Population migrations and the epidemic process of Flexner and Sonne dysentery

Analysis of the materials from the Khabarovsk Territory for the representative period of 25 years (1956-1980) revealed the influence of the migration of the population on the level and dynamics of morbidity in different kinds of dysentery, Flexner's dysentery shown to occur more frequently than Sonne dysentery. Intensive migrations increase the proportion of susceptible persons among the population, thus facilitating the formation and circulation of Shigella strains with pronounced virulence.     

Characteristics and trends in the development of an epidemic process of Sonne and Flexner dysentery among preschool children

The results of studies indicate that the morbidity rates of dysentery among children attending preschool institutions and children brought up at home converged in recent years. This phenomenon was most pronounced among children of the kindergarten age group. At the same time dysentery caused by Sh. sonnei and Sh. flexnery produced a higher morbidity rate among children attending nursery in comparison with that among children of the same age group brought up at home. Group infections in preschool institutions were caused by Sh. sonnei in 89.1% of cases and by Sh. flexneri in 10.9% of cases. Outbreaks due to the transfer of infection through everyday contacts were observed only in dysentery caused by Sh. sonnei, constituting 71.4% of the total number of dysentery outbreaks.     

The mechanism of the development of the epidemic process in Sonne dysentery

An epidemic outbreak of Sonne dysentery has been studied. The data of epidemiological monitoring before and after the epidemic have been analyzed. The real prognostication value of controlling the biological properties of Shigella sonnei and the increase of their intrapopulation heterogeneity at the period of the activation of the epidemic process of Sonne dysentery has been established.     

Patterns determining the dynamics of the epidemic process in Sonne dysentery and its relation to the type of causative agent]

The results of studying the dynamics of the epidemic process of dysentery, based on the data from 3 districts of Moscow, are presented. The study revealed the periodicity of 3 years in the course of the epidemic process of dysentery, occurring against the background of a considerable predominance of Sh. sonnei, biochemical type 2. The use of the cohort method for analyzing the age structure of dysentery cases showed the possibility of using this method to find out to what extent the epidemic process repeatedly affected the same groups of population.     

Changes in the etiologic structure of Sonne shigellosis in its multiyear dynamics

The dynamics of Sonne dysentery morbidity in connection with changes in the structure of S. sonnei circulating among the population of Leningrad for the period of 1959-1984 was studied. Considering such sign as the leading fermentovar, three smaller periods were established in this stretch of time. Changes in the structure of circulating shigellae were accompanied by changes in the intensity and direction of tendencies or decrease in the manifest and asymptomatic forms of infection, as well as in annual morbidity levels and seasonal rises. A slow decrease in morbidity, which started in 1974, occurs in the presence of the predominant circulation of S. sonnei, fermentovar II, among the population; this fermentovar showed greater virulence and immunogenicity than other biovars. One of the decisive moments characterizing the dynamics of the epidemic process of Sonne dysentery is the intensity of the circulation of shigellae in the S-form, and the intensity of the population immunity of the host, linked with this fact, is subject to phasic fluctuations during each annual epidemic cycle.     

Nature of the turtle shell: Morphogenetic causes of bone variability and its evolutionary implication

The turtle shell is characterized by a high degree of conservatism of the fundamental model and, at the same time, a high variability at the individual level. The components of the bony shell vary in origin. The costal and neural plates of the carapace are modified elements of the axial skeleton (ribs and neural arches) and the plastral plates are transformed dermal ossifications of the shoulder girdle and gastralia, peripheral, pygal, and suprapygal plates are similar to osteoderms of other reptiles. The variability of the structure of particular parts of the turtle shell is manifested differently. Most anomalies have been recorded in the caudal part of the carapace. The plastron is relatively stable in morphology. Variations in the bony shell structure are observed in (1) unusual shape and size of plates combined with normal number of plates, (2) presence of additional plates, and (3) absence of regular plates. Based on the morphogenetic characteris-tics, anomalies are subdivided into (1) variations caused by changes in the number of elements of the axial skeleton or their contacts with the dermis (neurals and costals); (2) variations due to changes in the number of horny scutes (peripherals); (3) variations connected with irregular osteogeny or disturbed growth of bones     

The epidemic process as a system. The social regulators of the epidemic process

The article deals with the mechanisms of spontaneous (urbanization, the international migration of population, the anthropogenic transformation of nature) and goal-oriented regulatory action on the epidemic process. Social factors have been shown to transform into ecological ones with the subsequent transformation of information in the parasitic system and their reflection in the social subsystem as the indices of the risk of infection and its socio-economical importance. Using the processes of urbanization as an example, the present work demonstrates that the mechanism of transmission acts as a filter whose specific features are determined by a range of social factors playing the most important role in the regulation of the epidemic process on the socio-ecosystemic level of its organization.     

Functional outline of the epidemic process

The present study has shown that on the level of the parasitic system the epidemic process is a biological system, wherein the host population serves as the internal regulator, the mechanism of transmission serves as the external regulator and the parasite population, as the regulated object. The biological regulating mechanisms of the epidemic process have fundamental differences in the groups of infectious with various mechanisms of transmission, and the specific nature of the mechanism of transmission determines the peculiar features of the biological mechanism which governs the self-regulation of the epidemic process. In contrast, on a higher level of the organization of the epidemic process, i. e. on the level of the socio-ecological system, the epidemic process is a biosocial system, wherein the human society serves as the regulator, the parasitic system serves as the regulated object and the mechanism of transmission plays the role of the filter which determines the scope of social factors, most important in the regulation of the epidemic process in a given infection. The spontaneous regulation of the epidemic process is the freed forward channel from the regulator to the regulated object, and the controlled regulation is the feedback channel.     

The system of the epidemic process

An original social-ecological concept of the epidemic process has been constructed on the basis of using social ecology, systemic approach and the basic principles of cybernetics. According to this concept, the epidemic process is regarded as a biosocial, hierarchic, integral system providing for the reproduction of the species of human parasites. At a higher level of organization, the epidemic process is an epidemiological social-ecological system consisting of two interacting subsystems: the biological (epidemiological ecosystem) and the social (social and economic conditions of life of the society) subsystems where the biological subsystem plays the role of the governed object and the social acts as the internal regulator of these interactions. On the basis of this concept a rational structure of the system of epidemiological surveillance over infectious diseases has been proposed according to which each level of the structure of the epidemic process should be subject to adequate monitoring.     

The neural induction process; its morphogenetic aspects

This posthumous review of early embryonic inductions concludes: 1) the amphibian egg has only two distinct components, animal and vegetal. Interactions at their mutual boundary forms meso-endoderm. This is "meso-endoderm induction", not just "mesoderm induction". 2) The dorso-ventral polarity of the yolk mass implies a dorsally situated inducing centre. 3) Accumulation of cells into one, two, three or many cell masses [problastopores] along the circumference of the meso-endoderm results in as many axes, implying a self-organizing capacity of meso-endoderm. 4) Induction of the meso-endoderm is slow, spreading cell to cell through the animal moiety from the boundary of the vegetal yolk mass towards the animal pole. 5) Interaction between mesoderm and ectoderm is a separate step leading to cranio-caudal differentiation of the archenteron roof. 6) The initial invaginating endoderm and mesoderm, representing the future pharynx endoderm and prechordal plate mesoderm, first contacts the most posterior presumptive neurectoderm after having passed the still uninvaginated trunk mesoderm. At that moment an antero-posterior level neural induction actually starts. 7) The ectoderm contraction wave coincides spatially and temporally with the induced neural plate. 8) Two successive homoiogenetic waves of inductive activity pass through the presumptive neurectoderm in the anterior direction, the first one, "activation", giving rise to neural differentiation and ultimately forebrain, the second one, "transformation", to more caudal CNS structures. These are separate, successive steps in CNS regional induction. 9) The midbrain represents a secondary formation in the neural plate. 10) The observed changes in morphogenesis may depend upon separate, successive binary decisions via [cell and] nuclear state splitters [involving differentiation waves].     

The epidemic process as a system. I. The structure of the epidemic process

A new epidemiological concept (socio-ecological) has been formulated on the basis of the principles of the theory of systems and the theory of information. In accordance with this concept, the epidemic process is organized on the same principle as living matter, and the stability of this process at all levels of its organization is ensured by the processes of self-regulation. The conditions of the life of human society have been shown to be organically incorporated into the structure of the epidemic process as a regulating subsystem on the socio-ecological level.