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Biomedical subjects

H Mizukami

Publications and source records attributed to H Mizukami.

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

Spectral studies of the Ca2+-dependent interaction of trifluoperazine with S100b.

S100b is a calcium-binding protein that will bind to many calmodulin target molecules in a Ca2+-dependent manner. In order to study the Ca2+-dependent binding properties of S100b, its interaction with a calmodulin antagonist, trifluoperazine (TFP), was investigated using [19F]- and [1H]-NMR and UV-difference spectroscopy. It was estimated from [19F]-NMR that in the absence of Ca2+, the k1/2 value of TFP was 130 microM, while its k1/2 value decreased to 28 microM in the presence of Ca2+. The addition of KCl was not antagonistic to the Ca2+-dependent interaction of TFP to S100b. The chemical exchange rate of TFP with Ca2+-bound S100b was estimated to be 9 x 10(2) sec-1. By comparison with TFP-calmodulin exchange rates, it is suggested that the TFP-binding site on S100b is structurally different from its binding sites on calmodulin. Proton NMR resonance broadening in the range 6.8-7.2 ppm, corresponding to phenylalanine nuclei of S100b, indicates that these residues may be involved in TFP binding. Addition of Ca2+ to a 1:1 mixture of S100b and TFP resulted in a red-shifted UV-difference spectrum, while no significant difference spectrum was detected when Mg2+ was added to a S100b-TFP solution. Thus, we suggest that Ca2+ induces the exposure of a hydrophobic domain on S100b containing one or more phenylalanine residues that will bind TFP but that this domain is different from the hydrophobic domain on calmodulin.

Calcium-Binding Proteins↗
PubMed1989

[Recording of the temperature distribution on a bed and its application to the assessment of body movement].

In order to assess body movements during sleep, a system which records the temperature on a bed was developed. The system consists of 16 temperature sensors and a data logger with a memory card (RAM card). The 15 temperature sensors were arranged in line with a separation of 6 cm on a flat cable which was placed between the bed sheet and the mattress in such a manner that it crossed the bed at the level of the breast. 15 temperatures on the bed and the room temperature were stored in a RAM card at interval from 30 seconds to 30 minutes. The memory card can store 504 successive data. The stored data were transferred into a micro computer. It was shown that posture changes and the body movements during sleep, could be recognised from the changes in the temperature profile, and these changes were well visualized by a three-dimensional display of the successive temperature profile on the bed.

Body Temperature↗
PubMed1989

[Management of pacemaker patients by bathtub ECG].

We evaluated the efficacy of a new method for recording electrocardiogram (ECG) of pacemaker patients in bathtub (bathtub ECG). ECG from the pacemaker implanted patients in the bathtub with tap water was recorded through three silver/silver chloride electrodes (4 x 4 cm) fitted on the inside wall of bathtub. Electric signal was connected to the isolated amplifier and recorded on the strip chart recorder. Contrast to the conventional method for recording standard ECG, bathtub ECG does not require body surface electrodes and is recorded at patients home. Although the amplitude of bathtub ECG was reduced approximately to a quarter of standard ECG, cardiac arrhythmia can be easily interpreted by bathtub ECG. In patients with pacemaker system, the amplitude of the pacing pulse recorded by bathtub ECG was much larger than that of QRS complex recorded by standard ECG. Therefore, we conclude that bathtub ECG would be a suitable method to follow up patients with pacemaker system.

Baths↗
PubMed1989

[Sex difference in alcoholic liver disease: with special reference to the severity of alcoholic hepatitis].

Purpose of this study was to elucidate the difference in severity of alcoholic liver diseases (ALD), especially of alcoholic hepatitis (AH) between female and male. We have experienced 15 female and 113 male patients with ALD laparoscopically and histologically proved during the past 10 years. In female patients, histological analysis revealed 8 cases of cirrhosis, 2 each cases of AH, fibrosis and chronic hepatitis, and 1 case of fatty liver. Occurrence of AH in female (13%) was significantly higher than male in which AH was seen in 3 cases (3%) (p less than 0.05). Duration of alcoholic abuse in female AH patients was shorter than male AH patients (5.5 +/- 0.5 years vs 24.0 +/- 2.9 years). Total alcohol consumed in female AH patients was less than male AH patients (256 +/- 52 kg vs 1560 +/- 703 kg). Abnormality in liver function tests including hepaplastin test, serum bilirubin, transaminases, lactate dehydrogenase, alkaline phosphatase, gamma-glutamyltranspeptidase, immunoglobulins was outstanding in female patients compared with male patients. Histological findings such as hepatocellular ballooning, neutrophilic infiltration, fatty change and wiremesh fibrosis were intensive in female patients compared with male patients. In conclusion, there were much more severe ALD like AH or cirrhosis in female than male patients. In female AH patients duration of alcoholic abuse was shorter and total alcohol consumed was less than male AH patients. And it was suggested that female AH is clinically and pathologically getting severe compared with male AH.

Adult↗
PubMed1987

Reaction of nitric oxide with heme proteins and model compounds of hemoglobin.

Rates for the reaction of nitric oxide with several ferric heme proteins and model compounds have been measured. The NO combination rates are markedly affected by the presence or absence of distal histidine. Elephant myoglobin in which the E7 distal histidine has been replaced by glutamine reacts with NO 500-1000 times faster than do the native hemoglobins or myoglobins. By contrast, there is no difference in the CO combination rate constants of sperm whale and elephant myoglobins. Studies on ferric model compounds for the R and T states of hemoglobin indicate that their NO combination rate constants are similar to those observed for the combination of CO with the corresponding ferro derivatives. The last observation suggests that the presence of an axial water molecule at the ligand binding site of ferric hemoglobin A prevents it from exhibiting significant cooperativity in its reactions with NO.

Animals↗
PubMed1986

The cobalt-nitrosyl stretching vibration as a sensitive resonance Raman probe for distal histidine-nitrosyl interaction in monomeric hemoglobins.

The Co-NO stretching vibration has been assigned in the resonance Raman spectra of various cobalt-substituted monomeric hemoglobins by employing isotope-labeling of nitrosyl (14N16O, 15N16O, 14N18O). Monomeric hemoglobins with a distal histidine (sperm whale myoglobin and leghemoglobin) exhibit this vibration at 573-575 cm-1, whereas hemoglobins without distal histidine (elephant myoglobin and insect hemoglobin from Chironomus thummi thummi, CTT III) show this vibration in the range of 553-558 cm-1. The Fe-NO stretching vibration which occurs in the range of 554-556 cm-1 does not reflect the distal histidine-ligand interaction. Therefore, the Co-NO moiety which is isoelectronic with the Fe-O2 moiety is a good monitor for distal effects on the exogenous ligand of hemoglobins, especially due to the fact that in hemoglobins with distal histidine the Fe-O2 stretching vibration (567-572 cm-1) is similar to the Co-NO stretching vibration.

Animals↗
PubMed1986

The effect of erythrocyte membrane on the birefringence formation of sickle cell hemoglobin.

The birefringence formation of sickle cell hemoglobin (HbS) in a thin liquid layer was observed while its environment was deoxygenated at different rates, and the effect of membrane was examined. Under slow rate of deoxygenation at 37 degrees C, at pH 7.4, the birefringence of purified HbS appeared at a concentration higher than 24% and its relative magnitude increased as the concentration was increased. Similarly, the partial pressure of oxygen, at which the birefringence formation was evident, increased from 0 to 27 torr as the concentration of HbS was increased from 24 to 28%, but it remained the same above this protein concentration. In all the samples tested relative birefringence was largest at the slow rate of deoxygenation (30 torrO2/min) and the magnitude decreased as the rate of deoxygenation was increased. The samples showed different sensitivity to the rate of deoxygenation. For example, while the total untreated hemolysate made by freeze-thawing of packed sickle cells was most resistant to the increased rates of deoxygenation, purified HbS was not. Washed open ghosts partially restored the birefringence formation pattern of purified HbS. The results indicate that the inner surface of the membranes of erythrocytes could behave as a template for large HbS polymer formation at relatively higher rates of deoxygenation.

Erythrocyte Membrane↗
PubMed1986

Severe jaundice in malignant lymphoma. Report of two autopsy cases.

Two autopsy cases of malignant lymphoma with marked hyperbilirubinemia (18.6 and 36.5 mg/dl at maximum) are presented. Histology revealed the portal area to be enlarged due to lymphoma cell infiltration and cholestasis in the hepatic lobules in both. Of 30 cases of malignant lymphoma treated in our department, hyperbilirubinemia was seen in 7 cases (23%) including these two cases (6.7%) which were severely jaundiced. The occurrence rate of jaundice in malignant lymphoma to all jaundiced diseases showing serum total bilirubin levels of more than 5 mg/dl was 0.7%.

Adult↗
PubMed1985

Resonance Raman studies of CO and O2 binding to elephant myoglobin (distal His(E7)----Gln).

Carbon monoxide and dioxygen were employed as resonance Raman-visible ligands for probing the nature of the heme-binding site in elephant myoglobin, which has glutamine in the distal position (E7) instead of the usual histidine. The distal histidine (E7) residue has been thought to be responsible for weakening carbon monoxide binding to hemoproteins. It is of interest to see how the His(E7)----Gln replacement affects such parameters as nu(Fe-N epsilon), nu(Fe-CO), delta(Fe-C-O), nu(C-O), delta(Fe-O-O), and nu(O-O) vibrational frequencies and relative intensities. Elephant myoglobin has a CO affinity approximately 6 times higher than that for human/sperm whale myoglobin (Mb). If this enhanced affinity were solely due to the removal of some of the steric hindrance that normally tilts the CO off the heme axis, one would expect the nu(Fe-CO) frequency to decrease and the nu(C-O) frequency to increase relative to the corresponding values in sperm whale Mb. However, the opposite was found. In addition, strong enhancement of the Fe-C-O bending mode was observed. These results suggest that the Fe-C-O linkage remains distorted. In elephant Mb, new interactions resulting from the conformational change accompanying ligand binding may be responsible for the increased CO binding. Similar spectra were obtained for elephant and sperm whale oxymyoglobin. This suggests that the interactions of bound O2 are not markedly affected by the glutamine replacement.

Animals↗
PubMed1984

A 1H NMR comparison of the met-cyano complexes of elephant and sperm whale myoglobin. Assignment of labile proton resonances in the heme cavity and determination of the distal glutamine orientation from relaxation data.

The met-cyano complex of elephant myoglobin has been investigated by high field 1H NMR spectroscopy, with special emphasis on the use of exchangeable proton resonances in the heme cavity to obtain structural information on the distal glutamine. Analysis of the distance dependence of relaxation rates and the exchange behavior of the four hyperfine shifted labile proton resonances has led to the assignment of the proximal His-F8 ring and peptide NHs and the His-FG3 ring NH and the distal Gln-E7 amide NH. The similar hyperfine shift patterns for both the apparent heme resonances as well as the labile proton peaks of conserved resonances in elephant and sperm whale met-cyano myoglobins support very similar electronic/molecular structures for their heme cavities. The essentially identical dipolar shifts and dipolar relaxation times for the distal Gln-E7 side chain NH and the distal His-E7 ring NH in sperm whale myoglobin indicate that those labile protons occupy the same geometrical position relative to the iron and heme plane. This geometry is consistent with the distal residue hydrogen bonding to the coordinated ligand. The similar rates and identical mechanisms of exchange with bulk water of the labile protons for the three conserved residues in the elephant and sperm whale heme cavity indicate that the dynamic stability of the proximal side of the heme pocket is unaltered upon the substitution (His----Gln). The much slower exchange rate (by greater than 10(4] of the distal NH in elephant relative to sperm whale myoglobin supports the assignment of the resonance to the intrinsically less labile amide side chain.

Animals↗
PubMed1984

A proton NMR investigation of the influence of distal glutamine on structural and dynamic properties of elephant metmyoglobin.

The proton NMR spectra of metmyoglobin from the Asian elephant, which has the replacement of glutamine for the usual distal histidine, are reported and analyzed. In the low pH region, we detect two interconvertible forms of the met-aquo-protein whose relative stabilities are independent of pH, but depend strongly on both temperature and solvent isotope composition. As the pH is raised, both species convert to the met-hydroxy form, as found for other myoglobins. The temperature dependence of the heme methyl shifts for both acidic protein forms indicates essentially high spin character for the iron, and the mean heme methyl shifts are interpreted as indicating one form with a very slightly weaker, and the other with a significantly stronger, axial ligand field than for the unique sperm whale met-aquo-myoglobin. The thermodynamic data for the equilibrium between the two species are consistent with differences of one hydrogen bond between coordinated water and the distal glutamine. Models are proposed where one form of the protein has not only the glutamine carboxyl oxygen acting as a hydrogen-bond acceptor, but also the amine group. We conclude that a distal glutamine can act both as a stronger and as a weaker hydrogen-bond acceptor towards coordinated water than the usual distal histidine. The relative rates of conversion of the two met-aquo-myoglobin forms to MetMbOH is found to be consistent with the proposed structures for the two forms.

Animals↗
PubMed1983

Interaction of ligands with the distal glutamine in elephant myoglobin.

The effects of distal glutamine (E7) replacement in elephant myoglobin were studied by comparing the temperature-dependent nitrosyl electron spin resonance spectra, redox potentials, and the acid-alkaline equilibria of elephant and human myoglobins. For myoglobins containing a distal histidine, the nitrosyl ESR spectra do not exhibit superhyperfine splitting until near liquid helium temperatures (Yoshimura, T., Ozaki, T., Shintani, Y., and Watanabe, H. (1979) Arch. Biochem. Biophys. 193, 301-313). Studies presented here show that the ESR spectra of nitrosyl elephant myoglobin exhibit 9-line superhyperfine splitting well above liquid nitrogen temperatures, similar to the temperature profiles of isolated heme complexes (Morse, R.H. (1980) Fed. Proc. 39, 2006). It is concluded that the shift in the spectral equilibrium to higher temperature indicates a diminished interaction between NO and the distal position in elephant myoglobin. In addition, the redox potential of elephant myoglobin was found to be nearly 100 mV greater than that of human myoglobin, and the pKa of the acid-alkaline equilibrium (oxidized myoglobin) was 8.5, being 0.4 unit less than that of other vertebrate myoglobins. These different reactivities between elephant and human myoglobins are discussed based on the nature of charge interactions between polar ligands and distal glutamine and histidine.

Animals↗
PubMed1981

An exceptional amino acid replacement on the distal side of the iron atom in proboscidean myoglobin.

Amino acid sequence determination of elephant myoglobin revealed the presence of the unusual substitution E7 His leads to Gln. Stereochemical analyses suggest that the most suitable residue which can functionally substitute for His at this position in vertebrate globins is Gln. Physiochemical studies imply that the slower rate of autooxidation of elephant myoglobin is the result of this substitution which may confer some selective advantage on the species. Comparative sequence data of paenungulate myoglobins suggest that the His leads to Gln mutation probably occurred in an ancestor of Elephantinae.

Amino Acid Sequence↗
PubMed1979

Purification and properties of strictosidine synthetase (an enzyme condensing tryptamine and secologanin) from Catharanthus roseus cultured cells.

Strictosidine synthetase, which catalyzes the condensation of tryptamine with secologanin to form strictosidine (isovincoside), was purified 740-fold to homogeneity from cultured cells of Catharanthus roseus in 10% yield. The specific activity is 5.85 nkat/mg. The molecular weight as estimated by gel filtration is 38,000. The isoelectric point is 4.6. Apparent Km values for tryptamine and secologanin are 0.83 and 0.46 mM, respectively. The enzyme shows a broad pH optimum between 5.0 and 7.5. The product of the enzymic reaction is exclusively strictosidine, while no trace of its epimer vincoside can be detected. Sulfhydryl inhibitors have no effect on the enzyme. End products in the biosynthetic pathway of indole alkaloids such as ajmalicine, vindoline, and catharanthine do not inhibit the activity of strictosidine synthetase.

Carbon-Nitrogen Lyases↗