Interaction of myosin subfragment 1 with F-actin studied by differential scanning calorimetry

The thermal unfolding of the myosin subfragment 1 (S1) and of filamentous actin (F-actin) in their strong complex obtained in the presence of ADP was studied by differential scanning calorimetry (DSC). It is shown that in the acto-S1 complexes S1 and F-actin melt separately, and thermal transitions of each protein can be easily followed. Interaction of S1 with F-actin significantly increases S1 thermal stability and also affects the thermal stability of F-actin. Although S1 unfolds at much lower temperature than F-actin, the molecules of S1 remain bound to F-actin even after full denaturation. Under these conditions S1 may induce cross-linking between actin filaments. It is concluded that DSC studies on the acto-S1 complexes offer a new and promising approach to investigate the structural changes which occur in the myosin head and in F-actin due to their interaction.

Differential scanning calorimetric study of the complexes of modified myosin subfragment 1 with ADP and vanadate or beryllium fluoride

The effects of various modifications of rabbit skeletal myosin subfragment 1 on the thermal denaturation of subfragment 1 in ternary complexes with Mg-ADP and orthovanadate (V1) or beryllium fluoride (BeFx) have been studied by differential scanning calorimetry. It has been shown that specific modifications of SH1 group of Cys-707 by different sulfhydryl reagents, trinitrophenylation of Lys-83, and reductive methylation of lysine residues promote the decomposition of the S1.ADP.Vi complex and change the character of structural transitions of the subfragment 1 molecule induced by the formation of this complex, but they have much less or no influence on subfragment 1 thermal stability in the S1.ADP.BeFx complex. Thus, the differential scanning calorimetric studies on modified subfragment 1 preparations reveal a significant difference between S1.ADP.Vi and S1.ADP.BeFx complexes. It is suggested that S1.ADP.Vi and S1.ADP.BeFx complexes represent structural analogues of different transition states of the ATPase cycle, namely the intermediate states S1**.ADP.Pi and S1*.ATP, respectively. It is also proposed that during formation of the S1.ADP.Vi complex the region containing both Cys-707 and Lys-83 plays an important role in the spread of conformational changes from the active site of subfragment 1 ATPase throughout the structure of the entire subfragment 1 molecule. In such a case, the effects of reductive methylation of lysine residues on the subfragment 1 structure in the S1.ADP.Vi complex are related to the modification of Lys-83.

[Disorders in the interferon system in patients with virus-associated and chlamydial infections]

A more than 80% incidence of herpes simplex virus, cytomegalovirus, and chlamydial infection was revealed in 58 patients with various gynecological diseases. In 50% cases the infection was mixed. An appreciable reduction of the gamma-interferon system was detected in 20 patients, which was caused by a concomitant infectious process, possibly provoking the development of the underlying disease. Treatment of such patients should include antiviral and antichlamydial therapy, as well as correction of defects in interferon production.

[Population-genetic variability of the house mouse Mus musculus L. 1758 S. stricto from the western, central, and southeastern area of species range]

Allozyme variation in nine populations of the house mouse Mus musculus L. s. str. was examined. Twenty-five out of 34 analyzed loci were shown to be polymorphic. Estimates of genetic variation were obtained for separate populations and for population groups classified according to their habitat. Populations from Moldova and Tadzhikistan displayed the lowest and highest amounts of allozyme variation, respectively. Variation in town populations was significantly greater than in rural ones. This can be explained by active human-induced migration of mice into towns. All Central Asian populations showed high levels of genic diversity, which is presumably related to their proximity to ancient centers of mice expansion. Allelic distributions in the populations were analyzed.

Combination of the electrogenic ionophores, valinomycin and CCCP, can lead to non-electrogenic K+/H+ exchange on bilayer lipid membranes

The method of pH shift measuring by means of a pH microelectrode was applied to measure hydrogen ion fluxes across a planar bilayer lipid membrane (BLM) in the presence of the potassium ion ionophore, valinomycin, and a protonophore, carbonylcyanide m-chlorophenylhydrazone (CCCP), under conditions of the voltage clamp. The voltage dependence of the flux was determined to be in the range of +/- 150 mV under the conditions of both symmetrical KCl as well as a KCl gradient across the BLM. Surprisingly, at a clamped zero voltage on BLM a significant hydrogen ion flux was observed in the presence of a KCL gradient and both valinomycin and CCCP. This finding was interpreted as a result of induction of non-electrogenic K+/H+ exchange in the presence of valinomycin and CCCP, presumably through the formation of electrically neutral complexes of these two ionophores and K+ (H+) ions: valinomycin-K(+)-CCCP- and/or possibly valinomycin-CCCP(-)-H+.

[Allozyme variability of the European bean Castor fiber 1758 (Castoridae, Rodentia) from the Voronezh State Nature Reserve]

Electrophoretic methods were used to study protein products of 32 gene loci in the blood of European and Canadian beavers held in captivity at the Voronezh State Nature Reserve. In the studied samples, the levels of polymorphism and average heterozygosity exceeded the average values of corresponding indices determined for beavers that inhabit temperate zones. To what extent the studied samples represent the state of the gene pool of parental populations is discussed. A comparison between allozyme spectra of samples of European and Canadian beavers revealed many coinciding polymorphic loci, on the one hand, and pronounced genetic divergence of these species, on the other.

[Posttraumatic liver failure]

An examination of 166 patients was performed at the early postshock period of trauma disease. Results of the investigation of the functional and morphological state of the liver, factors of pathogenesis of posttraumatic hepatic insufficiency are analyzed.

[Behavior of pachytene chromosomes in male mice heterozygotic for various translocations (Rb(8,17), T(16,17)43H)]

The electron microscopic analysis of synaptonemal complexes of the Robertsonian translocation heterozygotes (Rb/T) and heterozygotes of the reciprocal translocation (Rb(8, 17)/T(16, 17) 43H revealed three types of translocation configurations (TC). The observed TC were subdivided into three types according to the manner of synapsis: 1) full synapsis of homologues forming trivalent with interstitial centromere in 15%; 2) the centromeric asynapsis (8 and 17-16 chromosomes forming trivalent with the extension region of asynapsis and breakpoint of the reciprocal translocation on chromosome 17 in 70%; 3) centromeric asynapsis (only single chromosome 17-16 of trivalent, when the break point of reciprocal translocation and the absence of centromeric asynapsis of another chromosome 8 formed trivalent in 15%). The frequency of association between trivalents and the XY bivalents is 20% and close proximity is 15% for heterozygotes Rb/T. Which are fertile, while in the sterile heterozygotes Rb(8, 17)/T(16, 17) 43H it is 45% for association and 15% close proximity (total 60%). These data show the significant differences in the contact of translocation configurations with the XY bivalents of fertile heterozygotes, in comparison with the sterile. Thus, it is shown that the chromosome pairing of fertile and sterile mice is clearly distinguished.

[Characteristics of disorders of hemostasis and lipid metabolism in patients with different pathogenetic forms of angina pectoris]

The likely mechanisms responsible for the occurrence of angina pectoris, which were revealed by 24-hour ECG monitoring, were correlated with abnormalities in hemostasis and blood lipid spectrum. Changes in the blood lipid spectrum were demonstrated to play the leading role in the development of angina due to higher myocardial oxygen demand. Those in platelet hemostasis are mostly pronounced in impaired myocardial oxygen supply due to vessel spasm and/or formation of platelet aggregates.

[Relations between the duration of coupling interval and frequency fluctuations in ventricular ectopic complexes]

An attempt was made to electrocardiographically assess the likely mechanisms responsible for the occurrence of arrhythmias. The frequency of ventricular ectopic complexes was compared with fluctuations of coupling interval duration. An examination of 36 patients provided evidence for preliminary considerations concerning the causation between the frequency of ventricular ectopic complexes and the duration of coupling interval. The findings are promising from clinical and predictive points of view.

[Correction of hypercholesterolemia and dyslipoproteinemia by plasmapheresis in patients with stenocardia resistant to drug therapy]

Plasmapheresis was used to correct blood lipid composition in patients with angina at rest and angina of effort (functional classes 3-4). In addition to a drop in total cholesterol and triglycerides, cholesterol in low and very-low-density lipoproteins fell abruptly, while high-density-lipoprotein cholesterol, on the contrary, increased considerably. Clinical improvement of the patients was also recorded.

[Effect of gravitation plasmapheresis on central hemodynamics and indices of myocardial metabolism in patients with acute complicated myocardial infarct]

A study of 32 patients with complicated acute myocardial infarction, treated with gravitation plasmapheresis during the acute phase of the disease, demonstrated a significant drop in blood concentrations of compounds with high molecular weights (fibrinogen, cholesterol, triglycerides, total protein) as well as a significant activation of the heart's pumping function, while total peripheral resistance declined, as did the degree of myocardial ischemia. This is interpreted as an evidence of positive effect of plasmapheresis on central hemodynamics, myocardial metabolism and clinical course of myocardial infarction in such patients.

[Effect of positive pressure breathing on hemodynamics in patients with borderline arterial hypertension during water immersion]

Patients with borderline hypertension were exposed, while being immersed, to positive pressure breathing. During exposure cardiac output (CO), heart rate (HR), mean arterial pressure (MAP), total peripheral resistance (TPR), left ventricle work (W), blood content of head vessels (Qh), upper and lower lung lobes (Qu1 and Q11), liver (Q1) were measured. During immersion CO and MAD decreased, HR and TPR increased slightly, and W diminished. Simultaneously Qh, Qu1 and Q11 increased significantly while Q1 decreased considerably, indicating blood "centralization" during simulated microgravity. Courses of positive pressure breathing led to decreases in Qh, Qu1, Q11 and increase in Q1, i. e., they caused blood to be displaced from the head and lungs to the liver. Thus, the liver plays the role of a physiological pool which accumulates blood removed from the upper body by positive pressure.