Specific Conformational Change in Giant DNA Caused by Anticancer Tetrazolato-Bridged Dinuclear Platinum(II) Complexes: Middle-Length Alkyl Substituents Exhibit Minimum Effect.

Derivatives of the highly antitumor-active compound [{cis-Pt(NH3)2}2(µ-OH)(µ-tetrazolato-N2,N3)]2+ (5-H-Y), which is a tetrazolato-bridged dinuclear platinum(II) complex, were prepared by substituting a linear alkyl chain moiety at C5 of the tetrazolate ring. The general formula for the derivatives is [{cis-Pt(NH3)2}2(µ-OH)(µ-5-R-tetrazolato-N2,N3)]2+, where R is (CH2)nCH3 and n = 0 to 8 (complexes 1-9). The cytotoxicity of complexes 1-4 in NCI-H460 human non-small-cell lung cancer cells decreased with increasing alkyl chain length, and those of complexes 5-9 increased with increasing alkyl chain length. That is, the in vitro cytotoxicity of complexes 1-9 was found to have a U-shaped association with alkyl chain length. This U-shaped association is attributable to the degree of intracellular accumulation. Although circular dichroism spectroscopic measurement indicated that complexes 1-9 induced comparable conformational changes in the secondary structure of DNA, the tetrazolato-bridged complexes induced different degrees of DNA compaction as revealed by a single DNA measurement with fluorescence microsopy, which also had a U-shaped association with alkyl chain length that matched the association observed for cytotoxicity. Complexes 7-9, which had alkyl chains long enough to confer surfactant-like properties to the complex, induced DNA compaction 20 or 1000 times more efficiently than 5-H-Y or spermidine. A single DNA measurement with transmission electron microscopy revealed that complex 8 formed large spherical self-assembled structures that induced DNA compaction with extremely high efficiency. This result suggests that these structures may play a role in the DNA compaction that was induced by the complexes with the longer alkyl chains. The derivatization with a linear alkyl chain produced a series of complexes with unique cellular accumulation and DNA conformational change profiles and a potentially useful means of developing next-generation platinum-based anticancer drugs. In addition, the markedly high ability of these complexes to induce DNA compaction and their high intracellular accumulation emphasized the difference in mechanism of action from platinum-based anticancer drugs.

In vitro System for Assessing Dioxin Absorption by Intestinal Epithelial Cells and for Preventing this Absorption by Food Substances.

A system for assessing intestinal dioxin absorption was established by applying a Caco-2 cell monolayer and stable dioxin-responsive cell line. The stable dioxin-responsive cell line was established by introducing a plasmid incorporating the human CYP1A1 promoter into human hepatic HepG2 genomic DNA upstream of the luciferase gene. 2,3,7,8-Tetrachlorodibenzodioxin (TCDD) was added to the apical side of differentiated human intestinal epithelial Caco-2 cell monolayers that had been cultured on a semipermeable membrane. The basal medium was taken after an appropriate incubation time and added to the dioxin-responsive cells, the TCDD content then being analyzed by a luciferase assay. The amount of TCDD in the basal medium increased in a dose- and time-dependent manner, the results being sufficiently sensitive and reproducible. The inhibition of TCDD permeability to the Caco-2 cell monolayer by such food substances as chlorophyll, insoluble corn fiber and tea dregs were observed by this in vitro assessment system. The system will therefore be useful to identify food substances having a preventive effect on the intestinal absorption of dioxins.

Analysis of antimicrobial drug resistance of Staphylococcus aureus strains by WHONET 5: microbiology laboratory database software.

OBJECTIVES: To analyze our hospital laboratory microbiological data by using WHONET 5-Microbiology laboratory database software-, and to acquire information about antimicrobial resistance of Staphylococcus aureus strains among every ward. MATERIALS AND METHODS: The database of Staphylococcus aureus strains had been brought to our hospital microbiology laboratory from every ward in our hospital from September 2001 till December 2002. Analysis was performed under the condition as one isolate per one patient. Starting of "resistance profile" analysis in WHONET 5 and analyzing the microbiological laboratory testing reports for every ward. We chose Oxacillin, Levofloxacin, Erythromycin and Gentamicin as the antimicrobials that need to be investigated for resistance. We evaluated the monthly transition of resistance ratios with regard to the specific wards that have the moving lines of inpatients in order to verify the hypothesis that resistant strains may be carried from ward to ward along the moving lines of inpatients. RESULTS: The data of 2,113 Staphylococcus aureus strains were accumulated and analyzed. Overall Oxacillin resistance ratio in our hospital was 65.7%. The ward of the smallest Oxacillin resistance ratio was Pediatrics/Ophthalmology ward. The ratios of Oxacillin resistant were varied as from 67.9% to 96.7% regardless the categories of wards such as internal medicine or surgery. Multi-resistant MRSA strains were overwhelmingly dominant in the wards of surgery. The ratios of the Gentamicin sensitive strains that were resistant to Oxacillin were high over the every ward. The moving lines of inpatients existed between ICU/CCU ward and three rear wards. Two rear wards whose Oxacillin resistance changes were reflected to those of ICU/CCU, but one rear ward was not. CONCLUSION: Variation of resistant degree among wards were very obvious and large. We could survey the wards where patient-to-patient transmission of resistant organisms might occur along the moving lines of inpatients. WHONET 5 will be recognized as an analysis and surveillance tool for every infection control team to survey the suspicious wards.

Assessment system for dioxin absorption in the small intestine and prevention of its absorption by food factors.

It has been reported that 90% of the amount of dioxin in the whole body is absorbed orally with food. However, a concise and simple system to assess dioxin absorption in the small intestine has not yet been established. The present study reports a new in vitro assessment system for this purpose. A stable dioxin-responsive cell line was established by introducing a plasmid that incorporates a xenobiotic-responsive element upstream of the luciferase gene into human hepatic HepG2 genomic DNA. Dioxin was added to the apical side of differentiated human intestinal epithelial Caco-2 cell monolayers that had been cultured on a semipermeable membrane, and the basal medium was recovered after an appropriate incubation time. To the recovered medium was added dioxin-responsive HepG2, and a luciferase assay was performed. The established stable cell line clearly showed dose-and time-dependent response to dioxin. When a food factor such as chlorophyll, which has been reported to increase dioxin excretion in in vivo studies, was added with dioxin, a significant decrease in dioxin permeability to the Caco-2 monolayer was observed. This assessment system would be useful to search for those food factors that could prevent dioxin absorption in the small intestine.