Mutagenicity and DNA-modifying activity of 2-nitropropane

The results presented herein confirm the mutagenicity in Salmonella of 2-nitropropane and the relative inactivity of 1-nitropropane. The lack of mutagenicity of 1- and 2-aminopropane is also reported. In addition, we have demonstrated the in vitro DNA-modifying activity of 2-nitropropane, and present evidence to suggest that genetic activity of this nitroalkane may not be dependent on the enzymic reduction of the nitro function to the corresponding hydroxylamine.     

UV irradiation of polystyrene pipets releases PCR inhibitors

Wilms' tumor is a renal tumor that develops in childhood and is one of the most common malignant tumors in children under 5 years old. Bone metastases are extremely rare in Wilms' tumor, with only two reported cases in adults. We report the case of a patient who underwent nephrectomy for Wilms' tumor at the age of 10 years and presented with a bone mass in his left femur 13 years later.     

丙烯酸聚氨酯涂层的紫外老化行为

针对丙烯酸聚氨酯防腐涂层进行紫外加速老化实验,采用光泽度、色差检测以及SEM、FTIR分析,结合交流阻抗谱法(EIS),研究丙烯酸聚氨酯涂层的紫外老化行为.结果表明:用光泽度表征涂层光降解程度更灵敏;由接触角及色差等变化规律可将丙烯酸聚氨酯涂层紫外老化分为前期(慢速光老化)、中期(快速光老化)和后期(慢速光老化)三阶段.对涂层进行表面化学分析认为丙烯酸聚氨酯的紫外光降解主要是O-CH键及C-N键断裂导致的;涂层表面形貌和性能与EIS结果对比分析显示丙烯酸聚氨酯涂层发生明显降解之前防护性能已经明显下降.     

UV irradiation and heat shock mediate JNK activation via alternate pathways

To elucidate cellular pathways involved in Jun-NH2-terminal kinase (JNK) activation by different forms of stress, we have compared the effects of UV irradiation, heat shock, and H2O2. Using mouse fibroblast cells (3T3-4A) we show that while H2O2 is ineffective, UV and heat shock (HS) are potent inducers of JNK. The cellular pathways that mediate JNK activation after HS or UV exposure are distinctly different as can be concluded from the following observations: (i) H2O2 is a potent inhibitor of HS-induced but not of UV-induced JNK activation; (ii) Triton X-100-treated cells abolish the ability of UV, but not HS, to activate JNK; (iii) the free radical scavenger N-acetylcysteine inhibits UV- but not HS-mediated JNK activation; (iv) N-acetylcysteine inhibition is blocked by H2O2 in a dose-dependent manner; (v) a Cockayne syndrome-derived cell line exhibits JNK activation upon UV exposure, but not upon HS treatment. The significance of Jun phosphorylation by JNK after treatment with UV, HS, or H2O2 was evaluated by measuring Jun phosphorylation in vivo and also its binding activity in gel shifts. HS and UV, which are potent inducers of JNK, increased the level of c-Jun phosphorylation when this was measured by [32P]orthophosphate labeling of 3T3-4A cultures. H2O2 had no such effect. Although H2O2 failed to activate JNK in vitro and to phosphorylate c-Jun in vivo, all three forms of stress were found to be potent inducers of binding to the AP1 target sequence. Overall, our data indicate that both membrane-associated components and oxidative damage are involved in JNK activation by UV irradiation, whereas HS-mediated JNK activation, which appears to be mitochondrial-related, utilizes cellular sensors.     

Occurrence of fumonisins in corn-based food products

Corn-based food products obtained from commercial outlets in three different parts of the U.S., Maryland, Nebraska, and Arizona were analyzed for total fumonisins by a commercial competitive direct enzyme-linked immunosorbent assay (CD-ELISA) and for fumonisin B1 (FB1) by high-performance liquid chromatography (HPLC). The highest fumonisin concentrations were found in samples collected in Maryland, where all 18 samples were found positive for fumonisins (200 to 7,450 ng/g of food) by CD-ELISA and 15 of the 18 samples (83%) were found positive for FB1 (< 75 to 5,916 ng/g) by HPLC. Fumonisins were also detected by CD-ELISA in 14 of 15 samples collected in Arizona with concentrations ranging from 200 to 1,450 ng/g, but analyses by HPLC showed that only 8 of 15 samples (53%) were positive for FB1 (< 75 to 1,565 ng/g of food). Of the 23 samples collected in Nebraska, 20 (87%) were positive for fumonisins (200 to 2,500 ng/g) by CD-ELISA, but only 10 (44%) were positive for FB1 (< 75 to 927 ng/g) by HPLC. The highest fumonisin and FB1 concentrations were found in cornmeal samples, ranging up to 7,450 ng/g of cornmeal by CD-ELISA and 5,916 ng/g by HPLC. These findings indicate that there may be a risk of human exposure to fumonisins through the consumption of some corn-based foods.     

DNA repair after UV and gamma irradiation. II. Human lymphocytes

A technique of an in vitro microculture system has been set up in order to standardize DNA repair in adult human lymphocytes after ultraviolet and gamma irradiation measuring tritiated thymidine uptake. The results obtained in DNA unscheduled synthesis were different if ultraviolet or gamma rays were employed.     

Effect of bee pollen extract on glutathione system activity in mice liver under X-ray irradiation

It has been established that small x-irradiation dozes activate the lipid peroxidation and antioxidant system enzymes in mice liver. The introduction of bee pollen extract to animals normalized the activity of only several glutathione system enzymes in mice liver.     

铁掺杂钛基反蛋白石材料的性能表征及其可见光催化活性

采用溶胶凝胶法制备了不同掺杂比的铁掺杂二氧化钛反向蛋白石结构材料,通过扫描电镜,X射线能谱及紫外可见分光光度仪等对掺杂前后的样品进行比较,并采用罗丹明-B作为降解底物,对掺杂后样品在可见光下的光催化降解活性进行了研究.结果表明,铁掺杂后,样品的吸收带边发生红移,光响应区域扩展至550 nm,且样品中表面羟基氧的含量最高可提高到40%.铁掺杂样品的催化活性明显优于未掺杂的样品,其中掺杂比为10%的样品光催化降解活性最高,经可见光照射4 h后,其降解率可达85%以上.     

Estimating distributions of numbers of organisms in food products

Procedures of sampling and measurement contribute variability and uncertainty to exposure models that predict incidence and levels of organisms in food products. This paper focuses on methods that account for sampling and measurement error in fitting distributions of organisms in food products for use in exposure models for microbial risk assessment. Define y to be a measured density on a sample selected with stipulated probability from a population, and define x to be the "true" density for that sample. Designate the conditional distribution of y given the sample with "true" value x as g(y/x), and let F(x) be the unknown cumulative density of x. The distribution of the observed values y, h(y), can be expressed through the integral equation h(y) = integral of g(y/x) dF(x). Knowledge of g(y/x) and h(y) enables an estimate of the unknown distribution of the organism's F(x). In applications to risk assessment, use of continuous distributions described by a few parameters is desirable. Also desirable may be imputation or assignment of possible nonzero values for nondetect observations--those results below the limit of detection of the methodology--that may not be truly zero. This paper explores the use of the above formulation for estimating distributions of organisms used for microbial risk assessment and presents some simple examples.     

Determination of tin in food products using pyrocatechol violet

The practice of dietetic therapy is unusual today for patients suffering from renal failure without hypertension and reduction of glomerular filtration rate. Specific treatment is needed, however, for arterial hypertension, uremia, calculus and uralith disease. Experiments in rats showed, that a lot of uremic symptoms following poorly functioning kidneys are partly at least caused by disturbances in amino acid metabolism. Uremia patients with dysfunctioning plasma protein metabolism (transferrin, complement, cholinesterase, prealbumin and retinolbinding protein) need oral, respectively parenteral substitution of essential amino acids. This substitution is very important under catabolic stress conditions in uremic syndrome with and without vividialysis treatment.     

CeO2 nanoscale particles: Synthesis,characterization and photocatalytic activity under UVA light irradiation

CeO_2 nanoparticles(NPs) were synthesized in alkaline medium via the homogeneous precipitation method and were subsequently calcined at 80 ℃/24 h(assigned as CeO_2-80) and 500 ℃/2 h(assigned as CeO_2-500). The as-prepared materials and the commercial ceria(assigned as CeO_2-com) were characterized using TGA-MS, XRD, SEM-EDX, UV-vis DRS and IEP techniques. The photocatalytic performances of all obtained photocatalysts were assessed by the degradation of Congo red azo-dye(CR) under UVAlight irradiation at various environmental key factors(e.g., reaction time and calcination temperature).Results reveal that CeO_2 compounds crystalize with cubic phase, CeO_2-500 exhibits smaller crystallite size(9 nm vs 117 nm) than that of bare CeO_2-com. SEM analysis shows that the materials are sphericallike in shape NPs with strong assembly of CeO_2 NPs observed in the CeO_2-500 NPs. EDX analysis confirms the stoichiometry of CeO_2 NPs. UV-vis DRS measurement reveals that, CeO_2-500 NPs exhibits a red-shift of absorption band and a more narrow bandgap(2.6 eV vs 3.20 eV) than that of bare CeO_2-com. On the contrary, Urbach energy of Eu is found to be increased from 0.12 eV(CeO_2-com) to 0.17 eV(CeO_2-500),highlighting an increase of crystalline size and internal microstrain in the CeO_2-500 NPs sample. Zeta potential(IEP) of CeO_2-500 NPs is found to be 7.2. UVA-light-responsive photocatalytic activity is observed with CeO_2-500 NPs at a rate constant of 10×10~(-3) min~(-1), which is four times higher than that of CeO_2-com(K_(app)=2.4×10~(-3) min~(-1)) for the degradation of CR. Pseudo-first-order kinetic model gives the best fit. On the basis of the energy band diagram positions, the enhanced photocatalytic performance of CeO_2-500 nano-catalyst can be ascribed to O_2~-, 'OH and R'~+ as the primary oxidative species involved in the degradation of RC under UVA-light irradiation.