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Biomedical subjects

A Tsuji

Publications and source records attributed to A Tsuji.

At least 91 records · Page 5Linked to original sources
PubMed1999

Ocular effects of adrenomedullin.

The purpose of this study was to determine the expression and effects of adrenomedullin (AM), a novel vasodilator peptide, in the eye. Expression of AM mRNA was examined in the rat iris-ciliary body using reverse transcription-polymerase chain reaction (RT-PCR). In rabbits, intraocular pressure (IOP) was measured periodically after intravitreal injection (20 microl) of AM (10(-7)-10(-4)m) into one eye. In separate groups of rabbits, 30 min after intravitreal injection of either AM-(22-52) (10(-3)m), a specific AM receptor antagonist, or CGRP-(8-37) (10(-3)m), a CGRP1 receptor antagonist, into one eye, AM (10(-6)m) was injected into both eyes, and IOP was measured. Using different rabbits, aqueous protein and cAMP concentrations were determined 6 hr after injection of AM. Expression of AM mRNA was detected in the rat iris-ciliary body. In rabbits, intravitreally administered AM (10(-6)-10(-4)m) profoundly lowered IOP, and the maximum effect was observed at 4-8 h. The ocular hypotensive effect of AM was dose-dependent (10(-7)-10(-4)m). Pretreatment with CGRP-(8-37) did not significantly inhibit the ocular hypotensive effect of AM (10(-6)m), whereas pretreatment with AM-(22-52) completely abolished it. AM (10(-6)m) did not significantly affect aqueous protein concentration. The higher dose of AM (10(-5)m) induced a significant increase in aqueous protein, which was not associated with an increase in the aqueous cAMP content and was significantly inhibited by AM-(22-52) and CGRP-(8-37). These results demonstrate that AM is expressed in the iris-ciliary body and decreases IOP mainly via specific AM receptors, and suggest that AM may play a role in controlling IOP.

Adrenomedullin↗
PubMed1999

A new method for crosstalk correction in simultaneous dual-isotope myocardial imaging with Tl-201 and I-123.

We have developed a new method of crosstalk correction in simultaneous dual-isotope imaging with Tl-201 and I-123 by using crosstalk ratios and a blurring filter. Single isotope myocardial studies (10 for Tl-201 and 7 for I-123) were performed with a dual energy window acquisition mode and two low energy general-purpose collimators. Then two planar images acquired with dual energy windows for a Tl-201 line source and an I-123 line source were obtained to measure line spread functions (LSFs) and crosstalk ratios for each image. The line source experiments showed that the LSFs for the Tl-201 imaging window from the single Tl-201 source were very similar to those for the I-123 imaging window from the single Tl-201 source, but the LSFs for the Tl-201 imaging window from the single I-123 source had broad shapes which differed from those for the I-123 imaging window from the single I-123. To obtain accurate I-123 crosstalk images in the Tl-201 imaging window from the I-123 images in the I-123 imaging window, we designed a low-pass blurring filter. In 7 clinical I-123 MIBG studies, I-123 window images processed with this filter became very similar to the Tl-201 window image from the single I-123 source. The method proposed in this study can accurately correct the crosstalk in dual isotope studies with Tl-201 and I-123 and is easily applicable to conventional gamma camera systems with any dual energy window acquisition mode.

3-Iodobenzylguanidine↗
PubMed1999

Plasma lipids, lipoproteins and apolipoproteins and sudden cardiac death.

To investigate the risk factors for sudden cardiac death, in particular that triggered by coronary heart disease, we analysed 17 different lipids, lipoproteins and apolipoproteins in the plasma of patients who had suffered sudden death, including sudden cardiac death. Studies were carried out on 107 cadavers comprising 78 subjects where the cause of death was diagnosed as sudden cardiac death and 29 subjects diagnosed with other causes of sudden death. All 107 cases were classified into four groups according to the degree of coronary stenosis and the degree of cardiac hypertrophy. Plasma levels of total cholesterol (T-CHOL), triglyceride (TG), beta-lipoprotein (beta-LIPO), free fatty acid, phospholipid, free cholesterol, high density lipoprotein cholesterol, lipoprotein(a) [Lp(a)], lipoproteins (VLDL, LDL, HDL) and apolipoproteins (apoAI, apoAII, apoB, apoCII, apoCIII, apoE) were determined. The level of apoB showed a significant difference and positive correlation with the degree of coronary stenosis by two different statistical methods, while the levels of T-CHOL, TG, beta-LIPO, VLDL, apoCII, apoCIII and apoE showed significant differences with the degree of coronary stenosis by one statistical method. It was concluded that a high plasma level of apoB is a risk factor for coronary stenosis, with higher levels resulting in more severe degrees of coronary stenosis. Furthermore, a significant difference was found regarding only apoCIII both between the sudden cardiac death group and the sudden death from other causes group, and between each of the four groups classified according to the degree of coronary stenosis. It was thus concluded that a high plasma level of apoCIII indicates the possibility of a coronary stenotic origin for sudden cardiac death.

Adult↗
PubMed1999

Cellular and molecular mechanisms of dietary regulation on rat intestinal H+/Peptide transporter PepT1.

BACKGROUND & AIMS: Dietary regulation is one of the most important factors of intestinal peptide transport. However, the cellular and molecular mechanisms of dietary regulation of the intestinal peptide transport system remain unknown. This study investigated the molecular mechanism of transcriptional activation of intestinal peptide transporter (PepT1) gene by the dietary protein. The promoter region of the rat PepT1 gene was isolated and characterized. METHODS: PepT1 messenger RNA levels were determined by Northern blot analysis. In transient transfection experiments, effects of amino acid and dipeptide on luciferase activity were investigated. RESULTS: The proximal promoter region of the rat PepT1 gene has a TATA-like box and a GC box sequence. The luciferase activities of the clone -351 RPT-LUC responded to particular amino acids (phenylalanine, arginine, and lysine) and dipeptides (Gly-Sar, Gly-Phe, Lys-Phe, and Asp-Lys). An AP-1 binding site and an amino acid-responsible element were present at -295 and -277 nucleotides relative to the transcription start site in this region. CONCLUSIONS: These results suggest that the up-regulation of dipeptide transport activity by dietary protein is caused by transcriptional activation of the PepT1 gene by selective amino acids and dipeptides in the diet.

Animals↗
PubMed1999

Simultaneous determination of alpha-fetoprotein, human chorionic gonadotropin and estriol in serum of pregnant women by time-resolved fluoroimmunoassay.

We have developed a simple and rapid time-resolved fluoroimmunoassay (TR-FIA) for simultaneous determination of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG) and estriol (E3) using europium and samarium ion chelate. In the proposed method, we used a combination of a 96-well microtiter plate for the AFP and hCG assay and transferable solid phase plate for the E3 assay. Therefore, these analytes could be measured simultaneously. The measurable ranges for AFP, hCG and E3 by the proposed method were 3.91-1000 ng ml(-1), 877-250000 IU l(-1) and 0.39 100 ng ml(-1), respectively. The proposed method which utilized characteristics of a rare earth ion chelate, was convenient (unnecessary diluting samples), quick (96 assays for 2 h), and required only a small quantity sample (50 microl). The principle of this proposed method is applicable to other antigens.

Antibody Specificity↗
PubMed1999

Death attributed to amobarbital and levomepromazine intoxication.

A 29-year-old man, possibly a schizophrenic patient, was found dead 9 h after admission to a hospital. Autopsy revealed neither significant injuries nor diseases except for congestion of all organs. Microscopic examination revealed severe edema in the lung and slight centrilobular necrosis in the liver. Since amobarbital and levomepromazine were detected by drug screening, the concentrations of these drugs in the victim's body fluids and tissues were determined using gas chromatography-mass spectrometry. The whole blood concentrations of amobarbital and levomepromazine were 9.02 microg/ml and 231 ng/ml, respectively. These levels exceeded therapeutic ranges, but are not so toxic or fatal. However, on the basis of the findings in the literature and of the severe lung edema and centrilobular necrosis in the liver, the cause of his death was judged to be amobarbital and levomepromazine intoxication.

Journal Article↗
PubMed1999

Sudden unexpected death following stellate ganglion block.

A 29-year-old woman, who had been suffering from left facial palsy, died 3.5 hours after undergoing stellate ganglion block (SGB). Autopsy revealed subcutaneous emphysema of the body, bilateral pneumothorax and a huge post-tracheal hematoma. The lower half of the trachea was markedly flattened by pressure from this hematoma. The cause of death was certified as airway obstruction due to a post-tracheal hematoma following SGB. The doctor cut both the anterior and the posterior wall of the trachea, because the trachea was flattened by the hematoma. He then intubated and sent air into the post-tracheal space. We consider that the patient could have recovered if she had received the correct tracheotomy. We therefore conclude that there was professional error on the part of the doctor in the form of medical malpractice.

Journal Article↗
PubMed1999

Structural characterization of substrates for the anion exchange transporter in Caco-2 cells.

The present study was conducted to characterize the structural specificity of an anion exchange transporter in intestinal epithelial cells. The transport of carboxylic acids with hydroxyl group(s) at the 2, 3, 4, and/or 5 positions with respect to carboxylate was examined by using Caco-2 cells in the presence of bicarbonate ions on the basolateral side to enhance the activity of the anion-exchange transporter. In the presence of the bicarbonate ion gradient, transport of L-lactic acid consisted of a saturable process and a nonsaturable process as judged from the Eadie-Hofstee plot. The transport of L-lactic acid at 1 microM was reduced by sodium azide, dinitrophenol, and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). It was also reduced by 2-, 4-, and 5-hydroxycarboxylic acids such as hydroxyacetic acid, 4-hydroxybutyric acid, and 5-hydroxydecanoic acid, but not by 3-hydroxycarboxylic acids such as 3-hydroxypropionic acid and 3-hydroxybutyric acid. Transport of both 2- and 4-hydroxybutyric acids involved saturable and nonsaturable processes, whereas that of 3-hydroxybutyric acid was nonsaturable and was not inhibited by DIDS. These results indicate that 3-hydroxycarboxylic acids might not be substrates for this anion exchange transporter in intestinal epithelial cells, suggesting that the position of hydroxylation is significant for molecular recognition by the transporter.

Antiporters↗
PubMed1999

Physiologically based pharmacokinetics of digoxin in mdr1a knockout mice.

To determine the contribution of the mdr1a gene product to digoxin pharmacokinetics, we constructed a physiologically based pharmacokinetic model for digoxin in mdr1a (-/-) and mdr1a (+/+) mice. After intravenous administration, total body clearance and tissue-to-plasma concentration ratios for muscle and heart were decreased in mdr1a (-/-) mice as compared with mdr1a (+/+) mice, and in particular, the digoxin concentration in the brain was 68-fold higher than that in mdr1a (+/+) mice at 12 h. On the other hand, mdr1a gene disruption did not change the contributions of renal and bile clearances to total clearance, the plasma protein binding, or the blood-to-plasma partition coefficient. Brain concentration-time profiles in mdr1a (+/+) and mdr1a (-/-) mice showed a different pattern from those in plasma and other tissues, indicating digoxin accumulation in the brain tissue. Because there was no difference in the uptake or release of digoxin by brain tissue slices from the two types of mice, we assumed the brain tissue compartment to consist of two parts (a well-stirred part with influx and efflux clearance and an accumulative part). Simulation with this model gave excellent agreement with observation when active efflux clearance across the blood-brain barrier was assumed to be zero in mdr1a (-/-) mice. The observations in other tissues in both types of mice were also well simulated.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed1999

P-glycoprotein-dependent disposition kinetics of tacrolimus: studies in mdr1a knockout mice.

PURPOSE: This study was performed to evaluate the involvement of P-glycoprotein in disposition kinetics of tacrolimus (FK506), a substrate of P-glycoprotein, in the body. METHODS: The blood and tissue concentrations of FK506 after i.v. or p.o. administration (2 mg/kg) to normal and mdr1a knockout mice were measured by competitive enzyme immunoassay. RESULTS: The blood concentrations in knockout mice were significantly higher than those in normal mice. The value of the total clearance (CLtot) for knockout mice (19.3 mL/min/kg) was about 1/3 of that for normal mice (55.8 mL/min/kg)(P < 0.001), although there was no significant difference in the distribution volume at the steady-state (Vd(ss)) (about 4.6 L/kg) between both types of mice. FK506 rapidly penetrated the blood-brain barrier and the brain concentration reached a maximum, which was about 10 times higher in knockout mice than in normal mice, 1 hr after administration. The brain concentration in normal mice thereafter decreased slowly, whereas in knockout mice, an extremely high concentration was maintained for 24 hr. CONCLUSIONS: The pharmacokinetic behavior of FK506 in the tissue distribution is related with the function of P-glycoprotein encoded by the mdrla gene. The brain distribution of FK506 is dominated by the P-glycoprotein-mediated drug efflux and presumably also by the binding to FK-binding proteins (immunophilins) in the brain.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Primary systemic carnitine deficiency is caused by mutations in a gene encoding sodium ion-dependent carnitine transporter.

Primary systemic carnitine deficiency (SCD; OMIM 212140) is an autosomal recessive disorder characterized by progressive cardiomyopathy, skeletal myopathy, hypoglycaemia and hyperammonaemia. SCD has also been linked to sudden infant death syndrome. Membrane-physiological studies have suggested a defect of the carnitine transport system in the plasma membrane in SCD patients and in the mouse model, juvenile visceral steatosis. Although the responsible loci have been mapped in both human and mouse, the underlying gene has not yet been identified. Recently, we cloned and analysed the function of a novel transporter protein termed OCTN2. Our observation that OCTN2 has the ability to transport carnitine in a sodium-dependent manner prompted us to search for mutations in the gene encoding OCTN2, SLC22A5. Initially, we analysed the mouse gene and found a missense mutation in Slc22a5 in jvs mice. Biochemical analysis revealed that this mutation abrogates carnitine transport. Subsequent analysis of the human gene identified four mutations in three SCD pedigrees. Affected individuals in one family were homozygous for the deletion of a 113-bp region containing the start codon. In the second pedigree, the affected individual was shown to be a compound heterozygote for two mutations that cause a frameshift and a premature stop codon, respectively. In an affected individual belonging to a third family, we found a homozygous splice-site mutation also resulting in a premature stop codon. These mutations provide the first evidence that loss of OCTN2 function causes SCD.

Amino Acid Sequence↗
PubMed1999

A radiation hybrid map of the rat genome containing 5,255 markers.

A whole-genome radiation hybrid (RH) panel was used to construct a high-resolution map of the rat genome based on microsatellite and gene markers. These include 3,019 new microsatellite markers described here for the first time and 1,714 microsatellite markers with known genetic locations, allowing comparison and integration of maps from different sources. A robust RH framework map containing 1,030 positions ordered with odds of at least 1,000:1 has been defined as a tool for mapping these markers, and for future RH mapping in the rat. More than 500 genes which have been mapped in mouse and/or human were localized with respect to the rat RH framework, allowing the construction of detailed rat-mouse and rat-human comparative maps and illustrating the power of the RH approach for comparative mapping.

Animals↗
PubMed1999

Production of monoclonal antibody and development of enzyme-linked immunosorbent assay for kanamycin in biological matrices.

Monoclonal antibodies (MAbs) against kanamycin were prepared by using a kanamycin-bovine gamma-globulin conjugate for the immunization of mice. Splenocytes from BALB/c immunized mice were fused with P3X63Ag8U.1 myeloma cells. This resulted in two hybridoma cell lines. Fifty per cent inhibition concentrations (IC50) for the MAbs were 2 and 5 ng ml-1. One MAb (IC50 = 2 ng ml-1) was named #22 and was used to develop quantitative assays for kanamycin by means of an enzyme-linked immunosorbent assay (ELISA). The detection limit was 0.2 ng ml-1 and the standard deviations were 0.2-4.4% for intra-assay and 0.6-4.7% for inter-assay, respectively. The detection limits using peroxidase were 4 ppb in cattle milk, cattle plasma, cattle urine, swine plasma, swine urine and chicken plasma. Using the MAb #22 produced, a rapid test kit based on an immunochromatographic method was developed. The detection limits using the kit were 50 ppb in cattle milk, cattle plasma, cattle urine and chicken plasma.

Animals↗
PubMed1999

Genetic epidemiology of the carnitine transporter OCTN2 gene in a Japanese population and phenotypic characterization in Japanese pedigrees with primary systemic carnitine deficiency.

Serum free-carnitine levels were determined in 973 unrelated white collar workers in Akita, Japan. Fourteen of these participants consistently had serum free-carnitine levels below the fifth percentile (28 microM for females and 38 microM for males). The OCTN2 (organic cation transporter) gene was sequenced for these 14 subjects, for 22 subjects whose carnitine levels were below the fifth percentile in the first screening but were normal in the second measurement and in 69 individuals with normal carnitine levels for two separate measurements. Polymorphic sequences defined three major haplotypes with equal frequency. Mutations were identified in nine subjects with low carnitine levels: Trp132X (three individuals), Ser467Cys (four), Trp283Cys (one) and Met179Leu (one). In vitro expression studies in HEK cells indicated that Ser467Cys and Trp283Cys, but not Met179Leu, significantly reduced L-carnitine uptake relative to the normal control. Trp132X and Ser467Cys were associated with specific haplotypes, suggesting a founder effect. A conservative estimate of the overall prevalence of heterozygotes was 1.01% in the Akita prefecture, Japan, giving an estimated incidence of primary systemic carnitine deficiency (MIM 212140) as 1 in 40 000 births. An echocardiographic study of the families of patients with primary carnitine deficiency revealed that the heterozygotes for OCTN2 mutations were predisposed to late onset benign cardiac hypertrophy (odds ratio 15.1, 95% CI 1.39-164) compared with the wild-types. Sequencing of DNA isolated from three deceased siblings (1.5-8 years) in two families retrospectively confirmed that all three deceased subjects were homozygous for the OCTN2 mutations.

Base Sequence↗
PubMed1999

Subtilisin-like proprotein convertases, PACE4 and PC8, as well as furin, are endogenous proalbumin convertases in HepG2 cells.

Serum albumin is synthesized as a larger precursor form, proalbumin, which undergoes proteolytic processing at a dibasic site by a hepatic proprotein convertase within the secretory pathway to generate the mature form. Although furin, a member of the subtilisin-like proprotein convertase (SPC) family, was thought to be the only candidate hepatic convertase for proalbumin, SPC family members other than furin were recently suggested to also be involved in proalbumin processing. This study was designed to identify the endogenous proprotein convertases involved in proalbumin processing. Since human hepatoma HepG2 cells are highly differentiated and produce major plasma proteins, this cell line was used as a model for hepatocytes. Northern blot analysis revealed that PACE4, furin and PC8 of the SPC family were expressed in HepG2 cells as well as in the liver. Ribonuclease protection assay showed that PACE4A-II mRNA is the major transcript in HepG2 cells among the PACE4 isoforms. The coexpression studies showed that furin, PACE4A-II and PC8 were all able to convert proalbumin to albumin correctly. To elucidate the roles of these endogenous SPC family members in proalbumin processing, the antisense RNA for PACE4, furin and PC8 was stably expressed in HepG2 cells, respectively. The expression of each antisense RNA resulted in approximately 30% inhibition of endogenous proalbumin processing. We therefore concluded that PACE4 and PC8, as well as furin, are involved in the processing of proalbumin in HepG2 cells, and that these SPC family members are functionally redundant in this processing.

Furin↗
PubMed1999

Human subtilisin-like proprotein convertase, PACE4 (SPC4) gene expression is highly regulated through E-box elements in HepG2 and GH4C1 cells.

PACE4 (SPC4) is a member of the mammalian subtilisin-like proprotein convertase (SPC) family, which participates in maturation of precursor proteins. PACE4 is expressed at high levels in the anterior pituitary, central nervous system, the developing olfactory bulb, heart, and liver. Recently, we determined the gene structure of human PACE4. [Tsuji et al. (1997) J. Biochem. 122, 438-452]. The 5'-flanking region of PACE4 gene contains 12 E-boxes (E1 to E12) within 1 kb upstream of the transcription initiation site. To examine the function of these E-box elements in the regulation of PACE4 expression, deletion and mutation constructs of the 5'-flanking region were ligated to the luciferase gene and analyzed for promoter activity in HepG2 and GH4C1 cells, which express PACE4 at high level. Some differences were observed in the activity of each promoter construct between HepG2 and GH4C1 cells, although the overall profiles of activity for the promoter fragment series were similar regardless of cell type. We showed that the basal promoter activity of the PACE4 gene is first determined by sequences lying between -315 and -1 bp and further regulated by positive and negative elements in the upstream region. Site-directed mutagenesis of E-boxes in these regulatory elements showed that the E10 E-box act as positive regulator, whereas an E-box cluster (E4-E9) acts as a negative regulator in both cells. E2 E-box acts as a positive regulator only in HepG2 cells. Other E-boxes (E1, E3, and E12) had no effect on the promoter activity. These results indicate that E-box elements play a critical role in controlling PACE4 expression in HepG2 and GH4C1 cells and that PACE4 expression is regulated by a mechanism distinct from that of other SPC family proteases.

Base Sequence↗
PubMed1999

Inactivation of proprotein convertase, PACE4, by alpha1-antitrypsin Portland (alpha1-PDX), a blocker of proteolytic activation of bone morphogenetic protein during embryogenesis: evidence that PACE4 is able to form an SDS-stable acyl intermediate with alpha1-PDX.

PACE4 (SPC4), a member of the subtilisin-like proprotein convertase (SPC) family of proteases that cleave at paired basic amino acids, exhibits a dynamic expression pattern during embryogenesis and colocalizes with bone morphogenetic proteins (BMPs). Recently Cui et al. reported that the ectopic expression of alpha1-antitrypsin variant Portland (alpha1-PDX), an engineered serpin that contains the minimal SPC consensus motif in its reactive loop, blocks the proteolytic activation of BMP4, leading to abnormal embryogenic development [Cui, Y. et al. (1998) EMBO J. 17, 4735-4743]. TGFbeta-related factors such as BMPs are synthesized as inactive precursors and activated by limited proteolysis at multibasic amino acids. Therefore, an alpha1-PDX-inhibitable protease is thought to participate in BMP activation. However, conflicting properties, including sensitivity to alpha1-PDX, have been reported for PACE4. In this study, we examined whether alpha1-PDX is responsible for the inhibition of PACE4 by measuring the protease/inhibitor complex directly. Here we show that alpha1-PDX has the ability to form an SDS-stable acyl-intermediate (180 kDa) with PACE4 in vivo and in vitro. Further, we characterized the PACE4 secreted into the culture medium from Cos-1 cells by a specific immunological assay. An alpha1-PDX-insensitive and decanoyl-RVKR-chloromethylketone-sensitive 60-kDa protease(s) is greatly activated in conditioned medium by PACE4 overexpression, suggesting that the activation of an unknown protease(s) other than PACE4 is the cause of the variation in the properties of PACE4. PACE4 is a Ca(2+)-dependent protease with an optimal Ca(2+) requirement of 2 mM, and shows its highest activity at weakly basic pH. PACE4 activity is completely inhibited by EDTA and EGTA, but not by leupeptin. These results show that PACE4 activity can be inhibited by alpha1-PDX as well as furin (SPC1) and suggest that the inhibition of PACE4-mediated activation of factors such as BMPs by alpha1-PDX causes abnormal embryogenic development.

Animals↗