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Biomedical subjects

K Hotta

Publications and source records attributed to K Hotta.

At least 343 records · Page 19Linked to original sources
PubMed1978

Effect of myosin DTNB light chain on the actin-myosin interaction in the presence of ATP.

The influence of the DTNB light chain of myosin on its enzymatic activities was examined by studying the superprecipitation of actomyosin and the actin-activated ATPase of heavy meromyosin (HMM) [EC 3.6.1.3]. Although the Ca2+-, Mg2+-, and EDTA-ATPase activities of control and DTNB myosin were practically the same, the superprecipitation of actomyosin prepared from actin and DTNB myosin occurred more slowly than that of control myosin. The apparent binding constant obtained from double-reciprocal plots of actin-activated ATPase of DTNB HMM was lower than that of control HMM. Recombination of DTNB myosin and HMM with DTNB light chains restored the original properties of myosin and HMM. The removal of DTNB light chain from myosin had no effect on the formation of the rigor complex between actin and myosin. These results suggest that the DTNB light chain participates in the interaction of myosin with actin in the presence of ATP.

Actins↗
PubMed1977

Application of trinitrophenylation for the measurement of alpha-amino residues resulting from peptic digestion.

A sensitive and precise method for the measurement of peptic activity on protein substrate is described. alpha-Amino residues formed by pepsin digestion are photometrically measured by comparing the absorbances of digested and nondigested material which has been trinitrophenylated. The usual problem of high reagent-blank absorbance is eliminated by using an anion exchange resin, Dowex 1-X8. In contrast to Anson's method, the procedure requires only 1/100 the quantity of protein substrate for analysis. It was proved to be particularly useful for the estimation of initial rates of proteolysis.

Amino Acids↗
PubMed1977

A glycopeptide isolated from human gastric juice.

A glycopeptide containing 69% carbohydrate was isolated from human gastric juice. The complex was found to be homogeneous and to have mol.wt. 9600. The glycopeptide consisted of a protein core to which were linked, by O-glycosidic linkages to threonine and N-glycosidic linkages, carbohydrate side chains composed of N-acetylgalactosamine, N-acetylglucosamine, galactose, mannose, fucose and sialic acid, in the proportions 2:10:7:4:12:1.

Amino Acids↗
PubMed1977

Presence of a unit for actin-myosin interaction during the superprecipitation of actomyosin.

The interaction of actin with myosin was studied in the presence of ATP at low ionic strength by means of measurements of the actin-activated ATPase activity of myosin and superprecipitation of actomyosin. At high ATP concentrations the ATPase activities of myosin, heavy meromyosin (HMM) and myosin subfragment 1 (S-1) were activated by actin in the same extent. At low ATP concentrations the myosin ATPase activity was activated about 30-fold by actin, whereas those of HMM and S-1 were stimulated only several-fold. This high actin activation of myosin ATPase was coupled with the occurrence of superprecipitation. The activation of HMM or S-1 ATPase by actin shows a simple hyperbolic dependence on actin concentration, but the myosin ATPase was maximally activated by actin at a 2:1 molar ratio of actin to myosin, and a further increase in the actin concentration had no effect on the activation. These results suggest the presence of a unit for actin-myosin interaction, composed of two actin monomers and one myosin molecule in the filaments.

Actins↗
PubMed1977

Mobilization of cellular calcium and contraction-relaxation of vascular smooth muscle.

In order to clarify the Ca2+ mediated regulatory mechanism of vascular smooth muscle, the correlation between Ca2+ movements in the cell and mechanical response was investigated using isolated rat aorta and bovine basilar artery. K+ induced contraction of vascular smooth muscle required Ca2+ in the medium, and the contraction was always associated with a large increase in Ca2+ influx. In the absence of external Ca2+, norepinephrine (NE) or serotonin (5HT) induced rapid contraction of the aorta and basilar artery, respectively. Caffeine (20 mM) also induced tension in the absence of Ca2+. The results obtained in these experiments suggest that at least four kinds of calcium exist in bound from in the cell, i. e., (1) loosely and (2) tightly bound calcium on the external surface of the cell membrane, (3) calcium localized in the internal surface of the cell membrane and (4) calcium stored in the intracellular store site, such as the sarcoplasmic reticulum. The intracellulary stored calcium, both (3) and (4), which can be mobilized by the action of certain drugs (NE, 5HT or caffeine), probably plays an important role for the regulation of the mechanical activity of vascular smooth muscle.

Animals↗
PubMed1977

Dissociation of excitation and contraction in skeletal muscle induced by deuterium oxide and dantrolene-sodium.

The effect of D2O and dantrolene-Na (DAN) on the electrical and mechanical responses of single muscle fiber (mouse EDL and frog semitendinosus), Ca2+ uptake and release of sarcoplasmic reticulum (SR) and contractile proteins was investigated to elucidate the coupling mechanism between depolarization and contraction. Both agents inhibited tension development induced by depolarization and caffeine, especially the initial phase of contraction (more pronounced in fast muscle) without affecting excitation of membrane and contractile machinery. The effect of DAN can be antagonized by increasing Ca2+ concentration and lowering the temperature of the medium. Ca2+ uptake and release abilities of isolated SR were not altered significantly in DAN, but were reduced considerably in D2O. These results suggest than there is a Ca2+-mediated trigger mechanism for the rapid release of activator Ca2+ from internal storage (SR). DAN and D2O interfere predominantly the action of the site(s) of this mechanism, probably on the T-tubules. In addition, D2O decelerates Ca2+ release from SR per se.

Adenosine Triphosphatases↗
PubMed1976

Regulatory protein of bovine tracheal smooth muscle.

Myosin B exhibiting Ca2+ sensitivity in superprecipitation and Mg-ATPase [EC 3.6.1.3] activity was extracted from tracheal smooth muscle. Repeated washing with 2mM KCl and 1 mM NaHCO3 resulted in the loss of these activities. However, on addition of native tropomyosin, the myosin B regained its original properties. Native tropomyosin is the regulatory system in this smooth muscle.

Adenosine Triphosphatases↗
PubMed1976

Regulatory protein of vascular smooth muscle.

Preparations of native tropomyosin from the muscles of bovine aorta and carotid artery resensitized myosin B from either tissue. Neither preparation had any effect on desensitized myosin B from skeletal muscle but native tropomyosin from skeletal muscle could resensitize desensitized myosin B from vascular smooth muscles.

Animals↗
PubMed1976

System analysis of heart rate control in man.

The dynamic property of the heart rate response to exercise was determined and expressed in the frequency domain to establish a method of examining cardiovascular control function. The response of heart rate to a stimulus was measured at 5-s intervals in nine healthy young volunteers. The stimulus consisted of several runs of two-step exercise practiced in semirandom sequence for 19 min. The weight function of the system was estimated from autocorrelation function of the input signal and cross-correlation function between the input and output signals. The weight function was transformed into a transfer function and its Bode plot diagram was drawn. From the diagram, four dynamic parameters were determined. These parameters are as follows: K is a constant showing the theoretical steady-state increment of heart rate, and T1, T2, T3 are time constants. The values obtained in the present experiment with the healthy young males were: K 46.0 +/- 14.6 beats, T1, 2.12 +/- 0.44, T2, 1.12 +/- 0.16, and T3 0.70 +/- 0.07 min.

Adult↗
PubMed1976

Calcium uptake, release and Mg-ATPase activity of sarcoplasmic reticulum from arterial smooth muscle.

Sarcoplasmic reticulum (SR) isolated from rat aorta exhibited ATP dependent Ca2+ uptake in the presence of Mg2+. The maximum capacity and apparent binding constant were 23n moles/mg and 1.8 X 10(4) M (-1), respectively. The energy source of this active Ca2+ accumulation would be Mg-ATPase associated with the membrane. Ca2+ which was taken up inside of sarcoplasmic reticulum was released rapidly by washout with the medium containing no Ca2+. These facts suggest that sarcoplasmic reticulum in vascular smooth muscle cell may play and important role in the regulation of intracellular Ca2+ concentration.

Adenosine Triphosphatases↗