Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations

We construct a global atmospheric budget for acetaldehyde using a 3-D model of atmospheric chemistry (GEOS-Chem), and use an ensemble of observations to evaluate present understanding of its sources and sinks. Hydrocarbon oxidation provides the largest acetaldehyde source in the model (128 Tg a<sup>−1</sup>, a factor of 4 greater than the previous estimate), with alkanes, alkenes, and ethanol the main precursors. There is also a minor source from isoprene oxidation. We use an updated chemical mechanism for GEOS-Chem, and photochemical acetaldehyde yields are consistent with the Master Chemical Mechanism. We present a new approach to quantifying the acetaldehyde air-sea flux based on the global distribution of light absorption due to colored dissolved organic matter (CDOM) derived from satellite ocean color observations. The resulting net ocean emission is 57 Tg a<sup>−1</sup>, the second largest global source of acetaldehyde. A key uncertainty is the acetaldehyde turnover time in the ocean mixed layer, with quantitative model evaluation over the ocean complicated by known measurement artifacts in clean air. Simulated concentrations in surface air over the ocean generally agree well with aircraft measurements, though the model tends to overestimate the vertical gradient. PAN:NO<sub>x</sub> ratios are well-simulated in the marine boundary layer, providing some support for the modeled ocean source. We introduce the Model of Emissions of Gases and Aerosols from Nature (MEGANv2.1) for acetaldehyde and ethanol and use it to quantify their net flux from living terrestrial plants. Including emissions from decaying plants the total direct acetaldehyde source from the land biosphere is 23 Tg a<sup>−1</sup>. Other terrestrial acetaldehyde sources include biomass burning (3 Tg a<sup>−1</sup>) and anthropogenic emissions (2 Tg a<sup>−1</sup>). Simulated concentrations in the continental boundary layer are generally unbiased and capture the spatial gradients seen in observations over North America, Europe, and tropical South America. However, the model underestimates acetaldehyde levels in urban outflow, suggesting a missing source in polluted air. Ubiquitous high measured concentrations in the free troposphere are not captured by the model, and based on present understanding are not consistent with concurrent measurements of PAN and NO<sub>x</sub>: we find no compelling evidence for a widespread missing acetaldehyde source in the free troposphere. We estimate the current US source of ethanol and acetaldehyde (primary + secondary) at 1.3 Tg a<sup>−1</sup> and 7.8 Tg a<sup>−1</sup>, approximately 60{%} and 480% of the corresponding increases expected for a national transition from gasoline to ethanol fuel

Malignant Transformation of an HNF1a-Inactivated Hepatocellular Adenoma to Hepatocellular Carcinoma

Hepatocellular adenomas (HCA) are rare benign tumors of the liver, occurring predominantly in females using oral contraceptives. Our case describes a 66-year-old woman presenting with a palpable mass in her upper abdomen. Contrast-enhanced computed tomography and magnetic resonance imaging showed a large exophytic mass protruding from the caudal border of liver segments IV and V, without visible metastases. Laparoscopic resection of the tumor and gallbladder was performed. Histopathological examination showed a hepatocellular carcinoma with areas of HNF1a-HCA (H-HCA). This case shows that malignant transformation is possible in H-HCA. We present our preoperative decision-making process, as well as the role of imaging techniques in this rare case

Peribiliary glands are key in regeneration of the human biliary epithelium after severe bile duct injury

Peribiliary glands (PBG) are a source of stem/progenitor cells organized in a cellular network encircling large bile ducts. Severe cholangiopathy with loss of luminal biliary epithelium has been proposed to activate PBG, resulting in cell proliferation and differentiation to restore biliary epithelial integrity. However, formal evidence for this concept in human livers is lacking. We, therefore, developed a novel ex vivo model using precision-cut slices of extrahepatic human bile ducts obtained from discarded donor livers, providing an intact anatomical organization of cell structures, to study spatiotemporal differentiation and migration of PBG cells after severe biliary injury. Post-ischemic bile duct slices were incubated in oxygenated culture medium for up to a week. At baseline, severe tissue injury was evident with loss of luminal epithelial lining and mural stroma necrosis. In contrast, PBG remained relatively well preserved and different reactions of PBG were noted, including PBG dilatation, cell proliferation and maturation. Proliferation of PBG cells increased after 24 h of oxygenated incubation, reaching a peak after 72 h. Proliferation of PBG cells was paralleled by a reduction in PBG apoptosis and differentiation from a primitive and pluripotent (Nanog+/Sox9+) to a mature (CFTR+/secretin receptor+) and activated phenotype (increased expression of HIF-1α, Glut-1, and VEGF-A). Migration of proliferating PBG cells in our ex vivo model was unorganized, but resulted in generation of epithelial monolayers at stromal surfaces. CONCLUSION: Human PBG contain biliary progenitor cells and are able to respond to bile duct epithelial loss with proliferation, differentiation, and maturation to restore epithelial integrity. The ex vivo spatiotemporal behaviour of human PBG cells provides evidence for a pivotal role of PBG in biliary regeneration after severe injury. This article is protected by copyright. All rights reserved

Limited diagnostic accuracy and clinical impact of single-operator peroral cholangioscopy for indeterminate biliary strictures

BACKGROUND: Single-operator peroral cholangioscopy (sPOCS) is considered a valuable diagnostic modality for indeterminate biliary strictures. Nevertheless, studies show large variation in its characteristics and measures of diagnostic accuracy. Our aim was to estimate the diagnostic accuracy of sPOCS visual assessment and targeted biopsies for indeterminate biliary strictures. Additional aims were: estimation of the clinical impact of sPOCS and comparison of diagnostic accuracy with brush cytology. METHODS: A retrospective single-center study of adult patients who underwent sPOCS for indeterminate biliary strictures was performed. Diagnostic accuracy was defined as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). The clinical impact of sPOCS was assessed by review of medical records, and classified according to its influence on patient management. RESULTS: 80 patients were included, with 40 % having primary sclerosing cholangitis (PSC). Prior ERCP was performed in 88 %, with removal of a biliary stent prior to sPOCS in 55 %. The sensitivity, specificity, PPV, and NPV for sPOCS visual impression and targeted biopsies were 64 %, 62 %, 41 %, and 84 %, and 15 %, 65 %, 75 %, and 69 %, respectively. The clinical impact of sPOCS was limited; outcome changed management in 17 % of patients. Sequential brush cytology sensitivity, specificity, PPV, and NPV were 47 %, 95 %, 80 %, and 83 %. CONCLUSIONS: The diagnostic accuracy of sPOCS for indeterminate biliary strictures was found to be inferior to brush cytology, with a low impact on patient management. These findings are obtained from a select patient population with a high prevalence of PSC and plastic stents in situ prior to sPOCS

Brain atrophy accelerates cognitive decline in cerebral small vessel disease: The LADIS study

Objective: To examine the independent contributions and combined interactions of medial temporal lobe atrophy (MTA), cortical and subcortical atrophy, and white matter lesion (WML) volume in longitudinal cognitive performance. Methods: A total of 477 subjects with age-relatedWMLwere evaluated with brain MRI and annual neuropsychological examinations in 3-year follow-up. Baseline MRI determinants of cognitive decline were analyzed with linear mixed models controlling for multiple confounders. Results: MTA and subcortical atrophy predicted significantly steeper rate of decline in global cognitive measures as well as compound scores for psychomotor speed, executive functions, and memory after adjusting for age, gender, education, lacunes/infarcts, and WML volume. Cortical atrophy independently predicted decline in psychomotor speed. WML volume remained significantly associated with cognitive decline even after controlling for the atrophy scores. Moreover, significant synergistic interactions were found between WML and atrophy measures in overall cognitive performance across time and the rate of cognitive decline. Synergistic effects were also observed between baseline lacunar infarcts and all atrophy measures on change in psychomotor speed. The main results remained robust after exclusion of subjects with clinical stroke or incident dementia, and after additional adjustments for progression of WML and lacunes. Conclusions: Brain atrophy and WML are independently related to longitudinal cognitive decline in small vessel disease. MTA, subcortical, and cortical atrophy seem to potentiate the effect ofWML and lacunes on cognitive decline

The Survival Paradox of Elderly Patients After Major Liver Resections

The objective of this study is to assess the outcome of liver resections in the elderly in a matched control analysis. From a prospective single center database of 628 patients, 132 patients were aged 60 years or over and underwent a primary major liver resection. Of these patients, 93 could be matched one-to-one with a control patient, aged less than 60 years, with the same diagnosis and the same type of liver resection. The mean age difference was 16.7 years. Patients over 60 years of age had a significantly higher American Society of Anaesthesiologists (ASA) grade. All other demographics and operative characteristics were not different. In-hospital mortality and morbidity were higher in the patients over 60 years of age (11% versus 2%, p=0.017 and 47% versus 31%, p=0.024). One-, 3-, and 5-year survival rates in the patients over 60 years of age were 81%, 58%, and 42%, respectively, compared to 90%, 59%, and 42% in the control patients (p=0.558). Unified model Cox regression analysis showed that resection margin status (hazard ratio 2.51) and ASA grade (hazard ratio 2.26), and not age, were determining factors for survival. This finding underlines the important fact that in patient selection for major liver resections, ASA grade is more important than patient age

Emission factor ratios, SOA mass yields, and the impact of vehicular emissions on SOA formation

The underprediction of ambient secondary organic aerosol (SOA) levels by current atmospheric models in urban areas is well established, yet the cause of this underprediction remains elusive. Likewise, the relative contribution of emissions from gasoline- and diesel-fueled vehicles to the formation of SOA is generally unresolved. We investigate the source of these two discrepancies using data from the 2010 CalNex experiment carried out in the Los Angeles Basin (Ryerson et al., 2013). Specifically, we use gas-phase organic mass (GPOM) and CO emission factors in conjunction with measured enhancements in oxygenated organic aerosol (OOA) relative to CO to quantify the significant lack of closure between expected and observed organic aerosol concentrations attributable to fossil-fuel emissions. Two possible conclusions emerge from the analysis to yield consistency with the ambient data: (1) vehicular emissions are not a dominant source of anthropogenic fossil SOA in the Los Angeles Basin, or (2) the ambient SOA mass yields used to determine the SOA formation potential of vehicular emissions are substantially higher than those derived from laboratory chamber studies

Hypothermic oxygenated machine perfusion reduces bile duct reperfusion injury after transplantation of donation after circulatory death livers

INTRODUCTION: Dual hypothermic oxygenated machine perfusion (DHOPE) of the liver has been advocated as a method to reduce ischemia-reperfusion injury. This study aimed to determine whether DHOPE reduces IR injury of the bile ducts in DCD liver transplantation. MATERIALS AND METHODS: In a recently performed phase 1-trial, ten DCD livers were preserved with DHOPE after static cold storage (SCS) (www.trialregister.nl NTR4493). Bile duct biopsies were obtained at the end of SCS (before DHOPE; baseline) and after graft reperfusion in the recipient. Histological severity of biliary injury was graded according to an established semi-quantitative grading system. Twenty liver transplantations using DCD livers not preserved with DHOPE served as control. RESULTS: Baseline characteristics and the degree of bile duct injury at baseline (end of SCS) were similar between both groups. In controls, degree of stroma necrosis (P=0.002) and injury of the deep peribiliary glands (P=0.02) increased after reperfusion, compared to baseline. In contrast, in DHOPE preserved livers the degree of bile duct injury did not increase after reperfusion. Moreover, there was less injury of deep peribiliary glands (P=0.04) after reperfusion in the DHOPE group, compared to controls. CONCLUSION: This study suggests that DHOPE reduces ischemia-reperfusion injury of bile ducts after DCD liver transplantation. This article is protected by copyright. All rights reserved

Conversion of hydroperoxides to carbonyls in field and laboratory instrumentation: Observational bias in diagnosing pristine versus anthropogenically controlled atmospheric chemistry

Atmospheric volatile organic compound (VOC) oxidation mechanisms under pristine (rural/remote) and urban (anthropogenically-influenced) conditions follow distinct pathways due to large differences in nitrogen oxide (NO_x) concentrations. These two pathways lead to products that have different chemical and physical properties and reactivity. Under pristine conditions, isoprene hydroxy hydroperoxides (ISOPOOHs) are the dominant first-generation isoprene oxidation products. Utilizing authentic ISOPOOH standards, we demonstrate that two of the most commonly used methods of measuring VOC oxidation products (i.e., gas chromatography and proton transfer reaction mass spectrometry) observe these hydroperoxides as their equivalent high-NO isoprene oxidation products – methyl vinyl ketone (MVK) and methacrolein (MACR). This interference has led to an observational bias affecting our understanding of global atmospheric processes. Considering these artifacts will help close the gap on discrepancies regarding the identity and fate of reactive organic carbon, revise our understanding of surface-atmosphere exchange of reactive carbon and SOA formation, and improve our understanding of atmospheric oxidative capacity

Total Observed Organic Carbon (TOOC): A synthesis of North American observations

Measurements of organic carbon compounds in both the gas and particle phases measured upwind, over and downwind of North America are synthesized to examine the total observed organic carbon (TOOC) over this region. These include measurements made aboard the NOAA WP-3 and BAe-146 aircraft, the NOAA research vessel Ronald H. Brown, and at the Thompson Farm and Chebogue Point surface sites during the summer 2004 ICARTT campaign. Both winter and summer 2002 measurements during the Pittsburgh Air Quality Study are also included. Lastly, the spring 2002 observations at Trinidad Head, CA, surface measurements made in March 2006 in Mexico City and coincidentally aboard the C-130 aircraft during the MILAGRO campaign and later during the IMPEX campaign off the northwestern United States are incorporated. Concentrations of TOOC in these datasets span more than two orders of magnitude. The daytime mean TOOC ranges from 4.0 to 456 μgC m^−3 from the cleanest site (Trinidad Head) to the most polluted (Mexico City). Organic aerosol makes up 3–17% of this mean TOOC, with highest fractions reported over the northeastern United States, where organic aerosol can comprise up to 50% of TOOC. Carbon monoxide concentrations explain 46 to 86% of the variability in TOOC, with highest TOOC/CO slopes in regions with fresh anthropogenic influence, where we also expect the highest degree of mass closure for TOOC. Correlation with isoprene, formaldehyde, methyl vinyl ketene and methacrolein also indicates that biogenic activity contributes substantially to the variability of TOOC, yet these tracers of biogenic oxidation sources do not explain the variability in organic aerosol observed over North America. We highlight the critical need to develop measurement techniques to routinely detect total gas phase VOCs, and to deploy comprehensive suites of TOOC instruments in diverse environments to quantify the ambient evolution of organic carbon from source to sink