Biomedical subjects

I Yamazaki

Publications and source records attributed to I Yamazaki.

At least 55 records · Page 3Linked to original sources

PubMed1996

Comparison of thermal and guanidine hydrochloride denaturation behaviors of glucoamylase from the STA1 gene of Saccharomyces cerevisiae var. diastaticus.

To investigate the relationships between enzyme inactivation and conformational change, the effects of heat and guanidine hydrochloride (GnHC1) on the STA1 gene glucoamylase (STA1GA) of Saccharomyces cerevisiae var. diastaticus were examined by circular dichroism and fluorescence spectroscopies. A conformational change was observed in the thermal denaturation of STA1GA, while extensive enzyme inactivation occurred in GnHC1 denaturation before noticeable conformational change.

Circular Dichroism↗

PubMed1996

[Comparison between intermittent retrograde cold blood cardioplegia and retrograde crystalloid cardioplegia].

Intermittent retrograde cold blood cardioplegia was compared with retrograde crystalloid cardioplegia. Twenty-two adult patients underwent open heart surgery divided into two groups. Group BCP (n = 10) was protected with 15 degrees C blood containing potassium 15 mEq/l; Group CCP (n = 12) was protected with 4 degrees C St. Thomas' Hospital cardioplegic solution. Lactate, pyruvate, and CK-MB levels in coronary sinus blood were measured at 5 and 15 minutes after aortic unclamping and 5 minutes after weaning from cardiopulmonary bypass (CPB) in both groups. CPB time, cross-cross clamp time, incidence of postoperative low output syndrome and spontaneous return to sinus rhythm after aortic unclamping were not different between two groups. Cardiac index and pulmonary capillary wedge pressure measured immediately after weaning from CPB, were not different in both groups. Lactate level was significantly low in group BCP. Lactate uptaking ratio of myocardium was significantly high in group BCP. CK-MB levels were not different between two groups. Cold blood cardioplegia was seemed to provide better aerobic myocardial metabolism during aortic cross clamp. However, CK-MB levels and hemodynamic studies were not different.

Aged↗

PubMed1995

Veratryl alcohol oxidation by lignin peroxidase.

Lignin peroxidase (LiP) from the white rot fungus Phanerochaete chrysosporium catalyzes the H2O2-dependent oxidation of veratryl alcohol (VA), a secondary metabolite of the fungus, to veratryl aldehyde (VAD). The oxidation of VA does not seem to be simply one-electron oxidation by LiP compound I (LiPI) to its cation radical (VA.+) and the second by LiP compound II (LiPII) to VAD. Moreover, the rate constant for LiPI reduction by VA (3 x 10(5) M-1 s-1) is certainly sufficient, but the rate constant for LiPII reduction by VA (5.0 +/- 0.2 s-1) is insufficient to account for the turnover rate of LiP (8 +/- 0.4 s-1) at pH 4.5. Oxalate was found to decrease the turnover rate of LiP to 5 s-1, but it had no effect on the rate constants for LiP with H2O2 or LiPI and LiPII, the latter formed by reduction of LiPI with ferrocyanide, with VA. However, when LiPII was formed by reduction of LiPI with VA, an oxalate-sensitive burst phase was observed during its reduction with VA. This was explained by the presence of LiPII, formed by reduction of LiPI with VA, in two different states, one that reacted faster with VA than the other. Activity during the burst was sensitive to preincubation of LiPI with VA, decaying with a half-life of 0.54 s, and was possibly due to an unstable intermediate complex of VA.+ and LiPII. This was supported by an anomalous, oxalate-sensitive, LiPII visible absorption spectrum observed during steady state oxidation of VA. The first order rate constant for the burst phase was 8.3 +/- 0.2 s-1, fast enough to account for the steady state turnover rate of LiP at pH 4.5. Thus, it was concluded that oxalate decreased the turnover of LiP by reacting with VA.+ bound to LiPII. The VA.+ concentration measured by electron spin resonance spectroscopy (ESR) was 2.2 microM at steady state (10 microM LiP, 250 microM H2O2, and 2 mM VA) and increased to 8.9 microM when measured after the reaction was acid quenched. Therefore, we assumed the presence of two states of VA.+ bound to LiPII, one ESR-active and one ESR-silent. The ESR-silent species, which could be detected after acid quenching, would be responsible for the burst phase. Both of the VA.+ species disappeared in the presence of 5 mM oxalate. The ESR-active species reached a maximum (3.5 microM) at 0.5 mM VA under steady state. From these studies, a mechanism for VA oxidation by LiP is proposed in which a complex of LiPII and VA.+ reacts with an additional molecule of VA, leading to veratryl aldehyde formation.

Basidiomycota↗

PubMed1995

Formation of a porphyrin pi-cation radical in the fluoride complex of horseradish peroxidase.

Horseradish peroxidase (HRP) was oxidized by IrCl6(2-) to a mixture of compounds I and II, the rate of oxidation and the ratio of the mixture being greatly affected by pH (Hayashi & Yamazaki, 1979). Oxidation of HRP by IrCl6(2-) in the presence of fluoride was significantly accelerated. This resulted in the formation of a new compound which is a ferric fluoride complex containing a porphyrin pi-cation radical. The spectrum of the new compound showed a decreased absorption band in the Soret region and a broad band at 570 nm; which was converted to that of the original ferric fluoride complex by addition of ascorbate or hydroquinone. Addition of cyanide slowed down the oxidation of HRP by IrCl6(2-), and the oxidation product was the same as that obtained in the absence of cyanide. Compound I was formed when H2O2 was added to HRP in the presence of fluoride or cyanide. The one-electron reduction potential (Eo') of the oxidized HRP-fluoride complex was measured at several pH values, the Eo' value at pH 7 being 861 +/- 4 mV. The ratio of delta Eo' to delta pH was 49 mV/pH unit.

Ascorbic Acid↗

PubMed1995

Determination of rate constants for rapid peroxidase reactions.

We describe an improved enzyme-monitored stopped-flow method for determining rate constants for peroxidase reactions that are too rapid to measure by conventional pseudo-first-order methods. Ascorbate will reduce many substrate radicals as rapidly as they are generated by a peroxidase. This ensures a constant substrate concentration during the peroxidase reaction. We investigated the reactions of horseradish peroxidase compound I (HRP-I) with three standard substrates (chlorpromazine (CPZ), 2,2'-azino-bis[3-ethylbenzthiazoline-6-sulfonic acid] (ABTS), and p-methoxyphenol) in the presence and absence of ascorbate. The rate of reaction of CPZ with HRP-I is slow enough that it can be measured using pseudo-first-order conditions maintained by a minimum 10-fold excess of CPZ, or by the addition of ascorbate at very low CPZ concentrations. The same rate constant was obtained with either method. The rate of reaction of ABTS with HRP-I at lower pH (5.0-3.3) is rapid; consequently, we were unable to obtain rate constants using concentrations of ABTS which constitute pseudo-first-order conditions. However, using much lower ABTS concentrations with the addition of ascorbate, we obtained rate constants that ranged from 5 x 10(7) to 8 x 10(8) M-1 s-1. Hence, ascorbate provides a simplified way to maintain pseudo-first-order conditions for fast peroxidase reactions even at low substrate concentrations.

Ascorbic Acid↗

PubMed1995

X-ray absorption spectroscopy comparison of the active site structures of Phanerochaete chrysosporium lignin peroxidase isoenzymes H2, H3, H4, H5, H8, and H10.

The iron heme and its immediate environment can provide information that is pivotal to our understanding of the structural and mechanistic features that confer unusual properties to the heme peroxidases. X-ray absorption spectroscopy (XAS), which is ideally suited for the investigation of the local environment and electronic structure of the heme iron of hemeproteins, has been used to characterize a variety of lignin peroxidase and manganese-dependent peroxidase isoenzymes produced by the white rot fungus Phanerochaete chrysosporium. The data suggest no differences within the error in the first coordination shell of iron for the isoenzymes H2, H3, H4, H5, H8, and H10 examined in this study. The pyrrole nitrogens are at a distance of 2.05 +/- 0.015 A, and the proximal histidine nitrogens are at 1.93 +/- 0.02 A, while the sixth ligands are located at 2.17 +/- 0.03 A. Significant differences are observed in higher coordination shells which may be related to conformational differences in the heme.

Binding Sites↗

PubMed1995

Frequent development of pancreatic carcinomas in the Rana nigromaculata group.

In 1979, 2 species of pond frogs (Rana nigromaculata and Rana plancyi plancyi) were imported from China, and hybrids were made between these and Japanese, Korean, and Taiwanese pond frogs (R. nigromaculata, Rana plancyi fukienensis and Rana brevipoda) that had been kept for a number of years in the Laboratory for Amphibian Biology of Hiroshima University. From 1982, development of tumors, especially in the peritoneal cavity, was noticed frequently in the hybrids and also later, although rarely, in the Japanese pond frogs. Such tumors had never previously been observed among pond frogs in the laboratory. Histological and immunohistochemical studies identified the i.p. tumors to be pancreatic carcinomas with occasional production of insulin and/or somatostatin. Ultrastructural investigation revealed both endocrine and exocrine secretion granules together with C-type retrovirus particles in the carcinoma cells. Other tumors included a retroperitoneal rhabdomyosarcoma, liver adenomas, and an unclassifiable mesenchymal tumor of the foot pad.

Animals↗

PubMed1995

Initial spectroscopic characterization of the ciliate photoreceptor stentorin.

Stentorin serves as the primary photosensor in the single cell ciliate, Stentor coeruleus, for its photophobic and phototactic response to light of visible wavelengths. We separated two subunits, stentorin-2A and -2B, from the previous stentorin complex ('stentorin-2') of greater than half a million molecular mass isolated from the photoreceptor organelle (pigment granule). Stentorin-2B bears the chromophore covalently linked to an approx. 50 kDa apoprotein, as determined by SDS-urea-PAGE. Partial amino acid sequences were obtained from this 50 kDa subunit. Its visible and CD spectra were found to be similar to those of stentorin-2. The steady-state and time-resolved fluorescence spectra of stentorin-2B, in H2O and D2O buffers, were also similar to those of stentorin-2. This suggests that the 50 kDa subunit retains the spectral integrity and primary photoreactivity of the stentorin-complex. The picosecond time-resolved fluorescence study revealed that the short picosecond emission component (tau F approximately equal to 8-10 ps) was the predominant emitting species in stentorin-2B and -2, followed by longer decaying species. No deuterium solvent effect was seen in this fast-decaying species. The possible mechanism for the primary photoreaction appears to involve electron transfer coupled with proton transfer.

Amino Acids↗

PubMed1995

Decay studies of DMPO-spin adducts of free radicals produced by reactions of metmyoglobin and methemoglobin with hydrogen peroxide.

The 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin adduct of myoglobin (Mb) or hemoglobin (Hb) was formed when metmyoglobin (MetMb) or methemoglobin (MetHb) reacted with H2O2 in the presence of DMPO, and both decayed with half-life of a few minutes. The DMPO spin adduct of Mb decayed with biphasic kinetics with k1 = 0.645 min-1 and k2 = 0.012 min-1, indicating that the spin adduct consisted of two kinetically heterogeneous species, stable and unstable ones. The DPMO spin adduct of Hb, however, was homogeneous. Decay of both spin adducts was accelerated in the presence of tyrosine, tryptophan or cysteine, but not phenylalanine, methionine or histidine. The decay obeyed the first order kinetics at varying concentrations of the spin adducts. The decay was accelerated by denaturation and proteolysis of protein moiety. The decay rate was not affected by the extra addition of MetMb or MetHb to each spin adduct. The decay rate of the spin adduct of Mb was increased by hematin in the presence of H2O2 and decreased by catalase. Decay of stable spin adduct of Mb, however, was not significantly changed under any experimental conditions used. These results led us to conclude that instability of the DMPO-spin adducts of Mb and Hb is due to intramolecular redox reactions between the spin adducts and amino acid residues and/or products of the reaction between heme and H2O2.

Animals↗

PubMed1995

[Usefulness of allopurinol for prevention of myocardial reperfusion injury in open heart surgery].

Xanthine oxidase has been demonstrated to be an important factor in postischemic reperfusion injury. Allopurinol is the inhibitor of xanthine oxidase. In this study, we evaluated usefulness of allopurinol for prevention of myocardial reperfusion injury in open heart surgery. Twenty adult patients were divided into two groups; Ap-group (n = 10) were administered allopurinol for seven days just before operation and control-group (n = 10) were administered nothing. The dose of allopurinol was ranged 100-300 mg/day. The dose was determined according to renal function of patients. Coronary sinus blood hypoxanthine, xanthine, uric acid, lactate, pyruvate, CK, and CK-MB levels were measured at before CPB, 5 and 15 min. after aortic declamping, 5 min. after CPB. Hypoxanthine and xanthine levels in Ap-group were significantly higher than those in control-group at 5 and 15 min. after aortic declamping, 5 min. after CPB. Uric acid levels in Ap-group were significantly lower than those in control-group at 5 and 15 min. after aortic declamping, 5 min. after CPB. Lactate, pyruvate, CK, and CK-MB levels were not different between Ap-group and control group. We considered that allopurinol suppressed the reaction rate of xanthine oxidase. Therefore, the levels of intermediates, hypoxanthine and xanthine, were high and, the level of final product, uric acid was low in Ap-group. However, allopurinol had no efficacy for the level of lactate, pyruvate, CK, and CK-MB, in this study.

Aged↗

PubMed1994

Energy migration in allophycocyanin-B trimer with a linker polypeptide: analysis by the principal multi-component spectral estimation (PMSE) method.

Energy migration processes in allophycocyanin-B trimer with a linker polypeptide were analyzed using the principal multi-component spectral estimation (PMSE) method, which does not require assumption of component number, decay function, or the spectral band shape. We determined the number of spectral components showing independent kinetic behavior by the eigen-value of an auto-correlation matrix, and further the spectra of the components and their rise and decay curves. Two decay components were resolved at 20 degrees C: one corresponded to the decay of one type of beta-84 chromophore, and the other to the decay from the thermally equilibrated state between another type of beta-84 chromophore and the alpha-allophycocyanin B chromophore. An additional slow decay process was resolved at -196 degrees C. We also compared the component spectra obtained using the PMSE method with the decay-associated spectra obtained using the global analysis.

Cyanobacteria↗

PubMed1994

Oxidation-reduction properties of compounds I and II of Arthromyces ramosus peroxidase.

At neutral pH, compound I of Arthromyces ramosus peroxidase (ARP) was stable and was reduced to ferric ARP without apparent formation of compound II upon titration with ascorbate or hydroquinone. In the titration experiments, compound II was seen as an intermediate only at alkaline pH. However, measuring a difference spectrum in the Soret region by a stopped-flow method, we found that compound II was formed during the catalytic oxidation of ascorbate even at neutral pH. Using an EPR spectrometer with a microflow system, we measured the steady-state concentration of benzosemiquinone formed in the ARP-catalyzed oxidation of hydroquinone. The results clearly showed that ARP catalyzes the oxidation of hydroquinone by a one-electron-transfer mechanism, as does horseradish peroxidase. These observations led to the conclusion that compound I is reduced to compound II through a one-electron reduction by ascorbate or hydroquinone. Therefore, we concluded that ARP compound II is unusually unstable and is rapidly reduced to ferric enzyme without accumulation in the titration experiment. The unusual instability of ARP compound II is explained in terms of the high reduction potential of compound II. The reduction potentials (E0') of compounds I and II were measured at several pH values from redox equilibria with potassium hexachloroiridate on the basis of E0' = 0.90 V for the IrCL6(2)-IrCl6(3)- couple. These values were determined to be 0.915 and 0.982 V at pH 7, respectively, and decreased with increasing pH. This pH dependence was markedly changed by the buffer concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Ascorbic Acid↗

PubMed1994

Presence and significance of minor antenna components in the energy transfer sequence of the green photosynthetic bacterium Chloroflexus aurantiacus.

Antenna components in the energy transfer processes of a green photosynthetic bacterium Chloroflexus aurantiacus were spectrally investigated by time-resolved fluorescence spectroscopy at -196 degrees C on intact cells. Besides major antenna components so far reported, three minor components were resolved; those were Bchl c located at 785 nm, the baseplate Bchl a at 819 nm and Bchl a in the B808-866 complex at 910 nm. The last component was assigned to a longer wavelength antenna closely associated with a reaction center. An additional Bchl c fluorescence component was kinetically suggested to be present, which can be an energy donor to a major Bchl c. Presence of these minor components was signified in terms of (1) increase in the spectral overlap integral and (2) adjustment of the direction of dipole moments in the energy transfer sequence of intact cells.

Bacteria↗

PubMed1994

The effect of hemoglobin, hematin, and iron on neutrophil inactivation in superoxide generating systems.

When Escherichia coli was incubated with xanthine oxidase and acetaldehyde, the killing of E. coli was accelerated by iron-EDTA but inhibited by hematin or hemoglobin. On the other hand, when E. coli was incubated with human neutrophils in the presence of phorbol myristate acetate (PMA), all of these iron species at concentrations of a few micromolar accelerated the inactivation of neutrophils and in so doing protected the E. coli from being killed by the neutrophils. The inactivation of the neutrophils was accompanied by an increase in lipid peroxidation and by a decrease in viability measured with trypan blue. This inactivation was inhibited by scavengers such as deoxyribose, mannitol, or thiourea. Desferrioxamine B and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) both inhibited the inactivation mediated by iron-EDTA, but had no effect on the hematin- or hemoglobin-mediated inactivation. Vanadium (vanadyl ion), an effective Fenton reagent, behaved in the same way as iron-EDTA relative to the effects of DMPO on neutrophil inactivation. These results led us to conclude that neutrophils were inactivated during PMA stimulation by OH radicals in the presence of iron-EDTA and by some other oxidizing species when hematin or Hb is present. Ascorbate enhanced the inactivation of neutrophils mediated by these iron species. Catalase was very effective in inhibiting neutrophil inactivation. Superoxide dismutase was not as effective but the combination with catalase was most effective.

Adult↗

PubMed1994

[Diagnosis of gallbladder cancer by imaging techniques: problems, limitations and their explanations, especially with ss invasive cancer].

The preoperative diagnosis of less than ss depth gallbladder cancer is difficult. Its preoperative diagnosis rate was low (27.5%), and even lower with the presence of concomitant gallstone. In the latter case, the diagnosis rate was particularly low when the stones diameter was greater than 1 cm. Gallstones are frequently associated with macromorphologically invasive type of gallbladder cancer and this may be the reason for the lower diagnostic rate. We compared preoperative diagnosis rate of ultrasonography (US), computed tomography (CT) and drip infusion cholecystography (DIC) for each invasion depth. In US, the preoperative diagnosis rate for m depth invasion was 6/16 (37.5%), pm depth was 1/13 (7.7%), and ss depth was 14/41 (34.1%). In CT, its rate for m depth was 3/11 (27.3%), pm depth was 1/10 (10.0%), and ss depth was 11/37 (29.7%). In DIC, its rate for m depth was 3/11 (27.3%), pm depth was 1/10 (10.0%), and ss was depth 1/23 (4.3%). None of the currently used imaging techniques were very accurate in diagnosing gallbladder cancer. Thus, during preoperative work up, if one discovers a gallbladder full of stones, stones of greater than 1 cm in diameter, thickened gallbladder wall, or a non visualized gallbladder with DIC, gallbladder cancer must be highly suspected.

Cholecystography↗

PubMed1994

[A case of aortic and mitral regurgitation with two aneurysms in the mitral valve].

A 59-year-old male was found to have two aneurysms in the mitral valve, mitral regurgitation, and aortic regurgitation by the echocardiographic examination. The patient had a previous history of infectious endocarditis by streptococcus at the age of 24. Under the diagnosis of mitral aneurysms developed after infectious endocarditis, surgery was undertaken. A 5 x 8 mm sized perforation in the right coronary cusp and two aneurysms in the anterior mitral leaflet, 22 mm and 17 mm in size, were found intraoperatively. Both the mitral and aortic valves were replaced. Patients with a history of infectious endocarditis have to be followed up for a long period of time. Transesophageal echocardiogram is useful in those patients. Considering high prevalence of aortic valvular diseases in those with a mitral aneurysm after infectious endocarditis, aortic valves should be carefully evaluated.

Aneurysm, Infected↗

PubMed1993

Energy transfer processes in Rhodopseudomonas palustris grown under low-light conditions. Heterogeneous composition of LH 2 complexes and parallel energy flow pathways.

Excitation energy flow in the purple photosynthetic bacterium Rhodopseudomonas palustris grown under a low-light intensity was studied by time-resolved fluorescence spectroscopy in the ps time range. This bacterium synthesized the B824 component under this light condition. Time-resolved spectra at 20 degrees C indicated the sequential energy flow in the order of B803, B856, B882 and B900, long wavelength antenna. An emission from B803 was not observed. A remarkable feature was the emission from B824 throughout the measuring time. After the excitation pulse of 100 ps, the spectra did not change any further, indicating the establishment of an equilibrium among components. Based on the energy distribution after equilibrium, parallel energy transfer pathways to LH 1 were suggested; one including B824 integrated in the B803-824-856 complex, and the other, from the B803-856 complex to B882. The latter was the dominant energy flow pathway in this bacterium.

Bacterial Proteins↗

PubMed1993

Time-resolved fluorescence spectroscopy and photolysis of the photoreceptor blepharismin.

Blepharismin is the photoreceptor for the photophobic response in the ciliate Blepharisma japonicum (Scevoli, P., Bisi, F., Colombetti, G., Ghetti, F., Lenci, F., and Passarelli, V. (1987) J. Photochem. Photobiol.: B. Biol. 1, 75-84; Lenci, F., Ghetti, F., Gioffre, D., Heelis, P.F., Thomas, B., Phillips, G.O., and Song, P.-S. (1989) J. Photochem. Photobiol.: B. Biol. 3, 449-453). Blepharismin was solubilized from the red cells with 2% n-octylglucopyranoside. A crude pigment-protein preparation was then successively subjected to Bio-Gel A1.5 filtration, FPLC/hydroxyapatite and FPLC/DEAE ion-exchange chromatography. At least two spectrally distinct forms of blepharismin, with the respective absorbance maxima at 597 +/- 1 and 601 +/- 1 nm, were resolved. The steady state fluorescence emission maxima were at 602.5 and 617.5 nm, respectively. The fluorescence decay curves for these pigments were non-exponential. The major component possesses relatively short fluorescence lifetime (200-500 ps) for the former, according to a global analysis. This analysis suggests that the excited state of the shorter wavelength-absorbing form of blepharismin undergoes primary photoprocess faster than that of the free parental chromophore hypericin. Photolysis of blepharismin in solution yielded a irreversible product, accompanied by a 10-12 nm bathochromic shift of the absorbance maximum. However, the mechanistic nature of the time-resolved fluorescence and the photochemistry of blepharismin remains to be elucidated.

Animals↗