bluuebunny/crossref_metadata_2025 huggingface dataset:
Using the Canadian ITS architecture for evaluating the safety benefits of intelligent transportation systems
Authors: Vahidi Homayoun , Sayed Tarek
Published: January 2004

The benefits of intelligent transportation systems (ITS) are indirectly represented by the annual world market for ITS, which according to ITS Canada (2002) will be $90 billion CAN by 2011. Improved safety is often cited as the top goal of implementing ITS. Despite the magnitude of these investments and their underlying goal to improve transportation safety, there are deficiencies in the quantity and quality of reported ITS safety benefits. Many of the benefits reported to date suffer from poor data, lack of an evaluation framework, and inconsistent terminology used to attribute benefits to ITS application areas. This paper explores these issues, while attempting to address one of them, namely the lack of an evaluation framework for assessing the safety benefits of ITS. Accordingly, a unique framework is developed based on the Canadian ITS architecture. The framework includes the identification of evaluation metrics that are mapped to the market packages in the Canadian ITS architecture and correlated with each other to capture the "cause" and "effect" flow of benefits. This framework will benefit future ITS safety evaluations by providing a structure for undertaking evaluations using terminology consistent with the Canadian ITS architecture.Key words: intelligent transportation systems, ITS architecture, safety benefits, safety evaluation.
Proposed Canadian automated highway system architecture: object-oriented approach
Authors: Al-Qaysi Qoutaiba , Easa Said M , Ali Nouman
Published: January 2004

Recent advances in the fields of data communication and automated controls make the implementation of automated highway systems (AHSs) more possible. Currently, substantial research effort is being made on the design of intelligent transportation system (ITS) architectures in Europe, Japan, the United States, and Canada. These architectures, however, have major limitations inherit in the design methodology used. Most ITS developers use a process-oriented approach for the design of the architecture that reduces its quality attributes (stability and flexibility) to future changes. This paper presents an approach to implement object-oriented design methodology in the Canadian intelligent transportation system (C-ITS) architecture for AHS. It was also shown that the C-ITS architecture needs a backup communication system to be integrated within the C-ITS architecture. Such a backup system would aid the reliability of future transportation systems to be developed based on this architecture. The proposed C-ITS architecture promotes flexibility, stability, and communication and, as such, should be of interest to ITS developers and researchers.Key words: intelligent transportation systems, architecture, automated highways, object-oriented approach, backup communication.
Critical review of Canadian Standards Association standard CSA-A23.3-94 provisions for punching shear strength of edge column–slab connections
Authors: Sherif Alaa G , Dilger Walter H
Published: January 2004

The purpose of this paper is to critically review the punching shear strength provisions of the Canadian Standards Association standard CSA-A23.3-94 for edge column–slab connections. Tests from the literature and our own experiments are used to study the most important parameters affecting the punching shear strength of edge slab–column connections. Based on the test results the eccentric shear stress model is evaluated for edge column connections, and improvements are suggested.Key words: edge column–slab connections, flat concrete plates, shear strength, punching shear, shear reinforcement, moment transfer.
Effect of freeze–thaw cycling on the behaviour of reinforced concrete beams strengthened in flexure with fibre reinforced polymer sheets
Authors: Green Mark F , Dent Aaron J.S , Bisby Luke A
Published: January 2004

Externally bonded fibre reinforced polymer (FRP) plates and sheets for strengthening and rehabilitating existing reinforced concrete structures have recently received a great deal of attention within the civil engineering community. Many tests have shown the benefits of FRP, but more information is required on their behaviour in cold regions. Twenty-seven small-scale concrete beams (100 mm × 150 mm × 1220 mm) were strengthened with FRP in flexure (and in some cases also in shear), subjected to up to 200 freeze–thaw cycles, and tested to failure in four-point bending. Test results were compared with those predicted by theoretical models and reasonable agreement between the tests and the models was obtained. Current design guidelines for FRP-strengthened beams were compared against the test data and were found to be adequate for the artificially aged beams. The test data also indicated that no significant damage to the glass or carbon FRP-strengthened concrete beams had occurred because of freeze–thaw cycling.Key words: concrete, rehabilitation, fibre reinforced polymers, FRP, beams, freeze–thaw, cold region engineering, flexure, external strengthening.
Shake table tests on single-storey braced timber frames
Authors: Popovski Marjan , Prion Helmut G.L , Karacabeyli Erol
Published: January 2004

Concentrically braced timber frames are often used as lateral load resisting systems in wood buildings where large open spaces are required. For application in high-risk earthquake zones, however, the ductility of the system is a concern, since energy absorption is typically limited to the connection region. In this paper, results are presented from a series of shake table tests conducted on single-storey braced frame models with different connections. Diagonal braces with five different connection types were tested, four of which used bolts as fasteners, while one brace had timber riveted connections. Four of the connections had a matching set with an identical configuration that was previously tested quasi-statically. Findings from the tests are presented along with some comments on the seismic behavior of this type of structural system. It was found that the seismic response of the braced frames is highly influenced by the brace connections. Braced frames with small diameter (slender) bolts and timber rivets showed desirable seismic performance, as they were able to dissipate the highest amount of the seismic input energy. A comparison of the quasi-static and shake table tests revealed slight differences in the load–deformation properties of the brace connections.Key words: braced timber frames, seismic response, connections, timber rivets, bolts, ductility, shake table tests.
A capillary action test for the investigation of adhesion in repair technology
Authors: Courard Luc , Degeimbre Robert
Published: January 2004

When repair material is laid down on a concrete substrate, the porosity of concrete allows it to penetrate the substrate, increasing the probability of physical interactions, and subsequently increasing adhesion. Water absorption by immersion or usual capillary action tests do not provide enough information to understand what happens when contact occurs between the concrete substrate and the cement slurries used as a bonding layer. An adaptation of the capillary action test is presented; this is based on a continuous measurement of mass change of the sample. Major differences according to the type of surface preparation are pointed out: absorption rates as well as mass changes are greater for polished concrete substrates than for sandblasted ones. Centrifuged solutions of cement slurries modified with plasticizers and superplasticizers are used for water replacement in the adapted capillary action test. Results clearly show the influence of these admixtures: the greater the adhesion tension, the greater the wetting of the concrete substrate. Determination of these thermodynamic characteristics and performance of an adapted capillary action test provide a better understanding of the mechanisms of interface creation and promotion of adhesion.Key words: concrete, substrate, repair, capillary, absorption, impregnation, interface, centrifugation, superficial tension, pore radius.
Risk and benefits associated with international construction–consulting joint ventures in the English-speaking Caribbean
Authors: McIntosh Karl , McCabe Brenda
Published: January 2004

Research was undertaken to determine the major risk factors associated with international construction–consulting joint ventures (ICJVs) formed in the English-speaking Caribbean (ESC) with construction and consulting firms from Canada and the United States of America. The three highest ranked reasons for forming ICJVs are to improve competitive positions, enter new markets, and share risks and (or) profits. The three highest ranked benefits of the ICJVs are to enhance competitive position, obtain new work, and increase market share. There was some correlation between reasons for entering into these relationships and their perceived benefits. The three highest ranked risks were loss because of bureaucracy for late approvals, project delay, and cash flow problems of the client. The 10 highest ranked risks for both English-speaking Caribbean and North American firms were identical although the ranks changed slightly.Key words: construction management, international, risk factors, joint ventures, success factors.
A project manager's level of satisfaction in construction logistics
Authors: Jang Hyounseung , Russell Jeffrey S , Yi June Seong
Published: January 2004

Customer satisfaction and continuous improvement are the fundamental goals of construction logistics. While much research has been focusing on exploring the relationship between the contractors and the ultimate customers, known as the owner, to improve the understanding of the significance of customer satisfaction, the need to examine the relationship between material suppliers and contractors is highly in demand. The purpose of this study is to extend the framework for construction material logistics in customer satisfaction from owner to project manager level. This paper examines how construction logistics affect a project manager's level of satisfaction. A survey established the general importance that a project manager must place on the construction logistics. Accordingly, the most significantly correlated factors in customer satisfaction were obtained from a project manager's point of view. Two hundred twenty-three experienced project managers provided valuable data to the study. Five important factors related to satisfaction were found through interviews with project managers and a literature review. These included personnel, material flow, schedule adherence, contractor's organization, and information flow. The study results suggest that material flow and information flow are worthy of the most attention. Satisfying the above factors will greatly improve the construction logistics that will, as a result, immensely increase the project manager's level of satisfaction.Key words: construction logistics, customer satisfaction, project manager, survey.
Restoration and structural health monitoring of Manitoba's Golden Boy
Authors: Mufti Aftab A
Published: January 2004

Although bridges were among the first civil engineering structures to use structural health monitoring (SHM) technologies, research is now expanding to explore other types of applications, including Manitoba's famous Golden Boy statue. Global research is identifying the value of using SHM technologies for civil engineering applications. Structural health monitoring uses a variety of sensors to gather information about the behaviour of a structure. The information creates a valuable knowledge base that can be analyzed to help identify potential structural risks, develop safer and more efficient new structures, and determine more effective ways to rehabilitate existing structures. This paper briefly describes the history of the Manitoba Legislative Building and the Golden Boy and also the use of SHM technologies to help preserve the Golden Boy statue, an icon of provincial heritage.Key words: history, Golden Boy, statue, sculptors, architects, engineers, shaft, corrosion, sensors, monitoring.
La gestion à risque contrôlé des réservoirs hydroélectriques
Authors: Seidou Ousmane , Marche Claude , Robert Benoit , Rousselle Jean
Published: January 2004

Because of uncertainty on inflows, a hydroelectric system may at any time leave its normal zone of operation and fail. This paper proposes a way to continuously measure this risk of failure by presenting it in the form of time-varying indicators. These indicators are very flexible and could be defined according to the manager's needs. They are calculated by stochastic simulation by using inflows scenarios built according to the observed conditions and the statistical behaviour of the river. The utility of this dynamic risk is highlighted by an application on the Cabonga reservoir located in Quebec, Canada. For this reservoir, we define and evaluate six hypothetical management rules. Four of these rules are explicitly related to the instant level of risk on this reservoir. Opposition between risk and system performance was highlighted in a quantitative way.Key words: risk, reservoir management, decision support.
Characteristics of the squalene synthase inhibitors produced by aStreptomycesspecies isolated from soils
Authors: Choi Sung-Won , Bai Dong-Hoon , Yu Ju-Hyun , Shin Chul Soo
Published: January 2004

Microorganisms producing squalene synthase inhibitors were screened from soils. A high producer was selected and identified as a Streptomyces species. Two active inhibitors were obtained from culture broths via a series of purification processes involving solvent extraction, WK-10 cation-exchange column chromatography, HP-20 adsorption column chromatography, silica-gel column chromatography, preparative HPLC, and crystallization. The inhibitors were confirmed as macrolactins A and F with molecular weights of 402 by UV-absorption spectrometry, fast atom bombardment mass spectometry, and13C- and1H-NMR analyses. Kinetic results for macrolactins A and F showed that they appear to be noncompetitive inhibitors of rat liver squalene synthase with IC50values of 1.66 and 1.53 µmol/L, respectively. Since mammalian squalene synthase was used, these inhibitors have significant potential as therapeutic agents for hyperlipemia and suppression of cholesterol biosynthesis.Key words: squalene synthase inhibitor, Streptomyces species, macrolactins A and F.
Expression and characterization of the 42 kDa chitinase of the biocontrol fungusMetarhizium anisopliaeinEscherichia coli
Authors: Baratto César Milton , Vanusa da Silva Marcia , Santi Lucélia , Passaglia Luciane , Schrank Irene Silveira , Vainstein Marilene Henning , Schrank Augusto
Published: January 2004

Albeit Metarhizium anisopliae is the best-characterized entomopathogenic fungus, the role of some hydrolytic enzymes during host cuticle penetration has not yet been established. Three chitinase genes (chit1, chi2, chi3) from Metarhizium have already been isolated. To characterize the chitinase coded by the chit1 gene, we expressed the active protein (CHIT42) in Escherichia coli using a T7-based promoter expression vector. The recombinant protein, CHIT42, is active against glycol chitin and synthetic N-acetylglucosamine (GlcNAc) dimer and tetramer substrates. These activities suggest that the recombinant CHIT42 acts as an endochitinase.Key words: Metarhizium anisopliae, chitinases, chit genes, recombinant protein, enthomopathogenic fungi.
A survey ofCampylobacterspecies shed in faeces of beef cattle using polymerase chain reaction
Authors: Inglis G D , Kalischuk L D , Busz H W
Published: January 2004

A polymerase chain reaction (PCR)-based survey of campylobacters associated with faeces collected from 382 beef cattle was undertaken. To ensure the removal of PCR inhibitors present in faeces and determine if adequate extraction was achieved, faeces were seeded with internal control DNA (i.e., DNA designed to amplify with the Campylobacter genus primer set, but provide a smaller amplicon) before the extraction procedure. In only two samples (0.5%) were the internal control or Campylobacter genus amplicons not detected. In the remaining 380 faecal samples, Campylobacter DNA was detected in 83% of the faecal samples (80% of the faecal samples were positive for Campylobacter genus DNA, and 3% of the samples were negative for Campylobacter genus DNA but positive for DNA of individual species). The most frequently detected species was Campylobacter lanienae (49%), a species only recently connected to livestock hosts. Campylobacter jejuni DNA was detected in 38% of the faecal samples, and Campylobacter hyointestinalis and Campylobacter coli DNA were detected in 8% and 0.5% of the samples, respectively. Campylobacter fetus DNA was not detected. Twenty-four percent of the faecal samples contained DNA of at least two species of Campylobacter. Of these samples, the majority (81%) contained DNA of C. jejuni and C. lanienae. The results of this study indicate that beef cattle commonly release a variety of Campylobacter species into the environment and may contribute to the high prevalence of campylobacteriosis in humans inhabiting areas of intensive cattle production, such as southern Alberta. Furthermore, this study demonstrates the utility of using PCR as a rapid and accurate method for simultaneously detecting the DNA of a diverse number of Campylobacter species associated with bovine faeces.Key words: campylobacters, detection, technique, Bos taurus.
Screening of nonpolyenic antifungal metabolites produced by clinical isolates of actinomycetes
Authors: Lemriss S , Laurent F , Couble A , Casoli E , Lancelin J M , Saintpierre-Bonaccio D , Rifai S , Fassouane A , Boiron P
Published: January 2004

The purpose of this work was to screen clinical isolates of actinomycetes producing nonpolyenic antifungals. This choice was made to limit the problem of rediscovery of well-known antifungal families, especially polyenic antifungals. One hundred and ten strains were tested, using two diffusion methods and two test media, against three yeast species and three filamentous fungi. Among 54 strains (49%) showing antifungal activity, five strains belonging to the genus Streptomyces were active against all test organisms and appeared promising. These results indicate that clinical and environmental isolates of actinomycetes could be an interesting source of antifungal bioactive substances. The production of nonpolyenic antifungal substances by these five active isolates was investigated using several criteria: antibacterial activity, ergosterol inhibition, and UV-visible spectra of active extracts. One active strain responded to all three selection criteria and produced potentially nonpolyenic antifungal metabolites. This strain was retained for further investigation, in particular, purification, structure elucidation, and mechanism of action of the active product.Key words: actinomycetes, Streptomyces, clinical isolates, antifungal, non-polyene.
Actinobacterial chitinase-like enzymes: profiles of rhizosphere versus non-rhizosphere isolates
Authors: Gonzalez-Franco Ana C , Deobald Lee A , Spivak Aaron , Crawford Don L
Published: January 2004

The objective of this study was to determine if antifungal actinomycetes isolated from rhizosphere and non-rhizosphere soils exhibit different chitinase-like production and (or) induction patterns. Selected isolates from both habitats were compared. Chitinase-like levels and isoform characteristic patterns were evaluated over time in culture fluids of isolates grown on media containing different combinations of colloidal chitin and fungal cell wall (FCW) preparation. Supernatants were also subjected to native and non-native polyacrylamide gel electrophoresis (PAGE), using glycol chitin amended gels. For non-native PAGE, protein samples were denatured by two different approaches. Multiple active bands, ranging from 20 to 53 kDa and present in varying amounts, were detected in gels for most strains. Different substrate preferences were observed among strains, and different chitinase-like enzymes were produced, depending upon the substrate combinations used. The presence of FCW in the medium induced specific chitinase-like enzymes not observed otherwise. Enzymatic activities and profiles of the isolates, however, were strain and substrate specific rather than habitat specific. However, a sagebrush rhizosphere soil had a larger actinomycete community with higher chitinolytic activities than the nearby bulk soil. The use of PAGE to compare chitinase-like proteins induced in media with and without FCW was useful for identifying chitinase-like enzymes potentially involved in antifungal activity.Key words: chitinase, actinomycetes, hydrolytic enzymes, rhizosphere, antifungal.
Microbial production of isoquinoline from indene
Authors: Francis Mike McD. , Gould W Douglas
Published: January 2004

A purified microbial isolate, identified as a strain of Rhodococcus sp., metabolized indene primarily to iso quinoline and lesser amounts of indandiol and indanone. Isoquinoline production was dependent on the presence of microbial culture, indene, and ammonium ions as the source of nitrogen in the molecule. The ability to produce iso quin oline was induced by growth on benzene or naphthalene and by the presence of indene itself. The culture produced compounds tentatively identified as 3-methylisoquinoline and 3-ethylisoquinoline from 2-methylindene and from 2-ethylindene, respectively. Deuterated indene was converted to deuterated isoquinoline, deuterated indanone, and deuterated indandiol. Experiments with [15N]ammonium nitrate and ammonium [15N]nitrate confirmed ammonium as the source of nitrogen in the isoquinoline products.Key words: biotransformation, metabolism, methylisoquinoline, ethylindene.
Survival of lactococci during passage through mouse digestive tract
Authors: Kimoto Hiromi , Nomura Masaru , Kobayashi Miho , Mizumachi Koko , Okamoto Takashi
Published: January 2004

One of the important properties of probiotics is the ability to survive in the intestine. There have been few studies on the probiotic property of lactococci, since they are formally not considered to be natural inhabitants of the intestine. To evaluate lactococci as probiotic bacteria, we investigated their ability to survive during gastric transit by in vitro and in vivo tests. When exposed to an in vitro simulated gastrointestinal environment, such as low pH and bile, only Lactococcus lactis subsp. lactis bv. diacetylactis N7 showed a moderate survival rate among the four strains tested. The tested strains were orally administered to mice, and intestinal passage of the ingested strains was monitored by two methods: antibiotics and PCR. Viable cells of strain N7 were recovered from feces within 24–48 h after administration but not at 72 h. Lactococcus lactis subsp. cremoris ATCC 19257, which had a poor survival rate in vitro test, was also detected at 12 h but not at 24 h. These results indicate that lactococci can reach the mouse intestine alive, but not colonize it. If administered daily, viable strain N7 may exist continuously in the intestine. The effect of strain N7 on intestinal microbial balance and on animal health will be the subject of a further study.Key words: Lactococcus, survival, gastrointestinal tract, probiotics.
Insulin-exacerbated hypertension in captopril-treated spontaneously hypertensive rats: role of sympathoexcitation
Authors: Roysommuti Sanya , Mozaffari Mahmood S , Wyss J Michael
Published: January 2004

Insulin excess exacerbates hypertension in spontaneously hypertensive rats (SHR). This study examined the relative contribution of the reninangiotensin system and the sympathetic nervous system in this phenomenon. In SHR, daily subcutaneous injections of insulin were initiated either before short-term angiotensin-converting enzyme inhibition with captopril or after lifetime captopril treatment. Insulin treatment resulted in significant increases in mean arterial pressure and heart rate and captopril treatment lowered arterial pressure, but captopril did not lower arterial pressure more in the insulin-treated compared with control rats. To test the contribution of the sympathetic nervous system to this form of hypertension, each rat was intravenously infused with either a ganglionic blocker (i.e., hexamethonium) or a centrally acting α2-adrenergic receptor agonist (i.e., clonidine). Administration of either agent largely eliminated the differences in mean arterial pressure and heart rate between the insulin-treated and saline-treated SHR, irrespective of captopril treatment. These data indicate that in SHR, the ability of insulin to increase blood pressure is closely related to sympathoexcitation, which is unresponsive to blockade of angiotensin-converting enzyme.Key words: blood pressure, insulin, captorpil, hexamethonium, clonidine, rat.
Dietary restriction and fibre supplementation: oxidative stress and metabolic shifting for cardiac health
Authors: Diniz Yeda S , Cicogna Antonio C , Padovani Carlos R , Silva Maeli D.P , Faine Luciane A , Galhardi Cristiano M , Rodrigues Hosana G , Novelli Ethel L.B
Published: January 2004

Dietary modification ought to be the first line of strategy in prevention of the development of cardiac disease. The purpose of this study was to investigate whether dietary restriction, dietary-fibre-enriched diet, and their interactions might affect antioxidant capacity and oxidative stress in cardiac tissue. Male Wistar rats (180–200 g; n = 10) were divided into four groups: control ad libitum diet (C), 50% restricted diet (DR), fed with fibre-enriched diet (F), and 50% restricted fibre-enriched diet (DR-F). After 35 days of the treatments, F, DR, and DR-F rats showed low cholesterol, LDL-cholesterol, and triacylglycerol, and high HDL-cholesterol in serum. The DR, DR-F, and F groups had decreased myocardial lipoperoxide and lipid hydroperoxide. The DR-F and F treatments increased superoxide dismutase and glutatione peroxidase (GSH-Px). The DR treatment increased GSH-Px and catalase activities. Dietary fibre beneficial effects were related to metabolic alterations. The F and DR-F groups showed high cardiac glycogen and low lactate dehydrogenase/citrate synthase ratios, indicating diminished anaerobic and elevated aerobic myocardial metabolism in these animals. There was no synergistic effect between dietary restriction and dietary fibre addition, since no differences were observed in markers of oxidative stress in the F and DR-F groups. Dietary fibre supplementation, rather than energy intake and dietary restriction, appears to be the main process retarding oxidative stress in cardiac tissue.Key words: dietary fibre, dietary restriction, cardiac tissue, oxidative stress.
Endothelium-derived reactive oxygen species: their relationship to endothelium-dependent hyperpolarization and vascular tone
Authors: Ellis Anthie , Triggle Chris R
Published: January 2004

Opinions on the role of reactive oxygen species (ROS) in the vasculature have shifted in recent years, such that they are no longer merely regarded as indicators of cellular damage or byproducts of metabolism  they may also be putative mediators of physiological functions. Hydrogen peroxide (H2O2), in particular, can initiate vascular myocyte proliferation (and, incongruously, apoptosis), hyperplasia, cell adhesion, migration, and the regulation of smooth muscle tone. Endothelial cells express enzymes that produce ROS in response to various stimuli, and H2O2is a potent relaxant of vascular smooth muscle. H2O2itself can mediate endothelium-dependent relaxations in some vascular beds. Although nitric oxide (NO) is well recognized as an endothelium-derived dilator, it is also well established, particularly in the microvasculature, that another factor, endothelium-derived hyperpolarizing factor (EDHF), is a significant determinant of vasodilatory tone. This review primarily focuses on the hypothesis that H2O2is an EDHF in resistance arteries. Putative endothelial sources of H2O2and the effects of H2O2on potassium channels, calcium homeostasis, and vascular smooth muscle tone are discussed. Furthermore, given the perception that ROS can more likely elicit cytotoxic effects than perform signalling functions, the arguments for and against H2O2being an endogenous vasodilator are assessed.Key words: reactive oxygen species, hydrogen peroxide (H2O2), endothelium-derived hyperpolarizing factor (EDHF), endothelium, relaxation.
Direct and indirect mechanisms regulating secretion of glucagon-like peptide-1 and glucagon-like peptide-2
Authors: Brubaker Patricia L , Anini Younes
Published: January 2004

The proglucagon-derived peptide family consists of three highly related peptides, glucagon and the glucagon-like peptides GLP-1 and GLP-2. Although the biological activity of glucagon as a counter-regulatory hormone has been known for almost a century, studies conducted over the past decade have now also elucidated important roles for GLP-1 as an antidiabetic hormone, and for GLP-2 as a stimulator of intestinal growth. In contrast to pancreatic glucagon, the GLPs are synthesized in the intestinal epithelial L cells, where they are subject to the influences of luminal nutrients, as well as to a variety of neuroendocrine inputs. In this review, we will focus on the complex integrative mechanisms that regulate the secretion of these peptides from L cells, including both direct and indirect regulation by ingested nutrients.Key words: GLP-1, GLP-2, intestine, secretion, nutrients, neural.
Effects of pentobarbital on purinergic P2X receptors of rat dorsal root ganglion neurons
Authors: Kitahara Seiko , Yamashita Megumi , Ikemoto Yoshimi
Published: January 2004

Purinergic P2X receptors are ligand-gated ion channels that are activated by extracellular adenosine triphosphate (ATP) and are widely expressed not only in the central and peripheral nervous system but also in tissues throughout the body, playing an important role in the transfer of nociceptive information. Since the influence of barbiturates on P2X receptor subtypes is not known, we studied the effects of pentobarbital sodium (PB) on ATP responses in dorsal root ganglion (DRG) neurons. DRG neurons were dissected from 10- to 14-day-old rats and dissociated after enzyme treatment. Electrical measurements were performed using the nystatin-perforated patch recording mode under voltage-clamp conditions. Drugs were applied using the Y-tube method. ATP evoked three types of inward current at –60 mV: fast desensitizing, slow desensitizing, and mixed. The fast-type current was attributed to activation of P2X3 subtype and the slow type to the P2X2 subtype. PB suppressed the fast-type current in a concentration-dependent manner, while the slow type was slightly reduced. A noncompetitive inhibition was suggested by a downward shift of the ATP concentration–response curves. The current–voltage relationships showed inward rectification, and the extent of suppression was not affected by the holding potential. The reduction was greater in external solutions of higher pH. PB had subtype-specific effects on P2X receptors. The ionized form is likely to be responsible for the suppression of the P2X3 receptor current, which may result in a reduction of the excitability of central and peripheral neurons and may contribute to the anesthetic and analgesic actions of the agent.Key words: pentobarbital sodium, ATP, P2X receptors, rat DRG neurons, patch clamp.
Coexistence of potentiation and low-frequency fatigue during voluntary exercise in human skeletal muscle
Authors: Fowles J R , Green H J
Published: January 2004

The role of muscle potentiation in overcoming low-frequency fatigue (LFF) as it developed during submaximal voluntary exercise was investigated in eight males (age 26.4 ± 0.7 years, mean ± SE) performing isometric leg extension at ~30% of maximal voluntary contraction for 60 min using a 0.5-duty cycle (1 s contraction, 1 s rest). At 5, 20, 40, and 60 min, exercise was interrupted for 3 min, and the maximum positive rate of force development (+dF/dtmax) and maximal twitch force (Pt) were measured in maximal twitch contractions at 0, 1, 2, and 3 min of rest (R0, R1, R2, R3); they were also measured at 15 min of recovery following the entire 60-min exercise period. These measures were compared with pre-exercise (PRE) as an indicator of potentiation. Force at low frequency (10 Hz) was also measured at R0, R1, R2, and R3, and at 15 min of recovery, while force at high frequency (100 Hz) was measured only at R0 and R3 and in recovery. Voluntary exercise increased twitch +dF/dtmax at R0 following 5, 20, 40, and 60 min of exercise, from 2553 ± 150 N/s at PRE to 39%, 41%, 42%, and 36% above PRE, respectively (P < 0.005). Twitch +dF/dtmax decayed at brief rest (R3) following 20, 40, and 60 min of exercise (P < 0.05). Pt at R0 following 5 and 20 min of exercise was above that at PRE (P < 0.05), indicating that during the early phase of moderate- intensity repetitive exercise, potentiation occurs in the relative absence of LFF. At 40 and 60 min of exercise, Pt at R0 was unchanged from PRE. The LFF (10 Hz) induced by the protocol was evident at 40 and 60 min (R0–R3; P < 0.05) and at 15 min following exercise (P < 0.05). High-frequency force was not significantly compromised by the protocol. Since twitch force was maintained, these results suggest that as exercise progresses, LFF develops, which can be compensated for by potentiation.Key words: excitability, myosin light chain, phosphorylation, isometric exercise.
Reactivity of isolated human chorionic vessels: analysis of some influencing variables
Authors: Abad Antonio , Estañ Luis , Morales-Olivas Francisco J , Serra Vicente
Published: January 2004

The aim of the study was to determine whether 24 h of cold storage of samples, mode of delivery, and gestational age influenced in vitro human chorionic vascular reactivity (35 arteries and 34 veins). The following groups were compared: (i) fresh versus 24-h cold-stored (4 °C in Krebs–Henseleit solution) chorionic vascular rings from normal term placentas, (ii) fresh chorionic vascular rings from normal term placentas obtained after vaginal delivery versus those obtained after elective caesarean section, and (iii) fresh chorionic vascular rings from normal term placentas versus those obtained from preterm deliveries. Isometric recording of the concentration–response curve to KCl (5–120 mM) was assesed in each group. In vitro human chorionic vascular reactivity was influenced negatively by the 24-h cold storage of samples, with only 30% of stored samples being weakly reactive to KCl. Human chorionic vascular reactivity to KCl was unaffected by the mode of delivery. However, the response to KCl was gestational-age dependent. Thus, preterm vascular rings exhibited a significantly (P < 0.05) decreased response (Emax = 9.8 ± 0.0 mN; EC50 = 26.0 ± 1.3 mM) compared with term samples (Emax = 21.6 ± 2 mN; EC50 = 13.9 ± 1.6 mM). In conclusion, this study provides evidence that fresh term vascular rings are the tissues of choice for studying human chorionic vascular reactivity.Key words: human chorionic vessels, placenta, vascular reactivity.
Response of predator-naive newt larvae to food and predator presence
Authors: Orizaola Germán , Braña Florentino
Published: January 2004

For naive prey, the ability to recognize predators is advantageous at the time of first predator encounter. After predator detection, prey could avoid the risk of being eaten by modifying the patterns of activity and use of habitat. The use of refuges is considered one of the most widespread antipredator tactics. In laboratory experiments, we tested the effects of food (cladocerans, Daphnia sp.) and predator (brown trout, Salmo trutta) presence on larval newt (Triturus helveticus and Triturus alpestris) refuging behaviour, and the effect of refuge use on larval survival. Newt larvae came from lakes without fish and were reared in the laboratory from the egg stage so that they lacked any previous experience with brown trout. Larvae of both species increased refuge use and reduced significantly their emergence rate in the presence of predators. Food had no effect on refuge use or activity. For both species, refuge availability increased larval survival by more than twofold when the predator was present. These results suggest that naive newt larvae are able to detect predators and show an innate antipredator response.
How to cope with periods of drought? Age at maturity, longevity, and growth of marbled newts (Triturus marmoratus) in Mediterranean temporary ponds
Authors: Jakob Christiane , Miaud Claude , Crivelli Alain J , Veith Michael
Published: January 2004

We studied age at maturity, longevity, and growth in a marbled newt (Triturus marmoratus) population in southwestern France. Parameters of the life cycle such as date of migration, reproductive period, and terrestrial activity were documented for three neighbouring temporary ponds. This Mediterranean marbled newt population was characterized by aestivation and hibernation periods, a prolonged aquatic phase in adults, and a presence of juveniles in water. Aestivation and hibernation lead to distinct growth periods as determined by skeletochronology. Minimum age at maturity was 2 and 3 years, whereas maximum age observed was 8 and 9 years in males and females, respectively. A higher growth rate and a lower survival rate were found in this Mediterranean population compared with other populations exposed to variable environmental conditions in western Europe.
Characteristics of ponds used by trumpeter swans in a spring migration stopover area
Authors: LaMontagne Jalene M , Jackson Leland J , Barclay Robert M.R
Published: January 2004

We investigated pond habitat use by trumpeter swans (Cygnus buccinator) at spring migration stopover areas in southern Alberta in 1999 and 2000. Spring migration stopover areas may be critical to gaining energy stores required for successful breeding, but no studies of trumpeter swan migration habitat have previously been published. We conducted counts of trumpeter swans on 13 ponds located west of Calgary, Alberta, Canada, and divided the ponds into three groups based on their use by trumpeter swans (consistent high use, variable use, and consistent low/no use). We determined properties of all ponds, including pond area <1 m deep, distance from roads, days ice-covered while trumpeter swans were present, pH, conductivity, total phosphorus, percent macrophyte cover, and rhizome plus tuber dry mass per square metre. We used forward-stepping discriminant function analysis to determine which pond properties were most consistent with trumpeter swan use. Consistent high-use ponds had the greatest rhizome plus tuber dry mass per square metre and high conductivity. Ice cover also influenced pond use. Potamogeton pectinatus was the dominant macrophyte in all consistently used ponds. Our results are important for identifying ponds favoured by trumpeter swans and to ensure that adequate habitat is available during spring migration.
Social behavior and sexual dimorphism in the Bonaire whiptail, Cnemidophorus murinus (Squamata: Teiidae): the role of sexual selection
Authors: Baird Troy A , Vitt Laurie J , Baird Teresa D , Cooper, Jr. William E , Caldwell Janalee P , Pérez-Mellado Valentín
Published: January 2004

We measured body dimensions and coloration and quantified the behavior of females and males of two color phases in the Bonaire whiptail, Cnemidophorus murinus, to begin addressing the ultimate causation for sexual dimorphism in this species. Examination of size-adjusted body dimensions revealed that males have wider, longer, and deeper heads as well as somewhat longer forelegs and hind legs. Males were characterized by two distinct coloration patterns. Blue males displayed purple–blue dewlaps, blue–gray background coloration on the head and anterior torso, numerous light blue spots on the flanks, brown–orange coloration on the posterior torso, and a turquoise section on the proximal portion of the tail. By contrast, brown males were uniform olive–green to yellow–brown, with the exception of light blue spots on the lateral torso. Females were colored like brown males but lacked the blue spots. Testis length scaled with body size. Testes of only 26% of brown males were active, whereas all blue males had active testes. Blue males initiated aggressive encounters involving chases and displays directed toward other males much more frequently than females were aggressive with consexuals or with either type of male. Brown males were not observed to initiate aggression. Most blue male aggression was directed toward other blue males (70.6% of encounters), whereas 29.4% of encounters were with brown males. Blue males initiated 85.7% of the courtship encounters observed compared with only 7.1% initiated by brown males and 7.2% by females. Male-biased dimorphism in head and leg dimensions as well as coloration, together with higher rates of intrasexual aggression and courtship activity by blue males, are consistent with the hypothesis that sexual selection explains the evolution of sexual dimorphism in C. murinus.
Population characteristics of abundant bivalves (Mollusca, Vesicomyidae) at a sulphide-rich seafloor site near Lihir Island, Papua New Guinea
Authors: Stecher Jens , Tunnicliffe Verena , Türkay Michael
Published: January 2004

Extensive beds of sulphide-habitat-associated clams are present on the summit of Edison Seamount (1450 m depth) near Lihir Island, Papua New Guinea. These vesicomyids represent a new species. Imagery indicates that two major fields are several hundred metres in size. Four large grabs yielded over 270 live clams up to 23 cm in length plus many shells. The size structure of the populations suggests that settlement occurs in cohorts and that successful recruitment occurs mostly in areas with few adult clams. Dead juveniles were most abundant in the grabs with dense adults. Images from a towed camera sled included scales to allow density estimates that range up to 240 clams/m2(in small patches) with sizes averaging around 16.5 cm in length. A biometric relationship for length to wet mass allows calculation of estimates of biomass represented by clams measured in photographs. The average biomass value in Lihir clam beds is 13.3 kg/m2, with maximum values over 29 kg/m2(wet mass including shells). We compare these values with those of other studies that retrieved fewer specimens or imagery. We suggest that several overestimates populate the literature but that values around 30 kg/m2rival the biomass of intertidal bivalve beds.
Estimating the costs of locomotion in snow for coyotes
Authors: Crête M , Larivière S
Published: January 2004

Carnivores living in areas of deep snow face additional energy expenditures during winter owing to increased locomotory costs. Such costs may vary in function of snow depth and hardness (sinking depth of animal) and travel speed. We estimated energetic costs of locomotion through snow in wild coyotes (Canis latrans) using three coyote-sized domestic dogs (Canis familiaris) to develop regression models predicting heart rate (as surrogate for energy expenditure) in relation to sinking depth and travel speed. In the absence of snow, heart rates of dogs increased linearly with travel speed (R2= 0.24), whereas when snow was present, track sinking depth affected heart rate substantially more than did travel speed. To assess whether our results with domestic dogs could help explain the behaviour of wild coyotes, we snow-tracked coyotes in southeastern Quebec, Canada, during two winters. During a normal harsh winter, coyotes relied on artificially packed snow (snowmobile and animal trails) more than during a mild winter. Coyotes typically exerted a fine-scale selection for snow depth and hardness that effectively reduced their sinking depth by ~2 cm. We estimated that travelling over snow increased coyote heart rate by 4%–6% in comparison with locomotion on hard surfaces, whereas fine-scale selection saved a similar amount of extra energy. We hypothesize that the use of snow packed by anthropogenic activities, especially snowmobile trails, may not only facilitate coyote movements in deep snow environments but also allow occupation of marginal habitats such as forested areas of northeastern North America.
Effect of underwater seismic surveys on molting male Long-tailed Ducks in the Beaufort Sea, Alaska
Authors: Lacroix Deborah L , Lanctot Richard B , Reed John A , McDonald Trent L
Published: January 2004

Large numbers of Long-tailed Ducks (Clangula hyemalis) (10 000 – 30 000) undergo a postnuptial wing molt along barrier islands of the Beaufort Sea, Alaska. To investigate the potential effects of underwater seismic activities on this species, we monitored the number and diving behavior of molting Long-tailed Ducks before, during, and after seismic activities in a seismic area and two control areas nearby between July and September 2001. Aerial surveys documented a decline in duck numbers in both seismic and control areas during the period of seismic activity. We used automated data-collection computers to monitor the presence and diving behavior of radio-equipped Long-tailed Ducks residing within 2.5 km of a series of computer setups located along the barrier islands and on the mainland. A statistical analysis based on a modified before–after control–impact approach found no difference in indices of site fidelity or diving intensity between the seismic area and two control areas. Thus, we found no effect of seismic activity on movements and diving behavior of molting Long-tailed Ducks. These results should be evaluated carefully, however, as logistical and ecological factors limited our ability to detect more subtle disturbance effects. We recommend additional studies on other bird species to fully understand the effects of underwater seismic testing.
Conspecific familiarity and shoaling preferences in a wild guppy population
Authors: Godin Jean-Guy J , Alfieri Michael S , Hoare Daniel J , Sadowski Jennifer A
Published: January 2004

In nature, social groups of animals are typically nonrandom associations of individuals. Such group associations may in part be based on social familiarity among individuals, acquired through repeated past encounters and behavioural experiences with each other. The factors that potentially affect the tendency to associate with familiar individuals remain poorly understood. Here, we investigated whether shoaling preferences based on presumed familiarity occur in wild adult guppies (Poecilia reticulata) originating from a Trinidadian population that experiences relatively low predation intensity from fishes and whether any such preferences differ between the sexes. When tested shortly after being collected in the field, neither males nor females clearly preferred to shoal with familiar same-sex conspecifics (collected from the same pool in the river) over unfamiliar ones (from different pools). Importantly, our results differ from those previously reported for guppies originating from the same population as ours and for a high predation risk population in Trinidad, suggesting that the development of social familiarity and its role in the formation of shoals in nature vary both within and among populations in the guppy. We provide plausible explanations for these observed populational differences in shoaling preferences in the guppy and discuss certain ecological factors that may affect the development and expression of shoaling preferences based on familiarity in nature.