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Biomedical subjects

S Ohta

Publications and source records attributed to S Ohta.

At least 793 records · Page 44Linked to original sources
PubMed1985

A yeast mutant temperature-sensitive for mitochondrial assembly is deficient in a mitochondrial protease activity that cleaves imported precursor polypeptides.

We have previously described two yeast mutants which, at elevated temperature, stop growing and accumulate precursors to several imported mitochondrial proteins. We now show that one of these mutants (mas 1) is deficient in a matrix-located protease activity which cleaves the pre-sequences from mitochondrial precursor proteins. Isolated mas 1 mitochondria catalyze oxidative phosphorylation, exhibit respiratory control and import mitochondrial precursor polypeptides, but are defective in removing transient pre-sequences from imported precursors. The phenotype of the mas 1 mutant suggests that the matrix-located processing protease is essential for growth and for mitochondrial assembly.

Adenosine Diphosphate↗
PubMed1985

Physiological actions of phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis on KB III cells: alkaline phosphatase release and growth inhibition.

Phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis caused the release of alkaline phosphatase from KB III cells and plasma membrane preparations prepared from the cells. Phosphatidylinositol-specific phospholipase C added to the culture of KB III cells inhibited cell growth by 30%. The release of alkaline phosphatase induced by phospholipase C was dependent on, or proportional to, the reaction time and the concentrations of the phospholipase C, KB III cells and plasma membrane preparation. The Arrhenius plot for phosphatase-release reaction showed a single break at 18.1 degrees C for KB III cells or at 27.3 degrees C for the plasma membrane preparation. The activation energies of the phosphatase-release reaction were 3.2 and 29.2 kcal/mol for KB III cells, and 4.3 and 26.5 kcal/mol for the plasma membrane preparation. The released alkaline phosphatase had a mol. wt of 105,000 and isoelectric points of 4.05 (major) and 4.4 (minor).

Alkaline Phosphatase↗
PubMed1985

Three-dimensional structure of cytoskeletal system in human hepatocytes viewed by polyethylene-glycol-embedding method.

In an attempt to demonstrate the three-dimensional cytoskeletal system of human hepatocytes, we used two kinds of tissue processing. In one, specimens were immediately fixed with 1% glutaraldehyde, saponin 0.5 mg/ml, and tannic acid 2 mg/ml (procedure A) and in the other, cytoplasmic matrix and organelles were washed out with a solution containing saponin 0.5 mg/ml and 0.15% Triton X-100, followed by fixation with glutaraldehyde (procedure B). The specimens were embedded in polyethylene glycol, sectioned at 500 nm, critical point-dried and observed in a TEM. With procedure A, a fine lattice was shown to spread throughout the cytoplasm so as to connect plasma membranes with cytoplasmic organelles, condensed around the bile canaliculi. With procedure B, microfilaments, microtubules and intermediate filaments could be clearly visualized three-dimensionally instead of the lattice structure. At a higher magnification, microvilli of canaliculus were found to contain a core microfilament which were enmeshed in a pericanalicular filament plexus. This plexus looking like the terminal web of intestinal epithelia, encircled the canaliculus and was attached to the zonula adherens. Outside the plexus, intermediate filament network was shown attached to the desmosome. These morphological findings indicated that the cytoskeleton of human hepatocytes is composed of microfilaments, microtubules, intermediate filaments and the fine lattice structure, suggesting that the bile canaliculi could contract in vivo.

Actin Cytoskeleton↗
PubMed1985

Naviculo-cuneiform coalition. A report of two cases.

This solidus article reports on two unique cases of naviculo-medial cuneiform coalition in a 20-year-old man and a 22-year-old woman. In the first patient, arthrodesis was successful in relieving the localized pain, whereas in the second patient the pain gradually decreased without treatment.

Adult↗
PubMed1985

[The effects of DC high electric field exposure upon sensory receptors of cat's hindlimb].

Concerning the mechanisms of effects of high electric field exposure on animals there may be two possibilities; one is a possible effects upon organs due to induced electric current within the body, and another one is effects due to the electric field distributing over the body surface. The purpose of the present experiments is to investigate the latter possibility by recording action potentials from afferent fibers innervating various sensory receptors in the cat's hindlimb. Upon exposure of DC electric fields of 1.8 kV/cm or stronger cat's hairs were pulled to the upper electrode, and action potentials were evoked on afferent fibers innervating G1, G2 hair receptors and down hair receptors. No action potential was evoked in afferent fibers innervating type I, type II, field receptors, muscle spindles and joint receptors. These results indicate that high DC electric field induced the movement of hairs which eventually evoked action potentials innervating the hair receptors and those receptors situated under the skin were not influenced by the electric field.

Action Potentials↗
PubMed1984

A simple method of determining 4-hydroxyisovaleric acid and its level in a patient with isovaleric acidemia.

We developed a simple and rapid method for the quantitative determination of 4- hydroxyisovaleric acid using the conversion of this acid to the corresponding lactone,and measured its levels in the plasma of a patient with isovaleric acidemia during an episode of severe ketoacidosis. 4-Hydroxyisovaleric acid reached a peak two days after plasma isovaleric acid was at its highest level.

Acidosis↗