Biomedical subjects

B Ia Son'kin

Publications and source records attributed to B Ia Son'kin.

10 recordsLinked to original sources

PubMedDate not supplied

[Experience in the use of synchrotron radiation for the x-ray study of biopolymers].

The results of methodical work, carried out on the sources of synchrotron radiation (SR) with the aim of using SR as a powerful source of X-rays for studying biopolymer structure, are presented. The questions of monochromatization are considered. The technique designed for photoregistration of diffraction patterns within the wide range of scattering angles is described. X-ray diffraction patterns of feather ceratin, collagen and striated muscle are obtained with exposure periods ten times less than those in the case of X-ray tubes. The high resolution of diffraction lines, the absence of parasitic phone and the presence of reflections within the wide range of scattering angles are characteristic of these patterns.

Animals↗

PubMedDate not supplied

[Reduced sensitivity of glycerinated rabbit m.psoas fibers to diprotonated vanadate during decrease in pH].

Vanadate (Na3VO4) action of the isometric force of maximal Ca2(+)-activated fibre has been studied at pH from 6.3 to 7.3. Acidification was shown to decrease the force declining vanadate effect: appearance of the dissociation constant estimated from force--H2VO4--dependence increases about two-fold following the pH decreasing from 7.3 to 6.3. Therefore the well-known decline of the force at acidification is accompanied by a decrease of the sensitivity to vanadate. These both phenomena can have a common nature and reflect, for example, a decreasing complex AM.ADP+ responsible for the force and interaction with vanadate. Our findings permit to think that the changes in pH with fatigue increasing the diprotonated form of phosphate simultaneously reduce the sensitivity of the contractile system to this form.

Animals↗

PubMedDate not supplied

[Interaction of vanadate with the contractile system of striated muscles in the presence of natural analogs of ATP and ADP].

Vanadate produced dissociation of rigor-activated (calcium-free) fibres or rabbit m. psoas muscle in the presence of the studied various natural analogs of ATP (NTP) at optimal concentrations. By the degree of sensitivity to vanadate it is possible to establish the order ATP approximately greater than CTP greater than UTP greater than ITP greater than GTP. This series corresponds to the order for actomyosin NTPases qualitatively. Addition of corresponding NDP to fibres produced a decrease of the rigor fibres tension. Vanadate in comparable concentrations does not change the mechanical properties of fibres in the presence of NDP. At high concentration (greater than 10 mM) vanadate produced relaxation of the rigor fibres even in the absence of nucleotides. This effect is irreversible.

Adenosine Diphosphate↗

PubMedDate not supplied

[Changes in the force-pCa characteristics of the striated muscles of the skate after treatment with phalloidin].

The pCa/tension relationship of glycerinated skate thoracic fin muscle was found to fit well in the Hill equation. Phalloidin has been shown to decrease calcium sensitivity (shift of pK to the lower pCa by 0.27 +/- 0.08), tension at saturated pCa by 22 +/- 5%, and Hill coefficient by 0.37 +/- 0.21. As F-actin structural motility is restricted by phalloidin, these results are in agreement with the idea of participation of F-actin conformational changes in its switching by calcium ions and in ensuring cooperativity of this process.

Actins↗

PubMedDate not supplied

[The effect of pyrophosphate on the rigor fibers of rabbit m. psoas fibers].

The effect of MgPPi on the rigor force of glycerinated fibres in the range of ionic strength 75-250 mM at two temperatures 18 degrees and 5 degrees C was studied. At 18 degrees C the maximum of this effect was above the range of average ionic strength. At 5 degrees C the greatest effect of MgPPi was observed at low ionic strength.

Animals↗

PubMedDate not supplied

[Different sensitivity of cross-bridges in the muscle fiber sarcomere in Ca2+-activation].

The investigation of transient kinetics of force development by glycerinated rabbit m. psoas fibres at consecutive pCa stepwise drops in the presence of 0.1 mM Na3VO4 was carried out. Stationary content of trapped vanadate in the fibres at low levels of Ca2+-activation was deduced to be attained slowly as compared to the initial rate of force development and vanadate trapping. This result is considered an indication of the fact, that not all cross-bridges can be activated by turns at low levels of Ca2+-activation.

Animals↗

PubMedDate not supplied

[Mechano-chemical properties of actomyosin-ADP complexes in rabbit psoas muscle fibers].

The relaxing effect of vanadate on active contractile system is found to be completely absent from rigor skinned fibres with ADP even on their stretching up to the forces comparable with the active ones, though vanadate is likely to bind not very firmly with crossbridges not containing inorganic phosphate. Probable reasons of such distinction are considered. The complex actomyosin-ADP in the rigor fibres is supposed to have significantly lower free energy independently of its deformation than the one of the same composition in the active ones. Possible role of different actomyosin-ADP states in the mechanochemical cycle of crossbridge is discussed.

Actomyosin↗

PubMedDate not supplied

[Effect of vanadate on Ca++-activation in skeletal muscle].

Vanadate (0.1 mM) reduces tension of glycerinated rabbit psoas muscle fibers, shifts tension--pCa curve to lower pCa, increases the rate constant of delayed tension development and changes dependence of this rate constant on the level of Ca2+-activation. Vanadate influence stops the increase of the rate constant with the rise of Ca++-activated tension. Since actin-myosin-ADP complex is dissociated by vanadate, the muscle performance at low activation levels is supposed to be conditioned largely by the cross-bridges interacting with actin of the actin blocks switched on by myosin-ADP. Kinetics of such cross-bridges differs from that of the cross bridges interacting with actin activated by Ca++ binding to troponin C.

Actins↗

PubMedDate not supplied

[Interactions of vanadate with the contractile system of the rabbit psoas muscle in active, relaxed and rigor states].

Interaction between 0.1-0.3 mM vanadate (Vi) and muscle fibres was studied by measuring their force and stiffness. Only interaction with the fibres having cycling cross-bridges caused a strong decrease of these parameters. There was no vanadate effect on the rigor fibres and its complexes with Mg.AdP or Mg.beta-gamma-imido-ATP. Judging by the following transient tension in Vi-containing solutions Vi was slowly incorporated into relaxed fibres, Vi complex with muscle was stable under relaxation conditions, but it was splitted when actomyosin was formed. Formation of M.ADP.Vi+, the stable biochemical analogue of M.ADP.Pi ( Goodno C. C., Taylor E. W. Proc. Natl. Ac. Sci. USA, 1982, 79, p. 21) is assumed to be formed in muscle. On the basis of the difference between rigor contraction of ATP- and Vi-relaxed fibres a conclusion can be drawn that the Vi complex in muscle is not a mechanochemical analogue of the myosin intermediate developing force when interacting with actin.

Animals↗

PubMedDate not supplied

[Effect of phallotoxins on the mechanism of Ca2+-activation of glycerinated fibers of the rabbit psoas muscle].

The effect of phalloidin (Ph) and some of its derivatives on isometric tension and spectrum of mechanical relaxation times of single fibres was under investigation. It was shown that Ph had a great effect only at low levels of Ca2+-activation, evoking multi-phase changes of isometric tension and a sharp rise of the rate constant of delayed tension development up to value close to that for control fibres at high [Ca2+]. As to their efficiency to change Ca2+-sensitive parameters of the fibres, phallotoxins can be arranged as follows: Ph approximately equal to Ph-sulfone greater than Ph-sulfoxide B approximately equal to dethio-Ph greater than Ph-sulfoxide A greater than or equal to seco-Ph. There is a qualitative correlation of this sequence with the actin stabilising properties for all these substances with the exception of dethio-Ph. These findings are discussed from the viewpoint of two different "on" actin states, only one of them being Ph-sensitive.

Animals↗