Vol 55, No 4 (2019)

The review summarizes data on microglyocytes in the brain of mammals. General characteristics and features of their structure, functions and molecular organization at different ontogenetic stages are addressed. A special focus is on various hypotheses of the origin of microglia and current ideas about the involvement of microglyocytes in the regulation of neurogenesis and neuroinflammation. The data of recent experimental studies on toxic effects on microglia are critically analyzed. We point out the prospects for using the methods of selective microglia depletion (replacement) in modeling neuropathologies. This approach is supposed to enable assessment of the microglial contribution to the development of adaptive and neurodegenerative processes.

Activity and properties of two phosphohydrolases, nucleoside diphosphatase (NDPase) and 5′-nucleotidase, were assayed in subcellular fractions of turbellaria Phagocata sibirica Sabussov (Turbellaria, Planariidae). The highest activity of N D Pase was observed in microsomes while that of 5′-nucleotidase in mitochondria and cytosolic fractions (12 000 and 105 000 g). The correlation between the rates of the relevant enzymatic reactions and concentrations of substrates and metal ions as well as the impact of various effectors and divalent cations (Mg²⁺, Mn²⁺, Ca²⁺, Zn²⁺, Cu²⁺) on phosphohydrolase activities were studied.

Serotonin and its signaling pathways are involved in the central regulation of feeding behavior and energy metabolism. The most important role in this regulation is played by dopaminergic neurons of the dorsal raphe nucleus (DRN) and ventral tegmental area (VTA) which express tryptophan hydroxylase 2 (TPH2) catalyzing the rate-limiting step in serotonin synthesis. Changes in activity of the serotonin-synthesizing system in the DRN and VTA may significantly contribute to the development of metabolic disorders, including obesity. However, data on TPH2 expression in these brain regions in obesity are unavailable. The aim of this work was to compare immunohistochemically TPH2 expression in the DRN and VTA of C57Bl/6J (a/a) female mice with a diet-induced obesity (DIO) (caused by 8- and 16-week intake of high-calorie food) and C57Bl/6J (Ay/a) agouti mice with genetically predetermined melanocortin obesity. Double immunolabeling demonstrated that in DIO mice with a 16-week high-calorie diet TPH2 expression in the DRN (the main cerebral source of serotonin) decreases while in the VTA increases. In agouti mice, TPH2 expression in the DRN did not change while in the VTA increased. In DIO mice with a 8-week high-calorie diet and in C57Bl/6J (a/a) mice resistant to this diet, TPH2 expression did not change both in the DRN and VTA. Thus, DIO mice kept on a long-term (16 weeks) diet and agouti mice with melanocortin obesity exhibit specific changes in the serotonin synthesis that are lacking in diet-resistant mice. This finding indicates a crucial role of serotonin signaling in the organismal response to excessive caloric intake.

This polemic article focuses on the current concepts of the architectonics of the hyperpallial projective zone (Wulst) in the avian thalamofugal visual pathway and the distribution of calcium-binding proteins parvalbumin (PV) and calbindin (CB), as well as cytochrome oxidase (CO) activity, in these brain regions of birds, including our histochemical and immunohistochemical data obtained on the pigeon. In the principal thalamorecipient sensory area of the Wulst, n. interstitialis hyperpallium apicale/hyperpallium intercalatum (IHA/HI), three discrete zones are identified: the two, containing punctate PV-ir neuropil and a densely packed population of mainly small PV-ir stellate and granular cells, and a single zone formed by punctate CB-ir neuropil and mainly CB-ir cells. The IHA/HI area is distinguished by a high CO activity. In the hyperpallium apicale (HA) and hyperpallium densocellulare (HD), PV-ir and CB-ir neurons of varied morphotypes are scattered diffusely throughout neuropil which is moderately immunoreactive to both calcium-binding proteins. These areas are characterized by the presence of large pyramidal-like and multipolar PV-ir and CB-ir neurons with long branched dendrites forming a cellular/fibrous layer in the superficial HA area. It is concluded that the thalamofugal visual pathway in the pigeon has two, PV- and CB-specific, channels. We draw a comparative analysis of the variability of these channels in different avian species, which is supposed to be due to variable ecological and adaptive factors. Within the current idea about the organization and evolutionary origin of the avian Wulst and the mammalian striate (visual) cortex, the homology between these brain structures is discussed.