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Articles by A Yamada
Total Records ( 3 ) for A Yamada
  T Takeuchi , K Nishiyama , K. i Sugiura , M Takahashi , A Yamada , S Kobayashi , H Takahashi , H Natsugari and K. i. Kasai
 

Galβ1-4GlcNAc is thought to be a common disaccharide unit preferentially recognized by vertebrate galectins. Eight-amino-acid residues conserved in proteins belonging to the galectin family have been suggested to be responsible for recognition. Meanwhile, we isolated and analyzed endogenous N-glycans of Caenorhabditis elegans that were captured by a C. elegans galectin LEC-6 and demonstrated that the unit of recognition for LEC-6 is a Gal-Fuc disaccharide, though the linkage between these residues was not confirmed. In the present study, we chemically synthesized Galβ1-4Fuc and Galβ1-3Fuc labeled with 2-aminopyridine (PA) and demonstrated that LEC-6 interacts with PA-Galβ1-4Fuc more strongly than PA-Galβ1-3Fuc by frontal affinity chromatography (FAC). Galβ1-4Fuc also inhibited hemagglutination caused by LEC-6 more strongly than Galβ1-3Fuc. FAC analysis using LEC-6 point mutants revealed that some of the conserved amino acid residues which have proven to be important for the recognition of Galβ1-4GlcNAc are not necessary for the binding to Galβ1-4Fuc. Another major C. elegans galectin, LEC-1, also showed preferential binding to Galβ1-4Fuc. These results suggest that Galβ1-4Fuc is the endogenous unit structure recognized by C. elegans galectins, which implies that C. elegans glycans and galectins may have co-evolved through an alteration in the structures of C. elegans glycans and a subsequent conversion in the sugar-binding mechanism of galectins. Furthermore, since glycans containing the Galβ1-4Fuc disaccharide unit have been found in organisms belonging to Protostomia, this unit might be a common glyco-epitope recognized by galectins in these organisms.

  M Mitsuki , K Nara , T Yamaji , A Enomoto , M Kanno , Y Yamaguchi , A Yamada , S Waguri and Y. Hashimoto
 

Siglec-7, a sialic acid binding immunoglobulin-like lectin, predominantly transduces inhibitory signals through cytosolic immunoreceptor tyrosine-based inhibitory motifs (ITIMs). Here, we report that clustering of Siglec-7 with a specific F(ab')2 elicited cell death. Interestingly, a truncated Siglec-7 lacking the cytosolic ITIM domain still induced the cell death, suggesting that the ITIMs are not essential for the death signaling. Further analyses of the death signaling revealed that an oxygen radical scavenger, N-acetyl cysteine, completely inhibited the cell death, whereas a pancaspase inhibitor did not. In addition, caspase-3 activation, DNA ladder formation, and nuclear condensation were not detected during the death process, suggesting that the cell death is nonapoptotic. To identify the critical region for the death signaling, we prepared a series of shuffling chimeras between Siglec-7 and Siglec-9, the latter of which did not transduce a death signal. The critical region was mapped to the middle of the membrane-proximal C2-set domain, which contained only six amino acid differences between Siglec-7 and Siglec-9. Point mutation analyses of each of these six amino acids revealed that four of the six amino acids were critical for the death signal. A computer-assisted 3D modeling revealed that these four amino acids were proximally located on the surface of the C2-set domain. In conclusion, Siglec-7 induces nonapoptotic cell death, the signal for which is transduced by an extracellular C2-set domain.

  O Yamazaki , N Hanafusa , A Yamada , E Noiri and T. Fujita
 

Gastrointestinal (GI) bleeding is a common and troublesome complication of end-stage renal disease (ESRD). Patients often have various lesions in the small bowel and in either upper or lower GI tracts. Recently developed double-balloon endoscopy (DBE) enables observation of the entire small intestine through a combination of anterograde and retrograde approaches. Moreover, DBE is useful not only for diagnosis of small intestinal lesions; it provides a mode of treating the disease. This article presents patients with several small intestinal diseases from our facility. Their bleeding sources were identified using DBE. We also report two representative cases of angiodysplasia that had been diagnosed and treated successfully using DBE. One case particularly underscored the usefulness of the combination of capsule endoscopy (CE) and DBE as an electively diagnostic approach for patients with GI bleeding. Small intestinal bleeding is often observable repeatedly in a single patient, as described for case 1. In such circumstances, DBE can treat the lesions successfully without surgical procedures. In this report, ESRD patients, in whom comorbid conditions made it difficult to perform surgical procedures, receive great benefit from DBE.

 
 
 
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