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Biomedical subjects

F Marumo

Publications and source records attributed to F Marumo.

At least 109 records · Page 6Linked to original sources
PubMed1999

Induction of max by adrenomedullin and calcitonin gene-related peptide antagonizes endothelial apoptosis.

Adrenomedullin is a novel vasodilatory peptide originally isolated from pheochromocytoma. Recently, we found that adrenomedullin acts as an autocrine/paracrine apoptosis survival factor for rat endothelial cells. In the present study, we show that adrenomedullin induces the expression of Max, a heterodimeric partner of c-Myc, which may contribute to its ability to rescue endothelial cells from apoptosis. Max is a basic-helix-loop-helix-leucine zipper protein that forms heterodimers with its alternative partners, Mad and Mxi-1, to behave as an antagonist for Myc-Max heterodimer through competition for common DNA targets. The expression of Max is reported to be constitutive and more stable than c-Myc, and serum induces immediate c-Myc stimulation followed by modest Max up-regulation. In quiescent rat endothelial cells, adrenomedullin stimulated the expression of Max without affecting c-Myc. Quantitation with real-time quantitative PCR detected on the ABI Prism 7700 Sequence Detection System revealed that adrenomedullin and calcitonin gene-related peptide (CGRP), as well as serum, up-regulated Max mRNA levels and that down-regulation of Max mRNA after serum deprivation was prevented by adrenomedullin. Neither adrenomedullin nor CGRP affected c-Myc expression. Transfection of a Max-expressing plasmid into endothelial cells rescued the apoptosis induced by serum deprivation. Neutralization with anti-adrenomedullin antiserum or blockade with a CGRP receptor antagonist, CGRP(8-37), reduced Max mRNA levels in growing endothelial cells and enhanced apoptosis after serum starvation. Introduction of an antisense oligodeoxynucleotide against Max mRNA using transferrin receptor-operated transfer led to inhibition of both adrenomedullin-induced up-regulation of Max transcripts and its cell survival effect, whereas random, sense, or missense oligonucleotides were without effect. The negative regulation of E-box-driven transcription by adrenomedullin was demonstrated by using preproendothelin-1 promoter containing c-Myc-Max binding consensus sequence; the promoter activity of preproendothelin-1 was reduced by cotransfecting Max- and Mad-expressing plasmids as well as addition of adrenomedullin and CGRP. The present results demonstrate that adrenomedullin antagonizes serum deprivation-induced endothelial apoptosis by up-regulation of the max gene in an autocrine/ paracrine manner.

Adrenomedullin↗
PubMed1999

Radiofrequency catheter ablation for sinoatrial node reentrant tachycardia: electrophysiologic features of ablation sites.

The aim of this study was to investigate catheter ablation of sino-atrial reentrant tachycardia (SART) and the electrophysiologic characteristics of the ablation sites. From January 1990 to October 1997, 651 patients with supraventricular tachycardia were referred and 11 patients were found to have SART. Ablation was successful in all cases with a mean number of 3.3 radiofrequency (RF) current pulses. SART terminated during 22 of 36 RF pulses. In spite of prompt termination, tachycardia could be re-induced in 3 of 11 patients with its earliest activation site shifted. At effective ablation sites, the electrograms during tachycardia were characterized as fractionated (75+/-17 ms), and 38+/-16 ms prior to surface P wave, and 42+/-18 ms prior to the high right atrium. Unipolar electrograms revealed a sharp negative unipolar deflection, so called QS pattern, in 15 of 20 sites during SART and 15 of 15 sites during sinus rhythm. During effective applications, atrial premature beats (APB) with activation sequences identical to sinus rhythm appeared in 14 of 22 cases. Effective ablation sites of SART showed fractionated electrograms during tachycardia and sinus rhythm. Unipolar electrogram with a QS pattern and APB during energy application could be an indicator of the optimal ablation sites.

Adenosine Triphosphate↗
PubMed1999

Kinetics of pulmonary gas exchange during and while recovering from exercise in patients after anterior myocardial infarction.

The effect of exercise intensity on gas exchange kinetics was investigated during exercise and recovery, as well as the relationship between the kinetics during exercise and recovery. Twenty-three patients with a history of anterior myocardial infarction performed low-intensity (38.7+/-8.3 W) and high-intensity (68.8+/-15.0 W) exercise for 6 min. The time constants of oxygen uptake (VO2), carbon dioxide output (VCO2) and minute ventilation (VE) were significantly prolonged during high intensity exercise compared with low-intensity exercise (61.2+/-8.6 vs 52.3+/-10.3 s, p<0.005 for the time constant of VO2). The time constant of VO2 was similar during exercise and during recovery from exercise of high (61.2+/-8.6 vs 66.2+/-12.2 s) as well as low intensity (52.3+/-10.3 vs 55.0+/-10.1 s). However, the time constants of VCO2 and heart rate were significantly shorter during recovery than during exercise. The time constants of VCO2 and VE were significantly longer than that of VO2 during both exercise and recovery. In the present study, it was found that (1) the gas exchange kinetics were influenced by the intensity of exercise; (2) the kinetics during recovery did not necessarily reflect the kinetics during exercise except for VO2; and (3) the kinetics of VCO2 and VE were delayed as compared with the VO2 kinetics. These characteristics should be taken into account when using gas exchange kinetics to estimate cardiopulmonary responses to exercise in patients with left ventricular dysfunction.

Adult↗
PubMed1999

Thrombolytic therapy can reduce the arrhythmogenic substrate after acute myocardial infarction: a study using the signal-averaged electrocardiogram, endocardial catheter mapping and programmed ventricular stimulation.

Thrombolytic therapy improves survival after acute myocardial infarction (AMI) primarily by preserving left ventricular function. Its influence on the arrhythmogenic substrate remains uncertain. To investigate the electrophysiologic effects of thrombolytic therapy, signal-averaged electrocardiography, endocardial catheter mapping and programmed stimulation were performed in 93 consecutive patients with their first AMI who underwent thrombolytic therapy. Early reperfusion was achieved in 75 patients (group 1), but not in 18 patients (group 2). The incidence of the signal-averaged electrocardiogram abnormality was 11% in group 1 (8 of 75 patients) and 33% in group 2 (6 of 18 patients) (p<0.02). Catheter mapping detected delayed endocardial electrograms in 30 group 1 patients and 10 group 2 patients (p=NS). The spatial distribution of these electrograms was smaller, and the longest duration of endocardial electrograms was shorter in group 1 than in group 2 (p<0.01). Sustained monomorphic ventricular tachycardia was induced less commonly in group 1 (20%) than in group 2 (44%) (p<0.05). In conclusion, thrombolytic therapy can reduce the arrhythmogenic substrate and improve electrical stability after AMI. This antiarrhythmic effect may contribute, in part, to the improved survival of patients treated with thrombolytic drugs.

Adult↗
PubMed1999

Mechanism of overshoot in cardiac function during recovery from submaximal exercise in man.

BACKGROUND: A sudden increase (overshoot) in the left ventricular ejection fraction during the recovery from maximal exercise has been reported in patients with coronary artery disease, but its mechanism has not been fully clarified. We investigated whether this phenomenon may occur in normal subjects, and whether it depends on the intensity of exercise. METHODS: Thirteen normal subjects (mean [+/- SD] age, 59 +/- 8 years old) performed two levels (25 W and 50 W) of mild-intensity, constant-work-rate exercise for 6 min on a cycle ergometer. Left ventricular function was monitored continuously during the recovery from exercise using a computerized cadmium telluride detector. RESULTS: An overshoot was observed in the ejection fraction during the first minute of recovery compared with the end-exercise value. The overshoot in the ejection fraction during recovery after the 50-W exercise was greater than that seen after the 25-W exercise. An overshoot phenomenon in stroke volume was also observed during the recovery from 50-W exercise. CONCLUSIONS: The overshoot in cardiac function observed during the early phase of recovery, which was caused mainly by an immediate decrease in end-systolic volume, occurred even after exercise of mild intensity. This phenomenon appears to suggest the existence of a transient mismatch between cardiac contractility and afterload reduction during the recovery from mild-intensity exercise, even in normal subjects.

Aged↗
PubMed1999

Inducible nitric oxide synthase can be induced in the absence of active nuclear factor-kappaB in rat mesangial cells: involvement of the Janus kinase 2 signaling pathway.

The contribution of nuclear factor-kappaB (NF-kappaB) and interferon-gamma (IFN-gamma) signaling to nitric oxide generation is not completely understood. The effect of NF-kappaB release and its inhibition on nitrite production and the involvement of Janus kinase 2 (JAK2) in inducible nitric oxide synthase (iNOS) induction were investigated. The following assays were performed. (1) Nitrite produced by rat mesangial cells in primary culture was measured in incubations with tumor necrosis factor-alpha (TNF-alpha) or lipopolysaccharide (LPS), with or without IFN-gamma. Cells were stimulated with TNF-alpha or LPS plus IFN-gamma in the presence of NF-kappaB inhibitors, herbimycin A (HerA), or the more specific JAK2 inhibitor AG490. (2) Immunoblotting was performed against the p65 and p50 subunits of NF-kappaB and iNOS. (3) Electrophoretic mobility shift assays were performed against NF-kappaB in the presence of NF-kappaB inhibitors or AG490. (4) iNOS promoter activity was measured in the presence of AG490 or JAK2 antisense oligonucleotides. TNF-alpha or LPS alone did not induce nitrite production, but with IFN-gamma these compounds did induce nitrite production. Pyrrolidine dithiocarbamate (PDTC), N-acetyl-L-cysteine, dexamethasone (Dex), HerA, and AG490 partially inhibited LPS/ IFN-gamma- or TNF-alpha/IFN-gamma-induced nitrite production. p65 was inhibited by the three NF-kappaB inhibitors described above, whereas p50 was not. PDTC and Dex completely inhibited the p65/p50 heterodimer, but HerA and AG490 had little effect on p65/p50. AG490 and JAK2 antisense oligonucleotides suppressed iNOS promoter activity. It can be concluded that (1) iNOS can be induced without active NF-kappaB; (2) Dex, acetylsalicylic acid, and PDTC inhibit only p65; and (3) JAK2 is involved in iNOS induction, and the contribution of JAK2 to nitrite production is greater than that of NF-kappaB.

Animals↗
PubMed1999

[Age-related differences in IgA nephropathy].

To clarify age-related differences in the characteristics of IgA nephropathy, we investigated 117 patients of all ages. The number of patients in the second decade of age was larger than that in the other age decades. There was no difference in sex in all age brackets. About one half of the patients under ten years of age presented as acute nephritis, but their prognosis was favorable. Patients over 10 years, most of whom were detected by chance, tended to have a greater degree of proteinuria, a lesser degree of creatinine clearance, a higher frequency of hypertension, and a higher level of serum cholesterol with age. Although the intensity of mesangial cell proliferation was not changed, the grade of glomerulosclerosis, interstitial change, and arteriosclerosis increased and the prognosis became poor as age advanced. Treatment with corticosteroids and antiplatelet agents was less effective in adults, especially in the older age brackets than in children because the frequency of histologically chronic lesions increased. In these cases, lipid-lowering agents and angiotensin-converting enzyme inhibitors may be helpful in preventing the progression.

Adolescent↗
PubMed1999

Water channel AQP-1 in the primary cell culture of rat peritoneum.

To analyze the regulation of water channels in the peritoneum, we tried to establish a primary mesothelial cell culture system. Male Sprague-Dawley rats weighing about 250 g were anesthetized, and 10 mL of phosphate-buffered saline (PBS) containing 0.25% trypsin and 1 mmol/L ethylenediamine tetraacetic acid (EDTA) was infused into the peritoneal cavity for 15 minutes. Sediments from the recovered fluid were cultured in medium M199 supplemented with 10% fetal bovine serum (FBS). The culture was succeeded 4-6 times before experiments commenced. After exposure to the test medium, RNA was extracted and subjected to reverse transcriptase polymerase chain reaction (RT-PCR) for 10-19 cycles, then was measured by Southern blot analysis with a digoxin-labeled probe. Cultured cells were positively stained with mouse monoclonal anti-cytokeratin antibody, confirming their characteristics as mesothelial cells. Aquaporin-1 (AQP-1) message in the cultured cells increased with increases in glucose and mannitol concentrations when beta-actin message was used as an internal control. Tranexamic acid effected no change in AQP-1 message in the cultured mesothelial cells. This system offers potential as a simple approach to test the effects of osmolytes, cytokines, and vasoactive hormones on aquaporin expression and water transport in the peritoneum.

Animals↗
PubMed1998

Cloning and functional expression of human aquaporin8 cDNA and analysis of its gene.

The cDNA and the gene of human aquaporin8 (AQP8) were cloned from human testis cDNA and a genomic library, respectively. The AQP8 cDNA encodes 261 amino acids. The identity of the amino acid sequence to other aquaporins is highest with a plant water channel, gamma-TIP (40.4%), while AQP2 and AQP3 are 28.9 and 29.5% identical to human AQP8, respectively. The human AQP8 is only 74.9% identical to rat AQP8 and 76.0% identical to mouse AQP8. In Northern blot analysis, approximately 1.35-kb human AQP8 mRNA was expressed in pancreas and colon, but not in other tissues. Absence of human AQP8 in testis is noteworthy as rat AQP8 was abundantly expressed in testis. The expression of human AQP8 cRNA in Xenopus oocytes increased osmotic water permeability by 10-fold. AQP8 was not permeable to urea nor to glycerol. The AQP8 gene has five introns, and the locations of exon-intron boundaries were different from those of the other mammalian aquaporins, suggesting its separate phylogenetic origin.

Amino Acid Sequence↗
PubMed1998

The Fas/Fas ligand system is involved in the pathogenesis of autoimmune myocarditis in rats.

The mechanisms responsible for myocardial injury and cell death in myocarditis are still unclear. We examined whether myocardial cell death occurs via apoptosis in myosin-induced autoimmune myocarditis in rats and whether the Fas/Fas ligand (FasL) system plays a role in this apoptosis. On days 14, 17, 21, and 35 after immunization with porcine heart myosin, some cardiomyocytes and infiltrating lymphocytes were found to be apoptotic on in situ terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay, but none was on day 60 and in control rats. Apoptotic indices peaked at day 17, and laddering of genomic DNA from the affected myocardium was observed on days 17 and 21 on agarose gel electrophoresis. The expression of Fas mRNA and protein was detected on days 17 and 21 in some cardiomyocytes and infiltrating lymphocytes by Northern blot analysis and immunohistochemistry, respectively. In addition, FasL was detected in some infiltrating lymphocytes on days 14, 17, and 21 by both in situ hybridization and immunostaining, and FasL-positive lymphocytes were mainly CD4+ cells. Some rats were injected with anti-Fas Ab (0.1 mg/kg) or anti-FasL Ab (0.1 mg/kg), and subsequently, inflammatory lesions exhibited less severe than did untreated rats with myocarditis. These findings suggest that cell death via apoptosis of cardiomyocytes and lymphocytes is one of the mechanisms of myocardial injury in autoimmune myocarditis, and that the Fas/FasL system might play a role in the induction of this apoptosis.

Acute Disease↗
PubMed1998

Transfection of inducible nitric oxide synthase gene causes apoptosis in vascular smooth muscle cells.

BACKGROUND: Excess production of nitric oxide (NO) by inducible NO synthase (iNOS) has been implicated in a variety of physiological processes including vascular remodeling. To elucidate whether endogenous NO generated by iNOS is involved in the programmed cell death (apoptosis) of the vasculature, iNOS cDNA- expressing construct was transfected into rat and human vascular smooth muscle cells (VSMCs) by lipofection. METHODS AND RESULTS: VSMCs transiently transfected with iNOS cDNA functionally expressed 130 kd iNOS protein with full catalytic activity to generate massive NO in proportion to the doses of cDNA used; its enzymatic activity as well as NO production was completely blocked by an NOS inhibitor, NG-monomethyl-L-arginine (LNMMA). Overexpression of iNOS led to a marked inhibition of DNA synthesis as well as induction of apoptosis in VSMCs. Evidence for apoptotic cell death was provided by internucleosomal DNA fragmentation by agarose gel electrophoresis, positive staining for TdT-mediated dUTP biotin nick end-labeling, and appearance of hypodiploid cells by flow cytometry analysis. Apoptosis after transfection with iNOS cDNA was abrogated by LNMMA. Transfection of iNOS cDNA caused accumulation of the tumor suppressor gene p53 but not of bcl-2, which was also blocked by LNMMA. CONCLUSIONS: These results demonstrate that massive generation of endogenous NO derived from iNOS overexpression leads to a marked apoptosis in VSMCs, thus suggesting an important role of NO as a proapoptotic factor for VSMCs in the process of vascular remodeling.

Animals↗
PubMed1998

Molecular characterization of human Aquaporin-7 gene and its chromosomal mapping.

The cDNA for the seventh mammalian aquaporin (AQP7) was isolated from rat testis, and its expression demonstrated at the tail of late spermatids (Ishibashi et al., J. Biol. Chem. 272 (1997) 20,782-20,786). Here we report the isolation of the mouse and the human AQP7 cDNA and the human AQP7 gene. The human AQP7 gene is identical with human adipose AQP (AQPap or AQP7L). The deduced amino acid sequences of human and mouse AQP7 were 68% and 79% identical to those of rat AQP7, respectively. The mouse AQP7 is 67% identical to the human AQP7. Such a lower conservation of AQP7 among species is unusual in the aquaporin family. The human AQP7 gene is composed of six exons distributing over 6.5 kb. The exon-intron boundaries are identical to those of the human AQP3 gene. The intron sizes are also similar. Moreover, chromosomal localization of AQP7 was assigned to 9p13 by fluorescent in situ hybridization, where AQP3 is also localized, suggesting that 9p13 may be another site of an aquaporin cluster.

Amino Acid Sequence↗
PubMed1998

Levels of soluble Fas ligand in myocarditis.

Serum levels of soluble Fas ligand (sFasL) increased with the severity of congestive heart failure (p <0.01), and the percentages of apoptotic myocytes detected by in situ DNA nick-end labeling were significantly higher in the patients with increased levels of sFasL than in those with normal levels of sFasL (p <0.05). These findings indicated that sFasL may play an important role in pathogenesis of myocarditis.

Adult↗
PubMed1998

Down-regulation of adenylate cyclase coupled to adrenomedullin receptor in vascular smooth muscle cells.

Adrenomedullin activates receptor-mediated adenylate cyclase to cause vasorelaxation. To elucidate whether desensitization of adenylate cyclase coupled to vascular adrenomedullin receptors occurs, we studied the adenylate cyclase activity after treatment with rat adrenomedullin in cultured rat aortic vascular smooth muscle cells. Cyclic AMP (cAMP) generation induced by adrenomedullin was markedly decreased by pretreatment with adrenomedullin: a maximal reduction (approximately 80%) was induced after 2 h and persisted during 24 h. Desensitization was independent of protein kinase A, protein kinase C, protein tyrosine kinase or receptor sequestration, because pretreatment with either isoproterenol, forskolin, tetradecanoylphorbol acetate, cytochalasin D, or colchicine did not affect the adrenomedullin-stimulated cAMP response. Furthermore, preincubation with inhibitors for these protein kinases prior to pretreatment with adrenomedullin failed to affect the adrenomedullin-induced decrease in cAMP response following the second stimulation with adrenomedullin. The present results provide the evidence for the existence of desensitization of adenylate cyclase coupled to vascular adrenomedullin receptors.

Adenylyl Cyclases↗
PubMed1998

Molecular cloning of a new sodium bicarbonate cotransporter cDNA from human retina.

Sodium bicarbonate cotransport is an electrogenic process and a principal regulator of pH. A recently cloned sodium bicarbonate cotransporter (NBC1) is predominantly expressed in kidney. The presence of several isoforms is suggested from functional studies. We have cloned a new member of this family from human retina, which was named hNBC2 (for human sodium bicarbonate cotransporter 2). The hNBC2 has 1018 amino acid residues with 10 hydrophobic transmembrane domains. A cluster of five N-glycosylation sites is present at the second extracellular loop. It has 53% amino acids identity with hNBC1 and 38% identity with anion exchanger 1. Thus, NBC2 is a new member of the anion exchanger superfamily. Northern blot of human tissues revealed its expression in many tissues such as testis, spleen, ovary, small intestine, colon, thymus, heart, and muscle (8.5 kb). The predominant expression at retina was documented with Northern blot of rat tissues. NBC2 may be a major regulator of extracellular pH of retina where light stimulation produces an extracellular alkalization and may contribute as a solute transporter to the prevention of retinal detachment.

Amino Acid Sequence↗
PubMed1998

Expression of connexin32 and connexin43 gap junction proteins and E-cadherin in human lung cancer.

We used immunohistochemical staining to examine the expression of the gap junction proteins connexin32 and connexin43 and of the intercellular adhesion molecule, E-cadherin, that is thought to be a prerequisite for gap junctional intercellular communication (GJIC), in 24 specimens of human lung cancer. Connexin32 was not found in cancer tissue and there were significantly fewer spots of connexin43 in the poorly differentiated versus the well differentiated (P = 0.0005) and moderately differentiated (P = 0.0002) adenocarcinomas and in the poorly differentiated versus the well differentiated (P = 0.0182) and moderately differentiated (P = 0.004) squamous cell carcinomas of the lung. E-Cadherin was expressed in all but three cases of poorly differentiated non-small cell lung cancer that showed a heterogeneously decreased expression of E-cadherin. These findings suggest that GJIC is decreased in poorly differentiated non-small cell lung cancer.

Adenocarcinoma↗
PubMed1998

Molecular cloning of a DEG/ENaC sodium channel cDNA from human testis.

The number of members of the recently defined DEG/ENaC sodium channel superfamily is increasing. Their importance in Na transport, taste perception, acid sensing, and mechanotransduction has been implicated. We have cloned a new member of this superfamily from human testis, which was named hTNaC1 (for human testis sodium channel 1). The hTNaC1 has 532 amino acid residues with two hydrophobic transmembrane domains. It has the highest identity (82%) with a rat H(+)-gated Na channel specific for sensory neurons (DRASIC) and a low identity (29%) with an epithelial isoform (alpha-ENaC) of this superfamily. Northern blot of human tissues revealed its selective expression in testis (7 kb) and absence in other tissues. The identification of a new member of Na channel specifically expressed in testis will expand the role of this channel family to the reproduction physiology.

Acid Sensing Ion Channels↗