bluuebunny/crossref_metadata_2025 huggingface dataset:
Introduction to special section on Analysis of Zooplankton Distributions Using the Optical Plankton Counter
Authors: Vanderploeg Henry A. , Roman Michael R.
Published: May 2006

We briefly introduce the optical plankton counters (OPCs) currently in use and summarize major themes and conclusions of papers from this special section. These collected papers demonstrate that the OPC and the new laser OPC (LOPC) are useful tools for mapping fine‐scale distributions of zooplankton over broad expanses of space and for examining patterns in the size structure of zooplankton communities, which give insights into the top‐down and bottom‐up forces affecting them. The LOPC or OPC are particularly valuable sensors when used in conjunction with an array of other sensors on a tow body so that investigators can synoptically measure physical and biotic variables. Caution must be exercised in using the OPC or LOPC because there are times when nonzooplankton particles comprise a significant portion of the particles counted. The contribution of nonzooplankton particles to the total seston varies with system and conditions.
Fistel nach Gallensteinperforation in das Duodenum
Authors: Muehlenberg K , Wiedmann K. H.
Published: May 2006

Die 53-jährige Patientin wird durch Bauchschmerzen und Bluterbrechen symptomatisch. Die endoskopische retrograde Cholangiographie (ERC) zeigt drei auffällige Befunde.

Welche sind das?

Erlauben diese Befunde eine Diagnose? Wenn ja, welche?

Sind Differenzialdiagnosen möglich? Wenn ja, welche?
A two-dimensional adsorption kinetic model for thermal hysteresis activity in antifreeze proteins
Authors: Li Q. Z. , Yeh Y. , Liu J. J. , Feeney R. E. , Krishnan V. V.
Published: May 2006

Antifreeze proteins (AFPs) and antifreeze glycoproteins (AFGPs), collectively abbreviated as AF(G)Ps, are synthesized by various organisms to enable their cells to survive in subzero environments. Although the AF(G)Ps are markedly diverse in structure, they all function by adsorbing to the surface of embryonic ice crystals to inhibit their growth. This adsorption results in a freezing temperature depression without an appreciable change in the melting temperature. The difference between the melting and freezing temperatures, termed thermal hysteresis (TH), is used to detect and quantify the antifreeze activity. Insights from crystallographic structures of a number of AFPs have led to a good understanding of the ice-protein interaction features. Computational studies have focused either on verifying a specific model of AFP-ice interaction or on understanding the protein-induced changes in the ice crystal morphology. In order to explain the origin of TH, we propose a novel two-dimensional adsorption kinetic model between AFPs and ice crystal surfaces. The validity of the model has been demonstrated by reproducing the TH curve on two different β-helical AFPs upon increasing the protein concentration. In particular, this model is able to accommodate the change in the TH behavior observed experimentally when the size of the AFPs is increased systematically. Our results suggest that in addition to the specificity of the AFPs for the ice, the coverage of the AFPs on the ice surface is an equally necessary condition for their TH activity.
An efficient self-consistent field method for large systems of weakly interacting components
Authors: Khaliullin Rustam Z. , Head-Gordon Martin , Bell Alexis T.
Published: May 2006

An efficient method for removing the self-consistent field (SCF) diagonalization bottleneck is proposed for systems of weakly interacting components. The method is based on the equations of the locally projected SCF for molecular interactions (SCF MI) which utilize absolutely localized nonorthogonal molecular orbitals expanded in local subsets of the atomic basis set. A generalization of direct inversion in the iterative subspace for nonorthogonal molecular orbitals is formulated to increase the rate of convergence of the SCF MI equations. Single Roothaan step perturbative corrections are developed to improve the accuracy of the SCF MI energies. The resulting energies closely reproduce the conventional SCF energy. Extensive test calculations are performed on water clusters up to several hundred molecules. Compared to conventional SCF, speedups of the order of (N∕O)2 have been achieved for the diagonalization step, where N is the size of the atomic orbital basis, and O is the number of occupied molecular orbitals.
An exploration of electronic structure and nuclear dynamics in tropolone. I. The X̃A11 ground state
Authors: Burns Lori A. , Murdock Daniel , Vaccaro Patrick H.
Published: May 2006

The ground electronic state (X̃A11) of tropolone has been examined theoretically by exploiting extensive sets of basis functions [e.g., 6-311++G(d,p) and aug-cc-pVDZ] in conjunction with the high levels of electron correlation made possible by density functional (DFT/B3LYP), Møller-Plesset perturbation (MP2), and coupled-cluster [CCSD and CCSD(T)] methods. Unconstrained MP2 and CCSD optimization procedures performed with the reference 6-311++G(d,p) basis predict a slightly nonplanar equilibrium structure characterized by a small barrier to skeletal inversion (⩽10cm−1 magnitude). Complementary harmonic frequency analyses have shown this nonplanarity to be a computational artifact arising from adversely tuned carbon d-orbital exponents embodied in the standard definitions of several Pople-type basis sets. Correlation-consistent bases such as Dunning’s aug-cc-pVDZ are less susceptible to these effects and were employed to confirm that the X̃A11 hypersurface supports a rigorously planar global minimum. The fully optimized geometries and vibrational force fields obtained by applying potent coupled-cluster schemes to the relaxed-equilibrium (Cs) and transition-state (C2v) conformers of tropolone afford a trenchant glimpse of the key features that mediate intramolecular hydron exchange in this model system. By incorporating perturbative triples corrections at the substantial CCSD(T) level of theory, an interoxygen distance of rO⋯O=2.528Å was determined for the minimum-energy configuration, with the accompanying proton-transfer reaction being hindered by a barrier of 2557.0cm−1 height. The potential energy landscape in tropolone, as well as the nature of the attendant hydron migration process, is discussed within the framework of the encompassing G4 molecular symmetry group.
Raman spectroscopic investigation of carbon nanowalls
Authors: Ni Z. H. , Fan H. M. , Feng Y. P. , Shen Z. X. , Yang B. J. , Wu Y. H.
Published: May 2006

Two-dimensional carbon nanowalls (CNWs) were prepared by microwave plasma-enhanced chemical-vapor deposition and scanning electron microscopy was used to observe their morphologies. The Raman observations of different sample orientations and polarizations show that CNWs are well crystallized. Micro-Raman scattering measurements were also carried out with different excitation laser lines (325, 488, 514, 532, and 633nm). The D band shows a very strong shift of 46.19cm−1∕eV with excitation laser energy and this has been explained by the double resonance effect. The decreasing intensity ratios ID∕IG and ID′∕IG with increasing laser excitation energy were detected and discussed.
Molecular beam mass spectrometer equipped with a catalytic wall reactor forin situstudies in high temperature catalysis research
Authors: Horn R. , Ihmann K. , Ihmann J. , Jentoft F. C. , Geske M. , Taha A. , Pelzer K. , Schlögl R.
Published: May 2006

A newly developed apparatus combining a molecular beam mass spectrometer and a catalytic wall reactor is described. The setup has been developed for in situ studies of high temperature catalytic reactions (>1000°C), which involve besides surface reactions also gas phase reactions in their mechanism. The goal is to identify gas phase radicals by threshold ionization. A tubular reactor, made from the catalytic material, is positioned in a vacuum chamber. Expansion of the gas through a 100μm sampling orifice in the reactor wall into differentially pumped nozzle, skimmer, and collimator chambers leads to the formation of a molecular beam. A quadrupole mass spectrometer with electron impact ion source designed for molecular beam inlet and threshold ionization measurements is used as the analyzer. The sampling time from nozzle to detector is estimated to be less than 10ms. A detection time resolution of up to 20ms can be reached. The temperature of the reactor is measured by pyrometry. Besides a detailed description of the setup components and the physical background of the method, this article presents measurements showing the performance of the apparatus. After deriving the shape and width of the energy spread of the ionizing electrons from measurements on N2 and He we estimated the detection limit in threshold ionization measurements using binary mixtures of CO in N2 to be in the range of several hundreds of ppm. Mass spectra and threshold ionization measurements recorded during catalytic partial oxidation of methane at 1250°C on a Pt catalyst are presented. The detection of CH3∙ radicals is successfully demonstrated.
Efficient stimulated Raman pumping for quantum state resolved surface reactivity measurements
Authors: Maroni Plinio , Papageorgopoulos Dimitrios , Ruf Amanz , Beck Rainer D. , Rizzo Thomas R.
Published: May 2006

We describe the use of stimulated Raman pumping in a molecular beam to perform quantum state resolved gas-surface reactivity measurements for molecules prepared in totally symmetric vibrational states. Vibrational states of homonuclear diatomics as well as totally symmetric vibrations of polyatomic molecules cannot be prepared by direct infrared excitation but are accessible through stimulated Raman pumping by two laser fields when the difference between the incident laser frequencies matches the vibration. We generate a suitable resonant pair of high-energy pump and Stokes laser beams in an injection seeded Raman amplifier filled with the sample gas and equipped with internal gas recirculation. The ability to partially saturate the Raman pumping process in the molecular beam is used to quantify the fraction of vibrationally excited molecules in the irradiated volume, which is needed for quantitative reactivity measurements. We illustrate the method with state resolved reactivity measurements for CH4, prepared in its symmetric C–H stretch vibration on a Ni(100) single crystal surface.
Spin-dependent transport through a magnetic carbon nanotube-molecule junction
Authors: Zhang C. , Wang L.-L. , Cheng H.-P. , Zhang X.-G. , Xue Y.
Published: May 2006

The electronic structure and spin-dependent conductance of a magnetic junction consisting of two Fe-doped carbon nanotubes and a C60 molecule are investigated using a first-principles approach that combines the density functional theory with the nonequilibrium Greens function technique. The tunneling magnetoresistance ratio is found to be 11%. The density of states and transmission coefficient through the molecular junction are analyzed and compared to layered magnetic tunneling junctions. Our findings suggest new possibilities for experiments and for future technology.
Pulling crystal of practical size by metallic expansion method
Authors: He Y. Z.
Published: May 2006

A new thermal expansion method for crystal pulling was developed. A NaBi(WO4)2 crystal, with 2cm length and an average radius of 1.3cm, was pulled using this new method. Crystal with such a size is large enough for applications in most scientific experiments. It was shown that the new method was practically useful and further investigation for improvement might be warranted.
Space-charge-limited leakage current characteristics influenced by field-dependent permittivity in high dielectric constant and ferroelectric thin films
Authors: Li Jiantong , Dong Xianlin , Chen Ying , Zhang Yuanyuan
Published: May 2006

The current-voltage relationship dominated by space-charge-limited conduction for high dielectric constant and ferroelectric thin films, including (Ba,Sr)TiO3 and Pb(Zr,Ti)O3, is derived taking into account the electric field dependence of permittivity. Typical current-voltage characteristics are given by the derived relationship with empirical values for its parameters. The obtained current characteristics might account for the high-field quasi-Ohmic region observed experimentally in the leakage current characteristics of a very thin BaTiO3 single crystal in the previous study [Morrison et al., Appl. Phys. Lett. 86, 152903 (2005)].
Characteristics of Zr-based single- and multiple-barrier superconducting tunnel junctions
Authors: Nevirkovets I. P. , Chernyashevskyy O. , Ketterson J. B.
Published: May 2006

Using Zr oxide for the tunnel barrier formation, it is shown experimentally that the effect of pinholes is suppressed in the double-barrier versus single-barrier junction configuration. It is found that Josephson current in Nb∕Zr double-barrier junctions is much lower than in Nb∕Al junctions with comparable specific tunneling resistance and middle layer thickness. Multiple oxidation process is used to improve the quality of superconductor-insulator-superconductor Zr-based junctions.
DNA-Ormocer based biocomposite for fabrication of photonic structures
Authors: Gupta Preeti , Markowicz Przemyslaw P. , Baba Koichi , O’Reilly James , Samoc Marek , Prasad Paras N. , Grote James G.
Published: May 2006

We report microfabrication of high quality photonic structures such as two-dimensional photonic crystals and beam splitters from a high DNA load, photosensitive Ormocer nanocomposite. This nanocomposite combines the high dye loading capacity of DNA with the photopatternability and hardness of the Ormocer. The fabrication is performed with the two-photon lithography method. Detailed studies of the deoxyribonucleic acid distribution in the fabricated structures are conducted with Raman microscopy. We also demonstrate that the deoxyribonucleic acid based nanocomposite films cast on glass substrates are of high enough quality to support amplified spontaneous emission from dyes intercalated in the deoxyribonucleic acid.
Silicon nanowires for high-sensitivity glucose detection
Authors: Chen Weiwei , Yao Hui , Tzang Chi Hung , Zhu Junjie , Yang Mengsu , Lee Shuit-Tong
Published: May 2006

Silicon nanowires (SiNWs) were investigated as supporting matrices for enzyme immobilization to construct glucose biosensors. Glucose oxidase was adsorbed onto SiNWs after different treatments, either as grown, HF etched, or carboxylic acid (COOH) functionalized. The amperometric biosensor with COOH-functionalized SiNWs performed the best with a detection limit of 0.01mM glucose (signal-to-noise ratio=3). For real-time detection of glucose, SiNW biosensor showed a linear response in the range of 0.1–15mM. This work demonstrates the utility of SiNWs as a biosensor component and provides a general method to modify the surface of semiconducting nanomaterials for potential biomedical applications.
Design of nanostructures for photoelectric conversion using an organic vertical superlattice
Authors: Hiramoto Masahiro , Yamaga Takumi , Danno Mari , Suemori Kouji , Matsumura Yoshio , Yokoyama Masaaki
Published: May 2006

The intentional design to the 2.5nm scale based on a concept for the design of nanoscopic structures via film thickness control was demonstrated. We fabricated sandwich-type cells incorporating organic vertical superlattices by using a microtome and proved that structural design below the 10nm scale is necessary in order to realize solid-state organic solar cells. The present technique can be applied to the fabrication of novel optoelectronic devices with designed nanostructures that are composed of any kind of material.
Polarization-resolved photoluminescence study of individual GaN nanowires grown by catalyst-free molecular beam epitaxy
Authors: Schlager John B. , Sanford Norman A. , Bertness Kris A. , Barker Joy M. , Roshko Alexana , Blanchard Paul T.
Published: May 2006

Polarization- and temperature-dependent photoluminescence (PL) measurements were performed on individual GaN nanowires. These were grown by catalyst-free molecular beam epitaxy on Si(111) substrates, ultrasonically removed, and subsequently dispersed on sapphire substrates. The wires were typically 5–10μm in length, c-axis oriented, and 30–100nm in diameter. Single wires produced sufficient emission intensity to enable high signal-to-noise PL data. Polarized PL spectra differed for the σ and π polarization cases, illustrating the polarization anisotropy of the exciton emission associated with high-quality wurtzite GaN. This anisotropy in PL emission persisted even up to room temperature (4–296K). Additionally, the nanowire PL varied with excitation intensity and with (325nm) pump exposure time.
Electron emission from self-assembled quantum dots in strong magnetic fields
Authors: Schramm A. , Schulz S. , Schaefer J. , Zander T. , Heyn Ch. , Hansen W.
Published: May 2006

We probe with deep level transient spectroscopy electron states in self-assembled InAs quantum dots. Two pronounced maxima are observed that we associate with emission from different quantum-dot orbital states. Fine structure clearly establishes distinct emission rates for quantum dots with one or two electrons in the s state and up to four electrons in the p-like states. In order to confirm these assignments spectra have been recorded in strong magnetic fields. The observed magnetic field dispersion of the emission energies is described with a harmonic oscillator model using an effective electron mass of m*=0.03me.
Field emission of silicon nanowires
Authors: Zeng Baoqing , Xiong Guangyong , Chen Shuo , Jo S. H. , Wang W. Z. , Wang D. Z. , Ren Z. F.
Published: May 2006

Field emission of single crystal silicon nanowires of 100nm in diameter grown at 480°C from silane using Au as catalyst has been investigated. An emission current density of 1mA∕cm2 over a 0.2cm2 area was obtained at an electric field of 3.4V∕μm with a turn-on field of 2V∕μm at 0.01mA∕cm2. The annealing of the as-grown samples at 550°C in vacuum has drastically improved the field emission performance. The low growth and annealing temperatures make the process applicable to glass substrates.
Stable field emission from hydrothermally grown ZnO nanotubes
Authors: Wei A. , Sun X. W. , Xu C. X. , Dong Z. L. , Yu M. B. , Huang W.
Published: May 2006

Zinc oxide nanotube arrays were prepared by hydrothermal reaction in ammonia and zinc chloride solutions, and the field emission properties were tested. The turn-on field of the field emission was extrapolated to be about 7.0V∕μm at a current density of 0.1μA∕cm2. Meanwhile, the emission current densities reached 1mA∕cm2 at a bias field of 17.8V∕μm. The field enhancement factor β was estimated to be 910. The field emission of the zinc oxide nanotubes showed good stability. The variation of emission current density was less than 10% during a 24h test under a field of 15V∕μm.
Electric field dependence of the electric conductivity in liquid crystals made of bent-core molecules
Authors: Martins O. G. , Barbero G. , Pedreira A. M. , Jákli A. , Sawade H. , Figueiredo Neto A. M.
Published: May 2006

We investigate the influence of the electric field on the conductivity of an antiferroelectric liquid crystal formed by bananalike molecules. Our experimental analysis shows that large deviations of the current from a pure Ohmic behavior are observed for applied voltage of the order of the ones used for the determination of the spontaneous polarization in these types of materials. The measurements are performed in the isotropic and B2 phases. In the isotropic phase these deviations are interpreted in terms of the model proposed by Onsager, according to which, for weak electrolyte, the conductivity depends on the actual electric field present in the liquid. In the ordered phase we show that they are partially due to the external field induced reorientation of the director structure. A good agreement between the model and the experimental data is obtained, and an estimate of the coefficients taking into account the effect of the electric field on the conductivity is deduced. The relevance of this effect on the experimental determination of the spontaneous polarization is found to be of the order of 10%.
Spin-injection dynamics in a magnetic double quantum well studied by pump-probe absorption spectroscopy
Authors: Nishibayashi K. , Souma I. , Murayama A. , Oka Y.
Published: May 2006

We study spin-injection dynamics in a magnetic double quantum well by pump-probe absorption spectroscopy. Time dependences of the absorption saturation intensity show a tunneling of spin-polarized carriers from a diluted magnetic well (MW) of Cd0.92Mn0.08Te into a nonmagnetic well (NMW) of CdTe, where the individual tunneling of the electron and heavy hole is elucidated with time constants of 150ps and 1ns. The circular polarization degree of the absorption saturation in NMW increases from 0to70ps, which is caused by the injection of electron spin polarized in MW with a time constant of 54ps.
In situ fluorescence microscopy visualization and characterization of nanometer-scale carbon nanotubes labeled with 1-pyrenebutanoic acid, succinimidyl ester
Authors: Kim Jin-Woo , Kotagiri Nalinikanth , Kim Jeong-Hwan , Deaton Russell
Published: May 2006

In order to characterize hybrid bio/abio technology utilizing carbon nanotubes (CNTs), in situ, real-time, yet noninvasive methods of accurate and reliable imaging are needed for observing CNTs’ interactions with biological materials, i.e., DNA, in biologically relevant aqueous environments. Optical visualization and characterization of individual CNTs in aqueous solutions were explored in this study using 1-pyrenebutanoic acid, succinimidyl ester (PSE) and a conventional fluorescence microscope. The results demonstrate the potential of fluorescence microscopy based on PSE-based staining methodology monitoring with nanometer resolution of individual CNTs and their manipulation with biological materials in bio/abio hybrid systems.
Complex of linker histone H5 with the nucleosome and its implications for chromatin packing
Authors: Fan Li , Roberts Victoria A.
Published: May 2006

Linker histones are essential for chromatin filament formation, and they play key roles in the regulation of gene expression. Despite the determination of structures of the nucleosome and linker histones, the location of the linker histone on the nucleosome is still a matter of debate. Here we show by computational docking that the globular domain of linker histone variant H5 (GH5) has three distinct DNA-binding sites, through which GH5 contacts the DNA at the nucleosome dyad and the linker DNA strands entering and exiting the nucleosome. Our results explain the extensive mutagenesis and crosslinking data showing that side chains spread throughout the GH5 surface interact with nucleosomal DNA. The nucleosome DNA contacts positively charged side chains that are conserved within the linker histone family, indicating that our model extends to linker histone–nucleosome interactions in general. Furthermore, our model provides a structural mechanism for formation of a dinucleosome complex specific to the linker histone H5, explaining its efficiency in chromatin compaction and transcription regulation. Thus, this work provides a basis for understanding how structural differences within the linker histone family result in functional differences, which in turn are important for gene regulation.
Microtubule affinity-regulating kinase 2 functions downstream of the PAR-3/PAR-6/atypical PKC complex in regulating hippocampal neuronal polarity
Authors: Chen Y. M. , Wang Q. J. , Hu H. S. , Yu P. C. , Zhu J. , Drewes G. , Piwnica-Worms H. , Luo Z. G.
Published: May 2006

The PAR-3/PAR-6/atypical PKC (aPKC) complex is required for axon–dendrite specification of hippocampal neurons. However, the downstream effectors of this complex are not well defined. In this article, we report a role for microtubule affinity-regulating kinase (MARK)/PAR-1 in axon–dendrite specification. Knocking down MARK2 expression with small interfering RNAs induced formation of multiple axon-like neurites and promoted axon outgrowth. Ectopic expression of MARK2 caused phosphorylation of tau (S262) and led to loss of axons, and this phenotype was rescued by expression of PAR-3, PAR-6, and aPKC. In contrast, the polarity defects caused by an MARK2 mutant (T595A), which is not responsive to aPKC, were not rescued by the PAR-3/PAR-6/aPKC complex. Moreover, polarity was abrogated in neurons overexpressing a mutant of MARK2 with a deleted kinase domain but an intact aPKC-binding domain. Finally, suppression of MARK2 rescued the polarity defects induced by a dominant-negative aPKC mutant. These results suggest that MARK2 is involved in neuronal polarization and functions downstream of the PAR-3/PAR-6/aPKC complex. We propose that aPKC in complex with PAR-3/PAR-6 negatively regulates MARK(s), which in turn causes dephosphorylation of microtubule-associated proteins, such as tau, leading to the assembly of microtubules and elongation of axons.
Histamine signaling through the H2receptor in the Peyer’s patch is important for controllingYersinia enterocoliticainfection
Authors: Handley Scott A. , Dube Peter H. , Miller Virginia L.
Published: May 2006

Enteric pathogens such asYersinia enterocoliticareadily colonize and induce disease within the lymphatic tissues of the small intestine. To gain a comprehensive view of the host response to pathogens within these tissues, we determined the transcriptional profiles of intestinal lymphatic tissue infected withY. enterocolitica. Expression analysis using Affymetrix GeneChips revealed a complex host response in the Peyer’s patches and mesenteric lymph nodes after oral infection withY. enterocolitica. Interestingly, histidine decarboxylase (Hdc) was significantly up-regulated in response toY. enterocoliticainfection. HDC is the enzyme solely responsible for the production of the biogenic amine histamine. Although histamine is well known for its role in allergy and for its effects on immunity and inflammation, little is known about its role or specific histamine receptors during the host response to bacterial infection. In this study, we provide evidence that histamine signaling through the histamine H2but not the H1receptor is important for controllingY. enterocoliticainfection within the Peyer’s patches and mesenteric lymph nodes of mice.
Cytosolic chaperonin protects folding intermediates of Gβ from aggregation by recognizing hydrophobic β-strands
Authors: Kubota Susumu , Kubota Hiroshi , Nagata Kazuhiro
Published: May 2006

Cytosolic chaperonin containing
t
-complex polypeptide 1 (CCT)/TRiC is a group II chaperonin that assists in the folding of newly synthesized proteins. It is a eukaryotic homologue of the bacterial group I chaperonin GroEL. In contrast to the well studied functions of GroEL, the substrate recognition mechanism of CCT/TRiC is poorly understood. Here, we established a system for analyzing CCT/TRiC functions by using a reconstituted protein synthesis by using recombinant elements system and show that CCT/TRiC strongly recognizes WD40 proteins particularly at hydrophobic β-strands. Using the G protein β subunit (Gβ), a WD40 protein that is very rich in β-sheets, as a model substrate, we found that CCT/TRiC prevents aggregation and assists in folding of Gβ, whereas GroEL does not. Gβ has a seven-bladed β-propeller structure; each blade is formed from a WD40 repeat sequence encoding four β-strands. Detailed mutational analysis of Gβ indicated that CCT/TRiC, but not GroEL, preferentially recognizes hydrophobic residues aligned on surfaces of β-strands in the second WD40 repeat of Gβ. These findings indicate that one of the CCT/TRiC-specific targets is hydrophobic β-strands, which are highly prone to aggregation.
Suppression of methamphetamine-seeking behavior by nicotinic agonists
Authors: Hiranita Takato , Nawata Yoko , Sakimura Katsuya , Anggadiredja Kusnandar , Yamamoto Tsuneyuki
Published: May 2006

To understand the mechanism of methamphetamine (MAP) craving from the viewpoint of nicotinic acetylcholinergic transmission, we examined the responsible site of the brain for anticraving effects produced by nicotinic agonists by using a MAP self-administration paradigm in rats. Systemic nicotine and an acetylcholinesterase inhibitor, donepezil, attenuated the reinstatement of MAP-seeking behavior by means of the activation of nicotinic acetylcholinergic receptors, but not muscarinic acetylcholinergic receptors, in the nucleus accumbens core, prelimbic cortex, amygdala, and hippocampus. Among these regions, with the exception of the hippocampus, we also found functional differences in this reinstatement. The nicotinic antagonist mecamylamine alone did not reinstate MAP-seeking behavior. These results suggest that the inactivation of nicotinic acetylcholinergic transmission may be an essential factor in the appearance of MAP-seeking behavior, and, thus, the normalization of the inactivated state may result in the suppression of the reinstatement. Our findings also indicate that there are functional differences in the responsible brain subregions. Extending this view to the treatment of MAP dependence, our results suggest that activators of nicotinic acetylcholinergic transmission are possible anticraving agents.
An
S
-nitrosothiol (SNO) synthase function of hemoglobin that utilizes nitrite as a substrate
Authors: Angelo Michael , Singel David J. , Stamler Jonathan S.
Published: May 2006

Red blood cells (RBCs) act as O
2
-responsive transducers of vasodilator and vasoconstrictor activity in lungs and tissues by regulating the availability of nitric oxide (NO). Vasodilation by RBCs is impaired in diseases characterized by hypoxemia. We have proposed that the extent to which RBCs constrict vs. dilate vessels is, at least partly, controlled by a partitioning between NO bound to heme iron and to Cysβ93 thiol of hemoglobin (Hb). Hemes sequester NO, whereas thiols deploy NO bioactivity. In recent work, we have suggested that specific micropopulations of NO-liganded Hb could support the chemistry of
S
-nitrosohemoglobin (SNO-Hb) formation. Here, by using nitrite as the source of NO, we demonstrate that a (T state) micropopulation of a heme-NO species, with spectral and chemical properties of Fe(III)NO, acts as a precursor to SNO-Hb formation, accompanying the allosteric transition of Hb to the R state. We also show that at physiological concentrations of nitrite and deoxyHb, a
S
-nitrosothiol precursor is formed within seconds and produces SNO-Hb in high yield upon its prompt exposure to O
2
or CO. Deoxygenation/reoxygenation cycling of oxyHb in the presence of physiological amounts of nitrite also efficiently produces SNO-Hb. In contrast, high amounts of nitrite or delays in reoxygenation inhibit the production of SNO-Hb. Collectively, our data provide evidence for a physiological
S
-nitrosothiol synthase activity of tetrameric Hb that depends on NO-Hb micropopulations and suggest that dysfunction of this activity may contribute to the pathophysiology of cardiopulmonary and blood disorders.
Developmental basis for hind-limb loss in dolphins and origin of the cetacean bodyplan
Authors: Thewissen J. G. M. , Cohn M. J. , Stevens L. S. , Bajpai S. , Heyning J. , Horton W. E.
Published: May 2006

Among mammals, modern cetaceans (whales, dolphins, and porpoises) are unusual in the absence of hind limbs. However, cetacean embryos do initiate hind-limb bud development. In dolphins, the bud arrests and degenerates around the fifth gestational week. Initial limb outgrowth in amniotes is maintained by two signaling centers, the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA). Our data indicate that the cetacean hind-limb bud forms an AER and that this structure expresses Fgf8 initially, but that neither the AER nor Fgf8 expression is maintained. Moreover, Sonic hedgehog (Shh), which mediates the signaling activity of the ZPA, is absent from the dolphin hind-limb bud. We find that failure to establish a ZPA is associated with the absence of Hand2, an upstream regulator of Shh. Interpreting our results in the context of both the cetacean fossil record and the known functions of Shh suggests that reduction of Shh expression may have occurred ≈41 million years ago and led to the loss of distal limb elements. The total loss of Shh expression may account for the further loss of hind-limb elements that occurred near the origin of the modern suborders of cetaceans ≈34 million years ago. Integration of paleontological and developmental data suggests that hind-limb size was reduced by gradually operating microevolutionary changes. Long after locomotor function was totally lost, modulation of developmental control genes eliminated most of the hind-limb skeleton. Hence, macroevolutionary changes in gene expression did not drive the initial reduction in hind-limb size.
Liver-specific deletion of acetyl-CoA carboxylase 1 reduces hepatic triglyceride accumulation without affecting glucose homeostasis
Authors: Mao Jianqiang , DeMayo Francesco J. , Li Huiguang , Abu-Elheiga Lutfi , Gu Ziwei , Shaikenov Tattym E. , Kordari Parichher , Chirala Subrahmanyam S. , Heird William C. , Wakil Salih J.
Published: May 2006

In animals, liver and white adipose are the main sites for the
de novo
fatty acid synthesis. Deletion of fatty acid synthase or acetyl-CoA carboxylase (ACC) 1 in mice resulted in embryonic lethality, indicating that the
de novo
fatty acid synthesis is essential for embryonic development. To understand the importance of
de novo
fatty acid synthesis and the role of ACC1-produced malonyl-CoA in adult mouse tissues, we generated liver-specific ACC1 knockout (LACC1KO) mice. LACC1KO mice have no obvious health problem under normal feeding conditions. Total ACC activity and malonyl-CoA levels were ≈70–75% lower in liver of LACC1KO mice compared with that of the WT mice. In addition, the livers of LACC1KO mice accumulated 40–70% less triglycerides. Unexpectedly, when fed fat-free diet for 10 days, there was significant up-regulation of PPARγ and several enzymes in the lipogenic pathway in the liver of LACC1KO mice compared with the WT mice. Despite the significant up-regulation of the lipogenic enzymes, including a >2-fold increase in fatty acid synthase mRNA, protein, and activity, there was significant decrease in the
de novo
fatty acid synthesis and triglyceride accumulation in the liver. However, there were no significant changes in blood glucose and fasting ketone body levels. Hence, reducing cytosolic malonyl-CoA and, therefore, the
de novo
fatty acid synthesis in the liver, does not affect fatty acid oxidation and glucose homeostasis under lipogenic conditions.
Probiotic bacteriaBifidobacterium animalisMB5 andLactobacillus rhamnosusGG protect intestinal Caco-2 cells from the inflammation-associated response induced by enterotoxigenicEscherichia coliK88
Authors: Roselli Marianna , Finamore Alberto , Britti Maria Serena , Mengheri Elena
Published: May 2006

Probiotic bacteria may provide protection against intestinal damage induced by pathogens, but the underlying mechanisms are still largely unknown. We investigated whetherBifidobacterium animalisMB5 andLactobacillus rhamnosusGG (LGG) protected intestinal Caco-2 cells from the inflammation-associated response induced by enterotoxigenicEscherichia coli(ETEC) K88, by inhibiting pathogen attachment to the cells, which is the first step of ETEC pathogenicity, and regulating neutrophil recruitment, a crucial component of inflammation. A partial reduction of ETEC adhesion was exerted by probiotics and their culture supernatant fractions either undigested or digested with proteases. ETEC viability was unaffected by the presence ofB. animalis, LGG or their supernatant fractions in the culture medium, indicating an absence of probiotic bactericidal activity. Probiotics and their supernatant fractions, either undigested or digested with proteases, strongly inhibited the neutrophil transmigration caused by ETEC. BothB. animalisand LGG counteracted the pathogen-induced up regulation of IL-8, growth-related oncogene-α and epithelial neutrophil-activating peptide-78 gene expression, which are chemokines essential for neutrophil migration. Moreover, the probiotics prevented the ETEC-induced increased expression of IL-1β and TNF-α and decrease of transforming growth factor-α, which are regulators ofchemokine expression. These results indicate thatB. animalisMB5 and LGG protect intestinal cells from the inflammation-associated response caused by ETEC K88 by partly reducing pathogen adhesion and by counteracting neutrophil migration, probably through the regulation of chemokine and cytokine expression.
Quantifying dietary macronutrient sources of carbon for bone collagen biosynthesis using natural abundance stable carbon isotope analysis
Authors: Jim Susan , Jones Vicky , Ambrose Stanley H. , Evershed Richard P.
Published: May 2006

The diets of laboratory rats were isotopically and nutritionally manipulated using purifiedC3 and/or C4 macronutrients to investigate the routing of dietary carbonto bone collagen biosynthesis. Diets were formulated with purified proteins, carbohydrates andlipids of defined composition and natural abundance stable isotope ratios. Bulk protein and constituent amino acid δ13C values determined for whole diet and bone collagen provided the basis for assessing isotopic fractionation and estimating the degree of routing versus synthesis de novo of essential, non-essential and conditionally indispensable amino acids. Essential and conditionally indispensable amino acids were shown to be routed from diet to collagen with little isotopic fractionation whereas non-essential amino acids differed by up to 20‰. Mathematical modelling of the relationships between macronutrient and tissue δ13C values provided qualitative and quantitative insights into the metabolic and energetic controls on bone collagen biosynthesis. Essential amino acids comprise 21·7% of the carbon in collagen, defining the minimum amount of dietary carbon routing. Estimates of 42 and 28% routing were shown for the non-essential amino acids, glycine and aspartate, respectively. In total, the routing of non-essential and conditionally indispensable amino acids was estimated to equal 29·6% of the carbon in collagen. When the contribution of carbon from the essential amino acids is also considered, we arrive at an overall minimum estimate of 51·3% routing of dietary amino acid carbon into bone collagen.
A systematic review of the effects of calcium supplementation on body weight
Authors: Trowman Rebecca , Dumville Jo C. , Hahn Seokyung , Torgerson David J.
Published: May 2006

Animal studies and epidemiological studies have suggested that Ca supplementation (with Ca supplements or dairy products) may be associated with weight loss in human adults. We aimed toassess whether any association was present by reviewing relevant randomized controlled trials in human subjects. The study was a systematic review and subsequent meta-analysis of randomized controlled trials that used Ca supplementation as an intervention in persons 18 or more years of age, and that reported body weight as a final outcome. A total of thirteen randomized controlled trials were included in the meta-analysis. There was no association between the increased consumption of either Ca supplements or dairy products and weight loss after adjusting fordifferences in baseline weights between the control and intervention groups (P=0·19 and 0·85, respectively). We therefore concluded that Ca supplementation has no statistically significant association with a reduction in body weight.
Hydrothermal treatment of Novelose 330 results in high yield of resistant starch type 3 with beneficial prebiotic properties and decreased secondary bile acid formation in rats
Authors: Jacobasch Gisela , Dongowski Gerhard , Schmiedl Detlef , Müller-Schmehl Katrin
Published: May 2006

Annealing and heat-moisture treatment (HMT) are shown to be suitable methods to increase the yield of resistant starch type 3 (RS3) from Novelose 330 by up to 75%. Peak temperatures of approximately 121°C were used to produce to a sufficiently high thermal stability of the hydrothermal modified RS3 products for a wide range of applications. HMT significantly increased the crystallinity up to 40%.An in vivofeeding experiment with Wistar rats showed that fermentation of Novelose 330 dominated in the proximal colon, but degradation of HMT-Novelose was more dominant in the distal colon, leading to higher butyrate concentrations in this segment of the large bowel. Large-bowel surface and crypt length increased in the proximal colon in rats fed the Novelose 330-containing diet. In contrast, after the intake of HMT-Novelose, maximal values were found in the distal segment. The lower pH and higher butyrate concentration of the caecal and colonic contents significantlysuppressed the formation of secondary bile acids in RS3-fed rats. The formation of secondary bile acids was inhibited more strongly by HMT-Novelose than by Novelose 330. The Ki-67-immunopositive epithelial cells in the colon of RS3-fed rats indicated the establishment of an optimalbalance in the dynamic process of mucosal regeneration. HMT provides a method for the economical production of a high-quality RS3 with dominating prebiotic properties in the distal colon for health-promoting applications.
Soya isoflavone-enriched cereal bars affect markers of endothelial function in postmenopausal women
Authors: Hallund J. , Bügel S. , Tholstrup T. , Ferrari M. , Talbot D. , Hall W. L. , Reimann M. , Williams C.M. , Wiinberg N.
Published: May 2006

Soya isoflavones are thought to be cardioprotective due to their structural similarity to oestrogen. In order to investigate the effect of soya isoflavones on markers of endothelial function we conducted a randomised, double-blind, placebo-controlled, cross-over study with thirty healthy postmenopausal women. The women consumed cereal bars, with or without soya isoflavones (50mg/d), for 8 weeks, separated by an 8-week washout period. Systemic arterial complince (SAC), isobaric arterial compliance (IAC), flow-mediated endothelium-dependent vasodilation (FMD) and nitroglycerine-mediated endothelium-independent vasodilation (NMD) were measured at the beginning of the study and after each intervention period. Blood pressure (BP) and plasma concentrations of nitrite and nitrate (NOx) and endothelin-1 (ET-1) were measured at the beginning and end of each intervention period.NMD was 13·4 (sem 2·0) % at baseline and 15·5 (sem 1·1) % after isoflavone treatment compared with 12·4 (sem 1·0) % after placebo treatment (P=0·03). NOx increased from 27·7 (sem 2·7) to 31·1 (sem 3·2) μm after isoflavones treatment compared with 25·4 (sem 1·5) to 20·4 (sem 1·1) μm after placebo treatment (P=0·003) and a significant increase in the NOx:ET-1 ratio (P=0·005) was observed after the isoflavone treatment compared with placebo. A significant difference in SAC after the isoflavone and placebo treatment was observed (P=0·04). No significant difference was found in FMD, IAC, BP and ET-1. In conclusion, 8 weeks' consumption of cereals bars enriched with 50mg soya isoflavones/d increased plasma NOx concentrations and improved endothelium-independent vasodilation in healthy postmenopausal women.
Genistein modulates the effects of parathyroid hormone in human osteoblastic SaOS-2 cells
Authors: Chen Wen-Fang , Wong Man-Sau
Published: May 2006

Genistein and parathyroid hormone (PTH) are anabolic agents that stimulate bone formation through their direct actions in osteoblastic cells. In the present study, we aimed to determinewhether genistein modulates the actions of PTH in human osteoblastic SaOS-2 cells in an oestrogen-depleted condition. The present results showed that genistein (10−8to 10−6m) induced alkaline phosphatase (ALP) activity and osteoprotegrin (OPG) expression in SaOS-2 cells in a dose-dependent manner. These effects could be completely abolished by co-treatment with oestrogen antagonist ICI 182780 (7α-[9-[(4,4,5,5,5-pentafluoropentyl)sulfonyl]nonyl]-estra-1,3,5(10)-triene-3,17β-diol). Genistein (at 1μm) could stimulate the mRNA expression of receptor activator of NF-κB ligand (RANKL). As OPG and RANKL are known to modulate osteoclastogenesis, the ability of genistein to modulate OPG and RANKL expression in SaOS-2 cells suggested that it might modulate osteoclastogenesis through its direct actions on osteoblastic cells. PTH (at 10nm) stimulated ALP activity, induced RANKL mRNA expression and suppressed OPG mRNA expression in SaOS-2 cells, confirming its bi-directional effects on osteoblastic cells. Pre-treatment of SaOS-2 cells with genistein andoestrogen not only enhanced PTH-induced ALP activity, but also attenuated PTH up regulation ofRANKL mRNA expression and PTH down regulation of OPG mRNA expression. Taken together, the present study provides the first evidence that genistein could modulate the actions of PTH in human osteoblastic SaOS-2 cells in an oestrogen-depleted condition.
Previous feeding level influences plateau heat production following a 24 h fast in growing pigs
Authors: de Lange Kees , van Milgen Jaap , Noblet Jean , Dubois Serge , Birkett Stephen
Published: May 2006

Factorial approaches to estimate energy requirements of growing pigs require estimation of maintenance energy requirements. Heat production (HP) during fasting (FHP) may provide an estimate of maintenance energy requirements. Six barrows were used to determine effects of feedinglevel on components of HP, including extrapolated plateau HP following a 24h fast (FHPp). Based on a cross-over design, each pig was exposed to three feeding levels (1·55, 2·05 and 2·54MJ metabolisable energy/kg body weight (BW)0·60 per d) between 30 and 90kg BW. Following a 14d adaptation period, HP wasestimated using indirect calorimetry on pigs housed individually. Dynamics of HP were recordedin pigs for 5d during the fed state and during a subsequent 24h fast. Metabolisable energy intake was partitioned between thermal effect of feeding (HPf), activity HP (HPa), FHPp and energy retention. Feeding level influenced (P<0·05) total HP during the fed state, HPf and activity-free FHPp (609, 644 and 729 (se 31) kJ/kg BW0·60 per d for low, medium and high ME intakes, respectively). The value of FHPp when expressed per kg BW0·60 did not differ (P=0·34) between the three subsequent experimental periods. Feeding level did not (P=0·75) influence HPa. Regression of total HP during the fed state to zero metabolisable energy intake yielded a value of 489 (se 69) kJ/kg BW0·60 per d, which is a lower estimate ofmaintenanceenergy requirement than FHPp. Duration of adaptation of pigs to changes in feeding level and calculation methods should be considered when measuring or estimating FHPp, maintenance energy requirements and diet net energy content.
Nutrient–gene interactions in benefit–risk analysis
Authors: Hesketh John , Wybranska Iwona , Dommels Yvonne , King Maria , Elliott Ruan , Pico Catalina , Keijer Jaap
Published: May 2006

Individuals respond differently to nutrients and foods. This is reflected in different levels of benefits and risks at the same intake of a nutrient and, consequently, different ‘windows of benefit’ in terms of nutrient intake. This has led recently to the concept of ‘personalised nutrition’. Genetic factors such as single nucleotide polymorphisms may be one source of this inter-individual variation in benefit–risk response to nutrients. In 2004 a European Union-funded network of excellence in the area of nutrigenomics (European Nutrigenomics Organisation; NuGO) organised a workshop on the role of nutrient–gene interactions in determining benefit–risk of nutrients and diet. The major issues discussed at theworkshop are presented in the present paper and highlighted with examples from the presentations. The overall consensus was that although genetics provides a new vision where genetic information could in the future be used to provide knowledge on disease predisposition and nutritionalrequirements, such a goal is still far off and much more research is required before we can reliably include genetic factors in the risk–benefit assessment of nutrients and diets.