bluuebunny/crossref_metadata_2025_split huggingface dataset:
Asymmetric Synthesis of (S)‐Mirtazapine: Unexpected Racemization through an Aromatic ipso‐Attack Mechanism
Authors: van der Linden Marco , Borsboom Judith , Kaspersen Frans , Kemperman Gerjan 
Published: April 2008

AbstractAn asymmetric synthesis of (S)‐mirtazapine has been achieved from the synthesis of the racemate by using (S)‐1‐methyl‐3‐phenylpiperazine as the starting material. Unfortunately, significant racemization was encountered in the final step, which involved an electrophilic aromatic ring closure of a alcohol by concentrated sulfuric acid. A significantly higher ee was observed when polyphosphoric acid (PPA) was used instead. A remarkable correlation between the amount of PPA used and the ee of the product was revealed, namely, an increase in the ee upon decreasing the amount of PPA. This trend was paralleled by the formation of an increasing amount of a side‐product upon lowering the amount of PPA. The racemization and formation of a side‐product can be explained by an ipso‐attack mechanism during the electrophilic aromatic ring‐closure reaction. This mechanism was supported by a mechanistic study using a deuterium‐labeled substrate.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Stereoselective, Temperature‐Dependent [2+2] Cycloaddition of N,N‐Dialkylhydrazones to N‐Benzyl‐N‐(benzyloxycarbonyl)aminoketene
Authors: Marqués‐López Eugenia , Martín‐Zamora Eloísa , Díez Elena , Fernández Rosario , Lassaletta José M. 
Published: April 2008

AbstractThe Staudinger‐like [2+2] cycloaddition of aliphatic hydrazones derived from (2R,5R)‐1‐amino‐2,5‐dimethylpyrrolidine to N‐benzyl‐N‐(benzyloxycarbonyl)aminoketene takes place to afford the corresponding β‐lactams in good yields when iPr2EtN is used as the base. The reaction proceeds in all cases with excellent stereocontrol to afford exclusively products having the (3R) configuration. Temperature was observed to exert a strong influence on the cis/trans selectivity, allowing in most cases the obtention of single trans or cis cycloadducts simply by performing the reactions at 80 °C or room temperature, respectively. Additional experiments support the hypothesis that the observed stereochemistry is the result of C=N isomerization in the zwitterionic intermediate, which takes place by a nucleophilic addition―rotation―elimination mechanism effected by the nucleophiles present in the reaction medium. Release of the dialkylamino group by oxidative cleavage of the N–N bond affords valuable compounds such as α,β‐diamino acids and the azetidinone cores of monobactam antibiotics such as aztreonam and carumonam.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Structural Studies of the O‐Chain Polysaccharide from Plesiomonas shigelloides Strain 302–73 (Serotype O1)
Authors: Pieretti Giuseppina , Corsaro M. Michela , Lanzetta Rosa , Parrilli Michelangelo , Canals Rocìo , Merino Susana , Tomás Juan M. 
Published: April 2008

AbstractPlesiomonas shigelloides is a Gram‐negative bacterium belonging to the Enterobacteriaceae family. It has been found in an aquatic environment in the tropical and subtropical regions and is responsible for many gastrointestinal infections in humans, which take place from drinking untreated water or eating uncooked shellfish. Plesiomonas shigelloides has also been reported to provoke extraintestinal infections such as meningitis and bacteremia in immunocompromised adults and neonates. Despite the emerging importance of this pathogenic microorganism, only three different O‐antigens have been characterised so far. The structure of the O‐chain of the lipopolysaccharide (LPS) from Plesiomonas shigelloides strain 302–73 (serotype O1) was determined by chemical analysis, 1D and 2D NMR spectroscopy and MALDI‐TOF mass spectrometry. The polysaccharide was constituted by a linear pentasaccharidic repeating unit as follows: →3)‐α‐L‐PneNAc4OAc(1→4)‐α‐L‐FucNAc(1→4)‐α‐L‐FucNAc(1→4)‐α‐L‐FucNAc(1→3)‐β‐D‐QuiNAc4NHb(1→ (PneNAc = 2‐acetamido‐2,6‐dideoxy‐talose, Hb = (S)‐3‐hydroxybutanoyl) PneNAc O‐acetylation was not stoichiometric and was found to be about 75 %. The position of the O‐acetyl group and the amount of acetylation were deduced by NMR spectroscopic analysis. All the monosaccharides included in the repeating unit were deoxyamino sugars, which most probably, together with the presence of O‐acetyl groups, were responsible for the recovery of the LPS in the phenol layer of the phenol/water extract of dried bacteria cells.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Microchip analysis of plant glucosinolates
Authors: Fouad Maged , Jabasini Mohammad , Kaji Noritada , Terasaka Kazuyoshi , Tokeshi Manabu , Mizukami Hajime , Baba Yoshinobu 
Published: April 2008

AbstractWe describe a new and selective analytical method for the separation and quantitation of plant glucosinolates. The new method, which utilizes microchip CE (μ‐CE) with fluorescence detection, circumvents the multistep procedures characteristic of conventional methods. Glucosinolates form charge transfer complexes with the xanthene dyes phloxine‐B and eosin‐B. The glucosinolates–phloxine‐B complex cannot be excited at 470 nm. Thus, the decrease in peak intensity of phloxine‐B after complex formation is used to quantitatively measure total glucosinolates in Arabidopsis thaliana seeds. For qualitative analysis, complex formation with eosin‐B is used. The sensitivity of eosin‐B detection at excitation/emission 470 nm/540 nm was low. However, sensitivity increased following complex formation with sinigrin (≥3 μg/mL). A batch‐learning, self‐organizing map was applied to visualize and organize analytical data into 2‐D matrix with similar and related data clustered together or near each other. This organized matrix was used to optimize electrophoretic conditions for the analysis. This study suggests potential applications of μ‐CE in plant metabolomics analyses without use of labeling fluorophores.
Fabrication and integration of planar electrodes for contactless conductivity detection on polyester‐toner electrophoresis microchips
Authors: Coltro Wendell Karlos Tomazelli , da Silva José Alberto Fracassi , Carrilho Emanuel 
Published: April 2008

AbstractIn this report, we describe the microfabrication and integration of planar electrodes for contactless conductivity detection on polyester‐toner (PT) electrophoresis microchips using toner masks. Planar electrodes were fabricated by three simple steps: (i) drawing and laser‐printing the electrode geometry on polyester films, (ii) sputtering deposition onto substrates, and (iii) removal of toner layer by a lift‐off process. The polyester film with anchored electrodes was integrated to PT electrophoresis microchannels by lamination at 120°C in less than 1 min. The electrodes were designed in an antiparallel configuration with 750 μm width and 750 μm gap between them. The best results were recorded with a frequency of 400 kHz and 10 Vpp using a sinusoidal wave. The analytical performance of the proposed microchip was evaluated by electrophoretic separation of potassium, sodium and lithium in 150 µm wide×6 µm deep microchannels. Under an electric field of 250 V/cm the analytes were successfully separated in less than 90 s with efficiencies ranging from 7000 to 13 000 plates. The detection limits (S/N = 3) found for K+, Na+, and Li+ were 3.1, 4.3, and 7.2 μmol/L, respectively. Besides the low‐cost and instrumental simplicity, the integrated PT chip eliminates the problem of manual alignment and gluing of the electrodes, permitting more robustness and better reproducibility, therefore, more suitable for mass production of electrophoresis microchips.
Macrocyclic polyamine‐modified poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) monolith for capillary electrochromatography
Authors: Tian Yun , Yang Fangxing , Yang Xuemei , Fu Enqin , Xu Ying , Zeng Zhaorui 
Published: April 2008

Abstract1,4,10,13,16‐Pentaazatricycloheneicosane‐9,17‐dione (macrocyclic polyamine)‐modified polymer‐based monolithic column for CEC was prepared by ring opening reaction of epoxide groups from poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) (GMA‐co‐EDMA) monolith with macrocyclic polyamine. Conditions such as reaction time and concentration of macrocyclic polyamine for the modification reaction were optimized to generate substantial EOF and enough chromatographic interactions. Anodic EOF was observed in the pH range of 2.0–8.0 studied due to the protonation of macrcyclic polyamine at the surface of the monolith. Morphology of the monolithic column was examined by SEM and the incorporation of macrocyclic polyamine to the poly(GMA‐co‐EDMA) monolith was characterized by infrared (IR) spectra. Successful separation of inorganic anions, isomeric benzenediols, and benzoic acid derivatives on the monolithic column was achieved for CEC. In addition to hydrophobic interaction, hydrogen bonding and electrostatic interaction played a significant role in the separation process.
Pomeranian basin (NW Poland) and its sedimentary evolution during Mississippian times
Authors: Matyja Hanna 
Published: April 2008

AbstractThe Carboniferous sedimentary history of the Pomeranian Basin (NW Poland) begins with Hastarian open‐marine carbonates and is terminated with ?lower Asbian terrestrial deposits in the north‐eastern part and, ?upper Asbian or Brigantian, open‐marine shales in the south‐western part of the basin. The ?latest Viséan, Serpukhovian and early Bashkirian was a period of regional non‐deposition and erosion. In the Upper Bashkirian–Gzhelian strata, an alluvial depositional environment was recognized.The Mississippian depositional history of the area has been punctuated by several, regional‐scale events: (1) during the late Famennian–early Tournaisian times anoxic conditions developed over the entire basin. The results of both conodont and miospore studies show the presence of a stratigraphic gap within this sequence (which also show extremely reduced thicknesses), that comprises the uppermost Famennian (Middle and Upper praesulcata conodont zones) and the lowermost Hastarian (sulcata–sandbergi conodont zones). This stratigraphic gap probably resulted from some chemical and/or hydrodynamical factors rather than from any tectonic uplift; (2) volcanic activity on the nearby East European Craton (EEC), which was the source of large amounts of detrital (volcaniclastic) material supplied to the Pomeranian Basin during the Early crenulata–?early anchoralis‐latus chrons (late Hastarian–early Ivorian), caused with time the gradual shallowing of the sedimentary environment. This shallowing trend began in the Early typicus Chron (early Ivorian) and terminated with terrestrial deposits in the early Asbian.The sedimentary succession and specific phenomena recognized in this structurally unstable basin, displays a pattern partly different from that observed in some areas in Europe. It would appear that other local factors, such as tectonic mobility of the hinterland area (EEC) and the Pomeranian Basin floor, were the possible causes of observed variations and relative sea‐level changes. Copyright © 2008 John Wiley & Sons, Ltd.
Serum concentrations of laminin γ2 fragments in patients with head and neck squamous cell carcinoma
Authors: Kuratomi Yuichiro , Sato Shintaro , Monji Mikio , Shimazu Rintaro , Tanaka Gou , Yokogawa Kyoko , Inoue Akiko , Inokuchi Akira , Katayama Masahiko 
Published: April 2008

AbstractBackgroundThe laminin (LN) γ2 chain expression has been linked to tumor invasion and prognosis. To provide a convenient clinical use, procedures that analyze LNγ2 expression by using the serum and/or urine of patients should be developed.MethodsThe serum concentrations of the N‐terminal fragments of the LNγ2 chain in 73 patients with head and neck squamous cell carcinomas were measured by immunoassay.ResultsThe concentrations of the LNγ2 fragments ranged between 14.5 and 324.2 ng/mL, and the normal upper limit was estimated to be 50 ng/mL. The LNγ2 fragment concentrations increased according to the T classification. The amount of elevated LNγ2 fragment concentrations decreased after the use of curative treatments. Three patients displayed a continuous increase of the concentrations and subsequently died of the diseases.ConclusionsThe serum concentrations of the LNγ2 fragments may prove useful in assessing the treatment results and clinical courses of patients with head and neck squamous cell carcinomas. © 2008 Wiley Periodicals, Inc. Head Neck, 2008
High‐resolution multi‐voxel pattern analysis of category selectivity in the medial temporal lobes
Authors: Diana Rachel A. , Yonelinas Andrew P. , Ranganath Charan 
Published: April 2008

AbstractAlthough the parahippocampal cortex (PHc) is known to be critical for memory formation, little is known about what is encoded by this area. Using multi‐voxel pattern analysis of high‐resolution functional magnetic resonance imaging (MRI) data, we examined responses to blocks of categorically coherent stimuli and found that patterns of activity in PHc were selective for not only scenes, but also for other nonspatial object categories (e.g., faces and toys). This pattern of results was also found in the parahippocampal place area (PPA), indicating that this region is not sensitive exclusively to scenes. In contrast, neither the hippocampus nor perirhinal cortex (PRc) were found to be selective for category information. The results indicate that regions within the medial temporal lobe may support distinct functions, and that the PHc appears to be particularly sensitive to category‐level information. © 2008 Wiley‐Liss, Inc.
Lesions of the mammillary body region severely disrupt the cortical head direction, but not place cell signal
Authors: Sharp Patricia E. , Koester Kate 
Published: April 2008

AbstractThe rat limbic system contains a variety of location (place and grid) cells and directional (head direction; HD) cells, thought to be critical for navigation. The HD cells can be found throughout many portions of the hippocampal formation, as well as additional limbic cortical and subcortical regions. These HD‐containing regions are generally strongly interconnected anatomically. Earlier work, along with theoretical considerations, suggest that despite the ubiquitous presence of HD cells, there may be a single region which is critical for the initial formation of this HD signal. Specifically, it has been suggested that the critical HD cell network resides in a reciprocal loop formed by the interconnected lateral mammillary nucleus and dorsal tegmental nucleus of Gudden. Unlike the HD cells, place cells have not been observed in subcortical structures. They are, however, found in various forms throughout much of the hippocampal formation. Theoretical accounts of the place cells suggest that they are partly dependent on a path integration process which is, in turn, dependent on the HD cells. According to the above reasoning, lesions of the mammillary bodies should completely eliminate both HD and place/grid cells in the hippocampal formation. Here, we tested for both HD and place cell activity in various hippocampal formation sub regions following lesions of the mammillary bodies. We found that these lesions caused nearly complete elimination of the HD cell signal, but left the place cell signal largely intact. Our interpretation of these findings is somewhat limited by the fact that we did not provide a thorough test of the path integration abilities of the post lesion place cells. These findings pose a challenge for current theoretical accounts of place and grid cells. They also help to explain the role played by the mammillary bodies in spatial learning and memory. © 2008 Wiley‐Liss, Inc.
Hypoxic‐ischemic brain injury activates early hippocampal stem/progenitor cells to replace vulnerable neuroblasts
Authors: Miles Darryl K. , Kernie Steven G. 
Published: April 2008

AbstractAlthough the phenomenon of ongoing neurogenesis in the hippocampus is well described, it remains unclear what relevance this has in terms of brain self‐repair following injury. In a highly regulated developmental program, new neurons are added to the inner granular cell layer of the dentate gyrus (DG) where slowly dividing radial glial‐like type 1 neural stem/progenitors (NSPs) give rise to rapidly proliferating type 2 neural progenitors which undergo selection and maturation into functional neurons. The induction of these early hippocampal progenitors after injury may represent an endogenous mechanism for brain recovery and remodeling. To determine what role early hippocampal progenitors play in remodeling following injury, we utilized a model of hypoxic‐ischemic injury on young transgenic mice that express green fluorescent protein (GFP) specifically in neural progenitors. We demonstrate that this injury selectively activates programmed cell death in committed but immature neuroblasts, which is followed by proliferation of both early type 1 and later type 2 progenitors. This subsequently leads to newly generated neurons becoming stably incorporated into the DG. © 2008 Wiley‐Liss, Inc.
Resveratrol causes COX‐2‐ and p53‐dependent apoptosis in head and neck squamous cell cancer cells
Authors: Lin Hung‐Yun , Sun MingZeng , Tang Heng‐Yuan , Simone Tessa M. , Wu Yun‐Hsuan , Grandis Jennifer R. , Cao H. James , Davis Paul J. , Davis Faith B. 
Published: April 2008

AbstractCyclooxygenase‐2 (COX‐2) content is increased in many types of tumor cells. We have investigated the mechanism by which resveratrol, a stilbene that is pro‐apoptotic in many tumor cell lines, causes apoptosis in human head and neck squamous cell carcinoma UMSCC‐22B cells by a mechanism involving cellular COX‐2. UMSCC‐22B cells treated with resveratrol for 24 h, with or without selected inhibitors, were examined: (1) for the presence of nuclear activated ERK1/2, p53 and COX‐2, (2) for evidence of apoptosis, and (3) by chromatin immunoprecipitation to demonstrate p53 binding to the p21 promoter. Stilbene‐induced apoptosis was concentration‐dependent, and associated with ERK1/2 activation, serine‐15 p53 phosphorylation and nuclear accumulation of these proteins. These effects were blocked by inhibition of either ERK1/2 or p53 activation. Resveratrol also caused p53 binding to the p21 promoter and increased abundance of COX‐2 protein in UMSCC‐22B cell nuclei. Resveratrol‐induced nuclear COX‐2 accumulation was dependent upon ERK1/2 activation, but not p53 activation. Activation of p53 and p53‐dependent apoptosis were blocked by the COX‐2 inhibitor, NS398, and by transfection of cells with COX‐2‐siRNA. In UMSCC‐22B cells, resveratrol‐induced apoptosis and induction of nuclear COX‐2 accumulation share dependence on the ERK1/2 signal transduction pathway. Resveratrol‐inducible nuclear accumulation of COX‐2 is essential for p53 activation and p53‐dependent apoptosis in these cancer cells. J. Cell. Biochem. 104: 2131–2142, 2008. © 2008 Wiley‐Liss, Inc.
Differential intracellular transport and binding of verotoxin 1 and verotoxin 2 to globotriaosylceramide‐containing lipid assemblies
Authors: Tam Patty , Mahfoud Radhia , Nutikka Anita , Khine Aye Aye , Binnington Beth , Paroutis Paul , Lingwood Clifford 
Published: April 2008

AbstractAlthough verotoxin‐1 (VT1) and verotoxin‐2 (VT2) share a common receptor, globotriaosyl ceramide (Gb3), VT2 induces distinct animal pathology and is preferentially associated with human disease. Moreover VT2 cytotoxicity in vitro is less than VT1. We therefore investigated whether these toxins similarly traffic within cells via similar Gb3 assemblies. At 4°C, fluorescent‐VT1 and VT2 bound both coincident and distinct punctate surface Gb3 microdomains. After 10 min at 37°C, similar distinct/coincident micropunctate intracellular localization was observed. Most internalized VT2, but not VT1, colocalized with transferrin. After 1 h, VT1 and VT2 coalesced during retrograde transport to the Golgi. During prolonged incubation (3–6 h), VT1, and VT2 (more slowly), exited the Golgi to reach the ER/nuclear envelope. At this time, VT2 induced a previously unreported, retrograde transport‐dependent vacuolation. Cell surface and intracellular VT1 showed greater detergent resistance than VT2, suggesting differential ‘raft’ association. >90% 125I‐VT1 cell surface bound, or added to detergent‐resistant cell membrane extracts (DRM), was in the Gb3‐containing sucrose gradient ‘insoluble’ fraction, whereas only 30% 125I‐VT2 was similarly DRM‐associated. VT1 bound more efficiently to Gb3/cholesterol DRMs generated in vitro. Only VT1 binding was inhibited by high cholesterol/Gb3 ratios. VT2 competed less effectively for 125I‐VT1/Gb3 DRM‐binding but only VT2‐Gb3/cholesterol DRM‐binding was augmented by sphingomyelin. Differential VT1/VT2 Gb3 raft‐binding may mediate differential cell binding/intracellular trafficking and cytopathology. J. Cell. Physiol. 216: 750–763, 2008, © 2008 Wiley‐Liss, Inc.
Myocardial function improved by electromagnetic field induction of stress protein hsp70
Authors: George Isaac , Geddis Matthew S. , Lill Zachary , Lin Hana , Gomez Teodoro , Blank Martin , Oz Mehmet C. , Goodman Reba 
Published: April 2008

AbstractStudies on myocardial function have shown that hsp70, stimulated by an increase in temperature, leads to improved survival following ischemia‐reperfusion (I‐R). Low frequency electromagnetic fields (EMFs) also induce the stress protein hsp70, but without elevating temperature. We have examined the hemodynamic changes in concert with EMF pre‐conditioning and the induction of hsp70 to determine whether improved myocardial function occurs following I‐R injury in Sprague–Dawley rats. Animals were exposed to EMF (60 Hz, 8 µT) for 30 min prior to I‐R. Ischemia was then induced by ligation of left anterior descending coronary artery (LAD) for 30 min, followed by 30 min of reperfusion. Blood and heart tissue levels for hsp70 were determined by Western blot and RNA transcription by rtPCR. Significant upregulation of the HSP70 gene and increased hsp70 levels were measured in response to EMF pre‐exposures. Invasive hemodynamics, as measured using a volume conductance catheter, demonstrated significant recovery of systolic contractile function after 30 min of reperfusion following EMF exposure. Additionally, isovolemic relaxation, a measure of ventricular diastolic function, was markedly improved in EMF‐treated animals. In conclusion, non‐invasive EMF induction of hsp70 preserved myocardial function and has the potential to improve tolerance to ischemic injury. J. Cell. Physiol. 216: 816–823, 2008, © 2008 Wiley‐Liss, Inc.