Search PubMed⌕ Search

Biomedical subjects

K Yamaguchi

Publications and source records attributed to K Yamaguchi.

At least 397 records · Page 22Linked to original sources
PubMed1999

Identification of a novel gene, DAM1, amplified at chromosome 1p13.3-21 region in human breast cancer cell lines.

Screening for differentially expressed genes in cancer cell lines by the RNA differential display (DD) technique identified a novel mRNA that encodes a 26-kDa protein and is up-regulated in MCF-7 and BT-20 breast cancer cells. The predicted amino acid sequence showed 38% homology to Caenorhabditis elegans T12A2.7 protein, indicating that this is a possible human homologue for C. elegans T12A2.7 protein. The mRNA, designated DAM1 (DNA amplified in mammary carcinoma), was mapped at the 1p13.3-21 region, which is frequently altered in human breast cancer. By Southern blot analysis, we confirmed that the up-regulation of this novel gene is associated with gene amplification in MCF-7 (10-fold) and BT-20 (5-fold) cells. Our findings suggest that the DAM1 gene is a novel gene up-regulated by amplification in human breast cancer cell lines.

Amino Acid Sequence↗
PubMed1999

Mutation analysis of hBUB1 in aneuploid HNSCC and lung cancer cell lines.

Aneuploidy is frequently observed in many types of human cancer cells, suggesting that mutations of genes required for chromosomal stability may occur in human tumors. The BUB gene is a component of the mitotic checkpoint in budding yeast that delays anaphase in the presence of spindle damage thus increasing the probability of successful delivery of a euploid genome to each daughter cell. Recently, human homologues of the BUB gene were identified and mutant alleles of hBUB1 were detected in two colorectal tumor cell lines. Transfection of one mutant allele led to dominant disruption of the mitotic checkpoint control in a euploid cell, suggesting that aneuploidy in some tumors could be due to defects in the mitotic checkpoint. We analyzed the entire coding sequence of hBUB1 for mutation in 31 head and neck squamous cell carcinoma (HNSCC) and lung cancer cell lines, most with severe aneuploidy. We found expression of the hBUB1 gene in all cell lines and only a single nucleotide substitution in one cell line without a resultant change in amino acid sequence. Our study demonstrates that hBUB1 is rarely a target for genetic alterations in tumors of the respiratory tract.

Aneuploidy↗
PubMed1999

Rate of detection of lymph node metastasis is correlated with the depth of submucosal invasion in early stage gastric carcinoma.

BACKGROUND: Gastric carcinoma invading the submucosa is often accompanied by lymph node metastasis. However, the relation between the depth of submucosal invasion and the status of metastasis has not been investigated. The objective of this study was to clarify the relation between lymph node status and the histologic features of gastric carcinoma invading the submucosa. METHODS: The histopathology of 118 patients who underwent gastrectomy and lymph node dissection for gastric carcinoma invading the submucosa was examined. These pT1 tumors with invasion of the submucosa were confirmed by histologic examination of the resected specimens. Tumor size, depth of submucosal invasion, histologic type, and macroscopic type were investigated in association with presence or absence of and anatomic level of lymph node metastasis. RESULTS: Among the 118 patients, 16 (14%) had lymph node metastasis, and the status of metastasis significantly correlated with tumor size and depth of submucosal invasion. The frequency of metastasis to perigastric lymph nodes and extragastric lymph nodes was 0% and 0% for < or =1-cm tumors, 5% and 1% for 1- to 4-cm tumors, and 46% and 15% for >4-cm tumors, respectively. There was no lymph from a node metastasis in tumors with less than 300 microm of submucosal invasion. The frequency of lymph node metastasis for tumors with 300-1000 microm and >1000 microm of submucosal invasion were 19% and 14%, respectively. CONCLUSIONS: Tumor size and depth of submucosal invasion serve as simple and useful indicators of lymph node metastasis in early stage gastric carcinoma. Optimal lymph node dissection levels are as follows: 1) local resection (D0) for lesions < or =1 cm, 2) limited lymph node dissection (D1) for 1- to 4-cm lesions, and 3) radical lymph node dissection (D2) for lesions >4 cm. When submucosal invasion of a locally resected tumor is more than 300 microm, additional gastrectomy and lymph node dissection are necessary.

Adenocarcinoma↗
PubMed1999

Behavioral and morphologic studies of the chronically compressed cauda equina. Experimental model of lumbar spinal stenosis in the rat.

STUDY DESIGN: An experimental model in rats of chronically compressed cauda equina was produced, and behavioral and morphologic changes were examined. OBJECTIVES: To provide a useful model for analyzing the pathophysiologic changes of the cauda equina by chronic compression and to examine behavioral and morphologic changes in this model. SUMMARY OF BACKGROUND DATA: Several animal models have been reported in which various materials were used to compress the cauda equina. However, the pathophysiology of the cauda equina by chronic compression is not yet well understood. Studies in which rats were used are scarce. METHODS: A silicone sheet was applied to the spinal canal at L4 in the rat. Walking durations on treadmill tests and paw-withdrawal latencies to thermal stimuli were measured before and after the operation for 24 weeks. Histologic changes also were examined. RESULTS: Walking durations decreased after chronic compression. However, paw-withdrawal latencies were not significantly changed. Histologically, the number of large-diameter myelinated axons decreased after compression, whereas the number of small-diameter myelinated axons increased. Electron microscopic observation indicated that the continuous degeneration and regeneration of axons occurred throughout the chronic compression experiment. CONCLUSIONS: The current model and behavioral assessments may be useful in analyzing the pathophysiology of chronically compressed cauda equina.

Animals↗
PubMed1999

4-Phenylthiazole derivatives inhibit IL-6 secretion in osteoblastic cells and suppress bone weight loss in ovariectomized mice.

A series of 4-phenylthiazole derivatives were synthesized and tested their inhibitory effect on the interleukin-6 secretion stimulated by PTH in osteoblastic cells. SCRC2941-18, 2-amino-4-(4-chlorophenyl)-5-methylthiazole, was found to be the most potent inhibitor in the derivatives. Furthermore, SCRC2941-18 significantly suppressed the bone weight loss in the ovariectomized mice, an osteoporosis model.

Animals↗
PubMed1999

Crystal structure of the E166A mutant of extended-spectrum beta-lactamase Toho-1 at 1.8 A resolution.

Bacterial resistance to beta-lactams is mainly due to the production of beta-lactamase. Especially through the production of extended-spectrum beta-lactamases (ESBLs), bacteria have acquired resistance not only to penicillins, but also to expanded-spectrum cephems. Here, we describe the crystal structure of the E166A mutant of class A beta-lactamase Toho-1 at 1.8 A resolution, the first reported tertiary structure of an ESBL. Instead of the wild-type enzyme, a mutant Toho-1, in which Glu166 was replaced with alanine, was used for this study, because of the strong tendency of the wild-type enzyme to form twinned crystals. The overall structure of Toho-1 is similar to the crystal structures of non-ESBLs, with no pronounced backbone rearrangement of the framework. However, there are some notable local changes. First, a difference in the disposition of an arginine residue, which is at position 244 in non-ESBLs but at position 276 in Toho-1 and other ESBLs, was revealed and the role of this arginine residue is discussed. Moreover, changes in the hydrogen-bonding pattern and in the formation of the hydrophobic core were also observed near the Omega loop. In particular, the lack of hydrogen bonds in the vicinity of the Omega loop could be a cause of the extended substrate specificity of Toho-1. Through the generation of a model for the enzyme-substrate complex, a conformational change of Toho-1 occurring on complex formation is discussed based on the active-site cleft structure and the substrate profile.

Amino Acid Sequence↗
PubMed1999

Calbrain, a novel two EF-hand calcium-binding protein that suppresses Ca2+/calmodulin-dependent protein kinase II activity in the brain.

A cDNA clone that encodes a novel Ca2+-binding protein was isolated from a human brain cDNA library. The gene for this clone, termed calbrain, encodes a 70-amino acid polypeptide with a predicted molecular mass of 8.06 kDa. The analysis of deduced amino acid sequence revealed that calbrain contains two putative EF-hand motifs that show significantly high homology to those of the calmodulin (CaM) family rather than two EF-hand protein families. By Northern hybridization analysis, an approximate 1.5-kilobase pair transcript of calbrain was detected exclusively in the brain, and in situ hybridization study revealed its abundant expression in the hippocampus, habenular area in the epithalamus, and in the cerebellum. A recombinant calbrain protein showed a Ca2+ binding capacity, suggesting the functional potency as a regulator of Ca2+-mediated cellular processes. Ca2+/calmodulin-dependent kinase II, the most abundant protein kinase in the hippocampus and strongly implicated in the basic neuronal functions, was used to evaluate the physiological roles of calbrain. Studies in vitro revealed that calbrain competitively inhibited CaM binding to Ca2+/calmodulin-dependent kinase II (Ki = 129 nM) and reduced its kinase activity and autophosphorylation.

Amino Acid Sequence↗
PubMed1999

A mutant of deleted variant of hepatocyte growth factor (dHGF) with alanine substitution in the N-terminal basic region has higher activity in vivo.

In a previous study, we generated a mutant of dHGF (deleted variant of hepatocyte growth factor), termed #2, with higher specific activity than dHGF in assays of mitogenic activity on rat hepatocytes and America opossum kidney epithelial cells (OK). In the present study, we examine in vivo hepatotropic and renotropic activities of #2 and its distribution to target tissues, liver and kidney. Administration of #2 to normal rats significantly increased serum levels of total protein, albumin, free-cholesterol, and HDL-cholesterol and liver weight in a dose-dependent manner. Analysis of these parameters suggests that #2 is more potent than dHGF as a hepatotropic factor in vivo. In addition, #2 reduced mortality of mercuric chloride-administered mice and the effect was stronger than that of dHGF. When injected to mice, a larger amount of #2 than dHGF was rapidly distributed to the liver. Sixty minutes after injection, the concentrations of #2 in plasma, liver, and kidney were higher than those of dHGF. These distribution properties and the higher mitogenic activity in vitro may explain why #2 exerts more potent in vivo biological activity than dHGF.

Acute Kidney Injury↗
PubMed1999

An isoform of Nurr1 functions as a negative inhibitor of the NGFI-B family signaling.

NGFI-B, Nurr1 and NOR-1 constitute a distinct subfamily within the nuclear receptor superfamily. To clarify the transcriptional regulation by the NGFI-B family, we searched for other components that can bind to the NBRE response element, a known target sequence for these transcription factors. By low stringency hybridization using the DNA binding domain of NOR-1 as a probe, a C-terminal truncated Nurr1 isoform, named Nurr2, was isolated from a mouse MC3T3-E1 cell cDNA library. Nurr2 had a novel cryptic exon located upstream in the Nurr1 promoter region, and was generated by alternative splicing at exons 1, 2 and 6. The C-terminal region was encoded by frame-shifted exon 6, and so Nurr2 lacked the C-terminal sequences corresponding to the putative ligand binding domain or dimerization domain. Quantitative reverse transcriptase-PCR experiments confirmed the presence of the Nurr2 isoform in mouse, rat and human. It was, like Nurr1, highly expressed in the pituitary and the cerebral cortex. Nurr2 and Nurr1 were also concomitantly induced by forskolin in NIH3T3 cells. Functional analysis using a reporter gene, containing NBRE response elements, indicated that while the isoform was inactive by itself, it could inhibit transactivation by the members of the NGFI-B family. These results indicate that the C-terminal truncated isoform, Nurr2, may act as a negative regulator of the NGFI-B family signaling.

3T3 Cells↗
PubMed1999

XIAP, a cellular member of the inhibitor of apoptosis protein family, links the receptors to TAB1-TAK1 in the BMP signaling pathway.

Signals elicited by transforming growth factor-beta (TGF-beta) superfamily ligands are generated following the formation of heteromeric receptor complexes consisting of type I and type II receptors. TAK1, a member of the MAP kinase kinase kinase family, and its activator, TAB1, participate in the bone morphogenetic protein (BMP) signaling pathway involved in mesoderm induction and patterning in early Xenopus embryos. However, the events leading from receptor activation to TAK1 activation remain to be identified. A yeast interaction screen was used to search for proteins that function in the pathway linking the receptors and TAB1-TAK1. The human X-chromosome-linked inhibitor of apoptosis protein (XIAP) was isolated as a TAB1-binding protein. XIAP associated not only with TAB1 but also with the BMP receptors in mammalian cells. Injection of XIAP mRNA into dorsal blastomeres enhanced the ventralization of Xenopus embryos in a TAB1-TAK1-dependent manner. Furthermore, a truncated form of XIAP lacking the TAB1-binding domain partially blocked the expression of ventral mesodermal marker genes induced by a constitutively active BMP type I receptor. These results suggest that XIAP participates in the BMP signaling pathway as a positive regulator linking the BMP receptors and TAB1-TAK1.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Crystallization and preliminary X-ray study of iso-2 azurin from the methylotrophic bacterium, Methylomonas J.

The obligate methylotroph Methylomonas J possesses two distinct azurins. The iso-2 azurin, which functions as an electron acceptor for methylamine dehydrogenase, has been crystallized using two kinds of precipitants: PEG 4000 and ammonium sulfate. The crystals precipitated with PEG belong to the monoclinic system, space group P21, with unit-cell parameters a = 32.96, b = 33.67, c = 47.34 A and beta = 101.35 degrees. The crystals precipitated with ammonium sulfate belong to the orthorhombic system, space group C2221, with unit-cell parameters a = 31.52, b = 62.49 and c = 135.41 A. The crystals diffract to 1.6 and 1.9 A resolution, respectively, and were suitable for X-ray crystallographic studies. A Patterson search is being conducted using the recently reported structure of Alcaligenes xylosoxidans NCIMB 11015 as a starting model.

Alcaligenes↗
PubMed1999

Basic fibroblast growth factor inhibits osteoclast formation induced by 1alpha,25-dihydroxyvitamin D(3) through suppressing the production of osteoclast differentiation factor.

Basic fibroblast growth factor (bFGF) inhibited osteoclast-like cell (OCL) formation in cocultures of mouse spleen cells with either osteoblasts or a stromal cell line, ST2, in the presence of 1alpha, 25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. bFGF directly acted on osteoblasts/stromal cells, but not osteoclast progenitors, to inhibit 1,25(OH)(2)D(3)-induced OCL formation. bFGF suppressed the mRNA expression of osteoclast differentiation factor (ODF) but did not affect that of osteoclastogenesis inhibitory factor (OCIF) in ST2 cells treated with 1,25(OH)(2)D(3) and dexamethasone. Enzyme-linked immunosorbent assay showed that bFGF hardly affected OCIF production in the treated ST2 cells. A genetically engineered soluble form of ODF, but not anti-OCIF neutralizing antibody, abolished bFGF-mediated inhibition of OCL formation. bFGF suppressed the binding of (125)I-labeled OCIF to both ST2 cells and osteoblasts treated with 1,25(OH)(2)D(3). These findings indicate that bFGF inhibits 1,25(OH)(2)D(3)-induced OCL formation via suppression of ODF production by osteoblasts/stromal cells.

Animals↗
PubMed1999

Paradoxical synergistic effects of tumour necrosis factor and interleukin 1 in murine gut-derived sepsis with Pseudomonas aeruginosa.

The authors evaluated the synergistic effect of tumour necrosis factor (TNF) and interleukin 1 (IL-1) in gut-derived sepsis in mice. After colonization of Pseudomonas aeruginosa strain D4 in the gastrointestinal tract, cyclophosphamide was administered to induce bacterial translocation of the P. aeruginosa and thereby to cause gut-derived sepsis. In this model, treatment either with 8 microg/kg of recombinant human TNF-alpha (rhTNF-alpha) or 2 microg/kg of recombinant human interleukin 1alpha (rhIL-1alpha) solely did not affect the mortality, whereas combined administration of the same doses of rhTNF-alpha and rhIL-1alpha significantly increased the mortality rate in comparison with saline-treated mice. Bacterial counts in liver and blood were significantly higher in rhTNF-alpha and rhIL-1alpha treated mice than in saline-treated mice. Endogenous TNF-alpha and IL-1beta productions were stimulated after combined treatment with rhTNF-alpha and rhIL-1alpha. On the contrary to these adverse effects, combined treatment with 500 microg/kg of rhTNF-alpha and 50 microg/kg of rhIL-1alpha on the day before the administration of cyclophosphamide significantly reduced the mortality from septic infection. We conclude that TNF and IL-1 synergistically affect the mortality of mice after gut-derived sepsis due to P. aeruginosa in mice and the timing of treatment with these cytokines causes both extremes in their effects.

Animals↗
PubMed1999

Clinical evaluation of transhiatal bilateral splanchnicotomy for patients with intractable supramesenteric pain.

Although a transhiatal bilateral splanchnicotomy (TBS) has many advantages, it has not been widely employed as an effective minimal invasive therapy for intractable supramesenteric pain. Furthermore, the effects of TBS have not yet been clearly evaluated. Between 1995 and 1997, TBS was performed on 11 patients with intractable epigastric and/or flank pain due to unresectable pancreatic cancer, chronic pancreatitis, or an unknown cause. The effect of TBS on the pain was evaluated using a novel simple pain score and pain reduction percentage scaled on the basis of the medication and the judgments by patients themselves, respectively. The detection and cutting of the bilateral great splanchnic nerves were easily performed in all of the patients using common flexible chondrocostal retractors. The evaluation of the TBS effect using the pain score clearly demonstrated the early and late mean postoperative pain score (1.1 +/- 0.9 and 1.4 +/- 1.2: mean +/- SD) to be significantly (P = 0.0002 and P = 0.002, respectively) lower than the preoperative pain score (3.5 +/- 0.7). Furthermore, the mean postoperative pain reduction percentage (85% +/- 13%) evaluated by those patients was also significantly different (P < 0.0001). The present study showed no significant complications for TBS, except for minor complications such as the transient fall of blood pressure and reparable pleural damage. Interestingly, a long-term follow-up revealed that no complications related to the splanchnicotomy were observed. These results indicate that TBS is a useful treatment for patients with intractable supramesenteric pain caused by cancer as well as benign diseases.

Abdominal Pain↗
PubMed1999

Establishment and characterization of human pancreatic carcinoma lines with a high metastatic potential in the liver of nude mice.

To investigate of human pancreatic cancer metastasis to the liver, a pancreatic carcinoma line, HPC-3, was injected into the spleens of nude mice. The cells from a few liver metastatic foci of the mice injected with HPC-3 were expanded in vitro and subsequently injected into the spleens of nude mice. By repeating these procedures, we were able to obtain a cell line, designated HPC-3H4. The mice were observed to have liver metastasis in 6 of 6 (100%) cases injected with HPC-3H4, whereas the rate was 0% at 3 weeks after the intrasplenic injection of HPC-3. The tumorigenicity of HPC-3H4 was more rapid than that of HPC-3. The motile activity of HPC-3H4 was also stronger than that of HPC-3, and the adhesion to the extracellular matrix of HPC-3H4 was stronger than that of HPC-3. We also analyzed the cell surface expression of the metastasis-related adhesion molecules. As a result, no substantial changes were observed in the expression level of adhesion molecules. These results suggest that HPC-3H4 is useful for studies aimed at the prevention of liver metastasis.

Animals↗