Synthetic melatoninergic ligands: achievements and prospects.

Pineal hormone melatonin is widely used in the treatment of disorders of circadian rhythms. The presence of melatonin receptors in various animal tissues motivates the use of this hormone in some other diseases. For this reason, in recent years investigators continued the search for synthetic analogues of melatonin which are metabolically stable and selective to receptors. This review includes recent information about the most famous melatonin analogues, their structure, properties, and physiological features of the interaction with melatonin receptors.

Non-obvious Problems in Clark Electrode Application at Elevated Temperature and Ways of Their Elimination.

Well-known cause of frequent failures of closed oxygen sensors is the appearance of gas bubbles in the electrolyte. The problem is traditionally associated with insufficient sealing of the sensor that is not always true. Study of a typical temperature regime of measurement system based on Clark sensor showed that spontaneous release of the gas phase is a natural effect caused by periodic warming of the sensor to a temperature of the test liquid. The warming of the sensor together with the incubation medium causes oversaturation of electrolyte by dissolved gases and the allocation of gas bubbles. The lower rate of sensor heating in comparison with the medium reduces but does not eliminate the manifestation of this effect. It is experimentally established, that with each cycle of heating of measuring system up to 37°C followed by cooling the volume of gas phase in the electrolyte (KCl; 60 g/L; 400 µ L) increased by 0.6 µ L approximately. Thus, during just several cycles it can dramatically degrade the characteristics of the sensor. A method was developed in which the oxygen sensor is heated in contact with the liquid, (depleted of dissolved gases), allowing complete exclusion of the above-mentioned effect.

[Changes in lipids of granulation fibrous tissue in rats at various doses and routes of melatonin administration].

The experimental data indicate that melatonin actively influences time-causes of changes of lipid content in rats tissue during the inflammation process. Its effect depends on a dose, modes of administration (intraperitonial, hypodermic or local) and duration of treatment. A single dose intraperitonial administration of melatonin (4 mg/kg) did not influence lipid content in the granular-fibrose tissue, while repeated injections of this hormone limited the increase in contents of lipids and phospholipids at the 5th and 8th days of regeneration. Long-term subcutaneous injections of melatonin caused distinct changes of lipids: at the dose of 0.3 mg/kg it prevented, and at the dose of 4 mg/kg it promoted the increase of lipid content in the granular-fibrose tissue. Local application of a melatonin solution (1.5 mg/ml) at early periods of regeneration caused insignificant changes of total lipids and total phospholipids in the granular-fibrose tissue. However, the higher concentration (15 mg/ml) of melatonin caused the decrease of total lipids due to reduced content of cholesterol and triglycerides and the increase of total phospholipids and some of their fractions.

[Lipid parameters of the skin, cerebellum, and medulla oblongata during immersion stress in rats]. / Lipidnye pokazateli kozhi, mozzhechka i prodolgovatogo mozga pri vodno-immersionnom stress u krys.

The influence of short-form water immersion stress of rats on lipids in the skin, the cerebellum and the medulla oblongata was studied. The level of total lipids and absolute and relative contents of the main lipid fractions (phospholipids, nonesterified cholesterol, free fatty acids, triglycerides, and cholesterol esters) were measured. Stress induced delayed changes of the lipid component of the skin. The first significant changes of lipid fractions were only observed 20 h later after the stress procedure. These changes were retained (being at nearly constant levels) till the end of the second day. The decrease in contents of total lipids and esterified cholesterol was revealed in the cerebellum of stressed rats (in comparison to these levels in control rats). These results suggest the involvement of cholesterol metabolic system in the stress reaction. The content of total lipids decreased also in the medulla oblongata. However, levels of the main lipid fractions changed differently. The content of diglycerides increased and the content of cholesterol decreased. The data obtained suggest that degradation of triglycerides is the principle pathway of metabolic conversions of lipids. Free fatty acids formed during these processes are probably involved in the synthesis of phospholipids and cholesterol esters. The data indicate absolutely different mechanisms of interrelations between individual lipid fractions in the brain regions studied. Various roles of the brain structures in the stress response of the body may account for the differences revealed.