Quantal Sarcomere-length Changes in Relaxed Single Myofibrils

We carried out experiments on single isolated myofibrils in which thin filaments had been functionally removed, leaving the connecting (titin) filaments as the sole agent taking up the length change. With technical advances that gave sub-nanometer detectability we examined the time course of single sarcomere-length change when the myofibril was ramp-released or ramp-stretched by a motor. The sarcomere-length change was stepwise. Step sizes followed a consistent pattern: the smallest was ∼2.3 nm, and others were integer multiples of that value. The ∼2.3-nm step quantum is the smallest consistent biomechanical event ever demonstrated. Although the length change must involve the connecting filament, the size of the quantum is an order of magnitude smaller than anticipated from folding of Ig- or fibronectin-like domains, implying either that folding occurs in sub-domain units or that other mechanisms are involved

Ferrogels based on commertial microparticles of magnetite or strontium ferrite

This work was supported by Russian Science Foundation grant 18-19-00090

Коронарный парадокс

This work is a scientific and educational analytical review intended for practicing cardiologists. The purpose of the review is to draw physicians’ attention to the role of myocardial contractility in the regulation of coronary circulation. We consider the fundamental phenomenon of arterial compression (squeezing) in the left ventricular (LV) wall, creating an obstruction to blood flow during cardiac systole. This phenomenon formally resembles functional coronary artery stenosis. Based on a review of the literature, the positive role of arterial compression in coronary hemodynamics is interpreted. Understanding the mechanical relationship between the contractile and coronary systems in the cardiac wall may be useful for practicing physicians when choosing treatment tactics for patients, optimizing LV bypass during heart surgeries, and improving the efficiency of adaptation of the transplanted heart.Работа представляет собой научно-образовательный аналитический обзор, предназначенный для практикующих кардиологов. Цель обзора – обратить внимание врачей на роль сократительной функции миокарда в регуляции коронарного кровотока. Рассмотрен фундаментальный феномен компрессии (сдавливания) артерий в стенке левого желудочка, создающий препятствие течению крови в систолическую часть сердечного цикла. Это явление формально напоминает функциональный стеноз коронарных артерий. На основе анализа литературы дано толкование позитивному вкладу компрессии артерий в коронарную гемодинамику. Понимание механических взаимоотношений сократительной и коронарной систем в сердечной стенке может быть полезно практикующим врачам при выборе тактики лечения пациентов, оптимизации левожелудочкового обхода при операциях на сердце, а также повышения эффективности адаптации трансплантированного сердца

Ferrogels ultrasonography for biomedical applications

Ferrogels (FG) are magnetic composites that are widely used in the area of biomedical engineering and biosensing. In this work, ferrogels with different concentrations of magnetic nanoparticles (MNPs) were synthesized by the radical polymerization of acrylamide in stabilized aqueous ferrofluid. FG samples were prepared in various shapes that are suitable for different characterization techniques. Thin cylindrical samples were used to simulate the case of targeted drug delivery test through blood vessels. Samples of larger size that were in the shape of cylindrical plates were used for the evaluation of the FG applicability as substitutes for damaged structures, such as bone or cartilage tissues. Regardless of the shape of the samples and the conditions of their location, the boundaries of FG were confidently visualized over the entire range of concentrations of MNPs while using medical ultrasound. The amplitude of the reflected echo signal was higher for the higher concentration of MNPs in the gel. This result was not related to the influence of the MNPs on the intensity of the reflected echo signal directly, since the wavelength of the ultrasonic effect used is much larger than the particle size. Qualitative theoretical model for the understanding of the experimental results was proposed while taking into account the concept that at the acoustic oscillations of the hydrogel, the macromolecular net, and water in the gel porous structure experience the viscous Stocks-like interaction. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.18-19-00090Ministry of Education and Science of the Russian Federation, Minobrnauka: 3.1438.2017/46Funding: The Russian Scientific Foundation (grant 18-19-00090) supported the experimental parts of this study, including the design, performance and analysis of experiments.Acknowledgments: A.Yu. Zubarev thanks the program of the Ministry of Education and Science of the Russian Federation (project 3.1438.2017/46) for the support of his mathematical studies. We thank K.R. Mekhdieva, P.A. Shabadrov, V.Ya. Krokhalev, I.V. Beketov and A.M. Murzakaev for special support

Echogenic Advantages of Ferrogels Filled with Magnetic Sub-microparticles

Ultrasonic imaging of ferrogels (FGs) filled with magnetic nanoparticles does not reflect the inner structure of FGs due to the small size of particles. To determine whether larger particle size would improve the acoustic properties of FGs, biocompatible hydrogels filled with 100–400 nm iron oxide magnetic sub-microparticles with weight fraction up to 23.3% were synthesized and studied. Polymeric networks of synthesized FGs were comprised of chemically cross-linked polyacrylamide with interpenetrating physical network of natural polysaccharide—Guar or Xanthan. Cylindrical samples approximately 10 mm in height and 13 mm in diameter were immersed in a water bath and examined using medical ultrasound (8.5 MHz). The acoustic properties of FGs were characterized by the intensity of reflected echo signal. It was found that the echogenicity of sub-microparticles provides visualization not only of the outer geometry of the gel sample but of its inner structure as well. In particular, the echogenicity of FGs interior depended on the concentration of magnetic particles in the FGs network. The ultrasound monitoring of the shape, dimensions, and inner structure of FGs in the applied external magnetic field is demonstrated. It is especially valuable for the application of FGs in tissue engineering and regenerative medicine. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.The study was supported by the program of the Ministry of Health of the Russian Federation (project 121032300335-1). A.P. Safronov appreciates the Russian Science Foundation (grant 20-12-00031) financial support in the characterization of iron oxide particles, and in the synthesis and characterization of ferrogels

Features of ultrasound attenuation in ferrogels based on polyacrylamide and iron oxide microparticles

The purpose of the study was to evaluate the effect of FGs magnetic filler on the extent of ultrasound attenuation in the interior of composite.Цель исследования состояла в оценке влияния концентрации магнитного наполнителя ФГ на величину затухания ультразвука во внутренней структуре композита

Design magnetic matrices for cell technology supporting devices

Biomedical applications of magnetic materials are a hot topic of present day research. Special attention is paid for design and development of appropriate instrumentation. In this work magnetic system consisting of an equidistant set of commercial permanent magnets (6 × 4 assay) was proposed, designed and tested for further employment in the experiments in cell cultivation experiments. Magnetic field distribution was experimentally measured in 3 axes: OX, OY, OZ by gaussmeter. The results were statistically analyzed. Constant magnetic field near the center of XY plane was relatively homogeneous but at edges significant value of magnetic field gradient was observed. With increasing of Z distance, the decreasing of magnetic field strength was observed. Obtained parameters of a designed system are satisfactory and therefore it can be recommended for cell cultivation experiments when application of external magnetic field is desired. © Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 18-19-00090This research was funded by the Russian Science Foundation, grant number 18-19-00090