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Biomedical subjects

K Kume

Publications and source records attributed to K Kume.

At least 73 records · Page 4Linked to original sources
PubMed1998

Hepatic expression of multidrug resistance-associated protein-like proteins maintained in eisai hyperbilirubinemic rats.

The biliary excretion of several organic anions is mediated by the canalicular multispecific organic anion transporter (cMOAT), which is hereditarily defective in mutant rats such as Eisai hyperbilirubinemic rats (EHBR). In addition, using a kinetic study with isolated canalicular membrane vesicles, we recently suggested the presence of ATP-dependent organic anion transporter(s) other than cMOAT in EHBR [Pharm Res (NY) 12:1746-1755 (1995); J Pharmacol Exp Ther 282:866-872 (1997)]. The aim of this study is to provide a molecular basis for the presence of multiplicity in the biliary excretion of organic anions in rats. Based on the homology with human multidrug resistance-associated protein (hMRP), two cDNA fragments encoding the carboxyl-terminal ATP-binding cassette region were amplified by reverse transcription-polymerase chain reaction from EHBR liver. These fragments exhibited approximately 70% amino acid identity with hMRP and rat cMOAT;, therefore, they were designated MRP-like proteins (MLP-1 and MLP-2). The cloned full length cDNA of MLP-1 and -2 from the Sprague-Dawley (SD) rat liver and colon cDNA library was composed of 1502 and 1523 amino acids, respectively, had the characteristics of ATP-binding cassette transporters, and exhibited homology with hMRP and rat cMOAT. Northern blot analysis indicated that MLP-1 is expressed predominantly in the liver in both SD rats and EHBR, whereas hepatic expression of MLP-2 was observed only in EHBR. In addition, MLP-2 was markedly induced by ligation of the bile duct in SD rat liver. In both SD rats and EHBR, MLP-2 was expressed predominantly in the duodenum, jejunum, and colon. These findings suggest that MLP-1 and MLP-2 might be novel members of the MRP family responsible for the excretion of organic anions from these epithelial cells, and that MLP-2 is an inducible one.

ATP-Binding Cassette Transporters↗
PubMed1998

[A pediatric case of myeloperoxidase-antineutrophil cytoplasmic (ANCA)-related crescentic glomerulonephritis associated with propylthiouracil treatment for Graves' disease].

We treated a 13-year-old girl who developed myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA)-related crescentic glomerulonephritis (GN) during propylthiouracil (PTU) treatment for Graves' disease. MPO-ANCA-related crescentic GN during PTU therapy has been described previously in only one recent report of 2 children. We report this case here and describe 15 (13 adult cases) more patients with MPO-ANCA-related GN associated with PTU found in a literature review. The mean age at onset was 41.3 years, and the length of PTU administration ranged from 2 weeks to 6 years (mean 3.5 years). Clinical signs and symptoms were hematuria (100%), proteinuria (100%), arthralgia (7 of 16 cases; 43.8%), fever (4 cases; 20.0%), purpura (2 cases; 12.5%), skin ulcer (1 case; 6.3%) and dyspnea (1 case; 6.3%). These patients were treated with steroid (15 cases; 93.8%), cyclophosphamide (8 cases; 50.0%), steroid pulse therapy (4 cases; 25.0%), or plasma exchange (1 case; 6.3%), or were not treated (1 case; 6.3%). Most patients revealed crescentic GN (15 cases; 93.8%) on renal biopsy, while one exhibited mesangial proliferative GN (6.3%). For 2 of the 16 patients (12.5%) irreversible renal dysfunction persisted and hemodialysis was started. Patients with Graves' disease treated with PTU should be observed carefully by urinalysis and monitoring of the serum creatinine level.

Adolescent↗
PubMed1997

Role of cytosolic phospholipase A2 in allergic response and parturition.

Phospholipase A2 (PLA2) comprises a superfamily of enzymes that hydrolyse the ester bond of phospholipids at the sn-2 position. Among the members of this superfamily, cytosolic PLA2 has attracted attention because it preferentially hydrolyses arachidonoyl phospholipids and is activated by submicromolar concentrations of Ca2+ ions and by phosphorylation by mitogen-activated protein kinases (MAP kinases). Here we investigate the function of cytosolic PLA2 in vivo by using homologous recombination to generate mice deficient in this enzyme. These mice showed a marked decrease in their production of eicosanoids and platelet-activating factor in peritoneal macrophages. Their ovalbumin-induced anaphylactic responses were significantly reduced, as was their bronchial reactivity to methacholine. Female mutant mice failed to deliver offspring, but these could be rescued by administration of a progesterone-receptor antagonist to the mother at term. Considered together with previous findings, our results indicate that cytosolic PLA2 plays a non-redundant role in allergic responses and reproductive physiology.

Anaphylaxis↗
PubMed1997

Lipid mediators modulate NMDA receptor currents in a Xenopus oocyte expression system.

We determined the modulatory effects of various lipid mediators on mouse N-methyl-D-aspartate (NMDA) receptor currents in the Xenopus oocyte expression system. Arachidonic acid, but not oleic acid potentiated NMDA receptor activity. The epsilon1/zeta1 heterodimer of the NMDA receptor was more sensitive to arachidonic acid than was the epsilon2/zeta1 heterodimer. Platelet-activating factor (PAF) and lysophosphatidic acid (LPA) both activated the NMDA currents, and the effects were more evident in the epsilon2/zeta1 heterodimer than in epsilon1/zeta1. These activations were abolished by treatment with protein kinase inhibitors, suggesting a possible phosphorylation of the receptor. Thus, lipid mediators do have modulatory effects on NMDA receptor currents, the potentiating effects of which differ depending on subtype of the NMDA receptor.

Animals↗
PubMed1997

Platelet-activating factor (PAF) induces growth stimulation, inhibition, and suppression of oncogenic transformation in NRK cells overexpressing the PAF receptor.

Platelet-activating factor (PAF) is a phospholipid mediator with various physiological functions, including cellular growth and transformation. PAF exerts biological activities through G-protein-coupled receptors. In normal rat fibroblasts overexpressing a cloned PAF receptor, PAF induced immediate early oncogene expression and mitogenic responses. On the other hand, PAF strongly inhibited the epidermal growth factor-induced mitogenic growth response, growth acceleration, and anchorage-independent cell growth in a soft agar. Furthermore, PAF suppressed v-src- or v-ras-induced oncogenic morphological changes and anchorage-independent growth. Our observations suggest that PAF is a unique growth regulator with apparently diverse functions. Dual actions of PAF may relate to the point of action in the cell cycle; PAF stimulates the mitogenic response in G0-arrested cells in a pertussis toxin-sensitive manner, while it inhibits the G1 to S transition through a pertussis toxin-resistant manner.

Animals↗
PubMed1997

cDNA cloning and expression of murine 1-acyl-sn-glycerol-3-phosphate acyltransferase.

1-Acyl-sn-glycerol-3-phosphate (1-AGP), also known as lysophosphatidic acid (LPA), is an intermediate of de novo biosynthesis of glycerophospholipids and triacylglycerol. LPA is also attracting much attention because of its growth stimulating effects. Here we report cloning of murine cDNA encoding 1-AGP acyltransferase (1-AGPAT), which converts LPA into phosphatidic acid by incorporating acyl moiety at an-2 position. The cDNA contains an open reading frame coding for 285 amino acids, with highly hydrophobic regions in the N-terminal half. The Northern blot analysis using various mouse tissues revealed ubiquitous expressions of two transcripts. The cDNA was expressed in Escherichia coli JC201, a plsC mutant strain deficient in the 1-AGPAT activity, and the enzyme properties were examined. The enzyme utilized both saturated and unsaturated acyl-CoA as an acyl-donor, while it utilized LPA but not other lysophospholipids as an acceptor.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1997

Microplate chromatography assay for acetyl-CoA: lysoplatelet-activating factor acetyltransferase.

Acetyl-CoA:lysoplatelet-activating factor (1-O-alkyl-sn-glycero-3-phosphocholine) acetyltransferase (lysoPAF-AT) (EC 2.3.1.67) is a key enzyme in the biosynthesis of platelet-activating factor (PAF) and has been shown to be activated by various extracellular stimuli. A novel method to determine the enzyme activity is described here, which enables 96 simultaneous assays in a standard 96-well microplate format. The assay is based on the quantification of the incorporation of [3H]acetyl-CoA into PAF in the presence of lysoPAF. The radioactive products are separated from the substrate with a 96-well-formatted chromatography device using a Multiscreen plate (Millipore) prefilled with octyl-silica gel. As little as 1 mg octyl-silica gel was sufficient for the efficient recovery of the radioactive product, resulting in the very low background and thus high sensitivity. The enzyme activity could be measured directly with whole cell lysates from various cells cultured in 96-well microplate scale. This tailor-made microplate chromatography separation step is readily applicable for other kinds of enzyme assays.

Acetyltransferases↗
PubMed1997

Bronchial hyperreactivity, increased endotoxin lethality and melanocytic tumorigenesis in transgenic mice overexpressing platelet-activating factor receptor.

Although platelet-activating factor (PAF) has been shown to exert pleiotropic effects on isolated cells or tissues, controversy still exists as to whether it plays significant pathophysiological roles in vivo. To answer this question, we established transgenic mice over-expressing a guinea-pig PAF receptor (PAFR). The transgenic mice showed a bronchial hyperreactivity to methacholine and an increased mortality when exposed to bacterial endotoxin. An aberrant melanogenesis and proliferative abnormalities in the skin were also observed in the transgenic mice, some of which spontaneously bore melanocytic tumors in the dermis after aging. Thus, PAFR transgenic mice proved to be a useful model for studying the basic pathophysiology of bronchial asthma and endotoxin-induced death, and screening of therapeutics for these disorders. Furthermore, our findings provide new insights regarding the role of PAF in the morphogenesis of dermal tissues as well as the mitogenic activity of PAF and PAFR in vivo.

Animals↗
PubMed1997

Cloning and characterization of a murine platelet-activating factor receptor gene.

A murine gene encoding a platelet-activating factor receptor (PAFR) was cloned. The gene was mapped to a distal region of chromosome 4 both by fluorescence in situ hybridization and by molecular linkage analysis. Northern blot analysis showed a high expression of the PAFR message in peritoneal macrophages. When C3H/HeN macrophages were treated with bacterial lipopolysaccharide (LPS) or synthetic lipid A, the PAFR gene expression was induced. Bacterial LPS, but not lipid A, induced the level of PAFR mRNA in LPS-unresponsive C3H/HeJ macrophages. These induction patterns were parallel to those of tumor necrosis factor-alpha mRNA. Thus, the PAFR in macrophages plays important roles in LPS-induced pathologies.

Animals↗
PubMed1997

Molecular cloning of canalicular multispecific organic anion transporter defective in EHBR.

Several organic anions are excreted into the bile via a canalicular multispecific organic anion transporter (cMOAT), which is hereditarily defective in mutant rats, such as the Eisai hyperbilirubinemic rat (EHBR) and TR- rat. In the present study, we cloned cMOAT from the Sprague-Dawley rat liver cDNA library based on the homology with human multidrug resistance-associated protein (hMRP). cMOAT was encoded by 4,623-base pair (bp) cDNA with a homology of 53.0 and 46.3% with hMRP at the cDNA and deduced amino acid level, respectively. The deduced amino acid sequence was the same as that cloned in Wistar rats (C. C. Paulusma, P. J. Bosma, G. J. Zaman, C. T. Bakker, M. Otter, G. L. Sceffer, P. Borst, and R. P. Oude Elferink. Science Wash. DC 271: 1126, 1996) except for four amino acid substitutions. By screening the library, three kinds of cDNA species for cMOAT with the same open reading frame and different 3'-untranslated region lengths (0.2, 1.5, and 3.5 kbp) were isolated. The Northern blot analysis of poly(A)+ RNA from the liver revealed that the expression of plural bands (approximately 5, 6, and 8 kb) was defective in EHBR, and this may be due to the presence of these cDNA species. Expression of cMOAT was observed almost exclusively in the liver and to a lesser extent in the duodenum, kidney, and jejunum. Reverse transcription-polymerase chain reaction (RT-PCR) and subsequent sequence analysis of EHBR liver, kidney, duodenum, and jejunum revealed that 1-bp replacement from G to A at nucleotide 2564 resulted in the introduction of the premature stop codon in all tissues examined. This mutation was different from that observed in TR (C. C. Paulusma, P. J. Bosma, G. J. Zaman, C. T. Bakker, M. Otter, G. L. Sceffer, P. Borst, and R. P. Oude Elferink. Science Wash. DC 271: 1126, 1996). Because EHBR and TR- are allelic mutants and both strains exhibit an autosomal recessive inheritance in the biliary excretion of organic anions it was concluded that the impaired expression of this particular protein is related to the pathogenesis of hyperbilirubinemia in the mutant animals.

Amino Acid Sequence↗
PubMed1997

Experimental IgA nephropathy induced by coxsackie B4 virus in mice.

Viruses have been suspected to be etiological agents of IgA nephropathy. Recently, viruses were detected in renal tissues from patients with IgA nephropathy. We tried to cause lesions similar to IgA nephropathy by inoculating virus into mice and to detect virus RNA in the lesion by in situ hybridization. A group of mice were inoculated intravenously with coxsackie B4 virus once a month from 1 to 5 months of age and sacrificed monthly from 6 to 12 months of age. Mesangial proliferation and deposits that stained positive with periodic acid-Schiff in light microscopy and electron-dense deposits in electron microscopy were found from 6 months of age. Positive findings for IgG and IgA deposition in the mesangium were noted and the intensity of IgA deposition was predominant after 10 months of age. The signals of coxsackie B4 virus by in situ hybridization were observed in the lesions. These observations indicate that coxsackie B4 virus inoculated repeatedly into mice induces lesions similar to IgA nephropathy. The depositions of the lesions may be immune complexes of coxsackie B4 virus and these immune complexes injure renal tissues.

Animals↗
PubMed1997

Effect of sairei-to on prostaglandin E2-induced phosphatidylinositol breakdown in aminonucleoside nephrotic rat.

We describe the effects of Sairei-to, a Chinese herbal medicine, on aminonucleoside-induced nephrotic rats (ANNR), and analyze the urinary excretion of protein and phosphatidylinositol (PI) turnover via prostaglandin E2 (PGE2) receptors in isolated glomeruli. Sairei-to suppressed urinary excretion of protein and PGE2 in ANNR, and inhibited acceleration of PI turnover in isolated nephrotic glomeruli. The affected responsiveness of the PI turnover system to PGE2 in a nephrotic state was presumed to be normalized by Sairei-to. These findings suggest that Sairei-to restores abnormal changes in the PI turnover system in ANNR kidneys, and thereby inhibit excretion of protein into the urine.

Animals↗
PubMed1997

Experimental glomerulonephritis following successive inoculation of five different serotypes of group B coxsackieviruses in mice.

The purpose of the present investigation is to study renal injury by monthly viral inoculation into mice, using several different types of strains of enterovirus. A group of mice were inoculated intravenously with five different serotypes of group B coxsackieviruses (CB1 to CB5), once a month from 1 to 5 months of age and sacrificed monthly from 6 to 12 months of age. Mesangial proliferation and PAS-positive mesangial deposits in light microscopy and electron-dense deposits in electron microscopy were observed at maximum from 6 to 7 months of age. The CB viral RNA detected by in situ hybridization were observed in the mesangial lesion. By immunofluorescence findings, positive findings for IgG and IgA were observed. These results demonstrated that intermittent intravenous inoculation with different serotypes CB in mice provoked pathological changes closely resembling those in human proliferative glomerulonephritis. Moreover, the detection of CB viral RNA in glomerular lesions suggested that renal injury was induced by immune complexes correlated with CB viral replication in renal tissues.

Animals↗
PubMed1997

Changes in platelet calcium concentration by thromboxane A2 stimulation in patients with nephrotic syndrome of childhood.

In order to examine the intracellular thromboxane A2 (TXA2) signal transduction system in platelets of patients with nephrotic syndrome, we measured the levels of TXA2 metabolites in urine and blood and platelet calcium ion level as a result of STA2, an analog of STA2 (9,11-dimethylmethano-11,12-methano-TXA2) stimulation, and obtained the following results: (1) In pediatric patients with nephrotic syndrome, urinary thromboxane B2 (TXB2) and 11-dehydro-TXB2 excretion were signficantly higher in the onset and relapse groups compared to the remission and control groups. (2) The blood 11-dehydro-TXB2 level in the onset group was significantly higher than those in the remission and control groups. (3) Platelet calcium concentrations due to STA2 stimulation were significantly increased in the onset, relapse and remission groups compared to the control group. These findings suggest activation of the TXA2 signal transduction system in platelets of pediatric patients with nephrotic syndrome.

Blood Platelets↗