bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum fluctuation of electronic wave-packet dynamics coupled with classical nuclear motions
Authors: Amano Michiko , Takatsuka Kazuo
Published: February 2005

An ab initio electronic wave-packet dynamics coupled with the simultaneous classical dynamics of nuclear motions in a molecule is studied. We first survey the dynamical equations of motion for the individual components. Reflecting the nonadiabatic dynamics that electrons can respond to nuclear motions only with a finite speed, the equations of motion for nuclei include a force arising from the kinematic (nuclear momentum) coupling from electron cloud. To materialize these quantum effects in the actual ab initio calculations, we study practical implementation of relevant electronic matrix elements that are related to the derivatives with respect to the nuclear coordinates. Applications of the present scheme are performed in terms of the configuration state functions (CSF) using the canonical molecular orbitals as basis functions without transformation to particular diabatic basis. In the CSF representation, the nonadiabatic interaction due to the kinematic coupling is anticipated to be rather small, and instead it should be well taken into account through the off-diagonal elements of the electronic Hamiltonian matrix. Therefore it is expected that the nonadiabatic dynamics based on this CSF basis neglecting the kinematic coupling may work. To verify this anticipation and to quantify the actual effects of the kinematic coupling, we compare the dynamics with and without the kinematic-coupling terms using the same CSF set. Applications up to the fifth electronically excited states in a nonadiabatic collision between H2 and B+ shows that the overall behaviors of these two calculations are surprisingly similar to each other in an average sense except for a fast fluctuation reflecting the electronic time scale. However, at the same time, qualitative differences in the collision events are sometimes observed. Therefore it turns out after all that the kinematic-coupling terms cannot be neglected in the CSF-basis representation. The present applications also demonstrate that the nonadiabatic electronic wave-packet dynamics within ab initio quantum chemical calculation is feasible.
Quantum control of molecular motion including electronic polarization effects with a two-stage toolkit
Authors: Balint-Kurti Gabriel G. , Manby Frederick R. , Ren Qinghua , Artamonov Maxim , Ho Tak-San , Rabitz Herschel
Published: February 2005

A method for incorporating strong electric field polarization effects into optimal control calculations is presented. A Born–Oppenheimer-type separation, referred to as the electric-nuclear Born–Oppenheimer (ENBO) approximation, is introduced in which variations of both the nuclear geometry and the external electric field are assumed to be slow compared with the speed at which the electronic degrees of freedom respond to these changes. This assumption permits the generation of a potential energy surface that depends not only on the relative geometry of the nuclei but also on the electric field strength and on the orientation of the molecule with respect to the electric field. The range of validity of the ENBO approximation is discussed in the paper. A two-stage toolkit implementation is presented to incorporate the polarization effects and reduce the cost of the optimal control dynamics calculations. As an illustration of the method, it is applied to optimal control of vibrational excitation in a hydrogen molecule aligned along the field direction. Ab initio configuration interaction calculations with a large orbital basis set are used to compute the H–H interaction potential in the presence of the electric field. The significant computational cost reduction afforded by the toolkit implementation is demonstrated.
Is the Filinov integral conditioning technique useful in semiclassical initial value representation methods?
Authors: Spanner Michael , Batista Victor S. , Brumer Paul
Published: February 2005

The utility of the Filinov integral conditioning technique, as implemented in semiclassical initial value representation (SC-IVR) methods, is analyzed for a number of regular and chaotic systems. For nonchaotic systems of low dimensionality, the Filinov technique is found to be quite ineffective at accelerating convergence of semiclassical calculations since, contrary to the conventional wisdom, the semiclassical integrands usually do not exhibit significant phase oscillations in regions of large integrand amplitude. In the case of chaotic dynamics, it is found that the regular component is accurately represented by the SC-IVR, even when using the Filinov integral conditioning technique, but that quantum manifestations of chaotic behavior was easily overdamped by the filtering technique. Finally, it is shown that the level of approximation introduced by the Filinov filter is, in general, comparable to the simpler ad hoc truncation procedure introduced by Kay [J. Chem. Phys. 101, 2250 (1994)].
Ge fraction dependent improved thermal stability of in situ doped boron in polycrystalline Si1−xGex (⩽x⩽0.5) films on SiON
Authors: Miyao Masanobu , Tsunoda Isao , Sadoh Taizoh , Miyauchi Akihiro
Published: February 2005

Postannealing characteristics of in situ doped B atoms in poly-Si1−xGex (x⩽0.5) films on SiON have been investigated. Supersaturated electrically active B (2×1020cm−3) is obtained for as-chemical vapor deposition samples, and their thermal stability is significantly improved by increasing Ge fraction, e.g., the stability for poly-Si0.6Ge0.4 is ten times as high as that for poly-Si at 700–800°C. Such a Ge induced improvement will be a powerful tool to achieve poly-SiGe gate electrode for the next generation ultralarge scale integrated circuits. In addition, the deactivation process of electrically active B has been analyzed. Results indicated that deactivation processes consist of fast and slow processes. The former is due to movement of B atoms from substitutional to interstitial sites, which is enhanced by a local strain induced by the difference in atomic radii between Si and B atoms. The slow process was due to trapping of B at grain boundaries during grain growth. The two-state model based on the local strain compensation by Ge doping is proposed, which can well explain the Ge dependent thermal stability of electrically active B atoms.
Silica-supported silver nanoparticles: Tailoring of structure-property relationships
Authors: Barreca Davide , Gasparotto Alberto , Maragno Cinzia , Tondello Eugenio , Gialanella Stefano
Published: February 2005

Silica-supported silver nanoparticles were obtained by rf sputtering from Ar plasmas under soft synthesis conditions, with particular attention to the combined influence of rf power and total pressure on the system composition, nanostructure, morphology, and optical properties. In order to attain a thorough insight into the nucleation and growth phenomena of Ag nanoparticles on the silica substrate, several in situ and ex situ characterization techniques were used. In particular, a laser reflection interferometry system was employed for a real-time monitoring of the deposition process, providing useful and complementary information with respect to the other ex situ techniques (x-ray photoelectron spectroscopy and x-ray excited Auger electron spectroscopy, glancing incidence x-ray diffraction, atomic force microscopy, optical-absorption spectroscopy, and transmission electron microscopy). The above investigations evidenced the formation of silver-based nanosystems (average crystallite size ⩽10nm), whose features (metal content, Ag particle size and shape, structure and optical properties) could be carefully tailored by moderate and controlled variations of the synthesis parameters.
Surface microroughness of ion-beam etched optical surfaces
Authors: Savvides N.
Published: February 2005

Ion-beam etching (IBE) and ion-beam figuring techniques using low-energy ion-beam sources have been applied for more than ten years in the fabrication and finishing of extremely smooth high-performance optics. We used optical interferometric techniques and atomic force microscopy to study the evolution of the surface root-mean-square (rms) microroughness, Rq, as a function of depth of a material removed (0–3000nm) by a broad ion-beam source (Ar+ ions of energy 600eV and ion current density of 1mAcm−2). Highly polished samples of fused silica and Zerodur (Rq∼3.5Å) showed a small decrease in microroughness (to 2.5Å) after 3000-nm IBE removal while an ultrapolished single-crystal sapphire sample (Rq∼1Årms) retained its very low microroughness during IBE. Power spectral density functions over the spatial frequency interval of measurement (f=5×10−3−25μm−1) indicate that the IBE surfaces have minimal subsurface damage and low optical scatter.
Hamilton–Jacobi equations for nonholonomic dynamics
Authors: Pavon Michele
Published: February 2005

We derive generalized Hamilton–Jacobi equations for dynamical systems subject to linear velocity constraints. As long as a solution of the generalized Hamilton–Jacobi equation exists, the action is actually minimized (not just extremized).
First-principles study of Si–SiO2 interface and the impact on mobility
Authors: Liu X. -Y. , Jovanovic D. , Stumpf R.
Published: February 2005

For Si devices, the high-field effective mobility is generally reproducible irrespective of SiO2 quality. This suggests that interface scattering is an intrinsic property of the Si–SiO2 interface. We have performed first-principles density functional calculations of several crystalline models of the Si–SiO2 interface. Universal features are found in the local density of states of these model interfaces. Based on these intrinsic interfacial properties, an atomistic model for Si–SiO2 inversion layer mobility is constructed. Quantum transport simulations calibrated with the mobility model show excellent agreement with experimental data. The strain effects on mobility are also studied and show interesting features in strained Si∕Si1−xGex devices.
Effect of Ti substitution on the thermoelectric properties of (Zr,Hf)NiSn half-Heusler compounds
Authors: Sakurada S. , Shutoh N.
Published: February 2005

The effect of Ti substitution on the thermoelectric properties of (Zr,Hf)NiSn half-Heusler compounds was studied. It was found that the substitution of Ti for (Zr,Hf) reduced the thermal conductivity significantly to a low value of 3.0W∕mK at room temperature. In addition, a remarkable enhancement of the Seebeck coefficient due to Ti substitution was observed. Furthermore, doping of the Sn sites in (Ti,Zr,Hf)NiSn with Sb led to a reduction in the electrical resistivity and to a corresponding enhancement of the power factor. In Sb-doped (Ti,Zr,Hf)NiSn compounds, the dimensionless figure of merit, ZT, increased with the increase in temperature and reached a high maximum value of 1.5 at 700K.
Charge-state and energy enhancement of laser-produced ions due to nonlinear processes in preformed plasma
Authors: Láska L. , Jungwirth K. , Krása J. , Pfeifer M. , Rohlena K. , Ullschmied J. , Badziak J. , Parys P. , Wolowski J. , Gammino S. , Torrisi L. , Boody F. P.
Published: February 2005

At laser intensities above IL∼1×1014W∕cm2(ILλ2∼1×1014Wμm2∕cm2), nonlinear processes in preformed plasma, such as self-focusing, influence ion generation significantly and ions with higher charge states and energies can be produced than without interaction with preformed plasma. The step (spread) in plots of experimental data of ion energy per nucleon versus ILλ2 reported by other researchers most likely reflects high-intensity laser interactions with and without preformed plasma.
Mn-doped ZnO and (Mn, Cu)-doped ZnO thin films: Does the Cu doping indeed play a key role in tuning the ferromagnetism?
Authors: Hong Nguyen Hoa , Brizé Virginie , Sakai Joe
Published: February 2005

Zn 0.9 Mn 0.1 O and Zn0.85Mn0.1Cu0.05O thin films were grown by the pulsed laser deposition technique on R-cut Al2O3 substrates under various conditions. Both Zn0.9Mn0.1O and Zn0.85Mn0.1Cu0.05O films that were fabricated at 650 °C under an oxygen pressure of 0.1 Torr show ferromagnetism (FM) above room temperature. It appears that by applying appropriate conditions, doping Mn alone can induce FM in ZnO itself, while co-doping with Cu might enhance the magnetic moment for some extent in some specific cases, but not very crucially as theories have predicted. Growth conditions likely play more important roles to result in ferromagnetic samples.
Abrupt disruption of capping and a single source for recombinationally elongated telomeres in
Kluyveromyces lactis
Authors: Topcu Zeki , Nickles Kristy , Davis Charity , McEachern Michael J.
Published: February 2005

Eukaryotic cells, including some human cancers, that lack telomerase can sometimes maintain telomeres by using recombination. It was recently proposed that recombinational telomere elongation (RTE) in a telomerase-deletion mutant of the yeast
Kluyveromyces lactis
occurs through a roll-and-spread mechanism as described in our previous work. According to this model, a tiny circle of telomeric DNA is copied by a rolling-circle mechanism to generate one long telomere, the sequence of which is then spread to all other telomeres by gene-conversion events. In support of this model, we demonstrate here that RTE in
K. lactis
occurs by amplification of a sequence originating from a single telomere. When a mutationally tagged telomere is of normal length, its sequence is spread to all other telomeres at a frequency (≈10%) consistent with random selection among the 12 telomeres in the cell. However, when the mutationally tagged telomere is considerably longer than other telomeres, cellular senescence is partially suppressed, and the sequence of the tagged telomere is spread to all other telomeres in >90% of cells. Strikingly, the transition between a state resistant to recombination and a state capable of initiating recombination is abrupt, typically occurring when telomeres are ≈3–4 repeats long. Last, we show that mutant repeats that are defective at regulating telomerase are also defective at regulating telomere length during RTE.
Botulinum neurotoxin C initiates two different programs for neurite degeneration and neuronal apoptosis
Authors: Berliocchi Laura , Fava Eugenio , Leist Marcel , Horvat Volker , Dinsdale David , Read David , Nicotera Pierluigi
Published: February 2005

Clostridial neurotoxins are bacterial endopeptidases that cleave the major SNARE proteins in peripheral motorneurons. Here, we show that disruption of synaptic architecture by botulinum neurotoxin C1 (BoNT/C) in central nervous system neurons activates distinct neurodegenerative programs in the axo-dendritic network and in the cell bodies. Neurites degenerate at an early stage by an active caspase-independent fragmentation characterized by segregation of energy competent mitochondria. Later, the cell body mitochondria release cytochrome c, which is followed by caspase activation, apoptotic nuclear condensation, loss of membrane potential, and, finally, cell swelling and lysis. Recognition and scavenging of dying processes by glia also precede the removal of apoptotic cell bodies, in line with a temporal and spatial segregation of different degenerative processes. Our results suggest that, in response to widespread synaptic damage, neurons first dismantle their connections and finally undergo apoptosis, when their spatial relationships are lost.
Inhibition of endothelial cell migration by thrombospondin-1 type-1 repeats is mediated by β1 integrins
Authors: Short Sarah M. , Derrien Alexandrine , Narsimhan Radha P. , Lawler Jack , Ingber Donald E. , Zetter Bruce R.
Published: February 2005

The anti-angiogenic effect of thrombospondin-1 has been shown to be mediated through binding of the type-1 repeat (TSR) domain to the CD36 transmembrane receptor. We now report that the TSR domain can inhibit VEGF-induced migration in human umbilical vein endothelial cells (HUVEC), cells that lack CD36. Moreover, we identified β1 integrins as a critical receptor in TSR-mediated inhibition of migration in HUVEC. Using pharmacological inhibitors of downstream VEGF receptor effectors, we found that phosphoinositide 3-kinase (PI3k) was essential for TSR-mediated inhibition of HUVEC migration, but that neither PLCγ nor Akt was necessary for this response. Furthermore, β1 integrins were critical for TSR-mediated inhibition of microvascular endothelial cells, cells that express CD36. Together, our results indicate that β1 integrins mediate the anti-migratory effects of TSR through a PI3k-dependent mechanism.
Temporal separation of replication and recombination requires the intra-S checkpoint
Authors: Meister Peter , Taddei Angela , Vernis Laurence , Poidevin Mickaël , Gasser Susan M. , Baldacci Giuseppe
Published: February 2005

In response to DNA damage and replication pausing, eukaryotes activate checkpoint pathways that prevent genomic instability by coordinating cell cycle progression with DNA repair. The intra-S-phase checkpoint has been proposed to protect stalled replication forks from pathological rearrangements that could result from unscheduled recombination. On the other hand, recombination may be needed to cope with either stalled forks or double-strand breaks resulting from hydroxyurea treatment. We have exploited fission yeast to elucidate the relationship between replication fork stalling, loading of replication and recombination proteins onto DNA, and the intra-S checkpoint. Here, we show that a functional recombination machinery is not essential for recovery from replication fork arrest and instead can lead to nonfunctional fork structures. We find that Rad22-containing foci are rare in S-phase cells, but peak in G2 phase cells after a perturbed S phase. Importantly, we find that the intra-S checkpoint is necessary to avoid aberrant strand-exchange events during a hydroxyurea block.
Postwar Japanese Cotton Textile Investment in Brazil, 1955–1980
Authors: Delanghe Henri
Published: February 2005

The literature suggests that cotton textiles should be unattractive for foreign direct investment (FDI). The product is largely undifferentiated; sellers need an intimate knowledge of local markets; and textiles use process technology, which multinational firms cannot monopolize. Indeed, since the 1970s, cotton textiles has been one of the few industries in Brazil in which local capital dominates, joint ventures prevail, and American firms are almost completely absent. Yet, between 1955 and the mid-1970s, Brazil saw significant foreign direct investment in textiles from Japanese firms. There were two successive waves of Japanese investment in the Brazilian cotton textile industry. The first ran from the mid-1950s to the early 1960s. The second took place from the late 1960s to the mid-1970s. Four Japanese textile firms participated in the first wave—Kanebo, Toyobo, Tsuzuki, and Unitika. Four more—Daiwa, Kurabo, Nisshinbo, and Omi—participated in the second wave.
Response to Mivacurium in Patients Carrying the K Variant in the Butyrylcholinesterase Gene
Authors: Gätke Mona R. , Viby-Mogensen Jørgen , Østergaard Doris , Bundgaard Jens R.
Published: February 2005

Background

Mivacurium is hydrolyzed by the butyrylcholinesterase enzyme, and patients with hereditary changes of the enzyme often have prolonged duration of action of mivacurium. In this study, the authors investigated the significance of the most commonly occurring variant, the Kalow (K) variant, established using DNA analysis, for the response to mivacurium.

Methods

A total of 58 patients carrying either the wild-type butyrylcholinesterase or different combinations of the atypical (A) variant and the K variant were included. Patients who were homozygous for the A variant were given 0.03 mg/kg mivacurium. All other patients received 0.2 mg/kg mivacurium. The neuromuscular block was measured using train-of-four nerve stimulation and mechanomyography. Genotyping was performed with complete nucleotide sequencing.

Results

Heterozygosity of the K variant prolonged the time to train-of-four 0.70 from 26.6 to 34.5 min (30%; not significant) as compared with the wild type. Heterozygosity of the K variant linked to the A variant prolonged the corresponding time from 32 to 42.7 min (33%; P = 0.03) as compared with patients who were heterozygous for solely an A allele. For eight patients who were homozygous for both the A and K variants, the time to 25% recovery was 78-89 min as compared with 44-57 min in patients who were homozygous for the A variant or had only one linked K variant.

Conclusion

The K variant prolongs the duration of action of mivacurium. The current results indicate that the effect is modest when the K variant occurs heterozygously with the wild type or the A variant but is marked in patients who are homozygous for both the A and K variants.
Screening of the Entire Ryanodine Receptor Type 1 Coding Region for Sequence Variants Associated with Malignant Hyperthermia Susceptibility in the North American Population
Authors: Sambuughin Nyamkhishig , Holley Heather , Muldoon Sheila , Brandom Barbara W. , de Bantel Astrid M. , Tobin Joseph R. , Nelson Tom E. , Goldfarb Lev G.
Published: February 2005

Background

Malignant hyperthermia (MH) is a life-threatening and frequently fatal disorder triggered by commonly used anesthetics. MH susceptibility is a genetically determined predisposition to the development of MH. Mutations in the ryanodine receptor type 1 (RYR1) gene are the major cause of MH susceptibility. The authors sought to develop a reliable genetic screening strategy based on efficient and relatively inexpensive mutation-detection procedures.

Methods

A cohort (n = 30) of North American MH patients and MH-susceptible individuals was studied. RNA and DNA extracted from muscle tissue or blood lymphocytes were used for analysis. The entire RYR1 coding region was amplified in 57 overlapping fragments and subjected to denaturing high-performance liquid chromatography analysis followed by direct nucleotide sequencing to characterize RYR1 alterations.

Results

Nine previously reported and nine unknown RYR1 mutations were identified in 21 of 30 studied patients (70%). Some of the new mutations were located outside of known mutational "hot spots," suggesting that RYR1 contains previously unknown mutation-prone areas requiring analysis. The North American MH/MH-susceptible population is characterized by a high RYR1 allelic heterogeneity.

Conclusions

Denaturing high-performance liquid chromatography analysis of RNA samples extracted from the biopsied skeletal muscle followed by DNA sequencing is a highly efficient methodology for RYR1 mutation detection. This approach allows increasing the rate of mutation detection to 70% and identifying mutations in the entire RYR1 coding region.
Polymorphism of μ-Opioid Receptor Gene (OPRM1:c.118A>G ) Does Not Protect Against Opioid-induced Respiratory Depression despite Reduced Analgesic Response
Authors: Romberg Raymonda R. , Olofsen Erik , Bijl Hans , Taschner Peter E. M. , Teppema Luc J. , Sarton Elise Y. , van Kleef Jack W. , Dahan Albert
Published: February 2005

Background

The effect of a single nucleotide polymorphism of the mu-opioid receptor at nucleotide position 118 (OPRM1:c.118A>G) was investigated on morphine-6-glucuronide (M6G)-induced analgesia and respiratory depression in a group of healthy volunteers.

Methods

Sixteen subjects of either sex received 0.4 mg/kg (n = 8) or 0.6 mg/kg M6G (n = 8). At regular time intervals, the isocapnic acute hypoxic ventilatory response, pain tolerance (derived from a transcutaneous electrical acute pain model), and arterial blood samples were obtained. Data acquisition continued for 14 h after drug infusion. Population pharmacokinetic-pharmacodynamic sigmoid Emax models were applied to the respiratory and pain data. All collected data were analyzed using the statistical program NONMEM (San Francisco, CA).

Results

Four of the subjects were OPRM1:c.118GA heterozygotes, and the remainder of the subjects were OPRM1:c.118AA homozygotes. M6G analgesia: In contrast to analgesic responses in OPRM1:c.118AA homozygotes, responses were small and inconsistent in OPRM1:c.118GA heterozygotes and best described by the function Effect(t) = baseline (P < 0.01 vs. OPRM1:c.118AA homozygotes). Emax and C50 values in heterozygotes equaled 0.55 +/- 0.18 (or a 55% increase in current above baseline) and 161 +/- 42 ng/ml, respectively. M6G-induced respiratory depression: For the acute hypoxic response, neither Emax nor C50 (value = 282 +/- 72 ng/ml) differed between genotypes.

Conclusions

The data indicate that the OPRM1:c.118A>G polymorphism affects opioid analgesic and respiratory effects differentially. Despite reduced analgesic responses to M6G the OPRM1:c.118A>G single-nucleotide polymorphism does not protect against the toxic effects of the tested opioid. However, some caution in the interpretation of the data is needed because of the small sample size. Further studies are needed to explore the link between this polymorphism and respiratory/analgesic responses beyond the small human sample. In OPRM1:c.118AA homozygotes, the potency parameters differed by a factor of 2 for analgesic versus respiratory effect. In this respect, M6G differs favorably from morphine.
Effect of N -methyl-d-aspartate Receptor ε1Subunit Gene Disruption of the Action of General Anesthetic Drugs in Mice
Authors: Sato Yuki , Kobayashi Eiji , Murayama Takanori , Mishina Masayoshi , Seo Norimasa
Published: February 2005

Background

Recent molecular strategies demonstrated that the N-methyl-d-aspartate (NMDA) receptor is a major target site of anesthetic agents. In a previous article, the authors showed that knocking out the NMDA receptor epsilon1 subunit gene markedly reduced the hypnotic effect of ketamine in mice. In the current study, the authors examined the in vivo contribution of the NMDA receptor epsilon1 subunit to the action of other anesthetic drugs.

Methods

The authors determined the anesthetic effects of nitrous oxide on sevoflurane potency in NMDA receptor epsilon1 subunit knockout mice compared with those in wild-type mice. They then tested the hypnotic effect of gamma-aminobutyric acid-mediated agents, such as propofol, pentobarbital, diazepam, and midazolam, in knockout mice and wild-type mice.

Results

The anesthetic action of sevoflurane itself was unaffected by the abrogation of the NMDA receptor epsilon1 subunit. Adding nitrous oxide reduced the required concentration of sevoflurane to induce anesthesia in wild-type mice, whereas this sparing effect was diminished in knockout mice. Furthermore, propofol, pentobarbital, diazepam, and midazolam also had markedly attenuated effects in knockout mice.

Conclusions

Although it has been demonstrated that knocking out the expression of receptors may induce changes in the composition of the subunits, the network circuitry, or both, the current findings show consistently that the NMDA receptor epsilon1 subunit mediates nitrous oxide but not sevoflurane anesthesia. Furthermore, the attenuated anesthetic impact of propofol, pentobarbital, diazepam, and midazolam as well as ketamine in knockout mice suggests that the NMDA receptor epsilon1 subunit could be indirectly involved in the hypnotic action of these drugs in vivo.
Increased Pulmonary Venous Resistance Contributes to Increased Pulmonary Artery Diastolic–Pulmonary Wedge Pressure Gradient in Acute Respiratory Distress Syndrome
Authors: Her Charles , Mandy Szabolcs , Bairamian Mosses
Published: February 2005

Background

Pulmonary artery diastolic (PAD)-pulmonary wedge pressure (PWP) gradient has been shown to be increased in sepsis and acute respiratory distress syndrome (ARDS). Because pulmonary venous vasoconstriction induced by endotoxemia in sepsis or postcapillary leukocyte aggregation in ARDS or both can increase pulmonary venous resistance (Rpv), it is possible that the elevated Rpv increases PAD-PWP. The authors examined this possibility by assessing the correlation between Rpv and PAD-PWP gradient in patients with ARDS.

Methods

Included were 20 patients with ARDS who required surgical procedures during general anesthesia. Rpv was calculated as the difference between mean pulmonary artery (PA) output pressure and PWP divided by cardiac index. Mean PA output pressure was computed from harmonic form of the recorded PA pressure by applying an attenuating factor to its phasic components, for which Fourier analysis was used. Total pulmonary vascular resistance (TPVR) was calculated as the difference between mean PA input pressure and PWP divided by cardiac index. To avoid the effect of PA resistance on TPVR and Rpv, the relative pulmonary venous resistance (Rpv/TPVR) was used.

Results

There was a good correlation between Rpv/TPVR and PAD-PWP gradient (R = 0.698, P < 0.0001). When patients were classified into two groups based on PAD-PWP gradient, the Rpv/TPVR was 0.66 +/- 0.06 in the group with a PAD-PWP gradient of 6 mmHg or greater and 0.46 +/- 0.08 in the other group (P < 0.0001).

Conclusion

A strong correlation between Rpv/TPVR and PAD-PWP gradient suggests that the increased Rpv contributes to increased PAD-PWP gradient in patients with ARDS.
Inhibitory Effects of Lidocaine and Mexiletine on Vasorelaxation Mediated by Adenosine Triphosphate–sensitive K+Channels and the Role of Kinases in the Porcine Coronary Artery
Authors: Kimoto Yoshiki , Kinoshita Hiroyuki , Nakahata Katsutoshi , Dojo Mayuko , Hatano Yoshio
Published: February 2005

Background

Effects of antiarrhythmic drugs on coronary vasodilation mediated by K channels have not been studied. Modulator roles of protein kinase C and tyrosine kinase in the activity of K channels have also been unclear in the coronary artery. The current study examined whether lidocaine and mexiletine in the porcine coronary artery modify the vasorelaxation mediated by adenosine triphosphate-sensitive K channels via activation of protein kinase C and tyrosine kinase.

Methods

Porcine coronary arteries without endothelium were suspended for isometric force recording, and vasorelaxation to levcromakalim (10 to 10 m) was obtained. Changes in membrane potentials produced by levcromakalim (10 m) were also recorded.

Results

Glibenclamide completely abolished vasorelaxation as well as hyperpolarization in response to levcromakalim. Lidocaine and mexiletine significantly reduced these responses. Calphostin C, Go 6976, genistein, and erbstatin A partly restored vasorelaxation or hyperpolarization in response to levcromakalim in arteries treated with mexiletine but not in those with lidocaine, whereas these inhibitors did not alter the vasorelaxation to levcromakalim. Phorbol 12-myristate 13-acetate produced reduction of vasorelaxation in response to levcromakalim, which is recovered by calphostin C or Go 6976.

Conclusions

Therefore, lidocaine and mexiletine inhibit vasorelaxation mediated by the activation of adenosine triphosphate-sensitive K channels in the coronary artery. Protein kinase C and tyrosine kinase seem to have roles in the inhibitory effect of mexiletine but not in that of lidocaine. Class Ib antiarrhythmic drugs may reduce coronary vasodilation mediated by adenosine triphosphate-sensitive K channels via the differential modulator effects on these kinases.
Isoflurane Neuroprotection in Hypoxic Hippocampal Slice Cultures Involves Increases in Intracellular Ca2+and Mitogen-activated Protein Kinases
Authors: Gray Jonathan J. , Bickler Philip E. , Fahlman Christian S. , Zhan Xinhua , Schuyler Jennifer A.
Published: February 2005

Background

The volatile anesthetic isoflurane reduces acute and delayed neuron death in vitro models of brain ischemia, an action that the authors hypothesize is related to moderate increases in intracellular calcium concentration ([Ca2+]i). Specifically, the authors propose that during hypoxia, moderate increases in [Ca2+]i in the presence of isoflurane stimulates the Ca2+-dependent phosphorylation of members of the mitogen-activated protein kinase (MAP) kinase Ras-Raf-MEK-ERK pathway that are critical for neuroprotective signaling and suppression of apoptosis.

Methods

Death of CA1, CA3, and dentate neurons in rat hippocampal slice cultures was assessed by propidium iodide fluorescence 48-72 h after 60-75 min of hypoxia. [Ca2+]i in CA1 neurons was measured with fura-2 and fura-2 FF. Concentrations of the survival-signaling proteins Ras, MEK, MAP kinase p42/44, and protein kinase B (Akt) were assessed by immunostaining, and specific inhibitors were used to ascertain the role of Ca2+ and MAP kinases in mediating survival.

Results

Isoflurane, 1%, decreased neuron death in CA1, CA3, and dentate gyrus neurons after 60 but not 75 min of hypoxia. Survival of CA1 neurons required an inositol triphosphate receptor-dependent increase in [Ca2+]i of 30-100 nm that activated the Ras-Raf-MEK-ERK (p44/42) signaling pathway. Isoflurane also increased the phosphorylation of Akt during hypoxia.

Conclusions

Isoflurane stimulates the phosphorylation of survival signaling proteins in hypoxic neurons. The mechanism involves a moderate increase in [Ca2+]i from release of Ca from inositol triphosphate receptor-dependent intracellular stores. The increase in [Ca2+]i sets in motion signaling via Ras and the MAP kinase p42/44 pathway and the antiapoptotic factor Akt. Isoflurane neuroprotection thus involves intracellular signaling well known to suppress both excitotoxic and apoptotic/delayed cell death.
A Comparison of Median Effective Doses of Intrathecal Levobupivacaine and Ropivacaine for Labor Analgesia
Authors: Sia Alex T. , Goy Raymond W. , Lim Yvonne , Ocampo Cecilia E.
Published: February 2005

Background

The study was designed to determine and compare the median effective doses (MEDs) of intrathecal ropivacaine with levobupivacaine for labor analgesia.

Methods

In this double-blind study, 100 parturients in early labor were randomized to receive either intrathecal ropivacaine or levobupivacaine. For each drug, the patients were assigned to receive one of the five doses studied, namely 1, 1.5, 2, 2.5, or 3 mg. Effective analgesia was defined as a pain score (0-100 visual analog scale) of less than 10 within 15 min of injection, lasting for 45 min or more after the induction of analgesia. MEDs were derived from probit analysis. The duration of analgesia rendered by the two drugs at 2.5 and 3 mg was also compared.

Results

The MED for levobupivacaine was 1.07 mg (95% confidence interval, 0.88-1.25 mg), and the MED for ropivacaine was 1.40 mg (95% confidence interval, 1.20-1.61 mg). Levobupivacaine was found to be 1.31 (95% confidence interval, 1.04-2.01) times more potent than ropivacaine. At doses of 2.5 mg or greater, there was no significant difference in duration of analgesia between levobupivacaine (median, 63.5 min; range, 46-123 min) and ropivacaine (median, 59.0 min; range, 47-93 min; P = 0.18). We detected no difference in the incidence of hypotension, nausea and vomiting, motor block, or abnormal fetal heart tracing between the two drugs.

Conclusions

The MED of intrathecal ropivacaine for labor analgesia was significantly greater than levobupivacaine experimentally, but this significance was reduced when the comparison was based on molar potency. There was no difference in the duration of analgesia or adverse effects between the two drugs at higher doses (2.5 mg or greater).
α2-Adrenoceptor Activation by Clonidine Enhances Stimulation-evoked Acetylcholine Release from Spinal Cord Tissue after Nerve Ligation in Rats
Authors: Obata Hideaki , Li Xinhui , Eisenach James C.
Published: February 2005

Background

Spinally administered clonidine produces analgesia via alpha2-adrenergic receptors. The analgesic potency of clonidine and its dependency on muscarinic acetylcholine receptors increase in rats after nerve injury. The authors hypothesized that these changes reflect greater acetylcholine release from the spinal cord by clonidine, either through direct or indirect effects.

Methods

Male Sprague-Dawley rats were divided into two groups: no surgery or left L5 and L6 spinal nerve ligation (SNL). All experiments were performed 3 weeks after SNL. Crude synaptosomes were prepared from the spinal enlargement and loaded with [H]choline. Samples were incubated with clonidine in the absence or presence of KCl depolarization. The authors also examined the effect of clonidine on KCl evoked acetylcholine release using perfusion of spinal cord slices, in which some spinal circuitry is maintained.

Results

In synaptosomes, clonidine alone induced minimal acetylcholine release, which was actually greater in tissue from normal rats than in tissue from SNL rats. In the presence of KCl depolarization, however, clonidine enhanced acetylcholine release in tissue from SNL rats but inhibited release in tissue from normal rats. Similarly, in spinal cord slices, clonidine enhanced KCl evoked acetylcholine release in tissue from SNL animals but inhibited such release in tissue from normal animals. The alpha2-adrenoceptor antagonist idazoxan inhibited the effects of clonidine in slices from SNL rats.

Conclusion

These results suggest that clonidine enhances depolarization-induced acetylcholine release in neuropathic but not in normal spinal cord tissue. Interestingly, this enhanced acetylcholine release by clonidine occurs in a synaptosomal preparation, consistent with a direct effect on alpha2 adrenoceptors on cholinergic terminals. Enhanced release of acetylcholine by clonidine could contribute to increased analgesia of clonidine in neuropathic pain.
Dynamics of anti-M antibody response in a mouse model following intranasal infection with group A Streptococcus M-18
Authors: Gladstone Paul , Varghese George , Brahmadathan K N
Published: February 2005

Dynamics of anti-M antibody response following intranasal infection with group AStreptococcus(GAS) M-18 were investigated in a Swiss albino mouse model. Mice arranged in three groups were inoculated intranasally with 2.0 × 107c.f.u. ml−1of GAS M-18 on 1, 2 alternate and 3 alternate days. Plasma collected from the retro-orbital plexus was tested for antibodies by an in-house indirect ELISA. The antibody titres of the plasma samples varied from 1 : 8 to 1 : 1024 in the 1 day dose, from 1 : 4 to 1 : 256 in the 2 day dose and from 1 : 4 to 1 : 128 in the 3 day dose. Peak titres were seen on day 42 or 56 and in all cases the titres had declined by day 84. Swiss albino mouse can thus serve as a useful animal model to study different aspects of type-specific anti-M immune responses against GAS disease when designing candidate streptococcal vaccines.
Cytolethal distending toxin: creating a gap in the cell cycle
Authors: Heywood Wendy , Henderson Brian , Nair Sean P
Published: February 2005

Cytolethal distending toxin (CDT) is a novel bacterial toxin that is produced by a variety of pathogenic bacteria. The mechanism of cytotoxicity of CDT is unique in that it enters into eukaryotic cells and breaks double-stranded DNA. This initiates the cell's own DNA damage-response mechanisms, resulting in the arrest of the cell cycle at the G2/M boundary. Affected cells enlarge until they finally undergo programmed cell death. This review encompasses recent work on CDT and focuses on the molecular mechanisms used by this toxin to block cell-cycle progression, the benefit to the bacterium of possession of this toxin and the clinical relevance of intoxication.
Comparison of four molecular typing methods to assess genetic relatedness of Candida albicans clinical isolates in Taiwan
Authors: Chen Kuo-Wei , Lo Hsiu-Jung , Lin Yu-Hui , Li Shu-Ying
Published: February 2005

This report describes the investigation of the genetic profiles of 53 Candida albicans isolates collected from 18 hospitals in Taiwan using three PFGE-based typing methods (PFGE karyotyping, and PFGE of SfiI and BssHII restriction fragments) and one repetitive-sequence-PCR (rep-PCR) method. All four methods were able to identify clonal related isolates from the same patients. PFGE-BssHII exhibited the highest discriminatory power by discriminating 40 genotypes, followed by PFGE-SfiI (35 genotypes) and then by rep-PCR (31 genotypes), while PFGE karyotyping exhibited the lowest discriminatory power (19 genotypes). High discriminatory power can also be achieved by combining typing methods with different typing mechanisms, such as rep-PCR and PFGE-based typing methods. The results also showed that the genotype of each isolate was patient-specific and not associated with the source of the isolation, geographic origin or antifungal resistance.
Listeria monocytogenes in the Chinese food system: strain characterization through partial actA sequencing and tissue-culture pathogenicity assays
Authors: Zhou Xiaohui , Jiao Xinan , Wiedmann Martin
Published: February 2005

Human listeriosis is generally caused by consumption of ready-to-eat (RTE) foods that are stored for extended periods of time at refrigeration temperatures and that permit the growth of the causative agent, Listeria monocytogenes. Food-consumption patterns in China are undergoing rapid changes and more regular consumption of refrigerated-storage RTE foods may increase the risk of human listeriosis. In total, 40 L. monocytogenes isolates were obtained from food (n = 32) and sewage (n = 6) samples and from two human listeriosis cases that occurred in China. All isolates were characterized into molecular subtypes by DNA sequencing of the 597 bp 3′-terminal region of the virulence gene actA. Sequence data were used to classify the 40 Chinese L. monocytogenes isolates into sequence types and phylogenetic lineages, and to compare the sequence types of the Chinese isolates with those of isolates from the USA. Phylogenetic analyses showed that the Chinese isolates could be separated into two genetic lineages, with 14 and 26 isolates belonging to lineages I and II, respectively. Lineage II could be subdivided further into two clusters, IIA and IIB. Lineages I and II were identical to the two lineages described previously among US L. monocytogenes isolates. In total, 14 actA sequence types could be differentiated among the 40 Chinese L. monocytogenes isolates; two specific actA sequence types were found among both Chinese and US isolates. Isolates belonging to lineage II showed a significantly lower ability to invade and multiply within human intestinal epithelial Caco-2 cells than lineage I isolates. It was concluded that DNA sequencing of the 3′-terminal region of actA appears to be an effective method for rapid subtype and lineage classification of L. monocytogenes. As strains belonging to lineages I and II have previously been found among isolates from Europe and North America, these results show that L. monocytogenes clonal groups found in China are very similar to those found in the USA. Many L. monocytogenes strains may thus represent globally distributed clonal types. Together with the first description of two human listeriosis cases in China, these data indicate that changes in food-distribution and -consumption patterns in China and other countries will probably lead to the emergence of human listeriosis as a food-safety issue, as virulent strains of this pathogen appear to be present in the Chinese food supply.
Molecular characterization of a multidrug-resistant strain of enteroinvasive Escherichia coli O164 isolated in Japan
Authors: Ahmed Ashraf M , Miyoshi Shin-ichi , Shinoda Sumio , Shimamoto Tadashi
Published: February 2005

Enteroinvasive Escherichia coli (EIEC) O164 strain RIMD05091045 was isolated from a travelling patient suffering from diarrhoea at the Osaka airport quarantine facility in Japan. The strain showed multidrug resistance against streptomycin, spectinomycin, co-trimoxazole (trimethoprim/sulfamethoxazole) and ampicillin, and reduced susceptibility to ciprofloxacin. Molecular characterization of the multidrug-resistance phenotype revealed the presence of a class 1 integron containing three genes, a dihydrofolate reductase type XII gene, dfrXII, which confers resistance to trimethoprim, an aminoglycoside adenyltransferase gene, aadA2, which confers resistance to streptomycin and spectinomycin, and an ORF of unknown function. Southern blot hybridization and conjugation experiments showed that the class 1 integron was located on a transferable plasmid that was less than 90 kb in size. The resistance of EIEC O164 to ampicillin was found to be due to the presence of TEM-1 β-lactamase. On the other hand, a single mutation that has not previously been described, P158-to-S, was detected downstream of the quinolone-resistance-determining region of parC of topoisomerase IV and may be responsible for the reduced susceptibility to ciprofloxacin in this strain.
Postpartum hemorrhage: a prospective, comparative study in Angola using a new disposable device for oxytocin administration
Authors: Strand Roland T. , Da Silva Florinda , Jangsten Elisabeth , Bergström Staffan
Published: February 2005

Background.  Postpartum hemorrhage (PPH) is the single most common cause of maternal death in the world, and oxytocin is known to be effective for its prevention and treatment. The use of syringes can be problematic in areas affected by HIV. The aim of this study was to introduce Uniject™ (a new disposable device for administration of 10 IU oxytocin) as part of active management of the third stage of labor (AMTL) and try to reduce PPH.

Methods.  A prospective, comparative study was performed between March 1998 and May 2000 in Luanda. Seven hundred and eighty‐two parturient women with physiological management were compared to 814 with AMTL. Postpartum lost blood was collected using a plastic sheet during labor and a bucket placed under a cholera bed for 2 h postpartum. Student's t‐test and χ2 test were used.

Result.  PPH was reduced from 40·4 to 8·2% and severe PPH (≥1000 ml) from 7·5 to 1% in the AMTL group (P < 0·001).

Conclusions.  Uniject™ was well tolerated and offers an alternative for oxytocin administration. AMTL should be implemented also in resource‐poor settings as a routine management to reduce PPH.