Language：English   Publishing type：Research paper (scientific journal)   Publisher：SAGE Publications  

Animals frequently experience temperature fluctuations in their natural life cycle, including periods of low temperatures below their activity range. For example, poikilothermic animals are known to enter a hibernation-like state called brumation during transient cooling. However, the knowledge regarding the physiological responses of brumation is limited. Specifically, the impact of exposure to low-temperature conditions outside the range of temperature compensation on the subsequent circadian behavioral rhythms remains unclear. In this study, we investigated the effects of transient cooling on the behavioral circadian rhythm in the non-avian reptile, the bearded dragon ( Pogona vitticeps). Under constant light (LL) conditions at 30 °C, the animals exhibited a free-running rhythm, and exposure to low temperatures (4 °C) caused a complete cessation of locomotion. Furthermore, we revealed that the behavioral rhythm after rewarming is determined not by the circadian phase at the onset or the duration of cooling, but by the timing of cooling cessation.

DOI： 10.1177/07487304241273190

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Other Link： https://journals.sagepub.com/doi/full-xml/10.1177/07487304241273190

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Zoological Society of Japan  

DOI： 10.2108/zs230123

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Abstract

An increase in ambient temperature leads to an increase in sleep. However, the mechanisms behind this phenomenon remain unknown. This study aimed to investigate the role of microglia in the increase of sleep caused by high ambient temperature. We confirmed that at 35 °C, slow-wave sleep was significantly increased relative to those observed at 25 °C. Notably, this effect was abolished upon treatment with PLX3397, a CSF1R inhibitor that can deplete microglia, while sleep amount at 25 °C was unaffected. These observations suggest that microglia play a pivotal role in modulating the homeostatic regulation of sleep in response to the fluctuations in ambient temperature.

DOI： 10.1186/s12576-024-00929-0

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Other Link： https://link.springer.com/article/10.1186/s12576-024-00929-0/fulltext.html

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.jphs.2024.03.003

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1093/pnasnexus/pgad48

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Language：English   Publishing type：Research paper (scientific journal)  

Although diurnal animals displaying monophasic sleep patterns exhibit periodic cycles of alternating slow-wave sleep (SWS) and rapid eye movement sleep (REMS), the regulatory mechanisms underlying these regular sleep cycles remain unclear. Here, we report that in the Australian dragon Pogona vitticeps exposed to constant darkness (DD), sleep behavior and sleep-related neuronal activity emerged over a 24-h cycle. However, the regularity of the REMS/SWS alternation was disrupted under these conditions. Notably, when the lizards were then exposed to 12 h of light after DD, the regularity of the sleep stages was restored. These results suggest that sleep-related neuronal activity in lizards is regulated by circadian rhythms and that the regularity of REMS and SWS cycling is influenced by daytime light exposure.

DOI： 10.1093/pnasnexus/pgad481

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Public Library of Science (PLoS)  

Memory is a fundamental brain function that can be affected by a variety of external factors including environmental pollutants. One of these pollutants is methyl vinyl ketone (MVK), a hazardous substance found in cigarettes, industrial wastes, and car exhaust. Humans can be exposed to MVK under many circumstances; however, it is unclear whether MVK affects higher-order brain functions such as memory. Here, we examined the memory performances of mice receiving systemic MVK administration. We found that 1 mg/kg of MVK impaired spatial memory. We also showed that 1 mg/kg MVK activated glial cells and altered glial functions in several subregions of the hippocampus, a brain region involved in learning and memory. These results suggest that MVK induces memory deficits and activates glial cells in hippocampal subregions.

DOI： 10.1371/journal.pone.0289714

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

Microglia, as macrophages in the brain, are responsible for immune responses and synaptic remodeling. Although the function of microglia is regulated by circadian rhythms, it is still unclear whether microglia are involved in the generation and light entrainment of circadian rhythms of behavior. Here, we report that microglial depletion does not alter behavioral circadian rhythms. We depleted ~ 95% of microglia in the mouse brain by PLX3397, a CSF1R inhibitor, and analyzed the effect on the spontaneous behaviors of mice. We found that neither the free-running period under constant darkness nor light entrainment under jet-lag circumstances were influenced by the ablation of microglia. Our results demonstrate that the circadian rhythms of locomotor activity, an important output of the circadian clock in the brain, are likely a phenomenon not produced by microglia.

DOI： 10.1186/s13041-023-01021-1

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.neures.2023.01.011

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Toxicology  

DOI： 10.2131/jts.47.375

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Authorship：Lead author  

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/ijms20030779

Open Access

Language：English   Publishing type：Research paper (scientific journal)  

Cyclic-AMP is one of the most important second messengers, regulating many crucial cellular events in both prokaryotes and eukaryotes, and precise spatial and temporal control of cAMP levels by light shows great promise as a simple means of manipulating and studying numerous cell pathways and processes. The photoactivated adenylate cyclase (PAC) from the photosynthetic cyanobacterium Oscillatoria acuminata (OaPAC) is a small homodimer eminently suitable for this task, requiring only a simple flavin chromophore within a blue light using flavin (BLUF) domain. These domains, one of the most studied types of biological photoreceptor, respond to blue light and either regulate the activity of an attached enzyme domain or change its affinity for a repressor protein. BLUF domains were discovered through studies of photo-induced movements of Euglena gracilis, a unicellular flagellate, and gene expression in the purple bacterium Rhodobacter sphaeroides, but the precise details of light activation remain unknown. Here, we describe crystal structures and the light regulation mechanism of the previously undescribed OaPAC, showing a central coiled coil transmits changes from the light-sensing domains to the active sites with minimal structural rearrangement. Site-directed mutants show residues essential for signal transduction over 45 Å across the protein. The use of the protein in living human cells is demonstrated with cAMP-dependent luciferase, showing a rapid and stable response to light over many hours and activation cycles. The structures determined in this study will assist future efforts to create artificial light-regulated control modules as part of a general optogenetic toolkit.

DOI： 10.1073/pnas.1517520113

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1254/fpj.146.263

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Authorship：Lead author   Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1254/fpj.146.119

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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Presentation type：Oral presentation (general)  

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