Spatiotemporal asymmetry of associative synaptic plasticity in fear conditioning pathways

Input-specific long-term potentiation (LTP) in afferent inputs to the amygdala serves an essential function in the acquisition of fear memory. Factors underlying input specificity of synaptic modifications implicated in information transfer in fear conditioning pathways remain unclear. Here we show that the strength of naive synapses in two auditory inputs converging on a single neuron in the lateral nucleus of the amygdala (LA) is only modified when a postsynaptic action potential closely follows a synaptic response. The stronger inhibitory drive in thalamic pathway, as compared with cortical input, hampers the induction of LTP at thalamo-amygdala synapses, contributing to the spatial specificity of LTP in convergent inputs. These results indicate that spike timing-dependent synaptic plasticity in afferent projections to the LA is both temporarily and spatially asymmetric, thus providing a mechanism for the conditioned stimulus discrimination during fear behavior.     

New insights into tau-microtubules interaction revealed by isothermal titration calorimetry

Microtubule dynamic instability is tightly regulated by coordinated action of stabilizing and destabilizing microtubule associated proteins. Among the stabilizing proteins, tau plays a pivotal role in both physiological and pathological processes. Nevertheless, the detailed mechanism of tau-tubulin interaction is still subject to controversy. In this report, we studied for the first time tau binding to tubulin by a direct thermodynamic method in the absence of any tubulin polymerization cofactors that could influence this process. Isothermal titration calorimetry enabled us to evidence two types of tau-tubulin binding modes: one corresponding to a high affinity binding site with a tau:tubulin stoichiometry of 0.2 and the other one to a low affinity binding site with a stoichiometry of 0.8. The same stoichiometries were obtained at all temperatures tested (10-37°C), indicating that the mechanism of interaction does not depend on the type of tubulin polymer triggered upon tau binding. These findings allowed us to get new insights into the topology of tau on microtubules.     

Separation and characterization of deoxyribonucleases from hepatopancreas of freshwater snail in normality and under in vivo model intoxication

Deoxyribonucleases (DNases) differing in the subcellular localization and specificity towards native and denatured substrates and in products of cleavage of endogenous DNA were isolated for the first time from the hepatopancreas of freshwater snail by differential sedimentation and preparative isoelectrofocusing. It was defined found that treatment with phenol leads to activatesion of the most of the investigated DNases, especially in lysosomes, and induces two new DNases of lysosomal origin. The possible different participation of certain DNases of the snail hepatopancreas in the regulation of DNA degradation under intoxication is discussed.     

NADH Binds and Stabilizes the 26S Proteasomes Independent of ATP

The 26S proteasome is the end point of the ubiquitin- and ATP-dependent degradation pathway. The 26S proteasome complex (26S PC) integrity and function has been shown to be highly dependent on ATP and its homolog nucleotides. We report here that the redox molecule NADH binds the 26S PC and is sufficient in maintaining 26S PC integrity even in the absence of ATP. Five of the 19S proteasome complex subunits contain a putative NADH binding motif (GxGxxG) including the AAA-ATPase subunit, Psmc1 (Rpt2). We demonstrate that recombinant Psmc1 binds NADH via the GxGxxG motif. Introducing the ΔGxGxxG Psmc1 mutant into cells results in reduced NADH-stabilized 26S proteasomes and decreased viability following redox stress induced by the mitochondrial inhibitor rotenone. The newly identified NADH binding of 26S proteasomes advances our understanding of the molecular mechanisms of protein degradation and highlights a new link between protein homeostasis and the cellular metabolic/redox state.     

Water masses and zooplankton in a tributary of the Rybinsk Reservoir in its backwater zone

In 2008, transition (gradient) and stable zones in backwaters of the tributary of the Rybinsk Reservoir were distinguished according to water conductivity. The highest values of BOD₅ (biochemical oxygen demand) and the maximum zooplankton abundance within the backwater zone as well as in comparison with the neighboring systems (the river and the reservoir) were recorded in the transition zone where the marginal effect appeared.     

Phyto- and Zooplankton of Open Overgrown Shallows of the Rybinsk Reservoir Adjacent to a Mixed Grey Heron–Great Egret (<Emphasis Type="Italic">Ardea cinerea</Emphasis> L. and <Emphasis Type="Italic">A. alba</Emphasis> L.) Colony at a High Water Level

Phyto- and zooplankton communities developing in the open overgrown shallows of the Rybinsk Reservoir under the influence of a bird colony are shown to lose specific traits of quantitative characteristics and structure fluctuation in response to the elevated water level in contrast to previous findings. Possible reasons, such as the decomposition of sunken coastal vegetation playing the main role, accompanied by the development of semiaquatic macrophytes and trophic relations between algae and invertebrates, are discussed. It is found that increased atmospheric precipitation leads to an increased abundance of Copepoda in the zooplankton. Presumably, this effect correlates with more rapid and intensive inflow of avian vitality products rich in nitrogen into the water, resulting in a change in the stoichiometric ratio of nitrogen and phosphorus in zooplankton food objects to values favorable for copepods.     

Structure of Self-Aggregated Alamethicin in ePC Membranes Detected by Pulsed Electron-Electron Double Resonance and Electron Spin Echo Envelope Modulation Spectroscopies

PELDOR spectroscopy was exploited to study the self-assembled super-structure of the [Glu(OMe)^7,18,19]alamethicin molecules in vesicular membranes at peptide to lipid molar ratios in the range of 1:70-1:200. The peptide molecules were site-specifically labeled with TOAC electron spins. From the magnetic dipole-dipole interaction between the nitroxides of the monolabeled constituents and the PELDOR decay patterns measured at 77 K, intermolecular-distance distribution functions were obtained and the number of aggregated molecules (n ≈ 4) was estimated. The distance distribution functions exhibit a similar maximum at 2.3 nm. In contrast to Alm16, for Alm1 and Alm8 additional maxima were recorded at 3.2 and ∼5.2 nm. From ESEEM experiments and based on the membrane polarity profiles, the penetration depths of the different spin-labeled positions into the membrane were qualitatively estimated. It was found that the water accessibility of the spin-labels follows the order TOAC-1 > TOAC-8 ≈ TOAC-16. The geometric data obtained are discussed in terms of a penknife molecular model. At least two peptide chains are aligned parallel and eight ester groups of the polar Glu(OMe)^18,19 residues are suggested to stabilize the self-aggregate superstructure.     

Molecular genetic determinants of intraspecific polymorphism of the phytopathogenic fungus Cryphonectria parasitica

The review summarizes the current evidence on the phytopathogenic fungus Cryphonectria parasitica, which is a classic object for studying hypovirulence. Phenotypic manifestations of hypovirulence and themolecular mechanisms of action of the mycovirus Cryphonectria hypovirus (CHV) infecting the fungus are described in detail. Genetic determinants of vegetative incompatibility in C. parasitica (a phenomenon increasing polymorphism of the fungus and preventing CHV expansion) are considered. The data on C. parasitica polymorphism are correlated with the data on the distribution of different CHV species in the European, American, and Asian populations of the fungus.