Inhibitors of superoxide dismutases: A cautionary tale

An extensive search resulted in the identification of pamoic acid as an inhibitor of superoxide dismutases. Pamoic acid appeared to rapidly and reversibly inhibit all types of superoxide dismutases and did so in both the cytochrome c reduction and in the dianisidine photooxidation assays, used to measure this activity. It could nevertheless be shown that pamoic acid did not at all inhibit superoxide dismutase but rather diminished the sensitivity of the assays. The mechanism proposed to account for this effect involved oxidation of pamoate, by O₂^?, to yield a pamoate radical which can then reduce cytochrome c or oxidize pyrogallol. Pamoate thus competes with superoxide dismutase for the available O₂^?, without affecting the observable effects of that O₂^? upon cytochrome c or upon pyrogallol. It consequently makes these assays less responsive to superoxide dismutase, while appearing to be without effect in the absence of superoxide dismutase. Several of the predicted consequences of this proposal were affirmed. Other workers, interested in finding inhibitors for superoxide dismutases, are hereby forwarned of this subtle snare.     

Die Wirkung von Kernpolyedern (Baculovirus spec.) ausMamestra brassicae aufTrichogramma cacoeciae [Hym.: Trichogrammatidae] undChrysopa carnea [Neur.: Chrysopidae]

Zusammenfassung Kernpolyeder vonMamestra brassicae (L.) wurden auf Nebenwirkungen an zwei Entomophagen-Arten in der Basis- Konzentration (LC₁₀₀ für den natürlichen Wirt) sowie der 5- und 10 fachen Konzentration geprüft. Schadwirkung durch Kontakt mit frisch angetrocknetem Belag bzw. durch Verfüttern eines kontaminierten N?hrsubstrates auf den EiparasitenTrichogramma cacoeciae Marchal konnte nicht nachgewiesen werden. Ebenso wurde die Entwicklung vonT. cacoeciae in parasitierten Wirtseiern durch eine Tauchbehandlung mit der Kernpolyeder-Suspension in verschiedenen Intervallen nach der Parasitierung nicht gest?rt. Im Wahl- und Nichtwahlversuch konnte keine Repellentwirkung von Wirtseiern festgstellt werden, die in eine Kernpolyeder-Suspension getaucht worden waren. Die r?uberischen Larven vonChrysopa carnea Steph. waren gegenüber der 10fachen Basiskonzentration bei direktem Bespritzen der Larven, Kontakt mit einem frisch angetrockneten sprit zbelag sowie bei peroraler Aufnahme unempfindlich, wie die Frassleistung der Larven, die Fekundit?t der Imagines sowie die Schlüpfrate der Eier zeigte. Bei praktischen Eins?tzen von Kernpolyeder-Pr?paraten zur Bek?mpfung der Kohleule sind im Gegensatz zu den üblichen Anwendungen von Phosphors?ureestern keine direkten Nebenwirkungen auf die untersuchten Nutzinsekten zu erwarten.

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Summary The side effect of a water suspension of polyhedral inclusion bodies of nuclnear polyhedrosis virus (NPV) fromMamestra brassicae (L.) in a concentration of 1-, 5-, and 10-fold of the LC₁₀₀ for the natural host was tested on two beneficial insects. No reduction in the parasitization capacity ofTrichogramma cacoeciae Marchal (Hym.: Trichogrammatidae) was recorded when adults were exposed to a fresh dry film, or fed on contaminated honey-agar. The development of the parasite inSitotroga cerealella Oliv. host eggs was not affected when these were dipped in a suspension of the NPV at different time intervals after parasitization. In additional tests, it was shown that deposit of the NPV suspension had no repellent effect onTrichogramma. The feeding capacity of the predatory larve ofChrysopa carnea Steph., fecundity of the adults as well as viability of the eggs were not affected when the larvae were directly sprayed with the highest tested concentration of the suspension, exposed to fresh dry film or fed on contaminated diet. These experiments indicate that, in contrast to the use of the conventional organophosphorus insecticides, no hazard to the tested beneficial insects should be expected when the preparation of the polyhedral inclusion bodies will be used in the field.

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Nr. 2 der Serie: Wirkung von Insektenpathogenen auf Entomophagen. Als Nr. 1 gilt:S. Hassan & A. Krieg: über die schonende Wirkung vonBacillus thuringiensis-Pr?paraten auf den ParasitenTrichogramma cacoeciae (Hym.: Trichogrammatidae). — Z. Pfl. Krankh. Pfl. Schutz, 82, 515–521, 1975.     

Superoxide dismutase protects against paraquat-mediated dioxygen toxicity and mutagenicity: studies in Salmonella typhimurium

Paraquat is univalently reduced to the relatively stable, but oxygen-sensitive, paraquat radical (PQ.+). This PQ.+ can react with dioxygen to generate the superoxide radical, which can further generate other more deleterious species of oxygen free radicals (i.e., hydroxyl radical, OH.). These oxygen free radicals are known to cause chromosomal breaks; therefore, it was logical to postulate that paraquat is a mutagen. This proved to be the case when tested in a modified Ames test using a liquid incubation assay. Salmonella typhimurium strains TA98 and TA100 were grown in the presence of various concentrations of PQ, as well as in the presence of known mutagenic compounds: mitomycin C, azide, and proflavine. Paraquat was much more toxic and mutagenic in a simple nutritionally restricted medium than in a rich complex medium and these toxic and mutagenic effects were oxygen dependent. Furthermore, cells containing high levels of superoxide dismutase were more resistant to the toxic and mutagenic effects of paraquat than were cells containing a normal level of this enzyme.     

Consideration on some hormone binding proteins patterns during pregnancy

Serum concentrations of sex hormone binding globulin, transcortin, thyroxine binding globulin, transthyretin together with retinol binding protein, ceruloplasmin, transferrin and albumin were measured sequentially in pregnant women in order to derive more definite suppositions relating to the prime function of hormone binding proteins. Thus, the fact that except for transthyretin all other specific hormone binding proteins exhibited appreciable but significantly variable increases would suggest: a) the apparent existence of more complex mechanisms regulating protein metabolism during pregnancy than hitherto postulated (i.e. the general notion of an integrated estrogen influence); b) a major and distinctive role for each of the hormone binding proteins is plausible since alterations in hormonal requirements by the fetus as pregnancy progresses can not be provided by the almost constant transplacental transfer rate of the "free" hormone moiety.     

Southeast Asian Mitochondrial DNA Analysis Reveals Genetic Continuity of Ancient Mongoloid Migrations

Human mitochondrial DNAs (mtDNAs) from 153 independent samples encompassing seven Asian populations were surveyed for sequence variation using the polymerase chain reaction (PCR), restriction endonuclease analysis and oligonucleotide hybridization. All Asian populations were found to share two ancient AluI/DdeI polymorphisms at nps 10394 and 10397 and to be genetically similar indicating that they share a common ancestry. The greatest mtDNA diversity and the highest frequency of mtDNAs with HpaI/HincII morph 1 were observed in the Vietnamese suggesting a Southern Mongoloid origin of Asians. Remnants of the founding populations of Papua New Guinea (PNG) were found in Malaysia, and a marked frequency cline for the COII/tRNA(Lys) intergenic deletion was observed along coastal Asia. Phylogenetic analysis indicates that both insertion and deletion mutations in the COII/tRNA(Lys) region have occurred more than once.     

Reversed-phase chromatographic method for specific determination of glutathione in cultured malignant cells

A chromatographic method for the specific determination of glutathione in malignant cell lines is described. The method is based on the ability of glutathione-S-transferase to specifically and quantitatively conjugate glutathione to 1-chloro-2,4-dinitrobenzene and chromatographic quantitation of the resultant conjugate, dinitrophenyl-S-glutathione, by reversed-phase liquid chromatography. The assay can be performed on 20 000 g supernatants of cell homogenates without acid extraction. 2-Mercaptoethanol, a sulfhydryl compound often used as a thiol-protective agent to preserve enzymatic activities of a number of enzymes, did not interfere with glutathione determination by this method. The dinitrophenyl-S-glutathione isolated from either standard glutathione samples or from cell homogenates was shown to be identical to authentic dinitrophenyl-S-glutathione using mass spectrometry. Recovery of glutathione in standard samples by the current method was identical to that determined using 5,5′-dithiobis(2-nitrobenzoic acid). Exogenous glutathione added to supernatants of cell homogenate in the presence or absence of 2-mercaptoethanol was also completely recovered.