الفهرس 
Mammalian HibernationOnly 14 pages are availabe for public view
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Abstract
The grass frog Rana mascareniensis and the marsh frog Rana ridibunda hibernate in winter season in order to survive under unfavorable conditions such as decreased temperature and food. Aim: the present study aimed to investigate the cytoarchitecture of brain sub-regions affected by the natural thermal cycle’s fluctuations during the active period in summer and hibernation in the winter in Rana mascareniensis and Rana ridibunda. Materials and methods: R. mascareniensis and R. ridibunda species were collected from Abo Roash and El Mansuriya, El-Giza province, Egypt during the active period in summer (1st week of September 2019) and hibernation in the winter (4th week of January 2020). Histological and immunohistochemical studies (Na+/K+-ATPase and Pax6) were carried out in brain tissue of both species. In addition to the analysis of different heat shock proteins (HSP30, HSP40, HSP47, HSP70, HSP90 and HSP110), uncoupling proteins (UCP1&UCP2) and metallothionein gene expression in the olfactory bulb tissue. Results: during hibernation, degenerated neurons with condensed chromatin nuclei or vasogenic cytoplasm were found in different brain area with high rate nearby the pallium. Also, decreased immunohistochemical expressions of Na+/ K+-ATPase and Pax6 were seen in different brain sub-regions. Additionally, RT-qPCR technique in the olfactory bulb tissues recorded up-regulation of some heat shock proteins, UCP1, UCP2 and metallothionein genes. Conclusion: the high expression of heat shock proteins, UCPs and metallothionein genes may stabilize proteins at low temperature, cell homeostasis, thermal adaptation of brain and protection against ROS, respectively reflecting the importance of the olfactory bulb in the sensation of external temperature fluctuations and thermoregulation. Decreased Na+/ K+-ATPase and Pax6 activities may reflect the reduction in neuronal energy production and regeneration activities in winter. Adaptations of the brain to low temperature may play a crucial role in coordinating the stress responses.
Keywords: hibernation, active, winter, summer, brain, olfactory bulb, HSPs, UCPs, Metallothionein, Pax6, and Na+/ K+-ATPase.