Functional outcomes of structural peculiarities of striated muscle tropomyosin

Tropomyosin is a dimer coiled-coil actin-binding protein. Adjacent tropomyosin molecules connect each other ‘head-to-tail’ via an overlap junction and form a continuous strand that winds around an actin filament and controls the actin–myosin interaction. High cooperativity of muscle contraction largely depends on tropomyosin characteristics. Here we summarise experimental evidence that local peculiarities of tropomyosin structure have long-range effects and determine functional properties of the strand, including changes in its bending stiffness and interaction with actin and myosin. Point mutations and posttranslational modifications help to probe the roles of the conserved ‘non-canonical’ residues, clusters of stabilising and destabilising core residues, and core gap in tropomyosin function. The data suggest that tropomyosin structural lability including a diversity of homo- and heterodimers of different isoforms provide a balance of stiffness, flexibility, and strength of interaction with partner sarcomere proteins necessary for fine-tuning of Ca²⁺ regulation in various types of striated muscles.

     

Contractile function of the myocardium of the left ventricle in patients with isolated lesions of the aortic valve

Seventy-five patients (aged 17-53) with an isolated lesion to the aortal valve have been examined. The study of correlations between clinico-instrumental and angiocardiographic findings has shown that the isotonic overload of the left ventricle as against the isometric one causes more pronounced changes in the contractility of the left ventricular myocardium which are expressed in an increased heart volume, the development of electrocardiographic manifestations of the left ventricular overload, a considerable enhancement in the myocardium weight and in the residual and end diastolic volumes of the left ventricle. The value of the gradient of the systolic pressure in patients with isolated aortal ostium stenosis determines the intensity of myocardial alterations. In patients with aortal valve insufficiency, the value of the pulse pressure is directly correlated with the myocardial state. The contractile function of the left ventricular myocardium in patients with combined cardiac aortal disease is dependent on the predominance of isotonic or isometric overloads of the left ventricle.     

Prognostic significance of total blood cholesterol level and the possibility of dietary correction of hypercholesterolemia in the population

In a population of males aged 40-59 years, a routine epidemiological survey was performed, which was followed by a 5-year follow-up to examine the mortality rates and incidence of myocardial infarction and stroke treated by an active prophylactic measure program (Group 1) and conventional regimen (Group 2). The total cholesterol levels of 260 mg/dl or more were found to be of highly prognostic value to death from all causes, largely cardiovascular diseases, to development of myocardial infarction, stroke, and to higher risk of fatal cases of the diseases. It was ascertained that it was difficult to modify the dietary habits in subjects of mature age. By the end of the fifth follow-up year, the examined patients from Group 1 showed a reduction in the mean level of total cholesterol and hypercholesterolemia rates, following by a decrease in total and cardiovascular mortality by 6.5 and 5.7%, respectively, the incidence of myocardial infarction and stroke and the risk of death from these complications becoming lower.     

Effect of isosorbide dinitrate (isoket) on central hemodynamics and myocardial contraction in patients with ischemic heart disease

The authors studied the effect of isoket on the central hemodynamics and myocardial contractility as well as on the conditions of myocardial functioning in 38 patients aged 28-53 years and suffering from coronary heart disease. The infusion of 2 mg of isoket at a rate of 400 micrograms/min was followed by a decrease in the arterial pressure with the maximum drop seen on the seventh minute (by 26% from the baseline value), a reduction in the end-diastolic pressure by 50%, and a lengthening of the preejection period without any significant changes in either the cardiac output or the total peripheral resistance. Taken as a whole these changes justify the conclusion that the influence of dinitrate isosorbite (isoket) on the central hemodynamics is largely due to its venodilating action leading to a reduction of the pre-load which in turn improves myocardial functioning.     

Approaches to the secondary prevention of arterial hypertension among the population (data from a cooperative study on the multifactorial prevention of ischemic heart disease)

A cooperative study has reviewed the prevalence of arterial hypertension (AH) among 40- to 59-year-old male residents of three cities (Moscow, Minsk and Kaunas) and the possibility of organizing a long-term outpatient treatment of newly-detected AH cases as well as the efficiency of the latter. Of 16,703 individuals screened, AH was detected in 27.9%. Evidence is obtained that preventive and therapeutic procedures for hypertensive patients are in need of an improvement. In a middle-aged population, moderate AH is prevalent (nearly 67.7%). Coronary risk factors, such as hyperlipoproteinemia and excessive body weight, were more frequent in AH patients, as compared to the general population, an argument in favor of the need for an improved combined approach to AM control in the population. Active combined treatment of the recognized cases over 5 years proved effective as it brought arterial blood pressure back to normal. Patient participation in the treatment and its contribution to treatment efficiency are reviewed.     

Diagnosis of myocardial infarct with fatal outcome within the framework of multifactorial prevention of ischemic heart disease in Moscow

The death diagnosis of myocardial infarction (including acute heart failure) was recorded and verified on the basis of standard criteria during a 5-year implementation of the Program on Multifactorial Prevention of Coronary Heart Disease among males aged 40-59 years. The analysis demonstrated that the hyperdiagnosis of acute heart failure as a death cause was observed in 29.0% of cases, death being due to acute alcohol intoxication in 43% of all the inconsistent diagnoses.     

Acidosis modifies effects of phosphorylated tropomyosin on the actin-myosin interaction in the myocardium

Journal of Muscle Research and Cell Motility - Phosphorylation of α-tropomyosin (Tpm1.1), a predominant Tpm isoform in the myocardium, is one of the regulatory mechanisms of the heart...