Kouichi Nakagawa

Rapid Free Radical Reduction in the Perfused Rat Liver

The reduction of nitroxide free radicals was investigated in detail by Electron Paramagnetic Resonance (EPR) spectroscopy in perfused liver. The nitroxide free radical was rapidly reduced to the corresponding hydroxylamine more efficiently at the lower flow rate of 8 [ml/min], while at higher flow rates, the amount of reduced nitroxide showed a significant decrease. Oxidation of hydroxylamine using hydrogen peroxide provided dynamic information concerning the reduction of the free radical within the liver. In addition, liver homogenates were also investigated to determine the level of nitroxide uptake. The results suggested that a portion of the infused nitroxide was taken up by the liver and cleared from the circulation.

Investigation of Heavy-Ion-Induced Sucrose Radicals by Electron Paramagnetic Resonance

Abstract Nakagawa, K. and Sato, Y., Investigation of Heavy-Ion-Induced Sucrose Radicals by Electron Paramagnetic Resonance. Radiat. Res. 164, 336–338 (2005). The production of sucrose radicals with heavy-ion irradiation was investigated by an EPR (electron paramagnetic resonance) spectroscopic method. We examined the correlation between the production of sucrose radicals and the ion species, as well as LET (linear energy transfer). The spectral pattern obtained was the same for various ion species, including helium, carbon, neon, argon and iron ions. Quantitative EPR analyses showed that the production of sucrose radicals depended on both the ion species and the LET for the same dose of 50 Gy. The spin yield obtained showed a logarithmic correlation with the LET. In addition, the EPR response had a linear relationship with dose in the dose range of 5–60 Gy. Thus the present EPR results show that sucrose can be used to monitor the ionizing particle based on the radical yield.

The production of short-lived free radicals accompanying laser photoablation of cardiovascular tissue.

Using the method of spin trapping and electron paramagnetic resonance, free radicals have been detected accompanying laser ablation of cardiovascular tissue. Radicals were detected using both visible and ultraviolet laser energy from argon-ion and excimer laser sources. The results are discussed in terms of the relative efficiency of the laser wavelengths to produce free radicals and a comparison of the types of radicals produced by the action of pulsed versus cw laser energy.

Electron Paramagnetic Resonance Investigation of Stratum Corneum Lipid Structure

Electron paramagnetic resonance (EPR) in conjunction with a slow-tumbling simulation was utilized for defining stratum corneum (SC) lipid structure. We found that ordering calculated from the simulation is an appropriate index for evaluating SC lipids structure. The SC from two sites (mid-volar forearm and lower-leg) of human volunteers was stripped consecutively from one to three times using a glass plate coated with a cyanoacrylate resin. Aliphatic spin probes, 5-doxylstearic acid (5-DSA) and 3β-doxyl-5α-cholestane (CHL), were used to monitor SC ordering. EPR spectrum of 5-DSA incorporated in the SC demonstrated a characteristic peak for the first strip. However, EPR spectra of CHL in the SC did not show a clear difference for each strip, except for the peak intensity. The results imply that CHL is not incorporated into the lipid phase as easily as 5-DSA is. A slow-tumbling simulation of the EPR spectrum was performed to analyze the detailed lipid structure. The simulation results for 5-DSA show differences in values of the SC ordering as a function of depth. Thus, these results along with the simulation analysis provide a detailed SC layer structure.

Direct observation of laser generated free radicals from a myocardium target site

The first direct observation of unstable free radicals generated by laser irradiation of myocardium samples has been performed by EPR at 100 K. Characteristic iron signals are measured for pulsed laser ablation of the sample. The EPR results are discussed in relation to the relative efficiency of the various types of lasers to produce free radicals. A comparison is made of the types of free radicals produced by the action of pulsed vs continuous wave (cw) laser energy.

Comparison of free radicals produced by laser and ultrasound ablation of cardiovascular tissue.

Abstract— We have used the method of spin trapping and EPR to study the nature of the free radicals produced by laser photoreaction of cardiovascular tissue. The results obtained with argon‐ion (cw) and excimer (pulsed) lasers have been compared with radicals produced by ultrasonic disruption of the tissue samples. These comparative studies provide an understanding of the mechanism by which laser light energy effects photoablation of cardiovascular tissue in the pulsed vs cw mode of operation.

Stratum Corneum Lipid Structure Investigated by EPR Spin-Probe Method: Application of Terpenes

Electron paramagnetic resonance (EPR) in conjunction with a slow-tumbling simulation was utilized for defining stratum corneum (SC) lipid structure. SC from the back of hairless mouse (HOS:HR-1) was stripped consecutively from one to three or four times using a glass plate coated with a cyanoacrylate resin. Aliphatic spin probes, 5-doxylstearic acid (5-DSA) and 3β-doxyl-5α-cholestane (CHL), were used to evaluate the SC ordering. EPR spectrum of 5-DSA incorporated in the SC demonstrated a characteristic peak for the first strip. A slow-tumbling simulation for 5-DSA showed clear differences in EPR intensities as well as ordering values (S0) of the SC for control and terpenes treated SC. The α-terpineol enhanced the permeation of the single chain 5-DSA about three times more than that of the control. However, EPR spectra of CHL in the SC did not show a clear difference for each strip, except for the signal intensity. The results imply that CHL permeates into SC lipid differently from 5-DSA. The enhancement of the 5-DSA is more significant than that of CHL. Therefore, the present results can be useful for various drug administrations via the skin.

Pulsed UV Laser Generated Short-Lived free Radicals from Biological Samples

EPR characterization of the short-lived free radicals generated by pulsed UV laser ablation of biological samples has been investigated using a spin trap method. The obtained EPR spectra suggest that the trapped short-lived free radicals generated by excimer laser ablation of collagen and myocardium are identical. The obtained results are discussed in association with the production scheme of free radicals and an empirical mechanism of laser generated short-lived free radicals.