A putter head prevents a ball from sliding over a green while maintaining golfers’ preferred hitting feel and roll of the ball. In the ultrasonic diagnostic apparatus of the invention, a two-dimensional array probe 1 formed by arranging a plurality of ultrasonic elements two-dimensionally transmits an ultrasonic beam to a three-dimensional region and receives a reflected signal. The invention still further provides isolated TWIK proteins, fusion proteins, antigenic peptides and anti-TWIK antibodies.