Pecularities of the structure of glycogen as an indicator of the functional state of mauthner neurons in fish Percсottus glehni during wintering.

Mauthner neurons (MN)*, specific multifunctional neurons of fish, are a unique object for investigating the adaptive potentialities of the cell. The goal of the work was to study the structure of MN of fish Percсottus glehni during wintering under the conditions of hypothermia and deficit of oxygen and energy substrates. It was shown using a light microscope that the volume of the somatic moiety of neurons changes slightly at the beginning of wintering and is significantly reduced by the termination of wintering. It was found on the ultrastructural level that, at the beginning of wintering, glycogen exists in the central cytoplasm of MN in the form of large concentrated fields consisting of separate granules, whereas in the summer period the granules are distributed diffusely throughout the cell. In the vicinity of glycogen fields, lamellar structures of the smooth reticulum were seen. At the boundaries of glycogen fields, the aggregation of mitochondria and their active intrusion into glycogen fields were evident. By the end of wintering, the amount of glycogen significantly decreased, which was accompanied by a reduction of the smooth reticulum and rare contacts of mitochondria with glycogen fields. We assume that, because MN have a broader range of metabolic and functional possibilities than usual neurons in which glycogen is lacking or its content is negligible, they possess their own systems of glycolysis, glyconeogenesis, and deposition of glycogen. This allows them to maintain a sufficient level of energy supply under anaerobic conditions for performing the function of "guard neurons" during wintering.

Brain protection during cephalosomatic anastomosis.

Cephalosomatic anastomosis requires neuroprotective techniques, such as deep hypothermia, to preserve brain activity. Despite the failure of pharmacologic neuroprotection, new strategies, including ischemic pre- and postconitioning and the use of Perftoran, have to be explored to complement hypothermia. This article summarizes the field of brain protection during CSA and these promising strategies.

Maintenance of homeostasis in the aging hypothalamus: the central and peripheral roles of succinate.

Aging is the phenotype resulting from accumulation of genetic, cellular, and molecular damages. Many factors have been identified as either the cause or consequence of age-related decline in functions and repair mechanisms. The hypothalamus is the source and a target of many of these factors and hormones responsible for the overall homeostasis in the body. With advanced age, the sensitivity of the hypothalamus to various feedback signals begins to decline. In recent years, several aging-related genes have been identified and their signaling pathways elucidated. These gene products include mTOR, IKK-ß/NF-κB complex, and HIF-1α, an important cellular survival signal. All of these activators/modulators of the aging process have also been identified in the hypothalamus and shown to play crucial roles in nutrient sensing, metabolic regulation, energy balance, reproductive function, and stress adaptation. This illustrates the central role of the hypothalamus in aging. Inside the mitochondria, succinate is one of the most prominent intermediates of the Krebs cycle. Succinate oxidation in mitochondria provides the most powerful energy output per unit time. Extra-mitochondrial succinate triggers a host of succinate receptor (SUCN1 or GPR91)-mediated signaling pathways in many peripheral tissues including the hypothalamus. One of the actions of succinate is to stabilize the hypoxia and cellular stress conditions by inducing the transcriptional regulator HIF-1α. Through these actions, it is hypothesized that succinate has the potential to restore the gradual but significant loss in functions associated with cellular senescence and systemic aging.