bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Synthesis of Ordered MCM‐41 Titanosilicates with Very High Titanium Content via Ultrasound Radiation
Authors: Tang Xianghai , Wen Xin , Huang Weiping , Liu Suwen , Wang Yanqin , Palchik Oleg , Koltypin Yuri , Pickup David M. , Van Eck Ernst R.H. , Gedanken Aharon
Published: November 2004

A novel synthetic strategy has been developed for the fabrication of mesostructured titanosilicate with very high titanium content. By the combination of ultrasound radiation and a separate hydrolysis procedure, highly ordered MCM‐41 titanosilicates can be synthesized within 3 h from gels with Ti/Si ratios up to 1. The physicochemical properties of the materials were characterized by means of XRD, TEM, FT‐IR, UV‐Vis DRS, 29Si MAS NMR, and liquid nitrogen adsorption‐desorption measurements. The results suggested that during crystallization, sonication re‐dispersed and accelerated the condensation of inorganic species, and resulted in more condensed pore walls compared to those synthesized with the conventional methods. The presence of silica and ultrasound radiation remarkably suppressed the aggregation of titanium species, thus, at the medium titanium level, a relatively homogeneous dispersion of titanium within the MCM‐41 framework was attained.
Magnetic Nanocrystals Aligned on Mesoscopic Scale: Collective Properties and Their Use
Authors: Pileni Marie Paule , Ingert Dorothée , Lalatonne Yoann , Lisiecki Isabelle , Ngo Anh‐Tu , Motte Laurence , Petit Christophe , Russier Vincent
Published: November 2004

Magnetic nanocrystals organized in chain‐like structures behave as nanowires with a shape anisotropy induced by the structuration of the sample. This is valid for various types of magnetic nanomaterials. Furthermore, the coating of nanocrystals plays a major role in the mesoscopic structure of the film. γ‐Fe2O3 nanocrystals are used as a mask to reproduce the mesoscopic structure on a silicon wafer.
Playing With a Pair of Ultracold Atoms and Lasers: Towards a Novel Ultracold Photochemistry?
Authors: Dulieu Olivier , Pillet Pierre
Published: November 2004

The use of photoassociation of cold atoms has permitted the first demonstration of ultracold molecules in the microKelvin range. In this article we report the mechanisms and the dynamics studied in the case of the cesium dimer. The first key point is the efficiency of photoassociation for long‐range molecules, which involves a R−3 long‐range potential (R = interatomic distance) due to the dipole‐dipole interaction in the electronically excited potentials. The second one is the existence of the Condon point at intermediate distance to “stabilize” the electronically excited molecules reached by photoassociation after spontaneous decay towards ground state. Several molecular configurations are analyzed such as the so‐called double‐well route or the internal coupling route. We show the possibility to extend these concepts to the case of heteronuclear systems.
An Experimental Charge Density Study of the N‐H+…O−Bonds in a Proton‐Transfer System in Comparison with Regular N‐H…O and O‐H…N Hydrogen Bonds
Authors: Ranganathan Anupama , Kulkarni G.U. , Rao C.N.R.
Published: November 2004

An experimental charge density study has been carried out on N‐H+…O−bonds in the proton‐transfer compound piperazinium oxalate as well as on the normal O‐H…N bonds in the thiodiglycolic acid‐4,4′‐bipyridine complex, based on X‐ray diffraction measurements at 130 K. The results are compared with those of the normal N‐H…O bonds in 5‐nitrouracil. In spite of the different crystal geometries, the N‐H+…O−and the N‐H…O bonds exhibit similar values of electron density and the associated curvatures at the hydrogen‐acceptor bond critical points (BCPs). Surprisingly, the polarization parameters of the two BCPs are comparable (˜20%). The pseudoatomic charge on the protonated N atom (in N‐H+…O−) is, however, much smaller (‐0.05e) in comparison to the unprotonated case (˜ ‐0.2e). The O‐H…N hydrogen bonds exhibit shorter H…N distances compared to the charged and the uncharged H…O bonds. Accordingly, the electron densities and the curvatures evaluated at the H…N critical points are also much higher.
Collisions Transfer Coherence
Authors: Bargheer Matias , Gühr Markus , Schwentner Nikolaus
Published: November 2004

Ultrafast photoexcitation of molecules prepares coherent superpositions of vibrational states, forming wave packets. We show direct experimental evidence that impulsive collisions of photo‐fragments with large energy loss generate new coherent superpositions of vibrational states, causing coherence among previously unoccupied states. We demonstrate the effect in the model system of I2 molecules in Kr solids. This coherence transfer—even in the presence of very strong dissipation—may be used for control strategies in condensed‐phase photoreactions.
Electron Transfer and Redox Metalloenzyme Catalysis at the Single‐Molecule Level
Authors: Hansen Allan G. , Zhang Jingdong , Christensen Hans E. M. , Welinder Anne C. , Wackerbarth Hainer , Ulstrup Jens
Published: November 2004

Voltammetry based on single‐crystal, atomically‐planar metal electrodes is novel in bioelectrochemistry. Together with in situ scanning tunneling microscopy (STM) directly in aqueous buffer, single‐crystal voltammetry has disclosed new detail in molecular adsorption and interfacial electron transfer (ET). Image interpretation requires, however, theoretical support, as STM represents both electronic and topographic features. Molecules with accessible redox levels offer other insight into electron tunneling mechanisms, addressed in detail for ET metalloproteins. We present here in situ STM of the blue redox metalloenzyme copper nitrite reductase (Achromobacter xylosoxidans, Ax CuNiR) on Au(111) electrode surfaces modified by a self‐assembled cysteamine monolayer. Ax CuNiR displays strong nitrite reduction waves in this environment. Ax CuNiR/cysteamine/Au(111) surfaces were imaged at KNO2 concentrations where most of the enzyme is in the enzyme‐substrate bound state.

Molecular resolution for both cysteamine/Au(111) and Ax CuNiR/cysteamine/Au(111) electrode surfaces was achieved. The enzyme coverage is about 1.5 × 10−13 mol cm−2, which is low compared with an ideal close‐packed monolayer. The adlayer behaves as an assembly of individual molecules, reflected in distributions of molecular appearance, although a number of molecules do show the triangular shape of the trimeric Ax CuNiR structure. The apparent average molecular height is about 11 Å. This suggests that details of electronic structures and larger assemblies are needed to disentangle enzyme mechanisms at the single‐molecule level.
Mathematical modeling of the porosity of suspension poly(vinyl chloride)
Authors: Márquez Esteban F. , Lagos Luis L.
Published: November 2004

A mathematical model that describes the effect of conversion and polymerization temperature on the porosity of suspension poly(vinyl chloride) is proposed. The model considers that the packing of the primary particles that develop in the polymerizing drop begins at a conversion at which the particles become motionless. The model considers the morphology of the primary particles as a group of particles with a particular sphericity that form a network whose porosity decreases as conversion increases. Furthermore, the model considers the effect on porosity of the desorption of residual monomer and the difference in contraction and deformation between the pericellular membrane and the network of particles. The model contains three parameters that are estimated from data reported in the open literature. The agreement between experimental data and the theoretical predictions of the model are satisfactory. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3184–3194, 2004
Ornithine decarboxylase activity during the development of Anastrepha fraterculus (Diptera, Tephritidae)
Authors: Cardoso V.V. , Prestes P.R. , Casali E.A. , Moreira J.C.F. , Oliveira A.K.
Published: November 2004

Ornithine decarboxylase (ODC) (EC 4.1.1.17) is very important for polyamine biosynthesis, which is required for main biological events. In the present study, ODC activity was measured in samples of Anastrepha fraterculus's egg, larva, pupa body and abdomen, adult body, ovaries, and fat body of young females, and in ovaries of mature flies. The kinetic parameters (Km app and Vmax) for ODC activity were determined for pupa, larva, and young ovary. ODC activity showed fluctuations during A. fraterculus's life development. In its earlier stages, prior to emergence, the egg has high ODC‐specific activity probably due to embryogenesis, which is characterized by a high rate of cell division. This enzyme activity is also significantly high in the ovary and fat body of young females possibly related to the increased oogenesis and vitellogenesis. The kinetic parameters (Km app and Vmax) had great variation. Our results using GTP showed that the great variation in kinetic parameters can be accounted for by post‐translational modifications. Arch. Insect Biochem. Physiol. 57:151–159, 2004. © 2004 Wiley‐Liss, Inc.
An Electronic Perspective on the Reduction of an NN Double Bond at a Conserved Dimolybdenum Core
Authors: Padden Metzker Julia K. , McGrady John E.
Published: November 2004

Density functional theory has been used to assess the role of the bimetallic core in supporting reductive cleavage of the NN double bond in [Cp2Mo2(μ‐SMe)3(μ‐η1:η1‐HNNPh)]+. The HOMO of the complex, the Mo–Mo δ orbital, plays a key role as a source of high‐energy electrons, available for transfer into the vacant orbitals of the NN unit. As a result, the metal centres cycle between the MoIII and MoIV oxidation states. The symmetry of the Mo–Mo δ “buffer” orbital has a profound influence on the reaction pathway, because significant overlap with the redox‐active orbital on the NN unit (π* or σ*) is required for efficient electron transfer. The orthogonality of the Mo–Mo δ and N–N σ* orbitals in the η1:η1 coordination mode ensures that electron transfer into the N–N σ bond is effectively blocked, and a rate‐limiting η1:η1→η1 rearrangement is a necessary precursor to cleavage of the bond.
Cytokine inhibition of the hepatitis B virus core promoter
Authors: Romero R , Lavine J E
Published: November 2004

Hepatitis B virus (HBV) DNA contains consensus elements for transactivating proteins whose binding activity in other systems is regulated by inflammatory cytokines. Because HBV replicates within an environment of provoked inflammation, we speculated that the HBV core/pregenomic promoter may be regulated by cytokines produced in response to infection. To evaluate this hypothesis, the HBV core/pregenomic (C/P) promoter and associated cis-acting elements were placed upstream of a luciferase-encoding plasmid. This reporter construct was transfected into cytokine-sensitive hepatoma cells permissive for HBV replication, which were exposed to stimulated mononuclear cell-conditioned medium or human recombinant cytokines. Conditioned medium reduced luciferase expression by 80%. Tumor necrosis factor α (TNF-α), interferon gamma (IFN-γ), and interferon alfa (IFN-α) each reduced luciferase activity by 40%. Combinations of TNF-α and interferons mimicked the extent of conditioned medium inhibition. Non-specific effects from diminished cellular viability or growth were not responsible for decreased luciferase activity. Retention of HBV DNA 330 basepairs upstream of the C/P transcription start site was required to maintain the TNF-α effect. A 60% reduction in HBV replicative forms within intracellular core particles was demonstrated with TNF-α treatment of Hep G2 cells stably transfected with HBV DNA. The inhibitory action of these cytokines implicates a noncytolytic mechanism by which antigen-nonspecific immune responses in part regulate HBV replication in infected hepatocytes. This function may be beneficial in accelerating viral clearance, but in alternative circumstances could contribute to viral persistence by attenuating immunogen recognition.
Allograft rejection in pediatric recipients of living related liver transplants
Authors: Alonso E M , Piper J B , Echols G , Thistlethwaite J R , Whitington P F
Published: November 2004

The purpose of this study was to compare the incidence and severity of rejection episodes in a group of children receiving living related orthotopic liver transplants (LRLT) versus children receiving cadaveric liver transplants (CLT). Thirty-eight patients received primary LRLT and 54 patients received CLT during a 3-year period ending June 1993. Baseline immunosuppression consisted of cyclosporin, azathioprine, and corticosteroids. Rejection episodes were confirmed by liver histology and were treated initially with pulse intravenous methylprednisolone, 10 mg/kg/d for 3 days. Steroid-resistant rejection was treated with OKT3 or FK506. The median patient ages were 1.3 years for the CLT and .8 years for the LRLT recipients. Acute cellular rejection developed in 78% of the CLT grafts and 74% of the LRLT grafts (P = ns). However, steroid-resistant rejection was significantly less frequent in the LRLT recipients, 13% versus 43% in the CLT recipients (P < .01). Ductopenic rejection was diagnosed in 20% of CLT and 8% of LRLT grafts (P < .10), and graft loss caused by rejection was 9% in the CLT and 3% in the LRLT group (P = ns). In conclusion, the overall incidence of rejection is the same in LRLT and CLT recipients, but LRLT recipients are less likely than CLT recipients to develop steroid-resistant rejection or ductopenic rejection.
Selective inhibition of the reverse transcription of duck hepatitis B virus by binding of 2′,3′-dideoxyguanosine 5′-triphosphate to the viral polymerase
Authors: Howe A Y , Robins M J , Wilson J S , Tyrrell D L
Published: November 2004

Hepatitis B virus (HBV) replication is mediated by the viral polymerase that possesses three functional domains: primer, DNA polymerase/reverse transcriptase, and RNase H. Using the Pekin duck as an animal model, we demonstrate a novel mechanism of inhibition of duck hepatitis B virus (DHBV) by 2,6-diaminopurine 2′,3′-dideoxyriboside (ddDAPR), a prodrug of 2′,3′-dideoxyguanosine (ddG). A selective and irreversible inhibition of DHBV DNA replication is found in ducklings treated with high doses of ddDAPR (20 to 50 mg/kg), but not with similar doses of 2′,3′-dideoxycytidine (ddC). The inhibition mediated by ddDAPR occurs at a very early stage of the reverse transcription. Despite the inhibition of DHBV DNA replication by ddDAPR, the DNA polymerase and reverse transcriptase activities of the polymerase are found to remain active when tested on exogenous templates in activity gels. We have demonstrated direct binding of [α-32P]ddGTP to the DHBV polymerase expressed in an in vitro transcription and translation system. These results suggest that the binding of ddGTP to the polymerase blocks the initial DNA replication.
Molecular and functional characterization of bile acid transport in human hepatoblastoma HepG2 cells
Authors: Kullak-Ublick G A , Beuers U , Paumgartner G
Published: November 2004

Bile acids are taken up into human liver by Na+-dependent and Na+-independent transport mechanisms. In hepatocarcinogenesis, numerous liver-specific functions are lost and the uptake of organic anions is markedly reduced. We have investigated the molecular and functional derangements of bile acid transport in the human hepatoblastoma cell line HepG2. Uptake of [3H]-taurocholic acid was saturable and entirely Na+ independent, with the kinetic characteristics of the human liver organic anion transporting polypeptide (OATP). OATP, but not the Na+-dependent bile acid transporter (Na+-taurocholate-cotransporting polypeptide [NTCP]), was detectable by reverse-transcription polymerase chain reaction (RT-PCR) analysis of HepG2 RNA. The level of OATP expression in HepG2 cells was determined by Northern blot analysis and was found to be 40% in comparison with normal liver. Transfection of an OATP-derived phosphorothioate (PTO)-antisense oligonucleotide into HepG2 cells resulted in 77% inhibition of temperature-dependent bile acid uptake. Injection of HepG2 messenger RNA (mRNA) into Xenopus laevis oocytes significantly stimulated Na+-independent taurocholate uptake, indicating the expression of a bile acid transport protein. We conclude that bile acid uptake into human hepatoblastoma HepG2 cells is mediated by the multi-specific organic anion transporting polypeptide OATP. Therapeutic strategies employing bile acid-derived cytostatic agents for the treatment of hepatocellular carcinomas may therefore depend upon the expression of the Na+-independent bile acid transporter OATP in hepatic malignancies.
Liver Hepatocyte Growth Factor Does Not Always Correlate With Hepatocellular Proliferation in Human Liver Lesions: Its Specific Receptor C – Met Does
Authors: D'Errico A , Fiorentino M , Ponzetto A , Daikuhara Y , Tsubouchi H , Brechot C , Scoazec J , Grigioni W F
Published: November 2004

Increased levels of expression of hepatocyte growth factor (HGF) and its specific receptor

c–met

have been shown in the liver of several benign and malignant pathologies, both in experimental models and humans. We investigated by immunohistochemistry the presence of both HGF and

c–met

protoocogene product (

c–met

pp) in 20 hepatocellular carcinomas (HCCs), 5 focal nodular hyperplasias (FNHs), 4 cases of fulminant hepatitis (FH), and 1 case of regenerated liver. The

c–met

protooncogene product was expressed in all cases with marked overexpression in the HCCs and in ductular metaplasia. HGF was detected in the Ito cells of all cases and in neoplastic hepatocytes of 9 of 20 HCCs (45%). The proliferative index of each lesion was evaluated by means of the polyclonal antibody anti–cyclin A. When the level of expression of HGF and

c–met

protooncogene product with the percentage of cyclin A+ nuclei were compared, the closest relationship was between

c–met

protooncogene product and cyclin A+ nuclei were compared, the closest relationship was between

c–met

protooncogene product and cyclin A. In 11 of 20 HCCs (55%), there wa no correlation between HGF positivity and cyclin A. This seems to suggest that, independently of the levels of native liver HGF,

c–met

protooncogene product is the most active modulator of liver cell proliferation.
Serum Concentrations of 7α–Hydroxy–4–Cholesten–3–One Reflect Bile Acid Synthesis in Humans
Authors: Sauter G , Berr F , Beuers U , Fischer S , Paumgartner G
Published: November 2004

Serum concentrations of 7α–hydroxy–4–cholesten–3–one (α–HC) have recently been shown to reflect the activity of cholesterol 7α–hydroxylase in humans. To evaluate the relationship between α–HC in serum and bile acid synthesis, serum concentrations of α–HC, and rates of bile acid synthesis, as measured by the isotope dilution technique using gas chromatography–mass spectrometry, were determined simultaneously. Regression analysis revealed a positive linear correlation of serum α–Hc with synthesis of cholic acid (CA) (r = .59,

P

= .02), chenodeoxycholic acid (CDCA) (r = .75,

P

= .001), and total synthesis of both primary bile acids (r = .83,

P

< .001) in patients with gallstones and normal liver function (n = 15). α–HC was also correlated to input rates of deoxycholic acid (DCA) (r = .53,

P

<.05). Addition of patients with chronic cholestatic liver disease (n = 5) improved the correlation between serum α–HC and synthesis of CA (r = .75,

P

< .001), CDCA (r = .77,

P

< .001), and both primary bile acid combined (r = .87),

P

< .001. Our data are in agreement with the concept that synthesis of bile acids is regulated by cholesterol 7 α–hydroxylase activity and that α–HC in serum may serve as a convenient marker for the semiquantitative assessment of bile acid synthesis in humans.
Comparison of plasma‐sprayed hydroxyapatite coatings and zirconia‐reinforced hydroxyapatite composite coatings: In vivo study
Authors: Lee T. M. , Yang C. Y. , Chang E. , Tsai R. S.
Published: November 2004

The clinical use of plasma‐sprayed hydroxyapatite (HA) coatings on metal implants has been widely adopted because the HA coating can achieve the firmly and directly biological fixation with the surrounding bone tissue. However, the long‐term mechanical properties of HA coatings has been concern for the long‐term clinical application. Previous research showed that the concept of adding ZrO2 as second phase to HA significantly increased the bonding strength of plasma‐sprayed composite material. The present work aimed to explore the biological properties, including the histological responses and shear strength, between the plasma‐sprayed HA and HA/ZrO2 coating, using the transcortical implant model in the femora of canines. After 6 and 12 weeks of implantation, the HA coating revealed the direct bone‐to‐coating contact by the backscattered electron images (BEIs) of scanning electron microscope (SEM), but the osseointegration was not observed at the surface of HA/ZrO2 coating. For new bone healing index (NBHI) and apposition index (AI), the values for HA implants were significantly higher than that for HA/ZrO2 coatings throughout all implant periods. After push‐out test, the shear strength of HA‐coated implants were statistically higher than HA/ZrO2 coated implants at 6‐ and 12‐week implantation, and the failure mode of HA/ZrO2 coating was observed at the coating‐bone interface by SEM. The results indicate that the firm fixation between bone and HA/ZrO2 has not been achieved even after 12‐week implantation. Consequently, the addition of ZrO2 could improve the mechanical properties of coatings, while the biocompatibility was influenced by the different material characteristics of HA/ZrO2 coating compared to HA coatings. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 652–660, 2004
Human endothelial cell attachment and proliferation on a novel vascular graft prototype
Authors: Knetsch Menno L. W. , Aldenhoff Yvette B. J. , Schraven Martijn , Koole Leo H.
Published: November 2004

A new vascular prosthesis prototype was assessed for its ability to support an endothelial cell layer in vitro. A coiled tubular structure, constructed from polymer‐coated metallic wires, with an internal diameter of 690 μm, was used. Addition of heparin to the surface coating of the coil strongly enhanced the blood compatibility of the device. A series of coils with five different coatings, increasing in hydrophilicity, was studied. Heparin was added to one series, another series did not contain this anticoagulant drug. Upon contact with blood, a vascular prosthesis will instantaneously adsorb plasma proteins on its surface, and these proteins will influence the behavior of cells binding to the device. When coils were treated with human plasma proteins, mimicking the in vivo situation, human microvascular endothelial cells grew well on all coils studied, irrespective of the hydrophilicity of the underlying coating or the addition of heparin. For control coils, only endothelial cell growth on the most hydrophobic surfaces, and a moderate enhancing effect for heparin, were observed. This novel vascular graft prototype seems well suited for the support of an endothelial cell layer, especially when plasma proteins are adsorbed to its surface, and shows promise for in vivo testing. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 615–624, 2004
Wheat digalactosyldiacylglycerol molecular species profiling using porous graphitic carbon stationary phase
Authors: Deschamps Frantz S. , Gaudin Karen , Baillet Arlette , Chaminade Pierre
Published: November 2004

The potential of porous graphitic carbon stationary phase (PGC) was assessed for the separation of molecular species of digalactosyldiacylglycerol (DGDG). Detection was by an evaporative light scattering detector (ELSD). A conventional optimization strategy allowed definition of a quaternary non‐aqueous mobile phase and separation of 9 wheat DGDG molecular species with isocratic elution: methanol/toluene/tetrahydrofuran/chloroform 64.3/21.5/13.7/0.5 v/v with 0.1% of triethylamine and a stoichiometric amount of formic acid. The molecular species were identified by LC/MS. The chromatographic behavior of DGDG on PGC was then compared to previous studies. The addition of a carbon double bond on the alkyl chain decreased the retention. This contribution was less important when the number of unsaturations increased in the alkyl chain. The consequence of this retention behavior with PGC was an elution order of molecular species which did not agree with the partition number as observed with C18 grafted stationary phases.
Molecular structure retention relationships in comprehensive two‐dimensional gas chromatography
Authors: Marriott Philip J. , Massil Tracy , Hügel Helmut
Published: November 2004

Comprehensive two‐dimensional gas chromatography (GC×GC) offers new opportunities to develop relationships between molecular structure and retentions in the two dimensional (2D) separation space defined by the GC×GC retention in each dimension. Whereas single dimension GC provides only one retention property for a solute, and hence the specific relationship between retention and chemical property is not readily apparent or derivable, the 2D presentation of compounds in GC×GC provides a subtle and exquisite correlation of chemical property and retention unlike any other GC experiment. The ‘orthogonality’ of the two separation dimensions is intimately related to the manner in which different separation mechanisms, available through use of two dissimilar phases, are accessible to the different chemical compounds or classes in a sample mixture, and indeed the specific chemical classes present in the sample. The GC×GC experiment now permits various processes such as chemical decompositions, molecular interconversions, various non‐linear chromatography effects, and processes such as slow reversible interactions that may arise with stationary phases or in the injector or column couplings, to be identified and further investigated. Here, we briefly review implementation of the GC×GC method, consider the molecular selectivity of GC×GC, and highlight a selection of molecular processes that can be probed by using GC×GC.
How to utilize the true performance of monolithic silica columns
Authors: Ikegami Tohru , Dicks Edith , Kobayashi Hiroshi , Morisaka Hironobu , Tokuda Daisuke , Cabrera Karin , Hosoya Ken , Tanaka Nobuo
Published: November 2004

Ways of utilizing the true separation efficiency of monolithic silica (MS) columns were studied. The true performance of MS columns, both regular‐sized (rod‐type clad with PEEK resin, 4.6 mm ID, 10 cm) and capillary sized (in 100 or 200 μm fused silica capillary, 25–140 cm) was evaluated by calculating the contribution of extra‐column effects. HETP values of 7–9 μm were observed for solutes having retention factors (k values) of up to 4 for rod columns and up to 15 for a capillary column. The high permeability of MS columns allowed the use of long columns, with several connected together in the case of rod columns. Narrow‐bore connectors gave good results. Peak variance caused by a column connector ranges from 50 to 70% of that caused by one rod‐type column for up to three connectors or four columns in 80% methanol, but the addition of a 4th or 5th connector to add a 5th and 6th column, respectively, caused a much greater increase in peak variance, especially for long‐retained solutes, which is greater than the variance caused by one rod column. Rod columns seem to show slightly lower efficiency at a pressure higher than 10 MPa or so. The use of acetonitrile‐water as a mobile phase better preserved the ability of individual rod columns to generate up to 100,000 theoretical plates with 14 columns connected. Methods for eliminating extra‐column effects in micro‐HPLC were also studied. Split injection and on‐column detection resulted in optimum performance. A long MS capillary measuring 140 cm produced 160,000 theoretical plates. The column efficiency of a capillary column was not affected by the pressure, showing advantages over the rod columns that exhibited peak broadening caused by connectors and pressure.
In vivo activation of gelatinase B/MMP‐9 by trypsin in acute pancreatitis is a permissive factor in streptozotocin‐induced diabetes
Authors: Descamps Francis J , Martens Erik , Ballaux Florence , Geboes Karel , Opdenakker Ghislain
Published: November 2004

Matrix metalloproteinases, in particular gelatinase B/MMP‐9, are key mediators in autoimmune diseases like multiple sclerosis and rheumatoid arthritis, but their pathogenic roles in diabetes are not well established. Gelatinase B has previously been shown to be upregulated in pancreas tissue from patients with acute and chronic pancreatitis and was suggested to exacerbate diabetes by cleaving insulin. In this study, the role of gelatinase B in diabetes was investigated using two streptozotocin‐induced animal models of type I diabetes. In both a hyperacute and a subacute model, gelatinase B upregulation was found to be associated with disease activity. However, gelatinase B deficiency did not significantly protect against diabetes development, and wild‐type and gelatinase B‐deficient animals behaved similarly in terms of β‐cell apoptosis or necrosis. The fact that gelatinase B was found almost exclusively as the inactive pro‐enzyme in most of the streptozotocin‐induced diabetic animals may explain the lack of a gelatinase B effect. On the contrary, gelatinase B was completely activated in a minority (15%) of wild‐type animals. This coincided with exocrine pancreatic inflammation, as revealed by the presence of active trypsin. The discovery of in vivo activation of progelatinase B by trypsin in acute pancreatitis is extended in a model of caerulein‐induced pancreatitis. In the latter model, trypsinogen activation is systematically achieved and gelatinase B is found in its active form. In conclusion, gelatinase B itself is not a causative factor but, when activated by endogenous trypsin, is a permissive factor for insulin degradation and diabetes. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
The relationship of VEGF and PGE2 expression to extracellular matrix remodelling of the tenosynovium in the carpal tunnel syndrome
Authors: Hirata Hitoshi , Nagakura Takeshi , Tsujii Masaya , Morita Akimasa , Fujisawa Kohzo , Uchida Atsumasa
Published: November 2004

Tenosynovial thickening within the confined space of the carpal tunnel is thought to be the cause of the carpal tunnel syndrome (CTS). However, little is known about the pathological mechanism of tenosynovial thickening. In this study, the role of prostaglandin E2 (PGE2) and vascular endothelial growth factor (VEGF) (two representative molecules that can induce oedema by increasing vascular permeability) was analysed in CTS by using immunohistochemistry and enzyme‐linked immunosorptive assay (ELISA). Expression of these molecules was compared with the patients' clinical histories and a temporary increase in production of these molecules was found in cells within the vessels and synovial lining during the intermediate phase of the syndrome when the histology of the tenosynovium changes from oedematous to fibrotic. Statistical analysis clearly demonstrated that there is a close correlation between the expression of PGE2 and VEGF. Furthermore, immunohistochemical analysis with anti‐proliferating cell nuclear antigen (PCNA) revealed that the area with distinct VEGF expression closely matched the area where endothelial cells, vascular smooth muscle cells, and synovial lining cells proliferate. In contrast, despite marked alteration in the extracellular matrix (ECM) component of the tenosynovium, the fibroblasts responsible for most ECM framework production do not proliferate during any phase of CTS. Histological analysis demonstrated that angiogenesis takes place only during the intermediate phase. Since clusters of capillaries and arterioles are often surrounded by type III collagen‐rich, disorganized, degenerate connective tissue, which contains fewer fibroblasts than normal, angiogenesis appears to take place as a part of a regenerative reaction that results in fibrosis. These findings strongly indicate that both PGE2 and VEGF are expressed in the tenosynovium in CTS during the intermediate phase and induce the histological changes seen in the tenosynovium. Copyright © 2004 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Production and collision‐induced dissociation of gas‐phase, water‐ and alcohol‐coordinated uranyl complexes containing halide or perchlorate anions
Authors: Anbalagan Victor , Chien Winnie , Gresham Garold L. , Groenewold Gary S. , Van Stipdonk Michael J.
Published: November 2004

Electrospray ionization was used to generate mono‐positive gas‐phase complexes of the general formula [UO2A(S)n]+ where A = OH, Cl, Br, I or ClO4, S = H2O, CH3OH or CH3CH2OH, and n = 1–3. The multiple‐stage dissociation pathways of the complexes were then studied using ion‐trap mass spectrometry. For H2O‐coordinated cations, the dissociation reactions observed included the elimination of H2O ligands and the loss of HA (where A = Cl, Br or I). Only for the Br and ClO4 versions did collision‐induced dissociation (CID) of the hydrated species generate the bare, uranyl–anion complexes. CID of the chloride and iodide versions led instead to the production of uranyl hydroxide and hydrated UO. Replacement of H2O ligands by alcohol increased the tendency to eliminate HA, consistent with the higher intrinsic acidity of the alcohols compared to water and potentially stronger UO2O interactions within the alkoxide complexes compared to the hydroxide version. Copyright © 2004 John Wiley & Sons, Ltd.
Minimal residual disease in melanoma
Authors: Max Nicole , Keilholz Ulrich
Published: November 2004

A number of specific genes encoding for melanosomal proteins are selectively expressed in melanocytes and melanomas. For detection of circulating melanoma cells, the expression of the tyrosinase gene is most widely used. Several cohorts of melanoma patients from single institutions have been analyzed by various research groups for the presence of circulating melanoma cells in all stages of disease. The percentage of patients with evidence of occult tumor dissemination has been correlated with stage of disease in several, but not all, reports. Two prospective analyses suggest that the PCR result is of prognostic value in melanoma. Several laboratories have found PCR evidence for circulating melanoma cells in the vast majority of untreated patients with stage IV disease, although other groups have reported much lower frequencies. Taken together, there is a wide range of results. Methodological differences likely account for this discrepancy. With the availability of true quantitative RT‐PCR systems, such as the Light Cycler system, accurate quantification of tyrosinase transcripts over a range of 1–10,000 tumor cells per ml of blood is possible. Quantitative RT‐PCR systems also dramatically improve quality control, since exact quantitation of housekeeping gene mRNA facilitates determination of sample quality. Semin. Surg. Oncol. 20:319–328, 2001. © 2001 Wiley‐Liss, Inc.
Mature but not fetal or neonatal rat superior cervical ganglion transplants survive in the cortex of adult rats
Authors: Tuba Andrea , Kálmán Mihály , Senatorov Vladimir V. , Fülöp Zoltán
Published: November 2004

The transplantation of catecholaminergic tissues is a possible therapy for parkinsonism. Central nervous tissue is suitable for transplantation only in the immature stage, whereas peripheral nervous tissue can also be transplanted when mature. The present study compares the development of fetal (17–20 embryonic day, E17–20), neonatal (1–3 postnatal day, P1–3 and mature (5–6‐week‐old) rat superior cervical ganglia after transplantation into the cerebral cortex of adult rats. The mature transplants survived in greater proportion and preserved their structural characteristics, although a considerable proportion of the neurons died. The perinatal transplants only survived sporadically, decreased in size and the surviving remnants failed to display a structure comparable to the adult ganglion in situ. Thus, the use of adult donors is not only a possibility but a necessity when superior cervical ganglion (probably any ganglion) is transplanted. This principle is radically different from that seen in the case of central nervous tissues, and can be understood by the analysis of the time curves of cell proliferation and programmed cell death (apoptosis) observed during the perinatal development of sympathetic ganglia.
Types and activities of voltage‐operated calcium channels change during development of rat pituitary neurointermediate lobe
Authors: Beatty Diane M. , Sands Scott A. , Morris Stephen J. , Chronwall Bibie M.
Published: November 2004

Cultures of pituitary neurointermediate lobe cells were established from rats aged 1, 12, and 42 days to identify the types and assess the activities of Ca2+ channels present in melanotropes, glial‐like cells, and fibroblasts during development. Day 12 represents the time at which dopaminergic axons have become distributed throughout the lobe, glial cells begin to lose their radial orientation, and melanotropes robustly express the short isoform of the dopamine D2 receptor. Thus, we studied Ca2+ channels in relation to the event of innervation of melanotropes. Real‐time fluorescence video microscopy, in the presence of pharmacological agents, which block L‐, N‐, P‐, and T‐type channels, was used as an indirect measurement of channel activity. Assessment of cell type was verified by triple‐label fluorescence immunohistochemistry. In melanotropes, extracellular Ca2+ addition caused Ca2+ influx through ω‐conotoxin GVIA‐sensitive, N‐type channels on days 1 and 12 but not on day 42. The K+ depolarization induced an increase in intracellular Ca2+ concentration in all age‐groups. This effect was decreased by nifedipinc, an L‐type channel blocker, at all ages, and by ω‐agatoxin IVa, a P‐type blocker, only on day 42. These results demonstrate that the predominance of N‐ or P‐type channels on melanotropes is age‐dependent and can be correlated with other developmental changes. The T‐type blocker, NiSO4, had no effect. In glial‐like cells of all ages, extracellular Ca2+ addition resulted in an increase in intracellular Ca2+ concentration, which was inhibited only by NiSO4. The percentage of responsive glial‐like cells was equally high in days 1 and 12 cultures, then declined by day 42. The K+ depolarization had no effect on glial‐like cells. Fibroblasts did not respond significantly to extracellular Ca2+ or K+ depolarization, indicating little detectable activity by this methodology from functional voltage‐operated Ca2+ channels.
Dietary goitrogen‐induced changes in the transport of 2‐deoxy‐d‐glucose and amino acids across the rat blood‐brain barrier
Authors: Bala T.S.S. , Janardanasarma M.K. , Raghunath M.
Published: November 2004

The hypothesis that a defect in the rate‐limiting blood‐brain barrier (BBB) nutrient transport may be one of the factors responsible for the brain defects seen in some iodine deficiency disorders was tested in Wistar/NIN rats fed potassium thiocyanate (KSCN), a synthetic goitrogen. The BBB nutrient transport was measured by the brain uptake index (BUI) method. Feeding KSCN to female rats (from weaning) through their growth, pregnancy and lactation (G1) but not from conception (G2) or parturition (G3) resulted in a significant decrease (≈23%) in the BBB transport of 2‐deoxy‐d‐glucose (2‐DG) in their offspring at weaning, compared with controls (C). Post‐weaning KSCN‐feeding (G4) of control pups did not affect their BBB 2‐DG transport (BUI: 36.2±4.98, vs 38.8±4.11). The effects of different KSCN regimens on BBB transport of leucine (leu), tyrosine (tyr) and sucrose (background marker) were inconsistent, of smaller magnitude (≈10%) and appeared to be of little significance. Withdrawing KSCN from the diet of chronically KSCN‐fed (G1) mothers from conception (G5) or parturition (G6) prevented the impairment of BBB 2‐DG transport in pups (BUI: 27.0±4.98, 20.8±3.27, 26.9±3.99 and 28.3±3.47 in C, G1, G5 and G6 pups, respectively); this was reversed by feeding the control diet to G1 pups from weaning. Withdrawal of dietary KSCN did not affect BBB transport of leu, tyr and sucrose. The decreased BBB transport of 2‐DG in G1 pups appears to be due to a decrease in affinity (Kt app 5.46 vs 4.15 mM) rather than in the capacity (Tmax app 0.94 vs 0.91 μmoles/g/min) of the transport system. Intracarotid injections of KSCN per se had no effect on BBB 2‐DG transport, suggesting that the effects may be secondary to the altered thyroid status of the animal.
Group I intron-like insertions in SSU rDNA of Cladonia gracilis and C. rangiferina
Authors: PIERCEY-NORMORE Michele D. , HAUSNER Georg , GIBB Ewan A.
Published: November 2004

During a study on population genetics of three species of Cladonia using the nuclear ribosomal 18S DNA, two species contained group I intron-like sequences located in positions 788 and 940 with reference to the E. coli 16S rDNA gene. The intron in position 940 was not typical of group I introns and had previously been described only from the Parmeliaceae and Lecanoraceae, but here we report the occurrence of this intron in the Cladoniaceae. The intron in position 788 had characteristics of group I introns and had previously been reported from the Physciaceae. In this paper we provide for the first time a putative RNA fold for the nS788 intron, compare the secondary RNA structure of the Cladonia group I introns (nS788 and nS940) to that of other taxa, and infer a phylogenetic history among 15 members of the Lecanorales based on the evolutionary history of the nS788 group I intron. The RNA fold for nS788 contained two optional hairpins, P2.1 and a potentially newly described hairpin referred to as P5.1. The phylogenetic hypothesis supports the monophyly of the genus Cladonia. It also supports the separation of two large groups in the Physciaceae; the Buellia-group and the Physcia-group.
Aerodynamic forces of revolving hummingbird wings and wing models
Authors: Altshuler Douglas L. , Dudley Robert , Ellington Charles P.
Published: November 2004

A central challenge to the study of animal aerodynamics has been the measurement of forces generated by flapping wings. Relative to wings of other birds, hummingbird wings are of particular interest in that the smaller species operate in more viscous regimes (5000 < Re < 10 000) for which substantial drag and reduced lift:drag coefficients might be expected. Lift and drag forces were measured on mounted hummingbird wings and wing models spinning in continuous tipwise revolution about the wing base. Lift coefficients tended to increase as wing models became more realistic (i.e. with sharpened leading edges and with substantial camber). Lift:drag ratios of real wings were substantially higher than those of wing models, suggesting morphological contributions of feathers to lift enhancement and drag reduction. At Re= 5000, high values of the lift:drag ratio (8–16) at low angles of attack suggest that wings of hummingbirds are exceptionally good at producing lift.
Satellite‐linked dive recorders provide insights into the reproductive strategies of crabeater seals (Lobodon carcinophagus)
Authors: Southwell Colin
Published: November 2004

Insights into the reproductive strategies of crabeater seals Lobodon carcinophagus were obtained from satellite‐linked dive recorders deployed during the breeding season. All of the three females and seven males on which instruments were deployed hauled out continuously for extended periods of up to 24 days. The duration of extended haulout is consistent with a lactation period of around 3 weeks. In two cases where dive recorders were deployed on a male and female in the same group, the two animals stayed together on the ice continuously and entered the water at exactly the same time when extended haulout ceased. In both cases the male and female became geographically separated within a short time after entering the water, indicating that the association did not last beyond the period on the ice. Some males had multiple periods of extended haulout, suggesting they may try to find more than one female with which to mate. An optimal reproductive strategy with regard to the time spent on the ice may balance the conflicting needs of a short time imposed by the availability of breeding habitat and a long time to increase the reproductive success of males and females by finding more, or choosing between, mates.
Commencer: la suite, mais pas encore la fin
Authors: PEETERS BERT
Published: November 2004

L'objectif de cet article est de revoir et d'approfondir la description du verbe commencer entreprise dans Peeters (1993b), en profitant de l'enseignement de Georges Kleiber, dont nous exploitons le principe de la métonymie intégrée et l'idée que la construction commencer + objet direct est d'ordre métaphorique. Ce n'est qu'un début, puisqu'on s'occupera avant tout des constructions du type ‘commencer à + infinitif’. Comme, depuis 1993, d'importants progrès ont été réalisés dans le domaine de la métalangue sémantique naturelle d'Anna Wierzbicka, que notre description avait pour but de faire mieux connaître, une mise à jour s'impose de ce côté-là aussi.
Modeling of remote sensing of thin current sheet
Authors: Lee E. , Wilber M. , Parks G. K. , Min K. W. , Lee D.‐Y.
Published: November 2004

Cluster encountered a thin current sheet in the magnetotail during a substorm on Oct. 1, 2001. The phase space distributions observed by Cluster CIS showed large gradients in the phase space with ions existing only in one hemisphere of the phase space. It has been suggested that these non‐gyrotropic distributions come from remote sensing of a thin current sheet by spacecrafts outside the current sheet. We present the results of a test particle simulation that confirm non‐gyrotropic distributions can arise from remote sensing of a thin current sheet. These non‐gyrotropic distributions can yield large velocity moments even when the plasma is stationary. The large velocity moments are not in the convective flow direction that would be normal to the current sheet. Instead they are along the n × B direction where n is normal to the boundary. These modeling results reinforce the importance of examining full particle distributions when studying plasma sheet dynamics.
Are seismic waiting time distributions universal?
Authors: Davidsen Jörn , Goltz Christian
Published: November 2004

We show that seismic waiting time distributions in California and Iceland have many features in common as, for example, a power‐law decay with exponent α ≈ 1.1 for intermediate and with exponent γ ≈ 0.6 for short waiting times. While the transition point between these two regimes scales proportionally with the size of the considered area, the full distribution is not universal and depends in a non‐trivial way on the geological area under consideration and its size. This is due to the spatial distribution of epicenters which does not form a simple mono‐fractal. Yet, the dependence of the waiting time distributions on the threshold magnitude seems to be universal.