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Biomedical subjects

Y Yamaguchi

Publications and source records attributed to Y Yamaguchi.

At least 379 records · Page 21Linked to original sources
PubMed1998

Change in telomerase activity of rat organs during growth and aging.

Telomerase activity is usually undetectable in adult human tissues, but is positive in embryonic tissues and in cancers. In rodents, however, several organs of normal adult animals express substantial amounts of telomerase activity. In this study, we observed the changes in the telomerase activity in rat organs during growth and aging and found that telomerase activity showed chronological patterns which were characteristic to organs. In lung and brain, the high telomerase activity of embryonic stage decreased rapidly after birth. In lymphoid tissues, telomerase activity increased after birth and reached to its maximum at 4 to 7 week. In liver, it stayed at nearly constant level throughout life. The telomerase activity in regenerating rat liver decreased temporally immediately after partial hepatectomy, then increased to a level that is higher than normal control. In contrast, it rapidly diminished in the occluded lobes after ligation of portal vein branch.

Aging↗
PubMed1998

Neutrophil elastase enhances intercellular adhesion molecule-1 expression.

BACKGROUND: Elastase released from activated neutrophils is an important mediator of inflammatory tissue damage. We investigated the effect of human neutrophil elastase (NE) inhibitor (ONO-5046) on reperfusion injury after pancreaticoduodenal transplantation in rats by measuring the expression of intercellular adhesion molecule-1 (ICAM-1). Additional in vitro experiments were conducted to investigate the effect of NE on ICAM-1 mRNA transcription in a rat endothelial cell line (WK-5) and human umbilical vein endothelial cells (HUVEC). METHODS: In an in vivo experiment, male Wistar rats were transplanted with syngeneic pancreaticoduodenal grafts. An NE inhibitor, ONO-5046, was injected intravenously 5 min before vascular clamping and immediately after reperfusion at a dose of 10 mg/kg. ICAM-1 expression was determined by immunostaining and Northern analysis. In in vitro experiments, the effects of NE and chemical agents on ICAM-1 mRNA transcripts were determined in WK-5 cells and HUVEC. RESULTS: Pretreatment with ONO-5046 decreased ICAM-1 immunostaining in the pancreatic graft and inhibited the increase in ICAM-1 mRNA levels in grafts after reperfusion. ICAM-1 mRNA levels in WK-5 cells and HUVEC showed stimulation by NE, while ONO-5046 inhibited this increase. Calcium ionophore (A23187) augmented NE stimulation of ICAM-1 mRNA levels in these cells. In contrast, a phospholipase C inhibitor (U73122) blunted NE induction of ICAM-1 mRNA, and either calcium chelator (TMB-8) or a nuclear factor-kappa B inhibitor (pyrrolidine dithiocarbamate) completely inhibited induction. CONCLUSION: These results indicate that NE stimulates ICAM-1 expression in pancreatic grafts via intracellular Ca2+ influx and a phospholipase C signal transduction.

Animals↗
PubMed1998

Differential regulation of expression of hyaluronan-binding proteoglycans in developing brain: aggrecan, versican, neurocan, and brevican.

We have used a slot-blot radioimmunoassay to quantitate the levels of hyaluronan-binding chondroitin sulfate proteoglycans in developing rat brain from embryonic day 14 (E 14) to eight months postnatal. Recombinant nonhomologous regions of the core proteins were used for immunization to obtain polyclonal antibodies specific for aggrecan, the alpha and beta domains of versican mRNA splice variants, and N- and C-terminal portions of neurocan, while brevican was quantitated using a specific monoclonal antibody. The concentration of aggrecan increased steadily during brain development up to 5 months of age, when it reached a level that was 18-fold higher than at E14. Alternatively spliced versican isoforms containing the alpha domain of the glycosaminoglycan attachment region were present at a relatively low level during the late embryonic and early postnatal period, decreased by approximately 50% between 1 and 2 weeks postnatal, and then increased steadily in concentration to reach a maximum at 100 days that was 7-fold that present at 10 days postnatal. In contrast to these results, versican isoforms containing the beta domain more than doubled in concentration between E14 and birth, after which they decreased by greater than 90% to reach a low "mature" level that remained unchanged between 2 and 8 months. The N- and C-terminal portions of neurocan (produced by a developmentally-regulated proteolytic cleavage in the middle of its chondroitin sulfate attachment region) both increased in embryonic brain during development, reached a peak in the early postnatal period, and then declined thereafter. As in the case of aggrecan, only traces of brevican were detected in embryonic brain and its concentration increased steadily after birth to reach an adult level that was approximately 14-fold higher than that present in neonatal brain. These striking and distinctive changes in the concentrations of the different members of this family of structurally related proteoglycans in developing brain, including changes in opposite directions for versican mRNA splice variants, indicate that the individual proteoglycans and their isoforms probably serve unique functions during nervous tissue histogenesis.

Aggrecans↗
PubMed1998

Mechanisms of transcription in eosinophils: GATA-1, but not GATA-2, transactivates the promoter of the eosinophil granule major basic protein gene.

Granule major basic protein (MBP) is expressed exclusively in eosinophils, basophils, and placental trophoblasts. To identify the cis-elements and transcription factors involved in regulating MBP expression, we subcloned 3.2 kb of sequence upstream of the exon 9 transcriptional start site (P2 promoter) and serial 5' deletions into the pXP2 luciferase reporter vector. An 80% decrement in promoter activity was obtained when MBP sequences between bp -117 to -67 were deleted. To identify transcription factors that bind to and transactivate through the bp -117 to -67 region, we first compared the upstream genomic sequences of human and murine MBP; a potential GATA binding consensus site was conserved in the 50-bp region between the two genes. To determine which GATA proteins bind this consensus site, we performed electrophoretic mobility shift assays (EMSAs), which showed that both GATA-1 and GATA-2 can bind to this consensus site. To determine the functionality of this site, we tested whether GATA-1 and GATA-2, either individually or in combination, can transactivate the MBP promoter in the Jurkat T cell line. Cotransfection with a GATA-1 expression vector produced 20-fold augmentation of MBP promoter activity, whereas GATA-2 had no activity. In contrast, combined cotransfection of GATA-1 and GATA-2 decreased the ability of GATA-1 to transactivate the MBP promoter by approximately 50%. Our results provide the first evidence for a GATA-1 target gene in eosinophils, a negative regulatory role for GATA-2 in MBP expression, and possibly eosinophil gene transcription in general during myelopoiesis.

Binding Sites↗
PubMed1998

A significant reduction of macrophages expressing inducible nitric oxide synthase in rat hepatic allografts pretreated with donor-specific blood.

BACKGROUND: A single intravenous injection of donor-specific blood (DST) 7 days before transplantation significantly prolongs survival of hepatic allografts from fully allogeneic ACI(RT1a)-->LEW(RT1(1)) rats. The aim of this study was to investigate the kinetics of nitric oxide synthesis by macrophages in rat hepatic allografts treated with DST. METHODS: We investigated macrophages expressing inducible nitric oxide synthase in animal group I (receiving isografts), group II (hepatic allografts), and group III (hepatic allografts after donor-specific blood). RESULTS: Serum nitrite/nitrate, interferon-gamma, and tumor necrosis factor-alpha concentrations increased significantly in group II for 7 days after transplantation but were significantly much lower in groups I and III. Numbers of macrophages immunostained with an anti-macrophage nitric oxide synthase monoclonal antibody and inducible nitric oxide synthase mRNA levels in liver specimens also were much lower in groups I and III than in group II. In addition, Northern blot analysis demonstrated abundant interleukin-10 mRNA transcripts in the DST-treated hepatic allografts compared to untreated allografts. Double immunostaining revealed anti-macrophage synthase-containing cells, including both ED1+ and ED2+ cells, in liver and spleen as more numerous in group II. CONCLUSIONS: Inducible nitric oxide synthase is suppressed in immunologic unresponsiveness to grafts after donor-specific blood transfusion.

Animals↗
PubMed1998

ABR and temporal bone pathology in Hurler's disease.

This is believed to be the first report on estimating hearing loss in Hurler's disease, based on the correlation between ABR and temporal bone pathology. ABR findings revealed hearing loss to be about 70 dB or more as result of peripheral mixed impairment. A histological study of the temporal bones revealed almost all pathological findings in the conductive system, except for the hyperplastic arachnoid in the internal auditory canal. In the middle ear cavity, otitis media, residual mesenchyme and deformity of ossicles were found. We explain the conductive component to be due to otitis media and poor ossicular connection. However, the etiology of the sensorineural component remains speculative. In Hurler's disease, hearing loss with mental retardation is often found at infantile age. Therefore, assessing the extent of hearing loss exactly was difficult, for example, the severity. the etiology and incidence of sensorineural impairment. We emphasize the need for not only well-described pathological studies but also for more objective functional investigations, at least ABR.

Child, Preschool↗
PubMed1998

Prolonged survival of rat hepatic allografts treated with a pretransplant donor-specific blood transfusion is associated with reduced cytokine-induced neutrophil chemoattractant expression.

BACKGROUND: One intravenous injection of freshly heparinized donor blood 7 days before transplantation significantly prolongs hepatic allograft survival from ACI (RT1a) to LEW [RT1(1)] rats. The aim of this study was to investigate hepatic allograft expression of neutrophil chemoattractant and tumor necrosis factor in immunologic unresponsiveness. METHODS AND RESULTS: Cytokine-induced neutrophil chemoattractant levels in untreated hepatic allografts were significantly higher than in allografts treated with donor-specific transfusion. Additionally, more neutrophils infiltrated untreated than transfusion-treated hepatic allografts. The number of chemoattractant-positive cells was significantly lower in donor-specific transfused allografts than in untreated hepatic allografts. The number of ED1+ mononuclear cells infiltrating portal areas of untreated allografts increased over time and expressed abundant cytokine-induced neutrophil chemoattractant mRNA during acute rejection. This correlated with significantly higher levels of chemoattractant mRNA in untreated allograft livers on postoperative day 5 as compared with transfusion-treated allografts. Serum concentrations of tumor necrosis factor-alpha in untreated hepatic allograft recipients increased over time and peaked on day 7, while those in transfused allografts were maintained at lower levels. Moreover, in vitro chemoattractant production by peritoneal macrophages responded in a dose-dependent manner to tumor necrosis factor-alpha. CONCLUSION: Donor-specific transfusion treatment decreases tumor necrosis factor-alpha and chemoattractant expression as well as neutrophil accumulation in hepatic allografts.

Animals↗
PubMed1998

DSIF, a novel transcription elongation factor that regulates RNA polymerase II processivity, is composed of human Spt4 and Spt5 homologs.

We report the identification of a transcription elongation factor from HeLa cell nuclear extracts that causes pausing of RNA polymerase II (Pol II) in conjunction with the transcription inhibitor 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB). This factor, termed DRB sensitivity-inducing factor (DSIF), is also required for transcription inhibition by H8. DSIF has been purified and is composed of 160-kD (p160) and 14-kD (p14) subunits. Isolation of a cDNA encoding DSIF p160 shows it to be a homolog of the Saccharomyces cerevisiae transcription factor Spt5. Recombinant Supt4h protein, the human homolog of yeast Spt4, is functionally equivalent to DSIF p14, indicating that DSIF is composed of the human homologs of Spt4 and Spt5. In addition to its negative role in elongation, DSIF is able to stimulate the rate of elongation by RNA Pol II in a reaction containing limiting concentrations of ribonucleoside triphosphates. A role for DSIF in transcription elongation is further supported by the fact that p160 has a region homologous to the bacterial elongation factor NusG. The combination of biochemical studies on DSIF and genetic analysis of Spt4 and Spt5 in yeast, also in this issue, indicates that DSIF associates with RNA Pol II and regulates its processivity in vitro and in vivo.

Amino Acid Sequence↗
PubMed1998

Forced GATA-1 expression in the murine myeloid cell line M1: induction of c-Mpl expression and megakaryocytic/erythroid differentiation.

The "zinc-finger" transcription factor GATA-1 was first shown in cells of erythroid lineage. It is also expressed in cells of other hematopoietic lineages including megakaryocytes, mast cells, and eosinophils. GATA-1 is now considered to be one of the central regulators in hematopoietic cell differentiation. To further analyze the role of GATA-1 in controlling differentiation from hematopoietic stem cells, we investigated the phenotypic changes induced by the overexpression of murine GATA-1 in the murine myeloid leukemic cell line, M1. Forced expression of GATA-1 induced the appearance of erythroid cells and megakaryocytes as assessed by cellular morphology, acetylcholinesterase activity, and expression of platelet factor 4 and beta-globin mRNA synthesis. Because the c-mpl ligand, thrombopoietin, plays an important role in megakaryopoiesis, the expression of c-mpl and c-mpl ligand (thrombopoietin) mRNA was analyzed by Northern blot and reverse transcription-polymerase chain reaction (RT-PCR) in M1 cells overexpressing GATA-1. The c-mpl ligand mRNA was equally expressed both in parental M1 cells and in those transfected with the GATA-1 expression vector. In contrast, the mRNA expression of c-mpl was increased only in GATA-1 expressing M1 cells differentiated towards erythroid and megakaryocyte lineages. The increased expression of c-mpl mRNA induced by GATA-1 raised the question as to whether or not GATA-1 transactivated the c-mpl promoter. The activity of the c-mpl promoter in the presence of cotransfected GATA-1 was significantly increased compared with that of the control. A plasmid with the mutated GATA-binding site did not show transactivation ability in the cotransfection with a GATA expression vector. These findings suggest that the upregulation of c-mpl induced by GATA-1 expression in M1 cells is closely associated with erythroid and megakaryocytic differentiation.

Animals↗
PubMed1998

No deterioration in insulin sensitivity, but impairment of both pancreatic beta-cell function and glucose sensitivity, in Japanese women with former gestational diabetes mellitus.

To identify the primary pathogenic factors involved in the development of Type 2 diabetes mellitus (DM), we studied Japanese women with former gestational diabetes mellitus (GDM) who are at risk for the later development of Type 2 DM. We used the minimal model analysis derived from frequently sampled intravenous glucose tolerance test (FSIGT). The subjects consisted of eight non-obese women with a history of GDM and eight non-obese normal women as control subjects. The 75 g oral glucose tolerance test (75 g OGTT) performed within 6 months of delivery confirmed that all the subjects with former GDM had a normal glucose tolerance. Insulin sensitivity (SI) derived from the minimal model analysis was not different between the two groups. Glucose effectiveness at zero insulin (GEZI), reflecting tissue glucose sensitivity, was significantly lower in former GDM patients than in control subjects (1.18+/-0.34 vs 2.26+/-0.29 x 10(-2) min(-1), p < 0.05). The early phase insulin secretion found in FSIGT was markedly reduced to 56% of that observed in control subjects (1250+/-87.4 vs 2223+/-304.3 pmol l(-1) min, p < 0.01). Our results indicate that in former GDM patients, who are japanese and non-obese, impairment of the acute insulin response to glucose and a decrease in tissue glucose sensitivity rather than insulin sensitivity are the primary pathogenic factors involved.

Blood Glucose↗
PubMed1998

Un-cross-linked fibrin substrates inhibit keratinocyte spreading and replication: correction with fibronectin and factor XIII cross-linking.

Wound repair is characterized by the presence of a fibrin-rich matrix, but the effect of fibrin on re-epithelialization remains unclear. In this study, we determined the effects of different fibrin matrices on cultured human neonatal keratinocytes. Using purified fibrinogen and fibrin gels generated by the enzymatic action of thrombin, batroxobin (it leads to retention of fibrinopeptide B), or Agkistrodon contortrix thrombin-like enzyme (ACTE; it leads to retention of fibrinopeptide A), we determined the effect of each of these matrices on keratinocyte morphology, attachment, spreading, and replication as compared to tissue culture plastic. Morphologically, keratinocytes seeded on fibrin surfaces were more rounded and formed three-dimensional structures. Specific cell attachment, as measured at either 37 degrees C or 4 degrees C, was not altered on the different fibrin substrates (P > .05) but was increased on fibrinogen and factor XIII cross-linked fibrin (P < .01). However, keratinocytes seeded on fibrin, regardless of the presence or absence of fibrinopeptides A or B, showed a marked decrease (up to 71%) in cell numbers by days 5 (P = .0357) and 10 (P = .0114). Keratinocyte spreading was decreased by 78.8% (P = .0006), 80.3% (P = .0001), and 89.2% (P = .0001) on thrombin-, batroxobin-, and ACTE-generated fibrin, respectively, but not on fibrinogen-coated dishes. However, either the addition of fibronectin or cross-linking of fibrin with factor XIII allowed full keratinocyte spreading to occur (P = .0002 and P = .0013, respectively). We conclude that fibrin inhibits keratinocyte spreading in the absence of other matrix or plasma proteins or cross-linking by factor XIII.

Cell Adhesion↗
PubMed1998

Monocyte chemoattractant protein-1 enhances expression of intercellular adhesion molecule-1 following ischemia-reperfusion of the liver in rats.

Intercellular adhesion molecule-1 (ICAM-1) is important in neutrophil-dependent injury. We investigated the effects of monocyte chemoattractant protein-1 (MCP-1) produced by Kupffer cells on ICAM-1 expression after ischemia-reperfusion in rat liver by occluding the portal vein for 30 minutes. Serum concentrations of MCP-1 increased persistently. By Northern analysis, MCP-1 mRNA increased early and persisted. Kupffer cells harvested 6 hours after reperfusion also expressed this transcript. The transcript and protein also were produced by Kupffer cells from naive controls in response to reactive oxygen species. ICAM-1 mRNA transcripts increased, peaked 3 hours after reperfusion, and decreased gradually thereafter. The level of ICAM-1 mRNA transcripts in the WK-5 rat endothelial cell line were markedly enhanced by MCP-1. These results suggest that MCP-1 released by Kupffer cells early after ischemia-reperfusion modulates neutrophil-dependent tissue injury via ICAM-1.

Animals↗
PubMed1998

Infiltrating CD45RC- T cells are associated with immunologic unresponsiveness induced by donor class I major histocompatibility complex antigens in rats.

It has previously been shown that a single intravenous injection of freshly heparinized donor-specific blood transfusion (DST) before transplantation significantly prolongs the survival of fully allogeneic ACI (RT1a)-to-LEW(RT1(1)) rat hepatic allografts. Additionally, we have shown that pretreatment of LEW rats with PVG.r1 blood, which shares only the RT1.A major histocompatibility complex (MHC) region with ACI, significantly prolongs the survival of ACI hepatic allografts. In this study, we report the cellular identity of hepatic allograft leukocyte infiltrates following transplantation. Fluorescence-activated cell sorting (FACS) analysis revealed that CD4+ T cells infiltrating liver allografts could be divided into two subsets, CD45RC- CD4+ and CD45RC+ CD4+ T cells, and that the ratio of CD45RC- CD4+/CD45RC+ CD4+ T cells was significantly higher in hepatic allografts of recipients pretreated with DST or PVG.r1 blood as compared to untreated allografts. Further, CD8+ T cells that accumulated in the liver grafts could be similarly divided into two subsets, and the ratio of CD45RC- CD8+/CD45RC+ CD8+ T cells was also significantly higher in hepatic allografts of recipients pretreated with DST or PVG.r1 blood. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed that CD45RC- CD4+ T cells harvested from hepatic allografts pretreated with PVG.r1 blood expressed interleukin-4 (IL-4) and interleukin-10 (IL-10), but not interleukin-2 (IL-2) or interferon-gamma (IFN-gamma). In contrast, CD45RC- CD8+ T cells from hepatic allografts pretreated with PVG.r1 blood expressed IL-4, IL-10, and IFN-lambda, but not IL-2. These results indicate that the CD45RC leukocyte common antigen could be used to differentiate CD4+ and CD8+ T cells following pretreatment with DST or PVG.r1 blood. Persistent infiltration of CD45RC- CD4+ and CD45RC- CD8+ T cells, capable of secreting Th2-type cytokines may prevent allograft rejection by causing immunologic unresponsiveness.

Animals↗
PubMed1998

Xanthine oxidase inhibition attenuates kupffer cell production of neutrophil chemoattractant following ischemia-reperfusion in rat liver.

We investigated the effects of the xanthine oxidase inhibitor, BOF-4272, on the production of cytokine-induced neutrophil chemoattractant (CINC) following reperfusion injury in rat liver. Ischemia was induced for 30 minutes by portal vein occlusion. Animals were pretreated with intravenous injection of BOF-4272 (1 mg/kg) or heparin (50 U/kg) 5 minutes before vascular clamp. Both BOF-4272 and heparin limited increases in the chemoattractant compared with nonpretreated rats. Pretreatment with BOF-4272 plus heparin resulted in an additive effect. Most cells immunostained for chemoattractant were macrophages in sinusoids. In vitro chemoattractant production by Kupffer cells isolated from animals pretreated with heparin or BOF-4272 was significantly lower than by Kupffer cells from nonpretreated animals. Expression of transcripts in liver for chemoattractant peaked 3 hours after reperfusion in nonpretreated animals, while pretreatment with heparin or BOF-4272 significantly decreased chemoattractant mRNA levels. In vitro chemoattractant transcription and production could be induced in naive Kupffer cells by hypoxanthine and xanthine oxidase, but BOF-4272 prevented these increases. We conclude that Kupffer cells release chemoattractant in response to oxygen radicals reducible by xanthine oxidase inhibition.

Animals↗
PubMed1998

Fulminant hepatitis complicated by small intestine infection and massive hemorrhage.

A 34-year-old man diagnosed with fulminant hepatitis, caused by hepatitis B virus, and acute renal failure was referred to our hospital. After admission to the intensive care unit, the liver and renal failure were ameliorated. Melena requiring transfusion occurred during the course of his illness. Endoscopic examination demonstrated pseudomembranes, erosions, ulcers, and hemorrhage in the duodenum, the upper jejunum, and the terminal ileum, suggesting widespread lesions throughout the small intestine. Pseudomonas putida, Xanthomonas maltophilia, and Candida glabrata were cultured from ileal fluid. Candida glabrata was also detected in sputum, feces, and on an intravenous catheter tip. The patient was treated with amphotericin B and miconazole. The melena was ameliorated, but inflammation of the small intestine persisted. Although we had difficulty in treating the enteritis, the patient survived, and 1 year later colonoscopic examination demonstrated no abnormalities. The small intestine is a difficult site to examine, but endoscopic examination of this site is important when massive hemorrhage develops.

Adult↗