Interaction of nerve growth factor with tubulin. Studies on binding and induced polymerization

The interaction of the nerve growth factor with the neurotubule protein has been studied with the aim of elucidating the nature of the large complexes that they form when incubated together and the factors that control this event. The results show that the binding of nerve growth factor to tubulin is followed by the formation of large structures that, in certain experimental conditions, accelerate the rate of tubulin polymerization to form microtubules or catalyze their assembly in conditions where this process does not occur spontaneously. The formation of large nerve growth factor-tubulin complexes starts to occur only at a molar ratio of 1.0–1.5 NaCl or GTP strongly inhibit this process without a detectable effect on NGF binding. Two hypotheses are postulated to explain these finding. Firstly, that tubulin has two sites with different affinity for nerve growth factor and the polymerization occurs only when the second NGF molecule has interacted with the microtubule protein. Alternatively, free tubulin in solution is the limiting factor of the polymerization by hindering a site of tubulin-factor complexes present in solutio at a 1 : 1 molar ratio. In both cases, GTP, Na⁺ or H⁺ will affect the formation of large unsoluble, tubulin-NGF complexes, by changing their conformation or by decreasing electrostatic interactions.     

Determination of structural parameters from advanced molecular electronic spectroscopy: The double ionization of nitrous oxide by synchrotron radiation

The double photoionization of N₂O molecules, in the 30–50 eV energy range, has been studied by synchrotron radiation. In the whole energy range, dissociative ionization producing N⁺ + NO⁺ or N₂⁺ + O⁺ has been observed. These two processes appear to occur also below the vertical thresh-old of 35.8 eV, where the double ionization should be indirect. In the range between 35.8 and 38.5 eV. The two processes occur instead by direct coulomb explosion of the N₂O²⁺ dication. Above 38.5 eV, the dissociation leading to NO⁺ + N⁺ is also promoted by the formation of a dication metastable state, which decays by fluorescence to the ground state and then dissociates.      

Susceptibility to Antibiotics of Vibrio sp. AO1 Growing in Pure Culture or in Association with its Hydroid Host Aglaophenia octodonta (Cnidaria, Hydrozoa)

Vibrio harveyi is the major causal organism of vibriosis, causing potential devastation to diverse ranges of marine invertebrates over a wide geographical area. These microorganisms, however, are phenotypically diverse, and many of the isolates are also resistant to multiple antibiotics. In a previous study, we described a previously unknown association between Vibrio sp. AO1, a luminous bacterium related to the species V. harveyi, and the benthic hydrozoan Aglaophenia octodonta. In this study, we analyzed the susceptibility to antibiotics (ampicillin, streptomycin, tetracycline, or co-trimoxazole = mix of sulfamethoxazole and trimetoprim) of Vibrio sp. AO1 growing in pure culture or in association with its hydroid host by using microcosm experiments. The results of minimum inhibitory concentration (MIC) experiments demonstrated that Vibrio sp. AO1 was highly resistant to ampicillin and streptomycin in pure culture. Nevertheless, these antibiotics, when used at sub-MIC values, significantly reduced the hydroid fluorescence. Co-trimoxazole showed the highest inhibitory effect on fluorescence of A. octodonta. However, in all treatments, the fluorescence was reduced after 48 h, but never disappeared completely around the folds along the hydrocaulus and at the base of the hydrothecae of A. octodonta when the antibiotic was used at concentration completely inhibiting growth in vitro. The apparent discrepancy between the MIC data and the fluorescence patterns may be due to either heterogeneity of the bacterial population in terms of antibiotic susceptibility or specific chemical–physical conditions of the hydroid microenvironment that may decrease the antibiotic susceptibility of the whole population. The latter hypothesis is supported by scanning electron microscope evidence for development of bacterial biofilm on the hydroid surface. On the basis of the results obtained, we infer that A. octodonta might behave as a reservoir of antibiotic multiresistant bacteria, increasing the risk of their transfer into aquaculture farms.     

The Bacterial Cytoskeleton Modulates Motility,Type 3 Secretion,and Colonization in Salmonella

Although there have been great advances in our understanding of the bacterial cytoskeleton, major gaps remain in our knowledge of its importance to virulence. In this study we have explored the contribution of the bacterial cytoskeleton to the ability of Salmonella to express and assemble virulence factors and cause disease. The bacterial actin-like protein MreB polymerises into helical filaments and interacts with other cytoskeletal elements including MreC to control cell-shape. As mreB appears to be an essential gene, we have constructed a viable ΔmreC depletion mutant in Salmonella. Using a broad range of independent biochemical, fluorescence and phenotypic screens we provide evidence that the Salmonella pathogenicity island-1 type three secretion system (SPI1-T3SS) and flagella systems are down-regulated in the absence of MreC. In contrast the SPI-2 T3SS appears to remain functional. The phenotypes have been further validated using a chemical genetic approach to disrupt the functionality of MreB. Although the fitness of ΔmreC is reduced in vivo, we observed that this defect does not completely abrogate the ability of Salmonella to cause disease systemically. By forcing on expression of flagella and SPI-1 T3SS in trans with the master regulators FlhDC and HilA, it is clear that the cytoskeleton is dispensable for the assembly of these structures but essential for their expression. As two-component systems are involved in sensing and adapting to environmental and cell surface signals, we have constructed and screened a panel of such mutants and identified the sensor kinase RcsC as a key phenotypic regulator in ΔmreC. Further genetic analysis revealed the importance of the Rcs two-component system in modulating the expression of these virulence factors. Collectively, these results suggest that expression of virulence genes might be directly coordinated with cytoskeletal integrity, and this regulation is mediated by the two-component system sensor kinase RcsC.     

The Effects of Vaccination and Immunity on Bacterial Infection Dynamics In Vivo

Salmonella enterica infections are a significant global health issue, and development of vaccines against these bacteria requires an improved understanding of how vaccination affects the growth and spread of the bacteria within the host. We have combined in vivo tracking of molecularly tagged bacterial subpopulations with mathematical modelling to gain a novel insight into how different classes of vaccines and branches of the immune response protect against secondary Salmonella enterica infections of the mouse. We have found that a live Salmonella vaccine significantly reduced bacteraemia during a secondary challenge and restrained inter-organ spread of the bacteria in the systemic organs. Further, fitting mechanistic models to the data indicated that live vaccine immunisation enhanced both the bacterial killing in the very early stages of the infection and bacteriostatic control over the first day post-challenge. T-cell immunity induced by this vaccine is not necessary for the enhanced bacteriostasis but is required for subsequent bactericidal clearance of Salmonella in the blood and tissues. Conversely, a non-living vaccine while able to enhance initial blood clearance and killing of virulent secondary challenge bacteria, was unable to alter the subsequent bacterial growth rate in the systemic organs, did not prevent the resurgence of extensive bacteraemia and failed to control the spread of the bacteria in the body.     

Jasione sphaerocephala sp.nov. (Campanulaceae) from Italy

Jasione sphaerocephala Brullo, Marcend et Pavone sp.nov. is described from Calabria, S Italy. It grows in rocky places and has some resemblance to J. laevis and J. montana. The chromosome number is 2n = 14.     

Hyphal Growth of Phagocytosed Fusarium oxysporum Causes Cell Lysis and Death of Murine Macrophages

Fusarium oxysporum is an important plant pathogen and an opportunistic pathogen of humans. Here we investigated phagocytosis of F. oxysporum by J774.1 murine cell line macrophages using live cell video microscopy. Macrophages avidly migrated towards F. oxysporum germlings and were rapidly engulfed after cell-cell contact was established. F. oxysporum germlings continued hyphal growth after engulfment by macrophages, leading to associated macrophage lysis and escape. Macrophage killing depended on the multiplicity of infection. After engulfment, F. oxysporum inhibited macrophages from completing mitosis, resulting in large daughter cells fused together by means of a F. oxysporum hypha. These results shed new light on the initial stages of Fusarium infection and the innate immune response of the mammalian host.     

Endometriosis: New concepts in the pathogenesis

Endometriosis is a gynaecological disease defined by the histological presence of endometrial glands and stroma outside the uterine cavity. Though there are several theories, research scientists remain unsure as to the definitive cause(s) of endometriosis. Considering the relevant health problems caused by endometriosis, all new information on the pathogenesis of this disease, may have important clinical implications. Goal of this article is to summarize the latest advances in the pathogenesis of endometriosis, with particular emphasis on the embryological theory, that has been recently re-proposed. The possible clinical implications of these findings will be discussed.     

A fuzzy anomaly indicator for environmental monitoring at continental scale

Environmental status assessment and monitoring can be performed by the integration of multi-source datasets at continental and global scales. We propose a methodology for the development of a new anomaly indicator (AI) which can highlight the occurrence of anomalous conditions in a synthetic fashion by analysis of a set of spatial input data. Anomalous conditions are defined relative to long-term average assumed as normal or reference status of the vegetated land surface. The indicator is defined according to fuzzy set theory which is a powerful means of handling uncertain and imprecise knowledge of environmental systems. The indicator integrates, in an innovative way, the anomaly scores of a set of contributing factors extracted from the analysis of historical time series, mainly of Earth observations data. These time series are used to automatically derive the fuzzy membership functions that quantify the contribution of each factor to the final indicator. No reference data and expert knowledge are strictly required for the implementation of the AI although the methodology allows customization where this type of information is available. The method was tested over the African continent for the period 1996–2002; monthly AI values were derived with input datasets of vegetation phenology and rainfall estimates. The output AI continental maps bring new information by integrating multiple factors and they highlight patterns of anomalous conditions of the status of the environment. The analysis of the correlation with the El Niño Southern Oscillation (ENSO) shows that the AI is able to identify the effects of this phenomenon and its spatio-temporal dynamics. The 1997–1998 and 2000–2001 ENSO events are clearly highlighted by the highest AI values in specific regions of the continent. The indicator proposed is a valuable tool which can help guide in depth and detailed investigations of environmental conditions at local scale.