bluuebunny/crossref_metadata_2025 huggingface dataset:
The Adenovirus E3-6.7K Protein Adopts Diverse Membrane Topologies following Posttranslational Translocation
Authors: Moise Alexander R. , Grant Jason R. , Lippé Roger , Gabathuler Reinhard , Jefferies Wilfred A.
Published: December 2003

The E3 region of adenovirus codes for several membrane proteins, most of which are involved in immune evasion and prevention of host cell apoptosis. We explored the topology and targeting mechanisms of E3-6.7K, the most recently described member of this group, by using an in vitro translation system supplemented with microsomes. Here, we present evidence that E3-6.7K, one of the smallest signal-anchor proteins known, translocates across the membrane of the endoplasmic reticulum in a posttranslational, ribosome-independent, yet ATP-dependent manner, reminiscent of the translocation of tail-anchored proteins. Our analysis also demonstrated that E3-6.7K could achieve several distinct topological fates. In addition to the previously postulated type III orientation (N-luminal/C-cytoplasmic, termed
Ntm
E3-6.7K), we detected a tail-anchored form adopting the opposite orientation (N-cytoplasmic/C-luminal, termed
Ctm
E3-6.7K) as well as the possibility of a fully translocated form (N and C termini are both translocated, termed
NC
E3-6.7K). Due to the translocation of a positively charged domain, both the
Ctm
E3-6.7K and
NC
E3-6.7K topologies of E3-6.7K constitute exceptions to the “positive inside” rule. The
Ntm
E3-6.7K and
NC
E3-6.7K are the first examples of posttranslationally translocated proteins in higher eukaryotes that are not tail anchored. Distinct topological forms were also found in transfected cells, as both N and C termini of E3-6.7K were detected on the extracellular surface of transfected cells. The demonstration of unexpected topological forms and translocation mechanisms for E3-6.7K defies conventional thinking about membrane protein topogenesis and advises that both the mode of targeting and topology of signal-anchor proteins should be determined experimentally.
Pseudorabies Virus UL3 Gene Codes for a Nuclear Protein Which Is Dispensable for Viral Replication
Authors: Klupp Barbara G. , Granzow Harald , Fuchs Walter , Mundt Egbert , Mettenleiter Thomas C.
Published: December 2003

Many of the products of the ca. 80 genes encoded by alphaherpesviruses have already been identified and, at least tentatively, functionally characterized. Among the least characterized proteins are the products of the genes homologous to herpes simplex virus UL3, which are present only in the subfamily
Alphaherpesvirinae
. To identify the UL3 protein of the porcine alphaherpesvirus pseudorabies virus (PrV), the complete PrV UL3 open reading frame was cloned, expressed in
Escherichia coli
as a glutathione
S
-transferase fusion protein, and used for immunization of a rabbit. In Western blots, the generated antiserum specifically detected a 34-kDa protein in PrV-infected cells, which was absent from purified virus preparations, indicating that PrV UL3 encodes a nonstructural protein. In indirect immunofluorescence analysis, the anti-UL3 serum produced predominantly nuclear staining in transfected as well as in infected cells, which was not altered in the absence of other virus-encoded nuclear proteins such as the UL31 and UL34 gene products. To investigate UL3 function, a deletion mutant, PrV-ΔUL3F2, was constructed and characterized. This mutant replicated and formed plaques on noncomplementing cells indistinguishable from wild-type PrV, demonstrating that PrV UL3 is not required for virus propagation in cultured cells. Moreover, ultrastructural examinations revealed no impairment of capsid formation in the nucleus, nuclear egress of capsids, virion maturation in the cytoplasm, or virus release. Thus, the overall properties of PrV UL3 are similar to those described for the homologous herpes simplex virus proteins which may be indicative of a common, yet hitherto unknown, function in alphaherpesvirus replication. However, based on our studies, an involvement of the UL3 homologs in virion formation appears unlikely.
A Point Mutation in the Binding Subunit of a Retroviral Envelope Protein Arrests Virus Entry at Hemifusion
Authors: Zavorotinskaya Tatiana , Qian Zhaohui , Franks John , Albritton Lorraine M.
Published: December 2003

The transmembrane subunits of viral envelope proteins are thought to perform all of the functions required for membrane fusion during entry of enveloped viruses. However, changes in a conserved SPHQ motif near the N terminus of the receptor binding subunit of a murine leukemia virus (MLV) envelope protein block infection and induction of cell-cell fusion but not receptor binding. Here we report evidence that a histidine-to-arginine change at position 8 (H8R) in the SPHQ motif of Moloney MLV blocks infection by arresting virus-cell fusion at the hemifusion state. In cell-cell fusion assays, H8R envelope protein induced mixing of membrane outer leaflet lipids but did not lead to content mixing, a finding indicative of fusion pore formation. Kinetic studies of virus-cell fusion showed that lipid mixing of H8R virus membranes begins much later than for wild-type virus. The length of the delay in lipid mixing decreased upon addition of two second-site changes that increase H8R virus infection to 100-fold less than the wild-type virus. Finally, chlorpromazine, dibucaine, and trifluoperazine, agents that induce pores in an arrested hemifusion state, rescued infection by H8R virus to within 2.5-fold of the level of wild-type virus infection and cell-cell fusion to half that mediated by wild-type envelope protein. We interpret these results to indicate that fusion progressed to the hemifusion intermediate but fusion pore formation was inhibited. These results establish that membrane fusion of Moloney MLV occurs via a hemifusion intermediate. We also interpret these findings as evidence that histidine 8 is a key switch-point residue between the receptor-induced conformation changes that expose fusion peptide and those that lead to six-helix bundle formation.
Hepatitis C Virus Subgenomic Replicons in the Human Embryonic Kidney 293 Cell Line
Authors: Ali Samir , Pellerin Charles , Lamarre Daniel , Kukolj George
Published: December 2003

Hepatitis C virus (HCV) infects liver cells and its replication in other cells is incompletely defined. Human hepatoma Huh-7 cells harboring subgenomic HCV replicons were used in somatic cell fusion experiments with human embryonic kidney 293 cells as a means of examining the permissiveness of 293 cells for HCV subgenomic RNA replication. 293 cells were generally not permissive for replication of Huh-7 cell-adapted replicons. However, upon coculturing of the two cell lines, we selected rare replicon-containing cells, termed 293Rep cells, that resembled parental 293 cells. Direct metabolic labeling of cells with
33
P in the presence of actinomycin D and Northern blotting to detect the negative strand of the replicon demonstrated functional RNA replicons in 293Rep cells. Furthermore, Western blots revealed that 293Rep cells expressed the HCV nonstructural proteins as well as markers of the naïve 293 cells but not Huh-7 cells. Propidium iodide staining and fluorescence-activated cell sorting analysis of 293Rep cells revealed that clone 293Rep17 closely resembled naïve 293 cells. Transfection of total RNA from 293Rep17 into naïve 293 cells produced replicon-containing 293 cell lines with characteristics distinct from those of Huh-7-derived replicon cell lines. Relative to Huh-7 replicons, the 293 cell replicons were less sensitive to inhibition by alpha interferon and substantially more sensitive to inhibition by poly(I)-poly(C) double-stranded RNA. This study established HCV subgenomic replicons in nonhepatic 293 cells and demonstrated their utility in expanding the study of cellular HCV RNA replication.
Restrictions to the Adaptation of Influenza A Virus H5 Hemagglutinin to the Human Host
Authors: Harvey Ruth , Martin Andrew C. R. , Zambon Maria , Barclay Wendy S.
Published: December 2003

The binding specificities of a panel of avian influenza virus subtype H5 hemagglutinin (HA) proteins bearing mutations at key residues in the receptor binding site were investigated. The results demonstrate that two simultaneous mutations in the receptor binding site resulted in H5 HA binding in a pattern similar to that shown by human viruses. Coexpression of the ion channel protein, M2, from most avian and human strains tested protected H5 HA conformation during trafficking, indicating that no genetic barrier to the reassortment of the H5 surface antigen gene with internal genes of human viruses existed at this level.
An Aromatic Side Chain Is Required at Residue 8 of SU for Fusion of Ecotropic Murine Leukemia Virus
Authors: Qian Zhaohui , Albritton Lorraine M.
Published: December 2003

The surface glycoprotein (SU) of most gammaretroviruses contains a conserved histidine at its amino terminus. In ecotropic murine leukemia virus SU, replacement of histidine 8 with arginine (H8R) or deletion of H8 (H8del) abolishes infection and cell-cell fusion but has no effect on binding to the cellular receptor. We report here that an aromatic ring side chain is essential to the function of residue 8. The size of the aromatic ring appears to be important, as does its ability to form a hydrogen bond. In addition, infection by all of the nonaromatic amino acid substitutions could be partially rescued by the addition of two suppressor mutations (glutamine 227 to arginine [Q227R] and aspartate 243 to tyrosine [D243Y]) or by exposure to chlorpromazine, an agent that induces fusion pores in hemifusion intermediates to complete fusion, suggesting that, like the previously described H8R mutant, the mutants reported here also arrest membrane fusion at the hemifusion state. We propose that H8 is a key switch-point residue in the conformation changes that lead to membrane fusion and present a possible mechanism for how its substitution arrests fusion at the hemifusion state.
Nucleic Acid Binding-Induced Gag Dimerization in the Assembly of Rous Sarcoma Virus Particles In Vitro
Authors: Ma Yu May , Vogt Volker M.
Published: December 2003

As also found for other retroviruses, the Rous sarcoma virus structural protein Gag is necessary and sufficient for formation of virus-like particles (VLPs). Purified polypeptide fragments comprising most of Gag spontaneously assemble in vitro at pH 6.5 into VLPs lacking a membrane, a process that requires nucleic acid. We showed previously that the minimum length of a DNA oligonucleotide that can support efficient assembly is 16 nucleotides (nt), twice the protein's binding site size. This observation suggests that the essential role of nucleic acid in assembly is to promote the formation of Gag dimers. In order to gain further insight into the role of dimerization, we have studied the assembly properties of two proteins, a nearly full-length Gag (ΔMBDΔPR) capable of proper in vitro assembly and a smaller Gag fragment (CTD-NC) capable of forming only irregular aggregates but with the same pH and oligonucleotide length requirements as for assembly with the larger protein. In analyses by sedimentation velocity and by cross-linking, both proteins remained monomeric in the absence of oligonucleotides or in the presence of an oligonucleotide of length 8 nt (GT8). At pH 8, which does not support assembly, binding to GT16 induced the formation of dimers of ΔMBDΔPR but not of CTD-NC, implying that dimerization requires the N-terminal domain of the capsid moiety of Gag. Assembly of VLPs was induced by shifting the pH of dimeric complexes of ΔMBDΔPR and GT16 from 8 to 6.5. An analogue of GT16 with a ribonucleotide linkage in the middle also supported dimer formation at pH 8. Even after quantitative cleavage of the oligonucleotide by treatment of the complex with RNase, these dimers could be triggered to undergo assembly by pH change. This result implies that protein-protein interactions stabilize the dimer. We propose that binding of two adjacent Gag molecules on a stretch of nucleic acid leads to protein-protein interactions that create a Gag dimer and that this species has an exposed surface not present in monomers which allows polymerization of the dimers into a spherical shell.
Intrapatient Alterations in the Human Immunodeficiency Virus Type 1 gp120 V1V2 and V3 Regions Differentially Modulate Coreceptor Usage, Virus Inhibition by CC/CXC Chemokines, Soluble CD4, and the b12 and 2G12 Monoclonal Antibodies
Authors: Nabatov Alexey A. , Pollakis Georgios , Linnemann Thomas , Kliphius Aletta , Chalaby Moustapha I. M. , Paxton William A.
Published: December 2003

We studied human immunodeficiency virus type 1 (HIV-1) chimeric viruses altering in their gp120 V1V2 and V3 envelope regions to better map which genetic alterations are associated with specific virus phenotypes associated with HIV-1 disease progression. The V1V2 and V3 regions studied were based on viruses isolated from an individual with progressing HIV-1 disease. Higher V3 charges were linked with CXCR4 usage, but only when considered within a specific V1V2 and V3 N-linked glycosylation context. When the virus gained R5X4 dual tropism, irrespective of its V3 charge, it became highly resistant to inhibition by RANTES and highly sensitive to inhibition by SDF-1α. R5 viruses with higher positive V3 charges were more sensitive to inhibition by RANTES, while R5X4 dualtropic viruses with higher positive V3 charges were more resistant to inhibition by SDF-1α. Loss of the V3 N-linked glycosylation event rendered the virus more resistant to inhibition by SDF-1α. The same alterations in the V1V2 and V3 regions influenced the extent to which the viruses were neutralized with soluble CD4, as well as monoclonal antibodies b12 and 2G12, but not monoclonal antibody 2F5. These results further identify a complex set of alterations within the V1V2 and V3 regions of HIV-1 that can be selected in the host via alterations of coreceptor usage, CC/CXC chemokine inhibition, CD4 binding, and antibody neutralization.
Mosaic Evolution of the Severe Acute Respiratory Syndrome Coronavirus
Authors: Stavrinides John , Guttman David S.
Published: December 2003

Severe acute respiratory syndrome (SARS) is a deadly form of pneumonia caused by a novel coronavirus, a viral family responsible for mild respiratory tract infections in a wide variety of animals including humans, pigs, cows, mice, cats, and birds. Analyses to date have been unable to identify the precise origin of the SARS coronavirus. We used Bayesian, neighbor-joining, and split decomposition phylogenetic techniques on the SARS virus replicase, surface spike, matrix, and nucleocapsid proteins to reveal the evolutionary origin of this recently emerging infectious agent. The analyses support a mammalian-like origin for the replicase protein, an avian-like origin for the matrix and nucleocapsid proteins, and a mammalian-avian mosaic origin for the host-determining spike protein. A bootscan recombination analysis of the spike gene revealed high nucleotide identity between the SARS virus and a feline infectious peritonitis virus throughout the gene, except for a 200- base-pair region of high identity to an avian sequence. These data support the phylogenetic analyses and suggest a possible past recombination event between mammalian-like and avian-like parent viruses. This event occurred near a region that has been implicated to be the human receptor binding site and may have been directly responsible for the switch of host of the SARS coronavirus from animals to humans.
Alternative Polyadenylation of Adeno-Associated Virus Type 5 RNA within an Internal Intron Is Governed by both a Downstream Element within the Intron 3′ Splice Acceptor and an Element Upstream of the P41 Initiation Site
Authors: Qiu Jianming , Nayak Ramnath , Pintel David J.
Published: December 2003

Adeno-associated virus type 5 (AAV5) has a linear, single-stranded DNA genome of ca. 5 kb and an overlapping transcription profile featuring multiple promoters and a single intron in the center of the genome. Unlike the situation for the prototype AAV2, AAV5 RNAs transcribed from upstream promoters at map units 7 (P7) and 19 (P19), which encode the viral Rep proteins, are predominantly polyadenylated at a site within the intron [(pA)p]. RNAs generated from the AAV5 capsid gene promoter P41, which is only 78 nucleotides (nt) upstream of the intron donor, and 281 nt upstream of (pA)p, primarily readthrough (pA)p, are polyadenylated at a more distal site at the 3′ end of the genome [(pA)d] and ultimately spliced. The intron contains the core sequences sufficient for polyadenylation at (pA)p, which is governed by a G/U-rich downstream element that overlaps with the intron 3′ A2 splice acceptor. In addition, polyadenylation of P7- and P19-generated RNAs at (pA)p is influenced by an upstream element that lies 5′ to the start of the P41 transcript. Our results also suggest that splicing and polyadenylation of P41-generated RNA can compete for the same pool of precursor pre-mRNA molecules. The
cis
-acting signals within the A2 3′ splice site that govern polyadenylation and splicing of AAV5 RNAs must be optimized to program both (i) the levels of polyadenylation of P7- and P19-generated RNA at (pA)p required to generate the proper levels of the essential Rep proteins and (ii) the splicing of P41-generated RNAs to generate the proper ratio of capsid proteins during AAV5 infection.
CcpA-Dependent Carbon Catabolite Repression in Bacteria
Authors: Warner Jessica B. , Lolkema Juke S.
Published: December 2003

Carbon catabolite repression (CCR) by transcriptional regulators follows different mechanisms in gram-positive and gram-negative bacteria. In gram-positive bacteria, CcpA-dependent CCR is mediated by phosphorylation of the phosphoenolpyruvate:sugar phosphotransferase system intermediate HPr at a serine residue at the expense of ATP. The reaction is catalyzed by HPr kinase, which is activated by glycolytic intermediates. In this review, the distribution of CcpA-dependent CCR among bacteria is investigated by searching the public databases for homologues of HPr kinase and HPr-like proteins throughout the bacterial kingdom and by analyzing their properties. Homologues of HPr kinase are commonly observed in the phylum Firmicutes but are also found in the phyla Proteobacteria, Fusobacteria, Spirochaetes, and Chlorobi, suggesting that CcpA-dependent CCR is not restricted to gram-positive bacteria. In the α and β subdivisions of the Proteobacteria, the presence of HPr kinase appears to be common, while in the γ subdivision it is more of an exception. The genes coding for the HPr kinase homologues of the Proteobacteria are in a gene cluster together with an HPr-like protein, termed XPr, suggesting a functional relationship. Moreover, the XPr proteins contain the serine phosphorylation sequence motif. Remarkably, the analysis suggests a possible relation between CcpA-dependent gene regulation and the nitrogen regulation system (Ntr) found in the γ subdivision of the Proteobacteria. The relation is suggested by the clustering of CCR and Ntr components on the genome of members of the Proteobacteria and by the close phylogenetic relationship between XPr and NPr, the HPr-like protein in the Ntr system. In bacteria in the phylum Proteobacteria that contain HPr kinase and XPr, the latter may be at the center of a complex regulatory network involving both CCR and the Ntr system.
Bioprospecting for Microbial Endophytes and Their Natural Products
Authors: Strobel Gary , Daisy Bryn
Published: December 2003

Endophytic microorganisms are to be found in virtually every plant on earth. These organisms reside in the living tissues of the host plant and do so in a variety of relationships, ranging from symbiotic to slightly pathogenic. Because of what appears to be their contribution to the host plant, the endophytes may produce a plethora of substances of potential use to modern medicine, agriculture, and industry. Novel antibiotics, antimycotics, immunosuppressants, and anticancer compounds are only a few examples of what has been found after the isolation, culture, purification, and characterization of some choice endophytes in the recent past. The potential prospects of finding new drugs that may be effective candidates for treating newly developing diseases in humans, plants, and animals are great.
Molecular Basis of Bacterial Outer Membrane Permeability Revisited
Authors: Nikaido Hiroshi
Published: December 2003

Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions.
RNA Interference: Biology, Mechanism, and Applications
Authors: Agrawal Neema , Dasaradhi P. V. N. , Mohmmed Asif , Malhotra Pawan , Bhatnagar Raj K. , Mukherjee Sunil K.
Published: December 2003

Double-stranded RNA-mediated interference (RNAi) is a simple and rapid method of silencing gene expression in a range of organisms. The silencing of a gene is a consequence of degradation of RNA into short RNAs that activate ribonucleases to target homologous mRNA. The resulting phenotypes either are identical to those of genetic null mutants or resemble an allelic series of mutants. Specific gene silencing has been shown to be related to two ancient processes, cosuppression in plants and quelling in fungi, and has also been associated with regulatory processes such as transposon silencing, antiviral defense mechanisms, gene regulation, and chromosomal modification. Extensive genetic and biochemical analysis revealed a two-step mechanism of RNAi-induced gene silencing. The first step involves degradation of dsRNA into small interfering RNAs (siRNAs), 21 to 25 nucleotides long, by an RNase III-like activity. In the second step, the siRNAs join an RNase complex, RISC (RNA-induced silencing complex), which acts on the cognate mRNA and degrades it. Several key components such as Dicer, RNA-dependent RNA polymerase, helicases, and dsRNA endonucleases have been identified in different organisms for their roles in RNAi. Some of these components also control the development of many organisms by processing many noncoding RNAs, called micro-RNAs. The biogenesis and function of micro-RNAs resemble RNAi activities to a large extent. Recent studies indicate that in the context of RNAi, the genome also undergoes alterations in the form of DNA methylation, heterochromatin formation, and programmed DNA elimination. As a result of these changes, the silencing effect of gene functions is exercised as tightly as possible. Because of its exquisite specificity and efficiency, RNAi is being considered as an important tool not only for functional genomics, but also for gene-specific therapeutic activities that target the mRNAs of disease-related genes.
A Continuum of Anionic Charge: Structures and Functions ofd-Alanyl-Teichoic Acids in Gram-Positive Bacteria
Authors: Neuhaus Francis C. , Baddiley James
Published: December 2003

Teichoic acids (TAs) are major wall and membrane components of most gram-positive bacteria. With few exceptions, they are polymers of glycerol-phosphate or ribitol-phosphate to which are attached glycosyl andd-alanyl ester residues. Wall TA is attached to peptidoglycan via a linkage unit, whereas lipoteichoic acid is attached to glycolipid intercalated in the membrane. Together with peptidoglycan, these polymers make up a polyanionic matrix that functions in (i) cation homeostasis; (ii) trafficking of ions, nutrients, proteins, and antibiotics; (iii) regulation of autolysins; and (iv) presentation of envelope proteins. The esterification of TAs withd-alanyl esters provides a means of modulating the net anionic charge, determining the cationic binding capacity, and displaying cations in the wall. This review addresses the structures and functions ofd-alanyl-TAs, thed-alanylation system encoded by the dlt operon, and the roles of TAs in cell growth. The importance of dlt in the physiology of many organisms is illustrated by the variety of mutant phenotypes. In addition, advances in our understanding ofd-alanyl ester function in virulence and host-mediated responses have been made possible through targeted mutagenesis of dlt. Studies of the mechanism ofd-alanylation have identified two potential targets of antibacterial action and provided possible screening reactions for designing novel agents targeted tod-alanyl-TA synthesis.
Effects of sodium citrate ingestion before exercise on endurance performance in well trained college runners
Authors: Oöpik V , Saaremets I , Medijainen L , Karelson K , Janson T , Timpmann S
Published: December 2003

Objective:To test the hypothesis that sodium citrate administered two hours before exercise improves performance in a 5 km running time trial.

Methods:A total of 17 male well trained college runners (mean (SD) V̇o2max61.3 (4.9) ml/kg/min) performed a 5 km treadmill run with and without sodium citrate ingestion in a random, double blind, crossover design. In the citrate trial, subjects consumed 1 litre of solution containing 0.5 g of sodium citrate/kg body mass two hours before the run. In the placebo trial, the same amount of flavoured mineral water was consumed.

Results:The time required to complete the run was faster in the citrate trial than the placebo trial (1153.2 (74.1) and 1183.8 (91.4) seconds respectively; p = 0.01). Lower packed cell volume and haemoglobin levels were found in venous blood samples taken before and after the run in the citrate compared with the placebo trial. Lactate concentration in the blood sample taken after the run was higher in the citrate than the placebo trial (11.9 (3.0)v9.8 (2.8) mmol/l; p<0.001), and glucose concentration was lower (8.3 (1.9)v8.8 (1.7) mmol/l; p = 0.02).

Conclusion:The ingestion of 0.5 g of sodium citrate/kg body mass shortly before a 5 km running time trial improves performance in well trained college runners.
Dynamic force distribution during level walking under the feet of patients with chronic ankle instability
Authors: Nyska M , Shabat S , Simkin A , Neeb M , Matan Y , Mann G
Published: December 2003

Objectives:To examine changes in the pattern of force transfer between the foot and the floor associated with chronically sprained ankles by measuring the peak forces and their timing under several regions of the feet during level walking.

Methods:Twelve young male subjects (mean (SD) age 21 (2) years) with recurrent ankle sprains were studied. Seven of them had unilateral and bilateral chronic instability and laxity, and five had bilateral instability. Twelve healthy men (without orthopaedic or medical disease) served as a control group. Subjects walked at their own pace along a 7 m walkway, which included a Mini-EMED pressure distribution measuring system. The variables measured were relative peak force (fraction of body weight) and relative timing (fraction of stance time). These variables were measured under six regions of interest in each foot print: heel, midfoot, medial, central, and lateral forefoot, and toes.

Results:(a) A significant delay to the time of peak force under the central and lateral forefoot and toes in subjects with chronic ankle instability. (b) A significant decrease in the relative forces under the heel and toes and an increase in the relative forces under the midfoot and lateral forefoot in subjects with chronic ankle instability. (c) In the patients with unilateral instability, there were no significant differences in any of the variables between the injured and non-injured foot.

Conclusions:In patients with chronic ankle instability, there is a slowing down of weight transfer from heel strike to toe off, a reduced impact at the beginning and end of the stance phase, and a lateral shift of body weight.
Dehydration of football referees during a match
Authors: Da Silva A I , Fernandez R
Published: December 2003

Objectives:To study hydration status in referees (main) and assistant referees (linesmen) during official football matches.

Methods:Twelve male football referees were evaluated; all were volunteers. Before and after each match, the referee and one of the assistants were weighed without clothes and a blood sample was taken. Total water loss was determined for each subject from the change in body weight. The main haematological variables were analysed in the blood samples. Total plasma protein concentration and osmolarity were also determined. Variation in plasma volume was determined from changes in packed cell volume and a combination of changes in packed cell volume and haemoglobin concentrations.

Results:During a match, total body water loss was 1.60 (0.13) litres, equivalent to 2.05 (0.18)% of body weight. Body weight was reduced by 1.55 (0.12)%, showing that water ingestion during the interval replaces only 24.4% of the body fluids lost during the match. The assistants lost 0.79 (0.19) litre of water, equivalent to 1.05 (0.25)% of body weight. The referees showed a significant decrease in plasma volume of 4.99 (1.33)%. The assistants showed a non-significant increase in plasma volume. The reduction in plasma volume observed in the referees correlated significantly with total body water loss (r =  0.9623). From these data, it is possible to predict that a dehydration of 1% reflects a reduction in plasma volume of nearly 2.5%.

Conclusions:Referees are moderately dehydrated after a football match (2%), whereas assistants show a non-significant dehydration of 1% of their body weight.
Snowblading injuries in Eastern Canada
Authors: Bridges E J , Rouah F , Johnston K M
Published: December 2003

Objectives:To evaluate injury patterns of snowbladers and compare them with those of skiers and snowboarders. To determine possible effects of helmet use in these sports on injury to the head and neck.

Methods:This prospective case series observational study was conducted by collecting the injury reports from the ski patrol during the 1999–2000 season at Mont Tremblant ski resort, Quebec. All participants in downhill winter sports who presented themselves to the ski patrol with traumatic injury related to their sport were included. A concussion was defined as any loss of consciousness, amnesia, confusion, disorientation, vertigo, or headache that resulted from injury. The ski patroller reported helmet use on the accident report at the time of injury.

Results:Snowbladers present with a unique pattern of injury compared with skiers and snowboarders. The incidence of leg, knee, and ankle/foot injuries were 20.5%, 25.6%, and 10.3% respectively. Concussions represented 11% of all injuries. There was no increase in other injury, including neck injury, related to helmet use.

Conclusions:Unique injury patterns in snowbladers warrant reconsideration of equipment design. Concussion is a common injury on the ski slope. Although the effects of helmet use on concussion rate are inconclusive based on this study, helmet use did not increase the rate of neck injury, even when adjusted for age.
Effects of physical activity on exercise tests and respiratory function
Authors: Cheng Y J , Macera C A , Addy C L , Sy F S , Wieland D , Blair S N
Published: December 2003

Background:Exercise is an important component of pulmonary rehabilitation for patients with chronic lung disease.

Objective:To explore the role of physical activity in maintaining cardiac and respiratory function in healthy people.

Methods:Cardiorespiratory fitness was measured by a maximal treadmill test (MTT), and respiratory function was tested by spirometry. The cross sectional study included data from 24 536 healthy persons who were examined at the Cooper Clinic between 1971 and 1995; the longitudinal study included data from 5707 healthy persons who had an initial visit between 1971 and 1995 and a subsequent visit during the next five years. All participants were aged 25–55 years and completed a cardiorespiratory test and a medical questionnaire.

Results:In the cross sectional study, after controlling for covariates, being active and not being a recent smoker were associated with better cardiorespiratory fitness and respiratory function in both men and women. In the follow up study, persons who remained or became active had better MTT than persons who remained or became sedentary. Men who remained active had higher forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) than the other groups. Smoking was related to lower cardiorespiratory fitness and respiratory function.

Conclusions:Physical activity and non-smoking or smoking cessation is associated with maintenance of cardiorespiratory fitness. Change in physical activity habits is associated with change in cardiorespiratory fitness, but respiratory function contributed little to this association during a five year follow up.
How valid is a self reported 12 month sports injury history?: Figure 1
Authors: Gabbe B J , Finch C F , Bennell K L , Wajswelner H
Published: December 2003

Background:A past injury history is one of the most commonly cited risk factors for sports injury. Often, injury history data are collected by self report surveys, with the potential for recall bias.

Objective:To assess the accuracy of a 12 month injury history recall in a population of 70 community level Australian football players.

Methods:The retrospective, self reported injury histories of 70 community level Australian football players were compared with prospective injury surveillance records for the same 12 month period. The accuracy of the players’ recall of the number of injuries, injured body regions, and injury diagnosis was assessed.

Results:Recall accuracy declined as the level of detail requested increased. All players could recall whether or not they were injured during the previous year. Almost 80% were able to accurately recall the number of injuries and body regions injured, but not the diagnoses, whereas only 61% were able to record the exact number, body region, and diagnosis of each injury sustained.

Discussion:The findings of this study highlight the difficulty of using retrospectively collected injury data for research purposes. Any injury research relying on self reported injury history data to establish the relation between injury history and injury risk should consider the validity of the self report injury histories.
Physiology of accidental hypothermia in the mountains: a forgotten story
Authors: Ainslie P N , Reilly T
Published: December 2003

Hypothermia is a serious condition, often with fatal consequences. The physiology and mechanisms of hypothermia in mountainous areas are discussed. It is as important to facilitate heat loss, especially during periods of high exertion, as it is to maintain heat production and preserve insulation. This can be partly achieved by clothing adjustments.
AN IMAGE RETRIEVAL SYSTEM BASED ON THE IMAGE FEATURE OF COLOR DIFFERENCES ON EDGES IN SPIRAL SCAN ORDER
Authors: CHAN YUNG-KUAN , LIU YI-TUNG
Published: December 2003

In this paper, an image feature of color differences on edges in spiral scan order (CDESSO) is presented. This proposed CDESSO feature can characterize the principal pixel colors, color complexity and color differences among adjacent objects in an image. In addition, this paper employs the CDESSO feature to develop an image retrieval system. The CDESSO-based image retrieval system can provide a high accuracy rate in finding the database images that satisfy the users' requirement. Besides, it can also resist the scale variants of images as well as the shift and rotation variants of objects in images.
DISTRIBUTED VARIANCE IN LOCALIZED PRINCIPAL COMPONENTS OF WHITENED NATURAL SCENES
Authors: WATTERS PAUL A.
Published: December 2003

Naïve models of V1 simple cells, based on principal components analysis (PCA), have poor performance and do not form a distributed population code, limiting their scientific value and practical application in pattern recognition of natural scenes. This paper evaluates two strategies for enhancing the validity of PCA models that have been applied to comparable nonorthogonal models: pre-cortical "whitening", and local decomposition of visual features. The goal is to form a distributed population code. Four sets (landscapes, trees and plants, people and animals, and books and buildings) of sixteen natural images (256 × 256 pixels) were whitened and decomposed into 160 randomly selected local segments of either 8 × 8 or 16 × 16 pixels. The variance distribution of each representation was evaluated using a "distributed coding efficiency index" (DCE). Highly significant increases in DCE were observed for the principal components of local, whitened image segments compared to whole, nonwhitened images. This suggests that whitening and local decomposition may improve PCA performance for natural image processing, potentially providing more accurate simple cell models. In addition, the comparatively good performance of more complex, nonorthogonal models may be partially explained by their use of whitening and local decomposition.
A NEW SLOW-MOTION REPLAY EXTRACTOR FOR SOCCER GAME VIDEOS
Authors: FARN EN-JUNG , CHEN LING-HWEI , LIOU JENN-HANN
Published: December 2003

In this paper, we will present a method to extract slow-motion replays in a soccer game video. According to our observation, a slow-motion replay always happens as a single shot and appears between two gradual transitions. Based on this fact, a video will first be segmented into individual shots and only those shots appearing between two gradual transitions are considered as candidate shots. There are two kinds of slow-motion replays. One comes from a standard camera and consists of some repeating or inserted frames. The other is from a high-speed camera with larger variation between two consecutive frames. Based on these features, an extractor is then provided to check if a candidate shot is a slow motion replay. Some experimental results are given to show the effectiveness of the proposed method.
Stability and stabilizability of dynamicalsystems with multiple time‐varying delays:delay‐dependent criteria
Authors: Mehdi D. , Boukas E. K.
Published: December 2003

This paper deals with the class of uncertain systems with
multiple time delays. The stability
and stabilizability of this class of systems are considered.
Their robustness are also studied when the norm‐bounded
uncertainties are considered. Linear matrix inequality
(LMIs) delay‐dependent sufficient conditions for both
stability and stabilizability and their robustness are
established to check if a system of this class is stable and/or
is stabilizable. Some numerical examples are provided to show the
usefulness of
the proposed results.
The relationship between the local temperature and the local heat flux withina one‐dimensional semi‐infinite domain of heat wave propagation
Authors: Kulish Vladimir V. , Novozhilov Vasily B.
Published: December 2003

The relationship between the local temperature and the local heat
flux has been established for the homogeneous hyperbolic heat
equation. This relationship has been written in the form of a
convolution integral involving the modified Bessel functions. The
scale analysis of the hyperbolic energy equation has been
performed and the dimensionless criterion for the mode of energy
transport, similar to the Reynolds criterion for the flow
regimes, has been proposed. Finally, the integral equation,
relating the local temperature and the local heat flux, has been
solved numerically for those processes of surface heating whose
time scale is of the order of picoseconds.
Thermomechanical constraints and constitutive formulations in thermoelasticity
Authors: Baek S. , Srinivasa A. R.
Published: December 2003

We investigate three classes of constraints in a thermoelastic
body: (i) a deformation‐temperature constraint, (ii) a
deformation‐entropy constraint, and (iii) a deformation‐energy
constraint. These constraints are obtained as limits of
unconstrained thermoelastic materials and we show that
constraints (ii) and (iii) are equivalent. By using a limiting
procedure, we show that for the constraint (i), the entropy plays
the role of a Lagrange multiplier while for (ii) and (iii), the
absolute temperature plays the role of Lagrange multiplier. We
further demonstrate that the governing equations for materials
subject to constraint (i) are identical to those
of an unconstrained material whose internal energy is an affine
function of the entropy, while those for materials subject to
constraints (ii) and (iii) are identical to those of an
unstrained material whose Helmholtz potential is affine in the
absolute temperature. Finally, we model the thermoelastic
response of a peroxide‐cured vulcanizate of natural
rubber and show that imposing the constraint in which the
volume change depends only on the internal energy leads to very
good predictions (compared to experimental results) of the stress
and temperature response under isothermal and isentropic
conditions.
Platelets of Female Mice Are Intrinsically More Sensitive to Agonists Than Are Platelets of Males
Authors: Leng Xing-Hong , Hong Song Yun , Larrucea Susana , Zhang Wei , Li Tong-Tong , López José A. , Bray Paul F.
Published: December 2003

Objective—

It has been reported that women fare worse after ischemic coronary events, but the mechanisms remain unclear. Because platelets play a central role in the formation of occlusive thrombi at sites of ruptured atherosclerotic plaques, we studied male/female paired mouse littermates for sex differences in platelet function.

Methods and Results—

We compared platelet reactivity in male/female mouse littermates by monitoring agonist-induced fibrinogen (FGN) binding and platelet aggregation. Compared with the platelets from males, platelets from females bound more FGN in response to low concentrations of thrombin and collagen-related peptide. Female platelets also demonstrated greater aggregation in response to adenosine diphosphate and collagen-related peptide. Platelet protein tyrosine phosphorylation on activation also showed small differences between sexes. These differences are independent of platelet size and surface expression of α
IIb
β
3
and GPIb-IX-V, and they were not blocked by apyrase or aspirin. The sex differences we observed were intrinsic to platelets, because they were observed in washed platelets, but not when platelets were in plasma.

Conclusions—

The platelets of female mice were more reactive than those of males in a manner independent of COX-1 and secreted ADP.
Growth Hormone Induces Low-Density Lipoprotein Clearance but not Bile Acid Synthesis in Humans
Authors: Lind Suzanne , Rudling Mats , Ericsson Sverker , Olivecrona Hans , Eriksson Mats , Borgström Birgit , Eggertsen Gösta , Berglund Lars , Angelin Bo
Published: December 2003

Objective—

Growth hormone (GH) induces hepatic low-density lipoprotein (LDL) receptors and lowers plasma cholesterol. We characterized the influence of GH treatment on plasma LDL clearance in normal humans and investigated the relative role of LDL receptor (LDLR) activity and stimulation of bile acid synthesis in subjects with different LDLR expression.

Methods and Results—

Plasma clearance of autologous
125
I-LDL was measured before and during 3 weeks of treatment with GH (0.1 IU/kg per day) in 9 healthy young males. Plasma LDL cholesterol was reduced by 13% and the fractional catabolic rate of LDL increased by 27%. More marked changes were seen in a patient with hypopituitarism substituted with GH (0.07 IU/kg per day) for 3 months. In a second study, GH dose-dependently reduced LDL cholesterol and increased Lp(a) levels in 3 groups of males: younger and elderly healthy subjects and heterozygous familial hypercholesterolemia (FH). No effect on bile acid synthesis measured by the plasma marker 7α-hydroxy-4-cholesten-3-one was observed. In an LDLR-deficient FH homozygote, LDL cholesterol was not affected by GH.

Conclusions—

GH treatment reduces plasma LDL cholesterol by inducing LDL clearance. In humans, LDLR expression is a prerequisite for this effect, whereas it is not related to stimulation of bile acid synthesis.
B-Type Natriuretic Peptide and Ischemia in Patients With Stable Coronary Disease
Authors: Bibbins-Domingo Kirsten , Ansari Maria , Schiller Nelson B. , Massie Barry , Whooley Mary A.
Published: December 2003

Background—

In patients with symptoms of heart failure, elevations in B-type natriuretic peptide (BNP) accurately identify ventricular dysfunction. However, BNP levels are not specific for ventricular dysfunction in patients who do not have overt symptoms of heart failure, suggesting that other cardiac processes such as myocardial ischemia may also cause elevations in BNP.

Methods and Results—

To determine whether BNP elevations are associated with myocardial ischemia, we measured plasma BNP levels before performing exercise treadmill testing with stress echocardiography in outpatients with stable coronary disease. Of the 355 participants, 113 (32%) had inducible ischemia. Compared with participants in the lowest BNP quartile (0 to 16.4 pg/mL), those in the highest quartile of BNP (≥105 pg/mL) had double the risk of inducible ischemia (adjusted relative risk, 2.0; 95% CI, 1.2 to 2.6;
P
=0.008). The relation between elevated BNP levels and inducible ischemia was especially evident in the 206 participants who had a history of myocardial infarction (adjusted relative risk, 2.6; 95% CI, 1.5 to 3.7,
P
=0.002) and was absent in those without a history of myocardial infarction (adjusted relative risk, 1.0; 95% CI, 0.3 to 2.2;
P
=0.9). This association between BNP levels and inducible ischemia remained strong after adjustment for measures of systolic and diastolic dysfunction.

Conclusions—

Elevated levels of BNP are independently associated with inducible ischemia among outpatients with stable coronary disease, particularly among those with a history of myocardial infarction. The observed association between BNP levels and ischemia may explain why tests for BNP are not specific for ventricular dysfunction among patients with coronary disease.