bluuebunny/crossref_metadata_2025 huggingface dataset:
Dichloroacetate‐ and trichloroacetate‐induced phagocytic activation and production of oxidative stress in the hepatic tissues of mice after acute exposure
Authors: Hassoun Ezdihar A. , Dey Soumyadeep
Published: February 2008

Dichoroacetate (DCA) and trichloroacetate (TCA) are by‐products formed during chlorination of the drinking water and were found to be hepatotoxic and hepatocarcinogenic in rodents. In this study, the abilities of the compounds to induce oxidative stress and phagocytic activation have been studied in B6C3F1 mice. Groups of mice were administered 300 mg/kg of either DCA or TCA, p.o, and were sacrificed after 6 or 12 h. Peritoneal lavage cells (PLCs) were isolated and assayed for superoxide anion (SA) production, and hepatic tissues were assayed for the production of SA, lipid peroxidation (LP), and DNA‐single strand breaks (SSBs). TCA resulted in significant production of SA in the PLCs, and in the production of SA, LP, and DNA‐SSBs in the hepatic tissues, 12 h after dosing, as compared with the control. DCA administration, on the other hand, resulted in significant increases in the productions of LP and DNA‐SSBs in the hepatic tissues at both time points, and in SA production in PLCs and hepatic tissues, 6 h after dosing. However, DCA‐induced increases in SA production in PLC and hepatic tissues declined at the 12‐h time point, reaching control level in the hepatic tissues. These results may implicate the contribution of phagocytic activation to the induction of oxidative stress in the hepatic tissues and also the role of SA production in the induction of LP and/or DNA damage in those tissues, in response to the compounds. The results also suggest studying the involvement of these mechanisms in the long‐term hepatotoxicity/hepatocarcinogencity of the compounds. © 2008 Wiley Periodicals, Inc. J Biochem Mol Toxicol 22:27–34, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20210
Phosphorylation of Nrf2 in the transcription activation domain by casein kinase 2 (CK2) is critical for the nuclear translocation and transcription activation function of Nrf2 in IMR‐32 neuroblastoma cells
Authors: Apopa Patrick L. , He Xiaoqing , Ma Qiang
Published: February 2008

The antioxidant‐activated transcription factor nuclear factor erythroid 2‐related factor 2 (Nrf2) regulates the induction of cytoprotective genes against chemical toxicity and oxidative injuries. The role of phosphorylation in Nrf2 activation has been suggested but remains elusive. We report that phenolic antioxidant/pro‐oxidant tert‐butylhydroquinone (tBHQ) induced two forms of the Nrf2 protein in neuroblastoma cells (IMR‐32), which migrated as distinctive bands on SDS‐PAGE. In vitro treatment with λ phosphatase eliminated the slower migrating form and increased the amount of the faster migrating form of Nrf2. In vivo 32Pi‐phosphorylation resulted in 32Pi‐labeling of the Nrf2 protein in the presence of tBHQ that can be dephosphorylated by λ phosphotase, indicating that the slower migrating form is a phosphorylated Nrf2 protein and the faster form an unphosphorylated Nrf2. Unphosphorylated Nrf2 predominated in the cytoplasm, whereas the phosphorylated form preferentially localized in the nucleus. Nuclear Nrf2 can be dephosphorylated by λ phosphotase in vitro and be converted to the faster migrating form, implicating phosphorylation of Nrf2 in the cytoplasmic‐nuclear translocation of the protein. Deletional analyses from both the carboxyl‐ and amino‐ends revealed the transcription activation (TA) domains Neh4 (Nrf2‐ECH homology 4) and Neh5 (Nrf2‐ECH homology 5) as a major region necessary for the phosphorylation. The TA domains are characterized by the presence of multiple phosphorylation sites of casein kinase 2 (CK2). Moreover, CK2 phosphorylated the TA domains in vitro. Treatment with CK2 inhibitor 2‐dimethylamino‐4,5,6,7,‐tetrabromo‐1H‐benzimidazole (DMAT) blocked the induction of endogenous target genes of Nrf2 in cells and inhibited the TA activities of both the full length and the TA domains of Nrf2 to a large extent. Finally, phosphorylation of the TA domains correlated with the nuclear translocation of Nrf2 that was inhibited by DMAT in a concentration‐dependent manner. The findings demonstrated that phosphorylation of Nrf2 at the TA domains by CK2 is an integral component of Nrf2 activation necessary for the nuclear localization and transcription activation function of Nrf2 in neuroblastoma cells. © 2008 Wiley Periodicals, Inc. J Biochem Mol Toxicol 22:63–76, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20212
Serum levels of variants of transthyretin down‐regulation in cholangiocarcinoma
Authors: Liu Liyun , Wang Jianing , Liu Bo , Dai Songwei , Wang Xiaomin , Chen Junzhou , Huang Lingyun , Xiao Xueyuan , He Dacheng
Published: February 2008

Background

Cholangiocarcinoma (CC) is devastating neoplasm and very few specific biomarkers could be used in clinical diagnosis. A study was taken to find novel serum biomarkers for CC.

Methods

Surface enhanced laser desorption/ionization (SELDI) technology was used to analyze 427 serum samples including 56 CCs, 49 hepatobiliary diseases, 269 other cancer control, and 53 healthy individuals. The candidates were isolated and identified by SDS–PAGE, ESI/MS‐MS, Western blot, and immunoprecipitation. Liver functions of CC patients were examined and enzyme‐linked immunosorbent assay (ELISA) of transthyretin (TTR) and CA19‐9 were further performed in some sets of serum samples.

Results

13.76, 13.88, and 14.04 k m/z peaks in sera were significantly decreased in CC compared with the control groups (P < 0.001). Subsequently, these three peaks were identified as native TTR and its two variants. ELISA assay indicated that TTR levels were consistent with SELDI analysis in CC compared with healthy control and benign diseases of hepatobiliary (P < 0.001). Liver function test levels were obviously elevated for CC patients. TTR combining with CA19‐9 to differentiate CC from benign hepatobiliary diseases showed sensitivity and specificity were 98.2% and 100%, respectively.

Conclusion

The levels of TTR were significantly down‐regulated in sera of CC patients and may be complementary markers of CA19‐9 in diagnosis for CC. J. Cell. Biochem. 104: 745–755, 2008. © 2008 Wiley‐Liss, Inc.
In vivo and in vitro effects of a HIF‐1α inhibitor, RX‐0047
Authors: Dikmen Z. Gunnur , Gellert Ginelle C. , Dogan Pakize , Yoon Heejeong , Lee Young Bok , Ahn Chang Ho , Shay Jerry W.
Published: February 2008

HIF‐1α plays a major role in activating gene transcription and is important for maintaining homeostasis under hypoxic conditions. Since tumors are often in a hypoxic state, HIF‐1α is a potential target for the development of novel cancer therapeutics. This study was performed to determine the antitumoral efficacy of an antisense HIF‐1α inhibitor, RX‐0047 on different human cancer cell lines (MDA‐MB 231, HME50‐T, PC‐3, Panc‐1 and A549) in vitro. A549 lung cancer and PC‐3 prostate cancer cells containing a luciferase gene reporter were used for in vivo xenograft animal models. Progressive tumor development was quantified using live animal BLI (bioluminescence imaging) in addition to ex vivo imaging and histology. All cell lines tested were sensitive to inhibition of cell growth with 10 nM and higher ranges of RX‐0047, additionally RX‐0047 sensitizes cells to ionizing radiation treatments. Finally, RX‐0047 (30 mg/kg) inhibited the formation of human lung metastasis in xenograft mouse models and reduced tumor size in flank models. J. Cell. Biochem. 104: 985–994, 2008. © 2008 Wiley‐Liss, Inc.
CCAAT box is required for the induction of human thrombospondin‐1 gene by trichostatin A
Authors: Kang Jung‐Hoon , Kim Myung‐Jun , Chang Seo‐Yoon , Sim Sang Soo , Kim Myung‐Suk , Jo Yang‐Hyeok
Published: February 2008

Histone deacetylase (HDAC) inhibitors have been reported to inhibit angiogenesis as well as tumor growth. Thrombospondin‐1 (TSP1) has been recognized as a potent inhibitor of angiogenesis. Such an action of TSP1 may account for the effect of HDAC inhibitors. In the present study, we investigated the molecular mechanism by which trichostatin A, a HDAC inhibitor, induces the expression of TSP1 gene. Trichostatin A increased both mRNA and protein levels of TSP1 in HeLa cells. Promoter and actinomycin D chase assays showed that trichostatin A‐induced TSP1 expression was regulated at the transcriptional level without changing mRNA stability. CCAAT box on the TSP1 promoter was found to primarily mediate the trichostatin A response by deletion and mutation analyses of the TSP1 promoter. Electrophoretic mobility shift assay indicated that CCAAT‐binding factor (CBF) was specifically bound to the CCAAT box of TSP1 promoter. Moreover, chromatin immunoprecipitation assay showed that trichostatin A increased the binding of acetylated form of histone H3 to the CCAAT box region of TSP1 promoter. Taken together, these results strongly suggest that trichostatin A activates the transcription of TSP1 gene through the binding of transcription factor CBF to CCAAT box and the enhanced histone acetylation. Thus, the present study provides the clue that the inhibition of angiogenesis by trichostatin A is accomplished through the upregulation of TSP1, the anti‐angiogenic factor. J. Cell. Biochem. 104: 1192–1203, 2008. © 2008 Wiley‐Liss, Inc.
Revisiting ankyrin–InsP3receptor interactions: Ankyrin‐B associates with the cytoplasmic N‐terminus of the InsP3receptor
Authors: Kline Crystal F. , Cunha Shane R. , Lowe John S. , Hund Thomas J. , Mohler Peter J.
Published: February 2008

Inositol 1,4,5‐trisphosphate (InsP3) receptors are calcium‐release channels found in the endoplasmic/sarcoplasmic reticulum (ER/SR) membrane of diverse cell types. InsP3receptors release Ca2+from ER/SR lumenal stores in response to InsP3generated from various stimuli. The complex spatial and temporal patterns of InsP3receptor‐mediated Ca2+release regulate many cellular processes, ranging from gene transcription to memory. Ankyrins are adaptor proteins implicated in the targeting of ion channels and transporters to specialized membrane domains. Multiple independent studies have documented in vitro and in vivo interactions between ankyrin polypeptides and the InsP3receptor. Moreover, loss of ankyrin‐B leads to loss of InsP3receptor membrane expression and stability in cardiomyocytes. Despite extensive biochemical and functional data, the validity of in vivo ankyrin–InsP3receptor interactions remains controversial. This controversy is based on inconsistencies between a previously identified ankyrin‐binding region on the InsP3receptor and InsP3receptor topology data that demonstrate the inaccessibility of this lumenal binding site on the InsP3receptor to cytosolic ankyrin polypeptides. Here we use two methods to revisit the requirements on InsP3receptor for ankyrin binding. We demonstrate that ankyrin‐B interacts with the cytoplasmic N‐terminal domain of InsP3receptor. In summary, our findings demonstrate that the ankyrin‐binding site is located on the cytoplasmic face of the InsP3receptor, thus validating the feasibility of in vivo ankyrin–InsP3receptor interactions. J. Cell. Biochem. 104: 1244–1253, 2008. © 2008 Wiley‐Liss, Inc.
Acidic pH stimulates the production of the angiogenic CXC chemokine, CXCL8 (interleukin‐8), in human adult mesenchymal stem cells via the extracellular signal‐regulated kinase, p38 mitogen‐activated protein kinase, and NF‐κB pathways
Authors: Bischoff David S. , Zhu Jian‐Hua , Makhijani Nalini S. , Yamaguchi Dean T.
Published: February 2008

Blood vessel injury results in limited oxygen tension and diffusion leading to hypoxia, increased anaerobic metabolism, and elevated production of acidic metabolites that cannot be easily removed due to the reduced blood flow. Therefore, an acidic extracellular pH occurs in the local microenvironment of disrupted bone. The potential role of acidic pH and glu‐leu‐arg (ELR+) CXC chemokines in early events in bone repair was studied in human mesenchymal stem cells (hMSCs) treated with medium of decreasing pH (7.4, 7.0, 6.7, and 6.4). The cells showed a reciprocal increase in CXCL8 (interleukin‐8, IL‐8) mRNA levels as extracellular pH decreased. At pH 6.4, CXCL8 mRNA was induced >60× in comparison to levels at pH 7.4. hMSCs treated with osteogenic medium (OGM) also showed an increase in CXCL8 mRNA with decreasing pH; although, at a lower level than that seen in cells grown in non‐OGM. CXCL8 protein was secreted into the medium at all pHs with maximal induction at pH 6.7. Inhibition of the G‐protein‐coupled receptor alpha, Gαi, suppressed CXCL8 levels in response to acidic pH; whereas phospholipase C inhibition had no effect on CXCL8. The use of specific mitogen‐activated protein kinase (MAPK) signal transduction inhibitors indicated that the pH‐dependent increase in CXCL8 mRNA is due to activation of ERK and p38 pathways. The JNK pathway was not involved. NF‐κB inhibition resulted in a decrease in CXCL8 levels in hMSCs grown in non‐OGM. However, OGM‐differentiated hMSCs showed an increase in CXCL8 levels when treated with the NF‐κB inhibitor PDTC, a pyrrolidine derivative of dithiocarbamate. J. Cell. Biochem. 104: 1378–1392, 2008. © 2008 Wiley‐Liss, Inc.
Epinephrine increases DNA synthesis via ERK1/2s through cAMP, Ca2+/PKC, and PI3K/Akt signaling pathways in mouse embryonic stem cells
Authors: Kim Mi Ok , Na Sun Im , Lee Min Young , Heo Jung Sun , Han Ho Jae
Published: February 2008

Epinephrine is a catecholamine that plays important roles in regulating a wide variety of physiological systems by acting through the adrenergic receptors (ARs). The cellular responses to AR stimulation are mediated through various signaling pathways. Therefore, this study examined the effects of epinephrine on DNA synthesis and related signaling molecules in mouse embryonic stem cells (ESCs). Epinephrine increased DNA synthesis in a dose‐ and time‐dependent manner, as determined by the level of [3H]‐thymidine incorporation. AR subtypes (α1A, α2A, β1, β2, and β3) were expressed in mouse ESCs and their expression levels were increased by epinephrine. In this experiment, epinephrine increased cAMP levels, intracellular Ca2+ concentration ([Ca2+]i), and translocation of protein kinase C (PKC) from the cytosol to the membrane compartment. In addition, we observed Akt phosphorylation in response to epinephrine; this was stimulated by phosphorylation of the epidermal growth factor receptor (EGFR). Epinephrine also induced phosphorylation of ERK1/2 (p44/42 MAPKs), while inhibition of PKC or Akt blocked this phosphorylation. Epinephrine increased the mRNA levels of proto‐oncogenes (c‐fos, c‐jun, c‐myc), while inhibition of ERK1/2 decreased these mRNA levels. In experiments aimed at examining the involvement of cell cycle regulatory proteins, epinephrine increased the levels of cyclin E/cyclin‐dependent kinase 2 (CDK2) and cyclin D1/cyclin‐dependent kinase 4 (CDK4). In conclusion, epinephrine stimulates DNA synthesis via ERK1/2 through cAMP, Ca2+/PKC, and PI3K/Akt signaling pathways in mouse ESCs. J. Cell. Biochem. 104: 1407–1420, 2008. © 2008 Wiley‐Liss, Inc.
Study of galacto‐oligosaccharide formation from lactose using Pectinex Ultra SP‐L
Authors: Cardelle‐Cobas Alejandra , Villamiel Mar , Olano Agustin , Corzo Nieves
Published: February 2008

BACKGROUND:Galacto‐oligosaccharides (GOS) are synthesised from lactose by transglycosylation using β‐galactosidase (EC 3.2.1.23) and are recognised as prebiotics. The commercial enzyme preparation Pectinex Ultra SP‐L produced by Aspergillus aculeatus possesses β‐galactosidase activity; however, because its use has been directed towards the formation of 6′‐β‐galactosyl‐lactose, no data have been reported on the formation of other GOS. Since the composition of the oligosaccharide mixture obtained during lactose hydrolysis may affect the prebiotic properties, in this study the influence of various parameters (pH, temperature, time and enzyme and lactose concentrations) on the formation of GOS using Pectinex Ultra SP‐L was investigated.

RESULTS:High‐performance anion exchange chromatography with pulsed amperometric detection (HPAEC‐PAD) analysis allowed the detection of disaccharides other than lactose, trisaccharides and minor amounts of higher‐molecular‐weight GOS. The main GOS formed were a trisaccharide identified as β‐D‐Galp‐(1 → 6)‐Lac (6′‐β‐galactosyl‐lactose) and a disaccharide identified as β‐D‐Galp‐(1 → 6)‐D‐Gal (galactobiose). Other GOS detected were tentatively identified as β‐D‐Galp‐(1 → 6)‐D‐Glc (allolactose), β‐D‐Galp‐(1 → 3)‐D‐Glc and β‐D‐Galp‐(1 → 3)‐Lac. Trisaccharide formation was favoured by a pH increase from 4.5 to 6.5, whereas the disaccharide content increased as the pH decreased, reaching a level of 11% at pH 4.5. 6′‐β‐Galactosyl‐lactose production increased gradually with increasing temperature, attaining a maximum value of 17% at 60 °C after 7 h, whereas disaccharide formation was optimal at 50 °C, reaching a level of 10% after 24 h.

CONCLUSION:The results indicate that Pectinex Ultra SP‐L can be used to obtain GOS mixtures of different composition depending on the operating conditions. It has been shown for the first time that Pectinex Ultra SP‐L can be used for the selective formation of disaccharides. Copyright © 2008 Society of Chemical Industry
Study of Uniaxially Stretched Isotactic Poly(propylene) by 1H Solid‐State NMR and IR Spectroscopy
Authors: Hedesiu Cristian , Demco Dan E. , Remerie Klaas , Blümich Bernhard , Litvinov Victor M.
Published: February 2008

Changes in the amount of the rigid, semi‐rigid and soft fractions, molecular mobility and domain thickness of uniaxially stretched iPP were investigated as a function of temperature, draw ratio, drawing temperature and drawing rate. Correlations are established between the thicknesses of rigid domains and the amount of the rigid fractions of uniaxially stretched iPP. Also established are correlations between the thickness of rigid domains and the molecular mobility of the rigid fraction of uniaxially stretched iPP. The drawing temperature has an important effect on the strain‐induced transformation of the spherulitic morphology of iPP to a fibrillar one.

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Novel pH‐ and Temperature‐Responsive Block Copolymers with Tunable pH‐Responsive Range
Authors: He Chaoliang , Zhao Changwen , Chen Xuesi , Guo Zhaojun , Zhuang Xiuli , Jing Xiabin
Published: February 2008

A series of novel pH‐ and temperature‐responsive diblock copolymers composed of poly(N‐isopropylacrylamide) (PNIPAM) and poly[(L‐glutamic acid)‐co‐(γ‐benzyl L‐glutamate)] [P(GA‐co‐BLG)] were prepared. The influence of hydrophobic benzyl groups on the phase transition of the copolymers was studied for the first time. With increasing BLG content in P(GA‐co‐BLG) block, the thermal phase transition of the diblock copolymer became sharper at a designated pH and the critical curve of phase diagram of the diblock copolymer shifted to a higher pH region. Notably, when the BLG content in P(GA‐co‐BLG) block was more than 30 mol.‐%, the diblock copolymer responded sharply to a narrow pH change in the region of pH 7.4–5.5.

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Design and Synthesis of a New Conjugated Polyelectrolyte as a Reversible pH Sensor
Authors: Xu Qingling , An Lingling , Yu Minghui , Wang Shu
Published: February 2008

A highly pH sensitive water‐soluble polyfluorene derivative (PFP‐aa) has been designed and synthesized by Suzuki coupling reaction. The PFP‐aa contains two amino and four carboxylic acid groups in each repeat unit (RU). The protonation and deprotonation of both the carboxylate and amine are controlled by medium pH values. The polymer charge is anticipated to control electrostatic repulsion between polymer chains and lead to different levels of aggregation behaviors. Different fluorescent responses of the PFP‐aa are demonstrated as the environmental pH is changed from 3 to 12. Different sugars can bind to boronic acid to form boronic esters with different binding constants following proton release, thus generating diverse changes in pH. It is demonstrated that PFP‐aa can be used as a pH sensor to detect D‐fructose.

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Longitudinal MRI studies in the isoflurane‐anesthetized rat: long‐term effects of a short hypoxic episode on regulation of cerebral blood flow as assessed by pulsed arterial spin labelling
Authors: Wegener Susanne , Wong Eric C.
Published: February 2008

MRI is a powerful tool for measuring cerebral blood flow (CBF) longitudinally. However, most animal studies require anesthesia, potentially interfering with normal physiology. Isoflurane anesthesia was used here to study CBF regulation during repetitive scanning in rats. MR perfusion images were acquired using FAIR (flow‐sensitive alternating inversion recovery) arterial spin labeling, and absolute CBF was calculated. CBF changes in response to a hypoxic (12% O2) and hypercapnic (5% CO2) gas stimulus were monitored. Hypercapnia led to a robust increase in CBF compared with baseline (195.5 ± 21.5 vs 123.6 ± 17.9 ml/100 g/min), and hypoxia caused a smaller non‐significant increase in mean CBF values (145.4 ± 13.4 ml/100 g/min). Strikingly, when measurements were repeated 5 days later, CBF was dramatically reduced in hypoxia (93.2 ± 8.1 ml/100 g/min) compared with the first imaging session. Without application of the hypoxic and hypercapnic gases during the first MRI, baseline CBF and CBF changes in response to hypoxia at the second MRI were similar to naive rats. Blood gas analyses revealed a slight reduction in arterial oxygenation during the second period of anesthesia compared with the first. These findings indicate that, in isoflurane‐anesthetized rats, even a short hypoxic episode can have long‐lasting effects on cerebrovascular regulation. Copyright © 2008 John Wiley & Sons, Ltd.
19·9%‐efficient ZnO/CdS/CuInGaSe2 solar cell with 81·2% fill factor
Authors: Repins Ingrid , Contreras Miguel A. , Egaas Brian , DeHart Clay , Scharf John , Perkins Craig L. , To Bobby , Noufi Rommel
Published: February 2008

We report a new record total‐area efficiency of 19·9% for CuInGaSe2‐based thin‐film solar cells. Improved performance is due to higher fill factor. The device was made by three‐stage co‐evaporation with a modified surface termination. Growth conditions, device analysis, and basic film characterization are presented. Published in 2008 by John Wiley & Sons, Ltd.
Synthesis and characterization of epoxy‐based semi‐interpenetrating polymer networks sulfonated polyimides proton‐exchange membranes for direct methanol fuel cell applications
Authors: Lee Chi‐Hung , Wang Yen‐Zen
Published: February 2008

Novel epoxy‐based semi‐interpenetrating polymer networks (semi‐IPNs) of aromatic polyimide, derived from 2,2‐benzidinedisulfonic acid (BDSA), were prepared through a thermal imidization reaction. Dynamic scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were utilized to verify the synchronization of the imidization of sulfonated poly(amic acid) (SPAA) and the crosslinking reactions of epoxy. The semi‐IPNs of epoxy/sulfonated polyimides (SPI‐EPX) exhibit excellent film‐forming characteristics and mechanical integrity at room temperature. Conductivities at 100 °C of 0.0243 S cm−1 (SPI‐EP30) and 0.0141 S cm−1 (SPI‐EP50) were obtained, which are similar to that of the Nafion 117 (0.0287 S cm−1). The increase in the conductivity of SPI‐EP(30,40) with temperature is more rapid than that of Nafion 117. The SPI‐EPX exhibited lower methanol permeability than did Nafion117. The hydrolytic stability of the SPI‐EPX was followed by FTIR spectroscopy at regular intervals. SPI‐EPX prepared using epoxy‐based semi‐IPNs of sulfonated polyimide, SPI‐EP(40,50), exhibited higher hydrolytic stability than the phthalic polyimides (five‐membered ring polyimides).The microstructure was analyzed using atomic force microscopy (AFM) in the tapping mode, which demonstrated that SPI‐EP50 exhibited a nanophase that was separated into an essentially reticulated and venous hydrophobic and hydrophilic domains. Transmission electron microscopy (TEM) confirmed widespread and well‐connected hydrophilic domains, proving the higher hydrolytic stability and strong proton‐transporting properties of the SPI‐EPX membrane. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2262–2276, 2008
Synthesis of methacrylate derivatives oligomers by dithiobenzoate‐RAFT‐mediated polymerization
Authors: Hosseini Nejad Elham , Castignolles Patrice , Gilbert Robert G. , Guillaneuf Yohann
Published: February 2008

Reversible addition fragmentation chain transfer (RAFT) was used to synthesize methacrylic acid oligomers and oligo(methacrylic acid)‐b‐poly(methyl methacrylate) (PMAA‐b‐PMMA) with targeted degree of polymerization ≈ 10. Characterization is by size‐exclusion chromatography (SEC) and electrospray mass‐spectrometry. SEC data are presented as hydrodynamic volume distributions (HVDs), the only proper means to present comparative and meaningful SEC data when there is no unique relationship between size and molecular weight. The RAFT agent, (4‐cyanopentanoic acid)‐4‐dithiobenzoate (CPADB), produced dithiobenzoic acid as a side product during the polymerization of methacrylate derivatives. Precipitation in diethyl ether proved to be an easy way to remove this impurity from the PMAA‐RAFT oligomers. Both unpurified and purified macro‐RAFT agent were used to prepare amphiphilic PMAA‐b‐PMMA copolymers. Diblock copolymer prepared from the purified PMAA homopolymer had a narrower HVD in comparison to those obtained from the equivalent unpurified macro‐RAFT agent. This work shows that while cyanoisopropyl‐dithiobenzoate or CPADB are good RAFT agents for methacrylate derivatives, they exhibit some instability under typical polymerization conditions, and thus when oligomers are targeted, optimal control requires checking for the degradation product and appropriate purification steps when necessary (the same effect is present for larger polymers but is unimportant). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2277–2289, 2008
Synthesis and photopolymerizations of new phosphonated monomers for dental applications
Authors: Yeniad Bahar , Albayrak Aylin Ziylan , Olcum Nihan Celebi , Avci Duygu
Published: February 2008

Three novel phosphonated methacrylate monomers have been synthesized and studied for use in dental applications. Two of the monomers were synthesized from the reactions of glycidyl methacrylate (GMA) with (diethoxy‐phosphoryl)‐acetic acid (monomer 1) and (2‐hydroxy‐ethyl)‐phosphonic acid dimethyl ester (monomer 2). These monomers showed high crosslinking tendencies during thermal bulk and solution polymerizations. The third monomer (monomer 3) was prepared by the reaction of bisphenol A diglycidylether (DER) with (diethoxy‐phosphoryl)‐acetic acid and subsequent conversion of the resulting diol to the methacrylate with methacryloyl chloride. The homopolymerization and copolymerization behaviors of the synthesized monomers were also investigated with glycerol dimethacrylate (GDMA), triethylene glycol dimethacrylate (TEGDMA), and 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxy propyloxy) phenyl] propane (bis‐GMA) using photodifferential scanning calorimetry at 40 °C using 2,2′‐dimethoxy‐2‐phenyl acetophenone (DMPA) as photoinitiator. Monomer 1 showed polymerization rate similar or greater than dimethacrylates studied here but with higher conversion. The maximum rate of polymerizations decreased in the following order: 1∼TEGDMA>GDMA∼bis‐GMA∼3>2. A synergistic effect in the rate of polymerization was observed during copolymerizations. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2290–2299, 2008
Improvement of the Optical Transmission of Polymer Planar Waveguides by Plasma Treatment
Authors: Airoudj Aissam , Debarnot Dominique , Bêche Bruno , Boulard Brigitte , Poncin‐Epaillard Fabienne
Published: February 2008

The aim of the present work is to reduce the optical losses of glycidyl ether of bisphenol A (SU‐8) polymer planar waveguides using cold plasmas, which allow the substitution of H atoms by F. CF4 and mixtures of CF4/H2 RF plasma treatments were carried out for the surface fluorination of the SU‐8 waveguide. The observed decrease in the optical losses due to propagation in the Si/SiO2/fluorinated SU‐8 planar waveguides has been correlated with the surface fluorination as measured by XPS and CA measurements. In order to understand and to optimize the fluorination process, the plasma phase was analyzed by OES. Finally, the thickness of the fluorinated layer was estimated using modulated incident‐angle XPS.

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Analysis of the residue–residue coevolution network and the functionally important residues in proteins
Authors: Lee Byung‐Chul , Park Keunwan , Kim Dongsup
Published: February 2008

It is a common belief that some residues of a protein are more important than others. In some cases, point mutations of some residues make butterfly effect on the protein structure and function, but in other cases they do not. In addition, the residues important for the protein function tend to be not only conserved but also coevolved with other interacting residues in a protein. Motivated by these observations, the authors propose that there is a network composed of the residues, the residue–residue coevolution network (RRCN), where nodes are residues and links are set when the coevolutionary interaction strengths between residues are sufficiently large. The authors build the RRCN for the 44 diverse protein families. The interaction strengths are calculated by using McBASC algorithm. After constructing the RRCN, the authors identify residues that have high degree of connectivity (hub nodes), and residues that play a central role in network flow of information (CI nodes). The authors show that these residues are likely to be functionally important residues. Moreover, the CI nodes appear to be more relevant to the function than the hub nodes. Unlike other similar methods, the method described in this study is solely based on sequences. Therefore, the method can be applied to the function annotation of a wider range of proteins. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Insights into the role of oligomeric state on the biological activities of crotoxin: Crystal structure of a tetrameric phospholipase A2formed by two isoforms of crotoxin B fromCrotalus durissus terrificusvenom
Authors: Marchi‐Salvador Daniela P. , Corrêa Luiz C. , Magro Angelo J. , Oliveira Clayton Z. , Soares Andreimar M. , Fontes Marcos R. M.
Published: February 2008

Crotoxin B (CB or Cdt PLA2) is a basic Asp49‐PLA2found in the venom of Crotalus durissus terrificus and it is one of the subunits that constitute the crotoxin (Cro). This heterodimeric toxin, main component of the C. d. terrificus venom, is completed by an acidic, nontoxic, and nonenzymatic component (crotoxin A, CA or crotapotin), and it is related to important envenomation effects such as neurological disorders, myotoxicity, and renal failure. Although Cro has been crystallized since 1938, no crystal structure of this toxin or its subunits is currently available. In this work, the authors present the crystal structure of a novel tetrameric complex formed by two dimers of crotoxin B isoforms (CB1 and CB2). The results suggest that these assemblies are stable in solution and show that Ser1 and Glu92 of CB1 and CB2, respectively, play an important role in the oligomerization. The tetrameric and dimeric conformations resulting from the association of the isoforms may increase the neurotoxicity of the toxin CB by the creation of new binding sites, which could improve the affinity of the molecular complexes to the presynaptic membrane. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Mycobacterium tuberculosis isocitrate lyase (MtbIcl): Role of divalent cations in modulation of functional and structural properties
Authors: Kumar Ranjeet , Bhakuni Vinod
Published: February 2008

Isocitrate lyase (Icl), an enzyme that plays an important role in the regulation of isocitrate flux and anaplerotic replenishment of pool of substrate required for biosynthetic process in Mycobacterium tuberculosis is a potential drug target for the antituberculosis drugs. Divalent cations induce differential effect of activation and inhibition of MtbIcl functional activity. The study for the first time demonstrates that interaction of cations with MtbIcl results in differential modulation of the enzyme structure which is probably the underlying mechanism for differential modulation of functional activity of enzyme by divalent cations. The Mg2+ and Mn2+ ions act as activators of the enzyme and in their absence no enzymatic activity was observed. These cations do not induce any significant structural alteration in the enzyme as observed by far‐UV CD and solvent denaturation studies using chaotropic salts. However, the thermal denaturation studies demonstrate that they do interact with the noncatalytic α/β barrel core domain of the enzyme and destabilize it. The inhibitors Zn2+ and Cd2+ interact directly with the catalytic domain of the enzyme and unfold it as a result of which complete loss of the enzymatic activity is observed in their presence. The results obtained from the studies provide intriguing insight into the possible mechanism of divalent cation‐induced changes in structure, function, and stability of MtbIcl. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Alignment of the energy levels and charge injection barriers at interfaces for spin injection: La0.7Sr0.3MnO3 in contact with organic semiconductors
Authors: Grobosch M. , Knupfer M. , Dörr K. , Gangineni R. B.
Published: February 2008

For determination of the energy‐level alignment at inter‐ faces between La0.7Sr0.3MnO3 films and two typical organic semiconductors, copper‐phthalocyanine (CuPc) and α‐sexithiophene (α‐6T) we have performed a combined X‐ray and ultraviolet photoemission study. La0.7Sr0.3MnO3 thin films were grown by using the pulsed laser deposition (PLD) technique and subsequently ex‐situ cleaned before the organic materials were thermally evaporated. We show that under these conditions the interfaces are free from chemical interaction and are characterized by a short‐range interface dipole and large injection barriers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic properties of durene crystals: Implications for charge transport
Authors: Ortmann F. , Hannewald K. , Bechstedt F.
Published: February 2008

The electronic structure and charge anisotropy of durene (1,2,4,5‐tetramethylbenzene) crystals is studied by means of the density‐functional theory. Based on a comprehensive analysis of the band structure and effective‐mass tensors, we propose that durene is a high‐mobility material. We find larger bandwidths than those found for the common oligoacenes. Supplemented by an indepth analysis of the electron density, further insight is obtained into the anisotropy of this herringbone‐stacked material. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measuring carrier mobility in conventional multilayer organic light emitting devices by delayed exciton generation
Authors: Reineke S. , Lindner F. , Huang Q. , Schwartz G. , Walzer K. , Leo K.
Published: February 2008

The authors present an alternative method for the determination of the charge carrier mobility of organic thin films. In contrast to known methods like space charge limited current, field effect transistor and time of flight approaches, we determine the charge carrier mobility of a mixed film, serving as emission layer, within the conventional multilayer device architecture. We make use of a strong delayed generation feature in the electroluminescent decay, following a short voltage pump pulse in a time‐resolved set‐up. Taking into account the preferentially electron transporting properties of the film, the mobility of a N,N ′‐di(naphthalen‐2‐yl)‐N,N ′‐diphenyl‐benzidine (NPB):tris(1‐phenylisoquinoline) iridium [Ir(piq)3] mixed film is found to be on the order of 10–5 cm2 (Vs)–1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Charge transport parameters of HBC at different temperatures
Authors: Kirkpatrick J. , Marcon V. , Kremer K. , Nelson J. , Andrienko D.
Published: February 2008

We study the dependence on temperature of the charge transport parameters for hexabenzocoronene (HBC). Following from Marcus theory, two charge transport parameters will be calculated: the transfer integral and the difference in site energies. These parameters are strongly dependent on the orientation and position of molecules. Position and orientation of molecules are determined using molecular dynamics. Transfer integrals are calculated from a simplified INDO method. A technique to compute energetic disorder, that is the spread in site energies for the charge carriers, is developed. In the herringbone phase transfer integrals are higher, but so is energetic disorder. We consider three derivatives of HBC with different side chains, which lead to different phase behaviour and distributions of charge transport parameters. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultralong‐range radiative excitation transfer between quantum dots in a planar microcavity
Authors: Tarel Guillaume , Parascandolo Gaetano , Savona Vincenzo
Published: February 2008

We study the system of two quantum dots lying on the central plane of a planar semiconductor microcavity. By solving the full Maxwell problem, we demonstrate that the rate of resonant excitation transfer between the two dots decays as d–1/2 as a function of the distance d at long distance. This very longrange mechanism is due to the leaky and guided modes of the microcavity, which act as effective radiative transfer channels. At short distance, the d–3 dependence of the Förster mechanism, induced by the electrostatic dipole–dipole interaction, is recovered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Second‐order correlation function of entangled photons from a quantum dot in microcavity
Authors: Ajiki Hiroshi , Ishihara Hajime
Published: February 2008

We theoretically study cross‐polarized entangled photon generation from a single quantum dot in microcavity. Generation of co‐polarized non‐entangled photons is suppressed in the strong‐coupling limit due to the photon blockade effect. Normalized second‐order correlation function shows quantum beat resulting from interference between two kinds of entangled photons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strongly coupled organic microcavities with vibronic progressions
Authors: Fontanesi L. , La Rocca G. C.
Published: February 2008

The optical properties of an organic polycrystalline film of NTCDA with one vibronic replica, embedded in a microcavity, were measured by Holmes and Forrest in 2004. They observed strong exciton‐photon coupling and hybridization between the cavity mode and both the 0‐0 and 0‐1 vibronic transitions. The purpose of this work is to build a model to describe optical spectra of an organic microcavity with vibronic replicas in both weak and strong coupling regimes between photon and exciton modes. The problem has been handled with two approaches, a microscopic model and a macroscopic one. The active material vibronic spectra have been calculated in the Franck‐Condon framework.With these models we have reproduced the experimental spectra and we have also analyzed more complicated systems such as anisotropic monocrystalline materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spontaneous emission from an exciton in a quantum dot embedded in a microcavity
Authors: Inoue J. , Ochiai T. , Sakoda K.
Published: February 2008

Spontaneous emission properties of a quantum dot embedded in a semiconductor microcavity are theoretically investigated. High Q value of the cavity yields both weak and strong coupling states, the former of which is mainly focused. There, spontaneous emission spectrum has doublet shape, which is caused by a quantum interference. This interference is robust against detuning between the excitation of the quantum dot and cavity mode. The time domain analysis is performed for further characterization of the high Q weak coupling state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of unbound two‐exciton states on entangled photons generated from a cavity biexciton
Authors: Oka Hisaki , Ishihara Hajime
Published: February 2008

We theoretically investigate entangled‐photon generation via biexciton in a planar microcavity. When the exciton‐photon coupling is comparable to the biexciton binding energy, the biexciton can be stably coupled with the cavity photons (referred to as a cavity biexciton). Entangled photons are generated by the cascade decay of the cavity biexciton. We show that high‐efficient generation of entangled photons can be achieved when the superposition state of a cavity biexciton and two cavity polaritons formed by unbound two‐exciton states is realized. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Entanglement and parametric dynamics in quantum optics with interacting polaritons
Authors: Portolan S. , Di Stefano O. , Savasta S.
Published: February 2008

We report on a microscopic investigation of the polariton parametric emission in the presence of coherent and incoherent interaction processes by means of a full quantum description based on a nonequilibrium quantum Langevin approach for open systems applied to interacting‐electron complexes described within the dynamics controlled truncation scheme. It provides an easy recipe to calculate multi‐time correlation functions which are key‐quantities in quantum optics. In particular we report on calculations of polariton intensities (i.e. single time correlators) and spectra (i.e. two times correlators). We apply our scheme to a two‐pumps set‐up in microcavity recently proposed showing a quantitative analysis of the quantum correlation properties of the emitted photons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin‐wave excitation by spin‐polarized current in magnetic nanostructures
Authors: Consolo G.
Published: February 2008

A current‐driven magnetic point‐contact device can support both a quasi‐linear propagating spin‐wave mode and a nonlinear self‐localized evanescent spin‐wave bullet mode. In this work we show how the bias field orientation determines the nature of the excited modes. By using a micromagnetic framework we can describe the main properties of the observed modes, deriving also a satisfying agreement with analytical theories. It is also pointed out how the nature of these modes differs in: (i) threshold current of excitation, (ii) precession angle, (iii) frequency spectra, (iv) trajectory of the precessional motion, (v) spatial localization of the spin‐wave amplitude. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Image‐enhanced surgical navigation for endoscopic sinus surgery: evaluating calibration, registration and tracking
Authors: Lapeer R. , Chen M. S. , Gonzalez G. , Linney A. , Alusi G.
Published: February 2008

Background

Endoscopic sinus surgery (ESS) is generally applied to treat sinusitis when medication is not effective in eliminating the symptoms. Images captured by the endoscope are viewed on a monitor placed near the surgeon. Due to the separation of the handling of the endoscope from the viewing of the image, ESS requires surgeons to have well‐trained hand–eye coordination. Unlike the use of the stereo surgical microscope in ENT, the endoscope does not provide the stereo cue for depth perception, hence a surgeon can only perceive depth through motion and shading, which may affect the accuracy of tool placement. Whilst the skill and experience of the surgeon are important factors to the success of ESS, the assistance of image‐enhanced surgical navigation (IESN) can further reassure the surgeon's judgement and enhance surgical performance.

Methods

We developed and validated an IESN system (ARView) for a rigid zero‐degree endoscope, typically used for ESS. We present the interface, and calibration and registration (pre‐operative and intra‐operative) methods of the system. We then quantitatively assess the performance of each of the steps needed to generate the overlay of a real endoscope image with its ‘virtual’ counterpart, obtained from computed tomography (CT) image data of a real skull. These steps include calibration, registration, motion tracking and final overlay.

Results

Calibration results using a planar calibration object displayed optimized object space errors of 0.025 ± 0.013 mm, whilst a non‐planar calibration object displayed errors of 0.12 ± 0.08 mm. Target registration errors (TREs) near the region of interest (ROI), using our pre‐operative registration method with the calibration object located near the mouth of the patient (skull), were 2.3 ± 0.4 mm. The proposed photo‐consistency method for intra‐operative registration has not yet yielded satisfactory results for ESS‐based IESN. (RMS) values for tracking accuracy were found to be around 1.2 mm in a typical workspace of 400 × 400 mm. Object space overlay errors in a small measurement volume of 10 × 10 × 10 mm were found to be around 0.4 ± 0.02 mm.

Conclusions

We conclude that, in agreement with individual experiments, the current overall overlay accuracy is of the order of 2–3 mm in the x–y plane, which is in line with current conventional SN systems. The method which is most in need of improvement is registration, hence we wish to investigate the application of the proposed photo‐consistency method further. Copyright © 2008 John Wiley & Sons, Ltd.
Are the Brookhill–Wilk patents impediments to market growth in cybersurgery?
Authors: McLean T. R. , Torrance A. W.
Published: February 2008

Background

In the past, many surgeons could practise their craft with little or no knowledge of patent law. But in the world of robotic and computerized surgery, this is increasingly a myopic approach, because the principle means of protecting high‐tech surgical instruments is through the application of patent law. The issue is: does the Brookhill–Wilk patent, which covers the performance of remote robotic surgery, impede the growth of cybersurgery?

Methods

Review of the Brookhill–Wilk patent and relevant law.

Results

Patent law, which first took its form in the Middle Ages, attempts to balance the rewarding of innovation with the stifling of market growth. Using US patent law as a model, it would appear that the Brookhill–Wilk patent, a particular example of a medical process patent, could inhibit the growth of cybersurgery, as potential sums of money could be demanded by the patent holder from anyone who practises cybersurgery. However, two recent US Supreme Court cases appear to have seriously undermined the validity of a number of medical process patents, including the Brookhill–Wilk patent.

Conclusion

Based on recent changes in patent law, it is not expected that Brookhill–Wilk patent will hinder the growth of cybersurgery. Copyright © 2008 John Wiley & Sons, Ltd.
New visualization tools: computer vision and ultrasound for MIS navigation
Authors: Kilian P. , Plaskos C. , Parratte S. , Argenson J.‐N. A. , Stindel E. , Tonetti J. , Lavallée S.
Published: February 2008

Background

A versatile image acquisition method calledecho surgeticshas been developed for minimally invasive computer‐assisted orthopaedic procedures. The principle of echo surgetics is to use freehand three‐dimensional (3D) ultrasound to acquire relevant 3D bone surface and point data transcutaneously, eliminating access problems associated with conventional digitizers. The concept has been implemented in three technologies:Echo Point, Echo MatchingandEcho Morphing.

Methods

Cadaver experiments were carried out to evaluate the accuracy of (a) Echo Point for digitization of the anterior pelvic plane (APP) in total hip arthroplasty, and (b) Echo Morphing for reconstructing the distal femur in minimally invasive knee surgery.

Results and Conclusions

Echo Point provided significantly improved results (p< 0.001) over conventional digitization where mean tilt errors exceeded 20° . The Echo Morphing experiments demonstrated that with a reasonable number of points (ca. 1000) and initial attitude (IA) error (ca. 5–10 mm and 5–10° ) we can obtain an average accuracy of ∼1 mm that is sufficient for most of clinical applications. Copyright © 2008 John Wiley & Sons, Ltd.