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D Wei

Publications and source records attributed to D Wei.

At least 73 records · Page 4Linked to original sources
PubMed1997

[Identification of the anti-rIL-1ra McAb].

Using dot-immuno-blot and Western blotting techniques, we have identified the specificity of anti-rIL-1ra McAbs. The results showed that the anti-rIL-1ra McAb 2E4 specifically reacted with rIL-1ra, from which the recognizing signal of dot-immunoblot was significantly positive (+2) and a single rIL-1ra protein band (20 kd) was clearly recognized by Western blotting. The control results of PcAb recognization have further proved the high sensitivity of Western blotting and high specificity of rIL-1ra McAb 2E4. The successful identification of rIL-1ra McAb 2E4 will be helpful to further understand the biologic effects, especially the pro-inflammatory properties, to study the change of rIL-1ra level during inflammation, and to instruct the clinical use of rIL-1ra.

Animals↗
PubMed1997

[Improved MTT colorimetric assay for serum TNF activity].

The activity of serum tumor necrosis factor(TNF) is known to be related with the mechanism and prognosis of many diseases. The aim of this experiment was to look for an economic and reliable method for assaying the activity of serum TNF. We used the neutrophil solventor 20% SDS-50% DMF instead of the acidity solventor 0.04 mol/l acidified isopropy alcohol and established an improved 3-(4,5-dimethyl thiazoly)2,5-diphenyl-tetrazolium bromide (MTT) colorimetric assay for measuring the amount and function of living cell. We used this improved MTT colorimetric assay for measuring TNF activity of peripheral blood serum of healthy persons. It avoided the deposition of the protein in serum and medium and showed more repeatability, as compared with the conventional MTT colorimetric assay. The results showed: when the activity of target cell(TC)-L929 is > or = 95%, the density of TC is > or = 1 x 10(2)/well and the number of living cells in each well is positively correlated with the OD volume (OD570nm-OD630nm of purple formazan metabolite of MTT solution(r = 0.87, P < 0.01); when the density of TC is 5 x 10(4)/well, the level standard of TNF in each well is negatively correlated with the OD volume (OD570nm-OD630nm)r = 0.79, P < 0.01). Using this method, we measured the TNF activity of 20 healthy persons' peripheral blood serum. The mean +/- s of TNF activity is 20.95 +/- 3.2 IU/ml. This method is dependable, easy-to-do and economic, it has good repeatability within 3-12 hours.

Animals↗
PubMed1997

[Study on T lymphocyte recognition of tumor antigens on autologous CML cells].

OBJECTIVE: To investigate the existence of cytotoxic precursor cells in previously untreated or remissive chronic myelogenous leukemia(CML) patients,and identify their phenotypical and functional characteristics. METHODS: Bone marrow or peripheral blood mononuclear cells from CML patients were stimulated with autologous CML cells by using mixed lymphocyte tumor cell coculture. RESULTS: A kind of cytotoxic T lymphocytes could be generated from bone marrow or peripheral blood of CML patients. These T cells showed differential cytotoxicities against autologous and allogeneic CML cells and no activity to autologous and allogeneic normal bone marrow cells. They also exhibited no inhibitive effect on CFU-GM yields. LAK cells had no effect on autologous CML cells, but showed intensive cytotoxic activity to allogeneic CML cells. The T lymphocytes obtained were CD3+ CD56+ non-MHC restricted or CD3+ CD56- MHC restricted. HLA-DR and CD25 were expressed in a significantly larger proportion of T lymphocytes stimulated with autologous CML cells than those not stimulated. The T lymphocytes showed low proliferative response to autologous CML cell stimulation and no or least response to allogeneic CML cells, they showed also no response to EB virus-transformed autologous B cells(obtained in remission) pulsed with peptides corresponding to the BCR-ABL joining region. CONCLUSION: There is probably a common tumor antigen among CMLs, this leukemia-specific antigen can be recognized by T cells,and it shows no indication to be a p210 fusion sequence.

Amino Acid Sequence↗
PubMed1997

Towards a density functional treatment of chemical reactions in complex media.

We discuss two techniques involving density functional theory (i.e., ab initio molecular dynamics simulations and frozen density functional theory) which show promise for applications directed towards understanding reactions in complex media. Preliminary results for the simulation of the conformational dynamics of an isolated analogue of alanine dipeptide and for the interaction between F- and H2O are included. These results represent the first steps towards a combined theoretical approach of reactions in complex media.

Computer Simulation↗
PubMed1996

Effect of nuclear environment on the distribution of benzo[a]pyrene diol epoxide-induced adducts in the HPRT gene of human fibroblasts.

(+/-)-7beta,8alpha- Dihydroxy-9alpha,10alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]py rene (BPDE) is the principal reactive metabolite of the carcinogenic environmental pollutant benzo[a]pyrene. Intensive studies of the distribution of BPDE-induced adduct formation in chromatin DNA compared to that in protein-free DNA have been conducted. However, until recently, investigation of BPDE-induced adduct formation at the nucleotide level in intact mammalian cells has not been feasible. We used ligation-mediated polymerase chain reaction (LMPCR) in conjunction with Escherichia coli UvrABC excinuclease to investigate the distribution of BPDE-induced adducts in the non-transcribed strand of exon 3 of the HPRT gene in normal human fibroblasts at the level of individual nucleotides to single nucleotide resolution using synchronized cell populations. We found that the relative distribution of BPDE adducts in the region of interest was essentially the same in cells treated in early G1 phase, S-phase, late G2/M phase, and in cells blocked at metaphase. Furthermore, for almost all nucleotide positions, the relative distribution of BPDE adducts in the intact cells was very similar to that found when purified DNA was treated with BPDE in vitro. The only exception was that in vivo, adduct formation at a region of six consecutive guanines, i.e. nucleotides 207-212, was strongly enhanced compared with that seen with DNA treated in vitro. No obvious nucleosomal structures or other protein-DNA interaction were detected within the region of interest by in vivo footprinting with micrococcal nuclease and other reagents revealed. In vitro studies mapping BPDE-induced adduct formation using Sequenase and UvrABC excinuclease suggested that this region of six consecutive guanines adopts a special DNA conformation. Therefore, we conclude that rather than reflecting protein-DNA interaction, the enhanced BPDE-induced adduct formation at nucleotides 207-212 in vivo reflects the impact of the physiological environment in the cell nucleus on the local DNA conformation, and that this effect remains constant throughout the cell cycle.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1996

Automated detection of breast masses on mammograms using adaptive contrast enhancement and texture classification.

This paper presents segmentation and classification results of an automated algorithm for the detection of breast masses on digitized mammograms. Potential mass regions were first identified using density-weighted contrast enhancement (DWCE) segmentation applied to single-view mammograms. Once the potential mass regions had been identified, multiresolution texture features extracted from wavelet coefficients were calculated, and linear discriminant analysis (LDA) was used to classify the regions as breast masses or normal tissue. In this article the overall detection results for two independent sets of 84 mammograms used alternately for training and test were evaluated by free-response receiver operating characteristics (FROC) analysis. The test results indicate that this new algorithm produced approximately 4.4 false positive per image at a true positive detection rate of 90% and 2.3 false positives per image at a true positive rate of 80%.

Automation↗
PubMed1996

Image feature selection by a genetic algorithm: application to classification of mass and normal breast tissue.

We investigated a new approach to feature selection, and demonstrated its application in the task of differentiating regions of interest (ROIs) on mammograms as either mass or normal tissue. The classifier included a genetic algorithm (GA) for image feature selection, and a linear discriminant classifier or a backpropagation neural network (BPN) for formulation of the classifier outputs. The GA-based feature selection was guided by higher probabilities of survival for fitter combinations of features, where the fitness measure was the area Az under the receiver operating characteristic (ROC) curve. We studied the effect of different GA parameters on classification accuracy, and compared the results to those obtained with stepwise feature selection. The data set used in this study consisted of 168 ROIs containing biopsy-proven masses and 504 ROIs containing normal tissue. From each ROI, a total of 587 features were extracted, of which 572 were texture features and 15 were morphological features. The GA was trained and tested with several different partitionings of the ROIs into training and testing sets. With the best combination of the GA parameters, the average test Az value using a linear discriminant classifier reached 0.90, as compared to 0.89 for stepwise feature selection. Test Az values with a BPN classifier and a more limited feature pool were 0.90 with GA-based feature selection, and 0.89 for stepwise feature selection. The use of a GA in tailoring classifiers with specific design characteristics was also discussed. This study indicates that a GA can provide versatility in the design of linear or nonlinear classifiers without a trade-off in the effectiveness of the selected features.

Algorithms↗
PubMed1996

Site-specific excision repair of 1-nitrosopyrene-induced DNA adducts at the nucleotide level in the HPRT gene of human fibroblasts: effect of adduct conformation on the pattern of site-specific repair.

Studies showing that different types of DNA adducts are repaired in human cells at different rates suggest that DNA adduct conformation is the major determinant of the rate of nucleotide excision repair. However, recent studies of repair of cyclobutane pyrimidine dimers or benzo[a]pyrene diol epoxide (BPDE)-induced adducts at the nucleotide level in DNA of normal human fibroblasts indicate that the rate of repair of the same adduct at different nucleotide positions can vary up to 10-fold, suggesting an important role for local DNA conformation. To see if site-specific DNA repair is a common phenomenon for bulky DNA adducts, we determined the rate of repair of 1-nitrosopyrene (1-NOP)-induced adducts in exon 3 of the hypoxanthine phosphoribosyltransferase gene at the nucleotide level using ligation-mediated PCR. To distinguish between the contributions of adduct conformation and local DNA conformation to the rate of repair, we compared the results obtained with 1-NOP with those we obtained previously using BPDE. The principal DNA adduct formed by either agent involves guanine. We found that rates of repair of 1-NOP-induced adducts also varied significantly at the nucleotide level, but the pattern of site-specific repair differed from that of BPDE-induced adducts at the same guanine positions in the same region of DNA. The average rate of excision repair of 1-NOP adducts in exon 3 was two to three times faster than that of BPDE adducts, but at particular nucleotides the rate was slower or faster than that of BPDE adducts or, in some cases, equal to that of BPDE adducts. These results indicate that the contribution of the local DNA conformation to the rate of repair at a particular nucleotide position depends upon the specific DNA adduct involved. However, the data also indicate that the conformation of the DNA adduct is not the only factor contributing to the rate of repair at different nucleotide positions. Instead, the rate of repair at a particular nucleotide position depends on the interaction between the specific adduct conformation and the local DNA conformation at that nucleotide.

Base Sequence↗
PubMed1996

[Establishment of an effective way for separating and culturing tumor infiltrating lymphocytes].

The key to preparing TILs for clinical application is to enhance its capacity of proliferation and cytotoxicity. For this purpose we have made a study of methodology and established an effective way consisting of 3 processes to separate and culture TILs. It included: (1) mechanical splitting; (2) digesting with 0.05% collagenase I and 0.003% DNAase I mixture in room temperature for 6 hrs and 18hrs in cool, and (3) centrifuging with 75% and 100% Ficoll non-continuous grade density. The separated TILs were suspended in conditional culture medium for proliferation. Most of them reached the amount of 10(9) at the end of culture, which was essential for clinical therapy. Their NK and LAK activities were 56.3 +/- 11.7% and 48.6% +/- 10.6% respectively, in which the CD6+ T cells played an important role. The results suggest this a perfect way for separating and culturing TILs.

Cell Culture Techniques↗
PubMed1996

[Effects of wound wet dressing with cerium nitrate on cell-mediated immunity after severe burn].

Suppression of cell-mediated immunity (CM) and lowering of survival rate follow major thermal injury are associated with absorption of burn toxin. Wistar rats received 30% full-thickness burn, and were then treated with early burn excision or wet dressing of cerium nitrate for the wound. At day 14 postburn, both survival rates and peripheral blood Th/Ts rate were monitored. It was found that both excision and cerium nitrate could prevent marked lowering of survival rate and Th/Ts ratio were monitored. It was found that both excision and cerium nitrate could prevent markly lowering of survival rates and Th/Ts ratio induced by severe burn. This indicated that CE, in the early postburn days, may replace early burn excision to prevent the suppression of CMI following severe burn.

Animals↗
PubMed1996

[Preparation and identification of monoclonal antibody GB2 directed against human breast cancer serum antigen].

Spleen cells from BALB/c mice immunized with human breast cancer serum antigen were fused with murine myeloma SP 2/0 cells. After screening with ELISA and limited-dilution cloning, one hybridoma which could stably secrete specific antibody was obtained and designated McAbGB2. The titer of McAbGB2 was up to 1.2 x 10(6) after purified by ammonium sulfate and DEAE-cellulose. The McAbGB2 was defined as murine IgG1 by agarose double immunodiffusiong. Immunoblotting analysis revealed that the antigens with molecular weights of 116 kd and 45 kd recognized by McAbGB2 were distributed in human breast cancer tissue and serum.

Animals↗
PubMed1996

[Improved MTT colorimetric assay for NKC activity].

The established improved 3-(4,5-dimethyl thiazoly)2,5-diphenyl-tetrazolium bromide (MTT) colorimetric assay for measuring the amount and function of living cell by the authors has the characteristics of simplicity, dependability and good repeatability within 3-12 hours. We have used this improved MTT colorimetric assay in measuring natural kill cell (NKC) activity of human peripheral blood. The results show that when the activities of effector cell (EC) and target cell (TC) are > or = 95%, and the density of EC is > or = 3 x 10(2)/well and that of TC > or = 1.6 x 10(2)/well, the number of living cell is positively correlated with the OD570nm volume of purple formazan metabolite of MTT solution (re = 0.94, ri = 0.97, P < 0.001). When the ratio of EC/TC is 40:1, the NKC activity of peripheral blood of health adults is equal to that report by Zhang Chongjie et al. By this MTT colorimetric assay, the NKC activity of peripheral blood of 10 leukemic patients has been detected. The mean +/- s of NKC activity is 34.86 +/- 7.80%, which is postively correlated with the result (35.16 +/- 8.40%) of the inhibition of 3H-TdR incorporation assay performed at the same time (r = 0.876, P < 0.001). MTT colormetric assay for NKC activity avoids getting in touch with isotope. It is a convenient and valuable method.

Adult↗
PubMed1995

Site-specific rates of excision repair of benzo[a]pyrene diol epoxide adducts in the hypoxanthine phosphoribosyltransferase gene of human fibroblasts: correlation with mutation spectra.

When populations of repair-proficient diploid human fibroblasts were treated with (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) during early S phase, just as the hypoxanthine phosphoribosyltransferase gene (HPRT) was being replicated, 5% of the induced base substitutions were found at nt 212, and 5% of the substitutions were found at nt 229 in exon 3. However, when the population was treated in early G1 phase to allow at least 12 hr for repair before the onset of S phase, 21% of the substitutions were found at nt 212, and 10% were found at nt 229. No such cell-cycle-dependent difference in distribution of base substitutions occurred in excision-repair-deficient cells. To test whether the increase in the relative frequency of mutations resulted from inefficient repair at these sites, we adapted ligation-mediated PCR to measure the rates of removal of BPDE adducts from individual sites in exon 3 of the HPRT gene. Cells were treated with 0.5 microM BPDE in early G1 phase and harvested immediately or after 10, 20, and 30 hr for repair. the nontranscribed strand of exon 3 was analyzed for the original distribution of adducts and those remaining after repair, using Escherichia coli UvrABC excinuclease to excise the adducts and annealing a 5' biotinylated gene-specific primer to the DNA and extending it with Sequenase 2.0 to generate a blunt end at the site of each cut. A linker was ligated to the blunt end, and the desired fragments were isolated from the rest of the genomic DNA by using magnetic beads, amplified by PCR, and analyzed on a sequencing gel. The distribution of fragments of particular lengths indicated the relative number of BPDE adducts initially formed or remaining at specific sites. The rates of repair at individual sites varied widely along exon 3 of the HPRT gene and were very slow at nt 212 and 229, strongly supporting the hypothesis that inefficient DNA repair plays an important role in the formation of mutation hotspots.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1995

Comparison of body surface potential maps simulated with isotropic and anisotropic computer heart models.

Simulated body surface potential maps (SBSPM) with isotropic and anisotropic heart models were compared to investigate the effect of myocardial anisotropy on body surface electrocardiograms at a whole heart level. Rotative fiber orientations of total 90 degrees was incorporated into an isotropic heart model. The anisotropy of conduction velocity and intracellular electric conductivity was included in the simulation. SBSPM based on epicardial, intramural, and endocardial stimulation show high correlation with fiber orientations. On the other hand, the anisotropy cannot be distinguished from the SBSPM in the simulation of normal heart model.

Anisotropy↗
PubMed1995

Computer-aided classification of mammographic masses and normal tissue: linear discriminant analysis in texture feature space.

We studied the effectiveness of using texture features derived from spatial grey level dependence (SGLD) matrices for classification of masses and normal breast tissue on mammograms. One hundred and sixty-eight regions of interest (ROIS) containing biopsy-proven masses and 504 ROIS containing normal breast tissue were extracted from digitized mammograms for this study. Eight features were calculated for each ROI. The importance of each feature in distinguishing masses from normal tissue was determined by stepwise linear discriminant analysis. Receiver operating characteristic (ROC) methodology was used to evaluate the classification accuracy. We investigated the dependence of classification accuracy on the input features, and on the pixel distance and bit depth in the construction of the SGLD matrices. It was found that five of the texture features were important for the classification. The dependence of classification accuracy on distance and bit depth was weak for distances greater than 12 pixels and bit depths greater than seven bits. By randomly and equally dividing the data set into two groups, the classifier was trained and tested on independent data sets. The classifier achieved an average area under the ROC curve, Az, of 0.84 during training and 0.82 during testing. The results demonstrate the feasibility of using linear discriminant analysis in the texture feature space for classification of true and false detections of masses on mammograms in a computer-aided diagnosis scheme.

Biophysical Phenomena↗
PubMed1995

Comparative simulation of excitation and body surface electrocardiogram with isotropic and anisotropic computer heart models.

Comparative simulations between isotropic and anisotropic computer heart models were conducted to study the effects of myocardial anisotropy on the excitation process of the heart and on body surface electrocardiogram. The isotropic heart model includes atria, ventricles, and a special conduction system, and is electrophysiologically specified by parameters relative to action potential, conduction velocity, automaticity, and pacing. The anisotropic heart model was created by incorporating rotating fiber directions into the ventricles of the isotropic heart model. The orientation of the myocardial fibers in the ventricles of the model was gradually rotated counterclockwise from the epicardial layer to the endocardial layer for a total rotation of 90 degrees. The anisotropy of conduction velocity and intracellular electric conductivity was included in the simulation. Comparative simulations of the normal heart, LBBB, and RBBB showed no significant differences between the two models in the excitation processes of the whole heart or in the body surface electrocardiograms. However, it was easier to induce ventricular fibrillation in the anisotropic model than in the isotropic model. The comparative simulation is useful for investigating the effects of myocardial anisotropy at the whole heart level and for evaluating limitations of the isotropic heart model.

Action Potentials↗
PubMed1995

Estimation of cerebral blood flow from thermal measurement.

A thermal method has been developed to quantify continuous perfusion changes with self-calibration. A dynamic, one-dimensional bio-heat transfer model of the thermal probe and tissue describes the system response to either continuous or transient heating. A nonlinear least-squares fit of the model to experimental data yields estimates of the baseline perfusion and other model parameters. With a partial analytical solution of the model, the optimal estimation procedure is two orders of magnitude more efficient than with a total numerical solution of the model system. Experimental data is used to estimate the operating relations between perfusion and the temperature measurement. A new procedure has also been presented to obtain the dynamic response of the system for continuous measurement of perfusion.

Animals↗