[en] No abstract available

[en] Chemical decontamination is a technique applied to sub-systems of operational LWR plants for the purpose of reducing radiation exposure to plant workers. Several processes are routinely used for this operation, such as the LOMI process originally developed by EPRI. It is necessary to avoid base metal damage on items of plant which are to be returned operational service whereas removal of a thin layer of base metal is required to achieve the high decontamination effectiveness required for decommissioning. Operational decontamination processes therefore have limited value for decontamination of redundant plant items. EPRI has funded a research project with Bradtec Ltd. to develop a decontamination process for decommissioning which could achieve the necessary effectiveness, while retaining the major features of (and hence experience with) operational sub-system processes. The result of this program is the ''EPRI DfD process'' which is the subject of a patent application. The EPRI DfD process uses dilute fluoroboric acid under conditions of controlled oxidation potential to remove contamination from surfaces and collect the contamination on ion exchange resin. High effectiveness is achievable, for example decontamination factors of 8,000 on stainless steel and 2,000 on Inconel 600 reactor artifacts have been achieved with the process, and these figures are not considered to be limiting. The process can in principle be applied by decontamination vendors' existing equipment, and retains the waste management characteristics typical of sub-system decontamination. There is no chelant present in the ion exchange waste form

[en] The authors used 12-O-tetradecanoyl-phorbol-13-acetate (TPA) to directly stimulate protein kinase C (PKC) in order to examine the role of PKC in transduction of biological signals that increase metabolism of arachidonic acid. Release of radioactive arachidonic acid and prostaglandins from TPA-stimulated MDCK cells is inhibited by either of two PKC inhibitors: 1-(5-isoquinolinesulfonyl)piperazine and 1-octadecyl-2-methoxy-glycero-3-phosphocholine (ALP). ALP is unable to inhibit cyclooxygenase when added into an in vitro assay for this enzyme. Furthermore, TPA induces de novo synthesis of cyclooxygenase in MDCK cells but ALP fails to prevent this effect of TPA. Thus, cyclooxygenase activity appears to be independent of PKC and TPA can still induce de novo synthesis of cyclooxygenase even in the presence of the PKC inhibitor ALP. Also, ALP has no effect on the release of arachidonic acid which occurs upon addition of the calcium ionophore A23187 to MDCK cells suggesting that there are multiple mechanisms to mobilize arachidonic acid. Their data indicate that activation of PKC by TPA leads to increased release of arachidonic acid through regulation of phospholipase(s) by PKC

[en] The authors report that in Madin Darby canine kidney (MDCK) cells activation of protein kinase C by TPA correlates with activation of a phospholipase A₂. Exposure of MDCK cells to TPA induced protein kinase C translocation from the cytosol to the particulate fraction of the cells and stimulated the phosphorylation of proteins of 40,000 and 48,000 daltons. The dose response and time course for stimulation of protein phosphorylation by TPA was similar to that for the activation of a phospholipase A₂. Two compounds which inhibit protein kinase C by different mechanisms inhibited activation of protein kinase C in MDCK cells. Both 1-octadecyl-2-methoxy-glycero-3-phosphocholine (ET-18-OCH₃) and 1-(5-isoquinolinesulfonyl)piperazine inhibited protein kinase C from MDCK cells and inhibited the TPA stimulation of protein phosphorylation in the intact cells. Either compound inhibited the release of arachidonic acid from phospholipids induced by TPA and consequently decreased prostaglandin synthesis. Phospholipase A₂ was not directly inhibited since ET-18-OCH₃ failed to inhibit A23187 induced arachidonic acid release. Other studies showed that the ability of the cells to convert arachidonic acid into prostaglandins was not effects by the ET-18-OCH₃. Thus, activation of protein kinase C by TPA causes the activation of a phospholipase A₂ involved in arachidonic acid release in the MDCK cells

[en] 12-O-Tetradecanoyl-phorbol-13-acetate (TPA) treatment of Madin-Darby canine kidney (MDCK) cells resulted in an increased incorporation of ³²P/sub i/ and [methyl-³H]choline into choline-containing phosphoglycerides (PC). In pulse-chase experiments, TPA treatment caused an increased release of [methyl-³H]choline from the PC fraction of prelabeled cells. When cells were prelabeled with [³H]arachidonic acid and [¹⁴C]palmitic acid, TPA treatment resulted in an increased synthesis of ³H- and ¹⁴C-diglycerides. Further studies were done to determine the relationship between PC breakdown and diglyceride synthesis. Cells were preincubated with ether-linked 1-O-[³H]hexadecyl-2-lyso-sn-glycero-3-phosphocholine which was acylated to form 1-O-[³H]hexadecyl-2-acyl-sn-glycero-3-phosphocholine. Subsequent treatment of these cells with TPA resulted in an increased synthesis of 1-O-[³H]hexadecyl-2-acyl-sn-glycerol compared to that of cells not stimulated with TPA. These findings demonstrate that TPA stimulates PC turnover in MDCK cells and provides evidence for a novel mechanism of diglyceride formation by degradation of PC by a phospholipase C

[en] Reported here are studies on the biosynthetic pathway used by normal and BCG elicited alveolar macrophages for the synthesis of lyso(bis)phosphatidic acid [L(bis)PA]. Earlier observations by this laboratory have shown that although L(bis)PA is abundant in these cells, there is little de novo synthesis of this lipid. Diaceyl phosphatidylglycerol [PG] labeled with either [1,2,3-³H] glycerol or ³²P demonstrated that PG is used as an exogenous substrate for L(bis)PA formation; both glycerol moieties are incorporated. Other phospholipids do not have this capacity. BCG-elicited macrophages are capable of only one-quarter the synthesis of L(bis)PA seen with normal cells, and also show a decreased amount of cell associated substrate. In addition, [³H] 1-0-alkyl PG was used as a substrate to test the importance of the sn-1 acyl linkage in the synthetic pathway. This substrate produced less L(bis)PA while dramatically increasing the amounts of labelled phosphatidylethanolamine and phosphatidylcholine within the cell. The alkyl substrate also showed increased uptake by the cell. They conclude that the hydrolysis of the acyl group at the sn-1 position of PG is essential in the synthetic pathway leading to the production of L(bis)PA. They further suggest that the PG used by these cells as an exogenous substrate in vitro is obtained from the PG-rich surfactant surrounding the alveolar macrophage

[en] In order to dissect mechanisms of arachidonic acid (20:4) metabolism, two cell populations were investigated, resident (AM) and Bacillus Calmette-Guerin-activated (BCG-AM) rabbit alveolar macrophages. After purified AM were labeled overnight with [³H]20:4, radioactivity was localized primarily within lyso(bis)phosphatidic acid [L(bis)PA] (13.1%), phosphatidylethanolamine (PE) (22.8%) and phosphatidylcholine (PC) (26.7%), with lesser amounts recovered in phosphatidyl-serine (PS) plus phosphatidylinositol (PI) (9.2%). By contrast, analysis of the phospholipid classes from prelabeled BCG-AM revealed that the mass of L(bis)PA as well as its [³H]20:4 content was profoundly decreased while other BCG-AM phospholipids remained unchanged. When [³H]20:4-labeled AM were stimulated with 1 μM 12-0-tetradecanoyl-phorbol-13-acetate (TPA), a loss of [³H]20:4 was observed from L(bis)PA, PE, PC, and PS/PI with a corresponding increase in eicosanoid synthesis. BCG-AM exposed to either TPA or 3.8 μM Ca⁺² ionophore A23187 liberated [³H]20:4 solely from Pe and PC. BCG-AM, which exhibited depressed eicosanoid formation, consistently failed to deacylate [³H]20:4 from L(bis)PA or PI. Their evidence suggests that the diminution of eicosanoid synthesis by BCG-AM may be due to the reduction of 20:4 contained within specific phospholipid pools, namely L(bis)PA

[en] During in vitro incubation of liposomes or unilamellar vesicles prepared from egg-yolk or rat-liver phosphatidylcholine with human, monkey or rat plasma the phospholipid became associated with a high molecular weight protein-containing component. The phosphatidylcholine protein complex thus formed co-chromatographed with high-density lipoprotein on Ultrogel AcA34 and had the same immunoelectrophoretic properties as this lipoprotein. Release of phosphatidylcholine from liposomes was also observed when liposomes were incubated with pure monkey high-density lipoproteins. Under those conditions some transfer of protein from the lipoprotein to the liposomes was observed as well. The observed release of phospholipid from the liposomes is a one-way process, as the specific radioactivity of lipsome-associated phosphatidylcholine remained constant during incubation with plasma. It is concluded that either the lipoprotein particle takes up additional phospholipid or that a new complex is formed from protein constituents of the lipoprotein and the liposomal phosphatidylcholine. Massive release of entrapped ¹²⁵I-labeled albumin from the liposome during incubation with plasma suggests that the observed release of phosphatidylcholine from the liposomes has a highly destructive influence on the liposomal structure. The results are discussed with special reference to the use of liposomes as intravenous carriers of drugs and enzymes. (Auth.)

[en] The magnetic and structural properties of Co_xPt_100-x films with x=40,45 and 50 at%, have been investigated. The magnetic studies were focused on the dependence of magnetic hysteresis on the film thickness. The sample thicknesses varied between 10 and 200 nm. The coercivities of the as-grown, disordered fcc structure films did not change very much with thickness for all compositions studied. Upon annealing at 650 and 700degC, a structural transformation takes place to the ordered face centered tetragonal (fct) phase which has a high anisotropy resulting in large coercivities that show a pronounced thickness dependence for all the compositions studied. (orig.)