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A total of 1097 children aged 2 to 6 years who went to preschool children's facilities in Stavropol were examined. Of them there were 525 (47.7%) boys and 574 (52.3%) girls. For 40 years, the Stavropol preschool children have become higher and the height values are higher than the total Russian standards. The results obtained in the study region suggest that the total height of girls aged 2 to 7 years is insignificantly greater than that in boys. A comprehensive analysis of the health status of the study groups shows that at preschool age, the number of children having Health Group I decreased at the expense of an increase in Health Group III children. The reasons for a rise in the incidence of diseases at this age may be more cases of poor living conditions, tense adaptive processes in the presence of incomplete immunogenesis, physiological lymphoid tissue hyperplasia, high rates of allergic reactions.

The structure of vascular plexuses of brain ventricles in newborns developed under hypoxic conditions does not correspond to gestational age. Chronic hypoxia decreases activity of succinate dehydrogenase and iron content in vascular plexuses of brain ventricles.

The time course of virus accumulation was studied in guinea pigs aerogenously infected with Venezuelan equine encephalomyelitis virus, strain Trinidad. At first the agent was isolated from the lungs. The course of infection was characterized by viremia and infection of some organs and tissues of the lymphoid, hemopoietic, and central nervous systems, specifically, of the tonsils, lymph nodes, spleen, liver, bone marrow, some sections of the olfactory tract, and brain.

Time course of accumulation of Venezuelan equine encephalomyelitis virus (strain Trinidad) in the organism of white rats after respiratory infection was studied. Electronmicroscopic examination of the organs was carried out over the course of the disease. The virus was for the first time detected in the lungs of animals after aerogenous infection and in the olfactory area of the nasal cavity of animals infected by applying the virus into the nasal mucosa. Disease development in aerosol-infected rats was characterized by viremia and infection of the hemopoietic and lymphomyeloid systems, particularly of the thymus and bifurcation lymph nodes, as well as of the olfactory system and brain. At the late stage of infection the concentration of the agent in all the examined organs was below the detection threshold, and neutralizing antibodies were detected in the blood serum.

Spread of Venezuelan equine encephalitis (VEE) virus and damage of the central nervous system (CNS) in mice infected by respiratory route was studied. Virus concentration in organs and blood, "dose-effect" relationships, and ultrastructural lesions in various tissues were examined in immune and normal mice. We showed, via three independent methods--characteristic curve investigations, tissue virus concentration dynamics, and ultrastructural methods--the spread of VEE virus through the olfactory tract into the brain of immune mice. From these experiments it was concluded that in case of respiratory challenge VEE virus can enter the CNS of normal mice by both vascular and olfactory pathways, while in immune mice the main route is olfactory.

The experimental data on aerosol challenge of rabbits with Venezuelan equine encephalomyelitis (VEE) virus are presented. Lethal infection of rabbits was followed by a rise in body temperature (greater than 0.5 degrees C) within 1-2 days after challenge. Two waves of lethality in aerosol infection experiments were recorded. Three variants of the infection outcome were observed after VEE virus aerosol challenge of rabbits. The causes of death of the infected rabbits are discussed.

The role of virus spread in the induction of damage to the central nervous system (CNS) of mice infected with Venezuelan equine encephalitis virus (VEEV) via the respiratory route was studied. The virus concentration in various organs and in the blood, the sensitivity to different doses of virus, and ultrastructural lesions in various tissues were examined. It is concluded that VEEV can enter the CNS of nonimmunized mice both by vascular and by olfactory pathways, whereas in immunized mice the olfactory pathway is the main route.