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Biomedical subjects

S Fujimoto

Publications and source records attributed to S Fujimoto.

At least 1,117 records · Page 62Linked to original sources
PubMed1976

The aconitase of yeast. IV. Studies on iron and sulfur in yeast aconitase.

Chemical analyses were carried out to determine the active components of the crystalline aconitase [EC 4.2.1.3] of Candida lipolytica. The enzyme contained 2 atoms of non-heme iron, 1 atom of labile sulfur, and 6 sulfhydryl groups per molecule. One atom of the non-heme iron was released by the addition of metal-chelating agents such as sodium citrate, sodium nitrilotriacetate (NTA) or sodium ethylenediaminetetraacetate (EDTA) without loss of the enzyme activity. The non-heme iron and labile sulfur were released by the addition of sulfhydryl reagents such as rho-chloromercuribenzoate (PCMB), sodium mersalyl or urea with loss of the enzyme activity. o-Phenanthroline reacted with the iron atoms in the enzyme at pH 6.0 with loss of the activity. These results show that yeast aconitase is an iron-sulfur protein and that only one of the two non-heme iron atoms is essential for enzyme activity.

Aconitate Hydratase↗
PubMed1976

The aconitase of yeast. V. The reconstitution of yeast aconitase.

The apoenzyme of yeast aconitase [EC 4.2.1.3] was prepared by treatment of yeast aconitase with sodium mersalyl, followed by passage by passage of the reaction mixture through a column of Dowex A-1 and gel filtration on Sephadex G-25. The apoenzyme had no aconitase activity, but the active enzyme could be reconstituted by treatment of the apoenzyme with ferrous ions and sodium sulfide in the presence of 2-mercapto-ethanol. The reconstituted active enzyme was isolated by DEAE-Sephadex A-50 column chromatography and Sephadex G-100 gel filtration from the reaction mixture. The reconstituted enzyme was identical with the original untreated enzyme in terms of specific activity, iron content and spectral characteristics, but not in terms of labile sulfur content. A significant difference in visible spectra between the holo- and apoenzymes appeared to be due to the difference in iron and labile sulfur contents between the two proteins.

Aconitate Hydratase↗
PubMed1976

Effect of taurine on responses to noradrenaline, acetylcholine and ouabain in isolated auricles from digitalized guinea pigs.

Responses of the isolated heart from the guinea pig treated chronically with digitoxin until the T wave had disappeared were studied. The development of the abnormal ECG pattern was abolished by a simultaneous injection of taurine and digitoxin. Taurine also inhibited the change by digitoxin of the responses to acetylcholine and ouabain but not to noradrenaline. The causal relationship between the inhibitory effect of taurine and prevention of the development of arrhythmias remains obscure.

Acetylcholine↗
PubMed1976

Regualtion of the immune response to tumor antigens. I. Immunosuppressor cells in tumor-bearing hosts.

A/Jax mice were rendered immune to the syngeneic and transplantable methylcholanthrene-induced Sarcoma 1509a by the surgical removal of the tumor 7 days after implantation; subsequent injection i.v. transfer of 10(7) to 10(8) washed thymus or spleen cells of tumor-bearing animals (TBA) to immune animals significantly inhibited the rejection of the tumor; this suppressive effect was entirely abolished by the treatment of these lymphocytes with anti-theta serum or anti-thymocyte serum (ATS) and complement before adoptive transfer. On the other hand, an equal number of thymus or spleen cells of normal animals or of animals bearing an unrelated tumor had no suppressive effect. Treatment of normal syngeneic animals with ATS after tumor cell inoculation or splenectomy of TBA resulted in the suppression of the tumor growth. The serum of TBA had no effect on tumor growth in immune syngeneic mice. Together these results suggest that TBA possess immunosuppressor T cells regulating negatively their immune response to the tumor.

Animals↗
PubMed1976

Effect of N1-(2'-tetrahydrofuryl)-5-fluorouracil and 5-fluorouracil on nucleic acid and protein biosyntheses in Ehrlich ascites cells.

N1-(2'-Tetrahydrofuryl)-5-fluorouracil (FT-207) is a derivative of 5-fluorouracil (5-FU) and has been accepted as a new chemotherapeutic drug. The inhibitory effects of FT-207 and 5-FU on nucleic acid and protein biosyntheses in Ehrlich ascites cells were compared. Both drugs markedly inhibited the incorporation in vivo of the labeled precursors into nucleic acid and protein. The inhibitory effect of FT-207 on DNA and RNA synthesis lasted for a long period of time. Two hr after administration of 5-FU (250 mug/g body weight), the absolute size of uracil pool of liver increased by at least 50%. However, in an in vitro study, FT-207 at a concentration of 60 mug/ml produced no effect on the incorporation of precursors into DNA and RNA of Ehrlich ascites cells 3 hr incubation. If 5-FU was added to Ehrlich ascites cell suspension simultaneously with [5-3H]uridine, the incorporation of the labeled precursor into RNA increased by 30 to 50%.

Animals↗
PubMed1976

Regulation of the immune response to tumor antigens. II. The nature of immunosuppressor cells in tumor-bearing hosts.

Immunosuppressor (IS) cells were found to be generated in tumor-bearing animals (TBA) within 24 hr after inoculation of tumor cells of the methylcholanthrene-induced Sarcoma 1509a and appeared to persist in the hosts as long as the tumor was progressing. However, IS cells disappeared with 5 days after extirpation of the tumor. Increasing doses of thymus cells of TBA increased the degree of suppression of tumor rejection in immune syngeneic animals. Ten million thymus cells of TBA were capable of suppressing significantly the tumor rejection. The IS cells were detected in the thymus, spleens, and draining lymph nodes, as well as in bone marrow of TBA, but could not be detected in the peripheral circulating blood. Since immunosuppressive activity of bone marrow cells from TBA was entirely abolished by the in vitro treatment of the cells with anti-theta serum and complement, the observed immunosuppression appears to be mediated by the T cell population.

Animals↗
PubMed1976

Antibody response to lymphoma antigens in syngeneic and H-2 compatible mice.

The antibody response to immunization with A/J lymphoma L1117 cells by syngeneic A/J mice and by H-2 compatible B10.A mice has been show- to be highly specific for tumor antigens of the lymphoma cells. In both strains the response exhibits a very slow rise in cytotoxic antibody levels reaching a maximum only after 3 months of biweekly injections. It is also unusual in that cytotoxic activity is primarily due to IgM antibodies even after 20 weeks of immunization. The similarity between these characteristics and those reported for "T-independent" antigens suggests that tumor antigens on L1117 cells may be unable to stimulate helper T cells.

Animals↗
PubMed1976

Effect of drug combination of antitumor activity and myelotoxicity.

Relationship between the survival time of L-1210-bearing mice and myelosuppression of normal mice after combination chemotherapy was studied. In a variety of combinations of 6-mercaptopurine, 6-thioguanine, and cyclophosphamide, a combination of cyclophosphamide and 6-thioguanine produced the highest increase in life span (ILS) and the highest number of 60-day survivors of all. In contrast, a combination of 6-mercaptopurine and 6-thioguanine showed as low as ILS as did single agents. A combination of 6-mercaptopurine, cyclophosphamide, and 6-thioguanine exhibited the second best effect on survival time of leukemic mice. However, in myelosuppression as measured by changes in the total number of nucleated cells, in the number of hematopoietic colony-forming cell, and in peroxidase level of femoral bone-marrow, the combination of 6-mercaptopurine and 6-thioguanine showed no more toxicity than the other 2-drug combinations. In addition to these findings, the presence of a striking difference in the cell number in ascitic fluid of leukemic mice among the animals given 6-thioguanine, and those given other 2- or 3-drug combinations may suggest that the difference in the antileukemic activity is not due to the difference in the toxicity against the host, but due to the difference in the activity of direct action of combined drugs on leukemic cells in the peritoneal cavity or in other sites.

Animals↗