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Biomedical subjects

M Tada

Publications and source records attributed to M Tada.

At least 19 recordsLinked to original sources
PubMed1999

Endosonography during endoscopic mucosal resection to enhance its safety: a new technique.

BACKGROUND: We have performed endoscopic mucosal resection of the esophagus (172 cases), stomach (102 cases), and colon (28 cases) using a transparent plastic cap. Because the lesion-bearing mucosa is suctioned up inside the cap under endoscopic suction, the mucosa should be dissected sufficiently from the proper muscle layer to prevent perforation. METHODS: To avert the risk of perforation, we introduced endosonographic assessment of submucosal dissection (47 cases). In all cases, just keeping the ultrasonic probe on the surface of the mucosa allowed us to evaluate whether the mucosal lesion was lifted up sufficiently from the proper muscle layer after local saline injection. RESULTS: It was possible to confirm that the muscle layer was kept outside the strangulating snare by the same procedure (32 of 37 cases, 86.5%). CONCLUSIONS: We experienced five muscular resections in cases without the ultrasonic probe and no muscular resection with the ultrasonic probe. Thus we recommend endosonographic assessment during endoscopic mucosal resection to enhance its safety.

Colonic Neoplasms↗
PubMed1999

Washout of small stones in the bile duct by saline infusion using a side-holed balloon catheter in patients undergoing endoscopic papillary balloon dilation.

BACKGROUND: Complete bile duct clearance of stones should be achieved in patients managed with endoscopic papillary balloon dilation. However, complete retrieval of small stones or tiny fragments sometimes proves difficult using conventional devices. METHODS: We attempted the removal of fine stone fragments by saline infusion using a specially designed retrieval balloon catheter with a blind tip and a side hole located proximal to the balloon in 14 patients. RESULTS: Using this technique, bile duct clearance was achieved in a single attempt in 13 of 14 patients; 2 attempts were required in 1 patient. Cholecystitis occurred in 2 patients with gallstones in situ after the procedure. CONCLUSIONS: Saline washout using a side-holed retrieval balloon catheter effectively cleans stones and stone fragments from the bile duct in patients treated with endoscopic papillary balloon dilation.

Aged↗
PubMed1999

Helicobacter pylori infection and atrophic gastritis: a nested case-control study in a rural town in Japan.

A seroepidemiologic, nested case-control study was conducted to evaluate the risk for atrophic gastritis associated with Helicobacter pylori infection. Atrophic gastritis was diagnosed on the basis of serum pepsinogen levels: pepsinogen I level < or = 70 ng/ml and pepsinogen I/pepsinogen II ratio < or = 3.0. Cases were 23 men and 39 women who were not diagnosed with atrophic gastritis in 1987, but who were diagnosed with the condition in 1992. Controls were the 120 men and 282 women who did not meet the serologic criteria for atrophic gastritis in either time period. Neither cases nor controls had a history of upper gastrointestinal operations. Helicobacter pylori infection at the initial survey was associated with a significantly increased risk of atrophic gastritis incidence for both sexes combined (odds ratio = 3.72; 95% confidence interval, 1.78-7.79; P = 0.0005). Cigarette smoking and consumption of alcohol and green-yellow vegetables were not associated with incidence of atrophic gastritis.

Adult↗
PubMed1999

Evaluation of application techniques of fibrin sealant to prevent cerebrospinal fluid leakage: a new device for the application of aerosolized fibrin glue.

OBJECTIVE: This report evaluates the sealing effects of fibrin sealant applied on the dura mater using different techniques. METHODS: Three application methods were studied: a sequential layer method, a simultaneous method using a cannula, and a spray method using a newly developed spray device. The sealing effects of these methods were compared using in vitro histological analysis and a pressure resistance test. The clinical efficacy of the fibrin sealant to prevent water leakage through the dura mater was retrospectively analyzed in a total of 509 patients. The process of absorption of a clinically applied fibrin clot in vivo was examined using surgical specimens. RESULTS: The fibrin plate made using the spray method withstood a hydrostatic pressure greater than 200 cm H2O. A scanning electron microscopic study of the fibrin clots showed that the sequential and simultaneous methods produced a fibrin fiber network; in contrast, our spray method formed a dense fibrin tissue in which the fibrin molecules fused together forming stratified laminae. Of the 295 supratentorial craniotomies during which spraying was used, postsurgical cerebrospinal fluid leakage occurred in 9 cases (3.1%), whereas of the 214 craniotomies during which spraying was not used, cerebrospinal fluid leakage occurred in 19 cases (8.9%). Histological examinations of 10 surgical specimens obtained during second craniotomies revealed that the spray-made fibrin clots had been gradually replaced by mature granulation composed of collagenous connective tissue. CONCLUSION: The optimal technique for applying fibrin sealant is the spray method that aerosolizes fibrin glue and produces a tough fibrin plate.

Administration, Topical↗
PubMed1999

A blind comparison of the effectiveness of endoscopic ultrasonography and endoscopy in staging early gastric cancer.

BACKGROUND/AIMS: Endoscopic ultrasonography is expected to be useful for invasion depth staging of early gastric cancer. A prospective blind study of the staging characteristics of endoscopy and endoscopic ultrasonography for early gastric cancer was performed. METHODS: Findings of endoscopy and endoscopic ultrasonography using a 20 MHz thin ultrasound probe were independently reviewed and the results of 52 early gastric cancer lesions analysed. RESULTS: The overall accuracy rates in invasion depth staging of early gastric cancer were 63% for endoscopy and 71% for endoscopic ultrasonography. No statistically significant differences were observed in overall accuracy. Endoscopic ultrasonography tended to overstage, and lesions that were classified as mucosal cancer by endoscopic ultrasonography were very likely (95%) to be limited to the mucosa on histological examination. All 16 lesions staged as mucosal cancer independently but coincidentally by both methods were histologically limited to the mucosa. CONCLUSIONS: Endoscopic ultrasonography is expected to compensate for the understaging of lesions with submucosal invasion that are endoscopically staged as mucosal cancer.

Adult↗
PubMed1999

In vivo analysis using variants of zebrafish BMPR-IA: range of action and involvement of BMP in ectoderm patterning.

It has been an intriguing problem whether the polypeptide growth factors belonging to the transforming growth factor-beta (TGF-beta) superfamily function as direct and long-range signaling molecules in pattern formation of the early embryo. In this study, we examined the mechanism of signal propagation of bone morphogenetic protein (BMP) in the ectodermal patterning of zebrafish embryos, in which BMP functions as an epidermal inducer and a neural inhibitor. To estimate the effective range of zbmp-2, we first performed whole-mount in situ hybridization analysis. The zbmp-2-expressing domain and the neuroectoderm, marked by otx-2 expression, were complementary, suggesting that BMP has a short-range effect in vivo. Moreover, mosaic experiments using a constitutively active form of a zebrafish BMP type I receptor (CA-BRIA) demonstrated that the cell-fate conversion, revealed by ectopic expression of gata-3 and repression of otx-2, occurred in a cell-autonomous manner, denying the involvement of the relay mechanism. We also found that zbmp-2 was induced cell autonomously within the transplanted cells in the host ectoderm, suggesting that BMP cannot influence even the neighboring cells. This result is consistent with the observation that there is no gap between the expression domains of zbmp-2 and otx-2. Taken together, we propose that, in ectodermal patterning, BMP exerts a direct and cell-autonomous effect to fate uncommitted ectodermal cells to become epidermis.

Amino Acid Sequence↗
PubMed1998

Use of polyclonal antibodies against carcinogen-DNA adducts in analysis of carcinogenesis.

Polyclonal antibodies against 3,2'-dimethyl-4-aminobiphenyl (DMAB)- and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-DNA adducts were raised for their immunohistochemical demonstration in paraffin-embedded sections. Both carcinogens target multiorgans in rats with colon, mammary glands and prostate as common tumor sites. PhIP is particularly important because it is a cooked food-derived carcinogen to which man is exposed on a daily bases. Dose-related nuclear staining in various tissue of rats was observed 24 h after single applications of both carcinogens but no observable decrease in staining intensity was evident in most organs by 168 h. Staining specificity in terms of sites of tumor development was lacking. However, in target organs, semiquantitative data on adduct formation correlated with alteration in tumor response by modifying factor(s). Furthermore, human prostate tissue implanted into nude mice showed positive staining. Thus, the antibodies can be applied as tools to clarify tissue or cell-specific carcinogenesis, carcinogen-exposure levels and metabolic activation in various species, including man after tissue transplantation.

Aminobiphenyl Compounds↗
PubMed1998

Involvement of NF-Y in transcriptional regulation of the phospholamban gene.

To understand the transcriptional regulation of the phospholamban gene, we analyzed a 5'-upstream region of the gene. Using a series of deletion constructs, we demonstrated that the region from -96 bp to -78 bp, containing the CCAAT sequence, is essential for transcription of this gene. This region specifically bound to nuclear proteins extracted from rat hearts, and gel-shift assays using competitive oligonucleotides, antibodies and recombinant proteins showed that this region binds to the NF-YA and NF-YB, members of the CCAAT-binding nuclear protein family. This region-dependent transcription in cardiac myocytes transfected with antisense cDNAs encoding NF-YA and NF-YB was decreased to approximately 50% of that seen in cells transfected with the same sense cDNAs. We, therefore, conclude that the region from -96 bp to -78 bp plays a critical role in expression of the phospholamban gene, which is regulated by binding of the nuclear protein NF-Y.

Animals↗
PubMed1998

Immunohistochemical demonstration of carcinogen-DNA adducts in tissues of rats given 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP): detection in paraffin-embedded sections and tissue distribution.

A polyclonal antibody against 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-DNA adducts was raised for their immunohistochemical demonstration in paraffin-embedded sections. Specificity of this antibody was confirmed by competitive ELISA. Positive signals were immunohistochemically detected in acetone-fixed but not in formalin- or ethanol-fixed sections from F344 rats treated by gavage with a single dose of PhIP at 37.5-300 mg/kg and killed at 1, 2, and 7 days thereafter. Dose-dependent positive staining was observed in almost all organs of both sexes, including the colon, prostate, and mammary gland but largely independent of the tumor response. Repair activity, judged by disappearance of adducts with time, differed according to the organ or cell type. One exception was hepatocytes, the liver incidentally being a nontarget organ. The results suggest that the generated antibody is applicable for detection of cells targeted by PhIP in paraffin-embedded sections and also for the investigation of the mechanisms of PhIP-carcinogenesis.

Administration, Oral↗
PubMed1998

Absence of p53 gene mutations in a tumor panel representative of pilocytic astrocytoma diversity using a p53 functional assay.

Although p53-gene mutations occur with significant frequency in diffuse low-grade and high-grade astrocytomas, and are postulated to play an important role in tumorigenesis in these cases, the role of the p53 gene in pilocytic astrocytomas remains unclear. Published data using DNA-based assays for p53-gene analysis in these tumors have shown contradictory results in mutation frequency (0-14%). It is not known whether these heterogeneous results stem from the biological diversity of this tumor group or from technical problems. To re-evaluate p53-gene status in pilocytic tumors, we analyzed 18 tumors chosen to represent the clinical and biological heterogeneity of this tumor type with respect to anatomical location, patient age, gender, ethnic origin (Caucasian or Japanese) and the concomitant occurrence of neurofibromatosis type 1 (NF1). All primary tumors were histologically diagnosed as pilocytic astrocytoma (WHO grade I), except for one anaplastic pilocytic astrocytoma (WHO grade III) which developed in an NF1 patient and recurred as glioblastoma multiforme (WHO grade IV). p53 mutations were detected using an assay in yeast which tests the transcriptional activity of p53 proteins synthesized from tumor mRNA-derived p53-cDNA templates. None of 18 tumors, including 3 NF1-related tumors, showed p53-gene mutations between and including exons 4 and 11. We conclude that p53-gene mutations are extremely rare findings in pilocytic astrocytomas, and are absent even in those exceptional cases in which malignant progression of such tumors has occurred.

Adolescent↗
PubMed1998

Phospholamban domain Ib mutations influence functional interactions with the Ca2+-ATPase isoform of cardiac sarcoplasmic reticulum.

Alanine-scanning mutagenesis of amino acids 21-30, forming cytoplasmic domain Ib in phospholamban (PLN), revealed that mutation to Ala of Asn27, Gln29, and Asn30 results in gain of inhibitory function. In an earlier study (Kimura, Y., Kurzydlowski, K., Tada, M. , and MacLennan, D. H. (1997) J. Biol. Chem. 272, 15061-15064), gain of function in PLN transmembrane domain II mutants was correlated with pentamer destabilization, leading to proposals that the PLN monomer is the active inhibitory species, that dissociation of the PLN pentamer is one determinant of PLN inhibitory function and that dissociation of the PLN.cardiac sarco(endo)plasmic Ca2+-ATPase isoform (SERCA2a) complex is a second determinant. Because each of the new domain Ib mutants contained a normal ratio of pentamer to monomer in SDS-polyacrylamide gel electrophoresis, gain of function must have resulted from mechanisms other than destabilization of pentameric structure. Evidence that domain Ib and domain II mutants act through different sites and different mechanisms was provided by a monomeric double mutant, N30A/I40A, in which the enhanced inhibitory function of each single mutant was additive. Evidence for an alteration in stability of the PLN/SERCA2a heterodimer was obtained in a study of double mutant N27A/N34A in which inhibitory function was regained by combining a gain of function, domain Ib mutation with a loss of function domain II mutation. These results support the proposal that PLN inhibition of SERCA2a involves, first, depolymerization of PLN and, second, the formation of inhibitory interactions between monomeric PLN and SERCA2a.

Animals↗
PubMed1998

Direct association of the gap junction protein connexin-43 with ZO-1 in cardiac myocytes.

The gap junction protein connexin-43 is normally located at the intercalated discs of cardiac myocytes, and it plays a critical role in the synchronization of their contraction. The mechanism by which connexin-43 is localized within cardiac myocytes is unknown. However, localization of connexin-43 likely involves an interaction with the cytoskeleton; immunofluorescence microscopy showed that in cardiac myocytes, connexin-43 specifically colocalizes with the cytoskeletal proteins ZO-1 and alpha-spectrin. In transfected HEK293 cells, immunoprecipitation experiments using coexpressed epitope-tagged connexin-43 and ZO-1 indicated that ZO-1 links connexin-43 with alpha-spectrin. The domains responsible for the protein-protein interaction between connexin-43 and ZO-1 were identified using affinity binding assays with deleted ZO-1 and connexin-43 fusion proteins. Immunoblot analysis of associated proteins showed that the C-terminal domain of connexin-43 binds to the N-terminal domain of ZO-1. The role of this linkage in gap junction formation was examined by a dominant-negative assay using the N-terminal domain of ZO-1. Overexpression of the N-terminal domain of ZO-1 in connexin-43-expressing cells resulted in redistribution of connexin-43 from cell-cell interfaces to cytoplasmic structures; this intracellular redistribution of connexin-43 coincided with a loss of electrical coupling. We therefore conclude that the linkage between connexin-43 and alpha-spectrin, via ZO-1, may serve to localize connexin-43 at the intercalated discs, thereby generating functional gap junctions in cardiac myocytes.

Amino Acid Sequence↗
PubMed1998

Selective sensitivity to radiation of cerebral glioblastomas harboring p53 mutations.

Recent studies suggest that a balance may exist between the cell cycle arrest and apoptosis-inducing functions of the p53 tumor suppressor gene. Adenoviral p21 transduction attenuates apoptosis, whereas deletion of the p21 gene promotes it, and p21-null xenografts respond better than isogenic p21-wild type tumors to irradiation. Hence, the role of p53 in dictating the clinical response to radiotherapy and chemotherapy may be more complex than previously thought. We have analyzed survival and radiation response (regrowth-free period) of 42 patients with glioblastomas whose p53 status was determined by a sensitive yeast functional assay. Multivariate analysis revealed that p53 mutation is associated with longer survival (P < 0.02). Among 36 radiation-treated patients, the regrowth-free period after treatment was significantly longer for tumors with p53 mutations (P < 0.0001), and p53 mutation was the sole independent factor predictive of radiotherapeutic response (P < 0.01). Survival time after regrowth was independent of p53 status, suggesting that the difference in survival was related to the treatment rather than to the intrinsic aggressiveness of the tumor. Thus, in this Northern Japanese population, p53 mutation is a marker for better radiation response in glioblastomas, and this results in significantly longer survival.

Adolescent↗
PubMed1998

Phospholamban domain I/cytochrome b5 transmembrane sequence chimeras do not inhibit SERCA2a.

A series of chimeras between the transmembrane domains of phospholamban (PLN) and cytochrome b5 were coexpressed with the Ca2+-ATPase of cardiac sarcoplasmic reticulum (SERCA2a). The chimeric molecules were not inhibitory, in line with our view that inhibitory PLN/SERCA2a interactions occur in transmembrane sequences, while cytoplasmic interactions regulate the inhibitory interactions in a four-base circuit.

Animals↗
PubMed1998

Identification of a human homolog of the Drosophila neuralized gene within the 10q25.1 malignant astrocytoma deletion region.

The loss of chromosome 10 is the most frequent genetic alteration found in malignant astrocytomas. In particular, the long arm of chromosome 10 was previously reported to have two or more common deletion regions where tumor suppressor genes may be located. In this study, we performed deletion mapping of 44 malignant astrocytomas using 12 microsatellite markers on chromosome 10q and demonstrated that the minimal common region of loss of heterozygosity (LOH) was present between D10S192 and D10S566 localized at 10q25.1. Subsequently, we have identified a novel gene, termed h-neu, within the region frequently deleted and found that h-neu encodes a protein with strong homology to the Drosophila neuralized (D-neu) protein. Northern blot and RT-PCR analyses revealed that h-neu mRNA was expressed at very low levels in human malignant astrocytoma tissues and the majority of glioma cell lines examined, while normal brains expressed h-neu transcript. Furthermore, DNA sequencing analysis of the h-neu transcript revealed one of the glioma cell lines, U251MG, had a single nucleotide substitution which resulted in an amino acid change from glycine (GGC) to serine (AGC) at codon 253. The D-neu gene is known to serve a critical function in neurogenesis in Drosophila, and loss-of-function mutations produce hyperplasia of primitive neuronal cells. These observations led us to hypothesize that h-neu gene plays a role in determination of cell fate in the human central nervous system and may act as a tumor suppressor whose inactivation could be associated with malignant progression of astrocytic tumors.

Amino Acid Sequence↗
PubMed1998

Short alternative splice transcripts of the mdm2 oncogene correlate to malignancy in human astrocytic neoplasms.

The mdm2 oncogene encodes a 90-kDa nuclear phosphoprotein that binds and inhibits the function of the p53 tumor suppressor protein. It was recently reported that the expression of alternatively spliced variants of mdm2 correlated with malignancy in ovarian tumors and bladder carcinomas. We analyzed the presence of alternatively spliced mdm2 variants and studied their correlation to p53 status in a total of 66 human astrocytic tumors, including 32 glioblastomas multiforme, 17 anaplastic astrocytomas, 12 astrocytomas, and 5 pilocytic astrocytomas, using a specific nested reverse transcription-PCR technique. The full-length mdm2 transcript was demonstrated in all of the cases. Multiple-sized PCR products were found in 29 cases. Two of 5 pilocytic astrocytomas (40%), none of 12 astrocytomas, and 5 of 17 anaplastic astrocytomas (29%) showed alternative splice variants. In contrast, 22 of 32 glioblastomas (69%) showed the presence of splice variants, demonstrating a significantly higher frequency than in lower-grade astrocytomas (P < 0.0003). A majority of the splice variants were 707 base-type (mdm2-b), which was confirmed by sequence analysis. There was no apparent correlation of the presence of mdm2 splice variants with p53 gene status. These results suggest a new role for mdm2, independent of p53 gene status, as an oncogene in the development of malignant astrocytic tumors.

Alternative Splicing↗
PubMed1998

Intercellular calcium signaling via gap junction in connexin-43-transfected cells.

In excitable cells, intracellular Ca2+ is released via the ryanodine receptor from the intracellular Ca2+ storing structure, the sarcoplasmic reticulum. To determine whether this released Ca2+ propagates through gap junctions to neighboring cells and thereby constitutes a long range signaling network, we developed a cell system in which cells expressing both connexin-43 and ryanodine receptor are surrounded by cells expressing only connexin-43. When the ryanodine receptor in cells was activated by caffeine, propagation of Ca2+ from these caffeine-responsive cells to neighboring cells was observed with a Ca2+ imaging system using fura-2/AM. Inhibitors of gap junctional communication rapidly and reversibly abolished this propagation of Ca2+. Together with the electrophysiological analysis of transfected cells, the observed intercellular Ca2+ wave was revealed to be due to the reconstituted gap junction of transfected cells. We next evaluated the functional roles of cysteine residues in the extracellular loops of connexin-43 in gap junctional communication. Mutations of Cys54, Cys187, Cys192, and Cys198 to Ser showed the failure of Ca2+ propagation to neighboring cells in accordance with the electrical uncoupling between transfected cells, whereas mutations of Cys61 and Cys68 to Ser showed the same pattern as the wild type. [14C]Iodoacetamide labeling of free thiols of cysteine residues in mutant connexin-43s showed that two pairs of intramolecular disulfide bonds are formed between Cys54 and Cys192 and between Cys187 and Cys198. These results suggest that intercellular Ca2+ signaling takes place in cultured cells expressing connexin-43, leading to their own synchronization and that the extracellular disulfide bonds of connexin-43 are crucial for this process.

Calcium↗