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Biomedical subjects

F Marumo

Publications and source records attributed to F Marumo.

At least 127 records · Page 7Linked to original sources
PubMed1998

Calcium-dependent epidermal growth factor receptor transactivation mediates the angiotensin II-induced mitogen-activated protein kinase activation in vascular smooth muscle cells.

We have recently reported that angiotensin II (Ang II)-induced mitogen-activated protein kinase (MAPK) activation is mainly mediated by Ca2+-dependent activation of a protein tyrosine kinase through Gq-coupled Ang II type 1 receptor in cultured rat vascular smooth muscle cells (VSMC). In the present study, we found Ang II rapidly induced the tyrosine phosphorylation of the epidermal growth factor (EGF) receptor and its association with Shc and Grb2. These reactions were inhibited by the EGF receptor kinase inhibitor, AG1478. The Ang II-induced phosphorylation of the EGF receptor was mimicked by a Ca2+ ionophore and completely inhibited by an intracellular Ca2+ chelator. Thus, AG1478 abolished the MAPK activation induced by Ang II, a Ca2+ ionophore as well as EGF but not by a phorbol ester or platelet-derived growth factor-BB in the VSMC. Moreover, Ang II induced association of EGF receptor with catalytically active c-Src. This reaction was not affected by AG1478. These data indicate that Ang II induces Ca2+-dependent transactivation of the EGF receptor which serves as a scaffold for pre-activated c-Src and for downstream adaptors, leading to MAPK activation in VSMC.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Levels of soluble Fas in patients with myocarditis, heart failure of unknown origin, and in healthy volunteers.

This study showed that serum levels of sFas were elevated in patients with myocarditis, and that this elevation was correlated with sIL-2R level as a marker of T-cell activation. Therefore, sFas levels may be associated with T-cell activation in patients with myocarditis, and elevation of sFas may inhibit apoptosis in activated T cells, leading to persistent cell-mediated destruction of myocytes in myocarditis.

Adult↗
PubMed1998

Cloning and functional expression of a new aquaporin (AQP9) abundantly expressed in the peripheral leukocytes permeable to water and urea, but not to glycerol.

A new member (AQP9) of the aquaporin family was identified from human leukocytes by homology cloning using PCR. A full length clone was obtained by screening human liver cDNA library. AQP9 encodes a 295-amino-acid protein with the amino acid sequence identity with AQP3 (48%), AQP7 (45%), and other aquaporins (approximately 30%), suggesting that AQP3, AQP7, and AQP9 belong to a subfamily of the aquaporin family. Injection of AQP9-cRNA into Xenopus oocytes stimulated the osmotic water permeability 7-folds with a low activation energy (4.2 kcal/mol) which was inhibited by 0.3 mM mercury chloride by 48%. AQP9 also facilitated urea transport 4-folds. However, in contrast to AQP3 and AQP7, AQP9 did not stimulate the glycerol permeability, suggesting a unique permeability character. Northern blot analysis revealed the high expression of 3.5-kb messages in peripheral leukocytes >> liver > lung = spleen, but not in thymus. The possible role of AQP9 in the immunological function of leukocytes is intriguing and the identification of AQP9 with unique permeability profile may expand our understanding of water and small solute transport in the body.

Amino Acid Sequence↗
PubMed1998

Mutations in the interferon-sensitivity determining region of hepatitis C virus and transcriptional activity of the nonstructural region 5A protein.

Amino acid (aa) mutations in the interferon-sensitivity determining region (ISDR) (aa position 237-276 of the nonstructural region 5A [NS5A] protein consisting of 447 amino acids) of hepatitis C virus (HCV) are related to increased interferon sensitivity and low viral load, but its mechanism has not been clarified. Recently, the NS5A protein has been reported to have a transcriptional activation function, like other viral transactivator proteins known to repress interferon-induced gene expression, and the ISDR overlaps one of the acidic amino acid regions, putative domains conferring this activity. In the present study, we investigated the transcriptional activation function of the ISDR itself and the effect of amino acid mutations in the ISDR on this activity. The full-length or truncated NS5A cDNA with different ISDR sequences was cloned into a yeast or mammalian expression vector to form a fusion protein consisting of the GAL4 DNA-binding domain (GAL4-DBD) and NS5A protein. Following transfection, the transcriptional activities of these constructs were determined using beta-galactosidase (yeast) or chloramphenicol acetyltransferase (CAT) (mammalian cell) reporter gene expression under the control of GAL4 binding sites. In yeast, both the full-length sequence of NS5A-R (a clone with one aa mutation in the ISDR) and NS5A-S (a derivative of NS5A-R with six aa mutations in the ISDR) had no distinguishable transcriptional activity, whereas an amino-terminal deletion construct of NS5A-R (aa position 228-447) lacking 227 aa, showed remarkable activity with the relative value of 117.0 over that of the backbone vector. The same deletion mutant of NS5A-S produced five times higher activity with the relative value of 575.0, indicating that aa mutations in the ISDR profoundly affect this transcriptional activity. In a hepatoma cell line, HuH-7, the transcriptional activity was more prominent with a construct consisting of only the ISDR and short flanking sequences (aa 228-284) than larger deletion constructs of NS5A-R. Analysis using six different ISDR clones revealed that different mutations enhanced this activity to various extent compared with the wild-type ISDR. In particular, site-directed mutagenesis targeted to the aa position 252 showed that this aa residue had profound influence on the activity. These results suggest that the ISDR has a transcriptional activity, and it is enhanced by aa mutations that are also related to decreased viral load and increased interferon sensitivity. The possible association between transcriptional activation and interferon sensitivity or viral replication should be studied further.

Amino Acid Sequence↗
PubMed1998

Skeletal and smooth muscle alpha-actin mRNA in endomyocardial biopsy samples of dilated cardiomyopathy patients.

Skeletal or smooth muscle alpha-actin isoform is reexpressed in hypertrophied or failing heart in experimental animals, however, it has been unknown whether there is a switching of these genes in the human heart. In this study, we assessed alpha-actin isoform mRNA in biopsied specimens from the left ventricle of patients with dilated cardiomyopathy (DCM). The biopsy was performed in 21 patients (DCM; 16, normal; 5). Skeletal and smooth muscle alpha-actin mRNA levels were assessed by quantitative reverse transcriptase-polymerase chain reaction using a synthetic RNA as internal control. The level of both alpha-actin mRNAs correlated well with the mean cardiomyocyte diameter as an index of cardiac hypertrophy. Further, there was a clear correlation between the expression of skeletal alpha-actin mRNA or smooth muscle alpha-actin mRNA and the ejection fraction. These results suggested that mRNAs for skeletal and smooth muscle alpha-actin isoforms are increased in the hypertrophic and/or failing heart. These mRNAs may be an useful marker for the pathological state of cardiomyopathy.

Actins↗
PubMed1998

Flow cytometric method to detect lymphocyte transformation in drug-allergic hepatic injury.

Flow cytometric methods for the analysis of incorporated bromodeoxyuridine are extremely rapid and simple. We investigated whether these methods were useful for detecting drug-allergic hepatic injury in 18 patients with drug-allergic hepatic injury, 18 healthy controls, and 9 nonallergic patients receiving drugs. Peripheral blood mononuclear cells were stimulated with drug solutions. Incorporation of bromodeoxyuridine was detected after labeling with FITC, and S-phase cells were counted by flow cytometry. Percentages of S-phase cells in drug-stimulated culture minus those in spontaneous cultures were less than 1% in both healthy controls and nonallergic patients receiving drugs. Taking 1% as the upper limit, 13 patients (72%) were judged as positive. After the in vitro addition of interleukin-2, two patients among five who had been judged as negative were judged as positive. Lymphocyte transformation test by flow cytometry may be useful in the diagnosis of drug-allergic hepatic injury.

Case-Control Studies↗
PubMed1998

Cyclin D1, p16, and retinoblastoma gene regulate mitogenic signaling of endothelin in rat mesangial cells.

To elucidate the mechanisms by which endothelin (ET)-1 induces proliferation of mesangial cells, we investigated the involvement of the first gap phase of the cell cycle (G1) cyclin, cyclin-dependent kinase 4 (CDK4) activity, and the retinoblastoma gene product (pRb) in ET-1-stimulated cell cycle progression. In the present study, ET-1 stimulated CDK4 activity and cell cycle progression via ET A-type receptors and induced cyclin D1 mRNA and protein expression in rat mesangial cells. We also found that ET-1 stimulation of mesangial cell proliferation was inhibited by antisense oligonucleotides directed against cyclin D1 and by overexpression of a nonphosphorylatable form of pRb. To investigate the functional roles of p16INK4 and p21cip1 in ET-1-stimulated mesangial cell proliferation, we used adenovirus-mediated gene transfer. Endothelin-1-stimulated [3H]-thymidine incorporation, CDK4 kinase activity, and the percent of cells in S phase were found to be significantly inhibited by overexpression of p16INK4 and slightly inhibited by overexpression of p21cip1. Thus, ET-1 induced cyclin D1 expression and stimulated CDK4 activity and cell cycle progression via the A-type receptor in rat mesangial cells. These effects were regulated by the expression of cyclin D1, p16INK4, p21cip1, and phosphorylatable form of pRb. The results of the present study provide the basis for further investigation of basic and therapeutic approaches towards mesangial proliferative diseases.

Animals↗
PubMed1998

Controlled trial of falecalcitriol versus alfacalcidol in suppression of parathyroid hormone in hemodialysis patients with secondary hyperparathyroidism.

Active vitamin D3 is extensively used for the treatment of secondary hyperparathyroidism in hemodialysis patients. But it is often impossible to administer enough dose to suppress parathyroid hormone (PTH) level, because of hypercalcemia and hyperphosphatemia. New modalities with higher specificity for PTH suppression are desirable. We conducted a crossover comparative study of falecalcitriol, an active vitamin D3 analog, and alfacalcidol (1alpha[OH]D3). In this study, 25 hemodialysis patients with moderate to severe secondary hyperparathyroidism who had normal serum calcium levels were enrolled. They received daily oral doses of alfacalcidol during an 8-week observation period. Based on serum calcium levels and intact PTH, the subjects were allocated into two groups, and a comparative study was conducted using unmasked crossover design of two drugs x two periods. The dosage of both drugs was adjusted to maintain the initial serum calcium levels, and the relative change (%change) of serum biochemical parameters were compared. Comparison of two drugs in period 1 was taken as primary efficacy evaluation. Reproducibility of drug action was confirmed by comparing the effect of falecalcitriol between period 1 and 2. The percent change of PTH of falecalcitriol was lower than that of alfacalcidol: Those were, respectively, -7.89% and +30.42% for c-terminal PTH (P = 0.022), -4.39% and +38.88% for i-PTH (P = 0.077), and +3.68% and +30.52% for midregion PTH (P = 0.099). The similar changes were observed in the falecalcitriol group during period 2, confirming the reproducibility. Falecalcitriol was found to be superior to alfacalcidol in suppression of PTH levels in patients with moderate to severe secondary hyperparathyroidism when it is administered in equivalent doses that might maintain similar serum calcium levels.

Adult↗
PubMed1998

Cyclins and the cyclin-kinase system--their potential roles in nephrology.

Our understanding of the cell-cycle mechanisms has progressively advanced in the past few years. Cyclins and cyclin-dependent kinases play major roles as positive cell-cycle regulatory proteins and CDK inhibitors; while the Kip family and INK4 family are negative regulatory proteins in mesangial cells and renal tubular cells. An understanding of the cell cycle is essential for the rational design of novel pharmacotherapeutic approaches to suppress the excessive proliferation of mesangial cells in glomerular disease and hypertrophic tubular disease.

Animals↗
PubMed1998

Endothelin-B receptor-mediated suppression of endothelial apoptosis.

Endothelin (ET)-1 is an endothelium-derived vasoconstrictor as well as a mitogen. We have recently described a novel role of ET-1 as a survival factor for rat endothelial cells from serum deprivation-induced apoptosis. The present study was designed to determine which receptor subtype (ETA or ETB) is responsible for and what intracellular mediators are involved in endothelial apoptosis. Apoptotic cell death was evaluated by nucleosomal ladders on agarose gel electrophoresis and immunohistochemical study using anti-single-stranded DNA antiserum. ET-1 and an ETB receptor agonist suppressed endothelial apoptosis, whose effects were abrogated by an ETB receptor antagonist but not by an ETA receptor antagonist. Addition of an ETB receptor antagonist or nonselective ETA/B receptor antagonists, but not an ETA receptor antagonist, enhanced the apoptotic events caused by serum deprivation, suggesting an autocrine/paracrine role of endogenous ET-1 in protecting against endothelial apoptosis. The effect of ET-1 in suppressing apoptosis was unaffected by any of the following reagents: a phospholipase C inhibitor (U73122), a tyrosine kinase inhibitor (ST638), an MEK inhibitor (PD98059), a phosphatidylinositol-3 kinase inhibitors (wortmannin, LY294002). Taken together, these results confirm a role for ET-1 as an autocrine/paracrine survival factor for rat endothelial cells, in which neither phospholipase C, tyrosine kinase, MAP kinase, nor phosphatidylinositol-3 kinase is involved in mediating the antiapoptotic effect of ET-1.

Animals↗
PubMed1998

Endothelin-1 stimulates DNA synthesis of vascular smooth-muscle cells through transactivation of epidermal growth factor receptor.

To elucidate the molecular mechanism of the mitogenic effect of endothelin-1 (ET-1) on vascular smooth-muscle cells (VSMCs), we studied the effect of AG1478, a novel epidermal growth factor receptor (EGFR) kinase inhibitor, on p42/44 mitogen-activated protein (MAP) kinase activation, c-Fos expression, and DNA synthesis stimulated by ET-1. AG1478 dose-dependently (2.5 x 10(-8) M-2.5 x 10(-7) M) inhibited ET-1-induced MAP kinase activation. The ET-1-induced c-Fos protein expression was inhibited by AG1478 (2.5 x 10(-7) M). AG1478 also dose-dependently inhibited ET-1-stimulated [3H]thymidine incorporation. These data suggest that ET-1 induces MAP kinase activation, c-Fos expression, and promotes proliferation of VSMCs via transactivation of EGFR.

Animals↗
PubMed1998

Delayed kinetics of oxygen uptake during recovery after exercise in cardiac patients.

PURPOSE: Little is known about cardiovascular responses during recovery from exercise in patients with cardiovascular disease. The aim of this study was to determine the time constants of the kinetics of oxygen uptake and heart rate during recovery from exercise and to evaluate the influence of resting cardiac function on these kinetics in patients with left ventricular dysfunction. METHODS: A moderate exercise test was performed by 40 patients (57+/-10 yr old) with prior myocardial infarction at a constant work rate (40+/-8 W) for 6 min on a cycle ergometer. The time constants of oxygen uptake and heart rate during 6 min of recovery were compared in patients whose left ventricular ejection fractions were > or =35% (group 1, N = 20) and those with ejection fractions <35% (group 2, N = 20). RESULTS: The time constant of the decrease in oxygen uptake during exercise recovery was significantly prolonged (oxygen requirement was increased) in group 2 compared with group 1. Heart rate during recovery was consistently higher, and its time constant was prolonged in group 2 compared with group 1. The time constant of oxygen uptake was positively correlated with the time constant of heart rate. CONCLUSION: The recovery of oxygen uptake after exercise was significantly delayed, associated with delayed recovery of heart rate, in patients with severely impaired left ventricular function.

Aged↗
PubMed1998

Effects of isosorbide dinitrate on oxygen uptake kinetics in cardiac patients.

PURPOSE: Although nitrates are known to improve indices of exercise capacity in patients with coronary artery disease, their effects on oxygen uptake kinetics during the onset of exercise have not been clarified. We evaluated the acute effects of isosorbide dinitrate on the kinetics of oxygen uptake during the onset of exercise at a constant work rate in patients with coronary artery disease. METHODS: We studied 14 patients with coronary artery disease who performed 6 min of low-intensity exercise at a constant work rate on a cycle ergometer 30 min after oral administration of 10 mg of isosorbide dinitrate or placebo in a double-blind, crossover manner. Oxygen uptake was calculated from breath-by-breath analysis of respired gases. The time constant of oxygen uptake kinetics during the onset of exercise was determined by fitting a single exponential function to the oxygen uptake response. RESULTS: Heart rate was significantly increased at rest, and systolic blood pressure was significantly decreased both at rest and during exercise after administration of isosorbide dinitrate. The time constant of oxygen uptake was significantly shorter (the kinetics were faster) after administration of isosorbide dinitrate (39.4+/-10.1 vs 44.5+/-10.5 s, P = 0.038). CONCLUSIONS: Isosorbide dinitrate was found to speed the kinetics of the increase in oxygen uptake during constant work-rate exercise. The time constant of oxygen uptake, which reflects the rapidity of cardiovascular adaptation at the onset of exercise, seems to be a useful parameter of the effectiveness of therapy in patients with coronary artery disease.

Adult↗
PubMed1998

High energy radiofrequency catheter ablation for common atrial flutter targeting the isthmus between the inferior vena cava and tricuspid valve annulus using a super long tip electrode.

There have been controversies concerning the optimal target sites and approaches in radiofrequency catheter ablation of common atrial flutter. We attempted high energy radiofrequency catheter ablation targeting the isthmus between the inferior vena cava and tricuspid valve annulus (IVC-TV isthmus) with a super long (8 mm) tip electrode, and compared the efficacy of this anatomical approach with the electrophysiological approach targeting the posteroseptal right atrium posterior to the coronary sinus using a standard 4-mm tip electrode. Atrial flutter was successfully ablated in 12 of 12 patients (100%) without recurrence with the anatomical approach, while, in 7 of 9 patients (64%) with 2 recurrences with the electrophysiological approach. In comparison of ablation data between the anatomical and electrophysiological approaches, there were significant differences in the mean number of application pulses (anatomical vs electrophysiological: 2.3 +/- 0.8 vs 9.9 +/- 6.4, P < 0.01), applied wattage (39 +/- 12 W vs 24 +/- 6 W, P < 0.01), applied energy per application (1,986 +/- 426 J vs 659 +/- 323 J, P < 0.01), fluoroscopic time (26 +/- 11 min vs 74 +/- 30 minutes, P < 0.01), and procedure time (59 +/- 8 min vs 181 +/- 53 min, P < 0.01). In conclusion, the anatomical approach is superior to the electrophysiological one with respect to procedure and radiation time, and linear ablation at the IVC-TV isthmus with an 8-mm tip electrode and high energy application is highly effective and safe.

Aged↗
PubMed1998

Retrograde multiple and multifiber accessory pathway conduction in the Wolff-Parkinson-White syndrome: potential precipitating factor of atrial fibrillation.

INTRODUCTION: The determinants of susceptibility to atrial fibrillation (AF) and the existence of accessory pathway conduction have remained unidentified in the Wolff-Parkinson-White (WPW) syndrome. We tested the hypothesis that excitation inputs into the atrium over a retrograde multiple or multifiber accessory pathway during AV reentrant tachycardia (AVRT) could precipitate initiation of AF. METHODS AND RESULTS: Two hundred fifty consecutive patients with WPW syndrome underwent electrophysiologic study and radiofrequency catheter ablation. The patients were classified into two groups according to the study results: 29 with retrograde multiple or multifiber accessory pathway (MP) and 221 with retrograde single accessory pathway (SP). Compared with the SP patients, the MP patients showed a significantly higher incidence of clinical AF (MP vs SP: 19/29 vs 51/221, P < 0.01), induced AF (12/29 vs 32/221, P < 0.01), and initiated AF during ventricular pacing and AVRT (10/12 vs 17/32, P < 0.05). There were no differences between the two groups in incidence of clinical and induced AVRT (24/29 vs 200/221 and 25/29 vs 206/221, respectively), mean cycle length of induced AVRT, or electrophysiologic parameters of the accessory pathway. AF inducibility during AVRT or ventricular pacing was eliminated by partial ablation in 7 of 10 patients with MP. After total ablation, the incidence of induced AF was similar between the two groups (MP vs SP: 1/29 vs 11/221). CONCLUSION: The existence of a retrograde multiple or multifiber accessory pathway in patients with WPW syndrome is associated with a higher incidence of clinical and induced AF. Successful ablation of the retrograde multiple or multifiber accessory pathway can eliminate the induction of both AVRT and AF.

Adult↗
PubMed1998

Aquaporin-2 and -3: representatives of two subgroups of the aquaporin family colocalized in the kidney collecting duct.

Since the molecular identification of the first aquaporin in 1992, the number of proteins known to belong to this family has been rapidly increasing. These members may be separated into two subgroups based on gene structure, sequence homology, and function. Regulation of the water permeability of the collecting ducts of the kidney is essential for urinary concentration. Aquaporin-2 and -3, which are representative of these subgroups, are colocalized in the collecting ducts. Understanding these subgroups will elucidate the differences between aquaporin-2 and -3. Aquaporin-2 is a vasopressin-regulated water channel located in the apical membrane, and aquaporin-3 is a constitutive water channel located in the basolateral membrane. In contrast to aquaporin-3, which appears to be less well regulated, many studies have now identified multiple regulational mechanisms at the gene, protein, and cell levels for aquaporin-2, thus reflecting its physiological importance. Evidence of the participation of aquaporin-2 in the pathophysiology of water-balance disorders is accumulating.

Amino Acid Sequence↗
PubMed1998

A water channel of the nematode C. elegans and its implications for channel selectivity of MIP proteins.

A genome project focusing on the nematode Caenorhabditis elegans has demonstrated the presence of eight cDNAs belonging to the major intrinsic protein superfamily. We functionally characterized one of these cDNAs named C01G6.1. Injection of C01G6.1 cRNA increased the osmotic water permeability (Pf) of Xenopus oocytes 11-fold and the urea permeability 4.5-fold but failed to increase the glycerol permeability. It has been speculated that the MIP family may be separated into two large subfamilies based on the presence or absence of two segments of extra amino acid residues ( approximately 15 amino acids) at the second and third extracellular loops. Because C01G6.1 (designated AQP-CE1), AQP3, and glycerol facilitator (GlpF) all have these two segments, we replaced the segments of AQP-CE1 with those of AQP3 and GlpF to identify their roles. The functional characteristics of these mutants were principally similar to that of wild-type AQP-CE1, although the values of Pf and urea permeability were decreased by 39-74% and 28-65%, respectively. These results suggest that the two segments of extra amino acid residues may not contribute to channel selectivity or formation of the route for small solutes.

Amino Acid Sequence↗