bluuebunny/crossref_metadata_2025 huggingface dataset:
Dendritic signals from rat hippocampal CA1 pyramidal neurons during coincident pre‐ and post‐synaptic activity: a combined voltage‐ and calcium‐imaging study
Authors: Canepari Marco , Djurisic Maja , Zecevic Dejan
Published: February 2007

The non‐linear and spatially inhomogeneous interactions of dendritic membrane potential signals that represent the first step in the induction of activity‐dependent long‐term synaptic plasticity are not fully understood, particularly in dendritic regions which are beyond the reach of electrode measurements. We combined voltage‐sensitive‐dye recordings and Ca2+ imaging of hippocampal CA1 pyramidal neurons to study large regions of the dendritic arbor, including branches of small diameter (distal apical and oblique dendrites). Dendritic membrane potential transients were monitored at high spatial resolution and correlated with supra‐linear [Ca2+]i changes during one cycle of a repetitive patterned stimulation protocol that typically results in the induction of long‐term potentiation (LTP). While the increase in the peak membrane depolarization during coincident pre‐ and post‐synaptic activity was required for the induction of supra‐linear [Ca2+]i signals shown to be necessary for LTP, the change in the baseline‐to‐peak amplitude of the backpropagating dendritic action potential (bAP) was not critical in this process. At different dendritic locations, the baseline‐to‐peak amplitude of the bAP could be either increased, decreased or unaltered at sites where EPSP–AP pairing evoked supra‐linear summation of [Ca2+]i transients. We suggest that modulations in the bAP baseline‐to‐peak amplitude by local EPSPs act as a mechanism that brings the membrane potential into the optimal range for Ca2+ influx through NMDA receptors (0 to −15 mV); this may require either boosting or the reduction of the bAP, depending on the initial size of both signals.
Outwardly rectifying deflections in threshold electrotonus due to K+ conductances
Authors: Trevillion Louise , Howells James , Burke David
Published: February 2007

A transient decrease in excitability occurs regularly during the S1 phase of threshold electrotonus to depolarizing conditioning stimuli for sensory and, less frequently, motor axons. This has been attributed to the outwardly rectifying action of fast K+ channels, at least in patients with demyelinating diseases. This study investigates the genesis of this notch in healthy axons. Threshold electrotonus was recorded for sensory and motor axons in the median nerve at the wrist in response to test stimuli of different width. The notch occurred more frequently the briefer the test stimulus, and more frequently in sensory studies. In studies on motor axons, the notch decreased in latency and increased in amplitude as the conditioning stimulus increased or the limb was cooled. Low‐threshold axons displayed profound changes in strength–duration time constant even though the threshold electrotonus curves contained no detectable notch. When a 1.0 ms current was added to subthreshold conditioning stimuli to trigger EMG, the notch varied with the timing and intensity of the brief current pulse. This study finds no evidence for an outwardly rectifying deflection due to K+ channels, other than the slow accommodation attributable to slow K+ currents. In normal motor axons, a depolarization‐induced notch during the S1 phase of threshold electrotonus is the result of the conditioning stimulus exceeding threshold for some axons. The notch is more apparent in sensory axons probably because of the lower slope of the stimulus–response curve and their longer strength–duration time constant rather than a difference in K+ conductances. This may also explain the notch in demyelinating diseases.
Regulation and function of Ca2+–calmodulin‐dependent protein kinase II of fast‐twitch rat skeletal muscle
Authors: Rose Adam J. , Alsted Thomas J. , Kobberø J. Bjarke , Richter Erik A.
Published: February 2007

The activation and function of Ca2+–calmodulin‐dependent kinase II (CaMKII) in contracting rat skeletal muscle was examined. The increase in autonomous activity and phosphorylation at Thr287 of CaMKII of gastrocnemius muscle in response to contractions in situ was rapid and transient, peaking at 1–3 min, but reversed after 30 min of contractions. There was a positive correlation between CaMKII phosphorylation at Thr287 and autonomous CaMKII activity. In contrast to the rapid and transient increase in autonomous CaMKII activity, the phosphorylation of the putative CaMKII substrate trisk95/triadin was rapid and sustained during contractions. There were no changes in CaMKII activity and phosphorylation or trisk95 phosphorylation in the resting contralateral muscles during stimulation. When fast‐twitch muscles were contracted ex vivo, CaMKII inhibition resulted in a greater magnitude of fatigue as well as blunted CaMKII and trisk95 phosphorylation, identifying trisk95 as a physiological CaMKII substrate. In summary, skeletal muscle CaMKII activation was rapid and sustained during exercise/contraction and is mediated by factors within the contracting muscle, probably through allosteric activation via Ca2+–CaM. CaMKII may signal through trisk95 to modulate Ca2+ release in fast‐twitch rat skeletal muscle during exercise/contraction.
Voltage‐sensitive prestin orthologue expressed in zebrafish hair cells
Authors: Albert Jörg T. , Winter Harald , Schaechinger Thorsten J. , Weber Thomas , Wang Xiang , He David Z. Z. , Hendrich Oliver , Geisler Hyun‐Soon , Zimmermann Ulrike , Oelmann Katrin , Knipper Marlies , Göpfert Martin C. , Oliver Dominik
Published: February 2007

Prestin, a member of the solute carrier (SLC) family SLC26A, is the molecular motor that drives the somatic electromotility of mammalian outer hair cells (OHCs). Its closest reported homologue, zebrafish prestin (zprestin), shares ∼70% strong amino acid sequence similarity with mammalian prestin, predicting an almost identical protein structure. Immunohistochemical analysis now shows that zprestin is expressed in hair cells of the zebrafish ear. Similar to mammalian prestin, heterologously expressed zprestin is found to generate voltage‐dependent charge movements, giving rise to a non‐linear capacitance (NLC) of the cell membrane. Compared with mammalian prestin, charge movements mediated by zprestin display a weaker voltage dependence and slower kinetics; they occur at more positive membrane voltages, and are not associated with electromotile responses. Given this functional dissociation of NLC and electromotility and the structural similarity with mammalian prestin, we anticipate that zprestin provides a valuable tool for tracing the molecular and evolutionary bases of prestin motor function.
Numerical Simulation of In-Service Welding of a Pressurized Pipeline
Authors: Xue XiaoLong , Sang ZhiFu , Zhu JiaGui , Widera G. E. O.
Published: February 2007

The temperature field and stress distribution for in-service welding of a flowing media, pressurized pipeline are simulated by use of the finite element method (FEM). In order to investigate the effect of flowing media on the temperature field of in-service welding, the results are compared with those of a no-flow case. It is found that the flowing media took away most of the heat effects from welding. The cooling is accelerated and the peak temperature of the inner surface of the pipe is much lower than that of the no-flow case. An experiment was performed to verify the accuracy of the numerical model. The presence of internal pressure, i.e., flowing media, in the pipeline significantly affects the postcooling axial stress distribution.
Steady Analysis of the Thermodynamic Effect of Partial Cavitation Using the Singularity Method
Authors: Watanabe Satoshi , Hidaka Tatsuya , Horiguchi Hironori , Furukawa Akinori , Tsujimoto Yoshinobu
Published: February 2007

It is well known that the suction performance of turbopumps in cryogenic fluids is much better than that in cold water because of the thermodynamic effect of cavitation. In the present study, an analytical method to simulate partially cavitating flow with the thermodynamic effect in a cascade is proposed; heat transfer between the cavity and the ambient fluid is modeled by a one-dimensional unsteady heat conduction model under the slender body approximation and is coupled with a flow analysis using singularity methods. In this report, the steady analysis is performed and the results are compared with those of experiments to validate the model of the present analysis. This analysis can be easily extended into unsteady stability analysis for cavitation instabilities such as rotating cavitation and cavitation surge.
Protein Kinase C ß and Prolyl Isomerase 1 Regulate Mitochondrial Effects of the Life-Span Determinant p66
Shc
Authors: Pinton Paolo , Rimessi Alessandro , Marchi Saverio , Orsini Francesca , Migliaccio Enrica , Giorgio Marco , Contursi Cristina , Minucci Saverio , Mantovani Fiamma , Wieckowski Mariusz R. , Del Sal Giannino , Pelicci Pier Giuseppe , Rizzuto Rosario
Published: February 2007

The 66-kilodalton isoform of the growth factor adapter Shc (p66
Shc
) translates oxidative damage into cell death by acting as reactive oxygen species (ROS) producer within mitochondria. However, the signaling link between cellular stress and mitochondrial proapoptotic activity of p66
Shc
was not known. We demonstrate that protein kinase C β, activated by oxidative conditions in the cell, induces phosphorylation of p66
Shc
and triggers mitochondrial accumulation of the protein after it is recognized by the prolyl isomerase Pin1. Once imported, p66
Shc
causes alterations of mitochondrial Ca
2+
responses and three-dimensional structure, thus inducing apoptosis. These data identify a signaling route that activates an apoptotic inducer shortening the life span and could be a potential target of pharmacological approaches to inhibit aging.
Single Photon-Induced Symmetry Breaking of H
2
Dissociation
Authors: Martín F. , Fernández J. , Havermeier T. , Foucar L. , Weber Th. , Kreidi K. , Schöffler M. , Schmidt L. , Jahnke T. , Jagutzki O. , Czasch A. , Benis E. P. , Osipov T. , Landers A. L. , Belkacem A. , Prior M. H. , Schmidt-Böcking H. , Cocke C. L. , Dörner R.
Published: February 2007

H
2
, the smallest and most abundant molecule in the universe, has a perfectly symmetric ground state. What does it take to break this symmetry? We found that the inversion symmetry can be broken by absorption of a linearly polarized photon, which itself has inversion symmetry. In particular, the emission of a photoelectron with subsequent dissociation of the remaining H
+
2
fragment shows no symmetry with respect to the ionic H
+
and neutral H atomic fragments. This lack of symmetry results from the entanglement between symmetric and antisymmetric H
+
2
states that is caused by autoionization. The mechanisms behind this symmetry breaking are general for all molecules.
Production and Characterization of Monoclonal Antibodies against a Major Membrane Protein ofMycobacterium aviumsubsp.paratuberculosis
Authors: Bannantine John P. , Radosevich Thomas J. , Stabel Judith R. , Berger Sven , Griffin J. Frank T. , Paustian Michael L.
Published: February 2007

TheMycobacterium aviumsubsp.paratuberculosis35-kDa major membrane protein (MMP) encoded by MAP2121c is an important membrane antigen recognized in cattle with Johne's disease. In this study, purified recombinant MMP was used to produce two stable monoclonal antibodies, termed 8G2 and 13E1, which were characterized by immunoblotting, epitope mapping, and immunofluorescence microscopy.
Extent of Horizontal Gene Transfer in Evolution of Streptococci of the Salivarius Group
Authors: Delorme Christine , Poyart Claire , Ehrlich S. Dusko , Renault Pierre
Published: February 2007

The phylogenetically closely related species
Streptococcus salivarius
and
Streptococcus vestibularis
are oral bacteria that are considered commensals, although they can also be found in human infections. The relationship between these two species and the relationship between strains isolated from carriers and strains responsible for invasive infections were investigated by multilocus sequence typing and additional sequence analysis. The clustering of several
S. vestibularis
alleles and the extent of genomic divergence at certain loci support the conclusion that
S. salivarius
and
S. vestibularis
are separate species. The level of sequence diversity in
S. salivarius
alleles is generally high, whereas that in
S. vestibularis
alleles is low at certain loci, indicating that the latter species might have evolved recently. Cluster analysis indicated that there has been genetic exchange between
S. salivarius
and
S. vestibularis
at three of the nine loci investigated. Horizontal gene transfer between streptococci belonging to the
S. salivarius
group and other oral streptococci was also detected at several loci. A high level of recombination in
S. salivarius
was revealed by allele index association and split decomposition sequence analyses. Commensal and infection-associated
S. salivarius
strains could not be distinguished by cluster analysis, suggesting that the pathogen isolates are opportunistic. Taken together, our results indicate that there is a high level of gene exchange that contributes to the evolution of two streptococcal species from the human oral cavity.
TheyefM-yoeBToxin-Antitoxin Systems ofEscherichia coliandStreptococcus pneumoniae: Functional and Structural Correlation
Authors: Nieto Concha , Cherny Izhack , Khoo Seok Kooi , de Lacoba Mario García , Chan Wai Ting , Yeo Chew Chieng , Gazit Ehud , Espinosa Manuel
Published: February 2007

Toxin-antitoxin loci belonging to theyefM-yoeBfamily are located in the chromosome or in some plasmids of several bacteria. We cloned theyefM-yoeBlocus ofStreptococcus pneumoniae, and these genes encode bona fide antitoxin (YefMSpn) and toxin (YoeBSpn) products. We showed that overproduction of YoeBSpnis toxic toEscherichia colicells, leading to severe inhibition of cell growth and to a reduction in cell viability; this toxicity was more pronounced in anE. coliB strain than in twoE. coliK-12 strains. The YoeBSpn-mediated toxicity could be reversed by the cognate antitoxin, YefMSpn, but not by overproduction of theE. coliYefM antitoxin. The pneumococcal proteins were purified and were shown to interact with each other both in vitro and in vivo. Far-UV circular dichroism analyses indicated that the pneumococcal antitoxin was partially, but not totally, unfolded and was different than itsE. colicounterpart. Molecular modeling showed that the toxins belonging to the family were homologous, whereas the antitoxins appeared to be specifically designed for each bacterial locus; thus, the toxin-antitoxin interactions were adapted to the different bacterial environmental conditions. Both structural features, folding and the molecular modeled structure, could explain the lack of cross-complementation between the pneumococcal andE. coliantitoxins.
Group B Streptococcal Capsular Sialic Acids Interact with Siglecs (Immunoglobulin-Like Lectins) on Human Leukocytes
Authors: Carlin Aaron F. , Lewis Amanda L. , Varki Ajit , Nizet Victor
Published: February 2007

Group B
Streptococcus
(GBS) is classified into nine serotypes that vary in capsular polysaccharide (CPS) architecture but share in common the presence of a terminal sialic acid (Sia) residue. This position and linkage of GBS Sia closely resembles that of cell surface glycans found abundantly on human cells. CD33-related Siglecs (CD33rSiglecs) are a family of Sia-binding lectins expressed on host leukocytes that engage host Sia-capped glycans and send signals that dampen inflammatory gene activation. We hypothesized that GBS evolved to display CPS Sia as a form of molecular mimicry limiting the activation of an effective innate immune response. In this study, we applied a panel of immunologic and cell-based assays to demonstrate that GBS of several serotypes interacts in a Sia- and serotype-specific manner with certain human CD33rSiglecs, including hSiglec-9 and hSiglec-5 expressed on neutrophils and monocytes. Modification of GBS CPS Sia by O acetylation has recently been recognized, and we further show that the degree of O acetylation can markedly affect the interaction between GBS and hSiglec-5, -7, and -9. Thus, production of Sia-capped bacterial polysaccharide capsules that mimic human cell surface glycans in order to engage CD33rSiglecs may be an example of a previously unrecognized bacterial mechanism of leukocyte manipulation.
Real-Time PCR Assay for Detection of Quinolone-Resistant
Neisseria gonorrhoeae
in Urine Samples
Authors: Siedner Mark J. , Pandori Mark , Castro Lina , Barry Pennan , Whittington William L. H. , Liska Sally , Klausner Jeffrey D.
Published: February 2007

A need exists for the development of applicable surveillance tools to detect fluoroquinolone-resistant
Neisseria gonorrhoeae
(QRNG) in urine samples. We describe here a real-time PCR assay for detecting mutations in the Ser91 codon of the
gyrA
gene of
N. gonorrhoeae
in urine specimens. We tested 96 urine samples collected along with Gonorrhea Isolate Surveillance Project (GISP) urethral swab samples and compared the results with matched MICs of ciprofloxacin, as reported by the regional GISP laboratory. We then tested 100 urine specimens, known to be gonorrhea positive by nucleic acid amplification testing, provided by females to challenge the real-time PCR assay with urine specimens containing potentially less target DNA content than specimens from symptomatic males. With an MIC threshold of 0.125 μg of ciprofloxacin/ml, our assay correctly identified resistance in 41 of 44 (93.2%; 95% confidence interval [CI] = 81.3 to 98.6%) corresponding resistant culture specimens and correctly identified 51 of 51 (100%; 95% CI = 93.0 to 100%) susceptible specimens. One specimen did not amplify. The assay successfully amplified the
gyrA
amplicon and determined a susceptibility genotype in 72 of 100 (72%) urine specimens collected from female patients. We developed an assay for detecting QRNG in urine specimens that correlated well with MIC results of cultured specimens and had moderate sensitivity with urine specimens. This methodology might fulfill the need for a QRNG detection system for urine specimens, a useful characteristic in the age of nucleic acid amplification testing for gonococcal infection.
Survival of Fastidious and Nonfastidious Aerobic Bacteria in Three Bacterial Transport Swab Systems
Authors: Rishmawi Nabeel , Ghneim Raed , Kattan Randa , Ghneim Riyad , Zoughbi Madeleine , Abu-Diab Afaf , Turkuman Sultan , Dauodi Rula , Shomali Issa , Issa Abed El-Razeq , Siriani Issa , Marzouka Hiyam , Schmid Irmgard , Hindiyeh Musa Y.
Published: February 2007

In the present study, we followed the CLSI procedure M40-A to evaluate three specimen transport systems [the new BD CultureSwab MaxV(+), the new Remel BactiSwab, and the Medical Wire & Equipment Transwab] for the survival of fastidious and nonfastidious organisms for 0, 6, 24, and 48 h at room temperature. BD CultureSwab MaxV(+) outperformed the other two swabs for the recovery of the three fastidious organisms,
Haemophilus influenzae
,
Neisseria gonorrhoeae
, and
Neisseria meningitidis
for up to 48 h. Indeed, BD CultureSwab MaxV(+) maintained a constant number of viable
H. influenzae
and
N. meningitidis
for up to 48 h, and only a 2 log reduction was noted for
N. gonorrhoeae
, fulfilling the requirements of M40-A guidelines. However, unlike Remel BactiSwab and the Medical Wire & Equipment Transwab, which fulfilled the M40-A requirements for maintaining the viability of
Streptococcus pneumoniae
, BD CultureSwab MaxV(+) could not maintain the viability of
S. pneumoniae
reference or clinical strains past 6 h. Excellent overall sensitivity (98%) (95% confidence interval, 89.5 to 99.7) was observed when the BD CultureSwab MaxV(+) rectal swabs were compared to the “gold standard” stool cultures. Thus, the BD CultureSwab MaxV(+) rectal swab can be used when investigating gastrointestinal bacterial outbreaks or when health care providers face difficulties in obtaining stool samples, particularly from children.
Rotavirus Infection Alters Peripheral T-Cell Homeostasis in Children with Acute Diarrhea
Authors: Wang Yuhuan , Dennehy Penelope H. , Keyserling Harry L. , Tang Kevin , Gentsch Jon R. , Glass Roger I. , Jiang Baoming
Published: February 2007

The patterns of gene expression and the phenotypes of lymphocytes in peripheral blood mononuclear cells (PBMC) from children with diarrhea caused by rotavirus and healthy children were compared by using DNA microarray, quantitative PCR, and flow cytometry. We observed increased expression of a number of genes encoding proinflammatory cytokines and interferon or interferon-stimulated proteins and demonstrated activation of some genes involved in the differentiation, maturation, activation, and survival of B lymphocytes in PBMC of patients with rotavirus infection. In contrast, we observed a consistent pattern of lower mRNA levels for an array of genes involved in the various stages of T-cell development and demonstrated a reduction in total lymphocyte populations and in the proportions of CD4 and CD8 T lymphocytes from PBMC of patients. This decreased frequency of T lymphocytes was transient, since the proportions of T lymphocytes recovered to almost normal levels in convalescent-phase PBMC from most patients. Finally, rotavirus infection induced the activation and expression of the early activation markers CD83 and CD69 on a fraction of CD19 B cells and the remaining CD4 and CD8 T lymphocytes in acute-phase PBMC of patients; the expression of CD83 continued to be elevated and was predominantly exhibited on CD4 T lymphocytes in convalescent-phase PBMC. On the basis of these findings at the molecular, phenotypic, and physiologic levels in acute-phase PBMC, we conclude that rotavirus infection induces robust proinflammatory and antiviral responses and B-cell activation but alters peripheral T-cell homeostasis in children.
NFX1-123 and Poly(A) Binding Proteins Synergistically Augment Activation of Telomerase in Human Papillomavirus Type 16 E6-Expressing Cells
Authors: Katzenellenbogen Rachel A. , Egelkrout Erin M. , Vliet-Gregg Portia , Gewin Lindy C. , Gafken Philip R. , Galloway Denise A.
Published: February 2007

Overcoming senescence signals in somatic cells is critical to cellular immortalization and carcinogenesis. High-risk human papillomavirus (HPV) can immortalize epithelial cells in culture through degradation of the retinoblastoma protein by HPV E7 and activation of
hTERT
transcription, the catalytic subunit of telomerase, by the heterodimer HPV E6/E6-associated protein (E6AP). Recent work in our laboratory identified a novel repressor of
hTERT
transcription, NFX1-91, which is targeted for ubiquitin-mediated degradation by HPV type 16 (HPV16) E6/E6AP. In contrast, NFX1-123, a splice variant NFX1, increased expression from an
hTERT
promoter that was activated by HPV16 E6/E6AP. Here, we show that HPV16 E6 bound both NFX1-91 and NFX1-123 through the common central domain of NFX1 in the absence of E6AP. NFX1-123 positively regulated hTERT expression, as its knockdown decreased hTERT mRNA levels and telomerase activity and its overexpression increased telomerase activity. We identified new protein partners of NFX1-123, including several cytoplasmic poly(A) binding proteins (PABPCs) that interacted with NFX1-123 through its N-terminal PAM2 motif, a protein domain characteristic of other PABPC protein partners. Furthermore, NFX1-123 and PABPCs together had a synergistic stimulatory effect on
hTERT
-regulated reporter assays. The data suggest that NFX1-123 is integral to hTERT regulation in HPV16 E6-expressing epithelial cells and that the interaction between NFX1-123 and PABPCs is critical to hTERT activity.
The Nanovirus-Encoded Clink Protein Affects Plant Cell Cycle Regulation through Interaction with the Retinoblastoma-Related Protein
Authors: Lageix Sébastien , Catrice Olivier , Deragon Jean-Marc , Gronenborn Bruno , Pélissier Thierry , Ramírez Bertha Cecilia
Published: February 2007

Nanoviruses, multicomponent single-stranded DNA plant viruses, encode a unique cell cycle link protein, Clink, that interacts with retinoblastoma-related proteins (RBR). We have established transgenic
Arabidopsis thaliana
lines that conditionally express Clink or a Clink variant deficient in RBR binding. By controlled induction of Clink expression, we demonstrated the capacity of the Clink protein to alter RBR function in vivo. We showed that transcription of both S-phase-specific and G
2
/M-phase-specific genes was up-regulated depending on the RBR-binding proficiency of Clink. Concomitantly, ploidy levels increased in a substantial fraction of leaf cell nuclei. Also, leaf epidermis cells of transgenic plants producing Clink were smaller and more numerous, indicating additional cell divisions in this tissue. Furthermore, cytogenetic analyses following induction of Clink expression in mature leaves revealed the presence of metaphasic and anaphasic nuclei, clear evidence that Clink-mediated RBR inactivation is sufficient to induce quiescent cells to reenter cell cycle progression and, for at least a fraction of them, to pass through mitosis. Expression of Clink had no effect on genes transcribed by RNA polymerases I and III, suggesting that, in contrast to its mammalian homologue,
A. thaliana
RBR is not involved in the repression of polymerase I and polymerase III transcription. The results of these in vivo analyses firmly establish Clink as a member of the diverse class of multifunctional cell cycle modulator proteins encoded by small DNA viruses.
Bitopic Membrane Topology of the Stable Signal Peptide in the Tripartite Junín Virus GP-C Envelope Glycoprotein Complex
Authors: Agnihothram Sudhakar S. , York Joanne , Trahey Meg , Nunberg Jack H.
Published: February 2007

The stable signal peptide (SSP) of the GP-C envelope glycoprotein of the Junín arenavirus plays a critical role in trafficking of the GP-C complex to the cell surface and in its membrane fusion activity. SSP therefore may function on both sides of the lipid membrane. In this study, we have investigated the membrane topology of SSP by confocal microscopy of cells treated with the detergent digitonin to selectively permeabilize the plasma membrane. By using an affinity tag to mark the termini of SSP in the properly assembled GP-C complex, we find that both the N and C termini reside in the cytosol. Thus, SSP adopts a bitopic topology in which the C terminus is translocated from the lumen of the endoplasmic reticulum to the cytoplasm. This model is supported by (i) the presence of two conserved hydrophobic regions in SSP (hφ1 and hφ2) and (ii) our previous demonstration that lysine-33 in the ectodomain loop is essential for pH-dependent membrane fusion. Moreover, we demonstrate that the introduction of a charged side chain or single amino acid deletion in the membrane-spanning hφ2 region significantly diminishes SSP association in the GP-C complex and abolishes membrane fusion activity. Taken together, our results suggest that bitopic membrane insertion of SSP is centrally important in the assembly and function of the tripartite GP-C complex.
An Operational Definition of Relative Hardness
Authors: Politzer Peter , Murray Jane S. , Concha Monica C. , Jin Ping
Published: February 2007

After a brief review of polarizability, charge capacity and hardness, we look at some of the consequences of the requirement, in density functional theory, that the chemical potential and hardness be evaluated with the nuclear potential being held constant. The effects of this can be quite significant, one of them being that some molecules, especially closed-shell, may have zero chemical potentials. We propose that hardness be defined operationally through its inverse relationship to polarizability. Drawing upon correlations found earlier for the latter property, we present a formula for relative hardness in terms of the volume of a molecule and the average local ionization energy on its surface. The formula can also be applied to molecular components, e.g. functional groups, and we show - within the context of this approach - how their contributions combine to yield the hardness of the molecule. This involves a leveling-off effect that explains the relatively small range of hardness values obtained for a group of 33 molecules.
DR WHO: a workshop for house officer preparation
Authors: Cave Judith , Wallace Deirdre , Baillie Glenda , Klingenberg Michael , Phillips Catherine , Oliver Harriet , Rowles Katherine , Dunkley Lisa , Sturrock Alison , Dacre Jane
Published: February 2007

Background

Newly qualified doctors should be competent in advanced life support (ALS) and critical care. The Resuscitation Council has published a course about ALS for undergraduate medical students (the intermediate life support (ILS) course). However, there is no undergraduate-level course on assessing and treating critically ill patients, despite the fact that postgraduate courses on this topic are extremely popular. We have developed a new course called Direct Response Workshop for House Officer Preparation (DR WHO), which teaches both ALS and critical care at an undergraduate level.

Methods

We taught the Resuscitation Council ILS course to our 2003–4 cohort of final year medical students (n = 350), and the new course (DR WHO) to our 2004–5 cohort (n = 338). Students filled in feedback forms immediately after the courses, and a subset repeated the feedback forms 4 months after they had started work as house officers.

Course evaluation

Student and house officer feedback was positive. The DR WHO cohort was more confident in caring for critically ill patients (18/26 (69%) were confident after ILS, and 40/45 (89%) were confident after DR WHO (χ2 = 4.3; df = 1; p = 0.06)). Both cohorts were competent in ALS, each with a mean score of 18.6/20 in a finals level practical examination on this topic.

Conclusions

The DR WHO course is popular with the students and practical to run. The course needs to be re-evaluated to determine the long-term competency of graduates.
Endovascular abdominal aortic aneurysm repair
Authors: Norwood M G A , Lloyd G M , Bown M J , Fishwick G , London N J , Sayers R D
Published: February 2007

The operative mortality following conventional abdominal aortic aneurysm (AAA) repair has not fallen significantly over the past two decades. Since its inception in 1991, endovascular aneurysm repair (EVAR) has provided an alternative to open AAA repair and perhaps an opportunity to improve operative mortality. Two recent large randomised trials have demonstrated the short and medium term benefit of EVAR over open AAA repair, although data on the long term efficacy of the technique are still lacking. This review aimed at providing an overview of EVAR and a discussion of the potential benefits and current limitations of the technique.
ANALOG VLSI IMPLEMENTATION OF RESONATE-AND-FIRE NEURON
Authors: NAKADA KAZUKI , ASAI TETSUYA , HAYASHI HATSUO
Published: February 2007

We propose an analog integrated circuit that implements a resonate-and-fire neuron (RFN) model based on the Lotka-Volterra (LV) system. The RFN model is a spiking neuron model that has second-order membrane dynamics, and thus exhibits fast damped subthreshold oscillation, resulting in the coincidence detection, frequency preference, and post-inhibitory rebound. The RFN circuit has been derived from the LV system to mimic such dynamical behavior of the RFN model. Through circuit simulations, we demonstrate that the RFN circuit can act as a coincidence detector and a band-pass filter at circuit level even in the presence of additive white noise and background random activity. These results show that our circuit is expected to be useful for very large-scale integration (VLSI) implementation of functional spiking neural networks.
KOHONEN'S FEATURE MAPS FOR FLY ASH CATEGORIZATION
Authors: NATARAJA M. C. , JAYARAM M. A. , RAVIKUMAR C. N.
Published: February 2007

Fly ash is a common admixture used in concrete and may constitute up to 50% by weight of the total binder material. Incorporation of fly ash in Portland-cement concrete is highly desirable due to technological, economic, and environmental benefits. This article demonstrates the use of artificial intelligence neural networks for the classification of fly ashes in to different groups. Kohonen's Self Organizing Feature Maps is used for the purpose. As chemical composition of fly ash is crucial in the performance of concrete, eight chemical attributes of fly ashes have been considered. The application of simple Kohonen's one-dimensional feature maps permitted to differentiate three main groups of fly ashes. Three one-dimensional feature maps of topology 8–16, 8–24 and 8–32 were explored. The overall classification result of 8-16 topology was found to be significant and encouraging. The data pertaining to 80 fly ash samples were collected from standard published works. The categorization was found to be excellent and compares well with Canadian Standard Association's [CSA A 3000] classification scheme.
COOPERATION, COLLECTIVES FORMATION AND SPECIALIZATION
Authors: HAUERT CHRISTOPH
Published: February 2007

Cooperation in spatial evolutionary game theory has revealed various interesting insights into the problem of the evolution and maintenance of cooperative behavior. In social dilemmas, cooperators create and maintain a common resource at some cost to themselves while defectors attempt to exploit the resource without contributing. This leads to classical conflicts of interest between the individual and the community with the prisoner's dilemma as the most prominent mathematical metaphor to describe such situations. The evolutionary fate of cooperators and defectors sensitively depends on the interaction structure of the population. In spatially extended populations, the ability to form clusters or collectives often supports cooperation by limiting exploitation to the cluster boundaries but often collectives formation may also inhibit or even eliminate cooperation by hindering the dispersal of cooperators. Another attempt at resolving the conflict of interest allows individuals to drop out of unpromising public enterprises and hence changes compulsory interactions into voluntary participation. This leads to a cyclic dominance of cooperators, defectors and loners that do not participate and gives rise to oscillatory dynamics which again subtly depends on the population structure. Here we review recent advances in the dynamics of cooperation in structured populations as well as in situations where cooperative investments vary continuously. In such continuous games, the evolutionary dynamics driven by mutation and selection can lead to spontaneous diversification and specialization into high and low investing individuals which provides a natural explanation for the origin of cooperators and defectors.
Mathematical model of excitation-contraction in a uterine smooth muscle cell
Authors: Bursztyn Limor , Eytan Osnat , Jaffa Ariel J. , Elad David
Published: February 2007

Uterine contractility is generated by contractions of myometrial smooth muscle cells (SMCs) that compose most of the myometrial layer of the uterine wall. Calcium ion (Ca2+) entry into the cell can be initiated by depolarization of the cell membrane. The increase in the free Ca2+ concentration within the cell initiates a chain of reactions, which lead to formation of cross bridges between actin and myosin filaments, and thereby the cell contracts. During contraction the SMC shortens while it exerts forces on neighboring cells. A mathematical model of myometrial SMC contraction has been developed to study this process of excitation and contraction. The model can be used to describe the intracellular Ca2+ concentration and stress produced by the cell in response to depolarization of the cell membrane. The model accounts for the operation of three Ca2+ control mechanisms: voltage-operated Ca2+ channels, Ca2+ pumps, and Na+/Ca2+ exchangers. The processes of myosin light chain (MLC) phosphorylation and stress production are accounted for using the cross-bridge model of Hai and Murphy ( Am J Physiol Cell Physiol 254: C99–C106, 1988) and are coupled to the Ca2+ concentration through the rate constant of myosin phosphorylation. Measurements of Ca2+, MLC phosphorylation, and force in contracting cells were used to set the model parameters and test its ability to predict the cell response to stimulation. The model has been used to reproduce results of voltage-clamp experiments performed in myometrial cells of pregnant rats as well as the results of simultaneous measurements of MLC phosphorylation and force production in human nonpregnant myometrial cells.
Effect of cyclic stretch on β1D-integrin expression and activation of FAK and RhoA
Authors: Zhang Sarah Jingying , Truskey George A. , Kraus William E.
Published: February 2007

Integrins play a pivotal role in proliferation, differentiation, and survival in skeletal and cardiac myocytes. The β1D-isoform of the β1-integrin is specifically expressed in striated skeletal muscle. However, little is known about the role and the mechanisms by which the splice variant β1D-integrin regulates myogenesis and mechanotransduction. We observed that cyclic mechanical stretch increases β1D-integrin protein levels and activates the downstream cytoskeletal signaling proteins focal adhesion kinase (FAK) and RhoA. Elimination of native β1D-integrin expression by RNA interference in immature developing myoblasts abolished stretch-induced increases in FAK phosphorylation and further downregulated RhoA activity. Blocking of β1D-integrin expression prevented myocellular fusion to form multinucleated mature myotubes. Restoration of human β1D-integrin expression in β1D-integrin-deficient cells partially restored myotube formation. The onset of myofusion also requires the generation of nitric oxide (NO). The release of NO affects cytoskeletal proteins by mediating RhoA activity and protein degradation. Our previous study demonstrated that stretch-induced NO positively modulates mechanical properties of differentiating skeletal myocytes. We found a significant decrease in NO production and apparent elastic modulus in β1D-integrin-deficient cells, suggesting signaling interactions between β1D-integrin and neuronal NO synthase to mediate mechanotransduction and myogenesis in skeletal myocytes. These results suggest that, in addition to regulating differentiation, the β1D-integrin isoform plays a critical role in the response of skeletal myoblasts to cyclic stretch by activating the downstream components of FAK and RhoA activity and affecting NO release.
Wave intensity analysis of left ventricular filling: application of windkessel theory
Authors: Flewitt Jacqueline A. , Hobson Tracy N. , Wang Jiun , Johnston Clifton R. , Shrive Nigel G. , Belenkie Israel , Parker Kim H. , Tyberg John V.
Published: February 2007

We extend our recently published windkessel-wave interpretation of vascular function to the wave intensity analysis (WIA) of left ventricular (LV) filling dynamics by separating the pressure changes due to the windkessel from those due to traveling waves. With the use of LV compliance, the change in pressure due solely to LV volume changes (windkessel pressure) can be isolated. Inasmuch as the pressure measured in the cardiovascular system is the sum of its windkessel and wave components (excess pressure), it can be substituted into WIA, yielding the isolated wave effects on LV filling. Our study of six open-chest dogs demonstrated that once the windkessel effects are removed from WIA, the energy of diastolic suction is 2.6 times greater than we previously calculated. Volume-related changes in pressure (i.e., the windkessel or reservoir effect) must be considered first when wave motion is analyzed.
Somatostatin regulates hepatic growth hormone sensitivity by internalizing growth hormone receptors and by decreasing transcription of growth hormone receptor mRNAs
Authors: Very Nicole M. , Sheridan Mark A.
Published: February 2007

Somatostatins (SSs), a diverse family of peptide hormones, have been shown to inhibit the release of growth hormone (GH) from the pituitary. In this study, we used rainbow trout to determine whether or not SSs affect growth in an extrapituitary manner, in particular, by decreasing GH sensitivity in liver. SS-14 significantly decreased hepatic GH binding in fish implanted (5.8 × 10−11 mol/h) for 15 days and in isolated hepatocytes. The processing of 125I-labeled trout GH (tGH) by isolated hepatocytes was investigated to determine whether or not the decrease in GH binding capacity resulted from receptor internalization. The internalization of 125I-labeled tGH was time dependent. By 6 h, 100 ng/ml SS-14 increased internalization of 125I-labeled tGH 58% over that observed in controls. Steady-state levels of mRNAs encoding the two hepatic growth hormone receptors (GHRs) of trout, GHR 1 and GHR 2, were measured to determine whether or not decreased GH binding capacity also resulted from decreased GHR synthesis. SS-14 directly inhibited steady-state levels of GHR 1 and GHR 2 mRNA in isolated hepatocytes in a concentration-dependent manner. The inhibitory effects of SS-14 on steady-state levels of GHR mRNAs resulted from reduced GHR mRNA transcription and not from altered mRNA stability. These results indicate that SSs regulate hepatic GH sensitivity by increasing GHR internalization and by altering GHR expression and suggest that SSs coordinate growth at the level of the pituitary, as well as at extrapituitary levels.
Developmental changes of purinergic control of intestinal motor activity during metamorphosis in the African clawed frog,Xenopus laevis
Authors: Sundqvist Monika
Published: February 2007

Little is known about the purinergic regulation of intestinal motor activity in amphibians. Purinergic control of intestinal motility is subject to changes during development in mammals. The aim of this study was to investigate purinergic control of intestinal smooth muscle in the amphibian Xenopus laevis and explore possible changes in this system during the developmental phase of metamorphosis. Effects of purinergic compounds on mean force and contraction frequency in intestinal circular muscle strips from prometamorphic, metamorphic, and juvenile animals were investigated. Before metamorphosis, low concentrations of ATP reduced motor activity, whereas the effects were reversed at higher concentrations. ATP-induced relaxation was not inhibited by the P2-receptor antagonist pyridoxalphosphate-6-azophenyl-2′,4′-disulfonic acid (PPADS) but was blocked by the ecto-nucleotidase inhibitor 6- N, N-diethyl-d-β,γ-dibromomethylene ATP ( ARL67256 ), indicating that an ATP-derived metabolite mediated the relaxation response at this stage. Adenosine induced relaxation before, during, and after metamorphosis, which was blocked by the A1-receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). The stable ATP-analog adenosine 5′-[γ-thio]-triphosphate (ATPγS) and 2-methylthioATP (2-MeSATP) elicited contractions in the circular muscle strips in prometamorphic tadpoles. However, in juvenile froglets, 2-MeSATP caused relaxation, as did ATPγS at low concentrations. The P2Y11/P2X1-receptor antagonist NF157 antagonized the ATPγS-induced relaxation. The P2X-preferring agonist α-β-methyleneadenosine 5′-triphosphate (α-β-MeATP) evoked PPADS-sensitive increases in mean force at all stages investigated. This study demonstrates the existence of an adenosine A1-like receptor mediating relaxation and a P2X-like receptor mediating contraction in the X. laevis gut before, during, and after metamorphosis. Furthermore, the development of a P2Y11-like receptor-mediated relaxation during metamorphosis is shown.
Effect of urine fractionation on attachment of calcium oxalate crystals to renal epithelial cells: implications for studying renal calculogenesis
Authors: Grover Phulwinder K. , Thurgood Lauren A. , Ryall Rosemary L.
Published: February 2007

Our aim was to determine whether fractionation of human urine affects the attachment of calcium oxalate monohydrate (COM) crystals to renal cells. Urine collected from six healthy subjects was fractionated into sieved (S), centrifuged (C), centrifuged and filtered (CF), or ultrafiltered (UF). Attachment of [14C]COM crystals to Madin-Darby canine kidney (MDCK) cells was studied after precoating the crystals or the cells with the urine fractions and by using the same fractions as the binding medium. Protein content of the fractions and precoated crystals was analyzed with SDS-PAGE and Western blotting. All urine fractions inhibited crystal attachment. When fractions from the six urine samples were used to precoat the cells, the median inhibitions of crystal adhesion (∼40%) were not significantly different. Median inhibition after preincubation of crystals was the same for the S, C, and CF fractions (∼40%) but significantly greater than for the UF fraction (∼28%). When fractions were used as the binding medium, median inhibitions decreased from 64% in the S fraction to 47 (C), 42 (CF), and to 29% (UF). SDS-PAGE analysis showed that centrifugation and filtration reduced the amount of Tamm-Horsfall glycoprotein (THG), which was confirmed by Western blotting. Human serum albumin, urinary prothrombin fragment 1, and osteopontin, but not THG, were present in demineralized extracts of the precoated crystals. Fractionation of human urine affects the attachment of COM crystals to MDCK cells. Hence future studies investigating regulation of crystal-cell interactions should be carried out in untreated urine as the binding medium.
Susceptibility to pulmonary hypertension in inbred strains of mice exposed to cigarette smoke
Authors: Nadziejko Christine , Fang Kaije , Bravo Antonio , Gordon Terry
Published: February 2007

Cor pulmonale is a significant cause of morbidity and mortality in patients with emphysema, but it is not known whether alveolar destruction is directly involved in the disease pathogenesis. The purpose of this study was to examine the relationship between susceptibility to smoking-induced cor pulmonale and alveolar destruction in eight inbred strains of mice: 129XI/SvJ, A/J, A/HeJ, BALB/cJ, C3H/HeJ, C57BL/6J, DBA/2J, and SWR/J. The mice were exposed to filtered air or mainstream cigarette smoke at a concentration of 250 mg/m3 for 5.5 h/day, 5 days/wk for 5 mo, housed for 4 more months, and killed. The ratio of the weight of the right ventricle/left ventricle plus septum [RV/(LV + S)] was used to assess right ventricular hypertrophy. Alveolar mean linear intercept was used to quantify severity of alveolar destruction. Morphometric determination of blood vessel muscularization was done on sections from four mouse strains. Smoke exposure resulted in significant increases in RV/(LV + S) in the A/J and A/HeJ strains compared with air-exposed controls. The magnitude of the smoking-induced increase in RV/(LV + S) decreased as a function of the genetic distance of the other strains from the A/J and A/HeJ strains. Pulmonary vascular muscularization was significantly increased in smoke-exposed A/J and BALB/cJ mice but not in C3H/HeJ and C57BL/6 mice. Also, mouse strain susceptibility to smoking-induced pulmonary vascular muscularization did not correlate with changes in mean linear intercept. The data from this study suggest that alveolar destruction by itself is not sufficient to cause smoking-induced cor pulmonale in inbred mice.