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Biomedical subjects

M Nakamuta

Publications and source records attributed to M Nakamuta.

At least 55 records · Page 3Linked to original sources
PubMed1996

Mouse microsomal triglyceride transfer protein large subunit: cDNA cloning, tissue-specific expression and chromosomal localization.

Microsomal triglyceride transfer protein (MTP) catalyzes the transfer of triglyceride, cholesteryl ester, and phospholipid between membranes. It is essential for the secretion of apolipoprotein B from the cell. Mutations in MTP are a major cause of abetalipoproteinemia. The mouse is a popular animal model for lipoprotein metabolism. We have cloned and sequenced mouse MTP cDNA. The DNA-deduced amino acid sequence indicates that mouse MTP contains 894 amino acids; the mouse protein shows 93, 86, and 83% sequence identity to the hamster, human, and bovine sequences, respectively. Northern blot analysis indicates that mouse MTP mRNA is expressed at high levels in the small intestine and at substantially lower levels in the liver and that it is not detectable in six other tissues examined. The mouse MTP gene has been localized to the distal region of chromosome 3 by Southern blots of interspecific backcross panels using progeny derived from matings of (C57BL/6J x SPRET/Ei)F1 x SPRET/Ei. Comparison of MTP sequences from human, bovine, hamster, and mouse indicates that the C-terminal region of MTP is better conserved than its N-terminal region.

Animals↗
PubMed1996

Reversal of hypercholesterolemia in low density lipoprotein receptor knockout mice by adenovirus-mediated gene transfer of the very low density lipoprotein receptor.

We have used the technique of adenovirus-mediated gene transfer to study the in vivo function of the very low density lipoprotein receptor (VLDLR) in low density lipoprotein receptor (LDLR) knockout mice. We generated a replication-defective adenovirus (AdmVLDLR) containing mouse VLDLR cDNA driven by a cytomegalovirus promoter. Transduction of cultured Hepa (mouse hepatoma) cells and LDLR-deficient CHO-ldlA7 cells in vitro by the virus led to high-level expression of immunoreactive VLDLR proteins with molecular sizes of 143 kDa and 161 kDa. Digestion of the cell extract with the enzymes neuraminidase, N-glycanase, and O-glycanase resulted in the stepwise lowering of the apparent size of the 161-kDa species toward the 143-kDa species. LDLR (-/-) mice fed a 0.2% cholesterol diet were treated with a single intravenous injection of 3 x 10(9) plaque-forming units of AdmVLDLR. Control LDLR (-/-) mice received either phosphate-buffered saline or AdLacZ, a similar adenovirus containing the LacZ cDNA instead of mVLDLR cDNA. Comparison of the plasma lipids in the 3 groups of mice indicates that in the AdmVLDL animals, total cholesterol is reduced by approximately 50% at days 4 and 9 and returned toward control values on day 21. In these animals, there was also a approximately 30% reduction in plasma apolipoprotein (apo) E accompanied by a 90% fall in apoB-100 on day 4 of treatment. By FPLC analysis, the major reduction in plasma cholesterol in the AdmVLDLR animals was accounted for by a marked reduction in the intermediate density lipoprotein/low density lipoprotein (IDL/LDL) fraction. Plasma VLDL, IDL/LDL, and HDL were isolated from the three groups of animals by ultracentrifugal flotation. In the AdmVLDLR animals, there was substantial loss (approximately 65%) of protein and cholesterol mainly in the IDL/LDL fraction on days 4 and 9. Nondenaturing gradient gel electrophoresis indicates a preferential loss of the IDL peak although the LDL peak was also reduced. When 125I-IDL was administered intravenously into animals on day 4, the AdmVLDLR animals cleared the 125I-IDL at a rate 5-10 times higher than the AdLacZ animals. We conclude that adenovirus-mediated transfer of the VLDLR gene induces high-level hepatic expression of the VLDLR and results in a reversal of the hypercholesterolemia in 0.2% cholesterol diet-fed LDLR (-/-, mice. The VLDLR overexpression appears to greatly enhance the ability of these animals to clear IDL, resulting in a marked lowering of the plasma IDL/LDL. Further testing of the use of the VLDLR gene as a therapeutic gene for the treatment of hypercholesterolemia is warranted.

Adenoviridae↗
PubMed1995

Partial structure of the mouse glucokinase gene.

A complementary DNA for glucokinase (GK) was cloned from mouse liver total RNA by a combination of the polymerase chain reaction (PCR) and mouse liver cDNA library screening. Liver- and beta-cell-specific exons 1 were isolated by PCR using mouse and rat genomic DNAs. These clones were then used to screen a mouse genomic library; three genomic clones were isolated and characterized. The mouse GK gene spans over 20 kb, containing 11 exons including a liver- or beta-cell-specific exon 1, which encodes a tissue-specific 15-aa peptide at the N-terminus of the protein. Both types of GK contain 465 amino acid residues. The predicted amino acid sequence of mouse beta-cell-specific GK showed 98 and 96% identity to the rat and human enzymes, respectively; the corresponding values are 98 and 95%, respectively, for the liver-specific GK. Several transcription factor-binding consensus sequences are identified in the 5' flanking region of the mouse GK gene.

Amino Acid Sequence↗
PubMed1995

Alternative mRNA splicing and differential promoter utilization determine tissue-specific expression of the apolipoprotein B mRNA-editing protein (Apobec1) gene in mice. Structure and evolution of Apobec1 and related nucleoside/nucleotide deaminases.

Apolipoprotein (apo) B mRNA editing consists of a C-->U conversion involving the first base of the codon CAA, encoding Gln 2153, to UAA, a stop codon. Editing occurs in the intestine only in most mammals, and in both the liver and intestine in a few mammalian species including mouse. We have cloned the cDNA for the mouse apoB mRNA editing protein, apobec1. Expression of mouse apobec1 cDNA in HepG2 cells results in the editing of the intracellular apoB mRNA. The cDNA predicts a 229-amino acid protein showing 92, 66, and 70% identity to the rat, rabbit, and human proteins, respectively. Based on the estimated values of divergence of apobec1 sequences in terms of the numbers of synonymous and non-synonymous suhstitutions per site, we found that apobec1 is a fairly rapidly evolving protein. Sequence comparison among mammalian apobec1 sequences has permitted the identification of seven conserved regions that may be functionally important for editing activity. We present a phylogenetic tree relating apobec1 sequences to double-stranded RNA adenosine deaminase and other nucleotide/nucleoside deaminases. Northern blot analysis indicates that apobec1 mRNA exists in two different sizes, a approximately 2.2-kilobase (kb) form in small intestine and a approximately 2.4-kb form in liver, spleen, kidney, lung, muscle, and heart. To study the molecular basis for the different sized apobec1 mRNAs, we cloned the apobec1 gene and characterized its exon-intron organization together with the sequences expressed in the hepatic and intestinal mRNA. The mouse apobec1 gene contains 8 exons and spans approximately 25 kb, and is located in chromosome 6. The major hepatic mRNA contains all 8 exons, whereas the major small intestinal mRNA misses the first 3 exons and its transcription is initiated in exon 4. The intestinal mRNA also contains at its 5' end a unique 102-nucleotide piece that is absent in the liver mRNA. We also identified two alternatively spliced hepatic apobec1 mRNAs with different acceptor sites in exon 4. Transient expression studies using promoter-reporter gene constructs in HeLa, Hepa, and Caco-2 cells indicate that the 5'-flanking sequences of the liver mRNA (i.e. upstream of exon 1) have predominantly hepatic promoter activity and the 5'-flanking sequences of the major small intestine mRNA (i.e. upstream of exon 4) have preferential intestinal promoter activity.(ABSTRACT TRUNCATED AT 400 WORDS)

APOBEC-1 Deaminase↗
PubMed1994

Benign recurrent intrahepatic cholestasis: a long-term follow-up.

We report on a case with a 50-year history of benign recurrent intrahepatic cholestasis, including 33 years of follow-up at our hospital. The attacks of jaundice began at the age of 1 year and have been repeated more than 14 times to date. During the follow-up period at our hospital, the patient has suffered 6 attacks of cholestasis. During the episodes of cholestasis, a dissociation between the serum level of bilirubin and that of bile acids was observed. The analysis of serum bile acids during cholestasis showed that cholic acid and chenodeoxycholic acid were the main bile acids, and no appreciable amounts of the secondary bile acids were detected. Between episodes the liver function tests, including serum bile acids, were normal. Despite multiple attacks of cholestasis over many years, no permanent liver damage has occurred. This case reaffirms the essentially benign nature of this disease.

Adolescent↗
PubMed1994

The re-evaluation of sex steroids metabolism in patients with non-alcoholic liver cirrhosis.

We examined the serum levels of testosterone (T), androstenedione (delta 4-A), estrone (E1), estradiol (E2), and dehydroepiandrosterone sulfate (DHEA-S) in the non-alcoholic cirrhotic male patients when divided into compensated or decompensated state. Serum level of T was significantly elevated in compensated cirrhotic patients (9.63 +/- 1.00 ng/ml, mean +/- SE) compared to that in decompensated cirrhotic patients (5.63 +/- 0.69 ng/ml, p < 0.01) and in aged-matched normal controls (4.95 +/- 0.38 ng/ml, p < 0.01). Serum levels of E1, E2 and delta 4-A tended to be increased in decompensated cirrhotic patients, while there was not a significant difference decompensated cirrhosis compared to those of normal controls. Serum concentration of cholinesterase, indicative one of the representative residual liver function, showed a good positive correlation to T (r = 0.53, p < 0.01), and a negative correlations to E1 (r = -0.67, p < 0.01), E2 (r = -0.77, p < 0.01), delta 4-A (r = -0.57, r = p < 0.01). Also, we examined the relationship of the serum levels to gynecomastia or esophageal varices. The cirrhotics with gynecomastia showed significantly higher serum levels of E1, E2, and delta 4-A, and lower level of T than those without gynecomastia. And the cirrhotics with esophageal varices showed the greater level of T than those without esophageal varices. Our study suggests that low serum testosterone level of men with nonalcoholic cirrhotic is not a common finding, especially in compensated state.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Unique imagings of CT and MR in liver metastasis from gastric leiomyosarcoma.

We report unique features of computed tomography (CT) and magnetic resonance (MR) imaging in the metastatic lesion of the liver in a case of gastric leiomyosarcoma. A CT scan and MR image demonstrated presence of a huge multilocular cystic lesion in the liver, of which finding were unlike to those of usual smooth muscle tumors, but mimicked to those of cystadenomatous tumors. In addition, this case had an extremely long elapsing time over ten years from the radical operation for the primary site.

Aged↗
PubMed1993

High plasma concentration of myeloperoxidase in cirrhosis: a possible marker of hypersplenism.

Plasma myeloperoxidase levels in patients with cirrhosis were compared with those in patients with chronic hepatitis and healthy controls by means of a specific radioimmunoassay for myeloperoxidase. The mean concentration of plasma myeloperoxidase in cirrhotic patients (309.1 +/- 17.2 ng/ml, n = 41) was markedly higher than that in chronic hepatitis patients (222.6 +/- 17.2 ng/ml, n = 21) (p < 0.01) and normal controls (219.5 +/- 5.7 ng/ml, n = 50) (p < 0.01). Plasma myeloperoxidase showed good negative correlations with neutrocyte count (r = -0.32, p < 0.01), thrombocyte count (r = -0.40, p < 0.01), red blood cell count (r = -0.32, p < 0.01), serum albumin (r = -0.35, p < 0.01), and cholinesterase (r = -0.32, p < 0.02) and positive correlations with serum alkaline phosphatase (r = 0.49; p < 0.01) and lactate dehydrogenase (r = 0.31, p < 0.01) in patients with cirrhosis or chronic hepatitis. Among lactate dehydrogenase isozymes, a good positive correlation was seen between plasma myeloperoxidase and lactate dehydrogenase-2 (r = 0.40, p < 0.01) and lactate dehydrogenase-1 (r = 0.03, p < 0.02). Plasma myeloperoxidase was significantly higher in the cirrhotic and chronic hepatitis patients with splenomegaly (341.1 +/- 19.4 ng/ml, n = 31) than in those without splenomegaly (217.4 +/- 12.2 ng/ml, n = 29) (p < 0.01). We also examined the difference between plasma levels of myeloperoxidase in the portal and peripheral blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Diabetes mellitus-associated glycogen storage hepatomegaly: report of a case and review of the Japanese literature.

A huge hepatomegaly was seen in a 30-yr-old female diabetic who was treated with high dose of insulin for her uncontrollable food ingestion. The liver function at the peak of the hepatic enlargement showed a moderate increase of transaminases, alkaline phosphatase, and gamma-glutamyl transpeptidase. The histology of the enlarged liver revealed PAS-positive granules in enlarged hepatocytes, indicating the presence of massive glycogen storage. On admission, she was maintained under a calorie-restricted diet and received approximately 15 to 20 units per day of insulin supplement. At one month after admission, a marked shrinkage of her enlarged liver and restoration of normal liver function were observed concomitantly with the return of fair control of her blood sugar levels. One year later, she had an episode of diabetic ketoacidosis which subsequently was treated with a continuous low-dose infusion of insulin; however, she showed neither hepatomegaly nor liver dysfunction during this episode. There have been 20 cases reported of Japanese diabetics with marked hepatomegaly, in whom the vigorous treatment of diabetic ketoacidosis with insulin seemed to be a trigger of the enlarged liver. This has occurred mostly in patients with insulin-dependent diabetes mellitus. We present a case of non-insulin-dependent diabetes mellitus with glycogen storage hepatomegaly, presumably due to excessive insulin supplements. This suggests that glycogen storage hepatomegaly in diabetics may not be only due to an acute restoration from diabetic ketoacidosis, but may also be due to an overinsulinization in an attempt to maintain a euglycemic condition in spite of excess food intake.

Adult↗
PubMed1993

High plasma concentrations of endothelin-like immunoreactivities in patients with hepatocellular carcinoma.

The plasma levels of endothelin-like immunoreactivities (ET-IR) of patients with hepatocellular carcinoma (HCC) were compared with those of patients with liver cirrhosis (LC), using a specific radioimmunoassay for endothelin-1. The mean concentration of plasma ET-IR of 21 HCC patients (30.3 +/- 8.5 pg/ml, n = 21) (means +/- SD) was markedly higher than those in LC (22.1 +/- 4.7 pg/ml, n = 16) (p < 0.01), which were also elevated compared with those in normal subjects (9.4 +/- 1.6 pg/ml, n = 91). Moreover, the level of plasma ET-IR reflected the tumor size of HCC patients, which was estimated by the ultrasonic and computed tomographic examinations. Although there was no relation to other biochemical parameters indicating liver function or tumor markers such as alpha-fetoprotein, a good positive correlation was obtained between plasma ET-IR and C-reactive protein (CRP) concentrations of HCC patients (r = 0.805, p < 0.01). We measured the tissue contents of ET-IR in HCC and its adjacent LC tissue, but failed to find any significant difference between the mean content of HCC (0.50 +/- 0.38 ng/g) and LC (0.44 +/- 0.28 ng/g). The endothelial cell damage due to cancer growth may not be responsible for the high concentrations of plasma ET-IR of HCC, because plasma thrombomodulin concentrations were not correlated with plasma ET-IR levels in HCC patients. Our study implies that the high plasma concentration of ET-IR is pathogenomonic to HCC, although the site of production is still debatable.

Aged↗
PubMed1992

Molecular cloning, sequence analysis and expression of a cDNA encoding human type-1 angiotensin II receptor.

We isolated a cDNA encoding type-1 angiotensin II receptor from a human liver cDNA library. The cDNA had an open reading frame encoding a protein of 359 amino acid residues with a relative Mr of 41,060. The deduced amino acid sequence of the human angiotensin II (Ang II) receptor was 95.3% and 94.2% identical to those of bovine and rat type-1 Ang II receptors, respectively, and had a significant similarity with the G protein-coupled receptor. The rank order of the binding to the receptor expressed in COS-7 cells was Ang II greater than Ang III greater than Ang I. The expression of the Ang II receptor mRNA was detected in human liver, lung, adrenal and adrenocortical adenomas but not in adrenomedullary tumor, pheochromocytoma, by Northern blot analysis.

Amino Acid Sequence↗
PubMed1992

Anti-tolA antibody in non-A, non-B chronic liver disease.

We constructed a cDNA library against the plasma obtained from the patient with acute exacerbation of non-A, non-B liver cirrhosis, and immunoscreened this library with the sera obtained from the patients with non-A, non-B chronic liver disease. One positive clone lambda 22C containing about 1.2 kb cDNA insert was isolated from 10(6) clones. Nucleotide sequence determination and subsequent homology search revealed its identity to the tolA gene of Escherichia coli. Anti-tolA antibody was detected in 54.5% of the patients with NANB chronic liver disease whose sera were negative for antibody to hepatitis C virus (anti-C100). In contrast, anti-tolA was detected only of 14.6% patients with anti-C100 positive NANB chronic liver disease, 10.5% with hepatitis B surface antigen-positive chronic liver disease, 7.7% with alcoholic liver disease and 4.2% in normal control, and no positive case in acute hepatitis of etiology and in primary biliary cirrhosis. However, antibody to the core protein of hepatitis C virus (anti-JCC) was detected 50% of the patients whose sera were negative for anti-C100 but positive for anti-tolA. Recently, it has been reported that hepatitis C virus is rich in mutations and has some variants. These results indicated the presence of a common epitope between the tolA protein and some agent related to non-A, non-B hepatitis, especially to anti-C100 negative non-A, non-B hepatitis such as variants of hepatitis C virus which have mutations in C100 coded region.

Antibodies↗
PubMed1992

[A case of simple hepatic cyst accompanied with dilatation of the intrahepatic bile duct].

Here we report a rare case of simple hepatic cysts causing dilatation of the intrahepatic bile duct. A 75-year old female was admitted to Kyushu University Hospital because of liver dysfunction. Ultrasonogram and CT scan showed two neighboring cysts in the liver (S2, S4), and dilatation of the peripheral bile duct in left lateral segment of the liver. Echo-guided percutaneous aspiration of cyst fluid showed the elevated levels of CA19-9, but malignant cell were not seen. These findings suggested that the compression by these neighboring simple hepatic cysts caused the stenosis of the bile duct. The dilatation of the bile duct disappeared after the percutaneous ethanol sclerosing therapy for cyst.

Aged↗
PubMed1991

Cloning and sequence analysis of a cDNA encoding human non-selective type of endothelin receptor.

A cDNA encoding non-selective type (ETB) of endothelin receptor was isolated from a human liver cDNA library. The cDNA had an open reading frame encoding a protein of 442 amino acid residues with a relative Mr of 49,643. The deduced amino acid sequence of human ETB receptor was 88% and 64% identical to those of rat lung ETB receptor and bovine lung ET-1-specific (ETA) receptor, respectively, and contained a relatively long and proline-rich extracellular N-terminal region in addition to a significant similarity with the G protein-coupled receptor super-family with seven transmembrane segments.

Adult↗
PubMed1991

Inflammatory pseudotumor of the liver associated with acute myelomonocytic leukemia.

A patient with inflammatory pseudotumor of the liver associated with acute myelomonocytic leukemia (M4) is reported. He had spiking fever, epigastralgia, and elevated levels of serum C-reactive protein (CRP) and alkaline phosphatase (ALP). Ultrasonography showed a hypoechoic mass in the liver, and ultrasonically guided fine needle aspiration biopsy of the mass revealed that it was composed of fibrous connective tissue infiltrated with plasma cells, eosinophils, and neutrophils. Accordingly, a diagnosis of inflammatory pseudotumor of the liver was made. Marked reduction in the size of the lesion and a decrease of the levels of the CRP and ALP occurred without specific treatment. We emphasize the importance of ultrasonically guided aspiration biopsy in diagnosis of inflammatory pseudotumor of the liver without the need for surgery.

Biopsy, Needle↗
PubMed1989

Isolation and characterization of a family of rat endogenous retroviral sequences.

The complete nucleotide sequence of one representative rat genomic unit flanked on both sides with RAL elements, which have structural features specific to retroviral LTRs (1), was determined. The total unit was about 7.5 kbp long, and there was a partial homology to known retroviral sequences in gag, pol, and env regions. The sequence also contained minus- and plus-strand primer binding sites, thereby indicating a retroviral nature in replication. Transcription of the sequence was extensive in tumor cells and was strongly correlated with the state of methylation within 5' LTRs, which were highly methylated in the normal but not in the tumor state. In functional assays with bacterial chloramphenicol acetyltransferase constructs containing a series of deleted LTRs, there seemed to be both positive and negative cis-acting effector sequences.

Animals↗