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Biomedical subjects

E Imai

Publications and source records attributed to E Imai.

At least 73 records · Page 4Linked to original sources
PubMed1999

[A case of subclinical IgA nephropathy and cyclosporin associated arteriolopathy diagnosed by non-episode biopsy of graft kidney after renal transplantation].

We report a case of subclinical immunoglobulin A (IgA) nephropathy and cyclosporin associated arteriolopathy following renal transplantation. A 39-year-old male with chronic glomerulonephritis received kidney transplantation from a two- human leukocyte antigen (HLA) mismatched cadaveric donor. The initial immunosuppressive therapy was triple-drug therapy with cyclosporin, prednisolone and mizoribine. Four months after transplantation, he had an acute rejection episode, and the renal function was recovered by steroid pulse and 15-deoxyspergualin therapy. Eight years after transplantation, we conducted a non-episode biopsy of the renal allograft to examine subclinical lesions. The histopathological findings showed cyclosporin associate arteriolopathy (CAA) and IgA nephropathy. There was no sign of acute or chronic rejection. At the present time, the renal function of the allograft is good. In conclusion, the non-episode biopsy of renal allograft is useful for examination of subclinical lesions.

Biopsy↗
PubMed1998

Preventive effects of the deleted form of hepatocyte growth factor against various liver injuries.

The effects of a naturally occurring deleted form of hepatocyte growth factor (HGF) on hepatic disorder were studied in various models of hepatic failure. The pretreatment of rats and mice with the deleted form of HGF prevented the liver injuries and coagulopathy induced by endotoxin, dimethylnitrosamine and acetaminophen and reduced the mortality due to hepatic dysfunction induced by these hepatotoxins. The concurrent administration of the deleted form of HGF also prevented the liver injury and hepatic fibrosis in mice treated with alpha-naphthylisothiocyanate and in rats treated with dimethylnitrosamine. Moreover, the deleted form of HGF normalized the results of the bromosulphalein-clearance test and ameliorated jaundice in rats with periportal cholangiolitic hepatopathy induced by alpha-naphthylisothiocyanate. The deleted form of HGF also reversed the coagulopathy in rats with hepatic disorder induced by dimethylnitrosamine or by 70% resection of cirrhotic liver (induced by carbon tetrachloride). In Long Evans cinnamon rats receiving vehicle, 20 out of 21 animals died within 4 days after the onset of jaundice. After infusion of the deleted form of HGF for 4 days, 7 out of 20 Long-Evans cinnamon rats survived. These results indicate that the deleted form of HGF could have therapeutic potency in patients with severe hepatic failure.

Animals↗
PubMed1998

Inhibition of myo-inositol transport causes acute renal failure with selective medullary injury in the rat.

Myo-inositol is a major compatible osmolyte in the renal medulla that is accumulated under hypertonic conditions via the Na+/myo-inositol cotransporter (SMIT). We have recently reported that SMIT is predominantly present in the thick ascending limb of Henle (TAL) and is strongly induced by acute NaCl loading, suggesting an important role of myo-inositol in this nephron segment. In the present study, we sought to examine in vivo effects of inhibition of myo-inositol transport using a transport inhibitor, 2-O, C-methylene-myo-inositol (MMI). Intraperitoneal injection of MMI caused acute renal failure in the rats. Serum creatinine and urea nitrogen were significantly increased 12 hours after MMI injection. Morphologic study revealed that the tubular cells were extensively injured in the outer medulla. A considerable number of the tubular cells were injured in the cortex as well. Immunohistochemical study for Tamm-Horsfall protein (THP), which was used for identification of the TAL cells, showed that THP-positive cells were predominantly injured. The tubular injury apparently appeared to worsen when high concentration of NaCl was injected with MMI. Administration of myo-inositol prevented acute renal failure and improved the tubular injury after MMI injection. Furthermore, supplementation of betaine, another osmolyte in the TAL cells, partially prevented the toxic effects of MMI. These results suggest that myo-inositol play a crucial role in the TAL regarding osmoregulation of the cells.

Acute Kidney Injury↗
PubMed1998

Strategies of gene transfer to the kidney.

Kidney targeted gene transfer has been a realistic goal for many researchers since 1991, but unfortunately, to date there is no reliable gene transfer technique for gene therapy of renal diseases. However, at the experimental level, several in vivo gene transfer methods have attempted to target certain renal structures, for example, the HVJ-liposome method and renal perfusion of adenovirus for glomerular cells, intravenous injection of oligonucleotides (ODNs) for proximal tubule, intra-arterial injection of adenovirus followed by cold incubation with a vasodilator for interstitial vasculature of the outer medulla, and adenoviral injection into the renal pelvis for the inner medullary collecting duct. As an ex vivo gene transfer method targeting the glomerulus, the transfusion of genetically-modified mesangial cells has been attempted. Implantation of genetically-modified tubular epithelial cells into the subcapsular region has been employed for ex vivo transfection to the interstitium. Gene therapy has focused particularly on the transplanted kidney, where an exogenous gene can transferred in advance. In the future, an inducible system and individual cell targeting strategy should be developed. The improvement of gene transfer techniques, especially vectors for delivering genes, is crucial. The potential application of gene transfer technologies is enormous while the therapeutic approaches have just begun to be explored. Therapeutic interventions of the process of progression of glomerulonephritis in the rat have been directed towards inhibiting the actions of growth factors. Obviously, molecular biological intervention is coming of age and there is a tremendous excitement over its potential. We believe that gene transfer techniques will become common tools for the dissection of molecular aspects of diseases and possibly for gene therapy in the field of nephrology.

Animals↗
PubMed1998

Isolation of genes identified in mouse renal proximal tubule by comparing different gene expression profiles.

An expression profile is a list based on a large scale sequencing of 1000 cDNA clones, showing the expressed genes and the abundance of their transcripts in a given cell or tissue (Okubo K et al: Nature Genet 2:173, 1992). We constructed an expression profile of mouse renal proximal tubules (PT) carefully isolated by microdissection in order to characterize its gene expression. Altogether 1000 clones were analyzed; there were 646 types of transcripts in PT, among which 196 were identical or homologous to the previously reported genes. The most abundant transcript was kidney-androgen regulated protein. By comparing the expression profile of PT with those obtained from other sources, several genes were identified only in PT. They included known transcripts and transcripts that were not homologous to the known genes. Three (GS4001, 3991, and 4059) of the non-homologous genes were analyzed by Northern blotting and in situ hybridization, and GS4001 and 4059 were predominantly expressed in the kidney, whereas GS3991 was detected in the liver as well as in the kidney. The sequence analysis of the full-size cDNAs demonstrated that GS4001 was a new member of aspartic proteinases and GS4059 was a novel gene. It also revealed that GS3991 was a mouse homologue of SA gene known to be expressed in PT. The expression profile of mouse PT and its comparison with those of other tissues and cells provide an alternate way of isolating genes predominantly expressed in PT, and also provides probes to study the molecular mechanisms of gene expression in the kidney.

3T3 Cells↗
PubMed1998

Effects of hypertonic stress on transforming growth factor-beta activity in normal rat kidney cells.

Hypertonicity is known to modulate the expression of some genes and the action of several cytokines. We evaluated whether hypertonicity would increase the expression and/or activity of transforming growth factor-beta (TGF-beta) in normal rat kidney (NRK) cells. The bioassay for TGF-beta showed that mature TGF-beta activity was significantly increased when the cells were cultured in a hypertonic medium (500 mOsm/kg). Comparing to the isotonic medium, hypertonicity accelerated the increase in TGF-beta activity during the initial 24 hours after changing the medium. The activity was increased as the medium osmolality increased from 300 to 500 mOsm/kg. Raffinose was found to be the most effective in increasing TGF-beta activity. NaCl, glucose, and mannitol also increased TGF-beta activity. In contrast, total TGF-beta (mature and latent) activity and TGF-beta mRNA abundance did not change significantly, suggesting that hypertonicity activated TGF-beta without affecting the synthesis of TGF-beta. To determine whether collagen synthesis was increased by hypertonicity, we examined [3H] proline incorporation into NRK cells cultured in hypertonic medium. Proline incorporation increased in an osmolality-dependent manner. Raffinose was also the most effective solute at increasing the proline incorporation. Furthermore, anti-TGF-beta antibody prevented the increase in proline incorporation induced by hypertonicity. These results suggest that hypertonicity promotes the processing of latent TGF-beta to the biologically active form, resulting in the stimulation of collagen synthesis in NRK cells.

Animals↗
PubMed1998

Up-regulation of HSP47 in the mouse kidneys with unilateral ureteral obstruction.

BACKGROUND: Unilateral ureteral obstruction (UUO) is a well established experimental model of renal injury leading to interstitial fibrosis. The molecular and cellular mechanism(s) of interstitial fibrosis in UUO are beginning to be elucidated. In the progression of interstitial fibrosis in UUO, up-regulation of collagen synthesis is commonly observed. HSP47 is a collagen-binding stress protein and is thought to be a collagen-specific molecular chaperone, which plays a pivotal role during the biosynthesis and secretion of collagen molecules in the endoplasmic reticulum. The synthesis of HSP47 has been demonstrated to always parallel that of collagen in physiological and pathophysiological conditions. It is well recognized that renin-angiotensin system (RAS) is enhanced in the setting of UUO and that enhanced RAS has been implicated in the pathogenesis of interstitial fibrosis in the obstructed kidneys. METHODS: To investigate the role of HSP47 in the progression of interstitial fibrosis in mouse UUO, the expression of HSP47 was examined by Northern blotting, immunohistochemistry and in situ hybridization in the obstructed kidneys. To test the possible involvement of enhanced RAS on the HSP47 expression, we examined the effects of lisinopril, an angiotensin converting enzyme inhibitor, on interstitial fibrosis. HSP47 and type I collagen mRNA expression. RESULTS: By Northern blot analysis, HSP47 mRNA was significantly up-regulated at 12 hours (about twice that of sham operated kidneys) after the onset of ureteral obstruction, further increased and stayed at the increased level until seven days (about 8 times that of sham operated kidneys). HSP47 mRNA and protein expression were observed in the periglomerular and peritubular interstitial regions of the obstructed kidneys. Distribution of smooth muscle alpha actin and type I collagen immunoreactivity were similar to the HSP47 distribution pattern, suggesting that HSP47 was up-regulated in the myofibroblasts. Lisinopril ameliorated the expansion of cortical interstitium in the obstructed kidneys at four and seven days after ureteral obstruction. HSP47 mRNA expression was suppressed at four and seven days, whereas type I collagen mRNA was suppressed only at seven days after the onset of ureteral obstruction. CONCLUSIONS: These results demonstrate the early and persistent up-regulation of HSP47 during the progression of interstitial fibrosis in mouse UUO kidneys, and further suggest the potential role of HSP47 in the pathogenesis of interstitial fibrosis in the obstructed kidneys. Partial suppression of HSP47 mRNA expression by lisinopril at day 4 and day 7 after ureteral obstruction suggests that there are other immediate trigger(s) that induce the HSP47 mRNA expression. Identification of the molecular mechanism of HSP47 induction during UUO may give an insight into the novel aspects of the molecular pathophysiology of interstitial fibrosis in obstructive nephropathy.

Actins↗
PubMed1998

Expression of the Na+/myo-inositol cotransporter in the juxtaglomerular region.

Myo-inositol is a major compatible osmolyte in the renal medulla and is accumulated in cells under hypertonic conditions by uptake via a Na+/myo-inositol cotransporter (SMIT). SMIT is regulated by extracellular osmolarity at the transcription level. We investigated localization of SMIT in rat kidney by immunohistochemical staining using an anti-SMIT-antibody raised against a synthetic peptide corresponding to part of SMIT and by in situ hybridization. SMIT protein localized predominantly to the basolateral membranes of cells of the thick ascending limb of Henle (TAL) and inner medullary collecting duct (IMCD). Macula densa (MD) cells, identified as the Tamm-Horsfall-protein (THP)-unreactive cells surrounded by THP-reactive TAL cells, also stained for anti-SMIT. In situ hybridization yielded the intense SMIT signals in the TAL and IMCD and also in the juxtaglomerular (JG) region. Prior loading of the animal with a high concentration of NaCl rapidly induced SMIT mRNA; furosemide down-regulated it. The high level of SMIT expression suggests that MD cells are exposed to hypertonicity at the basolateral surface. Because SMIT expression seemed to be proportional to the magnitude of NaCl reabsorption, it may be a good marker for examination of the tubuloglomerular feedback mechanism in vivo.

Amino Acid Sequence↗
PubMed1998

Enhanced glomerular expression of caldesmon in IgA nephropathy and its suppression by glucocorticoid-heparin therapy.

BACKGROUND: Activation and consequent phenotypic modulation of mesangial cells is considered to play a crucial role in the process of glomerular disease progression. Caldesmon, a calmodulin and actin-binding protein, is a molecular marker of the phenotypic change in smooth-muscle cells. SUBJECTS AND METHODS: We studied whether the expression of caldesmon in mesangial cells was enhanced in the process of IgA nephropathy and whether it would be a marker of mesangial activation indicating prognostic significance in specific disease states. We performed immunohistochemical staining with anticaldesmon and alpha-smooth-muscle actin (alpha-SMA) antibodies in 32 biopsy specimens from IgA nephropathy patients and analysed them quantitatively with a computer-aided manipulator. RESULTS: The glomerular expression of caldesmon was enhanced in IgA nephropathy patients. We compared caldesmon expression with composite histological scores (cell score and matrix score), clinical parameters and expressions of alpha-SMA. There was a statistically significant correlation between the caldesmon score and the histological scores (cell score and matrix score, P<0.0001, P<0.01 respectively). Patients showing a high intensity of caldesmon expression (defined as caldesmon score > or = 35; H-group) had significantly higher urinary protein excretion than those showing a low intensity of caldesmon expression (defined as caldesmon score < 35; L-group) (1.2 +/- 1.2 g/24 h vs 0.41 +/- 0.53 g/24 h, P<0.05). Caldesmon and alpha-SMA expression had a statistically significant correlation (P<0.000). Next, 13 patients were treated with glucocorticoid-heparin for 4-8 weeks and re-biopsies were performed. After the therapy, the caldesmon and alpha-SMA scores were significantly lower than those before the therapy (P<0.01). DISCUSSION: These results suggest that the expression of caldesmon in glomeruli is associated with the progression of IgA nephropathy, and that glucocorticoid heparin therapy may reverse the phenotype of mesangial cells during the disease process of glomerulonephritis.

Actins↗
PubMed1998

A case of Guillain-Barré syndrome developed minimal change nephrotic syndrome simultaneously.

A case who developed Guillain-Barré syndrome (GBS) and nephrotic syndrome (NS) simultaneously is reported. In this case, the onset of nephrotic change of proteinuria coincided with the development of the neurological disturbance. Analysis of renal biopsy by light, immunofluorescent and electron microscopy showed minor glomerular abnormalities. The occurrence of GBS in association with NS is rare, and moreover most cases in the previous reports had membranous nephropathy. Only 1 case had minimal change nephrotic syndrome (MCNS). To our knowledge, this is the first report of a case beneficially treated with glucocorticoids, suggesting that immune disorder may play an important role in the association between MCNS and GBS.

Adult↗
PubMed1998

Towards gene therapy for renal diseases.

The rationale of the somatic gene therapy is the correction of diseases at the most fundamental level. Ideal gene therapy should be achieved by the replacement of the wrong gene sequence of genome with correct one. However, the gene technology to date is yet immature so as to correct the wrong gene sequence in vivo. Potentially, the present technology of gene transfer may provide: 1) correction of cellular dysfunction by expressing the deficient gene; 2) addition of new function for a cell by transferring an exogenous gene; 3) inhibition of unfavorable action of a cell by introducing a counteracting gene. In nephrology, the gene transfer targeted kidney has been challenged at the experimental level. HVJ-liposome method and recombinant adenovirus allow gene transfer to the particular cells in kidney in vivo. Ex vivo gene transfer using mesangial cells and macrophages are another option. Transplant kidney is also a good material for genetic engineering. The potential application of gene transfer is enormous while the therapeutic application have just begun to explored. We have been devoted to HVJ-liposome mediated gene transfer to the kidney and successfully demonstrated the suppression of the extracellular matrix accumulation of the glomeruli in the experimental glomerulonephritis through inhibition of the TGF-beta action by antisense oligonucleotides or soluble type receptor chimera for TGF-beta. We also applied this technology to the inhibition of interstitial fibrosis in unilateral ureter obstruction model. The new HVJ-liposome method improved in lipid composition allows gene transfer to tubulointerstitial fibroblast by retrograde approach from ureter. In consequence, introduced TGF-beta antisense suppressed the TGF-beta mRNA in concomitant with ameliorating interstitial fibrosis. We believe that the gene transfer technique will become common strategy to study the molecular aspect of the renal diseases and will be possibly applicable to molecular intervention in nephrology.

Animals↗
PubMed1997

Inhibition of shear stress-induced platelet aggregation by cilostazol, a specific inhibitor of cGMP-inhibited phosphodiesterase, in vitro and ex vivo.

Cilostazol(6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)-butoxy]-3,4- dihydro-2(1H)-quinolinone) selectively inhibits cGMP-inhibited phosphodiesterase (PDE3) and is a potent inhibitor of platelet aggregation induced by various agonists. Effect of cilostazol on shear stress-induced human platelet aggregation (SIPA) was examined in vitro and ex vivo. Cilostazol inhibited SIPA dose-dependently in vitro. The IC50 value of cilostazol for inhibition of SIPA was 15 +/- 2.6 microM (m +/- SE, n=5), which was very similar to that (12.5 +/- 2.1 microM) for inhibition of ADP-induced platelet aggregation. Cilostazol potentiates the inhibition of SIPA by PGE1 and enhances its ability to increase cAMP concentrations. A single oral adminstration of 100 mg cilostazol to healthy volunteers produced a significant inhibition of SIPA. This study demonstrates that cilostazol is an effective inhibitor of SIPA, which may be important for the prevention and the treatment of arterial occlusive diseases.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1997

Transcriptional activation of a hybrid promoter composed of cytomegalovirus enhancer and beta-actin/beta-globin gene in glomerular epithelial cells in vivo.

The aim of this study was to seek a promoter, transactivated selectively in renal cells in vivo by using transgenic (tg) mouse technology. We generated two kinds of tg mouse lines carrying a green fluorescence protein (GFP) cDNA driven either by cytomegalovirus enhancer and beta-actin/beta-globin promoter (CX-GFP) or by elongation factor 1alpha promoter (EF-GFP), and investigated the expression of GFP in the kidney. Microscopic examination of the renal tissues in CX-GFP-tg mice revealed that GFP was expressed only in glomeruli, mainly epithelial cells, but not in tubules, arteries and interstitium. Moreover, in situ hybridization demonstrated that GFP mRNA expression was localized in the glomerular cells. In contrast, GFP was not detectable in the kidney in any of the lines of EF-GFP-tg mouse. To exclude the possible involvement of the GFP cDNA as an enhancer, we constructed tg mice carrying the CX promoter driving a human CD4 cDNA. It was confirmed that the expression patterns of human CD4 in the kidney were quite similar to those of GFP in the kidney of CX-GFP-tg mice. These results strongly suggest that CX promoter could be transactivated in glomerular epithelial cells in vivo.

Actins↗
PubMed1997

Effects of partial nephrectomy on the expression of osmolyte transporters.

Na+/myo-inositol cotransporter (SMIT) and Na+/Cl-/betaine-gamma-amino-n-butyric acid transporter (BGT-1) are the major osmolyte transporters that are regulated by extracellular osmolarity. We have recently shown localization and rapid regulation of the mRNAs for these transporters in rat kidney. In the present study, we examined the expression of SMIT and BGT-1 in partial nephrectomized rats in order to assess the change in local osmolarity following reduction of renal mass. Four weeks after 5/6 nephrectomy (NX), the rats were compared to sham-operated control animals (CONT). Northern analysis using RNA of whole kidney indicated that there were little differences in the levels of SMIT and BGT-1 mRNAs between the two groups. In situ hybridization revealed that signals for both transporter mRNAs were markedly reduced in the inner medulla of the remnant kidney. In contrast, these signals in the outer medulla increased following nephrectomy. SMIT signals in the cortex increased as well. Grain density, determined by counting grain number per cell, revealed that the signals in the inner medullary collecting ducts were markedly reduced whereas those in the thick ascending limbs of Henle (TAL) as well as macula densa cells were significantly increased. The signals in the TAL and macula densa were reduced by furosemide administration. The increased expression in NX rats may reflect the increased NaCl transport and high local osmolarity in this segment.

Animals↗