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Biomedical subjects

H Akutsu

Publications and source records attributed to H Akutsu.

At least 73 records · Page 4Linked to original sources
PubMed1995

Molecular miscibility of phosphatidylcholine and phosphatidylethanolamine in binary mixed bilayers with acidic phospholipids studied by 2H- and 31P-NMR.

The intermolecular interactions and microscopic miscibility of the lipid bilayers of single component and binary mixtures with high content of saturated fatty acids were investigated by 2H- and 31P-NMR for phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and cardiolipin (CL). Their glycerol backbones were selectively deuterated by biosynthesis and chemical synthesis. Deuterium quadrupole splittings and phosphorus chemical shift anisotropies provided the consistent information for the molecular miscibility of each phospholipids. PE was found to be completely miscible with PG and CL. Since deuterium quadrupole splittings and phosphorus chemical shift anisotropy are identical for two components in the mixed bilayer, the dynamic structure from the glycerol backbone to phosphate group should be uniform in the binary mixture of these phospholipids. In contrast to PE, PC was not fully miscible with PG and CL at molecular resolution. The dynamic structure from the glycerol backbone to phosphate group is different for two components in the binary mixed bilayers. In the case of the mixed bilayers of PC and PE, both phospholipids are microscopically immiscible with each other. Thus, while PE, PG and CL can adapt to a new situation to form a uniform dynamic structure in mixed bilayers, PC has no ability for adaptation. The molecular miscibility in lipid bilayers was shown to depend on the molecular species and the nature of the molecular interactions. The biological significance of this result was discussed.

Lipid Bilayers↗
PubMed1995

Microdomain formation in phosphatidylethanolamine bilayers detected by 2H-NMR.

In deuterium NMR spectra of phosphatidylethanolamine bilayers with an extremely high content of saturated fatty acids, each C1 deuteron of the glycerol backbone gave rise to a doublet [Yoshikawa et al., (1988) Biochim. Biophys. Acta 944, 321-328]. This suggests the presence of two backbone conformations, the exchange between which is slow on an NMR time-scale. The origin of the two conformations has been investigated in this work using saturated 1,2-diacyl-sn-glycero-3-phosphoethanolamine specifically deuterated in the glycerol backbone. The results showed that the two conformations originate from different domains, which have different fatty acid compositions. The differential scanning calorimetry of the bilayers suggested that the size of the domain is not large enough to show an independent phase transition. Thus, the formation of microdomains in the phosphatidylethanolamine bilayers has been concluded. Conformational difference in different domains was shown to be restricted to the C1 position of the glycerol backbone. The microdomains of phosphatidylethanolamine were retained even in the presence of other phospholipids.

Calorimetry, Differential Scanning↗
PubMed1995

Discrimination of compound gratings: spatial-frequency channels or local features?

Models based on spatial-frequency channels and local features provide alternative explanations for suprathreshold pattern discrimination. We compared psychophysical discrimination data with the predictions of the Wilson and Gelb channel model and three local-feature models. The features were peak-valley local contrast, peak-peak local contrast, and luminance gradients. We measured visual sensitivity for discriminating compound gratings (F + 3F or F + 5F, in peaks-add or peaks-subtract phases) whose component contrasts were yoked together so that a contrast increment in one component was accompanied by an equal decrement in the other. The Wilson and Gelb model accounted for the results with peaks-add gratings, but failed to predict those with peaks-subtract gratings. None of the local-feature models explained the results by themselves. Most of the data fell close to an envelope composed of the lowest thresholds of the three feature-detector models, although there were important exceptions. Our findings are consistent with the view that suprathreshold pattern discrimination is mediated by mechanisms responsive to spatially localized features and that more than one type of feature is used.

Computer Simulation↗
PubMed1995

Evaluation of serum KL-6 levels in patients with pulmonary tuberculosis.

SETTING: KL-6, a human MUC-1 mucin preferentially expressed on type II pneumocytes, is a sensitive serum marker for evaluating alveolar damage of interstitial pneumonia and pulmonary fibrosis. Some patients with pulmonary tuberculosis develop severe respiratory dysfunction caused by extensive pulmonary fibrosis, compensatory emphysema and fibrous pleural thickening. OBJECTIVE: To evaluate the clinico-pathological significance of KL-6 in pulmonary tuberculosis. DESIGN: Serum KL-6 levels were measured in sera from 57 patients with active pulmonary tuberculosis and 38 healthy controls by a sandwich-type enzyme-linked immunosorbent assay. Immunohistochemistry was performed by an avidin-biotin-peroxidase complex method. RESULTS: KL-6 levels were significantly higher in the patients than in the healthy controls (518 +/- 693 [SD] vs 227 +/- 91 U/ml, P < 0.001) and increased significantly according to the extent of pulmonary lesions evaluated by chest X-ray (P < 0.001). There was a significant negative correlation between serum KL-6 levels and % vital capacity (VC) (r = 0.642, P < 0.05). KL-6 was strongly expressed on proliferated type II pneumocytes and cuboidal epithelial cells adjacent to thickened intralobular septa and pleura. CONCLUSIONS: In pulmonary tuberculosis, serum KL-6 originates from proliferated type II pneumocytes and cuboidal epithelial cells, and is a useful marker presenting the degree and extent of pulmonary fibroproductive lesions.

Aged↗
PubMed1995

A gene encoding a cytochrome c oxidase-like protein is located closely to the cytochrome c-553 gene in the anaerobic bacterium, Desulfovibrio vulgaris (Miyazaki F).

The gene encoding cytochrome c-553 from Desulfovibrio vulgaris (Miyazaki F) was cloned using a synthetic oligodeoxyribonucleotide probe. The nucleotide sequence indicated that cytochrome c-553 was synthesized as a precursor protein with an NH2-terminal signal sequence of 23 residues. In the cloned DNA fragment, there are three other open reading frames whose products have 191, 157, 541 amino acid residues, respectively. The putative ORF-4 product is highly homologous with the cytochrome c oxidase subunit I from various organisms.

Amino Acid Sequence↗
PubMed1995

Structural analysis of 11C, 15N labeled adenosine by solid-state NMR.

Two-dimensional solid-state 13C homonuclear and 13C-15N heteronuclear NMR experiments for dipolar correlations between isotropic chemical shifts were performed for adenosine uniformly labeled with 13C and 15N. All the 13C and 15N signals were assigned from the dipolar couplings. In the mixing periods of the experiments, 13C-13C and 13C-15N dipolar interactions under magic angle spinning conditions were recovered by USEME and TEDOR pulses respectively, which are rf multipulse sequences applied synchronously with sample spinning. Dipolar mixing periods were set to times at which only spin pairs connected with direct covalent bonds give rise to cross peaks in the 2-D spectra. Thus, these high resolution spectra unveil a network of 13C and 15N spins connected with covalent bonds in solids. Structural information obtained for adenosine by the 2-D solid-state NMR will be discussed.

Adenosine↗
PubMed1994

Novel FMN-binding protein from Desulfovibrio vulgaris (Miyazaki F). Cloning and expression of its gene in Escherichia coli.

A gene encoding a novel FMN-binding protein from Desulfovibrio vulgaris (Miyazaki F) was cloned, and its expression system was constructed in Escherichia coli. The 1.4-kilobase pair DNA fragment isolated from D. vulgaris (Miyazaki F) by double digestion with KpnI and SmaI was found to express a protein binding FMN as a prosthetic group under control of the lac promoter in E. coli. This DNA fragment contained several putative open reading frames. The partial amino acid sequence of the polypeptide portion of the purified FMN-binding protein and its tryptic peptides were completely consistent with those deduced from the nucleotide sequence of the third open reading frame in the cloned SmaI-SmaI fragment of D. vulgaris (Miyazaki F) DNA, which may include promoter and regulatory sequences. The nucleotide sequence of FMN-binding protein indicated that the protein is composed of 122 amino acids including an initiator Met residue and lacks a signal peptide for secretion. The main redox potential of the FMN-binding protein was measured as -325 mV using direct current cyclic and differential pulse voltammetric techniques and an electroreflectance method, suggesting that this FMN-binding protein functions as a redox protein like other FMN-binding proteins. Immunoblot analysis of the whole proteins from D. vulgaris (Miyazaki F) clearly indicated that this protein is expressed in this bacteria. However, the protein was found to have a primary structure distinct from those of other FMN-binding proteins and to be the smallest FMN-binding protein yet reported.

Amino Acid Sequence↗
PubMed1994

A detailed comparison of the refined structures of cytochrome c3 molecules from two strains in Desulfovibrio vulgaris: the relationship between the heme structures and their redox properties.

The refined structures of the cytochrome c3 molecules from Desulfovibrio vulgaris Miyazaki and Hildenborough have been compared in detail. Though there are no significant differences of the overall structure and spatial arrangement of four heme groups between two molecules, there are some unique features with regard to the local structures near the heme pockets. Two of the heme groups show significant differences including a hydrogen bonding scheme between the imidazole rings and water molecules in heme pocket. The water molecule near the heme 1 pocket in Miyazaki cytochrome c3 is replaced by the C delta 1 atom of Leu9 in the Hildenborough structure. The rotation around the C alpha-C beta bond of Leu9 results in the increase of the solvent accessibility of the portion of the heme 1 edge. On the other hand, in heme3 one water molecule is additionally included in the hydrogen bonding network with a N delta 1 atom of the imidazole ring and carbonyl oxygen atom of the main chain in Hildenborough cytochrome c3. This additional hydrogen bonding network will contribute to the possible passage between the imidazole ring and the molecular surface. These features have been related to the upfield shift of the C2 proton signals of NMR spectra and the low redox potentials of the cytochrome c3 molecules of Desulfovibrio vulgaris Hildenborough in comparison with those from Miyazaki.

Amino Acid Sequence↗
PubMed1994

Dynamic structures of intact chicken erythrocyte chromatins as studied by 1H-31P cross-polarization NMR.

The dynamic properties of DNA in intact chicken erythrocyte cells, nuclei, nondigested chromatins, digested soluble chromatins, H1, H5-depleted soluble chromatins and nucleosome cores were investigated by means of single-pulse and 1H-31P cross-polarization NMR. The temperature dependence of the phosphorus chemical shift anisotropy was identical for the former three in the presence of 3 mM MgCl2, suggesting that the local higher order structure is identical for these chromatins. The intrinsic phosphorus chemical shift anisotropy of the nucleosome cores was -159 ppm. The chemical shift anisotropy of DNA in the chromatins can be further averaged by the motion of the linker DNA. The spin-lattice relaxation time in the rotating frame of the proton spins (T1p) of the nondigested chromatins was measured at various locking fields. The result was analyzed on the assumption of the isotropic motion to get a rough value of the correlation time of the motion efficient for the relaxation, which was eventually ascribed to the segmental motion of the linker DNA with restricted amplitude. The 30 nm filament structure induced by NaCl was shown to be dynamically different from that induced by MgCl2. Side-by-side compaction of 30-nm filaments was suggested to be induced in the MgCl2 concentration range higher than 0.3 mM. Biological significance of the dynamic structure was discussed in connection with the results obtained.

Animals↗
PubMed1994

Dynamic properties of nucleic acids in biosupramolecular systems, as studied by 31P NMR.

The dynamic properties of nucleic acids in five different types of intact supramolecular systems, namely, chicken erythrocyte chromatin, the wild type and a deletion mutant of the lambda phage, lipid-containing phage PM2, and Alteromonas espejiana ribosomes, were investigated by means of 31P solid-state NMR. The nucleic acids in the different supramolecular systems showed unique dynamic properties, which are closely connected with their functions. The total anisotropy of the phosphorus chemical shift (delta sigma = sigma 33-sigma 11) of the ribosomes was 210 ppm at 5 degrees C. This anisotropy was much larger than those of any DNA complexes, suggesting the highly rigid structure of ribosomal RNA. In contrast, 160 ppm was the largest chemical shift anisotropy at 5 degrees C for B-form DNA in the supramolecular systems. This flexibility would be essential for DNAs to exert their functions. The involvement of a condensation protein in the PM2 phage was supported by the chemical shift anisotropy. The spin-lattice relaxation time in the proton rotating frame [T1 rho(H)] of the nucleic acids became shorter with the increase in the effective field in the rotating frame for all systems examined, showing that the motions of the nucleic acids effective for the relaxation are in the slow motional regime or in the range of omega 1 tau c = 1 at 5 degrees C. The motional state of DNA of the lambda phage was found to change at about 20 degrees C on the basis of the temperature dependence of the spin-lattice relaxation time of phosphorus (T1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Assessment of myocardial viability by thallium-201 reinjection imaging with sublingual nitroglycerin].

Although thallium-201 (201Tl) reinjection imaging improves the detection of myocardial viability compared to standard 3-4-hr redistribution (RD) imaging, it still underestimates the extent of viable myocardium. We examined whether 201Tl reinjection SPECT with sublingual nitroglycerin (NTG) had a higher sensitivity for viability detection than reinjection alone. Eighty patients with coronary artery disease were studied, 38 of them with an old myocardial infarction. At the peak of exercise, 111 MBq 201Tl was injected and the initial and the delayed SPECT images were obtained. Then, all patients were divided randomly into two groups, and in each group, SPECT data were obtained again after the injection of 37 MBq 201Tl with (NTG(+) group) or without 0.6 mg of sublingual NTG (NTG(-) group). Among 50 segments showing fixed defects on the delayed image in the NTG(+) group, 21 (42%) were found to be reversible on the reinjection image, as compared to 16 of 51 (31%) in the NTG(-) group. Twenty-two of 44 (50%) segments showing incomplete RD were found to be reversible in the NTG(+) group, while 17 of 42 (41%) segments in the NTG(-) group. Moreover, the ratio of reversible segments seen in the reinjection images was significantly higher in the collateralized regions of the NTG(+) group than in those of the NTG(-) group (20/26 vs. 14/28, p < 0.05). Thus, 201Tl reinjection SPECT with sublingual NTG improves the detection of ischemic but viable myocardium as compared to SPECT with reinjection alone.

Administration, Sublingual↗
PubMed1993

Multifocal intraocular lenses and glare.

In a previous paper, we reported finding deficits in the contrast sensitivity functions of patients with diffractive multifocal intraocular lenses (IOL's). The results were consistent with optical measurements of the modulation transfer function (MTF) of the IOL. When this MTF is treated as a linear spatial frequency filter, it predicts the existence of a glare effect; contrast threshold for the recognition of target letters should be elevated by a bright, adjacent stimulus. We tested this prediction by measuring contrast thresholds for recognizing 0.2 degrees Sloan letters on a background luminance of 11.2 cd/m2. The letters were presented inside bright (300 cd/m2) annular rings with inner diameters ranging from 0.42 to 1.22 degrees. Thresholds were measured for seven multifocal subjects, age-matched groups of monofocal subjects and phakic-control subjects, and a young group. Multifocal subjects exhibited a greater glare effect than monofocal subjects, and they in turn exhibited a greater effect than phakic-control subjects. The observed glare effect for multifocal subjects was about twice that expected from the spatial filtering property of the multifocal IOL.

Adult↗
PubMed1992

Reduction kinetics of the four hemes of cytochrome c3 from Desulfovibrio vulgaris by flash photolysis.

The reduction of the tetraheme cytochrome c3 (from Desulfovibrio vulgaris, strains Miyazaki F and Hildenbourough) by flavin semiquinone and reduced methyl viologen follows a monophasic kinetic profile, even though the four hemes do not have equivalent reduction potentials. Rate constants for reduction of the individual hemes are obtained subsequent to incrementally reducing the cytochrome by phototitration. The dependence of each rate constant on the reduction potential difference between the heme and the reductant can be described by outer sphere electron transfer theroy. Thus, the very low reduction potentials of the cytochrome c3 hemes compensate for the very large solvent accessibility of the hemes. The relative rate constants for electron transfer to the four hemes of cytochrome c3 are consistent with the assignments of reduction potential to hemes previously made by Park et al. (Park, J.-S., Kano, K., Niki, S. and Akutsu, H. (1991) FEBS Lett. 285, 149-151) using NMR techniques. The ionic strength dependence of the observed rate constant for reduction by the methyl viologen radical cation indicates that ionic strength substantially alters the structure and/or the heme reduction potentials of the cytochrome. This result is confirmed by reduction with a neutral flavin species (5-deazariboflavin semiquinone) in which the reactivity of the highest potential heme decreases and the reactivity of the lowest potential heme increases at high (500 mM) ionic strength, and by the sensitivity of heme methyl resonances to ionic strength as observed by 1H-NMR. These unusual ionic strength-dependent effects may be due to a combination of structural changes in the cytochrome and alterations of the electrostatic fields at elevated ionic strengths.

Cytochrome c Group↗
PubMed1992

Non-equivalent natures of the coordinated imidazole rings of cytochrome c3 from D. vulgaris Miyazaki F as studied by 1H NMR.

All of the C2 proton signals of the coordinated histidine residues in the 1H NMR spectrum of cytochrome c3 from D. vulgaris Miyazaki F were assigned by specific deuteration. They appeared at extremely high fields and scattered in a wide range from -4 to -22 ppm. This clearly shows that the chemical properties of the imidazole groups are quite different from one another. The extremely high-field shift of the C2 signal indicates that some of them must carry the imidazolate-like nature to some extent. This might be responsible for the extremely low redox potentials of the four hemes. On changing temperature, most of them showed Curie-type change. All of the C2 signals showed a small p2H dependence in the range of p2H 4.8-10.0.

Cytochrome c Group↗
PubMed1992

Archaea contain a novel diether phosphoglycolipid with a polar head group identical to the conserved core of eucaryal glycosyl phosphatidylinositol.

The structure of a major ether polar lipid of the methanogenic archaeon Methanosarcina barkeri was identified as glucosaminyl archaetidylinositol. This lipid had archaeol (2,3-di-O-phytanyl-sn-glycerol) as a core lipid portion, and the polar head group consisted of 1 mol each of phosphate, myo-inositol and D-GlcN. The polar head group was identified by means of chemical degradations, phosphatidylinositol-specific phospholipase C treatment, permethylation analysis, and fast atom bombardment-mass spectrometry as glucosaminylinositol phosphate, which was linked to the glycerol backbone via a phosphodiester bond. The stereochemical configuration of the phospho-myo-inositol residue of glucosaminyl archaetidylinositol was determined to be 1-D-myo-inositol 1-phosphate by measuring optical rotation of phospho-myo-inositol prepared by nitrous acid deamination and alkaline hydrolysis from the lipid. 1H NMR of the intact lipid showed that GlcN was linked to C-6 position of myo-inositol as an alpha-anomer. It is, finally, concluded that the complete structure of this lipid is 2,3-di-O-phytanyl-sn-glycero-1-phospho- 1'[6'-O-(2"-amino-2"-deoxy-alpha-D-glucopyranosyl)]-1'-D-myo-inositol. This lipid has a hybrid nature of an archaeal feature in alkyl glycerol diether core portion and an eucaryal feature in the polar head group identical to the conserved core structure (GlcNp(alpha 1-6)-myo-inositol 1-phosphate) of glycosylated phosphatidylinositol which serves as a membrane protein anchor in eucaryal cells.

Carbohydrate Sequence↗
PubMed1992

Contrast sensitivity and reading through multifocal intraocular lenses.

Multifocal intraocular lenses are intended to increase depth of focus for patients with cataracts, but optical considerations predict reduced retinal-image contrast. We evaluated visual performance through multifocal intraocular lenses by measuring contrast sensitivity functions and reading speed for age-matched groups with multifocal and monofocal intraocular lenses and two normal control groups. Contrast sensitivity functions of the patients with multifocal lenses did not differ significantly for optical distances differing by 2.5 diopters, indicating substantial depth of focus. Normal and monofocal contrast sensitivity functions were nearly identical, and both were about a factor of two higher than multifocal contrast sensitivity functions. Patients with multifocal lenses showed deficits in reading speed only for low-contrast text (less than 30%) and small letters (0.2 degree and 1.0 degree).

Aging↗