Search PubMed⌕ Search

Biomedical subjects

S Ebashi

Publications and source records attributed to S Ebashi.

At least 37 records · Page 2Linked to original sources
PubMed1987

Ca2+ in the heart.

Ca research in the heart was historically surveyed. First, reference was made to the development of the concept involving Ca2+ in the contraction of skeletal muscle. This was followed by an overview of studies on Ca regulation in cardiac muscle. Emphasis was laid on the fact that the "Ca era" today originated from Ca research in muscle initiated by Ringer and expanded by Heilbrunn.

Animals↗
PubMed1986

Superprecipitation is a model for in vitro contraction superior to ATPase activity.

We investigated which activity of myosin B (natural actomyosin), super-precipitation or ATPase, is better suited as a parameter for measuring in vitro contraction with emphasis on the response of myosin B to Sr2+. The Sr2+ concentration giving half-maximum (KSr2+) binding of Sr2+ to cardiac troponin was not different from that to skeletal troponin, whether the troponins were contained in the actomyosin system or in the isolated state. However, KSr2+ for the ATPase activity of cardiac myosin B is slightly smaller than that of skeletal myosin B. This difference in KSr2+ is more marked when superprecipitation was used as the indication for in vitro contraction. If the above results were compared with those of Kitazawa (1976) using glycerinated fibers of cardiac and skeletal muscle, the differences in KSr2+ between cardiac and skeletal muscle increased in the order: Sr-binding to troponin less than ATPase activity less than superprecipitation less than contraction of glycerinated fibers. The increase in the effect of pH on Ca2+-related properties is also in the order: Ca-binding to troponin less than or equal to ATPase activity less than superprecipitation less than contraction of glycerinated fibers. All the results coincide with one another that the results with super-precipitation are invariably more akin to those with glycerinated fibers than to those with the ATPase activity. It is concluded that superprecipitation is a better parameter for representing in vitro contraction than ATPase activity.

Actomyosin↗
PubMed1985

The effect of leiotonin fraction on stably phosphorylated smooth muscle myosin.

This study was designed to determine the effect of leiotonin on the actin-activation once the myosin is stably phosphorylated. Gizzard myosin was stably phosphorylated by ATP-gamma-S using the gizzard light chain kinase. Addition of leiotonin preparation to phosphorylated myosin reconstituted with actin and tropomyosin did not alter the ATPase activity. Furthermore, leiotonin did not confer the calcium sensitivity of the ATPase activity. These experiments show that the actin-activated ATPase activity of stably phosphorylated gizzard myosin is not altered by leiotonin.

Actins↗
PubMed1984

Ca2+ and the contractile proteins.

Troponin regulation can be divided into two categories, primary and secondary. While the former underlies the processes common to troponin-regulated muscles, the latter varies between different types of muscle. One example of secondary regulation is the Ca2+ dependent interaction of troponin T and troponin C, which tends to suppress the myosin-actin-ATP interaction at relatively high Ca2+ concentrations, say, 10(-4)M. This interaction is marked in fast skeletal muscle, but weak in cardiac muscle. Since the Ca2+ concentration in fast skeletal muscle can physiologically reach a high level, this interaction may be considered as a kind of self-defense mechanism to avoid excess contraction. Cardiac muscle, which carries out its contractile cycle at lower Ca2+ concentrations, does not require such a mechanism, but under pathological conditions where the Ca2+ concentration could reach a high level, the lack of this mechanism might be detrimental to the contractile system.

Adenosine Triphosphatases↗
PubMed1984

Detection of calcium binding proteins by 45Ca autoradiography on nitrocellulose membrane after sodium dodecyl sulfate gel electrophoresis.

A new simple method of detecting calcium binding proteins in a protein mixture is described. A sample which might include calcium binding proteins was subjected to SDS-polyacrylamide gel electrophoresis and then electrophoretically transferred to a nitrocellulose membrane. The membrane was then incubated with 45Ca to detect calcium binding proteins as radioactive bands by autoradiography. Purified troponin-C, calmodulin, myosin DTNB light chain, and parvalbumin were clearly identified by this method. In the whole homogenate of chicken skeletal muscle, myosin DTNB light chain, troponin-C, and 55K calcium binding protein were found to be radioactive. In the frog skeletal muscle, small molecular weight proteins of approximately 13-15K and 70K protein appeared to be the calcium binding proteins. In the case of the carp skeletal muscle, small molecular weight proteins including parvalbumin and two proteins of about 80K seemed to bind calcium ion. Two high molecular weight calcium binding proteins were present in the scallop striated muscle. The procedure described can be completed within 24 h and can detect as little as 2 micrograms of calcium binding protein in the starting sample. Under appropriate conditions it was possible to detect only high affinity calcium binding proteins.

Animals↗
PubMed1983

The effect of heart and skeletal muscle troponin complexes and calmodulin on the Ca2+-dependent reactions of phosphorylase kinase isoenzymes.

The dephosphorylated form of phosphorylase kinase was purified 700-fold from rabbit heart extract. The purified enzyme had a pH 6.8/pH 8.2 activity ratio of 0.04-0.08 and was completely dependent on Ca2+ with an apparent Ka value for Ca2+ of 2.59 microM at pH 6.8. At free Ca2+ concentrations between 0.057 microM and 400 microM, 1.5 microM rabbit heart troponin complex had no significant effect on the reaction. However, 1.5 microM rabbit skeletal muscle troponin complex stimulated the reaction 1.5-2-fold with a concomitant decrease in the Ka value for Ca2+ to 1.40 microM. No differences in the effects of these troponin complexes were observed when heart-type and skeletal muscle-type phosphorylase b isoenzymes from either rabbit or pig were used as substrate. Similar effects of heart and skeletal muscle troponin complexes were observed on the Ca2+-dependent reaction of the dephosphorylated form of phosphorylase kinase partially purified from rabbit skeletal muscle. A saturating concentration (1.36 microM) of bovine brain calmodulin stimulated 2-5-fold the Ca2+-dependent reaction of skeletal muscle phosphorylase kinase, but not the reaction of heart phosphorylase kinase. Heart troponin complex (12 microM) suppressed 80-100% the stimulatory effect of skeletal muscle troponin complex on the reactions of phosphorylase kinase isoenzymes, but had no significant effect on the stimulation by calmodulin of skeletal muscle phosphorylase kinase reaction.

Animals↗