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T Imai

Publications and source records attributed to T Imai.

At least 343 records · Page 19Linked to original sources
PubMed1997

ERC-55, a binding protein for the papilloma virus E6 oncoprotein, specifically interacts with vitamin D receptor among nuclear receptors.

VDR regulates gene expression in a ligand-dependent way by binding to cognate enhancer elements of target gene promoters. The ligand-dependent activation function, AF-2, of VDR is thought to require transcriptional co-activators/co-repressors together with basal transcriptional machinery. Using a yeast two hybrid system with VDR, we have isolated a mouse Ca(2+)-binding protein (designated as VAF1) specifically interacting in vivo and in vitro with VDR among nuclear receptors like RAR, RXR, ER and GR. VAF1 is a mouse homologue to human ERC-55, which has recently been shown to interact with human papillomavirus oncogenic protein, E6[1]. Unlike those of many previously identified co-activators, the VDR-VAF1 interaction was ligand-independent. Thus, VAF1 seems a putative VDR-specific cofactor modulating its function.

Amino Acid Sequence↗
PubMed1997

Molecular cloning of a novel human CC chemokine liver and activation-regulated chemokine (LARC) expressed in liver. Chemotactic activity for lymphocytes and gene localization on chromosome 2.

Partial overlapping cDNA sequences likely to encode a novel human CC chemokine were identified from the GenBank Expressed Sequence Tag data base. Using these sequences, we isolated full-length cDNA encoding a protein of 96 amino acid residues with 20-28% identity to other CC chemokines. By Northern blot, this chemokine was mainly expressed in liver among various tissues and strongly induced in several human cell lines by phorbol myristate acetate. We thus designated this chemokine as LARC from Liver and Activation-Regulated Chemokine. We mapped the LARC gene close to the chromosomal marker D2S159 at chromosome 2q33-q37 by somatic cell and radiation hybrid mappings and isolated two yeast artificial chromosome clones containing the LARC gene from this region. To prepare LARC, we subcloned the cDNA into a baculovirus vector and expressed it in insect cells. The secreted protein started at Ala-27 and was significantly chemotactic for lymphocytes. At a concentration of 1 microg/ml, it also showed a weak chemotactic activity for granulocytes. Unlike other CC chemokines, however, LARC was not chemotactic for monocytic THP-1 cells or blood monocytes. LARC tagged with secreted alkaline phosphatase-(His)6 bound specifically to lymphocytes, the binding being competed only by LARC and not by other CC or CXC chemokines. Scatchard analysis revealed a single class of receptors for LARC on lymphocytes with a Kd of 0.4 nM and 2100 sites/cell. Collectively, LARC is a novel CC chemokine, which may represent a new group of CC chemokines localized on chromosome 2.

Amino Acid Sequence↗
PubMed1997

Structural properties and RNA-binding activities of two RNA recognition motifs of a mouse neural RNA-binding protein, mouse-Musashi-1.

mouse-Musashi-1 (m-Msi-1) is an RNA-binding protein, abundantly expressed in the developing mammalian central nervous system (CNS). m-Msi-1 contains two RNA recognition motifs (RRMs). In this study, we found that the N-terminal RRM of m-Msi-1 (MMA) binds strongly to poly(G) and weakly to poly(U) in a way similar to that of the full-length m-Msi-1 protein characterized previously. The C-terminal RRM of m-Msi-1 (MMB), however, does not bind to RNA. In addition, the circular dichroism (CD) spectra of the two RRMs showed that the alpha-helical content of MMA is significantly higher than that of MMB, indicating that some differences in the secondary structure may be responsible for the distinct RNA binding properties of MMA and MMB.

Amino Acid Sequence↗
PubMed1997

Novel zinc-containing ferredoxin family in thermoacidophilic archaea.

The dicluster-type ferredoxins from the thermoacidophilic archaea such as Thermoplasma acidophilum and Sulfolobus sp. are known to contain an unusually long extension of unknown function in the N-terminal region. Recent x-ray structural analysis of the Sulfolobus ferredoxin has revealed the presence of a novel zinc center, which is coordinated by three histidine ligand residues in the N-terminal region and one aspartate in the ferredoxin core domain. We report here the quantitative metal analyses together with electron paramagnetic resonance and resonance Raman spectra of T. acidophilum ferredoxin, demonstrating the presence of a novel zinc center in addition to one [3Fe-4S] and one [4Fe-4S] cluster (Fe/Zn = 6.8 mol/mol). A phylogenetic tree constructed for several archaeal monocluster and dicluster type ferredoxins suggests that the zinc-containing ferredoxins of T. acidophilum and Sulfolobus sp. form an independent subgroup, which is more distantly related to the ferredoxins from the hyperthermophiles than those from the methanogenic archaea, indicating the existence of a novel group of ferredoxins, namely, a "zinc-containing ferredoxin family" in the thermoacidophilic archaea. Inspection of the N-terminal extension regions of the archaeal zinc-containing ferredoxins suggested strict conservation of three histidine and one aspartate residues as possible ligands to the novel zinc center.

Amino Acid Sequence↗
PubMed1997

Inhalation of diesel exhaust enhances antigen-specific IgE antibody production in mice.

To examine the effects of diesel exhaust (DE) inhalation on IgE antibody production, BALB/c mice were exposed to 0 (control), 3.0 and 6.0 mg/m3 DE inhalation for 3 weeks. Intranasal sensitization with ovalbumin (OA) three times at intervals of 3 weeks was conducted immediately before, immediately after and 3 weeks after DE inhalation. Body weight and thymus weight for the DE-exposed and control mice were essentially the same but spleen weight in mice exposed to 6 mg/m3 significantly increased. Anti-OA IgE antibody titers in the sera of mice exposed to 6 mg/m3 was significantly higher than the control. Total IgE and anti-OA IgG in sera for DE-exposed and control mice remained basically the same. To investigate cytokine production in mice exposed to 6 mg/m3, spleen cells from DE-exposed and control mice were stimulated with OA in vitro and cytokine production in the culture supernatants was measured by ELISA. In vitro antigen-stimulated interleukin-4 (IL-4) and -10 (IL-10) production in spleen cells of exposed mice significantly increased compared to the control. In vitro interferon (IFN)-gamma production in spleen cells of exposed mice markedly decreased. DE inhalation is thus shown to have adverse effect on antigen-specific IgE antibody production in mice through alteration of the cytokine network.

Administration, Inhalation↗
PubMed1997

Highly metastatic hepatocellular carcinomas induced in male F344 rats treated with N-nitrosomorpholine in combination with other hepatocarcinogens show a high incidence of p53 gene mutations along with altered mRNA expression of tumor-related genes.

The carcinogenic and metastatic processes are thought to consist of a sequence of steps, and animal models featuring highly metastatic lesions are clearly necessary to allow analysis of the whole process of transformation from preneoplastic changes to high grade metastatic tumors, and to access effectiveness of therapeutic treatments of advanced cancers in vivo. The purpose of the present study was to establish a model and to screen for reported genetic alterations in induced lesions. In the present study, it was confirmed that lung metastasis of hepatocellular carcinomas (HCCs) induced in male F344 rats by N-nitrosomorpholine (NNM), given in the drinking water at a dose of 120 ppm for 24 weeks, was significantly enhanced by additional carcinogenic pretreatments and that a single i.p. injection of 100 mg/kg body weight N-diethylnitrosamine (DEN) alone was sufficient for that purpose. Molecular biological analyses of the induced lesions revealed point mutations in the p53 gene in 60.9% of HCCs, and elevated expression of mRNAs for p53, c-myc, c-fos, TGF-alpha, TGF-beta1, alpha-fetoprotein, GST-P, and GGT, and decreased mRNA expression of EGF and EGFR in HCCs when compared to controls. No obvious association of gene alterations with metastatic potential of primary tumors was found except for an increase in the incidence of p53 mutations. Since the process of metastasis is thought to be sequential and selective, further comparative analysis of metastatic and primary lesions should clarify the mechanisms involved in the multi-step process of metastasis.

Animals↗
PubMed1997

Species differences for stereoselective hydrolysis of propranolol prodrugs in plasma and liver.

Species differences and substrate specificities for the stereoselective hydrolysis of fifteen O-acyl propranolol (PL) prodrugs were investigated in pH 7.4 Tris-HCl buffer and rat and dog plasma and liver subfractions. The (R)-isomers were preferentially converted to propranolol (PL) in both rat and dog plasma with the exception of isovaleryl-PL in rat plasma, although the hydrolytic activities of prodrugs in rat plasma were 5-119-fold greater than those in dog plasma. The prodrugs with promoieties (C(=O)CH(R)CH3) based on propionic acid showed marked preference for hydrolysis of the (R)-enantiomers in plasma from both species (R/S ratio 2.5-18.2). On the other hand, the hepatic hydrolytic activities of prodrugs were greater in dog than rat, especially in cytosolic fractions. The hydrolytic activity was predominantly located in microsomes of the liver in rat, while the cytosol also contributed to hepatic hydrolysis in dog. Hepatic microsomal hydrolysis in dog showed a preference for the (R)-isomers except acetyl- and propionyl-PL. Interestingly, in rat liver all types of prodrugs with substituents of small carbon number showed (S)-preference for hydrolysis. The hydrolyses of (R)- and (S)-isomers of straight chain acyl esters in rat liver microsomes were linearly and parabolically related with the carbon number of substituents, respectively, while these relationships were linear for both isomers in dogs.

Animals↗
PubMed1997

Friedreich-like ataxia with retinitis pigmentosa caused by the His101Gln mutation of the alpha-tocopherol transfer protein gene.

The alpha-tocopherol transfer protein (alpha-TTP) is a cytosolic liver protein that is presumed to function in the intracellular transport of alpha-tocopherol, the most biologically active form of vitamin E. We studied 4 unrelated patients with autosomal recessive Friedreich-like ataxia who had isolated vitamin E deficiency. A point mutation was identified in all of them at position 101 of the gene for alpha-TTP, where histidine (CAT) was replaced with glutamine (CAG). Three of the 4 patients developed retinitis pigmentosa subsequent to the onset of ataxia. Neurological symptoms included ataxia, dysarthria, hyporeflexia, and decreased proprioceptive and vibratory sensations. Electrophysiological and pathological examinations showed that the cardinal sites affected were the central axons of dorsal root ganglion cells and the retina, with minor involvement of the peripheral sensory nerve, optic nerve, and pyramidal tract. The vitamin E tolerance test performed showed that the absorption of vitamin E was normal but that its decrease from the serum was accelerated. Oral administration of vitamin E appeared to halt the progression of visual and neurological symptoms. We propose a new treatable syndrome of Friedreich-like ataxia and retinitis pigmentosa caused by a defect in the alpha-TTP gene.

Aged↗
PubMed1997

Novel lymphocyte-specific CC chemokines and their receptors.

By using a cloning method termed the signal sequence trap as well as by searching for chemokine homologous sequences in the database of expressed sequence tags, cDNA fragments potentially encoding novel CC chemokines were initially identified. Using these sequences, we have cloned five novel human CC chemokines termed TARC, LARC, ELC, SLC, and PARC. These chemokines are constitutively expressed especially in some lymphoid tissues with individually unique expression patterns. The recombinant proteins are all found to be selectively chemotactic for lymphocytes but not for monocytes or neutrophils. Each chemokine appears to interact with a class of receptors on lymphocytes that is not shared by any other chemokines so far tested. Furthermore, we have identified CCR4 as the specific receptor for TARC, GPR-CY4/DRY6/CKR-L3/STRL22 as that for LARC (CCR6), and EBI1/BLR2 as that for ELC (CCR7). Only the gene for PARC is mapped to the traditional CC chemokine gene cluster at chromosome 17q11.2, whereas those for TARC, LARC, ELC, and SLC are localized at different loci. Collectively, these five CC chemokines may constitute a new category of CC chemokines that are involved in trafficking and homing of particular subsets of lymphocytes in particular lymphoid tissue microenvironments.

Amino Acid Sequence↗
PubMed1997

Dexamethasone-induced up-regulation of adrenomedullin and atrial natriuretic peptide genes in cultured rat ventricular myocytes.

To determine whether adrenomedullin (AM), a novel 51-residue vasodilator peptide originally isolated from human pheochromocytoma, is expressed by the heart, and whether the expression of cardiac AM gene is regulated by glucocorticoids, the effect of dexamethasone (DEX) on the expression of protein and mRNA of AM and atrial natriuretic peptide (ANP) was tested in cultured ventricular myocytes prepared from the neonatal rats. Northern blot analysis of rat ventricular myocytes with cDNAs for rat AM and ANP as probes revealed distinct bands corresponding to the sizes of rat AM mRNA (1. 6 kb) and rat ANP mRNA (1 kb), respectively. Dexamethasone increased steady-state levels of both AM and ANP mRNA as well as secretion of both AM and ANP immunoreactivity in a time- and dose-dependent manner. The stimulatory effects of dexamethasone were completely abolished by a glucocorticoid antagonist (RU38486) and a RNA synthesis inhibitor (actinomycin D). The approximate half-lives of basal and dexamethasone-induced AM mRNA were about 4 h, suggesting that dexamethasone-induced up-regulation of AM mRNA was unlikely due to its decreased degradation. These data suggest that glucocorticoids directly stimulate gene expression of AM as well as ANP in rat ventricular myocytes.

Adrenomedullin↗
PubMed1997

Stereospecific activity and nature of metabolizing esterases for propranolol prodrug in hairless mouse skin, liver and plasma.

Cutaneous stereoselective hydrolyses of ten ester prodrugs of propranolol in hairless mouse were compared to those in liver and plasma. On the basis of protein content, the hydrolysis rate was greatest with liver homogenate followed by plasma and skin homogenate. The buffer showed the slowest and non-stereoselective hydrolysis. However, skin showed very high stereoselectivity (R/S ratio: 6.7-18.4) as compared with liver (0.7-2.0) and plasma (1.7-4.7). The microsomal esterase activity was higher than cytosolic esterase in liver, while an opposite relation was observed in skin. The smaller Km and larger Vmax values of the (R) isomer than those of the (S) isomer of caproyl- and/or butyryl-propranolol were found in skin and plasma, while Km was the same between (R) and (S) isomers in liver. Enzyme inhibition studies indicated that the carboxylesterases were primarily involved in prodrug hydrolysis in liver. On the other hand, skin and plasma were found to be rich in both carboxylesterases and cholinesterases. Interestingly, the (R) isomer was more sensitive towards butylcholinesterase in skin and plasma, while (S) isomer was more sensitive towards carboxylesterase in plasma. Moreover, no stereoselective inhibition was observed in liver. These data indicated that the hydrolyzing nature of skin esterases responsible for propranolol prodrug was sensitive against stereochemical configuration and more similar to those in plasma esterases than liver esterases.

Adrenergic beta-Antagonists↗
PubMed1997

Alteration of pharmacokinetics and nephrotoxicity of cisplatin by alginates.

This study was undertaken to demonstrate that alginates could form a complex with cisplatin and that the pharmacokinetics and nephrotoxicity of cisplatin could be altered by this complexation. The complexes were prepared with alginates of mean molecular weights of 10000 (AL-1) and 40000 (AL-2). The plasma clearances of cisplatin-alginate complexes were significantly reduced when compared with the drug alone. Urinary excretion of platinum (Pt) was increased when animals were dosed with the cisplatin-AL-1 complex, but not with the cisplatin-AL-2 complex. Renal clearance of cisplatin, when administered alone, was more rapid during the first 2 h than the rest of the study period (96 h) and was higher than its plasma clearance, which is consistent with irreversible binding of cisplatin to plasma protein. On the other hand, renal clearance of cisplatin-alginate complexes was not highly time dependent, and the values were more similar to those of plasma clearance. Complexation of cisplatin with alginates, especially AL-1, inhibited the accumulation of Pt in the kidneys and reduced blood urea nitrogen elevation by cisplatin. The in vitro antitumor activities against U937, P388, and cisplatin-resistant P388 (P388/cisplatin) cells were similar among cisplatin and its alginate complexes. These studies indicated that the pharmacokinetics and nephrotoxicity of cisplatin could be altered through complexation with alginate by (1) reducing cisplatin clearance, (2) inhibition of Pt accumulation of in the kidneys, and (3) reduction of apparent nephrotoxicity without decrease in in vitro antitumor activity.

Alginates↗
PubMed1997

Effects of absorption enhancers on the transport of model compounds in Caco-2 cell monolayers: assessment by confocal laser scanning microscopy.

Three typical absorption enhancers, i.e., sodium caprate (Cap-Na), sodium deoxycholate (Deo-Na), and dipotassium glycyrrhizinate (Grz-K), were compared in terms of their permeability-enhancing effects on hydrophilic and hydrophobic model compounds in Caco-2 cell monolayers. The transepithelial electrical resistance (TEER) of the monolayers was reduced concentration-dependently by treatment with Cap-Na and Deo-Na, while treatment with Grz-K increased the TEER. Two patterns of TEER reduction were observed: one pattern indicated that Cap-Na had a rapid reducing effect, and another indicated that Deo-Na had a delayed reducing effect. These reductions in the TEER were accompanied by the increased transepithelial transport of two hydrophilic model compounds, sodium fluorescein (Flu-Na; MW = 376, log P = -1.52) and fluorescein isothiocyanate-dextran 4000 (FD-4; MW = 4400, log P = -2.0), and one hydrophobic model compound, rhodamine 123 hydrate (Rh123; MW = 381, log P = 1.13). The transport-enhancing effects of Cap-Na and Deo-Na on these model compounds decreased in the following order: FD-4 > Rh123 > Flu-Na, while Grz-K was found to have no effect on the transport of any of these model compounds. Confocal laser scanning microscopy (CLSM) of Caco-2 cell monolayers revealed that Cap-Na and Deo-Na enhanced the transepithelial transport of the hydrophilic model compounds via the paracellular route and that of the hydrophobic model compound via both paracellular and transcellular routes. Semiquantitative visual information obtained from CLSM images reflected the results of the transport experiment.

Biological Transport↗
PubMed1997

Permeability of contrast media through hemodialysis membrane.

PURPOSE: To compare the permeability of 10 contrast media (CM) through the hemodialysis membrane. MATERIAL AND METHODS: An experimental model was constructed from clinical hemodialysis equipment. The 10 CM that were used were: diatrizoate, iothalamate, iopamidol, iohexol, iopromide, ioversol, iomeprol, ioxaglate, iodixanol and iotrolan. They were dissolved into the dialysate. Each solution ran into the blood circuit of the dialyzer at a rate of 200 ml/min and into the dialysate circuit of the dialysis machine at a rate of 500 ml/min. Permeability was expressed as clearance, calculated from the iodine concentration at the afferent and efferent lines of the dialyzer, and from the blood-flow rate. RESULTS: The clearance of all the monomeric CM was superior to that of all the dimeric CM. Values of clearance and molecular weight correlated well. CONCLUSION: The molecular weight of a contrast medium is the main factor that influences the efficiency of CM removal by hemodialysis.

Cellulose↗
PubMed1997

Reduction of glutathione S-transferase P-form mRNA expression in remodeling nodules in rat liver revealed by in situ hybridization.

Glutathione S-transferase P-form (GST-P) mRNA levels and distribution were sequentially analyzed by in situ hybridization histochemistry (ISH) in rat livers during and after induction of preneoplastic foci and nodules in the Solt-Farber model. Dot blot analysis showed GST-P transcripts in the liver to be elevated coincidental with the development of GST-P-positive lesions. GST-P ISH indicated that the majority of early foci and some of the resultant lesions showed uniformly high levels of GST-P mRNA. However, the majority of foci and nodules after completion of the selection regimen exhibited a progressive loss of staining for GST-P mRNA. Similar results were obtained for gamma-glutamyltransferase (GGT) transcripts, indicating that phenotypic reversion is controlled by factors operating at the level of gene expression in both cases. Expression of GST-P mRNA was high in all hepatocellular carcinoma samples, whereas the levels of GGT transcripts varied considerably, so that the two enzymes showed a degree of independence in their regulation. The present data for transcription suggest that GST-P is a stable marker of preneoplastic and neoplastic cells, not only at the protein but also at the mRNA level, throughout hepatocarcinogenesis in the rat. The reason why transcription of GST-P mRNA is switched off as part of the reversion to a normal organization remains to be elucidated.

2-Acetylaminofluorene↗
PubMed1997

Increased level of circulating adhesion molecules in the sera of breast cancer patients with distant metastases.

The adhesion of circulating cancer cells to the vascular endothelium is an important at step in the hematogenous metastasis of cancer. E-selectin expressed on endothelial cells and carbohydrate ligands expressed on cancer cells mediate this adhesion. We investigated the clinical significance of such cell adhesion molecules in breast cancer. The cytosol concentration of sialyl Lewis(x) was found more elevated in cancerous tissue than that in adjacent non-cancerous tissue. In the serum, sialyl Lewis(x) and soluble E-selectin were seen elevated in patients with advanced and recurrent breast cancer, especially in those with distant metastases. From the above, we have concluded that sialyl Lewis(x) and soluble E-selectin could be used as tumor markers with a close relationship to the metastasis of breast cancer.

Biomarkers, Tumor↗