Automatic nitrous oxide synchronization of mitotic human cell cultures

Large numbers of human cells can be reversibly arrested in mitosis by high-pressure nitrous oxide. The optimum schedule for this arrest requires that the high-pressure block be started around midnight to provide a mitotic population that can be released the next morning to progress in synchrony through the next cell cycle. We describe a simple and safe device which can be set up at the end of the day and automatically exposes the cells to high-pressure nitrous oxide overnight.