Four molecularly imprinted polymers (MIPs) were prepared in MeOH with esculin (=6,7‐dihydroxycoumarin 6‐(β‐D ‐glucopyranoside)=6‐(β‐D ‐glucopyranosyloxy)‐7‐hydroxy‐2H‐1‐benzopyran‐2‐one) as the imprinted molecule, methacrylic acid (=2‐methylprop‐2‐enoic acid; MAA), acrylamide (=prop‐2‐enamide; AM), 4‐vinylpyridine (=4‐ethenylpyridine; 4‐VP), or 2‐vinylpyridine (=2‐ethenylpyridine; 2‐VP) as the functional monomer, respectively, as well as ethylene glycol dimethacrylate (=2‐methylprop‐2‐enoic acid ethane‐1,2‐diyl ester; EGDMA) as the cross‐linking agent. The interaction between the template and the functional monomers was investigated by fluorescence and UV spectrophotometry, respectively, which revealed the presence of esculin/monomer complexes in the stoichiometric ratio 1 : 2 in the pre‐polymerization mixture. The resultant polymers were studied in equilibrium binding experiments to evaluate the recognition ability and the binding capacity towards esculin. The results showed that MIP1, prepared with MAA as the functional monomer, exhibited advantageous characteristics of high binding capacity, optimal imprinting effect, and good selectivity towards esculin. The Scatchard analysis indicated that there are two types of binding sites in MIP1, and its binding parameters including the apparent maximum numbers of binding sites and the dissociation constants were calculated. Finally, by packing an SPE column (SPE=solid‐phase extraction) with MIP1, the esculin was separated and enriched successfully by this sorbent from samples of Cortex fraxini, and the average recovery was up to 74.7%. 相似文献
To understand the physiological mechanisms underlying the blood-oxygenation-level-dependent (BOLD) signal, the acquisition of data must be optimized to achieve the maximum possible spatial resolution and specificity. The term "specificity" implies the selective enhancement of signals originating in the parenchyma, and thus best reflecting actual neural activity. Such spatial specificity is a prerequisite for imaging aimed at the elucidation of interactions between cortical micromodules, such as columns and laminae. In addition to the optimal selection of functional magnetic resonance imaging pulse sequences, accurate superposition of activation patterns onto corresponding anatomical scans, preferably acquired during the same experimental session, is necessary. At high resolution, exact functional-to-structural registration is of critical importance, because even small differences in geometry, that arise when different sequences are used for functional and anatomical scans, can lead to misallocation of activation and erroneous interpretation of data. In the present study, we used spin-echo (SE) echo planar imaging (EPI) for functional scans, since the SE-BOLD signal is sensitive to the capillary response, together with SE-EPI anatomical reference scans. The combination of these acquisition methods revealed a clear spatial colocalization of the largest fractional changes with the Gennari line, suggesting peak activity in Layer IV. Notably, this very same layer coincided with the largest relaxivity changes as observed in steady-state cerebral blood volume measurements, using the intravascular agent monocrystalline iron oxide nanoparticles (MION). 相似文献
Recent findings of neurological functioning in autism spectrum disorder (ASD) point to altered brain connectivity as a key feature of its pathophysiology. The cortical underconnectivity theory of ASD (Just et al., 2004) provides an integrated framework for addressing these new findings. This theory suggests that weaker functional connections among brain areas in those with ASD hamper their ability to accomplish complex cognitive and social tasks successfully. We will discuss this theory, but will modify the term underconnectivity to ‘disrupted cortical connectivity’ to capture patterns of both under- and over-connectivity in the brain. In this paper, we will review the existing literature on ASD to marshal supporting evidence for hypotheses formulated on the disrupted cortical connectivity theory. These hypotheses are: 1) underconnectivity in ASD is manifested mainly in long-distance cortical as well as subcortical connections rather than in short-distance cortical connections; 2) underconnectivity in ASD is manifested only in complex cognitive and social functions and not in low-level sensory and perceptual tasks; 3) functional underconnectivity in ASD may be the result of underlying anatomical abnormalities, such as problems in the integrity of white matter; 4) the ASD brain adapts to underconnectivity through compensatory strategies such as overconnectivity mainly in frontal and in posterior brain areas. This may be manifested as deficits in tasks that require frontal–parietal integration. While overconnectivity can be tested by examining the cortical minicolumn organization, long-distance underconnectivity can be tested by cognitively demanding tasks; and 5) functional underconnectivity in brain areas in ASD will be seen not only during complex tasks but also during task-free resting states. We will also discuss some empirical predictions that can be tested in future studies, such as: 1) how disrupted connectivity relates to cognitive impairments in skills such as Theory-of-Mind, cognitive flexibility, and information processing; and 2) how connection abnormalities relate to, and may determine, behavioral symptoms hallmarked by the triad of Impairments in ASD. Furthermore, we will relate the disrupted cortical connectivity model to existing cognitive and neural models of ASD. 相似文献
The cerebral cortex is the main target of analysis in many functional magnetic resonance imaging (fMRI) studies. Since only about 20% of the voxels of a typical fMRI data set lie within the cortex, statistical analysis can be restricted to the subset of the voxels obtained after cortex segmentation. While such restriction does not influence conventional univariate statistical tests, it may have a substantial effect on the performance of multivariate methods.
Here, we describe a novel approach for data-driven analysis of single-subject fMRI time series that combines techniques for the segmentation and reconstruction of the cortical surface of the brain and the spatial independent component analysis (sICA) of the functional time courses (TCs). We use the mesh of the white matter/gray matter boundary, automatically reconstructed from high-spatial-resolution anatomical MR images, to limit the sICA decomposition of a coregistered functional time series to those voxels which are within a specified region with respect to the cortical sheet (cortex-based ICA, or cbICA). We illustrate our analysis method in the context of fMRI blocked and event-related experimental designs and in an fMRI experiment with perceptually ambiguous stimulation, in which an a priori specification of the stimulation protocol is not possible.
A comparison between cbICA and conventional hypothesis-driven statistical methods shows that cortical surface maps and component TCs blindly obtained with cbICA reliably reflect task-related spatiotemporal activation patterns. Furthermore, the advantages of using cbICA when the specification of a temporal model of the expected hemodynamic response is not straightforward are illustrated and discussed. A comparison between cbICA and anatomically unconstrained ICA reveals that — beside reducing computational demand — the cortex-based approach improves the fitting of the ICA model in the gray matter voxels, the separation of cortical components and the estimation of their TCs, particularly in the case of fMRI data sets with a complex spatiotemporal statistical structure. 相似文献
Abstract Cadmium, copper, lead, manganese, and selenium concentrations and glutathione peroxidase (EC 1.11.1.19) activity have been determined in human kidney cortex specimens obtained at autopsy. Trace metal concentrations for each specimen were determined in the same digest, while glutathione peroxidase activity was assayed in tissue collected at a site adjacent to that selected for the trace metal determinations. Glutathione peroxidase activities were determined with two substrates, hydrogen peroxide and t-butylhydroperoxide. The effects of age, smoking history, sex, race, and blood pressure on kidney cortex trace metal levels and glutathione peroxidase activity were investigated. Mean kidney cortex cadmium concentration was found to be significantly higher in smokers than in nonsmokers (p=0.010). In addition, the mean kidney cortex lead concentration of hypertensive individuals was found to be significantly higher than that of non-hypertensive individuals (p=0.017), Glutathione peroxidase activities utilizing hydrogen peroxide substrate were inversely correlated to kidney cortex manganese levels (p=0.004). 相似文献