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Volume 101 (1993)
- Issue 6 Pages 349-
- Issue 5 Pages 289-
- Issue 4 Pages 197-
- Issue 3 Pages 101-
- Issue 2 Pages 59-
- Issue 1 Pages 1-
Volume 101, Issue 6
Displaying 1-5 of 5 articles from this issue
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Satoshi YAMAMOTO1993 Volume 101 Issue 6 Pages 349-361
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSChemical carcinogenesis can be subdivided at least into two stages, i.e., initiation and promotion, in the mouse skin carcinogenesis model. There is considerable evidence supporting the relevance of the above concept to chemical carcinogenesis of other organs. Initiation represents the stage in which a carcinogen interacts with DNA and causes irreversible damage on the genome. Subsequent repeated exposure to a tumor promoter leads to a phenotypic expression of the initiated cells to tumor cells. In our living environment, a large number of carcinogens may exist and exposure to a minute amount of carcinogen even once may be sufficient to generate initiated cells; therefore, prevention of carcinogenesis at the stage of initiation is not an easy task. In contrast to the initiation stage, the promotion stage is essentially reversible, and a relatively long period is required to accomplish this process. Therefore, prevention of chemical carcinogenesis in the promotion stage seems more practical than preventing carcinogenesis in the initiation stage. There is much evidence suggesting that arachidonic acid cascades play important roles both in the initiation and promotion stages. In the two-stage skin carcinogenesis, inhibitors of arachidonic acid cascades, especially lipoxygenase inhibitors, effectively prevent tumor formation by inhibiting the stage of tumor promotion caused by different types of tumor promoters. Although at present, the role(s) of lipoxygenase pathways in the mechanism of tumor promotion is not fully understood, the potential use of lipoxygenase inhibitors for the prevention of chemical carcinogenesis is anticipated.View full abstractDownload PDF (29569K) -
Noriko KASE, Kazuhiko TAKASAKI, Yasushi HIGASHIDE, Norihiko TAMURA, Bu ...1993 Volume 101 Issue 6 Pages 363-374
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSF-0401 is a novel dihydropyridine (DHP) derivative with potent vasodilative and anti-aggregatory actions. In the present study, we examined the mechanisms of the actions of F-0401 and obtained the following findings: F-0401 suppressed [3H] nitrendipine binding to rat heart membrane (Ki value: 2.2×10-7 M). CaCl2-induced contractions of rabbit aorta and guinea pig taenia coli were inhibited by F-0401 (pA2 values: 7.7 and 6.6). These results indicated that F-0401 had calcium antagonistic activity slightly less potent than that of the other DHP derivatives. In addition, F-0401 significantly inhibited the activity of thromboxane (TX) A2 synthetase (IC50 value: 2.5×10-7 M) and [3H] PAF binding to rabbit platelets (Ki value : 1.4×10-8 M). The other DHP derivatives tested did not affect TXA2 synthetic activity, and the PAF antagonism of the other derivatives were less than that of F-0401. Neither F-0401 nor the other DHP derivatives inhibited cAMP- or cGMP-dependent phosphodiesterase activity. These results revealed that F-0401 has calcium antagonistic, anti-PAF and TXA2 synthetase inhibitory actions in the same dose ranges.View full abstractDownload PDF (22484K) -
Naoyuki TSUTSUMI, Hideo NAGATA, Junko TSUYUKI, Arao UJIIE1993 Volume 101 Issue 6 Pages 375-384
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSWe developed a facile method for studying bone resorption using fetal rat femur by labelling the bone with 45Ca in vitro. We found that cartilages stimulated the bone resorption of a shaft which was obtained by cutting off both distal and proximal cartilages from the femur. When the shaft was co-cultured with the cartilages isolated by a 0.4-μm microporous membrane in the same Transwell™, the bone resorption of the shaft was increased. This finding suggests that the stimulation of bone resorption by the cartilages is not a result of recruitment of osteoclasts or the precursor cells from the cartilages . Indomethacin (10-6 M) failed to influence the bone resorbing activity of the cartilages. The bone resorbing activity in the supernatant obtained from the cartilage-culture was decreased by heating. The bone resorbing activity of the supernatant did not remain in the lipid-extract or the pronase-digested supernatant, but was present in a fraction whose molecular weight was greater than 50, 000. These results collectively suggest that the cartilages produce a bone resorption-stimulating factor(s) which is water-soluble, is a non-prostanoid material, contains protein and has a molecular weight greater than 50, 000.View full abstractDownload PDF (18880K) -
Naoyuki TSUTSUMI, Hideo NAGATA, Nobuhiko ARAI, Masami KOJIMA, Arao UJI ...1993 Volume 101 Issue 6 Pages 385-391
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSWe studied bone resorption of fetal rat femora in association with cartilage tissue. Some protease inhibitors, e.g., E-64, pepstatin A, phosphoramidon, amastatin, bestatin, foroxymithine, did not influence the bone resorption, but some serine protease inhibitors such as PMSF, TLCK, TPCK and elastatinal inhibited the bone resorption at 10-5 M, 10-4 M, 10-4 M, 10-4 M, respectively. A conditioned medium, obtained from cartilage tissue-cultured medium in the presence of 10-4 M TPCK, which was then excluded from the medium by dialysis after the culture, stimulated the bone resorption. Cycloheximide (0.1 to 10 μg/ml) and puromycin (0.3 to 30 μg/ml) inhibited the cartilage tissue-dependent bone resorption. A transient treatment of the femora with cycloheximide (3 μg/ml) for a day inhibited the bone resorption, but after the treatment, in the absence of cycloheximide, the femora gradually recovered the bone-resorbing activity. The conditioned medium, obtained from cartilage tissue-cultured medium in the presence of cycloheximide (3 μg/ml), which was then excluded from the medium by dialysis after the culture, failed to influence the bone resorption. These findings collectively suggest that cartilage tissue produces a bone resorption-stimulating factor(s) which is a serine protease or contains the protein as an inactive, latent form and then a certain serine protease converts it to an active form.View full abstractDownload PDF (13864K) -
[in Japanese], [in Japanese]1993 Volume 101 Issue 6 Pages 393-396
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSDownload PDF (11962K)
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