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Biomedical subjects

K Hotta

Publications and source records attributed to K Hotta.

At least 361 records · Page 20Linked to original sources
PubMed1976

Depolarization and contraction of skeletal muscle induced by intracellular stimulation -role of T-tubules in electro-chemical coupling.

Response of skeletal muscle fibers upon intracellular stimulation was investigated to elucidate the role of the T-system in the electro-chemical coupling process. Upon stimulation, the fiber generates twitch and tonic tension which is independent of the excitation of the membrane (not inhibited by TTX). The fiber placed in low Ca2+ medium (10(-7) M, controlled by EGTA-Ca) for more than ten minutes, exhibited explosive contraction; this phenonomenon was not observed in Na-free choline Ringer or glycerol-treated (T-tubule disrupted) fibers. Injection of a small amount of Mn2+ into the muscle cells produced strong, long lasting contraction without excitation of the membrane. Glycerol-treated fibers failed to respond to the stimulus using a Mn2+ electrode. These facts suggest that Ca2+ release or entry which probably caused by depolarization of T-tubule membrane in the presence of Na+, may be essential for the initiation of Ca2+ release from sarcoplasmic reticulum.

Animals↗
PubMed1975

Intermediate complex of ATP hydrolysis and synthesis by muscle proteins.

Myosin catalyzed exchange between 32Pi and ATP in reaction medium during its enzymatic hydrolysis of ATP only by a very small amount. Addition of actin increased to a great extent the rate of incorporation of 32Pi in the presence of Mg. Glycerinated smooth muscle fibers also exhibited the ability to exchange 32Pi and ATP upon the application of external force (repeated stretching and releasing). A schematic mechanism of the action of actin and external force on acceleration of 32Pi incorporation is proposed and the importance of the M-ADP complex for force generation is suggested.

Actins↗
PubMed1975

Biological studies of amiclenomycin.

The action of amiclenomycin (AM) in inhibiting growth of microorganisms is specific against mycobacteria in vitro, but the antibiotic does not show a therapeutic effect against tubercle bacilli in vivo. The action of AM is reversed by biotin, desthiobiotin (DTB) and 7,8-diaminopelargonic acid (DAPA), but not by 7-keto-8-aminopelargonic acid (KAPA), pimelic acid and glutaric acid. In the presence of AM, cultures of Mycobacterium smegmatis and Bacillus sphaericus accumulated KAPA, whereas the formation of DTB decreased. Therefore, AM is thought to inhibit KAPA-DAPA transamination in biotin biosynthesis. In M. smegmatic and B. sphaericus the conversions of KAPA to DAPA and of DTB to biotin were rate limiting in biotin synthesis. Accordingly, the synergistic antibiotic activity of AM, inhibiting the former, and actithiazic acid, inhibiting the latter reaction, would be simply explained.

Amino Acids, Diamino↗
PubMed1975

Studies of the mode of action of amiclenomycin.

Amiclenomycin (AM) was found to be a strong inhibitor of KAPA-DAPA aminotransferase of Brevibacterium divaricatum. This transamination was suggested to follow Ping Pong Bi Bi mechanism. Inhibition of this transamination by AM is of a noncompetitive type in a Lineweaver-Burk plot of initial velocity, but not in a Dixon plot. The activity of KAPA-DAPA aminotransferase drops abruptly after preincubation with AM, but its activity is restored by dialysis against 10 mM potassium phosphate buffer (pH 7.0). Inhibition by AM is decreased by an increase of KAPA in the reaction mixture, but not by an increase of S-adenosyl-L-methionine (SAM) or pyridoxal-5'-phosphate (PALP). These facts indicate that AM exerts its inhibitory action against KAPA-DAPA aminotransferase by binding to the enzyme, probably to the KAPA-DAPA binding site.

Amino Acids↗