Biomedical subjects

Gang Chen

Publications and source records attributed to Gang Chen.

At least 199 records · Page 11Linked to original sources

PubMed2004

Inhibitory effects of anti-sense PTTG on malignant phenotype of human ovarian carcinoma cell line SK-OV-3.

To construct eukaryotic expression vector expressing full length anti-sense pituitary tumor transforming gene (PTTG) mRNA and observe its blocking effect on the potential invasion of human ovarian carcinoma cell line SK-OV-3. PCR primers containing designed enzyme cut sites were used for cloning full-length PTTG gene fragment, and the resulting PCR product was inserted into the eukaryotic vector pcDNA3.1 in the antisense direction. The recombinant vector was then transfected into SK-OV-3 by Lipofectamine. The positive cell clone was screened by G418, PTTG and bFGF at protein level expression were detected by Western blot. The biological behavior change of transfection positive cells was observed by colony formation in soft agar assay. Our results showed that SK-OV-3 clones stably expressing full-length recombinant pcDNA3.1-PTTGas were obtained. The expressions of PTTG and bFGF protein in transfected cells were decreased by 61.5% and 52.3%, respectively as compared with non-transfected ones. The number of colony formation was reduced significantly in transfected cells as compared with empty vector transfected and non-transfected cells. It is concluded that the recombinant vector pcDNA3.1-PTTGas is a novel tool and provides an alternative anti-sense gene therapy targeted at PTTG in human carcinoma.

Cell Line, Tumor↗

PubMed2004

On prediction of the cesarean delivery risk in a large private practice.

OBJECTIVE: This study was undertaken to develop an easily usable integrated formula for predicting the probability of cephalopelvic disproportion/failure to progress (CPD) and cesarean delivery (CS) as a function of demographic factors in a middle-class private practice, and to evaluate risk factors for CS in a low-risk primiparous population. METHODS: We studied 3355 primiparous women who delivered singleton births between February 1993 and July 2001 in a large private practice. We calculated body mass index (BMI) and weight gain during pregnancy by using clinical data from a comprehensive clinical database. Multivariable logistic regression analysis was used to estimate the relationship between the probability of CS and CS carried out for CPD and 6 demographic factors: maternal age, maternal height, initial pregnancy BMI, pregnancy weight gain, gestational age, and birth weight. Three methods were used to assess the accuracy of the model: the Hosmer-Lemeshow goodness-of-fit statistic, association of predicted probabilities, and direct comparison of the formula to the actual data. Odds ratios with a 95% CI are also calculated for each of these factors. RESULTS: The overall rate of primiparous CS for the practice is 21.7%, with 11.7% carried out for CPD. Formulas were developed to predict the probability of CS and the probability of CS caused by CPD. Our analysis shows that both the risk of CS and the risk of CS caused by CPD are significantly associated with all 6 demographic factors. We also develop an easily usable Web page-based calculator to instantly estimate any woman's probability of a CS or CPD at the beginning or at the end of her pregnancy. CONCLUSION: The probability of CS and CS performed for CPD is higher for shorter, older, more obese women with large pregnancy weight gains, larger fetal birth weights, and longer gestation ages. Accurate formulas that predict the probabilities of CS and CS performed for CPD in this large private practice have been developed.

Adult↗

PubMed2004

Design and development of food safety knowledge and attitude scales for consumer food safety education.

OBJECTIVE: The objective of this study was to design and develop food safety knowledge and attitude scales based on food-handling guidelines developed by a national panel of food safety experts. DESIGN: Knowledge (n=43) and attitude (n=49) questions were developed and pilot-tested with a variety of consumer groups. Final questions were selected based on item analysis and on validity and reliability statistical tests. SUBJECTS/SETTING: Knowledge questions were tested in Washington State with participants in low-income nutrition education programs (pretest/posttest n=58, test/retest n=19) and college students (pretest/posttest n=34). Attitude questions were tested in Ohio with nutrition education program participants (n=30) and college students (non-nutrition majors n=138, nutrition majors n=57). STATISTICAL ANALYSES PERFORMED: Item analysis, paired sample t tests, Pearson's correlation coefficients, and Cronbach's alpha were used. RESULTS: Reliability and validity tests of individual items and the question sets were used to reduce the scales to 18 knowledge questions and 10 attitude questions. The knowledge and attitude scales covered topics ranked as important by a national panel of experts and met most validity and reliability standards. The 18-item knowledge questionnaire had instructional sensitivity (mean score increase of more than three points after instruction), internal reliability (Cronbach's alpha >.75), and produced similar results in test-retest without intervention (coefficient of stability=.81). Knowledge of correct procedures for hand washing and avoiding cross-contamination was widespread before instruction. Knowledge was limited regarding avoiding food preparation while ill, cooking hamburgers, high-risk foods, and whether cooked rice and potatoes could be stored at room temperature. The 10-item attitude scale had an appropriate range of responses (item difficulty) and produced similar results in test-retest ( P </=.01). Internal consistency ranged from alpha=.63 to .89. Students anticipating a career where food safety is valued had higher attitude scale scores than participants of extension education programs. CONCLUSIONS: Uses for the knowledge questionnaire include assessment of subject matter knowledge before instruction and knowledge gain after instruction. The attitude scale assesses an outcome variable that may predict food safety behavior.

Consumer Product Safety↗

PubMed2004

Cesium migration in saturated silica sand and Hanford sediments as impacted by ionic strength.

Large amounts of 137Cs have been accidentally released to the subsurface from the Hanford nuclear site in the state of Washington, USA. The cesium-containing liquids varied in ionic strengths, and often had high electrolyte contents, mainly in the form of NaNO3 and NaOH, reaching concentrations up to several moles per liter. In this study, we investigated the effect of ionic strengths on Cs migration through two types of porous media: silica sand and Hanford sediments. Cesium sorption and transport was studied in 1, 10, 100, and 1000 mM NaCl electrolyte solutions at pH 10. Sorption isotherms were constructed from batch equilibrium experiments and the batch-derived sorption parameters were compared with column breakthrough curves. Column transport experiments were analyzed with a two-site equilibrium-nonequilibrium model. Cesium sorption to the silica sand in batch experiments showed a linear sorption isotherm for all ionic strengths, which matched well with the results from the column experiments at 100 and 1000 mM ionic strength; however, the column experiments at 1 and 10 mM ionic strength indicated a nonlinear sorption behavior of Cs to the silica sand. Transport through silica sand occurred under one-site sorption and equilibrium conditions. Cesium sorption to Hanford sediments in both batch and column experiments was best described with a nonlinear Freundlich isotherm. The column experiments indicated that Cs transport in Hanford sediments occurred under two-site equilibrium and nonequilibrium sorption. The effect of ionic strength on Cs transport was much more pronounced in Hanford sediments than in silica sands. Effective retardation factors of Cs during transport through Hanford sediments were reduced by a factor of 10 when the ionic strength increased from 100 to 1000 mM; for silica sand, the effective retardation was reduced by a factor of 10 when ionic strength increased from 1 to 1000 mM. A two order of magnitude change in ionic strength was needed in the silica sand to observe the same change in Cs retardation as in Hanford sediments.

Adsorption↗

PubMed2004

Bacterial desorption in water-saturated porous media in the presence of rhamnolipid biosurfactant.

We investigated the effects of transients in elution chemistry on bacterial desorption in water-saturated porous media. Two typical Gram-positive bacterial strains of Lactobacillus casei and Streptococcus mitis were used as the model bacteria in this research. These two strains were first deposited in the porous medium, after which the medium with deposited bacteria was flushed with rhamnolipid biosurfactant solutions with a step increase in concentrations, and pulse-type bacterial releases were obtained. Bacterial desorption was quantified from bacterial breakthrough curves. It was found that bacterial retention in silica sand corresponded to bacterial interaction free energies with silica sand evaluated at the equilibrium distance, which were calculated based on independently determined bacterial, sediment and solution surface thermodynamic properties. With the increase in rhamnolipid biosurfactant concentrations, interactions between bacteria and silica sand decreased, and consequently less bacteria were retained. The decrease in interactions between bacteria and silica sand with increasing rhamnolipid biosurfactant concentrations was attributed to a decrease in the solution electron acceptor parameter of the Lewis acid/base component of surface tension, gamma3+. The increase in rhamnolipid biosurfactant concentrations favored the decrease in solution gamma3+, and consequently decreased the interactions between bacteria and silica sand.

Bacterial Physiological Phenomena↗

PubMed2004

Awareness and acceptance of current food safety recommendations during pregnancy.

OBJECTIVES: To better understand pregnant women's food safety attitudes and beliefs that affect food selection, preparation and handling behaviors, sources of food safety information, motivators and barriers to adopting current recommendations, and preferences for receiving food safety materials. METHODS: Eleven focus groups were conducted with 69 women (57 pregnant and 12 less than 6 months postpartum). The Health Belief Model guided development of the moderator's guide. In the presence of each focus group, participants completed a food safety attitude/behavior questionnaire. Sessions were audiotaped, transcribed, and analyzed for common themes across and within groups. RESULTS: Most participants indicated moderate concern about food safety and had made some food handling or consumption changes since becoming pregnant; however, many were not following 7 of the 12 specific recommendations discussed. Further, there was resistance to change habits, especially for less well-known recommendations. The women assumed their food is safe, and wanted strong evidence regarding why they should change current practices. Common barriers included lack of prior awareness of most recommendations, no prior illness from implicated foods and the convenience, perceived health benefits of, and personal preference for many risky foods discussed. Participants wanted food safety information that was quick and easy to read, sufficiently thorough, and specifically targeted to pregnant women. CONCLUSIONS: The women studied had not internalized the connection between risky food consumption during pregnancy and risk to the unborn child, but expressed interest in valid information that might cause them to change their behaviors. The information gained will be useful in developing food safety educational materials for pregnant women.

Attitude↗

PubMed2004

Evaluation of health-related quality-of-life measures in oncology drug product applications: issues and concerns.

Health-related quality-of-life outcomes as reported by patients are valuable data and ideally should be critical to evaluating clinical benefit. The unblinded or open-label designs commonly adapted in oncology trials have the potential to introduce selection bias, reporting bias, and analyses bias. In this paper, issues surrounding use of patient reported outcomes to evaluate oncology drug products, including definition of hypothesis, study design, analysis, and interpretation of patient reported outcome data, are reported.

Antineoplastic Agents↗

PubMed2004

Hypotheses and type I error in active-control noninferiority trials.

A fundamental assumption in the design and analysis of an active-control noninferiority trial is that the active control is truly effective. If this assumption does not hold, i.e., the active control is not effective, a harmful drug may be approved based on the result of a noninferiority trial. The assessment of the assumption is usually based on statistically significant results of historical randomized clinical trials on the active control, in which the conclusion may be falsely positive. This false positive rate, however, is not taken into consideration in current noninferiority trial test procedures. In this paper, various possible hypotheses for noninferiority trials are presented. The noninferiority hypotheses correctly associated with the objective of noninferiority trials are suggested. However, since there are no data collected for placebo in a noninferiority trial, this hypothesis cannot be directly tested by using data from noninferiority studies alone. The claim of noninferiority is based on the significant test for the control effect in historical trials and the significant test for noninferiority in a current noninferiority trial with a given fraction retention or margin. The false positive rate associated with such noninferiority test procedure is defined in this paper. The simulation result demonstrates the magnitude of the false positive rate inflation associated with the noninferiority test procedure.

Clinical Trials as Topic↗

PubMed2004

TMVA, a novel GPIb-binding protein, significantly prevents platelet microthrombi formation and prolongs discordant cardiac xenograft survival.

In xenotransplantation, donor endothelium is the first target of immunological attack. Activation of the endothelial cell by preformed natural antibodies leads to platelet binding via the interaction of the glycoprotein (GP) Ib and von Willebrand factor (vWF). TMVA is a novel GPIb-binding protein purified from the venom of Trimeresurus mucrosquamatus. In this study, the inhibitory effect of TMVA on platelet aggregation in rats and the effect on discordant guinea pig-to-rat cardiac xenograft survival were investigated. Three doses (8, 20 or 40 microg/kg) of TMVA were infused intravenously to 30 rats respectively. Platelet aggregation rate was assayed 0.5, 12, and 24 h after TMVA administration. Wister rats underwent guinea pig cardiac cervical heterotopic transplantation using single dosing of TMVA (20 microg/kg, i.v., 0.5 h before reperfusion). Additionally, levels of TXB(2) and 6-keto-PGF(1alpha) within rejected graft tissues were determined by radioimmunoassay. Treatment with TMVA at a dose of 20 or 40 microg/kg resulted in complete inhibition of platelet aggregation 0.5 h after TMVA administration. Rats receiving guinea pig cardiac xenografts after TMVA therapy had significantly prolonged xenograft survival. Histologic and immunopathologic analysis of cardiac xenografts in TMVA treatment group showed no intragraft platelet microthrombi formation and fibrin deposition. Additionally, the ratio of 6-keto-PGF(1alpha) to TXB(2) in TMVA treatment group was significantly higher than those in control group. We conclude that the use of this novel GPIb-binding protein was very effective in preventing platelet microthrombi formation and fibrin deposition in a guinea pig-to-rat model and resulted in prolongation of xenograft survival. The increased ratio of PGI(2)/TXA(2) in TMVA treatment group may protect xenografts from the endothelial cell activation and contribute to the prolongation of xenograft survival.

Adenosine Diphosphate↗

PubMed2004

Improved suppression of circulating complement does not block acute vascular rejection of pig-to-rhesus monkey cardiac transplants.

At present, acute vascular rejection (AVR) remains a primary obstacle inhibiting long-term graft survival in the pig-to-non-human primate transplant model. The present study was undertaken to determine whether repetitive injection of low dose Yunnan-cobra venom factor (Y-CVF), a potent complement inhibitor derived from the venom of Naja kaouthia can completely abrogate hemolytic complement activity and subsequently improve the results in a pig-to-rhesus monkey heterotopic heart transplant model. Nine adult rhesus monkeys received a heterotopic heart transplant from wild-type pigs and the recipients were allocated into two groups: group 1 (n = 4) received repetitive injection of low dose Y-CVF until the end of the study and group 2 (n = 5) did not receive Y-CVF. All recipients were treated with cyclosporine A (CsA), cyclophosphamide (CyP) and steroids. Repetitive Y-CVF treatment led to very dramatic fall in CH50 and serum C3 levels (CH50 < 3 units/C3 remained undetectable throughout the experiment) and successfully prevented hyperacute rejection (HAR), while three of five animals in group 2 underwent HAR. However, the continuous suppression of circulating complement did not prevent AVR and the grafts in group 1 survived from 8 to 13 days. Despite undetectable C3 in circulating blood, C3 deposition was present in these grafts. The venular thrombosis was the predominant histopathologic feature of AVR. We conclude that repetitive injection of low dose Y-CVF can be used to continuously suppress circulating complement in a very potent manner and successfully prevent HAR. However, this therapy did not inhibit complement deposition in the graft and failed to prevent AVR. These data suggest that using alternative pig donors [i.e. human decay accelerating factor (hDAF)-transgenic] in combination with the systemic use of complement inhibitors may be necessary to further control complement activation and improve survival in pig-to-non-human primate xenotransplant model.

Animals↗

PubMed2004

Epstein-Barr virus latent membrane protein LMP-2A is sufficient for transactivation of the human endogenous retrovirus HERV-K18 superantigen.

Superantigens are microbial proteins that strongly stimulate T cells. We described previously that the Epstein-Barr virus (EBV) transactivates a superantigen encoded by the human endogenous retrovirus, HERV-K18. We now report that the transactivation is dependent upon the EBV latent cycle proteins. Moreover, LMP-2A is sufficient for induction of HERV-K18 superantigen activity.

Animals↗

PubMed2004

The cauliflower mosaic virus 35S promoter extends into the transcribed region.

A 60-nucleotide region (S1) downstream of the transcription start site of the cauliflower mosaic virus 35S RNA can enhance gene expression. By using transient expression assays with plant protoplasts, this activity was shown to be at least partially due to the effect of transcriptional enhancers within this region. We identify sequence motifs with enhancer function, which are normally masked by the powerful upstream enhancers of the 35S promoter. A repeated CT-rich motif is involved both in enhancer function and in interaction with plant nuclear proteins. The S1 region can also enhance expression from heterologous promoters.

Base Sequence↗

PubMed2004

Rhamnolipid biosurfactant behavior in solutions.

The solution behavior of rhamnolipid biosurfactant that is determined by its surface thermodynamic properties often plays a central role in determining and controlling its performance in practical applications. In this study, rhamnolipid molecules exhibited a predominant hydrophilic surface, contributed by hydrophilic monomer head groups. Interaction free energies between rhamnolipid molecules at water surfaces, as estimated based on the distance-dependent decaying interaction contact areas, decayed exponentially with regards to separation distance. These interaction free energies were governed by hydrophilic monomer head groups of rhamnolipid molecules. The experimental observations in this study were consistent with the previous postulations.

Glycolipids↗

PubMed2004

Effects of low-fat and/or high-fruit-and-vegetable diets on plasma levels of 8-isoprostane-F2alpha in the Nutrition and Breast Health study.

Dietary patterns that involve both a decrease in fat and an increase in fruit and vegetable (FV) intake may decrease cancer risks. In this study, a total of 122 premenopausal women with a family history of breast cancer were randomized into one of four diets for 12 mo: nonintervention, low-fat (15% of energy from fat), high-FV(9 servings/d), and combination low-fat/high-FV Fasting blood samples were obtained at baseline and after 3, 6, and 12 mo. Levels of 8-isoprostane-F2a in plasma were deter-mined by immunoassay kits. Statistical analyses indicated that levels of 8-isoprostane-F2a decreased significantly with time in the low-fat arm, which is the only intervention that resulted in weight loss; there were no significant changes in the other three diet arms. It is unlikely that this is due to changes in levels of blood lipids because there was little change overtime in plasma total cholesterol, high-density lipoprotein,low-density lipoprotein (LDL), or triglyceride levels in any diet arm, although mean LDL did decrease slightly in women who reduced fat intake after adjustment for change in body mass index (BMI). Levels of baseline 8-isoprostane-F2a were significantly higher in obese women than in overweight or normal weight women, and change in BMI was significantly correlated with change in 8-isoprostane-F2a levels. These results indicate that low-fat diets or high-FV diets are unlikely to affect plasma levels of 8-isoprostane-F2a in healthy,premenopausal women who do not lose weight during dietary change.

Adult↗

PubMed2004

A flower image retrieval method based on ROI feature.

Flower image retrieval is a very important step for computer-aided plant species recognition. In this paper, we propose an efficient segmentation method based on color clustering and domain knowledge to extract flower regions from flower images. For flower retrieval, we use the color histogram of a flower region to characterize the color features of flower and two shape-based features sets, Centroid-Contour Distance (CCD) and Angle Code Histogram (ACH), to characterize the shape features of a flower contour. Experimental results showed that our flower region extraction method based on color clustering and domain knowledge can produce accurate flower regions. Flower retrieval results on a database of 885 flower images collected from 14 plant species showed that our Region-of-Interest (ROI) based retrieval approach using both color and shape features can perform better than a method based on the global color histogram proposed by Swain and Ballard (1991) and a method based on domain knowledge-driven segmentation and color names proposed by Das et al.(1999).

Algorithms↗

PubMed2004

Decryption of pure-position permutation algorithms.

Pure position permutation image encryption algorithms, commonly used as image encryption investigated in this work are unfortunately frail under known-text attack. In view of the weakness of pure position permutation algorithm, we put forward an effective decryption algorithm for all pure-position permutation algorithms. First, a summary of the pure position permutation image encryption algorithms is given by introducing the concept of ergodic matrices. Then, by using probability theory and algebraic principles, the decryption probability of pure-position permutation algorithms is verified theoretically; and then, by defining the operation system of fuzzy ergodic matrices, we improve a specific decryption algorithm. Finally, some simulation results are shown.

Algorithms↗

PubMed2004

Observation versus self-report: validation of a consumer food behavior questionnaire.

A reliable and validated set of food safety behavior questions that could be used with confidence when evaluating food safety education programs was identified in this study. A list of 29 food-handling and consumption behaviors rank-ordered within five pathogen control factors by nationally recognized food safety experts was the basis for the development of the behavior questions. Questions were evaluated for reliability and several forms of validity. During a kitchen activity session, 70 graduates of a nutrition education program completed four food preparation tasks while being observed and videotaped. The individuals also participated in an in-depth interview to validate behaviors that could not be observed during the food preparation activity, e.g., refraining from preparing food for others when experiencing diarrhea. Criterion validity was established by comparing questionnaire responses to observed behavior and interview responses. Twenty-eight questions met the validity criterion (> or = 70% agreement between observed and interviewed responses and self-reported responses), with three or more questions from each of five pathogen control factor areas. Observation assessments revealed that hand washing was more likely to be performed prior to beginning food preparation than between working with raw meats and fresh produce. Errors in methods of washing hands, utensils, and preparation surfaces between food preparation tasks were common. Most participants did not use thermometers to evaluate doneness but still cooked to safe internal temperatures. The results provide a tool that educators can use to evaluate food safety programs and will help guide the development of more effective food safety education programs targeting needed improvements in behavioral skills.

Adult↗

PubMed2004

[Recombinant adenovirus vector-mediated herpes simplex virus thymidine kinase gene transfer followed by ganiciclovir administration effectively inhibits growth of human small-cell lung cancer in a murine xenotransplant model].

OBJECTIVE: Adenovirus vector-mediated herpes simplex virus thymidine kinase gene (ADV-TK) transfer in combination with ganiciclovir (GCV) is one of the major gene therapy strategies to eradicate tumor cells. This study was aimed at determining the in vivo anti-tumor efficacy of ADV-TK in combination with ganiciclovir (GCV). METHODS: A murine xenotransplant model of human small-cell lung cancer was established. ADV-TK was administrated by intra-tumoral injection followed by intraperitoneal administration of GCV. The anti-tumor efficacy was evaluated using index of tumor volume, relative tumor volume, tumor weight, relative tumor proliferative rate, and tumor growth curve. RESULTS: In the presence of GCV, ADV-TK effectively inhibited growth of human small-cell lung cancer in a dose-dependent fashion. An inhibition plateau was not observed within the current dosage range. ADV-TK at a dose of 6.0 x 10(9) viral particles/kg in the presence of GCV lead to 64.6% and 81.7% inhibition of tumor growth respectively in two independent experiments. ADV-TK or GCV alone caused slight inhibition of tumor growth, which was not statistically significant as compared to the negative control group (P > 0.05). CONCLUSION: ADV-TK followed by GCV is highly efficacious to inhibit the growth of human small-cell lung cancer in a murine xenotransplant model. The results presented here are encouraging to warrant a further clinical evaluation of the potential therapeutic benefits of this strategy.

Adenoviridae↗