Early morphological and functional changes in the GABAergic system of hippocampus in the rat lithium-pilocarpine model of epilepsy

We studied early alterations in the GABAergic system of the rat hippocampus in the lithium–pilocarpine model of epilepsy. Twenty-four hours after the pilocarpine treatment, a decrease in the number of calretinin-positive interneurons was observed in the CA1 field of the hippocampus, whereas the number of parvalbumin-positive interneurons remained unchanged. The decreased levels of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD67) and the membrane GABA transporter GAT1 were revealed using Western blot analysis. These data indicate an altered excitation/inhibition balance in the hippocampus with excitation dominance.     

The imidazoline RX871024 stimulates insulin secretion in pancreatic beta-cells from mice deficient in K(ATP) channel function.

Effects of the imidazoline compound RX871024 on cytosolic free Ca(2+) concentration ([Ca(2+)]i) and insulin secretion in pancreatic beta-cells from SUR1 deficient mice have been studied. In beta-cells from wild-type mice RX871024 increased [Ca(2+)]i by blocking ATP-dependent K(+)-current (K(ATP)) and inducing membrane depolarization. In beta-cells lacking a component of the K(ATP)-channel, SUR1 subunit, RX871024 failed to increase [Ca(2+)]i. However, insulin secretion in these cells was strongly stimulated by the imidazoline. Thus, a major component of the insulinotropic activity of RX871024 is stimulation of insulin exocytosis independently from changes in K(ATP)-current and [Ca(2+)]i. This means that effects of RX871024 on insulin exocytosis are partly mediated by interaction with proteins distinct from those composing the K(ATP)-channel.     

Stress protein of cyanobacteria CP36: interaction with photoactive complexes and formation of supramolecular structures

Cyanobacterium Anacystis nidulans R2, Synechocystis sp. PCC 6803 (wild-type strain and mutants Delta2 and Delta3 lacking PSII and PSI, respectively), and Synechocystis sp. BO 9201 synthesize the pigment--protein complex CP36 (CPIV-4, CP43') under iron deficiency in the medium. Accumulation of CP36 is accompanied by structural reorganizations in the photosynthetic membranes. Integrating mean times of excitation relaxation (quenching) are 2.2 nsec (CP36), 1 nsec (PSI), and 420 psec (PSII in Fm state). The energy migration between CP36 and the photosystems can be described by a model of a one-layer ring of CP36 around core-complexes. The excitation from CP36 to PSI is transferred within <10 psec. The energy transfer from CP36 to PSII occurs during 170 psec. Cells with low content of CP36 probably contain only a latent fraction of unbound to phycobilisomes PSII which is the analog of PSIIbeta of higher plants. In PSI there are four binding sites for CP36 monomers per RC. PSII can bind up to 32 molecules of CP36 per RC. Cells with a large amount of CP36 contain monomer form of PSII core-complex which can bind eight tetramers of CP36 (8 binding sites). In conditions of iron deficiency only one monomer of a dimer PSII core-complex is destroyed and released chlorophyll is accumulated in CP36. Accumulation of CP36 in A. nidulans cells can be accompanied by membrane stacking which is similar to the stacking in chlorophyll b-containing organisms. The stacking can occur in the region of localization of PSII latent fraction bound to CP36. The membrane stacking shields PSII stromal surfaces from the aqueous phase for activation of electron transfer on the acceptor side of PSII.     

Atomic force microscopy-based single virus particle spectroscopy

Atomic force microscopy-based single virus particle force spectroscopy was developed using dielectrophoresis for fixing virions at the tip of an atomic force microscope (AFM) probe. Electron microscopic visualization was found to be necessary to prove the deposition of virus particles on the tip of the AFM probe, while fixation of single virions by incubating the tip with a virus suspension proved impossible. Force spectroscopy measurements were performed for the vaccinia virus, influenza virus, and bacteriophage AP22. ForceReader special software was designed for analyzing the force–distance curves.     

Structural appearance of linker histone H1/siRNA complexes

Efficient non-viral vectors for the in vivo siRNA transfer are still being searched for. Comparing the differences of the structural appearance of siRNA and pDNA one would assume differences in the assembling behaviour between these polyanions when using polycationic vectors such as nuclear proteins. The spontaneous assembly of nuclear proteins such as histone H1 (H1) with pDNA as polyanion which has intensively been investigated over the last decade, showed a particulate structure of the resulting complexes. For an efficient in vivo use small almost monomolecular structures are searched for. Using siRNA as the polyanion might enforce this structural prerequisite lacking unwanted aggregation processes, exploiting the molecular size of siRNA. We therefore investigated the structure of H1/siRNA complexes. Five commonly used methods characterizing the resulting assemblies such as retardation gels, static and dynamic light scattering, reduction of ethidium bromide fluorescence, analytical ultracentrifugation, and electron microscopy were used. From analytical ultracentrifugation we learned that under physiological salt conditions the siRNA-H1 binding was not cooperative, even though the gel analysis showed disproportionation which would be an indication for a cooperative binding mode. H1 formed very small and stable complexes with siRNA at a molar ratio of 1:1 and 1:2. In order to find out if the observed structural appearance of the H1/siRNA complexes is due to unspecific charge effects only or to special features of H1, polylysine was included in the study. Low molecular weight polylysine (K₁₆) showed also non-cooperative binding with siRNA.     

Study of soft X-ray emission from Z-pinches with a complex atomic composition

Results are presented from experimental studies of Z-pinches produced by implosion of aluminum and tungsten cylindrical wire arrays in the Angara-5-1 facility. The electron temperature T _e and density n _e of the high-temperature pinch plasma have been determined by analyzing line emission from multicharged ions. For the same mass and radius of the array and the same number of wires in it, the intensity of line emission of H- and He-like Al ions from an imploded Al + W wire array containing even a small amount of tungsten (7 wt %) is one order of magnitude lower than that from an Al array. As the W content increases, the total soft X-ray (SXR) yield increases, while the duration of the SXR pulse decreases. For the 30% W content in the array, the power and duration of the SXR pulse are nearly the same as those recorded during the implosion of a W array with the same linear mass and radius and the same number of wires. Results are also presented from experiments with nested wire arrays in which the outer and inner shells were made of Al and W wires, respectively. It is found that, in this case, the effect of tungsten on the line emission of aluminum is much weaker than that in experiments with arrays in which tungsten and aluminum wires were placed in the same shell, even if the mass of the inner (tungsten) shell was larger than that of the outer (aluminum) one. At the same time, the inner W shell plays a significant role in the implosion dynamics of a nested wire array, reducing the duration of the SXR pulse and increasing the SXR power.     

Immunophenotypic peculiarities of mobilized stem (CD34+) cells in blood from patients with severe spinal cord injury

Immunophenotype of mobilized stem blood cells (CD34+) was studied in 29 patients with late post-traumatic spinal lesions. The CD34+ cells demonstrated different levels of expression of CD45, CD38, monomorphic determinants HLA-DR and gp130 epitopes. Most patients presented with a CD34+ cell fraction with no or low expression of common leukocytic antigen CD45. Only 2 patients had greater than 15 percent of HLA-DR-CD38- cells in the CD34+ fraction. A common transducer molecule of interleukin-6 family cytokines gp130 was expressed on stem (CD34+) cells in all the cases, 26 percent of the patients had an activated gp130 phenotype, i.e. a combination of C7+ and A1- epitopes.     

X-ray structural studies of the fungal laccase from Cerrena maxima

Laccases are members of the blue multi-copper oxidase family. These enzymes oxidize substrate molecules by accepting electrons at a mononuclear copper centre and transferring them to a trinuclear centre. Dioxygen binds to the trinuclear centre and following the transfer of four electrons is reduced to two molecules of water. The X-ray structure of a laccase from Cerrena maxima has been elucidated at 1.9 A resolution using synchrotron data and the molecular replacement technique. The final refinement coefficients are Rcryst = 16.8% and Rfree = 23.0%, with root mean square deviations on bond lengths and bond angles of 0.015 A and 1.51 degrees , respectively. The type 1 copper centre has an isoleucine residue at the axial position and the "resting" state of the trinuclear centre comprises a single oxygen (OH) moiety asymmetrically disposed between the two type 3 copper ions and a water molecule attached to the type 2 ion. Several carbohydrate binding sites have been identified and the glycan chains appear to promote the formation of well-ordered crystals. Two tyrosine residues near the protein surface have been found in a nitrated state.     

Dynamics of P300 component of acoustic evoked potential in postraumatic unconsciousness

In order to reveal features of the brain reactions to external stimuli in the course of consciousness recovery after a severe craniocerebral injury, component P300 of acoustic evoked potential was analyzed in 9 patients with chronic and 32 patients with reversible unconsciousness. In patients with chronic unconsciousness, P300 parameters displayed a linear correlation with the current functional state. However, this component remained significantly different from its normal shape and varied only in a narrow range. In patients with reversible unconsciousness, time course of changes in amplitude and latency between recovery stages was of linear character with a tendency to normalization. The findings suggest that, in reversible unconsciousness states, processing of sensory information at different recovery stages may be performed with various functional systems that determine varying quality of processing, whereas changes in chronic unconsciousness are caused by a decrease in the number of active elements within the same functional system.