bluuebunny/crossref_metadata_2025 huggingface dataset:
Mistake proofing: changing designs to reduce error
Authors: Grout J R
Published: December 2006

Mistake proofing uses changes in the physical design of processes to reduce human error. It can be used to change designs in ways that prevent errors from occurring, to detect errors after they occur but before harm occurs, to allow processes to fail safely, or to alter the work environment to reduce the chance of errors. Effective mistake proofing design changes should initially be effective in reducing harm, be inexpensive, and easily implemented. Over time these design changes should make life easier and speed up the process. Ideally, the design changes should increase patients’ and visitors’ understanding of the process. These designs should themselves be mistake proofed and follow the good design practices of other disciplines.
2005 Alfred Bader Award Lecture Diaminopimelate and lysine biosynthesis - An antimicrobial target in bacteria
Authors: Vederas John C
Published: December 2006

The development of bacterial resistance to current antibiotic therapy has stimulated the search for novel antimicrobial agents. The essential peptidoglycan cell wall layer in bacteria is the site of action of many current drugs, such as β-lactams and vancomycin. It is also a target for a number of very potent bacterially produced antibiotic peptides, such as nisin A and lacticin 3147, both of which are highly posttranslationally modified lantibiotics that act by binding to lipid II, the peptidoglycan precursor. Another set of potential targets for antibiotic development are the bacterial enzymes that make precursors for lipid II and peptidoglycan, for example, those in the pathway to diamino pimelic acid (DAP) and its metabolic product, L-lysine. Among these, DAP epimerase is a unique nonpyridoxal phosphate (PLP) dependent enzyme that appears to use two active site thiols (Cys73 and Cys217) as a base and an acid to depro tonate the α-hydrogen of LL-DAP or meso-DAP from one side and reprotonate from the other. This process cannot be easily duplicated in the absence of the enzyme. A primary goal of our work was to generate inhibitors of DAP epi merase that would accurately mimic the natural substrates (meso-DAP and LL-DAP) in the enzyme active site and, through crystallographic analysis, provide insight into mechanism and substrate specificity. A series of aziridine-containing DAP analogs were chemically synthesized and tested as inhibitors of DAP epimerase from Haemophilus influenzae. Two diastereomers of 2-(4-amino-4-carboxybutyl)aziridine-2-carboxylic acid (AziDAP) act as rapid irreversible inactivators of DAP epimerase; the AziDAP analog of LL-DAP reacts selectively with the sulfhydryl of Cys73, whereas the corresponding analog of meso-DAP reacts with Cys217. AziDAP isomers are too unstable to be useful antibiotics. However, mass spectral and X-ray crystallographic analyses of the inactivated enzymes confirm that the thiol attacks the methylene group of the aziridine with concomitant ring opening to give a DAP analog bound in the active site. Further crystallographic analyses should yield useful mechanistic insights.Key words: enzyme mechanism, enzyme inhibition, antibiotics, aziridines, amino acids.
Synthesis and characterization of a series of novel phenol- and polyphenol-based glycerolipids
Authors: Schmidt Rolf , Carrigan Joseph G , DeWolf Christine E
Published: December 2006

A building block approach was used to design a modular synthetic route for the preparation of novel glycerolipids with phenolic and polyphenolic headgroups. Based on this scheme, it is possible to vary the substitution pattern of the headgroup, the stereochemistry of the backbone, and the length of the sidechains. Five glycerolipids with different headgroups and identical backbone stereochemistry and chain length have been prepared.Key words: glycerolipid, polyphenol, hydrogen bonding, lipid-protein interaction, self-adhering.
Synthesis of β-hydroxy dithiocarbamate derivatives via regioselective addition of dithiocarbamate anion to epoxide in water
Authors: Ziyaei-Halimjani Azim , Saidi Mohammad R
Published: December 2006

The reactions of different dithiocarbamate anions with epoxides were investigated in water. With this method, β-hydroxy dithiocarbamate derivatives were synthesized in high yields. The reaction was also carried out in DMF in the presence of lithium perchlorate with a simple work-up procedure, and the results are compared.Key words: hydroxy dithiocarbamate, dithiocarbamate anion, epoxide, water.
Medium effects on the α-effect in DMSO–H2O mixtures — Comparative studies ofp-nitrophenyl benzoate and acetate — Dissection of ground-state and transition-state effects
Authors: Um Ik-Hwan , Shin Young-Hee , Han Jeong-Yoon , Buncel Erwin
Published: December 2006

In a study of the origin of the α-effect and its dependence on the nature of the reaction medium as well as structural effects, we report herein a kinetic study of the reactions of p-nitrophenyl benzoate (PNPB) with butan-2,3-dione monoximate (Ox–, α-nucleophile) and p-chlorophenoxide (p-ClPhO–, the reference nucleophile) in dimethyl sulfoxide (DMSO)–H2O mixtures of varying compositions at 25.0 ± 0.1 °C. The second-order rate constants (kN) decrease modestly on addition of DMSO to the medium up to 10 mol% DMSO but increase significantly beyond that point for both nucleophiles. Ox–is more reactive than p-ClPhO–in all solvent mixtures studied (i.e., the α-effect). The α-effect increases as the DMSO content in the medium increases up to 40 mol% DMSO and then decreases beyond that point resulting in a bell-shaped α-effect profile. The bell-shaped α-effect profile obtained for the current reaction is similar to that found previously for the corresponding reaction of p-nitrophenyl acetate (PNPA), differing notably however, in the magnitude of the α-effect beyond 40 mol% DMSO. The PNPB/p-ClPhO–reaction gains greater rate enhancement than the PNPA/p-ClPhO–reaction in the DMSO-rich region, resulting in the smaller α-effect for PNPB beyond 40 mol% DMSO. It is proposed that the observed modulation of the α-effect by the solvent medium is explicable as a ground-state effect in the H2O-rich region and a transition-state effect in the DMSO-rich region.Key words: medium effect, the α-effect, ground state, transition state, solvation, desolvation.
ENTANGLEMENT, HAAG-DUALITY AND TYPE PROPERTIES OF INFINITE QUANTUM SPIN CHAINS
Authors: KEYL M. , MATSUI T. , SCHLINGEMANN D. , WERNER R. F.
Published: November 2006

We consider an infinite spin chain as a bipartite system consisting of the left and right half-chains and analyze entanglement properties of pure states with respect to this splitting. In this context, we show that the amount of entanglement contained in a given state is deeply related to the von Neumann type of the observable algebras associated to the half-chains. Only the type I case belongs to the usual entanglement theory which deals with density operators on tensor product Hilbert spaces, and only in this situation separable normal states exist. In all other cases, the corresponding state is infinitely entangled in the sense that one copy of the system in such a state is sufficient to distill an infinite amount of maximally entangled qubit pairs. We apply this results to the critical XY model and show that its unique ground state φS provides a particular example for this type of entanglement.
LINEAR SUPERPOSITION IN NONLINEAR WAVE DYNAMICS
Authors: BABIN A. , FIGOTIN A.
Published: November 2006

We study nonlinear dispersive wave systems described by hyperbolic PDE's in ℝdand difference equations on the lattice ℤd. The systems involve two small parameters: one is the ratio of the slow and the fast time scales, and another one is the ratio of the small and the large space scales. We show that a wide class of such systems, including nonlinear Schrodinger and Maxwell equations, Fermi–Pasta–Ulam model and many other not completely integrable systems, satisfy a superposition principle. The principle essentially states that if a nonlinear evolution of a wave starts initially as a sum of generic wavepackets (defined as almost monochromatic waves), then this wave with a high accuracy remains a sum of separate wavepacket waves undergoing independent nonlinear evolution. The time intervals for which the evolution is considered are long enough to observe fully-developed nonlinear phenomena for involved wavepackets. In particular, our approach provides a simple justification for numerically observed effect of almost non-interaction of solitons passing through each other without any recourse to the complete integrability. Our analysis does not rely on any ansatz or common asymptotic expansions with respect to the two small parameters but it uses rather explicit and constructive representation for solutions as functions of the initial data in the form of functional analytic series.
BISTABLE KINETIC MODEL DRIVEN BY AN INHOMOGENEOUS NOISE
Authors: AI BAO-QUAN , XIE HUI-ZHANG , WEN DE-HUA , LIU XUE-MEI , LIU LIANG-GANG
Published: November 2006

Steady state properties of a Brownian particle moving in a bistable kinetic system is investigated in the presence of an inhomogeneous noise. It is found that the inhomogeneous noise makes the system change from two-state system to one-state system, namely, the inhomogeneous noise can induce a phase transition. The particle will always move from a large intensity noise region to a small intensity region.
HIDDEN SYMMETRY AND QUANTUM PHASES IN SPIN-3/2 COLD ATOMIC SYSTEMS
Authors: WU CONGJUN
Published: November 2006

Optical traps and lattices provide a new opportunity to study strongly correlated high spin systems with cold atoms. In this article, we review the recent progress on the hidden symmetry properties in the simplest high spin fermionic systems with hyperfine spin F=3/2, which may be realized with atoms of 132 Cs , 9 Be , 135 Ba , 137 Ba , and 201 Hg . A generic SO(5) or isomorphically, Sp(4) symmetry is proved in such systems with the s-wave scattering interactions in optical traps, or with the on-site Hubbard interactions in optical lattices. Various important features from this high symmetry are studied in the Fermi liquid theory, the mean field phase diagram, and the sign problem in quantum Monte-Carlo simulations. In the s-wave quintet Cooper pairing phase, the half-quantum vortex exhibits the global analogue of the Alice string and non-Abelian Cheshire charge properties in gauge theories. The existence of the quartetting phase, a four-fermion counterpart of the Cooper pairing phase, and its competition with other orders are studied in one-dimensional spin-3/2 systems. We also show that counter-intuitively quantum fluctuations in spin-3/2 magnetic systems are even stronger than those in spin-1/2 systems.
ELECTRIC MODELS OF LARGE-SCALE SYSTEMS AND THEIR ANALOGY TO THERMODYNAMIC SYSTEMS
Authors: BERKOVICH Y. , GOLAN G.
Published: December 2006

The paper deals with electric models applied in the investigation of complex systems, such as transport, economic, and neuron systems. The increasing interest in such systems can be explained by the fact that they are characterized by parallel (collective) means of complex calculation processes, under the influence of inner information processes. Electric models can also be looked upon as original structures for neuron-like systems. The paper puts emphasis on comparison between the electric models suggested by the authors, on the one hand, and the mechanical and thermal models, on the other hand. It has been shown that entropy phenomena, typical for the latter, can be closely compared to those of electric models, which are distinguished by pure electric values. Also, it has been shown that irreversible processes of energy dissipation, e.g., entropy processes in mechanical models, are corresponded to processes of energy concentration, energy transfer, and/or energy exchange in electric models. This enables us to shed a new light on processes in electric circuit, especially those concerning with structural improvements of electric circuitry and their self-organization, meaning a neg-entropic information character of these processes. Models of two economic tasks have been considered, wherein the calculation process is characterized under the influence of these processes. Assumption on the importance of reactive elements such as carriers of neg-entropy in electric circuits was made as well.
INFLUENCE OF CORRELATED NOISES ON GROWTH OF A TUMOR IN A MODIFIED VERHULST MODEL
Authors: ZHONG WEI-RONG , SHAO YUAN-ZHI , HE ZHEN-HUI
Published: November 2006

We studied the effect of additive and multiplicative noises on the growth of a tumor based on a logistic growth model. The steady-state probability distribution and the average population of the tumor cells were given to explain the important roles of correlated noises in the tumor growth. We explored that multiplicative noise induces a phase transition of the tumor growth from a uni-stable state to a bi-stable state; the relationship between the intensity of multiplicative noise and the population of the tumor cells shows a stochastic resonance-like characteristic. It was also confirmed that additive noise weakened rather than extinguish the tumor growth. Homologous noises, however, promote the growth of a tumor. We also discussed about the relationship between the tumor treatment and the model.
Focal adhesion kinase mediates cell survival via NF-κB and ERK signaling pathways
Authors: Huang Danshan , Khoe Michelle , Befekadu Merone , Chung Sue , Takata Yasunori , Ilic Dusko , Bryer-Ash Michael
Published: November 2006

Focal adhesion kinase (FAK) is important to cellular functions such as proliferation, migration, and survival of anchorage-dependent cells. We investigated the role of FAK in modulating normal cellular responses, specifically cell survival in response to inflammatory stimuli and serum withdrawal, using FAK-knockout (FAK−/−) embryonic fibroblasts. FAK−/− fibroblasts were more vulnerable to TNF-α-induced apoptosis, as measured by terminal deoxynucleotidyl transferase positivity. FAK−/− fibroblasts also demonstrated increased procaspase-3 cleavage to p17 subunit, whereas this was undetectable in FAK+/+ fibroblasts. Insulin receptor substrate-1 expression was completely abolished and NF-κB activity was reduced, with a concomitant decrease in abundance of the anti-apoptotic protein Bcl-xL in FAK−/− cells. Upon serum withdrawal, FAK+/+ cells exhibited marked attenuation of basal ERK phosphorylation, while FAK−/− cells, in contrast, maintained high basal ERK phosphorylation. Moreover, inhibition of ERK phosphorylation potentiated serum withdrawal-induced caspase-3 activity. This was paralleled by increased insulin receptor substrate (IRS)-2 expression in FAK−/− cells, although both insulin- and IGF-1-mediated phosphorylation of Akt/PKB and GSK-3 were impaired. This suggests that IRS-2 protects against apoptosis upon serum withdrawal via the ERK signaling pathway. The specific role of FAK to protect cells from apoptosis is regulated by activation and phosphorylation of NF-κB and interaction between activated growth factor anti-apoptotic signaling pathways involving both phosphatidylinositol 3-kinase/Akt and MAPK/ERK1/2. We demonstrate that FAK is necessary for upregulation of the anti-apoptotic NF-κB response, as well as for normal expression of growth factor signaling proteins. Thus we propose a novel role for FAK in protection from cytokine-mediated apoptosis.
Regulation of the human biotin transporter hSMVT promoter by KLF-4 and AP-2: confirmation of promoter activity in vivo
Authors: Reidling Jack C. , Said Hamid M.
Published: November 2006

The mechanism of biotin uptake in human intestine has been well characterized and involves the human sodium-dependent multivitamin transporter (hSMVT), yet little is known about the molecular/transcriptional regulation of the system. Previous investigations cloned the 5′ regulatory region of the hSMVT gene and identified the minimal promoter. To expand these investigations, we compared activity of the hSMVT promoter in three human intestinal epithelial cell lines (NCM460, Caco-2, and HuTu-80) and contrasted a renal epithelial cell line (HEK-293). We analyzed the role of putative cis-elements in regulating promoter activity and confirmed activity of the cloned hSMVT promoter in vivo. In vitro studies demonstrated that all cell lines utilized the same minimal promoter region, and mutation of specific cis-regulatory elements [Kruppel-like factor 4 (KLF-4) and activator protein-2 (AP-2)] led to a decrease in promoter activity in all intestinal cell types but not in renal cells. Using electrophoretic mobility shift assays, we identified two specific DNA/protein complexes. Using oligonucleotide competition and antibody supershift analysis, we determined that KLF-4 and AP-2 were involved in forming the complexes. In HEK-293 cells, overexpressing KLF-4 increased the endogenous hSMVT message levels threefold and activated a cotransfected hSMVT promoter-reporter construct. In vivo studies using hSMVT promoter-luciferase transgenic mice established physiological relevance and showed the pattern of hSMVT promoter expression to be similar to endogenous mouse SMVT mRNA expression. The results demonstrate, for the first time, the importance of KLF-4 and AP-2 in regulating the activity of the hSMVT promoter in the intestine and provide direct in vivo confirmation of hSMVT promoter activity.
Oligomeric structure of the neutral amino acid transporters KAAT1 and CAATCH1
Authors: Bossi Elena , Soragna Andrea , Miszner Andreea , Giovannardi Stefano , Frangione Valeria , Peres Antonio
Published: November 2006

The highly homologous neutral amino acid transporters KAAT1 and CAATCH1, cloned from the midgut epithelium of the Manduca sexta larva, are members of the Na+/Cl−-dependent transporter family. Recent evidence indicates that transporters of this family form constitutive oligomers. CAATCH1 and KAAT1 give rise to specific kinds of current depending on the transported amino acid, cotransported ion, pH, and membrane voltage. Different substrates induce notably distinct transport-associated currents in the two proteins that represent useful tools in structural-functional studies. To determine whether KAAT1 and CAATCH1 form functional oligomers, we have constructed four concatameric proteins for electrophysiological analysis, consisting of one KAAT1 protein covalently linked to another KAAT1 (K-K concatamer) or to CAATCH1 (K-C concatamer) and vice versa (C-C concatamer and C-K concatamer), and eight constructs where the two transporters were linked to yellow or cyan fluorescent protein in the NH2 or COOH terminus, to determine the oligomer formation and the relative distance between the different subunits by fluorescence resonance energy transfer (FRET) analysis. Heterologous expression of the concatenated constructs and coinjection of the original proteins in different proportions allowed us to compare the characteristics of the currents to those of the oocytes expressing only the wild-type proteins. All the constructs were fully active, and their electrophysiological behavior was consistent with the activity as monomeric proteins. However, the FRET studies indicate that these transporters form oligomers in agreement with the LeuTAa atomic structure and confirm that the COOH termini of the adjacent subunits are closer than NH2 termini.
High salt intake reduces endothelium-dependent dilation of mouse arterioles via superoxide anion generated from nitric oxide synthase
Authors: Nurkiewicz Timothy R. , Boegehold Matthew A.
Published: November 2006

In skeletal muscle arterioles of normotensive rats fed a high salt diet, the bioavailability of endothelium-derived nitric oxide (NO) is reduced by superoxide anion. Because the impact of dietary salt on resistance vessels in other species is largely unknown, we investigated endothelium-dependent dilation and oxidant activity in spinotrapezius muscle arterioles of C57BL/6J mice fed normal (0.45%, NS) or high salt (7%, HS) diets for 4 wk. Mean arterial pressure in HS mice was not different from that in NS mice, but the magnitude of arteriolar dilation in response to different levels of ACh was 42–57% smaller in HS mice than in NS mice. Inhibition of nitric oxide synthase (NOS) with NG monomethyl l-arginine (l-NMMA) significantly reduced resting diameters and reduced responses to ACh (by 45–63%) in NS mice but not in HS mice. Arteriolar wall oxidant activity, as assessed by tetranitroblue tetrazolium reduction or hydroethidine oxidation, was greater in HS mice than in NS mice. Exposure to the superoxide scavenger 2,2,6,6-tetramethylpiperidine- N-oxyl (TEMPO) + catalase reduced this oxidant activity to normal and restored normal arteriolar responsiveness to ACh in HS mice but had no effect in NS mice. l-NMMA also restored arteriolar oxidant activity to normal in HS mice. ACh further increased arteriolar oxidant activity in HS mice but not in NS mice, and this effect was prevented with l-NMMA. These data suggest that a high salt diet promotes increased generation of superoxide anion from NOS in the murine skeletal muscle microcirculation, thus impairing endothelium-dependent dilation through reduced NO bioavailability.
Effects of heterogeneities on the partitioning of airway and tissue properties in normal mice
Authors: Ito Satoru , Lutchen Kenneth R. , Suki Béla
Published: November 2006

We measured the mechanical properties of the respiratory system of C57BL/6 mice using the optimal ventilation waveform method in closed- and open-chest conditions at different positive end-expiratory pressures. The tissue damping (G), tissue elastance (H), airway resistance (Raw), and hysteresivity were obtained by fitting the impedance data to three different models: a constant-phase model by Hantos et al. (Hantos Z, Daroczy B, Suki B, Nagy S, Fredberg JJ. J Appl Physiol 72: 168–178, 1992), a heterogeneous Raw model by Suki et al. (Suki B, Yuan H, Zhang Q, Lutchen KR. J Appl Physiol 82: 1349–1359, 1997), and a heterogeneous H model by Ito et al. (Ito S, Ingenito EP, Arold SP, Parameswaran H, Tgavalekos NT, Lutchen KR, Suki B. J Appl Physiol 97: 204–212, 2004). Both in the closed- and open-chest conditions, G and hysteresivity were the lowest and Raw the highest in the heterogeneous Raw model, and G and H were the largest in the heterogeneous H model. Values of G, Raw, and hysteresivity were significantly higher in the closed-chest than in the open-chest condition. However, H was not affected by the conditions. When the tidal volume of the optimal ventilation waveform was decreased from 8 to 4 ml/kg in the closed-chest condition, G and hysteresivity significantly increased, but there were smaller changes in H or Raw. In summary, values of the obtained mechanical properties varied among these models, primarily due to heterogeneity. Moreover, the mechanical parameters were significantly affected by the chest wall and tidal volume in mice. Contribution of the chest wall and heterogeneity to the mechanical properties should be carefully considered in physiological studies in which partitioning of airway and tissue properties are attempted.
Combined Activation and Deactivation of Visual Cortex During Tactile Sensory Processing
Authors: Merabet Lotfi B. , Swisher Jascha D. , McMains Stephanie A. , Halko Mark A. , Amedi Amir , Pascual-Leone Alvaro , Somers David C.
Published: November 2006

The involvement of occipital cortex in sensory processing is not restricted solely to the visual modality. Tactile processing has been shown to modulate higher-order visual and multisensory integration areas in sighted as well as visually deprived subjects; however, the extent of involvement of early visual cortical areas remains unclear. To investigate this issue, we employed functional magnetic resonance imaging in normally sighted, briefly blindfolded subjects with well-defined visuotopic borders as they tactually explored and rated raised-dot patterns. Tactile task performance resulted in significant activation in primary visual cortex (V1) and deactivation of extrastriate cortical regions V2, V3, V3A, and hV4 with greater deactivation in dorsal subregions and higher visual areas. These results suggest that tactile processing affects occipital cortex via two distinct pathways: a suppressive top-down pathway descending through the visual cortical hierarchy and an excitatory pathway arising from outside the visual cortical hierarchy that drives area V1 directly.
Endogenous mGluR Activity Suppresses GABAergic Transmission in Avian Cochlear Nucleus Magnocellularis Neurons
Authors: Lu Yong
Published: November 2006

GABAergic transmission in the avian cochlear nucleus magnocellularis (NM) of the chick is subject to modulation by γ-aminobutyric acid type B (GABAB) autoreceptors. Here, I investigated modulation of GABAergic transmission in NM by metabotropic glutamate receptors (mGluRs) with whole cell recordings in brain slice preparations. I found that tACPD, a nonspecific mGluR agonist, exerted dose-dependent suppression on evoked inhibitory postsynaptic currents (eIPSCs) in NM neurons. At concentrations of 100 or 200 μM, tACPD increased the failure rate of GABAergic transmission. Agonists for group I (3,5-DHPG, 200 μM), group II (DCG-IV, 2 μM), and group III (L-AP4, 10 μM) mGluRs produced a significant reduction in the amplitude of eIPSCs and a significant increase in failure rate, indicating the involvement of multiple mGluRs in this modulation. The frequency, but not the amplitude, of miniature IPSCs (mIPSCs) was decreased significantly by 3,5-DHPG or DCG-IV. Neither frequency nor amplitude of mIPSCs was affected by L-AP4. mGluR antagonists LY341495 (20 μM) plus CPPG (10 μM) significantly increased the amplitude of eIPSCs, indicating that endogenous mGluR activity suppresses GABA release to NM neurons. Furthermore, blockage of mGluRs increased GABA-evoked discharges recorded under physiological Cl−concentrations, whereas tACPD (100 μM) eliminated them. The results indicate that mGluRs play important roles in achieving balanced excitation and inhibition in NM and preserving fidelity of temporal information encoded by NM neurons.
Intracellular Recording Reveals Temporal Integration in Inferior Colliculus Neurons of Awake Bats
Authors: Voytenko S. V. , Galazyuk A. V.
Published: November 2006

The central nucleus of the inferior colliculus (IC) is a major integrative center in the central auditory system. It receives information from both the ascending and descending auditory pathways. To determine how single IC neurons integrate information over a wide range of sound frequencies and sound levels, we examined their intracellular responses to frequency-modulated (FM) sounds in awake little brown bats ( Myotis lucifugus). Postsynaptic potentials were recorded in response to downward FM sweeps of the range typical for little brown bats (80–20 kHz) and to three FM subcomponents (80–60, 60–40, and 40–20 kHz). The majority of recorded neurons responded to the 80- to 20-kHz downward FM sweep with a complex response. In this response an initial hyperpolarization was followed by depolarization with or without spike followed by hyperpolarization. Intracellular recordings in response to three FM subcomponents revealed that these neurons receive excitatory and inhibitory inputs from a wide range of sound frequencies. One third of IC neurons performed nearly linear temporal summation across a wide range of sound frequencies, whereas two thirds of IC neurons exhibited nonlinear summation with different degrees of nonlinearity. Some IC neurons showed different latencies of postsynaptic potentials in response to different FM subcomponents. Often responses to the later FM subcomponent occurred before responses to the earlier ones. This phenomenon may be responsible for response selectivity of IC neurons to FM sweeps.
Online Maintenance of Sensory and Motor Representations: Effects on Corticospinal Excitability
Authors: van den Hurk Paul , Mars Rogier B. , van Elswijk Gijs , Hegeman Judith , Pasman Jaco W. , Bloem Bastiaan R. , Toni Ivan
Published: November 2006

Flexible behavior requires the ability to delay a response until it is appropriate. This can be achieved by holding either a sensory or a motor representation online. Here we assess whether maintenance of sensory or motor material drives the motor system to different functional states, as indexed by alterations of corticospinal excitability. We used single-pulse TMS to measure corticospinal excitability evoked during the delay period of a novel paradigm in which task contingencies, rather than explicit verbal instructions, induced participants to use either sensory or motor codes to solve a delay-nonmatch-to-sample (DNMS) task. This approach allowed us to probe the state of the motor system while the participants were retaining either sensory or motor codes to cross the delay period, rather than the control of short-term storage driven by verbal instructions. When participants could prepare the movement in advance (preparation trials), the excitability of the motor cortex contralateral to the moving hand increased, whereas the excitability of the ipsilateral motor cortex decreased. The increase in excitability was confined to the prime mover, whereas the decrease in excitability extended to cortical territories controlling muscles unrelated to the response. Crucially, these changes in excitability were evoked only during preparation trials and not during trials in which subjects needed to maintain sensory items online (memory trials). We infer that short-term storage of sensory information and preparation of motor responses have differential and specific access to the output stage of the motor system.
Resonance or Integration? Self-Sustained Dynamics and Excitability of Neural Microcircuits
Authors: Muresan Raul C. , Savin Cristina
Published: November 2006

We investigated spontaneous activity and excitability in large networks of artificial spiking neurons. We compared three different spiking neuron models: integrate-and-fire (IF), regular-spiking (RS), and resonator (RES). First, we show that different models have different frequency-dependent response properties, yielding large differences in excitability. Then, we investigate the responsiveness of these models to a single afferent inhibitory/excitatory spike and calibrate the total synaptic drive such that they would exhibit similar peaks of the postsynaptic potentials (PSP). Based on the synaptic calibration, we build large microcircuits of IF, RS, and RES neurons and show that the resonance property favors homeostasis and self-sustainability of the network activity. On the other hand, integration produces instability while it endows the network with other useful properties, such as responsiveness to external inputs. We also investigate other potential sources of stable self-sustained activity and their relation to the membrane properties of neurons. We conclude that resonance and integration at the neuron level might interact in the brain to promote stability as well as flexibility and responsiveness to external input and that membrane properties, in general, are essential for determining the behavior of large networks of neurons.
Modulation of Serotonergic Neurotransmission by Nitric Oxide
Authors: Straub Volko A. , Grant James , O'Shea Michael , Benjamin Paul R.
Published: November 2006

Nitric oxide (NO) and serotonin (5-HT) are two neurotransmitters with important roles in neuromodulation and synaptic plasticity. There is substantial evidence for a morphological and functional overlap between these two neurotransmitter systems, in particular the modulation of 5-HT function by NO. Here we demonstrate for the first time the modulation of an identified serotonergic synapse by NO using the synapse between the cerebral giant cell (CGC) and the B4 neuron within the feeding network of the pond snail Lymnaea stagnalis as a model system. Simultaneous electrophysiological recordings from the pre- and postsynaptic neurons show that blocking endogenous NO production in the intact nervous system significantly reduces the B4 response to CGC activity. The blocking effect is frequency dependent and is strongest at low CGC frequencies. Conversely, bath application of the NO donor DEA/NONOate significantly enhances the CGC-B4 synapse. The modulation of the CGC-B4 synapse is mediated by the soluble guanylate cyclase (sGC)/cGMP pathway as demonstrated by the effects of the sGC antagonist 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). NO modulation of the CGC-B4 synapse can be mimicked in cell culture, where application of 5-HT puffs to isolated B4 neurons simulates synaptic 5-HT release. Bath application of diethylamine NONOate (DEA/NONOate) enhances the 5-HT induced response in the isolated B4 neuron. However, the cell culture experiment provided no evidence for endogenous NO production in either the CGC or B4 neuron suggesting that NO is produced by an alternative source. Thus we conclude that NO modulates the serotonergic CGC-B4 synapse by enhancing the postsynaptic 5-HT response.
Contextual Effects on Smooth-Pursuit Eye Movements
Authors: Spering Miriam , Gegenfurtner Karl R.
Published: November 2006

Segregating a moving object from its visual context is particularly relevant for the control of smooth-pursuit eye movements. We examined the interaction between a moving object and a stationary or moving visual context to determine the role of the context motion signal in driving pursuit. Eye movements were recorded from human observers to a medium-contrast Gaussian dot that moved horizontally at constant velocity. A peripheral context consisted of two vertically oriented sinusoidal gratings, one above and one below the stimulus trajectory, that were either stationary or drifted into the same or opposite direction as that of the target at different velocities. We found that a stationary context impaired pursuit acceleration and velocity and prolonged pursuit latency. A drifting context enhanced pursuit performance, irrespective of its motion direction. This effect was modulated by context contrast and orientation. When a context was briefly perturbed to move faster or slower eye velocity changed accordingly, but only when the context was drifting along with the target. Perturbing a context into the direction orthogonal to target motion evoked a deviation of the eye opposite to the perturbation direction. We therefore provide evidence for the use of absolute and relative motion cues, or motion assimilation and motion contrast, for the control of smooth-pursuit eye movements.
Long-Term Depression in Identified Stellate Neurons of Juvenile Rat Entorhinal Cortex
Authors: Deng Pan-Yue , Lei Saobo
Published: November 2006

The entorhinal cortex (EC) serves as a gateway to the hippocampus and plays a pivotal role in memory processing in the brain. Superficial layers of the EC convey the cortical input projections to the hippocampus, whereas deep layers of the EC relay hippocampal output projections back to the superficial layers of the EC or to other cortical regions. Whereas the EC expresses long-term potentiation (LTP) and depression (LTD), the underlying cellular and molecular mechanisms have not been determined. Because the axons of the stellate neurons in layer II of the EC form the perforant path that innervates the dentate gyrus granule cells of the hippocampus, we studied the mechanisms underlying the long-term plasticity in identified stellate neurons. Application of high-frequency stimulation (100 Hz for 1 s, repeated 3 times at an interval of 10 s) or forskolin (50 μM) failed to induce significant changes in synaptic strength, whereas application of pairing (presynaptic stimulation at 0.33 Hz paired with postsynaptic depolarization from −60 to −10 mV for 5 min) or low-frequency stimulation (LFS, 1 Hz for 15 min) paradigm-induced LTD. Pairing- or LFS-induced LTDs were N-methyl-d-aspartate receptor-dependent and occluded each other suggesting that they have the similar cellular mechanism. Pairing-induced LTD required the activity of calcineurin and involved AMPA receptor endocytosis that required the function of ubiquitin–proteasome system. Our study provides a cellular mechanism that might in part explain the role of the EC in memory.
Powder X-ray diffraction study of synthetic PdSn
Authors: Laufek František , Vymazalová Anna , Laufek František , Plášil Jakub
Published: November 2006

Improved X-ray powder diffraction data for synthetic PdSn are reported. Powder diffraction data were collected with a laboratory X-ray source (CuKα) for Rietveld refinement. Refined crystallographic data for PdSn (orthorhombic, Pnma) are a=6.1388(4), b=3.89226(3), c=6.3377(4) Å, V=151.43(2) Å3, Z=4, and Dx=9.87 g∕cm3.
Capillaries prepared from thin-walled heat-shrink poly(ethylene terephthalate) (PET) tubing for X-ray powder diffraction analysis
Authors: Reibenspies Joseph H. , Bhuvanesh Nattamai
Published: November 2006

Thin-walled heat-shrink poly(ethylene terephthalate) (PET) tubing is reported for use as an alternative for glass and Kapton® capillaries. PET tubing displays properties such as low X-ray absorption and smooth diffraction profiles. The 2.0 mm thin-walled (0.05 mm thick) and 0.5 mm thin-walled (0.02 mm thick) heat-shrink PET capillaries are 86% and 96% transparent to 1.54 Å X-rays. The low X-ray absorption and relatively smooth X-ray scattering profile of PET make it an ideal material for the home laboratory where the long wavelength, low flux, and low brilliance X-ray sources are employed. PET capillaries can be easily cut and manipulated and fixed to copper pins, which in turn can be employed in low-temperature and automated data collection routines.
Implications of the solubility of trivalent lanthanides in AAl2O4 (A=Ca, Sr, and Ba) for their role in phosphors
Authors: Saines Paul J. , Kennedy Brendan J.
Published: November 2006

The technique of standard addition in combination with powder X-ray diffraction was used to identify and quantify the amount of Ln3+ segregating into secondary phases from Ln3+doped alkaline earth aluminates. Results indicate that Ln3+ ions are more soluble in CaAl2O4 than SrAl2O4 and BaAl2O4, with this being rationalized by the structural details of the A sites. These results indicate that the enhancement of the luminescence afterglow obtained by doping AAl2O4:Eu2+ samples with Ln3+ ions is a result of much lower doping levels than previously thought.
Powder X-ray diffraction and Rietveld analysis of La1−xBaxCoO3 (0<x≤0.5)
Authors: Luo Wanju , Wang Fangwei
Published: November 2006

Detailed structural properties of La1−xBaxCoO3 (LBCO) have been investigated by means of X-ray powder diffraction and Rietveld analysis. A structural phase transformation from R3c to Pm3m at x=0.30–0.35 has been detected based on a comparison between the refinements of R3c and Pm3m. The Co–O bond length of the CoO6 octahedron expanded rapidly with increasing Ba content when x<0.1, and then it leveled off and kept constant at 0.1⩽x⩾0.35, where the Co–O–Co bond angle reaches 180°. The Co–O bond length expansion resumed with increasing Ba content beyond x=0.35.
Quantification of phases with partial or no known crystal structures
Authors: Scarlett Nicola V. Y. , Madsen Ian C.
Published: November 2006

Quantification of mixtures via the Rietveld method is generally restricted to crystalline phases for which structures are well known. Phases that have not been identified or fully characterized may be easily quantified as a group, along with any amorphous material in the sample, by the addition of an internal standard to the mixture. However, quantification of individual phases that have only partial or unknown structures is carried out less routinely. This paper presents methodology for quantification of such phases. It outlines the procedure for calibration of the method and gives detailed examples from both synthetic and mineralogical systems. While the method should, in principle, be generally applicable, its implementation in the TOPAS program from Bruker AXS is demonstrated here.
An easy to use X-ray collimator for Mao-Bell type diamond anvil cell
Authors: Sahu P. Ch. , Kumar N. R. Sanjay , Shekar N. V. Chandra , Subramanian N.
Published: November 2006

An incident beam X-ray collimator for Mao-Bell type diamond anvil cell (DAC) has been developed. Alignment of the collimator is carried outin situwhile viewing the image of the collimated X-ray spot formed on a thin layer of fluorescent material spread on the diamond anvil culets with the help of a microscope. Special precaution has been taken to meet the radiation safety requirements during alignment and routine use. This collimator is of immense help for laboratory based high pressure X-ray diffraction experiments.
Powder diffraction investigations of some organic hydrochlorides
Authors: Lasocha B. , Gawel B. , Lasocha W.
Published: November 2006

Amantadine hydrochloride, p-aminophenol hydrochloride, and methylamine hydrochloride, compounds often studied in pharmacology, were investigated by means of powder diffractometry. The chemical formula of the first compound is C10H17N HCl and crystallizes in the monoclinic system, space group C2∕c (15) with lattice parameters a=2.0279(6) nm, b=1.1171(2) nm, c=9.759(4) nm, and β=109.00(3)°. p-Aminophenol hydrochloride C6H7NO HCl crystallizes in the orthorhombic system, space group P222 with lattice parameters a=0.6619(2) nm, b=0.88461(2) nm, and c=0.6101(2) nm. Methylamine hydrochloride CH5N∙HCl crystallizes in the tetragonal system, space group P4∕nmm (129) with lattice parameters a=b=0.6068(1) nm and c=0.50689(8) nm.
Urinary Mineral Excretion in Preterm Neonates during the First Month of Life
Authors: Giapros Vasileios I. , Papaloukas Athanasios L. , Andronikou Styliani K.
Published: December 2006

Background: Estimation of urinary parameters in preterm infants is a useful method for identifying metabolic derangements. Objectives: A prospective, longitudinal, hospital-based study was designed to examine the variability and the associations in renal excretion of calcium (Ca), magnesium (Mg), phosphate (P) and sodium (Na) in formula-fed preterm infants during the first month of life. Patients: Thirty-four infants <32 weeks gestational age, clinically stable, not receiving nephrotoxic drugs. Methods: Measurements of serum and 8-hour urinary mineral and creatinine (Cr) concentrations were made in all infants during three periods (at 7–10, 14–17 and 21–26 days postnatally). The urinary parameters, FENa, FEP, UCa/UCr, UMg/UCr were calculated. 24- hour urinary excretion was estimated by extrapolation of the 8-hour values. Results: The 24-hour excretion values (median and range) (mmol/kg) during the three study periods were, respectively, for Ca: 0.027 (0.015–0.15), 0.030 (0.007–0.12), 0.031 (0.008–0.12), for P: 0.26 (0.07–0.83), 0.29 (0.06–0.67), 0.41 (0.22–0.70), for Mg: 0.025 (0.007–0.14), 0.025 (0.008–0.16), 0.027 (0.010–0.10) and for Na: 2.85 (0.8–15), 1.45 (0.3–17), 1.56 (0.6–4.3). Na excretion declined while the excretion of the other minerals remained stable. A positive correlation was observed between excretion of Ca, Mg and Na (Ca vs. Na r = 0.63, p < 0.0001; Ca vs. Mg r = 0.65, p < 0.0001; Na vs. Mg r = 0.38, p = 0.012) as well as between the renal parameters FENa, FEP, UCa/UCr, UMg/UCr and the respective 24-hour excretion values (r = 0.80, 0.86, 0.84, 0.81) Conclusions: Urinary excretion of Ca, P, and Mg in preterm formula-fed infants is stable during the first month of life while urinary Ca, Na and Mg are closely correlated during the same period.
A Patient with Progressive Multiple Myeloma Treated Successfully with Arsenic Trioxide after Allogeneic Bone Marrow Transplantation
Authors: Gesundheit B. , Shapira M.Y. , Ackerstein A. , Resnik I.B. , Bitan M. , Or R.
Published: December 2006

Multiple myeloma (MM) is an incurable progressive disease. Many therapeutic options are available to delay progression, including autologous and allogeneic bone marrow transplantation. At advanced stages, MM is often refractory to treatment. We report a heavily pretreated patient with graft-versus-host disease after bone marrow transplantations, treated at a terminal stage with a modified protocol for arsenic trioxide (ATO). This patient with poor clinical status tolerated the treatment very well. He had a remarkable clinical response and achieved complete remission. The mechanisms of ATO are presented and the potential role of ATO for MM is discussed.
Renal Cell Carcinoma in Children: Experience of a Single Center
Authors: Varan Ali , Akyüz Canan , Sarı Neriman , Büyükpamukçu Nebil , Çağlar Melda , Büyükpamukçu Münevver
Published: December 2006

Objective: To evaluate the clinical features and outcome of children withrenal cell carcinoma (RCC). Patients and Methods: Eleven patients with RCC who were diagnosed between 1972 and 2004 were retrospectively analyzed. Clinical features, histopathology, treatment regimens and outcomes of the patients were evaluated. Results: The male/female ratio was 3:8, with a median age of 10 years. The stage distribution was as follows: 3 patients in stage I, 1 patient in stage II, 3 patients in stage IIIb, and 4 patients in stage IV. Five of 7 patients with stage II-IV received an actinomycin D-based regimen, one received a cisplatin-based regimen, and the other was given 5-fluorouracil (5-FU). In the last patient, interferon-α was given in combination with 5-FU; 1 of the patients on the actinomycin D regimen received interferon-α as well. All of the stage I patients are alive without disease. Three patients with stage IIIb, stage IV and stage II disease are alive without disease 8, 14 and 26 years after their diagnosis, respectively. The other stage IV and stage IIIb patients died of the disease. Conclusion: Nephroureterectomy is the main treatment modality, and it is sufficient for stage I patients. For patients with stage II-IV RCC, interferon-α and/or actinomycin D-based chemotherapy is the treatment of choice.
Prevalence and Severity of Anaemia in Patients with Type 2 Diabetic Nephropathy and Different Degrees of Chronic Renal Insufficiency
Authors: Li Vecchi Maurizio , Fuiano Giorgio , Francesco Marino , Mancuso Domenico , Faga Teresa , Sponton Andrea , Provenzano Rossana , Andreucci Michele , Tozzo Carmela
Published: December 2006

Background/Aim: Type 2 diabetes mellitus is the single most common cause of chronic kidney disease (CKD); however its real impact on renal anaemia has not been established. The aim of this study was to evaluate whether onset, severity, and prevalence of anaemia during the course of CKD is different between type 2 diabetic and non-diabetic patients. Methods: We enrolled 281 patients with: (1) type 2 diabetes and no CKD (n = 75); (2) type 2 diabetes plus CKD (n = 106), and (3) CKD without type 2 diabetes (n = 100). According to K/DOQI guidelines, the patients with renal insufficiency (i.e., those with a glomerular filtration rate <60 ml/min) were subgrouped into three tertiles of CKD: (1) stage 3 (creatinine clearance 60–30 ml/min); (2) stage 4 (creatinine clearance 29–15 ml/min), and (3) stage 5 (creatinine clearance <15 ml/min). Results: Anaemia was observed in 16% of the diabetic patients without CKD; it was more frequent in the diabetic patients with CKD than in the non-diabetic patients with CKD (61.7 vs. 52%, p < 0.05). The comparison among the tertiles showed that the prevalence of anaemia was significantly higher only in diabetic CKD patients of stages 4 and 5. The prevalence was higher in females independently of type 2 diabetes mellitus. In diabetics with a normal renal function, the haemoglobin levels were higher than in diabeticsand non-diabetics with CKD, but the diabetics showed lower levels of haemoglobin than non-diabetics at stage 3 and stage 4 of CKD. Conclusions: Diabetic patients with CKD of stages 4 and 5 have a higher prevalence of anaemia than non-diabetic patients with comparable glomerular filtration rate. A higher awareness of this risk will allow earlier diagnosis and treatment.