Potentiation of Epithelial Innate Host Responses by Intercellular Communication

The epithelium efficiently attracts immune cells upon infection despite the low number of pathogenic microbes and moderate levels of secreted chemokines per cell. Here we examined whether horizontal intercellular communication between cells may contribute to a coordinated response of the epithelium. Listeria monocytogenes infection, transfection, and microinjection of individual cells within a polarized intestinal epithelial cell layer were performed and activation was determined at the single cell level by fluorescence microscopy and flow cytometry. Surprisingly, chemokine production after L. monocytogenes infection was primarily observed in non-infected epithelial cells despite invasion-dependent cell activation. Whereas horizontal communication was independent of gap junction formation, cytokine secretion, ion fluxes, or nitric oxide synthesis, NADPH oxidase (Nox) 4-dependent oxygen radical formation was required and sufficient to induce indirect epithelial cell activation. This is the first report to describe epithelial cell-cell communication in response to innate immune activation. Epithelial communication facilitates a coordinated infectious host defence at the very early stage of microbial infection

Listeria pathogenesis and molecular virulence determinants

The gram-positive bacterium Listeria monocytogenes is the causative agent of listeriosis, a highly fatal opportunistic foodborne infection. Pregnant women, neonates, the elderly, and debilitated or immunocompromised patients in general are predominantly affected, although the disease can also develop in normal individuals. Clinical manifestations of invasive listeriosis are usually severe and include abortion, sepsis, and meningoencephalitis. Listeriosis can also manifest as a febrile gastroenteritis syndrome. In addition to humans, L. monocytogenes affects many vertebrate species, including birds. Listeria ivanovii, a second pathogenic species of the genus, is specific for ruminants. Our current view of the pathophysiology of listeriosis derives largely from studies with the mouse infection model. Pathogenic listeriae enter the host primarily through the intestine. The liver is thought to be their first target organ after intestinal translocation. In the liver, listeriae actively multiply until the infection is controlled by a cell-mediated immune response. This initial, subclinical step of listeriosis is thought to be common due to the frequent presence of pathogenic L. monocytogenes in food. In normal indivuals, the continual exposure to listerial antigens probably contributes to the maintenance of anti-Listeria memory T cells. However, in debilitated and immunocompromised patients, the unrestricted proliferation of listeriae in the liver may result in prolonged low-level bacteremia, leading to invasion of the preferred secondary target organs (the brain and the gravid uterus) and to overt clinical disease. L. monocytogenes and L. ivanovii are facultative intracellular parasites able to survive in macrophages and to invade a variety of normally nonphagocytic cells, such as epithelial cells, hepatocytes, and endothelial cells. In all these cell types, pathogenic listeriae go through an intracellular life cycle involving early escape from the phagocytic vacuole, rapid intracytoplasmic multiplication, bacterially induced actin-based motility, and direct spread to neighboring cells, in which they reinitiate the cycle. In this way, listeriae disseminate in host tissues sheltered from the humoral arm of the immune system. Over the last 15 years, a number of virulence factors involved in key steps of this intracellular life cycle have been identified. This review describes in detail the molecular determinants of Listeria virulence and their mechanism of action and summarizes the current knowledge on the pathophysiology of listeriosis and the cell biology and host cell responses to Listeria infection. This article provides an updated perspective of the development of our understanding of Listeria pathogenesis from the first molecular genetic analyses of virulence mechanisms reported in 1985 until the start of the genomic era of Listeria research

Approximation of automorphisms of the rationals and the random graph

Let G be the group of order-preserving automorphisms of the rationals Q, or thegroup of colour-preserving automorphisms of the C-coloured random graph RC. We show that given any non-identity f A G, there exists g A G such that every automorphism in G is the limit of a sequence of automorphisms generated by f and g. Moreover, if, in some sense, f has no finite structure, then g can be chosen with a great deal of flexibility

Recent advancements in hydrophobic materials and their significant applications in corrosion prevention

Hydrophobic materials are formed based on the chemical concept of hydrophobicity Which is derived from a Greek term ‘hydro ’meaning water and ‘phobos ’meaning fear. Natural hydrophobes include alkanes, fats and oils. Hydrophobic substances resolutely refuse to mix with water (such as oils and fats) and hydrophobic materials and coatings prevent water from pooling on its surface. This phenomenon is also termed as "The Lotus Effect" since this is observed in the leaf of "Nelumbo" or "lotus flower". Hydrophobic materials are often used to remove oil from water, manage oil spills and remove nonpolar substances from polar compounds. These materials can be created using two methods. The simpler method is to coat a surface with wax, oil or grease. The other is using nanoengineering to help createa unique, nanopatterned textured surface. Hydrophobicity greatly improves the corrosion protective properties of the coatings. Hydrophobic coatings prevent water from pooling on its surface. In order to minimize the disruption to its molecular makeup, the water droplet pushes itself away from the surface to minimize its contact area, becoming a very tight droplet. Hydrophobic treatment is an effective, low cost preventative measure against corrosion of reinforcement in chloride contaminated environment. An attempt has been made to discuss wetting phenomena of hydrophobic materials, recent advancements in hydrophobic materials and their significant applications, in corrosion prevention

Typical self-healing materials-their mechanism and emerging applications

Any biological system in the world has its own mechanism of response towards cuts and cracks. Whenever there is an injury, it appears as wound and the biology starts the inflammatory (immediate) response followed by cell formation and matrix remodeling. This is kind of a long-term process. It provides perfect healing in the biological system (such as human-bodies, plants, trees etc.). Considering this phenomenon as the source of inspiration, a new kind of materials have been developed, which can response to the damage by their self and repairs known as ‘self-healing ’materials. Whenever and wherever the damage (crack, cut, rupture etc.) appears in the material, it triggers the healing mechanism and repairs the damage cracks or notches by chemical repair. This is kind of short-range process than biological one. To date, self-healing is demonstrated mainly in polymers and composites by three conceptual approaches namely capsule based healing system, vascular healing system and intrinsic healing system. It can be automatic without human intervention or may require some external energy or pressure. The synthetic self-healing systems work as three-step process. The first response towards the damage is triggering (actuation). The second response is transport of materials to the site of damage. The third response, analogous to matrix remodeling. This is the chemical repair process. Application of the self-healing martials is expected in all fields of science in the future. The very few developed applications to date are mainly in automotive, aerospace and building industries. An attempt has been made to discuss the mechanism of typical self-healing materials and their emerging applications

Graphene-recent advancements in its extraction, its comparative study with other materials and emerging applications

Graphene, a whole new structure of Carbon, was discovered by Geim and Novoselov in the year 2004. It is the thinnest, lightest and the strongest material ever existed. It is a monolayer of carbon atoms, which are tightly bound in the hexagon honeycomb lattice. It is the first two-dimensional (2D) atomic crystal. A large number of its material parameters such as mechanical stiffness, strength and elasticity, very high electrical and thermal conductivity, and many others are supreme. These properties suggest that graphene could replace other materials in existing applications. The combination of transparency, conductivity and elasticity will find use in flexible electronics, whereas transparency, impermeability and conductivity will find application in transparent protective coatings and barrier films. As a coating material, it can be used as the best anti-corrosion coating. Graphene can be reinforced with other compounds and provides great formability. It can be used as an alternative for the high strength to weight ratio requirements. Due to extremely high conductivity and flexibility, graphene is an ideal material for high speed electronics, transistors, data storage, LCDs, OLED displays, super capacitors, Solar Cells, Sensors etc. With such a great property, graphene has been an area of interest of both the experts and the layman. Graphene will be of even greater interest for industrial applications when massproduced graphene has the same outstanding performance as the best samples obtained in research laboratories. An attempt has been made to discuss recent advancements in its extraction, itscomparative evaluationwithother materialsandemerging applications