Arachidonic acid release from mammalian cells transfected with human groups IIA and X secreted phospholipase A(2) occurs predominantly during the secretory process and with the involvement of cytosolic phospholipase A(2)-alpha

Stable expression of human groups IIA and X secreted phospholipases A(2) (hGIIA and hGX) in CHO-K1 and HEK293 cells leads to serum- and interleukin-1beta-promoted arachidonate release. Using mutant CHO-K1 cell lines, it is shown that this arachidonate release does not require heparan sulfate proteoglycan- or glycosylphosphatidylinositol-anchored proteins. It is shown that the potent secreted phospholipase A(2) inhibitor Me-Indoxam is cell-impermeable. By use of Me-Indoxam and the cell-impermeable, secreted phospholipase A(2) trapping agent heparin, it is shown that hGIIA liberates free arachidonate prior to secretion from the cell. With hGX-transfected CHO-K1 cells, arachidonate release occurs before and after enzyme secretion, whereas all of the arachidonate release from HEK293 cells occurs prior to enzyme secretion. Immunocytochemical studies by confocal laser and electron microscopies show localization of hGIIA to the cell surface and Golgi compartment. Additional results show that the interleukin-1beta-dependent release of arachidonate is promoted by secreted phospholipase A(2) expression and is completely dependent on cytosolic (group IVA) phospholipase A(2). These results along with additional data resolve the paradox that efficient arachidonic acid release occurs with hGIIA-transfected cells, and yet exogenously added hGIIA is poorly able to liberate arachidonic acid from mammalian cells

Contribution of Each Leg to the Control of Unperturbed Bipedal Stance in Lower Limb Amputees: New Insights Using Entropy

The present study was designed to assess the relative contribution of each leg to unperturbed bipedal posture in lower limb amputees. To achieve this goal, eight unilateral traumatic trans-femoral amputees (TFA) were asked to stand as still as possible on a plantar pressure data acquisition system with their eyes closed. Four dependent variables were computed to describe the subject's postural behavior: (1) body weight distribution, (2) amplitude, (3) velocity and (4) regularity of centre of foot pressure (CoP) trajectories under the amputated (A) leg and the non-amputated (NA) leg. Results showed a larger body weight distribution applied to the NA leg than to the A leg and a more regular CoP profiles (lower sample entropy values) with greater amplitude and velocity under the NA leg than under the A leg. Taken together, these findings suggest that the NA leg and the A leg do not equally contribute to the control of unperturbed bipedal posture in TFA. The observation that TFA do actively control unperturbed bipedal posture with their NA leg could be viewed as an adaptive process to the loss of the lower leg afferents and efferents because of the unilateral lower-limb amputation. From a methodological point of view, these results demonstrate the suitability of computing bilateral CoP trajectories regularity for the assessment of lateralized postural control under pathological conditions

ADP Ribosylation Factors 1 and 4 and Group VIA Phospholipase A2 Regulate Morphology and Intraorganellar Traffic in the Endoplasmic Reticulum–Golgi Intermediate Compartment

In search of morphological determinants for the endoplasmic reticulum-Golgi intermediate compartment (ERGIC), we found that a concerted action of Arf1, Arf4, and PLA2G6-A controls the architecture of the ERGIC by regulating tubular carriers. This is predicted to impact the rate of transport and destination of cargos in the ERGIC

Effect of graphene dispersion and interfacial bonding on the mechanical properties of metal matrix composites: an overview

The mechanical properties of metal matrix composites (MMCs) reinforced with graphene are very much dependant on the uniform distribution of graphene in the matrix. The nature of bonding between the graphene reinforcement and metallic matrices is also critical and influences the performance of the final composite. In spite of an abundance of information on graphene reinforced metal matrices, less attention has been made on the graphene dispersion and its interface bonding with the matrix. This is surprising as almost all reports categorically emphasize on their importance; however, specific attention to these issues is very scarce. This is the main theme of this report to highlight the fundamentals of atomic structure of graphene as a contributing factor on dispersion along with the bonding mechanism involved at the interface between graphene and the metallic matrix. In the following sections, fabrication of metal-based composites reinforced with graphene through powder metallurgy (PM) has been studied. In this respect, the challenges of dispersion and interfacial bonding have been addressed in addition to their effects on the mechanical properties of composites. In this context, recently developed novel methods including coating graphene with nano-metallic particles, vacuum filtration, matrix-alloying, and defect engineering via plasma treatment along with their influence on mechanical properties have been discussed.Hanieh Ghodratia, Reza Ghomashch

Experimental Investigation of Welding Stresses in MWIC Weldability Test

The use of high-strength steels in the manufacture of energy pipelines, coupled with the transition to larger pipe diameters and greater wall thicknesses, has led to an increased potential for cracking including hydrogen assisted cracking of energy pipelines due to higher constraint induced stresses. In the present study, a modified version of the Welding Institute of Canada (MWIC) restraint test was used to simulate the constraint conditions of full-scale girth welds on energy pipelines, allowing the influence of welding process parameters on crack formation to be assessed. MWIC test samples of X70 grade high-strength low alloy pipeline steel were manually welded using two different welding processes, namely shielded metal arc welding (SMAW) and modified short-arc welding (MSAW). Residual strains, and hence stresses, in these samples were analysed quantitatively using neutron diffraction technique. Overall, results indicate that the modified WIC restraint test produces significant residual stresses and so is effective in constraining the root run and in consequence studying the hydrogen assisted cracking of high-strength pipeline steels

Eutectic nucleation in hypoeutectic Al-Si alloys

The nucleation mechanism of eutectic grains in hypoeutectic Al-Si foundry alloys has been investigated by examining deep etched specimens in high-resolution field emission gun scanning electron microscope (FEG-SEM) and by using in-situ Focused Ion Beam (FIB) milling and microscopy. Both unmodified and Sr-modified alloys were studied to characterize the nucleation mechanism of eutectic silicon flakes and fibers. It is proposed that following nucleation of eutectic Al on the primary α-Al dendrites, fine Si particles form at the solidification front upon which the eutectic Si flakes and fibers could develop. The formation of small Si particles is attributed to Si enrichment of the remaining melt due to the formation of eutectic Al (aluminum spikes) at the eutectic temperature. A hypothesis is then proposed to explain the mechanism of eutectic grains formation with main emphasis on the eutectic Si phase. © 2008 Elsevier Inc. All rights reserved.S. Nafisi, R. Ghomashchi, H. Val

Influence of simultaneous aging and plasma nitriding on fatigue performance of 17-4 PH stainless steel

Abstract not availableHamidreza Riazi, Fakhreddin Ashrafizadeh, Sayed Rahman Hosseini, Reza Ghomashch