Search PubMed⌕ Search

Biomedical subjects

Seiji Takeda

Publications and source records attributed to Seiji Takeda.

10 recordsLinked to original sources
PubMed2005

A RhoGDP dissociation inhibitor spatially regulates growth in root hair cells.

Root hairs are cellular protuberances extending from the root surface into the soil; there they provide access to immobile inorganic ions such as phosphate, which are essential for growth. Their cylindrical shape results from a polarized mechanism of cell expansion called tip growth in which elongation is restricted to a small area at the surface of the hair-forming cell (trichoblast) tip. Here we identify proteins that spatially control the sites at which cell growth occurs by isolating Arabidopsis mutants (scn1) that develop ectopic sites of growth on trichoblasts. We cloned SCN1 and showed that SCN1 is a RhoGTPase GDP dissociation inhibitor (RhoGDI) that spatially restricts the sites of growth to a single point on the trichoblast. We showed previously that localized production of reactive oxygen species by RHD2/AtrbohC NADPH oxidase is required for hair growth; here we show that SCN1/AtrhoGDI1 is a component of the mechanism that focuses RHD2/AtrbohC-catalysed production of reactive oxygen species to hair tips during wild-type development. We propose that the spatial organization of growth in plant cells requires the local RhoGDI-regulated activation of the RHD2/AtrbohC NADPH oxidase.

Arabidopsis↗
PubMed2005

Application of carbon nanotubes for detecting anti-hemagglutinins based on antigen-antibody interaction.

Carbon nanotube sensors detected anti-hemagglutinin binding to immobilized hemagglutinins. An ultra-sensitive detection method for antibodies or antigens in serum is required. Hemagglutinins were immobilized on the reverse side of a carbon nanotube, thereby producing a source and a drain. Electrode pads covered each edge of the nanotube. The I-V curves between the source and the drain were measured after incubation of anti-hemagglutinins with immobilized hemagglutinins in a buffered solution on the reverse side of the nanotube. The sensitivity of the CNT sensor was higher than that of an ELISA system. This method constitutes a new tool to analyze interaction among biomolecules on a substrate.

Animals↗
PubMed2005

Growth of silicon nanowires on H-terminated Si {111} surface templates studied by transmission electron microscopy.

We have studied the growth of silicon nanowires (SiNWs) by means of transmission electron microscopy. SiNWs are grown from nanocatalysts via the Vapor-Liquid-Solid (VLS) mechanism using silane (SiH4) gas as a source gas. The nanocatalysts are prepared on a hydrogen (H)-terminated Si surface. We have examined the formation mechanism of nanocatalysts on H-terminated surface and have observed several structural variants of SiNWs. According to the study we have suggested that many structural variations of SiNWs are possible, which modify the structural properties of SiNWs to great extents.

Journal Article↗
PubMed2005

Analysis of grain boundaries in CoCrTa and CoPtCrB HDD media by analytical transmission electron microscopy.

Crystallographic structures and elemental distributions of grain boundaries in cobalt (Co)-based hard disk drive (HDD) media of CoCrTa and CoPtCrB were analysed by analytical transmission electron microscopy (TEM). CoCrTa medium had crystalline grain boundaries with extremely distorted (0002) planes of hexagonal close-packed structure. The width of grain boundaries of 1.5 nm obtained by high-resolution TEM (HRTEM) imaging agreed with that of 1.5 nm obtained by energy-dispersive spectroscopy (EDS) mapping. The EDS analysis revealed that Cr was segregated to grain boundaries while Ta was not segregated to either grain boundaries or grains. Cobalt was retained within grains. CoPtCrB medium had amorphous grain boundaries and spots in grains. The EDS and electron energyloss spectroscopy analyses revealed that both Cr and B were segregated to grain boundaries and spots. Both Co and Pt were retained within grains. The width of the boundaries of 0.4 nm obtained by HRTEM differed from that of 1.5 nm obtained by high-angle angular dark-field scanning TEM; the former indicates the crystallographic boundary and the later corresponds to the magnetic boundary, which is significantly correlated to the magnetic properties of HDD media.

Journal Article↗
PubMed2004

Mechanical force analysis of peptide interactions using atomic force microscopy.

Some peptides have previously been reported to bind low molecular weight chemicals. One such peptide with the amino acid sequence His-Ala-Ser-Tyr-Ser was selectively screened from a phage library and bound to a cationic porphyrin, 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine (TMpyP), with a binding constant of 10(5) M(-1) (J. Kawakami, T. Kitano, and N. Sugimoto, Chemical Communications, 1999, pp. 1765-1766). The proposed binding was due to pi-electron stacking from two aromatic amino acids of histidine and tyrosine. In this study, the weak interactions between TMpyP and the peptide were further investigated by force curve analysis using atomic force microscopy (AFM). The mechanical force required to unbind the peptide-porphyrin complex was measured by vertical movement of the AFM tip. Peptide self-assembled monolayers were formed on both a gold-coated mica substrate and a gold-coated AFM tip. The TMpyPs could bind between the two peptide layers when the peptide-immobilized AFM tip contacted the peptide-immobilized substrate in solution containing TMpyP. In the retracting process a force that ruptured the interaction between TMpyPs and peptides was observed. The unbinding force values correlated to the concentration of TMpyP. A detection limit of 100 ng/mL porphyrin was obtained for the force measurement, and was similar to surface plasmon resonance sensor detection limits. Furthermore, we calculated the product of the observed force and the length of the molecular elongation to determine the work required to unbind the complexes. The obtained values of unbinding work were in a reasonable range compared to the binding energy of porphyrin-peptide.

Biomechanical Phenomena↗
PubMed2004

[Systemic sclerosis (scleroderma) and malignancy].

The association of malignancy with collagen diseases has been a focus of interest. Especially, relation between dermatomyositis and malignancy is well-recognized. I reviewed here about the coexistence of SSc and malignancy in literature. I would like to raise four points as characteristics of the relationship. (1) Special attention should be paid to the patients who is late-onset, with advanced skin sclerosis (ex. Barnett III type) and male. (2) There are three generalized mechanisms of the association. The first is the predisposition of the malignancy on the basis of organ fibrosis, such as pulmonary fibrosis and lung cancer. The second is the nature of paraneoplastic syndrome. Lastly, immunological derangement inherent to SSc might cause carcinogenesis. (3) It has been documented that the interval of the onsets of SSc and breast cancer is extremely short. (4) Longstanding reflux esophagitis and Barrett's esophagus with SSc is suspected to predispose to esophageal carcinoma.

Female↗
PubMed2003

RABBIT EARS, encoding a SUPERMAN-like zinc finger protein, regulates petal development in Arabidopsis thaliana.

Floral organs usually initiate at fixed positions in concentric whorls within a flower. Although it is understood that floral homeotic genes determine the identity of floral organs, the mechanisms of position determination and the development of each organ have not been clearly explained. We isolated a novel mutant, rabbit ears (rbe), with defects in petal development. In rbe, under-developed petals are formed at the correct position in a flower, and the initiation of petal primordia is altered. The rbe mutation affects the second whorl organ shapes independently of the organ identity. RBE encodes a SUPERMAN-like protein and is located in the nucleus, and thus may be a transcription factor. RBE transcripts are expressed in petal primordia and their precursor cells, and disappeared at later stages. When cells that express RBE are ablated genetically, no petal primordia arise. RBE is not expressed in ap1-1 and ptl-1 mutants, indicating that RBE acts downstream of AP1 and PTL genes. These characteristics suggest that RBE is required for the early development of the organ primordia of the second whorl.

Amino Acid Sequence↗
PubMed2002

Analysis of polarization by means of polarized cathodoluminescence spectroscopy in a TEM.

We have developed a novel method to determine the polarization of light emitted from nanometre-ordered spaces in materials by means of polarized cathodoluminescence (CL) spectroscopy with an ellipsoidal mirror in a transmission electron microscope. We have shown that simulation of CL intensities in full consideration of the effect of reflection on an ellipsoidal mirror is necessary to determine the polarization.

Journal Article↗