Entropy and Entropic Forces to Model Biological Fluids.

Living cells are complex systems characterized by fluids crowded by hundreds of different elements, including, in particular, a high density of polymers. They are an excellent and challenging laboratory to study exotic emerging physical phenomena, where entropic forces emerge from the organization processes of many-body interactions. The competition between microscopic and entropic forces may generate complex behaviors, such as phase transitions, which living cells may use to accomplish their functions. In the era of big data, where biological information abounds, but general principles and precise understanding of the microscopic interactions is scarce, entropy methods may offer significant information. In this work, we developed a model where a complex thermodynamic equilibrium resulted from the competition between an effective electrostatic short-range interaction and the entropic forces emerging in a fluid crowded by different sized polymers. The target audience for this article are interdisciplinary researchers in complex systems, particularly in thermodynamics and biophysics modeling.

Joint amplitude MEMS based measurement platform for low cost and high accessibility telerehabilitation: Elbow case study.

This paper, presents an inertial and magnetic sensor based technological platform, intended for articular amplitude monitoring and telerehabilitation processes considering an efficient cost/technical considerations compromise. The particularities of our platform offer possibilities of a high social impact by making telerehabilitation accessible to large population sectors in marginal socio-economic sectors, especially in underdeveloped countries where, in contrast to developed countries, specialists are scarce and high technology is not available or inexistent. This platform integrates high resolution low cost inertial and magnetic sensors with adequate user interfaces and communication protocols to perform a diagnostic service through the web, or other available communication networks. Elbow amplitude information is generated by sensors and then transferred to a computing device with adequate interfaces to make it accessible to inexperienced personnel, providing a high social value at a low cost. Experimental methodology includes two different sets of tests: the first one uses flexion - extension movements on a robotic arm to validate our platform (IMOCAP) articular amplitude measurements, against the robotic positioning system. The second set of tests was carried out on human patients to test IMOCAP in real operational conditions; results were validated with an optical positioning system. This paper presents experimental results showing the platform applicability to telerehabilitation processes.

Non-linear EEG analyses predict non-response to rTMS treatment in major depressive disorder.

OBJECTIVE: Several linear electroencephalographic (EEG) measures at baseline have been demonstrated to be associated with treatment outcome after antidepressant treatment. In this study we investigated the added value of non-linear EEG metrics in the alpha band in predicting treatment outcome to repetitive transcranial magnetic stimulation (rTMS). METHODS: Subjects were 90 patients with major depressive disorder (MDD) and a group of 17 healthy controls (HC). MDD patients were treated with rTMS and psychotherapy for on average 21 sessions. Three non-linear EEG metrics (Lempel-Ziv Complexity (LZC); False Nearest Neighbors and Largest Lyapunov Exponent) were applied to the alpha band (7-13 Hz) for two 1-min epochs EEG and the association with treatment outcome was investigated. RESULTS: No differences were found between a subgroup of unmedicated MDD patients and the HC. Non-responders showed a significant decrease in LZC from minute 1 to minute 2, whereas the responders and HC showed an increase in LZC. CONCLUSIONS: There is no difference in EEG complexity between MDD and HC and the change in LZC across time demonstrated value in predicting outcome to rTMS. SIGNIFICANCE: This is the first study demonstrating utility of non-linear EEG metrics in predicting treatment outcome in MDD.

Common functional polymorphisms in SLC6A4 and COMT genes are associated with circadian phenotypes in a South American sample.

The molecular study of circadian rhythms in humans could be an excellent approach to understand the relation between genes and behavior. It is possible that variations in genes involved in neurotransmission and/or synaptic plasticity, such as catechol-O-methyltransferase (COMT) and serotonin transporter (SLC6A4) could be of particular interest in understanding human circadian phenotypes. The aim of this study is to analyze the possible and novel associations of the functional polymorphisms in COMT and SLC6A4 genes (Val158Met and 5-HTTLPR) and circadian phenotypes in healthy Colombian subjects. 191 university students were genotyped for two functional polymorphisms in COMT and SLC6A4 genes (rs4680 and rs4795541). We applied two scales to measure phenotypic patterns of human circadian rhythms: Composite Scale of Morningness (CSM) and Epworth Sleepiness Scale (ESS). We found a significant association between 5-HTTLPR polymorphism and morning preference score (CSM) (p = 0.027) using an overdominant genotypic model and association of COMT Val158Met with daytime sleepiness (ESS scores) (p = 0.038) in a genotypic recessive model. These results were supported by differences in genotype frequencies between circadian typologies for SLC6A4 gene (p = 0.007) and categories of diurnal sleepiness for COMT gene (p = 0.032). Our results suggest, for the first time, a significant relationship between functional SLC6A4 and COMT polymorphisms with specific human circadian phenotypes: morning preference and diurnal sleepiness. These results need to be replicated in other populations. Further study of functional polymorphisms in other synaptic genes could be of relevance for the identification of novel candidate genes for circadian phenotypes, and related endophenotypes of neuropsychiatric importance, in healthy humans.

A novel association of two non-synonymous polymorphisms in PER2 and PER3 genes with specific diurnal preference subscales.

The circadian system is responsible for the generation and maintenance of physiological and behavioral rhythms in mammals and allows synchronization with the environment. Different polymorphisms in clock genes have been studied in healthy humans, providing inconsistent results in different populations. In this study, we evaluated the possibility that two non-synonymous polymorphisms in PER2 (p.Gly1244Glu, rs934945) and PER3 (p.Met1028Thr, rs2640909) genes might be associated with diurnal preference in healthy Colombian subjects. A total of 209 Colombian university students were genotyped for two functional polymorphisms in PER2 and PER3 genes (rs934945 and rs2640909). We applied the composite scale of morningness (CSM) to measure phenotypic patterns of human diurnal preference. Additionally, we extracted from the CSM three subscale scores ("morningness", "activity planning" and "morning alertness"). We used a false discovery rate approach (q values) for correction of multiple testing. PER2 (rs934945) showed a significant association with two CSM subscale scores: "activity planning" and "morning alertness". For PER3 (rs2640909), we observed an association with the "morningness" CSM subscale scores. We found a significant association between novel and functional polymorphisms in PER2 and PER3 genes with specific CSM subscales for diurnal preference. We showed for the first time the association of rs934945 with "morning alertness" and rs2640909 with "morningness". We suggest that these results should be replicated in order to confirm the association in other populations. Finally, the study of additional novel functional polymorphisms in other clock genes could be of relevance for a deep understanding of circadian phenotypes and neuropsychiatric disorders.