Tandem cationic and sol–gel photopolymerizations of a vinyl ether alkoxysilane

In the present study, a novel single hybrid monomer combining a vinylether and trimethoxysilane groups in the same molecule was synthesized by chemoselective hydrosilation and subjected to UV‐irradiation in the presence of a triarylsulfonium salt. Through the UV‐decomposition of this photoacid generator, two acid‐catalyzed processes occurred simultaneously: the cationic polymerization of the vinyl ether functions and the sol–gel polycondensation of the alkoxysilyl groups, leading to a type II polyvinyl‐polysilicate nanocomposite film. Both reaction kinetics were efficiently monitored by real‐time Fourier transform infrared spectroscopy, and the influence of different key experimental parameters was investigated (laminated conditions, UV irradiation equipment, and film thickness). A particular attention was also given to the complete characterization of the hybrid microstructure by associating ²⁹Si and ¹³C solid‐state NMR. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

An early and a late developing system for learning and retention in infant monkeys.

Separate groups of rhesus monkeys of different ages were tested in delayed nonmatching-to-sample and 24-hr concurrent discrimination-learning tasks considered to be measures of recognition memory and habit-formation systems, respectively, in an ontogenetic comparison of the development of these 2 systems. In Exp I, the visual-recognition abilities of 17 3-, 6-, or 12-mo-old Ss were measured, while 7 3-mo-old Ss were compared to adult controls on a discrimination-learning task in Exp II. Results show that infant Ss failed to learn the nonmatching task until they were approximately 4 mo old. With further maturation, learning ability gradually improved, but did not reach adult levels of proficiency even when Ss were 1 yr old. Postlearning evaluation with long delays and lists confirmed this slow ontogenetic development of recognition memory to adult levels of function. By contrast, 3–4 mo old Ss learned to discriminate long lists of object-pairs nearly as quickly as adults, despite 24-hr intertrial intervals. This striking dissociation in the ability of infants on the 2 tasks closely resembles the dissociation previously found in adults rendered amnesic by limbic lesions. Findings suggest that, whereas the nonlimbic habit system matures early in infancy, the limbic-dependent memory system develops more slowly. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanisms of same-different abstract-concept learning by rhesus monkeys (Macaca mulatta).

Experiments with 9 rhesus monkeys (Macaca mulatta) showed, for the first time, that abstract-concept learning varied with the training stimulus set size. In a sameldifferent task, monkeys required to touch a top picture before choosing a bottom picture (same) or white rectangle (different) learned rapidly. Monkeys not required to touch the top picture or presented with the top picture for a fixed time learned slowly or not at all. No abstract-concept learning occurred after 8-itern training but progressively improved with larger set sizes and was complete following 128-itern training. A control monkey with a constant 8-item set ruled out repeated training and testing. Contrary to the unique-species account, it is argued that different species have quantitative, not qualitative, differences in abstract-concept learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of the Bio‐Based Epoxy Prepolymer Structure on Network Properties

Three different bio‐based epoxy prepolymers are studied: one that is synthesized from isosorbide and two that are commercial prepolymers derived from sorbitol and cardanol. The chemical structures are analyzed by SEC, ESI–TOF MS, and FTIR analyses. The bio‐based prepolymers exhibit different structures, either aromatic with long aliphatic chains for the epoxy prepolymer derived from cardanol (DGECAR), with high functionality for the sorbitol polyglycidyl ether (SPGE) or a short and cyclic structure for the epoxy prepolymer derived from isosorbide (DGEDAS₀). A traditional petroleum‐based epoxy prepolymer, diglycidyl ether of bisphenol A (DGEBA) is also used for comparison. Gelation and reactivity of the different precursors with an isophorone diamine hardener are studied using rheological measurements and differential scanning calorimetry. Glass transition temperatures of the epoxy networks are evaluated and the thermal stability is also studied by thermo‐gravimetric analysis.

     

Pro-Calcific Environment Impairs Ischaemia-Driven Angiogenesis

Peripheral arterial disease (PAD) is characterised by accelerated arterial calcification and impairment in angiogenesis. Studies implicate vascular calcification as a contributor to PAD, but the mechanisms remain unclear. We aimed to determine the effect of calcification on ischaemia-driven angiogenesis. Human coronary artery endothelial cells (ECs) were treated with calcification medium (CM: CaCl₂ 2.7 mM, Na₂PO₄ 2.0 mM) for 24 h and exposed to normoxia (5% CO₂) or hypoxia (1.2% O₂; 5% CO₂ balanced with N₂). In normoxia, CM significantly inhibited tubule formation and migration and upregulated calcification markers of ALP, BMP2, and Runx2. CM elevated levels of calcification-protective gene OPG, demonstrating a compensatory mechanism by ECs. CM failed to induce pro-angiogenic regulators VEGFA and HIF-1α in hypoxia and further suppressed the phosphorylation of endothelial nitric oxide synthase (eNOS) that is essential for vascular function. In vivo, osteoprotegerin-deficient mice (OPG^−/−), a calcification model, were subjected to hind-limb ischaemia (HLI) surgery. OPG^−/− mice displayed elevated serum alkaline phosphatase (ALP) activity compared to wild-type controls. OPG^−/− mice experienced striking reductions in blood-flow reperfusion in both 8-week-old and 6-month-old mice post-HLI. This coincided with significant impairment in tissue ischaemia and reduced limb function as assessed by clinical scoring (Tarlov). This study demonstrated for the first time that a pro-calcific environment is detrimental to ischaemia-driven angiogenesis. The degree of calcification in patients with PAD can often be a limiting factor with the use of standard therapies. These highly novel findings require further studies for full elucidation of the mechanisms involved and have implications for the development of therapies to suppress calcification in PAD.     

Electronic Structure and Solvation Effects from Core and Valence Photoelectron Spectroscopy of Serum Albumin

X-ray photoelectron spectroscopy of bovine serum albumin (BSA) in a liquid jet is used to investigate the electronic structure of a solvated protein, yielding insight into charge transfer mechanisms in biological systems in their natural environment. No structural damage was observed in BSA following X-ray photoelectron spectroscopy in a liquid jet sample environment. Carbon and nitrogen atoms in different chemical environments were resolved in the X-ray photoelectron spectra of both solid and solvated BSA. The calculations of charge distributions demonstrate the difficulty of assigning chemical contributions in complex systems in an aqueous environment. The high-resolution X-ray core electron spectra recorded are unchanged upon solvation. A comparison of the valence bands of BSA in both phases is also presented. These bands display a higher sensitivity to solvation effects. The ionization energy of the solvated BSA is determined at 5.7 ± 0.3 eV. Experimental results are compared with theoretical calculations to distinguish the contributions of various molecular components to the electronic structure. This comparison points towards the role of water in hole delocalization in proteins.     

Abstract-concept learning and list-memory processing by capuchin and rhesus monkeys.

Three capuchin monkeys (Cebus apella) touched the lower of 2 pictures (same) or a white rectangle (different), increased same/different abstract-concept learning (52% to 87%) with set-size increases (8 to 128 pictures), and were better than 3 rhesus monkeys (Macaca mulatta). Three other rhesus that touched the top picture before choices learned similar to capuchins but were better at list-memory learning. Both species' serial position functions were similar in shape and changes with retention delays. Other species showed qualitatively similar shape changes but quantitatively different time-course changes. In abstract-concept learning, qualitative similarity was shown by complete concept learning, whereas a quantitative difference would have been a set-size slope difference. Qualitative similarity is discussed in relation to general-process versus modular cognitive accounts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term effects of selective neonatal temporal lobe lesions on learning and memory in monkeys.

Rhesus monkeys with neonatal damage to either the medial temporal lobe or the inferior temporal cortical area TE, and their normal controls, were reassessed in visual habit formation (24-hour intertrial interval task) and visual recognition (delayed nonmatching to sample [DNMS]) at 4–5 years of age and then tested on tactile and spatial DNMS. Results on the two visual tasks were the same as those obtained when the monkeys were under 1 year of age. Specifically, early medial temporal lesions, like late lesions, left habit formation intact but severely impaired recognition memory. Furthermore, the memory deficit extended to the tactile and spatial modalities. By contrast, early damage to TE, unlike late damage to it, yielded only mild deficits on both visual tasks and had no effect on tactile or spatial DNMS. Compensatory mechanisms that promote substantial and permanent recovery thus appear to be available after neonatal TE lesions but not after neonatal medial temporal lesions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of hemoglobin and its metabolites on energy metabolism in cultured cerebrovascular smooth-muscle cells

Cerebral arteries in spasm have been found to contain low levels of adenosine triphosphate (ATP), and it has been postulated that this change in levels results from hypoxia produced by arterial encasement in clotted material. This study was undertaken to determine whether any of four blood-derived agents, ferrous hemoglobin, methemoglobin, hemin, or bilirubin, is capable of reducing energy levels in cerebral artery smooth-muscle cells. Twenty-four-hour exposure of cultured canine basilar artery cells to ferrous hemoglobin and bilirubin led to a significant decline in ATP levels (to 8.9 nmol/mg protein and 2.8 nmol/mg protein, respectively) versus control (16.6 nmol/mg protein); methemoglobin and hemin showed no effect. Bilirubin but not hemoglobin was found to interfere with electron transport and with creatine phosphokinase activity in intact cells; however, bilirubin showed no inhibitory effect on this enzyme in cell-free conditions. The findings indicate that hemoglobin and bilirubin may be responsible for diminished energy levels in cerebral arteries. These observations also suggest that bilirubin may exert its effect on ATP by impairing mitochondrial function.     

A non-lethal chemically based approach to investigate the quality of harbour sediments

A non-lethal chemically based approach was used to investigate the quality of harbour sediments receiving combined road runoff and sewage effluents. A previous investigation of the behaviour of the amphipod Corophium volutator linked polycyclic aromatic hydrocarbons (PAH) in sediments corresponding to the probable effects levels listed in the sediment quality guidelines of the Canadian Council of the Marine Environment to a sediment avoidance response. Since the amphipods did not biotransform contaminants, bioaccumulation was the only fate pursued to examine the bioavailability of PAH. For five Halifax Harbour sediments, a relationship was established between the threshold effects level representing the amphipods' avoidance response and the bioaccumulation of PAH. A body burden of 0.3-1.1 mumol/kg (wet weight) was determined for the sum of abundant parental PAH in amphipods exposed to sediments that initiated the behavioural effect. PAH were much more available from spiked sediments than from field sediments, with biota-sediment accumulation factors of 2.2-7.8 compared to <0.01-0.3, respectively. Animals exposed to PAH-spiked sediments avoided contaminated sediments when their body burden was up to seven times higher than observed with field sediments. This latter result and two exposures to sediments collected further away from sewage discharges point to a role for unidentified chemicals in the body burden and behaviour relationship. Further research is warranted to develop this promising assessment tool.