A new hypervolume approach for assessing environmental risks.

Assessing risks of uncertain but potentially damaging events, such as environmental disturbances, disease outbreaks and pest invasions, is a key analytical step that informs subsequent decisions about how to respond to these events. We present a continuous risk measure that can be used to assess and prioritize environmental risks from uncertain data in a geographical domain. The metric is influenced by both the expected magnitude of risk and its uncertainty. We demonstrate the approach by assessing risks of human-mediated spread of Asian longhorned beetle (ALB, Anoplophora glabripennis) in Greater Toronto (Ontario, Canada). Information about the human-mediated spread of ALB through this urban environment to individual geographical locations is uncertain, so each location was characterized by a set of probabilistic rates of spread, derived in this case using a network model. We represented the sets of spread rates for the locations by their cumulative distribution functions (CDFs) and then, using the first-order stochastic dominance rule, found ordered non-dominant subsets of these CDFs, which we then used to define different classes of risk across the geographical domain, from high to low. Because each non-dominant subset was estimated with respect to all elements of the distribution, the uncertainty in the underlying data was factored into the delineation of the risk classes; essentially, fewer non-dominant subsets can be defined in portions of the full set where information is sparse. We then depicted each non-dominant subset as a point cloud, where points represented the CDF values of each subset element at specific sampling intervals. For each subset, we then defined a hypervolume bounded by the outermost convex frontier of that point cloud. This resulted in a collection of hypervolumes for every non-dominant subset that together serve as a continuous measure of risk, which may be more practically useful than averaging metrics or ordinal rank measures. Overall, the approach offers a rigorous depiction of risk in a geographical domain when the underlying estimates of risk for individual locations are represented by sets or distributions of uncertain estimates. Our hypervolume-based approach can be used to compare assessments made with different datasets and assumptions.

Characteristics of logs with signs of oviposition by the polyphagous xylophage Asian longhorned beetle (Coleoptera: Cerambycidae).

During the eradication program undertaken against Anoplophora glabripennis (Motschulsky) in the Greater Toronto Area, information was collected on the numerous signs of injury found on wounded trees. Herein, we used a portion of this information to assess the characteristics of logs with signs of oviposition (i.e., pits). Specifically, we related the basal diameter, type (log bole vs. log branch), height above ground, and branch hierarchy level of logs with pits to tree size (i.e., height and diameter at breast height) and level of infestation intensity. In general, pits were concentrated on logs from the bole and branches that were 8-14 cm in diameter in the lower 8 m of the bole and in the first 2 levels of the branching hierarchy. Oviposition pit location was strongly influenced by tree size-both height and diameter at breast height, with more pits on the lower bole in small trees and then higher on the bole and into the branches as tree size increased. As tree-level infestation intensity increased, pits were found on both larger and smaller diameter portions of the trees, presumably as preferred oviposition sites became saturated. These findings can improve the efficacy of surveillance activities for A. glabripennis.

Forest defoliator outbreaks alter nutrient cycling in northern waters.

Insect defoliators alter biogeochemical cycles from land into receiving waters by consuming terrestrial biomass and releasing biolabile frass. Here, we related insect outbreaks to water chemistry across 12 boreal lake catchments over 32-years. We report, on average, 27% lower dissolved organic carbon (DOC) and 112% higher dissolved inorganic nitrogen (DIN) concentrations in lake waters when defoliators covered entire catchments and reduced leaf area. DOC reductions reached 32% when deciduous stands dominated. Within-year changes in DOC from insect outbreaks exceeded 86% of between-year trends across a larger dataset of 266 boreal and north temperate lakes from 1990 to 2016. Similarly, within-year increases in DIN from insect outbreaks exceeded local, between-year changes in DIN by 12-times, on average. As insect defoliator outbreaks occur at least every 5 years across a wider 439,661 km2 boreal ecozone of Ontario, we suggest they are an underappreciated driver of biogeochemical cycles in forest catchments of this region.

A safety rule approach to surveillance and eradication of biological invasions.

Uncertainty about future spread of invasive organisms hinders planning of effective response measures. We present a two-stage scenario optimization model that accounts for uncertainty about the spread of an invader, and determines survey and eradication strategies that minimize the expected program cost subject to a safety rule for eradication success. The safety rule includes a risk standard for the desired probability of eradication in each invasion scenario. Because the risk standard may not be attainable in every scenario, the safety rule defines a minimum proportion of scenarios with successful eradication. We apply the model to the problem of allocating resources to survey and eradicate the Asian longhorned beetle (ALB, Anoplophora glabripennis) after its discovery in the Greater Toronto Area, Ontario, Canada. We use historical data on ALB spread to generate a set of plausible invasion scenarios that characterizes the uncertainty of the beetle's extent. We use these scenarios in the model to find survey and tree removal strategies that minimize the expected program cost while satisfying the safety rule. We also identify strategies that reduce the risk of very high program costs. Our results reveal two alternative strategies: (i) delimiting surveys and subsequent tree removal based on the surveys' outcomes, or (ii) preventive host tree removal without referring to delimiting surveys. The second strategy is more likely to meet the stated objectives when the capacity to detect an invader is low or the aspirations to eradicate it are high. Our results provide practical guidelines to identify the best management strategy given aspirational targets for eradication and spending.

Development and characterization of erythrosine nanoparticles with potential for treating sinusitis using photodynamic therapy.

BACKGROUND: Antimicrobial therapy for sinusitis has been shown to reduce or eliminate pathologic bacteria associated with rhinosinusitis and improve the symptoms associated with the disease. However, the continuing rise in antibiotic resistance, the ongoing problem with patient compliance, and the intrinsic difficulty in eradication of biofilms complicates antibiotic therapy. The introduction of photodynamic antimicrobial therapy (PAT) using erythrosine, a photosensitizer, could eliminate the bacteria without inducing antibiotic resistance or even requiring daily dosing. In the present study, erythrosine nanoparticles were prepared using poly-lactic-co-glycolic acid (PLGA) and evaluated for their potential in PAT against Staphylococcus aureus cells. METHODS: PLGA nanoparticles of erythrosine were prepared by nanoprecipitation technique. Erythrosine nanoparticles were characterized for size, zeta potential, morphology and in vitro release. Qualitative and quantitative uptake studies of erythrosine nanoparticles were carried out in S. aureus cells. Photodynamic inactivation of S. aureus cells in the presence of erythrosine nanoparticles was investigated by colony forming unit assay. RESULTS: Nanoprecipitation technique resulted in nanoparticles with a mean diameter of 385nm and zeta potential of -9.36mV. Erythrosine was slowly released from nanoparticles over a period of 120h. The qualitative study using flow cytometry showed the ability of S. aureus cells to internalize erythrosine nanoparticles. Moreover, erythrosine nanoparticles exhibited a significantly higher uptake and antimicrobial efficacy compared to pure drug in S. aureus cells. CONCLUSION: In conclusion, erythrosine-loaded PLGA nanoparticles can be a potential long term drug delivery system for PAT and are useful for the eradication of S. aureus cells.

Application of a convective-dispersion model to predict in vivo hepatic clearance from in vitro measurements utilizing cryopreserved human hepatocytes.

Growing interest in the prediction of in vivo pharmacokinetic data from purely in vitro data has grown into a process known as the in vitro-in vivo correlation (IVIC). IVIC can be used to determine the viability of new chemical entities in the early drug development phases, leading to a reduction of resource spending by many large pharmaceutical companies. Here, a convective-dispersion model was developed to predict the total hepatic clearance of six drugs using pharmacokinetic data obtained from in vitro metabolism studies in which the drug disappearance from suspensions of human cryopreserved hepatocytes was measured. Predicted in vivo hepatic clearances estimated by the convective-dispersion model were ultimately compared to the actual clearance values and to in vivo hepatic clearances that were scaled based on the well-stirred model. Finally, sensitivity studies were performed to determine the dependence of hepatic clearance on a number of physiological model parameters. Results reaffirmed that low clearance drugs exhibit rate-limited metabolism, and their hepatic clearances are thus independent of blood flow characteristics, whereas drugs with relatively higher clearance values show a more pronounced dependence on the flood flow properties of dispersion and convection. Absent a priori knowledge about the flow-dependent properties of a drug's clearance, the convective dispersion model applied to disappearance data acquired from cryopreserved human hepatocytes is likely to provide satisfactory estimates of hepatic drug clearance.

Oxygen and inulin transport measurements in a planar tissue-engineered bioartificial organ.

In vivo oxygen and inulin transport rates were measured in a planar tissue-engineered bioartificial organ implanted in a rat. A compartmental model was used to describe the transport of oxygen and inulin between the cell chamber, across the immunoisolation membrane, and within the neovascularized region adjacent to the immunoisolation membrane. A nonlinear regression analysis of the plasma inulin levels and the oxygen transport rate into the device provided information on the degree of vascularization in the region adjacent to the bioartificial organ. Key parameters that were obtained from the analysis of the in vivo transport data included the average capillary blood oxygen partial pressure, the Krogh tissue cylinder radius, the extracellular volume fraction, and the capillary blood residence time. These four parameters are important indicators for assessing the degree of vascularization in the tissue adjacent to the immunoisolation membrane in the bioartificial organ. The oxygen and inulin transport technique reported here is a useful tool for describing the in vivo transport characteristics of a bioartificial organ and for assessment of the vascularization within tissue engineered structures.