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  • Springer  (2)
  • 1995-1999  (2)
  • 1996  (2)
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Publisher
  • Springer  (2)
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  • 1995-1999  (2)
Year
  • 1
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Topical application and intraperitoneal administration of spiroarsoranes were carried out to cure central nervous system (CNS) trypanosomiasis in the chronic Trypanosoma brucei GVR 35 mouse model. Topical application appeared more efficient than intraperitoneal injection. The periods of aparasitaemia after treatment were longer but none of the mice was permanently cured. Combination treatment with eflornithine (DFMO) and the spiroarsoranes failed to show any synergistic effect. In addition, spiroarsorane I was evaluated against the T. b. rhodesiense KETRI 2634 strain, whereby 60-mg/kg treatment produced a noticeable prolongation of the life span of trypanosome-positive animals. These in vivo results suggests that the spiroarsoranes have difficulty in crossing the blood-brain barrier (BBB) and clearing the parasites from the CNS or, alternatively, that these strains are less sensitive to pentavalent arsenicals than the T. b. brucei CMP fast strain, which in the present study was more sensitive to spiroarsoranes whose lipophilicity corresponded to a log-P value ranging from 2.5 to 3.7.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  High levels of lactate dehydrogenase (LDH; EC 1. 1. 1. 27) activity have been detected in the filarial worm Molinema dessetae. The two major LDH isoenzymes (LDH1 and LDH2) from female worms were purified by successive chromatography on diethylaminoethyl (DEAE)-Sepharose, carboxymethyl (CM)-Sepharose, and hydroxyapatite columns followed by fast protein liquid chromatography (FPLC)-gel filtration. LDH1 and LDH2 isoenzymes were found to be dimers with subunits of 58 kDa. They had similar properties with regard to substrate and coenzyme affinity. The apparent Michaelis constants (K m values; mean ± SEM, n = 10) were 0.34 ± 0.04 mM for pyruvate, 0.25 ± 0.02 mM for reduced nicotinamide adenine dinucleotide (NADH), 2.5 ± 0.21 mM for lactate, and 0.18 ± 0.02 mM for NAD, which suggested that pyruvate reduction was the favored reaction. LDH1 and LDH2 were affected by p-chloromercuribenzoate and Hg2+, and such inhibitory effects could be reversed by the addition of thiol compounds (L-cysteine or β-mercaptoethanol) as observed for mammalian LDH. Oxalate acted as a noncompetitive inhibitor of pyruvate reduction (K i = 4.7 ± 0.35 mM; mean ± SEM, n = 10) and as a competitive inhibitor with lactate (K i = 2.3 ± 0.21 mM), whereas oxamate acted as a competitive inhibitor with pyruvate (K i = 3.3 ± 0.28 mM) and was noncompetitive with lactate (K i = 19 ± 1.2 mM). These substrate analogues exerted similar effects on mammalian LDH, but the inhibition constants were significantly different. The existence of structural and kinetic differences between mammal and filarial LDH isoenzymes prompted us to evaluate them as targets for chemotherapeutic attack.
    Type of Medium: Electronic Resource
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