Effects of brefeldin-A on Golgi morphology in human cultured fibroblasts observed in three-dimensional stereo scanning electron microscopy

Brefeldin A (BFA) has been reported to cause disassembly of the Golgi. We have used three-dimensional (3-D) high-resolution scanning electron microscopy (HRSEM) to investigate these effects in human skin fibroblast cells. The spontaneous reassembly during prolonged exposure to BFA and some effects of forskolin were observed. A BFA concentration of 5μg/ml caused Golgi complexes to become vesicular, resulting in a progressive decrease in the size of the Golgi. Morphologic changes were visible within 2 min of BFA incubation, and by 30 min no identifiable Golgi could be found. Spontaneous reassembly of the Golgi apparatus upon the removal of the BFA or with continued long-term exposure with BFA could not be confirmed. Preliminary experiments with forskolin were not effective in reversing or inhibiting the effects of BFA in human fibroblast cells grown in culture. This inability for spontaneous reassembly and nonreversal by forskolin may reflect a differential effect of BFA in various cell types. HRSEM has proven to be useful for observing 3-D morphologic effects of BFA in Golgi.     

Adult treatment with haloperidol increases dentate granule cell proliferation in the gerbil hippocampus

The effects of cibenzoline on transmembrane action potentials were examined in right ventricular papillary muscles and in single ventricular myocytes isolated from guinea-pig hearts. In papillary muscles, cibenzoline > or = 3 microM caused a significant decrease in the maximum upstroke velocity (Vmax) of the action potential without affecting the action potential duration. The inhibition of Vmax was enhanced at higher stimulation frequencies. In the presence of cibenzoline, trains of stimuli at rates > or = 0.2 Hz led to a use-dependent inhibition of Vmax. The time constant for Vmax recovery (tauR) from the use-dependent block was 26.2 s. The use-dependent block of Vmax with cibenzoline was enhanced and tauR was shortened when the resting potential was depolarized by high (8, 10 mM) [K+]o. The curve relating membrane potential and Vmax in single myocytes was shifted by cibenzoline (10 microM) in a hyperpolarizing direction by 7.1 mV. In myocytes treated with cibenzoline (10 microM), a 10-ms conditioning clamp to 0 mV caused a significant decrease in Vmax of the subsequent test action potential; the Vmax inhibition was enhanced modestly in association with a prolongation of the 0 mV clamp pulse duration. In the presence of cibenzoline (3 microM), application of a train of depolarizing pulses (10 ms, 200 ms) to myocytes from the resting level (-80 mV) to 0 mV resulted in a progressive Vmax reduction in a pulse number-dependent manner. Unlike glibenclamide (30 microM), cibenzoline (10 microM) did not prevent the hypoxia-induced shortening of action potential duration in papillary muscles. These findings indicate that the onset and offset kinetics of use-dependent Na+ channel block by cibenzoline are slow. Given its state dependence, cibenzoline may be a blocker of activated Na+ channels. The inhibitory action of this compound on the ATP-sensitive K+ current (I(K), ATP) would be minimal or negligible at concentrations causing sufficient Na+ channel block.     

Pilocytic astrocytomas of the posterior fossa. A follow-up study in 33 patients

The extent of resection in pilocytic astrocytoma of the posterior fossa often remains undefined and the indications for further treatment in incompletely resected tumours are a matter of debate. It has been also realized that the problem of hydrocephalus in patients with pilocytic astrocytoma of the posterior fossa has not yet been solved and the diagnostic impact of postoperative CT findings remains questionable. We retrospectively reviewed the data from 33 patients harbouring a pilocytic astrocytoma of the posterior fossa to evaluate the impact of surgical technique in terms of radicality and of postoperative imaging results upon prognosis and adjunctive treatment. In addition, the issue of hydrocephalus was considered and related to different treatment modalities. Thirty patients underwent surgical treatment whereas 3 had open biopsy of the tumour. Macroscopically gross total resection of the tumour was performed in 20 patients, whereas resection was partial in 10. Follow-up was obtained in 29 patients for a period which ranged between 2 and 184 months (85 months +/- 56 months). Outcome was good in 24 patients who had only slight neurological deficit and poor in 3 patients, who were severely disabled. Two patients died during the follow-up period. Recurrent tumour growth occurred in 2 cases with incompletely resected tumours. From the series presented, it was concluded that long-term follow-up with CT seems mandatory in cases with contrast-enhancing residual tumour. Recurrent tumour growth should be assumed in postsurgical patients with an enlarging area of enhancement shown in follow-up CT studies. Permanent ventriculoperitoneal shunting is required in certain patients with pre- or postoperative hydrocephalus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Single g-pulses and segregation in virtual µg Bridgman growth environments. A complementary two-dimensional approach

The binomial single g-pulses — dopant segregation in a generic virtual µg Bridgman growth arrangement is discussed here with the help of a time dependent two-dimensional scheme. To attain this objective, the so-called solid composition drop distribution has been previously defined enabling a global two-dimensional information of the segregation impact in each virtually grown crystal. Based on this parameter it has been concluded that, at equal g-dose, solid segregation is independent on the shape of the single external pulse and that, for single g-pulses of equal g-dose, compositional variations are practically independent on the activity time but depend on the crystal growth rate. Finally, taking into account all these set of results, the pertinence of the g-dose as the only self-consistent parameter to describe the segregation impact has been discussed.     

Extending the power line LAN up to the neighborhood transformer

This article reports on the performance of audio, video, multimedia, and other high-data-rate in-home networking applications. The article starts by describing the problems encountered in power line communication channels in terms of frequency response and noise characteristics, and explains how in-home power line LANs can be extended to the neighborhood transformer. OFDM physical layers providing speeds of 45 Mb/s and 200 Mb/s as well as QoS and security are introduced. Finally, the results of large tests involving several thousands of nodes are described.     

Material constant sensitivity boundary integral equation for anisotropic solids

In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd.     

Kinetic study of the reaction between molybdenum trioxide and gaseous carbon tetrachloride

The kinetics of the chlorination reaction of molybdenum trioxide with gaseous carbon tetrachloride has been studied at temperatures between 713 and 753 K. The effects of temperature, reaction time, residence time and gaseous reactant concentration on conversion were studied throughout the reaction. In all cases, there was an increase in conversion when the above operating variables were increased. The kinetic model proposed is consistent with and correlates the experimental data. In the range studied for the different variables, the step that controls the rate of reaction is the surface chemical reaction. Values of the rate constant and the activation energy were estimated.     

Leaching of sulfidized chalcopyrite with H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-NaCl-O<Subscript>2</Subscript>

The recovery of copper from chalcopyrite by leaching is complex not only due to the slow dissolution kinetics of this mineral in most aqueous media but also due to the production of solutions that are heavily contaminated with iron. On the contrary, the leaching of sulfidized chalcopyrite is very attractive because of a faster and more selective dissolution of copper compared to the leaching of the untreated chalcopyrite. In this work, the results of leaching in H₂SO₄-NaCl-O₂ solutions of sulfidized chalcopyrite concentrate are discussed. Experiments were carried out with chalcopyrite concentrates previously reacted with elemental sulfur at 375 °C for 60 minutes. The results showed that the concentration of chloride ions below 0.5 M, temperature, and leaching time are important variables for the extraction of Cu. On the other hand, Fe extraction was little affected by the same variables, remaining below 6 pct for all the experimental conditions tested. Microscopic observations of the leached particles showed that the elemental sulfur produced by the reaction does not form a coherent layer surrounding the particle, but rather concentrates in certain locations as large clusters. The leaching kinetics can be accurately described by a nonreactive core-shrinking rim topochemical expression for spherical particles 1 − (1 − 0.45X)^1/3=kt. The activation energy found was 76 kJ/mol for the range 85 °C to 100 °C.