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Biomedical subjects

Y Munakata

Publications and source records attributed to Y Munakata.

At least 37 records · Page 2Linked to original sources
PubMed1998

Human parvovirus B19 as a causative agent for rheumatoid arthritis.

Human parvovirus B19 (B19) DNA was detected in the synovial tissues in 30 of 39 patients with rheumatoid arthritis (RA), and infrequently in those with osteoarthritis and traumatic joints. On the other hand, the expression of the B19 antigen VP-1 was specific (27/27) in RA synovium with active synovial lesions, but not in osteoarthritis and controls. The target cells of B19 were macrophages, follicular dendritic cells, T cells, and B cells, but not synovial lining cells in the synovium. B19-negative bone marrow cells, tonsil cells, and macrophage cell line U-937 cells became positive for the expression of VP-1, and more productive for interleukin 6 and tumor necrosis factor alpha when cocultured with RA synovial cells. The expression of VP-1 and the production of interleukin 6 and tumor necrosis factor alpha was significantly inhibited by the addition of neutralizing antibody for B19, suggesting that B19 detected in RA synovial cells is infective. B19 is involved in the initiation and perpetuation of RA synovitis, leading to joint lesions.

Antigens, Viral↗
PubMed1998

Somatic mutation in autoantibody-associated VH genes of circulating IgM+IgD+ B cells.

Naive B cells expressing IgM and IgD on their surface have no or little somatic mutations in V genes. We have demonstrated that the human IgM+IgD+B cell clone (0-81), which expresses nephritogenic idiotypes, produces IgM anti-DNA antibodies which show monospecificity to DNA. Using a DNA probe which specifically links to the VH gene of antibody 0-81, we identified the counterpart germ-line V gene of 0-81, V3-7, which appears to be used by pathogenic autoantibodies in humans. Clone 0-81, which may belong to naive B cells in terms of cell phenotype, uses a somatically mutated V3-7 gene. We further studied DNA sequences of V3-7 genes in circulating IgM+IgD+B cells from normal subjects and patients with systemic lupus erythematosus (SLE). The results revealed that rearranged V3-7 genes in IgM+IgD+B cells from patients with SLE contained somatically mutated sequences at significantly increased frequencies. These data indicate an abnormal maturation of B cells in autoimmune states that may be associated with an escape of self-reactive B cells from the elimination process in the germinal center.

Amino Acid Sequence↗
PubMed1998

GABAC receptors mediate slow membrane potentials in neurons of the rat major pelvic ganglia.

Effects of gamma-aminobutyric acid (GABA) on the neuronal membrane of the rat major pelvic ganglia (MPG) were studied using intracellular recording techniques, in vitro. Application of GABA (100 microM) to MPG neurons induced a depolarization (GABAd) associated with a decreased membrane input resistance and a slow hyperpolarization (s-GABAh) associated with an increased membrane input resistance. The GABA depolarization had two phases, a fast depolarization (f-GABAd) and a subsequent slow depolarization (s-GABAd). Bicuculline (60 microM) blocked the f-GABAd but not the s-GABAd and s-GABAh. Picrotoxin (100 microM) blocked all the GABA responses. Imidazole-4-acetic acid (I4AA, 100 microM), a GABAc receptor antagonist, depressed the s-GABAd and s-GABAh, but did not block the f-GABAd. Cis-4-aminocrotonic acid (CACA), a GABAc receptor agonist, produced a depolarization followed by a hyperpolarization in MPG neurons. I4AA (100 microM) depressed the CACA-induced responses. It was concluded that GABAA receptors mediate the f-GABAd and that GABAc receptors mediate the s-GABAd and s-GABAh, in neurons of the rat MPG.

Animals↗
PubMed1998

Laparoscopic mesh repair of a reducible obturator hernia using an extraperitoneal approach.

We present a case of an 84-year-old woman with nonstrangulated, reducible obturator hernia treated with laparoscopic total extraperitoneal prosthetic hernia repair. Preoperative diagnosis was made based on the clinical findings. The patient's postoperative recovery has been uneventful, without complications. When a nonstrangulated obturator hernia is diagnosed preoperatively, this procedure is likely to be successful.

Aged↗
PubMed1997

Determination of adenosine deaminase binding domain on CD26 and its immunoregulatory effect on T cell activation.

CD26, a 110-kDa cell surface glycoprotein, exhibits dipeptidyl peptidase IV enzyme activity and plays an important role in T cell costimulation. In the present study, we examined both the exact adenosine deaminase (ADA) binding domain on CD26 and the functional consequences of mutated CD26 transfectants that were deficient for cell surface ADA. Using CD26 deletion, human-rat swap, and point mutations, we found that the residues of L340, V341, A342, and R343 on the CD26 molecule were essential amino acids for ADA binding. When these amino acids were mutated and transfected into Jurkat cells, the resultant CD26 transfectants expressed only CD26, not ADA, on the cell surface. The amount of IL-2 produced by wild-type and mutated CD26 transfectants was almost the same following stimulation with anti-CD3 plus PMA. However, the mutated CD26 transfectants were much more sensitive to the inhibitory effect of adenosine on IL-2 production than were the wild CD26 transfectants. These data suggest that ADA on the cell surface does not directly involve T cell activation. Conversely, CD26 alone does not result in modulating the inhibitory effect of adenosine. Only the ADA bound to CD26 on the cell surface was functional and could counteract the inhibitory effect of elevated extracellular adenosine.

Adenosine Deaminase↗
PubMed1997

Multiple transcripts for rat nucleoside diphosphate kinase alpha isoform are structurally categorized into two groups that exhibit cell-specific expression and distinct translation potential.

Rat nucleoside diphosphate (NDP) kinase is composed of two isoforms (alpha and beta) encoded by independent genes. The mRNAs are expressed ubiquitously; however, the level of expression is tissue-dependent and is also up- or down-regulated under certain conditions, including growth stimulation, differentiation, and tumor metastasis. To address the regulatory mechanisms of gene expression for the rat NDP kinase major isoform alpha (an nm23-H2/PuF homologue), we identified the transcription initiation sites in detail by RNase protection and 5'-rapid amplification of DNA ends and located the core promoter region by chloramphenicol acetyltransferase assay. The transcripts, initiated from an extraordinarily wide range of sites, were categorized into two groups; one transcribed from an upstream region was spliced in the untranslated region (group 1), whereas the other initiated in the downstream region was not (group 2). RNase protection demonstrated that the group 1 mRNA was the dominant form present in all tissues except heart and skeletal muscle. In situ hybridization revealed cell-specific expression of these mRNA species. Furthermore, they differed in the translational efficiency (the group 2 alpha > beta > the group 1 alpha). These findings suggest that the regulation of the NDP kinase expression at both transcriptional and posttranscriptional steps could be fundamentally governed by the selection of transcription initiation sites.

Animals↗
PubMed1997

Preoperative diagnosis of strangulated obturator hernia using ultrasonography.

BACKGROUND: Obturator hernia is rarely recognized before surgical intervention, since it is relatively infrequent and its definitive diagnosis is difficult. To change this situation, we introduced ultrasound examination in 1993 for differential diagnosis of strangulated obturator hernia among patients with bowel obstruction of unknown cause. PATIENTS AND METHODS: Between 1993 and 1995, we encountered 15 patients with suspected obturator hernia based on the presence of bowel obstruction of unknown cause and so-called predisposing factors. These patients underwent ultrasound examinations. RESULTS: The 4 patients with bowel obstruction caused by strangulated obturator hernia were all correctly diagnosed preoperatively by ultrasonography and were successfully cured by surgery. The time required for diagnosis was shorter than reported previously (average 16.5 h). CONCLUSIONS: Ultrasonography is useful and reliable for the diagnosis of strangulated obturator hernia and can decrease the morbidity and mortality associated with delayed diagnosis.

Aged↗
PubMed1997

Different regulatory effects of pentoxifylline on human T cell activation pathways.

Pentoxifylline (PTX), a methylxanthine derivative, was examined for its effects on T cell proliferation and cytokine production stimulated by cross-linking anti-CD3 alone, anti-CD3 with PMA, anti-CD3 with anti-CD26, or anti-CD3 with anti-CD28 mAb, respectively. PTX at a 3.5 x 10(-5) M concentration significantly inhibited T cell proliferation and the production of tumor necrosis factor-alpha, interleukin-2, and interleukin-4. Moreover, this effect was selective for stimulation by cross-linking anti-CD3 with PMA, or anti-CD3 with anti-CD26, but not by cross-linking anti-CD3 with anti-CD28. These results suggest that the inhibitory effect of PTX on T cell activation involves the CD3 and CD26, but not the CD28 signal pathway.

Cell Survival↗
PubMed1997

Rethinking infant knowledge: toward an adaptive process account of successes and failures in object permanence tasks.

Infants seem sensitive to hidden objects in habituation tasks at 3.5 months but fail to retrieve hidden objects until 8 months. The authors first consider principle-based accounts of these successes and failures, in which early successes imply knowledge of principles and failures are attributed to ancillary deficits. One account is that infants younger than 8 months have the object permanence principle but lack means-ends abilities. To test this, 7-month-olds were trained on means-ends behaviors and were tested on retrieval of visible and occluded toys. Means-ends demands were the same, yet infants made more toy-guided retrievals in the visible case. The authors offer an adaptive process account in which knowledge is graded and embedded in specific behavioral processes. Simulation models that learn gradually to represent occluded objects show how this approach can account for success and failure in object permanence tasks without assuming principles and ancillary deficits.

Child Development↗
PubMed1997

[V gene repertoire and pathogenic autoantibodies].

The studies for autoantibody-associated V genes have failed to find any V gene which might be specific for pathogenic autoantibodies in humans; Namely, both normal subjects and patients have immunoglobulin V genes which can encode autoantibodies. Also single V gene can encode antibodies for both foreign antigens and autoantigens. However, some germline V genes such as V3-7 and VH4-21 are preferentially used for autoantibodies and may be regarded as prototype V genes for autoantibodies. Although somatic mutation in V genes is characteristic in IgG autoantibodies, 0-81 idiotype-positive IgM antibodies, which may be precursor B cells for pathogenic anti-DNA antibody also included many somatic mutations in VH genes, indicating an intrinsic abnormality in B cell development in SLE. Some studies also indicated an abnormal V gene repertoire in autoimmune states. These results may be attributed to dysregulation of autoantibody-associated B cell development.

Animals↗
PubMed1996

Laparoscopic closure for perforation of the sigmoid colon by endoscopic linear stapler.

Immediate open surgery has been recommended for the management of perforation during colonoscopic examination. Laparoscopic closure for perforation of the sigmoid colon caused by diagnostic colonoscopy is described. The perforation site was identified in the antimesenteric border of the sigmoid colon by laparoscopic survey, and four ports were inserted in the lower abdomen. The margin of the perforation was lifted by two graspers, and the defect was completely closed using an endoscopic linear stapler. The patient recovered quickly without any associated complications. Postoperative barium enema showed no stenosis or leakage. This method is less invasive and allows earlier recovery of patients with colonic perforation.

Aged↗
PubMed1996

[Laparoscopic colo-rectal surgery].

Laparoscopic colorectal surgery was less invasive for patients although it was difficult to perform complete resection of colon combined with regional lymph node. The skillful manner of the laparoscopic surgery was required for the surgical team. The laparoscopic equipments, in order to perform curative dissection of mesenterium and intermediate lymph node, such as Ultrasonic-aspiration surgical unit (USU) or Harmonic scalpel laparoscopic coagulation shears (LCS), were useful for safer dissection of D2 regional lymph node. Meticulous manner of grasping forceps and special dissectors was made sufficient lymph node dissection. The reconstruction of extracorporeal anastomotic technique by hand or valtrac (biofragmentable anastomosis ring) were safer manner for anastomosis after resection of the right side colon. Reconstruction by double stapling technique of linear stapler and circular stapler was admired for anastomosis for left side colonic and rectal surgery. We had safely performed locar resection in 3, partial resection with Do dissection in 2, with D1 dissection in 14, with D2 dissection in 21 and right and left hemicolectomy in 1 each.

Anastomosis, Surgical↗
PubMed1996

[Cell adhesion molecules on lymphocytes and their role on signal transduction].

It has been shown that cell adhesion molecules, which mediate lymphocyte adhesion have an ability to provide costimulation signals in the cells. One of the representative adhesion molecules on T lymphocytes, b1 integrin is comprised by several subunits sharing a common b1 subunits, CD29, which is defined by monoclonal anti-4B4 antibody. We have demonstrated that b1 integrins function as a cell surface receptor for extracellular matrix (ECM) protein, such as collagen and fibronectin. We also found that fibronectin, ligand of b1 integrin, synergized with anti-CD3 antibody to promote proliferation of CD4 T cell in a serum free culture system, and also induced an independent signal which would be distinct from the CD3/TcR-mediated signal pathway of activation through the induction of an AP-1 transcription factor. Recent studies revealed that there is an accumulation of CD4+CD29+ T cells, memory T cells as well as prominent increase of a variety of inflammatory cytokines in the synovial fluid of patients with rheumatoid arthritis (RA). This suggests that b1 integrins may play an important role for the inflammatory mechanism in RA. Regulation of signal transduction mediated by adhesion molecules on lymphocytes may be the possible effective way for controlling the pathological inflammatory process in RA.

Arthritis, Rheumatoid↗
PubMed1995

A case of pulmonary arteriovenous malformation in a patient with brain abscess successfully treated with video-assisted thoracoscopic resection.

A 45-year-old women was admitted to the hospital with a brain abscess due to asymptomatic pulmonary arteriovenous malformation (PAVM). The brain abscess was removed by craniotomy and excision following antibiotic therapy. The stapled wedge excision of the lung with the PAVM was successful under video-assisted thoracoscopic surgery.

Angiography, Digital Subtraction↗
PubMed1994

Effects of peritoneal insufflation on hepatic and renal blood flow.

The effects of peritoneal insufflation with carbon dioxide on hepatic and renal blood flow have not been reported hitherto. We evaluated these effects in a porcine model of abdominal laparoscopic surgery. Seven anesthetized pigs underwent peritoneal insufflation in a step-wise manner to create intraabdominal pressures of 6, 12, 18 and 24 mmHg, and changes in the arterial and venous pressure, arterial blood gases, and hepatic and renal blood flow were monitored. Both the hepatic and renal blood flow decreased as the intraabdominal pressure increased. Therefore, in order to carry out laparoscopic abdominal surgery safely in patients with hepatic or renal impairment, low intraabdominal pressures or noninsufflating techniques are recommended.

Animals↗
PubMed1993

A second form (beta isoform) of nucleoside diphosphate kinase from rat. Isolation and characterization of complementary and genomic DNA and expression.

Complementary and genomic clones for a second form (the beta isoform) of rat nucleoside diphosphate kinase were isolated. Structural studies revealed that nucleotide and deduced amino acid sequences of the beta isoform were quite similar to those of the alpha isoform (identities were 82 and 89%, respectively), which were delineated in our previous study (Kimura, N., Shimada, N., Nomura, K., and Watanabe, K. (1990) J. Biol. Chem. 265, 15744-15749). The gene encoding the beta isoform, covering 10 kilobases and comprising five exons, was located in tandem in the immediate vicinity (at a 3-kilobase distance) of the 5' upstream of the alpha isoform gene which was recently reported from this laboratory (Ishikawa, N., Shimada, N., Munakata, Y., Watanabe, K., and Kimura, N. (1992) J. Biol. Chem. 267, 14366-14372), suggesting their generation by gene duplication. The exon-intron junctions were exactly conserved between the two genes. Southern blot analyses showed that unidentified fragments cross-reacted with the beta isoform cDNA probe besides those containing the genuine gene, and at least two of them were identified as possible processed pseudogenes. Northern and dot blot hybridization studies demonstrated that the alpha isoform was more expressed than the beta isoform in rat tissues examined except brain, from which the isoform designation was derived. These results suggest independent expression and specific roles of these isoforms in the cell. Comparative studies between rat and human isoforms indicate that the isoforms could have differentiated before the two species evolutionally diverged.

Amino Acid Sequence↗