Characterizing Sorption and Permeation Properties of Membrane Filters Used for Aquatic Integrative Passive Samplers

Aquatic integrative passive sampling is a promising approach to measure the time-weighted average concentration, yet our understanding for the sampling mechanisms of polar organic contaminants should be further advanced to fully exploit the potential of the method for real-world applications. This study aimed to characterize the sorption and permeation properties of poly­(ether sulfone) (PES) and poly­(tetrafluoroethylene) (PTFE) membrane filters (MFs) used for passive samplers. Batch sorption experiments with 14 probe chemicals showed that the sorption by PES was generally strong, with the respective sorption coefficients greater than the octanol–water partition coefficients by 2–3 log units. In contrast, the PTFE filter exhibited no significant sorption for all tested chemicals, representing a promising candidate MF that avoids lag-times and slow responses to fluctuating concentrations. Permeation experiments in a glass cell system and successive modeling demonstrated that, if no sorption to the MF occurs, the MF permeation of a chemical can be fully described with a first-order model that considers the transfer through the aqueous boundary layers and the diffusion in water-filled MF pores. Significant sorption to the MF coincided with substantial delay of permeation, which was successfully modeled with the local sorption equilibrium assumption. These findings have implications for improved sampler configurations and successful models for the chemical uptake

Altered glucose metabolism and hypoxic response in alloxan-induced diabetic atherosclerosis in rabbits

<div><p>Diabetes mellitus accelerates atherosclerosis that causes most cardiovascular events. Several metabolic pathways are considered to contribute to the development of atherosclerosis, but comprehensive metabolic alterations to atherosclerotic arterial cells remain unknown. The present study investigated metabolic changes and their relationship to vascular histopathological changes in the atherosclerotic arteries of rabbits with alloxan-induced diabetes. Diabetic atherosclerosis was induced in rabbit ilio-femoral arteries by injecting alloxan (100 mg/kg), injuring the arteries using a balloon, and feeding with a 0.5% cholesterol diet. We histologically assessed the atherosclerotic lesion development, cellular content, pimonidazole positive-hypoxic area, the nuclear localization of hypoxia-inducible factor-1α, and apoptosis. We evaluated comprehensive arterial metabolism by performing metabolomic analyses using capillary electrophoresis-time of flight mass spectrometry. We evaluated glucose uptake and its relationship to vascular hypoxia using ¹⁸F-fluorodeoxyglucose and pimonidazole. Plaque burden, macrophage content, and hypoxic areas were more prevalent in arteries with diabetic, than non-diabetic atherosclerosis. Metabolomic analyses highlighted 12 metabolites that were significantly altered between diabetic and non-diabetic atherosclerosis. A half of them were associated with glycolysis metabolites, and their levels were decreased in diabetic atherosclerosis. The uptake of glucose evaluated as ¹⁸F-fluorodeoxyglucose in atherosclerotic lesions increased according to increased macrophage content or hypoxic areas in non-diabetic, but not diabetic rabbits. Despite profound hypoxic areas, the nuclear localization of hypoxia-inducible factor-1α decreased and the number of apoptotic cells increased in diabetic atherosclerotic lesions. Altered glycolysis metabolism and an impaired response to hypoxia in atherosclerotic lesions under conditions of insulin-dependent diabetes might be involved in the development of diabetic atherosclerosis.</p></div

Apoptosis and hypoxic areas in diabetic and non-diabetic atherosclerosis.

<p>A. Representative double immunofluorescence staining of hypoxic areas and apoptotic cells in diabetic and non-diabetic atherosclerosis. Images are stained with fluorescein isothiocyanate-labeled anti-BrdU antibody (green), Dylight^™549 fluorophore-labeled anti-pimonidazole antibody (red), and merged. B. Numbers of apoptotic cells in diabetic and non-diabetic atherosclerosis (Mann-Whitney U-test).</p

Histological characteristics of control and atherosclerotic arteries in non-diabetic and diabetic rabbits, respectively, fed with 0.5% cholesterol diet.

<p>Histological characteristics of control and atherosclerotic arteries in non-diabetic and diabetic rabbits, respectively, fed with 0.5% cholesterol diet.</p

Expression of HIF-1α in atherosclerotic arteries of rabbits with and without alloxan-induced diabetes.

<p>A. Western blots of HIF-1α in nuclear extract of atherosclerotic arteries of diabetic and non-diabetic rabbits (Mann-Whitney U-test). Data are shown as fold change relative to non-DM and expressed as mean ± SD. B. Representative immunohistochemical images of macrophages, pimonidazole and HIF-1α in atherosclerotic arteries from diabetic and non-diabetic rabbits. C. Numbers of HIF-1α immunopositive nuclei in atherosclerotic arterial sections of diabetic and non-diabetic rabbits (Mann-Whitney u test). D. Correlations between pimonidazole-immunopositive areas and numbers of HIF-1α immunopositive nuclei in sections of atherosclerotic arteries in diabetic and non-diabetic rabbits (Spearman’s correlation coefficient).</p