Contact probing of prestressed adhesive membranes of living cells.

Atomic force microscopy (AFM) studies of living biological cells is one of main experimental tools that enable quantitative measurements of deformation of the cells and extraction of information about their structural and mechanical properties. However, proper modelling of AFM probing and related adhesive contact problems are of crucial importance for interpretation of experimental data. The Johnson-Kendall-Roberts (JKR) theory of adhesive contact has often been used as a basis for modelling of various phenomena including cell-cell interactions. However, strictly speaking the original JKR theory is valid only for contact of isotropic linearly elastic spheres, while the cell membranes are often prestressed. For the first time, effects caused by molecular adhesion for living cells are analytically studied taking into account the mechanical properties of cell membranes whose stiffness depends on the level of the tensile prestress. Another important question is how one can extract the work of adhesion between the probe and the cell. An extended version of the Borodich-Galanov method for non-direct extraction of elastic and adhesive properties of contacted materials is proposed to apply to experiments of cell probing. Evidently, the proposed models of adhesive contact for cells with prestressed membranes do not cover all types of biological cells because the structure and properties of the cells may vary considerably. However, the obtained results can be applied to many types of smooth cells and can be used to describe initial stages of contact and various other processes when effects of adhesion are of crucial importance. This article is part of a discussion meeting issue 'A cracking approach to inventing new tough materials: fracture stranger than friction'.

Are older adults also at higher psychological risk from COVID-19?

OBJECTIVE: Given the lack of information on the psychological impact of COVID-19 on people aged ≥60, we aimed to describe their psychological responses to this pandemic and lockdown situation and compare them with those under 60 years of age. METHODS: Secondary analysis of a larger online cross-sectional study designed to determine the psychological impact of the COVID-19 pandemic and lockdown across Spain. We analyzed a total of 1690 respondents aged ≥60 years and compared them with 13,363 respondents under 60 years of age. We employed the Depression, Anxiety, and Stress Scale and the Impact of Event Scale to evaluate psychological responses. RESULTS: In all, 52.6% of women and 34.3% of men were found to be probable cases of any emotional distress (p < 0.001). In both sexes, the most common psychological response was avoidance behavior (34.7% and 23.8%, respectively), followed by depression (28.5 and 14.2%). Older women and men were considered probable cases of any emotional distress less often than younger ones (women: 52.6% vs. 72.3%, p < 0.001; men: 34.3% vs. 50.6%, p < 0.001). Finally, the results of the binary logistic regression showed that only depressive and stress responses are psychological factors associated with age group [age ≥ 60 years, O.R. = 0.617 (95% CI = 0.501 - 0.759) and 0.437 (95% CI = 0.334 - 0.573), respectively]. CONCLUSION: Contrary to our hypothesis and despite the high percentage of emotional distress we found in older adults, especially women, they are actually at lower risk of developing depressive and stress consequences from COVID-19 and lockdown than those under 60 years of age. That said, we believe our results highlight the need for expert guidance in this age group, especially older women living alone.

Infarto agudo del miocardio en un paciente con situs inversus total / Acute myocardial infarction in a patient with total situs inversus

El situs inversus es una rara malformación congénita que puede afectar varios órganos y tiene un carácter hereditario. Consiste en una alineación errónea de los órganos dentro del cuerpo: se colocan del lado opuesto (imagen en espejo). Se presenta un paciente masculino de 64 años que lo padece, fumador inveterado, que después de un esfuerzo físico intenso comenzó con dolor precordial opresivo con sensación de muerte y relajación de esfínteres(AU)