Challenges of accounting nitrous oxide emissions from agricultural crop residues.

Crop residues are important inputs of carbon (C) and nitrogen (N) to soils and thus directly and indirectly affect nitrous oxide (N2 O) emissions. As the current inventory methodology considers N inputs by crop residues as the sole determining factor for N2 O emissions, it fails to consider other underlying factors and processes. There is compelling evidence that emissions vary greatly between residues with different biochemical and physical characteristics, with the concentrations of mineralizable N and decomposable C in the residue biomass both enhancing the soil N2 O production potential. High concentrations of these components are associated with immature residues (e.g., cover crops, grass, legumes, and vegetables) as opposed to mature residues (e.g., straw). A more accurate estimation of the short-term (months) effects of the crop residues on N2 O could involve distinguishing mature and immature crop residues with distinctly different emission factors. The medium-term (years) and long-term (decades) effects relate to the effects of residue management on soil N fertility and soil physical and chemical properties, considering that these are affected by local climatic and soil conditions as well as land use and management. More targeted mitigation efforts for N2 O emissions, after addition of crop residues to the soil, are urgently needed and require an improved methodology for emission accounting. This work needs to be underpinned by research to (1) develop and validate N2 O emission factors for mature and immature crop residues, (2) assess emissions from belowground residues of terminated crops, (3) improve activity data on management of different residue types, in particular immature residues, and (4) evaluate long-term effects of residue addition on N2 O emissions.

Metal and Pb isotope characterization of particulates encountered by foraging honeybees in Metro Vancouver.

Honeybees and their products are useful biomonitors of metal distribution in urban centres. This study investigates particulate sources that foraging honeybees encounter in Metro Vancouver. Metal concentrations and lead (Pb) isotope compositions were measured in topsoil (top 2 cm, n = 14) colocated with existing research hives and in particulate matter ≤10 µm (PM10, n = 27) collected throughout Metro Vancouver (British Columbia, Canada) during honeybee foraging hours over the course of one year (2018-2019). Topsoil served as a proxy for resuspended/coarse PM and, together with PM10, covered the size range of particulates collected by foraging bees both actively (pollen) and passively (dusts). Particulate matter ≤ 2.5 µm (PM2.5, n = 7) was collected on Whistler Mountain during two transpacific events (in spring 2014) to estimate the possible effect of transpacific particulate input on the Pb isotope composition of Western Canada aerosols. Metal concentrations and Pb isotopes in topsoil and PM from this study and bees and hive products from previous studies (collected in 2014-2019) reveal similar spatial trends: there were elevated amounts of some metals associated with anthropogenic activity (e.g., Pb, Zn, Sb) and less radiogenic Pb isotope compositions in most samples collected nearer to the city centre in comparison to samples collected in more suburban or rural areas. Bees and hive products have a smoothing effect on the spatiotemporal variability of the data; metal concentrations and Pb isotope compositions vary less in hive products than in PM, presumably because bees interact with multiple environmental domains while foraging. Wildfire smoke and transpacific input are phenomena that cause measurable shifts in Pb isotope compositions of PM, but not in hive matrices. The findings highlight important considerations to make (i.e., the smoothing effect) when linking public health data and decisions with environmental data from hive products in urban centres.

Predicting field N2O emissions from crop residues based on their biochemical composition: A meta-analytical approach.

Crop residue incorporation is a common practice to increase or restore organic matter stocks in agricultural soils. However, this practice often increases emissions of the powerful greenhouse gas nitrous oxide (N2O). Previous meta-analyses have linked various biochemical properties of crop residues to N2O emissions, but the relationships between these properties have been overlooked, hampering our ability to predict N2O emissions from specific residues. Here we combine comprehensive databases for N2O emissions from crop residues and crop residue biochemical characteristics with a random-meta-forest approach, to develop a predictive framework of crop residue effects on N2O emissions. On average, crop residue incorporation increased soil N2O emissions by 43% compared to residue removal, however crop residues led to both increases and reductions in N2O emissions. Crop residue effects on N2O emissions were best predicted by easily degradable fractions (i.e. water soluble carbon, soluble Van Soest fraction (NDS)), structural fractions and N returned with crop residues. The relationship between these biochemical properties and N2O emissions differed widely in terms of form and direction. However, due to the strong correlations among these properties, we were able to develop a simplified classification for crop residues based on the stage of physiological maturity of the plant at which the residue was generated. This maturity criteria provided the most robust and yet simple approach to categorize crop residues according to their potential to regulate N2O emissions. Immature residues (high water soluble carbon, soluble NDS and total N concentration, low relative cellulose, hemicellulose, lignin fractions, and low C:N ratio) strongly stimulated N2O emissions, whereas mature residues with opposite characteristics had marginal effects on N2O. The most important crop types belonging to the immature residue group - cover crops, grasslands and vegetables - are important for the delivery of multiple ecosystem services. Thus, these residues should be managed properly to avoid their potentially high N2O emissions.

Regional and global perspectives of honey as a record of lead in the environment.

Honey from Apis mellifera is a useful and inexpensive biomonitor for mapping metal distributions in urban centers. The sampling resolution of a biomonitoring survey (e.g., city versus global scale) determines which geochemical processes are reflected in the results. This study presents Pb isotopic compositions and metal concentrations in honey from around the world, sampled at varying resolutions: honey from Canada (n = 21), the United States (n = 111), Belgium (n = 25), and New Zealand (n = 10), with additional samples from Afghanistan, Brazil, Cuba, Germany, Liberia, Taiwan, and Turkey. Honey was sampled at high resolution in two uniquely different land-use settings (New York Metro Area and the Hawaiian island of Kaua'i), at regional-scale resolution in eastern North America (including the Great Lakes region), and Pb isotopic compositions of all samples were compared on a global scale. At high sampling resolution, metal concentrations in honey reveal spatially significant concentration gradients: in New York City, metals associated with human activity and city infrastructure (e.g., Pb, Sb, Ti, V) are more concentrated in honey collected within the city compared to honey from upstate New York, and metal concentrations in honey from Kaua'i suggest polluting effects of nearby agricultural operations. At lower resolution (regional and global scales), lead isotopic compositions of honey are more useful than metal concentrations in revealing large-scale Pb processes (e.g., the enduring legacy of global leaded gasoline use throughout the twentieth century) and the continental origin of the honey. Lead isotopic compositions of honey collected from N. America (especially from the eastern USA) are more radiogenic (206Pb/207Pb: 1.132-1.253, 208Pb/206Pb: 2.001-2.129) compared to European honey, and honey from New Zealand, which has the least radiogenic isotopic compositions measured in this study (206Pb/207Pb: 1.077-1.160, 208Pb/206Pb: 2.090-2.187). Thus, biomonitoring using honey at different resolutions reflects differing processes and, to some extent, a honey terroir defined by the Pb isotopic composition. The data presented here provide important (and current) global context for future studies that utilize Pb isotopes in honey. Moreover, this study exhibits community science in action, as most of the honey was collected by collaborators around the world, working directly with local apiarists and hobby beekeepers.

Evaluating Spatiotemporal Resolution of Trace Element Concentrations and Pb Isotopic Compositions of Honeybees and Hive Products as Biomonitors for Urban Metal Distribution.

Assessing metal distributions in cities is an important aspect of urban environmental quality management. Western honeybees (Apis mellifera) and their products are biomonitors that can elucidate small-scale metal distribution within a city. We compare range and variations in trace element (TE) concentrations and lead (Pb) isotopic compositions of honey, bee tissue, bee pollen, and propolis collected throughout Metro Vancouver (BC, Canada). Honey, bee, and bee pollen results have similar TE and isotopic trends; samples collected in urban and industrialized areas exhibit elevated concentrations of anthropogenically influenced TE (e.g., Pb, Zn, V, and Ti) and a less radiogenic Pb isotopic composition (i.e., lower 206Pb/207Pb and elevated 208Pb/206Pb) relative to their suburban and rural counterparts. For example, 206Pb/207Pb, 208Pb/206Pb in honey range from 1.126, 2.131 and 1.184, 2.063; extremes measured in honey from urban and suburban/rural areas, respectively. Except for propolis, measured and interpolated (kriged) results in all materials reflect the immediate zoning or land use setting near the hive, providing kilometer-scale geospatial resolution, suitable for monitoring urban systems. Statistical analysis reveals that no systematic variations or intra- or inter-annual trends exist in TE concentrations or Pb isotopic compositions, including among sampling and field methods (i.e., old vs. new hive equipment and honey from the brood nest box vs. honey super). The results of this systematic study using honeybees and hive products in Metro Vancouver provide a robust, current baseline for future comparison of local land use and environmental policy change.

Cd isotope fractionation during tobacco combustion produces isotopic variation outside the range measured in dietary sources.

Cadmium production has risen 1000-fold in the past 100 years, from under 20 to over 20,000 tons per year, causing anthropogenically-mobilized Cd to overwhelm natural sources in global cycling. Cadmium has no known biological function in humans, yet has biochemical behaviors similar to zinc and manganese, making exposure detrimental to human health. Identifying and quantifying the sources of Cd for human sub-populations is key to reducing exposures. Cadmium stable isotopes may provide a method for tracing Cd sources throughout the environment and the human body, but at present the limited database for high precision Cd isotopic compositions is inadequate to support such an analysis. Here, we provide new Cd isotope data on dietary sources, cigarette smoking components, and environmentally relevant standard reference materials. Results indicated that minor but significant variations are observed in food products (e.g., peanuts, sunflower seeds, spinach, kale, lettuce, cocoa powder; ~0.9‰ at 4 amu) that may be useful for tracing contamination in agricultural soils. In contrast, Cd isotope fractionation during smoking is larger (~6‰ at 4 amu) and has implications for tracing cadmium sources from tobacco combustion in the environment and throughout the human body. The primary inhaled component of cigarette smoke contains highest delta values (δ116/112Cd or δ114/110Cd ~5.2‰), while the second-hand smoke and cigarette ash have the lowest delta values (δ116/112Cd or δ114/110Cd ~-0.9‰). Used cigarette butts have δ114/110Cd ~2.4‰, in between the values measured in ash/s hand smoke and the inhaled smoke components. The high delta values of the inhaled smoke indicate that Cd isotopes may be used to determine the extent of Cd exposure due to smoking in human biological samples. This study provides new data for previously uncharacterized isotopic reservoirs that can be included in future studies of Cd source-exposure tracing.

Oxygen Perfusion (Persufflation) of Human Pancreata Enhances Insulin Secretion and Attenuates Islet Proinflammatory Signaling.

BACKGROUND: All human islets used in research and for the clinical treatment of diabetes are subject to ischemic damage during pancreas procurement, preservation, and islet isolation. A major factor influencing islet function is exposure of pancreata to cold ischemia during unavoidable windows of preservation by static cold storage (SCS). Improved preservation methods may prevent this functional deterioration. In the present study, we investigated whether pancreas preservation by gaseous oxygen perfusion (persufflation) better preserved islet function versus SCS. METHODS: Human pancreata were preserved by SCS or by persufflation in combination with SCS. Islets were subsequently isolated, and preparations in each group matched for SCS or total preservation time were compared using dynamic glucose-stimulated insulin secretion as a measure of ß-cell function and RNA sequencing to elucidate transcriptomic changes. RESULTS: Persufflated pancreata had reduced SCS time, which resulted in islets with higher glucose-stimulated insulin secretion compared to islets from SCS only pancreata. RNA sequencing of islets from persufflated pancreata identified reduced inflammatory and greater metabolic gene expression, consistent with expectations of reducing cold ischemic exposure. Portions of these transcriptional responses were not associated with time spent in SCS and were attributable to pancreatic reoxygenation. Furthermore, persufflation extended the total preservation time by 50% without any detectable decline in islet function or viability. CONCLUSIONS: These data demonstrate that pancreas preservation by persufflation rather than SCS before islet isolation reduces inflammatory responses and promotes metabolic pathways in human islets, which results in improved ß cell function.

In vitro characterization of neonatal, juvenile, and adult porcine islet oxygen demand, ß-cell function, and transcriptomes.

BACKGROUND: There is currently a shortage of human donor pancreata which limits the broad application of islet transplantation as a treatment for type 1 diabetes. Porcine islets have demonstrated potential as an alternative source, but a study evaluating islets from different donor ages under unified protocols has yet to be conducted. METHODS: Neonatal porcine islets (NPI; 1-3 days), juvenile porcine islets (JPI; 18-21 days), and adult porcine islets (API; 2+ years) were compared in vitro, including assessments of oxygen consumption rate, membrane integrity determined by FDA/PI staining, ß-cell proliferation, dynamic glucose-stimulated insulin secretion, and RNA sequencing. RESULTS: Oxygen consumption rate normalized to DNA was not significantly different between ages. Membrane integrity was age dependent, and API had the highest percentage of intact cells. API also had the highest glucose-stimulated insulin secretion response during a dynamic insulin secretion assay and had 50-fold higher total insulin content compared to NPI and JPI. NPI and JPI had similar glucose responsiveness, ß-cell percentage, and ß-cell proliferation rate. Transcriptome analysis was consistent with physiological assessments. API transcriptomes were enriched for cellular metabolic and insulin secretory pathways, while NPI exhibited higher expression of genes associated with proliferation. CONCLUSIONS: The oxygen demand, membrane integrity, ß-cell function and proliferation, and transcriptomes of islets from API, JPI, and NPI provide a comprehensive physiological comparison for future studies. These assessments will inform the optimal application of each age of porcine islet to expand the availability of islet transplantation.

Update on cellular encapsulation.

There is currently a significant disparity between the number of patients who need lifesaving transplants and the number of donated human organs. Xenotransplantation is a way to address this disparity and attempts to enable the use of xenogeneic tissues have persisted for centuries. While immunologic incompatibilities have presented a persistent impediment to their use, encapsulation may represent a way forward for the use of cell-based xenogeneic therapeutics without the need for immunosuppression. In conjunction with modern innovations such as the use of bioprinting, incorporation of immune modulating molecules into capsule membranes, and genetic engineering, the application of xenogeneic cells to treat disorders ranging from pain to liver failure is becoming increasingly realistic. The present review discusses encapsulation in the context of xenotransplantation, focusing on the current status of clinical trials, persistent issues such as antigen shedding, oxygen availability, and donor selection, and recent developments that may address these limitations.

Adrenergic receptor stimulation suppresses oxidative metabolism in isolated rat islets and Min6 cells.

Insulin secretion is stimulated by glucose metabolism and inhibited by catecholamines through adrenergic receptor stimulation. We determined whether catecholamines suppress oxidative metabolism in ß-cells through adrenergic receptors. In Min6 cells and isolated rat islets, epinephrine decreased oxygen consumption rates compared to vehicle control or co-administration of epinephrine with α2-adrenergic receptor antagonist yohimbine. Epinephrine also decreased forskolin-stimulated oxygen consumption rates, indicating cAMP dependent and independent actions. Furthermore, glucose oxidation rates were decreased with epinephrine, independent of the exocytosis of insulin, which was blocked with yohimbine. We evaluated metabolic targets through proteomic analysis after 4 h epinephrine exposure that revealed 466 differentially expressed proteins that were significantly enriched for processes including oxidative metabolism, protein turnover, exocytosis, and cell proliferation. These results demonstrate that acute α2-adrenergic stimulation suppresses glucose oxidation in ß-cells independent of nutrient availability and insulin exocytosis, while cAMP concentrations are elevated. Proteomics and immunoblots revealed changes in electron transport chain proteins that were correlated with lower metabolic reducing equivalents, intracellular ATP concentrations, and altered mitochondrial membrane potential implicating a new role for adrenergic control of mitochondrial function and ultimately insulin secretion.

Severe lead toxicity attributed to bullet fragments retained in soft tissue.

A man aged 30 years presented to an emergency department with a 1 month history of severe abdominal pain, jaundice, constipation, lower extremity weakness and weight loss. A peripheral blood smear was performed that showed basophilic stippling of erythrocytes prompting a blood lead level (BLL) evaluation. The patient had a BLL of >200 µg/dL. Retained bullet fragments were identified in the left lower extremity from a previous gunshot wound 10 years prior. Lead from the excised bullet fragment was consistent with the patient's blood lead by isotope ratio analysis. This case is a rare example of a severely elevated BLL attributed to bullet fragments in soft tissue. Bullets retained in soft tissue are not often considered a risk factor for a markedly elevated BLL because they become encapsulated within the tissue over time.

Acute Ischemia Induced by High-Density Culture Increases Cytokine Expression and Diminishes the Function and Viability of Highly Purified Human Islets of Langerhans.

BACKGROUND: Encapsulation devices have the potential to enable cell-based insulin replacement therapies (such as human islet or stem cell-derived ß cell transplantation) without immunosuppression. However, reasonably sized encapsulation devices promote ischemia due to high ß cell densities creating prohibitively large diffusional distances for nutrients. It is hypothesized that even acute ischemic exposure will compromise the therapeutic potential of cell-based insulin replacement. In this study, the acute effects of high-density ischemia were investigated in human islets to develop a detailed profile of early ischemia induced changes and targets for intervention. METHODS: Human islets were exposed in a pairwise model simulating high-density encapsulation to normoxic or ischemic culture for 12 hours, after which viability and function were measured. RNA sequencing was conducted to assess transcriptome-wide changes in gene expression. RESULTS: Islet viability after acute ischemic exposure was reduced compared to normoxic culture conditions (P < 0.01). Insulin secretion was also diminished, with ischemic ß cells losing their insulin secretory response to stimulatory glucose levels (P < 0.01). RNA sequencing revealed 657 differentially expressed genes following ischemia, with many that are associated with increased inflammatory and hypoxia-response signaling and decreased nutrient transport and metabolism. CONCLUSIONS: In order for cell-based insulin replacement to be applied as a treatment for type 1 diabetes, oxygen and nutrient delivery to ß cells will need to be maintained. We demonstrate that even brief ischemic exposure such as would be experienced in encapsulation devices damages islet viability and ß cell function and leads to increased inflammatory signaling.

High-Precision (MC-ICPMS) Isotope Ratio Analysis Reveals Contrasting Sources of Elevated Blood Lead Levels of an Adult with Retained Bullet Fragments, and of His Child, in Milwaukee, Wisconsin.

Exposure to the neurotoxic element lead (Pb) continues to be a major human health concern, particularly for children in US urban settings, and the need for robust tools for assessment of exposure sources has never been greater. The latest generation of multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) instrumentation offers the capability of using Pb isotopic signatures as a tool for environmental source tracking in public health. We present a case where MC-ICPMS was applied to isotopically resolve Pb sources in human clinical samples. An adult male and his child residing in Milwaukee, Wisconsin, presented to care in August 2015 with elevated blood lead levels (BLLs) (>200 µg/dL for the adult and 10 µg/dL for the child). The adult subject is a gunshot victim who had multiple bullet fragments embedded in soft tissue of his thigh for approximately 10 years. This study compared the high-precision isotopic fingerprints (<1 ‰ 2σ external precision) of Pb in the adult's and child's whole blood (WB) to the following possible Pb sources: a surgically extracted bullet fragment, household paint samples and tap water, and a Pb water-distribution pipe removed from servicing a house in the same neighborhood. Pb in the bullet and adult WB were nearly isotopically indistinguishable (matching within 0.05-0.56 ‰), indicating that bullet fragments embedded in soft tissue could be the cause of both acute and chronic elevated blood Pb levels. Among other sources investigated, no single source dominated the child's exposure profile as reflected in the elevated BLL.