Levels of mammary tumor virus particles (types A and B) and levels of the virus antigen were assayed in hormone-dependent and -independent mammary tumors of GR mice. Various transplant generations of seven separate tumor lines were investigated. The results indicated that the tumors consisted of different cell clones, each of which exhibited a separate progressive expression and subsequent loss...

Canine mammary gland tumors represent the second most frequent type of neoplasm in dogs, being an important problem within veterinary medical field. Canine mixed mammary tumors are the most common; the use of a transmission electron microscope (TEM) can contribute as a tool in its diagnosis by determining the characteristics of cellular components from numerous neoplasms. The aim of this study ...

The tumor suppressor phosphatase and tensin homologue (PTEN) is involved in cell proliferation, adhesion, and apoptosis. PTEN overexpression in mammary epithelium leads to reduced cell number and impaired differentiation and secretion. In contrast, overexpression of the proto-oncogene Wnt-1 in mammary epithelium leads to mammary hyperplasia and subsequently focal mammary tumors. To explore the ...

The gene encoding AIB1, an estrogen receptor coactivator, is amplified in a subset of human breast cancers. Here we show that overexpression of AIB1 in transgenic mice (AIB1-tg) leads to mammary hypertrophy, hyperplasia, abnormal postweaning involution, and the development of malignant mammary tumors. Tumors are also increased in other organs, including the pituitary and uterus. AIB1 overexpres...

The inhibitory effect of neutering on mammary gland tumor development in dogs has been well described. However, we observed that the effect of neutering on tumor malignancy may be altered by aging. Therefore, we characterized mammary tumors in aged dogs by analyzing the expression of cellular senescence markers. Expressions of p16, p38, p21, and p27 antibodies, which are senescence-associated m...

The removal of the Bittner virus by foster nursing C3H mice on mice that do not have the agent (e.g., C57BL) postpones the development of mammary tumors, but does not prevent it (1, 3-6, 8). All inbred strains of germ-free mice presently in existence have been derived by foster nursing their young on descendents of Swiss mice which were derived by hand feeding by the Notre Dame group (13). All ...

The effect of 1,3,5(10)-estratriene-3, 16 alpha, 17 beta-triol (estriol), 1, 3, 5(10)-estratriene-2,3-diol-17-one (2-hydroxyestrone), and 1,3,5(10)-estratriene-2,3,17 beta-triol (2-hydroxyestradiol) on the growth of dimethylbenz(a)anthracene-induced mammary tumor and of R3230AC-transplantable mammary tumor was compared with that produced by estradiol benzoate treatment. Estriol showed minimal i...

Although basic fibroblast growth factor (FGF2) was the first pro-angiogenic molecule discovered, it has numerous activities on the growth and differentiation of non-vascular cell types. FGF2 is both stimulatory and inhibitory, depending on the cell type evaluated, the experimental design used and the context in which it is tested. Here, we investigated the effects of manipulating endogenous FGF...

Modern pathologists have been challenged to "validate" mouse models of human cancer. Validation requires matching of morphological attributes of the model to human disease. Computers can assist in the validation process. However, adequate controlled, computer-readable vocabularies that can match terms do not currently exist in mouse pathology. Further, current standard diagnostic terminologies ...

Dose-response relationships for the induction of mammary tumors by a single i.p. injection of 1-methyl-1-nitrosourea (MNU) were studied. Groups of 30 female Sprague-Dawley rats were given i.p. injections of 50, 37.5, 25, 12.5, or 0 mg MNU/kg body weight at 50 days of age. Animals were palpated for tumor detection twice weekly throughout a 28-week observation period. Administration of MNU i.p. c...