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Biomedical subjects

K Mabuchi

Publications and source records attributed to K Mabuchi.

At least 163 records · Page 9Linked to original sources
PubMed1976

Environmental factors in cancer of the larynx: a second look.

During a retrospective case-control study of recent laryngeal cancer patients, several associated factors were studied to determine possible changes in the epidemiology of laryngeal cancer between 1956 and 1974. The large sex difference noted in the early survey (male: female ratio of 14.9:1) diminished considerably in the present sample (4.6:1) because more women are cigarette smokers in the cancer age group today than was the case 20 years ago. Laryngeal cancer patients tended to be less educated than the controls and included a smaller proportion of Jews and more Catholics than the control group. The risk for developing laryngeal cnacer was considerably lower for exsmokers and long-term (10+ years) filter cigarette smokers as compared with non-filter smokers. At each level of alcohol consumption, the risk increased as exposure to tobacco increased. Occupations associated with wood exposure were found to affect the development of laryngeal cancer, independently of smoking status. Future studies should include an extensive study of nutritional deficiencies associated with alcoholism to determine if a correlation exists between such deficiencies, socioeconomic status, and an increased risk of laryngeal cnacer.

Adult↗
PubMedDate not supplied

Actomyosin ATPase. I. Quantitative measurement of activity in cryostat sections.

A method for the quantitative study of the actomyosin ATPase activity (Ca,MG-ATPase) in thin sections cut in a cryostat is presented. This method is based on the liberation of 32P from [gamma 32P]ATP or 45Ca phosphate precipitation. The advantage of this method lies in the requirement for only a small muscle sample and the availability of serially cut sections for other assays including Ca uptake by sarcoplasmic retciulum and histochemical tests for oxidative and glycolytic enzymes. The actomyosin ATPase activity for various types of muscles determined by this method showed the same sequence found in isolated protein, that is, fast-twitch skeletal greater than slow-twitch skeletal greater than cardiac. The Ca,Mg-ATPase of cryostat sections showed Ca sensitivity. The fact that the sections retained Ca sensitivity at 37 degrees C, in contrast to myofibrils, which have been reported to lose Ca sensitivity at this temperature, indicates that the structural integrity of the contractile and regulatory apparatus is preserved to a higher degree in sections than in isolated myofibrils.

Actomyosin↗
PubMedDate not supplied

Actomyosin ATPase. II. Fiber typing by histochemical ATPase reaction.

A new method for fiber typing based on staining for actomyosin Ca,Mg-ATPase is presented. Inclusion of ethanol in the medium enhanced the differentiation of type 2A and 2B fibers. With this technique, type 1, 2A, and 2B fibers can be distinguished in a single-step procedure for human biopsy samples.

Actomyosin↗
PubMedDate not supplied

Characterization of rabbit masseter muscle fibers.

Myosins of histochemically distinguishable single fibers of rabbit masseter muscle--type 1, 2A, 2B, and slow fibers--have been characterized by gel electrophoresis under dissociating (sodium dodecyl sulfate) and nondissociating (inorganic pyrophosphate) conditions, and by analysis of peptide maps of the heavy chains following limited proteolytic degradation. Type 2B fibers contain more LC3 homodimer than type 2A fibers; peptide maps of their heavy chain are different although the two myosins comigrate on pyrophosphate gel electrophoresis. Slow fiber myosin migrates more slowly than fast myosin and has a distinct peptide map. Differences were also found among fibers of the same histochemical type but originating in different muscles. In adductor magnus 2B myosin the LC1 + LC3 heterodimer band is the strongest, while in masseter 2B myosin the heterodimer is the weakest. Statistical considerations suggest that in masseter there is a mechanism preferentially forming the homodimers. More work is needed to determine the mechanism by which phenotypical differences occur among various fiber types in the same muscle and between corresponding fiber types in different muscles.

Adenosine Triphosphatases↗
PubMedDate not supplied

Electron microscopic study of tropomyosin binding to actin filaments reveals tethered molecules representing weak binding.

The binding of tropomyosin (Tm) to actin filaments was studied using the rotary shadowing technique. Electron micrographs showed, in addition to free Tm molecules, some Tm molecules bound to actin filaments at only one end creating "tethered molecules." The ratio of free and bound Tm was determined by comparing densities of free Tm molecules in micrographs with those in Tm alone specimens. At a 1 to 7 ratio of 17 nM chicken gizzard Tm (gTm) and 120 nM actin filaments, the sum of the tethered (7%) and the free was only 29% of total Tm. The missing Tm molecules are likely to be those bound to actin filaments lengthwise and not visualized by the technique. At a lower ratio of Tm (3 nM) to actin (120 nM), the majority of bound Tm appeared to be tethered. At a lower actin concentration but a higher ratio of Tm (12 nM) to actin (24 nM), 57% of bound Tm appeared to be tethered. The populations of free and tethered molecules were also affected by different salt and glycerol concentrations or type of Tm used: more with rabbit skeletal (sTm) than with gTm. The tethering indicates that the interaction of Tm molecules to actin filaments is stronger at one end than at the rest of the molecule. The bundling of actin filaments was observed under certain conditions (e.g., approximately 2 microM actin and approximately 0.5 microM sTm), suggesting that both ends of Tm molecules can bind to actin filaments but one end binds much more weakly than the other. All of these observations support the fact that free and tethered molecules are under rapid equilibrium and that incidental encounter of the ends of two tethered Tm molecules which are at the right positions, or of one tethered and a free molecule, would strengthen the remaining actin binding site(s), resulting in tight binding, thus, the tethered molecules represent a weak form of binding.

Actin Cytoskeleton↗