PubMed Health⌕ Search

Biomedical subjects

M Szabolcs

Publications and source records attributed to M Szabolcs.

At least 55 records · Page 3Linked to original sources
PubMed1985

R46 and pKM101 plasmid-mediated resistance to ionizing radiation in Escherichia coli.

The ability of the R46 R factor and its derivative pKM101 to modify sensitivity to 60Co gamma radiation was studied. In Escherichia coli K12 both plasmids enhanced bacterial survival after 60Co gamma irradiation. This effect was dependent on recA+ genotype but not on recB+, recB+ recC+, and recF+ genotypes. 5-Fluorouracil eliminated the R46 R factor from the parent and its rec- mutant strains. These strains lost not only the antibiotic resistance coded for R46 R factor but their radioresistance as well.

Cobalt Radioisotopes↗
PubMed1983

Possible role of a regulatory gene product upon the myo-inositol-1-phosphate synthase production in Neurospora crassa.

The regulatory effect of inositol on inositol-1-phosphate synthase in Neurospora crassa strains was studied. Inositol represses enzyme production in the cultures of the wild type and that of the thermosensitive inositol-requiring mutant grown at 22 degrees C. Enzyme activity as well as the quantity of enzyme protein decreased sharply in both strains by increasing concentrations of inositol in the medium. Inositol-requiring strains used in our experiments can be divided into two groups. The first group produces a protein related immunologically to inositol phosphate synthase, but which is enzymatically inactive. The synthesis of this defective enzyme was also repressed by inositol. In the second group, this protein was found to be completely lacking, in both the thermosensitive mutant grown at 37 degrees C, and in a strain requiring inositol due to a reciprocal translocation. The thermostability and the cross immunoelectrophoresis of the enzyme suggest that in the case of the thermosensitive inositol-requiring mutant, the mutation did not occur in the structural gene of the enzyme, but its regulation was probably affected.

Carbohydrate Epimerases↗
PubMed1983

Isolation and physiochemical properties of an adenosine-rich gluten fraction.

Gluten proteins were isolated from the 0.01 mol acetic acid extract of bread. It was observed that precipitation of gluten provoked by 200 mM NaCl could partly be inhibited by adenosine. Based on this finding a method for isolation of the gluten fraction resisting saline precipitation in the presence of adenosine was elaborated. This fraction termed by us gluten-A-S, was found to have a lower glutamine + glutaminic acid and a higher proline and phenylalanine content than gluten. By sodium dodecylsulphate polyacrylamide gel electrophoresis gluten-A-S was shown to contain components of 58 000 and 34 000 dalton molecular weight after mercaptoethanol treatment while without the latter it contained a component of 74 000 dalton. The absorption maximum of the compound is at 260 mm; E280nm/E260nm = 0.5. In accordance with previous findings, gluten-A-S was found to contain 50-100 nmol adenosine per mg protein in a strong binding. It seems that in addition to the small amount of tightly bound adenosine, gluten-A-S contains a larger quantity of adenosine loosely bound to the protein. The physiological effects of dissociable adenosine bound to gluten and its possible role in the pathomechanism of gluten sensitive enteropathy is discussed in detail.

Adenosine↗
PubMed1982

Separation of Neurospora crassa myo-inositol-1-phosphate synthase from glucose-6-phosphate dehydrogenase by affinity chromatography.

The purification of Neurospora crassa myo-inositol-1-phosphate synthase (EC 5.5.1.4) was studied by affinity chromatography using the substrate (glucose-6-phosphate), the inhibitor (pyrophosphate), the coenzyme (NAD+) and the coenzyme analogues (5'AMP and Cibacron Blue F3G-A) of the enzyme as adsorbents attached to agarose gel. Myo-inositol-1-phosphate synthase could be separated completely from the contaminating substance, glucose-6-phosphate dehydrogenase (EC 1.1.1.49), on Blue Sepharose CL-6B and on pyrophosphate-Sepharose. The purified enzyme had a specific activity of 16 400 U/mg. The sodium dodecyl sulfate/polyacrylamide gel electrophoresis of the 60 micrograms of this purified enzyme gave a homogenous band. The enzyme was found to be composed of four identical subunits having a molecular weight of 65 000.

Carbohydrate Epimerases↗
PubMed1979

Demonstration of myo-inositol-1-phosphate synthase and its assumed defective variant in various Neurospora crassa strains by immunological methods.

Immunological experiments were performed to demonstrate myo-inositol-1-phosphate synthase (EC 5.5.1.4) and its assumed defective variant in various Neurospora crassa stains. An enzymatically inactive protein fraction was isolated from the inl-mutant by the same procedure as that of the enzyme. It consisted of several components by gel electrophoresis, and produced a positive immune reaction demonstrated by immunodiffusion using immune sera produced against the enzyme. Using immunodisc gel electrophoresis it produced an immunoprecipitate of slightly lower mobility than the enzyme itself. Similarly, positive immune reactions were obtained with the enzyme using immune sera produced against the protein fraction isolated from the inl- mutant. Enzyme activity was demonstrated both in a strain transformed by wild-type DNA and in a spontaneous revertant. The enzymes were subsequently isolated from both strains, and some properties were compared with those of the wild-type enzyme. The specific activities were lower but the Michaelis constants were nearly the same. The immunodisc gel electrophoretic patterns of these enzymes were similar to that of the protein fraction from the inositol requiring mutant.

Animals↗
PubMed1977

Association of precipitins and coeliac disease.

Four fractions, fraction A,B, C, and D, were isolated from the aqueous extract of wheat flour on a Sephadex G-75 column. It was found that the repeated gel-filtrated fraction A reacts as an antigen with the sera of coeliac patients. On the basis of its molecular weight and amino acid compositions, it is gliadin. Each of the 28 coeliac patients had heat-stable precipitating antibody and higher than normal IgE levels were found in the sera of only three individuals. Specific antigliadin IgE in low quantity was found in only one case. The sera reacting with antigens in high titres were absorbed by anti-IgG and anti-IgA whereupon the antibody level considerably decreased. The main circulating antibody of the patients was IgG.

Amino Acids↗
PubMed1977

Conditions of transformation by DNA of Neurospora crassa.

The DNA uptake and transformation of inositol-requiring recipient Neurospora strains were investigated. Exponentially growing cultures can accumulate 5-10 fold quantities of donor DNA than older ones. The rate of DNA uptake depends on the physiological state of the recipient cell, and on the molecular weight of donor DNA. The exocellular DNase activity of the recipient culture may influence the DNA uptake and the transformation process. "Young" inositol-requiring Neurospora crassa cultures can be transformed by wild type DNA reproducibly, but with low efficiency.

Chromosome Mapping↗
PubMed1977

Investigations on myo-inositol-1-phosphate synthase from the wild type and the inositol-dependent mutant of Neurospora crassa.

The inositol-dependent mutant of Neurospora crassa lacks inositol-1-phosphate synthetase activity. This defect can be revorted by the addition of high-molecular DNA isolated from the wild type. To elucidate the biochemical background of inositol dependence, inositol-1-phosphate synthetase was studied. A method has been developed fro the isolation of the enzyme from the wild type strain in 10 mg scale by salt fractionation, gel filtration and ion-exchange chromatography. The specific activity of the purified enzyme is 4750 U/mg protein and its purity has increased about 100-fold. Polyacrylamide gel electrophoresis indicated that, in addition to the main enzymatically active band, several accompanying proteins occur in very small amount. The molecular weight of the enzyme is 225,000 daltons. Probably it consists of four subunits, two with a molecular weight of 64,000 daltons and another two of 50,000 daltons. An enzymatically inactive protein has been isolated from the mutant with the same procedure as that of the enzyme; it migrated at gel electrophoreis similarly to the enzyme. It may be supposed that the isolated protein is the defective enzyme molecule.

Carbohydrate Epimerases↗
PubMed1977

Circulating antibodies in coeliac disease.

Antibodies produced against gliadin were demonstrated in the sera of patients suffering from coeliac disease as well as of immunized rabbits and rats. In the patient sera the specific antibodies proved to be of the IgG type. IgE may have a role in sensitization against gliadin only in the cell-fixed state.

Animals↗
PubMed1976

The effect of La3+ on the characteristics of fragmented sarcoplasmic reticulum.

Fragmented sarcoplasmic reticulum (FSR) was prepared from the white muscles of the catfish (Amiurus nebulosus). The effect of La3+ on the functional characteristics of FSR was studied. La3+ in a concentration higher than 10(-4) M was found to decrease or arrest Ca2+ accumulation, cholinesterase activity and the activation of ATPase by Ca2+. La3+ added after the elimination of membrane-bound Ca2+ of FSR (1 mM EGTA, pH 7.1) does not substitute Ca2+ in its functions. The cholinesterase activity of FSR solubilized by deoxycholate and purified by gelfiltration is inhibited by La3+ present in a concentration higher than 10(-4) M and simultaneously with inhibition, the absorbance at 280 nm is increased. Ca2+ gives rise to similar changes only in concentrations higher than 10(-2) M.

Animals↗