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Biomedical subjects

Hong Gao

Publications and source records attributed to Hong Gao.

At least 19 recordsLinked to original sources
PubMed2026

The H3K27me3 reader GmLHP1 impairs Phytophthora sojae resistance by repressing ethylene precursor accumulation in soybean.

Phytophthora root rot, caused by Phytophthora sojae, is a devastating soilborne disease of soybean (Glycine max). However, the epigenetic regulation of soybean responses to P. sojae remains incompletely understood. Here, using genetic, molecular and biochemical approaches, we characterized the functions of LIKE HETEROCHROMATIN PROTEIN 1 (GmLHP1) and its downstream regulatory network. We demonstrated that GmLHP1, as a reader of H3K27me3, negatively regulates soybean resistance to P. sojae. GmLHP1 binds to H3K27me3 peptides in vitro and colocalizes with H3K27me3 marks genome-wide in vivo. The integrated chromatin immunoprecipitation sequencing and RNA sequencing analysis identified the ethylene biosynthesis pathway gene 1-AMINO-CYCLOPROPANE-1-CARBOXYLATE SYNTHASE 18 (GmACS18) as being enriched for H3K27me3 and bound by GmLHP1, leading to its transcriptional downregulation. Notably, GmLHP1 associates with the GmACS18 promoter by directly binding to AATTAA motifs and recognizing H3K27me3 marks. Moreover, GmACS18 enhances defense against P. sojae by accumulating the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC). Further analysis unveiled that recognition of H3K27me3 by GmLHP1 is essential for regulating soybean resistance to P. sojae through repressing GmACS18 transcription and decreasing ACC accumulation. Our findings reveal a novel epigenetic regulatory mechanism in which the H3K27me3 reader GmLHP1 blocks soybean resistance to P. sojae by repressing ethylene precursor ACC accumulation.

ACC accumulation↗
PubMed2007

In vitro biodegradation and biocompatibility of gelatin/montmorillonite-chitosan intercalated nanocomposite.

The intercalated nanocomposite of gelatin/montmorillonite-chitosan (Gel/MMT-CS) was prepared via the solution intercalation process. In vitro degradation tests showed that the nanocomposite had a lower degradation rate than Gel-CS composite. And the introduced intercalation structure endowed Gel/MMT-CS nanocomposite with a controllable degradation rate when changing the MMT content. Cells attachment, spread and proliferation on the Gel/MMT-CS membranes were investigated by scanning electron microscopy (SEM) and mitochondrial activity assay. The results provided evidences of good adhesion, proliferation and morphology of rat stromal stem cells on Gel/MMT-CS membranes compared to the tissue culture plates (TCPs), making the Gel/MMT-CS nanocomposite a promising candidate towards tissue engineering.

Absorbable Implants↗
PubMed2006

Screening of tetracycline residues in fish muscles by CCD camera-based solid-surface fluorescence.

A methodology for the screening of tetracyclines (TCs), including tetracycline (TC), oxytetracycline (OTC), and chlorotetracycline (CTC), in different fish muscle matrices has been proposed. This method was based on in situ fluorescent derivation of TCs, transferring weakly fluorescing TCs to highly fluorescent species, on alkaline-activated solid silica gel G plates (SGGPs). By coupling solid-surface fluorescence (SSF) with charge-coupled device (CCD) camera imaging, a CCD camera-based SSF (CCD-SSF) methodology has been developed. Calibration curve, repeatability, selectivity, limit of detection (LOD), and limit of quantification (LOQ) have been explored for evaluating the performance of the method itself. Linear calibration curves were obtained over a range of 0.20-1.0 ng/spot for all three TCs. The LODs, defined as 3sigma, for TC, OTC, and CTC were 0.14, 0.15, and 0.16 ng/spot, respectively. The trueness of method was validated by HPLC, and no significant difference between CCD-SSF and HPLC was found, on a basis of 95% confidence level. By spiked recovery studies, a linear calibration curve ranging from 20 to 300 microg/kg of TC in fish muscle samples with a correlation coefficient (R 2) equal to 0.994 was obtained. The total average recovery for TC in fish muscle samples from six different fish matrices, fortified with TC at 50, 100, and 200 microg/kg levels, was 75.7% with average relative standard deviations (RSDs) ranging from 2.0 to 7.7%. RSDs ranged from 2.5 to 5.8% and from 5.2 to 7.6% for in-day and interday repeatability, respectively. The detection and quantification limits in fish muscle matrices were 16 and 53 microg/kg of TCs, respectively. The newly developed CCD-SSF method has been applied to the screening of the TC residues in fish muscle samples. The method has been demonstrated to bear some advantages, such as its simplicity, high throughput, low cost, use of fewer pollutants, and reasonable sensitivity.

Animals↗
PubMed2006

The impact of sample imbalance on identifying differentially expressed genes.

BACKGROUND: Recently several statistical methods have been proposed to identify genes with differential expression between two conditions. However, very few studies consider the problem of sample imbalance and there is no study to investigate the impact of sample imbalance on identifying differential expression genes. In addition, it is not clear which method is more suitable for the unbalanced data. RESULTS: Based on random sampling, two evaluation models are proposed to investigate the impact of sample imbalance on identifying differential expression genes. Using the proposed evaluation models, the performances of six famous methods are compared on the unbalanced data. The experimental results indicate that the sample imbalance has a great influence on selecting differential expression genes. Furthermore, different methods have very different performances on the unbalanced data. Among the six methods, the welch t-test appears to perform best when the size of samples in the large variance group is larger than that in the small one, while the Regularized t-test and SAM outperform others on the unbalanced data in other cases. CONCLUSION: Two proposed evaluation models are effective and sample imbalance should be taken into account in microarray experiment design and gene expression data analysis. The results and two proposed evaluation models can provide some help in selecting suitable method to process the unbalanced data.

Algorithms↗
PubMed2006

Ga-assisted synthesis and optical properties of ZnO submicron- and nanotowers.

Tower-like ZnO submicron- and nanostructures were synthesized by simply evaporating a mixture of Zn and Ga. Scanning electron microscopy and transmission electron microscopy observations showed that the regular hexagonal tower-like structure is likely to be made up in a layer-by-layer fashion and consist of sheets. According to our experiments, the amount of Ga has a large effect on their morphologies. The growth of such tower-like structures is ascribed to the vapor-solid mechanism. The introduction of Ga hinders the growth of ZnO along the [0001] direction, resulting in the formation of the novel tower-like structures. In addition, the photoluminescence of such structures shows a strong green-light emission.

Journal Article↗
PubMed2006

Farnesoid X receptor agonist reduces serum asymmetric dimethylarginine levels through hepatic dimethylarginine dimethylaminohydrolase-1 gene regulation.

The farnesoid X receptor (FXR, NR1H4) is a bile acid-responsive nuclear receptor that plays critical roles in the transcriptional regulation genes involved in cholesterol, bile acid, triglyceride, and carbohydrate metabolism. By microarray analysis of hepatic genes from female Zucker diabetic fatty (ZDF) rats treated with the FXR agonist GW4064, we have identified dimethylarginine dimethylaminohydrolase-1 (DDAH1) as an FXR target gene. DDAH1 is a key catabolic enzyme of asymmetric dimethylarginine (ADMA), a major endogenous nitric-oxide synthase inhibitor. Sequence analysis of the DDAH1 gene reveals the presence of an FXR response element (FXRE) located 90 kb downstream of the transcription initiation site and within the first intron. Functional analysis of the putative FXRE demonstrated GW4064 dose-dependent transcriptional activation from the element, and we have demonstrated that the FXRE sequence binds the FXR-RXR heterodimer. In vivo administration of GW4064 to female ZDF rats promoted a dose-dependent and >6-fold increase in hepatic DDAH1 gene expression. The level of serum ADMA was reduced concomitantly. These findings provide a mechanism by which FXR may increase endothelium-derived nitric oxide levels through modulation of serum ADMA levels via direct regulation of hepatic DDAH1 gene expression. Thus, beneficial clinical outcomes of FXR agonist therapy may include prevention of atherosclerosis and improvement of the metabolic syndrome.

Amidohydrolases↗
PubMed2006

Noncovalent complexes of APS reductase from M. tuberculosis: delineating a mechanistic model using ESI-FTICR MS.

ESI-FTICR MS was utilized to characterize a 4Fe-4S containing protein Mycobacterium tuberculosis APS reductase. This enzyme catalyzes the reduction of APS to sulfite and AMP with reducing equivalents from the protein cofactor, thioredoxin. Under nondenaturing conditions, a distribution of the apoprotein, a 2Fe-2S intermediate, and the 4Fe-4S holoprotein were observed. Accurate mass measurements indicated an oxidation state of +2 for the 4Fe-4S cluster, with no disulfide bond in the holoenzyme. Gas-phase stability of the 4Fe-4S cluster was investigated using both in-source and collision induced dissociation, which provided information regarding the relative gas-phase binding strength of iron towards protein ligands and inorganic sulfides. Noncovalent complexes of the holoprotein with several ligands, including APS, thioredoxin, and AMP, were also investigated. Calculated values of dissociation constants for the complexes indicate that AMP binds with a higher affinity to the enzyme intermediate than to the free enzyme. The implications of the binary and ternary complexes observed by gas-phase noncovalent interactions in the mechanism of APS reduction are discussed.

Adenosine Monophosphate↗
PubMed2006

Substrate recognition, protein dynamics, and iron-sulfur cluster in Pseudomonas aeruginosa adenosine 5'-phosphosulfate reductase.

APS reductase catalyzes the first committed step of reductive sulfate assimilation in pathogenic bacteria, including Mycobacterium tuberculosis, and is a promising target for drug development. We report the 2.7 A resolution crystal structure of Pseudomonas aeruginosa APS reductase in the thiosulfonate intermediate form of the catalytic cycle and with substrate bound. The structure, high-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry, and quantitative kinetic analysis, establish that the two chemically discrete steps of the overall reaction take place at distinct sites on the enzyme, mediated via conformational flexibility of the C-terminal 18 residues. The results address the mechanism by which sulfonucleotide reductases protect the covalent but labile enzyme-intermediate before release of sulfite by the protein cofactor thioredoxin. P. aeruginosa APS reductase contains an [4Fe-4S] cluster that is essential for catalysis. The structure reveals an unusual mode of cluster coordination by tandem cysteine residues and suggests how this arrangement might facilitate conformational change and cluster interaction with the substrate. Assimilatory 3'-phosphoadenosine 5'-phosphosulfate (PAPS) reductases are evolutionarily related, homologous enzymes that catalyze the same overall reaction, but do so in the absence of an [Fe-S] cluster. The APS reductase structure reveals adaptive use of a phosphate-binding loop for recognition of the APS O3' hydroxyl group, or the PAPS 3'-phosphate group.

Amino Acid Sequence↗
PubMed2006

Expression of pituitary adenylate cyclase-activating polypeptide 1 and 2 receptor mRNA in gallbladder tissue of patients with gallstone or gallbladder polyps.

AIM: To detect the expression of pituitary adenylate cyclase-activating polypeptide receptor 1 (VPCAP1-R)and VPCAP2-R mRNA in gallbladder tissues of patients with gallstone or gallbladder polyps. METHODS: The expression of VPCAP1-R and VPCAP2-R mRNA in gallbladder tissues was detected in 25 patients with gallstone,8 patients with gallbladder polyps and 7 donors of liver transplantation by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: The VPCAP2-R mRNA expression level in the control group (1.09+/-0.58) was lower than that in the gallbladder polyp group (1.64+/-0.56) and the gallstone group (1.55+/-0.45) (P<0.05) while the VPCAP1-R mRNA expression level in the control group (1.15+/-0.23) was not apparently different from that in the gallbladder polyp group (1.28+/-0.56) and the gallstone group (1.27+/-0.38). CONCLUSION: The abnormal expression of VPCAP2-R mRNA in gallbladder tissue may play a role in the formation of gallbladder stone and gallbladder polyps.

Adult↗
PubMed2006

Engineering the acetyl-CoA transportation system of candida tropicalis enhances the production of dicarboxylic acid.

Dicarboxylic acids (DCAs) can be obtained by oxidizing alkanes by Candida tropicalis. Through alpha-monocarboxylic acids (MCAs), alpha- and omega-oxidation yield alpha- or omega-DCAs, respectively. However, both MCAs and DCAs may be degraded to acetyl-CoA by beta-oxidation, resulting in a limited DCA yield. Acetyl-CoA can be transported into the mitochondrion for the TCA cycle by carnitine acetyltransferase (CAT), by which the energy generation and beta-oxidation are connected. In this paper, we present a method to reconstruct the metabolic pathway by inhibiting the acetyl-CoA transportation system. Metabolic engineering is applied on the acetyl-CoA transportation system, but not the key enzymes in beta-oxidation. Starting with the original strain W10-1, cat heterozygote CZ-15 and cat homozygote CKC-11 were obtained by gene knockout. The CAT specific activity in CZ-15 was about 50% lower than that in W10-1, resulting in a 21.0% increase of the DCA concentration, and a 12% increase of the molar conversion of alkane, reaching 61.6%. However, no CAT activity was detected in CKC-11, and CKC-11 could not grow on alkane. These results indicate that inhibition of beta-oxidation via reconstruction of the transportation process between organelles can facilitate DCA production, but that totally blocking the & betagr;-oxidation would be harmful for energy supply. We thus provide a novel insight into regulation of the beta-oxidation system and metabolic flux. Further understanding of beta-oxidation and the acetyl-CoA transportation system in Candida tropicalis is reached through examination of fermentation data by metabolic flux analysis.

Acetyl Coenzyme A↗
PubMed2006

Construction and expression of bivalent membrane-anchored DNA vaccine encoding Sjl4FABP and Sj26GST genes.

In order to construct a eukaryotic co-expression plasmid containing membrane-anchored Sjcl4FABP and Sjc26GST genes and identify their expression in vitro, Sj14 and Sj26 genes were obtained by RT-PCR with total RNA of Schistosoma japonicum adult worms as the template and cloned into eukaryotic expression plasmid pVAC to construct recombinant plasmids pVAC-Sj14 and pVAC-Sj26. Then a 23 amino-acid signal peptide of human interleukin-2 (IL-2) upstream Sj14 or Sj26 gene and a membrane-anchored sequence containing 32 amino-acids of carboxyl-terminal of human placental alkaline phosphatase (PLAP) downstream were amplified by PCR as the template of plasmid pVAC-Sj14 or pVAC-Sj26 only to get two gene fragments including Sj14 gene and Sj26 gene. The two modified genes were altogether cloned into a eukaryotic co-expression plasmid pIRES, resulting in another new recombinant plasmid pIRES-Sj26-Sj14. The expression of Sj14 and Sj26 genes was detected by RT-PCR and indirect immunofluorescent assays (IFA) when the plasmid pIRES-Sj26-Sj14 was transfected into eukaryotic Hela cells. Restriction enzyme analysis, PCR and sequencing results revealed that the recombinant plasmids pVAC-Sj14, pVAC-Sj26 and plRES-Sj26-Sj14 were successfully constructed and the expression of modified Sj14 and Sj26 genes could be detected by RT-PCR and IFA. A bivalent membrane-anchored DNA vaccine encoding Sj14 and Sj26 genes was acquired and expressed proteins were proved to be mostly anchored in cellular membranes.

Animals↗
PubMed2006

Measurement of portal pressure: when, how, and why to do it.

Many of the clinical complications of cirrhosis are the direct consequences of the evaluation of portal venous pressure (PVP). The degree of portal hypertension has been shown to correlate with the severity of liver disease, both functionally and histologically. Direct measurement of PVP, however, is invasive and cannot be routinely performed. As a surrogate, the hepatic venous pressure gradient (HVPG) has been widely accepted as a measurement of PVP. The ease, accuracy, and safety of HVPG measurement has made it a valuable tool in the research arena and, increasingly, in clinical practice.

Blood Pressure Determination↗
PubMed2006

[Effects of interventional therapy with norcantharidin microsphere on hepatoma in rats and its mechanism].

OBJECTIVE: To investigate the effects of interventional therapy with norcantharidin-alginic acid/poly acid anhydride microspheres (N-MS) infusion via hepatic artery on hepatoma in rats. METHODS: N-MS was prepared by emulsion-chemical crosslink technique. Eighty-nine hepatoma-bearing rats were randomly divided into five groups, which were normal saline group, norcantharidin (NCTD) group, blank microsphere (B-MS) group, NCTD-lipiodol group and N-MS group. Normal saline, NCTD, B-MS, NCTD-lipiodol and N-MS were injected via hepatic artery accordingly. After the interventional therapy, eight rats from each group were observed for survival time, and the rest rats were killed on the 8th day after intervention to measure the tumor volume and necrostic degree. The apoptotic index of liver tumor cells was detected by TUNEL staining, and the expression of ki-67 was assayed by immuno-histochemical streptavidin-biotin peroxidase method. RESULTS: The survival time of the rats in the N-MS group was prolonged as compared with those in the other four groups, and the tumor volume of the rats in the N-MS group was smaller than those in the other four groups. The tumor growth rate and the expression level of ki-67 in the N-MS group were both significantly lower than those in the other four groups. The tumor necrotic degree and the apoptotic index in the N-MS group were significantly higher than those in the other four groups. CONCLUSION: Interventional therapy with N-MS could yield preferable therapeutic effects on hepatomas in rats. This anti-tumor efficacy may be associated with microvessel embolization in liver tumor and the sustained releasing of NCTD. Its inhibiting effect on tumor cell proliferation maybe result from decreasing the expression of Ki-67 and inducing the tumor cell apoptosis.

Alginates↗
PubMed2006

[Determination of tetracyclines by a new spectrum technique].

Tetracyclines are light-fluorescence substances, which cannot be detected directly by fluorometry. Herein a new spectrum method was proposed to detect tetracyclines directly by fluorometry. Under optimal conditions, the calibration graph is linear over the range 0.10-9.00 microg x mL(-1) for tetracyclines, and the detection limits of tetracycline, oxytetracycline, chlortetracycline and doxycycline are 0.065, 0.067, 0.068 and 0.070 microg x mL(-2), respectively.

Anti-Bacterial Agents↗
PubMed2006

[Protective effects of recombinant intestinal trefoil factor against intestinal injuries induced by endotoxin in young rats].

OBJECTIVE: This study aimed to investigate the protective effects of recombinant intestinal trefoil factor (rITF) against intestinal injuries and the possible mechanism by examining the changes of diamine oxidase (DAO) and TNF-alpha and the intestinal ultrastructural changes in lipopolysaccharide (LPS) induced intestinal injuries. METHODS: Ninety-six ten-day-old Wistar rats were randomly injected with either normal saline (1 mL/kg, Control group), LPS (1 mL/kg) or LPS (1 mL/kg) + rITF (0.1 mL) intraperioneally. At 2, 6, 24 and 72 hrs after administration plasma DAO activity was determined using absorption spectrometry; and the intestinal protein and mRNA expression of TNF-alpha were measured using immunohistochemistry and RT-PCR methods. The intestinal ultrastructural changes were observed by electron microscopy. RESULTS: The plasma DAO activity in the LPS group began to increase at 2 hrs, peaked at 6 hrs and remained at significantly higher levels until 72 hrs after administration compared with the Control group (P < 0.01). The plasma DAO activity in the LPS + rITF group decreased noticeably compared with the LPS group at all time points (P < 0.01 or 0.05). A significant difference in the plasma DAO activity was only observed at 6 hrs after administration between the LPS + rITF and the Control group. The expression of TNF-alpha protein in the LPS group significantly increased at each time point, peaking at 6 hrs after LPS administration, with the IODT of TNF-alpha of 37,247.64 +/- 3,387.59 vs 6,191.02 +/- 482.32 (P < 0.01) compared with the Control group. rITF treatment decreased the expression of TNF-alpha protein although it remained significantly higher than in the Control group (P < 0.01). The TNF-alpha mRNA was weakly expressed in the Control group but strikingly increased after LPS injection (P < 0.01). Compared with the LPS group, the TNF-alpha mRNA expression in the LPS + rITF group decreased at all time points (P < 0.01 or 0.05). Vacuole changes of mitochodrium, cell nucleus condense, break and depletion of part of microvilli, and widen and disrupted tight junction were observed in the LPS group. The ultrastructural changes of intestinal tissues were improved in the LPS + rITF group. CONCLUSIONS: rITF can decrease the plasma DAO activity and inhibit the expression of TNF-alpha, resulting in a protective effect against intestinal injuries induced by LPS in young rats.

Amine Oxidase (Copper-Containing)↗