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Notes: [Auszug] Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes a range of economically important plant diseases. Here we report the complete genome sequence of X. fastidiosa clone 9a5c, which causes citrus variegated chlorosis—a serious disease of orange trees. The genome ...

Notes: Na+ channels in the dendrites of rat CA1 pyramidal neurons display a profound activity-dependent inactivation, termed slow inactivation, that limits excitability in the dendrites even at low physiological rates of firing. The magnitude of this slow inactivation is powerfully modulated by a protein kinase C-dependent process. Because activation of kinases is a rapid and common feature of a number of seizure models, we hypothesized that a loss of slow inactivation of Na+ channels might exacerbate other changes in excitability. Thus, we observed the effects of a brief (5 min) chemical convulsant treatment on Na+ currents and action potentials in hippocampal slices. We found that slow inactivation decreased significantly and remained decreased for at least 30 min after return to control conditions. Pretreatment with either chelerythrine, a protein kinase C inhibitor, or U0126, a mitogen-activated protein kinase/extracellular signal regulated kinase kinase (MEK) inhibitor, blocked this reduction of slow inactivation. These results demonstrate that a brief period of hyperexcitability leads to a rapid, protein kinase-dependent loss of slow inactivation of Na+ channels that would contribute to and perhaps prolong the hyperexcitable state.

Notes: The hyperfine fields at nd (n=3,4,5) impurities and at noble impurities diluted in ferromagnetic compounds GdX (X=Zn, Cd) are discussed in the framework of a two center model. In these systems it is observed that all impurities enter substitutionally at the "nonmagnetic" X lattice site, thus creating a strong local charge perturbation. In our model, one calculates the local magnetic moment in the charge perturbed conduction band at the origin. The magnetization of the s–p conduction band arises from the Gd 4f moments. Then one obtains the conduction electron polarization contribution to the hyperfine field. The transition (and noble) impurities also create an Anderson–Moriya d resonance in the strongly perturbed Slater–Koster local density of states at the origin, thus originating an additional local moment and thereby a core polarization contribution to the magnetic hyperfine field. The self-consistently calculated hyperfine fields are in quite good agreement with available experimental data. © 2000 American Institute of Physics.

Notes: Ferroelectric materials with Bi-layered structure such as SrBi2Ta2O9 and SrBi2Nb2O9 are now intensively investigated in view of their applications in nonvolatile computer memories and high-temperature piezoelectric transducers. When Sr2+ is substituted with Ba2+, a significant disorder is induced and the material exhibits broadening of the phase transition. Such broadening is essential for applications since it allows achieving smooth temperature characteristics while maintaining high dielectric and piezoelectric properties. In this work, stoichiometric dense BaBi2Nb2O9 (BBN) ceramics are sintered using a mixed oxide route. Dielectric and ferroelectric properties are investigated in a broad range of temperatures and frequencies. Strong dispersion of the complex relative dielectric permittivity is observed including typical relaxor features such as shift of the permittivity maximum with frequency and broadening of the relaxation time spectrum with decreasing temperature. The dielectric relaxation obeys the Vögel–Fulcher relationship with anomalously low freezing temperature (Tf(approximate)100 K), which is much lower than the permittivity maximum in the radio-frequency range. Polarization hysteresis loops testify linear properties of BBN at all temperatures above Tf. The properties of BBN ceramics are compared to conventional relaxor systems such as Pb(Mg, Nb)O3 and (Pb, La)(Zr, Ti)O3. © 2001 American Institute of Physics.

Notes: Pollen allergens are multivalent proteins that cross-link IgE antibodies on mast or basophil cells, inducing secretion of biologic mediators, and resulting in various allergic symptoms. The IgE-binding regions of the Parietaria judaica (Pj) pollen major allergen rPar j 2 were investigated. Twenty-nine single sera from Pj-allergic subjects were tested by Western blot against five recombinant peptides. At least four putative IgE-binding epitopes were identified. The analysis of their diffusion suggested a heterogeneous IgE-binding response. In fact, 75% of the sera reacted with peptide 1–54, 48% with peptide 48–101, 24% with peptide 1–30, 7% with peptide 29–54, and none with peptide 48–76. These five peptides were analyzed with the histamine-release assay. Only peptide 48–101 was capable of inducing degranulation and release of histamine. These results suggest that the recombinant rPar j 2 allergen contains IgE epitopes that are heterogeneously recognized by sensitive patients, and that therefore the therapeutic approach based on the use of haptenic peptides needs a careful evaluation.

Notes: The feeding ecology of the lesser weever, Echiichthys vipera, from the adjacent coastal areas of the Douro and Tagus estuaries (Portugal) was studied between October 2000 and July 2002. The stomach contents of 246 individuals were analysed and diet was characterized by the numerical, gravimetric, occurrence and vacuity indices. Variation of feeding habits with fish length (〈95 and 〉95 mm) and geographical area was considered. Diet of the lesser weever comprised a large variety of prey (28 species), the most important of which were crustaceans (numerical index, NI = 93.5%; occurrence index, OI = 75.6%), namely Mysidacea (especially Schistomysis sp.), Amphipoda (mainly Gammarus subtypicus) and Isopoda (Idotea spp.), and also Teleostei (mostly larval stages that posted a gravimetric index, GI = 53.0%). Diet varied with fish length, with large individuals showing a larger diversity of prey items. Furthermore, specimens from Douro also showed a higher diversity of prey items than those from Tagus. More than 50% of the stomachs were empty, being the highest vacuity values relative to smaller fishes as well as to individuals from the Tagus estuary adjacent coastal area.

Notes: Fish species densities from 1025 hauls obtained with beam trawl and stow net catches from the southern Tagus and northern Elbe estuaries were analysed for two different periods of time between 1978 and 1997. The data were related with environmental factors to compare species composition and densities, contributions of different ecological guilds, structuring environmental key factors, intra-annual cyclicity and interperiodical stability of ichthyofaunas in large European estuaries at different latitudes. Although the total number of species in both the Tagus and Elbe estuaries (Tagus: 57 species, Elbe: 58 species) was very similar, significant differences were estimated in species compositions, species densities and number of species, and individuals of the different ecological guilds between both estuaries. A total of 15 species occurred in both estuaries but only two of these species, the catadromous Anguilla anguilla and the marine estuarine opportunist Pleuronectes flesus, contributed substantially to the total abundance. Marine species together contributed more than 5% of the total number of species in the Tagus and Elbe estuaries, whereas their contribution in number of individuals amounted to 22% in the Tagus and only 9% in the Elbe. In terms of number of individuals, the ichthyofauna of the Tagus estuary was dominated by estuarine species (especially Pomatoschistus spp.) contributing 68% of the total abundance. In contrast, the fish fauna of the Elbe estuary was dominated by high numbers of anadromous species (88%) individuals, especially Osmerus eperlanus. Canonical corresponding analyses (CCA) indicated that, besides intra-annual variables, salinity and mouth distance were two of the most important environmental factors structuring the fish communities in both estuaries. Moreover, water depth was found to be an important environmental factor in the Tagus estuary, whereas the water temperature substantially affected the ichthyofaunal composition in the Elbe estuary. In both estuaries, contributions by number of species and number of individuals of the different ecological guilds were not statistically different between the two periods considered, 1978–80 and 1995–97 for the Tagus, and 1981–86 and 1989–95 for the Elbe. Nevertheless, from 1981–86 until 1989–95 a remarkable increase of about 4.5 times in the densities of O. eperlanus was observed in the Elbe estuary, probably related to improved water quality, especially of oxygen conditions in the nurseries since 1990. This was also supported by the results of CCA, suggesting important influences of the years 1989 and 1990 on the Elbe estuary fish assemblage. Climate change as a result of global warming may be evident for the observed changes of the densities of P. flesus which decreased in the southern Tagus estuary and, in contrast, increased in the northern Elbe estuary during comparable periods of time. It is recommended to use the ecological guild classification scheme which was applied for the Tagus and Elbe estuaries for further studies of European estuarine fish assemblages.

Notes: In the present study, the nursery role of the coastal areas adjacent to the Douro estuary for pouting, Trisopterus luscus Linnaeus, 1758, was analysed. The distribution and abundance patterns, diet and growth of T. luscus were studied based on samples collected on seven occasions from November 2000 to March 2002 using a 12 m otter-trawl with 18 mm mesh size at 12 sites within the estuary and six sites in the adjacent coastal areas. This species occurred only in the coastal areas adjacent to the estuary and a marked seasonal pattern was reported, which reflected the peak abundance of juveniles that use this area as a nursery ground. No marked relationships were obtained between T. luscus abundance and the environmental variables considered. Nonetheless, the highest densities of pouting were recorded at sites where water temperature was high compared with the other sampling areas. Diet of T. luscus juveniles was mainly composed of crustaceans Decapoda, Mysidacea and Amphipoda. The growth rate determined for T. luscus juveniles off the Portuguese coast was higher than those reported for North European areas, and was similar to those obtained in the eastern Mediterranean.

Notes: Abstract Human osteoblastic alveolar bone cells were cultured for 28 days in control conditions and in the presence of three non-lethal concentrations of AISI 316L stainless steel (SS) corrosion products. Cells were exposed to SS corrosion products in two experimental situations: (i) in selected stages of the incubation time (during the first, second, third and fourth week of culture); and (ii) during the 28 days incubation period. Cultures were characterized for cell proliferation, total protein content, alkaline phosphatase activity (ALP) and ability to form mineralized deposits; culture media was analyzed for ionized calcium (Ca) and phosphorus (P) concentrations throughout the incubation period. The presence of SS corrosion products during the different stages of the incubation period did not significantly affect the cell proliferation; however, a significant dose-dependent deleterious effect was observed on the levels and pattern of ALP activity, concentration of ionized Ca and P in the culture medium and, also, ability to form mineralized deposits, especially in cultures exposed during the first and second week of culture (respectively, lag phase and exponential cell growth phase). Similar effects were observed in cultures exposed to the SS corrosion products during the 28 days incubation period. However, the presence of such products during the third week (when the mineralization process occurs) and, also, during the fourth week, resulted in little or no significant effects on the behavior of alveolar bone cells. Results suggested that SS corrosion products above certain non-lethal concentrations may disturb the proliferation/differentiation relationship of osteoblastic human alveolar bone cell cultures. ©©2000 Kluwer Academic Publishers

Notes: In the title compound, C4H10NO2+·C2F3O2−, the main N—C—COOH skeleton of the protonated amino acid is nearly planar. The C=O/C—N and C=O/O—H bonds are syn and the two methyl groups are gauche to the methylene H atoms. The conformation of the cation in the crystal is compared to that given by ab initio calculations (Hartree–Fock, self-consistent field molecular-orbital theory). The trifluoroacetate anion has the typical staggered conformation with usual bond distances and angles. The cation and anion form dimers through a strong O—H...O hydrogen bond which are further interconnected in infinite zigzag chains running parallel to the a axis by N—H...O bonds. Weaker C—H...O interactions involving the methyl groups and the carboxy O atoms of the cation occur between the chains.