Hereditary dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurologic disorder characterized by variable combinations of myoclonus, epilepsy, cerebellar ataxia, choreoathetosis and dementia. By specifically searching published brain cDNA sequences for the presence of CAG repeats we identified unstable expansion of a CAG in a gene on chromosome 12 in all the 22 DRPLA patients examined. A good correlation between the size of the CAG repeat expansion and the ages of disease onset is found in this group. Patients with earlier onset tended to have a phenotype of progressive myoclonus epilepsy and larger expansions. We propose that the wide variety of clinical manifestations of DRPLA can now be explained by the variable unstable expansion of the CAG repeat.

Digital image analysis (DIA) is applied to extract various types of physical information from an image of high-order structures in polymer systems observed under an optical microscope. DIA can be applied to analyze the pattern formation phenomena in general. Various numerical operations in real and wave-number space make it possible to extract physical information unobtainable by other methods, such as the use of light scattering. The possibility of valuable operations in DIA are presented with examples. The technique itself is useful not only in polymer systems but also in various fields such as studies of liquid crystals, biological systems, metals, and pattern formation in solution or chemical reaction.

A morphological and kinetic change is found in the late stage of surface pattern formation on a gel plate. It results from a dynamic ordering process originating from a strong constraint from the bottom surface. The scattering function changes its form from a single-peaked, broad function to a multipeaked one, reflecting the morphological change from a treelike pattern to a honeycomblike one. The characteristic size of the pattern initially grows as / ,/2 , and then relaxes to its equilibrium value. This kinetic change coincides well with the morphological one.

In a binary mixture of oligomers of styrene and f-caprolactone, we have studied a transition from metastability to instability by changing a quench depth systematically under an off-critical quench condition. The concentration distribution function turns out to be a good fingerprint for determining whether phase separation is nucleation-growth type or spinodal-decomposition type. We also demonstrate clear morphological and kinetic evidence of a diffuse metastable-unstable transition or crossover phenomena theoretically predicted for the system with a finite-range interaction.

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