Distribution and bioavailability of mercury in size-fractioned atmospheric particles around an ultra-low emission power plant in Southwest China.

Ultra-low emission (ULE) technology retrofits significantly impact the particulate-bound mercury (Hg) emissions from coal-fired power plants (CFPPs); however, the distribution and bioavailability of Hg in size-fractioned particulate matter (PM) around the ULE-retrofitted CFPPs are less understood. Here, total Hg and its chemical speciation in TSP (total suspended particles), PM10 (aerodynamic particle diameter ≤ 10 µm) and PM2.5 (aerodynamic particle diameter ≤ 2.5 µm) around a ULE-retrofitted CFPP in Guizhou Province were quantified. Atmospheric PM2.5 concentration was higher around this ULE-retrofitted CFPP than that in the intra-regional urban cities, and it had higher mass Hg concentration than other size-fractioned PM. Total Hg concentrations in PM had multifarious sources including CFPP, vehicle exhaust and biomass combustion, while they were significantly higher in autumn and winter than those in other seasons (P < 0.05). Regardless of particulate size, atmospheric PM-bound Hg had lower residual fractions (< 21%) while higher HCl-soluble fractions (> 40%). Mass concentrations of exchangeable, HCl-soluble, elemental, and residual Hg in PM2.5 were higher than those in other size-fractioned PM, and were markedly elevated in autumn and winter (P < 0.05). In PM2.5, HCl-soluble Hg presented a significantly positive relationship with elemental Hg (P < 0.05), while residual Hg showed the significantly positive relationships with HCl-soluble Hg and elemental Hg (P < 0.01). Overall, these results suggested that atmospheric PM-bound Hg around the ULE-retrofitted CFPP tends to accumulate in finer PM, and has higher bioavailable fractions, while has potential transformation between chemical speciation.

Influence of gut microecology in the development of malignant tumors and its potential therapeutic application: A review.

A microbial ecosystem is a complex community of multiple bacterial interactions. The potential role of gut microbiota in human health has already attracted the attention of many researchers. Dysregulation of the gut microbial community has been suggested to be closely associated with the progression of various chronic diseases. Malignant neoplasms represent a major global health burden and are now the leading cause of death. The formation of tumors is often thought to be influenced by genetic and environmental factors. Recent research advances have indicated that multiple malignancies may also be attributed to the gut microbiota. In this review, we highlight the complex interactions between gut microbes and their metabolites, as well as the potential impact of gut microecology on the occurrence and development of tumors. In addition, potential strategies for targeted therapy of tumors using gut microecology are discussed. In the near future, intestinal microecology is likely to be used for early screening of tumors and subsequent clinical treatment.

Biosynthesis and Pharmacological Activities of Flavonoids, Triterpene Saponins and Polysaccharides Derived from Astragalus membranaceus.

Astragalus membranaceus (A. membranaceus), a well-known traditional herbal medicine, has been widely used in ailments for more than 2000 years. The main bioactive compounds including flavonoids, triterpene saponins and polysaccharides obtained from A. membranaceus have shown a wide range of biological activities and pharmacological effects. These bioactive compounds have a significant role in protecting the liver, immunomodulation, anticancer, antidiabetic, antiviral, antiinflammatory, antioxidant and anti-cardiovascular activities. The flavonoids are initially synthesized through the phenylpropanoid pathway, followed by catalysis with corresponding enzymes, while the triterpenoid saponins, especially astragalosides, are synthesized through the universal upstream pathways of mevalonate (MVA) and methylerythritol phosphate (MEP), and the downstream pathway of triterpenoid skeleton formation and modification. Moreover, the Astragalus polysaccharide (APS) possesses multiple pharmacological activities. In this review, we comprehensively discussed the biosynthesis pathway of flavonoids and triterpenoid saponins, and the structural features of polysaccharides in A. membranaceus. We further systematically summarized the pharmacological effects of bioactive ingredients in A. membranaceus, which laid the foundation for the development of clinical candidate agents. Finally, we proposed potential strategies of heterologous biosynthesis to improve the industrialized production and sustainable supply of natural products with pharmacological activities from A. membranaceus, thereby providing an important guide for their future development trend.

Physiological and Transcriptional Responses of Apocynum venetum to Salt Stress at the Seed Germination Stage.

Apocynum venetum is a semi-shrubby perennial herb that not only prevents saline-alkaline land degradation but also produces leaves for medicinal uses. Although physiological changes during the seed germination of A. venetum in response to salt stress have been studied, the adaptive mechanism to salt conditions is still limited. Here, the physiological and transcriptional changes during seed germination under different NaCl treatments (0-300 mmol/L) were examined. The results showed that the seed germination rate was promoted at low NaCl concentrations (0-50 mmol/L) and inhibited with increased concentrations (100-300 mmol/L); the activity of antioxidant enzymes exhibited a significant increase from 0 (CK) to 150 mmol/L NaCl and a significant decrease from 150 to 300 mmol/L; and the content of osmolytes exhibited a significant increase with increased concentrations, while the protein content peaked at 100 mmol/L NaCl and then significantly decreased. A total of 1967 differentially expressed genes (DEGs) were generated during seed germination at 300 mmol/L NaCl versus (vs.) CK, with 1487 characterized genes (1293 up-regulated, UR; 194 down-regulated, DR) classified into 11 categories, including salt stress (29), stress response (146), primary metabolism (287), cell morphogenesis (156), transcription factor (TFs, 62), bio-signaling (173), transport (144), photosynthesis and energy (125), secondary metabolism (58), polynucleotide metabolism (21), and translation (286). The relative expression levels (RELs) of selected genes directly involved in salt stress and seed germination were observed to be consistent with the changes in antioxidant enzyme activities and osmolyte contents. These findings will provide useful references to improve seed germination and reveal the adaptive mechanism of A. venetum to saline-alkaline soils.

Enhancement of NOx adsorption performance on zeolite via a facile modification strategy.

Adsorption is a promising technology for simultaneously capturing nitrogen oxides (NOx) from flue gases and recycling NO2 as a profitable chemical, for which a robust and efficient adsorbent provides the key step for success in practical applications. This work reports the enhancement of NOx adsorption performances with less cost of desorption energy on Cu-ZSM-5 zeolites prepared by a facile and rapid (690 s) modification method, the incipient-wetness impregnation coupled with microwave drying (IM). In comparisons to H-ZSM-5, Na-ZSM-5 and conventionally liquid-phase ion-exchanged counterparts under sub-1000 ppm NOx feed concentrations and room temperature, the IM sample renders a record NOx adsorption capacity (qt,NOx) of 0.878 mmol/g from dry gas stream on zeolites, and an applicable qt,NOx of 0.1 mmol/g from wet gas stream with a proper copper loading (2.1 wt%). The temperature programmed desorption of NOx on the optimal IM sample saturated with NOx from wet gas stream exhibit primary peak temperature lower than reported Cu-ZSM-5 and significant NO2 proportion (72.6 %) in desorbed NOx. Deeper insights into advantageous NOx oxidative adsorption over the properly-loaded Cu-ZSM-5 in terms of diverse adsorbate states and competitiveness towards H2O were gained, showing IM method a promising sorbent improvement strategy for practical use.

Ambient ozone pollution at a coal chemical industry city in the border of Loess Plateau and Mu Us Desert: characteristics, sensitivity analysis and control strategies.

In this study, ambient ozone (O3) pollution characteristics and sensitivity analysis were carried out in Yulin, a city in the central area of the Loess Plateau during 2017 to 2019 summer. O3 concentrations increased for 2017 to 2019. Correlation and statistics analysis indicated high temperature (T > 25 °C, low relative humidity (RH < 60%), and low wind speed (WS < 3 m/s) were favorable for O3 formation and accumulation, and the O3 pollution days (MDA8 O3 > 160 µg/m3) were predominantly observed when the wind was traveling from the easterly and southerly. O3 concentration in urban area of Yulin was higher than that in background. The pollution air masses from Fenwei Plain increase the level and duration of O3 pollution. In order to clarify the formation mechanism and source of O3, online measurements of volatile organic compounds (VOCs) were conducted from 7 July to 10 August in 2019. The average of VOCs concentration was 26 ± 12 ppbv, and large amounts of alkenes followed by aromatics, characteristic pollutants of the coal chemical industry, were detected in the ambient air. To further measure the sensitivity, the observation-based model (OBM) simulation was conducted. Empirical Kinetic Modeling Approach (EKMA) plot and relative incremental reactivity (RIR) value indicated Yulin located on VOCs-limited regime. That implied a slight decrease of NOx may increase O3 concentration. When the emission reduction ratio of anthropogenic VOCs/NOx higher than 1:1, the O3 will decrease. O3 control strategies analysis shows that the O3 targets of 5% and 10% O3 concentration reductions are achievable through precursor control, but more effort is needed to reach the 30% and 40% reduction control targets.

A preliminary study on pollution characteristics of surfactant substances in fine particles in the Beibu Gulf Region of China.

The pollution characteristics of surfactant substances in fine particles (PM2.5) in spring were studied in the Beibu Gulf Region of China, 68 samples of PM2.5 were collected at Weizhou Island in Beihai City from March 12 to April 17, 2015. The Anionic Surfactant Substances (ASS) and Cationic Surfactant Substances (CSS) in the samples were analyzed using Byethyl Violet Spectrophotometry and Disulfide Blue Spectrophotometry, respectively. Combined with the data from backward trajectory simulation, the effects of air pollutants from remote transport on the pollution characteristics of surfactant substances in PM2.5 in the Beibu Gulf Region were analyzed and discussed. The results showed that the daily mean concentrations of ASS and CSS in spring in the Beibu Gulf Region were 165.20 pmol/m3 and 8.05pmol/m3, and the variation ranges were 23.21-452.55 pmol/m3 and 0.65-31.31 pmol/m3, accounting for 1.82‰ ± 1.65‰ and 0.12‰ ± 0.11‰ of the mass concentration of PM2.5, respectively. These concentrations were lower than those in comparable regions around the world. There was no clear correlation between the concentrations of ASS and CSS in PM2.5 and the mass concentrations of PM2.5. Tourism and air transport had a positive contribution on the concentrations of ASS. The concentration of surfactant substances in PM2.5 was significantly impacted by wind speed and wind direction. Atmospheric temperature, air pressure and precipitation had little effect on the concentrations of surfactant substances. Surfactant substances in PM2.5 significantly impacted visibility. Results also showed that the main sources of surfactant substances were from the southern China and Southeast Asia.

An improved overall risk probability-based method for assessing the combined health risks of chemical mixtures: An example about mixture of aflatoxin B1 and microcystin LR by dietary intake.

Previous studies on the risk assessment of chemicals with respect to human health have focused mainly on the safety of individual substances. Recently, public health policy emphasizes the combined effects of mixtures. An overall risk probability (ORP)-based method long with the combined toxicity factor (cuv) can be used to evaluate the combined toxicity of chemical mixtures from the environment and foods on human health. However, the procedure for calculating the cuv accurately and quantitatively in the ORP method is yet unclear. In this study, an improved ORP-based method (IORP) was developed by introducing a variable time t, and the cuv was analyzed quantitatively using simultaneous equations and based on the principle of least squares regression. This phenomenon can be explained based on the example of the mixture of aflatoxin B1 (AFB1) and microcystin LR (MC-LR) by dietary intake in order to understand the application of this method. The IORP approach makes it possible for estimating the combined effects of mixtures for human health by dietary pathway.

Characterizing carbonyl compounds and their sources in Fuzhou ambient air, southeast of China.

In recent years, ozone (O3) concentrations in the southeastern coastal areas of China have shown a gradual upward trend. As precursors and intermediates in the formation of O3, carbonyl compounds play key roles in the atmospheric photochemical oxidation cycle. To explore the main pollution characteristics of carbonyl compounds in a typical coastal city in southeast China, ambient samples were collected in Fuzhou (the provincial capital of Fujian province, located on the southeast coast of China) and analyzed using high-performance liquid chromatography with ultraviolet detection. The study was continuously carried out at an urban site (Jinjishan) and a suburban site (Gushan) in Fuzhou from May 8 to 20, 2018. The total concentration of 16 carbonyl compounds at the urban site was 15.45 ± 11.18 ppbv, and the total concentration at the suburban site was 17.57 ± 12.77 ppbv. Formaldehyde (HCHO), acetaldehyde, and acetone were the main species detected in the samples, and acetone had the highest concentration among the species detected. The suburban site had a higher formaldehyde/acetaldehyde ratio and lower acetaldehyde/propionaldehyde ratio than the urban site, implying that biogenic sources potentially contributed to the carbonyl compound concentrations at the suburban site. The results of an observation-based model showed that anthropogenic hydrocarbons promoted HCHO production on May 17 at the urban site. Compared to biogenic emissions, anthropogenic activity is a more important source of carbonyl compounds.

Relationship between digestive diseases and COVID-19 severity and mortality: A protocol for systematic review and meta-analysis.

BACKGROUND: Digestive diseases have been often reported in COVID-19 patients, but whether COVID-19 patients with existing digestive comorbidities are at an increased risk of serious disease and death remains unclear. This study aims to evaluate the association between digestive diseases and COVID-19 severity and mortality. METHODS: PubMed, Embase.com, the Cochrane Central Register of Controlled Trials, Web of Science, China National Knowledge Infrastructure, Wanfang, and SinoMed will be searched to identify relevant studies up to October 1, 2020. We will use the Newcastle-Ottawa quality assessment scale to assess the quality of included studies. We will use Stata to perform pairwise meta-analyses using the random-effects model with the inverse variance method to estimate the association between digestive diseases and the mortality and severity of COVID-19. Subgroup analyses and sensitivity analyses will be conducted to investigate the sources of heterogeneity. We will create a "Summary of findings' table presenting our primary and secondary outcomes using the GRADEpro Guideline Development Tool software. RESULTS: The results of this study will be published in a peer-reviewed journal. CONCLUSIONS: This study will comprehensively evaluate the association between digestive diseases and the severity and mortality of patients with COVID-19. The results of this study will provide high-quality evidence to support clinical practice and guidelines development.

[Variational Trend and Characteristics of Air Pollution in Baoding City].

To understand the trends and characteristics of air pollution in Baoding in recent years, an analysis of air quality and air pollutant concentrations in Baoding from 2013 to 2018 was carried out. The results showed that: 1 from 2013 to 2018, the comprehensive index of Baoding dropped from 11.6 to 6.6, the days of severe pollution decreased from 114 days to 27 days, and cumulative concentration of pollutants during severe pollution decreased from 57.34% to 20.59%. This indicated that the air quality of Baoding city has improved year on year from 2013 to 2018. Not only has the number of heavy pollution days and the annual average concentration of pollutants decreased, but also the proportion of cumulative concentrations of pollutants during heavy pollution has decreased. the difference between the average concentration level of Baoding city and "2+26" Cities is getting smaller and smaller. ② Summer ρ(O3-8h) increased year on year. In 2017 and 2018, the heavy pollution days caused by O3 accounted for 17.0% and 14.8% of the heavy pollution days of the year, respectively, and the ozone pollution gradually became prominent; the characteristic value of NO2 in autumn was higher than that of SO2, CO, PM2.5, and PM10, indicating that the type of pollution in autumn was more motorized. The sources of pollution in winter changed from the partial combustion of coal in 2013-2014 to a mixed influence of partial combustion of coal and incomplete combustion in 2015-2018. ③ In 2016, 2017, and 2018, a high cumulative concentrations of PM2.5 during the high pollution season that accounted for 5.56%, 6.21%, and 2.58% declined as compared to that during the same period in 2015; this was the largest decline among the six pollutants; PM10 followed; The decreases of SO2 and NO2 were small, indicating that the emergency measures were better in cutting peaks of particulate matter than the gaseous pollutants during heavy pollution in Baoding. In a heavy pollution event during the high pollution season in 2018, partial-burning coal-type pollution increased as compared to that during the high pollution season in 2017, indicating that the coal combustion was still one of the pollution sources that Baoding city needed to control. In summary, Baoding should strengthen the management and control of motor vehicles in autumn, and gradually change from the original coal control measures to a combination of coal control and diesel control in winter; in the future, the focus of air pollution prevention and control should be strengthened toward O3 pollution.

Inorganic ion chemistry of local particulate matter in a populated city of North China at light, medium, and severe pollution levels.

Twenty-six pairs of PM2.5 and PM10 samples were collected during haze episodes in Zhengzhou (113°28' E, 34°37' N), a highly populated city in North China. The samples were used to examine the inorganic ion chemistry of particulate matter (PM) of local origin at light (PM2.5 < 60 µg m-3 and PM10 < 135 µg m-3), medium (PM2.5: 60-170 µg m-3 and PM10: 135-325 µg m-3), and severe (PM2.5 > 170 µg m-3 and PM10 > 325 µg m-3) pollution levels. At the light and severe pollution levels, the increase of PM10 was accounted for by the increase of PM2.5, and the variation of PM10-2.5 was small. In contrast, the increase of PM10 at the medium pollution level was caused by the increase in both PM2.5 and PM10-2.5. Sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), and chloride in the form of ammonium chloride (Cl-S) accounted for 47.8% and 60.3% of the PM2.5 mass at the light and severe levels, respectively. These values indicate a large contribution of secondary inorganic species to the PM2.5 growth. As the pollution level changed from light to medium, the contribution of SO42- to the growth of PM2.5 decreased from 49.0% to 15.1%, while those of NO3- and Cl-S increased from 25.1% and 0.6% to 32.5% and 2.8%, respectively, indicating the substantial production of nitrate and chloride. At the severe level, the contribution of SO42- was 30.1%, while those of NO3- and Cl-S were 5.9% and 0.5%, respectively, suggesting a hindering effect of sulfate on the production of nitrate and chloride. These results indicate that the production of secondary species with the increase of PM2.5 was dominated by sulfate-associated conversions at the light and severe pollution levels and was substantially influenced by nitrate- and chloride-associated conversions at the medium pollution level. The estimation of carbonate presence in the PM indicates that part of the carbonate in coarse particles (PM10-2.5) of crustal origin enhanced sulfate production via heterogeneous surface reactions. Quantification of the contribution of primary and secondary species to PM2.5 showed that it was dominated by both primary and secondary particles at the light pollution level, and it was mainly composed of secondary species at the severe pollution level.

TOF-SIMS surface analysis of chemical components of size-fractioned urban aerosols in a typical heavy air pollution event in Beijing.

Size-fractioned atmospheric aerosol particles were collected during a typical heavy air pollution event in Beijing. The organic and inorganic components on the surfaces of the samples were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The variation characteristics of the surface chemical composition and influencing factors were studied, and the possible sources of these chemical compositions were identified through principal component analysis. The results showed that inorganic components such as crustal elements and sulfate, and organic components such as aliphatic hydrocarbons and oxygen-containing organic groups were present. Some surface components, such as polycyclic aromatic hydrocarbons, heavy metals and fluorides may exert adverse effects on human health. The species and relative percentages of the chemical components varied with particle size, diurnal and pollution progress. During a heavy pollution event, the species and relative percentages of secondary components such as oxygen-containing organic groups and sulfurous compounds increased, indicating that particles aged during this event. The surface chemical composition of the aerosol particles was affected mainly by emissions from coal combustion and motor vehicles. In addition, air pollution, meteorological factors, and air mass transport also exerted a significant effect on the surface chemical composition of aerosol particles.

A preliminary analysis of the surface chemistry of atmospheric aerosol particles in a typical urban area of Beijing.

Atmospheric aerosol particle samples were collected using an Ambient Eight Stage (Non-Viable) Cascade Impactor Sampler in a typical urban area of Beijing from 27th Sep. to 5th Oct., 2009. The surface chemistry of these aerosol particles was analyzed using Static Time of Flight-Secondary Ion Mass Spectrometry (Static TOF-SIMS). The factors influencing surface compositions were evaluated in conjunction with the air pollution levels, meteorological factors, and air mass transport for the sampling period. The results show that a variety of organic ion groups and inorganic ions/ion groups were accumulated on the surfaces of aerosol particles in urban areas of Beijing; and hydrophobic organic compounds with short- or middle-chain alkyl as well as hydrophilic secondary inorganic compounds were observed. All these compounds have the potential to affect the atmospheric behavior of urban aerosol particles. PM1.1-2.1 and PM3.3-4.7 had similar elements on their surfaces, but some molecules and ionic groups demonstrated differences in Time of Flight-Secondary Ion Mass Spectrometry spectra. This suggests that the quantities of elements varied between PM1.1-2.1 and PM3.3-4.7. In particular, more intense research efforts into fluoride pollution are required, because the fluorides on aerosol surfaces have the potential to harm human health. The levels of air pollution had the most significant influence on the surface compositions of aerosol particles in our study. Hence, heavier air pollution was associated with more complex surface compositions on aerosol particles. In addition, wind, rainfall, and air masses from the south also greatly influenced the surface compositions of these urban aerosol particles.

[Preparation of novel gypenosides long-circulating liposomes consisted by sphingomyelin and beta-sitosterol modified by PEG].

OBJECTIVE: To explore the feasibility of preparing novel gypenosides long-circulating liposomes with PEG grafted on beta-sitosterol (PEG-Sito). METHOD: Succinicanhydride was adopted to connect beta-sitosterol and PEG 2000. Sphingomyelin and PEG-Sito was used as material to prepare gypenosides long-circulating liposomes by using ethanol injection method. Encapsulation efficiency was determined by using protamine precipitation method. H-NMR was used to verify the synthesis of PEG-Sito, the novel gypenosides long-circulating liposomes were characterized by particle size, zeta potential and atomic force microscope. RESULT: The synthesis of PEG-Sito was verified by 1H-NMR. Encapsulation efficiency of long-circulating liposomes prepared by ethanol injection method was 74.3%, particle size was 288.1 nm, zeta potential was -20.25 mV, the morphology were round observed by AFM. CONCLUSION: The novel gypenosides long-circulating liposomes prepared with PEG-Sito was feasible, it had a high encapsulation efficiency and good morphology.

Interleukin-18 promoter polymorphisms and plasma levels are associated with increased risk of periodontitis: a meta-analysis.

OBJECTIVE: Emerging evidence has showed that interleukin-18 (IL-8) promoter polymorphisms and plasma IL-18 levels may be associated with increased risk of periodontitis, but individually published results are inconclusive. The aim of this meta-analysis was to derive a more precise estimation of these associations. METHODS: A literature search of PubMed, Cochrane Library, Embase, Web of Science, SpringerLink, China BioMedicine and China National Knowledge Infrastructure databases was conducted on articles published before April 1st, 2013. Crude odds ratio (OR) or standardized mean difference (SMD) with 95 % confidence intervals (CI) were calculated. RESULTS: Nine case-control studies were included with a total of 576 periodontitis patients and 458 healthy controls. Two common polymorphisms (-607A > C and -137G>C) in the IL-18 gene were addressed. Our meta-analysis results indicated that the C variant of IL-18 -607A>C polymorphism was associated with increased periodontitis risk (C allele vs. A allele: OR = 1.86, 95 % CI: 1.30-2.65, P = 0.001; AC+CC vs. AA: OR = 2.64, 95 % CI: 1.34-5.21, P = 0.005). There was also a significant association between the C variant of IL-18 -137G>C polymorphism and an increased periodontitis risk (C allele vs. G allele: OR = 1.47, 95 % CI: 1.13-1.91, P = 0.004; GC+CC vs. GG: OR = 1.66, 95 % CI: 1.21-2.29, P = 0.002). Furthermore, the mean levels of plasma IL-18 of periodontitis patients were also higher than those of healthy controls (SMD = 1.18, 95 % CI: 0.51-1.85, P = 0.001). CONCLUSION: The current meta-analysis suggests that IL-18 promoter polymorphisms and plasma IL-18 levels are associated with increased risk of periodontitis. IL-18 promoter polymorphisms and elevated plasma IL-18 levels may be useful biomarkers for predicting the development of periodontitis.

[Preparation and liver targeting of floxuridinyl dibutyrate solid lipid nanoparticles].

This paper described the preparation and liver targeting traits of new solid lipid nanoparticles (SLN) containing floxuridinyl dibutyrate (FUDRB) modified with beta-D-galactosides (G2). FUDRB-SLN and FUDRB-G2SLN were prepared by thin layer ultrasonic technique. Transmission electron microscopy micrograph analysis demonstrated that the particle sizes of FUDRB-SLN and FUDRB-G2SLN were (137.5 +/- 11.1) nm and (95.0 +/- 10.7) nm. Drug loading were 9.64% and 8.56%, and entrapment efficiency were 99.81% and 96.23%, respectively. The concentrations of floxuridine (FUDR) in serum and some organs (liver, kidney and lung) were determined by RP-HPLC after iv administration of SLN. FUDR release was confirmed, and a significant enrichment of SLN modified with G2 was observed in liver with G2 complex (targeting rates of SLN-G2 was 8.28 for liver) in comparison with FUDR-sol (targeting rate was 2.56). FUDR could be detected in liver in mice at 480 min after iv administration of FUDRB-G2SLN. These results suggested that incorporation of G2 (4%-5%, g/g) into SLN enhanced the liver targeting-ability of FUDRB. SLN containing G2 could be a useful drug carrier system for liver targeting.

[Physical and chemical characteristics of individual mineral particles in an urban fog episode].

Field emission scanning electron microscopy (FESEM) and scanning electron microscopy with energy dispersive X-ray detector (SEM-EDX) were used to study the four aerosol samples collected in Beijing air during the fog and non-fog episodes in winter. Size-distribution of mineral particles in fog sample displayed two major peaks at the size range of 0.1-0.3 microm and 1-2.5 microm. EDX analyses indicated that the major chemical compositions varied greatly in the individual mineral particles of the fog and non-fog episodes, especially the sulfur. A total of 9 different mineral categories were classified, namely, "Si-rich", "Ca-rich", "S-rich", "Fe-rich", "Mg-rich", "Al-rich", "Ti-rich", "K-rich" and "Cl-rich". About 55% of the "Ca-rich" in the fog samples comprised of Ca (50% +/- 1.2%)and S (37% +/- 1.6%) and about 72% of the "S-rich" comprised of S (44% +/- 1.5%) and Ca (33% +/- 2%), illustrating that particles with abundant sulfur were also enriched with abundant calcium. It is suggested that the "Ca-rich" alkali minerals could alleviate acidity of the fog water in Beijing air. The S/Ca mean ratio of mineral particles in the fog sample was 6.11, being 8 times higher than the S/Ca mean ratio of the non-fog samples (0.73). This result showed that sulfuration on the surfaces of aerosol particles was extremely severe, and that the conversion efficiency from SO2 to sulfates was relatively high.

Bioreactivity of particulate matter in Beijing air: results from plasmid DNA assay.

An in vitro plasmid assay was employed to study the bioreactivity of PM (particulate matter) in Beijing air. It was found that the TD20 (toxic dose of PM causing 20% of plasmid DNA damage) of Beijing PM can be as low as 28 microg ml(-1) and as high as >1000 microg ml(-1). Comparison of the physical properties, such as morphology and size distribution, and oxidative potential indicates that the PM(2.5) (particulate matter with an aerodynamic diameter of 2.5 microm or less) has a stronger oxidative capacity than PM(10) (particulate matter with an aerodynamic diameter of 10 microm or less), and that the higher number percentages of soot aggregates and lower number percentages of mineral and fly ashes are associated with the higher oxidative capacity. Although the mass of PM(10) during dust storms is commonly 5 times higher than that during non-dust storm episodes, the oxidative capacity of PM(10)s of dust storms is much lower than that of the non-dust storm PM(10)s. The water-soluble fractions and intact whole particle solutions of Beijing airborne particles produce similar plasmid assay results, demonstrating that the bioreactivity of Beijing airborne particles is mainly sourced from the water-soluble fraction. In the samples with stronger bioreactivity, the total analyzed water soluble Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As and Pb (ppm) concentrations are higher. The water soluble zinc shows a good negative correlation with TD20s, suggesting that the water-soluble zinc is probably the major element responsible for the plasmid DNA damage.

Characterization of the alpha-1,2-N-acetylglucosaminyltransferase of Neisseria gonorrhoeae, a key control point in lipooligosaccharide biosynthesis.

The biosynthesis of the lipooligosaccharide (LOS) in Neisseria meningitidis has a control point that regulates the extension of the alpha-chain on heptose (I) of the LOS. The gene that encodes the protein responsible for this control had been identified elsewhere, but the enzyme encoded by the gene was not characterized. We have now shown that this same control mechanism operates in the related species, Neisseria gonorrhoeae, using a gene knockout and subsequent characterization of the LOS species produced. We also cloned and expressed the enzyme from both of these pathogens. Using a synthetic acceptor substrate, we have shown unequivocally that the enzyme is an alpha-1,2-N-acetylglucosaminyltransferase. Experiments with both the core oligosaccharide and the synthetic acceptors suggests that the addition of the alpha-1,2-N-acetylglucosamine moiety on the heptose (II) residue precedes the addition of the ethanolamine phosphate at the O3 position on this heptose (II), and that in the absence of the alpha-1,2-N-acetylglucosamine moiety leads to the addition of an extra ethanolamine phosphate on the heptose (II) residue. Our data do not support the hypothesis that ethanolamine phosphate at O3 of heptose (II) is added and is then required for the addition of the N-acetylglucosamine at O2 by the LgtK enzyme. This enzyme represents a control point in the biosynthesis of the LOS of this pathogen and is a potential target for therapeutic intervention.