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T Yanagida

Publications and source records attributed to T Yanagida.

At least 181 records · Page 10Linked to original sources
PubMed1983

Studies on conformation of F-actin in muscle fibers in the relaxed state, rigor, and during contraction using fluorescent phalloidin.

F-actin in a glycerinated muscle fiber was specifically labeled with fluorescent phalloidin-(fluorescein isothiocyanate) FITC complex at 1:1 molar ratio. Binding of phalloidin-FITC to F-actin affected neither contraction of the fiber nor its regulation by Ca2+. Comparison of polarized fluorescence from phalloidin-FITC bound to F-actin in the relaxed state, rigor, and during isometric contraction of the fiber revealed that the changes in polarization accompanying activation are quantitatively as well as qualitatively different from those accompanying transition of the fiber from the relaxed state to rigor. The extent of the changes of polarized fluorescence during isometric contraction increased with decreasing ionic strength, in parallel with increase in isometric tension. On the other hand, polarized fluorescence was not affected by addition of ADP or by stretching of the fiber in rigor solution. It is concluded from these observations that conformational changes in F-actin are involved in the process of active tension development.

Actins↗
PubMed1982

Local potassium concentration changes in the retina and the electroretinographic (ERG) b-wave.

Intraretinal injections of high- and low-K+ Ringer's solutions generate potentials which are opposite in polarity but otherwise similar in both their shapes and retinal depth profiles. We provide evidence that the principal generator of the K+-mediated potential is the Müller (glial) cell, but that the FRG b-wave cannot be explained solely by this K+-mediated potential without considering involvement of the electrical activities of neuronal cells.

Animals↗
PubMed1982

Interaction of myosin with thin filaments during contraction and relaxation: effect of ionic strength.

The influence of ionic strength on the isometric tension, stiffness, shortening velocity and ATPase activity of glycerol-treated rabbit psoas muscle fiber in the presence and the absence of Ca2+ has been studied. When the ionic strength of an activating solution (containing Mg2+-ATP and Ca2+) was decreased by varying the KCl concentration from 120 to 5 mM at 20 degrees C, the isometric tension and stiffness increased by 30% and 50%, respectively. The ATPase activity increased 3-fold, while the shortening velocity decreased to one-fourth. At 6 degrees C, similar results were obtained. These results suggest that at low ionic strengths ATP is hydrolyzed predominantly without dissociation of myosin cross-bridges from F-actin. In the absence of Ca2+, with decreasing KCl concentration the isometric tension and stiffness developed remarkably at 20 degrees C. However, the ATPase activity and shortening velocity were very low. At low ionic strength, even in the absence of Ca2+ myosin heads are bound to thin filaments. The development of the tension and stiffness were greatly reduced at 6 degrees C or at physiological ionic strength.

Adenosine Triphosphatases↗
PubMed1982

The effect of crosslinking of thin filament with glutaraldehyde on the contractility of muscle fiber.

The effect of crosslinking of F-actin with glutaraldehyde on the contractility of muscle ghost fiber containing reconstituted thin filament (i.e. F-actin-tropomyosin-troponin complex) and irrigated with myosin was investigated. The results show that: (i) crosslinking inhibited development of isometric tension and shortening of the fiber in the presence of MgATP, (ii) superprecipitation of the complex of myosin with crosslinked thin filament was considerably delayed, (iii) crosslinking inhibited neither binding of myosin heads to the filament nor activation of myosin ATPase. It is suggested that alterations of actin structure due to the formation of intra- and/or intermonomer crosslinks can essentially affect the process of contractility.

Actins↗
PubMed1982

[Moderate dose methotrexate with citrovorum factor rescue therapy in the treatment of head and neck cancer].

A clinical trial of moderate dose methotrexate (MTX)-CF rescue was conducted in 12 institutions. Thirty-seven patients with head and neck carcinoma entered this trial, of which 32 were evaluable. MTX was administered 350 mg/m2 (500 mg/body) by i.v. drip over 6 hours. Three hours after completion of MTX infusion, CF rescue was started. There was no complete response in 32 patients. Nine patients showed partial response with the response rate of 28%. The response rates were 21% for the group of patients treated previously, and 75% for the group untreated previously. MTX concentration in plasma was determined at 6, 24, 48 and 72 hours after the initiation of MTX infusion, and the assay results revealed a safe range. GI disturbances were seen at the rates of 11 to 38%. Bone marrow suppression was mild and no renal toxicity was observed. We concluded that the moderate dose MTX-CF rescue therapy was useful for head and neck carcinoma. As a next step, we are planning to conduct a clinical trial of high-dose MTX.

Adult↗
PubMed1982

[Pharmacokinetics of cis-platinum diammine dichloride].

Levels of cis-platinum diammine dichloride (CPDD) were determined in the serum, urine and ascites by the flameless atomic absorption spectrophotometry. Samples were obtained from the patients with ovarian cancer (5 cases) and cervical cancer (1 case). The patients were given CPDD by infusion every three weeks. The treatment schedules were as follows: A, 14-16 mg/body/day X 5 days; B, 20 mg/body/day X 5 days; C, 50 mg/body X 1 day. The levels of CPDD in the serum of the patients treated under schedules A and B became higher after the repeated administration from day 1 through 5. In the patients treated under schedules A and B, a more complex serum elimination curve was seen, while a simple biphasic clearance pattern was observed in the patient treated under schedule C. The concentration of CPDD in the serum arose with the increase of doses. A measurable concentration of CPDD was still detected 14 days after the end of administration. The urinary recovery at 24 hours after administration of CPDD ranged from 17.0 to 21.0% under schedules A and B. On the other hand, it was 54.2% under schedule C. The overall urinary recovery of CPDD ranged from 25.3 to 35.3% which suggested the retention of CPDD. The urinary excretion of CPDD and the concentration of CPDD in urine showed close relation with a urine volume per hour. The levels of CPDD remained lower in the ascites compared to those of the serum. No significant elevation in the serum creatinine or BUN were recognized in all patients.

Ascites↗
PubMed1981

Comparison of intermonomer interactions within polymers of chicken gizzard and rabbit skeletal muscle actins.

Comparison of interactions between the monomers of chicken gizzard and skeletal muscle actin revealed: 1. A more pronounced increase of the extent of polymerization of chicken gizzard than skeletal muscle actin with temperature, which resulted in higher positive changes of entropy and enthalpy of the former than of the latter species. 2. A difference in spectral changes accompanying polymerization: the changes at 295 nm, attibuted to environmental changes around tryptophan residues, were less pronounced for gizzard than for skeletal actin. 3. A difference in the amount of heavy meromyosin added to gizzard and to skeletal F-actin, with which the degree of flow birefringence of the acto-HMM complex is minimum: this amount was lower in the former than in the latter case. These results indicate quantitative differences between intermonomer interactions involved in polymerization of both actin species and also a possible difference in cooperativity between the monomers within the polymers of gizzard and skeletal actin.

Actins↗