A rapid and sensitive assay of -galactosidase in yeast cells

A steel laminate gasket comprises first, second and third plates. The gasket is provided with a first sealing device for sealing around a cylinder hole, which is integrally formed with one of the first, second and third plates, a second sealing device situated inside the first sealing device, and a third sealing device for sealing around a through hole of an engine. The third sealing device is formed on at least one of the first, second and third plates. Sealing layers are provided between the plates outside the second sealing device relative to the cylinder hole.