Food Resource Partitioning between Two Invasive Gobiid Species (Pisces,Gobiidae) in the Littoral Zone of the River Danube,Hungary

At present, the invasive round and bighead gobies are the most abundant benthic fish species in the near shore zone of the Middle Danube. We compared their diet seasonally in natural and artificial habitats and contrasted it with the food supply. The composition of the macroinvertebrate community was determined mainly by seasonal changes, whereas habitat type had smaller effect. Round gobies followed these changes flexibly. They consumed mainly chironomids in the spring, whilst amphipods and molluscs in the summer and autumn. Bighead gobies relied on amphipods in each season and in both habitats, and consumed fish, too, including round goby (intraguild predation). Diet overlap was determined by the morphological differences of the species allowing a varying degree of differentiation according to the seasonally changing food supply. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The extracellular matrix of hydra is a porous sheet and contains type IV collagen

Hydra, as an early diploblastic metazoan, has a well-defined extracellular matrix (ECM) called mesoglea. It is organized in a tri-laminar pattern with one centrally located interstitial matrix that contains type I collagen and two sub-epithelial zones that resemble a basal lamina containing laminin and possibly type IV collagen. This study used monoclonal antibodies to the three hydra mesoglea components (type I, type IV collagens and laminin) and immunofluorescent staining to visualize hydra mesoglea structure and the relationship between these mesoglea components. In addition, hydra mesoglea was isolated free of cells and studied with immunofluorescence and scanning electron microscopy (SEM). Our results show that type IV collagen co-localizes with laminin in the basal lamina whereas type I collagen forms a grid pattern of fibers in the interstitial matrix. The isolated mesoglea can maintain its structural stability without epithelial cell attachment. Hydra mesoglea is porous with multiple trans-mesoglea pores ranging from 0.5 to 1 μm in diameter and about six pores per 100 μm² in density. We think these trans-mesoglea pores provide a structural base for epithelial cells on both sides to form multiple trans-mesoglea cell–cell contacts. Based on these findings, we propose a new model of hydra mesoglea structure.     

The goodpasture autoantigen. Identification of multiple cryptic epitopes on the NC1 domain of the alpha3(IV) collagen chain

Goodpasture (GP) disease is an autoimmune disorder in which autoantibodies against the alpha3(IV) chain of type IV collagen bind to the glomerular and alveolar basement membranes, causing progressive glomerulonephritis and pulmonary hemorrhage. Two major conformational epitope regions have been identified on the noncollagenous domain of type IV collagen (NC1 domain) of the alpha3(IV) chain as residues 17-31 (E(A)) and 127-141 (E(B)) (Netzer, K.-O. et al. (1999) J. Biol. Chem. 274, 11267-11274). To determine whether these regions are two distinct epitopes or form a single epitope, three GP sera were fractionated by affinity chromatography on immobilized NC1 chimeras containing the E(A) and/or the E(B) region. Four subpopulations of GP antibodies with distinct epitope specificity for the alpha3(IV)NC1 domain were thus separated and characterized. They were designated GP(A), GP(B), GP(AB), and GP(X), to reflect their reactivity with E(A) only, E(B) only, both regions, and neither, respectively. Hence, regions E(A) and E(B) encompass critical amino acids that constitute three distinct epitopes for GP(A), GP(B), and GP(AB) antibodies, respectively, whereas the epitope for GP(X) antibodies is located in a different unknown region. The GP(A) antibodies were consistently immunodominant, accounting for 60-65% of the total immunoreactivity to alpha3(IV)NC1; thus, they probably play a major role in pathogenesis. Regions E(A) and E(B) are held in close proximity because they jointly form the epitope for Mab3, a monoclonal antibody that competes for binding with GP autoantibodies. All GP epitopes are sequestered in the hexamer configuration of the NC1 domain found in tissues and are inaccessible for antibody binding unless dissociation of the hexamer occurs, suggesting a possible mechanism for etiology of GP disease. GP antibodies have the capacity to extract alpha3(IV)NC1 monomers, but not dimers, from native human glomerular basement membrane hexamers, a property that may be of fundamental importance for the pathogenesis of the disease.     

Oxamides as novel NR2B selective NMDA receptor antagonists

A novel series of oxamides derived from indole-2-carboxamides was identified as potent NR2B selective NMDA receptor antagonists. Several members of this group showed good analgesic activity in the mouse formalin test.     

Goodpasture autoantibodies unmask cryptic epitopes by selectively dissociating autoantigen complexes lacking structural reinforcement: novel mechanisms for immune privilege and autoimmune pathogenesis

Rapidly progressive glomerulonephritis in Goodpasture disease is mediated by autoantibodies binding to the non-collagenous NC1 domain of alpha3(IV) collagen in the glomerular basement membrane. Goodpasture epitopes in the native autoantigen are cryptic (sequestered) within the NC1 hexamers of the alpha3alpha4alpha5(IV) collagen network. The biochemical mechanism for crypticity and exposure for autoantibody binding is not known. We now report that crypticity is a feature of the quaternary structure of two distinct subsets of alpha3alpha4alpha5(IV) NC1 hexamers: autoantibody-reactive M-hexamers containing only monomer subunits and autoantibody-impenetrable D-hexamers composed of both dimer and monomer subunits. Goodpasture antibodies only breach the quaternary structure of M-hexamers, unmasking the cryptic epitopes, whereas D-hexamers are resistant to autoantibodies under native conditions. The epitopes of D-hexamers are structurally sequestered by dimer reinforcement of the quaternary complex, which represents a new molecular solution for conferring immunologic privilege to a potential autoantigen. Dissociation of non-reinforced M-alpha3alpha4alpha5(IV) hexamers by Goodpasture antibodies is a novel mechanism whereby pathogenic autoantibodies gain access to cryptic B cell epitopes. These findings provide fundamental new insights into immune privilege and the molecular mechanisms underlying the pathogenesis of human autoimmune Goodpasture disease.     

Structural and nucleotide-binding properties of YajQ and YnaF,two Escherichia coli proteins of unknown function

Structural genomics is a new approach in functional assignment of proteins identified via whole-genome sequencing programs. Its rationale is that nonhomologous proteins performing similar or related biological functions might have similar tertiary structure. We used dye pseudoaffinity chromatography, two-dimensional gel electrophoresis, and mass spectrometry to identify two novel Escherichia coli nucleotide-binding proteins, YnaF and YajQ. YnaF exhibited significant sequence identity with MJ0577, an ATP-binding protein from a hyperthermophile (Methanococcus jannaschii), and with UspA, a protein from Haemophilus influenzae that belongs to the Universal Stress Protein family. YnaF conserves the ATP-binding site and the dimeric structure observed in the crystal of MJ0577. The protein YajQ, present in many bacterial genomes, is missing in eukaryotes. In the absence of significant similarities of YajQ to any solved structure, we determined its structural and ligand-binding properties by NMR and isothermal titration calorimetry. We demonstrate that YajQ is composed of two domains, each centered on a beta-sheet, that are connected by two helical segments. NMR studies, corroborated with local sequence conservation among YajQ homologs in various bacteria, indicate that one of the beta-sheets is mostly involved in biological activity.     

Effects of temperature on water diffusion in human erythrocytes and ghosts--nuclear magnetic resonance studies

The temperature-dependence of water diffusion across human erythrocyte membrane was studied on isolated erythrocytes and resealed ghosts by a doping nuclear magnetic resonance technique. The conclusions are the following: (1) The storage of suspended erythrocytes at 2 degrees C up to 24 h or at 37 degrees C for 30 min did not change the water exchange time significantly, even if Mn2+ was present in the medium. This indicates that no significant penetration of Mn2+ is taking place under such conditions. (2) In case of cells previously incubated at 37 degrees C for longer than 30 min with concentrations of p-chloromercuribenzene sulfonate (PCMBS) greater than 0.5 mM, the water-exchange time gradually decreased if the cells were stored in the presence of Mn2+ for more than 10 min at 37 degrees C. (3) When the Arrhenius plot of the water-exchange time was calculated on the basis of measurements performed in such a way as to avoid a prolonged exposure of erythrocytes to Mn2+ no discontinuity occurred, regardless of the treatment with PCMBS. (4) No significant differences between erythrocytes and resealed ghosts regarding their permeability and the activation energy of water diffusion (Ea,d) were noticed. The mean value of Ea,d obtained on erythrocytes from 35 donors was 24.5 kJ/mol. (5) The value of Ea,d increased after treatment with PCMBS, in parallel with the percentage inhibition of water diffusion. A mean value of 41.3 kJ/mol was obtained for Ea,d of erythrocytes incubated with 1 mM PCMBS for 60 min at 37 degrees C and 28.3 kJ/mol for ghosts incubated with 0.1 mM PCMBS for 15 min, the values of inhibition being 46% and 21% respectively.     

Phosphite uptake and distribution in potato tubers following foliar and postharvest applications of phosphite‐based fungicides for late blight control

Foliar and postharvest applications of phosphite (Phi)‐based fungicides are used to control the oomycete Phytophthora infestans which is responsible for the occurrence of late blight in potatoes. Optimisation of the usage of Phi‐based fungicides for disease control during the growing season and in subsequent storage can lead to improved potato production and processing quality. In order to assess the efficiency of Phi translocation to tubers, following foliar and postharvest treatments of potato crops with the Phi‐based fungicides, the amount of Phi in tubers was determined by a high‐performance ion chromatography method. The quantity of Phi found in tubers increased with the total amount of Phi‐based fungicides applied during the growing season. Foliar applications of Phi resulted in an uneven distribution of Phi in the three tuber regions analysed, with high concentrations being identified in the tuber cortex (32.5–166.4 µg g^?1 fresh tissue) and medulla regions followed by the skin area. Postharvest treatment of tubers led to a different distribution of Phi, with the highest concentrations of Phi found in the skin (411.0–876.6 µg g^?1 fresh tissue) followed by the cortex and medulla regions. As foliar treatments are essential to protect the aerial parts of the plants during the growth season, the best disease management practices of tubers should include the postharvest treatment in addition to foliar applications. The use of both types of treatments ensures that concentrations of Phi in excess of 100 µg g^?1 fresh tissue are present in tuber skin and cortex areas; such concentrations are needed to suppress the growth of P. infestans on tubers during storage.     

Current velocity shapes co‐existence patterns among invasive Dikerogammarus species

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