Modification Of Alpha Research Articles

Initial adhesion behavior of osteoblast onto Zr-1Cr alloy

Event Abstract Back to Event Initial adhesion behavior of osteoblast onto Zr-1Cr alloy Satoshi Migita1*, Kunitaka Araki1, So Okuyama1 and Su Yalatu2 1 Yamagata University, Graduate School of Science and Engineering, Japan 2 Osaka University, Graduate School of Engineering, Japan Introduction: Zirconium (Zr) has a lower cytotoxicity, and high corrosion resistance due to passive oxide formation on its surface. However, the mechanical reliability of unalloyed Zr is insufficient for use as structural biomaterials. We employed Cr, as an alloying element, and created Zr1Cr alloy. In this study, we investigated an initial adhesion behavior of osteoblast onto the alloy. The cells were observed by fluorescent microscope, and the cell shape were processed through imaging analysis. Materials and Methods: Zr1Cr alloy was prepared by arc melting furnace and cast into the mold. After molding, Z1Cr processed to disk (6 mm in diameter × 2 mm in thickness). The disks were mirror-polished and rinsed for cell culture. Pure Zr purchased from Nilaco Corp., Tokyo, Japan. Protein adsorption property of Zr1Cr was analyzed using micro BCA-based colorimetric detection method. Bovine serum albumin (BSA; Wako, Tokyo, Japan ) was used as a model protein. A mouse osteoblast-like cell, MC3T3-E1 (RIKEN BioResource Center, Ibaraki, Japan) were cultured in minimum essential medium Eagle, alpha modification (alpha-MEM; Invitrogen, Carlsbad, CA, USA) supplemented with 10% fetal bovine serum (JRH Biosciences, Inc., Lenexa, KS, USA) and antibiotic-antimycotic (Invitrogen). To evaluate initial adhesion behavior, cell attachment and spreading was investigated following the cells cultured on the Zr1Cr disks for 4 h. Results and Discussion: The amount of protein adsorption on Zr1Cr alloy was statistically greater than that on Zr. This result reflected relative permittivity of passive oxide. Osteoblast was cultured on each disks for 4 h. An adhesion activity of osteoblast on Zr1Cr alloy was similar to Zr. Thus, cytotoxicity of Zr1Cr was low. However, cell morphology was dramatically changed on Zr1Cr compared to Zr. Cells cultured on Zr1Cr was showed smaller adhesive area than that on Zr surface (Figure 1). Zr1Cr surface appeared to inhibit the elongation of the cells. In the 24 h incubation, almost cells were detached from Zr1Cr surface. Conclusion: In this study, we investigated initial adhesion behavior onto Zr1Cr alloy. The alloy was showed lower cytotoxicity, however, Cr, as an alloying element, appeared to inhibit a cell adhesion and elongation. The present data provide a basis for development of a technique for controlling of tissue compatibility of materials surface. Keywords: biomaterial, Implant, Biocompatibility, tissue compatibility Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Metallic biomaterials and alloys Citation: Migita S, Araki K, Okuyama S and Yalatu S (2016). Initial adhesion behavior of osteoblast onto Zr-1Cr alloy. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.01511 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. * Correspondence: Dr. Satoshi Migita, Yamagata University, Graduate School of Science and Engineering, Yonezawa, Yamagata, Japan, Email1 Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Satoshi Migita Kunitaka Araki So Okuyama Su Yalatu Google Satoshi Migita Kunitaka Araki So Okuyama Su Yalatu Google Scholar Satoshi Migita Kunitaka Araki So Okuyama Su Yalatu PubMed Satoshi Migita Kunitaka Araki So Okuyama Su Yalatu Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effect of Cell Seeding Conditions on the Efficiency of In Vivo Bone Formation.

To optimize methods for seeding cells on granular-type beta-tricalcium phosphate (β-TCP). Bone marrow stromal cells were obtained from rat long bones and cultured in flasks with Minimum Essential Medium, Alpha Modification (αMEM) supplemented with 10% fetal bovine serum (FBS), dexamethasone, ascorbic acid, β -glycerophosphate, and antibiotics. The influence of differential cell seeding densities and dynamic cell seeding conditions (rotation) was investigated using different sizes of β -TCP granules and a subcutaneous implantation model. Higher cell seeding densities contributed to efficient in vivo bone formation. The rotational seeding did not affect the efficiency but contributed to the uniformity. Although the granule size did not affect the efficiency under the conditions used in this study, large granules showed more uniform distribution of bone regeneration, while small granules showed nonuniform but dense bone formation. Mixtures of relatively large and small granules may be beneficial for both uniform and efficient bone regeneration. These findings may contribute to stable bone tissue engineering with bone marrow stromal cells and β -TCP granules as a scaffold.

Study Biocompatibility and Osteogenic Differentiation Potential of Human Umbilical Cord Mesenchymal Stem Cells (hUCMSCs) with Gelatin Solvent

The human umbilical cord is a source of numerous Mesenchymal Stem Cells (MSCs), making it as a potential source of allogeneic multipotent cell for bone tissue engineering. The aims of this study were to find: 1) Human Umbilical Cord Mesenchymal Stem Cells (hUCMSCs) phenotypic characterization, 2) The in-vitro osteogenic differentiation potential of hUCMSCs, 3) The cytotoxicity of gelatin solvent to hUCMSCs using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. As a result, through characterization of hUCMSCs, the majority of target cells expressed specific MSCs markers, Cellular Differentiation (CD)73, smaller number of subpopulation expressed CD90 with only minimal subpopulation expressed CD105 and all negative MSCs markers. Osteoblastic differentiation was found in a significantly high number of cells when in vitro osteogenic differentiation of hUCMSCs with Alizarin Red staining was done. Biocompatibility analysis using the MTT assay showed that gelatin solvent and Alpha modification of minimum essential medium Eagle (α-MEM) was non-toxic for hUCMSCs in vitro. The study concluded that hUCMSCs isolated from human umbilical cord was capable of undergoing in vitro osteogenesis, indicating its potential as allogeneic stem cells for clinical application in bone tissue engineering.

Nanoscale Mechanical Stimulation of Human Mesenchymal Stem Cells

Introduction: Mechanical stimulation of human mesenchymal stem cells has demonstrated changes in many cell behaviours such as adhesion, migration, growth and differentiation through mechanotransductive pathways. These include experiments on effect of nanotopography 1, shear stress, stiffness of extracellular matrix 2, strain, stress and acoustic wave energy 3 on cells. In this research we were looking for mesenchymal stem cell responses to nanoscale mechanical vibrations in Z-axis. The changes in cell number and shape, differentiation and genetic changes were compared after stimulation with static control groups. Methods: A simple protocol for the stimulation of cells in nanoscale Z-axis has been developed for this project (Figure 1). Piezo actuator (type: P-010.00H by PI CeramicO) connected to the cell culture dish moves the entire surface up and down. The amount of displacement is dependent on the voltage applied. Attaching an aluminium disk to the base of the Petri dish ensures faithful transfer of the vibration to the cells. Human mesenchymal stem cells from bone marrow (PromoCellO) were seeded with 104 cells/dish. After 4 hours seeding and cell settlement, the cells were stimulated for 24 hours, 1 week, and 2 weeks. Experiments were performed in an incubator with optimal temperature 37°C and 5% CO2 concentration. The Petri dish was 60 mm x 15mm standard tissue culture treated polystyrene dish (52mm base diameter) from CorningO Incorporated and cell culture media used was MEM alpha modification with L-Glutamine and nucleosides from PAA laboratories (Austria) supplemented with 10% FBS and antibiotics (penicillin and streptomycin). Results: We observed significant responses after 1 and 2-week stimulations in cell number, cell shapes and phenotypical markers. Microarray was performed for all groups. Cell count showed normal cell growth with stimulation. However, cell surface area, cell perimeter, and arboration after 1-week stimulation showed significant increases. Immunofluorescent studies have showed significant increase in osteocalcin production after stimulation. Conclusions: Nanoscale mechanical vibration showed significant changes in human mesenchymal stem cell behaviours. Cell morphology changed to become more polygonal and increased expression of the osteoblast markers were noted. These findings with gene regulation changes suggesting nanoscale mechanostimulation has stimulated osteoblastogenesis. Keywords: Mesenchymal, Nanoscale, Stem Cells.

Bis-enoxacin Inhibits Bone Resorption and Orthodontic Tooth Movement

Enoxacin inhibits binding between the B-subunit of vacuolar H+-ATPase (V-ATPase) and microfilaments, and also between osteoclast formation and bone resorption in vitro. We hypothesized that a bisphosphonate derivative of enoxacin, bis-enoxacin (BE), which was previously studied as a bone-directed antibiotic, might have similar activities. BE shared a number of characteristics with enoxacin: It blocked binding between the recombinant B-subunit and microfilaments and inhibited osteoclastogenesis in cell culture with IC50s of about 10 µM in each case. BE did not alter the relative expression levels of various osteoclast-specific proteins. Even though tartrate-resistant acid phosphatase 5b was expressed, proteolytic activation of the latent pro-enzyme was inhibited. However, unlike enoxacin, BE stimulated caspase-3 activity. BE bound to bone slices and inhibited bone resorption by osteoclasts on BE-coated bone slices in cell culture. BE reduced the amount of orthodontic tooth movement achieved in rats after 28 days. Analysis of these data suggests that BE is a novel anti-resorptive molecule that is active both in vitro and in vivo and may have clinical uses. Abbreviations: BE, bis-enoxacin; V-ATPase, vacuolar H+-ATPase; TRAP, tartrate-resistant acid phosphatase; αMEM D10, minimal essential media, alpha modification with 10% fetal bovine serum; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; RANKL, receptor activator of nuclear factor kappa B-ligand; NFATc1, nuclear factor of activated T-cells; ADAM, a disintegrin and metalloprotease domain; OTM, orthodontic tooth movement.

Acacetin and Chrysin, Two Polyphenolic Compounds, Alleviate Telomeric Position Effect in Human Cells

We took advantage of the ability of human telomeres to silence neighboring genes (telomere position effect or TPE) to design a high-throughput screening assay for drugs altering telomeres. We identified, for the first time, that two dietary flavones, acacetin and chrysin, are able to specifically alleviate TPE in human cells. We further investigated their influence on telomere integrity and showed that both drugs drastically deprotect telomeres against DNA damage response. However, telomere deprotection triggered by shelterin dysfunction does not affect TPE, indicating that acacetin and chrysin target several functions of telomeres. These results show that TPE-based screening assays represent valuable methods to discover new compounds targeting telomeres.

Gender and Estradiol as Major Factors in the Expression and Dimerization of nNOSα in Rats with Experimental Diabetic Gastroparesis

The molecular mechanisms of cellular changes responsible for diabetic gastroparesis, primarily seen in middle-aged women, still remain incompletely defined. We hypothesized that a decrease in the expression, dimerization, and post-translational modification of neuronal nitric oxide synthase alpha (nNOSα) is estrogen mediated and responsible for the gender-specific prevalence of this malady. We induced diabetes by injecting male and female rats with streptozotocin. Male diabetic rats without gastroparesis were then injected with estrogen for 3 weeks and evaluated for gastroparesis development. Gastric tissues were analyzed for the elucidation of biochemical events associated with diabetes and gastroparetic dysfunction. Although male diabetic, gastroparetic (either streptozotocin- or estrogen-induced) rats exhibited similarity in disease pathology to that of females, the molecular mechanisms of development were different. Our results indicate that slow gastric emptying in both male diabetic, gastroparetic rat groups was not associated with the level of expression of nNOSα in gastric tissues. However, nNOSα dimerization, which reflects nNOSα activation, did decline slightly in the antrum of diabetic males with estrogen-induced gastroparesis, suggesting a possible estrogen role. Females with diabetic gastroparesis, in contrast, demonstrated significantly impaired levels and dimerization of nNOSα in the antrum and pylorus. Although the precise mechanism remains unknown, nNOSα dimerization impairment in female antrum is apparently associated with reduced phosphorylation of Ser(1416) in the activation loop of nNOSα. Taken together, these results demonstrate that gender and estrogens may be leading factors, through molecular changes involved in nitric oxide synthesis down-regulation, within the antrum and pylorus of female diabetic, gastroparetic rats.

The tDCS effect on alpha brain oscillation for correct vs. incorrect object use. The contribution of the left DLPFC

Representation of the instrumentally incorrect use of an object was explored in the present research taking into account the role of the dorsolateral prefrontal cortex (DLPFC). Specifically the “inhibitory” effect performed by tDCS (transcranial Direct Current Stimulation) on DLPFC was analyzed by measuring alpha frequency band modulation when subjects processed congruous/incongruous object-related action. Thirty-four subjects performed the congruence detection task within a dynamic context (a sequence of four action frames), where the final one could be congruous or incongruous. The stimulation effect (cathode applied on the DLPFC and anode on the control site) was analyzed comparing the RTs (response times) and alpha modifications before and after the stimulation. A significant alpha increasing was found for incongruous actions in case of cathodic stimulation of DLPFC compared with the pre-stimulation condition. Moreover, RTs showed a significant reduction in response to incongruous condition after tDCS stimulation. It was suggested that the inhibition of DLPFC may limit the “incongruence effect” induced by the semantic anomaly. Secondly, the contribution of the frontal area for the semantic processing of action was demonstrated. Finally, tDCS influence on cortical oscillations was largely supported, showing alpha modulation induced by DLPFC inhibition.

Effect of Hot Rolling on the Structure of TC21 Alloy with Acicular Alpha

The modification of acicular alpha of TC21 titanium alloy during hot rolling was investigated for finer grains under the condition of optimized preheating time. Two different preheating schedules were used to roll TC21 alloy plates at strains of 0.36, 0.69, and 1.2. The results show that preheating time has a great effect on microstructure evolution. By and large, under a given set of deformation conditions, the materials with shorter preheating time more rapidly formed finer equiaxed grains compared to the materials with longer preheating time. The nature of the modification of acicular alpha to equiaxed morphology was identified to be a two-step process: the formation of the necklace-like structure by geometric dynamic recrystallization, and then the separation of alpha lamellae by boundary splitting along subboundaries and the subsequent globularization by migration of interfaces.

Synthesis and characterization of new zirconium 4-sulfophenylphosphonates

New way for the preparation of 4-sulfophenylphosphonic acid is proposed based on the hydrolysis of sulfamoylphenylphosphonic acid under hydrothermal conditions. 4-Sulfophenylphosphonic acid was successfully used for the preparation of zirconium sulfophenylphosphonate and zirconium phosphate sulfophenylphosphonate with formulae Zr(HO 3SC 6H 4PO 3) 2·2H 2O and Zr(HPO 4) 0.7(HO 3SC 6H 4PO 3) 1.3·2H 2O. Both compounds are layered with the interlayer distances of around 19.9 Å, which agrees well with the presumed structure derived from the structure of the alpha modification of zirconium phosphate monohydrate (α-ZrP). The inorganic part of the title compounds is identical with that of α-ZrP, with the sulfophenyl groups jutting out of the layers into the interlayer space. Both compounds were further characterized by FTIR and solid-state NMR, which confirmed the presence of strongly acidic hydrogen on the sulfonic group. Based on the NMR findings, the structure of hydrogen bonding in the interlayer space was proposed. The 2D 1H– 1H spin-exchange and double-quantum NMR experiments further revealed various mutually interacting hydrogen atoms differing in their mobility. In contrast to α-ZrP, protons in the newly prepared systems exhibit significantly higher dynamics. The proton conductivity ( σ) of both compounds was determined at 100 °C as a function of relative humidity (RH) in the range 50–90% and as a function of temperature between 70 and 150 °C, at RH = 75%. The phosphate phosphonate compound is more conductive than the pure phosphonate compound, the highest σ values being 0.063 S cm − 1 (at 100 °C and 90% RH) and 0.073 S cm − 1 (at 150 °C and 75% RH). Due to their insolubility in water, good thermal stability and the considerably high protonic conductivity the described layered compounds are promising candidates for application as components of composite proton exchange membranes in fuel cells.

Over-expression of Arabidopsis thaliana carotenoid hydroxylases individually and in combination with a β-carotene ketolase provides insight into in vivo functions

Carotenoids represent a group of widely distributed pigments derived from the general isoprenoid biosynthetic pathway that possess diverse functions in plant primary and secondary metabolism. Modification of alpha- and beta-carotene backbones depends in part on ring hydroxylation. Two ferredoxin-dependent non-heme di-iron monooxygenases (AtB1 and AtB2) that mainly catalyze in vivo beta-carotene hydroxylations of beta,beta-carotenoids, and two heme-containing cytochrome P450 (CYP) monooxygenases (CYP97A3 and CYP97C1) that preferentially hydroxylate the epsilon-ring of alpha-carotene or the beta-ring of beta,epsilon-carotenoids, have been characterized in Arabidopsis by analysis of loss-of-function mutant phenotypes. We further investigated functional roles of both hydroxylase classes in modification of the beta- and epsilon-rings of alpha-carotene and beta-carotene through over-expression of AtB1, CYP97A3, CYP97C1, and the hydroxylase candidate CYP97B3. Since carotenoid hydroxylation is required for generation of ketocarotenoids by the bkt1(CrtO) beta-carotene ketolase, all hydroxylase constructs were also introduced into an Arabidopsis line expressing the Haematococcus pluvalis bkt1 beta-carotene ketolase. Analysis of foliar carotenoid profiles in lines overexpressing the individual hydroxylases indicate a role for CYP97B3 in carotenoid biosynthesis, confirm and extend previous findings of hydroxylase activities based on knock-out mutants, and suggest functions of the multifunctional enzymes in carotenoid biosynthesis. Hydroxylase over-expression in combination with bkt1 did not result in ketocarotenoid accumulation, but instead unexpected patterns of alpha-carotene derivatives, accompanied by a reduction of alpha-carotene, were observed. These data suggest possible interactions between the beta-carotene ketolase bkt1 and the hydroxylases that impact partitioning of carbon flux into different carotenoid branch pathways.

Critical Phenomena in Magnetic Nanowires

In this paper we report the first experimental study of critical phenomena in case of magnetic nanowires of nickel near the ferromagnetic-paramagnetic transition from the electrical transport properties. Nickel nanowire arrays, prepared by potentiostatic electrodeposition of nickel inside pores of nanoporous anodic alumina template were well characterized by X-ray Diffraction, Transmission electron microscopy and Energy dispersive Spectroscopy. Precise electrical resistance measurement of the nanowire arrays of wire diameter 20 nm have been done in the temperature range between 300 K to 700 K. We see a drop in the Curie temperature as observed from the resistivity anomaly. We analyzed the resistance data near the critical region and extracted the critical exponent alpha directly from the resistance. We observed a decrease in the critical part of the resistivity including a decrease in the magnitude of the critical exponent alpha and severe modification in the correction to scaling.

A new CE‐ESI‐MS method for the detection of stable hemoglobin acetaldehyde adducts, potential biomarkers of alcohol abuse

A new CE-ESI-MS method was developed to provide a simple way to study changes to hemoglobin (HbA) induced by acetaldehyde (Ach) in vitro. Instrumental parameters were univariately optimized in order to maximize the sensitivity of the CE-ESI-MS method. The electrophoretic separations were carried out in poly-E323-coated capillaries using 60 mM formic acid raised to pH 3.0 with ammonia and containing 5% 2-propanol while the sheath liquid, 2-propanol/water (30:70) with 0.1% formic acid, was delivered at 1.0 microL/min through a coaxial sheath flow electrospray interface. The HbA was incubated with Ach for intervals up to 24 h at concentration varying in the window 0.2-20 mM. Four stable Ach-hemoglobin adducts in the hemoglobin tryptic digest were observed at the submillimolar Ach concentration and characterized by MS/MS experiments: although the alpha and beta N-amino terminal modifications were expected, the two internal ones arising, respectively, from the condensation of Ach molecules on the histidine residue in position 4 in alpha4 (i.e. the fourth peptide after tryptic digestion of alpha chain starting from amino terminal) and on the asparagine residue in position 2 in beta3, were identified for the first time. During the in vitro experiments higher concentrations of Ach were also used; however, it was not possible to identify any other stable modification of hemoglobin. Interestingly, those stable modifications are the only ones in vivo identified in the hemoglobin of moderate alcohol drinkers.

Hypoxia-amplified Proliferation of Human Dental Pulp Cells

Introduction Postnatal human dental pulp is a potentially promising source of progenitor cells. Sustaining and amplifying progenitor cell populations would be beneficial for basic science research with application in pulpal regeneration. Hypoxia has been observed to promote the undifferentiated cell state in various stem cell populations. The purpose of this study was to examine human dental pulp cells (DPCs) proliferation in normoxia and hypoxia. Methods Dental pulp cells were obtained from third molars of adult patients and cultured in alpha modification of Eagle's medium culture medium with 10% fetal bovine serum. For cell proliferation, DPCs were divided into two groups: (1) DPCs incubated in normoxic conditions (20% oxygen tension) and (2) DPC incubated in hypoxic conditions (3% oxygen tension). Cell proliferation assays were performed every 2 to 3 days from day 3 to day 14 by trypsinization and quantification of cells with a hemacytometer. Fluorescence-activated cell sorting analysis was completed to investigate stem cell markers, CD133, and STRO-1. Results DPCs proliferated significantly more in hypoxia than in normoxia (ie, two-fold throughout the experiment, p < 0.0001). The primitive stem cell marker, CD133, decreased in hypoxia, whereas the osteoprogenitor marker, STRO-1, increased by 8.5-fold. Conclusions This study suggested that hypoxia is an effective treatment to amplify numbers of progenitor cells from human dental pulp.

Method for Discontinuous Current Mode Compensation of Line-Commutated Converters

The implementation of a new method to control line-commutated converters in discontinuous conduction mode is presented. The method is based on the modification of the thyristor's firing angle alpha using a linear approximation, yielding nearly the same dynamic performance as in continuous conduction mode. The firing angle is corrected by adding a supplementary angle Deltaalpha, calculated by estimating the average output current. The proposed technique significantly reduces computational burden, thus being suitable for online calculation. Both simulations and experimental results are presented on a 1-kW laboratory prototype.

Method for Discontinuous Current Mode Compensation of Line-Commutated Converters

The implementation of a new method to control line-commutated converters in discontinuous conduction mode is presented. The method is based on the modification of the thyristor's firing angle alpha using a linear approximation, yielding nearly the same dynamic performance as in continuous conduction mode. The firing angle is corrected by adding a supplementary angle Deltaalpha, calculated by estimating the average output current. The proposed technique significantly reduces computational burden, thus being suitable for online calculation. Both simulations and experimental results are presented on a 1-kW laboratory prototype.

A quantum mechanical study of TiCl3α, β and γ crystal phases: geometry, electronic structure and magnetism

The electronic structure of different magnetic states of alpha, beta and gamma modifications of TiCl(3) has been computed employing the density functional theory with periodic boundary conditions and localized Gaussian basis sets. The analysis of the density of the electronic states (DOS) and of the spin density makes it possible to classify these halides as Mott-Hubbard insulators, where the band gap appears a result of large on-site Coulomb interaction. For each crystalline phase, the relative stability of different magnetic states has been analyzed in terms of exchange mechanisms. The electronic population data along with the spin density maps support the assumption of a d(1) Titanium ion in a distorted octahedral crystal field, notwithstanding the not fully ionic character of TiCl(3) modifications. Dispersion forces are particularly important for this material: a classical correction (of the type f(R)/R(6)) has been added to the DFT energies and gradients, providing a good agreement with structural data.

Impact resistance of all-polypropylene composites composed of alpha and beta modifications

The impact behaviour of self-reinforced polypropylene (PP) composites was studied. α and β polymorphs of isotactic PP homopolymer and random copolymer (with ethylene) were used for matrix materials, whereas the reinforcement was a fabric woven from highly stretched split PP yarns. The composite sheets were produced by the film-stacking method and consolidated by hot pressing at 5 and 15 °C above the melting temperature ( T m) of the matrix-giving PP grade. The composite sheets were subjected to static tensile, dynamic falling weight impact and impact tensile tests at room temperature. Dynamic mechanical thermal analysis (DMTA) was also performed on the related composites and their constituents. The results indicated that the β-modification of the PP homopolymer is more straightforward than that of the PP copolymer. Stiffness and strength usually increased while the toughness (tensile impact strength, perforation impact energy) decreased with increasing temperature of consolidation. This was assigned to differences in the failure mode based on fractographic results.

Effect of stir-casting on the microstructure and adhesive wear characteristics of cast Al—Si—Cu alloy

This paper describes the microstructure, hardness, and wear characteristics of cast aluminium—silicon alloy produced by a stir-casting technique. A hypoeutectic (Al—7% Si—0.8% Cu) alloy was cast under different stirring speeds. The stirring of semi-solid metal (SSM) slurries was performed under continuous cooling conditions from liquidus temperature. Wear characteristics of the alloys under investigation were studied using a pin-on-flat wear system over a range of normal loads (10—40 N) at constant average sliding speed (0.2 m/s) against cast iron and stainless steel counter surfaces. Stir-casting resulted in a material with higher microhardness and lower wear rates than conventional cast alloy. Both the stir-cast and conventional cast alloy showed higher weight loss against the stainless steel compared with that against the cast iron counter surface. Optical microscopy of the conventional cast and stir-cast alloys showed that the stir-casting results in spheroidization and refinement of primary alpha aluminium and modification of eutectic silicon. The scanning electron microscopy of wear surfaces was carried out to investigate the mode of wear. Attempts were made to establish the structure property relationship.

Post-Translational Modification and Differential Protein Binding Partners of CCAAT Enhancer Binding Protein Alpha (C/EBPα) p42 Versus p30 May Contribute to Aberrant C/EBPα Activity in Acute Leukemia

CCAAT enhancer binding protein alpha (C/EBPα) is the founding member of a family of basic region/leucine zipper (bzip) transcription factors and has been shown to be a master regulator of granulopoiesis It is expressed at high levels throughout myeloid differentiation and has been shown to bind to the promoters of multiple myeloid- specific gene promoters at different stages of myeloid maturation. Profound hematopoietic abnormalities have been reported for mice nullizygous for including a selective early block in the differentiation of C/EBPα, granulocytes. Mutations in C/EBPα have been demonstrated in a subset of patients with AML presenting with a normal karyotype. These mutations can result in the expression of a 30kD dominant negative C/EBPα isoform which contributes to loss of C/EBPα function. We have sought to understand the molecular basis for this observation. We and others have demonstrated that C/EBPα is post-translationally modified by small ubiquitin-related modifier (SUMO) at a lysine residue (K159) that lies within a region of the C/EBPα protein that can negatively affect transcriptional activity. We have demonstrated that the levels of sumoylated p42C/EBPα decrease upon normal neutrophil maturation and that transactivation of the myeloid-specific lactoferrin (LF) promoter reporter is significantly enhanced by a p42 sumoylation mutant of C/EBPα (K159A). Additionally, in oligonucleotide pull down assays, we show that sumoylated p42C/EBPα binds to the C/EBP site in the LF promoter in immature myeloid cells (which do not express LF) while loss binding and LF of sumoylation correlates with loss of p42C/EBPα expression in more mature cells. Based on these observations we is associated with the negative conclude that sumoylated p42C/EBPα regulation of LF in early myeloid cells. We further demonstrate that sumoylated p42C/EBPα remains bound to the LF promoter following ATRA induction of the leukemic NB4 cells, which do not express LF despite induction of morphologic maturation. Based on these observations we conclude that during normal myeloid differentiation, sumoylated p42C/EBPα is associated with the negative regulation of LF in early myeloid cells, and that LF expression upon maturation is associated with loss of binding of sumoylated p42 C/EBPα In leukemic cells induced toward mature neutrophils, sumoylated p42C/EBPα remains bound to the LF promoter, contributing to the lack of expression of LF in these cells. We show in addition, that p30 C/EBPα can also be sumoylated. In transactivation assays, however, sumoylated p42C/EBPα suppresses LF promoter activity more efficiently than p30C/EBPα in 293 cells. In order to identify differential protein binding partners of p30 and p42C/EBPα that could account for the differential transcriptional activity of the two isoforms, we have used a one step purification method that allows isolation of biotinylated C/EBPα p30 and p42- containing complexes using magnetic-streptavidin beads. The K562 myelomonocytic cell line stably expressing a biotin ligase (BirA) plasmid was transfected with p30C/EBPα or p42C/EBPα each containing a 23 amino acid tag at the N-terminus that allows for in vivo biotinylation. Proteins complexed with the two C/EBP isofoms have been isolated and are currently being identified by LC- MS MS analysis. Their differential association with the two isofoms of C/EBPα will be confimed by coimmunoprecipitation assays in normal myeloid and in leukemic cells. The identification of differentially bound proteins to p30 and p42 C/EBPα may identify molecular targets for future drug development.