Biomedical subjects

Dai-Qing Li

Publications and source records attributed to Dai-Qing Li.

6 recordsLinked to original sources

PubMed2005

Characterization of the PCR inhibitory effect of bile to optimize real-time PCR detection of Helicobacter species.

The inhibitory effect of human and porcine bile samples to detect Helicobacter DNA was studied by adding different concentrations of bile samples to PCR mixtures of six thermostable DNA polymerases containing cagA specific primers and Helicobacter pylori DNA. PCR products were amplified by using the Rotorgene system and SYBR Green I. Among the six DNA polymerases tested, rTth had the lowest sensitivity to bile inhibitors, whereas Taq and Tfl had the highest sensitivity. Bile proteins did not inhibit AmpliTaq DNA polymerase, whereas the fraction containing mainly bile acids and their salts inhibited the amplification capacity of AmpliTaq. Heating human bile at 98 degrees C and adding casein and formamide to the reaction mixture reduced the PCR inhibitory effect of bile. Therefore, a pre-PCR treatment based on dilution and heating of bile, adding casein and formamide to the reaction mixture of rTth DNA polymerase was found efficient to amplify DNA directly in bile.

Animals↗

PubMed2005

CaV2.3 calcium channels control second-phase insulin release.

Concerted activation of different voltage-gated Ca( (2+) ) channel isoforms may determine the kinetics of insulin release from pancreatic islets. Here we have elucidated the role of R-type Ca(V)2.3 channels in that process. A 20% reduction in glucose-evoked insulin secretion was observed in Ca(V)2.3-knockout (Ca(V)2.3(-/-)) islets, close to the 17% inhibition by the R-type blocker SNX482 but much less than the 77% inhibition produced by the L-type Ca(2+) channel antagonist isradipine. Dynamic insulin-release measurements revealed that genetic or pharmacological Ca(V)2.3 ablation strongly suppressed second-phase secretion, whereas first-phase secretion was unaffected, a result also observed in vivo. Suppression of the second phase coincided with an 18% reduction in oscillatory Ca(2+) signaling and a 25% reduction in granule recruitment after completion of the initial exocytotic burst in single Ca(V)2.3(-/-) beta cells. Ca(V)2.3 ablation also impaired glucose-mediated suppression of glucagon secretion in isolated islets (27% versus 58% in WT), an effect associated with coexpression of insulin and glucagon in a fraction of the islet cells in the Ca(V)2.3(-/-) mouse. We propose a specific role for Ca(V)2.3 Ca(2+) channels in second-phase insulin release, that of mediating the Ca(2+) entry needed for replenishment of the releasable pool of granules as well as islet cell differentiation.

Animals↗

PubMed2005

[Prodrug structural modifications of cyclovirobuxine D and their biological activity].

AIM: To search for compounds for the treatment of cardiovascular diseases through prodrug structural modifications of cyclovirobuxine D, a single efficient composition distilled from Box plant in China, which was used to treat angina and myocardial infarction. METHODS: According to prodrug design principle, a series of cyclovirobuxine D analogues were prepared, suc as succinate, phosphate and amino acid ester, and their biological activities were tested. RESULTS: Seven new compounds were obtained and confirmed with 1H NMR, MS, and element analysis. CONCLUSION: In pharmacology experiment, for treating arrhythmia induced by aconitine, succinate and amino acid ester of cyclovirobuxine D (I and VII) showed better activities than that of cyclovirobuxine D. The normal rhythm of the heart duration of I and VII were ( 11.53 +/- 7.62) min and (12.68 +/- 9.25) min, compared with 0.9% NaCl solution and cyclovirobuxine D, (2.36 +/- 1.68) min and (10.25 +/- 6.59) min (P < 0.01), respectively. Another pharmacology experiment, for treating arrhythmia induced by chloroform, the negative ratio of I and VII were 80% and 82%, compared with 0.9% NaCl solution and cyclovirobuxine D, 43% and 52% (P < 0.05), respectively. The difference between new compounds and cyclovirobuxine D was distinct.

Aconitine↗

PubMed2001

The N-terminal of thrombospondin-1 is essential for coagulase-negative staphylococcal binding.

Bacterial binding was studied to determine whether thrombospondin-1 (TSP) acts as a ligand in attachment of coagulase-negative staphylococci (CNS). Twenty-five of 27 CNS strains bound soluble TSP. Staphylococcus epidermidis J9P bound 125I-labelled TSP in a dose-dependent manner. Scatchard plot analysis of the binding of TSP by strain J9P revealed two Kd values of 6.4 x 10(-9) M and 2.9 x 10(-8) M. The binding structures of strain J9P were sensitive to protease and were resistant to heat treatment. Unlabelled TSP and recombinant von Willebrand factor inhibited binding of TSP by strain J9P, but other proteins or monosaccharides did not. Heparin inhibited binding of TSP to strain J9P and two other S. epidermidis strains, BD5703 and BD969. Fusion proteins of the type 1 repeats, type 2 repeats, type 3 repeats and C-terminal domain of TSP or the synthetic Arg-Gly-Asp peptide did not inhibit binding of TSP to bacteria. TSP promoted adhesion of S. epidermidis strains when it was immobilised on polymer surfaces. These results indicate that the specific interaction between CNS and TSP may contribute to bacterial adhesion on biomaterial surfaces. The N-terminal heparin-binding domain of TSP appears to be the major region for recognition by CNS.

Bacterial Adhesion↗

PubMed2000

Binding of von Willebrand factor by coagulase-negative staphylococci.

Coagulase-negative staphylococci (CNS) are the most common infectious micro-organisms isolated from prosthetic devices. To determine whether von Willebrand factor (vWF) acts as an adhesin in bacterial recognition, bacterial binding of recombinant vWF (rvWF) was studied. Eleven CNS strains, belonging to S. epidermidis, S. haemolyticus and S. hominis species, bound soluble rvWF, but to a lesser extent than S. aureus. S. epidermidis strain H2-W bound 125I-labelled rvWF in a dose-dependent manner. The binding could be inhibited by unlabelled rvWF and thrombospondin, but not by fibrinogen, vitronectin or the carbohydrates N-acetylgalactoseamine, D-galactose, D-glucose, and D-fucose. Pre-incubation of rvWF with type I collagen and Arg-Gly-Asp-Ser (RGDS) peptides did not inhibit binding, whereas pre-incubation of rvWF with heparin decreased binding significantly. The interaction between CNS and rvWF was sensitive to proteinase treatment of bacterial cells. CNS strains bound to immobilised rvWF an extent greater or equal to the positive control strain S. aureus Cowan I. rvWF binding structures from bacterial cell wall were detected by immunoblot. Cowan I strain had 140-, 90- and 38-kDa binding molecules. S. haemolyticus strain SM131 and S. epidermidis strain H2-W had two (120 and 60 kDa) and five (120, 90, 60, 52 and 38 kDa) binding molecules, respectively. Similar binding structures were formed when cell wall extracts from these strains were incubated with thrombospondin. These results indicate that specific ligand-receptor interaction between CNS and rvWF may contribute to bacterial adhesion and colonisation on biomaterial surfaces. Heparin-binding domains of rvWF might be the crucial regions for bacterial attachment. rvWF and thrombospondin may recognise similar molecules in staphylococcal cell wall extracts.

Bacterial Adhesion↗

PubMedDate not supplied

Protein adsorption on ex vivo catheters and polymers exposed to peritoneal dialysis effluent.

BACKGROUND: Deposition of proteins on surfaces of medical devices has been recognized to putatively relate to the process of regulation of biomaterial-associated complications by attachment of fibrin clots, eukaryotic cells, and microbes. The molecules adsorb to a varying extent, depending not only on the physicochemical properties of the biomaterial, but also on the composition of the host fluid. OBJECTIVE: Adsorption of proteins on catheters exposed both ex vivo and in vitro to dialysate of patients on peritoneal dialysis (PD) was studied. METHODS: Peritoneal dialysis effluent was collected from 5 patients with end-stage renal disease on continuous ambulatory PD. Tenckhoff catheters were obtained from 16 patients. Deposition of proteins on excised Tenckhoff catheters and tubing of different materials exposed to PD effluent in vitro was studied using 125iodine-labeled antibodies. Adhesion of Staphylococcus aureus and Staphylococcus epidermidis strains was quantified on tubing exposed to PD effluent in vitro. RESULTS: The presence of albumin, transferrin, immunoglobulin G, fibrinogen, fibronectin, von Willebrand factor, vitronectin, and thrombospondin was determined at various concentrations in PD effluent. All proteins analyzed were detected on PD catheters removed from patients. The extent of protein deposition on Tenckhoff catheters exposed to PD effluent, in vitro, rapidly reached a plateau and remained constant, as it did on polyvinyl chloride and polyethylene tubing. Adhesion of staphylococci was enhanced on Tenckhoff catheters exposed to PD effluent compared to unused PD solution. CONCLUSIONS: The data identify surface exposed proteins that may serve as adhesion sites for microbes on peritoneal catheters indwelled in patients undergoing PD.

Adolescent↗