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K Tamada

Publications and source records attributed to K Tamada.

At least 19 recordsLinked to original sources
PubMed2005

Langmuir-Blodgett-Kuhn and self-assembled films of asymmetrically substituted poly(paraphenylene).

Asymmetrically substituted poly(paraphenylene) (PhPPP) with hydrophilic and hydrophobic side chains was investigated. The polymer behavior at the air-water interface was studied on the basis of surface pressure-area (pi-A) isotherms and compression/expansion hysteresis measurements. PhPPP can form stable monolayers with an area per repeat unit of A=0.20+/-0.02 nm2 and a collapse pressure in the range of pi=25 mN/m. Then, Langmuir-Blodgett-Kuhn (LBK) films of PhPPP were prepared by horizontally and vertically transferring the Langmuir monolayers onto hydrophilic solid substrates at pi=12 mN/m. Cross-section analysis of the AFM tapping-mode topography images of a single transferred monolayer reveals a thickness of d0=0.9+/-0.1 nm. Taking into account the obtained monolayer thickness, curve-fitting calculations of angular scan data of LB monolayers measured using surface plasmon resonance (SPR) spectroscopy lead to a value for the refractive index of n=1.78+/-0.02 at lambda=632.8 nm. Next, the spontaneous formation of a PhPPP monolayer by adsorption from solution was studied ex situ by atomic force microscopy and UV-vis spectroscopy and in situ by using SPR spectroscopy. Stable self-assembled monolayers of PhPPP can be formed on hydrophilic surfaces with a thickness similar to that of the monolayer obtained using the LB method. The characterization results confirmed the amphiphilic character and the self-assembly properties of PhPPP, as well as the possibility of preparing homogeneous monolayer and multilayer films.

Adsorption↗
PubMed2005

Pericryptal fibroblast sheath in intestinal metaplasia and gastric carcinoma.

BACKGROUND AND AIMS: In the progression of chronic gastritis, gastric mucosal cells deviate from the normal pathway of gastric differentiation to an intestinal phenotype which is closely related to gastric carcinoma. However, to date, it has not been elucidated whether the intestinal metaplasia is merely a change in the epithelium or whether the underlying mesenchyme also changes from gastric type to intestinal type. We have investigated the relationship between intestinal metaplasia and the pericryptal fibroblast sheath (PCFS) in the mesenchyme. In addition, we also examined PCFS in gastric carcinoma. METHODS: We determined the existence of PCFS in the intestinal metaplastic mucosa and carcinoma of both human and Cdx2 transgenic mouse stomach. PCFS was determined using the antibody against alpha-smooth muscle actin and electron microscopic observations. RESULTS: PCFS formed an almost complete layer around the small and large intestinal crypts while it did not exist around the normal gastric glands in both mice and humans. PCFS was seen around the glands of intestinal metaplastic mucosa in both Cdx2 transgenic mouse and human stomachs. However, PCFS was virtually absent in the intestinal-type gastric adenocarcinoma area. CONCLUSION: We successfully demonstrated that the epithelium as well as the mesenchyme changed from the gastric type to the intestinal type in intestinal metaplasia and that PCFS disappeared in intestinal-type gastric carcinoma.

Actins↗
PubMed2003

Activin A is an autocrine activator of rat pancreatic stellate cells: potential therapeutic role of follistatin for pancreatic fibrosis.

BACKGROUND AND AIM: The present study was conducted to examine the effect of activin A on activation of rat pancreatic stellate cells (PSCs). METHODS: PSCs were prepared from rat pancreas using collagenase digestion and centrifugation with Nycodenz gradient. Activation of PSCs was examined by determining smooth muscle actin expression with western blotting. The presence of activin A receptors in PSCs was investigated by reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and immunocytochemistry. Expression of activin A and transforming growth factor beta (TGF-beta) mRNA was examined by RT-PCR. Activin A and TGF-beta peptide concentrations were examined with ELISA. Existence of activin A peptide in PSCs was investigated by immunocytochemistry. Collagen secretion was determined by Sirius red dye binding. RESULTS: Activin A receptors I and IIa were present in PSCs. PSCs expressed activin A mRNA and secreted activin A. Activin A enhanced PSC activation and collagen secretion in a dose dependent manner. TGF-beta and activin A increased each other's secretion and mRNA expression of PSCs. Follistatin decreased TGF-beta mRNA expression and TGF-beta secretion of PSCs, and inhibited both PSC activation and collagen secretion. CONCLUSION: Activin A is an autocrine activator of PSCs. Follistatin can inhibit PSC activation and collagen secretion by blocking autocrined activin A and decreasing TGF-beta expression and secretion of PSCs.

Actins↗
PubMed2002

Endoscopic transpapillary bile duct biopsy with the combination of intraductal ultrasonography in the diagnosis of biliary strictures.

BACKGROUND: When endoscopic retrograde cholangiopancreatography (ERCP) guided bile duct biopsy fails to demonstrate malignancy, it remains unclear how to manage patients with presumably malignant strictures. AIMS: To evaluate the value of intraductal ultrasonography (IDUS) when bile duct biopsy is negative. METHODS: Sixty two patients with strictures of the bile duct were studied prospectively. During ERCP, IDUS was performed using an ultrasonic probe (diameter 2.0 mm; frequency 20 MHz). Following IDUS, a bile duct biopsy was performed using forceps (diameter 1.8 mm). The IDUS images of the tumour were classified as polypoid lesions, localised wall thickening, intraductal sessile tumours, sessile tumour outside of the bile duct, or absence of apparent lesion. The bile duct wall structures at the site of the tumour as well as the maximum diameter of the tumour were also analysed. The IDUS findings were compared with the histological findings or clinical course. RESULTS: When the IDUS images showed a polypoid lesion (n=19), localised wall thickening (n=8), intraductal sessile tumour (n=13), and sessile tumour outside of the bile duct (n = 20), the sensitivities of the biopsy were 80%, 50%, 92%, and 53%, respectively. Multiple regression analysis showed that the presence of sessile tumour (intraductal or outside of the bile duct: p<0.05), tumour size greater than 10.0 mm (p<0.001), and interrupted wall structure (p<0.05) were independent variables that predicted malignancy. CONCLUSION: When biopsy fails to demonstrate evidence of malignancy, the presence of sessile tumour (intraductal or outside of the bile duct), tumour size greater than 10.0 mm, and interrupted wall structure on IDUS images are factors that can predict malignancy.

Adult↗
PubMed2001

The critical role of LIGHT, a TNF family member, in T cell development.

Negative selection refers to the selective deletion of autoreactive thymocytes but its molecular events have not been well defined. In this study, we demonstrate that a cellular ligand for herpes virus entry mediator and lymphotoxin receptor (LIGHT), a newly identified member of the TNF superfamily, may play a critical role in negative selection. Using TCR transgenic mice, we find that the blockade of LIGHT signaling in vitro and in vivo prevents negative selection induced by peptide and intrathymically expressed Ags, resulting in the rescue of thymocytes from apoptosis. Furthermore, the thymi of LIGHT transgenic mice show severe atrophy with remarkably reduced CD4(+)CD8(+) double-positive cells caused by increased apoptosis, suggesting that LIGHT can delete immature T cells in vivo. Taken together, these results demonstrate a critical role of LIGHT in thymic negative selection of the T cell repertoire.

Animals↗
PubMed2001

Progressive depletion of peripheral B lymphocytes in 4-1BB (CD137) ligand/I-Ealpha)-transgenic mice.

Interaction of 4-1BB (CD137) and its ligand (4-1BBL) is thought to positively regulate cell-mediated and humoral immune responses. We have prepared transgenic mouse strains that express 4-1BBL cDNA under the control of MHC class II I-Ealpha promoter. The 4-1BBL-transgenic mice show progressive splenomegaly and selective depletion of B220(+) B cells accompanied with low levels of circulating IgG and defective humoral responses to Ag challenge. In addition, splenocytes from the transgenic mice fail to provide stimulation for allogeneic T cells in both lymphoproliferative and CTL responses in vitro, whereas their T cells remain functionally normal. Our results reveal unexpected functions of 4-1BBL in the regulation of humoral immune responses and Ag presentation.

4-1BB Ligand↗
PubMed2001

RELT, a new member of the tumor necrosis factor receptor superfamily, is selectively expressed in hematopoietic tissues and activates transcription factor NF-kappaB.

The members of tumor necrosis factor receptor (TNFR) superfamily have been designated as the "guardians of the immune system" due to their roles in immune cell proliferation, differentiation, activation, and death (apoptosis). This study reports the cloning of a new member of the TNFR superfamily, RELT (Receptor Expressed in Lymphoid Tissues). RELT is a type I transmembrane glycoprotein with a cysteine-rich extracellular domain, possessing significant homology to other members of the TNFR superfamily, especially TNFRSF19, DR3, OX40, and LTbeta receptor. The messenger RNA of RELT is especially abundant in hematologic tissues such as spleen, lymph node, and peripheral blood leukocytes as well as in leukemias and lymphomas. RELT is able to activate the NF-kappaB pathway and selectively binds tumor necrosis factor receptor-associated factor 1. Although the soluble form of RELT fusion protein does not inhibit the one-way mixed lymphocyte reaction, immobilized RELT is capable of costimulating T-cell proliferation in the presence of CD3 signaling. These results define a new member of the TNFR superfamily that may be a potential regulator of immune responses.

Amino Acid Sequence↗
PubMed2001

B7-H1 costimulation preferentially enhances CD28-independent T-helper cell function.

B7-H1 is a recently described B7-like molecule that costimulates T-cell growth and cytokine secretion without binding to CD28, cytotoxic T-lymphocyte antigen-4 (CTLA-4), and inducible costimulator (ICOS). In this report, a mouse homologue of human B7-H1 is identified, and its immunologic functions are studied in vitro and in vivo. Mouse B7-H1 shares 69% amino acid homology to the human counterpart. Similar to human B7-H1, mouse B7-H1 can be induced to express on macrophages, T cells, and B cells and to enhance T-cell proliferation and secretion of interleukin-10 (IL-10), interferon-gamma, and granulocyte-macrophage colony-stimulating factor but not IL-2 and IL-4. Furthermore, B7-H1 preferentially costimulates CD4+ T cells independently of CD28 and enhances mixed lymphocyte responses to allogeneic antigens. In contrast to B7-1, expression of B7-H1 on murine P815 tumor cells by transfection fails to increase allogeneic and syngeneic cytolytic T-cell responses in vitro and in vivo. Administration of B7-H1Ig fusion protein, however, enhances keyhole limpet hemocyanin- specific T-cell proliferation and 2,4,6-trinitrophenyl-specific immunoglobulin G2a antibody production. The study thus identifies a unique costimulatory pathway that preferentially affects T-helper cell functions.

Amino Acid Sequence↗
PubMed2001

Cholangiographic findings of early-stage extrahepatic bile duct carcinoma.

BACKGROUND: To clarify the cholangiographic findings of early-stage (T1, tumor confined to the mucosal or fibromuscular layer) extrahepatic bile duct carcinoma. METHODS: Cholangiographic images were retrospectively analyzed without other information in 55 patients with extrahepatic bile duct carcinoma who underwent surgical treatment. Tumor stages were T1 (n = 10). T2 (n = 17), and T3 (n = 28). Cholangiographic findings were classified as "diffuse sclerosis," "stenosis," "papillary polypoid filling defect," or "nodular polypoid filling defect". "Papillary polypoid filling defect" was the term used when the width of the base was smaller than the width of the polypoid filling defect. RESULTS: T1 patients showed papillary polypoid filling defects (n = 8) or nodular polypoid filling defects (n = 2) on cholangiography. When cholangiography showed papillary polypoid filling defects, 8 of the 14 resected patients showed T1 stage tumor histologically. CONCLUSIONS: In this study, 57% (8/14) of resected patients with papillary polypoid filling defects showed T1 stage tumor. No T1 stage tumor showed stenosis or diffuse sclerosis.

Adult↗
PubMed2001

Looping technique for transpapillary selective biopsy of the left hepatic duct.

PURPOSE: Because biopsy forceps tend to turn towards the right hepatic duct during endoscopic retrograde cholangiopancreatography (ERCP), selective access to the left hepatic duct is difficult. METHODS: In this study, we managed to insert biopsy forceps selectively into the left hepatic duct, by using a looping technique, in three patients. Biopsy forceps were inserted into the right hepatic duct by the conventional method. The elevator of the endoscope was kept down, and the shaft of the biopsy forceps was then advanced to the duodenal cavity until it formed a loop between the endoscope and the papilla. During the procedure, the tip of the forceps was kept at the hepatic hilus. RESULTS: In this condition, we were able to slowly rotate the tip of the forceps and direct the forceps towards the left. Sufficient material from the left hepatic duct was obtained in all patients. CONCLUSIONS: The looping technique was useful for selective access to the left hepatic duct.

Adult↗
PubMed2001

Transpapillary intraductal US prior to biliary drainage in the assessment of longitudinal spread of extrahepatic bile duct carcinoma.

BACKGROUND: The utility of intraductal US via the transpapillary route prior to biliary drainage in the assessment of longitudinal extension of extrahepatic bile duct carcinoma was investigated. METHODS: In 19 patients with extrahepatic bile duct carcinoma who underwent surgical resection, an ultrasonic probe (diameter, 2.0 mm; frequency, 20 MHz) was inserted into the bile duct via the transpapillary route prior to biliary drainage. Longitudinal cancer extension along the bile duct was prospectively determined and compared with the histologic findings in the resected specimens. RESULTS: Results on the hepatic side were as follows: Intraductal US demonstrated more extensive longitudinal cancer spread than cholangiography in 9 of 19 patients with one instance of overdiagnosis. The accuracy of intraductal US in assessing the extent of spread (84%) was superior to that of cholangiography (47%) (p < 0.05). Results on the duodenal side were as follows: In patients with suprapancreatic bile duct cancer (n = 14), intraductal US demonstrated more extensive longitudinal cancer spread than cholangiography in 8 of 14 patients. The accuracy of intraductal US in assessing the extent of the spread (86%) was superior to that of cholangiography (43%) (p < 0.05). CONCLUSIONS: Transpapillary intraductal US prior to biliary drainage is useful in demonstrating longitudinal extension of bile duct cancer. However, the surgical margins were inaccurate in some patients.

Aged↗
PubMed2001

B7-H3: a costimulatory molecule for T cell activation and IFN-gamma production.

We describe here a newly identified member of the human B7 family, designated B7 homolog 3 (B7-H3), that shares 20-27% amino acid identity with other B7 family members. B7-H3 mRNA is not detectable in peripheral blood mononuclear cells, although it is found in various normal tissues and in several tumor cell lines. Expression of B7-H3 protein, however, can be induced on dendritic cells (DCs) and monocytes by inflammatory cytokines and a combination of phorbol myristate acetate (PMA) + ionomycin. Soluble B7-H3 protein binds a putative counter-receptor on activated T cells that is distinct from CD28, cytotoxic T lymphocyte antigen 4 (CTLA-4), inducible costimulator (ICOS) and PD-1. B7-H3 costimulates proliferation of both CD4+ and CD8+ T cells, enhances the induction of cytotoxic T cells and selectively stimulates interferon gamma (IFN-gamma) production in the presence of T cell receptor signaling. In contrast, inclusion of antisense B7-H3 oligonucleotides decreases the expression of B7-H3 on DCs and inhibits IFN-gamma production by DC-stimulated allogeneic T cells.Thus, we describe a newly identified costimulatory pathway that may participate in the regulation of cell-mediated immune responses.

Amino Acid Sequence↗
PubMed2001

Comparison of intraductal ultrasonography with percutaneous transhepatic cholangioscopy for the identification of residual bile duct stones during lithotripsy.

BACKGROUND: An imaging modality that can be used to identity small stones after a biliary lithotripsy is required. Intraductal ultrasonography was evaluated by using percutaneous transhepatic cholangioscopy as the gold standard. METHODS: Lithotripsy, under percutaneous transhepatic cholangioscopy guidance, was performed in 20 patients. A thin-caliber ultrasonic probe (2.0 mm in diameter and 20 MHz frequency) was inserted into the bile duct through the percutaneous tract after lithotripsy, and residual stones were identified. This was followed by percutaneous transhepatic cholangioscopy. RESULTS: In the extrahepatic bile ducts, intraductal ultrasonography provided images of all the stones demonstrated on cholangioscopy (n = 11). The sensitivity was superior to that of cholangiography (P < 0.005). However, in the intrahepatic bile ducts, intraductal ultrasonography only visualized the stones located in the cannulated lobe. Extrahepatic stones smaller than 5.0 mm in diameter or in a common hepatic duct larger than 15.0 mm in diameter were missed by cholangiography, but were visualized by the use of intraductal ultrasonography (P < 0.05). CONCLUSIONS: Intraductal ultrasonography is equivalent to cholangioscopy in the extrahepatic bile ducts. Cholangiography and intraductal ultrasonography should be used in combination to image intrahepatic and extrahepatic stones.

Aged↗
PubMed2001

Epinephrine irrigation for the prevention of pancreatic damage after endoscopic balloon sphincteroplasty.

BACKGROUND AND AIM: Endoscopic balloon sphincteroplasty (EBS) is an alternative to sphincterotomy for the treatment of bile duct stones. The purpose of this study was to determine if epinephrine irrigation of the papilla can prevent the pancreatic damage associated with EBS. METHODS: A total of 173 patients with bile duct stones were treated by EBS. After conventional endoscopic retrograde cholangiography, EBS was performed by using a biliary dilatation catheter (balloon diameter: 8 mm). The duct was then cleared by using Dormia baskets or retrieval balloon catheters. Mechanical lithotripsy was performed before extraction when the stones were greater than 8 mm in diameter. In 81 patients, the dilated orifice was irrigated with 40-120 mL (50 +/- 37 mL) of 1:1,000,000 epinephrine (epinephrine group). In the remaining 92 patients, epinephrine irrigation was not performed (control group). Acute pancreatitis was defined by a serum amylase concentration fivefold greater than the upper limits of normal in association with abdominal pain. RESULTS: After EBS, serum amylase concentrations were significantly increased in both groups. However, the degree of hyperamylasemia was less in the epinephrine group than in the control group (617 +/- 611 vs 1037 +/- 1491 IU/L, P < 0.05). The incidence of pancreatitis was lower in the epinephrine group than in the control group (1.2 vs 7.6%, P < 0.05). CONCLUSIONS: Epinephrine irrigation is a simple and useful method to prevent post-EBS pancreatic damage and pancreatitis.

Adult↗
PubMed2001

Intraductal ultrasonography for hepatocellular carcinoma with tumor thrombi in the bile duct: comparison with polypoid cholangiocarcinoma.

BACKGROUND AND AIM: Tumor thrombi in the bile duct caused by hepatocellular carcinoma (HCC), and cholangiocarcinoma show polypoid lesions on cholangiographic findings. This study prospectively compared the images of intraductal ultrasonography between HCC and polypoid cholangiocarcinoma. METHODS: In five patients with tumor thrombi in the bile duct caused by HCC, a 2.0 mm diameter ultrasonic probe with a frequency of 20 MHz was inserted into the bile duct via the transpapillary route (n = 4) or the transhepatic route (n = 1). The images were compared to that of 65 patients with cholangiocarcinoma. RESULTS: In all patients with HCC, intraductal ultrasonography showed a 'polypoid tumor with a narrow base'. In 16 of 65 patients with cholangiocarcinoma, it showed a 'polypoid tumor with a narrow base'. When intraductal ultrasonography showed a 'polypoid tumor with a narrow base', the findings of a positive 'nodule within a nodule' (40 vs 0%; P < 0.05), and the absence of a 'papillary-surface pattern' (80 vs 13%; P < 0.05) were more highly associated with tumor thrombi caused by HCC than to polypoid-type cholangiocarcinoma. CONCLUSIONS: Intraductal ultrasonography was useful to distinguish between tumor thrombi caused by HCC and polypoid-type cholangiocarcinoma.

Aged↗
PubMed2001

Endoscopic partial resection of a duodenal duplication cyst.

A case of symptomatic duodenal duplication cyst is reported. The patient underwent endoscopic partial resection of the cystic wall using the O-ring ligation kit. After resection, the abdominal pain disappeared. Endoscopic partial resection is useful for diagnosis and treatment of duodenal duplication cyst.

Adult↗