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J Imai

Publications and source records attributed to J Imai.

At least 19 recordsLinked to original sources
PubMed2006

Effusion and solid lymphomas have distinctive gene and protein expression profiles in an animal model of primary effusion lymphoma.

Lymphoma usually forms solid tumours in patients, and high expression levels of adhesion molecules are observed in these tumours. However, Kaposi's sarcoma-associated herpesvirus (KSHV)-related primary effusion lymphoma (PEL) does not form solid tumours and adhesion molecule expression is suppressed in the cells. Inoculation of a KSHV-associated PEL cell line into the peritoneal cavity of severe combined immunodeficiency mice resulted in the formation of effusion and solid lymphomas in the peritoneal cavity. Proteomics using two-dimensional difference gel electrophoresis and DNA microarray analyses identified 14 proteins and 105 genes, respectively, whose expression differed significantly between effusion and solid lymphomas. Five genes were identified as having similar expression profiles to that of lymphocyte function-associated antigen 1, an important adhesion molecule in leukocytes. Among these, coronin 1A, an actin-binding protein, was identified as a molecule showing high expression in solid lymphoma by both DNA microarray and proteomics analyses. Western and northern blotting showed that coronin 1A was predominantly expressed in solid lymphomas. Moreover, KSHV-encoded lytic proteins, including viral interleukin-6, were highly expressed in effusion lymphoma compared with solid lymphoma. These data demonstrate that effusion and solid lymphomas possess distinctive gene and protein expression profiles in our mouse model, and suggest that differences in gene and protein expression between effusion and solid lymphomas may be associated with the formation of effusion lymphoma or invasive features of solid lymphoma. Furthermore, the results obtained using this combination of proteomics and DNA microarray analyses indicate that protein synthesis partly reflects, but does not correlate strictly with, mRNA production.

Acquired Immunodeficiency Syndrome↗
PubMed2006

Restoration of transforming growth factor-beta type II receptor reduces tumorigenicity in the human adrenocortical carcinoma SW-13 cell line.

Transforming growth factor-beta (TGF-beta) is a potent growth suppressor. Acquisition of TGF-beta resistance has been reported in many tumors, and has been associated with reduced TGF-beta receptor expression. In this study, we examined TGF-beta 1, TGF-beta type I receptor (TbetaRI) and TGF-beta type II receptor (TbetaRII) expression in SW-13 adrenocortical carcinoma cells by Northern and Western blot analysis. SW-13 cells did not express TbetaRII mRNA or protein. We have investigated the role of TbetaRII in modulating tumorigenic potential using stably transfected SW-13 cells with TbetaRII expression plasmid. TbetaRII-positive SW-13 cell growth was inhibited by exogenous human TGF-beta1 (hTGF-beta1) in a dose-dependent manner. In contrast, SW-13 cells and control clones transfected with empty vector remained hTGF-beta1-insensitive. Xenograft examination in athymic nude mice demonstrated that TbetaRII-positive SW-13 cells reduced tumor-forming activity. Reconstructing the TbetaRII can lead to reversion of the malignant phenotype of TbetaRII-negative human adrenocortical carcinoma, which contains SW-13 cells. Reduced TbetaRII expression may play a critical role in determining the malignant phenotype of human adrenocortical carcinoma.

Adrenal Cortex Neoplasms↗
PubMed2001

CREB-H: a novel mammalian transcription factor belonging to the CREB/ATF family and functioning via the box-B element with a liver-specific expression.

The expression of liver-specific genes is regulated by unequivocally allocated transcription factors via proper responsible elements within their promoters. We identified a novel transcription factor, CREB-H, and found that its expression was restricted in the liver among 16 human tissues tested. A region of CREB-H exhibited significant homology to the basic leucine zipper (b-Zip) domain of members of the CREB/ATF family: mammalian LZIP and Drosophila BBF-2 that binds to box-B, a Drosophila enhancer modulating the fat-body-specific gene expression. CREB-H contained a hydrophobic region representing a putative transmembrane domain, like LZIP. Constructing a variety of CREB-H fusion proteins with the GAL4 DNA-binding domain disclosed that CREB-H functioned as a transcriptional activator and its N-terminal 149 amino acids accounted for the activation ability. Gel mobility sift assays revealed that CREB-H did not bind to the C/EBP, AP-1 and NF-kappaB elements but specifically bound to CRE and the box-B element. Luciferase reporter assays demonstrated that like BBF-2, CREB-H activated transcription via the box-B element and that a deletion of the putative transmembrane domain increased the activation of reporter expression significantly. Furthermore, a fusion protein of GFP and full-length CREB-H was localized in reticular structures surrounding the nucleus, whereas a fusion protein of GFP and a deletion mutant lacking the putative transmembrane domain was mainly in the nucleus. These findings suggest that CREB-H plays an important role in transcriptional regulation of genes specifically expressed in the liver, and that the putative transmembrane domain may be associated with modulation of its function as the transcriptional activator.

Activating Transcription Factors↗
PubMed2001

Suppression of tumourigenicity, and induction of differentiation of the canine mammary tumour cell line MCM-B2 by sodium phenylacetate.

The authors evaluated the cell growth inhibition, reduction of tumourigenicity, and differentiation-inducing effects of sodium phenylacetate (NaPA) on a canine mammary tumour cell line. Treatment of the canine mammary tumour cell line (MCM-B2) with NaPA lead to the arrest of cell growth. Sodium phenylacetate induced changes in the cells to non-malignant characteristics, as indicated by a reduction of colony formation in semi-solid agar and a decrease in tumour formation in athymic mice. Moreover, NaPA induced morphological changes from a spindle-shaped to an epithelial-like appearance, and significant accumulation of lipid droplets in the cytoplasm. Immunohistochemically, these treated cells reacted clearly with the antibody for keratin/cytokeratin. Sodium phenylacetate treatment increased the expression of the milk-specific genes alpha-lactalbumin and beta-casein. The results of this study warrant an evaluation of NaPA in a clinical trial to establish its possible value as adjunctive treatment of malignant canine mammary tumours.

Animals↗
PubMed2001

Pharmacokinetic behaviour of cisplatin in peritoneal fluid after intraperitoneal administration of cisplatin-loaded microspheres.

The objective of this study was to establish a pharmacokinetic model for the estimation of unchanged cis-dichlorodiammine-platinum (II) (CDDP) concentration in peritoneal fluid after intraperitoneal administration of cisplatin-loaded microspheres (CDDP-MS) and to elucidate the accuracy of this model by comparisons between actual and simulated values after intraperitoneal administration of CDDP-MS. We developed a method enabling the precise and quick assessment of the drug concentration in the peritoneal cavity. The pharmacokinetic parameters obtained after intravenous bolus injection at a dose of 2 mg kg(-1) were total body clearance (1026 mL h(-1) kg(-1)), elimination rate constant (3.24 h(-1)) and distribution volume of systemic circulation (316.7 mL kg(-1)). After an intraperitoneal bolus injection at a dose of 5 mg kg(-1), the absorption rate constant from the peritoneal cavity (3.64 h(-1)) and the distribution volume of the peritoneal cavity (13.5 mL kg(-1)) were determined. The protein-binding rate constant in ascites was 0.58 h(-1). Using these pharmacokinetic parameters, we established a pharmacokinetic model consisting of two compartments. Administration of CDDP-MS at a dose of 10 mg kg(-1), which released CDDP over 7 days in-vitro, yielded sustained concentrations of unchanged CDDP (1-2 mg mL(-1)) in the peritoneal cavity that persisted for 7 days, and that were predictable by applying the in-vitro dissolution profile to the pharmacokinetic model. The findings obtained from this study are useful for understanding the basic pharmacokinetic characteristics of unchanged CDDP in the peritoneal cavity and may also be important in the development of optimized CDDP-MS formulations.

Algorithms↗
PubMed2001

Molting of Gnathostoma doloresi (Nematoda: Gnathostomatoidea) in the definitive host.

Premolt, molting, and postmolt worms of Gnathostoma doloresi (Nematoda: Gnathostomatoidea) recovered from the stomach wall of naturally infected wild boars Sus scrofa leucomystax in Miyazaki, Japan, were examined morphologically. The only molt observed was that from the advanced third-stage to the adult stage. It is strongly suggested that the gnathostomes molt only once in the definitive host.

Animals↗
PubMed2000

Macrophage-mediated activation of camptothecin analogue T-2513-carboxymethyl dextran conjugate (T-0128): possible cellular mechanism for antitumor activity.

Camptothecin (CPT) analogue T-2513-carboxymethyl (CM) dextran conjugate (T-0128) suppressed human tumor xenografts that were refractory to CPTs. This improvement was explained by its altered pharmacokinetics, but the cellular mechanism of action is still not clear. For this reason, in the present study we examined the determinants of T-0128 action at the cellular level. In vitro tests showed that T-0128 was inactive, indicating that the requirement for its activity lies in the release of linked T-2513, accompanied by the cellular uptake of the conjugate. The accumulation varied between cell lines: tumor cells, including Walker-256 carcinoma and B16 melanoma, showed only a marginal uptake and an undetectable drug release in the medium. In contrast, macrophage-like cells, such as J774.1, internalized T-0128 very efficiently, and liberated T-2513. With regard to the mode of accumulation, fluid-phase pinocytosis seems to be a key factor based on the followings: a similar cell-specificity existed in the uptake of FITC dextran, a marker of fluid-phase pinocytosis. Also, the macrophage uptake of T-0128 increased almost linearly with its medium concentration and was insensitive to dextran sulfate, a ligand for macrophage scavenger receptor. Comparative efficacy studies of T-0128 in the presence and absence of macrophages demonstrated that macrophages increased the efficacy of T-0128. The enhancement could be explained in terms of increases in the amount of released T-2513. Overall, these results lead us to the conclusion that T-0128 acts like a Trojan horse with the help of macrophages: T-0128 is taken up by macrophages in tumor tissues, and the liberated T-2513 kills tumor cells.

Animals↗
PubMed2000

Complete regression of xenografted human carcinomas by camptothecin analogue-carboxymethyl dextran conjugate (T-0128).

Clinically available camptothecins (CPTs), such as irinotecan (CPT-11) and topotecan, represent one of the most promising classes of antitumor agents, despite their toxicity. To improve their pharmacological profiles, a new macromolecular prodrug, denoted T-0128, was synthesized. This prodrug is a novel CPT analogue (T-2513)-carboxymethyl (CM) dextran conjugate via a triglycine spacer, with a molecular weight of Mr 130,000. This study was designed to test the concept that the rational design of a CPT-polymer conjugate would increase the efficacy of the parent drug. The in vivo antitumor study against Walker-256 carcinoma demonstrated that T-0128 was 10 times as active as T-2513, supporting this concept. Additionally, comparative efficacy studies of T-0128, T-2513, CPT-11, and topotecan were performed using a panel of human tumor xenografts in nude mice, showing the advantage of T-0128 over these CPTs. The maximal tolerated doses (MTDs) of T-0128, T-2513, and CPT-11 were comparable. Even a single i.v. injection of T-0128 at 6 mg/kg (based on the amount of T-2513 bound to CM dextran) induced complete regression of MX-1 mammary carcinoma. T-0128 at 10 mg/kg weekly for 3 weeks (one-tenth of its MTD) cured LX-1 lung carcinoma. Also, T-0128 below its MTD consistently cured or regressed St-4 gastric and HT-29 colorectal tumor xenografts that are highly refractory to CPTs. These demonstrate the broad range of therapeutic doses achieved with T-0128. Pharmacokinetic studies were performed to correlate the efficacy results obtained for T-0128 with plasma and tissue drug concentrations using Walker-256 tumor-bearing rats. Results showed that after i.v. administration of T-0128, the conjugate continued to circulate at a high concentration for an extended period, resulting in tumor accumulation. In the tumor, the sustained release of T-2513 occurred. In contrast, T-2513 disappeared rapidly from the body. The significant increases in the amount and exposure time of released T-2513 in the tumor explain well the enhanced efficacy of T-0128. In conclusion, this study indicated that T-0128 improved the potency of T-2513, demonstrating the proof of the above concept.

Animals↗
PubMed2000

Role of HSP90 in salt stress tolerance via stabilization and regulation of calcineurin.

The role of HSP90 in stress tolerance was investigated in Saccharomyces cerevisiae. Cells showing 20-fold overexpression of Hsc82, an HSP90 homologue in yeast, were hypersensitive to high-NaCl or H-LiCl stresses. Hsc82-overexpressing cells appeared similar to calcineurin-defective cells in salt sensitivity and showed reduced levels of calcineurin-dependent gene expression. Co-overexpression of Cna2, the catalytic subunit of calcineurin, suppressed the hypersensitivity. Cna2 and Hsc82 coimmunoprecipitated from control cells grown under normal conditions but not from stressed cells. In contrast, coimmunoprecipitation was detected with Hsc82-overexpressing cells even after exposure to stresses. Cna2 immune complexes from stressed control cells showed a significant level of calcineurin activity, whereas those from stressed Hsc82-overexpressing cells did not. Treatment of extracts from Hsc82-overexpressing cells with Ca(2+)-calmodulin increased the calcineurin activity associated with Cna2 immune complexes. Geldanamycin, an inhibitor of HSP90 abolished the coimmunoprecipitation but did not activate calcineurin. When the expression level of Hsc82 decreased to below 30% of the normal level, cells also became hypersensitive to salt stress. In these cells, the amount of Cna2 was reduced, likely as a result of degradation. The present results showed that Hsc82 binds to and stabilizes Cna2 and that dissociation of Cna2 from Hsc82 is necessary for its activation.

Blotting, Western↗
PubMed2000

Structure-activity relationship of orally potent tripeptide-based HIV protease inhibitors containing hydroxymethylcarbonyl isostere.

We designed and synthesized a new class of peptidomimetic human immunodeficiency virus protease inhibitors containing a unique unnatural amino acid, allophenylnorstatine [Apns; (2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid], with a hydroxymethylcarbonyl isostere as the active moiety. From a structure-activity relationship study of HIV-1 protease inhibition, enzyme selectivity for other aspartyl proteases, the antiviral activity and pharmacokinetics in rats, 24c (KNI-227) and 24d (KNI-272, our first clinical candidate) were found to be selective and orally potent HIV protease inhibitors. Moreover, an improvement of the pharmacokinetic features of KNI-272 provided two long-lasting and highly bioavailable compounds (24g: JE-2178, 24h: JE-2179).

Animals↗
PubMed2000

Molecular cloning and phylogenetic analysis of canine beta-casein.

A canine beta-casein cDNA was isolated from mammary tissue by polymerase chain reaction (PCR) using degenerate primers. It encodes 250 amino acids protein containing the conserved sequence motif of beta-casein. It showed the highest homology with snow-leopard (Uncia uncia (55-62% identity). It also showed 44-53% identity with human, 33-42%, identity with mouse, 29-37%, identity with rat, 43-53% identity with rabbit, 41-48% identity with pig, 44-51% identity with cattle and 44-50% identity with sheep. A 1.2-kb mRNA was detected in mammary tissue by Northern blot analysis. Phylogenetic analysis revealed that canine beta-casein formed a branch with lesser panda and snow leopard, which were grouped into carnivore.

Amino Acid Sequence↗
PubMed1999

Induction of c-met proto-oncogene expression at the metastatic site.

In metastatic processes, gene expression may variously alter through interactions between tumor and host stromal cells at the metastatic site. Using a tail vein injection-lung metastatic model and differential display, we analyzed alteration of gene expression in experimentally metastasized lesions. We found that expression of the c-met proto-oncogene was elevated in the lungs metastasized by MC-1 cells. The up-regulation of c-met was also observed in the lungs metastasized by B16 melanoma cells. In situ hybridization analysis revealed that the elevation of c-met expression apparently occurred in tumor cells but did not in lung stromal cells at the metastatic site. The c-Met protein was also highly expressed and phosphorylated. The upregulation of c-met appeared to be caused by induction of gene expression but not to be due to preferential selection of tumor cells highly expressing c-met. These findings suggest that the c-met proto-oncogene is up-regulated at the transcription level through some interactions between tumor and host stromal cells.

Animals↗
PubMed1999

Rho3 of Saccharomyces cerevisiae, which regulates the actin cytoskeleton and exocytosis, is a GTPase which interacts with Myo2 and Exo70.

The Rho3 protein plays a critical role in the budding yeast Saccharomyces cerevisiae by directing proper cell growth. Rho3 appears to influence cell growth by regulating polarized secretion and the actin cytoskeleton, since rho3 mutants exhibit large rounded cells with an aberrant actin cytoskeleton. To gain insights into how Rho3 influences these events, we have carried out a yeast two-hybrid screen using an S. cerevisiae cDNA library to identify proteins interacting with Rho3. Two proteins, Exo70 and Myo2, were identified in this screen. Interactions with these two proteins are greatly reduced or abolished when mutations are introduced into the Rho3 effector domain. In addition, a type of mutation known to produce dominant negative mutants of Rho proteins abolished the interaction with both of these proteins. In contrast, Rho3 did not interact with protein kinase C (Pkc1), an effector of another Rho family protein, Rho1, nor did Rho1 interact with Exo70 or Myo2. Rho3 did interact with Bni1, another effector of Rho1, but less efficiently than with Rho1. The interaction between Rho3 and Exo70 and between Rho3 and Myo2 was also demonstrated with purified proteins. The interaction between Exo70 and Rho3 in vitro was dependent on the presence of GTP, since Rho3 complexed with guanosine 5'-O-(3-thiotriphosphate) interacted more efficiently with Exo70 than Rho3 complexed with guanosine 5'-O-(3-thiodiphosphate). Overlapping subcellular localization of the Rho3 and Exo70 proteins was demonstrated by indirect immunofluorescence. In addition, patterns of localization of both Exo70 and Rho3 were altered when a dominant active allele of RHO3, RHO3(E129,A131), which causes a morphological abnormality, was expressed. These results provide a direct molecular basis for the action of Rho3 on exocytosis and the actin cytoskeleton.

Actins↗
PubMed1998

Intrasolid Interfacial Fractality of a Less-Crystalline Solid.

Small angle X-ray scattering (SAXS) measurements have been carried out on pitch (PIT) and cellulose (CEL)-based activated carbon fibers (ACFs). In the higher angle region, the scattering intensity did not obey the classical Porod's law. This suggests that ACFs have a rough surface and their roughness is expressed by the concept of surface fractal. The surface fractal dimension was determined from SAXS for each ACF. ACFs were treated at high temperature in argon in order to control the nanographitic crystallinity. PIT and CEL lost their microporosity upon heat treatment above 1773 and 2073 K, respectively. These nonporous ACFs showed also a strong SAXS caused by the electron density difference at the interface between microcrystalline and amorphous phase. This interface also had a fractal dimension, which was defined as the interfacial fractal dimension. The surface or interfacial fractal dimension of ACF depended on the heating temperature. As the treating temperature increased, the surface or interfacial fractal dimension decreased from 2.8 to 2.0. Both PIT and CEL showed a similar temperature dependence on each other. The surface or interfacial fractal dimension was reduced with the growth of nanographites, and upon heating at 3173 K, the intrasolid interfacial fractal dimension became 2. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

The effects of genetic polymorphisms of CYP2C9 and CYP2C19 on phenytoin metabolism in Japanese adult patients with epilepsy: studies in stereoselective hydroxylation and population pharmacokinetics.

PURPOSE: The aim of this study was to clarify the effects of genetic polymorphisms of cytochrome P450 (CYP) 2C9 and 2C19 on the metabolism of phenytoin (PHT). In addition, a population pharmacokinetic analysis was performed. METHODS: The genotype of CYP2C9 (Arg144/Cys, Ile359/Leu) and CYP2C19(*1, *2 or *3) in 134 Japanese adult patients with epilepsy treated with PHT were determined, and their serum concentrations of 5-(4-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) enantiomers, being major metabolites of PHT, were measured. A population pharmacokinetic analysis (NONMEM analysis) was performed to evaluate whether genetic polymorphism of CYP2C9/19 affects the clinical use of PHT by using the 336 dose-serum concentration data. RESULTS: The mean maximal elimination rate (Vmax) was 42% lower in the heterozygote for Leu359 allele in CYP2C9, and the mean Michaelis-Menten constants (Km) in the heterozygous extensive metabolizers and the poor metabolizers of CYP2C19 were 22 and 54%, respectively, higher than those without the mutations in CYP2C9/19 genes. (R)- and (S)-p-HPPH/PHT ratios were lower in patients with mutations in CYP2C9 or CYP2C19 gene than those in patients without mutations. CONCLUSIONS: Although the hydroxylation capacity of PHT was impaired with mutations of CYP2C9/19, the impairment was greater for CYP2C9. In view of the clinical use of PHT, two important conclusions were derived from this population study. First, the serum PHT concentration in patients with the Leu359 allele in CYP2C9 would increase dramatically even at lower daily doses. Second, the patients with CYP2C19 mutations should be treated carefully at higher daily doses of PHT.

Aryl Hydrocarbon Hydroxylases↗