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C Chen

Publications and source records attributed to C Chen.

At least 1,027 records · Page 57Linked to original sources
PubMed1993

Combination of DNA single strand synthesis with PCR to construct mung bean trypsin inhibitor gene.

This paper using the synthesis of mung bean trypsin inhibitor gene as an example, presented a new method for gene synthesis. The principle of the method was based on the combination of the single strand strategy and the PCR technique. The synthesis was very simple, convenient and rapid. The mung bean trypsin inhibitor is a protein composed of 72 amino acid residues. Its amino acid sequence has been determined, but the DNA sequence of gene still unknown. The synthetic mung bean trypsin inhibitor gene was 248 bp in length. It contains the encoded sequence, the start and stop codons, the restriction sites of EcoRI and BamHI at both ends, The codon selection of the synthetic gene was carried out according to the codon usage of other plant protease inhibitor gene or plant gene. The synthetic double-stranded DNA was digested with EcoRI and BamHI or PstI first, then cloned into plasmid pUC19. The synthetic gene was proved to be correct by the restriction map and the sequence analysis using the dideoxy-mediated chain termination method.

Amino Acid Sequence↗
PubMed1993

[Studies on residual antimalarial activity of tripynadine in mice and monkeys].

This paper reports the experiments in which tripynadine free base at a dose 4.5 times that of ED50 was given to mice by intragastric administration. On the 20th day following the administration the mice were inoculated with 1 x 10(7) RBC infected with Plasmodium berghei ANKA strain. The infection rate was zero, implying that all mice had acquired protection. Although the residual activity time of tripynadine phosphate was longer than that of tripynadine free base or piperaquine phosphate, but tripynadine phosphate caused vomiting in monkeys during the medication. The residual antimalarial activity of tripynadine hydroxynaphthoate was less than that of tripynadine phosphate or tripynadine free base. A total dose of 200 mg/kg of tripynadine free base ensured residual antimalarial activity against P. cynomolgi bastianellii for 20 days. However, the residual activity decreased evidently when the total dose was reduced to 100 mg/kg. In short, it seems that the residual antimalarial activity of tripynadine free base is slightly less than that of piperaquine in monkeys.

Animals↗
PubMed1993

Beta-[3H]funaltrexamine-labeled mu-opioid receptors: species variations in molecular mass and glycosylation by complex-type, N-linked oligosaccharides.

We previously showed that under defined conditions beta-[3H]funaltrexamine (beta-[3H]FNA) covalently labeled mu-opioid receptors with high specificity in bovine striatal membranes. beta-[3H]FNA-labeled mu-opioid receptors migrated as a broad band with a molecular mass range of 68-97 kDa. It is controversial whether beta-FNA binds irreversibly to mu-opioid receptors in other species. In this study, we demonstrated that beta-[3H]FNA also labeled mu-opioid receptors with high specificity in brain membranes of the guinea pig, rat, and mouse. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography revealed that in each species beta-[3H]FNA specifically bound to a protein in which labeling was greatly reduced by naloxone. These labeled receptors had broad molecular mass ranges, and the molecular masses were different among these species, in the order of cow > guinea pig > rat > mouse. Membranes were subjected to solubilization with 2% Triton X-100 and wheat germ lectin (WGL) affinity chromatography. N-Acetylglucosamine eluted a peak of radioactivity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography showed that in all four species the mu receptor was the only protein labeled with beta-[3H]FNA in the WGL eluate. The molecular masses of labeled mu-opioid receptors were 70-88 kDa (median, 77 kDa) for the cow, 66-80 kDa (median, 72 kDa) for the guinea pig, 60-75 kDa (median, 67 kDa) for the rat, and 60-72 kDa (median, 66 kDa) for the mouse. In addition, we investigated the nature of the carbohydrate moieties linked to the receptor protein and whether the species variation in the molecular mass was due to variable degrees of glycosylation. The bovine WGL eluate was treated with various glycosidases. Neuraminidase treatment decreased the receptor molecular mass by 6-7 kDa, whereas alpha-mannosidase had no effect. Removal of N-linked carbohydrates at asparagine residues by peptide-N4-[N-acetyl-beta-glucosaminyl]asparagine amidase (N-Glycanase) resulted in a much sharper specifically labelled protein band of 43 kDa. These results indicate that mu-opioid receptors are heavily glycosylated and the major carbohydrate moieties are of the complex type, N-linked to asparagine. After the WGL eluates for the four species were treated with N-Glycanase, the labeled receptors became much sharper bands with very similar molecular masses, i.e., 43 kDa for the cow and guinea pig, 39 kDa for the rat, and and 40 kDa for the mouse.(ABSTRACT TRUNCATED AT 400 WORDS)

Amidohydrolases↗
PubMed1993

[Synthesis of pyronaridine related compounds and comparison of antimalarial activities].

The paper reports the synthesis of pyronaridine (I) related compounds II-V for exploring whether the antimalarial activity of pyronaridine is by virtue of a nitrogen atom at position 1 in the ring and a pair of pyrrolidinyl Mannich base side chains in its structure. The condensation of 2-methoxy-6,9-dichloroacridine or 4,7-dichloro-1,5-naphthyridine with 4-hydroxy-3,5-bis-(pyrrolidinyl-1'-methyl) aniline yielded the related compound II, 1-deazapyronaridine, or V, 5-azabispyroquine, respectively. 2-Methoxy-7,10-dichlorobenzo (b) 1,5-naphthyridine or 4,7-dichloro-1,5-naphthyridine was condensed with 4-diethylamino-1-methylbutylamine to obtain the related compound III, azacrin, or IV, 5-azachloroquine, respectively. The results of in vivo tests against Plasmodium berghei chloroquine-resistant ANKA strain, drug-sensitive P. berghei N line and drug-resistant P. yoelii nigeriensis line showed that all the related compounds II-V were less effective than pyronaridine (I). It suggests that the nitrogen atom at position 1 and pyrrolidinyl Mannich base side chains on the structure of pyronaridine play an important and indispensable role for antimalarial activity of pyronaridine. The pyrrolidinyl Mannich bases impart increased activity to the corresponding compounds.

Animals↗
PubMed1993

Effects of argipressin injected into medial amygdaloid body on blood pressure and heart rate in rats.

Graded injections of argipressin (Arg, 150, 300, and 600 ng/1.5 microliters CSF, 2 min) into the medial amygdaloid body in anesthetized rats produced a dose-related increase in the mean arterial pressure and heart rate (Maximal delta MAP = 2.9 +/- 1.5 kPa, Maximal delta HR = 67 +/- 38 bpm), which lasting > 40 min at 600 ng dosage. Naloxone (15 micrograms/15 microliters CSF) injected into the lateral ventricle blocked the cardiovascular responses to Arg. These results suggest that Arg exerts a central action on the cardiovascular system via the opioid in the lateral ventricle.

Amygdala↗
PubMed1993

The current status and future prospects of altering the pathogenic microflora of periodontal disease.

Modern periodontal therapy aims to suppress or eradicate periodontal pathogens and to maintain a posttreatment flora that is compatible with health. Systemic and local antimicrobial therapies have demonstrated effectiveness against several periodontal pathogens. Sustained-release devices, or irrigators, for local application of antimicrobial agents to periodontal pockets show great promise. Replacement therapy and periodontal vaccines, although still in the early research phase, represent very interesting approaches for preventing periodontitis. Using modern molecular genetic methods, it is theoretically possible to clone virulence determinants of periodontal pathogens into a nonpathogenic organism. The carrier organism with the expressed foreign antigens may be implanted in the oral cavity or the intestinal tract to induce long-lasting immunity against the targeted periodontal pathogens.

Anti-Bacterial Agents↗
PubMed1992

[Floating intracardiac metastasis].

Two years after the removal of an embryonic testicular tumour from a now 26-year-old man, his general health deteriorated and a holosystolic murmur was heard over the tricuspid valve area. A chest X-ray film demonstrated lung metastases. Biochemical tests were within normal limits, but the human chorionic gonadotrophin level was elevated to 81,030 mU/ml. Echocardiography revealed mild tricuspid regurgitation and a floating mass between the right atrium and ventricle, in contact with the tricuspid valve. The described findings did not support the diagnosis of embolus or inflammatory vegetation. Because of the danger of embolization and obstruction of the pulmonary outflow tract the mass was removed surgically. Enzyme-histological examination identified the tissue as a metastasis of the testicular tumour. The patient's condition at first improved, but he soon died of bleeding from the lung which was infiltrated by trophoblast-containing metastases of the testicular tumour.

Adult↗
PubMed1992

Generation and analysis of random point mutations in an antibody CDR2 sequence: many mutated antibodies lose their ability to bind antigen.

We have investigated the impact of mutations on the binding functions of the phosphocholine (PC)-specific T15 antibody in the absence of antigen selection pressure. The H chain complementarity determining region 2 (CDR2) sequence of T15 antibody was saturated with point mutations by in vitro random mutagenesis. From the mutant library, 289 clones were screened by direct DNA sequencing. The point mutations generated by this method were randomly distributed throughout the CDR2 region and included all kinds of substitutions. 46 unique mutant antibodies, containing one to four point mutations each, were expressed in SP2/0 myeloma cells. Functional analysis on these antibodies has provided insights into several aspects of somatic mutation. (a) The majority (26/46) of mutant antibodies either lost (20/46) or had reduced (6/46) ability to bind PC-protein conjugates or R36a, a PC-expressing strain of Streptococcus pneumoniae. In contrast, none of the mutant antibodies displayed increased binding for these PC antigens. Taken together with calculations of destructive mutations elsewhere in the V region, the data suggest that somatic mutation may cause extensive wastage among B cells during clonal expansion after antigen stimulation. (b) The frequency of binding-loss mutants increased sharply when a second mutation was introduced into the CDR2 sequence; it appears that, in some cases, two or more mutations are needed to destroy binding. (c) The mutant antibodies were tested for their reactivity to 11 non-PC antigens as well as to three PC analogues. None of the mutants gained new reactivity or changed their ability to discriminate structural analogues, supporting the notion that the major role of somatic mutation is to increase or decrease affinity rather than to create new specificities. (d) Mutations in at least five different positions in CDR2 were deleterious, suggesting that these residues may be essential for antigen binding. Three of these positions are novel in that they had not been identified to be important for binding PC by previous crystallographic analysis. (e) Introduction of mutations into two highly conserved residues in CDR2 did not alter the overall conformation of the V region as judged by antiidiotypic analysis, and, in some cases, did not affect the antigen binding function. The results thus indicate that even nonconservative substitutions of invariant residues need not be deleterious, suggesting that their conservation may be due to reasons other than maintaining antibody structure or specificity.

Amino Acid Sequence↗
PubMed1992

A two-dimensional YAC pooling strategy for library screening via STS and Alu-PCR methods.

We have developed a simple two-dimensional YAC pooling strategy to facilitate YAC library screening via STS and Alu-PCR approaches. The method has been implemented using the human total genomic YAC library of Olson and coworkers, and its validity tested by isolation of many chromosomes 19- and 21-specific YACs. The Alu-PCR approach is notable in that it is hybridization-based, such that PCR primer pairs do not need to be repeatedly synthesized and tested for each screening step.

Base Sequence↗