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Biomedical subjects

K Nakao

Publications and source records attributed to K Nakao.

At least 19 recordsLinked to original sources
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

Identification and endothelin-induced activation of multiple extracellular signal-regulated kinases in aortic smooth muscle cells.

In order to explore intracellular signaling pathways of the mitogenic action of endothelin (ET), we examined the effect of ET on activities of extracellular signal-regulated kinases (ERKs) in rat aortic smooth muscle cells (SMCs). Treatment of rat aortic SMCs with ET-1 increased kinase activities toward myelin basic protein (MBP). Both 43- and 41-kDa proteins were activated when kinase assays were done in MBP-containing polyacrylamide gels after SDS-PAGE. These proteins were identified as ERK1 and ERK2 with immunoprecipitation and immunoblotting using antipeptide antibodies, respectively. These results indicate that ERKs mediate signal transduction by ET.

Amino Acid Sequence↗
PubMed1992

Organization, structure, chromosomal assignment, and expression of the gene encoding the human endothelin-A receptor.

We have isolated and characterized the gene for the human endothelin-A receptor. Southern blot analyses demonstrated a single copy gene for the receptor. The gene spans more than 40 kilobases and contains eight exons and seven introns. Intron 1 exists in the 5'-noncoding region, and introns 2-7 occur in the coding region. The locations of introns 2-7 exist before or after the regions encoding the membrane-spanning domains. The transcription start site, determined by primer extension experiments, is 502 base pairs upstream of the methionine initiation codon. The 5'-flanking region lacks a typical TATA box but contains a potential SP-1-binding site 27 base pairs upstream of the transcription start site. Using human-rodent somatic hybrid cell DNA, the gene was assigned to human chromosome 4. Northern blot analyses revealed a 4.3-kilobase mRNA in a wide variety of human tissues, at the highest level in the aorta and at a substantial level in the cultured human mesangial cells. This is the first report of cloning of a gene for a member of the endothelin receptor family. The present study should give a clue to the discovery of possible disorders of the endothelin-A receptor, as well as facilitate the elucidation of the mechanisms by which the gene expression is regulated.

Amino Acid Sequence↗
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↗
PubMed1992

Factor VII hyperactivity in chronic dialysis patients.

To study factor VII (F VII) hyperactivity in chronic dialysis patients, we measured the plasma levels of F VII activity (F VII c) and antigen (F VII Ag), prothrombin activation fragments 1 + 2 (F1 + 2), thrombin-antithrombin III complexes (TAT), and thrombomodulin in 28 patients on hemodialysis. Marked elevation of F VII c was found in long-term dialysis patients (185 +/- 30%). This hyperactivity was accompanied by both elevation of the F VII Ag level (153 +/- 28%) and enhanced activation of F VII zymogen, expressed as the F VII c/F VII Ag ratio (1.23 +/- 0.23), but pseudocholinesterase activity was decreased. The 6 patients with ischemic heart disease had slightly higher F VII c (200 +/- 25%) than those without ischemic heart disease (181 +/- 30%), although the difference was not significant. Increased F VII c was accompanied by factor Xa hyperactivity (a high plasma F1 + 2 level) in the long-term dialysis patients, but there was no significant elevation of plasma TAT levels when compared with controls matched for age, sex, and the presence or absence of diabetes mellitus. Plasma TAT levels were significantly correlated with plasma thrombomodulin levels, suggesting that thrombin generation in blood as a result of hemodialysis could induce systemic endothelial cell injury.

Aged↗
PubMed1992

C-type natriuretic peptide-22 differentiates between natriuretic peptide receptors in rat choroid plexus and subfornical organ.

Atrial natriuretic peptide (ANP) receptors in the rat choroid plexus and subfornical organ were characterized with C-type natriuretic peptide-22 (CNP-22) and 125I-Tyr0-CNP-22. The receptor autoradiographic method we used revealed that 125I-Tyr0-CNP-22 specifically bound to the choroid plexus, but only slightly to the subfornical organ, areas densely labeled with 125I-alpha-rat ANP (125I-rANP). CNP-22 significantly inhibited 125I-rANP binding to the choroid plexus; however, the peptide did not affect 125I-rANP binding to the subfornical organ. Thus, the characteristics of ANP receptors in the rat choroid plexus and subfornical organ are probably different.

Amino Acid Sequence↗
PubMed1992

Enhanced DNA synthesis in rat hepatoma cells by conditioned media from Kupffer cells incubated with supernatants of tumor necrosis factor-alpha-pretreated hepatocytes.

The effects of tumor necrosis factor-alpha (TNF-alpha) on DNA synthesis in AH66 rat hepatoma cells and rat hepatocytes were analysed by means of [3H]thymidine incorporation. DNA synthesis in AH66 cells was suppressed when AH66 cells were directly incubated with TNF-alpha. When primary culture of rat Kupffer cells was incubated with hepatocyte conditioned media pretreated with TNF-alpha (0-200 U/ml), and AH66 cells were then treated with these hepatocyte/Kupffer cell-conditioned media, TNF-alpha used in the pretreatment caused a dose-dependent increase in DNA synthesis in AH66 cells with a maximum effect amounting to a more than 10-fold increase. In contrast, DNA synthesis in primary culture of rat hepatocytes was not stimulated by the TNF-alpha-pretreated hepatocyte/Kupffer cell conditioned media. These results suggest that TNF-alpha-mediated hepatocyte-Kupffer cell interaction selectively promotes proliferation of rat hepatoma cells.

Animals↗
PubMed1992

[Natriuretic peptide family].

The natriuretic peptide system consists of at least three endogenous ligands: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP), and three receptors, ANP-A receptor (guanylate cyclase A), ANP-B receptor (guanylate cyclase B) and clearance receptor (C receptor). ANP, the prototype of natriuretic peptides, is mainly produced in the atrium and secreted into the circulation as a cardiac hormone. ANP is also produced in the ventricle and in the central nervous system. BNP, first isolated from the porcine brain, has a marked divergence in its molecular size and sequence among species. In humans and rats, the major site of production of BNP is the ventricle of the heart. BNP is also secreted into the circulation as a cardiac hormone. The plasma BNP level in normal subjects is approximately one sixths of the plasma ANP level; however, the plasma BNP level markedly increases in heart failure, renal failure and hypertension and the augmentation of the BNP secretion is much larger than that of the ANP secretion. In addition, clearance of BNP from the circulation is slower than that of ANP. Furthermore, BNP is secreted more urgently than ANP in acute heart failure. CNP distributes mainly in the central nervous system and pituitary gland. No significant amount of CNP is detectable in the heart and plasma. Thus, CNP is a local regulator rather than a cardiac hormone. Three natriuretic receptors have ligand selectivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Interaction of interferon-alpha with interleukin-1 beta or tumor necrosis factor-alpha on hepatitis B virus enhancer activity.

The interaction of IFN-alpha with IL-1 beta or TNF-alpha on hepatitis B surface antigen (HBsAg) expression was analysed in hepatitis B virus (HBV)-DNA integrated PLC/PRF/5 and non-integrated HuH-7 human hepatoma cells. Secretion of HBsAg in PLC/PRF/5 cells was reduced by IFN-alpha, IL-1 beta or TNF-alpha, and synergistically depressed when IFN-alpha was used in combination with IL-1 beta or TNF-alpha. By Northern blot analysis, the levels of HBsAg mRNA were suppressed by IFN-alpha in combination with IL-1 beta or TNF-alpha. In the chloramphenicol acetyltransferase plasmid transfection assay, IFN-alpha in combination with IL-1 beta or TNF-alpha caused a much greater suppression of HBV enhancer activity than IFN-alpha, IL-1 beta or TNF-alpha alone in both hepatoma cells. These findings suggest that the interaction of IFN-alpha with IL-1 beta or TNF-alpha synergistically represses HBV enhancer activity, resulting in depressed expression of HBsAg.

Carcinoma, Hepatocellular↗
PubMed1992

Role of steroid 11 beta-hydroxylase and steroid 18-hydroxylase in the biosynthesis of glucocorticoids and mineralocorticoids in humans.

A gene encoding steroid 18-hydroxylase (P-450C18) was isolated from a human genomic DNA library. It was identified as CYP11B2, which was previously postulated to be a pseudogene or a less active gene closely related to CYP11B1, the gene encoding steroid 11 beta-hydroxylase (P-45011 beta) [Mornet, E., Dupont, J., Vitek, A. & White, P. C. (1989) J. Biol. Chem. 264, 20961-20967]. The nucleotide sequence of the promoter region of the P-450C18 gene is strikingly different from that of the P-45011 beta gene, although the sequences of their exons are 93% identical. The transient expression in Y-1 adrenal tumor cells of CAT constructs with a series of deletion mutants of promoter regions of both genes indicated that the two genes are regulated differently. P-450C18 as expressed in COS-7 cells exhibits steroid 18-hydroxylase activity to catalyze the synthesis of aldosterone and 18-oxocortisol and exhibits steroid 11 beta-hydroxylase activity as well. In contrast, P-45011 beta as expressed in the cultured cells exhibits steroid 11 beta-hydroxylase activity exclusively but fails to catalyze the synthesis of aldosterone and 18-oxocortisol. These results indicate that P-45011 beta and P-450C18 are products of two different genes and that the former participates in the synthesis of glucocorticoids whereas the latter participates in the synthesis of mineralocorticoids in humans.

Amino Acid Sequence↗
PubMed1992

Congenitally defective aldosterone biosynthesis in humans: the involvement of point mutations of the P-450C18 gene (CYP11B2) in CMO II deficient patients.

The gene for steroid 18-hydroxylase (P-450C18) has been recently assigned to encode corticosterone methyl oxidases Type I and Type II which were previously postulated to catalyze the final two steps in the biosynthesis of aldosterone in humans. Molecular genetic analysis of the P-450C18 gene is three patients from three different families affected with CMO II deficiency has indicated that a point mutation of CGG----TGG (181Arg----Trp) in exon 3 and one of GTG----GCG (386Val----Ala) in exon 7 occur exclusively in the gene of the patients. Analysis of PCR products by restriction enzymes (HapII and HphI) has indicated that the patients are homozygous and the unaffected parent is heterozygous for both mutations, in accordance with the established concept that CMO II deficiency is inherited in an autosomal recessive manner. These data clearly provide the molecular genetic basis for the characteristic biochemical phenotype of CMO II clinical variants.

Aldosterone↗
PubMed1992

Reduced erythropoietin secretion in senile anemia.

To investigate the etiology of the age-related decrease in hemoglobin (Hb) concentration, we measured serum erythropoietin (EPO), serum iron, total iron binding capacity, and serum ferritin levels in 247 elderly subjects aged 60-99 years. EPO levels were determined by radioimmunoassay. An age-related increase in the serum EPO concentration (r = 0.220; P < 0.01) and a significant inverse relationship between EPO and Hb concentrations were found in normal elderly subjects without anemia (r = -0.302; P < 0.001), but not in 111 younger controls. Serum EPO levels were slightly higher in elderly subjects with pre-anemic iron deficiency than in the normal elderly subjects (P < 0.05). These results suggest that the EPO secretion is accelerated in the elderly even though the Hb remains above 12.0 g/dl, probably as a compensatory mechanism for peripheral tissue hypoxia. An inverse relationship between the EPO and Hb concentrations was found in the elderly subjects with iron deficiency anemia, but not in those with unexplained senile anemia. The changes of EPO levels were also assessed in 20 elderly subjects who had developed anemia when reviewed after 12 months. Serum EPO levels increased in relation to the decrease in Hb concentration in those with iron deficiency anemia, but not in those with unexplained senile anemia. Reduced EPO secretion thus seems to play a role in the progression of unexplained senile anemia, and recombinant human EPO may possibly be effective for treating this type of anemia by mobilizing excess iron.

Aged↗
PubMed1992

Primary malignant lymphoma of the spleen.

We treated two patients with primary splenic malignant lymphoma. One was a 63-year-old man with diffuse histiocytic non-Hodgkin's lymphoma accompanied by multiple liver metastases which were composed of necrotic tissue probably due to preoperative transarterial chemoembolization (TAE). He eventually died of liver failure two years and six months after splenectomy. The autopsy revealed that a large part of the cirrhotic liver had been occupied by a diffuse-type hepatocellular carcinoma, but no recurrence of the malignant lymphoma was found in the liver or other organs. The second patient was a 40-year-old woman with a massive invasion of the stomach, colon, pancreas, and diaphragm by a splenic tumor. The splenic tumor and the adjacent involved organs were resected. Pathologically, well-differentiated diffuse lymphocytic non-Hodgkin's malignant lymphoma was evident. No recurrence has been found for six years and two months. Based on an evaluation of the 71 patients with primary splenic malignant lymphoma reported to data in Japan, the patients treated by a curative resection in an early clinical stage have a more favorable prognosis.

Adult↗
PubMed1992

Inhibitory effect of prostaglandin delta 12-PGJ2 on cell proliferation and alpha-fetoprotein expression in HuH-7 human hepatoma cells.

9-deoxy-delta 9,delta 12-13,14-dihydro-prostaglandin D2 (delta 12-PGJ2) is a potent inhibitor of proliferation of tumor cells. In the present study, the effect of delta 12-PGJ2 on the alpha-fetoprotein(AFP) and the albumin gene expression was analyzed in HuH-7 human hepatoma cells. delta 12-PGJ2 inhibited the cell growth and reduced the medium AFP concentrations dose-dependently. To determine whether this decline of AFP depends only on the relative decrease in cell numbers by delta 12-PGJ2, or is in part, due to the decrease in the cellular AFP synthesis by delta 12-PGJ2, Northern blot analysis was performed in this study. By Northern blotting, it was shown that delta 12-PGJ2 caused a marked reduction in the levels of the AFP mRNA and the albumin mRNA. In contrast, the level of the beta-actin mRNA was not changed by delta 12-PGJ2. In the transient chloramphnicol acetyltransferase plasmid transfection experiments, delta 12-PGJ2 did not suppress the AFP enhancer activity, which possibly regulates both the AFP and the albumin gene expression in HuH-7 hepatoma cells, but resulted in the selective repression of the AFP and the albumin promoter activity. These results suggest that delta 12-PGJ2 suppresses not only cell growth but also expression of the AFP gene and the albumin gene at the transcriptional level in human hepatoma cells.

Albumins↗
PubMed1992

Increased expression of atrial myosin light chain 1 in the overloaded human left ventricle: possible expression of fetal type myocytes.

We examined the isoforms of myosin light chain 1 in the human left ventricles using pyrophosphate and sodium dodecyl sulfate polyacrylamide gel electrophoresis, peptide mapping, and immunoblotting with monoclonal antibodies against human atrial light chain 1. The relationship between hemodynamic parameters and light chain 1 isoform composition was compared among groups of patients with hypertrophic cardiomyopathy (n = 8), dilated cardiomyopathy (n = 9) and aortic stenosis (n = 5), and controls (n = 6). (1) The light chain 1, which differed from ventricular light chain 1 found in the normal adult ventricle, was highly expressed in the overload left ventricle, and was identical to atrial and fetal ventricular light chain 1 with respect to the physiochemical and immunological properties. (2) The expression of atrial/fetal light chain 1 was augmented in the subendocardial area in comparison with the mid- or subepicardial areas in the hypertrophied left ventricles. (3) The values (%) of the relative expression of atrial/fetal light chain 1 to total light chains 1 determined by densitometric analysis were significantly higher in patients with dilated cardiomyopathy (40.2 +/- 5.8) and those with aortic stenosis (43.1 +/- 6.2) than in the controls (16.9 +/- 2.5) (p less than 0.01), but there was no significant difference between the patients with hypertrophic cardiomyopathy (28.0 +/- 3.7) and the controls. (4) The values of the ratio significantly correlated with those of peak circumferential wall stress (r = 0.53, p less than 0.005). These results suggest that atrial/fetal light chain 1 is expressed in the left ventricles in response to the increased hemodynamic load.

Adult↗