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Biomedical subjects

I Yamazaki

Publications and source records attributed to I Yamazaki.

At least 91 records · Page 5Linked to original sources
PubMed1989

Resonance Raman characterization of hog thyroid peroxidase. An SERRS study.

Resonance Raman (RR) spectra of hog thyroid peroxidase (TPO) were observed for the first time and compared with those of lactoperoxidase (LPO) and horseradish peroxidase (HRP). Since TPO purified by monoclonal antibody-assisted immunoaffinity chromatography was strongly fluorescent, the surface enhancement technique using Ag colloid adsorption was used for the oxidized form, but ordinary RR spectra could be obtained for the reduced form. The RR spectra of TPO were distinct from those of HRP in both the oxidized and reduced states and indicated the presence of six-coordinated iron-protoporphyrin.

Animals↗
PubMed1989

Primary photoprocesses of phytochrome. Picosecond fluorescence kinetics of oat and pea phytochromes.

The primary photoprocesses of etiolated oat and pea phytochromes (Pr forms) are diffusion-modulated by the microscopic viscosity within the chromophore pocket. The chromophore pocket is preferentially accessible to glycerol but not to Ficoll. Glycerol preferentially retarded the rate (rate constant ca. 1-2 X 10(10) s-1) of the initial reaction from the Qy excited state of phytochrome, whereas it increased the long fluorescence lifetime (nanosecond) component that can be attributed to either an emitting intermediate or to modified/conformationally heterogeneous phytochrome populations. The picosecond time-resolved fluorescence spectra of different phytochrome preparations (i.e., full-length vs 6/10-kDa NH2-terminus truncated forms of phytochromes from monocot and dicot plants) revealed no significant differences. The spectra in the picosecond time scale showed no spectral shifts, but at longer time scales of up to approximately 1.90 ns, significant blue spectral shifts were observed. The shifts were more in the truncated than in the full-length pea phytochrome. Comparison of the fluorescence decay data and the picosecond time-resolved fluorescence spectra suggests differences in conformational flexibility/heterogeneity among the preparations of the monocot vs dicot phytochromes and the full-length native vs the amino terminus truncated phytochromes.

Kinetics↗
PubMed1989

Characteristics of an ovariectomized osteopenic rat model.

Although osteoporosis induced by ovariectomy (Ovx) in the rat has been widely used as a model for postmenopausal osteoporosis in humans, the findings of different investigators are not always consistent. This might be mainly due to differences in the age of the animals at Ovx, time after Ovx, and the variables measured. Therefore, in the present study, Ovx was performed at 4, 10, or 52 weeks and bone changes were observed in rats for 6 months. The effects of Ovx on body weight, femoral length, and femoral volume were marked in rats operated on at the age of 4 weeks, slight in rats operated on at the age of 52 weeks, and intermediate in rats operated on at the age of 10 weeks. A reduction in the ratio of cortical thickness to bone width at the midshaft of the femur was observed only in rats ovariectomized at 52 weeks of age. The specific gravity of the femur and the density of the metaphysis of the femur decreased after Ovx in all rats. The ratio of ash weight to dry weight of the femur, a measure of the normal calcification of bone, was unchanged shortly after Ovx but gradually decreased in all rats.

Absorptiometry, Photon↗
PubMed1989

Electron spin resonance spectrum of Tyr-151 free radical formed in reactions of sperm whale metmyoglobin with ethyl hydroperoxide and potassium irridate.

A five-line ESR spectrum was observed at room temperature in reactions of sperm whale metmyoglobin with ethyl hydroperoxide (EtOOH) at pH 9.5 and with potassium irridate at pH's 7.0 and 9.5. A spectrum with the same g value and hyperfine splitting constant appeared in a reaction of sperm whale apomyoglobin with potassium irridate and was assigned to a tyrosyl radical on the basis of optical spectrum data obtained under the same reaction conditions. It was concluded that this radical arose from Tyr-151 for the following reasons. (i) This ESR spectrum could not be observed in the reaction of horse heart metmyoglobin, which lacks Tyr-151. (ii) Sperm whale metmyoglobin no longer gave this spectrum when treated with tetranitromethane (TNM) under conditions in which approximately one tyrosine is lost in sperm whale metmyoglobin but none is lost in horse heart metmyoglobin. (iii) A complex ESR spectrum observed in the reaction of sperm whale metmyoglobin with EtOOH at neutral pH was found to be a mixture of this five-line spectrum and one arising from an unidentified free radical formed in the reaction of horse heart metmyoglobin with EtOOH. The TNM-treated sperm whale metmyoglobin gave the same ESR spectrum as that observed in the reaction of horse heart metmyoglobin with EtOOH.

Animals↗
PubMed1989

Temperature-induced changes in the coenzyme environment of D-amino acid oxidase revealed by the multiple decays of FAD fluorescence.

A temperature-dependent change in the microenvironment of the coenzyme, FAD, of D-amino acid oxidase was investigated by means of steady-state and picosecond time-resolved fluorescence spectroscopy. Relative emission quantum yields from FAD bound to D-amino acid oxidase revealed the temperature transition when concentration of the enzyme was lowered. The observed fluorescence decay curves were well described with four-exponential decay functions. The amplitude of the shortest lifetime (tau 0), approximately 25 ps, was always negative, which indicates that the fluorescence of D-amino acid oxidase at approximately 520 nm appears after a metastable state of the excited isoalloxazine decays. The other components with positive amplitudes were assigned to dimer or associated forms of the enzyme, monomer, and free FAD dissociated from the enzyme. Ethalpy and entropy changes of intermediate states in the quenching processes were evaluated according to the absolute rate theory. The temperature transition was much more pronounced in the monomer than in the dimer or associated forms of the enzyme.

Animals↗
PubMed1989

Primary fibrosarcoma of the liver. Immunohistochemical and electron microscopic studies.

An autopsy case of primary fibrosarcoma occurring in the liver of a 75-year-old female is presented. The tumor, arising from the lateral upper portion of the right lobe, measured 14 cm in greatest dimension. Light microscopy of the tumor revealed homogeneous, spindle-shaped cells with abundant collagen fibers showing a classic herring-bone pattern. Immunoreactive vimentin was found in the tumor cells. Electron microscopically, the tumor cells were rich in rough endoplasmic reticulum without a basement membrane, and were surrounded by large amounts of collagen fibers. The fibroblastic character of the tumor cells was suggested by light and electron microscopy. This may be the first reported case of primary hepatic fibrosarcoma examined by immunohistochemistry and electron microscopy.

Aged↗
PubMed1988

Molecular mechanism of iodide transport by thyroid plasmalemmal vesicles: cooperative sodium activation and asymmetrical affinities for the ions on the outside and inside of the vesicles.

The 125I- uptake by plasmalemmal vesicles from porcine thyroid was measured by a Millipore filtration method using 2 mM ClO4- as a reaction stopper. Effective uptake occurred in the presence of high concentrations of extravesicular Na+ (Na+o). In the presence of Na-ionophores such as monensin and nigericin, no uptake was observed and the accumulated I- was released. The initial rate of I- uptake increased with the concentration of extravesicular I- (I-o) according to simple saturation kinetics and [I-o] giving a half-maximum rate of about 5 microM. The dependence of the rate on [Na+o] showed cooperativity with a Hill coefficient of 1.8, and a KNa value of 0.0064 M2, suggesting that the binding of at least 2 Na+ ions to a carrier molecule was required to transport an I- ion. Further kinetic data were consistent with a mechanism in which bindings of the ions were rapid and the Na+ binding occurred prior to the I- binding. Intravesicular Na+ inhibited the I- uptake and the inhibition constant (KiNa) was about 4 mM, independently of [I-o] and [Na+o]. Intravesicular I- inhibited the I- uptake with an apparent KiI value of about 100 microM. The results suggest that the differences in the Na+- and I- -binding modes between outside and inside of the vesicles are important factors causing the I- uptake against its concentration gradient.

Animals↗
PubMed1987

The mechanism of oxyperoxidase formation from ferryl peroxidase and hydrogen peroxide.

Formation of oxyperoxidase from the reaction of ferryl horseradish peroxidase with H2O2 is inhibited by a small amount of tetranitromethane (TNM), a powerful scavenger of superoxide anion radical. The inhibition by TNM, however, does not exceed 35% as the TNM concentration is increased above 5 microM. The stoichiometry of the reaction in the presence of TNM suggests the following equation for TNM-sensitive formation of oxyperoxidase. Ferryl peroxidase + H2O2----(ferric peroxidase + O2- + H+)----oxyperoxidase The kinetic study on the TNM-resistant formation of oxyperoxidase suggests that the displacement of the oxygen with H2O2 takes place at the sixth coordination position at maximal rates of 0.048 and 0.054 s-1 for peroxidases A and C, respectively, at 5 degrees C. The TNM-sensitive and -resistant reactions are concluded to occur in parallel, and both yield oxyperoxidase. In either mechanism, the protonated form of ferryl peroxidase is active and the pK alpha value is 7.1 for peroxidase A and 8.6 for peroxidase C. Oxyperoxidase decomposes spontaneously with a large activation energy (23.0 kcal/mol), and the reaction of ferryl peroxidase with H2O2 reaches a steady level of oxyperoxidase, which depends on pH and the concentration of H2O2.

Ferric Compounds↗
PubMed1987

Free radical mechanisms in enzyme reactions.

Free radicals are formed in prosthetic groups or amino acid residues of certain enzymes. These free radicals are closely related to the activation process in enzyme catalysis, but their formation does not always result in the formation of substrate free radicals as a product of the enzyme reaction. The role of free radicals in enzyme catalysis is discussed.

Animals↗
PubMed1987

Electron spin resonance spectra of free radicals formed in the reaction of metmyoglobins with ethylhydroperoxide.

Free radicals of myoglobins were measured at room temperature with an ESR spectrometer equipped with a flow apparatus. When horse heart MetMb was mixed with an equimolar amount of ethyl hydroperoxide (EtOOH), a well resolved ESR spectrum with 6 lines and a shoulder was observed. It reached a maximum in a few seconds and decayed with a half-life of about 10 s when the final concentrations of MetMb and EtOOH were 200 microM. This decay rate was the same at a MetMb concentration of 50 microM. The maximum molar radical concentration amounted to about half of the total myoglobin. In the case of sperm whale myoglobin, a similar 6-line spectrum reached a maximum in 1 s and decayed with a half-life of a few seconds. In this case, however, a small and poorly resolved doublet spectrum remained, the half-life of which was about 8 min. An effect of O2 on the signal decay was evident for horse heart myoglobin, but not for sperm whale myoglobin.

Animals↗
PubMed1987

The effect of polymerization of horseradish peroxidase on the peroxidase activity in the presence of excess H2O2: a background for a homogeneous enzyme immunoassay.

The phenol oxidation catalyzed by horseradish peroxidase (HRP) is slowed down by the presence of excess H2O2. This inhibition is due to accumulation of Compound III, which is a catalytically sluggish form of HRP. When HRP is polymerized through covalent bonds, Compound III becomes unstable and the peroxidase activity is less sensitive to excess H2O2. Under suitable experimental conditions, the phenol oxidation is increased by about 20-fold upon polymerization of the enzyme. This fact represents the principle of a homogeneous enzyme immunoassay reported by Hoshino et al. (J. Biochem. 97, 113-118 (1985)). The ratio of the peroxidase activities of monomeric and polymerized HRPs is 1 : 4 when phenol is replaced by resorcinol, and the difference is no larger when guaiacol and catechol are used as electron donors.

Horseradish Peroxidase↗
PubMed1987

Effect of ipriflavone on accessory sexual organs and bone metabolism in male rats.

Ipriflavone administered for 10 days to orchiectomized rats did not show androgenic or androgen-augmenting activities. The wet weight of the accessory sexual organs, and dry weight, ash content and calcium content of the femur were decreased by orchiectomy and were restored by androgen administration, but were not influenced by ipriflavone administered alone or in combination with androgen for 21 days. In intact rats, ipriflavone increased these variables slightly or definitely. Basal and calcium-stimulated calcitonin levels in orchiectomized rats were not influenced by pretreatment with estrone (0.25, 0.5 and 1 microgram/kg body weight/day) or ipriflavone (100 mg/kg body weight/day) for 42 days but were increased significantly by simultaneous pretreatment with these compounds. Therefore, it might be concluded that the increase in bone variables in intact rats that received ipriflavone resulted, at least in part, from the augmentation by ipriflavone of estrogen, which exists in the peripheral blood of male rats, in addition to intrinsic androgen, which maintains bone mineral content.

Animals↗