Iron (III) stimulation of lipid hydroperoxide-dependent lipid peroxidation.

In an experimental system where both Fe2+ autoxidation and generation of reactive oxygen species is negligible, the effect of FeCl2 and FeCl3 on the peroxidation of phosphatidylcholine (PC) liposomes containing different amounts of lipid hydroperoxides (LOOH) was studied; Fe2+ oxidation, oxygen consumption and oxidation index of the liposomes were measured. No peroxidation was observed at variable FeCl2/FeCl3 ratio when PC liposomes deprived of LOOH by triphenylphosphine treatment were utilized. By contrast, LOOH containing liposomes were peroxidized by FeCl2. The FeCl2 concentration at which Fe2+ oxidation was maximal, defined as critical Fe2+ concentration [Fe2+]*, depended on the LOOH concentration and not on the amount of PC liposomes in the assay. The LOOH-dependent lipid peroxidation was stimulated by FeCl3 addition; the oxidized form of the metal increased the average length of radical chains, shifted to higher values the [Fe2+]* and shortened the latent period. The iron chelator KSCN exerted effects opposite to those exerted by FeCl3 addition. The experimental data obtained indicate the kinetics of LOOH-dependent lipid peroxidation depends on the Fe2+/Fe3+ ratio at each moment during the time course of lipid peroxidation. The results confirm that exogenously added FeCl3 does not affect the LOOH-independent but the LOOH-dependent lipid peroxidation; and suggest that the Fe3+ endogenously generated exerts a major role in the control of the LOOH-dependent lipid peroxidation.

[Intermediate medications in endodontics: a quantitative in-vitro evaluation of 2 phenolic derivatives]. / Medicazioni intermedie in endodonzia: valutazione quantitativa in vitro di due derivati fenolici.

In a series of in vitro experiments with dental elements obtained after an extraction, the persistence in the pulpal chamber of two phenolic compounds largely used as dental medicaments has been evaluated. The substances, p-chlorophenol and eugenol were put in a small piece of cotton inside the dental elements where they were left for 7 days. Spectrophotometric UV determination of p-chlorophenol and eugenol were made after 3 and 7 days. Our results indicate that 25% of the initial amount of p-chlorophenol is found after three days and nearly 1/5 after 7 days. The figures for eugenol are: 1/3 after three days and 1/6 of the initial amount after 7 days. The authors therefore suggest the substances under study be used as dental medicaments with an optimum of three days of interval between two medications, even if a longer interval may be observed due to the good in situ persistence of the two phenols.

[Metabolism of ornithine in human gingival tissue]. / Metabolismo dell'ornitina in tessuto gengivale umano.

The behavior of two enzymes of the ornithine pathway, leading to the formation of proline and, eventually, of collagen, arginase and ornithine oxo-acid aminotransferase has been investigated in normal and inflamed gingival tissue. Both enzymatic activities show a statistically significant decrease in pathological samples as compared to normal ones. The data on arginase activity may be in agreement with the already documented low level of urea in pathological gingival fluid, while a decrease of the ornithine aminotransferase activity could be linked to the phenomenon of gingival retraction, i.e. the lack of complete regeneration of gingival tissue usually observed in chronically inflamed subjects, that would be reasonably parallel to a decreased proline/collagen synthesis.

Effects of taurine and hypotaurine on lipid peroxidation.

It has been suggested that hypotaurine might inhibit lipid peroxidation in vivo by scavenging the initiator OH. The results presented demonstrate that hypotaurine affects other reactions relevant to the initiation, propagation and termination phases of lipid peroxidation. Hypotaurine a) decreases Fe2+ autoxidation, either spontaneous or catalyzed by Fe3+, that may generate perferryl iron; b) decreases Fe2+ oxidation, by cumene hydroperoxide, that forms the alkoxy radical; c) inhibits the lipid hydroperoxide dependent lipid peroxidation, favoring the onset of the termination phase. Hypotaurine does not affect the autoxidation of Fe2+ bound to phosphatidic acid containing liposomes. Taurine is ineffective in all the experimental systems tested.