In Vitro Preparation of a Growth Factor from Plerocercoids of the Tapeworm,Spirometra mansonoides 1

A growth-stimulating effect in mice infected with plerocercoid (spargana) larvae of the tapeworm, Spirometra mansonoides was first demonstrated by Mueller (1). Later work showed that other plerocercoid-infected laboratory animals (rats, hamsters and deer mice) gained weight at an accelerated rate when compared to uninfected controls (2).

The effects of these plerocercoids (spargana) have been compared to the actions of several mammalian hormones: thyroxin (3), insulin (4), and growth hormone (5).

Hypophysectomized (hypox) rats infected with plerocercoids grow considerably faster than noninfected hypox rats (5, 6). In addition, serum from wormy hypox rats when injected into uninfected hypox rats also enhances growth (7).

Steelman et al. (5) attempted to develop an in vitro source of plerocercoid growth factor (PGF) by incubating plerocercoids for 24-28 hr in Mixture 199 to which was added calf serum and chick embryo extract. They found a growth-promoting factor in the supernatant, and proposed that some protein source, either from calf serum and chick embryo extract or purified plasma proteins, was necessary for the production of PGF by the cultured worms. Isolation of the PGF from such a complex and crude medium would be difficult and the present investigation was undertaken to determine if PGF could be collected after shorter incubation periods in media containing fewer crude materials. If successful, the technique would provide large quantities of relatively high specific activity material for purifying and identifying the active factor.

Methods. Plerocercoids. All stages of the life cycle of S. mansonoides were maintained in our laboratory according to the techniques of Mueller (8). Plerocercoids to be incubated were removed from infected mice, rinsed twice in 0.85% saline, and placed in incubation media at a concentration of 100 plero-cercoids/10 ml of medium.