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Biomedical subjects

S Seki

Publications and source records attributed to S Seki.

At least 451 records · Page 25Linked to original sources
PubMed1978

[Analysis of the right ventricular function by simulation (author's transl)].

In the previous experiments it was reported that either the interventricular septum of the free wall of the right ventricle was replaceable with a non-contractile prosthesis. It was also reported that a new chamber constructed on the epicardium had capability of producing a pulsatile pressure. This study was to determine contribution of the septum and the free wall on performance of the right ventricle by using a simulator. Left-ward shift of the interventricular groove was not found along the basal half of the long axis and was limited only along the apical half. Bulging of the septum toward the right ventricular cavity did not occur at all, but on contrary the septum moved toward left, denying contribution of the septal movement to pump action of the right ventricle.

Animals↗
PubMed1977

Differential effects of heparin on replicative DNA synthesis and unscheduled DNA synthesis.

The effect of heparin on DNA synthesis was compared between replicative DNA synthesis and unscheduled DNA synthesis. Replicative DNA synthesis in permeable cells or nuclei prepared from rapidly growing mouse ascites sarcoma cells was inhibited by heparin. Unscheduled DNA synthesis in nuclei isolated from normal rat liver or from mouse ascites sarcoma cells in stationary phase was stimulated by heparin at low concentrations but inhibited by high heparin concentrations. DNA polymerase activity assayed with activated calf thymus DNA and DNA polymerase alpha purified partially from mouse ascites sarcoma cells was inhibited with either calf thymus histones or heparin. DNA synthesis inhibited with histones was partially reactivated by heparin. Replicative DNA synthesis in permeable cells was inhibited by adding histones to the assay mixture, and the inhibited DNA synthesis was partially reactivated by low concentrations of heparin. These results indicated that the replicated sites (or replication machinery) in permeable cells or nuclei were largely unrestricted by histones and that heparin inhibition of replicative DNA synthesis was due to the direct inhibitory interaction of heparin with some essential component(s), such as DNA polymerase, of replication machinery.

Animals↗
PubMed1977

DNA synthesis in detergent-treated mouse ascites sarcoma cells.

Mouse ascites sarcoma cells (SR-C3H/He cells) were made permeable to nucleoside triphosphates by treatment with nonionic detergents in a nearly isotonic condition. The permeable cells synthesized DNA in the presence of the four deoxyribonucleoside triphosphates, ATP, Mg2+, and the proper ionic environment. The optimum detergent concentration for DNA synthesis was 0.015--0.020% with Triton X-100, 0.020% with Nonidet P-40, and about 0.0025% with Brij 58. Higher concentrations of detergents were rather inhibitory to DNA synthesis. DNA synthesis in Triton-permeabilized cells was thought to be replicative, and the activity in the optimum conditions was much higher than that measured in hypotonic permeable cells or in isolated nuclei. These studies show the potential usefulness of detergent treatment for examining DNA replication in mammalian cells in vitro.

Animals↗
PubMed1977

Myocardial protection during open-heart surgery: intermittent aortic crossclamping versus coronary perfusion.

Twenty-seven patients undergoing open-heart surgery were divided into three groups, i.e., control, intermittent aortic crossclamping and coronary perfusion groups. Myocardial oxygen extraction, lactate extraction, arterial-coronary sinus hydrogen ion difference, potassium difference and glucose difference were determined during the operation, as well as, postoperative stroke and cardiac indices and comparisons were made. When the ascending aorta was not crossclamped, myocardial metabolism was well preserved during and after the perfusion at a flow rate of 2.0 L./min/m2. Intermittent aortic crossclamping for 15 minutes alternating with a period of perfusion for five minutes at 30 degrees C was sufficient to protect the myocardium from ischemia. Perfusion of the left coronary artery alone at a flow rate of six per cent of total body perfusion (150 to 200 ml per minute) at 30 degrees C was sufficient to protect the myocardium when the aorta was opened. Since intermittent perfusion of the left coronary artery may produce myocardial derangement, coronary perfusion should be continuous. Otherwise topical cardiac cooling or other means of myocardial protection should be used.

Adolescent↗
PubMed1977

Mechanodynamics at the interventricular sulcus--reciprocal effect of the ventricles on the ventricular function.

The forces acting on IVS were analyzed to delineate reciprocal effects of the two ventricles on the ventricular fucntion as a whole. The resultant force (FT) was dependent on the LV pressure but independent on the RV pressure. But the composite forces (F1 and F2) of FT were affected by the LV and RV pressures. In a normal heart F1 increased with increasing LV and/or RV pressures. But in F2 increase occurred only with increasing RV pressure. In the LV pressure increase occurred only when the RV pressure was 10 mmHg and decrease did when the RV pressure was 50 mmHg, while stable at 30 mmHg. Directions of both the forces (F1 and F2) diverged as the RV pressure increased and the LV pressure decreased. When FRV was hypertrophic, increases of the magnitudes of the forces were decreased when the pressures of the LV and RV were higher. The angle between the forces was also decreased so that the efficiency of the forces was risen. When a portion of the ventricles lost its contractility, FT increased, particularly, when FLV lost its contractility. But these increases seemed to well be within range of compensation.

Biomechanical Phenomena↗
PubMed1977

DNA synthesis inpermeable mouse ascites sarcoma cells.

DNA synthesis was studied in mouse ascites sarcoma cells using a permeable cell system. The sarcoma was induced by the Schmidt-Ruppin strain of Rous sarcoma virus. The cells were made permeable to nucleoside triphosphates by treatment with a hypotonic buffer containing 10 mM Tris Cl, 4 mM MgCl2, 1 mM EDTA, and 6 mM 2-mercaptoethanol (pH 8.0). DNA-synthetic activity in the permeable cells was highly dependent on four deoxyribonucleoside triphosphates, adenosine triphosphates, Mg2+, and a proper ionic environment. The activity was stimulated about 50% by the addition of an appropriate concentration of cytidine triphosphate, guanosine triphosphate, and uridine triphosphate in an assay mixture containing adenosine triphosphate and four deoxyribonucleoside triphosphates. DNA synthesis was confined to the nucleus and was sensitive to N-ethylmaleimide and DNase. The activity assayed by the permeable cell system correlated closely with the DNA-replicating activity assayed by [3H]deoxythymidine incorporation in intact cells. The close correlation between DNA synthesis in vitro and in vivo was further confirmed in cultured sarcoma cells synchronized with DNA synthesis. Analysis of the DNA synthesized in vitro by alkaline cesium sulfate density gradient centrifugation showed that over half the DNA synthesized in permeable cells was due to elongation of strands initiated in vivo. The permeable cell system appears to be a useful method for examining DNA replication of cells in suspensions.

Animals↗
PubMed1976

Dissociation and reconstitution of the DNA replicase system of HeLa cell nuclei.

The DNA replication system of S-phase HeLa nuclei has been dissociated by cautious extraction at 0 degrees C with 0.25 M NaCl. Replicase activity has been reestablished by recombination of the fractions and reduction of the salt concentration. The reconstituted system, like the starting nuclei, depended on ATP, 4dNTP, MgCl2, the proper ionic strength and the soluble cytoplasmic protein fraction. The activity of the nuclear extract showed a cell cycle dependency and was elevated in the nuclei of cells at the G1 leads to S boundary. In the presence of Mg2+ the major activity of the nuclear extract precipitated during dialysis to reduce the salt concentration; this precipitate exhibited DNA polymerase alpha activity. Chromatography of the active extracts over phosphocellulose separated the replicase supporting factors into three fractions. The major activity eluted in the fraction containing the DNA polymerase alpha activity; the other two active fractions were devoid of polymerase activity. The fraction containing DNA polymerase alpha from the nuclear extracts supported DNA replicase activity in salt-extracted nuclei whereas an equivalent level of DNA polymerase alpha from the cytoplasm was not effective. The data suggest that the DNA polymerase alpha of the salt extracts of S-phase nuclei is either different than the cytoplasmic enzyme or is associated with some essential replicase-supporting factor.

Cell Nucleus↗