Vol 42, No 2 (2016)

To determine the strained adaptation to cold, the cardiovascular reactivity under local cold exposure and the characteristics of regulation of the circulatory system in persons with high individual susceptibility to cold was studied. It was shown that the subjective characteristics of high susceptibility to cold in the form of initial symptoms of Raynaud’s phenomenon correlated with the symptoms of aggravated and generalized cold-induced vasoconstriction (CIV) during the local cold test. The analysis of the heart rate variability (HRV) in persons with aggravated CIV revealed a decrease in the parameters of the time-domain characteristics of HRV (RRNN, SDNN, RMSSD, pNN₅₀, and coefficient of variation) as well as a decrease in the total power (TP) of the frequency-domain characteristics and the absolute values of the frequency bands (VLF, LF, and HF) with a relative increase of the LF component. This reflects possible changes in the autonomic regulation of the cardiovascular system, which manifest themselves in a reduced contribution of reflectory mechanisms to the heart rate regulation followed by relative predominance of baroreflex regulation. The diagnostic value of aggravated cold-induced vasoconstriction in identifying disorders of adaptation to cold or premorbid state of the cardiovascular system is discussed.

The dynamics of the main electroencephalographic patterns and their relationship with natural illumination periods have been described in this study. We have determined periods, which are the most favorable for brain functioning and development of cognitive function in northerner schoolchildren. We have found that adaptive changes in bioelectric activity of the brain take place during transitional seasons. An increase in the activity of all EEG rhythms in spring and predominance of the slow-wave Δ and θ activity in autumn have been found. The discovered dynamics of amplitude and spectral parameters of EEG are not dependent on age-related changes. The formation of bioelectric activity of the brain in northerner schoolchildren was mostly affected by the sex of a child and changes in the daytime duration.

A common variant of inherited deficiency of type 1A carnitine palmitoyltransferase (CPT1A) first detected in Canadian Inuits has also been detected in the indigenous populations of various regions of Alaska, northern Canada, and Greenland. However, the prevalence of the P479L genotype in neonates has not been evaluated to date. The frequency of the P479L allele in two populations of Taymyr Peninsula (Dolgan-Nganasan and Nenets) has been assessed in the study. Dried blood spots from newborns born in 2010–2013 were collected in two populations: 108 samples were collected from Dolgan-Nganasans (the settlements Syndasko, Kataryk, and Levinskie Peski) and 105 samples were collected from Nganasans (the Nosok settlement). Allelic variants c.1436C/T (rs 80356779) of the carnitine palmitoyltransferase (CPT1A) gene were investigated in these samples. Genotyping for the P479L mutation was based on analysis of restriction fragment length polymorphism. DNA extracted from the dried blood spots was initially amplified using polymerase chain reaction with the following primers: 5’-CTGGCCAGGTTTGGATTTT-3’ and 5’-TCCAGGATGAAGCAGAGAGG-3’. Restriction endonuclease BstMC (SibEnzim, Novosibirsk, Russia) was used for restriction of the amplicons obtained: a 252-bp fragment was obtained after restriction if the subject carried the T-allele, and an 83-bp fragment was obtained if the subject carried the C-allele. There was a distinct difference in the frequency of the P479L genotype between the two populations, with seven heterozygotes identified in the Dolgan-Nganasan population (7/108; 0.07; 95% confidence interval, 0.03–0.13) and no carriers of the mutant gene identified in the Nenets population (0/105), p = 0.006. The frequency of the rare T-allele in the Dolgan-Nganasan population was 0.03. The results of the study support the hypothesis of the influence of the traditional diet and “evolutionary advantage” for carriers of the P479L mutation residing in certain Arctic regions. We assume that a certain increase in the prevalence of the genetic variant P479L in the Dolgan population may be due to proximity of the area of residence to the coast and adherence to a high-fat diet. Furthermore, we believe that our data and the results of similar studies addressing the frequency of the P479L mutation can be successfully used for the analysis of the origin and migration of certain indigenous peoples of the Far North.

The results of analysis of specific characteristics of the heart rate variability (HRV) regulation in preschool children living under the Arctic high-latitude conditions are presented. The principal ageand gender-specific differences in the HRV regulation have been inferred from the intergroup evaluations of the HRV indicators in boys and girls. A functional developmental delay has been shown in 2.5-year-old girls compared with boys of the same age group. The applied orthostatic test has shown lower reserve capacities in children of the senior group compared with the junior group. It has been shown that the mechanisms of the regulation of cardiac rhythm in girls experience higher strain during orthostasis as compared with boys. The division of children into age groups with an age difference of one year has allowed the detection of the tendency towards basically different responses to functional loads during orthostasis. The mean HRV values characteristic of four- to six-year-old children living in the Arctic are presented. It has been shown that the children living at middle latitudes have a higher adaptive potential compared with the children living in high-latitude Arctic areas.

We investigated the features of the structural and functional organization of the left heart (ventricle—LV, atrium—LA) and the state of systemic hemodynamics at rest and in response to a single dose of cardioselective β₁-blocker (BB) Egilok. We examined the patients with stage II (1–2 degrees) of arterial hypertension (AH); the study was performed in summer and winter in the northern regions of Russia. It was found that the process of adaptation to cold is accompanied by the inhibition of the pacemaker, a decrease in the rate of active diastolic blood filling of the LV and transaortic blood flow in the aortic root (VAo), an increase in the contractility of the LV posterior wall and interventricular septum (IVS). The negative chronotropic cardiac effect in these conditions results in the reduction of heart productivity per minute in 65% of cases. In winter we observed a more pronounced diastolic LV dysfunction and a decrease in the connectivity of active relaxation of LV posterior wall and LA walls with certain structural and functional cardiac parameters. In contrast to summer, in winter period BB causes a decrease in the active relaxation of LA walls and IVS and LA contractility, which leads to a decrease in the blood filling of passive and active LV. At the same time, LV systolic function (ejection fraction, VAo) and the rhythm and the performance of the heart (stroke volume and cardiac output) decreases; the hypotensive effect accompanied by an increase in peripheral vascular resistance is more pronounced. In winter, the effect of BB reduces the correlation between IVS and LV posterior wall contractions, but the feedback rate or passive to active LV diastolic hyperemia and after load increases. We suggest that in winter component “contractile apparatus” retains its the leading role in the organization of intracardiac response to the BB in patients with hypertension; in addition, new dominant components were formed: “contingency of the LV wall contraction with afterload” and “reverse contingency of early and late diastolic LV function.”

Age-related decrease in blood concentration of testosterone and dehydroepiandrosterone sulfate was found in mining workers living in the European North. The correlation analysis reveals associations of both hormones with biological age and testosterone with plasma lipid profile. The age dependence of cardiovascular risk and the hormonal mechanisms of its development are discussed.

The first study on the frequencies of polymorphic variants of the GSTP1 gene encoding glutathione-S-transferase P1 in Tundra Nenets and Nganasan populations was performed. The subject of the study was the single nucleotide polymorphisms rs1695 (Ile105Val substitution in the protein sequence) and rs1138272 (Ala114Val substitution) that had previously been shown to be associated with cancer and other multifactorial diseases. The data for Tundra Nenets of the Yamalo-Nenets autonomous okrug, Nganasans of the Taimyr Peninsula, and Russian residents of the Northern Siberia were compared. The frequencies of the mutant 105Val and 114Val variants were 10.8% and 0.8% in Nganasans, 23.7% and 4.8% in Nenets, and 35.8% and 9.1% in Russian population samples, respectively. The differences within all pairs of populations were significant for each allele. These differences may characterize the population-level susceptibility to cancer and other multifactorial diseases.