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Biomedical subjects

K Asada

Publications and source records attributed to K Asada.

At least 181 records · Page 10Linked to original sources
PubMed1984

A new method for external fixation with single crystal alumina ceramic screw nail and its biomechanical study.

Through the use of the Hoffmann external fixator, we have recognized the importance of strength of fixation between the screw nail and the bone in the external fixation and have fully realized the necessity of an affinity of the screw nail to the soft tissue at the thrusting site of the screw nail. We made a screw nail for external fixation with single crystal alumina ceramic on an experimental basis and after its basic test of strength, tried its clinical application by the Hoffmann external fixator. When this screw nail was used, it was found difficult to fix the screw nails thrusted in each different direction by the Hoffmann external fixator because of the small elasticity of the sapphire screw nail itself. However when the screw nails were fixed by force, a great stress concentration occurred in them or the bone around them and this caused their breakage and loosening. To protect this, we have developed a new external fixator which enables to hold, connect and fix each screw nail at the individual thrusting positions and directions and is therefore completely universal to each plane.

Adult↗
PubMed1983

Superoxide anion permeability of phospholipid membranes and chloroplast thylakoids.

The permeability of phospholipid membranes to the superoxide anion (O-2) was determined using soybean phospholipid vesicles containing FMN in the internal space. The efflux of O-2 generated by the illumination of FMN was so slow that more than 90% of the radicals were spontaneously disproportionated within the vesicles before they could react with cytochrome c at the membrane exterior. The amount of diffused O-2 was proportional to the intravesicular concentration of O-2 over a range from 1 to 10 microM which was deduced from its disproportionation rate. The permeability coefficient of the phospholipid bilayer for O-2 was estimated to be 2.1 X 10(-6) cm s-1 at pH 7.3 and 25 degrees C. Superoxide dismutase trapped inside vesicles was not reactive with extravesicular O-2 unless Triton X-100 was added. O-2 generated outside spinach chloroplast thylakoids did not interact with superoxide dismutase or cytochrome c which had been enclosed in the thylakoids. Thus, chloroplast thylakoids also showed little permeability to O-2.

Chloroplasts↗
PubMed1982

Structure of replication origin of the Escherichia coli K-12 chromosome: the presence of spacer sequences in the ori region carrying information for autonomous replication.

The replication origin region of the Escherichia coli K-12 chromosome has been cloned, and a region of 245 base-pairs has been shown to contain all the information for autonomous replication (defined ori). In order to obtain further information on the sequence organization in the defined ori stretch, various types of mutation were introduced by in vitro techniques at a restriction site (AvaII site) which locates near the middle of ori. When the correlation between these mutations and replicating function was examined, different effects were obtained with the types of mutation: the replicating function was completely destroyed by either insertion or deletion of short sequences, but not by base-substitutions. Based on these observations and on the fact that multi-gene products are involved in the initiation of replication, we assume that two categories of sequences are present within the ori stretch, one specifying interaction with initiation factors (recognition sequences) and the other spacing the recognition sequences in appropriate distances (spacer sequences), and that the AvaII site is located in the spacer region.

Base Composition↗
PubMed1982

A flash-photometric method for determination of reactivity of superoxide: application to superoxide dismutase assay.

Pulse-generation of O2- by a flash was used to determine the reactivity of O2-, O2- was produced within 10 ms by a flash of light through the excitation of FMN in the presence of N,N,N',N'-tetramethylethylenediamine and oxygen. Kinetic analysis of cytochrome c reduction by O2- generated by flash yielded the reaction rate constant between cytochrome c and O2- and the spontaneous disproportionation rate constant of O2-. We applied it for superoxide dismutase assay using a linear relation between superoxide dismutase concentration and the apparent rate constant of cytochrome c reduction by O2-. The catalytic rate constant and activation energy at pH 7.3 of bovine liver Cu,Zn-superoxide dismutase were found to be 1.75 x 10(9) M-1 . s-1 at 25 degrees C and 26.9 kJ . M-1, respectively. The kinetics of O2- decay can be also monitored at 240 nm in this flash-photometric system and gave the spontaneous disproportionation rate constant of O2- and the catalytic rate constant of superoxide dismutase.

Animals↗
PubMed1982

Original surface replacement total hip prosthesis with alumina ceramic prosthetic head without cement.

We have developed a surface replacement total hip prosthesis of H.D.P. socket to ceramic head type having a polycrystal alumina ceramic prosthetic head and without bone cement for fixation. The strength test was done on this hip prosthesis, and comparative studies were made between the metal prosthetic head and the ceramic prosthetic head, using calculation models prepared in consideration of friction and the prosthetic head's inside diameter. Besides, the cadaver femur was replaced by the prosthetic head, and the impact test and the fatigue test by means of repeated loading were done. As we could consequently confirm that it could be fully used for clinical practice, we have manufactured various instruments to be used for surgery, and we are now actually practicing it.

Aged↗
PubMed1981

Tris-induced cross-linking of thylakoid peptides; thiol oxidation catalyzed by Tris-Cu2+ complexes as a possible mechanism.

After Tris(hydroxymethyl)aminomethane[Tris buffer]-treatment cross-linking of the chloroplast thylakoid peptides of 11, 13, 18, 43, 55, and 87 kdaltons was observed on SDS-polyacrylamide gel electrophoresis. Tris-induced disulfide formation was suggested by the decrease of thiol groups of the chloroplast thylakoids in Tris medium at pHs above 8. In addition to the finding that Tris coordinates to Cu2+ in the forms of Tris-Cu2+ and Tris2-Cu2+ whose successive stability constants are 5.78 x 10(3) M-1 and 4.46 x 10(6) M-2, respectively, it was observed that Tris-Cu2+ complexes catalyze cysteine oxidation. Sinc release of copper from the chloroplast thylakoids is enhanced by increasing the concentration of Tris, oxidation of thiols by Tris-Cu2+ complexes formed in chloroplast thylakoids is a possible mechanism for the cross-linking of chloroplast thylakoid peptides.

Chloroplasts↗
PubMed1981

Analgesic effect of fentiazac after tooth extraction or minor oral surgery.

A new nonsteroidal anti-inflammatory agent, fentiazac, was used for analgesia after tooth extractions and minor oral surgery in two Japanese dental hospitals. The drug was administered as a single oral dose of either 50 mg or 100 mg. The 50-mg dose provided rapid analgesic effect, but its effect lasted only two to three hours in a number of patients. At a dose of 100 mg, fentiazac proved effective for 85% of 53 patients, usually providing marked reduction of disappearance of pain within one hour or less. Among patients in whom pain reappeared, the mean time for recurrence was four hours, indicating a satisfactory duration of analgesic effect. One side effect--loss of appetite--was reported by one patient in the entire series of 71 subjects. It is concluded that fentiazac is a highly effective analgesic agent with a wide margin of safety for use after dental procedures that produce pain.

Acetates↗