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Biomedical subjects

Q Cheng

Publications and source records attributed to Q Cheng.

At least 127 records · Page 7Linked to original sources
PubMed1994

Purification of (-)-epigallocatechin from enzymatic hydrolysate of its gallate using high-speed counter-current chromatography.

Epigallocatechin gallate (EGCG) was hydrolyzed at various concentrations of tannase under pH 6.0 at 35 degrees C, and the reaction mixtures were separated by high-speed counter-current chromatography with a two-phase solvent system composed of hexane-ethyl acetate-water (1:13:20). The best results were obtained when 2 mg/ml of the enzyme buffer solution was added to 0.3 M EGCG buffers at a rate of 0.1 ml/min. Using 10 mg of the enzyme, 342 mg of epigallocatechin were obtained at a purity of 99.1%.

Carboxylic Ester Hydrolases↗
PubMed1994

NK-kappa B subunit-specific regulation of the I kappa B alpha promoter.

Stimulation of endothelial cells by cytokines and bacterial lipopolysaccharide leads to activation of the transcription factor NF-kappa B. NF-kappa B in turn regulates the expression of several genes involved in the inflammatory reaction, including cell adhesion molecules, interleukins, and transcription factors. One of these induced genes encodes an inhibitor of NF-kappa B, ECI-6/I kappa B alpha, that contains in its 5' regulatory region six consensus binding sites for NF-kappa B. We demonstrate here that these sites display striking differences in their ability in vitro to bind to various NF-kappa B subunits. In vivo, all six sites contribute, though to varying degrees, to transcription from the ECI-6/I kappa B alpha promoter, as demonstrated by deletion and mutation analysis. Among the NF-kappa B subunits tested p65, the p65/p50 heterodimer and, to a lesser extent, c-Rel, are able to activate transcription, whereas p50 or p50/Re1B were inactive. Since many genes regulated by NF-kappa B contain only one or two DNA-binding sites for this transcription factor, the presence of six functional NF-kappa B-binding sites in the ECI-6/I kappa B alpha promoter represents a unique feature of this gene.

Amino Acid Sequence↗
PubMed1994

Selective inhibition of E-selectin, ICAM-1, and VCAM in endothelial cells.

Endothelial cells, as they normally exist in the vasculature as quiescent cells, perform several functions. In an inflammatory response, endothelial cells are activated to up-regulate a number of genes, including E-selectin (ELAM-1), VCAM-1, ICAM-1, interleukin (IL)-1, IL-8 and plasminogen activator inhibitor-1 (PAI-1). Very little is known about factors that regulate the activation process. We describe here that a heat-stable protein, normally present in the alpha-globulin fraction of serum, inhibits induced expression of E-selectin, ICAM-1, and VCAM-1 in vitro and also impedes the accumulation of mRNA for these molecules. Inhibition of E-selectin, the only gene tested in this respect, is at the level of transcription. At the same time, the alpha-globulins do not, under the same conditions, repress mRNA accumulation for IL-1, IL-8, or PAI-1. The effect of the inhibitor does not relate to constraints on function of nuclear-factor kappa B, the induced activity of which is not interfered with at the early time points at which the suppression of these three genes is seen.

Alpha-Globulins↗
PubMed1994

Sequence variation in the circumsporozoite protein gene of Plasmodium vivax appears to be regionally biased.

We have sequenced the circumsporozoite protein gene from 16 isolates from China, the Philippines, Papua New Guinea and the Solomon Islands. We found very limited polymorphisms in the non-repetitive regions of the circumsporozoite gene from these isolates. All samples from China contained a 36-base insert 3' to the repeats previously seen only in a North Korean isolate. Limited variation was found in the repeat regions, which allowed these and previously sequenced isolates to be classified into groups based on repeat structure. These groupings also correlate with the geographical origin of the isolates.

Amino Acid Sequence↗
PubMed1994

Plasmodium falciparum genetic diversity can be characterised using the polymorphic merozoite surface antigen 2 (MSA-2) gene as a single locus marker.

The genetic diversity of Solomon Island Plasmodium falciparum isolates was examined using MSA-2 as a single locus marker. Amplification of MSA-2 gene fragments showed size polymorphism and the presence of mixed infections. Sequence analysis indicated a global representation of MSA-2 alleles with representatives of 3D7/CAMP allelic subfamilies and the FCQ-27 allelic family being identified. A simplified method of characterisation, utilising PCR-RFLPs of MSA-2 gene fragments, was developed. The RFLPs allowed identification of allelic families and further distinction within the 3D7/CAMP family. The amplification of MSA-2 gene fragments from culture derived lines revealed a loss of diversity for a number of Solomon Island isolates. Genomic diversity was confirmed for Solomon Island lines, along with Papua New Guinean and Thai lines, by the generation of 7H8/6 fingerprints. All lines were distinct and band sharing frequencies and Wagner tree construction failed to identify any geographic clustering.

Amino Acid Sequence↗
PubMed1994

[DNA sequencing of circumsporozoite protein genes of Plasmodium vivax from four different countries in west Pacific region: comparative study on the flank sequences].

P. vivax CSP gene of 18 isolates from infected blood of patients living in China, Philippines, Solomon Islands and Papua New Guinea in West Pacific region has been sequenced from both terminal end. The total readable sequence in most isolates was about 725 base pair (bp), including the first two repeat units (70-330 bp) to the N terminus, and the last two repeat units to the C terminus (763-1,228 bp). Comparison and analysis of these obtained sequences with the published sequences of N.K., Thai., Belem, Sal-l. and BZL strains showed that:the N and C terminus sequences flanking the centre repeats in CSP gene were highly conserved in all isolates and identical with the 5 published sequences but a double base pair substitution in each end and a remarkable polymorphism in the postrepeat variable region in C terminus were found, including some diversities with obvious geographic characteristics which have not been reported previously.

Animals↗
PubMed1993

Cytokine-inducible expression in endothelial cells of an I kappa B alpha-like gene is regulated by NF kappa B.

The transient expression of many different genes is mediated by the inducible transcription factor p50-p65 NF kappa B, which in turn is regulated by complex formation with its inhibitor I kappa B alpha. We describe here that in porcine aortic endothelial cells, either IL-1 alpha, TNF alpha or LPS upregulates an inhibitor of NF kappa B which we refer to as ECI-6. ECI-6 is by structural and functional criteria an I kappa B alpha protein, the porcine homologue of MAD-3, pp40 and RL/IF-1. We have studied the promoter of the ECI-6/I kappa B alpha gene and provide three lines of evidence that its expression is directly regulated by NF kappa B. First, the 5' regulatory region of ECI-6/I kappa B alpha contains two sites that bind NF kappa B in electrophoretic mobility shift assays. Second, expression following transfection of an ECI-6/I kappa B alpha promoter-luciferase reporter construct is dependent on a co-transfected NF kappa B-p65 subunit. Third, pretreatment of endothelial cells with antioxidants, agents that inhibit activation of NF kappa B, inhibit the expression of ECI-6/I kappa B alpha. We conclude that the regulated expression of ECI-6/I kappa B alpha could represent a novel feedback mechanism by which NF kappa B downregulates its own activity after transient activation of target genes has been achieved.

Amino Acid Sequence↗
PubMed1993

Aqueous and vitreous concentration of mitomycin C by topical administration after glaucoma filtration surgery in rabbits.

PURPOSE: The authors investigated the aqueous and vitreous pharmacokinetics of mitomycin after postoperative topical administration in rabbits. METHODS: Filtration surgery was performed in one eye of each rabbit. On the first postoperative day, mitomycin solution (0.4 mg/ml) was administered by either topical drop or cellulose sponge in both eyes of each rabbit. Aqueous and vitreous paracenteses were performed at 0.25, 0.5, 1, 2, 3, and 4 hours thereafter. Three rabbits were tested at each time interval for each type of administration. RESULTS: After topical drop administration, the peak aqueous concentration was 0.03 +/- 0.02 microgram/ml (mean +/- standard error) in surgical eyes and 0.06 +/- 0.03 microgram/ml in control eyes. After sponge administration, the peak aqueous concentration was 0.10 +/- 0.03 microgram/ml in surgical eyes and 0.08 +/- 0.04 microgram/ml in control eyes. Peak aqueous concentrations from drop and sponge applications were achieved at 1 to 2 hours after administration. Vitreous levels were well below the concentration known to cause retinal toxicity at all time intervals tested. CONCLUSION: Postoperative topical administration of mitomycin was successful in delivering mitomycin into the aqueous humor of rabbit eyes. Alternative methods of mitomycin application from the currently popular intraoperative administration may be beneficial in situations in which mitomycin delivery across intact conjunctiva may be desirable.

Administration, Topical↗
PubMed1993

Polymorphism in Plasmodium vivax MSA1 gene--the result of intragenic recombinations?

The diversity in a 925 bp portion of the Plasmodium vivax MSA1 gene in isolates from the Philippines, China, the Solomon Islands and Papua New Guinea was investigated. A total of 74 base pair changes was found in the amplified fragment from 18 isolates. Most of these changes were single or double base pair substitutions. In several regions, these point changes were tightly linked with one set always present or always absent in the different isolates. Seven such blocks were identified. These blocks were present in different combinations in the different isolates indicating that extensive intragenic recombination has occurred.

Amino Acid Sequence↗
PubMed1992

The 42-kilodalton rhoptry-associated protein of Plasmodium falciparum.

The gene coding for a 42-kDa rhoptry protein of Plasmodium falciparum has been cloned. On the basis of prior monkey vaccination studies, this protein is regarded as an important vaccine candidate, but its identity has been the subject of considerable uncertainty. Analysis of the cloned sequence shows that it is a basic, hydrophobic protein, without repetitive elements, unrelated to any of the previously postulated gene products and shows minimal sequence diversity. The availability of the corresponding recombinant protein will enable studies of its efficacy in human vaccine trials to be undertaken.

Amino Acid Sequence↗
PubMed1992

A locus that contributes to colonization of the intestinal tract by Bacteroides thetaiotaomicron contains a single regulatory gene (chuR) that links two polysaccharide utilization pathways.

Previously, we isolated two Tn4351-generated mutants of Bacteroides thetaiotaomicron (46-1 and CS3) that were unable to grow either on heparin or on chondroitin sulfate. This phenotype was unexpected, since the heparin and chondroitin sulfate utilization pathways had appeared from earlier studies to be independent of each other. Mutants 46-1 and CS3 were also of interest because both were unable to compete successfully with wild-type B. thetaiotaomicron in the intestinal tracts of germfree mice. Thus, both appeared to have a colonization defect. We have now cloned the chromosomal locus in which the transposon insertions in 46-1 and CS3 occurred. Southern blot analysis showed that the Tn4351 insertions in 46-1 and CS3 were about 100 bp apart. Using complementation and insertional mutagenesis, we localized the region affected by the 46-1 and CS3 insertions to within 2.5 kbp. This DNA segment was sequenced and found to contain a 401-codon open reading frame (ORF1) and the N-terminal segment of a second open reading frame (ORF2), which was downstream of ORF1 and transcribed in the same direction. The deduced amino acid sequence of ORF1 showed significant homology to that of a putative positive regulator of an arylsulfatase gene in Klebsiella aerogenes. ORF2 was at least 381 amino acids long and did not exhibit homology to any proteins in the data bases searched. Transposon insertions in both mutants 46-1 and CS3 disrupted ORF1. The results of insertional mutagenesis and complementation experiments indicated that ORF2 was not essential for growth on chondroitin sulfate or heparin. Thus, the chondroitin sulfate-negative and heparin-negative phenotypes of 46-1 and CS3 appear to be due to the interruption of a regulatory gene encoded by ORF1 and not to a polar effect of the insertions on a downstream gene(s). The gene encoding ORF1 has been designated chuR, for regulation of chondroitin sulfate and heparin utilization. Transcriptional fusion studies showed that the expression of chuR occurred at the same level under inducing and noninducing conditions, in contrast to the regulated expression of structural genes of the chondroitin sulfate utilization system. chuR was not autoregulated, nor was its expression affected by a mutation (46-4) that eliminated the expression of all chondroitin sulfate utilization genes but did not affect the utilization of heparin.

Amino Acid Sequence↗
PubMed1992

[Effect of cordyceps sinensis on cellular immunity in rats with chronic renal insufficiency].

Animal model of chronic renal failure (CRF) was induced in wistar rats by 5/6 nephrectomy. Half of the rats were treated with Cordyceps sinensis (CS) in form of decoction. It was found that CS has mitogenic effect on spleen lymphocytes, and is capable of increasing the production of IL-2 from splenocytes of the CRF rats. IL-2 absorbency of the splenocytes was promoted by CS. CS also exhibited such therapeutic effects on CRF animal as to decrease the level of BUN and serum creatinine and to increase the level of hemoglobin. These results indicate that CS has a regulative effect on cellular immunity in CRF rats.

Adjuvants, Immunologic↗
PubMed1991

Identification of a common Plasmodium epitope (CPE) recognised by a pan-specific inhibitory monoclonal antibody.

A Plasmodium falciparum genomic expression library was screened with a monoclonal antibody produced from mice infected with Plasmodium yoelii. Eleven unique clones were isolated all of which contained the sequence NKND, IKND or KKND. This sequence was confirmed as the epitope of M26-32 by testing a series of overlapping peptides and the allowable substitutions determined by testing the binding of M26-32 to peptides containing all possible single amino acid replacements of NKND. Potential epitopes of M26-32 occur in many plasmodial proteins and this is consistent with the large number of proteins recognised in these parasites by Western blotting. Since this monoclonal antibody shows marked in vitro inhibition of P. falciparum growth, these data suggest that an anti-malarial vaccine may be produced by targeting such common plasmodial epitopes without necessarily identifying the corresponding antigens.

Amino Acid Sequence↗