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Biomedical subjects

S Kawaguchi

Publications and source records attributed to S Kawaguchi.

At least 19 recordsLinked to original sources
PubMed2001

The crystal structure of the ttCsaA protein: an export-related chaperone from Thermus thermophilus.

The CsaA protein was first characterized in Bacillus subtilis as a molecular chaperone with export-related activities. Here we report the 2.0 Angstrom-resolution crystal structure of the Thermus thermophilus CsaA protein, designated ttCsaA. Atomic structure and experiments in solution revealed a homodimer as the functional unit. The structure of the ttCsaA monomer is reminiscent of the well known oligonucleotide-binding fold, with the addition of extensions at the N- and C-termini that form an extensive dimer interface. The two identical, large, hydrophobic cavities on the protein surface are likely to constitute the substrate binding sites. The CsaA proteins share essential sequence similarity with the tRNA-binding protein Trbp111. Structure-based sequence analysis suggests a close structural resemblance between these proteins, which may extend to the architecture of the binding sites at the atomic level. These results raise the intriguing possibility that CsaA proteins possess a second, tRNA-binding activity in addition to their export-related function.

Amino Acid Sequence↗
PubMed2001

Structure of the EMAPII domain of human aminoacyl-tRNA synthetase complex reveals evolutionary dimer mimicry.

The EMAPII (endothelial monocyte-activating polypeptide II) domain is a tRNA-binding domain associated with several aminoacyl-tRNA synthetases, which becomes an independent domain with inflammatory cytokine activity upon apoptotic cleavage from the p43 component of the multisynthetase complex. It comprises a domain that is highly homologous to bacterial tRNA-binding proteins (Trbp), followed by an extra domain without homology to known proteins. Trbps, which may represent ancient tRNA chaperones, form dimers and bind one tRNA per dimer. In contrast, EMAPII domains are monomers. Here we report the crystal structure at 1.14 Angstroms of human EMAPII. The structure reveals that the Trbp-like domain, which forms an oligonucleotide-binding (OB) fold, is related by degenerate 2-fold symmetry to the extra-domain. The pseudo-axis coincides with the dyad axis of bacterial TtCsaA, a Trbp whose structure was solved recently. The interdomain interface in EMAPII mimics the intersubunit interface in TtCsaA, and may thus generate a novel OB-fold-based tRNA-binding site. The low sequence homology between the extra domain of EMAPII and either its own OB fold or that of Trbps suggests that dimer mimicry originated from convergent evolution rather than gene duplication.

Amino Acid Sequence↗
PubMed2000

Free energy requirement for domain movement of an enzyme.

Domain movement is sometimes essential for substrate recognition by an enzyme. X-ray crystallography of aminotransferase with a series of aliphatic substrates showed that the domain movement of aspartate aminotransferase was changed dramatically from an open to a closed form by the addition of only one CH(2) to the side chain of the C4 substrate CH(3)(CH(2))C((alpha))H(NH(3)(+))COO(-). These crystallographic results and reaction kinetics (Kawaguchi, S., Nobe, Y., Yasuoka, J., Wakamiya, T., Kusumoto, S., and Kuramitsu, S. (1997) J. Biochem. (Tokyo) 122, 55-63; Kawaguchi, S. and Kuramitsu, S. (1998) J. Biol. Chem. 273, 18353-18364) enabled us to estimate the free energy required for the domain movement.

Aspartate Aminotransferases↗
PubMed2000

A VH11V kappa 9 B cell antigen receptor drives generation of CD5+ B cells both in vivo and in vitro.

B lymphocytes can be divided into different subpopulations, some with distinctive activation requirements and probably mediating specialized functions, based on surface phenotype and/or anatomical location, but the origins of most of these populations remain poorly understood. B cells constrained by transgenesis to produce an Ag receptor derived from a conventional (B-2) type cell develop a B-2 phenotype, whereas cells from mice carrying a B-1-derived receptor acquire the B-1 phenotype. In this study transgenic enforced expression of a B cell receptor (mu/kappa) originally isolated from a CD5+ (B-1a) B cell generates B-1 phenotype cells in bone marrow cultures that show a distinctive B-1 function, survival in culture. Despite their autoreactivity, we find no evidence for receptor editing or that the paucity of B-2 cells is the result of tolerance-induced selection. Finally, Ca2+ mobilization studies reveal a difference between transgenic B-1 cells in spleen and peritoneal cavity, with cells in spleen much more responsive to anti-B cell receptor cross-linking. We discuss these results in terms of specificity vs lineage models for generation of distinctive B cell subpopulations.

Adoptive Transfer↗
PubMed2000

Macromolecular surfactant as a pseudo-stationary phase in micellar electrokinetic capillary chromatography.

We examined polymers of sodium 11-acrylamidoundecanoate [poly(Na 11-AAU)] with a very high molecular mass (>10(6)) for their potential use as a pseudo-stationary phase in micellar electrokinetic capillary chromatography (MEKC). Size-exclusion chromatography and capillary electrophoresis studies reveal that the polymers are highly charged, and have a densely packed chain structure. For aromatic compounds, the polymeric surfactant showed significantly different selectivity than sodium dodecyl sulfate (SDS). It was suggested that one molecule of poly(Na 11-AAU) forms one micelle. The structural stability of this pseudo-stationary phase permitted its use with relatively high percentages of organic modifiers in the buffer medium, allowing the separation of highly hydrophobic compounds which are difficult to analyze by conventional MEKC with SDS.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2000

The molecular structure of hyperthermostable aromatic aminotransferase with novel substrate specificity from Pyrococcus horikoshii.

Aromatic amino acid aminotransferase (ArATPh), which has a melting temperature of 120 degrees C, is one of the most thermostable aminotransferases yet to be discovered. The crystal structure of this aminotransferase from the hyperthermophilic archaeon Pyrococcus horikoshii was determined to a resolution of 2.1 A. ArATPh has a homodimer structure in which each subunit is composed of two domains, in a manner similar to other well characterized aminotransferases. By the least square fit after superposing on a mesophilic ArAT, the ArATPh molecule exhibits a large deviation of the main chain coordinates, three shortened alpha-helices, an elongated loop connecting two domains, and a long loop transformed from an alpha-helix, which are all factors that are likely to contribute to its hyperthermostability. The pyridine ring of the cofactor pyridoxal 5'-phosphate covalently binding to Lys(233) is stacked parallel to F121 on one side and interacts with the geminal dimethyl-CH/pi groups of Val(201) on the other side. This tight stacking against the pyridine ring probably contributes to the hyperthermostability of ArATPh. Compared with other ArATs, ArATPh has a novel substrate specificity, the order of preference being Tyr > Phe > Glu > Trp > His>> Met > Leu > Asp > Asn. Its relatively weak activity against Asp is due to lack of an arginine residue corresponding to Arg(292)* (where the asterisk indicates that this is a residues supplied by the other subunit of the dimer) in pig cytosolic aspartate aminotransferase. The enzyme recognizes the aromatic substrate by hydrophobic interaction with aromatic rings (Phe(121) and Tyr(59)*) and probably recognizes acidic substrates by a hydrophilic interaction involving a hydrogen bond network with Thr(264)*.

Amino Acid Sequence↗
PubMed2000

Author reply

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Journal Article↗
PubMed2000

Management of nodular goiters and their operative indications.

It remains controversial whether or not nodular goiters should be treated surgically or conservatively. This report reviews our 9-year experience of treating nodular goiters in 334 patients, 44 of whom underwent surgery, and compares the methods of treatment employed from 1990 to 1999 with those employed from 1971 to 1989 when 171 operations were carried out. In accordance with diagnoses made using fine-needle aspiration biopsy (FNAB) and ultrasonography, patients were treated as follows. Those with cysts were given percutaneous ethanol injection therapy (PEIT), and those with solid tumors underwent surgery if cancer of >class 3 was suspected or if the tumors were >3 cm. Consequently, 44 patients with solid tumors underwent surgery and 72 with cysts were treated by PEIT. The number of operations performed annually decreased to half of the pre-1990 figure. During the follow-up of those patients who did not undergo surgery, four with solid tumors and two with cysts later required surgery due to suspected carcinoma of >class 3 in 3 patients or as a result of personal choice in 3 patients. The growth of solid tumors was not able to be measured in most cases. These results indicate that the number of operations performed for nodular goiters can be reduced by PEIT. An accurate cytological diagnosis supports this therapeutic strategy.

Biopsy, Needle↗
PubMed2000

Color and translucency of in vivo natural central incisors.

STATEMENT OF PROBLEM: The range of shades in shade guides is not consistent with natural teeth, and there is no information on the color and translucency of the natural tooth for all age groups. Therefore, it is important to obtain a database of the characteristics of the natural tooth from a wide age group. PURPOSE: This study obtained information on color and translucency of natural teeth for all age groups, and attempted to clarify the difference of the color and translucency between natural teeth and VITA Lumin Vacuum shade guide. MATERIAL AND METHODS: Natural central incisors of 87 subjects (42 men and 45 women; age range from 13 to 84 years) and 16 shades of VITA Lumin Vacuum shade guide were evaluated. Color and translucency of 5 sites, each 1.0 mm in diameter, on the surfaces of individual teeth were measured for L*, a*, and b*, using a color computer according to CIELAB color spaces. RESULTS: At the center site, negative correlation was found between age and L*, with positive correlation between age and b*. Both a* and b* of the natural tooth increased when moving in the direction of the cervical site, but translucency decreased in the direction of the root. The a* value for the natural tooth was significantly higher than those for VITA Lumin Vacuum shade guide. CONCLUSION: This study found that the older the subject, the darker and more yellow the color at the center site of the natural tooth. Both reddish and yellowish colors of natural teeth tend to increase from the incisal to cervical, whereas translucency decreases. Red-green chromaticity of VITA Lumin Vacuum shade guide was not distributed to cover the natural tooth.

Adolescent↗
PubMed2000

VAMP-2 promotes neurite elongation and SNAP-25A increases neurite sprouting in PC12 cells.

Recent studies suggest that the soluble N-ethylmaleimide-sensitive factor attached protein (SNAP) receptor (SNARE)-mediated membrane fusion system is involved in vesicle fusion in the plasma membrane that allows expansion for neurite elongation. There have been several reports analyzing the effects of neurite outgrowth by inhibition of SNAREs. In this study, we took the opposite approach by overexpressing green fluorescent protein (GFP)-fusion SNAREs, including VAMP-2, SNAP-25A, and syntaxin1A, in PC12 cells to investigate the role of SNAREs in the neurite outgrowth of PC12 cells. Neurite outgrowth analysis demonstrated that: (1) GFP-VAMP-2 increased the length of individual neurites, without changing the number of neurites per cell; (2) GFP-SNAP-25A increased the number of neurites per cell, with no change in the length of the individual neurites. In both cases, the total length of neurites per cell was increased; (3) GFP-syntaxin1A resulted in no significant change, either in neurite length, or in the number of neurites per cell. These findings suggest that when overexpressed in PC12 cells, VAMP-2 can promote neurite elongation, while SNAP-25A can stimulate neurite sprouting. On the other hand, overexpression of syntaxin1A neither promotes nor inhibits neurite outgrowth. Thus VAMP-2 and SNAP-25A play different roles in neurite elongation and sprouting.

Animals↗
PubMed2000

Suppression of inhibitory synaptic potentiation by presynaptic activity through postsynaptic GABA(B) receptors in a Purkinje neuron.

At inhibitory synapses on a cerebellar Purkinje neuron, the depolarization caused by heterosynaptic climbing fiber activation induces long-lasting potentiation accompanied by an increase in GABA(A) receptor responsiveness. Here we show that activation of a presynaptic inhibitory interneuron during the conditioning postsynaptic depolarization suppresses the potentiation. The suppression is due to postsynaptic GABA(B) receptor activation by GABA released from presynaptic terminals. The results suggest that GABA(B) receptor activation decreases the activity of cAMP-dependent protein kinase through the G(i)/G(o) proteins. The presynaptic activity-dependent suppression of synaptic plasticity is a novel regulatory mechanism of synaptic efficacy at individual synapses and may contribute to the learning and computational ability of the cerebellar cortex.

Animals↗
PubMed2000

Extensive cervical laminoplasty for patients with long segment OPLL in the cervical spine: an alternative to the anterior approach.

We investigated treatment of long segment cervical OPLL by posterior decompression using a laminoplasty technique. Our aim was to both decompress the spinal cord and also to preserve neck motion. There were 38 patients treated by this posterior approach. Twenty-eight patients underwent C1-C7 expanding laminoplasty, 4 patients underwent C1-T1 expanding laminoplasty, and 6 patients C2-C7 expanding laminoplasty. The transverse width of the open-door laminoplasty was sufficient to achieve decompression of not only the spinal cord but also the nerve root outlets at each laminoplasty level. There were no complications related to this surgical technique, nor late deterioration in the mean follow up period of 4. 5 years. We propose expanding laminoplasty as an important option for the treatment of long segment cervical OPLL.

Decompression, Surgical↗
PubMed2000

Colour Doppler flow imaging of the superior ophthalmic vein in dural arteriovenous fistulas before and after surgery.

The aim of this study was to examine the clinical significance of the colour Doppler flow imaging (CDFI) findings of the superior ophthalmic vein (SOV) in intracranial dural arteriovenous fistulas (DAVF). The SOV was examined by CDFI in 12 cases of DAVF before and after surgery. Before surgery, the average SOV diameter was 3.57+/-1.18 mm (mean +/- standard deviation, which was significantly wide (P<0.05) compared with the control value. One case showed reversed flow. Four cases showed an abnormal waveform. The cases with the more severe clinical symptoms showed wider SOV diameters and more abnormal waveforms than those with mild clinical symptoms. Postoperatively, the mean SOV diameter and mean resistance index improved significantly (P< 0.05); the flow direction and waveform became normal in each. The SOV CDFI findings were found to be useful as screening and follow-up techniques for the intracranial DAVFs.

Adult↗
PubMed2000

Surgery for dural arteriovenous fistula in superior sagittal sinus and transverse sigmoid sinus.

The aim of this study was to evaluate the outcome of surgically treated dural arteriovenous fistula (DAVF). The authors performed surgical removal of DAVF in 12 patients. The locations of DAVF were the transverse sigmoid sinus in seven patients and superior sagittal sinus in five patients. These 12 patients had undergone endovascular embolisation prior to removal. Among them, six patients were completely cured, according to angiography immediately after embolisation, but these six patients showed the recurrence of DAVF within 1 year. The other six patients showed a decrease of feeding vessels. Therefore, all 12 patients underwent surgical removal of DAVF. The surgical strategies were as follows. The feeding vessels and the cortical veins with retrograde filling were occluded and cut. The affected sinus was skeletonised, and if it was occluded or almost occluded, the sinus was removed. Postoperatively, transient aphasia was seen in one patient. There was no surgical morbidity or mortality. During the follow-up period (mean 2.9 years), no recurrence of DAVF was seen. Surgical treatment is a safe and effective treatment manoeuvre for DAVF around the transverse sigmoid sinus and superior sagittal sinus.

Adult↗
PubMed2000

Induction of apoptosis in glioma cells by recombinant human Fas ligand.

OBJECTIVE: Fas ligand (FasL) belongs to the tumor necrosis factor family and has the ability to induce apoptosis in susceptible target cells by binding to its receptor, Fas. It has been demonstrated recently that the FasL/Fas system plays a pivotal role in the cytocidal activity of T lymphocytes in the immune system. FasL may act as a cytotoxic effector molecule to Fas-expressing malignant tumor cells. We reported previously that Fas is commonly expressed in human brain tumor cells. In this study, we examine the possible application of FasL to therapy for malignant brain tumors. METHODS: To develop an expression system yielding large amounts of FasL, we constructed a baculovirus vector containing complementary deoxyribonucleic acid of human FasL under the control of a polyhedrin promoter. We produced human FasL in Spodoptera frugiperda (Sf9) insect cells infected by the recombinant baculovirus carrying FasL complementary deoxyribonucleic acid and studied the cytocidal activity of FasL against the T98G human glioblastoma cell line. RESULTS: FasL expression in Sf9 cells was confirmed immunocytochemically with rabbit antibody raised against the cytoplasmic domain of human FasL. The FasL released into the supernatant of cultured Sf9 cells was also verified by Western blotting, and it specifically induced apoptosis in T98G cells. The induced apoptosis by recombinant human FasL was confirmed by annexin V-fluorescein isothiocyanate staining. CONCLUSION: The present results suggest that the induction of apoptosis by the Fas/FasL system could be a new strategy for the treatment of malignant brain tumors, which are resistant to conventional therapies.

Animals↗
PubMed2000

Effect of direct arterial bypass on the prevention of future stroke in patients with the hemorrhagic variety of moyamoya disease.

OBJECT: The authors evaluated the effects of superficial temporal artery-middle cerebral artery (STA-MCA) bypass in the prevention of future stroke, including rebleeding or an ischemic event, in patients suffering from hemorrhagic moyamoya disease by comparing this method with indirect bypass and conservative treatment. METHODS: Twenty-two patients who had hemorrhagic moyamoya disease but no aneurysm comprised the study group. These patients' clinical charts were examined with respect to their treatment and clinical course after an initial hemorrhagic episode. The mean age of the patients was 43 years and the follow-up period ranged from 0.8 to 15.1 years, with a mean of 8 years. Eleven patients (50%) were conservatively treated. Among the 11 patients who were surgically treated, STA-MCA bypass was performed in six patients (27%) and encephaloduroarteriosynangiosis (EDAS) in the other five patients (23%). Nine patients (41%) presented with an ischemic or rebleeding event during the follow-up period. The incidence of future stroke events in patients who had undergone an STA-MCA bypass was significantly lower (p<0.05) than that in patients who had been treated conservatively or with EDAS. Kaplan-Meier plots comparing stroke-free times in patients treated with direct bypass and those in patients who conservatively or with indirect bypass showed a significant difference (p<0.05) in favor of direct bypass. CONCLUSIONS: The effect of STA-MCA bypass on the prevention of recurrent hemorrhage or an ischemic event in patients with hemorrhagic moyamoya disease has been statistically confirmed in this study.

Adult↗