Search PubMed⌕ Search

Biomedical subjects

T Yokoo

Publications and source records attributed to T Yokoo.

At least 19 recordsLinked to original sources
PubMed2005

Extraction of the average and differential dynamical response in stimulus-locked experimental data.

In optical imaging experiments of primary visual cortex, visual stimuli evoke a complicated dynamics. Typically, any stimulus with sufficient contrast evokes a response. Much of the response is the same regardless of which stimulus is presented. For instance, when oriented drifting gratings are presented to the visual system, over 90% of the response is the same from orientation to orientation. Small differences may be seen, however, between the responses to different orientations. A problem in the analysis of optical measurements of the response to stimulus in cortical tissue is the distinction of the 'global' or 'non-specific' response from the 'differential' or 'stimulus-specific' response. This problem arises whenever the signal of interest is the difference in response to various stimuli and is evident in many kinds of uni- and multivariate data. To this end, we present enhancements to a frequency-based method that we previously introduced called the periodic stacking method. These enhancements allow us to separately estimate the dynamics of both the average signal across all stimuli (the 'global' response) and deviations from the average amongst the various stimuli (the 'stimulus-specific' response) evoked in response to a set of stimuli. We also discuss improvements in the signal-to-noise ratio, relative to standard trial averaging methods, that result from the data-adaptive smoothing in our method.

Animals↗
PubMed2003

Stem cell gene therapy for chronic renal failure.

Recently, stem cell research has attracted considerable attention because it could be used for the regeneration of damaged organs that are untreatable by conventional techniques, and several stem cells (or progenitor cells), such as endothelial stem cells and neural stem cells have been discovered. Following the progression of this field of research, the potential for stem cell gene therapy has increased and several therapeutic benefits have already been reported. Although this approach was originally investigated for fatal or hereditary diseases, chronic renal failure is also a candidate for stem cell gene therapy. We have proposed two different therapeutic strategies for chronic renal failure depending on whether the bone marrow stem cells differentiate and commit into mesenchymal or hematopoietic stem cells. In the case of diseases, which need reconstitution of residential renal cells, such as congenital enzyme deficiency diseases, mesenchymal stem cells should be transplanted, and in contrast, hematopoietic stem cells may be used for gene delivery for diseases, which need foreign cytokines and growth factors, such as glomerulonephritis. This article reviews the recent investigation on this tailor-made stem cell gene therapy for chronic renal failure and discusses the potential of this novel strategy and the major practical challenges of its clinical application.

Genetic Therapy↗
PubMed2002

Effect of peroxisome proliferator-activated receptor gamma on thromboxane A(2) and prostaglandin E(2) production in macrophage cell lines.

We studied the effect of peroxisome proliferator-activated receptor gamma (PPARgamma) activation on thromboxane A(2)(TXA(2)) and prostaglandin E(2)(PGE(2)) production in monocyte/macrophage cell lines. In present experiment, we used human peripheral blood monocyte (PBMC), monocyte-cell line THP-1 and mouse macrophage-like cell line RAW264.7. The expression of PPARgamma is reported in PBMC and THP-1. Synthetic PPARgamma ligands (troglitazone or BRL49653) inhibited TXA(2) production and enhanced PGE(2) production of PBMC and THP-1. When treated with 0.5-10 microM of troglitazone, there were no significant changes of TXA(2) and PGE(2) production of RAW264.7 cells, which express very low levels of PPARgamma. When RAW264.7 cells was transfected with PPARgamma expression plasmid and treated with troglitazone, PPARgamma was activated in a dose-dependent manner. In PPARgamma-transfected RAW264.7, TXA(2) production was decreased and PGE(2) production was increased by troglitazone treatment. But it needs high concentration of troglitazone (10 microM) for increasing PGE(2) production. These results suggest that PPARgamma may have negative effect on TXA(2) production, and also have slightly positive effect on PGE(2) production of macrophage.

Animals↗
PubMed2001

Genetically modified bone marrow continuously supplies anti-inflammatory cells and suppresses renal injury in mouse Goodpasture syndrome.

In chronic inflammation, macrophages and neutrophils, which are derived from bone marrow, play a pivotal role. Therefore, reconstitution of bone marrow with anti-inflammatory stem cells may modify inflammation. In this study, transplantation-based gene therapy was applied to glomerular inflammation for a long-lasting suppression of the glomerular damage seen in chronic nephritis. Bone marrow cells were harvested from male donor mice, which had received 5-fluorouracil 3 days previously, and transduced with an interleukin 1 (IL-1) receptor antagonist (IL-1Ra) or a mock gene using a retrovirus vector. After confirmation that transduced cells possessed the transgene at approximately 0.7 copies per cell and secreted recombinant IL-1Ra, these cells were infused into sublethally irradiated (6 Gy) female recipients once daily for 4 consecutive days. These female recipient mice had the male Y antigen in bone marrow, liver, and spleen, and 10% to 20% of their spleen cells possessed the transgene even 8 weeks after transplantation. Glomerulonephritis was then induced in these mice. Renal function and histology were retarded in the mice whose bone marrow was reconstituted with IL-1Ra-producing cells compared with mock transduced cells. In situ hybridization using a Y painting probe revealed that transplanted donor cells were recruited into the glomerulus upon induction of nephritis, suggesting therapeutic effects were channeled through the secretion of IL-1Ra from these cells. Furthermore, the survival rate after a second challenge with nephrotoxic antibody was significantly improved in the IL-1Ra chimera. These results suggest that reconstitution of bone marrow for continuous supply of anti-inflammatory cells may be a useful strategy for the treatment of chronic inflammation.

Animals↗
PubMed2001

Anomalous temperature dependence of the magnetic field induced antiferromagnetic moment in the antiferroquadrupolar ordered state of CeB6.

The magnetic field induced antiferromagnetic moment M(AF) at low magnetic fields in the antiferroquadrupolar (AFQ) ordered phase of CeB6 was investigated by elastic neutron diffraction experiments for H parallel [110]. The peak intensity at the AF magnetic reciprocal point (1 / 2,1 / 2,1 / 2) corresponding to M(2)(AF) increases with decreasing temperature below the AFQ ordering temperature T(Q), and exhibits a broad maximum at T approximately 3 K and decreases with a further decrease of temperature. This unusual behavior of M(AF) at low fields is explained as a result of the competition between the AF-octupolar and AF-exchange interactions in the O(xy) type AFQ ordered state.

Journal Article↗
PubMed2001

Genetically modified bone marrow-derived vehicle cells site specifically deliver an anti-inflammatory cytokine to inflamed interstitium of obstructive nephropathy.

In this study, we used genetically modified bone marrow-derived CD11b(+)CD18(+) vehicle cells to deliver IL-1 receptor antagonist (IL-1ra) for treatment of inflamed renal interstitium in an animal model of unilateral ureteral obstruction (UUO). Vehicle cells that expressed the ICAM-1 ligands, CD11b and CD18, were obtained from bone marrow cells of DBA/2j mice and adenovirally transduced with the IL-1ra gene or glucocerebrosidase (GC) gene ex vivo. In kidneys treated to develop UUO, levels of ICAM-1, IL-1 beta, and IL-1R expression increased within 3 days compared with contralateral untreated kidneys in the same mice. Similarly, the macrophage infiltration in the cortical interstitium increased after 3 days in UUO kidneys, but not untreated kidneys. After UUO developed, DBA/2j mice were injected i.v. with either IL-1ra(+) vehicle cells (IL-1ra-treated mice) or GC(+) vehicle cells (GC-treated mice) at 24 h after UUO. Six days after the injection of these vehicle cells, marked increase of CD11b(+) IL-1ra(+) vehicle cells was observed in the ICAM-1-positive interstitium of UUO kidneys from IL-1ra-treated mice. In contrast, no CD11b(+) IL-1ra(+) cells appeared in ICAM-1-negative contralateral kidneys from these mice. Furthermore, the infiltration of macrophages (p < 0.001), expression of ICAM-1 (p < 0.005), and presence of alpha-smooth muscle actin (p = 0.005) in the interstitium of UUO kidneys were significantly decreased in IL-1ra-treated mice compared with GC-treated mice. These findings suggest that IL-1 may contribute to the development of renal interstitial injury and that our method can deliver a functioning gene encoding an antiinflammatory cytokine gene specifically at that site by interacting with local adhesion molecules.

Animals↗
PubMed2001

An optimization approach to signal extraction from noisy multivariate data.

We consider a problem of blind signal extraction from noisy multivariate data, in which each datum represents a system's response, observed under a particular experimental condition. Our prototype example is multipixel functional images of brain activity in response to a set of prescribed experimental stimuli. We present a novel multivariate analysis technique, which identifies the different activity patterns (signals) that are attributable to specific experimental conditions, without a priori knowledge about the signal or the noise characteristics. The extracted signals, which we term the generalized indicator functions, are optimal in the sense that they maximize a weighted difference between the signal variance and the noise variance. With an appropriate choice of the weighting parameter, the method returns a set of images whose signal-to-noise ratios satisfy some user-defined level of significance. We demonstrate the performance of our method in optical intrinsic signal imaging of cat cortical area 17. We find that the method performs effectively and robustly in all tested data, which include both real experimental data and numerically simulated data. The method of generalized indicator functions is related to canonical variate analysis, a multivariate analysis technique that directly solves for the maxima of the signal-to-noise ratio, but important theoretical and practical differences exist, which can make our method more appropriate in certain situations.

Animals↗
PubMed2001

Transplantation-based gene therapy for inflammatory diseases: focus on glomerulonephritis.

Over the past decade, bone marrow transplantation has come to be considered an ideal therapeutic strategy for the treatment of certain diseases affecting the hematopoietic system such as hemophilia, and several clinical trials have been performed. Although traditionally used for the treatment of lethal diseases, it is speculated that this approach could also be used in the treatment of non-lethal but much more common diseases, which are resistant to conventional therapies, and affect a large number of patients physically and even financially. Inflammation may be one target for transplantation-based gene therapy, since macrophages and neutrophils, which are basically derived from hematopoietic stem cells, have been identified as key determinants in the development of diseases. This article focuses on the glomerulonephritis as a model of local inflammation and reviews recent investigations on transplantation-based gene therapy for inflammatory diseases.

Bone Marrow Cells↗
PubMed2000

Reduction of lysosomal storage in murine mucopolysaccharidosis type VII by transplantation of normal and genetically modified macrophages.

This study examined the ability of macrophages to serve as target cells of gene therapy for mucopolysaccharidosis (MPS) type VII using a murine model. Bone marrow cells were harvested from syngeneic normal mice and differentiated to macrophages. These cells were given to nonmyeloablated MPS VII mice. After transplantation, donor cells populated the liver and spleen. The pathologic improvement at day 38 after transplantation was significant and glycosaminoglycan storage was reduced. To develop gene therapy using this system, a retroviral vector expressing human beta-glucuronidase (HBG) was used to infect macrophages cultivated from MPS VII mice and given to nonmyeloablated MPS VII mice. At 38 days after transplantation, HBG-positive cells were still observed histochemically and pathologic improvement was significant. These observations suggest that macrophage transplantation is a promising method for treatment of murine MPS VII without myeloablation, and macrophages may be good target cells for ex vivo gene therapy for MPS VII.

Animals↗
PubMed1999

Prophylaxis of antibody-induced acute glomerulonephritis with genetically modified bone marrow-derived vehicle cells.

Glomerulonephritis is an inflammatory disease of the renal glomerulus, which often progresses either slowly or rapidly, ending in renal death despite the availability of various antiinflammatory drugs. Gene therapy may be a promising method of suppressing the progression of glomerulonephritis through the blockage of key inflammatory molecule(s). However, the difficulty of local gene delivery into the glomerulus has made the clinical use of gene therapy difficult. As a solution to this issue, we applied a novel ex vivo technique that may allow site-specific gene delivery into the inflamed site and thus suppress local inflammation in the glomerulus, and examined the feasibility of this system as a prophylaxis of glomerulonephritis. The gene encoding the antiinflammatory cytokine interleukin 1 receptor antagonist (IL-1ra) was delivered into animal models of inflamed glomeruli evoked by anti-glomerular basement membrane antibody; this animal model is an analog of the human Goodpasture syndrome. Vehicle cells did indeed accumulate in the glomeruli on the induction of nephritis and were confirmed to secrete recombinant IL-1ra. Renal functions as well as morphology were preserved by this intervention for up to 14 days after IL-1ra introduction. These data demonstrate the possible application of gene therapy for acute glomerulonephritis. A gene encoding an antiinflammatory molecule, IL-1 receptor antagonist, was delivered into inflamed glomeruli, using a technique that may allow site-specific gene delivery into inflamed tissues. The progression of experimental acute glomerulonephritis was effectively suppressed by this intervention for at least 14 days after gene introduction. This success may strengthen the rationale for gene therapy in the treatment of inflammatory diseases such as glomerulonephritis.

Acute Disease↗
PubMed1999

Measurement of serum levels of des-gamma-carboxy prothrombin in patients with hepatocellular carcinoma by a revised enzyme immunoassay kit with increased sensitivity.

BACKGROUND: Des-gamma-carboxy prothrombin (DCP) is a useful tumor marker for hepatocellular carcinoma (HCC). The conventional enzyme immunoassay (EIA) kit for DCP lacks adequate sensitivity to detect small HCC. Thus, a revised EIA kit for DCP has been developed. In this revised DCP kit, the blank value has been reduced, making it now possible to obtain a normal value. The authors used this revised EIA kit for DCP with increased sensitivity and evaluated its usefulness as a tumor marker for HCC. METHODS: Serum DCP and alpha-fetoprotein (AFP) levels were determined in 60 patients with HCC, 60 with cirrhosis, 57 with chronic hepatitis, and 273 normal subjects. The cutoff value for the revised DCP kit was determined to be 40 mAU/mL, and the values for the conventional DCP kit and AFP were 100 mAU/mL (0.1 AU/mL) and 20 ng/mL, respectively. RESULTS: The mean DCP value was 17.5 mAU/mL in the normal subjects, and the detection limit was 10 mAU/mL for this revised DCP kit. The positivity rate for DCP in patients with HCC was 60% by the revised DCP kit, in contrast to 40% by the conventional DCP kit. The sensitivity, specificity, and accuracy of the revised kit were 60%, 92.3%, and 81.4%, respectively, whereas those of the conventional kit were 40%, 98.3%, and 78.5%. Thirty-five percent of HCC tumors smaller than 2 cm and 78.1% of those larger than 3 cm were positive for DCP by the revised kit. The corresponding figures were 20% and 56.3% with the conventional kit. Twelve (33.3%) of the 36 HCC patients who were negative for DCP by the conventional kit were positive by the revised kit. When the revised DCP kit was used in combination with AFP, 86.7% of the HCC patients and 78.3% of the patients with solitary HCC were positive for at least 1 of these markers. CONCLUSIONS: The revised DCP kit is more useful than the conventional DCP kit as a tumor marker for HCC and should be used in combination with AFP.

Adult↗
PubMed1998

Inflamed site-specific gene delivery using bone marrow-derived CD11b+CD18+ vehicle cells in mice.

We report a novel technique that may allow site-specific gene delivery into inflamed tissues. Bone marrow cells from DBA/2 mice were incubated for 7 days in L-929 cell-conditioned medium containing elements that favor the development of mononuclear cells, such as colony-stimulating factors. Flow cytometric analysis revealed that 99.1 +/- 0.9% of the subcloned cells were positive for CD11b and CD18, both of which are ligands of the intercellular adhesion molecule 1 (ICAM-1). These vehicle cells were labeled with a fluorescent lipophilic probe and returned intravenously to the DBA/2 mice. The mice then received, for 1 week, intraperitoneal injections of either lipopolysaccharide (LPS) to enhance ICAM-1 expression in the glomerulus, or saline as a control. In the LPS-treated mice, labeled vehicle cells were detected within the glomerulus cross-section (gcs) 24 hr after the first injection (0.73 +/- 0.10/gcs). The number of labeled vehicle cells within the glomerulus gradually increased for 1 week (1.47 +/- 0.19/gcs) and decreased after discontinuation of the LPS injections. However, in the saline-treated control group, only a negligible number of vehicle cells could be detected in the glomerulus (0.05 +/- 0.03/gcs). A second administration of LPS 4 weeks after injection of the vehicle cells was also able to promote accumulation in the glomerulus. Furthermore, immunohistochemical analysis revealed that the kinetics of the vehicle cell recruitment into the glomerulus corresponded to the level of ICAM-1 expression. On the assumption that the LPS-induced ICAM-1 expression may regulate the site and timing of the delivery of vehicle cells into the glomerulus, vehicle cells were transduced with human glucocerebrosidase (GC) gene, using an adenovirus vector, and reintroduced into the mice. The basal expression of GC gene in the isolated glomeruli of vehicle cell-treated mice rose by 1.7-fold compared with endogenous activity, whereas the GC activity was enhanced 3.2-fold by LPS treatment. Polymerase chain reaction designed to detect human GC-specific sequence revealed that isolated glomeruli of vehicle cell-treated mice contained exclusively the vehicle cell-oriented GC. This indicates that vehicle cells can be used to carry a certain gene to a specific inflamed site. Injection of vehicle cells, with or without LPS, had small effect on urinary protein excretion or serum creatinine levels. These findings suggest that our novel method allows site-specific gene delivery into inflamed glomeruli through interaction of adhesion molecules.

Animals↗
PubMed1997

c-Jun/AP-1, but not NF-kappa B, is a mediator for oxidant-initiated apoptosis in glomerular mesangial cells.

Oxidant stress is a trigger of cell death in various cell types. Hydrogen peroxide (H2O2) induced mesangial cell death with nuclear condensation and DNA fragmentation typical of apoptosis. To explore molecular mechanisms involved in this process, redox-sensitive transacting molecules, activator protein-1 (AP-1) and nuclear factor-kappa B (NF-kappa B), have been brought into focus. Northern blot analysis and transient transfection assays using reporter plasmids showed that H2O2 activated both AP-1 and NF-kappa B. Downregulation of c-Jun/AP-1 using a transdominant negative mutant of c-jun, an antisense c-jun, or a pharmacologic inhibitor curcumin inhibited the H2O2-initiated apoptosis. In contrast, inhibition of the NF-kappa B activation using a transdominant negative mutant of the p50 NF-kappa B subunit did not affect the H2O2-triggered cellular death. These data elucidated that c-Jun/AP-1, but not NF-kappa B, is involved in the oxidant-initiated cell death program in glomerular mesangial cells.

Animals↗
PubMed1997

IL-1beta depresses expression of the 70-kilodalton heat shock protein and sensitizes glomerular cells to oxidant-initiated apoptosis.

The 70-kDa heat shock protein (hsp70) is induced by several physical stimuli, whereas little is understood about the regulation and function of this molecule during inflammation. We found that the proinflammatory cytokine IL-1beta depressed hsp70 expression in glomerular mesangial cells and that IL-1-pretreated cells were more susceptible to apoptotic death triggered by oxidant stress. To examine whether the altered expression of hsp70 causes the effect of IL-1beta on apoptosis, rat mesangial cells were stably transfected with a hsp70 cDNA under the control of a constitutively active regulatory element. Compared with mock-transfected cells, the established cells overexpressing hsp70 showed resistance to the effect of IL-1beta. The effects of IL-1beta on hsp70 expression and apoptosis were also examined in isolated rat glomeruli. Consistent with the results from mesangial cells, IL-1beta repressed the expression of hsp70 and enhanced the oxidant-initiated apoptosis in the glomerulus. The relationship between glomerular hsp70 and apoptosis was further investigated using an experimental model of anti-glomerular basement membrane glomerulonephritis in which IL-1 and oxidants play crucial roles. Compared with normal expression, the expression of hsp70 was significantly reduced in the inflamed glomeruli. Furthermore, the nephritic glomeruli exhibited oligonucleosomal DNA fragmentation typical of apoptosis. These findings suggested a novel mechanism by which IL-1 may induce glomerular injury. IL-1beta has the potency to affect intrinsic cytoprotective machinery and thereby sensitizes glomerular cells to oxidant-initiated apoptosis. We identified hsp70 as a potential molecular target in this process.

Animals↗
PubMed1997

Usefulness of ED036 kit for measuring serum PIVKA-II levels in small hepatocellular carcinoma.

As a tumor marker for hepatocellular carcinoma (HCC), serum protein induced by vitamin K absence or antagonist-II (PIVKA-II) has high specificity, yet its sensitivity is relatively low, marking it less suitable to serve as an adjunct in the diagnosis of small HCC. Recently, the ED036 kit (Eisai, Tokyo, Japan), whose detection limit is approximately ten times superior to that of a conventional kit (Eitest MONOP II, Eisai) has been developed. In this study, serum PIVKA-II levels in serum samples from 83 patients with benign chronic liver diseases (CLD) and 129 patients with HCC were measured with those two kits. With the ED036 kit, the cut-off value was set at 40 mAU/ml. For PIVKA-II measured with the ED036 kit, sensitivity was 45.0%, specificity 92.8%, and accuracy 63.7%, when we discriminated patients with HCC from those with CLD without HCC. While maintaining a high specificity, of 92.8%, the ED036 kit showed a significantly higher sensitivity than the conventional kit (45.0% versus 27.9%; P < 0.0001). With patients who had HCC consisting of a single nodule 30 mm or less in diameter, the positivity rate for serum PIVKA-II with the ED036 kit was significantly greater than the rate with the conventional kit (21.4% versus 9.5%; P < 0.005). Thus, the ED036 kit was thought to be more useful than the conventional kit as a tumor marker for small HCC.

Adult↗
PubMed1997

Unexpected protection of glomerular mesangial cells from oxidant-triggered apoptosis by bioflavonoid quercetin.

Bioflavonoid quercetin is known as an anti-cancer agent that induces apoptosis of tumor cells. Currently, however, little is understood about the effect of this drug on the function of normal cells. In this report, we address an unexpected, novel action of quercetin against apoptosis. Pretreatment with quercetin protected mesangial cells from hydrogen peroxide (H2O2)-induced apoptosis. A similar effect was observed in other cell types including LLC-PK1 epithelial cells and NRK49F fibroblasts. To explore the molecular mechanisms involved, we tested the effect of quercetin on c-Jun/activator protein-1 AP-1), the crucial mediator for H2O2-initiated apoptosis. Northern blot analysis revealed that quercetin suppressed the c-jun expression by H2O2. This was correlated with blunted activation of 12-O-tetradecanoylphorbol 13-acetate response element (TRE) in response to H2O2. These results suggested that quercetin inhibited apoptosis via intervention in the c-Jun/AP-1 pathway. To further investigate the action of quercetin, its effect on tyrosine kinases was studied. Immunoblot analysis revealed that H2O2 induced tyrosine phosphorylation. Quercetin inhibited this process in a dose-dependent manner. Inactivation of tyrosine kinases was an event upstream of c-Jun/AP-1, because tyrosine kinase inhibitors suppressed both activation of c-Jun/AP-1 and induction of apoptosis by H2O2. These findings elucidated the novel action of quercetin as an apoptosis inhibitor. This cytoprotective effect was found to be via suppression of the tyrosine kinase-c-Jun/AP-1 pathway triggered by oxidant stress.

Animals↗