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Peng Chen

Publications and source records attributed to Peng Chen.

At least 55 records · Page 3Linked to original sources
PubMed2004

Biomimetic growth of apatite on hydrogen-implanted silicon.

Hydrogen in silicon has been widely applied in semiconductor fields. In this paper, the application of hydrogen-implanted silicon wafer in biomedical fields was explored by investigating its bioactivity. Hydrogen implanted silicon wafers were prepared using plasma immersion ion implantation. The surface structures of the 1.4 x 10(17) cm(-2) hydrogen-implanted silicon wafers were investigated using atomic force microscopy and transmission electron microscopy (TEM). The hydrogen depth profiles were acquired by SIMS and the crystal quality of the as-implanted silicon was studied by channeling Rutherford backscattering spectrometry (RBS). The bioactivity of the implanted silicon was evaluated using the biomimetic growth of apatite on its surface after it was soaked in simulated body fluid for a period of time. The TEM, SIMS and RBS results indicate the formation of an amorphous hydrogenated silicon (a-Si:Hx) layer has been formed on the surface of the hydrogen-implanted silicon wafer. After immersion in SBF for 14 days, bone-like apatite is observed to nucleate and grow on the surface. With longer soaking time, more apatite appeared on the surface of the hydrogen implanted silicon but our control experiments did not reveal any apatite formation on the surface of the un-implanted silicon wafer, hydrogenated crystalline silicon wafer (with hydrogen, but no amorphous surface), or argon-implanted silicon wafer (amorphous surface but without hydrogen). Our results indicated that the bioactivity of silicon wafer can be improved after hydrogen implantation and the formation of the amorphous hydrogenated silicon (a-Si:Hx) surface also plays a synergistic role to improve the bioactivity.

Alpha Particles↗
PubMed2004

Differential expression of chemokines and chemokine receptors in murine islet allografts: the role of CCR2 and CCR5 signaling pathways.

Chemokines and their receptors play a pivotal role in the initiation and amplification of the immune response. Investigated was their differential expression after syngeneic and allogeneic islet transplantation. During the 7 d after transplantation, the chemokines MCP-1, MCP-2, RANTES, MIG, IP-10, I-TAC, and two CC chemokine receptors CCR2 and CCR5 were highly expressed in allografts when compared with isografts. Disrupting the CCR2 and CCR5 pathways individually resulted in prolongation of the survival time 16.1 +/- 0.4 and 15.8 +/- 0.9 d, respectively, of fully major histocompatibility complex-mismatched islet grafts compared with wild-type controls (11.2 +/- 1.0 d). Blockade of both receptors had no synergistic effect. Rapamycin-treated wild-type recipients rejected their grafts at 17.4 +/- 2.2 d, in contrast to rapamycin-treated CCR2-/- recipients at 38 +/- 8.6 d (P = 0.025). The disruption of the CCR2 and CCR5 signaling, alone or in combination, moderately prolong islet allograft survival. However, the combination of low-dose immunosuppression and targeting of CCR2 greatly augmented islet graft survival.

Animals↗
PubMed2004

The modified wobble nucleoside uridine-5-oxyacetic acid in tRNAPro(cmo5UGG) promotes reading of all four proline codons in vivo.

In Salmonella enterica serovar Typhimurium five of the eight family codon boxes are decoded by a tRNA having the modified nucleoside uridine-5-oxyacetic acid (cmo5U) as a wobble nucleoside present in position 34 of the tRNA. In the proline family codon box, one (tRNAProcmo5UGG) of the three tRNAs that reads the four proline codons has cmo5U34. According to theoretical predictions and several results obtained in vitro, cmo5U34 should base pair with A, G, and U in the third position of the codon but not with C. To analyze the function of cmo5U34 in tRNAProcmo5UGG in vivo, we first identified two genes (cmoA and cmoB) involved in the synthesis of cmo5U34. The null mutation cmoB2 results in tRNA having 5-hydroxyuridine (ho5U34) instead of cmo5U34, whereas the null mutation cmoA1 results in the accumulation of 5-methoxyuridine (mo5U34) and ho5U34 in tRNA. The results suggest that the synthesis of cmo5U34 occurs as follows: U34 -->(?) ho5U -->(CmoB) mo5U -->(CmoA?) cmo5U. We introduced the cmoA1 or the cmoB2 null mutations into a strain that only had tRNAProcmo5UGG and thus lacked the other two proline-specific tRNAs normally present in the cell. From analysis of growth rates of various strains and of the frequency of +1 frameshifting at a CCC-U site we conclude: (1) unexpectedly, tRNAProcmo5UGG is able to read all four proline codons; (2) the presence of ho5U34 instead of cmo5U34 in this tRNA reduces the efficiency with which it reads all four codons; and (3) the fully modified nucleoside is especially important for reading proline codons ending with U or C.

Amino Acid Sequence↗
PubMed2004

Fusion rate: a time-to-event phenomenon.

OBJECT: The term "fusion rate" is generally denoted in the literature as the percentage of patients with successful fusion over a specific range of follow up. Because the time to fusion is a time-to-event phenomenon a more accurate method of representation may be made using the Kaplan-Meier method of estimation. METHODS: The current study was performed to illustrate that fusion rate is more accurately represented by median times as calculated using survival analysis. Patients undergoing a cervical decompressive corpectomy and reconstruction formed the basis of the primary analysis. A secondary analysis was made to evaluate the difference in the fusion times for one- compared with multilevel corpectomy cases. Data were collected at a tertiary care institution over a 5-year period with 6-month follow up after the last recruitment. Descriptive statistics of baseline patient characteristics, the extent of disease, and the surgical intervention were obtained. Fusion was the final outcome, and it was defined as the "event." The presence of any trabeculae bridging between the vertebral body and allograft signified the occurrence of an event. Postoperative static radiographs were evaluated by independent neuroradiologists to assess the presence of fusion. Fusion rate was determined using the Kaplan-Meier estimate. The median time to fusion was calculated, as were the 95% confidence intervals (CIs). These were stratified for patients who underwent one- and two-level vertebrectomy. The log-rank test was used to differentiate between one-level and multilevel corpectomy. Multivariate analysis was performed using Cox regression for further evaluation, by adjusting for covariates (age, sex, smoking history). Fifty-seven patients underwent single- or multilevel corpectomy and fusion. The male/female ratio was similar, with a median age of 53 years. Fourteen patients had a history of cigarette smoking. Thirty-six patients underwent a one-level corpectomy, 20 a two-level corpectomy, and one patient underwent a three-level corpectomy. The analysis was restricted to one- and two-level cases. The median time to fusion for the cephalad and caudad aspect of the graft-host interface was 88 days (95% CI 82-94 days) and 85 days (95% CI 77-93 days), respectively. As generally reported in the literature, this translates to a 92% (by 2.1 years) and 93% (by 1.5 years) fusion rate, for the cephalad and caudad, respectively. The median time to fusion for the cephalad aspect of the graft for one-level vertebrectomy was 87 days (95% CI 83-91 days), whereas for two-level vertebrectomy was 90 days (95% CI 59-121 days). The median time to fusion for the caudal aspect of the graft-host interface was 85 days (95% CI 80-90 days) for one-level corpectomy and 90 days (95% CI 83-97 days) for the two-level cases. There was no statistically significant difference in the median time to fusion for one- and two-level corpectomy at either the superior or inferior aspect of the graft (p = 0.19 and 0.84, respectively). This held true even after adjusting for covariates. CONCLUSIONS: Fusion rate is a time-to-event phenomenon and is more accurately represented using the Kaplan-Meier method of estimation.

Bone Transplantation↗
PubMed2004

[Effects of fraction from Phyllanthus urinaria on thrombosis and coagulation system in animals].

OBJECTIVE: To investigate the effects of PUW (a fraction containing 60% corilagin from a Chinese herbal plant Phyllanthus urinaria) on thrombosis and coagulation system. METHODS: Myers's method was used to evaluate the protection of intravenously administered PUW against the male mouse sudden death caused by injection of 75 mg/kg arachidonic acid in the tail vein; Charlton's method was modified to observe antithrombotic effect of PUW in rat electrically stimulated carotid artery thrombosis model; and the model of venous thrombosis was produced to investigate the antithrombotic effect of PUW. Rosette assay was used to observe the effect of PUW on platelet-neutrophil adhesion. The effects of PUW were monitored on euglobulin lysis time (ELT), prothrombin time (PT), kaolin partial thromboplastin time (KPTT), and bleeding time (BT) in rats, according to the methods of Kowalski, HUANG Zheng-Liang, and GU Yue-Fang, et al, respectively. RESULTS: The results showed that PUW administered intravenously significantly decreased the mouse mortality, prolonged the occlusion time of rat carotid arteries, and reduced the wet and dry thrombus weight of the inferior vena cava, respectively. PUW markedly inhibited the binding of activated platelets to neutrophils, obtaining 39.7 mg/L of the medium inhibitory concentration. Intravenously administered PUW significantly shortened ELT, prolonged KPTT while had no influence on PT; PUW increased BT in rat tail tips but the BT caused by PUW was much shorter than that by aspirin or urokinase. CONCLUSION: It is suggested that PUW has the potential of antithrombosis due to its inhibition of platelet-neutrophil adhesion. PUW shows the tendency to bleeding, however, it could not cause serious bleeding side effect as compared with aspirin or urokinase.

Animals↗
PubMed2004

Effects of copper-aspirin complex on platelet-neutrophil interactions.

AIM: To investigate the effects of copper-aspirin complex on rat thrombosis and the interaction between platelets and neutrophils. METHODS: The model of electrically stimulated carotid artery thrombosis in Sprague Dawley rats was used; the effects of copper-aspirin complex on rat platelet-neutrophil adhesion and platelet aggregation stimulated by activated neutrophils were observed by rosette assay and Born's method, respectively. RESULTS: Intragastric copper-aspirin complex (5, 7, and 10 mg/kg) dose-dependently prolonged the occlusion time; it significantly decreased the rosette number formed between thrombin-activated platelets and neutrophils; the 50 % of inhibitory concentration (IC50) was (54.6+/-4.3) micromol/L. Copper-aspirin complex markedly inhibited rat platelet aggregation induced by either cell free supernatant of activated neutrophils or by activated neutrophil suspension. The values of IC50 were (224.5+/-16.2) micromol/L and (820.5+/-21.4) micromol/L, whereas aspirin had no influence. CONCLUSION: Copper-aspirin complex inhibited platelet-neutrophil interactions through a different property from aspirin and resulted in a more potent antithrombotic activity.

Animals↗
PubMed2004

[A preliminary report on treatment of myelodysplastic syndrome with cyclosporin a and androgen].

The study was aimed to explore clinical result of cyclosporin A (CsA) and androgens for treatment of myelodysplastic syndrome (MDS) with refractory anemia. Four cases of MDS-RA were treated with CsA and androgens, while the changes of blood counts, bone marrow and chromosome were observed. The results showed that substantial hematological response was observed in all four patients, that their anemia improved and all transfusion-dependent patients achieved transfusion independence. In conclusion, CsA and Adr therapy was well tolerated. CsA and Adr therapy offer an alternative treatment of MDS with RA. The mechanisms of the benifical effect from this therapy remain the subject of an ongoing study.

Adolescent↗
PubMed2004

[Modulation of the activities and mRNA expression of cytochrome P450 isoenzymes in rat liver by Panax gingseng and coadministration with Veratrum nigrum].

OBJECTIVE: To study the modulatory effect of Panax gingseng and coadministration with Veratrum nigrum on the activity and mRNA expression of cytochrome P450 isoenzymes in rat liver. METHOD: Rat liver microsomal cytochrome P450, b5, aminopyrine N-demethylase(APND), p-nitrophenol-hydroxylase(pNPH)activities were quantitated by UV chromatography. The mRNA expression level of five CYP isoenzymes CYP1A1, CYP2B1/2, CYP2C11, CYP2E1 and CYP3A1 were detected by semi-quantitative reverse transcriptase-polymerase chain reaction(RT-PCR). RESULT: P. gingseng coadministrated with V. nigrum obviously decreased the P450 contents of liver microsomes, and the b5 contents. Both single and combined used inhibited the activities of aminopyrine N-demethylase. At the mRNA level, the expression of CYP2C11 markedly induced exposure to V. nigrum, but combinative groups decreased the expression of CYP2C11. The combination of P. gingseng and V. nigrum induced the expression of CYP1A1. P. gingseng has inhibitory effect on CYP2B1/2 and inductive effect used with V. nigrum. The combination of P. gingseng with V. nigrum also induced the expression of CYP3A1. CONCLUSION: P. gingseng used singly has some different modulation effects compared with combinative used, which may occur because of drug-drug interaction based on cytochrome P450. To elucidate the drug-drug interaction, it needs further analysis and metabolism research.

Aminopyrine N-Demethylase↗
PubMed2004

Changes of expressions of VEGF, bFGF, and angiogenesis, and effect of benazepril, bFGF on angiogenesis in acute myocardial infarction model of the rabbits.

OBJECTIVE: To explore the changes of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and angiogenesis, and the effects of bFGF, angiotensin converting enzyme inhibiter(ACEI) benazepril on the angiogenesis in acute myocardial infarction (AMI) model of rabbits, and to provide a probable evidence for the treatment of AMI. METHODS: AMI model was established by ligating anterior descending branch of coronary artery of Japan-Sino hybridization white rabbits. The postoperative rabbits were randomly divided into 6 groups and each group was treated with different drugs. Groups 1 and 2 were treated with normal saline (NS) for 28 and 14 days (d), group 3 and 4 with bFGF for 28 and 14 d, groups 5 with benazepril for 14 d, and group 6 with benazepril and bFGF for 14 d respectively. The rabbits were killed on the 14th or 28th d and their hearts were excised, sectioned and stained with HE, Masson trichrome to observe VEGF, bFGF and CD(34) under a microscope, which were quantified with a computer-assisted morphometry. RESULTS: Compared with group 1, the granulation tissue of infarction zone (IZ) in group 2 freshened up, and the capillary density (CD) in IZ was increased (P = 0.002). The CD in the IZ as well as VEGF and bFGF in groups 3 and 4 were increased respectively (P = 0.011-0.037). In group 5 the changes of VEGF and bFGF were not found in the IZ and the border zone (BZ) while CD was significantly increased (35.4% and 25.6%, P = 0.036 and 0.037). Compared with group 2, the CD in the IZ and BZ of group 6 was significantly increased (63.4% and 44.3% P = 0.007 and 0.007), meanwhile VEGF and bFGF were increased. Compared with group 5, only VEGF was increased. CONCLUSION: Intravenous bFGF may increase VEGF and bFGF significantly, thus promoting the angiogenesis in the IZ and BZ in cardiac infarction as VEGF and bFGF are the potent angiogenic growth factors. Benazepril may promote angiogenesis in the IZ and BZ in cardiac infarction, but its mechanism is irrelative to the expression of VEGF and bFGF. The combination of benazepril and bFGF may promote, to some extent, the expression of VEGF and bFGF, but their effect on angiogenesis has not been found.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2004

[Clinical application of lateral lag screw in fixing intracapsular sagittal condylar fracture].

OBJECTIVE: To introduce the clinical application and curative effect of lateral lag screw technique in fixing condylar intracapsular sagittal fractures. METHODS: Thirteen condyles with intracapsular sagittal fracture of 11 cases were fixed using lateral lag screw technique. Curative effects were observed by clinical and radiological follow-up for 6 approximately 30 months (mean 12 months) postoperatively. RESULTS: The favorable results were obtained in all cases. All patients were satisfied with the clinical results. slight malocclusion existed in 2 cases. Radiological abnormalities were seen in 3 cases by CT scanning, but without any obvious function disturbances. CONCLUSIONS: Lateral lag screw technique is a simple and effective treatment in fixing intracapsular sagittal condylar fractures.

Adolescent↗
PubMed2003

Activation of N2O reduction by the fully reduced micro4-sulfide bridged tetranuclear Cu Z cluster in nitrous oxide reductase.

The tetranuclear CuZ cluster catalyzes the two-electron reduction of N2O to N2 and H2O in the enzyme nitrous oxide reductase. This study shows that the fully reduced 4CuI form of the cluster correlates with the catalytic activity of the enzyme. This is the first demonstration that the S = 1/2 form of CuZ can be further reduced. Complementary DFT calculations support the experimental findings and demonstrate that N2O binding in a bent mu-1,3-bridging mode to the 4CuI form is most efficient due to strong back-bonding from two reduced copper atoms. This back-donation activates N2O for electrophilic attack by a proton.

Copper↗
PubMed2003

[Observation of bone marrow mesenchymal stem cells after subretinally transplanted into laser-injured rat retina].

OBJECTIVE: Bone marrow mesenchymal stem cells (MSCs) develop into hematopoietic and mesenchymal lineages but have not been known to participate in production of retina. Eye was known as an immunologically privileged organ. Because of its special structure, it's difficult for blood cells to enter retina. This article is to trace bone marrow mesenchymal stem cell (MSCs) after subretinally transplanted into Nd: YAG laser-injured rat retinal without in vitro differentiation induction. METHOD: 4', 6-diamidino-2-phenylindole (DAPI)-labeled MSCs were used to trace the change of MSCs after transplantation on day 10, 20, 35 and 50. The sequenced sections were used for Immunohistochemistry identification for neuronal nuclei (NeuN), neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP) and pancytokeratin (CK). Electroretinogram (ERG) b waves were recorded for each eye of the laser injured group, the laser injured transplanted group and the laser injured with saline injection control group before, right after or at every end of 1 to 7 weeks. RESULTS: On day 10, the DAPI positive cells were mainly crowded around the transplanted site. On day 20 the positive area enlarged and scattered into RPE layer, photoreceptor layer, bipolar layer and ganglion cell layer. Then the positive area enlarged more widely on day 35 and more cells could be found migrate to the lesion site. The positive area didn't enlarge much on day 50 than on day 35. No formation of rosettes was found during the observation. But the expression of NeuN, NSE, GFAP and CK was not uniform as the normal retina. Cell proliferation was still found. But HE staining showed that the lesion in the transplanted group was better than that of the control group. Correspondingly ERG b-wave value at week 5 was higher than the control group. CONCLUSION: From these cells, a proportion of the cells regenerated from bone marrow can be differentiated into retina in vivo. Although the MSCs-derived cells could not precisely express neuro-like proteins, they could help recover lesion and ERG b-wave value.

Animals↗
PubMed2003

Phospholipase activity of phospholipase C-gamma1 is required for nerve growth factor-regulated MAP kinase signaling cascade in PC12 cells.

Phospholipase C-gamma1 (PLC-gamma1) hydrolyzes phosphatidylinositol 4,5-bisphosphate to the second messengers inositol 1,4,5-trisphosphate and diacylglycerol (DAG). PLC-gamma1 is implicated in a variety of cellular signalings and processes including mitogenesis and calcium entry. However, numerous studies demonstrate that the lipase activity is not required for PLC-gamma1 to mediate these events. Here, we report that the phospholipase activity of PLC-gamma1 plays an essential role in nerve growth factor (NGF)-triggered Raf/MEK/MAPK pathway activation in PC12 cells. Employing PC12 cells stably transfected with an inducible form of wild-type PLC-gamma1 or lipase inactive PLC-gamma1 with histidine 335 mutated into glutamine in the catalytic domain, we show that NGF provokes robust activation of MAP kinase in wild-type but not in lipase inactive cells. Both Ras/C-Raf/MEK1 and Rap1/B-Raf/MEK1 pathways are intact in the wild-type cells. By contrast, these signaling cascades are diminished in the mutant cells. Pretreatment with cell permeable DAG analog 1-oleyl-2-acetylglycerol rescues the MAP kinase pathway activation in the mutant cells. These observations indicate that the lipase activity of PLC-gamma1 mediates NGF-regulated MAPK signaling upstream of Ras/Rap1 activation probably through second messenger DAG-activated Ras and Rap-GEFs.

Animals↗
PubMed2003

Spectroscopy and bonding in side-on and end-on Cu2(S2) cores: comparison to peroxide analogues.

Spectroscopic methods combined with density functional calculations were used to study the disulfide-Cu(II) bonding interactions in the side-on micro -eta(2):eta(2)-bridged Cu(2)(S(2)) complex, [[Cu(II)[HB(3,5-Pr(i)(2)pz)(3)]](2)(S(2))], and the end-on trans- micro -1,2-bridged Cu(2)(S(2)) complex, [[Cu(II)(TMPA)](2)(S(2))](2+), in correlation to their peroxide structural analogues. Resonance Raman shows weaker S-S bonds and stronger Cu-S bonds in the disulfide complexes relative to the O-O and Cu-O bonds in the peroxide analogues. The weaker S-S bonds come from the more limited interaction between the S 3p orbitals relative to that of the O 2s/p hybrid orbitals. The stronger Cu-S bonds result from the more covalent Cu-disulfide interactions relative to the Cu-peroxide interactions. This is consistent with the higher energy of the disulfide valence level relative to that of the peroxide. The ground states of the side-on Cu(2)(S(2))/Cu(2)(O(2)) complexes are more covalent than those of the end-on Cu(2)(S(2))/Cu(2)(O(2)) complexes. This derives from the larger sigma-donor interactions in the side-on micro -eta(2):eta(2) structure, which has four Cu-disulfide/peroxide bonds, relative to the end-on trans- micro -1,2 structure, which forms two bonds to the Cu. The larger disulfide/peroxide sigma-donor interactions in the side-on complexes are reflected in their more intense higher energy disulfide/peroxide to Cu charge transfer transitions in the absorption spectra. The large ground-state covalencies of the side-on complexes result in significant nuclear distortions in the ligand-to-metal charge transfer excited states, which give rise to the strong resonance Raman enhancements of the metal-ligand and intraligand vibrations. Particularly, the large covalency of the Cu-disulfide interaction in the side-on Cu(2)(S(2)) complex leads to a different rR enhancement profile, relative to the peroxide analogues, reflecting a S-S bond distortion in the opposite directions in the disulfide/peroxide pi(sigma) to Cu charge transfer excited states. A ligand sigma back-bonding interaction exists only in the side-on complexes, and there is more sigma mixing in the side-on Cu(2)(S(2)) complex than in the side-on Cu(2)(O(2)) complex. This sigma back-bonding is shown to significantly weaken the S-S/O-O bond relative to that of the analogous end-on complex, leading to the low nu(S)(-)(S)/nu(O)(-)(O) vibrational frequencies observed in the resonance Raman spectra of the side-on complexes.

Copper↗
PubMed2003

Amperometric detection of quantal catecholamine secretion from individual cells on micromachined silicon chips.

We have fabricated electrochemical electrodes in picolitersized wells for measuring catecholamine release from individual cells with millisecond resolution. Each well-electrode roughly conforms to the shape of the cell in order to capture a large fraction of released catecholamine with high time resolution. Using this device, we can resolve spikes in amperometric current corresponding to quantal catecholamine release via exocytosis. In addition, we have combined amperometric recording on the chip with patch-clamp recordings of membrane capacitance as an assay of exocytosis. A quantitative comparison of the two methods suggests that a large fraction of catecholamine release is oxidized on the surface of the well-electrode. This technology has applications in cell-based biosensor development, high-throughput screening of drugs, and basic science investigations.

Animals↗
PubMed2003

Spectroscopic and electronic structure studies of the diamagnetic side-on CuII-superoxo complex Cu(O2)[HB(3-R-5-iPrpz)3]: antiferromagnetic coupling versus covalent delocalization.

Magnetic, vibrational, and optical techniques are combined with density functional calculations to elucidate the electronic structure of the diamagnetic mononuclear side-on CuII-superoxo complex. The electronic nature of its lowest singlet/triplet states and the ground-state diamagnetism are explored. The triplet state is found to involve the interaction between the Cu xy and the superoxide pi v * orbitals, which are orthogonal to each other. The singlet ground state involves the interaction between the Cu xy and the in-plane superoxide pi v * orbitals, which have a large overlap and thus strong bonding. The ground-state singlet/triplet states are therefore fundamentally different in orbital origin and not appropriately described by an exchange model. The ground-state singlet is highly delocalized with no spin polarization.

Copper↗