Mirror‐symmetric microtubule assembly and cell interactions drive lumen formation in the zebrafish neural rod

By analysing the cellular and subcellular events that occur in the centre of the developing zebrafish neural rod, we have uncovered a novel mechanism of cell polarisation during lumen formation. Cells from each side of the neural rod interdigitate across the tissue midline. This is necessary for localisation of apical junctional proteins to the region where cells intersect the tissue midline. Cells assemble a mirror‐symmetric microtubule cytoskeleton around the tissue midline, which is necessary for the trafficking of proteins required for normal lumen formation, such as partitioning defective 3 and Rab11a to this point. This occurs in advance and is independent of the midline cell division that has been shown to have a powerful role in lumen organisation. To our knowledge, this is the first example of the initiation of apical polarisation part way along the length of a cell, rather than at a cell extremity. Although the midline division is not necessary for apical polarisation, it confers a morphogenetic advantage by efficiently eliminating cellular processes that would otherwise bridge the developing lumen.     

Rates of readmission and death associated with leaving hospital against medical advice: a population-based study

Background:

Leaving hospital against medical advice may have adverse consequences. Previous studies have been limited by evaluating specific types of patients, small sample sizes and incomplete determination of outcomes. We hypothesized that leaving hospital against medical advice would be associated with increases in subsequent readmission and death.

Methods:

In a population-based analysis involving all adults admitted to hospital and discharged alive in Manitoba from Apr. 1, 1990, to Feb. 28, 2009, we evaluated all-cause 90-day mortality and 30-day hospital readmission. We used multivariable regression, adjusted for age, sex, socioeconomic status, year of hospital admission, patient comorbidities, hospital diagnosis, past frequency of admission to hospital, having previously left hospital against medical advice and data clustering (patients with multiple admissions). For readmission, we assessed both between-person and within-person effects of leaving hospital against medical advice.

Results:

Leaving against medical advice occurred in 21 417 of 1 916 104 index hospital admissions (1.1%), and was associated with higher adjusted rates of 90-day mortality (odds ratio [OR] 2.51, 95% confidence interval [CI] 2.18–2.89), and 30-day hospital readmission (within-person OR 2.10, CI 1.99–2.21; between-person OR 3.04, CI 2.79–3.30). In our additional analyses, elevated rates of readmission and death associated with leaving against medical advice were manifest within 1 week and persisted for at least 180 days after discharge.

Interpretation:

Adults who left the hospital against medical advice had higher rates of hospital readmission and death. The persistence of these effects suggests that they are not solely a result of incomplete treatment of acute illness. Interventions aimed at reducing these effects may need to include longitudinal interventions extending beyond admission to hospital.Patients leaving hospital against medical advice have been discussed in the medical literature for more than 50 years.¹ Reported to occur in 1%–2% of patients in general hospitals,^2,3 the numbers are large; in the United States, 368 000 patients left against medical advice in 2007,³ and rates higher than 10% have been documented in certain subgroups, including Canadian patients with HIV and predominantly poor residents of inner city areas.^4,5 The main concern over leaving hospital against medical advice is that it may increase morbidity or mortality. Previous studies attempting to assess this effect^2,4–13 have all been restricted to specific types of patients, and most studies were limited by small sample sizes and incomplete determination of outcomes. In this study, we used data that avoided these limitations to test the hypothesis that patients who leave hospital against medical advice have higher rates of hospital readmission and death.     

Activity of Commercial Enzymes on Settlement and Adhesion of Cypris Larvae of the Barnacle Balanus amphitrite,Spores of the Green Alga Ulva linza,and the Diatom Navicula perminuta

Fouling species produce adhesive polymers during the settlement, adhesion and colonization of new surfaces in the marine environment. The present paper tests the hypothesis that enzymes of the appropriate specificity may prevent biofouling by hydrolysing these adhesive polymers. Seventeen commercially available enzyme preparations designed originally for bulk use in a range of end-use applications were tested for their effects on the settlement and/or adhesion of three major fouling species, viz. the green alga Ulva linza, the diatom Navicula perminuta and the barnacle Balanus amphitrite. The serine-proteases were found to have the broadest antifouling potential reducing the adhesion strength of spores and sporelings of U. linza, cells of N. perminuta and inhibiting settlement of cypris larvae of B. amphitrite. Mode-of-action studies on the serine-protease, Alcalase, indicated that this enzyme reduced adhesion of U. linza in a concentration-dependent manner, that spores of the species could recover their adhesive strength if the enzyme was removed and that the adhesive of U. linza and juvenile cement of B. amphitrite became progressively less sensitive to hydrolysis as they cured.     

Settlement Behaviour of Marine Invertebrate Larvae Measured by EthoVision 3.0

Submerged marine surfaces are rapidly colonized by fouling organisms. Current research is aimed at finding new, non-toxic, or at least environmentally benign, solutions to this problem. Barnacles are a major target organism for such control as they constitute a key component of the hard fouling community. A range of standard settlement assays is available for screening test compounds against barnacle cypris larvae, but they generally provide little information on mechanism(s) of action. Towards this end, a quick and reliable video-tracking protocol has been developed to study the behaviour of the cypris larvae of the barnacle, Balanus amphitrite, at settlement. EthoVision 3.0 was used to track individual cyprids in 30-mm Petri dishes. Experiments were run to determine the optimal conditions vis-à-vis acclimation time, tracking duration, number of replicates, temperature and lighting. A protocol was arrived at involving a two Petri dish system with backlighting, and tracking over a 5-min period after first acclimating the cyprids to test conditions for 2 min. A minimum of twenty replicates was required to account for individual variability in cyprid behaviour from the same batch of larvae. This methodology should be widely applicable to both fundamental and applied studies of larval settlement and with further refinements, to that of smaller fouling organisms such as microalgae and bacteria.     

Consistent and variable leaf anatomical characters in Carex (Cyperaceae)

The anatomy and morphology of leaves in Carex have the potential to be taxonomically useful. However, studies on the variability of leaf characteristics in the genus are sparse. Researchers therefore risk using leaf anatomical characters without the knowledge of whether they are consistent in a species. We examined 22 qualitative and seven quantitative leaf anatomy characters from transverse leaf sections to test their consistency across 11 Carex spp. The characters were clearly described and primarily microscopic. Some characters were found to exhibit high levels of intraspecific variation, whereas other characters exhibited high levels of consistency in a species, including the shape of the leaf section, the density of papillae and the size of epidermal cells. Caution must be applied when choosing leaf anatomy to delimit taxa because of the intraspecific variability found in some characters, but sufficient numbers of invariant characters exist to provide useful taxonomic separation. © 2013 The Linnean Society of London, Botanical Journal of the Linnean Society, 2013, 172 , 371–384.     

An Unbiased Approach to Identifying Tau Kinases That Phosphorylate Tau at Sites Associated with Alzheimer Disease

Neurofibrillary tangles, one of the hallmarks of Alzheimer disease (AD), are composed of paired helical filaments of abnormally hyperphosphorylated tau. The accumulation of these proteinaceous aggregates in AD correlates with synaptic loss and severity of dementia. Identifying the kinases involved in the pathological phosphorylation of tau may identify novel targets for AD. We used an unbiased approach to study the effect of 352 human kinases on their ability to phosphorylate tau at epitopes associated with AD. The kinases were overexpressed together with the longest form of human tau in human neuroblastoma cells. Levels of total and phosphorylated tau (epitopes Ser(P)-202, Thr(P)-231, Ser(P)-235, and Ser(P)-396/404) were measured in cell lysates using AlphaScreen assays. GSK3α, GSK3β, and MAPK13 were found to be the most active tau kinases, phosphorylating tau at all four epitopes. We further dissected the effects of GSK3α and GSK3β using pharmacological and genetic tools in hTau primary cortical neurons. Pathway analysis of the kinases identified in the screen suggested mechanisms for regulation of total tau levels and tau phosphorylation; for example, kinases that affect total tau levels do so by inhibition or activation of translation. A network fishing approach with the kinase hits identified other key molecules putatively involved in tau phosphorylation pathways, including the G-protein signaling through the Ras family of GTPases (MAPK family) pathway. The findings identify novel tau kinases and novel pathways that may be relevant for AD and other tauopathies.     

Assessing breeding success in common woodland birds using a novel method

Capsule Repeated counts of fledged broods can provide a useful estimate of breeding success for most common woodland birds.

Aims To assess the efficacy of comparing fledged-brood survey data with territory mapping using simple mark–recapture analysis techniques to provide an estimate of breeding success for common woodland birds that does not involve finding nests.

Methods Three observers undertook territory mapping surveys of adults, followed by counts of fledged broods four times a week during May–July 2007 in two 15 ha woods each, both in southern England. Using known fledging to maturity periods, these counts were used to calculate daily detection probabilities for broods of ubiquitous species. These enabled fledged brood territory occupancy probabilities (i.e. brood to territory ratios) to be estimated that take account of the possibility that broods were present but missed by surveys.

Results Of the 19 species found in all six woods, mean daily detection probability estimates for fledged broods of 17 species ranged from 0.17 to 0.50 with significant variation between woods for 12 species, but within region/observer for four species. The mean probability of detecting a brood at least once was over 75% using four visits per week and over 50% using two visits. Only for Great Spotted Woodpeckers Dendrocopos major and Garden Warblers Sylvia borin was the fledging period too short and the daily detection probability too low to provide a reasonable estimate of the territory occupancy probability.

Conclusion Daily detection probabilities for fledged broods of most common woodland birds were sufficiently high to enable useable estimates of fledged-brood territory occupancy probabilities to be made based on a survey programme involving two or three visits per week between late May and the end June. The method used may have application as a means of providing a relatively easily derived productivity index for woodland bird monitoring programmes or for research studies.     

The X-ray crystal structure of APR-B,an atypical adenosine 5′-phosphosulfate reductase from Physcomitrella patens

Sulfonucleotide reductases catalyse the first reductive step of sulfate assimilation. Their substrate specificities generally correlate with the requirement for a [Fe₄S₄] cluster, where adenosine 5′-phosphosulfate (APS) reductases possess a cluster and 3′-phosphoadenosine 5′-phosphosulfate reductases do not. The exception is the APR-B isoform of APS reductase from the moss Physcomitrella patens, which lacks a cluster. The crystal structure of APR-B, the first for a plant sulfonucleotide reductase, is consistent with a preference for APS. Structural conservation with bacterial APS reductase rules out a structural role for the cluster, but supports the contention that it enhances the activity of conventional APS reductases.     

Cytidine derivatives as IspF inhibitors of Burkolderia pseudomallei

Published biological data suggest that the methyl erythritol phosphate (MEP) pathway, a non-mevalonate isoprenoid biosynthetic pathway, is essential for certain bacteria and other infectious disease organisms. One highly conserved enzyme in the MEP pathway is 2C-methyl-d-erythritol 2,4-cyclodiphosphate synthase (IspF). Fragment-bound complexes of IspF from Burkholderia pseudomallei were used to design and synthesize a series of molecules linking the cytidine moiety to different zinc pocket fragment binders. Testing by surface plasmon resonance (SPR) found one molecule in the series to possess binding affinity equal to that of cytidine diphosphate, despite lacking any metal-coordinating phosphate groups. Close inspection of the SPR data suggest different binding stoichiometries between IspF and test compounds. Crystallographic analysis shows important variations between the binding mode of one synthesized compound and the pose of the bound fragment from which it was designed. The binding modes of these molecules add to our structural knowledge base for IspF and suggest future refinements in this compound series.     

Chk1 Inhibits E2F6 Repressor Function in Response to Replication Stress to Maintain Cell-Cycle Transcription

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