• Parasites, Hosts and Diseases
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• v.49 no.2
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• pp.125-131
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• 2011

The use of sulfadoxine and pyrimethamine (SP) for treatment of vivax malaria is uncommon in most malarious areas, but Plasmodium vivax isolates are exposed to SP because of mixed infections with other Plasmodium species. As P. vivax is the most prevalent species of human malaria parasites in Iran, monitoring of resistance of the parasite against the drug is necessary. In the present study, 50 blood samples of symptomatic patients were collected from 4 separated geographical regions of south-east Iran. Point mutations at residues 57, 58, 61, and 117 were detected by the PCR-RFLP method. Polymorphism at positions 58R, 117N, and 117T of P. vivax dihydrofolate reductase (Pvdhfr) gene has been found in 12%, 34%, and 2% of isolates, respectively. Mutation at residues F57 and T61 was not detected. Five distinct haplotypes of the Pvdhfr gene were demonstrated. The 2 most prevalent haplotypes were F57S58T61S117 (62%) and F57S58T61N117 (24%). Haplotypes with 3 and 4 point mutations were not found. The present study suggested that P. vivax in Iran is under the pressure of SP and the sensitivity level of the parasite to SP is diminishing and this fact must be considered in development of malaria control programs.

• Journal of Microbiology
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• v.45 no.5
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• pp.379-387
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• 2007

A hundred and seventeen antibiotic-resistant Escherichia coli strains were isolated from public tap and spring waters which were polluted by fecal coliforms. There were no significant differences between two water sources as to the coliform pollution level (p> 0.05). All E. coli isolates were detected to be resistant to one or more antibiotics tested. Nearly 42% of the isolates showed multiresistant phenotype. Three (2.5%) of these isolates contained class 1 integron. Sequencing analysis of variable regions of the class 1 integrons showed two gene cassette arrays, dfr1-aadA1 and dhfrA17-aadA5. Resistance to ampicillin, tetracycline or trimethoprim-sulfamethoxazole was transferable according to the results of conjugation experiments. The rate of tetracycline resistance was 15%. tet(A)-mediated tetracycline resistance was widespread among tetracycline-resistant E. coli isolates. Genotyping by BOX-polymerase chain reaction (BOX-PCR) showed that some of the strains were epidemiologically related. This is the first report on the prevalence and characterization of class 1 integron-containing E. coli isolates of environmental origin in Turkey.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.37-37
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• 2005

Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein hormone consisting of non-covalently linked two subunits, the ${\alpha}$ and ${\beta}$ subunit. It has been used as a infertility drug for ovulation to mimic luteinizing hormone $(LH).^{1)}$ A stable cell line was established by transfection of Rc/CMV-i-dhfr-hCG, expression vector containing hCG ${\alpha}-$ and ${\beta}-genes$, into dihydrofolate reductase-deficient CHO cells and subesquent methotrexate-mediated gene amplification. Anchorage-dependent CHO cells were adapted into a serum-free and/or animal component-free suspension medium through gradual serum weaning for the hCG production. The established cell line showed typical morphological characteristics and growth profile of CHO cells, and could produce FSH with passage-to-passage consistency. The high density perfusion culture of the CHO cells was carried out in Celligen Plus bioreactor equipped with a spin-filter as a internal cell retention device. The cell density reached up to $>1x10^{7}$ cells/ml in less than 7 days and a perfusion-control strategy based on cellular consumption rates of glucose was $established.^{2)}$ Biologically active recombinant hCG was purified by a series of chromatographic steps including anion exchange chromatography and hydrophobic interaction chromatography to homogeneity. The highly purified recombinant hCG was characterized for physicochemical, immunological and biological properties.

• Molecular & Cellular Toxicology
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• v.3 no.2
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• pp.137-144
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• 2007

The mechanism of cytotoxicity of doxifluridine, a prodrug fluorouracil (5-FU), has been ascribed to the misincorporation of fluoropyrimidine into RNA and DNA and to the inhibition of the nucleotide synthetic enzyme thymidylate synthase. Increased understanding of the mechanism of 5-FU has led to the development of strategies that increases its anticancer activity or predicts its sensitivity to patients. Using GeneChip?? Rhesus Macaque Genome arrays, we analyzed gene expression profiles of doxifluridine after two weeks repeated administration in cynomolgus monkey. Kegg pathway analysis suggested that cytoskeletal rearrangement and cell adhesion remodeling were commonly occurred in colon, jejunum, and liver. However, expression of genes encoding extracellular matrix was distinguished colon from others. In colon, COL6A2, COL18A1, ELN, and LAMA5 were over-expressed. In contrast, genes included in same category were down-regulated in jejunum and liver. Interestingly, MMP7 and TIMP1, the key enzymes responsible for ECM regulation, were overexpressed in colon. Several studies were reported that both gene reduced cell sensitivity to chemotherapy-induced apoptosis. Therefore, we suggest they have potential as target for modulation of 5-FU action. In addition, the expression of genes which have been previously known to involve in 5-FU pathway, were examined in three organs. Particularly, there were more remarkable changes in colon than in others. In colon, ECGF1, DYPD, TYMS, DHFR, FPGS, DUT, BCL2, BAX, and BAK1 except CAD were expressed in the direction that was good response to doxifluridine. These results may provide that colon is a prominent target of doxifluridine and transcriptional profiling is useful to find new targets affecting the response to the drug.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.2
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• pp.117-127
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• 2001

The high-level expression of a human single chain urokinase-type plasminogen activator (scu-PA) was achieved by employing a methotrexate (MTX)-dependent gene amplification system in Chinese hamster ovary (CHO) cells. By cotransfecting and coamplifying a scu-PA expression plasmid and dihydrofolate reductase (DHFR) minigene, several scu-PA expressing CHO cell lines were selected and gene-amplified. These recombinant cell lines, NGpUKs, secreted a completely processed scu-PA of 54 kD and up to 60mg/L was accumulated in the culture medium when they were adapted to an optimal MTX concentration. Over 95% of the scu-PA expressed was secreted in the culture medium and identified having the proper function of a plasminogen activator when activated by plasmin. Based on a genomic Southern analysis, a representative subclone, MGpUK-5, exhibited MTX-dependent scu-PA gene amplification, plus the initial single-copy gene of scu-PA eventually turned into about 150 copies of the amplified gene of scu-PA after gradual adaptation to 2.0$\mu$M of MTX. Meanwhile, the transcripts kof the scu-PA gene increased, although -early saturation of transcription was identified at 0.1$\mu$M of MTX. The scu-PA production by the MGpUK-5 subclone also increased relative to the gene amplification and increased transcripts, however, the relationship was not linearly proportional. Accordingly, since the MGpUK cell lines expressed elevated levels of enzymatically active scu-PA, these cell lines could be applied to the largescale production of scu-PA.

• International Journal of Oral Biology
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• v.30 no.3
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• pp.85-90
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• 2005

Homeostatic pH is very important for various cellular processes, including metabolism, survival, and death. An imbalanced-pH might induce cellular acidosis, which is involved in many abnormal events such as apoptosis and malignancy. One of several factors contributing to the onset of metabolic acidosis is the production of lactate and protons by lactate dehydrogenase (LDH) in anaerobic glycolysis. LDH is an important enzyme that catalyzes the reversible conversion of pyruvate to lactate. This study sought to examine whether decreases in extracellular pH induce apoptosis of CHO cells, and to elucidate the role of mitogen-activated protein kinases (MAPKs) in acidification-induced apoptosis. To test apoptotic signaling by acidification we used CHO dhfr cells that were sensitive to acidification, and CHO/anti-LDH cells that are resistant to acidification-induced apoptosis and have reduced LDH activity by stable LDH antisense mRNA expression. In the present study, cellular lactic acid-induced acidification and the role of MAPKs signaling in acidification-induced apoptosis were investigated. Acidification, which is caused by $HCO{_3}^-$-free conditions, induced apoptosis and MAPKs (ERK, JNK, and p38) activation. However, MAPKs were slightly activated in acidic conditions in the CHO/anti-LDH cells, indicating that lactic acid-induced acidification induces activation of MAPKs. Treatment with a p38 inhibitor, PD169316, increased acidification-induced apoptosis but apoptosis was not affected by inhibitors for ERK (U0126) or JNK (SP600125). Thus, these data support the hypothesis that activation of the p38 MAPK during acidification-induced apoptosis contributes to cell survival.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.121-129
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• 2002

Using recombinant Chinese hamster ovary (CHO) cells, strategies for developing high producers for the recombinant human Transforming Growth $Factor-{\beta}1$ ($TGF-{\beta}1$) protein are proposed and their physiological characteristics in cell cultures were investigated. $TGF-{\beta}1$ is a pleiotrophic polypeptide involved in various biological activities, including cell growth, differentiation, and deposition of extracellular matrix proteins. The CHO cells included human $TGF-{\beta}1$ cDNA in conjunction with a dihydrofolate reductase (DHFR) gene, which was cotransfected into the cells to amplify the transfected $TGF-{\beta}1$ cDNA. As a first-round screening of the transfected cells, a relatively high $TGF-{\beta}1$-producing cell line was selected, and then, it acquired a resistance to increasing concentrations of methotrexate (MTX) up to $60{\mu}M$,resulting in a significant improvement in its $TGF-{\beta}1$ biosynthetic ability. After applying a monoclonal selection strategy to the MTX-resistant cells, more productive cells were screened, including the APP-3, App-5, and App-8 cell lines. These high producers were compared with two other cell lines (AP-l cell line without amplification of transfected $TGF-{\beta}1$ cDNA and nontransfectant of $TGF-{\beta}1$ cDNA) in terms of cell growth, $TGF-{\beta}1$ productivity, sugar uptake, and byproduct formation, in the presence or absence of MTX in the culture medium. Consequently, both monoclonal selection as well as an investigation of the physiological characteristics were found to be needed for the efficient screening of higher $TGF-{\beta}1$ producers, even after the transfection and amplification of the transfected gene.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.759-766
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• 2003

Recombinant Chinese hamster ovary (rCHO) cell lines expressing a high level of human thrombopoietin (hTPO) or its analog, TPO33r, were obtained by transfecting expression vectors into dihydrofolate reductase-deficient (dhfr) CHO cells and subsequent gene amplification in media containing stepwise increments in methotrexate (MTX) level such as 20, 80, and 320 nM. The parental clones with a hTPO expression level $>0.40\;{\mu}g/ml$ (27 out of 1,200 clones) and the parental clones with a TPO33r expression level $>0.20\;{\mu}g/ml$ (36 out of 400 clones) were subjected to 20 nM MTX. The clones that displayed an increased expression level at 20 nM MTX were subjected to stepwise increasing levels of MTX such as 80 and 320 nM. When subjected to 320 nM MTX, most clones did not display an increased expression level, since the detrimental effect of gene amplification on growth reduction outweighed its beneficial effect of specific TPO productivity ($q_{TPO}$) enhancement at 320 nM MTX. Accordingly, the highest producer subclones ($1-434-80^{*}$ for hTPO and $2-3-80^{*}$ for TPO33r), whose $q_{TPO}$ was 2- to 3-fold higher than that of their parental clones selected at 80 nM MTX, were isolated by limiting dilution method and were established as rCHO cel1 lines. The $q_{TPO}$ of $1-434-80^{*}\;and\;2-3-80^{*}\;was\;5.89{\pm}074\;and\;1.02{\pm}0.23\;{\mu}g/10^6$ cells/day, respectively. Southern and Northern blot analyses showed that the enhanced $q_{TPO}$ of established rCHO cell lines resulted mainly from the increased TPO gene copy number and subsequent increased TPO mRNA level. The hTPO and TPO33r produced from the established rCHO cell lines were biologically active in vivo, as demonstrated by their ability to elevate platelet counts in treated mice.

• IMMUNE NETWORK
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• v.3 no.4
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• pp.302-309
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• 2003

Background: CTLA4 (CD152), which is expressed on the surface of T cells following activation, has a much higher affinity for B7 molecules comparing to CD28, and is a negative regulator of T cell activation. In contrast to stimulating and agonistic capabilities of monoclonal antibodies specific to CTLA-4, CTLA4Ig fusion protein appears to act as CD28 antagonist and inhibits in vitro and in vivo T cell priming in variety of immunological conditions. We've set out to confirm whether inhibition of the CD28-B7 costimulatory response using a soluble form of human CTLA4Ig fusion protein would lead to persistent inhibition of alloreactive T cell activation. Methods: We have used CHO-$dhfr^-$ cell-line to produce CTLA4Ig fusion protein. After serum free culture of transfected cell line we purified this recombinant molecule by using protein A column. To confirm characterization of fusion protein, we carried out a series of Western blot, SDS-PAGE and silver staining analyses. We have also investigated the efficacy of CTLA4Ig in vitro such as mixed lymphocyte reaction (MLR) & cytotoxic T lymphocyte (CTL) response and in vivo such as experimental autoimmune encephalomyelitis (EAE), graft versus host disease (GVHD) and skin-graft whether this fusion protein could inhibit alloreactive T cell activation and lead to immunosuppression of activated T cell. Results: In vitro assay, CTLA4Ig fusion protein inhibited immune response in T cell-specific manner: 1) Human CTLA4Ig inhibited allogeneic stimulation in murine MLR; 2) CTLA4Ig prevented the specific killing activity of CTL. In vivo assay, human CTLA4Ig revealed the capacities to induce alloantigen-specific hyporesponsiveness in mouse model: 1) GVHD was efficiently blocked by dose-dependent manner; 2) Clinical score of EAE was significantly decreased compared to nomal control; 3) The time of skin-graft rejection was not different between CTLA4Ig treated and control group. Conclusion: Human CTLA4Ig suppress the T cell-mediated immune response and efficiently inhibit the EAE, GVHD in mouse model. The mechanism of T cell suppression by human CTLA4Ig fusion protein may be originated from the suppression of activity of cytotoxic T cell. Human CTLA4Ig could not suppress the rejection in mouse skin-graft, this finding suggests that other mechanism except the suppression of cytotoxic T cell may exist on the suppression of graft rejection.