Biomedical subjects

Yan Tong

Publications and source records attributed to Yan Tong.

13 recordsLinked to original sources

PubMed2006

Transcriptome kinetics of arsenic-induced adaptive response in zebrafish liver.

Arsenic is a prominent environmental toxicant and carcinogen; however, its molecular mechanism of toxicity and carcinogenicity remains poorly understood. In this study, we performed microarray-based expression profiling on liver of zebrafish exposed to 15 parts/million (ppm) arsenic [As(V)] for 8-96 h to identify global transcriptional changes and biological networks involved in arsenic-induced adaptive responses in vivo. We found that there was an increase of transcriptional activity associated with metabolism, especially for biosyntheses, membrane transporter activities, cytoplasm, and endoplasmic reticulum in the 96 h of arsenic treatment, while transcriptional programs for proteins in catabolism, energy derivation, and stress response remained active throughout the arsenic treatment. Many differentially expressed genes encoding proteins involved in heat shock proteins, DNA damage/repair, antioxidant activity, hypoxia induction, iron homeostasis, arsenic metabolism, and ubiquitin-dependent protein degradation were identified, suggesting strongly that DNA and protein damage as a result of arsenic metabolism and oxidative stress caused major cellular injury. These findings were comparable with those reported in mammalian systems, suggesting that the zebrafish liver coupled with the available microarray technology present an excellent in vivo toxicogenomic model for investigating arsenic toxicity. We proposed an in vivo, acute arsenic-induced adaptive response model of the zebrafish liver illustrating the relevance of many transcriptional activities that provide both global and specific information of a coordinated adaptive response to arsenic in the liver.

Adaptation, Physiological↗

PubMed2006

[Determination of acetylharpagide in Ajuga decumbens by HPLC].

OBJECTIVE: To establish a method of the quantitative determination of acetylharpagide in Ajuga decumbens. METHOD: The chromatographic conditions were as follows: a Phenomenex Luna C18 column was used, the mobile phase was composed of acetontrile-water (15:85), the flow rate was 1.0 mL x min(-1) and the UV absorbance detection was set at 197 nm. RESULT: Linearity of acetylharpagide was in the range of 0.6-3.6 microg (r = 0.9993), and the average recovery and RSD were 99.13% and 2.48%, respectively. CONCLUSION: The contents of acetylharpagide ranged 0.40%-6.39% in A. decumbens. The method was simple, accurate and sensitive.

Ajuga↗

PubMed2005

Conservation of gene expression signatures between zebrafish and human liver tumors and tumor progression.

The zebrafish (Danio rerio) has been long advocated as a model for cancer research, but little is known about the real molecular similarities between zebrafish and human tumors. Comparative analysis of microarray data from zebrafish liver tumors with those from four human tumor types revealed molecular conservation at various levels between fish and human tumors. This approach provides a useful strategy for identifying an expression signature that is strongly associated with a disease phenotype.

Amino Acid Sequence↗

PubMed2005

Development of estrogen-responsive transgenic medaka for environmental monitoring of endocrine disrupters.

To develop a transgenic fish system to monitor environmental pollution, we generated a mvtg1:gfp transgenic medaka line, in which the gfp reporter gene was under the control of medaka vitellogenin1 (mvtg1) gene promoter. In this transgenic line, GFP was exclusively expressed in the liver of the mature adult female. Male and juvenile transgenic fish did not express GFP but could be induced to express GFP in the liver after exposure to 17-beta-estradiol (E2). Concurrent accumulation of mvtg1 and gfp mRNAs was observed during both development and estrogen treatment, indicating that the gfp transgene was faithfully expressed under the mvtg1 promoter. Dose- and time-dependent induction of GFP expression by E2 was investigated in male transgenic fish. The lowest-observed-effect concentration (LOEC) of E2 to induce GFP expression was 0.5 microg/L by observation of live fish and 0.05-0.1 microg/L by observation of dissection-exposed liver in a 30 day exposure experiment. GFP expression was observed within 36 h after treatment in high concentrations of E2 (5 microg/L), and it took longer to detect GFP expression under lower concentrations of E2. By removal and readdition of E2, we demonstrated that GFP expression was repeatedly induced. Finally, we also demonstrated that GFP expression could be induced by other estrogenic compounds, including 17-alpha-ethynylestradiol (EE2, 0.05 microg/L), diethylstibestrol (DES, 5 microg/L), estriol (10 microg/ L), and bisphenol A (BPA, 1 mg/L), but not by weak estrogenic chemicals such as nonylphenol (NP, up to 1 mg/ L) and methoxychlor (MXC, up to 20 microg/L). Our experiments indicated the broad application of the transgenic line to monitor a wide range of estrogenic chemicals.

Animals↗

PubMed2005

Transcriptome analysis of zebrafish embryogenesis using microarrays.

Zebrafish (Danio rerio) is a well-recognized model for the study of vertebrate developmental genetics, yet at the same time little is known about the transcriptional events that underlie zebrafish embryogenesis. Here we have employed microarray analysis to study the temporal activity of developmentally regulated genes during zebrafish embryogenesis. Transcriptome analysis at 12 different embryonic time points covering five different developmental stages (maternal, blastula, gastrula, segmentation, and pharyngula) revealed a highly dynamic transcriptional profile. Hierarchical clustering, stage-specific clustering, and algorithms to detect onset and peak of gene expression revealed clearly demarcated transcript clusters with maximum gene activity at distinct developmental stages as well as co-regulated expression of gene groups involved in dedicated functions such as organogenesis. Our study also revealed a previously unidentified cohort of genes that are transcribed prior to the mid-blastula transition, a time point earlier than when the zygotic genome was traditionally thought to become active. Here we provide, for the first time to our knowledge, a comprehensive list of developmentally regulated zebrafish genes and their expression profiles during embryogenesis, including novel information on the temporal expression of several thousand previously uncharacterized genes. The expression data generated from this study are accessible to all interested scientists from our institute resource database (http://giscompute.gis.a-star.edu.sg/~govind/zebrafish/data_download.html).

Journal Article↗

PubMed2005

Thermodynamic analysis of subunit interactions in Escherichia coli molybdopterin synthase.

The molybdopterin (MPT) synthase complex in Escherichia coli consists of two MoaE subunits and two MoaD subunits in a heterotetrameric structure with the two MoaE subunits forming a central dimer. Each MoaD subunit binds to a single MoaE molecule to form two identical MoaE/MoaD interfaces. Here we define the thermodynamic properties of the interaction between MoaE and MoaD in MPT synthase using a H/D exchange and matrix-assisted laser desorption/ionization (MALDI) mass spectroscopy based method termed SUPREX (stability of unpurified proteins from rates of H/D exchange). SUPREX-derived protein folding free energies and m values are reported for MoaE in the presence and absence of MoaD and MoaD-SH, the thiocarboxylated form of MoaD that is essential for the catalytic activity of MPT synthase. The protein folding free energy measurements were used to calculate a dissociation constant of 17 +/- 7 microM for the binding of MoaD to MoaE in inactive MPT synthase and a dissociation constant of 2.6 +/- 0.9 microM for the binding of MoaD-SH to MoaE in active MPT synthase. The increased binding affinity of MoaD-SH for MoaE is consistent with a previously proposed mechanism for the MPT synthase reaction. Using the increased m values exhibited by MoaE in the presence of either MoaD subunit, the solvent accessible surface area buried upon formation of the subunit interface in MPT synthase was estimated to be 2378 A(2) for inactive MPT synthase and 4117 A(2) for active MPT synthase.

Coenzymes↗

PubMed2005

Demonstration of site-directed recombination in transgenic zebrafish using the Cre/loxP system.

To test the Cre/loxP recombination system in zebrafish, a stable transgenic zebrafish line was developed by using a floxed (loxP flanked) gfp (green fluorescent protein) gene construct under the muscle-specific mylz2 promoter. Like our previous non-floxed gfp transgenic line under the same promoter, the new transgenic line expresses GFP reporter faithfully in fast skeletal muscles to the same intensity. To demonstrate the excision of floxed gfp transgene, in vitro synthesized Cre RNA was injected into embryos of floxed gfp transgenic zebrafish and we found a dramatic reduction of GFP expression. To confirm the excision, PCR was performed and a DNA fragment of correct size was amplified as predicted from the Cre/loxP mediated excision. Finally, we cloned the fragment and sequence information confirmed that the excision occurred at the precise site as predicted. Our experiments demonstrated that the Cre/loxP system can function efficiently and accurately in the zebrafish system.

Animals↗

PubMed2005

[Antioxidant and anti-inflammatory effects of cyanidin from cherries on rat adjuvant-induced arthritis].

OBJECTIVE: To assess the possible antioxidant and anti-inflammatory activity of cyanidin from cherries on adjuvant induced arthritis (AA) in SD rats. METHOD: Arthritis was induced by the complete Freud's adjuvant in male Sprague Dauley rats and assessed based on paw swelling. Rats were randomly divided into normal group (NM), adjuvant arthritis group (AA) and three cyanidin-treated groups in high dosage (HA), middle dosage (MA), and low dosage (LA). The morphological changes in the hind limbs were conducted under a light microscope. We detected glutathione (GSH) in whole blood and malonaldehyde (MDA), superoxide dismutase (SOD), total antioxidative capacity (T-AOC) activity in serum by special kits to assess the antioxidant effects of cyanidin on AA. Moreover, the prostaglandin E2 (PGE2) levels in paw tissues were determined by radioimmunoassay and TNF-alpha levels in serum were determined using ELISA kits specific for rat. RESULT: The cyanidin could protect against the paws swelling in AA rats. From the day 14 after AA induction, the swellings of the cyanidin treated groups at high dosage and low dosage were significantly reduced compared with the model group (P < 0.05, 0.01). Histological examination of sections through the hind limbs revealed alleviation of inflammatory reaction in the joint after the treatment. The cyanidin at high and low dosage could increase the GSH, SOD activity and T-AOC levels in whole blood or serums and decrease MDA in AA rats (P < 0.01). The cyanidin could decrease the PGE2 levels in paw tissues and the TNF-alpha levels in serum at high and low dosages (P < 0.01). CONCLUSION: The cyanidin could protect against the paws swelling in AA rats, and alleviate the inflammatory reaction in the joint, and the mechanism might be via the increase activity of GSH, SOD and T-AOC that improve the total antioxidative capacity and scavenge the free radicals, perhaps as a result of that the levels of the PGE2 in paw tissues and TNF-alpha contents in serum were decreased. The results suggest that the cyanidin from cherries could be one of the potential candidates for the alleviation of arthritis.

Animals↗

PubMed2004

Molecular cloning of zebrafish and medaka vitellogenin genes and comparison of their expression in response to 17beta-estradiol.

In the present study, both zebrafish and medaka vitellogenin genes have been isolated and used as a biomarker to compare the two small aquarium fish in response to estrogen treatment and thus to evaluate the two fish models in development of a biomonitoring system for environmental estrogens. The isolated zebrafish vitellogenin gene, zvtg1, is the most abundantly expressed vitellogenin gene in zebrafish and its complete protein sequence of 1360 amino acids was deduced from a genomic and a cDNA clone. The isolated medaka vitellogenin (mvtg1) genomic clone covers 1053 amino acids in the N-terminal. Both zebrafish zvtg1 and medaka mvtg1 are specifically expressed in female liver and their expression can be induced by 17beta-estradiol (E2) in male fish both by intramuscular injection and immersion treatment. A real-time reverse transcriptase polymerase chain reaction (RT-PCR) assay was developed for quantification of vitellogenin mRNA level in both control fish and E2-treated fish. The lowest-observed-effect concentrations of E2 for the induction of vitellogenin mRNAs were observed at 1 microg/l for zebrafish and 0.1 microg/l for medaka in a 2-day exposure experiment. Further kinetics studies of the two fish models indicated that medaka was able to respond much faster to E2 treatment than zebrafish, while the zebrafish can attain a much higher level of vitellogenin mRNAs than medaka after a long-term E2 treatment. The implication of these observations may be that the medaka system is better in monitoring acute treatment while the zebrafish system is better in monitoring chronic exposure.

Amino Acid Sequence↗

PubMed2004

[Determination of carvacrol and thymol in Mosla chinensis by HPLC].

OBJECTIVE: To establish a quantitative method of determination of carvacrol and thymol in Mosla chinensis. METHOD: The sample was extracted with 95% ethanol, ODS column was used with methanol-water-acetic acid (60:40:2) as mobile phase. The detection wavelength was set at 274 nm. RESULT: The linearities of carvacrol and thymol were respectively in the range of 0.23-2.15 microg (r = 0.9999) and 0.39-2.36 microg (r = 0.9999); the average recoveries were 99.9% (RSD 1.4%) and 98.6% (RSD 1.3%); the RSD of repeatability were 1.1% and 1.6%. CONCLUSION: The method is reliable, and can be used for quality control of M. chinensis.

Chromatography, High Pressure Liquid↗

PubMed2004

[Study on qualitative and quantitative methods for yinhuang liangxiao granule].

OBJECTIVE: To establish the quality standard of yinhuang langxiao granule. METHOD: The Panax notoginseng, Arnebia euchromq, Cornus officinalis, Lonicera japonica, Artemisiae annua were identified by TLC. The content of chrysophanol in granule was determined by HPLC. RESULT: Spots of samples on TLC can be well separated and the method had good specificity. The average recovery of chrysophanol was 98.7% and RSD was 0.67%. CONCLUSION: An accurate, simple and effective quality-controlling method has been developed, which can be used for quality control for yinhuang langxiao granule.

Anthraquinones↗

PubMed2003

Recapitulation of fast skeletal muscle development in zebrafish by transgenic expression of GFP under the mylz2 promoter.

A 1,934-bp muscle-specific promoter from the zebrafish mylz2 gene was isolated and characterized by transgenic analysis. By using a series of 5' promoter deletions linked to the green fluorescent protein (gfp) reporter gene, transient transgenic analysis indicated that the strength of promoter activity appeared to correlate to the number of muscle cis-elements in the promoter and that a minimal -77-bp region was sufficient for a relatively strong promoter activity in muscle cells. Stable transgenic lines were obtained from several mylz2-gfp constructs. GFP expression in the 1,934-bp promoter transgenic lines mimicked well the expression pattern of endogenous mylz2 mRNA in both somitic muscle and nonsomitic muscles, including fin, eye, jaw, and gill muscles. An identical pattern of GFP expression, although at a much lower level, was observed from a transgenic line with a shorter 871-bp promoter. Our observation indicates that there is no distinct cis-element for activation of mylz2 in different skeletal muscles. Furthermore, RNA encoding a dominant negative form of cAMP-dependent protein kinase A was injected into mylz2-gfp transgenic embryos and GFP expression was significantly reduced due to an expanded slow muscle development at the expense of GFP-expressing fast muscle. The mylz2-gfp transgene was also transferred into two zebrafish mutants, spadetail and chordino, and several novel phenotypes in muscle development in these mutants were discovered.

Animals↗

PubMed2002

[Comparative studies on isolation and purification of Chinese medicine decoction].

OBJECTIVE: To evaluate different methods by treating water-decocted liquid of 6 Chinese medical herbs and 4 co-prescription respectively with alcohol, ultrafilter, macroporousresin and clarifier. METHOD: The contents of target component in those extracts were determined with HPLC or titration, and quantitative and qualitative determination of the impurity components, such as polysaccharide and protein, was made. RESULT: Each method showed its advantages and disavantages. CONCLUSION: Different method can be chosen according to the clinical and preparation demands or the characteristic of components.

Drug Combinations↗