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Biomedical subjects

N Tamura

Publications and source records attributed to N Tamura.

At least 145 records · Page 8Linked to original sources
PubMed1996

Molecular cloning of rat leptin receptor isoform complementary DNAs--identification of a missense mutation in Zucker fatty (fa/fa) rats.

We cloned the full-length rat leptin receptor (Ob-R) isoform complementary DNAs (cDNAs) and examined the gene expression in rats. We also identified a mutation in Ob-R in Zucker fatty (fa/fa) rats. Three alternatively spliced isoforms (Ob-Ra, Ob-Rb, and Ob-Re) have been identified, which are closely related to the gp130 signal-transduction component of class I cytokine receptors. Rat Ob-Ra and Ob-Rb were single transmembrane proteins, which differ in the C-terminal amino acid sequences. On the other hand, Ob-Re had no transmembrane domain and was a soluble form of the receptor. Reverse transcription-polymerase chain reaction analysis revealed that Ob-R isoform messenger RNAs (mRNAs) are expressed in a wide variety of rat tissues in tissue-specific manners. A missense mutation (an A to C conversion at nucleotide position 806) was found in the extracellular domain of all the isoforms in Zucker fatty (fa/fa) rats, which resulted in an amino acid change from Gln to Pro at + 269 (the Gln269Pro mutation). These Ob-R isoform mRNAs were present in the brain from Zucker fatty (fa/fa) rats at comparable amounts to those in their lean littermates. The present study provides new insight into the molecular mechanisms for Ob-R.

Alternative Splicing↗
PubMed1996

Augmented expression of obese (ob) gene during the process of obesity in genetically obese-hyperglycemic Wistar fatty (fa/fa) rats.

Expression of the obese (ob) gene is up-regulated in the adipose tissue in several obese rodent models. To study the regulation of the ob gene expression during the development of obesity, we examined the ob gene expression in genetically obese-hyperglycemic Wistar fatty (fa/fa) rats at several stages of obesity. The ob mRNA levels in the adipose tissue from Wistar fatty rats was unequivocally augmented and continued to rise in the process of obesity. Furthermore, the ob gene expression in this obese model was much more rapidly enhanced in the mesenteric fat than in the subcutaneous fat. Moreover, the ob gene expression was more greatly augmented in the mesenteric fat than the lipoprotein lipase gene expression. These results suggest the presence of obesity-linked and region-specific regulation of the ob gene expression.

Adipose Tissue↗
PubMed1996

Two cardiac natriuretic peptide genes (atrial natriuretic peptide and brain natriuretic peptide) are organized in tandem in the mouse and human genomes.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), which act as cardiac hormones, are produced mainly by the atrium and ventricle, respectively, and are involved in body fluid homeostasis and blood pressure control. The ANP and BNP gene expressions are markedly augmented in ventricles of patients with a wide variety of cardiovascular diseases. It has been demonstrated that the ANP and BNP genes are tightly linked on mouse chromosome 4 and on the distal short arm of human chromosome 1. However, the precise physical map of the ANP and BNP genes has never been elucidated. In the present study, we characterized the genomic DNA fragment containing the ANP and BNP genes in mice and humans. Three genomic DNA clones harboring the entire mouse BNP gene were isolated from a 129/Sv mouse genomic DNA library. Nucleotide sequence analysis revealed that a phage clone (lambda mBNP #3) contains at its 3'-end the 5'-flanking region and the first 209-bp sequence of the first exon of the mouse ANP gene. In mice, the BNP gene was located about 12 kb upstream of the ANP gene. By polymerase chain reaction, we isolated an approximately 11-kb human genomic DNA fragment containing the third exon of the BNP gene and the first and second exons of the ANP gene. In humans, the BNP gene was located upstream of the ANP gene, approximately 8 kb apart. The present study provides the direct evidence that the ANP and BNP genes are organized in tandem in the mouse and human genomes.

Animals↗
PubMed1996

Expression of the RET proto-oncogene in normal human tissues, pheochromocytomas, and other tumors of neural crest origin.

In order to evaluate the roles of the RET proto-oncogene in normal human tissues and tumors derived from the neural crest cells, we examined the expression of RET in a variety of adult human tissues, pheochromocytomas, medullary thyroid carcinomas (MTCs), ganglioneuromas, and a neurinoma. Northern blot analysis demonstrated that RET is normally expressed in the adrenal medulla and cerebellum among adult human tissues. RET transcripts were detected in all of 11 sporadic and one familial pheochromocytomas. The levels of RET mRNA were higher in 8 of 12 pheochromocytomas than in the normal adrenal medulla, indicating that RET is overexpressed in the majority of sporadic pheochromocytomas. There was a considerable difference in the level of RET expression in each pheochromocytoma ranging from 0.2 to 10 times the transcripts found in the normal adrenal medulla. The sizes of the transcripts of 7.0, 6.0, 4.5, and 3.9 kb were the same as those found in the adrenal medulla, suggesting no rearrangements of the RET gene in pheochromocytomas. Southern blot analysis revealed neither amplification nor gross structural changes in the RET gene. RET was also expressed at high levels in four MTCs examined, whereas its transcripts were detected at low abundance in only one of three ganglioneuromas. RET was not expressed in a neurinoma. These results suggest that RET may play some roles in a limited range of adult human tissues, and that its high levels of expression may have relevance to development or growth of pheochromocytomas and MTCs.

Adult↗
PubMed1996

Positional cloning of a gene for Hermansky-Pudlak syndrome, a disorder of cytoplasmic organelles.

Hermansky-Pudlak syndrome (HPS) is an often-fatal autosomal recessive disease in which albinism, bleeding, and lysosomal storage result from defects of diverse cytoplasmic organelles: melanosomes, platelet dense bodies, and lysosomes. HPS is the most common single-gene disorder in Puerto Rico, with an incidence of 1 in 1,800. We have identified the HPS gene by positional cloning, and found homozygous frameshifts in this gene in Puerto Rican, Swiss, Irish and Japanese HPS patients. The HPS polypeptide is a novel transmembrane protein that is likely to be a component of multiple cytoplasmic organelles and that is apparently crucial for their normal development and function. The different clinical phenotypes associated with the different HPS frameshifts we observed suggests that differentially truncated HPS polypeptides may have somewhat different consequences for subcellular function.

Albinism, Oculocutaneous↗
PubMed1996

Requirement of CD80 and CD86 molecules for antigen presentation by eosinophils.

The authors analysed the antigen-presenting ability of eosinophils purified from peritoneal exudate cells of interleukin-5 (IL-5) transgenic mice. The granulocyte-macrophage colony-stimulating factor (GM-CSF)-treated eosinophils induced proliferative responses of primed lymph node T cells and thymus T cells to staphylococcal enterotoxin B (SEB), while untreated eosinophils induced little or no response. GM-CSF-treated eosinophils also induced proliferation of ovalbumin (OVA)-primed lymph node T cells to OVA. Although untreated eosinophils expressed no MHC class II molecule on the surface the eosinophils could be induced to express major histocompatibility complex (MHC) class II molecules when treated with GM-CSF. In the present study, anti-I-Ak monoclonal antibodies (MoAbs) strongly inhibited proliferation of thymus T cells and proliferation of OVA-primed lymph node T cells in response to OVA, but weakly inhibited proliferation of primed T cells in response to SEB. Furthermore, CD80 (B7-1) and CD86 (B7-2) were expressed on the surfaces of untreated eosinophils. The expression of those two molecules on the eosinophils was increased by incubation with GM-CSF. Moreover, anti-CD80 or anti-CD86 MoAbs blocked proliferative responses of primed lymph node T cells and thymus T cells to SEB, and also blocked responses of primed lymph node T cells to OVA. Thus, CD80 and CD86 play an important role in stimulation of T cells by eosinophils.

Animals↗
PubMed1996

cDNA cloning and gene expression of human type Ialpha cGMP-dependent protein kinase.

The type I cGMP-dependent protein kinase (cGK) is one of the major pathways for the cGMP cascade and has been demonstrated to inhibit platelet aggregation, relax smooth muscle cells, and control cardiocyte contractility. There are two subtypes of the type I cGK, cGKIalpha and cGKIbeta. The former is more sensitive to cGMP than the latter. In humans, cGKIbeta cDNA was isolated, but the full structure and tissue-specific gene expression of cGKIalpha have not been determined. The significance of cGK in human cardiovascular diseases has not been investigated at the molecular level. In the present study, we isolated the full-length human CGKIalpha cDNA (-36 to +2177; the translation start site: +1) enclosing the 671-amino acid protein. Nucleotides +267 to +2177 of the isolated cDNA were identical to the corresponding nucleotides of human cGKIbeta cDNA. Southern blot analysis suggested that human cGKIalpha and cGKIbeta are generated by alternative splicing of a single gene assigned to chromosome 10. By Northern blot analysis, we detected abundant human cGKIalpha mRNA (7.0 kb) in the aorta, heart, kidneys, and adrenals. In contrast, human cGKIbeta mRNA (7.0 kb) was detected abundantly only in the uterus. In cultured vascular smooth muscle cells, the type I cGK mRNA concentration was reduced to 10% of the basal level by 4 x 10(-10) mol/L platelet-derived growth factor. Angiotensin II (10(-8) mol/L), transforming growth factor-beta (4 x 10(-11) mol/L), and tumor necrosis factor-alpha (6 x 10(-6) mol/L) also exhibited an inhibitory effect on type I cGK gene expression. These findings suggest a pathophysiological implication of the type I cGK in cardiovascular diseases, including hypertension and atherosclerosis.

Amino Acid Sequence↗
PubMed1996

Prognostic value of Ia+ T lymphocytes in bronchoalveolar lavage fluid in pulmonary sarcoidosis.

We investigated the value of the la+ T-lymphocyte (CD3+ HLA-DR+) ratio in bronchoalveolar lavage fluid (BALF) for predicting the outcome of pulmonary sarcoidosis. Analysis of the BALF la+ T% in 166 patients with pulmonary sarcoidosis by dual-color flow cytometry revealed a wide range of values, of from 0.5 to 85.3%. Although the majority of patients had less than 40% la+ T cells in their BALF, a minor peak was observed at 50 to 60%. The BALF la+ T% value was not influenced by smoking, sex, or age, thus differing from other BALF activation markers. Fifty patients could be followed up precisely for 3 yr after their initial bronchoalveolar lavage (BAL) to evaluate outcome with respect to chest X-ray findings, clinical symptoms, serum angiotensin converting enzyme (ACE) activity, and extrapulmonary involvement. The 50 patients were divided into two groups, with a BALF la+ T% < 40% (n = 34) and > or = 40% (n = 16), respectively. Serum ACE activity returned to normal within 1 yr in the < 40% group, but remained high for the entire follow-up period in the > or = 40% group. The significant difference was observed in the persistence of pulmonary involvement between the two groups except for four patients who showed Stage 0 disease (p < 0.02). Thirteen of 31 patients in the < 40% group showed normalization of chest X-ray findings after three years, whereas only one out of 15 patients in the > or = 40% group showed resolution of pulmonary involvement. Our results suggest that the BALF la+ T% may be a novel marker for predicting the long-term prognosis in pulmonary sarcoidosis.

Adolescent↗
PubMed1996

Optically active antifungal azoles. VI. Synthesis and antifungal activity of N-[(1R,2R)-2-(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazo l-1- yl)propyl]-N'-(4-substituted phenyl)-3(2H,4H)-1,2,4-triazolones and 5(1H,4H)-tetrazolones.

A new series of optically active antifungal azoles, N-[(1R,2R)-2-(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-tria zol-1- yl)propyl]-N'-(4-substituted phenyl)-3(2H,4H)-1,2,4-triazolones (1,2) and 5(1H,4H)-tetrazolones (3), were prepared from the triflate derivative of (1S)-1-[(2R)-2-(2,4-difluorophenyl)-2-oxiranyl]ethanol (13) by an SN2 displacement reaction with the anion of an azolone (17-19) and subsequent ring-opening reaction with 1H-1,2,4-triazole. The optically active oxiranylethanol 13 was synthesized from methyl (R)-lactate in a stereo-controlled manner. The azolones 1-3 prepared showed potent antifungal activities in vitro and in vivo.

Antifungal Agents↗
PubMed1996

The RET proto-oncogene in sporadic pheochromocytomas.

In order to evaluate the role of RET proto-oncogene in the development and growth of pheochromocytomas, we examined mutations in RET and expression of RET in 7 cases of sporadic pheochromocytomas. Tumors were screened for mutations in exons 10 and 11 and codon 918 which are identified in multiple endocrine neoplasia types 2A and 2B. No mutations were found in these regions in all of the sporadic pheochromocytomas examined. On the other hand, RET mRNA was detected in all pheochromocytomas and the levels of RET expression were higher in 5 of 7 pheochromocytomas than in normal adrenal medulla, indicating that RET is overexpressed in a sizable portion of sporadic pheochromocytomas. These results suggest that high levels of expression of RET may have relevance to the development or growth of sporadic pheochromocytomas.

Adrenal Gland Neoplasms↗
PubMed1996

[A case of familial amyotrophic lateral sclerosis with markedly decreased accumulation on 123I-MIBG myocardiac scintigraphy and atonic bladder].

A 63-year-old Japanese woman with familial amyotrophic lateral sclerosis (ALS) showed cardiac hypofunction and neurogenic bladder. Her autonomic function was evaluated by means of 123I-metaiodobenzylguanidine (MIBG) cardiac scintigraphy and urodynamic study. (1) MIBG scintigraphy: Both early and late imagings showed severe defects of myocardial 123I-MIBG accumulation despite the normal accumulation of 201thallium. (2) Urodynamic study: Atonic bladder was observed on cystometry. These data indicate that both sympathetic and parasympathetic nerve functions were disturbed, suggesting the possibility that autonomic disturbance in familial ALS may differ from those in sporadic ALS, in which increased sympathetic nervous function has been reported.

3-Iodobenzylguanidine↗
PubMed1996

Tissue factor pathway inhibitor production by human mesangial cells in culture.

Fibrin formation within the glomeruli has been observed in various forms of human and experimental glomerulonephritis and it may play an important role in progressive glomerular injury. Furthermore it has been hypothesized that glomerular fibrin deposition may occur through activation of either the intrinsic or extrinsic coagulation pathway. It has been demonstrated that a procoagulant activity (PCA) which is compatible with tissue factor is present in the glomeruli and becomes increased in human proliferative glomerulonephritis and in animal models of nephritis. Tissue factor pathway inhibitor (TFPI) regulates the extrinsic pathway of blood coagulation through its ability to inhibit tissue factor activity. TFPI is present in plasma and in platelets, and it is now thought to be produced mainly by endothelial cells. We examined whether human mesangial cells (HMC) could produce TFPI and attempted to clarify regulatory factors which affect TFPI production. Cultured HMC were used and TFPI in the cell supernatants was measured by ELISA using a specific antibody. Cultured HMC showed the production of TFPI. Immunoblot analysis revealed 40 kD protein of TFPI. The concentration of TFPI was significantly increased following the incubation with thrombin and heparin, including low molecular weight heparin, in a dose- and time-dependent manner. However, fetal calf serum, phorbol myristate acetate, lipopolysaccharide, IL-1 beta and tissue factor did not stimulate TFPI synthesis. Our data show that cultured HMC have the ability to produce TFPI which inhibits fibrin formation. It is possible that thrombin-induced enhancement of TFPI synthesis may be caused by the autoregulatory system of blood coagulation and that with heparin it may represent another anticoagulatory effect of heparin.

Anticoagulants↗