Akio Iwashima

Inhibitory effects of fucoxanthin, a natural carotenoid, on N-myc expression and cell cycle progression in human malignant tumor cells

Fucoxanthin, a natural carotenoid prepared from brown algae, inhibited the growth of GOTO cells, a human neuroblastoma cell line. Fucoxanthin at 10 micrograms/ml reduced the growth rate of GOTO cells to 38% of the control at day 3 after drug treatment. Flowcytometric analysis revealed that fucoxanthin caused the arrest in the G0-G1 phase of cell cycle. Expression of N-myc gene was proved to be decreased by fucoxanthin as early as 4 h after treatment at 10 micrograms/ml and that may be important for the mechanism of anti-proliferative action of the carotenoid.

Inhibitory effects of dihydroagarofuran sesquiterpenes on Epstein-Barr virus activation

To search for possible antitumor promoters, we carried out a primary screening of thirty-seven dihydroagarofuran sesquiterpenes from Tripterygium wilfordii Hook fil. var. regelii Makino and Euonymus sieboldianus Blume, using their possible inhibitory effects on the Epstein-Barr virus early antigen (EBV-EA) activation which is induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Some of these sesquiterpenes, triptofordin F-2 (Takaishi et al., 1988), 1,2,6,8,15-pentaacetoxy-9-benzoyloxy-4-hydroxy-beta-dihydroagarofuran and triptogelin A-1 (Takaishi et al., 1990) were observed to significantly inhibit the EBV-EA activation at low doses. Based on the results, the structural requirements for the activity of these compounds were discussed [corrected].

Carrier-mediated transport of thiamine in baker's yeast

Abstract 1. 1. The characteristics of a system of [ 14 C]thiamine uptake were investigated in bakers yeast ( Saccharomyces cerevisaie ). 2. 2. [ 14 C]Thiamine uptake by the system was found to be an energy- and temperature-dependent process which has an optimal pH at 4.5. 3. 3. Most of [ 14 C]thiamine taken up existed intracellularly in free form, which accumulated against a large concentration difference. 4. 4. The apparent K m for [ 14 C]thiamine uptake was 1.8·10 −7 M, and the uptake of labeled thiamine was inhibited by several thiamine analogues, except for oxythiamine. 5. 5. Short-chain fatty acids (C 2 –C 6 ) strongly inbibited [ 14 C]thiamine uptake. 6. 6. Caproate, which has a most pronounced inhibitory effect on [ 14 C]thiamine uptake, brought about the exit of [ 14 C]thiamine taken up. 7. 7. Pyrithiamine inhibited significantly [ 14 C]thiamine exit caused by caproate, whereas oxythiamine did not. 8. 8. It was discussed whether the uptake of thiamine in bakers yeast occurs by a carrier-mediated active process.

Anti-tumour-promoting glyceroglycolipids from the green alga, Chlorella vulgaris

Two new monogalactosyl diacylglycerols were isolated from the freshwater green alga, Chlorella vulgaris, as anti-tumour promoters, together with three monogalactosyl diacylglycerols and two digalactosyl diacylglycerols. The new monogalactosyl diacylglycerol containing (7Z,10Z)-hexadecadienoic acid showed a more potent inhibitory effect toward tumour promotion than the other glycerolipids isolated.

Isothiocyanates inhibit cell cycle progression of Hela cells at G2/m phase

To analyze the inhibitory effects of isothiocyanates on the growth of human cancer cells, the effects of these compounds on the cell cycle progression of HeLa cells were studied by flow cytometry. The accumulation of cells at G2/M phase was observed at 16 h after treatment with 10 microM allyl isothiocyanate, 2.5 microM benzyl or phenethyl isothiocyanate, at which concentrations the cell growth was inhibited to 41-79% of control. These results suggest that isothiocyanates delay the cell cycle progression of HeLa cells, leading to inhibition of cell growth.

Berberine Sulfate Inhibits Tumor-Promoting Activity of Teleocidin in Two-Stage Carcinogenesis on Mouse Skin

Berberine sulfate, an isoquinoline alkaloid isolated from Hydrastis canadensis L., inhibited the effects of the tumor promoters 12-O-tetradecanoylphorbol-13-acetate and teleocidin, such as increased 32Pi-incorporation into phospholipids of cell membrane and hexose transport. Berberine sulfate also markedly suppressed the promoting effect of teleocidin on skin tumor formation in mice initiated with 7,12-dimethylbenz[a]anthracene.

Production of anti-tumour-promoting furano-naphthoquinones in Tabebuia avellanedae cell cultures

Abstract Callus and cell suspension cultures of Tabebuia avellanedae produce promising antitumour-promoting furanonaphthoquinones, 5-hydroxy-2-(1-hydroxyethyl)naphtho[2,3- b ]furan-4,9-dione and 2-acetyl-5-hydroxy-naphtho[2,3- b ]furan-4,9-dione in high yields.

Antitumor-Promoting Activity of Garlic Extracts

Garlic extract was proved to inhibit one of the earliest phenomena caused by 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a tumor promoter, in vitro; i.e., the enhancement of phospholipid metabolism. And also the first stage of tumor promotion in two-stage mouse skin carcinogenesis in vivo was suppressed by the treatment with garlic extract. Thus, garlic extract seems to be effective to inhibit initial events caused by TPA type tumor promoters in vitro and in vivo.

Isolation and characterization of a thiamin transport gene, THI10, from Saccharomyces cerevisiae

We isolated a thiamin transporter gene,THI10, from a genomic library of Saccharomyces cerevisiae by the complementation of a yeast mutant defective in thiamin transport activity. The THI10 gene contained an open reading frame of 1,794 base pairs encoding a 598-amino acid polypeptide with a calculated molecular weight of 66,903. The nucleotide sequence of THI10 is completely identical to that of an anonymous DNA (open reading frame L8083.2) mapped to chromosome XII; two other genes (open reading framesYOR071c and YOR192c) in chromosome XV are extremely similar to THI10. Moreover, the THI10gene product showed significant sequence homology with yeast allantoin and uracil transporters. Hydropathy profile suggested that THI10 product is highly hydrophobic and contains many transmembrane regions. Gene disruption of the THI10 locus completely abolished the thiamin transport activity and thiamin binding activity in yeast plasma membrane fraction. Both the transport and thiamin binding activities were restored in the disrupted cells when the THI10 open reading frame was expressed by yeast GAL1 promoter, suggesting that the THI10 gene encodes for the thiamin transport carrier protein. Northern blot analysis demonstrated thatTHI10 gene expression is regulated at the mRNA level by intracellular thiamin pyrophosphate and that it requires a positive regulatory factor encoded by THI3 gene.

Presence of d-aspartate oxidase in rat liver and mouse tissues

Rat liver D-aspartate oxidase activity, which had been reported to be undetectable, was found to be well detectable in dialyzed liver homogenate. The requirements of the enzyme for activity and its sensitivity to inhibitors were identical with the known properties of the enzyme from other sources. We also demonstrated for the first time the presence of the enzyme activity in mouse tissues and some other rat tissues using dialyzed tissue homogenates.