bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in matrix phosphorylation during bovine dentin development
Authors: Verdelis Kostas , Lukashova Lyudmilla , Yamauchi Mitsuo , Atsawasuwan Peter , Wright John T. , Peterson Margaret G. E. , Jha Divya , Boskey Adele L.
Published: August 2007

Phosphorylation of the organic matrix proteins of dentin is important for the initiation of mineralization, but its relevance in later mineralization stages is controversial. The objective of this study was to analyze changes in the total matrix phosphate content during dentin development and to identify their origin. Amino acid and total matrix phosphate analyses of microdissected developing mantle and circumpulpal fetal bovine dentin specimens were performed. The amino acid composition showed few changes during mantle and circumpulpal dentin maturation. However, the total matrix phosphate content showed a significant, positive correlation with tissue maturation in both mantle and circumpulpal dentin, with a two‐ and a three‐fold increase, respectively, being observed. The data indicate that changes occur in the pattern of phosphorylation of matrix proteins during dentin maturation, which we suggest may play a functional role in later stages of tooth mineralization.
Dentine sealing provided by smear layer/smear plugs vs. adhesive resins/resin tags
Authors: Carrilho Marcela R. , Tay Franklin R. , Sword Jeremy , Donnelly Adam M. , Agee Kelli A. , Nishitani Yoshihiro , Sadek Fernanda T. , Carvalho Ricardo M. , Pashley David H.
Published: August 2007

The aim of this study was to evaluate the ability of five experimental resins, which ranged from hydrophobic to hydrophilic blends, to seal acid‐etched dentine saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents (100% resin) or as solutions solvated with absolute ethanol (70% resin/30% ethanol). Fluid conductance was measured at 20 cm H2O hydrostatic pressure after sound dentine surfaces were: (i) covered with a smear layer; (ii) acid‐etched; or (iii) bonded with neat or solvated resins, which were applied to acid‐etched dentine saturated with water or ethanol. In general, the fluid conductance of resin‐bonded dentine was significantly higher than that of smear layer‐covered dentine. However, when the most hydrophobic neat resins (R1 and R2) were applied to acid‐etched dentine saturated with ethanol, the fluid conductance was as low as that produced by smear layers. The fluid conductance of resin‐bonded dentine saturated with ethanol was significantly lower than for resin bonded to water‐saturated dentine, except for resin R4. Application of more hydrophobic resins may provide better sealing of acid‐etched dentine if the substrate is saturated with ethanol instead of with water.
Enamel matrix proteins bind to wound matrix proteins and regulate their cell‐adhesive properties
Authors: Narani Nazanin , Owen Gethin Rhys , Häkkinen Lari , Putnins Edward , Larjava Hannu
Published: August 2007

Enamel matrix proteins (EMP) induce periodontal regeneration and accelerate dermal wound healing, but the cellular mechanisms of these processes are unclear. We investigated the binding of EMP to the wound matrix proteins fibronectin, laminin‐1, collagen type I, and collagen type IV and analyzed the interaction of epithelial cells and periodontal ligament fibroblasts (PDLF) with EMP and composite matrices of EMP + fibronectin or EMP + collagen. The adhesion of PDLF to EMP was concentration‐ and integrin‐dependent and did not require de novo protein synthesis. EMP supported PDLF migration. In contrast, keratinocytes did not adhere to EMP if their protein synthesis was blocked. EMP showed concentration‐dependent binding of fibronectin, peaking at 100 µg ml−1 (before the precipitation point) of EMP. Type I collagen binding to EMP peaked at a low (1 µg ml−1) and narrow concentration range. Neither laminin‐1 nor type IV collagen bound to EMP. Collagen and fibronectin, bound to EMP, showed significantly reduced (> 50%) binding of both epithelial cells and PDLF compared with the equivalent concentration of these proteins alone. PDLF, but not epithelial cell, adhesion was rescued by increasing the EMP concentration. These findings show that EMP binds to wound extracellular matrix proteins and regulates their adhesive properties. Such interactions may favor fibroblast adhesion over epithelial cells, potentially promoting connective tissue regeneration.
Adoption of Food Safety and Quality Controls: Do Firm Characteristics Matter? Evidence from the Canadian Food Processing Sector
Authors: Herath Deepananda , Hassan Zuhair , Henson Spencer
Published: August 2007

This study explores the association between the adoption of food safety and quality assurance practices in the Canadian food processing sector and firm characteristics. A conceptual model is developed recognizing that the relative importance of a firm's incentives to adopt enhanced food safety and quality assurance practices is influenced by the firm's characteristics and activities. Binomial logit models are estimated to explore the association between adoption of various combinations of food safety and quality assurance practices including hazard analysis and critical control point (HACCP). The findings show that the adoption of food safety and quality practices varies widely between individual firms according to, among others, firm size, country of ownership and control, level of innovativeness, level of export orientation, forms of food safety inspection, and the subsector in which the firm operates. Incentives of being able to access foreign markets play an important role in influencing HACCP adoption.

La présente étude analyse le lien entre l'adoption de pratiques visant la salubrité et l'assurance de la qualité des aliments au sein de l'industrie canadienne de la transformation et les caractéristiques des entreprises. Nous avons élaboré un modèle conceptuel reconnaissant que l'importance relative des incitatifs qui motivent une entreprise à adopter des pratiques améliorées en matière de salubrité et d'assurance de la qualité des aliments est influencée par les caractéristiques et les activités de l'entreprise. Nous avons estimé des modèles logit binomiaux pour examiner le lien entre l'adoption de diverses combinaisons de pratiques visant la salubrité et l'assurance de la qualité des aliments, y compris les systèmes HACCP (analyse des risques et maîtrise des points critiques). Les résultats ont montré que l'adoption de ces pratiques variait considérablement d'une entreprise à l'autre en fonction, entre autres, de la taille de l'entreprise, du pays de propriété et de contrôle, du degré d'innovation, du degré de vocation exportatrice, des programmes d'inspection de la salubrité des aliments et du sous‐secteur dans lequel une entreprise évolue. La perspective de pénétrer les marchés étrangers joue un rôle important dans l'adoption de systèmes HACCP.
Vertical Economies and the Structure of U.S. Hog Farms
Authors: Azzam Azzeddine , Skinner Cari S.
Published: August 2007

Scale economies are often touted as the factor behind the trend in the structure of the U.S. hog industry toward fewer and larger hog farms. However, since hog production is multistage and farms either integrate or separate the stages, the appropriate measures are multistage economies. In theory, a smaller and, presumably, high‐cost operation, by the standards of single stage/output scale economies, may still be cost‐competitive if it enjoys multistage economies — that is if vertical scope economies more than offset stage‐specific scale diseconomies. Whether that holds in practice remains heretofore unexplored in the agricultural economics literature. Using a unique data set on hog farms in the U.S. Midwest, we estimate a multistage cost function and provide the first‐ever estimates of multistage economies, stage‐specific economies, and vertical scope economies in hog production.

Les économies d'échelle sont souvent soupçonnées d'être le facteur qui influence la tendance observée dans la structure de l'industrie porcine aux États‐Unis, soit des porcheries moins nombreuses mais de plus grande taille. Cependant, comme la production porcine est une production à plusieurs stades et que les producteurs peuvent choisir d'intégrer ces stades ou d'exploiter un seul stade, les mesures appropriées sont les économies d'échelle liées aux stades multiples. En théorie, une petite porcherie, qui a probablement des coûts élevés selon les critères des économies d'échelle liées à un seul stade, peut tout de même être concurrentielle quant aux coûts si elle profite des économies d'échelle liées aux stades multiples, c'est‐à‐dire si les économies de gamme verticales font plus que compenser les déséconomies d'échelle liées à un seul stade. La vérification de cette théorie dans la pratique demeure, jusqu'ici, inexploitée dans la littérature agroéconomique. En utilisant un ensemble de données sur des porcheries situées dans le Midwest américain, nous avons estimé une fonction de coût lié aux stades multiples et nous présentons les premières estimations d'économies d'échelle liées aux stades multiples, d'économies d'échelle liées à un seul stade et d'économies de gamme verticales dans la production porcine.
Accounting for Risk and Stability in Technology Adoption
Authors: Engler‐Palma Alejandra , Hoag Dana L.
Published: August 2007

The reasons for sluggish adoption of long‐run agricultural systems are not well understood. Researchers have identified risk and uneven cash flows as two likely culprits, yet the literature has done little to investigate their impacts simultaneously. We explore the unique influence of risk, risk preference, stability, and stability preferences on the adoption of long‐run investments. We developed risk‐stability‐segregated expected utility (RSSEU) to disentangle risk from stability and then compute the impacts of risk, stability, and preferences over a range of values found in previous studies. Results clearly demonstrate that adoption decisions are influenced differentially by risk and stability. An unstable income can overwhelm the risk effect or visa versa, depending on a person's preferences for risk and stability. Disentangling risk and stability could be very important if economists are to understand how decisions are made. For example, we found that the impact of risk on individual behavior is very low when the expected income flow is unstable. In this case, policies that smooth expected income over time will be more effective than ones that reduce risk. In contrast, risky technologies with a stable income path are more appropriately addressed with instruments like insurance or facilitating futures markets.

Les raisons de la lente adoption des systèmes agricoles à long terme ne sont pas bien comprises. Selon certains chercheurs, le risque et les flux de trésorerie irréguliers sont deux facteurs probables; toutefois peu de travaux se sont penchés sur leur impact simultané. Nous avons exploré l'influence du risque, des préférences pour le risque, de la stabilité et des préférences pour la stabilité sur l'adoption d'investissements à long terme. Nous avons élaboré une espérance d'utilité distincte risque‐stabilité(risk‐stability‐segregated expected utility) pour dégager le risque de la stabilité et pour calculer l'impact du risque, de la stabilité et des préférences à partir d'une série de valeurs tirées d’études antérieures. Les résultats ont clairement montré que les décisions d'adoption sont influencées différemment par le risque et la stabilité. Un revenu instable peut accabler l'effet du risque ou vice versa, selon les préférences d'une personne pour le risque et pour la stabilité. Si les économistes veulent comprendre de quelles façons les décisions sont prises, il serait important de dégager le risque de la stabilité. Par exemple, nous avons observé que l'impact du risque sur le comportement individuel est très faible lorsque les flux de revenus sont instables. Dans ce cas, les politiques qui adoucissent les revenus prévus au fil du temps seront plus efficaces que celles qui diminuent le risque. En revanche, des instruments tels que les assurances et les marchés à termes sont des moyens plus efficaces lorsque les technologies comportent des risques et que les revenus sont stables.
Clay Aquitards as Archives of Holocene Paleoclimate: δ18O and Thermal Profiling
Authors: Hendry M. Jim , Woodbury A.D.
Published: August 2007

Paleoclimatic conditions in the Holocene were reconstructed from a detailed vertical profile of pore water δ18O and a series of downhole thermal profiles at a thick, hydrogeologically simple, aquitard research site in the Northern Great Plains of Saskatchewan. Reconstructions were obtained using the theory of one‐dimensional diffusive transport and an empirical Bayesian inversion technique. Inversion of the δ18O profile shows that input signal consists of a sudden increase of +6‰ (corresponding to a temperature increase of about 18°C) at about 12,000 years before present (BP), after which no measurable change in δ18O is apparent to present day. This research shows, at this location, that there is no evidence of large amplitude temperature shifts in the Holocene and supports the commonly used assumption in ground water studies of constant atmospheric δ18O values throughout the Holocene. Inversion of the temperature profiles suggests the ground surface temperature increased primarily in the last half of the 20th century, with a peak temperature (about 3°C) circa 1990. For both profiles, the ability to resolve historical variability decays rapidly with time. For the temperature profiles, the decay in resolution precluded the development of reliable estimates of climatic conditions prior to about 1950 and, in the case of the δ18O profile, it prevented the precise definition of climate changes (e.g., Hypsithermal and Little Ice Age) in the Holocene.
Modeling Transient Discharge into a Tunnel Drilled in a Heterogeneous Formation
Authors: Perrochet Pierre , Dematteis Antonio
Published: August 2007

An analytical model is developed to predict transient discharge flow into a tunnel drilled at various speeds through a heterogeneous formation. This model relies on simplifying assumptions commonly enforced in hydrogeologic engineering, and combines the convolution and superposition principles to account for composite sections with arbitrary parametric contrasts. An application to the data monitored during the exploratory drilling of an Alpine tunnel confirms the validity of the approach.
Three‐Dimensional Flow in the Storative Semiconfining Layers of a Leaky Aquifer
Authors: Sepúlveda Nicasio
Published: August 2007

An analytical solution for three‐dimensional (3D) flow in the storative semiconfining layers of a leaky aquifer fully penetrated by a production well is developed in this article to provide a method from which accurate hydraulic parameters in the semiconfining layers can be derived from aquifer test data. The analysis of synthetic aquifer test data with the 3D analytical solution in the semiconfining layers provided more accurate optimal hydraulic parameters than those derived using the available quasi‐two‐dimensional (2D) solution. Differences between the 3D and 2D flow solutions in the semiconfining layers become larger when a no flow boundary condition is imposed at either at the top of the upper semiconfining layer or at the bottom of the lower semiconfining layer or when the hydraulic conductivity ratio of the semiconfining layer to the aquifer is larger than 0.001. In addition, differences between the 3D and 2D flow solutions in the semiconfining layers are illustrated when the thickness ratio of the semiconfining layer to the aquifer is changed. Analysis of water level data from two hypothetical and one real aquifer test showed that the 3D solution in the semiconfining layers provides lower correlation coefficients among hydraulic parameters than the 2D solution.
A Simple Pore Water Hydrogen Diffusion Syringe Sampler
Authors: Vroblesky Don A. , Chapelle Francis H. , Bradley Paul M.
Published: August 2007

Molecular hydrogen (H2) is an important intermediate product and electron donor in microbial metabolism. Concentrations of dissolved H2 are often diagnostic of the predominant terminal electron‐accepting processes in ground water systems or aquatic sediments. H2 concentrations are routinely measured in ground water monitoring wells but are rarely measured in saturated aquatic sediments due to a lack of simple and practical sampling methods. This report describes the design and development (including laboratory and field testing) of a simple, syringe‐based H2 sampler in (1) saturated, riparian sediments, (2) surface water bed sediments, and (3) packed intervals of a fractured bedrock borehole that are inaccessible by standard pumped methods.
Deep Air Sparging—15 to 46 m beneath the Water Table
Authors: Klinchuch Leslie A. , Goulding Nigel , James Steven R. , Gies Jerehmy J.
Published: August 2007

Air sparging can be successfully applied to deep aquifers to remediate significant hydrocarbon mass in order to ultimately reach a point at which monitored natural attenuation can manage dissolved phase plumes. Air sparging is typically applied in shallow ground water conditions, less than 15 m beneath the water table (bwt). Deep air sparging, 15 to 46 m bwt, is more challenging but a viable alternative for treatment of residual petroleum hydrocarbons and dissolved phase constituents within a thick smear zone. An application to remediate an aquifer impacted by gasoline‐range petroleum hydrocarbons at depths greater than 76 m below ground surface (bgs) and up to 40 m thick (vertically) is reported here. Deep air sparging at 15, 31, and 46 m bwt was assessed using diagnostic tools involving flow rate, pressure, tracer gas, water table elevation, vapor concentration, and ground water chemistry measurements. The diagnostic tools identified preferential flow directions and a maximum depth of effective air injection. The full‐scale deep air sparging/soil vapor extraction (SVE) system removed more than 150,000 kg of hydrocarbon mass at the study site over a 3‐year period and ultimately greater than 100,000 kg/year with system expansion.
Comparison of Factorial and Scenario Analysis Methods for Assessing Uncertainty in the Design of Permeable Reactive Barriers
Authors: Painter Brett D.M. , Milke Mark W.
Published: August 2007

The method chosen to incorporate uncertainty into remediation design can have a significant effect on the feasibility and potential success of a remediation project. Three methods for analyzing uncertainty are explored to better allow their application to optimization of remediation designs: scenario analysis combined with one‐way sensitivity analysis, factorial analysis, and fractional factorial analysis. The three methods are analyzed using a deterministic optimization model for design of a permeable reactive barrier (PRB) to remediate nitrate contamination. Although the combined scenario/one‐way sensitivity approach is simpler than the factorial approaches, it has the comparative disadvantage of missing potentially important interactions between design inputs. Fractional factorial analysis is shown to have the added advantage of being useful in screening the importance of a number of model inputs without a large number of computer experiments. Hypothetical examples highlight the likely importance of uncertainty in hydraulic conductivity when choosing the optimal PRB design specification and the potential interaction of this input and the incoming pollutant concentration.
Combined Treatment of Perchlorate and RDX in Ground Water Using a Fluidized Bed Reactor
Authors: Fuller Mark E. , Hatzinger Paul B. , Condee Charles W. , Togna A. Paul
Published: August 2007

A bench‐scale study was conducted to assess the effectiveness of biological treatment of comingled perchlorate and hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) in ground water using fluidized bed reactors (FBRs). In addition, the ability of FBRs to treat low concentrations of perchlorate was examined. Pilot‐scale FBRs were fed either acetic acid or molasses as an electron donor to facilitate simultaneous perchlorate and RDX reduction. The acetic acid‐fed FBR consistently removed perchlorate from an influent level of 100 μg/L to below 6 μg/L, and values below the method detection limit of 1 μg/L occurred approximately 70% of the time. RDX breakthrough from all FBRs was minimal due to sorption of the explosive on the granulated activated carbon media, but mass balance calculations indicated that more than 99.5% of the total RDX entering the acetic acid‐fed FBR was biologically degraded. Approximately 80% of the RDX fed to the control FBR (i.e., no substrate addition) was accounted for at the end of the study; the remainder was assumed to have been degraded. Molasses was much less effective than acetic acid as an electron donor for treatment of perchlorate and RDX. This work demonstrates that combined treatment of perchlorate and RDX is feasible using FBR technology, and that very low levels of perchlorate (less than 100 μg/L) can be effectively treated in an FBR.
MODELING THE LONG TERM IMPACTS OF USING RIGID STRUCTURES IN STREAM CHANNEL RESTORATION1
Authors: Niezgoda Sue L. , Johnson Peggy A.
Published: August 2007

Abstract: Natural channel designs often incorporate rigid instream structures to protect channel banks, provide grade control, promote flow deflection, or otherwise improve channel stability. The long term impact of rigid structures on natural stream processes is relatively unknown. The objective of this study was to use long term alluvial channel modeling to evaluate the effect of rigid structures on channel processes and assess current and future stream channel stability. The study was conducted on Oliver Run, a small stream in Pennsylvania relocated due to highway construction. Field data were collected for one year along the 107 m reach to characterize the stream and provide model input, calibration, and verification data. FLUVIAL‐12 was used to evaluate the long term impacts of rigid structures on natural channel adjustment, overall channel stability, and changing form and processes. Based on a consideration of model limitations and results, it was concluded that the presence of rigid structures reduced channel width‐to‐depth ratios, minimized bed elevation changes due to long term aggradation and degradation, limited lateral channel migration, and increased the mean bed material particle size throughout the reach. Results also showed how alluvial channel modeling can be used to improve the stream restoration design effort.
FLOW ANALYSIS OF LANDSLIDE DAMMED LAKE WATERSHEDS: A CASE STUDY1
Authors: Lee Kwan Tun , Lin Yi‐Ting
Published: August 2007

Abstract: The Chi‐Chi earthquake, which occurred on September 21, 1999, and had a magnitude of 7.3 on the Richter scale, resulted in an extensive landslide that blocked the Ching‐Shui Creek in Taiwan, forming a large lake with a storage volume of 40 million m3. This paper describes an analytical procedure used to perform flow analysis of the Tsao‐Ling watershed, which includes the new landslide dammed lake. In this study, a digital elevation model was applied to obtain the watershed geomorphic factors and stage‐area storage function of the landslide dammed lake. Satellite images were used to identify the landslide area and the land cover change that occurred as a result of the earthquake. Two topography‐based runoff models were applied for long term and short term streamflow analyses of the watershed because the watershed upstream of the landslide dam was ungauged. The simulated daily flow and storm runoff were verified using limited available measured data in the watershed, and good agreement was obtained. The proposed analytical procedure for flow analysis is considered promising for application to other landslide dammed lake watersheds.
MULTITEMPORAL SCALE HYDROGRAPH PREDICTION USING ARTIFICIAL NEURAL NETWORKS1
Authors: Melesse Assefa M. , Wang Xixi
Published: August 2007

Abstract: An artificial neural network (ANN) provides a mathematically flexible structure to identify complex nonlinear relationship between inputs and outputs. A multilayer perceptron ANN technique with an error back propagation algorithm was applied to a multitime‐scale prediction of the stage of a hydro‐logically closed lake, Devils Lake (DL), and discharge of the Red River of the North at Grand Forks station (RR‐GF) in North Dakota. The modeling exercise used 1 year (2002), 5 years (1998–2002), and 27 years (1975–2002) of data for the daily, weekly, and monthly predictions, respectively. The hydrometeorological data (precipitations P(t), P(t‐1), P(t‐2), P(t‐3), antecedent runoff/lake stage R(t‐1) and air temperature T(t) were partitioned for training and for testing to predict the current hydro‐graph at the selected DL and RR‐GF stations. Performance of ANN was evaluated using three combinations of daily datasets (Input I = P(t)), P(t‐l), P(t‐2), P(t‐3), T(t) and R(t‐l); Input II = Input‐l less P(t) P(t‐l), P(t‐2), P(t‐3); and Input III = Input‐II less T(t)). Comparison of the model output using Input I data with the observed values showed average testing prediction efficiency (E) of 86 percent for DL basin and 46 percent for RR‐GF basin, and higher efficiency for the daily than monthly simulations.
RUNOFF EVENT IMPACTS ON A WATER SUPPLY RESERVOIR: SUSPENDED SEDIMENT LOADING, TURBID PLUME BEHAVIOR, AND SEDIMENT DEPOSITION1
Authors: Effler Steven W. , Matthews David A. , Kaser Josef W. , Prestigiacomo Anthony R. , Smith David G.
Published: August 2007

Abstract: The impacts of runoff events on external suspended solids loading to Schoharie Reservoir, New York, and patterns of light scattering and sediment deposition in this reservoir are assessed. The assessment is based on monitoring of suspended solids concentrations in the reservoir's primary tributary, detailed vertical profiles of optical backscattering (a surrogate measure of light scattering) in the reservoir water column, and analysis of sediment trap collections, over a seven‐month interval of high runoff. These impacts are reported to be tightly temporally coupled and strongly positively related to the magnitude of runoff events. The primary tributary entered the reservoir as a plunging inflow during runoff events, causing conspicuous subsurface peaks in light scattering, with vertical patterns that varied strongly for different events. Deposition quantified by near‐bottom trap deployments is reported to be more representative than results from metalimnetic deployments that were generally within, rather than below, the turbid layers. Direct inputs of sediment, transported by density currents, are found to drive deposition, rather than resuspension/redeposition. More than 50 percent of the reported deposition occurred in less than 15 percent of the study period, associated with the four largest runoff events.
Acute regulation of mouse AE2 anion exchanger requires isoform‐specific amino acid residues from most of the transmembrane domain
Authors: Stewart A. K. , Kurschat C. E. , Vaughan‐Jones R. D. , Shmukler B. E. , Alper S. L.
Published: August 2007

The widely expressed anion exchanger polypeptide AE2/SLC4A2 is acutely inhibited by acidic intracellular (pHi), by acidic extracellular pH (pHo), and by the calmodulin inhibitor, calmidazolium, whereas it is acutely activated by NH4+. The homologous erythroid/kidney AE1/SLC4A1 polypeptide is insensitive to these regulators. Each of these AE2 regulatory responses requires the presence of AE2's C‐terminal transmembrane domain (TMD). We have now measured 36Cl− efflux from Xenopus oocytes expressing bi‐ or tripartite AE2–AE1 chimeras to define TMD subregions in which AE2‐specific sequences contribute to acute regulation. The chimeric AE polypeptides were all functional at pHo 7.4, with the sole exception of AE2(1‐920)/AE1(613‐811)/AE2(1120‐1237). Reciprocal exchanges of the large third extracellular loops were without effect. AE2 regulation by pHi, pHo and NH4+ was retained after substitution of C‐terminal AE2 amino acids 1120–1237 (including the putative second re‐entrant loop, two TM spans and the cytoplasmic tail) with the corresponding AE1 sequence. In contrast, the presence of this AE2 C‐terminal sequence was both necessary and sufficient for inhibition by calmidazolium. All other tested TMD substitutions abolished AE2 pHi sensitivity, abolished or severely attenuated sensitivity to pHo and removed sensitivity to NH4+. Loss of AE2 pHi sensitivity was not rescued by co‐expression of a complementary AE2 sequence within separate full‐length chimeras or AE2 subdomains. Thus, normal regulation of AE2 by pH and other ligands requires AE2‐specific sequence from most regions of the AE2 TMD, with the exceptions of the third extracellular loop and a short C‐terminal sequence. We conclude that the individual TMD amino acid residues previously identified as influencing acute regulation of AE2 exert that influence within a regulatory structure requiring essential contributions from multiple regions of the AE2 TMD.
Multiple vesicle recycling pathways in central synapses and their impact on neurotransmission
Authors: Kavalali Ege T.
Published: August 2007

Short‐term synaptic depression during repetitive activity is a common property of most synapses. Multiple mechanisms contribute to this rapid depression in neurotransmission including a decrease in vesicle fusion probability, inactivation of voltage‐gated Ca2+ channels or use‐dependent inhibition of release machinery by presynaptic receptors. In addition, synaptic depression can arise from a rapid reduction in the number of vesicles available for release. This reduction can be countered by two sources. One source is replenishment from a set of reserve vesicles. The second source is the reuse of vesicles that have undergone exocytosis and endocytosis. If the synaptic vesicle reuse is fast enough then it can replenish vesicles during a brief burst of action potentials and play a substantial role in regulating the rate of synaptic depression. In the last 5 years, we have examined the impact of synaptic vesicle reuse on neurotransmission using fluorescence imaging of synaptic vesicle trafficking in combination with electrophysiological detection of short‐term synaptic plasticity. These studies have revealed that synaptic vesicle reuse shapes the kinetics of short‐term synaptic depression in a frequency‐dependent manner. In addition, synaptic vesicle recycling helps maintain the level of neurotransmission at steady state. Moreover, our studies showed that synaptic vesicle reuse is a highly plastic process as it varies widely among synapses and can adapt to changes in chronic activity levels.
Development of gerbil medial superior olive: integration of temporally delayed excitation and inhibition at physiological temperature
Authors: Chirila Florin V. , Rowland Kevin C. , Thompson Jesse M. , Spirou George A.
Published: August 2007

The sensitivity of medial superior olive (MSO) neurons to tens of microsecond differences in interaural temporal delay (ITD) derives in part from their membrane electrical characteristics, kinetics and timing of excitatory and inhibitory inputs, and dendrite structure. However, maturation of these physiological and structural characteristics are little studied, especially in relationship to the onset of auditory experience. We showed, using brain slices at physiological temperature, that MSO neurons exhibited sensitivity to simulated temporally delayed (TD) EPSCs (simEPSC), injected through the recording electrode, by the initial phase of hearing onset at P10, and TD sensitivity was reduced by block of low threshold potassium channels. The spike generation mechanism matured between P10 and P16 to support TD sensitivity to adult‐like excitatory stimuli (1–4 ms duration) by P14. IPSP duration was shorter at physiological temperature than reported for lower temperatures, was longer than EPSP duration at young ages, but approached the duration of EPSPs by P16, when hearing thresholds neared maturity. Dendrite branching became less complex over a more restricted time frame between P10 and P12. Because many physiological and structural properties approximated mature values between P14 and P16, we studied temporal integration of simEPSCs and IPSPs at P15. Only a narrow range of relative onset times (< 1 ms) yielded responses showing sensitivity to TD. We propose that shaping of excitatory circuitry to mediate TD sensitivity can begin before airborne sound is detectable, and that inhibitory inputs having suboptimal neural delays may then be pruned by cellular mechanisms activated by sensitivity to ITD.
Compartmentalized NMDA receptor signalling to survival and death
Authors: Soriano Francesc X. , Hardingham Giles E.
Published: August 2007

The ability of Ca2+ influx through the N‐methyl d‐aspartate subclass of glutamate receptor (NMDA receptor) to both kill neurons and to promote survival under different circumstances is well established. Here we discuss the signal pathways that mediate this dichotomous signalling, and the factors that influence whether an NMDA receptor‐dependent Ca2+ signal results in a net pro‐survival or pro‐death effect. The magnitude of NMDA receptor activation, be it intensity or duration, is of course very important in determining the nature of the response to an episode of NMDA receptor activity, with excitotoxic death pathways requiring higher levels than survival pathways. However, the NMDA receptor is not merely a conduit for Ca2+ influx: the consequences of NMDA receptor activity can be influenced by signalling molecules that physically associate with the NMDA receptor or indeed the location (synaptic versus extrasynaptic) of the receptor. Furthermore, we discuss the possibility that the Ca2+ effectors of survival and death are in different subcellular locations, and thus depend on the spatial characteristics of the Ca2+ transient. A greater understanding of these issues may point to ways of selectively blocking pro‐death signalling in neurological disorders such as stroke, where global NMDA receptor antagonists have proved ineffective.
Cell tracking using magnetic resonance imaging
Authors: Hoehn Mathias , Wiedermann Dirk , Justicia Carles , Ramos‐Cabrer Pedro , Kruttwig Klaus , Farr Tracy , Himmelreich Uwe
Published: August 2007

Cell tracking by in vivo magnetic resonance imaging (MRI) requires strategies of labelling the cells with MRI contrast agents. The principal routes to achieve efficient cell labelling for neurological applications are discussed with methodological advantages and caveats. Beyond temporo‐spatial localization of labelled cells, the investigation of functional cell status is of great interest to allow studies of functional cell dynamics. The two major approaches to reach this goal, use of responsive contrast agents and generation of transgenic cell lines, are discussed.
Common Sequence Variants in the
LOXL1
Gene Confer Susceptibility to Exfoliation Glaucoma
Authors: Thorleifsson Gudmar , Magnusson Kristinn P. , Sulem Patrick , Walters G. Bragi , Gudbjartsson Daniel F. , Stefansson Hreinn , Jonsson Thorlakur , Jonasdottir Adalbjorg , Jonasdottir Aslaug , Stefansdottir Gerdur , Masson Gisli , Hardarson Gudmundur A. , Petursson Hjorvar , Arnarsson Arsaell , Motallebipour Mehdi , Wallerman Ola , Wadelius Claes , Gulcher Jeffrey R. , Thorsteinsdottir Unnur , Kong Augustine , Jonasson Fridbert , Stefansson Kari
Published: August 2007

Glaucoma is a leading cause of irreversible blindness. A genome-wide search yielded multiple single-nucleotide polymorphisms (SNPs) in the 15q24.1 region associated with glaucoma. Further investigation revealed that the association is confined to exfoliation glaucoma (XFG). Two nonsynonymous SNPs in exon 1 of the gene
LOXL1
explain the association, and the data suggest that they confer risk of XFG mainly through exfoliation syndrome (XFS). About 25% of the general population is homozygous for the highest-risk haplotype, and their risk of suffering from XFG is more than 100 times that of individuals carrying only low-risk haplotypes. The population-attributable risk is more than 99%. The product of
LOXL1
catalyzes the formation of elastin fibers found to be a major component of the lesions in XFG.
NUCLEAR MEDIUM EFFECTS IN J/Ψ PRODUCTION AT HERA-B
Authors: AYALA FILHO A. L. , BRENNER MARIOTTO C. , GONÇALVES V. P.
Published: August 2007

In this paper we estimate the influence of the shadowing effect and initial state parton energy loss in the quarkonium production at HERA-B. We analyze the xF behavior of the effective exponent α(xF) and present a comparison with the preliminary HERA-B data for J/Ψ production. Moreover, we estimate the magnitude of these effects in the J/Ψ production at RHIC.
CHAIN CONFIGURATIONS IN LIGHT NUCLEI
Authors: TORILOV S. YU. , GRIDNEV K. A. , GREINER W.
Published: August 2007

We consider a semiclassical model of light nuclei, where the nucleus has a crystal-like shape and is built solely from α-particles. We analyze the role of linear configurations in this model, which correspond to super-deformed nuclei. The strong deformed shape for the doubly even nuclei from 12 C to 24 Mg has been determined according to this model. The obtained results show a good agreement with the experimental data.
UNFOLDING CONTINUOUS PHOTON SPECTRUM EMITTED FROM 90Sr-90Y IN EQUILIBRIUM
Authors: ALMAZ E. , CENGIZ A. , TARTAR A.
Published: August 2007

This paper presents an experiment with the 2×2 inch NaI(Tl) detector to measure the internal bremsstrahlung of 90 Sr -90 Y in equilibrium beta particle emitters using the beta-stopper method in the range 10–1750 keV. The Gold algorithm is applied to unfold the internal bremsstrahlung spectrum of 90 Sr -90 Y beta source. Unfolded IB spectrum is compared with the KUB theory. There is good agreement between the theory and the unfolded measured spectrum in the energy range below 1000 keV. Beyond this energy, there are discrepancies between the theory and unfolded spectrum.
A review of the engineering behaviour of soils and rocks with respect to groundwater
Authors: Bell F.G. , Cripps J.C. , Culshaw M.G.
Published: August 2007

The effect of groundwater on the engineering behaviour of soils and rocks is of fundamental importance, indeed to paraphrase Tergazhi — without water there would be no soil mechanics. This paper reviews these effects in terms of the variation in the properties and behaviour of soils and rocks brought about by changes in moisture content, and associated changes, notably in effective stress, and by the dissolution of parts of the rock or soil mass.
Hypoxia divergently regulates production of reactive oxygen species in human pulmonary and coronary artery smooth muscle cells
Authors: Wu Winnie , Platoshyn Oleksandr , Firth Amy L. , Yuan Jason X.-J.
Published: August 2007

Acute hypoxia causes pulmonary vasoconstriction and coronary vasodilation. The divergent effects of hypoxia on pulmonary and coronary vascular smooth muscle cells suggest that the mechanisms involved in oxygen sensing and downstream effectors are different in these two types of cells. Since production of reactive oxygen species (ROS) is regulated by oxygen tension, ROS have been hypothesized to be a signaling mechanism in hypoxia-induced pulmonary vasoconstriction and vascular remodeling. Furthermore, an increased ROS production is also implicated in arteriosclerosis. In this study, we determined and compared the effects of hypoxia on ROS levels in human pulmonary arterial smooth muscle cells (PASMC) and coronary arterial smooth muscle cells (CASMC). Our results indicated that acute exposure to hypoxia (Po2 = 25–30 mmHg for 5–10 min) significantly and rapidly decreased ROS levels in both PASMC and CASMC. However, chronic exposure to hypoxia (Po2 = 30 mmHg for 48 h) markedly increased ROS levels in PASMC, but decreased ROS production in CASMC. Furthermore, chronic treatment with endothelin-1, a potent vasoconstrictor and mitogen, caused a significant increase in ROS production in both PASMC and CASMC. The inhibitory effect of acute hypoxia on ROS production in PASMC was also accelerated in cells chronically treated with endothelin-1. While the decreased ROS in PASMC and CASMC after acute exposure to hypoxia may reflect the lower level of oxygen substrate available for ROS production, the increased ROS production in PASMC during chronic hypoxia may reflect a pathophysiological response unique to the pulmonary vasculature that contributes to the development of pulmonary vascular remodeling in patients with hypoxia-associated pulmonary hypertension.
Effects of reduced tidal volume ventilation on pulmonary function in mice before and after acute lung injury
Authors: Thammanomai Apiradee , Majumdar Arnab , Bartolák-Suki Erzsébet , Suki Béla
Published: August 2007

We investigated the influence of load impedance on ventilator performance and the resulting effects of reduced tidal volume (Vt) on lung physiology during a 30-min ventilation of normal mice and 10 min of additional ventilation following lavage-induced injury at two positive end-expiratory pressure (PEEP) levels. Respiratory mechanics were regularly monitored, and the lavage fluid was tested for the soluble E-cadherin, an epithelial cell adhesion molecule, and surfactant protein (SP) B. The results showed that, due to the load dependence of the delivered Vt from the small-animal ventilator: 1) uncontrolled ventilation in normal mice resulted in a lower delivered Vt (6 ml/kg at 3-cmH2O PEEP and 7 ml/kg at 6-cmH2O PEEP) than the prescribed Vt (8 ml/kg); 2) at 3-cmH2O PEEP, uncontrolled ventilation in normal mice led to an increase in lung parenchymal functional heterogeneity, a reduction of SP-B, and an increase in E-cadherin; 3) at 6-cmH2O PEEP, ventilation mode had less influence on these parameters; and 4) in a lavage model of acute respiratory distress syndrome, delivered Vt decreased to 4 ml/kg from the prescribed 8 ml/kg, which resulted in severely compromised lung function characterized by increases in lung elastance, airway resistance, and alveolar tissue heterogeneity. Furthermore, the low Vt ventilation also resulted in poor survival rate independent of PEEP. These results highlight the importance of delivering appropriate Vt to both the normal and injured lungs. By leaving the Vt uncompensated, it can significantly alter physiological and biological responses in mice.
Assessment of Suitability of Thrombolysis in Middle Cerebral Artery Infarction: A Proof of Concept Study of a Stereologically-Based Technique
Authors: Phan Thanh G. , Donnan Geoffrey A. , Koga Masatoshi , Mitchell L. Anne , Molan Maurice , Fitt Gregory , Chong Winston , Holt Michael , Reutens David C.
Published: August 2007

Background: The extent of cerebral ischemia, assessed by the Alberta Stroke Program Early CT Score (ASPECTS) method and unaided visual determination of the CT Summit Criterion, correlates with increased risk of intracerebral hemorrhage following rt-PA administration. Concerns about the accuracy of the unaided visual assessment in the estimation of infarct size and the conservative nature of the ASPECTS method led us to develop a new method (MCAGrid) based on stereological grid counting and a digital atlas of the middle cerebral artery (MCA) infarct territory. Methods: We tested the hypotheses that the stereological method increases the accuracy of infarct estimation and that the number of patients deemed eligible for thrombolysis is greater with this method than with existing methods. Four experienced radiologists with extensive neuroradiological experience examined the CT images of 19 patients with MCA territory stroke and determined patient eligibility for thrombolysis by: unaided visual determination of the CT Summit Criterion, MCAGrid, and the ASPECTS score. The χ2 test was used to compare the differences in the number of patients deemed ‘eligible’ for thrombolysis by the 3 imaging methods. Further, the unaided visual assessment and MCAGrid were compared with volumes calculated following manual segmentation of infarct, and the sensitivity, specificity and positive and negative likelihood ratios for these techniques were calculated. Results: In general, MCAGrid was better than unaided visual assessment in the prediction of >1/3 involvement of the MCA territory by infarct. The number of patients considered as ‘eligible’ for thrombolysis based on imaging criteria was significantly lower when ASPECTS criteria (15/76) were used than when unaided visual determination of the CT Summit Criterion (32/76; p < 0.01) or MCAGrid (59/76; p < 0.001) criteria were used. Conclusion: The choice of methods for rating infarct extent affects the number of patients ‘eligible’ for thrombolysis significantly. Furthermore, MCAGrid increased the accuracy with which infarct extent was estimated. These results provide justification for a prospective study of this technique in the setting of acute stroke.
Increase of Stroke Incidence after Weekend Regardless of Traditional Risk Factors: Takashima Stroke Registry, Japan; 1988–2003
Authors: Turin Tanvir Chowdhury , Kita Yoshikuni , Murakami Yoshitaka , Rumana Nahid , Sugihara Hideki , Morita Yutaka , Hirose Kunihiko , Okayama Akira , Nakamura Yasuyuki , Ueshima Hirotsugu
Published: August 2007

Background and Purpose: The study purpose was to identify patterns of variation in stroke incidence among days of the week and examine if it is modified by conventional stroke risk factors: hypertension, diabetes, drinking and smoking. Methods: Data were obtained from the Takashima Stroke Registry, which covers a stable population of roughly 55,000 residents of Takashima County in central Japan. A total of 1,773 stroke cases (men: 943 and women: 830) occurred between 1988 and 2003. We divided the days into 3 groups: ‘weekend’, ‘after weekend’ and ‘rest of the week’, and calculated stroke incidence rates and incidence rate ratios. To identify the effect of conventional risk factors on the variation, proportion of differences between observed and expected stroke incidences were considered. Results: The stroke incidence for the after weekend group (250.1 per 100,000 person years, 95% CI: 222.0–278.3) was higher than for the other day groups among men. The after weekend increase was observed mainly among older men aged 65 years or more. Among the stroke subtypes, the incidence for cerebral infarction was highest in the after weekend group (857.2, 95% CI: 730.6–983.8) and was 1.37 times (95% CI: 1.12–1.68) higher than in the rest of the week group. Tendency of after weekend increase was observed regardless of the presence or absence of risk factor history. Conclusions: Week day variation for stroke was observed predominantly among older men regardless of presence and absence of risk factor history. Information about the weekly trend regarding episode of increased stroke incidence can be used as a surrogate predictor for stroke onset and would be helpful in designing more effective insights for preventive strategies.