Optogenetics: Novel Tools for Controlling Mammalian Cell Functions with Light

In optogenetics, targeted illumination is used to control the functions of cells expressing exogenous light-activated proteins. Adoption of the optogenetic methods has expanded rapidly in recent years. In this review, we describe the photosensitive channel proteins involved in these methods, describe techniques for their targeting to neurons and other cell types both within and outside the nervous system, and discuss their applications in the field of neuroscience and beyond. We focus especially on the channelrhodopsin protein ChR2, the photosensitive protein most commonly employed in optogenetics. ChR2 has been used by many groups to control neuronal activity, both in vitro and in vivo, on short time scales and with exquisite anatomical precision. In addition, we describe more recently developed tools such as opsin/G protein-coupled receptor chimeric molecules and a light-activated transgene system. In addition, we discuss the potential significance of optogenetics in the development of clinical therapeutics. Although less than a decade old, optogenetics is already responsible for enormous progress in disparate fields, and its future is unquestionably bright

On one-dimensional sound analysis of a duct network with Helmholtz resonators

The outer orifice correction for Helmholtz resonators attached to the sidewall ofcircular ducts was studied. For the outer orifice correction when the axis direction ofthe orifice coincides with that of the duct, .explicit expressions were given by Ingard and Rschevkin. But their application to duct sections with duct-sidewall resonators is beyond their premise. An explicit expression ofthe outer orifice correction for duct-sidewall resonators was derived by conducting three-dimensionalboundary-element analyses. Application ofthis outer orifice correction improves significantly the accuracy of the one-dimensional wave analysis for the acoustic properties of duct sections which have sidewall resonators.会議名称:The 31th International Congress and Exposition on Noise Control Engineering : additional proceedings, Sound Quality Symposium 2002主催学会:INCE/US

Effect of acoustic liners on sound transmission of wall apertures for ventilation

Sound reduction techniques of the axial 1st mode transmission of an aperture for ventilation purpose in a plane rigid wall were studied by conducting boundary element numerical simulations. First, the effectiveness of the boundary element approach, and the dependence of the insertion loss of a wall with an aperture on the incidence angle were investigated. Then, the effectiveness of the sound reduction techniques, such as mounting acoustical liners to the aperture perimeter, attachment of a disk shape hoods, and insertion of a Helmholtz resonator were examined.会議名称:The 30th International Congress and Exposition on Noise Control Engineering主催学会:NA

Hybrid model of light propagation in random media based on the time-dependent radiative transfer and diffusion equations

Numerical modeling of light propagation in random media has been an important issue for biomedical imaging, including diffuse optical tomography (DOT). For high resolution DOT, accurate and fast computation of light propagation in biological tissue is desirable. This paper proposes a space–time hybrid model for numerical modeling based on the radiative transfer and diffusion equations (RTE and DE, respectively) in random media under refractive-index mismatching. In the proposed model, the RTE and DE regions are separated into space and time by using a crossover length and the time from the ballistic regime to the diffusive regime, View the MathML sourceρDA~10/μt′ and View the MathML sourcetDA~20/vμt′ where View the MathML sourceμt′ and v represent a reduced transport coefficient and light velocity, respectively. The present model succeeds in describing light propagation accurately and reduces computational load by a quarter compared with full computation of the RTE

Renormalization of the highly forward-peaked phase function using the double exponential formula for radiative transfer

Numerical calculation of photon migration in biological tissue using the radiative transfer equation (RTE) has attracted great interests in biomedical optics and imaging. Because biological tissue is a highly forward-peaked scattering medium, renormalization of the phase function in numerical calculation of the RTE is crucial. This paper proposes a simple approach of renormalizing the phase function by the double exponential formula, which was heuristically modified from the original one. Firstly, the validity of the proposed approach was tested by comparing numerical results for an average cosine of the polar scattering angle calculated by the proposed approach with those by the conventional approach in highly forward-peaked scattering. The results show that calculation of the average cosine converged faster using the proposed approach than using the conventional one as a total number of discrete angular directions increases. Next, the accuracy of the numerical solutions of the RTE using the proposed approach was examined by comparing the numerical solutions with the analytical solutions of the RTE in a homogeneous medium with highly forward-peaked scattering. It was found that the proposed approach reduced the errors of the numerical solutions from those using the conventional one especially at a small value of the total number of the directions. This result suggests that the proposed approach has a possibility to improve the accuracy for the numerical results of the RTE in the highly scattering medium

Light propagation model of titanium dioxide suspensions in water using the radiative transfer equation

Constructions of numerical schemes for solving the radiative transfer equation (RTE) are crucial to evaluate light propagation inside photocatalytic systems. We develop accurate and efficient schemes of the three-dimensional and time-dependent RTE for numerical phantoms modeling aqueous titanium dioxide suspensions, in which the anisotropy of the forward-directed scattering varies and the strength of absorption is comparable to that of scattering. To improve the accuracy and efficiency of the numerical solutions, the forward-directed phase function is renormalized in the zeroth or first order with a small number of discrete angular directions. Then, we investigate the influences of the forward-directed scattering on the numerical solutions by comparing with the analytical solutions. The investigation shows that with the anisotropy factor less than approximately 0.7 corresponding to the moderate forward-directed scattering, the numerical solutions of the RTE using the both of the zeroth and first order renormalization approaches are accurate due to the reductions of the numerical errors of the phase function. With the anisotropy factor more than approximately 0.7 corresponding to the highly forward-directed scattering, the first order renormalization approach still provides the accurate results, while the zeroth order approach does not due to the large errors of the phase function. These results suggest that the developed scheme using the first order renormalization can provide accurate and efficient calculations of light propagation in photocatalytic systems

Low Reactive Level Laser Therapy for Mesenchymal Stromal Cells Therapies

Low reactive level laser therapy (LLLT) is mainly focused on the activation of intracellular or extracellular chromophore and the initiation of cellular signaling by using low power lasers. Over the past forty years, it was realized that the laser therapy had the potential to improve wound healing and reduce pain and inflammation. In recent years, the term LLLT has become widely recognized in the field of regenerative medicine. In this review, we will describe the mechanisms of action of LLLT at a cellular level and introduce the application to mesenchymal stem cells and mesenchymal stromal cells (MSCs) therapies. Finally, our recent research results that LLLT enhanced the MSCs differentiation to osteoblast will also be described