bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoactivation of an Inhibitor of the 12/15‐Lipoxygenase Pathway
Authors: Herre Stephan , Schadendorf Torsten , Ivanov Igor , Herrberger Christian , Steinle Wencke , Rück‐Braun Karola , Preissner Robert , Kuhn Hartmut 
Published: June 2006

AbstractLipoxygenases are lipid‐peroxidizing enzymes that have been implicated in the pathogenesis of inflammatory diseases and lipoxygenase inhibitors may be developed as anti‐inflammatory drugs. Structure comparison with known lipoxygenase inhibitors has suggested that (2Z)‐2‐(3‐benzylidene)‐3‐oxo‐2,3‐dihydrobenzo[b]thiophene‐7‐carboxylic acid methyl ester might inhibit the lipoxygenase pathway but we found that it exhibited only a low inhibitory potency for the pure 12/15‐lipoxygenase (IC50=0.7 mM). However, photoactivation, which induces a Z‐to‐E isomerization of the double bond, strongly augmented the inhibitory potency and an IC50 value of 0.021 mM was determined for the pure E isomer. Similar isomer‐specific differences were observed with the recombinant enzyme and its 12‐lipoxygenating Ile418Ala mutant, as well as in intracellular lipoxygenase activity. Structure modeling of the enzyme/inhibitor complex suggested the molecular reasons for this isomer specificity. Since light‐induced isomerization may proceed in the skin, such photoreactive compounds might be developed as potential drugs for inflammatory skin diseases.
Solid‐Supported [2+2+2] Cyclotrimerizations
Authors: Young Douglas D. , Senaiar Ramesh S. , Deiters Alexander 
Published: June 2006

AbstractThe transition‐metal‐catalyzed [2+2+2] cyclotrimerization of a diyne and an alkyne provides a convergent route to highly‐substituted aromatic rings. This reaction possesses distinct drawbacks, especially low chemo‐ and regioselectivities, which hamper its application in combinatorial synthesis. These problems have been solved by the development of solid‐supported [2+2+2]‐cycloaddition reactions. If conducted on a solid‐support, this reaction enables rapid combinatorial access to diverse sets of carbo‐ and heterocyclic small‐molecule arrays. The scope of this methodology has been investigated by examining different immobilization strategies, different diyne precursors, and a variety of functionalized alkyne reaction partners. Overall, isoindoline, phthalan, and indan libraries were assembled in good to excellent yields and with high purities.
Preparation of Allyltin Reagents Grafted on Solid Support: Clean and Easily Recyclable Reagents for Allylation of Aldehydes
Authors: Chrétien Jean‐Mathieu , Zammattio Françoise , Gauthier Delphine , Le Grognec Erwan , Paris Michaël , Quintard Jean‐Paul 
Published: June 2006

AbstractThe preparation of polymer‐supported allyltin reagents was shown to be possible for both unfunctionalized and functionalized allyl units. These reagents were treated with aldehydes in the presence of cerium(III) or indium(III) salts to afford high yields of homoallylic alcohols, practically uncontaminated with organotin residues (less than 5 ppm). Some mechanism aspects are briefly discussed and the potential for regeneration and reuse of these supported reagents is pointed out.
Self‐Assembly and Molecular Dynamics of Oligoindenofluorenes
Authors: Elmahdy Mahdy M. , Floudas George , Oldridge Luke , Grimsdale Andrew C. , Müllen Klaus 
Published: June 2006

AbstractThe optical properties, self‐assembly mechanism, thermal properties, and the associated molecular dynamics of a series of stable blue‐emitting oligoindenofluorenes up to the polymer were investigated by photoluminescence, wide‐angle X‐ray scattering, polarizing optical microscopy, differential scanning calorimetry, and dielectric spectroscopy. Oligomers of indenofluorenes possess high structural order and form smectic mesophases, as opposed to the nematic mesophases formed in the corresponding oligofluorenes. The α process associated with the liquid‐to‐glass transition displays an asymmetric broadening of relaxation times (non‐Debye process), with a non‐Arrhenius temperature dependence of relaxation times and a strong molecular weight dependence. The low dielectric loss and low ionic conductivity revealed the absence of ketone structural defects, which is consistent with the observed stable blue emission.
New Dinuclear Face‐ and Edge‐Sharing Bioctahedral Ruthenium Compounds Containing 1,2‐Bis(diphenylphosphanyloxy)ethane
Authors: Bravo Jorge , Castro Jesús , García‐Fontán Soledad , Rodríguez‐Martínez M. Carmen , Rodríguez‐Seoane Pilar 
Published: June 2006

AbstractThe bidentate diphosphinite ligand 1,2‐bis(diphenylphosphanyloxy)ethane (L), Ph2P–O–(CH2)2–O–PPh2, can be sequentially incorporated into a series of dinuclear chloro‐bridged ruthenium compounds using [RuCl2(DMSO)4] as a precursor to give the new bioctahedral compounds [Ru2(μ‐Cl)3(DMSO)3Cl(η2‐L)] (1), [Ru2(μ‐Cl)3(DMSO)Cl(η2‐L)2] (2) and [Ru2Cl2(η2‐L)2{η1‐L(O)}2(μ‐Cl)2] (3). Compound 3 contains two partially oxidised diphosphinite ligands that act in a monodentate manner. These compounds can also be obtained by direct reaction of [RuCl2(DMSO)4] with the appropriate stoichiometric amount of L but in the case of 3 (in which prolonged heating is necessary) the reaction affords two mononuclear compounds [RuCl2(η2‐L)(Ph2POPPh2)] (7) and [RuCl(CO)(η2‐L)(Ph2POCH2)] (8), with ligand fragments coordinated to the metal probably originating in metal‐mediated disruptions of L. Reaction of 2 with the monodentate ligands PPh3 – n(OEt)n (n = 1–3) (L′) affords the dinuclear doubly chloro‐bridged compound [Ru2(μ‐Cl)2Cl2(η2‐L)2(L′)2] (4), the dinuclear triply chloro‐bridged compound [{Ru(η2‐L)(L′)}2(μ‐Cl)3]Cl (5) and the mononuclear compound [RuCl2(η2‐L)(L′)2] (6). The solid‐state structures of 2 (transoid isomer), 5 (transoid isomer), 6, 7 and 8 are reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Characterization of a Byproduct in the Alkylation of DMIT: Alkylation on the Least Nucleophilic Sulfur Atom
Authors: Petersen Bo M. , Bjernemose Jens K. , Jeppesen Jan O. 
Published: June 2006

AbstractIt is generally accepted that the alkylation of (Et4N)2[Zn(DMIT)2] (1) is a very clean reaction that produces 4,5‐bis(alkylthio)‐1,3‐dithiole‐2‐thiones 4 in very high yields. Although this procedure has been widely used, we have found that, in addition to the 4,5‐bis(alkylthio)‐1,3‐dithiole‐2‐thione products 4, highly unexpected byproducts are formed during the alkylation reaction in which the thione functionalities of DMIT in (Et4N)2[Zn(DMIT)2] (1) are alkylated instead of the more reactive thiolate groups. These byproducts were identified as a novel type of compounds, namely bis(2‐alkylthio‐1,3‐dithiol‐1‐ium‐4,5‐dithiolato)zinc compounds 3, being composed of two identical 2‐alkylthio‐1,3‐dithiol‐1‐ium‐4,5‐dithiolate moieties coordinated to a single zinc(II) atom and were characterized by elemental analyses and different spectroscopic techniques as well as single‐crystal X‐ray structure analyses. A comparison of the physical properties of compounds 3 and (Et4N)2[Zn(DMIT)2] (1) has been carried out. The outcome of these investigations revealed significant differences in the physical properties of these two systems. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Spectroscopic, Structural and Theoretical Investigation of Alkenyl Ruthenium Complexes Supported by Sulfur–Nitrogen Mixed‐Donor Ligands
Authors: Wilton‐Ely James D. E. T. , Wang Ming , Benoit David M. , Tocher Derek A. 
Published: June 2006

AbstractA series of molecules bearing both sulfur and nitrogen donors has been investigated as ligands for σ‐alkenyl ruthenium complexes. On deprotonation, the ligands, 4‐amino‐2‐mercaptopyrimidine (HL1), 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole (HL2), 2‐mercaptothiazoline (HL3), 4‐hydroxy‐2‐mercaptopyrimidine (HL4) and 2‐mercaptoquinoline (HL5) all react with alkenyl complexes of the form [RuRCl(CO)(BTD)(PPh3)2] [R = CH=CHC6H5, CH=CHC6H4Me‐4, C(C≡CPh)=CHPh; BTD = 2,1,3‐benzothiadiazole] through loss of chloride and BTD ligands to yield [RuR(L)(CO)(PPh3)2]. Four of these ligands have alternative potential coordination modes and donor groups. In all cases complexation occurs to form four‐membered nitrogen–sulfur chelates with the pendant amino or hydroxy functionality playing no role in coordination. In the case of the 4‐aminopyrimidine‐2‐thiolate (L1) ligand, this was confirmed by a single‐crystal X‐ray study. 2‐Mercaptothiazoline (L3) has the ability to coordinate through two sulfur donors, however, chelation to nitrogen and sulfur donors is preferred as demonstrated by a structural study. This observation is supported by theoretical calculations, which show that a complex displaying the nitrogen–sulfur chelate is of significantly lower energy than one bonded to the ligand through two sulfur donors, despite lone pairs being available in both cases. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Evaluation of the radioprotective effect of Liv 52 in mice
Authors: Jagetia Ganesh C. , Ganapathi Narsipura G. , Venkatesh Ponemone , Rao Nageshwar , Baliga Manjeshwar S. 
Published: June 2006

AbstractLiv 52 is a mixture of botanicals that is used clinically to treat various hepatic disorders. In this study, the radioprotective activity of Liv 52 was evaluated in mice given whole‐body exposure to different doses of γ‐radiation. In addition, a series of studies was conducted to explore the mechanism of radioprotection. Radioprotection was evaluated by the ability of Liv 52 to reduce both the frequency of bone marrow micronucleated erythrocytes and the lethality produced by 60Co γ‐radiation. Mice were treated by oral gavage once daily for seven consecutive days with 500 mg/kg body weight Liv 52 or carboxymethylcellulose vehicle prior to radiation. Micronucleated polychromatic erythrocytes (MPCEs), micronucleated normochromatic erythrocytes (MNCEs), and the PCE/NCE ratio were measured at 0.25–14 days after exposure to whole‐body radiation doses of 0, 0.5, 1.5, 3.0, or 4.5 Gy; animal survival was monitored after doses of 7, 8, 9, 10, 11, or 12 Gy. Pretreatment of mice with Liv 52 significantly reduced the frequency of radiation‐induced MPCEs and MNCEs. Irradiation reduced the PCE/NCE ratio in a dose‐related manner for up to 7 days following irradiation; Liv 52 pretreatment significantly mitigated against these reductions. Liv 52 treatment also reduced the symptoms of radiation sickness and increased mouse survival 10 and 30 days after irradiation. Liv 52 pretreatment elevated the levels of reduced glutathione (GSH), increased the activities of glutathione transferase, GSH peroxidase, GSH reductase, superoxide dismutase, and catalase, and lowered lipid peroxidation (LPx) and the activities of alanine amino transferase and aspartate aminotransferase 30 min after exposure to 7 Gy of γ‐radiation. Liv 52 pretreatment also reduced radiation‐induced LPx and increased GSH concentration 31 days following the exposure. The results of this study indicate that pretreatment with Liv 52 reduces the genotoxic and lethal effects of γ‐irradiation in mice and suggest that this radioprotection may be afforded by reducing the toxic effects of the oxidative products of irradiation. Environ Mol. Mutagen., 2006. © 2006 Wiley‐Liss, Inc.
A brief overview of mechanisms of mitochondrial toxicity from NRTIs
Authors: Kohler James J. , Lewis William 
Published: June 2006

AbstractNucleoside reverse transcriptase inhibitors (NRTIs) in combinations with other antiretrovirals (highly active antiretroviral therapy, HAART) are the cornerstones of AIDS therapy, turning HIV infection into a manageable clinical entity. Despite the initial positive impact of NRTIs, therapeutic experience revealed serious side effects that appeared to originate in the mitochondria and which ultimately manifested as dysfunction of that organelle. It may be reasonable to consider that as the AIDS epidemic continues and as survival with HIV infection is prolonged by treatment with HAART, long‐term side effects of NRTIs may become increasingly common. This consideration may be underscored in children who are born to HIV‐infected mothers who received NRTI therapy in utero during gestation. The long‐term effect of that NRTI exposure in utero is not clear yet. This review examines some proposed mechanisms of NRTI mitochondrial toxicity, including genetic predisposition, defects in mitochondria DNA replication, the encompassing “DNA pol‐γ hypothesis,” the relationship between mitochondrial nucleotide and NRTI pools, mitochondrial DNA mutation and dysfunction, and oxidative stresses related to HIV infection and NRTIs. Mechanisms of mitochondrial toxicity are reviewed with respect to key cell biological, pathological, and pharmacological events. Environ. Mol. Mutagen., 2006. © 2006 Wiley‐Liss, Inc.
The research and development strategy for water utilisation in agriculture–responding to diverse needs of farmers in South Africa
Authors: Backeberg Gerhard R. , Sanewe Andrew J. 
Published: June 2006

AbstractMajor differences exist between the environment in which research is carried out and farming is practised. The challenge for research is to develop an agenda and design projects that address real‐life problems. On a national and regional level, key issues for research include increased productivity of water for crop and livestock production and eradication of hunger and poverty. More specifically, utilisation and development of water resources must therefore be analysed in relation to the needs and requirements of people. People using water in agriculture comprise a diverse group of subsistence, emergent and commercial farmers within interrelated subsectors of agriculture such as irrigated and dryland farming, woodlands and forestry, grasslands and livestock watering, and aquaculture. The strategic implementation plan for research and development (R&D) must determine objectives, adopt a course of action and allocate resources. Taking research into practice must be purposefully managed according to the innovation cycle. Using estimation of crop water requirements and irrigation water scheduling as examples, it is shown that high‐quality research has to be followed by comprehensive knowledge dissemination to achieve successful application. More emphasis should be placed on development through technology exchange, training and extension in order to narrow the gap between research and practice. Copyright © 2006 John Wiley & Sons, Ltd.
Cell mimetic lateral stabilization of outer cell mimetic bilayer on polymer surfaces by peptide bonding and their blood compatibility
Authors: Kaladhar K. , Sharma Chandra P. 
Published: June 2006

AbstractThe biological lipid bilayer membranes are stabilized laterally with the help of integral proteins. We have simulated this with an optimized ternary phospholipid/glycolipid/cholesterol system, and stabilized laterally on functionalized poly methyl methacrylate (PMMA) surfaces, using albumin, heparin, and polyethylene glycol as anchors. We have earlier demonstrated the differences due to orientation and packing of the ternary phospholipid monolayers in relation to blood compatibility (Kaladhar and Sharma, Langmuir 2004;20:11115–11122). The structure of albumin is changed here to expose its interior hydrophobic core by treating with organic solvent. The interaction between the hydrophobic core of the albumin molecule and the hydrophobic core of the lipid molecules is confirmed by incorporating the molecule into bilayer membranes. The secondary structure of the membrane incorporated albumin is studied by CD spectral analysis. The structure of the altered albumin molecule contains more β‐sheet as compared to the native albumin. This conformation is also retained in membranes. The partitioning of the different anchors based on its polarity and ionic interactions in the monolayer is studied from the pressure‐area (π‐A) isotherm of the lipid monolayers at the air/water interface using Langmuir‐Blodgett (LB) trough facility. Such two monolayers are deposited onto the functionalized PMMA surface using LB trough and crosslinked by carbodiimide chemistry. The structure of the deposited bilayer is studied by depth analysis using contact mode AFM in dry conditions. The stabilized bilayer shows stability up to 1 month by contact angle studies. Preliminary blood compatibility studies reveal that the calcification, protein adsorption, as well as blood‐cell adhesion is significantly reduced after the surface modification. The reduced adsorption of ions, proteins, and cells to the modified surfaces may be due to the fluidity of the microenvironment along with the contribution of the mobile PEG groups at the surface and the phosphorylcholine groups of the phospholipids. The stability of the anchored bilayer under low shear stress conditions promises that the laterally stabilized supported bilayer system can be used for low shear applications like small diameter vascular graft and modification of biosensors, and so forth. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
In vitro attachment of osteoblasts on contaminated rough titanium surfaces treated by Er:YAG laser
Authors: Friedmann Anton , Antic Lilly , Bernimoulin Jean‐Pierre , Purucker Peter 
Published: June 2006

AbstractMicrobial contamination of implant surfaces inhibits formation of new osseous tissues. Biocompatibility of sandblasted large grid (SLA) surface, after previous in vitro cocultivation with Porphyromonas gingivalis and concomitant Er:YAG laser irradiation of microorganisms, was tested by attachment of newly cultured osteoblasts. A total of 36 customized titanium cubes with SLA surface were placed into human osteoblast culture for 14 days. After removal of 1 control cube, 35 other cubes were contaminated with precultured P. gingivalis (ATCC33277) and incubated in broth medium for 1 week. Ablation was carried out on 32 cubes. Each side was treated for 23.5 s with a pulsed, water‐cooled laser beam. After irradiation, cubes were again placed into fresh osteoblast culture for 2 weeks. One randomly selected single side per cube was analyzed by scanning electron microscope in 22 cubes. On other 10 cubes, vitality of attached cells was tested with ethidiumbromide staining by fluorescence microscopy. Three negative controls revealed constantly adherent P. gingivalis, and no osteoblasts were detectable after P. gingivalis contamination on the surfaces. Laser‐treated specimens showed newly attached osteoblasts, extending over 50–80% of the surface. Positive control cube (without bacterial contamination) showed over 80% cell coverage of the surface. Vitality of widely stretched osteoblasts was confirmed by FITC staining. Our results indicate that Er:YAG laser was effective in removing P. gingivalis and cell compounds, offering an acceptable surface for new osteoblast attachment. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Attachment of human epithelial cells and periodontal ligament fibroblasts to tooth dentin
Authors: Messer Regina L. W. , Davis Cortney M. , Lewis Jill B. , Adams Yolanda , Wataha John C. 
Published: June 2006

AbstractA goal of treatment in periodontal therapy is to regenerate a new fibroblastic attachment rather than to repair lost attachment with a long junctional epithelium. To date, there is no evidence that fibroblastic attachment formed during regeneration is stronger or less susceptible to periodontal breakdown than a long junctional epithelial attachment. We measured the rate and strength of attachment of epithelial cells (NHEK) and periodontal ligament fibroblasts (PDLF) cultured individually and cocultured to dentin surfaces to determine which cell type has a faster attachment rate and greater adhesive strength to human dentin, and whether the cell types attach independently. Longitudinal dentin slices were seeded with either PDLF or NHEK for 2 or 24 h. The specimens were placed into a parallel plate flow chamber and defined laminar shear stresses were applied. Shear stress was created by step increases in fluid flow rate. Effluent fluid was collected and cell numbers (detached) were counted using a hemocytometer. Cocultures of PDLF and NHEK at three seeding ratios (10:1, 1:1, 1:10) were also tested. Each cell type attached equally well to polystyrene or dentin. PDLF showed a stronger attachment to polystyrene and dentin at 24 versus 2 h. NHEK attached to polystyrene or dentin equally well at 2 and 24 h. NHEK were more strongly attached after 2 h when compared to PDLF. PDLF were more strongly attached after 24 h versus NHEK. When NHEK and PDLF were seeded together on dentin at a 1:1 ratio, PDLF appeared to be more strongly attached than NHEK at 2 but not 24 h. At a ratio of 10 PDLF:1 NHEK, PDLF appeared to be more strongly attached at 2 and 24 h. At a ratio of 1 PDLF:10 NHEK, NHEK appeared to be more strongly attached at 2 h, but PDLF showed a trend of stronger attachment at 24 h. We conclude that epithelial cells attach more quickly to dentin surfaces than PDLF, but do not demonstrate increased attachment strength over time (PDLF do show increased attachment strength overtime). The purported advantages of periodontal regeneration over periodontal repair are supported by our results. Furthermore, our results support the concept of guided tissue regeneration. On the basis of on cellular competition experiments, epithelial cells and PDLF do not act independently, because epithelial cells enhanced the attachment rate of PDLF. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Mechanical properties of OI type III bone tissue measured by nanoindentation
Authors: Fan Zaifeng , Smith Peter A. , Eckstein Eugene C. , Harris Gerald F. 
Published: June 2006

AbstractNanoindentation was used to characterize the intrinsic mechanical properties of bone tissue from eight (8) children with type III Osteogenesis Imperfecta (OI). The bone samples were harvested from the cortex portion at the site of bowing (the mid 2/3 of the shaft of the tibia/femur). Unlike normal bone tissue, OI type III cortical bone exhibited more isotropic material properties. Young's modulus and hardness values measured in the longitudinal direction did not show significant differences from the transverse measurements. No differences were observed in modulus or hardness in an analysis of the cortical and trabecular samples. The deformation patterns of the OI type III bone during nanoindentation were found to be similar to those of normal adult bone in an analysis of the ratio of modulus to hardness. No correlation was found between nanoindentation measurement and age in an analysis of regression. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Mimicking cell–cell interactions at the biomaterial–cell interface for control of stem cell differentiation
Authors: Beckstead Benjamin L. , Santosa Daniel M. , Giachelli Cecilia M. 
Published: June 2006

AbstractThe ability to regulate stem cell proliferation and differentiation has relevance in numerous medical applications, including medical devices, tissue engineering, and regenerative medicine. To control cellular behavior at the biomaterial or scaffold interface, many studies have employed surface modifications that mimic the extracellular matrix. Strikingly absent is the immobilization of cell‐surface ligands to the biomaterial surface. One cell‐to‐cell signaling pathway that has been shown to regulate tissue development and stem cell fate is the Notch pathway. Recently, the Notch signaling pathway was identified as a key regulator of epithelial differentiation. Utilizing this knowledge, we applied an affinity immobilization scheme designed to attach and orient the Notch ligand, Jagged‐1, in an active conformation on a biomaterial surface. When epithelial stem cells were plated on the bound ligand, the Notch/CBF‐1 signaling pathway was stimulated and the cells upregulated both intermediate‐ and late‐stage differentiation markers. In addition, the ligand promoted tight clustering and extensive stratification. Soluble Jagged‐1 showed no Notch/CBF‐1 signaling and very little, if any, cell differentiating activity. The high potency of bound Jagged‐1 suggests that modification of a surface with a Notch ligand presents a powerful method to control stem cell differentiation at the cell–biomaterial interface. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006