Analysis of the enantiomers of chiral pesticides and other pollutants in environmental samples by capillary electrophoresis.

The generic method described here involves typical capillary electrophoresis (CE) techniques, with the addition of cyclodextrin chiral selectors to the electrolyte for enantiomer separation and also, in the case of neutral analytes, the further addition of a micelle-forming compound such as sodium dodecyl sulfate (SDS) for separation by the micellar electrokinetic chromatography (MEKC) mode of CE. This generic method has broad application for the separation and analysis of enantiomers of chiral pesticides and other small molecules in a variety of environmental matrices. Aqueous samples such as surface water are analyzed after simple filtration, but centrifugation is sometimes necessary for soil-water slurry samples. Soils and sediment must be extracted with a polar organic solvent such as methanol, which needs only to be evaporated to near dryness, diluted with water, and filtered before CE analysis. Simple borate or phosphate-based buffers are usually used in the CE electrolyte. The method must be optimized for the electrolyte composition, including the correct chiral selector and its concentration, as well as for column conditions and instrumental variables such as voltage. Specific methodologies for application of this generic CE method to follow the enantioselective microbial transformation of ruelene, a neutral organophosphorus insecticide, dichlorprop, an ionic phenoxyalkanoic acid herbicide, and bromochloroacetic acid, a drinking water disinfection byproduct, are provided

Resting Cerebral Blood Flow Alterations in Chronic Traumatic Brain Injury: An Arterial Spin Labeling Perfusion fMRI Study

Non-invasive measurement of resting state cerebral blood flow (CBF) may reflect alterations of brain structure and function after traumatic brain injury (TBI). However, previous imaging studies of resting state brain in chronic TBI have been limited by several factors, including measurement in relative rather than absolute units, use of crude spatial registration methods, exclusion of subjects with substantial focal lesions, and exposure to ionizing radiation, which limits repeated assessments. This study aimed to overcome those obstacles by measuring absolute CBF with an arterial spin labeling perfusion fMRI technique, and using an image preprocessing protocol that is optimized for brains with mixed diffuse and focal injuries characteristic of moderate and severe TBI. Resting state CBF was quantified in 27 individuals with moderate to severe TBI in the chronic stage, and 22 demographically matched healthy controls. In addition to global CBF reductions in the TBI subjects, more prominent regional hypoperfusion was found in the posterior cingulate cortices, the thalami, and multiple locations in the frontal cortices. Diffuse injury, as assessed by tensor-based morphometry, was mainly associated with reduced CBF in the posterior cingulate cortices and the thalami, where the greatest volume losses were detected. Hypoperfusion in superior and middle frontal cortices, in contrast, was associated with focal lesions. These results suggest that structural lesions, both focal and diffuse, are the main contributors to the absolute CBF alterations seen in chronic TBI, and that CBF may serve as a tool to assess functioning neuronal volume. We also speculate that resting reductions in posterior cingulate perfusion may reflect alterations in the default-mode network, and may contribute to the attentional deficits common in TBI