Chorea-acanthocytosis (ChAc) is a rare autosomal recessive neurodegenerative disorder caused by loss of function mutations in the vacuolar protein sorting 13 homolog A (VPS13A) gene that encodes chorein. It is characterized by adult-onset chorea, peripheral acanthocytes, and neuropsychiatric symptoms. In the present study, we performed a comprehensive mutation screen, including sequencing and copy number variation (CNV) analysis, of the VPS13A gene in ChAc patients. All 73 exons and flanking regions of VPS13A were sequenced in 35 patients diagnosed with ChAc. To detect CNVs, we also performed real-time quantitative PCR and long-range PCR analyses for the VPS13A gene on patients in whom only a single heterozygous mutation was detected. We identified 36 pathogenic mutations, 20 of which were previously unreported, including two novel CNVs. In addition, we investigated the expression of chorein in 16 patients by Western blotting of erythrocyte ghosts. This demonstrated the complete absence of chorein in patients with pathogenic mutations. This comprehensive screen provides an accurate and useful method for the molecular diagnosis of ChAc.

The dynamic fluid reaction forces and moments of a long annular seal were experimentally studied. A new testing apparatus was constructed in order to measure restoring forces and moments caused by the cylindrical whirling motion of a rotor. Experiments were conducted at various rotor speeds, whirling speeds, and with different pressure drops across the long seal. The rotor and outer cylinder were set in concentric alignment. The tangential force component was derived from the measured fluid force in order to determine the unstable threshold. Moments developed by the long seal were also obtained. Restoring forces and moments were expressed as stiffness, damping coefficients and added mass. These coefficients were then compared with Childs’ theory and found to be compatible.

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The mutual interaction effects of cylindrical and conical whirl on the dynamic fluid forces and moments, which act on a long annular seal, were studied experimentally. A whirling motion composed of cylindrical and conical whirls is actuated by intentionally giving the phase difference between the seal exit and inlet whirling movements. This whirling motion is believed to generate during actual pump running. The experiment was conducted by changing the phase difference, at various rotor speeds and with a pressure difference between the seal inlet and exit. The result of this study revealed that fluid forces and moments are greatly dependent on the phase difference of the whirl, namely the long seal has a significant coupling between displacements and rotations. Furthermore, dynamic fluid forces and moments were derived theoretically, assuming that total fluid force acting on the rotor could be determined by superposing fluid forces due to conical and cylindrical whirling movements. It was confirmed that the experimental results moderately agree with the theoretical values, if the rotor and seal are set in concentric alignment, the principle of superposition becomes applicable.

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