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Biomedical subjects

S Yoshikawa

Publications and source records attributed to S Yoshikawa.

At least 109 records · Page 6Linked to original sources
PubMed1995

Structures of metal sites of oxidized bovine heart cytochrome c oxidase at 2.8 A.

The high resolution three-dimensional x-ray structure of the metal sites of bovine heart cytochrome c oxidase is reported. Cytochrome c oxidase is the largest membrane protein yet crystallized and analyzed at atomic resolution. Electron density distribution of the oxidized bovine cytochrome c oxidase at 2.8 A resolution indicates a dinuclear copper center with an unexpected structure similar to a [2Fe-2S]-type iron-sulfur center. Previously predicted zinc and magnesium sites have been located, the former bound by a nuclear encoded subunit on the matrix side of the membrane, and the latter situated between heme a3 and CuA, at the interface of subunits I and II. The O2 binding site contains heme a3 iron and copper atoms (CuB) with an interatomic distance of 4.5 A; there is no detectable bridging ligand between iron and copper atoms in spite of a strong antiferromagnetic coupling between them. A hydrogen bond is present between a hydroxyl group of the hydroxyfarnesylethyl side chain of heme a3 and an OH of a tyrosine. The tyrosine phenol plane is immediately adjacent and perpendicular to an imidazole group bonded to CuB, suggesting a possible role in intramolecular electron transfer or conformational control, the latter of which could induce the redox-coupled proton pumping. A phenyl group located halfway between a pyrrole plane of the heme a3 and an imidazole plane liganded to the other heme (heme a) could also influence electron transfer or conformational control.

Animals↗
PubMed1995

Enhanced formation of isoamyl alcohol in Zygosaccharomyces rouxii due to elimination of feedback inhibition of alpha-isopropylmalate synthase.

Mutants of the 'miso' yeast, Zygosaccharomyces rouxii, that produced a large amount of isoamyl alcohol, an important flavour in miso fermentation, were isolated from 5,5,5-trifluoro-DL-leucine-resistant mutants, an analogue of L-leucine. One of the mutants, M21-10, produced a three-fold higher level of isoamyl alcohol than the wild-type strain MY21 in miso fermentation. The activity of alpha-isopropylamalate synthase, one of the enzymes used for L-leucine synthesis, in the mutant M21-10 was not inhibited by the addition of L-leucine, a feedback inhibitor.

2-Isopropylmalate Synthase↗
PubMed1995

Effects of ethyleneglycol chain length of dodecyl polyethyleneglycol monoether on the crystallization of bovine heart cytochrome c oxidase.

Tetragonal crystals that diffracted X-rays up to 5 A resolution were obtained from bovine heart cytochrome c oxidase isolated and solubilized with dodecyl octaethyleneglycol monoether, CH3(CH2)11O(CH2CH2O)8H. Comparison of observed structure factors between data sets each obtained from a different native crystal gave correlation coefficients of 0.92, 0.84 and 0.57 at 10 A, 7 A and 6 A resolution, respectively. The space group and the cell dimensions of the crystal are I4(1) or I4(3) and a = b = 253 A, c = 507 A, respectively. The perfection and stability of the tetragonal crystals are significantly higher than those of the hexagonal crystals of the protein stabilized with Brij-35, CH3(CH2)11O(CH2CH2O)23H (whose details are reported elsewhere). Examination of the effect of ethyleneglycol chain length on the crystallization revealed that only dodecyl polyethyleneglycol monoethers with eight and seven units were appropriate for producing this type of crystal, indicating an optimum size of the detergent for crystallization of the membrane protein.

Animals↗
PubMed1995

Effects of overall oxidation state on infrared spectra of heme a3 cyanide in bovine heart cytochrome c oxidase. Evidence of novel mechanistic roles for CuB.

Effects of changes in oxidation state at the other metal centers on oxidized heme a3 cyanide of bovine heart cytochrome c oxidase have been investigated. Only one CN- binds, giving Fe3+a3CN, in fully-oxidized cytochrome c oxidase and its 1-, 2-, and 3-electron reduction products. Soret/visible spectra for the heme a3 cyanide are independent of overall redox level, whereas distinct shifts in C-N infrared stretch band frequency occur upon reduction, reflecting changes in the polarity of the ligand (CN-) environment. Catalysis of O2 reduction can be critically dependent upon such changes in polarity at the reduction site. These findings indicate that CuB, when reduced, exists in two forms whose relative stabilities are independent of Fea and CuA oxidation states and, when oxidized, is in only one stable form. These results are consistent with the oxidation of Cu+B triggering proton pumping and with the involvement of a CuB ligand in respiratory control. Electron equivalents introduced into the enzyme are distributed equally among Fea, CuA, and CuB, which raises the possibility that all four electrons used in O2 reduction are donated via Cu+B, which is favorably positioned with respect to Fea3 (the O2 binding site) in order to carry out this role in electron transfers.

Animals↗
PubMed1995

Acoustical behavior of brass player's lips.

The controversial problem of whether a brass player's lip movements are best modeled as outward striking or as upward striking is approached by measuring the phase difference between mouthpiece pressure and lip displacement. In analogy with the phase of the input impedance to a resonant system, the negative/positive value of this phase difference suggests an outward-striking/upward-striking oscillation. On the basis of this speculation, the experimental results revealed the following: (1) Large lip-driven pipes support both outward-striking and upward-striking oscillations because of the lip's high flexibility in the absence of a mouthpiece; (2) mouthpiece-nonresonant tube systems almost support the outward-striking oscillation over a wide frequency range; (3) mouthpiece-resonant tube systems totally support the outward-striking oscillation; (4) the French horn and trumpet exhibit the outward-striking oscillation for the lowest mode and the upward-striking oscillation for higher modes. The oscillation transition in brass instruments, which corresponds well to the change of mouthpiece pressure waveform from a low-pitch, nonsinusoidal one to a higher-pitch, more sinusoidal one, depends mainly on the nonlinear acoustic impedance of the lip opening. If its magnitude is negligible, the cavity coupling between the mouthpiece cup and player's mouth yields a capacitive input impedance that favors the outward-striking oscillation; if its magnitude is significant, the cavity decoupling is likely to yield an inertive input impedance that favors the upward-striking oscillation. Since both the time-varying Bernoulli pressure at the lip opening and the area receiving this pressure are generally apt to increase as the blowing pressure increases, the upward-striking oscillation tends to dominate higher mode tones in brass instruments.

Humans↗
PubMed1995

Periodic angioedema with eosinophilia: increased serum level of interleukin 5.

A 48-year-old man developed episodic non pitting edema and eosinophilia. Symptoms were alleviated promptly when treated with prednisolone. However, major basic protein (MBP), eosinophil cationic protein (ECP), and eosinophil-derived neurotoxin (EDN) levels in the serum as well as the total number of eosinophils remained high. During periods of attack serum levels of interleukin-5 (IL-5) were elevated, but the levels were lowered following treatment, suggesting that IL-5 is involved in periodic angioedema with eosinophilia.

Angioedema↗
PubMed1995

Effect of prone position on apnea severity in obstructive sleep apnea.

We describe a patient with obstructive sleep apnea (OSA) whose apnea-hypopnea index (AHI) improved remarkably in the prone position accompanied by an improved sleep quality, despite a higher AHI in the supine position and even in the lateral position. Magnetic resonance imaging revealed the most dilated upper airway in the prone position, which suggests the role of anatomical narrowing of the upper airway as an important component in the pathophysiology of positional apnea patients. Further studies are needed to determine the therapeutic efficacy of a prone sleeping position in patients with OSA.

Humans↗
PubMed1995

[Two types of facial impression judgments and recognition memory for faces].

The author investigated the semantic processing advantage effect on facial recognition memory using two types of personality traits and two types of recognition tests. In Experiment 1, based on the personality impression ratings for smiling and neutral faces made by 40 subjects, four expression-independent (i.e., intelligent, reliable, determined, and ambitious) and four expression-dependent (i.e. extroverted, friendly, affectionate, and likeable) personality trait words were selected. In Experiment 2, two groups of 22 subjects (expression-dependent trait group and expression-independent trait group) were asked to rate 32 faces in terms of physical features or personality traits. This was followed by an unexpected yes-no recognition test in which identical pictures of the target faces or the same person's expression-changed faces were randomly presented with distractor faces. In identical-picture recognition condition, the semantic processing advantage emerged in both expression-dependent and expression-independent trait groups, whereas in expression-changed recognition condition the advantage appeared only in expression-independent trait group. It was discussed that the semantic-codes explanation would be plausible to explain the results obtained.

Adult↗
PubMed1994

New crystal forms and preliminary X-ray diffraction studies of mitochondrial cytochrome bc1 complex from bovine heart.

Two new crystal forms of the cytochrome bc1 complex (ubiquinol:ferricytochrome c oxidoreductase, EC. 1.10.2.2) from bovine heart mitochondria were obtained by the batch method with polyethylene glycol 4000 as the precipitant, when buffer was exchanged from Tris-HCl to potassium phosphate. The first crystal form belongs to the hexagonal space group P61 or P6(5) with unit-cell constants of a = b = 131 A and c = 720 A. The reproducibility of crystallization and the quality of this crystal form were improved by an addition of ZnCl2 to the protein solution. The second crystal form, obtained from the enzyme preparation purified by crystallization, belongs to the tetragonal space group P4(1) or P4(3) with unit-cell constants of a = b = 190 A and c = 445 A. Both crystals diffracted X-rays to 6.5 A resolution and gave sharper diffraction spots than the previous monoclinic form. X-ray intensity data to 8.0 A resolution for the hexagonal crystal and to 7.0 A resolution for the tetragonal one were collected with synchrotron radiation.

Animals↗
PubMed1994

Selective resonance Raman observation of the "607 nm" form generated in the reaction of oxidized cytochrome c oxidase with hydrogen peroxide.

Resonance Raman spectra were measured selectively for the "607 nm" form, which had been assigned to a peroxy intermediate formed in the reaction of oxidized cytochrome c oxidase with hydrogen peroxide at ambient temperature. A single oxygen isotope-sensitive band was found at 803 cm-1 for the reaction with H2(16)O2 (at 769 cm-1 with H2(18)O2) upon excitation at 607 nm, the wavelength of the difference absorption maximum characteristic of the "peroxy" intermediate. Upon excitation at shorter wavelengths (down to 580 nm), the Raman spectrum simply became weaker without yielding any new features. When H2(16)O18O was used, two bands were observed at 803 and 769 cm-1 (within an accuracy of 0.5 cm-1), but with only half the intensity of those observed with H2(16)O2 or H2(18)O2, which ruled out the possibility that the 803 cm-1 band arose from the O-O or Fe-O2 stretching of the FeIII(O-O-) heme. Conversely, the 34-cm-1 downshift with 18O is in good agreement with the calculated 16O/18O shift (35 cm-1) expected for the diatomic Fe = 16O oscillator at 803 cm-1. This band exhibited an upshift by 1.3 cm-1 in 2H2O, similar to the case of compound II of horseradish peroxidase at neutral pH, and indicative of the presence of a hydrogen bond to the FeIV = O oxygen. The 803/769 cm-1 pair of resonance Raman bands were also observed upon blue excitation, as is the case for the bands found in the dioxygen cycle of this enzyme (Ogura, T., Takahashi, S., Hirota, S., Shinzawa-Itoh, K., Yoshikawa, S., Appelman, E. H., and Kitagawa, T. (1993) J. Am. Chem. Soc. 115, 8527-8536). This observation provides the first direct characterization of the 607 nm form of this enzyme in its reaction with H2O2.

Animals↗
PubMed1994

Cloning of a Drosophila melanogaster homologue of the mouse type-I bone morphogenetic proteins-2/-4 receptor: a potential decapentaplegic receptor.

The Drosophila melanogaster (Dm) decapentaplegic (dpp) gene product plays an essential role during several stages of Dm development. The DPP protein is a member of the transforming growth factor-beta (TGF-beta) superfamily and an orthologue of mammalian bone morphogenetic proteins (BMP-2 and -4). Recently, a cDNA clone encoding the mouse Ser/Thr kinase receptor specific for BMP-2/-4 (mTFR11) was isolated. Here, we describe the deduced primary structure, the cytogenetic position and expression pattern of the Dm homologue of mTFR11 (DTFR), a putative DPP receptor. The cytogenetic position of the Dm dtfr gene was mapped to 25D. DTFR has striking homology to mTFR11, especially in the cytoplasmic domain (approx. 63%), including a Ser + Gly-rich box that is characteristic of type-I receptors for the TGF-beta superfamily. Although the amino acid (aa) sequence of the extracellular domain is less conserved than that of the cytoplasmic domain, the extracellular domains of these two molecules were more homologous (approx. 27%) to each other than any other receptors for the TGF-beta superfamily. The spacing of Cys residues in the extracellular domain, which is considered crucial to ligand specificity, is highly conserved in these two receptors. During Dm embryonic development, its expression pattern changes in a dynamic fashion with high levels of expression in mesoderm and midgut, with some relation to dpp mutant phenotypes.

Amino Acid Sequence↗
PubMed1994

Facial shape and judgements of female attractiveness.

The finding that photographic and digital composites (blends) of faces are considered to be attractive has led to the claim that attractiveness is averageness. This would encourage stabilizing selection, favouring phenotypes with an average facial structure. The 'averageness hypothesis' would account for the low distinctiveness of attractive faces but is difficult to reconcile with the finding that some facial measurements correlate with attractiveness. An average face shape is attractive but may not be optimally attractive. Human preferences may exert directional selection pressures, as with the phenomena of optimal outbreeding and sexual selection for extreme characteristics. Using composite faces, we show here that, contrary to the averageness hypothesis, the mean shape of a set of attractive faces is preferred to the mean shape of the sample from which the faces were selected. In addition, attractive composites can be made more attractive by exaggerating the shape differences from the sample mean. Japanese and caucasian observers showed the same direction of preferences for the same facial composites, suggesting that aesthetic judgements of face shape are similar across different cultural backgrounds. Our finding that highly attractive facial configurations are not average shows that preferences could exert a directional selection pressure on the evolution of human face shape.

Adult↗
PubMed1994

Embolisation of orbital varix.

A 34-year-old man with intermittent exophthalmos, found to have a large varix in the right orbit, was treated by endovascular surgery. Percutaneous transfemoral venous catheterisation and embolisation of the orbital varix was performed on two occasions. A Tracker 18 microcatheter was introduced through the right inferior petrosal sinus, cavernous sinus, superior ophthalmic vein and then into the varix, following a guidewire. Superselective venography of the right ophthalmic vein showed the varix. A total of 204 platinum microcoils was used to pack the varix. At the time of discharge, the exophthalmos had largely resolved. As this technique is much less invasive than surgical resection, we recommend an attempt at endovascular embolisation of orbital varices prior to surgical removal.

Adult↗
PubMed1994

[Idiopathic osteoporosis].

Idiopathic osteoporosis is a syndrome appearing in adult men and women, and is different from idiopathic juvenile osteoporosis which appears in the growth period. It is characterised histomorphometrically by decreased values in bone volume, trabecular thickness, active osteoid surface, mineralization surface and bone formation rate. Hypercalciuria, which appears in many cases, is thought to reflect this depressed metabolic state of the bone. Diagnosis depends on the exclusion of all the primary endocrine disturbances and metabolic bone disease. The presence of subclinical metabolic abnormality should be carefully searched out.

Adult↗
PubMed1993

Stabilization of alpha-helix in C-terminal fragments of neuropeptide Y.

To elucidate the alpha-helix-stabilizing effect of amino acids at the helical ends, we prepared analogs of C-terminal fragments of neuropeptide Y (NPY) containing an alpha-helical part. The helix-stabilizing tendency of N-terminal amino acid in NPY (12-36) was found to be as follows: Thr > Ser > Gly > Gln > Cys > Asn > Asp > Val > Phe > Glu > Lys > Tyr > Ala = Trp > His > Arg, suggesting the importance of end capping. The capping effect was not evident when N-termini in NPY (11-36) and NPY (13-36) were replaced. Under the same conditions as those for the receptor binding, [Thr12]NPY (12-36) had about 4-fold higher alpha-helix content than [Arg12]NPY (12-36). However, there was no apparent relationship between the helix content and binding affinity to the Y2 receptor.

Amino Acid Sequence↗