Fire,Agency and Scale in the Creation of Aboriginal Cultural Landscapes

Much recent literature explores controlled burning practices used by people of different cultures to manipulate landscapes. Because humans have only recently been able to suppress fires occurring at larger scales these studies focus on activities occurring at the scale of sites as making the greatest contribution to creating cultural landscapes. In this study we examine the role of fire in the construction of Anishinaabe cultural landscapes in the boreal forest of northwestern Ontario. Through our work with elders of Pikangikum First Nation we examined Anishinaabe knowledge and relationships to fire occurring across spatial and temporal scales. Pikangikum residents perceive forest fires as beings which possesses agency and who intentionally create order in landscapes. This notion suggests that cultural landscapes are more than the physical remains of the sum of human activities. The possibility of non-human agents having a role in the creation of meaningful spaces prompts us to call for a reassessment both of the scale of inquiry and the nature of cultural landscapes. We conclude with a discussion of the benefits and potential constraints to inclusion of indigenous cultural landscapes in current co-management arrangements.     

Fate Specification and Tissue-specific Cell Cycle Control of the Caenorhabditis elegans Intestine

Coordination between cell fate specification and cell cycle control in multicellular organisms is essential to regulate cell numbers in tissues and organs during development, and its failure may lead to oncogenesis. In mammalian cells, as part of a general cell cycle checkpoint mechanism, the F-box protein β-transducin repeat-containing protein (β-TrCP) and the Skp1/Cul1/F-box complex control the periodic cell cycle fluctuations in abundance of the CDC25A and B phosphatases. Here, we find that the Caenorhabditis elegans β-TrCP orthologue LIN-23 regulates a progressive decline of CDC-25.1 abundance over several embryonic cell cycles and specifies cell number of one tissue, the embryonic intestine. The negative regulation of CDC-25.1 abundance by LIN-23 may be developmentally controlled because CDC-25.1 accumulates over time within the developing germline, where LIN-23 is also present. Concurrent with the destabilization of CDC-25.1, LIN-23 displays a spatially dynamic behavior in the embryo, periodically entering a nuclear compartment where CDC-25.1 is abundant.     

A prospective cluster-randomized trial to implement the Canadian CT Head Rule in emergency departments

Background

The Canadian CT Head Rule was developed to allow physicians to be more selective when ordering computed tomography (CT) imaging for patients with minor head injury. We sought to evaluate the effectiveness of implementing this validated decision rule at multiple emergency departments.

Methods

We conducted a matched-pair cluster-randomized trial that compared the outcomes of 4531 patients with minor head injury during two 12-month periods (before and after) at hospital emergency departments in Canada, six of which were randomly allocated as intervention sites and six as control sites. At the intervention sites, active strategies, including education, changes to policy and real-time reminders on radiologic requisitions were used to implement the Canadian CT Head Rule. The main outcome measure was referral for CT scan of the head.

Results

Baseline characteristics of patients were similar when comparing control to intervention sites. At the intervention sites, the proportion of patients referred for CT imaging increased from the “before” period (62.8%) to the “after” period (76.2%) (difference +13.3%, 95% CI 9.7%–17.0%). At the control sites, the proportion of CT imaging usage also increased, from 67.5% to 74.1% (difference +6.7%, 95% CI 2.6%–10.8%). The change in mean imaging rates from the “before” period to the “after” period for intervention versus control hospitals was not significant (p = 0.16). There were no missed brain injuries or adverse outcomes.

Interpretation

Our knowledge–translation-based trial of the Canadian CT Head Rule did not reduce rates of CT imaging in Canadian emergency departments. Future studies should identify strategies to deal with barriers to implementation of this decision rule and explore more effective approaches to knowledge translation. (ClinicalTrials.gov trial register no. NCT00993252)More than six million instances of head and neck trauma are seen annually in emergency departments in Canada and the United States.¹ Most are classified as minimal or minor head injury, but in a very small proportion, deterioration occurs and neurosurgical intervention is needed for intracranial hematoma.^2,3 In recent years, North American use of computed tomography (CT) for many conditions in the emergency department, including minor head injury, has increased five-fold.^1,4 Our own Canadian data showed marked variation in the use of CT for similar patients.⁵ Over 90% of CT scans are negative for clinically important brain injury.^6–8 Owing to its high volume of usage, such imaging adds to health care costs. There have also been increasing concerns about radiation-related risk from unnecessary CT scans.^9,10 Additionally, unnecessary use of CT scanning compounds the Canadian problems of overcrowding of emergency departments and inadequate access to advanced imaging for nonemergency outpatients.Clinical decision rules are derived from original research and may be defined as tools for clinical decision-making that incorporate three or more variables from a patient’s history, physical examination or simple tests.^11–13 The Canadian CT Head Rule comprises five high-risk and two medium-risk criteria and was derived by prospectively evaluating 3121 adults with minor head injury (Figure 1) (Appendix 1, available at www.cmaj.ca/cgi/content/full/cmaj.091974/DC1).⁶ The resultant decision rule was then prospectively validated in a group of 2707 patients and showed high sensitivity (100%; 95% confidence interval [CI ] 91–100) and reliability.¹⁴ The results of its validation suggested that, in patients presenting to emergency departments with minor head trauma, a rate of usage of CT imaging as low as 62.4% was possible and safe.Open in a separate windowFigure 1The Canadian CT Head Rule, as used in the study. Note: CSF = cerebrospinal fluid, CT = computed tomography, GCS = Glasgow Coma Scale.Unfortunately, most decision rules are never used after derivation because they are not adequately tested in validation or implementation studies.^15–19 We recently successfully implemented a similar rule, the Canadian C-Spine Rule, at multiple Canadian sites.²⁰ Hence, the goal of the current study was to evaluate the effectiveness and safety of an active strategy to implement the Canadian CT Head Rule at multiple emergency departments. We wanted to test both the impact of the rule on rates of CT imaging and the effectiveness of an inexpensive and easily adopted implementation strategy. In addition, we wanted to further evaluate the accuracy of the rule.     

2-Phenyl-9H-purine-6-carbonitrile derivatives as selective cathepsin S inhibitors

Starting from previously disclosed equally potent cathepsin K and S inhibitor 4-propyl-6-(3-trifluoromethylphenyl)pyrimidine-2-carbonitrile 1, a novel 2-phenyl-9H-purine-6-carbonitrile scaffold was identified to provide potent and selective cathepsin S inhibitors.     

6-Phenyl-1H-imidazo[4,5-c]pyridine-4-carbonitrile as cathepsin S inhibitors

6-Phenyl-1H-imidazo[4,5-c]pyridine-4-carbonitrile analogues were identified as potent and selective cathepsin S inhibitor against both purified enzyme and in human JY cell based cellular assays. This core has a very stable thio-trapping nitrile war-head in comparison with the well reported pyrimidine-2-carbonitrile cysteine cathepsin inhibitors. Compound 47 is also very potent in in vivo mouse spleenic Lip10 accumulation assays.     

A novel series of positive modulators of the AMPA receptor: Structure-based lead optimization

Starting from lead compound 1, we demonstrate how X-ray structural data can be used to understand SAR and expediently optimize bioavailability in a novel series of AMPA receptor modulators, furnishing 5 with improved bioavailability and robust in vivo activity.     

A Mutation in the Mitochondrial Fission Gene Dnm1l Leads to Cardiomyopathy

Mutations in a number of genes have been linked to inherited dilated cardiomyopathy (DCM). However, such mutations account for only a small proportion of the clinical cases emphasising the need for alternative discovery approaches to uncovering novel pathogenic mutations in hitherto unidentified pathways. Accordingly, as part of a large-scale N-ethyl-N-nitrosourea mutagenesis screen, we identified a mouse mutant, Python, which develops DCM. We demonstrate that the Python phenotype is attributable to a dominant fully penetrant mutation in the dynamin-1-like (Dnm1l) gene, which has been shown to be critical for mitochondrial fission. The C452F mutation is in a highly conserved region of the M domain of Dnm1l that alters protein interactions in a yeast two-hybrid system, suggesting that the mutation might alter intramolecular interactions within the Dnm1l monomer. Heterozygous Python fibroblasts exhibit abnormal mitochondria and peroxisomes. Homozygosity for the mutation results in the death of embryos midway though gestation. Heterozygous Python hearts show reduced levels of mitochondria enzyme complexes and suffer from cardiac ATP depletion. The resulting energy deficiency may contribute to cardiomyopathy. This is the first demonstration that a defect in a gene involved in mitochondrial remodelling can result in cardiomyopathy, showing that the function of this gene is needed for the maintenance of normal cellular function in a relatively tissue-specific manner. This disease model attests to the importance of mitochondrial remodelling in the heart; similar defects might underlie human heart muscle disease.     

Membrane Topology of Outer Membrane Protein AlgE,Which Is Required for Alginate Production in Pseudomonas aeruginosa

The ubiquitous opportunistic human pathogen Pseudomonas aeruginosa secretes a viscous extracellular polysaccharide, called alginate, as a virulence factor during chronic infection of patients with cystic fibrosis. In the present study, it was demonstrated that the outer membrane protein AlgE is required for the production of alginate in P. aeruginosa. An isogenic marker-free algE deletion mutant was constructed. This strain was incapable of producing alginate but did secrete alginate degradation products, indicating that polymerization occurs but that the alginate chain is subsequently degraded during transit through the periplasm. Alginate production was restored by introducing the algE gene. The membrane topology of the outer membrane protein AlgE was assessed by site-specific insertions of FLAG epitopes into predicted extracellular loop regions.Pseudomonas aeruginosa is an ubiquitous opportunistic human pathogen responsible for chronic infections of the lungs of patients with cystic fibrosis (CF), in whom it is the leading cause of mortality and morbidity (9). The establishment of a chronic infection in the lungs of patients with CF coincides with the switch of P. aeruginosa to a stable mucoid variant, producing copious amounts of the exopolysaccharide alginate; this is typically a poor prognostic indicator for these patients (24, 31). Alginate is a linear unbranched exopolysaccharide consisting of 1,4-linked monomers of β-d-mannuronic acid and its C-5 epimer, α-l-guluronic acid, which is known to be produced by only two bacterial genera, Pseudomonas and Azotobacter (34). The switch to a mucoid phenotype coincides with the appearance of a 54-kDa protein in the outer membrane; this protein has been identified and has been designated AlgE (13, 31).The genes encoding the alginate biosynthesis machinery are located within a 12-gene operon (algD-alg8-alg44-algK-algE-algG-algX-algL-algI-algJ-algF-algA). AlgA and AlgD, along with AlgC (not encoded in the operon), are involved in precursor synthesis (34). Alg8 is the catalytic subunit of the alginate polymerase located at the inner membrane (35). AlgG is a C-5 mannuronan epimerase (19). AlgK contains four putative Sel1-like repeats, similar to the tetratricopeptide repeat motif often found in adaptor proteins involved in the assembly of multiprotein complexes (3, 10). AlgX shows little homology to any known protein, and its role is unclear (14). Knockout mutants of AlgK, AlgG, and AlgX have nonmucoid phenotypes, although they produce short alginate fragments, due to the activity of the alginate lyase (AlgL), which degrades the nascent alginate (1, 14, 19-21, 36). AlgF, AlgI, and AlgJ are involved in acetylation of alginate, but they are not ultimately required for its production (12). The membrane-anchored protein, Alg44, is required for polymerization and has a PilZ domain for the binding of c-di-GMP, a secondary messenger essential for alginate production (16, 25, 33). The periplasmic C terminus of Alg44 shares homology with the membrane fusion proteins involved in the bridging of the periplasm in multidrug efflux pumps (11, 43). The periplasmic alginate lyase, AlgL, appears to be required for the translocation of intact alginate across the periplasm (1, 26). AlgE is an outer membrane, anion-selective channel protein through which alginate is presumably secreted (30). A protein complex or scaffold through which the alginate chain can pass and be modified and which spans the periplasm bridging the polymerase located (Alg8) at the outer membrane pore (AlgE) has been proposed (21). Indeed, it has been demonstrated that both the inner and the outer membranes are required for the in vitro polymerization of alginate (35).The requirement of AlgE for the biosynthesis of alginate in P. aeruginosa was first observed by complementation of an alginate-negative mutant derived by chemical mutagenesis with a DNA fragment containing algE (8) Secondary structure predictions suggested that AlgE forms an 18-stranded β barrel with extended extracellular loops. Several of these loops show high densities of charged amino acids, suggesting a functional role in the translocation of the anionic alginate polymer (29, 30). Preliminary analysis of AlgE crystals has been reported (48).In this study, the role of AlgE in alginate biosynthesis was investigated and the membrane topology of AlgE was assessed by site-directed insertion mutagenesis.