Search PubMed⌕ Search

Biomedical subjects

T Yanagida

Publications and source records attributed to T Yanagida.

At least 145 records · Page 8Linked to original sources
PubMed1990

Mechanochemical coupling in actomyosin energy transduction studied by in vitro movement assay.

In order to study the mechanochemical coupling in actomyosin energy transduction, the sliding distance of an actin filament induced by one ATP hydrolysis cycle was obtained by using an in vitro movement assay that permitted quantitative and simultaneous measurements of (1) the movements of single fluorescently labeled actin filaments on myosin bound to coverslip surfaces and (2) the ATPase rates. The sliding distance was determined as (the working stroke time in one ATPase cycle, tws) x (the filament velocity, v). tws was obtained from the ATPase turnover rate of myosin during the sliding (kt), the ATP hydrolysis time (delta t) and the ON-rate at which myosin heads enter into the working stroke state when they encounter actin (kON); tws approximately 1/kt-delta t-1/kON. kt was estimated from the ATPase rates of the myosin-coated surface during the sliding of actin filaments. delta t has been determined as less than 1/100 per second, kON was estimated by analyzing the movements of very short (40 nm) filaments. The resulting sliding distance during one ATP hydrolysis cycle near zero load was greater than 100 nm, which is about ten times longer than that expected for a single attachment-detachment cycle between an actin and a myosin head. This leads to the conclusion that the coupling between the ATPase and attachment-detachment cycles is not determined rigidly in a one-to-one fashion.

Actins↗
PubMed1990

Loose coupling between chemical and mechanical reactions in actomyosin energy transduction.

In order to study the mechanochemical coupling in actomyosin energy transduction, the sliding distance of an actin filament induced by a myosin head during one ATP hydrolysis cycle was obtained using an in vitro movement assay, which permitted quantitative and simultaneous measurements of (1) the movements of single fluorescently-labeled actin filaments on myosin bound to coverslip surfaces and (2) the ATPase rates. The sliding distance was determined as (the working-stroke time in one ATPase cycle, Tws) x (the filament velocity, v). The working-stroke time (Tws) was obtained from the ATPase turnover rate of myosin during the sliding (kT), the ATP hydrolysis time on myosin heads (delta T) and the ON-rate at which myosin heads enter into the working-stroke when they encounter actin (kON); Tws approximately 1/kT-delta T-1/kON. kON was estimated by analyzing the movements of very short (40 nm) filaments. The resulting sliding distance during one ATP hydrolysis cycle near zero load was greater than 100 nm, which is about 10 times longer than that expected for a single attachment-detachment cycle between an actin monomer and a myosin head. This leads to the conclusion that the coupling between the chemical and mechanical reactions is not rigid in a one to one fashion.

Actins↗
PubMed1989

Kinetics of HDL-apo A-I in the WHHL rabbit, an animal model of familial hypercholesterolemia.

Plasma high density lipoproteins (HDL) and their major protein, apolipoprotein (apo) A-I, are deficient in homozygous Watanabe heritable hyperlipidemic (WHHL) rabbits. As the pathophysiology of subnormal HDL-apo A-I is unclear, we examined kinetic parameters of HDL-apo A-I in WHHL rabbits and normolipidemic Japanese White (control) rabbits. The total plasma mass of HDL-apo A-I was significantly smaller (P less than 0.01) in WHHL rabbits than in controls (less than one-third). Mean fractional catabolic rates (FCR) computed from the specific radioactivity decay curves of HDL-apo A-I were significantly greater (P less than 0.01) in WHHL rabbits than in controls (0.874 +/- 0.052 vs. 0.502 +/- 0.060/day, respectively). Mean synthetic rates of HDL-apo A-I were significantly lower (P less than 0.01) in WHHL rabbits than in controls (8.67 +/- 0.59 vs. 18.14 +/- 3.75 mg/kg body weight/day, respectively). We conclude that the deficiency of plasma HDL-apo A-I in the WHHL rabbits resulted from an increase in FCR and a decrease in apo A-I synthesis.

Animals↗
PubMed1989

Construction of a secretion vector production of peptide hormones in Escherichia coli (extracellular production of calcitonin as fused protein).

A new secretion vector, pEAP84 which contained a unique restriction site (BglII) at the 3' end of the penicillinase gene to produce a fused protein, and the Ex-kil region to make the outer membrane permeable, was constructed from pEAP82. A recombinant plasmid p84h06, which contained a synthetic gene for human calcitonin with a cyanogen bromide cleavage site at the junction site of the fused protein, was constructed and introduced into Escherichia coli. The hybrid protein produced in E. coli carrying p84h06 was secreted into the culture medium. The amino acid composition of this product was consistent with that deduced from the DNA sequence. Mature calcitonin was obtained following cyanogen bromide cleavage of the fused protein.

Amino Acid Sequence↗
PubMed1989

The elementary process in the actomyosin energy transduction system.

The sliding distance of an actin filament induced by a myosin head during one ATP hydrolysis cycle was determined by measuring minimum length of actin filaments moving on myosin-coated glass surface as fast as long ones and the ATPase rate during sliding. The results indicate that the sliding distance is greater than 100nm, suggesting that the mechanical reaction can occur many times during one chemical (ATP hydrolysis) cycle.

Actins↗
PubMed1989

[Simulation of the electroretinographic slow P III component by injection of K+-free Ringer's solution in the frog retina].

A decrease in extracellular potassium concentration [( K+]o) was caused by injecting a small amount of K+ -free Ringer's solution into the photoreceptor layer of the isolated frog retina. The response induced by K+ -free Ringer's solution was receptor side-positive, and the depth profile of the response resembled that of the response (slow P III) induced by spot illumination. This result supports the notion that the slow P III is generated by Müller cells as they hyperpolarize in response to a light-induced decrease in [K+]o in the photoreceptor layer.

Animals↗
PubMed1989

[Relationship between chemotaxis and surface antigen of neutrophils].

Neutrophils migrate from the peripheral vessels into the local tissues and cause acute inflammation. It was speculated that there was heterogeneity among neutrophils in terms of migration. Neutrophils were classified into two groups according to their migratory speed. The relationship between the amount of chemotaxis-associated antigen of cell surface and neutrophilic functions were examined. The classification of neutrophils into fast cells and slow ones was performed using Boyden chambers and nucleopore filters (10 microns). In the chemotactic examinations, neutrophils which migrated toward the lower compartments were named fast locomotive group, and cell stayed in the upper part of Boyden chambers were named slow locomotive group. Both groups were reacted with anti-human granulocyte monoclonal antibody termed TM316 and treated with FITC-conjugated anti-mouse IgM(kappa) antibodies. The results revealed that fast locomotive cells expressed greater amount of TM316 associated antigens and generated stronger chemiluminescence than slow locomotive cells. These results indicate that neutrophils are not homogeneous in terms of functions and surface antigens.

Animals↗
PubMed1988

Force measurements by micromanipulation of a single actin filament by glass needles.

Single actin filaments (approximately 7 nm in diameter) labelled with fluorescent phalloidin can be clearly seen by video-fluorescence microscopy. This technique has been used to observe motions of single filaments in solution and in several in vitro movement assays. In a further development of the technique, we report here a method to catch and manipulate a single actin filament (F-actin) by glass microneedles under conditions in which external force on the filament can be applied and measured. Using this method, we directly measured the tensile strength of a filament (the force necessary to break the bond between two actin monomers) and the force required for a filament to be moved by myosin or its proteolytic fragment bound to a glass surface in the presence of ATP. The first result shows that the tensile strength of the F-actin-phalloidin complex is comparable with the average force exerted on a single thin filament in muscle fibres during isometric contraction. This force is increased only slightly by tropomyosin. The second measurement shows that the myosin head (subfragment-1) can produce the same ATP-dependent force as intact myosin. The magnitude of this force is comparable with that produced by each head of myosin in muscle during isometric contraction.

Actin Cytoskeleton↗
PubMed1988

Direct observation of molecular motility by light microscopy.

We used video-fluorescence microscopy to directly observe the sliding movement of single fluorescently labeled actin filaments along myosin fixed on a glass surface. Single actin filaments labeled with phalloidin-tetramethyl-rhodamine, which stabilizes the filament structure of actin, could be seen very clearly and continuously for at least 60 min in 02-free solution, and the sensitivity was high enough to see very short actin filaments less than 40 nm long that contained less than eight dye molecules. The actin filaments were observed to move along double-headed and, similarly, single-headed myosin filaments on which the density of the heads varied widely in the presence of ATP, showing that the cooperative interaction between the two heads of the myosin molecule is not essential to produce the sliding movement. The velocity of actin filament independent of filament length (greater than 1 micron) was almost unchanged until the density of myosin heads along the thick filament was decreased from six heads/14.3 nm to 1 head/34 nm. This result suggests that five to ten heads are sufficient to support the maximum sliding velocity of actin filaments (5 micron/s) under unloaded conditions. In order for five to ten myosin heads to achieve the observed maximum velocity, the sliding distance of actin filaments during one ATP cycle must be more than 60 nm.

Actins↗
PubMed1988

Minimum structural unit required for energy transduction in muscle.

The sliding of actin filaments was directly measured along single-headed myosin filaments on which the density of the heads was widely varied, using video-fluorescence microscopy. The results showed that the double-headed structure of myosin is not essential for inducing the sliding movement of actin filaments. The minimum number of myosin heads required for supporting movement of actin filaments at a maximum velocity of 5 micron/s at 23 degrees C was estimated to be 4, at most 16. This led to the conclusion that the sliding distance of actin filaments induced during a single ATP hydrolysis cycle is probably 160 nm or more, at least 40 nm under unloaded conditions.

Actin Cytoskeleton↗
PubMed1988

Congenital fistulas of the lacrimal sac.

Four patients with congenital lacrimal sac fistulas are presented. All cases were unilateral and not associated with an occluded nasolacrimal duct. In three cases, the fistula and surrounding skin were surgically removed. The fourth case required no treatment. Microscopic examination revealed that the fistulas were lined with stratified, squamous epithelium with or without keratosis, suggesting that they may have developed as outgrowths from the sac or common canaliculus.

Adolescent↗