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Biomedical subjects

Hiroshi Okamoto

Publications and source records attributed to Hiroshi Okamoto.

At least 19 recordsLinked to original sources
PubMed2006

Overexpression of human CD38/ADP-ribosyl cyclase enhances acetylcholine-induced Ca2+ signalling in rodent NG108-15 neuroblastoma cells.

The role of cyclic ADP-ribose (cADPR) and its synthetic enzyme, CD38, as a downstream signal of muscarinic acetylcholine receptors (mAChRs) was examined in neuroblastoma cells expressing M1 mAChRs (NGM1). NGM1 cells were further transformed with both wild-type and mutant (C119K/C201E) human CD38. The dual transformed cells exhibited higher cADPR formation than ADPR production and elevated intracellular free Ca(2+) concentrations ([Ca(2+)](i)) in response to ACh. These phenotypes were analyzed in detail in a representative CD38 clone. The intracellular cADPR concentration by ACh application was significantly increased by CD38 overexpression. Digital image analysis by a confocal microscopy revealed that topographical distribution of the sites of Ca(2+) release was unchanged between control and overexpressed cells. These results indicate that cADPR is an intracellular messenger of Ca(2+) signalling, suggesting that CD38 can contribute to mAChR-cADPR signalling.

ADP-ribosyl Cyclase↗
PubMed2006

Osteopontin and cardiovascular system.

A matricellular protein, osteopontin (OPN), is expressed in response to mechanical stress and similar stimuli in the heart, integrates the inter-ECM signal transduction network of component cells, and maintains efficient contractility through quantitative and qualitative control of extracellular matrix (ECM) proteins. In particular, OPN is re-expressed in the process of tissue damage; combines with other cell growth factors, cytokines, chemokines, and proteases as a cytokine itself or as an adhesion molecule; and controls the differentiation and growth of cells involved in restoration of tissues by controlling inter-cellular signal transduction and production of ECM proteins through regulation of expression levels and activity. A study using mice lacking a functional OPN gene indicated that tissue restoration fails and collagen deposition is inhibited through matrix metalloproteinases (MMPs) in mice lacking OPN. Thus, while OPN accelerates the cardiovascular remodeling process, it also regulates the balance of various inter-cellular activities. In addition, OPN not only promotes arteriosclerosis but is also closely associated with angiogenesis. With the roles of OPN expected to be clinically elucidated, the clinical use of OPN for control of cardiovascular remodeling may be feasible. Points (1) Osteopontin (OPN) efficiently propagates contraction in the heart as a matricellular protein and thereby controls ECM proteins both quantitatively and qualitatively. (2) The quantitative and qualitative control of ECM proteins is involved in interaction with OPN receptors including those of the integrin family, CD44, and others. (3) OPN promotes myocardial remodeling through TGFbeta and MMPs. (4) OPN not only promotes arteriosclerosis but is also closely associated with arteriosteogenesis. (5) In animals lacking OPN, tissue remodeling process is inhibited, especially in terms of fibrosis after myocardial infarction. (6) While the significance of OPN as an immune system molecule is still unclear in detail, the significance of OPN in the regenerative immune system has begun to be determined.

Amino Acid Sequence↗
PubMed2006

REG I expression predicts long-term survival among locally advanced thoracic squamous cell esophageal cancer patients treated with neoadjuvant chemoradiotherapy followed by esophagectomy.

BACKGROUND: The prognosis for patients with locally advanced thoracic esophageal cancer is extremely unfavorable. We have been administering neoadjuvant chemoradiotherapy (CRT) followed by esophagectomy to these patients and studying whether REG I expression in untreated endoscopic biopsy specimens is predictive of patient responsiveness to CRT and/or survival after treatment. METHODS: Between 1992 and 2003, 47 patients with T4 (direct invasion of adjacent organs) thoracic esophageal cancers were administered neoadjuvant CRT followed by esophagectomy. REG I expression was assessed in untreated endoscopic biopsy specimens and correlated with clinical and histological responses and survival in 37 patients who had also undergone curative surgery. RESULTS: Among the 37 cases that received CRT followed by surgery, the therapeutic response rate for neoadjuvant CRT was 68%, and a complete histological response in resected specimens from the primary lesion was achieved in 8 (22%) patients. These clinical and histological responses to neoadjuvant CRT did not significantly correlate with survival, however. By contrast, 9 patients were judged REG-positive based on analysis of their untreated endoscopic biopsy specimens, and their cumulative survival rate was significantly higher than that of the 28 REG-negative patients (P = 0.0073). Univariate analysis showed REG I expression to be a prognostic factor (P = 0.0386) that increased the risk of death 8.4-fold. CONCLUSIONS: Evaluation of REG I expression in untreated endoscopic biopsy specimens may provide a basis for new treatments of locally advanced thoracic squamous cell esophageal cancers.

Adult↗
PubMed2006

Angiotensin II stimulates endothelial NO synthase phosphorylation in thoracic aorta of mice with abdominal aortic banding via type 2 receptor.

Abdominal aortic banding in mice induces upregulation of angiotensin II (Ang II) type 2 (AT2) receptors in the pressure-overloaded thoracic aorta. To clarify mechanisms underlying the vascular AT2 receptor-dependent NO production, we measured aortic levels of endothelial NO synthase (eNOS), eNOS phosphorylated at Ser633 and Ser1177, protein kinase B (Akt), and Akt phosphorylated at Ser473 in thoracic aortas of mice after banding. Total eNOS, both forms of phosphorylated eNOS, Akt, and phosphorylated Akt levels, as well as cGMP contents, were significantly increased 4 days after banding. The administration of PD123319 (an AT2 receptor antagonist) or icatibant (a bradykinin B2 receptor antagonist) abolished the banding-induced upregulation of both forms of phosphorylated eNOS, as well as elevation of cGMP, but did not affect the upregulation of eNOS, Akt, and phosphorylated Akt. In the in vitro experiments using aortic rings prepared from banded mice, Ang II produced significant increases in both forms of phosphorylated eNOS, as well as cGMP, and these effects were blocked by PD123319 and icatibant. Ang II-induced eNOS phosphorylation and cGMP elevation in aortic rings were inhibited by protein kinase A (PKA) inhibitors H89 and KT5720 but not by phosphatidylinositol 3-kinase inhibitors wortmannin and LY24002. The contractile response to Ang II was attenuated in aortic rings from banded mice via AT2 receptor, and this attenuation was blocked by PKA inhibitors. These results suggest that the activation of AT2 receptor by Ang II induces phosphorylation of eNOS at Ser633 and Ser1177 via a PKA-mediated signaling pathway, resulting in sustained activation of eNOS.

Angiotensin II↗
PubMed2006

Computational algorithms and neuronal network models underlying decision processes.

Animals or humans often encounter such situations in which they must choose their behavioral responses to be made in the near or distant future. Such a decision is made through continuous and bidirectional interactions between the environment surrounding the brain and its internal state or dynamical processes. Therefore, decision making may provide a unique field of researches for studying information processing by the brain, a biological system open to information exchanges with the external world. To make a decision, the brain must analyze pieces of information given externally, past experiences in a similar situation, possible behavioral responses, and predicted outcomes of the individual responses. In this article, we review results of recent experimental and theoretical studies of neuronal substrates and computational algorithms for decision processes.

Algorithms↗
PubMed2006

Pancreatic regenerating protein (reg I) and reg I receptor mRNA are upregulated in rat pancreas after induction of acute pancreatitis.

AIM: Pancreatic regenerating protein (reg I) stimulates pancreatic regeneration after pancreatectomy and is mitogenic to ductal and beta-cells. This suggests that reg I and its receptor may play a role in recovery after pancreatic injury. We hypothesized that reg I and its receptor are induced in acute pancreatitis. METHODS: Acute pancreatitis was induced in male Wistar rats by retrograde injection of 3% sodium taurocholate into the pancreatic duct. Pancreata and serum were collected 12, 24, and 36 h after injection and from normal controls (4 rats/group). Reg I receptor mRNA, serum reg I protein, and tissue reg I protein levels were determined by Northern analysis, enzyme-linked immunosorbent assay (ELISA), and Western analysis, respectively. Immunohistochemistry was used to localize changes in reg I and its receptor. RESULTS: Serum amylase levels and histology confirmed necrotizing pancreatitis in taurocholate treated rats. There was no statistically significant change in serum reg I concentrations from controls. However, Western blot demonstrated increased tissue levels of reg I at 24 and 36 h. This increase was localized primarily to the acinar cells and the ductal cells by immunohistochemistry. Northern blot demonstrated a significant increase in reg I receptor mRNA expression with pancreatitis. Immunohistochemistry localized this increase to the ductal cells, islets, and acinar cells. CONCLUSION: Acute pancreatitis results in increased tissue reg I protein levels localized to the acinar and ductal cells, and a parallel threefold induction of reg I receptor in the ductal cells, islets, and acinar cells. These changes suggest that induction of reg I and its receptor may be important for recovery from acute pancreatitis.

Amylases↗
PubMed2006

Potential oscillations in galvanostatic electrooxidation of formic acid on platinum: a mathematical modeling and simulation.

We have modeled temporal potential oscillations during the electrooxidation of formic acid on platinum on the basis of the experimental results obtained by time-resolved surface-enhanced infrared absorption spectroscopy (J. Phys. Chem. B 2005, 109, 23509). The model was constructed within the framework of the so-called dual-path mechanism; a direct path via a reactive intermediate and an indirect path via strongly bonded CO formed by dehydration of formic acid. The model differs from earlier ones in the intermediate in the direct path. The reactive intermediate in this model is formate, and the oxidation of formate to CO2 is rate-determining. The reaction rate of the latter process is represented by a second-order rate equation. Simulations using this model well reproduce the experimentally observed oscillation patterns and the temporal changes in the coverages of the adsorbed formate and CO. Most properties of the voltammetric behavior of formic acid, including the potential dependence of adsorbate coverages and a negative differential resistance, are also reproduced.

Journal Article↗
PubMed2006

Cholesteryl ester transfer protein promotes the formation of cholesterol-rich remnant like lipoprotein particles in human plasma.

BACKGROUND: Cholesteryl ester transfer protein (CETP) is suggested to be involved in the cholesterol level in remnant like lipoprotein particles (RLP), but there is no direct evidence that CETP increases cholesterol-rich RLP in plasma. METHODS: Human plasma was incubated with or without HDL containing [(3)H]-labeled cholesteryl ester ([(3)H]CE), recombinant CETP or CETP inhibitors at 37 degrees C in vitro. RESULTS: The RLP-cholesterol (RLP-C) level increased time-dependently and the amount of RLP-C increase (DeltaRLP-C) by the incubation was positively correlated with triglyceride (TG) level in plasma (r=0.597, P=0.0070). [(3)H]CE in HDL was transferred to RLP fraction under 37 degrees C incubation, and the amount of [(3)H]CE transferred to RLP correlated significantly with DeltaRLP-C in plasma (r=0.611, P=0.0156). Human recombinant CETP enhanced the RLP-C increase, while CETP inhibitor JTT-705 and anti-human CETP monoclonal antibody inhibited both the RLP-C increase and [(3)H]CE transfer to RLP. On the other hand, an inhibition of lecithin: cholesterol acyltransferase (LCAT) did not affect the RLP-C increase. In triglyceride-rich lipoproteins (TRL) fraction, JTT-705 inhibited [(3)H]CE transfer to RLP more strongly than that to non-RLP. CONCLUSIONS: CETP promotes the formation of cholesterol-rich RLP through the transfer of CE from HDL to TRL and CETP inhibitors are useful to reduce RLP-C.

Amides↗
PubMed2006

Expression of m-Golsyn/Syntabulin gene during mouse brain development.

We recently isolated the cDNA for the mouse Golsyn/Syntabulin (m-Golsyn/Syntabulin) gene and mapped it to mouse chromosome 15B3.2 syntenic with human chromosome 8q23, on which a locus responsible for primary open-angle glaucoma had been located. In the present study, we examined the expression of m-Golsyn/Syntabulin protein in various regions of mouse brain and its developmental changes by use of anti-GOLSYN antibody. m-Golsyn/Syntabulin protein was detected in various brain regions at embryonic day 14 and throughout the postnatal stages. Furthermore, as the histogenesis and maturation of brain proceeded, strong expression of the protein became detectable in cells of the choroid plexus, piriform cortex, pyramidal cell layer, and Purkinje cell layer. In situ hybridization analysis of the mouse brain revealed that localization of the m-Golsyn/Syntabulin transcript was very similar to that of m-Golsyn/Syntabulin protein, confirming the high-level expression of the m-Golsyn/Syntabulin gene in the specific brain regions. High-level expression of m-Golsyn/Syntabulin protein was also observed in the ocular tissues including the ciliary body, which is known as a site for the production of aqueous humor. These results may indicate a significant role for this protein in neuronal cells and other types of cells such as those of the choroid plexus and ciliary body.

Animals↗
PubMed2006

Beam-shaping technique for improving the beam quality of a high-power laser-diode stack.

We report a beam-shaping technique that reconfigures the beams to improve the beam quality and enhance the power density for a ten-array high-power laser-diode stack by using two optical rectangular cubes and two stripe-mirror plates. The reshaped beam has threefold improvement in beam quality, and its power density is effectively enhanced. On the basis of this technique, we focus the beam of the high-power laser-diode stack to effectively end pump a high-power fiber laser.

Journal Article↗
PubMed2006

Dynamical valence fluctuation at the charge-density-wave phase boundary in iodide-bridged Pt compound [Pt(chxn)2I]I2.

We synthesized a novel iodo-bridged linear chain platinum compound, having the quasi-two-dimensional charge-density-wave (CDW) ground state and the smallest band gap. In this compound, we discovered an anomalous valence state in the boundary region at which the CDW phase alternates in the crystal by means of ESR, X-ray diffuse scattering, STM, and electrical resistivity. This anomalous state can be explained by the fast fluctuation between Pt(IV)-I...Pt(II) and Pt(II)...I-Pt(IV) in the double well potential. This is the first observation of the dynamical fluctuation of the CDW phase among the quasi one-dimensional halogen-bridged complexes.

Journal Article↗
PubMed2006

Identification of mouse orthologue of endogenous secretory receptor for advanced glycation end-products: structure, function and expression.

The cell-surface RAGE [receptor for AGE (advanced glycation end-products)] is associated with the development of diabetic vascular complications, neurodegenerative disorders and inflammation. Recently, we isolated a human RAGE splice variant, which can work as a decoy receptor for RAGE ligands, and named it esRAGE (endogenous secretory RAGE). In the present study, we have isolated the murine equivalent of esRAGE from brain polysomal poly(A)+ (polyadenylated) RNA by RT (reverse transcription)-PCR cloning. The mRNA was generated by alternative splicing, and it encoded a 334-amino-acid protein with a signal sequence, but lacking the transmembrane domain. A transfection experiment revealed that the mRNA was actually translated as deduced to yield the secretory protein working as a decoy in AGE-induced NF-kappaB (nuclear factor kappaB) activation. RT-PCR and immunoblotting detected esRAGE mRNA and protein in the brain, lung, kidney and small intestine of wild-type mice, but not of RAGE-null mice. The esRAGE expression was increased in the kidney of diabetic wild-type mice. The present study has thus provided an animal orthologue of esRAGE for clarification of its roles in health and disease.

Alternative Splicing↗