Search PubMed⌕ Search

Biomedical subjects

S Shoukry

Publications and source records attributed to S Shoukry.

At least 19 recordsLinked to original sources
PubMed1993

Use of fluorescently tagged DNA and an automated DNA sequencer for the comparison of the sequence selectivity of SN1 and SN2 alkylating agents.

This paper describes the application of the novel nonradioactive technique for studying the sequence selectivity of selected alkylating agents. N-Nitroso-N-methylurea (MNU) and N-methyl-N'-nitro-nitrosoguanidine (MNNG) were chosen from the SN1 group of alkylating agents. Dimethyl sulphate (DMS) was used to represent alkylation profile produced by the SN2 compounds. Results of SN1 compounds indicated that in a run (G)3 the latter two Gs are more susceptible to alkylation than the most 5' G. Moreover, in a GG sequence the 3' G seems to be more alkylated. This effect is more evident when the GG site was preceded by a 5' pyrimidine. These findings suggest that a regio-selective mechanism, rather than the formation of diazonium ions, accounts for DNA alkylation by SN1 compounds. On the other hand, DMS showed preferential alkylation of the 5' end in a (G)3 run. However, at GG sequences no clear preferred site of alkylation could be distinguished. Lack of specificity of SN2 compound would seem to suggest that other factors as well as the primary DNA structure may play a role in determining the extent of alkylation at a certain site.

Alkylating Agents↗
PubMed1991

A new technique for determining the distribution of N7-methylguanine using an automated DNA sequencer.

We have developed a method to determine rapidly the sequence specificity of DNA alkylation resulting from chemical treatment. The utility of this approach is demonstrated here in a study of the sequence specificity of alkylation by dimethylsulphate (DMS). The method is independent of the sequence chosen and makes use of the polymerase chain reaction (PCR) to generate a fluorescently labelled DNA target. In this study, a 302 bp segment of the Escherichia coli lacI gene was amplified and the product purified by liquid chromatography on a Mono Q column. This DNA was alkylated with DMS and treated with hot piperidine to produce single-strand breaks at sites of N7 alkylation. The distribution of the break points, and hence the position and extent of alkylation, were determined on an Applied Biosystems 370A automated DNA sequencer.

Alkylation↗
PubMed1983

Inactivation of yeast fatty acid synthetase by modifying the beta-ketoacyl reductase active lysine residue with pyridoxal 5'-phosphate.

Treatment of yeast fatty acid synthetase with pyridoxal 5'-phosphate inhibited the enzyme. Assays of the partial activities of the pyridoxal phosphate-treated synthetase showed that only the beta-ketoacyl reductase was significantly inhibited. NADPH prevented inactivation of the enzyme by pyridoxal phosphate, indicating that pyridoxal modifies a residue near or in the beta-ketoacyl reductase site. The pyridoxal-treated synthetase shows a fluorescence spectrum with a maximum of 426 nm after uv irradiation at 325 nm. Binding of the pyridoxal phosphate to the synthetase is reversible as shown by the disappearance of the fluorescence band after dialysis of pyridoxal-treated enzyme. Reduction with NaBH4 of the pyridoxal-treated enzyme eliminates this fluorescence maximum and causes the appearance of a new band at 393 nm. These observations suggest that pyridoxal phosphate interacts with the synthetase by forming a Schiff base with lysine residue at the beta-ketoacyl reductase site. Amino acid analyses of the HCl hydrolysates of the borohydride-reduced, pyridoxal-treated synthetase showed the presence of 6 mol of N6-pyridoxal derivative of lysine per mole of fatty acid synthetase, indicating the presence of six sites of beta-ketoacyl reductase in the native enzyme. Autoradiography of sodium dodecyl sulfate-polyacrylamide gels of the pyridoxal phosphate enzyme reduced with NaB3H4 indicates that the alpha subunit contains the beta-ketoacyl reductase domain. These findings are consistent with the proposed structure of the alpha 6 beta 6 complex required for palmitoyl-CoA synthesis.

Alcohol Oxidoreductases↗
PubMed1982

A new antitumour substance, 7-oxabicyclo (2.2.1)-5-heptene-2,3-dicarboxylic anhydride.

7-Oxabicyclo(2.2.1)-5-heptene-2,3-dicarboxylic anhydride has been found to possess antitumour activity against Ehrlich ascites carcinoma cells. The tumour cells incubated with the drug showed a decrease in the viable counts and cell proliferation. These effects were confirmed by in vivo studies in Swiss albino mice. The compound has a direct cytotoxic effect on the tumour cells. Vacuolization and disruption of the cytoplasm accompanied by unequal nuclear division and scattered chromosomes were recorded. In addition, 250 and 10 mg/kg were found to be the MTD and MED respectively. A dose of 25 mg/kg injected i.p. for 5 consecutive days in the tumour-transplanted animals caused a significant increase in their survival period. The compound has been shown to have a significant inhibitory effect on the DNA and RNA biosynthesis of EAC cells after 3 hr of administration; the protein biosynthesis was less affected. Meanwhile, the cellular contents of these metabolites were significantly reduced.

Animals↗
PubMed1980

Effect of calorie restriction and protein deficiency on protein metabolism in rats.

The changes induced by the deficiency of calories or nitrogen on the protein metabolism in rats were investigated. Animals were fed either a restricted normal diet, a protein-deficient diet or control diet ad libitum. Rats receiving protein-free diet failed to grow, while the growth of animals given restricted diet was less than those fed ad libitum. Despite that, the dietary deficiency of either calories or proteins caused the loss of protein and increased the incorporation of 1-C14 glycine into liver proteins. The contents of liver-free amino acids and urea were significantly increased only in the protein-deficient rats.

Amino Acids↗
PubMed1979

Staphcoccomycin, a new basic macrolide antibiotic.

Staphcoccomycin (SCM) is a new member of the basic macrolide family of antibiotics which was isolated from the fermentation broth of Streptomyces sp. AS-NG 16. The production, purification and determination of physical and chemical properties of this novel metabolite have been completed. Comparison of the mass fragmentation patterns of SCM and its peracetate with those of angolamycin peracetate suggested a des-mycarosyl derivative of angolamycin. Moreover, the molecular ion peak (m/e 771) corresponded to C39H65NO14 and the 1H-NMR of SCM was also consistent with the proposed structure.

Animals↗
PubMed1977

Kuwaitimycin, effect on synthesis of lipids in Bacillus subtillis cells.

The effects exerted by kuwaitimycin on synthesis of lipids as well as some metabolic activities of Bacillus subtilis were studied. The antibiotic not only arrested the inocrporation of 14C-acetate into the microbial lipids but also altered the fatty acids pattern, contents of i-C 15, a-C 15, i-C 17 and a-C 17 WERE MARKEDLY REDUCED, CONCOMITANT WITH AN INCREASE IN THE CONtents of i-C 14 AND N-C 14. Moreover, the rates of synthesis of phospholipids were decreased by the drug, especially that of phosphatidyl ethanolamine.

Anti-Bacterial Agents↗
PubMed1976

4,4'-isopropylidine-bis(2-isopropyl)phenol, a new inhibitor for cell wall formation of Bacillus subtilis.

4,4'-Isopropylidine-bis[2-isopropyl]phenol was found to possess antimicrobial activity against gram-positive bacteria and some fungi, whereas it had no effect on gram-negative organisms. The drug has a potent inhibitory action on the synthesis of cell wall mucopeptides of Bacillus subtilis by inhibiting the enzyme d-glutamate ligase, which is responsible for the incorporation of d-glutamic acid into uridine 5'-diphosphate-muramyl-l-alanine. The drug had a weak lytic effect on protoplasts and inhibited protein synthesis, whereas no significant effect on the synthesis of deoxyribonucleic acid and ribonucleic acid was found.

Alanine↗
PubMed1976

The mode of action of ASK-753 on Bacillus subtilis.

The mode of action of ASK-753 on Bacillus subtilis was examined. Unlike proper sideromycin antibiotics ferrioxamine B failed to antagonize the antimicrobial effects of ASK-753. The antibiotic could inhibit the biosynthesis of nucleic acids; effect on the RNA was more pronounced. ASK-753 affected the stability of prelabelled DNA of B, subtilis in growing or resting cultures; the effect on the latter was more pronounced. Lysis of B, subtilis protoplasts could be attained at 30 degrees C but not at 4 degrees C which excludes a possible detergent affect of the drug. The drug exerted a potent inhibiting influence on protein synthesis by arresting the activity of lysyl-tRNA synthetase and thus could prevent the incorporation of 14C-lysine.

Anti-Bacterial Agents↗
PubMed1975

On the effect of N-methyl-bis (3-mesyloxypropyl) amine hydroxychloride on Bacillus subtilis cells.

N-Methyl-bis (3-mesyloxypropyl)amine hydrochloride is now in use as an antitumer drug. In view of its activity against some bacteria the present work was conducted to study its mode of action of Bacillus subtilis. The compound was found to induce irreversible damage to bacterial DNA whereas its effect on RNA was temporary and depending on maintenance of effective concentrations of the compound.

Antineoplastic Agents↗