MODEM: a multi-agent hierarchical structure to model the human motor control system

In this study, based on behavioral and neurophysiological facts, a new hierarchical multi-agent architecture is proposed to model the human motor control system. Performance of the proposed structure is investigated by simulating the control of sit to stand movement. To develop the model, concepts of mixture of experts, modular structure, and some aspects of equilibrium point hypothesis were brought together. We have called this architecture MODularized Experts Model (MODEM). Human motor system is modeled at the joint torque level and the role of the muscles has been embedded in the function of the joint compliance characteristics. The input to the motor system, i.e., the central command, is the reciprocal command. At the lower level, there are several experts to generate the central command to control the task according to the details of the movement. The number of experts depends on the task to be performed. At the higher level, a “gate selector” block selects the suitable subordinate expert considering the context of the task. Each expert consists of a main controller and a predictor as well as several auxiliary modules. The main controller of an expert learns to control the performance of a given task by generating appropriate central commands under given conditions and/or constraints. The auxiliary modules of this expert learn to scrutinize the generated central command by the main controller. Auxiliary modules increase their intervention to correct the central command if the movement error is increased due to an external disturbance. Each auxiliary module acts autonomously and can be interpreted as an agent. Each agent is responsible for one joint and, therefore, the number of the agents of each expert is equal to the number of joints. Our results indicate that this architecture is robust against external disturbances, signal-dependent noise in sensory information, and changes in the environment. We also discuss the neurophysiological and behavioral basis of the proposed model (MODEM).     

Comparative Evaluation of α-Amylase Refolding Through Two Different Artificial Chaperone Systems

Two different artificial chaperone systems were evaluated in this work using either detergents or CDs as the stripping agents. Upon dilution of urea-denatured α-amylase to a non-denaturing urea concentration in the presence of the capturing agent, complexes of the detergent and non-native protein molecules are formed and thereby the formation of protein aggregates is prevented. The so-called captured protein is unable to refold from the detergent-protein complex states unless a stripping agent is used to remove the detergent molecules. Our results by fluorescence, UV, turbidity measurement, circular dichroism, surface tension and activity assay indicated that the extent of refolding assistance was different due to different inter- and intra- molecular interactions in the two different systems. However, the high activity recovery in the presence of detergents, as the stripping agent, suggests that they can constitute suitable replacement for the more expensive and common stripping agent of cyclodextrins.     

A modified particle swarm optimization algorithm for parameter estimation of a biological system

Background

Mathematical modeling has achieved a broad interest in the field of biology. These models represent the associations among the metabolism of the biological phenomenon with some mathematical equations such that the observed time course profile of the biological data fits the model. However, the estimation of the unknown parameters of the model is a challenging task. Many algorithms have been developed for parameter estimation, but none of them is entirely capable of finding the best solution. The purpose of this paper is to develop a method for precise estimation of parameters of a biological model.

Methods

In this paper, a novel particle swarm optimization algorithm based on a decomposition technique is developed. Then, its root mean square error is compared with simple particle swarm optimization, Iterative Unscented Kalman Filter and Simulated Annealing algorithms for two different simulation scenarios and a real data set related to the metabolism of CAD system.

Results

Our proposed algorithm results in 54.39% and 26.72% average reduction in root mean square error when applied to the simulation and experimental data, respectively.

Conclusion

The results show that the metaheuristic approaches such as the proposed method are very wise choices for finding the solution of nonlinear problems with many unknown parameters.

     

Effect of Molybdenum Nanoparticles on Blood Cells,Liver Enzymes,and Sexual Hormones in Male Rats

Despite an increasing surge in application of nanoparticles in industries, there is a serious lack of information concerning their impact on human health and the environment. The present study investigated effects of molybdenum nanoparticles (Mo NPs) injected intraperitoneally into Sprague-Dawley rats at different doses of Mo NPs (5, 10, and 15 mg/kg BW per day) during a period of 28 days. Hematological and biochemical parameters as well as sexual hormones and histopathological examinations of the liver and testis were assessed and compared with control group. The results showed that the serum levels of testosterone decreased significantly in both groups of 10 and 15 mg (Mo NPs)/kg BW in comparison with the control group (p < 0.05). However, there were insignificant differences observed in luteinizing hormone (LH) levels and hematological parameters when compared with the control group (p > 0.05). The results of liver enzymes showed that serum levels of aspartate aminotransferase (AST) decreased significantly in both dosage groups of 5 and 10 mg/kg BW (Mo NPs) when compared with the control group (p < 0.05), and significant decrease obtained in lactate dehydrogenase (LDH) levels at dose of 5 mg/kg BW in comparison with the control group (p < 0.05). The histopathological examination of testis showed a decrease in number of Leydig cells. Also, the number of chronic inflammatory cells increased in portal triad and parenchyma in liver tissue of rats exposed to Mo NPs.     

Administration of the Glial Condition Medium in the Nucleus Accumbens Prolong Maintenance and Intensify Reinstatement of Morphine-Seeking Behavior

Accumulating evidence suggested that glial cells are involved in synaptic plasticity and behavioral changes induced by drugs abuse. The role of these cells in maintenance and reinstatement of morphine (MRP) conditioned place preference (CPP) remains poorly characterized. The aim of present study was to investigate the direct role of glial cells in nucleus accumbens (NAc) in the maintenance and reinstatement of MRP-seeking behavior. CPP induced with injection of MRP (5 mg/kg, s.c. for 3 days), lasted for 7 days after cessation of MRP treatment and priming dose of MRP (1 mg/kg, s.c.) reinstated the extinguished MRP-induced CPP. The astrocyte-conditioned medium (ACM) and neuroglia conditioned medium (NCM) exposed to MRP (10 and 100 µM) have been microinjected into the NAc. Intra-NAc administration of ACM during extinction period failed to change the maintenance of MRP-CPP, but MRP 100-treated ACM could slightly increase the magnitude of reinstatement. In contrast to ACM, intra-NAc administration of MRP 100-treated NCM caused slower extinction by 3 days and significantly increased the magnitude of reinstatement. Our findings suggest the involvement of glial cells activation in the maintenance and reinstatement of MRP-seeking behaviors, and provides new evidence that these cells might be a potential target for the treatment of MRP addiction.

     

Persons with Haemophilia in Sweden- Experiences and Strategies in Everyday Life. A Single Centre Study

Introduction/Aim

Haemophilia is caused by deficiency in coagulation factor VIII or IX. Treatment with the missing coagulation factors has been available in most developed countries for several decades. The aim was to explore the experiences of adults living with severe or moderate haemophilia and their coping strategies at a single centre in Sweden.

Method

The interview study had a qualitative empirical approach and was analyzed on the basis of the method empirical phenomenological psychology. The sample included 14 participants, mean age 42 (19–80 y), who met the inclusion criteria and to saturation of information. Results: General characteristics were; All were satisfied with and grateful for access to medication. An acceptance of the disorder and willingness to live a normal life was identified among all participants. They were all content with the care provided by Haemophilia Treatment Centre (HTC) and felt supported by its multidisciplinary team. Four typologies were identified; Protective adults and assertive children during up-bringing, finding a role in social context, symptoms and treatments, fear of limited resources in the future. Task-, emotional- and avoidance coping strategies were seen in the interviews. The most prominent coping strategy was task oriented.

Conclusion

This interview study with Swedish PWH shows that they strive for normality and adaptation in social activities throughout life finding their own niche. The PWH expressed the importance of knowledge and support from the comprehensive medical team at HTC and therefore it seems important to continue comprehensive medical care at HTC in order to follow-up the haemophilia persons regularly.