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Biomedical subjects

S Chen

Publications and source records attributed to S Chen.

At least 649 records · Page 36Linked to original sources
PubMed1999

[Studies on detection of Plasmodium falciparum and Plasmodium vivax in blood samples by multiplex polymerase chain reaction].

AIM: To establish a sensitive and specific PCR-based method to detect Plasmodium falciparum and P. vivax in blood samples in a single amplification reaction. METHODS: Malaria parasite DNA in blood was amplified by the multiplex polymerase chain reaction using two sets of primers derived from the P. f. moderately-repetitive DNA sequence and COIII gene of P.v. RESULTS: A 206-bp product for P. f. and a 370-bp product for P.v. were amplified by multiplex PCR, being able to detect parasitemia level as low as 5 x 10(-7) for P. f. and 1.02 x 10(-6) for P. v. and having no cross-reaction with human leucocyte DNA. A total of 783 blood samples on the filter paper collected from patients attending to malaria clinics in malaria endemic areas were detected. The positive rate of multiplex PCR was 85.8%, the misdiagnosis rate was 0, and the under-diagnosis rate was 0.1%, while these three rates of microscopic examination were 84.9%, 3.1% and 1.0%, respectively. The concordance between the two methods was 95.8%. CONCLUSION: The multiplex PCR method made the malaria detection more sensitive and specific than the microscopic examination and should be suitable for the diagnosis of malaria in mixed endemic areas, large-scale epidemiological studies, follow-up of drug treatment and donor blood screening.

Animals↗
PubMed1999

[Expression and identification of recombinant 22.6 kDa fusion protein of Schistosoma japonicum].

AIM: To obtain a large amount of purified 22.6 kDa antigen of Schistosoma japonicum (Sj22.6) in large quantity. METHODS: The sequence of the gene fragment encoding Sj22.6 was reformed by PCR and subcloned into plasmid vector pGEX-1 lambda T that coded for the 26 kDa GST antigen of Schistosoma japonicum (Sj26 GST). The recombinant plasmid was transformed into E. coli TG2 and then the positive recombinant clone was expressed by induction with IPTG. RESULTS: The recombinant Sj22.6/Sj26 GST fusion protein was expressed in 5.1% of total bacterial protein and was easy to be purified with glutathione sepharose 4B. Moreover, the purified recombinant Sj22.6 antigen could be cut off easily from the fusion protein with thrombin and had high immunogenicity. CONCLUSION: The purified recombinant Sj22.6 protein and Sj22.6/Sj26 GST fusion protein had the same immunological activity as the native Sj22.6 kDa protein.

Animals↗
PubMed1999

[Studies on immunoprotection in mice after immunization with Schistosoma japonicum 22.6 kDa recombinant protein].

AIM: To evaluate the immunoprotective effect of Schistosoma japonicum recombinant 22.6 kDa (rSj22.6) and Sj22.6/Sj26 GST fusion protein. METHODS: The Sj22.6/Sj26 GST fusion protein was prepared by affinity chromatography using glutathione Sepharose 4B. The purified rSj22.6 could be cleaved easily from the fusion protein with Thrombin. 17 and 12 mice immunized with rSj22.6 and Sj22.6/Sj26 GST separately were each challenged with 40 +/- 1 S. japonicum cercariae. RESULTS: In BALB/c mice, the rSj22.6 and Sj22.6/Sj26 GST could induce 32.1 (P < 0.005) and 34.9% (P < 0.02) worm reduction, respectively, as well as 28.4% (P < 0.02) and 45.1% (P < 0.005) total egg reduction, respectively. CONCLUSION: Bpth rSj22.6 and Sj22.6/Sj26 GST fusion protein are partially effective against S. japonicum.

Animals↗
PubMed1999

[Variations of the middle meatus mucosa ultrastructure after endoscopic sinus surgery].

OBJECTIVE: To explore the variations of middle meatus ultrastructure after endoscopic sinus surgery. METHOD: 10 cases whose middle meatus mucosa recovered well after undergoing endoscopic sinus surgery were screened, and postoperative electron microscope examinations of middle meatus mucosa were made in the first, second, third and forth month. RESULT: In the first month after operation, there was obvious fibre proliferation in the mucosa. In the second month, there was fibre proliferation and dissolution existing simultaneously. In the third month, the mucosa's structure resumed fundamentally to normal, but its function was not perfect. In the forth month, the mucosa was completely normal and can function normally. CONCLUSION: The mucosa of middle meatus can resume completely after endoscopic sinus surgery but need at least four months. It is very important to have a long time reexamination for improving therapeutic effect.

Adult↗
PubMed1999

[Determination of trace arsenic using GFAAS with metal-coated graphite tube].

The sensitivity, precision and disturbance-resisting property were studied by using metal-coated graphite tube for electrically heated atomic absorption spectrometry. The surface characteristic of the metal-coated graphite tube was studied by using X-ray diffraction meter and scanning electron microscope. The mechanism of satisfactory performance was discussed.

Arsenic↗
PubMed1999

[Determination and analysis of physical factors affecting insulin fluorescent spectrum].

Insulin is an important factor which regulates cell metabolism and growth. The influences on insulin fluorescent spectrum by pulse electrical field, concentration and temperature were determined in this paper. It was proved that pulse electrical field, concentration and temperature could influence insulin fluorescent spectrum, and thus influence insulin confirmation and insulin biological activity. The mechanism of insulin influenced by pulse electrical field is different to temperature. It is possible that the electrical field influences the insulin fluorescent spectrum by changing Tyr position and the temperature influences the insulin fluorescent spectrum by molecule thermal motion. The insulin confirmation influenced by electrical field is steady.

Fluorescence↗
PubMed1999

[Raman spectra of complexes of rare earth nitrate with histidine].

Raman spectra of solid complexes RE(His)(NO3)3 x H2O (RE = La-Nd, Sm-Lu, Y; His = L-alpha-histidine ) have been investigated. The results indicate that RE3+ coordinates with one O atome of carboxyl group in the complex, while amino group and imidazole ring do not take part in coordination and NO3 is double coordination. The vibration peaks of carboxyl group delta(v)COO-(as-s) were plotted against the atomic number of the lanthanoids, which obeys Oddo-Harkins law.

Histidine↗
PubMed1999

The use of rectus abdominis sheath for wrapping of the hydroxyapatite orbital implants.

Because of the decreasing availability of whole eye donation, the source of banked sclera is becoming less available. We used autogenous Rectus abdominis sheath (RAS) as an alternative to banked sclera in wrapping the hydroxyapatite (HA)orbital implant. Five anophthalmic patients were included in this study from July 1994 to December 1997. Identical surgical methods were used in every case. The average follow-up time was 18.4 months. The motility associated with sheath-wrapped HA implants was excellent and good vascular ingrowth was found in each patient during peg drilling. The complications are minimal in all the cases. Use of RAS as wrapping material for HA orbital implant has promising results. The RAS served as a practical substitute for banked donor sclera.

Abdominal Muscles↗
PubMed1998

Hop as an adaptor in the heat shock protein 70 (Hsp70) and hsp90 chaperone machinery.

Hop, an abundant and conserved protein of unresolved function, binds concomitantly with heat shock protein 70 (Hsp70) and Hsp90, participates with heat shock proteins at an intermediate stage of progesterone receptor assembly, and is required for efficient assembly of mature receptor complexes in vitro. A largely untested hypothesis is that Hop functions as an adaptor that targets Hsp90- to Hsp70-substrate complexes; if true, then loss of either Hsp70 binding or Hsp90 binding by Hop should equally disrupt its ability to promote assembly of mature receptor complexes. To generate Hop mutants that selectively disrupt heat shock protein interactions, highly conserved amino acids in the previously mapped Hsp70 and Hsp90 binding domains of Hop and in a conserved C-terminal domain were targeted for small substitutions and deletions. In co-precipitation assays, these mutants displayed selective loss of association with heat shock proteins. In assays using Hop-depleted rabbit reticulocyte lysate for the cell-free assembly of receptor complexes, none of the Hop mutants inhibited Hsp70 binding to receptor, but all mutants were defective in supporting Hsp90-receptor interactions. Thus, Hop has a novel role in the chaperone machinery as an adaptor that can integrate Hsp70 and Hsp90 interactions.

Amino Acid Sequence↗
PubMed1998

Opposite roles of apolipoprotein E in normal brains and in Alzheimer's disease.

We have characterized the interaction between apolipoprotein E (apoE) and amyloid beta peptide (Abeta) in the soluble fraction of the cerebral cortex of Alzheimer's disease (AD) and control subjects. Western blot analysis with specific antibodies identified in both groups a complex composed of the full-length apoE and Abeta peptides ending at residues 40 and 42. The apoE-Abeta soluble aggregate is less stable in AD brains than in controls, when treated with the anionic detergent SDS. The complex is present in significantly higher quantity in control than in AD brains, whereas in the insoluble fraction an inverse correlation has previously been reported. Moreover, in the AD subjects the Abeta bound to apoE is more sensitive to protease digestion than is the unbound Abeta. Taken together, our results indicate that in normal brains apoE efficiently binds and sequesters Abeta, preventing its aggregation. In AD, the impaired apoE-Abeta binding leads to the critical accumulation of Abeta, facilitating plaque formation.

Alzheimer Disease↗
PubMed1998

Modulation of aromatase expression in the breast tissue by ERR alpha-1 orphan receptor.

We have previously identified a silencer element (S1) that is situated between promoters I.3 and II of the human aromatase gene and that down-regulates the action of these promoters. We recently applied the yeast one-hybrid approach to screen a human breast tissue hybrid cDNA expression library for genes encoding the proteins binding to the silencer region. Most proteins identified from this approach belong to the nuclear receptor superfamily. Fifty % of the positive clones encode for ERR alpha-1, and other positive clones include EAR-2, EAR-3 (COUP-TF1), RAR gamma, and p120E4F. Because ERR alpha-1 was found to be the major protein interacting with S1, we decided to examine the regulatory action of ERR alpha-1 on promoter I.3 of the human aromatase gene. Using a reporter plasmid that includes the aromatase genomic fragment containing promoter I.3 and S1, ERR alpha-1 was found to have a positive regulatory function in breast cancer SK-BR-3 cells. Gel mobility shift assays have confirmed that ERR alpha-1 binds to S1 in a dose-dependent manner, and DNase I footprinting analysis has revealed that ERR alpha-1 binds to a region, 5'-AAGGTCAGAAAT-3', which is within S1 and between 96 and 107 bp relative to the transcriptional start site of promoter I.3. In addition, despite the fact that the nuclear receptor SF1 was shown previously to bind to the same site and to mediate a cAMP response in ovary, our yeast one-hybrid screening did not find any SF-1 clones. Gel mobility shift assays further revealed that SF-1 can bind to the silencer element with an affinity comparable with ERR alpha-1. Because our reverse transcription-PCR analysis was not able to detect SF1 mRNA in breast cancer tissue or in SK-BR-3 cells, it is thought that SF1 protein is not expressed in breast cancer tissue. Two ERR alpha-1 RNA variants with differences at the 5'-end have been reported. Our reverse transcription-PCR analysis identified the shorter variant in 28 of 32 breast tumor specimens and the longer variant in only 1 specimen. In addition, the shorter variant was detected in breast cancer SK-BR-3 cells as well as in a breast tumor fibroblast line WS3TF. The results suggest that ERR alpha-1 is one of the nuclear proteins interacting with S1 in breast cancer tissue. It is thought that the silencer element in the human aromatase gene may function differently in different tissues because of distinct expression patterns of transcription factors.

Aromatase↗
PubMed1998

Diva, a Bcl-2 homologue that binds directly to Apaf-1 and induces BH3-independent cell death.

We have identified and characterized Diva, which is a novel regulator of apoptosis. Sequence analysis revealed that Diva is a member of the Bcl-2 family of proteins containing Bcl-2 homology domain 1, 2, 3, and 4 (BH1, BH2, BH3, and BH4) regions and a carboxyl-terminal hydrophobic domain. The expression of Diva mRNA was detected in multiple embryonic tissues but was restricted to the ovary and testis in adult mice. The expression of Diva promoted the death of 293T, Ramsey, and T47D cells as well as that of primary sensory neurons, indicating that Diva is a proapoptotic protein. Significantly, Diva lacks critical residues in the conserved BH3 region that mediate the interaction between BH3-containing proapoptotic Bcl-2 homologues and their prosurvival binding partners. Consistent with this, Diva did not bind to cellular Bcl-2 family members including Bcl-2, Bcl-XL, Bcl-w, Mcl-1, and A1/Bfl-1. Furthermore, mutants of Diva lacking the BH3 region fully retained their proapoptotic activity, confirming that Diva promotes apoptosis in a BH3-independent manner. Significantly, Diva interacted with a viral Bcl-2 homologue (vBcl-2) encoded by the Kaposi's sarcoma-associated herpesvirus. Consistent with these associations, apoptosis induced by Diva was inhibited by vBcl-2 but not by Bcl-XL. Importantly, Diva interacted with Apaf-1, an adapter molecule that activates caspase-9, a central death protease of the apoptotic pathway. The expression of Diva inhibited the binding of Bcl-XL to Apaf-1, as determined by immunoprecipitation assays. Thus, Diva represents a novel type of proapoptotic Bcl-2 homologue that promotes apoptosis independently of the BH3 region through direct binding to Apaf-1, thus preventing Bcl-XL from binding to the caspase-9 regulator Apaf-1.

Amino Acid Sequence↗
PubMed1998

A specific RNA-protein interaction at yeast polyadenylation efficiency elements.

The specific RNA-protein interactions responsible for the production of mature 3' ends of eukaryotic mRNAs are not well understood. Sequence elements at the 3' ends of yeast genes have been identified that specify the position of the poly(A) site and the efficiency of polyadenylation. To provide additional insights into the interaction between important sequences that direct 3'-end formation in vivo and nuclear proteins, we utilized gel mobility shift assays and UV-crosslinking studies. The data indicate that a protein, with an apparent molecular weight of 80 kDa, interacts specifically with pre-mRNA at the (UA)3efficiency element. Although the interaction is specific, it can be competed by RNA sequences that do not contain the same type of efficiency element; that is, a sequence lacking a (UA)3repeat. This result implies that the protein binding site is flexible. Using immunoprecipitation techniques, the protein has been identified as Hrp1, a heteronuclear RNA binding protein. The role of Hrp1p in 3'-end formation including RNA processing and transcription termination is addressed.

Adenosine Triphosphatases↗