CALM supports clathrin-coated vesicle completion upon membrane tension increase

The most represented components of clathrin-coated vesicles (CCVs) are clathrin triskelia and the adaptors clathrin assembly lymphoid myeloid leukemia protein (CALM) and the heterotetrameric complex AP2. Investigation of the dynamics of AP180-amino-terminal-homology (ANTH) recruitment during CCV formation has been hampered by CALM toxicity upon overexpression. We used knock-in gene editing to express a C-terminal–attached fluorescent version of CALM, while preserving its endogenous expression levels, and cutting-edge live-cell microscopy approaches to study CALM recruitment at forming CCVs. Our results demonstrate that CALM promotes vesicle completion upon membrane tension increase as a function of the amount of this adaptor present. Since the expression of adaptors, including CALM, differs among cells, our data support a model in which the efficiency of clathrin-mediated endocytosis is tissue specific and explain why CALM is essential during embryogenesis and red blood cell development.

Myocardial stress of the left ventricle during occupational vibration

Aim. Study of intramyocardial stress of the left ventricle (LV) in persons exposed to occupational vibration and patients with hand-arm vibration syndrome (HAVS). Materials and methods. We examined 15 individuals exposed to vibration, 44 individuals with grade 1 HAVS, 10 individuals with grade 2. The control group consisted of 20 persons without cardiovascular pathology, who had not been exposed to hazardous occupational factors. The main occupational hazards in persons with HAVS were vibration, noise, physical exertion. Echocardiography was carried out to determine the total volume of LV (Vtotal); the volume of myocardium (Vm); myocardial mass (LVMM); myocardial mass index (LVMMI); systolic intraventricular pressure; the intensity of the functioning of the LV structures; LV circumferential and meridional diastolic and systolic stresses (σcd, σcs and σmd, σms respectively); LV tension in the circumferential and meridional direction during systole and diastole (Tcs, Tcd and Tms, Tmd respectively). Results. In persons exposed to vibration, in comparison with those who have not been exposed to occupational hazards, there is an increase in σmd by 2.5 times (p < 0.05) and σcd by 2.8 times (p < 0.05). The tension increases during systole and diastole both in the circumferential (Tcs by 17.35%, p < 0.05; Tms by 2.74 times, p < 0.05) and in the meridional (Tcd by 14.59%, p < 0.05; Tmd by 2.76 times, p < 0.05) directions. In persons with grade 1 HAVS, there is an increase during diastole σmd by 2.2 times (p < 0.05), σcd by 2.4 times (p < 0.05), and Tmd (p < 0.05) and Tms by 2.5 times (p < 0.05). In patients with grade 2 HAVS, in contrast to those with grade 1 and persons exposed to vibration, there is a change in the working conditions of LV. With the same values of Vtotal, Vm, LVMM and LVMMI, as in the described groups, in patients with grade 2 HAVS, there is a decrease by 12.3% (p < 0.05) in systolic intraventicular pressure against the background of an increase in σmd by 14.7% (p < 0.05), Tmd by 13.6% (p < 0.05), as well as σms by 2.25 times (p < 0.05) and Tcd by 1.97 times (p < 0.05). Conclusion. In the group of persons exposed to vibration and patients with grade 1 HAVS, in contrast to those who are not exposed to occupational hazards, there is an increase in stress and tension, primarily in the circumferential direction during diastole, which indicates the activation of the heterometric type of autoregulation of activity of the heart. In patients with grade 2 HAVS, stress and tension increase in the meridional direction during systole, which indicates the levelling of LV hyperfunction by isotonic type.

Increased lateral tension is sufficient for epithelial folding in Drosophila

ABSTRACTThe folding of epithelial sheets is important for tissues, organs and embryos to attain their proper shapes. Epithelial folding requires subcellular modulations of mechanical forces in cells. Fold formation has mainly been attributed to mechanical force generation at apical cell sides, but several studies indicate a role of mechanical tension at lateral cell sides in this process. However, whether lateral tension increase is sufficient to drive epithelial folding remains unclear. Here, we have used optogenetics to locally increase mechanical force generation at apical, lateral or basal sides of epithelial Drosophila wing disc cells, an important model for studying morphogenesis. We show that optogenetic recruitment of RhoGEF2 to apical, lateral or basal cell sides leads to local accumulation of F-actin and increase in mechanical tension. Increased lateral tension, but not increased apical or basal tension, results in sizeable fold formation. Our results stress the diversification of folding mechanisms between different tissues and highlight the importance of lateral tension increase for epithelial folding.

Experimental study on the influence of coal powders on the performance of water-based polymer drilling fluid

Coal powders, as cuttings, invade the drilling fluid along a coal seam during coalbed methane development, thereby changing the properties of the drilling fluid. Therefore, this work aims to investigate the influence of coal powders on drilling fluid performance. The powders of lignite, anthracite, and contrasting shale were added to a water-based polymer drilling fluid. Then, the rheology, filtration, lubricity, and adhesiveness were measured, and the natural degradation, as well as the wettability were further evaluated. The results show that some parameters of the drilling fluid, including viscosity, lubrication coefficient, adhesion coefficient, contact angle, and surface tension, increase after adding coal powders, while other parameters, such as filtration loss and natural degradation, decrease. Compared with lignite and shale, anthracite powders, with the lowest mineral content, exhibit the smallest change in the rheological property, lubricity, adhesion, and natural degradation of the drilling fluid. Moreover, the content and size of the coal powders generally have opposing effects on the drilling fluid. When the coal powder content reaches 3 wt.%, the surface tension and contact angle of the drilling fluid show more evident changes than other parameters. Based on the analysis of the stress intensity factor, the drilling fluid with coal powders exceeding 100 mesh can reduce the capillary force in microfractures, and in combination with other factors (such as reduced filtration loss and sealing and supporting of the microfractures), improves wellbore stability. Therefore, coal powders with suitable particle sizes and concentration levels are expected to become a new drilling fluid material to protect coal field reservoirs.

Effect of surfactant redistribution on the flow and stability of foam films

The viscous froth model for two-dimensional (2D) dissipative foam rheology is combined with Marangoni-driven surfactant redistribution on a foam film. The model is used to study the flow of a 2D foam system consisting of one bubble partially filling a constricted channel and a single spanning film connecting it to the opposite channel wall. Gradients of surface tension arising from film deformation induce tangential flow that redistributes surfactant along the film. This redistribution, and the consequent changes in film tension, inhibit the structure from undergoing a foam-destroying topological change in which the spanning film leaves the bubble behind; foam stability is thereby increased. The system’s behaviour is categorized by a Gibbs–Marangoni parameter, representing the ratio between the rate of motion in tangential and normal directions. Larger values of the Gibbs–Marangoni parameter induce greater variation in surface tension, increase the rate of surfactant redistribution and reduce the likelihood of topological changes. An intermediate regime is, however, identified in which the Gibbs–Marangoni parameter is large enough to create a significant gradient of surface tension but is not great enough to smooth out the flow-induced redistribution of surfactant entirely, resulting in non-monotonic variation in the bubble height, and hence in foam stability.

The use of EEG biofeedback to improve memory, concentration, attention and reduce emotional tension

Biofeedback is a method of giving patients computerised feedback signals about changes in the physiological state of their body. This allows them to learn how to consciously modify functions not controlled consciously. This method allows active and conscious involvement of the patient in controlling their own physiological processes. The therapy aims to regulate the frequency of human brain waves. The human brain produces different ranges of waves that are characteristic of different types of human activity, a mechanism used in this method. The use of this method in routine rehabilitation with a specifically designed computer programme provides physicians, physiotherapists, neuropsychologists and speech therapists with a new tool for treatment, opportunities for improvement in treatment, and helps them better plan and develop treatment strategies using Evidence-Based Medicine. The aim of the work is to discuss how EEG Biofeedback software can be applied in neurorehabilitation and to discuss the use of EEG Biofeedback software in order to improve memory, concentration, attention, reduce emotional tension, increase resistance to stress, improve self-control, self-esteem and relaxation. Key words EEG biofeedback, neurorehabilitation, computer software in rehabilitation Article received: 14.01.2019; Accepted: 17.09.2019

Force Barrier for Lipid Sorting in the Formation of Membrane Nanotubes

Understanding lipid sorting of multicomponent cell membranes associated with tubular deformation is of essential importance to many cell activities such as filopodial growth and protein-mediated vesiculation. Here, we conduct theoretical analysis to investigate how the membrane tubulation induced by an external pulling force over a finite region is regulated by the coupling between the lipid composition and the membrane bending rigidity and tension. It is shown that the presence of the lipid-disordered phase facilitates the nanotube formation by reducing the force barrier. As the pulling region size and the membrane tension increase, the membrane tubulation becomes discontinuous regardless of the coupling effect. The direct proportional relationships between the maximum pulling force and size of pulling region at different coupling scenarios are identified. Analytical solutions for the linear force-extraction relation and the membrane configurations in the early stage of the membrane extraction are obtained. Our results indicate that in the case of a relatively small pulling region, the coupling between the membrane composition and mechanical properties plays an important role in regulating the membrane extraction, and such an effect due to the phase separation diminishes gradually as the pulling region enlarges and the force barrier becomes dominated by a large pulling region.

Cholesterol depletion by MβCD enhances membrane tension, its heterogeneity and affects cellular integrity

Cholesterol depletion in cells by MβCD remodels the plasma membrane’s mechanics and its interactions with the underlying cytoskeleton. Decoupling the two effects and studying various alterations to the membrane’s mechanical parameters is important for understanding cholesterol’s role in cellular response to stress. By mapping membrane height fluctuations in single cells, we report that MβCD treatment reduces temporal fluctuations and flattens out the membrane – but does not supress activity-driven fluctuations. We find that membrane tension increase contributes most to the altered fluctuations, among the multiple mechanical parameters computed. Maps also reveal an enhanced long-range heterogeneity within single cells, both in amplitude of fluctuations and membrane tension on cholesterol depletion. To check if this alters the tenacity of membrane to mechanical stress we use hypo-osmotic shock. We find that on MβCD treatment, cells are more prone to rupture than control cells, and this is not hindered by actomyosin perturbations. We report increased rupture sizes on cholesterol depletion and argue that, together, this indicates decreased lysis and line tension. Therefore, we show that cholesterol depletion directly affects cell membranes not only by enhancing membrane-cytoskeleton interactions, but also by increasing membrane tension while reducing lysis tension – hence making cells prone to rupture.

Supporting ESL Students in Distance Learning Courses

Skill gaps between faculty's expectations around assessments and student work are common pedagogical themes. When misunderstandings are compounded by linguistic barriers and variances in cultural expectations, a simple error can have unforeseen impact on student success and the student-faculty relationship. In this chapter, the author explores sociocultural theory and second language acquisition research for tools that can improve communication between faculty and English language learner students. A proactive strategy is proposed that promotes understanding of the learner, investigates faculty assumptions, uses transparency in communication of assumptions, and provides ongoing support to faculty and students to reduce tension, increase understanding, and promote student success.

Monitoring of underground subsurface structures in Ekaterinburg

This paper presents the issues of technical state of subsurface structures in operation and the erection of buildings under available development. It is stated that detailed monitoring of technical state of underground tunnels is essential, since the structure is unique and technologically complex. The aspects of geotechnical monitoring of underground tunnels are considered. The principles of geodesic monitoring of underground rings, tension increase in tube lining and pressure from the building under construction on the ground are described. Recommendations for underground tunnel monitoring are presented.