Effect of humic acid on the composition of osmolytes and lipids in a melanin-containing phytopathogenic fungus Alternaria alternata.

Humic substances (HS) have a direct impact on living cells, causing a wide range of various biological effects, and stimulating or inhibiting fungal growth. Therefore, it is important to reveal cellular indicators that could indicate the nature and level of HS' effects on living organisms. Paying attention to the important role of lipid and osmolytes in adaptation to stress, the aim of this work was to study the composition of osmolytes and lipids in the growth dynamics of the phytopathogenic melanin-containing fungus Alternaria alternata under the influence of humic acid (HA). HA was isolated from a commercial peat humic product. For cultivation, liquid Czapek medium with the addition of 200 mg/l HA (HA variant) was used, and with no HA for the control variant. The main osmolytes of the fungal mycelium were glucose, mannitol, and trehalose. Both in the control and in HA variants, a general pattern was observed during the growth process; the amount of glucose increased against the background of a decrease of mannitol. In the control, the amount of trehalose increased significantly by the stage of active melanin formation (day 4), while under the influence of HA, such an increase was not observed. Membrane lipids were represented by phospholipids, sphingolipids, and sterols. A characteristic feature of A. alternata was a high proportion of phosphatidic acids (PA) in the composition of membrane lipids. The amount and proportion of PA decreased during growth in the control, while under the influence of HA such decline was not observed. The influence of HA induced the increase in the amount of sterols (St) and phosphatidylcholines (PC) that were able to stabilise the membrane lipid bilayer. We can assume that general cellular response of A. alternata to HA influence, being expressed as a higher amount of PA, PC, St and a lower level of trehalose in comparison with the control, indicates the an absence of inhibition of growth processes of this phytopathogenic melanin-producing fungus. The effect of HA on the qualitative and quantitative composition of the osmolytes and membrane lipids of A. alternata may cause changes of virulence and stress resistance of this phytopathogen.

[The role of duplex ends in the spontaneous interaction of homologous linear DNA fragments]. / Rol' kontsevykh uchastkov dupleksov v spontannom vzaimodeistvii gomologichnykh lineinykh fragmentov DNK.

The spontaneous interaction of homologous linear DNA fragments was studied with a model of purified PCR products by agarose gel electrophoresis. To interact, duplexes required not only homology of internal regions, but also complementary ends. Fragments differing in terminal sequences did not interact. The yield of Holliday junctions (HJ), the simplest product of DNA-DNA interaction, depended on dissociation of fragment ends. Compared with genomic fragments, those with low-melting AT ends interacted with each other more efficiently and those with high-melting GC ends, less efficiently. Incubation temperature affected the equilibrium HJ concentration in solution of homologous fragments. A conclusion was made that HJ formation is initiated by nucleation of dissociated duplex ends.

Different pathways of neurohormonal hypothalamic control of the adrenal cortex function in young and old rats.

The pathways of hypothalamic control of the adrenal cortex function were studied in the experiments on young and old male Wistar rats. Immunohistochemical, morphometric, densitometric and radioimmunoassay methods were used. It was shown that in young rats under stress vasopressin (VP) is released into the portal circulation and probably in this way stimulates ACTH and enhances secretion of corticosterone in the adrenal cortex. In old rats stress-reaction is delayed and less adequate compared to young animals. It seems likely that in old rats VP is secreted into the general circulation mainly via the posterior pituitary lobe (PP), exerting a direct influence on the adrenal cortex. The conclusion is made that in old rats regulation of the adrenal cortex function is realised via the pathway phylogenetically more ancient than in young animals.

[Nucleolar apparatus of neurosecretory cells in the hypothalamus of rats of different age during acute immobilization stress]. / Kharakteristika iadryshkovogo apparata neirosekretornykh kletok gipotalamusa u krys raznogo vosrasta pri ostroi immobilizatsii zhivotnykh.

To determine condition and adaptive capacity of cell nucleoli at ageing, the effect of acute immobilization on the hypothalamic neurosecretory cells was investigated in young and old male Wistar rats. Using immunohistochemical methods and nucleolometry we have shown that: 1) the nuclear volume in all neurosecretory cells is increased; 2) the share of cells, containing nucleoli with marginal position or multiple nucleoli in the nuclei, displays opposite changes in young and in old rats under stress condition. We suppose that adaptive mechanisms are different in young and old animals. Although, both kinds of morphological reorganization result in the increase in functional activity.

The hypothalamo-hypophyseal system in Acipenseridae. XI. Morphological and immunohistochemical analysis of nonapeptidergic and corticoliberin-immunoreactive elements in hypophysectomized sterlet (Acipenser ruthenus L.).

The regeneration of the hypothalamo-hypophyseal system (HHS) has been studied in the sterlet following hypophysectomy (HypoX). Significant portions of nonapeptide and corticoliberinergic (CRH) neurosecretory cells (NSCs) underwent degeneration. Surviving NSCs had a great regenerative ability; damaged axons formed anew, uncharacteristicly for intact fishes, axovasal and axoventricular contacts. There are some specific features of the reorganization of the ANHyp in sterlet after HypoX: (a) blood capillaries from the meninges penetrate deep into the wall of the infundibular recess and form unusual axovasal contacts; (b) "neurovascular regeneratory complexes" appear; (c) single CRH-immunoreactive axons grow into the meninges. Morphological data show progressive appearance of dendroventricular contacts in the preoptic nucleus, formation of new axoventricular and axovasal contacts, and activation of surviving NSCs after HypoX. An ability to recognize HHS to release neurohormones into the CSF and bloodstream is suggested.

[Changes in the oxytocinergic neurosecretory cells in the accessory magnocellular neuroendocrine nuclei of the rat hypothalamus during aging]. / Izmeneniia oksitotsinergicheskikh neirosekretornykh kletok v dobavochnykh krupnokletochnykh neiroéndokrinnykh iadrakh gipotalamusa u krys pri starenii.

Histophysiology of accessory magnocellular nuclei of hypothalamus was studied in young (3-6 months) and old (14-29 months) male Wistar rats. Using non-labeled antibodies to oxytocin and karyolometry activation of protein synthesis combined with inhibition of oxytocin transport along the fibres was shown to occur in 4 (circular, fornical, dorso- and ventrolateral) of 5 accessory nuclei in old rats. This was not observed in anterior commissural nucleus. A hypothesis on compensatory role of accessory magnocellular nuclei of hypothalamus in regulation of neuroendocrine homeostasis in old rats is discussed.

[The characteristics of the formation of the hypothalamo-hypophyseal neurosecretory system in the Arctic lemming Dicostonyx torquatus of Wrangel Island in the postnatal development period]. / Nekotorye osobennosti formirovaniia gipotalamo-gipofizarnoi neirosekretornoi sistemy kopytnogo lemminga Dicrostonyx torquatus ostrova Vrangelia v postnatal'nom periode razvitiia.

Hypothalamo-hypophyseal neurosecretory system (HHNS) of 1-30 days old lemmings Dicrostonyx torquatus from the Wrangel Island in the year of a decreased but still highly dense population was studied by paraldehyde fucshin method and immunohistochemically using antisera to vasopressin and oxytocin. In the period of first two weeks of postnatal development the rate of HHNS formation was found to have significant individual differences and to be slower than HHNS formation in laboratory rats due to less stable and suitable environmental conditions. Like in rats the rate of differentiation of the supraoptic nucleus in lemmings was faster than that of the paraventricular one. Formation of the median eminence was retarded as compared to the hypophyseal posterior lobe. Vasopressin-immunoactive structures appeared earlier than oxytocin-immunoreactive ones both in the neurosecretory centers and in the neurohaemal regions. By 21-30 days the development the HHNS system was practically completed and the levels of maturation of studied structures in different individuals became closer. In this period an accumulation of neurosecretory material was observed in all parts of the HHNS which is probably connected with activation of the system under the condition of stress due to a high population density.

[The reaction to stress of the nonapeptidergic hypothalamic centers in old and young rats]. / Reaktsiia na stress nonapepidergicheskikh gipotalamicheskikh tsentrov u starykh i molodykh krys.

Diversities in reaction to immobilization stress in senile and juvenile animals were studied in 60 male Wistar line rats. Nonapeptidergic neurosecretory centres of hypothalamus were analysed morphometrically. Functional activity changes were found in vasopressin and oxytocin synthetic hypothalamic systems in senile and juvenile animals in different after-stress terms.

[The vasopressin- and oxytocinergic systems of rat strains selected for their capacity to acquire active avoidance]. / Vazopressin- i oksitotsinergicheskie sistemy u linii krys, selektirovannykh po sposobnosti k vyrabotke aktivnogo izbeganiia.

Vasopressin- and oxytocinergic structures of the hypothalamus were stained immunochemically. Volume of the nucleoli of the neurosecretory cells in the paraventricular, supraoptic and anterior commissural nuclei was calculated as a measure of neurohormone synthesis. The amount of the neurosecretory material in the neurohaemal organs (external median eminence and posterior pituitary) was estimated cytophotometrically. It was shown that both synthesis and secretion of the neurohormones were higher in intact KLA rats as compared to KHA rats. In three days after inescapable electroshock opposite changes in synthesis and secretion of both oxytocin and vasopressin were revealed: a rise in KHA rats and a fall down in KLA ones. It is suggested that differences between KHA and KLA rats in the reaction of vasopressin- and oxytocinergic systems to stress is due to different strategy of rats behavior at electroshock.

[Nontraditional "large-cell" neuroendocrine formations (accessory nuclei) in the brain of Anamnia and Amniota]. / Netraditsionnye "krupnokletochnye" neironnye formatsii (dobavochnye iadra) v golovnom mozgu nekotorykh Anamnia i Amniota.

Using immunochemical PAP-method nonapeptidergic neuroendocrine formations in the hypothalamus and adjacent brain areas of fishes (the sterlet Acipenser ruthenus, the shark Scylliorhinus canicula), amphibians (the frog Rana temporaria), reptiles (the snake Natrix natrix), mammals (rats and dogs) and human have been studied. In Amniota and human accessory nuclei (AN) in addition to main "magnocellular" nuclei (supraoptic, postoptic and paraventricular) were discovered. Two AN, circular and dorsolateral ones, were found in snakes, and circular, dorsolateral, forniceal and extrahypothalamic AN were revealed in rat, dog and human brain. In Anamnia, sharks and frogs, in contrast to sterlets, the dorsolateral sub-nucleus inside preoptic nucleus was identified. AN similarity in the phylogenetic row of vertebrates and mechanisms of AN creation in phylo- and ontogenesis were discussed.