bluuebunny/crossref_metadata_2025 huggingface dataset:
The privacy and safety impact of technology choices for command, communications and control of the public highway
Authors: Crowcroft Jon
Published: February 2006

Monitoring, and command,communications and control of private vehicles on the public highway is now high on the political agenda. This is both because it is becoming feasible, and because it may be desirable. From the economic perspective, more efficient se of road resources may be achievable. From a safety perspective, it would clearly be good to reduce road injury and death statistics below the current "9/11"'s-worth per year in the UK (and other similar sized European countries).Various prototypes, proposals and projects are being undertaken. There are a number of technologies that interact as well as numerous legal, political and economic stakeholders. In this note, we pay particular attention to the impact on privacy and safety of di .erent approaches to the overall problem.The purpose is to draw attention to the potential unintended consequences that result from decisions being made at the time of writing, in this arena.
Adjusting forward error correction with temporal scaling for TCP-friendly streaming MPEG
Authors: Wu Huahui , Claypool Mark , Kinicki Robert
Published: February 2006

New TCP-friendly constraints require multimedia flows to reduce their data rates under packet loss to that of a conformant TCP flow. To reduce data rates while preserving real-time playout, temporal scaling can be used to discard the encoded multimedia frames that have the least impact on perceived video quality. To limit the impact of lost packets, Forward Error Correction (FEC) can be used to repair frames damaged by packet loss. However, adding FEC requires further reduction of multimedia data, making the decision of how much FEC to use of critical importance. Current approaches use either inflexible FEC patterns or adapt to packet loss on the network without regard to TCP-friendly data rate constraints. In this article, we analytically model the playable frame rate of a TCP-friendly MPEG stream with FEC and temporal scaling, capturing the impact of distributing FEC within MPEG frame types with interframe dependencies. For a given network condition and MPEG video encoding, we use our model to exhaustively search for the optimal combination of FEC and temporal scaling that yields the highest playable frame rate within TCP-friendly constraints. Analytic experiments over a range of network and application conditions indicate that adjustable FEC with temporal scaling can provide a significant performance improvement over current approaches. Extensive simulation experiments based on Internet traces show that our model can be effective as part of a streaming protocol that chooses FEC and temporal scaling patterns that meet dynamically-changing application and network conditions.
Investigating sophisticated security breaches
Authors: Casey Eoghan
Published: February 2006

Sophisticated intruders take full advantage of the lack of forensic readiness. To respond more effectively to such attacks, computer security professionals and digital investigators must combine talents and work together.
Coding for the Code
Authors: Steimann Friedrich , Kühne Thomas
Published: February 2006

Despite the considerable effort invested by industry and academia in modeling standards such as UML (Unified Modeling Language), software modeling has long played a subordinate role in commercial software development. Although modeling is generally perceived as state of the art and thus as something that ought to be done, its appreciation seems to pale along with the progression from the early, more conceptual phases of a software project to those where the actual handcrafting is done. As a matter of fact, while models have been found useful for documentation purposes and as rough sketches of implementations, their ultimate value has been severely limited by their ambiguity and tendency to get out of sync with the final code.
Lessons from resource allocators for large-scale multiuser testbeds
Authors: Ricci Robert , Oppenheimer David , Lepreau Jay , Vahdat Amin
Published: February 2006

Resource allocation is a key aspect of shared testbed infrastructures such as PlanetLab and Emulab. Despite their many differences, both types of testbed have many resource allocation issues in common. In this paper we explore issues related to designing a general resource allocation interface that is sufficient for a wide variety of testbeds, current and future. Our explorations are informed by our experience developing and running Emulab's "assign" resource allocator and the "SWORD" resource discoverer, our experience with the PlanetLab and Emulab testbeds, and our projection of future testbed needs.
Application systems development
Authors: Cronan Timothy P.
Published: February 2006

Computer system utilization in business has increased in recent years. Computer systems are commonly an integral part of accounting, finance, management, marketing, and production information systems. These computer systems in conjunction with the major business functions have developed into information systems, decision support systems, and business data processing applications. These systems for decision support were routinely developed by data processing (and computer science) personnel. As more systems were developed and system utilization increased, problems in system acceptability and performance have surfaced.
On Time Series Analysis of Public Health and Biomedical Data
Authors: Zeger Scott L. , Irizarry Rafael , Peng Roger D.
Published: February 2006

This paper gives an overview of time series ideas and methods used in public health and biomedical research. A time series is a sequence of observations made over time. Examples in public health include daily ozone concentrations, weekly admissions to an emergency department, or annual expenditures on health care in the United States. Time series models are most commonly used in regression analysis to describe the dependence of the response at each time on predictor variables including covariates and possibly previous values in the series. For example, Bell et al. ( 2 ) use time series methods to regress daily mortality in U.S. cities on concentrations of particulate air pollution. Time series methods are necessary to make valid inferences from data by accounting for the correlation among repeated responses over time.
Albumin inhibits adipogenesis and stimulates cytokine release from human adipocytes
Authors: Schlesinger Janet B. , van Harmelen Vanessa , Alberti-Huber Catherine E. , Hauner Hans
Published: February 2006

Bovine serum albumin (BSA) is commonly used in adipocyte experiments as a binding protein for fat-soluble substances. Therefore, it is of interest to investigate whether BSA per se is influencing the functioning of human adipocytes in vitro. In the present study, we investigated the potential of BSA to affect the proliferation and differentiation capacity of human preadipocytes. BSA was found to inhibit adipose differentiation in a dose-dependent manner (being significant at concentrations of 2.5 μM), whereas proliferation was not affected. We further investigated the effect of BSA on the secretory function of adipocytes focusing on the release of selected cytokines. Preadipocytes and freshly isolated adipocytes incubated with BSA secreted significantly higher amounts of IL-6, -8, and -10, and TNF-α compared with cells incubated without BSA. The effects on cytokine secretion seemed to reside at the level of gene expression because BSA increased TNF-α and IL-6 mRNA in a dose-dependent manner. The results of the present study indicate that the presence of BSA in the culture medium has considerable effects on adipocyte function in vitro. These effects should be carefully considered for in vitro studies of adipose tissue.
Multiple signaling pathways are involved in endothelin-1-induced brain endothelial cell migration
Authors: Milan Johanna , Charalambous Christiana , Elhag Rashid , Chen Thomas C. , Li Wei , Guan Shengxi , Hofman Florence M. , Zidovetzki Raphael
Published: February 2006

We have observed that the vasoactive peptide endothelin-1 is a potent inducer of migration of primary human brain-derived microvascular endothelial cells. By blocking signal transduction pathways with specific inhibitors, and using dominant negative mutant infections, we have demonstrated that multiple pathways are involved in endothelin-1-induced migration. Absolutely required for migration are protein tyrosine kinase Src, Ras, protein kinase C (PKC), phosphatidylinositol 3-kinase, ERK, and JNK; partial requirements were exhibited by cAMP-activated protein kinase and p38 kinase. Partial elucidation of the signal transduction sequences showed that the MAPKs ERK, JNK, and p38 are positioned downstream of both PKC and cAMP-activated protein kinase in the signal transduction scheme. The results show that human brain endothelial cell migration has distinct characteristics, different from cells derived from other vascular beds, or from other species, often used as model systems. Furthermore, the results indicate that endothelin-1, secreted by many tumors, is an important contributor to tumor-produced proangiogenic microenvironment. This growth factor has been associated with increased microvessel density in tumors and is responsible for endothelial cell proliferation, migration, invasion, and tubule formation. Because many signal transduction pathways investigated in this study are potential or current targets for anti-angiogenesis therapy, these results are of critical importance for designing physiological antiangiogenic protocols.
Oncostatin M differentially regulates CXC chemokines in mouse cardiac fibroblasts
Authors: Lafontant Pascal J. , Burns Alan R. , Donnachie Elizabeth , Haudek Sandra B. , Smith C. Wayne , Entman Mark L.
Published: February 2006

Ischemia-reperfusion injury in the heart is characterized by marked infiltration of neutrophils in the myocardial interstitial space. Studies in human, canine, and murine models have revealed oncostatin M (OSM) expression in infiltrating leukocytes. In an effort to assess possible roles of OSM in the myocardium, we used cardiac fibroblasts (mCFs) isolated from adult mouse heart to determine whether recombinant murine OSM regulates the synthesis and release of MIP2/CXCL2, KC/CXCL1, and LIX/CXCL5, which are three potent neutrophil chemoattractants in the mouse. Our results demonstrate that mCFs express OSM receptors and that, within the IL-6 cytokine family, OSM uniquely induces significant release of KC and LIX in mCFs. In addition, although OSM activates the JAK-signal transducers and activators of transcription and MAPK pathways, we demonstrate that the OSM-mediated CXC chemokine release in mCFs is also dependent on the activation of the phosphatidylinositol 3-kinase pathway.
Dynamic biophysical strain modulates proinflammatory gene induction in meniscal fibrochondrocytes
Authors: Ferretti Mario , Madhavan Shashi , Deschner James , Rath-Deschner Birgit , Wypasek Ewa , Agarwal Sudha
Published: February 2006

Fibrochondrocytes of meniscus adapt to changes in their biomechanical environment by mechanisms that are yet to be elucidated. In this study, the mechanoresponsiveness of fibrochondrocytes under normal and inflammatory conditions was investigated. Fibrochondrocytes from rat meniscus were exposed to dynamic tensile forces (DTF) at various magnitudes and frequencies. The mechanoresponsiveness was assessed by examining the expression of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α), and matrix metalloproteinase-13 mRNA expression. The mRNA and protein analyses revealed that DTF at magnitudes of 5% to 20% did not induce proinflammatory gene expression. IL-1β induced a rapid increase in the iNOS mRNA. DTF strongly repressed IL-1β-dependent iNOS induction in a magnitude-dependent manner. Exposure to 15% DTF resulted in >90% suppression of IL-1β-induced mRNA within 4 h and this suppression was sustained for the ensuing 20 h. The mechanosensitivity of fibrochondrocytes was also frequency dependent and maximal suppression of iNOS mRNA expression was observed at rapid frequencies of DTF compared with lower frequencies. Like iNOS, DTF also inhibited IL-1β-induced expression of proinflammatory mediators involved in joint inflammation. The examination of temporal effects of DTF revealed that 4- or 8-h exposure of DTF was sufficient for its sustained anti-inflammatory effects during the next 20 or 16 h, respectively. Our findings indicate that mechanical signals act as potent anti-inflammatory signals, where their magnitude and frequency are critical determinants of their actions. Furthermore, mechanical signals continue attenuating proinflammatory gene transcription for prolonged periods of time after their removal.
Aortic smooth muscle and endothelial plasma membrane Ca2+ pump isoforms are inhibited differently by the extracellular inhibitor caloxin 1b1
Authors: Pande Jyoti , Mallhi Kanwaldeep K. , Sawh Ahilya , Szewczyk Magdalena M. , Simpson Fiona , Grover Ashok K.
Published: February 2006

Plasma membrane Ca2+ pumps (PMCA) that expel Ca2+ from cells are encoded by four genes (PMCA1–4). In this study, we show that aortic endothelium and smooth muscle differ in their PMCA isoform mRNA expression: endothelium expressed predominantly PMCA1, and smooth muscle expressed PMCA4 and a lower level of PMCA1. In this study, we report a novel peptide (caloxin 1b1, obtained by screening for binding to extracellular domain 1 of PMCA4), which inhibited PMCA extracellularly, selectively, and had a higher affinity for PMCA4 than PMCA1. It inhibited the PMCA Ca2+-Mg2+-ATPase activity in leaky erythrocyte ghosts (mainly PMCA4) with a Ki value of 46 ± 5 μM, making it 10× more potent than the previously reported caloxin 2a1. It was isoform selective because it inhibited the PMCA1 Ca2+-Mg2+-ATPase in human embryonic kidney-293 cells with a higher Ki value (105 ± 11 μM) than for PMCA4. Caloxin 1b1 was selective in that it did not inhibit other ATPases. Because caloxin 1b1 had been selected to bind to an extracellular domain of PMCA, it could be added directly to cells and tissues to examine its effects on smooth muscle and endothelium. In deendothelialized aortic rings, caloxin 1b1 (200 μM) produced a contraction. It also increased the force of contraction produced by a submaximum concentration of phenylephrine. In aortic rings with endothelium intact, precontracted with phenylephrine and relaxed partially with a submaximum concentration of carbachol, caloxin 1b1 increased the force of contraction rather than potentiating the endothelium-dependent relaxation. In cultured cells, caloxin 1b1 increased the cytosolic [Ca2+] more in arterial smooth muscle cells than in endothelial cells. Thus caloxin 1b1 is the first highly selective extracellular PMCA inhibitor that works better on vascular smooth muscle than on endothelium.
Temperature dependence of human ether-à-go-go-related gene K+ currents
Authors: Vandenberg Jamie I. , Varghese Anthony , Lu Yu , Bursill Jane A. , Mahaut-Smith Martyn P. , Huang Christopher L.-H.
Published: February 2006

The function of voltage-gated human ether-à-go-gorelated gene ( hERG) K+ channels is critical for both normal cardiac repolarization and suppression of arrhythmias initiated by premature excitation. These important functions are facilitated by their unusual kinetics that combine relatively slow activation and deactivation with rapid and voltage-dependent inactivation and recovery from inactivation. The thermodynamics of these unusual features were examined by exploring the effect of temperature on the activation and inactivation processes of hERG channels expressed in Chinese hamster ovary cells. Increased temperature shifted the voltage dependence of activation in the hyperpolarizing direction but that of inactivation in the depolarizing direction. This increases the relative occupancy of the open state and contributes to the marked temperature sensitivity of hERG current magnitude observed during action potential voltage clamps. The rates of activation and deactivation also increase with higher temperatures, but less markedly than do the rates of inactivation and recovery from inactivation. Our results also emphasize that one cannot extrapolate results obtained at room temperature to 37°C by using a single temperature scale factor.
Modulation of hepatocellular swelling-activated K+ currents by phosphoinositide pathway-dependent protein kinase C
Authors: Lan Wen-Zhi , Wang Penny Y. T. , Hill Ceredwyn E.
Published: February 2006

K+ channels participate in the regulatory volume decrease (RVD) accompanying hepatocellular nutrient uptake and bile formation. We recently identified KCNQ1 as a molecular candidate for a significant fraction of the hepatocellular swelling-activated K+ current ( IKVol). We have shown that the KCNQ1 inhibitor chromanol 293B significantly inhibited RVD-associated K+ flux in isolated perfused rat liver and used patch-clamp techniques to define the signaling pathway linking swelling to IKVol activation. Patch-electrode dialysis of hepatocytes with solutions that maintain or increase phosphatidylinositol 4,5-bisphosphate (PIP2) increased IKVol, whereas conditions that decrease cellular PIP2 decreased IKVol. GTP and AlF4− stimulated IKVol development, suggesting a role for G proteins and phospholipase C (PLC). Supporting this, the PLC blocker U-73122 decreased IKVol and inhibited the stimulatory response to PIP2 or GTP. Protein kinase C (PKC) is involved, because K+ current was enhanced by 1-oleoyl-2-acetyl- sn-glycerol and inhibited after chronic PKC stimulation with phorbol 12-myristate 13-acetate (PMA) or the PKC inhibitor GF 109203X. Both IKVol and the accompanying membrane capacitance increase were blocked by cytochalasin D or GF 109203X. Acute PMA did not eliminate the cytochalasin D inhibition, suggesting that PKC-mediated IKVol activation involves the cytoskeleton. Under isotonic conditions, a slowly developing K+ current similar to IKVol was activated by PIP2, lipid phosphatase inhibitors to counter PIP2 depletion, a PLC-coupled α1-adrenoceptor agonist, or PKC activators and was depressed by PKC inhibition, suggesting that hypotonicity is one of a set of stimuli that can activate IKVol through a PIP2/PKC-dependent pathway. The results indicate that PIP2 indirectly activates hepatocellular KCNQ1-like channels via cytoskeletal rearrangement involving PKC activation.
Quantifying EGJ morphology and relaxation with high-resolution manometry: a study of 75 asymptomatic volunteers
Authors: Pandolfino John E. , Ghosh Sudip K. , Zhang Qing , Jarosz Andrew , Shah Nimeesh , Kahrilas Peter J.
Published: February 2006

Our aim was to define normal esophagogastric junction (EGJ) morphology and relaxation characteristics using high-resolution manometry (HRM). To this end, 75 asymptomatic controls underwent HRM with a solid-state manometric assembly incorporating 36 circumferential sensors spaced at 1-cm intervals positioned to record from the hypopharynx to the stomach. Ten 5-ml water swallows were obtained. EGJ relaxation was quantified by 1) nadir pressure, 2) the lowest 3-s mean residual pressure after swallow (E-sleeve), and 3) the transsphincteric gradient 2–6 s after swallowing measured from 2 cm above to 2 cm below the EGJ. A new parameter, integrated relaxation resistance (IRR), was also calculated. The IRR calculation accounted for both the duration of EGJ relaxation and instantaneous E-sleeve-type relaxation pressures during the entire interval of relaxation. The means and ranges (5–95th percentile) for nadir lower esophageal sphincter relaxation pressure (mean: 3.9 mmHg, range: 0–10.1 mmHg) and E-sleeve relaxation pressure (mean: 8.1 mmHg, range: 4.1–15.1 mmHg) were consistent with previously reported values. The mean relaxation interval was 7.95 ± 0.2 s (mean ± SE), whereas the median relaxation pressure during that interval was 10.7 ± 0.5 mmHg (mean ± SE). Mean IRR was 1.3 mmHg/s (95th percentile: 3.0 mmHg/s). Mean EGJ length was 3.7 cm. In conclusion, HRM provides a seamless dynamic representation of pressure within and across the EGJ. In addition to providing conventional EGJ relaxation parameters, this technology also creates opportunities to quantify more precise measures of EGJ relaxation and morphology.
Activation of subfornical organ neurons in rats through pre- and postsynaptic α-adrenoceptors
Authors: Honda Eiko , Ono Kentaro , Kataoka Shinji , Inenaga Kiyotoshi
Published: February 2006

The effects of noradrenaline (NA) and its analogs on subfornical organ (SFO) neurons in rat slice preparations were investigated by using whole cell patch-clamp recording. In the current-clamp mode, the application of NA at 10–100 μM produced membrane depolarization (63%, 17 responsive neurons/27 neurons tested) and hyperpolarization (22%, 6/27 neurons). In the voltage-clamp mode, NA application at 1–100 μM produced inward currents (69%, 42/61 neurons) and outward currents (23%, 14/61 neurons). These currents remained in the presence of TTX or both glutamate and GABA receptor antagonists. In most of the neurons (25/31 neurons) showing inward currents in the presence of NA, the membrane conductance was not changed by voltage ramps or hyperpolarizing pulse stimulation. Similar responses were obtained by the application of the α1-agonist phenylephrine. The phenylephrine-induced inward currents were inhibited by the α1-antagonist prazosin. The α2-agonist clonidine decreased the frequency of spontaneous GABAergic inhibitory postsynaptic currents (4/10 neurons). In addition, RT-PCR assay and immunohistochemical staining showed the existence of α1-adrenoceptors in the SFO. The results suggest that SFO neurons in rats are activated postsynaptically through α1-adrenoceptors and that the activation is enhanced by suppressing GABAergic inhibitory synaptic inputs through presynaptic α2-adrenoceptors.
Role of an Identified Looming-Sensitive Neuron in Triggering a Flying Locust's Escape
Authors: Santer Roger D. , Rind F. Claire , Stafford Richard , Simmons Peter J.
Published: February 2006

Flying locusts perform a characteristic gliding dive in response to predator-sized stimuli looming from one side. These visual looming stimuli trigger trains of spikes in the descending contralateral movement detector (DCMD) neuron that increase in frequency as the stimulus gets nearer. Here we provide evidence that high-frequency (>150 Hz) DCMD spikes are involved in triggering the glide: the DCMD is the only excitatory input to a key gliding motor neuron during a loom; DCMD-mediated EPSPs only summate significantly in this motor neuron when they occur at >150 Hz; when a looming stimulus ceases approach prematurely, high-frequency DCMD spikes are removed from its response and the occurrence of gliding is reduced; and an axon important for glide triggering descends in the nerve cord contralateral to the eye detecting a looming stimulus, as the DCMD does. DCMD recordings from tethered flying locusts showed that glides follow high-frequency spikes in a DCMD, but analyses could not identify a feature of the DCMD response alone that was reliably associated with glides in all trials. This was because, for a glide to be triggered, the high-frequency spikes must be timed appropriately within the wingbeat cycle to coincide with wing elevation. We interpret this as flight-gating of the DCMD response resulting from rhythmic modulation of the flight motor neuron's membrane potential during flight. This means that the locust's escape behavior can vary in response to the same looming stimulus, meaning that a predator cannot exploit predictability in the locust's collision avoidance behavior.
Inflammation-Susceptible Lewis Rats Show Less Sensitivity Than Resistant Fischer Rats in the Formalin Inflammatory Pain Test and With Repeated Thermal Testing
Authors: Lariviere William R. , Sattar M. Abdus , Melzack Ronald
Published: February 2006

Comparisons between Lewis and Fischer inbred strains of rats are used frequently to study the effect of inherent differences in function of the hypothalamic-pituitary-adrenal axis on pain-relevant traits, including differential susceptibility to chronic inflammatory disease and differential responsiveness to analgesic drugs. Increasing use of genetic models including transgenic knockout mice and inbred strains of rodents has raised our awareness of, and the importance of, thorough characterization (or phenotyping) of the strains of rodents being compared. Furthermore, genetic variability in analgesic sensitivity is correlated with, and may be caused by, genetically determined baseline sensitivity. Thus in this study, baseline inflammatory and thermal nociceptive sensitivities were measured in awake male and female Lewis and Fischer rats to examine whether the results could explain relevant strain differences reported in the literature. The effect of maternal separation was also examined and no effect was found on nociceptive sensitivity, corticosterone responses, or the development of adjuvant-induced arthritis, a model of rheumatoid arthritis. Lewis rats and female rats were more sensitive to thermal nociception in the tail withdrawal test (mean of 3 trials) than Fischer rats and male rats, respectively. Unexpectedly, the more inflammation-susceptible Lewis rats were less sensitive in the formalin inflammatory nociception test, and showed a significant decrease in sensitivity with repeated thermal nociceptive testing, whereas Fischer rats did not. These results affect the interpretation of previously observed results. Further study of the underlying mechanisms and the relevance to differential susceptibility to chronic inflammation is warranted.
Doublet Discharges in Motoneurons of Young and Older Adults
Authors: Christie Anita , Kamen Gary
Published: February 2006

The purpose of this study was to investigate the occurrence of motor unit doublet discharges in young and older individuals at different rates of increasing force. Participants included eight young (21.9 ± 3.56 yr) and eight older (74.1 ± 8.79 yr) individuals, with equal numbers of males and females in each group. Motor unit activity was recorded from the tibialis anterior during isometric dorsiflexion using a four-wire needle electrode. Subjects performed three ramp contractions from zero to 50% maximal voluntary contraction (MVC) force at each of three rates: 10, 30, and 50% MVC/s. Overall, the occurrence of doublets was significantly higher in the young than in the older individuals. However, neither group showed differences in the occurrence of doublets across the three rates of force production. Doublet firings were observed in 45.6 (young) and 35.1% (old) of motor units at 10% MVC/s; 48.6 (young) and 22.5% (old) of motor units at 30% MVC/s; and 48.4 (young) and 31.4% (old) at 50% MVC/s. The maximal firing rate was significantly higher and the force at which the motor units were recruited was significantly lower for those units that fired doublets than those that did not. The force at which doublets occurred ranged from 3.42 to 50% MVC in the young subjects and from 0 (force onset) to 50% MVC in the older subjects. The results of this study suggest that the occurrence of doublets is dependent on both motor unit firing rate and force level. The lower incidence of doublets in older individuals may be attributable to changes in the intrinsic properties of the motoneurons with aging, which appear to play a role in doublet discharges.
Atypical Phenotypes From Flatworm Kv3 Channels
Authors: Klassen Tara L. , Buckingham Steven D. , Atherton Donna M. , Dacks Joel B. , Gallin Warren J. , Spencer Andrew N.
Published: February 2006

Divergence of the Shaker superfamily of voltage-gated (Kv) ion channels early in metazoan evolution created numerous electrical phenotypes that were presumably selected to produce a wide range of excitability characteristics in neurons, myocytes, and other cells. A comparative approach that emphasizes this early radiation provides a comprehensive sampling of sequence space that is necessary to develop generally applicable models of the structure–function relationship in the Kv potassium channel family. We have cloned and characterized two Shaw-type potassium channels from a flatworm ( Notoplana atomata) that is arguably a representative of early diverging bilaterians. When expressed in Xenopus oocytes, one of these cloned channels, N.at-Kv3.1, exhibits a noninactivating, outward current with slow opening kinetics that are dependent on both the holding potential and the activating potential. A second Shaw-type channel, N.at-Kv3.2, has very different properties, showing weak inward rectification. These results demonstrate that broad phylogenetic sampling of proteins of a single family will reveal unexpected properties that lead to new interpretations of structure–function relationships.
Does Unilateral Pedaling Activate a Rhythmic Locomotor Pattern in the Nonpedaling Leg in Post-Stroke Hemiparesis?
Authors: Kautz S. A. , Patten C. , Neptune R. R.
Published: February 2006

Recent investigation in persons with clinically complete spinal cord injury has revealed that locomotor activity in one limb can activate rhythmic locomotor activity in the opposite limb. Although our previous research has demonstrated profound influences of the nonparetic limb on paretic limb motor activity poststroke, the potency of interlimb pathways for increasing recruitment of the paretic limb motor pattern is unknown. This experiment tested whether there is an increased propensity for rhythmic motor activity in one limb (pedaling limb) to induce rhythmic motor activity in the opposite limb (test limb) in persons poststroke. Forty-nine subjects with chronic poststroke hemiparesis and twenty controls pedaled against a constant mechanical load with their pedaling leg while we recorded EMG and pedal forces from the test leg. For the experimental conditions, subjects were instructed to either pedal with their test leg (bilateral pedaling) or rest their test leg while it was either stationary or moved anti-phased (unilateral pedaling). In persons poststroke, unilateral pedaling activated a complete pattern of rhythmic alternating muscle activity in the nonpedaling, test leg. This effect was most clearly demonstrated in the most severely impaired individuals. In most of the control subjects, unilateral pedaling activated some muscles in the nonpedaling leg weakly, if at all. We propose that, ipsilateral excitatory pathways associated with contralateral pedaling in control subjects are increasingly up-regulated in both legs in persons with hemiparesis as a function of increased hemiparetic severity. This enhancement of interlimb pathways may be of functional importance since contralateral pedaling induced a complete motor pattern of similar amplitude to the bilateral pattern in both the paretic and nonparetic leg of the subjects with severe hemiparesis.
Synaptic and Somatic Effects of Axotomy in the Intact, Innervated Rat Sympathetic Neuron
Authors: Sacchi Oscar , Rossi Maria Lisa , Canella Rita , Fesce Riccardo
Published: February 2006

A biophysical description of the axotomized rat sympathetic neuron is reported, obtained by the two-electrode voltage-clamp technique in mature, intact superior cervical ganglia in vitro. Multiple aspects of neuron functioning were tested. Synaptic conductance activated by the whole presynaptic input decreased to 29% of the control value (0.92 μS per neuron) 1 day after axotomy and to 18% after 3 days. Despite the decrease in amplitude of the macroscopic current, miniature excitatory postsynaptic current (mEPSC) mean conductance, acetylcholine (ACh) equilibrium potential, and EPSC decay time constant were unaffected. Synaptic efficacy was tested during paired-pulse or maintained stimulation (5, 10, and 15 Hz, 10-s duration). Quantal release in axotomized neurons was preserved during the tetanus despite the reduction of the initial EPSC amplitude, suggesting that ACh secretion depended on the number of surviving synapses; each of them exhibited dynamic behavior during trains similar to that of normal synapses. Facilitation of EPSC amplitude was noted in 2-day axotomized neurons during the first few impulses in the train. Voltage-dependent potassium currents (the delayed IKD and the transient IA) exhibited an early drastic decrease in peak amplitude; these effects persisted 7 days after axotomy. Marked changes in IA kinetics occurred after injury: the steady-state inactivation curve shifted by up to +17 mV toward positive potentials and the voltage sensitivity of inactivation removal became steeper. IA impairment was reflected in a reduced inward threshold charge for discharge and reduced spike repolarization rate. Synaptic and somatic data were applied in a mathematical model to describe the progressive decrease in the safety factor, and the eventual failure of ganglionic transmission after axotomy.
Dopamine D1/5 Receptor Modulation of Firing Rate and Bidirectional Theta Burst Firing in Medial Septal/Vertical Limb of Diagonal Band Neurons In Vivo
Authors: Fitch Thomas E. , Sahr Robert N. , Eastwood Brian J. , Zhou Feng C. , Yang Charles R.
Published: February 2006

The medial septum/vertical limb of diagonal band complex (MS/vDB) consists of cholinergic, GABAergic, and glutamatergic neurons that project to the hippocampus and functionally regulate attention, memory, and cognitive processes. Using tyrosine hydroxlase (TH) immunocytochemistry and dark-field light microscopy, we found that the MS/vDB is innervated by a sparse network of TH-immunoreactive (putative catecholaminergic) terminals. MS/vDB neurons are known to fire in rhythmic theta burst frequency of 3–7 Hz to pace hippocampal theta rhythm. Extracellular single-unit recording in theta and non-theta firing MS/vDB neurons and antidromically identified MS/vDB-hippocampal neurons were made in urethan-anesthetized rats. Tail-pinch noxious stimuli and ventral tegmental area (VTA) stimulation (20 Hz) evoked spontaneous theta burst firing in MS/vDB neurons. Systemic D1/5 antagonists SCH23390 or SCH39166 (0.1 mg/kg iv) alone suppressed the spontaneous theta bursts, suggesting a tonic facilitatory endogenous dopamine D1 “tone” that modulates theta bursts in vivo. Activation of D1/5 receptor by dihydrexidine (10 mg/kg iv) led to an increase in mean firing rate in 60% of all theta and non-theta MS/vDB neurons with an increase in the number of theta bursts and spikes/burst in theta cells. In strong theta firing MS/vDB neurons, D1/5 receptor stimulation suppressed the occurrence of theta burst firing, whereas the overall increase in spontaneous mean firing rate remained. In low baseline theta MS/vDB neurons D1/5 receptor stimulation increases the occurrence of theta bursts along with a net increase in mean firing rate. Atropine injection consistently disrupts theta burst pattern and reduced the time spent in theta firing. Collectively, these data suggest that dopamine D1/5 stimulation enhances the mean firing rate of most MS/vDB neurons and also provides a state-dependent bidirectional modulation of theta burst occurrence. Some of these MS/vDB neurons may be cholinergic or GABAergic that may indirectly regulate theta rhythm in the hippocampus.
Cortical Effects of Brief Daily Periods of Unrestricted Vision During Early Monocular Form Deprivation
Authors: Sakai E. , Bi H. , Maruko I. , Zhang B. , Zheng J. , Wensveen J. , Harwerth R. S. , Smith E. L. , Chino Y. M.
Published: February 2006

Experiencing daily brief periods of unrestricted vision during early monocular form deprivation prevents or reduces the degree of resulting amblyopia. To gain insight into the neural basis for these “protective” effects, we analyzed the monocular and binocular response properties of individual neurons in the primary visual cortex (V1) of macaque monkeys that received intermittent unrestricted vision. Microelectrode-recording experiments revealed significant decreases in the proportion of units that were dominated by the treated eyes, and the magnitude of this ocular dominance imbalance was correlated with the degree of amblyopia. The sensitivity of V1 neurons to interocular spatial phase disparity was significantly reduced in all treated monkeys compared with normal adults. With unrestricted vision, however, there was a small but significant increase in overall disparity sensitivity. Binocular suppression was prevalent in monkeys with constant form deprivation but significantly reduced by the daily periods of unrestricted vision. If neurons exhibited consistent responses to stimulation of the treated eye, monocular response properties obtained by stimulation of the two eyes were similar. These results suggest that the observed protective effects of brief periods of unrestricted vision are closely associated with the ability of V1 neurons to maintain their functional connections from the deprived eye and that interocular suppression in V1 may play an important role in regulating synaptic plasticity of these monkeys.
Vesicle Depletion and Synaptic Depression at a Mammalian Ribbon Synapse
Authors: Singer Joshua H. , Diamond Jeffrey S.
Published: February 2006

We estimated the size of the readily releasable pool (RRP) of vesicles at a ribbon synapse in the rat retina by making paired voltage-clamp recordings from presynaptic rod bipolar cells (RBCs) and postsynaptic AII amacrine cells in an in vitro retinal slice preparation. The RRP at each active zone was estimated to constitute seven vesicles, in the range of estimated RRP sizes at conventional synapses. During sustained presynaptic Ca2+ entry, the RRP could be released with a time constant of about 4 ms. This ribbon synapse exhibited pronounced paired-pulse depression (PPD), which was attributable primarily to vesicle depletion. Recovery from PPD was slow (τ ≈ 4 s) but could be accelerated by increasing the duration of the depressing stimulus. The small RRP and very high release probability likely contribute to the transient characteristics of neurotransmission at RBC synapses.
VEGF as a Key Mediator of Angiogenesis in Cancer
Authors: Carmeliet Peter
Published: February 2006

Vascular endothelial growth factor (VEGF) is a homodimeric glycoprotein with a molecular weight of approximately 45 kDa. It is the key mediator of angiogenesis (the formation of new blood vessels), and binds two VEGF receptors (VEGF receptor-1 and VEGF receptor-2), which are expressed on vascular endothelial cells. In healthy humans, VEGF promotes angiogenesis in embryonic development and is important in wound healing in adults. VEGF is the key mediator of angiogenesis in cancer, in which it is up-regulated by oncogene expression, a variety of growth factors and also hypoxia. Angiogenesis is essential for cancer development and growth: before a tumor can grow beyond 1–2 mm, it requires blood vessels for nutrients and oxygen. The production of VEGF and other growth factors by the tumor results in the ‘angiogenic switch’, where new vasculature is formed in and around the tumor, allowing it to grow exponentially. Tumor vasculature formed under the influence of VEGF is structurally and functionally abnormal. Blood vessels are irregularly shaped, tortuous, have dead ends and are not organized into venules, arterioles and capillaries. They are also leaky and hemorrhagic, which leads to high interstitial pressure. These characteristics mean that tumor blood flow is suboptimal, resulting in hypoxia and further VEGF production. This central role of VEGF in the production of tumor vasculature makes it a rational target for anticancer therapy.
Bevacizumab Combined with Standard Fluoropyrimidine-Based Chemotherapy Regimens to Treat Colorectal Cancer
Authors: Hurwitz Herbert , Kabbinavar Fairooz
Published: February 2006

For several decades, 5-fluorouracil (5-FU) with or without leucovorin defined the standard of care for the treatment of metastatic colorectal cancer (CRC). The addition of other chemotherapy regimens to 5-FU has improved survival, but often at the expense of increased toxicity. Recent advances in our understanding of the molecular basis of CRC have led to the production of novel targeted agents, such as bevacizumab (Avastin®). Bevacizumab is currently approved for the first-line treatment of metastatic CRC and is currently being tested in combination with standard therapies for a range of indications. Phase II/III trials have demonstrated that the addition of bevacizumab to 5-FU-based first-line chemotherapy improves survival, progression-free survival and response rate compared with chemotherapy alone. Combination therapy does not appear to exacerbate side effects known to be associated with the chemotherapy regimen. The most common side effects attributable to bevacizumab therapy include hypertension, proteinuria and bleeding. Although uncommon, gastrointestinal perforation and arterial thromobembolic events are the most serious side effects reported to date. Bevacizumab is currently being evaluated in combination with oxaliplatin (Eloxatin®)-based therapies and preliminary data are encouraging. Ongoing trials of bevacizumab in combination with standard first-line chemotherapy regimens will evaluate bevacizumab’s potential in a range of cancer types.
Managing Patients Treated with Bevacizumab Combination Therapy
Authors: Gordon Michael S. , Cunningham David
Published: February 2006

The anti-angiogenic agent bevacizumab (Avastin®) has been rationally designed to target vascular endothelial growth factor (VEGF), a key mediator of tumor angiogenesis. Based on its limited roles in adults, VEGF inhibition using bevacizumab would be expected to have limited side effects. Furthermore, because its mechanism of action is different to that of standard chemotherapeutic agents, bevacizumab would not be expected to cause typical cytotoxic agent-related toxicity or to exacerbate the toxicity of concomitant chemotherapy. We have reviewed clinical trials published to date, primarily in metastatic colorectal cancer, and describe the safety profile of bevacizumab. The review focuses on hypertension, proteinuria, arterial thrombosis, effects on wound healing, bleeding and gastrointestinal (GI) perforation, which are the principal bevacizumab-related events seen in clinical trials. These events are for the most part mild to moderate in severity and clinically manageable (hypertension, proteinuria, minor bleeding) or occur uncommonly (wound healing complications, GI perforations and arterial thrombosis). The side-effect profile of bevacizumab makes it a suitable adjunct to standard chemotherapy in settings where efficacy has been demonstrated, and it is now approved for use in the USA, the European Union and other markets worldwide.
The Future Development of Bevacizumab in Colorectal Cancer
Authors: Díaz-Rubio Eduardo , Schmoll Hans-Joachim
Published: February 2006

Bevacizumab (Avastin®), the first approved therapy designed to inhibit tumor angiogenesis, has significant clinical benefits in the management of colorectal cancer (CRC). When bevacizumab is added to IFL (5-fluorouracil [5-FU]/leucovorin [LV]/irinotecan [Camptosar®]) as first-line therapy for metastatic CRC, significant overall and progression-free survival benefits are obtained. Similar survival benefits may be achieved when bevacizumab is added to 5-FU/LV alone. In addition, additive and synergistic effects with a range of chemotherapeutic agents illustrate that bevacizumab has considerable potential in combination with existing therapeutic options. Clinical data indicate that bevacizumab is the only agent in addition to chemotherapy that has demonstrated survival benefit in the first- and second-line settings. In addition, bevacizumab is expected to produce clinical benefit in the adjuvant setting: inhibition of vascular endothelial growth factor should prevent the angiogenic switch in micrometastases, which is a key factor in malignancy. The clinical program is examining the activity of bevacizumab in combination with the likely future standard of care in both the metastatic and adjuvant treatment settings. Phase III trials (NO16966C, CONcePT and TREE-2) are studying the benefit of combining bevacizumab with oxaliplatin (Eloxatin®)-based regimens. Similarly, in the adjuvant setting, phase III trials are assessing the efficacy and tolerability of bevacizumab in combination with oxaliplatin-based chemotherapy (AVANT, NSABP C-08).
Investigating the Potential of Bevacizumab in Other Indications: Metastatic Renal Cell, Non-Small Cell Lung, Pancreatic and Breast Cancer
Authors: de Gramont Aimery , Van Cutsem Eric
Published: February 2006

Bevacizumab (Avastin®) has unprecedented survival benefit in patients with metastatic colorectal cancer. Trials are already in progress to investigate the potential of bevacizumab in indications including metastatic renal cell cancer (RCC), non-small cell lung cancer (NSCLC), pancreatic cancer, breast and ovarian cancer. Bevacizumab offers the potential to increase survival without substantially altering the toxicity profile in these tumor types. Bevacizumab has shown activity in patients with refractory metastatic RCC, where progression-free survival (PFS) was significantly longer in patients treated with bevacizumab (10 mg/kg every 2 weeks) than those treated with placebo (hazard ratio = 2.55, p < 0.001). In addition, combining bevacizumab with erlotinib (Tarceva®) has shown a median time to progression of more than 11 months. In NSCLC, a phase II trial revealed that adding bevacizumab to chemotherapy increased therapeutic benefit compared with chemotherapy alone. Adverse events were mild and easily managed, but six patients receiving bevacizumab developed severe hemoptysis. Entry criteria for NSCLC trials have been adjusted to exclude patients with squamous cell histology to try to avoid this issue. Adding bevacizumab (10 mg/kg) to the current standard of care, gemcitabine, in stage IV pancreatic cancer has also shown promising efficacy. Partial responses were seen in 19% of patients, with a further 48% having stable disease. Several ongoing clinical trials are also studying bevacizumab with various chemotherapy and radiotherapy regimens. Bevacizumab combined with carboplatin (Paraplatin®)/paclitaxel (Taxol®) was further examined in a phase III randomized trial that accrued 878 patients with advanced non-squamous cell NSCLC. Patients given chemotherapy (paclitaxel and carboplatin) plus bevacizumab had a higher response rate, longer PFS and an increase in survival compared with patients on chemotherapy alone. Both regimens were generally well tolerated. Bevacizumab has also shown activity in patients with metastatic breast cancer. In 715 patients, a significant, 2-fold increase in response rate was observed in patients receiving bevacizumab plus paclitaxel compared with paclitaxel alone. Median PFS was also significantly increased (p < 0.001). Bevacizumab has the potential to provide significant efficacy benefits for patients with metastatic RCC, NSCLC, pancreatic cancer, and other tumor types when used first line in combination with standard therapy.