Self-organization in a polymer system appears when a balance is achieved between long-range repulsive and short-range attractive forces between the chemically different building blocks. Block copolymers forming supramolecular assemblies in aqueous media represent materials which are extremely useful for the construction of drug delivery systems especially for cancer applications. Such formulations suppress unwanted physicochemical properties of the encapsulated drugs, modify biodistribution of the drugs towards targeted delivery into tissue of interest and allow triggered release of the active cargo. In this review, we focus on general principles of polymer selforganization in solution, phase separation in polymer systems (driven by external stimuli, especially by changes in temperature, pH, solvent change and light) and on effects of copolymer architecture on the self-assembly process., M. Hrubý, S. K. Filippov, P. Štěpánek., and Obsahuje bibliografii
An exhibition, Bulgarian Codex Suprasliensis from the 1Gth Century in the Context of Byzantine-Slavic Mutual Relationships was organized by the Bulgarian Embassy in Prague and the ASCR. under the auspices of the President of the Academy of Sciences, Professor W.f.( Draho& at the seat of the ASCR in Prague. A unique exposition presented one of the oldest Old Slavic remembrances, Codex Suprasliensis. This venerable document was created in the 10' century at a religious center established by the disciples of Cyril and Methodius in the then capital of Bulgaria, Preslav. and it is written in the Glagolitic alphabet. and Václav Čermák.
One hundred years ago Heike Kamerlingh Onnes arrived to one of the most important breakthroughs of 20th century physics - he discovered superconductivity. His finding as in many other cases in the history of science had been a result of use of a very new experimental technique. He used the cryogenic equipment in his Leiden's laboratory with the liquid helium cryocooler and measured electrical properties of metals near the absolute zero temperature. When cooled down to extremely low temperatures, near 4 Kelvin, very pure mercury suddenly lost its electrical resistance completely. Many major physicists of 20th century, experimentalists as well as theorists, devoted their life efforts to exploration of the mysterious properties of superconductors. Superconductivity has been shown to be one of the rare cases where quantum physics is observed on a macroscopic scale. Many chemical elements and thousands of compounds have been found to be superconducting. Fifty years after the discovery important practical applications such as strong magnets for laboratories and magnetic-resonance-imaging in hospitals came to the market. But more than seventy five years the superconducting materials had been functioning only at extreme cold, below 23 K (-250°C). In 1986 the "hightemperature superconductor's" era started with materials superconducting at -100°C. This paper surveys the history and the latest research into one of today's most fascinating physics and promising technologies., Peter Samuely., and Obsahuje bibliografii
The effect of suramin, an inhibitor of G protein regulated signalling, was studied on the membrane currents induced by noxious heat and by capsaicin in cultured dorsal root ganglia neurones isolated from neonatal rats. Whole-cell responses induced by a heat ramp (24-52 °C) were little affected by suramin. The noxious heat-activated currents were synergistically facilitated in the presence of 0.3 µM capsaicin 13.2-fold and 6.3-fold at 40 °C and 50 °C, respectively. In 65% of neurones, the capsaicin-induced facilitation was inhibited by 10 µM suramin to 35±6 % and 53±6 % of control at 40 °C and 50 °C (S.E.M., n=15). Suramin 30 µM caused a significant increase in the membrane current produced by a nearly maximal dose (1 µM) of capsaicin over the whole recorded temperature range (2.4-fold at 25 °C and 1.2-fold at 48 °C). The results demonstrate that suramin differentially affects the interaction between capsaicin and noxious heat in DRG neurones and thus suggest that distinct transduction pathways may participate in vanilloid receptor activation mechanisms., V. Vlachová, A. Lyfenko, L. Vyklický, † R.K. Orkand., and Obsahuje bibliografii
Materials on the basis of cycloolefin copolymers (COC) are suitable for subchondral defect repairs. The objective of this study was to evaluate the influence of surface modification of COC and COC/LLDPE blends on the viability and gene expression of chondrocytes. Human chondrocytes were incubated on the surface of the studied materials. Half of the materials were plasmatically modified with a subsequent type II collagen application. The gene expression of matrix metalloproteinases (MMP-1,-3,-13), pro-inflammatory cytokines (IL-1, TNF-alpha) and apoptotic molecules (BAX, Bcl-2) was evaluated using quantitative Taq-Man PCR after 48 h incubation. Chondrocyte viability was evaluated by the MTT test after 2, 4 and 8 days of incubation. The synthesis of MMPs was measured by ELISA assay in cell culture medium after 48 h of incubation. Chondrocytes incubated on plasmatically modified in contrast to unmodified materials demonstrated significantly increased gene expression of IL-1 (p<0.05), MMP-1 and MMP-3 (p<0.05 for both comparisons) as well as MMP-13 (p<0.001). Increased gene expression was confirmed by significantly increased production of active forms of particular MMPs into the cell culture medium. Unlike surface unmodified polymers, the modified materials showed timedependent reduction of chondrocyte viability. The gene expression of TNF-α and apoptotic molecules by chondrocytes was not significantly changed by different materials. Cycloolefin copolymers and their blends may represent suitable materials for tissue engineering, however, their surface modification followed by collagen type II application may, at least under in vitro conditions, reduce the viability of chondrocytes and induce their pro-destructive behavior. The potential benefit or disadvantage of surface modifications of materials for osteochondral defect repairs needs to be further elucidated., M. Polanská ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Brachylaimus fuscatus metacercaria develops unencysled in the terrestrial snail Ponsadenia duplocincta. For the first time in a larval stage of the genus Brachylaimus a distinctive surface structure has been observed. This structure of net-like interconnected ridges of the tegument was present on the whole body surface with the exception of the anterior part. Beside this structure scanning electron microscopy revealed five types of papillae. Three types, dome-like papillae, papillae with a finger-like process, and hollow papillae with a short cilium, were localized mainly in the suckers. Hollow papillae without a cilium were arranged in groups or singly around the ventral sucker and genital pore. Ribbed papillae were observed on the ventral body surface.