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Yongjun Wang

Publications and source records attributed to Yongjun Wang.

35 records · Page 2Linked to original sources
PubMed2005

Hepatocyte CYP2E1 overexpression and steatohepatitis lead to impaired hepatic insulin signaling.

Insulin resistance and increased cytochrome P450 2E1 (CYP2E1) expression are both associated with and mechanistically implicated in the development of nonalcoholic fatty liver disease. Although currently viewed as distinct factors, insulin resistance and CYP2E1 expression may be interrelated through the ability of CYP2E1-induced oxidant stress to impair hepatic insulin signaling. To test this possibility, the effects of in vitro and in vivo CYP2E1 overexpression on hepatocyte insulin signaling were examined. CYP2E1 overexpression in a hepatocyte cell line decreased tyrosine phosphorylation of insulin receptor substrate (IRS)-1 and IRS-2 in response to insulin. CYP2E1 overexpression was also associated with increased inhibitory serine 307 and 636/639 IRS-1 phosphorylation. In parallel, the effects of insulin on Akt activation, glycogen synthase kinase 3, and FoxO1a phosphorylation, and glucose secretion were all significantly decreased in CYP2E1 overexpressing cells. This inhibition of insulin signaling by CYP2E1 overexpression was partially c-Jun N-terminal kinase dependent. In the methionine- and choline-deficient diet mouse model of steatohepatitis with CYP2E1 overexpression, insulin-induced IRS-1, IRS-2, and Akt phosphorylation were similarly decreased. These findings indicate that increased hepatocyte CYP2E1 expression and the presence of steatohepatitis result in the down-regulation of insulin signaling, potentially contributing to the insulin resistance associated with nonalcoholic fatty liver disease.

Adenoviridae↗
PubMed2005

Amphioxus allantoicase: molecular cloning, expression and enzymatic activity.

Allantoicase, one of the purine metabolism enzymes, is progressively truncated during the chordate evolution, yet it is unknown when its activity became phylogenetically extinct. In this study, a cDNA encoding allantoicase was isolated from the gut cDNA library of amphioxus Branchiostoma belcheri tsingtauense. It is 2441 bp long, and contains an open reading frame encoding a protein of 392 amino acid residues. RT-PCR analysis showed that amphioxus allantoicase was strongly expressed in the hepatic caecum, and weakly expressed in other tissues including hind-gut, gill, muscle, notochord, testis and ovary. The parallel experiment was performed measuring the allantoicase activity in the same tissues revealed that its activity was high in the hepatic caecum, but low or undetectable in other tissues examined. These suggest that allantoicase remains in action in the primitive chordate amphioxus.

Animals↗
PubMed2005

Characterization and expression profile of AmphiCD63 encoding a novel member of TM4SF proteins from amphioxus Branchiostoma belcheri tsingtauense.

The study on CD antigen genes remains lacking in the cephalochordate amphioxus to date. In this report, the cDNA encoding CD63 was identified for the first time from the gut cDNA library of amphioxus Branchiostoma belcheri tsingtauense. Primary structural examination showed that the protein encoded by the cDNA contained four potential transmembrane domains characteristic of transmembrane 4 superfamily (TM4SF) proteins and a conserved CCG motif in the putative major extracellular loop. BLAST search revealed that the cDNA is closely associated with other known CD63 antigen genes, and it was thus designated AmphiCD63. Phylogenetic analysis indicated that AmphiCD63 is extremely close to vertebrate CD63, CD151 and CD53, suggesting they may have been evolved from a common ancestral gene. RT-PCR analysis exhibited that AmphiCD63 mRNA was abundant in muscle, ovary, foregut including hepatic caecum and hindgut, while it was present at considerably lower levels in notochord and gill and absent in testis.

Amino Acid Sequence↗
PubMed2005

[Correlation analysis on the damage of Mikania micrantha to plant communities in Neilingdind Island of Guandong Province, China].

The analysis showed that 58 species of trees, short-trees and shrubs in Neilingding Island of Guangdong Province were damaged by M. micrantha, of which, woody trees accounted for 67%. Short-trees and sunny shrubs were damaged most seriously, followed by the communities with low canopy density consisted of only 2 dominant species, and those with high canopy density consisted of 5 or 6 dominant species. The coverage of M. micrantha mainly related to the vertical structure of plant communities. The taller the community height and the more the synusia, the lesser was the coverage of M. micrantha. The damaging ratio mainly related to species diversity and community density. The higher the species diversity and community density, the lower the damaging ratio was. The damaging degree mainly related to the coverage of other liana. The more the coverage of other liana, the higher was the damaging degree of M. micrantha.

China↗
PubMed2004

Hepatocyte resistance to oxidative stress is dependent on protein kinase C-mediated down-regulation of c-Jun/AP-1.

The prevention of injury from reactive oxygen species is critical for cellular resistance to many death stimuli. Resistance to death from the superoxide generator menadione in the hepatocyte cell line RALA255-10G is dependent on down-regulation of the c-Jun N-terminal kinase (JNK)/AP-1 signaling pathway by extracellular signal-regulated kinase 1/2 (ERK1/2). Because protein kinase C (PKC) regulates both oxidant stress and JNK signaling, the ability of PKC to modulate hepatocyte death from menadione through effects on AP-1 was examined. PKC inhibition with Ro-31-8425 or bisindolylmaleimide I sensitized this cell line to death from menadione. Menadione treatment led to activation of PKCmicro, or protein kinase D (PKD), but not PKCalpha/beta, PKCzeta/lambda, or PKCdelta/. Menadione induced phosphorylation of PKD at Ser-744/748, but not Ser-916, and translocation of PKD to the nucleus. PKC inhibition blocked menadione-induced phosphorylation of PKD, and expression of a constitutively active PKD prevented death from Ro-31-8425/menadione. PKC inhibition led to a sustained overactivation of JNK and c-Jun in response to menadione as determined by in vitro kinase assay and immunoblotting for the phosphorylated forms of both proteins. Cell death from PKC inhibition and menadione treatment resulted from c-Jun activation, since death was blocked by adenoviral expression of the c-Jun dominant negative TAM67. PKC and ERK1/2 independently down-regulated JNK/c-Jun, since inhibition of either kinase failed to affect activation of the other kinase, and simultaneous inhibition of both pathways caused additive JNK/c-Jun activation and cell death. Resistance to death from superoxide therefore requires both PKC/PKD and ERK1/2 activation in order to down-regulate proapoptotic JNK/c-Jun signaling.

Animals↗
PubMed2004

CYP2E1 overexpression alters hepatocyte death from menadione and fatty acids by activation of ERK1/2 signaling.

Chronic oxidative stress induced by overexpression of the cytochrome P450 isoform 2E1 (CYP2E1) has been implicated in hepatocyte injury and death. However, the mechanism by which CYP2E1 overexpression may promote cell death is unknown. Acute oxidative stress activates mitogen-activated protein kinases (MAPK), suggesting that chronic oxidant generation by CYP2E1 may regulate cellular responses through these signaling pathways. The effect of CYP2E1 overexpression on MAPK activation and their function in altering death responses of CYP2E1-overexpressing hepatocytes were investigated. Chronic CYP2E1 overexpression led to increased extracellular signal-regulated kinase 1/2 (ERK1/2) activation constitutively and in response to oxidant stress from the superoxide generator menadione. CYP2E1-overexpressing cells were resistant to menadione toxicity through an ERK1/2-dependent mechanism. Similar to menadione, the polyunsaturated fatty acid (PUFA) arachidonic acid (AA) induced an increased activation of ERK1/2 in hepatocytes that overexpressed CYP2E1. However, CYP2E1-overexpressing cells were sensitized to necrotic death from AA and the PUFA gamma-linolenic acid, but not from saturated or monounsaturated fatty acids. Death from PUFA resulted from oxidative stress and was blocked by inhibition of ERK1/2, but not p38 MAPK or activator protein-1 signaling. CYP2E1 expression induced ERK1/2 activation through increased epidermal growth factor receptor (EGFR)/c-Raf signaling. Inhibition of EGFR signaling reversed CYP2E1-induced resistance to menadione and sensitization to AA toxicity. In conclusion, chronic CYP2E1 overexpression leads to sustained ERK1/2 activation mediated by EGFR/c-Raf signaling. This adaptive response in hepatocytes exposed to chronic oxidative stress confers differential effects on cellular survival, protecting against menadione-induced apoptosis, but sensitizing to necrotic death from PUFA.

Animals↗
PubMed2004

Evolution and expression of the amphioxus AmphiHMGB gene encoding an HMG-box protein.

Amphioxus HMGB gene, AmphiHMGB, encoding a high mobility group (HMG) protein was identified from the gut cDNA library of Branchiostoma belcheri tsingtauense. Primary structural examination indicates that it is a member of HMGB family. Molecular phylogenetic analysis suggests that AmphiHMGB represents the archetype of chordate HMGB genes including HMGB1, HMGB2 and HMGB3 although it may have lost its C-terminal domain during evolution. Northern blotting revealed that AmphiHMGB expression was restricted mainly to guts in the adult, and AmphiHMGB transcripts were in greater abundance in gastrula and neurula though they were markedly low in 1-day larva.

Amino Acid Sequence↗
PubMed2004

Characterization of an NBS-LRR resistance gene homologue from soybean.

Conserved motifs such as the nucleotide-binding site (NBS) were found in many characterized plant disease resistance genes. Based on the NBS domain, resistance gene analogs have been isolated in our previous study and were used as probes to screen a soybean (Glycine max) cDNA library. A full-length cDNA, KR4, was isolated by screening the library and rapid amplification of cDNA ends method. Sequence analysis revealed that the cDNA was 3818 bp in length and the open reading frame coded for a polypeptide of 1211 amino acids with an NBS and five leucine-rich repeats domains, which were identified by Pfam protein analysis. Sequence alignment showed that KR4 was similar to 12 protein of tomato. Southern analysis indicated that the KR4 gene had low copies in soybean genome and it was mapped on the molecular linkage group E. Its expression was also investigated and it was found that KR4 was induced by exogenous salicylic acid and responded upon infection of soybean mosaic virus strain N3.

Amino Acid Sequence↗
PubMed2003

Oxidant-induced hepatocyte injury from menadione is regulated by ERK and AP-1 signaling.

Oxidative stress has been implicated as a mechanism for a variety of forms of liver injury. Although reactive oxygen species (ROS) may damage cellular macromolecules directly, oxidant-induced cell death may result from redox effects on signal transduction pathways. To understand the mechanisms of hepatocyte death from oxidative stress, the functions of the mitogen-activated protein kinases (MAPKs) were determined during oxidant-induced hepatocyte injury from menadione. Low, nontoxic, and high toxic concentrations of the superoxide generator menadione were established in the RALA255-10G rat hepatocyte cell line. Death from menadione was blocked by catalase and ebselen, indicating that death was secondary to oxidant generation and not arylation. Treatment with a nontoxic menadione concentration resulted in a brief activation of extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK). In contrast, treatment with a toxic menadione concentration induced a prolonged activation of both ERK and JNK. Chemical inhibition of ERK function sensitized RALA hepatocytes to death from previously nontoxic menadione concentrations in association with sustained JNK activation. Adenoviral expression of a dominant-negative protein for c-Jun, a downstream substrate for JNK, blocked death from menadione. The pro-apoptotic effect of c-Jun was not mediated through the mitochondrial death pathway. In conclusion, RALA hepatocyte resistance to oxidant-induced death from menadione is dependent on ERK, whereas cell death is mediated by AP-1 activation. These findings identify signaling pathways that may be therapeutic targets in the prevention or treatment of oxidant-induced liver injury.

Animals↗
PubMed2003

Presence and characterization of complement-like activity in the amphioxus Branchiostoma belcheri tsingtauense.

The humoral fluid of Branchiostoma belcheri tsingtauense was examined for the presence of complement-like activity. The humoral fluid showed hemolytic activity for rabbit erythrocytes and those from species representing mammals, birds, amphibians and fish, but not sensitized sheep erythrocytes. There was no relationship between phylogeny of the target erythrocytes and degree of hemolysis. The hemolytic activity was optimally assayed at 20 degrees C, at pH 7.5, and in the presence of 10 mM Mg2+. The hemolytic activity was Mg2+-dependent and heat-sensitive, and was abrogated by treatment with rabbit anti-human C3 serum, zymosan, methylamine, hydrazine, and phenylmethylenesulfonyl fluoride. In addition, Western blotting and titration by turbidimetric immunoassay (TIA) revealed that amphioxus humoral fluid contained C3 component, and its concentration is about 1.17 mg/ml, which is comparable to C3 concentration in human or dog sera. These suggest that the hemolytic activities displayed by amphioxus humoral fluid appear to represent the vertebrate complement system probably operating via the alternative pathway.

Animals↗
PubMed2003

[Energy situation of Sonneratia apetala-S. caseloris forest in Futian of Shenzhen].

Based on the measurement of biomass and productivity, the caloric value of different fractions of two species in S. apetala-S. caseloris forest, and their standing crop of energy and net energy production were determined. There were some differences in caloric values among the fractions of S. apetala and S. caseloris, and the caloric value of leaf was the highest, while that of the fine-roots was the lowest. The caloric values of various fractions of S. apetala were much higher than those of S. caseloris. The standing crop of energy in S. apetala-S. caseloris forest was 84,744.72 kJ.m-2. The standing crop of energy accumulated in S. apetala population was 54,693.26 kJ.m-2, accounting for 64.54% of the total, and that of S. caseloris population was 30,051.46 kJ.m-2, accounting for 35.46%. The energy return value of litters was 24,549.54 kJ.m-2.yr-1, that of S. apetala population was 17,233.99 kJ.m-2.yr-1(accounting for 70.16%), and that of S. caseloris population was 7,325.55 kJ.m-2.yr-1(29.84%). The net energy production was 50,391.4 kJ.m-2.yr-1 for S. apetala-S. caseloris forest in 1999, in which the net energy production of S. apetala population was 31,778 kJ.m-2.yr-1.

Biomass↗
PubMed2002

[Accumulation and cycle of heavy metal in Sonneratia apetala and S. caseolaris Mangrove Community at Futian of Shenzhen, China].

The absorption, accumulation, distribution and cycle of Cu, Pb, Zn, Cr and Ni in S. apetala and S. caseolaris Mangrove Community at Futian Mangrove Nature Reserve of Shenzhen were studied. The results showed that the Cu, Pb, Zn, Cr and Ni contents in forest soil were increased from bottom to surface layer, and the storage of the five heavy metals in the surface layer(depth 0-30 cm) was Zn > Pb > Ni > Cr > Cu. The concentration ability was S. caseolaris > S. apetala > K. candel. The existing accumulation of Cu, Pb, Zn, Cr and Ni in the community were respectively 23,019.61 micrograms/m2, 23,429.65 micrograms/m2, 117,870.41 micrograms/m2, 6835.79 micrograms/m2, 12,995.08 micrograms/m2. The annual absorption were 6592.20 micrograms/m2, 2664.77 micrograms/m2, 24,123.56 micrograms/m2, 853.25 micrograms/m2, 1990.86 micrograms/m2, respectively. The annual return were 3179.50 micrograms/m2, 1300.64 micrograms/m2, 8401.31 micrograms/m2, 398.99 micrograms/m2, 646.20 micrograms/m2, respectively. The annual net retention accumulation of Cu, Pb, Zn, Cr and Ni in the community were 3413.07 micrograms/m2, 1364.13 micrograms/m2, 15,722.25 micrograms/m2, 454.25 micrograms/m2, 1344.66 micrograms/m2. The turn over period of Cu, Pb, Zn, Cr and Ni were 8, 19, 15, 18 and 21 years.

China↗
PubMed2002

[A study on the diagnosis and etiology of cerebral venous thrombosis].

OBJECTIVE: To determine the clinical characteristic and common etiologies of cerebral venous thrombosis (CVT) in China. METHODS: Clinical and neuroimaging data of 91 cases of CVT were analyzed retrospectively. RESULTS: 91 CVT patients (49 men, 42 women), aged from 9 to 57 years, were diagnosed with MRI (78 cases, 85.71%), MRA (37 cases, 40.66%) or DSA (32 cases, 35.16%). 27 cases (29.67%) had a clinical pattern of isolated intracranial hypertension, 56 cases (61.54%) of focal deficits and/or seizures, 3 cases of subacute encephalopathy and 5 cases of cavernous sinus thrombosis. Oral contraceptive was the most common cause, being found in 12 cases (13.19%). CONCLUSIONS: Understanding of the clinical characteristics of CVT and using of MRI and MRA examination as early as possible is the key in CVT diagnosis. Oral contraceptive is the most common etiology.

Adolescent↗
PubMed2002

[Evaluation of the factors leading to delay from stroke onset to arrival at hospital].

OBJECTIVE: To investigate the delay in time from stroke onset to arrival at the emergency department (ED) and to evaluate the factors associated with the delay. METHODS: In this prospective study, the factors influencing the delay in time from stroke onset to patients arrival at the ED and ED-CT and access to ED-treatment were explored in 623 patients with acute stroke. The data recorded included patients' knowledge of stroke. RESULTS: The median time from onset to ED was 5.17 hours. Stepwise regression analysis showed that significant risk factors related to arrival delay included living alone at onset of the illness, no facility of ambulance transportation, presence of brain infarct, mild degree of neurological symptoms, long distance from home to hospital, not seeking seeking any help within the first hour, less attention to the stroke onset (P < 0.05 or P < 0.001). The median time from arrival at the ED to arrival at the CT scan was 10 minutes. 75.8% patients finished CT scan within 30 minutes and 78.2% were treated within one hour. CONCLUSIONS: There is significant time delay from stroke onset to patients arrival at the ED. Further health education is necessary to increase the public awareness of seeking medical help after stroke onset and having ambulance transportation to an acute-care hospital.

Aged↗
PubMed2002

[Progress in studies on an exotic vicious weed Mikania micrantha].

Mikania micrantha is a perennial weed of Astraceae native to south and central America. It has invaded Southeast Asia, Pacific region and South China. Because Mikania micrantha grows very fast and is hard to control, it has become one of the world's worst weed. In this paper, the history and status of the study on Mikania micrantha was reviewed. The research on Mikania micrantha was mainly focused on its biology, ecology, harm and control. Although some progress in the research was obtained, there is no dramatic breakthrough in the control of Mikania micrantha so far. There fore, it needs more work to solve the problems resulted from the invading Mikania micrantha.

China↗
PubMedDate not supplied

Characterization and expression of AmphiCL encoding cathepsin l proteinase from amphioxus Branchiostoma belcheri tsingtauense.

An amphioxus complementary DNA, AmphiCL, encoding cathepsin L proteinase was isolated from the gut cDNA library of Branchiostoma belcheri tsingtauense. It is 1480 bp long, and its longest open reading frame codes for a precursor protein, which consists of 327 amino acid residues including a signal peptide (preregion), a propeptide, and a mature proteinase. Northern blot showed that AmphiCL was expressed in the gill, testis, hepatic cecum, and hind-gut with a molecular size of about 1480 bp. AmphiCL was also expressed at low level in the muscle, notochord, and ovary as revealed by the more sensitive reverse transcriptase polymerase chain reaction techniques. Semiquantitative RT-PCR also showed that although AmphiCL expression in the gut was significantly downregulated by feeding Arthrospira platensis powder, a protein-rich food, its expression in the same tissue was upregulated by exposure to lipopolysaccharide, an integral component of the outer membrane of gram-negative bacteria. This suggests that although the involvement of AmphiCL in food digestion remains to be confirmed, AmphiCL may play a role in inflammatory reaction in amphioxus.

Amino Acid Sequence↗