Biomedical subjects

M Imagawa

Publications and source records attributed to M Imagawa.

At least 37 records · Page 2Linked to original sources

PubMed2000

Cyclopentenone prostaglandins as potential inducers of phase II detoxification enzymes. 15-deoxy-delta(12,14)-prostaglandin j2-induced expression of glutathione S-transferases.

Exposure of cells to a wide variety of chemoprotective compounds confers resistance to a broad set of carcinogens. For a subset of the chemoprotective compounds, protection is generated by an increase in the abundance of protective enzymes, such as glutathione S-transferases (GSTs). In the present study, we developed a cell culture system that potently responds to phenolic antioxidants and found that antitumor prostaglandins (PGs) are potential inducers of GSTs. We screened primary hepatocytes and multiple cell lines for inducing GST activity upon incubation with the phenolic antioxidant (tert-butylhydroquinone) and found that rat liver epithelial RL34 cells most potently responded. Based on an extensive screening of diverse chemical agents on the induction of GST activity in RL34 cells, the J2 series of PGs, 15-deoxy-Delta(12,14)-prostaglandin J2 (15-deoxy-Delta(12,14)-PGJ2) in particular, were found to be potential inducers of GST. Enhanced gene expression of Class pi GST isozyme (GSTP1) by 15-deoxy-Delta(12,14)-PGJ2 was evident as a drastic elevation of the mRNA level. Hence, we examined the molecular mechanism underlying the 15-deoxy-Delta(12, 14)-PGJ2-induced GSTP1 gene expression. From functional analysis of various deletion mutant genes, we found that the 15-deoxy-Delta(12, 14)-PGJ2 reponse element was localized in a region containing a GSTP1 enhancer I (GPEI) that consists of two imperfect phorbol 12-O-tetradecanoylphorbol-13-acetate response elements. When the GPEI was combined with the minimum GSTP1 promoter, the element indeed showed an enhancer activity in response to 15-deoxy-Delta(12, 14)-PGJ2. Point mutations of either of the two imperfect 12-O-tetradecanoylphorbol-13-acetate response elements in GPEI completely abolished the enhancer activity. Gel mobility shift assays demonstrated that 15-deoxy-Delta(12,14)-PGJ2 specifically stimulated the binding of nuclear proteins including the transcription factor c-Jun, but not Nrf2, to GPEI. These results suggest that 15-deoxy-Delta(12,14)-PGJ2 induces the expression of the rat GSTP1 gene through binding of proteins, including c-Jun, to a specific GPEI.

Animals↗

PubMed2000

Redox regulation of glutathione S-transferase induction by benzyl isothiocyanate: correlation of enzyme induction with the formation of reactive oxygen intermediates.

Here we report the molecular mechanism underlying the induction of glutathione S-transferase (GST) in rat liver epithelial RL34 cells treated with a cancer chemopreventive isothiocyanate compound, benzylisothiocyanate (BITC). BITC was found to significantly induce GST activity in RL34 cells. Northern and Western blot analyses demonstrated that BITC specifically enhanced the production of the class pi GST isozyme (GSTP1). Our studies demonstrated for the first time that the addition of BITC to the cells resulted in an immediate increase in the reactive oxygen intermediates (ROIs) detected by a fluorescence probe, 2',7'-dichlorofluorescin diacetate. The level of the ROIs in the cells treated with BITC (10 microM) was approximately 50-fold higher than those in the control cells. Furthermore, glutathione depletion by diethyl maleate significantly enhanced BITC-induced ROI production and accelerated the BITC-induced elevation of the GST activity, whereas pretreatment of the cells with glutathione inhibited both the ROI production and GST induction. The structure-activity relationship of the isothiocyanates also indicated that the ROI-producing activities closely correlated with their GST-inducing potencies. Moreover, the GSTP1 enhancer I-containing region was found to be essential for induction of the GSTP1 gene by intracellular ROI inducers such as BITC and diethyl maleate. These data suggest the involvement of the redox regulation on the induction of GSTP1 by BITC.

Animals↗

PubMed2000

Sacculo-ocular reflex connectivity in cats.

The otolith system contributes to the vestibulo-ocular reflexes (VOR) when the head moves linearly in the horizontal plane or tilts relative to gravity. The saccules are thought to detect predominantly accelerations along the gravity vector. Otolith-induced vertical eye movements following vertical linear accelerations are attributed to the saccules. However, information on the neural circuits of the sacculo-ocular system is limited, and the effects of saccular inputs on extraocular motoneurons remain unclear. In the present study, synaptic responses to saccular-nerve stimulation were recorded intracellularly from identified motoneurons of all twelve extraocular muscles. Experiments were successfully performed in eleven cats. Individual motoneurons of the twelve extraocular muscles--the bilateral superior recti (SR), inferior recti (IR), superior obliques (SO), inferior obliques (IO), lateral recti (LR), and medial recti (MR) were identified antidromically following bipolar stimulation of their respective nerves. The saccular nerve was selectively stimulated by a pair of tungsten electrodes after removing the utricular nerve and the ampullary nerves of the semicircular canals. Stimulus intensities were determined from the stimulus-response curves of vestibular N1 field potentials in order to avoid current spread. Intracellular recordings were performed from 129 extraocular motoneurons. The majority of the neurons showed no response to saccular-nerve stimulation. In 17 (30%) of 56 extraocular motoneurons related to vertical eye movements (bilateral SR and IR), depolarizing and/or hyperpolarizing postsynaptic potentials (PSPs) were observed in response to saccular-nerve stimulation. The latencies of PSPs ranged from 2.3 to 8.9 ms, indicating that the extraocular motoneurons received neither monosynaptic nor disynaptic inputs from saccular afferents. The majority of the latencies of the depolarization, including depolarization-hyperpolarization, were in the range of 2.3-3.3 ms. Latencies of hyperpolarizations were typically longer than those of depolarizations. Only one contralateral SO motoneuron of 43 recorded oblique extraocular motoneurons (bilateral SO and IO) showed a depolarization-hyperpolarization in response to saccular-nerve stimulation at a latency of 2.5 ms. None of 30 recorded horizontal extraocular motoneurons (bilateral LR and MR) responded to stimulation of the saccular nerve. The neural linkage in the sacculo-ocular system is relatively weak in comparison to the utriculo-ocular and sacculo-collic systems, suggesting that the role of the sacculo-ocular system in stabilizing eye position may be reduced when compared with utriculo-ocular and semi-circular canal-ocular reflexes.

Animals↗

PubMed2000

Convergence of posterior semicircular canal and saccular inputs in single vestibular nuclei neurons in cats.

Convergence between posterior canal (PC) and saccular (SAC) inputs in single vestibular nuclei neurons was investigated in decerebrated cats. Postsynaptic potentials were recorded intracellularly after selective stimulation of the SAC and PC nerves. Stimulation of either the SAC or PC nerve orthodromically activated 143 vestibular nuclei neurons. Of these, 61 (43%) were antidromically activated by stimulation of the C1-C2 junction, 14 (10%) were antidromically activated by stimulation of the oculomotor or trochlear nucleus, and 14 (10%) were antidromically activated by stimulation of both the oculomotor or trochlear nucleus and the spinal cord. Fifty-four (38%) neurons were not activated by stimulation of either or both. We named these neurons vestibulospinal (VS), vestibulo-ocular (VO), vestibulooculo-spinal (VOS) and vestibular (V) neurons, respectively. Both PC and SAC inputs converged in 47 vestibular nuclei neurons (26 VS, 2 VO, 6 VOS and 13 V neurons). Of these, 19 received monosynaptic excitatory inputs from both nerves. This input pattern was frequently seen in VS neurons. Approximately half of the convergent VS neurons descended to the spinal cord through the lateral vestibulospinal tract. The remaining half and all the convergent VOS neurons descended to the spinal cord through the medial vestibulospinal tract. Most of the convergent neurons were located in the lateral nucleus or descending nucleus.

Animals↗

PubMed2000

Low density lipoprotein receptor-related protein gene polymorphisms and risk for late-onset Alzheimer's disease in a Japanese population.

Low density lipoprotein (LDL) receptor-related protein (LRP) gene polymorphisms located in the 5' region and in exon 3, and the apolipoprotein E (APOE) genotype were determined in 100 Japanese patients affected by late-onset Alzheimer's disease (AD). We matched 246 controls for age and found no association between the polymorphism located in the 5' region of the LRP gene. The distribution of LRP exon 3 genotypes and alleles did not differ between AD and the control groups. However, the frequency of T allele in the Alzheimer's group having APOE-epsilon4 was lower than that in the control group having APOE-epsilon4, but it was only marginally significant (p = 0.022). Age of onset was significantly younger in the patients with CC genotype than those carrying the T allele (p = 0.03), and this trend was more evident among non-APOE-epsilon4 carriers (p = 0.008). These results support the possibility that ApoE and LRP may contribute to the development of AD.

Age of Onset↗

PubMed2000

Calcium supplement necessary to correct hypocalcemia after total parathyroidectomy for renal osteodystrophy.

BACKGROUND: Prediction of the extent of calcium supplement will facilitate safe and efficient management of hypocalcemia in the early postoperative stage of total parathyroidectomy with autotransplantation (PTXa) in patients with renal osteodystrophy. METHODS: The correlation between the extent of calcium deficiency, estimated by the amount of calcium supplement over 48 h after PTXa and using various parameters such as carboxy terminal parathyroid hormone (c-PTH), intact PTH (i-PTH), alkaline phosphatase (ALP), serum calcium, serum phosphorus, duration of hemodialysis, total weight of resected parathyroid glands and degree of subperiosteal resorption of the middle phalanx was examined in 49 patients who underwent PTX with subcutaneous autotransplantation. Bone mineral density (BMD) was also determined before, 3 months and 1 year after PTXa with dual energy X-ray absorptiometry (DEXA) in 13 patients. RESULTS: There was a positive correlation between pre-operative i-PTH level (r=0.56, P<0.0005) or ALP level (r=0.50, P<0.0005) and the amount of calcium supplement over 48 h after PTXa in these patients. Furthermore, the degree of subperiosteal resorption, determined by Jensen's classification, was significantly correlated with the amount of calcium supplement after PTX (P<0.05). Bone mineral density 3 months after (P<0.0005) and 1 year after PTXa (P<0.001) significantly increased compared with BMD before PTXa in all patients examined. CONCLUSION: These findings suggest that the pre-operative determination of i-PTH, ALP levels and degree of subperiosteal resorption allow the management of hypocalcemia safely and efficiently in renal osteodystrophy patients after PTXa.

Adult↗

PubMed2000

Gene expression of CCAAT/enhancer-binding protein delta mediated by autoregulation is repressed by related gene family proteins.

CCAAT/enhancer-binding protein delta (C/EBPdelta) transcription factor is rapidly induced at an early stage of acute phase response. We previously reported that this induction was mainly mediated by acute phase response factor/signal transducers and activators of transcription 3 (APRF/STAT3). Furthermore, the high expression level of C/EBPdelta is maintained by autoregulation mechanisms through the C/EBPdelta binding sites located downstream of C/EBPdelta gene. Thereafter, the expression of C/EBPdelta gene decreases rapidly to the basal level. However, these mechanisms are still unknown. According to both transfection and DNA binding analyses, liver-enriched inhibitory protein (LIP), the shorter form of C/EBPbeta and C/EBP-homologous protein 10 (CHOP10), were found to inhibit C/EBPdelta gene expression. DNA binding analysis has further indicated that both LIP and CHOP10 form heterodimers with C/EBPdelta, and inhibit the binding of C/EBPdelta homodimer to the C/EBPdelta binding sites located downstream of C/EBPdelta gene. Taken together, these findings indicated that the maintained expression of C/EBPdelta gene by autoregulation was inhibited and decreased to the basal level as a result of the competition of other C/EBP family proteins. Thus, C/EBPdelta gene expression is mediated by the gene regulation circuit through the downstream C/EBPdelta binding sites.

Animals↗

PubMed1999

Presenilin 1 suppresses the function of c-Jun homodimers via interaction with QM/Jif-1.

Presenilin 1 (PS1) is the causative gene for an autosomal dominant familial Alzheimer's disease (AD) mapped to chromosome 14. Here we show that QM/Jun-interacting factor (Jif)-1, a negative regulator of c-Jun, is a candidate to mediate the function of PS1 in the cell. We screened for proteins that bind to PS1 from a human embryonic brain cDNA library using the two-hybrid method and isolated one clone encoding the QM/Jif-1 gene. The binding of QM/Jif-1 to full-length PS1 was confirmed in vitro by pull-down assay, and in vivo by immunoprecipitation assays with human samples, including AD brains. Immunoelectronmicroscopic analysis showed that QM/Jif-1 and PS1 are colocalized at the endoplasmic reticulum, and the nuclear matrix in human brain neurons. Chloramphenicol acetyltransferase assays in F9 cells showed that PS1 suppresses transactivation by c-Jun/c-Jun but not by c-Jun/c-Fos heterodimers, consistent with the reported function of QM/Jif-1. By monitoring fluorescent recombinant protein and by gel mobility shift assays, PS1 was shown to accelerate the translocation of QM from the cytoplasm to the nucleus and to thereby suppress the binding of c-Jun homodimer to 12-O-tetradecanoylphorbol-13- acetate (TPA)-responsive element (TRE). PS1 suppressed c-jun-associated apoptosis by retinoic acid in F9 embryonic carcinoma cells, whereas this suppression of apoptosis is attenuated by mutation in PS1. Collectively, the novel function of PS1 via QM/Jif-1 influences c-jun-mediated transcription and apoptosis.

Adult↗

PubMed1999

Three isoforms of mammalian hyaluronan synthases have distinct enzymatic properties.

Three mammalian hyaluronan synthase genes, HAS1, HAS2, and HAS3, have recently been cloned. In this study, we characterized and compared the enzymatic properties of these three HAS proteins. Expression of any of these genes in COS-1 cells or rat 3Y1 fibroblasts yielded de novo formation of a hyaluronan coat. The pericellular coats formed by HAS1 transfectants were significantly smaller than those formed by HAS2 or HAS3 transfectants. Kinetic studies of these enzymes in the membrane fractions isolated from HAS transfectants demonstrated that HAS proteins are distinct from each other in enzyme stability, elongation rate of HA, and apparent K(m) values for the two substrates UDP-GlcNAc and UDP-GlcUA. Analysis of the size distributions of hyaluronan generated in vitro by the recombinant proteins demonstrated that HAS3 synthesized hyaluronan with a molecular mass of 1 x 10(5) to 1 x 10(6) Da, shorter than those synthesized by HAS1 and HAS2 which have molecular masses of 2 x 10(5) to approximately 2 x 10(6) Da. Furthermore, comparisons of hyaluronan secreted into the culture media by stable HAS transfectants showed that HAS1 and HAS3 generated hyaluronan with broad size distributions (molecular masses of 2 x 10(5) to approximately 2 x 10(6) Da), whereas HAS2 generated hyaluronan with a broad but extremely large size (average molecular mass of >2 x 10(6) Da). The occurrence of three HAS isoforms with such distinct enzymatic characteristics may provide the cells with flexibility in the control of hyaluronan biosynthesis and functions.

Animals↗

PubMed1999

Expression, DNA-binding specificity and transcriptional regulation of nuclear factor 1 family proteins from rat.

Nuclear factor 1 (NF1) family proteins, which are encoded by four different genes (NF1-A, NF1-B, NF1-C and NF1-X), bind to the palindromic sequence and regulate the expression of many viral and cellular genes. We have previously purified NF1-A and NF1-B from rat liver as factors that bind to the silencer in the glutathione transferase P gene, and have also reported the repression domain of NF1-A. In the present study we cloned five cDNA species (NF1-B1, NF1-B2, NF1-B3, NF1-C2 and NF1-X1) and compared their expression profiles and the affinity and specificity of the DNA binding of these NF1 family members. By Northern blot analysis, we found that the expression profiles of the NF1s are indistinguishable in the various tissues of the rat. The DNA-binding affinities of NF1-A and NF1-X are higher than those of NF1-B and NF1-C, whereas all four NF1 proteins showed the same DNA-binding specificity. Transfection analyses revealed that the function of NF1-B on the transcriptional regulation differed between NF1-B isoforms and was affected by the factor(s) that bind to the promoter regions. In addition, we identified the transcriptional regulatory domain of NF1-B, which is enriched with proline and serine residues.

Amino Acid Sequence↗

PubMed1999

Cross-striolar and commissural inhibition in the otolith system.

Neural connections from the saccular and utricular nerves to the ipsilateral vestibular neurons and the commissural effects were studied by using intracellular recordings of excitatory (E) and inhibitory (I) postsynaptic potentials (PSPs) in vestibular neurons of cats after focal stimulation of the saccular and the utricular maculae. Neural circuits from the maculae to vestibular neurons, termed cross-striolar inhibition, may provide a mechanism for increasing the sensitivity to linear acceleration and tilt of the head. It was examined whether secondary vestibular neurons activated by an ipsilateral otolith organ received a commissural inhibition from a contralateral otolith organ that occupied the same geometric plane. Results suggest that utricular-activated vestibular neurons receiving commissural inhibition may provide a mechanism for increasing the sensitivity to horizontal linear acceleration and tilt of the head. The commissural inhibition of the saccular system was much weaker than that of the utricular system.

Afferent Pathways↗

PubMed1999

Identification of an enhancer element of class Pi glutathione S-transferase gene required for expression by a co-planar polychlorinated biphenyl.

3,3',4,4',5-Pentachlorobiphenyl (PenCB), one of the most toxic co-planar polychlorinated biphenyl congeners, specifically induces class Pi glutathione S-transferase (GSTP1) as well as cytochrome P-450 1A1 in primary cultured rat liver parenchymal cells [Aoki, Matsumoto and Suzuki (1993) FEBS Lett. 333, 114-118]. However, the 5'-flanking sequence of the GSTP1 gene does not contain a xenobiotic responsive element, to which arylhydrocarbon receptor binds. Using a chloramphenicol acetyltransferase assay we demonstrate here that the enhancer termed GSTP1 enhancer I (GPEI) is necessary for the stimulation by PenCB of GSTP1 gene expression in primary cultured rat liver parenchymal cells. GPEI is already known to contain a dyad of PMA responsive element-like elements oriented palindromically. It is suggested that a novel signal transduction pathway activated by PenCB contributes to the stimulation of GSTP1 expression.

Animals↗

PubMed1999

Identification of inducible genes at the early stage of adipocyte differentiation of 3T3-L1 cells.

Adipocyte differentiation takes place via a complex series of steps. While PPARgamma2 and C/EBPalpha are known to be master regulators, the events at the earliest stage of adipocyte differentiation are not yet known. In this study, we cloned the genes which are induced at the beginning of differentiation of 3T3-L1 preadipocyte cells. Of 58 clones obtained, only a few were already reported as the genes that are expressed differentially during adipocyte development. More than 30 clones are known but have been newly identified here as differentially expressed genes. Nineteen clones seemed to be unknown genes. The expression of RGS2, HSP105, Rho (TC10), VDR, and HIF-1alpha genes isolated here rapidly increased after the addition of inducers, and after 3-12 h the levels of expression decreased. The expression patterns of these mRNAs were different among growth-arrested and proliferating 3T3-L1 cells and NIH-3T3 cells, strongly indicating that some of the proteins identified here have crucial roles in the program of adipocyte differentiation.

1-Methyl-3-isobutylxanthine↗

PubMed1999

[A case of renal actinomycosis].

A case of renal actinomycosis is reported. A 63-year-old man was admitted to our hospital for further examinations of a right renal mass, complaining of dull pain in his right loin and progressive weight loss. Laboratory findings showed an anemia with a grossly raised ESR, CT, MRI and ultrasonography revealed a solid mass of the right kidney. Chest CT films revealed several infiltrates in the bilateral lobes. A diagnosis of neoplasm or inflammatory mass of the right kidney was considered, and the right nephrectomy was performed. Microscopically, characteristic colonies of actinomyces were seen, and histological diagnosis was renal actinomycosis. The patient made good progress after operation and was subsequently treated with penicillin.

Actinomycosis↗

PubMed1999

[Laparoscopic radical nephrectomy for renal cell carcinoma--transperitoneal anterior approach].

PURPOSE: To evaluate the usefulness of transperitoneal anterior approach in laparoscopic radical nephrectomy for patients with renal cell carcinoma. MATERIAL: Ten patients (Eight males and two females) with small renal cell carcinoma less than 7 cm in diameter were treated with laparoscopic radical nephrectomy between June 1997 and May 1999. Clinical stage was T1aN0M0 in 6 cases and T1bN0M0 in 4 cases. METHOD: Of the 10 patients, the initial four received preoperative embolization of the renal artery. Under general anesthesia laparoscopic radical nephrectomy via transperitoneal anterior approach was performed in all patients. This procedure facilitates initiated early access to the renal vessels as does open radical nephrectomy. The kidney was dissected en bloc with Gerota's fascia and delivered from the small skin incision without morcellation. RESULT: Two patients needed conversion to open surgery. The mean operating time of eight patients except for conversion cases was 247 minutes and the mean blood loss was 258 ml. There was no major complication associated with laparoscopic procedure. CONCLUSION: Transperitoneal anterior approach in laparoscopic radical nephrectomy is a suitable and useful procedure for the treatment of small renal cell carcinoma because it enables us to avoid possible tumor manipulation by early access to the renal vessels as open radical nephrectomy.

Adult↗

PubMed1999

[Extra-intestinal complications of ulcerative colitis: hematologic complication].

Iron deficiency anemia, autoimmune hemolytic anemia, folic acid deficiency megaloblastic anemia, granulocytopenia, acute or chronic leukemia, idiopathic thrombocytopenic purpura have been reported as blood diseases among the extra-intestinal complications with ulcerative colitis until now. Iron deficiency anemia is most frequently seen, and it often derives from apparent or inapparent continuous gastrointestinal bleeding. Autoimmune hemolytic anemia produces antierythrocyte membrane autoantibody while idiopathic thrombocytopenic purpura produces antithrombocyte autoantibody leading to anemia or thrombocytopenia. For folic acid deficiency megaloblastic anemia and granulocytopenia, adverse reaction of sulfasalazine being administered to the patients with ulcerative colitis has been pointed out. While the cases with acute or chronic leukemia are reported increasingly, its cause is still unknown. For treatment of ulcerative colitis, it is considered necessary to find blood complications by carrying out general examinations of peripheral blood and examinations of blood picture, serum iron and folic acid routinely.

Agranulocytosis↗

PubMed1998

Functional characterization of the bovine conglutinin promoter: presence of a novel element for transcriptional regulation of a C-type mammalian lectin containing a collagen-like domain.

Bovine conglutinin is a Ca2+-dependent serum lectin that is specific for N-acetylglucosamine and a member of the collectin (collagen-like lectin) family. Here we report the identification of the cis-acting elements involved in regulating expression of the conglutinin gene. The 5'-flanking region of the conglutinin gene was cloned and sequenced by gene walking using vector (cassette)-ligation mediated PCR. A genomic fragment encompassing -741 to +50 bp had significant promoter activity when linked to the luciferase reporter gene and transfected into the human hepatoma cell line HepG2. Transfection analysis using a series of luciferase vector/5'-stepwise deletion mutants of the promoter constructs indicated that the sequence of 7 base pairs at around -180 bp from the transcription initiation site was necessary for the full expression of the conglutinin gene. The site-directed mutagenesis in the AP-1 (Activator Protein-1) sequence, immediately downstream of the positively controlling cis-element at around -180 bp, resulted in a marked loss of the promoter activity. The novel positively controlling cis-element and the AP-1 sequence regulated synergistically the expression of the conglutinin gene. Gel retardation assay and DNase I footprint analysis demonstrated the presence of the nuclear proteins that bind to these two cis-elements.

Animals↗

PubMed1998

Morphology of single afferents of the saccular macula in cats.

The morphology of single saccular afferents was studied by the intracellular horseradish peroxidase (HRP) method. Four neurons were sufficiently stained to allow reconstruction of their axonal arborizations. The main axon of these neurons bifurcated into an ascending and a descending branch at the level of the lateral nucleus. The ascending branches of two axons gave off collaterals with boutons in the caudal part of the superior nucleus, while the other two ascending branches lacked such terminations. By contrast, characteristics of the descending axonal arborization patterns of all the four neurons were substantially the same. The descending branches coursed caudally through the lateral part of the descending nucleus, and gave off up to 14 collaterals with boutons that extended throughout this nucleus. These collaterals also reached the ventral part of the lateral nucleus, the lateral border of the medial nucleus, and group f. A few axon collaterals ramified even outside the border of the vestibular nuclei into the spinal trigeminal nucleus and the reticular formation surrounding it. Axon collaterals from the stem axon also terminated in the interstitial nucleus of the vestibular nerve. There was a noticeable absence of any projection to the y group.

Action Potentials↗