Goro Takada

Ultrastructural study of the childhood mitochondrial myopathic syndrome associated with lactic acidosis

The quadriceps femoris muscle and the muscularis mucosae of the rectum from two children with mitochondrial myopathic syndrome associated with lactic acidosis were studied by electron microscopy. Striking morphological abnormalities of mitochondria were noted not only in the skeletal but also in the smooth muscle cells. Endothelial cells of blood capillaries distributed in these affected muscles were so greatly swollen that the capillary lumen was almost occluded. In contrast, surface epithelial and glandular epithelial cells of the rectum contained normal mitochondria, and fenestrated capillaries in the propria mucosae remained intact. Long-term ischemia resulting from occlusive changes of the capillary wall may be responsible for the mitochondrial alterations of muscle cells.

Hollow fibers for delivery of harmonic pulses of Q-switched Nd:YAG lasers

Flexible hollow fibers for delivery of the second, third, and fourth harmonic pulses of Q-switched Nd:YAG lasers are introduced. For the doubled (532-nm) wavelength, we fabricated a hollow fiber with an internal metal and polymer film by using a silver-mirror plating and a liquid-phase-coating method. For tripled (355-nm) and quadrupled (266-nm) Nd:YAG in the ultraviolet region, we fabricated aluminum hollow fibers with or without an internal polymer layer by using the metal-organic chemical-vapor deposition method. Both types of fiber show high stability for the transmission of high-peak power laser pulses with low transmission losses.

Hollow fiber delivery of Q-switched multiple-order Nd:YAG laser light

We proposed a use of hollow fibers for delivery of harmonic pulses of high-peak power, Nd:YAG laser light Hollow fibers with an internal silver and polymer layer were fabricated by a liquid phase coating technique and, in an experiment using the 2nd-order Nd:YAG laser, it was shown that the fiber has low-loss property because of the smooth inner surface and proper coating materials. High-power capability of the fiber is also shown when the hollow core is purged with helium gas.

Delivery of powerful radiation in visible spectral region by special waveguides

For delivery of powerful radiation in visible spectral region--cyclic olefin polymer-coated silver (COP/Ag) hollow glass waveguides with a length of 1 m and inner diameters of 1 mm were tested. As radiation sources--alexandrite electro- optically Q-switched laser generating tunable radiation centered at 750 nm (fundamental) or 357 nm (SHG) and two Q- switched and mode-locked Nd:YAG lasers generating wavelengths 1064 nm (fundamental) or 532 nm (SHG) were used. In every case, the output beam was coupled into the COP/Ag hollow glass waveguide. Coupling of radiation was optimized investigating several waveguide input protectors made from different materials to avoid spark generation at high radiation intensity. Transmittance/attenuation as a function of the input laser energy was measured in dependence to input radiation wavelength. The input/output time radiation characteristics and the spatial distributions of the output beams were also investigated. Transmission efficiency of the COP/Ag waveguides was found to be 80 - 95% in the spectral range from green to near infrared. In the blue region, transmittance was 66%. The measured transmission properties make COP/Ag hollow glass waveguides very promising for delivery of high-power laser pulses in medicine and also in other applications.

Hollow fibers for Nd:YAG and excimer lasers

Hollow fibers are developed for transmitting high-power lasers emitting ultraviolet, visible, and infrared light. For Nd:YAG lasers, a glass hollow fiber with silver and polymer inner coating enables low-loss transmission of high- peak power, pulsed laser light. For ArF-excimer lasers, a hollow fiber with inner aluminum coating transmits the ultraviolet laser light with low attenuation.