Vol 23, No 2 (2016)

Goal of study: to carry out an analysis of drinking water viral contamination dynamics in the Arkhangelsk region for development of proposals improving water supply of the population. In order to reveal markers of viral contamination in water, there have been carried out examinations of water samples by a laboratory in the Center for Hygiene and Epidemiology in the Arkhangelsk Region from 2006 to 2014 with use of different methods. With use of the virological method and the method of enzyme immunoassay (EIA), there were examined 934 drinking water samples from the public drinking water supply system, and with use of the method of polymerase chain reaction (PCR) - 617 water samples. Presence of enteroviruses and their genetic material in drinking water samples was confirmed in the laboratory in 2008, 2010 and 2014. In what connection, the proportion of samples with positive research results for enteroviruses with use of the PCR method was in 2008 - 4.5 %, in 2010 - 7.4 %, in 2014 - 1.6 %. In the analysis with use of the virological method, a positive result was received in 2010 - there were isolated 3 strains of Coxsackie enteroviruses В5 (2.4 %) and in 2014 - there was isolated 1 strain of Coxsackie enteroviruses В3 (0.5 %). The results of the analysis of water samples carried out with use of the EIA method with the goal to reveal hepatitis А virus and rotaviruses antigens have shown annually registered facts of presence of markers of these causative agents in piped water. Thus in the mentioned years, the proportion of samples containing group-specific antigens of rotaviruses was 1.3 %, hepatitis A virus antigen - 0.5 %. Annually in water samples, there are detected DNA/RNA of the following microorganisms: Salmonella spp., rotaviruses of A group, Noroviruses of 2 genotype, astroviruses, adenoviruses of F group. In the structure of the detected DNA/RNA of the causative agents, there prevail rotaviruses of A group (57.4 %) and adenoviruses of F group (24.1 %). There have been proposed recommendations for solution of problems of water situation improvement for supply of good drinking water to the Arkhangelsk region population.

The article presents the features of asymmetry of cerebral blood flow determined with use of rheoencephalography of 97 boys aged 7-10 years and 56 boys aged 11-14 years with the attention deficit hyperactivity disorder. It has been found that in primary school the children showed reduction in blood filling intensity and improvement of elastic properties of blood vessels for distribution and resistance in the carotid region, increased elastic properties of blood vessels in the vertebrobasilar area on the left. Obviously, these changes in the cerebral blood flow reflected the specific characteristics of the cerebral blood flow in children with this disorder. For children at secondary school age, there is registered an increase of the blood flow intensity, the tone of large arteries and elastic properties of blood vessels for distribution and resistance in carotid and vertebrobasilar area on the left, which corresponds to the existing ideas about organization of hemodynamic processes in the brain and the role of the left-hemispheric dominance in children in ontogenesis.

The article presents the results of studies of the behavioral response in 53 elderly people (60-65 years of age). The purpose of the study is to compare physiological parameters of a behavioral response in men and women in old age. Indicators of decision-making strategies in a free, probabilistic and deterministic environments were assessed through a computer complex for psychophysiological researches KPFK-99 «PSIHOMAT», which includes a test computer system «Binatest». It was found that older people behavior strategy in a free environment has the character of a random search. Stereotype of choice, which is important to adapt to changing environmental conditions and to organize complex behavioral programs, is typical for men between the age of 60-65. Manifestation of impulsivity, as well as lower rates of operations thinking when analyzing the situation and making the right decision, indicating incomplete digestion of probabilistic structure are seen in women between the age of 60-65. In a deterministic environment, when increasing the rate of activity, there was a decrease of accuracy of the assignment in men. It is noted that in tasks where you need to quickly perceive the details and often switch attention, women show greater efficiency.

The goal of research is to examine the characteristics of the hormones of the pituitary-gonadal and pituitary-thyroid gland systems in the peripheral blood of the male population living in different areas of Russia, taking into account the population groups. The study involved 136 men aged 22 to 50 years old, who are permanently resident in the North no less than three generations. Among them there are 80 local residents of Arkhangelsk (64° 32' N), 19 local residents of Vologda (59° 13' N) and 37 local residents of Nes, Nenets Autonomous Okrug (66° 36' N). According to the basis of nationality group of men living in Nes was divided into: Russian - 23 people and settled aboriginal population (Nenets, Komi) - 14 people. We have shown that functional activity of the pituitary-thyroid axis (thyrotropin, thyroxine, free triiodothyronine) in the male Caucasoid and settled aboriginal population of the polar region exceeds its level in the inhabitants of the circumpolar area (Arkhangelsk). At the same time, men living in the mid-latitude area (Vologda) had minimal activity of the pituitary-thyroid axis (triiodothyronine, free thyroxine), compared with polar and circumpolar areas. It was shown that the functional activity of the pituitary-gonadal axis in men living in Vologda (luteinizing hormone, follicle-stimulating hormone, inhibin B, free testosterone, dehydroepiandrosterone sulfate) and in Nes (follicle-stimulating hormone, inhibin B, testosterone, free testosterone, sex-hormone-binding globuline) was higher compared with the inhabitants of the city of Arkhangelsk. The levels of sperm antibodies were minimal in men living in Nes. At the same time, changing the traditional way of life from nomadic to a settled one leads to the negative tendencies such as the decrease of the synthesis reserves of steroid hormones in the settled aboriginal population that is shown by the decreased serum levels of progesterone and dehydroepiandrosterone sulfate.

In this paper, we have described the main principles of cross-sectional studies planning and data analysis. A theoretical base for cross-sectional studies' design has been presented as well as advantages and disadvantages of this type of studies. We present the methods for sample size calculation and data analysis using statistical software. Calculation of confidence intervals using free software "Epi Info" and online calculators has also been presented. The main effect measures used in cross-sectional studies have been described. Examples of cross-sectional studies in the fields of clinical medicine, dentistry and public health performed in the Arkhangelsk region have been given. The primary audience for this article consists of master and doctoral students whose research is still in the planning phase. This paper supplements, but does not substitute the literature in the field of clinical epidemiology.