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Biomedical subjects

R Wang

Publications and source records attributed to R Wang.

At least 325 records · Page 18Linked to original sources
PubMed1999

[A study on formation of N-(nitrosomethyl) urea in experimental pig stomach gavaged with fish sauce].

OBJECTIVE: To study formation of N-(nitrosomethyl) urea (NMU), which is categorized as N-nitrosamides -- a sort of strong chemical carcinogen, by perfusion with fish sauce via pig stomach fistula, which is used daily as cooking flavor by local residents in Changle County, Fujian Province, a highly-prevalent area for gastric cancer. METHODS: Fistulization was performed in fasting experimental pigs' stomach, and their gastric juice was suctioned 30 minutes after perfusion with fish sauce and sodium nitrite via fistula. Gastric juice specimen was purified and concentrated and determined for NMU with high performance liquid chromatography-photolysis pyrolysis-thermal energy analyzer. RESULTS: NMU was detected in the pig stomach at pH 1 - 2, where NMU formed. Formation of NMU depended on the amount of nitrite added in a dose-dependent relationship. Level of NMU in gastric juice reached 25.4 and 7.97 micromol/L, respectively, when 3.48 and 0.87 mmol of sodium nitrite were fed into the stomach. No NMU could be detected, as 0.22 mmol of sodium nitrite fed. CONCLUSION: Under the condition of pH 1 - 2 and presence of sodium nitrite, NMU was synthesized in the stomachs of experimental pigs fed with fish sauce via gastric fistula. It is postulated that N-nitrosamides, such as NMU could be formed endogenously in the stomachs of local residents who consume fish sauce often and have a higher exposure to nitrite in their stomachs.

Animals↗
PubMed1999

[Application of in vitro micronucleus tests using L5178Y mouse lymphoma and WTK1 human lymphoblastoid cell lines to antimutagenicity assay].

In the in vitro micronucleus (MN) tests using L5178Y mouse lymphoma and WTK1 human lymphoblastoid cell lines, 2 well-known antimutagens, Vitamin C (Vc) and the sodium and copper salt of chlorophyll (Chl), were tested to evaluate their ability to inhibit the mutagenicity of mitomycin C(MMC). Three kinds of treatment were designed, namely the simultaneous treatment with Vc (or Chl) and MMC, the use of Vc (or Chl) before the use of MMC, and the use of Vc (or Chl) after the use of MMC. The results showed that Vc and Chl had no MN inductivity in the two cell lines; that simultaneous treatment with Vc and MMC and pre-treatment with Vc effectively reduced MMC-induced MN cell frequencies; and that simultaneous treatment and pre-treatment with Chl at dose level of 0.12 mg/ml, significantly reduced MMC-induced MN cell frequencies of L5178Y cells. The antimutagenic effect of Chl on WTK1 cells was found in simultaneous and pre-treatment at dose levels of 0.12 and 0.06 mg/ml.

Animals↗
PubMed1999

[High performance thin layer chromatographic (HPTLC) determination of PAF in cerebrospinal fluid of patients with subarachnoid hemorrhage(SAH)].

The Platelet Activating Factor (PAF) is believed to be the major function in human after cerebral vascular spasm and cerebral ischemia. PAF has been found to participate in cerebral vascular spasm and cerebral ischemia by the basic and clinical study. The symptom of cerebral vascular spasm and cerebral ischemia has appeared with SAH. It has not been reported that the rule and change of PAF with SAH. In the present work, the concentration of PAF in human cerebral spinal fluid (CSF) with SAH were determined by high performance layer thin chromatography. The TLC plate was coated with high performance silica gel G using V(chloroform):V(methanol):V(water) = 65:35:6 as developing solvent. The PAF was determined by TLC scanning method and detected at 630 nm. The method was applied to determine the concentration of PAF in 16 CSF samples with SAH. The samples were collected in 1-3 d, 7-10 d and 14-21 d. CSF samples were deproteinized with methanol and chloroform. After centrifugation, the chloroform layer separated was dried at room temperature with nitrogen and stored under 20 degrees C in the refrigerator. The linear range of the method was 0.5-2.5 micrograms/L with regression coefficient of 0.9990. The lower limit of detection were 50 ng/L. The recovery of the method was 98.6%. The method enables a simple, rapid and reproducible quantification of PAF with SAH.

Chromatography, High Pressure Liquid↗
PubMed1999

[Human motion analysis system based on common video-camera].

A new human motion analysis system based on common video-camera is introduced in this paper. The image processing technique is used to recognize and track anatomic landmarks, which makes data processing more quickly and accurately. The system is cost-effective and can be easily operated because the common video-cameras instead of special instruments are used. Furthermore, the system can also be used for detection and analysis of other low-speed moving objects.

Algorithms↗
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

[Fractal dimension analysis of the surface EMG].

Fractal analysis is a new method for biomedical signal processing. Present research on surface EMG and its parameterization method were introduced in this paper. Experiments were performed on three conditions: (1) different muscle contraction degree, (2) different static load, (3) different motion pattern. Problems and prospects in engineering application were also discussed here.

Adult↗
PubMed1999

[The problems and solutions of the leakage current checking in medical electrical equipments].

It is an important safety checking item to check leakage current of medical electric equipments. In the national standard, there are definite and strict stipulations for the leakage current-checking and the checkers. But this important checking is often misrepresented with general current measurements. So the checking is not up to the standard and the results are not dependable. In this paper, the special demands for the checking and the key technique of the checkers have been expounded in detail.

Electricity↗
PubMed1998

The Arabidopsis CHL1 protein plays a major role in high-affinity nitrate uptake.

The CHL1 (NRT1) gene of Arabidopsis encodes a nitrate-inducible nitrate transporter that is thought to be a component of the low-affinity (mechanism II) nitrate-uptake system in plants. A search was performed to find high-affinity (mechanism I) uptake mutants by using chlorate selections on plants containing Tag1 transposable elements. Chlorate-resistant mutants defective in high-affinity nitrate uptake were identified, and one had a Tag1 insertion in chl1, which was responsible for the phenotype. Further analysis showed that chl1 mutants have reduced high-affinity uptake in induced plants and are missing a saturable component of the constitutive, high-affinity uptake system in addition to reduced low-affinity uptake. The contribution of CHL1 to constitutive high-affinity uptake is higher when plants are grown at more acidic pH, conditions that increase the level of CHL1 mRNA. chl1 mutants show reduced membrane depolarization in root epidermal cells in response to low (250 microM) and high (10 mM) concentrations of nitrate. Low levels of nitrate (100 microM) induce a rapid increase in CHL1 mRNA. These results show that CHL1 is an important component of both the high-affinity and the low-affinity nitrate-uptake systems and indicate that CHL1 may be a dual-affinity nitrate transporter.

Anion Transport Proteins↗
PubMed1998

[Development of an in vitro model of culture using mouse fetal long bone].

An in vitro model of culture using mouse fetal long bone was firstly established using self-made turning-equipment. The bone formation, mineralization and resorption were observed simultaneously in cultured bone. It provided a useful model for investigating the relationship between bone, development and the effect of nutrients, toxicants and other factors.

Animals↗
PubMed1998

Adhesive and signaling properties of a naturally occurring allele of glycoprotein IIIa with an amino acid substitution within the ligand binding domain-the Pena/Penb platelet alloantigenic epitopes.

Platelet membrane glycoprotein IIIa (GPIIIa) is the most polymorphic integrin subunit in man, with at least seven recognized allelic isoforms present in the human gene pool. Whether these allelic variants of the GPIIb-IIIa complex differ in the ability to interact with the adhesive ligand fibrinogen (Fg) is still unknown. Since the Pena and Penb allelic forms of GPIIIa are distinguished by a single Arg143Gln amino acid substitution within the RGD binding domain of GPIIIa and anti-Pena human alloantibodies have been shown to bind GPIIb-IIIa on the platelet surface and inhibit ADP-induced platelet aggregation, we expressed both forms of this integrin in Chinese hamster ovary (CHO) cells and examined the relative adhesive properties. Both allelic forms of GPIIb-IIIa were expressed on the cell surface and were recognized by a well-characterized panel of murine and human monoclonal and polyclonal antibodies. Like Pena, the Penb form of GPIIb-IIIa could undergo conformational changes in response to RGD peptide binding, and could be induced by activating antibodies to bind Fg and the Fg mimetic antibody P1-55. The binding affinity for Fg of the Pena form of the GPIIb-IIIa complex was not significantly different from that of the Penb form, nor was its ability to signal to focal adhesion kinase, suggesting that Arg143Gln polymorphism has little or no effect on integrin function. Examination of the functional consequences of other integrin polymorphisms may be necessary to determine whether they constitute a risk factor for thrombosis or hemorrhage.

Alleles↗
PubMed1998

Induction of antigen-specific cytotoxic T lymphocytes in humans by a malaria DNA vaccine.

CD8+ cytotoxic T lymphocytes (CTLs) are critical for protection against intracellular pathogens but often have been difficult to induce by subunit vaccines in animals. DNA vaccines elicit protective CD8+ T cell responses. Malaria-naïve volunteers who were vaccinated with plasmid DNA encoding a malaria protein developed antigen-specific, genetically restricted, CD8+ T cell-dependent CTLs. Responses were directed against all 10 peptides tested and were restricted by six human lymphocyte antigen (HLA) class I alleles. This first demonstration in healthy naïve humans of the induction of CD8+ CTLs by DNA vaccines, including CTLs that were restricted by multiple HLA alleles in the same individual, provides a foundation for further human testing of this potentially revolutionary vaccine technology.

Adult↗
PubMed1998

Fungal metabolite FR901228 inhibits c-Myc and Fas ligand expression.

Activation of T lymphocytes often leads to cellular activation, production of cytokines, entry into cell cycle, and expression of Fas (CD95) and Fas ligand (FasL). Although it is well established that the interaction of Fas and FasL results in apoptosis, mechanisms for regulated expression of Fas and FasL are unclear. Our previous work with antisense oligodeoxynucleotides suggested that the protooncogene c-myc is obligatory for activation-induced apoptosis. To study the relationship between c-myc and the Fas/FasL expression, we employed the antisense method and a newly identified fungal metabolite, FR901228, which has been shown to specifically inhibit expression of c-myc in fibroblasts. We found that FR901228 could effectively block activation-induced apoptosis in T cell hybridomas and this was correlated with its specific inhibition of c-myc expression. Both FR901228 and antisense oligodeoxynucleotide to c-myc had similar effect in inhibiting FasL expression. These treatments did not affect activation-induced production of IL-2, nor the expression of Fas. In addition, FR901228 inhibited the expression of FasL in 3T3 fibroblasts, but not these transfected with c-myc, supporting a specific role of c-myc in this process. Thus, c-Myc plays a fundamental role in the regulation of the expression of FasL, but not Fas and IL-2. Our data further defined the requirement of c-Myc in activation-induced apoptosis in T cells.

3T3 Cells↗
PubMed1998

Identification of the gene (lgtG) encoding the lipooligosaccharide beta chain synthesizing glucosyl transferase from Neisseria gonorrhoeae.

The lipooligosaccharide from Neisseria gonorrhoeae (GC), consists of lipid A, an oligosaccharide core and three branches, alpha, beta, and gamma. We report the cloning of the gene (lgtG, lipooligosaccharide glycosyl transferase G) encoding the glucosyl transferase of GC that initiates the beta chain which consists of a lactosyl moiety. This gene contains a homopolymeric tract of cytidine [poly(C)] and we demonstrate that changes in the number of Cs in poly(C) account for the variation of beta chain expression in different GC strains. Biochemical analyses and mass spectrometry clearly attribute the reactivity of mAb 2C7 to the presence of the lactosyl beta chain. In addition, we demonstrate that in the absence of the lactosyl group, a phosphoethanolamine is added to generate a new antigenic epitope as evidenced by the gain of reactivity to mAb 2-L1-8. These results show that, like the alpha chain, the beta chain of lipooligosaccharide is subject to antigenic variation.

Antibodies, Monoclonal↗
PubMed1998

Protein kinase C regulates Fas (CD95/APO-1) expression.

Fas (CD95/APO-1) is a transmembrane protein of the TNF/neuron growth factor receptor family. Ligation of Fas by specific Abs or Fas ligand (FasL/CD95 ligand) induces rapid apoptotic cell death in a variety of cell types. Despite progress in understanding the death signals transduced from Fas, very little is known with regard to the mechanisms by which Fas expression is regulated. Using our previously established murine T cell hybridoma model A1.1, we show that specific protein kinase C (PKC) inhibitors could block activation-induced Fas expression and apoptosis. The activation of PKC with PMA or 1-oleoyl-2-acetyl-sn-glycerol could mimic the TCR signal by inducing the expression of Fas but not FasL. PKC-dependent Fas expression was also observed in several murine and human tumor cell lines. Since the inhibition of Ca2+ redistribution by an inhibitor of intracellular Ca2+ mobilization, 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride, inhibited TCR-induced FasL but not Fas, the expression of Fas appears to be independent of Ca2+ mobilization. Significantly, expression of the newly identified Fas-regulatory gene, TDAG51, was found to be dependent upon the activity of PKC. PKC activation only induced Fas expression in cells expressing wild-type TDAG51. Thus, Fas expression is likely mediated by PKC through TDAG51.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

Termination of peripheral tolerance to a T cell epitope by heteroclitic antigen analogues.

Treating mice with an immunodominant T cell epitope from moth cytochrome c (MCC(88-103)) can induce T cell unresponsiveness under certain conditions of administration. In this report, we determined whether T cell tolerance to MCC(88-103) in adult animals can be overcome by immunization with cross-reactive analogues of the tolerizing Ag. A panel of analogues of the tolerogen were tested for their capacity to terminate the tolerant state following in vivo immunization. As analyzed by their stimulatory capacity for a representative MCC(88-103)-specific T cell clone, this panel covered a wide range of cross-reactivity, including nonantigenic, antagonistic, weakly, and strongly antigenic peptides. Interestingly, only heteroclitic analogues, as measured in vitro by their enhanced antigenicity for the T cell clone that was specific for MCC(88-103), were capable of breaking tolerance. Thus, an immune response to the cross-reactive, heteroclitic analogues of tolerized self Ags may represent a mechanism by which Ag molecular mimicry operates.

Animals↗
PubMed1998

Structural homology between the Rap30 DNA-binding domain and linker histone H5: implications for preinitiation complex assembly.

The three-dimensional structure of the human Rap30 DNA-binding domain has been solved by multinuclear NMR spectroscopy. The structure of the globular domain is strikingly similar to that of linker histone H5 and its fold places Rap30 into the "winged" helix-turn-helix family of eukaryotic transcription factors. Although the domain interacts weakly with DNA, the binding surface was identified and shown to be consistent with the structure of the HNF-3/fork head-DNA complex. The architecture of the Rap30 DNA-binding domain has important implications for the function of Rap30 in the assembly of the preinitiation complex. In analogy to the function of linker histones in chromatin formation, the fold of the Rap30 DNA-binding domain suggests that its role in transcription initiation may be that of a condensation factor for preinitiation complex assembly. Functional similarity to linker histones may explain the dependence of Rap30 binding on the bent DNA environment induced by the TATA box-binding protein. Cryptic sequence identity and functional homology between the Rap30 DNA-binding domain and region 4 of Escherichia coli sigma70 may indicate that the sigma factors also possess a linker histone-like activity in the formation of a prokaryotic closed complex.

Base Sequence↗
PubMed1998

Identification and cloning of an orphan G protein-coupled receptor of the glycoprotein hormone receptor subfamily.

Mining of the EST database identified a human EST that was predicted to encode a novel member of the glycoprotein hormone receptor subfamily. Based on the sequence information, the full-length coding region of this gene was isolated and sequenced. This gene, designated HG38, is predicted to encode a polypeptide of 907 amino acid residues with a putative signal peptide sequence at its very N-terminus. HG38 is most closely related to members of the glycoprotein hormone receptor subfamily with approximately 35% overall identity at the protein sequence level. As with the glycoprotein hormone receptors, HG38 contains a long extracellular domain with a total of 16 leucine-rich repeats. Northern blot analysis showed that HG38 was expressed in skeletal muscle, placenta, spinal cord, and various regions of the brain. Radiation hybrid mapping placed HG38 into human chromosome 12q22-23. HG38 is most likely to be a receptor for a novel class of glycoprotein ligands.

Amino Acid Sequence↗