Browsing by Keyword "Physiology (medical)"
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Item 3-Hydroxy-3-methylglutaryl coenzyme a reductase inhibitors decrease Fas ligand expression and cytotoxicity in activated human T lymphocytes(2003-09-23) Blanco-Colio, Luis Miguel; Muñoz-García, Begoña; Martín-Ventura, Jose Luis; Lorz, Corina; Díaz, Cristina; Hernández, Gonzalo; Egido, Jesús; Centros PRE-FUSION TECNALIA - (FORMER)Background-HMG-CoA reductase inhibitors reduce cardiovascular mortality, although the mechanisms of action have not been completely elucidated. The presence of T cells and apoptotic cells in atherosclerotic plaques is well established, the reduction of cellular content being a marker of their vulnerability. One of the main mechanisms of cell death activation is the Fas-Fas ligand (FasL) system. Methods and Results-We studied whether HMG-CoA reductase inhibitors can regulate FasL expression and cytotoxicity in human T cells (Jurkat cells). Activation of Jurkat cells with phorbol esters and ionomycin increased FasL expression, an effect prevented by atorvastatin or simvastatin. Mevalonate and geranylgeranylpyrophosphate but not farnesylpyrophosphate prevented the effect of atorvastatin, indicating that protein geranylation was involved in FasL expression. The C3 exotoxin, which selectively inactivates Rho proteins, also decreased FasL expression on T cells. Overexpression of constitutively active RhoA increased FasL expression in Jurkat cells, and dominant-negative RhoA decreased FasL expression in activated cells, indicating that RhoA is implicated in FasL expression. Atorvastatin also decreased cytotoxic activity of activated Jurkat cells on FasL-sensitive cells. Finally, atorvastatin treatment reduced FasL expression in peripheral blood mononuclear cells and human carotid atherosclerotic plaques. Conclusions-Atorvastatin regulates FasL expression in T cells, probably because of the inhibition of RhoA prenylation. These results provide novel information by which atorvastatin may regulate the cytotoxic activity of T cells and the number of cells in the atherosclerotic plaque.Item Measuring resistance to externally induced movement of the wrist joint in chronic stroke patients using an objective hand-held dynamometer(2023-01) Mahmoud, Wala'; Haugland, Morten; Ramos-Murguialday, Ander; Hultborn, Hans; Ziemann, Ulf; Medical TechnologiesObjective: We evaluated the resistance to externally induced wrist extension in chronic stroke patients. We aimed to objectively measure and distinguish passive (muscle and soft tissue stiffness) and active (spasticity and spastic dystonia) components of the resistance. Methods: We used a hand-held dynamometer, which measures torque, joint movement and electromyography (EMG) simultaneously, to assess the resistance to externally induced wrist extension. Slow and fast stretches were applied to the affected and unaffected wrists in 57 chronic stroke patients (57 ± 11 years). We extracted from the data parameters that represent passive and muscle activity components and assessed the validity, test–retest reliability and the clinical utility of the measurement. Results: The analysis showed (1) a significant difference in the passive and muscle activity components between the affected and unaffected sides; (2) a significant correlation between passive and muscle activity components and the modified Ashworth scale (MAS); (3) a significant difference between the subgroups of patients stratified by the MAS; (4) an excellent intra-rater reliability on each of the passive and muscle activity components with intra-class coefficients between 0.92 and 0.99; (5) and small measurement error. Conclusions: Using a hand-held dynamometer, we were able to objectively measure the resistance to muscle stretch in the wrist joint in chronic stroke patients and discriminate muscle overactivity components from muscle and soft tissue stiffness. We demonstrated validity, test–retest reliability and the clinical utility of the measurement. Significance: Quantification of the different components of resistance to externally induced movement enables the objective evaluation of neurorehabilitation effects in chronic stroke patients.Item Neuromuscular electrical stimulation induced brain patterns to decode motor imagery(2013-09) Vidaurre, C.; Pascual, J.; Ramos-Murguialday, A.; Lorenz, R.; Blankertz, B.; Birbaumer, N.; Müller, K. R.; Medical TechnologiesObjective: Regardless of the paradigm used to implement a brain-computer interface (BCI), all systems suffer from BCI-inefficiency. In the case of patients the inefficiency can be high. Some solutions have been proposed to overcome this problem, however they have not been completely successful yet. Methods: EEG from 10 healthy users was recorded during neuromuscular electrical stimulation (NMES) of hands and feet and during motor imagery (MI) of the same limbs. Features and classifiers were computed using part of these data to decode MI. Results: Offline analyses showed that it was possible to decode MI using a classifier based on afferent patterns induced by NMES and even infer a better model than with MI data. Conclusion: Afferent NMES motor patterns can support the calibration of BCI systems and be used to decode MI. Significance: This finding might be a new way to train sensorimotor rhythm (SMR) based BCI systems for healthy users having difficulties to attain BCI control. It might also be an alternative to train MI-based BCIs for users who cannot perform real movements but have remaining afferents (ALS, stroke patients).Item Relationship between electrocardiogram‐based features and personality traits: Machine learning approach: Machine learning approach(2022-01) Boljanić, Tanja; Miljković, Nadica; Lazarevic, Ljiljana B.; Knezevic, Goran; Milašinović, Goran; SGBackground: Based on the known relationship between the human emotion and standard surface electrocardiogram (ECG), we explored the relationship between features extracted from standard ECG recorded during relaxation and seven personality traits (Honesty/humility, Emotionality, eXtraversion, Agreeableness, Conscientiousness, Openness, and Disintegration) by using the machine learning (ML) approach which learns from the ECG-based features and predicts the appropriate personality trait by adopting an automated software algorithm. Methods: A total of 71 healthy university students participated in the study. For quantification of 62 ECG-based parameters (heart rate variability, as well as temporal and amplitude-based parameters) for each ECG record, we used computation procedures together with publicly available data and code. Among 62 parameters, 34 were segregated into separate features according to their diagnostic relevance in clinical practice. To examine the feature influence on personality trait classification and to perform classification, we used random forest ML algorithm. Results: Classification accuracy when clinically relevant ECG features were employed was high for Disintegration (81.3%) and Honesty/humility (75.0%) and moderate to high for Openness (73.3%) and Conscientiousness (70%), while it was low for Agreeableness (56.3%), eXtraversion (47.1%), and Emotionality (43.8%). When all calculated features were used, the classification accuracies were the same or lower, except for the eXtraversion (52.9%). Correlation analysis for selected features is presented. Conclusions: Results indicate that clinically relevant features might be applicable for personality traits prediction, although no remarkable differences were found among selected groups of parameters. Physiological associations of established relationships should be further explored.Item Surface-distributed low-frequency asynchronous stimulation delays fatigue of stimulated muscles.(2013-12) Maneski, Lana Z.Popović; Malešević, Nebojša M.; Savić, Andrej M.; Keller, Thierry; Popović, Dejan B.; Tecnalia Research & InnovationOne important reason why functional electrical stimulation (FES) has not gained widespread clinical use is the limitation imposed by rapid muscle fatigue due to non-physiological activation of the stimulated muscles. We aimed to show that asynchronous low-pulse-rate (LPR) electrical stimulation applied by multipad surface electrodes greatly postpones the occurrence of muscle fatigue compared with conventional stimulation (high pulse rate, HPR). We compared the produced force vs. time of the forearm muscles responsible for finger flexion in 2 stimulation protocols, LPR (fL = 10 Hz) and HPR (fH = 40 Hz). Results: Surface-distributed low-frequency asynchronous stimulation (sDLFAS) doubles the time interval before the onset of fatigue (104 ± 80%) compared with conventional synchronous stimulation. Combining the performance of multipad electrodes (increased selectivity and facilitated positioning) with sDLFAS (decreased fatigue) can improve many FES applications in both the lower and upper extremities.Item Transition from the locked in to the completely locked-in state: A physiological analysis(2011-05) Murguialday, A. Ramos; Hill, J.; Bensch, M.; Martens, S.; Halder, S.; Nijboer, F.; Schoelkopf, B.; Birbaumer, N.; Gharabaghi, A.; Medical TechnologiesObjective: To clarify the physiological and behavioral boundaries between locked-in (LIS) and the completely locked-in state (CLIS) (no voluntary eye movements, no communication possible) through electrophysiological data and to secure brain-computer-interface (BCI) communication. Methods: Electromyography from facial muscles, external anal sphincter (EAS), electrooculography and electrocorticographic data during different psychophysiological tests were acquired to define electrophysiological differences in an amyotrophic lateral sclerosis (ALS) patient with an intracranially implanted grid of 112 electrodes for nine months while the patient passed from the LIS to the CLIS. Results: At the very end of the LIS there was no facial muscle activity, nor external anal sphincter but eye control. Eye movements were slow and lasted for short periods only. During CLIS event related brain potentials (ERP) to passive limb movements and auditory stimuli were recorded, vibrotactile stimulation of different body parts resulted in no ERP response. Conclusions: The results presented contradict the commonly accepted assumption that the EAS is the last remaining muscle under voluntary control and demonstrate complete loss of eye movements in CLIS. The eye muscle was shown to be the last muscle group under voluntary control. The findings suggest ALS as a multisystem disorder, even affecting afferent sensory pathways. Significance: Auditory and proprioceptive brain-computer-interface (BCI) systems are the only remaining communication channels in CLIS.Item Transitions between repetitive tapping and upper limb freezing show impaired movement-related beta band modulation(2020-10) Scholten, Marlieke; Schoellmann, Anna; Ramos-Murguialday, Ander; López-Larraz, Eduardo; Gharabaghi, Alireza; Weiss, Daniel; Medical TechnologiesObjective: Freezing phenomena in idiopathic Parkinson's disease (PD) constitute an important unaddressed therapeutic need. Changes in cortical neurophysiological signatures may precede a single freezing episode and indicate the evolution of abnormal motor network processes. Here, we hypothesize that the movement-related power modulation in the beta-band observed during regular finger tapping, deteriorates in the transition period before upper limb freezing (ULF). Methods: We analyzed a 36-channel EEG of 13 patients with PD during self-paced repetitive tapping of the right index finger. In offline analysis, we compared the transition period immediately before ULF (‘transition’) with regular tapping regarding movement-related power modulation and interregional phase synchronization. Results: From time-frequency analyses, we observed that the tap cycle related beta-band power modulation over the left sensorimotor area was diminished in the transition period before ULF. Furthermore, increased beta-band power was observed in the transition period compared to regular tapping centered over the left centro-parietal and right frontal areas. Phase synchronization between the left fronto-parietal areas and the left sensorimotor area was elevated during transition compared to regular tapping. Conclusion: Together, these results indicate that diminished beta band power modulation and increased phase synchronization precede ULF. Significance: We demonstrate that pathological cortical motor processing is present in the transition phase from regular tapping to an ULF episode.