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Biomedical subjects

Akio Noguchi

Publications and source records attributed to Akio Noguchi.

8 recordsLinked to original sources
PubMed2006

An isoflavone conjugate-hydrolyzing beta-glucosidase from the roots of soybean (Glycine max) seedlings: purification, gene cloning, phylogenetics, and cellular localization.

Soybeans (Glycine max (L.) Merr.) and certain other legumes excrete isoflavones from their roots, which participate in plantmicrobe interactions such as symbiosis and as a defense against infections by pathogens. In G. max, the release of free isoflavones from their conjugates, the latent forms, is mediated by an isoflavone conjugate-hydrolyzing beta-glucosidase. Here we report on the purification and cDNA cloning of this important beta-glucosidase from the roots of G. max seedlings as well as related phylogenetic and cellular localization studies. The purified enzyme, isoflavone conjugate-hydrolyzing beta-glucosidase from roots of G. max seedling (GmICHG), is a homodimeric glycoprotein with a subunit molecular mass of 58 kDa and is capable of directly hydrolyzing genistein 7-O-(6 ''-O-malonyl-beta-d-glucoside) to produce free genistein (k(cat), 98 s(-1); K(m), 25 microM at 30 degrees C, pH 7.0). GmICHG cDNA was isolated based on the amino acid sequence of the purified enzyme. GmICHG cDNA was abundantly expressed in the roots of G. max seedlings but only negligibly in the hypocotyl and cotyledon. An immunocytochemical analysis using anti-GmICHG antibodies, along with green fluorescent protein imaging analyses of Arabidopsis cultured cells transformed by the GmICHG:GFP fusion gene, revealed that the enzyme is exclusively localized in the cell wall and intercellular space of seedling roots, particularly in the cell wall of root hairs. A phylogenetic analysis revealed that GmICHG is a member of glycoside hydrolase family 1 and can be co-clustered with many other leguminous beta-glucosidases, the majority of which may also be involved in flavonoid-mediated interactions of legumes with microbes.

Cells, Cultured↗
PubMed2005

Modified osteoplastic orbitozygomatic craniotomy. Technical note.

The authors report on a surgical technique involving a one-piece osteoplastic bone flap, which incorporates the frontal, temporal, and lateral portions of the orbital rim as a technically simpler alternative to the standard orbitozygomatic (OZ) craniotomy. The orbital rim component extends just laterally from the supraorbital foramen/notch to the frontozygomatic suture. This craniotomy obviates the need for removing the zygoma and has evolved from the authors' experience in more than 200 patients with a variety of pathological lesions, both vascular and tumorous. The osteoplastic aspect of this technique was initially evaluated in 14 cadaveric sites in seven heads dissected prior to implementing this procedure clinically. The osteoplastic bone flap minimally obstructs the surgical view and provides all the advantages of a standard OZ craniotomy. Temporalis muscle atrophy leading to temporal hollowing is avoided, a bone union to the calvaria is improved, and the possibility of bone infection is decreased. The osteoplastic component of the technique adds to the improved long-term cosmesis and warrants active consideration in the art of neurosurgery.

Bone Transplantation↗
PubMed2005

Extradural anterior clinoidectomy. Technical note.

The anterior clinoid process (ACP), located on the skull base, is a relatively small structure, although its removal provides enormous gain in facilitating the management of lesions--either tumors or aneurysms--in the paraclinoid region and upper basilar artery. The extensive surgical field gained contributes to safer exposure of the neurovascular elements in the vicinity while avoiding excessive and hazardous retraction of the brain. In this report the authors present a technically simpler avenue for performing an extradural anterior clinoidectomy after reviewing the anatomy of the ACP and its anatomical variations. Additionally, the original Dolenc procedure and its subseqtient derivatives are compared and contrasted to the authors' simpler and less laborious technique. Different clinical situations in which to use the procedure are described based on the authors' experience from 60 cases (40 aneurysm cases and 20 tumor cases) during a 4-year period.

Brain Neoplasms↗
PubMed2005

Supraorbital craniotomy for parasellar lesions. Technical note.

The authors present a modification to a previously reported supraorbital craniotomy procedure that is smaller, simpler, safe, and cosmetically pleasing. Minimal brain retraction is used without compromising the surgical exposure of the orbital roof, floor of the anterior fossa, and the parasellar region to treat tumoral lesions that are located medial to the ipsilateral optic nerve as well as aneurysms of the anterior communicating artery.

Brain Neoplasms↗
PubMed2004

Extended middle fossa approach: quantitative analysis of petroclival exposure and surgical freedom as a function of successive temporal bone removal by using frameless stereotaxy.

OBJECT: Conventional wisdom regarding skull base surgery says that more extensive bone removal equals greater exposure. Few researchers have quantitatively examined this assertion, however. In this study the authors used a frameless stereotactic system to measure quantitatively the area of petroclival exposure and surgical freedom for manipulation of instruments with successive steps of temporal bone removal. METHODS: With the aid of high-power magnification and a high-speed drill, 12 cadaveric specimens were dissected in four predetermined, successive bone removal steps: 1) removal of the Kawase triangle; 2) removal of the Glasscock triangle; 3) removal of the cochlea together with skeletonization of the anterior internal auditory canal; and 4) inferior displacement of the zygoma. Step 1 offered 62 +/- 43 mm2 of exposed petroclival area, with 84 +/- 69 mm2 of surgical freedom; Step 2, 61 +/- 22 and 76 +/- 58 mm2; Step 3, 128 +/- 47 and 109 +/- 87 mm2; and Step 4, 135 +/- 38 and 102 +/- 69 mm2, respectively. CONCLUSIONS: The middle fossa approach provided a means surgically to expose the petroclival area. When examined quantitatively by using a frameless stereotactic device, the authors determined that the removal of the cochlea and skeletonization of the anterior internal auditory canal (Step 3) provided the most significant increase in both exposure and surgical freedom. Removal of the zygoma improved neither exposure nor surgical freedom.

Cadaver↗
PubMed2003

Altering the substrate chain-length specificity of an alpha-glucosidase.

Dextran glucosidases show high sequence identity (50%) to Bacillus sp. SAM1606 alpha-glucosidase, which is more specific for short-chain substrates. Sequence comparison of these enzymes as well as molecular modeling studies predicted that the extension of loop 4 of the (beta/alpha)(8)-barrel fold may be responsible for the narrower specificity of SAM1606 alpha-glucosidase with respect to substrate chain length. Indeed, deletion mutants of SAM1606 alpha-glucosidase that lack this extension showed higher relative activities toward dextran and long-chain isomaltooligosaccharides. Kinetic and thermodynamic analyses of oligosaccharide hydrolysis catalyzed by SAM1606 alpha-glucosidase and its deletion mutants suggested that the loss of such extension(s) in loop 4 should energetically destabilize the Michaelis complexes with long-chain substrates to result in smaller differences between the activation free energies for the enzymatic hydrolyses of isomaltoheptaose and isomaltose than those observed for the wild-type enzyme. This is the reason that dextran glucosidase, whose loop 4 is shorter in length, shows broader substrate chain-length specificity than does SAM1606 alpha-glucosidase.

Amino Acid Sequence↗
PubMed2003

Deciphering the molecular basis of the broad substrate specificity of alpha-glucosidase from Bacillus sp. SAM1606.

The alpha-glucosidase of Bacillus sp. strain SAM1606 is a member of glycosyl hydrolase family 13, and shows an extraordinarily broad substrate specificity and is one of very few alpha-glucosidases that can efficiently hydrolyze the alpha-1,1-glucosidic linkage of alpha,alpha'-trehalose (trehalose). Phylogenetic analysis of family-13 enzymes suggests that SAM1606 alpha-glucosidase may be evolutionally derived from an alpha-1,6-specific ancestor, oligo-1,6-glucosidase (O16G). Indeed, replacement of Pro(273*) and Thr(342*) of B. cereus O16G by glycine and asparagine (the corresponding residues in the SAM1606 enzyme), respectively, was found to cause 192-fold enhancement of the relative catalytic efficiency for trehalose, suggesting that O16G may easily "evolved" into an enzyme with an extended substrate specificity by substitution of a limited number of amino acids, including that at position 273* (an asterisk indicates the amino-acid numbering of the SAM1606 sequence). To probe the role of the amino acid at position 273* of alpha-glucosidase in determination of the substrate specificity, the amino acid at position 273 of SAM1606 alpha-glucosidase was replaced by all other naturally occurring amino acids, and the resultant mutants were kinetically characterized. The results showed that substitution of bulky residues (e.g., isoleucine and methionine) for glycine at this position resulted in large increases in the K(m) values for trehalose and maltose, whereas the affinity to isomaltose was only minimally affected by such an amino-acid substitution at this position. Three-dimensional structural models of the enzyme-substrate complexes of the wild-type and mutant SAM1606 alpha-glucosidases were built to explore the mechanism responsible for these observations. It is proposed that substitution by glycine at position 273* could eliminate steric hindrance around subsite +1 that originally occurred in parental O16G and is, at least in part, responsible for the acquired broad substrate specificity of SAM1606 alpha-glucosidase.

Amino Acid Sequence↗