Studies on liver damage induced by nanosized-titanium dioxide in mouse.

The aim of the study was to examine the liver tissue damage induced by nanosized-TiO2 in mouse. The biochemical parameters of liver, namely glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase and alkaline phosphatase were enhanced approximately 18%, 35% and 69% by exposure to nanosized-TiO2, respectively. The nanosized-TiO2 accumulated in the periphery of sinusoid in liver when the ultrastructure was examined through transmission electron microscopy. Enzymes, such as superoxide dismutase, catalase and aldehyde dehydrogenase were significantly inhibited by 22%, 38% and 15%, respectively, whereas glutathione peroxidase was constant following exposure to nanosized-TiO2.

Inhibitory effect of antioxidants on the benz[a]anthracene-induced oxidative DNA damage in lymphocyte.

Benz[a]anthracene is a ubiquitous environmental contaminant formed during the incomplete combustion of organic material. Some of the metabolites of benz[a]anthracene are known to be toxic and carcinogenic. In this investigation, benz[a]anthracene-induced oxidative damage to lymphocyte DNA was evaluated with the Comet assay (single cell gel electrophoresis). The level of oxidative DNA damage caused by benz[a]anthracene increased in a dose-dependent manner (24, 49) and oxidative DNA damage was significantly inhibited by 5 and 10 μg ml-1 ascorbate, 5 μg ml-1 polyphenols, as well as 5 and 10 μg ml-1 curcumin. Moreover, traditional Korean medicinal herbs such as Acanthopanax and ginseng significantly reduced DNA damage. The results demonstrate that antioxidant supplementation to lymphocytes inhibits oxidative DNA damage in vitro, supporting an inhibitory effect against oxidative DNA damage, probably due to reduction of reactive oxygen species production induced by benz[a]anthracene.

Antibacterial effects of minerals from ores indigenous to Korea.

We tested the antibacterial properties of a mix of minerals consisting mainly of sericite, talc, and halloysite from Korea. The preparation showed clear growth inhibition of the gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, and the grampositive bacteria Staphylococcus aureus subsp. aureus, S. epidermidis, and Bacillus cereus, as well as the anaerobic bacterium Propionibacterium acnes. These results indicate that this preparation, made from ore minerals indigenous to Korea, could be used to develop new antibacterial reagents.

Isolation of cadmium-induced DNA sequence in microalga Nannochloropsis oculata.

The gene induced in response to Cd exposure in microalga Nannochloropsis oculata was examined in this investigation. In order to isolate this gene by using nested PCR, degenerated primers were designed on the basis of highly conserved regions of the amino acid sequences of various phytochelatin synthase. The size of the nested PCR amplification product from Nannochloropsis oculata by using two degenerated primers was measured to be 266 bp. The 266 bp DNA fragment was sequenced, and it might be induced by Cd exposure in microalga Nannochloropsis oculata.

Regulation of the expression of GA-insensitive gene homolog by light in Oryza sativa c.v. DongJin.

To understand the mechanism by which light regulates a gibberellin (GA)-insensitive gene in DongJinByeo (Oryza sativa cv DongJin), both green and etiolated DongJinByeo seedlings were submerged in water and treated with GA. Total RNA from the seedlings was isolated and hybridized with cDNA of a GA-insensitive gene homolog. The amount of transcript for the GA-insensitive gene homolog was higher in green seedlings than in etiolated seedlings in the absence of GA. However upon the addition of GA, greater accumulations of the gene transcript occurred in etiolated seedlings than in green seedlings. This result indicates the possibility that the expression of the GA-insensitive gene homolog transcript may be inhibited by light in the presence of GA. Light seems to regulate multilaterally the accumulation of the transcript of the GA-insensitive gene homolog in DongJinByeo (Oryza sativa cv DongJin).

Isoperoxidases show differing sensitivity to salicylic acid.

The effects of salicylic acid (SA) on the activity of total peroxidase and the patterns of isoperoxidases of cultured tobacco cells were investigated. The total peroxidase activity of tobacco cells was inhibited by 70% when the cells were treated with 5 mM SA for one week. The peroxidase activity of tobacco cells is declined by 90% in the presence of 30 mM SA. Moreover, the activity of isoperoxidases C3, A1, and A3 decreased dramatically with increasing SA concentration, while, one of the anodic isoperoxidases, A2, was somewhat resistant to SA treatment. When isoperoxidase C3 was isolated, SA inhibited the activity of purified C3 in a concentration-dependent manner. The IC50 of isoperoxidase C3 was approximately 0.45 mM. However, the inhibition of isoperoxidase C3 activity was removed by the addition of Fe2+ ion. The possible mechanism of inhibition of peroxidase by SA is discussed.

Environmental stress-induced extracellular isoperoxidase RC3 from rice.

Effects of various environmental stresses such as heavy metals, salts and low (high) temperature on the secretion of peroxidase isozyme into the medium were examined in rice (Oryza sativa cv. Nak-Dong) suspension culture. The major extracellular peroxidases secreted into the medium by various stresses were cationic isoperoxidases. A far migrating cationic isoperoxidase RC3 was isolated from the medium after application of CaCl2, the effective stimulator for peroxidase secretion. Isolation of extracellular isoperoxidase RC3 was accomplished by ammonium sulfate fractionation, CM-cellulose cation-exchange chromatography, and Sephacryl S-100 gel filtration. The enzyme was a glycoprotein having molecular weight of approximately 34 KDa as determined by SDS-PAGE and 38 KDa by Sephacryl S-100 gel filtration. The pI value of the enzyme was 8.9. Kinetic studies revealed that the optimum pH of the enzyme was 6.0 for guaiacol and H2O2, and the Km values for guaiacol and H2O2 were 10.5 mM and 3.2 mM, respectively.