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Biomedical subjects

S Seki

Publications and source records attributed to S Seki.

At least 469 records · Page 26Linked to original sources
PubMed1975

A permeable cell system for studying DNA replication in synchronized HeLa cells.

Treatment of HeLa cells with a hypotonic buffer solution makes them permeable to nucleotides. Cells which are in S-phase at the time of treatment continue to synthesize DNA when supplied with the four deoxyriboside triphosphates, ATP, Mg2+, and the proper ionic environment. DNA replication extends from sites which were active in the cells prior to treatment. The product is confined to the nucleus and is sensitive to deoxyribonuclease. Under optimum conditions, up to 5% of the HeLa genome can be replicated from exogenous nucleotides. In synchronized cultures the level of DNA replicase activity, as measured in permeable cells at different points in the cell cycle, correlates with the rate of [14C] thymidine incorporation measured in the living, untreated cells.

Cell Division↗
PubMed1975

A requirement for RNA, protein and DNA synthesis in the establishment of DNA replicase activity in synchronized HeLa cells.

DNA replicase activity of synchronized cultures of HeLa cells was assayed by a permeable cell technique during normal S-phase and under conditions of restricted RNA, protein, or DNA synthesis. Inhibition studies with puromycin, cycloheximide, actinomycin D, and 2-mercapto-1-(beta-4-pyridethyl)benzimidazole revealed that the establishment as well as the maintenance of DNA replicase activity in S-phase cells was dependent on the continued synthesis of both RNA and protein. Measurements during limitation of DNA replication by hydroxyurea, cytosine arabinoside, or restricted availability of thymidine indicate that a low level of DNA synthesis is required to activate or assemble some subunits of DNA replicase. Evidence for the existence of short-lived RNA and protein factors essential for DNA replicase activity is discussed.

Cell Division↗
PubMed1975

Prediction of prognosis in open-heart-surgery by regional difference in leg surface temperature.

Change of the surface temperature of the leg during open-heart-surgery was determined in five patients, in whom either side of the femoral artery was ligated for cannulation. While the surface temperature at the patella was least influenced, that at the ankle paralleled closely the changes in the core body temperature and blood supply to the leg. Their difference (P-A difference) was studied to see if they can be used to predict prognosis of patients undergoing open-heart surgery. The P-A difference was followed for several hours after the open-heart surgery. It was marked positive when the surface temperature at the patella was higher than that at the ankle. Total of 54 patients were studied. Only one out of 29 patients with negative P-A difference succumbed. This is in sharp contrast to the 25 remaining patients with positive P-A difference, from whom as many as 12 died. In addition, the postoperative course of the 13 survivors from the latter group was more eventful. Since P-A difference seemed to indicate accurately cardiac output by reflecting the state of the peripheral circulation, it can be used as a useful parameter in prediction of the prognosis in open-heart surgery.

Adolescent↗
PubMed1975

Motion of the tricuspid valve annulus in anesthetized intact dogs.

Phasic variations in the size, position, and geometry of the tricuspid valve annulus during the cardiac cycle were studied in five normal anethetized dogs 2-6 weeks after 8-11 lead beads had been sutured on the endocardial surface of the valve ring during cardiopulmonary bypass. Field-by-field measurements from biplane videoangiograms were used to assess changes in valve ring size and shape during control hemodynamic conditions and during increased heart rates. In addition, the percutaneous production of a complete atrioventricular block in two dogs enabled us to observe the effect of isolated atrial contractions on the valve annulus. During normal sinus rhythm, progressive narrowing of the annulus during atrial and ventricular contractions reduced its area by 20-39% of the maximal valve circumference during diastole; approximately two-thirds of the total ring narrowing was associated with atrial systole. These findings suggest that one of the functions of atrial contraction is the reduction in size of the atrioventricular valve orifices prior to the onset of ventricular systole.

Anesthesia, General↗
PubMed1975

Consturction of new right ventricle on the epicardium: a possible correction for underdevelopment of the right ventricle.

By covering almost the entire right ventricular free wall and the anterior wall of the left ventricle with a Teflon cloth, we constructed a new chamber on the epicardium of a canine heart. An aortic homograft with the aortic valve was anastomosed to the right atrium as an inlet of this chamber. Another aortic homograft was sutured to the main pulmonary artery as an outlet. Pressure produced in this chamber ranged 25 to 55 mm. Hg and its first derivative was 450 to 1,870 mm. Hg per second. Thus this chamber had an excellent capability of epicardium will yield more physiological benefits to patients with an agenetic or hypoplastic right ventricle than do the current surgical procedures, in which a conduit is interposed between the right atrium and the main pulmonary artery. The procedures proposed could pressurize the pulmonary circulation and produce a pulsatile flow.

Animals↗