bluuebunny/crossref_metadata_2025 huggingface dataset:
Learning to be a good orthographic reader
Authors: Castles Anne , Nation Kate
Published: February 2008

Recent years have brought about rapid advances in our understanding of reading and how it develops, particularly in relation to the importance of alphabetic coding skills. However, much less has been known about the transition from alphabetic decoding to the rapid and automatic orthographic recognition of words, which is the hallmark of skilled reading. The purpose of this special issue is to focus specifically on orthographic processes in reading and how they are acquired. The present paper provides an overview of the special issue, drawing attention to key themes that run through the various contributions.
The neuronal glycine transporter GLYT2 associates with membrane rafts: functional modulation by lipid environment
Authors: Núñez Enrique , Alonso‐Torres Pablo , Fornés Amparo , Aragón Carmen , López‐Corcuera Beatriz
Published: February 2008

The neuronal glycine transporter GLYT2 is a plasma membrane protein that removes the neurotransmitter glycine from the synaptic cleft, thereby aiding the pre‐synaptic terminal reloading and the termination of the glycinergic signal. Missense mutations in the gene encoding GLYT2 (SLC6A5) cause hyperekplexia in humans. The activity of GLYT2 seems to be highly regulated. In this report, we demonstrate that GLYT2 is associated with membrane rafts in the plasma membrane of brainstem terminals and neurons. The transporter is localized to Triton X‐100‐insoluble light synaptosomal membranes together with flotillin‐1, a marker protein for membrane rafts, in a methyl‐β‐cyclodextrin (MβCD)‐sensitive manner. In brainstem primary neurons, the GLYT2 punctuate pattern visualized by confocal microscopy was modified by cholesterol depletion with MβCD, unlike other non‐raft neuronal markers. GLYT2‐associated gold particles were observed by electron microscopy on purified rafts from brainstem synaptosomes. Furthermore, either in brainstem terminals and cultured neurons, the pharmacological reduction of the levels of raft components, cholesterol and sphingomyelin, impairs both the association of GLYT2 with membrane rafts and its transport activity. Thus, GLYT2 may require membrane raft location for optimal function, and therefore the lipid environment may constitute a new mechanism to modulate GLYT2.
Rediscovering the Taproot: Is Classical Pragmatism the Route to Renew Public Administration?
Authors: Shields Patricia M.
Published: February 2008

The origins of the influential American philosophy classical pragmatism and of American public administration overlap. On the surface, it appears that classical pragmatism had no influence on the emerging field of American public administration. Why were the two never properly wed? This essay first traces the historical connections that link public administration and classical pragmatism. Second, using a framework that is simple to remember, the tenets of classical pragmatism—practical, pluralistic, participatory, and provisional—are explored and applied to public administration. The marriage of classical pragmatism and public administration should prove endlessly fertile.
Sharpening a Knife Cleverly: Organizational Change, Policy Paradox, and the “Weaponizing” of Administrative Reforms
Authors: Durant Robert F.
Published: February 2008

Prior research has leavened substantially our understanding of how, why, and with what consequences public organizations respond to pressures for administrative reforms. Left underdeveloped theoretically, however, is the hypothesis that agency actors may also assess the ability of administrative reforms both to advance their policy goals and to become “weapons” in battles within agencies for advancing them. To illustrate this possibility, this article analyzes how the Clinton administration’s National Performance Review and related Defense Reform Initiative interacted with its efforts to “green” the U.S. military in the post–Cold War era. Analysis of this clash between defense and environmental values indicates that (1) agency actors did evaluate the potential impacts of administrative reforms on their policy goals before supporting or opposing them; (2) they tried to hijack those reforms as weapons for advancing their policy goals in intraorganizational battles; and (3) the “weaponizing” of these reforms produced policy complications and consequences that proponents neither anticipated nor welcomed. Thus, reform in the administrative domain created unanticipated consequences by spilling over into the policy domain and being hijacked, weaponized, or otherwise miscarried or used opportunistically in intraorganizational policy battles. The study concludes by arguing that these dynamics merit more attention than they have received from either administrative reform proponents or researchers seeking to develop theories of administrative reform.
Examining the Nature and Significance of Leadership in Government Organizations
Authors: Trottier Tracey , Van Wart Montgomery , Wang XiaoHu
Published: February 2008

Though the mainstream organizational literature has advanced in the last 20 years with the integration of transformational and distributed leadership theories, as well as genuine attempts at comprehensive models, the public sector literature has lagged, especially in utilizing large‐scale empirical studies. This study takes advantage of a very large government data set to test the utility of one of the best known theories, the “full range” leadership theory of Bernard Bass. It addresses three important research questions: How inclusive is Bass’s operational definition of leadership? How much of an impact do Bass’s leadership competencies have on follower satisfaction? Finally, how important is transformational leadership compared to transactional leadership in government settings? The results indicate that Bass’s broad definition of leadership comes quite close to capturing what federal employees perceive to be effective leadership. The relationship between good leadership in an organization and follower satisfaction is also presented as an important outcome in the federal government. Finally, both transactional and transformational leadership are perceived as important in the federal government, although transformational leadership is considered slightly more important even after shifting one important factor, individualized consideration, back to the transactional model.
Turnover among City Managers: The Role of Political and Economic Change
Authors: McCabe Barbara Coyle , Feiock Richard C. , Clingermayer James C. , Stream Christopher
Published: February 2008

Executive turnover can have profound effects on city policies, programs, and commitments such as contracting or issuing debt. This article identifies how political changes, reflected in the composition of the city council, and economic changes in the community influence city manager turnover. Analysis of manager turnover patterns in 143 large U.S. cities with council‐manager governments from 1987 to 1999 allows us to distinguish “push” and “pull” factors that can induce city managers to leave their jobs. The empirical analysis demonstrates that political conflict and economic development can influence the likelihood that a city manager will exit a community, but these effects can be complex. In particular, the influence of community economic development on turnover includes a temporal dimension not revealed in previous research. We conclude by discussing the findings’ implications for career patterns in city management.
Citizenship and the production of landscape and knowledge in contemporary Canadian nuclear fuel waste management
Authors: STANLEY ANNA
Published: February 2008

This article considers the relationship between Aboriginal peoples in Canada and the nuclear industry in the contemporary geography of Canadian Nuclear Fuel Waste management. It explores the ways in which the knowledge produced by the Canadian nuclear industry, through the work of the Nuclear Waste Management Organization about nuclear waste, its management and its effects, gains primacy over the knowledge and experience of the Serpent River First Nation (SRFN). I identify a discourse of citizenship as instrumental to pursuing and maintaining industry control over knowledge produced about this policy issue. Of particular interest is the manner in which this discourse operates to disqualify and subjugate the alternative experiences of, and knowledge about, nuclear waste and radioactivity contained in the oral histories and testimonies of the SRFN. I suggest that the discourse marginalizes the knowledge of the SRFN through the use of scaled representations of identity and place, to create a particular ‘Canadian’ account of the fuel chain and its effects.
The imprints of tourism on Puerto Vallarta, Jalisco, Mexico
Authors: EVERITT JOHN , MASSAM BRYAN H. , CHÁVEZ‐DAGOSTINO ROSA M. , SÁNCHEZ RODRIGO ESPINOSA , ROMO EDMUNDO ANDRADE
Published: February 2008

Tourism is a major economic activity with significant social, political and environmental repercussions that affect people and places in virtually every corner of the contemporary world. This study focuses on tourism development in Puerto Vallarta (PV), Jalisco, Mexico. The region has been almost completely transformed by this industry in a relatively short period of time since the development of the first major hotel in 1948. The article begins by discussing the development of PV as a place, as a coastal tourist resort and also as a set of quite different cultural landscapes. Building on this we specifically identify, describe and discuss some of the major cultural imprints of tourism upon PV, including hotels, restaurants, the gay community, art galleries and Internet cafes as well as ecological imprints of
Investigation of New Epoxy Resins for the Gel Casting of Ceramics
Authors: Mao Xiaojian , Shimai Shunzo , Dong Manjiang , Wang Shiwei
Published: February 2008

Four water‐soluble epoxy resins that might be useful for aqueous gelation in an air atmosphere were studied for the gel casting of ceramics. The investigation was mainly focused on aspects of solubility, viscosity, suspension viscosity, and gelled body properties. The results demonstrated that ethylene glycol diglycidyl ether (EGDGE) and glycerol polyglycidyl ether (GPGE) were excellent for the gel casting of ceramics, and that polyethylene glycol diglycidyl ether and resorcinol diglycidyl ether were not suitable under the tested experimental conditions. The addition of 0.25 mL/g hardener was preferable for both EGDGE and GPGE.
Apolipoprotein E‐polymorphism, frailty and mortality in older adults
Authors: Rockwood Kenneth , Nassar Bassam , Mitnitski Arnold
Published: February 2008

Although apolipoprotein E (ApoE) polymorphism is associated with variable risks of several illnesses, and with mortality, no persuasive relationship has been demonstrated with frailty. Here, the clinical examination cohort (n= 1452 older adults, aged 70+ years at baseline) of the Canadian Study of Health and Aging was evaluated, with 5‐year follow‐up data. Frailty was defined using both the phenotypic definition from the Cardiovascular Health Study (Frailty‐CHS) and the ‘Frailty Index’, from which age‐specific trajectories of deficit accumulation can be estimated. In age‐sex adjusted analyses, people with ApoE 4 allele had a higher risk of death (hazard ratio [HR]= 1.20; 95% confidence interval: 1.01–1.45), but this relationship was not significant when adjusted for cognitive impairment (1.06; 95% confidence interval: 0.88–1.27). There was no association between frailty and ApoE polymorphism, defined in age‐sex adjusted models either as Frailty‐CHS (ApoE4 HR 1.17; 95% confidence interval: 0.98–1.40, frailty HR 1.37; 95% confidence interval: 1.28–1.46) or by the Frailty Index (ApoE4 HR 1.07; 95% confidence interval: 0.90–1.29, frailty HR 35.3; 95% confidence interval: 20.4–61.1). The data do not support an association between ApoE polymorphism and frailty. This result did not depend on how frailty was defined.
Gap junctional communication in human osteoclasts in vitro and in vivo
Authors: Schilling A. F. , Filke S. , Lange T. , Gebauer M. , Brink S. , Baranowsky A. , Zustin J. , Amling M.
Published: February 2008

Bone‐forming cells are known to be coupled by gap junctions, formed primarily by connexin43 (Cx43). The role of Cx43 in osteoclasts has so far only been studied in rodents, where Cx43 is important for fusion of mononuclear precursors to osteoclasts. Given the potential importance for human diseases with pathologically altered osteoclasts, we asked whether a similar influence of Cx43 can also be observed in osteoclasts of human origin. For this purpose, Cx43 mRNA expression was studied in a time course experiment of human osteoclast differentiation by RT‐PCR. Localization of Cx43 in these cells was determined by immunohistochemistry and confocal microscopy. For the assessment of the effect of gap junction inhibition on cell fusion, gap junctions were blocked with heptanol during differentiation of the cells and the cells were then evaluated for multinuclearity. Paraffin sections of healthy bone and bone from patients with Paget's disease and giant cell tumour of the bone were used to study Cx43 expression in vivo. We found mRNA and protein expression of Cx43 in fully differentiated osteoclasts as well as in precursor cells. This expression decreased in the course of differentiation. Consistently, we found a lower expression of Cx43 in osteoclasts than in bone marrow precursor cells in the histology of healthy human bone. Blockade of gap junctional communication by heptanol led to a dose‐dependent decrease in multinuclearity, suggesting that gap junctional communication precedes cell fusion of human osteoclasts. Indeed, we found a particularly strong expression of Cx43 in the giant osteoclasts of patients with Paget's disease and giant cell tumour of the bone. These results show that gap junctional communication is important for fusion of human mononuclear precursor cells to osteoclasts and that gap junctional Cx43 might play a role in the regulation of size and multinuclearity of human osteoclasts in vivo.
Influence of collagen type II and nucleus pulposus cells on aggregation and differentiation of adipose tissue‐derived stem cells
Authors: Lu Z. F. , Zandieh Doulabi B. , Wuisman P. I. , Bank R. A. , Helder M. N.
Published: February 2008

Tissue microenvironment plays a critical role in guiding local stem cell differentiation. Within the intervertebral disc, collagen type II and nucleus pulposus (NP) cells are two major components. This study aimed to investigate how collagen type II and NP cells affect adipose tissue‐derived stem cells (ASCs) in a 3D environment. ASCs were cultured in collagen type I or type II hydrogels alone, or co‐cultured in transwells with micromass NP cells for 4 and 14 days. ASCs seeded in collagen type II gels acquired dentritic cell shapes, and orchestrated cell density‐dependent gel contraction rates. Up‐regulation of collagen type X, but not of other chondrogenic markers was observed at day 4, irrespective of the hydrogel type. Strikingly, in co‐cultures with NP cells, more pronounced differentiation of ASCs along the cartilaginous lineage was observed (up‐regulation of collagen IIA, IIB and aggrecan gene expression, as well as stronger alcian blue staining), when ASCs were embedded in collagen type II in comparison with type I hydrogels. Interestingly, strong cellular condensations/aggregations were observed in ASC‐seeded type II, but not type I gels, and this aggregation was markedly delayed when the same gels were co‐cultured with NP cells. The NP cell‐mediated inhibition of ASC aggregation in collagen type II gels coincided with down‐regulation of integrin subunit α2 gene expression. We conclude that soluble factors released by NP cells can direct chondrogenic differentiation of ASCs in collagen hydrogels, and that combination with a nucleus‐mimicking collagen type II microenvironment enhances differentiation towards a more pronounced cartilage/NP lineage relative to collagen type I hydrogels.
Protein tyrosine phosphatases: structure–function relationships
Authors: Tabernero Lydia , Aricescu A. Radu , Jones E. Yvonne , Szedlacsek Stefan E.
Published: February 2008

Structural analysis of protein tyrosine phosphatases (PTPs) has expanded considerably in the last several years, producing more than 200 structures in this class of enzymes (from 35 different proteins and their complexes with ligands). The small–medium size of the catalytic domain of ∼280 residues plus a very compact fold makes it amenable to cloning and overexpression in bacterial systems thus facilitating crystallographic analysis. The low molecular weight PTPs being even smaller, ∼150 residues, are also perfect targets for NMR analysis. The availability of different structures and complexes of PTPs with substrates and inhibitors has provided a wealth of information with profound effects in the way we understand their biological functions. Developments in mammalian expression technology recently led to the first crystal structure of a receptor‐like PTP extracellular region. Altogether, the PTP structural work significantly advanced our knowledge regarding the architecture, regulation and substrate specificity of these enzymes. In this review, we compile the most prominent structural traits that characterize PTPs and their complexes with ligands. We discuss how the data can be used to design further functional experiments and as a basis for drug design given that many PTPs are now considered strategic therapeutic targets for human diseases such as diabetes and cancer.
Analysis and biological relevance of advanced glycation end‐products of DNA in eukaryotic cells
Authors: Breyer Viola , Frischmann Matthias , Bidmon Clemens , Schemm Annelen , Schiebel Katrin , Pischetsrieder Monika
Published: February 2008

Advanced glycation end‐products (AGEs) of DNA are formed spontaneously by the reaction of carbonyl compounds such as sugars, methylglyoxal or dihydroxyacetone in vitro and in vivo. Little is known, however, about the biological consequences of DNA AGEs. In this study, a method was developed to determine the parameters that promote DNA glycation in cultured cells. For this purpose, the formation rate of N2‐carboxyethyl‐2′‐deoxyguanosine (CEdG), a major DNA AGE, was measured in cultured hepatic stellate cells by liquid chromatography (LC)‐MS/MS. In resting cells, a 1.7‐fold increase of CEdG formation rate was observed during 14 days of incubation. To obtain insights into the functional consequences of DNA glycation, CEdG was introduced into a luciferase reporter gene vector and transfected into human embryonic kidney (HEK 293 T) cells. Gene activity was determined by chemiluminescence of the luciferase. Thus, CEdG adducts led to a dose‐dependent and highly significant decrease in protein activity, which is caused by loss of functionality of the luciferase in addition to reduced transcription of the gene. When the CEdG‐modified vector was transformed into Escherichia coli, a loss of ampicillin resistance was observed in comparison to transformation with the unmodified plasmid. These results indicate that CEdG accumulates in the genomic DNA of resting cells, which could lead to diminished protein activity.
Induction of actin cytoskeleton rearrangement by methyl okadaate – comparison with okadaic acid
Authors: Vilariño Natalia , Ares Isabel R. , Cagide Eva , Louzao M. Carmen , Vieytes Mercedes R. , Yasumoto Takeshi , Botana Luis M.
Published: February 2008

Methyl okadaate is a derivative of the lipophilic polyether okadaic acid (OA), a well‐known inducer of apoptosis. OA inhibits Ser/Thr protein phosphatases (PPs), among them types 1 and 2A (PP1 and PP2A), whereas methyl okadaate lacks PP1/PP2A inhibitory activityin vitro. As progressive loss of neuronal cytoarchitecture is a major event that precedes neuronal death, in this work we studied comparatively the effects of both toxins on actin cytoskeleton organization in human neuroblastoma cells by filamentous actin (F‐actin) labeling with the specific dye Oregon Green 514 Phalloidin. Neither methyl okadaate nor OA modified the amount of F‐actin per cell. However, confocal microscopy imaging showed that methyl okadaate induced reorganization of actin cytoskeleton, loss of the typical flattened morphology and adoption of a round shape, and a reduction in the number of neurites, with a consequent loss of cell attachment. These effects were identical to those induced by OA, although methyl okadaate potency was approximately 10‐fold lower. In order to investigate the role of membrane potential and cytosolic Ca2+concentration in morphological changes induced by these toxins, the cells were stained with bis‐(1,3‐dibutylbarbituric acid)‐trimethine oxonol and fura‐2. No toxin effect was detected on membrane potential or calcium influx, indicating that these two signals are not responsible for cytoskeletal/morphological change induction. Methyl okadaate induced an increase of Ser/Thr phosphorylation of cellular proteins detected by western blot, showing similar phosphorylation profiles to OA. Our data suggest that methyl okadaate is an active compound that shares a pharmacological target with OA that may be a Ser/Thr phosphatase, probably different from PP1 and PP2A.
A unique tetrameric structure of deer plasma haptoglobin – an evolutionary advantage in the Hp 2‐2 phenotype with homogeneous structure
Authors: Lai I. H. , Lin Kung‐Yu , Larsson Mikael , Yang Ming Chi , Shiau Chuen‐Huei , Liao Ming‐Huei , Mao Simon J. T.
Published: February 2008

Similar to blood types, human plasma haptoglobin (Hp) is classified into three phenotypes: Hp 1‐1, 2‐1 and 2‐2. They are genetically inherited from two alleles Hp 1 and Hp 2 (represented in bold), but only the Hp 1‐1 phenotype is found in almost all animal species. The Hp 2‐2 protein consists of complicated large polymers cross‐linked by α2‐β subunits or (α2‐β)n (where n ≥ 3, up to 12 or more), and is associated with the risk of the development of diabetic, cardiovascular and inflammatory diseases. In the present study, we found that deer plasma Hp mimics human Hp 2, containing a tandem repeat over the α‐chain based on our cloned cDNA sequence. Interestingly, the isolated deer Hp is homogeneous and tetrameric, i.e. (α‐β)4, although the locations of −SH groups (responsible for the formation of polymers) are exactly identical to that of human. Denaturation of deer Hp using 6 m urea under reducing conditions (143 mmβ‐mercaptoethanol), followed by renaturation, sustained the formation of (α‐β)4, suggesting that the Hp tetramers are not randomly assembled. Interestingly, an α‐chain monoclonal antibody (W1), known to recognize both human and deer α‐chains, only binds to intact human Hp polymers, but not to deer Hp tetramers. This implies that the epitope of the deer α‐chain is no longer exposed on the surface when Hp tetramers are formed. We propose that steric hindrance plays a major role in determining the polymeric formation in human and deer polymers. Phylogenetic and immunochemical analyses revealed that the Hp 2 allele of deer might have arisen at least 25 million years ago. A mechanism involved in forming Hp tetramers is proposed and discussed, and the possibility is raised that the evolved tetrameric structure of deer Hp might confer a physiological advantage.
The Pdx1 family is structurally and functionally conserved between Arabidopsis thaliana and Ginkgo biloba
Authors: Leuendorf Jan E. , Genau Andreas , Szewczyk Agnieszka , Mooney Sutton , Drewke Christel , Leistner Eckhard , Hellmann Hanjo
Published: February 2008

Vitamin B6 is one of the most important compounds in living organisms, and its biosynthesis has only recently been understood. Because it is required for more than 100 biochemical reactions, lack of the vitamin is fatal. This is of special importance to mammals and humans, which cannot biosynthesize the vitamin and thus depend on its external uptake. Here we describe the cloning of a vitamin B6 biosynthetic gene GbPDX1 from Ginkgo biloba. The gene is expressed in seeds, leaf and trunk tissue. Using yeast 2‐hybrid and pull‐down assays, we show that the protein can interact with itself and with members of Arabidopsis thaliana AtPDX1 and AtPDX2 families. Furthermore, we prove the function of GbPDX1 in vitamin B6 biosynthesis by complementation of an Arabidopsis AtPDX1.3 mutant rsr4‐1, at the phenotypical level and increasing vitamin B6 levels caused by ectopic GbPDX1 expression in the mutant background. Overall, this study provides a first description of Ginkgo vitamin B6 metabolism, and demonstrates a high degree of conservation between Ginkgo and Arabidopsis.
Tracing Coalbed Natural Gas–Coproduced Water Using Stable Isotopes of Carbon
Authors: Sharma S. , Frost C.D.
Published: February 2008

Recovery of hydrocarbons commonly is associated with coproduction of water. This water may be put to beneficial use or may be reinjected into subsurface aquifers. In either case, it would be helpful to establish a fingerprint for that coproduced water so that it may be tracked following discharge on the surface or reintroduction to geologic reservoirs. This study explores the potential of using δ13C of dissolved inorganic carbon (DIC) of coalbed natural gas (CBNG)–coproduced water as a fingerprint of its origin and to trace its fate once it is disposed on the surface. Our initial results for water samples coproduced with CBNG from the Powder River Basin show that this water has strongly positive δ13CDIC (12‰ to 22‰) that is readily distinguished from the negative δ13C of most surface and ground water (−8‰ to −11‰). Furthermore, the DIC concentrations in coproduced water samples are also high (more than 100 mg C/L) compared to the 20 to 50 mg C/L in ambient surface and ground water of the region. The distinctively high δ13C and DIC concentrations allow us to identify surface and ground water that have incorporated CBNG‐coproduced water. Accordingly, we suggest that the δ13CDIC and DIC concentrations of water can be used for long‐term monitoring of infiltration of CBNG‐coproduced water into ground water and streams. Our results also show that the δ13CDIC of CBNG‐coproduced water from two different coal zones are distinct leading to the possibility of using δ13CDIC to distinguish water produced from different coal zones.
Weakly Nonlinear Approximation of Periodic Flow in Phreatic Aquifers
Authors: Smith Anthony J.
Published: February 2008

Published frequency‐domain solutions of periodic flow in aquifers apply strictly to mathematically linear systems that arise when aquifer diffusivity is assumed constant in space and time. This assumption can be invalid in phreatic aquifers that experience spatiotemporal variation in the free surface position and consequent variation in saturated thickness. A weakly nonlinear approach to formulating and solving periodic flow problems in the frequency domain can be applied in situations where conventional linearized approximations break down. The weakly nonlinear equations provide robust approximations of the true nonlinear response and require much less computational effort and time to solve than the full nonlinear problem. Nondimensional rules of thumb are presented for choosing between linear, weakly nonlinear and nonlinear solution strategies.
Geochemical Tracers to Evaluate Hydrogeologic Controls on River Salinization
Authors: Moore Stephanie J. , Bassett R. L. , Liu Beiling , Wolf Christopher P. , Doremus Dale
Published: February 2008

The salinization of rivers, as indicated by salinity increases in the downstream direction, is characteristic of arid and semiarid regions throughout the world. Historically, salinity increases have been attributed to various mechanisms, including (1) evaporation and concentration during reservoir storage, irrigation, and subsequent reuse; (2) displacement of shallow saline ground water during irrigation; (3) erosion and dissolution of natural deposits; and/or (4) inflow of deep saline and/or geothermal ground water (ground water with elevated water temperature). In this study, investigation of salinity issues focused on identification of relative salinity contributions from anthropogenic and natural sources in the Lower Rio Grande in the New Mexico‐Texas border region. Based on the conceptual model of the system, the various sources of water and, therefore, salinity to the Lower Rio Grande were identified, and a sampling plan was designed to characterize these sources. Analysis results for boron (δ11B), sulfur (δ34S), oxygen (δ18O), hydrogen (δ2H), and strontium (87Sr/86Sr) isotopes, as well as basic chemical data, confirmed the hypothesis that the dominant salinity contributions are from deep ground water inflow to the Rio Grande. The stable isotopic ratios identified the deep ground water inflow as distinctive, with characteristic isotopic signatures. These analyses indicate that it is not possible to reproduce the observed salinization by evapotranspiration and agricultural processes alone. This investigation further confirms that proper application of multiple isotopic and geochemical tracers can be used to identify and constrain multiple sources of solutes in complex river systems.
Bottomfast Ice Mapping and the Measurement of Ice Thickness on Tundra Lakes Using C‐Band Synthetic Aperture Radar Remote Sensing1
Authors: Hirose T. , Kapfer M. , Bennett J. , Cott P. , Manson G. , Solomon S.
Published: February 2008

Abstract:  Industrial activity in Canada’s north is increasing, placing demands on the use of water from lakes to build ice roads. Winter water withdrawal from these lakes has the potential to impact overwintering fish. Removal of water from small lakes can decrease oxygen and habitat available to fish. To address this issue, a protocol has been developed by the Department of Fisheries and Oceans outlining water withdrawal thresholds. Bathymetric surveys are the traditional method to determine lake depth, but are costly given the remoteness of northern lakes. This paper investigates the use of satellite C‐band synthetic aperture radar (SAR) remote sensing technology as a potential alternative or complement to traditional survey methods. Previous research has shown that a SAR can detect the transition from grounded to floating ice on lakes, or if a lake is completely frozen. Grounded ice has a dark signature while floating ice appears very bright in contrast. Similar results were observed for the datasets acquired in the study area. This suggests that lakes that freeze completely to the bottom can be identified using SAR. Such water bodies would not be viable fish overwintering habitat and can therefore be used as water sources without thresholds necessary. However, attempts to accurately calculate the depth of the ice at the grounded‐floating ice boundary using bathymetric profiles acquired in the summer and lake ice thickness measurements from a reference lake near Inuvik proved to be unreliable.
A Tool for Modeling the Winter Oxygen Depletion Rate in Arctic Lakes1
Authors: White D.M. , Clilverd H.M. , Tidwell A.C. , Little L. , Lilly M.R. , Chambers Molly , Reichardt D.
Published: February 2008

Abstract:  Many arctic lakes freeze completely in winter. The few that retain unfrozen water for the entire winter period serve as overwintering fish habitat. In addition to serving as fish habitat, water in arctic lakes is needed for industrial and domestic use. Permits for water extraction seek to maximize water use without impacting dissolved oxygen (DO) levels and endangering fish habitat. The relationship between lake volume, winter DO budget, and extraction of water through pumping has historically not been well understood. A management model that could estimate end‐of‐winter DO would improve our understanding of the potential impacts of different management strategies. Using under‐ice DO measurements (November to April) taken from two natural lakes and one flooded gravel mine on the North Slope of Alaska, a physically based model was developed to predict end‐of‐winter DO concentration, water‐column DO profiles, and winter oxygen depletion rate in arctic lakes during periods of ice cover. Comparisons between the measured and model‐predicted oxygen profiles in the three study lakes suggest that the depth‐based DO modeling tool presented herein can be used to adequately predict the amount of DO available in arctic lakes throughout winter.
The Potential Use of Synthetic Aperture Radar for Estimating Methane Ebullition From Arctic Lakes1
Authors: Walter Katey M. , Engram Melanie , Duguay Claude R. , Jeffries Martin O. , Chapin F.S.
Published: February 2008

Abstract:  Arctic lakes are significant emitters of methane (CH4), a potent greenhouse gas, to the atmosphere; yet no rigorous quantification of the magnitude and variability of pan‐Arctic lake emissions exists. In this study, we demonstrate the potential for a new method using synthetic aperture radar (SAR) imagery to detect methane bubbles in lake ice to scale up whole‐lake measurements of CH4 ebullition (bubbling) to regional scales. We estimated ebullition from lakes, which is often the dominant mode of lake emissions, by mapping the distribution of bubble clusters frozen in early winter ice across surfaces of seven tundra lakes and one boreal forest lake in Alaska. Applying previously measured ebullition rates associated with four distinct classes of bubble clusters found in lake ice, we estimated whole‐lake emissions from individual lakes. The percent surface area of lake ice covered with bubbles (R2 = 0.68) and CH4 ebullition rates from lakes (R2 = 0.59) and were correlated with radar return values from RADARSAT‐1 Standard Beam mode 3 for the tundra lakes, suggesting that with appropriate scaling and consideration for variability in lake‐ice conditions, this technique has the potential to be used for estimating broader‐scale regional and pan‐Arctic lake methane emissions.
Exploratory Analysis of the Winter Chemistry of Five Lakes on the North Slope of Alaska1
Authors: Chambers Molly K. , White Daniel M. , Lilly Michael R. , Hinzman Larry D. , Hilton Kristie M. , Busey Robert C.
Published: February 2008

Abstract:  Lakes are important water resources on the North Slope of Alaska. Freshwater is required for oilfield production as well as exploration, which occurs largely on ice roads and pads. Since most North Slope lakes are shallow, the quantity and quality of the water under ice at the end of winter are important environmental management issues. Currently, water‐use permits are a function of the presence of overwintering fish populations, and their sensitivity to low oxygen concentrations. Sampling of five North Slope lakes during the winter of 2004‐2005 shed some light on the winter chemistry of four lakes that were used as water supplies and one undisturbed lake. Field analysis was conducted for oxygen, conductivity, pH, and temperature throughout the lake depth, as well as ice thickness and water depth. Water samples were retrieved from the lakes and analyzed for Na, Ca, K, Mg, Fe, dissolved‐organic carbon, and alkalinity in the laboratory. Lake properties, rather than pumping, were the best predictors of oxygen depletion, with the highest dissolved‐oxygen levels maintained in the lake with the lowest concentration of constituents. Volume weighted mean dissolved‐oxygen concentrations ranged from 4 to 94% of saturation in March. Dissolved oxygen and specific conductance data suggested that the lakes began to refresh in May.
A Review of Water Level Fluctuations on Aquatic Biota With an Emphasis on Fishes in Ice‐Covered Lakes1
Authors: Cott Peter A. , Sibley Paul K. , Somers W. Murray , Lilly Michael R. , Gordon Andrew M.
Published: February 2008

Abstract:  The effects of water level fluctuations on fish and other aquatic biota, with an emphasis on winter water withdrawal in northern regions is reviewed. Water demands for population growth and development are adding pressure on water reserves, particularly when coupled with changing climatic conditions. Water level fluctuations can have adverse effects on the environment, most notably to hydrologic and biotic processes ranging in magnitude from the micro‐scale to landscape level. Water level management of lakes and reservoirs can affect all forms of aquatic biota. The severity of effect is dependant on the magnitude, duration and timing of the fluctuation, and the species exposed. In northwestern Canada and northern Alaska, water is withdrawn from water bodies to construct ice‐roads and other winter based developments. Biota in small, isolated water bodies are particularly sensitive to reductions in winter water levels. Water withdrawals can reduce the oxygen available to overwintering fish, while reduced water levels can reduce habitat for fish and furbearers, and freeze littoral areas killing plants, invertebrates, and fish eggs. Regulatory winter water withdrawal thresholds have been developed in the Northwest Territories and Alaska and continue to be refined as new data becomes available. The use of thresholds can help minimize or avoid negative impacts to the environment, particularly fish, from winter water withdrawal activities. Many different factors may influence the effect that winter water withdrawal has on a water body, such as basin shape, substrate and location. More research is warranted to better understand the linkages between anthropogenic and natural water level fluctuations and their combined effect on aquatic ecosystems. A general decision support system is proposed for minimizing risk to aquatic life from winter water withdrawal activities.
Involvement of FKHRL1 in melanoma cell survival and death
Authors: Hilmi C. , Larribere L. , Deckert M. , Rocchi S. , Giuliano S. , Bille K. , Ortonne J.P. , Ballotti R. , Bertolotto C.
Published: February 2008

Melanoma is a highly aggressive tumour characterized by a strong resistance to apoptotic stimuli that give rise to a selective advantage for tumour progression and metastasis formation. Therefore, it is of paramount importance to better understand the mechanisms involved in this resistance to apoptosis. In this report, we focused our attention on FKHRL1, a member of the forkhead family of transcription factors, which controls expression of genes involved in cell cycle progression and apoptosis. In melanoma cells, we show that IGF1, which exerts pro‐survival properties, induces the phosphorylation and nuclear exclusion of FKHRL1 in a PI3K/AKT‐dependent pathway. Moreover, we observe that over‐expression of a non‐phosphorylable mutant of FKHRL1 (FKHRL1‐TM), constitutively localized to the nucleus, promotes apoptotic cell death of melanoma cells. Finally, we find that FKHRL1‐TM decreases the expression of survivin, a member of the inhibitor of apoptosis protein and that survivin re‐expression partially rescues the deleterious effects of FKHRL1. Taken together, these findings reveal, in melanoma cells, that endogenous FKHRL1 is a downstream target of the PI3K/AKT pathway and suggest that the phosphorylation of this transcription factor may be involved in the pro‐survival effects of growth factors such as IGF1. On the other hand, forced nuclear localization of FKHRL1 decreases melanoma cell growth and may serve as a therapeutic strategy against melanoma.
LIGR, a protease‐activated receptor‐2‐derived peptide, enhances skin pigmentation without inducing inflammatory processes
Authors: Lin Connie B. , Chen Nannan , Scarpa Richard , Guan Fei , Babiarz‐Magee Laura , Liebel Frank , Li Wen‐Hwa , Kizoulis Menas , Shapiro Stanley , Seiberg Miri
Published: February 2008

The protease‐activated receptor‐2 (PAR‐2) is a seven transmembrane G‐protein‐coupled receptor that could be activated by serine protease cleavage or by synthetic peptide agonists. We showed earlier that activation of PAR‐2 with Ser‐Leu‐Ile‐Gly‐Arg‐Leu‐NH2(SLIGRL), a known PAR‐2 activating peptide, induces keratinocyte phagocytosis and increases skin pigmentation, indicating that PAR‐2 regulates pigmentation by controlling phagocytosis of melanosomes. Here, we show that Leu‐Ile‐Gly‐Arg‐NH2(LIGR) can also induce skin pigmentation. Both SLIGRL and LIGR increased melanin deposition in vitro and in vivo, and visibly darkened human skins grafted onto severe combined immuno‐deficient (SCID) mice. Both SLIGRL and LIGR stimulated Rho‐GTP activation resulting in keratinocyte phagocytosis. Interestingly, LIGR activates only a subset of the PAR‐2 signaling pathways, and unlike SLIGRL, it does not induce inflammatory processes. LIGR did not affect many PAR‐2 signaling pathways, including [Ca2+] mobilization, cAMP induction, the induction of cyclooxgenase‐2 (COX‐2) expression and the secretion of prostaglandin E2, interleukin‐6 and ‐8. PAR‐2 siRNA inhibited LIGR‐induced phagocytosis, indicating that LIGR signals via PAR‐2. Our data suggest that LIGR is a more specific regulator of PAR‐2‐induced pigmentation relative to SLIGRL. Therefore, enhancing skin pigmentation by topical applications of LIGR may result in a desired tanned‐like skin color, without enhancing inflammatory processes, and without the need of UV exposure.
N‐Acetylcysteine ameliorates skeletal muscle pathophysiology in mdx mice
Authors: Whitehead Nicholas P. , Pham Catherine , Gervasio Othon L. , Allen David G.
Published: February 2008

Duchenne muscular dystrophy (DMD) is a severe degenerative muscle disease caused by a mutation in the gene encoding dystrophin, a protein linking the cytoskeleton to the extracellular matrix. In this study we investigated whether the antioxidant N‐acetylcysteine (NAC) provided protection against dystrophic muscle damage in the mdx mouse, an animal model of DMD. In isolated mdx muscles, NAC prevented the increased membrane permeability and reduced the force deficit associated with stretch‐induced muscle damage. Three‐week‐old mdx mice were treated with NAC in the drinking water for 6 weeks. Dihydroethidium staining showed that NAC treatment reduced the concentration of reactive oxygen species (ROS) in mdx muscles. This was accompanied by a significant decrease in centrally nucleated fibres in muscles from NAC‐treated mdx mice. Immunoblotting showed that NAC treatment decreased the nuclear protein expression of NF‐κB, a transcription factor involved in pro‐inflammatory cytokine expression. Finally, we show that NAC treatment reduced caveolin‐3 protein levels and increased the sarcolemmal expression of β‐dystroglycan and the dystrophin homologue, utrophin. Taken together, our findings suggest that ROS play an important role in the dystrophic pathogenesis, both in terms of activating damage pathways and in regulating the expression of some dystrophin‐associated membrane proteins. These results offer the prospect that antioxidants such as NAC could have therapeutic potential for DMD patients.
Increased maternofetal calcium flux in parathyroid hormone‐related protein‐null mice
Authors: Bond H. , Dilworth M. R. , Baker B. , Cowley E. , Requena Jimenez A , Boyd R. D. H. , Husain S. M. , Ward B. S. , Sibley C. P. , Glazier J. D.
Published: February 2008

The role of parathyroid hormone‐related protein (PTHrP) in fetal calcium homeostasis and placental calcium transport was examined in mice homozygous for the deletion of the PTHrP gene (PTHrP−/− null; NL) compared to PTHrP+/+ (wild‐type; WT) and PTHrP+/− (heterozygous; HZ) littermates. Fetal blood ionized calcium was significantly reduced in NL fetuses compared to WT and HZ groups at 18 days of pregnancy (dp) with abolition of the fetomaternal calcium gradient. In situ placental perfusion of the umbilical circulation at 18 dp was used to measure unidirectional clearance of 45Ca across the placenta in maternofetal (CaKmf) and fetoplacental (CaKfp) directions; CaKfp was < 5% of CaKmf for all genotypes. At 18 dp, CaKmf across perfused placenta and intact placenta (CaKmf(intact)) were similar and concordant with net calcium accretion rates in vivo. CaKmf was significantly raised in NL fetuses compared to WT and HZ littermates. Calcium accretion was significantly elevated in NL fetuses by 19 dp. Placental calbindin‐D9K expression in NL fetuses was marginally enhanced (P < 0.07) but expression of TRPV6/ECaC2 and plasma membrane Ca2+‐ATPase (PMCA) isoforms 1 and 4 were unaltered. We conclude that PTHrP is an important regulator of fetal calcium homeostasis with its predominant effect being on unidirectional maternofetal transfer, probably mediated by modifying placental calbindin‐D9K expression. In situ perfusion of mouse placenta is a robust methodology for allowing detailed dissection of placental transfer mechanisms in genetically modified mice.
Interplay between neuromodulator‐induced switching of short‐term plasticity at sensorimotor synapses in the neonatal rat spinal cord
Authors: Barrière Grégory , Tartas Maylis , Cazalets Jean‐René , Bertrand Sandrine S.
Published: February 2008

In the present study, we investigated the modulation of short‐term depression (STD) at synapses between sensory afferents and rat motoneurons by serotonin, dopamine and noradrenaline. STD was elicited with trains of 15 stimuli at 1, 5 and 10 Hz and investigated using whole‐cell voltage‐clamp recordings from identified motoneurons in the neonatal rat spinal cord in vitro. STD was differentially modulated by the amines. Dopamine was effective at all stimulation frequencies, whereas serotonin affected STD only during 5 and 10 Hz stimulus trains and noradrenaline during 1 and 5 Hz trains. Dopamine and serotonin homogenized the degree of depression observed with the different stimulation modalities, in contrast to noradrenaline, which amplified the rate differences. The different modulatory profiles observed with the amines were partly due to GABAergic interneuron activity. In the presence of GABAA and GABAB receptor antagonists, the rate and/or kinetics of STD did not vary with the stimulation frequency in contrast to the control condition, and noradrenaline failed to alter either synaptic amplitude or STD, suggesting indirect actions. Dopamine and serotonin strongly decreased STD and converted depression to facilitation at 5 and 10 Hz during the blockade of the GABAergic receptors in 50% of the neurons tested. Altogether, these results show that STD expressed at sensorimotor synapses in the neonatal rat not only is a function of the frequency of afferent firing but also closely depends on the neuromodulatory state of these connections, with a major contribution from GABAergic transmission.
Anodic Electrochemical Pretreatment Time and Potential Affect the Electrochemical Characteristics of Moderately Boron-Doped Diamond Electrode
Authors: Zhang Wei , Xie Shaoai , Chen Hongjin , Li Mei , Ma Li , Jia Jinping
Published: February 2008

Boron-doped diamond (BDD) electrodes, both as-prepared and electrochemically oxidized were studied. The relation between the anodic oxidation treatment time, anodic potential and electrochemical characteristics has been discussed. Electron transfer processes in all BDD electrode surface were studied by cyclic voltammetry. The ferric/ferrous sulfate and ferri/ ferrocyanide redox systems were chosen respectively to act as the probe of one-electron trans- fer processes. The relation between ∆Ep and ψ, the dimensionless parameter, was obtained with a correlation coefficient greater than 0.9987 by mathematics fitting function. The rate constants of the electron transfer reaction, k0, were evaluated using the ∆Ep values. The k0 values for all BDD electrodes ranged from 3.33 × 10-5 to 4.72 × 10-5 cm s-1 in 0.1 M FeSO4/ 0.1 M H2SO4 and from 1.01 × 10-4 to 2.49 × 10-4 cm s-1 in 0.1 M K4[Fe(CN)6]/0.1 M H2SO4 system, which were in the standard range for a quasi-reversible system, respectively. The electrochemical properties of the BDD electrodes changed as a function of the surface anodic treatment time and potential. The anodic oxidation at low potential stripped mainly the impurities of BDD surface, sp2-carbon, and had little effect on the modification of the surface. While increasing the anodic potential up to +2.0 V, the anodic oxidation stripped the impurities of the BDD surface at first and carried out the modification of the BDD surface from hydrogen-terminated hydrophobic to oxygen-terminated hydrophilic surface with increasing anodic treatment time.