A simple machine vision-driven system for measuring optokinetic reflex in small animals.

The optokinetic reflex (OKR) is useful to monitor the function of the visual and motor nervous systems. However, OKR measurement is not open to all because dedicated commercial equipment or detailed instructions for building in-house equipment is rarely offered. Here we describe the design of an easy-to-install/use yet reliable OKR measuring system including a computer program to visually locate the pupil and a mathematical procedure to estimate the pupil azimuth from the location data. The pupil locating program was created on a low-cost machine vision development platform, whose graphical user interface allows one to compose and operate the program without programming expertise. Our system located mouse pupils at a high success rate (~90 %), estimated their azimuth precisely (~94 %), and detected changes in OKR gain due to the pharmacological modulation of the cerebellar flocculi. The system would promote behavioral assessment in physiology, pharmacology, and genetics.

A novel missense mutation causing a G487R substitution in the S2-S3 loop of human ether-à-go-go-related gene channel.

INTRODUCTION: Mutations of human ether-à-go-go-related gene (hERG), which encodes a cardiac K(+) channel responsible for the acceleration of the repolarizing phase of an action potential and the prevention of premature action potential regeneration, often cause severe arrhythmic disorders. We found a novel missense mutation of hERG that results in a G487R substitution in the S2-S3 loop of the channel subunit [hERG(G487R)] from a family and determined whether this mutant gene could induce an abnormality in channel function. METHODS AND RESULTS: We made whole-cell voltage-clamp recordings from HEK-293T cells transfected with wild-type hERG [hERG(WT)], hERG(G487R), or both. We measured hERG channel-mediated current as the "tail" of a depolarization-elicited current. The current density of the tail current and its voltage- and time-dependences were not different among all the cell groups. The time-courses of deactivation, inactivation, and recovery from inactivation and their voltage-dependences were not different among all the cell groups. Furthermore, we performed immunocytochemical analysis using an anti-hERG subunit antibody. The ratio of the immunoreactivity of the plasma membrane to that of the cytoplasm was not different between cells transfected with hERG(WT), hERG(G487R), or both. CONCLUSION: hERG(G487R) can produce functional channels with normal gating kinetics and cell-surface expression efficiency with or without the aid of hERG(WT). Therefore, neither the heterozygous nor homozygous inheritance of hERG(G487R) is thought to cause severe cardiac disorders. hERG(G487R) would be a candidate for a rare variant or polymorphism of hERG with an amino acid substitution in the unusual region of the channel subunit.