All living organisms experience physiological changes regulated by endogenous circadian rhythms. The main factor controlling the circadian clock is the duration of daylight. The aim of this research was to identify the impact of various lighting conditions on physiological parameters and gut microbiota composition in rats. 3 groups of outbred rats were subjected to normal light-dark cycles, darkness and constant lighting. After 1 and 3 months we studied urinary catecholamine levels in rats; indicators of lipid peroxidation and antioxidant activity in the blood; protein levels of BMAL1, CLOCK and THRA in the hypothalamus; composition and functional activity of the gut microbiota. Subjecting the rats to conditions promoting desynchronosis for 3 months caused disruptions in homeostasis. Changing the lighting conditions led to changes in almost all the physiological parameters that we studied. Catecholamines can be regarded as a synchronization super system of split-level circadian oscillators. We established a correlation between hypothalamic levels of Bmal1 and urinary catecholamine concentrations. The magnitude of changes in the GM taxonomic composition was different for LL/LD and DD/LD but the direction of these changes was similar. As for the predicted functional properties of the GM which characterize its metabolic activity, they didn’t change as dramatically as the taxonomic composition. All differences may be viewed as a compensatory reaction to new environmental conditions and the organism has adapted to those conditions.

Background: All living organisms have developed during evolution complex time-keeping biological clocks that allowed them to stay attuned to their environments. Circadian rhythms cycle on a near 24 h clock. These encompass a variety of changes in the body ranging from blood hormone levels to metabolism, to the gut microbiota composition and others. The gut microbiota, in return, influences the host stress response and the physiological changes associated with it, which makes it an important determinant of health. Lactobacilli are traditionally consumed for their prophylactic and therapeutic benefits against various diseases, namely, the inflammatory bowel syndrome, and even emerged recently as promising psychobiotics. However, the potential role of lactobacilli in the normalization of circadian rhythms has not been addressed. Results: Two-month-old male rats were randomly divided into three groups and housed under three different light/dark cycles for three months: natural light, constant light and constant darkness. The strain Levilactobacillus brevis 47f was administered to rats at a dose of 0.5 ml per rat for one month and The rats were observed for the following two months. As a result, we identified the biomarkers associated with intake of L. brevis 47f. Changing the light regime for three months depleted the reserves of the main buffer in the cell—reduced glutathione. Intake of L. brevis 47f for 30 days restored cellular reserves of reduced glutathione and promoted redox balance. Our results indicate that the levels of urinary catecholamines correlated with light/dark cycles and were influenced by intake of L. brevis 47f. The gut microbiota of rats was also influenced by these factors. L. brevis 47f intake was associated with an increase in the relative abundance of Faecalibacterium and Roseburia and a decrease in the relative abundance of Prevotella and Bacteroides. Conclusions: The results of this study show that oral administration of L. brevis 47f, for one month, to rats housed under abnormal lightning conditions (constant light or constant darkness) normalized their physiological parameters and promoted the gut microbiome's balance.

The possibility of using methods for determining the oxidative status of an organism (enzymatic and non-enzymatic links of the cellular antioxidant system) to assess the antioxidant properties of peptides of the pituitary gland of the reindeer (Rangifer tarandus) were investigated in an experimental study conducted with a combined effect of factors of different nature on rats: a physical factor — prolonged light desynchronosis (different light modes) and a chemical factor - acute severe poisoning with depriving toxicant (sodium thiopental, LD₅₀). The pharmacological correction of the oxidative status of cells in the animals of the experimental subgroups was carried out with the peptide product of the pituitary gland, intranasally injecting the surviving rats with the bioproduct at a dose of 100 µg/kg, once in the first half of the objective day for 14 days after poisoning with sodium thiopental. The surviving animals of the control groups were similarly injected with saline. The effectiveness of the correction of the disruptions of the cellular oxidative status with the peptide product of the pituitary gland was tested 30 days after the onset of the combined effect of stress factors on rats. It was found that the use of this bioactive peptide product in experimental animals exposed to different light modes and a chemical factor contributed to a decrease in the initially increased indicators of lipid peroxidation in rat erythrocytes and an increase in the initially reduced indicators of the enzymatic link of antioxidant protection. The activity of superoxide dismutase, glutathione peroxidase, glutathione transferase, as well as glucose-6-phosphate dehydrogenase increased after pharmacological correction. The concentration of reduced glutathione also increased in erythrocytes. The maximum changes were observed in the experimental subgroup of rats exposed to the combined effects of constant illumination and depriming toxicant. It was also found that the revealed positive changes in the indicators of the enzymatic link of antioxidant protection in animals of the experimental subgroups are associated with the maintenance of a sufficient concentration of reduced glutathione in red blood cells, which contributed to the maintenance of the cellular redox balance, when the conditions of the external lighting regime are violated.

BACKGROUND: Low-dose exposure of mercury compounds to the human body for a long time leads to the accumulation of a toxicant in tissues, causing damage to health. Mercury can be delivered to a developing fetus through the placenta or to an infant through breast milk. Erythrocytes are the preferred cell for mercury accumulation, reaching a concentration 20 times higher than the concentration in blood plasma. Erythrocytes have powerful antioxidant protection. The antioxidant protection system of the cell plays an important role in maintaining of homeostasis in the cell. Despite of the apparent vastness of researches of the antioxidant system and lipid peroxidation, changes after subacute poisoning with heavy metals have not been sufficiently studied. AIM: Study changes in biochemical parameters in Wistar rats erythrocytes with subacute poisoning with mercury acetate. MATERIALS AND METHODS: 30 days and 44 days after the administration of mercury acetate at a dose of 4 mg/kg in the hemolysate of red blood cells of rats, the indicators of the antioxidant system and lipid peroxidation were determined. RESULTS: The administration of mercury acetate for 30 days significantly increased the activity of SOD, GP and reduced the activity of GT. An increase of DC concentration was noted. 14 days after the end of the injection of the toxicant, the imbalance of the AOS enzyme link persists. An increase of DC and MDA concentrations was revealed. CONCLUSIONS: The data obtained demonstrate a violation of the antioxidant balance in erythrocytes after a 30-day administration of mercury acetate. 14 days after the end of the injection of the toxicant, changes in the enzyme link of AOS persist. Intensification of the processes of lipoperoxidation of erythrocyte membranes has been established. In the delayed period after poisoning, there is a tendency to disturbance the balance of AOS of erythrocytes, the intensity of LPO processes increases.

BACKGROUND: Disruption of circadian rhythms can cause significant damage to sensory processing, learning, and memory. At the same time, the structure of the endogenous biological clock contributes to the adaptation of the organism to changes in the conditions for the existence of a biosystem in the external environment. The possibility of synchronization of the endogenous rhythms of the organism with disturbed light periodicity is an urgent problem of modern society, where different rhythms of labor, motor, cognitive activity are used. AIM: To study the effect of peptides from the pituitary gland of the Reindeer on the parameters of cognitive functions in rats with a long-term change in the light regime on models with altered cellular oscillation due to oxidative stress caused by poisoning of animals with sodium thiopental in a half-lethal dose. MATERIALS AND METHODS: The study was conducted on 56 white Wistar male rats after acute poisoning with sodium thiopental at a dose of 85 mg/kg under conditions of light desynchronosis. In the passive avoidance conditioned reflex test, the cognitive functions of animals were assessed after a two-week pharmacological correction with a cellular extract of the pituitary gland of the Reindeer at a dose of 100 mg/kg. RESULTS: The peptide extract of the pituitary gland of the Reindeer contributes to the change in the higher integrative functions of the central nervous system in case of disturbed periodicity of the light signal. The results obtained indicate the chronobiotic activity of the peptide extract of the pituitary gland of the Reindeer at a dose of 100 g/kg when administered intranasally. CONCLUSIONS: The light regime change for 1 month under conditions of altered cellular oscillation led to impaired of the higher integrative functions of the central nervous system in rats, which was accompanied by an increase in the rate of reflex extinction and a disturbance of the processes of memory consolidation; under conditions of constant light, these disorders are more pronounced. The result of the pharmacological correction of these changes with the reindeer pituitary peptide extract was an improvement in the processes of memory consolidation and information reproduction (an increase in the number of trained animals with a change in the light regime).