Age changes in the tigroid substance of neutrons of the lateral preoptic nucleus of hypothalamus under different light modes

The article presents analysis of the results of the original histochemical studies of tigroid substance of neurons of the lateral preoptic nucleus of hypothalamus in mature and old rats under the influence of different light modes. In all observations, the tigroid substance was located in the cytoplasm of neurons of the lateral preoptic nucleus of hypothalamus in the form of individual granular formations of different sizes and shapes. The amount of tigroid substance of neurons of the lateral preoptic nucleus of hypothalamus in mature rats is greater than in older rats. At the same time, it should be noted that different experimental conditions significantly affected the amount of tigroid substance in neurons of the lateral preoptic nucleus of hypothalamus in old rats. In particular, under conditions of light deprivation, the optical density of specific histochemical staining for tigroid substance in neurons of the lateral preoptic nucleus of hypothalamus increased significantly (p<0,001), and under conditions of light stimulation, on the contrary, probably decreased (p<0,001).

Features of the expression of melatonin MT1 receptors in the general cover of rats caused by light deprivation

Background. It has now been established that any change in the synchronized work of the circadian clock leads to a disruption of the body's regulatory systems, which consists in the development of metabolic disorders and tissue damage. Objective: to study the dynamics of the expression of the MT1 melatonin receptor in the skin of white male rats under light deprivation. Methods. In this work, using immunohistochemistry, the features of the expression of receptors for melatonin (MT1) were studied. The experiments were performed on outbred male rats weighing 170-220 g, which were divided into 2 groups; intact - animals kept under standard fixed lighting conditions (12 h light / 12 h dark); Group 2 - animals with simulated light deprivation in conditions of round-the-clock darkness (24 hours of darkness). Results. A strong circadian dependence of the expression of MT1 melatonin receptors in the general integument was established. In the cells of the epidermis and sebaceous glands, by the 14th day, MT1 expression significantly decreased, which then sharply increased by the 21st day. In the keratinocytes of the epidermis, a wavelike character of changes in indicators is noted throughout the study: an increase (7th day) - a decrease (14th day) - a sharp increase (21st day). Conclusion. Initially, light deprivation leads to a decrease in the number of immunopositive cells, and then their level increases compensatory, which is one of the manifestations of the body's adaptation mechanisms to chronodestruction.

Effect of exogenous melatonin and flaxseed oil on the expression state of MT1 receptors in rat skin under light deprivation

Most of the skin cells have their own autonomous functional circadian system, which is able to control physiological and biochemical processes in the general integument. A special role in these processes is assigned to the “clock” hormone of the pineal gland, melatonin, which acts on target cells through specific receptors (MT1, MT2, MT3 and RORα). Any disturbance of circadian rhythms can lead to rearrangements (disturbances) in the receptor apparatus of the cells of the general cover, which require a certain correction. Consequently, there is a need to search for effective and reliable drugs that will prevent the negative consequences caused by chronodestruction. In the present work, we studied the effectiveness of the effect of exogenous melatonin and flaxseed oil on the expression of MT1 receptors in the general coat of rats under light deprivation. An experimental study was carried out on 130 white outbred male rats (170-220 g), which were randomly divided into 5 groups: intact, light deprivation animals, light deprivation animals, which were injected intragastrically with flaxseed oil and melatonin. On days 7, 14 and 21, histological material was taken (fragments of the skin of the interscapular region of the back). For immunohistochemical studies, serial sections were stained using MTNR1A polyclonal antibodies. For morphometric data analysis, the Image Scope Color and ImageJ computer programs were used. All statistical data processing was performed using the Statistica 10.0 software. Differences were considered significant at a significance level of less than 0.01 (p <0.01). In the course of the experiment, it was found that light deprivation contributes to a change in the activity of expression of the MT1 melatonin receptors in the epidermis, sebaceous glands and hair follicles. Studies have shown that the administration of flaxseed oil, melatonin, and their combination to rats with desynchronosis is accompanied by the leveling of the adverse effect of desynchronosis on the studied parameters of MT1 receptors. The most pronounced corrective effect on the expression of MT1 receptors is observed with the introduction of exogenous melatonin on the 21st day of the experiment.

LIGHT DEPREVATION INFLUENCE ON MORPHOFUNCTIONAL STATE OF NEURONS OF THE HYPOTHALAMUS SUPRAOPTIC NUCLEI IN RATS

The supraoptic nucleus (SON) of the hypothalamus is one of the key neurosecretorylinks that ensure the joining of the nervous and endocrine regulation mechanismsinto the general neuroendocrine system, thereby participating in the realization of thebody’s response to experimental influences. Despite deep and comprehensive studies ofthe hypothalamus, until now there are no unified ideas about its individual reactivityand the degree of involvement of these structures in the stress response, caused by prolonged exposure to constant darkness (light deprivation).The aim of this work is to study the effect of light deprivation on the morphofunctionalstate of the supraoptic nucleus of the hypothalamus in rats.Material and methods. The experiments were carried out on nonlinear male white rats,which were divided into 2 series of studies, biomaterial sampling of which was taken at14.00 and 02.00 h using morphofunctional and statistical research methods.Results. The study of the morphometric characteristics of the neurons of thehypothalamus SON revealed the diurnal dynamics of indices. Under the light regime12.00C:12.00T, a daily rhythm of the morpho-functional activity of SON neurons witha maximum activity is registered in rats in the daytime.When the animals were kept under conditions of constant darkness (00C:24.00T), anincrease in the size of its nucleus 21.1±2.4% (r=0.73), caused by an increase in thearea of the neuron nucleolus (r=0.89), which constituted 61.94±7.07 µm2, was revealedat 14.00. Attention was also drawn to a significant decrease in the nuclear-cytoplasmicratio (NCR) relative to intact animals, which constituted 2.07±0.041 units. Lightdeprivation led at 14.00 to a significant RNA concentration decrease in the nucleus35.3±2.1%, and in the nucleolus 26.6±1.9%.The studies, carried out at 02.00 h, revealed that the area of the neuron nucleuswas 98.33±5.40µm2and significantly larger than that in the intact animals. Thesechanges were accompanied by an increase in the area of the nucleolus, which was48.90±6.892µm2(r=0.87) and the area of the neuron cytoplasm, which was within217.61±7.19 µm2(r=0.91). The NCR of a neuron in the SON of the hypothalamus at02:00 was lower than that in the intact animals 2.67±0.17%. A significant increasein RNA concentration in the nucleus, nucleolus and cytoplasm of neurons in thehypothalamic SON was noted relative to the indices of animals of the previous timeinterval, which were under conditions of constant darkness.Compared to the daytime period (14.00 h), up to 02.90 h, NCR increase was revealedin the nighttime observation period in the neurons under study, which constituted2.55±0.022 units.Conclusions. 1. Photoperiod duration significantly affects the daily activity of thehypothalamus SON. 2. Permanent darkness (light deprivation) does not lead to aninversion of the rhythm of the morphofunctional activity of the neurons under study,the maximum values, as in intact animals, are registered in the daytime interval. 3.Light deprivation causes a significant increase in the area of the neuron, its nucleus,nucleolus in the night and day intervals of observation. At the same time, a decrease inthe nuclear-cytoplasmic ratio, a decrease in the concentration of RNA in the nucleusand nucleolus of the neuron of SON of the hypothalamus of rats in the daytime isobserved.

ONTOGENETIC ASPECTS OF MELATONIN RECEPTORS 1A DENSITY IN THE LATERAL PREOPTIC NUCLEUS OF THE HYPOTHALAMUS UNDER VARIOUS LIGHT CONDITIONS

The aim: To find out density of melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus in mature and old rats under various light conditions. Materials and methods: The study was carried out on 72 albino mature and old rats with light conditions appropriate for the experiment. To find out circadian differences of melatonin receptors 1A the material for the study was taken at 2 p.m. and 2 a.m. Visualization of primary antibodies against melatonin receptors 1A (Abcam) was conducted by means of the polymeric system Dako and diaminobenzidine staining under the microscope Delta Optical Evolution 100. The intensity of staining was assessed on the digital copies of images according to computer microdensitometry method. Results: Immunohistochemical examinations conducted enable to suggest that melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus respond to different light conditions. In particular, intensity of immunohistochemical staining to melatonin receptors 1A under conditions of light deprivation increases both in mature and old rats, but it decreases under conditions of light stimulation. The parameter is higher at 2 a.m. as compared with 2 p.m. Intensity of immunohistochemical staining to melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus is always lower in old rats than in mature ones. Conclusions: Density of melatonin receptors 1A in the neurons of the lateral preoptic nucleus of the hypothalamus is subordinated to the circadian rhythm: it increases at night and decreases in the daytime. At the same time, light stimulation results in disorders of the rhythm and development of desynchronization.

In situ Responses of the Eelgrass Zostera marina L. to Water Depth and Light Availability in the Context of Increasing Coastal Water Turbidity: Implications for Conservation and Restoration

Accelerating losses of seagrass meadows has led to efforts to restore these highly productive and beneficial ecosystems globally. Depth and light availability are critical determinants of seagrass restoration success. Eelgrass (Zostera marina L.) is the dominant seagrass species in the temperate northern hemisphere, but its global distribution has reduced dramatically. The main aims of this study were to determine: (1) the depth limit for Z. marina survival in Ailian Bay, north China, and (2) how light availability affects the growth and recruitment of Z. marina as a basis for identifying a suitable depth range for successful restoration. To achieve these aims, Z. marina shoots were transplanted from a nearby donor site, Swan Lake, to an experimental site, Ailian Bay, and the temporal responses of Z. marina shoots to light availability at water depths ranging from 1 to 8 m were investigated using in situ suspended cultures. Four suspended shoot transplantation experiments were conducted in 4 years. The results showed that the transplanted Z. marina shoots could survive and branch during an annual growth cycle, permanently underwater, at a depth ≤3 m. Due to the local turbidity of the waters in Ailian Bay, a depth of 4 m led to sufficient light deprivation (reduced to 6.48–10.08% of surface irradiance) to negatively affect seagrass shoot density and clonal reproduction. In addition, reproductive shoot density also tended to decline with water depth and light deprivation. Our results indicated that Z. marina population recruitment, through sexual and asexual (clonal growth) reproduction, were negatively affected by increasing water depth and light deprivation. These findings may provide a suitable depth range for the successful restoration of Z. marina in local coastal waters. They may also be applied to the management and restoration of Z. marina globally.

Antidepressant Effect of Blue Light on Depressive Phenotype in Light-Deprived Male Rats

Blue light has been previously reported to play a salient role in the treatment of seasonal affective disorder. The present study aimed to investigate whether blue light had antidepressant effect on light-deprivation-induced depression model, and the underlying visual neural mechanism. Blue light mitigated depression-like behaviors induced by light deprivation as measured by elevated sucrose preference and reduced immobility time. Blue light enhanced melanopsin expression and light responses in the retina. We also found the upregulation of serotonin and brain derived neurotrophic factor expression in the c-fos-positive areas of rats treated with blue light compared with those maintained in darkness. The species gap between nocturnal albino (Sprague-Dawley rat) and diurnal pigmented animals (human) might have influenced extrapolating data to humans. Blue light has antidepressant effect on light-deprived Sprague-Dawley rats, which might be related to activating the serotonergic system and neurotrophic activity via the retinoraphe and retinoamygdala pathways. Blue light is the effective component of light therapy for treatment of depression.

The State of Oxidative Metabolism in the Cardiac and Skeletal Muscle Tissue in Conditions of Light Deprivation

The article considers the features of oxidative metabolism of cardiac and skeletal muscle tissue in the changed photoperiod, under the influence of round-the-clock light deprivation in combination with the introduction of exogenous melatonin. Material and methods. The experimental study was performed on male Wistar rats. Two groups were formed for research: intact and experimental. The animals of the intact group were in standard housing and feeding conditions, without changes in light regime. The animals of the experimental group for 30 days were in conditions of round-the-clock light deprivation on the background of the introduction of melatonin at a dose of 1.0 mg/kg body weight. Results and discussion. The level of production of reactive oxygen species was evaluated by the formation of a superoxide anion radical. To assess the prooxidant-antioxidant system in the homogenate of the studied tissues was determined by the concentration of thiobarbituric acid reactive substances. The efficiency of the enzyme link was evaluated by catalase and superoxide dismutase activity. We revealed an increase in the production of superoxide anion radical due to the activity of phagocytes compared to the intact group in the heart muscle under conditions of light deprivation on the background of the introduction of melatonin. In skeletal muscle tissue homogenate the production of superoxide anion radical by the mitochondrial electron transport chain production is likely was reduced compared to the intact group. Light deprivation on the background of exogenous administration of melatonin reduces the intensity of production of reactive oxygen species, which is confirmed by a decrease in the level of superoxide anion radical in the homogenate of the quadriceps femoris muscle tissues of experimental animals. Melatonin as an antioxidant reduces the production of superoxide anion radical by mitochondrial oxidation in the quadriceps femoris muscle. In this case, the excess melatonin stabilizes the fluidity of the membrane, reducing its permeability, which may indicate the protective properties of this substance. Conclusion. Thus, modeling the conditions of excess melatonin modifies the generation of superoxide anion radical from various sources. The above experimental conditions contribute to multidirectional changes in the quantitative generation of the superoxide anion radical in the heart and skeletal muscles. Changes in the indicators of prooxidant-antioxidant status in the homogenate of the studied tissues under the selected experimental conditions were not detected