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Dive into the research topics where Yasutada Imamura is active.

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Featured researches published by Yasutada Imamura.


Micron | 2001

The fibril structure of type V collagen triple-helical domain

Kazunori Mizuno; Eijiro Adachi; Yasutada Imamura; O Katsumata; Taisuke Hayashi

Although the triple-helical structure of fibrillar collagen is regarded in general as being quite similar, each type of collagen molecule has inherent characteristics in the triple-helical domain. Few studies have ever been performed in terms of the aggregate structure of the triple-helical domain of fibrillar collagen. Reconstituted aggregates from the purified triple-helical domain of each type of fibrillar collagen might amplify the subtle differences in the structural characteristics of each type of collagen molecule. In this study, the reconstituted aggregate structure of pepsin-treated type V collagen (type Vp collagen), that is, virtually its triple-helical domain was characterized by transmission electron microscopy. Pepsin-treated type I (type Ip) and type II (type IIp) collagen were compared with type Vp collagen. Unique features of the aggregate structure of the triple-helical domain of the type V collagen can be summarized as follows:These results suggested that the lateral packing of the triple-helical domain of type V collagen is determined by its molecular structure. The characteristics of type Vp collagen fibrils might be explained by their characteristic amino acid composition. A significant feature of the triple-helical domain of type V collagen is the high content of glycosylated hydroxylysine residues. Molecular model building of the collagenous structure suggests that a change in surface roughness is conspicuous by incorporating the glycosylated hydroxylysine residues. More than a ten-fold content of bulky glycosylated hydroxylysine residues in type V collagen compared to that of type I might have a significant influence on both the intermolecular and interfibrillar interactions of the triple-helical domain of type V collagen molecule.


Neuroscience | 2005

Type IX collagen is crucial for normal hearing

Kenji Asamura; Satoko Abe; Yasutada Imamura; Attila Aszodi; Nobuyoshi Suzuki; Shigenari Hashimoto; Yutaka Takumi; Toshihiko Hayashi; Reinhard Fässler; Yusuke Nakamura; Shin-ichi Usami

cDNA microarray analysis indicated that COL9A1 and COL9A3 are highly expressed in the human inner ear, suggesting that type IX collagen has a crucial functional role in the inner ear. This study further confirmed, by means of real-time PCR, the presence of collagen type IX genes in the mouse inner ear. Immunocytochemical analysis also revealed that type IX collagen is distributed in the tectorial membrane, where it co-localizes with type II collagen, indicating that type IX collagen may contribute to the three-dimensional integrated structure of type II collagen molecules. Mice with targeted disruption of the col9a1 gene were shown through assessment by auditory brain stem response to have hearing loss, suggesting an important role of type IX collagen in maintaining normal hearing. At the light microscopic level, the tectorial membrane of knock-out mice was found to be abnormal in shape, and electron microscopy confirmed disturbance of organization of the collagen fibrils. An antibody against type II collagen failed to detect type II collagen in the tectorial membrane of type IX collagen knock-out mice, suggesting that a lack of type IX collagen may affect the three-dimensional structure of type II collagen molecules. These findings indicate that genes encoding each chain of type IX collagen may fulfill an important function associated with the tectorial membrane in the auditory system.


Virus Research | 1987

Nucleotide sequence of the hemagglutinin-neuraminidase gene of Newcastle disease virus avirulent strain D26: evidence for a longer coding region with a carboxyl terminal extension as compared to virulent strains

Hiroki Sato; Seisuke Hattori; Ishida N; Yasutada Imamura; Masao Kawakita

The nucleotide sequence of DNA clones complementary to the genomic RNA of an extremely avirulent strain D26 of Newcastle disease virus was analyzed, and the sequence of 2102 nucleotides directly following F gene reported previously (Sato et al., 1987, Virus Res. 7, 241-255), and corresponding to HN0 gene was determined. A long open reading frame coding for the HN0 peptide of 616 amino acid residues was found in this sequence. It was flanked by the consensus sequences N1 and N2 (Ishida et al., 1986, Nucleic Acids Res. 14, 6551-6564), and the former was shown by the primer extension method to serve as the transcriptional initiation site. The deduced amino acid sequence of the HN0 peptide was highly homologous to that of the HN peptides of strains Beaudette C and B1, but had a carboxyl terminal extension of 39 amino acid residues with a potential glycosylation site in it. The terminal extension is likely to be excised during the processing, and this is consistent with the observation that unglycosylated HN0 is larger in size than unglycosylated HN. A microheterogeneity among the cDNA clones in the nucleotide sequence was also noted which may be relevant to the synthesis of a small amount of an HN-sized peptide in strain D26-infected cells.


Platelets | 2008

Collagen-type specificity of glycoprotein VI as a determinant of platelet adhesion

Stephanie M. Jung; Yukitoshi Takemura; Yasutada Imamura; Toshihiko Hayashi; Eijiro Adachi; Masaaki Moroi

Of the two physiologically important platelet collagen receptors, glycoprotein (GP) VI is the receptor responsible for platelet activation. However, its reactivities towards different types of vascular collagen have not been directly and quantitatively analysed with collagen preparations of defined composition, although the other major platelet collagen receptor integrin α2β1 was shown to react with collagen types I-VI and VIII under either static or flow conditions. We analysed the collagen type specificity of GPVI binding to identify the physiological contribution of the various vascular collagens and how platelet reactivity towards the various collagens may be affected by fibril size. We used two methods to analyse the binding of recombinant GPVI (GPVI-Fc2) to different types of bovine collagen: binding to collagen microparticles in suspension and binding to immobilized collagen. GPVI-Fc2 bound to type I-III collagens that can form large fibrils, but not to type V that only forms small fibrils. The apparent GPVI binding to types IV and V could be ascribed to type I collagen that was a contaminant in each of these preparations. Kinetic analyses of the binding data showed that type III collagen fibrils have both a higher Kd and Bmax than types I and II. Flow adhesion studies demonstrated that type III collagen supports the formation of larger platelet aggregates than type I. Our present results suggest that the physiological importance of type III collagen is to induce thrombus formation. Furthermore, these studies indicate that GPVI mainly binds to collagen types that can form large collagen fibrils.


Bioorganic & Medicinal Chemistry Letters | 2011

β-PNA: Peptide nucleic acid (PNA) with a chiral center at the β-position of the PNA backbone

Toru Sugiyama; Yasutada Imamura; Yosuke Demizu; Masaaki Kurihara; Masashi Takano; Atsushi Kittaka

Peptide nucleic acid (PNA) monomers with a methyl group at the β-position have been synthesized. The modified monomers were incorporated into PNA oligomers using Fmoc chemistry for solid-phase synthesis. Thermal denaturation and circular dichroism (CD) studies have shown that PNA containing the S-form monomers was well suited to form a hybrid duplex with DNA, whose stability was comparable to that of unmodified PNA-DNA duplex, whereas PNA containing the R-form monomers was not.


Connective Tissue Research | 2007

Graded Arrangement of Collagen Fibrils in the Equine Superficial Digital Flexor Tendon

Takafumi Watanabe; Yasutada Imamura; Yoshinao Z. Hosaka; Hiromi Ueda; Kazushige Takehana

By using ultramorphological and biochemical methods, we analyzed the regional differences between the three parts of the equine superficial digital flexor tendon (SDFT), namely, the myotendinous junction (MTJ), middle metacarpal (mM), and osteotendinous junction (OTJ). Cross-sectional images showed unique distributions of collagen fibrils of varying diameters in each region. Small collagen fibrils (diameter <100 nm) were distributed predominantly in the MTJ region, and the OTJ region was relatively rich in large collagen fibrils (diameter >200 nm). In the mM region, the collagen fibrils were intermediately distributed between the MTJ and OTJ. The results indicate a graded arrangement of collagen fibrils in the tendon. Type V collagen was detected preferentially in the MTJ region. Since type V collagen is believed to be one of the collagens regulating collagen fibril formation, its possible functionality in the MTJ region in terms of fibril formation and fibril arrangement in the tendon has been discussed here.


Journal of Anatomy | 2012

Concerted and adaptive alignment of decorin dermatan sulfate filaments in the graded organization of collagen fibrils in the equine superficial digital flexor tendon

Takafumi Watanabe; Yasutada Imamura; Daisuke Suzuki; Yoshinao Z. Hosaka; Hiromi Ueda; Kohzy Hiramatsu; Kazushige Takehana

The equine superficial digital flexor tendon (SDFT) has a graded distribution of collagen fibril diameters, with predominantly small‐diameter fibrils in the region of the myotendinous junction (MTJ), a gradual increase in large‐diameter fibrils toward the osteotendinous junction (OTJ), and a mixture of small‐ and large‐diameter fibrils in the middle metacarpal (MM) region. In this study, we investigated the ultrastructure of the SDFT, to correlate the spatial relationship of the collagen fibrils with the graded distribution. The surface‐to‐surface distances of pairs of fibrils were found to be almost constant over the entire tendon. However, the center‐to‐center distances varied according to fibril diameter. Decorin is the predominant proteoglycan in normal mature tendons, and has one dermatan sulfate (DS) or chondroitin sulfate (CS) filament as a side chain which is associated with the surfaces of the collagen fibrils via its core protein. We identified a coordinated arrangement of decorin DS filaments in the equine SDFT. The sizes of the decorin DS filaments detected by Cupromeronic blue staining showed a unique regional variation; they were shortest in the MM region and longer in the MTJ and OTJ regions, and a considerable number of filaments were arranged obliquely to adjacent collagen fibrils in the MTJ region. This regional variation of the filaments may be an adaptation to lubricate the interfibrillar space in response to local mechanical requirements. The results of this study suggest that the MTJ region, which receives the muscular contractile force first, acts as a buffer for mechanical forces in the equine SDFT.


Journal of Biochemistry | 2008

Intercellular accumulation of type V collagen fibrils in accordance with cell aggregation.

Takanori Kihara; Yasutada Imamura; Yukitoshi Takemura; Kazunori Mizuno; Eijiro Adachi; Toshihiko Hayashi

We reported previously that human fibroblasts form clumps when cultured on a dish coated with reconstituted type V collagen fibrils. Essentially all the type V collagen fibrils, initially coated on the dish, were recovered in the cell clumps that had eventually formed during the culture. We interpreted that type V collagen fibrils adhere to cells more strongly than to the dish and are detached by cell movements. In this study, type V collagen was suspended with fibroblasts to examine the fate of the type V collagen fibrils and to determine whether the fibrils affect the behaviour of the cells directly adherent to the dish. The added type V collagen accumulated in the intercellular space concomitantly with the local aggregation of fibroblasts. scanning electron microscope examination indicated that type V collagen fibrils were found in the vicinity of cells in cultures without ascorbic acid where essentially no collagen secretion takes place. These results indicate that type V collagen forms fibrils and the fibrils are accumulated in the intercellular spaces. The accumulated type V collagen fibrils work as a cementing material for cell clump formation. This phenomenon is discussed in relation to the possible involvement of type V collagen fibrils in tissue organization.


Cell and Tissue Research | 2004

Reconstituted type V collagen fibrils as cementing materials in the formation of cell clumps in culture

Takanori Kihara; Yukitoshi Takemura; Yasutada Imamura; Kazunori Mizuno; Toshihiko Hayashi

Previous studies have reported that type V collagen is an anti-adhesive substrate for cultured cells in that the cells detach from culture dishes coated with type V collagen molecules or polypeptides derived from them. We have noticed that human fetal lung fibroblasts (TIG-1) initially show no reduction in adherence to and spreading on a dish coated with reconstituted type V collagen fibrils but eventually detach from the dish and form cell clumps. To determine the way in which reconstituted type V collagen fibrils are involved in cell clump formation, we have followed the fate of the fluorescence of type V collagen fibrils pre-labeled with fluorescein isothiocyanate. Essentially, all the fluorescence disappeared from the dish surface as the cells detached and was condensed in the cell clumps. The cells that were recovered from clumps and dissociated into separate cells by trypsin treatment proliferated normally after they were seeded on a bare culture dish. This result and those from gel electrophoresis, fluorescence microscopy, and a cell proliferation assay indicate that the cell detachment from the dish is not caused by cell necrosis or apoptosis but by cellular motility together with the unique features of type V collagen fibrils. Not only the adherence of type V collagen fibrils to TIG-1 cells is much stronger than that to the culture dish, but the fibrils are retained on the cellular surface. The strong adherence of type V collagen fibrils to cells plays a role in cementing TIG-1 cells together.


Heliyon | 2015

Non-Triple Helical Form of Type IV Collagen α1 Chain

Hiroaki Sugiyama; Kazuhiro Tokunaka; Toshihiko Hayashi; Yasutada Imamura; Makoto Morita; Masayuki Yamato

Type IV collagen with a triple-helical structure composed of three α chains is a major component of basement membrane. Previously, we reported that non-triple helical form of type IV collagen α1 chain (NTHα1(IV)) was isolated from human placenta and the culture media of human cells. In the present study, we report on the localization of NTH α1(IV) with a monoclonal antibody #370, exclusively reactive for the nascent chain, in the rabbit tissues. The staining was found on the basement membrane of blood vessels, of endomysium, of nerve, and of kidney but not on epithelial basement membrane. In a rabbit angiogenic model, #370 antibody staining was exclusively observed in neovascular tip region of endothelial cells, where no staining with anti-type IV collagen antibody was seen. Distinct localizations suggest that NTHα1(IV) is produced and stably deposited in endothelial cells and the surroundings under physiological conditions with some physiological roles in relation to the dynamics of vascular system.

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Toru Sugiyama

Iwate Medical University

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