Multiple quantum filtered nuclear magnetic resonance of 23Na+ in uniformly stretched and compressed hydrogels

Stretching or compressing hydrogels creates anisotropic environments that lead to motionally averaged alignment of embedded guest quadrupolar nuclear spins such as 23Na+. These distorted hydrogels can elicit a residual quadrupolar coupling that gives an oscillation in the trajectories of single quantum coherences (SQCs) as a function of the evolution time during a spin-echo experiment. We present solutions to equations of motion derived with a Liouvillian superoperator approach, which encompass the coherent quadrupolar interaction in conjunction with relaxation, to give a full analytical description of the evolution trajectories of rank-1 (T^1±1), rank-2 (T^2±1), and rank-3 (T^3±1) SQCs. We performed simultaneous numerical fitting of the experimental 23Na nuclear magnetic resonance (NMR) spectra and rank-2 (T^2±1) and rank-3 (T^3±1) SQC evolution trajectories measured in double and triple quantum filtered experiments, respectively. We estimated values of the quadrupolar coupling constant CQ, rotational correlation time τC, and 3 × 3 Saupe order matrix. We performed simultaneous fitting of the analytical expressions to the experimental data to estimate values of the quadrupolar coupling frequency ωQ/2π, residual quadrupolar coupling ωQ/2π, and corresponding spherical order parameter S0*, which showed a linear dependence on the extent of uniform hydrogel stretching and compression. The analytical expressions were completely concordant with the numerical approach. The insights gained here can be extended to more complicated (biological) systems such as 23Na+ bound to proteins or located inside and outside living cells in high-field NMR experiments and, by extension, to the anisotropic environments found in vivo with 23Na magnetic resonance imaging.

Choices are inevitable: A qualitative exploration of the lifecosts of systemic lupus erythematosus

OBJECTIVES

Individuals with systemic lupus erythematosus experience considerable economic challenges. The aim of this research is to qualitatively investigate experiences of the lifecosts (direct and indirect economic costs and beyond) to those with systemic lupus erythematosus in Canada.

METHODS

Using a biopsychosocial conceptual framework and integrated knowledge translation approach, qualitative semi-structured interviews were conducted with 3 physicians, 5 representatives from systemic lupus erythematosus advocacy groups, and 29 adult systemic lupus erythematosus patients. Themes emerged deductively and inductively, and the theme code set was used to code all transcripts.

RESULTS

Three dominant themes emerged: (1) impacts of systemic lupus erythematosus on quality of life, relationships, and health; (2) costs linked to healthcare; and (3) impacts of living with systemic lupus erythematosus on employment/economic standing.

DISCUSSION

Whereas previous work has focused almost exclusively on the direct, individual costs of systemic lupus erythematosus, the biopsychosocial approach taken here emphasizes not only the individual and intermediate factors (such as the workplace and family), but also the system-level factors (i.e. system-level policies) that influence quality of life, healthcare, and employment/economic experiences of those with systemic lupus erythematosus. Results indicate a need to target interventions beyond the individual and their immediate context, and recognize that lifecosts are shaped significantly by systems-level action.

Validation of the Saint Louis University Quality of Life Questionnaire in Older Adults with Alzheimer's Disease

BACKGROUND/OBJECTIVES

Alzheimer's disease (AD) is the most common cause of dementia and negatively impacts individuals' quality of life (QOL). One essential component of disease management in older adults with AD is the maintenance and improvement of QOL. The QOL-AD is a tool that can be administered to evaluate QOL in AD patients, but it can take too long to administer in a patient visit. The purpose of this study was to investigate the validity of a more brief, 6-item QOL questionnaire, LIFEAD, comparing it to the QOL-AD in older adults with mild to moderate cognitive dysfunction.

DESIGN

Prospective validation study.

SETTING

Participants were patients presenting to internal medicine and geriatrics outpatient clinics and a nursing home.

PARTICIPANTS

285 adults 65 and older with mild to moderate cognitive impairment.

MEASUREMENTS

QOL was assessed using LIFEAD and the QOL-AD. Demographic data were collected and level of depression was determined through a demographic questionnaire and the PHQ-8, respectively.

RESULTS

QOL-AD mean item scores ranged from 2.27-3.32 with an average scale total of 36.28 ± 6.48. LIFEAD mean item scores ranged from 2.26-2.51 with an average scale total of 14.28 ± 2.87. A majority (68%) of patients rated all items on LIFEAD as either average or good. The correlation between LIFEAD and the QOL-AD was 0.71 (p<0.001). Both LIFEAD and the QOL-AD showed strong internal consistency with a Cronbach's alpha of 0.82 and 0.87, respectively.

CONCLUSION

This study validated LIFEAD and exhibited LIFEAD can assess QOL in older adults with mild to moderate cognitive dysfunction in the clinic or nursing home. LIFEAD is a short, practical questionnaire and is easily administered in approximately 1 minute. Further research on LIFEAD could be done with larger samples, in different clinical populations, and including persons of other ethnic backgrounds.

Nuclear singlet relaxation by scalar relaxation of the second kind in the slow-fluctuation regime

The singlet state of nuclear spin-1/2 pairs is protected against many common relaxation mechanisms. Singlet order, which is defined as the population difference between the nuclear singlet and triplet states, usually decays more slowly than the nuclear magnetization. Nevertheless, some decay mechanisms for nuclear singlet order persist. One such mechanism is called scalar relaxation of the second kind (SR2K) and involves the relaxation of additional nuclei ("third spins") which have scalar couplings to the spin-1/2 pair. This mechanism requires a difference between the couplings of at least one third spin with the two members of the spin-1/2 pair, and depends on the longitudinal relaxation time of the third spin. The SR2K mechanism of nuclear singlet relaxation has previously been examined in the case where the relaxation rate of the additional spins is on the time scale of the nuclear Larmor frequency. In this paper, we consider a different regime, in which the longitudinal relaxation of the third spins is on a similar time scale to the J-coupling between the members of the spin pair. This regime is often encountered when the spin-1/2 pair has scalar couplings to nearby deuterium nuclei. We show that the SR2K mechanism may be suppressed in this regime by applying a radiofrequency field which is resonant either with the members of the spin pair, or with the third spins. These phenomena are analyzed theoretically and by numerical simulations, and demonstrated experimentally on a diester of [¹³C₂, ²H₂]-labeled fumarate in solution.

Searching for rigour in the reporting of mixed methods population health research: a methodological review

The environments in which population health interventions occur shape both their implementation and outcomes. Hence, when evaluating these interventions, we must explore both intervention content and context. Mixed methods (integrating quantitative and qualitative methods) provide this opportunity. However, although criteria exist for establishing rigour in quantitative and qualitative research, there is poor consensus regarding rigour in mixed methods. Using the empirical example of school-based obesity interventions, this methodological review examined how mixed methods have been used and reported, and how rigour has been addressed. Twenty-three peer-reviewed mixed methods studies were identified through a systematic search of five databases and appraised using the guidelines for Good Reporting of a Mixed Methods Study. In general, more detailed description of data collection and analysis, integration, inferences and justifying the use of mixed methods is needed. Additionally, improved reporting of methodological rigour is required. This review calls for increased discussion of practical techniques for establishing rigour in mixed methods research, beyond those for quantitative and qualitative criteria individually. A guide for reporting mixed methods research in population health should be developed to improve the reporting quality of mixed methods studies. Through improved reporting, mixed methods can provide strong evidence to inform policy and practice.

Nonlinear damping and quasi-linear modelling

The mechanism of energy dissipation in mechanical systems is often nonlinear. Even though there may be other forms of nonlinearity in the dynamics, nonlinear damping is the dominant source of nonlinearity in a number of practical systems. The analysis of such systems is simplified by the fact that they show no jump or bifurcation behaviour, and indeed can often be well represented by an equivalent linear system, whose damping parameters depend on the form and amplitude of the excitation, in a 'quasi-linear' model. The diverse sources of nonlinear damping are first reviewed in this paper, before some example systems are analysed, initially for sinusoidal and then for random excitation. For simplicity, it is assumed that the system is stable and that the nonlinear damping force depends on the nth power of the velocity. For sinusoidal excitation, it is shown that the response is often also almost sinusoidal, and methods for calculating the amplitude are described based on the harmonic balance method, which is closely related to the describing function method used in control engineering. For random excitation, several methods of analysis are shown to be equivalent. In general, iterative methods need to be used to calculate the equivalent linear damper, since its value depends on the system's response, which itself depends on the value of the equivalent linear damper. The power dissipation of the equivalent linear damper, for both sinusoidal and random cases, matches that dissipated by the nonlinear damper, providing both a firm theoretical basis for this modelling approach and clear physical insight. Finally, practical examples of nonlinear damping are discussed: in microspeakers, vibration isolation, energy harvesting and the mechanical response of the cochlea.

Engaging First Nation and Inuit communities in asthma management and control: assessing cultural appropriateness of educational resources

INTRODUCTION

Asthma is a growing concern in First Nations and Inuit communities. As with many health indicators and outcomes, Aboriginal peoples living in remote areas experience greater disparities in respiratory health compared with non-Aboriginal Canadians. Therefore, it is critically important to take into account their unique needs when developing asthma educational materials and resources. The purpose of this study is to assess the cultural relevance of existing asthma education materials for First Nations and Inuit peoples. Five First Nations and Inuit communities from across Canada participated in the project.

METHODS

A combination of quantitative evaluations (eg surveys) and qualitative approaches (eg open discussion, live chats) were used to assess printed and web-based asthma education materials. Participants represented First Nations and Inuit communities from across Canada and were selected on the basis of age and role: 6 to 12 years old (children), 12 and over (youth), parents and grandparents, community leaders and teachers, and community advisory group members.

RESULTS

In general, the results showed that although participants of all age categories liked the selection of asthma educational materials and resources, they identified pictures and images related to First Nations and Inuit people living and coping with asthma as ways of improving cultural relevance. This reinforces findings that tailoring materials to include Aboriginal languages, ceremonies and traditions would enhance their uptake. Our findings also demonstrate that visually based content in both printed and virtual form were the preferred style of learning of all participants, except young children who preferred to learn through play and interactive activities.

CONCLUSIONS

Asthma is a growing concern in First Nations and Inuit communities. Given this concern, it is essential to understand cultural needs and preferences when developing asthma education materials and resources. The findings from this research emphasize the need to adapt existing asthma educational materials to better suit First Nations and Inuit cultures and the importance of directly engaging community members in the process.

Frequency-dependent properties of the tectorial membrane facilitate energy transmission and amplification in the cochlea

The remarkable sensitivity, frequency selectivity, and dynamic range of the mammalian cochlea relies on longitudinal transmission of minuscule amounts of energy as passive, pressure-driven, basilar membrane (BM) traveling waves. These waves are actively amplified at frequency-specific locations by a mechanism that involves interaction between the BM and another extracellular matrix, the tectorial membrane (TM). From mechanical measurements of isolated segments of the TM, we made the important new (to our knowledge) discovery that the stiffness of the TM is reduced when it is mechanically stimulated at physiologically relevant magnitudes and at frequencies below their frequency place in the cochlea. The reduction in stiffness functionally uncouples the TM from the organ of Corti, thereby minimizing energy losses during passive traveling-wave propagation. Stiffening and decreased viscosity of the TM at high stimulus frequencies can potentially facilitate active amplification, especially in the high-frequency, basal turn, where energy loss due to internal friction within the TM is less than in the apex. This prediction is confirmed by neural recordings from several frequency regions of the cochlea.

Multifunctional design of inertially-actuated velocity feedback controllers

The vibration of a structure can be controlled using either a passive tuned mass damper or using an active vibration control system. In this paper, the design of a multifunctional system is discussed, which uses an inertial actuator as both a tuned mass damper and as an element in a velocity feedback control loop. The natural frequency of the actuator would normally need to be well below that of the structure under control to give a stable velocity feedback controller, whereas it needs to be close to the natural frequency of a dominant structural resonance to act as an effective tuned mass damper. A compensator is used in the feedback controller here to allow stable feedback operation even when the actuator natural frequency is close to that of a structural mode. A practical example of such a compensator is described for a small inertial actuator, which is then used to actively control the vibrations both on a panel and on a beam. The influence of the actuator as a passive tuned mass damper can be clearly seen before the feedback loop is closed, and broadband damping is then additionally achieved by closing the velocity feedback loop.

The place of health and the health of place: dengue fever and urban governance in Putrajaya, Malaysia

This case study investigates the connections among urban planning, governance and dengue fever in an emerging market context in the Global South. Key informant interviews were conducted with leading figures in public health, urban planning and governance in the planned city of Putrajaya, Malaysia. Drawing on theories of urban political ecology and ecosocial epidemiology, the qualitative study found the health of place - expressed as dengue-bearing mosquitoes and dengue fever in human bodies in the urban environment - was influenced by the place of health in a hierarchy of urban priorities.

Comparing school environments with and without legislation for the prevention and management of anaphylaxis

BACKGROUND

  School personnel in contact with students with life-threatening allergies often lack necessary supports, creating a potentially dangerous situation. Sabrina's Law, the first legislation in the world designed to protect such children, requires all Ontario public schools to have a plan to protect children at risk. Although it has captured international attention, the differences a legislative approach makes have not been identified. Our study compared the approaches to anaphylaxis prevention and management in schools with and without legislation.

METHODS

  Legislated (Ontario) and nonlegislated (Alberta, British Columbia, Newfoundland and Labrador, and Quebec) environments were compared. School board anaphylaxis policies were assessed for consistency with Canadian anaphylaxis guidelines. Parents of at-risk children and school personnel were surveyed to determine their perspectives on school practices. School personnel's EpiPen5 technique was assessed.

RESULTS

  Consistency of school board policies with anaphylaxis guidelines was significantly better in a legislated environment (P=0.009). Parents in a legislated environment reported more comprehensive anaphylaxis emergency forms (P<0.001), while school personnel in nonlegislated environments reported more comprehensive forms (P=0.004). Despite school personnel in both environments receiving EpiPen5 training (>80%), suboptimal technique was commonly observed. However, school personnel in the legislated environment had better technique (P<0.001).

CONCLUSION

  Our results suggest that school boards in legislated environments have made greater efforts to support students at risk for anaphylaxis compared to nonlegislated environments. However, significant gaps exist in both environments, especially with respect to EpiPen5 administration, content, and distribution of anaphylaxis emergency forms, and awareness of school procedures by school personnel and parents.

You cannot prevent a disease; you only treat diseases when they occur: knowledge, attitudes and practices to water-health in a rural Kenyan community

OBJECTIVE

Almost 1 billion individuals lack access to improved water supplies, with 2.6 billion lacking adequate sanitation. This leads to the propagation of multiple waterborne diseases. The objective of this study was to explore local knowledge, attitudes and practices to understand the mechanisms and pre-conditions for sustainable uptake and use of these facilities.

METHODS

Data collection took place in a rural Kenyan community in September 2009. A qualitative approach was taken, with 4 focus groups and 25 in-depth interviews conducted. Participant characteristics varied by age, gender, education, marital status, employment and community standing.

RESULTS

Few participants reported current access to improved water and sanitation facilities. Though they expressed desire for latrines and water sources, barriers including lack of funds and social capital, decrease the ability for installation. Participants understood that there was a link between the quality of water and their health, however, perceived benefits of current contaminated sources outweigh the potential health impacts and proliferate their continued use.

CONCLUSION(S)

While water-health links are understood to varying degrees within the community, contextual (physical environment), compositional (individual) and collective (community) factors interact to influence health. Community challenges, such as lack of unity, lack of education and lack control were identified as the main barriers to initiating change, despite a desire for increased access to safe water and sanitation.

Prescribing of psychotropic medication to the intellectually disabled by community paediatricians - a survey

BACKGROUND

Children with intellectual disability are often managed by community paediatricians and have a high prevalence of mental disorder. We do not know whether community paediatricians feel adequately trained to treat this group although we know that paediatricians contribute significantly to psychotropic prescribing for children.

METHODS

Psychotropic medication prescribing by community paediatricians to the intellectually disabled in the north-west and northern regions, community paediatricians' perceived training needs in this area and the availability of specialized psychiatric services were surveyed. Postal questionnaires were sent to all members of the British Association of Community Child Health in the north and north western regions (n= 155), between summer 2004 and autumn 2005.

RESULTS

A total of 70.1% (n= 110) of questionnaires were returned of which 66 were completed. The most common reason for non-completion was that the respondent did not look after the intellectually disabled. A total of 54.5% of respondents did not have access to specialist psychiatry services for children and adolescents with an intellectual disability. Community paediatricians were most likely to prescribe for sleep disorders and attention deficit hyperactivity disorder (ADHD). There was a significant relationship between perceived adequacy of training and paediatrics prescribing for ADHD, but there was no such relationship for sleep disorders. The vast majority of community paediatricians did not feel adequately trained to prescribe for challenging behaviour or depression, although a small minority did prescribe.

CONCLUSIONS

Community paediatricians play a substantial role in prescribing psychotropic medications for this group. A substantial minority of community paediatricians do not feel that they have enough training to prescribe for ADHD and sleep disorders, and perceived competency is more likely to inform prescribing for ADHD than for sleep disorders. This may have implications for training. Although these children pose complex difficulties, access to specialist mental health services for children and adolescents with intellectual disability remains patchy, especially in the north-west, and further development of these services is needed.

Levitation-free vibrated droplets: resonant oscillations of liquid marbles

A spherical conducting droplet in an alternating electric field is known to undergo shape oscillations. When the droplet is supported by a substrate, the shape is no longer a complete sphere, but shape resonances are still observed. To obtain a completely spherical droplet, some kind of levitation is needed, unless the droplet is in microgravity, and this has previously been provided by gas films or magnetic or other external forces. In this work, we report observations of shape oscillations of a hydrophobic-powder-coated droplet of water. A droplet of water rolled on a hydrophobic powder self-coats such that the water becomes encapsulated as a liquid marble. When the powder is a spherical hydrophobic grain with a contact angle greater than 90 degrees , it adheres to the solid-water interface with more than half of its diameter projecting from the liquid, thus ensuring the encapsulated water does not come into contact with any substrate. These liquid marbles are highly mobile and can be regarded as completely nonwetting droplets possessing contact angles of 180 degrees . In this work, we show that they also provide a new mechanism equivalent to levitating droplets and provide droplets with small contact areas and completely mobile contact lines for studies of shape oscillations. Liquid marbles were created using hydrophobic lycopodium and droplets of water containing potassium chloride and were excited into motion using an electrowetting-on-dielectric configuration with applied frequency swept from 1 to 250 Hz. Both an up-and-down motion and an oscillation involving multiple nodes were observed and recorded using a high-speed camera. The resonant oscillation modes of small liquid marbles were fitted to the theory for vibrations of a free spherical volume of fluid. This work demonstrates the principle that oscillation modes of completely nonwetting droplets can be studied using a simple powder coating approach without the need for an active mechanism for levitation.

Electrowetting of nonwetting liquids and liquid marbles

Transport of a water droplet on a solid surface can be achieved by differentially modifying the contact angles at either side of the droplet using capacitive charging of the solid-liquid interface (i.e., electrowetting-on-dielectric) to create a driving force. Improved droplet mobility can be achieved by modifying the surface topography to enhance the effects of a hydrophobic surface chemistry and so achieve an almost complete roll-up into a superhydrophobic droplet where the contact angle is greater than 150 degrees . When electrowetting is attempted on such a surface, an electrocapillary pressure arises which causes water penetration into the surface features and an irreversible conversion to a state in which the droplet loses its mobility. Irreversibility occurs because the surface tension of the liquid does not allow the liquid to retract from these fixed surface features on removal of the actuating voltage. In this work, we show that this irreversibility can be overcome by attaching the solid surface features to the liquid surface to create a liquid marble. The solid topographic surface features then become a conformable "skin" on the water droplet both enabling it to become highly mobile and providing a reversible liquid marble-on-solid system for electrowetting. In our system, hydrophobic silica particles and hydrophobic grains of lycopodium are used as the skin. In the region corresponding to the solid-marble contact area, the liquid marble can be viewed as a liquid droplet resting on the attached solid grains (or particles) in a manner similar to a superhydrophobic droplet resting upon posts fixed on a solid substrate. When a marble is placed on a flat solid surface and electrowetting performed it spreads but with the water remaining effectively suspended on the grains as it would if the system were a droplet of water on a surface consisting of solid posts. When the electrowetting voltage is removed, the surface tension of the water droplet causes it to ball up from the surface but carrying with it the conformable skin. A theoretical basis for this electrowetting of a liquid marble is developed using a surface free energy approach.

An exploratory spatial analysis of pneumonia and influenza hospitalizations in Ontario by age and gender

Pneumonia and influenza represent a significant public health burden in Canada and abroad. Knowledge of how this burden varies geographically provides clues to understanding the determinants of these illnesses, and insight into the effective management of health-care resources. We conducted a retrospective, population-based, ecological-level study to assess age- and gender-specific spatial patterns of pneumonia and influenza hospitalizations in the province of Ontario, Canada from 1992 to 2001. Results revealed marked variability in hospitalization rates by age, as well as clear and statistically significant patterns of high rates in northern rural counties and low rates in southern urban counties. A moderate yet significant level of positive spatial autocorrelation (Moran's I=0.21, P<0.05) was found in the global data, with significant, age-specific clusters of high values or 'hot spots' identified in several northern counties. Findings illustrate the need for geographically focused prevention strategies, and resource and service allocation policies informed by regional and population-specific demands.

The political ecology of health: perceptions of environment, economy, health and well-being among ‘Namgis First Nation

Informed by Mayer's (Progr. Hum. Geogr 20 (1996) 441) political ecology of disease framework, this paper investigates First Nation's perceptions of the links between environment, economy and health and well-being. A case study of 'Namgis First Nation (Alert Bay, British Columbia, Canada) is used to explore the risks and benefits of salmon aquaculture for British Columbia's First Nations. Analysis of interview data (n = 23) indicates strong links between reduced access to environmental resources, marginal participation in the economy, and declining community health and well being. Results suggest that aquaculture development has further decreased the community's access to environmental resources, thereby restricting those economic, social, and cultural activities that determine good health and well-being for this community.

The "click" mechanism in dipteran flight: if it exists, then what effect does it have?

This paper is concerned with the flight mechanism of diptera. For many years it was thought that the flight mechanism incorporated a "click". In recent years, however, doubt has been cast as to whether this exists, or whether it is an artifact of experimental procedure. The aim of this paper is to contribute to this debate by presenting an investigation into the advantages or disadvantages of such a mechanism by conducting a dynamic analysis of a simplified model of such a mechanism. It is shown that, provided the mechanism is driven well below its resonance frequency and it is well-damped, i.e., it does a lot of work, then the flight mechanism with a "click" has distinct advantages over a system that does not have a "click" but is driven at its resonant frequency.

A gene from the locus of enterocyte effacement that is required for enteropathogenic Escherichia coli to increase tight-junction permeability encodes a chaperone for EspF

Disruption of the barrier properties of the enterocyte tight junction is believed to be important in the pathogenesis of diarrhea caused by enteropathogenic Escherichia coli (EPEC). This phenotype can be measured in vitro as the ability of EPEC to reduce transepithelial resistance (TER) across enterocyte monolayers and requires the products of the locus of enterocyte effacement (LEE) and, in particular, the type III secreted effector protein EspF. We report a second LEE-encoded gene that is also necessary for EPEC to fully reduce TER. rorf10 is not necessary for EPEC adherence, EspADB secretion, or formation of attaching and effacing lesions. However, rorf10 mutants have a diminished TER phenotype, reduced intracellular levels of EspF, and a reduced ability to translocate EspF into epithelial cells. The product of rorf10 is a 14-kDa intracellular protein rich in alpha-helices that specifically interacts with EspF but not with Tir or other EPEC secreted proteins. These properties are consistent with the hypothesis that rorf10 encodes a type III secretion chaperone for EspF, and we rename this protein CesF, the chaperone for EPEC secreted protein F.

From diversity comes understanding: health promotion capacity-building and dissemination research in Canada

Non-communicable diseases are the major cause of preventable death in industrialized countries and a growing concern elsewhere (Singapore Declaration, 1998). Modifiable risk factors for these diseases are prevalent [e.g., in Canada, 75% of adults have at least one modifiable risk factor for cardiovascular disease (CVD)] (Heart and Stroke Foundation of Canada, 1997).

Functional analysis of the enteropathogenic Escherichia coli type III secretion system chaperone CesT identifies domains that mediate substrate interactions

In many Gram-negative bacteria, a key indicator of pathogenic potential is the possession of a specialized type III secretion system, which is utilized to deliver virulence effector proteins directly into the host cell cytosol. Many of the proteins secreted from such systems require small cytosolic chaperones to maintain the secreted substrates in a secretion-competent state. One such protein, CesT, serves a chaperone function for the enteropathogenic Escherichia coli (EPEC) translocated intimin receptor (Tir) protein, which confers upon EPEC the ability to alter host cell morphology following intimate bacterial attachment. Using a combination of complementary biochemical approaches, functional domains of CesT that mediate intermolecular interactions, involved in both chaperone-chaperone and chaperone-substrate associations, were determined. The CesT N-terminal is implicated in chaperone dimerization, whereas the amphipathic alpha-helical region of the C-terminal, is intimately involved in substrate binding. By functional complementation of chaperone domains using the Salmonella SicA chaperone to generate chaperone chimeras, we show that CesT-Tir interaction proceeds by a mechanism potentially common to other type III secretion system chaperones.

Antibiotic-resistant cell-detaching Escherichia coli strains from Nigerian children

The properties of 23 cell-detaching Escherichia coli strains that were isolated from stool specimens in Nigeria are described. Common properties of the strains included the presence of genes encoding alpha-hemolysin (100%), pyelonephritis-associated pili (100%), and cytotoxic necrotizing factor 1 (70%) as well as lactose negativity (70%) and multiple antibiotic resistance (74%). Antibiotic resistance was shown in most cases to be transferable and associated with the presence of class 1 integrons. Phenotypic properties and pulsed-field gel electrophoresis analysis demonstrated that the majority of the strains, particularly multiply resistant, lactose-negative O4:H40 strains, were closely related. Multiply-resistant cell-detaching E. coli strains may represent an important reservoir for antibiotic resistance genes.

Mapping health in the Great Lakes areas of concern: a user-friendly tool for policy and decision makers

The role of the physical environment as a determinant of health is a major concern reported by the general public as well as by many policymakers. However, it remains one of the health determinants for which few available measures or indicators are readily available. This lack of data is compounded by the fact that evidence for direct cause-and-effect relationships in the literature is often equivocal, leading to feelings of uncertainty among the lay public and often leading to indecision among policymakers. In this article we examine one aspect of the physical environment--water pollution in the Great Lakes Areas of Concern (AOCs)--and its potential impacts on a wide range of (plausible) human health outcomes. Essentially, the International Joint Commission, the international agency that oversees Great Lakes water quality and related issues, worked with Health Canada to produce a report for each of the 17 AOCs on the Canadian side of the Great Lakes, outlining a long list of health outcomes and the potential relationships these might have with environmental exposures known or suspected to exist in the Great Lakes basin. These reports are based solely on secondary health data and a thorough review of the environmental epidemiologic literature. The use of these reports by local health policymakers as well as by public health officials in the AOCs was limited, however, by the presentation of vast amounts of data in a series of tables with various outcome measures. The reports were therefore not used widely by the audience for whom they were intended. In this paper we report the results of an undertaking designed to reduce the data and present them in a more policy-friendly manner, using a geographic information system. We do not attempt to answer directly questions related to cause and effect vis-à-vis the relationships between environment and health in the Great Lakes; rather, this work is a hypothesis-generating exercise that will help sharpen the focus of research into this increasingly important area of public health concern.

Environmental risk and (re)action: air quality, health, and civic involvement in an urban industrial neighbourhood

This paper explores the links between (perceived) environmental risk and community (re) action in an urban industrial neighbourhood in Hamilton, Ontario, Canada. In-depth interviews were conducted with residents of an area with a documented history of adverse air quality, in order to determine the relative influence of social capital (networks, norms, and social trust) and place attachment (sense of belonging in a neighbourhood) in deciding to take civic action around this particular environmental issue. The interviews illustrate the complexity of lay understandings of air pollution, and indicate that social capital is a primary contributor to the decision to take certain kinds of action, while attachment to place plays a lesser role.

Determinants of implementing heart health: promotion activities in Ontario public health units: a social ecological perspective

This paper reports the results of a study undertaken to explain levels of implementation of heart health promotion activities observed in Ontario public health agencies in 1997. Organizational-level data were collected by surveying all 42 health departments in 1994, 1996 and 1997 as part of the Canadian Heart Health Initiative Ontario Project. Guided by social ecological and organizational theories, the model examines relationships between implementation and four sets of possible determinants of activity: (1) the predisposition of agencies to undertake heart health promotion activities, (2) their capacity to undertake these activities, (3) internal organizational factors and (4) external system factors. A small set of five variables explains almost half of the variance in implementation (R2 = 0.46): organizational capacity (beta = 0.40), priority given to heart health (beta = 0.36), coordination of programs (beta = 0.19), use of resource centers (beta = 0.12) and participation in networks (beta = 0.09). The results suggest that models integrating organizational and socio-ecological theories can help us understand the implementation of community-based heart health promotion activities by public health agencies. Implications for future research, policy and practice are discussed.

EspG, a novel type III system-secreted protein from enteropathogenic Escherichia coli with similarities to VirA of Shigella flexneri

The function of the rorf2 gene located on the locus of enterocyte effacement (LEE) pathogenicity island of enteropathogenic Escherichia coli (EPEC) has not been described. We report that rorf2 encodes a novel protein, named EspG, which is secreted by the type III secretory system and which is translocated into host epithelial cells. EspG is homologous with Shigella flexneri protein VirA, and the cloned espG (rorf2) gene can rescue invasion in a Shigella virA mutant, indicating that these proteins are functionally equivalent in Shigella. An EPEC espG mutant had no apparent defects in in vitro assays of virulence phenotypes, but a rabbit diarrheagenic E. coli strain carrying a mutant espG showed diminished intestinal colonization and yet diarrheal attack rates similar to those of the wild type. A second EspG homolog, Orf3, is encoded on the EspC pathogenicity islet. The cloned orf3 gene could also rescue invasion in a Shigella virA mutant, but an EPEC espG orf3 double mutant was not diminished in any tested in vitro assays for EPEC virulence factors. Our results indicate that EspG plays an accessory but as yet undefined role in EPEC virulence that may involve intestinal colonization.

Complete nucleotide sequence and analysis of the locus of enterocyte Effacement from rabbit diarrheagenic Escherichia coli RDEC-1

The pathogenicity island termed the locus of enterocyte effacement (LEE) is found in diverse attaching and effacing pathogens associated with diarrhea in humans and other animal species. To explore the relation of variation in LEE sequences to host specificity and genetic lineage, we determined the nucleotide sequence of the LEE region from a rabbit diarrheagenic Escherichia coli strain RDEC-1 (O15:H-) and compared it with those from human enteropathogenic E. coli (EPEC, O127:H6) and enterohemorrhagic E. coli (EHEC, O157:H7) strains. Differing from EPEC and EHEC LEEs, the RDEC-1 LEE is not inserted at selC and is flanked by an IS2 element and the lifA toxin gene. The RDEC-1 LEE contains a core region of 40 open reading frames, all of which are shared with the LEE of EPEC and EHEC. orf3 and the ERIC (enteric repetitive intergenic consensus) sequence present in the LEEs of EHEC and EPEC are absent from the RDEC-1 LEE. The predicted promoters of LEE1, LEE2, LEE3, tir, and LEE4 operons are highly conserved among the LEEs, although the upstream regions varied considerably for tir and the crucial LEE1 promoter, suggesting differences in regulation. Among the shared genes, high homology (>95% identity) between the RDEC-1 and the EPEC and EHEC LEEs at the predicted amino acid level was observed for the components of the type III secretion apparatus, the Ces chaperones, and the Ler regulator. In contrast, more divergence (66 to 88% identity) was observed in genes encoding proteins involved in host interaction, such as intimin (Eae) and the secreted proteins (Tir and Esps). A comparison of the highly variable genes from RDEC-1 with those from a number of attaching and effacing pathogens infecting different species and of different evolutionary lineages was performed. Although RDEC-1 diverges from some human-infecting EPEC and EHEC, most of the variation observed appeared to be due to evolutionary lineage rather than host specificity. Therefore, much of the observed hypervariability in genes involved in pathogenesis may not represent specific adaptation to different host species.

The locus of enterocyte effacement (LEE)-encoded regulator controls expression of both LEE- and non-LEE-encoded virulence factors in enteropathogenic and enterohemorrhagic Escherichia coli

Regulation of virulence gene expression in enteropathogenic Escherichia coli (EPEC) and enterohemorrhagic E. coli (EHEC) is incompletely understood. In EPEC, the plasmid-encoded regulator Per is required for maximal expression of proteins encoded on the locus of enterocyte effacement (LEE), and a LEE-encoded regulator (Ler) is part of the Per-mediated regulatory cascade upregulating the LEE2, LEE3, and LEE4 promoters. We now report that Ler is essential for the expression of multiple LEE-located genes in both EPEC and EHEC, including those encoding the type III secretion pathway, the secreted Esp proteins, Tir, and intimin. Ler is therefore central to the process of attaching and effacing (AE) lesion formation. Ler also regulates the expression of LEE-located genes not required for AE-lesion formation, including rorf2, orf10, rorf10, orf19, and espF, indicating that Ler regulates additional virulence properties. In addition, Ler regulates the expression of proteins encoded outside the LEE that are not essential for AE lesion formation, including TagA in EHEC and EspC in EPEC. delta ler mutants of both EPEC and EHEC show altered adherence to epithelial cells and express novel fimbriae. Ler is therefore a global regulator of virulence gene expression in EPEC and EHEC.

Peroxynitrite reversibly inhibits Ca(2+)-activated K(+) channels in rat cerebral artery smooth muscle cells

Peroxynitrite (ONOO(-)) is a contractile agonist of rat middle cerebral arteries. To determine the mechanism responsible for this component of ONOO(-) bioactivity, the present study examined the effect of ONOO(-) on ionic current and channel activity in rat cerebral arteries. Whole cell recordings of voltage-clamped cells were made under conditions designed to optimize K(+) current. The effects of iberiotoxin, a selective inhibitor of large-conductance Ca(2+)-activated K(+) (BK) channels, and ONOO(-) (10-100 microM) were determined. At a pipette potential of +50 mV, ONOO(-) inhibited 39% of iberiotoxin-sensitive current. ONOO(-) was selective for iberiotoxin-sensitive current, whereas decomposed ONOO(-) had no effect. In excised, inside-out membrane patches, channel activity was recorded using symmetrical K(+) solutions. Unitary currents were sensitive to increases in internal Ca(2+) concentration, consistent with activity due to BK channels. Internal ONOO(-) dose dependently inhibited channel activity by decreasing open probability and mean open times. The inhibitory effect of ONOO(-) could be overcome by reduced glutathione. Glutathione, added after ONOO(-), restored whole cell current amplitude to control levels and reverted single-channel gating to control behavior. The inhibitory effect of ONOO(-) on membrane K(+) current is consistent with its contractile effects in isolated cerebral arteries and single myocytes. Taken together, our data suggest that ONOO(-) has the potential to alter cerebral vascular tone by inhibiting BK channel activity.

Partnering in and for heart health promotion: findings from a survey of community organizations

This paper presents the results of a survey conducted with representatives (n = 283) of community health agencies linked to heart health activity in Ontario in order to: 1) describe their levels of involvement in heart health promotion, 2) describe the nature and extent of partnering undertaken in the context of community-based heart health promotion, and 3) assess the extent to which community development approaches vis-à-vis partnering are being employed in Ontario heart health promotion. The survey included a series of questions regarding level of agency involvement in heart health promotion activities organized around four areas: tobacco, nutrition, physical activity and general heart health. Respondents were also asked to report the nature and extent of partnering that took place. Results indicate that levels of involvement varied significantly across activity area and by organization, although every agency type reported some level of involvement in each of the four activity areas. Overall, agencies surveyed continue to employ traditional settings (i.e., schools and community) as well as strategies (i.e., public education) but report a substantial amount of partnering and collaboration when undertaking community-based heart health promotion activities.

The practice of community development approaches in heart health promotion

There has been a recent shift in public health policy towards population-based approaches to the reduction of cardiovascular disease. This shift has been accompanied by a re-examination of strategies appropriate to the goal. Often, community development approaches, designed to affect socio-environmental change, are suggested as the most appropriate strategy for affecting community-wide change. Despite the fact that community development approaches have been used by several of the major community-based heart health initiatives, evidence of their use and usefulness remains sparse. This paper presents the findings of a qualitative study of the factors (i.e. community context, facilitators, barriers) affecting the use of community development approaches to heart health promotion in Ontario, Canada. Key informant interviews (n = 30) were conducted with stake-holders representing voluntary agencies, community health providers, boards of education and local coalitions in eight of the 42 health unit areas across Ontario. The qualitative analysis reveals (1) that the use of comprehensive community development approaches is limited and (2) that community agencies typically employ elements of community development approaches (e.g. community organization, community-based), often in combination and adapted to suit local conditions. The resulting landscape of community development approaches is characterized by a continuum of collaborative practices indicating that no one type of community approach is appropriate for all initiatives and in all communities. Therefore, from a programmatic perspective, it may not be realistic to advocate community development as the goal to which all communities should strive.

Environmental risk perception and well-being: effects of the landfill siting process in two southern Ontario communities

In the context of siting (environmentally) noxious land uses, recent research suggests that the well-being of individuals and communities is impacted as much by the decision-making process as the outcome itself. The study results presented in this paper stem from an ongoing, two-stage quantitative/qualitative investigation of impacts on individual and community well-being associated with the environmental assessment process in Ontario, Canada. This research uses a parallel case-study design to investigate two proposed landfill sites in southern Ontario. Qualitative in-depth interviews (n = 36), conducted across a variety of stakeholder groups, were used to address the following objectives: to explore the nature of concerns experienced by individuals faced with a local landfill site proposal; to explore the effects of the siting process on individuals and communities; and to examine the coping strategies employed by individuals in response to impacts experienced. The work attempts to apply theories of risk society (as conceptualised by Beck and Giddens) at a community scale. In so doing, we build on the work of health geographers attempting to link the social and contextual with the medical. Overall, substantial impacts on individual and community well-being were reported across all stakeholder groups interviewed: these included stress, disempowerment, hostility and divisions within the community. The experience of psychosocial impacts and effectiveness of coping strategies is shaped by certain factors associated with the site and the siting process (including uncertainty and the perceived lack of meaningful participation). The links between risk, process and impacts are theorized using a conceptual framework which incorporates site and process factors, effects on daily life (e.g. feelings of losing control, mistrust), and Gidden's conception of 'ontological security'. These findings have implications for environmental decision-making, as they suggest a need to locate the delicate balance point between community involvement and an expedient decision-making process within variable community contexts.

A longitudinal study of the health impacts of a petroleum refinery

Emissions from a petroleum refinery in Oakville, Ont., have been the source of longstanding health concerns among residents in the surrounding community. Between 1992 and 1997, the refinery implemented extensive odour reduction measures through improvements in waste water treatment, in sulphur recovery and combustion. In this paper, we present the main findings of a recent longitudinal analysis using data from community health surveys conducted in 1992 and 1997, before and after implementation of the odour reduction plan. The results show a decline in the frequency of odour perception and annoyance by residents whereas the reporting of cardinal and general symptoms among adults and children was virtually unchanged. Odour perception and annoyance were strongly related to symptom reporting in both years supporting the hypothesis that the effect of refinery emissions on residents' health is odour mediated. The findings extend our understanding of the psychosocial basis of symptom reporting in the vicinity of refineries.

Restructuring public health in Ontario: implications for heart health promotion

Community-based heart health promotion is viewed as an effective means of reducing cardiovascular disease risk. Although public health agencies have a central role in the implementation and dissemination of heart health programmes, their effectiveness is being challenged by major structural changes to Provincial public health systems across Canada, although the impacts of the changes have received relatively little attention in the research literature. As part of the Canadian Heart Health Initiative--Ontario Project (CHHIOP), this study used a qualitative approach to address the perceived implications of these changes to Ontario's public health system for heart health promotion. Interviews (n = 38) were conducted in eight public health units with staff most familiar with managing and/or delivering heart health activities. The results are mixed; that is, while many see the future of heart health promotion programming in Ontario as being at risk, others see recent changes as a step forward toward their institutionalization, particularly in light of recent funding decisions made by the Ministry of Health's Health Promotion Branch.

Restructuring public health in Ontario: implications for heart health promotion

Community-based heart health promotion is viewed as an effective means of reducing cardiovascular disease risk. Although public health agencies have a central role in the implementation and dissemination of heart health programmes, their effectiveness is being challenged by major structural changes to Provincial public health systems across Canada, although the impacts of the changes have received relatively little attention in the research literature. As part of the Canadian Heart Health Initiative--Ontario Project (CHHIOP), this study used a qualitative approach to address the perceived implications of these changes to Ontario's public health system for heart health promotion. Interviews (n = 38) were conducted in eight public health units with staff most familiar with managing and/or delivering heart health activities. The results are mixed; that is, while many see the future of heart health promotion programming in Ontario as being at risk, others see recent changes as a step forward toward their institutionalization, particularly in light of recent funding decisions made by the Ministry of Health's Health Promotion Branch.

Identification of CesT, a chaperone for the type III secretion of Tir in enteropathogenic Escherichia coli

The locus of enterocyte effacement of enteropathogenic Escherichia coli encodes a type III secretion system, an outer membrane protein adhesin (intimin, the product of eae ) and Tir, a translocated protein that becomes a host cell receptor for intimin. Many type III secreted proteins require chaperones, which function to stabilize proteins, prevent inappropriate protein-protein interactions and aid in secretion. An open reading frame located between tir and eae, previously named orfU, was predicted to encode a protein with partial similarity to the Yersinia SycH chaperone. We examined the potential of the orfU gene product to serve as a chaperone for Tir. The orfU gene encoded a 15 kDa cytoplasmic protein that specifically interacted with Tir as demonstrated by the yeast two-hybrid assay, column binding and coimmunoprecipitation experiments. An orfU mutant was defective in attaching-effacing lesion formation and Tir secretion, but was unaffected in expression of other virulence factors. OrfU appeared to stabilize Tir levels in the cytoplasm, but was not absolutely necessary for secretion of Tir. Based upon the physical similarities, phenotypic characteristics and the demonstrated interaction with Tir, orfU is redesignated as cesT for the chaperone for E. coli secretion of T ir.

The cloned locus of enterocyte effacement from enterohemorrhagic Escherichia coli O157:H7 is unable to confer the attaching and effacing phenotype upon E. coli K-12

The locus of enterocyte effacement (LEE) pathogenicity island of enterohemorrhagic Escherichia coli (EHEC) O157:H7 possesses the same genes in identical order and orientation as the LEE of enteropathogenic E. coli (EPEC) O127:H6 but is unable to form attaching and effacing (A/E) lesions or to secrete Esp proteins when it is cloned in an E. coli K-12 background. The A/E phenotype could not be restored by trans complementation with a variety of cloned EPEC LEE fragments, suggesting functional and/or regulatory differences between the LEE pathogenicity islands of EPEC O127:H6 and EHEC O157:H7.

Broadband performance of an active headrest

This paper presents a study of the attenuation of broadband random acoustic disturbances, when using a feedback active headrest system, as originally suggested by Olson and May. Previous studies showed that a practical active headrest can be designed for tonal disturbances using feedforward controllers. However, many applications, such as jet aircraft and cars, require feedback systems to control random disturbances over a wide frequency bandwidth. In this work, robust feedback controllers are designed to control broadband random disturbances in the low-frequency range based on measured data from a laboratory headrest system. The results show that a practically useful performance can be achieved, but only if the controller is designed to minimize the pressure at a "virtual microphone" close to the listener's ears, and that the performance is maintained reasonably well with movements of the listener's head. The paper emphasizes the importance of both the acoustics and the control in the design of broadband active headrest systems.

The power of perception: health risk attributed to air pollution in an urban industrial neighbourhood

This paper describes a multi-stakeholder process designed to assess the potential health risks associated with adverse air quality in an urban industrial neighborhood. The paper briefly describes the quantitative health risk assessment conducted by scientific experts, with input by a grassroots community group concerned about the impacts of adverse air quality on their health and quality of life. In this case, rather than accept the views of the scientific experts, the community used their powers of perception to advantage by successfully advocating for a professionally conducted community health survey. This survey was designed to document, systematically and rigorously, the health risk perceptions community members associated with exposure to adverse air quality in their neighborhood. This paper describes the institutional and community contexts within which the research is situated as well as the design, administration, analysis, and results of the community health survey administered to 402 households living in an urban industrial neighborhood in Hamilton, Ontario, Canada. These survey results served to legitimate the community's concerns about air quality and to help broaden operational definitions of 'health.' In addition, the results of both health risk assessment exercises served to keep issues of air quality on the local political agenda. Implications of these findings for our understanding of the environmental justice process as well as the ability of communities to influence environmental health policy are discussed.

The Per regulon of enteropathogenic Escherichia coli : identification of a regulatory cascade and a novel transcriptional activator, the locus of enterocyte effacement (LEE)-encoded regulator (Ler)

Enteropathogenic Escherichia coli (EPEC) is the prototype organism of a group of pathogenic Gram-negative bacteria that cause attaching and effacing (AE) intestinal lesions. All EPEC genes necessary for the AE phenotype are encoded within a 35.6 kb pathogenicity island termed the locus of enterocyte effacement (LEE). The LEE encodes 41 predicted open reading frames (ORFs), including components of a type III secretion apparatus and secreted molecules involved in the disruption of the host cell cytoskeleton. To initiate our studies on regulation of genes within the LEE, we determined the genetic organization of the LEE, defining transcriptional units and mapping transcriptional start points. We found that components of the type III secretion system are transcribed from three polycistronic operons designated LEE1, LEE2 and LEE3. The secreted Esp molecules are part of a fourth polycistronic operon designated LEE4. Using reporter gene fusion assays, we found that the previously described plasmid-encoded regulator (Per) activated operons LEE1, LEE2 and LEE3, and modestly increased the expression of LEE4 in EPEC. Using single-copy lacZ fusions in K-12-derived strains, we determined that Per only directly activated the LEE1:lacZ fusion, and did not directly activate the other operons. Orf1 of the LEE1 operon activated the expression of single-copy LEE2:lacZ and LEE3:lacZ fusions in trans and modestly increased the expression of LEE4:lacZ in K-12 strains. Orf1 was therefore designated Ler, for LEE-encoded regulator. Thus, the four polycistronic operons of the LEE that encode type III secretion components and secreted molecules are now included in the Per regulon, where Ler participates in this novel regulatory cascade in EPEC.

Moving experiences: a qualitative analysis of health and migration

This paper describes a qualitative analysis of the health and health care experiences of South Asian Fijian women now living in the lower mainland area of British Columbia, Canada. A particular focus is put on the health impacts of the migration experience. A thematic analysis of in-depth interviews informs the discussion of individual women's, as well as service providers', views of health meanings, physical and emotional health concerns, experiences with the health care system, and women's roles as care-givers. The findings have implications for how health and illness are conceptualized, and how health services are provided to particular groups in particular places.

Assessing public health capacity to support community-based heart health promotion: the Canadian Heart Health Initiative, Ontario Project (CHHIOP)

This paper presents initial findings of the Canadian Heart Health Initiative, Ontario Project (CHHIOP). CHHIOP has two primary objectives. The programmatic objective is to coordinate and refine a system for supporting effective, sustained community-based heart health activities. This paper addresses the scientific objective: to develop knowledge of factors that influence the development of predisposition and capacity to undertake community-based heart health activities in public health departments. A systems theory framework for an ecological approach to health promotion informs the conceptualization of the key constructs, measured using a two-stage longitudinal design which combines quantitative and qualitative methods. This paper reports the results of the first round of quantitative survey data collected from all health departments in Ontario (N = 42) and individuals within each health department involved in heart health promotion (n = 262). Results indicate low levels of implementation of heart health activities, both overall and for particular risk factors and settings. Levels of capacity are also generally low, yet predisposition to undertake heart health promotion activities is reportedly high. Analyses show that implementation is positively related to capacity but not predisposition, while predisposition and capacity are positively related. Overall, results suggest predisposition is a necessary but not sufficient condition for implementation to occur; capacity-related factors appear to be the primary constraint. These findings are used to inform strategies to address CHHIOP's programmatic objective.

Peroxynitrite is a contractile agonist of cerebral artery smooth muscle cells

On reperfusion of ischemic tissue, a prolonged phase of vasoconstriction occurs, the mechanism of which is poorly understood. However, it is known that peroxynitrite (ONOO-) is formed during reperfusion. In this study the contractile properties of ONOO- were investigated in Wistar rat middle cerebral arteries. The effects of ONOO- on vessel diameter were dose dependent. Low-dose ONOO- (10 microM) caused vessels to constrict by 15%. At an intermediate concentration of 25 microM, the effect of ONOO- was variable, whereas at the highest concentration (100 microM), vessels underwent persistent dilation and became insensitive to the endogenous vasoconstrictor 5-hydroxytryptamine. At the single cell level, ONOO- caused cerebral artery smooth muscle cells to contract. Reduced, but not oxidized, glutathione completely inhibited the contractile action of ONOO- on single cells. Vehicle and decomposed ONOO- each had minimal effect on cell length. These data show that ONOO- is a contractile agonist of middle cerebral arteries, at the single cell and whole vessel levels, suggesting that formation of ONOO- may contribute mechanistically to ischemic brain injury during stroke. Moreover, relatively high concentrations of ONOO- result in vascular paralysis.

An ecologic analysis of psychosocial stress and heart disease in British Columbia

Cardiovascular disease is the leading cause of death in Canada. However, much heart disease incidence cannot be explained by known risk factors, and evidence points to the potential role played by the psychosocial environment. This study involves an ecologic analysis exploring the relationships between psychosocial stress and ischaemic heart disease (IHD) in British Columbia. First, data from the Canada Health Promotion Survey correlated stress indicators (i.e., education, marital status) with self-reported stress levels. Results showed gender differences in stress. Stage II consisted of a multivariate analysis of ischaemic heart disease mortality in B.C. Results indicate a strong association between heart disease outcomes and educational background for both males and females. Findings of this study support a link between IHD and psychosocial factors. The results of the multiple regression must be interpreted with caution, given the use of an ecologic analysis. Additional research at the individual level is needed to fully understand these relationships.

Characterization of the roles of hemolysin and other toxins in enteropathy caused by alpha-hemolytic Escherichia coli linked to human diarrhea

Escherichia coli strains producing alpha-hemolysin have been associated with diarrhea in several studies, but it has not been clearly demonstrated that these strains are enteropathogens or that alpha-hemolysin is an enteric virulence factor. Such strains are generally regarded as avirulent commensals. We examined a collection of diarrhea-associated hemolytic E. coli (DHEC) strains for virulence factors. No strain produced classic enterotoxins, but they all produced an alpha-hemolysin that was indistinguishable from that of uropathogenic E. coli strains. DHEC strains also produced other toxins including cytotoxic necrotizing factor 1 (CNF1) and novel toxins, including a cell-detaching cytotoxin and a toxin that causes HeLa cell elongation. DHEC strains were enteropathogenic in the RITARD (reversible intestinal tie adult rabbit diarrhea) model of diarrhea, causing characteristic enteropathies, including inflammation, necrosis, and colonic cell hyperplasia in both small and large intestines. Alpha-hemolysin appeared to be a major virulence factor in this model since it conferred virulence to nonpathogenic E. coli strains. Other virulence factors also appear to be contributing to virulence. These findings support the epidemiologic link to diarrhea and suggest that further research into the role of DHEC and alpha-hemolysin in enteric disease is warranted.

The particulate methane monooxygenase from methylococcus capsulatus (Bath) is a novel copper-containing three-subunit enzyme. Isolation and characterization

The particulate methane monooxygenase (pMMO) is known to be very difficult to study mainly due to its unusual activity instability in vitro. By cultivating Methylococcus capsulatus (Bath) under methane stress conditions and high copper levels in the growth medium, membranes highly enriched in the pMMO with exceptionally stable activity can be isolated from these cells. Purified and active pMMO can be subsequently obtained from these membrane preparations using protocols in which an excess of reductants and anaerobic conditions were maintained during membrane solubilization by dodecyl beta-D-maltoside and purification by chromatography. The pMMO was found to be the major constituent in these membranes, constituting 60-80% of total membrane proteins. The dominant species of the pMMO was found to consist of three subunits, alpha, beta, and gamma, with an apparent molecular mass of 45, 26, and 23 kDa, respectively. A second species of the pMMO, a proteolytically processed version of the enzyme, was found to be composed of three subunits, alpha', beta, and gamma, with an apparent molecular mass of 35, 26, and 23 kDa, respectively. The alpha and alpha' subunits from these two forms of the pMMO contain identical N-terminal sequences. The gamma subunit, however, exhibits variation in its N-terminal sequence. The pMMO is a copper-containing protein only and shows a requirement for Cu(I) ions. Approximately 12-15 Cu ions per 94-kDa monomeric unit were observed. The pMMO is sensitive to dioxygen tension. On the basis of dioxygen sensitivity, three kinetically distinct forms of the enzyme can be distinguished. A slow but air-stable form, which is converted into a "pulsed" state upon direct exposure to atmospheric oxygen pressure, is considered as type I pMMO. This form was the subject of our pMMO isolation effort. Other forms (types II and III) are deactivated to various extents upon exposure to atmospheric dioxygen pressure. Under inactivating conditions, these unstable forms release protons to the buffer (approximately 10 H+/94-kDa monomeric unit) and eventually become completely inactive.