Cortical potential imaging using L-curve and GCV method to choose the regularisation parameter

Background

The electroencephalography (EEG) is an attractive and a simple technique to measure the brain activity. It is attractive due its excellent temporal resolution and simple due to its non-invasiveness and sensor design. However, the spatial resolution of EEG is reduced due to the low conducting skull. In this paper, we compute the potential distribution over the closed surface covering the brain (cortex) from the EEG scalp potential. We compare two methods – L-curve and generalised cross validation (GCV) used to obtain the regularisation parameter and also investigate the feasibility in applying such techniques to N170 component of the visually evoked potential (VEP) data.

Methods

Using the image data set of the visible human man (VHM), a finite difference method (FDM) model of the head was constructed. The EEG dataset (256-channel) used was the N170 component of the VEP. A forward transfer matrix relating the cortical potential to the scalp potential was obtained. Using Tikhonov regularisation, the potential distribution over the cortex was obtained.

Results

The cortical potential distribution for three subjects was solved using both L-curve and GCV method. A total of 18 cortical potential distributions were obtained (3 subjects with three stimuli each – fearful face, neutral face, control objects).

Conclusions

The GCV method is a more robust method compared to L-curve to find the optimal regularisation parameter. Cortical potential imaging is a reliable method to obtain the potential distribution over cortex for VEP data.

     

Specific immunotherapy of experimental myasthenia gravis in vitro: the "guided missile" strategy

We describe a strategy for specific immunotherapy of myasthenia gravis (MG) based on genetic engineering of antigen presenting cells (APCs) to present the autoantigen acetylcholine receptor (AChR) and express the "warhead" Fas ligand (FasL). For transduction of APCs we prepared recombinant attenuated vaccinia virus vectors carrying the following three gene constructs: (i) AChR fused to LAMP1 to present AChR and target AChR-specific T cells; (ii) FasL to eliminate the targeted T cells; and (iii) truncated FADD to protect APCs from self-destruction by FasL. The engineered APCs effectively expressed the genes of interest and killed AChR-specific T cells in culture by the Fas/FasL pathway. T cells specific for an unrelated antigen were spared. Our in vitro demonstration that engineered APCs target and kill antigen-specific T cells represents a promising novel strategy for specific immunotherapy of MG and other autoimmune diseases.     

Gene transfer of baculoviral p35 by adenoviral vector protects human cerebral neurons from apoptosis

Apoptosis plays an important role in neuronal cell death in both chronic and acute human neurological diseases, including ALS, Huntington's disease, cerebral ischemia, and HIV encephalopathy. We evaluated the ability of an extremely powerful antiapoptotic agent, baculoviral p35, to prevent apoptosis and cell death of human cerebral neurons that undergo severe neurotoxic changes in a culture system when treated with agents that are implicated in human neurological disorders, that is, tumor necrosis factor (TNFalpha) and the HIV proteins Tat and gp120. P35 is a potent broad-spectrum antiapoptotic protein derived from baculovirus, that inhibits nearly all caspases, and has other antiapoptotic actions as well. Adenoviral vectors expressing p35 (Ad. p35) or a control gene (lacZ) efficiently transduced human neurons. Treatment of control cultures with the toxic agents TNFalpha, TNFalpha plus Actinomycin D, or Tat and gp120, induced neurotoxicity and death of neurons. Transduction of neurons with Ad. p35 blocked apoptosis, and eliminated cell death due to TNFalpha, or Tat and gp120. Viral vector transfer of the p35 gene efficiently protects human neurons from TNFalpha, or Tat and gp120-induced apoptosis and cell death. These results suggest that p35 transduction of neurons by viral vectors could be therapeutically useful in the treatment of human neurodegenerative diseases.     

Nonglutamate pore residues in ion selection and conduction in voltage-gated Ca(2+) channels

High-affinity, intrapore binding of Ca(2+) over competing ions is the essential feature in the ion selectivity mechanism of voltage-gated Ca(2+) channels. At the same time, several million Ca(2+) ions can travel each second through the pore of a single open Ca(2+) channel. How such high Ca(2+) flux is achieved in the face of tight Ca(2+) binding is a current area of inquiry, particularly from a structural point of view. The ion selectivity locus comprises four glutamate residues within the channel's pore. These glutamates make unequal contributions to Ca(2+) binding, underscoring a role for neighboring residues in pore function. By comparing two Ca(2+) channels (the L-type alpha(1C), and the non-L-type alpha(1A)) that differ in their pore properties but only differ at a single amino acid position near the selectivity locus, we have identified the amino-terminal neighbor of the glutamate residue in motif III as a determinant of pore function. This position is more important in the function of alpha(1C) channels than in alpha(1A) channels. For a systematic series of mutations at this pore position in alpha(1C), both unitary Ba(2+) conductance and Cd(2+) block of Ba(2+) current varied with residue volume. Pore mutations designed to make alpha(1C) more like alpha(1A) and vice versa revealed that relative selectivity for Ba(2+) over K(+) depended almost solely on pore sequence and not channel type. Analysis of thermodynamic mutant cycles indicates that the motif III neighbor normally interacts in a cooperative fashion with the locus, molding the functional behavior of the pore.     

The soluble sema domain of the RON receptor inhibits macrophage-stimulating protein-induced receptor activation

RON is a receptor tyrosine kinase of the MET family that is involved in cell proliferation, cell survival, and cell motility in both normal and disease states. Macrophage-stimulating protein (MSP) is the RON ligand whose binding to RON causes receptor activation. RON is a trans-membrane heterodimer comprised of one alpha- and one beta-chain originating from a single-chain precursor and held together by several disulfide bonds. The intracellular part of RON contains the kinase domain and regulatory elements. The extracellular region is characterized by the presence of a sema domain (a stretch of approximately 500 amino acids with several highly conserved cysteine residues), a PSI (plexin, semaphorins, integrins) domain, and four immunoglobulin-like folds. Here we show that a soluble, secreted molecule representing the sema domain of RON (referred to as ron-sema) has a dominant negative effect on the ligand-induced receptor activation and is capable of inhibiting RON-dependent signaling pathways and cellular responses. Results suggest that the sema domain of RON participates in ligand binding by the full-length receptor. The ability of ron-sema to suppress growth of MSP-responsive cells in culture, including cancer cells, points to a potential therapeutic use of this molecule, and forced expression of it could potentially be used as a gene therapy tool for treating MSP-dependent types of cancer.     

Combined prime-boost vaccination against tick-borne encephalitis (TBE) using a recombinant vaccinia virus and a bacterial plasmid both expressing TBE virus non-structural NS1 protein

Background  

Heterologous prime-boost immunization protocols using different gene expression systems have proven to be successful tools in protecting against various diseases in experimental animal models. The main reason for using this approach is to exploit the ability of expression cassettes to prime or boost the immune system in different ways during vaccination procedures. The purpose of the project was to study the ability of recombinant vaccinia virus (VV) and bacterial plasmid, both carrying the NS1 gene from tick-borne encephalitis (TBE) virus under the control of different promoters, to protect mice against lethal challenge using a heterologous prime-boost vaccination protocol.     

Correcting effect of the locus coeruleus on ophthalmic hypertension of the hypothalamic genesis

We studied the intraocular pressure and the humor aquosus volume changes after a chronic emotional stress produced by a prolonged electrical stimulation of the multiple ventromedial (VMHN) hypothalamic nuclei and the locus coeruleus. The VMHN stimulation caused an increase in the intraocular pressure and production of the humor aquosus, as well as a decrease in the outflow ratio. Stimulation of the locus coeruleus increased the intraocular pressure to a lesser extent. A combined effect of both types of stimulation normalised the intraocular pressure due to a decrease in the humor aquosus production, the outflow ratio remaining unchanged.     

Activation of morphogenesis and proliferation by low specificity chemical effectors

Activation of highly specific biochemical processes by simple chemical agents is demonstrated for morphogenesis (anlage and development of female gametophyte in cereal) and mitosis (in cell cultures and animal and plant tissues). The effects of these agents are tissue-specific. Structure--activity relationship is analyzed in this group of compounds. Thus, the phenomenon reveals the exact pathways of the influence of allelopathic and anthropogenic chemical agents on evolution of plant biocenoses.