Transcutaneous vagus nerve stimulation (tVNS) is a noninvasive technique that engages central neuromodulatory pathways and has been shown to modulate sensory processing across multiple modalities. Here, we investigated whether tVNS influences human olfactory perception. Sixty-seven healthy adults were assigned to one of two stimulation frequency groups, 25 Hz (beta) or 55 Hz (gamma), and each received 20 min of tVNS applied to the left cymba concha as well as a control condition with identical stimulation delivered to the left earlobe. Odor discrimination, odor intensity, and visual attention were assessed before and after stimulation. Gamma frequency tVNS significantly decreased odor discrimination performance, whereas beta frequency did not. Odor intensity ratings increased modestly following stimulation in both groups, with a stronger effect observed after gamma-frequency tVNS. There were no changes in visual attention, and the stimulation intensity, which was selected by the participant, was not associated with olfactory outcomes. These findings demonstrate that tVNS can modulate human olfactory processing in a frequency-dependent manner. The selective effect of gamma frequency, that is, the known processing frequency of the human olfactory bulb, implies inhibitory interneuron engagement in the olfactory bulb. These findings demonstrate that noninvasive tVNS can modulate human olfactory processing in a frequency-specific manner and highlight stimulation frequency as a critical parameter for future translational applications.

Abnormal scars, such as keloids and hypertrophic scars, are fibroproliferative disorders that develop following wounds or infections extending into the reticular dermis, with cutaneous mechanical tension considered an aggravating factor. The detailed mechanisms underlying keloid formation and patterns of extension remain unclear. Recent studies suggest that microvascular hyperpermeability, potentially resulting from structural alterations in the vascular basement membrane and increased microvascular density in the superficial dermis, may contribute to keloid development. We report a single case of an earlobe keloid treated with surgical excision followed by postoperative radiotherapy (8 Gy in a single fraction). The resected tissue was histologically confirmed as a keloid. Immunohistochemical staining for fibrinogen and CD31 was performed on cryosections to evaluate vascular permeability. Fluorescence images were acquired using a confocal laser scanning microscope. The patient showed no recurrence during at least 12 months of follow-up. Fibrinogen deposition was observed predominantly in the superficial dermis at the keloid apex, with stronger signals than those in deeper regions of the keloid and adjacent normal skin. Fibrinogen is a key factor in wound healing and fibrosis, and its deposition within the extracellular matrix may reflect vascular hyperpermeability. Our findings suggest that areas of fibrinogen leakage may represent potential sites of future collagen deposition and keloid progression. However, this observation is based on a single case, and further studies are warranted to clarify the role of fibrinogen in keloid pathogenesis.

Peripheral oxygen saturation (SpO2) estimation using photoplethysmography (PPG) is typically based on the pulsatile components of red and infrared (IR) PPG signals acquired from peripheral sites, such as the finger or earlobe. Although these sites provide strong PPG signals, they are less suitable for integrated monitoring with electrocardiography (ECG), including arrhythmia detection. Simultaneous acquisition of PPG and ECG from a chest-worn device may therefore enable continuous and integrated physiological monitoring. However, chest PPG is characterized by lower perfusion and greater susceptibility to respiratory and motion artifacts, making reliable extraction of pulsatile red and IR components challenging. In this study, we developed and clinically evaluated a real-time SpO2 estimation algorithm based on chest reflectance PPG. Green PPG, which provides a relatively distinct pulsatile waveform under low-perfusion conditions, was used for beat detection. A heart-rate-adaptive analysis window, normalized cross-correlation-based signal quality assessment, and least-squares estimation of the AC amplitude ratio were combined to calculate the red-to-IR ratio of ratios, from which SpO2 was estimated using a calibration equation. Algorithm performance was evaluated against reference arterial oxygen saturation (SaO2) measured using a blood gas analyzer. The proposed method achieved an accuracy root mean square of 2.91% relative to the reference SaO2. These results support the technical feasibility of chest reflectance PPG-based SpO2 estimation and its accuracy under controlled desaturation conditions.

While the recently developed tissue clearing protocols pathoDISCO and activeDISCO significantly accelerate the clearing of large tissue specimens through active chemical dehydration using 2,2-dimethoxypropane, the final step of refractive index (RI) matching with viscous organic solvents as dibenzyl ether (DBE) remains restricted by slow passive diffusion. To overcome this bottleneck, we applied 40 kHz ultrasound using a standard, cost-effective laboratory bath to significantly enhance the diffusion kinetics of the clearing medium into large specimens. Our investigation on multi-centimeter-sized porcine muscle and human earlobe samples demonstrates that 40 kHz acoustic oscillations generated by a standard ultrasound cleaning device not only accelerate the clearing process but also yield superior and stable long-term optical transparency. We also tested 1 MHz high-frequency ultrasound but it offered no kinetic advantages and tended to induce tissue micro-fractures, an artifact we have not observed at 40 kHz at comparable energy levels. We therefore propose that standard 40 kHz ultrasound baths, ubiquitous in laboratories for cleaning purposes, represent an ideal and accessible tool for optimizing solvent-based tissue clearing.