bluuebunny/crossref_metadata_2025 huggingface dataset:
How cellular processing of superparamagnetic nanoparticles affects their magnetic behavior and NMR relaxivity
Authors: Lévy Michael , Wilhelm Claire , Devaud Martin , Levitz Pierre , Gazeau Florence
Published: May 2012

Cellular processing of nanomaterials may affect their physical properties at the root of various biomedical applications. When nanoparticles interact with living cells, their spatial distribution is progressively modified by cellular activity, which tends to concentrate them into intracellular compartments, changing in turn their responsivity to physical stimuli. In this paper, we investigate the consequences of cellular uptake on the related magnetic properties and NMR relaxivity of iron oxide nanoparticles. The superparamagnetic behavior (field‐dependent and temperature‐dependent magnetization curves investigated by SQUID (Superconducting Quantum Interference Device) measurements) and nuclear magnetic relaxation dispersion (NMRD) R1 profiles of citrate‐coated maghemite nanoparticles (mean diameter 8 nm) were characterized in colloidal suspension and after being uptaken by several types of cells (tumor cells, stem cells and macrophages). The temperature‐dependent magnetization as well as the NMRD profile were changed following cellular uptake depending on the stage of endocytosis process while the field‐dependent magnetization at room temperature remained unchanged. Magnetic coupling between nanoparticles confined in cell lysosomes accounts for the modification in magnetic behavior, thereby reflecting the local organization of nanoparticles. NMR longitudinal relaxivity was directly sensitive to the intracellular distribution of nanoparticles, in line with Transmission Electron Microscopy TEM observations. This study is the first attempt to link up magnetic properties and NMR characterization of iron oxide nanoparticles before and after their cell processing. Copyright © 2012 John Wiley & Sons, Ltd.
Cyclen‐Based Cationic Lipids Containing Carbamate Linkages as Efficient Gene Delivery Vectors with Low Toxicity
Authors: Huang Qing‐Dong , Ren Jiang , Chen Hong , Ou Wen‐Jing , Zhang Ji , Fu Yun , Zhu Wen , Yu Xiao‐Qi
Published: May 2012

Two novel cationic lipids based on protonated cyclen and steroid (cholesterol or diosgenin) moieties with carbamate linkage have been designed and synthesized for gene delivery. Cationic liposomes were easily prepared from each of these lipids individually or from the mixtures of each cationic lipid and dioleoylphosphatidyl ethanolamine (DOPE). Several studies including dynamic light scattering, gel retardation assay, ethidium bromide intercalation assay, and transmission electron microscopy (TEM) imaging demonstrate that these amphiphilic molecules are able to bind and compact DNA into nanoparticles which may act as nonviral gene delivery agents. Results from in vitro transfection show that in association with (DOPE), two cationic lipids can induce effective gene transfection in HEK 293, A549, and H460 cells. Especially, in tumor cells (A549 and H460), the gene transfection efficiency of two cationic lipids were found to be higher than that of commercially available Lipofectamine 2000. The lipoplexes formed from both cationic lipids were found to have low cytotoxicity in three cell lines even at high N/P ratios.
A simulation study for the distribution law of relative moments of evolution
Authors: Jäntschi Lorentz , Bolboacă Sorana D. , Sestraş Radu E.
Published: May 2012

Nine selection‐survival strategies were implemented in a genetic algorithm experiment, and differences in terms of evolution were assessed. The moments of evolution (expressed as generation numbers) were recorded in a contingency of three strategies (i.e., proportional, tournament, and deterministic) for two moments (i.e., selection for crossover and mutation and survival for replacement). The experiment was conducted for the first 20,000 generations in 46 independent runs. The relative moments of evolution (where evolution was defined as a significant increase in the determination coefficient relative to the previous generation) when any selection‐survival strategy was used fit a Log‐Pearson type III distribution. Moreover, when distributions were compared to one another, functional relationships were identified between the population parameters, revealing a degeneration of the Log‐Pearson type III distribution in a one‐parametrical distribution that can be assigned to the chosen variable—evolution strategy. The obtained theoretical population distribution allowed comparison of the selection‐survival strategies that were used. © 2012 Wiley Periodicals, Inc. Complexity, 2012.
Tunable synthesis of hierarchical TiO2 spheres consisting of rutile nanowires for dye‐sensitized solar cells and photocatalysis
Authors: Wang Hequan , Yu Xiao , Li Haibo , Du Yu , Xin Ling
Published: May 2012

Hierarchical TiO2 spheres consisting of rutile nanowires (HTS) are successfully prepared in the bulk solution via a non‐polar solvent/polar solution interfacial syntheses strategy. The effect of reaction temperature on the morphology, size, BET surface area and monodispersion of HTS is studied systematically. Increasing reaction temperature decreases the diameter of spheres in micro‐scale whereas increases the diameter of nanowires in nano‐scale for these HTS. Monodisperse HTS are formed at 230 °C for 20 h, which can suitably be served as light scattering structure for dye‐sensitized solar cell with the additional advantage of rapid electron transport rate. A high efficiency of 8.54% was achieved for the composite DSSC consisting of nanoparticles and monodispersed HTS (synthesized at 230 °C), showing 31.38% improvement compared with that (6.5%) of the DSSCs made from pure P25 nanoparticles at the similar thickness. Furthermore, the photocatalytic performances of HTS for the degradation of methyl orange were also investigated. Contrary to the effect on the performance of DSSC, the HTS synthesized at 150 °C show higher photocatalytic degradation efficiency due to larger BET surface area.
Reactivity of (E)‐4‐Hydroxy‐2‐nonenal with Fluorinated Phenylhydrazines: Towards the Efficient Derivatization of an Elusive Key Biomarker of Lipid Peroxidation
Authors: Matera Riccardo , Gabbanini Simone , Valvassori Alice , Triquigneaux Mathilde , Valgimigli Luca
Published: May 2012

4‐Hydroxynonenal (4‐HNE) is a major product of the oxidation of ω‐6‐polyunstaturated lipids and an effector of radical‐mediated oxidative damage, whose analytical determination requires chemical derivatization. In this work, its reactivity with fluorinated phenylhydrazines was explored both under preparative and analytical settings. A five‐step synthesis of 4‐HNE on gram‐scale with an overall yield of 30 % is described. Reaction of 4‐HNE with ortho‐, meta‐, or para‐CF3‐phenylhydrazine, as well as with the 3,5‐di‐CF3, 2,4‐di‐CF3, or pentafluoro analogues, in MeCN with 0.5 mM TFA yields the corresponding hydrazones with rate constants kf of 2.8 ± 0.4, 1.7 ± 0.1, 3.0 ± 0.2, 0.6 ± 0.1, 0.5 ± 0.1, and 3.5 ± 0.5 M–1 s–1, respectively at 298 K. At higher temperatures, the hydrazones undergo intramolecular cyclization to form 1,6‐dihydropyridazines that, depending on the solvent and temperature, may further react with the hydrazine to yield tetrahydropyridazine adducts and their oxidation products. Other reaction products were isolated, depending on the reaction conditions, and the complex reactivity of 4‐HNE with the above nucleophiles is discussed. Due to the good yield and rate of formation of the hydrazone adducts, their stability and favorable UV absorbance, 2‐(trifluoromethyl)phenylhydrazine and 2,3,4,5,6‐pentafluorophenylhydrazine are the most interesting candidates for the development of rapid and efficient analytical derivatizations of 4‐HNE.
Stabilities of Immonium Ions Derived from N‐Heterocyclic Carbenes Probed by Collision‐Induced Dissociation Mass Spectrometry
Authors: Polyakova Svetlana M. , Kunetskiy Roman A. , Schröder Detlef
Published: May 2012

We report efficient methods for the synthesis of both symmetrically and non‐symmetrically substituted bis(imidazol‐2‐yliden)ammonium ions and a new family of bis(imidazol‐2‐ylidene)formamidines. The fragmentation pathways of these cations were studied in detail by electrospray ionization combined with tandem mass spectrometry. Interestingly, in these cations direct C–N bond cleavage leading to loss of alkyl radicals can compete with rearrangement reactions leading to closed‐shell fragments. The experimental results for the major fragmentation channels are compared with those derived from DFT calculations. Inter alia, a novel rearrangement of the cationic species involving specific alkyl migrations between the two imidazole subunits has been found.
Toxicokinetic and toxicodynamic model for diazinon toxicity—mechanistic explanation of differences in the sensitivity of Daphnia magna and Gammarus pulex
Authors: Kretschmann Andreas , Ashauer Roman , Hollender Juliane , Escher Beate I.
Published: May 2012

A mechanistic toxicokinetic and toxicodynamic model for acute toxic effects (immobilization, mortality) of the organothiophosphate insecticide diazinon in Daphnia magna is presented. The model was parameterized using measured external and internal (whole-body) concentrations of diazinon, its toxic metabolite diazoxon, and the inactive metabolite 2-isopropyl-6-methyl-4-pyrimidinol, plus acetylcholinesterase (AChE) activity measured during exposure to diazinon in vivo. The toxicokinetic and toxicodynamic model provides a coherent picture from exposure to the resulting toxic effect on an organism level through internally formed metabolites and the effect on a molecular scale. A very fast reaction of diazoxon with AChE (pseudo first-order inhibition rate constant ki = 3.3 h−1) compared with a slow formation of diazoxon (activation rate constant kact = 0.014 h−1) was responsible for the high sensitivity of D. magna toward diazinon. Recovery of AChE activity from inhibition was slow and rate-determining (99% recovery within 16 d), compared with a fast elimination of diazinon (99% elimination within 17 h). The obtained model parameters were compared with toxicokinetic and toxicodynamic parameters of Gammarus pulex exposed to diazinon from previous work. This comparison revealed that G. pulex is less sensitive because of a six times faster detoxification of diazinon and diazoxon and an approximately 400 times lower rate for damage accrual. These differences overcompensate the two times faster activation of diazinon to diazoxon in G. pulex compared to D. magna. The present study substantiates theoretical considerations that mechanistically based effect models are helpful to explain sensitivity differences among different aquatic invertebrates. Environ. Toxicol. Chem. 2012; 31: 2014–2022. © 2012 SETAC
A new species and some notes on the genus Nonea (Boraginaceae) in Iran
Authors: Falatoury Atiye Nejhad , Pakravan Maneezheh , Tavassoli Akhtar
Published: May 2012

The new species Nonea iranica (Boraginaceae‐Boragineae) is described from central region of Iran. It shows a combination of morphological characteristics concerning root, flower and fruit that distinguishes it from N. caspica and N. polychoroma. The palynological examination supports the results of morphological observations. The doubts about two species of Iran, N. longiflora and N. stenosolen, are discussed. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Expression of olfactory‐type cyclic nucleotide‐gated channels in rat cortical astrocytes
Authors: Podda Maria Vittoria , Leone Lucia , Piacentini Roberto , Cocco Sara , Mezzogori Daniele , D'Ascenzo Marcello , Grassi Claudio
Published: May 2012

Cyclic nucleotide‐gated (CNG) channels are nonselective cation channels activated by cyclic AMP (cAMP) or cyclic GMP (cGMP). They were originally identified in retinal and olfactory receptors, but evidence has also emerged for their expression in several mammalian brain areas. Because cGMP and cAMP control important aspects of glial cell physiology, we wondered whether CNG channels are expressed in astrocytes, the most functionally relevant glial cells in the CNS. Immunoblot and immunofluorescence experiments demonstrated expression of the CNG channel olfactory‐type A subunit, CNGA2, in cultured rat cortical astrocytes. In patch‐clamp experiments, currents elicited in these cells by voltage ramps from −100 to +100 mV in the presence of the cGMP analogue, dB‐cGMP, were significantly reduced by the CNG channel blockers, L‐cis‐diltiazem (LCD) and Cd2+. The reversal potentials of the LCD‐ and Cd2+‐sensitive currents were more positive than that of K+, as expected for a mixed cation current. Noninactivating, voltage‐independent currents were also elicited by extracellular application of the membrane permeant cGMP analogue, 8‐Br‐cGMP. These effects were blocked by LCD and were mimicked by natriuretic peptide receptor activation and inhibition of phosphodiesterase activity. Voltage‐independent, LCD‐sensitive currents were also elicited by 8‐Br‐cGMP in astrocytes of hippocampal and neocortical brain slices. Immunohistochemistry confirmed a broad distribution of CNG channels in astrocytes of the rat forebrain, midbrain, and hindbrain. These findings suggest that CNG channels are downstream targets of cyclic nucleotides in astrocytes, and they may be involved in the glial‐mediated regulation of CNS functions under physiological and pathological conditions. © 2012 Wiley Periodicals, Inc.
Modulation by pregnenolone sulfate of filtering properties in the hippocampal trisynaptic circuit
Authors: Scullin Chessa S. , Partridge L. Donald
Published: May 2012

Short‐term synaptic plasticity alters synaptic efficacy on a timescale that is relevant to encoding information in spike trains. The dynamics of this plasticity, combined with that of the feedback and feedforward contributions of local interneurons, impose frequency‐dependent properties on neuronal networks with implications for nervous system function. The trisynaptic network of the hippocampus is especially well suited to selectively filter components of frequency‐dependent signals that are transmitted from the entorhinal cortex. We measured presynaptic [Ca2+]i in perforant path, mossy fiber, or Schaffer collateral terminals while simultaneously measuring field potentials of principal cells of the dentate, CA3, or CA1 synaptic fields over a range of stimulus frequencies of 2 to 77 Hz. In all three synaptic fields, the average [Ca2+]i during a 500 ms stimulus train rose monotonically with stimulus frequency. The average population spike amplitude during this stimulus train, however, exhibited a non‐linear relationship to frequency that was distinct for each of the three synaptic fields. The dentate synaptic field exhibited the characteristics of a low pass filter, while both CA synaptic fields had bandpass filter characteristics with a gain that was greater than 1 in the passband frequencies. Importantly, alteration of the dynamic properties of this network could significantly impact information processing performed by the hippocampus. Pregnenolone sulfate (PregS), has frequency‐dependent effects on paired‐ and multipulse plasticity in the dentate and CA1 synaptic fields of the hippocampal formation. We investigated the PregS‐dependent modulation of the dynamic properties of transmission by the principal cells of the three hippocampal synaptic fields. Importantly, PregS is capable of altering the pattern separation capabilities that may underlie hippocampal information processing. © 2012 Wiley Periodicals, Inc.
From policy to reality: clinical managers' views of the organizational challenges of primary care reform in Portugal
Authors: Lapão Luís Velez , Dussault Gilles
Published: May 2012

The primary healthcare reform in Portugal is based on the development of a new management model and clinical governance framework. The objective is to strengthen primary healthcare services to reduce the inappropriate utilization of secondary and emergency services and to make efficiency gains and to better control costs. New interventions include the introduction of a system of production‐based incentives for family health units. This paper presents an initial assessment of the implementation of the new policies and tries to explain the gap between its expected results and what was observed in the field 5 years later. We used a Strengths, Weaknesses, Opportunities, and Threats analysis conducted in 12 regions, to collect the perceptions of members of Clinical Councils of Health Centers Groups, responsible for the implementation of the reform. The analysis looked at the dimensions of coverage, productivity, technical quality, and service quality. It identifies weaknesses in human resources management (shortages, incentives, team management) and lack of support from central and regional management. There is a perceived gap between the framework for reform as defined by law and the support made available for its implementation, leading to tensions between decision makers, managers, and health professionals. Copyright © 2012 John Wiley & Sons, Ltd.
Multimodal photoacoustic ophthalmoscopy in mouse
Authors: Song Wei , Wei Qing , Feng Liang , Sarthy Vijay , Jiao Shuliang , Liu Xiaorong , Zhang Hao F.
Published: May 2012

Photoacoustic ophthalmoscopy (PAOM) is a novel imaging technology that measures optical absorption in the retina. The capability of PAOM can be further enhanced if it could image mouse eyes, because mouse models are widely used for various retinal diseases. The challenges in achieving high‐quality imaging of mouse retina, however, come from the much smaller eyeball size. Here, we report an optimized imaging system, which integrates PAOM, spectral‐domain optical coherence tomography (SD‐OCT), and autofluorescence‐scanning laser ophthalmoscopy (AF‐SLO), for mouse eyes. Its multimodal capability was demonstrated by imaging transgenic Nrl‐GFP mice that express green fluorescent protein (GFP) in photoreceptors. SD‐OCT provided guidance of optical alignment for PAOM and AF‐SLO, and complementary contrast with high depth‐resolution retinal cross sections. PAOM visualized the retinal vasculature and retinal pigment epithelium melanin, and AF‐SLO measured GFP‐expressing in retinal photoreceptors. The in vivo imaging results were verified by histology and confocal microscopy. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Catch up in bone acquisition in young adult men with late normal puberty
Authors: Darelid Anna , Ohlsson Claes , Nilsson Martin , Kindblom Jenny M , Mellström Dan , Lorentzon Mattias
Published: May 2012

The aim of this study was to investigate the development of bone mineral density (BMD) and bone mineral content (BMC) in relation to peak height velocity (PHV), and to investigate whether late normal puberty was associated with remaining low BMD and BMC in early adulthood in men. In total, 501 men (mean ± SD, 18.9 ± 0.5 years of age at baseline) were included in this 5-year longitudinal study. Areal BMD (aBMD) and BMC, volumetric BMD (vBMD) and cortical bone size were measured using dual-energy X-ray absorptiometry (DXA) and pQCT. Detailed growth and weight charts were used to calculate age at PHV, an objective assessment of pubertal timing. Age at PHV was a strong positive predictor of the increase in aBMD and BMC of the total body (R2 aBMD 11.7%; BMC 4.3%), radius (R2 aBMD 23.5%; BMC 22.3%), and lumbar spine (R2 aBMD 11.9%; BMC 10.5%) between 19 and 24 years (p < 0.001). Subjects were divided into three groups according to age at PHV (early, middle, and late). Men with late puberty gained markedly more in aBMD and BMC at the total body, radius, and lumbar spine, and lost less at the femoral neck (p < 0.001) than men with early puberty. At age 24 years, no significant differences in aBMD or BMC of the lumbar spine, femoral neck, or total body were observed, whereas a deficit of 4.2% in radius aBMD, but not in BMC, was seen for men with late versus early puberty (p < 0.001). pQCT measurements of the radius at follow-up demonstrated no significant differences in bone size, whereas cortical and trabecular vBMD were 0.7% (p < 0.001) and 4.8% (p < 0.05) lower in men with late versus early puberty. In conclusion, our results demonstrate that late puberty in males was associated with a substantial catch up in aBMD and BMC in young adulthood, leaving no deficits of the lumbar spine, femoral neck, or total body at age 24 years. © 2012 American Society for Bone and Mineral Research.
Effect of low-dose calcium supplements on bone loss in perimenopausal and postmenopausal Asian women: A randomized controlled trial
Authors: Nakamura Kazutoshi , Saito Toshiko , Kobayashi Ryosaku , Oshiki Rieko , Kitamura Kaori , Oyama Mari , Narisawa Sachiko , Nashimoto Mitsue , Takahashi Shunsuke , Takachi Ribeka
Published: May 2012

Current standard-dose calcium supplements (eg, 1000 mg/d) may increase the risk for cardiovascular events. Effectiveness of lower-dose supplements in preventing bone loss should thus be considered. This study aimed to assess whether calcium supplements of 500 or 250 mg/d effectively prevent bone loss in perimenopausal and postmenopausal Japanese women. We recruited 450 Japanese women between 50 and 75 years of age. They were randomly assigned to receive 500 mg of calcium (as calcium carbonate), 250 mg of calcium, or placebo daily. Medical examinations conducted three times over a 2-year follow-up period assessed bone mineral density (BMD) of the lumbar spine and femoral neck. One-factor repeated measures ANOVA was used for statistical tests. Subgroup analyses were also conducted. Average total daily calcium intake at baseline for the 418 subjects who underwent follow-up examinations was 493 mg/d. Intention-to-treat analysis showed less dramatic decreases in spinal BMD for the 500-mg/d calcium supplement group compared to the placebo group (1.2% difference over 2 years, p = 0.027). Per-protocol analysis (≥80% compliance) revealed that spinal BMD for the 500-mg/d and 250-mg/d calcium supplement groups decreased less than the placebo group (1.6%, p = 0.010 and 1.0%, p = 0.078, respectively), and that femoral neck BMD for the 500-mg/d calcium supplement group decreased less relative to the placebo group (1.0%, p = 0.077). A low-dose calcium supplement of 500 mg/d can effectively slow lumbar spine bone loss in perimenopausal and postmenopausal women with habitually low calcium intake, but its effect on the femoral neck is less certain. Calcium supplementation dosage should thus be reassessed. (Clinical Trials Registry number: UMIN000001176). © 2012 American Society for Bone and Mineral Research.
Hematopoietic progenitor constituents and adherent cell progenitor morphology isolated from black‐rumped agouti (Dasyprocta prymnolopha, Wagler 1831) bone marrow
Authors: Da Rocha Andressa Rego , Alves Flávio Ribeiro , Neto NapoleãO Martins Argôlo , Dos Santos Luciano Fonseca , De Almeida Hatawa Melo , De Carvalho Yulla Klinger Pereira , Bezerra Dayseanny De Oliveira , Ferraz Maíra Soares , Pessoa Gerson Tavares , De Carvalho Maria Acelina Martins
Published: May 2012

Stem cells are present in the adult tissues of most diverse species. Bone marrow is recognized to be the most exploited site to obtain stem cells and cell progenitors. The objective of the present study was to characterize hematopoietic progenitor (HP) morphology and analyze the performance of adherent cell progenitors (ACPs) cultivated in vitro from black‐rumped agouti bone marrow (Dasyprocta prymnolopha). Bone marrow aspirates were obtained from tibia crest and used to prepare histological slides and identify cell morphology. Cells were also scattered on culture plates for later isolation, expansion, and quantification. Smears obtained from bone marrow demonstrated HPs at different stages of maturity. In culture, these cells showed fibroblastoid morphology and a strong tendency to form colonies, demonstrated by the presence of cell aggregates, cytoplasmic elongations lying side by side. An 80% cell confluence was observed at 18 days in culture and progressive reduction in the percentage of nonadherent mononuclear cells. After eight passes, a mean cell viability of 96.07% was observed, from a pool of 1.6 × 107 cells (ACP). Thirteen 25‐cm2 culture bottles were trypsinized, resuspended in freezing medium, stored in 14 criotubes at a concentration of 1 × 106 cells per milliliter, and placed in liquid nitrogen at −196°C. Agouti bone marrow demonstrated high plasticity, moreover different HP lines, and a population of adherent cells demonstrated morphology similar to mesenchymal stem cells in culture. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.
Oral tissue response to ovine grafting biomaterial: Morphological and morphometric study using scanning electron and light microscopy tissue response to ovine grafting biomaterial
Authors: Zielak Joao Cesar , Mathias Alvaro Luiz , Silva Rosiellen Da , Ton Bruno Skronski , Cidral Sobreiro Aline Graziela , Giovanini Allan Fernando , Deliberador Tatiana Miranda , Filho Flares Baratto , Ulbrich Lucienne Miranda
Published: May 2012

OBJECTIVE: To evaluate the oral tissue response to an experimental particle ovine biomaterial by scanning electron microscopy (SEM) and light microscopy (LM). MATERIAL AND METHODS: Forty‐eight rats had surgical periodontal defects treated with either blood clotting (control), bovine biomaterial™ (B), or an experimental ovine biomaterial (O). Data from SEM analysis (defect exposure, root surface exposure, diameter of matrix fibers and bundles, and globuli areas; n = 5) were applied to Shapiro–Wilk, Kruskal–Wallis, and Dunn's test, whereas LM analysis (tissue cicatrization characteristics and diameter defect; n = 3) had data applied to two‐way analysis of variance. Animals were monitored for 1 and 3 weeks. RESULTS: By SEM, the O samples showed significant differences from B and C in the area of defect exposure (H2,15 = 8.66; P < 0.05). In both periods, O and B samples showed similar results for matrix fiber diameters, differently than C samples (H2,15 = 14.0; P < 0.05). All other SEM variables were considered equivalent among the groups (P > 0.05). Under LM, an acute and chronic granulomatous inflammation was seen in the presence of both biomaterials (B and O, 1 week); both the control and the ovine grafting samples showed mature bone in the repair site (3 weeks); the defect diameter showed similar values among groups, at both monitoring periods (F2,12 = 1.0401; P > 0.05). CONCLUSION: The ovine particles of this study showed a favorable response to oral tissue repair, demonstrating to be a potential source for the development of bone grafting biomaterials. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.
Effect of processing methods for transmission electron microscopy on corneal collagen fibrils diameter and spacing
Authors: Akhtar Saeed
Published: May 2012

Introduction: The corneal tissue was processed in fixatives and embedded in resin for transmission electron microscopy to observe the ultrastructure of the collagen fibrils (CFs). The effect of these processing methods on the CF diameter and the interfibrillar spacing was studied. Methods: Four normal human corneal buttons were used for this study. A part of each cornea was fixed in 2.5% glutaraldehyde containing cuprolinic blue in sodium acetate buffer and embedded in spurr's resin (SpurrCB). A second part of each cornea was fixed in 2.5% glutaraldehyde + osmium tetroxide and embedded spurr's resin (SpurrOsm). The third part of each cornea was fixed in paraformaldehyde (4%) and embedded in LR White at 4°C (LRWhite). Ultrathin sections were stained with uranyl acetate and lead citrate. Results: In the tissue, fixed in SpurrCB, the diameter was 38.4 ± 5.9 nm and spacing between CF was 52.5 ± 5.3 nm. In the tissue fixed in SpurrOsm, the diameter was 28.37 ± 5.84 nm and spacing between CF was 45 ± 4.57 nm. In the tissue fixed in LR White, the CF diameter was 24 ± 2.3 nm and spacing between CF was 39.0 ± 4.2 nm. The diameters and interfibrillar spacing of the tissue processed by SpurrCB, SpurrOsm, and LRWhite were significantly different (P < 0.001) from one another. Conclusion: Our study shows that there is a variation in the CF diameter and spacing depending on the method of fixation and embedding resins used. This needs to be considered when comparative studies using different methods are done. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.
A cell‐based smoothed discrete shear gap method using triangular elements for static and free vibration analyses of Reissner–Mindlin plates
Authors: Nguyen‐Thoi T. , Phung‐Van P. , Nguyen‐Xuan H. , Thai‐Hoang C.
Published: May 2012

The cell‐based strain smoothing technique is combined with discrete shear gap method using three‐node triangular elements to give a so‐called cell‐based smoothed discrete shear gap method (CS‐DSG3) for static and free vibration analyses of Reissner–Mindlin plates. In the process of formulating the system stiffness matrix of the CS‐DSG3, each triangular element will be divided into three subtriangles, and in each subtriangle, the stabilized discrete shear gap method is used to compute the strains and to avoid the transverse shear locking. Then the strain smoothing technique on whole the triangular element is used to smooth the strains on these three subtriangles. The numerical examples demonstrated that the CS‐DSG3 is free of shear locking, passes the patch test, and shows four superior properties such as: (1) being a strong competitor to many existing three‐node triangular plate elements in the static analysis; (2) can give high accurate solutions for problems with skew geometries in the static analysis; (3) can give high accurate solutions in free vibration analysis; and (4) can provide accurately the values of high frequencies of plates by using only coarse meshes. Copyright © 2012 John Wiley & Sons, Ltd.
Analyzing interaction between coplanar square cracks using an efficient boundary element‐free method
Authors: Sun Yuzhou , M Liew K.
Published: May 2012

This paper examines the interaction between coplanar square cracks by combining the moving least‐squares (MLS) approximation and the derived boundary integral equation (BIE). A new traction BIE involving only the Cauchy singular kernels is derived by applying integration by parts to the traditional boundary integral formulation. The new traction BIE can be directly applied to a crack surface and no displacement BIE is necessary because all crack boundary conditions (both upper and lower ones) are incorporated. A boundary element‐free method is then developed by combining the derived BIE and MLS approximation, in which the crack opening displacement is first expressed as the product of weight functions and the characteristic terms, and the unknown weight is approximated with the MLS approximation. The efficiency of the developed method is tested for isotropic and transversely isotropic media. The interaction between two and three coplanar square cracks in isotropic elastic body is numerically studied and the case of any number of coplanar square cracks is deduced and discussed. Copyright © 2012 John Wiley & Sons, Ltd.
Use of mutation profiles to refine the classification of endometrial carcinomas
Authors: McConechy Melissa K , Ding Jiarui , Cheang Maggie CU , Wiegand Kimberly C , Senz Janine , Tone Alicia A , Yang Winnie , Prentice Leah M , Tse Kane , Zeng Thomas , McDonald Helen , Schmidt Amy P , Mutch David G , McAlpine Jessica N , Hirst Martin , Shah Sohrab P , Lee Cheng‐Han , Goodfellow Paul J , Gilks C Blake , Huntsman David G
Published: May 2012

The classification of endometrial carcinomas is based on pathological assessment of tumour cell type; the different cell types (endometrioid, serous, carcinosarcoma, mixed, undifferentiated, and clear cell) are associated with distinct molecular alterations. This current classification system for high‐grade subtypes, in particular the distinction between high‐grade endometrioid (EEC‐3) and serous carcinomas (ESC), is limited in its reproducibility and prognostic abilities. Therefore, a search for specific molecular classifiers to improve endometrial carcinoma subclassification is warranted. We performed target enrichment sequencing on 393 endometrial carcinomas from two large cohorts, sequencing exons from the following nine genes: ARID1A, PPP2R1A, PTEN, PIK3CA, KRAS, CTNNB1, TP53, BRAF, and PPP2R5C. Based on this gene panel, each endometrial carcinoma subtype shows a distinct mutation profile. EEC‐3s have significantly different frequencies of PTEN and TP53 mutations when compared to low‐grade endometrioid carcinomas. ESCs and EEC‐3s are distinct subtypes with significantly different frequencies of mutations in PTEN, ARID1A, PPP2R1A, TP53, and CTNNB1. From the mutation profiles, we were able to identify subtype outliers, ie cases diagnosed morphologically as one subtype but with a mutation profile suggestive of a different subtype. Careful review of these diagnostically challenging cases suggested that the original morphological classification was incorrect in most instances. The molecular profile of carcinosarcomas suggests two distinct mutation profiles for these tumours: endometrioid‐type (PTEN, PIK3CA, ARID1A, KRAS mutations) and serous‐type (TP53 and PPP2R1A mutations). While this nine‐gene panel does not allow for a purely molecularly based classification of endometrial carcinoma, it may prove useful as an adjunct to morphological classification and serve as an aid in the classification of problematic cases. If used in practice, it may lead to improved diagnostic reproducibility and may also serve to stratify patients for targeted therapeutics. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Activation of Wnt signalling promotes development of dysplasia in Barrett's oesophagus
Authors: Moyes Lisa H , McEwan Hamish , Radulescu Sorina , Pawlikowski Jeff , Lamm Catherine G , Nixon Colin , Sansom Owen J , Going James J , Fullarton Grant M , Adams Peter D
Published: May 2012

Barrett's oesophagus is a precursor of oesophageal adenocarcinoma, via intestinal metaplasia and dysplasia. Risk of cancer increases substantially with dysplasia, particularly high‐grade dysplasia. Thus, there is a clinical need to identify and treat patients with early‐stage disease (metaplasia and low‐grade dysplasia) that are at high risk of cancer. Activated Wnt signalling is critical for normal intestinal development and homeostasis, but less so for oesophageal development. Therefore, we asked whether abnormally increased Wnt signalling contributes to the development of Barrett's oesophagus (intestinal metaplasia) and/or dysplasia. Forty patients with Barrett's metaplasia, dysplasia or adenocarcinoma underwent endoscopy and biopsy. Mice with tamoxifen‐ and β‐naphthoflavone‐induced expression of activated β‐catenin were used to up‐regulate Wnt signalling in mouse oesophagus. Immunohistochemistry of β‐catenin, Ki67, a panel of Wnt target genes, and markers of intestinal metaplasia was performed on human and mouse tissues. In human tissues, expression of nuclear activated β‐catenin was found in dysplasia, particularly high grade. Barrett's metaplasia did not show high levels of activated β‐catenin. Up‐regulation of Ki67 and Wnt target genes was also mostly associated with high‐grade dysplasia. Aberrant activation of Wnt signalling in mouse oesophagus caused marked tissue disorganization with features of dysplasia, but only selected molecular indicators of metaplasia. Based on these results in human tissues and a mouse model, we conclude that abnormal activation of Wnt signalling likely plays only a minor role in initiation of Barrett's metaplasia but a more critical role in progression to dysplasia. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
MYC‐regulated genes involved in liver cell dysplasia identified in a transgenic model of liver cancer
Authors: Hunecke Danele , Spanel Reinhard , Länger Florian , Nam Suk Woo , Borlak Juergen
Published: May 2012

Foci of liver cell dysplasia (LCD) are distinct morphological entities and may evolve into hepatocellular carcinomas (HCCs). While most HCCs overexpress c‐Myc, its role in LCD remains uncertain. Therefore, a c‐Myc transgenic model of HCC was investigated to understand the genetic events forcing liver cells into dysplasia and subsequent malignant transformation. Specifically, whole genome scans enabled fingerprinting of genes at different stages of disease, ie LCD and HCC, while laser microdissected LCD lesions were used to validate regulation of candidate genes by quantitative real‐time RT‐PCR, ieMybbp1a, Rps7, Rps19, Rpl10a, Skp1a, Tfdp1, Nhp2, andBola2. EMSA band shift assays confirmed c‐Myc DNA binding at regulatory sequences of candidate gene‐specific promoters. Additionally, published ChIP‐seq data helped to define the candidate genes as c‐Myc bona fide targets. Treatment of the human hepatoma cell line HepG2 with hepatic growth factor (Hgf) caused c‐Myc protein induction and transcriptional up‐regulation of candidate genes, albeit at different levels when individual genes were compared. A significant increase of HepG2 entering the G1‐phase was associated with up‐regulation of the candidate genes in an Hgf concentration‐dependent matter. Finally, we confirmed regulation of candidate genes in patients' samples with low‐ and high‐grade dysplasia and HCC staged T1 to T3, while their expression was unchanged in focal nodular hyperplasia and hepatic adenoma, therefore asserting the diagnostic value and clinical significance of these candidate genes. Overall, novel c‐Myc targeted genes were identified and may contribute to hepatocyte transformation by altering cell cycle control, thereby contributing to c‐Myc's oncogenic activity. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
New epoxy thermosets obtained from diglycidylether of bisphenol a and modified hyperbranched polyesters with long aliphatic chains cured by diisocyanates
Authors: Flores Marjorie , Fernández‐Francos Xavier , Jiménez‐Piqué Emilio , Foix David , Serra Àngels , Ramis Xavier
Published: May 2012

Hyperbranched polyesters modified with long aliphatic chains with vinyl or epoxy groups as chain ends were synthesized and added as modifiers to diglycidyl ether of bisphenol A/toluene‐2,4‐diisocyanate mixtures in the presence of benzyldimethylamine as catalyst. The influence of the addition of these modifiers on the curing was investigated by thermal analysis and infrared spectroscopy. The materials obtained were investigated by electron microscopy and some mechanical characteristics were determined by nanoindentation tests. Epoxy terminated hyperbranched led to homogeneous materials with high crosslinking densities, whereas vinyl terminated hyperbranched produced phase separated morphologies. The materials showing phase separation presented a tough fracture, whereas the homogeneous materials obtained with epoxidated hyperbranched showed increased brittleness on increasing the proportion of modifier. On increasing the proportion of vinyl terminated hyperbranched in the thermosets, Young's modulus and hardness decreased but the addition of epoxy terminated hyperbranched did not influence these parameters. The addition of vinylic hyperbranched to the formulations produced a decrease in the curing shrinkage, whereas the epoxidic hyperbranched did not. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Aliphatic–aromatic polyester–polyaniline composites: preparation, characterization, antibacterial activity and conducting properties
Authors: Wu Chin‐San
Published: May 2012

Poly(butylene adipate‐co‐terephthalate) (PBAT) composites containing polyaniline (PANI) were prepared using a melt blending process. Acrylic‐acid‐grafted PBAT (PBAT‐g‐AA) and PANI were used to improve the compatibility and dispersibility of PANI within the PBAT matrix. The composites were characterised morphologically using scanning electron microscopy, chemically using Fourier transform IR spectrometry and 13C solid‐state nuclear magnetic resonance, and optically using UV‐visible spectroscopy. The electrical conductivity of the composites was also evaluated with a resistance tester and a cyclic voltameter. Escherichia coli (BCRC 10239) was chosen as the standard bacterium for determining the antibacterial properties of the composite materials. The anti‐static properties of the composites were also evaluated. The PBAT‐g‐AA/PANI composite showed markedly enhanced antibacterial and anti‐static properties due to the formation of amide bonds by the condensation of the carboxylic acid groups of PBAT‐g‐AA with the amino groups of PANI. The optimal level of PANI was 9 wt%, as excess PANI led to separation of the two organic phases, lowering their compatibility. Copyright © 2012 Society of Chemical Industry
Molecular dynamics simulation of thionated hen egg white lysozyme
Authors: Huang Wei , Eichenberger Andreas P. , van Gunsteren Wilfred F.
Published: May 2012

Understanding of the driving forces of protein folding is a complex challenge because different types of interactions play a varying role. To investigate the role of hydrogen bonding involving the backbone, the effect of thio substitutions in a protein, hen egg white lysozyme (HEWL), was investigated through molecular dynamics simulations of native as well as partly (only residues in loops) and fully thionated HEWL using the GROMOS 54A7 force field. The results of the three simulations show that the structural properties of fully thionated HEWL clearly differ from those of the native protein, while for partly thionated HEWL they only changed slightly compared with native HEWL. The analysis of the torsional‐angle distributions and hydrogen bonds in the backbone suggests that the α‐helical segments of native HEWL tend to show a propensity to convert to 310‐helical geometry in fully thionated HEWL. A comparison of the simulated quantities with experimental NMR data such as nuclear overhauser effect (NOE) atom–atom distance bounds and 3JHNHα‐couplings measured for native HEWL illustrates that the information content of these quantities with respect to the structural changes induced by thionation of the protein backbone is rather limited.
Resistance testing and the effectiveness of difenacoum against Norway rats (Rattus norvegicus) in a tyrosine139cysteine focus of anticoagulant resistance, Westphalia, Germany
Authors: Buckle Alan , Endepols Stefan , Klemann Nicole , Jacob Jens
Published: May 2012

BACKGROUND: Anticoagulant resistance in Norway rats at foci in Belgium, Denmark, France, Germany, the Netherlands and the United Kingdom is genetically characterised by the same single nucleotide polymorphism (SNP) and consequent amino acid exchange from tyrosine to cysteine at location 139 of the vkorc1 gene (i.e. tyrosine139cysteine or Y139C). The purpose of this study was to assess the degree of resistance among rats at two infested farm sites in the Y139C focus in Westphalia, Germany, using blood clotting response (BCR) tests, and to determine the practical efficacy of applications of a commercial 50 ppm difenacoum bait (Neokil™) against them.

RESULTS: BCR tests showed that the difenacoum resistance factor (RF) among the Y139C rats was about 2.5. DNA analysis for the Y139C mutation revealed that it was present among rats at the two sites with a prevalence of 75 and 93%. Applications of difenacoum bait at the two sites achieved 86.8 and 59.9% control. The different outcomes did not appear to be due to differences either in the degree and prevalence of resistance or in the quantities of poisoned bait consumed.

CONCLUSION: The study showed that, although the RF for difenacoum among rats carrying the Y139C SNP was apparently low, an acceptable level of control of resistant Norway rat infestations was not achieved using difenacoum. Continued use of anticoagulants against rats that are resistant to them will exacerbate resistance problems in terms of both increased severity and prevalence. These conclusions are likely to apply elsewhere in Europe where the Y139C SNP occurs. Copyright © 2012 Society of Chemical Industry
An in vitro Study on the DNA Damaging Effects of Phytochemicals Partially Isolated from an Extract of Glinus lotoides
Authors: Demma Jemal , El‐Seedi Hesham , Engidawork Ephrem , Aboye Teshome Leta , Göransson Ulf , Hellman Björn
Published: May 2012

An extract of Glinus lotoides, a medicinal plant used in Africa and Asia for various therapeutic purposes, was recently shown to cause DNA damage in vitro. To further explore the potential genotoxicity of this plant, fractionation of the crude extract was performed using reverse phase solid‐phase extraction and a stepwise gradient elution of methanol in water. Four fractions were collected and subsequently analysed for their DNA damaging effects in mouse lymphoma cells using an alkaline version of the comet assay. To identify potential genotoxic and non‐genotoxic principles, each fraction was then subjected to liquid chromatography coupled to mass spectrometry, LC‐MS/MS. 1D and 2D nuclear magnetic resonance analyses were used to confirm the identity of some saponins. Although fractions containing a mixture of flavonoids and oleanane‐type saponins or oleanane‐type saponins alone produced no DNA damage, those containing hopane‐type saponins exhibited a pronounced DNA damaging effect without affecting the viability of the cells. To conclude, even if this study presents evidence that hopane‐type of saponins are endowed with a DNA damaging ability, further studies are needed before individual saponins can be cited as a culprit for the previously reported genotoxicity of the crude extract of G. lotoides. Copyright © 2012 John Wiley & Sons, Ltd.
Quantum chemical insights into the dissociation of nitric acid on the surface of aqueous electrolytes
Authors: Mishra Himanshu , Nielsen Robert J. , Enami Shinichi , Hoffmann Michael R. , Colussi Agustín J. , Goddard William A.
Published: May 2012

Recent experiments in our laboratory have shown that the probability of gaseous HNO3 deprotonation on the surface of water is dramatically enhanced by anions. Herein, we report a quantum chemical study of how a HNO3 molecule transfers its proton upon approaching water clusters containing or not a chloride ion. We find that HNO3 always binds to the outermost water molecules both via donating and accepting hydrogen‐bonds, but the free energy barrier for subsequent proton transfer into the clusters is greatly reduced in the presence of Cl−. As the dissociation of HNO3 embedded in water clusters is barrierless, we infer that interfacial proton transfer to water is hindered by the cost of creating a cavity for NO3−. Our findings suggest that nearby anions catalyze HNO3 dissociation by preorganizing interfacial water and drawing the proton—away from the incipient [H+‐‐‐NO3−] close ion‐pairs generated at the interface. This catalytic mechanism would operate in the 1 mM Cl− range (1 Cl− in ∼5.5 × 104 water molecules) covered by our experiments if weakly adsorbed HNO3 were able to explore extended surface domains before desorbing or diffusing (undissociated) into bulk water. © 2012 Wiley Periodicals, Inc.