Biomedical subjects

Limei Wang

Publications and source records attributed to Limei Wang.

10 recordsLinked to original sources

PubMed2006

Application of signature-tagged mutagenesis to the study of virulence of Erwinia amylovora.

To identify genes that contribute to the virulence of Erwinia amylovora in plants, 1892 mutants were created and screened in pools of < or =96 mutants using signature-tagged mutagenesis. Nineteen mutants were not recovered from apple shoots following inoculation, which suggested that the insertions in these mutants affected genes important for bacterial survival in planta. DNA flanking the Tn5 insertions in the 19 mutants was sequenced and analysed by blast. One mutant had a Tn5 insertion in amsE, a gene involved in the biosynthesis of exopolysaccaride (EPS). Fourteen mutants had insertions in loci that were implicated in biosynthesis or transport of particular amino acids or nucleotides, a site-specific recombinase active during cell division and several putative proteins of unknown function; the flanking DNA of the remaining four mutants lacked significant homology with any DNA in the database. When inoculated individually to hosts, 10 of the 19 mutants caused significantly less disease and multiplied less, as compared with the wild-type strain.

Erwinia amylovora↗

PubMed2006

Sulfated polymannuroguluronate, a novel anti-acquired immune deficiency syndrome drug candidate, blocks neuroinflammatory signalling by targeting the transactivator of transcription (Tat) protein.

Impaired inflammatory functions may be critical factors in the mechanisms of severe CNS disorders classified as the human immunodeficiency virus-1 (HIV-1)-associated dementia (HAD). Evidence indicates that a viral gene product, the transactivator of transcription protein (Tat), can markedly contribute to these events. We herein report that sulfated polymannuroguluronate (SPMG), a novel anti-acquired immunodeficiency syndrome drug candidate now in a phase II clinical trial, significantly reversed Tat-induced release of pro-inflammatory cytokines [tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta) and IL-6] and dose dependently decreased the accumulation of reactive oxygen species and nitric oxide in THP-1 cells. Furthermore, SPMG potently arrested Tat-triggered protein kinase C (PKC)-dependent PKC-mu activation, and blocked the downstream extracellular-signal regulated kinase 1/2- and c-jun amino-terminal kinase-mediated signalling pathways. These molecular mechanisms could be attributed to the fact that SPMG preferentially bound to the basic domain (amino acids 47-57) of the Tat protein with high affinity (K(D) approximately 8.69 x 10(-10) m), leading to abrogation of Tat-mediated neuroinflammation and neurotoxicity. These data demonstrate that SPMG might serve as a valuable therapeutic intervention for Tat-induced profound pro-inflammatory effects in the brain, and subsequent pathologic events of HAD.

Acquired Immunodeficiency Syndrome↗

PubMed2006

Inhibitory effect of melatonin on diquat-induced lipid peroxidation in vivo as assessed by the measurement of F2-isoprostanes.

Melatonin is a powerful antioxidant and free radical scavenger. A large body of in vivo and in vitro evidence shows that melatonin effectively inhibits membrane lipid peroxidation; this damage was based on the measurement of malondialdehyde and/or 4-hydroxynonenal levels. In the current study, for the first time using a more sensitive and specific biomarker, i.e. F2-isoprostanes, we investigate the effect of melatonin on diquat-induced lipid peroxidation in Fischer 344 rats. When diquat (40 mg/kg body weight) was intraperitoneally injected into rats, the levels of liver F2-isoprostanes were significantly increased at 1, 3, and 6 hr while plasma free F2-isoprostanes concentrations were augmented at 3, 6, and 12 hr after administration of the toxin. In addition, the plasma alanine aminotransferase activity level was measured as a parameter of hepatoxicity; the activity of this enzyme was augmented at 3, 6, and 12 hr after diquat administration when compared with levels of this constituent in untreated control rats. Pretreatment with melatonin (20 mg/kg) 30 min before diquat administration resulted in a significant reduction in both tissue and plasma F2-isoprostanes levels, and plasma alanine aminotransferase activity. These findings, using a sensitive and specific index of lipid peroxidation, show that the hepatoxicity of diquat, at least partially, is a consequence of reactive oxygen species-induced lipid damage. Melatonin's protective effects likely relate to its direct free radical scavenging ability and/or due to other antioxidative processes induced by the indole.

Alanine Transaminase↗

PubMed2004

Three-year efficacy and acceptability of the GyneFix 200 intrauterine system.

OBJECTIVE: This study was conducted to evaluate the efficacy of a "mini" version of the frameless intrauterine system (IUS; GyneFix), which has a copper surface area of approximately 200 mm(2). The small GyneFix version consists of four copper cylinders instead of six and is only 2 cm long. MATERIALS AND METHODS: A total of 392 insertions were performed in an open nonrandomized study in parous (76%) and nulligravid/nulliparous (24%) women in Belgium and China. This interim analysis reports on 13,699 women-months of use. All women were followed-up for a minimum of 12 months, up to 3 years and longer. RESULTS: Four pregnancies occurred with the GyneFix 200 IUS in this study, of which one occurred after unnoticed expulsion of the device, yielding a cumulative failure rate of 0.48 at 3 years. The cumulative removal rate for medical reasons was 1.65 at 3 years and the expulsion rate was 0.39. These low event rates resulted in a high continuation of use (93.92 at 3 years). Neither perforations nor pelvic inflammatory disease cases were encountered in this study. CONCLUSION: The present study suggests that the GyneFix 200 IUS is highly effective and probably as effective as the standard GyneFix IUS. This is attributed to the anchoring of the device to the fundus of the uterus, promoting its contraceptive action. The total surface area of the device, releasing a maximum amount of copper ions, is the fundamental difference between it and conventional IUDs and is probably essential in obtaining the high contraceptive efficacy seen in this study. The small total surface area of the GyneFix 200 IUS also minimizes menstrual bleeding and is an improvement over larger types of conventional IUDs, as indicated by the low removal rate for abnormal bleeding with the small GyneFix.

Adolescent↗

PubMed2004

[Environmental quality assessment of regional agro-ecosystem in Loess Plateau].

Based on the detection and analysis of the contamination status of agro-ecosystem with apple-crops intercropping as the dominant cropping model in Loess Plateau, the individual factor and comprehensive environmental quality were assessed by multilevel fuzzy synthetic evaluation model, analytical hierarchy process(AHP), and improved standard weight deciding method. The results showed that the quality of soil, water and agricultural products was grade I, the social economical environmental quality was grade II, the ecological environmental quality was grade III, and the comprehensive environmental quality was grade I. The regional agro-ecosystem dominated by apple-crops intercropping was not the best model for the ecological benefits, but had the better social economical benefits.

Agriculture↗

PubMed2003

Microwave-assisted headspace solid-phase microextraction for the analysis of bioemissions from Eucalyptus citriodora leaves.

Microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) was developed as a simple and effective method for fast sampling of volatile organic compounds (VOCs) from Eucalyptus citriodora Hook (E. citriodora) leaves. During microwave heating, a simple shielding device made of aluminum foil was used to protect the SPME fiber from microwave irradiation while allowing the sample to be heated. A room temperature water bath was also used to allow microwave heating to be conducted in a more controlled manner. The inner heating caused by microwave irradiation dramatically accelerated the emission of VOCs from the sample, but no marked change in headspace temperature in the sample vial was found. Under optimum conditions, the extraction efficiencies obtained with microwave heating were much higher than those obtained without microwave heating for all fibers used, namely, 7-microm polydimethylsiloxane (PDMS), 100-microm polydimethylsiloxane (PDMS), 65-microm polydimethylsiloxane/divinylbenzene (PDMS/DVB), and 75-microm carboxen/polydimethylsiloxane (CAR/PDMS). The improvement of extraction efficiency using MA-HS-SPME allowed more VOC events to be detected, with more balanced extraction of VOCs of lower and higher molecular masses. Moreover, a good linear relationship was found between sample size and GC-FID response (total peak area of VOCs), indicating the usefulness of MA-HS-SPME for quantitative analysis of individual volatile compounds in E. citriodora leaves.

Chromatography, Gas↗

PubMed2003

On-site monitoring of biogenic emissions from Eucalyptus dunnii leaves using membrane extraction with sorbent interface combined with a portable gas chromatograph system.

Membrane extraction with sorbent interface, combined with a portable gas chromatograph system (MESI-Portable GC) for continuous on-line monitoring of biogenic volatile organic compounds (BVOCs) emissions (from leaves of Eucalytus dunnii in a greenhouse), is presented herein. A sampling chamber was designed to facilitate the extraction and identification of the BVOCs emitted by the Eucalytus dunnii leaves. Preliminary experiments, including; enrichment times, microtrap temperatures, stripping gas flow rates, and desorption temperatures were investigated to optimize experimental parameters. The main components of BVOCs released by the Eucalytus dunnii leaves were identified by comparing the retention times of peaks with those of authentic standard solutions. They were then confirmed with solid phase microextraction coupled with gas chromatography and mass spectrometry (SPME-GC-MS). BVOC emission profiles of [small alpha]-pinene, eucalyptol, and [gamma]-terpinene emitted by intact and damaged Eucalytus dunnii leaves were obtained. The findings suggest that the MESI-Portable GC system is a simple and useful tool for field monitoring changes in plant emissions as a function of time.

Chromatography, Gas↗

PubMed2002

Sampling and monitoring of biogenic emissions by eucalyptus leaves using membrane extraction with sorbent interface (MESI).

Membrane extraction with sorbent interface (MESI) has been applied to monitor plant fragrance volatiles emitted into indoor air. The main components of the MESI system are a membrane module and a trap, which can be connected directly to a GC or GC-MS for simultaneous multicomponent extraction and monitoring. A polydimethylsiloxane (PDMS) membrane and two different traps, PDMS and Tenax, as well as a DC current supply for trap desorption have been applied in this research. After the membrane module is placed in contact with the plant, the MESI/GC-MS provides semicontinuous characterization of volatile compounds emitted. The MESI device has been applied to monitor the biogenic volatile organic compounds released during the first 8 h after a branch was cut from a Eucalyptus dunnii tree. The study demonstrates that the MESI system is a simple and useful tool for monitoring changes in emission processes as a function of time.

Chemistry Techniques, Analytical↗

PubMed2002

Efficacy of a mini version of the frameless GyneFix intrauterine system (IUS) with effective copper surface area of 200 mm2. dirk.wildemeersch@contrel.be.

This study was conducted to evaluate the efficacy of a 'mini' version of the frameless intrauterine system (IUS) (GyneFix) that has a copper surface area of approximately 200 mm(2). The GyneFix-mini consists of four copper cylinders instead of six and is only 2 cm long. A total of 301 insertions were performed in an open nonrandomized pilot study in parous (77%) and nulligravid/nulliparous (23%) women in Belgium and China. This interim analysis reports on 4110 women-months of use. All women were followed-up for a minimum of 12 months. Two pregnancies occurred with the mini GyneFix IUS in this study. However, only one occurred with the device in situ. The cumulative removal rate for medical reasons (bleeding and pain) was 0.39 at 1 year. The expulsion rate was 1.04. These low event rates resulted in a high continuation rate (95.02 at 1 year). Neither perforations nor pelvic inflammatory disease cases were encountered in this study. This study indicates that only a minimal amount of copper, positioned in the upper part of the uterine cavity, is sufficient to provide a high contraceptive effect. This is made possible by anchoring the active contraceptive substance to the fundus of the uterus. The fact that 100% of the copper surface area of the frameless IUS is available for copper release is an additional advantage.

Adolescent↗

PubMedDate not supplied

Correlation of serum VEGF levels with clinical stage, therapy efficacy, tumor metastasis and patient survival in ovarian cancer.

Vascular endothelial growth factor (VEGF) has been shown to play an important role in tumor growth and progression. However, the clinical implications of VEGF expression in ovarian tumors are not fully understood. We therefore investigated the serum level of VEGF in patients with ovarian tumors and explored the potential use of VEGF as a tumor marker for diagnosis, treatment and prognosis of human ovarian cancer. The serum VEGF (sVEGF) levels in 120 patients with ovarian carcinoma, 25 patients with benign ovarian tumor and 90 healthy female blood donors were measured by an enzyme-linked immunosorbent assay in this study. We also determined the levels of sVEGF in patients with epithelial ovarian cancer before and after surgery. Our results showed that: (i) ovarian cancer patients had significantly higher levels of sVEGF compared to those of patients with benign ovarian tumor or those of healthy individuals. As a cut-off at 100 pg/ml, the sensitivity and specificity of sVEGF levels for diagnosing ovarian carcinoma were 77.1% and 87%, respectively. (ii) sVEGF levels were markedly elevated in patients with advanced stage or poorly-differentiated ovarian cancer, as well as in those with more ascites (>500 ml), as compared to patients with early stage and well-differentiated ovarian cancer, or those with less ascites (<500 ml). However, there was no significant difference in sVEGF levels among different pathological subtypes of ovarian carcinoma. (iii) The post-operative sVEGF levels were significantly lower than the pre-operative sVEGF levels. (iv) We measured significantly higher levels of sVEGF in patients with metastasis as compared to patients lacking metastasis. Lastly (v) the average survival-time in patients with higher levels of sVEGF (>100 pg/ml) was 28 months, while the average survival-time in patients with lower levels of sVEGF (<100 pg/ml) was 35 months, indicating that the elevations in sVEGF level are correlated with patient survival and tumor metastasis in ovarian carcinoma. These data suggest that VEGF may be a useful serological biomarker for clinical diagnosis and prognosis of ovarian cancer, for follow-up of ovarian tumor metastasis and for monitoring the efficacy of therapy in patients with ovarian carcinomas.

Adult↗