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Biomedical subjects

A Kayser

Publications and source records attributed to A Kayser.

At least 37 records · Page 2Linked to original sources
PubMed1984

Inhibition of the reactions catalysed by a type I topoisomerase and catenating enzyme of Trypanosoma cruzi by DNA-intercalating drugs. Preferential inhibition of the catenating reaction.

A catenating enzyme and a type I topoisomerase were purified from Trypanosoma cruzi. We investigated the inhibitory effect of DNA-intercalating drugs on topoisomerisations catalysed by these enzymes. Inhibition of catenation was detected by electrophoretic analysis in neutral agarose gels. However, the inhibition of relaxation was not readily detectable in these gels since supercoiled DNA, which was relaxed in the presence of an intercalating drug, returned to a supercoiled state when the drug was removed. Thus electrophoretic analyses were made in gels containing chloroquine so that unreacted DNA could be distinguished from DNA relaxed by the enzyme. The results show that the catenation was more sensitive to DNA-intercalating drugs than the relaxation.

Animals↗
PubMed1983

A specific inhibitor of type I DNA-topoisomerase of Trypanosoma cruzi: dimethyl-hydroxy-ellipticinium.

2-6 dimethyl-9-hydroxyellipticinium inhibited the relaxation of supercoiled DNA by the type I topoisomerase of T. cruzi. Since DNA relaxed in the presence of an intercalating drug prior to electrophoresis became supercoiled when the ligand was removed, we analysed the topoisomerisation in gels containing another ligand, chloroquine. The inhibition which is reported here, concerning a type I topoisomerase, is of an exceptional efficiency.

Animals↗
PubMed1983

A type I DNA topoisomerase from Trypanosoma cruzi.

A type I DNA topoisomerase has been isolated from the nuclei of the flagellate Trypanosoma cruzi, using poly(ethylene glycol) fractionation and chromatography on hydroxyapatite and on phosphocellulose. The relaxation activity was ATP-independent, enhanced by Mg2+ and spermidine. The enzyme removed supercoils from negative and positive superhelical DNAs. Topoisomerase activity was associated with a polypeptide of Mr about 65000 as shown by glycerol gradient centrifugation and by electrophoresis on sodium dodecyl sulfate/polyacrylamide gels.

Animals↗
PubMed1983

[Inhibition by ellipticine derivatives of the reactions catalysed by the topoisomerases: preferential inhibition of topoisomerase II].

We have studied inhibitory effects of ellipticine derivatives on the topoisomerisation reactions by Rat liver enzymes. We used the reactions of relaxation of supercoiled DNA, catalysed by topoisomerase I without ATP and by topoisomerase II with ATP, and also the reaction of decatenation of DNA networks by topoisomerase II. When studying intercalating agents--as elliptieine derivatives are--a problem arose. To distinguish relaxed DNA from native DNA we run our samples in electrophoretic gels containing an intercalating agent: chloroquine. Topoisomerase II, which was inhibited at concentrations about 10(-6) M, was more sensitive than topoisomerase I.

Alkaloids↗
PubMed1982

[Partial purification and characterization of nuclear DNA-topoisomerases from trypanosomes (author's transl)].

We have prepared an extract presenting two types of topoisomerase activity from a nuclear fraction of Trypanosoma cruzi. The first one was revealed by the relaxation of supercoiled DNA molecules and was independent of ATP. Mg++ enhanced the reaction, without being necessary. Activity was observed between pH 5.4 and pH 8.5. The second activity was revealed by the formation of catenated molecules in the presence of ATP.

Animals↗
PubMed1979

Diurnal variations of estriol and cortisol in serum and urine in late pregnancy with and without fenoterol-therapy.

The serum concentration of unconjugated estriol, total estriol, cortisol in one hour intervals and the urinary excretion of total estrogens and cortisol in three hour intervals was determined in eleven apparently healthy women between 26 and 40 weeks of gestation. They were divided into two groups, in order to study the influence of Fenoterol treatment on the daily variation of the measured parameters. Six patients were treated with Fenoterol and five patients received no medication. Between the two groups no statistical differences could be detected for the measured parameters. Regular and marked diurnal variations in cortisol have been observed, whereas total and unconjugated estriol showed small and irregular daily changes. These daily variations of "estriol" were of the same magnitude as the two-fold methodical standard deviation. For this reason it is not necessary to standardize the sampling time.

Circadian Rhythm↗
PubMed1978

[Spirochetes: coiling direction].

On electron micrographs of spirochetes, the axial fibers are alternatively visible and hidden, i.e. above then under the cytoplasmic cylinder. From this observation the sense of coiling can be inferred. Leptospires are right-handed structures. So are other spirochetes, but it is less conspicuous. The opposite, however, appears on most published photographs and on schematic drawings. The explanation would be that the preparation introduced into the electron microscope was not facing the photographic plate, but turned to the electron beam. Also the picture must not be turned over, neither in the photographic laboratory nor when used as a slide.

Leptospira↗