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Biomedical subjects

Rui Li

Publications and source records attributed to Rui Li.

At least 37 records · Page 2Linked to original sources
PubMed2006

Saturation effect and forward-dominant second-harmonic generation in single-defect photonic crystals with dual localizations.

We study the forward-dominant output of second-harmonic generation (SHG) in single-defect and dual-localized photonic crystals within the saturation limit. We propose that an asymmetric structure can be used to improve the performance of the enhanced SHG. We get two empirical expressions for the total saturation SHG efficiency and the forward factor and provide a reasonable explanation. The theoretical results predict a nearly 100% conversion efficiency and a nearly 100% forward output. Our work is very valuable for designing nonlinear photonic devices. As a test, a practical asymmetrical structure is presented.

Journal Article↗
PubMed2006

The production of polyhydroxyalkanoates in recombinant Escherichia coli.

Polyhydroxyalkanoates, the natural polyester that many microorganisms accumulate to store carbon and reducing equivalents, have been considered as a future alternative of traditional plastic due to their special properties. In Escherichia coli, a previous non-polyhydroxyalkanoates producer, pathway engineering has been developed as a very powerful approach to set up microbial production process through the introduction of direct genetic changes by recombinant DNA technology. Various metabolic pathways leading to the polyhydroxyalkanoates accumulation with desirable properties at low-cost and high-productivity have been developed. At the same time, high density fermentation technology of E. coli provides an efficient polyhydroxyalkanoates production strategy. This review focused on metabolic engineering, fermentation and downstream process aiming to polyhydroxyalkanoates production in E. coli.

Escherichia coli↗
PubMed2006

Angiotensin II-induced C-reactive protein generation: inflammatory role of vascular smooth muscle cells in atherosclerosis.

BACKGROUND: As the major target of Angiotensin II (Ang II) in the vessel wall, vascular smooth muscle cells (VSMCs) are a tentative source to produce C-reactive protein (CRP). However, it is largely unknown if Ang II is capable of inducing CRP production in VSMCs. METHODS AND RESULTS: Ang II induced a concentration-dependent release of CRP in cultured rat VSMCs as measured by sandwich ELISA. Real-time PCR revealed that Ang II significantly upregulated CRP mRNA level in vitro. Ang II-induced CRP generation in aortic VSMCs was also investigated using double-labeled fluorescent immunohistochemistry and in situ hybridization in subchronic Ang II administration in rats. Losartan but not PD123319 markedly blocked the Ang II-induced CRP production in cultured VSMCs, suggesting that such effect was mediated via Ang II type 1 receptor. Further, Western blotting analysis showed that mitogen-activated protein kinase (MAPK) activation was obligatory in Ang II-induced CRP production, since specific MAPK inhibitor PD098059 almost abolished the action. CONCLUSIONS: We identified that Ang II is capable of inducing CRP generation in VSMCs, in which Ang II type 1 receptor followed by MAPK signal pathway is involved. It strengthened the role of Ang II-induced CRP production by VSMCs in the inflammatory process in atherosclerosis.

Angiotensin II↗
PubMed2006

Core-corona polymer composite particles by self-assembled heterocoagulation based on a hydrogen-bonding interaction.

Poly(ethylene glycol dimethacrylate-co-acrylic acid) (poly(EGDMA-co-AA)) small microspheres were effectively self-assembled on poly(ethylene glycol dimethacrylate-co-4-vinylpyridine) (poly(EGDMA-co-VPy)) surfaces to form a core-corona structure with a raspberry-like polymer composite by a hydrogen interaction mechanism through an affinity complex between the carboxylic acid group and pyridine group. The control of coverage of the poly(EGDMA-co-AA) corona on the surface of poly(EGDMA-co-VPy) was studied in detail via adjustment of the nature of the mass ratio between the core and corona. The effects of the pH and solvent used on the morphology of the self-assembled core-corona polymer composites were investigated. The nature of the interaction between the core and corona polymer particles was identified as hydrogen bonding with FT-IR spectroscopy.

Acrylates↗
PubMed2006

PQN and DQN: algorithms for expression microarrays.

An ideal expression algorithm should be able to tell truly different expression levels with small false positive errors and be robust to assay changes. We propose two algorithms. PQN is the non-central trimmed mean of perfect match intensities with quantile normalization. DQN is the non-central trimmed mean of differences between perfect match and mismatch intensities with quantile normalization. The quantiles for normalization can be either empirical or theoretical. When array types and/or assay change in a study, the normalization to common quantiles at the probe set level is essential. We compared DQN, PQN, RMA, GCRMA, DCHIP, PLIER and MAS5 for the Affymetrix Latin square data and our data of two sets of experiments using the same bone marrow but different types of microarrays and different assay. We found the computation for AUC of ROC at affycomp.biostat.jhsph.edu can be improved.

Algorithms↗
PubMed2006

[Cross-sectional investigation of prevalence of type 2 diabetes in Shanghai].

OBJECTIVE: To investigate the prevalence of type 2 diabetes and impaired glucose regulation among the permanent urban and rural inhabitants in Shanghai. METHODS: Questionnaire survey, physical examination, and laboratory testing were conducted among 14401 urban and rural inhabitants aged 15 - 74 in Shanghai selected by multistage cluster random sampling. The data about the prevalence of type 2 diabetes and impaired glucose regulation were collected and analyzed. RESULTS: The respondent rate of this investigation was 80.5% (11,589/14,401). The prevalence rates of type 2 diabetes, impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) were 8.6% (1000/11,589), 6.9% (802/11,589), and 1.0% (120/11,589) respectively (the standardized rates were 6.2%, 5.1% and 0.8%). The prevalence rates of type 2 diabetes, IGT, and IFG were significantly higher in those with overweight, obesity, central obesity, and hypertension. The prevalence rates of type 2 diabetes, IGT, and IFG in men were 8.9% (412/4621), 6.4% (296/4621), and 1.0% (47/4621) respectively, all not significantly different from those of the women, i.e. e., 8.4% (588/6968), 7.3% (506/6968), and 1.0% (73/6968) respectively (all P > 0.05). The prevalence rates of type 2 diabetes and IGT in the urban area were 11.2% (730/6500) and 6.4% (419/6500) respectively, both significantly higher than those in the rural area, i.e., 5.3% (270/5089) and 7.5% (383/5089) respectively (both P < 0.05). The prevalence rate of IFG in the urban area was 1.2% (77/6500), not significantly different from that in the rural area (0.8%, 43/5039, P > 0.05). The prevalence of type 2 diabetes, IGT, and IFG increased apparently with age, body mass index, waist hip ratio, and waist circumference. The ratios of undiagnosed type 2 diabetes in the urban area and rural area were 39.6% (289/730) and 69.3% (187/270) respectively (chi(2) = 74.07, P < 0.01). CONCLUSION: The prevalence rate of type 2 diabetes in Shanghai is higher than the mean national level and shows an increasing tendency. Screening of type 2 diabetes in rich rural areas should be emphasized.

Adolescent↗
PubMed2006

Occupancy of striatal and extrastriatal dopamine D2 receptors by clozapine and quetiapine.

Clozapine and quetiapine have a low incidence of extrapyramidal side effects at clinically effective doses, which appears to be related to their significantly lower occupancy of striatal dopamine D2 receptors (DA D2r) compared to typical antipsychotic drugs (APDs). Animal studies have indicated that clozapine and quetiapine produce selective effects on cortical and limbic regions of the brain and in particular on dopaminergic neurotransmission in these regions. Previous PET and SPECT studies have reported conflicting results regarding whether clozapine produces preferential occupancy of cortical DA D2r. To examine whether clozapine and/or quetiapine produce preferential occupancy of DA D2r in cortex and limbic regions, we studied the occupancy of putamenal, ventral striatal, thalamic, amygdala, substantia nigra, and temporal cortical DA D2r using PET with [18F]fallypride in six schizophrenic subjects receiving clozapine monotherapy and in seven schizophrenic subjects receiving quetiapine monotherapy. Doses were chosen clinically to minimize psychopathology at tolerable levels of side effects such as drowsiness. All had minimal positive symptoms at the time of the study. Regional receptor occupancies were estimated using mean regional DA D2r levels calculated for 10 off-medication schizophrenic subjects. Both clozapine and quetiapine produced lower levels of putamenal DA D2r occupancy than those reported for typical APDs, 47.8 and 33.5%, respectively. Clozapine produced preferential occupancy of temporal cortical vs putamenal DA D2r, 59.8% (p=0.05, corrected for multiple comparisons), and significantly lower levels of occupancy in the substantia nigra, 18.4% (p=0.0015, corrected for multiple comparisons). Quetiapine also produced preferential occupancy of temporal cortical DA D2r, 46.9% (p=0.03, corrected for multiple comparisons), but did not spare occupancy of substantia nigra DA D2r. The therapeutic effects of clozapine and quetiapine appear to be achieved at less than the 65% threshold for occupancy seen with typical APDs, consistent with the involvement of non-DA D2r mechanisms in at least partially mediating the therapeutic effects of these drugs. Preferential occupancy of cortical DA D2r, sparing occupancy of substantia nigra receptors, and non-DA D2r-mediated actions may contribute to the antipsychotic actions of these and other atypical APDs.

Adolescent↗
PubMed2006

(-)-Epigallocatechin gallate regulates dopamine transporter internalization via protein kinase C-dependent pathway.

Dopamine transporter (DAT) provides not only an integral component of dopaminergic neurotransmission but also a molecular gateway for the accumulation of some neurotoxins such as 1-methyl-4-phenylpyridinium (MPP(+)), a metabolite of 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). Previous study reported that the neuroprotective effects of green tea polyphenols against MPP(+)-induced neurotoxicity were related to its inhibitory effect on MPP(+) uptake via DAT in dopaminergic cells. To extend the study, we investigated (-)-epigallocatechin gallate (EGCG), a monomer of green tea polyphenols, on DAT internalization in DAT-overexpressed PC12 cells. We found that EGCG (1-100 microM) can induce a dose-dependent inhibition of dopamine uptake in DAT-PC12 cells. In parallel, treatment of EGCG decreased membrane-bound DAT by 15% to 60%. Furthermore, protein kinase C (PKC) inhibitor GF109203X at 2 microM can markedly diminish the inhibitory effects of EGCG on dopamine uptake and reverse the EGCG-induced internalization of DAT. In addition, semiquantitative RT-PCR analysis indicated that EGCG did not affect DAT mRNA expression in the PC12 cells. These data suggest that EGCG exerts its inhibitory effect on DAT by modulating DAT internalization, in which PKC activation may be involved.

Animals↗
PubMed2006

Contribution of AMPA and NMDA receptors to early and late phases of LTP in hippocampal slices.

Alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptor mediated responses were investigated in rat hippocampal slices under 4h of long-term potentiation (LTP) expression. A modified medium containing the NMDA receptor antagonist AP5 and low concentration of Mg(2+) was used to monitor isolated AMPA responses. NMDA components were determined from composite excitatory postsynaptic potentials (EPSPs) under brief (15-20 min) wash-out of AP5. LTP was induced in a medium with low concentration of AP5, resulting in an about two-fold larger increase of the AMPA component than of the NMDA component at both 1h and 4h after induction. Similar results were obtained if LTP was induced in "normal Mg(2+)" and the NMDA components were assessed at the end of experiment, from either composite or isolated NMDA EPSPs, with or without blockade of GABAergic inhibition. It is generally believed that LTP undergoes biochemical and/or structural conversions during the first few hours. Our study, however, shows constant expression of LTP, at least in terms of AMPA versus NMDA components, during this time. The data support the notion that LTP initiates as a predominant amplification of AMPA receptors and remains so for at least 4h.

Animals↗
PubMed2006

The electrochemical reaction mechanism of selenocystine on selenium-gold film modified glassy carbon electrode.

A simple and selective voltammetric method based on selenium-gold film modified glassy carbon electrode has been developed for investigating electrochemical reaction mechanism of selenocystine. With N2 saturated, redox reactions between selenocystine (SeC) and selenocysteine (SeCys) were judged to be two simple electron-transfer processes. With air saturated, the reduction reaction was diagnosed to be EC catalytic reaction (the chemical oxidation reaction of the SeCys by O2 (C) following the electron-transfer reaction (E)) and oxidation reaction is a simple electron-transfer process. With pure O2 saturated, only reduction peak was observed and the reaction was judged to be EC catalytic reaction. The electron-transfer numbers of redox reaction were calculated to be 2 by chronocoulometry and rotating disk electrode.

Carbon↗
PubMed2006

Unexpected ring-opening reactions of aziridines with aldehydes catalyzed by nucleophilic carbenes under aerobic conditions.

[reaction: see text] The chemoselective ring opening of N-tosyl aziridines with aldehydes catalyzed by an N-heterocyclic carbene was investigated under aerobic conditions. Unexpected carboxylates of 1,2-amino alcohols from the corresponding aldehydes, rather than the acyl anion ring-opened beta-amino ketones, were exclusively obtained. A plausible mechanism for this unprecedented carbene-mediated reaction was also proposed.

Aldehydes↗
PubMed2006

Sprouty 2, an inhibitor of mitogen-activated protein kinase signaling, is down-regulated in hepatocellular carcinoma.

The Sprouty proteins are increasingly being recognized to be deregulated in various types of cancers. This deregulation is often associated with aberrant signaling of receptor tyrosine kinases and its downstream effectors, leading to the mitogen-activated protein kinase (MAPK) signaling pathway. In human hepatocellular carcinoma, where the MAPK activity is enhanced via multiple hepatocarcinogenic factors, we observed a consistent reduced expression of the sprouty 2 (Spry2) transcript and protein in malignant hepatocytes compared with normal or cirrhotic hepatocytes. The expression pattern of Spry2 in hepatocellular carcinoma resembles that of several potential tumor markers of hepatocellular carcinoma and also that of several angiogenic factors and growth factor receptors. In contrast to previous studies of Spry2 down-regulation in other cancers, we have ruled out loss of heterozygosity or the methylation of promoter sites, two common mechanisms responsible for the silencing of genes with tumor suppressor properties. Functionally, we show that Spry2 inhibits both extracellular signal-regulated kinase signaling as well as proliferation in hepatocellular carcinoma cell lines, whereas knocking down Spry2 levels in NIH3T3 cells causes mild transformation. Our study clearly indicates a role for Spry2 in hepatocellular carcinoma, and an understanding of the regulatory controls of its expression could provide new means of regulating the angiogenic switch in this hypervascular tumor, thereby potentially controlling tumor growth.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Prize-based contingency management does not increase gambling.

A contingency management (CM) intervention that provides drug-abstinent patients a chance to win prizes of varying magnitudes is efficacious in retaining patients in treatment and reducing drug use. However, this intervention has been criticized as possibly increasing gambling because it contains an element of chance. Gambling behaviors before, during and 3 months after participation in a multi-site study of CM were compared for stimulant users randomly assigned to 12 weeks of standard care with (N=407) or without (N=396) prize-based CM. Among study participants enrolled in outpatient non-methadone drug abuse treatment (N=415), 26% reported gambling during the observation period, and this rate was 37% among participants (N=388) enrolled in methadone maintenance programs. No differences in gambling over time were noted between those assigned to the prize CM versus standard care conditions, indicating that this prize CM procedure does not adversely impact gambling behavior among stimulant abusers.

Adult↗
PubMed2006

Effects of lower-cost incentives on stimulant abstinence in methadone maintenance treatment: a National Drug Abuse Treatment Clinical Trials Network study.

BACKGROUND: Contingency management interventions that provide tangible incentives based on objective indicators of drug abstinence have improved treatment outcomes of substance abusers, but have not been widely implemented in community drug abuse treatment settings. OBJECTIVE: To compare outcomes achieved when a lower-cost prize-based contingency management treatment is added to usual care in community methadone hydrochloride maintenance treatment settings. DESIGN: Random assignment to usual care with (n = 198) or without (n = 190) abstinence incentives during a 12-week trial. SETTING: Six community-based methadone maintenance drug abuse treatment clinics in locations across the United States. PARTICIPANTS: Three hundred eighty-eight stimulant-abusing patients enrolled in methadone maintenance programs for at least 1 month and no more than 3 years. INTERVENTION: Participants submitting stimulant- and alcohol-negative samples earned draws for a chance to win prizes; the number of draws earned increased with continuous abstinence time. MAIN OUTCOME MEASURES: Total number of stimulant- and alcohol-negative samples provided, percentage of stimulant- and alcohol-negative samples provided, longest duration of abstinence, retention, and counseling attendance. RESULTS: Submission of stimulant- and alcohol-negative samples was twice as likely for incentive as for usual care group participants (odds ratio, 1.98; 95% confidence interval, 1.42-2.77). Achieving 4 or more, 8 or more, and 12 weeks of continuous abstinence was approximately 3, 9, and 11 times more likely, respectively, for incentive vs usual care participants. Groups did not differ on study retention or counseling attendance. The average cost of prizes was 120 dollars per participant. CONCLUSION: An abstinence incentive approach that paid 120 dollars in prizes per participant effectively increased stimulant abstinence in community-based methadone maintenance treatment clinics.

Adult↗
PubMed2006

ESI-QqTOF-MS/MS and APCI-IT-MS/MS analysis of steroid saponins from the rhizomes of Dioscorea panthaica.

Using high-resolution quadrupole time-of-flight mass spectrometry along with an electrospray ionization source (ESI-QqTOF-MS), accurate molecular weights of 13 steroid saponins extracted from the rhizomes of Dioscorea panthaica were acquired and the corresponding molecular formulae obtained. In order to elucidate the fragmentation pathways of steroid saponins in D. panthaica, 10 authentic samples were investigated using ESI-QqTOF-MS/MS. In addition, atmospheric pressure chemical ionization mass spectrometry combined with ion trap tandem mass spectrometry (APCI-IT-MS/MS) was used to analyze the structures of 13 steroid saponins in D. panthaica. Through the analysis of their tandem mass data, diagnostic fragment ions of the spirostanol and furostanol steroid saponins in D. panthaica were detected as m/z 271.2056 and 253.1951. In addition, four pairs of isomers were detected and the possible structures of four unknown steroid saponins in D. panthaica speculated. ESI-TOF and APCI-MS(n) have proved to be effective tools for research on fragmentation mechanism of steroid saponins and the rapid determination of native steroid saponins in extract mixture, thereby avoiding tedious derivation and separation steps.

Carbohydrate Sequence↗
PubMed2006

Differentiation of three pairs of aconite alkaloid isomers from Aconitum nagarum var. lasiandrum by electrospray ionization tandem mass spectrometry.

Three pairs of isomers of aconite alkaloids from Aconitum nagarum var. lasiandrum have been investigated by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) employing ion-trap and quadrupole time-of-flight mass spectrometers in positive mode. Based on the differences of their fragmentation pathways and special fragment ions, three pairs of isomers of aconite alkaloids were differentiated. In addition, fragmentation laws of some veatchines and the discrepancy of fragmentation mechanisms between veatchine-type and aconitine-type alkaloid were also concluded. In the case of veatchines, a radical would be formed by homolysis of C18--C4 or C18--H bonds, followed by elimination of a series of C(2)H(2) and C(2)H(4). Moreover, the retro-Diels-Alder (RDA) reaction occurred in the E-ring and double-electron transfer triggered by the positive charge on C1 led to the formation of diagnostic ions at m/z 216. With regard to aconitine-type alkaloids, the N-substituent is not eliminated easily. Although there is no carbonyl group on some aconitine-type alkaloids, with hydroxyl and methoxyl on C15 and C16 respectively, CO was readily eliminated through tautomerization.

Aconitum↗
PubMed2006

Neighborhood-pixels algorithm combined with Sono-CT in the diagnosis of cirrhosis: an experimental study.

The goal was to investigate the role of neighborhood-pixels algorithm (NPA) in analyzing the echogram of experimental cirrhosis and the value of high frequency real-time compound imaging (Sono-CT) in improving texture analysis. A cirrhosis model was established by subcutaneously injecting CCl(4) in 80 rats. The total group of rats were divided into a control group and four treatment groups (treated for 6, 8, 10 and 12, weeks respectively). The texture of hepatic-echograms was analyzed using a "neighborhood-pixels" algorithm. Images were obtained under conventional imaging mode and Sono-CT, respectively. The second texture parameter (FP(2)) was estimated and compared in different groups and under different modes. FP(2) increased gradually with the time of treatment and group differences were significant (p < 0.01). In these groups, FP(2) was higher under Sono-CT than under conventional condition (p < 0.01) and group differences in FP(2) under both conditions were significant (p < 0.01). Thus, FP(2) measured by neighborhood-pixels algorithm can reflect the dynamic change of the texture of echogram of cirrhosis in rats and Sono-CT can improve texture analysis by neighborhood-pixels algorithm, thus facilitating the early diagnosis of cirrhosis.

Algorithms↗