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Biomedical subjects

X Shi

Publications and source records attributed to X Shi.

At least 163 records · Page 9Linked to original sources
PubMed2000

Changes in bronchoalveolar lavage indices associated with radiographic classification in coal miners.

Previous studies on symptomatic coal miners have shown that alveolar macrophages, recovered by bronchoalveolar lavage (BAL), release excessive amounts of reactive oxygen species (ROS) and inflammatory cytokines. It has been proposed that these secretions may mediate cell injury and initiate the disease process. We hypothesized that acellular bronchoalveolar lavage fluid (BALF) indices in coal miners chronically exposed to coal dust may reflect the status of important homeostatic modulations in the lung that lead to the development of coal workers' pneumoconiosis (CWP). To test this hypothesis, we measured inflammatory status, oxidant burden, antioxidant defenses, cytokines, growth factors, fibronectin, and alpha(1)-antitrypsin (alpha(1)-AT) in the BALF of healthy never-smoker control subjects, never-smoker underground coal miners with negative radiographs (ILO 0/0-1/0), and two miners with moderate changes in the chest radiographs (ILO 2/2). Interestingly, indices of injury and inflammation increased with the progression of disease in coal miners. Antioxidant enzymes, such as catalase, glutathione peroxidase, and superoxide dismutase, showed a 19-fold, 22-fold, and 6-fold increase above control, respectively, in coal miners with category 2/2 CWP. Significant increases in the secretion of IL-1, IL-6, TNF-alpha, TGF-beta, fibronectin, and alpha(1)-AT also were evident in coal miners with disease. This up-regulation of antioxidant defenses and cytokines was not evident in coal miners in the absence of clinically evident radiographic disease. In addition, the concentration of lipid peroxidation by products in the BALF of coal miners without evidence of radiographic disease showed a moderate 3-fold increase, whereas, in coal miners with category 2/2 CWP it showed a 59-fold increase compared to control subjects. These results are in good agreement with our hypothesis that development of CWP and its progression may be correlated with an oxidative stress and up-regulation of cytokines and mediators of growth.

Adult↗
PubMed2000

Design of a novel membrane-destabilizing peptide selectively acting on acidic liposomes.

The design of amphipathic peptides resulted in a novel peptide with a selective ability to destabilize lipid bilayers of acidic liposomes. The newly synthesized peptide, termed mast 21, is a 21-residue long amino acid chain and can only act effectively on acidic liposomes lacking cholesterol. Moreover, mast 21 killed gram-positive and gram-negative bacteria, and it had no hemolytic activity. The antimicrobial and hemolytic activities paralleled the results of membrane destabilizing activity using liposomes. Circular dichroism and Trp-fluorescence emission spectra showed changes in the peptide conformation and circumstances around the peptide during interaction with liposomes. These changes were consistent with an increased alpha-helical content and a less polar environment for the tryptophan residue of the peptide. Mast 21 was observed under dark-field microscopy in real time attacking liposomes. Acidic liposomes were attacked, which resulted in peeling of the lipid bilayer with its subsequent destruction.

Amino Acid Sequence↗
PubMed2000

Genetic heterogeneity of Pneumocystis carinii from rats of several regions and strains.

Pneumocystis carinii is a major opportunistic pathogen which has been found in the lungs of a wide variety of mammalian host species, and the fact suggests the possibility of intraspecific variation. Until now, P. carinii from different mammalian species are differentiated as subspecies, and the rats are known to be infected by two subspecies. The present study investigated genetic heterogeneity of P. carinii isolates from two strains of rats in Korea and China by molecular karyotyping, RFLP and sequencing analysis. Karyotypes of P. carinii were grouped into three, two from two strains of rats in Korea and one from rats in China. However RFLP of PCR product of ribosomal and MSG gene of the P. carinii isolates showed same pattern. The sequence homology rates of alpha-tubulin DNA of the P. carinii isolates were 96% in Seoul Wistar rats, 93% in Seoul Sprague-Dawley rats, and 85% in Chinese Sprague-Dawley rats. The present finding confirmed that P. carinii from rats in Korea are grouped into two karyotype strains which are different from that of P. carinii from rats in China. The Chinese isolate shows a little different sequences of alpha-tubulin DNA.

Animals↗
PubMed2000

On the role of hydroxyl radical and the effect of tetrandrine on nuclear factor--kappaB activation by phorbol 12-myristate 13-acetate.

Nuclear factor kappaB (NF-kappaB) is considered to be an important target for therapeutic intervention because of its role in the regulation of proinflammatory and profibrotic mediators. The present study examined the role of hydroxyl (*OH) radical and the effect of tetrandrine, an alkaloid extracted from the Chinese medicinal herb Stephania tetrandra, on NF-kappaB activation by a tumor promoter, phorbol 12-myristate 13-acetate (PMA) in human lymphoid T cells (ie, Jurkat cells). Exogenous superoxide dismutase (SOD) enhanced the NF-kappaB activation by PMA, while catalase blocked it. Formate, a scavenger of *OH radical, also was inhibitory, as was deferoxamine, a metal chelator. These data suggest an important role of *OH radical in PMA-induced NF-kappaB activation. Incubation of the cells with tetrandrine prior to the stimulation of the cells was found to inhibit PMA-induced NF-kappaB activation. Tetrandrine activity was so potent that 50 microM of tetrandrine was sufficient to inhibit activation of NF-kappaB completely. Electron spin resonance (ESR) spin trapping was used to investigate the antioxidant action of tetrandrine using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trap. Tetrandrine is an antioxidant for both *OH and superoxide (O2-)radicals. The reaction rate constant of tetrandrine with *OH is 1.4 x 10(10) M(-1)sec(-1), which is comparable with several well established antioxidants, such as ascorbate, glutathione, and cysteine. The Fenton reaction (Fe(II) + H2O2-->Fe(III) + *OH + OH-) and xanthine/xanthine oxidase were used as sources of *OH and O2- radicals. The free radical scavenging activity of tetrandrine is responsible for its inhibition of PMA-induced NF-kappaB activation.

Alkaloids↗
PubMed2000

[Construction of prokaryotic expression vector of hALR and its expression in E.Coli].

OBJECTIVE: To construct prokaryotic expression vector of hALR and express rhALR in E.Coli. through PCR and recombinant gene technology. METHODS: The coding region with Nde I and BamH I sites of hALR was obtained from pUC19-hALR constructed with PCR method. PCR product and plasmid pET11a were digested by corresponding endonucleases, respectively. The fragments cut were ligated by T(4) DNA ligase to gain recombinant expression vector. The recombinant plasmid pET11a-hALR was electrotransformed into BL(21) (DE(3)) strain. The rhALR was expressed in the bacteria under induction of IPTG. RESULTS: Endonucleases digesting and DNA sequening confirmed that the coding region of hALR was correctly inserted into the vector. The rhALR was successfully expressed in E.Coli. Its MW. With 1. 5A10(4) was in correspondence with theoretic value and its amount is 30% of total bacteria protein. It existed not only in supernatant but also in precipitation of broken bacteria. CONCLUSION: The successes in construction of expressive vector of hALR and in expression of rhALR in E.Coli. make it possible to study further on its biological functions and antibody preparation.

Cloning, Molecular↗
PubMed2000

Antioxidant properties of pyrrolidine dithiocarbamate and its protection against Cr(VI)-induced DNA strand breakage.

Pyrrolidine dithiocarbamate (PDTC) is considered an antioxidant and is frequently used to study the role of free radical reactions in various biological processes and against free radical-induced cellular injuries. However, its antioxidant properties are not characterized. In this study, electron spin resonance (ESR) was used to investigate the antioxidant potential of PDTC with hydroxyl radical (*OH) and superoxide anion radicals (O2*-). The Fenton reaction [Fe(II) + H2O2 --> Fe(II) + *OH + OH-)] and xanthine and xanthine oxidase were used as sources of *OH and O2*- radicals, respectively. The results show that PDTC effectively scavenges *OH radicals with a reaction rate constant of approximately 2.73 x 10(10) M(-1) s(-1), which is comparable to other efficient *OH radical scavengers, such as ascorbate and glutathione. PDTC is also able to scavenge O2*- radicals. Through its antioxidant properties, PDTC protects against Cr(VI)-induced DNA strand breakage.

Antioxidants↗
PubMed2000

[Improved liposome encapsulated hemoglobin by electret technology and its influence on the blood rheologic behavior in vitro].

To study the influence of different electret properties of Liposome Encapsulated Hemoglobin(LEH) on the blood rheologic behavior in vitro, four kinds of LEH have been prepared. Their electret properties have been determined by using Thermally Stimulated Depolarization Current(TSDC). The results show that 4# LEH, whose Ta is 12 degrees C and Ia is -5.6 x 10(-9) A, has the best electret property, furthermore, the results of the thrombus formation in vitro also show that the addition of 4# LEH induces the lightest thrombus figuration in vitro. It is obvious that the rational improvement of the electret property of LEH can meliorate the surface charge of blood and effectively inhibit the formation of thrombus.

Blood Viscosity↗
PubMed2000

Anti-HBV effect of targeted antisense RNA against HBV C gene.

OBJECTIVE: To investigate the anti-HBV effect of targeted antisense RNA to hepatic cells. METHODS: pREP4-aC which would transcript antisense RNA against HBV C gene in eukaryotic cells were delivered into 2.2.15 cells by glactosylated poly-L-lisine (Gal-PLL), and the positive cells were selected. HBsAg, HBeAg and HBV DNA produced by 2. 2.15 cells were detected with ELISA or Southern blot during the experiment, and the cytotoxicity of targeted antisense on 2.2.15 cells was observed. RESULTS: The inhibition effect on HBsAg, HBeAg and HBV DNA occurred at the 24th hour after delivery and reached the highest level at the 6th day, and kept at lest two months. No cytotoxicity on 2.2.15 cells was observed. CONCLUSION: The targeted antisense against HBV C gene by delivery of Gal-PLL could effectively inhibit the antigen expression of HBV and DNA replication.

Antiviral Agents↗
PubMed2000

Role of molecular oxygen in the generation of hydroxyl and superoxide anion radicals during enzymatic Cr(VI) reduction and its implication to Cr(VI)-induced carcinogenesis.

Electron spin resonance (ESR) spin trapping measurements provide evidence for the generation of hydroxyl radicals (*OH) in the reduction of Cr(VI) by glutathione reductase (GSSG-R) in the presence of NADPH as a cofactor. Catalase inhibited the *OH generation, while the addition of H2O2 enhanced it, indicating that the *OH radical generation involves a Fenton-like reaction. The metal chelator, deferoxamine, inhibited the *OH generation with a concomitant generation of a deferoxamine nitroxide radical. EDTA and 1,10-phenanthroline also inhibited the *OH generation. Experiments performed under argon atmosphere decreased the yield of the *OH formation, showing that molecular oxygen plays a critical role. ESR spin trapping and measurements of fluorescence change of scopoletin in the presence of horseradish peroxidase show that reduction of Cr(VI) by GSSG-R/NADPH generates superoxide anion radicals (O2*-) as well as H2O2. It can be concluded that *OH radical is generated by the reaction of H2O2 with Cr(V), which is produced by enzymatic one-electron reduction of Cr(VI). H2O2 is produced by the reduction of molecular oxygen via O2*- as an intermediate. The *OH radicals generated by these reactions are capable of causing DNA strand breaks, which can be inhibited by catalase, formate, and experiments performed under argon.

Carcinogenicity Tests↗
PubMed2000

Predisposing factors in occupational lung cancer: inorganic minerals and chromium.

Reactive oxygen species (ROS) have been implicated in the pathogenesis of cancer. Inhalation of inorganic minerals such as asbestos and crystalline silica, and metals such as arsenic, beryllium, chromium, nickel, and vanadium, may promote directly and indirectly enhanced generation of ROS at a persistent level in concert with chronic inflammation. Perpetual ROS generation can cause specific molecular changes resulting in the activation or inactivation of transcription factors that may alter gene expression leading to cell proliferation, differentiation, and carcinogenesis. The mechanisms involved in the signal transduction leading to these processes are the subject of intense investigation. In this review, some of the recent findings from our laboratories concerning key molecular events elicited by asbestos, crystalline silica, and chromium are presented. These include genotoxicity, DNA damage, lipid peroxidation, activation of transcription factors activator protein-1 (AP-1) or nuclear factor kappa B (NF-kappaB), and p53 or k-ras gene alterations. From these studies, it is evident that ROS signaling is critical for the responses of cytokines, growth factors, and activation or inactivation of transcription factors that promote carcinogenesis.

Asbestos↗
PubMed2000

Participation of MAP kinase p38 and IkappaB kinase in chromium (VI)-induced NF-kappaB and AP-1 activation.

Epidemiological studies demonstrate that environmental and occupational exposure of chromium(VI) [Cr(VI)] or Cr(VI)-containing particles can cause a number of human diseases, including inflammation and cancer. The biological mechanisms responsible for the initiation and progression of diseases resulting from exposure to Cr(VI) are not fully understood. The present studies evaluated the ability of Cr(IV) to induce activation of NF-kappaB and AP-1, two important transcription factors governing the expression of many early response genes involved in inflammation and carcinogenesis. The activation of NF-kappaB and AP-1 by Cr(IV) was dose dependent. Aspirin, a well-established antioxidant, substantially inhibited Cr(VI)-induced activation of both NF-kappaB and AP-1. SB202190, a specific inhibitor for p38, attenuated AP-1 activation induced by Cr(IV), whereas PD98059, a specific inhibitor for Erk, exhibited no effect on Cr(IV)-induced AP-1 activation. Blockage of NF-kappaB signaling pathway by a transient transfection of a dominant negative expressing vector for IkappaB kinase beta resulted in inhibition of Cr(IV)-induced NF-kappaB, but not AP-1 activation. These data suggest that the activation of AP-1 or NF-kappaB by Cr(IV) is through the involvement of MAP kinase or IKK pathway, respectively.

Animals↗
PubMed2000

Activation of androgen response element by cadmium: a potential mechanism for a carcinogenic effect of cadmium in the prostate.

Cadmium is a transition metal that has been widely used in industry. Epidemiological and animal studies have demonstrated a carcinogenic effect of cadmium on the prostate. Although it has been established that androgen is required for this cancer-inducing process, it is not clear how cadmium interacts with androgen. In this study, the carcinogenic mechanism of cadmium was explored with a focus on interaction of androgen and cadmium at the gene transcription level. An androgen response luciferase reporter was used for analysis of the cadmium activity in the transient transfection assay. Human prostate epithelial cells (LNCap) and liver cells (HepG2) were transfected by the reporter. The result showed that cadmium was able to activate the reporter in the absence of androgen, and that this activation was dependent on the presence of androgen receptor. Cadmium could enhance the androgen response when both androgen and cadmium were applied together to the reporter-transfected cells. Activation of the reporter by cadmium was not associated with cell proliferation or interleukin 6 (IL-6) production, which was proposed to be involved in cadmium-induced carcinogenesis in other experimental systems. Cadmium exhibited a weak ability to induce AP-1. The results demonstrate that cadmium has an androgen-like activity in prostate epithelial cells, and this activity implies a new mechanism for the carcinogenic effect of cadmium in the prostate.

Androgens↗
PubMed2000

[Recognition of multiple information of human auricular points by linear model].

The three variables of the electric characteristic of human auricular points can be regarded as observed targets that reflect the physiologic or pathologic changes. Medical principle design follows the theory of the channels and collaterals and the viscera-state doctrine of traditional Chinese medicine and that of the pattern recognition. The linear integration model can be established by drawing the characteristic variables of the correlation groups of the auricular points and applying the multi-variable normalization. With this model, the recognition of the three variations of the auricular points can be of use for differential diagnosis. In this paper, the test to identify the cases of Upper-Digestive tract achieves good result. This research, based on the integration of modern science with traditional Chinese medicine, provides a method for building the specialist system of the auricular point diagnosis, and probably has some prospect in clinical application.

Acupuncture Points↗
PubMed2000

Laboratory interproximal access efficacy of two toothbrushes with cross-angulated bristling.

Interproximal access efficacy (IAE) has been evaluated in a laboratory method using pressure-sensitive paper placed around simulated anterior and posterior teeth, using horizontal or vertical brushing motions. The two toothbrushes evaluated in this study were the Oral-B Cross Action Medium 40 and the Dr. Best X-Activ Mittel. Twenty-four tests on each toothbrush design were conducted, and results were statistically analyzed using ANOVA. In all of the individual evaluations, using either vertical or horizontal brushing motions on either anterior or posterior simulated teeth, the Dr. Best X-Activ Mittel toothbrush was significantly (p < 0.001) more effective than the Oral-B Cross Action Medium 40 in achieving IAE. When individual IAE data from the vertical, horizontal, anterior and posterior assessments were combined to assess overall IAE, the Dr. Best X-Activ Mittel toothbrush had a significantly (p < 0.001) higher mean value than the Oral-B Cross Action Medium 40 mean value.

Equipment Design↗
PubMed2000

Laboratory evaluation of two bi-level toothbrush products for subgingival access and gingival margin cleaning.

Recent technological advances have enabled the production of split or feathered endings of individual toothbrush filaments. The purpose of this laboratory study was to compare a bi-level manual toothbrush containing standard end-rounded bristles with the same shaped toothbrush containing feathered filaments, 3 mm deep, on the outer raised bi-level rows to achieve subgingival access (SA) and remove artificial plaque at the gingival margin, or gingival margin cleaning (GMC). Simulated gingivae were prepared with a 0.2 mm space between the gingivae and tooth surface. The toothbrushes were aligned with the papillae at the gingival margin, and were tested using wet brushing conditions for 60 seconds at two strokes per second with a 15 mm stroke. Four toothbrushes of each type were evaluated four times, for a total of 16 assays per design. The SA maximum depth was recorded on pressure-sensitive paper under the simulated gingivae, and the length of gingival margin cleaning was recorded as the GMC efficacy. Readings were performed with 3x magnification by one investigator. In these laboratory assays, the bi-level toothbrush with feathered outer-row bristles significantly (p < 0.001) increased the ability of the bristles to achieve SA by 35.7% and GMC efficacy by 54.5% compared to an identical bi-level toothbrush with end-rounded bristles.

Dental Plaque↗
PubMed2000

The relationship between Th1/Th2-type cells and disease activity in patients with systemic lupus erythematosus.

OBJECTIVE: To investigate the imbalance of Th1/Th2-type cytokines in patients with systemic lupus erythematosus (SLE) and its relation to disease activity. METHODS: Intracellular cytokines were determined by flow-cytometry following whole-blood culture. RESULTS: Patients with systemic lupus erythematosus disease activity index (SLEDAI) > 10 had statistically significantly fewer CD4+ or CD8+ T cells producing IFN-gamma than patients with SLEDAI = 0, SLEDAI 1-10 or healthy controls (P < 0.01, P < 0.01 or P < 0.05, respectively). Patients with SLEDAI > 10 also had decreased ratio of IFN-gamma/IL-4 positive CD4+ or CD8+ T cells, compared with patients with SLEDAI = 0, SLEDAI 1-10 or healthy controls (P < 0.05). The decreased Th1 or Tc1 cells and the ratios of IFN-gamma: IL-4 positive CD4+ T-cells were significantly correlated with disease activity (P < 0.05). CONCLUSION: SLE is characterized by an imbalance of Th1/Th2 and Tc1/Tc2 cytokines. The decreased Th1 or Tc1 cells and the Th1/Th2 ratio are related to disease activity.

Adult↗