Uremic medium increases cytokine-induced PAI-1 secretion by cultured endothelial cells

The overall fibrinolytic activity is depressed in patients with chronic renal failure where a prothrombotic state is described, thereby enhancing the risk of vascular occlusive events. The mechanism responsible for fibrinolysis derangement has not yet been elucidated. To evaluate the effect of the uremic environment on the fibrinolytic activity of endothelial cells, we studied plasminogen activator (t-PA) and plasminogen activator inhibitor type 1 (PAI-1) production by human umbilical vein endothelial cells (HUVEC) in culture, exposed either to uremic or normal sera, before and after cytokine stimulation. Twenty uremics were studied: 11 were on conservative dietary treatment and nine were on maintenance hemodialysis. Eight healthy subjects served as controls. Before cytokine stimulation, no difference in the HUVEC supernatant concentration of t-PA and PAI-1 was found among the groups studied. After stimulation with interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha, the HUVEC supernatant levels of PAI-1 in the uremics were higher than in the controls, whereas the supernatant levels of t-PA did not differ. Our data provide evidence that uremic serum, in concert with IL-1 or TNF-alpha, can enhance PAI-1 secretion by endothelial cells, thereby depressing the fibrinolytic system. This impaired endothelial fibrinolytic response to hypercoagulation could favor vascular events, which are the major cause of morbidity and mortality in patients with chronic uremia.     

Use of caustic magnesia to remove cadmium, nickel, and cobalt from water in passive treatment systems: column experiments

In the present study caustic magnesia obtained from calcination of magnesium carbonate was tested in column experiments as an alternative material for passive remediation systems to remove divalent metals. Caustic magnesia reacts with water to form magnesium hydroxide, which dissolves increasing the pH to values higher than 8.5. At these pH values, cadmium is precipitated as otavite and to a minor amount as a hydroxide. Cobalt and nickel are precipitated as hydroxides which form isostructural solids with brucite. Thus, metal concentrations as high as 75 mg/L in the inflowing water are depleted to values below 10 microg/L. Magnesia dissolution is sufficiently fast to treat flows as high as 0.5 m3/m2 x day. For reactive grain size of 2-4 mm, the column efficiency ends due to coating of the grains by precipitates, especially when iron and aluminum are present in the solution.     

Influence of the structure of soft and stiff chain fragments on properties of segmented polyurethanes. I. Phase morphology

Model segmented polyurethanes (SPUs) prepared from either oxypropylene glycol oligomer or butylene adipate glycol oligomer, both of molar mass 2 kg/mol (soft fragments, SFT), and three different diisocyanates (all-trans 4,4'-dicyclohexylmethane diisocyanate, t, t-HMDI-1.0; HMDI with 20% of trans isomers, t, t-HMDI-0.2; and 4, 4'-diphenylmethane diisocyanate, MDI) (stiff fragments, STF) were characterized by specific heat capacity measurements in the temperature interval 140-540 K, and by wide-angle and small-angle X-ray scattering at room temperature. Limited miscibility of SFT and STF chain components resulted in incomplete separation into a regular three-dimensional macrolattice of STF-rich microdomains and SFT-rich microphases. The composition of STF-rich microdomains was estimated by fitting the softening temperatures to the Couchman's equation, whereas the relative contents of SFT-rich and STF-rich microphases were assessed by comparing the specific heat capacity change at the glass transition temperatures to corresponding additive values. The overall degree of microphase separation, as well as the mean macrolattice spacings between STF microdomains decreased in the order, MDI > t, t-HMDI-1.0 ? t, t-HMDI-0.2. The conformation of STF fragments within the STF-rich microdomains changed from nearly extended (for MDI) through slightly contracted (for t, t-HMDI-1.0) to strongly contracted (for t, t-HMDI-0.2).     

Biosurfactant- and biodegradation-enhanced partitioning of polycyclic aromatic hydrocarbons from nonaqueous-phase liquids

A study was conducted on the effect of two different biological factors, microbial surfactants and biodegradation, on the kinetics of partitioning of polycyclic aromatic hydrocarbons (PAHs) from nonaqueous-phase liquids (NAPLs). The effect of rhamnolipid biosurfactants on partitioning into the aqueous phase of naphthalene, fluorene, phenanthrene, and pyrene, initially dissolved in di-2-ethylhexyl phthalate (DEHP) or 2,2,4,4,6,8,8-heptamethylnonane (HMN), was determined in multiple-solute experiments. Biosurfactants at a concentration above the CMC enhanced the partitioning rate of fluorene, phenanthrene, and pyrene but were ineffective with naphthalene. Enhancement of partitioning was also observed in the presence of suspended humic acid-clay complexes, which simulated the solids often present in the subsurface. Biosurfactants sorbed to the complexes modified PAH partitioning between the NAPL and these solids, increasing the fraction of solid-phase PAH. Biodegradation-driven partitioning was estimated in mineralization experiments with phenanthrene initially present in HMN and three representative soil bacterial strains, differing in their potential adherence to the NAPL. In the three cases, the rates of mineralization were very similar and significantly higher than the abiotic rate of partitioning. Our study suggests that in NAPL-polluted sites, partitioning of PAH may be efficiently enhanced by in situ treatments involving the use of biosurfactants and biodegradation.     

Dimensionality of color space in natural images

The color histogram (or color cloud) of a digital image displays the colors present in an image regardless of their spatial location and can be visualized in (R,G,B) coordinates. Therefore, it contains essential information about the structure of colors in natural scenes. The analysis and visual exploration of this structure is difficult. The color cloud being thick, its more dense points are hidden in the clutter. Thus, it is impossible to properly visualize the cloud density. This paper proposes a visualization method that also enables one to validate a general model for color clouds. It argues first by physical arguments that the color cloud must be essentially a two-dimensional (2D) manifold. A color cloud-filtering algorithm is proposed to reveal this 2D structure. A quantitative analysis shows that the reconstructed 2D manifold is strikingly close to the color cloud and only marginally depends on the filtering parameter. Thanks to this algorithm, it is finally possible to visualize the color cloud density as a gray-level function defined on the 2D manifold.     

Engineering and performance of a contactless linear slider based on superconducting magnetic levitation for precision positioning

In this paper, a contactless linear slider for precision positioning able to operate in cryogenic environments is presented. The device, based on superconducting magnetic levitation, does not present contact between the slider (composed of a permanent magnet) and the guideline (made of high-temperature superconducting disks) of the mechanism, thereby avoiding any tribological problems. Moreover, the slider is self-stable and the superconductors provide inherent guidance to the permanent magnet in the sliding DoF due to the high translational symmetry of the magnetic field that leads to low power consumption. A sub-micrometre resolution and a symmetric stroke over ±9 mm have been demonstrated at cryogenic temperatures. In addition, a set of design rules for this kind of mechanism has been proposed and experimentally validated. These rules demonstrate that the performance of the device can be tuned just by modifying some geometrical parameters of the mechanism. In this way, the sensitivity and stiffness, resolution, angular run outs and power consumption can be adjusted for different applications and requirements.     

Platelet activating factor (PAF) and kidney failure progression

Many mediators of phlogosis may play an important role in renal glomerular pathology. PAF seems to have a prominent role. The aim of this study is the evaluation of the mechanism of action by which PAF may contribute to renal glomerular damage.     

Determination of secondary structure of normal fibrin from human peripheral blood

The secondary structure of human fibrin from normal donors and from bovine and suilline plasma was studied by Fourier transform ir spectroscopy and a quantitative analysis of its secondary structure was suggested. For this purpose, a previously experimented spectrum deconvolution procedure based on the use of the Conjugate Gradient Minimisation Algorithm with the addition of suitable constraints was applied to the analysis of conformation-sensitive amide bands. This procedure was applied to amide I and III analysis of bovine and suilline fibrin, obtained industrially, and to amide III analysis of human fibrin clots. The analysis of both amide I and III in the first case was useful in order to test the reliability of the method. We found bovine, suilline, and human fibrin to contain about 30% alpha-helix (amide I and III components at 1653 cm-1, and 1312 and 1284 cm-1, respectively), 40% beta-sheets (amide I and III components at 1625 and 1231 cm-1, respectively) and 30% turns (amide I and III components at 1696, 1680, 1675 cm-1, and 1249 cm-1, respectively). The precision of the quantitative determination depends on the amount of these structures in the protein. Particularly, the coefficient of variation is < 10% for percentage values of amide I and III components > 15 and 5%, respectively. The good agreement of our quantitative data, obtained separately by amide I and amide III analysis, and consistent with a previous fibrinogen (from commercial sources) study that reports only information about fibrin beta-sheet content obtained by factor analysis, leads us to believe that the amounts of secondary structures found (alpha-helix, beta-sheets, and turns) are accurate.