In vitroanalysis of insoluble salt formation mechanism associated with Mg corrosion-variations depending on the diffusion environment in model tissue.

Magnesium (Mg) alloys have attracted attention as biodegradable metals, but the details of their corrosion behavior under biological environment have not been elucidated. Previous studies have suggested that diffusion through blood flow may influence Mg corrosion. Therefore, to understand the degradation behaviors of Mg, we analyzed insoluble salt precipitation associated with Mg corrosion in model tissue with different diffusion rates. A pure Mg specimen was immersed into a model tissue prepared with cell culture medium supplemented by a thickener at a different concentration (0.2%-0.5%) to form the gel. Micro-focus x-ray computed tomography of the gel was performed to observe gas cavity formation around the specimen. The insoluble salt layer formed on the specimen surface were analyzed by scanning electron microscopy with energy-dispersive x-ray spectroscopy, and Raman spectroscopy. As results, gas cavity formation was observed for all specimens. At day 7, the gas cavity volume was the highest at 0.5% thickener gel followed by 0.3% thickener gel. The insoluble salts were classified into three types based on their morphology; plate-like, granular-like, and crater-like salts. The crater-like salts were observed to cover 16.8 ± 3.9% of the specimen surface immersed in the 0.5% thickener gel, at the specimen area contacted to the gas cavity. The crater-like salts were composed by Mg hydroxide and carbonate from the deepest to the top layer. In plate-like or granular-like salts, Mg carbonate was formed in the deepest layer, but phosphates and carbonates, mainly containing calcium not Mg, were formed on the surface layer. In conclusion, the increase in the thickener concentration increased the gas cavity volume contacting to the specimen surface, resulting in the increase in precipitation of Mg hydroxide and carbonate, composing crater-like salts. Mg hydroxide and carbonate precipitation suggests the local increase in OH-concentration, which may be attributed to the decrease in diffusion rate.

Radioprotective effect of alk(en)yl thiosulfates derived from allium vegetables against DNA damage caused by X-ray irradiation in cultured cells: antiradiation potential of onions and garlic.

To evaluate a radioprotective effect of sodium n-propyl thiosulfate (NPTS) and sodium 2-propenyl thiosulfate (2PTS) derived from onions and garlic, respectively, rat hepatoma H4IIE cells and mouse lymphoma L5178Y cells were preincubated with each of these compounds for 48 hours at 37°C before receiving 10 Gy of X-ray irradiation. Cell damage caused by the irradiation was quantified as comet tail moment, which represents the degree of DNA damage. X-ray-induced DNA damage was significantly decreased in both H4IIE and L5178Y cells by micromolar concentrations of NPTS and 2PTS compared with the control without the compounds. The protective effect was more potent with 2PTS than NPTS. Onions and garlic have antiradiation potential.

High sensitivity of fibroblast cell lines derived from LEC rats to heat treatment.

A fibroblast cell line derived from LEC rat was approximately twofold more sensitive to heat treatment at 45 degrees C than were that from WKAH rat in terms of heating time required to attain 50% loss of survival in a colony forming assay. The present study was carried out for understanding the mechanism underlying the higher sensitivity of LEC rat cells to heat treatment. Although apoptosis was not found in WKAH rat cells, the percentages of apoptotic cells in LEC rat cells significantly increased after heat treatment. LEC rat cells showed significantly lower sensitivity in induction of cell death and apoptosis to ceramide, a lipid signaling molecule that is associated with heat-induced apoptosis, than did WKAH rat cells. SP600125, an inhibitor of JNK suppressed the induction of cell death in both heated LEC and WKAH rat cells, but SB203580, an inhibitor of p38 mapk, did not. The relative surviving fractions of heated LEC and WKAH rat cells in the presence of both SB203580 and SP600125 were higher than those of cells in the presence of SP600125 alone. The amounts of hsp70 protein in WKAH rat cells increased from 4 to 12 hr after heat treatment, but did not in LEC rat cells. These results suggest that higher thermosensitivity in the fibroblast cell line from LEC rat is due to low inducibility of hsp70 protein after heat treatment.

Protective effect of a lignan-containing flaxseed extract against CCl(4)-induced hepatic injury.

Carbon tetrachloride (CCl(4)) -induced hepatotoxicity is a commonly used model for investigating lipid peroxidation-related tissue injury. In the present study, the effect of flaxseed extract was observed on histological sections, glutathione-content and DNA strand breaks. Lignan-containing flaxseed extract (1.6 g/kg body weight/day) was daily administered with intragastric injection to rats for three days, on the fourth day, CCl(4) (2 g/kg) was intraperitoneally injected. Liver tissue was sampled at 24 hr after administering CCl(4). Liver-necrosis was observed in CCl(4)-injected rats without pretreatment of flaxseed extract. Pretreatment of flaxseed extract reduced extent of the necrosis found 24 hr after the intraperitoneal administration of CCl(4). Pretreatment of flaxseed extract protect against CCl(4)-induced decrease of reduced glutathione-content measured from reactions with 5,5'-dithiobis-(2-nitrobenzoic acid) and also protect against the elevation of DNA strand breaks in the liver cells measured by comet assay. Flaxseed-extract appears to protect liver cells against CCl(4)-induced necrosis.