Separating toxicity and shading in algal growth inhibition tests of nanomaterials and colored substances.

Nanoparticles and colored substances can inhibit algal growth by light shading and chemical toxicity. This study presents two complementary approaches to account for shading in algal growth inhibition tests of engineered nanomaterials (ENMs) and colored substances. The first approach distinguishes between shading effects and toxicity by varying the light path in parallel algal growth inhibition tests. This Multiple Path-Length (MPL) test was applied to TiO2 ENMs and the colored substances sodium picramate and Rhodamine B. A left shifting of concentration-response curves, with increasing light path lengths, indicated shading for Rhodamine B, sodium picramate and TiO2 ENMs. EC50-values obtained at the shortest light path length were generally found best suited to quantify the toxicity of ENMs and colored substances. The second approach addresses shading at the cellular level, where particles can attach to the cell surface and affect photo-pigment content and composition. Pigments associated with photosystem I and II were determined at varying light intensities and concentrations of TiO2 ENMs. The photo-pigments that increased in response to physical shading, decreased after TiO2 ENMs exposure. This indicates that toxicity rather than cellular shading dominated the response of algae exposed to TiO2 ENMs. Additional tests were conducted with the nanomaterials CeO2 and goethite to evaluate the applicability of this approach to other ENMs. On this basis, we recommend MPL testing for determining EC50-values that are not confounded by shading in the test solution, and the pigment-based approach for investigating shading on the cellular level.

The Analgesic Effect of Oxygen in Suspected Acute Myocardial Infarction: A Substudy of the DETO2X-AMI Trial.

OBJECTIVES: In this substudy of the DETO2X-AMI (An Efficacy and Outcome Study of Supplemental Oxygen Treatment in Patients With Suspected Myocardial Infarction) trial, the authors aimed to assess the analgesic effect of moderate-flow oxygen supplementation in patients with suspected acute myocardial infarction (AMI) treated with percutaneous coronary intervention (PCI) and to study the effect of oxygen supplementation on the use of opiates and sedatives during PCI. BACKGROUND: Routine oxygen in normoxemic patients with AMI does not provide clinical benefit. However, oxygen may relieve ischemic pain. METHODS: Patients were randomly allocated to oxygen or ambient air according to the main study protocol. After PCI, peak level of pain during PCI was measured by the Visual Analogue Scale. The total amount of opiates and sedatives was reported. RESULTS: A total of 622 patients were enrolled: 330 in the oxygen group and 292 in the ambient air group. There was no significant difference in peak level of pain (oxygen 4.0 [1.0 to 6.0] vs. air 3.0 [0.6 to 6.0]; p = 0.37), use of opiates (mg) (oxygen 0.0 [0.0 to 3.0] vs. air 0.0 [0.0 to 3.0]; p = 0.31), or use of sedatives between the groups (median [interquartile range]) (oxygen 2.5 [0.0 to 2.5] vs. air 2.5 [0.0 to 2.5]; p = 0.74). CONCLUSIONS: In the present study, the authors did not find any analgesic effect of routine oxygen as compared with ambient air, and no differences in the use of sedatives and opiates during PCI. Our results indicate that moderate-flow oxygen supplementation does not relieve pain in normoxemic patients with suspected AMI undergoing treatment with PCI and should thus not be used for this purpose.