Neuronal survival and calcium influx induced by basic fibroblast growth factor in chick ciliary ganglion neurons

Basic fibroblast growth factor (bFGF/FGF2) exhibits widespread biological activities in the nervous system. However, little is known about the cascade of intracellular events that links the activation of its tyrosine kinase receptors to these effects. Here we report that, in ciliary ganglion neurons from chick embryo, this trophic factor significantly enhanced neuronal survival. The percentage of surviving neurons was reduced when intracellular calcium was chelated by adding a membrane-permeable BAPTA ester to the culture medium, while antagonists of L- and N-type voltage-dependent calcium channels were ineffective. The ionic signals in response to bFGF stimulation have been studied using cytofluorimetric and patch-clamp techniques. In single-cell Fura-2 measurements, bFGF elicited a long lasting rise of the cytosolic calcium concentration that was dependent on [Ca2+]o. In whole-cell experiments, we observed a reversible depolarization of the membrane resting potential and an inward cationic current. Single channel experiments, performed in the cell-attached configuration, provide evidence for the activation of two families of Ca2+-permeable cationic channels. Moreover, inositol 1,4,5-trisphosphate opens channels with similar properties, suggesting that this cytosolic messenger can be responsible for the calcium influx induced by bFGF.     

Influence of structural properties and kinetic constraints on Bacillus cereus growth

The influence of structural properties and kinetic constraints on the behavior of Bacillus cereus was investigated on agar media. Dimensional criteria were used to study the growth in bacterial colonies. The architecture of the agar gel as modified by the agar content was found to influence the colony size, and smaller colonies were observed on media containing 50 to 70 g of agar liter-1. Except at low nutrient levels, colonies responded to nutrient gradients by decreasing in size the farther away they were from the nutrient source, and the decrease in colony size was influenced by the agar content. The diffusivities of glucose and a protein (insulin-like growth factor) were not affected by the gel architecture, suggesting that other factors, such as mechanical factors, could influence microbial growth in the agar systems used. Increasing the viscosity of the liquid phase of the agar media by adding polyvinylpyrrolidone resulted in a reduction in colony size. When the agar concentration was increased, the colony areas were not influenced by the viscosity of the system.     

Sensitivity and reproducibility of RT-PCR to detect Borna disease virus (BDV) RNA in blood: implications for BDV epidemiology

Borna disease virus (BDV) infection of domestic animals and humans appears to have a worldwide distribution. There is evidence suggesting an association of BDV with certain psychiatric disorders. However, more comprehensive epidemiological studies are required to establish rigorously a link between BDV and human mental disorders, and to evaluate the role of carrier animals as potential source of BDV for human infection. The use of RT-PCR to detect BDV RNA in peripheral blood mononuclear cells (PBMCs) of infected individuals is a powerful tool to address these questions. The comparison of discrepant results reported by different investigators using this approach is hampered by the lack of controls to assess the sensitivity and reproducibility of the assays. Procedures are now described that allow the establishment of standardized controls to evaluate the performance of the RT-PCR assays. This RT-PCR assay detected reproducibly 100 copies of BDV p40 RNA in 5 microg of RNA. The data illustrate that the number of PBMCs used for RNA preparation, rather than the amount of RNA, has a critical influence on the outcome of the RT-PCR assay. Evidence is provided that levels of BDV in blood do not necessarily reflect viral load in brain.     

Degradation behaviour of a composite material for thermal protection systemsPart II Process simulation

Mass and energy balance equations have been solved in order to simulate the behavior of a silicon-based ablative composite used as a thermal protection shield for a non-animated space capsule. A method to calculate some of the parameters in the energy balance equation, is proposed, taking advantage of combined thermal analysis techniques. Furthermore, degradation kinetics in the hypothesis of constant volume is used to solve the mass balance. The results of the computer simulation are compared with the experimental data, obtained using plasma arc testing. The model can be used for both material selection and thickness calculation for thermal protection shields. © 1998 Kluwer Academic Publishers