Defined nutrient medium for the in vitro maintenance of Xenopus laevis oocytes

A procedure is described for the isolation and culture of large numbers of follicle cell-free Xenopus laevis oocytes in all stages of development. The isolation procedure involves the incubation of pieces of ovary in a calcium-free solution OR2 containing 0.2% collagenase. A defined nutrient medium for the maintenace of the oocytes in vitro is presented. It is shown that this medium, referred to as DNOM, can maintain certain morpological and functional characteristics of oocytes for periods up to 3 weeks.