Biomedical subjects

Q Du

Publications and source records attributed to Q Du.

At least 37 records · Page 2Linked to original sources

PubMed2000

Low-speed rotary countercurrent chromatography using a convoluted multilayer helical tube for industrial separation

An industrial-scale countercurrent chromatographic system was developed using a slowly rotating helical device which can be automated and left unattended during the operation. It uses a multilayer coiled column consisting of long convoluted Teflon tubing of 0.85 cm i.d., which provides sufficient retention of the stationary phase under a relatively high flow rate. The column is mounted on a seal-less continuous-flow rotary device which eliminates various complications such as leakage and clogging as often caused by the use of a conventional rotary seal. Using a multilayer coiled column with a 10-L capacity, 150 g of crude tea extract was successfully purified, yielding 40 g of epigallocatechin gallate of over 92.7% purity at a recovery rate of 82.6%. The present system can be scaled up for a kilogram-scale separation.

Journal Article↗

PubMed2000

Hereditary breast cancer: a review.

Breast cancer is the most common female malignancy and a major cause of death in middle-aged women. A positive family history of breast cancer is one of the strongest risk factors for the disease. In addition, many afflicted breast cancer families are characterized by early onset and bilateral tumors, and also, in some cases, associated malignancies, most commonly ovarian cancer. It is estimated that 5-10% of all breast cancer cases are due to autosomal dominant genes segregating with the disease. Mutations in the BRCA1 and BRCA2 genes are known to predispose to breast and ovarian cancer in many families. Other genes are only involved in very rare syndromes, and additional genes remain to be disclosed.

Animals↗

PubMed2000

Pre-clinical experimental studies of indomethacin-releasing copper intrauterine device.

Effects of two types of intrauterine device (IUD) on the prostaglandins and endothelin (ET) in uterus and on the endometrial morphology in rats and rabbits, and Cu2+ releasing amounts of both IUDs in vitro were observed. The results showed that the inhibiting action of the indomethacin-releasing copper IUD (FICu-IUD) on the PGI2 was stronger than that on the TXA2, the ratio of 6-keto-PGF1 alpha/TXB2 was reduced with the increase of the doses. There were significant differences between the groups. The FICu-IUD could inhibit the rising of the ET level and lighten the endometrial impairment caused by the FCu-IUD, and promote copper ion release. It was suggested that indomethacin released by FICu-IUD could effectively reduce abnormal uterine bleeding.

Animals↗

PubMed2000

[Polymorphisms of chemokine receptor alleles influencing genetic susceptibility to HIV-1 infection in Mongolia population in China].

OBJECTIVE: Mutant frequency and polymorphism of HIV-1 resistance CCR5-Delta32, CCR2b-64I and SDF1-3'A alleles were investigated in Chinese population from Mongolian ethnic origin. METHODS: Whole blood samples from 134 Mongolian subjects were collected randomly and their genomic DNA were extracted using Qiagen Blood Kit. Allelic frequency was identified by means of PCR or PCR-RFLP analysis. Allelic polymorphism in population and between sex in the sample as well as correlation of the three genes were analyzed by chi(2) test. RESULTS: The frequencies of the three alleles were as following: CCR5-Delta32 1.1%, CCR2b-64I 24.8% and SDF1-3'A 22.0% respectively. Distribution of the three mutant alleles among the Mongolian population was in accordance with Hardy-Weinberg equilibrium. Statistical analysis showed there was a higher frequency of CCR2b-64I in female than in male subjects (29.2% vs 19.7%). No Statistical difference was found in the allelic frequencies of both CCR5-Delta32 and SDF1-3'A between male and female individuals. CONCLUSION: Compared with the Caucasian American, there were higher frequencies of CCR2b-64I and SDF1-3'A alleles and lower frequency of CCR5-Delta32 allele found in Mongolian population while the factors responsible for the variation of genetic polymorphisms in different ethnic populations need to be clarified.

Adolescent↗

PubMed2000

[Erythroid differentiation denucleation factor: a family of erythroid regulators for mammalian erythroid terminal differentiation/tumor suppression and the cloning of their related genes].

The role of regulation of erythroid differentiation denucleation factor(EDDF) on mammalian erythroid differentiation and myeloma cell malignancy as well as cloning of their stage related genes were serially studied. Through a series of cybrid and hybridization experiments between mammalian erythroid cells and erythroleukemia or non-erythroid myeloma cells, we have demonstrated a novel family of erythroid regulators(EDDFs) in the mammalian differentiating erythroblasts which with an active peak occurred concomitantly with marked decreases in DNA, RNA and the nuclear anchoring vimentin-IF, but increased in hemoglobin synthesis in cytoplasm prior to the denucleation process during terminal differentiation. The results of cell fusion experiments verified that the supplement of regulators(EDDFs) was critical to the recovery of the originally lost features of terminal differentiation and the reversion of malignant phenotype of tumor cells. Here we showed that the erythroid regulator family EDDFs were essential regulators for the sequential expression of stage related genes of erythroid terminal differentiation, and for the redifferentiation of tumor cells to express the originally inactive globe genes, repressed the oncogenes, and vimentin-IF system, thus initiated nuclear condensation and denucleation. The EDDF gene family consisted of MEDDF, HEDDF-1, HEDRF-1, HEDRF-2 and HCNBP-1 were cloned. All were novel cDNA sequences that have been searched and registered in GenBank. They expressed varying in a stage specific manner, and acted on corresponding genes of terminal differentiation.

Activins↗

PubMed2000

[Expression and glycosylation of rotavirus strain SA11 VP4 protein in a recombinant adenovirus].

OBJECTIVE: A modified VP4 gene of rotavirus SA11 strain was expressed by a recombinant human adenovirus. METHODS: A whole VP4 gene was obtained with PCR and induced the signal peptide at the gene N terminal. The chimera gene was cloned into pCMV plasmid that consist of human cytomagolovirus promoter and then cloned the gene to transfer human adenovirus type 5 vector. Homologues recombinant was performed by co-transfection to 293 cell line with recombinant plasmid and viral genome using CaPO4 precipitation. RESULTS: VP4 gene is 2,362 base pair in length mutation was not found in whole VP4 gene sequence. Expressed product in recombinant adnovirus was confirmed to be specific and more antigenicity by indirect immunofluorescence assay. Both Western blot and immunoprecipitation assays showed that expressed protein molecular weight was higher than wild type VP4 protein and that modified product was corresponding to a glycosylation of VP4 protein. CONCLUSIONS: It may be a effective method to modify interested gene for enhancing stability, antigenicity and immunogenicity of expressive product.

Adenoviruses, Human↗

PubMed2000

[Laser-time-resolved fluorescence spectroscopy in immunoassays].

This paper described a laser-excited time-resolved fluoroimmunoassay set. It made lanthanide ion to couple the anhydrde of diethylenetriaminepentaacetic acid (DTPAA) for labeling antibodies. The experiment used polystyrene tap coated with HCV antigen as the solid phase and a chelate of the rare earth metal europium as fluorescent label. A nitrogen laser beam was used to excite the Eu3- chelates and after 60 microseconds delay time, the emission fluorescence was measured. Background fluorescence of short lifetimes caused by serum components and Raman scattering can be eliminated by set the delay time. In the system condition, fluorescent spectra and fluorescent lifetimes of Eu3+ beta-naphthoyltrifluroacetone (NTA) chelates were measured. The fluorescent lifetime value is 650 microseconds. The maximum emission wavelength is 613 nm. The linear range of europium ion concentration is 1 x 10(-7)-1 x 10(-11) g.mL-1 and the detection limit is 1 x 10(-13) g.mL-1. The relative standard deviation of determination (n = 12) for samples at 0.01 ng.mL-1 magnitude is 6.4%. Laser-TRFIA was also found to be suitable for diagnosis of HCV. The sensitivity and specificity were comparable to enzyme immunoassay. The result was obtained with laser-TRFIA for 29 human correlated well with enzyme immunoassay.

Animals↗

PubMed1999

A Comparative Study of Surface Acid-Base Characteristics of Natural Illites from Different Origins.

The acid-base characteristics of naturally occurring illites, collected from different locations, were investigated by potentiometric titrations. The experimental data were interpreted using the constant capacitance surface complexation model. Considerable release of Al and Si from illite samples and subsequent complexation or precipitation of hydroxyl aluminosilicates generated during the acidimetric forward titration and the alkalimetric back titration, respectively, were observed. Therefore, the acidimetric supernatant, rather than the neutral one, was regarded as the system blank for each illite suspension to yield the surface site concentrations. In order to describe the acid-base chemistry of aqueous illite surfaces, two surface proton-reaction models, introducing the corresponding reactions between the dissolved aluminum species and silicic acid, as well as a surface Al-Si complex on homogeneous illite surface sites, were proposed as follows: The K(f2) constant in Model II was obtained by simulating the complex formation between the dissolved aluminum species and silicic acid that occurred in acidimetric supernatant when the hydroxide was added. Additionally, the following cation exchange reaction was also considered for a special case, where a large amount of K(+) is released during the corresponding acidimetric titration, in which a high concentration of protons are consumed. Optimization results indicated that both models could provide a good description of the titration behavior for all aqueous illite systems in this study. The intrinsic acidity constants for the different illites were similar in Model I, showing some generalities in their acid-base properties. Model I may be considered as a simplification of Model II, evident in the similarities between the corresponding constants. In addition, the formation constant for surface Al-Si species (complexes or precipitates) is relatively stable in this study. Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

A point mutation in the ethylene-inducing xylanase elicitor inhibits the beta-1-4-endoxylanase activity but not the elicitation activity.

Ethylene-inducing xylanase (EIX) elicits plant defense responses in certain tobacco (Nicotiana tabacum) and tomato cultivars in addition to its xylan degradation activity. It is not clear, however, whether elicitation occurs by cell wall fragments released by the enzymatic activity or by the xylanase protein interacting directly with the plant cells. We cloned the gene encoding EIX protein and overexpressed it in insect cells. To determine the relationship between the two activities, substitution of amino acids in the xylanase active site was performed. Substitution at glutamic acid-86 or -177 with glutamine (Gln), aspartic acid (Asp), or glycine (Gly) inhibited the beta-1-4-endoxylanase activity. Mutants having Asp-86 or Gln-177 also lost the ability to induce the hypersensitive response and ethylene biosynthesis. However, mutants having Gln-86, Gly-86, Asp-177, or Gly-177 retained ability to induce ethylene biosynthesis and the hypersensitive response. Our data show that the xylanase activity of EIX elicitor can be separated from the elicitation process, as some of the mutants lack the former but retain the latter.

Amino Acid Sequence↗

PubMed1999

Isolation of an apoptosis suppressor gene of the Spodoptera littoralis nucleopolyhedrovirus.

Spodoptera frugiperda SF9 cells infected with mutants of the Autographa californica nucleopolyhedrovirus (AcMNPV) which lack a functional p35 gene undergo apoptosis, aborting the viral infection. The Spodoptera littoralis nucleopolyhedrovirus (SlNPV) was able to suppress apoptosis triggered by vDeltaP35K/pol+, an AcMNPV p35 null mutant. To identify the putative apoptotic suppressor gene of SlNPV, overlapping cosmid clones representing the entire SlNPV genome were individually cotransfected along with genomic DNA of vDeltaP35K/pol+. Using this complementation assay, we isolated a SlNPV DNA fragment that was able to rescue the vDeltaP35K/pol+ infection in SF9 cells. By further subcloning and rescue, we identified a novel SlNPV gene, Slp49. The Slp49 sequence predicted a 49-kDa polypeptide with about 48.8% identity to the AcMNPV apoptotic suppressor P35. SLP49 displays a potential recognition site, TVTDG, for cleavage by death caspases. Recombinant AcMNPVs deficient in p35 bearing the Slp49 gene did not induce apoptosis and showed successful productive infections in SF9 cells, indicating that Slp49 is a functional homologue of p35. A 1.5-kbp Slp49-specific transcript was identified in SF9 cells infected with SlNPV or with vAc496, a vDeltaP35K/pol+-recombinant bearing Slp49. The discovery of Slp49 contributes to the identification of important functional motifs conserved in p35-like apoptotic suppressors and to the future isolation of p35-like genes from other baculoviruses.

Amino Acid Sequence↗

PubMed1998

Differential effects of heterogeneous nuclear ribonucleoprotein K on Sp1- and Sp3-mediated transcriptional activation of a neuronal nicotinic acetylcholine receptor promoter.

The neuronal nicotinic acetylcholine receptor gene family consists of 11 members, alpha2-alpha9 and beta2-beta4. Three of the genes, those encoding the alpha3, alpha5, and beta4 subunits, are clustered tightly within the genome. These three subunits constitute the predominant acetylcholine receptor subtype expressed in the peripheral nervous system. The genomic proximity of the three genes suggests a regulatory mechanism ensuring their coordinate expression. However, it is likely that gene-specific regulatory mechanisms are also functioning because the expression patterns of the three genes, although similar, are not identical. Previously we identified regulatory elements within the beta4 promoter region and demonstrated that these elements interact specifically with nuclear proteins. One of these elements, E1, interacts with the regulatory factor Puralpha as well as three other unidentified DNA-binding proteins with molecular masses of 31, 65, and 114 kDa. Another element, E2, interacts with Sp1 and Sp3. Because E1 and E2 are immediately adjacent to one another, we postulated that the proteins that bind to the elements interact to regulate beta4 gene expression. Here we report the identification of the 65-kDa E1-binding protein as heterogeneous nuclear ribonucleoprotein K and demonstrate that it affects the transactivation of beta4 promoter activity by Sp1 and Sp3 differentially.

Animals↗

PubMed1998

Heuristic lipophilicity potential for computer-aided rational drug design: optimizations of screening functions and parameters.

In this research we test and compare three possible atom-based screening functions used in the heuristic molecular lipophilicity potential (HMLP). Screening function 1 is a power distance-dependent function, bi/[formula: see text] Ri-r [formula: see text] gamma, screening function 2 is an exponential distance-dependent function, bi exp(-[formula: see text] Ri-r [formula: see text]/d0), and screening function 3 is a weighted distance-dependent function, sign(bi) exp[-xi [formula: see text] Ri-r [formula: see text]/magnitude of bi)]. For every screening function, the parameters (gamma, d0, and xi) are optimized using 41 common organic molecules of 4 types of compounds: aliphatic alcohols, aliphatic carboxylic acids, aliphatic amines, and aliphatic alkanes. The results of calculations show that screening function 3 cannot give chemically reasonable results, however, both the power screening function and the exponential screening function give chemically satisfactory results. There are two notable differences between screening functions 1 and 2. First, the exponential screening function has larger values in the short distance than the power screening function, therefore more influence from the nearest neighbors is involved using screening function 2 than screening function 1. Second, the power screening function has larger values in the long distance than the exponential screening function, therefore screening function 1 is effected by atoms at long distance more than screening function 2. For screening function 1, the suitable range of parameter gamma is 1.0 < gamma < 3.0, gamma = 2.3 is recommended, and gamma = 2.0 is the nearest integral value. For screening function 2, the suitable range of parameter d0 is 1.5 < d0 < 3.0, and d0 = 2.0 is recommended. HMLP developed in this research provides a potential tool for computer-aided three-dimensional drug design.

Computer-Aided Design↗

PubMed1998

[The pre-experiment on space crystallization of pig heart mitochondrial F1-ATPase].

ATP synthase (H(+)-ATPase) plays a key role in oxidative phosphorylation. Its catalytic moiety F1-ATPase is under intense structural study because of different crystallographic results and diverse hypotheses of its catalytic mechanism. To obtain high quality crystals, F1-ATPase sample is going to be carried to outer space by recovable satellite for crystal growth under microgravity. And to make it suitable for space crystal growth, F1-ATPase was purified from pig heart and the conditions were optimized for its maintenance, transportation, and crystallization. By using hanging drop vapor diffusion method and sitting drop vapor diffusion method, the crystals were obtained within 5 d and with a size of 0.1 mm x 0.1 mm x 0.l mm on the 7th day. The reproducibility of these experiments is also good.

Animals↗

PubMed1998

[Determination of chemical constituents of the volatile oil from Curcuma longa by gas chromatography-mass spectrometry].

The study of chemical constituents of the volatile oil from Curcuma longa is reported. The volatile oil was extracted by steam distillation. Fifteen components in the oil were separated and identified by gas chromatography-mass spectrometry(GC/MS). The results were elucidated based on the NBS standard mass spectral data. The total ion current chromatogram showed their mass fraction by normalization method. alpha-curcumene, alpha-zingiberene, 1,8-cineole and zerumbone, which had been reported before were found in Curcuma longa volatile oil, but 1-(3-cyclopentylpropyl)-2,4-dimethylbenzene, beta-sesquiphellandrene, germacrene etc identified simultaneously in the oil had never been reported. The major chemical constituent of the volatile oil from Curcuma longa is alpha-curcumene.

Curcuma↗

PubMed1998

[Study on tissue culture of Poligonum multiflorum].

In the present thesis, suitable medium for callus inducement and relationship between culture time and callus growth of Poligonum multiflorum were studied by mono-factorial and orthogonal design test. The experiments showed that the best medium for callus inducement was MS + 2,4-D 1 mg/L + 6-BA 1 mg/L + IBA 0.5 mg/L, dark culture was better than light culture, callus grew fast when it was cultured 12 days, whole plant could be induced by callus, the induce rate was 95%.

Culture Media↗

PubMed1997

Transcriptional regulation of neuronal nicotinic acetylcholine receptor genes. A possible role for the DNA-binding protein Puralpha.

Nicotinic acetylcholine receptors constitute a multigene family (alpha2-alpha9, beta2-beta4) expressed in discrete temporal and spatial patterns within the nervous system. The receptors are critical for proper signal transmission between neurons and their targets. The molecular mechanisms underlying receptor gene expression have not been completely elucidated but clearly involve regulation at the level of transcription. We previously identified a novel 19-base pair (bp) transcriptional regulatory element in the promoter region of the rat beta4 subunit gene. This 19-bp element interacts specifically with DNA-binding proteins enriched in nuclear extracts prepared from adult rat brain. Using a combination of cellulose-phosphate, DNA-cellulose, and DNA sequence-specific affinity chromatographies, we purified the 19-bp element binding activity approximately 19,000-fold. Analysis by denaturing gel electrophoresis revealed the presence of four polypeptides in the most purified fraction, ranging in molecular masses between 31 and 114 kDa. Peptide sequence analysis revealed that one of the polypeptides is the bovine homologue of the transcriptional regulatory factor, Puralpha. Electrophoretic mobility shift assays indicated that Puralpha interacts directly and specifically with the 19-bp element. In addition, mobility shift assays using an anti-Puralpha monoclonal antibody revealed the presence of Puralpha, or an immunologically related protein, in nuclear extracts prepared from brain tissue. We hypothesize that the interaction between Puralpha and the 19-bp element is critical for proper expression of the beta4 subunit gene.

Amino Acid Sequence↗

PubMed1997

Acid-Base Properties of Aqueous Illite Surfaces

In this paper, the acid-base properties of illite/water suspensions are examined using the constant capacitance surface complexation model. On the basis of results of potentiometric titrations and solubility experiments, we conclude that the proton reactions in the supernatants of illite suspensions can be successfully represented by proton reactions of Al(H2O)63+ and Si(OH)4 in water solutions. For illustrating the acidic characteristics of aqueous illite surfaces, two surface protonation models are proposed: (1) one site-one pKa model, identical withSOH right arrow over left arrow identical withSO- + H+, pKaint = 4.12-4.23; (2) two sites-two pKas model, identical withSIOH right arrow over left arrow identical withSIO- + H+, pKintaI = 4.17-4.44, and identical withSIIOH right arrow over left arrow identical withSIIO- + H+, [dipKintaII = 6.35-7.74. Evaluation of these two models indicates that both of them can give good descriptions of the experimental data of systems with different illite concentrations and ionic strengths and that the one site-one pKa model can be considered as a simplification of the two sites-two pKas model. Since both models assume only deprotonation reactions at the illite surfaces, they suggest that the surface behavior of the illite is similar to that of amorphous SiO2. Model assumptions, experimental procedures, and evaluative criteria are detailed in the paper.

Journal Article↗

PubMed1997

Adsorption of Copper at Aqueous Illite Surfaces

In this paper, we conducted potentiometric titrations, batch adsorption experiments and FT-IR analysis to study the uptake of copper in illite/water suspensions and then applied the constant capacitance surface complexation model to interpret the reaction mechanism at the aqueous illite surfaces. Our research shows that the copper adsorption at these surfaces is strongly dependent on pH and that the adsorption causes a deprotonation of surface groups. We propose that the uptake of copper in the carbonate-free illite suspensions can be explained by the formation of mononuclear surface complexes, identical withSOCu+ and identical withSOCuOH, and a multinuclear surface complex, identical withSOCu2(OH)2+, followed by the formation of a bulk precipitate, Cu(OH)2(s), or a surface precipitate, identical withSOCu2(OH)3(sp). For the illite suspensions containing carbonates, we propose that the copper-illite interaction can be depicted by the formation of mononuclear surface complexes, identical withSOCu+ and identical withSOCuOH, followed by the formation of a copper hydroxylcarbonate precipitate, Cu2(OH)2CO3(s), rather than a copper hydroxide precipitate. The existence of Cu2(OH)2CO3(s) in the carbonate-containing illite suspensions was identified by FT-IR analysis.

Journal Article↗