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Biomedical subjects

Yu Liu

Publications and source records attributed to Yu Liu.

At least 109 records · Page 6Linked to original sources
PubMed2005

Causes and control of filamentous growth in aerobic granular sludge sequencing batch reactors.

Poor long-term stability of aerobic granules developed in sequencing batch reactors (SBRs) remains a limitation to widespread use of aerobic granulation in treating wastewater. Filamentous growth has been commonly reported in aerobic granular sludge SBR. This review attempts to address the instability problem of aerobic granular sludge SBR from the perspective of filamentous growth in the system. The possible causes of filamentous growth are identified, including long retention times of solids, low substrate concentration in the liquid phase, high substrate gradient within the granule, dissolved oxygen deficiency in the granule, nutrient deficiency inside granule, temperature shift and flow patterns. Because of cyclic operation of aerobic granular sludge SBR and peculiarities of aerobic granules, various stresses can be present simultaneously and can result in progressive development of filamentous growth in aerobic granular sludge SBR. Overgrowth of filamentous bacteria under stress conditions appears to be a major cause of instability of aerobic granular sludge SBR. Specific recommendations are made for controlling filamentous growth.

Bacteria, Aerobic↗
PubMed2005

Human M-ficolin is a secretory protein that activates the lectin complement pathway.

Three types of ficolins have been identified in humans: L-ficolin, M-ficolin, and H-ficolin. Similar to mannose-binding lectin, L-ficolin and H-ficolin are the recognition molecules in the lectin complement pathway. Another human ficolin, M-ficolin, is a nonserum ficolin that is expressed in leukocytes and lung; however, little is known about its physiologic roles. In this study, we report the characterization of M-ficolin in terms of its protein localization and lectin activity. M-ficolin was localized in secretory granules in the cytoplasm of neutrophils, monocytes, and type II alveolar epithelial cells in lung. M-ficolin precipitated with mannose-binding lectin-associated serine proteases (MASP)-1 and MASP-2 in a co-immunoprecipitation assay, indicating that M-ficolin forms complexes with MASP-1 and MASP-2. M-ficolin-MASP complexes activated complement on N-acetylglucosamine (GlcNAc)-coated microplates in a C4 deposition assay. M-ficolin bound to several neoglycoproteins bearing GlcNAc, N-acetylgalactosamine, and sialyl-N-acetyllactosamine, suggesting that M-ficolin can recognize the common carbohydrate residues found in microbes. Indeed, M-ficolin bound to Staphylococcus aureus through GlcNAc. These results indicate that M-ficolin, like its family members, functions as a recognition molecule of the lectin complement pathway and plays an important role in innate immunity.

Complement Activation↗
PubMed2005

Studies of intestinal drug transport using an in silico epithelio-mimetic device.

We report the development and use of a synthetic, discrete event, discrete space model that functions as an epithelio-mimetic device (EMD). It is intended to facilitate the study of intestinal transport of drug-like compounds. We represent passive paracellular and transcellular transport, carrier-mediated transport and active efflux using stand-alone components. Systematic verification of the EMD over a wide physiologically realistic range is essential before we can use it to address questions regarding the details of the interacting mechanisms that are believed to influence absorption. We report details of key verification experiments. We demonstrate that this device can generate behaviors similar to those observed in the in vitro Caco-2 transwell system. To do that we used a series of hypothetical drugs and we simulated behaviors for two clinically used drugs, alfentanil and digoxin. The results support the feasibility and practicability of the EMD as a tool to expand the experimental options for better understanding the biological processes involved in intestinal transport and absorption of compounds of interest.

Alfentanil↗
PubMed2005

Identification of a novel gene, HCR2, in aorta of hypercoagulable rats using suppression subtractive hybridization.

Screening and identification of novel genes involved in hypercoagulable state (HCS) is important in understanding the underlying mechanisms of development of atheroslerosis, which implicated in critical vascular diseases such as coronary heart disease and stroke. HCS was induced in rats with high carbohydrate diet. Subtractive hybridization experiments between aorta tissues from hypercoagulable rats and controls showed that a novel cDNA (GenBank Accession No. AY234417), designated as hypercoagulability related gene-2 (HCR2), was highly expressed in aorta tissue. The predicted protein encoded by HCR2 contains 78 amino acids, which has a theoretical isoelectric point (pI) of 8.59 and molecular weight (MW) of 8841.7 based on sequence analysis. Our data suggest that HCR2 may be involved in HCS and identification of the gene may contribute to our understanding of the mechanisms for the production of a hypercoagulable state of several critical clinical disorders.

Amino Acid Sequence↗
PubMed2005

Electrochemiluminescence of terbium (III)-two fluoroquinolones-sodium sulfite system in aqueous solution.

The electrochemiluminescence (ECL) of Tb3+-enoxacin-Na2SO3 system (ENX system) and Tb3+-ofloxacin-Na2SO3 system (OFLX system) in aqueous solution is reported. ECL is generated by the oxidation of Na2SO3, which is enhanced by Tb3+-fluoroquinolone (FQ) complex. The ECL intensity peak versus potential corresponds to oxidation of Na2SO3, and the ECL emission spectra (the peaks are at 490, 545, 585 and 620 nm) match the characteristic emission spectrum of Tb3+, indicating that the emission is from the excited state of Tb3+. The mechanism of ECL is proposed and the difference of ECL intensity between ENX system and OFLX system is explained. Conditions for ECL emission were optimized. The linear range of ECL intensity versus concentrations of pharmaceuticals is 2.0 x 10(-10) -8.0 x 10(-7)mol l(-1) for ENX and 6.0 x 10(-10) -6.0 x 10(-7)mol l(-1) for OFLX, respectively. A theoretical limit of detection is 5.4 x 10(-11)mol l(-1) for ENX and 1.6 x 10(-10)mol l(-1) for OFLX, respectively. The ECL was satisfactorily applied to the determination of the two FQs in dosage form and urine sample.

Electrochemistry↗
PubMed2005

Neuronal activity in primary motor cortex differs when monkeys perform somatosensory and visually guided wrist movements.

This study was designed to investigate how activity patterns of primary motor cortical (MI) neurons change when monkeys perform the same movements guided by somatosensory and/or visual cues. Two adult male rhesus monkeys were trained to make wrist extensions and flexions after holding a steady position during an instructed delay period lasting 0.5-2.0 s. Monkeys held against a 0.07 Nm load that opposed flexion movements. Wrist movements were guided by vibratory cues (VIB-trials), visual cues (VIS-trials), or both in combination (COM-trials). Extracellular recordings of 188 MI neurons were made during all three paradigms. Individual neurons were counted twice, once for each movement direction, yielding 376 cases. All neurons had significant task-related activity (TRA) changes relative to delay period activity during at least one of the three paradigms. TRA was analyzed to determine if it was different as a function of the sensory cue(s) that initiated movement and that specified movement endpoints. Cases were grouped by whether the TRA changes were greater in VIB- or VIS-trials; this defined their "bias". One hundred and eighteen cases (31.4%) had greater TRA changes in VIB-trials (Vb-neurons), whereas 185 (49.2%) showed greater TRA changes in VIS-trials (Vs-neurons). The remaining 73 cases (19.4%) had similar TRA changes in VIB- and VIS-trials (Nb-neurons). For Vb- and Vs-neurons, earlier TRA onsets and greater TRA changes were observed in the trials for which these neurons were biased. During the COM-trials, the TRA was intermediate. During the trials for which the activity was not biased, the TRA was the least. For Nb-neurons, no significant TRA differences were observed across paradigms. TRA changes of MI neurons may represent movement planning-related inputs from other central, presumably cortical, sources as well as contribute to motor outflow from the cortex. These data suggest that Vb- and Vs-neurons are affected differently by somatosensory- and visually related central inputs, resulting in different TRAs, even for essentially identical movements. Such differences may depend not only on the type of sensory information that initiates movement but also whether that information specifies movement endpoints or might interfere with movement monitoring.

Animals↗
PubMed2005

[The role of hypoxia on expression of cyclooxygenase-2 in synovial fibroblasts derived from human temporomandular joint].

OBJECTIVE: To investigate the effects of hypoxia on expression of COX-2 in synovial fibroblasts derived from human TMJ and to analyze the biological role of COX-2 on TMJ disorders. METHODS: Synovial fibroblasts were induced by hypoxia, COX-2 expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting. Moreover, cells were stimulated by hypoxia or celecoxib or both of them, prostaglandin E(2) (PGE(2)), matrix metalloproteinase 2, 9 (MMP-2, MMP-9) release was detected by enzyme-linked immunosorbent assay (ELISA) or gelatin zymography. Cells that were placed under normoxic conditons were used as controls. RESULTS: (1) In response to hypoxia, at 4 h (1.51 +/- 0.34), 8 h (1.39 +/- 0.57), significant elevation of COX-2 mRNA expression occurred, compared with data (0.65 +/- 0.24), (0.71 +/- 0.15) under normoxic condition (both P < 0.05). (2) The elevation of COX-2 protein was detectable at 6 h (0.29 +/- 0.06), 12 h (0.51 +/- 0.09), 24 h (0.68 +/- 0.11), contrasted with normoxia (all P < 0.01). Therefore, it is suggested that COX-2 expression pattern present a time-dependent response to hypoxic conditions. (3) The concentration of PGE(2) released by synovial fibroblasts under 12 h hypoxic condition (7.6 ng/ml +/- 0.8 ng/ml) was significantly higher than those under normoxic condition (2.5 ng/ml +/- 0.4 ng/ml, P < 0.01) or in response to celecoxib combined with hypoxia (4.3 ng/ml +/- 0.4 ng/ml, P < 0.05). (4) The amount of MMP-2, MMP-9 produced by synovial fibroblasts under 12 h hypoxic condition was upregulated compared with that under normoxia or in response to celecoxib combined with hypoxia. CONCLUSIONS: Hypoxia is, at least in part, responsible for the pathogenesis of TMJ disorders, probably by promoting COX-2 expression of synovial fibroblasts derived from TMJ.

Cell Hypoxia↗
PubMed2005

Cyclodextrins as carriers for cinchona alkaloids: a pH-responsive selective binding system.

A series of cyclodextrin-cinchona alkaloid inclusion complexes were prepared from beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin and four cinchona alkaloids in ca. 90% yields, and their inclusion complexation behavior was investigated at pH 7.2 and 1.5 by means of fluorescence, UV/Vis and 2D NMR spectroscopy. The results showed that the cinchona alkaloids can be efficiently encapsulated in the cyclodextrin cavity in an acidic environment and sufficiently released in a neutral environment, which makes these cyclodextrin derivatives the potential carriers for cinchona alkaloids. The binding ability and molecular selectivity of cyclodextrins toward cinchona alkaloids were discussed from the viewpoint of the size-fit concept and multiple recognition mechanism between host and guest.

Binding Sites↗
PubMed2005

The role of SBR mixed liquor volume exchange ratio in aerobic granulation.

Four sequencing batch reactors (SBR) were operated at different volume exchange ratios of 20-80%. Results showed that a rapid aerobic granulation could be achieved in SBR run at high volume exchange ratios, and the characteristics of mature aerobic granules in terms of mean size, SVI, granule fraction, EPS and calcium content were all closely related to the volume exchange ratio applied to SBR. To interpret the role of volume exchange ratio in aerobic granulation, a concept of minimum settling velocity of bioparticles was proposed, which is the function of both settling time and volume exchange ratio. It was further demonstrated that the effect of volume exchange ratio on aerobic granulation in SBR would be realized through selecting the minimum settling velocity of bioparticles. In fact, the minimum settling velocity would serve as a major selection pressure exerted on bioparticles. It appeared from this study that the production of EPS was stimulated significantly by high volume exchange ratio, which was associated with marketable accumulation of calcium ion in aerobic granulation. It is expected that this study may offer insights into the mechanism of aerobic granulation.

Aerobiosis↗
PubMed2005

Spectrophotometric study on the controlling factor of molecular selective binding of dyes by bridged bis(beta-cyclodextrin)s with diselenobis(benzoyl) linkers.

A series of beta-cyclodextrin (beta-CD) dimers with 4,4'-diselenobis(benzoyl) linkers, that is, 6,6'-[4,4'-diselenobis(benzoyloxyl)]-bridged bis(beta-CD) (1a), 6,6'-[4,4'-diselenobis[2-(benzoylamino)ethyleneamino]]-bridged bis(beta-CD) (2a), and 6,6'-[4,4'-diselenobis[2-(benzoylamino)-3,6-diazaoctylamino]]-bridged bis(beta-CD) (3a), were synthesized in moderate yields by the reaction of 4,4'-diselenobis(benzoic acid) with beta-CD or oligo(ethylenediamino)-6-deoxy-beta-CD. Their binding behaviors with some structure-related substrates, such as acridine red (AR), neutral red (NR), rhodamine B (RhB), ammonium 8-anilino-1-naphthalenesulfonate (ANS), and 6-p-toluidino-2-naphthalenesulfonic acid (TNS), were investigated in aqueous phosphate buffer solution (pH 7.20) at 298.15 K by means of fluorescence, NMR, as well as circular dichroism spectroscopy and compared with those of their 2,2'-diselenobis(benzoyl)-linked analogues, that is, 6,6'-[2,2'-diselenobis(benzoyloxyl)]-bridged bis(beta-CD) (1b), 6,6'-[2,3'-diselenobis[2-(benzoylamino)ethyleneamino]]-bridged bis(beta-CD) (2b), and 6,6'-[2,2'-diselenobis[2-(benzoylamino)-3,6-diazaoctylamino]]-bridged bis(beta-CD) (3b). The results showed that bis(beta-CD)s 1a-3a, whose Se-Se bonds were located at the para position of the carboxyl group, gave stronger binding abilities toward nonlinear guests (RhB and ANS) than their analogues 1b-3b, whose Se-Se bonds were located at the ortho position relative to the carboxyl group. The molecular binding ability and selectivity of model substrates by these ditopic hosts were sufficiently discussed to reveal not only the cooperative contributions of the linker group and CD cavities upon inclusion complexation with dye guest molecules but also the controlling factors for the molecular selective binding.

Journal Article↗
PubMed2005

Analysis of the 2.0 A crystal structure of the protein-DNA complex of the human PDEF Ets domain bound to the prostate specific antigen regulatory site.

PDEF, a prostate epithelial specific transcription factor, is a member of the Ets family of DNA binding proteins. Here we report a 2.0 A crystal structure of the PDEF Ets domain in complex with a natural, high-affinity DNA binding site in the promoter/enhancer region of the human prostate specific antigen gene. Comparison of the PDEF-DNA complex with other Ets complexes revealed key features that are shared among Ets members, as well as important differences in substrate specification at both the "GGA" core and the flanking regions of the DNA site. The combination of the serine residue at position 308 and the glutamine at position 311 explains the previous observation that the PDEF binds preferentially to a thymine at the +4 position of its binding site. Despite the common essential features that are shared among Ets members, PDEF demonstrates distinct patterns of interactions at different positions of DNA in achieving sequence specific recognition. Collectively, the common and unique interactions with both the DNA bases and the backbone phosphates lead to substrate specificity and individual preference for certain DNA sites.

3' Flanking Region↗
PubMed2005

Cooperative interaction of human XPA stabilizes and enhances specific binding of XPA to DNA damage.

Human xeroderma pigmentosum group A (XPA) is an essential protein for nucleotide excision repair (NER). We have previously reported that XPA forms a homodimer in the absence of DNA. However, what oligomeric forms of XPA are involved in DNA damage recognition and how the interaction occurs in terms of biochemical understanding remain unclear. Using the homogeneous XPA protein purified from baculovirus-infected Sf21 insect cells and the methods of gel mobility shift assays, gel filtration chromatography, and UV-cross-linking, we demonstrated that both monomeric and dimeric XPA bound to the DNA adduct of N-acetyl-2-aminofluorene (AAF), while showing little affinity for nondamaged DNA. The binding occurred in a sequential and protein concentration-dependent manner. At relatively low-protein concentrations, XPA formed a complex with DNA adduct as a monomer, while at the higher concentrations, an XPA dimer was involved in the specific binding. Results from fluorescence spectroscopic and competitive binding analyses indicated that the specific binding of XPA to the adduct was significantly facilitated and stabilized by the presence of the second XPA in a positive cooperative manner. This cooperative binding exhibited a Hill coefficient of 1.9 and the step binding constants of K(1) = 1.4 x 10(6) M(-)(1) and K(2) = 1.8 x 10(7) M(-)(1). When interaction of XPA and RPA with DNA was studied, even though binding of RPA-XPA complex to adducted DNA was observed, the presence of RPA had little effect on the overall binding efficiency. Our results suggest that the dominant form for XPA to efficiently bind to DNA damage is the XPA dimer. We hypothesized that the concentration-dependent formation of different types of XPA-damaged DNA complex may play a role in cellular regulation of XPA activity.

2-Acetylaminofluorene↗
PubMed2005

Supramolecular structures and assembly and luminescent properties of quinacridone derivatives.

The synthesis and single-crystal X-ray structures of two quinacridone derivatives, N,N'-di(n-butyl)quinacridone (1) and N,N'-di(n-butyl)-1,3,8,10-tetramethylquinacridone (2), are reported, and the 1H NMR, absorption, photoluminescent (PL), and electroluminescent (EL) characteristics are presented. Both these crystal structures are characterized by intermolecular pi...pi and hydrogen bonding interactions. The intermolecular pi...pi interactions lead to the formation of molecular columns in the solids of 1 and 2, and the interplanar contact distances between two adjacent molecules are 3.48 and 3.55 angstroms, respectively. Crystals of 1 display shorter intermolecular pi...pi contacts and higher density than 2. These results suggest that tighter intermolecular interactions exist in 1. The 1H NMR, absorption, and PL spectra of 1 and 2 in solutions exhibit concentration-dependent properties. The PL quantum yields of 1 in solutions decrease more quickly with the increase of concentration compared to that of 2 in solutions. For solid thin films of Alq3:1 (Alq3 = tris(8-hydroxyquinolinato)aluminum), emission intensities dramatically decrease and obvious red shifts are observed when the dopant concentration is above 4.2%, while for films of Alq3:2, a similar phenomenon occurs when the concentration is above 6.7%. EL devices with Alq3:1 as emitting layer only show high efficiencies (20.3-14.5 cd/A) within the narrow dopant concentration range of 0.5-1.0%. In contrast, high efficiencies (21.5-12.0 cd/A) are achieved for a wider dopant concentration range of 0.5-5.0% when Alq3:2 films are employed as emitting layer. The different PL and EL concentration-dependent properties of the solid thin films Alq3:1 and Alq3:2 are attributed to their different molecular packing characteristics in the solid state.

Journal Article↗
PubMed2005

Inclusion complexes of azadirachtin with native and methylated cyclodextrins: solubilization and binding ability.

The inclusion complexation behavior of azadirachtin with several cyclodextrins and their methylated derivatives has been investigated in both solution and the solid state by means of XRD, TG-DTA, DSC, NMR, and UV-vis spectroscopy. The results show that the water solubility of azadirachtin was obviously increased after resulting inclusion complex with cyclodextrins. Typically, beta-cyclodextrin (beta-CD), dimethyl-beta-cyclodextrin (DMbetaCD), permethyl-beta-cyclodextrin (TMbetaCD), and hydroxypropyl-beta-cyclodextrin (HPbetaCD) are found to be able to solubilize azadirachtin to high levels up to 2.7, 1.3, 3.5, and 1.6 mg/mL (calculated as azadirachtin), respectively. This satisfactory water solubility and high thermal stability of the cyclodextrin-azadirachtin complexes, will be potentially useful for their application as herbal medicine or healthcare products.

Cyclodextrins↗
PubMed2005

Distribution of EPS and cell surface hydrophobicity in aerobic granules.

This study described the distribution of extracellular polysaccharides (EPS) and hydrophobicity in aerobic granule as well as the essential role of EPS in maintaining the stable structure of aerobic granules. Aerobic granules showed a heterogeneous structure, which had an outer shell with high biomass density and an inner core having a relatively low biomass density. Results showed that the outer shell of aerobic granule was composed of poorly soluble and noneasily biodegradable EPS, whereas its core part was filled with readily soluble and biodegradable EPS. It was further found that the shell of aerobic granule exhibited a higher hydrophobicity than the core of granule. The insoluble EPS present in the granule shell would play a protective role with respect to the structure stability and integrity of aerobic granules.

Aerobiosis↗
PubMed2005

Fluorinated nanodiamond as a wet chemistry precursor for diamond coatings covalently bonded to glass surface.

The chemical reaction between fluoro-nanodiamond (F-ND) powder, solubilized in o-dichlorobenzene, and a glass surface, functionalized with the silane coupling agent, 3-aminopropyltriethoxysilane (APTES), was found to proceed under heating at 130 degrees C for 24-40 h and to result in covalent bonding of F-ND particles to a glass substrate, forming a 10-40 nm thick nanocrystalline film. The observed process presents a novel and cost-effective approach to fabrication of diamond coatings on glass by using wet chemistry instead of CVD and can be extended to other materials.

Journal Article↗
PubMed2005

catena-Poly[[aquabis(1H-benzimidazole-kappa N3)manganese(II)]-mu-adipato].

In the title polymeric complex, [Mn(C6H8O4)(C7H6N2)2(H2O)]n, the MnII atom is surrounded by two adipate dianions, two benzimidazole molecules and one coordinated water molecule. The Mn atoms and coordinated water molecule are located on a twofold axis, and the bridging adipate ligand is located on an inversion center. The adipate dianions bridge neighboring MnII atoms to form polymeric chains. Each MnII atom is seven-coordinate, the longest Mn-O bond length being 2.5356 (16) A.

Journal Article↗