Chemical inhibitors when timing is critical: a pharmacological concept for the maturation of T cell contacts

Cellular signal transduction proceeds through a complex network of molecular interactions and enzymatic activities. The timing of these molecular events is critical for the propagation of a signal and the generation of a specific cellular response. To define the timing of signalling events, we introduce the combination of high-resolution confocal microscopy with the application of small-molecule inhibitors at various stages of signal transduction in T cells. Inhibitors of Src-family tyrosine kinases and actin dynamics were employed to dissect the role of the lymphocyte-specific tyrosine kinase Lck in the formation and maintenance of T cell receptor/CD3-dependent contacts. Anti-CD3epsilon-coated coverslips served as a highly defined stimulus. The kinetics of the recruitment of the yellow fluorescent protein-tagged signalling protein ZAP-70 were detected by high-resolution confocal microscopy. The analysis revealed that at 5 min after receptor engagement, Lck activity was required for maintenance of contacts. In contrast, after 20 min of receptor engagement, the contacts were Lck-independent. The relevance of the timing of inhibitor application provides a pharmacological concept for the maturation of T cell-substrate contacts.     

Understanding aluminum behaviour in aqueous alkaline solution using coupled techniques: Part I. Rotating ring-disk study

Rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) measurements have been undertaken to study the behaviour of pure aluminum electrodes in alkaline media. The measurements did consist of linear sweep voltammetry from anodic to cathodic potentials on 4N, 5N or 5N5-aluminum samples in 4 M aqueous potassium hydroxide solution. In the potential range studied (−0.7 V versus NHE to −2.5 V versus NHE) the aluminum undergoes oxidation/dissolution into aluminates anions at high electrode potential while it yields strong hydrogen evolution at low potentials. Thanks to the RRDE technique, we show that hydrogen starts to evolve from the aluminum electrode even above the open circuit potential. Also, the oxidation state of superficial aluminum varies according to the electrode potential: whereas non-conducting aluminum oxides are present above the open-circuit potential hindering hydrogen evolution reaction (HER), they tend to disappear below the ocp, due to the strong hydrogen evolution, following the probable porous oxide layer blow up induced by the hydrogen bubbles formation. In consequence at very low potential, HER occurs on bare aluminum, HER kinetics being much faster than on oxide-covered aluminum.     

Wood-induced catalytic activation of PF adhesives autopolymerization vs. PF/wood covalent bonding

The reaction of polycondensation of phenol-formaldehyde (PF) resins in the presence of wood was confirmed to have a lower energy of activation than of the PF resin alone. Under the low temperature and short curing times characteristic of the application of PF resins as thermosetting wood adhesives DSC, TGA, chemical kinetics, and IR of PF resins and relevant model compounds were carried out. These indicated that two effects appear to be present when a PF resin cures on a wood surface, both induced by the polymeric constituents of the substrate, namely carbohydrates and lignin. These appear to be (1) the catalytic activation of the resin self-condensation induced particularly by carbohydrates such as crystalline and amorphous cellulose and hemicelluloses and (2) the formation of resin/substrate covalent bonding, particularly in the case of lignin. The first appears to be, by far, the major cause of the lowering of the activation energy of PF resins curing. The contribution of the second has been found to be very small and often negligble under the conditions pertaining to thermosetting wood adhesives applications. Molecular mechanics results appear to indicate that the marked catalytic activation of PF resins autocondensation and curing appears to be induced by the strong set of PF adhesive/substrate secondary forces interactions which appear to weaken bonds which, by cleavage, lead to PF resins autocondensation. © 1994 John Wiley & Sons, Inc.     

Injection molding shrinkage of PP: Experimental progress

Injection molding shrinkage deals with dimensional differences between a molded part and the cavity. By adding an array of orthogonal marks into a mold, local shrinkage values may be obtained by comparing dimensions of this array with dimensions of the array replicated on the surface of the parts. A profilograph is employed to obtain dimensional measurements, in the parallel to flow direction and in the cross flow direction. A sensitivity analysis is conducted to determine aspects of shrinkage evaluation causing uncertainty on the results. Prominent sources of uncertainty found are mark straightness defect and part warpage. Uncertainty on shrinkage is evaluated to 0.00025 mm/mm for a distance between the marks of 6.350 mm. Shrinkages have been evaluated locally for molded plates. Different distribution forms were observed for parallel to flow and cross flow shrinkage. Important anisotropy is also observed. The effects of holding pressure and injection velocity on shrinkages have been evaluated using a 2³ factorial design of experiment for three locations on the plates. Finally, shrinkages for three mold geometries have been compared: constant thickness plate, variable in thickness symmetrical plate, and variable in thickness asymmetrical plate. Variable in thickness plates showed the importance of solidification dynamics on final shrinkages. POLYM. ENG. SCI., 46:1275–1283, 2006. © 2006 Society of Plastics Engineers     

Study of the telomerization of dimethylaminoethyl methacrylate (DMAEMA) with mercaptoethanol. Application to the synthesis of a new macromonomer

The telomerization of dimethylaminoethyl methacrylate (DMAEMA) with mercaptoethanol initiated by 2,2′-azobisisobutyronitrile was first investigated at 70 °C and the influence of the type of solvent was studied. The results showed that well-defined telomers of DMAEMA could not be synthetized via telomerization of DMAEMA in water or water/acetonitrile mixture since the telomerization reaction is in competition with the nucleophilic addition of thiol onto the monomer. Transfer constants for mercaptoethanol in benzene and acetonitrile were determined by Mayo's and O'Brien's methods. The transfer constant obtained in acetonitrile (0,6) was higher than that obtained in benzene. This difference can be explained by the fact that the thiol was consumed by two reactions: nucleophilic addition and telomerization. The influence of solvents on the polymerization kinetics was enlightened. These results were applied to the synthesis of macromonomers of DMAEMA with isocyanatoethyl methacrylate (IEM). These macromonomers were copolymerized with styrene.     

Co‐injection molding of PVC with other thermoplastics: Processing,properties, and applications

Rigid poly(vinyl chloride) (PVC) was co‐injected with glass‐fiber‐reinforced PVC (GFR‐PVC), polypropylene (PP), acrylonitrile‐butadiene‐styrene copolymer (ABS), and polycarbonate (PC) by using the Mono‐sandwich co‐injection process. Up to three through‐thickness skin‐core morphologies were observed along the length of the sample. Near the gate, the core was always a single, continuous layer. In some cases, the core diverged into multiple or discontinuous layers. Farther from the gate, flow of the core ceased, leaving a skin‐only region. The skin and core layers were more uniformly distributed through the test plaque when injection speed was low. Adhesion between PVC and PP was poor. Skin and core layers delaminated, and mechanical properties were poor. The PVC adhered well to GFR‐PVC, ABS, and PC. No layer delamination occurred, and mechanical properties were intermediate between those of the skin and core components alone. Dropped dart impact energy was controlled more by the skin layer than the core. In rigid PVC/GFR‐PVC co‐injected samples, impact energy was 2.5 times greater when GFR‐PVC was the core than when GFR‐PVC was the skin.     

Synthesis and characterization of long-chain fatty acid cellulose ester (FACE)

Long-chain fatty acid cellulose esters (FACE) were synthesized by the acid chloride-pyridine reaction with different degrees of substitution (DS). The hydrolyzed soybean oil was used as unsaturated fatty acids, its unsaturation degree, and composition were analyzed by ¹H and ¹³C NMR methods. The chemical structures of FACE were confirmed by solid-state ¹³C NMR, and substitution reaction of fatty acid chloride on cellulose were analyzed by IR spectroscopy. FACE(s) are insoluble in common organic solvents, such as benzene, toluene, THF, etc., at refluxing temperature. As the DS increased, the tensile strength of extruded FACE films decreased, but elongation increased. © 1994 John Wiley & Sons, Inc.     

Biochemical,functional, and histochemical effects of essential fatty acid deficiency in rat kidney

The present study was designed to examine the effects of EFA deficiency (EFAD) on biochemical, functional, and structural aspects of the kidney in growing and adult rats fed a normal or EFAD diet for 9 wk after weaning. Food and fluid intake (FI), urine volume, and Na⁺ and K⁺ excretions were measured weekly from weeks 4 to 8 by placing the rats in individual metabolic cages for 24 h. At week 9, Li⁺ and a 5% water load, respectively, were administered at 14 and 1.5 h prior to glomerular and proximal tubular function studies, as assessed by 3-h creatinine (C_Cr) and Li⁺ (C_Li+) clearances. Hematocrit and urine volume; serum and urine [Cr], [Li⁺], [Na⁺], and [K⁺]; and renal FA distribution were also measured. Data [corrected to 100 g/body weight (bw) and presented as means ±SEM] were significant, at P<-0.05. Despite a similar ingestion of solids from weeks 4 to 7 (weeks 7 to 10 of life), the rats on the EFAD diet showed a decreased body weight from week 5. From weeks 4 to 8, Fl and urine volume were similar for both groups, but the Fl increased at week 6 in the EFAD group; 24-h Na⁺ and K⁺ excretions were similar at all weeks, except for an increase in the EFAD group for both ions at week 7. In the EFAD group, C_Cr and C_Li+ decreased by 27 and 56.3%, respectively (385.7±33.4 vs. 280±21.1, and 21.0±2.1 vs. 9.2±1.1 μL/min/100 g; n=9 vs. 10), the latter result suggesting increased proximal reabsorption. The 3-h Na⁺ and K⁺ excretions were similar, but the Li⁺ decreased (0.78±0.06×10⁻² vs. 0.32±0.03×10⁻² μeq/min/100 g) in the EFAD group, giving additional support to the suggestion. Renal structure was normal and similar for both groups, but the EFAD group showed a more prominent proximal tubule brush border, together with heavier periodic acid-Schiff staining in all specimens from weeks 5 to 9. In the EFAD group, FA of the n−9 and n−7 series were higher, but most of the n−6 series were lower as a percentage of total lipids in the medulla and cortex. Medullary levels of 20∶4n−6 were maintained, 22∶4n−6 declined twice, arachidonic acid was maintained, and 20∶5n−3 was lower. The EFAD diet affected glomerular function, proximal tubular structure and function, and FA distribution in the rat kidney.     

Lipids of seven cereal grains

Grain samples of representative varieties of barley, corn, oats, rye, sorghum, triticale, and wheat grown commercially in the north central US were analyzed. Chemical constituents of the varieties studied are presented to provide an overview of their characteristics. Lipids of the milled grain samples were solvent extracted, classified by silicic acid column chromatography, and separated by thin layer chromatography. Fatty acid composition of the total lipid was determined by gas liquid chromatography and the fatty acid content was determined by saponification and extraction. Total lipid content of the grains ranged from 2.3% for ‘Polk’ wheat to 6.6% for ‘Chief’ oats. Lipid composition varied considerably. The row crops, corn and sorghum, have a high neutral lipid and low glycolipid content. The small grain varieties have a more balanced distribution among neutral lipids, glycolipids, and phospholipids. Fatty acid composition of the total lipid was similar for all grains. Minor qualitative differences were noted among the lipid classes of the 7 cereals.     

Zinc-rich powder coatings corrosion in sea water: influence of conductive pigments

The effect of addition of conductive pigments like carbon blacks on the corrosion behavior of zinc-rich powder paints coated steel in artificial sea water was investigated. Open circuit potential measurements were used to characterize the cathodic protection ability and duration. Micro-Raman spectroscopy analysis was performed in order to identify the corrosion products and to follow the penetration of the solution inside the coatings.

Two different effects were pointed out: an increase of the porosity induced by carbon addition and a galvanic action between zinc and carbon pigments. The performance of the powder coatings, strongly improved if the carbon amount is sufficient, was compared to the one reported for solvent-based zinc-rich paints.