Increased sensitivity in PCR detection of tdh-positive Vibrio parahaemolyticus in seafood with purified template DNA

PCR is an important method for the detection of thermostable direct hemolysin gene (tdh)-positive (pathogenic hemolysin-producing) strains of Vibrio parahaemolyticus in seafood because tdh-negative (nonpathogenic) V. parahaemolyticus strains often contaminate seafood and interfere with the direct isolation of tdh-positive V. parahaemolyticus. In this study, the use of PCR to detect the tdh gene of V. parahaemolyticus in various seafoods artificially contaminated with tdh-positive V. parahaemolyticus was examined. PCR was inhibited by substances in oysters, squid, mackerel, and yellowtail but not by cod, sea bream, scallop, short-necked clam, and shrimp. To improve detection, DNA was purified by either the silica membrane method, the glass fiber method, or the magnetic separation method, and the purified DNA was used as the PCR primer template. For all samples, the use of the silica membrane method and the glass fiber method increased detection sensitivity. The results of this study demonstrate that the use of properly purified template DNA for PCR markedly increases the effectiveness of the method in detecting pathogenic tdh-positive V. parahaemolyticus in contaminated seafood.

Lethal effect of the expression of a killer gene SMK1 in Saccharomyces cerevisiae

Expression of the SMK1 gene which encodes the yeast killer toxin SMKT is lethal in Saccharomyces cerevisiae. Effects of deletion and site-directed mutagenesis of SMK1 on the lethality and the secretion of the gene products were examined. Deletion of the interstitial gamma peptide or the C-terminal loop from Ala208 to the C-terminal Asp222 had no effect on the lethality. Those SMK1 products that lacked either the gamma peptide or the C-terminal loop were expressed in the cells but were not secreted into the culture medium, suggesting that these peptides may have a role in secretion or in protein stability. On the other hand, deletion of the signal sequence resulted in complete loss of the lethal activity. Entering the secretory pathway may be critical for the lethality. Further, deletion of the region from the C-terminus to Leu207 resulted in loss of the lethal activity. Leu207 is located at the C-terminus of the central strand of the beta-sheet structure of SMKT and its side chain is thrust into a hydrophobic environment between the beta-sheet and the alpha-helices. The result obtained upon substitutions of Ala, Ser or Glu for Leu207 suggested that the side chain of Leu207 stabilizes the hydrophobic environment that contributes to the overall structure of the SMK1 product.

Antioxidant activity of a medicine based on Aspergillus oryzae NK koji measured by a modified t-butyl peroxyl radical scavenging assay

A koji-based medicine composed of powder of Aspergillus oryzae NK koji, dried yeast, and lactobacilli koji had high antioxidant activity measured by a modified t-butyl peroxyl radical scavenging assay. This activity was mainly derived from A. oryzae NK koji. Digestion of koji-making grain germ medium with several commercial enzymes also increased antioxidant activity. By two weeks of oral administration of A. oryzae NK koji, the serum lipid peroxide levels elevated in STZ-induced diabetic rats could be decreased significantly.

Single-shot UV autocorrelator that uses a two-photon-induced photoacoustic signal in water

A single-shot autocorrelation of an ultrashort UV pulse is measured by detecting a two-photon-induced photoacoustic signal in water. A supersonic wave representing the autocorrelation function is detected by a polyvinylidene fluoride piezoelectric film with a spatial resolution of less than 60 microm. The detection sensitivity is higher than that of a multiphoton-induced fluorescence method by approximately 2 orders of magnitude.

Circulating antibodies against c-myc oncogene product in sera of colorectal cancer patients

We developed a Western blot assay using purified human c-myc protein expressed in E. coli in order to look for circulating anti-c-myc antibodies in human sera. The presence of IgG antibodies against c-myc was observed in 25 out of 44 sera from patients with colorectal cancer diagnosed and treated at the Hôpital Curie in Paris, compared to the sera of 46 normal donors of which only 8 samples were positive (p = 0.001).

2-Methylthio-1,4-naphthoquinone, a unique sulfur-containing quinone from a thermophilic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus

A quinone was extracted and purified from the cells of an extremely thermophilic hydrogen bacterium, Hydrogenobacter thermophilus TK-6 (IAM 12695). Its chemical structure was determined as 2-methylthio-3-VI, VII-tetrahydromultiprenyl-1,4-naphthoquinone by elemental analysis, 1H nuclear magnetic resonance spectroscopy, mass spectroscopy, and infrared spectroscopy of the quinone and by gas-liquid chromatography and gas chromatography-mass spectroscopy analysis of the ozonolysis products of the quinone. It was shown that the other five strains of H. thermophilus have the same quinone system. We named the quinone with the 2-methylthio-1,4-naphthoquinone nucleus "methionaquinone." The abbreviation of MTK is recommended for this class of quinone.