Biomedical subjects

Juan Li

Publications and source records attributed to Juan Li.

At least 37 records · Page 2Linked to original sources

PubMed2006

On-line coupling of dynamic microwave-assisted extraction with high-performance liquid chromatography for determination of andrographolide and dehydroandrographolide in Andrographis paniculata Nees.

A novel technique based on dynamic microwave-assisted extraction (DMAE) coupled on-line with high-performance liquid chromatography (HPLC) through a flow injection interface has been developed for determination of andrographolide and dehydroandrographolide in Andrographis paniculata Nees. A TM(010) microwave resonance cavity built in the laboratory was applied to concentrating the microwave energy. An extraction vessel was placed in microwave irradiation zone. The extraction was performed in a recirculating system. When a number of extraction cycles were completed, the fractional extract (20muL) was driven to the analytical column by 65% aqueous methanol and was measured by diode array detector (DAD) at 225nm. The optimized extraction conditions are follows: extraction solvent 60% aqueous methanol; microwave forward power 80W; extraction time 6min; extraction solvent flow-rate 1.0mLmin(-1). The detection and quantification limits obtained are 0.5 and 1.7microgmL(-1) for andrographolide and 0.6 and 1.9microgmL(-1) for dehydroandrographolide, respectively. The within-day and between-day precision (RSD) are 2.1% and 3.7% for andrographolide and 1.7% and 4.1% for dehydroandrographolide, respectively. Mean recoveries for andrographolide and dehydroandrographolide are 97.7% and 98.7%, respectively. Compared with ultrasonic extraction used in the Chinese pharmacopoeia, the proposed method was demonstrated to obtain higher extraction yield in a shorter time. In addition, only small quantities of solvent (5mL) and sample (10mg) were required.

Andrographis↗

PubMed2006

A small interfering CD147-targeting RNA inhibited the proliferation, invasiveness, and metastatic activity of malignant melanoma.

CD147 plays a critical role in the invasive and metastatic activity of malignant melanoma cells by stimulating the surrounding fibroblasts to express matrix metalloproteinases and vascular endothelial growth factor. We developed a system that blocks CD147 in the human malignant melanoma cell line, A375, using RNA interference. By transfecting melanoma cells with the small interfering RNA (siRNA) that targets human CD147, we were able to establish two stable clones in which CD147 expression was significantly down-regulated. This resulted in the decreased proliferation and invasion of A375 cells in vitro. CD147 siRNA also down-regulated the expression of vascular endothelial growth factor in these cells and reduced the migration of vascular endothelial cells. The reduction in the CD147 level suppressed the size of s.c. tumors and the microvessel density in an A375 s.c. nude mouse xenograft model. In addition, the in vivo metastatic potential of A375 cells transfected with CD147 siRNA was suppressed in a nude mouse model of pulmonary metastasis.

Animals↗

PubMed2006

Preliminary studies of application of CdTe nanocrystals and dextran-Fe3O4 magnetic nanoparticles in sandwich immunoassay.

BACKGROUND: The favorable properties of water-soluble CdTe nanocrystals as novel biological luminescent label over conventional fluorescent probes have attracted considerable interest. The magnetic separation technique has widely been applied to various aspects in biotechnology in recent years. In this paper, we made use of CdTe nanocrystals and dextran-Fe3O4 magnetic nanoparticles for fluorescence immunoassay. METHODS: The CdTe nanocrystals and dextran-Fe3O4 magnetic nanoparticles were applied to immunoassay for the determination of human immunoglobulin G (HIgG). A rabbit anti-HIgG antibody (primary antibody) was immobilized on magnetic nanoparticles, which was used as a solid support. A sheep anti-HIgG antibody (secondary antibody) was attached to the surface of the CdTe nanocrystals via electrostatic interaction. The immunoassay was based on a sandwich immunoreaction of primary antibody on the magnetic nanoparticles, HIgG (or serum sample), and the secondary antibody labeled with CdTe nanocrystals. RESULTS: The CdTe label was compared with a fluorescein isothiocyanate (FITC) label. The CdTe is an order of magnitude more sensitive than the FITC. The immunoassay method was applied to determining the HIgG in practical samples and the results obtained are in good agreement with those obtained by nephelometry. CONCLUSION: This technique may be applied in many types of antibody-antigen system.

Animals↗

PubMed2006

Database for chicken full-length cDNAs.

The generation of full-length cDNA databases is essential for functional genomics studies as well as for correct annotation of species genomic sequences. Human and mouse full-length cDNA projects have provided the biomedical research community with a large amount of gene information. Recent completion of the chicken genome sequence draft now enables a similar full-length cDNA project to be initiated for this species. In this report, we introduce the development of a chicken full-length cDNA database, which will facilitate future research work in this biological system. In this project, chicken expressed sequence tags (ESTs) were aligned onto human and mouse full-length cDNAs (or open reading frames) on the basis of their similarity. More than 588,000 chicken ESTs were aligned to approximately 170,000 full-length human and mouse templates obtained from the NEDO, RIKEN, and MGC databases. Many of these templates have known biological functions, and their orthologous chicken genes in the EMBL database are also provided in our database, which is available at http://bioinfo.hku.hk/chicken/. We will continue to collect known chicken full-length cDNAs to update the database for public use. The cDNA alignment results presented herein and on our database will be useful for animal science and veterinary researchers wishing to clone and to confirm full-length chicken cDNAs of interest.

Animals↗

PubMed2006

The vibrational structures of furan, pyrrole, and thiophene cations studied by zero kinetic energy photoelectron spectroscopy.

The vibrational structures of the electronic ground states ((approximately)X (2)A(2)) of furan, pyrrole, and thiophene cations have been studied by zero kinetic energy (ZEKE) photoelectron spectroscopic method. In addition to the strong excitations of the symmetric a(1) vibrational modes, other three symmetric vibrational modes (a(2), b(1), and b(2)) have been observed unambiguously. These results which cannot be explained by the Franck-Condon principle illustrate that the vibronic coupling and the Coriolis coupling may play important roles in understanding the vibrational structures of the five-membered heterocycle cations. The vibrationally resolved ZEKE spectra are assigned with the assistance of the density function theory calculations, and the fundamental frequencies for many vibrational modes have been determined for the first time. The first adiabatic ionization energies for furan, pyrrole, and thiophene were determined as 8.8863, 8.2099, and 8.8742 eV, respectively, with uncertainties of 0.0002 eV.

Journal Article↗

PubMed2006

The intragenomic polymorphism of a partially inverted repeat (PIR) in Gallus gallus domesticus, potential role of inverted repeats in satellite DNAs evolution.

We report here the molecular characterization of the basic repeating unit of a novel repetitive family, partially inverted repeat (PIR), previously identified from chicken genome. This repetitive DNA family shares a close evolutionary relationship with XhoI/EcoRI repeats and chicken nuclear-membrane-associated (CNM) repeat. Sequence analyses reveal the 1430 bp basic repeating unit can be divided into two regions: the central region ( approximately 1000 bp) and the flanking region ( approximately 430 bp). Within the central region, a pair of repeats (86 bp) flanks the central core ( approximately 828 bp) in inversed orientation. Due to the tandem array feature shared by the repeating units, the inverted repeats fall between the central core and flanking region. Southern blot analyses further reveal the intragenomic polymorphism of PIR, and the molecular size of repeating units ranges from 1.1 kb to 1.6 kb. The identified monomer variants may result from multiple crossing-over events, implying the potential roles of inverted repeats in satellite DNAs variation.

Animals↗

PubMed2006

Candida pseudorugosa sp. nov., a novel yeast species from sputum.

Two yeast strains, strains XH 1026 and XH 1164, isolated from the sputum of an intensive care unit patient with acute pneumonia, were originally identified as Candida albicans and C. tropicalis, respectively. Sequence analysis of the 26S rRNA gene D1/D2 domain and the internal transcribed spacer (ITS) region indicated that the two strains represent a novel yeast species closely related to C. rogusa. The name Candida pseudorugosa sp. nov. is therefore proposed (type strain, AS 2.3107 [CBS 10433]). The new species is able to grow at 42 degrees C and is resistant or insusceptible to amphotericin B (MIC, 2 microg/ml), caspofungin (MIC, 64 microg/ml), itraconazole (MIC, 1 microg/ml), and nystatin (MIC, 16 microg/ml); dose-dependent susceptible to fluconazole (MIC, 16 microg/ml); and susceptible to flucytosine (MIC, 0.125 microg/ml) and voriconazole (MIC, 0.125 to 0.25 microg/ml). The code for C. pseudorugosa sp. nov. provided by the API 20C AUX system is identical to that for C. rugosa. The colonies of the new species on CHROMagar Candida appear blue-green, similar to those of C. albicans. In addition to the molecular method based on D1/D2 domain or ITS region sequencing, use of the combination of the API system and CHROMagar Candida is helpful for the correct identification of C. pseudorugosa sp. nov.

Aged↗

PubMed2006

Co-localization of the alpha-subunit of BK-channels and c-PLA2 in GH3 cells.

Large conductance, calcium-activated potassium channels (maxi K- or BK-channels) can be regulated by arachidonic acid produced by c-Phospholipase A2 (c-PLA2). Since in every excised patch from GH3 cells where there was BK-channel activity, treatment with either a stimulator or inhibitor of c-PLA2 resulted in a corresponding increase or decrease in BK-channel activity, we hypothesized that there must be a close association between BK-channel proteins and c-PLA2 in the cell membrane. To test this hypothesis, we first determined whether the two proteins would co-immunoprecipitate. We then used confocal imaging of fluorescently tagged proteins to determine where in the cells BK-channel proteins and c-PLA2 co-localize. The alpha-subunit of the BK-channel was strongly co-immunoprecipitated by c-PLA2 antibodies, suggesting that most of the BK channel alpha-subunits are associated with c-PLA2. This interaction was not affected by pharmacologically inhibiting c-PLA2 suggesting that the association does not require functionally active c-PLA2. Following dual immunohistochemical labeling and confocal microscopy, image analysis revealed that in the cytosol there was some co-localization, but most of the c-PLA2 was separate from BK-channel proteins. On the other hand, the c-PLA2 and BK-channel proteins at the plasma membrane were strongly co-localized. Immunoprecipitation experiments conducted with plasma membrane proteins support these findings. We conclude that c-PLA2 is likely physically associated with BK-channel proteins at the cell surface.

Animals↗

PubMed2006

[Characteristics of acid-base balance in patients with chronic severe hepatitis: analysis of 126 cases].

OBJECTIVE: To investigate the characteristics of acid-base balance in patients with chronic severe hepatitis. METHODS: Samples of venous blood and arterial blood were collected from 126 patients with chronic severe hepatitis, 106 males and 20 females, aged 44 +/- 13 (25 - 74), to undergo measurement of the potassium, sodium, and chloride ions, and urea nitrogen and creatine, blood electrolytes and blood gas analysis respectively. RESULTS: Acid-base disturbance (ABD) was found in 115 of the 126 patients (91.3%). 40 of the 115 patients with ABD (31.7%) had respiratory alkalosis combined with metabolic alkalosis, 32 of them (25.4%) had respiratory alkalosis combined with metabolic acidosis; 28 of them (22.2%) had pure respiratory alkalosis, and 8 (6.3%) had pure metabolic acidosis. Five patients had triple acid-base disturbance, 4 of which had respiratory alkalosis (combined with metabolic alkalosis and metabolic acidosis, 3.2%), and 1 of which had respiratory acidosis (combined with metabolic alkalosis and metabolic acidosis, 0.8%). There was no significantly difference in the prevalence rates of pure acid-base disturbance and multiple acid-base disturbances between the patients with cirrhosis-base chronic severe hepatitis and those with chronic hepatitis-based chronic severe hepatitis. Hypoxia symptoms were seen in 34 patients (27%). 103 patients died. All the 15 patients with their blood pH < 7.35 died. CONCLUSION: ABD in the patients with chronic severe hepatitis is mainly alkalosis with respiratory alkalosis as the basic ABD type. The appearance of ABD is not associated with the underlying illness. Patients of chronic severe hepatitis often suffer from hypoxia. Low blood pH is an important factor causing death.

Acid-Base Imbalance↗

PubMed2006

HSP70 gene fused with Hantavirus S segment DNA significantly enhances the DNA vaccine potency against hantaviral nucleocapsid protein in vivo.

Heat shock proteins (HSPs) have been shown to act as adjuvants when coadministered with peptide antigens or given as fusion proteins and enhance the vaccination efficiency. To evaluate the enhancement of the potency of Hantaan virus (HTNV) nucleocapsid protein (NP) immunogenicity by heat shock protein 70 (HSP70), we developed a novel chimeric HTNV S-HSP70 DNA vaccine plasmid by genetically linking HSP70 gene to the full-length HTNV S segment DNA (HTNV S DNA). C57BL/6 mice were immunized with this plasmid followed by a subsequent boost with homologous recombinant protein. The levels of HTNV NP-specific antibody and cellular immune response were measured by use of ELISA, fluorescence activated cell sorter (FACS) analysis, cytotoxicity assay, and IFN-gamma ELISPOT assay. We found that HTNV S-HSP70 DNA vaccination significantly increased the levels of HTNV NP-specific antibody, IgG2a/IgG1 ratio, IFN-gamma producing CD8+ T-cell precursor frequencies, and cytotoxic T lymphocyte (CTL) response when compared with immunization with HTNV S DNA alone or HTNV S DNA physically mixed with HSP70 DNA. By contrast, HSP70 DNA or vector DNA immunization could not induce appreciable levels of specific antibodies and CTL response. Thus, we demonstrate for the first time that HSP70-based HTNV S DNA can induce both humoral and cellular immune response specific for HTNV NP and is a promising candidate DNA vaccine for HTNV infection.

Animals↗

PubMed2006

Inversion vibration of PH3+(X2A2") studied by zero kinetic energy photoelectron spectroscopy.

We report the first rotationally resolved spectroscopic studies on PH3+(X2A2") using zero kinetic energy photoelectron spectroscopy and coherent VUV radiation. The spectra about 8000 cm(-1) above the ground vibrational state of PH3+(X2A2") have been recorded. We observed the vibrational energy level splittings of PH3+(X2A2") due to the tunneling effect in the inversion (symmetric bending) vibration (nu2+). The energy splitting for the first inversion vibrational state (0+/0-) is 5.8 cm(-1). The inversion vibrational energy levels, rotational constants, and adiabatic ionization energies (IEs) for nu2+ = 0-16 have been determined. The bond angles between the neighboring P-H bonds and the P-H bond lengths are also obtained using the experimentally determined rotational constants. With the increasing of the inversion vibrational excitations (nu2+), the bond lengths (P-H) increase a little and the bond angles (H-P-H) decrease a lot. The inversion vibrational energy levels have also been calculated by using one dimensional potential model and the results are in good agreement with the experimental data for the first several vibrational levels. In addition to inversion vibration, we also observed firstly the other two vibrational modes: the symmetric P-H stretching vibration (nu1+) and the degenerate bending vibration (nu4+). The fundamental frequencies for nu1+ and nu4+ are 2461.6 (+/-2) and 1043.9 (+/-2) cm(-1), respectively. The first IE for PH3 was determined as 79670.9 (+/-1) cm(-1).

Journal Article↗

PubMed2006

Determination of arbidol in human plasma by LC-ESI-MS.

A sensitive, specific and accurate method for determination of arbidol in human plasma was developed. Arbidol and internal standard were extracted from plasma samples by liquid-liquid extraction with diethyl ether. The chromatographic separation was accomplished on a Shiseido C18 3 microm analytical column (100 mm x 2.0 mm i.d.) at a flow rate of 0.3 mL/min isocratically. Detection was performed on a single quadrupole mass spectrometer by selected ion monitoring (SIM) mode via electrospray ionization (ESI) source. The method had a chromatographic run time of 6 min and a good linear relationship over the range 1-1000 ng/mL. The limit of quantitation for arbidol in plasma was 1 ng/mL. The intra-day and inter-day precision (R.S.D.%) was lower than 7% and accuracy ranged from 95 to 105%. The proposed method enables unambiguous identification and quantification of arbidol in vivo and has been successfully applied to study the pharmacokinetics of arbidol in healthy male Chinese volunteers.

Adult↗

PubMed2006

N,N-dimethyl-beta-alanine as an inexpensive and efficient ligand for palladium-catalyzed Heck reaction.

N,N-Dimethyl-beta-alanine was found to be a more powerful phosphine-free ligand than the previously reported ligand, N,N-dimethylglycine, in the Pd-catalyzed Heck reaction for a variety of aryl bromides, aryl iodides, and activated aryl chlorides with a practical turnover number of 10(3). Both kinetic and theoretical studies suggested that N,N-dimethyl-beta-alanine led to faster oxidative addition of an aryl halide to Pd than N,N-dimethylglycine. [reaction: see text]

Catalysis↗

PubMed2006

Distinct role of the N-terminal tail of the Na,K-ATPase catalytic subunit as a signal transducer.

Mounting evidence suggests that the ion pump, Na,K-ATPase, can, in the presence of ouabain, act as a signal transducer. A prominent binding motif linking the Na,K-ATPase to intracellular signaling effectors has, however, not yet been identified. Here we report that the N-terminal tail of the Na,K-ATPase catalytic alpha-subunit (alphaNT-t) binds directly to the N terminus of the inositol 1,4,5-trisphosphate receptor. Three amino acid residues, LKK, conserved in most species and most alpha-isoforms, are essential for the binding to occur. In wild-type cells, low concentrations of ouabain trigger low frequency calcium oscillations that activate NF-kappaB and protect from apoptosis. All of these effects are suppressed in cells overexpressing a peptide corresponding to alphaNT-t but not in cells overexpressing a peptide corresponding to alphaNT-t deltaLKK. Thus we have identified a well conserved Na,K-ATPase motif that binds to the inositol 1,4,5-trisphosphate receptor and can trigger an anti-apoptotic calcium signal.

Animals↗

PubMed2006

Low doses of ouabain protect from serum deprivation-triggered apoptosis and stimulate kidney cell proliferation via activation of NF-kappaB.

It now generally is agreed that Na,K-ATPase, in addition to its role in the maintenance of Na+ and K+ gradients across the cell membrane, plays a role in communicating information from the extracellular environment to intracellular signaling pathways. It was reported recently that interaction between ouabain-bound Na,K-ATPase and the 1,4,5-trisphosphate receptor (IP3R) triggers slow calcium oscillations and activation of NF-kappaB. Here it is demonstrated that this signaling pathway can serve to prevent cell death and promote cell growth. Rat renal proximal tubular cells in primary culture first were grown in the presence of 10% serum and then exposed to 0.2% serum for 24 h to induce apoptosis. Serum starvation increased the apoptotic index from 1.21 +/- 0.26 to 14.01 +/- 1.17%. Ouabain in concentrations that did not inhibit Na,K-ATPase activity (1 to 10 nM) completely abolished the apoptotic effect of serum starvation. Ouabain protection from apoptosis was not observed when release of calcium from intracellular stores via the IP3R was prevented. It was shown that the NH2 terminal tail of the Na,K-ATPase alpha subunit plays a key role in ouabain-triggered calcium oscillations. It was found that ouabain did not protect from apoptosis in serum-deprived cells that expressed a mutant Na,K-ATPase alpha subunit with deletion of the NH2 terminal tail. Ouabain exposure (10 nM for 24 h) significantly increased translocation of NF-kappaB from cytoplasm to nucleus. Helenalin, an inhibitor of NF-kappaB, abolished the antiapoptotic effect of ouabain. Ouabain (0.1 to 10 nM) also was found to stimulate proliferation and increase the viability of kidney cells. These effects were abolished when release of calcium via the IP3R was prevented.

Animals↗

PubMed2006

A neutral protease from Bacillus nematocida, another potential virulence factor in the infection against nematodes.

A neutral protease (npr) (designated Bae16) toxic to nematodes was purified to homogeneity from the strain Bacillus nematocida. The purified protease showed a molecular mass of approximately 40 kDa and displayed optimal activity at 55 degrees C, pH 6.5. Bioassay experiments demonstrated that this purified protease could destroy the nematode cuticle and its hydrolytic substrates included gelatin and collagen. The gene encoding Bae16 was cloned, and the deduced amino acid sequence showed 94% sequence identity with npr gene from B. amyloliquefaciens, but had low similarity (13-43%) with the previously reported virulence serine proteases from fungi or bacteria, which reflected their differences. Recombinant mature Bae16 (rm-Bae16) was expressed in Escherichia coli BL21 using pET30 vector system, and its nematicidal activity confirmed that Bae16 could be involved in the infection process. Our present study revealed that the npr besides the known alkaline serine protease could serve as a potential virulence factor in the infection against nematodes, furthermore, the two proteases with different characteristics produced by the same strain co-ordinated efforts to kill nematodes. These data helped to understand the interaction between this bacterial pathogen and its host.

Animals↗

PubMed2006

The characteristics of the spectra of superior venae cavae in patients with right heart failure.

BACKGROUND: Aimed to elucidate the characteristics of the spectra of superior venae cavae (SVC) in respiratory cycles in patients with right heart failure. METHODS: The spectra of SVC of 30 patients with right heart failure and 30 paired healthy subjects were recorded through right supraclavicular fossa view. The profiles of spectra of superior venae cavae were observed, and peak velocity and velocity time integral (VTI) of every wave of SVC under spontaneous respiration were measured for statistical analysis. RESULTS: In healthy subjects, the peak velocities and VTI of S wave and D wave increased in inspiratory phase and diminished in expiratory phase, and which of S wave were larger than which of D wave in whole respiratory cycle. In patients with right heart failure, spectral variations of SVC could be classified into three patterns: Pattern I: peak velocities and VTI of S wave were larger than that of D wave in early inspiratory phase, but peak velocities and VTI of D wave were larger than those of S wave in late inspiratory phase and early expiratory phase [Pattern I-1], even in whole respiratory cycle [Pattern I-2]; Pattern II: the S wave disappeared and was substituted by inverse wave with low amplitude in whole respiratory cycle. Pattern III: the profiles of the spectra of SVC in patients were similar to those of healthy subjects. In the whole, the respiratory variation ratios of peak velocities and VTI of S wave and D wave were diminished in patients compared with those in healthy subjects. CONCLUSION: The spectra of superior venae cavae in patients with right heart failure were abnormal, and these characteristics could be used as signs in evaluating right heart failure.

Blood Flow Velocity↗

PubMed2006

Mini-dystrophin efficiently incorporates into the dystrophin protein complex in living cells.

Dystrophin is a critical muscle cell structural protein which when deficient results in Duchenne muscular dystrophy. Recently miniature versions of the dystrophin gene have been constructed that ameliorate the pathology in mouse models. To characterize mini-dystrophin's incorporation into the dystrophin protein complex in living cells, two fusion proteins were constructed where mini-dystrophin is fused to the N- or C-terminus of an enhanced green fluorescent protein reporter gene. Both fusion proteins correctly localize at the plasma membrane in vitro and in vivo. Live cell microscopy establishes that mini-dystrophin translocates directly to the PM of differentiating muscle cells, within 4 h of expression. Latrunculin A treatment, actin and beta-dystroglycan binding domain deletion constructs, and co-immunoprecipitation assays demonstrate that mini-dystrophin is firmly anchored to the sarcolemma primarily through its connections to beta-dystroglycan, mimicking effects seen with wild type dystrophin. Furthermore, point mutations made within the putative beta-dystroglycan anchoring ZZ domain of mini-dystrophin result in an ablation of beta-dystroglycan binding and a nuclear translocation of the protein. These results demonstrate that mini-dystrophin is efficiently bound and incorporated into the dystrophin protein complex, via beta-dystroglycan in living cells, similarly to the full length dystrophin protein.

Actins↗