Mice, Inbred AKRAKR murine leukemia virus: A strain of Murine leukemia virus (LEUKEMIA VIRUS, MURINE) isolated from spontaneous leukemia in AKR strain mice.Hydroxyprostaglandin Dehydrogenases: Catalyzes reversibly the oxidation of hydroxyl groups of prostaglandins.20-Hydroxysteroid Dehydrogenases: A group of enzymes that catalyze the reversible reduction-oxidation reaction of 20-hydroxysteroids, such as from a 20-ketosteroid to a 20-alpha-hydroxysteroid (EC 18.104.22.168) or to a 20-beta-hydroxysteroid (EC 22.214.171.124).Aldehyde Reductase: An enzyme that catalyzes reversibly the oxidation of an aldose to an alditol. It possesses broad specificity for many aldoses. EC 126.96.36.199.3-Hydroxysteroid Dehydrogenases: Catalyze the oxidation of 3-hydroxysteroids to 3-ketosteroids.Leukemia Virus, Murine: Species of GAMMARETROVIRUS, containing many well-defined strains, producing leukemia in mice. Disease is commonly induced by injecting filtrates of propagable tumors into newborn mice.Leukemia, Experimental: Leukemia induced experimentally in animals by exposure to leukemogenic agents, such as VIRUSES; RADIATION; or by TRANSPLANTATION of leukemic tissues.Ketosteroids: Steroid derivatives formed by oxidation of a methyl group on the side chain or a methylene group in the ring skeleton to form a ketone.Hydroxysteroid Dehydrogenases: Enzymes of the oxidoreductase class that catalyze the dehydrogenation of hydroxysteroids. (From Enzyme Nomenclature, 1992) EC 1.1.-.3-alpha-Hydroxysteroid Dehydrogenase (B-Specific): A 3-hydroxysteroid dehydrogenase which catalyzes the reversible reduction of the active androgen, DIHYDROTESTOSTERONE to 5 ALPHA-ANDROSTANE-3 ALPHA,17 BETA-DIOL. It also has activity towards other 3-alpha-hydroxysteroids and on 9-, 11- and 15- hydroxyprostaglandins. The enzyme is B-specific in reference to the orientation of reduced NAD or NADPH.Alcohol Oxidoreductases: A subclass of enzymes which includes all dehydrogenases acting on primary and secondary alcohols as well as hemiacetals. They are further classified according to the acceptor which can be NAD+ or NADP+ (subclass 1.1.1), cytochrome (1.1.2), oxygen (1.1.3), quinone (1.1.5), or another acceptor (1.1.99).Thymus Neoplasms: Tumors or cancer of the THYMUS GLAND.