Biomedical subjects

Takuya Yamamoto

Publications and source records attributed to Takuya Yamamoto.

23 records · Page 2Linked to original sources

PubMed2003

Dynamic equilibrium of a supramolecular dimeric rhomboid and trimeric hexagon and determination of its thermodynamic constants.

A supramolecular dimeric rhomboid and its trimeric counterpart, a hexagon, are generated by design via the directional bonding methodology of self-assembly. The different-sized supramolecular macrocycles formed by Pt-coordination undergo a concentration- and temperature-dependent dynamic equilibrium. The two structures are characterized by multinuclear NMR and ESI-MS. Extensive study of the dynamic equilibrium of the two species in solution is performed to obtain its thermodynamic properties. By varying the ionic strength, mu, of the solutions, the true thermodynamic equilibrium constant, K, is determined at each experimental temperature (K(253) = 36 +/- 7, K(273) = 18 +/- 6, K(293) = 10 +/- 3, K(313) = 9 +/- 2, K(333) = 5 +/- 2, and K(353) = 3.0 +/- 0.2). By applying these values of true K at the respective temperatures to the van't Hoff equation extended with the entropy term, the standard enthalpy and entropy changes are determined for the equilibrium: with Delta H degrees = -18 +/- 1 kJ mol(-1) and Delta S degrees = -43 +/- 4 J mol(-1) K(-1), respectively, for the forward reaction (rhomboid to hexagon) of the equilibrium. The rhomboid is selectively crystallized, and its crystal structure is determined by X-ray diffraction. The structure reveals a significant amount of porosity as well as distortion of the rhomboid from planarity, leading to channels that can be observed from two viewing positions of the packing.

Crystallization↗

PubMed2003

Percutaneous CT-guided puncture and steroid injection for the treatment of lumbar discal cyst: a case report.

STUDY DESIGN: A case report of discal cyst treated by percutaneous CT-guided puncture and steroid injection. OBJECTIVES: To present the efficacy of percutaneous CT-guided puncture and steroid injection for the treatment of this disorder. SUMMARY OF THE BACKGROUND DATA: Surgical removal of the cyst is usually performed for the treatment of this disorder. However, it was recently reported that direct CT-guided puncture and steroid injection was useful for the treatment of intraspinal synovial cyst. METHODS: A 37-year-old man experienced low back pain and right lower extremity pain with sensory abnormality over the right leg and foot. MRI revealed an extradural spherical mass with low signal intensity on T1-weighted imaging and high signal intensity on T2-weighted imaging behind the L5 vertebral body. On discography, contrast medium rapidly flowed into the cyst through a thin channel from the neighboring disc cavity. Based on these findings, a diagnosis of discal cyst was made. Percutaneous CT-guided puncture and steroid injection were performed. RESULTS: Low back pain, right extremity pain, and numbness disappeared immediately after the procedure. On MRI examination, the cyst gradually diminished in size after the procedure. CONCLUSION: CT-guided percutaneous puncture and steroid injection may be a useful procedure for the treatment of discal cyst.

Adult↗

PubMed2002

Modular structure of a docking surface on MAPK phosphatases.

Mitogen-activated protein kinases (MAPKs) must be precisely inactivated to achieve proper functions in the cells. Ten members of dual specificity phosphatases specifically acting on MAPKs, termed MAPK phosphatases (MKPs), have been reported. Each member has its own substrate specificity that should be tightly regulated. However, the molecular mechanism underlying the regulation of the specificity is largely unknown. In the MAPK signaling pathways, docking interactions, which are different from transient enzyme-substrate interaction, are known to regulate the enzymatic specificity. Here we have identified and characterized a docking surface of MKPs. Our results show that a docking surface is composed of a tandem alignment of three subregions (modules): a cluster of positively charged amino acids, a cluster of hydrophobic amino acids, and a cluster of positively charged amino acids (positive-hydrophobic-positive). This modular structure well fits the docking groove on MAPKs that we have previously identified and may contribute to regulating the docking specificity of the MKP family. The position, number, and species of charged amino acids in each module including the central hydrophobic subregion are important factors in regulation of docking to specific MAPKs. This modular structure in the docking interaction may define a novel model of protein-protein interaction that would also regulate other systems.

Amino Acid Sequence↗

PubMed2002

Self-assembly of molecular prisms via an organometallic "clip".

[reaction: see text] Under the appropriate conditions, the combination of two tritopic pyridyl ligands with three metal-containing molecular "clips" spontaneously generates supramolecular coordination cages with trigonal prismatic frameworks.

Magnetic Resonance Spectroscopy↗

PubMed2002

Double-stranded nef RNA interferes with human immunodeficiency virus type 1 replication.

RNA interference (RNAi) has been reported to be post-transcriptional gene silencing (PTGS) by approximately 500 nucleotide-(nt)-long double-stranded (ds) RNA that specifically targets homologous sequences of messenger RNA. In this report, we describe inhibition of HIV-1 transcription by synthetic dsRNAs constructed with mutated nef genes (nef dsRNAs) derived from long-term non-progressors (LTNPs) using cotransfection of the target gene-expressing plasmid and dsRNA. The effects of nef dsRNAs were examined with luciferase (Luc) reporter which is combined with the HIV-1 (SF2) LTR in persistently HIV-1-infected T cell and macrophage cell lines. At 48 hr, a defective nef dsRNA (556 nt) suppressed Luc activity more potently than did SF2 full-length nef dsRNA (744 nt), suggesting that approximately 500 nt-long nef dsRNA could interfere with the HIV-1 transcription.

Gene Products, nef↗