122 research outputs found
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 βΌ2.3 nm, and others were integer multiples of that value. The βΌ2.3-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
Regularities of ultrasonography of suspensions of alumina nanoparticles in biological media
This paper studies the echo-contrast properties of an alumina nanopowder suspension using ultrasonography (US) fully corresponding in its characteristics to the techniques of medical ultrasound diagnostics of organs and tissues. The purpose of this study was to search for the possible effect of the ionic and protein composition of the biological medium on the intensity of the reflected echo signal of the contrast material based on nanoparticles. It was found that the pH of the blood promotes the maximum use of echo contrast options of alumina nanopowder suspensions. Particle size measurements in the suspension using the dynamic light scattering technique showed the stabilizing effect of blood serum and plasma on the nanopowder suspension, resulting in the attenuation of the echo signal. The data offer a basis for the development of new contrast materials based on nanoparticles for the ultrasound imaging of the heart and blood vessels. The considered mechanisms of the established phenomena make it possible to elucidate the processes of interaction of metal oxide nanoparticles with biological molecules. Β© 2013 Pleiades Publishing, Ltd
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 100β400 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 polysaccharideβGuar 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. Β© 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
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. Β© 2019 by the authors. Licensee MDPI, Basel, Switzerland.18-19-00090Ministry of Education and Science of the Russian Federation,Β 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
ΠΠΎΡΠΎΠ½Π°ΡΠ½ΡΠΉ ΠΏΠ°ΡΠ°Π΄ΠΎΠΊΡ
This work is a scientific and educational analytical review intended for practicing cardiologists. The purpose of the review is to draw physiciansβ 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.Π Π°Π±ΠΎΡΠ° ΠΏΡΠ΅Π΄ΡΡΠ°Π²Π»ΡΠ΅Ρ ΡΠΎΠ±ΠΎΠΉ Π½Π°ΡΡΠ½ΠΎ-ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°ΡΠ΅Π»ΡΠ½ΡΠΉ Π°Π½Π°Π»ΠΈΡΠΈΡΠ΅ΡΠΊΠΈΠΉ ΠΎΠ±Π·ΠΎΡ, ΠΏΡΠ΅Π΄Π½Π°Π·Π½Π°ΡΠ΅Π½Π½ΡΠΉ Π΄Π»Ρ ΠΏΡΠ°ΠΊΡΠΈΠΊΡΡΡΠΈΡ
ΠΊΠ°ΡΠ΄ΠΈΠΎΠ»ΠΎΠ³ΠΎΠ². Π¦Π΅Π»Ρ ΠΎΠ±Π·ΠΎΡΠ° β ΠΎΠ±ΡΠ°ΡΠΈΡΡ Π²Π½ΠΈΠΌΠ°Π½ΠΈΠ΅ Π²ΡΠ°ΡΠ΅ΠΉ Π½Π° ΡΠΎΠ»Ρ ΡΠΎΠΊΡΠ°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΡΠ½ΠΊΡΠΈΠΈ ΠΌΠΈΠΎΠΊΠ°ΡΠ΄Π° Π² ΡΠ΅Π³ΡΠ»ΡΡΠΈΠΈ ΠΊΠΎΡΠΎΠ½Π°ΡΠ½ΠΎΠ³ΠΎ ΠΊΡΠΎΠ²ΠΎΡΠΎΠΊΠ°. Π Π°ΡΡΠΌΠΎΡΡΠ΅Π½ ΡΡΠ½Π΄Π°ΠΌΠ΅Π½ΡΠ°Π»ΡΠ½ΡΠΉ ΡΠ΅Π½ΠΎΠΌΠ΅Π½ ΠΊΠΎΠΌΠΏΡΠ΅ΡΡΠΈΠΈ (ΡΠ΄Π°Π²Π»ΠΈΠ²Π°Π½ΠΈΡ) Π°ΡΡΠ΅ΡΠΈΠΉ Π² ΡΡΠ΅Π½ΠΊΠ΅ Π»Π΅Π²ΠΎΠ³ΠΎ ΠΆΠ΅Π»ΡΠ΄ΠΎΡΠΊΠ°, ΡΠΎΠ·Π΄Π°ΡΡΠΈΠΉ ΠΏΡΠ΅ΠΏΡΡΡΡΠ²ΠΈΠ΅ ΡΠ΅ΡΠ΅Π½ΠΈΡ ΠΊΡΠΎΠ²ΠΈ Π² ΡΠΈΡΡΠΎΠ»ΠΈΡΠ΅ΡΠΊΡΡ ΡΠ°ΡΡΡ ΡΠ΅ΡΠ΄Π΅ΡΠ½ΠΎΠ³ΠΎ ΡΠΈΠΊΠ»Π°. ΠΡΠΎ ΡΠ²Π»Π΅Π½ΠΈΠ΅ ΡΠΎΡΠΌΠ°Π»ΡΠ½ΠΎ Π½Π°ΠΏΠΎΠΌΠΈΠ½Π°Π΅Ρ ΡΡΠ½ΠΊΡΠΈΠΎΠ½Π°Π»ΡΠ½ΡΠΉ ΡΡΠ΅Π½ΠΎΠ· ΠΊΠΎΡΠΎΠ½Π°ΡΠ½ΡΡ
Π°ΡΡΠ΅ΡΠΈΠΉ. ΠΠ° ΠΎΡΠ½ΠΎΠ²Π΅ Π°Π½Π°Π»ΠΈΠ·Π° Π»ΠΈΡΠ΅ΡΠ°ΡΡΡΡ Π΄Π°Π½ΠΎ ΡΠΎΠ»ΠΊΠΎΠ²Π°Π½ΠΈΠ΅ ΠΏΠΎΠ·ΠΈΡΠΈΠ²Π½ΠΎΠΌΡ Π²ΠΊΠ»Π°Π΄Ρ ΠΊΠΎΠΌΠΏΡΠ΅ΡΡΠΈΠΈ Π°ΡΡΠ΅ΡΠΈΠΉ Π² ΠΊΠΎΡΠΎΠ½Π°ΡΠ½ΡΡ Π³Π΅ΠΌΠΎΠ΄ΠΈΠ½Π°ΠΌΠΈΠΊΡ. ΠΠΎΠ½ΠΈΠΌΠ°Π½ΠΈΠ΅ ΠΌΠ΅Ρ
Π°Π½ΠΈΡΠ΅ΡΠΊΠΈΡ
Π²Π·Π°ΠΈΠΌΠΎΠΎΡΠ½ΠΎΡΠ΅Π½ΠΈΠΉ ΡΠΎΠΊΡΠ°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΠΈ ΠΊΠΎΡΠΎΠ½Π°ΡΠ½ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌ Π² ΡΠ΅ΡΠ΄Π΅ΡΠ½ΠΎΠΉ ΡΡΠ΅Π½ΠΊΠ΅ ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ ΠΏΠΎΠ»Π΅Π·Π½ΠΎ ΠΏΡΠ°ΠΊΡΠΈΠΊΡΡΡΠΈΠΌ Π²ΡΠ°ΡΠ°ΠΌ ΠΏΡΠΈ Π²ΡΠ±ΠΎΡΠ΅ ΡΠ°ΠΊΡΠΈΠΊΠΈ Π»Π΅ΡΠ΅Π½ΠΈΡ ΠΏΠ°ΡΠΈΠ΅Π½ΡΠΎΠ², ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ Π»Π΅Π²ΠΎΠΆΠ΅Π»ΡΠ΄ΠΎΡΠΊΠΎΠ²ΠΎΠ³ΠΎ ΠΎΠ±Ρ
ΠΎΠ΄Π° ΠΏΡΠΈ ΠΎΠΏΠ΅ΡΠ°ΡΠΈΡΡ
Π½Π° ΡΠ΅ΡΠ΄ΡΠ΅, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΏΠΎΠ²ΡΡΠ΅Π½ΠΈΡ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ Π°Π΄Π°ΠΏΡΠ°ΡΠΈΠΈ ΡΡΠ°Π½ΡΠΏΠ»Π°Π½ΡΠΈΡΠΎΠ²Π°Π½Π½ΠΎΠ³ΠΎ ΡΠ΅ΡΠ΄ΡΠ°
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.Π¦Π΅Π»Ρ ΠΈΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΡ ΡΠΎΡΡΠΎΡΠ»Π° Π² ΠΎΡΠ΅Π½ΠΊΠ΅ Π²Π»ΠΈΡΠ½ΠΈΡ ΠΊΠΎΠ½ΡΠ΅Π½ΡΡΠ°ΡΠΈΠΈ ΠΌΠ°Π³Π½ΠΈΡΠ½ΠΎΠ³ΠΎ Π½Π°ΠΏΠΎΠ»Π½ΠΈΡΠ΅Π»Ρ Π€Π Π½Π° Π²Π΅Π»ΠΈΡΠΈΠ½Ρ Π·Π°ΡΡΡ
Π°Π½ΠΈΡ ΡΠ»ΡΡΡΠ°Π·Π²ΡΠΊΠ° Π²ΠΎ Π²Π½ΡΡΡΠ΅Π½Π½Π΅ΠΉ ΡΡΡΡΠΊΡΡΡΠ΅ ΠΊΠΎΠΌΠΏΠΎΠ·ΠΈΡΠ°
- β¦