Microinjection into Xenopus oocytes: a precise semi-automatic instrument and optimal parameters for injection of mRNAs.

A new apparatus for the injection of Xenopus oocytes is described which provides semi-automatic cell handling together with highly accurate and reproducible volume delivery. Using the system requires very little skill, yet it gives 6.3% average reproducibility in the 5 to 70 nl volume range. The instrument uses a fixed injector system driven by an Inchworm piezoelectric positioner or, in a low-cost version, by a Rainin EDP-2 battery-operated motorized pipette. A movable, vacuum-operated oocyte holder minimizes lateral movement of the oocyte during injection. Oocytes injected with the system show better survival and enhanced expression of mRNA compared with those injected with a widely used type of manual injector (Coleman, 1984).