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Biomedical subjects

K Yagi

Publications and source records attributed to K Yagi.

At least 721 records · Page 40Linked to original sources
PubMed1977

Incubation of myosin with exogenous small components (g1, g2, or g3) in KSCN or LiCl and properties of g-exchanged myosins.

Myosin was incubated with a large excess of exogenous g1, g2 or g3 in 0.6 M KSCN (or in 4 M LiCl) for 1-2 h at 0-2 degrees C. KSCN (or LiCl) was then removed by dialysis. The composition of g-chains in the resulting myosin was analyzed by SDS-gel electrophoresis. When myosin was incubated with g1, the amount of g1 in myosin increased and the increment was nearly counterbalanced by a decrease in g3, whereas an opposite change was observed on incubation with g3. The amount of g2 was not changed by these treatments. The same ATPase activity as that of control myosin was observed in the presence of Ca2+ or EDTA with the myosins incubated with g1, g2, or g3, but the activity in the presence of Mg2+ was about one-half of the control. The Ca2+ sensitivity of actomyosin containing the treated myosins was slightly higher than that of actomyosin containing the control myosin. Spin-labeled g1 or spin-labeled g3 was incorporated into myosin, but the ESR spectra of two spin labels were not distinguishable. No information could be obtained from the ESR spectra by the addition of Ca2+, Mg2+, nucleotides or actin. Inhibition of ATPase activity was observed when SH groups g1 or g3 in myosin were chemically modified.

Actins↗
PubMed1977

Calcium-binding subunit of myosin light chain kinase.

Myosin light chain kinase from frozen rabbit skeletal muscle was separated into two protein components by DEAE-cellulose column chromatography. One component (MW 20,000) was a Ca2+-binding protein. Both components and Ca2+ were essential for the enzyme activity.

Animals↗
PubMed1977

Inhibition by Mg2+ of the interaction of Ca2+ with spin-labeled g2 bound to myosin.

According to the measurement of ESR spectrum, Ca2+ induced conformational change of spin-labeled g2 bound to myosin in the presence of 1 mM Mg2+. The half-maximal changes were observed at pCa 6.8 and at pCa 3.7. Spin-labeled phosphorylated g2 bound to myosin showed one transition at pCa 4.5, which shifted to pCa 6.5 after the dephosphorylation with E. coli alkaliphosphatase.

Calcium↗
PubMed1977

Separation of two different heavy meromyosins. Evidence for the presence of myosin isozymes in rabbit skeletal muscle.

Heavy meromyosin prepared from rabbit skeletal myosin by chymotryptic digestion was separated into two different heavy meromyosins by Sepharose 4B-6 aminohexyl PPi column chromatography. SDS-gel electrophoresis of one fraction of heavy meromyosin, which was eluted with 75 mM ammonium acetate, showed that it contained the small polypeptide chains, g3 and g2, as well as the large chains. The other fraction of heavy meromyosin, which was eluted with 85 mM ammonium acetate, contained g1 and g2. We concluded that the two heavy meromyosins arose from two different populations (isozymes) of myosin. No significant difference in Ca2+-ATPase activity was detected between the two heavy meromyosins.

Adenosine Triphosphatases↗
PubMed1977

Plasma levels of human chorionic somatomammotrophin, progesterone, unconjugated oestradiol and oestriol, and alpha-foetoprotein in patients with hydatidiform moles.

Human chorionic somatomammotrophin (HCS), progesterone, and unconjugated oestradiol and oestriol were measured in the plasma of 13 patients with intact hydatidiform moles from week 9 to 19 of pregnancy and in 89 normal women from week 5 to 20 of pregnancy. Plasma alpha-foetoprotein (AFP) was also measured in 9 out of 13 patients and in 23 of the normal women from week 13 to 20 of pregnancy. All the compounds were measured by radioimmunoassay. The plasma HCS concentration in 35 samples from 13 patients with hydatidiform moles ranged from 10 to 910 ng/ml; this was lower than that in normal pregnancy of corresponding duration in eight patients; within the normal range in four patients and high in one patient. The plasma progesterone concentration ranged from 17-5 to 79-2 ng/ml; it was higher than that in normal pregnancy in eight patients and within the normal range in five patients. The plasma unconjugated oestradiol concentration ranged from 1-82 to 8-10 ng/ml; it was higher than normal in six patients and within the normal range in seven patients. The plasma unconjugated oestriol concentration ranged from 0-168 to 1-37 ng/ml, the levels at 15-19 weeks of gestation being significantly lower than those in normal pregnancy at this time (P less than 0-005). Plasma AFP was not detectable in the nine patients (less than 10 ng/ml) whereas it ranged from 10 to 80 ng/ml in 18 out of 23 women in week 13-20 of normal pregnancy. The present results suggest that both plasma oestriol and AFP could be helpful in the diagnosis of hydatidiform mole at about 12-14 weeks though diagnosis could not be made with absolute certainty.

Estradiol↗
PubMed1977

Incorporation of the Ca2+ -binding component (g2) into heavy meromyosin and subfragment-1 of pig cardiac myosin.

A new protein component was found in heavy meromyosin and in subfragment-1 (S-1) prepared by chymotrypsin digestion of pig cardiac myosin in the presence of Ca2+. The molecular weight of this protein was estimated as 15,000 dalton. It was able to bind Ca2+ and showed a similar UV absorption spectrum to that of the g2 light chain. Heavy meromyosin and subfragment-1 which contained the 15,000 dalton component incorporated exogenous g2 and the 15,000 dalton component disappeared after such treatment. We concluded that the 15,000 dalton component was produced from g2 by limitted proteolysis. The subfragment-1 was separated into two protein fractions in equal yield by recycling the gel filtration. One contained the 15,000 dalton component and was able to bind Ca2+ while the other did not contain the component and was unable to bind Ca2+. According to analysis by SDS gel electrophoresis, the large polypeptide chain (the f component) of the first S-1 was approximately 5,000 dalton larger than the f component of the second S-1. The polypeptide corresponding to 5,000 dalton was designated polypeptide-C, because it was released from the C terminal of the f component. It seems to be essential for the attachment of the Ca2+-binding light chain g2. The location of g2 in myosin may thus be at the polypeptide-C which links the head to the tail of myosin.

Animals↗
PubMed1976

Labelling of sarcoplasmic reticulum membranes with 1-dimethylaminonaphthalene-5-sulfonyl chloride.

1. Sarcoplasmic reticulum membranes were labelled with 1-dimethylaminonaphtalene-5-sulfonyl chloride (DnsCl). Analyses of the dansylated membranes demonstrated that the most of the dye was associated with ATPase (ATP phosphohydrolase, EC 3.6.1.3) and phosphatidylethanolamine in the membranes. 2. Dansylation of the membranes could be performed without significant decrease in the ATPase activity. 3. Partial differentiation of fluorescence of Dns-phosphatidylethanolamine from that of Dns-ATPase could be achieved by changing excitation wavelength; Dns-ATPase emmitted in the shorter wavelength region, while Dns-phosphatidylethanolamine emmitted in the longer wavelength region. 4. Fluorescence polarization of the dye bound to the membranes indicated that both the ATPase and phosphatidylethanolamine were strongly immobilized in the membranes, while the ratio of freely rotating dye to the "frozen" dye bound to the ATPase was larger than that bound to the phosphatide.

Adenosine Triphosphatases↗
PubMed1976

Lipoperoxide formation in the retina in ocular siderosis.

Insertion of iron nail into the vitreous cavity provoke the formation of lipoperoxide in the retina. In acord with the increase in lipoperoxide in the retina, ERG began to decrease. In vitro experiment using isolated retina, lipoperoxide was found to be increased in the presence of ferric or ferrous ions, while it was inhibited by adding antioxidants or ethylenediamine tetraacetate. From these results, direct cause of retinal degeneration in siderosis could be ascribed to the formation of lipoperosice by iron-ions liberated from the piece of iron, resulting into the degeneration of the visual cell layers of the retina.

Animals↗
PubMed1976

15N nuclear magnetic resonance of flavins.

Ninety-nine percent 15N-enriched flavins were synthesized and their proton decoupled 15N resonances were observed. The enriched compounds were [1,3-15N]riboflavin, [1,3,5-15N]riboflavin, [1,3-15N]riboflavin 5'-phosphate, [1,3,5-15N]riboflavin 5'-phosphate, and [1,3,5-15N] flavin adenine dinucleotide, [1,3,5-15N] lumiflavin, and [1,3,5-15N] lumichrome. By comparison of their spectra and from th- nuclear Overhauser effect data each 15N resonance peak could be assigned to each 15N nucleus. The order of the chemical shifts well corresponds to that of the calculated pi-electron densities. The N-3 nucleus gives the most intense inverted peak and the N-5 nucleus a small noninverted peak. By changing pH from neutral to alkaline, the chemical shift and the intensity of signal were mostly affected in the N-3 resonance of riboflavin 5'-phosphate. The N-5 signal of flavin adenine dinucleotide showed a fairly large downfield shift with the increase of temperature. These observations can be well interpreted by the chemical structure and the proposed conformation of riboflavin 5'-phosphate and flavin adenine dinucleotide.

Flavin-Adenine Dinucleotide↗
PubMed1976

Oxidation of sarcosine and N-alkyl derivatives of glycine by D-amino-acid oxidase.

1. Sarcosine was oxidized by D-amino-acid oxidase (D-amino-acid: O2 oxidoreductase (deaminating), EC 1.4.3.3) to yield methylamine and glyoxylic acid. A seriies of N-alkyl glycines were also oxidized by this enzyme. 2. N-Acetyl- and N-Phenylglycine inhibited the oxidase by competing with the substrate, while N-methyl-N-acetylglycine did not bind to the enzyme. This suggests the requirement of at least one unsubstituted hydrogen atom at the amino group ofglycine for binding. 3. The primary step in the reaction was the release of a proton from the substrate, indicating the formation of a substituted imino acid, which was spontaneously hydrolyzed to glyoxylic acid acid and an amine.

Animals↗
PubMed1976

Formation of lipoperoxide in the retina of rabbit exposed to high concentration of oxygen.

When rabbit was exposed to high concentrations of oxygen, lipoperoxide in the retina was increased at 12 h of the exposure, after which period amplitude of electro-retinogram decreased. The degeneration was observed in the visual cell layer of the retina of the exposed animal. The exposure increased lipoperoxide in isolated retina. These data show the intervention of lipoperoxide in retinal degeneration by exposure to high concentration of oxygen.

Animals↗