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22692. Mechanical properties of mitral allografts are not reasonably influenced by cryopreservation in sheep model
- Creator:
- Jaroslav Hlubocký, Aleš Mokráček, Nováček, V., Jan Vojáček, Jan Burkert, Petra Kochová, Klepáček, J., Pepper, J., and Jaroslav Špatenka
- Format:
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, mitrální chlopeň, mitral valve, mitral allograft, cryopreservation, maxwell model, viscoelastic properties, 14, and 612
- Language:
- English
- Description:
- A mitral allograft is us ed exceptionally in the mitral, as well as in the tricuspid position, mostly as an experimental surgical procedure. The authors decided to evaluate the possibility of inserting a cryopreserved mitral allograft into the tricuspid position in a sheep experimental model. Within the framework of this experimental project the mechanical properties of the cryopreserved mitral allograft were tested. A novel methodology studying the functional unit composed of mitral annulus, leaflet, chordae tendinaea, and papillary muscle is presented. A five-parameter Maxwell model was applied to characterize the viscoelastic behavior of sheep mitral valves. A control group of 39 fresh mitral specimens and a test group of 13 cryopreserved mitral allografts from tissue bank were tested. The testing protocol consisted of six loading cycles with 1 mm elongation every 5 min. There was no significant difference in the mean values of the determined parameters (p> 0.05) which confirms the main hypothesis that cryopreservation does not influence significantly material parameters characterizing the tissue mechanics. Slight discrepancy is observed in variances of viscous parameters suggesting that the values of the test group may be spread over larger interval due to the treatment., J. Hlubocký ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
22693. Mechanical response of porous scaffolds for cartilage engineering
- Creator:
- Josef Jančář, Slovíková, A., Evžen Amler, Petr Krupa, Helga Kecová, Ladislav Plánka, Petr Gál, and Alois Nečas
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, nanovlákna, kyselina hyaluronová, mezenchymální kmenové buňky, nanofibers, hyaluronic acid, mesenchymal stem cells, chitosan, hydroxyapatite, joint resurfacing, 14, and 612
- Language:
- English
- Description:
- a1_Mechanical properties of scaffolds seeded with mesenchymal stem cells used for cartilage repair seem to be one of the critical factors in possible joint resurfacing. In this paper, the effect of adding hyaluronic acid, hydroxyapatite nanoparticles or chitosan nanofibers into the cross-linked collagen I on the mechanical response of the lyophilized porous scaffold has been investigated in the dry state at 37 oC under tensile loading. Statistical significance of the results was evaluated using ANOVA analysis. The results showed that the addition of hyaluronic acid significantly (p<<0.05) reduced the tensile elastic modulus and enhanced the strength and deformation to failure of the modified cross-linked collagen I under the used test conditions. On the other hand, addition of hydroxyapatite nanoparticles and chitosan nanofibers, respectively, increased the elastic modulus of the modified collagen ten-fold and four-fold, respectively. Hydroxyapatite caused significant reduction in the ultimate deformation at break while chitosan nanofibers enhanced the ultimate deformation under tensile loading substantially (p<<0.05). The ultimate tensile deformation was significantly (p<<0.05) increased by addition of the chitosan nanofibers. The enhanced elastic modulus of the scaffold was translated into enhanced resistance of the porous scaffolds against mechanical load compared to scaffolds based on cross-linked neat collagen or collagen with hyaluronic acid with similar porosity. It can be concluded that enhancing the rigidity of the compact scaffold material by adding rigid chitosan nanofibers can improve the resistance of the porous scaffolds against compressive loading, which can provide more structural protection to the seeded mesenchymal stem cells when the construct is implanted into a lesion., a2_Moreover, scaffolds with chitosan nanofibers seemed to enhance cell growth compared to the neat collagen I when tested in vitro as well as the scaffold stability, extending its resorption to more than 10 weeks., J. Jančář, A. Slovíková, E. Amler, P. Krupa, H. Kecová, L. Plánka, P. Gál, A. Nečas., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
22694. Mechanická podpora oběhu v léčbě kardiogenního šoku – přehled
- Creator:
- Šimek, Martin, Hutyra, Martin, Zuščich, Ondřej, and Klváček, A.
- Format:
- print, text, and regular print
- Type:
- model:article, article, Text, práce podpořená grantem, and TEXT
- Subject:
- kardiogenní šok--patofyziologie--terapie, podpůrné srdeční systémy, kardiostimulace umělá, vybavení a zásobování, intraaortální balónková pumpa, kontrapulzace, klinické zkoušky jako téma, randomizované kontrolované studie jako téma, pozorovací studie jako téma, retrospektivní studie, prospektivní studie, mimotělní membránová oxygenace--přístrojové vybavení--využití, katétry, echokardiografie transezofageální--přístrojové vybavení, koronární angioplastika--metody, výsledky a postupy - zhodnocení (zdravotní péče), metaanalýza jako téma, algoritmy, and lidé
- Language:
- Czech and English
- Description:
- Udržení adekvátní perfuze cílových orgánů hraje zásadní roli v managementu kardiogenního šoku, který je stále zatížen vysokou mortalitou. Pokud farmakologická léčba společně se snahou o ovlivnění příčiny srdečního poškození selhávají, je nutno bezprostředně zvážit zavedení mechanické podpory oběhu k zajištění orgánové perfuze. K dočasné podpoře oběhu je využíváno více typů podpor zahrnující intraaortální balonkovou kontrapulzaci, mimotělní membránovou oxygenaci, perkutánně nebo chirurgicky implantované srdeční podpory. V přehledu je šířeji diskutována problematika jednotlivých typů podpor oběhu, zkušenosti s nimi a jejich role v managementu kardiogenního šoku., The maintenance of adequate end‑organ perfusion is the cornerstone of cardiogenic shock management, which still carries a poor prognosis. Mechanical circulatory support to ensure organ perfusion is required once pharmacological therapy together with the effort to affect the cause of heart failure is less effective or fails. There are currently several circulatory support options, including intra‑aortic balloon counterpulsation, extracorporeal membrane oxygenation and percutaneously or surgically implanted ventricular assist devices. The role of, and experience with, each of these support devices in the management of cardiogenic shock is broadly discussed in this review., and Šimek M., Hutyra M., Zuščich O., Klváček A.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22695. Mechanické podpory a transplantace srdce v léčbě chronického srdečního selhání
- Creator:
- Fila, Petr, Bedáňová, Helena, Horváth, Vladimír, Ondrášek, Jiří, Piler, Pavel, and Němec, Petr
- Format:
- print, text, and regular print
- Type:
- model:article, article, Text, práce podpořená grantem, and TEXT
- Subject:
- srdeční selhání--terapie, kardiostimulace umělá--metody, transplantace srdce--dějiny--kontraindikace--metody--trendy--využití, podpůrné srdeční systémy--klasifikace, kardiochirurgické výkony, pooperační péče, and lidé
- Language:
- Czech and English
- Description:
- Zlatým standardem léčby konečného stadia srdečního selhání je transplantace srdce. Nedostatek dárců omezuje množství provedených srdečních transplantací. Transplantační centra potřebují těmto pacientům nabídnout alternativu pro léčbu srdečního selhání. Mechanické srdeční podpory jsou používány jako tzv. most k transplantaci u pacientů na čekací listině (dlouhodobé podpory). Tento souhrnný článek popisuje současný stav léčby chronického srdečního selhání transplantací srdce a implantací mechanické srdeční podpory., Heart transplantation is the gold standard for patients with end‑stage heart failure. The available donor supply limits the number of cardiac transplants. Transplant centres need to provide alternative therapy for these patients with heart failure. The mechanical circulatory support systems are used as a bridge to transplantation in heart transplant candidates (long‑term support). This review describes the current status of heart transplantation and long‑term mechanical circulatory support devices for treatment of chronic heart failure., and Fila P., Bedáňová H., Horváth V., Ondrášek J., Piler P., Němec P.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22696. Mechanism of action of homocysteine and its thiolactone in hemostasis system
- Creator:
- Karolczak, K. and Olas, B.
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie, homocystein, hemostáza, human physiology, homocysteine, hemostasis, homocystein thiolakton, homocysteine thiolactone, 14, and 612
- Language:
- English
- Description:
- In the article, the actions of homocysteine (Hcys) and its metabolite - cyclic thioester – homocysteine thiolactone (HTL) on complex process of hemostasis, which regulates the flowing properties of blood, are described. Possible interaction of Hcys and HTL with endothelial cells, blood platelets, plasmatic fibrinogen and plasminogen, as the important major components of hemostasis are also discussed. The modification of hemostatic proteins (N-homocysteinylated or S-homocysteinylated proteins) induced by Hcys or its thiolactone, and links of homocysteine or homocysteine thiolactone to •NO metabolism seem to be the main reason of biotoxicty of homocysteine in cardiovascular diseases., K. Karolczak, B. Olas., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
22697. Mechanism of electrocardiographic T-wave flattening in diabetes mellitus: experimental and simulation study
- Creator:
- Sedova, K. A., Azarov, J. E., Arteyeva, N. V., Ovechkin, A. O., Vaykshnorayte, M. A., Vityazev, M. A., Bernikova, O. G., Shmakov, D. N., and Kneppo, P.
- Type:
- article, model:article, and TEXT
- Subject:
- diabetes, dispersion of repolarization, repolarization gradients, T-vector, and T-wave
- Language:
- English
- Description:
- In the present study we investigated the contribution of ventricular repolarization time (RT) dispersion (the maximal difference in RT) and RT gradients (the differences in RT in apicobasal, anteroposterior and interventricular directions) to T-wave flattening in a setting of experimental diabetes mellitus. In 9 healthy and 11 diabetic (alloxan model) open-chest rabbits, we measured RT in ventricular epicardial electrograms. To specify the contributions of apicobasal, interventricular and anteroposterior RT gradients and RT dispersion to the body surface potentials we determined T-wave voltage differences between modified upper- and lower-chest precordial leads (T-wave amplitude dispersions, TWAD). Expression of RT gradients and RT dispersion in the correspondent TWAD parameters was studied by computer simulations. Diabetic rabbits demonstrated flattened T-waves in precordial leads associated with increased anteroposterior and decreased apicobasal RT gradients (P<0.05) due to RT prolongation at the apex. For diabetics, simulations predicted the preserved T-vector length and altered sagittal and longitudinal TWAD proven by experimental measurements. T-wave flattening in the diabetic rabbits was not due to changes in RT dispersion, but reflected the redistributed ventricular repolarization pattern with prolonged apical repolarization resulting in increased anteroposterior and decreased apicobasal RT gradients.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22698. Mechanism of Na+ Deprivation-Induced Catecholamine Secretion From Freshly Isolated Bovine Adrenal Chromaffin Cells
- Creator:
- Isosaki, M. and Nakashima, T.
- Format:
- print, bez média, and svazek
- Type:
- article, studie, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, fyziologie člověka, human physiology, Na+-Ca2+ exchange, Na+ deprivation, Catecholamine secretion, Adrenal medulla · Chromaffin, 14, and 612
- Language:
- English
- Description:
- We have studied the mechanism of Na+ deprivation-induced catecholamine secretion from freshly isolated bovine adrenal chromaffin cells. Na+ deprivation-induced catecholamine secretion depended on free extracellular Ca2+ concentrations and was almost parallel to 45Ca2+ influx into the cells under various experimental conditions. Furthermore, Na+ deprivation-induced 45Ca2+ influx and catecholamine secretion were actually induced by a relative Na+ concentration gradient across the plasma membrane, but not by simple omission of Na+ from the medium. These results indicate that the deprivation of Na+ from the medium changes the relative Na+ gradient across the plasma membrane and results in Ca2+ influx via a reverse mode of Na+-Ca2+ exchange rather than by inducing Ca2+ entry through Ca2+ channels by eliminating the competition between extracellular Na+ and Ca2+., M. Isosaki, T. Nakashima., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
22699. Mechanism of Public Relations in Poland Archaeology. Archaeology for the Public /
- Creator:
- Dąbal, Joanna
- Type:
- text
- Subject:
- archeologie, vztahy archeologie-veřejnost, popularizace vědy, světové dějiny od r. 1945 do současnosti, Polsko, archeologická metodologie a organizace, experimentální archeologie, and pomocné vědy historické a ostatní příbuzné obory
- Language:
- English
- Description:
- x
- Rights:
- unknown
22700. Mechanism of rigid overlaying of carboniferous strata failure in face mining in the case of a multiseams deposit
- Creator:
- Eva Jiránková, Staš, Lubomír, Vlastimil Kajzar, and Doležalová, Hana
- Format:
- print, bez média, and svazek
- Type:
- article, články, model:article, and TEXT
- Subject:
- Geologie. Meteorologie. Klimatologie, geodynamika, geodynamics, tensor stress measurement, longwall mining, subsidence trough, rock mass, overlying strata, 7, and 551
- Language:
- English
- Description:
- The technique of assessing the failure of rigid overlying strata is applicable to deep mining with thick coal seams (a thickness of more than 1 m in the Ostrava-Karvina Coalfield), and in one case to longwall mining with controlled caving. The assessment of failure of rigid overlying strata makes it possible to distinguish whether the rigid overlying strata of rocks has been deformed or whether a strutting arch has been formed over the goaf below which is an area that is free from stress. Good knowledge of the mining, technical and geological conditions of a given site is a prerequisite for successful evaluation. There are advantages to utilising surface measurements for interpreting the effects of changes in rock mass, especially in areas of high overlying strata. The practical importance of failure assessment of overlying strata consists in determining the size of the mined-out area where the deformation of the rigid overlying strata occurred, which is dependent on the character of the rock mass. This paper is set in the context of the expected width of the goaf during deformation of rigid overlying strata within parameters that describe the mining and geological conditions of the locality. Changes in the area of the goaf, based the results of tensometric measurements, will also be placed in context., Eva Jiránková, Lubomír Staš, Vlastimil Kajzar and Hana Doležalová., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public