Structure-Function Analysis of Invasion Plasmid Antigen C (IpaC) from Shigella flexneri

Shigella flexneri causes a self-limiting gastroenteritis in humans, characterized by severe localized inflammation and ulceration of the colonic mucosa. Shigellosis most often targets young children in underdeveloped countries. Invasion plasmid antigen C (IpaC) has been identified as the primary effector protein for Shigella invasion of epithelial cells. Although an initial model of IpaC function has been developed, no detailed structural information is available that could assist in a better understanding of the molecular basis for its interactions with the host cytoskeleton and phospholipid membrane. We have therefore initiated structural studies of IpaC, IpaC I′, (residues 101–363 deleted), and IpaC ΔH (residues 63–170 deleted). The secondary and tertiary structure of the protein was examined as a function of temperature, employing circular dichroism and high resolution derivative absorbance techniques. ANS (8-anilino-1-napthalene sulfonic acid) was used to probe the exposure of the hydrophobic surfaces under different conditions. The interaction of IpaC and these mutants with a liposome model (liposomes with entrapped fluorescein) was also examined. Domain III (residues 261–363) was studied using linker-scanning mutagenesis. It was shown that domain III contains periodic, sequence-dependent activity, suggesting helical structure in this section of the protein. In addition to these structural studies, investigation into the actin nucleation properties of IpaC was conducted, and actin nucleation by IpaC and some of the mutants was exhibited. Structure-function relationships of IpaC are discussed

Subcellular localization of MC4R with ADCY3 at neuronal primary cilia underlies a common pathway for genetic predisposition to obesity.

Most monogenic cases of obesity in humans have been linked to mutations in genes encoding members of the leptin-melanocortin pathway. Specifically, mutations in MC4R, the melanocortin-4 receptor gene, account for 3-5% of all severe obesity cases in humans1-3. Recently, ADCY3 (adenylyl cyclase 3) gene mutations have been implicated in obesity4,5. ADCY3 localizes to the primary cilia of neurons 6 , organelles that function as hubs for select signaling pathways. Mutations that disrupt the functions of primary cilia cause ciliopathies, rare recessive pleiotropic diseases in which obesity is a cardinal manifestation 7 . We demonstrate that MC4R colocalizes with ADCY3 at the primary cilia of a subset of hypothalamic neurons, that obesity-associated MC4R mutations impair ciliary localization and that inhibition of adenylyl cyclase signaling at the primary cilia of these neurons increases body weight. These data suggest that impaired signaling from the primary cilia of MC4R neurons is a common pathway underlying genetic causes of obesity in humans

A Review on the Mechanical Modeling of Composite Manufacturing Processes

© 2016, The Author(s). The increased usage of fiber reinforced polymer composites in load bearing applications requires a detailed understanding of the process induced residual stresses and their effect on the shape distortions. This is utmost necessary in order to have more reliable composite manufacturing since the residual stresses alter the internal stress level of the composite part during the service life and the residual shape distortions may lead to not meeting the desired geometrical tolerances. The occurrence of residual stresses during the manufacturing process inherently contains diverse interactions between the involved physical phenomena mainly related to material flow, heat transfer and polymerization or crystallization. Development of numerical process models is required for virtual design and optimization of the composite manufacturing process which avoids the expensive trial-and-error based approaches. The process models as well as applications focusing on the prediction of residual stresses and shape distortions taking place in composite manufacturing are discussed in this study. The applications on both thermoset and thermoplastic based composites are reviewed in detail

Genetic ablation or chemical inhibition of phosphatidylcholine transfer protein attenuates diet?induced hepatic glucose production†‡

 Phosphatidylcholine transfer protein (PC?TP, synonym StARD2) is a highly specific intracellular lipid binding protein that is enriched in liver. Coding region polymorphisms in both humans and mice appear to confer protection against measures of insulin resistance. The current study was designed to test the hypotheses that Pctp?/? mice are protected against diet?induced increases in hepatic glucose production and that small molecule inhibition of PC?TP recapitulates this phenotype. Pctp?/? and wildtype mice were subjected to high?fat feeding and rates of hepatic glucose production and glucose clearance were quantified by hyperinsulinemic euglycemic clamp studies and pyruvate tolerance tests. These studies revealed that high?fat diet?induced increases in hepatic glucose production were markedly attenuated in Pctp?/? mice. Small molecule inhibitors of PC?TP were synthesized and their potencies, as well as mechanism of inhibition, were characterized in vitro. An optimized inhibitor was administered to high?fat?fed mice and used to explore effects on insulin signaling in cell culture systems. Small molecule inhibitors bound PC?TP, displaced phosphatidylcholines from the lipid binding site, and increased the thermal stability of the protein. Administration of the optimized inhibitor to wildtype mice attenuated hepatic glucose production associated with high?fat feeding, but had no activity in Pctp?/? mice. Indicative of a mechanism for reducing glucose intolerance that is distinct from commonly utilized insulin?sensitizing agents, the inhibitor promoted insulin?independent phosphorylation of key insulin signaling molecules. Conclusion: These findings suggest PC?TP inhibition as a novel therapeutic strategy in the management of hepatic insulin resistance

Transcriptional Regulation in Non-Alcoholic Fatty Liver Disease

Obesity is the primary risk factor for the pathogenesis of non-alcoholic fatty liver disease (NAFLD), the worldwide prevalence of which continues to increase dramatically. The liver plays a pivotal role in the maintenance of whole-body lipid and glucose homeostasis. This is mainly mediated by the transcriptional activation of hepatic pathways that promote glucose and lipid production or utilization in response to the nutritional state of the body. However, in the setting of chronic excessive nutrition, the dysregulation of hepatic transcriptional machinery promotes lipid accumulation, inflammation, metabolic stress, and fibrosis, which culminate in NAFLD. In this review, we provide our current understanding of the transcription factors that have been linked to the pathogenesis and progression of NAFLD. Using publicly available transcriptomic data, we outline the altered activity of transcription factors among humans with NAFLD. By expanding this analysis to common experimental mouse models of NAFLD, we outline the relevance of mouse models to the human pathophysiology at the transcriptional level

Levosimendan for ischemic preconditioning in thoracic aortic aneurysm repair

Background and Aim: Postoperative neurologic deficit is the most devastating complication after surgical thoracic aorta repair. Cerebrospinal fluid drainage and some medications are used for spinal cord protection during and after the operation. Methods: A 25-year-old patient applied to our clinic with a traumatic descending aortic aneurysm. We performed a surgical repair for the aneurysm but could not achieve to place a lumbar catheter to provide cerebrospinal fluid drainage. Levosimendan was chosen for spinal cord ischemic preconditioning because of its vasodilatory effects. Results: Postoperative course was uneventful. Hemodynamic and neurologic complication was not observed, and the patient was discharged from the hospital in the postoperative 5th day. Conclusions: Levosimendan can be used for preconditioning and spinal cord protection from ischemic injury during descending aorta repair. We clearly benefit from the vasodilator peculiarity of the drug for improving spinal cord perfusion

Mechanical Modelling of Pultrusion Process: 2D and 3D Numerical Approaches

The process induced variations such as residual stresses and distortions are a critical issue in pultrusion, since they affect the structural behavior as well as the mechanical properties and geometrical precision of the final product. In order to capture and investigate these variations, a mechanical analysis should be performed. In the present work, the two dimensional (2D) quasi-static plane strain mechanical model for the pultrusion of a thick square profile developed by the authors is further improved using generalized plane strain elements. In addition to that, a more advanced 3D thermo-chemical-mechanical analysis is carried out using 3D quadratic elements which is a novel application for the numerical modelling of the pultrusion process. It is found that the 2D mechanical models give relatively reasonable and accurate stress and displacement evolutions in the transverse direction as compared to the 3D model. Moreover, the generalized plane strain model predicts the longitudinal process induced stresses more similar to the ones calculated in the 3D model as compared with the plane strain model