[Biological age as an index of human health level, aging and ecological well-being].

Methodology of estimating the integral health and aging level is based on the system index of biological age (BA). The paper introduces the reader to the BA principles and structure, search for meaningful aging biomarkers, useful tests, and applications in present-day biomedicine. The concept of BA is directly linked with the theory of organism vitality. BA biomarkers must provide a detailed picture of the process of aging. Number of biomarkers cannot be large, while their changes with aging must be uniform in every population member and fairly distinct though with moderate interindividual variations. Prognosis of the vital trajectory requires estimation of risk factors, i.e. hereditary and acquired factors that affect lifespan, and also longevity factors, i.e. genetic and environmental factors crucial for clinical medicine and gerontological prophylaxis properly. At present, BA gains wide recognition in clinical and preventive medicine, physiology and biology as a method to evaluate the general state of health, ecological well-being, adaptation to extreme factors, as well as the rate and degree of organism aging.

[The system theory of aging: methodological principles, basic tenets and applications].

The paper deals with the system theory of aging constructed on the basis of present-day scientific methodology--the system approach. The fundamental cause for aging is discrete existence of individual life forms, i.e. living organisms which, from the thermodynamic point of view, are not completely open systems. The primary aging process (build-up of chaos and system disintegration of aging organism) obeys the second law of thermodynamics or the law of entropy increase in individual partly open systems. In living organisms the law is exhibited as synergy of four main aging mechanisms: system "pollution" of organism, loss of non-regenerative elements, accumulation of damages and deformations, generation of variability on all levels, and negative changes in regulation processes and consequent degradation of the organism systematic character. These are the general aging mechanisms; however, the regulatory mechanisms may be important equally for organism aging and search for ways to prolong active life.

[A system of simulation models of the epidemic process based on a socioecological concept]. / Sistema imitatsionnykh modelei épidemicheskogo protsessa na osnove sotsial'no-ékologicheskoi kontseptsii.

In this paper different methods of modeling the epidemic process for different types of infectious diseases are discussed. We propose a concept of modeling for an essentially nonhomogeneous human population, taking into account biological, ecological and social factors. The method of an "epidemiological tree" has been developed, which makes it possible to divide the population into so-called "epidemiologically active groups". The method is invariant with respect to nosological forms. The paths of the spread of an infectious disease among the population are described in the form of the oriented graphic presentation of the interaction of individual epidemiologically active groups. The dynamic characteristics of the epidemic process are calculated by means of the system of differential equations. For illustration, the proposed approach is applied to HIV infection used as an example.