Schwann cell dedifferentiation from a myelinating to a progenitor-like cell underlies the remarkable ability of peripheral nerves to regenerate following injury. However, the molecular identity of ...the differentiated and dedifferentiated states in vivo has been elusive. Here, we profiled Schwann cells acutely purified from intact nerves and from the wound and distal regions of severed nerves. Our analysis reveals novel facets of the dedifferentiation response, including acquisition of mesenchymal traits and a Myc module. Furthermore, wound and distal dedifferentiated Schwann cells constitute different populations, with wound cells displaying increased mesenchymal character induced by localized TGFβ signaling. TGFβ promotes invasion and crosstalks with Eph signaling via N-cadherin to drive collective migration of the Schwann cells across the wound. Consistently, Tgfbr2 deletion in Schwann cells resulted in misdirected and delayed reinnervation. Thus, the wound microenvironment is a key determinant of Schwann cell identity, and it promotes nerve repair through integration of multiple concerted signals.
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•Wound Schwann cells have a distinct dedifferentiation program•TGFβ signaling reprograms wound Schwann cells to invasive mesenchymal-like cells•TGFβ crosstalks with Eph signaling to drive collective Schwann cell migration•Loss of TGFβ signaling in Schwann cells delays nerve regeneration
Clements et al. show that the nerve-injury-induced Schwann cell dedifferentiation program is modulated by the wound microenvironment through TGFβ. TGFβ promotes regeneration by reprogramming Schwann cells to invasive, mesenchymal-like cells and crosstalking with Eph signaling to drive collective migration.
The peripheral nervous system has remarkable regenerative capacities in that it can repair a fully cut nerve. This requires Schwann cells to migrate collectively to guide regrowing axons across a ...‘bridge’ of new tissue, which forms to reconnect a severed nerve. Here we show that blood vessels direct the migrating cords of Schwann cells. This multicellular process is initiated by hypoxia, selectively sensed by macrophages within the bridge, which via VEGF-A secretion induce a polarized vasculature that relieves the hypoxia. Schwann cells then use the blood vessels as “tracks” to cross the bridge taking regrowing axons with them. Importantly, disrupting the organization of the newly formed blood vessels in vivo, either by inhibiting the angiogenic signal or by re-orienting them, compromises Schwann cell directionality resulting in defective nerve repair. This study provides important insights into how the choreography of multiple cell-types is required for the regeneration of an adult tissue.
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•Hypoxia within the nerve bridge is selectively sensed by macrophages•Macrophage-derived VEGF-A induces a polarized vasculature within the bridge•Blood vessels are used as tracks to direct Schwann cell migration across the wound•Macrophage-induced blood vessels are essential for nerve regeneration
Repairing a cut nerve requires collective migration of Schwann cells guided by a polarized vasculature that is induced by macrophages within the hypoxic bridge.
Most of what is known concerning the luminal passage of materials through nanopores arises from electrical measurements. Whether nanopores are biological, solid-state, synthetic, hybrid, ...glass-capillary-based, or protein ion channels in cells and tissues, characteristic signatures embedded in the flow of ionic current are foundational to understanding functional behavior. In contrast, this work describes passage through a nanopore that occurs without producing an electrical signature. We refer to the phenomenon as “silent translocation.” By definition, silent translocations are invisible to the standard tools of electrophysiology and fundamentally require a simultaneous ancillary measurement technique for positive identification. As a result, this phenomenon has been largely unexplored in the literature. Here, we report on a derivative of Cyanine 5 (sCy5a) that passes through the α-hemolysin (αHL) nanopore silently. Simultaneously acquired single-molecule fluorescence and single-channel electrical recordings from bilayers formed over a closed microcavity demonstrate that translocation does indeed take place, albeit infrequently. We report observations of silent translocation as a function of time, dye concentration, and nanopore population in the bilayer. Lastly, measurement of the translocation rate as a function of applied potential permits estimation of an effective energy barrier for transport through the pore as well as the effective charge on the dye, all in the absence of an information-containing electrical signature.
Neuromuscular synapse formation depends upon coordinated interactions between motor neurons and muscle fibers, leading to the formation of a highly specialized postsynaptic membrane and a highly ...differentiated nerve terminal. Synapse formation begins as motor axons approach muscles that are prepatterned in the prospective synaptic region in a manner that depends upon Lrp4, a member of the LDL receptor family, and muscle-specific kinase (MuSK), a receptor tyrosine kinase. Motor axons supply Agrin, which binds Lrp4 and stimulates further MuSK phosphorylation, stabilizing nascent synapses. How Agrin binds Lrp4 and stimulates MuSK kinase activity is poorly understood. Here, we demonstrate that Agrin binds to the N-terminal region of Lrp4, including a subset of the LDLa repeats and the first of four β-propeller domains, which promotes association between Lrp4 and MuSK and stimulates MuSK kinase activity. In addition, we show that Agrin stimulates the formation of a functional complex between Lrp4 and MuSK on the surface of myotubes in the absence of the transmembrane and intracellular domains of Lrp4. Further, we demonstrate that the first Ig-like domain in MuSK, which shares homology with the NGF-binding region in Tropomyosin Receptor Kinase (TrKA), is required for MuSK to bind Lrp4. These findings suggest that Lrp4 is a cis-acting ligand for MuSK, whereas Agrin functions as an allosteric and paracrine regulator to promote association between Lrp4 and MuSK.
Background: How Agrin binds Lrp4 and stimulates MuSK kinase activity is poorly understood.
Results: We identify domains in Lrp4 important for Agrin to bind Lrp4 and MuSK and stimulate MuSK phosphorylation.
Conclusion: Different domains in Lrp4 bind Agrin and MuSK and stimulate MuSK phosphorylation.
Significance: Lrp4 functions as a ligand for MuSK, whereas Agrin promotes association between Lrp4 and MuSK.
Readmission prediction models have been developed and validated for targeted in-hospital preventive interventions. We aimed to externally validate the Potentially Avoidable Readmission-Risk Score ...(PAR-Risk Score), a 12-items prediction model for internal medicine patients with a convenient scoring system, for our local patient cohort.
A cohort study using electronic health record data from the internal medicine ward of a Swiss tertiary teaching hospital was conducted. The individual PAR-Risk Score values were calculated for each patient. Univariable logistic regression was used to predict potentially avoidable readmissions (PARs), as identified by the SQLape algorithm. For additional analyses, patients were stratified into low, medium, and high risk according to tertiles based on the PAR-Risk Score. Statistical associations between predictor variables and PAR as outcome were assessed using both univariable and multivariable logistic regression.
The final dataset consisted of 5,985 patients. Of these, 340 patients (5.7%) experienced a PAR. The overall PAR-Risk Score showed rather poor discriminatory power (C statistic 0.605, 95%-CI 0.575-0.635). When using stratified groups (low, medium, high), patients in the high-risk group were at statistically significant higher odds (OR 2.63, 95%-CI 1.33-5.18) of being readmitted within 30 days compared to low risk patients. Multivariable logistic regression identified previous admission within six months, anaemia, heart failure, and opioids to be significantly associated with PAR in this patient cohort.
This external validation showed a limited overall performance of the PAR-Risk Score, although higher scores were associated with an increased risk for PAR and patients in the high-risk group were at significantly higher odds of being readmitted within 30 days. This study highlights the importance of externally validating prediction models.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background
People with advanced ovarian or gastrointestinal cancer may develop malignant bowel obstruction (MBO). They are able to tolerate limited, if any, oral or enteral (via a tube directly into ...the gut) nutrition. Parenteral nutrition (PN) is the provision of macronutrients, micronutrients, electrolytes and fluid infused as an intravenous solution and provides a method for these people to receive nutrients. There are clinical and ethical arguments for and against the administration of PN to people receiving palliative care.
Objectives
To assess the effectiveness of home parenteral nutrition (HPN) in improving survival and quality of life in people with inoperable MBO.
Search methods
We searched the following electronic databases: Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 1), MEDLINE (Ovid), Embase (Ovid), BNI, CINAHL, Web of Science and NHS Economic Evaluation and Health Technology Assessment up to January 2018, ClinicalTrials.gov (http://clinicaltrials.gov/) and in the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal (http://apps.who.int/trialsearch/). In addition, we handsearched included studies and used the ‘Similar articles’ feature on PubMed for included articles.
Selection criteria
We included any studies with more than five participants investigating HPN in people over 16 years of age with inoperable MBO.
Data collection and analysis
We extracted the data and assessed risk of bias for each study. We entered data into Review Manager 5 and used GRADEpro to assess the quality of the evidence.
Main results
We included 13 studies with a total of 721 participants in the review. The studies were observational, 12 studies had only one relevant treatment arm and no control and for the one study with a control arm, very few details were given. The risk of bias was high and the certainty of evidence was graded as very low for all outcomes. Due to heterogeneity of data, meta‐analysis was not performed and therefore the data were synthesised via a narrative summary.
The evidence for benefit derived from PN was very low for survival and quality of life. All the studies measured overall survival and 636 (88%) of participants were deceased at the end of the study. However there were varying definitions of overall survival that yielded median survival intervals between 15 to 155 days (range three to 1278 days). Three studies used validated measures of quality of life. The results from assessment of quality of life were equivocal; one study reported improvements up until three months and two studies reported approximately similar numbers of participants with improvements and deterioration. Different quality of life scales were used in each of the studies and quality of life was measured at different time points. Due to the very low certainty of the evidence, we are very uncertain about the adverse events related to PN use. Adverse events were measured by nine studies and data for individual participants could be extracted from eight studies. This revealed that 32 of 260 (12%) patients developed a central venous catheter infection or were hospitalised because of complications related to PN.
Authors' conclusions
We are very uncertain whether HPN improves survival or quality of life in people with MBO as the certainty of evidence was very low for both outcomes. As the evidence base is limited and at high risk of bias, further higher‐quality prospective studies are required.
Aim
To investigate how mentors form judgements and reach summative assessment decisions regarding student competence in practice.
Background
Competence assessment is a significant component of ...pre‐registration nursing programmes in the United Kingdom. Concerns exist that assessments are subjective, lack consistency and that mentors fail to judge student performance as unsatisfactory.
Design
A two‐stage sequential embedded mixed‐methods design. Data collected 2012–2013.
Methods
This study involved a whole student cohort completing a UK undergraduate adult nursing programme (N = 41). Stage 1: quantitative data on mentor conduct of assessment interviews and the final decision recorded (N = 330 from 270 mentors) were extracted from student Practice Assessment Documents (PADs). Stage 2: mentor feedback in student PADs was used in Stimulated Recall interviews with a purposive sample of final placement mentors (N = 17). These were thematically analysed. Findings were integrated to develop a theoretically driven model of mentor decision‐making.
Results
Course assessment strategies and documentation had limited effect in framing mentor judgements and decisions. Rather, mentors amassed impressions, moderated by expectations of an “idealized student” by practice area and programme stage that influenced their management and outcome of the assessment process. These impressions were accumulated and combined into judgements that informed the final decision. This process can best be understood and conceptualized through the Brunswik's lens model of social judgement.
Conclusion
Mentor decisions were reasoned and there was a shared understanding of judgement criteria and their importance. This impression‐based nature of mentor decision‐making questions the reliability and validity of competency‐based assessments used in nursing pre‐registration programmes.
The processes of life take place in multiple dimensions, but imaging these processes in even three dimensions is challenging. Here, we describe a workflow for 3D correlative light and electron ...microscopy (CLEM) of cell monolayers using fluorescence microscopy to identify and follow biological events, combined with serial blockface scanning electron microscopy to analyse the underlying ultrastructure. The workflow encompasses all steps from cell culture to sample processing, imaging strategy, and 3D image processing and analysis. We demonstrate successful application of the workflow to three studies, each aiming to better understand complex and dynamic biological processes, including bacterial and viral infections of cultured cells and formation of entotic cell-in-cell structures commonly observed in tumours. Our workflow revealed new insight into the replicative niche of Mycobacterium tuberculosis in primary human lymphatic endothelial cells, HIV-1 in human monocyte-derived macrophages, and the composition of the entotic vacuole. The broad application of this 3D CLEM technique will make it a useful addition to the correlative imaging toolbox for biomedical research.
Malnutrition is a problem in advanced cancer, particularly ovarian cancer where malignant bowel obstruction (MBO) is a frequent complication. Parenteral nutrition is the only way these patients can ...received adequate nutrition and is a principal indication for palliative home parenteral nutrition (HPN). Giving HPN is contentious as it may increase the burden on patients. This study investigates patients' and family caregivers' experiences of HPN, alongside nutritional status and survival in patients with ovarian cancer and MBO.
This mixed methods study collected data on participant characteristics, clinical details and body composition using computed tomography (CT) combined with longitudinal in-depth interviews underpinned by phenomenological principles. The cohort comprised 38 women with ovarian cancer and inoperable MBO admitted (10/2016 to 12/ 2017) to a tertiary referral hospital. Longitudinal interviews (n = 57) were carried out with 20 women considered for HPN and 13 of their family caregivers.
Of the 38 women, 32 received parenteral nutrition (PN) in hospital and 17 were discharged on HPN. Nutritional status was poor with 31 of 33 women who had a CT scan having low muscle mass, although 10 were obese. Median overall survival from admission with MBO for all 38 women was 70 days (range 8-506) and for those 17 on HPN was 156 days (range 46-506). Women experienced HPN as one facet of their illness, but viewed it as a "lifeline" that allowed them to live outside hospital. Nevertheless, HPN treatment came with losses including erosion of normality through an impact on activities of daily living and dealing with the bureaucracy surrounding the process. Family caregivers coped but were often left in an emotionally vulnerable state.
Women and family caregivers reported that the inconvenience and disruption caused by HPN was worth the extended time they had at home.
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