[Regeneration of the Skin Pigment System during Larval Development of the Clawed Frog].

We demonstrate regeneration capability of the skin pigment system of clawed frog larvae after local damage to melanophores without skin rupture. The contribution to recovery of pigmentation of the injured area of de novo differentiation of melanophores is compared to contribution of mitotic division of undamaged melanophores localized on the boundaries of the injured area. The regeneration process is observed during various stages of pigment system development of larvae. We establish that, compared to ontogenetic dynamics, pigmentation development in animals is more intense during the regeneration.

[Metabolic syndrome and melatonin].

Metabolic syndrome (MS) is characterized by the following symptoms: obesity, AH, dyslipidemia, insulin resistance. Pathophysiologically, MS is underlain by disorders of many biochemical and physiological processes, such as elevated levels of low density lipoproteins, hyperstimulation of pancreatic b-cells, increased insulin secretion, substitution of lipid metabolism for carbohydrate one, overgrowth of adipose tissue, excess production of adiponectin, leptin and other signal molecules and a rise in their local intravascular concentration, weight gain. Endogenous and exogenous melatonin inhibits these pathophysiological mechanisms, normalizes metabolism, equilibrates insulin secretion, prevents pancreatic hyperfunction, phosphorylates insulin receptors, inactivates active oxygen and nitrogen species including those produced in LDLP metabolism. Melatonin has specific MT1 and MT2 receptors localized in all body cells. Due to this, it exerts combined preventive action in patients with MS. Recently, melatonin has been reported to have therapeutic effect in MS; it may be recommended to treat this condition.

[Melatonin promotes and synchronizes protein synthesis in hepatocyte culture from old rats].

The effect of 1 to 1000 nM melatonin was studied on daily cultures of rat hepatocytes on slides in serum-free medium. The minimum melatonin concentration (1 nM) proved to synchronize protein synthesis in asynchronous sparse cultures of hepatocytes from rats of different age, and a circahoralian rhythm of protein synthesis was revealed in them. In dense weekly synchronous hepatocytes from old rats (2.5-years-old with the weight of about 600 g), melatonin improved cell synchronization to the level of young animals. Melatonin treatment increased the mean rate of protein synthesis in rats of different age.

[The loach--the object of experimental embryologic research in the Department of Embryology]. / V'iun--ob''ekt éksperimental'no-émbriologicheskikh issledovanii na kafedre émbriologii.

This paper provides a history of research at the Department of Embryology on the teleostean loach fish Misgurnus fossilis L. as a model. The use of the loach in education is briefly described.

[The activity of melanin-aggregating hormones in the blood and eyes in the early postnatal development of rats]. / Aktivnost' melaninagregiruiushchikh gormonov v krovi i glazakh v rannem postnatal'nom razvitii u krys.

The activity of melanin-aggregating hormones (MAH) in the blood serum and homogenates of the eyes in four strains of rats was determined using the method of bioassay on dermal melanophores of tadpoles (Rana temporaria). This test-system is sensitive to melatonin at concentration of 25.1 mg/ml and higher. MAH is detected in the blood at 9th and in eye homogenates at 15th days after birth in grey Norway rats, while in albino Wistar and pale hooded Campbell rats with hereditary retinal degeneration MAH is observed at the 3rd and 4th postnatal days respectively. No increase of MAH activity is found in black hooded Hunter rats with inherent retinal degeneration during the first five days after birth. Thus, Wistar and Campbell rats differ significantly from grey and Hunter rats by MAH activity in the blood and eyes during early postnatal development.

[Melanotropic activity in the hypophysis and blood of Wistar rats in early postnatal development]. / Melanotropnaia aktivnost' v gipofize i krovi u krys linii Vistar v rannem postnatal'nom razvitii.

The activity of melanotropins in pituitary homogenates and blood of Wistar rats obtained from the nursery Stolbovaia (Russian Academy of Medical Sciences) was studied using the method of biological testing (Hogben, Slome, 1931; Golichenkov, 1980). In order to elucidate, to what extent the normal status of melanotropic activity is retained in albino rats, two experimental series were performed. Melanotropic activity was determined in (1) intact rats and (2) in rats receiving subcutaneous injections of parachlorophenylalanine, a specific inhibitor of serotonin synthesis. Melanotropic activity of Wistar rats hypophysis during the studied period of development was similar to that of normal pigmented rats. However, the peak of melanotropic activity of blood which is characteristically observed in pigmented rats on day 3 of postnatal development is absent in the case of Wistar rats. The experimentally induced decrease in the serotonin level did not result in the increased melanotropic activity of blood. These data suggest that certain structures of hypophysis responsible for MSH secretion can be disturbed in Wistar rats. A short-term peak of blood MSH in rats during the first week after birth is known to provide for maturation of dopaminergic neurons located in the arcuate nucleus of the hypothalamus. Consequently, the absence of such peak in Wistar rats should result in neuroendocrine disturbances such as inadequate functioning of dopaminergic neurons responsible for melanotropin secretion by hypophysis beginning from the second week after birth (Lichtensteiger, Schlumpf, 1986).