Biomedical subjects

H Nakanishi

Publications and source records attributed to H Nakanishi.

At least 19 recordsLinked to original sources

PubMed2003

Sawtooth oscillation in current-carrying plasma in the large helical device.

Sawtooth oscillations have been observed in current-carrying helical plasmas by using electron-cyclotron-emission diagnostics in the Large Helical Device. The plasma current, which is driven by neutral beam injection, reduces the beta threshold of the sawtooth oscillation. When the central q value is increased due to the plasma current, the core region crashes, and, when it is decreased, the edge region crashes annularly. Observed rapid mixture of the plasma in the limited region suggests that these sawtooth crashes are reconnection phenomena. Unlike previous experiments, no precursor oscillation has been observed.

Journal Article↗

PubMed2003

Intractable malleolar bursitis treated with lateral calcaneal artery adipofascial flap.

Infections of the malleolar bursa, which is an adventitious bursa, rarely progress to intractable infectious bursitis. We present two cases of intractable malleolar bursitis. We performed successful transplantation of the lateral calcaneal artery adipofascial flap that resulted in healing of the bursitis. We discuss classification of bursae, treatments for bursitis and characteristics of the lateral calcaneal artery adipofascial flap.

Aged↗

PubMed2003

Significance of dihydropyrimidine dehydrogenase activity in renal cell carcinoma.

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme in the pathway of uracil and thymine catabolism. DPD is also the principal enzyme involved in the degradation of 5-fluorouracil (5-FU), an anticancer chemotherapeutic agent that is used clinically to treat renal cell carcinoma (RCC). Little is known about the significance of DPD activity in human cancers. We investigated the activity of DPD in 68 RCC and the relationship between DPD activity and the sensitivity to 5-FU. The levels of DPD activity in RCC and normal kidney samples were determined by the 5-FU degradation assay. The sensitivity to 5-FU was assessed by the microculture tetrazolium dye assay. The activity of DPD was approximately 2-fold higher in normal kidney compared with RCC. DPD activity in Stage I/II RCC was approximately 2-fold higher than that in Stage III/IV RCC. The levels of DPD activity in Grade 1 and Grade 2 RCC were 3 and 2-fold higher, respectively, than that in the Grade 3 cancers. There was an inverse correlation between DPD activity in RCC cells and their sensitivity to 5-FU. Furthermore, 5-chloro-2,4-dihydroxypyridine (CDHP), a potent DPD inhibitor, enhanced the sensitivity to 5-FU. The current study is the first to demonstrate that the level of DPD activity was inversel correlated with both the progression of the disease and increased grade of RCC, and that DPD activity was inversely associated with the sensitivity of RCC to 5-FU, which was enhanced by a DPD inhibitor. These results suggest that a low DPD activity may be associated with the malignant potential of RCC. In addition, it may be possible to overcome 5-FU resistance by using DPD inhibitors in the treatment protocols of 5-FU-based chemotherapy for RCC.

Adult↗

PubMed2003

Nonviral genetic transfer of Fas ligand induced significant growth suppression and apoptotic tumor cell death in prostate cancer in vivo.

To accomplish efficient nonviral gene therapy against prostate cancer (PC), Epstein-Barr virus (EBV)-based plasmid vectors containing EBNA1 gene and oriP were employed and combined with a cationic polymer or cationic lipid. When EBV-plasmid/poly-amidoamine dendrimer complex was injected into PC-3-derived tumors established in severe combined immunodeficiency mice, a considerable expression of marker gene was obtained in the tumors, and the expression level was more than eight-fold higher than that achieved by conventional plasmid vector/dendrimer. Since most PC cells express the apoptotic signal molecule Fas (Apo-1/CD95) on their surface, Fas ligand (FasL) gene was transferred into PC cells to kill the tumor cells. In vitro transfection with pGEG.FasL (an EBV-plasmid with the FasL gene) significantly reduced the viability of PC cells, which subsequently underwent apoptosis. Intratumoral injections of pGEG.FasL into PC induced significant growth suppression of the xenograft tumors, in which typical characteristics of apoptosis were demonstrated by TUNEL staining and electron microscopic observations. When pGEG.FasL transfer was accompanied by systemic administrations of cisplatin, the tumors were inhibited even more remarkably, leading to prolonged survival of the animals. FasL gene transfection by means of EBV-based plasmid/cationic macromolecule complexes may provide a practical therapeutic strategy against PC.

Antineoplastic Agents↗

PubMed2003

The expression of nectin-1alpha in normal human skin and various skin tumours.

BACKGROUND: A novel cell-cell adhesion system that consists of nectin and afadin has been identified at cadherin-based cell-cell adherens junctions. Nectin is a Ca2+-independent homophilic and heterophilic cell adhesion molecule that belongs to the immunoglobulin superfamily. Nectin has recently been shown to serve as an alpha-herpesvirus entry and cell-cell spread mediator. In spite of the ubiquitous expression of nectin-1alpha, its detailed localization in human skin has not been examined so far. OBJECTIVES: To investigate the localization of nectin-1alpha in normal human skin and the alteration of its expression in malignant skin tumours. METHODS: Immunohistochemistry was employed to determine the expression of nectin-1alpha and other adhesion molecules. RESULTS: We detected nectin-1alpha in normal human epidermis, follicles and eccrine ducts. Nectin-1alpha was colocalized with E-cadherin at cell-cell adherens junctions of the epidermis. The concentration of the nectin-afadin system at cell-cell adherens junctions was reduced in the early stage of malignant transformation of keratinocytes, such as in basal cell carcinomas and squamous cell carcinomas, where the cadherin-catenin system was preserved. Nectin-1alpha at cell-cell adherens junctions was reduced in human epithelial cancer cells located at the advancing border of the tumour. CONCLUSIONS: Our results showed that nectin-1alpha is located at cell-cell adherens junctions in human skin and that reduction of nectin-1alpha at cell-cell adherens junctions may be involved in the invasion of squamous cell tumours.

Aged↗

PubMed2003

Cellular differentiation status of epithelial polyps of the colorectum: the gastric foveolar cell-type in hyperplastic polyps.

AIMS: The 'metaplastic' polyp of the colorectum, a synonym for the hyperplastic polyp, was named based only on features of the crypt epithelium. It is considered non-neoplastic, but the precise cellular differentiation status remains to be proven. METHODS AND RESULTS: Forty-eight hyperplastic polyps, 12 serrated adenomas, 45 tubular adenomas and five juvenile polyps were studied for their phenotypic expression using gastric (foveolar or pyloric gland cell), small intestinal (goblet cell), and colonic (goblet cell) cellular markers by immunohistochemical and mucin histochemical techniques. Gastric foveolar cell-type differentiation was significantly expressed in hyperplastic polyps, while colonic differentiation was also consistently preserved. Neither gastric pyloric-type nor small intestinal differentiation was observed. The same cell differentiation status as hyperplastic polyps was observed in serrated adenomas but not in tubular adenomas or juvenile polyps. CONCLUSIONS: A large proportion of hyperplastic polyps are composed of hybrid epithelium, with bidirectional differentiation to both gastric foveolar and colonic epithelial cells in the same crypt. Therefore hyperplastic polyps might be interpreted as the outcome of abnormal cell differentiation of stem cells. The same phenotypic expression suggests that hyperplastic polyps and serrated adenomas share the same cell lineage.

Adenoma↗

PubMed2003

In vivo killing of Porphyromonas gingivalis by toluidine blue-mediated photosensitization in an animal model.

Porphyromonas gingivalis is one of the major causative organisms of periodontitis and has been shown to be susceptible to toluidine blue-mediated photosensitization in vitro. The aims of the present study were to determine whether this technique could be used to kill the organism in the oral cavities of rats and whether this would result in a reduction in the alveolar bone loss characteristic of periodontitis. The maxillary molars of rats were inoculated with P. gingivalis and exposed to up to 48 J of 630-nm laser light in the presence of toluidine blue. The number of surviving bacteria was then determined, and the periodontal structures were examined for evidence of any damage. When toluidine blue was used together with laser light there was a significant reduction in the number of viable P. gingivalis organisms. No viable bacteria could be detected when 1 mg of toluidine blue per ml was used in conjunction with all light doses used. On histological examination, no adverse effect of photosensitization on the adjacent tissues was observed. In a further group of animals, after time was allowed for the disease to develop in controls, the rats were killed and the level of maxillary molar alveolar bone was assessed. The bone loss in the animals treated with light and toluidine blue was found to be significantly less than that in the control groups. The results of this study show that toluidine blue-mediated lethal photosensitization of P. gingivalis is possible in vivo and that this results in decreased bone loss. These findings suggest that photodynamic therapy may be useful as an alternative approach for the antimicrobial treatment of periodontitis.

Alveolar Bone Loss↗

PubMed2002

Island dynamics in the large-helical-device plasmas.

In the Large Helical Device plasma discharges, the size of an externally imposed island with mode number ( n/m = 1/1) decreases substantially when the plasma is collisionless ( nu(*)< approximately 1) and the beta is finite ( > approximately 0.1%) at the island location. For the collisional plasmas with finite beta, on the other hand, the size of the island increases. However, there is a threshold in terms of the vacuum island size below which the island enlargement is not seen.

Journal Article↗

PubMed2002

Potentiation of the sensitivity of renal cell carcinoma cells to TRAIL-mediated apoptosis by subtoxic concentrations of 5-fluorouracil.

Cytotoxic chemotherapy has shown little antitumour activity against renal cell carcinoma (RCC). Although immunotherapy is relatively effective against RCC, the response rate is approximately 20%. Therefore, there is an urgent need to increase this response rate. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo-2L) is one member of the tumour necrosis factor ligand family that selectively induces apoptosis of cancer cells. Since several cytotoxic anticancer drugs including 5-fluorouracil (5-FU) also mediate apoptosis, we reasoned that combined treatment of cancer cells with TRAIL and drugs might result in synergy and overcome the resistance of the cancer cell. This study has examined whether TRAIL can synergise with 5-FU in both cytotoxic and apoptotic assays against drug-resistant RCC cells. Cytotoxicity was determined by an 1-day microculture tetrazolium dye assay. Synergy was assessed by isobolographic analysis. Treatment of Caki-1 cells with TRAIL in combination with 5-FU resulted in a synergistic cytotoxic effect. Synergy was also achieved in freshly derived RCC cells from 3 patients. The enhanced cytotoxicity was obtained irrespective of the sequence of the treatment, but the highest cytotoxicity was observed when Caki-1 cells were treated with TRAIL and 5-FU simultaneously. The synergy achieved in cytotoxicity with TRAIL and 5-FU was shown to be due to apoptosis. The mechanisms responsible for the synergistic cytotoxicity and apoptosis were examined. Treatment of Caki-1 cells with 5-FU enhanced the expression of p53 and bax, but had no effect on the expression of bcl-2. Incubation of Caki-1 cells with TRAIL enhanced the intracellular accumulation of 5-FU and 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP). Treatment of Caki-1 cells with TRAIL downregulated the expression of thymidylate synthase (TS) and dihydropyrimidine dehydrogenase (DPD) modestly, and upregulated the expression of orotate phosphoribosyltransferase (OPRT). However, the expression level of thymidine phosphorylase (TP) was not affected by TRAIL. This study demonstrates that combined treatment of RCC cells with TRAIL and 5-FU overcomes their resistance. The sensitisation obtained with freshly isolated RCC cells required low subtoxic concentrations of 5-FU. These findings support the potential application in vivo of a combination of TRAIL and 5-FU in the treatment of TRAIL/5-FU-resistant RCC.

Antimetabolites, Antineoplastic↗

PubMed2001

Pilt, a novel peripheral membrane protein at tight junctions in epithelial cells.

Tight junctions (TJs) serve as a barrier that prevents solutes and water from passing through the paracellular pathway, and as a fence between the apical and basolateral plasma membranes in epithelial cells. TJs consist of transmembrane proteins (claudin, occludin, and JAM) and many peripheral membrane proteins, including actin filament (F-actin)-binding scaffold proteins (ZO-1, -2, and -3), non-F-actin-binding scaffold proteins (MAGI-1), and cell polarity molecules (ASIP/PAR-3 and PAR-6). We identified here a novel peripheral membrane protein at TJs from a human cDNA library and named it Pilt (for protein incorporated later into TJs), because it was incorporated into TJs later after the claudin-based junctional strands were formed. Pilt consists of 547 amino acids with a calculated M(r) of 60,704. Pilt has a proline-rich domain. In cadherin-deficient L cells stably expressing claudin or JAM, Pilt was not recruited to claudin-based or JAM-based cell-cell contact sites, suggesting that Pilt does not directly interact with claudin or JAM. The present results indicate that Pilt is a novel component of TJs.

Adaptor Proteins, Signal Transducing↗

PubMed2001

Involvement of nitric oxide released from microglia-macrophages in pathological changes of cathepsin D-deficient mice.

Cathepsin D (CD) deficiency has been shown to induce ceroid-lipofuscin storage in lysosomes of mouse CNS neuron (Koike et al., 2000). To understand the behavior of microglial cells corresponding to these neuronal changes, CD-deficient (CD-/-) mice, which die at approximately postnatal day (P) 25 by intestinal necrosis, were examined using morphological as well as biochemical approaches. Light and electron microscopic observations revealed that microglia showing large round cell bodies with few processes appeared in the cerebral cortex and thalamus after P16. At P24, microglia often encircled neurons that were occupied with autolysosomes, indicating increased phagocytic activity. These morphologically transformed microglia markedly expressed inducible nitric oxide synthase (iNOS), which was also detected in the intestine of the mice. To assess the role of microglial nitric oxide (NO) in neuropathological changes in CD-/- mice, l-N(G)-nitro-arginine methylester (l-NAME), a competitive NOS inhibitor, or S-methylisothiourea hemisulfate (SMT), an iNOS inhibitor, was administered intraperitoneally for 13 consecutive days. The total number of terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling-positive cells counted in the thalamus was found to be significantly decreased by chronic treatment of l-NAME or SMT, whereas neither the neuronal accumulation of ceroid-lipofuscin nor the microglial phagocytic activity was affected by these treatments. Moreover, the chronic treatment of l-NAME or SMT completely suppressed hemorrhage-necrotic changes in the small intestine of CD-/- mice, resulting in normal growth of the body weight of the mice. These results suggest that NO production via iNOS activity in microglia and peripheral macrophages contributes to secondary tissue damages such as neuronal apoptosis and intestinal necrosis, respectively.

Animals↗

PubMed2001

Identification of splicing variants of Frabin with partly different functions and tissue distribution.

Frabin is a GDP/GTP exchange protein for Cdc42 small G protein with actin filament-binding activity. Frabin consists of the actin filament-binding domain, the Dbl homology domain, the first pleckstrin homology domain, the FYVE-finger domain, and the second pleckstrin homology domain in this order from the N-terminus. Frabin forms filopodia through direct activation of Cdc42 and lamellipodia through indirect activation of Rac small G protein. We isolated here two smaller splicing variants of frabin and named the original one, middle-size one, and smallest one frabin-alpha, -beta, and -gamma, respectively. Frabin-beta lacked the second pleckstrin homology domain and frabin-gamma lacked the FYVE-finger domain and the second pleckstrin homology domain. These three variants were expressed in all of the tissues examined but their expression levels are different depending on tissues. In L fibroblasts, all the three variants formed filopodia. As to lamellipodia, frabin-alpha formed them; frabin-beta formed them to a small extent; and frabin-gamma did not. In MDCK epithelial cells, frabin-alpha formed microspikes but frabin-beta or -gamma did not.

Alternative Splicing↗

PubMed2001

Observation of the "self-healing" of an error field island in the large helical device.

It was observed that the vacuum magnetic island produced by an external error magnetic field in the large helical device shrank in the presence of plasma. This was evidenced by the disappearance of flat regions in the electron temperature profile obtained by Thomson scattering. This island behavior depended on the magnetic configuration in which the plasmas were produced.

Journal Article↗

PubMed2001

Real-time observation of micrometastasis formation in the living mouse liver using a green fluorescent protein gene-tagged rat tongue carcinoma cell line.

Initial arrest, attachment, extravasation and subsequent extravascular growth of tumor cells in the secondary organs are believed to be crucial events for hematogenous metastasis, but the actual processes in living animals remain unclear. For the present study, we established green fluorescent protein (GFP)-expressing rat tongue carcinoma cell lines (RSC3) that permit real-time analysis of micrometastasis formation in combination with intravital video microscopy (IVVM). With this system, GFP-expressing metastatic (LM-EGFP) and non-metastatic (E2-EGFP) cell lines could be visualized at the cellular level in live mice for more than 1 month. Real-time IVVM analysis of liver metastases after intraportal injection of cells via a mesenteric vein revealed that both LM-EGFP and E2-EGFP tumor cells arrest similarly in sinusoidal vessels near terminal portal venules within 0.4 sec, during which time no evidence of a "rolling"-like movement along endothelial cell surfaces was observed. Quantitative analysis of GFP-positive foci showed that E2-EGFP cells were completely sheared from the liver sinusoid within 3 days, with no solitary dormant cells, whereas a substantial number of LM-EGFP cells remained in the liver, probably due to stable attachment to the sinusoidal wall. Confocal laser scanning microscopic study in combination with laminin immunohistochemistry revealed that only LM-EGFP cells started growth at 3 to 4 days after inoculation and that most of the growing foci were surrounded by subsinusoidal basement membrane. Our results suggest that micrometastasis formation by LM-EGFP cells consists of initial tumor cell arrest due to size constraints of the vessel, stable attachment to subsinusoidal basement membrane and subsequent intravascular growth before extravasation. The difference in metastatic potential between the 2 lines may reside in their capacity to attach stably to the vessel wall rather than their potential for initial cell arrest or subsequent growth. The system used in the present study may be a powerful tool for analyzing targets for various anti-metastatic agents in the sequential process of metastasis.

Animals↗

PubMed2001

Cooperation of Cdc42 small G protein-activating and actin filament-binding activities of frabin in microspike formation.

Frabin is a GDP/GTP exchange protein for Cdc42 with actin filament (F-actin)-binding activity. Cdc42 is a small GTP-binding protein that forms filopodia-like microspikes in a variety of cells. Expression of frabin indeed forms microspikes through at least activation of Cdc42 in MDCK cells and fibroblasts such as COS7, L, and NIH3T3 cells. However, the role of the F-actin-binding activity of frabin in the microspike formation remains unknown. We have examined here this role of frabin by expressing various frabin mutants, which have lost Cdc42-activating or F-actin-binding activity, with or without a dominant active mutant of Cdc42 in MDCK and COS7 cells. We show here that for the microspike formation, either of the Cdc42-activating and F- actin-binding activities of frabin alone is not sufficient and both the activities are necessary and that both the activities play a cooperative role in the microspike formation. The present results, together with the earlier finding that Cdc42 reorganizes the actin cytoskeleton at least through the N-WASP-Arp2/3 complex, suggest that frabin directly and indirectly reorganizes the actin cytoskeleton through its F-actin-binding and Cdc42-activating activities, respectively, in a cooperative manner, eventually leading to microspike formation.

3T3 Cells↗

PubMed2001

Reduction of ion thermal diffusivity associated with the transition of the radial electric field in neutral-beam-heated plasmas in the large helical device.

Recent large helical device experiments revealed that the transition from ion root to electron root occurred for the first time in neutral-beam-heated discharges, where no nonthermal electrons exist. The measured values of the radial electric field were found to be in qualitative agreement with those estimated by neoclassical theory. A clear reduction of ion thermal diffusivity was observed after the mode transition from ion root to electron root as predicted by neoclassical theory when the neoclassical ion loss is more dominant than the anomalous ion loss.

Journal Article↗

PubMed2001

Involvement of enhanced sensitivity of N-methyl-D-aspartate receptors in vulnerability of developing cortical neurons to methylmercury neurotoxicity.

The developing cortical neurons have been well documented to be extremely vulnerable to the toxic effect of methylmercury (MeHg). In the present study, a possible involvement of N-methyl-D-aspartate (NMDA) receptors in MeHg neurotoxicity was examined because the sensitivity of cortical neurons to NMDA neurotoxicity has a similar developmental profile. Rats on postnatal day 2 (P2), P16, and P60 were orally administered MeHg (10 mg/kg) for 7 consecutive days. The most severe neuronal damage was observed in the occipital cortex of P16 rats. When MK-801 (0.1 mg/kg), a non-competitive antagonist of NMDA, was administered intraperitoneally with MeHg, MeHg-induced neurodegeneration was markedly ameliorated. Furthermore, there was a marked accumulation of nitrotyrosine, a reaction product of peroxynitrite and L-tyrosine, after chronic treatment of MeHg in the occipital cortex of P16 rats. The accumulation of nitrotyrosine was also significantly suppressed by MK-801. In the present electrophysiological study, the amplitude of synaptic responses mediated by NMDA receptors recorded in cortical neurons of P16 rats was significantly larger than those from P2 and P60 rats. These observations strongly suggest that a generation of peroxynitrite through activation of NMDA receptors is a major causal factor for MeHg neurotoxicity in the developing cortical neurons. Furthermore, enhanced sensitivity of NMDA receptors may make the cortical neurons of P16 rats most susceptible to MeHg neurotoxicity.

Age Factors↗

PubMed2001

Roles of cell-cell adhesion-dependent tyrosine phosphorylation of Gab-1.

Gab-1 is a multiple docking protein that is tyrosine phosphorylated by receptor tyrosine kinases such as c-Met, hepatocyte growth factor/scatter factor receptor, and epidermal growth factor receptor. We have now demonstrated that cell-cell adhesion also induces marked tyrosine phosphorylation of Gab-1 and that disruption of cell-cell adhesion results in its dephosphorylation. An anti-E-cadherin antibody decreased cell-cell adhesion-dependent tyrosine phosphorylation of Gab-1, whereas the expression of E-cadherin specifically induced tyrosine phosphorylation of Gab-1. A relatively selective inhibitor of Src family kinases reduced cell-cell adhesion-dependent tyrosine phosphorylation of Gab-1, whereas expression of a dominant-negative mutant of Csk increased it. Disruption of cell-cell adhesion, which reduced tyrosine phosphorylation of Gab-1, also reduced the activation of mitogen-activated protein kinase and Akt in response to cell-cell adhesion. These results indicate that E-cadherin-mediated cell-cell adhesion induces tyrosine phosphorylation by a Src family kinase of Gab-1, thereby regulating the activation of Ras/MAP kinase and phosphatidylinositol 3-kinase/Akt cascades.

Adaptor Proteins, Signal Transducing↗