Viktor A. Ilyukha

The study is aimed at determining tissue antioxidant levels in juvenile and adult northern birch mice (Sicista betulina Pallas, 1779) at the northern periphery of its range (Republic of Karelia). Our results indicate a mixed pattern of age-related changes in the antioxidant defense system: aging is accompanied by a decrease in catalase activity in the kidneys as well as an increase in heart catalase activity and kidney, cardiac, and skeletal muscle superoxide dismutase activity. The levels of low-molecular antioxidants, i.e., reduced glutathione (GSH) (kidneys and heart) and α-tocopherol (heart and skeletal muscle), are lower in juvenile northern birch mice compared to adults animals, which is probably associated not only with the active growth and high mobility of juvenile mice during the dispersal period, but also with the stress of physiological systems due to living in northern conditions and preparing for hibernation. Higher levels of GSH and α-tocopherol are found in the hearts of adult northern birch mice compared to other small mammal species of the order Rodentia living in the Republic of Karelia, which indicates the important role of low-molecular weight antioxidants in protecting tissues against oxidative damage in this species.

Background. Among the environmental factors that influence the increase in the frequency of occurrence of psychoemotional states, great importance is attributed to the light conditions. However, the mechanisms of behaviour regulation in the mammals in non-standard light conditions and the role of melatonin in this process have not been fully studied.The aim of the study. To assess the effects of specific northern light conditions and melatonin on the behavior of Mesocricetus auratus.Methods. The animals were divided into 4 groups: LD (control), NL (northern light conditions), and LD + mel and NL + mel (melatonin, 100 μg/animal). The study of behavioral reactions, the level of emotional and phobic anxiety state of animals was carried out in the “Open field” and “Dark chamber with holes” installations.Results. Keeping M. auratus in NL had a negative effect on their behavior – a decrease in motor activity (horizontal and vertical) and the “hole-exploratory behavior”, an increase in the number of freezing and grooming reactions and the time of the first peeking out of the upper hole were revealed. It was shown that melatonin contributed to an increase in exploratory activity and a decrease in the number of anxiety acts in NL + mel group compared to NL group; the opposite effect of the hormone on these parameters was observed in LD + mel group.Conclusion. The obtained results indicate the important role of photoperiod and melatonin in regulating the behavior of seasonally breeding species.

The strategies to cope the repetitive cycles of hypoxia/reoxygenation associated with diving may vary among different mammal species. The aim of this research was to analyze the antioxidant defenses in tissues of semiaquatic rodents, such as Ondatra zibethicus (L., 1766), Arvicola amphibius (L., 1758) and non-diving closely related rodent species—Myodes glareolus (Schreber, 1780) and Alexandromys oeconomus (Pallas, 1776). Adult females and males were captured in August–September in northwestern Russia (Republic of Karelia). Revealed species-specific differences in the studied values suggest that O. zibethicus, the larger animal with longer dive duration, possess the greater enzymatic antioxidant capacity in their tissues than A. amphibius, which tissues frequently rely on the low molecular weight antioxidant glutathione.The results of this study support the hypothesis that besides having common or very similar adaptations of the antioxidant system to diving hypoxia/reoxygenation the closely related rodent species possess different adjustments or strategies of these adaptations that is species-dependent and probably connected with oxygen stores, basal metabolic rate and diving behavior.

Vitamins A and E are known as nutrients involved in metabolic processes and facilitating the adaptation of animals. The metabolism of these vitamins is closely related to lipid metabolism, which has seasonal variations in animals inhabiting northern latitudes. The aim of this study was to investigate the concentrations of retinol (vitamin A) and α-tocopherol (vitamin E) in the cold season (October to February) in tissues of Canidae species that have different ecological characteristics: the blue fox (Vulpes syn. Alopex lagopus), silver fox (Vulpes vulpes), their interspecific hybrids (Vulpes×Vulpes), raccoon dog (Nyctereutes procyonoides), and grey wolf (Canis lupus). In addition, age-related differences in the levels of these vitamins were determined. Results showed the distribution of retinol and α-tocopherol in the body of the canids was similar, with larger amounts being found in the liver and kidney cortex, which play a regulatory role in the metabolism of these nutrients. The higher retinol level in the liver of wolves and interspecific hybrids of blue fox and silver fox, as compared to the retinol level in the liver of other species, might be species-specific and could also be attributed to dietary differences. The blue fox and raccoon dog both have a higher capacity for α-tocopherol accumulation in the cold season, apparently due to their ability to store substantial fat reserves. Retinol and α-tocopherol levels were generally higher in the tissues of mature animals. canids, cold season, ecological features, retinol, α-tocopherol

Background. Due to the growing light pollution and the development of new territories, including northern ones, the search for drugs that increase the adaptive capacity of the organism is promising.The aim. We studied the effects of the exogenous melatonin (100 µg/day/animal) on antioxidant status of liver and small intestine in Syrian hamsters (Mesocricetus auratus) in the light conditions of North-West of Russia (Petrozavodsk, northern lighting – NL).Materials and methods. Female hamsters were exposed to a 12/12 light/dark cycle (LD; n = 12) or NL for 3 months. In NL light conditions hamsters were divided into two groups: NL-control (received placebo; n = 12) and NL-mel (received melatonin; n = 12). The study was conducted from the period of the summer solstice – June 25 (NL: 19.36/4.24) to September 25 (NL: 12/12) (autumn equinox).Results. Animals were kept in the NL conditions had decreased the levels of GSH and activities of antioxidant enzymes (superoxide dismutase (SOD) and catalase) at initial stage of experiment as well as increased TBA reactive substances (TBARS) level at the beginning and after a month of the experiment in the liver in comparison to control (LD). It was observed that in the small intestine the activities of SOD and the levels of GSH (initial and intermediate stages) and TBARS (end of the experiment) were significantly higher in NL in comparison to LD. Liver and small intestine TBARS concentrations after one and three months of the experiment were decreased in NL-mel in comparison to NL-control.Conclusion. The results of the study indicate the sensitivity of the antioxidant defense system in the tissues of the liver and small intestine of Syrian hamster to the photoperiod and exogenous melatonin. The present study revealed that exogenous melatonin was able to reduce the level of TBARS and increase the activity of SOD and CAT in the light conditions of North-West of Russia.

We studied the effect of long-term light deprivation which began at different stages of ontogeny on the content of α-tocopherol in rats during the first 3 months of postnatal development. In the offspring postnatally exposed to constant darkness, the level of α-tocopherol in the liver, kidneys, heart, skeletal muscles, and lungs was significantly decreased at the early stages of postnatal ontogeny (2 weeks and 1 month). In rats kept under constant darkness after birth, the content of α-tocopherol in the lungs was also reduced at the age of 1 month. The modulating effect of light deprivation on the level of α-tocopherol can be associated both with the impact of disturbed circadian rhythms and with increased content of melatonin in the body.