Acceleration of permeability barrier recovery by exposure of skin to 10-30 kHz sound

Positive effect of inaudible high-frequency components of sounds on glucose tolerance: a quasi-experimental crossover study

Although stress significantly impacts on various metabolic syndromes, including diabetes mellitus, most stress management techniques are based on psychological and subjective approaches. This study examined how the presence or absence of the inaudible high-frequency component (HFC) of sounds, which activates deep-brain structures, affects glucose tolerance in healthy participants using the oral glucose tolerance test (OGTT). Sounds containing HFC suppressed the increase in glucose levels measured by incremental area under the curve in the OGTT compared with the otherwise same sounds without HFC. The suppression effect of HFC was more prominent in the older age group and the group with high HbA1c. This suggests that sounds with HFC are more effective in improving glucose tolerance in individuals at a higher risk of glucose intolerance.

Do epidermal keratinocytes have sensory and information processing systems?

It was long considered that the role of epidermal keratinocytes is solely to construct a water-impermeable protective membrane, the stratum corneum, at the uppermost layer of the skin. However, in the last two decades, it has been found that keratinocytes contain multiple sensory systems that detect environmental changes, including mechanical stimuli, sound, visible radiation, electric fields, magnetic fields, temperature and chemical stimuli, and also a variety of receptor molecules associated with olfactory or taste sensation. Moreover, neurotransmitters and their receptors that play crucial roles in the brain are functionally expressed in keratinocytes. Recent studies have demonstrated that excitation of keratinocytes can induce sensory perception in the brain. Here, we review the sensory and information processing capabilities of keratinocytes. We discuss the possibility that epidermal keratinocytes might represent the earliest stage in the development of the brain during the evolution of vertebrates.

Effects of trans-2-nonenal and olfactory masking odorants on proliferation of human keratinocytes

Malodorous compounds induce stress responses, mood changes, an increase of skin conductance, activation of the sympathetic nervous system and other physiological changes, and it has been suggested that sensing malodors could provide warning of danger to health. Furthermore, the human body secretes various malodorous compounds as waste products of metabolism, including trans-2-nonenal ((E)-2-nonenal), the amount of which increases with aging. In the present study, we examined the effects of some endogenous malodorous compounds ((E)-2-nonenal, nonanal, pentanal, hexanal, hexanoic acid, hexylamine and isovaleric acid) on cultured human keratinocytes. (E)-2-Nonenal decreased the viability and promoted apoptosis of cultured keratinocytes. It also reduced the thickness and the number of proliferative cells in a three-dimensional epidermal equivalent model. Co-application of masking odorants (dihydromycenol, benzaldehyde, linalool, phenethyl alcohol, benzyl acetate and anisaldehyde), but not non-masking odorants (1,8-cineol, β-damascone, and o-t-butylcyclohexyl acetate), reduced the effect of (E)-2-nonenal on keratinocyte proliferation, and restored the thickness and number of proliferative cells in a three-dimensional epidermal equivalent model.

Using therapeutic ultrasound to promote irritated skin recovery after surfactant-induced barrier disruption

BACKGROUND

Surfactant-induced skin barrier disruption can enhance blood flow and water content in the superficial skin. The effect of therapeutic ultrasound on accelerating the recovery of superficial skin after skin barrier disruption has seldom been studied.

OBJECTIVE

To understand the effects of therapeutic ultrasound on barrier recovery, we used the sodium lauryl sulfate irritation model and treatment with ultrasound intervention.

METHODS

The study allocated 30 healthy subjects into an ultrasound group (n = 15) and a control group (n = 15), each divided into three subgroups (sodium lauryl sulfate at concentrations of 1.0%, 0.5%, and 0%). Pulsed ultrasound (1 MHz, 0.3 W/cm²_SATA) was applied to ultrasound subgroups. The treatment effect was evaluated by the recovery rate of enhanced blood flow and water content.

RESULTS

The results indicated a surfactant dose-dependent effect on blood flow, but not on water content. The recovery rates of enhanced blood flow were higher in the 0.5% and 1.0% ultrasound subgroups than in the control subgroups throughout the experiment. However, recovery rates of water content were higher in the ultrasound subgroups than in the control subgroups only on Day2.

CONCLUSIONS

Pulsed ultrasound accelerated the barrier recovery by reducing the enhanced blood flow and water content after skin barrier disruption.

Wireless Power Transfer to Millimeter-Sized Nodes Using Airborne Ultrasound

We propose the use of airborne ultrasound for wireless power transfer to mm-sized nodes, with intended application in the next generation of the Internet of Things (IoT). We show through simulation that ultrasonic power transfer can deliver 50 [Formula: see text] to a mm-sized node 0.88 m away from a ~ 50-kHz, 25-cm² transmitter array, with the peak pressure remaining below recommended limits in air, and with load power increasing with transmitter area. We report wireless power recovery measurements with a precharged capacitive micromachined ultrasonic transducer, demonstrating a load power of 5 [Formula: see text] at a simulated distance of 1.05 m. We present aperture efficiency, dynamic range, and bias-free operation as key metrics for the comparison of transducers meant for wireless power recovery. We also argue that long-range wireless charging at the watt level is extremely challenging with existing technology and regulations. Finally, we compare our acoustic powering system with cutting edge electromagnetically powered nodes and show that ultrasound has many advantages over RF as a vehicle for power delivery. Our work sets the foundation for further research into ultrasonic wireless power transfer for the IoT.

Frequencies of inaudible high-frequency sounds differentially affect brain activity: positive and negative hypersonic effects

The hypersonic effect is a phenomenon in which sounds containing significant quantities of non-stationary high-frequency components (HFCs) above the human audible range (max. 20 kHz) activate the midbrain and diencephalon and evoke various physiological, psychological and behavioral responses. Yet important issues remain unverified, especially the relationship existing between the frequency of HFCs and the emergence of the hypersonic effect.

In this study, to investigate the relationship between the hypersonic effect and HFC frequencies, we divided an HFC (above 16 kHz) of recorded gamelan music into 12 band components and applied them to subjects along with an audible component (below 16 kHz) to observe changes in the alpha2 frequency component (10–13 Hz) of spontaneous EEGs measured from centro-parieto-occipital regions (Alpha-2 EEG), which we previously reported as an index of the hypersonic effect.

Our results showed reciprocal directional changes in Alpha-2 EEGs depending on the frequency of the HFCs presented with audible low-frequency component (LFC). When an HFC above approximately 32 kHz was applied, Alpha-2 EEG increased significantly compared to when only audible sound was applied (positive hypersonic effect), while, when an HFC below approximately 32 kHz was applied, the Alpha-2 EEG decreased (negative hypersonic effect). These findings suggest that the emergence of the hypersonic effect depends on the frequencies of inaudible HFC.

Morphological and functional differences in coculture system of keratinocytes and dorsal-root-ganglion-derived cells depending on time of seeding

Previous study indicated that in a coculture system of keratinocytes and dorsal-root-ganglion-derived (DRG) cells, mechanical stimulation of keratinocytes induced ATP-mediated calcium propagation and excitation of DRG cells. Here, we examined two different coculture systems of keratinocytes and DRG cells. In one, we seeded keratinocytes first and then seeded DRG cells on the keratinocytes. In this system, nerve fibres from DRG cells passed between keratinocytes. Mechanical stimulation of keratinocytes did not induce excitation of DRG cells. In the other, we seeded both cell types together. At first, each cell type grew separately, forming cell aggregates. Then, nerve fibres grew out from the DRG cell aggregates to keratinocyte aggregates and penetrated into them. In this system, mechanical stimulation of keratinocytes induced excitation of the nerve fibres, but the excitation was not completely blocked by apyrase, an ATP-degrading enzyme. These results suggest that coculture of keratinocytes and DRG can generate a variety of structures, depending on the seeding conditions.

Roles of transient receptor potential proteins (TRPs) in epidermal keratinocytes

Epidermal keratinocytes are the epithelial cells of mammalian skin. At the basal layer of the epidermis, these cells proliferate strongly, and as they move towards the skin surface, differentiation proceeds. At the uppermost layer of the epidermis, keratinocytes undergo apoptosis and die, forming a thin, water-impermeable layer called the stratum corneum. Peripheral blood vessels do not reach the epidermis, but peripheral nerve fibers do penetrate into it. Until recently, it was considered that the main role of epidermal keratinocytes was to construct and maintain the water-impermeable barrier function. However, since the functional existence of TRPV1, which is activated by heat and low pH, in epidermal keratinocytes was identified, our understanding of the role of keratinocytes has changed enormously. It has been found that many TRP channels are expressed in epidermal keratinocytes, and play important roles in differentiation, proliferation and barrier homeostasis. Moreover, because TRP channels expressed in keratinocytes have the ability to sense a variety of environmental factors, such as temperature, mechanical stress, osmotic stress and chemical stimuli, epidermal keratinocytes might form a key part of the sensory system of the skin. The present review deals with the potential roles of TRP channels expressed in epidermal keratinocytes and focuses on the concept of the epidermis as an active interface between the body and the environment.