain, liver and kidney) and is slightly inducible by an elevated temperature. Hsp90alpha mRNA is present in the brain, but is hardly detectable in the kidney and liver of unstressed animals. In the brain, this gene is greatly upregulated following thermal stress, whereas in the liver and kidney heat shock has only minor effects on its expression. Hsp90alpha, but not hsp90beta, responds to an elevated level of Cd in a dose-, time- and tissue-dependent manner.

Amino Acid Sequence↗
PubMed1997

In vivo and in vitro effects of deltamethrin on cytochrome P450 monooxygenase activity in carp (Cyprinus carpio L) liver.

The in vivo and in vitro effects of the insecticide deltamethrin (DM) on hepatic cytochrome P450 (Cyt P450) monooxygenase were examined in adult carp. The in vivo experiments were carried out with 0.2 microgram/l DM at 20 degrees C. The changes in the hepatic microsomal Cyt P450 content and the Cyt P450-dependent monooxygenase activities were studied in DM-treated fish. Although there were no changes in the Cyt P450 content during the exposure time, after treatment for 24 h all the investigated isoenzyme activities (para-nitrophenetole-O-deethylase, p-NPOD; aminopyrene-N-demethylase, APND; ethylmorphine-N-demethylase, EMND; 7-ethoxycoumarin-O-deethylase, ECOD; and ethoxyresorufin-O-deethylase, EROD) were significantly inhibited. After 72 h, all the activities were still lower than in the control animals. In vitro incubation of liver microsomes with DM led to a concentration-dependent decrease in total microsomal Cyt P450 content. A complete loss of Cyt P450 occurred after a 5-min incubation with 60 microM DM. The maximum in the difference spectra of microsomes was shifted to higher wavelength, showing the strong interaction of DM with Cyt P450. EROD and ECOD activities were inhibited by DM. The in vitro kinetic results on ECOD revealed that the inhibition was of non-competitive type, with K1 = 9.8 +/- 2.3 microM. This study indicates important biochemical effects of DM in fish liver, and suggests that exposure to DM may cause loss of the Cyt P450-dependent metabolism in fish.

Animals↗
PubMed1993

Activity of a chimeric promoter with the doubled CaMV 35S enhancer element in protoplast-derived cells and transgenic plants in maize.

A reproducible and efficient transformation system has been developed for maize that is based on direct DNA uptake into embryogenic protoplasts and regeneration of fertile plants from protoplast-derived transgenic callus tissues. Plasmid DNA, containing the beta-glucuronidase (GUS) gene, under the control of the doubled enhancer element (the -208 to -46 bp upstream fragment) from CaMV 35S promoter, linked to the truncated (up to -389 bp from ATG) promoter of wheat, alpha-amylase gene was introduced into protoplasts from suspension culture of HE/89 genotype. The constructed transformation vectors carried either the neomycin phosphotransferase (NPTII) or phosphinothricin acetyltransferase (PAT) gene as selective marker. The applied DNA uptake protocol has resulted at least in 10-20 resistant calli, or GUS-expressing colonies after treatment of 10(6) protoplasts. Vital GUS staining of microcalli has made possible the shoot regeneration from the GUS-stained tissues. 80-90% of kanamycin or PPT resistant calli showed GUS activity, and transgenic plants were regenerated from more than 140 clones. Both Southern hybridization and PCR analysis showed the presence of introduced foreign genes in the genomic DNA of the transformants. The chimeric promoter, composed of a tissue specific monocot promoter, and the viral enhancer element specified similar expression pattern in maize plants, as it was determined by the full CaMV 35S promoter in dicot and other monocot plants. The highest GUS specific activity was found in older leaves with progressively less activity in young leaves, stem and root. Histochemical localization of GUS revealed promoter function in leaf epidermis, mesophyll and vascular bundles, in the cortex and vascular cylinder of the root. In roots, the meristematic tip region and vascular tissues stained intensively. Selected transformants were grown up to maturity, and second-generation seedlings with segregation for GUS activity were obtained after outcrossing. The GUS-expressing segregants carried also the NPTII gene as shown by Southern hybridization.

Aminobutyrates↗
PubMed1992

Immobilized triosephosphate isomerases. A comparative study.

Pig muscle triosephosphate isomerase was covalently attached to polyacrylamide and silica-based supports possessing carboxylic or aldehyde functional groups or activated with p-benzoquinone. A silica-based support activated with p-benzoquinone proved to be the most advantageous. There were no profound alterations in the catalytic properties as a result of the immobilization. The immobilization enhanced the resistance against urea and heat treatment. At the start of the treatments, the enzyme was activated. The extent of activation depended on the pH, and on the buffer and salt concentrations. Increase of the ionic strength decreased or eliminated the activation. The phosphate ion had a specific effect on the thermal inactivation.

Animals↗
PubMed1989

Immobilization of pig muscle aldolase on a silica-based support.

Pig muscle aldolase was covalently attached to a silica-based support possessing aldehyde functional groups. The activity of the immobilized enzyme was 37 U/g solid, and the specific activity calculated on a bound protein basis was 1.9 U/mg protein. The optimum pH for the catalytic activity was pH 7.5. The apparent optimum temperature was found to be 45 degrees C. The Km app value of the immobilized aldolase with D-fructose 1,6-diphosphate as substrate was 1.25 X 10(-4) M. The conformational stability was improved by the immobilization. The immobilized aldolase was used for the continuous splitting of D-fructose 1,6-diphosphate.

Animals↗
PubMed1986

Enzymatic determination of isocitrate by amperometric monitoring of the rate of oxygen consumption.

A coupled enzymatic method elaborated for NAD+-dependent dehydrogenases has been adapted for NADP+-dependent isocitrate dehydrogenase, in combination with amperometric measurements. The isocitrate dehydrogenase activity dependent linearly on the isocitrate concentration in the range 0-2 X 10(-4) M. Application of this method affords a sensitive estimation of isocitrate even in turbid liquids such as fermentation broths.

Electrodes↗
PubMed1985

Characterization and comparison of soluble and immobilized pig muscle aldolases.

Pig muscle aldolase was insolubilized by covalent attachment to a polyacrylamide matrix containing carboxylic functional groups. The catalytic activity of the Akrilex C-aldolase was 2014 units/g solid, i.e., an activity loss of only about 5% relative to the initial activity. The pH optimum for catalytic activity shifted form 7.25 to 7.5 and the apparent temperature optimum from 313 to 318 K. The Michaelis constant of the insolubilized enzyme was significantly higher than that of the soluble aldolase. Heat- and urea-inactivation experiments revealed that the immobilization increased the stability of the enzyme.

Animals↗
PubMed1985

Isolation and characterization of pig muscle aldolase. A comparative study.

Aldolase with a specific activity of 10.8 units/mg protein was isolated from pig muscle. Its molecular weight was found to be 150,000. The optimum pH for the catalytic activity was 7.25 and the apparent temperature optimum was 313 K. The Km value was 2.9 X 10(-5) M with FDP as substrate, and 2.8 X 10(-3) M with F1P as substrate. The thermal stability of this pig muscle enzyme was higher than that of the rabbit muscle enzyme. The thermal inactivation of the pig aldolase did not show simple first-order kinetics. The higher conformational stability of the pig aldolase than that of the rabbit enzyme was demonstrated by its higher resistance to the denaturing effect of urea.

Animals↗