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Biomedical subjects

Tao Chen

Publications and source records attributed to Tao Chen.

At least 73 records · Page 4Linked to original sources
PubMed2005

Electrochemical behavior of poly(ferrocenyldimethylsilane-b-dimethylsiloxane) films.

The electrochemical behavior of poly(ferrocenyldimethylsilane-b-dimethylsiloxane) (PFDMS-b-PDMS) films deposited on a glassy carbon electrode was investigated by means of cyclic voltammetry (CV). The influences of the solvent, film thickness, temperature, and PDMS block length in PFDMS-b-PDMS on the electrode process were discussed. It was found that in 0.1 M aqueous LiClO(4) the electrochemical processes of the films on a glassy carbon electrode were complex and have a low rate of electron transport and mass diffusion. The kinetic parameters obtained indicated that the electrode process was controlled by both the electrode reaction and mass diffusion.

Journal Article↗
PubMed2005

Tamoxifen can reverse multidrug resistance of colorectal carcinoma in vivo.

AIM: To investigate the effect of tamoxifen (TAM) on multidrug resistance (MDR) of colorectal carcinoma in vivo and its relationship with estrogen receptor (ER). METHODS: Multidrug resistance was determined by means of semi-quantitative retro-transcription polymerase chain reaction (RT-PCR) to test mdr1 gene mRNA and ER expression was studied by immunohistochemistry. Tumor tissues from three cases of human colon carcinoma, which had mdr1(+)/ER(+), mdr1(+)/ER(-), mdr1(-) expressions, were planted subcutaneously in the neck of nude mice to establish three xenograft models. These models were subdivided into four subgroups randomly: Doxorubicin (DOX)-treated group, TAM-treated group, DOX and TAM group and control group. The dimensions of these xenografts were measured after each course of treatment and the xenografts were removed at the end of the experiments for measurements of weight and the variation of mdr1 mRNA level with RT-PCR. In each course, TAM (15 mg/(kg/d)) was administrated orally per day in the first seven days and DOX (3.6 mg/kg) was injected peritoneally on the first day. Data was evaluated by q and t tests. RESULTS: In the animal models with mdr1(-) tumor, the weights and volumes of the planted tumor in DOX group ((39.1+/-2.29) mg, (31.44+/-1.61) mm(3)) and TAM and DOX group ((38.72+/-2.56) mg, (31.31+/-1.74) mm(3)), which were lesser than that of control group ((45.48+/-3.92) mg, (36.42+/-2.77)mm(3), P = 0.037, P = 0.016 respectively) significantly. In the animal models with mdr1(+)/ER(+) tumor, the weights and volumes of planted tumor were not affected by DOX or TAM treatment; however, in TAM and DOX group ((425.5+/-28.58) mg, (340.35+/-22.28) mm(3)), they were significantly less than that of control group ((634.23+/-119.41) mg, (507.45+/-93.34) mm(3), P = 0.022, P = 0.045 respectively), which are similar to that in the models with mdr1(+)/ER(-) tumor. No significant changes were found in the expressive level of mdr1 mRNA following these treatments. CONCLUSION: The expression of mdr1 gene corresponds to the sensitivity of colon cancer to anti-tumor drugs in vivo. TAM can reverse the MDR of colorectal carcinoma in nude mice, which is independent of the expression of ER; however, no change was observed in the expressive level of mdr1 mRNA.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Mutagenic effects of 4-hydroxynonenal triacetate, a chemically protected form of the lipid peroxidation product 4-hydroxynonenal, as assayed in L5178Y/Tk+/- mouse lymphoma cells.

The lipid peroxidation product 4-hydroxynon-2-enal (4-HNE) is cytotoxic and genotoxic at superphysiological concentrations. To characterize the mechanism of action of 4-HNE, we assessed genotoxic damage by 4-HNE and by 4-HNE triacetate [4-HNE(Ac)(3)] using the mouse lymphoma assay that measures the mutant frequency in the Tk gene. As a strong electrophile, 4-HNE reacts readily with nucleophilic centers on cellular components. When added extracellularly, it may react preferentially with proteins in culture medium or on the cell surface and not reach deeper cellular targets such as nuclear DNA. Therefore, 4-HNE(Ac)(3), a protected form of 4-HNE that is metabolically converted to 4-HNE in cells (Neely MD, Amarnath V, Weitlauf C, and Montine TJ, Chem Res Toxicol 15:40-47, 2002), was assayed in addition to 4-HNE. When added in serum-containing medium, 4-HNE was not mutagenic in the mouse lymphoma assay up to 38 muM (cytotoxicity = 13%). In contrast, exposure to 4-HNE(Ac)(3), which mimics intracellular formation of 4-HNE, resulted in dose-dependent induction of mutations. At 17 muM 4-HNE(Ac)(3) (cytotoxicity = 33%), the mutant frequency was 719 x 10(-6) (>7-fold higher than the spontaneous mutant frequency). Loss of heterozygosity analysis in the Tk mutants revealed that the majority of mutations induced by 4-HNE(Ac)(3) resulted from clastogenic events affecting a large segment of the chromosome. The results indicate that, in the presence of serum that approximates physiological conditions, 4-HNE generated intracellularly but not extracellularly is a strong mutagen via a clastogenic action at concentrations that may occur during oxidative stress.

Aldehydes↗
PubMed2005

Characterization of cytokine/chemokine profiles of severe acute respiratory syndrome.

RATIONALE: There is currently no optimal treatment or effective drug for severe acute respiratory syndrome (SARS), because the immunopathologic mechanism is poorly understood. OBJECTIVES: To explore the immune mechanism underlying the pathogenesis of SARS, we studied the expression profile of cytokines/chemokines in the blood and the immunopathology of the lung and lymphoid tissues. METHODS: Fourteen cytokines/chemokines in the blood of 23 patients with SARS were dynamically screened, using a bead-based multiassay system. Reverse transcription-polymerase chain reaction was performed to amplify mRNA. Histopathology of the lung and lymphoid tissues at autopsy was examined, using methods of immunohistochemistry and double immunofluorescence staining. MAIN RESULTS: Interferon-inducible protein-10 (IP-10) was markedly elevated in the blood during the early stage of SARS, and remained at a high level until convalescence. Moreover, IP-10 was highly expressed in both lung and lymphoid tissues, where monocyte-macrophage infiltration and depletion of lymphocytes were observed. The levels of interleukin-6, interleukin-8, and monocyte chemoattractant protein-1 were concomitantly increased in the blood of the patients with superinfection, and the mRNAs for these cytokines were also increased in lung tissues. CONCLUSIONS: Induction of IP-10 is a critical event in the initiation of immune-mediated acute lung injury and lymphocyte apoptosis during the development of SARS. Superinfection after the immune injury is the main cause of death. The prompt elevation of interleukin-6, interleukin-8, and monocyte chemoattractant protein-1 is a sign of superinfection, indicating a high risk of death.

Adult↗
PubMed2005

Endogenous estrogen status, but not genistein supplementation, modulates 7,12-dimethylbenz[a]anthracene-induced mutation in the liver cII gene of transgenic big blue rats.

A growing number of studies suggest that isoflavones found in soybeans have estrogenic activity and may safely alleviate the symptoms of menopause. One of these isoflavones, genistein, is commonly used by postmenopausal women as an alternative to hormone replacement therapy. Although sex hormones have been implicated as an important risk factor for the development of hepatocellular carcinoma, there are limited data on the potential effects of the estrogens, including phytoestrogens, on chemical mutagenesis in liver. Because of the association between mutation induction and the carcinogenesis process, we investigated whether endogenous estrogen and supplemental genistein affect 7,12-dimethylbenz[a]anthracene (DMBA)-induced mutagenesis in rat liver. Intact and ovariectomized female Big Blue rats were treated with 80 mg DMBA/kg body weight. Some of the rats also received a supplement of 1,000 ppm genistein. Sixteen weeks after the carcinogen treatment, the rats were sacrificed, their livers were removed, and mutant frequencies (MFs) and types of mutations were determined in the liver cII gene. DMBA significantly increased the MFs in liver for both the intact and ovariectomized rats. While there was no significant difference in MF between the ovariectomized and intact control animals, the mutation induction by DMBA in the ovariectomized groups was significantly higher than that in the intact groups. Dietary genistein did not alter these responses. Molecular analysis of the mutants showed that DMBA induced chemical-specific types of mutations in the liver cII gene. These results suggest that endogenous ovarian hormones have an inhibitory effect on liver mutagenesis by DMBA, whereas dietary genistein does not modulate spontaneous or DMBA-induced mutagenesis in either intact or ovariectomized rats.

Amino Acids↗
PubMed2005

Active demethylation of individual genes in intracytoplasmic sperm injection rabbit embryos.

Intracytoplasmic sperm injection (ICSI), as an assisted reproduction technique, has been widely used in animal and human. However, its possible effect on epigenetic changes has not been well studied. To investigate whether ICSI can induce aberrant DNA methylation changes in rabbit preimplantation embryos, we examined the methylation status of the SP-A promoter region and the satellite sequence Rsat IIE by bisulfite-sequencing technology. The SP-A promoter region was extensively demethylated before the first round of DNA replication commences, and the unmethylated status was maintained until morula when dynamic remethylation occurred. A similar but more moderate demethylation process was observed in satellite sequence Rsat IIE. These results are in contrast with the previous reports of no active demethylation in normal rabbit embryos, suggesting that the active demethylation we observed may be induced by ICSI.

Animals↗
PubMed2005

Micro flow-through PCR in a PMMA chip fabricated by KrF excimer laser.

As the third PCR technology, micro flow-through PCR chip can amplify DNA specifically in an exponential fashion in vitro. Nowadays many academies in the world have successfully amplified DNA using their own-made flow-through PCR chip. In this paper, the ablation principle of PMMA at 248 nm excimer laser was studied, then a PMMA based flow-through PCR chip with 20 cycles was fabricated by excimer laser at 19 kv and 18 mm/min. The chip was bonded together with another cover chip at 105( composite function)C, 160 N and 20 minutes. In the end, it was integrated with electrical thermal thin films and Pt 100 temperature sensors. The temperature controllers was built standard PID digital temperature controller, the temperature control precision was +/- 0.2( composite function)C. The temperature grads between the three temperature zones were 16.5 and 22.2( composite function)C respectively, the gaps between the temperature zones could realize heat insulation.

Equipment Design↗
PubMed2005

Design of recombinant stem cell factor-macrophage colony stimulating factor fusion proteins and their biological activity in vitro.

Stem cell factor (SCF) and macrophage colony stimulating factor (M-CSF) can act in synergistic way to promote the growth of mononuclear phagocytes. SCF-M-CSF fusion proteins were designed on the computer using the Homology and Biopolymer modules of the software packages InsightII. Several existing crystal structures were used as templates to generate models of the complexes of receptor with fusion protein. The structure rationality of the fusion protein incorporated a series of flexible linker peptide was analyzed on InsightII system. Then, a suitable peptide GGGGSGGGGSGG was chosen for the fusion protein. Two recombinant SCF-M-CSF fusion proteins were generated by construction of a plasmid in which the coding regions of human SCF (1-165aa) and M-CSF (1-149aa) cDNA were connected by this linker peptide coding sequence followed by subsequent expression in insect cell. The results of Western blot and activity analysis showed that these two recombinant fusion proteins existed as a dimer with a molecular weight of approximately 84 KD under non-reducing conditions and a monomer of approximately 42 KD at reducing condition. The results of cell proliferation assays showed that each fusion protein induced a dose-dependent proliferative response. At equimolar concentration, SCF/M-CSF was about 20 times more potent than the standard monomeric SCF in stimulating TF-1 cell line growth, while M-CSF/SCF was 10 times of monomeric SCF. No activity difference of M-CSF/SCF or SCF/M-CSF to M-CSF (at same molar) was found in stimulating the HL-60 cell linear growth. The synergistic effect of SCF and M-CSF moieties in the fusion proteins was demonstrated by the result of clonogenic assay performed with human bone mononuclear, in which both SCF/M-CSF and M-CSF/SCF induced much higher number of CFU-M than equimolar amount of SCF or M-CSF or that of two cytokines mixture.

Animals↗
PubMed2005

Isolation of trehalose-6-phosphate phosphatase gene from tobacco and its functional analysis in yeast cells.

Trehalose is a nonreducing disaccharide composed of two glucose units joined by an alpha, alpha-1, 1 linkage, and has been found in bacteria, yeast, fungi, invertebrates and plants. Accumulation of trehalose in organisms plays a role in enhancing the stress tolerance. A trehalose-6-phosphate phosphatase gene, NtTPPL, was isolated from tobacco in this report. The predicted NtTPPL protein has a putative trehalose_PPase domain. The transcription of the NtTPPL gene was significantly induced by heat stress, and was only slightly induced by NaCl, PEG and low-temperature treatments. When expressing in yeast tps2 mutant, NtTPPL rescued the mutant phenotype under high temperature. This result indicated that NtTPPL functioned as a trehalose-6-phosphate phosphatase in yeast and may play similar roles in plants.

Amino Acid Sequence↗
PubMed2005

Expression of a novel recombinant stem cell factor/macrophage colony-stimulating factor fusion protein in baculovirus-infected insect cells.

A novel human stem cell factor (SCF)/macrophage colony-stimulating factor (M-CSF) fusion protein gene was constructed, in which the coding regions of human SCF cDNA (1-165aa) and the truncated M-CSF cDNA (1-149aa) were connected by a linker sequence encoding a short peptide GGGGSGGGGSGG. The SCF/M-CSF gene was cloned into baculovirus transfer vector pVL1392 under the control of polyhedrin promoter and expressed in the Sf9 cells (Spodoptera frugiperda). SDS-PAGE and Western blot analysis showed that the purified fusion protein was a homodimer with a molecular weight about 84kDa under non-reducing conditions or a monomer about 42kDa under reducing conditions. The specific activity of rhSCF/M-CSF was 17 times as high as that of monomeric rhSCF to stimulate the proliferation of TF-1 cell. The results of macrophages colony-forming (CFU-M) assay performed with human bone marrow mononuclear cells demonstrated that rhSCF/M-CSF was more potent in promoting CFU-M than the equimolar of SCF, M-CSF or that of two cytokines mixture.

Animals↗
PubMed2005

In vitro culture and mtDNA fate of ibex-rabbit nuclear transfer embryos.

Rabbit oocyte can be used as the recipient in interspecies somatic cell nuclear transfer (iSCNT). This work was undertaken in order to study the developmental competence of Capra ibex somatic cells reprogrammed by rabbit oocytes and the fate of mitochondria in iSCNT embryos. Metaphase II (MII) oocytes from superovulated rabbit were used as nuclear recipients. The nuclear donors were Capra ibex somatic cells with different proliferative status: population doubling time (PDL) = 15 +/- 2 (group 1), 35 +/- 2 (group 2), 55 +/- 2 (group 3) and 70 +/- 2 (group 4). Oocytes reconstructed with electrical pulses (2.1kV/cm, 10 micros, 2 times) were activated (1.4kV, 20 micros, 2 times) and then cultured in Medium199 containing 10% fetal bovine serum at 38.5 degrees C, 5% CO2 in air. In groups 1, 2, 3 and 4, the fusion rates were 35.83%, 66.03%, 65.40% and 35.35%, respectively. Similar cleavage rates were observed among the four groups. However, the developmental potential to morula/blastocyst from early nuclear donor embryos (16.42%/10.45%) was significantly higher (p < 0.05) than in terminal donor embryos (9.52%/3.81%). Polymerase chain reaction analysis of the mitochondrial (mt) DNA cytb gene demonstrated that mtDNAs from ibex and rabbit could be detected at various developmental stages before implantation. In conclusion, our results provide some original information about rescuing Capra ibex using the iSCNT technique. These results indicate that: (1) enucleated rabbit oocytes make Capra ibex fibroblast nuclei reprogramme; (2) the proliferative status of donor cells affects the efficiency of iSCNT; and (3) rabbit ooplasm rescues the donor-derived mtDNAs, resulting in mtDNA heteroplasmy before implantation.

Animals↗
PubMed2005

Lymphatic chemotherapy induces apoptosis in lymph node metastases in a rabbit breast carcinoma model.

The purpose of the study was to evaluate the potential of lymphatic chemotherapy in inducing apoptosis in axillary lymph node metastases in a rabbit breast cancer model. A total of 30 female New Zealand rabbits with mammary implantation of VX2 carcinomas were divided into three groups randomly, with ten in each. Treatment was carried out once axillary lymph node reached 5 mm in the maximum diameter. Group A received a subcutaneous injection of liposomal adriamycin (LADR) adjacent to the breast tumor. Group B received free adriamycin (FADR) administered into the auricular vein. Group C received a sham treatment. The dose of adriamycin in each administration was 1 mg/kg in groups A and B. Treatment was repeated every 48 h. Axillary lymph nodes were dissected out 48 h after the third treatment. The nodal sizes before and after the treatment were measured. The therapeutic effect was evaluated in terms of the node volume ratio and apoptotic index (AI) of metastatic cells in nodes identified with TUNEL technique. The significance of difference was determined with one-way ANOVA followed by the Fischer LSD test. Compared to group C, the enlargement of lymph nodes was sufficiently slowed down in both groups A and B, and group A showed a further strong inhibitory effect than group B (P = 0.002). Apparent VX2 cell apoptosis was detected in the lymph nodes of groups A and B. The average AI in group B (15.31%) was significantly higher than in group C (5.16%). The highest AI was found in animals of group A (21.73%), with a further significant difference from group B (P = 0.000). These data suggest that lymphatic chemotherapy appears to be a promising method to induce apoptosis in lymph node metastases

Animals↗
PubMed2005

Effects of daidzein, genistein, and 17beta-estradiol on 7,12-dimethylbenz[a]anthracene-induced mutagenicity and uterine dysplasia in ovariectomized rats.

Phytoestrogens, primarily isoflavones daidzein (DZ) and genistein (GE), are increasingly used by postmenopausal women as an alternative to hormone replacement therapy due to reports that estrogen therapy increases the risk of breast and endometrial cancers. These compounds, as estrogen receptor agonists, may influence chemical carcinogenesis in estrogen-responsive tissues such as the uterus. We utilized ovariectomized (OVX) rats to model menopause and assessed the effects of dietary DZ, GE, or 17beta-estradiol (E2) on carcinogen-induced mutagenesis and carcinogenesis in the rat uterus. Big Blue transgenic rats (derived from Fischer 344 strain) were exposed to 7,12-dimethylbenz[a]anthracene (DMBA) in the presence or absence of the supplements. At 16- or 20-wk sacrifice, the uteri were removed and processed to determine mutant frequencies (MFs) and immunohistochemical or histopathological parameters, respectively. In rats treated with DMBA alone, a significant increase in lacI MFs (P < 0.01) in both OVX and intact (INT) rats was observed. The DMBA-induced MFs were not significantly altered by dietary DZ, GE, or E2 in both OVX and INT rats. Although dysplasia was not induced in the uterus of OVX and INT rats treated with DMBA alone, it was detected in 55% of OVX rats fed E2 alone and in 100% of OVX rats fed E2 along with DMBA exposure. Cell proliferation also was significantly higher in OVX rats fed E2 and treated with DMBA. In rats fed the isoflavones and treated with DMBA, the incidence of dysplasia was either reduced or virtually absent in both OVX and INT groups. These results indicate that a high incidence of dysplasia was associated with E2 feeding with or without DMBA treatment in the OVX rats, whereas the incidence was low in rats fed DZ or GE and treated with DMBA, suggesting a weak estrogen receptor agonist of DZ or GE in the rat uterus. The absence of dysplasia in OVX rats exposed to DMBA alone also suggests, in part, a promotional mechanism via estrogen- or isoflavone-driven cell proliferation.

Animals↗
PubMed2005

[Studies on PANK2 gene mutations in Chinese patients with Hallervorden-Spatz syndrome].

OBJECTIVE: To study pantothenate kinase 2 (PANK2) gene mutations in Chinese patients with Hallervorden-Spatz syndrome (HSS). METHODS: PANK2 gene mutations were detected by PCR, DNA sequence analyses, restriction enzyme digestion and PCR-single strand conformation polymorphism in 5 patients, 3 unaffected family members and 51 unrelated healthy persons. RESULTS: Novel compound heterozygous PANK2 gene mutations, A803G and T1172A, in exons 3 and 5, respectively, were found in one patient. At the same time, 3 types of single nucleotide polymorphisms, -38 t>a in 5'-UTR, IVS1+42 c>a and G77C in exon 1, were confirmed; among them, -38 t>a, IVS1+42 c>a, were first reported. CONCLUSION: PANK2 gene mutations can cause HSS in Chinese patients.

Adolescent↗
PubMed2005

[Application of adenosine triphosphate tumor chemosensitive assay system to individual chemotherapy for hepatocellular carcinoma].

BACKGROUND & OBJECTIVE: Present chemotherapy for hepatocellular carcinoma (HCC) is not effective. To improve the effect of chemotherapy, in vitro chemo-drug sensitive testing system, adenosine triphosphate tumor chemosensitive assay (ATP-TCA) system, was used to evaluate efficacies of chemotherapeutic drugs, and to guide clinical individual chemotherapy for HCC patients. METHODS: ATP-TCA system was applied to test efficacies of 5-fluorouracil (5-FU), mitomycin (MMC), cisplatin (DDP), oxaliplatin (OXA), epirubicin (EPI), gemcitabine (GEM), irinotecan (CPT-11), etoposide (VP-16), and paclitaxel (PTX) on 50 HCC samples. Twenty-three HCC patients received ATP-TCA-directed chemotherapy (ATP-TCA group)û 20 HCC patients received surgery and routine treatments (control group). Clinical outcomes of these patients were observed for 162 weeks. RESULTS: The assessable rate of ATP-TCA result is 90.8%. In the 50 samples, the sensitive (moderate to high degree) rates were 46% to PTX, 44% to CPT-11, 36% to GEM, 14% to MMC, 12% to EPI, 8% to DDP, 6% to VP-16, 6% to OXA, and 4% to 5-FU, respectively. In clinical trial, at the research end-point, no significant differences were found in partial remission (PR), complete remission (CR), stable disease (SD), and mortality between ATP-TCA group and control group (P > 0.05), but progression disease (PD) rate was significantly higher in control group than in ATP-TCA group (60.00% vs.13.04%, P=0.003); significant differences were found in overall response rate (ORR) (60.86% vs. 30.00%, P =0.043), overall survival (OS) (78.91 weeks vs. 27.21 weeks, P=0.006), and progress-free survival (PFS) (30.52 weeks vs. 4.78 weeks, P=0.005) between ATP-TCA group and control group. CONCLUSIONS: ATP-TCA system might be useful in evaluating the efficacy of chemotherapeutic drugs on HCC samples, and in planning individualized chemotherapy regimen for HCC patients. PTX, CPT-11 and GEM might be potential drugs for the treatment of HCC. ATP-TCA-guided chemotherapy might prolong survival time of HCC patients.

Adenosine Triphosphate↗
PubMed2005

Effects of deep low temperature on secondary branches enclosed in Glisson's system of pig hepatic lobes.

BACKGROUND: Hepatic cryosurgery, a safe and effective approach for an unresectable hepatoma, has been extensively applied in clinical setting. But whether direct deep freezing to the tumor involving special location, i.e., Glisson's system of certain hepatic lobe could cause the impairment of the duct system or post impairment effect remains a mystery. Consequently, the aim of the study was to investigate the effect of freezing on the secondary branches enclosed in the Glisson's system of certain hepatic lobes. METHODS: Twenty pigs were divided into 2 groups randomly. The treated group: the area of secondary branches of the Glisson's system in the left lateral lobe was frozen by a cryoprobe at deep low temperature for 3 minutes, with the blockage of blood flow from the porta hepatis. The control group: only the blockage of the porta hepatis was performed for 3 minutes. Serologic examinations, color Doppler examination and pathological observation were used for evaluation of this procedure postoperatively. RESULTS: The frozen hepatic parenchyma, the wall of the frozen secondary bile duct and portal vein showed necrosis. However, the frozen hepatic artery ramification did not show any obvious changes postoperatively. Eight weeks after cryosurgery, the lumen of the hepatic artery and portal vein maintained unobstructed. Meanwhile, atrophy and fibroplasia occurred in the related hepatic lobe. All the animals recovered well. CONCLUSIONS: Animals could tolerate the direct deep-freezing of the area of secondary branches enclosed in the Glisson' s system. The therapeutic effect could be attained by the necrosis of the frozen hepatic parenchyma.

Alanine Transaminase↗