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Biomedical subjects

N Miyasaka

Publications and source records attributed to N Miyasaka.

At least 37 records · Page 2Linked to original sources
PubMed2001

Abundant expression of common cytokine receptor gamma chain (CD132) in rheumatoid joints.

OBJECTIVE: Activated macrophages upregulate surface expression of common cytokine receptor gamma chains (gammac, CD132), triggering of which induces secretion of proinflammatory cytokines. Rheumatoid synovial tissues contain a number of macrophages that play a pathogenic role by secreting proinflammatory cytokines. We studied the expression of gammac in the rheumatoid synovial tissues. METHODS: Cryosections of synovial tissues from patients with active rheumatoid arthritis (RA) or with osteoarthritis (OA) were stained with an anti-gammac Mab. Single-cell suspensions from the rheumatoid synovial tissues were stained with the same antibody and an anti-CD14 monoclonal antibody (Mab) for 2-color flow cytometric analysis. A soluble form of gammac in synovial fluids collected from rheumatoid or OA joints was quantitated by ELISA. RESULTS: Rheumatoid synovial tissues, but not the OA tissues, expressed gammac at a high level. Flow cytometric analysis showed that gammac were expressed by virtually all CD 14 positive synovial cells in RA. Synovial fluid derived from the rheumatoid joints contained a high concentration of soluble gammac. CONCLUSION: Membrane bound and soluble forms of gammac are abundant in rheumatoid joints. They might play a complex role in the pathology of RA.

Arthritis, Rheumatoid↗
PubMed2001

Astrocytic swelling in the ipsilateral substantia nigra after occlusion of the middle cerebral artery in rats.

BACKGROUND AND PURPOSE: Focal cerebral ischemia results in neuronal changes in remote areas that have fiber connections with the ischemic area. We reported previously that a high-signal-intensity lesion was observed in the substantia nigra after striatal infarction on T2-weighted MR images in both clinical and experimental cases. However, the origin of these changes in signal intensity remains unclear. The aim of this study was to investigate the nigral changes by examining the correlation between the apparent diffusion coefficient (ADC) and the tissue structure. METHODS: Sprague-Dawley rats were subjected to middle cerebral artery occlusion. Four days after the occlusion, when T2-weighted images revealed the presence of an area of high signal intensity in the ipsilateral substantia nigra, diffusion-weighted imaging was performed using a 4.7-T superconductive MR unit, and the ADCs were calculated and imaged. Histopathologic examination by both light and electron microscopy was performed on day 4 after surgery. RESULTS: Diffusion-weighted images showed an area of high signal intensity in the ipsilateral substantia nigra, and the ADC map revealed uniform reduction of the ADC in this area. Swelling of astrocytic end-feet was observed, especially in the pars reticulata. CONCLUSION: These findings suggest that MR changes in the ipsilateral substantia nigra after striatal injury consist mainly of swelling in the astrocytic end-feet.

Animals↗
PubMed2001

[A case of dermatomyositis complicated with pneumomediastinum that was successfully treated with cyclosporin A].

We reported the case of a 39-year-old man with dermatomyositis (DM) complicated with subcutaneous emphysema and pneumomediastinum during steroid therapy. The patient had complained of muscle weakness, dyspnea and skin eruption on his anterior chest wall 6 months prior to admission. He was diagnosed as having DM on the basis of an elevation in myogenic enzymes, myogenic changes in electromyography, a skin biopsy and a muscle biopsy. Chest roentgenogram revealed interstitial pneumonia (IP) in the lower lobes of the lungs. The administration of prednisolone (60 mg/day) was initiated, which resulted in improvement of DM. Fifteen days after the initiation of the steroid therapy, the patient developed subcutaneous emphysema and pneumomediastinum. Additional administration of cyclosporin A (CsA) enabled us to rapidly taper the dose of prednisolone without aggravating the diseases. Several reports have shown that vasculitis might be involved in the pathogenesis of pneumomediastinum in DM patients. Infection and tissue fragility due to steroid therapy worsen the outcome of those patients. CsA therapy may improve the outcome through the anti-vasculitic- and steroid sparing-effects.

Adult↗
PubMed2000

Rap1 is activated by erythropoietin or interleukin-3 and is involved in regulation of beta1 integrin-mediated hematopoietic cell adhesion.

The CrkL adaptor protein is involved in signaling from the receptor for erythropoietin (Epo) as well as interleukin (IL)-3 and activates beta(1) integrin-mediated hematopoietic cell adhesion through its interaction with C3G, a guanine nucleotide exchange factor for Rap1. We demonstrate here that Epo as well as IL-3 activates Rap1 in an IL-3-dependent hematopoietic cell line, 32D, expressing the Epo receptor. The cytokine-induced activation of Rap1 was augmented in cells that inducibly overexpress CrkL or C3G. The CrkL-mediated enhancement of cell adhesion was inhibited by expression of a dominant negative mutant of Rap1, Rap1A-17N, whereas an activated mutant of Rap1, Rap1A-63E, activated beta(1) integrin-dependent adhesion of hematopoietic cells. In 32D cells, Rap1 was also activated by phorbol 12-myristate 13-acetate and ionomycin, which also enhanced cell adhesion to fibronectin, whereas, an inhibitor of phospholipase C, inhibited both cytokine-induced activation of Rap1 and cell adhesion. It was also demonstrated that Rap1 as well as CrkL is involved in signaling from the EpoR endogenously expressed in a human leukemic cell line, UT-7. These results suggest that Epo and IL-3 activate Rap1 at least partly through the CrkL-C3G complex as well as through additional pathways most likely involving phospholipase Cgamma and strongly implicate Rap1 in regulation of beta(1) integrin-mediated hematopoietic cell adhesion.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Adenoviral transfer of cyclin-dependent kinase inhibitor genes suppresses collagen-induced arthritis in mice.

In rheumatoid synovial tissues, synovial fibroblasts are activated by proinflammatory cytokines and proliferate to develop hyperplastic pannus tissues, which irreversibly damage the affected joints. We recently reported that the cyclin-dependent kinase inhibitors p16(INK4a) and p21(Cip1) are not expressed in vivo in rheumatoid synovial fibroblasts, but are readily inducible in vitro. This observation was followed by the successful treatment of rat adjuvant arthritis by local p16(INK4a) gene transfer, showing that the inhibition of the cell cycle of the synovial cells ameliorates the arthritis. In this study, we show that another animal model of rheumatoid arthritis, murine collagen-induced arthritis, can be effectively treated by local gene transfer of p21(Cip1) as well as that of p16(INK4a). The anti-arthritic effects were observed even when the treatment was conducted after the arthritis had developed. Furthermore, the effects included suppression of the expression of proinflammatory cytokines such as IL-1ss, IL-6, and TNF-alpha. Our results demonstrate that the ectopic expression of cyclin-dependent kinase inhibitors not only prevents synovial overgrowth but also ameliorates the proinflammatory milieu in the affected joints. The induction of p21(Cip1) in rheumatoid synovial tissues by pharmacological agents may also be an effective strategy to treat rheumatoid arthritis.

Adenoviridae↗
PubMed2000

Identification of negative regulatory regions within the first exon and intron of the BCL6 gene.

Chromosomal translocations involving BCL6 gene are frequent in human B-cell lymphomas. Chromosomal breaks preferentially occur within a 3-kb region containing the first exon and intron. Recent reports have revealed that internal deletions or point mutations also are common in this region, suggesting that structural alteration of this region may be a crucial event in the development of lymphomas. In this study, we identified two regions in the BCL6 gene that negatively regulate BCL6 expression. One region, ES, is located within the first exon between nucleotides +472 and +543, and a second region, IS, is located between +783 and + 918 of the first intron. A consensus nucleotide sequence for the binding of the BCL6 protein itself was found within the ES region. An electrophoretic mobility shift assay and a co-transfection experiment using a BCL6 expression vector showed that transcription of the BCL6 gene was negatively regulated by the BCL6 gene product. The IS region which is included in the regions commonly deleted in B-cell lymphomas had a silencer activity. Structural alterations of these two regions may play roles in the deregulated expression of the BCL6 gene in B-cell lymphomas.

Cell Transformation, Neoplastic↗
PubMed2000

Latexin, a carboxypeptidase A inhibitor, is expressed in rat peritoneal mast cells and is associated with granular structures distinct from secretory granules and lysosomes.

Latexin, a protein possessing inhibitory activity against rat carboxypeptidase A1 (CPA1) and CPA2, is expressed in a neuronal subset in the cerebral cortex and cells in other neural and non-neural tissues of rat. Although latexin also inhibits mast-cell CPA (MCCPA), the expression of latexin in rat mast cells has not previously been confirmed. In the present study we examined the expression and subcellular localization of latexin in rat peritoneal mast cells. Western blot and reverse-transcriptase-mediated PCR analyses showed that latexin was contained and expressed in the rat peritoneal mast cells. Immunocytochemically, latexin immunofluorescence was localized on granular structures distinct from MCCPA-, histamine- or cathepsin D-immunopositive granules. Immunoelectron microscopy revealed that latexin was associated with a minority population of granules. The latexin-associated granules were separated from MCCPA- or histamine-containing granules on a self-generating density gradient of polyvinylpyrrolidone-coated silica-gel particles (Percoll). Treatments with high ionic strength and heparinase released latexin from the granules, suggesting that latexin is non-covalently associated with a heparin-like component of the granules. MCCPA and histamine were released from the mast cells after non-immunological and immunological stimulation with compound 48/80, A23187 and anti-IgE antibody, whereas latexin was not released. These results show that latexin is synthesized in rat peritoneal mast cells and suggest that it is associated with a unique type of intracellular granules distinct from MCCPA- and histamine-containing secretory granules and lysosomes.

Animals↗
PubMed2000

Stage-specific expression of mucosal addressin cell adhesion molecule-1 during embryogenesis in rats.

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is essential for lymphocyte trafficking to gut-associated lymphoid tissues and is implicated in inflammatory disorders in the gut and pancreatic islets. In this study, we examined the functional role of MAdCAM-1 during rat ontogeny using newly generated specific mAb. As previously observed in mice and humans, MAdCAM-1 was preferentially expressed in high endothelial venules (HEV) in gut-associated lymphoid tissues and venules of lamina propria in adult rats. Lymphocyte rolling and adhesion on HEV in Peyer's patches (PP) were completely abrogated with neutralizing anti-MAdCAM-1 mAb, in agreement with the notion that MAdCAM-1 is the principal HEV ligand for lymphocyte rolling and adhesion in adult PP. In the developing gastrointestinal tract, MAdCAM-1 was widely expressed in the venules of the lamina propria of fetal rats. In addition, MAdCAM-1 was also expressed in follicular dendritic cells in the neonatal PP. Interestingly, MAdCAM-1 expression was found also in nonmucosal tissues during ontogeny. MAdCAM-1 was transiently expressed in blood vascular endothelial cells in the fetal skin and neonatal thymus. Notably, MAdCAM-1-positive blood vessels were localized mainly in the cortico-medullary junction in the neonatal thymus and about 10-20% of thymocytes, most of which were either CD4, CD8 double positive or single positive specifically reacted with soluble MAdCAM-1 via integrin alpha4beta7. After birth, MAdCAM-1 expression in thymus blood vessels disappeared and concomitantly, the soluble MAdCAM-1-reactive thymocytes were rapidly down-regulated. Our results suggest that MAdCAM-1 functions as a vascular addressin in not only mucosal, but also nonmucosal lymphoid tissues during ontogeny.

Aging↗
PubMed2000

Deficiency of a STE20/PAK family kinase LOK leads to the acceleration of LFA-1 clustering and cell adhesion of activated lymphocytes.

Lymphocyte-oriented kinase (LOK) is a member of the STE20/p21-activated kinase (PAK) family and expressed predominantly in lymphoid organs. Generation of LOK-deficient mice revealed that the leukocyte-function-associated antigen (LFA-1)/intercellular adhesion molecules (ICAM)-mediated aggregation of mitogen-stimulated T cells was greatly enhanced in the absence of LOK. Though levels of total LFA-1 and ICAMs as well as the active form of LFA-1 on T cell blasts were comparable in the presence and absence of LOK, clustering of active LFA-1 detected by binding of soluble ICAM-1 was accelerated in the absence of LOK. These results suggest that LOK is potentially involved in the regulation of LFA-1-mediated lymphocyte adhesion.

Animals↗
PubMed2000

Mannose trimming targets mutant alpha(2)-plasmin inhibitor for degradation by the proteasome.

We have previously characterized the molecular and cellular mechanisms of alpha(2)-plasmin inhibitor (alpha(2)PI) deficiency. The mutant alpha(2)PI-Nara and alpha(2)PI-Okinawa proteins were found to be retained and degraded in cells stably expressing these mutant forms of alpha(2)PI. Degradation of the two mutant alpha(2)PI proteins, mediated by proteasomes, occurred after a lag time of 1.5 h during which glucose trimming took place. The mutant alpha(2)PI proteins were not ubiquitinated. Inhibition of mannosidase activity blocked the degradation of the mutant alpha(2)PI proteins without resulting in any changes in their binding to calnexin. Inhibition of glucose removal completely blocked the interaction between the alpha(2)PI proteins and the molecular chaperone calnexin. Under these conditions, mannose residues were removed from the oligosaccharides even when glucose residues were not processed. With mannose removal, the glucose-untrimmed mutant forms of alpha(2)PI, which failed to bind to calnexin, were degraded by proteasomes. The initiation of mannose trimming was a prerequisite for their degradation. Our findings show that modification of oligosaccharides of the mutant forms of alpha(2)PI determines their recognition by the degradation apparatus and that mannose trimming is important for targeting the mutant alpha(2)PI proteins for the degradation pathway.

1-Deoxynojirimycin↗
PubMed2000

Time course of trace of diffusion tensor [Trace(D)] and histology in brain edema.

We examined the correlation between changes in the trace of diffusion tensor [Trace(D)], regional water content and tissue ultrastructure relating to cellular (cytotoxic) and vasogenic brain edema. Cellular edema was induced by left middle cerebral artery occlusion in cats (Kuroiwa T et al., 1998). Vasogenic edema was induced in the white matter of cats by a cold lesion (Kuroiwa T et al., 1999). In cellular edema, the water content increase correlated linearly with the Trace(D) decrease in both the gray and white matter. However, both the slopes and intercepts of the correlation lines were significantly different. Hydropic astrocytic swelling was seen in both structures, and in the white matter, oligodendrocytic and myelinated axonal swelling were observed. In vasogenic edema, the increase in Trace(D) showed a significant linear correlation with the increase in tissue water content. Histologically, nerve fibers were dissociated and the extracellular space was markedly enlarged with protein-rich fluid. These result showed that the different slopes and intercepts of the water content--Trace(D) correlation lines for different subtype of brain edema, which reflect different ultrastructural localization of water, should be taken into account when evaluating brain edema using Trace(D) mapping.

Animals↗
PubMed2000

Marked anterograde decremental conduction over a rapidly conducting accessory pathway after radiofrequency ablation.

We report on a patient with the Wolff-Parkinson-White syndrome who temporarily exhibited a marked anterograde decremental conduction over a rapidly conducting accessory atrioventricular pathway after successful radiofrequency ablation. By recording the intracardiac electrogram via the ablation catheter placed at the successful ablation site, we were able to exclude the possibility of the occurrence of anterograde decremental conduction in the atrial or ventricular myocardium between the accessory pathway and the recording electrodes.

Catheter Ablation↗
PubMed2000

Cerebral ischemic hypoxia: discrepancy between apparent diffusion coefficients and histologic changes in rats.

PURPOSE: To compare the apparent diffusion coefficients (ADCs) and histologic changes in young rats subjected to cerebral ischemic hypoxia (IH). MATERIALS AND METHODS: Fifteen 3-week-old rats were subjected to a 30-minute IH insult (unilateral common carotid arterial ligation and exposure to 8% oxygen) and were examined at diffusion-weighted magnetic resonance imaging and light and electron microscopy on cessation of the insult (n = 5), 60 minutes after resuscitation (n = 5), or 48 hours after resuscitation (n = 5). Twelve control rats either underwent unilateral common carotid arterial ligation or were subjected to hypoxia. RESULTS: The experimental rats showed primary ADC reduction during the insult, transient ADC recovery after resuscitation, and secondary ADC reduction 48 hours after the insult. Histologic examination revealed dendritic swelling and mild swelling of the perivascular astrocytic end-feet during the primary ADC reduction phase, dark neurons and pronounced swelling of the perivascular astrocytic end-feet during the transient ADC recovery phase, and severely retracted dark neurons and extensive swelling of the astrocytic end-feet during the secondary ADC reduction phase. CONCLUSION: Transient ADC normalization after cerebral IH does not necessarily mean that histologic normalization has occurred. The transient ADC recovery phase appeared to have limited potential for neuronal salvage.

Animals↗
PubMed2000

Induction of anti-DNA antibodies by immunization with anti-DNA antibodies: mechanism and characterization.

Two well-characterized IgG monoclonal antibodies, reactive with double-stranded (ds) DNA and nucleosomes, were administered to normal BALB/c mice to examine the reproducibility and the biology of a previously reported model of anti-DNA antibody induction by immunization with anti-DNA antibodies. The monoclonal antibodies were purified either with or without a high-salt wash to remove nucleosomal antigens bound to them during the cell culture. Both monoclonal antibodies, but not normal IgG, induced significant IgG anti-dsDNA antibody production from 1 week to 25 weeks after the last immunization. The antibodies produced in this manner possess different binding preferences to ds synthetic polynucleotides than the antibodies used for the immunization, and they did not react with nucleosomes. The monoclonal antibodies purified with the high-salt wash were more effective in anti-DNA antibody induction than those purified without the high-salt wash. Even when bound to these monoclonal antibodies, neither dsDNA, nucleosomes, or ds synthetic polynucleotides exert significant antigenicity. For example, anti-DNA antibodies produced by mice immunized with an immune complex formed by poly(dA-dT) and one of the monoclonal antibodies that has a high affinity to this polynucleotide did not show an increased affinity to poly(dA-dT). Together, these results suggest that anti-DNA antibody molecules or processed antibody peptides, and not DNA/nucleosomes carried by anti-DNA antibodies, play a role in this model of anti-DNA antibody production.

Animals↗
PubMed2000

Identification of basic fibroblast growth factor-responsive genes by mRNA-differential display in an immortalized neural stem cell line.

Basic fibroblast growth factor (bFGF) has been shown to stimulate proliferation and differentiation of neural stem cells through regulation of gene expressions. To clarify the roles of bFGF during early neurogenesis, we performed a series of differential display with mRNAs from an immortalized neural stem cell line treated with bFGF for different periods. We isolated ten independent cDNAs whose mRNA levels were regulated by bFGF. Some of these cDNA were identical to known genes, including calmodulin and thrombospondin 1, while others were unknown genes. One of these unknown genes up-regulated by bFGF (clone 2C) was specifically expressed in the brain among various rat tissues. It is expected that further analysis of clone 2C will reveal important roles of bFGF in the regulation of brain development.

Animals↗
PubMed2000

Histopathologic correlates of temporal diffusion changes in a rat model of cerebral hypoxia/ischemia.

BACKGROUND AND PURPOSE: Although diffusion-weighted MR imaging is a powerful tool for evaluating brain ischemia, histopathologic correlates of temporal diffusion changes in cerebral hypoxia/ischemia have not been extensively examined. Diffusion-weighted MR imaging was used to evaluate the relationship between the time course of apparent diffusion coefficient (ADC) changes and the histopathologic findings in cerebral hypoxia/ischemia. METHODS: Thirty 3-week-old rats were subjected to either a 15-, 30-, or 60-minute hypoxic/ischemic insult (unilateral common carotid artery ligation and exposure to 8% oxygen), during and after which diffusion- and T2-weighted MR imaging was performed. Each animal was killed 48 hours or 6 hours after the insult, and fixed sections of the parietal cortex were examined by light microscopy. Ten other (control) rats were subjected to only unilateral common carotid artery ligation or hypoxia. RESULTS: The experimental rats showed three patterns of ADC change, depending on the duration of the hypoxic/ischemic insult: transient (15-minute), biphasic (15-, 30-, or 60-minute), and persistent (60-minute) ADC reduction patterns. The transient ADC reduction pattern (reduction during the insult and recovery after resuscitation) was associated with selective neuronal death. The biphasic and persistent ADC reduction patterns (transient recovery and no recovery after resuscitation, respectively) were associated with cerebral infarction. CONCLUSION: Different temporal patterns of ADC change are associated with different histopathologic findings. Although the clinical manifestations of these different histopathologic presentations are not yet defined, this study indicates that sequential diffusion studies are a potentially powerful tool in the evaluation of hypoxic/ischemic brain injury.

Animals↗