Comparison of Central and Peripheral Arterial Blood Pressure Gradients in Critically Ill Patients: A Systematic Review and Meta-Analysis

OBJECTIVES

Measurement of blood pressure taken from different anatomical sites, are often perceived as interchangeable, despite them representing different parts of the systemic circulation. We aimed to perform a systematic review and meta-analysis on blood pressure differences between central and peripheral arterial cannulation in critically ill patients.

DATA SOURCES

We searched MEDLINE, Cochrane Central Register of Controlled Trials, and Embase from inception to December 26, 2023, using Medical Subject Headings (MeSH) terms and keywords.

STUDY SELECTION

Observation study of adult patients in ICUs and operating rooms who underwent simultaneous central (femoral, axillary, or subclavian artery) and peripheral (radial, brachial, or dorsalis pedis artery) arterial catheter placement in ICUs and operating rooms.

DATA EXTRACTION

We screened and extracted studies independently and in duplicate. We assessed risk of bias using the revised Quality Assessment for Studies of Diagnostic Accuracy tool.

DATA SYNTHESIS

Twenty-four studies that enrolled 1598 patients in total were included. Central pressures (mean arterial pressure [MAP] and systolic blood pressure [SBP]) were found to be significantly higher than their peripheral counterparts, with mean gradients of 3.5 and 8.0 mm Hg, respectively. However, there was no statistically significant difference in central or peripheral diastolic blood pressure (DBP). Subgroup analysis further highlighted a higher MAP gradient during the on-cardiopulmonary bypass stage of cardiac surgery, reperfusion stage of liver transplant, and in nonsurgical critically ill patients. SBP or DBP gradient did not demonstrate any subgroup specific changes.

CONCLUSIONS

SBP and MAP obtained by central arterial cannulation were higher than peripheral arterial cannulation; however, clinical implication of a difference of 8.0 mm Hg in SBP and 3.5 mm Hg in MAP remains unclear. Our current clinical practices preferring peripheral arterial lines need not change.

Immune checkpoint inhibitors and pericardial disease: a systematic review

INTRODUCTION

Despite the growing use of immune checkpoint inhibitors (ICI) in cancer treatment, data regarding ICI-associated pericardial disease are primarily derived from case reports and case series. ICI related pericardial disease can be difficult to diagnose and is associated with significant morbidity. We conducted a systematic review to further characterize the epidemiology, clinical presentation, and outcomes of this patient population.

METHODS

A search of four databases resulted in 31 studies meeting inclusion criteria. Patients > 18 years old who presented with ICI mediated pericardial disease were included. Intervention was medical + surgical therapy and outcomes were development of cardiac tamponade, morbidity, and mortality.

RESULTS

Thirty- eight patients across 31 cases were included. Patients were majority male (72%) with a median age of 63. Common symptoms included dyspnea (59%) and chest pain (32%), with 41% presenting with cardiac tamponade. Lung cancer (81%) was the most prevalent, and nivolumab (61%) and pembrolizumab (34%) were the most used ICIs. Pericardiocentesis was performed in 68% of patients, and 92% experienced symptom improvement upon ICI cessation. Overall mortality was 16%.

DISCUSSION

This study provides the most comprehensive analysis of ICI-mediated pericardial disease to date. Patients affected were most commonly male with lung cancer treated with either Nivolumab or Pembrolizumab. Diagnosis may be challenging in the setting of occult presentation with normal EKG and physical exam as well as delayed onset from therapy initiation. ICI-associated pericardial disease demonstrates high morbidity and mortality, as evidenced by a majority of patients requiring pericardiocentesis.

Association Between Length of Maternity Leave and Breastfeeding Duration in the United States: A Systematic Review

OBJECTIVE

To perform a systematic review to assess the association between the length of maternity leave and breastfeeding duration in the United States.

DATA SOURCES AND METHODS OF STUDY SELECTION

This review was conducted with a five-stage model for reviews. We included publications from 2000 to 2023, U.S.-based studies written in English, and primary research and peer-reviewed articles. In February 2023, a medical librarian conducted a search across seven databases, yielding 1,540 results. ClinicalTrials.gov was later searched, yielding no results. After duplicates were removed, 835 abstracts were screened. A full-text article review was then conducted of the remaining 34 articles.

TABULATION, INTEGRATION, AND RESULTS

Twenty-three articles met inclusion criteria, two of which were reviews. Of the nonreview articles, all found a positive relationship between increased maternity leave and duration of breastfeeding. Data showed that earlier return to work for the birth parent decreased the odds of breastfeeding dyads meeting breastfeeding recommendations. Many studies adjusted for confounders (eg, race, socioeconomic status); however, Black or Latinx mothers still experience shorter breastfeeding durations or lower breastfeeding exclusivity when given equal leave compared with White mothers.

CONCLUSION

Results show a positive relationship between length of maternity leave and breastfeeding duration. Advocacy for longer, paid parental leave and more robust research rooted in rigorous methods are needed.

Physical and Chemical Compatibility of Medications Commonly Used in Critically Ill Patients With Balanced Crystalloids: A Systematic Review

OBJECTIVE

Evaluate available evidence of physical and/or chemical compatibility of commonly used medications in critically ill patients with balanced crystalloids.

DATA SOURCES

Ovid MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews were queried from inception to September 2022.

STUDY SELECTION AND DATA EXTRACTION

This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. English-language studies reporting physical and/or chemical compatibility data between 50 selected medications and balanced crystalloids were included. A previously designed tool to assess risk of bias was adapted for use.

DATA SYNTHESIS

Twenty-nine studies encompassing 39 (78%) medications and 188 unique combinations with balanced crystalloids were included. Combinations included 35 (70%) medications with lactated Ringer's, 26 (52%) medications with Plasma-Lyte, 10 (20%) medications with Normosol, and one (2%) medication with Isolyte. Studies commonly evaluated physical and chemical compatibility (55.2%). More medications were evaluated via Y-site than admixture. Incompatibilities were identified in 18% of combinations comprising 13 individual drugs.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

This systematic review evaluates the compatibility of select critical care medications with balanced crystalloid solutions. Results may be used as a tool to guide clinicians on balanced crystalloid compatibility, potentially increasing ubiquitous use and reducing patient exposure to normal saline.

CONCLUSION AND RELEVANCE

Data are limited regarding chemical/physical compatibility of commonly used medications in critically ill patients with balanced crystalloids. Additional compatibility studies are warranted, particularly methodologically rigorous studies assessing Plasma-Lyte, Normosol, and Isolyte. Of the evaluated medications, there was a low frequency of incompatibilities with balanced crystalloids.

Optimal antiplatelet strategy following coronary artery bypass grafting: a meta-analysis

OBJECTIVE

Coronary artery bypass grafting (CABG) is an established revascularisation strategy for multivessel and left main coronary artery disease. Although aspirin is routinely recommended for patients with CABG, the optimal antiplatelet regimen after CABG remains unclear. We evaluated the efficacies and risks of different antiplatelet regimens (dual (DAPT) versus single (SAPT), and dual with clopidogrel (DAPT-C) versus dual with ticagrelor or prasugrel (DAPT-T/P)) after CABG.

METHODS

We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and performed a comprehensive literature search using PubMed, Ovid Medline, Ovid Embase and Cochrane Central Register of Controlled Trials. Data were extracted and pooled using random-effects models and Review Manager (V.5.4).

RESULTS

Among the 2970 article abstracts screened, 215 full-text articles were reviewed and 38 studies totaling 77 447 CABG patients were included for analyses. DAPT compared with SAPT was associated with significantly lower all-cause mortality (OR 0.65 with 95% CI 0.50 to 0.86; p=0.002), cardiovascular mortality (OR 0.53, 95% CI 0.33 to 0.84; p=0.008), and major adverse cardiac and cerebrovascular events (MACCE) (OR 0.68, 95% CI 0.51 to 0.91; p=0.01), but higher rates of major (OR 1.30, 95% CI 1.08 to 1.56; p=0.007) and minor bleeding (OR 1.87, 95% CI 1.28 to 2.74; p=0.001) after CABG. DAPT-T/P compared with DAPT-C was associated with significantly lower all-cause (OR 0.43, 95% CI 0.29 to 0.65; p≤0.0001) and cardiovascular mortality (OR 0.44, 95% CI 0.24 to 0.80; p=0.008), and no differences on other cardiovascular or bleeding outcomes after CABG.

CONCLUSION

In patients with CABG, DAPT compared with SAPT and DAPT-T/P compared with DAPT-C were associated with reduction in all-cause and cardiovascular mortality, especially in patients with acute coronary syndrome. Additionally, DAPT was associated with reduction in MACCE, but higher rates of major and minor bleeding. An individualised approach to choosing antiplatelet regimen is necessary for patients with CABG based on ischaemic and bleeding risks.

Liposomal bupivacaine versus conventional anesthetic or placebo for hemorrhoidectomy: a systematic review and meta-analysis

BACKGROUND

Liposome bupivacaine (LB) is a long-acting anesthetic to enhance postoperative analgesia. Studies evaluating the efficacy of the LB against an active comparator (bupivacaine or placebo) on acute postoperative pain control in hemorrhoidectomy procedures are few and heterogeneous. Therefore, we performed a systematic review and meta-analysis comparing LB's analgesic efficacy and side effects to conventional/placebo anesthetic in hemorrhoidectomy patients.

METHODS

We performed a systematic review and meta-analysis of randomised controlled trials investigating the use of LB after haemorrhoidectomy. We searched the literature published from the time of inception of the datasets to August 19, 2022. The electronic databases included English publications in Ovid MEDLINE In-Process & Other Non-Indexed Citations, Ovid MEDLINE, Ovid EMBASE, and Scopus.

RESULTS

A total of 338 patients who underwent a hemorrhoidectomy procedure enrolled in three randomized clinical trials were included. The overall mean age was 45.84 years (SD ± 11.43), and there was a male predominance (53.55% male). In total 194 patients (52.2%) received LB and 144 (47.8%) received either bupivacaine or placebo. Pain scores at 72 h in the LB (199, 266, and 300 mg) were significantly lower than in the bupivacaine HCl group (p = 0.002). Compared to the bupivacaine/placebo group, the time to first use of opioids in the LB group was significantly longer at LB 199 mg (11 h vs. 9 h), LB 266 mg (19 h vs. 9 h), and LB 300 mg (19 h vs. 8 h) (p < 0.05). Moreover, compared to the bupivacaine/epinephrine group, it was significantly lower in the LB 266 mg group (3.7 vs. 10.2 mg) and at LB 300 mg (13 vs. 33 mg) (p < 0.05). Finally, regarding adverse effects, the conventional anesthetic/placebo group reported more pain in bowel movement than LB groups (OR 2.60, 95% CI 1.31-5.16).

CONCLUSIONS

Comparing LB to conventional anesthetic/placebo anesthetic for hemorrhoidectomy, we found a statistically significant reduction in pain through 72 h, decreased opioid requirements, and delayed time to first opioid use. Moreover, the conventional anesthetic/placebo group reported more pain in bowel movement than LB groups.

Clinical characteristics, evaluation and outcomes of chylopericardium: a systematic review

OBJECTIVE

Chylopericardium (CPE) is a rare condition associated with accumulation of triglyceride-rich chylous fluid in the pericardial cavity. Due to minimal information on CPE within the literature, we conducted a systematic review of all published CPE cases to understand its clinical characteristics, management and outcomes.

METHODS

We performed a literature search and identified cases of patients with CPE from 1946 until May 2021 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We identified relevant articles for pooled analyses of clinical, diagnostic and outcome data.

RESULTS

A total of 95 articles with 98 patients were identified. Patient demographics demonstrated male predominance (55%), with a mean age of 37±15 years. Time from symptom onset to diagnosis was 5 (Q1 4.5, Q3 14) days, with 74% of patients symptomatic on presentation. Idiopathic CPE (60%) was the most common aetiology. Cardiac tamponade secondary to CPE was seen in 38% of cases. Pericardial fluid analysis was required in 94% of cases. Lymphangiography identified the leakage site in 59% of patients. Medical therapy (total parenteral nutrition, medium-chain triglycerides or octreotide) was undertaken in 63% of cases. In our cohort, 32% progressed towards surgical intervention. During a median follow-up of 180 (Q1 180, Q3 377) days, CPE recurred in 16% of cases. Of the patients with recurrence, 10% were rehospitalised.

CONCLUSION

CPE tends to develop in younger patients and may cause serious complications. Many patients fail medical therapy, thereby requiring surgical intervention. Although overall mortality is low, associated morbidities warrant close follow-up and possible reintervention and hospitalisations.

Differentiated Instruction as a Viable Framework for Meeting the Needs of Diverse Adult Learners in Health Professions Education

Health professions education (HPE) instructors are often challenged with simultaneously teaching adult learners of varying educational levels, needs, and backgrounds. With an increased focus on interprofessional education, instructors may be tasked with teaching extremely diverse audiences during a single educational session. While some aspects of differentiated instruction (DI) have been implemented within HPE contexts, the DI framework appears to be relatively unknown in many fields. Evidence from a range of educational fields outside of HPE supports the use of DI as a framework to enhance fairness, diversity and inclusion while meeting core instructional needs. In this Monograph, we explore DI and offer strategies for implementation amenable to many HPE settings.

Adjunctive Vasopressors in Patients with Septic Shock: Protocol for a Systematic Review and Meta-Analysis

Background

Over one-third of patients with septic shock have adjunctive vasopressors added to first-line vasopressors. However, no randomized trial has detected improved mortality with adjunctive vasopressors. Published systematic reviews and meta-analysis have sought to inform the use of adjunctive vasopressors, yet each published review has limitations that hinder its interpretation. This review aims to overcome the limitations of previous reviews by systematically synthesizing the direct evidence for adjunctive vasopressor therapy use in adult patients with septic shock.

Methods

We will conduct a systematic review and meta-analysis of randomized controlled trials evaluating adjunctive vasopressors (vasopressin analogues, angiotensin II, hydroxocobalamin, methylene blue, and catecholamine analogues) in adult patients with septic shock. Relevant studies will be identified through comprehensive searches of MEDLINE, Embase, CENTRAL, and reference lists of previous systematic reviews. Only randomized trials comparing adjunctive vasopressors (>75% of subjects on vasopressors at enrollment) to standard care vasopressors in adults with septic shock (>75% of subjects having septic shock) will be included. Titles and abstracts will be screened, full-text articles assessed for eligibility, and data extracted from included studies. Outcomes of interest include short-term mortality, intermediate-term mortality, kidney replacement therapy, digital/peripheral ischemia, and venous thromboembolism. Pairwise meta-analysis using a random-effects model will be utilized to estimate the risk ratio for the outcomes. Risk of bias will be adjudicated with the Cochrane Risk of Bias 2 tool, and GRADE will be used to rate the certainty of the body of evidence.

Discussion

Although adjunctive vasopressors are commonly used in patients with septic shock their effect on patient-important outcomes is unclear. This study is planned to use rigorous systematic review methodology, including strict adhere to established guidelines, in order to overcome limitations of previously-published reviews and inform clinical practice and treatment guidelines for the use of adjunctive vasopressors in adults with septic shock.

Systematic review registration

PROSPERO CRD4202327984.

Disease State Transition Probabilities Across the Spectrum of NAFLD: A Systematic Review and Meta-Analysis of Paired Biopsy or Imaging Studies

BACKGROUND & AIMS

We conducted a meta-analysis to summarize the rates of progression to and regression of nonalcoholic fatty liver (NAFL), nonalcoholic steatohepatitis (NASH), and fibrosis in adults with nonalcoholic fatty liver disease (NAFLD).

METHODS

We searched PubMed/Medline and 4 other databases from 1985 through 2020. We included observational studies and randomized controlled trials in any language that used liver biopsy or imaging to diagnose NAFLD in adults with a follow-up period ≥48 weeks. Rates were calculated as incident cases per 100 person-years and pooled using the random-effects Poisson distribution model. Heterogeneity was assessed using the I2 statistic.

RESULTS

We screened 9744 articles and included 54 studies involving 26,738 patients. Among observational studies, 20% of healthy adults developed NAFL (incidence rate, 4.8/100 person-years) while 21% of people with fatty liver had resolution of NAFL (incidence rate, 2.4/100 person-years) after a median of approximately 4.5 years. In addition, 31% of patients developed NASH after 4.7 years (incidence rate, 7.4/100 person-years), whereas in 29% of those with NASH, resolution occurred after a median of 3.5 years (incidence rate, 5.1/100 person-years). Time to progress by 1 fibrosis stage was 9.9, 10.3, 13.3, and 22.2 years for F0, F1, F2, and F3, respectively. Time to regress by 1 stage was 21.3, 12.5, 20.4, and 40.0 years for F4, F3, F2, and F1, respectively. Rates estimated from randomized controlled trials were higher than those from observational studies.

CONCLUSIONS

In our meta-analysis, progression to NASH was more common than regression from NASH. Rates of fibrosis progression were similar across baseline stage, but patients with advanced fibrosis were more likely to regress than those with mild fibrosis.

Right ventricle-specific therapies in acute respiratory distress syndrome: a scoping review

OBJECTIVE

To summarize knowledge and identify gaps in evidence regarding treatment of right ventricular dysfunction (RVD) in acute respiratory distress syndrome (ARDS).

DATA SOURCES

We conducted a comprehensive search of MEDLINE, Embase, CINAHL, Web of Science, and the Cochrane Central Register of Controlled Trials.

STUDY SELECTION

Studies were included if they reported effects of treatments on right ventricular function, whether or not the intent was to modify right ventricular function.

DATA EXTRACTION

Data extraction was performed independently and in duplicate by two authors. Data items included the study design, patient population, type of intervention, comparison group, and RV-specific outcomes.

DATA SYNTHESIS

Of 1,430 studies screened, 51 studies reporting on 1,526 patients were included. By frequency, the included studies examined the following interventions: ventilator settings (29.4%), inhaled medications (33.3%), extracorporeal life support (13.7%), intravenous or oral medications (13.7%), and prone positioning (9.8%). The majority of the studies were non-randomized experimental studies (53%), with the next most common being case reports (16%). Only 5.9% of studies were RCTs. In total, 27% of studies were conducted with the goal of modifying RV function.

CONCLUSIONS

Given the prevalence of RVD in ARDS and its association with mortality, the dearth of research on this topic is concerning. This review highlights the need for prospective trials aimed at treating RV dysfunction in ARDS.

Fecal Microbiota Transplantation and Medical Therapy for Clostridium difficile Infection : Meta-analysis of Randomized Controlled Trials

GOALS

The aim was to assess the effectiveness of fecal microbiota transplantation (FMT) against medical therapy (MT).

BACKGROUND

FMT has shown good outcomes in the treatment of Clostridium difficile infection (CDI). We aimed to conduct a systematic review and meta-analysis to compare the effectiveness of FMT versus MT for CDI.

STUDY

We performed a comprehensive search to identify randomized controlled trials comparing FMT against MT in patients with CDI. Outcomes of interest were clinical cure as determined by the resolution of diarrhea and/or negative C. difficile testing. Primary CDI is defined as the first episode of CDI confirmed endoscopically or by laboratory analysis. Recurrent C. difficile infection (RCDI) is defined as laboratory or endoscopically confirmed episode of CDI after at least 1 course of approved antibiotic regimen.

RESULTS

A total of 7 studies with 238 patients were included in meta-analysis. Compared with MT, FMT did not have a statistically significant difference for clinical cure of combined primary and RCDI after first session [risk ratio (RR): 1.52, 95% confidence interval (CI): 0.90, 2.58; P =0.12; I2 =77%] and multiple sessions of FMT (RR: 1.68; CI: 0.96, 2.94; P =0.07; I2 =82%). On subgroup analysis, FMT has statistically higher rate of response than MT (RR: 2.41; CI: 1.20, 4.83; I2 =78%) for RCDI. However, for primary CDI there is no statistically significant difference between FMT and MT (RR: 1.00; CI: 0.72, 1.39; I2 =0%).

CONCLUSION

As per our analysis, FMT should not be utilized for every patient with CDI. It is more effective in RCDI, but the results were not significant in patients with primary CDI.

Virtual global health in graduate medical education: a systematic review

OBJECTIVES

To synthesize recent virtual global health education activities for graduate medical trainees, document gaps in the literature, suggest future study, and inform best practice recommendations for global health educators.

METHODS

We systematically reviewed articles published on virtual global health education activities from 2012-2021 by searching MEDLINE, EMBASE, Cochrane Library, ERIC, Scopus, Web of Science, and ProQuest Dissertations & Theses A&I. We performed bibliography review and search of conference and organization websites. We included articles about primarily virtual activities targeting for health professional trainees. We collected and qualitatively analyzed descriptive data about activity type, evaluation, audience, and drivers or barriers. Heterogeneity of included articles did not lend to formal quality evaluation.

RESULTS

Forty articles describing 69 virtual activities met inclusion criteria. 55% of countries hosting activities were high-income countries. Most activities targeted students (57%), with the majority (53%) targeting trainees in both low- to middle- and high-income settings. Common activity drivers were course content, organization, peer interactions, and online flexibility. Common challenges included student engagement, technology, the internet, time zones, and scheduling. Articles reported unanticipated benefits of activities, including wide reach; real-world impact; improved partnerships; and identification of global health practice gaps.

CONCLUSIONS

This is the first review to synthesize virtual global health education activities for graduate medical trainees. Our review identified important drivers and challenges to these activities, the need for future study on activity preferences, and considerations for learners and educators in low- to middle-income countries. These findings may guide global health educators in their planning and implementation of virtual activities.

Anti-reflux mucosectomy for refractory gastroesophageal reflux disease: a systematic review and meta-analysis

Background and study aims  Anti-reflux mucosectomy (ARMS) is an emerging endoscopic treatment for refractory gastroesophageal reflux disease (GERD). We conducted a systematic review and meta-analysis to evaluate the safety and efficacy ARMS in refractory GERD. Methods  A comprehensive search of multiple databases (through March 2020) was performed to identify studies that reported outcomes of ARMS for refractory GERD. Outcomes assessed included technical success, clinical response, and adverse events (AEs). Clinical response was defined as discontinuation (complete) or reduction (partial) of proton pump inhibitors post-ARMS at follow up. Results  A total of 307 patients (mean age 46.9 [8.1] years, 41.5 % females) were included from 10 studies. The technical success and clinical response rates were 97.7 % (95 % confidence interval [CI], 94.6-99.0) and 80.1 % (95 % CI, 61.6-91.0), respectively. The pooled rate of complete and partial clinical response was 65.3 % (95 % CI, 51.4-77.0) and 21.5 % (95 % CI, 14.2-31.2), respectively. The rate of AEs was 17.2 % (95 % CI, 13.1-22.2) with most common AE being dysphagia/esophageal stricture followed by bleeding with rates of 11.4 % and 5.0 %, respectively. GERD health-related quality of life (GERD-HRQL) (mean difference [MD] = 14.9, P  < 0.001), GERD questionnaire (GERD-Q) (MD = 4.85, P  < 0.001) and mean acid exposure time (MD = 2.39, P  = 0.01) decreased significantly post-ARMS as compared to pre-procedure. There was no difference in terms of clinical response and AEs between ARMS and ARMS with banding on subgroup analysis. Conclusions  ARMS is a safe and effective procedure for treatment of refractory GERD with high rates of clinical response, acceptable safety profile and significant improvement in GERD-related quality of life. Prospective studies are needed to validate our findings.

Pericardial Involvement in Sarcoidosis

Pericardial disease secondary to sarcoidosis is a rare clinical entity with no observational studies in previous research. Therefore, we evaluated reported cases of pericarditis because of sarcoidosis to further understand its diagnosis and management. We performed a systematic review of previous research until December 16, 2020 in MEDLINE, Embase, Scopus, Cochrane Central Register of Controlled Trials, and Web of Science. Case reports and case series demonstrating pericardial involvement in sarcoidosis were included. Fourteen reports with a total of 27 patients were identified. Dyspnea (82%) was the most common presentation, with the lungs being the primary site of sarcoidosis in most patients (77%). The most frequently encountered pericardial manifestations were pericardial effusion (89%), constrictive pericarditis and cardiac tamponade (48%). Management of these patients included use of corticosteroids (82%), colchicine (11%), and nonsteroidal anti-inflammatory agents (7%). Similar to the general population, the most common intervention in these patients was pericardiocentesis (59%), pericardial window (30%), and pericardiectomy (19%). Overall, the majority of this population (70%) achieved clinical improvement during median follow-up time of 8 months. In conclusion, the prevalence and incidence of sarcoid-induced pericarditial disease remain unclear. Clinical manifestations of pericardial involvement are variable, though many patients present with asymptomatic pericardial effusions. No consensus exists on the treatment of this special population, but corticosteroids and combination therapies are considered first-line therapies because of their efficacy in suppressing pericardial inflammation and underlying sarcoidosis. Patients with refractory cases of pericarditis may also benefit therapeutically from the addition of nonsteroidal anti-inflammatory agents, colchicine, and/or biologics.

Teaching spirituality to medical students: a systematic review

PURPOSE

Though it has become increasingly clear that religion and spirituality are important aspects of whole patient care, little is known about how this topic is taught to medical students. This systematic review examined the structure of courses teaching spirituality to medical students and assessed their impact on reported student outcomes.

METHODS

In October 2020, the authors conducted a systematic review of the literature from 1926 to 2020 to identify published articles describing medical school spirituality curricula. Included studies were English-language articles that described spirituality courses predominantly designed for medical students, specified a curricular structure, and evaluated outcomes of the course. The authors used the Medical Education Research Study Quality Instrument (MERSQI) to assess the quality of the included studies and summarized course structures, curricular content, and study outcomes.

RESULTS

Nineteen publications of the 1889 reviewed met the inclusion criteria. These studies were of moderate quality (mean MERSQI = 9.9). The majority of curricula were taught in United States medical schools. Courses were evenly split between mandatory versus elective classes, with mandatory courses having a shorter duration and higher total student participation. Most studies with clear student outcome evaluation had a pre- and post-test design. Common themes throughout the curricula included teaching how to take a spiritual history, delineating differences between spirituality and religion, and experience shadowing chaplains interacting with patients.

CONCLUSIONS

This broad systematic review of the literature revealed a small but growing number of studies describing specific course structure and curricula for teaching spirituality at the medical student level. For the most concise approach, one short, mandatory didactic session followed by application with standardized or hospital patients can be an effective method of introducing students to the importance of spirituality. Important topics to address include the differences between religion and spirituality, recognizing spiritual distress, how to take a spiritual history, and the relevance of spirituality to student well-being. Measured student outcomes should encompass behavioral changes during patient care in addition to changes in knowledge and attitudes. Suggested methods of evaluation include reflective writing and adding a standardized patient case in which the patient is in spiritual distress in an Objective Structured Clinical Examination (OSCE).

The impact of right ventricular injury on the mortality in patients with acute respiratory distress syndrome: a systematic review and meta-analysis

BACKGROUND

Previous studies have found various incidences of right ventricular (RV) injury and its association with clinical outcome in patients with acute respiratory distress syndrome (ARDS). In this systematic review and meta-analysis, we aimed to investigate the impact of the presence of RV injury on mortality in patients with ARDS.

METHOD

We searched Medline, Embase, and the Cochrane Central Register of Controlled Trials for studies investigating the association between RV injury and mortality. Two authors independently evaluated whether studies meet eligibility criteria and extracted the selected patients' and studies' characteristics and outcomes. RV injury was diagnosed by trans-thoracic echocardiogram (TTE), trans-esophageal echocardiogram (TEE) and PAC (pulmonary artery catheter) in the included studies. The primary outcome was the association between mortality and the presence of RV injury in patients with ARDS. The overall reported mortality was defined as either the intensive care unit (ICU) mortality, in-hospital mortality, or mortality within 90 days, and short-term mortality was defined as ICU-mortality, in-hospital mortality, or mortality within 30 days.

RESULTS

We included 9 studies (N = 1861 patients) in this meta-analysis. RV injury that included RV dysfunction, RV dysfunction with hemodynamic compromise, RV failure, or acute cor-pulmonale was present in 21.0% (391/1,861). In the pooled meta-analysis, the presence of RV injury in patients with ARDS was associated with significantly higher overall mortality (OR 1.45, 95% CI 1.13-1.86, p-value = 0.003, I² = 0%), as well as short-term mortality (OR 1.48, 95% CI 1.14-1.93, p-value = 0.003, I² = 0%).

CONCLUSION

In this systematic review and meta-analysis including 1861 patients with ARDS, the presence of RV injury was significantly associated with increased overall and short-term mortality.

TRIAL REGISTRATION

The protocol was registered at PROSPERO (CRD42020206521).

Systematic review of augmented reality in urological interventions: the evidences of an impact on surgical outcomes are yet to come

PURPOSE

To perform a systematic literature review on the clinical impact of augmented reality (AR) for urological interventions.

METHODS

As of June 21, 2018, systematic literature review was performed via Medline, Embase and Cochrane databases in accordance with the PRISMA guidelines and registered at PROSPERO (CRD42018102194). Only full text articles in English were included, without time restrictions. Articles were considered if they reported on the use of AR during urological intervention and the impact on the surgical outcomes. The risk of bias and the quality of each study included were independently assessed using the standard Cochrane Collaboration risk of bias tool and the Risk Of Bias In Non-randomised Studies-of Interventions Tool (ROBINS-I).

RESULTS

131 articles were identified. 102 remained after duplicate removal and were critically reviewed for evidence synthesis. 20 studies reporting on the outcomes of the use of AR during urological interventions in a clinical setting were considered. Given the mostly non-comparative design of the studies identified, the evidence synthesis was performed in a descriptive and narrative manner. Only one comparative study was found, with the remaining 19 items being single-arm observational studies. Based on the existing evidence, we are unable to state that AR improves the outcomes of urological interventions. The major limitation of AR-assisted surgery is inaccuracy in registration, translating into a poor navigation precision.

CONCLUSIONS

To date, there is limited evidence showing superior therapeutic benefits of AR-guided surgery when compared with the conventional surgical approach to the respective disease.

Directly observed therapy of chronic hepatitis C with ledipasvir/sofosbuvir in people who inject drugs at risk of nonadherence to direct-acting antivirals

An important subgroup of people who inject drugs (PWID) receiving opioid agonist therapy (OAT) cannot be treated in the setting of a hepatology centre and would not regularly ingest their medication when handed to them for self-administration. Our hypothesis was that chronic hepatitis C in these patients could be ideally managed if modern, interferon-free regimens were administered together with OAT under direct observation of a physician or nurse at a low-threshold facility. In this open-label, noninterventional, proof-of-concept study (ClinicalTrials.gov number, NCT02638233), 40 PWID at risk of nonadherence to direct-acting antivirals (DAA) and previously untreated chronic hepatitis C virus genotype 1 infection without cirrhosis were treated with ledipasvir/sofosbuvir for 8 weeks. Patients received antiviral treatment together with OAT under direct observation of a physician or nurse at a low-threshold facility. By following the concept of directly observed therapy, excellent adherence to antiviral therapy was achieved as follows: only 0.16% (95% CI: 0.03-0.47) of scheduled dates for ingestion of the antiviral therapy in combination with OAT were missed by the 40 patients. The rate of sustained virological response 12 weeks after end of therapy was 100% (95% CI: 91.2-100.0). Between week 12 and week 24 of follow-up reinfections were recorded in 2 of 40 patients (5%). Directly observed therapy of chronic hepatitis C is highly effective in PWID at risk of nonadherence to DAA. By this new concept, a group of difficult-to-treat patients can be cured, who could not have been treated in settings of studies published so far.

CAP2, cyclase-associated protein 2, is a dual compartment protein

Cyclase-associated proteins (CAPs) are evolutionarily conserved proteins with roles in regulating the actin cytoskeleton and in signal transduction. Mammals have two CAP genes encoding the related CAP1 and CAP2. We studied the distribution and subcellular localization of CAP1 and CAP2 using specific antibodies. CAP1 shows a broad tissue distribution, whereas CAP2 is significantly expressed only in brain, heart and skeletal muscle, and skin. CAP2 is found in the nucleus in undifferentiated myoblasts and at the M-line of differentiated myotubes. In PAM212, a mouse keratinocyte cell line, CAP2 is enriched in the nucleus, and sparse in the cytosol. By contrast, CAP1 localizes to the cytoplasm in PAM212 cells. In human skin, CAP2 is present in all living layers of the epidermis localizing to the nuclei and the cell periphery. In in vitro studies, a C-terminal fragment of CAP2 interacts with actin, indicating that CAP2 has the capacity to bind to actin.

Formins and VASPs may co-operate in the formation of filopodia

Filopodia are finger-like cell protrusions composed of parallel arrays of actin filaments, which elongate through actin polymerization at their tips. These highly dynamic structures seem to be used by many cell types as sensing organs to explore environmental cues and have been implicated in cell motility as well as in cell-substrate adhesion. Formins are highly conserved multidomain proteins that play important roles in the nucleation of actin and the formation of linear actin filaments, yet their role in filopodia formation has remained poorly defined. The Dictyostelium diaphanous-related formin dDia2 is strongly enriched in filopodia tips. Genetic and biochemical analysis revealed that this protein is important for cell migration and cell adhesion, but most importantly for the formation of filopodia. Recently, we have identified the Dictyostelium VASP (vasodilator-stimulated phosphoprotein) orthologue as a binding partner of dDia2 and provide evidence for a co-operative role of both proteins in filopodia formation.

The genome of the social amoeba Dictyostelium discoideum

The social amoebae are exceptional in their ability to alternate between unicellular and multicellular forms. Here we describe the genome of the best-studied member of this group, Dictyostelium discoideum. The gene-dense chromosomes of this organism encode approximately 12,500 predicted proteins, a high proportion of which have long, repetitive amino acid tracts. There are many genes for polyketide synthases and ABC transporters, suggesting an extensive secondary metabolism for producing and exporting small molecules. The genome is rich in complex repeats, one class of which is clustered and may serve as centromeres. Partial copies of the extrachromosomal ribosomal DNA (rDNA) element are found at the ends of each chromosome, suggesting a novel telomere structure and the use of a common mechanism to maintain both the rDNA and chromosomal termini. A proteome-based phylogeny shows that the amoebozoa diverged from the animal-fungal lineage after the plant-animal split, but Dictyostelium seems to have retained more of the diversity of the ancestral genome than have plants, animals or fungi.

Villin-type headpiece domains show a wide range of F-actin-binding affinities

The villin-type "headpiece" domain is a modular motif found at the extreme C-terminus of larger "core" domains in over 25 cytoskeletal proteins in plants and animals. Although headpiece is classified as an F-actin-binding domain, it has been suggested that some expressed fusion-proteins containing headpiece may lack F-actin-binding in vivo. To determine the intrinsic F-actin affinity of headpiece domains, we quantified the F-actin affinity of seven headpiece domains and three N-terminal truncations, under identical in vitro conditions. The constructs are folded and adopt the native headpiece structure. However, they show a wide range of affinities that can be grouped into high, low, and nonspecific-binding categories. Computer models of the structure and charged surface potential of these headpiece domains suggest features important for high F-actin affinity. We conclude that not all headpiece domains are intrinsically F-actin-binding motifs, and suggest that the surface charge distribution may be an important element for F-actin recognition.

Characterization of CD36/LIMPII homologues in Dictyostelium discoideum

The CD36/LIMPII family is ubiquitously expressed in higher eukaryotes and consists of integral membrane proteins that have in part been characterized as cell adhesion receptors, scavenger receptors, or fatty acid transporters. However, no physiological role has been defined so far for the members of this family that localize specifically to vesicular compartments rather than to the cell surface, namely lysosomal integral membrane protein type II (LIMPII) from mammals and LmpA from the amoeba Dictyostelium discoideum. LmpA, the first described CD36/LIMPII homologue from lower eukaryotes, has initially been identified as a suppressor of the profilin-minus phenotype. We report the discovery and initial characterization of two new CD36/LIMPII-related proteins, both of which share several features with LmpA: (i) their size is considerably larger than that of the CD36/LIMPII proteins from higher eukaryotes; (ii) they show the characteristic "hairpin" topology of this protein family; (iii) they are heavily N-glycosylated; and (iv) they localize to vesicular structures of putative endolysosomal origin. However, they show intriguing differences in their developmental regulation and exhibit different sorting signals of the di-leucine or tyrosine-type in their carboxyl-terminal tail domains. These features make them promising candidates as a paradigm for the study of the function and evolution of the as yet poorly understood CD36/LIMPII proteins.

Dictyostelium discoideum: a genetic model system for the study of professional phagocytes. Profilin, phosphoinositides and the lmp gene family in Dictyostelium

Profilin is a key regulator of actin polymerization, and plays a pivotal role at the interface of the phosphoinositide signal transduction pathway and the cytoskeleton. Recent evidence suggests the involvement of profilin in the regulation of phagocytosis and macropinocytosis, and the transport along the endosomal pathway. Disruption of profilin leads to a complex phenotype that includes abnormal cytokinesis, a block in development and defects in the endosomal pathway. Macropinocytosis, fluid phase efflux and secretion of lysosomal enzymes were reduced, whereas the rate of phagocytosis was increased as compared to wild-type cells. The lmpA gene, a homolog of the CD36/LIMPII family, was identified as a suppressor for most of the profilin-minus defects. This gene encodes an integral membrane protein, it localizes to lysosomes and macropinosomes, and binds to phosphoinositides. Even though phosphatidylinositol lipids constitute only a small fraction of total lipids in the membranes of eukaryotic cells, they play an important role in vesicle transport, signal transduction and cytoskeletal regulation. Disruption of lmpA in wild-type cells resulted in defects in fluid phase efflux and macropinocytosis, but not in phagocytosis. The discovery and initial characterization of two additional members of the CD36/LIMPII family in Dictyostelium, lmpB and lmpC, that exhibit intriguing differences in developmental regulation and their putative sorting signals, suggests that a set of lysosomal integral membrane proteins contribute to the crosstalk between vesicles and cytoskeletal proteins.

Filamins as integrators of cell mechanics and signalling

Filamins are large actin-binding proteins that stabilize delicate three-dimensional actin webs and link them to cellular membranes. They integrate cellular architectural and signalling functions and are essential for fetal development and cell locomotion. Here, we describe the history, structure and function of this group of proteins.

Clinical utility of the modified barium swallow

The purpose of this investigation was to evaluate the immediate and clinically relevant information gained from the modified barium swallow study and to determine the impact of the procedure on patient management. A database containing a nonrandom sample of 608 swallowing studies was reviewed. Results showed that only 10.4% of the studies were classified as normal examinations and aspiration occurred in 32.4%. However, swallowing abnormality without aspiration was recorded in 57.2% of the studies. Five additional outcome variables were assessed: referrals made to other specialties, effectiveness of applied compensatory strategies, treatment recommendations, mode of intake change, and diet grade change. Nearly 83% of the 608 studies showed change in at least one of the variables: needed referral to a specialist was identified on 26.3%; compensatory strategies that improved swallow physiology were identified on 48.4%; swallowing therapy was recommended on 37.2%; changes in mode of intake occurred on 31.4%; and diet texture changes were recommended on 43.8%. The low percentage of normal studies coupled with the high percentage of change in measurable variables indicate high clinical utility for the modified barium swallow study. The misguided tendency to refer to the modified barium study only as a tool for identifying aspiration and the appropriate utilization of the examination for identification of underlying abnormality in swallowing physiology are explained.

Inactivation of lmpA, encoding a LIMPII-related endosomal protein, suppresses the internalization and endosomal trafficking defects in profilin-null mutants

Profilin is a key phosphoinositide and actin-binding protein connecting and coordinating changes in signal transduction pathways with alterations in the actin cytoskeleton. Using biochemical assays and microscopic approaches, we demonstrate that profilin-null cells are defective in macropinocytosis, fluid phase efflux, and secretion of lysosomal enzymes but are unexpectedly more efficient in phagocytosis than wild-type cells. Disruption of the lmpA gene encoding a protein (DdLIMP) belonging to the CD36/LIMPII family suppressed, to different degrees, most of the profilin-minus defects, including the increase in F-actin, but did not rescue the secretion defect. Immunofluorescence microscopy indicated that DdLIMP, which is also capable of binding phosphoinositides, was associated with macropinosomes but was not detected in the plasma membrane. Also, inactivation of the lmpA gene in wild-type strains resulted in defects in macropinocytosis and fluid phase efflux but not in phagocytosis. These results suggest an important role for profilin in regulating the internalization of fluid and particles and the movement of material along the endosomal pathway; they also demonstrate a functional interaction between profilin and DdLIMP that may connect phosphoinositide-based signaling through the actin cytoskeleton with endolysosomal membrane trafficking events.

Mapping the functional surface of domain 2 in the gelsolin superfamily

The crystal structure of the F-actin binding domain 2 of severin, the gelsolin homologue from Dictyostelium discoideum, has been determined by multiple isomorphous replacement and refined to 1.75 A resolution. The structure reveals an alpha-helix-beta-sheet sandwich similar to the domains of gelsolin and villin, and contains two cation-binding sites, as observed in other domain 1 and domain 2 homologues. Comparison of the structures of several gelsolin family domains has identified residues that may mediate F-actin binding in gelsolin domain 2 homologues. To assess the involvement of these residues in F-actin binding, three mutants of human gelsolin domain 2 were assayed for F-actin binding activity and thermodynamic stability. Two of the mutants, RRV168AAA and RLK210AAA, demonstrated a lowered affinity for F-actin, indicating a role for those residues in filament binding. Using both structural and biochemical data, we have constructed a model of the gelsolin domain 1-domain 2-F-actin complex. This model highlights a number of interactions that may serve as positive and negative determinants of filament end- and side-binding.

Cloning and characterization of beta-COP from Dictyostelium discoideum

We have isolated a cDNA coding for beta-COP from Dictyostelium discoideum by polymerase chain reaction using degenerate primers derived from rat beta-COP. The complete cDNA clone has a size of 2.8 kb and codes for a protein with a calculated molecular mass of 102 kDa. Dictyostelium beta-COP exhibits highest homology to mammalian beta-COP, but it is considerably smaller due to a shortened variable region that is thought to form a linker between the highly conserved N- and C-terminal domains. Dictyostelium beta-COP is encoded by a single gene, which is transcribed at moderate levels into two RNAs that are present throughout development. To localize the protein, full-length beta-COP was fused to GFP and expressed in Dictyostelium cells. The fusion protein was detected on vesicles distributed all over the cells and was strongly enriched in the perinuclear region. Based on coimmunofluorescence studies with antibodies directed against the Golgi marker comitin, this compartment was identified as the Golgi apparatus. Beta-COP distribution in Dictyostelium was not brefeldin A sensitive being most likely due to the presence of a brefeldin A resistance gene. However, upon DMSO treatment we observed a reversible disassembly of the Golgi apparatus. In mammalian cells DMSO treatment had a similar effect on beta-COP distribution.

Dictyostelium discoideum: a new host model system for intracellular pathogens of the genus Legionella

The soil amoeba Dictyostelium discoideum is a haploid eukaryote that, upon starvation, aggregates and enters a developmental cycle to produce fruiting bodies. In this study, we infected single-cell stages of D. discoideum with different Legionella species. Intracellular growth of Legionella in this new host system was compared with their growth in the natural host Acanthamoeba castellanii. Transmission electron microscopy of infected D. discoideum cells revealed that legionellae reside within the phagosome. Using confocal microscopy, it was observed that replicating, intracellular, green fluorescent protein (GFP)-tagged legionellae rarely co-localized with fluorescent antibodies directed against the lysosomal protein DdLIMP of D. discoideum. This indicates that the bacteria inhibit the fusion of phagosomes and lysosomes in this particular host system. In addition, Legionella infection of D. discoideum inhibited the differentiation of the host into the multicellular fruiting stage. Co-culture studies with profilin-minus D. discoideum mutants and Legionella resulted in higher rates of infection when compared with infections of wild-type amoebae. Because the amoebae are amenable to genetic manipulation as a result of their haploid genome and because a number of cellular markers are available, we show for the first time that D. discoideum is a valuable model system for studying intracellular pathogenesis of microbial pathogens.

The actin cytoskeleton of Dictyostelium: a story told by mutants

Actin-binding proteins are effectors of cell signalling and coordinators of cellular behaviour. Research on the Dictyostelium actin cytoskeleton has focused both on the elucidation of the function of bona fide actin-binding proteins as well as on proteins involved in signalling to the cytoskeleton. A major part of this work is concerned with the analysis of Dictyostelium mutants. The results derived from these investigations have added to our understanding of the role of the actin cytoskeleton in growth and development. Furthermore, the studies have identified several cellular and developmental stages that are particularly sensitive to an unbalanced cytoskeleton. In addition, use of GFP fusion proteins is revealing the spatial and temporal dynamics of interactions between actin-associated proteins and the cytoskeleton.

Dissection of functional domains by expression of point-mutated profilins in Dictyostelium mutants

Profilin is a ubiquitous cytoskeletal protein whose function is fundamental to the maintenance of normal cell physiology. By site-directed mutagenesis of profilin II from Dictyostelium discoideum the point mutations K114E and W3N were generated by PCR thus changing actin and poly-(L)-proline-binding activity respectively. W3N profilin is no longer able to bind to poly-(L)-proline concomitant with a slight reduction in actin binding. The K114E profilin exhibited a profound decrease in its ability to interact with actin, whereas binding to poly-(L)-proline was essentially unchanged. Binding to phospholipids was indistinguishable from the wild-type profilin. The in vivo properties of the point-mutated profilins were studied by expressing either W3N or K114E in profilin-minus D. discoideum mutants which have defects in the F-actin content, cytokinesis and development (Haugwitz et al., Cell 79, 303-314, 1994). Expression of K114E or W3N displayed a reduction in the F-actin content, normal cell morphology, and the transformants were capable of undergoing complete development. Interestingly, only cells that drastically overexpressed W3N could restore the aberrant phenotype, whereas the mutant protein K114E with its fully functional poly-(L)-proline binding and its strongly reduced actin-binding activities rescued the phenotype at low concentrations. Wild-type and both mutated profilins are enriched in phagocytic cups during uptake of yeast particles. These data suggest a) that a functional poly-(L)-proline-binding activity is more important for suppression of the mutant phenotype than the G-actin binding activity of profilin, and b) that the enrichment of profilin in highly active phagocytic cups might be independent of either poly-(L)-proline or actin-binding activities.

Dictyostelium as model system for studies of the actin cytoskeleton by molecular genetics

The actin cytoskeleton is an essential structure for most movements at the cellular and intracellular level. Whereas for contraction a muscle cell requires a rather static organisation of cytoskeletal proteins, cell motility of amoeboid cells relies on a tremendously dynamic turnover of filamentous networks in a matter of seconds and at distinct regions inside the cell. The best model system for studying cell motility is Dictyostelium discoideum. The cells live as single amoebae but can also start a developmental program that leads to multicellular stages and differentiation into simple types of tissues. Thus, cell motility can be studied on single cells and on cells in a tissue-like aggregate. The ability to combine protein purification and biochemistry with fairly easy molecular genetics is a unique feature for investigation of the cytoskeleton and cell motility. The actin cytoskeleton in Dictyostelium harbours essentially all classes of actin-binding proteins that have been found throughout eukaryotes. By conventional mutagenesis, gene disruption, antisense approaches, or gene replacements many genes that code for cytoskeletal proteins have been disrupted, and altered phenotypes in transformants that lacked one or more of those cytoskeletal proteins allowed solid conclusions about their in vivo function. In addition, tagging the proteins or selected domains with green fluorescent protein allows the monitoring of protein redistribution during cell movement. Gene tagging by restriction enzyme mediated integration of vectors and the ongoing international genome and cDNA sequencing projects offer the chance to understand the dynamics of the cytoskeleton by identification and functional characterisation of all proteins involved.

Assessing the role of the ASP56/CAP homologue of Dictyostelium discoideum and the requirements for subcellular localization

The CAP (cyclase-associated protein) homologue of Dictyostelium discoideum is a phosphatidylinositol 4,5-bisphosphate (PIP(2)) regulated G-actin sequestering protein which is present in the cytosol and shows enrichment at plasma membrane regions. It is composed of two domains separated by a proline rich stretch. The sequestering activity has been localized to the C-terminal domain of the protein, whereas the presence of the N-terminal domain seems to be required for PIP(2)-regulation of the sequestering activity. Here we have constructed GFP-fusions of N- and C-domain and found that the N-terminal domain showed CAP-specific enrichment at the anterior and posterior ends of cells like endogenous CAP irrespective of the presence of the proline rich region. Mutant cells expressing strongly reduced levels of CAP were generated by homologous recombination. They had an altered cell morphology with very heterogeneous cell sizes and exhibited a cytokinesis defect. Growth on bacteria was normal both in suspension and on agar plates as was phagocytosis of yeast and bacteria. In suspension in axenic medium mutant cells grew more slowly and did not reach saturation densities observed for wild-type cells. This was paralleled by a reduction in fluid phase endocytosis. Development was delayed by several hours under all conditions assayed, furthermore, motile behaviour was affected.

Molecular architecture of the rod domain of the Dictyostelium gelation factor (ABP120)

The Dictyostelium discoideum gelation factor is a two-chain actin-cross-linking protein that, in addition to an N-terminal actin-binding domain, has a rod domain constructed from six tandem repeats of a 100-residue motif that has an immunoglobulin fold. To define the architecture of the rod domain of gelation factor, we have expressed in E. coli a series of constructs corresponding to different numbers of gelation factor rod repeats and have characterised them by chemical crosslinking, ultracentrifugation, column chromatography, matrix-assisted laser desorption ionisation (MALDI) mass spectrometry and NMR spectroscopy. Fragments corresponding to repeats 1-6 and 5-6 dimerise, whereas repeats 1-5 and single repeats 3 and 4 are monomeric. Repeat 6 interacts weakly and was present as monomer and dimer when analysed by analytical ultracentrifugation. Proteolytic digestion of rod5-6 resulted in the generation of two polypeptides that roughly corresponded to rod5 and part of rod6. None of these polypeptides formed dimers after chemical crosslinking. Stable dimerisation therefore appears to require repeats 5 and 6. Based on these data a model of gelation factor architecture is presented. We suggest an arrangement of the chains where only the carboxy-terminal repeats interact as was observed for filamin/ABP280, the mammalian homologue of gelation factor.

The crystal structure of the Physarum polycephalum actin-fragmin kinase: an atypical protein kinase with a specialized substrate-binding domain

Coordinated temporal and spatial regulation of the actin cytoskeleton is essential for diverse cellular processes such as cell division, cell motility and the formation and maintenance of specialized structures in differentiated cells. In plasmodia of Physarum polycephalum, the F-actin capping activity of the actin-fragmin complex is regulated by the phosphorylation of actin. This is mediated by a novel type of protein kinase with no sequence homology to eukaryotic-type protein kinases. Here we present the crystal structure of the catalytic domain of the first cloned actin kinase in complex with AMP at 2.9 A resolution. The three-dimensional fold reveals a catalytic module of approximately 160 residues, in common with the eukaryotic protein kinase superfamily, which harbours the nucleotide binding site and the catalytic apparatus in an inter-lobe cleft. Several kinases that share this catalytic module differ in the overall architecture of their substrate recognition domain. The actin-fragmin kinase has acquired a unique flat substrate recognition domain which is supposed to confer stringent substrate specificity.