bluuebunny/crossref_metadata_2025 huggingface dataset:
Commissural interneurons with input from group I and II muscle afferents in feline lumbar segments: neurotransmitters, projections and target cells
Authors: Jankowska E. , Bannatyne B. A. , Stecina K. , Hammar I. , Cabaj A. , Maxwell D. J.
Published: December 2008

The aim of this study was to analyse neurotransmitter content, projection areas and target cells of commissural interneurons with input from group I and/or II muscle afferents in lumbar segments in the cat. Axonal projections of 15 intracellularly labelled commissural interneurons were reconstructed. Ten interneurons (nine located in laminae VI–VII, one in lamina VIII) were glutamatergic; only one interneuron (located in lamina VIII) was glycinergic. Contralateral terminal projections were found both in motor nuclei and within laminae VI–VIII. In order to identify target cells of commissural interneurons, effects of stimulation of contralateral group I and II muscle afferents were investigated on interneurons within these laminae. Three tests were used: intracellular records from individual interneurons, modulation of probability of activation of extracellularly recorded interneurons and modulation of their actions on motoneurons using disynaptic PSPs evoked in motoneurons as a measure. All these tests revealed much more frequent and/or stronger excitatory actions of contralateral afferents. The results indicate that commissural interneurons with input from contralateral group I and II afferents target premotor interneurons in disynaptic pathways from ipsilateral group I and II afferents and that excitatory disynaptic actions of contralateral afferents on these interneurons are mediated primarily by intermediate zone commissural interneurons. A second group of commissural interneurons activated by reticulospinal neurons, previously described, frequently had similar, but occasionally opposing, actions to the cells described here, thus indicating that these two subpopulations may act on the same premotor interneurons and either mutually enhance or counteract each other's actions.
Distinctive nicotinic acetylcholine receptor functional phenotypes of rat ventral tegmental area dopaminergic neurons
Authors: Yang Kechun , Hu Jun , Lucero Linda , Liu Qiang , Zheng Chao , Zhen Xuechu , Jin Guozhang , Lukas Ronald J. , Wu Jie
Published: December 2008

Dopaminergic (DAergic) neuronal activity in the ventral tegmental area (VTA) is thought to contribute generally to pleasure, reward, and drug reinforcement and has been implicated in nicotine dependence. nAChRs expressed in the VTA exhibit diverse subunit compositions, but the functional and pharmacological properties are largely unknown. Here, using patch‐clamp recordings in single DAergic neurons freshly dissociated from rat VTA, we clarified three functional subtypes of nAChRs (termed ID, IID and IIID receptors) based on whole‐cell current kinetics and pharmacology. Kinetic analysis demonstrated that comparing to ID, IID receptor‐mediated current had faster activation and decay constant and IIID receptor‐mediated current had larger current density. Pharmacologically, ID receptor‐mediated current was sensitive to the α4β2‐nAChR agonist RJR‐2403 and antagonist dihydro‐β‐erythroidine (DHβE); IID receptor‐mediated current was sensitive to the selective α7‐nAChR agonist choline and antagonist methyllycaconitine (MLA); while IIID receptor‐mediated current was sensitive to the β4‐containing nAChR agonist cytisine and antagonist mecamylamine (MEC). The agonist concentration–response relationships demonstrated that IID receptor‐mediated current exhibited the highest EC50value compared to ID and IIID receptors, suggesting a relatively low agonist affinity of type IID receptors. These results suggest that the type ID, IID and IIID nAChR‐mediated currents are predominately mediated by activation of α4β2‐nAChR, α7‐nAChR and a novel nAChR subtype(s), respectively. Collectively, these findings indicate that the VTA DAergic neurons express diversity and multiplicity of functional nAChR subtypes. Interestingly, each DAergic neuron predominantly expresses only one particularly functional nAChR subtype, which may have distinct but important roles in regulation of VTA DA neuronal function, DA transmission and nicotine dependence.
An internal model of a moving visual target in the lateral cerebellum
Authors: Cerminara Nadia L. , Apps Richard , Marple‐Horvat Dilwyn E.
Published: December 2008

In order to overcome the relatively long delay in processing visual feedback information when pursuing a moving visual target, it is necessary to predict the future trajectory of the target if it is to be tracked with accuracy. Predictive behaviour can be achieved through internal models, and the cerebellum has been implicated as a site for their operation. Purkinje cells in the lateral cerebellum (D zones) respond to visual inputs during visually guided tracking and it has been proposed that their neural activity reflects the operation of an internal model of target motion. Here we provide direct evidence for the existence of such a model in the cerebellum by demonstrating an internal model of a moving external target. Single unit recordings of Purkinje cells in lateral cerebellum (D2 zone) were made in cats trained to perform a predictable visually guided reaching task. For all Purkinje cells that showed tonic simple spike activity during target movement, this tonic activity was maintained during the transient disappearance of the target. Since simple spike activity could not be correlated to eye or limb movements, and the target was familiar and moved in a predictable fashion, we conclude that the Purkinje cell activity reflects the operation of an internal model based on memory of its previous motion. Such a model of the target's motion, reflected in the maintained modulation during the target's absence, could be used in a predictive capacity in the interception of a moving object.
GABAergic activities enhance macrophage inflammatory protein‐1α release from microglia (brain macrophages) in postnatal mouse brain
Authors: Cheung Giselle , Kann Oliver , Kohsaka Shinichi , Făerber Katrin , Kettenmann Helmut
Published: December 2008

Microglial cells (brain macrophages) invade the brain during embryonic and early postnatal development, migrate preferentially along fibre tracts to their final position and transform from an amoeboid to a ramified morphology. Signals by which the invading microglia communicate with other brain cells are largely unknown. Here, we studied amoeboid microglia in postnatal corpus callosum obtained from 6‐ to 8‐day‐old mice. These cells accumulated on the surface of acute brain slices. Whole‐cell patch‐clamp recordings revealed that the specific GABAA receptor agonist muscimol triggered a transient increase in conductance typical for inward rectifying potassium channels in microglia. This current increase was not mediated by microglial GABAA receptors since microglial cells removed from the slice surface no longer reacted and cultured microglia only responded when a brain slice was placed in their close vicinity. Muscimol triggered a transient increase in extracellular potassium concentration ([K+]o) in brain slices and an experimental elevation of [K+]o mimicked the muscimol response in microglial cells. Moreover, in adult brain slices, muscimol led only to a minute increase in [K+]o and microglial cells failed to respond to muscimol. In turn, an increase in [K+]o stimulated the release of chemokine macrophage inflammatory protein‐1α (MIP1‐α) from brain slices and from cultures of microglia but not astrocytes. Our observations indicate that invading microglia in early postnatal development sense GABAergic activities indirectly via sensing changes in [K+]o which results in an increase in MIP1‐α release.
Wet Gas Separation in Gas-Liquid Cylindrical Cyclone Separator
Authors: Molina Robiro , Wang Shoubo , Gomez Luis E. , Mohan Ram S. , Shoham Ovadia , Kouba Gene
Published: December 2008

A novel gas-liquid cylindrical cyclone (GLCC©, ©The University of Tulsa, 1994), equipped with an annular film extractor (AFE), for wet gas applications has been developed and studied experimentally and theoretically. Detailed experimental investigation of the modified GLCC has been carried out for low and high pressure conditions. The results show expansion of the operational envelope for liquid carry-over and improved performance of the modified GLCC. For low pressures, the modified GLCC can remove all the liquid from the gas stream, resulting in zero liquid carry-over (separation efficiency=100%). For high pressure conditions, the GLCC with a single AFE has separation efficiency >80% for gas velocity ratio, vsg/vann≤3. A mechanistic model and an aspect ratio design model for the modified GLCC have been developed, including the analysis of the AFE. The model predictions agree with the experimental data within ±15% for low pressure and ±25% for high pressure conditions.
Evaluation of “Marching Algorithms” in the Analysis of Multiphase Flow in Natural Gas Pipelines
Authors: Ayala Luis F. , Alp Doruk
Published: December 2008

Marching algorithms are the rule rather than the exception in the determination of pressure distribution in long multiphase-flow pipes, both for the case of pipelines and wellbores. This type of computational protocol is the basis for most two-phase-flow software and it is presented by textbooks as the standard technique used in steady state two-phase analysis. Marching algorithms acknowledge the fact that the rate of change of common fluid flow parameters (such as pressure, temperature, and phase velocities) is not constant but varies along the pipe axis while performing the integration of the governing equations by dividing the entire length into small pipe segments. In the marching algorithm, governing equations are solved for small single sections of pipe, one section at a time. Calculated outlet conditions for a particular segment are then propagated to the next segment as its prescribed inlet condition. Calculation continues in a “marching” fashion until the entire length of the pipe has been integrated. In this work, several examples are shown where this procedure might no longer accurately represent the physics of the flow for the case of natural gas flows with retrograde condensation. The implications related to the use of this common technique are studied, highlighting its potential lack of compliance with the actual physics of the flow for selected examples. This paper concludes by suggesting remedies to these problems, supported by results, showing considerable improvement in fulfilling the actual constraints imposed by the set of simultaneous fluid dynamic continuum equations governing the flow.
Basin Analog Investigations Answer Characterization Challenges of Unconventional Gas Potential in Frontier Basins
Authors: Singh Kalwant , Holditch Stephen A. , Ayers Walter B.
Published: December 2008

To meet future global oil and gas demands, the energy industry will need creative thinking that leads to the discovery and development of new fields. Unconventional gas resources, especially those in frontier (exploratory) basins, will play an important role in fulfilling future energy needs. To develop unconventional gas resources, we must first identify their occurrences and quantify their potential. Basin analog systems investigation (BASIN) is a computer software that can rapidly and inexpensively evaluate the unconventional gas resource potential of frontier basins. BASIN is linked to a database that includes petroleum systems and reservoir properties data from 25 intensely studied North American “reference” basins that have both conventional and unconventional oil and gas resources. To use BASIN, limited data from a frontier or “target” basin are used to query the database of North American reference basins and rank these reference basins as potential analogs to the frontier basin. Based on analog comparisons, we can predict unconventional gas resources and make preliminary engineering decisions concerning resource development and the best drilling, completion, stimulation, and production practices to use in the frontier basin. Initial software validation shows consistent results. If a basin is selected as the target basin while the same basin is also in the reference basin list, the results show that the basin is a 100% analog to itself. Other basins in the reference basin list are less than 100% analogs. Also, BASIN performed favorably when it was tested against analog basin decisions made by of a team of industry experts. BASIN rapidly and inexpensively identifies and ranks reference basins as analogs to a frontier basin, providing insights to potential gas resources and indicating the preliminary best engineering practice for resource development. It is an effective tool that provides guidance to inexperienced professionals and new perceptions for seasoned experts.
Transient Surface Strains and the Deconvolution of Thermoelastic States and Boundary Conditions
Authors: Segall A. E. , Engels D. , Hirsh A.
Published: December 2008

Thermoelastic states as they pertain to thermal-shock are difficult to determine since the underlying boundary conditions must be known or measured. For direct problems where the boundary conditions such as temperature or flux, are known a priori, the procedure is mathematically tractable with many analytical solutions available. Although this is more practical from a measurement standpoint, the inverse problem where the boundary conditions must be determined from remotely determined temperature and/or flux data are ill-posed and therefore inherently sensitive to errors in the data. Moreover, the limited number of analytical solutions to the inverse problem rely on assumptions that usually restrict them to timeframes before the thermal wave reaches the natural boundaries of the structure. Fortunately, a generalized solution based on strain-histories can be used instead to determine the underlying thermal excitation via a least-squares determination of coefficients for generalized equations for strain. Once the inverse problem is solved and the unknown boundary condition on the opposing surface is determined, the resulting polynomial can then be used with the generalized direct solution to determine the thermal- and stress-states as a function of time and position. For the two geometries explored, namely a thick-walled cylinder under an internal transient with external convection and a slab with one adiabatic surface, excellent agreement was seen with various test cases. The derived solutions appear to be well suited for many thermal scenarios provided that the analysis is restricted to the time interval used to determine the polynomial and the thermophysical properties that do not vary with temperature. While polynomials were employed for the current analysis, transcendental functions and/or combinations with polynomials can also be used.
Initiation and Arrest of Delayed Hydride Cracking in Zr–2.5Nb Tubes
Authors: Kim Young S.
Published: December 2008

Using Kim’s delayed hydride cracking (DHC) model, this study reanalyzes the critical temperatures for DHC initiation and arrest in Zr–2.5Nb tubes that had previously been investigated with the previous DHC models. At the test temperatures above 180°C, DHC initiation temperatures fell near the terminal solid solubility for precipitation temperatures, requiring some undercooling or ΔT from the terminal solid solubility for dissolution (TSSD) temperatures, and increased toward TSSD with the number of thermal cycles. At the test temperatures below 180°C, DHC initiation occurred at temperatures near TSSD with little ΔT. DHC arrest occurred on heating toward TSSD where the hydrogen concentration difference between the bulk region and a crack tip ΔC decreased to a minimum ΔCmin, under which nucleation of the hydrides was restrained. ΔCmin after the first thermal cycle increased with increasing temperature, demonstrating that nucleation of the hydrides becomes more difficult with increasing temperatures. Different DHC initiation and arrest temperatures with the test temperatures or hydrogen concentrations are discussed in view of a supersaturation of hydrogen (ΔC) for nucleation of hydrides in the zirconium matrix.
A Preliminary Assessment of the Ke Factor Proposed in the EN13445 Standard for Fatigue Analysis of Unwelded Material
Authors: Pereira Hélder F. S. G. , De Jesus Abílio M. P. , Ribeiro Alfredo S. , Fernandes António A.
Published: December 2008

This paper presents an investigation about the plasticity correction factor, Ke, proposed in the Part 3-Clause 18 of the EN13445 standard, for correction of the elastic stress ranges exceeding twice the yield stress, resulting from mechanical loading. The plasticity correction factors are analyzed using a calculation strategy based on a comparison between results from linear elastic and elastoplastic analyses. Several materials, elastoplastic models, and geometries are considered in the study. The performed analyses revealed, for an important number of the situations, an underestimation of the Ke factor when calculated according to the standard procedures. A greater emphasis should be dedicated in the standard to the elastoplastic analysis, since the fatigue resistance data presented in the standard are strain-life type data, overcoming the need for the plasticity correction factor. The elastoplastic analysis should be the preferred approach for evaluation of the strains/stresses for fatigue analysis.
Pharmacokinetics and Bioequivalence Evaluation of Two Fixed-Dose Tablet Formulations of Dihydroartemisinin and Piperaquine in Vietnamese Subjects
Authors: Chinh Nguyen Trong , Quang Nguyen Ngoc , Thanh Nguyen Xuan , Dai Bui , Geue Jason P. , Addison Russell S. , Travers Thomas , Edstein Michael D.
Published: December 2008

The two fixed-dose combinations of dihydroartemisinin and piperaquine (Artekin and Arterakine) were found to be bioinequivalent in healthy Vietnamese subjects. However, because the peak plasma concentrations and areas under the concentration-time curves of dihydroartemisinin and piperaquine were only marginally different between the two formulations, similar therapeutic efficacies are expected in the treatment of malaria infections.
Cytomorphological and Genetic Characterization of Troglobitic
Leptolyngbya
Strains Isolated from Roman Hypogea
Authors: Bruno Laura , Billi Daniela , Bellezza Simona , Albertano Patrizia
Published: December 2008

Six
Leptolyngbya
strains, isolated from the archaeological surfaces of hypogean sites, were phenotypically and genetically characterized by light and electron microscopy and 16S rRNA gene and 16S-23S internally transcribed spacer (ITS) sequencing. Three phycoerythrin-rich (red) and three phycocyanin-rich (green) isolates were assigned to different operational taxonomic units (OTUs). Among the green isolates, one strain showed an OTU intraspecific variation due to differences in the ITS sequences and genomic polymorphism. Within the ITS sequence, variable regions, conserved domains and tRNA
Ile
and tRNA
Ala
genes showed high sequence identity among the phylotypes. Together, these data indicated a relatedness of the six strains to other
Leptolyngbya
from subaerophytic and geothermal environments and allowed the definition of novel
Leptolyngbya
OTUs.
GAP45 Phosphorylation Controls Assembly of the
Toxoplasma
Myosin XIV Complex
Authors: Gilk Stacey D. , Gaskins Elizabeth , Ward Gary E. , Beckers Con J. M.
Published: December 2008

Toxoplasma gondii
motility is powered by the myosin XIV motor complex, which consists of the myosin XIV heavy chain (MyoA), the myosin light chain (MLC1), GAP45, and GAP50, the membrane anchor of the complex. MyoA, MLC1, and GAP45 are initially assembled into a soluble complex, which then associates with GAP50, an integral membrane protein of the parasite inner membrane complex. While all proteins in the myosin XIV motor complex are essential for parasite survival, the specific role of GAP45 remains unclear. We demonstrate here that final assembly of the motor complex is controlled by phosphorylation of GAP45. This protein is phosphorylated on multiple residues, and by using mass spectroscopy, we have identified two of these, Ser
163
and Ser
167
. The importance of these phosphorylation events was determined by mutation of Ser
163
and Ser
167
to Glu and Ala residues to mimic phosphorylated and nonphosphorylated residues, respectively. Mutation of Ser
163
and Ser
167
to either Ala or Glu residues does not affect targeting of GAP45 to the inner membrane complex or its association with MyoA and MLC1. Mutation of Ser
163
and Ser
167
to Ala residues also does not affect assembly of the mutant GAP45 protein into the myosin motor complex. Mutation of Ser
163
and Ser
167
to Glu residues, however, prevents association of the MyoA-MLC1-GAP45 complex with GAP50. These observations indicate that phosphorylation of Ser
163
and Ser
167
in GAP45 controls the final step in assembly of the myosin XIV motor complex.
Dual Functions for the
Schizosaccharomyces pombe
Inositol Kinase Ipk1 in Nuclear mRNA Export and Polarized Cell Growth
Authors: Sarmah Bhaskarjyoti , Wente Susan R.
Published: December 2008

The inositol 1,3,4,5,6-pentakisphosphate (IP
5
) 2-kinase (Ipk1) catalyzes the production of inositol hexakisphosphate (IP
6
) in eukaryotic cells. Previous studies have shown that IP
6
is required for efficient nuclear mRNA export in the budding yeast
Saccharomyces cerevisiae
. Here, we report the first functional analysis of
ipk1
+
in
Schizosaccharomyces pombe. S. pombe
Ipk1 (SpIpk1) is unique among Ipk1 orthologues in that it harbors a novel amino (N)-terminal domain with coiled-coil structural motifs similar to those of BAR (Bin-amphiphysin-Rvs) domain proteins. Mutants with
ipk1
+
deleted (
ipk1
Δ) had mRNA export defects as well as pleiotropic defects in polarized growth, cell morphology, endocytosis, and cell separation. The SpIpk1 catalytic carboxy-terminal domain was required to rescue these defects, and the mRNA export block was genetically linked to SpDbp5 function and, likely, IP
6
production. However, the overexpression of the N-terminal domain alone also inhibited these functions in wild-type cells. This revealed a distinct noncatalytic function for the N-terminal domain. To test for connections with other inositol polyphosphates, we also analyzed whether the loss of
asp1
+
function, encoding an IP
6
kinase downstream of Ipk1, had an effect on
ipk1
Δ cells. The
asp1
Δ mutant alone did not block mRNA export, and its cell morphology, polarized growth, and endocytosis defects were less severe than those of
ipk1
Δ cells. Moreover,
ipk1
Δ
asp1
Δ double mutants had altered inositol polyphosphate levels distinct from those of the
ipk1
Δ mutant. This suggested novel roles for
asp1
+
upstream of
ipk1
+
. We propose that IP
6
production is a key signaling linchpin for regulating multiple essential cellular processes.
Host Glycosaminoglycan Confers Susceptibility to Bacterial Infection in
Drosophila melanogaster
Authors: Baron Miriam J. , Wong Sandra L. , Nybakken Kent , Carey Vincent J. , Madoff Lawrence C.
Published: December 2008

Many pathogens engage host cell surface glycosaminoglycans, but redundancy in pathogen adhesins and host glycosaminoglycan-anchoring proteins (heparan sulfate proteoglycans) has limited the understanding of the importance of glycosaminoglycan binding during infection. The alpha C protein of group B streptococcus, a virulence determinant for this neonatal human pathogen, binds to host glycosaminoglycan and mediates the entry of bacteria into human cells. We studied alpha C protein-glycosaminoglycan binding in
Drosophila melanogaster
, whose glycosaminoglycan repertoire resembles that of humans but whose genome includes only three characterized membrane heparan sulfate proteoglycan genes. The knockdown of glycosaminoglycan polymerases or of heparan sulfate proteoglycans reduced the cellular binding of alpha C protein. The interruption of alpha C protein-glycosaminoglycan binding was associated with longer host survival and a lower bacterial burden. These data indicate that the glycosaminoglycan-alpha C protein interaction involves multiple heparan sulfate proteoglycans and impairs bacterial killing. Host glycosaminoglycans, anchored by multiple proteoglycans, thereby determine susceptibility to infection. Because there is homology between
Drosophila
and human glycosaminoglycan/proteoglycan structures and many pathogens express glycosaminoglycan-binding structures, our data suggest that interfering with glycosaminoglycan binding may protect against infections in humans.
Binding of Complement Factor H (fH) to
Neisseria meningitidis
Is Specific for Human fH and Inhibits Complement Activation by Rat and Rabbit Sera
Authors: Granoff Dan M. , Welsch Jo Anne , Ram Sanjay
Published: December 2008

Complement factor H (fH), a molecule that downregulates complement activation, binds to
Neisseria meningitidis
and increases resistance to serum bactericidal activity. We investigated the species specificity of fH binding and the effect of human fH on downregulating rat (relevant for animal models) and rabbit (relevant for vaccine evaluation) complement activation. Binding to
N. meningitidis
was specific for human fH (low for chimpanzee fH and not detected with fH from lower primates). The addition of human fH decreased rat and rabbit C3 deposition on the bacterial surface and decreased group C bactericidal titers measured with rabbit complement 10- to 60-fold in heat-inactivated sera from human vaccinees. Administration of human fH to infant rats challenged with group B strain H44/76 resulted in an fH dose-dependent increase in CFU/ml of bacteria in blood 8 h later (
P
< 0.02). At the highest fH dose, 50 μg/rat, the geometric mean number of CFU per ml was higher than that in control animals (1,050 versus 43 [
P
< 0.005]). The data underscore the importance of binding of human fH for survival of
N. meningitidis
in vitro and in vivo. The species specificity of binding of human fH adds another mechanism toward our understanding of why
N. meningitidis
is strictly a human pathogen.
Transcriptional Map of Respiratory Versatility in the Hyperthermophilic Crenarchaeon
Pyrobaculum aerophilum
Authors: Cozen Aaron E. , Weirauch Matthew T. , Pollard Katherine S. , Bernick David L. , Stuart Joshua M. , Lowe Todd M.
Published: December 2008

Hyperthermophilic crenarchaea in the genus
Pyrobaculum
are notable for respiratory versatility, but relatively little is known about the genetics or regulation of crenarchaeal respiratory pathways. We measured global gene expression in
Pyrobaculum aerophilum
cultured with oxygen, nitrate, arsenate and ferric iron as terminal electron acceptors to identify transcriptional patterns that differentiate these pathways. We also compared genome sequences for four closely related species with diverse respiratory characteristics (
Pyrobaculum arsenaticum
,
Pyrobaculum calidifontis
,
Pyrobaculum islandicum
, and
Thermoproteus neutrophilus
) to identify genes associated with different respiratory capabilities. Specific patterns of gene expression in
P. aerophilum
were associated with aerobic respiration, nitrate respiration, arsenate respiration, and anoxia. Functional predictions based on these patterns include separate cytochrome oxidases for aerobic growth and oxygen scavenging, a nitric oxide-responsive transcriptional regulator, a multicopper oxidase involved in denitrification, and an archaeal arsenate respiratory reductase. We were unable to identify specific genes for iron respiration, but
P. aerophilum
exhibited repressive transcriptional responses to iron remarkably similar to those controlled by the ferric uptake regulator in bacteria. Together, these analyses present a genome-scale view of crenarchaeal respiratory flexibility and support a large number of functional and regulatory predictions for further investigation. The complete gene expression data set can be viewed in genomic context with the Archaeal Genome Browser at archaea.ucsc.edu.
Comparative Genomics and Molecular Dynamics of DNA Repeats in Eukaryotes
Authors: Richard Guy-Franck , Kerrest Alix , Dujon Bernard
Published: December 2008

Repeated elements can be widely abundant in eukaryotic genomes, composing more than 50% of the human genome, for example. It is possible to classify repeated sequences into two large families, “tandem repeats” and “dispersed repeats.” Each of these two families can be itself divided into subfamilies. Dispersed repeats contain transposons, tRNA genes, and gene paralogues, whereas tandem repeats contain gene tandems, ribosomal DNA repeat arrays, and satellite DNA, itself subdivided into satellites, minisatellites, and microsatellites. Remarkably, the molecular mechanisms that create and propagate dispersed and tandem repeats are specific to each class and usually do not overlap. In the present review, we have chosen in the first section to describe the nature and distribution of dispersed and tandem repeats in eukaryotic genomes in the light of complete (or nearly complete) available genome sequences. In the second part, we focus on the molecular mechanisms responsible for the fast evolution of two specific classes of tandem repeats: minisatellites and microsatellites. Given that a growing number of human neurological disorders involve the expansion of a particular class of microsatellites, called trinucleotide repeats, a large part of the recent experimental work on microsatellites has focused on these particular repeats, and thus we also review the current knowledge in this area. Finally, we propose a unified definition for mini- and microsatellites that takes into account their biological properties and try to point out new directions that should be explored in a near future on our road to understanding the genetics of repeated sequences.
Possible Effects of Microbial Ecto-Nucleoside Triphosphate Diphosphohydrolases on Host-Pathogen Interactions
Authors: Sansom Fiona M. , Robson Simon C. , Hartland Elizabeth L.
Published: December 2008

In humans, purinergic signaling plays an important role in the modulation of immune responses through specific receptors that recognize nucleoside tri- and diphosphates as signaling molecules. Ecto-nucleoside triphosphate diphosphohydrolases (ecto-NTPDases) have important roles in the regulation of purinergic signaling by controlling levels of extracellular nucleotides. This process is key to pathophysiological protective responses such as hemostasis and inflammation. Ecto-NTPDases are found in all higher eukaryotes, and recently it has become apparent that a number of important parasitic pathogens of humans express surface-located NTPDases that have been linked to virulence. For those parasites that are purine auxotrophs, these enzymes may play an important role in purine scavenging, although they may also influence the host response to infection. Although ecto-NTPDases are rare in bacteria, expression of a secreted NTPDase in Legionella pneumophila was recently described. This ecto-enzyme enhances intracellular growth of the bacterium and potentially affects virulence. This discovery represents an important advance in the understanding of the contribution of other microbial NTPDases to host-pathogen interactions. Here we review other progress made to date in the characterization of ecto-NTPDases from microbial pathogens, how they differ from mammalian enzymes, and their association with organism viability and virulence. In addition, we postulate how ecto-NTPDases may contribute to the host-pathogen interaction by reviewing the effect of selected microbial pathogens on purinergic signaling. Finally, we raise the possibility of targeting ecto-NTPDases in the development of novel anti-infective agents based on potential structural and clear enzymatic differences from the mammalian ecto-NTPDases.
Mechanisms of Severe Acute Respiratory Syndrome Pathogenesis and Innate Immunomodulation
Authors: Frieman Matthew , Baric Ralph
Published: December 2008

The modulation of the immune response is a common practice of many highly pathogenic viruses. The emergence of the highly pathogenic coronavirus severe acute respiratory virus (SARS-CoV) serves as a robust model system to elucidate the virus-host interactions that mediate severe end-stage lung disease in humans and animals. Coronaviruses encode the largest positive-sense RNA genome of ∼30 kb, encode a variety of replicase and accessory open reading frames that are structurally unique, and encode novel enzymatic functions among RNA viruses. These viruses have broad or specific host ranges, suggesting the possibility of novel strategies for targeting and regulating host innate immune responses following virus infection. Using SARS-CoV as a model, we review the current literature on the ability of coronaviruses to interact with and modify the host intracellular environment during infection. These studies are revealing a rich set of novel viral proteins that engage, modify, and/or disrupt host cell signaling and nuclear import machinery for the benefit of virus replication.
A new integrative model of lateral epicondylalgia: Figure 1
Authors: Coombes B K , Bisset L , Vicenzino B
Published: December 2008

Tennis elbow or lateral epicondylalgia is a diagnosis familiar to many within the general community and presents with an uncomplicated clinical picture in most cases. However, the underlying pathophysiology presents a more complex state and its management has not been conclusively determined. Research on this topic extends across anatomical, biomechanical and clinical literature; however, integration of findings is lacking. We propose that the current understanding of the underlying pathophysiology of lateral epicondylalgia can be conceptualised as encompassing three interrelated components: (i) the local tendon pathology, (ii) changes in the pain system, and (iii) motor system impairments. This paper presents a model that integrates these components on the basis of a literature review with the express aim of assisting in the targeting of specific treatments or combinations thereof to individual patients.
Exercise physiologist’s role in clinical practice
Authors: Franklin B , Fern A , Fowler A , Spring T , deJong A
Published: December 2008

The use of exercise testing has expanded greatly to help guide decisions about medical management and prognosis in a broad spectrum of patients. Numerous epidemiological studies in people with and without documented coronary artery disease have identified a low level of cardiorespiratory fitness as an independent risk factor for all-cause and cardiovascular mortality and that exercise capacity is inversely associated with healthcare costs. Accordingly, unfit men and women should be counselled to exercise in home-based or group preventative or rehabilitative programmes. In the era of managed care, the use of specialised exercise professionals for the supervision of exercise testing and training may represent a safe and cost-effective alternative to many hospitals, clinics and private physician practices. Clinical exercise physiologists (CEPs) can play a critical role in favourably modifying clients’ level of cardiorespiratory fitness and physical activity habits. We detail the training of CEPs and outline the clinical settings where they have contributed substantially to healthcare delivery. We also outline the role of registered clinical exercise physiologists. It is important that exercise prescription is not left to a few individuals or small groups. It needs a concerted programme with all those in a position to make a difference actively contributing.
Current Velocity in Streams and the Composition of Benthic Algal Mats
Authors: Reiter Michael A. , Carlson Robert E.
Published: December 2008

Water velocity is commonly accepted as a factor in the development of benthic algal mats in streams. Within a stream, two different zones of velocity are observed: the free-water velocity of the open water and the local velocity near the stream substrate. A closed laboratory flume system was used to observe the taxonomic composition of benthic algal mats and corresponding changes in the local velocities under different free-water velocities. As the algal mat developed under each experimental velocity, local velocities diminished and eventually became equal in all sections, while free-water velocities remained different. After a period of maximum taxonomic diversity during the first 2 wk of mat development, taxonomic composition, relative abundance of the taxa, and dry weight biomass became increasingly similar in the three velocity regimes, although the mats appeared different upon casual observation. Differences in composition and morphology in natural algal mats may not result from differences in current velocity, and the idea of a "closed monolayer" algal mat may not be appropriate in all situations.
Microhabitat–Preference Curves of Blackfly Larvae (Diptera: Simuliidae): A Comparison of Three Estimation Methods
Authors: Morin Antoine , Harper Pierre-Paul , Peters Robert Henry
Published: December 2008

Three analytical techniques are available to describe the observed response of stream-dwelling organisms to variations in their physicochemical environment: the incremental method, polynomial regression on a single factor, and multiple regression. The efficacy of these tools as descriptors of the responses has not been compared. We used the three methods to describe density and microhabitat–preference curves for Prosimulium mixtum/fuscum, Stegopterna mutata, and Simulium aureum in response to distance from the lake, current velocity, and water depth in a stream draining a Laurentian lake. The incremental method yielded the least precise estimates of density and biased estimates of optimal current velocity for two of the three species; multiple regression yielded the most precise estimates of density and unbiased estimates of optimal conditions, whereas polynomial regression on a single factor was intermediate. From this comparison, we suggest that the multiple-regression approach to estimate microhabitat–preference curves be used in developing optimal management stategies. Further, we suggest that rare species should be excluded from such analysis because of the low precision of density estimates for rare organisms.
Variation in Male Parr Maturation Within and Among Populations of Atlantic Salmon, Salmo salar
Authors: Myers Ransom A. , Hutchings Jeffrey A. , Gibson R. John
Published: December 2008

The covariation of growth and maturation in male Atlantic salmon parr, Salmo salar, produces a relationship characterized by a size threshold below which individuals generally do not mature. The threshold of 70–72 mm fork length is evident both within and among populations. Parr maturation can reduce growth during the second year of life by an average of 4.0%. Among-year variation in growth rate affects the yearly incidence of maturation for males at age 1 + but has no detectable effect on the total proportion of male parr maturing in a population. Increases in the proportion of mature parr in the Matamek River, Quebec, can be explained by variation in growth alone; there is no evidence for genetic changes in this population.
Benthic Bacterial Biomass and Production in Two Blackwater Rivers
Authors: Findlay Stuart , Meyer Judy L. , Risley Rebecca
Published: December 2008

Bacterial biomass and production in sediments of two blackwater rivers were measured via epifluorescent direct counts and rate of thymidine incorporation into DNA. Biomass ranged from 3 to 1500 mg C∙m−2 and production ranged from 0.01 to 22.0 mg C∙m−2∙h−1. Both biomass and production were correlated with organic content of the sediment. Neither biomass nor production was related to temperature. Allochthonous detritus apparently serves as a growth substrate for sediment bacteria. Despite differences in water chemistry and flow between the two rivers, comparison of similar sites between rivers showed similar bacterial standing stock and production. During most of the year these fourth- and sixth-order rivers are highly heterotrophic, yet at low water autochthonous carbon may serve as growth substrate for bacteria.
Theory, Practice, and Effects of Mysis relicta Introductions to North American and Scandinavian Lakes
Authors: Lasenby D. C. , Northcote T. G. , Fürst M.
Published: December 2008

Fisheries biologists have greatly altered the natural distribution of the crustacean Mysis relicta by introducing it into many lakes in both North America and Scandinavia to serve as a supplementary food source for fish. The original concept of Mysis as a deepwater benthic organism which remains isolated in the profundal zone of lakes needs to be modified to include its downstream dispersal capabilities. After introduction to a lake, Mysis will probably eventually reach all lakes in the downstream watershed. Recent studies indicate that rates of increase of introduced Mysis populations probably depend on available food and temperature. As well, introduced populations have been shown to modify benthic, phytoplankton, zooplankton, and fish communities. Most Mysis introductions have taken place without consideration of general criteria suggested for introduced species.
Decline in Natural Fisheries — A Genetic Analysis and Suggestion for Recovery
Authors: Wohlfarth Giora W.
Published: December 2008

Overfishing and pollution of the aquatic environment, in addition to their direct effects on natural fisheries, may have also influenced natural fish populations genetically. Overfishing drastically reduces population size and, since the larger individuals are selectively removed, is equivalent to selection for smaller sized fish. Adaptation of natural fish populations to their environment must have been reduced by rapid environmental changes resulting from pollution and infestation. Inbreeding, negative selection, and lack of adaption are here considered as the genetic causes for the decline of natural fisheries and lack of recovery. Restocking programs involving hatchery stocks are unlikely to solve this problem, since these stocks were selected for adaptation to hatchery environments and not to natural environments. A series of studies have demonstrated heterosis of interstrain crossbreds, mainly between hatchery and wild stocks of salmonids, for performance in natural waters. Two strategies could be implemented in restocking programs: stocking spawners of a domestic strain (preferably of one sex) for interbreeding with the resident population or direct stocking of crossbred fry. This should be tested in small isolated bodies of water and needs to be accompanied by a monitoring program in order to evaluate the results and minimize hazards.
A Small RNA Virus Isolated from Salmonid Fishes in California, USA
Authors: Hedrick R. P. , Yun S. , Wingfield W. H.
Published: December 2008

Beginning in the summer of 1988, examinations of numerous salmonid broodstocks in northern California, USA, revealed widespread infections with a previously undescribed virus. The virus was isolated from ovarian fluids of adult rainbow trout (Oncorhynchus mykiss), cutthroat trout (O. clarki), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis) and from kidney and spleen samples of juvenile brown and brook trout. The virus was not associated with above-normal losses in adult or juvenile fish. Virions purified from infected CHSE-214 cells were hexagonal with a mean diameter of 37.5 nm (SD = 0.41) and did not possess an envelope. The virus induced a diffuse degenerative cytopathic effect in CHSE-214 cells 14–28 d after inoculation with ovarian fluids or tissue homogenates. The virus replicated in CHSE-214 cells at temperatures from 10 to 20 °C with an optimum at 15 °C. Replication of the virus was not inhibited by addition of 5-bromo-2-deoxyuridine (BUDR) to the growth medium. There was no virus-induced mortality but virus was recovered for periods of up to 3–5 wk following waterborne exposures of rainbow and brown trout and kokanee salmon (O. nerka) but not from chinook (O. tshawytscha) or coho salmon (O. kisutch).
An Experimental Analysis of Macrophyte Growth Forms as Fish Foraging Habitat
Authors: Dionne Michele , Folt Carol L.
Published: December 2008

In this laboratory study we measured the independent effects of macrophyte growth form, plant density, and prey abundance on the foraging rate of the pumpkinseed sunfish (Lepomis gibbosus). We demonstrate that macrophyte growth forms are not all similar in their effects on fish foraging. Prey capture rates of pumpkinseeds foraging among Scirpus validus (cylindrical stems) were 53 and 365% times greater than for Potamogeton amplifolius (leafy stems) for cladoceran (Sida crystallina) and larval damselfly (Coenagrionidae) prey, respectively. Plant growth form influenced prey capture rates more than charges in natural plant density. Plant density effects ranged from none on damselfly capture rates to a 29% decline in cladoceran capture rate over a twofold increase in plant density. Our results indicate that in plant-structured habitats, variation in plant growth form can be an important determinant of fish foraging and habitat associations.
Relation between Mercury Concentrations in Walleye (Stizostedion vitreum vitreum) and Northern Pike (Esox lucius) in Ontario Lakes and Influence of Environmental Factors
Authors: Wren C. D. , Scheider W. A. , Wales D. L. , Muncaster B. W. , Gray I. M.
Published: December 2008

We examined the relation between mercury levels in walleye (Stizostedion vitreum vitreum) and northern pike (Esox lucius) in Ontario lakes. Walleye and northern pike occurred together in 79 of the 346 study lakes. The length-standardized mercury concentrations in coexisting walleye and northern pike in the 79 lakes were highly correlated (r2 = 0.60). The mean mercury concentrations in walleye and northern pike of standardized length from these lakes were 0.65 and 0.52 μg/g, respectively. Lacustrine characteristics associated with lake dystrophy (dissolved organic carbon and iron) were positively correlated with mercury levels in both species. Variables associated with acidity (pH and alkalinity) and hardness (calcium, conductivity, and magnesium) were negatively correlated with mercury concentrations in northern pike but not walleye.
Under-Ice Circulation and the Residence Time of a Shallow Bay
Authors: Kenney Bernard C.
Published: December 2008

Vertical temperature profiles measured along the axis of Wupaw Bay in March of three consecutive years showed that the water column was inversely stratified under ice. The depth of the (inverse) thermocline varied monotonically along the length of the bay, with the most rapid change occurring in the channel connecting the bay to Southern Indian Lake. Using prototype instrumentation, the associated two-layer current in the connecting channel was measured. The current near bottom often exceeded 1 cm/s and was directed out of the bay. The upper layer current generally flowed into the bay but was more variable than the bottom current and at times reversed direction. Although the circulation is relatively weak, the water exchange through the channel makes an important contribution to the residence time of water in Wupaw Bay during March. A short (2 h) time series showed that the temperature structure was highly variable below the surface mixed layer. High-frequency random fluctuations in temperature were observed together with active overturning events indicative of significant levels of turbulence under ice. Nonlinear effects also dominated regions with the largest temperature gradients where temperature oscillations appeared wavelike but were higher in frequency than the measured Brunt–Vaisala frequency.
SECOND-ORDER CORRECTIONS TO QED COUPLING AT LOW TEMPERATURE
Authors: MASOOD SAMINA S. , HASEEB MAHNAZ
Published: December 2008

We calculate the second-order corrections to vacuum polarization tensor of photons at low temperatures, i.e. T ≪ 1010 K (T ≪ me). The thermal contributions to the QED coupling constant are evaluated at temperatures below the electron mass that is T < me. Renormalization of QED at these temperatures has explicitly been checked. The electromagnetic properties of such a thermal medium are modified. Parameters like electric permittivity and magnetic permeability of such a medium are no more constant and become functions of temperature.