6-[¹⁸F] Fluorine-3,4-dihydroxyphenyl-L-alanine (¹⁸F-Dopa) was used for the diagnosis of malfunction of the D₂ dopaminergic presynaptic system with positron emission tomography (PET). However ¹⁸F-Dopa has multiple metabolic pathways: for example, it is metabolized to 3-O-methyl-6-¹⁸F-4- hydroxyphenylalanine, which deteriorate the images of ¹⁸F-dopamine. In order to eliminate such contaminations, L-¹⁸F-meta-tyrosine (L-¹⁸FmT) was synthesized and used to obtain clear images of high uptake of L-¹⁸FmT on the striatum of four normal monkeys.
 Two models of Parkinson's disease were generated by injection of 1-methy-4-phenyl-1,2,3,6-tetra hydropyridine in the monkey. Dynamic and static images were obtained after intravenous injection of 185 MBq of L-¹⁸FmT, using a high-resolution animal PET system SHR-2000. In the normal monkey, there was a symmetrical uptake of L-¹⁸FmT specifically on the striatum with a striatum-to-occipital lobe uptake ratio of about 4.0 at 110 min after injection. On the other hand, in the Parkinson model there was no uptake on the diseased side of the striatum. These results indicate that L-¹⁸FmT is a good radiotracer for imaging of D₂ dopaminergic presynaptic function.

View full abstract

The present investigation was undertaken to explore the value of stereoscopic observation of colloidal gold cytochemistry in structures with thickness less than those of ultrathin epon-embedded or ultrathin frozen sections. With the introduction of stereoscopy, it has become possible to clearly view the three-dimensional distribution of synaptic vesicles in the axonal fibers of the terminals of the rat spinal dorsal horn. It is known that calcitonin generelated peptide immunoreactivity appears in the dense-cored vesicles (DCVs). Stereoscopy revealed that immunolabelling remains on the surface of the area over the DCVs in ultrathin epon-embedded sections. On the other hand, in ultrathin frozen sections, stereoscopy showed that immunolabelling was restricted to the surface of the DCVs which were labelled throughout the section. These results suggest that stereoscopy is quite powerful in more accurately determining the relationship between immunolabelling and the organelle ultrastructure in both ultrathin epon-embedded and ultrathin frozen sections.

View full abstract

A technique is described to obtain confocal microscopic images of normal, human skin in vivo based on autofluorescence. The natural autofluorescence was induced by ultraviolet light (365 nm) and blue light (488 nm), and the fluorescence was detected at wavelengths longer than 515 nm. Optical sections of the stratum corneum were obtained from the anterior surface of the index finger and the volar surface of the human forearm. Three-dimensional, pseudocolor depth-coded projections were formed from stacks of optical sections to an approximate depth of 85 microns from the skin surface. Individual squames could be observed. Cells in the process of sloughing are highly fluorescent. Hair shows high intensity autofluorescence. Regions around the openings of sweat glands show high intensity autofluorescence when illuminated with ultraviolet light. Three-dimensional confocal microscopy of human skin based on autofluorescence may have a diagnostic potential in dermatology.

View full abstract