Use of a Bayesian maximum-likelihood classifier to generate training data for brain–machine interfaces

Brain–machine interface decoding algorithms need to be predicated on assumptions that are easily met outside of an experimental setting to enable a practical clinical device. Given present technological limitations, there is a need for decoding algorithms which (a) are not dependent upon a large number of neurons for control, (b) are adaptable to alternative sources of neuronal input such as local field potentials (LFPs), and (c) require only marginal training data for daily calibrations. Moreover, practical algorithms must recognize when the user is not intending to generate a control output and eliminate poor training data. In this paper, we introduce and evaluate a Bayesian maximum-likelihood estimation strategy to address the issues of isolating quality training data and self-paced control. Six animal subjects demonstrate that a multiple state classification task, loosely based on the standard center-out task, can be accomplished with fewer than five engaged neurons while requiring less than ten trials for algorithm training. In addition, untrained animals quickly obtained accurate device control, utilizing LFPs as well as neurons in cingulate cortex, two non-traditional neural inputs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90824/1/1741-2552_8_4_046009.pd

Estimation of electrode location in a rat motor cortex by laminar analysis of electrophysiology and intracortical electrical stimulation

While the development of microelectrode arrays has enabled access to disparate regions of a cortex for neurorehabilitation, neuroprosthetic and basic neuroscience research, accurate interpretation of the signals and manipulation of the cortical neurons depend upon the anatomical placement of the electrode arrays in a layered cortex. Toward this end, this report compares two in vivo methods for identifying the placement of electrodes in a linear array spaced 100 µm apart based on in situ laminar analysis of (1) ketamine–xylazine-induced field potential oscillations in a rat motor cortex and (2) an intracortical electrical stimulation-induced movement threshold. The first method is based on finding the polarity reversal in laminar oscillations which is reported to appear at the transition between layers IV and V in laminar 'high voltage spindles' of the rat cortical column. Analysis of histological images in our dataset indicates that polarity reversal is detected 150.1 ± 104.2 µm below the start of layer V. The second method compares the intracortical microstimulation currents that elicit a physical movement for anodic versus cathodic stimulation. It is based on the hypothesis that neural elements perpendicular to the electrode surface are preferentially excited by anodic stimulation while cathodic stimulation excites those with a direction component parallel to its surface. With this method, we expect to see a change in the stimulation currents that elicits a movement at the beginning of layer V when comparing anodic versus cathodic stimulation as the upper cortical layers contain neuronal structures that are primarily parallel to the cortical surface and lower layers contain structures that are primarily perpendicular. Using this method, there was a 78.7 ± 68 µm offset in the estimate of the depth of the start of layer V. The polarity reversal method estimates the beginning of layer V within ±90 µm with 95% confidence and the intracortical stimulation method estimates it within ±69.3 µm. We propose that these methods can be used to estimate the in situ location of laminar electrodes implanted in the rat motor cortex.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90825/1/1741-2552_8_4_046018.pd

Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. 5: Variability of the ultraviolet continuum and emission lines of NGC 3783

We report on the results of intensive ultraviolet spectral monitoring of the Seyfert 1 galaxy NGC 3783. The nucleus of NGC 3783 was observed with the International Ultraviolet Explorer satellite on a regular basis for a total of 7 months, once every 4 days for the first 172 days and once every other day for the final 50 days. Significant variability was observed in both continuum and emission-line fluxes. The light curves for the continuum fluxes exhibited two well-defined local minima or 'dips,' the first lasting is less than or approximately 20 days and the second is less than or approximately 4 days, with additional episodes of relatively rapid flickering of approximately the same amplitude. As in the case of NGC 5548 (the only other Seyfert galaxy that has been the subject of such an intensive, sustained monitoring effort), the largest continuum variations were seen at the shortest wavelengths, so that the continuum became 'harder' when brighter. The variations in the continuum occurred simultaneously at all wavelengths (delta(t) is less than 2 days). Generally, the amplitude of variability of the emission lines was lower than (or comparable to) that of the continuum. Apart from Mg II (which varied little) and N V (which is relatively weak and badly blended with Ly(alpha), the light curves of the emission lines are very similar to the continuum light curves, in each case with a small systematic delay or 'lag.' As for NGC 5548, the highest ionization lines seem to respond with shorter lags than the lower ionization lines. The lags found for NGC 3783 are considerably shorter than those obtained for NGC 5548, with values of (formally) approximately 0 days for He II + O III), and approximately 4 days for Ly(alpha) and C IV. The data further suggest lags of approximately 4 days for Si IV + O IV) and 8-30 days for Si III + C III). Mg II lagged the 1460 A continuum by approximately 9 days, although this result depends on the method of measuring the line flux and may in fact be due to variability of the underlying Fe II lines. Correlation analysis further shows that the power density spectrum contains substantial unresolved power over timescales of is less than or approximately 2 days, and that the character of the continuum variability may change with time

Physiological consequences of beta-lactoglobulin adsorption on hydrophobic surfaces: making a bad food allergen even worse?

Beta-lactoglobulin (BLG) is abundant in bovine whey and is a major food allergen. The physiological consequences of technological treatments of BLG are much debated, also because multiple mechanisms seem to be involved in BLG recognition and uptake. Since food protein allergens are consumed in the presence of other food components, we aimed at understanding the consequences of conformational changes ensuing from the interaction of BLG with hydrophobic interfaces (such as oil-in-water emulsions), and how these can affect its immunoreactivity and uptake by cells of the immune human system. BLG increases its immunoreactivity after interaction with the interface, and the immunoreactivity of interface-bound BLG remains high after trypsin hydrolysis, at least when compared with the protein hydrolyzed in solution. However, the physical state of BLG does not influence the rate of its uptake by antigen presenting cells, e.g. monocytes, although different uptake pathways seem to operate for free and interface-bound BLG. These results highlight the importance of the protein physical state with respect to physiologically relevant properties, with significant practical implications

Food proteins conjugates to magnetic nanoparticles : evaluation of their cellular toxicity

Introduction Advances in processes for producing nanostructured materials coupled with appropriate formulation strategies has made possible the production and stabilisation of magnetic nanosupports that have potential applications in biochemical and biotechnological fields. This kind of support is generally synthesized by encapsulating magnetic materials with a polymer layer. The interest for magnetic nanosupports is not only limited to the obvious ease of their separation under micro- and nanofluidic conditions, or to their entrapment in coatings and films. Most relevant is the fact that nanostructures can be conjugated to biologically active molecules, including hormones, antibodies, drugs, and various peptides, taken up by cells, and circulated among tissues expressing their cognate receptors (1). For all the studies described above, it is fundamental to set up appropriate tests aimed at assessing the citotoxicity of nanoparticles. In this work we investigated the citotoxicity of unmodified and protein-coniugated dextran-coated nanoparticles using the human intestinal cell lines HT-29 and Caco2, differentiated in vitro toward an enterocityc phenotype. Materials and methods Cytotoxicity was assessed by the colorimetric tetrazolium assay (2) performed in HT-29 cells differentiated in RPMI 1640 medium. The cell proliferation rate was quantified by bromodeoxyuridine (BrdU) incorporation into DNA, while the apoptosis was monitored by quantification of the activity of caspase 3 and 7 (Apo-ONE® assay). Effects on tight junctions permeability were evaluated by TEER measurements in differentiated Caco2 cells. Results: Dextran-coated iron oxide magnetic nanoparticles were modified through simple chemical procedures in order to obtain a functionalized and activated coating which allowed easy covalent binding of different bioactive proteins. Proteins considered in our studies included food allergens, enzymes, and antibodies to food proteins. Immunological approaches were used to demonstrate the coupling of the proteins to the activated dextran-coated nanoparticles. Cell viability after 24-48 hours incubation with unmodified and conjugated nanoparticles showed the absence of any citotoxic effect, indicating a full biocompatibility of these particles with this in vitro intestinal cellular model. Both the cell proliferation rate and the apoptotic marker were unaffected by 24 hours incubation with the same nanoparticles. TEER measurement in differentiated Caco2 cells demonstrated that both unmodified and conjugated nanoparticles increase the Trans-Epithelial Electrical Resistance, thus revealing a direct effect on the paracellular permeability of intestinal cells. This result suggests that both unmodified and conjugated nanoparticles may act as protective agents against foreign molecules that are potentially dangerous for the integrity of the epithelial barrier made by the cellular tight junctions. Further studies will assess the use of the conjugates between magnetic nanoparticles and bioactive proteins as biological tracers in order to monitoring the intracellular and/or intratissutal path of specific proteins, with particular reference to food allergens of protein nature and to food-derived compounds of known toxicity

Specific and non-specific pathways to the cellular uptake of beta-lactoglobulin, a major food allergen

Beta-lactoglobulin (BLG) is abundant in bovine whey and is a major food allergen. The physiological consequences of technological treatments of BLG are much debated, also because multiple mechanisms seem to be involved in BLG recognition and uptake. Since food protein allergens are consumed in the presence of other food components, we aimed at understanding the consequences of conformational changes ensuing from the interaction of BLG with hydrophobic interfaces (such as oil-in-water emulsions), and how these can affect its capability of binding to specific antibodies, to be taken up by cells, and to activate response by cells of the immune human system. BLG increases its immunoreactivity after interaction with the interface, and affinity of interface-bound BLG towards specific monoclonal antibodies remains high after trypsin hydrolysis, at least when compared with the protein hydrolyzed in solution. However, the physical state of BLG does not influence the rate of its uptake by antigen presenting cells, e.g. monocytes, but competition experiments indicate that different uptake pathways seem to be operate operating for free and interface-bound BLG. These results highlight the importance of the protein physical state with respect to physiologically relevant properties, with significant practical implications. MM and MM are the grateful recipients of postdoctoral fellowships from the University of Milan. A stay of RGB in Denmark was made possible by the Erasmus-Placement program

Recognition and uptake of nanoparticle-conjugated food allergens by human monocytes

Stable biocompatible magnetic nanoparticles have demonstrated their potential in targeting biologically active molecules - including hormones, allergens, and various peptides - to specific cells or tissues expressing their cognate receptors, and may represent versatile and non-invasive tools for monitoring cellular functions both in vitro and in vivo. In this study, betalactoglobulin, one of the major whey proteins and food allergens, was covalently conjugated to biocompatible dextran-coated magnetic nanoparticles. The conjugated protein retained its structure and immunoreactivity towards monoclonal and polyclonal antibodies. BLG-conjugated nanoparticles were taken up by human monocytes much more efficiently than non-conjugated particles, allowing easy magnetic separation of cells that had adsorbed the allergen. To verify whether this approach could be complemented with others for improving our current understanding of the intracellular and intratissutal path of food allergens, BLG was conjugated to magnetic nanoparticles also labeled with a fluorescent probe. The uptake of these materials by human monocytes was monitored through flow cytometry and confocal microscopy, in comparison with fluorescent nanoparticles devoid of the allergen or conjugated with human serum albumin. Both approaches confirm a higher uptake of the BLG-conjugated particles, and confocal microscopy provided direct evidence of actual internalization of the particles into the cytoplasm. These results open up the possibility to use a combination of these approaches for monitoring the fate of food allergens in cells that may be involved in the immune response to food