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Biomedical subjects

S Seki

Publications and source records attributed to S Seki.

At least 433 records · Page 24Linked to original sources
PubMed1980

Effects of 2',3'-dideoxythymidine triphosphate on replicative DNA synthesis and unscheduled DNA synthesis in permeable mouse sarcoma cells.

2',3'-Dideoxythymidine triphosphate differentially inhibited replicative DNA synthesis in permeable mouse ascites sarcoma cells and unscheduled DNA synthesis in bleomycin-treated permeable cells or in isolated rat liver nuclei. The mode of inhibition of 2',3'-dideoxythymidine triphosphate was competitive with respect to deoxythymidine triphosphate. 2',3'-Dideoxythymidine triphosphate inhibited replicative DNA synthesis with a Ki of 8 microM, whereas unscheduled DNA synthesis was more sensitive, the Ki being 0.5 microM. Referring to the differential sensitivity of DNA polymerases alpha and beta to 2',3'-dideoxythymidine triphosphate and to other related information reported previously, the present results suggested that DNA polymerase alpha is playing a major role in replicative DNA synthesis, and DNA polymerase beta in unscheduled DNA synthesis.

Animals↗
PubMed1980

Myocardial protection of only the left coronary artery perfusion in patients with isolated aortic valve replacement.

Effectiveness of only left coronary perfusion on myocardial protection was assessed by measuring serially cardiac functions such as cardiac index (CI), stroke index (SI), left ventricular minute work index (LVWI) and left ventricular stroke work index (LVSWI) in 22 consecutive patients with isolated, scheduled aortic valve replacement. The cardiac functions were determined 2,4 and 6 hours after open heart surgery. Correlation coefficients(r) between coronary perfusion time and the cardiac functions were less than 0.23, such being statistically insignificant. SI and LVSWI were in statistically significant inverse correlation to the preoperative NYHA classification and extracorporeal circulation(ECC) time for 4 hours following open heart surgery, and CI and LVWI for 2 hours. The correlation coefficients were highest at the 2nd postoperative hour and then decreased with passage of time. Therefore, the cardiac dysfunctions occurring in the postoperative period correlated either to the preoperative NYHA classification or ECC time, or both. It does, however, seem likely that the dysfunctions were correlated to ECC time as the recovery time of 4 hours from the dysfunction is too short for preoperatively existing dysfunction. Therefore, it was concluded that the continuous perfusion of only the left coronary artery was not the determinant factor of the postoperative dysfunctions and that the ECC time afforded detrimental effects, although such continued for 4 hours in terms of SI and LVSWI, and 2 hours in term of CI and LVWI.

Adult↗
PubMed1980

[Measurement of casting shrinkage with U-type tungsten die (author's transl)].

A simple method was developed for the accurate measurement of casting shrinkage using a U-type tungsten die. A wax pattern was prepared on the die and both were invested together in phosphate bonded investment. Cobalt-chromium alloy, Regalloy shot 2, was cast and its shrinkage was calculated from the distance of the gap created between the die and the cast piece. In order to evaluate the effects of some manipulative variables on the cast shrinkage value of the alloy, mold temperature, kind of liquid for the investment and powder/liquid ratio were varied and shrinkage values were obtained. The results showed that the shrinkage value was not affected by the kind of liquid and the power/liquid ratio, but significantly decreased as the mold temperature raised up to 600 degree C. However, this effect was eliminated by means of substractive correction of the thermal expansion of the tungsten die. Thus, the casting shrinkage of the cobalt-chromium alloy, Regalloy shot 2, was calculated to be 2.08 +/- 0.02%. The casting shrinkage of pure gold was also measured with the same procedure. The casting shrinkage was calculated to be 1.73 +/- 0.04% and highly consistent with the value (1.74%) reported by R. Earnshaw. This suggested that the developed method was sufficiently effective for the accurate measurement of casting shrinkage.

Dental Casting Investment↗
PubMed1979

Effects of some polyamines, polyanions and antitumor drugs on replicative DNA synthesis and unscheduled DNA synthesis in vitro.

The effects of various compounds on replicative DNA synthesis in permeable mouse ascites sarcoma cells and on unscheduled DNA synthesis in permeable cells or in isolated rat liver nuclei were studied. Polyamines such as spermidine, putrescine and cadaverine inhibited replicative DNA synthesis. Unscheduled DNA synthesis was inhibited by spermidine and cadaverine, but slightly stimulated by putrescine at low concentrations. Aurintricarboxylic acid, a low molecular weight polyanion, inhibited both replicative DNA synthesis and unscheduled DNA synthesis. Replicative DNA synthesis was inhibited by heparin, a high molecular weight polyanion, whereas unscheduled DNA synthesis was stimulated at low heparin concentrations. Antitumor drugs such as daunomycin, neocarzinostatin and bleomycin inhibited replicative DNA synthesis. Unscheduled DNA synthesis was inhibited by daunomycin, slightly induced by neocarzinostatin and highly induced by bleomycin. The present system was thought to be useful for studying the separate effects of various drugs on either replicative DNA synthesis or unscheduled DNA synthesis in vitro.

Animals↗
PubMed1979

Studies on nitrate reductase of Clostridium perfringens. II. Purification and some properties of ferredoxin.

A ferredoxin was purified from Clostridium perfringens by DEAE-cellulose chromatography and Sephadex G-50 gel filtration. It had absorption maxima at 390 and 280 nm. The molecular weight was estimated to be 6,000 by Sephadex gel filtration and from the results of amino acid analysis. The isoelectric point was 3.0. It contained four atoms of iron, four atoms of labile sulfur, and six cysteine residues. This ferredoxin as well as ferredoxin from C. pasteurianum acted as an electron donor for nitrate reductase from C. perfringens. The ferredoxin could also act as an electron donor for the hydrogenase from C. pasteurianum in hydrogen evolution.

Amino Acids↗
PubMed1978

Inhibition of replicative DNA synthesis and induction of unscheduled DNA synthesis in permeable sarcoma cell by bleomycin.

Unscheduled DNA synthesis was induced by bleomycin in isolated rat liver nuclei and in permeable mouse ascites sarcoma cells. ATP significantly enhanced the bleomycin effect of inducing unscheduled DNA synthesis. Replicative DNA synthesis in permeable mouse ascites sarcoma cells was inhibited by bleomycin. The apparent inhibition or stimulation by bleomycin of in vitro DNA synthesis was thought to be determined by a balance between inhibited DNA replicase activity and induced unscheduled DNA synthesis.

Animals↗
PubMed1978

Fractionation of aurintricarboxylic acid and effects of its components on nuclear swelling and nucleic acid synthesis.

Crude aurintricarboxylic acid synthesized by the conventional method was fractionated into 8 components (A1-A8) by silica gel thin layer chromatography. Some of the components were isolated and their effects were tested on nuclear swelling and on in vitro RNA synthesis and DNA synthesis using isolated polymerases. Only two components with low RF (A7 and A8) induced strong nuclear swelling. The other components were almost inactive. Formaurin-dicarboxylic acid, a contaminating polyanion of crude aurintricarboxylic acid, was synthesized separately. It was as effective as the two active components in nuclear swelling and inhibited RNA and DNA polymerases on naked DNA template. However, it stimulated RNA synthesis on chromatin template probably by dissociating histones from DNA. Unfractionated aurintricarboxylic acid showed the same effects at higher concentrations. A preliminary analysis indicated one of the inactive components (A4) is genuine aurintricarboxylic acid. The results suggest that the observed activity of crude aurintricarboxylic acid is due to some contaminating substances, one of which is formaurindicarboxylic acid.

Animals↗
PubMed1978

Relation of stroke and cardiac indices to serum catecholamines following open heart surgery.

Serum catecholamines (epinephrine, dopamine and norepinephrine) were measured two, four and six hours after open heart surgery. The ratios of stroke index (SI) and cardiac index (CI) to catecholamines (CA) were determined. Patients studied consisted of 27 with congenital and 14 with acquired heart disease. Extracorporeal circulation (ECC) time was longer than 90 minutes in 17 and shorter in 24 patients. SI and CI diminished in elder patients with congenital disease (Group Cg-ad), patients with acquired disease (Group Ac) and patients with a longer ECC time (Group L). Therefore, elder age and/or longer ECC time seems to be responsible to the lower indices. However, the ratios of the indices to CA showed that the lower indices indicated the poor response of the myocardium to CA in Group Ac and Group L. The response was larger in Group Cg-ad and the lower indices were related to lower serum CA level. It was concluded, therefore, that the indices of stroke volume and cardiac output had inverse correlation to ECC time, but not to age, namely, prolonged ECC compromised more severely the myocardium and resulted in the poor response of the myocardium to CA. Subsequently, to compensate for the poor response, serum CA levels were elevated probably to maintain due SI and CI in patients with prolonged ECC.

Adolescent↗
PubMed1978

Swelling and replicative DNA synthesis of detergent-treated mouse ascites sarcoma cells.

Previous investigation showed that mouse ascites sarcoma cells permeabilized with appropriate concentrations of detergents (Triton X-100, Nonidet P-40 and Brij 58) had high replicative DNA synthesis in the presence of the four deoxyribonucleoside triphosphates, ATP, Mg2+ and proper ionic environment. The present study showed the optimum detergent concentration for DNA synthesis coincided closely with the minimum detergent concentration for inducing cell swelling. Phase contrast microscopy and electron microscopy of Triton-permeabilized cells showed the characteristic swollen cytoplasms and nucleus. Autoradiographic study showed that the DNA synthesis in permeable cells was confined to the nucleus. Cell viability and [3H] deoxythymidine uptake were impaired at much lower concentrations of Triton X-100 than the optimum concentration for in vitro DNA synthesis. In Triton-permeabilized cells, the minimum Triton concentration that produced cell swelling also seemed to produce high repliative DNA synthesis, which reflects the in vivo state of DNA synthesis.

Animals↗