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Biomedical subjects

F Marumo

Publications and source records attributed to F Marumo.

At least 325 records · Page 18Linked to original sources
PubMed1995

Effects of cadmium on glutathione metabolism in Hep G2 cells.

Effects of cadmium on hepatic glutathione (GSH) metabolism were characterized in a human-derived hepatoma cell line, Hep G2 cells. Intracellular GSH concentrations were significantly increased after incubation with cadmium at 5 and 10 microM for 24 and 48 hr. The rate of resynthesis of GSH after depleting cellular GSH by 0.5 mM of diethylmaleate was higher in cadmium (5 microM)-pretreated cells than that in untreated controls. GSH efflux from cadmium-pretreated cells was two-fold higher than that in untreated controls. On the other hand, incubation with cadmium at 5 and 10 microM for 60 min did not decrease GSH efflux. These findings suggest that increased intracellular GSH concentrations are attributed to enhanced synthesis of GSH under cadmium exposure, although the possibility of decreased intracellular consumption of GSH should further to be studied.

Animals↗
PubMed1995

[Effects of a prosthetic dental device used to treat obstructive sleep apnea syndrome, and compliance of patients using the device].

We studied the short-term effects and complications of the use of a dental device (prosthetic mandibular advancement: PMA) in 72 patients with obstructive sleep apnea syndrome (OSAS), and the compliance of these patients with this treatment. In 61 (84.5%) of the 72 patients, the apnea index decreased by more than 50%. The lowest SaO2 and symptom scores also improved significantly. The severity of OSAS was not related to the percent reduction in apnea index. Complications of PMA use were observed in 22 patients (30.6%), but no severe adverse effects were observed. Sixty-two of the 72 patients continued using the PMA throughout the entire study period (overall compliance rate, 86.1%). In addition, the long-term compliance rate (more than 5 years) was 61.5%. We conclude that the effects of PMA in patients with OSAS are clinically significant, that there are no severe complications, and that compliance with treatment is good.

Adolescent↗
PubMed1995

Endothelin-1 as an autocrine growth factor for endothelial cells.

To elucidate the role of endothelin-1 (ET-1) as an autocrine growth factor for vascular endothelial cells (ECs), we studied the effects of phosphoramidon, an inhibitor of ET-1-converting enzyme, on the production of ET-1-like immunoreactivity (LI), [125I]ET-1 binding activity, ETB receptor mRNA expression, phosphoinositide breakdown, and DNA synthesis in cultured bovine carotid artery ECs. Phosphoramidon dose-dependently decreased ET-1-LI production but reciprocally increased [125I]ET-1 binding capacity. ET-1 and ET-3 equipotently inhibited the binding of [125I]ET-1 only in the presence of phosphoramidon. Northern blot analysis revealed that ETB receptor mRNA expression was more evident in phosphoramidon-treated cells than in nontreated cells. In the presence of phosphoramidon, ET-1 and ET-3 equipotently stimulated inositol 1,4,5-trisphosphate formation and [3H]-thymidine incorporation into cultured ECs. Both phosphoramidon and anti-ET-1 antibody inhibited basal [3H]thymidine incorporation. These data suggest that endogenous ET-1 constitutively secreted by ECs is an autocrine growth factor via ETB receptors.

Animals↗
PubMed1995

Autocrine regulation of the endothelin-1 gene in rat endothelial cells.

We studied whether endothelin (ET)-1 regulates its own transcription in cultured rat aortic endothelial cells (ECs) in an autocrine manner and attempted to elucidate its cellular and molecular mechanism. By Northern blot analysis using rat preproET-1 cDNA as a probe, ET-1 increased steady-state levels of preproET-1 mRNA as early as 30 min, which persisted during 4 h incubation. ET-1 also increased steady-state c-fos mRNA levels, which returned to an undetectable level by 2 h. ET-1 dose-dependently upregulated preproET-1 mRNA expression. The effect was inhibited by nonselective ETA/ETB receptor antagonist but not a selective ETA receptor antagonist. The ET-1-induced preproET-1 mRNA expression was suppressed by a protein kinase C (PKC) inhibitor and by pretreatment with phorbol ester, which depeleted engdogenous PKC. The approximate half-life of preproET-1 mRNA stimulated by ET-1 (approximately 20 min) was similar to that stimulated by phorbol ester. Our data demonstrate that ET-1 upregulates its own gene expression through ETB receptor-mediated PKC activation, suggesting a possible autocrine positive feedback system in vascular endothelium.

Animals↗
PubMed1995

Plasma human brain natriuretic peptide in chronic renal failure.

Brain natriuretic peptide (BNP) is a polypeptide hormone which is homologous with atrial natriuretic peptide (ANP). Since the 2 hormones partially share common secretory regulation we simultaneously assessed plasma BNP and ANP in patients with chronic glomerulonephritis without apparent cardiac involvement. Blood samples were taken from patients with serum creatinine (Cr) 0.5-1.2 mg/dl (normal renal function), patients with Cr > 1.2 mg/dl (chronic renal failure) and dialysis patients. BNP did not correlate with serum Cr, which indicated our antibody did not recognize accumulated metabolites due to decreased renal function. BNP and ANP decreased after dialysis-(p < 0.01). Changes of BNP during HD correlated with changes in body weight (p < 0.05). Plasma BNP concentrations were 12.0 +/- 22.0 pg/ml in patients with normal renal function, 17.6 +/- 23.4 pg/ml in chronic renal failure, and 91.5 +/- 93.5 in dialysis patients (p < 0.05 compared with patients with normal renal function). Plasma BNP/ANP ratios were 0.507 +/- 0.646 in patients with normal renal function, 0.392 +/- 0.842 in chronic renal failure, and 0.573 +/- 0.431 in dialysis patients (p < 0.05, compared with chronic renal failure). Increased ANP in chronic renal failure and dialysis indicates volume overload on atrium. In contrast, BNP increased only in dialysis patients, which indicates differences of hemodynamic stress in chronic renal failure and dialysis. We conclude that simultaneous measurements of plasma BNP and ANP further discriminate salt-water and hemodynamic abnormalities in dialysis patients.

Adult↗
PubMed1994

Sequential activation of Raf-1 kinase, mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase by hyperosmolality in renal cells.

In the renal medulla during antidiuresis, the extracellular fluid becomes hyperosmotic. Madin-Darby canine kidney (MDCK) epithelial cells adapt in hyperosmotic conditions and serve as a useful tissue culture model for cellular responses to hyperosmolality. We demonstrate that hyperosmolality stimulates phospholipase C, Raf-1 kinase mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase activities and that it increases phosphorylation of Raf-1 kinase, and p42 MAP kinase in MDCK cells. Stimulation of these kinases is osmolality-dependent (from 300 to 600 mosm/kg H2O). The time course of activation is sequential; the peak stimulation for Raf-1 kinase is at 5 min, at 10 min for MAP kinase kinase and MAP kinase, and at 20 min for S6 kinase. The activation of Raf-1 kinase and MAP kinase is inhibited by phorbol 12-myristate 13-acetate pretreatment in the presence of calphostin C or H-7. Tyrosine kinase inhibitors (genistein, herbimycin) do not significantly suppress hyperosmolality-induced MAP kinase activity. The increase of Ins-1,4,5-P3 levels by hyperosmolality suggests that activation of these kinases is mediated at least partially via activation of phospholipase C. Thus, hyperosmolality stimulates the serine/threonine kinases, Raf-1 kinase, MAP kinase kinase, MAP kinase, and S6 kinase, via predominantly protein kinase C-dependent, tyrosine kinase-independent pathways in MDCK cells.

Amino Acid Sequence↗
PubMed1994

Evolution and selection of hepatitis C virus variants in patients with chronic hepatitis C.

It has been shown that hepatitis C virus (HCV) populations in vivo are composed of different but highly homologous HCV genomes (quasispecies) as shown in the hypervariable region (HVR) that exists in the N-terminal of the envelope 2 gene of HCV, and that the predominant sequence of the HVR of HCV genomes changes rapidly over time. To further investigate genetic backgrounds of the change in the HVR of HCV genomes, 45 plasma samples serially obtained from nine patients with chronic hepatitis C were studied using population-based analyses. Total RNA was recovered and the envelope gene containing the HVR was amplified by the reverse transcription and nested polymerase chain reaction. The amplified cDNA was examined by the single strand conformation polymorphism (SSCP) analysis. Furthermore, 43 HCV sequences, separated by the SSCP analysis from three patients were determined by the dideoxy chain termination method, and the phylogenetic analysis was performed using the neighbor joining method. The SSCP analysis demonstrated that HCV population within each individual were composed of 1 to 6 quasispecies. These quasispecies populations in vivo changed sequentially in eight of nine patients. Gradual selections of coexisting quasispecies were observed over 6- to 18-month periods in three patients, whereas complete replacements of previous quasispecies by new quasispecies were repeatedly observed over few-month intervals in five patients. The phylogenetic analysis on these quasispecies revealed the continuous accumulation of mutations in two patients and discontinuous appearance of evolutionarily distant quasispecies in one patient. These results indicate that HCV genomes in vivo form quasispecies populations, and that these quasispecies populations change during the natural course of chronic infection. Genetic mechanisms underlining the change of the HVR of HCV genome appear to be either continuous accumulation of mutations or selective overgrowth of preexisting minor variants from the large spectrum of quasispecies populations.

Aged↗
PubMed1994

Isolation of human aquaporin-CD gene.

The human gene encoding aquaporin-CD (AQP-CD) was isolated, and its structural organization was characterized. The gene appeared to exist as a single copy in the human genome and comprises four exons distributing over 5 kilobases. The size range of exons is 81-761 base pairs, and that for introns is approximately 3000 to approximately 250 base pairs. The exon-intron boundaries of human AQP-CD gene are identified at identical positions in other related genes, the human AQP-CHIP gene and the human major intrinsic protein gene. The major transcription initiation sites were identified to positions 93 and 94 base pairs upstream of the ATG initiation codon by primer extension and ribonuclease protection assay. The 5'-flanking region of the hAQP-CD gene was characterized by a TATA box, two GATA consensus sequences, an AP-1 site, an AP-2 site, three E-boxes, and a cyclic AMP-responsive element. These structural features will lead to a better understanding of the mechanisms of tissue-specific expression and the regulation by dehydration in AQP-CD gene and will also be of help in search for possible genetic disorders in human AQP-CD gene.

Amino Acid Sequence↗
PubMed1994

Two isoforms of a chloride channel predominantly expressed in thick ascending limb of Henle's loop and collecting ducts of rat kidney.

Complementary DNAs encoding rat kidney chloride channels (ClC-K2L and ClC-K2S) were isolated by a polymerase chain reaction cloning strategy. Degenerate primers were designed based on the significant amino acid identity of the previously cloned chloride channels (ClC-0, -1, -2, and -K1). The 687-amino acid protein encoded by ClC-K2L is about 80% identical to rat ClC-K1 and about 40% identical to ClC-0, -1, and -2. ClC-K2S encodes a 632-amino acid protein in which 55 amino acids containing the putative second membrane-spanning domain of ClC-K2L are deleted. Chloride currents induced by both clones were very similar in terms of inhibitor sensitivity and anion selectivity (Br- > I- > Cl- >> cyclamate-). Northern blot with total ClC-K2L as a probe under high stringency revealed its message predominantly in kidney, especially in the outer and inner medulla. Reverse transcription polymerase chain reaction technique using microdissected nephron segments revealed that the main site of expression of both clones in kidney was the thick ascending limb of Henle's loop and collecting ducts, where the existence of a variety of chloride channels and their importance for maintaining body fluid homeostasis have been demonstrated. These results suggest that ClC-K2L and -K2S are chloride channels in the thick ascending limb and collecting ducts and may be important routes for transcellular chloride transport like ClC-K1.

Amino Acid Sequence↗
PubMed1994

Specific receptors for adrenomedullin in cultured rat vascular smooth muscle cells.

The effects of synthetic rat adrenomedullin (rAM), a novel vasorelaxant peptide originally isolated from human pheochromocytoma, on receptor binding and cAMP generation were studied in cultured rat vascular smooth muscle cells (VSMC). A binding study using [125I]rAM revealed the presence of a single class of high-affinity (Kd 1.3 x 10(-8) M) binding sites for rAM in VSMC. The apparent Ki of rat calcitonin gene-related peptide (rCGRP) was 3 x 10(-7) M. Affinity labeling of VSMC membranes with [125I]rAM revealed two distinct labeled bands with apparent molecular weights of 120 and 70 kDa, both of which were abolished by excess unlabeled rAM or rCGRP, rAM stimulated cAMP formation with an approximate EC50 of 10(-8) M, the effect of which was additive with isoproterenol, but not with rCGRP. The rAM-induced cAMP response was unaffected by propranolol, indomethacin, or quinacrine, but inhibited by a CGRP receptor antagonist, human CGRP[8-37]. These data suggest that VSMC possesses specific AM receptors functionally coupled to adenylate cyclase with which CGRP interacts.

Adrenomedullin↗
PubMed1994

Different development of apical and basolateral Na-H exchangers in LLC-PK1 renal epithelial cells: characterization by inhibitors and antisense oligonucleotide.

LLC-PK1 cells are known to possess respective Na(+)-H+ exchangers (NHE) in apical and basolateral membranes. We examined the developmental difference between these NHEs. LLC-PK1 cells seeded on a filter membrane at a saturation density formed a confluent monolayer after 1 day. Intracellular pH (pHi) was measured 1-6 days after seeding using 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. The activities of apical and basolateral NHEs were estimated separately by the initial pHi responses to Na+ after NH3/NH4+ prepulses in the absence of HCO3- at 37 degrees C. Significant apical and basolateral NHE activities were detected at day 1 (1 day after seeding). Apical NHE activity increased 2.9-fold during days 1-3. By contrast, basolateral NHE activity remained unchanged up to day 6. At day 1, both apical and basolateral NHEs showed sensitivity to inhibition by ethylisopropyl amiloride (EPIA). Apical NHE acquired 4.5-fold resistance to EIPA during days 1-3, whereas the EIPA sensitivity of basolateral NHE was constant. As a result, apical NHE became 29-times more resistant to EPIA than basolateral NHE at day 3 or 4. Treatment with an antisense oligonucleotide targeting NHE-1 (inhibitor-sensitive NHE) mRNA decreased basolateral NHE activity at days 2 and 4, and apical NHE activity at day 2. These results suggest: (1) NHE-1 is distributed over the plasma membrane in early confluent LLC-PK1 monolayers; and (2) then, NHE-2 (inhibitor-resistant NHE) gradually begins to be expressed specifically in the apical membrane, and the distribution of NHE-1 becomes confined to basolateral membrane.

Amiloride↗
PubMed1994

Sequential change of the hypervariable region of the hepatitis C virus genome in acute infection.

Hepatitis C virus (HCV) infection is characterized by persistence of liver inflammation that often leads to end-stage liver disease, although the mechanisms are not fully understood. A hypervariable region (HVR) has been reported in the E2/NS1 region of the HCV genome, in which striking diversity is found among different HCV isolates. To investigate the association of the HVR alterations with the clinical courses of HCV infection, a longitudinal analysis of the HVR in patients with acute HCV infection was carried out. Plasma samples were obtained at several times in three patients with acute hepatitis C. Plasma RNA was extracted and reverse transcribed, and DNA fragments that included the HVR were amplified by PCR. The sequences of the HVR were directly determined from the PCR products by the dideoxy chain termination method, from which amino acid sequences were deduced. In all cases, plasma HCV-RNA disappeared with the improvement of the initial alanine aminotransferase (ALT) elevation, but HCV-RNA reappeared about 1 year later with or without deterioration of the hepatitis. In a case of sporadic acute hepatitis, the HCV in the recurrent phase had seven amino acid substitutions in the HVR compared with that in the acute phase, although no amino acid changes were noted during the initial acute phase. In a case of posttransfusion hepatitis, a marked difference was observed between the acute and the recurrent phases, with an amino acid homology of 30% (8/27). The mutation rate of the HVR had a tendency to accelerate as the HCV infection progressed to the chronic stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1994

Insulin-like growth factor-II induces hypertrophy with increased expression of muscle specific genes in cultured rat cardiomyocytes.

In the present study, we examined whether insulin-like growth factor-II (IGF-II) induces hypertrophy of cultured neonatal rat cardiomyocytes. IGF-II (10(-7) M) increased the cell surface area of, and the protein content in, cardiomyocytes after 48 h-exposure. IGF-II dose-dependently (10(-10)-10(-7) M) stimulated protein synthesis as evaluated by [3H]leucine incorporation; the maximum response was 1.7-fold increase over control at 10(-7) M. Since the response of cardiac hypertrophy is characterized by enhanced expression of muscle specific genes, effects of IGF-II on steady-state levels of mRNA for myosin light chain 2 (MLC2), troponin I and alpha-actin isoforms (skeletal and cardiac isoforms) were evaluated by Northern blot analysis. IGF-II (10(-7) M) increased mRNA levels for MLC2, troponin I and skeletal alpha-actin, as early as 60 min with a maximum response after 6 h, whereas cardiac alpha-actin mRNA levels were unaffected. Calcium channel blocker, nicardipine, inhibited IGF-II-stimulated skeletal alpha-actin mRNA levels, however, inhibitor of protein kinase C, H-7, unaffected. These results suggest that IGF-II plays a potential role in cardiac hypertrophy.

Animals↗
PubMed1994

Cadmium-induced osteomalacic and osteopetrotic lesions in ovariectomized rats.

The effects of long-term administration of cadmium (Cd) chloride on the bone were studied using ovariectomized rats. The rats were injected iv with the compound at doses of 1.0 and 2.0 mg/kg, 5 days a week, for 13 weeks. The serum concentrations of calcium and inorganic phosphorus were significantly increased from 8 weeks in the 2.0 mg/kg group. The bone Cd content was gradually increased for 13 weeks in a dose-dependent manner. Calcium and phosphorus contents in the bone, and serum levels of parathyroid hormone and osteocalcin, were not significantly different between Cd-treated and control rats. Histopathologically, chronic Cd nephropathy such as tubular atrophy and interstitial fibrosis was observed with clinical polyuria and increased enzymuria. The skeletal changes were detected mainly in the femur and tibia. In the metaphysis of Cd-treated rats, cancellous bone mass increased with time. This change was detected as an increased opacity by a roentgenogram. In the cortical bone of the midshaft haversian canals were dilated with clearly bordered osteoid seams and showed a motheaten pattern in rats in the 2.0 mg/kg group at 13 weeks. In the present study, we report Cd nephropathy and osteomalacic changes in ovariectomized rats with iv injection of CdCl2 for 13 weeks. Although an involvement of the indirect action of Cd through renal failure could not be ruled out in this experiment, our biochemical and pathological data suggested that osteomalacia was induced by a direct action of Cd on the bone through abnormal calcium homeostasis.

Animals↗
PubMed1994

Critical capillary oxygen partial pressure and lactate threshold in patients with cardiovascular disease.

OBJECTIVES: The aim of this study was to determine the relation between femoral vein oxygen partial pressure (PO2) and lactate increase during exercise in patients with cardiovascular disease. BACKGROUND: Considerable controversy surrounds the relation between the increase in lactate during exercise and the oxygen supply to the exercising muscles. We assumed that femoral vein PO2 would be a measure of end-capillary PO2 during leg-cycling exercise and that it would decrease to a "floor" level when the critical capillary PO2 (the PO2 below which the capillary-mitochondrial difference would be too low to allow oxygen consumption) was reached. At the critical capillary PO2, anaerobic metabolism should take place, and lactate should increase in the effluent blood. METHODS: Ten patients with cardiovascular disease performed two 6-min constant work rate tests (moderate and heavy intensity) and an incremental exercise test to the symptom-limited maximum on a cycle ergometer. Femoral vein blood was repeatedly sampled through a percutaneous catheter before and during each exercise test. RESULTS: The PO2 rapidly decreased toward a minimal value with increasing oxygen uptake for all three tests in all patients. After reaching its nadir (18.2 +/- 2.0 mm Hg), the PO2 remained unchanged in five patients but increased in the other five patients despite the further increase in work rate and oxygen uptake. The relation between PO2 and oxygen uptake was characteristic for each patient and independent of the protocol used for the study. Femoral vein lactate did not change appreciably until PO2 reached the minimal (critical) value. Thereafter, it dramatically increased without a further decrease in PO2. The minimal PO2 was positively correlated with the peak oxygen uptake (r = 0.70, p = 0.01). CONCLUSIONS: During leg-cycling exercise, muscle capillary PO2 reaches a minimal value in the midrange of the subjects' work capacity before lactate concentration increases in patients with cardiovascular disease. The lack of further decrease in PO2 at the oxygen uptake at which lactate starts to increase suggests that the minimal capillary PO2 is the "critical" capillary PO2.

Aged↗
PubMed1994

Cloning and expression of a protein kinase C-regulated chloride channel abundantly expressed in rat brain neuronal cells.

cDNA (CIC-3) encoding a protein kinase C-regulated chloride channel was cloned and characterized. The open reading frame encodes 760 amino acids, which possess significantly amino acid identity with previously cloned CIC chloride channels. The chloride currents expressed in Xenopus oocytes injected with CIC-3 cRNA were completely blocked by activation of protein kinase C by 12-O-tetradecanoylphorbol 13-acetate. Abundant expression of CIC-3 mRNA was observed in rat brain, especially in the olfactory bulb, hippocampus, and cerebellum. These findings suggest that CIC-3 may play an important role in neuronal cell function through regulation of membrane excitability by protein kinase C.

Amino Acid Sequence↗