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Hiroyuki Kojima

Publications and source records attributed to Hiroyuki Kojima.

15 recordsLinked to original sources
PubMed2004

Interparticle spacing control in the superlattices of carboxylic acid-capped gold nanoparticles by hydrogen-bonding mediation.

We have demonstrated that carboxylic acid-capped gold nanoparticles were self-assembled to form two-dimensional (2D) and/or three-dimensional (3D) superlattices at an air/water interface in the presence of a bifunctional hydrogen-bonding mediator such as 4-pyridinecarboxylic acid (PyC) or trans-3-(3-pyridyl)acrylic acid (PyA). Transmission electron microscopy revealed a hexagonal close-packed arrangement of nanoparticles in the superlattice with an extension of interparticle spacing. In the 2D superlattices, larger particles produced a higher-quality assembly having long-range translational ordering. Attenuated total reflectance IR (ATR-IR) spectroscopy revealed the presence of hydrogen bonds between the mediator used and the capping agents of carboxylic acid on nanoparticle surfaces. Since the experimentally obtained interparticle separation distance agreed approximately with that obtained by the geometrical model calculations, we conclude that the hydrogen-bonding mediation controlled the interparticle spacing or structure by monomolecular incorporation between adjacent nanoparticles in the superlattices.

Journal Article↗
PubMed2004

Membrane-associated prostaglandin E synthase-1 is required for neuropathic pain.

It is widely accepted that prostaglandin (PG) E2 is the principal pro-inflammatory prostanoid and plays an important role in inflammatory pain. However whether PGE2 is involved in neuropathic pain remains unknown. PGE2 is produced from arachidonic acid via PGH2 by at least three PGE synthases (PGES), cytosolic PGES (cPGES), and membrane-associated PGES (mPGES)-1 and -2. In the present study, to clarify the involvement of PGE2 and identify PGES mediating neuropathic pain, we applied a neuropathic pain model prepared by L5 spinal nerve transection to mPGES-1 knockout (mPGES-1-/-) mice. Whereas they retained normal nociceptive responses, mPGES-1-/- mice did not exhibit mechanical allodynia and thermal hyperalgesia over a week. These results demonstrate that PGE2 produced by mPGES-1 is involved in neuropathic pain.

Animals↗
PubMed2004

Transformation of Spirulina platensis strain C1 (Arthrospira sp. PCC9438) with Tn5 transposase-transposon DNA-cation liposome complex.

Spirulina platensis is one of the most commercially important species of microalgae. Thus, it is an attractive candidate for genetic manipulation and the development of novel practical applications. However, this process is hampered by the absence of a stable gene transfer system, specifically the limited number of suitable vectors and transformation methods available for this organism. Artificial transposon systems developed by extracting the essential elements from natural transposons have been extensively studied, and recently a mutated transposase and transposon system was reported to improve transformation efficiency by electroporation. We applied a modified transformation strategy using a natural Tn5 transposon, transposase, and cation liposome complex by electroporation to improve the transformation efficiency for Spirulina platensis strain C1 (Arthrospira sp. PCC9438). Aggregation of cells became visible after 3 weeks during 2.0 microg/ml chloramphenicol selection, and growth continued for more than 12 months. Transfected chloramphenicol acetyltransferase (CAT) genes were detected in the genomic DNA by Southern hybridization. Transformed cells demonstrated CAT activity, but non-transformed cells did not.

Base Sequence↗
PubMed2004

Cross-talk between endocrine-disrupting chemicals and cytokine signaling through estrogen receptors.

STAT3 mainly acts as a signal transducer of IL-6 family cytokines and transcriptionally activates specific target genes. STAT3 has also been demonstrated to mediate cellular transformation and is found in numerous cancers. Endocrine-disrupting chemicals (EDCs) are a diverse group of chemicals that bind to estrogen receptors (ERs), mimic estrogenic actions, and may have adverse effects on human health. In our previous study, we demonstrated that estrogens suppressed the STAT3-mediated transcription activity through ERs. In this study, we examined the effects of EDCs on STAT3-mediated signaling through ERs. Surprisingly, some of EDCs enhanced STAT3-mediated transcription activity through ERs. This finding strongly suggests that EDCs may play an important role in the endocrine functions by mimicking cytokine activity by stimulating STAT3 actions through ERs.

Cell Line, Tumor↗
PubMed2004

Screening for estrogen and androgen receptor activities in 200 pesticides by in vitro reporter gene assays using Chinese hamster ovary cells.

We tested 200 pesticides, including some of their isomers and metabolites, for agonism and antagonism to two human estrogen receptor (hER) subtypes, hERalpha and hERbeta, and a human androgen receptor (hAR) by highly sensitive transactivation assays using Chinese hamster ovary cells. The test compounds were classified into nine groups: organochlorines, diphenyl ethers, organophosphorus pesticides, pyrethroids, carbamates, acid amides, triazines, ureas, and others. These pesticides were tested at concentrations < 10-5 M. Of the 200 pesticides tested, 47 and 33 showed hER- and hERbeta-mediated estrogenic activities, respectively. Among them, 29 pesticides had both hERalpha and hERbeta agonistic activities, and the effects of the organochlorine insecticides beta-benzene hexachloride (BHC) and delta-BHC and the carbamate insecticide methiocarb were predominantly hERbeta rather than hERalpha agonistic. Weak antagonistic effects toward hERalpha and hERbeta were shown in five and two pesticides, respectively. On the other hand, none of tested pesticides showed hAR-mediated androgenic activity, but 66 of 200 pesticides exhibited inhibitory activity against the transcriptional activity induced by 5alpha-dihydrotestosterone. In particular, the antiandrogenic activities of two diphenyl ether herbicides, chlornitrofen and chlomethoxyfen, were higher than those of vinclozolin and p,p -dichlorodiphenyl dichloroethylene, known AR antagonists. The results of our ER and AR assays show that 34 pesticides possessed both estrogenic and antiandrogenic activities, indicating pleiotropic effects on hER and hAR. We also discussed chemical structures related to these activities. Taken together, our findings suggest that a variety of pesticides have estrogenic and/or antiandrogenic potential via ER and/or AR, and that numerous other manmade chemicals may also possess such estrogenic and antiandrogenic activities.

Androgen Receptor Antagonists↗
PubMed2004

[CT].

The development of multidetector-row CT(MDCT), which can rapidly scan a large longitudinal volume and enables us to obtain thinner section collimation with a shorter acquisition time, obtained isotropic voxel data for three-dimensional(3D) imaging. Isotropic voxel data enables us to obtain sagittal and coronal images with the spatial resolution which is identical to axial images. Excellent volume data, which was acquired by MDCT, obtain serviceable 3D images by using various reconstruction methods, such as multi-planar reconstruction(MPR), maximum intensity projection(MIP), minimum intensity projection(MinIP), surface rendering, volume rendering and virtual endoscopy. However, relation between Ct and MRI is still complementary even in the times of MDCT.

Humans↗
PubMed2003

Enhancement of ischemia-induced angiogenesis by eNOS overexpression.

It remains undetermined whether continuous endothelial nitric oxide (NO) overexpression exerts angiogenic action. We surgically induced hindlimb ischemia in transgenic mice overexpressing endothelial NO synthase in the endothelium (eNOS-Tg) and studied neocapillary formation, ischemia-induced vascular endothelial growth factor (VEGF) expression, cGMP accumulation, and Akt/PKB signaling. Laser Doppler imaging revealed a markedly increased recovery of blood perfusion in ischemic limbs of eNOS-Tg mice (44% increase) compared with that in wild-type mice. Angiography showed a marked increase in basal and ischemia-induced collateral vessel formation in eNOS-Tg mice. Basal capillary densities and tissue cGMP levels were increased in eNOS-Tg mice (1.8-fold and 1.6-fold versus wild-type mice, respectively). Ischemia-induced neocapillary formation and cGMP accumulation were markedly increased in eNOS-Tg mice (3.6-fold and 4.1-fold versus preischemia levels, respectively), whereas those in wild-type mice were much less (1.8-fold and 1.5-fold, respectively). Basal and time-dependent VEGF expression in ischemic muscles did not differ between eNOS-Tg and wild-type mice. Basal and VEGF-mediated Akt phosphorylation in aortas was similar between eNOS-Tg and wild-type mice. Aortic basal eNOS expression was increased 3.3-fold, and VEGF-mediated eNOS phosphorylation was markedly induced in aortas of eNOS-Tg compared with preischemia levels (4.2-fold), whereas much smaller changes were observed in wild-type mice (1.8-fold increase). Our study demonstrates that overexpression of eNOS protein causes a marked increase in neocapillary formation in response to tissue ischemia without affecting ischemia-induced VEGF expression or VEGF-mediated Akt phosphorylation.

Angiography↗
PubMed2003

Escherichia coli can be transformed by a liposome-mediated lipofection method.

Transformation of Escherichia coli is a basic technique for genetic engineering. We used a liposome-mediated lipofection method to transform electrocompetent E. coli cells which has little natural competence of foreign DNA without electroporation treatment, and got transformants with simple and quick treatment by a plasmid or a transposon and transposase complex.

DNA Transposable Elements↗
PubMed2003

Effects of a diphenyl ether-type herbicide, chlornitrofen, and its amino derivative on androgen and estrogen receptor activities.

Chlornitrofen (CNP) was widely used in large quantities as a herbicide in rice paddy fields in Japan during 1965-1994. Recently, there has been concern that chemicals in the environment may disrupt the endocrine function of wildlife and humans, but little is known about the effect of CNP on endocrine function. We have developed reporter gene assays for human androgen receptor (hAR) and human estrogen receptor-alpha (hER alpha) using Chinese hamster ovary cells. Using this assay method, we measured CNP and its amino derivative (CNP-amino) for hAR and hER alpha agonist/antagonist activities, comparing them with several well-known AR antagonists or ER agonists. We found that CNP and CNP-amino have potent antiandrogenic activities as well as estrogenic activities. The order of their antiandrogenic activity was CNP > vinclozolin > o,p-DDT = p,p-DDE > CNP-amino, and the order of their estrogenic activity was o,p-DDT > CNP-amino > p,p-DDT > CNP. We investigated the binding ability of CNP and CNP-amino to hAR and hER alpha using a receptor competitive-binding assay. The order of their binding potencies to hAR was CNP > o,p-DDT = p,p-DDE = CNP-amino > vinclozolin, and that of their binding potencies to hER alpha was o,p-DDT > CNP-amino > p,p-DDT = CNP. These results suggest that both CNP and CNP-amino may act as endocrine disruptors via AR and ER alpha in humans and other animals. Our reporter gene assays are highly sensitive and specific and are suitable for screening AR and ER alpha agonist/antagonists among numerous environmental chemicals.

Amino Acids↗
PubMed2002

Angiogenesis by implantation of peripheral blood mononuclear cells and platelets into ischemic limbs.

BACKGROUND: Peripheral blood mononuclear cells (PBMNCs), platelets, and polymorphonuclear leukocytes (PMNs) contain various angiogenic factors and cytokines. METHODS AND RESULTS: Unilateral hindlimb ischemia was surgically induced in athymic nude rats, and fluorescence-labeled human blood cells (PBMNCs [10(7) cells]+platelets [10(9)] or PBMNCs [10(7)]+platelets [10(9)]+PMNs [10(7)]) were intramuscularly implanted into the ischemic limbs. Laser Doppler imaging revealed markedly increased blood perfusion in PBMNC+platelet-implanted limbs (44% increase, P<0.001) compared with control implantation of human umbilical vein vascular endothelial cells. The addition of PMNs to PBMNCs+platelets attenuated blood perfusion (27% decrease, P<0.01). Neocapillary densities were increased by implantation of PBMNCs+platelets or platelets alone (3.5-fold and 2.4-fold, respectively; P<0.001), whereas PMNs inhibited (32%, P<0.05) PBMNC+ platelet-mediated capillary formation. There was no incorporation of implanted PBMNCs into neocapillaries, whereas PBMNCs and platelets accumulated around arterioles after implantation. Cellular extract from PBMNCs+platelets, in which vascular endothelial growth factor (VEGF), basic fibroblast growth factor, platelet-derived growth factor-AB, and transforming growth factor-beta were detected, markedly stimulated tubule formation of human umbilical vein vascular endothelial cells. Anti-VEGF neutralizing antibody markedly inhibited tubule formation and in vivo vessel formation. Neutrophil elastase inhibitor blocked the antiangiogenic action of PMNs, whereas inhibitors of oxygen metabolites had no effect. CONCLUSIONS: This study demonstrated that implantation of PBMNCs and platelets into ischemic limbs effectively induces collateral vessel formation by supplying angiogenic factors (mainly VEGF) and cytokines, suggesting that this cell therapy is useful as a novel strategy for therapeutic angiogenesis.

Angiogenesis Inducing Agents↗
PubMedDate not supplied

Stenting of the superior mesenteric artery as a preoperative treatment for total pancreatectomy.

The patient was 58-year-old male with mucinous cyst adenocarcinoma of the pancreas. Prior to total pancreatectomy, preoperative CT and angiography showed a high-grade arteriosclerotic stenosis of about 1.0 cm in length in the ostium of the superior mesenteric artery (SMA), as well as the development of collateral vessels in the area around the head of the pancreas. A stent was placed in the SMA stenosis to preserve intestinal blood flow in the SMA region after total pancreatectomy, which was performed 25 days after stent placement. The postoperative SMA blood flow was favorable, with no postoperative intestinal ischemia, and the patient had an uneventful postoperative course.

Blood Vessel Prosthesis Implantation↗
PubMedDate not supplied

Usefulness of CT during renal arteriography: a case of percutaneous radiofrequency ablation for renal cell carcinoma.

A 64-year-old man with a unilateral 15 mm diameter renal cell carcinoma underwent percutaneous radiofrequency ablation (RFA) assisted by CT during renal arteriography (angio-CT). Prior to placement of the needle electrode, a 5 Fr angio-catheter was placed in the right renal artery, and angio-CT was performed before, during and after the procedure. Since multiple angio-CT can be performed using a small amount of diluted contrast agent, RFA can be monitored without impairing renal function. As a result, this imaging combination was found to be useful for determining the end point of ablation.

Carcinoma, Renal Cell↗
PubMedDate not supplied

CT perfusion of the liver during selective hepatic arteriography: pure arterial blood perfusion of liver tumor and parenchyma.

PURPOSE: To quantify pure arterial blood perfusion of liver tumor and parenchyma by using CT perfusion during selective hepatic arteriography. METHODS: A total of 44 patients underwent liver CT perfusion study by injection of contrast medium via the hepatic artery. CT-perfusion parameters including arterial blood flow, arterial blood volume, and arterial mean transit time in the liver parenchyma and liver tumor were calculated using the deconvolution method. The CT-perfusion parameters and vascularity of the tumor were compared. RESULTS: A complete analysis could be performed in 36 of the 44 patients. For liver tumor and liver parenchyma, respectively, arterial blood flow was 184.6 +/- 132.7 and 41.0 +/- 27.0 ml/min/ 100 g, arterial blood volume was 19.4 +/- 14.6 and 4.8 +/- 4.2 ml/100 g, and arterial mean transit time was 8.9 +/- 4.2 and 10.2 +/- 5.3 sec. Arterial blood flow and arterial blood volume correlated significantly with the vascularity of the tumor; however no correlation was detected between arterial mean transit time and the vascularity of the tumor. CONCLUSION: This technique could be used to quantify pure hepatic arterial blood perfusion.

Aged↗