Features extracted from delta, theta, alpha, beta and gamma bands spanning low frequency range are commonly used to classify scalp-recorded electroencephalogram (EEG) for designing brain-computer interface (BCI) and higher frequencies are often neglected as noise. In this paper, we implemented an experimental validation to demonstrate that high frequency components could provide helpful information for improving the performance of the mental task based BCI. Electromyography (EMG) and electrooculography (EOG) artifacts were removed by using blind source separation (BSS) techniques. Frequency band powers and asymmetry ratios from the high frequency band (40-100 Hz) together with those from the lower frequency bands were used to represent EEG features. Finally, Fisher discriminant analysis (FDA) combining with Mahalanobis distance were used as the classifier. In this study, four types of classifications were performed using EEG signals recorded from four subjects during five mental tasks. We obtained significantly higher classification accuracy by adding the high frequency band features compared to using the low frequency bands alone, which demonstrated that the information in high frequency components from scalp-recorded EEG is valuable for the mental task based BCI.
Mechanical stretch plays a crucial role in articular joints. In rheumatoid arthritis (RA), it is well known that fibroblast-like synoviocytes (FLS) produce matrix metalloproteinases (MMPs), resulting in local invasion into and degradation of bone and cartilage. We sought to examine whether mechanical stretch regulates the expression and underlying signal pathways of MMP secretion (MMP-1, -3, -13) in RA-FLS. FLS were grown on elastic silicone membrane in an equibiaxial strain apparatus and were exposed to 6% mechanical stretch (equivalent to gentle stretch exercise) for 15 min and 75 min, respectively. Semiquantitative PCR and real-time PCR were used to measure and analyze gene expression. Protein levels were determined by Western blotting. The results showed that 15 min of mechanical stretch inhibited MMP-1 and MMP-13 mRNA and protein level. However, the degree of inhibition by 75 min of stretch in expression of MMP-1 and MMP-13 was lower compared with 15 min stretch groups. The mRNA expression of ERK-1, ets-1 and citied-2 were increased by 6% mechanical stretch under both time points, however c-jun and c-fos mRNA level were affected differently after 15 min and 75 min mechanical stretch compared to control group. There were no significant changes on MMP-3 and ets-2 mRNA level under both 6% mechanical stretch time points. In the presence of pro-inflammatory cytokines (IL-1beta and TNF-alpha), the stretch also reduced the mRNA expression of MMP-1 and MMP-13. In short, our results showed that gentle mechanical strain affects MMP-1 and MMP-13 expression, potentially through the ERK-1-ets-1-cited-2-c-jun signaling pathway.
Fibroblast-like synoviocytes (FLSs) are one of the main contributors of prostaglandin E(2) (PGE(2)) in the hyperplastic synovium of rheumatoid arthritis (RA) patients. cyclooxygenase-2 (COX-2)/PGE(2) pathway is involved in the proliferation of several cell types. We have previously shown that mechanical stretch affects COX-2 and PGE(2) production in human RA FLSs; however, its role in cell proliferation remains to be elucidated. In this study, a comparison is drawn between human RA and normal FLSs to understand the role of mechanical stretch and PGE(2) on the proliferation of FLSs. The results showed that physiological level (6%, 1 Hz) of cyclic mechanical stretch significantly decreased the proliferation of RA FLSs but not normal FLSs, while the induction of apoptosis was not observed by stretch in either RA or normal FLSs. IL-1β (5 ng/ml)-induced COX-2/PGE(2) levels are downregulated by stretch in RA FLSs only. Further investigation showed that high concentration (100 and 500 ng/ml) of PGE(2) significantly induced cell proliferation only in RA FLSs, and this induction failed to be suppressed by stretch. In conclusion, this study demonstrated that elevated levels of PGE(2) in the synovial cavity are involved in the proliferation of RA FLSs, and cyclic mechanical stretch regulates the RA synovial hyperplasia.
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