Short term bioassay and bioassay chemistry of materials related to synthetic fossil fuels

An abstract was prepared for one paper. Abstracts of the five additional papers appeared previously in ERA

Liposomes Recruit IpaC to the Shigella flexneri Type III Secretion Apparatus Needle as a Final Step in Secretion Induction

Shigella flexneri contact with enterocytes induces a burst of protein secretion via its type III secretion apparatus (TTSA) as an initial step in cellular invasion. We have previously reported that IpaD is positioned at the TTSA needle tip (M. Espina et al., Infect. Immuno. 74:4391-4400, 2006). From this position, IpaD senses small molecules in the environment to control the presentation of IpaB to the needle tip. This step occurs without type III secretion induction or IpaC recruitment to the S. flexneri surface. IpaC is then transported to the S. flexneri surface when target cell lipids are added, and this event presumably mimics host cell contact. Unlike IpaB mobilization, IpaC surface presentation is closely linked to secretion induction. This study demonstrates that sphingomyelin and cholesterol are key players in type III secretion induction and that they appear to interact with IpaB to elicit IpaC presentation at the TTSA needle tip. Furthermore, IpaB localization at the needle tip prior to membrane contact provides the optimal set of conditions for host cell invasion. Thus, the S. flexneri type III secretion system can be induced in a stepwise manner, with the first step being the stable association of IpaD with the needle tip, the second step being the sensing of small molecules by IpaD to mobilize IpaB to the tip, and the third step being the interaction of lipids with IpaB to induce IpaC localization at the needle tip concomitant with translocon insertion into the host membrane and type III secretion induction. Shigella flexneri, the causative agent of shigellosis, is responsible for more than 1 million deaths each year, especially among children in developing regions (www.who.int/vaccines-documents/DocsPDF99/www9947.pdf). Once ingested, S. flexneri crosses M cells and passes into the underlying gut-associated lymphoid tissues of the colon (20), where it kills macrophages (29) and then invades epithelial cells by macropinocytosis (17). The S. flexneri invasive phenotype localizes genetically to a 31-kb region of its large virulence plasmid and is absolutely tied to its type III secretion system (TTSS) (6, 23). TTSSs are used by numerous gram-negative bacteria to introduce bacterially derived effector proteins into the membrane and cytoplasm of a target cell, resulting in the subversion of normal cell functions (8). Linking the bacterium and host cell in this process is the type III secretion apparatus (TTSA), which structurally resembles a molecular needle and syringe. The system is controlled by a basal body (the syringe) that spans both bacterial membranes and an external needle that provides a conduit from the basal body to the sensory needle tip complex (8, 28). The needle in S. flexneri is comprised of a polymer of MxiH and is approximately 50 nm long and 7 nm in diameter, with a central channel that is about 2.5 nm in diameter (5). At the top of the MxiH needle resides the tip protein IpaD, most likely as a pentamer, which serves as an environmental sensor for the MxiH-IpaD tip complex (4, 7). When the presence of bile salts such as deoxycholate (DOC) is sensed by IpaD, the first translocator protein, IpaB, is mobilized to the TTSA needle tip to form an MxiH-IpaD-IpaB ternary complex. At this stage, the TTSA structure is primed for subsequent host cell contact (19, 24). In previous studies IpaC had not been found to localize to the S. flexneri surface of the log-phase bacterium (7, 19). As a next step in describing the process of type III secretion, we show here that liposomes trigger mobilization of IpaC to the needle tip complex, where it is immediately inserted into the host cell membrane, along with IpaB, to complete the TTSA conduit into the host cell just prior to initiating host cytoskeleton rearrangements. IpaC is most efficiently recruited to the S. flexneri surface with a defined liposome composition that includes phospholipids, sphingomyelin (SM), and cholesterol (Chol). Furthermore, IpaC recruitment occurs concomitantly with induction of type III secretion of IpaB, IpaC, and IpaD into the S. flexneri culture supernatant. It thus appears that IpaB mobilization to the S. flexneri TTSA needle tip represents a second discrete step in TTSA assembly, with the final third step being IpaC recruitment to the needle tip, which occurs after IpaB contacts and inserts into the host cell membrane

The N-terminus of IpaB provides a potential anchor to the Shigella type III secretion system tip complex protein IpaD

The type III secretion system (T3SS) is an essential virulence factor for Shigella flexneri, providing a conduit through which host-altering effectors are injected directly into a host cell to promote uptake. The type III secretion apparatus (T3SA) is comprised of a basal body, external needle, and regulatory tip complex. The nascent needle is a polymer of MxiH capped by a pentamer of invasion plasmid antigen D (IpaD). Exposure to bile salts (e.g. deoxycholate) causes a conformational change in IpaD and promotes recruitment of IpaB to the needle tip. It has been proposed that IpaB senses contact with host cell membranes, recruiting IpaC and inducing full secretion of T3SS effectors. While the steps of T3SA maturation and their external triggers have been identified, details of specific protein interactions and mechanisms have remained difficult to study due to the hydrophobic nature of the IpaB and IpaC translocator proteins. Here we explored the ability for a series of soluble N-terminal IpaB peptides to interact with IpaD. We found that DOC is required for the interaction and that a region of IpaB between residues 11–27 is required for maximum binding, which was confirmed in vivo. Furthermore, intramolecular FRET measurements indicated that movement of the IpaD distal domain away from the protein core accompanied the binding of IpaB11-226. Together these new findings provide important new insight into the interactions and potential mechanisms that define the maturation of the Shigella T3SA needle tip complex and provide a foundation for further studies probing T3SS activation

Monopelopia caraguata (Chironomidae: Tanypodinae: Pentaneurini) and Phytotelmatocladius delarosai (Chironomidae: Orthocladiinae) : Two Phytotelmatous Chironomids Distributed from Florida to Argentina

Fil: Siri, Augusto. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Limnología Dr. Raúl A. Ringuelet; ArgentinaFil: Donato, Mariano. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Sistemática y Biología Evolutiva; Argentin

Tourism, inclusive growth and decent work: a political economy critique

This paper interrogates the ideas of ‘sustained’ and ‘inclusive’ growth that are intrinsic to one of three UN Sustainable Development Goals (SDG 8 - Decent Work and Growth) adopted by the UN World Tourism Organisation’s (UNWTO) 2030 sustainable tourism agenda. It provides a Marxian-inspired political economy critique of the UNWTO’s embrace of SDG8 and highlights the blind spot within the UNWTO’s inclusive growth-led SDG agenda with respect to questions of equity and social justice. The paper contends that the UNWTO’s SDG-led agenda is contradicted by the logics of growth, competitiveness and profit-making that drive the continued expansion and development of tourism. Rather than addressing the structural injustices that entrench inequalities and reproduce exploitative labour practices, the notion of sustained and inclusive growth reinforces the primacy of capital and market notions of justice and continues to perpetuate a growth driven tourism development model. The paper contributes to a critical theorization of sustainable tourism and offers an informed critique of the current political agenda for sustainable tourism and its potential outcomes

CD11b+, Ly6G+ Cells Produce Type I Interferon and Exhibit Tissue Protective Properties Following Peripheral Virus Infection

The goal of the innate immune system is containment of a pathogen at the site of infection prior to the initiation of an effective adaptive immune response. However, effector mechanisms must be kept in check to combat the pathogen while simultaneously limiting undesirable destruction of tissue resulting from these actions. Here we demonstrate that innate immune effector cells contain a peripheral poxvirus infection, preventing systemic spread of the virus. These innate immune effector cells are comprised primarily of CD11b+Ly6C+Ly6G- monocytes that accumulate initially at the site of infection, and are then supplemented and eventually replaced by CD11b+Ly6C+Ly6G+ cells. The phenotype of the CD11b+Ly6C+Ly6G+ cells resembles neutrophils, but the infiltration of neutrophils typically occurs prior to, rather than following, accumulation of monocytes. Indeed, it appears that the CD11b+Ly6C+Ly6G+ cells that infiltrated the site of VACV infection in the ear are phenotypically distinct from the classical description of both neutrophils and monocyte/macrophages. We found that CD11b+Ly6C+Ly6G+ cells produce Type I interferons and large quantities of reactive oxygen species. We also observed that depletion of Ly6G+ cells results in a dramatic increase in tissue damage at the site of infection. Tissue damage is also increased in the absence of reactive oxygen species, although reactive oxygen species are typically thought to be damaging to tissue rather than protective. These data indicate the existence of a specialized population of CD11b+Ly6C+Ly6G+ cells that infiltrates a site of virus infection late and protects the infected tissue from immune-mediated damage via production of reactive oxygen species. Regulation of the action of this population of cells may provide an intervention to prevent innate immune-mediated tissue destruction

Timing is everything: the regulation of type III secretion

Type Three Secretion Systems (T3SSs) are essential virulence determinants of many Gram-negative bacteria. The T3SS is an injection device that can transfer bacterial virulence proteins directly into host cells. The apparatus is made up of a basal body that spans both bacterial membranes and an extracellular needle that possesses a channel that is thought to act as a conduit for protein secretion. Contact with a host-cell membrane triggers the insertion of a pore into the target membrane, and effectors are translocated through this pore into the host cell. To assemble a functional T3SS, specific substrates must be targeted to the apparatus in the correct order. Recently, there have been many developments in our structural and functional understanding of the proteins involved in the regulation of secretion. Here we review the current understanding of protein components of the system thought to be involved in switching between different stages of secretion

The relationships between exogenous and endogenous antioxidants with the lipid profile and oxidative damage in hemodialysis patients

Background: We sought to investigate the relationships among the plasma levels of carotenoids, tocopherols, endogenous antioxidants, oxidative damage and lipid profiles and their possible effects on the cardiovascular risk associated with hemodialysis (HD) patients. Methods: The study groups were divided into HD and healthy subjects. Plasma carotenoid, tocopherol and malondialdehyde (MDA) levels, as well as erythrocyte reduced glutathione (GSH), were measured by HPLC. Blood antioxidant enzymes, kidney function biomarkers and the lipid profiles were analyzed by spectrophotometric methods. Results: Plasma lycopene levels and blood glutathione peroxidase (GPx) activity were significantly decreased in HD patients compared with healthy subjects. Total cholesterol, low-density lipoprotein cholesterol (LDL-c), creatinine, urea, MDA, GSH, superoxide dismutase (SOD) and catalase (CAT) were significantly increased in HD (p < 0.05). Lycopene levels were correlated with MDA (r = -0.50; p < 0.01), LDL-c (r = -0.38; p = 0.01) levels, the LDL-c/HDL-c index (r = -0.33; p = 0.03) and GPx activity (r = 0.30; p = 0.03). Regression models showed that lycopene levels were correlated with LDL-c (β estimated = -31.59; p = 0.04), while gender was correlated with the TC/HDL-c index and triglycerides. Age did not present a correlation with the parameters evaluated. GPx activity was negatively correlated with MDA levels and with the LDL-c/HDL-c and CT/HDL-c indexes. Conclusions: Lycopene may represent an additional factor that contributes to reduced lipid peroxidation and atherogenesis in hemodialysis patients