bluuebunny/crossref_metadata_2025 huggingface dataset:
TEMPERATURE PROFILE OF RESISTIVITY OF MANGANITES
Authors: KHAN SHAKEEL , SINGH R. J.
Published: November 2007

In the resistivity–temperature curves of La 0.7 Ca 0.3 MnO 3 and La 0.75 Ca 0.25 MnO 3, five distinct regions have been identified. For example, in La 0.7 Ca 0.3 MnO 3, the regions are:

(1) from the lowest temperature of measurement to 200 K where resistivity is directly proportional to temperature with a small slope,

(2) the reciprocal of resistivity follows Bloch's T3/2 law,

(3) resistivity is directly proportional to temperature with a large slope,

(4) the cusp region, where there are FM clusters of reduced dimensions and varying degrees of correlated polarons or bipolarons and small polarons,

(5) the semiconducting region having small polarons.

The regions 1, 2 and 3 together appear to replicate the spontaneous magnetization curves of the materials. The effect of magnetic field on the resistivity–temperature curves are as follows:

(a) resistivity is reduced. In particular, the resistivity peak with magnetic field occurs at a temperature μH/K downward from the T c of the curve without magnetic field;

(b) resistivity peak is displaced by μ · μH/K towards the higher temperature side compared to the resistivity peak without magnetic field;

(c) cusp region is broadened;

(d) magnetoresistance is appreciable only within 10% of Tp on both sides.

All these observations suggest that temperature profile of resistivity of manganites is controlled by magnetic effects.
FT-IR AND RAMAN SPECTROSCOPIC STUDIES OF GADOLINIUM DOPED B2O3 · TeO2 GLASS MATRIX
Authors: GRIGUTA L. , ARDELEAN I.
Published: November 2007

Glasses from x Gd 2 O 3 · (100-x)[ B 2 O 3 · TeO 2] system with 0 ≤ x ≤ 10 mol% have been prepared and studied by means of FT-IR absorption and Raman scattering. Being complementary spectroscopic techniques, both types of measurements FT-IR and Raman revealed that the network structure of the studied glasses is based on BO 3 and BO 4 units placed in different structure groups and also TeO 4, TeO 3 structural units. No absorption characteristic for Gd 2 O 3 was evidenced but some changes in the structure of B 2 O 3 · TeO 2 glass matrix are due to its presence.
AHARONOV–BOHM OSCILLATIONS AND FANO RESONANCE IN A MESOSCOPIC RING WITH A SIDE-COUPLED QUANTUM DOT
Authors: XIONG YONG-JIAN , HE ZHOU-BO
Published: November 2007

We calculate the transmission coefficient through an Aharonov–Bohm ring with a multi-level quantum dot side-coupled to one arm. Whenever a quantum dot level is tuned across the Fermi energy, the coupled arm is blocked for electron tunneling, namely anti-resonance. This leads to the suppression of the Aharonov–Bohm oscillations, accompanied by a phase jump of π in the oscillations. The Aharonov–Bohm phase also changes sharply by π in between neighboring anti-resonances due to the multi-level effect. The transmission has an expression of the generalized Fano form with a complex Fano parameter q in the presence of the Aharonov–Bohm flux.
TUNNELING TIME OF A PARTICLE: TWO-DIMENSIONAL APPROACH
Authors: PARK CHANG-SOO
Published: November 2007

A two-dimensional problem of tunneling of a particle is studied to propose an experiment to measure tunneling time. We consider a 2D rectangular barrier in which the particle undergoes both tunneling and free lateral motion at the same time. The two processes are coupled by the same tunneling time, which leads to a simple relation between the tunneling time and the corresponding lateral shift such that L = vτ. Since the lateral speed v is constant the tunneling time can be obtained by measuring the lateral shift. The shifted length can be controlled by an initial lateral speed and become over a hundred nanometers when the particle is provided with sufficient initial lateral speed. The present model may also be used for examining the relationships between characteristic tunneling times suggested in previous articles. We also demonstrate physical differences between the 2D problem of a particle tunneling and the frustrated total internal reflection of electromagnetic waves.
Detection and mapping of shrink–swell clays in SW France, using ASTER imagery
Authors: Bourguignon A. , Delpont G. , Chevrel S. , Chabrillat S.
Published: November 2007

Current mapping methods for shrink–swell clays in France are based on the use of existing 1:50 000 geological maps. However, stratigraphy is the primary basis of current published geological mapping, which is detrimental to the accurate mapping of clay minerals, argillaceous lithologies and clayey soils. In the study region, Pyrenean forefront molasse deposits have been mapped in a stratigraphy-dominated way, grouped into a single mapping unit, even though they are made up of eight sequences of continental sands, gravels, clays and lacustrine limestones. Mapping shrink–swell clay hazardous terrain can be improved by spectral methods, allowing rapid delineation of argillaceous units and the identification of their mineralogy, especially with regard to illite, chlorite and kaolinite. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) allows a new approach to regional clay mineral mapping, via the six spectral bands in its short-wave infrared domain, particularly wavelengths between 2.145 and 2.43 µm.
Remote sensing of onshore hydrocarbon seepage: problems and solutions
Authors: van der Werff H. M. A. , Noomen M. F. , van der Meijde M. , van der Meer F. D.
Published: November 2007

Optical remote sensing has in the last two decades been extensively tested for the detection of hydrocarbons at the Earth's surface. The spectral absorption features of seepage-related hydrocarbons can easily be confused with those of man-made bituminous surfaces such as tarred roads. The characteristic low albedo of bituminous surfaces can, at the same time, easily be confused with other dark surfaces such as shade. This paper presents the results of two pixel-based classifications that have been carried out on hyperspectral imagery acquired over seepage areas. The first classification algorithm is a ‘minimum distance to class means’ (MDC), which is sensitive to spectral absorption features as well as albedo differences. The second algorithm is a ‘spectral angle mapper’ (SAM), which is not sensitive to albedo differences. Both algorithms are applied for the detection of crude oil resulting from macroseepage and an anomalous halo of bare soil resulting from microseepage. The results show that, at best, only 48% and 29% of the pixels that respectively contain crude oil and seepage-related bare soil could be detected, with the inclusion of many false anomalies. Confusion mainly results from the physical characteristics of the anomalies, as these are not unique to seepages. It is concluded that remote sensing of natural hydrocarbon seepages can be improved by image processing algorithms that make use of spatial information.
Remote sensing for terrain analysis of linear infrastructure projects
Authors: Manning J.
Published: November 2007

This paper examines recent developments in remote sensing applied to civil engineering projects, particularly those involving terrain analysis of linear infrastructure features. Applications using high-resolution satellite data (e.g. IKONOS and Quickbird), laser altimetry and digital elevation models (DEMs) are discussed. Guidelines are given for the stages of a project in which different remote sensing techniques could be employed. The case is also made for greater use of archive remote sensing datasets, which can be a valuable source of information about landscape dynamics.
Space technology for disaster management: data access and its place in the community
Authors: Andrews Deller M. E.
Published: November 2007

The ways in which remotely sensed data can be used to manage and alleviate the consequences of natural disasters have never been fully exploited. If prediction of impending disaster is to be useful, those affected by catastrophe and those who come to their aid must work together. A global strategy based on a vision for disaster management will fail if those affected by hazards are not involved in their own disaster preparation, relief efforts and rehabilitation. Local people are experts in ground knowledge; all that is needed is for those with expertise in remote sensing to pass on their skills, knowledge and data in a way that can be understood and valued. To do this, those threatened by catastrophe must understand how disaster relates to their lives, how satellite data can be used with confidence to prepare for local hazards and how to apply information that can help lessen the effects of catastrophe. This can be achieved by making available remotely sensed images with simple explanations that enhance vegetation, topography and geology. With timely, reliable information, preventive measures can be taken; surface features identified on satellite images can guide refugee placement and hazards can be anticipated and contained.
Mapping volcanic terrain using high-resolution and 3D satellite remote sensing
Authors: Kervyn M. , Kervyn F. , Goossens R. , Rowland S. K. , Ernst G. G. J.
Published: November 2007

Most of the hazardous volcanoes, especially those in developing countries, have not been studied or regularly monitored. Moderate-to-high spatial resolution and 3D satellite remote sensing offers a low-cost route to mapping and assessing hazards at volcanoes worldwide. The capabilities of remote sensing techniques are reviewed and an update of recent developments is provided, with emphasis on low-cost data, including optical (Landsat, ASTER, SPOT, CORONA), topographic (3D ASTER, SRTM) and synthetic aperture radar data. Applications developed here illustrate capabilities of relevant remote sensing data to map hazardous volcanic terrain and derive quantitative data, focusing on mapping and monitoring of volcanic morphology. Limitations of the methods, assessment of errors and planned new sensors are also discussed.
Comparison and validation of Airborne Thematic Mapper thermal imagery using ground-based temperature data for Grímsvötn caldera, Vatnajökull, Iceland
Authors: Stewart S. F. , Pinkerton H. , Blackburn G. A. , Guðmundsson M. T.
Published: November 2007

Grímsvötn, Iceland's most active volcano, is also one of the most powerful geothermal areas in Iceland. This subglacial volcano is located in the centre of Vatnajökull, Europe's largest temperate ice cap, and it erupted most recently in 1998 and 2004. As part of continuing research on heat flux, morphological changes and volcanic processes at Grímsvötn, thermal anomalies were mapped using remote sensing Natural Environmental Research Council (NERC) Airborne Research and Survey Facility (ARSF) data. The 2001 Airborne Thematic Mapper (ATM) thermal images of the Grímsvötn subglacial caldera reveal distinct areas of geothermal activity and provide an overview of the thermal anomalies associated with water and rock exposures. A crater lake located on the 1998 eruption site is shown to have a surface temperature of 30–35 °C. There is a good correlation between the ARSF data and ground-based temperature measurements. The thermal images also revealed previously undetected areas of high heat flow. Factors that complicate the interpretation and comparison of different datasets from an ice-covered area include recent cornice collapses and variations in atmospheric humidity. To reduce uncertainty in future missions, temperature measurements should be made at points whose position is well constrained using differential global positioning system. In addition, humidity and temperature measurements should be made at the time of flight.
Aerial photography and digital photogrammetry for landslide monitoring
Authors: Walstra J. , Chandler J. H. , Dixon N. , Dijkstra T. A.
Published: November 2007

A review is given of the techniques that are available to extract relevant information from multi-temporal aerial photographs for use in the monitoring stage of landslide assessments. It is shown that aerial photograph interpretation reveals qualitative information on surface characteristics, which is helpful in detecting landslide features and inferring the mechanisms involved. Photogrammetrically derived products can be used to quantify these processes, providing distinctive advantages. Comparison of digital elevation models (DEMs) from different times provides detailed information on changes in surface topography, whereas orthophotos can be used to measure horizontal displacements. The various factors influencing the quality of the products are also identified. Examples from a case study on the Mam Tor landslide are used to illustrate the benefits of the different approaches.
Geomorphology and urban geology of Bukavu (R.D. Congo): interaction between slope instability and human settlement
Authors: Trefois P. , Moeyersons J. , Lavreau J. , Alimasi D. , Badryio I. , Mitima B. , Mundala M. , Munganga D. O. , Nahimana L.
Published: November 2007

The city of Bukavu, on the south coast of Lake Kivu in the Democratic Republic of Congo, suffers from frequent landsliding, which leads to continual damage and destruction of buildings, roads, waterworks and sewerage infrastructure. Thirty-one landslides identified on aerial photographs of 1954 and 1973 are located outside the Bukavu micro-rift and are related to actively incising rivers. Their origin is thought to be due to increases in hydrostatic pressure. Six landslides occur within the Bukavu micro-rift, four of which are much larger and wider than other slope failures in the study region. These large landslides are adjacent to, or crossed by, active faults. They fall far below the topographic threshold envelope, a relationship of slopes at the head of the slide and the surface area drained into it, indicating seismic or anthropomorphic triggering. The Bukavu landslides still reactivate occasionally. Deforestation, followed by a large increase in the population, have been indirect causes of the reactivated mass wasting processes. On the steep slopes in the south of the city the high density of newly built houses has led to reduced water infiltration and enhanced runoff, causing landslides and mudflows. Very high spatial resolution IKONOS satellite images have recently been used as base maps for geohazard assessments of Bukavu. A geographical information system (GIS) has been developed for Bukavu's planners: this shows the locations of buildings, roads and tracks, the river network, the water distribution system and the sewerage infrastructure, as well as areas of slope instability.
Landslide susceptibility assessment for St. Thomas, Jamaica, using geographical information system and remote sensing methods
Authors: Miller S. , Harris N. , Williams L. , Bhalai S.
Published: November 2007

The St. Thomas district of Jamaica is prone to slope failure, which has resulted in extensive damage and in some cases loss of life. To reduce the effect from landslides, there was an urgent need to map and assess areas that may be prone to future failure. The interpretation of aerial photographs, together with geomorphological mapping and field surveys, was used to produce inventory maps of the landslides. The factors conditioning the slopes for failure were assessed and a weighting value was assigned to them. The weighting was achieved by using the principle of Bayesian conditional probability. The weighted factors were combined in a geographical information system (GIS) to produce a landslide susceptibility model for the study area. Comparison of the model with the existing landslides showed that 97% of the landslides fell within the high and very high susceptibility zones of the model. Comparison of the model with landslides that occurred during 2002, and that were not used in the construction of the model, shows that 83 of the 89 slides that occurred fell within the high and very high susceptibility zones. The landslide susceptibility model will be one of the first steps in assessing the risks that landslides pose to lives and new developments (housing, agriculture, physical infrastructure) in the region.
Applications of remote sensing for geohazard mapping in coastal and riverine environments
Authors: Teeuw R.
Published: November 2007

This paper reviews various types of remote sensing that can be applied to mapping and monitoring riverine and coastal geohazards. It focuses on flooding, ground instability, erosion and sedimentation, mainly drawing on examples from the UK. Both airborne and space-borne systems are examined, with assessments of the merits, limitations and relative costs of each system. Remote sensing offers a wide range of useful techniques for mapping coastal and riverine features, particularly where there are access problems associated with sites prone to flooding or slope instability.
Application of hyperspectral remote sensing data in the monitoring of the environmental impact of hazardous waste derived from abandoned mine sites
Authors: Ferrier G. , Rumsby B. , Pope R.
Published: November 2007

The release of hazardous mine waste from abandoned gold mining areas is a major global environmental problem. The complexity of the processes, the scale of the mine sites, problems with accessibility and the lack of site information mean that field-based survey methods are often too costly and provide incomplete coverage. The results of a study of an abandoned gold mine at Rodalquilar in southern Spain have demonstrated the potential of airborne-mounted hyperspectral remote sensing instruments to resolve the distributions of mine waste and secondary iron species on the mine site and in adjacent rivers. The advantages of using higher spatial resolution hyperspectral data in identifying secondary iron species and resolving geomorphological settings of mine waste accumulations were also demonstrated. Integration of laboratory-derived correlations of secondary iron species, cyanide and heavy metals concentrations with the results of the remote sensing study allowed the identification of locations of hazardous materials over the study area and a more accurate understanding of the environmental status of the Rodalquilar area.
The role of VASP in regulation of cAMP- and Rac 1-mediated endothelial barrier stabilization
Authors: Schlegel N. , Burger S. , Golenhofen N. , Walter U. , Drenckhahn D. , Waschke J.
Published: November 2007

Regulation of actin dynamics is critical for endothelial barrier functions. We provide evidence that the actin-binding protein vasodilator-stimulated phosphoprotein (VASP) is required for endothelial barrier maintenance. Baseline permeability was significantly increased in VASP-deficient (VASP−/−) microvascular myocardial endothelial cells (MyEnd) in the absence of discernible alterations of immunostaining for adherens and tight junctions. We tested whether VASP is involved in the endothelium-stabilizing effects of cAMP or Rac 1. Forskolin and rolipram (F/R) to increase cAMP and cytotoxic necrotizing factor 1 (CNF-1) to activate Rac 1 were equally efficient to stabilize barrier functions in VASP−/− and wild-type (wt) cells. In wt cells, VASP was phosphorylated in response to F/R but did not localize to intercellular junctions. In contrast, CNF-1 and expression of constitutively active Rac 1 induced translocation of VASP to cell borders in wt cells, where it colocalized with active Rac 1. In VASP−/− cells, Rac 1 activity was reduced to 0.4 of wt levels in controls and increased ∼20-fold in response to CNF-1 compared with 7-fold activation in wt cells. Moreover, inactivation of Rac 1 by lethal toxin led to a greater increase of permeability compared with wt cells. All these data suggest that VASP is involved in the regulation of Rac 1 activity. Taking these findings together, our study indicates that VASP at least in part stabilizes endothelial barrier functions by control of Rho-family GTPases.
Fas Ag-FasL coupling leads to ERK1/2-mediated proliferation of gastric mucosal cells
Authors: Li Hanchen , Cai Xun , Fan Xueli , Moquin Brian , Stoicov Calin , Houghton JeanMarie
Published: November 2007

When cells within the gastric mucosa progress from metaplasia to dysplasia to cancer, they acquire a Fas Ag apoptosis-resistant phenotype. It is unusual to completely abolish the pathway, suggesting other forms of Fas Ag signaling may be important or even necessary for gastric cancer to progress. Little is known about alternate signaling of the Fas Ag pathway in gastric mucosal cells. Using a cell culture model of rat gastric mucosal cells, we show that gastric mucosal cells utilize a type II signaling pathway for apoptosis. Under conditions of low receptor stimulation or under conditions where apoptosis is blocked downstream of the death-inducing signal complex, Fas Ag signaling proceeds toward proliferative signaling. Under conditions favoring proliferative signaling, cFLIP is recruited to the Fas-associated death domain-like interleukin-1β-converting enzyme at the death-inducing signal complex and activates ERK1/2. ERK1/2 in turn activates NF-κB. ERK1/2 stimulates proliferation, whereas NF-κB activation results in upregulation of the antiapoptotic protein survivin, further promoting proliferation over apoptosis. These results suggest that factors that inhibit apoptosis confer a growth advantage to the cells beyond the survival advantage of avoiding apoptosis and in effect convert the Fas Ag signaling pathway from a tumor suppressor to a tumor promoter.
Epidermal growth factor stimulates Rac activation through Src and phosphatidylinositol 3-kinase to promote colonic epithelial cell migration
Authors: Dise Rebecca S. , Frey Mark R. , Whitehead Robert H. , Polk D. Brent
Published: November 2007

Regulated intestinal epithelial cell migration plays a key role in wound healing and maintenance of a healthy gastrointestinal tract. Epidermal growth factor (EGF) stimulates cell migration and wound closure in intestinal epithelial cells through incompletely understood mechanisms. In this study we investigated the role of the small GTPase Rac in EGF-induced cell migration using an in vitro wound-healing assay. In mouse colonic epithelial (MCE) cell lines, EGF-stimulated wound closure was accompanied by a doubling of the number of cells containing lamellipodial extensions at the wound margin, increased Rac membrane translocation in cells at the wound margin, and rapid Rac activation. Either Rac1 small interfering (si)RNA or a Rac1 inhibitor completely blocked EGF-stimulated wound closure. Whereas EGF failed to activate Rac in colon cells from EGF receptor (EGFR) knockout mice, stable expression of wild-type EGFR restored EGF-stimulated Rac activation and migration. Pharmacological inhibition of either phosphatidylinositol 3-kinase (PI3K) or Src family kinases reduced EGF-stimulated Rac activation. Cotreatment of cells with both inhibitors completely blocked EGF-stimulated Rac activation and localization to the leading edge of cells and lamellipodial extension. Our results present a novel mechanism by which the PI3K and Src signaling cascades cooperate to activate Rac and promote intestinal epithelial cell migration downstream of EGFR.
Carbon monoxide liberated from carbon monoxide-releasing molecule CORM-2 attenuates inflammation in the liver of septic mice
Authors: Cepinskas Gediminas , Katada Kazuhiro , Bihari Aurelia , Potter Richard F.
Published: November 2007

Recent studies suggest that exogenously administered CO is beneficial for the resolution of acute inflammation. In this study, we assessed the role of CO liberated from a systemically administered tricarbonyldichlororuthenium-(II)-dimer (CORM-2) on modulation of liver inflammation during sepsis. Polymicrobial sepsis in mice was induced by cecal ligation and perforation (CLP). CORM-2 (8 mg/kg iv) was administered immediately after CLP induction, and neutrophil [polymorphonuclear leukocyte (PMN)] tissue accumulation, activation of transcription factor, NF-κB, and changes in adhesion molecule ICAM-1 expression (inflammation-relevant markers) were assessed in murine liver 24 h later. In addition, the effects and potential mechanisms of CORM-2-released CO in modulation of vascular endothelial cell proinflammatory responses were assessed in vitro. To this end, human umbilical vein endothelial cells (HUVEC) were stimulated with LPS (1 μg/ml) in the presence or absence of CORM-2 (10–100 μM) and production of intracellular reactive oxygen species (ROS), (DHR123 oxidation) and NO (DAF-FM nitrosation) and subsequent activation of NF-κB were assessed 4 h later. In parallel, expression of ICAM-1 and inducible NO synthase (iNOS) proteins along with PMN adhesion to LPS-challenged HUVEC were also assessed. Induction of CLP resulted in increased PMN accumulation, ICAM-1 expression, and activation of NF-κB in the liver of septic mice. These effects were significantly attenuated by systemic administration of CORM-2. In in vitro experiments, CORM-2-released CO attenuated LPS-induced production of ROS and NO, activation of NF-κB, increase in ICAM-1 and iNOS protein expression and PMN adhesion to LPS-stimulated HUVEC. Taken together, these findings indicate that CO released from systemically administered CORM-2 provides anti-inflammatory effects by interfering with NF-κB activation and subsequent downregulation of proadhesive vascular endothelial cell phenotype in the liver of septic mice.
Function, expression, and characterization of the serotonin transporter in the native human intestine
Authors: Gill Ravinder K. , Pant Nitika , Saksena Seema , Singla Amika , Nazir Talat M. , Vohwinkel Lisa , Turner Jerrold R. , Goldstein Jay , Alrefai Waddah A. , Dudeja Pradeep K.
Published: November 2007

The enteric serotonin transporter (SERT) plays a critical role in modulating serotonin availability and thus has been implicated in the pathogenesis of various intestinal disorders. To date, SERT expression and function in the human intestine have not been investigated. Current studies were designed to characterize the function, expression, distribution, and membrane localization of SERT in the native human intestine. Real-time PCR studies showed relatively higher SERT mRNA expression in the human small intestine compared with colon (ileum >> duodenum >> jejunum). Northern blot analysis revealed three mRNA hybridizing species encoding SERT (3.0, 4.9, and 6.8 kb) in the human ileum. Consistent with SERT mRNA expression, SERT immunostaining was mainly detected in the epithelial cells of human duodenal and ileal resected tissues. Notably, SERT expression was localized predominantly to the apical and intracellular compartments and was distributed throughout the crypt-villus axis. Immunoblotting studies detected a prominent protein band (∼70 kDa) in the ileal apical plasma membrane vesicles (AMVs) isolated from mucosa obtained from organ-donor intestine. Functional studies showed that uptake of [3H]serotonin (150 nM) in human ileal AMVs was 1) significantly increased in the presence of both Na+and Cl−; 2) inhibited (∼50%) by the neuronal SERT inhibitor, fluoxetine (10 μM) and by unlabeled 5-HT; and 3) exhibited saturation kinetics indicating the presence of a carrier-mediated process. Our studies demonstrated differential expression of SERT across various regions of the human intestine and provide evidence for the existence of a functional SERT capable of removing intraluminal serotonin in human ileal epithelial cells.
Susceptibility to systolic dysfunction in the myocardium from chronically infarcted spontaneously hypertensive rats
Authors: Norton Gavin R. , Veliotes Demetri G. A. , Osadchii Oleg , Woodiwiss Angela J. , Thomas D. Paul
Published: November 2007

We explored whether the hypertensive heart is susceptible to myocardial dysfunction in viable noninfarcted tissue post-myocardial infarction (MI), the potential mechanisms thereof, and the impact of these changes on pump function. Six to seven months after the ligation of the left anterior descending coronary artery, left ventricular (LV) myocardial systolic function, as assessed from the percent shortening of the noninfarcted lateral wall segmental length determined over a range of filling pressures (ultrasonic transducers placed in the lateral wall in anaesthetized, open-chest, ventilated rats) and the percent thickening of the posterior wall (echocardiography), was reduced in infarcted spontaneous hypertensive rats (SHR-MI) ( P < 0.05) but not in normotensive Wistar-Kyoto (WKY-MI) animals compared with corresponding controls [SHR-sham operations (Sham) and WKY-Sham]. This change in the regional myocardial function in SHR-MI, but not in WKY-MI, occurred despite a similar degree of LV dilatation (increased LV end-diastolic dimensions and volume intercept of the LV end-diastolic pressure-volume relation) in SHR-MI and WKY-MI rats and a lack of difference in LV relative wall thinning, LV wall stress, apoptosis [terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling (TUNEL)], or necrosis (pathological score) between SHR-MI and WKY-MI rats. Although the change in regional myocardial function in the SHR-MI group was not associated with a greater reduction in baseline global LV chamber systolic function [end-systolic elastance (LV Ees) and endocardial fractional shortening determined in the absence of an adrenergic stimulus], in the presence of an isoproterenol challenge, noninfarct-zone LV systolic myocardial dysfunction manifested in a significant reduction in LV Ees in SHR-MI compared with WKY-MI and SHR and WKY-Sham rats ( P < 0.04). In conclusion, these data suggest that with chronic MI, the hypertensive heart is susceptible to the development of myocardial dysfunction, a change that cannot be attributed to excessive chamber dilatation, apoptosis, or necrosis, but which in turn contributes toward a reduced cardiac adrenergic inotropic reserve.
Endotoxin downregulates peroxisome proliferator-activated receptor-γ via the increase in TNF-α release
Authors: Zhou Mian , Wu Rongqian , Dong Weifeng , Jacob Asha , Wang Ping
Published: November 2007

The nuclear receptor peroxisome proliferator-activated receptor-γ (PPAR-γ) is anti-inflammatory in a cell-based system and in animal models of endotoxemia. We have shown that PPAR-γ gene expression is downregulated in macrophages after lipopolysaccharide (LPS) stimulation. However, it remains unknown whether hepatic PPAR-γ is altered in sepsis and, if so, whether LPS directly downregulates PPAR-γ. To study this, rats were subjected to sepsis by cecal ligation and puncture (CLP). Hepatic tissues were harvested at 5, 10, and 20 h after CLP. PPAR-γ gene expression and protein levels were determined by RT-PCR and Western blot analysis, respectively. The results showed that PPAR-γ gene expression decreased at 10 and 20 h and that its proteins levels were reduced at 20 h after CLP. PPAR-γ levels were also decreased in animals that were administered LPS. To determine the direct effects of LPS on PPAR-γ downregulation, LPS binding agent polymyxin B (PMB) was administered intramuscularly after CLP. The administration of PMB significantly reduced plasma levels of endotoxin, but it did not prevent the downregulation of PPAR-γ expression. We found that circulating levels of TNF-α still remained significantly elevated in PMB-treated septic animals. We, therefore, hypothesize that the decrease of PPAR-γ expression is TNF-α dependent. To investigate this, Kupffer cells (KCs) were isolated from normal rats and stimulated with LPS or TNF-α. TNF-α significantly attenuated PPAR-γ gene expression in KCs. Although LPS decreased PPAR-γ in KCs, the downregulatory effect of LPS was blocked by the addition of TNF-α-neutralizing antibodies. Furthermore, the administration of TNF-α-neutralizing antibodies to animals before the onset of sepsis prevented the downregulation of PPAR-γ in sepsis. We, therefore, conclude that LPS downregulates PPAR-γ expression during sepsis via an increase in TNF-α release.
Chronic activation of plasma renin is log-linearly related to dietary sodium and eliminates natriuresis in response to a pulse change in total body sodium
Authors: Kjolby Mads , Bie Peter
Published: November 2007

Responses to acute sodium loading depend on the load and on the level of chronic sodium intake. To test the hypothesis that an acute step increase in total body sodium (TBS) elicits a natriuretic response, which is dependent on the chronic level of TBS, we measured the effects of a bolus of NaCl during different low-sodium diets spanning a 25-fold change in sodium intake on elements of the renin-angiotensin-aldosterone system (RAAS) and on natriuresis. To custom-made, low-sodium chow (0.003%), NaCl was added to provide four levels of intake, 0.03–0.75 mmol·kg−1·day−1for 7 days. Acute NaCl administration increased PV (+6.3–8.9%) and plasma sodium concentration (∼2%) and decreased plasma protein concentration (−6.4–8.1%). Plasma ANG II and aldosterone concentrations decreased transiently. Potassium excretion increased substantially. Sodium excretion, arterial blood pressure, glomerular filtration rate, urine flow, plasma potassium, and plasma renin activity did not change. The results indicate that sodium excretion is controlled by neurohumoral mechanisms that are quite resistant to acute changes in plasma volume and colloid osmotic pressure and are not down-regulated within 2 h. With previous data, we demonstrate that RAAS variables are log-linearly related to sodium intake over a >250-fold range in sodium intake, defining dietary sodium function lines that are simple measures of the sodium sensitivity of the RAAS. The dietary function line for plasma ANG II concentration increases from theoretical zero at a daily sodium intake of 17 mmol Na/kg (intercept) with a slope of 16 pM increase per decade of decrease in dietary sodium intake.
Effects of hindbrain melanin-concentrating hormone and neuropeptide Y administration on licking for water, saccharin, and sucrose solutions
Authors: Baird John-Paul , Rios Catalina , Loveland Jasmine L. , Beck Janine , Tran Alice , Mahoney Carrie E.
Published: November 2007

Melanin-concentrating hormone (MCH) and neuropeptide Y (NPY) are orexigenic peptides found in hypothalamic neurons that project throughout the forebrain and hindbrain. The effects of fourth ventricle (4V) infusions of NPY (5 μg) and MCH (5 μg) on licking for water, 4 mM saccharin, and sucrose (0.1 and 1.0 M) solutions were compared to identify the contributions of each peptide to hindbrain-stimulated feeding. NPY increased mean meal size only for the sucrose solutions, suggesting that caloric feedback or taste quality is pertinent to the orexigenic effect; MCH infusions under identical testing conditions failed to produce increases for any tastant. A second experiment also observed no intake or licking effects after MCH doses up to 15 μg, supporting the conclusion that MCH-induced orexigenic responses require forebrain stimulation. A third experiment compared the 4V NPY results with those obtained after NPY infusions (5 μg) into the third ventricle (3V). In contrast to the effects observed after the 3V NPY injections and previously reported forebrain intracerebroventricular (ICV) NPY infusion studies, 4V NPY failed to increase meal frequency for any taste solution or ingestion rate in the early phases of the sucrose meals. Overall, 4V NPY responses were limited to intrameal behavioral processes, whereas forebrain ICV NPY stimulation elicited both consummatory and appetitive responses. The dissociation between MCH and NPY effects observed for 4V injections is consistent with reports that forebrain ICV injections of MCH and NPY produced nearly dichotomous effects on the pattern of licking microstructure, and, collectively, the results indicate that the two peptides have separate sites of feeding action in the brain.
Forebrain neurons that project to the gustatory parabrachial nucleus in rat lack glutamic acid decarboxylase
Authors: Saggu Shalini , Lundy Robert F.
Published: November 2007

Evidence suggests that GABA might mediate the inhibitory influence of centrifugal inputs on taste-evoked responses in the parabrachial nucleus (PBN). Previous studies show that activation of the gustatory cortex (GC), bed nucleus of the stria terminalis (BNST), central nucleus of the amygdala (CeA), and lateral hypothalamus (LH) inhibits PBN taste responses, GABAergic neurons are present in these forebrain regions, and GABA reduces the input resistance of PBN neurons. The present study investigated the expression of glutamic acid decarboxylase immunoreactivity (GAD_67 ir) in GC, BNST, CeA, and LH neurons that project to the PBN in rats. After anesthesia (50 mg/kg ip Nembutal), injections of the retrograde tracer Fluorogold (FG) were made in the physiologically defined gustatory PBN. Brain tissue containing the above forebrain structures was processed and examined for FG and GAD_67 ir. Similar to previous studies, each forebrain site contained retrogradely labeled neurons. Our results suggest further that the major source of input to the PBN taste region is the CeA (608 total cells) followed by GC (257 cells), LH (106 cells), and BNST (92 cells). This suggests a differential contribution to centrifugal control of PBN taste processing. We further show that despite the presence of GAD_67 neurons in each forebrain area, colocalization was extremely rare, occurring only in 3 out of 1,063 FG-labeled cells. If we assume that the influence of centrifugal input is mediated by direct projections to the gustatory region of the PBN, then GABAergic forebrain neurons apparently are not part of this descending pathway.
Single-breath test in lateral decubitus reflects function of single lungs grafted for interstitial lung disease
Authors: Van Muylem Alain , Gevenois Pierre Alain , Kallinger Elizabeth , Bankier Alexander A. , Knoop Christiane , Verleden Geert , Estenne Marc
Published: November 2007

After single-lung transplantation (SLT) for emphysema, heterogeneity of ventilation distribution in the graft can be assessed by measuring the slope of the alveolar plateau, computed from a single-breath test, performed in lateral decubitus with this lung in the nondependent position. We tested the validity of this technique in patients with SLT for interstitial lung diseases (ILD). Twelve patients with SLT for ILD, 12 nontransplanted patients with ILD, and 10 healthy control subjects performed single-breath washouts in right and left lateral decubitus; nitrogen slope ( SN2) and the difference between SF6 and He slopes ( SSF6- SHe) were measured between 75 and 100% of expired volume. In 10 transplant recipients, the volume of each lung was measured in both postures by computerized tomography. Slopes were unaffected by posture in normal control subjects and patients with ILD. On the other hand, SN2 and SSF6- SHe in transplant recipients were smaller with the graft in the nondependent than in the dependent position (0.366 ± 0.445 vs. 1.035 ± 0.498 for SN2; 0.094 ± 0.201 vs. 0.218 ± 0.277 for SSF6- SHe). Values of SN2 and SSF6- SHe obtained in the former position were similar to those obtained in normal controls, while values obtained in the latter position were similar to those obtained in nontransplanted patients with ILD. Computerized tomography studies with the graft in the nondependent position indicated that this lung contributed 82% of the volume expired below functional residual capacity. We conclude that, in patients with SLT for ILD, the slope of the alveolar plateau obtained with the graft in the nondependent position reflects heterogeneity of ventilation distribution in this lung.
Short-term modulation of the exercise ventilatory response in young men
Authors: Wood Helen E. , Mitchell Gordon S. , Babb Tony G.
Published: November 2007

Arterial isocapnia is a hallmark of moderate exercise in humans and is maintained even when resting arterial Pco2(PaCO2) is raised or lowered from its normal level, e.g., with chronic acid-base changes or acute increases in respiratory dead space. When resting ventilation and/or PaCO2are altered, maintenance of isocapnia requires active adjustments of the exercise ventilatory response [slope of the ventilation (V̇e)-CO2production (V̇co2) relationship, ΔV̇e/ΔV̇co2]. On the basis of animal studies, it has been proposed that a central neural mechanism links the exercise ventilatory response to the resting ventilatory drive without need for changes in chemoreceptor feedback from rest to exercise, a mechanism referred to as short-term modulation (STM). We tested the hypothesis that STM is elicited by increased resting ventilatory drive associated with added external dead space (DS) in humans. Twelve young men were studied in control conditions and with added DS (200, 400, and 600 ml; randomized) at rest and during mild-to-moderate cycle exercise. ΔV̇e/ΔV̇co2increased progressively as DS volume increased ( P < 0.0001). While resting end-tidal Pco2(PetCO2) increased with DS, the change in PetCO2from rest to exercise was not increased, indicating that increased chemoreceptor feedback from rest to exercise cannot account for the greater exercise ventilatory response. We conclude that STM of the exercise ventilatory response is induced in young men when resting ventilatory drive is increased with external DS, confirming the existence of STM in humans.
Central chemoreflex sensitivity and sympathetic neural outflow in elite breath-hold divers
Authors: Dujic Zeljko , Ivancev Vladimir , Heusser Karsten , Dzamonja Gordan , Palada Ivan , Valic Zoran , Tank Jens , Obad Ante , Bakovic Darija , Diedrich Andre , Joyner Michael J , Jordan Jens
Published: November 2007

Repeated hypoxemia in obstructive sleep apnea patients increases sympathetic activity, thereby promoting arterial hypertension. Elite breath-holding divers are exposed to similar apneic episodes and hypoxemia. We hypothesized that trained divers would have increased resting sympathetic activity and blood pressure, as well as an excessive sympathetic nervous system response to hypercapnia. We recruited 11 experienced divers and 9 control subjects. During the diving season preceding the study, divers participated in 7.3 ± 1.2 diving fish-catching competitions and 76.4 ± 14.6 apnea training sessions with the last apnea 3–5 days before testing. We monitored beat-by-beat blood pressure, heart rate, femoral artery blood flow, respiration, end-tidal CO2, and muscle sympathetic nerve activity (MSNA). After a baseline period, subjects began to rebreathe a hyperoxic gas mixture to raise end-tidal CO2 to 60 Torr. Baseline MSNA frequency was 31 ± 11 bursts/min in divers and 33 ± 13 bursts/min in control subjects. Total MSNA activity was 1.8 ± 1.5 AU/min in divers and 1.8 ± 1.3 AU/min in control subjects. Arterial oxygen saturation did not change during rebreathing, whereas end-tidal CO2 increased continuously. The slope of the hypercapnic ventilatory and MSNA response was similar in both groups. We conclude that repeated bouts of hypoxemia in elite, healthy breath-holding divers do not lead to sustained sympathetic activation or arterial hypertension. Repeated episodes of hypoxemia may not be sufficient to drive an increase in resting sympathetic activity in the absence of additional comorbidities.
The use of functional MRI to evaluate cervical flexor activity during different cervical flexion exercises
Authors: Cagnie Barbara , Dickx Nele , Peeters Ian , Tuytens Jan , Achten Eric , Cambier Dirk , Danneels Lieven
Published: November 2007

The purpose of this study was to investigate the recruitment pattern of deep and superficial neck flexors evoked by three different cervical flexion exercises using muscle functional MRI. In 19 healthy participants, transverse relaxation time (T2) values were calculated for the longus colli (Lco), longus capitis (Lca), and sternocleidomastoid (SCM) at rest and following three exercises: conventional cervical flexion (CF), craniocervical flexion (CCF), and a combined craniocervical flexion and cervical flexion (CCF-CF). CCF-CF gave the highest T2 increase for all muscles. CCF displayed a significantly higher T2 increase for the Lca compared with the Lco and the SCM. When comparing the CCF and CF, no significant difference was found for the Lca, whereas the Lco and SCM displayed a higher T2 increase during CF compared with CCF. This study shows that muscle functional MRI can be used to characterize the specific activation levels and recruitment patterns of the superficial and deep neck flexors during different cervical flexion exercises. During CCF-CF, all synergists are maximally recruited, which makes this exercise useful for high-load training. CCF may provide a more specific method to assess and retrain Lca muscle performance compared with CF and CCF-CF. This study highlights the need to differentiate between the Lco and Lca when evaluating their function, since these results demonstrate a clear difference in activation of both muscles.
Noncommutative Control in the Rotational Vestibuloocular Reflex
Authors: Tchelidze Tamara , Hess Bernhard J. M.
Published: November 2007

To investigate the role of noncommutative computations in the oculomotor system, three-dimensional (3D) eye movements were measured in seven healthy subjects using a memory-contingent vestibulooculomotor paradigm. Subjects had to fixate a luminous point target that appeared briefly at an eccentricity of 20° in one of four diagonal directions in otherwise complete darkness. After a fixation period of ∼1 s, the subject was moved through a sequence of two rotations about mutually orthogonal axes in one of two orders (30° yaw followed by 30° pitch and vice versa in upright and 30° yaw followed by 20° roll and vice versa in both upright and supine orientations). We found that the change in ocular torsion induced by consecutive rotations about the yaw and the pitch axis depended on the order of rotations as predicted by 3D rotation kinematics. Similarly, after rotations about the yaw and roll axis, torsion depended on the order of rotations but now due to the change in final head orientation relative to gravity. Quantitative analyses of these ocular responses revealed that the rotational vestibuloocular reflexes (VORs) in far vision closely matched the predictions of 3D rotation kinematics. We conclude that the brain uses an optimal VOR strategy with the restriction of a reduced torsional position gain. This restriction implies a limited oculomotor range in torsion and systematic tilts of the angular eye velocity as a function of gaze direction.
Development of Thalamocortical Response Transformations in the Rat Whisker-Barrel System
Authors: Shoykhet Michael , Simons Daniel J.
Published: November 2007

Extracellular single-unit recordings were used to characterize responses of thalamic barreloid and cortical barrel neurons to controlled whisker deflections in 2, 3-, and 4-wk-old and adult rats in vivo under fentanyl analgesia. Results indicate that response properties of thalamic and cortical neurons diverge during development. Responses to deflection onsets and offsets among thalamic neurons mature in parallel, whereas among cortical neurons responses to deflection offsets become disproportionately smaller with age. Thalamic neuron receptive fields become more multiwhisker, whereas those of cortical neurons become more single-whisker. Thalamic neurons develop a higher degree of angular selectivity, whereas that of cortical neurons remains constant. In the temporal domain, response latencies decrease both in thalamic and cortical neurons, but the maturation time-course differs between the two populations. Response latencies of thalamic cells decrease primarily between 2 and 3 wk of life, whereas response latencies of cortical neurons decrease in two distinct steps—the first between 2 and 3 wk of life and the second between the fourth postnatal week and adulthood. Although the first step likely reflects similar subcortical changes, the second phase likely corresponds to developmental myelination of thalamocortical fibers. Divergent development of thalamic and cortical response properties indicates that thalamocortical circuits in the whisker-to-barrel pathway undergo protracted maturation after 2 wk of life and provides a potential substrate for experience-dependent plasticity during this time.
Fixed Points of Weakly Compatible Maps Satisfying a General Contractive Condition of Integral Type
Authors: Altun Ishak , Türkoğlu Duran , Rhoades Billy E
Published: November 2007

We prove a fixed point theorem for weakly compatible maps satisfying a general contractive condition of integral type.