Lipid and Protein Sorting by, and Generation of, Membrane Curvature in Model Systems

The potential physiological relevance of liquid-liquid phase separation in lipid membranes to the formation and stability of “lipid rafts” in cellular plasma membranes has prompted extensive investigation of the physical chemistry underlying these phenomena. Furthermore, the concept of lipid rafts – 10-200 nm regions of cellular membrane enriched in specific lipids and proteins to enable complex processes – has led naturally to questions concerning the sorting of both lipids and proteins between membranes of different organelles within the cell, each with distinct lipid and protein composition. The shapes and, more specifically, the curvatures of membrane transport intermediates have been invoked to play a role in both lipid and protein sorting. In addition, lipid and protein composition may directly affect the membrane curvature. In this contribution, the line tension and dipole density differences between demixed fluid phases of monolayers comprised of dimyristoylphosphatidylcholine and dihydrocholesterol were investigated by measuring the two-dimensional thermal fluctuations of domain boundaries. These parameters are essential determinants of domain stability, and their quantification will yield an increased understanding of the physical processes responsible for aspects of lateral phase separation. Furthermore, phase-separated giant unilamellar vesicles from which are pulled thin cylindrical tubes are employed to understand domain nucleation in curvature gradients, complemented by measurements of the biophysical force required to pull such tubes. These results indicate that strong lipid-lipid interactions can lead to lipid sorting by curvature, as well as present diffusion barriers to enable selective sorting of lipids and proteins. Finally, the curvature generation of Drosophila amphiphysin N-BAR domain is quantitatively assessed through the tube-pulling assay as before but performed using homogenous lipid membranes. Fluorescently-labeled protein preferentially sorted into the high (positive) curvature of the tubes from the essentially flat vesicle. Furthermore, the measured tube force decreased to lower equilibrium values in a protein concentration-dependent manner. Future measurements on other BAR domains will improve upon previous qualitative comparisons of curvature generation ability. Collectively, the results provide quantitative assessment of several biophysical parameters underlying the lateral sorting of lipids and proteins

University Education: The Challenges of 21st Century

The article discusses the prospects for the universities development in the modern knowledge society. The main objective of the research is to determine the conditions for the universities transformation from relatively close knowledge-generating structures to the full-fledged constituents of the civil society. To this end, various factors are examined that form the external environment of universities and impact the establishment of their internal context. The research is conducted with the use of comparative analysis method which allows revealing the common and specific features in the development trends of American, European, and Russian universities. The state and market are considered as significant elements of the external environment. It is shown that in the democratic post-industrial society the state traditionally playing a key role in universities development delegates a number of its functions in terms of university management to the civil societies. The substantiation is provided for the necessity to form the universities’ strategy in the market environment as a means for enhancing their competitiveness. The author further shows how such factors as globalization, internationalization and demography change impact the implementation of both the challenging task of establishing world class universities and the objective to implement the principle of equal opportunities in the educational field. Eventually, a number of conditions are defined that will allow making universities and higher education as a whole not only part of innovative economy but also the foundation for sustainable and fair society

Quadruplewild-type (WT) GIST: defining the subset of GIST that lacks abnormalities of KIT, PDGFRA, SDH, or RAS signaling pathways

A subset of GISTs lack mutations in the KIT/PDGFRA or RAS pathways and yet retain an intact succinate dehydrogensase (SDH) complex. We propose that these KIT/PDGFRA/SDH/RAS-P WT GIST tumors be designated as quadruple wild-type (WT) GIST. Further molecular and clinicophatological characterization of quadruple WT GIST will help to determine their prognosis as well as assist in the optimization of medical management, including clinical test of novel therapies

Why the visual recognition system might encode the effects of illumination

A key problem in recognition is that the image of an object depends on the lighting conditions. We investigated whether recognition is sensitive to illumination using 3-D objects that were lit from either the left or right, varying both the shading and the cast shadows. In experiments 1 and 2 participants judged whether two sequentially presented objects were the same regardless of illumination. Experiment 1 used six objects that were easily discriminated and that were rendered with cast shadows. While no cost was found in sensitivity, there was a response time cost over a change in lighting direction. Experiment 2 included six additional objects that were similar to the original six objects making recognition more difficult. The objects were rendered with cast shadows, no shadows, and as a control, white shadows. With normal shadows a change in lighting direction produced costs in both sensitivity and response times. With white shadows there was a much larger cost in sensitivity and a comparable cost in response times. Without cast shadows there was no cost in either measure, but the overall performance was poorer. Experiment 3 used a naming task in which names were assigned to six objects rendered with cast shadows. Participants practised identifying the objects in two viewpoints lit from a single lighting direction. Viewpoint and illumination invariance were then tested over new viewpoints and illuminations. Costs in both sensitivity and response time were found for naming the familiar objects in unfamiliar lighting directions regardless of whether the viewpoint was familiar or unfamiliar. Together these results suggest that illumination effects such as shadow edges: (1) affect visual memory; (2) serve the function of making unambigous the three-dimensional shape

Myocardial perfusion and viability by positron emission tomography in infants and children with coronary abnormalities correlation with echocardiography,coronary angiography, and histopathology

AbstractObjectivesThis study was designed to assess the feasibility and accuracy of positron emission tomography (PET) imaging in infants and children.BackgroundPositron emission tomography is employed in adults for the evaluation of myocardial perfusion and the detection of myocardial viability.MethodsPerfusion and metabolism findings on PET in infants and children with suspected coronary abnormalities (age 14 days to 12 years old, mean 3.3 ± 4.0 years) were correlated with findings on coronary angiography, echocardiography, and myocardial histopathology. The segmental myocardial uptake of the flow tracer 13N-ammonia and of the glucose tracer 18F-deoxyglucose (18FDG) was graded on a five-point scale and compared with the angiographic perfusion score, with regional wall motion, and the presence of fibrosis.ResultsThere was an agreement of r = 0.72 (p < 0.05) between regional myocardial perfusion and angiography. The correlation of histopathologic changes with normal, moderately, and severely reduced segmental 13N-ammonia uptake was 87%, 60%, and 75%, respectively. Segmental myocardial 18FDG uptake and histopathologic findings were concordant in 48 (79%) of 64 segments without fibrosis; absence of viability by perfusion and metabolism imaging correlated with the presence of fibrosis in 21 (84%) of 25 segments.ConclusionsThe observed agreements between the findings on PET perfusion and metabolism imaging with those on coronary angiography, echocardiography, and histopathology support the utility and accuracy of PET for characterizing myocardial perfusion abnormalities and viability in pediatric patients

Magnetoresistance Anisotropy of Polycrystalline Cobalt Films: Geometrical-Size- and Domain-Effects

The magnetoresistance (MR) of 10 nm to 200 nm thin polycrystalline Co-films, deposited on glass and insulating Si(100), is studied in fields up to 120 kOe, aligned along the three principal directions with respect to the current: longitudinal, transverse (in-plane), and polar (out-of-plane). At technical saturation, the anisotropic MR (AMR) in polar fields turns out to be up to twice as large as in transverse fields, which resembles the yet unexplained geometrical size-effect (GSE), previously reported for Ni- and Permalloy films. Upon increasing temperature, the polar and transverse AMR's are reduced by phonon-mediated sd-scattering, but their ratio, i.e. the GSE remains unchanged. Basing on Potters's theory [Phys.Rev.B 10, 4626(1974)], we associate the GSE with an anisotropic effect of the spin-orbit interaction on the sd-scattering of the minority spins due to a film texture. Below magnetic saturation, the magnitudes and signs of all three MR's depend significantly on the domain structures depicted by magnetic force microscopy. Based on hysteresis loops and taking into account the GSE within an effective medium approach, the three MR's are explained by the different magnetization processes in the domain states. These reveal the importance of in-plane uniaxial anisotropy and out-of-plane texture for the thinnest and thickest films, respectively.Comment: 10 pages, 9 figure

Clinical Activity of Ripretinib in Patients with Advanced Gastrointestinal Stromal Tumor Harboring Heterogeneous KIT/PDGFRA Mutations in the Phase III INVICTUS Study

Ripretinib; Mutacions; Neoplàsies gastrointestinalsRipretinib; Mutations; Gastrointestinal neoplasmsRipretinib; Mutaciones; Neoplasias gastrointestinalesPurpose: Most patients with gastrointestinal stromal tumor (GIST) have activating mutations in KIT/PDGFRA and are initially responsive to tyrosine kinase inhibitors (TKI). The acquisition of secondary mutations leads to refractory/relapsed disease. This study reports the results of an analysis from the phase III INVICTUS study (NCT03353753) characterizing the genomic heterogeneity of tumors from patients with advanced GIST and evaluating ripretinib efficacy across KIT/PDGFRA mutation subgroups. Patients and Methods: Tumor tissue and liquid biopsy samples that captured circulating tumor DNA were collected prior to study enrollment and sequenced using next-generation sequencing. Subgroups were determined by KIT/PDGFRA mutations and correlation of clinical outcomes and KIT/PDGFRA mutational status was assessed. Results: Overall, 129 patients enrolled (ripretinib 150 mg once daily, n = 85; placebo, n = 44). The most common primary mutation subgroup detected by combined tissue and liquid biopsies were in KIT exon 11 (ripretinib, 61.2%; placebo, 77.3%) and KIT exon 9 (ripretinib, 18.8%; placebo, 15.9%). Patients receiving ripretinib demonstrated progression-free survival (PFS) benefit versus placebo regardless of mutation status (HR 0.16) and in all assessed subgroups in Kaplan–Meier PFS analysis (exon 11, P < 0.0001; exon 9, P = 0.0023; exon 13, P < 0.0001; exon 17, P < 0.0001). Among patients with wild-type KIT/PDGFRA by tumor tissue, PFS ranged from 2 to 23 months for ripretinib versus 0.9 to 10.1 months for placebo. Conclusions: Ripretinib provided clinically meaningful activity across mutation subgroups in patients with advanced GIST, demonstrating that ripretinib inhibits a broad range of KIT/PDGFRA mutations in patients with advanced GIST who were previously treated with three or more TKIs

A multicenter, dose-finding, phase 1b study of imatinib in combination with alpelisib as third-line treatment in patients with advanced gastrointestinal stromal tumor

Alpelisib; Gastrointestinal stromal tumor; ImatinibAlpelisib; Tumor estromal gastrointestinal; ImatinibAlpelisib; Tumor estromal gastrointestinal; ImatinibBackground Acquired resistance to approved tyrosine kinase inhibitors limits their clinical use in patients with gastrointestinal stromal tumor (GIST). This study investigated the safety, tolerability and efficacy of alpelisib, a phosphatidylinositol 3-kinase inhibitor, used in combination with imatinib in patients with advanced GIST who had failed prior therapy with both imatinib and sunitinib. Methods This phase 1b, multicenter, open-label study consisted of 2 phases: dose escalation and dose expansion. Dose escalation involved 200 mg once daily (QD) alpelisib, initially, followed by 250 and 350 mg. These were combined with 400 mg QD imatinib until maximum tolerated dose (MTD) and/or a recommended phase 2 dose (RP2D) of alpelisib in combination with imatinib was determined. This MTD/RP2D dose was tested to evaluate the clinical activity of this combination in dose expansion. Results Fifty-six patients were enrolled, 21 and 35 in the dose escalation and expansion phases, respectively. The MTD of alpelisib given with imatinib was determined as 350 mg QD. Combination treatment showed partial response in 1 (2.9%) and stable disease in 15 (42.9%) patients. Median progression-free survival was 2 months (95% CI 1.8–4.6). Overall, 92.9% patients had adverse events (AEs) while 46.4% had grade 3/4 AEs, hyperglycemia being the most common (23.2%). Conclusions The MTD of alpelisib was estimated as 350 mg QD when used in combination with imatinib 400 mg QD after oral administration in patients with advanced GIST. The safety and tolerability profile of this combination was acceptable; however, the combination did not demonstrate sufficient clinical activity to justify additional clinical testing.The study was funded by the Novartis Pharma AG, Basel, Switzerland