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Biomedical subjects

N Yagi

Publications and source records attributed to N Yagi.

At least 163 records · Page 9Linked to original sources
PubMed1984

Lateral shrinkage of the myofilament lattice in chemically skinned muscles during contraction.

A toe muscle was isolated from a hind limb of the mouse and treated with saponin to make the sarcolemma more permeable to the solutes of the bathing medium. The equatorial X-ray diffraction pattern was recorded to determine the 1,0 spacing of the hexagonal myofilament lattice. The spacing in relaxed muscle at a sarcomere length of 2.5 microns was 408 A. When the muscle was maximally activated at pCa 4.4, a steady isometric tension of 1.3 kg/cm2 was produced and the spacing decreased to 384 A. A decrease in spacing of the same magnitude was observed when a relaxed muscle went into rigor, although the rigor tension was only 0.1 kg/cm2, 8% of the maximum contractile tension. From the intensity ratio of the 1,0 and 1,1 reflections the number of myosin heads transferred radially to the vicinity of the thin filament was calculated. During the maximum activation at pCa 4.4 the amount of the radial transfer was 96% of that in rigor. When the muscle was activated at a lower calcium concentration, the lattice shrinkage was smaller and the radial transfer was also smaller. These findings suggest that the lateral force underlying the lattice shrinkage may be due to lateral elasticity of cross-bridges.

Actins↗
PubMed1984

Mechanism of lipid peroxide formation in polychlorinated biphenyls (PCB) and dichlorodiphenyltrichloroethane (DDT)-poisoned rats.

To clarify the mechanism of lipid peroxide formation in polychlorinated biphenyls (PCB)-poisoned rats, the following two experiments were carried out. Experiment No. 1: Rats were separated into three groups. Group 1 was fed a normal diet, group 2 was fed a PCB-supplemented diet, and group 3 was fed a dichlorodiphenyltrichloroethane (DDT)-supplemented diet. After 5 months, the rats were killed. The thiobarbituric acid (TBA) values in livers of the PCB- and DDT-exposed rats had increased. The activity of catalase was increased in the PCB-fed rats but decreased after the administered of DDT. The glutathione peroxidase activity was decreased only in the PCB-administered rats. These results indicate that PCB and DDT have some effects to enhance lipid oxidation. It is probable that the decrease in glutathione peroxidase is the major reason for the increase of lipid oxidation in PCB-poisoned rats. The mechanism of lipid peroxidate production in DDT-poisoned rats could be different from the case of PCB poisoning. Experiment No. 2: Rats were separated into two groups. To one group, normal diet was given and to the other group PCB-supplemented diet was given. After 1 month, the rats were killed. In PCB-exposed rats, activities of glutathione reductase and glutathione S-transferase were increased. The increase in glutathione reductase and glutathione S-transferase were increased. The increase in glutathione reductase could be a compensation for a decrease in glutathione peroxidase. It is probable that PCB is metabolized to make glutathione conjugates by the action of glutathione S-transferase.

Animals↗
PubMed1984

Cross-bridge movements during a slow length change of active muscle.

Tension changes caused by slow stretch or release of actively contracting muscle are accompanied by axial displacements of myosin heads (i.e., cross-bridges) from the positions characteristic of isometric contraction. The direction of the axial displacement appears to affect the rate of cross-bridge detachment or reattachment during muscle-length changes.

Animals↗
PubMed1984

Combined use of integrated electromyography and score rating method for evaluation and prognosis of facial paralysis.

Degrees of peripheral facial paralysis were assessed by the paralysis score table in a modification of May's method together with the integrated EMG method. Paralysis scores and integrated EMGs from the frontal, orbicularis oculi and orbicularis oris muscles were obtained from 68 patients with facial paralysis. A linear regression analysis was tried in the cases of complete recovery with the following equation: Y = B log X + A, where Y = percentage of paralysis score or integrated EMG, B = recovery rate, A = constant and X = days after onset. The correlation coefficient of paralysis score and the days expressed in logarithmic form was 0.979. The paralysis scores obtained showed good correlation (0.933-0.941) with the value of the integrated EMG. The paralysis score for facial paralysis was thus confirmed by the objective EMG method. Recovery process from facial paralysis can be analysed numerically by the application of linear regression analysis in both methods.

Electromyography↗
PubMed1983

Prenatal maturation of endocochlear potential and electrolyte composition of inner ear fluids in guinea pigs.

The maturation of the endocochlear potential (EP) and the inner ear fluid ionic composition were studied in fetal and neonate guinea pigs. The concentration of sodium and potassium in endolymph and perilymph approximated adult values more than 2 weeks before birth. Endolymph had acquired its specific ionic composition before the onset of cochlear microphonics (52-55 gestation days, results of other authors). Positive EP was recorded starting on day 62 of gestation. The EP rose fast to reach near adult level at birth. It is speculated that the negative EP recorded after the onset of cochlear microphonics was an artifact, probably a result of fetal hypoxia. The significance of the negative EP recorded before the onset of the cochlear microphonics is discussed in relation to the source of the anoxic negative EP in the adult animal.

Animals↗
PubMed1982

The state of cardiac contractile proteins during the diastolic phase.

The molecular events underlying contraction and relaxation of heart muscle were studied by the X-ray diffraction method. In quiescent heart muscle most myosin heads were in the vicinity of the thick filaments. When heart muscle contracted, myosin heads moved to the vicinity of the thin filaments to react with actin. On relaxation of muscle, myosin heads returned to the thick filaments. However, in cyclically contracting heart muscle a significant fraction of myosin heads remained in the vicinity of the thin filaments until the end of the diastolic phase. Therefore, the molecular state during the diastolic phase was considerably different from that in the quiescent state. Paired-pulse stimulation, which enhanced the tension development, increased the number of myosin heads near the thin filaments not only during the systolic phase but also during the diastolic phase. Thus the diastolic molecular state was modified by inotropic intervention. These findings suggest that the diastolic phase should be regarded as a dynamic phase rather than a static phase.

Animals↗
PubMed1981

Effects of glycerol on sodium and potassium concentrations in guinea pig perilymph.

Serum, cerebrospinal fluid (CSF), scala vestibuli perilymph, and scala tympani perilymph were collected from 85 normal guinea pigs both before and after i.v. administration of glycerol (1 ml/kg), and the sodium and potassium concentrations were assessed using a microflame photometer. Marked increases in sodium concentrations were observed in scala tympani perilymph and CSF, while there was a slight decrease in the serum and there was no significant change in scala vestibuli perilymph. These increases in sodium concentrations are considered to occur in the dehydration process in the body fluids mentioned above. On the other hand, increase in the potassium concentrations was found only in scala vestibuli perilymph and thus cannot be explained by simple dehydration process. This potassium elevation in scala vestibuli perilymph should be understood by further experiment on endolymph. It became evident that scala vestibuli perilymph differs from scala tympani perilymph and CSF in the dynamics of electrolytes after glycerol administration. In this regard, the nature of the scala vestibuli as fluid space should be studied in future. The above findings obtained in the present study may imply the significance in elucidating the glycerol effect on hearing of endolymphatic hydrops case.

Animals↗
PubMed1981

Changes of thick filament structure during contraction of frog striated muscle.

The strongest myosin-related features in the low-angle axial x-ray diffraction pattern of resting frog sartorius muscle are the meridional reflections corresponding to axial spacings of 21.4 and 14.3 nm, and the first layer line, at a spacing 42.9 nm. During tetanus the intensities of the first layer line and the 21.4-nm meridional decrease by 62 and 80% respectively, but, when the muscle is fresh, the 14.3-nm meridional intensity rises by 13%, although it shows a decrease when the muscle is fatigued. The large change in the intensity of the 21.4-nm meridional reflection suggests that the projected myosin cross-bridge density onto the thick filament axis changes during contraction. The model proposed by Bennett (Ph.D. Thesis, University of London, 1977) in which successive cross-bridge levels are at 0,3/8, and 5/8 of the 42.9-nm axial repeat in the resting muscle, passing to 0, 1/3, and 2/3 in the contracting state, can explain why the 21.4-nm reflection decreases in intensity while the 14.3-nm increases when the muscle is activated. The model predicts a rather larger increase of the 14.3-nm reflection intensity during contraction than that observed, but the discrepancy may be removed if a small change of shape or tilt of the cross-bridges relative to the thick filament axis is introduced. The decrease of the intensity of the first layer line indicates that the cross-bridges become disordered in the plane perpendicular to the filament axis.

Animals↗
PubMed1981

Biochemical and biophysical behaviors of plasma albumin. II. Comparison of plasma albumin from normal subjects and nephrotic patients.

Biochemical and biophysical analyses were made to study the properties of serum albumin from nephrotic patients of two types, remissive stage and relapsed state, and the results were compared with those in normal subjects. Two different ion exchange columns were prepared to isolate and purify each albumin sample and the materials eluted through the two columns were identified. The nephrotic elution materials, especially in the state of relapse, were of some difference from those of normal subjects. alpha-Helix contents estimated by circular dichroism spectra were found to be closer to normal albumin in remissive state than in the state of relapse. The binding of fluorescent probe, 1-anilino-8-naphthalene sulfonate, to albumin was examined by calculating the binding parameter, the dissociation constant and number of binding sites. The binding parameters were closer to those of normal albumin in remissive stage than the state of relapse.

Adolescent↗
PubMed1981

Metabolic detoxication of bis-(2-hydroxy-3, 5-dichlorophenyl)-sulfoxide in man.

The metabolic detoxication of bis(2-hydroxy-3, 5-dichlorophenyl)sulfoxide (BTS) in man was investigated. Bis(2-hydroxy-3, 5-dichlorophenyl)sulfide (BT) was identified in beta-glucuronidase treated urine following the administration of BTS by thin-layer chromatography, gas chromatography, ultraviolet spectrum and quantitative analysis. No other metabolites were detectable. BT-glucuronide was also identified in urine. It was assumed that BTS was reduced to BT and successively conjugated with glucuronide in man, and excreted as BT-glucuronide in the urine.

Antiplatyhelmintic Agents↗