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Biomedical subjects

T Saeki

Publications and source records attributed to T Saeki.

At least 163 records · Page 9Linked to original sources
PubMed1991

A new anti-platelet drug, E5510, has multiple suppressive sites during receptor-mediated signal transduction in human platelets.

The mode of action of E5510, 4-cyano-5,5-bis(4-methoxyphenyl)-4-pentenoic acid, which has very potent anti-platelet activities, was investigated by examining its effects on the biochemical responses in the process of human platelet activation. In a whole-cell system, E5510 inhibited the increased turnover of inositol phospholipids arising from phospholipase C activation, arachidonic acid release from phospholipids by phospholipase A2, mobilization of intracellular free Ca2+, protein kinase C activation, and thromboxane A2 production. In a cell-free system, E5510 inhibited cyclooxygenase activity and cyclic AMP-dependent phosphodiesterase activity in a dose-dependent manner. An elevation of cyclic AMP in platelets was also observed at a relatively high concentration of E5510. It was suggested that receptor-mediated turnover of inositol phospholipids, intracellular Ca2+ increase, arachidonic acid release from phospholipids and protein kinase C activation might be indirectly inhibited by the increased cyclic AMP level in platelets. Thromboxane A2 production in the whole-cell system was very strongly inhibited by E5510, and the IC50 for this effect was 100 times lower than that of direct inhibition of cyclooxygenase in the cell-free system. It was concluded that although the primary mode of action of E5510 is the inhibition of the cyclooxygenase pathway of positive signal transduction in platelets, E5510 has another mode of action by increasing platelet cyclic AMP, which can act as a negative messenger in platelet signal transduction, and these multiple sites of action synergistically antagonize platelet cellular activation.

Arachidonic Acid↗
PubMed1991

The inhibitory effect of a novel antiatheromatous agent, E5050, on the intimal thickening of aorta in cholesterol-fed rabbit in vivo.

The development of atheromatous lesions in the aortic arch of 0.5% cholesterol-fed rabbits was biochemically and morphologically examined. The animals were killed at week twelve (Cont-12W) or sixteen (Cont-16W). Both the micrographic and biochemical studies showed that the main atheromatous lesions in the Cont-12W group were fatty streaks, whereas those in the Cont-16W group were fibrous plaques. In these models, oral ingestion of 0.2% and 0.4% E5050, which has an antiproliferative effect on smooth muscle cells, had no effect on the surface involvement or the lipid content of the aortic arch at the sixteenth week, but reduced the degree of intimal thickening and the DNA content in the aortic arch in a dose-dependent manner. These results strongly suggest that E5050 suppresses the intimal thickening through its inhibitory effect on the proliferation of smooth muscle cells.

Animals↗
PubMed1991

Effects of post-treatment incubation on recombinogenesis in incision-proficient and incision-deficient strains of Saccharomyces cerevisiae: I. Recombinogenesis after UV- and gamma-ray-irradiation.

After UV-irradiation of G1 phase cells, most gene conversion and crossing-over took place in cells of incision-proficient strains without post-irradiation incubation. In contrast, incision-deficient cells markedly induced both of these recombinational events only after irradiated cells were incubated for several hours in liquid growth medium before selection. These results indicate that when G1 cells are irradiated with UV recombinational events are initiated during that G1 phase in incision-proficient strains; whereas, they are not initiated in irradiated incision-deficient strains before the cells reach the S/G2 phase. Experimental gamma-ray results also suggest that post-irradiation incubation is not required for incision-proficient and -deficient strains to initiate mitotic recombinational events. Taken together, these results show that the formation of incision nicks and of post-replication gaps in DNA appears to be necessary for the initiation of recombinational events after UV treatment; whereas, it is not required after gamma-irradiation.

Gamma Rays↗
PubMed1991

Effects of post-treatment incubation on recombinogenesis in incision-proficient and incision-deficient strains of Saccharomyces cerevisiae: II. Recombinogenesis after the photoaddition of furocoumarins.

After the photoaddition of mono- and bifunctional furocoumarins to G1 phase cells, most gene conversion and crossing-over occurred without post-irradiation incubation of these cells in incision-proficient strains. In contrast, incision-deficient cells showed marked induction of both recombinational events only after treated cells had been incubated for several hours before selection. These results indicate that when furocoumarins are photoadded to G1 cells, initiation of recombinational events occurs during the same G1 phase in the incision-proficient cells; whereas, it occurs only after post-irradiation DNA replication in incision-deficient cells. The action of the PSO2 gene product specific for the repair of DNA crosslinks in recombination induction is discussed and compared to the actions of the excision repair genes RAD1 and RAD2.

Furocoumarins↗
PubMed1991

Production of a site specifically cleavable P-glycoprotein-beta-galactosidase fusion protein.

We have fused full length and the carboxyl-half of human MDR1 cDNA with the E. coli lacZ gene via a collagen linker and allowed their expression in yeast Saccharomyces cerevisiae. Using antibodies against beta-galactosidase we partially purified the fusion proteins by immunoprecipitation and show here that the full length fusion protein has ATPase activity. By contrast, the fusion protein containing the carboxyl-half of P-glycoprotein did not show ATPase activity, indicating that both domains of P-glycoprotein are necessary. By treatment of the immunoprecipitated fusion protein with collagenase, P-glycoprotein was released from the beta-galactosidase moiety. The results shown here open the possibility for a large scale purification of P-glycoprotein using this site specifically cleavable fusion protein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Expression of human P-glycoprotein in yeast cells--effects of membrane component sterols on the activity of P-glycoprotein.

A human MDR1 cDNA was introduced into yeast cells. Immunoblot analysis and indirect immunostaining showed that some of the P-glycoprotein produced was situated in its native orientation in the yeast plasma membrane. Drug-binding activities of the recombinant P-glycoproteins were markedly decreased compared to that of the authentic P-glycoprotein. To identify the bases of decreased binding we studied the effects of membrane component sterols on the azidopine binding and found that ergosterol, which is the main sterol in the yeast membrane, and calciferol, which is produced from ergosterol by UV irradiation, inhibited azidopine binding. These sterols in yeast membrane probably inhibit the function of human P-glycoprotein as a multidrug transporter in yeast cells, because expression of P-glycoprotein in yeast cells did not confer resistance to doxorubicin.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1991

Modulation of mesangial cell proliferation by endothelial cells in coculture.

The effects of direct cell contact between endothelial (ECs) and mesangial cells (MCs) on MCs proliferation were examined in a coculture system in vitro. Mitomycin C treated ECs (M-ECs) were plated on culture dishes and MCs were cocultured with these M-ECs. Cell number was measured at the end of days 1, 3, and 5. In the coculture system with direct contact, the growth of cocultured MCs was modulated as follows: 1) the growth of MCs was inhibited up to day 3, and 2) a high level of proliferation was observed between days 3 and 5. This biphasic pattern of growth could not be detected in coculture of fibroblasts with MCs. In coculture without direct contact, using intercup chambers, the kinetics in cell proliferation between cocultured MCs and MCs alone were essentially the same. Conditioned media derived from cocultures up to day 3 in a contact-dependent manner inhibited the 3H-thymidine uptake of MCs. From these results, it would thus appear that MCs proliferation is regulated by intercellular contact with ECs.

Animals↗
PubMed1990

Inhibitory effects of a novel antiatheromatous agent, E5050, on aortic smooth muscle cell proliferation, in vitro.

The effect of a novel antiatheromatous agent, N-(3-[4'-(2'',6''-dimethylheptyl)phenyl]butanoyl)ethanolamin e (E5050), on the proliferation of porcine aortic smooth muscle cells was studied in vitro. E5050 dose-dependently inhibited DNA synthesis as well as proliferation of cells stimulated with 10% fetal calf serum with no cytotoxic effects. An inhibitory effect of E5050 on DNA synthesis was also confirmed in cells stimulated with human platelet extract and with a combination of platelet-derived growth factor and human plasma-derived serum. DNA synthesis in smooth muscle cells stimulated with other mitogens, such as fibroblast growth factor and insulin, was inhibited by E5050 and this inhibitory effect was positively correlated with the E5050 uptake into smooth muscle cells. These results indicate that E5050 inhibits smooth muscle cell proliferation stimulated by various mitogenic factors. It is suggested that E5050 prevents atherogenesis and inhibits the progression of fibromuscular lesions by interfering with the proliferation of arterial smooth muscle cells.

Animals↗
PubMed1990

Prospective randomized controlled study on bestatin in resectable gastric cancer--third report.

The efficacy of Bestatin as adjuvant immunochemotherapy for patients with resectable gastric cancer was investigated. Ninety-six patients with similar background factors were randomized into two groups; a control group and an experimental group, the patients in the experimental group receiving a daily oral dose of 60 mg Bestatin over a long period. All 96 patients were treated with a bolus intravenous injection of mitomycin C (MMC) plus oral administration of tegafur (FT-207, FT). The survival rate of the patients in the MMC + FT + Bestatin group was more favorable than that of the patients in the MMC + FT group, but the difference was not statistically significant. The survival rates of the MMC + FT + Bestatin group patients in the stratification of stage III + IV and positive histological serosal invasion, ps(+), were significantly superior to those of the MMC + FT group patients (Logrank test: p less than 0.05). Moreover, in patients with positive histological serosal invasion, the recurrence of peritoneal dissemination was significantly suppressed in the MMC + FT + Bestatin group.

Adjuvants, Immunologic↗
PubMed1990

Prediction of the resistance of human tumors to adriamycin by chemosensitivity tests and DNA analysis of the multidrug resistance gene.

In order to predict natural resistance to Adriamycin (ADM), the amplification of multidrug resistance gene 1 (MDR1) was investigated in 50 human cancer specimens using Southern blot analysis. Genomic DNA was extracted from both human solid tumors and adjacent normal tissues for the analysis. MDR1 gene amplification was not observed in any of the patients tested, including 5 patients in whom ADM was not clinically effective. On the other hand, chemosensitivity tests performed on the tumor cells of these 5 patients indicated resistance to ADM. Our results therefore indicate that MDR1 gene amplification is rarely seen among clinical samples and that conventional chemosensitivity tests might be more useful for the prediction of ADM resistance in cancer patients than the analysis of MDR1 gene amplification.

Blotting, Southern↗
PubMed1990

Production of infectious swine vesicular disease virus from cloned cDNA in mammalian cells.

Full-length cDNA clones of the swine vesicular disease virus (SVDV) were constructed from subgenomic cDNA clones in the expression vector pSVL (pSVLS00). The direct transfection of mammalian cells with plasmid pSVLS00 results in the production of infectious virus. The recovered virus was neutralized completely by anti-SVDV guinea-pig serum, but did show a difference in plaque morphology from the parental virus.

Animals↗
PubMed1990

Transforming growth factor-alpha expression is enhanced in human mammary epithelial cells transformed by an activated c-Ha-ras protooncogene but not by the c-neu protooncogene, and overexpression of the transforming growth factor-alpha complementary DNA leads to transformation.

MCF-10A cells are a spontaneously immortalized normal human mammary epithelial cell line. MCF-10A cells were transfected with two expression vector plasmids containing either a human point-mutated c-Ha-ras protooncogene or the rat c-neu protooncogene. c-Ha-ras-transfected MCF-10A cells grow as colonies in soft agar, exhibit a 3- to 4-fold increase in their growth rate in serum-free medium, and show a reduced mitogenic response to exogenous epidermal growth factor (EGF) or transforming growth factor-alpha (TGF alpha) as compared to MCF-10A cells. c-Ha-ras-transfected MCF-10A cells express a 4- to 8-fold increase in TGF alpha mRNA levels and secrete 4- to 6-fold more TGF alpha protein as compared to MCF-10A cells. Addition of either an anti-TGF alpha neutralizing monoclonal antibody or an anti-EGF receptor blocking monoclonal antibody to the Ha-ras-transformed MCF-10A cells produces a 50 to 80% inhibition of colony formation of these cells in soft agar. c-neu-transfected MCF-10A cells grown in soft agar and exhibit an increase in their growth rate in serum-free medium at a level comparable to that observed in Ha-ras-transformed MCF-10A cells. Addition of an anti-c-erbB-2 monoclonal antibody inhibits the anchorage-independent growth of these cells in soft agar. However, c-neu-transformed MCF-10A cells show no increase in TGF alpha secretion and no change in their responsiveness to exogenous EGF or TGF alpha. A recombinant retroviral vector containing the human TGF alpha gene was also introduced into MCF-10A cells. TGF alpha-infected MCF-10A cells secrete 15- to 20-fold more TGF alpha protein than MCF-10A cells, form colonies in soft agar, exhibit an enhanced growth rate in serum-free medium, and show a decreased mitogenic response to exogenous EGF or TGF alpha at a level equivalent to Ha-ras-transformed MCF-10A cells. Growth of TGF alpha-infected MCF-10A cells in soft agar is completely inhibited by anti-TGF alpha neutralizing or anti-EGF receptor blocking monoclonal antibodies. These results suggest that TGF alpha is an intermediary in the transformation of human mammary epithelial cells by an activated c-Ha-ras gene, but not by the c-neu gene, and demonstrate that overexpression of this growth factor is able to transform immortalized human mammary epithelial cells which also express a sufficient complement of functional EGF receptors.

Blotting, Northern↗
PubMed1990

Transforming growth factor-alpha: an oncodevelopmental growth factor.

Transforming growth factor-alpha (TGF-alpha) is a 50-amino-acid mitogenic peptide that is structurally and, in some cases, functionally related to members of the epidermal growth factor (EGF) family of peptides. TGF-alpha is initially synthesized as a high-molecular-weight, glycosylated, membrane-associated precursor of approximately 160 amino acids. The low-molecular-weight TGF-alpha peptide as well as the precursor are biologically active in a number of systems and can function as transforming proteins when overexpressed. TGF-alpha binds to and activates the EGF receptor, and TGF-alpha and the EGF receptor are coexpressed in a number of human and rodent tumors and tumor cell lines--which suggests that TGF-alpha can function as an autocrine or paracrine growth factor. TGF-alpha is transiently expressed in some fetal and adjacent maternal tissues during development and is also expressed in a number of adult tissues; this pattern of expression suggests that the growth factor is involved in several distinct physiological functions.

Amino Acid Sequence↗
PubMed1990

[A case of colony stimulating factor (CSF) producing gastric carcinoma].

A gastric carcinoma associated with marked leukocytosis is reported. The case involved a 70-year-old male who was admitted to Akita Kumiai General Hospital because of general fatigue and vertigo in October, 1989. A palpable, hard, uneven mass was found in the epigastrium. Further, an upper gastrointestinal series revealed a large filling defect in the gastric body. Also, an endoscopic examination disclosed an uneven mass, and specimens that were biopsied showed an adenocarcinoma. The white blood cell (WBC) count was 45,800/microliter and had a 96% presence of neutrophils, and an examination of the bone marrow showed excessive myeloid hyperplasia. The WBC gradually increased, reaching up to 67,800/microliter. Finally, an EIA assay of the serum colony stimulating factor (CSF) disclosed a marked increase. After a gastrectomy, the WBC promptly decreased to the normal range and the CSF activity in a supernatant of a tumor-cell-conditioned medium showed a higher value. Thus, this tumor was diagnosed as being a CSF-producing gastric carcinoma.

Adenocarcinoma↗
PubMed1990

[Development of Tc-99m labeled activated carbon microspheres and clinical application].

We have developed Tc-99m labeled activated carbon microspheres (99mTc-CH44) for use in mammary lymphoscintigraphy and detailed analysis of mammary lymph flow. 99mTc-CH44 was prepared according to the EDTA complex method. The labeling rate immediately after preparation was 97.7 +/- 2.6% at 37 degrees C and was 94.9 +/- 2.6% after 24-hour continuous shaking. The release of 99mTcO4- from 99mTc-CH44 was determined in vitro, using a simulation model. In this assay, the 99mTcO4- release rate in one hour was 6.6% and that in 6 hours was 38%. When 2ml (2mCi, 74MBq) of 99mTc-CH44 was injected into the mammary glands of 12 patients with breast tumors, the axillary, subclavian and parasternal lymph nodes of 10 patients were visualized 60 minutes later. In analysis of lymph flow in 25 rats using 99mTc-CH44 the lymph flow from the foot pad through the popliteal to the intraperitoneal lymph nodes was known to have only one route when examined by gross finding and histology. However, the examination using RI-technique indicated two routes. The examination in 9 patients with breast cancer indicated that the use of 99mTc-CH44 allowed detailed analysis of lymph flow. These results suggest that 99mTc-CH44 is useful for the preoperative mammary lymphoscintigraphy and detailed analysis of mammary lymph flow.

Adult↗
PubMed1989

Evidence that C4b-binding protein is an acute phase protein.

C4b-binding protein is a regulatory factor for both complement and coagulation systems. We found that a human hepatoma cell line, Hep G2, was capable of synthesizing C4b-binding protein and that the secretion of C4b-binding protein was enhanced by interleukin-6 and tumor necrosis factor, which are known to be modulators of acute phase proteins. In addition, the plasma content of C4b-binding protein was found to increase in patients of acute pneumonia. These results suggest that C4b-binding protein is an acute phase protein.

Acute-Phase Proteins↗
PubMed1989

Expression of the binding molecules for factor B and its fragment, Bb, of human complement on human monocytes after in vitro cultivation.

We have examined the expression of the binding molecules for Bb of human complement on the surface of resting and cultured human monocytes. Flow cytometry using biotinylated anti-B antibodies and phycoerythrin-avidin showed that although resting monocytes did not bind Bb significantly, monocytes cultivated for 24 h in the presence of fetal calf serum were capable of binding with Bb and its precursor B, but not with Ba fragment. The Bb-binding molecules were pronase-sensitive, suggesting that membrane proteins are associated with the Bb-binding molecules. In addition to human monocytes, liquid paraffin-induced guinea pig inflammatory macrophages were also found to express Bb-binding molecules on their surface. This implies that Bb receptor-like molecules become expressed during activation and differentiation of monocytes, just as observed with the C3d-receptor of monocytes.

Animals↗