Assessment of the toxicity of weathered petroleum hydrocarbon impacted soils to native plants from a site in the Canadian Subarctic.

Remedial guidelines for petroleum hydrocarbons (PHCs) in soil aid in the mitigation of risks to human health and the environmental. However, some remediation guidelines may overestimate the potential for adverse effects to native plant species, contributing to unnecessary remedial efforts in attempts to meet the guidelines. At sites where PHC-contaminated soils undergo weathering, some PHCs may persist but with decreased bioavailability to organisms. In this study, the toxicity of both coarse and fine-grained subarctic soils, contaminated with weathered PHCs were assessed using five native plant species (Picea mariana, Achillea millefolium, Alnus viridis, Elymus trachycaulus and Salix bebbiana). Soil toxicity tests were conducted in a growth chamber with parameters set to simulate the site's subarctic climate conditions. Reference toxicant tests using boric acid were conducted to provide confidence in the interpretation of the results for the PHC-contaminated soils, and also provide new information on the sensitivities of the four boreal species to boric acid. All plants exhibited reduced growth and germination rates as boric acid concentrations increased. Despite exceeding the Canada-wide standard guidelines for Fraction 3 PHCs, field-collected contaminated soils had no significant negative impacts on the growth (i.e., length, dry weight and emergence) of any of the plant species tested.

Assessment of insulin sensitivity (S I) and glucose effectiveness (S G) from a standardized hyperglucidic breakfast test in type 2 diabetics exhibiting various levels of insulin resistance.

We investigated the measurement of insulin sensitivity (S I) with a standardized hyperglucidic breakfast (SHB) compared to minimal model analysis of an intravenous glucose tolerance test (S I-IVGTT) in 17 patients clinically referred as type 2 diabetics, not yet treated by insulin, and representing a wide range of body mass index and S I. To classify the patients, ten meal-tolerance test-based calculations of S I (MTT-S I) were compared to S I-IVGTT, and their reference values and distribution were measured on a separate sample of 200 control SHBs and 209 control IVGTTs. Eight MTT-SI indices exhibit significant correlations with S I-IVGTT: Mari's OGIS index, BIGTT-SI|0-30-120, BIGTT-SI|0-60-120, 1/G b I m, Caumo's oral minimal model (OMM), Sluiter's index "A" = 10(4)/(I p·G p), Matsuda's composite index given by the formula ISIcomp = 10(4)/(I b G b I m G m)(0.5), S I = 1/I b G b I m G m with r (2) ranging between 0,53 and 0,28. S I-IVGTT and S I-MTT exhibited in the lower range a very different (non-normal) pattern of distribution and thus the cutoff value for defining insulin resistance varied among indices. With such cutoffs, S I-MTT < 6.3 min(-1)/(µU/ml) 10(-4) with Caumo's OMM was the best predictor of insulin resistance defined as S I-IVGTT < 2 min(-1)/(µU/ml) 10(-4). Other indices, including OGIS and BIGTT, resulted in more misclassifications of patients. HOMA-IR and QUICKI were poor predictors. The formula [Formula: see text] satisfactorily predicts IVGTT-derived glucose effectiveness in type 2 diabetics. Thus, SHB appears suitable for the measurement of S I and S G in type 2 diabetics, and the OMM seems to provide the most accurate SHB-derived index in this population.