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H Kojima

Publications and source records attributed to H Kojima.

At least 73 records · Page 4Linked to original sources
PubMed2001

Endothelin-1 plays a major role in portal hypertension of biliary cirrhotic rats through endothelin receptor subtype B together with subtype A in vivo.

BACKGROUND/AIMS: Endothelin-1 has been suggested to play a key role in cirrhotic portal hypertension, but a role of its receptors in vivo is not fully elucidated. METHODS: Biliary cirrhosis was induced by bile duct ligation. Expressions of endothelin-1 and its receptors were evaluated by radioimmunoassay and/or reverse-transcription polymerase chain reaction. Hemodynamics were studied using endothelin receptor agonist or antagonist. RESULTS: Portal pressure and hepatic endothelin-1 concentrations progressively increased in parallel after bile duct ligation. Gene expression of hepatic prepro-endothelin-1 and endothelin B receptor enhanced after bile duct ligation, while that of endothelin A receptor was unchanged. Intraportal administration of endothelin-1 or endothelin B receptor agonist sarafotoxin 6c (0.5 nmol/kg, respectively) progressively raised portal pressure in both sham and cirrhotic rats. Portal hypertensive effect of sarafotoxin 6c was more intense in cirrhotic rats than sham animals. Neither endothelin A receptor antagonist FR139317 (1 mg/kg) nor endothelin B receptor antagonist BQ788 (1 mg/kg) alone ameliorated cirrhotic portal hypertension. Only the combined endothelin A and B blockade was associated with a decrease in portal pressure in cirrhotic rats. CONCLUSIONS: These results indicate that endothelin-1 plays a major role in cirrhotic portal hypertension through endothelin receptor subtype B together with subtype A in vivo.

Animals↗
PubMed2001

Role of phosphatidylinositol-3 kinase and its association with Gab1 in thrombopoietin-mediated up-regulation of platelet function.

OBJECTIVE: Human blood platelets are easily available physiologic target cells for thrombopoietin (TPO). TPO up-regulates platelet aggregation and alpha-granule secretion induced by various agonists. We investigated the role of phosphatidylinositol 3-kinase (PI3K) and its association with Gab1 in TPO-mediated up-regulation of platelet function. MATERIALS AND METHODS: PI3K inhibitors (wortmannin and LY294002) and a MAP/ERK-kinase (MEK) inhibitor (PD98059) were used to investigate the role of these kinases in TPO-mediated up-regulation of platelet function. To elucidate the molecules associated with PI3K, we performed immunoprecipitation and pull-down experiments followed by immunoblotting. In vitro kinase assay also was performed to detect extracellular signal-regulated kinase (ERK) kinase activity. RESULTS: TPO up-regulated platelet alpha-granule secretion and aggregation induced by thrombin, which was dose-dependently inhibited by preincubation with wortmannin or LY294002. Immunoprecipitation and pull-down experiments revealed that regulatory subunit of PI3K, p85, was rapidly associated with tyrosine-phosphorylated Gab1 via its n- and c-terminal SH2 domains. Pretreatment of platelets with TPO dramatically augmented the thrombin-induced ERK activation, which was almost completely inhibited by LY294002. Furthermore, a MEK inhibitor, PD98059, not completely but significantly inhibited TPO-mediated up-regulation of thrombin-induced alpha-granule secretion. CONCLUSION: TPO induces the association of tyrosine-phosphorylated Gab1 with p85-PI3K. In downstream signaling, ERK is PI3K-dependently activated, which plays a critical role for TPO-mediated up-regulation of platelet function.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Gene therapy for hepatocellular carcinoma based on tumour-selective suicide gene expression using the alpha-fetoprotein (AFP) enhancer and a housekeeping gene promoter.

The aim of this study was to examine whether the human alpha-fetoprotein (AFP) enhancer could be used to induce hepatocellular carcinoma (HCC)-selective expression of the herpes simplex virus thymidine kinase (HSV-tk) gene which is under the control of the phosphoglycerate kinase (pgk) promotor. The human AFP enhancer was linked with the non-tissue-specific, human housekeeping pgk promoter in a retroviral vector. AFP-producing HCC cells infected with retroviruses carrying the HSV-tk gene under the control of the AFP enhancer/pgk promoter were much more susceptible to the prodrug, ganciclovir (GCV), than those infected with the same retroviruses without the AFP enhancer. Non-HCC cells infected with retroviruses carrying the HSV-tk gene under the control of the AFP enhancer/pgk promoter exhibited profoundly increased resistance to GCV compared with those infected with the same retroviruses without the AFP enhancer. Northern blot analysis revealed that the AFP enhancer caused enhanced HSV-tk expression in AFP-producing HCC cells and suppressed HSV-tk expression in non-HCC cells. Our results indicate that the AFP enhancer could give HCC selectivity to the pgk promoter, and that this novel strategy may be useful for HCC-selective cancer gene therapy.

Blotting, Northern↗
PubMed2001

Does the control of alanine aminotransferase levels lead to a regression of liver fibrosis in chronic hepatitis C patients?

The aim of this study was to investigate the effect of various medications other than interferon (IFN) on liver fibrosis in chronic hepatitis C (CH-C) patients, and the results were compared with those obtained in CH-C patients without therapy. Fifty CH-C patients (32 men and 18 women; mean age 58.5 years) without previous IFN therapy, who randomly received medicines other than IFN such as Stronger Neo-Minophagen C, Ursodeoxycholic acid and a herbal medicine, Sho-saiko-to (TJ-9) (Group I), and as a control group, 45 CH-C patients (27 men and 18 women; mean age 56.6 years) without therapy (Group II) were examined. All patients had persistent alanine aminotransferase (ALT) elevation more than 6 months before this study and were also subdivided into three subgroups according to different pattern of ALT during the observation period, i.e. (a): persistently ALT<60 IU/l (below about twice the upper limit of normal range); (b): persistently ALT>/=60 IU/l; and (c) other than (a) and (b). All patients were biopsied twice before starting this study and during observation period and the liver fibrosis was compared between them by staging in each case. When the fibrosis stage was the same between two specimens, we determined whether the degree of fibrosis had improved or worsened by computed image analysis. Blood tests for fibrosis marker, serum aminoterminal peptide of type III procollagen (P III P) and liver enzyme such as albumin (Alb) and zinc turbidity test (ZTT) levels, and platelet (Plt) counts were also examined on the two times of liver biopsy. As a result, there were no significant differences in fibrotic improvement rate when assessed by both staging only and staging together with fibrotic ratio, determined by computed image analysis and also in yearly change of P III P (P/Y) and fibrosis (F/Y), the changed rate of Alb, ZTT levels and Plt counts between Group I and Group II, except for P/Y in subgroup (a) which was rather higher in Group I than in Group II. There were also no significant relationship between the changes of histological activity and fibrosis staging in both groups. In conclusion, other medications than IFN could not significantly improve both liver fibrosis and its associated laboratory data irrespective of ALT levels in CH-C patients as compared to the control group during average 3 years' follow-up period.

Journal Article↗
PubMed2001

Isolation of some glycosides as aroma precursors in young leaves of Japanese pepper (Xanthoxylum piperitum DC.).

To clarify the formation mechanism for the major alcoholic aroma compounds in young leaves of Japanese pepper, the glycosides were isolated as aroma precursors. The presence of glycosides of the main alcoholic aroma constituents was indirectly determined by enzymatic hydrolysis and trifluoroacetylation (TFA) of the glycoside-containing fraction. After Amberlite XAD-2 column chromatography, ODS flash chromatography, and high-performance liquid chromatography (HPLC), two new compounds, namely, (3S,6S)-cis-linalool-3,7-oxide beta-D-glucopyranoside and 2-methylpropanyl 6-O-beta-D-apiofuranosyl-beta-D-glucopyranoside, were isolated. In addition, (3S,6R)-cis-linalool-3,6-oxide beta-D-glucopyranoside, which absolute configuration was the first determined, and six known glycosides, citronellyl beta-D-glucopyranoside, linalyl 6-O-beta-D-apiofuranosyl-beta-D-glucopyranoside, (Z)-3-hexenyl beta-D-glucopyranoside, benzyl 6-O-beta-D-apiofuranosyl-beta-D-glucopyranoside, dendranthemoside A, and 3,6-dihydroxy-5,6-dihydro-beta-ionol 9-beta-D-glucopyranoside, were isolated. All of these glycosides were isolated for the first time from the leaves of Japanese pepper. Their structures were established on the basis of spectral data and chemical evidence. The ratios of stereoisomers of the aglycon moieties of citronellyl beta-D-glucopyranoside and linalyl 6-O-beta-D-apiofuranosyl-beta-D-glucopyranoside were investigated by a chiral GC analysis and compared with those of free citronellol and linalool in the aroma concentrate.

Capsicum↗
PubMed2001

Identification of a gene, ABCG5, important in the regulation of dietary cholesterol absorption.

The molecular mechanisms regulating the amount of dietary cholesterol retained in the body, as well as the body's ability to exclude selectively other dietary sterols, are poorly understood. An average western diet will contain about 250-500 mg of dietary cholesterol and about 200-400 mg of non-cholesterol sterols. About 50-60% of the dietary cholesterol is absorbed and retained by the normal human body, but less than 1% of the non-cholesterol sterols are retained. Thus, there exists a subtle mechanism that allows the body to distinguish between cholesterol and non-cholesterol sterols. In sitosterolemia, a rare autosomal recessive disorder, affected individuals hyperabsorb not only cholesterol but also all other sterols, including plant and shellfish sterols from the intestine. The major plant sterol species is sitosterol; hence the name of the disorder. Consequently, patients with this disease have very high levels of plant sterols in the plasma and develop tendon and tuberous xanthomas, accelerated atherosclerosis, and premature coronary artery disease. We previously mapped the STSL locus to human chromosome 2p21 and further localized it to a region of less than 2 cM bounded by markers D2S2294 and D2S2291 (M.-H.L. et al., manuscript submitted). We now report that a new member of the ABC transporter family, ABCG5, is mutant in nine unrelated sitosterolemia patients.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed2001

Fine mapping of a gene responsible for regulating dietary cholesterol absorption; founder effects underlie cases of phytosterolaemia in multiple communities.

Sitosterolaemia (also known as phytosterolaemia, MIM 210250) is a rare recessive autosomal inherited disorder, characterised by the presence of tendon and tuberous xanthomas, accelerated atherosclerosis and premature coronary artery disease. The defective gene is hypothesised to play an important role in regulating dietary sterol absorption and biliary secretion, thus defining a molecular mechanism whereby this physiological process is carried out. The disease locus was localised previously to chromosome 2p21, in a 15 cM interval between microsatellite markers D2S1788 and D2S1352 (based upon 10 families, maximum lodscore 4.49). In this study, we have extended these studies to include 30 families assembled from around the world. A maximum multipoint lodscore of 11.49 was obtained for marker D2S2998. Homozygosity and haplotype sharing was identified in probands from non-consanguineous marriages from a number of families, strongly supporting the existence of a founder effect among various populations. Additionally, based upon both genealogies, as well as genotyping, two Amish/Mennonite families, that were previously thought not to be related, appear to indicate a founder effect in this population as well. Using both homozygosity mapping, as well as informative recombination events, the sitosterolaemia gene is located at a region defined by markers D2S2294 and Afm210xe9, a distance of less than 2 cM.

Arteriosclerosis↗
PubMed2001

Long-term histological prognosis and serum fibrosis markers in chronic hepatitis C patients treated with interferon.

BACKGROUND: Interferon (IFN) therapy is effective in 20-40% of patients with chronic hepatitis C, but the relationship between histological changes and the response to interferon is still unclear. We investigated the long-term histological prognosis and the changes of serum fibrosis markers after interferon therapy relation to the response. METHODS AND RESULTS: One hundred and eighteen patients with chronic hepatitis C who received interferon therapy were divided into four groups based on the detection of viremia and the serum alanine aminotransferase (ALT) level after treatment. A histological examination was performed by using the histological activity index and the criteria of the METAVIR score. Serum fibrosis markers were used to measure the levels of hyaluronic acid and type IV collagen 7s. Responders, whose serum ALT levels became normal after treatment, demonstrated histological improvement. Histological improvement was more rapid in sustained virological responders with hepatitis C virus (HCV) RNA seronegativity than in biochemical responders with HCV-RNA seropositivity. Only sustained virological responders exhibited histological cure. In partial responders, whose serum ALT levels decreased to less than twice the upper of normal, and non-responders whose serum ALT levels were not reduced, liver fibrosis was unchanged or showed progression. Serum fibrosis markers increased with progression of the histological stage and varied depending on the response to interferon. CONCLUSION: Normalization of serum ALT levels after interferon therapy led to a histological improvement, and that with viral clearance achieved histological cure. Serum fibrosis markers were useful indicators for long-term according to the response of IFN therapy.

Adult↗
PubMed2001

Visualization of oxygen-concentration-dependent production of nitric oxide in rat hippocampal slices during aglycemia.

Our novel fluorescent indicator, DAF-FM, permits the bioimaging of nitric oxide (NO) in living cells with high resolution in space and time, with stable intensity above pH 5.8. A membrane-permeable derivative, DAF-FM DA, was applied to imaging of NO generated in rat hippocampal slices by exposure to an aglycemic medium. NO production was observed mainly in the CA1 area, and was dependent on the concentration of O(2). During exposure to an anoxic-aglycemic medium, NO was hardly produced, while marked elevation of intracellular Ca(2+) was observed. Production of NO increased sharply as soon as the perfusate was changed to the normal medium. These results suggest that NO synthase is activated after reperfusion rather than during ischemia.

Animals↗
PubMed2001

The phenobarbital response enhancer module in the human bilirubin UDP-glucuronosyltransferase UGT1A1 gene and regulation by the nuclear receptor CAR.

The UDP-glucuronosyltransferase, UGT1A1, is the critical enzyme responsible for detoxification of the potentially neurotoxic bilirubin by conjugating it with glucuronic acid. For decades, phenobarbital (PB) treatment for hyperbilirubinemia has been known to increase expression of the UGT1A1 gene in liver. We have now delineated the PB response activity to a 290-bp distal enhancer sequence (-3483/-3194) of the UGT1A1 gene. The enhancer contains 3 putative nuclear receptor motifs, and it was activated by the nuclear orphan receptor, human constitutive active receptor (hCAR), in cotransfected HepG2 cells. Bacterially expressed hCAR, acting as a heterodimer with in vitro-translated retinoid X receptor (RXRalpha), only bound to 1 of the 3 NR motifs, named gtNR1 in a gel-shift assay. Consistently, mutations of the gtNR1 site significantly decreased the activation by hCAR of the 290-bp DNA in transfection assays. Moreover, the 290-bp DNA was effectively activated in mouse primary hepatocytes in response to PB, offering an excellent clinical test for the examination of the responsiveness of the UGT1A1 to PB in the human population, particularly individuals with hyperbilirubinemia.

Base Sequence↗
PubMed2001

Muscle plasma membrane changes in dystrophin gene exon 52 knockout mouse.

Changes in muscle plasma membranes in mice lacking exon 52 of the dystrophin gene (mdx52 mouse) were studied using the freeze-fracture technique. The extensor digitorum longus (EDL) muscle plasma membrane of the mdx52 mouse at 8 weeks of age showed significantly increased caveola density (p < 0.05 by two-tailed t-test) and significantly decreased densities of intramembranous particles (IMPs), orthogonal arrays (OAs) and orthogonal array subunit particles (OASPs) (p < 0.05 by two-tailed t-test, p < 0.01 by Wilcoxon rank-sum test, p < 0.05 by two-tailed t-test, respectively) on the protoplasmic face when compared with those of control EDL muscles. These changes are more similar to those seen in DMD than those in the mdx mouse at the same age as reported previously. Thus, the gene abnormality in the different exon of the mouse dystrophin gene seems to induce somewhat different changes in the muscle plasma membrane.

Animals↗
PubMed2001

Suppression of CYP3A2 mRNA expression in the warfarin-resistant roof rat, Rattus rattus: possible involvement of cytochrome P450 in the warfarin resistance mechanism.

1. The continual use of warfarin as a rodenticide has caused the development of populations of warfarin-resistant roof rat. To study the biochemical mechanism of warfarin resistance, the mRNA expression levels of the major P450 forms in the warfarin-resistant and -susceptible roof rat liver following exposure to warfarin were quantified by competitive RT-PCR. 2. The constitutive levels of CYP2C11 and CYP3A2 mRNAs in the warfarin-resistant and -susceptible roof rat were extremely low compared with those in the STD rat. In response to warfarin administration, the CYP3A2 mRNA level in the warfarin-susceptible rat increased to about 3-fold of that before the treatment, whereas in the warfarin-resistant roof rat, CYP3A2 mRNA remained at a low level. 3. The present results suggest the possibility that reduced synthesis of CYP3A2 mRNA is involved in the warfarin-resistant mechanism in the roof rat.

Animals↗
PubMed2001

Dynamic behavior of microtubules during dynein-dependent nuclear migrations of meiotic prophase in fission yeast.

During meiotic prophase in fission yeast, the nucleus migrates back and forth between the two ends of the cell, led by the spindle pole body (SPB). This nuclear oscillation is dependent on astral microtubules radiating from the SPB and a microtubule motor, cytoplasmic dynein. Here we have examined the dynamic behavior of astral microtubules labeled with the green fluorescent protein during meiotic prophase with the use of optical sectioning microscopy. During nuclear migrations, the SPB mostly follows the microtubules that extend toward the cell cortex. SPB migrations start when these microtubules interact with the cortex and stop when they disappear, suggesting that these microtubules drive nuclear migrations. The microtubules that are followed by the SPB often slide along the cortex and are shortened by disassembly at their ends proximal to the cortex. In dynein-mutant cells, where nuclear oscillations are absent, the SPB never migrates by following microtubules, and microtubule assembly/disassembly dynamics is significantly altered. Based on these observations, together with the frequent accumulation of dynein at a cortical site where the directing microtubules interact, we propose a model in which dynein drives nuclear oscillation by mediating cortical microtubule interactions and regulating the dynamics of microtubule disassembly at the cortex.

Biological Transport↗
PubMed2001

Molecular biological diagnosis of congenital and acquired cholesteatoma on the basis of differences in telomere length.

OBJECTIVE: To establish a molecular biological basis for differentiation of congenital and acquired cholesteatoma. STUDY DESIGN: The time of onset was estimated for congenital cholesteatoma and for acquired cholesteatoma by comparing the telomere length and the telomerase activity in the tissues of both diseases with the values of those parameters in normal external ear canal skin. METHODS: The telomere length was determined by extracting DNA from each tissue and then applying the Southern blot technique to hybridize it with a 32P-labeled telomeric oligonucleotide (TAAGGG)8 probe. The telomerase activity was analyzed by a modification of the polymerase chain reaction-based telomeric repeat amplification protocol. RESULTS: The telomere length in congenital cholesteatoma tissue was shorter than the length in normal external ear canal skin from the same patient, whereas in acquired cholesteatoma tissue the telomere length was almost the same as in the normal external ear canal skin. Some of the acquired cholesteatoma tissue specimens and normal external ear canal skin specimens were positive for telomerase activity, but all of the specimens of congenital cholesteatoma tissue were negative for telomerase activity. No correlation was found between the presence of telomerase activity and the telomere length. CONCLUSIONS: The present results indicate that congenital cholesteatoma manifests at an earlier time compared with acquired cholesteatoma, and the results can be thought to support the theory that congenital cholesteatoma originates from vestigial fetal tissue or aberrant tissue. In addition, the finding that telomerase activity was weak in the congenital cholesteatoma tissue suggests the possibility that vestigial fetal tissues and aberrant tissues are naturally eliminated in normal subjects as a result of apoptosis.

Adolescent↗
PubMed2001

Predicting visual outcome after macular hole surgery using scanning laser ophthalmoscope microperimetry.

AIMS: To determine if postoperative visual outcome after successful macular hole surgery can be predicted with preoperative scanning laser ophthalmoscope (SLO) microperimetry. METHODS: A prospective non-comparative study of 16 eyes in 15 patients examined before the surgery. RESULTS: Visual outcome following macular hole surgery correlated with the "maximum parahole sensitivity", the highest intensity of stimulus to which the patient did not respond to any of the stimuli around the hole. Preoperative visual acuity, duration of the symptoms, size of the macular hole, and the "minimum parahole sensitivity", the lowest intensity to which the patient responded to all the stimuli around the hole, did not correlate significantly with postoperative visual acuity. CONCLUSION: Preoperative assessment of patients using SLO microperimetry is a good predictor of visual outcome after macular hole surgery.

Aged↗
PubMed2001

Differentiation of immature enterocytes into enteroendocrine cells by Pdx1 overexpression.

The development of a variety of enteroendocrine cells of the gut is poorly understood. We tested whether immature intestinal stem cells were switched to multiple enteroendocrine hormone-producing cells by in vitro transfer of a homeobox gene. We transfected the pancreatic-duodenal homeobox 1 gene (Pdx1) into IEC-6 cells, an embryonic intestinal epithelial cell line derived from a normal rat, and selected the cells that overexpressed Pdx1 by 150-fold compared with control. The cells were examined for differentiation into enteroendocrine cells by immunocytochemical and electron microscopic analyses. Transfected cells cultured on micropore filters formed a trabecular network piled up on monolayer cells. These trabecular cells showed nuclear localization of Pdx1 protein and contained well-developed rough endoplasmic reticulum as well as many secretory granules of pleomorphic shape in the cytoplasm. Antibodies against chromogranin A, serotonin, cholecystokinin, gastrin, and somatostatin stained these secretory granules in the cytoplasm. Furthermore, immunofluorescence double staining analysis showed that different hormones were produced within a cell. These results provide the evidence that immature intestinal epithelial cells can differentiate into multiple hormone-producing enteroendocrine cells in response to overexpression of Pdx1.

Animals↗
PubMed2001

Detection of minimal residual disease in a patient having acute myelogenous leukemia with t(16;21)(p11;q22) treated by allogeneic bone marrow transplantation.

A 29-year-old woman having acute myelogeneous leukemia-M1 subtype with the chromosomal abnormality t(16;21)(p11;q22) is presented. Complete blood count at onset showed a hemoglobin level of 7.2 g/dl, a platelet count of 48 x 10(9)/l, and a white blood cell count of 161.2 x 10(9)/l with 99% blasts and 1% lymphocytes. Bone marrow aspiration revealed massive proliferation of blasts that were positive for CD13, CD33, CD34, CD56 and myeloperoxidase, and negative for other T-cell, B-cell and monocytic markers. After achieving complete remission following conventional chemotherapy, she received an HLA-matched bone marrow transplantation (BMT) from her sibling after conditioning with busulfan, etoposide and cyclophosphamide. However, 9 months later, the leukemia relapsed as a painful extramedullary mass in her left femur. In spite of intensive re-induction chemotherapy, she died of progressive disease and sepsis. Although we could not detect the TLS/FUS-ERG fusion transcripts by reverse transcriptase-polymerase chain reaction in pre-BMT remission phase, they were clearly detectable in bone marrow cells obtained 6 months after transplantation with no translocation detected by conventional cytogenetics. We consider that even high-dose chemotherapy with BMT may not be effective in the eradication of this type of leukemia, and that the detection of minimal residual disease possibly contributes to the better planning of the therapeutic strategy.

Adult↗