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K Ikuta

Publications and source records attributed to K Ikuta.

At least 127 records · Page 7Linked to original sources
PubMed1998

Essential role of IL-7 receptor alpha in the formation of Peyer's patch anlage.

We investigated the role of IL-7 receptor alpha (IL-7Ralpha) signal in the formation of Peyer's patch (PP) anlage. Although pan-lymphopenia is a common phenotype of rag2-/- and il7ralpha-/- mice, a close inspection revealed nodules corresponding to PP in the adult rag2-/- but not in the il7ralpha-/- mouse. In our previous study, three histologically distinct steps in the formation of PP were identified. The first is the appearance of VCAM-1 + spots in the intestine, which probably represents an initial stage of the formation of the PP anlage. Accumulation of cells bearing IL-7Ralpha, CD4 or Ia in this region then follows and eventually entry of mature lymphocytes expressing CD3 or B220 occurs just before birth. Based on this criterion, we next investigated which of these events is defective in mice with severe combined immunodeficiency. Formation of VCAM-1 + spots and cluster formation of IL-7Ralpha+ cells proceed normally in the rag2-/- mouse which completely lacks mature lymphocytes. In contrast, no VCAM-1+ spots were detected in the embryonic nor neonatal il7ralpha-/- mice, suggesting that IL-7Ralpha signal is involved in the early phase of PP anlage formation. The same defect was found in the jak3-/- mouse. In addition to the appearance of VCAM1+ spots, the clustering of IL-7Ralpha+ cells was absent in the jak3-/- mouse, though IL-7Ralpha+ cells are found to scatter over the intestine. These results indicate that IL-7Ralpha is an essential signal for an early step of PP anlage formation, without which the subsequent processes cannot be initiated.

Animals↗
PubMed1998

Enhancement of human immunodeficiency virus type 1 infectivity by Nef is producer cell-dependent.

The growth kinetics of wild-type and nef mutant viruses of human immunodeficiency virus type 1 were comparatively analysed in several human CD4+ cell lines. Delayed replication of nef mutant virus was observed in all cell lines examined. To determine the stage in the virus replication cycle that is affected by Nef, a single-round replication assay was performed. Initially, the expression of marker genes in transfected cells was examined in order to study the role of Nef in the late phase of infection. The results obtained indicated that Nef is dispensable during the transcription to virion production stage. Next, the effect of Nef on the early phase was investigated with a single-round infection. It was demonstrated that Nef is required in the early phase of the virus replication cycle, from virion adsorption to integration. Finally, the infectivity of virus stocks prepared from four cell lines was determined. The relative infectivity of the nef mutant from the four cell lines differed. Taken together, we conclude that Nef acts via modulation of viral particles to enhance virus infectivity in a cell-dependent manner.

Gene Products, nef↗
PubMed1998

Generation of endogenous tumour necrosis factor-alpha in MOLT-4 cells during the acute replication phase of human immunodeficiency virus type 1 determines the subsequent latent infection.

We have characterized the mechanism for human immunodeficiency virus type 1 (HIV-1) latent infection in a human T cell line MOLT-4 subclone no. 8 (MOLT-#8). The inocula used were HIV-1 recovered from MT-4 during the acute (NL-A) and persistent (NL-P) phases after HIV-1 infection. On infection of MOLT-#8 with NL-A, viral antigens first appeared in almost 100% of the cells whereafter the numbers of viable antigen-positive cells declined. In contrast, following infection with NL-P the expression of viral antigens was maintained in almost 100% of the cells. In fact, limiting dilution of NL-P-infected cells allowed us to isolate 43 subclones, all of which were positive for viral antigen expression in almost 100% of the cells (type I). In sharp contrast, only two of 41 subclones from NL-A-infected cells were of type I. Seven subclones were latently infected with HIV-1; latent HIV-1 in six subclones (type II), but not in one type III subclone, was activated by tumour necrosis factor (TNF)-alpha or phorbol 12-myristate 13-acetate. The remaining subclones were negative for the viral genome. Of particular note is the effect of endogenous TNF-alpha generated during the acute phase of virus replication which shifted the virus phenotype. Thus, the presence of TNF-alpha during the acute phase of virus replication seems to play a key role in the selective destruction of cells expressing higher levels of viral antigens and in subsequent establishment of latent infection in host T cells.

Antigens, Viral↗
PubMed1998

Dependence on host cell cycle for activation of human immunodeficiency virus type 1 gene expression from latency.

Human immunodeficiency virus type 1 (HIV-1) establishes latent infection of a certain population of CD4+ host cells which could be long-term reservoirs for HIV-1. The expression of viral genes in such long-term infected cells is strongly regulated by cellular status, such as the phase of the cell cycle or stage of cell differentiation. Here, viral gene expression in synchronized U1 cells, a monocytic cell clone latently infected with HIV-1, was characterized. The expression of HIV-1 antigens was detected exclusively at G2/M phase in U1 cells, irrespective of phorbol myristate acetate (PMA) treatment. The induction of HIV-1 gene expression in PMA-treated cells was due to the recruitment of NF-kappaB with DNA-binding activity at G2/M phase. Activated NF-kappaB was induced only by PMA treatment during the late G1 to S, but not after entering G2 phase, indicating that the transcriptional factor(s) involved in viral gene expression is also largely regulated by the host cell cycle. In contrast, the enhancement of antigen expression by treatment with tumour necrosis factor-alpha (TNF-alpha) was cell cycle-independent. In fact, NF-kappaB was activated 2 h after TNF-alpha treatment at all stages of the cell cycle. Thus, the mechanisms of HIV-1 activation from latency in U1 cells by PMA and TNF-alpha treatment are different. The model system using U1 cells shown here may provide insight into the mechanisms responsible for HIV-1 gene expression from latency.

Cell Cycle↗
PubMed1998

Immunohistochemical detection of 4-hydroxy-2-nonenal-modified-protein adducts in human alcoholic liver diseases.

4-Hydroxy-2-nonenal (HNE) is one of the major components of lipid peroxidation product and has been shown to react with proteins to form HNE-protein adducts. HNE-protein adducts are relatively stable and can be used as a marker of radical-mediated cellular damage. We report herein the immunohistochemical analysis of HNE-protein adducts in human alcoholic liver diseases using a specific monoclonal antibody HNEJ-2. Cytoplasm of hepatocytes and bile duct epithelia was positively stained for HNE-protein adducts, and the nucleus was negligibly stained. The immunohistochemical intensity of hepatocytes was classified into three groups: strong, moderate, and faint staining. Strong staining was found in 43% of alcoholic liver diseases and in 4% of viral liver diseases. Hepatocytes of alcoholic liver diseases contained a higher amount of HNE-protein adducts than those of viral liver diseases, and the difference was statistically significant (p = 0.005; chi2 test). Semiquantitative analysis of the histological intensities of HNE-protein adducts and iron indicated a significant positive correlation (p = 0.084; Spearman's rank correlation). The localization of HNE-protein adducts and iron in hepatocytes appeared to be identical. These data suggested the correlation between HNE-protein adducts and iron. Our results indicate that HNE-protein adducts, a marker of oxidative stress-induced damage, are increased in human alcoholic liver damage, and that hepatic siderosis may act on the production of free radicals.

Aldehydes↗
PubMed1998

Two proline-rich nuclear localization signals in the amino- and carboxyl-terminal regions of the Borna disease virus phosphoprotein.

Borna disease virus (BDV) uses a unique strategy of replication and transcription which takes place in the nucleus, unlike other known, nonsegmented, negative-stranded RNA viruses of animal origin. In this process, viral constituents necessary for replication must be transported to the nucleus from the cytoplasm. We report here the evidence that BDV P protein, which may play an important role in viral replication and transcription, is transported into the nucleus in the absence of other viral constituents. This transportation is accomplished by its own nuclear localization signals (NLSs), which are present in both N-terminal (29PRPRKIPR36) and C-terminal (181PPRIYPQLPSAPT193) regions of the protein. These two NLSs can function independently and both have several Pro residues as key amino acids.

Amino Acid Sequence↗
PubMed1998

Positive and negative syndromes, and Borna disease virus infection in schizophrenia.

The relationship between Borna disease virus (BDV) infection and positive and negative syndromes in schizophrenia was investigated. By nested RT-PCR and Western blotting, BDV-specific RNA and anti-BDV antibodies were examined in blood from 67 schizophrenic patients (DSM-III-R) in Japan, and the psychometric properties of the Positive and Negative Syndrome Scale (PANSS) were analyzed. There were significant (p < 0.05) differences in the composite index denoting the positive minus negative difference indicating a dominant contribution by negative items, and the proportion of negative type (positive minus negative value below zero) patients, between patients positive and negative for anti-BDV p24 antibodies. It is possible that BDV infection with induction of BDV p24 antibodies may be associated with negative syndromes in schizophrenic patients.

Adult↗
PubMed1998

Cavitary pulmonary metastases of gallbladder cancer.

We report a case of multiple cavitary pulmonary metastases of gallbladder cancer. Radiologically, every cavity displayed a very thin wall containing only air inside. The postmortem histopathological examination showed that: (1) the cavities were surrounded by normal alveoli; (2) these walls were composed mostly of adenocarcinoma cells; (3) necrotic or mucous substance was sparse in the cavity space; (4) cancer cells infiltrated along the surface of the alveolar septa, and (5) the morphology of the cancer cells of the gallbladder and the lung was the same. It seemed likely that the thin-walled cavities in the lung might result from central breakdown of the tumor and subsequent expectoration of debris through the connected airways.

Adenocarcinoma↗
PubMed1998

[Superoxide generation and human cytomegalovirus infection].

Reactive oxygen intermediates (ROI) such as superoxide (O2-), hydrogen peroxide (H2O2) and hydroxyl radicals (.OH) are involved in the pathogenicity of various diseases. There is also evidence that superoxide is involved in disease progression following infection by influenza virus, HIV-1 and human cytomegalovirus (HCMV). Healthy donor-derived peripheral blood monocytes/macrophages, which seem to be the major reservoir for HCMV in vivo, showed significantly higher generation of O2- after HCMV infection. The importance of O2- in cytomegalovirus pneumonitis was also supported in a mouse model system using mouse cytomegalovirus. In addition, the importance of HCMV-induced ROI was also shown in the restenosis and atherosclerosis of smooth muscle cells. This review highlights the relationship between HCMV infection and ROI.

Animals↗
PubMed1998

[Cord blood stem cell transplantation and cord blood bank].

Human cord blood provides a rich source of hematopoietic stem cells. On the basis of the finding, umbilical cord blood has been postulated to be an alternative and efficacious source of hematopoietic stem cells for allogeneic reconstitution. Early results of cord blood stem cell transplantation (CBSCT) show that the incidence and severity of graft versus host disease has been low in HLA mismatched transplants. Cord blood banking has several advantages such as lack of donor risk, indefinite storage, speed of donor search, viral safety. More than four hundred cases of unrelated CBSCT have been performed in the world. Kanagawa cord blood bank has been established on 1995 and other some private cord blood banks have been established in Japan. Eleven cases of unrelated CBSCT have been reported in Japan. Large scaled public cord blood bank should be established in near future.

Adolescent↗
PubMed1997

Role of cytosolic phospholipase A2 in allergic response and parturition.

Phospholipase A2 (PLA2) comprises a superfamily of enzymes that hydrolyse the ester bond of phospholipids at the sn-2 position. Among the members of this superfamily, cytosolic PLA2 has attracted attention because it preferentially hydrolyses arachidonoyl phospholipids and is activated by submicromolar concentrations of Ca2+ ions and by phosphorylation by mitogen-activated protein kinases (MAP kinases). Here we investigate the function of cytosolic PLA2 in vivo by using homologous recombination to generate mice deficient in this enzyme. These mice showed a marked decrease in their production of eicosanoids and platelet-activating factor in peritoneal macrophages. Their ovalbumin-induced anaphylactic responses were significantly reduced, as was their bronchial reactivity to methacholine. Female mutant mice failed to deliver offspring, but these could be rescued by administration of a progesterone-receptor antagonist to the mother at term. Considered together with previous findings, our results indicate that cytosolic PLA2 plays a non-redundant role in allergic responses and reproductive physiology.

Anaphylaxis↗
PubMed1997

Detection of Borna disease virus genome in normal human brain tissue.

Borna disease virus (BDV), a neurotropic virus naturally infecting horses and sheep, has been suggested to be associated with human psychiatric disorders. Thus far no extensive studies have been done, providing the evidence of BDV genome in normal human brain tissue. We therefore examined four brain regions of 30 normal autopsy brains for BDV p24 genome. By highly sensitive nested reverse transcriptase (RT)-mediated PCR analysis, we found positive PCR products in two brains: one in frontal and temporal cortices and hippocampus and another in frontal cortex and olfactory bulb. Our results suggest that BDV can infect human brain tissue latently, without causing an apparent neuropsychiatric disorder.

Adult↗
PubMed1997

A novel acyl-CoA thioesterase enhances its enzymatic activity by direct binding with HIV Nef.

In addition to playing a crucial role in the pathogenesis of AIDS, HIV nef induces down-regulation of CD4 expression and TCR signaling and also regulates the sorting pathway in host T cells. To elucidate the Nef function in HIV progression, we searched for a cellular component which interacts with Nef. A human cDNA encoding a novel acyl-CoA thioesterase (hACTE-III) was isolated as an HIV nef-binding protein by yeast two-hybrid system. hACTE-III is homologous to E. coli thioesterase II but to none of the mammalian thioesterases and therefore belongs to a new type. hACTE-III exhibits enzymatic specificity for a broad range of fatty acyl-CoAs. The hACTE-III-binding region within Nef is localized in the central region (amino acids 109-152). hACTE-III greatly enhances its enzymatic activity upon direct binding to Nef. Considering that either Nef-overexpression or impaired fatty acid regulation induces alteration of subcellular morphology, the augmented hACTE-III function by Nef-binding might induce dysfunction of T cells.

Amino Acid Sequence↗
PubMed1997

NMR assignment of the galactomannan of Candida lipolytica.

The chemical structure of the cell wall galactomannan of Candida lipolytica was analyzed using two-dimensional NMR techniques without chemical fragmentation. The H-1-H-2-correlated cross-peaks of the galactomannan indicated that it consists of an alpha-1,6-linked mannan backbone moiety with side chains. A sequential NMR assignment of the side chains through nuclear Overhauser effect (NOE) cross-peaks indicated that the triose side chain contains an alpha-1,2-linked galactopyranose unit at the non-reducing terminal. The structure was significantly different from the galactomannan of Trichophyton. The molar ratio of the side chains calculated from the H-1 signal dimensions indicated that ca. 45% of the backbone alpha-1,6-linked mannose units are not substituted with side chains and are responsible for the reactivity of the galactomannan with factor 9 serum.

Candida↗
PubMed1997

Increased B-lymphopoiesis by interleukin 7 induces bone loss in mice with intact ovarian function: similarity to estrogen deficiency.

Estrogen deficiency caused by ovariectomy (OVX) results in a marked bone loss due to stimulated bone resorption by osteoclasts. During our investigations of the pathogenesis of bone loss in estrogen deficiency, we found that OVX selectively stimulates B-lymphopoiesis which results in marked accumulation of B220-positive pre-B cells in mouse bone marrow. To examine the possible correlation between stimulated B-lymphopoiesis and bone loss, 8-week-old female mice were treated with interleukin (IL) 7, which stimulates B-lymphopoiesis in bone marrow. We also examined bone mass in IL-7 receptor-knockout mice that exhibit marked suppression of B-lymphopoiesis in the bone marrow. The increased B-lymphopoiesis induced by IL-7 administration resulted in marked bone loss by stimulation of osteoclastic bone resorption in mice with intact ovarian function. The changes in both B-lymphopoiesis and bone mass in IL-7-treated female mice were similar to those in age-matched OVX mice. In contrast, the trabecular bone volume of the femur was greatly increased in both female and male IL-7 receptor-knockout mice when compared with the respective wild-type and heterozygous littermates. These results show that the perturbation of B-lymphopoiesis in the bone marrow is closely linked to the change in bone mass. We propose here that the increased B-lymphopoiesis due to estrogen deficiency is involved in the mechanism of stimulated bone resorption.

Animals↗
PubMed1997

Murine interleukin 4 transgenic heart allograft survival prolonged with down-regulation of the Th1 cytokine mRNA in grafts.

BACKGROUND: Data supporting the differential activation of T helper (Th) 2 cells in transplantation acceptance/tolerance in rodents have been presented by several investigators. However, the differential activation of Th2 cells may be simply the result of allograft acceptance/tolerance induction instead of a contribution to the maintenance of grafts. METHODS: Therefore, we established interleukin (IL)-4 transgenic mice under the control of a cardiac alpha-myosin heavy chain promotor and transplanted IL-4-expressing heart allografts into unmodified recipients to determine the actual contribution of the Th2 bias to allograft acceptance. RESULTS: Among 16 newborn C57BL/6J (B6) mice, three were positive for the IL-4 transgene. Serum IL-4 levels of transgenic versus control B6xC3H F1 mice were not statistically different. Reverse-transcriptase polymerase chain reaction showed that the transgenic B6xC3H F1 mice expressed IL-4 mRNA in the heart and in the lung, whereas control mice did not express IL-4 in any organ. IL-4 mRNA expression in the transgenic but not in the control heart was also confirmed by RNAse protection assay and fluorescence in situ hybridization. The survival of IL-4 transgenic B6xC3H heart grafts heterotopically placed in C3H recipients was prolonged compared with that of nontransgenic grafts (19.0+/-9.1 vs. 6.8+/-2.2 days, P=0.003). Interferon-gamma mRNA expression in IL-4 transgenic heart grafts on the fifth posttransplant day as assessed by Northern blotting was suppressed compared with that in control grafts. Reverse-transcriptase polymerase chain reaction analysis showed that IL-2 mRNA was suppressed in the IL-4 transgenic grafts compared with that in control grafts, while IL-4 mRNA was observed only in IL-4 transgenic grafts. IL-10 mRNA was detected at similar levels in both transgenic and control grafts. CONCLUSIONS: A Th2 bias may contribute to allograft acceptance in part by inducing the down-regulation of Th1-cytokine mRNAs, but it may not be sufficient to induce indefinite graft survival.

Animals↗