The TET (ten-eleven translocation) family of α-ketoglutarate (α-KG)-dependent dioxygenases catalyzes the sequential oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), ...5-formylcytosine and 5-carboxylcytosine, leading to eventual DNA demethylation. The TET2 gene is a bona fide tumor suppressor frequently mutated in leukemia, and TET enzyme activity is inhibited in IDH1/2-mutated tumors by the oncometabolite 2-hydroxyglutarate, an antagonist of α-KG, linking 5mC oxidation to cancer development. We report here that the levels of 5hmC are dramatically reduced in human breast, liver, lung, pancreatic and prostate cancers when compared with the matched surrounding normal tissues. Associated with the 5hmC decrease is the substantial reduction of the expression of all three TET genes, revealing a possible mechanism for the reduced 5hmC in cancer cells. The decrease of 5hmC was also observed during tumor development in different genetically engineered mouse models. Together, our results identify 5hmC as a biomarker whose decrease is broadly and tightly associated with tumor development.
The Positive Matrix Factorization (PMF) receptor model and the Observation Based Model (OBM) were combined to analyze volatile organic compound (VOC) data collected at a suburban site (WQS) in the ...PRD region. The purposes are to estimate the VOC source apportionment and investigate the contributions of these sources and species of these sources to the O3 formation in PRD. Ten VOC sources were identified. We further applied the PMF-extracted concentrations of these 10 sources into the OBM and found "solvent usage 1", "diesel vehicular emissions" and "biomass/biofuel burning" contributed most to the O3 formation at WQS. Among these three sources, higher Relative Incremental Reactivity (RIR)-weighted values of ethene, toluene and m/p-xylene indicated that they were mainly responsible for local O3 formation in the region. Sensitivity analysis revealed that the sources of "diesel vehicular emissions", "biomass/biofuel burning" and "solvent usage 1" had low uncertainties whereas "gasoline evaporation" showed the highest uncertainty.
► Ten sources of VOCs were identified by the PMF receptor model in the PRD region. ► In terms of mass percentage, solvent was the largest contributor, followed by vehicle emissions. ► Solvent, diesel vehicles and biomass/biofuel burning were the top three VOC contributors to O3 formation. ► Among these three sources, ethene, toluene and m/p-xylene were responsible for O3 formation. ► Biomass/biofuel burning had low uncertainty whereas gasoline evaporation showed high uncertainty.
Solvent usage, diesel vehicular emissions and biomass/biofuel burning were the major contributors to the photochemical O3 formation in the PRD region.
•VOC sources and their contributions to O3 formation were investigated by combining the positive matrix factorization (PMF) model and the observation-based model (OBM) for the first time in Hong ...Kong.•Paint and sealant solvents, diesel exhaust and LPG usage were the key contributors to O3 formation.•The O3 reduction efficiency would be the highest when the identified VOC sources and the major species from these sources were cut by certain percentages.
Since volatile organic compounds (VOCs) are important precursors of ozone (O3), identification and quantification of their emission sources are prerequisite for the formulation and implementation of O3 pollution control policies. In this study, seven major sources of VOCs were identified and their contributions to photochemical O3 formation were evaluated at an urban site (TW) in Hong Kong by the combined application of the positive matrix factorization (PMF) model and the observation based model (OBM). The relative incremental reactivity (RIR)-weighted values, which considered both the reactivity and abundance of VOCs, suggested that paint and sealant solvents, diesel exhaust and liquefied petroleum gas (LPG) usage were the key contributors to O3 formation. Among the identified sources, xylenes and ethylbenzene in paint and sealant solvents, toluene in gasoline exhaust, butanes, ethene, propene and propane in LPG usage and n-butane and ethene in diesel exhaust made significant contributions. Sensitivity analysis on the basis of relative O3 reduction efficiency (RORE), using the reduction of VOCs from 10% to 90% as input, indicated that the O3 reduction was the most effective when the identified VOC sources and the major species from these sources were cut by specific percentages. The findings provide valuable insights into the formulation and implementation of VOCs and O3 control strategies in Hong Kong.
A field measurement study of volatile organic compounds (VOCs) was simultaneously carried out in October–December 2007 at an inland Pearl River Delta (PRD) site and a Hong Kong urban site. A receptor ...model i.e. positive matrix factorization (PMF) was applied to the data for the apportionment of pollution sources in the region. Five and six sources were identified in Hong Kong and the inland PRD region, respectively. The major sources identified in the region were vehicular emissions, solvent use and biomass burning, whereas extra sources found in inland PRD included liquefied petroleum gas and gasoline evaporation. In Hong Kong, the vehicular emissions made the most significant contribution to ambient VOCs (48
±
4%), followed by solvent use (43
±
2%) and biomass burning (9
±
2%). In inland PRD, the largest contributor to ambient VOCs was solvent use (46
±
1%), and vehicular emissions contributed 26
±
1% to ambient VOCs. The percentage contribution of vehicular emission in Hong Kong in 2007 is close to that obtained in 2001–2003, whereas in inland PRD the contribution of solvent use to ambient VOCs in 2007 was at the upper range of the results obtained in previous studies and twice the 2006 PRD emission inventory. The findings advance our knowledge of ozone precursors in the PRD region.
Aims/hypothesis
Alginate-encapsulated human islet cell grafts have not been able to correct diabetes in humans, whereas free grafts have. This study examined in immunodeficient mice whether ...alginate-encapsulated graft function was inferior to that of free grafts of the same size and composition.
Methods
Cultured human islet cells were equally distributed over free and alginate-encapsulated grafts before implantation in, respectively, the kidney capsule and the peritoneal cavity of non-obese diabetic mice with severe combined immunodeficiency and alloxan-induced diabetes. Implants were followed for in vivo function and retrieved for analysis of cellular composition (all) and insulin secretory responsiveness (capsules).
Results
Free implants with low beta cell purity (19 ± 1%) were non-functional and underwent 90% beta cell loss. At medium purity (50 ± 1%), they were functional at post-transplant week 1, evolving to normoglycaemia (4/8) or to C-peptide negativity (4/8) depending on the degree of beta cell-specific losses. Encapsulated implants immediately and sustainably corrected diabetes, irrespective of beta cell purity (16/16). Most capsules were retrievable as single units, enriched in endocrine cells that exhibited rapid secretory responses to glucose and glucagon. Single capsules with similar properties were also retrieved from a type 1 diabetic recipient at post-transplant month 3. However, the vast majority were clustered and contained debris, explaining the poor rise in plasma C-peptide.
Conclusions/interpretation
In immunodeficient mice, i.p. implanted alginate-encapsulated human islet cells exhibited a better outcome than free implants under the kidney capsule. They did not show primary non-function at low beta cell purity and avoided beta cell-specific losses by rapidly establishing normoglycaemia. Retrieved capsules presented secretory responses to glucose, which was also observed in a type 1 diabetic recipient.
Trial registration:
ClinicalTrials.gov NCT01379729
Funding:
This study was supported by grants from the JDRF (centre grant 4-2005-1327), the Research Foundation Flanders (G.0801.10), the 6th and 7th Framework Program of the European Commission (numbers 512145 and 241883), and the Agency for Innovation by Science and Technology in Flanders (IWT-TBM7 090884).
Ferric sulfates were observed on Mars during orbital remote sensing and surface explorations. These observations have stimulated our systematic experimental investigation on the formative conditions, ...stability fields, phase boundaries, and phase transition pathways of these important minerals. We report here the results from the first step of this project: eight synthesized anhydrous and hydrous crystalline ferric sulfates and their structural characters reflected through spectroscopic studies. A few phenomena observed during the 150 sets of on-going experiments for stability field study are also reported, which reveal the structural distortions that can happen under environmental conditions relevant to Mars.
Two models (the Positive Matrix Factorization (PMF) model and a photochemical box model with Master Chemical Mechanism (PBM-MCM)) were applied to analyze the formaldehyde (HCHO) data collected in ...July 2006 at an urban site (GPEMC) in the Pearl River Delta (PRD), southern China. Three major HCHO sources (secondary formation, vehicular exhaust, and solvent usage) were identified and they were found to contribute in average 53%, 31% and 16% respectively to the total HCHO loading at GPEMC. Alkenes was the most important group contributing to the secondary formation of HCHO, followed by aromatics and alkanes. Among them, trans-2-butene had the largest contribution to secondary HCHO formation, with the average percentage of 16 ± 4%, followed by i-butene, cis-2-butene, propene, isoprene and m,p-xylene. Secondary HCHO and HCHO emitted from vehicular emissions contributed comparably to ground-based measured O
and HO
radical at GPEMC, higher than that from solvent usage (1.3 ± 0.1 ppbv and (4.1 ± 0.3) × 10
molecule/cm
for O
and HO
radical). Our results highlight the importance of secondary HCHO formation for both photochemical formation of ozone and the oxidative capacity of the atmosphere in this region. It is hence critical for policy makers to propose strategies for controlling VOCs from vehicular emissions in order to reduce secondary HCHO formation. Our results also have important implication for improving the understanding of the source apportionments of HCHO and their contributions to photochemical pollution in the PRD region in China.
Field measurements were simultaneously conducted at a mountain (Mt.) site (Tai Mao Shan, TMS) and an urban site (Tsuen Wan, TW) at the foot of the Mt. TMS in Hong Kong. An interesting event with ...consecutive high-ozone (O3) days from 08:00 on 28 Oct. to 23:00 on 03 Nov., 2010 was observed at Mt. TMS, while no such polluted event was found at the foot of the mountain. The Weather Research and Forecasting (WRF)-Community Multiscale Air Quality (CMAQ) models were used to understand this event. Model performance evaluation showed that the simulated meteorological parameters and air pollutants were well in agreement with the observations. The index of agreement (IOA) of temperature, relative humidity, wind direction and wind speed were 0.93, 0.83, 0.46 and 0.60, respectively. The multi-day high O3 episode at Mt. TMS was also reasonably reproduced (IOA=0.68). Horizontally, the photochemical processes determined the O3 levels in southwestern Pearl River Delta (PRD) and the Pearl River Estuary (PRE), while in eastern and northern PRD, the O3 destruction was over the production during the event. Vertically, higher O3 values at higher levels were found at both Mt. TMS and TW, indicating a vertical O3 gradient over Hong Kong. With the aid of the process analysis module, we found positive contribution of vertical transport including advection and diffusion to O3 mixing ratios at the two sites, suggesting that O3 values at lower locations could be affected by O3 at higher locations via vertical advection and diffusion over Hong Kong.
•Consecutive high-O3 days were observed at a mountain waist site.•Simultaneously, no high-O3 polluted event was found at the foot of the mountain.•Horizontally, photochemical processes determined O3 levels in southwestern PRD and PRE.•Vertically, higher O3 values at higher levels were found at both sites.•Vertical transport made contribution to the O3 levels at the two sites.
Photochemical smog, characterized by high concentrations of ozone (O3) and fine particles (PM2.5) in the atmosphere, has become one of the top environmental concerns in China. Volatile organic ...compounds (VOCs), one of the key precursors of O3 and secondary organic aerosol (SOA) (an important component of PM2.5), have a critical influence on atmospheric chemistry and subsequently affect regional and global climate. Thus, VOCs have been extensively studied in many cities and regions in China, especially in the North China Plain, the Yangtze River Delta and the Pearl River Delta regions where photochemical smog pollution has become increasingly worse over recent decades. This paper reviews the main studies conducted in China on the characteristics and sources of VOCs, their relationship with O3 and SOA, and their removal technology. This paper also provides an integrated literature review on the formulation and implementation of effective control strategies of VOCs and photochemical smog, as well as suggestions for future directions of VOCs study in China.
Display omitted
•Characteristics and sources of VOCs in China are reviewed.•Relationship of VOCs with O3 and SOA in China are reviewed.•Integrated literature review on the control strategies of VOCs and photochemical smog is provided.•Future directions of VOC study in China are suggested.
Abstract
Understanding the sources of lunar water is crucial for studying the history of lunar evolution, as well as the interaction of solar wind with the Moon and other airless bodies. Recent ...orbital spectral observations revealed that the solar wind is a significant exogenous driver of lunar surficial hydration. However, the solar wind is shielded over a period of 3–5 days per month as the Moon passes through the Earth’s magnetosphere, during which a significant loss of hydration is expected. Here we report the temporal and spatial distribution of polar surficial OH/H
2
O abundance, using Chandrayaan-1 Moon Mineralogy Mapper (
M
3
) data, which covers the regions inside/outside the Earth’s magnetosphere. The data shows that polar surficial OH/H
2
O abundance increases with latitude, and that the probability of polar surficial OH/H
2
O abundance remains at the same level when in the solar wind and in the magnetosphere by controlling latitude, composition, and lunar local time. This indicates that the OH/H
2
O abundance in the polar regions may be saturated, or supplemented from other possible sources, such as Earth wind (particles from the magnetosphere, distinct from the solar wind), which may compensate for thermal diffusion losses while the Moon lies within the Earth’s magnetosphere. This work provides some clues for studies of planet–moon systems, whereby the planetary wind serves as a bridge connecting the planet with its moons.
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