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Biomedical subjects

S Seki

Publications and source records attributed to S Seki.

At least 325 records · Page 18Linked to original sources
PubMed1988

An exonuclease possibly involved in the initiation of repair of bleomycin-damaged DNA in mouse ascites sarcoma cells.

A protein factor having exonucleolytic activity on bleomycin-damaged DNA and providing priming sites for DNA polymerases existed in a DNA polymerase beta fraction partially purified by ion exchange chromatography from an extract of permeable mouse ascites sarcoma (SR-C3H/He) cells. The exonuclease was separated from DNA polymerase beta by single-stranded DNA-cellulose chromatography, and partially characterized. The enzyme is suggested to be involved in the initial step of repair of bleomycin-damaged DNA in removing 3' ends (3'-phosphoglycolate termini) of bleomycin-damaged DNA.

Animals↗
PubMed1988

Rubredoxin as an intermediary electron carrier for nitrate reduction by NAD(P)H in Clostridium perfringens.

The NAD(P)H-dependent nitrate reductase system in Clostridium perfringens was reconstituted with rubredoxin (Rd), nitrate reductase (NaR), and an unadsorbed fraction, on a DEAE-cellulose column, of the extract (designated as fraction A), under nitrogen gas. Ferredoxin in place of Rd was not effective as an electron carrier in this reconstituted system. NAD(P)H-dependent nitrate reducing activity was also obtained by replacing fraction A with ferredoxin-NADP+ reductase from spinach. We propose the following scheme for the electron transfer in this NAD(P)H dependent nitrate reduction system. NAD(P)H----NAD(P)H-Rd reductase----Rd----NaR----NO3-.

Clostridium perfringens↗
PubMed1988

Specific incorporation of 4-S-cysteinylphenol into human melanoma cells.

The incorporation of 4-S-cysteinylphenol (4-S-CP), a tyrosine analog, into malignant melanoma cells was evaluated. 4-S-CP was specifically incorporated into the melanotic melanoma cells (HMV-II), which have activity for melanin synthesis, but was scarcely incorporated into HeLA S3 or HMV-I cells, which have no activity for melanin synthesis. Electron microscopic autoradiography revealed that the intracellular localization of 4-S-CP was closely correlated with melanogenesis and that 4-S-CP served as an initial substrate for tyrosinase and was utilized in melanin synthesis. On the basis of these findings we hypothesize that tyrosinase is required for intracellular incorporation of 4-S-CP. This specific incorporation of 4-S-CP into melanoma cells should be useful in the development of an effective procedure for chemotherapy of malignant melanomas and in analysis of melanin synthesis.

Autoradiography↗
PubMed1988

Acid-base changes in ischemic myocardium and intervention with hypothermia or bicarbonate.

Effects of ischemia and reperfusion on acid-base changes in relation to myocardial contractility, and the effects of correcting H+ were studied by lowering PCO2 or increasing HCO3- levels. The hearts were perfused by working heart mode and whole heart ischemia was induced by use of a one way valve followed by myocardial warming (37 degrees C, normothermia), cooling (18 degrees C, hypothermia) or warming plus 2.1 mM NaHCO3 for 15 min. The hearts were then reperfused for 20 min. Coronary effluent was collected through pulmonary artery cannulation and used for the measurement of acid-base changes. There were close correlations between the decrease in coronary flow and LV pressure, LV dP/dt. Close correlations were also observed between the decline in LV pressure and the rise in PCO2, H+, and the decline in HCO3-. A highly significant correlation was seen between H+ and lactate production. Myocardial contractility decreased to the same extent in 3 groups during ischemia, whereas its recovery rate in both the hypothermia and HCO3- -treated groups were significantly higher than in the normothermia group. The increment of H+ was significantly less in both the hypothermia and HCO3- -treated groups than in normothermia. These results indicate that lactate production is the major H+ producing source and the correction of H+ could minimize the ischemic insult and at the same time contribute to the reperfusion injury.

Acid-Base Imbalance↗
PubMed1987

Accuracy of suture placement.

Three groups of seven surgeons were each randomly selected from three larger groups with surgical experience of less than 1, 6-10 and 16-20 years. Each surgeon was asked to aim a needle at an exit point using two methods: 'jiggling' (readjustment of the needle in aiming at the target) allowed and jiggling not allowed. The results were not as precise as expected. An improvement from group 1 to group 2 was noticed in both methods (P less than 0.01), but from group 2 to 3 there was improvement only in the method where jiggling was allowed (P less than 0.01). All groups showed a tendency to overshoot the target (P less than 0.01): a shift towards the surgeon in group 1 (P less than 0.05) and towards the opposite side in groups 2 (P less than 0.01) and 3 (P less than 0.05). Jiggling significantly reduced the inaccuracy, and it was concluded that pinpoint accuracy improved with surgical experience. However, the experienced surgeons improve their accuracy by jiggling, with the potential danger of tissue damage by needle adjustment.

Clinical Competence↗
PubMed1987

Chromatin organization in detergent-lysed chicken erythrocyte nuclei.

A method for electron microscopic demonstration of supranucleosomal (20-30 nm chromatin) fiber loops was developed. Chicken erythrocytes were treated with varying concentrations of detergents, such as Joy, sodium N-lauroyl sarcosinate, and sodium laurylsulfate, and then fixed with a formalin solution. The fixed cells were centrifuged onto an electron microscope grid, followed by staining and metal shadowing. Thin-sectioned specimens of the fixed cells were prepared routinely. Although supranucleosomal fiber loops could be observed when any one of these detergents was used, Joy gave the best result. Electron micrographs of rotary-shadowed specimens of erythrocyte ghosts formed by treatment with a low concentration (0.07-0.11 w/w%) of Joy showed a halolike, radial arrangement of supranucleosomal fiber loops around the ghost cells. The width of the halo was about 3 micron. By increasing the detergent concentration (approximately 8% Joy), nucleosome fibers and naked DNA appeared and increased in number, indicating that the supranucleosomal fibers were disassembled by the action of the detergent. Thin-sectioned specimens of cells treated with 0.09% Joy showed granulofibrillar chromatin radially dispersed from the nuclear cage. The fibers were thought to be identical with the supranucleosomal fibers observed in the rotary-shadowed specimens.

Animals↗
PubMed1987

Poor oxygenation in the lungs of patients with hyperosmolar hyperglycemic non-ketotic diabetic coma after cardiac surgery.

The ratio of PaO2 to FiO2 was often low (300 or less) in four patients with complications of hyperosmolar hyperglycemic non-ketotic diabetic coma (HHNKDC) following open heart surgery. Four of our patients had poor oxygenation and subsequent spontaneous recovery from in the immediate post-operative period, although HHNKDC occurred only in one during this period. In the 3 others, poor oxygenation without accompanying HHNKDC lasted for 1-6 days and HHNKDC developed about 2 weeks after open heart surgery at time when poor oxygenation reoccurred. If a working diagnosis of congestive heart failure was made only on the basis of the most common probability, and the fluid supply was restricted, HHNKDC would readily occur or be aggravated by the dehydration iatrogenically produced. It is thus concluded that HHNKDC should be included in diagnoses for pulmonary dysfunction.

Blood Glucose↗
PubMed1987

Accuracy of suture techniques of surgeons with different surgical experience.

The pinpoint accuracy in the suturing techniques of 35 surgeons was measured by the distance deviated from an expected needle exit. The grip of the needle holder used by the surgeons was their habitual one. Accuracy was tested using two ways of suturing; namely with, and without wavering a needle to aim at an exit after suturing began. Where the surgeons did not waver the needle, accuracy improved both when the surgical experience was greater than one year (p less than 0.05) and again when the experience exceeded 10-15 years (not significant). Difference of the accuracy between individual surgeons disappeared in those surgeons with 15 to 20 years experience. Where the surgeons wavered the needle, improvement was more marked in the former period and less in the latter. Wavering improved the accuracy in each group (p less than 0.01), but with the possible danger of injuring tissue. In conclusion, accuracy was not as precise as most surgeons' confidence believed. A significant improvement was observed with 1-year experience, but the improvement thereafter was poor. Fifteen to 20 years experience was not enough to acquire a suturing technique not necessitating needle wavering in the tissue, still yielding a 1.7 mm deviation in a 2 cm suture-stride. It was however enough to eliminate surgeons' individual differences in accuracy.

General Surgery↗
PubMed1987

The protective effect of cyclosporin A on experimentally-induced acute hepatic injury in mice.

When heat-killed Propionibacterium acnes (P. acnes) and a small amount of endotoxin lipopolysaccharide (LPS) were intravenously injected into mice at a week's interval, most of them died of massive hepatic cell necrosis. This experimentally-induced acute liver injury was significantly inhibited by cyclosporin A (CsA), resulting in a remarkable improvement of the survival rate. This protective effect of CsA on acute liver injury was also histopathologically confirmed. To study the mechanism by which CsA protected the mice from fatal hepatic injury, adherent cells prepared from the murine liver 7 days after P. acnes injection were incubated with LPS in the presence of CsA, and the effect of CsA on the production of the cytotoxic factor from the adherent cells was estimated. As a result, CsA inhibited the activation of liver adherent cells and suppressed the release of the cytotoxic factor.

Animals↗
PubMed1987

Effects of ATP and other nucleotides on DNA repair synthesis in bleomycin-pretreated permeable mouse sarcoma cells.

Effects of ATP and some other nucleotides (AMP, ADP, CTP, GTP, UTP and dATP) on reparative DNA synthesis and repair patch ligation in bleomycin-pretreated permeable mouse sarcoma cells were studied. Reparative DNA synthesis was significantly stimulated by 2.5 mM ATP, ADP or dATP. The stimulation was observed on both DNA polymerase alpha- and beta-dependent reparative DNA synthesis. ATP concentration required for repair patch ligation was much lower than that required for the stimulation of reparative DNA synthesis. An apparent Km value for ATP of the repair patch ligation was about 40 microM. ADP supported repair patch ligation after being converted into ATP by adenylate kinase in permeable cells.

Adenosine Diphosphate↗
PubMed1987

Studies on nitrate reductase of Clostridium perfringens. IV. Identification of metals, molybdenum cofactor, and iron-sulfur cluster.

Nitrate reductase of Clostridium perfringens was purified by an improved method using immuno-affinity chromatography. The purified preparation contained Mo, Fe, and acid-labile sulfide; the Mo content was 1 mol per mol and the Fe 3.7 mol per mol of the enzyme. The inactive enzyme obtained from cells grown in the presence of tungstate did not hold Mo but contained 1 mol of W. The content of Fe was not increased. The presence of molybdenum cofactor in the nitrate reductase was indicated by the formation of molybdopterin form A in the oxidation of the enzyme by iodine and by the complementation of NADPH-nitrate reductase with the heart-treated enzyme in the extract of Neurospora crassa nit-1. The Clostridium nitrate reductase had an absorption maximum at 279 nm and shoulders at 320, 380, 430, and 520 nm. This enzyme seems to contain an iron sulfur cluster since the reduced enzyme showed decreased absorption in visible region. The CD spectrum of the enzyme has a positive peak at 425 nm and negative ones at 310, 360, and 595 nm. It was compared with the CD spectrum of ferredoxin (2Fe-2S or 4Fe-4S cluster) and the nitrate reductase of Plectonema boryanum.

Chromatography, Affinity↗