Search PubMed⌕ Search

Biomedical subjects

K Kumaki

Publications and source records attributed to K Kumaki.

49 records · Page 3Linked to original sources
PubMed1975

Genetic expression of aryl hydrocarbon hydroxylase activity in the mouse.

Monooxygenases require NADPH and molecular oxygen during the metabolism of numerous endogenous hydrophobic substrates and carcinogenic and toxic exogenous chemicals. The complexity of these membrane-bound multicomponent drug-metabolizing enzyme systems is reviewed. What "aryl hydrocarbon (benzo[a]pyrene) hydroxylase activity" actually represents is reviewed and discussed. At least two forms of the hydroxylase activity exist and we suggest that they are associated with different molecular species of membrane-bound CO-binding hemoprotein (i.e., they are associated with different enzyme active-sties). At least two, and probably more than two, nonlinked loci are responsible for the genetic expression of new cytochrome P1450 formation and aryl hydrocarbon hydroxylase induction--and the stimulation of 10 other monooxygenase "activities"--in the mouse treated with certain aromatic hydrocarbons. The individual variability of hydroxylase activity in an inbred and in a random-bred strain of micr is illustrated. The basal hydroxylase activity appears to be inherited differently from the aromatic hydrocarbon-inducible hydroxylase activity. The potent inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin can stimulate increases in these hepatic monooxygenase activities and p1450 formation in so-called "nonresponsive" mice, whereas inducers such as beta-naphthoflavone and 3-methylcholanthrene cannot. Thus, the genetically "nonresponsive" micr apparently possess the structural and regulatory genes necessary for expression of these inducible monooxygenase activities and associated new formation of cytochrome P1450. We suggest that a mutation has occurred in the "nonresponsive" inbred strains that results in production of an inducer-binding receptor having a diminished affinity for aromatic hydrocarbons.

Animals↗
PubMedDate not supplied

Inhibitory effect of alkane-6,8-diols, the components of safflower, on tumor promotion by 12-O-tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mouse skin.

Erythro-alkane-6,8-diols were isolated from the flowers of Carthamus tinctorius. 12-0-Tetradecanoylphorbol-13-acetate (TPA, 1 microgram/ear), a tumor-promoting agent, was applied to the ears of mice to induce inflammation. Of 8 alkane-6,8-diols assayed, the C27, C31, C32, C33 and C35 alkane diols inhibited the inflammation. The 50% inhibitory dose of these compounds for TPA-induced inflammation was 0.5-0.7 mg/ear. However, C21, C23 and C25 alkane-6,8-diols were found to have no effect. Furthermore, the mixture of erythro-alkane-6,8-diols from the flowers of C. tinctorius markedly suppressed the promoting effect of TPA on skin tumor formation in mice following initiation with 7,12-dimethylbenz[a]anthracene.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

Inhibitory effect of taraxastane-type triterpenes on tumor promotion by 12-O-tetradecanoylphorbol-13-acetate in two-stage carcinogenesis in mouse skin.

Two taraxastane-type hydroxy triterpenes, taraxasterol and faradiol, isolated from the flowers of Compositae plants Cynara scolymus (artichoke) and Chrysanthemum morifilolium (chrysanthemum), respectively, showed strong inhibitory activity against 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in mice. At 2.0 mumol/mouse, these compounds inhibited markedly the tumor-promoting effect of TPA (1 microgram/mouse) on skin tumor formation following initiation with 7,12-dimethylbenz[alpha]anthracene (50 micrograms/mouse).

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

In vivo nuclear uptake of a vitamin D analog (OCT) in different tumor cell populations of FA-6 cancer xenograft in nude mice by receptor autoradiography.

1 alpha, 25-dihydroxyvitamin D3 [1 alpha, 25(OH)2D3] and its analogs have been shown to repress the production of parathyroid hormone-related peptide (PTHrP) in tumors, which is a major factor causing humoral hypercalcemia associated with various cancers. Since vitamin D analogs may be applicable to the treatment of cancer patients, the present study was undertaken to examine whether OCT, an analog with little calcemic activity, is incorporated into tumor tissues, and to identify cellular and subcellular sites of its specific uptake and retention. [26-3H]OCT was injected i.v. into nude mice inoculated with a human pancreatic carcinoma cell line (FA-6). At 1 hour after the injection, intracellular concentration of radioactivity was visualized by receptor (thaw-mount) autoradiography. The results indicate a heterogeneous distribution of radioactivity in nuclei of certain large cancer cells as well as in single or clustered small and elongated cells within the tumor, while connective tissue cells outside of the tumor remained free of nuclear labeling. The data suggest that OCT acts selectively at the genome of cancer cells during a certain maturational stage and also of a second population of small fibroblast-like cells that may have been transplanted with the tumor or are host-derived.

Animals↗