Development and characterization of the BALB/cNIV mouse strain.

The strain BALB/cNIV/Crgl was developed by infecting BALB/c/Crgl mice with mouse mammary tumor virus from C3Hf mice. A BALB/c normal mammary duct was transplanted into the gland-free fat pad of a hormone-stimulated female C3Hf X BALB/c F1 mouse. A hyperplastic alveolar nodule was found in the BALB/c ductal outgrowth and was transplanted into another hybrid gland-free fat pad.

Transplantation of mouse mammary epithelial cells grown in primary collagen gel cultures.

A technique for the transplantation of mouse mammary epithelial cells, grown in collagen gels, has been developed that demonstrates that the phenotype of the cells prior to culture was not altered by the culture conditions. Mammary epithelial cells from virgin and midpregnant C57BL/Crgl mice; virgin, midpregnant, and multiparous nonpregnant BALB/cfC3H/Crgl mice; a BALB/c hyperplastic alveolar nodule line, and mammary tumors from BALB/cfC3H/Crgl mice were embedded inside collagen gels and grown for 10 to 14 days in the presence of 25% swine serum plus cholera toxin (0.01 microgram/ml).

Recovery of transformed nodule and ductal mammary cells from carcinogen-treated C57BL mice.

Transformed nodule and ductal mammary cells were recovered by cell dissociation and transplantation of mammary cells from C57BL/Crgl mice treated with 7,12-dimethylbenz(a)anthracene. Four-week-old mice were divided into the following groups: Group A, not treated; Group B, 2 pituitary isografts under the kidney capsule; Group C, 1.0 mg 7,12-dimethylbenz(a)anthracene intragastrically at 5 and 6 weeks of age; and Group D, 2 pituitary isografts and 1.

Effect of parity on recovery of inapparent nodule-transformed mammary gland cells in vivo.

Inapparent nodule-transformed cells were recovered from five late-pregnant, first-pregnancy BALB/cfC3H females 4 months of age and from five late-pregnant multiparous females 6 to 7 months of age. Mammary tissues were removed from each donor and dissociated by means of the enzyme collagenase (0.1%), hyaluronidase (0.