bluuebunny/crossref_metadata_2025 huggingface dataset:
INTERACTION OF INFRARED ELECTROMAGNETIC WAVES IN RESONANT LAYERED STRUCTURES WITH n-GaAs SEMICONDUCTOR FILM
Authors: GRIMALSKY V. , KOSHEVAYA S. , ESCOBEDO-A J.
Published: April 2009

Interaction of infrared electromagnetic (EM) waves in a layered structure with n- GaAs film is investigated theoretically. An oblique incidence of EM wave is considered, when the total internal reflection and resonant transmission occur. It is demonstrated that this structure modulates effectively the infrared EM wave. The modulation mechanism is due to the transfer of electrons from the upper valley to the higher ones in a strong bias electric field. An interaction of strong incident infrared EM pulses with this structure is also considered in the case of the absence of a bias electric field. Both the nonlinear switching of short pulses and the modulation instability of long strong pulses take place.
FORMATION AND COLLISION OF (1 + 1)-DIMENSIONAL DIPOLE SOLITONS IN THE STRONGLY NON-LOCAL NON-LINEAR MEDIA
Authors: HE Y. J. , LUO L. , ZHU W. L. , WANG H. Z.
Published: April 2009

We theoretically show that stable (1 + 1)-dimensional dipole solitons can be supported by strong non-local non-linear media. Such solitons can evolve from stable swinging motion by virtue of the strong non-local potential. Interesting properties of various collisions between dipole solitons are revealed. The collision between dipole solitons periodically occurs and leads to revivable fission of solitons. The collision of multipole solitons is also investigated.
STUDIES ON GROWTH AND CHARACTERIZATION OF BIS THIOUREA LEAD CHLORIDE: A NOVEL NONLINEAR OPTICAL CRYSTAL
Authors: KIRUBAVATHI K. , SELVARAJU K. , KUMARARAMAN S.
Published: April 2009

Single crystals of the metal-organic nonlinear optical material bis thiourea lead chloride were grown from solution growth technique for the first time. The grown crystals were characterized by single crystal X-ray diffraction analysis to confirm the crystal structure. The presence of various functional groups and the coordination of metal ions to thiourea were confirmed by Fourier transform infrared analysis. UV-Vis. spectrum was recorded to study the optical transparency of the grown crystals. The second order nonlinear optical property of the grown crystal was examined by Kurtz powder technique and mechanical behavior was studied by Vickers micro hardness test.
POLARIZATION COUPLING OF LIGHT WAVES IN PERIODICALLY POLED LITHIUM NIOBATE AND ITS APPLICATIONS
Authors: CHEN XIANFENG , LIU KUN , SHI JIANHONG
Published: April 2009

In this paper, we review current research on the applications of periodically poled lithium niobate (PPLN) by use of polarization coupling in our and other research groups. Tunable wavelength Solc-type filter, polarization controller and electro-optical switch based on PPLN are presented, which show potential applications in optical communications and optical information processing.
Earnings Management by Japanese Bank Managers Using Discretionary Loan Loss Provisions
Authors: Kwak Wikil , Lee Ho-Young , Eldridge Susan W.
Published: April 2009

This paper investigates Japanese bank managers' use of the discretionary component of loan loss provisions to manage earnings during the recession of the late 1990s. Although studies of US banks document that bank managers use loan loss provisions to smooth earnings, manage regulatory capital, and signal undervaluation, factors that may affect discretionary loan loss provisions in Japanese banks have not been empirically examined. We find that discretionary loan loss provisions for our sample of Japanese banks are positively related to the demand for external financing, realized securities gains, and prior year taxes and are negatively related to capital and pre-managed earnings.
Intraday Patterns, Announcement Effects, and Volatility Persistence in the Japanese Government Bond Futures Market
Authors: Shi Weihua , Eisenberg Larry , Lee Cheng-few
Published: April 2009

Following Bollerslev et al. (2000), this study characterizes the high-frequency volatility of the Japanese Government Bond (JGB) futures on the Tokyo Stock Exchange (TSE) in terms of intraday calendar effects, announcement effects and volatility persistence effects. The results indicate that, unlike the case for the US Treasury bond futures, only four out of 21 scheduled macroeconomic announcements are found to have a significant impact on volatilities, and their instantaneous and daily influences are rather small. At both instantaneous and daily frequencies, volatility persistence effects have the largest influence on volatility, while macroeconomic announcements have only a negligible impact.
Corporate Asset Sales in Taiwan
Authors: Sun Meijui , Chen K. C.
Published: April 2009

In this paper, we study a sample of 179 corporate asset sales in Taiwan between 1993 and 2003. We find that corporate asset sales in Taiwan enhance parent firm value with cumulative abnormal returns of 1.7715% for the pre-announcement five-day period and 0.6086% for the two-day announcement window. This finding is consistent with the evidence discovered in both UK and US. We also examine whether asset-sale gains are positively related to managerial performance, private lender monitoring, the use of proceeds, the type of asset sales, the profitability of asset sales, and the relative size of asset sales. Our cross-sectional regression results indicate that all variables, except private debt monitoring and relative size, appear with their predicted signs, but not all of them are statistically significant. During longer event windows, we find that only managerial performance measured by Tobin's q and the use of asset-sale proceeds can explain the gains from corporate asset sales in Taiwan.
Analysis of Unsolicited Credit Ratings in Japan: New Evidence from Moody's
Authors: Fairchild Lisa M. , Flaherty Susan M. V. , Shin Yoon S.
Published: April 2009

Previous studies show that the unsolicited ratings of S&P and Fitch are lower than the solicited ratings assigned by these two agencies. The unsolicited ratings of S&P and Fitch are based on publicly available information for a firm. However, no previous study has examined the unsolicited ratings of Moody's because Moody's does not disclose whether its ratings are solicited or unsolicited. Using Moody's solicited and unsolicited ratings collected from a survey of Japanese firms, we find that unsolicited credit ratings are still lower than solicited ratings even though firms with unsolicited ratings provide Moody's with some degree of inside information. We also compare the unsolicited ratings of S&P with those of Moody's and find that Moody's ratings are no different than those assigned by S&P although S&P's unsolicited ratings are based on public information. Therefore, we conclude that, regardless of the rating agency, unsolicited ratings are lower than solicited ratings because firms with unsolicited ratings provide incomplete private information to rating agencies.
Extending the Maturity of a Defaulting Debt — The Longstaff Model Revisited
Authors: Lee Shyan Yuan , Chung Yi Fang
Published: April 2009

This paper uses differing objective functions under the Longstaff model (1990) to discuss the strategic choices faced by the creditor when deciding whether to grant maturity extension on a defaulted loan. The results reveal that: (1) it ensures that the return per unit of risk is higher after maturity extension than before; (2) it recognizes that the risk profile of the firm substantially affects the strategic behavior of the creditor; and (3) it demonstrates that the higher the profit sharing percentage the creditor get, the more willing it will be to extend maturity.
Real Exchange Rate Behavior under Peg: Evidence from the Chinese RMB and Malaysian MYR
Authors: E Yongjian , Gu Anthony Yanxiang , Yang Chau-Chen
Published: April 2009

The exchange-rate behavior of the Chinese yuan (RMB) and the Malaysian ringgit (MYR) indicates that the real exchange rate volatility of both the pegged currency/the anchor currency (the US dollar), and the pegged currency/the non-anchor currencies (Japanese yen and British pound) are lower under the pegged regime. The dynamic behavior of the pegged currencies' real exchange rates is consistent with the anchor currency as the speed of convergence of the Big Mac real exchange rates of the RMB, MYR, and the dollar against the floating currencies are almost identical during the pegged period. This may be due to similar inflation rate movements in the related economies. These results do not support the opinion that China has manipulated the value of its currency.
CO-OCCURRENCE PROBABILITIES AND WAVELET-BASED SPOOF FINGERPRINT DETECTION
Authors: NIKAM SHANKAR BHAUSAHEB , AGARWAL SUNEETA
Published: April 2009

Perspiration phenomenon is very significant to detect the liveness of a finger. However, it requires two consecutive fingerprints to notice perspiration, and therefore may not be suitable for real time authentications. Some other methods in the literature need extra hardware to detect liveness. To alleviate these problems, in this paper, to detect liveness a new texture-based method using only the first fingerprint is proposed. It is based on the observation that real and spoof fingerprints exhibit different texture characteristics. Textural measures based on gray level co-occurrence matrix (GLCM) are used to characterize fingerprint texture. This is based on structural, orientation, roughness, smoothness and regularity differences of diverse regions in a fingerprint image. Wavelet energy signature is also used to obtain texture details. Dimensionalities of feature sets are reduced by Sequential Forward Floating Selection (SFFS) method. GLCM texture features and wavelet energy signature are independently tested on three classifiers: neural network, support vector machine and K-nearest neighbor. Finally, two best classifiers are fused using the "Sum Rule''. Fingerprint database consisting of 185 real, 90 Fun-Doh and 150 Gummy fingerprints is created. Multiple combinations of materials are used to create casts and moulds of spoof fingerprints. Experimental results indicate that, the new liveness detection method is very promising, as it needs only one fingerprint and no extra hardware to detect vitality.
USER AUTHENTICATION USING FUSION OF FACE AND PALMPRINT
Authors: KUMAR AJAY , ZHANG DAVID
Published: April 2009

This paper presents a new method of personal authentication using face and palmprint images. The facial and palmprint images can be simultaneously acquired by using a pair of digital camera and integrated to achieve higher confidence in personal authentication. The proposed method of fusion uses a feed-forward neural network to integrate individual matching scores and generate a combined decision score. The significance of the proposed method is more than improving performance for bimodal system. Our method uses the claimed identity of users as a feature for fusion. Thus the required weights and bias on individual biometric matching scores are automatically computed to achieve the best possible performance. The experimental results also demonstrate that Sum, Max, and Product rule can be used to achieve significant performance improvement when consolidated matching scores are employed instead of direct matching scores. The fusion strategy used in this paper outperforms even its existing facial and palmprint modules. The performance indices for personal authentication system using two-class separation criterion functions have been analyzed and evaluated. The method proposed in this paper can be extended for any multimodal authentication system to achieve higher performance.
TRANSLATION AND SCALE INVARIANTS OF HAHN MOMENTS
Authors: GOH HOCK-ANN , CHONG CHEE-WAY , BESAR ROSLI , ABAS FAZLY SALLEH , SIM KOK-SWEE
Published: April 2009

Hahn moments are a superset of Tchebichef and Krawtchouk moments. The formulation for Hahn moments is however comparably more complex than other moments. So far only research work on translation and scale invariants for Tchebichef moments has been presented but not on Hahn moments. In this paper, a moment normalization method to achieve translation and scale invariants of Hahn moments is proposed. This method applies the concept of mapping functions used in image normalization. The mapping functions, once determined, are plugged into the moment generating functions to generate moment invariants. The proposed method is simpler and flexible. Experimental results show that faster execution and more precise moment invariants can be achieved using the invariant generating functions.
A NEURO-WAVELET MODEL USING FUZZY VECTOR QUANTIZATION FOR EFFICIENT IMAGE COMPRESSION
Authors: SINGH VIPULA , RAJPAL NAVIN , MURTHY K. SRIKANTA
Published: April 2009

Images have large data quantity. For storage and transmission of images, high efficiency image compression methods are under wide attention. In this paper, we propose a neuro- wavelet based model for image compression, which combines the advantages of wavelet transform and neural network and uses fuzzy vector quantization on hidden layer coefficients. Images are decomposed using wavelet filters into a set of sub bands with different resolution corresponding to different frequency bands. Different quantization and coding schemes are used for different sub bands based on their statistical properties. The coefficients in the lowest frequency band are compressed by differential pulse code modulation (DPCM) and the coefficients in higher frequency bands are compressed using neural network. The coefficients of the hidden layer of the neural network are further fuzzy vector quantized, which increases the compression ratio. The visual quality of the image has been increased by introducing fuzziness to vector quantization algorithm. Satisfactory reconstructed images with large compression ratios have been achieved using this scheme.
A GPU-BASED ALGORITHM FOR APPROXIMATELY FINDING THE LARGEST COMMON POINT SET IN THE PLANE UNDER SIMILARITY TRANSFORMATION
Authors: AIGER DROR , KEDEM KLARA
Published: April 2009

We consider the following geometric pattern matching problem: Given two sets of points in the plane, P and Q, and some (arbitrary) δ > 0, find the largest subset B ⊂ P and a similarity transformation T (translation, rotation and scale) such that h(T(B),Q) < δ, where h(.,.) is the directional Hausdorff distance. This problem stems from real world applications, where δ is determined by the practical uncertainty in the position of the points (pixels). We reduce the problem to finding the depth (maximally covered point) of an arrangement of polytopes in transformation space. The depth is the cardinality of B, and the polytopes that cover the deepest point correspond to the points in B. We present an algorithm that approximates the maximum depth with high probability, thus getting a large enough common point set in P and Q.

The algorithm is implemented in the GPU framework, thus it is very fast in practice. We present experimental results and compare their runtime with those of an algorithm running on the CPU.
Toward a General Model of Knowledge Creation in Virtual Teams
Authors: Wipawayangkool Kamphol
Published: May 2009

Virtual teams have made such an impact on organisations' knowledge management. As a result, the phenomenon of knowledge creation in virtual teams obviously deserves researchers' attention. Nonetheless, literature on virtual teams has not been much theory-grounded. Thus, to explore the influence of virtual teams on knowledge creation and fill the scarcity of theoretical foundation in the literature, this paper firstly proposes a theoretical model of knowledge creation process in virtual teams called Adaptive Social-Externalisation by primarily drawing from Nonaka's Organisational Knowledge Creation theory as well as Adaptive Structuration theory and Agency theory. Secondly, the characteristics of the process are also derived as Adaptiveness, Simultaneity, and Goal Congruency and Information Symmetry and can be used to determine the effectiveness of both knowledge creation and overall performance of a virtual team. Both theoretical and practical implications are then discussed.
Simultaneous overexpression of Oct4 and Nanog abrogates terminal myogenesis
Authors: Lang Kuan Chih , Lin I. Hsuan , Teng Han Fang , Huang Yi Cheng , Li Chung Leung , Tang Kam Tsun , Chen Shen Liang
Published: April 2009

Oct4 and Nanog are two embryonic stem (ES) cell-specific transcription factors that play critical roles in the maintenance of ES cell pluripotency. In this study, we investigated the effects of Oct4 and Nanog expression on the differentiation state of myogenic cells, which is sustained by a strong positive feedback loop. Oct4 and Nanog, either independently or simultaneously, were overexpressed in C2C12 myoblasts, and the expression of myogenic lineage-specific genes and terminal differentiation was observed by RT-PCR. Overexpression of Oct4 in C2C12 cultures repressed, while exogenous Nanog did not significantly alter C2C12 terminal differentiation. The expression of Pax7 was reduced in all Oct4-overexpressing myoblasts, and we identified a major Oct4-binding site in the Pax7 promoter. Simultaneous expression of Oct4 and Nanog in myoblasts inhibited the formation of myotubes, concomitant with a reduction in the endogenous levels of hallmark myogenic markers. Furthermore, overexpression of Oct4 and Nanog induced the expression of their endogenous counterparts along with the expression of Sox2. Using mammalian two-hybrid assays, we confirmed that Oct4 functions as a transcriptional repressor whereas Nanog functions as a transcriptional activator during muscle terminal differentiation. Importantly, in nonobese diabetic (NOD) severe combined immunodeficiency (SCID) mice, the pluripotency of C2C12 cells was conferred by overexpression of Oct4 and Nanog. These results suggest that Oct4 in cooperation with Nanog strongly suppresses the myogenic differentiation program and promotes pluripotency in myoblasts.
Intestinal ischemia-reperfusion injury: reversible and irreversible damage imaged in vivo
Authors: Guan Yanfang , Worrell Roger T. , Pritts Timothy A. , Montrose Marshall H.
Published: April 2009

The early events in an intestinal ischemic episode have been difficult to evaluate. Using in vivo microscopy we have analyzed in real-time the effects of short (15 min) and long (40–50 min) ischemia with subsequent reperfusion (IR), evaluating structure, integrity, and functioning of the mouse jejunal mucosa while monitoring blood flow by confocal microscopy. IR was imposed by inflation/deflation of a vascular occluder, and blood flow was monitored and confirmed with scanning confocal imaging. After short ischemia, villus tip cells revealed a rapid increase (23%) in the intracellular NAD(P)H concentration (confocal autofluorescence microscopy), and the pH-sensitive probe BCECF showed a biphasic response of the intracellular pH (pHi), quickly alkalinizing from the resting value of 6.8 ± 0.1 to 7.1 ± 0.1 but then strongly acidifying to 6.3 ± 0.1. Upon reperfusion, values returned toward control. In contrast, results were heterogeneous after long IR. During long ischemia, one-third of the epithelial cells remained viable with reversible changes upon reperfusion, but remaining cells lost membrane integrity (Lucifer Yellow uptake, LY) and had membrane blebs during ischemia. These effects became more pronounced as the reperfusion interval progressed when cells exhibited more severely affected NAD(P)H and pHi values, larger blebs, and more LY uptake and eventually were shed from the villus. Results from stereo microscopy suggest that these irreversible effects of IR may have occurred as a result of incomplete restorations of local blood flow, especially at the antimesenteric side of the intestine. We conclude that the adverse effects of short ischemia on the jejunum epithelium are fully reversible during the reperfusion interval. However, after long ischemia, reperfusion cannot restore normal structure and functioning of a majority of cells, which deteriorate further. Our results provide a basis for defining the cellular events that cause tissue to transit from reversible to irreversible damage during IR.
Enhancement of Ih, but not inhibition of IM, is a key mechanism underlying the PACAP-induced increase in excitability of guinea pig intrinsic cardiac neurons
Authors: Tompkins John D. , Lawrence Yancey T. , Parsons Rodney L.
Published: April 2009

Pituitary adenylate cyclase-activating polypeptide (PACAP) increases excitability of guinea pig cardiac neurons, an effect mediated by PACAP-selective PAC1 receptors. In dissociated guinea pig cardiac neurons, PACAP causes a positive shift of the voltage dependence of activation of the hyperpolarization-activated nonselective cation current ( Ih). This observation suggested that an enhancement of Ih contributed to the increase in excitability in neurons within whole-mount cardiac ganglia preparations. To evaluate the role of Ih in the PACAP-induced increase in excitability, we compared the increase in action potentials generated by 10 nM PACAP in control neurons and in neurons treated with ZD7288 (10 or 100 μM) or CsCl (2 or 2.5 mM), drugs known to inhibit Ih. In control cells exposed to PACAP, 1-s depolarizing current pulses elicited multiple action potential firing in 79% of the neurons. In ZD7288- or CsCl-containing solutions, the 10 nM PACAP-induced increase in excitability was markedly suppressed, with 7% and 21% of the neurons generating multiple action potentials, respectively. Prior results indicated that PACAP initiates depolarization by activating an inward current, which is separate from its enhancement of Ih. Here, we show that a PACAP-induced depolarization was comparable in control neurons and neurons bathed in a CsCl-containing solution, an observation indicating that CsCl did not interfere with activation of the PAC1 receptor by PACAP. Additional experiments indicated that pretreatment with the putative M current ( IM) inhibitor 1 mM BaCl2, but not 10 μM XE991, initiated multiple firing in a majority of neurons, with resting potentials maintained at approximately −60 mV. Furthermore, in Ba2+-treated cells, 10 nM PACAP increased the number of action potentials generated. Our results indicate that PACAP enhancement of Ih, rather than inhibition of IM and other 1 mM Ba2+-sensitive K+ currents, is a key ionic mechanism contributing to the peptide-induced increase in excitability for neurons within whole-mount cardiac ganglia preparations.
Changes in cerebral blood flow, cerebral metabolites, and breathing movements in the sheep fetus following asphyxia produced by occlusion of the umbilical cord
Authors: Yan Edwin B. , Baburamani Ana A. , Walker Adrian M. , Walker David W.
Published: April 2009

Severe global fetal asphyxia, if caused by a brief occlusion of the umbilical cord, results in prolonged cerebral hypoperfusion in fetal sheep. In this study, we sought evidence to support the hypothesis that cerebral hypoperfusion is a consequence of suppressed cerebral metabolism. In the 24 h following complete occlusion of the umbilical cord for 10 min, sagittal sinus blood flow velocity was significantly decreased for up to 12 h. Capillary blood flow, measured using microspheres, decreased at 1 and 5 h after cord occlusion in many brain regions, including cortical gray and white matter. Microdialysis probes implanted in the cerebral cortex revealed an increase in extracellular glucose concentrations in gray matter for 7–8 h postasphyxia, while lactate increased only briefly, suggesting decreased cerebral glucose utilization over this time. Although these data, as well as the concurrent suppression of breathing movements and electrocortical activity, support the concept of hypometabolic hypoperfusion, the significant increase of pyruvate and glycerol concentrations in dialysate fluid obtained from the cerebral cortex at 3–8 h after cord occlusion suggests an eventual loss of membrane integrity. The prolonged increase of breathing movements for many hours suggests loss of the pontine/thalamic control that produces the distinct pattern of fetal breathing movements.
Microbial experimental evolution
Authors: Bennett Albert F. , Hughes Bradley S.
Published: April 2009

Microbes have been widely used in experimental evolutionary studies because they possess a variety of valuable traits that facilitate large-scale experimentation. Many replicated populations can be cultured in the laboratory simultaneously along with appropriate controls. Short generation times and large population sizes make microbes ideal experimental subjects, ensuring that many spontaneous mutations occur every generation and that adaptive variants can spread rapidly through a population. Another highly useful experimental feature is the ability to preserve and store ancestral and evolutionarily derived clones. These can be revived in parallel to allow the direct measurement of the competitive fitness of a descendant compared with its ancestor. The extent of adaptation can thereby be measured quantitatively and compared statistically by direct competition among derived groups and with the ancestor. Thus, fitness and adaptation need not be matters of qualitative speculation, but are quantitatively measurable variables in these systems. Replication allows the quantification of heterogeneity in responses to imposed selection and thereby statistical distinction between changes that are systematic responses to the selective regimen and those that are specific to individual populations.
Chronic immunoneutralization of brain angiotensin-(1-12) lowers blood pressure in transgenic (mRen2)27 hypertensive rats
Authors: Isa Katsunori , García-Espinosa Maria Antonia , Arnold Amy C. , Pirro Nancy T. , Tommasi Ellen N. , Ganten Detlev , Chappell Mark C. , Ferrario Carlos M. , Diz Debra I.
Published: April 2009

Angiotensin-(1-12) [ANG-(1-12)] is a newly identified peptide detected in a variety of rat tissues, including the brain. To determine whether brain ANG-(1-12) participates in blood pressure regulation, we treated male adult (mRen2)27 hypertensive rats (24–28 wk of age) with Anti-ANG-(1-12) IgG or Preimmune IgG via an intracerebroventricular cannula for 14 days. Immunoneutralization of brain ANG-(1-12) lowered systolic blood pressure (−43 ± 8 mmHg on day 3 and −26 ± 7 mmHg on day 10 from baseline, P < 0.05). Water intake was lower on intracereroventricular day 6 in the Anti-ANG-(1-12) IgG group, accompanied by higher plasma osmolality on day 13, but there were no differences in urine volume, food intake, or body weight during the 2-wk treatment. In Preimmune IgG-treated animals, there were no significant changes in these variables over the 2-wk period. The antihypertensive effects produced by endogenous neutralization of brain ANG-(1-12) suggest that ANG-(1-12) is functionally active in brain pathways regulating blood pressure.
SOD1 deficiency causes salt sensitivity and aggravates hypertension in hydronephrosis
Authors: Carlström Mattias , Brown Russell D. , Sällström Johan , Larsson Erik , Zilmer Mihkel , Zabihi Sheller , Eriksson Ulf J. , Persson A. Erik G.
Published: April 2009

Hydronephrosis causes renal dysfunction and salt-sensitive hypertension, which is associated with nitric oxide deficiency and abnormal tubuloglomerular feedback (TGF) response. We investigated the role of oxidative stress for salt sensitivity and for hypertension in hydronephrosis. Hydronephrosis was induced in superoxide dismutase 1-transgenic (SOD1-tg), SOD1-deficient (SOD1-ko), and wild-type mice and in rats. In mice, telemetric measurements were performed during normal (0.7% NaCl) and high-sodium (4% NaCl) diets and with chronic tempol supplementation. The 8-iso-prostaglandin-F2α(F2-IsoPs) and protein excretion profiles and renal histology were investigated. The acute effects of tempol on blood pressure and TGF were studied in rats. In hydronephrosis, wild-type mice developed salt-sensitive hypertension (114 ± 1 to 120 ± 2 mmHg), which was augmented in SOD1-ko (125 ± 3 to 135 ± 4 mmHg) but abolished in SOD1-tg (109 ± 3 to 108 ± 3 mmHg). SOD1-ko controls displayed salt-sensitive blood pressure (108 ± 1 to 115 ± 2 mmHg), which was not found in wild types or SOD1-tg. Chronic tempol treatment reduced blood pressure in SOD1-ko controls (−7 mmHg) and in hydronephrotic wild-type (−8 mmHg) and SOD1-ko mice (−16 mmHg), but had no effect on blood pressure in wild-type or SOD1-tg controls. SOD1-ko controls and hydronephrotic wild-type and SOD1-ko mice exhibited increased fluid excretion associated with increased F2-IsoPs and protein excretion. The renal histopathological changes found in hydronephrotic wild-type were augmented in SOD1-ko and diminished in SOD-tg mice. Tempol attenuated blood pressure and normalized TGF response in hydronephrosis [ΔPSF: 15.2 ± 1.2 to 9.1 ± 0.6 mmHg, turning point: 14.3 ± 0.8 to 19.7 ± 1.4 nl/min]. Oxidative stress due to SOD1 deficiency causes salt sensitivity and plays a pivotal role for the development of hypertension in hydronephrosis. Increased superoxide formation may enhance TGF response and thereby contribute to hypertension.
Diet-derived nutrients mediate the inhibition of hypothalamic NPY neurons in the arcuate nucleus of mice during refeeding
Authors: Becskei Csilla , Lutz Thomas A. , Riediger Thomas
Published: April 2009

Fasting activates orexigenic neuropeptide Y neurons in the hypothalamic arcuate nucleus (ARC) of mice, which is reversed by 2 h refeeding with standard chow. Here, we investigated the contribution of diet-derived macronutrients and anorectic hormones to the reversal of the fasting-induced ARC activation during 2 h refeeding. Refeeding of 12-h-fasted mice with a cellulose-based, noncaloric mash induced only a small reduction in c-Fos expression. Refeeding with diets, containing carbohydrates, protein, or fat alone reversed it similar to chow; however, this effect depended on the amount of intake. The fasting-induced ARC activation was unchanged by subcutaneously injected amylin, CCK (both 20 μg/kg), insulin (0.2 U/kg and 0.05 U/kg) or leptin (2.6 mg/kg). Insulin and leptin had no effect on c-Fos expression in neuropeptide Y or proopiomelanocortin-containing ARC neurons. Interestingly, CCK but not amylin reduced the ghrelin-induced c-Fos expression in the ARC in ad libitum-fed mice, suggesting that CCK may inhibit orexigenic ARC neurons when acting together with other feeding-related signals. We conclude that all three macronutrients and also non-nutritive, ingestion-dependent signals contribute to an inhibition of orexigenic ARC neurons after refeeding. Similar to the previously demonstrated inhibitory in vivo action of peptide YY, CCK may be a postprandial mediator of ARC inhibition.
Mice lacking the ADP ribosyl cyclase CD38 exhibit attenuated renal vasoconstriction to angiotensin II, endothelin-1, and norepinephrine
Authors: Thai Tiffany L. , Arendshorst William J.
Published: April 2009

ADP ribosyl (ADPR) cyclases comprise a family of ectoenzymes recently shown to influence cytosolic Ca2+concentration in a variety of cell types. At least two ADPR cyclase family members have been identified in mammals: CD38 and CD157. We recently found reduced renal vascular reactivity to angiotensin II (ANG II), endothelin-1 (ET-1), and norepinephrine (NE) in the presence of the broad ADPR cyclase inhibitor nicotinamide. We hypothesized that CD38 mediates effects attributed to ADPR cyclase. We found expression of ADPR cyclases CD38 and CD157 mRNA in spleen, thymus, skin, and preglomerular arterioles of wild-type (WT) animals. Mice lacking CD38 showed decreased CD157 expression in most tissues tested. No difference in systolic or mean arterial pressure was observed between strains in either conscious or anesthetized states, whereas heart rate was reduced 10–20% in CD38−/− animals ( P < 0.05). During anesthesia, CD38−/− mice had reduced basal renal blood flow (RBF) and urine excretion ( P < 0.05). RBF responses to intravenous injection of ANG II, ET-1, and NE were attenuated ∼50% in CD38−/− vs. WT mice ( P < 0.01 for all). The systemic pressor response to ANG II was decreased in the absence of CD38 ( P < 0.01), whereas that to NE was normal ( P > 0.05); ET-1 was administered at a nonpressor dose. Nicotinamide effectively inhibited ANG II-induced renal vasoconstriction in WT mice ( P < 0.001), but had no effect on renal responses to ANG II in CD38−/− mice ( P > 0.5). Overall, our observations indicate the presence of two ADPR cyclase family members in renal preglomerular resistance arterioles and the importance of CD38 participation in acute vascular responses to all three vasoconstrictors in the renal microcirculation.
PPARγ agonists inhibit vasopressin-mediated anion transport in the MDCK-C7 cell line
Authors: Nofziger Charity , Brown Kathleen K. , Smith Chari D. , Harrington Wallace , Murray David , Bisi John , Ashton Thalia T. , Maurio Frank P. , Kalsi Kameljit , West T. Aaron , Baines Deborah , Blazer-Yost Bonnie L.
Published: April 2009

PPARγ agonists are synthetic ligands for the peroxisome proliferator-activated receptor-γ (PPARγ). These agents have insulin-sensitizing properties but can cause fluid retention, thereby limiting their usefulness in patients at risk for cardiovascular disease. The side effect etiology is unknown, but the nature of presentation suggests modulation of renal salt and water homeostasis. In a well-characterized cell culture model of the principal cell type [Madin-Darby canine kidney (MDCK)-C7], PPARγ agonists inhibit vasopressin-stimulated Cl−secretion with agonist dose-response relationships that mirror receptor transactivation profiles. Analyses of the components of the vasopressin-stimulated intracellular signaling pathway indicated no PPARγ agonist-induced changes in basolateral membrane conductances, intracellular cAMP, protein kinase A, or total cellular adenine nucleotides. The PPARγ agonist-induced decrease in anion secretion is the result of decreased mRNA of the final effector in the pathway, the apically located cystic fibrosis transmembrane regulator (CFTR). These data showing that CFTR is a target for PPARγ agonists may provide new insights into the physiology of PPARγ agonist-induced fluid retention.
A mathematical model of O2transport in the rat outer medulla. I. Model formulation and baseline results
Authors: Chen Jing , Layton Anita T. , Edwards Aurélie
Published: April 2009

The mammalian kidney is particularly vulnerable to hypoperfusion, because the O2supply to the renal medulla barely exceeds its O2requirements. In this study, we examined the impact of the complex structural organization of the rat outer medulla (OM) on O2distribution. We extended the region-based mathematical model of the rat OM developed by Layton and Layton ( Am J Physiol Renal Physiol 289: F1346–F1366, 2005) to incorporate the transport of RBCs, Hb, and O2. We considered basal cellular O2consumption and O2consumption for active transport of NaCl across medullary thick ascending limb epithelia. Our model predicts that the structural organization of the OM results in significant Po2gradients in the axial and radial directions. The segregation of descending vasa recta, the main supply of O2, at the center and immediate periphery of the vascular bundles gives rise to large radial differences in Po2between regions, limits O2reabsorption from long descending vasa recta, and helps preserve O2delivery to the inner medulla. Under baseline conditions, significantly more O2is transferred radially between regions by capillary flow, i.e., advection, than by diffusion. In agreement with experimental observations, our results suggest that 79% of the O2supplied to the medulla is consumed in the OM and that medullary thick ascending limbs operate on the brink of hypoxia.
Kidney ischemia-reperfusion injury induces caspase-dependent pulmonary apoptosis
Authors: Hassoun Heitham T. , Lie Mihaela L. , Grigoryev Dmitry N. , Liu Manchang , Tuder Rubin M. , Rabb Hamid
Published: April 2009

Distant organ effects of acute kidney injury (AKI) are a leading cause of morbidity and mortality. While little is known about the underlying mechanisms, limited data suggest a role for inflammation and apoptosis. Utilizing a lung candidate gene discovery approach in a mouse model of ischemic AKI-induced lung dysfunction, we identified prominent lung activation of 66 apoptosis-related genes at 6 and/or 36 h following ischemia, of which 6 genes represent the tumor necrosis factor receptor (TNFR) superfamily, and another 23 genes are associated with the TNFR pathway. Given that pulmonary apoptosis is an important pathogenic mechanism of acute lung injury (ALI), we hypothesized that AKI leads to pulmonary proapoptotic pathways that facilitate lung injury and inflammation. Functional correlation with 1) terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling and 2) active caspase-3 (aC3) activity, immunoblotting, and immunohistochemistry (IHC) identified kidney IRI-induced pulmonary apoptosis at 24 h, and colocalization studies with CD34 identified predominantly endothelial apoptosis. Mice were treated with the caspase inhibitor Z-VAD-FMK (0.25 mg ip) or vehicle 1 h before and 8 h after sham or kidney IRI, and bronchoalveolar lavage fluid protein was measured at 36 h as a surrogate for lung leak. Caspase inhibition reduced lung microvascular changes after kidney IRI. The pulmonary apoptosis seen in wild-type control mice during AKI was absent in TNFR−/−mice. Using an initial genomic approach to discovery followed by a mechanistic approach to disease targeting, we demonstrate that pulmonary endothelial apoptosis is a direct mediator of the distant organ dysfunction during experimental AKI.
Expanded prediction equations of human sweat loss and water needs
Authors: Gonzalez R. R. , Cheuvront S. N. , Montain S. J. , Goodman D. A. , Blanchard L. A. , Berglund L. G. , Sawka M. N.
Published: April 2009

The Institute of Medicine expressed a need for improved sweating rate (ṁsw) prediction models that calculate hourly and daily water needs based on metabolic rate, clothing, and environment. More than 25 years ago, the original Shapiro prediction equation (OSE) was formulated as ṁsw (g·m−2·h−1) = 27.9· Ereq·( Emax)−0.455, where Ereq is required evaporative heat loss and Emax is maximum evaporative power of the environment; OSE was developed for a limited set of environments, exposures times, and clothing systems. Recent evidence shows that OSE often overpredicts fluid needs. Our study developed a corrected OSE and a new ṁsw prediction equation by using independent data sets from a wide range of environmental conditions, metabolic rates (rest to ≤450 W/m2), and variable exercise durations. Whole body sweat losses were carefully measured in 101 volunteers (80 males and 21 females; >500 observations) by using a variety of metabolic rates over a range of environmental conditions (ambient temperature, 15–46°C; water vapor pressure, 0.27–4.45 kPa; wind speed, 0.4–2.5 m/s), clothing, and equipment combinations and durations (2–8 h). Data are expressed as grams per square meter per hour and were analyzed using fuzzy piecewise regression. OSE overpredicted sweating rates ( P < 0.003) compared with observed ṁsw. Both the correction equation (OSEC), ṁsw = 147·exp (0.0012·OSE), and a new piecewise (PW) equation, ṁsw = 147 + 1.527· Ereq − 0.87· Emax were derived, compared with OSE, and then cross-validated against independent data (21 males and 9 females; >200 observations). OSEC and PW were more accurate predictors of sweating rate (58 and 65% more accurate, P < 0.01) and produced minimal error (standard error estimate < 100 g·m−2·h−1) for conditions both within and outside the original OSE domain of validity. The new equations provide for more accurate sweat predictions over a broader range of conditions with applications to public health, military, occupational, and sports medicine settings.
Spinal NMDA receptor activation is necessary for de novo, but not the maintenance of, A2a receptor-mediated phrenic motor facilitation
Authors: Golder F. J.
Published: April 2009

Adenosine 2a (A2a) receptor agonists elicit persistent increases in phrenic nerve activity by transactivating the neurotrophin receptor, TrkB, near phrenic motoneurons. Our working model proposes that A2a receptor-mediated TrkB receptor activation strengthens glutamatergic synapses onto phrenic motoneurons. Activation of glutamate N-methyl d-aspartate (NMDA) receptors has been implicated in other models of phrenic motor plasticity. Thus we hypothesized that NMDA receptor activation also would contribute to A2a receptor-mediated phrenic motor facilitation. Adult male Sprague-Dawley rats were anesthetized with urethane, mechanically ventilated, neuromuscularly paralyzed, and bilaterally vagotomized. The A2a receptor agonist CGS-21680 and the NMDA receptor-channel blocker MK-801 were administered intrathecally over the C4 spinal segment. Phrenic nerve activity was recorded before, during, and after drug administration. MK-801 (concentration range 0.1, 1.0, 10.0, and 100 μM) was administered 30 min before CGS-21680 (50 μM). MK-801 dose-dependently blocked A2a receptor-mediated phrenic motor facilitation. When administered at 60 min post-CGS-21680, MK-801 prevented further increases in phrenic nerve activity compared with the CGS-21680 alone (CGS-21680 alone at 120 min: 114 ± 19%; CGS-21680 and MK-801 at 60 min post-CGS-21680: 61 ± 11%, above baseline, P < 0.05) but did not return phrenic motor output to baseline values. Our data suggest that NMDA receptor activation is necessary for de novo A2a receptor-mediated phrenic motor facilitation and that the maintenance of preexisting phrenic motor facilitation does not involve NMDA receptor-dependent mechanisms.
Contribution of Sensorimotor Integration to Spinal Stabilization in Humans
Authors: Goodworth Adam D. , Peterka Robert J.
Published: April 2009

The control of upper body (UB) orientation relative to the pelvis in the frontal plane was characterized by analyzing responses to external perturbations consisting of continuous pelvis tilts (eyes open [EO] and eyes closed [EC]) and visual surround tilts (EO) at various amplitudes. Lateral sway of the lower body was prevented on all tests. UB sway was analyzed by calculating impulse–response functions (IRFs) and frequency–response functions (FRFs) from 0.023 to 10.3 Hz for pelvis tilt tests and FRFs from 0.041 to 1.5 Hz for visual tests. For pelvis tilt tests, differences between FRFs were limited to frequencies <3 Hz and were dependent on stimulus amplitude. IRFs were nearly identical across all pelvis tilt tests for the first 0.2 s, but showed amplitude-dependent changes in their time course at longer time lags. The availability of visual orientation cues (EO vs. EC) had only a small effect on the UB sway during pelvis tilt tests. This small effect of vision was consistent with the small UB sway evoked on visual tilt tests. Experimental results were interpreted using a feedback model of UB orientation control that included time-delayed sensory integration, short-latency reflexive mechanisms, and intrinsic biomechanical properties of the UB. Variation in model parameters indicated that subjects shifted toward reliance on vestibular information and away from proprioceptive information as pelvis tilt amplitudes increased. For visual tilt stimuli, model parameters indicated that subjects shifted toward reliance on vestibular and proprioceptive information and away from visual information as the stimulus amplitude increased.
Zona Incerta: A Role in Central Pain
Authors: Masri Radi , Quiton Raimi L. , Lucas Jessica M. , Murray Peter D. , Thompson Scott M. , Keller Asaf
Published: April 2009

Central pain syndrome (CPS) is a debilitating condition that affects a large number of patients with a primary lesion or dysfunction in the CNS. Despite its discovery over a century ago, the pathophysiological processes underlying the development and maintenance of CPS are poorly understood. We recently demonstrated that activity in the posterior thalamus (PO) is tightly regulated by inhibitory inputs from zona incerta (ZI). Here we test the hypothesis that CPS is associated with abnormal inhibitory regulation of PO by ZI. We recorded single units from ZI and PO in animals with CPS resulting from spinal cord lesions. Consistent with our hypothesis, the spontaneous firing rate and somatosensory evoked responses of ZI neurons were lower in lesioned animals compared with sham-operated controls. In PO, neurons recorded from lesioned rats exhibited significantly higher spontaneous firing rates and greater responses to noxious and innocuous stimuli applied to the hindpaw and to the face. These changes were not associated with increased afferent drive from the spinal trigeminal nucleus or changes in the ventroposterior thalamus. Thus CPS can result from suppressed inputs from the inhibitory nucleus zona incerta to the posterior thalamus.
Dynamic Characterization of Agonist and Antagonist Oculomotoneurons During Conjugate and Disconjugate Eye Movements
Authors: Van Horn Marion R. , Cullen Kathleen E.
Published: April 2009

In this report, we provide the first quantitative characterization of the relationship between the spike train dynamics of medial rectus oculomotoneurons (OMNs) and eye movements during conjugate and disconjugate saccades. We show that a simple, first-order model (i.e., containing eye position and velocity terms) provided an adequate model of neural discharges during both on and off-directed conjugate saccades, while a second-order model, which included a decaying slide term, significantly improved the ability to fit neuronal responses by ∼10% ( P < 0.05). To understand how the same neurons drove disconjugate eye movements, we evaluated whether sensitivities estimated during conjugate saccades could be used to predict responses during disconjugate saccades. For the majority of neurons (68%), a conjugate-based model failed, and instead neurons preferentially encoded the position and velocity of the ipsilateral eye. Similar to our previous results with abducens motoneurons, we also found that position and velocity sensitivities of OMNs decreased with increasing velocity, and the simulated population drive of OMNs during disconjugate saccades was less (∼10%) than during conjugate saccades. Taken together, our results provide evidence that the activation of the antagonist, as well as agonist, motoneuron pools must be considered to understand the neural control of horizontal eye movements across different oculomotor behaviors. Moreover, we propose that the undersampling of smaller motoneurons (e.g., nontwitch) was likely to account for the missing drive observed during disconjugate saccades; these cells are thought to be more specialized for vergence movements and thus could provide the additional input required to command disconjugate eye movements.
Influence of Subcortical Inhibition on Barrel Cortex Receptive Fields
Authors: Hirata Akio , Aguilar Juan , Castro-Alamancos Manuel A.
Published: April 2009

Influence of subcortical inhibition on barrel cortex receptive fields. By the time neural responses driven by vibrissa stimuli reach the barrel cortex, they have undergone significant spatial and temporal transformations within subcortical relays. A major regulator of these transformations is thought to be subcortical GABA-mediated inhibition, but the actual degree of this influence is unknown. We used disinhibition produced by GABA receptor antagonists to unmask the excitatory sensory responses that are normally suppressed by inhibition in the main subcortical sensory relays to barrel cortex; principal trigeminal (Pr5) and primary thalamic (VPM) nuclei. We found that, within subcortical relays, inhibition only slightly suppresses short-latency receptive field responses, but robustly suppresses long-latency center and surround receptive field responses. However, the long-latency subcortical effects of inhibition are mostly not reflected in the barrel cortex. The most robust effect of subcortical inhibition on barrel cortex responses is to transiently suppress the receptive field responses of high-frequency sensory stimuli. This transient adaptation caused by subcortical inhibition recovers within a few stimuli and gives way to a steady-state adaptation that is independent of subcortical inhibition.