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

Platelet activating factor stimulates arachidonic acid release in differentiated keratinocytes via arachidonyl non-selective phospholipase A2

Platelet activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is known to be present in excess in psoriatic skin, but its exact role is uncertain. In the present study we demonstrate for the first time the role of group VI PLA2 in PAF-induced arachidonic acid release in highly differentiated human keratinocytes. The group IVα PLA2 also participates in the release, while secretory PLA2s play a minor role. Two anti-inflammatory synthetic fatty acids, tetradecylthioacetic acid and tetradecylselenoacetic acid, are shown to interfere with signalling events upstream of group IVα PLA2 activation. In summary, our major novel finding is the involvement of the arachidonyl non-selective group VI PLA2 in PAF-induced inflammatory responses

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

Rheological study of 356 Al-Si foundry alloy prepared by a new innovative SSM process

SEED (Swirled Enthalpy Equilibration Device) is established itself as a new technology amongst the many Semi-Solid Metal (SSM) processes, where swirling of the mush plays an important role in modifying the dendritic structure of as-cast parts. A range of semi solid metal structures, dendritic, rosette and/or globular morphology of primary phase, can be prepared using SEED. The current article reports on the application of rheological tests in characterizing microstructural evolution during SSM processing of 356 Al-Si foundry alloy. A simple parallel plate test machine, designed and constructed at our labs, was used to determine viscosity values for each structure and identify the optimum structure with superior die filling characteristics. Such findings have important technological and economical implications during high pressure die casting of semi- solid metals. The strain-time graphs for 356 Al-Si foundry alloy indicated lower viscosity values for globular microstructure, i.e. improved die filling.O. Lashkari, R. Ghomashchi, and F. Adjerschhttp://au.wiley.com/WileyCDA/WileyTitle/productCd-0873395816,descCd-tableOfContents.htmlhttp://www.tms.org/Meetings/Annual-05/AnnMtg05Home.htm

Deformation behavior of semi-solid A356 Al-Si alloy at low shear rates: The effect of sample size

The rheological behavior of semi-solid metal slurries at low shear rates can be characterized by parallel plate compression tests of cylindrical discs where the height (h) is much smaller than the diameter (d) and the axial flow is assumed negligible or zero against the radial flow. In order to confirm the validity of required aspect ratio, two sets of cylindrical test samples with (h/d) of 0.4, d = 24 mm small discs, and 1.8, d = 75 mm billets, were prepared with similar microstructures. The small specimens were tested in a parallel plate squeezing flow rheometer to determine the viscosities which were compared to the viscosity values of samples (billets) with larger aspect ratios using a similar large scale apparatus. For the billets, rheocast samples, it was shown that the dendritic primary α-Al structure has the highest viscosity. The viscosity decreases when the structure comprises a rosette or globular morphology. Similar results were obtained for the discs, thixocast samples, where the specimens have similar initial microstructure. The results confirmed that for low shear rates, less than 10-2 s-1, the viscosity of semi-solid alloy is dependent mainly on the morphology of the primary particles and not the sample size. © 2006.Omid Lashkari, Reza Ghomashchi, Frank Ajersc

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

Application of SEM-EBSD for measurement of plastic strain fields associated with weld metal hydrogen assisted cold cracking

The requirement for more efficient use of materials for pipelines has lead to the application of high strength low alloy steels such as X70 and X80 in pipelines. As the strength of these alloys has increased so has the risk of hydrogen assisted cold cracking (HACC). In Australia to minimize construction time, the root runs of girth welds are produced by shielded metal arc welding using cellulosic electrodes without either pre or post heating. Well defined welding criteria have been developed and are incorporated into the weld procedures for the elimination of HACC in the heat affected zone but the risk of cracking to the weld metal is still of concern. It has been reported that plastic deformation occurs prior to the formation of hydrogen cracks in weld metal. Therefore the evaluation of plastic strains at the micro- and nano-scale and their relationship to the weld metal microstructure could be of great significance in assessing the susceptibility of welds to weld metal hydrogen assisted cold cracking (WMHACC). A method for analysing plastic strains on the micro- and nano-scales using electron backscattered diffraction (EBSD) has been developed. This technique is based on the degradation and rotation of diffraction patterns as a result of crystallographic lattice distortion resulting from plastic deformation. The analysis can be automated to produce an Image Quality (IQ) map in order to relate the spatial distribution of plastic deformation to microstructural features e.g. grains or cracks. The development and assessment of techniques using Scanning Electron Microscopy (SEM) and EBSD for the determination of local plastic strain distribution in E8010 weld metal used for the root pass of X70 pipeline girth welds is discussed.I. H. Brown, W. L. Costin, F. Barbaro and R. Ghomashch

Effect of fraction solid and shear rate on the viscosity of conventionally cast semi-solid A356 Al-Si alloys

COM 2006: 45th Annual Conference of Metallurgists of CIM held in conjunction with the 36th Annual Hydrometallurgy Meeting and the 17th International Symposium 'ICSOBA 2006', October 1-4 , 2006 Montreal, Quebec, CanadaO. Lashkari, R. Ghomashchi, A. Charette and F. Ajerschhttp://www.metsoc.org/com2006/index.as