Biomedical subjects

Weijun Chen

Publications and source records attributed to Weijun Chen.

13 recordsLinked to original sources

PubMed2006

Exploring a possible way to synthesize novel better antioxidants based on vitamin E: a DFT study.

The promoting effect of heterocyclic ring and heteroatom on the antioxidant properties of vitamin E has been investigated systemically by using density functional theory. The calculated results show that the heteroatom plays a more important role in promoting the antioxidant properties than the heterocyclic ring, indicating that replacing O atom by S or Se is impossible to synthesize the novel better antioxidants. Furthermore, the bond dissociation enthalpy (BDE) and ionization potential (IP) of the corresponding molecules are decreased dramatically when the O atom is replaced by NH. In addition, the calculated results also reveal that reducing the atom number of heterocyclic ring is an ideal way to synthesize novel antioxidants with better antioxidant activity than vitamin E.

Amines↗

PubMed2006

The ortho hydroxy-amino group: another choice for synthesizing novel antioxidants.

Four ortho hydroxy-amino derivatives have been designed based on the structures of flavonoids to explore the effect of the ortho hydroxy-amino group on the antioxidant properties of molecules, and their bond dissociation enthalpies (BDE), ionization potentials (IP), the highest occupied molecular orbitals (HOMO), and spin densities have been calculated. The results reveal that the ortho hydroxy-amino group plays an important role in promoting the antioxidant properties of molecules because of its lowering effect on BDE, IP, and spin density. The derivatives with ortho hydroxy-amino group show stronger antioxidant activity than the derivatives with mono hydroxy or ortho dihydroxy group. Thus, the ortho hydroxy-amino group can be used as another potential functional group to synthesize novel antioxidants as guessed.

Amino Acids↗

PubMed2006

Severe acute respiratory syndrome diagnostics using a coronavirus protein microarray.

To monitor severe acute respiratory syndrome (SARS) infection, a coronavirus protein microarray that harbors proteins from SARS coronavirus (SARS-CoV) and five additional coronaviruses was constructed. These microarrays were used to screen approximately 400 Canadian sera from the SARS outbreak, including samples from confirmed SARS-CoV cases, respiratory illness patients, and healthcare professionals. A computer algorithm that uses multiple classifiers to predict samples from SARS patients was developed and used to predict 206 sera from Chinese fever patients. The test assigned patients into two distinct groups: those with antibodies to SARS-CoV and those without. The microarray also identified patients with sera reactive against other coronavirus proteins. Our results correlated well with an indirect immunofluorescence test and demonstrated that viral infection can be monitored for many months after infection. We show that protein microarrays can serve as a rapid, sensitive, and simple tool for large-scale identification of viral-specific antibodies in sera.

Algorithms↗

PubMed2006

An in vitro screening assay to discover novel inhibitors of 4-coumarate:CoA ligase.

4-Coumarate:CoA ligase (4CL, EC 6.2.1.12) exists only in plants and plays an important role in the phenylpropanoid pathway. Identification of inhibitors targeting 4CL provides a novel approach for developing effective plant growth inhibitors (PGIs). The full-length gene of tobacco 4CL (Nt4CL1) was cloned and expressed in Escherichia coli Cast & Chalm. The recombinant 4CL protein was extracted and purified by several purification steps including gel-filtration and anion-exchange chromatography. 4CL activity assay was miniaturized and optimized using a 96-well microplate and a reader. Among 28 existing herbicides, propanil and swep strongly inhibited in vitro 4CL enzyme activity, and they were selected for further studies. The process of this assay can be developed into a high-throughput screening system of PGI targeting 4CL in the phenylpropanoid pathway.

Amino Acid Sequence↗

PubMed2006

A natural sweetener, Momordica grosvenori, attenuates the imbalance of cellular immune functions in alloxan-induced diabetic mice.

Momordica grosvenori (MG), a traditional medicinal herb in China used as a substitute sugar for obese and diabetic patients, exhibited an enhancement of immunity. Heme oxygenase-1 (HO-1) is among the acute phase proteins that play an important role in the inflammatory process and have antiinflammatory activities with their antioxidant properties. The hypothesis that MG could modulate an imbalance of the cellular immune system and prevent the progression of diabetes mellitus, via induction of HO-1 protein expression was investigated. Diabetes was induced in male Balb/c mice by intraperitoneal injection of alloxan (200 mg/kg). The mice were randomly assigned to non-diabetic and diabetic groups, and further subdivided according to their treatments: control (distilled water), low dose MG (150 mg/kg) and high dose MG (300 mg/kg), which were administered by gavage in 24 h cycles over a 30 day period. MG administration effectively regulated the immune imbalance in diabetic mice, principally by upregulating the CD4(+) T lymphocyte subsets, and remodeling the intracellular cytokine profiles (reducing the expression of pro-inflammatory Th1 cytokines towards a beneficial Th2 pattern), ascribed to its induction and upregulation of HO-1. In conclusion, MG exhibited antidiabetic effects and may be used as a new natural drug for the treatment of diabetes.

Alloxan↗

PubMed2005

Dynamic changes of serum SARS-coronavirus IgG, pulmonary function and radiography in patients recovering from SARS after hospital discharge.

OBJECTIVE: The intent of this study was to examine the recovery of individuals who had been hospitalized for severe acute respiratory syndrome (SARS) in the year following their discharge from the hospital. Parameters studied included serum levels of SARS coronavirus (SARS-CoV) IgG antibody, tests of lung function, and imaging data to evaluate changes in lung fibrosis. In addition, we explored the incidence of femoral head necrosis in some of the individuals recovering from SARS. METHODS: The subjects of this study were 383 clinically diagnosed SARS patients in Beijing, China. They were tested regularly for serum levels of SARS-CoV IgG antibody and lung function and were given chest X-rays and/or high resolution computerized tomography (HRCT) examinations at the Chinese PLA General Hospital during the 12 months that followed their release from the hospital. Those individuals who were found to have lung diffusion abnormities (transfer coefficient for carbon monoxide [DLCO] < 80% of predicted value [pred]) received regular lung function tests and HRCT examinations in the follow-up phase in order to document the changes in their lung condition. Some patients who complained of joint pain were given magnetic resonance imaging (MRI) examinations of their femoral heads. FINDINGS: Of all the subjects, 81.2% (311 of 383 patients) tested positive for serum SARS-CoV IgG. Of those testing positive, 27.3% (85 of 311 patients) were suffering from lung diffusion abnormities (DLCO < 80% pred) and 21.5% (67 of 311 patients) exhibited lung fibrotic changes. In the 12 month duration of this study, all of the 40 patients with lung diffusion abnormities who were examined exhibited some improvement of lung function and fibrosis detected by radiography. Of the individuals receiving MRI examinations, 23.1% (18 of 78 patients) showed signs of femoral head necrosis. INTERPRETATION: The lack of sero-positive SARS-CoV in some individuals suggests that there may have been some misdiagnosed cases among the subjects included in this study. Of those testing positive, the serum levels of SARS-CoV IgG antibody decreased significantly during the 12 months after hospital discharge. Additionally, we found that the individuals who had lung fibrosis showed some spontaneous recovery. Finally, some of the subjects developed femoral head necrosis.

Antibodies, Viral↗

PubMed2005

Follow-up study on pulmonary function and lung radiographic changes in rehabilitating severe acute respiratory syndrome patients after discharge.

OBJECTIVES: To follow-up on the changes in lung function and lung radiographic pictures of severe acute respiratory syndrome (SARS) patients discharged from Xiaotangshan Hospital in Beijing (by regularly receiving examination), and to analyze retrospectively the treatment strategy in these patients. METHODS: Surviving SARS patients were seen at least twice within 3 months after discharge and underwent SARS-associated coronavirus (SARS-CoV) IgG antibody testing, pulmonary function testing, and chest radiography and/or high-resolution CT (HRCT) examinations at Chinese PLA General Hospital. The treatments received at Xiaotangshan Hospital were analyzed retrospectively and were correlated to later status. RESULTS: Positive SARS-Co virus IgG antibody results were seen in 208 of 258 patients, with 21.3% (55 of 258 patients) still having a pulmonary diffusion abnormality (D(LCO) < 80% of predicted). By comparing the 155 survivors with positive SARS-CoV IgG antibody results and D(LCO) > or = 80% predicted with the 50 patients with negative SARS-CoV IgG results, we found that 53 patients with positive SARS-CoV IgG results and a lung diffusion abnormality had endured a much longer course of fever and received larger doses of glucocorticoid, as well as higher ratios of oxygen inhalation and noninvasive ventilation treatment. For these patients, 51 of 53 patients with positive SARS-CoV IgG results and a lung diffusion abnormality underwent pulmonary function testing after approximately 1 month. D(LCO) improved in 80.4% of patients (41 of 51 patients). Of the patients with a lung diffusion abnormality, 40 of 51 patients showed lung fibrotic changes in the lung image examination and 22 patients (55%) showed improvement in lung fibrotic changes 1 month later. CONCLUSION: These findings suggest that lung fibrotic changes caused by SARS disease occurred mostly in severely sick patients and may be self-rehabilitated. D(LCO) scores might be more sensitive than HRCT when evaluating lung fibrotic changes.

Adolescent↗

PubMed2005

SARS-associated coronavirus transmitted from human to pig.

Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) was isolated from a pig during a survey for possible routes of viral transmission after a SARS epidemic. Sequence and epidemiology analyses suggested that the pig was infected by a SARS-CoV of human origin.

Animal Feed↗

PubMed2004

Adeno-associated virus Rep78/Rep68 promotes localized melting of the rep binding element in the absence of adenosine triphosphate.

We have applied fluorescence anisotropy and molecular beacon fluorescence methods to study the interactions between the Adeno-associated virus Rep78/Rep68 protein and the 23-bp Rep binding element (RBE). Rep78/Rep68 stably interacted with both the single- and double-stranded conformations of the RBE, but the interaction mechanisms of single- and double-stranded DNA appeared to be fundamentally different. The stoichiometry of Rep78 association with both the separate top and bottom strands of the RBE was 1:1, and the relative dissociation constant (K(D)) values of these associations were calculated to be 2.3x10(-8) and 3.2x10(-8) M, respectively. In contrast, the stoichiometry of Rep78 association with the double-stranded RBE was 2:1, and the dissociation constant was determined to be 4.2x10(-15) M(2). Moreover, Rep78/Rep68 interaction with the 23-bp duplex RBE appeared to cause localized melting of the double-stranded DNA substrate in the absence of adenosine triphosphate (ATP). This melting activity showed slower kinetics than binding and may contribute to the initiation of ATP-dependent Rep78 helicase activity.

Adenosine Triphosphate↗

PubMed2004

Real-time quantitative fluorescent reverse transcriptase-PCR for detection of severe acute respiratory syndrome-associated coronavirus RNA.

AIM: SARS-associated coronavirus (SARS-CoV) has been confirmed as the pathogen for severe acute respiratory syndrome (SARS). The aim of our study was to construct a sensitive and specific real-time quantitative fluorescent (QF) reverse transcriptase (RT)-PCR method for the detection of SARS-CoV RNA. METHODS: Stored blood specimens from 44 patients with confirmed SARS were used along with blood samples from two sets of controls, 30 healthy volunteers who had no contact with SARS patients, and 30 healthy doctors and nurses who had contact with SARS patients but were without symptoms of SARS. Two pairs of primers were synthesized by the Shanghai Sangon Company according to SARS-CoV BJ01 strain sequence (AY278488), and then a pair of primers were designed and compared with a pair of primers published by WHO. RESULTS: Using serial dilutions of SARS-CoV, the 44 blood samples from SARS patients specimens were tested. Using a 0.01% dilution of SARS-CoV, all 44 clinical samples tested positive in our assay. In comparison, using a 0.1% dilution of SARS-CoV, 26 of the 44 samples tested positive using the WHO primers. In the QF-RT-PCR assay, there was a linear amplification from 100 copies to 10(8) copies of the control RNA per RT-PCR and at least 10 copies, and sometimes even 1 copy, of target RNA tested positive in our assay. CONCLUSION: The primer we developed is sufficiently sensitive and specific to diagnose symptomatic SARS-CoV infections and for monitoring virus load.

Case-Control Studies↗

PubMed2004

Antibody response and viraemia during the course of severe acute respiratory syndrome (SARS)-associated coronavirus infection.

To understand the time-course of viraemia and antibody responses to severe acute respiratory syndrome-associated coronavirus (SARS-CoV), RT-PCR and ELISA were used to assay 376 blood samples from 135 SARS patients at various stages of the illness, including samples from patients who were in their early convalescent phase. The results showed that IgM antibodies decreased and became undetectable 11 weeks into the recovery phase. IgG antibodies, however, remained detectable for a period beyond 11 weeks and were found in 100 % of patients in the early convalescent phase. SARS-CoV viraemia mainly appeared 1 week after the onset of illness and then decreased over a period of 1 month, becoming undetectable in the blood samples of the convalescent patients. At the peak of viraemia, viral RNA was detectable in 75 % of blood samples from patients who were clinically diagnosed with SARS 1 or 2 weeks before the test.

Adolescent↗

PubMed2003

A genome sequence of novel SARS-CoV isolates: the genotype, GD-Ins29, leads to a hypothesis of viral transmission in South China.

We report a complete genomic sequence of rare isolates (minor genotype) of the SARS-CoV from SARS patients in Guangdong, China, where the first few cases emerged. The most striking discovery from the isolate is an extra 29-nucleotide sequence located at the nucleotide positions between 27,863 and 27,864 (referred to the complete sequence of BJ01) within an overlapped region composed of BGI-PUP5 (BGI-postulated uncharacterized protein 5) and BGI-PUP6 upstream of the N (nucleocapsid) protein. The discovery of this minor genotype, GD-Ins29, suggests a significant genetic event and differentiates it from the previously reported genotype, the dominant form among all sequenced SARS-CoV isolates. A 17-nt segment of this extra sequence is identical to a segment of the same size in two human mRNA sequences that may interfere with viral replication and transcription in the cytosol of the infected cells. It provides a new avenue for the exploration of the virus-host interaction in viral evolution, host pathogenesis, and vaccine development.

Base Sequence↗

PubMed2002

[Influence of flow shear stress on apoptosis of arterial endothelium in vivo].

To explore the changes of wall shear stress(WSS) effect on arterial endothelial cell(EC) apoptosis after reducing arterial blood flow. The reducing flow model was established in 60 rabbits. Endothelial stretched preparations were made at 8 different time intervals from 0 to 30 days. The apoptosis rate of arterial endothelial cells (AEC) was measured with TdT-mediated dUTP-biotin nick end labeling(TUNEL) method. The results showed that the apoptosis rate of AEC was significantly higher from 1 day to 7 days after decreasing WSS than that of control, which peaked on day 3. While with progressively increasing in WSS, the apoptosis rate restored to the level of control from 14 days to 30 days. These suggest that the apoptosis state of AEC might be markedly influenced by the changes of WSS. The persist decreasing of WSS may be the important factor which induces the cell apoptosis.

Animals↗