[Thermodynamic characteristics of collagen fibrils reconstructed in vitro at different temperatures and concentrations].

The results of a calorimetric study of type I collagen fibrillogenesis were analyzed. The dependence of the half-width of the temperature transition of a collagen solution on the concentration and temperature of collagen formation was studied. It was demonstrated that, by varying temperature and collagen concentration, one can regulate the density of packing and dimensions of cooperative fibril blocks. At temperatures below the physiological level (25 degrees C and 30 degrees C), and a relatively low concentration of collagen (0.3 mg/ml), fibrils with the lowest density of packing are formed. The degree of order does not change as the collagen concentration increases twofold but grows as the concentration increases fourfold. It was shown that, at the physiological temperature (35 degrees C), fibrils with a dense packing of molecules are formed at all collagen concentrations studied. The value of fibril formation enthalpy is minimal at a temperature of 35 degrees C, pH 7.2, an ionic strength of 0.17 M and a concentration of 1.2 mg/ml. Based on the results obtained, a conclusion was made that the packing density of fibrils formed at physiological temperature does not depend on collagen concentration over the concentration range of 0.3 - 1.2 mg/ml.

[The programmed cell death of murine BW5147 thymoma under the action of dexamethasone]. / Programmiruemaia gibel' kletok timomy myshi BW5147 pod deistviem deksametazona.

By flow cytometry, imitation modelling and biochemical analysis, the mode and kinetics of dexamethasone-treated T-lymphoma cell death were studied. The hormone was shown to induce delays in pre- and postsynthetic phases of the cell cycle and the death of part of cells. A short exposure to dexamethasone reveals its cytostatic rather than cytolytic effect. Following G2/M delay and cytokinesis, part of cells dies. A reduced serum concentration (2%) causes shorter delays in the cell cycle and a more rapid cell death. Dexamethasone stimulates apoptosis which is indicated by internucleosomal DNA fragmentation, and by a coincidence in time of the processes of DNA degradation and increase in the other membrane permeability. These results are discussed in relation to the cell death and proliferation.

[Collagen gels, chondroitin-4-sulfate. Proteolytic stability]. / Kollagenovye geli, khondroitin-4-sul'fat, ustoichivost' k proteolizu.

Differential scanning microcalorimetry and polarized thermomicroscopic methods were used for studying of collagen type I and chondroitin-4-sulfate complexes. It was shown that fast heating till 37 degrees C lead to collagen gel formation, which is stable for collagenase action.

[Self-assembly of collagen type I molecules without telopeptides]. / Izuchenie samosborki molekul kollagena tipa I s udalennymi telopeptidami.

The effect of temperature on the kinetics of formation of fibrils from rat tail collagen molecules devoid of telopeptides was studied. It was shown that the rats of fibril formation at 30 and 35 degrees C increases five- and eightfold, respectively, as compared with that at 25 degrees C. It was found that enthalpy of fibril denaturation at 30 degrees C is maximal for the collagen both with intact telopeptides and devoid of telopeptides. It was found that essential for the fibrilogenesis of type I collagen devoid of telopeptides are temperatures of 30 and 35 degrees C.

[Formation of collagen type I fibrils in vitro]. / Issledovanie obrazovaniia fibrill kollagena tipa I in vitro.

The assembly of collagen fibrils as a function of temperature and collagen concentration was studied. It was shown that temperature increases from 25 to 35 degrees C, the degree of ordering of collagen fibrils increases 1.5-fold at collagen concentration above 1 mg/ml and 2-fold at low collagen concentration. A maximum ordering of fibril structure occurs under conditions close to physiological (T approximately 35 degrees C and collagen concentration 1.2 mg/ml). As temperature is elevated from 30 to 35 degrees C, the packing of collagen molecules in fibrils becomes more ordered: the values of enthalpy and entropy of the transition of fibrils from the native to a disordered state decrease at all collagen concentrations used. At high collagen concentration, the dimensions of cooperative blocks in fibrils formed at 25 and 30 degrees C coincide with those of cooperative blocks of monomeric collagen in solution. Upon increasing the temperature to 35 degrees C, the dimensions of cooperative blocks increase.

[Dynamics of spontaneous beating of cardiomyocytes in vitro depend on the number of involved cells]. / Izmenenie dinamiki sokrashchenii kardiomiotsitov in vitro pri uvelichenii chisla vzaimodeistvuiushchikh kletok.

The dynamics of cardiomyocyte spontaneous beatings with fractal dimension calculation was studied. It was shown that isolated single cardiomyocyte beats stochastically, but when a number of cells synchronized a significant changes in the dynamics appear: deterministic chaos could be detected. Several reasons are discussed as a possible explanation of such a behavior: the effect of system volume increasing and specific influence of gap-junctions on the rhythm formation.

[The use of 1H-NMR spectroscopy for the study of cell cultures]. / Primenenie 1H-IaMR spektroskopii dlia issledovaniia kul'tur kletok.

Production of lactate by the HSR-1, HSR-8, HET-SR fibroblasts have been investigated by 1H-NMR method. Were investigated both monolayer cell cultures and cells immobilized in collagen lattice. Represented data demonstrate the possibility of the NMR-spectroscopy to investigate growth's processes in the cell cultures.

[Use of polarized thermomicroscopy for recording formation and degrading processes of collagen fibrils]. / Primenenie poliarizatsionnoi termomikroskopii dlia registratsii protsessov formirovaniia i degradatsii kollagenovykh fibrill.

Polarized thermomicroscopic method were used for registration of collagen fibril formation and thermal degradation processes. It was compared with differential scanning microcalorimetry and optical density measurement methods and recommended as a fast method for registration of collagen fibril formation and degradation processes.

[Effect of thermoreverse polymer matrix and collagen on the growth of human fibroblasts]. / Vliianie matriksa na osnove termoreversivnykh polimerov i kollagena na rost fibroblastov cheloveka.

The effect of a support composed of polymers based on poly-N-isopropyl acrylamide and poly-t-butyl acrylamide and collagen on human fibroblasts was studied. As the temperature was decreased to 4 degrees C, the polymeric support is converted to a diluted state and cells spontaneously detached from it. The presence of collagen in the support prevented the detachment of cells and increased cell growth. It was shown by microcalorimetry, that in a copolymer-collagen mixture, a microstratification takes place.