Authors' response to Letters to the Editor re: Clinical public health: harnessing the best of both worlds in sickness and in health

We are pleased that our paper on clinical public health1 received support from Dr. Shah,2 who also provides important historical aspects of clinical public health. Dr. Shah was the inaugural director of a newly created residency program (Community Medicine, now known as Public Health and Preventive Medicine) at the University of Toronto in 1976. Although he claims to have failed to “bring clinicians and public health professionals together to define the common elements and synergy needed,”2 we believe he did not fail, because his efforts ignited sparks among his students (including several co-authors of this paper1). Building on his important legacy, subsequent generations of clinicians and public health professionals have made strides towards effective collaboration of clinical medicine and public health.

Clinical public health: harnessing the best of both worlds in sickness and in health

INTRODUCTION

Effective, sustained collaboration between clinical and public health professionals can lead to improved individual and population health. The concept of clinical public health promotes collaboration between clinical medicine and public health to address complex, real-world health challenges. In this commentary, we describe the concept of clinical public health, the types of complex problems that require collaboration between individual and population health, and the barriers towards and applications of clinical public health that have become evident during the COVID-19 pandemic.

RATIONALE

The focus of clinical medicine on the health of individuals and the aims of public health to promote and protect the health of populations are complementary. Interdisciplinary collaborations at both levels of health interventions are needed to address complex health problems. However, there is a need to address the disciplinary, cultural and financial barriers to achieving greater and sustained collaboration. Recent successes, particularly during the COVID-19 pandemic, provide a model for such collaboration between clinicians and public health practitioners.

CONCLUSION

A public health approach that fosters ongoing collaboration between clinical and public health professionals in the face of complex health threats will have greater impact than the sum of the parts.

Defining Clinical Public Health

PURPOSE

To solve complex health issues, an innovative and multidisciplinary framework is necessary. The Clinical Public Health (CPH) Division was established at the University of Toronto (UofT), Canada to foster inte-gration of primary care, preventive medicine and public health in education, practice and research. To better understand how the construct of CPH might be applied, we surveyed clinicians, researchers and public health professionals affiliated with the CPH Division to assess their understanding of the CPH concept and its utility in fostering broad collaboration.

METHODS

A two-wave anonymous survey of the active faculty of the CPH Division, UofT was conducted across Canada. Wave 1 participants (n = 187; 2016) were asked to define CPH, while Wave 2 participants (n = 192; 2017) were provided a synthesis of Wave 1 results and asked to rank each definition. Both waves were asked about the need for a common definition, and to comment on CPH.

RESULTS

Response rates for the first and second waves were 25% and 22%, respectively. Of the six definitions of CPH from Wave 1, "the intersection of clinical practice and public health," was most highly ranked by Wave 2 participants. Positive perceptions of CPH included multidisciplinary collaboration, new fields and insights, forward thinking and innovation. Negative perceptions included CPH being a confusing term, too narrow in scope or too clinical.

CONCLUSION

The concept of Clinical Public Health can foster multidisciplinary collaboration to address com-plex health issues because it provides a useful framework for bringing together key disciplines and diverse professional specialties.

Integrating clinical medicine and population health: where to from here?

Efforts to contain healthcare costs have led a renewed clinician interest in addressing population-level outcomes, with some proposing that the integration of population health into clinical practice represents a novel concept entitled "clinical population medicine" (CPM). This commentary offers an examination of the function and utility of CPM. In reviewing relevant literature, we note several inconsistencies in CPM's purported mandate, which ranges from simply incorporating the social determinants of health into clinical practice to broad involvement in community health planning. The latter of these seems to overlap, and potentially conflict, with the work of public health practitioners, and cited examples of activities used to define "CPM" seem to apply a label to established clinician activities around the determinants of health that would be captured more simply as research, evaluation, or advocacy undertaken by clinicians in other areas of practice. Our analysis suggests that CPM may have value in encouraging clinicians to incorporate community determinants and contextual considerations into their practices, but must take care to remain complementary and distinct from public health practice.

Exploring the experience of residents during the first six months of family medicine residency training

BACKGROUND

The shift from undergraduate to postgraduate education signals a new phase in a doctor's training. This study explored the resident's perspective of how the transition from undergraduate to postgraduate (PGME) training is experienced in a Family Medicine program as they first meet the reality of feeling and having the responsibility as a doctor.

METHODS

Qualitative methods explored resident experiences using interpretative inquiry through monthly, individual in-depth interviews with five incoming residents during the first six months of training. Focus groups were also held with residents at various stages of training to gather their reflection about their experience of the first six months. Residents were asked to describe their initial concerns, changes that occurred and the influences they attributed to those changes.

RESULTS

Residents do not begin a Family Medicine PGME program knowing what it means to be a Family Physician, but learn what it means to fulfill this role. This process involves adjusting to significant shifts in responsibility in the areas of Knowledge, Practice Management, and Relationships as they become more responsible for care outcomes.

CONCLUSION

This study illuminated the resident perspective of how the transition is experienced. This will assist medical educators to better understand the early training experiences of residents, how these experiences contribute to consolidating their new professional identity, and how to better align teaching strategies with resident learning needs.

Choosing Wisely® in Preventive Medicine: The American College of Preventive Medicine's Top 5 List of Recommendations

The Choosing Wisely(®) initiative is a national campaign led by the American Board of Internal Medicine Foundation, focused on quality improvement and advancing a dialogue on avoiding wasteful or unnecessary medical tests, procedures, and treatments. The American College of Preventive Medicine (ACPM) Prevention Practice Committee is an active participant in the Choosing Wisely project. The committee created the ACPM Choosing Wisely Task Force to lead the development of ACPM's recommendations with the intention of facilitating wise decisions about the appropriate use of preventive care. After utilizing an iterative process that involved reviewing evidence-based literature, the ACPM Choosing Wisely Task Force developed five recommendations targeted toward overused services within the field of preventive medicine. These include: (1) don't take a multivitamin, vitamin E, or beta carotene to prevent cardiovascular disease or cancer; (2) don't routinely perform prostate-specific antigen-based screening for prostate cancer; (3) don't use whole-body scans for early tumor detection in asymptomatic patients; (4) don't use expensive medications when an equally effective and lower-cost medication is available; and (5) don't perform screening for cervical cancer in low-risk women aged 65 years or older and in women who have had a total hysterectomy for benign disease. The Task Force also reviewed some of the barriers to implementing these recommendations, taking into account the interplay between system and environmental characteristics, and identified specific strategies necessary for timely utilization of these recommendations.

The American College of Preventive Medicine Position Statement on Hepatitis C Virus Infection

The American College of Preventive Medicine Prevention Practice Committee contributes to policy guidelines and recommendations on preventive health topics for clinicians and public health decision makers. After review of the currently available evidence, the College is providing a consensus-based set of recommendations designed to increase screening for and prevention of hepatitis C virus infection, increase linkage to care, improve access to treatment, and encourage development of hepatitis C virus-related quality measures.

Optimizing Canadian breast cancer screening strategies: a perspective for action

While controversies regarding optimal breast cancer screening modalities, screening start and end ages, and screening frequencies continue to exist, additional population-based randomized trials are unlikely to be initiated to examine these concerns. Simulation models have been used to evaluate the efficacy and effectiveness of various breast cancer screening strategies, however these models were all developed using US data. Currently, there is a need to examine the optimal screening and treatment policies in the Canadian context. In this commentary, we discuss the current controversies pertaining to breast cancer screening, and describe the fundamental components of a simulation model, which can be used to inform breast cancer screening and treatment policies.

Optimizing Canadian breast cancer screening strategies: a perspective for action

While controversies regarding optimal breast cancer screening modalities, screening start and end ages, and screening frequencies continue to exist, additional population-based randomized trials are unlikely to be initiated to examine these concerns. Simulation models have been used to evaluate the efficacy and effectiveness of various breast cancer screening strategies, however these models were all developed using US data. Currently, there is a need to examine the optimal screening and treatment policies in the Canadian context. In this commentary, we discuss the current controversies pertaining to breast cancer screening, and describe the fundamental components of a simulation model, which can be used to inform breast cancer screening and treatment policies.

Eosinophil peroxidase induces the expression and function of acid-sensing ion channel-3 in allergic rhinitis: in vitro evidence in cultured epithelial cells

BACKGROUND

Acid-sensing ion channels (ASIC) are a family of acid-activated ligand-gated cation channels. As tissue acidosis is a feature of inflammatory conditions, such as allergic rhinitis (AR), we investigated the expression and function of these channels in AR.

OBJECTIVES

The aim of the study was to assess expression and function of ASIC channels in the nasal mucosa of control and AR subjects.

METHODS

Immunohistochemical localization of ASIC receptors and functional responses to lactic acid application were investigated. In vitro studies on cultured epithelial cells were performed to assess underlying mechanisms of ASIC function.

RESULTS

Lactic acid at pH 7.03 induced a significant rise in nasal fluid secretion that was inhibited by pre-treatment with the ASIC inhibitor amiloride in AR subjects (n = 19). Quantitative PCR on cDNA isolated from nasal biopsies from control and AR subjects demonstrated that ASIC-1 was equally expressed in both populations, but ASIC-3 was significantly more highly expressed in AR (P < 0.02). Immunohistochemistry confirmed significantly higher ASIC-3 protein expression on nasal epithelial cells in AR patients than controls (P < 0.01). Immunoreactivity for EPO+ eosinophils in both nasal epithelium and submucosa was more prominent in AR compared with controls. A mechanism of induction of ASIC-3 expression relevant to AR was suggested by the finding that eosinophil peroxidase (EPO), acting via ERK1/2, induced the expression of ASIC-3 in epithelial cells. Furthermore, using a quantitative functional measure of epithelial cell secretory function in vitro, EPO increased the air-surface liquid depth via an ASIC-dependent chloride secretory pathway.

CONCLUSIONS

This data suggests a possible mechanism for the observed association of eosinophils and rhinorrhoea in AR and is manifested through enhanced ASIC-3 expression.

Predictors of competing mortality to invasive breast cancer incidence in the Canadian National Breast Screening study

Background

Evaluating the cost-effectiveness of breast cancer screening requires estimates of the absolute risk of breast cancer, which is modified by various risk factors. Breast cancer incidence, and thus mortality, is altered by the occurrence of competing events. More accurate estimates of competing risks should improve the estimation of absolute risk of breast cancer and benefit from breast cancer screening, leading to more effective preventive, diagnostic, and treatment policies. We have previously described the effect of breast cancer risk factors on breast cancer incidence in the presence of competing risks. In this study, we investigate the association of the same risk factors with mortality as a competing event with breast cancer incidence.

Methods

We use data from the Canadian National Breast Screening Study, consisting of two randomized controlled trials, which included data on 39 risk factors for breast cancer. The participants were followed up for the incidence of breast cancer and mortality due to breast cancer and other causes. We stratified all-cause mortality into death from other types of cancer and death from non-cancer causes. We conducted separate analyses for cause-specific mortalities.

Results

We found that “age at entry” is a significant factor for all-cause mortality, and cancer-specific and non-cancer mortality. “Menstruation length” and “number of live births” are significant factors for all-cause mortality, and cancer-specific mortality. “Ever noted lumps in right/left breasts” is a factor associated with all-cause mortality, and non-cancer mortality.

Conclusions

For proper estimation of absolute risk of the main event of interest common risk factors associated with competing events should be identified and considered.

P. aeruginosa LPS stimulates calcium signaling and chloride secretion via CFTR in human bronchial epithelial cells

BACKGROUND

Pseudomonas aeruginosa airway infection is associated with a high mortality rate in cystic fibrosis. Lipopolysaccharide (LPS), a main constituent of the outer membrane of P. aeruginosa, is responsible for activation of innate immune response but its role on airway epithelium ion transport, is not well known. The aim of this study was to determine the role for P. aeruginosa LPS in modulating chloride secretion and intracellular calcium in the human bronchial epithelial cell line, 16HBE14o-.

METHODS

We used intracellular calcium imaging and short-circuit current measurement upon exposure of cells to P. aeruginosa LPS.

RESULTS

Apical LPS stimulated intracellular calcium release and calcium entry and enhanced chloride secretion. This latter effect was significantly inhibited by CFTR(inh)-172 and BAPTA-AM (intracellular Ca(2+) chelator).

CONCLUSIONS

Our data provides evidence for a new role of P. aeruginosa LPS in stimulating calcium entry and release and a subsequent chloride secretion via CFTR in human bronchial epithelium.

Incidence of invasive breast cancer in the presence of competing mortality: the Canadian National Breast Screening Study

Mortality due to causes other than breast cancer is a potential competing risk which may alter the incidence probability of breast cancer and as such should be taken into account in predictive modelling. We used data from the Canadian National Breast Screening Study (CNBSS), which consist of two randomized controlled trials designed to evaluate the efficacy of mammography among women aged 40-59. The participants in the CNBSS were followed up for incidence of breast cancer and mortality due to breast cancer and other causes; this allowed us to construct a breast cancer risk prediction model while taking into account mortality for the same study population. In this study, we use 1980-1989 as the study period. We exclude the prevalent cancers from the CNBSS to estimate the probability of developing breast cancer, given the fact that women were cancer-free at the beginning of the follow-up. By the end of 1989, from 89,434 women, 944 (1.1 %) were diagnosed with invasive breast cancer, 922 (1.0 %) died from causes other than breast cancer, and 87,568 (97.9 %) were alive and not diagnosed with invasive breast cancer. We constructed a risk prediction model for invasive breast cancer based on 39 risk factors collected at the time of enrolment or the initial physical examination of the breasts. Age at entry (HR 1.07, 95 % CI 1.05-1.10), lumps ever found in left or right breast (HR 1.92, 95 % CI 1.19-3.10), abnormality in the left breast (HR 1.26, 95 % CI 1.07-1.48), history of other breast disease, family history of breast cancer score (HR 1.01, 95 % CI 1.00-1.01), years menstruating (HR 1.02, 95 % CI 1.01-1.03) and nulliparity (HR 1.70, 95 % CI 1.23-2.36) are the model's predictors. We investigated the effects of time-dependent factors. The model is well calibrated with a moderate discriminatory power (c-index 0.61, 95 % CI 0.59-0.63); we use it to predict the 9-year risk of developing breast cancer for women of different age groups. As an example, we estimated the probability of invasive cancer at 5 years after enrolment to be 0.00448, 0.00556, 0.00691, 0.00863, and 0.01034, respectively, for women aged 40, 45, 50, 55, and 59, all of whom had never noted lumps in their breasts, had 32 years of menstruating, 1-2 live births, no other types of breast disease and no abnormality found in their left breasts. The results of this study can be used by clinicians to identify women at high risk of breast cancer for screening intervention and to recommend a personalized intervention plan. The model can be also utilized by a woman as a breast cancer risk prediction tool.

Determining mortality rates attributable to Clostridium difficile infection

To determine accuracy of measures of deaths attributable to Clostridium difficile infection, we compared 3 measures for 2007–2008 in Ontario, Canada: death certificate; death within 30 days of infection; and panel review. Data on death within 30 days were more feasible than panel review and more accurate than death certificate data.

Measuring data reliability for preventive services in electronic medical records

Background

Improvements in the quality of health care services are often measured using data present in medical records. Electronic Medical Records (EMRs) contain potentially valuable new sources of health data. However, data quality in EMRs may not be optimal and should be assessed. Data reliability (are the same data elements being measured over time?) is a prerequisite for data validity (are the data accurate?). Our objective was to measure the reliability of data for preventive services in primary care EMRs during the transition to EMR.

Methods

Our data sources were randomly selected eligible patients’ medical records and data obtained from provincial administrative datasets. Eighteen community-based family physicians in Toronto, Ontario that implemented EMRs starting in 2006 participated in this study. We measured the proportion of patients eligible for a service (Pap smear, screening mammogram or influenza vaccination) that received the service. We compared the change in rates of selected preventive services calculated from the medical record audits with the change in administrative datasets.

Results

In the first year of EMR use (2006) services decreased by 8.7% more (95% CI −11.0%– − 6.4%, p < 0.0001) when measured through medical record audits as compared with administrative datasets. Services increased by 2.4% more (95% CI 0%–4.9%, p = 0.05) in the medical record audits during the second year of EMR use (2007).

Conclusion

There were differences between the change measured through medical record audits and administrative datasets. Problems could include difficulties with organizing new data entry processes as well as continued use of both paper and EMRs. Data extracted from EMRs had limited reliability during the initial phase of EMR implementation. Unreliable data interferes with the ability to measure and improve health care quality

Identifying public health competencies relevant to family medicine

Public health situations faced by family physicians and other primary care practitioners, such as severe acute respiratory syndrome (SARS) and more recently H1N1, have resulted in an increased interest to identify the public health competencies relevant to family medicine. At present there is no agreed-on set of public health competencies delineating the knowledge and skills that family physicians should possess to effectively face diverse public health challenges. Using a multi-staged, iterative process that included a detailed literature review, the authors developed a set of public health competencies relevant to primary care, identifying competencies relevant across four levels, from "post-MD" to "enhanced." Feedback from family medicine and public health educator-practitioners regarding the set of proposed "essential" competencies indicated the need for a more limited, feasible set of "priority" areas to be highlighted during residency training. This focused set of public health competencies has begun to guide relevant components of the University of Toronto's Family Medicine Residency Program curriculum, including academic half-days; clinical experiences, especially identifying "teachable moments" during patient encounters; resident academic projects; and elective public health agency placements. These competencies will also be used to guide the development of a family medicine-public health primer and faculty development sessions to support family medicine faculty facilitating residents to achieve these competencies. Once more fully implemented, an evaluation will be initiated to determine the degree to which these public health competencies are being achieved by family medicine graduates, especially whether they attained the knowledge, skills, and confidence necessary to effectively face diverse public health situations-from common to emergent.

Implementation of electronic medical records: effect on the provision of preventive services in a pay-for-performance environment

OBJECTIVE

To study the effect of electronic medical record (EMR) implementation on preventive services covered by Ontario's pay-for-performance program.

DESIGN

Prospective double-cohort study.

PARTICIPANTS

Twenty-seven community-based family physicians.

SETTING

Toronto, Ont.

INTERVENTION

Eighteen physicians implemented EMRs, while 9 physicians continued to use paper records.

MAIN OUTCOME MEASURE

Provision of 4 preventive services affected by pay-for-performance incentives (Papanicolaou tests, screening mammograms, fecal occult blood testing, and influenza vaccinations) in the first 2 years of EMR implementation.

RESULTS

After adjustment, combined preventive services for the EMR group increased by 0.7%, a smaller increase than that seen in the non-EMR group (P = .55, 95% confidence interval -2.8 to 3.9).

CONCLUSION

When compared with paper records, EMR implementation had no significant effect on the provision of the 4 preventive services studied.

Implementation of electronic medical records: theory-informed qualitative study

OBJECTIVE

To apply the diffusion-of-innovations theory to the examination of factors that are perceived by family physicians as influencing the implementation of electronic medical records (EMRs).

DESIGN

Qualitative study with 2 focus groups 18 months after EMR implementation; participants also took part in a concurrent quantitative study examining EMR implementation and preventive services.

SETTING

Toronto, Ont.

PARTICIPANTS

Twelve community-based family physicians.

METHODS

We employed a semistructured interview guide. The interviews were audiotaped and transcribed verbatim; 2 researchers independently categorized and coded the transcripts and then met to compare and contrast their findings, category mapping, and interpretations. Findings were then mapped to an existing theoretical framework.

MAIN FINDINGS

Multiple barriers to EMR implementation were described. These included lack of relative advantage for many processes, high complexity of the system, low compatibility with physician needs and past experiences, difficulty with adaptation of the EMR to the organization and adaptation of the organization to the EMR, and lack of organizational slack. Positive factors were the presence of a champion and relative advantages for some processes.

CONCLUSION

Early EMR implementation experience is consistent with theoretical concepts associated with implementation of innovations. A problematic implementation process helps to explain, at least in part, the lack of improvement in preventive services in our quantitative results.

Early childhood caries and infant oral health: Paediatricians' and family physicians' knowledge, practices and training

OBJECTIVES

To assess the knowledge of early childhood caries and to examine the current preventive oral health-related practices and training among Canadian paediatricians and family physicians who provide primary care to children younger than three years.

METHODS

A cross-sectional, self-administered survey was mailed to a random sample of 1928 paediatricians and family physicians.

RESULTS

A total of 1044 physicians met the study eligibility criteria, and of those, 537 returned completed surveys, resulting in an overall response rate of 51.4% (237 paediatricians and 300 family physicians). Six questions assessed knowledge of early childhood caries; only 1.8% of paediatricians and 0.7% of family physicians answered all of these questions correctly. In total, 73.9% of paediatricians and 52.4% of family physicians reported visually inspecting children's teeth; 60.4% and 44.6%, respectively, reported counselling parents or caregivers regarding teething and dental care; 53.2% and 25.6%, respectively, reported assessing children's risk of developing tooth decay; and 17.9% and 22.3%, respectively, reported receiving no oral health training in medical school or residency. Respondents who felt confident and knowledgeable and who considered their role in promoting oral health as "very important" were significantly more likely to carry out oral health-related practices.

CONCLUSION

Although the majority of paediatricians and family physicians reported including aspects of oral health in children's well visits, a reported lack of dental knowledge and training appeared to pose barriers, limiting these physicians from playing a more active role in promoting the oral health of children in their practices.

Is referral to a spine surgeon a double-edged sword?: patient concerns before consultation

OBJECTIVE

To assess the concerns of adult patients with spine-related complaints during the period between referral to and consultation with a spine surgeon.

DESIGN

Prospective survey.

SETTING

Toronto, Ont.

PARTICIPANTS

A total of 338 consecutive, nonemergent patients before consultation with a single spine surgeon over a 5-month period.

MAIN OUTCOME MEASURES

Patient concerns, effect of referral to a spine surgeon, and effect of waiting to see a spine surgeon.

RESULTS

The issues patients reported to be most concerning were ongoing pain (45.6% rated this as most concerning), loss of function (23.4%), need for surgery (12.1%), and permanence of the condition (9.6%). Regression analysis demonstrated that older age was an independent predictor of increased level of concern regarding pain (P=.01) and disability (P=.04). Forty-seven percent of all patients listed the need for surgery among their top 3 concerns. Mere referral to a spine surgeon (P=.03) was an independent predictor of increased concern regarding the need for surgery. Sex, diagnosis, surgical candidacy, and actual wait time were not predictive of increased concerns. Patients reported family physicians to be their most influential information source regarding spinal conditions.

CONCLUSION

Timely provision of more specific information regarding the benign and non-surgical nature of most degenerative spinal conditions might substantially reduce patients' exaggerated concerns regarding the probability of surgery for a considerable number of patients referred to spine surgeons.

Cytosolic phospholipase A2-α expression in breast cancer is associated with EGFR expression and correlates with an adverse prognosis in luminal tumours

Background:

The eicosanoid signalling pathway promotes the progression of malignancies through the production of proliferative prostaglandins (PGs). Cytosolic phospholipase A₂α (cPLA₂α) activity provides the substrate for cyclooxygenase-dependent PG release, and we have previously found that cPLA₂α expression correlated with EGFR/HER2 over-expression in a small number of breast cancer cell lines.

Methods:

The importance of differential cPLA₂α activity in clinical breast cancer was established by relating the expression of cPLA₂α in tissue samples from breast cancer patients, and two microarray-based gene expression datasets to different clinicopathological and therapeutic parameters.

Results:

High cPLA₂α mRNA expression correlated with clinical parameters of poor prognosis, which are characteristic of highly invasive tumours of the HER2-positive and basal-like subtype, including low oestrogen receptor expression and high EGFR expression. High cPLA₂α expression decreased overall survival in patients with luminal cancers, and correlated with a reduced effect of tamoxifen treatment. The cPLA₂α expression was an independent predictive parameter of poor response to endocrine therapy in the first 5 years of follow-up.

Conclusion:

This study shows a role of cPLA₂α in luminal breast cancer progression, in which the enzyme could represent a novel therapeutic target and a predictive marker.

Effective and cost-effective clinical trial recruitment strategies for postmenopausal women in a community-based, primary care setting

INTRODUCTION

Little evidence exists to guide investigators on the effectiveness and cost-effectiveness of various recruitment strategies in primary care research. The purpose of this study is to describe the effectiveness and cost-effectiveness of eight clinical trial recruitment methods for postmenopausal women in a community-based setting.

METHODS

A retrospective analysis of the yield and cost of eight different recruitment methods: 1) family physician (FP) recruiters, 2) FP referrals, 3) community presentations, 4) community events, 5) newsletters, 6) direct mailings, 7) posters, and 8) newspaper advertisements that were used to recruit postmenopausal women to a randomized clinical trial (RCT) evaluating the effectiveness of gabapentin in treating hot flashes.

RESULTS

We recruited 197 postmenopausal women from a total of 904 screened, with 291 of the remainder being ineligible and 416 declining to participate. Of the 904 women screened, 34 (3.8%) were from FP recruiters and 35 (3.9%) were from other FP referrals while 612 (67.7%) resulted from newspaper advertisements. Of the 197 women enrolled, 141 (72%) were from newspaper advertisements, with 26 (13%) following next from posters. Word of mouth was identified as an additional unanticipated study recruitment strategy. Metropolitan newspaper advertising at $112.73 (Canadian) per enrolled participant and posters at $119.98 were found to be cost-effective recruitment methods.

CONCLUSION

Newspaper advertisements were the most successful method to recruit postmenopausal women into a community-based, primary care RCT.

Canadian medical students' perceptions of public health education in the undergraduate medical curriculum

PURPOSE

To understand the perceptions and attitudes of Canadian medical students toward their undergraduate medical public health curriculum and to identify student suggestions and priorities for curriculum change.

METHOD

Five focus groups of 11 or 12 medical students from all years of medical school were recruited at McMaster University Faculty of Health Sciences, Université de Sherbrooke Faculty of Medicine and Health Sciences, University of Toronto Faculty of Medicine, University of Manitoba Faculty of Medicine, and University of British Columbia Faculty of Medicine between February and April 2006. A professional facilitator was hired to conduct the focus groups using a unique, computer-based facilitation system. Questions in both the focus group and an accompanying survey sought to determine medical students' understanding and exposure to public health and how this impacted their attitudes and choices toward careers in the public health medical specialty of community medicine. The transcripts were independently reviewed and analyzed by each of the authors to identify themes.

RESULTS

Four major themes related to students' desired curriculum change were identified: (1) poor educational experiences in public health courses, (2) lack of positive role models, especially exposure to community medicine specialists, (3) emphasis on statistics and epidemiology, and (4) negative attitudes toward public health topics.

CONCLUSIONS

Students are disillusioned, disengaged, and disappointed with the public health curriculum currently being provided at the Canadian medical schools studied. Many medical students would prefer a public health curriculum that is more challenging and has more applied field experience and exposure to public health physician role models.

Assessing Canadian medical students' familiarity with and interest in pursuing a career in community medicine

OBJECTIVES

Following the SARS outbreak, large gaps in the public health workforce have been identified. This study sought to understand the perceptions and attitudes of Canadian medical students with regard to public health to determine how this impacted their choice towards a career in Community Medicine (CM).

METHODS

Five focus groups of 11-12 medical students from all years were recruited at McMaster University, Université de Sherbrooke, University of Toronto, University of Manitoba and the University of British Columbia. A professional facilitator was hired to conduct the focus groups using a unique computer-based facilitation system. Questions in both the focus group and an accompanying survey sought to determine medical students' understanding and exposure to public health and how this impacted their attitude and choice towards a career in community medicine. The transcripts were independently reviewed and analyzed by each of the authors to identify themes.

RESULTS

Four major themes related to choosing Community Medicine as a career were identified: 1) poor understanding of the role of Community Medicine specialists in public health practice, 2) perceived lack of clinical work and relevance of public health to clinical practice, 3) perceived lack of exclusivity of Community Medicine specialty, 4) incentives and disincentives to pursuing Community Medicine.

CONCLUSION

Better education of students on the role of CM specialists through increasing exposure to role models and demystifying inaccurate perceptions of CM through integration of public health with clinical medicine may potentially increase medical student entry into Community Medicine.

Primary care physicians' views of routine follow-up care of cancer survivors

PURPOSE

Routine follow-up of adult cancer survivors is an important clinical and health service issue. Because of a lack of evidence supporting advantages of long-term follow-up care in oncology clinics, there is increasing interest for the locus of this care to be provided by primary care physicians (PCPs). However, current Canadian PCP views on this issue have been largely unknown.

METHODS

A mail survey of a random sample of PCPs across Canada, stratified by region and proximity to urban centers, was conducted. Views on routine follow-up of adult cancer survivors and modalities to facilitate PCPs in providing this care were determined.

RESULTS

A total of 330 PCPs responded (adjusted response rate, 51.7%). After completion of active treatment, PCPs were willing to assume exclusive responsibility for routine follow-up care after 2.4 +/- 2.3 years had elapsed for prostate cancer, 2.6 +/- 2.6 years for colorectal cancer, 2.8 +/- 2.5 years for breast cancer, and 3.2 +/- 2.7 years for lymphoma. PCPs already providing this care were willing to provide exclusive care sooner. The most useful modalities PCPs felt would assist them in assuming exclusive responsibility for follow-up cancer care were (1) a patient-specific letter from the specialist, (2) printed guidelines, (3) expedited routes of rereferral, and (4) expedited access to investigations for suspected recurrence.

CONCLUSION

With appropriate information and support in place, PCPs reported being willing to assume exclusive responsibility for the follow-up care of adult cancer survivors. Insights gained from this survey may ultimately help guide strategies in providing optimal care to these patients.

Epithelial pH and ion transport regulation by proton pumps and exchangers

This study reports on the interaction between transepithelial Na+ transport and H+ secretory and intracellular pH (pHi) regulating mechanisms in the model 'tight' epithelium of frog skin. We have used 22Na isotope fluxes and fixed end-point titration to measure undirectional Na+ fluxes, net Na absorption (J(net)Na) and proton secretion (J(net)H), and electrophysiological techniques (double-barrelled ion-sensitive microelectrodes and cell membrane current--voltage relations) to determine intracellular activities of Na+, Cl- and H+ and the conductance of apical membranes to Na+ (gNa) and of basolateral membranes to K+ (gK). In dilute mucosal solutions or in the absence of a permeant anion (Cl-) or counter-current (open-circuit conditions) to accompany Na+ uptake, the J(net)Na is electrically coupled to J(net)H via an electrogenic apical H+-ATPase (located in mitochondria-rich cells). Both fluxes proceed via mitochondria-rich cells and are inhibited by blockers of carbonic anhydrase and H+-ATPase and stimulated by aldosterone and acid load. In high NaCl-containing mucosal solutions or in short-circuit conditions, the J(net)Na becomes uncoupled from J(net)H and proceeds mainly via the principal cells in the epithelium, in which pHi is regulated by basolateral Na+/H+ and Cl-/HCO3- exchangers. Under these conditions, J(net)Na, gNa and gK vary directly and in parallel with pHi, when pHi is changed by permeable weak acids or bases. There is also co-variance between gNa and pHi accompanying spontaneous variations in J(net)Na and when Na+ transport is stimulated by aldosterone or inhibited with ouabain. We conclude that the level of intracellular H+, modulated by H+ pump and Na+/H+ and Cl-/HCO3- exchangers provides an intrinsic regulation of epithelial Na+ transport.

A prospective population-based study of the predictors of undergoing total joint arthroplasty

OBJECTIVE

To examine prospectively the predictors of time to total joint arthroplasty (TJA).

METHODS

This was a prospective cohort study with a median followup time of 6.1 years. We included participants from an existing population-based cohort of 2,128 individuals, ages 55 years and older with disabling hip and/or knee arthritis and no prior TJA, from 2 regions of Ontario, Canada, 1 urban with low TJA rates and 1 rural with high rates. The main outcome measure was the occurrence of a TJA based on procedure codes in the hospital discharge abstract database.

RESULTS

At baseline, the mean age of the patients was 71.5 years, 67.9% had a high school education or higher, 73.4% were women, the mean arthritis severity (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]) score was 41.1 (maximum possible score 100), and 20.0% were willing to consider TJA. Greater probability of undergoing TJA was associated with higher (worse) baseline WOMAC scores (hazard ratio [HR] 1.22 per 10-unit increase, P < 0.001), age (compared with age <or=62 years, the HR increased to 1.57 for 63-68 years, 1.46 for 69-74 years, and 1.51 for 75-81 years, and fell to 0.44 for >or=82 years; P < 0.05 for all), better health (HR 1.14 per 10-unit increase in Short Form 36 general health survey score, P < 0.001), and willingness to consider TJA (HR 4.92, P < 0.001). When willingness was excluded from the model, education level, but not sex or income, became a significant predictor of TJA receipt.

CONCLUSION

Willingness to consider TJA was the strongest predictor of the time to first TJA. Given that previous research indicates that willingness is largely explained by perceptions of the indications for and risks associated with TJA and not disease severity, this finding supports the need for population education about arthritis treatments, including TJA.

Rapid anti-secretory effects of glucocorticoids in human airway epithelium

Glucocorticoids are anti-inflammatory molecules classically described as acting through a genomic pathway. Similar to many steroid hormones, glucocorticoids also induce rapid non-genomic responses. The present paper provides a general overview of the rapid non-genomic effects of glucocorticoids in airway and will be mainly focused on a retrospective of the authors work on rapid effects of glucocorticoids in airway epithelial cell transport. Using fluorescence microscopy, short circuit current measurements in human bronchial epithelial (16HBE14o(-)) cells, we reported rapid non-genomic effects of dexamethasone on cell signalling and ion transport. Dexamethasone (1 nM) rapidly stimulated Na(+)/H(+) exchanger activity and pH(i) regulation in 16HBE14o(-) cells. Dexamethasone also produced a rapid decrease of intracellular [Ca(2+)](i) to a new steady state concentration and inhibited the large and transient [Ca(2+)](i) increase induced by apical adenosine tri-phosphate (ATP). Dexamethasone also reduced by 1/3 the Ca(2+)-dependent Cl(-) secretion induced by apical ATP. The rapid effects of dexamethasone on intracellular pH and Ca(2+) were not affected by inhibitors of transcription, cycloheximide or by the classical glucocorticoid and mineralocorticoid receptors antagonists, RU486 and spironolactone, respectively. The rapid responses to glucocorticoid were reduced by the inhibitors of adenylated cyclase, cAMP-dependent protein kinase (PKA) and mitogen-activated protein kinase (ERK1/2). Our results demonstrate, that dexamethasone at low concentrations, rapidly regulates intracellular pH, Ca(2+) and PKA activity and inhibits Cl(-) secretion in human bronchial epithelial cells via a non-genomic mechanism which neither involve the classical glucocorticoid nor mineralocorticoid receptor.

Effect of an undergraduate medical curriculum on students' self-directed learning

PURPOSE

Lifelong, self-directed learning (SDL) has been identified as an important ability for medical graduates. To evaluate the effect of the University of Toronto Faculty of Medicine's revised undergraduate medical curriculum on students' SDL, a cross-sectional study was conducted.

METHOD

A questionnaire package was mailed to 280 randomly selected students, 70 from each of the four years of the curriculum. The package contained the two most widely recognized, extensively used, and validated instruments of SDL (Guglielmino's 58-item Self-Directed Learning Readiness Scale and Oddi's 24-item Continuous Learning Inventory) and Ryan's two-part Self-Assessment Questionnaire. An identification number and sociodemographic questions were included with the questionnaires. Data analysis was completed using chi-square for differences of proportions, analysis of variance for differences between means, and linear regression for trends.

RESULTS

A total of 250 (89.3%) complete questionnaire packages were returned. No significant trend in SDL was evident by curriculum year, and similar SDL levels were observed for women and men. However, a significant positive trend in SDL was found with the highest level of premedical education achieved (undergraduate only, masters, or doctoral). Further, students' perceptions concerning the importance of SDL decreased according to year in the curriculum.

CONCLUSION

This study found no evidence that students' self-reported SDL is positively influenced by the current undergraduate medical curriculum at the University of Toronto Faculty of Medicine.

Using publicly available directories to trace survey nonresponders and calculate adjusted response rates

In population-based surveys, sample lists are often out of date by the time data collection begins. Consequently, response rates, and the perceived validity of the survey, may be compromised by the unknowing inclusion of ineligible subjects. A strategy to address this issue is ascertainment of survey nonrespondents' eligibility status, enabling post hoc adjustment of response rates. In 1995-1996, population surveys were carried out in two Ontario, Canada, communities. Despite intensive follow-up, the status of 8949 (18.6%) of the 48218 potential subjects in these surveys remained unknown. In response, 500 "unknowns" from each community were randomly selected for tracing by using publicly available telephone directories and, where applicable, city directories. These tracing efforts classified persons into one of three groups: "ineligible" (moved before the mailing), "true nonresponder" (present when the survey was mailed), and "remains unknown" (no directory listing found). Publicly available directories clarified the status of 76.0% of potential participants, reducing the proportion of "unknowns" from 18.6% to 4.6%. Applying the estimated proportions of "ineligibles" from each area resulted in response rates adjusted from 63.8% to 71.2% and from 72.8% to 74.9% in the survey areas. Publicly available directories were used to successfully trace the majority of survey nonresponders, thus strengthening confidence in the survey's results.

Rapid non-genomic inhibition of ATP-induced Cl- secretion by dexamethasone in human bronchial epithelium

A non-genomic antisecretory role for dexamethasone at low concentrations (0.1 nM to1 microM) is described in monolayers of human bronchial epithelial cells in primary culture and in a continuous cell line (16HBE14o- cells). Dexamethasone produced a rapid decrease of [Ca(2+)](i) (measured with fura-2 spectrofluorescence) to a new steady-state concentration. After 15 min exposure to dexamethasone (1 nM), [Ca(2+)](i) was reduced by 32 +/- 11 nM (n = 7, P < 0.0001) from a basal value of 213 +/- 36 nM (n = 7). We have shown previously that aldosterone (1 nM) also produces a rapid fall in [Ca(2+)](i); however, after the decrease in [Ca(2+)](i) induced by dexamethasone, subsequent addition of aldosterone did not produced any further lowering of [Ca(2+)](i). The rapid response to dexamethasone was insensitive to pretreatment with cycloheximide and unaffected by the glucocorticoid type II and mineralocorticoid receptor antagonists RU486 and spironolactone, respectively. The rapid [Ca(2+)](i) decrease induced by dexamethasone was inhibited by the Ca(2+)-ATPase pump inhibitor thapsigargin (1 microM), the adenylate cyclase inhibitor MDL hydrochloride (500 microM) and the protein kinase A inhibitor Rp-adenosine 3',5'-cyclic monophosphorothioate (200 microM), but was not affected by the protein kinase C inhibitor, chelerythrine chloride (0.1 microM). Treatment of 16HBE14o- cell monolayers with dexamethasone (1 nM) inhibited the large and transient [Ca(2+)](i) increase induced by apical exposure to ATP (10(-4) M). Dexamethasone (1 nM) also reduced by 30 % the Ca(2+)-dependant Cl(-) secretion induced by apical exposure to ATP (measured as the Cl(-)-sensitive short-circuit current across monolayers mounted in Ussing chambers). Our results demonstrate, for the first time, that dexamethasone at low concentrations inhibits Cl(-) secretion in human bronchial epithelial cells. The rapid inhibition of Cl(-) secretion induced by the synthetic glucocorticoid is associated with a rapid decrease in [Ca(2+)](i) via a non-genomic mechanism that does not involve the classical glucocorticoid or mineralocorticoid receptor. Rather, it is a result of rapid non-genomic stimulation of thapsigargin-sensitive Ca(2+)-ATPase, via adenylate cyclase and protein kinase A signalling.

Cellular mechanisms for apical ATP effects on intracellular pH in human bronchial epithelium

The effect of external ATP on intracellular pH (pH(i)) was investigated using a pH imaging system in a human bronchial epithelial cell line (16HBE14o-) loaded with BCECF-AM. The steady-state pH(i) of 16HBE14o- epithelial monolayers was 7.137 +/- 0.027 (n = 46). Apical addition of ATP (10(-4) M) to epithelial monolayers induced a rapid and sustained pH(i) decrease of 0.164 +/- 0.024 pH units (n = 17; P < 0.001). The intracellular acidification was rapidly reversed upon removal of external ATP. In contrast, the non-hydrolysable ATP analogue AMP-PNP did not produce any significant change in pH(i). Inhibition of purinoreceptors by suramin did not affect the acidification induced by apical ATP. Inhibition of Na+-H+ exchange by apical Na+ removal or addition of amiloride (0.5 mM) reduced the apical ATP-induced pH(i) decrease, suggesting the involvement of a Na+-H+ exchanger or surface pH effects on the ATP-induced pH(i) response. Inhibitors of proton channels such as ZnCl2 (10(-4) M) also partially inhibited the ATP response. The pH(i) response to ATP was dependent on the external pH (pH(o)), with increasing acidification produced at lower pH(o) values. Neither the basal pH(i) nor the ATP-induced intracellular acidification was affected by thapsigargin (a Ca2+-ATPase inhibitor), chelerythrine chloride (a protein kinase C (PKC) inhibitor), RpcAMP (a protein kinase A (PKA) inhibitor) or PMA (a PKC activator). Therefore, the intracellular acidification of human bronchial epithelial cells induced by apical ATP does not involve signalling via Ca2+, PKC or PKA nor binding to a purinoreceptor. We interpret the effect of ATP to produce an intracellular acidification as a three step process: activation of H+ channels, inhibition of Na+-H+ exchange and influx of protonated ATP.

Renin-angiotensin system expression and secretory function in cultured human ciliary body non-pigmented epithelium

BACKGROUND

Renin-angiotensin system (RAS) components have been identified in human ciliary body and aqueous humour, pointing to a role for the RAS in the regulation of aqueous humour dynamics. Here, the authors examine the functional expression of a RAS and the effects of angiotensin II (AII) on a signal transduction pathway and ion secretion mechanism in cultured human ciliary body non-pigmented epithelium (HNPE).

METHODS

RAS expression was examined in cultured HNPE cells using polymerase chain reaction (PCR) analysis. Secretory function was determined using spectrofluorescence imaging microscopy to measure cell calcium (Ca(2+)(I)) and volume responses. Single channel patch clamp techniques were employed to investigate ion channel activity.

RESULTS

PCR analysis demonstrated the expression of angiotensinogen and the AT(1b) receptor in HNPE cells. A large conductance potassium (BK) channel (mean 190 (SEM 5.6) pS, n = 22 cells), was observed in plasma membrane patches. This channel was calcium sensitive with channel open probability (Po) increasing with increasing Ca(2+)(I) (K(0.5) 10.79 (0.44) microM Ca(2+), Hill coefficient of 1.04 (0.04)). AII (100 nM) increased the number (N) of active BK channels in HNPE cells and also the probability of channel opening (Po). N.P(o) increased from 0.008 (0.002) to 1.38 (0.4) following the addition of AII (p=0.0064). AII also induced a rapid rise in Ca(2+)(I) from resting values of 112 (14) nM to a peak of 992 (106) nM (p<10(-4)). A simultaneous cell volume reduction of 24.70% (3.34%) (p<10(-4)) occurred during this calcium signal. Losartan (1 microM) significantly blocked the AII induced BK channel activation (p=0.0131), the Ca(2+)(I) response (p<10(-4)), and the AII induced volume effect (p=0.0046).

CONCLUSION

It was demonstrated that AII activates a Ca(2+)(I) signalling system which subsequently increases potassium ion channel activity. These effects are accompanied simultaneously by cell volume loss, indicating that AII acts as receptor operated secretagogue in HNPE cells. The ability of an AT(1) receptor antagonist to inhibit these processes may thus offer a new family of pharmaceutical agents to the current armamentarium in the treatment of glaucoma.

Effect of motor vehicle emissions on respiratory health in an urban area

Motor vehicles emit particulate matter < 2.5 microm in diameter (PM(2.5)), and as a result, PM(2.5) concentrations tend to be elevated near busy streets. Studies of the relationship between motor vehicle emissions and respiratory health are generally limited by difficulties in exposure assessment. We developed a refined exposure model and implemented it using a geographic information system to estimate the average daily census enumeration area (EA) exposure to PM(2.5). Southeast Toronto, the study area, includes 334 EAs and covers 16 km(2) of urban area. We used hospital admission diagnostic codes from 1990 to 1992 to measure respiratory and genitourinary conditions. We assessed the effect of EA exposure on hospital admissions using a Poisson mixed-effects model and examined the spatial distributions of variables. Exposure to PM(2.5) has a significant effect on admission rates for a subset of respiratory diagnoses (asthma, bronchitis, chronic obstructive pulmonary disease, pneumonia, upper respiratory tract infection), with a relative risk of 1.24 (95% confidence interval, 1.05-1.45) for a log(10) increase in exposure. We noted a weaker effect of exposure on hospitalization for all respiratory conditions, and no effect on hospitalization for nonrespiratory conditions.

Chloride dependent intracellular pH effects of external ATP in cultured human non-pigmented ciliary body epithelium

PURPOSE

To examine the effects of extracellular adenosine 5-triphosphate (ATP) on intracellular pH ([pH](i)) in cultured human non-pigmented ciliary body epithelium (HNPE).

METHODS

Intracellular pH was measured using spectrofluorescence video microscopy in isolated HNPE cells loaded with the cell-permeable acetoxymethyl ester form of the fluorescent probe BCECF.

RESULTS

In 5%CO(2)/HCO(3)(-) buffered Ringer's the resting [pH](i) was 7.25 +/- 0.006 (mean +/- SEM). Application of 10 microM ATP significantly decreased [pH](i) to 7.00 +/- 0.007 (P < 10(-5), n = 14). In the presence of 1 mM suramin, a P(2) receptor inhibitor, this process was significantly blocked. This [pH](i) effect required the presence of Cl(-) and was significantly inhibited by 0.1 mM diisothiocyanatostilbene-2-2'-disulfonic acid or acetazolamide (500 microM), indicating the involvement of a Cl(-)/HCO(3)( +) exchange mechanism. This response exhibited little dependence on external Na(+) and remained unaffected by the addition of the Na(+)/H( +) exchanger inhibitor amiloride (1 mM). Clamping intracellular calcium levels by incubation in the cell permeable calcium chelator, the acetoxymethyl ester form of BAPTA (100 microM) in low extracellular calcium solution (pCa9) did not affect the ATP-induced [pH](i) signal. In addition, the vacuolar H(+)-ATPase (V-ATPase) inhibitor, bafilomycin A(1) (1 microM), failed to alter the [pH](i) transient.

CONCLUSION

We have demonstrated that extracellular ATP leads to a sustained increase in [H(+)](i) in HNPE cells via a purinergic receptor activated pathway which is independent of the intracellular calcium signaling system. This study demonstrates that the ATP induced [pH]( i) transient is mediated through an upregulation in Cl(-)/HCO( 3)(-) exchange across the plasmamembrane in HNPE cells.

Extracellular ATP effects on calcium signaling in cultured human non-pigmented ciliary body epithelium

PURPOSE

To determine the effects of extracellular ATP on calcium signaling in cultured human non-pigmented ciliary body epithelium (HNPE).

METHODS

Intracellular calcium (Ca(2+)(i)) was measured using spectrofluorescence video microscopy in isolated HNPE cells loaded with the fluorescent dye Fura-2.

RESULTS

Nucleotides caused a transient oscillatory increase in Ca(2+)(i) with a potency order of ATP = UTP > ADP > AMP> alpha,beta-methylene-ATP. Treatment with thapsigargin (100 nM), an inhibitor of endoplasmic Ca(2+)-ATPase pumps, produced a sustained increase in Ca(2+)(i). Subsequent exposure to ATP caused a rapid reduction in Ca(2+)(i) and this effect was reduced by pre-exposure to vanadate and to a lesser extent in sodium free solution. Prolonged exposure to ATP in the presence of thapsigargin caused a transient spike increase in Ca(2+)(i) which was prevented by exposure to low extracellular Ca(2+) (1 nmol/l), verapamil, nifedipine or the microfilament disrupting agent, cytochalasin B.

CONCLUSIONS

These results provide evidence for ATP mobilisation of Ca(2+) from intracellular stores via P2Y2 receptor activation in HNPE cells. ATP also primarily activates a vanadate-sensitive Ca(2+ )-ATPase pump, in addition to having a smaller effect on the Na( +)/ Ca(2+) exchanger in terminating the calcium signal. Capacitative calcium entry, possibly via an L-type Ca(2+) channel, is implicated in generating a calcium signal following emptying of intracellular stores and is sensitive to cytoskeleton disruption. ATP can thus regulate a potent intracellular signal for secretion, suggest-ing that purinergic receptors may provide a therapeutic target in glaucoma.

Rapid and non-genomic reduction of intracellular [Ca(2+)] induced by aldosterone in human bronchial epithelium

1. Using a Ca(2+) imaging system and fura-2 AM (5 microM) we showed that exposure of polarised monolayers of human bronchial epithelial cells (16HBE14o- cell line) to aldosterone produced a fast intracellular [Ca(2+)] ([Ca(2+)](i)) decrease, in 70 % of cells. Exposure to aldosterone (1 nM) reduced the [Ca(2+)](i) by 39 +/- 9 nM (n = 282, P < 0.0001) within 10 min, from a basal [Ca(2+)](i) of 131 +/- 19 nM (n = 282). 2. The effect of aldosterone on [Ca(2+)](i) was not affected by inhibitors of the classical genomic pathway, cycloheximide (1 microM) or spironolactone (10 microM). The aldosterone-induced [Ca(2+)](i) decrease was inhibited by thapsigargin (1 microM), pertussis toxin (24 h at 200 ng ml(-1)), the adenylate cyclase inhibitors 2',3'-dideoxyadenosine (200 microM) and MDL-12,330A hydrochloride (500 microM), and the protein kinase A inhibitor R(P)-adenosine 3',5'-cyclic monophosphorothioate (200 microM). In addition, treatment of 16HBE14o- monolayers with aldosterone (1 nM) inhibited by approximately 30 % the large and transient [Ca(2+)](i) increase induced by apical exposure to uridine triphosphate (UTP, 0.1 mM), a known secretagogue in airway epithelia. 3. Our results demonstrate for the first time that in human bronchial epithelial cells, aldosterone decreases [Ca(2+)](i) levels via a non-genomic mechanism. The hormone-induced changes to [Ca(2+)](i) involve stimulation of thapsigargin-sensitive Ca(2+)-ATPase, via G-protein-, adenylate cyclase- and protein kinase A-coupled signalling pathways.

Sex and salt hormones: rapid effects in epithelia

Recent evidence points to protein kinase C isoforms as highly specific receptors for aldosterone and estradiol in epithelia. The end targets of the kinase activation are Na(+)/H(+) exchange and K(+) and Ca(2+) channels. The physiological role of the nongenomic response is to increase electrolyte absorption and inhibit secretion in pluripotential epithelia.

17beta-oestradiol stimulates capacitative Ca2+ entry in human endometrial cells

Oestrogen plays an essential role in regulating growth and differentiation in the human endometrium which undergoes dynamic morphological and functional changes during the menstrual cycle in preparation for implantation. In this tissue, it has been suggested that intracellular calcium could be a key signal in transducing early responses to steroid hormones. Here, we have investigated the rapid effects of 17beta-oestradiol on [Ca2+]i in a human endometrial cell line (RL95-2). Using confocal imaging microscopy, we show that physiological concentrations of 17beta-oestradiol trigger rapid and transient increases in [Ca2+]i. Our results demonstrate that 17beta-oestradiol-induced [Ca2+]i variations are critically dependent on calcium influx via lanthanum-sensitive calcium channels. Moreover, the 17beta-oestradiol-induced Ca2+ influx is significantly increased by the depletion of intracellular stores by thapsigargin and decreased by chelerythrine chloride, an inhibitor of protein kinase C. These data indicate a non-genomic action of 17beta-oestradiol to stimulate capacitative Ca2+ entry through store-operated calcium channels via a PKC-sensitive pathway.

17beta-oestradiol acutely regulates Cl- secretion in rat distal colonic epithelium

In this study we used the short circuit current (ISC) technique to measure the non-genomic effects of the female sex steroid 17beta-oestradiol (E2) on electrogenic transepithelial ion transport in rat distal colonic epithelium. Basal ISC was largely composed of a transepithelial Cl- secretory component with minimal electrogenic Na+ movement. E2 (1-100 nM) caused a significant decrease in basal ISC after 15 min. In addition, pre-treating colonic epithelial tissues with E2 (0.1-100 nM) for 10 min significantly reduced forskolin (20 microM)-induced Cl- secretion. E2 also down-regulated Cl- secretion which was pre-stimulated by forskolin. Cl- secretory responses to the Ca2+-dependent secretagogue carbachol (10 microM) were also significantly reduced in the presence of E2 (10- 100 nM). However, E2 had no effect on amiloride-sensitive Na+ absorption. The rapid anti-secretory effect of E2 was abolished in the presence of the intracellular Ca2+ chelator BAPTA (50 microM) or the protein kinase C (PKC) inhibitor chelerythrine chloride (1 microM). However, in the presence of the nuclear oestrogen receptor antagonist tamoxifen (10 microM), E2 still produced an inhibition of Cl- secretion. Testosterone, progesterone and 17alpha-oestradiol had no significant effect on colonic Cl- secretion. Also, E2 (100 nM) did not alter Cl- secretion in colonic epithelia isolated from male rats. We conclude that E2 inhibits colonic Cl- secretion via a non-genomic pathway that involves intracellular Ca2+ and PKC. It is possible that this gender-specific mechanism contributes to the salt and water retention associated with high E2 states.

Mitogenic effects of oestrogen mediated by a non-genomic receptor in human colon

BACKGROUND

Oestrogens are important mitogens in epithelial cancers, particularly where tumours express complementary receptors. While the traditional model of oestrogen action involves gene-directed (genomic) protein synthesis, it has been established that more rapid, non-genomic steroid hormone actions exist. This study investigated the hypothesis that oestrogen rapidly alters cell membrane activity, intracellular pH and nuclear kinetics in a mitogenic fashion.

METHODS

Crypts isolated from human distal colon and colorectal cancer cell lines were used as robust models. DNA replication and intracellular pH were measured by radiolabelled thymidine incorporation (12 h) and spectrofluorescence imaging respectively. Genomic protein synthesis, sodium-hydrogen exchanger (NHE) and protein kinase C (PKC) activity were inhibited with cycloheximide, ethylisopropylamiloride and chelerythrine chloride respectively.

RESULTS

Oestrogen induced a rapid (less than 5 min) cellular alkalinization of crypts and cancer cells that was sensitive to NHE blockade (P < 0.01) or PKC inhibition (P < 0.01). Oestrogen increased thymidine incorporation by 44 per cent in crypts and by up to 38 per cent in cancer cells (P < 0.01), and this was similarly reduced by inhibiting the NHE (P < 0.01) or PKC (P < 0.05).

CONCLUSION

Oestrogen rapidly activates cell membrane and nuclear kinetics by a non-genomic mechanism mediated by PKC but not gene-directed protein synthesis.

Rapid activation of basolateral potassium transport in human colon by oestradiol

1. We investigated the effect of oestradiol on basolateral potassium channels in human colonic epithelium. 2. Ion transport was quantified using short circuit current (I:(sc)) measurements of samples mounted in Ussing chambers. Serosal K transport was studied using nystatin permeabilization of the apical membrane. Intracellular pH changes were quantified using spectroflouresence techniques. 3. Experiments were performed with either 10 nM or 1 microM Ca(2+) in the apical bathing solution. With 10 nM Ca(2+) in the apical bathing solution addition of oestradiol (1 nM) to the basolateral bath produced a rapid increase in current (delta I(K)=11.2+/-1.2 microA.cm(-2), n=6). This response was prevented by treatment of the serosal membrane with tolbutamide (1 microM). With 1 microM Ca(2+) in the apical bathing solution addition of oestradiol produced a rapid fall in current (delta I(K)=-12.8+/-1.4 microA.cm(-2)), this response was prevented by treatment of the basolateral membrane with tetra-pentyl-ammonium (TPeA). These responses were rapid and occurred independently of protein synthesis. 4. Inhibition of basolateral Na(+)/H(+) exchange with either amiloride or a low sodium bathing solution prevented this response. These responses were prevented by inhibition of protein kinase C (PKC) with bis-indolyl-maleimide. 5. Oestradiol (1 nM) produced a rapid intracellular alkanization (mean increase=0.11 pH units; n=6; P<0.01). 6. These results suggest that oestradiol rapidly modulates serosal K transport in human colon. These effects depend upon intact Na(+)/H(+) exchange and protein kinase C. We propose a non-classical, possibly membrane linked, mechanism for oestradiol action in human colonic epithelium.

CFTR regulation of intracellular calcium in normal and cystic fibrosis human airway epithelia

In cystic fibrosis airway epithelia, mutation of the CFTR protein causes a reduced response of Cl(-) secretion to secretagogues acting via cAMP. Using a Ca(2+) imaging system, the hypothesis that CFTR activation may permit ATP release and regulate [Ca(2+)](i) via a receptor-mediated mechanism, is tested in this study. Application of external nucleotides produced a significant increase in [Ca(2+)](i) in normal (16HBE14o(-) cell line and primary lung culture) and in cystic fibrosis (CFTE29o(-) cell line) human airway epithelia. The potency order of nucleotides on [Ca(2+)](i) variation was UTP >> ATP > UDP > ADP > AMP > adenosine in both cell types. The nucleotide [Ca(2+)](i) response could be mimicked by activation of CFTR with forskolin (20 microm) in a temperature-dependent manner. In 16HBE14o(-) cells, the forskolin-induced [Ca(2+)](i) response increased with increasing temperature. In CFTE29o(-) cells, forskolin had no effect on [Ca(2+)](i) at body temperature-forskolin-induced [Ca(2+)](i) response in CF cells could only be observed at low experimental temperature (14 degrees C) or when cells were cultured at 26 degrees C instead of 37 degrees C. Pretreatment with CFTR channel blockers glibenclamide (100 microm) and DPC (100 microm), with hexokinase (0.5 U/mg), and with the purinoceptor antagonist suramin (100 microm), inhibited the forskolin [Ca(2+)](i) response. Together, these results demonstrate that once activated, CFTR regulates [Ca(2+)](i) by mediating nucleotide release and activating cell surface purinoceptors in normal and CF human airway epithelia.