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Biomedical subjects

Qiang Chen

Publications and source records attributed to Qiang Chen.

At least 55 records · Page 3Linked to original sources

Systematic high-yield production of human secreted proteins in Escherichia coli.

Human secreted proteins play a very important role in signal transduction. In order to study all potential secreted proteins identified from the human genome sequence, systematic production of large amounts of biologically active secreted proteins is a prerequisite. We selected 25 novel genes as a trial case for establishing a reliable expression system to produce active human secreted proteins in Escherichia coli. Expression of proteins with or without signal peptides was examined and compared in E. coli strains. The results indicated that deletion of signal peptides, to a certain extent, can improve the expression of these proteins and their solubilities. More importantly, under expression conditions such as induction temperature, N-terminus fusion peptides need to be optimized in order to express adequate amounts of soluble proteins. These recombinant proteins were characterized as well-folded proteins. This system enables us to rapidly obtain soluble and highly purified human secreted proteins for further functional studies.

Chromosome Mapping↗

Melatonin enhances antinociceptive effects of delta-, but not mu-opioid agonist in mice.

This present study examines the effect of melatonin on antinociceptive action induced by opioid agonists in mice using the tail-flick test. When injected either by intraperitoneal (i.p.) (1, 5, 25 mg/kg) or by intracerebroventricular (i.c.v.) (0.25, 0.5, 1 mg/kg) routes, melatonin significantly enhanced the delta-opioid agonist deltorphin I induced antinociception, but not mu-opioid agonist endomorphin-1. Further investigation showed that i.c.v. luzindole (0.5 mg/kg) (an antagonist of melatonin receptor) significantly antagonized the enhanced antinociceptive effect of i.c.v. melatonin. These results demonstrated that melatonin can specifically enhance the antinociception induced by specific opioid receptor agonist (i.e., delta opioid agonist) acting on melatonin receptor and that melatonin may have augmentation effect on analgesia with delta-, but not mu-opioid agonists in mice.

Analgesics, Opioid↗

Alternative IMP binding in feedback inhibition of hypoxanthine-guanine phosphoribosyltransferase from Thermoanaerobacter tengcongensis.

Crystal structures of Thermoanaerobacter tengcongensis hypoxanthine-guanine phosphoribosyltransferase (HGPRT) apoenzyme and the enzyme-inosine monophosphate (IMP) complex have been determined to 2.5A and 2.2A resolution, respectively. The active form of the enzyme was identified as a tetramer in solution and the K(i) value of IMP was measured to be 45 microM for alpha-D-phosphoribosyl-1-pyrophosphate (PRPP). Conformation of the flexible loop in T.tengcongensis HGPRT, which is involved in substrate PRPP binding, is different from that observed in phosphoribosyltransferases (PRTs). It contains a 3-10 helix, and a unique double serine repeat. This loop is ordered even in the apoenzyme and assumes a half-closed conformation. The primary magnesium ion is directly coordinated by side-chains of Glu101 and Asp102, and water molecules in the apoenzyme, suggesting a possible prerequisite role for substrate PRPP binding. Most interestingly, an alternative IMP binding mode is found in the structure of T.tengcongensis HGPRT-IMP complex. The 5'-phosphate of IMP occupies the PPi position usually seen in PRT-PRPP complexes. This new observation is consistent with the lower K(i) value of IMP and may suggest a mechanism involving multiple modes of interactions between IMP and T.tengcongensis HGPRT in product release and feedback inhibition. The structure of T.tengcongensis HGPRT is compared with those of mesophilic HPRTs, and several possible features contributing to its thermostability are elucidated. Overall, T.tengcongensis HGPRT appears to be more diverged from other PRTs.

Amino Acid Sequence↗

Structure-activity relationship of the novel bivalent and C-terminal modified analogues of endomorphin-2.

Endomorphin-2 (Tyr-Pro-Phe-Phe-NH(2)) is a putative endogenous mu-opioid receptor ligand. To develop potent analgesics with less side effects related to it, we used the methods of dimerization and C-terminal modification. Through dimerization we got the 'balanced agonists' with potent analgesic activity and we have developed the structure-activity relationship between the selectivity and the distance of the two tyrosine pharmacophores. Modification at the C-terminal increased the selectivity of endomorphin-2 to mu-opioid receptor with binding affinity conserved.

Analgesics↗

Neuropeptide FF receptors exert contractile activity via inhibition of nitric oxide release in the mouse distal colon.

Neuropeptide FF (NPFF) and NPVF, two closely NPFF related peptides, have different affinities for the two NPFF receptors (NPFF1 and NPFF2). To assess the peripheral effects of NPFF receptors in the gastrointestinal tract motility, NPFF and NPVF were tested in the mouse isolated distal colon. Both NPFF (1-15 microM) and NPVF (1-15 microM) dose-dependently caused significant colonic contractions. Pre-treatment with the putative NPFF antagonist, BIBP3226 (30 microM) abolished the contractile responses to the two neuropeptides (3 microM). They had no additional contractile activities in colonic preparations contracted by Nomega-nitro-L-arginine (30 microM). Moreover, the contractions of these two neuropeptides were weakened by L-arginine (2 mM). The responses to NPFF (5 microM) and NPVF (5 microM) were not modified by atropine or naloxone (1 microM). Furthermore, NPFF (1 microM) and NPVF (1 microM) did not influence the contractive responses to acetylcholine (0.1-10 microM), morphine (1 microM) or nociceptin (0.1 microM). These data suggest that NPFF and NPVF cause contractions of the mouse distal colon via their NPFF receptors and this effect is mediated by NO but not by cholinergic pathways, independently from opioid system. In addition, the isolated bioassay may be applied as a simple parameter to characterize the potential NPFF agonists and antagonists.

Acetylcholine↗

Study on the therapeutic mechanism of the active principle of the Chinese drug Paeoniae Radix 801 through affinity biosensors IAsys plus quartz crystal microbalance.

OBJECTIVE: To study the targeted point and mechanism of the function of the blood-activating and stasis-removing Chinese drugs, Paeoniae Radix 801(PR801) in its cardiovascular protective effects and its specific binding with endothelin 1 (ET-1) as well as the dynamics of the two's interactive function by means of using affinity biosensors: IAsys Plus and quartz crystal microbalance (IAQCM). METHODS: ET-1 was immobilized on the surfaces of IAQCM by using the new surface modification methods. The PR801 in the solution was detected by modified substrates and the specific binding between PR801 and ET-1 was studied. RESULTS: The curves went up or down after adding PR801. There is specific binding between PR801 and ET-1. The bound mass were 0.458 ng/mm(2) and 133.54 ng/cm(2), respectively. There exists relatively good stability with these two methods. CONCLUSION: The affinity biosensors: IAQCM can be used to study the interaction mechanism between PR801 and ET-1, providing a new way to study the interaction mechanism of TCM. PR801 can bind ET-1 specifically in the experiments. Therefore, ET-1 is another target that PR801 can bind specifically besides thromboxane A(2).

Biosensing Techniques↗

Effects of propyl gallate on interaction between TNF-alpha and sTNFR-I using an affinity biosensor.

AIM: To study the effects of propyl gallate on the interaction of tumor necrosis factor-alpha (TNF-alpha) with its soluble receptor, sTNFR-I. METHODS: Interactions between TNF-alpha and sTNFR-I were analyzed using an IAsys biosensor. sTNFR-I was immobilized on the carboxymethyl dextran (CMD) surface of the IAsys biosensor cuvettes, and TNF-alpha preincubated with different concentrations of propyl gallate was added to the cuvettes. The resonant angle shift caused by the binding between TNF-alpha and sTNFR-I was then recorded. RESULTS: sTNFR-I was immobilized on the CMD surface at a density of 2.76 ng/mm(2). TNF-alpha then bound the immobilized sTNFR-I specifically, and propyl gallate was able to enhance the binding between TNF-alpha and sTNFR-I in a dose-dependent manner. CONCLUSION: The binding between TNF-alpha and sTNFR-I is one of the targets that propyl gallate can act on in vivo. The IAsys biosensor offers a new clue as to the study on the mechanisms of action of propyl gallate.

Antioxidants↗

Expression of porcine prorelaxin in transgenic tobacco.

In vitro studies demonstrate that porcine relaxin may possess various therapeutic effects. In this study, we explore the possibility of expressing porcine relaxin in transgenic tobacco. Tobacco was selected because it is a non-food, non-feed crop, and recombinant protein production can readily be scaled up. The cDNA of porcine preprorelaxin was under the regulation of two different constitutive promoters. DNA analysis by polymerase chain reaction verified that all transgenic plants contained the correct size of gene insert. Preliminary studies showed the presence of putative prorelaxin bands in both silver-stained SDS-PAGE and western blot. The results also indicated that tobacco-produced prorelaxin may not be properly processed to yield the mature relaxin.

Animals↗

[TIC4]endomorphins, analogues of endomorphins, have significantly enhanced vasorelaxant effects in rat aorta rings.

[Tic(4)]EM1 and [Tic(4)]EM2, new endomorphins (EMs) analogues, caused relaxation of rat aorta rings precontracted with phenylphrine in a concentration-dependent manner and were 240- to 370-fold more potent than EMs. This effect was inhibited by endothelium removal or by incubation with NO synthase inhibitor L-NNA or opioid receptor antagonist naloxone. The results demonstrate that [Tic(4)]EMs have NO- and endothelium-dependent vasorelaxant effects which are mediated by the opioid receptor.

Animals↗

[Comparison of resuscitation with Parkland formula and with improved protocol on hemodynamics in projectile-burn combined wound in dogs with seawater immersion].

OBJECTIVE: To compare hemodynamic effects of resuscitation with Parkland formula or with the improved protocol on projectile-burn combined wound in dogs with seawater immersion. METHODS: A model of projectile-burn combined wound in dogs with seawater immersion was reproduced, and 20 dogs were randomized into three groups: projectile-burn combined wound with seawater immersion (immersion group, n=8), Parkland formula resuscitation (lactated Ringer's solution 4 ml/kg per 1%total body surface area for 24 hours, standard resuscitation group, n=6), and improved protocol groups (lactated Ringer's solution 2.5 ml/kg per 1% total body surface area colloid solution 6% hetastarch 0.5 ml/kg per 1% total body surface area for 24 hours, improved group, n=6). Changes of hemodynamics and central temperature (CT) before injury, and 4, 7, 10, 20 and 28 hours after injury were observed. The mortality was observed. RESULTS: After resuscitation with Parkland formula, CT as well as hemodynamic indexes and amount of urine were improved, but central venous pressure (CVP) and the amount of urine were higher in early period of resuscitation. CVP was (14.7+/-3.1)cm H2O and the amount of urine was (2.38+/-0.18)ml.h(-1).kg(-1) at 7 hours after injury. Hemodynamics was not stable during later period of experiment. After resuscitation with the improved protocol, the hemodynamics ameliorated better than resuscitation with Parkland formula. No animals died in improved group, but 4 and 1 died respectively in immersion group and standard resuscitation group. CONCLUSION: Fluid resuscitation according to the improved protocol is more suitable for projectile-burn combined wound in dogs with seawater immersion than resuscitation with Parkland formula.

Animals↗

[Measure for human motion parameters based on model].

Measure for human motion parameters is a main method to generate computer simulation of human motion and to control humanoid robot motion. Recently, extensive researches on this sensing method have been carried out by abroad and domestic researchers. This paper introduces present research status of human motion parameters in order to provide references for scientific research fields of human bionics, humanoid robot, etc.

Computer Simulation↗

[Preventive efficacies of china-made tropisetron hydrochloride and Navoban on chemotherapy-induced nausea and vomiting: a randomized controlled clinical trial].

BACKGROUND & OBJECTIVE: Navoban (import tropisetron hydrochloride) can effectively prevent chemotherapy-induced nausea and vomiting; however, it is too expensive to be used extensively in clinic. This study was designed to compare the antiemetic efficacies and side effects of China-made tropisetron hydrochloride with Navoban. METHODS: A multicenter and randomized controlled trial was carried out. A total of 132 cancer patients were randomized into 2 groups and received 5 mg of China-made tropisetron hydrochloride (group A, 66 patients) or Navoban (group B, 66 patients) intravenously before cisplatin- or adriamycin-based chemotherapy. The gastrointestinal reactions induced by chemotherapy and side effects of the antiemetics were recorded within 7 days after chemotherapy. RESULTS: Acute nausea was prevented completely in 48.5% of the patients in group A and in 43.8% of group B; acute vomiting was prevented completely in 69.7% of the patients in group A and in 67.2% of group B. Delayed nausea was prevented completely in 25.8% of the patients in group A and in 28.1% of group B; delayed vomiting was prevented completely in 47.0% of the patients in group A and in 51.6% of group B. No significant differences in complete control of nausea and vomiting showed between group A and group B (P > 0.05). Both antiemetic regimens were well tolerated, and no difference in adverse events between the 2 groups was observed (P > 0.05). CONCLUSION: China-made tropisetron hydrochloride is as effective as Navoban in the prevention of chemotherapy-induced nausea and vomiting, and only causes mild, infrequent side effects.

Adult↗

Vasorelaxant responses to endomorphin1[psi] and endomorphin2[psi], analogues of endomorphins, in rat aorta rings.

Endomorphin-1 (Tyr-Pro-Trp-Phe-NH2, EM1) and endomorphin-2 (Tyr-Pro-Phe-Phe-NH2, EM2), the endogenous selective mu-opioid receptor agonists, can inhibit phenylephrine (PE) induced contraction which is related to the release of nitric oxide from vascular endothelium in aorta rings of rats and rabbits. The reduced (CH2NH) amide bond is a useful peptide bond surrogate in the design of opioid mimetics because it could enhance conformational flexibility and metabolic stability. The present work was designed to investigate the vascular activities of interrelated endomorphin analogues: endomorphin-1[psi] (Tyr[psi(CH2NH)]Pro-Trp-Phe-NH2, EM1[psi]) and endomorphin-2[psi] (Tyr[psi(CH2NH)]Pro-Phe-Phe-NH2, EM2[psi]). The effect of EM1[psi] (1, 2, 3, 4, 5 microM) and EM2[psi] (0.001, 0.01, 0.1, 1, 5 microM) were evaluated on rat thoracic aortic rings pre-contracted with PE (0.1 microM). EM1[psi] and EM2[psi] both caused a concentration-dependent relaxation. The IC50 of EM1[psi] and EM2[psi] was 3.332 microM and 1.226 microM, respectively. The vasorelaxant effect of EMs[psi] is 216.9 and 237.1 fold more potent than EMs. Moreover, the vasorelaxant effect of EMs[psi] was blocked by naloxone (NaCl, 1 microM) and was reduced by N(omega)-nitro-L-arginine (L-NNA, 1 microM) and removal of endothelium. The present study demonstrated that EMs[psi] had more potent vasorelaxant effects and their activities were naloxone-sensitive and endothelium-dependent and partially NO-dependent, similar to the mechanism of parent EMs.

Animals↗

[A randomized controlled trail of taxol-based combination regimens for advanced gastric cancer].

BACKGROUND & OBJECTIVE: Standard chemotherapy for advanced gastric cancer remains undefined. Phase II trials show that taxol is effective in treating advanced gastric cancer. This multi-center prospective open randomized controlled study was to compare the efficacy of Taxol plus calcium folinate (CF)/5-fluorouracil (5-FU), Taxol plus oxaliplatin (OXA), and CF/5-FU plus cisplatin (DDP) on advanced gastric cancer, and analyze their toxicities. METHODS: Patients with measurable unresectable and/or metastatic gastric carcinoma were randomized into CF/5-FU+DDP (control), CF/5-FU + Taxol, and Taxol + OXA groups, and received up to 8 cycles of chemotherapy. Treatment efficacy and adverse events were evaluated according to WHO criteria. RESULTS: A total of 180 patients were enrolled from May 2002 to May 2004, and randomized into the 3 groups; each group contained 60 patients. Of the 180 patients, 14 received 2 cycles of chemotherapy, 49 received 4 cycles, and 103 received 8 cycles. Treatment outcomes of 166 cases were evaluable. The response rate (RR) of naive patients or the patients with retroperitoneal lymph node metastasis was significantly higher in CF/5-FU+Taxol and Taxol+OXA groups than in control group (50.00% and 80.00% vs. 20.75%, P<0.05; 65.96% and 85.71% vs. 36.36%, P<0.05). But the RR of the patients with liver metastasis was similar among the 3 groups (28.57% and 39.13% vs. 34.62%, P>0.05). The occurrence rates of nausea/vomiting, anepithymia, stomatitis, and kidney damage were lower in study groups than in control group, but the occurrence rates of myelosuppression and peripheral nerve damage were higher in study groups than in control group. Allergic response occurred in 7 (5.88%) patients in study group, and 3 (2.52%) of them were serious. There was no treatment-related death. CONCLUSIONS: Despite its hematotoxicity, the treatment efficacy of Taxol-based combination regimens on advanced gastric cancer is better than that of CF/5-FU + DDP regimen with tolerable toxicities. We recommend Taxol-based combination regimens as first-line regimens for advanced gastric cancer.

Adult↗

Cardiovascular effects of endomorphins in alloxan-induced diabetic rats.

Endomorphins, the endogenous, potent and selective mu-opioid receptor agonists, have been shown to decrease systemic arterial pressure (SAP) in rats. In the present study, responses to endomorphins were investigated in systemic vascular bed of alloxan-induced diabetic rats and in non-diabetic rats. Diabetes was induced by alloxan (220 mg/kg, i.p.) in male Wistar rats. At 4-5 weeks after the onset of diabetes, intravenous injections of endomorphins (1-30 nmol/kg) led to an increase of SAP and heart rate (HR) consistently and dosed-dependently. SAP increased 7.68+/-3.73, 11.19+/-4.55, 21.19+/-2.94 and 27.48+/-6.21% from the baseline at the 1, 3, 10 and 30 nmol/kg dose, respectively, of endomorphin 1 (n=4; p<0.05), and similar changes were observed in response to endomorphin 2. The hypertension could be antagonized markedly by i.p. 2 mg/kg of naloxone. On the other hand, bilateral vagotomy would attenuate the effects of hypertension and diminished the changes of HR in response to endomorphins. With diabetic rats, 6-10 weeks after the induction of diabetes, intravenous injections of endomorphins produced non-dose-related various changes in SAP, such as a single decrease, or a single increase, or biphasic changes characterized by an initial decrease followed by a secondary increase, or no change at all. These results suggest that diabetes may lead to the dysfunction of the cardiovascular system in response to endomorphins. Furthermore, the diabetic rats of 4-5 weeks after alloxan-treatment, the increase in SAP and HR caused by i.v. endomorphins might be explained by a changed effect of vagus and by a naloxone-sensitive mechanism.

Analgesics, Opioid↗

Clinical and experimental study of oxaliplatin in treating human gastric carcinoma.

AIM: To evaluate the therapeutic effectiveness of oxaliplatin on human gastric carcinoma and to explore its mechanisms. METHODS: Twenty-two cases of stage IV gastric carcinoma received 4-6 (mean 4.6) cycles of first line combined chemotherapy with oxaliplatin (oxaliplatin 85 mg/m(2), iv, gtt, 1 h, d 1; leukovorin 200 mg/m(2), iv, gtt, 1 h, d 1 and d 2; 5-FU 300 mg/m(2),iv, d 1 and d 2, 5-FU, continuous iv, gtt, 48 h; 1 cycle/2 wk). Response rate, progression-free survival (PFS), total survival time, toxic side effects were evaluated. The inhibitory effect of oxaliplatin on human gastric cell line SGC-7901 was detected and IC(50) was calculated by MTT. Transmission electron microscopy, flow cytometry and TUNEL were performed to evaluate the apoptosis of cell line induced by the drug. The expression of Caspase-3 m-RNA was detected by RT-PCR. AC-DEVD-CHO, a Caspase-3 specific inhibitor, was used to elucidate the role of activated Caspase-3 in the process of apoptosis induced by oxaliplatin. RESULTS: Total response (complete and partial) occurred in 9 (40.9%) patients. Mean PFS was 4.2 mo and mean total survival time was 7.2 mo. Cumulative neurotoxicity (all grade I-II), vomiting and diarrhea, myelosuppression appeared in 93.5%, 20%, 32.9% patients, respectively. IC(50) was calculated to be 0.71 mg/L by MTT assay. A maximal inhibitory rate reached 85.3%. Apoptosis index was elevated after incubated with 1 mmol/L oxaliplatin for 30 min, but without statistic significance (P>0.05). However it could be detected at a much higher degree both by flowcytometry and by TUNEL with a statistical significance (68.47+/-7.92% and 8.23+/-2.67%, respectively, P<0.05) after incubated with 1 mmol/L oxaliplatin for 2 d. By means of RT-PCR, we detected an enhancement of Caspase-3 m-RNA expression induced by oxaliplatin which was also in positive correlation with the apoptotic level. AC-DEVD-CHO, a Caspase-3 specific inhibitor, could significantly inhibit and delay apoptosis induced by oxaliplatin. CONCLUSION: Oxaliplatin is effective and well-tolerated in patients with advanced gastric carcinoma. Oxaliplatin could significantly inhibit the growth of human gastric cell line SGC-7901. The induction of Caspase-3 m-RNA expression, activation of Caspase-3 and promotion of apoptosis may be some of the therapeutic mechanisms of oxaliplatin on gastric carcinoma. Annexin-V-fluorescein labeling flow cytometry is much more sensitive than TUNEL in detecting early stage apoptosis.

Adult↗

Study in vitro and in vivo of nociceptin/orphanin FQ(1-13)NH2 analogues substituting N-Me-Gly for Gly2 or Gly3.

In the present study, two analogues containing N-Me-Gly (Sarcosine, Sar) were synthesized to further investigate the structural-activity relationships of orphanin FQ/nociceptin (OFQ/NC, NC). The replacement of Gly(2) or Gly(3) with Sar increased the flexibility and decreased the hydrophobicity of the N-terminal tetrapeptide. The activity of the analogues was investigated in a series of assays in vivo and in vitro. [Sar(2)]NC(1-13)NH(2) was found to (1) produce dose-dependent inhibition of the electrically induced contraction in MVD assay (pEC(50) = 6.14); (2) produce significant hyperalgesia effects in a dose-dependent manner when intracerebroventricularly (i.c.v.) injected in mice. The inhibitive effects of [Sar(2)]NC(1-13)NH(2) in MVD assay could be significantly antagonized by [Nphe(1)]NC(1-13)NH(2), and partially antagonized by naloxone; the hyperalgesic effect of [Sar(2)]NC(1-13)NH(2) could be significantly antagonized by naloxone, and partially antagonized by [Nphe(1)]NC(1-13)NH(2). On the contrary, [Sar(3)]NC(1-13)NH(2) showed no effects in these assays. All the findings suggest that the flexibility of the peptide bond between Phe(1) and Gly(2) and between Gly(2) and Gly(3) play an important role in NC-OP(4) receptor interaction, and the hydrophobicity of the N-terminal tetrapeptide showed no significant effect on this interaction. The present work also helps to provide a novel method to elucidate structural and conformational requirements of the opioid peptide-receptor interaction.

Amino Acid Substitution↗

Investigating the role of secA2 in secretion and glycosylation of a fimbrial adhesin in Streptococcus parasanguis FW213.

Adhesion of Streptococcus parasanguis FW213, a primary colonizer, to the tooth surface is mediated mainly by peritrichous long fimbriae. The fimbrial structural unit, Fap1, is indispensable for fimbriae biogenesis, adhesion to an in vitro tooth model and biofilm formation. Mature Fap1 is a glycoprotein with an apparent molecular mass of 200 kDa. Glycosylated Fap1 is not present in some mutants screened from a transposon mutant library. Localization of the transposition sites revealed a gene determined to be secA2, which is distinct from the canonical secA gene. In FW213, glycosylated Fap1 was present in all the subcellular fractions including the cytoplasm. In VT1574, a non-polar mutant of secA2 generated by in frame deletion, Fap1 was not secreted. Glycosylated Fap1 was present in the membrane and cytoplasm of the mutant, although in greatly reduced amounts. Fap1 secretion and abundance were restored when VT1574 was complemented by a plasmid-borne secA2. The secretion defect of the secA2 mutation appears to be limited to a small group of proteins such as Fap1 and FimA. These data suggested that Fap1 secretion rather than glycosylation was the major effect of the deletion of secA2; however, this deletion also had an impact on Fap1 abundance. Two more secA2 mutants with different regions deleted were tested for their ability to secrete Fap1. One mutant was completely unable to secrete Fap1 while the other was able to secrete, but in a decreased amount. These data suggest that the region deleted in the latter mutant (nucleotides 2032-2337) is dispensable for Fap1 secretion.

Adenosine Triphosphatases↗