Biomedical subjects

F Marumo

Publications and source records attributed to F Marumo.

At least 181 records · Page 10Linked to original sources

PubMed1997

Alteration in water channel AQP-2 by removal of AVP stimulation in collecting duct cells of dehydrated rats.

Dehydration increased the expression of aquaporin of collecting duct (AQP-2) and translocated AQP-2 to the apical plasma membranes from cytoplasmic vesicles of collecting duct cells. We determined whether the abrupt decrease in circulating arginine vasopressin (AVP) by giving excess water affects the expression of AQP-2 mRNA and subcellular localization of AQP-2 in collecting duct cells of the dehydrated rats. The 72-h water deprivation increased plasma AVP levels to 3.1 pg/ml and the expression of AQP-2 mRNA by 336% in rats, which were concomitantly abolished by the 40 ml/kg oral water load. A 50% inhibition ofAQP-2 mRNA expression was obtained with 20 min after the forced water load. In immunohistochemistry and electron microscopy, the AQP-2 was manifestly present around the apical edge of collecting duct cells in the 72-h dehydrated rats. The AQP-2 was diffusely translocated into the cytoplasm 1 h after the forced water administration. These results indicate that AVP plays the on-off regulation of AQP-2 mRNA expression and that a majority of AQP-2 is regulated by the shuttle recycling in the collecting duct cells.

Animals↗

PubMed1997

Expression of AQP family in rat kidneys during development and maturation.

The mRNA expression and localization of the aquaporin (AQP) family in rat kidney were examined by ribonuclease protection assay and immunohistochemistry. AQP1, AQP2, AQP3, and AQP4 mRNA were hardly detectable in 16-day gestation fetuses. AQP1 mRNA was explosively expressed at 1 wk, keeping the level throughout life. AQP2 mRNA expression was apparently noticed in 18-day fetuses and was enhanced gradually with age to reach a plateau at 4 wk. AQP3 and AQP4 mRNA expression was significantly found at birth but was not changed remarkably thereafter. AQP2 protein appeared first at the apical side of collecting duct cells in 18-day fetuses. The staining intensity at the site increased with age, and basolateral staining was added in adult rats. AQP3 was distinctly demonstrated at the basolateral side of collecting duct cells after birth, and the staining intensity was almost stable throughout life. The progressive induction of AQP2 expression in the first 4 wk after birth is presumed to contribute to the maturation of urinary concentrating capacity during the kidney development.

Aging↗

PubMed1997

Immunolocalization and effect of dehydration on AQP3, a basolateral water channel of kidney collecting ducts.

Aquaporin-3 (AQP3) is unique in its structure (lowest homology with other aquaporins) and in its function (significantly conductive to both small nonelectrolytes and water). However, there is a controversy among researchers on its water transport and induction by dehydration. We examined its localization and the effect of dehydration on its expression in the kidney, as well as its water channel activity when expressed in Xenopus oocytes. In vitro translation using reticulocyte lysate revealed that the size of rat AQP3 was 26 kDa, and the band shifted to around 31 kDa with microsomal fraction, which was sensitive to the digestion with N-glycosidase F. In Western blot analysis of rat kidney medulla, AQP3 appeared as a sharp band at 27 kDa and a broad band at 34-40 kDa. In immunohistochemistry, AQP3 was localized to principal cells and absent in intercalated cells in outer medulla. In inner medulla, AQP3 was restricted to inner medullary collecting duct (IMCD) cells. AQP3 was confined to the basolateral membrane of these cells. Although dehydration of rats for 2 days did not change the distribution pattern of AQP3 in IMCD cells, the dehydration increased AQP3 mRNA by twofold with slight increase of its protein level in kidney medulla. Finally, we confirmed its water channel activity when expressed in Xenopus oocytes. The human AQP3 stimulated osmotic water permeability by eightfold, which was inhibited by 0.3 mM mercury chloride by 34% and reversed by beta-mercaptoethanol. Our results indicate that AQP3 is a glycosylated protein and a mercury-sensitive water channel localized at the basolateral membrane of principal cells and IMCD cells, and its expression is induced by dehydration at both protein and mRNA level.

Animals↗

PubMed1997

Microlocalization and effects of adrenomedullin in nephron segments and in mesangial cells of the rat.

We examined microlocalization of mRNA coding for adrenomedullin (AM), using reverse transcription-polymerase chain reaction (RT-PCR), and the effects of AM on adenosine 3',5'-cyclic monophosphate (cAMP) generation and water transport in microdissected rat nephron segments. We also examined intraglomerular site of the expression of AM and AM-stimulated cAMP generation in cultured rat mesangial cells (MC). RT-PCR demonstrated the signals for AM mRNA in glomerulus (Glm), cortical collecting duct (CCD), outer medullary collecting duct (OMCD), and inner medullary collecting duct (IMCD) but not in proximal convoluted tubule (PCT) or medullary thick ascending limb (MTAL). AM (10(-7) M) stimulated cAMP generation in Glm >> CCD = IMCD > OMCD but not in PCT or MTAL, which corresponded to the results of the expression of AM mRNA. AM (10(-8) M) slightly increased osmotic water permeability by 24% in perfused terminal IMCD. Northern blot analysis revealed high expression of AM mRNA in MC. AM (10(-7) M) stimulated cAMP generation in MC both in the presence and absence of fetal calf serum, suggesting that AM-dependent cAMP generation was evident both in cycling MC and in quiescent MC. AM may work as a diuretic peptide mainly by increasing glomerular filtration rate via cAMP in MC.

Adrenomedullin↗

PubMed1997

Cloning of rat and mouse aquaporin-2 gene promoters and identification of a negative cis-regulatory element.

The promoters of rat and mouse aquaporin-2 (AQP-2) genes were cloned and compared with that of human genes. Nucleotide identity up to -593 bp was 62%, and consensus sequences such as TATA box and adenosine 3',5'-cyclic monophosphate responsive element were conserved. Deoxyribonuclease I footprint assay revealed a footprinted region at -210 to -184 bp in rat AQP-2 gene promoter produced by nuclear extract from nonexpressing (liver) tissue. The sequence of this region included a GATA motif but otherwise showed no homology with any other previously known cis-elements. Electromobility shift assay and ultraviolet cross-linking analysis confirmed that specific binding proteins to this element were present in kidney, spleen, and liver and that these proteins were distinct from GATA factors. Both deletion and mutation of this cis-element abolished the protein DNA binding and increased promoter activity in in vitro reporter gene assay using rat cultured hepatocyte Ac2F cells, suggesting the negative regulatory role of this cis-element. These results indicate that tissue-specific expression of AQP-2 gene may in part be regulated by this novel negative acting cis-element.

Animals↗

PubMed1997

Experimental IgA nephropathy induced by a low-dose environmental mycotoxin, nivalenol.

Based on the hypothesis that IgA nephropathy (IgAN) is triggered by some exogenous antigen(s) which induces dysregulation of the mucosal immune system, we developed an experimental model of orally induced IgAN by an environmental mycotoxin, nivalenol (NIV), which often contaminates agricultural products in Southeast Asia and Japan. In the present study, low doses of oral NIV reproducibly induced significant IgA deposits in the glomerular mesangium and elevated serum IgA levels in mice irrespective of the strain; the degree of immunopathological changes analogous to human IgAN was associated with the dose and duration of NIV treatment. Furthermore, a competitive enzyme-linked immunosorbent assay with an NIV analogue-protein conjugate disclosed that the IgA antibody in the sera from the NIV model mice had a higher affinity to the mycotoxin. Conclusively, these findings suggest that NIV induces some pathological changes in mice which resemble those in human IgAN, and that this mycotoxin is associated with pathogenesis in some types of glomerulonephritis.

Animals↗

PubMed1997

Response of fibrinolytic proteins and endothelin 1 to venous occlusion in patients on chronic hemodialysis.

The main purpose of the present study was to determine whether any abnormalities in the response of fibrinolytic activity to venous occlusion could be observed in patients undergoing chronic hemodialysis (HD patients). A 10-min venous occlusion test was performed in 13 HD patients and in 9 healthy subjects. The arm opposite to the arteriovenous fistula was occluded in HD patients. The following factors were measured: tissue plasminogen activator (t-PA), plasminogen activator inhibitor 1 (PAI-1), plasmin-alpha2-plasmin inhibitor complex (PIC), stabilized fibrin degradation product (D-dimer), and von Willebrand factor antigen determined by enzyme immunoassay, and endothelin 1 by radioimmunoassay with two antibodies. Preocclusion levels of PIC, D-dimer, von Willebrand factor, and endothelin 1 were significantly higher and those of t-PA significantly lower in HD patients than in controls. During the occlusion, there was a positive correlation between the percent changes in t-PA and von Willebrand factor and between those in von Willebrand factor and PIC. There was no correlation between percent and absolute changes during the occlusion in endothelin 1 and those in t-PA, PAI-1, PIC, D-dimer, or von Willebrand factor. There was no significant difference between HD patients and controls as to the percent changes in hematocrit, t-PA, PIC, D-dimer and von Willebrand factor. HD patients demonstrated a significantly greater percent change in PAI-1 than controls. The mechanism by which endothelin 1 is released in response to the occlusion appears to differ from that for t-PA, PAI-1, and von Willebrand factor. PAI-1 may be readily released in response to stimuli to blood vessels in HD patients.

Blood Vessels↗

PubMed1997

Endothelin-1 as an autocrine/paracrine apoptosis survival factor for endothelial cells.

Endothelin-1 (ET-1), an endothelium-derived vasoactive peptide, functions as a potent vasoconstrictor as well as mitogen. We show here a novel role for ET-1 as an apoptosis survival factor for cultured rat endothelial cells. When we rendered endothelial cells obtained from rat aorta quiescent by serum starvation, significant portions of cultured cells underwent apoptotic death as demonstrated by nucleosomal laddering on agarose gel electrophoresis, flow cytometry analysis with FACS, and the TdT-mediated dUTP biotin nick-end labeling (TUNEL) method. ET-1 dose-dependently (10[-12] to 10[-6] mol/L) suppressed the apoptosis induced by serum starvation. The ET(B) receptor antagonist (BQ788; 10[-6] mol/L) and ET(A/B) receptor antagonists (PD142893 and PD145065; 10[-6] mol/L), but not the ET(A) receptor antagonist (BQ123; 10[-6] mol/L), blocked the apoptosis protective effect of 10[-7] mol/L ET-1. Nonimmune rabbit serum reduced the apoptotic event induced by serum deprivation, whereas neutralization of endogenous ET-1 by polyclonal anti-ET-1 antiserum abrogated this protective effect. The ET(B) receptor antagonist (BQ788; 10[-8] to 10[-6] mol/L), but not the ET(A) receptor antagonist (BQ123; 10[-8] to 10[-6] mol/L), significantly inhibited proliferation of endothelial cells. These data suggest that ET-1, as well as mitogen, functions as an apoptosis survival factor for endothelial cells in an autocrine/paracrine manner via the ET(B) receptor.

Animals↗

PubMed1997

Treatment for advanced hepatocellular carcinoma by transarterial chemotherapy using reservoirs or one-shot arterial chemotherapy.

A prospective trial was performed in patients with advanced hepatocellular carcinoma to assess the therapeutic efficacy of transcatheter arterial chemotherapy using implanted reservoirs (12 patients) or conventional transcatheter arterial chemotherapy (8 patients). Epirubicin at a dose of 40 mg/m2 was given every month in the former, while epirubicin at a dose of 60 mg/m2 was administered every 3 months in the latter. During the 6 months from the introduction of these therapies, hospitalized periods were shorter and total hospital costs were less in the reservoir group than in the conventional chemotherapy group (p < 0.05 and p < 0.01, respectively). Transcatheter arterial chemotherapy using implanted reservoirs can be carried out on a day-care basis and may be beneficial for the treatment of patients with advanced hepatocellular carcinoma.

Aged↗

PubMed1997

Biphasic regulation of the preproendothelin-1 gene by c-myc.

Endothelin-1 (ET-1), a potent vasoconstrictive/mitogenic peptide originally isolated from vascular endothelium, stimulates the expression of immediate early response genes such as c-myc. The c-myc protooncogene participates in regulating the cascade of events that follow mitogenic stimulation of quiescent cells. Using a panel of isogenic fibroblast cell lines with differential c-myc expression levels (obtained by disrupting one c-myc gene copy with targeted homologous recombination and subsequently stably transfecting the heterozygous cells with an exogenous c-myc transgene), we demonstrate that c-Myc protein regulates ET-1 gene transcription in a biphasic fashion: as an activator at low concentrations and as a repressor at high concentrations. Using rat endothelial cells treated with antisense c-myc oligodeoxynucleotides, we also show that c-myc regulates ET-1 synthesis and secretion in a biphasic manner. The present report, therefore, demonstrates the existence of a signal transduction pathway that regulates the synthesis and secretion of ET-1 via the immediate early transcription factor, c-Myc.

Animals↗

PubMed1997

Adrenomedullin as an autocrine/paracrine apoptosis survival factor for rat endothelial cells.

Adrenomedullin is a potent vasorelaxant/hypotensive peptide recently isolated from human pheochromocytoma. We demonstrate here a novel role of this peptide as an apoptosis survival factor for rat endothelial cells. When rendered quiescent by serum deprivation, a fraction of endothelial cell cultures showed morphological and biochemical features characteristic of apoptosis. Adrenomedullin significantly suppressed apoptosis without inducing cell proliferation. Rat endothelial cells that contained high affinity binding sites for adrenomedullin expressed adrenomedullin gene and released the peptide into culture media. Addition of preimmune rabbit serum prevented apoptosis, whereas rabbit antiadrenomedullin antiserum partially, but significantly, abrogated the protective effect of the preimmune serum, suggesting its autocrine/paracrine role. Although adrenomedullin induced intracellular cAMP formation, other cAMP-elevating agonists, such as prostaglandin I2 and forskolin, did not affect apoptosis. Furthermore, adenosine 3',5'-cyclicmonophosphothioate Rp-isomer, a cAMP antagonist, did not block the cell survival effect of adrenomedullin. Adrenomedullin neither increased intracellular Ca2+ concentrations nor inositol-1,4,5-trisphosphate levels in rat endothelial cells. These results demonstrate that adrenomedullin suppresses serum deprivation-induced apoptosis of rat endothelial cells via cAMP-independent mechanism.

Adrenal Gland Neoplasms↗

PubMed1997

Urinary excretion of aquaporin-2 in the diagnosis of central diabetes insipidus.

We determined whether alteration in urinary excretion of aquaporin-2 (UAQP-2) is of value to diagnose central diabetes insipidus (CDI). First, UAQP-2 was determined in 16 normal subjects under ad libitum water drinking (n = 6) and after an overnight dehydration (n = 10). UAQP-2 has a positive correlation with plasma arginine vasopressin (AVP) levels (r = 0.61, P < 0.05) but not with urinary osmolality (Uosm). Second, a hypertonic saline (5% NaCl)-infusion test was studied in 5 normal subjects (21 to 25 yr old) and 10 patients with CDI (22-68 yr). After drinking water ad libitum, they were given 20 mL/kg water orally and then given 5% NaCl (0.05 mL/kg x min) i.v. for 120 min. Finally, 0.1 U of AVP was administered i.v. During the period, 30-min urine collections were made. In the normal subjects, after the infusion of 5% NaCl, plasma AVP levels and Uosm markedly increased in parallel with an increase in plasma osmolality (Posm, 294-320 mOsm/kg H2O; Uosm, 102-737 mOsm/kg H2O; AVP, 0.4-2.6 pg/mL, P < 0.001). In the CDI patients, plasma AVP and Uosm failed to increase, despite an increase in Posm (Posm, 306-332; Uosm, 102-164; AVP, 0.9-1.2). UAQP-2 was markedly greater in the normal subjects than the CDI patients (7.2 vs. 0.9 pmol/L/mg creatinine, P < 0.05) under water intake ad libitum. UAQP-2 was changeable in the wide range in physiological condition. After the 5%-NaCl infusion, UAQP-2 elevated to 12.5 from 0.9 pmol/L x mg creatinine in the normal subjects. In contrast, UAQP-2 remained low during the 5%-NaCl infusion in the CDI patients. Exogenous AVP promptly increased UAQP-2 to a similar extent in two groups of the normal subjects and the CDI patients. These results indicate that measurement of UAQP-2 is of value to diagnose CDI in the 5%-NaCl infusion test.

Adult↗

PubMed1997

Radiofrequency catheter ablation of posteroseptal atrioventricular accessory pathways--location-specific electrographic characteristics of successful ablation sites.

The electrographic features of successful sites of radiofrequency catheter ablation were analyzed in 33 cases of posteroseptal accessory pathways and compared with those from 155 cases of free wall accessory pathways. The atrioventricular intervals in the posteroseptal cases were significantly longer than in the free wall cases (posteroseptal vs left and right free wall; 38 vs 33 and 26 msec, respectively; p < 0.05), and the incidences of continuous electrograms (42 vs 63 and 79%; p < 0.01) and PQS-pattern unipolar electrograms (50 vs 76 and 78%; p < 0.05) were significantly lower in the posteroseptal cases. The V-delta intervals in the posteroseptal cases were significantly longer than in the left free wall cases (17 vs 13 msec; p < 0.05), but shorter than in the right free wall cases (17 vs 23 msec; p < 0.05). No statistically significant difference in the incidence of Kent potentials among the 3 groups was observed. In radiofrequency ablation of posteroseptal pathways, the length of the atrioventricular interval and the incidences of continuous electrograms and PQS-pattern unipolar electrograms may be unsatisfactory even at the appropriate target site, but the V-delta interval and Kent potential are good indicators of suitable target sites.

Adolescent↗

PubMed1997

Porphyria cutanea tarda with constrictive pericarditis in a family.

Two cases of familial porphyria cutanea tarda (PCT) with constrictive pericarditis are described. A 50-year-old woman and her 48-year-old younger brother were admitted because of right ventricular heart failure. Constrictive pericarditis was diagnosed by RV pressure waveform and echocardiogram. The patients were diagnosed as PCT based on clinical symptoms, histologic findings and elevated urinary excretion levels of uroporphyrin. Even to this day, over 40% of the etiology of constrictive pericarditis remains unknown. There is a possibility of overlooking porphyria cutanea tarda in constrictive pericarditis patients. This report describes the first documented cases of familial PCT with constrictive pericarditis.

Coproporphyrins↗

PubMed1997

Cardiomyopathy in a case of Crow-Fukase syndrome.

Crow-Fukase syndrome or POEMS syndrome is a variant of plasma cell dyscrasia that is characterized by polyneuropathy, organomegaly, endocrinopathy, the presence of M-protein in serum, and dermatological changes. A 60-year-old man presented with features of Crow-Fukase syndrome, such as the presence of M-protein in serum, dermatological changes, and osteosclerotic changes, but did not have polyneuropathy. To our knowledge, this is the first case of Crow-Fukase syndrome in which the presence of hypertrophic cardiomyopathy has been confirmed by a left endomyocardial biopsy. The findings suggest that hypertrophic cardiomyopathy may be a manifestation of organomegaly in patients with Crow-Fukase syndrome.

Cardiomyopathy, Hypertrophic↗

PubMed1997

Overexpression of cell cycle inhibitors (p16INK4 and p21Cip1) and cyclin D1 using adenovirus vectors regulates proliferation of rat mesangial cells.

To elucidate the mechanisms of the cell cycle of mesangial cells, adenovirus vectors containing coding sequences of cyclin D1 (AxCAD1), p16INK4 (AxCAp16) and p21Cip1 (AxCAp21) were produced and investigated to determine whether transfer of these genes changes serum- and PDGF-induced proliferation of rat mesangial cells. Efficiency of the transfer of the genes was examined by Northern and Western blot analyses. The cell cycle of mesangial cells was evaluated by measurement of [3H]-thymidine incorporation, flow cytometry, and cyclin-dependent kinase 4 kinase assay. Expression of cyclin D1, p16INK4 and p21Cip1 was observed from 24 h after the infection, and the expression increased up to 48 h. AxCAp16 and AxCAp21 caused a significant inhibition in the [3H]-thymidine incorporation to 47% and 76%, respectively. AxCAp16 and AxCAp21 also inhibited the mitogen-induced increase in cyclin-dependent kinase 4 kinase activity and reduced the percentage of cells in S phase. Coinfection of AxCAp16 with AxCAp21 showed no additive inhibition. Overexpression of cyclin D1 reduced cell size and increased the percentage of the cells in S and G2 phase. These findings suggest that p16INK4 and p21Cip1 function as inhibitors of the proliferation of mesangial cells induced by growth-promoting factors and that deregulated expression of cyclin D1 causes cell cycle disturbances. Adenovirus-mediated gene transfer of p16INK4 and p21Cip1 serves as a potential therapeutic approach to mesangial proliferative diseases.

Adenoviruses, Human↗

PubMed1997

Expression of PDGF and PDGF receptor mRNA in glomeruli in IgA nephropathy.

This study investigated the mRNA expression of the platelet-derived growth factor (PDGF) A-chain and B-chain and PDGF-beta receptor in glomeruli of 15 immunoglobulin A (IgA) nephropathy kidneys and those with minimal-change lesion (N = 7), membranous nephropathy (N = 3), and focal segmental glomerulonephritis (N = 5), by using competitive RT-PCR methods. The level of PDGF B-chain and beta receptor mRNA expression in IgA nephropathy was significantly higher than in the other forms of glomerulonephritis, but mRNA expressions of PDGF A-chain were not significantly different. Significant correlations were observed between the urinary protein level and the mRNA level of PDGF-beta receptor expression and PDGF B-chain expression, and between the serum creatinine level and the mRNA level of PDGF-beta receptor expression. The PDGF B-chain and beta-receptor may be upregulated and accelerate cell proliferation in a paracrine or autocrine manner and may play a role in the pathogenesis of IgA nephropathy.

Becaplermin↗

PubMed1997

Transcriptional regulation of aquaporin-2 water channel gene by cAMP.

Aquaporin-2 (AQP-2) water channel is a key molecule for urinary concentration whose expression is augmented by dehydration in vivo. To elucidate the regulatory mechanism of this phenomenon in vitro, mouse collecting duct cell lines were established from a transgenic mouse harboring temperature-sensitive simian virus 40 large T antigen gene and then screened for the AQP-2 expression, using ribonuclease protection assay. In one cell line designated C4, the endogenous AQP-2 mRNA level measured by ribonuclease protection assay increased fourfold after treatment with chlorophenylthio-cAMP (cpt-cAMP) (400 microM). In contrast, phorbol 12-myristate 13-acetate did not affect the AQP-2 mRNA level. To identify the molecular mechanism(s) of cAMP-induced upregulation of AQP-2 mRNA in C4 cells, luciferase assay was performed using various 5'-flanking regions of the human AQP-2 gene. Luciferase activity in C4 cells transfected with constructs containing approximately 2.8-kbp or 224-bp 5'-flanking region showed a 3.5-fold increase by cpt-cAMP treatment, indicating that the 224-bp 5'-flanking region contains the elements necessary for cAMP-induced regulatory mechanisms. This region contains cAMP-responsive element (CRE), and the deletion of the core sequence of CRE (GACGTCA) or introduction of mutation into CRE (GTGGTCA) completely abolished the responsiveness to cpt-cAMP, confirming the key role of CRE in the cAMP-induced transcriptional activation of the AQP-2 gene. Electrophoretic mobility shift assay revealed the existence of proteins binding to CRE in C4 cells and in rat kidney. The binding of CRE proteins to CRE was increased in the nuclear extract from cpt-cAMP-treated C4 cells and dehydrated rat kidney compared with those from controls. These results demonstrated that the CRE in the AQP-2 gene promoter is a key cis-element for cAMP-mediated transcriptional regulation of this gene and may be important for in vivo regulation of AQP-2 expression in a dehydrated state.

Animals↗