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Biomedical subjects

K Sakurai

Publications and source records attributed to K Sakurai.

At least 235 records · Page 13Linked to original sources
PubMed1989

Quantitative computed tomographic evaluation of femoral bone mineral content in renal osteodystrophy compared with radial photon absorptiometry.

The computed tomography (CT) numbers of cortical bone at the level of 20 cm (CT20) and of spongiosa in the lateral condyle at the level of 2 cm (CT02) from the distal end of the femur were obtained by a quantitative CT method and compared with the bone mineral density of mostly cortical bone within the radius (BMD) by photon absorptiometry. The study included 47 patients with chronic renal failure not dialyzed or induced to regular hemodialysis within 4 weeks of the study (group 1), 28 patients on regular hemodialysis for more than one month (group 2), and ten healthy volunteers (group 3). The measures of bone mineral content (BMC), namely CT20, CT02, and BMD, were compared in terms of their abilities to distinguish members in the various groups. For group 1 and group 3, the greatest variation in BMC was in the difference in CT02, which was primarily a measurement of the BMC of spongiosa. For groups 1 and 2, the greatest variation was in the difference in BMD, which was primarily a measurement of the BMC of cortex. The reproducibility of CT02 was estimated as almost equal to the difference in CT02 values at intervals of 10 months' duration of hemodialysis. The results indicated that CT02 was a useful measurement for evaluating the progress in the early stage of the renal osteodystrophy, and it is recommended that the bone mineral measurement with this QCT method should be performed once or twice a year.

Adult↗
PubMed1989

A single gene directs synthesis of a precursor protein with beta- and alpha-amylase activities in Bacillus polymyxa.

The Bacillus polymyxa amylase gene comprises 3,588 nucleotides. The mature amylase comprises 1,161 amino acids with a molecular weight of 127,314. The gene appeared to be divided into two portions by the direct-repeat sequence located at almost the middle of the gene. The 5' region upstream of the direct-repeat sequence was shown to be responsible for the synthesis of beta-amylase. The 3' region downstream of the direct-repeat sequence contained four sequences homologous with those in other alpha-amylases, such as Taka-amylase A. The 48-kilodalton (kDa) amylase isolated from B. polymyxa was proven to have alpha-amylase activity. The amino acid sequences of the peptides generated from the 48-kDa amylase showed complete agreement with the predicted amino acid sequence of the C-terminal portion. The B. polymyxa amylase gene was therefore concluded to contain in-phase beta- and alpha-amylase-coding sequences in the 5' and 3' regions, respectively. A precursor protein, a 130-kDa amylase, directed by a plasmid, pYN520, carrying the entire amylase gene, had both beta- and alpha-amylase activities. This represents the first report of a single protein precursor in procaryotes that gives rise to two enzymes.

Amino Acid Sequence↗
PubMed1989

[Studies on biological damage by active oxygens. III. Generation of hydroxyl radical and inhibition of insulin release in hypoxanthine-xanthine oxidase system in the presence of pancreatic islet cells].

The hydroxyl radicals (HO.) spin adduct of 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) was obtained in the hypoxanthine-xanthine oxidase (HX-X.O.) system in the presence of isolated islet cells by using electron spin resonance spectroscopy. There was a significant increase in the concentration of DMPO-OH spin adduct dependent on the increase in a number of islet cells. In the absence of islet cell, the DMPO-OOH spin adduct formed by superoxide together with a small amount of DMPO-OH spin adduct was detected in HX-X.O. system. These results suggest that HO. is greatly produced in the HX-X.O. system in the presence of islet cells. The generation of HO. was partially inhibited by the addition of superoxide dismutase or catalase and completely by the combined use of both enzymes. Iron-chelator, diethylenetriaminepentaacetic acid and iron-binding protein, apotransferrin also inhibited the generation of HO., suggesting a possible participation of a trace iron in the islet cells. The inhibition of insulin release from islet cell, as well as the amount of DMPO-OH spin adduct, was dependent on the concentration of X.O. These results indicate that the HO. is produced by the site-specific action with islet cells in HX-X.O. system, suggesting a possible involvement of HO. in the oxygen damages of islet cells.

Animals↗
PubMed1989

[Studies on thermal stimulation accompanying visible-light irradiation].

Visible-light-cured composite resin is one of the most frequently used materials in clinical practice. The use of this material inevitably involves dental pulp stimulation, i.e., thermal stimulation due to visible-light irradiation, during the restoration procedure. To determine the variations of temperature involved in visible-light irradiation, the author examines differences in temperature generated by various types of visible-light curing units. Changes in the temperature under varying conditions of irradiation were also examined. The results were as follows: 1) Among the visible-light curing units used in the present study, the highest temperature was obtained from Translux CL (a rise of 17 degrees C) whereas Hiliomat showed the lowest value (a rise of 7 degrees C). 2) The temperature increased with prolongation of irradiation time, reaching a maximum level (a rise of 15 degrees C) at 60s. 3) The temperature increased with shortening of irradiation distance, reaching a maximum level (a rise of 20 degrees C) at 3mm.

Composite Resins↗
PubMed1989

Generation of free radicals by alloxan in the presence of bovine serum albumin: a role of protein sulfhydryl groups in alloxan cytotoxicity.

The interaction of alloxan with bovine serum albumin was studied. When alloxan was incubated with bovine serum albumin, oxygen consumption, H2O2 formation, and diminution of sulfhydryl groups of the protein were observed. During the reaction of alloxan with the protein, superoxide radicals were generated; and under anaerobic conditions, ESR signal of alloxan free radicals was observed. These results strongly suggest that alloxan mediates electron transfer from the protein sulfhydryl groups to oxygen.

Alloxan↗
PubMed1989

[Temporary restoration using light-cured resin].

In spite of various problems involved in chemically cured resin (self-curing resin), e.g., irritability, and heat and shrinkage at polymerization, it has traditionally been the material of choice in the production of temporary restorations. However, light-cured resin, which does not have the disadvantages of chemically cured resin, has recently been developed and applied to clinical treatment. The present study was conducted to examine the clinical application of light-cured resin to temporary crowns. Two types of light-cured resin and one type of chemically cured resin were examined for their mechanical properties. The properties involved in handling and setting, and the methods of producing crowns were also studied. The results were as follows: 1) In the tensile strength test, there was no significant difference between the two types of light-cured resin, i.e., Triad and Unifast LC. The tensile strength of Unifast, a chemically cured resin, was slightly greater than the others, the difference being significant. 2) The Vickers hardness test showed no significant differences between the three types of resin. 3) The mechanical properties of Triad were not influenced by differences in the curing unit (the unit for general oral use or exclusive use) used for polymerization. 4) The test of setting properties revealed that Unifast LC needed longer than Unifast from the 2nd through the 4th clinical stage. In particular, Unifast LC required about 2.5 times the duration needed by Unifast at the 2nd stage in the tray method. 5) The heat generation test showed that the exothermic temperature in Unifast was significantly higher than in the two types of light-cured resin. 6) Heat generation associated with light curing was noted during the use of a light-curing unit for oral use.

Dental Restoration, Temporary↗
PubMed1988

Fibrolamellar carcinoma of the liver in the Orient.

We describe, in a 56-year-old man, the first case of fibrolamellar carcinoma of the liver (FCL) in the Orient. Contrary to patients seen in the Western world, our patient has many characteristics of ordinary hepatocellular carcinoma seen in the Orient, i.e., middle age, male, HBsAg carrier, elevated alpha-fetoprotein, presence of HBsAg in the hepatocytes, and chronic hepatitis. These clinicopathological findings suggest a possible relationship between exposure of HB virus and FCL.

Carcinoma↗
PubMed1988

Iron release from ferritin by alloxan radical.

Alloxan in the presence of reduced glutathione released iron from ferritin which is the major intracellular iron storage protein. Superoxide dismutase inhibited by only about 30% the alloxan-dependent iron release from ferritin but completely inhibited the iron release from ferritin induced by hypoxanthine-xanthine oxidase. Under anaerobic conditions, the ESR spectrum of alloxan radical was obtained and interaction with ferritin resulted in a marked diminution of the alloxan radical signal. These results indicate that alloxan radical rapidly releases iron from ferritin.

Alloxan↗
PubMed1988

Effects of PSK on resistance to bacterial infection in splenectomized mice.

Nontumor-bearing C3H/He mice were splenectomized and intravenously inoculated 7 days later with Streptococcus pneumoniae, Pseudomonas aeruginosa, or Escherichia coli. The survival rate was reduced by splenectomy in the animals inoculated with S. pneumoniae, but did not change in those inoculated with P. aeruginosa or E. coli. When splenectomy was performed 2 days after transplantation of X5563, and bacteria were inoculated 7 days after the operation, the survival rate was reduced even in those inoculated with P. aeruginosa or E. coli, and elimination of the bacteria from the blood and liver was delayed. This reduction in resistance to infection was alleviated by oral administration of PSK after the splenectomy.

Animals↗
PubMed1988

Effects of class I drugs on reentrant ventricular tachycardia in a canine model of myocardial infarction: on their antiarrhythmic and proarrhythmic mechanisms.

Mechanisms by which Class I drugs interrupt or facilitate reentrant ventricular tachycardia (VT) induced by programmed stimulation were analysed in dogs with 7-day-old myocardial infarction. Activation time and effective refractory period (ERP) were determined at 48 sites of survived epicardial layer within the infarction zone (IZ) and surrounding normal zone. Two mg/kg of lidocaine (L), propafenone (P) and flecainide (F) were administered intravenously. Induction of sustained VT was prevented by P in 7 of 10 cases, in 3 of 5 cases by F and in one of 8 cases by L (P vs L, p less than 0.01). Proarrhythmic effects were encountered in a case of P and 2 cases of F. Conduction velocity within the IZ was reduced by each drug to the same extent. The ERP within the IZ was prolonged by each drug, however, the mean extent of change differed significantly among the drugs (P 37% greater than F 26% greater than L 10%). In cases in which an antiarrhythmic effect was achieved, it was the result of abolition of the re-excitation at retrograde exit site of reentry circuit, which was considered to be due to prolongation of refractoriness at the site. These results suggest that prolongation of local refractoriness within the IZ is the major antiarrhythmic mechanism. The proarrhythmic effect was accompanied by an increased dispersion of local ERP as well as by a marked reduction of conduction velocity within the IZ.

Animals↗
PubMed1988

Observations on rapid ventricular pacing during reentrant ventricular tachycardia in canine myocardial infarction--the use of epicardial mapping in demonstrating the modes of resetting, concealed perpetuation and termination of reentry.

The changes in activation sequences in and around the epicardial reentrant circuit were analyzed during rapid pacing against ventricular tachycardia by using a canine infarction model. In 13 episodes of sustained ventricular tachycardia induced by a premature stimulation technique in eight dogs, reentry circuits were located in the superficial subepicardial myocardium in eight. Pacing stimuli were clearly demonstrated to enter the reentrant circuit in two directions: one wavefront collided with the orthodromic reentrant wavefront and the other entered prematurely into the reentrant circuit to reset the tachycardia (resetting phenomenon). With a faster pacing rate, stimuli failed to reset the tachycardia due to slower entry into the circuit despite the fact that most epicardial recording sites were activated by pacing wavefronts (concealed perpetuation). Termination of tachycardia was achieved by a local conduction block in the center of the reentrant circuit. A pacing impulse which encountered the local block was also shown to reinitiate the tachycardia using a different reentrant pathway. These different phenomena could be observed in consecutive pacing beats. These epicardial mapping data provided a direct electrophysiological basis for the mechanisms of reentrant ventricular tachycardia and the mode of its termination.

Animals↗
PubMed1988

[Changes in concentration of cefotetan in blood and lung tissue after intravenous administration].

Cefotetan (CTT), a newly-developed cephamycin antibiotic, has been used widely for the treatment of various infectious diseases because of its excellent antibacterial potency and dynamic transport in vivo. Although the drug transfer to almost every organ, tissue, and body fluid has been studied, only a few reports are available regarding the transfer to lung tissue. In the present study, 1 g of CTT was intravenously injected in a single dose to each of 22 patients subjected to pulmonary resection. Subsequently, its concentrations in blood and lung tissue were measured in sequence. The degree of transfer of the drug to the lung tissue was calculated to evaluate the pharmacodynamics of CTT in vivo. The following results were obtained in this analysis. 1. The T1/2(beta) of the concentration in blood was 4.18 hours, and AUC0-infinity was 478.7 micrograms.hr/ml. 2. Cmax in the lung tissue was 31.5 micrograms/g, and Tmax was 0.83 hour, and tissue concentrations decreased in parallel to blood concentrations. CTT was transferred to the lung tissue to achieve high concentrations following an intravenous administration. Since high concentrations are maintained for a long period of time, this antibiotic is expected to exert an excellent effect in the prevention and the treatment of respiratory infections.

Aged↗