The technique of needle microinjection has become a prominent experime ntal approach in biological research. Cellular organelles, DNA and RNA, enzymes, structural proteins, metabolites, ions and antibodies are j ust some of the molecular and cellular elements that have been transpo sed from test tubes into living cells by needle injection. This techni que is broadly used as a valuable tool for the study of many different cell responses in a variety of systems. From individual cell signalin g responses, such as regulation of metabolic pathways and second funct ion of second messengers, the...