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Biomedical subjects

S Yoshikawa

Publications and source records attributed to S Yoshikawa.

At least 73 records · Page 4Linked to original sources
PubMed1998

Crystal structural studies of a membrane protein complex, cytochrome c oxidase from bovine heart.

Membrane proteins invest the membranes of living cells and organelles with such functions as energy conversion, molecular transport and signal transduction. The number of known structures of membrane proteins is less than 20, which is too few to understand the highly organized biological reactions in a cell. The whole procedure, including crystallization, for bovine heart cytochrome c oxidase is described as an example of crystal structural analysis of a membrane protein. Structural features of membrane proteins and structure-function relationships of the enzyme are also discussed.

Animals↗
PubMed1998

Effects of sexual dimorphism on facial attractiveness.

Testosterone-dependent secondary sexual characteristics in males may signal immunological competence and are sexually selected for in several species. In humans, oestrogen-dependent characteristics of the female body correlate with health and reproductive fitness and are found attractive. Enhancing the sexual dimorphism of human faces should raise attractiveness by enhancing sex-hormone-related cues to youth and fertility in females, and to dominance and immunocompetence in males. Here we report the results of asking subjects to choose the most attractive faces from continua that enhanced or diminished differences between the average shape of female and male faces. As predicted, subjects preferred feminized to average shapes of a female face. This preference applied across UK and Japanese populations but was stronger for within-population judgements, which indicates that attractiveness cues are learned. Subjects preferred feminized to average or masculinized shapes of a male face. Enhancing masculine facial characteristics increased both perceived dominance and negative attributions (for example, coldness or dishonesty) relevant to relationships and paternal investment. These results indicate a selection pressure that limits sexual dimorphism and encourages neoteny in humans.

Adult↗
PubMed1998

Syntheses of potent Leu-enkephalin analogs possessing beta-hydroxy-alpha,alpha-disubstituted-alpha-amino acid and their characterization to opioid receptors.

Novel Leu-enkephalin (Leu-Enk) (1) analogs possessing various types of alpha-substituted serine instead of its glycine residue in the position 2 were synthesized via an efficient O,N-migration method. The binding characteristics of the synthetic analogs using Chinese hamster ovary (CHO) cells expressed cloned rat mu-, delta-, and kappa-receptors revealed that [(1R,2S)-Ahh2]Enk (7) was the most potent agonist of delta-opioid receptors among all the synthetic analogs tested, and was 10 times more potent than the native Leu-Enk.

Amino Acids↗
PubMed1998

Redox-coupled crystal structural changes in bovine heart cytochrome c oxidase.

Crystal structures of bovine heart cytochrome c oxidase in the fully oxidized, fully reduced, azide-bound, and carbon monoxide-bound states were determined at 2.30, 2.35, 2.9, and 2.8 angstrom resolution, respectively. An aspartate residue apart from the O2 reduction site exchanges its effective accessibility to the matrix aqueous phase for one to the cytosolic phase concomitantly with a significant decrease in the pK of its carboxyl group, on reduction of the metal sites. The movement indicates the aspartate as the proton pumping site. A tyrosine acidified by a covalently linked imidazole nitrogen is a possible proton donor for the O2 reduction by the enzyme.

Animals↗
PubMed1998

Position dependence of non-polar amino acid intrinsic helical propensities.

Until now and based on the success of the helix/coil transition theory it has been assumed that the alpha-helical propensities of the amino acids are position independent. This has been critical to derive the set of theoretical parameters for the 20 natural amino acids. Here, we have analyzed the behavior of several non-polar residues, Val, Ile, Leu, Met and Gly at the N-cap, at each position of the first helical turn and at a central helical position of a 16-residue peptide model system that starts with eight consecutive alanine residues. We have interpreted the results from these experiments with the model of the helix/coil transition (AGADIR), that indicates that the intrinsic helical propensity is position dependent. Gly, Val and Ile are more favorable at the first turn than in the middle of the alpha-helix, while for Leu and Met we observe the opposite behavior. The differences between the observed helical propensities are as large as 1.0 kcal/mol in some cases. Molecular modeling calculations using the ECEPP/2 force-field equipped with a hydration potential show that this effect can be explained by the combination of three factors: (a) the side-chains in the first helix turn are more solvent-exposed; (b) they have fewer intramolecular van der Waals' contacts; and (c) they posses higher configurational entropy than that in the central position of an alpha-helix. The position-dependent results of the calculations are in reasonable agreement with the experimental estimates and with the intrinsic propensities of the amino acids derived from the statistical analysis of the protein structure database.

Algorithms↗
PubMed1998

Localization of 5-HT2A receptor in rat cerebral cortex and olfactory system revealed by immunohistochemistry using two antibodies raised in rabbit and chicken.

Serotonin 2A receptor (5-HT2A receptor) is widely distributed in the central nervous system, and has been suggested to be involved in a variety of behavioral conditions and neuropsychiatric disorders. Two polyclonal antibodies were raised against the N-terminus peptide of rat 5-HT2A receptor in chickens (5-HT2A-N) and a glutathione S-transferase fusion protein that contained the C-terminus of the mouse 5-HT2A receptor in rabbits (5-HT2A-C). Affinity-purified 5-HT2A-N and -C antibodies reacted strongly with a single band of 77-78 kDa in postsynaptic density proteins prepared from the rat cortex. The distribution pattern of immunoreactive structures in the rat brain was virtually the same for the two antibodies. The highest levels of immunoreactivity were observed in the olfactory bulb, neocortex, claustrum, piriform cortex, mamillary bodies, pontine nuclei, red nucleus and cranial motor nuclei. In the olfactory bulb, mitral cells were intensely labeled. In the neocortex, many immunoreactive neurons were found in layers II-VI. In layer IV of the neocortex, strong neuropil labeling was observed. In a double-labeling study using chicken 5-HT2A-N and rabbit anti-glial fibrillary acidic protein (GFAP) antibody, a considerable number of GFAP positive cells also showed 5-HT2A immunoreactivity. By using an immunoelectron microscopic technique, 5-HT2A receptor immunoreaction was shown to be localized just beneath the postsynaptic membrane thickening of asymmetric synapses.

Amino Acid Sequence↗
PubMed1998

Adenocarcinoma arising in the retrorectal space: report of a case.

We herein present an extremely rare case of adenocarcinoma of unknown origin arising in the retrorectal space. The imaging and endoscopic findings misled us to preoperatively diagnose a "submucosal tumor." This histological findings were highly suggestive of adenocarcinoma, and its unexpected early and aggressive recurrence required thorough investigation on the true cell type and its origin. Both radiochemotherapy findings and conclusive findings of immunohistochemical staining finally revealed this tumor to be an ordinary adenocarcinoma. It was impossible to identify its origin histologically, because this case was so advanced that it had already replaced the entire entity with adenocarcinoma without leaving any clues as to its former nature. We thus assumed this tumor to be an adenocarcinoma of unknown origin arising in the retrorectal space.

Adenocarcinoma↗
PubMed1998

Tracing axons.

For more than a century, neuroscientists have gained insight into brain function by examining its complex patterns of connectivity. To achieve this, a wide variety of axon-tracing techniques have been employed to chart the projections of neurons. New, experimentally flexible, reporter-based tracers, many of which are fusion proteins designed to target axons and dendrites, are being developed and are assisting the molecular characterization of the nervous system.

Animals↗
PubMed1998

Molecular modelling of Me(2+)-(8-hydroxy-quinolinate)2 complexes using ZINDO and ESSF methods.

The Me2+ (8-hydroxy-quinolinate)1-2 system was studied using semi-empirical (ZINDO) and molecular mechanics (ESFF) methods for a range of bivalent metals comprising alkaline earth metals (up to Sr2+) and the first two rows of transition metals. The structural validation of the optimisation calculations showed that ESFF is in general an efficient predictor of the structure of the complexes. On the other hand, ZINDO offers an appropriate tool for describing the mechanisms of complex formation for the studied system. The spectral validation based on the comparison of spectral data with predicted molecular geometric parameters shows that ZINDO offers a better tool for describing the mechanisms of complex formation. Finally, the consistent relationship (in relative terms) between SCF energies and equilibrium constants, and between computed charges at the oxygen ligation atom and pH, showed that ZINDO can be used as a tool for the design of chelating agents. For the system studied the CPU times are not prohibitive, even for a metal-comprehensive investigation.

Computer Simulation↗
PubMed1998

Crystal structure of bovine heart cytochrome c oxidase at 2.8 A resolution.

Thirteen different polypeptide subunits, each in one copy, five phosphatidyl ethanolamines and three phosphatidyl glycerols, two hemes A, three Cu ions, one Mg ion, and one Zn ion are detectable in the crystal structure of bovine heart cytochrome c oxidase in the fully oxidized form at 2.8 A resolution. A propionate of hems a, a peptide unit (-CO-NH-), and an imidazole bound to CuA are hydrogen-bonded sequentially, giving a facile electron transfer path from CUA to heme a. The O2 binding and reduction site, heme a3, is 4.7 A apart from CuB. Two possible proton transfer paths from the matrix side to the cytosolic side are located in subunit I, including hydrogen bonds and internal cavities likely to contain randomly oriented water molecules. Neither path includes the O2 reduction site. The O2 reduction site has a proton transfer path from the matrix side possibly for protons for producing water. The coordination geometry of CuB and the location of Tyr244 in subunit I at the end of the scalar proton path suggests a hydroperoxo species as the two electron reduced intermediate in the O2 reduction process.

Animals↗
PubMed1998

The full expression of the ity phenotype in ityr mice requires C3 activation by Salmonella lipopolysaccharide.

Our previous study has shown that the rapid and sufficient activation of complement by Salmonella lipopolysaccharide occurs in genetically resistant (Ityr) A/J mice. To assess whether the level of complement activation by a virulent strain of Salmonella typhimurium regulates the level of murine natural resistance, we compared levels of serum complement activation by S. typhimurium and kinetics of serum-opsonized S. typhimurium grown in macrophages using several strains of resistant (Ityr) and susceptible (Itys) mice. Itys macrophages killed intracellular S. typhimurium to the same extent as did Ityr macrophages when the pathogen was opsonized with Ityr serum. Opsonization of S. typhimurium with Itys serum reduced intracellular killing activity in Ityr macrophages to the same level as seen with Itys macrophages. Incubation of S. typhimurium with 25% Mg2+ EGTA (5 mm MgCl2-3 mm ethylene glycol-bis (beta-aminotheyl either)-N,N,N',N'-tetraacetic acid)-chelated Ityr serum resulted in higher levels of C3 deposition onto the surface of this bacteria, C3b generation and also C3 consumption, compared with that with Mg2+ EGTA-chelated Itys serum. Opsonization of S. typhimurium with A/J serum prior to infection increased early resistance in Itys mice. Infection with a virulent strain of S. typhimurium induced the expression of interleukin-10 (IL-10) mRNA at higher levels in C57BL/6 mice than in A/J mice. However, opsonization of S. typhimurium with A/J serum decreased bacterial growth in the spleen of C57BL/6 mice to the same level as observed for A/J mice in association with decreased expression levels of IL-10 mRNA. Moreover, administration of anti-C3 antibodies reduced the resistance of A/J mice in association with a decrease in serum levels of C3. These results indicate that the high level of complement activation via the alternative pathway in Ityr serum by a virulent strain of S. typhimurium reduces the virulence of this pathogen, which may contribute to the full expression of Ity phenotype in Ityr mice.

Animals↗
PubMed1998

Phenotypic diversity of Pseudoalteromonas citrea from different marine habitats and emendation of the description.

Four strains of marine, aerobic, agar-decomposing bacteria with one polar flagellum and with DNA G + C contents of 38.9-40.2 mol% were isolated from the Far-Eastern mussels Crenomytilus grayanus and Patinopecten yessoensis. These four strains were identified as Pseudoalteromonas; however, they were phenotypically different from species described previously according to carbon compound utilization tests and the BIOLOG identification system. High agar-decomposing activity was found in two strains, in one of which agarase, alpha-galactosidase, pustulanase and laminarinase had been detected. The level of DNA homology of three of the strains was 70-100%. The fourth isolate was genetically less related to the others (67% DNA relatedness) and phenotypically was more distant from other members of this group; however, all four strains were assigned to a single species genotypically. DNA from the strains isolated from mussels showed 40-45% genetic relatedness with the DNA of Alteromonas atlantica, 8-36% with DNA of Pseudoalteromonas haloplanktis subsp. haloplanktis, Pseudoalteromonas haloplanktis subsp. tetraodonis, Pseudoalteromonas undina, Pseudoalteromonas nigrifaciens and Pseudoalteromonasas carrageenovora, 53% with Pseudoalteromonas elyakovii, 32-48% with marine P. nigrifaciens from mussels and 14-16% with Alteromonas macleodii. The DNA-DNA hybridization data revealed that the levels of relatedness between the strains isolated and the type strains of Pseudoalteromonas citrea and Pseudoalteromonas fuliginea described recently were significant (95-85%). These results were confirmed by serological data employing polyclonal antibodies to cell surface antigens. The strains isolated from mussels were identified as P. citrea. The hybridization data showed that the name P. fuliginea Romanenko et al. 1994 should be recognized as a junior subjective synonym of P. citrea Gauthier 1977. A notable phenotypic diversity of P. citrea which might be a reflection of their ecological habitats is discussed.

Animals↗
PubMed1998

[Optimization of arbitrarily primed polymerase chain reaction (AP-PCR)-based DNA fingerprinting of Mycobacterium tuberculosis and its clinical application].

Since the number of outbreaks of pulmonary tuberculosis is increasing in Japan, epidemiological analysis is important to prevent the disease. Since Mycobacterium tuberculosis lacks the variety of biotypes among strains, genetical analysis is considered to be a promising measure to differentiate various of this pathogen. We applied arbitrarily primed polymerase chain reaction (AP-PCR)-based DNA fingerprinting to clinically isolated strains of M. tuberculosis. Although genetic analyses of M. tuberculosis by AP-PCR were reported by several investigators, reproducibilities of their results were not sufficient to be widely accepted as a reliable epidemiological tool. To attain high reprodicibulity, we attempted to optimize AP-PCR conditions including primers and annealing temperature, and to purity of DNA preparations. In this study, high reproducibility was attained by using the mixed primers of 1309F and 92R, and DNA preparations with an absorbance ratio (A260/A280) of higher than 1.50. Twenty two clinical isolates, including strains isolated from one incidence of nosocomial infection and from that of intrafamilial infection were analyzed by the optimized method; consequently they were grouped into 16 types. This AP-PCR method requires only one week subculture of M. tuberculosis and less than 24 hours for analysis. This AP-PCR method allowed us to obtain the highly reproducible results within a considerably short term, which would be applicable to clinical epidemiological investigation.

DNA Fingerprinting↗
PubMed1998

Enhancement of antimicrobial activity of neuropeptide Y by N-terminal truncation.

The activity of neuropeptide Y (NPY) against Candida albicans, which was revealed to be fungicidal, was enhanced significantly by the truncation of amino acid residues at the N terminus. The most active peptides (MICs, approximately 1 microM) were about 10-fold more potent than the intact NPY (MIC, approximately 10 microM). The enhancement was weakened by the replacement of the N terminus by negatively charged residues and/or acylation of the alpha-amino group. These results suggest that only the alpha-helical region of NPY is necessary for the antimicrobial activity and that the net charge of the peptide is important for the activity.

Amino Acid Sequence↗
PubMed1998

Caenorhabditis elegans anti-apoptotic gene ced-9 prevents ced-3-induced cell death in Drosophila cells.

ced-9, a member of the bcl-2 gene family in Caenorhabditis elegans plays a central roles in preventing cell death in worms. Overexpression of human bcl-2 can partially prevent cell death in C. elegans. However, it remains to be elucidated whether ced-9 can regulate cell death when expressed in other organisms. We demonstrated that the CED-9 protein is co-localized with BCL-2 in COS cells and Drosophila Schneider's L2 (SL2) cells, suggesting that the site of CED-9 action is located to specific cytoplasmic compartments. Overexpression of ced-9 only poorly protected cells from the death induced by ced-3 in HeLa cells, but ced-9 significantly reduced the cell death induced by ced-3 in Drosophila SL2 cells. Furthermore, apoptosis of SL2 cells that was induced by a Drosophila cell-death gene, reaper, was shown to be partially prevented by ced-9, bcl-2 and bcl-xL. These results suggest that the signaling pathway that is required for the anti-apoptotic function of bcl-2 family members, including ced-9, is conserved in Drosophila cells. In addition, SL2 cells provide a unique systems for dissecting the main machinery of cell death.

Animals↗
PubMed1997

Effects of covalent dimerization on the structure and function of the carboxy-terminal fragment of neuropeptide Y.

To determine whether or not the dimeric structure of neuropeptide Y (NPY) that is found in solution is necessary for its function, we investigated the effects of covalent dimerization on the structure and function of NPY using the carboxy-terminal fragment, NPY(12-36), in which residues 12 and 31 (located at both ends of alpha-helical region) were replaced by Cys residues. Among the three species (the parallel dimer, the anti-parallel dimer, and the intramolecularly cross-linked monomer) obtained by oxidation of the fragment, the anti-parallel dimer was predominant. NMR analysis showed that both parallel and anti-parallel dimers had alpha-helices similar to that of intact NPY, suggesting that covalent dimerization might have little effect on the helical structure. A binding assay with Y2 receptors on porcine hippocampal membranes revealed that the IC50 value of the anti-parallel dimer was almost the same as that of NPY (13-36), which is known as a Y2-specific ligand. By contrast, the binding by the parallel dimer was weaker by more than one order of magnitude. Our results suggest that the formation of dimers of NPY is not essential for binding to the receptor.

Amino Acid Sequence↗
PubMed1997

Architecture of helix bundle membrane proteins: an analysis of cytochrome c oxidase from bovine mitochondria.

We have analyzed the structure of mitochondrial cytochrome c oxidase in terms of general characteristics thought to be important for describing the architecture of helix bundle membrane proteins. Many aspects of the structure are similar to what has previously been found for the photosynthetic reaction center and bacteriorhodopsin. Our results lead to a considerably more precise general picture of membrane protein architecture than has hitherto been possible to obtain.

Amino Acids↗