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A Ohtsuru

Publications and source records attributed to A Ohtsuru.

67 records · Page 4Linked to original sources
PubMed1994

Reciprocal regulation of alpha-fetoprotein and albumin gene expression by butyrate in human hepatoma cells.

BACKGROUND/AIMS: Butyrate, a product of colonic bacterial flora, functions as an antiproliferative agent and induces cell differentiation in a variety of cell types. In the present study, the effects of butyrate on cell growth and expression of alpha-fetoprotein (AFP) and albumin genes in HuH-7 human hepatoma cells were investigated. METHODS: The HuH-7 cells were treated with sodium butyrate (0-1 mmol/L), and numbers of viable cells were counted at 24, 48, and 72 hours after treatment. To elucidate the effects of sodium butyrate on AFP and albumin gene expression, Northern blotting and transient chloramphenicol acetyltransferase plasmid transfection experiments were performed. RESULTS: Cell growth was dose dependently inhibited by sodium butyrate. By Northern blot analysis, the level of AFP messenger RNA was reduced by treatment with sodium butyrate, whereas the level of albumin messenger RNA was elevated by this treatment. In transient chloramphenicol acetyltransferase plasmid transfection experiments, sodium butyrate repressed the AFP promoter activity but did not change the AFP enhancer or silencer activities. In contrast, the albumin promoter activity was stimulated by sodium butyrate. CONCLUSIONS: These results suggest that butyrate leads to the reciprocal differentiating regulation of AFP and albumin gene expression at the transcriptional level in human hepatoma cells.

Albumins↗
PubMed1994

Changes in the prevalence of HBeAg-negative mutant hepatitis B virus during the course of chronic hepatitis B.

Hepatitis B virus with a G-to-A point mutation at nucleotide 83 in the precore region (mutant hepatitis B virus 83), which cannot produce HBeAg, is commonly found in HBe antibody-positive hepatitis B virus carriers. We analyzed the consecutive changes in the prevalence of mutant hepatitis B virus 83 during the course of chronic hepatitis B virus infection. Forty-five patients with chronic hepatitis B who were followed up for more than 2 yr in our hospital were studied by polymerase chain reaction in combination with a restriction fragment length polymorphism assay. Mutant hepatitis B virus 83 was found in 14 of 18 (78%) HBe antibody-positive patients and in 8 of 27 (30%) HBeAg-positive patients at baseline. Eighteen of the 22 patients who had mutant hepatitis B virus 83 (82%) showed mixed viral populations of wild-type hepatitis B virus and mutant hepatitis B virus 83, whereas 4 (18%) had only mutant hepatitis B virus 83 and were positive for HBe antibody. During a 2 yr follow-up period, mutant hepatitis B virus 83 was newly detected in 9 of 23 (39%) patients who had wild-type hepatitis B virus alone at baseline. The proportion of mutant hepatitis B virus 83 to whole hepatitis B virus in the serum of 18 patients with mixed viral populations at baseline fluctuated during follow-up. In contrast, wild-type hepatitis B virus was never detected throughout the study in all four patients who had only mutant hepatitis B virus 83 at baseline.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Growth hormone directly and indirectly stimulates articular chondrocyte cell growth.

Although growth hormone (GH) is known to regulate cartilage growth and differentiation during development, it is still unclear whether the cell growth of articular chondrocytes is stimulated directly by GH or mediated by GH-induced insulin-like growth factor-I (IGF-I). In the present study, we focused on whether GH directly or indirectly stimulates articular chondrocyte proliferation. Monolayer articular chondrocytes from 5-week-old male Sprague-Dawley rats were cultured in Ham's F-12/Dulbecco's modified essential medium supplemented with 10% fetal bovine serum. Stimulation of DNA synthesis by GH was dose-dependent between 0.1 and 1 microg/ml, and the maximum active concentration of GH was 500 ng/ml, which induced a 3.5-fold increase over control values. Anti-IGF-I antiserum neutralized about 80% of GH-induced DNA synthesis. GH stimulated the secretion of IGF-I into the conditioned medium in a dose-responsive manner. To determine whether GH stimulated DNA synthesis directly, we investigated the time-course changes in mRNA expression of IGF-I and the proto-oncogene c-myc. Induction of IGF-I mRNA occurred at 4 h, and reached a maximum level at 12 h, whereas the expression of c-myc mRNA was induced within 4 h, and continued to increase until 72 h after GH treatment. Furthermore, administration of cycloheximide, an inhibitor of protein synthesis, resulted in the superinduction of both IGF-I and c-myc mRNAs. These results suggest that early induction of c-myc is due to a direct stimulatory effect of GH, and that long-term induction of c-myc was attributable to an indirect effect of GH in which GH-induced secondary proliferative factors may act in an autocrine/paracrine manner. The superinduction of c-myc gene by cycloheximide also indicates that fresh protein synthesis of an intermediate protein was not required for GH-induced c-myc expression. Western ligand blot analysis of IGF-binding proteins revealed that cultured rat articular chondrocytes produced a predominant 41 kDa and a faint 32 kDa form, and that GH significantly stimulated the secretion of the 41 kDa form without affecting expression of the 32 kDa form. Furthermore, a specific IGF-I binding study suggested that the increase in DNA synthesis induced by GH was not associated with changes in affinity or in the number of IGF-I binding sites. These results support the conclusion that the stimulatory effect of GH was mainly mediated by GH-induced IGF-I production in monolayer rat articular chondrocytes. However, it is likely that GH may also have a direct stimulatory effect by inducing c-myc proto-oncogene expression.

Animals↗
PubMed1994

Expression of parathyroid hormone-related peptide in relation to perturbations of gastric motility in the rat.

We studied the expression of PTH-related peptide (PTHrP) and its mRNA in rat gastric smooth muscle in relation to various gastric motility states. Male rats were divided into groups subjected to fasting, feeding ad libitum, cold restraint stress, pyloric ligation, and carbachol stimulation. Cold restraint stress induced abnormal contractions. Rhythmic and moderate contractions were produced by carbachol administration, and marked distension was induced by pyloric ligation. PTHrP mRNA expression was weak in the physiological fasting and feeding states, but was markedly increased by pyloric ligation and carbachol stimulation. PTHrP and its mRNA were localized to the proper muscle layer and muscularis mucosa, but not in the mucosa by immunohistochemistry and in situ hybridization. The gene expression of PTHrP receptor in the gastric tissue was confirmed by reverse transcription-polymerase chain reaction, but serum PTHrP levels did not increase in all groups. These findings suggest that PTHrP acts as an autocrine or paracrine factor in gastric smooth muscle that responds to muscle activity caused by distension and cholinergic stimulation. However, PTHrP gene expression was decreased by stress despite the presence of strong contractions, and the sufficient relaxation did not occur. PTHrP suppression by stress is caused by the increase in corticosterone, as pretreatment of metyrapone, an inhibitor of 11 beta-hydroxylation, enhanced PTHrP gene expression in association with serum corticosterone suppression. In conclusion, PTHrP might be an important gastrointestinal peptide that regulates gastric contractile activity and is influenced by the serum corticosterone level.

Animals↗
PubMed1994

Correlation between suppression of c-myc and antiproliferative effect of transforming growth factor-beta 1 in thyroid carcinoma cell growth.

The growth regulatory activity of transforming growth factor-beta 1 (TGF beta 1) was studied in a clonal strain of thyroid papillary carcinoma cell (NPA). Despite the presence of TGF beta 1 and its receptor messenger RNA in thyroid carcinoma, the molecular mechanism of TGF beta 1 action on cell growth of thyroid carcinoma has not yet been elucidated. Exogenously added TGF beta 1 inhibited DNA synthesis and cell growth in a dose- and time-dependent manner at concentrations of 0.1-10 ng/ml. TGF beta 1 inhibited not only basal but also fetal bovine serum-stimulated cell proliferation. Steady state levels of c-myc messenger RNA transcripts were inhibited by TGF beta 1 after 0.5-h treatment. Antisense, but not sense, c-myc oligodeoxynucleotides also caused suppression of NPA cell growth in a dose-responsive manner. Transfection studies of the 5'-up-stream flanking region (UFR) of c-myc/chloramphenicol acetyltransferase chimera genes suggest the presence of a TGF beta 1-responsive DNA element in the 2.3-kilobase c-myc 5'-UFR. Deletion mutant studies indicate the element lies between -106 to 70 relative to the P1 transcription start site. Studies with the gel mobility shift assay using 23-basepair double strand DNA showed the presence of at least two nuclear factors in NPA cell. TGF beta 1 treatment did not cause any alteration in TGF beta 1-induced mobility; however, the reduction of a positive band was selectively observed during 30 min to 2 h after treatment with TGF beta 1. In contrast, the position and intensity of another band were not altered by TGF beta 1 treatment. These results demonstrate that the inhibition of a nuclear factor binding to the c-myc 5'-UFR and subsequent suppression of c-myc gene expression are directly involved in the antiproliferative action of TGF beta 1 in NPA cell growth.

Base Sequence↗
PubMed1993

Autocrine/paracrine function of parathyroid hormone-related peptide in rat osteoblast-like cells.

Parathyroid hormone-related peptide (PTHrP) may be synthesized in or near its target tissues and acts by autocrine and/or paracrine fashions. The rat clonal strain of the osteoblast-like cell, ROS 17/2.8-5, can express low levels of PTHrP in the cytoplasm; however, the autocrine function of PTHrP in ROS cells has not yet been clarified. We created PTHrP expression vectors and transfected them into cells in order to elucidate the functional role of PTHrP on their own target cells. Sense and antisense rat PTHrP expression vectors (pSV2 neo-ECE-rPLP) were transfected into ROS cells independently and cultured for 72 hours. Cells overexpressing PTHrP were detected by immunocytochemical analysis and confirmed by Northern blot analysis, respectively. These transfected cells demonstrated mitogenic activity as determined by BrdU uptake staining. These findings suggest the functional role of PTHrP on their own PTHrP expressing cells via an autocrine/paracrine fashion. These PTHrP-overexpressing ROS cells provide a model in vitro system to clarify the mechanism by which PTHrP acts in an autocrine/paracrine fashion.

Animals↗
PubMed1993

Skeletal muscle glucose transporter gene expression is not affected by injecting growth-hormone-secreting cells in young rats.

To elucidate the diabetogenic effect of growth hormone on glucose metabolism the regulation of glucose transporter (GLUT) gene expression was examined in rat skeletal muscles. Female Wistar-Furth rats were implanted subcutaneously with growth-hormone-producing pituitary tumour (GH3) cells. Animals were killed 4 or 9 weeks after GH3 cell injection. Although body weight, serum growth hormone and insulin-like growth factor I levels were remarkably elevated during the 4-9 week period, serum blood glucose levels were within normal range. Muscles were obtained from the quadriceps muscle, diaphragm and heart, respectively. Northern blot analysis and Western blot analysis were performed using specific cDNA probes and antibodies. During the 4-9 week period, the levels of muscle GLUT1 and 4 mRNA (corrected by beta-actin mRNA level) in each muscle from the rats injected with tumour cells were not significantly different from those of control rats. Chronic elevation of growth hormone in these rats did not cause any change in GLUT 1 and 4 expression compared to the controls during the euglycaemic period. These results provide the first evidence that chronic growth hormone elevation itself does not affect a key gene of in vivo glucose metabolism.

Animals↗
PubMed1993

Expression of parathyroid hormone related peptide in human pituitary tumours.

The presence of parathyroid hormone related peptide (PTHrP) was studied in 20 patients with pituitary adenomas and one patient with pituitary adenocarcinoma. PTHrP expression was shown in almost all of the pituitary adenomas (95%) and in 100% (n = 7) growth hormone producing pituitary adenomas. A metastatic lesion from a pituitary growth hormone producing adenocarcinoma revealed strongly expressed PTHrP. It was weakly detected in normal pituitary cells in all of the specimens (n = 10). There was no significant correlation, however, between PTHrP expression and the clinical or pathological features of growth hormone producing tumours. Apart from an important role in the physiological function of the pituitary gland, PTHrP may be closely related to somatotroph tumorigenicity.

Adenocarcinoma↗
PubMed1992

Hepatocyte growth factor down-regulates the alpha-fetoprotein gene expression in PLC/PRF/5 human hepatoma cells.

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes; however, in certain human hepatoma cell lines, the growth is inhibited by HGF. In the present study, the effect of HGF on the alpha-fetoprotein (AFP) gene expression was analyzed in PLC/PRF/5 human hepatoma cells. HGF did not inhibit cell proliferation, but dose-dependently suppressed AFP secretion at the concentrations of 10 ng/ml or less. By Northern blot analysis, the levels of AFP mRNA were suppressed by HGF, whereas the levels of beta-actin mRNA used as a control did not show any significant changes. In the transient chloramphenicol acetyltransferase plasmid transfection assays, the AFP promoter activity was repressed by HGF, in contrast, the AFP enhancer activity was not affected by HGF. These results suggest that the AFP gene expression is down-regulated by HGF through the suppression of its promoter activity in human hepatoma cells.

Animals↗
PubMed1992

Expression in human hepatocellular carcinoma of nucleoside diphosphate kinase, a homologue of the nm23 gene product.

BACKGROUND: Expression of nucleoside diphosphate (NDP) kinase, which is highly homologous to the nm23 gene product in a variety of species, has been found to be inversely associated with metastatic potential in human breast cancer. PURPOSE: The present study was conducted to clarify the association of NDP kinase expression with metastatic potential in human hepatocellular carcinoma. METHODS: The immunohistochemical expression of NDP kinase was analyzed in 30 patients with histopathologically proven hepatocellular carcinoma. These patients included nine with distant metastases and 21 without distant metastases. Tissue specimens were reacted with rabbit anti-rat NDP kinase antibody and stained by the biotin-streptavidin complex method. The relative staining intensities were evaluated by comparing primary tumor sites with adjacent nontumorous liver tissue or with metastatic sites, RESULTS: The expression of NDP kinase in primary sites in patients with distant metastases was significantly less intense than that in patients without distant metastases (P = .018). NDP kinase was expressed significantly less intensely in metastatic sites than in primary sites (P = .005). The intensity of NDP kinase expression did not statistically correlate with tumor size or number of lesions in the liver, histopathological classification of tumor, associated liver diseases, hepatitis virus markers, or tumor markers. CONCLUSION: These results suggest that the reduced expression of NDP kinase is closely associated with distant metastatic potential in hepatocellular carcinoma. IMPLICATIONS: It is possible that both NDP kinase and the nm23 gene product may be active in the progression and differentiation of tumor cells and that their reduced expression induces a high metastatic potential in tumor cells. Studies using Northern blotting or in situ hybridization should be planned to confirm our findings.

Adult↗
PubMed1991

Transforming growth factor beta 1 differentially regulates alpha-fetoprotein and albumin in HuH-7 human hepatoma cells.

Transforming growth factor beta 1 (TGF-beta 1) is known to inhibit hepatocyte growth in vitro and in vivo. In this study, we analyzed the effect of TGF-beta 1 on alpha-fetoprotein (AFP) and albumin gene expression in HuH-7 human hepatoma cells. TGF-beta 1 inhibited cell growth in a dose dependent manner. The cellular secretion rate of AFP but not albumin was suppressed significantly by TGF-beta 1. TGF-beta 1 caused a significant reduction in the level of AFP mRNA. In contrast, the levels of albumin mRNA or beta-actin mRNA were not changed by TGF-beta 1. In transient transfection experiments, TGF-beta 1 resulted in selective repression of AFP promoter activity. These results suggest that TGF-beta 1 is one of the key factors involved in the differential regulation of the AFP gene and the albumin gene.

Carcinoma, Hepatocellular↗
PubMed1990

Changes in HBsAg carrier rate in Goto Islands, Nagasaki Prefecture, Japan.

Annual mass examinations in an area where hepatitis B virus (HBV) infection is very prevalent revealed that 12.1% of inhabitants born during 1946-50 were positive for hepatitis B surface antigen (HBsAg), compared with only 0.6% of those born during 1971-75. To find out why the HBV carrier rate has fallen, changes in the modes of HBV infection were examined. The HBsAg positivity rate among mothers who gave birth to HBV carrier children in 1965 and before was 26.8% and that for such mothers whose babies were born in 1966 and after was 66.7%, whereas the HBsAg positivity rate among children born to HBV carrier mothers in 1965 and before and in 1966 and after were 30.8% and 28.3%, respectively. None of the 503 inhabitants who had no HBV markers in 1976 had become carriers by 1981. These findings indicate that the decrease in the prevalence of HBV carriage is caused mainly by the reduction in occurrence of horizontal transmission of HBV in infancy.

Adolescent↗