Modified thalamocortical model: A step towards more understanding of the functional contribution of astrocytes to epilepsy

It is evident that the cortex plays a primary role in seizure generation. At the same time, various experimental results clearly confirm that thalamic neurons are also actively involved in seizure generation and spreading. On the other hand, recent neurophysiologic findings suggest that astrocytes regulate dynamically the synaptic activity in neuronal networks. Therefore, in the present study, the thalamocortical neural population model (TCPM) is modified by embedding into the model the functional role of astrocytes in the regulation of synaptic transmission. Using the modified TCPM (MTCPM) we examined the hypothesis that one of the possible causes of neural hypersynchronization is the dysfunction of astrocytes in the regulatory feedback loop. Then, two MTCPMs are coupled via excitatory synapses and the astrocytes are also coupled together through gap junctions. Utilizing the MTCPM and CMTCPM, the transition from normal to malfunctioned states is analyzed using a dynamical system approach. In this way, the hypothesis is investigated and it is demonstrated that the healthy astrocytes provide feedback control to regulate neural activity. That is, the astrocytes compensate to a large extent variations in the coupling between neural populations and maintain the balance between the excitation and inhibition levels. However, the malfunctioned astrocytes are no longer able to regulate and/or compensate the excessive increase of the inter-population coupling strength. As a consequence, disruption of the signaling function of astrocytes could contribute to the neuronal hyperexcitability and generating epileptiform activity. These results suggest that astrocytes might be one of the potential targets for the treatment of epilepsy.     

Analyses of Arabidopsis trr14 T-DNA Insertion Mutants Reveal an Essential Role in Seed Germination

TRR14 is an unknown protein that was first identified as a component of Arabidopsis responses to trehalose treatment. Phylogenic analysis showed that TRR14 belongs to a seven-gene family in Arabidopsis. Close homologues of TRR14 were found in plants and many cyanobacteria. GFP expression analysis showed that TRR14 is located in the chloroplast. GUS::TRR14 expression was found in leaves, flowers, stems and siliques. We investigated the functional roles of TRR14 in Arabidopsis thaliana under salt and drought stress. By a reverse genetic approach, two trr14 T-DNA insertion mutants were isolated from the SALK collection. Functional analysis of the trr14 mutants revealed enhanced sensitivity of the mutants to salt and drought stress, compared with the wild type plants. Further experiments indicated that the trr14 mutants have reduced seed germination, root length, survival rate and chlorophyll content under stress conditions. In addition activity of oxidative enzymes like peroxidase, catalase and polyphenol oxidase was reduced under salt and drought treatments. Thus, the present data indicate that a novel protein, TRR14, is involved in plant salt and drought tolerance.     

Phototaxis and impaired motility in adenylyl cyclase and cyclase receptor protein mutants of Synechocystis sp. strain PCC 6803

We have carefully characterized and reexamined the motility and phototactic responses of Synechocystis sp. adenylyl cyclase (Cya1) and catabolite activator protein (SYCRP1) mutants to different light regimens, glucose, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and cyclic AMP. We find that contrary to earlier reports, cya1 and sycrp1 mutants are motile and phototactic but are impaired in one particular phase of phototaxis in comparison with wild-type Synechocystis sp.     

Vascular wall resident progenitor cells: a source for postnatal vasculogenesis

Here, we report the existence of endothelial precursor (EPC) and stem cells in a distinct zone of the vascular wall that are capable to differentiate into mature endothelial cells, hematopoietic and local immune cells, such as macrophages. This zone has been identified to be localized between smooth muscle and adventitial layer of human adult vascular wall. It predominantly contains CD34-positive (+) but CD31-negative (-) cells, which also express VEGFR2 and TIE2. Only few cells in this zone of the vascular wall are positive for CD45. In a ring assay using the fragments of human internal thoracic artery (HITA), we show here that the CD34+ cells of the HITA-wall form capillary sprouts ex vivo and are apparently recruited for capillary formation by tumor cells. New vessels formed by these vascular wall resident EPCs express markers for angiogenically activated endothelial cells, such as CEACAM1, and also for mature endothelial cells, such as VE-cadherin or occludin. Vascular wall areas containing EPCs are found in large and middle sized arteries and veins of all organs studied here. These data suggest the existence of a ;vasculogenic zone' in the wall of adult human blood vessels, which may serve as a source for progenitor cells for postnatal vasculogenesis, contributing to tumor vascularization and local immune response.     

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).     

Discovery of potent inhibitors of interleukin-2 inducible T-cell kinase (ITK) through structure-based drug design

Interleukin-2 inducible T-cell kinase (ITK) is a member of the Tec kinase family and is involved with T-cell activation and proliferation. Due to its critical role in acting as a modulator of T-cells, ITK inhibitors could provide a novel route to anti-inflammatory therapy. This work describes the discovery of ITK inhibitors through structure-based design where high-resolution crystal structural information was used to optimize interactions within the kinase specificity pocket of the enzyme to improve both potency and selectivity.     

Evaluation of antioxidant properties and total phenolic contents of some strains of microalgae

Antioxidant activities of both cells and extracellular substances were evaluated in 12 soil-isolated strains of microalgae according to FRAP and DPPH-HPLC assays. Their total phenolic contents were also determined by Folin–Ciocalteu method. Extractions were performed with hexane, ethyl acetate, and water. The results of FRAP assay showed that algal cells contained considerable amounts of antioxidants from 0.56 ± 0.06 to 31.06 ± 4.00 μmol Trolox g⁻¹ for Microchaete tenera hexane extract and Chlorella vulgaris water extract, respectively. In water fractions of extracellular substances, the antioxidants were from 1.30 ± 0.15 μmol Trolox g⁻¹ for Fischerella musicola to 73.20 ± 0.16 μmol Trolox g⁻¹ for Fischerella ambigua. Also, DPPH-HPLC assay represented high antioxidant potential of water fractions. The measured radical-scavenging activities of the studied microalgae were at least 0.15 ± 0.02 in Nostoc ellipsosporum cell mass to a maximum of 109.02 ± 8.25 in C. vulgaris extracellular substance. The amount of total phenolic contents varied in different strains of microalgae and ranged from zero in hexane extract to 19.15 ± 0.04 mg GAE g⁻¹ in C. vulgaris extracellular water fraction. Significant correlation coefficients between two measured parameters indicated that phenolic compounds were a major contributor to the microalgal antioxidant capacities.     

Interactions between the human sweet-sensing T1R2-T1R3 receptor and sweeteners detected by saturation transfer difference NMR spectroscopy

The sweet receptor is a member of the G-protein coupled receptor family C that detects a wide variety of chemically and structurally diverse sweet-tasting molecules. We recently used saturation transfer difference spectroscopy (STD) to monitor the direct binding of a set of sweet agonists and antagonists to the human taste receptor in membranes prepared from human embryonic kidney (HEK293) cells transfected with and expressing the sweet receptor [F.M. Assadi-Porter, M. Tonelli, E. Maillet, K. Hallenga, O. Benard, M. Max, J.L. Markley, J. Am. Chem. Soc. 130 (2008) 7212-7213]. Here we review this work and related studies, discuss the procedures involved, and expand on their potential for identifying specific binding interactions of ligands to the membrane spanning and extracellular regions of the full heterodimeric sweet taste receptor. Whereas activity assays are unable to distinguish mutations that alter ligand-binding sites from those that alter signal transduction downstream of the binding site, STD NMR now allows us to make this distinction.     

Quantitation of sorafenib and its active metabolite sorafenib N-oxide in human plasma by liquid chromatography–tandem mass spectrometry

A simple and rapid method with high performance liquid chromatography/tandem mass spectrometry is described for the quantitation of the kinase inhibitor sorafenib and its active metabolite sorafenib N-oxide in human plasma. A protein precipitation extraction procedure was applied to 50 μL of plasma. Chromatographic separation of the two analytes, and the internal standard [²H₃¹³C]-sorafenib, was achieved on a C₁₈ analytical column and isocratic flow at 0.3 mL/min for 4 min. Mean within-run and between-run precision for all analytes were <6.9% and accuracy was <5.3%. Calibration curves were linear over the concentration range of 50–10,000 ng/mL for sorafenib and 10–2500 ng/mL for sorafenib N-oxide. This method allows a specific, sensitive, and reliable determination of the kinase inhibitor sorafenib and its active metabolite sorafenib N-oxide in human plasma in a single analytical run.