bluuebunny/crossref_metadata_2025 huggingface dataset:
Stereochemical requirements for the modulation by retinoic acid of thyroid hormone activation of Ca2+-ATPase and binding at the human erythrocyte membrane
Authors: Smith T J , Davis F B , Davis P J
Published: August 2015

Physiological concentrations of retinoic acid can block the activation of human erythrocyte Ca(2+)-ATPase in vitro by thyroid hormone [Smith, Davis & Davis (1989) J. Biol. Chem. 264, 687-689]. The present studies were undertaken to ascertain the nature of this blockade. Two binding sites for L-thyroxine (T4) were demonstrated on washed erythrocyte membranes; the high-affinity site had a Kd value of 2.7 x 10(-10)M and a Bmax. of 76 fmol/mg of protein. The lower-affinity site possessed a Kd of 1 x 10(-8) M. Retinoic acid was as potent a displacer of radiolabelled T4 as was the unlabelled hormone. Certain retinoic acid analogues with either ring or fatty acid side chain modifications retained some ability to displace [125I]T4 binding and to block iodothyronine activation of Ca(2+)-ATPase. The side chain terminal carboxyl group was essential for full activity of the retinoic acid molecule. Its absence or replacement with an ethylsulphone group rendered the molecule considerably less active in the ATPase model. Retinol, 13-cis-retinoic acid, benzene-substituted all-trans-retinoic acid and polyprenoic acid all failed to influence iodothyronine binding or to block activation of Ca(2+)-ATPase by T4. There was good agreement between the ability of an analogue to displace [125I]iodothyronine binding and its ability to inhibit the T4-dependent activation of the Ca(2+)-ATPase. It would appear from these observations that retinoic acid can modulate the activation of erythrocyte membrane Ca(2+)-ATPase by thyroid hormone through a mechanism which involves displacement of iodothyronine from binding sites. These activities apparently derive from both the ring structure and the fatty acid side chain of the retinoic acid molecule.
A survey of membrane peptidases in two human colonic cell lines, Caco-2 and HT-29
Authors: Howell S , Kenny A J , Turner A J
Published: August 2015

The expression of cell-surface peptidases was examined in two human colon carcinoma cell lines, Caco-2 and HT-29. Enzymic assays revealed the presence of eight cell-surface peptidases on a Caco-2 cell line (passage number 82-88), namely aminopeptidase N, dipeptidyl peptidase IV, peptidyl dipeptidase A (angiotension-converting enzyme), aminopeptidase P, aminopeptidase W, endopeptidase-24.11, gamma-glutamyl transpeptidase and membrane dipeptidase. The presence of dipeptidyl peptidase IV and endopeptidase-24.11 was also confirmed immunochemically. After 15 days culture, the activities of aminopeptidase P, peptidyl dipeptidase A and alkaline phosphatase activities on Caco-2 cells reached a plateau, and that of membrane dipeptidase began to decline. In contrast, aminopeptidase N, dipeptidyl peptidase IV and endopeptidase-24.11 activities were still rising after 26 days in culture. Caco-2 cells of passage number 181-183 were found to lack endopeptidase-24.11, but maintained dipeptidyl peptidase IV expression. Two populations of HT-29 cells were surveyed. Both the standard, undifferentiated population and a differentiated population expressed only three peptidases: dipeptidyl peptidase IV, aminopeptidase W and carboxypeptidase M. In the differentiated HT-29 cells the activity of dipeptidyl peptidase IV after 14-21 days was beginning to plateau whereas aminopeptidase W activity was still rising and that of carboxypeptidase M had begun to decline. These differences in activity profiles observed among this group of cell-surface peptidases indicate that these cell lines, especially Caco-2, are useful models to study the regulation of their expression.
Stimulation of NADH oxidase activity from rat liver plasma membranes by growth factors and hormones is decreased or absent with hepatoma plasma membranes
Authors: Bruno M , Brightman A O , Lawrence J , Werderitsh D , Morré D M , Morre D J
Published: August 2015

Plasma membranes of rat liver isolated by aqueous two-phase partition exhibited basal levels of NADH oxidase activity that were increased approx. 2-fold by addition of hormones and growth factors to which liver cells were known to respond. In contrast, hepatoma plasma membranes demonstrated an intrinsically increased level of NADH oxidase, which was not stimulated further by addition of growth factors. The results suggest that the NADH oxidase of the hepatoma plasma membrane is no longer correctly coupled to hormone and growth-factor receptors. This biochemical defect may parallel the loss of growth control that is characteristic of neoplastic transformation in hepatocarcinogenesis and other transformation systems.
Protein kinase-dependent effects of okadaic acid on hepatocytic autophagy and cytoskeletal integrity
Authors: Holen I , Gordon P B , Seglen P O
Published: August 2015

The protein phosphatase inhibitor okadaic acid suppressed autophagy completely in isolated rat hepatocytes, as measured by the sequestration of electroinjected [3H]raffinose into sedimentable autophagic vacuoles. Okadaic acid was effectively antagonized by the general protein kinase inhibitors K-252a and KT-5926, the calmodulin antagonist W-7, and by KN-62, a specific inhibitor of Ca2+/calmodulin-dependent protein kinase II (CaMK-II). These inhibitors also antagonized a cytoskeleton-disruptive effect of okadaic acid, manifested as the disintegration of cell corpses after breakage of the plasma membrane. CaMK-II, or a closely related enzyme, would thus seem to play a role in the control of autophagy as well as in the control of cytoskeletal organization.
Glycogenolytic effect of pancreastatin in isolated rat hepatocytes is mediated by a cyclic-AMP-independent Ca2+-dependent mechanism
Authors: Sánchez V , Lucas M , Calvo J R , Goberna R
Published: August 2015

We have studied the effect of pig pancreastatin on glucose and lactate production in freshly isolated rat hepatocytes. Pancreastatin stimulated the rate of glucose output, whereas, in contrast with glucagon, it failed to modify the rate of lactate production. The effective concentration of pancreastatin was in the range 0.1-100 nM, with half-maximal rate close to 1 nM. The ability of pancreastatin to increase glucose output was abolished by chelation of the calcium in the medium. By itself, pancreastatin did not increase cyclic AMP (cAMP) levels and had no influence on cAMP levels in glucagon-stimulated hepatocytes. Our results point out a possible role of pancreastatin in glycogenolysis. This appears to be mediated by a cAMP-independent Ca(2+)-dependent mechanism.
The herpes simplex virus immediate-early protein ICP27 stimulates the transcription of cellular Alu repeated sequences by increasing the activity of transcription factor TFIIIC
Authors: Jang K L , Latchman D S
Published: August 2015

Infection with herpes simplex virus (HSV) results in an increase in the transcription of the endogenous Alu repeated sequence by RNA polymerase III. This effect is also observed in uninfected cells stably transformed with a plasmid expressing the HSV immediate-early protein ICP27 or in cells transfected with the gene encoding this protein. Both uninfected cells expressing ICP27 and cells infected with virus producing functional ICP27 display increased activity of the cellular transcription factor TFIIIC when compared with untreated cells. This increase is not observed, however, in cells infected with a mutant strain of virus which does not produce ICP27. Hence ICP27 induces elevated Alu transcription by activating transcription factor TFIIIC, which is the limiting factor for such transcription. This is the first report of increased activity of a cellular transcription factor during HSV infection, when most cellular gene activity is inhibited.
Purification and characterization of the blue-green rat phaeochromocytoma (PC12) tyrosine hydroxylase with a dopamine-Fe(III) complex. Reversal of the endogenous feedback inhibition by phosphorylation of serine-40
Authors: Andersson K K , Vassort C , Brennan B A , Que L , Haavik J , Flatmark T , Gros F , Thibault J
Published: August 2015

Tyrosine hydroxylase (TH) was purified from tumours of rat phaeochromocytoma (PC12) cells by a three-step purification procedure giving 30 mg of pure enzyme in 3 days. The enzyme sedimented with an S(eo),w value of 9.2 S and revealed an apparent subunit molecular mass of 62 kDa with a minor 60 kDa component. Two-dimensional gel isoelectric focusing/electrophoresis and tryptic digestion revealed that the heterogeneity could be accounted for by limited proteolysis of the 62 kDa component and the presence of covalently bound phosphate. The enzyme had a strong blue-green colour (epsilon 700 = 3.1 +/- 0.2 mM-iron-1.cm-1). The resonance Raman spectrum obtained with lambda excitation = 605 nm revealed the presence of an Fe(III)-catecholamine complex in the isolate enzyme, similar to that observed in the bovine adrenal enzyme [Andersson, Cox, Que, Flatmark & Haavik (1988) J. Biol. Chem. 263, 18621-18626]. In the rat PC12 enzyme, all of the iron present (0.53 +/- 0.03 atom per subunit) seems to be chelated by the feedback inhibitors (0.49 +/- 0.05 mol of dopamine and 0.10 +/- 0.03 mol of noradrenaline per mol of subunit). The e.p.r. spectra at 3.6 K show g-values at 7.0, 5.2 and 1.9 as observed for other catecholate-complexed enzymes. After phosphorylation of serine-40 and addition of L-tyrosine a new rhombic (magnitude of E/D = 0.33) e.p.r. species could be observed. Phosphorylation of serine-40 by cyclic AMP-dependent protein kinase increased the catalytic activity; depending on assay conditions, up to 80-110-fold activation could be observed when measured at high TH (i.e. high endogenous catecholamine) concentration.
Identification of a protein transiently phosphorylated by activators of endothelial cell function as the heat-shock protein HSP27. A possible role for protein kinase C
Authors: Santell L , Bartfeld N S , Levin E G
Published: August 2015

Several agonists of endothelial cell function (thrombin, histamine, dioctanoylglycerol, phorbol 12-myristate 13-acetate, interleukin-1) have previously been shown to enhance the level of phosphorylation of an undefined 29,000-M(r) protein (P29). Comparison of this protein with other phosphoproteins suggested that it may be related to the mammalian heat-shock protein HSP27. Immunoprecipitation and immunoblot analysis with antibodies specific for human HSP27 demonstrated that P29 was immunochemically identical with HSP27. Further characterization of agonist-induced phosphorylation of HSP27 indicated that phosphorylation occurred exclusively on serine residues, and phosphopeptide analysis of tryptic- and chymotryptic-cleavage products demonstrated that the phosphopeptides generated were identical for each agonist and okadaic acid. Down-regulation of protein kinase C-alpha by prolonged treatment with phorbol esters eliminated the ability of phorbol 12-myristate 13-acetate, dioctanoylglycerol, thrombin and histamine to phosphorylate HSP27 above background levels and deceased interleukin-1-stimulated HSP27 phosphorylation by 60%. These data suggest that the various agonists employed stimulate HSP27 phosphorylation through similar mechanisms and that protein kinase C is probably involved.
Epitope mapping by cDNA expression of a monoclonal antibody which inhibits the binding of von Willebrand factor to platelet glycoprotein IIb/IIIa
Authors: Piétu G , Ribba A S , Chérel G , Meyer D
Published: August 2015

In order to study the structure-function relationship of von Willebrand Factor (vWF), we have located the epitope of a well-characterized monoclonal antibody (MAb) to vWF (MAb 9). This MAb reacts with the C-terminal portion of the vWF subunit, SPII fragment [amino acids (aa) 1366-2050], which includes an Arg-Gly-Asp (RGD) sequence at positions 1744-1746, and totally inhibits vWF and SPII binding to platelet membrane glycoprotein IIb/IIIa (GPIIb/IIIa). A recombinant DNA library was constructed by cloning small (250-500 nucleotides) vWF cDNA fragments into the lambda gt11 vector and these inserts were expressed as fusion proteins with beta-galactosidase. Immunological screening of the library with 125I-MAb 9 identified three immunoreactive clones. vWF inserts were amplified by the PCR and their sequences demonstrated overlapping nucleotides from positions 7630 to 7855 of vWF cDNA, coding for aa residues 1698-1773 of the mature subunit, indicating that this is the epitope of MAb 9. vWF-beta-galactosidase fusion protein reacted with 125I-MAb 9 by Western blotting. In a solid-phase radioimmunoassay, the purified fusion proteins decreased the binding of vWF to 125I-MAb 9 by 50%, and this inhibition was dose-dependent between 3.5 and 120 nM. Therefore the epitope of MAb 9 is located within aa 1698-1773 of the vWF subunit, which includes the RGD sequence implicated in the binding of adhesive proteins of GPIIb/IIIa.
A nucleotide receptor in vascular endothelial cells is specifically activated by the fully ionized forms of ATP and UTP
Authors: Lustig K D , Sportiello M G , Erb L , Weisman G A
Published: August 2015

Extracellular ATP causes an increase in the concentration of cytoplasmic free calcium ([Ca2+]i) in bovine pulmonary-artery endothelial (BPAE) cells that results in the synthesis and release of prostacyclin (PGI2), a potent vasodilator and inhibitor of platelet aggregation. We show here that PGI2 release in BPAE cells correlates with the concentration of the fully ionized form of extracellular ATP (ATP4-) and not with the concentration of other ionic forms of ATP. Concentrations as low as 10 nM-ATP4- elicited an increase in PGI2 release [EC50 (concn. giving half-maximal stimulation) 3 microM] in BPAE cells incubated in an iso-osmotic medium, pH 7.4, lacking Ca2+ and Mg2+. When the pH or the Mg2+ concentration of the medium was varied so as to maintain a constant level of ATP4-, while varying the concentration of proton-ATP (HATP3-) or MgATP2- respectively, PGI2 release remained constant. An inhibitory effect of extracellular Mg2+ on PGI2 release could be attributed solely to a decrease in the concentration of ATP4-. In contrast with Mg2+, extracellular Ca2+ stimulated PGI2 release induced by ATP. Several results suggest that extracellular Ca2+ modulates PGI2 release by increasing Ca2+ uptake through an ATP(4-)-activated plasma-membrane channel. In BPAE cells incubated in Ca(2+)-free medium, ATP elicited a transient increase in [Ca2+]i that declined to the basal level within 60 s. In cells incubated in Ca(2+)-containing medium, ATP caused an increase in [Ca2+]i that had two components: a transient peak in [Ca2+]i (0-60 s) and a sustained increase in [Ca2+]i that was maintained for several minutes after ATP addition. Increasing the concentration of extracellular calcium from 0.25 mM to 10 mM had no effect on the transient rise in [Ca2+]i induced by ATP, but significantly enhanced the magnitude of the sustained increase in [Ca2+]i. Alterations in the magnitude of the sustained increase in [Ca2+]i would likely modulate PGI2 release, which was not complete until 2 min after ATP addition. Extracellular Ca2+ also stimulated PGI2 release induced by bradykinin. Bradykinin caused a sustained increase in [Ca2+]i in BPAE cells in the presence of extracellular Ca2+. Finally, the magnitude of PGI2 release induced by UTP, a more potent agonist than ATP, correlated with the concentration of extracellular fully ionized UTP (UTP4-). These findings support the hypothesis that nucleotide receptors in BPAE cells recognize the fully ionized form of ATP and UTP and are coupled to signal-transduction pathways involving the mobilization of intracellular Ca2+, the influx of extracellular Ca2+ and the subsequent release of PGI2.
Activation of calpain I in thrombin-stimulated platelets is regulated by the initial elevation of the cytosolic Ca2+ concentration
Authors: Ishii H , Suzuki Y , Kuboki M , Morikawa M , Inoue M , Kazama M
Published: August 2015

The source and concentration of Ca2+ required to activate calpain I were investigated in thrombin-stimulated platelets. The concentration of cytosolic free Ca2+ ([Ca2+]i) was measured in platelets containing fura-2-AM, and exhibited a biphasic response after stimulation with 0.05, 0.1 or 0.5 NIH units of thrombin/ml. An initial transient elevation, which was predominantly dependent upon Ca2+ released from the internal stores into the cytosol, peaked at 15 s after stimulation, and a secondary sustained elevation, which was due to Ca2+ influx, was observed following the initial elevation. Calpain I was present at about 540 ng/10(8) unstimulated platelets, as measured by immunoblotting using rabbit anti-(human calpain I) IgG. Calpain I was activated 10 s after thrombin stimulation, as determined by the appearance of the 78 kDa and 76 kDa forms on immunoblots. The activation ratio of calpain I was calculated as the amount of the 78 + 76 kDa forms as a percentage of the total (80 + 78 + 76 kDa), and was influenced by the extent of the initial transient [Ca2+]i elevation after stimulation. An initial increase in [Ca2+]i of 300 nM was required to achieve the maximal activation (60%) of calpain I, and half-maximal activation occurred at 160 nM- Ca2+]i. These results suggest that the activation of calpain I in platelets is regulated by the initial elevation in Ca2+]i after thrombin stimulation, and does not necessarily require a Ca2+ influx.
Purification, characterization and cDNA cloning of human lung surfactant protein D
Authors: Lu J , Willis A C , Reid K B M
Published: August 2015

Human pulmonary surfactant protein D (SP-D) was identified in lung lavage by its similarity to rat SP-D in both its molecular mass and its Ca(2+)-dependent-binding affinity for maltose [Persson, Chang & Crouch (1990) J. Biol. Chem. 265, 5755-5760]. For structural studies, human SP-D was isolated from amniotic fluid by affinity chromatography on maltose-Sepharose followed by f.p.l.c. on Superose 6, which showed it to have a molecular mass of approx. 620 kDa in non-dissociating conditions. On SDS/PAGE the human SP-D behaved as a single band of 150 kDa or 43 kDa in non-reducing or reducing conditions respectively. The presence of a high concentration of glycine (22%), hydroxyproline and hydroxylysine in the amino acid composition of human SP-D indicated that it contained collagen-like structure. Collagenase digestion yielded a 20 kDa collagenase-resistant globular fragment which retained affinity for maltose. Use of maltosyl-BSA as a neoglycoprotein ligand in a solid-phase binding assay showed that human SP-D has a similar carbohydrate-binding specificity to rat SP-D, but a clearly distinct specificity from that of other lectins, such as conglutinin, for a range of simple saccharides. Amino acid sequence analysis established the presence of collagen-like Gly-Xaa-Yaa triplets in human SP-D and also provided sequence data from the globular region of the molecule which was used in the synthesis of oligonucleotide probes. Screening of a human lung cDNA library with the oligonucleotide probes, and also with rabbit anti-(human SP-D), allowed the isolation of two cDNA clones which overlap to give the full coding sequence of human SP-D. The derived amino acid sequence indicates that the mature human SP-D polypeptide chain is 355 residues long, having a short non-collagen-like N-terminal section of 25 residues, followed by a collagen-like region of 177 residues and a C-terminal C-type lectin domain of 153 residues. Comparison of the human SP-D and bovine serum conglutinin amino acid sequences indicated that they showed 66% identity despite their marked differences in carbohydrate specificity.
Differences in 2-oxoglutarate dehydrogenase regulation in liver and kidney
Authors: Smith B C , Clotfelter L A , Cheung J Y , LaNoue K F
Published: August 2015

In response to acidosis, renal ammoniagenesis is stimulated, enhancing urinary buffering power, while hepatic ammoniagenesis and ureagenesis decrease, so as to spare bicarbonate consumed in the urea cycle. 2-Oxoglutarate (2-OG) levels can regulate ammoniagenesis in kidney and gluconeogenesis in liver and kidney. Since the activity of 2-oxoglutarate dehydrogenase (2-OGDH) has an important influence on cellular levels of 2-OG, this study evaluated the effects of pH on 2-OGDH in liver and kidney and found that: (1) the isolated enzyme from both organs has the same pH-sensitivity; (2) 2-OGDH flux measured in intact mitochondria was inhibited by increasing H+ in liver, but stimulated in kidney; (3) transport of 2-OG into the mitochondria was not rate-limiting; (4) liver mitochondrial 2-OGDH exhibited a strong preference for 2-OG generated within the mitochondria from glutamate-oxaloacetate transaminase (GOT), suggesting that channelling between GOT and 2-OGDH occurs. Since complexation between 2-OGDH and GOT occurs in vitro, we propose that the degree of complexation is higher in liver than in kidney, such that most of the 2-OGDH may be complexed to GOT in liver. In the liver the inherent H(+)-sensitivity of 2-OGDH is masked by the pH-sensitivity of GOT and the glutamate-aspartate carrier.
Expression of rat liver NAD(P)H:quinone-acceptor oxidoreductase in Escherichia coli and mutagenesis in vitro at Arg-177
Authors: Chen H H , Ma J X , Forrest G L , Deng P S K , Martino P A , Lee T D , Chen S
Published: August 2015

A prokaryotic expression plasmid, pKK-DT2, containing the cDNA of rat liver NAD(P)H:quinone-acceptor oxidoreductase (EC 1.6.99.2; DT-diaphorase) was constructed and used to transform Escherichia coli strain JM109. The rat liver quinone reductase was expressed in strain in JM109 and was inducible with isopropyl beta-D-thiogalactopyranoside (IPTG). The expressed rat protein was purified by affinity chromatography and had kinetic and physical properties identical with the protein purified from rat liver in that it could utilize either NADH or NADPH as the electron donor and its activity was inhibited by dicoumarol. In addition, we have generated four mutants, Arg-177----His (R177H), Arg-177----Ala (R177A), Arg-177----Cys (R177C) and Arg-177----Leu (R177L), using this expression system. Several of the mutants behaved anomalously on SDS/PAGE, but all of the mutant proteins had the expected M(r) as determined by electrospray m.s. These results and those obtained from enzyme kinetic analysis, u.v./visible absorption spectral analysis, and flavin and tryptophan fluorescence analysis of the wild-type enzyme and four mutants indicated that mutations at Arg-177 changed the conformation of the enzyme, resulting in a decrease in enzyme activity. Replacing Arg-177 with leucine altered the protein conformation and decreased FAD incorporation.
Duck liver ‘malic’ enzyme. Expression in Escherichia coli and characterization of the wild-type enzyme and site-directed mutants
Authors: Hsu R Y , Glynias M J , Satterlee J , Feeney R , Clarke A R , Emery D C , Roe B A , Wilson R K , Goodridge A G , Holbrook J J
Published: August 2015

A cDNA for duck liver ‘malic’ enzyme (EC 1.1.1.40) was subcloned into pUC-8, and the active enzyme was expressed in Escherichia coli TG-2 cells as a fusion protein including a 15-residue N-terminal leader from beta-galactosidase coded by the lacZ′ gene. C99S and R70Q mutants of the enzyme were generated by the M13 mismatch technique. The recombinant enzymes were purified to near homogeneity by a simple two-step procedure and characterized relative to the enzyme isolated from duck liver. The natural duck enzyme has a subunit molecular mass of approx. 65 kDa, and the following kinetic parameters for oxidative decarboxylation of L-malate at pH 7.0: Km NADP+ (4.6 microM); Km L-malate (73 microM); kcat (160 s-1); Ka (2.4 microM) and Ka′ (270 microM), dissociation constants of Mn2+ at ‘tight’ (activating) and ‘weak’ metal sites; and substrate inhibition (51% of kcat. at 8 mM-L-malate). Properties of the E. coli-derived recombinant wild-type enzyme are indistinguishable from those of the natural duck enzyme. Kinetic parameters of the R70Q mutant are relatively unaltered, indicating that Arg-70 is not required for the reaction. The C99S mutant has unchanged Km for NADP+ and parameters for the ‘weak’ sites (i.e. inhibition by L-malate, Ka′); however, kcat. decreased 3-fold and Km for L-malate and Ka each increased 4-fold, resulting in a catalytic efficiency [kcat./(Km NADP+ x Km L-malate x Ka)] equal to 3.7% of the natural duck enzyme. These results suggest that the positioning of Cys-99 in the sequence is important for proper binding of L-malate and bivalent metal ions.
Characterization of two dipeptidases purified from hepatic schistosome egg granulomas in mice. Leukotriene D4 hydrolases of granulomatous tissue
Authors: Sato N , Ito Y , Iida T , Fukuyama K , Epstein W L
Published: August 2015

Extracts prepared from tissue with granulomatous inflammation experimentally produced in liver of CBA-strain mice showed increased hydrolysis of leukotriene D4 (LTD4), Leu-Leu and Ala-Gly as compared with normal hepatic cells. Two dipeptidases, Leu-Leu dipeptidase and Ala-Gly dipeptidase, were purified from hepatic granulomas, and quantitative conversion of LTD4 into leukotriene E4 (LTE4) by both enzymes was demonstrated. M(r) values of the purified enzymes were 178,000 for Leu-Leu dipeptidase and 183,000 for Ala-Gly dipeptidase. The enzymes showed homogeneity, appearing as a single band on SDS/PAGE, and the M(r) values of the subunits were 56,000 and 57,000 for Leu-Leu and Ala-Gly dipeptidase respectively. The amino acid compositions of the two enzymes differed considerably from each other. The activity of Leu-Leu dipeptidase was inhibited by bestatin and captopril and stabilized with MnCl2. The Km for LTD4 was 25 microM with a V(max.) of 49.0 mumols/min per mg. In contrast, the activity of Ala-Gly dipeptidase was inhibited by cilastatin, cytinylglycine, EDTA and dithiothreitol, and also by captopril. The Km for LTD4 was 5.3 microM with a V(max.) of 50.4 mumols/min per mg. The findings indicate that the conversion of LTD4 into LTE4 by microsomal dipeptidases is elevated during granulomatous tissue reaction. This enzyme activity may become useful for biochemical quantification of the pathological tissue reaction that occurs in organized granulomas.
Oligomeric tumour necrosis factor α slowly converts into inactive forms at bioactive levels
Authors: Corti A , Fassina G , Marcucci F , Barbanti E , Cassani G
Published: August 2015

The stability of oligomeric human tumour necrasis factor alpha (TNF) at bioactive levels has been studied by two immunoenzymatic assays: one able to specifically detect oligomeric and not monomeric TNF (O-e.l.i.s.a.) and the other able to detect both forms (OM-e.l.i.s.a.). The selectivity of O-e.l.i.s.a. and OM-e.l.i.s.a. for oligomeric and monomeric TNF was demonstrated with isolated forms prepared by partial dissociation of recombinant TNF with 10% (v/v) dimethyl sulphoxide and gel-filtration h.p.l.c. Evidence for instability of oligomeric TNF were obtained in physiological buffers, as well as in serum and cell-culture supernatants, as a function of TNF concentration. In particular, only a half of the TNF antigen was recovered in the oligomeric form after 72 h incubation (37 degrees C) at 0.12 nM, whereas no apparent dissociation was detected at 4 nM. The structural changes observed at picomolar concentrations were rapidly reversed by raising the concentration of TNF to about 2 nM by ultrafiltration, suggesting that subunit dissociation and reassociation reactions occur in the picomolar and nanomolar range respectively. The cytolytic activity of L-M cells correlates with oligomeric-TNF levels after incubation at picomolar concentrations. Moreover, isolated oligomeric TNF was cytotoxic towards L-M cells, whereas monomeric TNF was virtually inactive. In conclusion, the results suggest that bioactive oligomeric TNF is unstable at picomolar levels and slowly converts into inactive monomers, supporting the hypothesis that quaternary-structure changes in TNF may contribute to the fine regulation of TNF cytotoxicity.
Free class‐AB flipped voltage follower using bulk‐driven technique
Authors: Molinar‐Solis J.E. , Gurrola‐Navarro M.A. , Padilla I. , Ocampo J.J. , Muñiz C.
Published: August 2015

A new configuration of the flipped voltage follower (FVF) offering class‐AB operation is presented. The idea uses a bulk‐driven transistor instead of the constant current source of the typical FVF topology. This feature enhances the sourcing capability for class‐AB operation and the symmetrical slew rate. The key element is changing the basic structure of the original FVF circuit with no additional devices. A detailed analysis of the circuit and simulations using Spice are presented. The experimental results from a manufactured circuit prototype using CMOS 0.35 μm technology demonstrate the feasibility of the proposal.
Feature recovery for noise‐robust speaker verification
Authors: Huang Houjun , Xu Yunfei , Zhou Ruohua , Yan Yonghong
Published: August 2015

Noisy condition is an important extrinsic degradation affecting speaker verification system performance. A feature‐recovery approach is proposed to eliminate noise‐dependent variability in feature space. A frame of the noisy feature vector is recovered using the information of itself and the neighbour feature vectors. Experiments are conducted on noisy test sets for text‐dependent speaker verification tasks and the results indicate that the system can achieve significant performance improvement by using recovered feature vectors.
Acoustic detection based on coherence bandwidth
Authors: Lee Changeun , Kim Donghyeon , Kim Kiman
Published: August 2015

Traditional security systems which include video cameras continuously recording and transmitting data for surveillance systems require a password to prevent entry by unauthorised persons. Actually, such systems have weaknesses such as blind spots or danger of stealth. This reported work focuses on intruder detection in indoor environments, which is based on acoustic channel characteristics. The basic concept of this study is to compute the coherence bandwidth from the measured room impulse response. The coherence bandwidth is influenced by channel delay profiles. Intruders give rise to changes in room channel impulse response inside the room. This variation causes change in the channel delay profile. Experiments have been performed to validate the effectiveness of the proposed method.
Gain‐guided optical fibre refractive index synthesis starting from arbitrary modal electric field
Authors: Thraskias C.A. , Boucouvalas A.C.
Published: August 2015

Novel results on how to reconstruct gain‐guided optical fibres starting from arbitrary modal electric fields are presented. It is known that gain‐guided optical fibre refractive index profiles are described in terms of complex numbers. Therefore, to achieve the design of such fibres from a knowledge of modal electric fields one is required to use complex refractive index profile waveguides, where one can determine the required refractive index profile on both real and imaginary parts of the refractive index. The novelty here is that the reconstruction starts by using complex‐valued desired electric fields. This inverse problem is solved via modelling the waveguide transversely as a transmission line and working inversely from the electric field. Example reconstructions of refractive index profiles are offered which are useful for high‐power lasers, in designing optical fibres for sensors, where one may require specifically shaped electric fields from a waveguide, and also in refractive index profiling instrumentation.
Design of new low‐noise and low‐power CMOS differential pair
Authors: Nebhen J. , Meillère S. , Masmoudi M. , Seguin J‐L. , Aguir K.
Published: August 2015

A novel structure of a CMOS differential pair is presented, which is suitable for low supply voltages and low power consumption as well as a much higher gain than that of a conventional differential pair. This structure is based on the new technique of composite transistors. The need for the design of integrated circuits at low voltage, with low power consumption and how this constraint is reflected in the design of digital and analogue integrated circuits are demonstrated.
Design of ultra‐wideband capacitive circle absorber
Authors: She Jianjian , Lu Zhanbo , Sun Dan , Quan Yan Xue
Published: August 2015

A practical capacitive circuit absorber with low ohm resistive sheets is presented, which is constructed by multilayer low ohm resistive sheets, polymethacrylimide foam and polyethylene terephthalate. For convenience of manufacture and practical engineering applications, a unique low ohm rectangular resistive sheet with a rotational symmetry pattern is employed, which is used to replace high ohm square resistive sheets. Based on the design of the low ohm sheet pattern and the absorber configuration, a prototype absorber is fabricated. The measured results show that the reflectivity of the absorber with a total thickness of 17.9 mm is −10 dB in 1.5–18 GHz for normal incidence. The absorber is shown to have the characteristics of low density and high intensity.
VLSI architecture of lossless ECG compression design based on fuzzy decision and optimisation method for wearable devices
Authors: Chen Shih‐Lun , Tuan Min‐Chun , Chi Tsun‐Kuang , Lin Tin‐Lan
Published: August 2015

A hardware‐oriented lossless electrocardiogram compression algorithm is presented for very large‐scale integration (VLSI) circuit design. To achieve high performance and low complexity, a novel prediction method based on the fuzzy decision and particle swarm optimiser (PSO) was developed. The accuracy of prediction was advanced efficiently by using the PSO algorithm to find the optimal parameters, which provided 64 situations for the fuzzy decision. Moreover, a novel low‐complexity and high‐performance entropy‐coding algorithm based on Huffman coding was developed, which used one limited Huffman coding to encode a main region and five‐region codes to encode the extending regions. The average compression rate of the whole MIT‐BIH Arrhythmia database was up to 2.84 by combing the proposed fuzzy‐based PSO prediction and Huffman region entropy‐coding techniques. The VLSI architecture contained only a 1.9 K gate count and its core area was 5965 μm2 synthesised using a 90 nm CMOS process. It consumed 201 μW when operating at a 200 MHz processing rate. Compared with previous low‐complexity designs, the average compression rate is not only improved by more than 6.4% but also reduced the gate count by at least 8.2%.
Adaptive transmission in amplify‐and‐forward cooperative communications using orthogonal space–time block codes under spatially correlated antennas
Authors: Torabi Mohammad , Frigon Jean François , Haccoun David
Published: August 2015

This study analyses the impact of antenna correlation on orthogonal space–time block coding in amplify‐and‐forward cooperative relay networks in conjunction with different adaptive transmission techniques over Rayleigh fading channels. Closed‐form expressions are derived for the cumulative distribution function, and probability distribution function of the total signal‐to‐noise ratio. For each considered adaptive transmission technique, the authors derive closed‐form expressions for the average channel capacity, outage probability, average spectral efficiency and the average bit error rate of the system. Using numerical evaluations, the performances for different cases are compared in order to evaluate and quantify the effects of spatial correlation on the system performance.
Digital video steganalysis toward spread spectrum data hiding
Authors: Zarmehi Nematollah , Akhaee Mohammad Ali
Published: August 2015

In this study, the authors propose a steganalytic scheme for digital video spread spectrum (SS) data hiding. The proposed method estimates both the hidden message and the gain factor of the SS embedding rules. In this method, the cover frames are first estimated and are compared with the received video frames. Then, the residual matrix is computed and specific features are extracted from this matrix as well as the video frames and estimated frames. The support vector machine, then applies to the extracted features to classify the video as either clean or suspicious. If the video is declared suspicious, both the hidden message and the embedding process gain factor are estimated and consequently the original video is reconstructed. The simulation results confirm the success of the authors’ proposed method in detecting the stego video, estimation of the hidden message and gain factor as well as reconstruction of the original video.
Probleme bei der Verwendung von Qualitätsberichtsdaten für die Versorgungsforschung
Authors: Kraska R. , de Cruppe W. , Geraedts M.
Published: August 2015

Zusammenfassung Hintergrund Seit 2005 sind die Krankenhäuser gesetzlich verpflichtet, strukturierte Qualitätsberichte (QB) zu veröffentlichen. Aufgrund der ausführlichen Datengrundlage werden die QB zunehmend in der Gesundheitsversorgungsforschung für Sekundärdatenanalysen verwendet. Bislang wurde nicht thematisiert, dass erhebliche methodische Schwierigkeiten vorliegen, die verzerrte Analyseergebnisse bedingen können. Ziel dieses Beitrages ist es, die methodischen Probleme bei der Verwendung von QB systematisch aufzulisten und Lösungsstrategien vorzuschlagen.

Methode Den Analysen lagen die QB aus den Jahren 2006–2008–2010–2012 zugrunde, welche mittels eines individuellen Datenlinkages zu einer Datenbank aggregiert wurden. Anschließend erfolgte eine beispielhafte sowohl quer- als auch längsschnittliche Korrelationsanalyse zwischen einem der berichteten Qualitätsindikatoren und der Personalausstattung der Krankenhäuser. Die auftretenden methodischen Probleme wurden qualitativ und quantitativ beschrieben und Lösungswege abgeleitet.

Ergebnisse In den Berichtsjahren gaben 2–15% der Krankenhäuser keinen individuellen QB ab. Bei 2–16% der QB ist nicht erkennbar, ob es sich um einen Verbund- oder Standortbericht handelt. Zudem enthalten 6–66% der Standortberichte fälschlicherweise Daten des Verbundes. 10% der Krankenhäuser ändern im Laufe der Jahre ihre Institutionskennziffer (IK), in 5% der Fälle wird über die Jahre hinweg die gleiche IK-Standort-Kombination für verschiedene Krankenhäuser verwendet. Demnach sind 10–20% der QB über die IK nicht eindeutig verknüpfbar. Als Abhilfe wird unter anderem eine Verknüpfung aller QB über die IK, Adresse und Bettenanzahl vorgeschlagen. Anhand dieser können Verbund- und Standortberichte sowie fehlende Berichterstattungen eindeutig identifiziert und berücksichtigt werden.

Schlussfolgerung Bei Sekundärdatenanalysen mit Qualitätsberichtsdaten ist mit einer inkonsistenten Datengrundlage sowie Schwierigkeiten bei der Datenverknüpfung zu rechnen, die zu Verzerrungen von berechneten Parametern und somit zu einer Verfälschung und Einschränkung der Aussagekraft von Untersuchungsergebnissen führen können. Nur eine eindeutige Identifizierung der berichtenden Krankenhäuser garantiert aussagekräftige Ergebnisse.
Reference Correlations of the Thermal Conductivity of Cyclopentane,iso-Pentane, andn-Pentane
Authors: Vassiliou C.-M. , Assael M. J. , Huber M. L. , Perkins R. A.
Published: August 2015

New, wide-range reference equations for the thermal conductivity of cyclopentane, iso-pentane, and n-pentane are presented. The equations are based in part upon a body of experimental data that has been critically assessed for internal consistency and for agreement with theory whenever possible. In the case of the dilute-gas thermal conductivity, a theoretically based correlation was adopted in order to extend the temperature range of the experimental data. In the critical region, the enhancement of the thermal conductivity is well represented by theoretically based equations containing just one adjustable parameter, estimated by a predictive scheme. The thermal-conductivity equations behave in a physically reasonable manner over a wide range of conditions that correspond to the range of validity of the most accurate equations of state for each fluid. The estimated uncertainties of the correlations are dependent on the availability of accurate experimental data for validation, and are different for each fluid, varying from 1% (at the 95% confidence level) for the liquid phase of iso-pentane over the temperature range 307 K<T<355 K at pressures up to 400 MPa (where high-accuracy data are available) to a more typical 4% for the liquid phase of cyclopentane over the temperature range 218 K < T < 240 K at pressures to 250 MPa. Estimated uncertainties in the gas phase are typically on the order of 3%–5%. For all three fluids, uncertainties in the critical region are much larger, since the thermal conductivity approaches infinity at the critical point and is very sensitive to small changes in density.
The large volume press facility at ID06 beamline of the European synchrotron radiation facility as a High Pressure-High Temperature deformation apparatus
Authors: Guignard Jeremy , Crichton Wilson A.
Published: August 2015

We report here the newly developed deformation setup offered by the 20MN (2000T) multi-anvil press newly installed at sector 7 of the European synchrotron radiation facility, on the ID06 beamline. The press is a Deformation-DIA (D-DIA) type apparatus, and different sets of primary anvils can be used for deformation experiments, from 6 mm to 3 mm truncations, according to the target pressure needed. Pressure and temperature calibrations and gradients show that the central zone of the assemblies is stable. Positions of differential RAMs are controlled with a sub-micron precision allowing strain rate from 10−4 to 10−6 s−1. Moreover, changing differential RAM velocity is immediately visible on sample, making faster reaching of steady state. Lattice stresses are determined by the shifting of diffraction peak with azimuth angle using a linear detector covering typically a 10° solid-angle in 2θ mounted on rotation perpendicular to the beam. Acquisition of diffraction pattern, at a typical energy of 55 keV, is less than a minute to cover the whole azimuth-2θ space. Azimuth and d-spacing resolution are respectively better than 1° and 10−3 Å making it possible to quantify lattice stresses with a precision of ±20 MPa (for silicates, which have typically high values of elastic properties), in pure or simple shear deformation measurements. These mechanical data are used to build fully constrained flow laws by varying P-T-σ−ε̇ conditions with the aim to better understanding the rheology of Earth’s mantle. Finally, through texture analysis, it is also possible to determine lattice preferred orientation during deformation by quantifying diffraction peak intensity variation with azimuth angle. This press is therefore included as one of the few apparatus that can perform such experiments combining with synchrotron radiation.
Monte Carlo simulations of a model two-dimensional, two-patch colloidal particles
Authors: Rżysko W. , Sokołowski S. , Staszewski T.
Published: August 2015

We carried out Monte Carlo simulations of the two-patch colloids in two-dimensions. Similar model investigated theoretically in three-dimensions exhibited a re-entrant phase transition. Our simulations indicate that no re-entrant transition exists and the phase diagram for the system is of a swan-neck type and corresponds solely to the fluid-solid transition.
Static property and current-driven precession of 2π-vortex in nano-disk with Dzyaloshinskii-Moriya interaction
Authors: Liu Xianyin , Zhu Qiyuan , Zhang Senfu , Liu Qingfang , Wang Jianbo
Published: August 2015

An interesting type of skyrmion-like spin texture, 2π-vortex, is obtained in a thin nano-disk with Dzyaloshinskii-Moriya interaction. We have simulated the existence of 2π-vortex by micromagnetic method. Furthermore, the spin polarized current is introduced in order to drive the motion of 2π-vortex in a nano-disk with diameter 2 R = 140 nm. When the current density matches with the current injection area, 2π-vortex soon reaches a stable precession (3∼4 ns). The relationship between the precession frequency of 2π-vortex and the current density is almost linear. It may have potential use in spin torque nano-oscillators.
Observation of suppressed Auger mechanism in type-I quantum well structures with delocalized electron-hole wavefunctions
Authors: Hassani Nia Iman , Fathipour Vala , Mohseni Hooman
Published: August 2015

We report the first observation of non-threshold Auger mechanism for a quantum well structure with Type-I band alignment. Excitation-dependent photoluminescence measurements were used to extract the Auger recombination coefficients from 77 K up to room temperature. The results verify the role of interface mediated momentum exchange as well as suppression of Auger recombination for delocalized electron-hole wavefunctions.
EOMCC over excited state Hartree-Fock solutions (ESHF-EOMCC): An efficient approach for the entire ground state potential energy curves of higher-order bonds
Authors: Sajeev Y.
Published: August 2015

The equation-of-motion coupled cluster (EOMCC) method based on the excited state Hartree-Fock (ESHF) solutions is shown to be appropriate for computing the entire ground state potential energy curves of strongly correlated higher-order bonds. The new approach is best illustrated for the homolytic dissociation of higher-order bonds in molecules. The required multireference character of the true ground state wavefunction is introduced through the linear excitation operator of the EOMCC method. Even at the singles and doubles level of cluster excitation truncation, the nonparallelity error of the ground state potential energy curve from the ESHF based EOMCC method is small.
Can r-graphene oxide replace the noble metals in SERS studies: the detection of acrylamide
Authors: Segal Elad , Gedanken Aharon
Published: August 2015

Environmental context
The need for detecting and sensing hazardous materials that can contaminate our food and water is growing each and every year. Regulation of these contaminants to safeguard human health depends on the ability to detect them at ultra-low concentrations in the environment. This work proposes a simple and efficient substrate preparation for detecting acrylamide, a toxic and carcinogenic material usually found in drinking water.

Abstract
Polyacrylamide acts as a very common water purifier worldwide. Unfortunately, it leaves hazardous and toxic residues of its monomer, acrylamide (C3H5NO), in water sources. The World Health Organization (WHO), the Food and Agriculture Organisation of the United Nations (FAO) and the European Union (EU) set the maximum contaminant level of acrylamide in drinking water to 0.1–0.5µgL–1. This environmental risk encouraged our efforts to develop surface-enhanced Raman spectroscopy (SERS) probes that are easy and simple to fabricate, and also have superb detection ability. We report down to 0.071µgL–1 acrylamide detection with good reproducibility, which is even lower than the WHO, FAO and EU requirements, and may be used as a powerful analytical alternative for detection. In this manuscript, we present a practical route to fabricate these detection substrates for detection of ultra-low concentrations of aqueous acrylamide solutions. The facile method is based on deposition of graphene oxide on Si wafers by ultrasonication, followed by surface reduction. These substrates require no adhesion layer or pretreatment with O2 plasma or aminopropyl triethoxysilane for the coating process. Sonochemical deposition of silver nanoparticles on the substrates is also carried out and the product compared with the proposed Si–reduced graphene oxide wafers.