Noriaki Fukatsu

Animals remain awake in unfamiliar environments to assess potential safety threats, a process involving changes in neuronal activity within sleep–wake regulatory brain regions. However, the specific circuits and neurotransmitters involved remain poorly understood. Here, we show that neurotensin (NTS) peptides in corticotropin-releasing factor (CRF) neurons of the lateral part of the interstitial nucleus of the posterior limb of the anterior commissure (IPACL) play a key role in maintaining wakefulness in response to environmental changes. Activation of IPACL ^CRF neurons increased wakefulness, whereas their inhibition or deletion of NTS reduced wakefulness in novel environments. These neurons are activated in response to exposure to a novel environment and project primarily to the substantia nigra pars reticulata (SNr) and release NTS, which modulates wakefulness. These findings suggest that NTS signaling from IPACL ^CRF neurons to the SNr is essential for sustaining wakefulness in unfamiliar or changing environments.

Narcolepsy is a sleep disorder caused by deficiency of orexin signaling. However, the neural mechanisms by which deficient orexin signaling causes the abnormal rapid eye movement (REM) sleep characteristics of narcolepsy, such as cataplexy and frequent transitions to REM states, are not fully understood. Here, we determined the activity dynamics of orexin neurons during sleep that suppress the abnormal REM sleep architecture of narcolepsy. Orexin neurons were highly active during wakefulness, showed intermittent synchronous activity during non-REM (NREM) sleep, were quiescent prior to the transition from NREM to REM sleep, and a small subpopulation of these cells was active during REM sleep. Orexin neurons that lacked orexin peptides were less active during REM sleep and were mostly silent during cataplexy. Optogenetic inhibition of orexin neurons established that the activity dynamics of these cells during NREM sleep regulate NREM–REM sleep transitions. Inhibition of orexin neurons during REM sleep increased subsequent REM sleep in “orexin intact” mice and subsequent cataplexy in mice lacking orexin peptides, indicating that the activity of a subpopulation of orexin neurons during the preceding REM sleep suppresses subsequent REM sleep and cataplexy. Thus, these results identify how deficient orexin signaling during sleep results in the abnormal REM sleep architecture characteristic of narcolepsy.

The blood and lymphatic vasculature networks are not yet fully understood even in mouse because of the inherent limitations of imaging systems and quantification methods. This study aims to evaluate the usefulness of the tissue-clearing technology for visualizing blood and lymphatic vessels in adult mouse. Clear, unobstructed brain/body imaging cocktails and computational analysis (CUBIC) enables us to capture the high-resolution 3D images of organ- or area-specific vascular structures. To evaluate these 3D structural images, signals are first classified from the original captured images by machine learning at pixel base. Then, these classified target signals are subjected to topological data analysis and non-homogeneous Poisson process model to extract geometric features. Consequently, the structural difference of vasculatures is successfully evaluated in mouse disease models. In conclusion, this study demonstrates the utility of CUBIC for analysis of vascular structures and presents its feasibility as an analysis modality in combination with 3D images and mathematical frameworks.

Background and objective: Bronchoscopy is an airborne particle‐generating procedure. However, few methods for safe bronchoscopy have been developed. To reduce airborne particles during bronchoscopy, we created an ‘e‐mask’, which is a simple, disposable mask for patients. Our objective was to evaluate the e‐mask's protective ability against airborne particles and to assess respiratory adverse events and complications.Methods: Patients with stage 2–4 chronic obstructive pulmonary disease were excluded. We performed visualization and quantifying experiments on airborne particles with and without the e‐mask. We prospectively evaluated whether wearing the e‐mask during bronchoscopy was associated with the incidence of patients requiring >5 L/min oxygen to maintain >90% oxygen saturation, and patients with >45 mm Hg end‐tidal carbon dioxide (EtCO₂) elevation, in addition to complications, compared to historical controls.Results: In the visualization experiment, more than ten thousand times of airborne particles were generated without the e‐mask than with the e‐mask. The volume of airborne particles was significantly reduced with the e‐mask, compared to that without the e‐mask (p = 0.011). Multivariate logistic regression analysis revealed that wearing the e‐mask had no significant effect on the incidence of patients requiring >5 L/min oxygen to maintain >90% oxygen saturation, (p = 0.959); however, wearing the e‐mask was a significant factor in >45 mm Hg EtCO₂ elevation (p = 0.026). No significant differences in complications were observed between the e‐mask and control groups (5.8% vs. 2.5%, p = 0.395).Conclusion: Wearing the e‐mask during bronchoscopy significantly reduced the generation of airborne particles during bronchoscopy without increasing complications.