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N Arita

Publications and source records attributed to N Arita.

At least 37 records · Page 2Linked to original sources
PubMed1999

Efficient production of recombinant human erythropoietin by replenishment of microcarriers in the hollow fiber culture cassette.

Human erythropoietin (EPO)-producing recombinant BHK cells were cultured in culture medium containing microcarriers, and then microcarriers attached with cells were replenished in the hollow fiber culture cassette. By culture for 14 days, it was possible to produce 450 micrograms of the recombinant EPO, which corresponded to over two-fold of the recombinant EPO production by control hollow fiber culture without microcarriers.

Animals↗
PubMed1999

Rapid infusion of high-dose methotrexate resulting in enhanced penetration into cerebrospinal fluid and intensified tumor response in primary central nervous system lymphomas.

OBJECT: Twenty-nine nonimmunocompromised patients with primary central nervous system (CNS) lymphoma were treated with high-dose methotrexate (MTX) therapy followed by irradiation. The authors investigated the correlation of infusion schedules with MTX penetration into cerebrospinal fluid (CSF), tumor response, and survival to develop a regimen that would lead to better clinical results. METHODS: In this study, 100 mg/kg MTX was administered on either a rapid (3-hour) or regular (6-hour) infusion schedule for two or three cycles. Of 28 assessable patients, a complete or partial response was achieved in 15 (93.8%) of 16 who received rapid and in seven (58.3%) of 12 who received regular infusion therapy (p = 0.034). Rapid infusion significantly increased levels of MTX in the CSF (p < 0.001) and resulted in significant tumor volume reduction (p < 0.001). The mean tumor volume after the first, second, and third cycle of rapid infusion therapy was reduced to 34%, 14%, and 9%, respectively, of the initial volume, whereas the corresponding values were 54%, 42%, and 37% for regular infusion. The reduction between the second and third cycle was small and not significant for either schedule. Despite the longer median survival time in patients who underwent rapid MTX infusion and irradiation (> 60 compared with 20 months), the difference in survival was not significant (p = 0.147) because of the small number of patients enrolled. The median survival time was 39.3 months for all assessable patients who received high-dose MTX and radiation therapy, and the median relapse-free survival time was 35.2 months. CONCLUSIONS: Rapid infusion enhanced both MTX penetration into the CSF and tumor response and may improve patient survival. Administration of three or more cycles of therapy should be carefully weighed in terms of cytoreductive benefits.

Adult↗
PubMed1998

Telomerase activity and alterations in telomere length in human brain tumors.

Telomerase activity was examined in 170 human brain tumor tissues, and terminal restriction fragment (TRF) length was examined in 152 of the 170. Telomerase activity was detected in 61.7% (66 of 107) of the neuroepithelial tumors. However, the detection rates of telomerase activity were widely different for different histopathological entities. In the case of astrocytic tumors, the detection rate was 20.0% (3 of 15) for grade II astrocytomas, 40.0% (6 of 15) for anaplastic astrocytomas, and 72.3% (34 of 47) for glioblastomas. The mean TRF length of the tumors with telomerase activity was significantly shorter than that of the tumors with undetectable telomerase activity for each tumor entity. In grade II and anaplastic astrocytomas, telomerase activity was an indicator of early histological progression and reduced survival of the patients, although there was no difference in MIB-1 staining indices between the tumors with and without telomerase activity at onset. In three astrocytic tumors, concurrence of telomere shortening and telomerase reactivation was observed at recurrence; in these cases, tumors progressed to a higher grade. Ten glioblastomas that progressed from lower-grade tumors exhibited telomerase activity, and their TRF lengths were reduced in 80% (8 of 10). In contrast, telomerase activity was detected in only 63.3% (19 of 30; P < 0.05) and the TRF length remained compatible with normal values in 56.7% (17 of 30; P < 0.01) of de novo glioblastomas. Thus, telomerase activity strongly correlated with potential tumor progression in the short term as well as with progression itself of the astrocytic tumors, whereas telomeres may still have been in the process of shortening in some of the de novo glioblastomas. High telomerase activity was exhibited in all primitive neuroectodermal tumors, anaplastic oligoastrocytomas, neuroblastomas, and oligodendrogliomas. TRF length was reduced in the majority (14 of 15) of three previously high-grade tumors, whereas it was compatible with that of normal brain tissues in the oligodendrogliomas, suggesting that telomerase activity with shortened telomeres correlates with the aggressive growth of high-grade neuroepithelial tumors. Tumor cell lines could be established from 17.2% (5 of 29) of neuroepithelial tumors with telomerase activity but not from tumors without this activity (P < 0.05), suggesting that telomerase reactivation is an essential event in the neuroepithelial cell immortalization in vitro. In nonneuroepithelial tumors, telomerase activity was detected in malignant tumors, such as germ cell tumors, lymphomas, metastatic adenocarcinomas, hemangiopericytomas, and an anaplastic meningioma. In contrast, such activity was not detected in benign tumors, including meningiomas, pituitary adenomas, hemangioblastomas and schwannomas, except for one hemangioblastoma that recurred four times and displayed malignant features at the fourth recurrence. These findings suggest that telomerase activity can be an index of malignant potential or malignancy itself in nonneuroepithelial brain tumors.

Adolescent↗
PubMed1998

Dose-dependent doxycycline-mediated adrenocorticotropic hormone secretion from encapsulated Tet-on proopiomelanocortin Neuro2A cells in the subarachnoid space.

We previously reported that polymer-encapsulated mouse neuroblastoma cells that are capable of secreting beta-endorphin may reduce pain sensitivity in rats after capsule implantation into the cerebrospinal fluid (CSF)-filled subarachnoid space of the spinal cord. The neuroblastoma cells carry the proopiomelanocortin (POMC) gene that encodes the precursor of adrenocorticotropic hormone (ACTH) and beta-endorphin. To control the expression of these hormones in the present study, a promoter that is inducible by administration of tetracycline derivatives such as doxycycline (Dox) was linked to the POMC gene. Encapsulated cells in the CSF space of rats stimulated by four intraperitoneal doses of Dox responded with ACTH expression as determined in a subsequence 36-hr in vitro incubation. The amount of ACTH released was dependent on the in vivo Dox dose. These findings indicate that gene expression in xenogeneic cells in the CSF space can be manipulated by injection of a relatively innocuous drug, and suggest that this system may be applicable to cell transplantation therapy in patients with central nervous system diseases that require temporary control of ligand delivery.

Adrenocorticotropic Hormone↗
PubMed1998

In vitro and in vivo potentiation of radiosensitivity of malignant gliomas by antisense inhibition of the RAD51 gene.

The mammalian RAD51 gene is a homologue of the yeast RAD51 and E. coli RecA genes, which are related to the repair of DNA double-strand breaks and are also involved in recombination repair and various SOS responses to DNA damage by gamma-irradiation and alkylating reagents. In this study, we investigated both in vitro and in vivo whether inhibition of the RAD51 gene by antisense oligonucleotides (ODNs) enhances the radiosensitivity of mouse malignant gliomas. A volume of 100 nM of RAD51 antisense ODNs inhibited the level of mRNA by more than 95% and reduced the protein expression by about 70%. Treatment of mouse 203G glioma cells with 100 nM of RAD51 antisense ODNs significantly enhanced the radiation-induced cell kill compared to control cells, and cells treated with sense or scrambled ODNs. When the glioma cells were implanted in the cisterna magna of mice followed by treatment with RAD51 antisense ODNs, the survival time of the mice was markedly prolonged compared to that of the untreated group (p < 0.001, logrank test). In addition, the combination of antisense ODNs and irradiation extended the survival time of the glioma-bearing mice much longer than could be achieved with radiation alone (p < 0.0001, logrank test). These results suggest that inhibition of RAD51 can be expected to serve as a novel potentiator for radiation therapy in malignant gliomas by inhibiting DNA double-strand break repair.

Animals↗
PubMed1998

Integrin alpha3beta1-mediated interaction with laminin-5 stimulates adhesion, migration and invasion of malignant glioma cells.

Gliomas, characterized by their progressively invasive phenotype, express integrin alpha3beta1 as a major receptor for the extracellular matrix both in vivo and in vitro. Since the integrin alpha3beta1 has been shown to be a specific receptor for laminin-5 (alpha3beta3gamma2), we examined the effects of purified human laminin-5 on adhesion, migration and invasion of human glioma cells. Among different types of laminin variants and other matrix proteins including fibronectin and vitronectin, laminin-5 was most potent in promoting adhesion and migration of different kinds of glioma cells. Laminin-5-mediated adhesion and migration were specifically inhibited by monoclonal antibodies against integrin alpha3 and beta1 chains, confirming the role of integrin alpha3beta1 as the major laminin-5 receptor. Invasion of the reconstituted basement membrane (i.e., Matrigel) by glioma cells was also selectively stimulated by laminin-5. Out results show that laminin-5 is the major extracellular stimulant for glioma cell adhesion, migration and invasion. The immunohistochemical distribution of laminin gamma2 chain, a laminin subunit unique to laminin-5, showed that it was expressed in the tumor parenchyma of human glioma tissues. Expression of laminin alpha3, beta3 and gamma2 chains in glioma tissues and in glioma cell lines was also demonstrated at the messenger RNA level by reverse transcription polymerase chain reaction. Our results, taken together, show that laminin-5 may be involved in the invasive phenotype of malignant gliomas both in vitro and in vivo.

Antigens, CD↗
PubMed1998

Identification of brain-specific splicing variants of the hDLG1 gene and altered splicing in neuroblastoma cell lines.

The human homologue of Drosophila tumor suppressor dlg, hDLG1, is one of the proteins known to interact with APC, a tumor suppressor for colorectal cancer. Alternative splicing of this gene generates transcripts either with [insertion 1 (I1)] or without 99 nucleotides in the 5' part of the dlg homology repeats (DHR) domain. We found almost equivalent expression of these two splicing variants in most human tissues; however, in skeletal muscle the transcript with the 99-bp insertion was predominant, and in the brain, that without the 99-bp insertion was expressed predominantly. We also examined alternative splicing in the region between the SH3 and GUK domains where two different sizes of insertions, 34 nucleotides (I2) or 100 nucleotides (I3), had been reported, and found various splicing patterns among the tissues examined. In brain we detected six different, alternatively spliced transcripts, two of which included a novel, 36-bp, brain-specific exon encoding a peptide bearing significant homology to a portion of rat synapse-associated protein, SAP97/PSD95. Subsequently, we investigated the splicing patterns of the hDLG1 gene in 24 neuroblastoma cell lines. In two-thirds of these lines, the splicing patterns were altered from those observed in normal brain tissue. As one-third retained the normal brain-splicing pattern, the loss of normal splicing of hDLG1 may not in itself cause formation of tumors, but it might reflect the biological character of individual neuroblastomas.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Inhibition of signal transduction by a splice variant of the growth hormone-releasing hormone receptor expressed in human pituitary adenomas.

We have previously shown that some of human growth hormone (GH)-producing pituitary adenomas preferentially express a larger transcript of GH-releasing hormone (GHRH) receptor (GHRH-R). This transcriptional variant is presumed to be produced by alternative messenger RNA splicing and contains premature stop codon in frame, predicted to yield a truncated GHRH-R. Functional expression study indicated that the variant receptor was unable to transduct GHRH signals. To determine the functional relationship between the splice-variant and the wild-type GHRH-R, the expression vector for the variant GHRH-R transcript was transfected into COS-7 cells together with or without that for the wild GHRH-R transcript. In cells transfected with both GHRH-R expression vectors, GHRH-dependent cyclic adenosine monophosphate (cAMP) induction was decreased to 39% of that in the cells transfected with the wild-type GHRH-R expression vector alone. This inhibition was found to be irrespective of the concentration (10(-8) to 10(-5) mol/L) of GHRH. These findings suggest that the splice variant form of GHRH-R functions as a dominant-negative modulator in GHRH-induced cellular signaling.

Adenoma↗
PubMed1998

In vivo etoposide-resistant C6 glioma cell line: significance of altered DNA topoisomerase II activity in multi-drug resistance.

We have established an in vivo etoposide-resistant glioma cell line (C6/VP) from C6 rat glioma cells by stepwise exposure to increasing doses of etoposide. The C6/VP cells were 10 times more resistant to etoposide than the parental C6 cells. In addition C6/VP cells demonstrated cross-resistance to vincristine and vinblastine, but not to ADM or m-AMSA. Interestingly, the cells had collateral sensitivity to ACNU, cisDDP and Ara-C. The C6/VP cells did not express the MDR gene or p-glycoprotein, while they showed 16 times less topoisomerase II catalytic activity compared to the C6 cells. Although there was no significant difference between C6 and C6/VP cells in amounts of topoisomerase II in nuclear extracts, the C6/VP cells had 2.9 times higher amounts of the enzyme than C6 cells in nuclear scaffold prepared from a relatively low-salt buffer (0.5 M NaCl). Northern blot analysis demonstrated that mRNAs of topoisomerase IIalpha isoforms were expressed both in C6 and C6/VP cells, and that the amounts of topoisomerase IIalpha in C6/VP cells were 14 times greater than in C6 cells. The total uptake of etoposide in tumor tissues derived from C6/VP cells was 3 times less than those derived from parental C6 cells. These results indicate that the C6/VP acquired a multi-drug resistance phenotype by a reduction of the catalytic activity of topoisomerase II and/or diminished accumulation of drugs. This phenotype did not involve the p-glycoprotein. Alterations of topoisomerase II in the C6/VP cells also were accompanied by an increased amount of the topoisomerase IIalpha isoform, most of which was localized in the nuclear scaffold (matrix). This suggests that altered binding of topoisomerase II to topologically organized DNAs in the nuclear scaffold may be the molecular basis of this multi-drug resistance phenotype.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Role of fibronectin-stimulated tumor cell migration in glioma invasion in vivo: clinical significance of fibronectin and fibronectin receptor expressed in human glioma tissues.

In order to clarify the role of fibronectin in glioma invasion in vivo, we analyzed the relationship between fibronectin-stimulated cell migration and adhesion in 14 primary glioma cells and the expression of fibronectin and the fibronectin receptor in the corresponding tumor tissues. The tumors comprised nine glioblastomas (GB) and five anaplastic gliomas (AG) consisting of two astrocytomas, two oligoastrocytomas and one ependymoma. All glioma cells tested in the primary cell culture were found to migrate to fibronectin in a dose-dependent manner. The extent of cell migration to fibronectin was not significantly different for the GB and AG groups. On the other hand, cell adhesion to fibronectin in the AG was much stronger than that in the GB group. Immunohistochemistry demonstrated that fibronectin positively stained in the extracellular matrix (ECM) in eight cases and that the fibronectin receptor was positive in tumor cell membranes in 10 cases. In addition, cellular fibronectin isoforms containing ED-A and ED-B sequences were found to be immunolocalized in the tumor cells and the ECM of GB. These isoforms were also specifically expressed in tumor vessels within tumor tissues, but not in those within normal brain tissues. Cell migration tended to be expressed more strongly by glioma cells derived from tumor tissues in which fibronectin was positively immunolocalized in the ECM than from tissues with negative fibronectin in the ECM. Four glioma cells derived from GB whose tumor cells did not positively stain for fibronectin receptors migrated much less extensively to fibronectin than other glioma cells whose tissues showed positive staining for the fibronectin receptor. Of these four GB, two had loss of heterozygosity in the locus of fibronectin receptor beta1 gene. These results suggest that fibronectin deposited in the extracellular matrix of tumors, which can be derived from both plasma and the tumor cell itself, strongly promotes the migration of glioma cells, and that expression of the fibronectin receptor may play a critical role in the biological behavior of the tumor cells, particularly in fibronectin-stimulated cell migration in vivo.

Astrocytoma↗
PubMed1998

Neural cell adhesion molecule L1 in gliomas: correlation with TGF-beta and p53.

AIMS: To assess immunohistochemically whether the neural cell adhesion molecule L1, which is a member of the immunoglobulin superfamily and has been shown recently to be a stimulating factor for glioma migration, is expressed in glioma tissues, and to investigate factors that can regulate this expression. METHODS: Twenty seven glioma tissue specimens including 13 glioblastomas, seven anaplastic astrocytomas, and seven astrocytomas were examined. Immunohistochemical analyses of L1, p53, and transforming growth cell factor beta (TGF-beta) were performed on each tumour using both polyclonal and monoclonal antibodies. RESULTS: Nine (33%) specimens (six glioblastomas and three anaplastic astrocytomas) had L1 positive immunostaining. p53 positive staining was detected in 10 (43%) of 23 glioma specimens (seven glioblastomas and three anaplastic astrocytomas). TGF-beta positive immunostaining was observed in 12 (52%) of the 23 glioma specimens (six glioblastomas, four anaplastic astrocytomas, and two astrocytomas). There was a statistical correlation between both p53 and L1 expression and TGF-beta and L1 expression. No such correlation was found between p53 and TGF-beta expression. CONCLUSIONS: These results suggest that mutation of the p53 gene or expression of TGF-beta may upregulate the expression of the L1 gene, thus resulting in high grade migration of glioma cells.

Antigens, Neoplasm↗
PubMed1997

Microsatellite instability and mutated type II transforming growth factor-beta receptor gene in gliomas.

Microsatellite instability has been reported in familial cancer syndrome and in various kinds of human sporadic tumors. We investigated the replication error (RER) and mutation rate of the transforming growth factor-beta type II receptor (TGF-beta RII) gene to determine the frequency of the RER+ phenotype and elucidate the relation between the mutation of the TGF-beta RII gene and RER in the tumorigenesis of glioma. We screened genomic DNA from 40 gliomas, comprised from 24 glioblastomas (GB), 11 anaplastic astrocytomas (AA) and five astrocytomas (AS) and compared the results with DNA from corresponding leukocytes. Seven of the 40 (18%) gliomas had the RER+ phenotype: five (21%) of 24 GB and two (18%) of 11 AA. In six gliomas we detected mutation of the TGF-beta RII gene. Five (71%) of seven RER+ and one (3%) of 33 RER-tumors had one A deletion in the (A)10 repeat of the TGF-beta RII gene. No mutations were detected in the (GT)3 repeat area of the TGF-beta RII gene. As the normal cells of these glioma patients had no mutations, we concluded that the mutations were somatic. We posit that the observed mutations inactivate the receptor through a frameshift mutation resulting in protein truncation. Our data suggest that the TGF-beta RII (A)10 repeat may be one area of genomic instability in the early stages of malignant glioma tumorigenesis.

Astrocytoma↗
PubMed1997

Absence of apoptosis in somatotropinomas treated with octreotide.

Octreotide is a potent agonist of somatostatin that lowers the serum level of growth hormone (GH), and reduces the size of somatotropinomas. However, the detailed mechanism of shrinkage of this tumour is not known. We, therefore, evaluated 11 patients with somatotropinomas who were treated with octreotide 300 micrograms/day for 2-5 weeks to observe the morphological changes in the tumour using electron microscopy and the immunocytochemical study of apoptosis using polyclonal anti-single stranded DNA. Findings were compared with those obtained with bromocriptine treatment (10 mg/day, 2 weeks) of 5 patients with somatotropinomas, and 11 patients who received no preoperative treatment (control group). The octreotide group showed neither increase in stromal tissue nor cell death. The size of tumour cells appeared to be slightly reduced. No typical apoptotic bodies were seen on the electron micrographs. The apoptotic index in the octreotide group (0.40 +/- 0.60%; mean +/- SD) resembled that in the control group (0.81 +/- 0.79%). In contrast, the bromocriptine group showed some cell death and an increase in stromal tissue. The bromocriptine group also showed the apoptotic index which (20.1 +/- 14.8%) was significantly higher than that of the control group (0.81 +/- 0.79%). Thus, octreotide did not induce apoptosis in somatotropinomas despite the presence of tumour shrinkage. Because of the lack of fibrosis observed in the octreotide-treated tumours, the preoperative administration of octreotide may help to improve the outcome of the transsphenoidal operation.

Adenoma↗
PubMed1997

A fatal case of fungal endocarditis of the tricuspid valve associated with long-term venous catheterization and treatment with antibiotics in a patient with a history of alcohol abuse.

We report a fatal case of fungal (candidal) endocarditis of the tricuspid valve with clinico-pathologically interesting findings following and associated with candidal pneumonia during long-term central venous catheterization (CVC) for intravenous therapy and long-term treatment with antibiotics for bacterial and fungal infection in a patient with a history of alcohol abuse. We review the literature on fungal cardiac infection related to long-term catheterization and alcohol abuse, and discuss the pathogenesis.

Aged↗
PubMed1997

Fibronectin-mediated cell migration promotes glioma cell invasion through chemokinetic activity.

In order to investigate the biological role of fibronectin in glioma cell invasion, we studied the relation between migratory responses or adhesiveness of glioma cells to fibronectin and the in vitro invasion in three human malignant glioma cell lines, A172, T98G and U373MG. All these cell lines chemotactically migrated in a dose-dependent manner to fibronectin in concentrations ranging from 0.5 to 10 microg/ml, with A172 cells showing the strongest migration and U373 cells the weakest. Checkerboard analyses demonstrated that A172 and T98G cells showed much stronger chemokinetic responses to fibronectin than U373MG cells. In contrast to the migratory responses, A172 and U373MG cells showed an almost equally high adhesion to fibronectin and T98G cells a low adhesion. The degree of expression of the integrin alpha5 subunit correlated well with the strength of glioma cell adhesion to fibronectin rather than that of migration to the molecule. Furthermore, the cell adhesion to fibronectin was almost completely inhibited by arginine-glycine-aspartic acid (RGD)-containing peptides, but the fibronectin-stimulated cell migration was only partially inhibited. An in vitro invasion assay disclosed that U373MG cells invaded the artificial basement membrane barrier the most and A172 cells the least. However, addition of fibronectin to the glioma cells markedly enhanced the invasive activity of A172 and T98G cells but had little effect on that of U373MG cells. These results indicate that fibronectin-stimulated migration can be one of the factors promoting invasiveness of glioma cells and that the chemokinetic activity of fibronectin may play a crucial role in glioma invasion through conferring motor-driving force on the glioma cells.

Cell Adhesion↗
PubMed1997

A patient with acromegaly who showed remarkable improvement of hyperglycemia after treatment with octreotide.

A case with diabetes mellitus associated with growth hormone (GH)-producing pituitary adenoma is described. A 56-year-old woman who had been treated for diabetes mellitus for 3 years, was admitted for the treatment of hyperglycemia. She showed a few acromegalic features and her plasma GH level was 146 +/- 16 ng/ml. After improvement of plasma glucose level by insulin injection, octreotide therapy (100 micrograms/8 hours) was started. Seven days after the initiation of octreotide therapy, the fasting plasma glucose level was almost normalized without insulin injection. After the octreotide treatment, urinary C-peptide excretion was significantly decreased and the plasma GH level became within normal range. In this case, octreotide appears to have improved the insulin sensitivity by reducing the plasma GH level.

Acromegaly↗
PubMed1996

Antisense inhibition of the RAD51 enhances radiosensitivity.

The mammalian RAD51 gene is a homologue of the yeast RAD51 and E. coli RecA genes, which are involved in recombination and DNA repair. We examined the role of RAD51 protein in mouse cells using RAD51 antisense phosphorothioate oligonucleotides (ODNs). The extraluminal delivery of 50 nM or 100 nM of antisense ODNs with lipofection to mouse cells resulted 90% suppression of RAD51 protein expression. The antisense ODNs significantly inhibited the cell growth and the treated cells became more sensitive to gamma-irradiation than the control groups. These results indicate mouse RAD51 plays an essential role in cell proliferation and radioresistant activity.

Animals↗