HPLC—荧光检测测定五种多环芳烃

本文采用HPLC—荧光检测测定五种多环芳烃化合物。在shim-pack CLC-ODS柱上,以70％的乙腈水溶液作流动相,20min内同时分离测定了(艹屈)、苊、蒽、荧蒽、芘等五种多环芳烃。     

Effect of 1,3-dithia-2-thioxo-cyclopent-4-ene and its derivatives on liver injury induced by carbon tetrachloride and orotic acid in rats

The protective effect of 1,3-dithia-2-thioxo-cyclopent-4-ene (DT827A) and its two derivatives of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827B) and 4-(4-fluorophenyl)-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827C) on liver injury induced by carbon tetrachloride (CCl4) and orotic acid was studied using male rats. The approximate lethal doses were about 100 mg/kg for DT827A-treated animals and more than 800 mg/kg for the other two compounds-treated groups. Single oral administration of the three test compounds at the dose levels of 2 and 10 mg/kg 1 hour before CCl4 exposure revealed a protective effect on the findings of centrolobular necrosis, balloon cells and macrophage infiltration in histopathological findings in livers in the order of DT827B-treated rats > DT827A-treated rats > DT827C-treated rats. Repeated oral administration of the compounds at the dose levels of 2 and 10 mg/kg/day for 10 consecutive days revealed a protective effect against liver injury on the findings of centrolobular necrosis, balloon cells and macrophage infiltration in the order of DT827B-treated rats > DT827A-treated rats [symbol: see text] DT827C-treated rats. Simultaneous administration of the compounds at the dose level of 10 mg/kg/day together with a high sucrose diet containing orotic acid for 12 days revealed an inhibitory effect on fatty liver formation in the order of DT827B-treated rats > DT827C-treated rats > DT827A-treated rats. A hepatoprotective potential of the DT827 series compounds was suggested under the conditions of these studies, and DT827B was considered to be the most effective.     

High-strength glass-ceramic ferrule for SC-type single-mode optical fiber connector

A high-strength Li/sub 2/O-Al/sub 2/O/sub 3/-SiO/sub 2/ glass-ceramic ferrule has been realized by using a precise glass-ceramic drawing technique which was developed to reduce production costs. With the ion-exchange process that applies the residual compressive stress to the surface layer, the bending strength of the ferrule reached about 500 MPa, which is similar to that of an alumina ferrule. It maintained a bending strength of 310 MPa after scratching. The Young's modulus and micro Vickers hardness are similar to those of silica-glass optical fiber. The linear expansion coefficient is far smaller than that of zirconia. These characteristics suggest the stable physical contact and the easy endface polishing as the optical connector.     

Changes in tissue and blood polyamines during N-butyl-N-(4-hydroxybutyl) nitrosamine-induced bladder carcinogenesis in rats

(BACKGROUND): Polyamine are recognized as cell growth factors. We studied in order to determine whether alterations in the levels of tissue and blood polyamines were useful biochemical markers for bladder tumor. (METHODS): The concentrations of three polyamines, diamine, spermidine and spermine, in urinary bladder and blood were determined during N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced bladder carcinogenesis in male F344 rats. At 5 weeks of age, rats were given 0.05% BBN in the drinking water for 20 weeks. (RESULTS): BBN induced bladder hyperplasia in 4 of 5 rats at 8 weeks, papillomas in 2 of 5 rats at 12 weeks, and transitional cell carcinoma in all the rats by 20 weeks. The levels of total polyamine in both bladder and blood of the rats during 12-20 weeks were significantly higher than those of the control animals given water alone. The elevation of total polyamine was mainly due to the increase of spermidine of the three polyamines, which was coincident with the incidence of bladder tumors. (CONCLUSION): The results indicated that the polyamines are excellent biochemical markers for bladder tumors.     

Effects of cyclooxygenase-2 selective and nitric oxide-releasing nonsteroidal antiinflammatory drugs on mucosal ulcerogenic and healing responses of the stomach

Effects of selective cyclooxygenase-2 (COX-2) inhibitors (NS-398) and nitric oxide (NO) -releasing aspirin (NO-ASA) on gastric ulcerogenic and healing responses were examined in comparison with nonselective COX inhibitors such as indomethacin and aspirin (ASA). Hypothermic stress (28-30 degrees C, 4 hr) induced gastric lesions in anesthetized rats with an increase of acid secretion. The lesions induced by hypothermic stress were markedly worsened by subcutaneous administration of both indomethacin and ASA but were not affected by either NS-398 or NO-ASA, although the increased acid secretion during hypothermia was not affected by any of the drugs. On the other hand, the healing of gastric ulcers induced in mice by thermal cauterization (70 degrees C, 15 sec) was significantly delayed by daily subcutaneous administration of indomethacin and ASA as well as NS-398, but not by NO-ASA. COX-2 mRNA was not detected in the intact mucosa but was positively expressed in the ulcerated mucosa, most potently on day 3 after ulceration. Prostaglandin contents in the intact mouse stomach were reduced by indomethacin, ASA, and NO-ASA, while the increased prostaglandin generation in the ulcerated mucosa was inhibited by all drugs including NS-398. After subcutaneous administration of NO-ASA to pylorus-ligated rats and mice, high amounts of NOx were detected in both the gastric contents and serum. In addition, both NS-398 and NO-ASA showed an equipotent antiinflammatory effect against carrageenan-induced paw edema in rats as compared with indomethacin and ASA. These results suggest that both indomethacin and ASA not only increased the mucosal ulcerogenic response to stress but impaired the healing response of gastric ulcers as well. The former action was due to inhibition of COX-1, while the latter effect was accounted for by inhibition of COX-2 and was mimicked by the COX-2-selective inhibitor NS-398. NO-ASA, although it inhibited both COX-1 and COX-2 activity, had no deleterious effects on gastric ulcerogenic and healing responses.     

Influence of substituents on the reorientational behavior in photocrosslinkable polymer liquid crystal films with p-substituted cinnamoyloxybiphenyl side groups by irradiating with linearly polarized ultraviolet light and annealing

This paper describes the synthesis and influence of the substituent on the reorientation behavior of photocrosslinkable methacrylate polymer liquid crystals (PPLCs), which contain p-substituted cinnamoyloxybiphenyl (CB) side groups. Irradiating with linearly polarized ultraviolet (LPUV) light induced optical anisotropy of all PPLC films due to an axis-selective photoreaction of the mesogenic groups. The thermally enhanced reorientation direction depended on the substituent groups and liquid crystalline nature of the PPLC. A high in-plane reorientational order (S>0.6) parallel to the polarization of LPUV light was obtained for PPLCs with p-methoxy-CB and p-methyl-CB side groups, while out-of-plane reorientation was predominant for p-fluoro-CB and p-trifluoromethyl-CB side groups.     

Host range and interference studies of three classes of pig endogenous retrovirus

Recent interest in the use of porcine organs, tissues, and cells for xenotransplantation to humans has highlighted the need to characterize the properties of pig endogenous retroviruses (PERVs). Analysis of a variety of pig cells allowed us to isolate and identify three classes of infectious type C endogenous retrovirus (PERV-A, PERV-B, and PERV-C) which have distinct env genes but have highly homologous sequences in the rest of the genome. To study the properties of these env genes, expression plasmids for the three env genes were constructed and used to generate retrovirus vectors bearing corresponding Env proteins. Host range analyses by the vector transduction assay showed that PERV-A and PERV-B Envs have wider host ranges, including several human cell lines, compared with PERV-C Env, which infected only two pig cell lines and one human cell line. All PERVs could infect pig cells, indicating that the PERVs have a potential to replicate in pig transplants in immunosuppressed patients. Receptors for PERV-A and PERV-B were present on cells of some other species, including mink, rat, mouse, and dog, suggesting that such species may provide useful model systems to study infection and pathogenicity of PERV. In contrast, no vector transduction was observed on nonhuman primate cell lines, casting doubt on the utility of nonhuman primates as models for PERV zoonosis. Interference studies showed that the three PERV strains use receptors distinct from each other and from a number of other type C mammalian retroviruses.     

A role of the amino acid residue located on the fifth position before the first aspartate-rich motif of farnesyl diphosphate synthase on determination of the final product

Farnesyl diphosphate (FPP) synthase catalyzes consecutive condensations of isopentenyl diphosphate with allylic substrates to give FPP, C-15 compound, as a final product and does not catalyze a condensation beyond FPP. Recently, it was observed that, in Bacillus stearothermophilus FPP synthase, a replacement of tyrosine with histidine at position 81, which is located on the fifth amino acid before the first aspartate-rich motif, caused the mutated FPP synthase to catalyze geranylgeranyl diphosphate (C-20) synthesis (Ohnuma, S.-i., Nakazawa, T., Hemmi, H., Hallberg, A.-M., Koyama, T., Ogura, K., and Nishino, T. (1996) J. Biol. Chem. 271, 10087-10095). Thus, we constructed 20 FPP synthases, each of which has a different amino acid at position 81, and analyzed them. All enzymes except for Y81P can catalyze the condensations of isopentenyl diphosphate. The final products and the product distributions are different from each other. Y81A, Y81G, and Y81S can produce hexaprenyl diphosphate (C-30) as their final product. The final product of Y81C, Y81H, Y81I, Y81L, Y81N, Y81T, and Y81V are geranylfarnesyl diphosphate (C-25), and Y81D, Y81E, Y81F, Y81K, Y81M, Y81Q, and Y81R cannot produce polyprenyl diphosphates more than geranylgeranyl diphosphate. Substitution of tryptophan does not affect the product specificity of FPP synthase. The average chain length of products is inversely proportional to the accessible surface area of substituted amino acid. However, no significant relation between the final chain length and the kinetic constants Km and Vmax are observed. These observations strongly indicate that the amino acid does not come into contact with the substrates but directly contacts the omega-terminal of an elongating allylic product. This interaction must prevent further condensation of isopentenyl diphosphate.     

Ageing characteristics of Cu–Cr in-situ composite

The ageing behaviour of a Cu–15 wt% Cr in-situ composite was investigated systematically by means of hardness testing, electrical conductivity measurement, scanning electron microscopy, analytical transmission electron microscopy and high-resolution electron microscopy. The material was found to have a peak hardness after ageing at around 773 K and a peak electrical conductivity at around 873 K. In contrast with the dilute Cu–Cr alloys, Cr-rich clusters were observed at the early aged condition in the Cu matrix, which matches not only the results of mechanical and physical property measurement but also the theoretical prediction. In addition, the precipitates at peak hardened condition in the Cu matrix were determined to be Cr Guinier–Preston zones. Cr ribbon as the in-situ reinforcing element shows no measurable ageing effect due to the high-temperature solution treatment. © 1998 Chapman & Hall