Abstract
Previous studies 1 , 2 , 3 , 4 , 5 , 6 indicate the presence, in at least certain tissues of high cancer strain mice, of a substance or substances whose presence is essential to spontaneous mammary carcinoma. In these studies lactating mammary tissues inclusive of their contained milk have been brought into suspension and partial solution by micro-homogenization and the resulting fluid separated into several fractions by the use of an ultracentrifuge.
Procedure. Fostered female C3H mice 1 month old were employed as test animals. Lactating breast tissues were obtained immediately after death by etherization, from high cancer C3H and A strain mice. The material was immediately homogenized with addition of between one and two times its volume of sterile distilled water. The resulting fluid was spun in the centrifuge at 15,000 rpm, giving a maximum accelerational force of 15,000 x g, for 30 minutes. Three layers resulted, a fatty top layer, designated as the fat fraction, a middle aqueous layer, the first supernatant fluid, and a bulky precipitate, the first sediment. The fat fraction was removed and employed as noted below. The aqueous layer was removed by suction without disturbing the sediment. The first supernatant fluid was then spun at 40,000 rpm, corresponding to 110,000 x g, for a period of 60 minutes. The final supernatant fluid was removed without disturbing the second sediment.
The materials used for feeding or injection were (1) homogenized tissue, (2) fat fraction, (3) first sediment, (4) second sediment, and (5) final supernatant fluid. The amount of material of each fraction which was injected or fed was usually that which was obtained in that fraction from 1 g of original tissue.
Get full access to this article
View all access options for this article.