The influence of melatonin on stress-induced ultramicroscopic changes of the neurons of the supraoptic nuclei of the rat hypothalamus

The aim: to study the effect of melatonin on the ultrastructural state of the supraoptic nuclei of the hypothalamus of rats under immobilization stress.Materials and methods. The experiments were performed on non-linear male white rats weighing 200-220 g. The animals were divided into 3 study series, in each of which the biomaterial was collected at 2 p.m. and at 2 a.m. using electron microscopic method. Long immobilization stress was simulated by keeping rats in special plastic penal cages for 6 hours daily for 7 consecutive days. Melatonin (Sigma, USA, 99.5% purification degree) at a dose of 0.5 mg/kg, in 1.0 ml of solvent (0.9% ethanol solution on physiologic saline) was injected daily, intraperitoneally.Results. When the animals were kept under the standard light regime, the ultrastructural organization of the hypothalamic nuclei at 2 p.m. indicated their low functional activity in comparison with the studies carried out at 2 a.m. Prolonged exposure of rats to immobilization stress was reflected in a significant rearrangement of the ultrastructural organization of supraoptic nuclei of the hypothalamus. The established changes can be considered as a manifestation of neurosecretory activity suppression, a decrease in neurosecretase production by hypothalamic neurons. Melatonin injections against the background of immobilization stress resulted in relative normalization of ultrastructural state of neurons of supraoptic nuclei of the hypothalamus of animals. In particular, studies at 2 a.m. revealed light neurosecretory cells containing a large nucleus, it was pyknotically altered. Karyolema invaginations, euchromatin dominance in the nucleus were observed. Heterogeneous changes were observed on the part of mitochondria. Enlarged tubules of granular endoplasmic reticulum were seen. At the same time, a small number of ribosomes and few hormonal granules were noticeable in neuroplasm. The mentioned picture of neurosecretory cells reflects a relative improvement in their electron microscopic state, which is evidenced by the appearance of neurosecretory granules. However, the ultrastructure of other organelles of the studied neurons indicates a depleted state caused by prolonged immobilization.Conclusions. 1. In animals under standard photoperiod conditions, the structural organization of supraoptic neurons of the hypothalamic nuclei during the nighttime of the experiment reflects the intensity of intracellular synthesizing processes (at 2 a.m.). A decrease in the activity of the structures under study is noted during the daytime. 2. Under immobilization stress, the ultrastructural organization of the above neurons indicates a pronounced disturbance of reactive nature with the signs of decreased functional ability of the structures and the phenomena of edema and destruction during the period of observation. 3. Melatonin injections against the background of immobilization stress led to a relative improvement in the ultrastructural state of the animals’ hypothalamic nuclei neurons, which is evidenced by the appearance of neurosecretory granules. However, the ultrastructure of other organelles of the studied neurons indicated a depleted state caused by prolonged immobilization.

Dynamics of changes in nonspecific resistance of guinea pigs under conditions of formation of experimental periodontitis and immobilization stress

The aim of our study was to determine the phagocytic activity of leukocytes and nitrosine tetrazolium test (NST - test) in the dynamics of experimental periodontitis (EP) and immobilization stress (IS). It is established in the work that the indicators studied by us, namely phagocytic number, phagocytic index and NST - test increase on the 3 rd, 5 th and 15 th days of our experiment. The above tests have a high diagnostic value and allow to characterize the degree of activity of the inflammatory process and determine the participation of individual parts of the body's defense mechanisms. The obtained results make it possible to express the opinion that polymorphonuclear leukocytes take an active part in the formation of EP and IS, as well as indicate the stimulation of metabolic processes in leukocytes.

Evaluation of endogenous intoxication indicators in the dynamics of experimental periodontitis and immobilization stress

The aim of our work was to investigate the peculiarities of changes in endogenous intoxication rates: medium mass molecules (MMM) and erythrocyte intoxication index (EII) in the blood of guinea pigs in the formation of combined pathology - experimental periodontitis (EP) and immobilization stress (IS).The results of biochemical studies showed that at all stages of development of combined pathology - experimental periodontitis and immobilization stress there is a consistent increase in the degree of endogenous intoxication, which dominated on the 15th day of the experiment, namely increased content of medium mass molecules (МMМ254 , MMM280) and EII in the blood by 58.5% (p≤0.05), 80.3% (p≤0.05) and 95.7% (p≤0.05), respectively, compared with the first group of animals is a clear manifestation of the formation of endogenous intoxication. These changes are obviously the result of insufficient elimination of toxic products on the background of the inflammatory process in periodontal tissues and stress.

Peculiarities of changes in a functional condition of pro-oxidant and antioxidant systems in guinea pigs’ lungs in experimental allergic alveolitis under the conditions of immobilization stress

We have analyzed the results of investigation of alterations in indices of pro-oxidant (conjugated diene and malondialdehyde) and antioxidant (superoxide dismutase, ceruloplasmin, catalase) systems in guinea pigs’ lungs in experimental allergic alveolitis in the dynamics of EAA development under the conditions of immobilization stress. The investigation was conducted on 62 female guinea pigs weighing 180-220 g, divided into 4 groups: I – intact guinea pigs (n=20), II – guinea pigs (n=14) with EAA under the conditions of IS (1st day); III – guinea pigs (n=14) with EAA under the conditions of IS (2nd day); IV – guinea pigs (n=14) with EAA under the conditions of IS (64th day). The results of experimental investigation showed that a significant increase in conjugated diene level in animals’ lungs was observed at all stages of EAA development under the conditions of immobilization stress as compared with control group, indicating activation of this marker. The same changes occurred with MDA content, indicating excessive accumulation of this lipid peroxidation product in lung tissue. Intensive synthesis of free radical compounds caused activation of some components of enzymatic system of antioxidant defense. In particular, a moderate decrease in superoxide dismutase activity in lung tissue is observed in response to increased level of LOPs at early stages of EAA and immobilization stress development as compared with the indices in intact animals. The same situation is observed with catalase and ceruloplasmin activity in the lungs of guinea pigs with modeled AA and IS.

Peroxiredoxin 6 Knockout Mice Demonstrate Anxiety Behavior and Attenuated Contextual Fear Memory after Receiving Acute Immobilization Stress

Stress can elicit glucocorticoid release to promote coping mechanisms and influence learning and memory performance. Individual memory performance varies in response to stress, and the underlying mechanism is not clear yet. Peroxiredoxin 6 (PRDX6) is a multifunctional enzyme participating in both physiological and pathological conditions. Several studies have demonstrated the correlation between PRDX6 expression level and stress-related disorders. Our recent finding indicates that lack of the Prdx6 gene leads to enhanced fear memory. However, it is unknown whether PRDX6 is involved in changes in anxiety response and memory performance upon stress. The present study reveals that hippocampal PRDX6 level is downregulated 30 min after acute immobilization stress (AIS) and trace fear conditioning (TFC). In human retinal pigment epithelium (ARPE-19) cells, the PRDX6 expression level decreases after being treated with stress hormone corticosterone. Lack of PRDX6 caused elevated basal H2O2 levels in the hippocampus, basolateral amygdala, and medial prefrontal cortex, brain regions involved in anxiety response and fear memory formation. Additionally, this H2O2 level was still high in the medial prefrontal cortex of the knockout mice under AIS. Anxiety behavior of Prdx6−/− mice was enhanced after immobilization for 30 min. After exposure to AIS before a contextual test, Prdx6−/− mice displayed a contextual fear memory deficit. Our results showed that the memory performance of Prdx6−/− mice was impaired when responding to AIS, accompanied by dysregulated H2O2 levels. The present study helps better understand the function of PRDX6 in memory performance after acute stress.

Peculiarities of disorders of nitrogen oxide system in the blood at adrenalin-induced myocardial injury in conditions of immobilization stress and their correction by L-arginine

The aim: of the study was to elucidate the changes to nitric oxide activity in the blood during adrenaline-induced myocardial injury under immobilization stress and to establish the corrective effect of L-arginine. Methods: determination of free arginine was conducted by the method of Aleinikova T.L., total nitric oxide products in the blood by the method of Schmidt H.H., the total activity of nitric oxide synthase by the method of Sumbaiev V.V.. Immobilization stress was reproduced by the method of Horizontov P.D. Adrenaline-induced myocardial injury was reproduced by the method of Markova O.O. L-arginine was injected based on scientific data by Kiryanova N.A. Results. Studies have shown that on days 1 and 3 with adrenaline-induced myocardial injury under immobilization stress there was an increase in nitric oxide products in the blood, respectively, according to control. The use of L-arginine on the 5th day, led to a decrease in levels of NO products in the blood by less than, lower against the group of animals with MI and IS, to treatment. Conclusions. Thus, biochemical studies of NO system in the dynamics of IS and MI showed an increase in food content and total synthase activity of NO on the background of reduced levels of L-arginine, which were detected at all stages of the study and especially expressed on the 1st day before treatment. The use of the drug L-arginine, made it possible to identify its corrective effect on impaired metabolic processes in MI and IS