bluuebunny/crossref_metadata_2025 huggingface dataset:
Shear-strength characteristics of a residual soil
Authors: Rahardjo H. , Lim T.T. , Chang M.F. , Fredlund D.G.
Published: June 2008

Shallow landslides in natural residual soils slopes are common all over the world. The slip surfaces associated with these landslides are often situated above the groundwater table. Therefore, it is important to quantify the contribution of negative pore-water pressure to the shear strength of soil. The shear-strength characteristics of residual soil from the Jurong Formation in Singapore were assessed using multistage, consolidated drained triaxial tests. These tests involved shearing under either a constant net confining pressure and varying matric suctions or under a constant matric suction and varying net confining pressures. An extended form of the Mohr–Coulomb equation was used to interpret the test results. The test results show that for matric suctions up to 400 kPa, the angle of internal friction associated with the matric suction, [Formula: see text], is similar to the effective angle of internal friction, [Formula: see text], which averages 26° for the residual soil of the Jurong Formation. The residual soil can maintain a high degree of saturation for matric suctions as high as 400 kPa. Examples involving stability analyses of a residual soil slope with varying pore-water pressure profiles indicate that soil suction contributes significantly to the factor of safety, particularly for shallow slip surfaces. Key words : residual soil, unsaturated soil, matric suction, shear strength, multistage triaxial test, slope stability.
Isothermal modeling of sand–bentonite mixtures at elevated temperatures
Authors: Lingnau B.E. , Graham J. , Tanaka N.
Published: June 2008

Two models are proposed for describing the stress–strain behavior of sand–bentonite (buffer) mixtures at elevated temperatures: (1) isothermal pseudoelasticity and (2) isothermal elastic-plasticity. Data to support the models come from consolidated undrained triaxial compression tests performed on dense saturated buffer specimens at effective confining stresses up to 9.0 MPa and temperatures of 26°, 65°, and 100 °C. Measurements indicate that volumes decrease with increasing temperature if the tests are carried out under drained conditions. These trends can be modelled by a family of hardening lines in semilog compression space. Power law relationships are presented for undrained shear-strength envelopes that increase in size with an increase in temperature. The slopes of unload-reload lines, κ, in semilog compression space vary with temperature and can be related to systematic variation in the friction angle [Formula: see text]. The shear modulus G50 at 50% peak strength also depends on temperature. Several plotting techniques are used to show the existence of different state boundary surfaces for each test temperature. Key words : sand–bentonite, buffer, compression, shear strength, temperature, modelling.
Quasi-overconsolidation and creep phenomena in shallow marine and estuarine organo-calcareous silts, Fiji
Authors: Shorten Graham G.
Published: June 2008

Nearshore, estuarine deposits of Holocene organo-calcareous silt provide the most common setting for foundation failure in Fiji. Creep is implicated in long-term settlement. Although the geological history indicates the deposits should be normally consolidated throughout, there is increasing apparent overconsolidation towards the surface. This finding is contrary to what might be expected if delayed compression alone was operating. The phenomenon appears to be related instead to organic content and may be affected by strain rates during consolidation. Oedometer tests extending over 7 months indicate the rate of volume change due to creep follows the Singh–Mitchell relationship, but calculation of secondary compression from radiocarbon dates suggests that the very long-term rate is higher than might be expected. Creep appears to be stress dependent, at least below the preconsolidation pressure, in common with other marine sediments. Key words : silt, organic, preconsolidation pressure, overconsolidation ratio, secondary compression, creep, radiocarbon dating.
One-dimensional freezing of seawater in a constrained volume
Authors: Szilder Krzysztof , Lozowski Edward P. , Forest Tom W.
Published: June 2008

A numerical time-dependent model of the one-dimensional fusion of seawater with limited salt rejection has been developed. The process of latent heat release, as brine cools and freezes, as well as changes of the specific heat capacity and thermal conductivity of sea ice with temperature have been incorporated into the model. The model predicts the variation of the brine temperature and the motion of the liquid–solid interface. Laboratory experiments have been performed to verify the model. Five centimetre layers of fresh water and brine of salinities 5, 10, 15, and 20%o were poured on an insulated surface and exposed to cold air from above. A comparison between the experimental results and the model prediction shows satisfactory agreement. Key words : sea ice, freezing, salinity, heat conduction, ice islands.
Development of geotechnical limit state design
Authors: Meyerhof Geoffrey G.
Published: June 2008

The historical development of limit state design in geotechnical engineering is reviewed. Total and partial factors of safety used for the design of land–based and offshore structures are compared. It is found that the factors of safety in different codes for the ultimate and serviceability limit states design of earthworks, earth retaining structures, and land-based and offshore foundations are very similar. Partial factors in the ultimate limit state design are linked to the variability of the loads and soil parameters, the design approximations, and construction tolerances. They influence the nominal probability of failure of the type of structure considered and the seriousness of failure, which differ for land-based and offshore structures. These probabilities are compared with human fatality risks of common experiences. The serviceability limit states are governed by structural and operational constraints and the intended service life of the land-based or offshore structure. The corresponding partial factors are generally taken as unity. Key words : codes, earth structures, foundations, human risks, limit states design, probability of failures, factors of safety.
Utilisation d'équations constitutives du comportement du sol pour la prédiction d'essais triaxiaux sur des granulats calcaires
Authors: Jrad M. , Masrouri F. , Monnet J.
Published: June 2008

This paper analyses the three-dimensional consolidation and shear behavior of cohesionless soil. It is divided in two parts: In the first part, the law of soil behavior is described. So far, the soil was assumed to be elastoplastic with associated plastic flow and stress hardening behavior. In this study, a new version of the Chaffois–Monnet law presents the yield function during consolidation and shearing in a single energy equation which avoids numerical errors due to the iterative process of the finite element computation, and numerical gap between consolidation and shearing. This new model uses only eight parameters with geotechnical significance. In the second part of this study, the results of the model are compared with experimental data from consolidated drained triaxial tests on three types of limestone aggregates. The validity of the model is finally discussed, and the relationship between the internal angle of friction and the mean stress is shown. Key words : behavior law, elastoplastic, associated, plastic flow, limestone aggregate, triaxial test.
Brazilian tensile strength test of lightly cemented sand
Authors: Das B.M. , Yen S.C. , Dass R.N.
Published: June 2008

Tensile stress – tensile strain relationships for lightly cemented sand specimens obtained by conducting Brazilian tensile strength tests have been presented. The tensile strain measurement was done by using an optical image analysis technique. In addition to the tensile strength tests, some unconfined compression tests on sand specimens with varying cement contents were also performed. Based on the results of the above tests, a nondimensional tensile stress – tensile strain relationship has been presented. Also the variation of the tensile and compressive strength and strain ratios with varying cement contents have been discussed. Key words : lightly cemented sand, optical image analysis, tensile strain, tensile strength, unconfined compression strength.
Controlling the quality of groundwater parameters: some examples
Authors: Chapuis Robert P.
Published: June 2008

Hydraulic head, gradient, hydraulic conductivity, transmissivity, and storativity are input data that should be collected according to applicable codes and standards. These must be defined without ambiguity, and they must be mutually compatible. Feasibility studies and the design of facilities are based on these data. A firm providing professional services in hydrogeology can improve quality in this area only by examining the reasons for poor quality: the reasons are not found in standards or codes. This paper provides examples to illustrate variou aspects of the work to be done to control the quality of groundwater seepage parameters. The paper has a narrow focus within the context of total quality management. Key words : groundwater, parameters, quality control.
FERROELECTRIC AND PIEZOELECTRIC PROPERTIES OF Gd3+ AND Y3+ MODIFIED PKN ELECTROCERAMICS
Authors: RAO K. SAMBASIVA , PRASAD D. MADHAVA , KRISHNA P. MURALI , LEE JOON HYUNG
Published: June 2008

Ceramics with the composition Pb 1-x K 2x-3y M y Nb 2 O 6 (PKMN) with x = 0.29, y = 0.145 and M = Gd 3+, Y 3+ were synthesized by the solid-state reaction route between the corresponding oxides and carbonates. The crystal structure was confirmed by X-ray diffraction (XRD). The temperature dependence of dielectric properties were measured from 35 to 595°C. Well-developed P–E (polarization–electric field) hysteresis loops were observed in the materials. Determining the piezoelectric constants, Kp = 20%, Kt = 49%, d33 = 110, and quality factor, Qm = 33, reveals that the material Y 3+-modified PKN can be useful for transducer applications.
GEOMETRIC VARIATIONS OF THE BOLTZMANN ENTROPY
Authors: KALOGEROPOULOS NIKOS
Published: June 2008

We perform a calculation of the first and second order infinitesimal variations, with respect to energy, of the Boltzmann entropy of constant energy hypersurfaces of a system with a finite number of degrees of freedom. We comment on the stability interpretation of the second variation in this framework.
EXPLICIT AND EXACT SOLUTIONS TO THE mKdV-SINE-GORDON EQUATION
Authors: XIE YUANXI
Published: June 2008

By introducing an auxiliary ordinary differential equation and solving it by the method of variable separation, rich types of explicit and exact solutions of the mKdV-sine-Gordon equation are presented in a simple manner.
REALIZATION OF THE GREENBERG–HORNE–ZEILINGER (GHZ) STATE AND SWAP GATE WITH SUPERCONDUCTING QUANTUM-INTERFERENCE DEVICES IN A CAVITY VIA ADIABATIC PASSAGE
Authors: ZHENG AN-SHOU , CHENG YONG-JIN , LIU JI-BING , LI TIE-PING
Published: June 2008

We propose an alternative scheme to prepare the Greenberg–Horne–Zeilinger (GHZ) state and realize a SWAP gate by using Superconducting Quantum-interference devices (SQUIDs) coupled to a cavity. The present scheme, based on the adiabatic evolution of dark state, constitutes a decoherence-free method in the sense that spontaneous emission and cavity damping are avoided. Besides, the standard GHZ state can be directly obtained without measurement or any auxiliary SQUIDs and the construction of the SWAP gate does not require a composition of elementary gates from a universal set. Thus the procedure is simplified and decoherence is greatly suppressed.
Copper is taken up efficiently from albumin and α2-macroglobulin by cultured human cells by more than one mechanism
Authors: Moriya Mizue , Ho Yi-Hsuan , Grana Anne , Nguyen Linh , Alvarez Arrissa , Jamil Rita , Ackland M. Leigh , Michalczyk Agnes , Hamer Pia , Ramos Danny , Kim Stephen , Mercer Julian F. B. , Linder Maria C.
Published: June 2008

Ionic copper entering blood plasma binds tightly to albumin and the macroglobulin transcuprein. It then goes primarily to the liver and kidney except in lactation, where a large portion goes directly to the mammary gland. Little is known about how this copper is taken up from these plasma proteins. To examine this, the kinetics of uptake from purified human albumin and α2-macroglobulin, and the effects of inhibitors, were measured using human hepatic (HepG2) and mammary epithelial (PMC42) cell lines. At physiological concentrations (3–6 μM), both cell types took up copper from these proteins independently and at rates similar to each other and to those for Cu-dihistidine or Cu-nitrilotriacetate (NTA). Uptakes from α2-macroglobulin indicated a single saturable system in each cell type, but with different kinetics, and 65–80% inhibition by Ag(I) in HepG2 cells but not PMC42 cells. Uptake kinetics for Cu-albumin were more complex and also differed with cell type (as was the case for Cu-histidine and NTA), and there was little or no inhibition by Ag(I). High Fe(II) concentrations (100–500 μM) inhibited copper uptake from albumin by 20–30% in both cell types and that from α2-macroglobulin by 0–30%, and there was no inhibition of the latter by Mn(II) or Zn(II). We conclude that the proteins mainly responsible for the plasma-exchangeable copper pool deliver the metal to mammalian cells efficiently and by several different mechanisms. α2-Macroglobulin delivers it primarily to copper transporter 1 in hepatic cells but not mammary epithelial cells, and additional as-yet-unidentified copper transporters or systems for uptake from these proteins remain to be identified.
NFATc3 regulates BK channel function in murine urinary bladder smooth muscle
Authors: Layne JJ , Werner ME , Hill-Eubanks DC , Nelson MT
Published: June 2008

The nuclear factor of activated T-cells (NFAT) is a Ca2+-dependent transcription factor that has been reported to regulate the expression of smooth muscle contractile proteins and ion channels. Here we report that large conductance Ca2+-sensitive potassium (BK) channels and voltage-gated K+ (KV) channels may be regulatory targets of NFATc3 in urinary bladder smooth muscle (UBSM). UBSM myocytes from NFATc3-null mice displayed a reduction in iberiotoxin (IBTX)-sensitive BK currents, a decrease in mRNA for the pore-forming α-subunit of the BK channel, and a reduction in BK channel density compared with myocytes from wild-type mice. Tetraethylammonium chloride-sensitive KV currents were elevated in UBSM myocytes from NFATc3-null mice, as was mRNA for the Shab family member KV2.1. Despite KV current upregulation, bladder strips from NFATc3-null mice displayed an elevated contractile response to electrical field stimulation relative to strips from wild-type mice, but this difference was abrogated in the presence of the BK channel blocker IBTX. These results support a role for the transcription factor NFATc3 in regulating UBSM contractility, primarily through an NFATc3-dependent increase in BK channel activity.
Acid-sensing ion channel 3 (ASIC3) cell surface expression is modulated by PSD-95 within lipid rafts
Authors: Eshcol Jayasheel O. , Harding Anne Marie S. , Hattori Tomonori , Costa Vivian , Welsh Michael J. , Benson Christopher J.
Published: June 2008

Acid-sensing ion channel 3 (ASIC3) is a H+-gated cation channel primarily found in sensory neurons, where it may function as a pH sensor in response to metabolic disturbances or painful conditions. We previously found that ASIC3 interacts with the postsynaptic density protein PSD-95 through its COOH terminus, which leads to a decrease in ASIC3 cell surface expression and H+-gated current. PSD-95 has been implicated in recruiting proteins to lipid rafts, which are membrane microdomains rich in cholesterol and sphingolipids that organize receptor/signaling complexes. We found ASIC3 and PSD-95 coimmunoprecipitated within detergent-resistant membrane fractions. When cells were exposed to methyl-β-cyclodextrin to deplete membrane cholesterol and disrupt lipid rafts, PSD-95 localization to lipid raft fractions was abolished and no longer inhibited ASIC3 current. Likewise, mutation of two cysteine residues in PSD-95 that undergo palmitoylation (a lipid modification that targets PSD-95 to lipid rafts) prevented its inhibition of ASIC3 current and cell surface expression. In addition, we found that cell surface ASIC3 is enriched in the lipid raft fraction. These data suggest that PSD-95 and ASIC3 interact within lipid rafts and that this raft interaction is required for PSD-95 to modulate ASIC3.
Female ROMK null mice manifest more severe Bartter II phenotype on renal function and higher PGE2production
Authors: Yan Qingshang , Yang Xinbo , Cantone Alessandra , Giebisch Gerhard , Hebert Steven , Wang Tong
Published: June 2008

ROMK null mice with a high survival rate and varying severity of hydronephrosis provide a good model to study type II Bartter syndrome pathophysiology ( 26 ). During the development of such a colony, we found that more male than female null mice survived, 58.7% vs. 33.3%. To investigate the possible mechanism of this difference, we compared the survival rates, renal functions, degree of hydronephrosis, as well as PGE2and TXB2production between male and female ROMK wild-type and null mice. We observed that female ROMK Bartter's mice exhibited lower GFR (0.37 vs. 0.54 ml·min−1·100 g BW−1, P < 0.05) and higher fractional Na+excretion (0.66% vs. 0.48%, P < 0.05) than male Bartter's. No significant differences in acid-base parameters, urinary K+excretion, and plasma electrolyte concentrations were observed between sexes. In addition, we assessed the liquid retention rate in the kidney to evaluate the extent of hydronephrosis and observed that 67% of male and 90% of female ROMK null mice were hydronephrotic mice. Urinary PGE2excretion was higher in both sexes of ROMK null mice: 1.35 vs. 1.10 ng/24 h in males and 2.90 vs. 0.87 ng/24 h in females. TXB2excretion was higher in female mice in both wild-type and ROMK null mice. The increments of urinary PGE2and TXB2were significantly higher in female null mice than males, 233.33% vs. 22.74% of PGE2and 85.67% vs. 20.36% of TXB2. These data demonstrate a more severe Bartter phenotype in female ROMK null mice, and higher PGE2and TXB2production may be one of the mechanisms of this manifestation.
Regulation of pyruvate dehydrogenase in the common killifish,Fundulus heteroclitus, during hypoxia exposure.
Authors: Richards Jeffrey G. , Sardella Brian A. , Schulte Patricia M.
Published: June 2008

We examined the metabolic responses of the hypoxia-tolerant killifish ( Fundulus heteroclitus) to 15 h of severe hypoxia and recovery with emphasis on muscle substrate usage and the regulation of the mitochondrial protein pyruvate dehydrogenase (PDH), which controls carbohydrate oxidation. Hypoxia survival involved a transient activation of substrate-level phosphorylation in muscle (decreases in [creatine phospate] and increases in [lactate]) during which time mechanisms to reduce overall ATP consumption were initiated. This metabolic transition did not affect total cellular [ATP], but had an impact on cellular energy status as indicated by large decreases in [ATP]/[ADPfree] and [ATP]/[AMPfree] and a significant loss of phosphorylation potential and Gibbs free energy of ATP hydrolysis (Δ fG′). The activity of PDH was rapidly (within 3 h) decreased by ∼50% upon hypoxia exposure and remained depressed relative to normoxic samples throughout. Inactivation of PDH was primarily mediated via posttranslational modification following the accumulation of acetyl-CoA and subsequent activation of pyruvate dehydrogenase kinase (PDK). Estimated changes in cytoplasmic and mitochondrial [NAD+]/[NADH] did not parallel one another, suggesting the mitochondrial NADH shuttles do not function during hypoxia exposure. Large increases in the expression of PDK (PDK isoform 2) were consistent with decreased PDH activity; however, these changes in mRNA were not associated with changes in total PDK-2 protein content assessed using mammalian antibodies. No other changes in the expression of other known hypoxia-responsive genes (e.g., lactate dehydrogenase-A or -B) were observed in either muscle or liver.
Quercetin reduces susceptibility to influenza infection following stressful exercise
Authors: Davis J. M. , Murphy E. A. , McClellan J. L. , Carmichael M. D. , Gangemi J. D.
Published: June 2008

Exercise stress is associated with increased risk for upper respiratory tract infection. We have shown that exercise stress can increase susceptibility to infection. Quercetin, a flavonoid present in a wide variety of fruits and vegetables, has been reported to inhibit infectivity and replication of a broad spectrum of viruses and may offset the increase in susceptibility to infection associated with stressful exercise. This study examined the effects of quercetin feedings on susceptibility to the influenza virus A/Puerto Rico/8/34 (H1N1) following stressful exercise. Mice were randomly assigned to one of four treatment groups: exercise-placebo, exercise-quercetin, control-placebo, or control-quercetin. Exercise consisted of a run to fatigue (∼140 min) on a treadmill for 3 consecutive days. Quercetin (12.5 mg/kg) was administered via gavage for 7 days before viral challenge. At 30 min after the last bout of exercise or rest, mice ( n = 23–30) were intranasally inoculated with a standardized dose of influenza virus (0.04 hemagglutinating units). Mice were monitored daily for morbidity (time to sickness), symptom severity, and mortality (time to death) for 21 days. Exercise stress was associated with an increased susceptibility to infection [morbidity, mortality, and symptom severity on days 5–7 ( P < 0.05)]; quercetin offset the increase in susceptibility to infection [morbidity, mortality, and symptom severity on days 5–7 ( P < 0.05)] that was associated with stressful exercise. These data suggest that short-term quercetin feedings may prove to be an effective strategy to lessen the impact of stressful exercise on susceptibility to respiratory infection.
Effect of aldosterone on BK channel expression in mammalian cortical collecting duct
Authors: Estilo Genevieve , Liu Wen , Pastor-Soler Nuria , Mitchell Phillip , Carattino Marcelo D. , Kleyman Thomas R. , Satlin Lisa M.
Published: June 2008

Apical large-conductance Ca2+-activated K+(BK) channels in the cortical collecting duct (CCD) mediate flow-stimulated K+secretion. Dietary K+loading for 10–14 days leads to an increase in BK channel mRNA abundance, enhanced flow-stimulated K+secretion in microperfused CCDs, and a redistribution of immunodetectable channels from an intracellular pool to the apical membrane (Najjar F, Zhou H, Morimoto T, Bruns JB, Li HS, Liu W, Kleyman TR, Satlin LM. Am J Physiol Renal Physiol 289: F922–F932, 2005). To test whether this adaptation was mediated by a K+-induced increase in aldosterone, New Zealand White rabbits were fed a low-Na+(LS) or high-Na+(HS) diet for 7–10 days to alter circulating levels of aldosterone but not serum K+concentration. Single CCDs were isolated for quantitation of BK channel subunit (total, α-splice variants, β-isoforms) mRNA abundance by real-time PCR and measurement of net transepithelial Na+(JNa) and K+(JK) transport by microperfusion; kidneys were processed for immunolocalization of BK α-subunit by immunofluorescence microscopy. At the time of death, LS rabbits excreted no urinary Na+and had higher circulating levels of aldosterone than HS animals. The relative abundance of BK α-, β2-, and β4-subunit mRNA and localization of immunodetectable α-subunit were similar in CCDs from LS and HS animals. In response to an increase in tubular flow rate from ∼1 to 5 nl·min−1·mm−1, the increase in JNawas greater in LS vs. HS rabbits, yet the flow-stimulated increase in JKwas similar in both groups. These data suggest that aldosterone does not contribute to the regulation of BK channel expression/activity in response to dietary K+loading.
Renal blood flow and dynamic autoregulation in conscious mice
Authors: Iliescu Radu , Cazan Radu , McLemore Gerald R. , Venegas-Pont Marcia , Ryan Michael J.
Published: June 2008

Autoregulation of renal blood flow (RBF) occurs via myogenic and tubuloglomerular feedback (TGF) mechanisms that are engaged by pressure changes within preglomerular arteries and by tubular flow and content, respectively. Our understanding of autoregulatory function in the kidney largely stems from experiments in anesthetized animals where renal perfusion pressure is precisely controlled. However, normally occurring variations in blood pressure are sufficient to engage both myogenic and TGF mechanisms, making the assessment of autoregulatory function in conscious animals of significant value. To our knowledge, no studies have evaluated the dynamics of RBF in conscious mice. Therefore, we used spectral analysis of blood pressure and RBF and identified dynamic operational characteristics of the myogenic and TGF mechanisms in conscious, freely moving mice instrumented with ultrasound flow probes and arterial catheters. The myogenic response generates a distinct resonance peak in transfer gain at 0.31 ± 0.01 Hz. Myogenic-dependent attenuation of RBF oscillations, indicative of active autoregulation, is apparent as a trough in gain below 0.3 Hz (−6.5 ± 1.3 dB) and a strong positive phase peak (93 ± 9 deg), which are abolished by amlodipine infusion. Operation of TGF produces a local maximum in gain at 0.05 ± 0.01 Hz and a positive phase peak (62.3 ± 12.3 deg), both of which are eliminated by infusion of furosemide. Administration of amlodipine eliminated both myogenic and TGF signature peaks, whereas furosemide shifted the myogenic phase peak to a slower operational frequency. These data indicate that myogenic and TGF dynamics may be used to investigate the effectiveness of renal autoregulatory mechanisms in conscious mice.
Disease-dependent mechanisms of albuminuria
Authors: Comper Wayne D. , Hilliard Lucinda M. , Nikolic-Paterson David J. , Russo Leileata M.
Published: June 2008

The mechanism of albuminuria is perhaps one of the most complex yet important questions in renal physiology today. Recent studies have directly demonstrated that the normal glomerulus filters substantial amounts of albumin and that charge selectivity plays little or no role in preventing this process. This filtered albumin is then processed by proximal tubular cells by two distinct pathways; dysfunction in either one of these pathways gives rise to discrete forms of albuminuria. Most of the filtered albumin is returned to the peritubular blood supply by a retrieval pathway. Albuminuria in the nephrotic range would arise from retrieval pathway dysfunction. The small quantities of filtered albumin that are not retrieved undergo obligatory lysosomal degradation before urinary excretion as small peptide fragments. This degradation pathway is sensitive to metabolic factors responsible for hypertrophy and fibrosis, particularly molecules such as angiotensin II and transforming growth factor-β1, whose production is stimulated by hyperglycemic and hypertensive environments. Dysfunction in this degradation pathway leads to albuminuria below the nephrotic range. These new insights into albumin filtration and processing argue for a reassessment of the role of podocytes and the slit diaphragm as major direct determinants governing albuminuria, provide information on how glomerular morphology and “tubular” albuminuria may be interrelated, and offer a new rationale for drug development.
MCP-1/CCR2 system is involved in high glucose-induced fibronectin and type IV collagen expression in cultured mesangial cells
Authors: Park Jehyun , Ryu Dong-Ryeol , Li Jin Ji , Jung Dong-Sub , Kwak Seung-Jae , Lee Sun Ha , Yoo Tae-Hyun , Han Seung Hyeok , Lee Jung Eun , Kim Dong Ki , Moon Sung Jin , Kim Kunhong , Han Dae Suk , Kang Shin-Wook
Published: June 2008

Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that plays an important role in the recruitment of macrophages. Although previous studies have demonstrated the importance of MCP-1 in the pathogenesis of diabetic nephropathy (DN) in terms of inflammation, the role of MCP-1 and its receptor (C-C chemokine receptor 2; CCR2) in extracellular matrix (ECM) accumulation under diabetic conditions has been largely unexplored. This study was undertaken to investigate the functional role of the MCP-1/CCR2 system in high glucose-induced ECM (fibronectin and type IV collagen) protein expression in cultured mesangial cells (MCs). Mouse MCs were exposed to medium containing 5.6 mM glucose (NG), NG+24.4 mM mannitol (NG+M), or 30 mM glucose (HG) with or without mutant MCP-1 (mMCP-1), CCR2 small interfering (si)RNA, or CCR2 inhibitor (RS102895). To examine the relationship between MCP-1 and transforming growth factor (TGF)-β1, MCs were also treated with TGF-β1 (2 ng/ml) with or without mMCP-1 or CCR2 siRNA. Transient transfection was performed with Lipofectamine 2000 for 24 h. Cell viability was determined by an MTT assay, mouse and human MCP-1 and TGF-β1 levels by ELISA, and CCR2 and ECM protein expression by Western blotting. Transfections of mMCP-1 and CCR2 siRNA increased human MCP-1 levels and inhibited CCR2 expression, respectively. HG-induced ECM protein expression and TGF-β1 levels were significantly attenuated by mMCP-1, CCR2 siRNA, and RS102895 ( P < 0.05). MCP-1 directly increased ECM protein expression, and this increase was inhibited by an anti-TGF-β1 antibody. In addition, TGF-β1-induced ECM protein expression was significantly abrogated by the inhibition of the MCP-1/CCR2 system ( P < 0.05). These results suggest that an interaction between the MCP-1/CCR2 system and TGF-β1 may contribute to ECM accumulation in DN.
Formation and maintenance of ventilatory long-term facilitation require NMDA but not non-NMDA receptors in awake rats
Authors: McGuire Michelle , Liu Chun , Cao Ying , Ling Liming
Published: June 2008

N-methyl-d-aspartate (NMDA) receptor antagonism in the phrenic motonucleus area eliminates phrenic long-term facilitation (pLTF; a persistent augmentation of phrenic nerve activity after episodic hypoxia) in anesthetized rats. However, whether NMDA antagonism can eliminate ventilatory LTF (vLTF) in awake rats is unclear. The role of non-NMDA receptors in LTF is also unknown. Serotonin receptor antagonism before, but not after, episodic hypoxia eliminates pLTF, suggesting that serotonin receptors are required for induction, but not maintenance, of pLTF. However, because NMDA and non-NMDA ionotropic glutamate receptors are directly involved in mediating the inspiratory drive to phrenic, hypoglossal, and intercostal motoneurons, we hypothesized that these receptors are required for both formation and maintenance of vLTF. vLTF, induced by five episodes of 5-min poikilocapnic hypoxia (10% O2) with 5-min normoxia intervals, was measured with plethysmography in conscious adult male Sprague-Dawley rats. Either (±)-2-amino-5-phosphonovaleric acid (APV; NMDA antagonist, 1.5 mg/kg) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; non-NMDA antagonist, 10 mg/kg) was systemically (ip) injected ∼30 min before hypoxia. APV was also injected immediately after or 20 min after episodic hypoxia in additional groups. As control, vehicle was similarly injected in each rat 1–2 days before. Regardless of being injected before or after episodic hypoxia, vehicle did not alter vLTF (∼23%), whereas APV eliminated vLTF while having little effect on baseline ventilation or hypoxic ventilatory response. In contrast, CNQX enhanced vLTF (∼34%) while decreasing baseline ventilation. Collectively, these results suggest that activation of NMDA but not non-NMDA receptors is necessary for formation and maintenance of vLTF in awake rats.
Testing for recombinant human erythropoietin in urine: problems associated with current anti-doping testing
Authors: Lundby Carsten , Achman-Andersen Niels J. , Thomsen Jonas J. , Norgaard Anne M. , Robach Paul
Published: June 2008

Background: the main action of recombinant human erythropoietin (rHuEpo) is to increase the oxygen carrying capacity of the blood. To prevent a possible misuse of rHuEpo, this is tested in urine samples collected from athletes by World Anti-Doping Agency (WADA)-accredited laboratories. Recently the test has met serious critiques, and the aims of the present study were to investigate the detection power of the test as well as the variability in the test power comparing the results of two WADA-accredited laboratories. Methods: eight human subjects were studied for 7 wk and treated with rHuEpo for 4 wk with 2 wk of “boosting” followed by 2 wk of “maintenance” and a post period of 3 wk. Urine samples were obtained during all periods. Results: laboratory A determined rHuEpo misuse in all subjects during the boosting period, whereas laboratory B found no misuse, with one sample to be negative, and the remaining seven to be suspicious. The detection rates decreased throughout the maintenance and post period when total hemoglobin mass and exercise performance were elevated. During this period, laboratory A found only two of 24 samples to be positive and three to be suspicious, and laboratory B found no positive or suspicious samples. Conclusion: this study demonstrates a poor agreement in test results comparing two WADA-accredited laboratories. Moreover, after the initial rHuEpo boosting period the power to detect rHuEpo misuse during the maintenance and post periods appears minimal.
Exercise training improves peripheral chemoreflex function in heart failure rabbits
Authors: Li Yu-Long , Ding Yanfeng , Agnew Chad , Schultz Harold D.
Published: June 2008

An enhancement of peripheral chemoreflex sensitivity contributes to sympathetic hyperactivity in chronic heart failure (CHF) rabbits. The enhanced chemoreflex function in CHF involves augmented carotid body (CB) chemoreceptor activity via upregulation of the angiotensin II (ANG II) type 1 (AT1)-receptor pathway and downregulation of the neuronal nitric oxide synthase (nNOS)-nitric oxide (NO) pathway in the CB. Here we investigated whether exercise training (EXT) normalizes the enhanced peripheral chemoreflex function in CHF rabbits and possible mechanisms mediating this effect. EXT partially, but not fully, normalized the exaggerated baseline renal sympathetic nerve activity (RSNA) and the response of RSNA to hypoxia in CHF rabbits. EXT also decreased the baseline CB nerve single-fiber discharge (4.9 ± 0.4 vs. 7.7 ± 0.4 imp/s at Po2 = 103 ± 2.3 Torr) and the response to hypoxia (20.6 ± 1.1 vs. 36.3 ± 1.3 imp/s at Po2 = 41 ± 2.2 Torr) from CB chemoreceptors in CHF rabbits, which could be reversed by treatment of the CB with ANG II or a nNOS inhibitor. Our results also showed that NO concentration and protein expression of nNOS were increased in the CBs from EXT + CHF rabbits, compared with that in CHF rabbits. On the other hand, elevated ANG II concentration and AT1-receptor overexpression of the CBs in CHF state were blunted by EXT. These results indicate that EXT normalizes the CB chemoreflex in CHF by preventing an increase in afferent CB chemoreceptor activity. EXT reverses the alterations in the nNOS-NO and ANG II-AT1-receptor pathways in the CB responsible for chemoreceptor sensitization in CHF.
Privileged Coding of Convex Shapes in Human Object-Selective Cortex
Authors: Haushofer Johannes , Baker Chris I. , Livingstone Margaret S. , Kanwisher Nancy
Published: June 2008

What is the neural code for object shape? Despite intensive research, the precise nature of object representations in high-level visual cortex remains elusive. Here we use functional magnetic resonance imaging (fMRI) to show that convex shapes are encoded in a privileged fashion by human lateral occipital complex (LOC), a region that has been implicated in object recognition. On each trial, two convex or two concave shapes that were either identical or different were presented sequentially. Critically, the convex and concave stimuli were the same except for a binocular disparity change that reversed the figure–ground assignment. The fMRI response in LOC for convex stimuli was higher for different than that for identical shape pairs, indicating sensitivity to differences in convex shape. However, when the same stimuli were seen as concave, the response for different and identical pairs was the same, indicating lower sensitivity to changes in concave shape than convex shape. This pattern was more pronounced in the anterior than that in the posterior portion of LOC. These results suggest that convex contours could be important elements in cortical object representations.
Neck Muscle Synergies During Stimulation and Inactivation of the Interstitial Nucleus of Cajal (INC)
Authors: Farshadmanesh Farshad , Chang Pengfei , Wang Hongying , Yan Xiaogang , Corneil Brian D. , Crawford J. Douglas
Published: June 2008

The interstitial nucleus of Cajal (INC) is thought to control torsional and vertical head posture. Unilateral microstimulation of the INC evokes torsional head rotation to positions that are maintained until stimulation offset. Unilateral INC inactivation evokes head position-holding deficits with the head tilted in the opposite direction. However, the underlying muscle synergies for these opposite behavioral effects are unknown. Here, we examined neck muscle activity in head-unrestrained monkeys before and during stimulation (50 μA, 200 ms, 300 Hz) and inactivation (injection of 0.3 μl of 0.05% muscimol) of the same INC sites. Three-dimensional eye and head movements were recorded simultaneously with electromyographic (EMG) activity in six bilateral neck muscles: sternocleidomastoid (SCM), splenius capitis (SP), rectus capitis posterior major (RCPmaj.), occipital capitis inferior (OCI), complexus (COM), and biventer cervicis (BC). INC stimulation evoked a phasic, short-latency (∼5–10 ms) facilitation and later (∼100–200 ms) a more tonic facilitation in the activity of ipsi-SCM, ipsi-SP, ipsi-COM, ipsi-BC, contra-RCPmaj., and contra-OCI. Unilateral INC inactivation led to an increase in the activity of contra-SCM, ipsi-SP, ipsi-RCPmaj., and ipsi-OCI and a decrease in the activity of contra-RCPmaj. and contra-OCI. Thus the influence of INC stimulation and inactivation were opposite on some muscles (i.e., contra-OCI and contra-RCPmaj.), but the comparative influences on other neck muscles were more variable. These results show that the relationship between the neck muscle responses during INC stimulation and inactivation is much more complex than the relationship between the overt behaviors.
Kinetic Isolation of a Slowly Recovering Component of Short-Term Depression During Exhaustive Use at Excitatory Hippocampal Synapses
Authors: Garcia-Perez Elizabeth , Lo Donald C. , Wesseling John F.
Published: June 2008

This study examines the kinetics of the longest lasting form of short-term depression at excitatory hippocampal synapses. After initial depletion of the readily releasable pool (RRP), continued 20-Hz stimulation was found to be fast enough to maximally drive presynaptic neurotransmitter exocytosis; maximal is defined here as the rate needed to maintain the RRP in a nearly empty steady state. Induction of depression proceeded in two distinct phases. The first was caused by RRP depletion, whereas the second is shown to reflect the progressive reduction of the overall rate at which new vesicles are supplied to the RRP and is termed “supply-rate depression.” Supply-rate depression is identified further with the emergence, during heavy use, of a rate-limiting vesicle trafficking step that slows the timing of RRP replenishment by switching from a fast (τ ≅ 7 s) to a slow (τ ≅ 1 min) vesicle supply mechanism. Both mechanisms apparently follow first-order kinetics. After the induction of the maximum amount of depression, individual synapses were able to output only <1 quantum of neurotransmitter per synapse per second, matching previous predictions based on cell biological measurements of synaptic vesicle cycling. Surprisingly, the onset of supply-rate depression occurred with a marked delay, not having a detectable impact on synaptic function until after several seconds of continuous use. The delayed onset is not consistent with traditional vesicle trafficking models, but may be important for limiting the impact of supply-rate depression to pathological episodes and might function as a native antiepilepsy device.
Postnatal Development of Onset Transient Responses in Macaque V1 and V2 Neurons
Authors: Zhang Bin , Smith Earl L. , Chino Yuzo M.
Published: June 2008

Vision of newborn infants is limited by immaturities in their visual brain. In adult primates, the transient onset discharges of visual cortical neurons are thought to be intimately involved with capturing the rapid succession of brief images in visual scenes. Here we sought to determine the responsiveness and quality of transient responses in individual neurons of the primary visual cortex (V1) and visual area 2 (V2) of infant monkeys. We show that the transient component of neuronal firing to 640-ms stationary gratings was as robust and as reliable as in adults only 2 wk after birth, whereas the sustained component was more sluggish in infants than in adults. Thus the cortical circuitry supporting onset transient responses is functionally mature near birth, and our findings predict that neonates, known for their “impoverished vision,” are capable of initiating relatively mature fixating eye movements and of performing in detection of simple objects far better than traditionally thought.
Powder X-ray diffraction study of a new polymorph of Al2(WO4)3
Authors: Mukherjee G. D. , Vijayakumar V. , Godwal B. K. , Achary S. N. , Tyagi A. K.
Published: June 2008

A new polymorph of Al2(WO4)3 is observed from in situ high pressure powder X-ray diffraction (ADXRD) measurements at 3.4 GPa. The ADXRD pattern at 3.4 GPa could be explained based on a monoclinic lattice (space group P21) with unit cell parameters: a=9.5884(24), b=12.5204(38), c=7.8463(33) Å, and β=91.98(2)°.
Determination of lattice parameters from synchrotron powder data: A study using high temperature data for tungsten and alumina
Authors: Ball C. J.
Published: June 2008

The lattice parameters of α-alumina have been determined for temperatures in the range 20<T<1050 °C, using the lattice parameter of tungsten as a thermometer and a simple furnace in the diffractometer on the Australian beamline at the Photon Factory, Tsukuba, Japan. It is shown that the accuracy of this technique for measurement of cell parameters at temperatures up to ∼1200 °C is limited at present by uncertainty in the cell parameters of the reference material (i.e., tungsten) at high temperatures. Some problems with the equipment are discussed.
Effect of layer structure boundary on the hectorite basal diffraction
Authors: Kang Il Mo , Kim Myung Hun , Kim Youn Joong , Moon Hi-Soo , Song Yungoo
Published: June 2008

This study examined basal peak irrationalities according to boundary conditions of the hectorite basal diffraction unit (BDU), which were recognized as the total assembly of 2:1 phyllosilicate layer plus interlayer material. The hectorite basal profiles were computer-simulated using the three kinds of BDU settings identified from the middle of octahedral sheets in the nearest neighbor (centrosymmetric model), the middle of interlayers in the nearest neighbor (centrosymmetric model), and a basal oxygen plane to the margin of interlayer in contact with the next phyllosilicate layer (non-centrosymmetric model). In the results of simulations, irrationality and asymmetry of the hectorite basal peaks relied straightforwardly on the BDU scattering modulations for the non-Bragg angles containing information on the synergic scattering events of phyllosilicate layer and interlayer material. Among the concerned BDU boundaries, the non-centrosymmetric model more effectively represented the real hectorite profile than the two previously reported centrosymmetric models.
A neutron diffraction study on ceria-neodia solid solutions
Authors: Chakraborty Keka R. , Krishna P. S. R. , Chavan S. V. , Tyagi A. K.
Published: June 2008

Neutron diffraction studies were carried out to ascertain the structural details of the composition Ce0.5Nd0.5O1.750. The structure was unequivocally found to be that of C-type cubic. The refinement on an F-type cubic lattice was found to be unacceptable because of high R values. Selected bond distances are also being reported. In addition, the neutron diffraction studies on a typical defective F-type composition Ce0.75Nd0.25O1.875 were also carried out.
X-ray powder diffraction characterization of disilver trihydrogen paraperiodate
Authors: Masciocchi Norberto , Gianni Davide
Published: June 2008

X-ray powder diffraction data for the trigonal form of disilver trihydrogen paraperiodate, Ag2H3IO6, are reported. The cell parameters are a=5.941 89(3), c=12.7253(1) Å, V=389.089(6) Å3, and ρ=5.65 g cm−3 for Z=3. A full-profile Rietveld refinement confirms the monophasic nature of the sample and the presence of two-dimensional corrugated layers of the A2BO6 type linked by hydrogen bonds. Short unsupported Ag–Ag contacts (about 3.02 Å) of the argentophilic type are also shown.
Rfactors in Rietveld analysis: How good is good enough?
Authors: Toby Brian H.
Published: June 2008

The definitions for important Rietveld error indices are defined and discussed. It is shown that while smaller error index values indicate a better fit of a model to the data, wrong models with poor quality data may exhibit smaller values error index values than some superb models with very high quality data.
Nanotomography of Cell Surfaces with Evanescent Fields
Authors: Wagner Michael , Weber Petra , Strauss Wolfgang S. L. , Lassalle Henri-Pierre , Schneckenburger Herbert
Published: June 2008

The technique of variable‐angle total internal reflection fluorescence microscopy (TIRFM) and its application to nanotomography of cell surfaces are described. Present applications include (1) 3D imaging of chromosomes in their metaphase to demonstrate axial resolution in the nanometre range, (2) measurements of cell‐substrate topology, which upon cholesterol depletion shows some loosening of cell‐substrate contacts, and (3) measurements of cell topology upon photodynamic therapy (PDT), which demonstrate cell swelling and maintenance of focal contacts. The potential of the method for in vitro diagnostics, but also some requirements and limitations are discussed.
Rituximab Administration in Third Trimester of Pregnancy Suppresses Neonatal B-Cell Development
Authors: Klink D. T. , van Elburg R. M. , Schreurs M. W. J. , van Well G. T. J.
Published: June 2008

We describe the effect on the neonate of administration of rituximab to a woman with idiopathic thrombocytopenic purpura (ITP). Rituximab, an anti-CD20 antibody, was given weekly for 4 weeks to a woman with ITP in her third trimester of pregnancy. One month after the last rituximab administration a healthy girl was born. She had normal growth and development during the first six months. At birth, B-lymphocytes were not detectable. Rituximab levels in mother and neonate were 24000 and 6700 ng/mL, respectively. Only 7 cases of rituximab administration during pregnancy were described. No adverse events are described for fetus and neonate. We demonstrate that rituximab passes the placenta and inhibits neonatal B-lymphocyte development. However, after 6 months B-lymphocyte levels normalized and vaccination titres after 10 months were adequate. No infection-related complications occurred. Rituximab administration during pregnancy appears to be safe for the child but further studies are warranted.