1.2C–4Cr–4Mo–10W–3.5V–10Co–Fe high-speed steel (JIS SKH57; ISO HS10-4-3-10) is often manufactured via casting and forging. By applying powder metallurgy, the properties of the abovementioned material can be improved. In this study, the effects of sintering conditions on the formation of precipitates and pores are evaluated. Additionally, strength with and without hydrostatic pressure during sintering is evaluated via static bending and impact tests. Sintering via hot isostatic pressing (HIP) at 1463 K can effectively eliminate pores and prevent the coarsening of precipitates. Toughness and strength improved by 50% by applying HIP.
The fruits of Gamazumi (Viburnum dilatatum THUNB) have been previously reported to suppress the adverse effects of oxidative stress in rats. To reduce time and cost, we attempted to establish optimal conditions for extracting bioactive components from Gamazumi fruits using supercritical carbon dioxide. To verify whether the conventional hexane extraction may be replaced by the supercritical carbon dioxide extraction, component analysis results and antigenotoxic potential in mice were used to compare bioactivity of the supercritical carbon dioxide and hexane extracts. At the same extraction pressure, the extraction rate was maximized when supercritical carbon dioxide with a low temperature was used, and extraction efficiency was improved. GC/MS analysis revealed that vitamins E and stigmasterols were included in supercritical carbon dioxide and hexane extracts, and that no qualitative differences between supercritical carbon dioxide and hexane extracts were observed. The antigenotoxic potential of Gamazumi extracts was studied in mice exposed to cigarette smoke inhalation. Mice received single or 5 consecutive oral administrations of Gamazumi extracts at 0, 3, and 6 h prior to smoke inhalation. Although single administration decreased nuclei tail length in the stomach when both administration and the intervals of smoke inhalation were short, five consecutive administrations decreased tail length in the lung and stomach regardless of the interval. At short intervals, inhaled cigarette smoke and orally administered extracts may be simultaneously present in the gastric cavity, and direct reaction between cigarette smoke and extract is possible. The antioxidant activity of Gamazumi extracts may result in antigenotoxic potential. There were no differences in component analysis and antigenotoxic potential between supercritical carbon dioxide and hexane extracts of Gamazumi; thus, it is possible to replace the conventional hexane extraction with the supercritical carbon dioxide extraction.
The dry flower buds of Sophora japonica L. are used as a hemostatic agent in traditional Chinese medicine. In the comet assay, aqueous extracts of S. japonica decreased and increased the tail length significantly in cultured human lymphoblastoid WTK1 cells exposed to UV in the absence and presence of DNA repair inhibitors, respectively. The extract did not affect the tail length in methyl methanesulfonate-exposed cells. In the present study, the aqueous extract of the flower buds of S. japonica was separated by repeated column chromatography, yielding four types of flavonoid glycosides. Among them, only rutin, similar to the extract, decreased and increased the tail length significantly in WTK1 cells exposed to UV in the absence and presence of DNA repair inhibitors hydroxyurea (10 mM) and cytosine-1-β-D-arabinofuranoside (1.8 mM), respectively. The genotoxicity-suppressing effect of rutin was further studied using the micronucleus test. Rutin significantly decreased the frequency of micronucleated binucleate cells in UV-exposed WTK1 cells but did not affect this frequency in UV-exposed XPL3KA (Xeroderma pigmentosum group C) cells. These results suggest that the anti-genotoxic potential of rutin is due to an enhanced incision step of global genome repair (GGR) sub-pathways in nucleotide excision repair (NER). Herein, we show that S. japonica exhibits heretofore unknown anti-genotoxic potential against UV by enhancing the incision of GGR sub-pathways in NER, and that its anti-genotoxic component is rutin.
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