Identification and quantitative detection of isomeric benzo[a]pyrene diolepoxide--DNA adducts by low-temperature conventional fluorescence methods

The pyrene-like fluorescence of adducts derived from the covalent binding of (+/-)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene [+/-]-anti-BPDE] to DNA increases in intensity by factors of 20 or more as the temperature is lowered from ambient to approximately 100 K. This effect is primarily associated with the strong quenching of the pyrene-like fluorescence of BPDE-deoxyguanosyl adducts at room temperature, and the suppression of the electron-transfer quenching mechanism at 100 K. In contrast, the fluorescence of BPDE-deoxyadenosyl adducts is not quenched at ambient temperatures, and the fluorescence yields of (+/-)-anti-BPDE-poly(dA-dT).(dA-dT) adducts increases by only a factor of 2 in this same temperature range. Utilizing an internal fluorescein fluorescence standard to correct for differences in light scattering and variations in instrumental factors, a fluorescence method is described for quantitatively determining the levels of benzo[a]pyrene diolepoxide derivatives covalently bound to cellular DNA at 100 K. The method is illustrated with (+/-)-reverse-BPDE [(+/-)-trans-9,10-dihydroxy-anti-7, 8-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene]. Adduct levels as low as 10 pmol in a 400 microliters sample volume can be detected and identified from their excitation and fluorescence emission spectra using a conventional and commercially available fluorometer. In the case of modified DNA extracted from BPDE-treated Chinese hamster ovary cells or from mouse skin (approximately 1 BPDE residue/20,000 bases), such an analysis requires only 100 micrograms of DNA. Conformationally different adducts derived from the binding of the isomeric (+/-)-anti-BPDE, (+/-)-reverse-BPDE or (+/-)-syn-BPDE to cellular DNA can be distinguished by their low-temperature fluorescence excitation spectra. Specifically, the quasi-intercalated site I BPDE adducts (believed to be associated with cis-addition stereochemistry) can be distinguished from site II adducts situated at external BPDE binding sites (trans-addition stereochemistry). These results suggest that the fates of these conformationally different BPDE-DNA adducts, e.g. due to enzymatic repair, can be monitored as a function of time in DNA extracted from intact, functioning cells.

[A logistic regression analysis of relations between juvenile myopia and TV-watching, trace elements, and psychological characteristics]

With a paired study, 23 factors were investigated in 204 school children aged 9-14 in Taiyuan. The results of analysis of logistic regression showed that there was a close relationship between juvenile myopia and TV-watching distance, myopia in parents, Zn: Cu ratio in hair, N score of EPQ, Pscore of EPQ, and verbal IQ. The relations between myopia and some factors were discussed.

[The study of standard of classroom temperature for middle and primary schools in freezing and cold regions in winter]

In order to study the standard of appropriate temperature for classroom in freezing and cold regions, field and laboratory research were conducted. The results indicated: the appropriate temperature for classroom was 16-18 degrees C or 15-20 degrees C, according to the children's sense of cold and hot at different classroom temperature. The most appropriate classroom temperature was 18-20 degrees C, according to the changes of certain physiological indexes of children. 16-18 degrees C is recommended to be the standard of temperature for the middle and primary school classrooms in the cold regions in China.

[Isolation and structure determination of furan sesquiterpene from Chinese traditional herb ezhu (rhizome of Curcuma zedoaria Rosc.)]

It has been reported that curdione is a major component in Chinese traditional herb ezhu. But no curdione was found in the herb ezhu collected from Guangdong province, instead a furan sesquiterpene was isolated. Its structure and configuration were determined by the analysis of IR, UV, MS, NMR and circular dichroism.

[Medicinal Polygonatum in northwest China]

This paper reports 16 species of medicinal plants of Polygonatum found in northwest China, along with their distribution, ecological conditions, infraspecies variations and clinical applications. A key to the species is provided.

Pathological changes of hyperphonated cat vocal folds

To investigate the pathological changes of hyperphonated vocal folds 15 cats were used and over-cry was induced by mechanical stimuli. The longest experiment time was 15 weeks. All of the larynges were taken and the vocal folds were examined grossly and microscopically. The results were as follows: 1) liquid exudate accumulation beneath the epithelium developed in all of the experimental animals; 2) thickening of the epithelium was noticed in cats which had hyperphonated for more than 4 weeks; 3) acute laryngitis occurred in three cats.