Interior fixed points of unit-sphere-preserving Euclidean maps

Schirmer proved that there is a class of smooth self-maps of the unit sphere in Euclidean n-space with the property that any smooth self-map of the unit ball that extends a map of that class must have at least one fixed point in the interior of the ball. We generalize Schirmer’s result by proving that a smooth self-map of Euclidean n-space that extends a self-map of the unit sphere of that class must have at least one fixed point in the interior of the unit ball.

Infant gut microbiota and the hygiene hypothesis of allergic disease

Folate status of gut microbiome affects Caenorhabditis eleganslifespan

Effect of a multifactorial interdisciplinary intervention on mobility-related disability in frail older people: randomised controlled trial

Background Interventions that enhance mobility in frail older people are needed to maintain health and independence, yet definitive evidence of effective interventions is lacking. Our objective was to assess the impact of a multifactorial intervention on mobility-related disability in frail older people. Methods We conducted a randomised, controlled trial with 241 frail community-dwelling older people in Sydney, Australia. Participants were classified as frail using the Cardiovascular Health Study definition, did not have severe cognitive impairment and were recently discharged from an aged care and rehabilitation service. The experimental group received a 12 month multifactorial, interdisciplinary intervention targeting identified frailty components. Two physiotherapists delivered a home exercise program targeting mobility, and coordinated management of psychological and medical conditions with other health professionals. The control group received usual care. Disability in the mobility domain was measured at baseline and at 3 and 12 months using the International Classification of Functioning, Disability and Health framework. Participation (involvement in life situations) was assessed using the Life Space Assessment and the Goal Attainment Scale. Activity (execution of mobility tasks) was measured using the 4-metre walk and self-report measures. Results The mean age of participants was 83.3 years (SD: 5.9 years). Of the participants recruited, 216 (90%) were followed-up at 12 months. At this time point, the intervention group had significantly better scores than the control group on the Goal Attainment Scale (odds ratio 2.1; 95% confidence interval (CI) 1.3 to 3.3, P = 0.004) and Life Space Assessment (4.68 points, 95% CI 1.4 to 9.9, P = 0.005). There was no difference between groups on the global measure of participation or satisfaction with ability to get out of the house. At the activity level, the intervention group walked 0.05 m/s faster over 4 m (95% CI 0.0004 to 0.1, P = 0.048) than the control group, and scored higher on the Activity Measure for Post Acute Care ( P < 0.001). Conclusions The intervention reduced mobility-related disability in frail older people. The benefit was evident at both the participation and activity levels of mobility-related disability. Trial registration Australia and New Zealand Clinical Trials Register (ANZCTR): ANZCTRN12608000507381 .

Podosomes in migrating microglia: components and matrix degradation

Background To perform their functions during development and after central nervous system injury, the brain’s immune cells (microglia) must migrate through dense neuropil and extracellular matrix (ECM), but it is not known how they degrade the ECM. In several cancer cell lines and peripheral cells, small multi-molecular complexes (invadopodia in cancer cells, podosomes in nontumor cells) can both adhere to and dissolve the ECM. Podosomes are tiny multi-molecular structures (0.4 to 1 μm) with a core, rich in F-actin and its regulatory molecules, surrounded by a ring containing adhesion and structural proteins. Methods Using rat microglia, we performed several functional assays: live cell imaging for chemokinesis, degradation of the ECM component, fibronectin, and chemotactic invasion through Matrigel™, a basement membrane type of ECM. Fluorescent markers were used with high-resolution microscopy to identify podosomes and their components. Results The fan-shaped lamella at the leading edge of migrating microglia contained a large F-actin-rich superstructure composed of many tiny (<1 μm) punctae that were adjacent to the substrate, as expected for cell–matrix contact points. This superstructure (which we call a podonut) was restricted to cells with lamellae, and conversely almost every lamella contained a podonut. Each podonut comprised hundreds of podosomes, which could also be seen individually adjacent to the podonut. Microglial podosomes contained hallmark components of these structures previously seen in several cell types: the plaque protein talin in the ring, and F-actin and actin-related protein (Arp) 2 in the core. In microglia, podosomes were also enriched in phosphotyrosine residues and three tyrosine-kinase-regulated proteins: tyrosine kinase substrate with five Src homology 3 domains (Tks5), phosphorylated caveolin-1, and Nox1 (nicotinamide adenine dinucleotide phosphate oxidase 1). When microglia expressed podonuts, they were able to degrade the ECM components, fibronectin, and Matrigel™. Conclusion The discovery of functional podosomes in microglia has broad implications, because migration of these innate immune cells is crucial in the developing brain, after damage, and in disease states involving inflammation and matrix remodeling. Based on the roles of invadosomes in peripheral tissues, we propose that microglia use these complex structures to adhere to and degrade the ECM for efficient migration.

Dendritic cell CNS recruitment correlates with disease severity in EAE via CCL2 chemotaxis at the blood–brain barrier through paracellular transmigration and ERK activation

Background Transmigration of circulating dendritic cells (DCs) into the central nervous system (CNS) across the blood–brain barrier (BBB) has not thus far been investigated. An increase in immune cell infiltration across the BBB, uncontrolled activation and antigen presentation are influenced by chemokines. Chemokine ligand 2 (CCL2) is a potent chemoattractant known to be secreted by the BBB but has not been implicated in the recruitment of DCs specifically at the BBB. Methods Experimental autoimmune encephalomyelitis (EAE) was induced in C57BL/6 mice by injection of MOG 35–55 peptide and pertussis toxin intraperitoneally. Animals with increasing degree of EAE score were sacrificed and subjected to near-infrared and fluorescence imaging analysis to detect and localize the accumulation of CD11c + -labeled DCs with respect to CCL2 expression. To further characterize the direct effect of CCL2 in DC trafficking at the BBB, we utilized an in vitro BBB model consisting of human brain microvascular endothelial cells to compare migratory patterns of monocyte-derived dendritic cells, CD4 + and CD8 + T cells. Further, this model was used to image transmigration using fluorescence microcopy and to assess specific molecular signaling pathways involved in transmigration. Results Near-infrared imaging of DC transmigration correlated with the severity of inflammation during EAE. Ex vivo histology confirmed the presence of CCL2 in EAE lesions, with DCs emerging from perivascular spaces. DCs exhibited more efficient transmigration than T cells in BBB model studies. These observations correlated with transwell imaging, which indicated a paracellular versus transcellular pattern of migration by DCs and T cells. Moreover, at the molecular level, CCL2 seems to facilitate DC transmigration in an ERK1/2-dependent manner. Conclusion CNS recruitment of DCs correlates with disease severity in EAE via CCL2 chemotaxis and paracellular transmigration across the BBB, which is facilitated by ERK activation. Overall, these comprehensive studies provide a state-of-the-art view of DCs within the CNS, elucidate their path across the BBB, and highlight potential mechanisms involved in CCL2-mediated DC trafficking.

Acetate supplementation reduces microglia activation and brain interleukin-1β levels in a rat model of Lyme neuroborreliosis

Background We have found that acetate supplementation significantly reduces neuroglia activation and pro-inflammatory cytokine release in a rat model of neuroinflammation induced with lipopolysaccharide. To test if the anti-inflammatory effect of acetate supplementation is specific to a TLR4-mediated injury, we measured markers of neuroglia activation in rats subjected to B. burgdorferi -induced neuroborreliosis that is mediated in large part by a TLR2-type mechanism. Methods In this study, rats were subjected to Lyme neuroborreliosis following an intravenous infusion of B. burgdorferi (B31-MI-16). Acetate supplementation was induced using glyceryl triacetate (6g/kg) by oral gavage. Immunohistochemistry, qPCR, and western blot analyses were used to measure bacterial invasion into the brain, neuroglial activation, and brain and circulating levels of interleukin 1β. Statistical analysis was performed using one-way analysis of variance (ANOVA) followed by a Tukey’s post hoc tests or using a Student’s t test assuming unequal variances when appropriate. Results We found that acetate supplementation significantly reduced microglia activation by 2-fold as determined by immunohistochemical and western blot analysis. Further, acetate supplementation also reduced the expression of the pro-inflammatory cytokine IL-1β by 2-fold as compared to controls. On the other hand, the inoculation of rats with B. burgdorferi had no effect on astroglial activation as determined by immunocytochemistry and western blot analysis despite significant increases in circulation levels of antigen toward B. burgdorferi and presence of the bacteria in the central nervous system. Conclusions These results suggest that microglial activation is an essential component to neuroborreliosis and that acetate supplementation may be an effective treatment to reduce injury phenotype and possibly injury progression in Lyme neuroborreliosis.

Regulation of podosome formation, microglial migration and invasion by Ca2+-signaling molecules expressed in podosomes

Background Microglia migrate during brain development and after CNS injury, but it is not known how they degrade the extracellular matrix (ECM) to accomplish this. Podosomes are tiny structures with the unique ability to adhere to and dissolve ECM. Podosomes have a two-part architecture: a core that is rich in F-actin and actin-regulatory molecules (for example, Arp2/3), surrounded by a ring with adhesion and structural proteins (for example, talin, vinculin). We recently discovered that the lamellum at the leading edge of migrating microglia contains a large F-actin-rich superstructure (‘podonut’) composed of many podosomes. Microglia that expressed podosomes could degrade ECM molecules. Finely tuned Ca 2+ signaling is important for cell migration, cell-substrate adhesion and contraction of the actomyosin network. Here, we hypothesized that podosomes contain Ca 2+ -signaling machinery, and that podosome expression and function depend on Ca 2+ influx and specific ion channels. Methods High-resolution immunocytochemistry was used on rat microglia to identify podosomes and novel molecular components. A pharmacological toolbox was applied to functional assays. We analyzed roles of Ca 2+ -entry pathways and ion channels in podosome expression, microglial migration into a scratch-wound, transmigration through pores in a filter, and invasion through Matrigel™-coated filters. Results Microglial podosomes were identified using well-known components of the core (F-actin, Arp2) and ring (talin, vinculin). We discovered four novel podosome components related to Ca 2+ signaling. The core contained calcium release activated calcium (CRAC; Orai1) channels, calmodulin, small-conductance Ca 2+ -activated SK3 channels, and ionized Ca 2+ binding adapter molecule 1 (Iba1), which is used to identify microglia in the CNS. The Orai1 accessory molecule, STIM1, was also present in and around podosomes. Podosome formation was inhibited by removing external Ca 2+ or blocking CRAC channels. Blockers of CRAC channels inhibited migration and invasion, and SK3 inhibition reduced invasion. Conclusions Microglia podosome formation, migration and/or invasion require Ca 2+ influx, CRAC, and SK3 channels. Both channels were present in microglial podosomes along with the Ca 2+ -regulated molecules, calmodulin, Iba1 and STIM1. These results suggest that the podosome is a hub for sub-cellular Ca 2+ -signaling to regulate ECM degradation and cell migration. The findings have broad implications for understanding migration mechanisms of cells that adhere to, and dissolve ECM.

Cerebrospinal fluid and plasma cytokines after subarachnoid haemorrhage: CSF interleukin-6 may be an early marker of infection

Background Cytokines and cytokine receptor concentrations increase in plasma and cerebrospinal fluid (CSF) of patients following subarachnoid haemorrhage (SAH). The relationship between plasma and CSF cytokines, and factors affecting this, are not clear. Methods To help define the relationship, paired plasma and cerebrospinal fluid (CSF) samples were collected from patients subject to ventriculostomy. Concentrations of key inflammatory cytokines, interleukin (IL)-1ß, IL-1 receptor antagonist (IL-1Ra), IL-1 receptor 2, IL-6, IL-8, IL-10, tumour necrosis factor (TNF)-α, and TNF receptors (TNF-R) 1 and 2 were determined by immunoassay of CSF and plasma from 21 patients, where samples were available at three or more time points. Results Plasma concentrations of IL-1ß, IL-1Ra, IL-10, TNF-α and TNF-R1 were similar to those in CSF. Plasma TNF-R2 and IL-1R2 concentrations were higher than in CSF. Concentrations of IL-8 and IL-6 in CSF were approximately10 to 1,000-fold higher than in plasma. There was a weak correlation between CSF and plasma IL-8 concentrations (r = 0.26), but no correlation for IL-6. Differences between the central and peripheral pattern of IL-6 were associated with episodes of ventriculostomy-related infection (VRI). A VRI was associated with CSF IL-6 >10,000 pg/mL ( P = 0.0002), although peripheral infection was not significantly associated with plasma IL-6. Conclusions These data suggest that plasma cytokine concentrations cannot be used to identify relative changes in the CSF, but that measurement of CSF IL-6 could provide a useful marker of VRI.

The biochemistry of acetaminophen hepatotoxicity and rescue: a mathematical model

Background Acetaminophen (N-acetyl-para-aminophenol) is the most widely used over-the-counter or prescription painkiller in the world. Acetaminophen is metabolized in the liver where a toxic byproduct is produced that can be removed by conjugation with glutathione. Acetaminophen overdoses, either accidental or intentional, are the leading cause of acute liver failure in the United States, accounting for 56,000 emergency room visits per year. The standard treatment for overdose is N-acetyl-cysteine (NAC), which is given to stimulate the production of glutathione. Methods We have created a mathematical model for acetaminophen transport and metabolism including the following compartments: gut, plasma, liver, tissue, urine. In the liver compartment the metabolism of acetaminophen includes sulfation, glucoronidation, conjugation with glutathione, production of the toxic metabolite, and liver damage, taking biochemical parameters from the literature whenever possible. This model is then connected to a previously constructed model of glutathione metabolism. Results We show that our model accurately reproduces published clinical and experimental data on the dose-dependent time course of acetaminophen in the plasma, the accumulation of acetaminophen and its metabolites in the urine, and the depletion of glutathione caused by conjugation with the toxic product. We use the model to study the extent of liver damage caused by overdoses or by chronic use of therapeutic doses, and the effects of polymorphisms in glucoronidation enzymes. We use the model to study the depletion of glutathione and the effect of the size and timing of N-acetyl-cysteine doses given as an antidote. Our model accurately predicts patient death or recovery depending on size of APAP overdose and time of treatment. Conclusions The mathematical model provides a new tool for studying the effects of various doses of acetaminophen on the liver metabolism of acetaminophen and glutathione. It can be used to study how the metabolism of acetaminophen depends on the expression level of liver enzymes. Finally, it can be used to predict patient metabolic and physiological responses to APAP doses and different NAC dosing strategies.