Four genes of Medicago truncatula controlling components of a nod factor transduction pathway

Rhizobium nodulation (Nod) factors are lipo-chitooligosaccharides that act as symbiotic signals, eliciting several key developmental responses in the roots of legume hosts. Using nodulation-defective mutants of Medicago truncatula, we have started to dissect the genetic control of Nod factor transduction. Mutants in four genes (DMI1, DMI2, DMI3, and NSP) were pleiotropically affected in Nod factor responses, indicating that these genes are required for a Nod factor-activated signal transduction pathway that leads to symbiotic responses such as root hair deformations, expressions of nodulin genes, and cortical cell divisions. Mutant analysis also provides evidence that Nod factors have a dual effect on the growth of root hair: inhibition of endogenous (plant) tip growth, and elicitation of a novel tip growth dependent on (bacterial) Nod factors. dmi1, dmi2, and dmi3 mutants are also unable to establish a symbiotic association with endomycorrhizal fungi, indicating that there are at least three common steps to nodulation and endomycorrhization in M. truncatula and providing further evidence for a common signaling pathway between nodulation and mycorrhization.

Significant post-transplant hypogammaglobulinemia in six heart transplant recipients: an emerging clinical phenomenon?

BACKGROUND

The recent development of powerful agents such as mycophenolate mofetil and tacrolimus has altered current regimens for the prevention and treatment of allograft rejection. Questions have been raised about these newer regimens in terms of susceptibility to opportunistic infections and effects on host defenses. Severe hypogammaglobulinemia has been infrequently described in solid organ transplant recipients, but has been recently noted in six heart transplant recipients at one center, of whom five were receiving a combination of tacrolimus, mycophenolate mofetil, and prednisone.

METHODS

Case summaries of six recent heart transplant recipients with total immunoglobulin G (IgG) levels of less than 310 mg/dl, five of whom had cytomegalovirus (CMV) infection and three of whom had multiple infections including Nocardia, invasive Trichophyton, and Acinetobacter bacteremia. Previous literature was reviewed with the aid of a Medline search using the search terms hypogammaglobulinemia; kidney, liver, heart, lung, and organ transplantation; mycophenolate mofetil; tacrolimus; cyclosporine; azathioprine; and nocardiosis.

RESULTS

We here report six cardiac transplant recipients seen over a period of one year who were found to have immunoglobulin G levels of 310 mg/dl or below (normal: 717-1400 mg/dl). The first five patients were diagnosed because of evaluation for infections; the sixth, who was asymptomatic with an IgG level of 175, was found during screening for hypogammaglobulinemia instituted as a result of these first five patients. All six patients had received steroid pulses for rejection; all received mycophenolate mofetil; and 5/6 had been switched from cyclosporine to tacrolimus because of steroid-resistant rejection. Transient neutropenia (absolute neutrophil count less than 1000) was observed in 2/6; 3/6 had received OKT3 therapy for refractory rejection. These six patients were treated with a combination of antimicrobials, immunoglobulin replacement, and decrease in immunosuppressive therapy.

CONCLUSION

The finding of unexpected hypogammaglobulinemia and concomitant infectious complications in six heart transplant recipients highlights a possible complication in a subset of patients receiving newer immunosuppressive agents. A larger prospective study is underway to determine risk factors for development of post-transplant hypogammaglobulinemia and to assess pre-transplant immune status of these recipients. Monitoring of immunoglobulin levels in high-risk patients receiving intensified immunosuppressive therapy for rejection may help to prevent infectious complications.

Towards a "good" death: end-of-life narratives constructed in an intensive care unit

End-of-life decisions regarding the withdrawal and withholding of life supporting technology have become commonplace within intensive care units (ICUs). In this paper, we examine the dialogue between ICU team members and families regarding limitation of treatment as a therapeutic narrative--that is, as a story which frames therapeutic events as well as the critically ill patient's experience in a meaningful and psychologically comforting way for families and health care providers alike. The key themes of these end-of-life narratives are discussed, as well as the qualities that the stories share with other narratives of the same genre.

Ventilator associated pneumonia: perspectives on the burden of illness

OBJECTIVE

The objective of this narrative review is to summarize selected current concepts and clinical evidence regarding the burden of illness of VAP, including its epidemiology, diagnosis, attributable mortality and risk factors.

DATA SOURCES & SELECTION

Studies were identified through MEDLINE, EMBASE, bibliographies of primary and review articles and personal files.

RESULTS

While cross sectional studies inform us about VAP prevalence, longitudinal studies inform us of the cumulative risk and conditional risk of developing VAP. Reported VAP rates are modulated by factors related to case mix, causative microorganisms, interventions that influence risk over time, and VAP definitions employed. Population-specific and organism-specific VAP rates are needed to avoid misleading benchmarking between different ICUs, and to minimize inappropriate between-study comparisons. Observational studies have shown that invasive sampling techniques versus non-invasive approaches to diagnose VAP facilitates more targeted antibiotic treatment; however, the influence of the diagnostic method on endpoints such as mortality is less clear. VAP is associated with approximately a 4 day increase in length of ICU stay and an attributable mortality of approximately 20-30%. Fixed VAP risk factors include underlying cardiorespiratory disease, neurologic injury and trauma. Modifiable VAP risk factors include supine body position, witnessed aspiration, paralytic agents and antibiotic exposure. If modifiable risk factors tested in randomized trials lower VAP rates, such as semirecumbency versus supine positioning, these represent effective VAP prevention strategies.

CONCLUSIONS

Ventilator-associated pneumonia is a major morbid outcome among critically ill patients. Studies evaluating more effective prevention and treatment strategies are needed.

School-based telemedicine: teachers', nurses' and administrators' perceptions

In 1997, a telemedicine project began in Kansas which brought health-care directly into elementary schools using interactive video-links. The project initially involved four schools, but was expanded to cover 10 schools, including two middle and one high school. We examined the organizational issues related to telemedicine links to schools. Specific attention was paid to the perceptions of the nurses, teachers and key administrators. The research involved analysing archive data and interviewing participants in the project from the schools and the medical centre. The results showed the difficulties in delivering health-care, especially by telemedicine, to under-served urban children. However, the data also revealed that these can be overcome. Once they had experienced it at first hand, almost all concerned began to see telemedicine as an effective and important asset to the delivery of health-care.

Noninvasive positive pressure ventilation in the setting of severe, acute exacerbations of chronic obstructive pulmonary disease: more effective and less expensive

OBJECTIVE

The use of noninvasive ventilation for patients with acute respiratory failure has become increasingly popular over the last decade. Although the literature provides good evidence for the effectiveness of noninvasive ventilation in addition to standard therapy compared with standard therapy alone in patients with chronic obstructive pulmonary disease (avoiding intubation and improving hospital mortality), the associated costs have not been rigorously measured. Adding noninvasive positive pressure ventilation (NPPV) to standard therapy in the setting of a severe, acute exacerbation of chronic obstructive pulmonary disease (COPD) in patients with respiratory acidosis who are at high risk of requiring endotracheal intubation is both more effective and less expensive.

DESIGN

Economic evaluation based on theoretical model.

SETTING

This analysis base case was modeled for a tertiary care, teaching hospital.

PATIENTS OR OTHER PARTICIPANTS

Carefully selected patients with severe exacerbations of COPD.

INTERVENTION

The two alternative therapies compared were standard therapy (oxygen, bronchodilators, steroids, and antibiotics) and standard therapy plus NPPV.

MEASUREMENTS AND MAIN RESULTS

As the hypothesis was dominance, the main outcomes modeled and calculated were costs, mortality rate, and rates of intubation between the two interventions. To determine clinical effectiveness, we used a meta-analysis of randomized trials evaluating the impact of NPPV on hospital survival. A decision tree was constructed and probabilities were applied at each chance node using research evidence and a comprehensive regional database. To provide data for this economic evaluation, MEDLINE literature searches were conducted. Bibliographies of relevant articles were reviewed, as were personal files. To estimate the costs of the alternative therapeutic approaches, eight types of hospitalization days were costed using the London Health Sciences Center costing data. Sensitivity analyses were performed, varying all assumptions made. The meta-analysis yielded an odds ratio for hospital mortality in the NPPV arm, compared with standard therapy, of 0.22 (95% confidence interval, 0.10-0.66). By using baseline case assumptions, we found a cost savings of $3,244 (1996, Canadian), per patient admission, if NPPV were adopted in favor of standard therapy. These findings present a scenario of clear dominance for treatment with NPPV. Sensitivity analyses did not alter the results appreciably.

CONCLUSIONS

We conclude that from a hospital's perspective, NPPV and standard therapy for carefully selected patients with acute, severe exacerbations of COPD are more effective and less expensive than standard therapy alone.

Effect of smoking cessation on mortality after myocardial infarction: meta-analysis of cohort studies

OBJECTIVE

To determine the effect of smoking cessation on mortality after myocardial infarction.

DATA SOURCES

English- and non-English-language articles published from 1966 through 1996 retrieved using keyword searches of MEDLINE and EMBASE supplemented by letters to authors and searching bibliographies of reviews.

STUDY SELECTION

Selection of relevant abstracts and articles was performed by 2 independent reviewers. Articles were chosen that reported the results of cohort studies examining mortality in patients who quit vs continued smoking after myocardial infarction.

DATA EXTRACTION

Mortality data were extracted from the selected articles by 2 independent reviewers.

DATA SYNTHESIS

Twelve studies were included containing data on 5878 patients. The studies took place in 6 countries between 1949 and 1988. Duration of follow-up ranged from 2 to 10 years. All studies showed a mortality benefit associated with smoking cessation. The combined odds ratio based on a random effects model for death after myocardial infarction in those who quit smoking was 0.54 (95% confidence interval, 0.46-0.62). Relative risk reductions across studies ranged from 15% to 61%. The number needed to quit smoking to save 1 life is 13 assuming a mortality rate of 20% in continuing smokers. The mortality benefit was consistent regardless of sex, duration of follow-up, study site, and time period.

CONCLUSION

Results of several cohort studies suggest that smoking cessation after myocardial infarction is associated with a significant decrease in mortality.

Development and laboratory evaluation of a new toothbrush with a novel brush head design

Despite many developments in manual toothbrush design, plaque removal at the back of the mouth and at approximal surfaces remains inadequate, yet it is at these sites in particular that plaque accumulates and leads to the development of gingival disease. Improved oral hygiene can be achieved by better brushing technique and by increasing brushing time, but a change in behavior patterns is almost impossible to achieve for the majority of individuals. What is required is a brush head design that maximizes plaque removal, regardless of how the user brushes. As a result of a detailed investigation into the action of bistles during brushing, the Oral-B CrossAction toothbrush has been developed. It incorporates bristles angled at 16 degrees in a unique CrissCross design arranged along the horizontal axis of the toothbrush. Laboratory studies have demonstrated that this development significantly enhances interproximal penetration and cleaning effectiveness when compared with an identical brush head with vertical rather than angled bristles. Laboratory comparisons with more than 80 leading manual toothbrushes from around the world demonstrate a consistent, significant advantage for the new CrossAction toothbrush, both with respect to interproximal penetration and cleaning effectiveness. These results suggest that the CrossAction toothbrush has the potential to remove greater amounts of plaque, especially from the approximal surfaces, than conventional toothbrushes incorporating vertical bristles or more traditional tuft designs.

Using and understanding sedation scoring systems: a systematic review

OBJECTIVE

To systematically review instruments for measuring the level and effectiveness of sedation in adult and pediatric ICU patients.

STUDY IDENTIFICATION

We searched MEDLINE, EMBASE, the Cochrane Library and reference lists of the relevant articles. We selected studies if the sedation instrument reported items related to consciousness and one or more additional items related to the effectiveness or side effects of sedation.

DATA ABSTRACTION

We extracted data on the description of the instrument and on their measurement properties (internal consistency, reliability, validity and responsiveness).

RESULTS

We identified 25 studies describing relevant sedation instruments. In addition to the level of consciousness, agitation and synchrony with the ventilator were the most frequently assessed aspects of sedation. Among the 25 instruments, one developed in pediatric ICU patients (the Comfort Scale), and 3 developed in adult ICU patients (the Ramsay scale, the Sedation-Agitation-Scale and the Motor Activity Assessment Scale), were tested for both reliability and validity. None of these instruments were tested for their ability to detect change in sedation status over time (responsiveness).

CONCLUSION

Many instruments have been used to measure sedation effectiveness in ICU patients. However, few of them exhibit satisfactory clinimetric properties. To help clinicians assess sedation at the bedside, to aid readers critically appraise the growing number of sedation studies in the ICU literature, and to inform the design of future investigations, additional information about the measurement properties of sedation effectiveness instruments is needed.

Use of a screen log to audit patient recruitment into multiple randomized trials in the intensive care unit. Canadian Critical Care Trials Group

OBJECTIVE

To develop and evaluate a screen log for monitoring enrollment in multiple randomized clinical trials conducted in a single center.

SETTING

University-affiliated 20-bed tertiary care medical-surgical intensive care unit (ICU).

PATIENTS

Consecutive ICU patients admitted between April 1995 and March 1997.

METHODS

We developed a screen log for multicentered studies conducted in our ICU. Using a multiple-project, unicenter perspective, we evaluated the screen log as a tool for monitoring eligibility and enrollment of patients in four multicentered randomized trials focused on stress ulcer prophylaxis, blood transfusion thresholds, immunotherapy for sepsis and mechanical ventilation strategies.

RESULTS

The screen log was used as an instrument to monitor trial execution. We recorded all aspects of study enrollment and created a taxonomy of reasons for nonenrollment into each trial. We calculated enrollment efficiency rates and used these data to develop strategies to maximize accrual. The screen log became a communication tool that fostered research-oriented continuous quality improvement initiatives for the management of concurrently conducted randomized trials in our ICU.

CONCLUSIONS

Intensivists participating in several clinical trials may be interested in monitoring and maximizing enrollment when conducting multiple studies and understanding the influence of each trial on enrollment into the others. The unicenter, multiple-project screen log is one tool that may help to achieve these goals.

Gay and lesbian physicians in training: a qualitative study

BACKGROUND

Gay and lesbian physicians in training face considerable challenges as they become professionalized. Qualitative research is necessary to understand the social and cultural factors that influence their medical training. In this study we explored the significance of gay or lesbian identity on the experiences of medical training using naturalistic methods of inquiry.

METHODS

Semi-structured interviews, focus groups and an e-mail listserv were used to explore professional and personal issues of importance to 29 gay and lesbian medical students and residents in 4 Canadian cities. Data, time, method and investigator triangulation were used to identify and corroborate emerging themes. The domains explored included career choice, "coming out," becoming a doctor, the environment and career implications.

RESULTS

Gay or lesbian medical students and residents experienced significant challenges. For all participants, sexual orientation had an effect on their decisions to enter and remain in medicine. Once in training, the safety of a variety of learning environments was of paramount importance, and it affected subsequent decisions about identity disclosure, residency and career path. Respondents' assessment of professional and personal risk was influenced by the presence of identifiable supports, curricula inclusive of gay and lesbian sexuality and health issues and effective policies censuring discrimination based on sexual orientation. The need for training programs to be proactive in acknowledging and supporting diversity was identified.

INTERPRETATION

Considerable energy and emotion are spent by gay and lesbian medical students and residents navigating training programs, which may be, at best, indifferent and, at worst, hostile.

Visualization of data

Data visualization has developed in several directions: theoretical; methodological; and in new application areas. Advances include the development of a grammar of graphics, deeper understanding of human perception and implications for graphical layout, and better approaches to visualizing multi-dimensional data and large data sets. Gene expression is a notable new application area for visualization of large data sets.

Examination of the oral mucosa and peripheral blood cells of patients with recurrent aphthous ulceration for human herpesvirus DNA

OBJECTIVE

The purpose of this study was to exam the oral mucosa and peripheral blood cells of patients with recurrent aph-thous ulceration (RAU) for the presence of the following human herpesviruses: herpes simplex viruses 1 and 2, varicella zoster virus, Epstein-Barr virus, cytomegalovirus, human herpesvirus-6, and human herpesvirus-7.

STUDY DESIGN

Fifty-eight subjects with RAU and 10 control subjects were recruited at an academic referral center and enrolled in this prospective, nonrandomized, case-controlled study. Each of the subjects with RAU was seen during an acute episode, and swab specimens from lesional (RAU-acute/lesion) and clinically normal (RAU-acute/normal) oral mucosa were obtained. Each of 2 subjects with RAU was evaluated during more than one acute episode. Three subjects with RAU were seen between active episodes, and swab specimens were taken from clinically normal (RAU-convalescent) oral mucosa. Swab specimens from clinically normal (control/normal) oral mucosa were obtained from the control subjects. Peripheral blood specimens were obtained from subjects with RAU and control subjects at the time the swab specimens were performed. Through use of polymerase chain reaction, all swab and peripheral blood specimens were examined for the presence of human herpesvirus DNA. Statistical significance was determined by means of chi(2) analysis.

RESULTS

Herpes simplex virus and human herpesvirus-6 were found in a higher percentage of mucosal specimens from the control subjects (herpes simplex virus, 4/10; human herpesvirus-6, 5/9) than from the subjects with RAU (RAU-acute/lesion: 3/45 herpes simplex virus, 13/53 human herpesvirus-6; RAU-acute/normal: 7/48 herpes simplex virus, 9/53 human herpesvirus-6). No difference was demonstrated between RAU-acute/lesion, RAU-acute/normal, and RAU-convalescent mucosal specimens for any of the human herpesviruses. Different human herpesviruses were identified from individual subjects with RAU during subsequent episodes of disease. Epstein-Barr virus (6/35), human herpesvirus-6 (3/40), and human herpesvirus-7 (7/43) were detected in the peripheral blood mononuclear cells during acute RAU but not in RAU-convalescent or control peripheral blood mononuclear cells.

CONCLUSIONS

The detection of human herpesvirus DNA from the oral mucosa and peripheral blood mononuclear cells of patients with RAU appears to represent normal viral shedding rather than a direct causal mechanism in this disorder.

Development, dissemination, implementation and evaluation of a clinical pathway for oxygen therapy

BACKGROUND

Oxygen is commonly administered to patients in hospital, but prescribing and monitoring of such therapy may be suboptimal. The objective of this study was to develop, disseminate, implement and evaluate a multidisciplinary clinical pathway for the administration of oxygen.

METHODS

The authors developed a clinical pathway for the ordering, titration and discontinuation of oxygen, which was disseminated through teaching sessions, in-service training sessions and information posters in a medical clinical teaching unit (CTU). Implementation of the pathway was ensured by means of reminders and patient-centred audit and feedback to CTU nurses and house staff. During a 3-month intervention phase, consecutive patients requiring supplemental oxygen were treated according to the pathway. During a 1-month "wash-out" phase followed by a 3-month non-intervention phase, patients were treated at the discretion of the CTU team. Clinical and economic data were collected in both phases.

RESULTS

In the 2 phases, patient characteristics, the concentration and duration of oxygen prescribed, the frequency of oxygen saturation monitoring, the frequency of arterial blood gas testing and the clinical outcomes were similar. However, there were more discontinuation orders in the intervention phase (p < 0.001). In the intervention phase, costs were higher for monitoring of oxygen saturation ($44.95/patient v. $36.17/patient, p = 0.048) and for order transcription ($2.71/patient v. $1.28/patient, p < 0.001); total costs, including those for personnel, were also higher in the intervention phase ($76.93/patient v. $56.67/patient, p = 0.02). The cost of education about the oxygen pathway was $45.71/patient. When the education cost was included, the total cost of oxygen therapy during the intervention phase was $122.64/patient; this was significantly higher than the total cost of oxygen therapy during the non-intervention phase ($56.67/patient) (p < 0.001).

INTERPRETATION

This multidisciplinary, multimethod oxygen pathway led to changes in oxygen-prescribing behaviour, consumed more resources than standard management and was not associated with changes in patient outcome. Appropriate management of oxygen prescribing and monitoring by physicians and nurses take time and costs money.

Evaluating the performance of academic medical education administrators

Educators have devoted little attention to formal evaluation of educational administrative personnel. The authors surveyed the educational administrators working in McMaster University's Department of Medicine residency program and found they felt they were receiving little useful feedback. The authors also surveyed the colleagues, residents, and administrative staff with whom the administrators worked and found they felt they had inadequate input into the administrators' evaluation. In response to these results, a measurement instrument was developed based on existing job descriptions and feedback was obtained on administrators' performance from relevant individuals. After three yearly evaluations, administrators and evaluators acknowledged much broader input into evaluation but saw little evaluation-related improvement in performance. Of the administrators, 85% felt the process should continue as did 91% of the evaluators. An evaluation process may not alter perceived performance when it is already good but there may be other benefits to rigorous evaluation.

Risk factors for clinically important upper gastrointestinal bleeding in patients requiring mechanical ventilation. Canadian Critical Care Trials Group

OBJECTIVE

To evaluate the incidence and risk factors for clinically important upper gastrointestinal bleeding in critically ill patients requiring mechanical ventilation.

DESIGN

In duplicate, blinded adjudicators determined the presence of clinically important gastrointestinal bleeding using a priori criteria, evaluating relevant clinical, laboratory, and diagnostic data. Cox proportional hazards regression analyses were used to examine baseline and time-dependent risk factors for bleeding.

SETTING

Sixteen university-affiliated intensive care units (ICUs) in Canada.

PATIENTS

A total of 1,077 critically ill ICU patients ventilated for at least 48 hrs.

INTERVENTIONS

Patients were randomized to stress ulcer prophylaxis with intravenous ranitidine or nasogastric sucralfate; otherwise, management was at the discretion of the ICU team.

MEASUREMENTS AND MAIN RESULTS

Demographic data included patient characteristics, Acute Physiology and Chronic Health Evaluation II score, and multiple organ dysfunction (MOD) score. Each day in the ICU, physiologic measurements including MOD score, feeding, and other treatment variables were recorded. The significant risk factors for upper gastrointestinal bleeding in the univariable analyses were low platelet count, maximum serum creatinine, maximum MOD score, maximum pulmonary component of the MOD score, maximum hepatic component of the MOD score, maximum renal component of the MOD score, enteral nutrition, and stress ulcer prophylaxis with ranitidine. The only independent predictors of bleeding in the multivariable analysis were maximum serum creatinine (relative risk = 1.16 [95% confidence interval = 1.02-1.32]), enteral nutrition (relative risk = 0.30 [95% confidence interval = 0.13-0.67]), and ranitidine administration (relative risk = 0.39 [95% confidence interval = 0.17-0.83]).

CONCLUSIONS

In critically ill ventilated patients, renal failure was independently associated with an increased risk of clinically important gastrointestinal bleeding, whereas enteral nutrition and stress ulcer prophylaxis with ranitidine conferred significantly lower bleeding rates.