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Biomedical subjects

Tao Li

Publications and source records attributed to Tao Li.

At least 199 records · Page 11Linked to original sources
PubMed2003

A methylated oligonucleotide inhibits IGF2 expression and enhances survival in a model of hepatocellular carcinoma.

IGF-II is a mitogenic peptide that has been implicated in hepatocellular oncogenesis. Since the silencing of gene expression is frequently associated with cytosine methylation at cytosine-guanine (CpG) dinucleotides, we designed a methylated oligonucleotide (MON1) complementary to a region encompassing IGF2 promoter P4 in an attempt to induce DNA methylation at that locus and diminish IGF2 mRNA levels. MON1 specifically inhibited IGF2 mRNA accumulation in vitro, whereas an oligonucleotide (ON1) with the same sequence but with nonmethylated cytosines had no effect on IGF2 mRNA abundance. MON1 treatment led to the specific induction of de novo DNA methylation in the region of IGF2 promoter hP4. Cells from a human hepatocellular carcinoma (HCC) cell line, Hep 3B, were implanted into the livers of nude mice, resulting in the growth of large tumors. Animals treated with MON1 had markedly prolonged survival as compared with those animals treated with saline or a truncated methylated oligonucleotide that did not alter IGF2 mRNA levels in vitro. This study demonstrates that a methylated sense oligonucleotide can be used to induce epigenetic changes in the IGF2 gene and that inhibition of IGF2 mRNA accumulation may lead to enhanced survival in a model of HCC.

Base Sequence↗
PubMed2003

Deletion of Helicobacter pylori vacuolating cytotoxin gene by introduction of directed mutagenesis.

AIM: To construct a vacA-knockout Helicobacter pylori mutant strain, whose only difference from the wild strain is its disrupted vacA gene. METHODS AND RESULTS: A clone containing kanamycin resistance gene used for homologous recombination was constructed in a directional cloning procedure into pBluescript II SK, and then transformed into vacA+ H pylori by electroporation. Colonies growing on the selective media containing kanamycin were harvested for chromosomal DNA extraction, and the allelic exchange was determined by polymerase chain reactions and sequencing. Loss of vacuolating activity of the vacA-knockout strain was confirmed by examining the gastric cells co-cultured with cell-free supernatants from H pylori wild strain or the mutant. CONCLUSION: We constructed a vacA-knockout strain of H pylori through direct mutagenesis, which creates an important precondition for the future research on virulence comparison with gene expression analysis.

Bacterial Proteins↗
PubMed2003

Vascularity of hepatic VX2 tumors of rabbits: assessment with conventional power Doppler US and contrast enhanced harmonic power Doppler US.

AIM: To investigate the characteristics of the vascularity of hepatic metastasis. METHODS: Six New Zealand rabbits, weighing averagely 2.7+/-0.4 kg, were selected and operated to establish hepatic VX2 tumor carrier model. Hepatic VX2 tumors were then imaged with conventional B mode US, second harmonic imaging (SHI), color Doppler flow imaging (CDFI), power Doppler imaging (PDI) and harmonic PDI by a transducer S8 connected to HP-5 500 ultrasound system. A kind of self made echo contrast agent was intravenously injected at a dose of 0.01 mL/kg through ear vein, and then the venous passage was cleaned with sterilized saline. RESULTS: Totally, 6 hypoechoic lesions and 3 hyperechoic lesions were found in the six carrier rabbits with a mean size about 2.1+/-0.4 cm under conventional B mode ultrasound, they were oval or round in shape with a clear outline or a hypoechoic halo at the margin of the lesions. Contrast agent could not change the echogenicity of the lesions under conventional B mode and SHI, however, it could greatly increase the flow sensitivity of the lesions under PDI and harmonic PDI. Nutrient artery of these metastatic lesions might also be well depicted under contrast enhanced PDI and harmonic PDI. CONCLUSION: Our result suggested that contrast enhanced PDI, especially harmonic PDI, was a promised method in the detection of vascularity of hepatic tumor nodules.

Animals↗
PubMed2003

Assessment of hepatic VX2 tumors of rabbits with second harmonic imaging under high and low acoustic pressures.

AIM: To investigate the possible clinical application value of second harmonic imaging under low acoustic pressure. METHODS: Six New Zealand rabbits, averaging 2.7+/-0.4 kg, were selected and operated upon to construct hepatic VX2 tumor carrier model. Hepatic VX2 tumors were imaged with B mode Ultrasonography (US), and second harmonic imaging (SHI) under high mechanic index (1.6) and low mechanic index (0.1). Echo agent was intravenously injected through ear vein at a dose of 0.01 mL/kg under B mode US and high MI SHI, and 0.05 mL/kg under low MI SHI, and then the venous channel was cleaned with sterilized saline. All the images were recorded by magnetic optics (MO), and they were analyzed further by at least two independent experienced sonographers. RESULTS: Totally 6 hypoechoic and 3 hyperechoic lesions were found in the six carrier rabbits with a mean size about 2.1+/-0.4 under B mode ultrasound, they were oval or round in shape with a clear outline or a hypoechoic halo at the margin of the lesions. Contrast agent could not change the echogenicity of the lesions under B mode US and SHI under high acoustic pressure. However, it could greatly increase the real time visualization sensitivity of the lesions with SHI under low acoustic pressure. CONCLUSION: Our results suggest that contrast enhanced SHI with low MI and a bubble non-destructive method would be much more helpful than conventional SHI in our future clinical applications.

Air↗
PubMed2003

[Association study of heroin dependence and catechol-O-methyltransferase gene].

OBJECTIVE: To detect the relationship between heroin dependence and catechol-O-methyltransferase (COMT) gene. METHODS: Genotype and allele frequencies of 108 val/met and 900 Ins C/Del C polymorphisms of COMT gene were examined in 313 heroin-dependent subjects and 214 normal controls. RESULTS: No differences in genotype and allele frequencies of 108 val/met polymorphism of COMT gene were observed between heroin-dependent subjects and normal controls (genotype-wise: chi-square=1.67, P=0.43; allele-wise: chi-square=1.23, P=0.27). No differences in genotype and allele frequencies of 900 Ins C/Del C polymorphism of COMT gene were observed between heroin-dependent subjects and normal controls (genotype-wise: chi-square=3.73, P=0.16; allele-wise: chi-square=0.76, P=0.38). CONCLUSION: The results suggested that neither 108 val/met polymorphism nor 900 Ins C/Del C polymorphism of COMT gene was associated with heroin dependence.

Adolescent↗
PubMed2003

[Brain-derived neurotrophic factor mRNA expressions in rat brain induced by short-term in vivo exposure to deltamethrin].

OBJECTIVE: To elucidate the mechanism of damage on central nervous system (CNS) caused by deltamethrin (DM). METHODS: The mRNA and protein expressions of brain-derived neurotrophic factor (BDNF) in the cerebral cortex and hippocampus of the rats exposed to DM were measured by retro-transcription-polymerase chain reaction (RT-PCR), dot blot, flow cytometry analysis and immunohistochemistry. RESULTS: After exposure to DM at high-dose (DM1, 25.0 mg x kg(-1) x d(-1), i.p.) once and low-dose (DM2, 12.5 mg x kg(-1) x d(-1), i.p.) for 5 days, the level of BDNF mRNA and protein expression in the cerebral cortex and hippocampus of the rats increased significantly. The levels of BDNF mRNA and protein expression in the cerebral cortex and hippocampus measured by of RT-PCR in the rats with DM1 and DM2 were higher than those in the controls by 48% and 56%, and 59% and 54%, respectively. And, those measured by dot blot in the rats with MD1 and MD2 were 186% and 161%, and 148% and 158% of those in the controls, respectively, basically similar to those measured by RT-PCR. Flow cytometric analysis showed that the levels of BDNF mRNA and protein expression in the cerebral cortex and hippocampus in the rats with DM1 and DM2 were higher than those in the controls by 53% and 89%, and 45% and 46%, respectively. Immunohistochemical analysis showed that protein expression in the cerebral cortex of the rats with DM1 and DM2 were 129% and 147% of those in the controls, same as the flow cytometric analysis, but those were significantly higher in the hippocampus mainly in the CA1 and DG areas of the rats with MD1 and the CA3 and DG areas of the rats with DM2. CONCLUSIONS: DM could induce BDNF mRNA and protein expression in the cerebral cortex and hippocampus of the rats, which could play an important role in repairing of nerve damage.

Animals↗
PubMed2003

[Optimization of T7-based RNA amplification system for cDNA microarray].

cDNA microarrays are powerful parallel tools for gene expression profiling analysis, which help us to understand the molecular mechanism of diseases and to identify potential targets for therapeutic intervention. However, their broader application are hampered by the large amount of RNA required: up to 200 microg of total RNA or 5 microg of mRNA for one chip, making analysis of small samples difficult. In this work, combined with a template switching effect, the T7 RNA linear amplification procedure was optimized, providing multiple copies of anti-sense RNA with reduced sample inputs: no more than 3 microg total RNA for one chip. Using the same RNA sample in all cases, the anti-sense RNA labeling method was compared with standard total RNA and mRNA methods by two sets of self-comparison experiments. Furthermore, the three methods in profiling analysis were compared with the same pair RNA samples. All the results indicated that the fidelity, reproducibility, and reliability showed no significant difference with conventional total RNA or mRNA microarrays.

DNA-Directed RNA Polymerases↗
PubMed2003

A novel orthotopic tumor model to study growth factors and oncogenes in hepatocarcinogenesis.

An orthotopic xenograft tumor model of hepatocellular carcinoma was created by injection of Hep 3B cells directly into the liver parenchyma of nude mice. Tumors were localized primarily in the injected lobe of the liver, beginning from the third week after tumor cell implantation. Thereafter, tumors grew rapidly, and animals usually died from hepatocellular carcinoma within 2 months. Insulin-like growth factor II, an embryonic growth factor and mitogen, is overexpressed in these tumors at both mRNA and protein levels. Oncogenes, such as c-myc, c-fos, and c-jun, are also up-regulated in this model. alpha-Fetal protein can be detected shortly after implantation and correlates with tumor growth, and measurement of serum alpha-fetal protein serves as an early biomarker to monitor the effect of antitumor therapy. Using this model, we have shown that inhibition of insulin-like growth factor II expression by a short methylated oligonucleotide prolongs survival. This in situ tumor model thus provides a fast, reliable, and reproducible means to study the therapeutic effect of inhibitors of growth factors and oncogenes in liver cancer.

Animals↗
PubMed2003

[Expression of 5-hydroxytamine receptors in hepatic stellate cell and action of 5-hydroxytamine on biological characteristics of hepatic stellate cell].

OBJECTIVE: To investigate the expression of 5-hydroxytamine receptors in hepatic stellate cells HSCs and action of 5-hydroxytamine on biological characteristics of HSC. METHODS: Liver ex vivo perfusion of collagenase and density gradient centrifugation were used to isolate hepatic stellate cell. RT-PCR was used to detect the expression of 5-hydroxytamine receptor subtypes 1A, 2A, 2B and 3. Western blot hybridization was used to elucidate the effect of 5-hydroxytamine and its 2A receptor antagonist ketanserin and 3 receptor antagonist ondanosetron on expression of transforming growth factor-beta1 (TGF-beta1) and Smad4 in HSC. HSCs were cultured on silicone membrane. The effect of 5-hydroxytamine, ketanserin and ondanosetron on cell contraction were studied. RESULTS: HSC expressed 5-hydroxytamine receptors subtypes 1A, 2A and 2B. 5-hydroxytamine significantly increased the expression of TGF-beta1 and Smad4 in HSC (P < 0.05). This was antagonized by ketanserin, not by ondanosetron. 5-hydroxytamine induced cell contraction in a dose-dependant manner. Ketanserin antagonized this action, but ondanosetron did not. CONCLUSIONS: HSCs express 5-hydroxytamine receptors. 5-hydroxytamine could affect the biological characteristics of HSC through its receptor mediation, and may play a role in the pathogenesis of liver cirrhosis and portal hypertension.

Animals↗
PubMed2003

[The effect of shear stress and flow pattern on proliferation of vascular endothelial cells].

The non-random distribution of atherosclerosis was related to local hemodynamic environment. The stabilization of endothelium was important in this process. We studied the effect of magnitude of shear stress on proliferation of endothelial cells. It was shown the proliferation of endothelial cells was inhibited by shear stress, and was related to the magnitude of shear stress. A parallel plate sudden-expansion flow chamber was constructed, and the effect of flow pattern was also studied. It was shown the inhibition effect produced by shear stress was decreased in this chamber.

Animals↗
PubMed2003

[A study on the relationship between urinary 1-hydroxypyrene level and early genetic effect among coke oven workers].

OBJECTIVE: To investigate the relationship between the urinary 1-hydroxypyrene level and cytokinesis-block micronucleus and the olive moment of comet assay in peripheral blood lymphocyte in coke oven workers. METHODS: One hundred and thirty-three workers from a coke plant and 28 referents without occupational PAH exposure were recruited in this study. Urinary level of 1-hydroxypyrene was measured by alkaline hydrolysis combined with high performance liquid chromatography as an internal exposure dose, and the DNA and chromosomal damage of peripheral blood lymphocyte were evaluated with comet assay and cytokinesis-block micronucleus method. Personal information including occupational history, age, sex, smoking and alcohol drinking, was collected by questionnaire. RESULTS: There existed a good correlationship between the urinary level of 1-hydroxypyrene and frequency of micronuclei per 1 000 binucleated cells or the olive moment of comet assay in the study subjects, after adjusting for sex, age, smoking and alcohol drinking (r > 0.25, P < 0.01). One hundred and sixty-one subjects were divided into three groups by their urine 1-hydroxypyrene level (expressed as 0.30 - 2.44, 2.45 - 7.09 and 7.10 - 33.10 micro mol/mol Cr), and the geometric means of their urinary levels of 1-hydroxypyrene were 1.14, 4.32 and 12.49 micro mol/mol Cr, respectively. After adjusting for age, sex, smoking and alcohol drinking by multiple nonparametric analysis of covariance, the median of olive moment of comet assay in the group of 7.10 - 33.10 micro mol/mol Cr was 3.67, significantly higher than that in the groups of 0.30 - 2.44 and 2.45 - 7.09; and the micronuclei frequencies in the groups of 2.45 - 7.09 and 7.10 - 33.10 micro mol/mol Cr were 8.00 per thousand and 7.50 per thousand, respectively, significantly higher than that in the group of 0.30 - 2.44 micro mol/mol Cr (6.00 per thousand ). CONCLUSIONS: The comet assay of peripheral blood lymphocyte was more suitable to detect the PAHs-induced early genotoxicity, than the cytokinesis-block micronucleus.

Adult↗
PubMed2003

[Effects of deltamethrin on cell survival rate and intracellular free Ca2+ concentration in primary cultured astrocytes of rat].

OBJECTIVE: To study the effects of deltamethrin (DM) on cell survival rate and intracellular Ca(2+) ([Ca(2+)]i) concentration in primary cultured astrocytes of rat. METHODS: The cell survival rate was measured by Typan Blue assay; the intracellular [Ca(2+)]i concentration was determined by the fluorescent Ca(2+) indicator Fura-2/AM. RESULTS: The survival rate of astrocytes was decreased to 91.9% after astrocytes were incubated with 1 x 10(-5) mol/L DM for 72 h (P < 0.05). The cell survival rates were 89.0%, 84.8%, 81.2% and 79.2% respectively when astrocytes were administered with 1 x 10(-4) mol/L DM for 4, 12, 24 and 72 h, which were remarkably lower than control groups (P < 0.01). Comparing with controls and before DM treatment, sharp increases in [Ca(2+)]i concentration [(451.4 +/- 42.3), (536.9 +/- 47.5) and (870.9 +/- 100.5) nmol/L respectively] were observed when astrocytes were incubated with 1 x 10(-7), 1 x 10(-6) and 1 x 10(-5) mol/L DM for 5 minutes (P < 0.01). After astrocytes were treated with 1 x 10(-8), 1 x 10(-7), 1 x 10(-6), 1 x 10(-5) mol/L DM for 15 minutes, the [Ca(2+)]i concentrations were decreased to (124.3 +/- 6.0), (131.3 +/- 19.1), (118.9 +/- 1.4), (136.6 +/- 3.8) nmol/L respectively, which were significantly different from those of controls and before treatment. And this situation was almost keeping stable to 30 min. CONCLUSION: The cell survival rate was decreased and the [Ca(2+)]i concentration was temporarily increased when astrocytes were treated with DM.

Animals↗
PubMed2003

[Expression of a novel human interleukin-13 in E.coli and its biological activity assay].

AIM: To express a novel Gln98-deleted human interleukin-13 in E.coli. METHODS: Total RNA was isolated from Jurkat cells costimulated with PHA and ConA. A 358 bp-specific DNA fragment encoding hIL-13 was amplified by semi-nested RT-PCR. DNA sequencing showed that the target DNA was a Gln98-deleted novel splicing of hIL-13. This hIL-13 cDNA and plasmid pBV220 were ligated at BamH I and EcoR I sites to construct the expression vector. After transforming E.coli strain DH5alpha, the expression of the novel splicing hIL-13 gene was induced by shifting culture temperature from 30 degrees Celsius to 42 degrees Celsius. The expression product was then purified by chromatography on Sepharcryl-200 gel column, and the bioactivity was detected by MTT colorimetry on the growth of TF-1 cell line. RESULTS: The novel rhIL-13 was expressed in the form of inclusion bodies. After purification and renaturation, the specific activity of the novel rhIL-13 was 1.6x10(6) IU/mg. CONCLUSION: The novel rhIL-13 with biological activity has been obtained, which lays the foundation for treating cancer and septicemia by the cytokine in future.

DNA, Complementary↗
PubMed2003

[MGAP-A microbe genome annotation platform].

A Microbe Genome Annotation Platform (MGAP) was developed and applied to the cynobacterium PCC7002 genome annotation. Various bioinformatics software tools from sequence analysis to gene identification and function prediction were implemented in MGAP. Protein sequence databases SWISSPROT and PDBseq, protein information resource InterPro and COG were also integrated in the platform. The web interface of MGAP has the functionality to display a circular map of gene distribution and GC contents throughout the genome. Detailed information such as the DNA and protein sequence, the location of genes on chromosomes can be viewed by clicking the corresponding object within the map. MGAP is based on a PC/Linux system affordable for small biological laboratories and has the advantage of using free software tools including MySQL, Apache and Perl.

Cyanobacteria↗
PubMed2002

p53 codon 72 polymorphism (C/G) and the risk of human papillomavirus-associated carcinomas in China.

BACKGROUND: Human papillomavirus (HPV) plays an important role in the development of carcinomas at various body sites. It was found previously that the p53 codon 72 polymorphism (C/G) is a high-risk factor for the development HPV-associated cervical carcinoma. However, it still was considered controversial in several studies of cervical and esophageal carcinoma. METHODS: In the current study, the authors used an allele specific polymerase chain reaction (PCR) method to analyze correlation between the p53 codon 72 (C/G) polymorphism and HPV-associated, noncancerous esophageal epithelium as well as esophageal, ovarian, and breast carcinoma in the Chinese population. Esophageal balloon cytology examination samples were obtained from high-incidence and low-incidence populations for esophageal carcinoma in Anyang (Henan Province). RESULTS: Thirty-six of 48 esophageal balloon samples from the high-incidence population were HPV positive, and 13 of 33 esophageal balloon samples from the low-incidence population were HPV positive. Thirty-nine of 62 esophageal carcinoma samples from Anyang Tumor Hospital were HPV positive. Twenty-six of 39 ovarian carcinoma samples from the Second Affiliated Hospital of Inner Mongolia Medical College were HPV positive. Nineteen of 82 breast carcinoma samples from Beijing Cancer Hospital were HPV positive. It is noteworthy that the distribution of the p53 codon 72 Arg homozygous genotype in HPV positive samples of esophageal epithelium, ovarian carcinoma, and breast carcinoma was significantly higher compared with HPV negative tumor samples. (P < 0.05). CONCLUSIONS: The current results suggest that the p53 codon 72 Arg homozygous genotype is one of the high-risk genetic factors for HPV-associated malignancies among the Chinese population.

Alleles↗
PubMed2002

A new method for culturing Plasmodium falciparum shows replication at the highest erythrocyte densities.

Plasmodium falciparum replicates poorly in erythrocyte densities greater than a hematocrit of 20%. A new method to culture the major malaria parasite was developed by using a hollow fiber bioreactor that preserves healthy erythrocytes at hematocrit up to 100%. P. falciparum replicated equally well at all densities studied. This method proved advantageous for large-scale preparation of parasitized erythrocytes (and potentially immunogens thereof), because high yields ( approximately 10(10) in 4 days) could be prepared with less cost and labor. Concomitantly, secreted proteins were concentrated by molecular sieving during culture, perhaps contributing to the parasitemic limit of 8%-12% with the 3D7 strain. The finding that P. falciparum can replicate at packed erythrocyte densities suggests that this system may be useful for study of the pathogenesis of fatal cerebral malaria, of which one feature is densely packed blood cells in brain microvasculature.

Animals↗