bluuebunny/crossref_metadata_2025 huggingface dataset:
REPRESENTATION OF PATHWISE STATIONARY SOLUTIONS OF STOCHASTIC BURGERS' EQUATIONS
Authors: LIU YONG , ZHAO HUAIZHONG
Published: December 2009

In this paper, we show that the stationary solution u(t, ω) of the differentiable random dynamical system U: ℝ+ × L2[0, 1] × Ω → L2[0, 1] generated by the stochastic Burgers' equation with large viscosity, denoted by ν, driven by a Brownian motion in L2[0, 1], is given by: u(t, ω) = U(t, Y(ω), ω) = Y(θ(t, ω)), where Y(ω) can be represented by the following integral equation: [Formula: see text] Here θ is the group of P-preserving ergodic transformations on the canonical probability space [Formula: see text] such that θ(t, ω)(s) = W(t + s) - W(t), where W is the L2[0, 1]-valued Brownian motion on the probability space [Formula: see text], Tν is the linear operator semigroup on L2[0, 1] generated by νΔ.
ON YOUNG TOWERS ASSOCIATED WITH INFINITE MEASURE PRESERVING TRANSFORMATIONS
Authors: BRUIN H. , NICOL M. , TERHESIU D.
Published: December 2009

For a σ-finite measure preserving dynamical system (X, μ, T), we formulate necessary and sufficient conditions for a Young tower (Δ, ν, F) to be a (measure theoretic) extension of the original system. Because F is pointwise dual ergodic by construction, one immediate consequence of these conditions is that the Darling–Kac theorem carries over from F to T. One advantage of the Darling–Kac theorem in terms of Young towers is that sufficient conditions can be read off from the tail behavior and we illustrate this with relevant examples. Furthermore, any two Young towers with a common factor T, have return time distributions with tails of the same order.
GUIDED DEVELOPMENT OF INDEPENDENT INQUIRY IN AN ANATOMY/PHYSIOLOGY LABORATORY
Authors: Chaplin Susan B.
Published: December 2009

Student-originated projects are increasingly utilized in the biology laboratory as a means of engaging students and revitalizing the laboratory experience by allowing them one to two weeks to collect data on a manipulated variable of their choice by use of an introduced technique. Such experiments fail as good models of investigative learning when they place more emphasis on novel ideas than on hypothesis testing, experimental design, statistical rigor, or use of the primary literature. In addition, students get used to the routine and tend to design the same type of simplistic experiments in each course unless challenged. Laboratories in a Comparative Anatomy and Physiology course at the University of St. Thomas were reorganized to encourage the development of investigative skills in a stepwise fashion throughout the semester. Initial labs concentrated on experimental design and statistical analysis, then use of the primary literature in interpretation of the data was emphasized, and finally, students were asked to design their experiments and analyze their data on the basis of models from the primary literature.
INQUIRY-BASED LABORATORY COURSE IMPROVES STUDENTS’ ABILITY TO DESIGN EXPERIMENTS AND INTERPRET DATA
Authors: Myers Marcella J. , Burgess Ann B.
Published: December 2009

We redesigned our intermediate-level organismal physiology laboratory course to center on student-designed experiments in plant and human physiology. Our primary goals were to improve the ability of students to design experiments and analyze data. We assessed these abilities at the beginning and end of the semester by giving students an evaluation tool consisting of an experimental scenario, data, and four questions of increasing complexity. To control for nontreatment influences, the improvement scores (final minus initial score for each question) of students taking both the laboratory and the companion lecture course were compared with those of students taking the lecture course only. The laboratory + lecture group improved more than the lecture-only group for the most challenging question. This evidence suggests that our inquiry-based curriculum is achieving its primary goals. The evaluation tool that we developed may be useful to others interested in measuring experimental analysis abilities in their students.
REGULATION OF CARDIAC EXCITATION-CONTRACTION COUPLING: A CELLULAR UPDATE
Authors: Korzick Donna H.
Published: December 2009

The primary purpose of this paper is to present a basic overview of some “relatively” new ideas related to the regulation of cardiac performance and underlying excitation-contraction (EC) coupling that have yet to be incorporated to textbooks currently used for introductory graduate-level physiology courses. Within the context of cardiac EC coupling, this review incorporates information on microdomains and local control theory, with particular emphasis on the role of Ca2+ sparks as a key regulatory component of ventricular myocyte contraction dynamics. Recent information pertaining to Ca2+ release mechanisms specific to the sarcoplasmic reticulum is also presented, as well as the idea of the ryanodine receptor as a macromolecular signaling complex. Because of the potential relationship to maladaptive functional responses under conditions of cardiovascular pathology, the regulatory role of cardiac adrenergic and additional G protein-coupled receptors known to regulate cardiac function is included, and fundamental concepts related to intracellular signaling are discussed. Finally, information on the roles of vascular and cardiac nitric oxide as an important regulator of cardiac performance is included to allow students to begin to think about the ubiquitous role of nitric oxide in the regulation of the cardiovascular system. An important point of emphasis is that whole organ cardiac dynamics can be traced back to the cellular events regulating intracellular Ca2+ homeostasis and as such provides an important conceptual framework from which the students can begin to think about whole organ physiology in health and disease.
Two-Dimensional Oxygen Map For Graphic Representation of Different Hypoxic Conditions
Authors: Kostianev S. , Iluchev D.
Published: December 2009

As educators, we are continually designing new methods and procedures to enhance learning. During this process, good ideas are frequently generated and tested, but the extent of such activities may not be adequate for a full manuscript. Nonetheless, the ideas may be quite beneficial in improving the teaching and learning of physiology. Illuminations is a column designed to facilitate the sharing of these ideas (illuminations). The format of submissions is quite simple: a succinct description of about one or two double-spaced pages (less title and authorship) of something you have used for the classroom, teaching, lab, conference room, etc. You may include one or two simple figures or references. Submit ideas for inclusion in Illuminations directly to the Associate Editor in charge, Stephen DiCarlo (sdicarlo@med.wayne.edu).
Electrophysiological properties of human induced pluripotent stem cells
Authors: Jiang Peng , Rushing Stephanie N. , Kong Chi-wing , Fu Jidong , Lieu Deborah Kuo-Ti , Chan Camie W. , Deng Wenbin , Li Ronald A.
Published: December 2009

Human embryonic stem cells (hESCs) can self-renew while maintaining their pluripotency. Direct reprogramming of adult somatic cells to induced pluripotent stem cells (iPSCs) has been reported. Although hESCs and human iPSCs have been shown to share a number of similarities, such basic properties as the electrophysiology of iPSCs have not been explored. Previously, we reported that several specialized ion channels are functionally expressed in hESCs. Using transcriptomic analyses as a guide, we observed tetraethylammonium (TEA)-sensitive (IC50 = 3.3 ± 2.7 mM) delayed rectifier K+ currents ( IKDR) in 105 of 110 single iPSCs (15.4 ± 0.9 pF). IKDR in iPSCs displayed a current density of 7.6 ± 3.8 pA/pF at +40 mV. The voltage for 50% activation ( V1/2) was −7.9 ± 2.0 mV, slope factor k = 9.1 ± 1.5. However, Ca2+-activated K+ current ( IKCa), hyperpolarization-activated pacemaker current ( If), and voltage-gated sodium channel (NaV) and voltage-gated calcium channel (CaV) currents could not be measured. TEA inhibited iPSC proliferation (EC50 = 7.8 ± 1.2 mM) and viability (EC50 = 5.5 ± 1.0 mM). By contrast, 4-aminopyridine (4-AP) inhibited viability (EC50 = 4.5 ± 0.5 mM) but had less effect on proliferation (EC50 = 0.9 ± 0.5 mM). Cell cycle analysis further revealed that K+ channel blockers inhibited proliferation primarily by arresting the mitotic phase. TEA and 4-AP had no effect on iPSC differentiation as gauged by ability to form embryoid bodies and expression of germ layer markers after induction of differentiation. Neither iberiotoxin nor apamin had any function effects, consistent with the lack of IKCa in iPSCs. Our results reveal further differences and similarities between human iPSCs and hESCs. A better understanding of the basic biology of iPSCs may facilitate their ultimate clinical application.
Activation of vasopressin neurons leads to phenotype progression in a mouse model for familial neurohypophysial diabetes insipidus
Authors: Hiroi Maiko , Morishita Yoshiaki , Hayashi Masayuki , Ozaki Nobuaki , Sugimura Yoshihisa , Nagasaki Hiroshi , Shiota Akira , Oiso Yutaka , Arima Hiroshi
Published: December 2009

Familial neurohypophysial diabetes insipidus (FNDI) is a rare disease that is inherited in an autosomal dominant manner. In a previous study, we made a mouse model for FNDI, which showed progressive polyuria accompanied by inclusion bodies in the arginine vasopressin (AVP) neurons formed by aggregates in the endoplasmic reticulum. The present study was conducted to determine whether the activities of AVP neurons are related to the phenotype progression in the FNDI model. In the first experiment, female heterozygous mice were administered either desmopressin (dDAVP) or a vehicle (control) subcutaneously with osmotic minipumps for 30 days. The dDAVP treatment significantly decreased the urine volume, AVP mRNA expression, and inclusion bodies in the AVP neurons. Urine volume in the dDAVP group remained significantly less than the control for 14 days even after the minipumps were removed. In the second experiment, the males were fed either a 0.2% Na or 2.0% Na diet for 6 mo. Urine AVP excretion was significantly increased in the 2.0% Na group compared with the 0.2% Na group for the first 2 mo but gradually decreased thereafter. Throughout the experiments, urine volume increased progressively in the 2.0% Na group but not in the 0.2% Na group. Immunohistochemical analyses revealed that inclusion bodies in the AVP cells had significantly increased in the 2.0% Na compared with the 0.2% Na group. These data demonstrated that activation of AVP neurons could accelerate the aggregate formation as well as the progression of the polyuria in the FNDI model mice.
Exposure to reduced gravity impairs junctional transmission at the semicircular canal in the frog labyrinth
Authors: Rossi Maria Lisa , Rubbini Gemma , Gioglio Luciana , Martini Marta , Fesce Riccardo
Published: December 2009

The effects of microgravity on frog semicircular canals have been studied by electrophysiological and morphological approaches. Reduced gravity (microG) was simulated by a random positioning machine (RPM), which continually and randomly modified the orientation in space of the anesthetized animal. As this procedure stimulates the semicircular canals, the effect of altered gravity was isolated by comparing microG-treatment with an identical rotary stimulation in the presence of normal gravity (normoG). Electrophysiological experiments were performed in the isolated labyrinth, extracted from the animals after the treatment, and mounted on a turntable. Junctional activity was measured by recording quantal events (mEPSPs) and spikes from the afferent fibers close to the junction, at rest and during rotational stimulation. MicroG-treated animals displayed a marked decrease in the frequency of resting and evoked mEPSP discharge, vs. both control and normoG (mean decrease ∼50%). Spike discharge was also depressed: 57% of microG-treated frogs displayed no spikes at rest and during rotation at 0.1 Hz, vs. 23–31% of control or normoG frogs. Among the firing units, during one cycle of sinusoidal rotation at 0.1 Hz microG-treated units emitted an average of 41.8 ± 8.06 spikes, vs. 77.2 ± 8.19 in controls. Patch-clamp analysis on dissociated hair cells revealed altered Ca2+handling, after microG, consistent with and supportive of the specificity of microG effects. Marked morphological signs of cellular suffering were observed after microG, mainly in the central part of the sensory epithelium. Functional changes due to microgravity were reversible within a few days.
Characterization of vasopressin-responsive collecting duct adenylyl cyclases in the mouse
Authors: Strait Kevin A. , Stricklett Peter K. , Chapman Mark , Kohan Donald E.
Published: December 2009

Little is known about collecting duct adenylyl cyclase (AC) isoforms or regulation in the mouse. We performed RT-PCR for AC isoforms 1–9 in microdissected cortical (CCD) and outer medullary (OMCD) and acutely isolated inner medullary (IMCD) collecting duct. All collecting duct regions contained AC3, AC4, and AC6 mRNA, while CCD and OMCD, but not IMCD, also contained AC5 mRNA. Acutely isolated IMCD expressed AC3, AC4, and AC6 proteins by Western blot analysis. The mIMCD3 cell line expressed AC2, AC3, AC4, AC5, and AC6 mRNA; M-1 CCD cells expressed AC2, 3, 4, and 6, while mpkCCD cell lines contained AC3, AC4, and AC6 mRNA. AVP stimulated cAMP accumulation in acutely isolated mouse IMCD; this was reduced by chelation of extracellular calcium (EGTA) and almost completely abolished by blockade of calmodulin (W-7). Blockade of calmodulin kinase with KN-93 or endoplasmic reticulum calcium ATPase (thapsigargin) also reduced the AVP response. A similar inhibitory effect of W-7, KN-93, and thapsigargin was seen on forskolin-stimulated cAMP content in acutely isolated mouse IMCD. These three agents had the same pattern of blockade of AVP- or forskolin-stimulated AC activity in acutely isolated rat IMCD. AVP responsiveness in primary cultures of mouse IMCD was also reduced by W-7, KN-93, and thapsigargin. Small interfering RNA (siRNA) designed to knock down AC3 or AC6 in primary cultured mouse IMCD significantly reduced AVP-stimulated cAMP accumulation. Together, these data are consistent with a role of AC3 and AC6 in the activation of mouse collecting duct by AVP.
Distributed lag and spline modeling for predicting energy expenditure from accelerometry in youth
Authors: Choi Leena , Chen Kong Y. , Acra Sari A. , Buchowski Maciej S.
Published: December 2009

Movement sensing using accelerometers is commonly used for the measurement of physical activity (PA) and estimating energy expenditure (EE) under free-living conditions. The major limitation of this approach is lack of accuracy and precision in estimating EE, especially in low-intensity activities. Thus the objective of this study was to investigate benefits of a distributed lag spline (DLS) modeling approach for the prediction of total daily EE (TEE) and EE in sedentary (1.0–1.5 metabolic equivalents; MET), light (1.5–3.0 MET), and moderate/vigorous (≥3.0 MET) intensity activities in 10- to 17-year-old youth ( n = 76). We also explored feasibility of the DLS modeling approach to predict physical activity EE (PAEE) and METs. Movement was measured by Actigraph accelerometers placed on the hip, wrist, and ankle. With whole-room indirect calorimeter as the reference standard, prediction models ( Hip, Wrist, Ankle, Hip+ Wrist, Hip+ Wrist+ Ankle) for TEE, PAEE, and MET were developed and validated using the fivefold cross-validation method. The TEE predictions by these DLS models were not significantly different from the room calorimeter measurements (all P > 0.05). The Hip+ Wrist+ Ankle predicted TEE better than other models and reduced prediction errors in moderate/vigorous PA for TEE, MET, and PAEE (all P < 0.001). The Hip+ Wrist reduced prediction errors for the PAEE and MET at sedentary PA ( P = 0.020 and 0.021) compared with the Hip. Models that included Wrist correctly classified time spent at light PA better than other models. The means and standard deviations of the prediction errors for the Hip+ Wrist+ Ankle and Hip were 0.4 ± 144.0 and 1.5 ± 164.7 kcal for the TEE, 0.0 ± 84.2 and 1.3 ± 104.7 kcal for the PAEE, and −1.1 ± 97.6 and −0.1 ± 108.6 MET min for the MET models. We conclude that the DLS approach for accelerometer data improves detailed EE prediction in youth.
Effect of aerobic exercise on tumor physiology in an animal model of human breast cancer
Authors: Jones Lee W. , Viglianti Benjamin L. , Tashjian Jessica A. , Kothadia Sejal M. , Keir Stephen T. , Freedland Stephen J. , Potter Michael Q. , Jung Moon Eui , Schroeder Thies , Herndon James E. , Dewhirst Mark W.
Published: December 2009

Recent epidemiologic studies report that regular exercise may be associated with substantial reductions in cancer-specific and all-cause mortality following a breast cancer diagnosis. The mechanisms underlying this relationship have not been identified. We investigated the effects of long-term voluntary wheel running on growth and progression using an animal model of human breast cancer. We also examined effects on the central features of tumor physiology, including markers of tumor blood perfusion/vascularization, hypoxia, angiogenesis, and metabolism. Athymic female mice fed a high-fat diet were orthotopically (direct into the mammary fat pad) implanted with human breast cancer cells (MDA-MB-231 at 1 × 106) into the right dorsal mammary fat pad and randomly assigned (1:1) to voluntary wheel running ( n = 25) or a nonintervention (sedentary) control group ( n = 25). Tumor volume was measured every three days using digital calipers. All experimental animals were killed when tumor volume reached ≥1,500 mm3. Kaplan-Meier (KM) analysis indicated that tumor growth (survival) was comparable between the experimental groups (exercise 44 days vs. control 48 days; KM proportional hazard ratio = 1.41, 95% confidence interval, 0.77–2.58, P = 0.14). However, tumors from exercising animals had significantly improved blood perfusion/vascularization relative to the sedentary control group ( P < 0.05). Histological analyses indicated that intratumoral hypoxia levels (as assessed by hypoxia-inducible factor 1) were significantly higher in the exercise group relative to sedentary control ( P < 0.05). Aerobic exercise can significantly increase intratumoral vascularization, leading to “normalization” of the tissue microenvironment in human breast tumors. Such findings may have important implications for inhibiting tumor metastasis and improving the efficacy of conventional cancer therapies.
Priming exercise speeds pulmonary O2 uptake kinetics during supine “work-to-work” high-intensity cycle exercise
Authors: DiMenna Fred J. , Wilkerson Daryl P. , Burnley Mark , Bailey Stephen J. , Jones Andrew M.
Published: December 2009

We manipulated the baseline metabolic rate and body position to explore the effect of the interaction between recruitment of discrete sections of the muscle fiber pool and muscle O2 delivery on pulmonary O2 uptake (V̇o2) kinetics during cycle exercise. We hypothesized that phase II V̇o2 kinetics (τp) in the transition from moderate- to severe-intensity exercise would be significantly slower in the supine than upright position because of a compromise to muscle perfusion and that a priming bout of severe-intensity exercise would return τp during supine exercise to τp during upright exercise. Eight male subjects [35 ± 13 (SD) yr] completed a series of “step” transitions to severe-intensity cycle exercise from an “unloaded” (20-W) baseline and a baseline of moderate-intensity exercise in the supine and upright body positions. τp was not significantly different between supine and upright exercise during transitions from a 20-W baseline to moderate- or severe-intensity exercise but was significantly greater during moderate- to severe-intensity exercise in the supine position (54 ± 19 vs. 38 ± 10 s, P < 0.05). Priming significantly reduced τp during moderate- to severe-intensity supine exercise (34 ± 9 s), returning it to a value that was not significantly different from τp in the upright position. This effect occurred in the absence of changes in estimated muscle fractional O2 extraction (from the near-infrared spectroscopy-derived deoxygenated Hb concentration signal), such that the priming-induced facilitation of muscle blood flow matched increased O2 utilization in the recruited fibers, resulting in a speeding of V̇o2 kinetics. These findings suggest that, during supine cycling, priming speeds V̇o2 kinetics by providing an increased driving pressure for O2 diffusion in the higher-order (i.e., type II) fibers, which would be recruited in the transition from moderate- to severe-intensity exercise and are known to be especially sensitive to limitations in O2 supply.
Assessment of air space size characteristics by intercept (chord) measurement: an accurate and efficient stereological approach
Authors: Knudsen Lars , Weibel Ewald R. , Gundersen Hans Jørgen G. , Weinstein Felix V. , Ochs Matthias
Published: December 2009

The mean linear intercept (chord) length ( Lm) is a useful parameter of peripheral lung structure as it describes the mean free distance in the air spaces. It is often misinterpreted as a measure of “alveolar size,” and its estimation is fraught with a number of pitfalls. We present two methods for the accurate estimation of Lm: 1) the indirect method, which derives Lm from the volume-to-surface ratio of air spaces estimated by point counting methods, and 2) the direct method, which uses a set of random intercepts and calculates Lm from their frequency distribution, for which we introduce a new and accurate method. Both methods are efficient and, with proper precautions, unbiased. The meaning of Lm is assessed in two different examples. In a physiological study, the effect of different inflation levels is studied, showing that Lm critically depends on lung inflation. In an experimental study on emphysema-like changes in a genetic mouse model, the effect of heterogeneity of air space size is assessed; these results are obtained partly because of differences in lung volume due to altered recoil in the emphysematous lungs. In conclusion, although Lm is not a robust parameter of internal lung structure because it crucially depends on lung volume, it is still a valid measure for which accurate and efficient methods are available that yield additional parameters such as size distribution or alveolar surface area.
Group I Afferent Pathway Contributes to Functional Knee Stability
Authors: Friemert B. , Franke S. , Gollhofer A. , Claes L. , Faist M.
Published: December 2009

The hamstring reflex response has been suggested to play a substantial role in knee joint stabilization during anterior tibial translation. The present study was performed to determine which afferent pathways contribute to the hamstring reflex as well as the potential effects of specific afferent pathways on functional knee stability. Short- and medium-latency hamstring reflexes (SLR and MLR) were evoked by anterior tibial translation in 35 healthy subjects during standing with 30° knee flexion. Nerve cooling, tizanidine, and ischemia were employed to differentiate afferent pathways. Two hours of thigh cooling ( n = 10) resulted in a significant increase in MLR latency and, to a lesser extent, SLR latency. No significant changes were recorded in reflex sizes or maximum tibial translation. The ingestion of tizanidine ( n = 10), a suppressor of group II afferents, strongly reduced the MLR size while SLR size or latency of both reflex responses was not significantly affected. Maximum tibial translation was unchanged [5.3 ± 1.9 to 4.8 ± 2 (SD) mm; P = 0.410]. Ischemia in the thigh ( n = 15) led to a highly significant depression in SLR size (89 ± 4%; P < 0.001) but only a slight and not significant decline of MLR size. In these subjects maximum tibial translation increased significantly (6.9 ± 1.6 to 9.4 ± 3.2 mm; P = 0.028). It is concluded that the hamstring SLR is mediated by Ia afferents, while group II afferents mainly contribute to the MLR. Suppression of SLR may increase maximum anterior tibial translation, thus indicating a possible functional role of Ia afferents in knee joint stabilization.
Quantitative Estimation of Calcium Dynamics From Ratiometric Measurements: A Direct, Nonratioing Method
Authors: Joucla Sébastien , Pippow Andreas , Kloppenburg Peter , Pouzat Christophe
Published: December 2009

Measuring variations of intracellular free calcium concentration through the changes in fluorescence of a calcium-sensitive dye is a ubiquitous technique in neuroscience. Despite its popularity, confidence intervals (CIs) on the estimated parameters of calcium dynamics models are seldom given. To address this issue, we have developed a two-stage model for ratiometric measurements obtained with a charge-coupled device (CCD) camera. Its first element embeds a parametric calcium dynamics model into a fluorescence intensity model and its second element probabilistically describes the fluorescence measurements by a CCD camera. Using Monte Carlo simulations, we first show that the classical ratiometric transformation gives reliable CIs for time constants only and not baseline calcium concentration nor influx. We then introduce a direct method, which consists of fitting directly and simultaneously the fluorescence transients at both wavelengths, without any data ratioing. This approach uses a probabilistic description of the camera, leading to the construction of meaningful CIs for the calcium parameters. Moreover, using approaches inspired by constrained linear regression, we can take into account the finite precision on calibrated parameters (such as the dye dissociation constant in the cell). These key features are illustrated on simulated data using Monte Carlo simulations. Moreover, we illustrate the strength of the direct method on experimental recordings from insect olfactory interneurons. In particular, we show how to handle a time-dependent buffer concentration, thereby considerably improving our goodness of fit. The direct method was implemented in the open-source software R and is freely distributed in the CalciOMatic package.
Adaptive Changes in Anticipatory Postural Adjustments With Novel and Familiar Postural Supports
Authors: Hall Leanne M. , Brauer Sandra , Horak Fay , Hodges Paul W.
Published: December 2009

Anticipatory postural adjustments (APAs) serve to stabilize posture prior to initiation of voluntary movement. This study examined the effects of changes in postural support on APAs using novel and familiar support paradigms. We also investigated whether postural strategies were refined with practice and how the CNS responded when multiple supports were available. Twelve healthy subjects stood on dual force platforms and performed 20 randomized left and right rapid leg-lift tasks in response to a visual cue under four conditions: unsupported, bilateral handgrip, bite plate, and a combined handgrip and bite plate condition. Vertical ground reaction forces, electromyography of limb, trunk and jaw muscles, and forces exerted on the support apparatus were recorded. Shift in center-of-pressure amplitude and duration were reduced with increased support. Muscles were recruited in advance of the focal movement when able to contribute to stability, and activity was modulated based on the amount of support available. The CNS adapted anticipatory postural strategies immediately with changes in condition regardless of familiarity with the support; however, adaptation was only complete at the first repetition in conditions that involved familiar support strategies. Tasks that involved a novel bite strategy continued to adapt with practice. In the multiple support condition, both hand and bite strategies were immediately incorporated; however, the contribution of each was not identical to conditions where supports were provided individually. This study emphasizes the flexibility of the CNS to organize postural strategies to meet the demands of postural stability in both familiar and novel situations.
Motor Patterns During Walking on a Slippery Walkway
Authors: Cappellini Germana , Ivanenko Yuri P. , Dominici Nadia , Poppele Richard E. , Lacquaniti Francesco
Published: December 2009

Friction and gravity represent two basic physical constraints of terrestrial locomotion that affect both motor patterns and the biomechanics of bipedal gait. To provide insights into the spatiotemporal organization of the motor output in connection with ground contact forces, we studied adaptation of human gait to steady low-friction conditions. Subjects walked along a slippery walkway (7 m long; friction coefficient ≃ 0.06) or a normal, nonslippery floor at a natural speed. We recorded gait kinematics, ground reaction forces, and bilateral electromyographic (EMG) activity of 16 leg and trunk muscles and we mapped the recorded EMG patterns onto the spinal cord in approximate rostrocaudal locations of the motoneuron (MN) pools to characterize the spatiotemporal organization of the motor output. The results revealed several idiosyncratic features of walking on the slippery surface. The step length, cycle duration, and horizontal shear forces were significantly smaller, the head orientation tended to be stabilized in space, whereas arm movements, trunk rotations, and lateral trunk inclinations considerably increased and foot motion and gait kinematics resembled those of a nonplantigrade gait. Furthermore, walking on the slippery surface required stabilization of the hip and of the center-of-body mass in the frontal plane, which significantly improved with practice. Motor patterns were characterized by an enhanced (roughly twofold) level of MN activity, substantial decoupling of anatomical synergists, and the absence of systematic displacements of the center of MN activity in the lumbosacral enlargement. Overall, the results show that when subjects are confronted with unsteady surface conditions, like the slippery floor, they adopt a gait mode that tends to keep the COM centered over the supporting limbs and to increase limb stiffness. We suggest that this behavior may represent a distinct gait mode that is particularly suited to uncertain surface conditions in general.
Cutaneous Afferents From the Monkeys Fingers: Responses to Tangential and Normal Forces
Authors: Wheat H. E. , Salo L. M. , Goodwin A. W.
Published: December 2009

Control of tangential force plays a key role in everyday manipulations. In anesthetized monkeys, forces tangential to the skin were applied at a range of magnitudes comparable to those used in routine manipulations and in eight different directions. The paradigm used enabled separation of responses to tangential force from responses to the background normal force. For slowly adapting type I (SAI) afferents, tangential force responses ranged from excitatory through no response to suppression, with both a static and dynamic component. For fast adapting type I (FAI) afferents, responses were dynamic and excitatory only. Responses of both afferent types were scaled by tangential force magnitude, elucidating the neural basis for previous human psychophysical scaling data. Most afferents were direction selective with a range of preferred directions and a range in sharpness of tuning. Both the preferred direction and the degree of tuning were independent of the background normal force. Preferred directions were distributed uniformly over 360° for SAI afferents, but for FAI afferents they were biased toward the proximo-ulnar direction. Afferents from all over the glabrous skin of the distal segment of the finger responded; there was no evident relationship between the position of an afferent's receptive field on the finger and its preferred direction or its degree of tuning. Nor were preferred directions biased either toward or away from the receptive field center. In response to the relatively large normal forces, some afferents saturated and others did not, regardless of the positions of their receptive fields. Total afferent response matched human psychophysical scaling functions for normal force.
Functional Connectivity of the Macaque Posterior Parahippocampal Cortex
Authors: Vincent Justin L. , Kahn Itamar , Van Essen David C. , Buckner Randy L.
Published: December 2009

Neuroimaging experiments in humans suggest that regions in parietal cortex and along the posterior midline are functionally connected to the medial temporal lobe and are active during memory retrieval. It is unknown whether macaques have a similar network. We examined functional connectivity in isoflurane-anesthetized macaques to identify a network associated with posterior parahippocampal cortex (PPHC). Functional connectivity was observed between the PPHC and retrosplenial, posterior cingulate, superior temporal gyrus, and inferior parietal cortex. PPHC correlations were distinct from regions in parietal and temporal cortex activated by an oculomotor task. Comparison of macaque and human PPHC correlations revealed similarities that suggest the temporal-parietal region identified in the macaque may share a common lineage with human Brodmann area 39, a region thought to be involved in recollection. These results suggest that macaques and humans may have homologous PPHC-parietal pathways. By specifying the location of the putative macaque homologue in parietal cortex, we provide a target for future physiological exploration of this area's role in mnemonic or alternative processes.
Endogenous Serotonin Acts on 5-HT2C-Like Receptors in Key Vocal Areas of the Brain Stem to Initiate Vocalizations in Xenopus laevis
Authors: Yu Heather J. , Yamaguchi Ayako
Published: December 2009

Serotonin initiates various rhythmic behaviors in vertebrates. Previously we have shown that serotonergic neurons innervate the central vocal pathway in the African clawed frog ( Xenopus laevis ). We also discovered that exogenous serotonin applied to isolated brains in vitro activates fictive vocalizations by activating 5-HT2C-like receptors. In this study, we examined the location of 5-HT2C-like receptors and determined whether endogenously released serotonin also initiates vocalizations by activating 5-HT2C-like receptors in male Xenopus brains. To this end, we first identified the specific location of 5-HT2C-like receptors using immunohistochemistry. We next examined which of the populations of neurons that express 5-HT2C-like receptors are functionally relevant for initiating fictive vocalizations by applying a 5-HT2Creceptor agonist to brains transected at various levels. Of four populations of immunopositive neurons, we showed that 5-HT2C-like receptors located in two areas of the brain stem vocal circuit, the raphe nucleus and motor nucleus IX-X, initiate fictive vocalizations. We next showed that endogenous serotonin can also activate fictive vocalizations by increasing the extracellular concentration of endogenous serotonin using a selective serotonin reuptake inhibitor (SSRI). The SSRI-induced vocal initiation is also mediated by activation of 5-HT2C-like receptors because blockade of these receptors prevents fictive vocalization. The results suggest that in vivo release of serotonin initiates male vocalizations by activating 5-HT2C-like receptors in the brain stem vocal nuclei.
Spatiotemporal Receptive Field Properties of a Looming-Sensitive Neuron in Solitarious and Gregarious Phases of the Desert Locust
Authors: Rogers Stephen M. , Harston George W. J. , Kilburn-Toppin Fleur , Matheson Thomas , Burrows Malcolm , Gabbiani Fabrizio , Krapp Holger G.
Published: December 2009

Desert locusts ( Schistocerca gregaria ) can transform reversibly between the swarming gregarious phase and a solitarious phase, which avoids other locusts. This transformation entails dramatic changes in morphology, physiology, and behavior. We have used the lobula giant movement detector (LGMD) and its postsynaptic target, the descending contralateral movement detector (DCMD), which are visual interneurons that detect looming objects, to analyze how differences in the visual ecology of the two phases are served by altered neuronal function. Solitarious locusts had larger eyes and a greater degree of binocular overlap than those of gregarious locusts. The receptive field to looming stimuli had a large central region of nearly equal response spanning 120° × 60° in both phases. The DCMDs of gregarious locusts responded more strongly than solitarious locusts and had a small caudolateral focus of even further sensitivity. More peripherally, the response was reduced in both phases, particularly ventrally, with gregarious locusts showing greater proportional decrease. Gregarious locusts showed less habituation to repeated looming stimuli along the eye equator than did solitarious locusts. By contrast, in other parts of the receptive field the degree of habituation was similar in both phases. The receptive field organization to looming stimuli contrasts strongly with the receptive field organization of the same neurons to nonlooming local-motion stimuli, which show much more pronounced regional variation. The DCMDs of both gregarious and solitarious locusts are able to detect approaching objects from across a wide expanse of visual space, but phase-specific changes in the spatiotemporal receptive field are linked to lifestyle changes.
Zero Diffusion‐Dispersion‐Smoothing Limits for a Scalar Conservation Law with Discontinuous Flux Function
Authors: Holden H. , Karlsen K. H. , Mitrovic D.
Published: December 2009

We consider multidimensional conservation laws with discontinuous
flux, which are regularized with vanishing diffusion and dispersion terms and with smoothing of the flux discontinuities.
We use the approach of H‐measures to investigate the zero diffusion‐dispersion‐smoothing limit.
Stability Analysis of Stochastic Reaction‐Diffusion Cohen‐Grossberg Neural Networks with Time‐Varying Delays
Authors: Huang Chuangxia , Yang Xinsong , He Yigang
Published: December 2009

This paper is concerned with pth moment exponential stability of stochastic reaction‐diffusion Cohen‐Grossberg neural networks with time‐varying delays. With the help of Lyapunov method, stochastic analysis, and inequality techniques, a set of new suffcient conditions on pth moment exponential stability for the considered system is presented. The proposed results generalized and improved some earlier publications.
Common Fixed Points of Generalized Contractive Hybrid Pairs in Symmetric Spaces
Authors: Abbas Mujahid , Khan Abdul Rahim
Published: December 2009

Several fixed point theorems for hybrid pairs of single-valued and multivalued occasionally weakly compatible maps satisfying generalized contractive conditions are established in a symmetric space.
The Cancer Stem Cell Concept in Progression of Head and Neck Cancer
Authors: Chen Zhuo (Georgia)
Published: December 2009

Human head and neck cancer (HNC) is a highly heterogeneous disease. Understanding the biology of HNC progression is necessary for the development of novel approaches to its prevention, early detection, and treatment. A current evolutional progression model has limitations in explaining the heterogeneity observed in a single tumor nest. Accumulating evidence supports the existence of cancer stem cells (CSCs) as small subpopulations in solid tumors, including HNC. These CSCs can be selected by appropriate cell surface markers, which are cancer type specific and have been confirmed by uniquein vitroandin vivoassays. Selected CSC populations maintain a self-renewal capability and show aggressive behaviors, such as chemoresistance and metastasis. In addition to introducing the CSC concept in solid tumors, this short review summarizes current publications in HNC CSC and the prospective development and application of the CSC concept to HNC in the clinic.
Fractal Time Series—A Tutorial Review
Authors: Li Ming
Published: December 2009

Fractal time series substantially differs from conventional one in its statistic properties. For instance, it may have a heavy‐tailed probability distribution function (PDF), a slowly decayed autocorrelation function (ACF), and a power spectrum function (PSD) of 1/f type. It may have the statistical dependence, either long‐range dependence (LRD) or short‐range dependence (SRD), and global or local self‐similarity. This article will give a tutorial review about those concepts. Note that a conventional time series can be regarded as the solution to a differential equation of integer order with the excitation of white noise in mathematics. In engineering, such as mechanical engineering or electronics engineering, engineers may usually consider it as the output or response of a differential system or filter of integer order under the excitation of white noise. In this paper, a fractal time series is taken as the solution to a differential equation of fractional order or a response of a fractional system or a fractional filter driven with a white noise in the domain of stochastic processes.
On the Analysis and Evaluation of Direct Containment Heating with the Multidimensional Multiphase Flow Code MC3D
Authors: Meignen Renaud , Janin Tanguy
Published: December 2009

In the course of a postulated severe accident in an NPP, Direct Containment Heating (DCH) may occur after an eventual failure of the vessel. DCH is related to dynamical, thermal, and chemical phenomena involved by the eventual fine fragmentation and dispersal of the corium melt out of the vessel pit. It may threaten the integrity of the containment by pressurization of its atmosphere. Several simplified modellings have been proposed in the past but they require a very strong fitting which renders any extrapolation regarding geometry, material, and scales rather doubtful. With the development of multidimensional multiphase flow computer codes, it is now possible to investigate the phenomenon numerically with more details. We present an analysis of the potential of the MC3D code to support the analysis of this phenomenon, restricting our discussion to the dynamical processes. The analysis is applied to the case of French 1300 MWe PWR reactors for which we derive a correlation for the corium dispersal rate for application in a Probabilistic Safety Analysis (PSA) level 2 study.
Smoking Cessation and Relapse during a Lung Cancer Screening Program
Authors: Anderson Christy M. , Yip Rowena , Henschke Claudia I. , Yankelevitz David F. , Ostroff Jamie S. , Burns David M.
Published: December 2009

Background: The potential for negative screening to reduce smoking cessation and long-term abstinence is a concern in lung cancer screening. We examine whether consistently negative results during long-term participation in a lung cancer screening program reduce cessation or increase relapse.

Methods: Participants (N = 2,078) in the Early Lung Cancer Action Program received annual screenings and periodic smoking behavior surveys over a follow-up period as long as 12 years. Point abstinence and prolonged abstinence were examined among 730 baseline smokers. Relapse was examined among 1,227 former smokers who quit for 1 year or more at enrollment, 121 recent quitters at enrollment, and 155 baseline smokers who quit during follow-up. Abstinence and relapse for participants with consistently negative computerized tomography scan results were compared with those with non-cancer–positive results using stratified Cox models.

Results: Baseline smokers with negative computerized tomography scans had a 28% lower likelihood of achieving point abstinence at one or more follow-up assessments compared with those with positive scans (hazard ratio, 0.72; P < 0.0004), but consistently negative scans were not associated with a lower likelihood of prolonged abstinence. A consistently negative scan was not associated with a higher likelihood of relapse back to smoking for long-term former smokers, recent quitters, or those who quit during follow-up.

Conclusions: We did not detect a lower long-term smoking abstinence or increased relapse over a 6-year period of follow-up among individuals participating in a lung cancer screening program who have a consistently negative screening compared with those with a positive, but noncancer, screening result. (Cancer Epidemiol Biomarkers Prev 2009;18(12):3476–83)
Determinants of Hair Nicotine Concentrations in Nonsmoking Women and Children: A Multicountry Study of Secondhand Smoke Exposure in Homes
Authors: Kim Sungroul , Wipfli Heather , Navas-Acien Ana , Dominici Francesca , Avila-Tang Erika , Onicescu Georgiana , Breysse Patrick , Samet Jonathan M. ,   on behalf of the FAMRI Homes Study Investigators
Published: December 2009

The main purpose of this study was to identify and evaluate determinants of hair nicotine concentrations in nonsmoking women and children exposed to secondhand tobacco smoke at home. Hair samples were collected from nonsmoking women (n = 852) and from children (n = 1,017) <11 years of age living in households (n = 1,095) with smokers from 31 countries from July 2005 to October 2006. Participants' ages, activity patterns and socioeconomic characteristics including education and employment status, and hair treatment information were collected. Multilevel linear regression modeling was used to identify the main determinants of hair nicotine concentration measured by gas chromatography coupled with mass spectrometry. Increased indoor air nicotine concentration at home were associated with increased hair nicotine concentrations in nonsmoking women and children. This association was not changed after controlling for other explanatory variables. After controlling for age, length of exposure, and socioeconomic characteristics, hair nicotine concentrations in nonsmoking children and women were estimated to be increased by 3% and 1%, respectively, for a 1 μg/m3 increase in air nicotine concentration. The association between children's exposure to secondhand tobacco smoke at home and hair nicotine concentration was stronger among younger children and children with longer exposure at home. (Cancer Epidemiol Biomarkers Prev 2009;18(12):3407–14)
The Association between Cigarette Smoking and Risk of Colorectal Cancer in a Large Prospective Cohort from the United States
Authors: Hannan Lindsay M. , Jacobs Eric J. , Thun Michael J.
Published: December 2009

Background: Many studies have reported a 20% to 60% increase in risk of colorectal cancer associated with active smoking. However, neither the U.S. Surgeon General nor the IARC have classified the relationship as causal because of concern about residual confounding.

Methods: In a prospective study of 184,187 people followed from 1992 to 2005, we used Cox proportional hazard models to examine the relationship of cigarette smoking to incident colorectal cancer, controlling for screening and multiple known and putative risk factors. Information on smoking and time-varying covariates was updated in 1997, 1999, 2001, and 2003.

Results: The incidence of colorectal cancer was significantly higher in current [hazard ratios (HR), 1.27; 95% confidence intervals (CI), 1.06-1.52] and former smokers (HR, 1.23; 95% CI, 1.11-1.36) compared with lifelong nonsmokers in analyses that controlled for 13 covariates, including screening. The relative risk was greatest among current smokers with at least 50 years of smoking (HR, 1.38; 95% CI, 1.04-1.84). Among former smokers, risk of colorectal cancer decreased with greater time since cessation (P trend = 0.0003), and also decreased with earlier age at cessation (P trend = 0.0014). No association was seen among former smokers who had quit before age of 40 years or abstained for 31 years or more.

Conclusions: Long-term cigarette smoking is associated with colorectal cancer, even after controlling for screening and multiple other risk factors. (Cancer Epidemiol Biomarkers Prev 2009;18(12):3362–7)