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Biomedical subjects

A Ishijima

Publications and source records attributed to A Ishijima.

26 records · Page 2Linked to original sources
PubMed1992

Super helix formation of actin filaments in an in vitro motile system.

Muscle contraction results from relative sliding of actin and myosin filaments. However, the possibility that actin filaments twist or rotate during sliding has not yet been experimentally investigated. We found that a super helix of an actin filament is formed in an in vitro motile system. This fact suggests that an actin filament twists and rotates due to a torque component of a sliding force generated at cross-bridges.

Actin Cytoskeleton↗
PubMed1992

Hepatitis B surface antigen particles of subtypes adw and adr, and compound subtype (adwr) in symptom-free carriers in Japan.

Of sera from 1,878 Japanese blood donors who carried hepatitis B surface antigen (HBsAg), 420 were subtyped as adw (22.4%) and 1,443 as adr (76.8%); only 15 (0.8%) contained HBsAg of subtype ayw or ayr. Sera with HBsAg/adr had higher HBsAg titres than those with HBsAg/adw (geometric mean of haemagglutination titre: 10.1 +/- 2.4 vs. 9.7 +/- 2.4, p less than 0.01), and a higher prevalence of hepatitis B e antigen (24% vs. 13%, p less than 0.001). Carriers of HBsAg/adr progressively predominated over those of HBsAg/adw with increasing age. Of sera from 1,863 carriers of HBsAg/adw or HBsAg/adr, 182 (9.8%) contained HBsAg particles with both subtypic determinants in the w/r allele. The presence of w and r determinants on the same particles was ascertained by sandwiching them between monoclonal antibody with the specificity for w and that with the specificity for r. HBsAg particles of compound subtype (adwr) were found more often in sera with hepatitis B e antigen than those without it (145/403 [36.0%] vs. 37/1,460 [2.5%], p less than 0.001). Sera with HBsAg/adwr particles had HBsAg titres higher than those without them (12.4 +/- 1.9 vs. 9.7 +/- 2.3, p less than 0.001). HBsAg/adwr particles arise from phenotypic mixing of the S-gene product of wild-type virus and that of mutants with point mutations for subtypic changes. The results obtained indicated that HBV strains of subtype adr have a higher replicative activity than those of adw, and suggested that mutations in the S gene for subtypic changes would be associated with an active replication of hepatitis B virus.

Adult↗
PubMed1992

Correlation between anti-HBc titers and HBV DNA in blood units without detectable HBsAg.

Hepatitis B virus (HBV) DNA was tested for in 294 blood units which had antibody against hepatitis B core antigen (anti-HBc) as the isolated serological marker of HBV infection. After amplification by polymerase chain reaction, HBV DNA was detected in 12 (6.9%) of 175 units that were positive for anti-HBc with hemagglutination inhibition titers greater than or equal to 2(6), significantly more often than in none of 119 units with titers less than or equal to 2(5) (p less than 0.01). These results indicate that the exclusion of blood units with isolated high-titer anti-HBc would be effective for further decreasing the risk of posttransfusion hepatitis B.

Base Sequence↗
PubMed1991

Sub-piconewton force fluctuations of actomyosin in vitro.

A new system has been developed for measuring the forces produced by a small number (less than 5-150) of myosin molecules interacting with a single actin filament in vitro. The technique can resolve forces of less than a piconewton and has a time resolution in the submillisecond range. It can thus detect fluctuations of force caused by individual molecular interactions. From analysis of these force fluctuations, the coupling between the enzymatic ATPase activity of actomyosin and the resulting mechanical impulses can be elucidated.

Actins↗
PubMed1991

[Evaluation of hepatitis B virus markers for surrogate testing of hepatitis C].

To evaluate the surrogate markers of non-A, non-B hepatitis virus (es) carriage state, the relationship between antibody to hepatitis C virus (HCV) and antibody to HBc/HBs and liver enzyme (ALT) was sought in Saitama prefecture. Out of 36,642 blood donor samples, 410 (1.1%) samples were positive for anti-HCV. Anti-HCV was found in 1.79% of donors with anti-HBs and/or anti-HBc, which is 1.7 fold of the frequency found in donors (1.04%) negative for anti-HBc/HBs. In contrast to the reports from Europe or USA, a poor correlation of anti-HCV with the serological history of hepatitis B infection was observed. These results indicate that hepatitis B and hepatitis C were transmitted independently in the Japanese, which is more homogeneous socioeconomically than the European or American populations. On the other hand, anti-HCV prevalence was in close correlation to ALT level as observed in the USA and in Europe. As we predicted previously, ALT can be expected to reduce the incidence of post-transfusion non-A, non-B hepatitis, however, anti-HBc can not.

Alanine Transaminase↗
PubMed1986

Accumulated strain mechanism for length determination of thick filaments in skeletal muscle. I. Experimental bases.

The kinetics of dissociation of myosin from both ends of thick filaments in glycerinated skeletal muscle fibres and myofibrils was studied in the presence of MgATP by use of an optical diffraction method and phase-contrast microscopy. The dissociation velocity, v (identical to -dL/dt where L is the length of thick filaments at time t), increased with increasing KCl concentration (0.225 to 0.5 M), or increasing pH (6.5 to 8.0) but hardly changed with temperature (5 and 25 degrees C), micromolar concentrations of Ca2+ or sarcomere length (2.4 and 2.75 micron). Over a wide range of filament length, the dissociation velocity could be expressed by v0exp(alpha L), where v0 and alpha are positive constants depending upon the dissociation condition. When the effects of crossbridge formation are minimized it was thus shown that the structural stability of thick filaments in a muscle fibre and a myofibril gradually decreases from the central part to the tips of the filaments. On the basis of these results we propose that the length of thick filaments is largely regulated by an accumulated strain mechanism in which the free energy of association of myosin molecules increases with filament length.

Animals↗
PubMedDate not supplied

The rare red cell phenotype Gerbich negative in Japanese.

Two Japanese propositi with the rare Gerbich -negative (Ge-) phenotype were found by screening serum of donors for antibodies. These are the first two examples of Ge negative in Japanese. Both had the Gerbich type of Ge-negative phenotype (Ge: -1, -2, -3,), showed some depression of Kell system antigens, and had anti-Ge in their sera. The parents of each of the propositi were first cousins, and one of the propositi had two Ge-negative siblings.

Adolescent↗