Biomedical subjects

Qing Liu

Publications and source records attributed to Qing Liu.

At least 37 records · Page 2Linked to original sources

PubMed2006

Hairpin DNA probe based electrochemical biosensor using methylene blue as hybridization indicator.

In this paper, a label-free, rapid and simple method was proposed to study the hybridization specificity of hairpin DNA probe using methylene blue (MB) as a hybridization indicator. Thiolated hairpin DNA probe was immobilized on the gold electrode by self-assembly. The voltammetric signals of MB were investigated at these modified electrodes by means of cyclic voltammetry (CV) detection. Single-base mutation oligonucleotide and random oligonucleotide can be easily discriminated from complementary target DNA. The effect of mismatch position in target DNA was investigated. Experimental results showed that mutation in the center of target DNA had greatest effect on the hybridization with hairpin DNA probe. The relationship between electrochemical responses and DNA target concentration was also studied. The reduction current of MB intercalation decreased with increasing the concentration of target DNA. Taken together, these experiments demonstrate that the hybridization indicator MB provides great promise for rapid and specific measurement of target DNA.

Biosensing Techniques↗

PubMed2006

Enhancement of periodontal tissue regeneration by locally controlled delivery of insulin-like growth factor-I from dextran-co-gelatin microspheres.

The present work focused on the design of novel hydrogel microspheres based on both dextran- and gelatin-derived biomaterials, and discussed whether locally controlled delivery of IGF-I from dextran-co-gelatin hydrogel microspheres (DG-MP) was useful for periodontal regeneration enhancement. Microspheres were synthesized when gelatin was cooperating with glycidyl methacrylate (GMA) derivatized dextrans (Dex-GMA) and the resultant DG-MP with a hydrogel character of which the cross-linking density could be controlled by the degree of substitution (DS, the number of methacrylates per 100 glucopyranose residues) of Dex-GMA. In this study, three types of DG-MP (DG-MP4.7, DG-MP6.3 and DG-MP7.8) obtained from gelatin and Dex-GMA (differing in DS: 4.7, 6.3 and 7.8 respectively) were prepared and characterized by swelling and degradation properties, drug release kinetics and biological capability in promoting tissue regeneration. By swelling in aqueous positively charged IGF-I solutions, the protein could be encapsulated in DG-MP by polyionic complexation with negatively charged acidic gelatin. No obvious influence of Dex-GMA's DS on DG-MP's configuration and size was observed, and the release and degraded properties showed no significant difference between three types of DG-MP in PBS buffer either. However, high DS of Dex-GMA could lower microsphere's swelling, prolong its degraded time and minimize IGF-I burst release markedly in dextranase-containing PBS, where IGF-I release from a slow release type of microspheres (DG-MP7.8) could be maintained more than 28 days, and an effective protein release kinetics without a significant burst but a relevantly constant release after the initial burst was achieved. IGF-I in DG-MP resulted in more new bone formation in the periodontal defects within 4 or 8 weeks than IGF-I in blood clot directly did (P < 0.01). The observed newly formation of periodontal tissues including the height and percentage of new bone and new cementum on the denuded root surfaces of the furcation area in DG-MP7.8 group were more than that in other groups (P < 0.05). The adequate width of regenerative periodontal ligament (PDL), regular Sharpey's fibers and alveolar bone reconstruction could be observed only in DG-MP7.8 group. These combined results demonstrate that effective release kinetics can be realized by adjusting the DS of Dex-GMA and followed cross-linking density of DG-MP, and that locally controlled delivery of IGF-I from slow release type of DG-MP may serve as a novel therapeutic strategy for periodontal tissue regeneration.

Animals↗

PubMed2006

Widely tunable optical bandpass filter by use of polymer long-period waveguide gratings.

We report the design and fabrication of a widely tunable optical bandpass filter based on using two identical long-period gratings formed along a polymer channel waveguide with a section of the waveguide core removed. The peak transmission of the passband of the fabricated filter is approximately 60% and the bandwidth of the passband is approximately 6 nm. The filter is thermally tunable over the C + L band (1520-1610 nm) for both TE and TM polarizations with a temperature control of approximately 30 degrees C.

Journal Article↗

PubMed2006

A folate receptor-targeted liposomal formulation for paclitaxel.

A novel liposomal formulation of paclitaxel targeting the folate receptor (FR) was synthesized and characterized. This formulation was designed to overcome vehicle toxicity associated with the traditional Cremophor EL-based formulation and to provide the added advantages of prolonged systemic circulation time and selective targeting of the FR, which is frequently overexpressed on epithelial cancer cells. The formulation had the composition of dipalmitoyl phosphatidylcholine/dimyristoyl phosphatidylglycerol/monomethoxy-polyethylene glycol (PEG)2000-distearoyl phosphatidylethanolamine/folate-PEG3350-distearoyl phosphatidylethanolamine (DPPC/DMPG/mPEG-DSPE/folate-PEG-DSPE) at molar ratios of (85.5:9.5:4.5:0.5) and a drug-to-lipid molar ratio of 1:33. The liposomes were prepared by polycarbonate membrane extrusion. The mean particle size of the liposomes was 97.1 nm and remained stable for at least 72 h at 4 degrees C. FR-targeted liposomes of the same lipid composition entrapping calcein were shown to be efficiently taken up by KB oral carcinoma cells, which are highly FR+. FR-targeted liposomes containing paclitaxel showed 3.8-fold greater cytotoxicity compared to non-targeted control liposomes in KB cells. Plasma clearance profiles of paclitaxel in the liposomal formulations were then compared to paclitaxel in Cremophor EL formulation. The liposomal formulations showed much longer terminal half-lives (12.33 and 14.23 h for FR-targeted and non-targeted liposomes, respectively) than paclitaxel in Cremophor EL (1.78 h). In conclusion, the paclitaxel formulation described in this study has substantial stability and favorable pharmacokinetic properties. The FR-targeted paclitaxel formulation is potentially useful for treatment of FR+ tumors and warrants further investigation.

Animals↗

PubMed2006

Experimental demonstrations of the digital correction of complex wave errors caused by arbitrary phase-shift errors in phase-shifting interferometry.

In previous papers we proposed a digital method of correcting both amplitude and phase distortions caused by arbitrary phase-shift errors in standard four-frame phase-shifting interferometry (PSI), then extended it to the most generalized PSI, and showed the validity of this technique by computer simulations. Here some new simulations and a series of optical experiments with a plane wave, a spherical wave, and a piece of glass as objects are reported. The experimental results have further proved the correctness of our theoretical analysis and confirmed that our method is able to suppress double-frequency fringes in the retrieved amplitude map and the distortions in the phase map that are introduced by phase-shift errors such as to effectively eliminate the wave ripples and wall-like structures that are present in the unwrapped phase map owing to these errors. In addition, our technique can reduce the density of invalid pixels, which are barriers in phase unwrapping. Therefore the accuracy of both amplitude and phase measurements can be considerably improved.

Journal Article↗

PubMed2006

GAP1 family members constitute bifunctional Ras and Rap GTPase-activating proteins.

GAP1(IP4BP) is a member of the GAP1 family of Ras GTPase-activating proteins (Ras GAPs) that includes GAP1(m), CAPRI, and RASAL. Composed of a central Ras GAP domain, surrounded by amino-terminal C(2) domains and a carboxyl-terminal pleckstrin homology/Bruton's tyrosine kinase domain, GAP1(IP4BP) has previously been shown to possess an unexpected GAP activity on the Ras-related protein Rap, besides the predicted Ras GAP activity (Cullen, P. J., Hsuan, J. J., Truong, O., Letcher, A. J., Jackson, T. R., Dawson, A. P., and Irvine, R. F. (1995) Nature 376, 527-530). Here we have shown that GAP1(IP4BP) is indeed an efficient Ras/Rap GAP, having K(m)s of 213 and 42 microm and estimated k(cat)s of 48 and 16 s(-1) for Ras and Rap, respectively. For this dual activity, regions outside the Ras GAP domain are required, as the isolated domain (residues 291-569) retains a pronounced Ras GAP activity yet has very low activity toward Rap. Interestingly, mutagenesis of the Ras GAP arginine finger, and surrounding residues important in Ras binding, inhibit both Ras and Rap GAP activity of GAP1(IP4BP). Although the precise details by which GAP1(IP4BP) can function as a Rap GAP remain to be determined, these data are consistent with Rap associating with GAP1(IP4BP) through the Ras-binding site within the Ras GAP domain. Finally, we have established that such dual Ras/Rap GAP activity is not restricted to GAP1(IP4BP). Although GAP1(m) appears to constitute a specific Ras GAP, CAPRI and RASAL display dual activity. For CAPRI, its Rap GAP activity is modulated upon its Ca(2+)-induced association with the plasma membrane.

Animals↗

PubMed2006

MASPIT: three-hybrid trap for quantitative proteome fingerprinting of small molecule-protein interactions in mammalian cells.

Organic small molecules generally act by perturbing the function of one or more cellular target proteins, the identification of which is essential to an understanding of the molecular basis of drug action. Here we describe the application of methotrexate-linked small molecule ligands to a mammalian three-hybrid interaction trap for proteome-wide identification of small molecule targets, quantification of the targeting potency of unmodified small molecules for such targets in intact cells, and screening for inhibitors of small molecule-protein interactions. During the course of this study we also identified the pyrido[2,3-d]pyrimidine PD173955, a known SRC kinase inhibitor, as a potent inhibitor of several ephrin receptor tyrosine kinases. This finding could perhaps be exploited in the design of inhibitors for this kinase subfamily, members of which have been implicated in the pathogenesis of various diseases, including cancer.

Blotting, Western↗

PubMed2006

Downregulation of desmuslin in primary vein incompetence.

OBJECTIVE: Primary vein incompetence is one of the most common diseases of the peripheral veins, but its pathogenesis is unknown. These veins present obvious congenital defects, and examination of gene expression profiles of the incompetent vein specimens may provide important clues. The aim of this study was to screen for genes affecting the primary vein incompetence phenotype and test the differential expression of certain genes. METHODS: We compared gene expression profiles of valvular areas from incompetent and normal great saphenous veins at the saphenofemoral junctions by fluorescent differential display reverse-transcription polymerase chain reaction (FDD RT-PCR). Differentially expressed complimentary DNAs (cDNAs) were confirmed by Northern blotting and semi-quantitative RT-PCR. Similarity of the cDNAs sequences to GenBank sequences was determined. Gene expression status was then determined by Western blot analysis and immunohistochemical techniques. RESULTS: There were >30 differentially expressed cDNA bands. Sequence analysis revealed that a cDNA fragment obviously downregulated in incompetent great saphenous vein was a portion of the messenger RNA (mRNA) encoding desmuslin, a newly discovered intermittent filament protein. Northern blotting and semi-quantitative RT-PCR analysis revealed a similar mRNA expression profile of the desmuslin gene in other samples. Western blotting and immunohistochemical techniques localized the desmuslin protein mainly in the cytoplasm of venous smooth muscle cells. The amount of desmuslin was greatly decreased in the smooth muscle cells of incompetent veins. CONCLUSIONS: The expression of many genes is altered in primary vein incompetence. Up- or downregulation of these genes may be involved in the pathogenesis of this disease. Desmuslin expression is downregulated in the abnormal veins. Its effect on the integrity of smooth muscle cells might be related to malformation of the vein wall. Further studies are needed to investigate other differentially expressed cDNAs and the exact role of desmuslin in this disease. CLINICAL RELEVANCE: Primary vein incompetence is a frequent and refractory disease of the peripheral veins. Exploring its pathogenesis may enhance our comprehension and management of this disease. We used reliable techniques to detect disease-related genes and confirmed downregulation of desmuslin in abnormal veins. Alteration of these genes might be used as disease markers or gene therapy targets.

Base Sequence↗

PubMed2006

CDNA-AFLP combined with functional analysis reveals novel genes involved in the hypersensitive response.

To identify genes required for the hypersensitive response (HR), we performed expression profiling of tomato plants mounting a synchronized HR, followed by functional analysis of differentially expressed genes. By cDNA-AFLP analysis, the expression profile of tomato plants containing both the Cf-4 resistance gene against Cladosporium fulvum and the matching Avr4 avirulence gene of this fungus was compared with that of control plants. About 1% of the transcript-derived fragments (442 out of 50,000) were derived from a differentially expressed gene. Based on their sequence and expression, 192 fragments, referred to as Avr4-responsive tomato (ART) fragments, were selected for VIGS (virus-induced gene silencing) in Cf-4-transgenic Nicotiana benthamiana. Inoculated plants were analyzed for compromised HR by agroinfiltration of either the C. fulvum Avr4 gene or the Inf1 gene of Phytophthora infestans, which invokes a HR in wild-type N. benthamiana. VIGS using 15 of the ART fragments resulted in a compromised HR, whereas VIGS with fragments of ART genes encoding HSP90, a nuclear GTPase, an L19 ribosomal protein, and most interestingly, a nucleotide binding-leucine rich repeat (NB-LRR)-type protein severely suppressed the HR induced both by Avr4 and Inf1. Requirement of an NB-LRR protein (designated NRC1, for NB-LRR protein required for HR-associated cell death 1) for Cf resistance protein function as well as Inf1-mediated HR suggests a convergence of signaling pathways and supports the recent observation that NB-LRR proteins play a role in signal transduction cascades downstream of resistance proteins.

Algal Proteins↗

PubMed2006

Directed evolution of an artificial bifunctional enzyme, gamma-glutamyl kinase/gamma-glutamyl phosphate reductase, for improved osmotic tolerance of Escherichia coli transformants.

To produce the artificial bifunctional enzyme gamma-glutamyl kinase/gamma-glutamyl phosphate reductase, a mutant library of the proBA fusion gene from Bacillus subtilis was created by error-prone PCR. Selecting by functional complementation of the proline auxotroph Escherichia coli JM83 and NaCl tolerance, we isolated a mutant of the proBA fusion gene that improved the osmotolerance of host cells of E. coli JM83. A single amino acid replacement (Asn177Asp) located in a conserved domain in gamma-glutamyl kinase leads to overproduction of proline by host cells. The mutated gamma-glutamyl kinase/gamma-glutamyl phosphate reductase enzyme was rendered about 100-fold less sensitive to proline-mediated feedback inhibition than the control.

Amino Acid Sequence↗

PubMed2006

Ubiquitin-proteasome pathway function is required for lens cell proliferation and differentiation.

PURPOSE: The ubiquitin proteasome pathway is involved in the regulation of many cellular processes, such as cell cycle control, signal transduction, transcription, and removal of obsolete proteins. The objective of this work was to investigate roles for this proteolytic pathway in controlling the differentiation of lens epithelial cells into lens fibers. METHODS: bFGF-induced cell proliferation was monitored in rat lens epithelial explants by bromodeoxyuridine (BrdU) incorporation. Indicators of lens differentiation included expression of crystallins, lens major intrinsic protein 26 (MIP26), CP49, and filensin and morphologic changes such as cell multilayering and elongation or loss of nuclei. Clasto-lactacystin-beta-lactone, the proteasome-specific inhibitor, was used to study the role of the proteasome in controlling the proliferation and differentiation processes. RESULTS: Explants treated with bFGF initially underwent enhanced proliferation, as indicated by BrdU incorporation and multilayering of the epithelial cells. By 4 days of bFGF treatment, most cells withdrew from the cell cycle, as indicated by diminished BrdU incorporation. After 7 days of treatment with bFGF, lens epithelial explants displayed characteristics of lens fibers, including higher ratios of crystallins to other cytoplasmic proteins and expression of large quantities of MIP26, CP49, and filensin. Adding the proteasome inhibitor to the medium simultaneously with bFGF (day 0) or at day 4 prohibited or delayed bFGF-induced cell proliferation and differentiation. This was indicated by reduced BrdU incorporation and decreased expression of beta- and gamma-crystallins, MIP26, CP49, and filensin. Proteasome inhibition also significantly decreased the number of layers and the sizes of differentiating fibers. CONCLUSIONS: These data show that proteasome activity is required not only for lens cell proliferation but also required for the transition from the epithelial phenotype to the fiber phenotype.

Animals↗

PubMed2006

Ubiquitin-conjugating enzyme 3 delays human lens epithelial cells in metaphase.

PURPOSE: Ubc3/Cdc34 is a ubiquitin-conjugating enzyme (Ubc) with well established functions in the G1-to-S-phase transition. Expecting to find similar effects in human lens epithelial cells (HLECs), the authors explored roles for this ubiquitin-conjugating enzyme in regulation of the HLEC cycle. METHODS: Catalytically incompetent Ubc3 (C88S, L97S), wild-type (wt)Ubc3, and mutant (mt)Ubc2 (C93A) were expressed in HLECs, by using an adenoviral vector, and cell cycle progression was assessed. RESULTS: Expression of mt- and wtUbc3, but not empty virus or mtUbc2, delayed the cell cycle in metaphase, rather than the expected G1 phase. Expression of both Ubc3s also stabilized M-phase regulators, cyclin A, cyclin B, and securin. Thus, it appeared that the Ubc3 enzymes were playing roles different from canonical proteolytic functions in targeting G1/S regulators for degradation. We also directly investigated the effect of inhibiting the proteasome on the cell cycle of HLECs. When the proteasome inhibitor was added to S-phase cells, the M-phase regulators were stabilized, and the cells were arrested in the G2/M phase. In contrast, if the proteasome inhibitor was added before the cells entered the S phase, stabilization of the G1 kinase inhibitors p21WAF and p27KIP was observed and the cells were arrested in the G1 phase. CONCLUSIONS: The ubiquitin-proteasome pathway is involved in regulation of transitions between all phases of the HLEC cycle. However, in contrast with previously described roles for Ubc3 in governing G1/S transitions, expression of Ubc3 delays the HLEC cycle in metaphase. The data suggest novel roles for Ubc3 that do not involve the transfer of ubiquitin in the M phase in the HLEC cell cycle.

Adenoviridae↗

PubMed2006

[Comparative study on normal tongue manifestation in patients with primary liver cancer and healthy adults].

OBJECTIVE: To find out some microscopically visible morphological differences in normal tongue manifestation between patients with primary liver cancer and healthy adults, and provide some beneficial evidences for microcosmic syndrome differentiation of tongue inspection. METHODS: Microcirculations of the tongue tip, which represented the macroscopical normal tongue manifestation, were observed under an optical microscope in patients with primary liver cancer and healthy adults. Exfoliated cells from tongue coating were examined by hematoxylin-eosin staining. RESULTS: The proportion of normal tongue manifestation was larger in healthy adults (38.89%) than that in patients with primary liver cancer (2.32%). The total score of microcirculation of tongue tip and the maturation index of exfoliated cells from tongue coating were both higher in patients with primary liver cancer than those in healthy adults with normal tongue manifestation (P<0.01, P<0.05). CONCLUSION: Normal tongue manifestation, which is macroscopically visible, can be observed in both patients with primary liver cancer and healthy adults, but there exists obvious difference in microcosmic view.

Adult↗

PubMed2006

[Correlation between the width of lingual vein and the changes of hemodynamics of portal system in patients with primary liver cancer].

OBJECTIVE: To explore the correlation between the width of lingual varix and changes of hemodynamics of portal system in patients with primary liver cancer so as to supply the data for the forecast of portal hypertension by observing lingual varix. METHODS: The diameter of lingual vein (Dlv) was measured by vernier caliper as dependent variable, and the diameters and indexes of hemodynamics of portal vessels were measured by Doppler as independent variables, then a multipe stepwise analysis was performed. RESULTS: The diameters of portal vein (Dpv) and splenic vein (Dsv) entered the formula Dlv (mm) = 0.185 + 0.311 Dsv (mm) + 0.236 Dpv (mm) when the entry and removal values were alpha(in)=0.10 and alpha(out)=0.15, respectively. CONCLUSION: The width of lingual vein is closely correlated with the diameters of portal vein and splenic vein in patients with primary liver cancer.

Adult↗

PubMed2006

[Variability of human cytomegalovirus UL144 gene in low-passage clinical isolates analyzed by HMA-SSCP].

BACKGROUND: Human cytomegalovirus (HCMV) infection is an important infectious agent that results in neonatal disease and congenital deformity. HCMV infection may affect in many organs. The different symptoms and tissue tropism of HCMV infection perhaps resulted from the genetic polymorphism of HCMV. HCMV UL144 open reading frames encode a homologue of the tumor necrosis factor receptor. It seems important to study the strain-specific variability of UL144 sequence in low-passage clinical isolates and to discuss if the variability related to the clinical HCMV infection. METHODS: HCMV-UL144 gene was amplified by PCR assay in 65 low-passage clinical isolates and urine from 7 healthy children who were HCMV-DNA positive by quantitative PCR. All the positive PCR products were analyzed by Heteroduplex mobility assay and single-stranded conformation polymorphism (HMA-SSCP) and 32 of them were sequenced. RESULTS: Fifty-five isolates and 5 urine specimens were HCMV-UL144 positive by PCR. Sequencing and HMA-SSCP analysis showed that significant strain-specific variability was present in the UL144 ORFs. Comparing UL144 sequences and the corresponding symptoms showed that genotype 2 did not exist in megacolon isolates. And genotype 1 and 3 were the major types among microcephaly and jaundice isolates respectively. CONCLUSION: HCMV-UL144 existed in almost all the low passage isolates. HMA-SSCP assay is an easy and effective method to detect the genetype of HCMV-UL144 sequence. The characteristic of sequences in different isolates showed that UL144 gene may play an important role in HCMV infection.

Cytomegalovirus↗

PubMed2006

[Polymorphisms of HCMV US28 gene of the clinical isolates from children].

BACKGROUND: To study the polymorphism of human cytomegalovirus US28 gene in children and investigate the relationship between the polymorphism and pathogenesis. METHODS: The FQ-PCR was carried out to determine the DNA quantity of clinical isolate and then the segmental PCR and HMA-SSCP were performed to test the mutation of US28 gene. The typical isolates from different diseases were selected to clone and sequence, then the results were analyzed. RESULTS: The nucleic acid mutation is frequent among the sequence of US28, those mutations focus on the two ends of US28, but most of them are sense mutation. The important functional groups of US28 are highly conserved. The amino acid mutation of some isolates resulted in the change of secondary structure, but the phylogenetic tree analysis did not show any clear association between the pathogenesis and the distribution of clinical isolates. The comparison of US28 sequences from AIDS patients with the sequences from children in our study showed that both sequences have their own specific high mutation points. CONCLUSION: There is polymorphism among the HCMV-US28 gene of clinical isolates from children. There observed no clear relationship was between the pathogenesis and the distribution of clinical isolates.

Base Sequence↗

PubMed2006

[Study on the compositions in the interface of corrosion inhibition membrane/copper plating layer/iron substrate by depth etching and photoelectron spectroscopy].

In order to explore the reason for the weak bond intensity between pyro-phosphate copper plating layer and iron substrate, spectrum technology was adopted. The compositions of various elements in the perpendicular interface were analyzed. The effect of surface roughness in the metal substrate on various elements distribution was discussed. According to etching time, the membrane layer was divided into three portions: surface layer with nitrogen and oxygen content decreasing quickly, mesosphere of basic fixed composition, and mix disturbing layer with substrate element appearing and occupying a half thickness. Through analyzing oxygen content in the mix layer, it was concluded that the oxygen layer in the interface of copper layer/iron substrate was the main cause of influencing the bond intensity between the plating layer and substrate.

English Abstract↗

PubMed2006

[Responses of enzymes in terrestrial plants to enhanced UV-B radiation].

With the destruction of ozone layer, ultraviolet-B (UV-B, 280 to approximately 320nm) radiation has being enhanced at the earth's surface. The energy of UV-B irradiation is far higher than that of visible light, which could be absorbed by biomacromolecules such as protein and nuclei acid. Enzyme is a sort of protein catalyzing the biochemical processes, and its content and activity in plant have strong responses to enhanced UV-B radiation. This paper summarized the research advances in the effects of enhanced UV-B radiation on the key enzymes, mainly including antioxidant enzymes, ribulose-1, 5-diphosphoscarboxylase, nitrate reductase and glutamine synthetase in terrestrial plants. Some suggestions for future research in this field were put forward.

Peroxidase↗