PubMed Health⌕ Search

Biomedical subjects

Yan Liu

Publications and source records attributed to Yan Liu.

At least 73 records · Page 4Linked to original sources
PubMed2006

Preparation of a novel composite particles and its application in the fluorescent detection of proteins.

A new fluorescence method for the detection of proteins with novel composite nanoparticles (CdS/PPA) has been developed. The composite nanoparticles have been prepared through an in-situ polymerization method under ultrasonic irradiation. The surface of the composite nanoparticles was covered with functional groups (-COOH). These groups may play a major role in the improving the water solubility and biocompatibility of the nanoparticles. The composite particles is combined with proteins in NaAc-HCl buffer solution (pH=1.99), which can result in strong fluorescence, and the response is linearly proportional to the concentration of proteins. In lambdaem/lambdaex=650 nm/365 nm place (the stoke' shift is 285 nm), its fluorescent strength reaches the maximum. Under the optimum conditions, the linear range is 0.10-20.0 microg.ml(-1) with the detection limit of 41 ng.ml(-1) for HSA, and 0.10-15.0 microg.ml(-1) with the detection limit of 35 ng.ml(-1) for Human gamma-IgG . The method has been applied to the determination of the total protein in human serum samples collected from the hospital and the results are satisfactory.

Calibration↗
PubMed2006

Steryl esters and phenylethanol esters from Syringa komarowii.

Three new steryl esters and a new phenylethanol ester, together with 22 known compounds were isolated from the aqueous ethanolic extract of the whole plants of Syringa komarowii. The new compounds were elucidated as stigmastane-3beta,6alpha-diol 3-O-tetradecanoate (1), stigmastane-3beta,6alpha-diol 3-O-palmitate (2), stigmastane-3beta,6alpha-diol 3-O-stearate (3), and 2-(4-hydroxyphenyl)-ethyl dotriacontanoate (4) on the basis of extensive spectral data and chemical evidences.

Esters↗
PubMed2006

Effect of initial pH control on enhanced biological phosphorus removal from wastewater containing acetic and propionic acids.

In the literature most of the studies on the effect of pH on enhanced biological phosphorous removal were conducted with the acetate wastewater, and the pH was controlled during the entire anaerobic and aerobic stages. This paper investigated the influence of anaerobic initial pH control, which will be more practical than the entire process pH control strategy, on enhanced biological phosphorus removal from wastewater containing acetic and propionic acids. Typical pH profile showed that both the initial alkaline and acidic pH tended to neutralize due to the consumption of short-chain fatty acid (SCFA) and intracellular pH regulation by polyphosphate accumulating organisms (PAOs). It was observed that the glycogen degradation and polyhydroxyalkanoates (PHA) accumulation decreased with increasing initial pH, which disagreed with previous reports. In the literature the metabolisms of both glycogen and PHA by PAOs in the acetate wastewater were independent of pH. An anaerobic mechanism model was proposed to explain the intra- and extra-cellular pH buffer nature of PAOs, and to address the reasons for increased polyphosphate degradation and decreased PHA synthesis and glycogen degradation at higher pH. The optimal initial pH for higher soluble ortho-phosphorus (SOP) removal efficiency should be controlled between 6.4 and 7.2. This pH control strategy will be easier to use in practice of wastewater treatment plant.

Acetates↗
PubMed2006

In vitro release and in vivo absorption in beagle dogs of meloxicam from Eudragit FS 30 D-coated pellets.

The objective of this study was to develop meloxicam-loaded colon-specific pellets coated with Eudragit FS 30 D and further evaluate their in vitro release and in vivo absorption in beagle dogs. Meloxicam-loaded cores (drug loading, 4.8%, w/w) were prepared by layering drug-binder (HPMC)-solubilizer (beta-cyclodextrin) solution onto nonpareils (710-850 microm) and then coated with a copolymer of methyl acrylate, methyl methacrylate and methacrylic acid (Eudragit FS 30 D). The obtained pellets with 15% (w/w) coating level had a spherical form and a smooth surface with coating thickness approximately 28 microm. The in vitro drug release from the pellets was pH-dependent with sufficient gastric resistance (pH 1.2: no release; pH 6.8: 6%; pH 7.0: 52%; pH 7.2: 100%; pH 7.4: 100%, after 3 h incubation). In vivo study was carried out using pentagastrin-pretreated beagle dogs. The onset of meloxicam absorption from the coated pellets with 15% (w/w) Eudragit FS 30 D (3.0+/-0.8 h) was significantly delayed (p<0.05) compared to that from the uncoated drug-layered cores (0.6+/-0.3 h). The area under the meloxicam plasma concentration-time curve (AUC(0-->96)(h) was not significantly different between the two preparations (p>0.05), although AUC(0-->96)(h) obtained after oral administration of coated pellets (142.5+/-59.6 microg h/ml) was lower than that obtained after administration of uncoated drug-layered cores (180.8+/-61.9 microg h/ml). These results suggested that meloxicam could be delivered to the colon with 15% (w/w) coating level of Eudragit FS 30 D and this polymer coating had no significant influence on the relative bioavailability of meloxicam of the pellets.

Animals↗
PubMed2006

Two-dimensional LNA/DNA arrays: estimating the helicity of LNA/DNA hybrid duplex.

We measured the helical repeats of a non-natural nucleic acid, locked nucleic acid (LNA), by incorporating LNA strands into the outer arms of a DNA double crossover (DX) molecule; atomic force microscopy (AFM) imaging of the two-dimensional (2D) arrays self-assembled from these DX molecules allows us to derive the helical repeat of the LNA/DNA hetero-duplex to be 13.2 +/- 0.9 base pairs per turn.

Base Sequence↗
PubMed2006

Simple and sensitive method for spectrofluorimetric determination of dodecyl benzene sulfonic acid sodium.

The interaction of poly(diallyldimethyl ammonium chloride) (PDDA) with dodecyl benzene sulfonic acid sodium (DBS) has been studied by fluorescence spectra. The fluorescence of DBS can be greatly enhanced by addition of PDDA, owing to the interaction between PDDA and DBS. The enhancement intensity of fluorescence was proportional to the concentration of DBS over the range 2.5x10(-7) to 9.6x10(-5)molL(-1). Its detection limit is 3.5x10(-7)molL(-1). The method has high sensitivity and selectivity and was applied to the determination of trace amounts of DBS in water samples with satisfactory result.

Benzenesulfonates↗
PubMed2006

Combinatorial self-assembly of DNA nanostructures.

Here we report a modular design of self-assembly of DNA nanostructures in a combinatorial approach; a square with approximately 25 nm cavity dimension, a chair with approximately 80 nm in height and a line with approximately 100 nm in length are formed through combinations of four cross-shaped DNA tiles which are kept constant and six variable linker tiles.

DNA↗
PubMed2006

The centrosomal protein nephrocystin-6 is mutated in Joubert syndrome and activates transcription factor ATF4.

The molecular basis of nephronophthisis, the most frequent genetic cause of renal failure in children and young adults, and its association with retinal degeneration and cerebellar vermis aplasia in Joubert syndrome are poorly understood. Using positional cloning, we here identify mutations in the gene CEP290 as causing nephronophthisis. It encodes a protein with several domains also present in CENPF, a protein involved in chromosome segregation. CEP290 (also known as NPHP6) interacts with and modulates the activity of ATF4, a transcription factor implicated in cAMP-dependent renal cyst formation. NPHP6 is found at centrosomes and in the nucleus of renal epithelial cells in a cell cycle-dependent manner and in connecting cilia of photoreceptors. Abrogation of its function in zebrafish recapitulates the renal, retinal and cerebellar phenotypes of Joubert syndrome. Our findings help establish the link between centrosome function, tissue architecture and transcriptional control in the pathogenesis of cystic kidney disease, retinal degeneration, and central nervous system development.

Activating Transcription Factor 4↗
PubMed2006

Negative regulation of Fc epsilonRI-mediated signaling and mast cell function by the adaptor protein LAX.

LAX is a transmembrane adaptor protein that is expressed in both T and B cells. Upon stimulation via the antigen receptors, it is tyrosine-phosphorylated and binds Grb2 and the p85 subunit of phosphatidylinositol 3-kinase. Disruption of the Lax gene causes hyperresponsiveness in T and B lymphocytes. Here, we showed that LAX was also expressed in mast cells. Upon engagement of the Fc epsilonRI, LAX was also phosphorylated and interacted with Grb2 and p85. LAX-deficient mast cells were hyperresponsive to stimulation via the Fc epsilonRI, as evidenced by enhanced degranulation, p38 MAPK, Akt, and phosphatidylinositol 3-kinase activation. This hyperresponsiveness was likely a consequence of reduced LAB expression after sensitization of mast cells with anti-dinitrophenyl IgE. In addition, Fc epsilonRI-mediated cytokine production and cell survival were also enhanced. These data suggested that LAX negatively regulates mast cell function.

Adaptor Proteins, Vesicular Transport↗
PubMed2006

Synthesis and pharmacological activities of xanthone derivatives as alpha-glucosidase inhibitors.

Considerable interest has been attracted in xanthone and its derivatives because of their large variety of pharmacological activities. In this project, a series of hydroxylxanthones and their acetoxy and alkoxy derivatives were synthesized and evaluated as alpha-glucosidase inhibitors, aimed at clarifying the structure-activity correlation. The results indicated that these xanthone derivatives were capable of inhibiting in vitro alpha-glucosidase with moderate to good activities. Among them, polyhydroxylxanthones exhibited the highest activities and thus may be exploitable as a lead compound for the development of potent alpha-glucosidase inhibitors.

Enzyme Inhibitors↗
PubMed2006

A study of DNA tube formation mechanisms using 4-, 8-, and 12-helix DNA nanostructures.

This paper describes the design and characterization of a new family of rectangular-shaped DNA nanostructures (DNA tiles) containing 4, 8, and 12 helices. The self-assembled morphologies of the three tiles were also investigated. The motivation for designing this set of DNA nanostructures originated from the desire to produce DNA lattices containing periodic cavities of programmable dimensions and to investigate the mechanism of DNA tube formation. Nine assembly scenarios have been investigated through the combination of the three different tiles and three sticky end association strategies. Imaging by atomic force microscopy (AFM) revealed self-assembled structures with varied cavity sizes, lattice morphologies, and orientations. Six samples show only tube formation, two samples show both 2D lattices (>2 microm) and tubes, and one sample shows only 2D lattices without tubes. We found that a lower tile dimensional anisotropy, weaker connection, and corrugated design favor the large 2D array formation, while the opposite (higher tile anisotropy, stronger connection, and uncorrugated design) favors tube formation. We discuss these observations in terms of an energy balance at equilibrium and the kinetic competition between diffusion-limited lateral lattice growth versus fluctuation of the lattice to form tubes at an early stage of the assembly. The DNA nanostructures and their self-assembly demonstrated herein not only provide a new repertoire of scaffolds to template the organization of nanoscale materials, but may also provide useful information for investigating other self-assembly systems.

Anisotropy↗
PubMed2006

Prospective study of predictors of vitamin D status and cancer incidence and mortality in men.

BACKGROUND: Vitamin D has potent anticancer properties, especially against digestive-system cancers. Many human studies have used geographic residence as a marker of solar ultraviolet B and hence vitamin D exposure. Here, we considered multiple determinants of vitamin D exposure (dietary and supplementary vitamin D, skin pigmentation, adiposity, geographic residence, and leisure-time physical activity-to estimate sunlight exposure) in relation to cancer risk in the Health Professionals Follow-Up Study. METHODS: Among 1095 men of this cohort, we quantified the relation of these six determinants to plasma 25-hydroxy-vitamin D [25(OH)D] level by use of a multiple linear regression model. We used results from the model to compute a predicted 25(OH)D level for each of 47,800 men in the cohort based on these characteristics. We then prospectively examined this variable in relation to cancer risk with multivariable Cox proportional hazards models. RESULTS: From 1986 through January 31, 2000, we documented 4286 incident cancers (excluding organ-confined prostate cancer and nonmelanoma skin cancer) and 2025 deaths from cancer. From multivariable models, an increment of 25 nmol/L in predicted 25(OH)D level was associated with a 17% reduction in total cancer incidence (multivariable relative risk [RR] = 0.83, 95% confidence interval [CI] = 0.74 to 0.92), a 29% reduction in total cancer mortality (RR = 0.71, 95% CI = 0.60 to 0.83), and a 45% reduction in digestive-system cancer mortality (RR = 0.55, 95% CI = 0.41 to 0.74). The absolute annual rate of total cancer was 758 per 100,000 men in the bottom decile of predicted 25(OH)D and 674 per 100,000 men for the top decile; these respective rates were 326 per 100,000 and 277 per 100,000 for total cancer mortality and 128 per 100,000 and 78 per 100,000 for digestive-system cancer mortality. Results were similar when we controlled further for body mass index or physical activity level. CONCLUSIONS: Low levels of vitamin D may be associated with increased cancer incidence and mortality in men, particularly for digestive-system cancers. The vitamin D supplementation necessary to achieve a 25(OH)D increment of 25 nmol/L may be at least 1500 IU/day.

Adult↗
PubMed2006

Calbindin-D28k decreases L-type calcium channel activity and modulates intracellular calcium homeostasis in response to K+ depolarization in a rat beta cell line RINr1046-38.

Calbindin-D(28k), acts as a modulator of depolarization induced calcium transients in the pancreatic beta cell. However, specific mechanisms have not been defined. Here we show for the first time that the calcium binding protein calbindin-D(28k) acts by affecting calcium influx through voltage-dependent calcium channels in RIN pancreatic beta cells. Whole-cell patch-clamp recordings revealed that Ca(2+) current amplitudes of calbindin-D(28k) expressing RINr1046-38 beta cells were smaller than the Ca(2+) current amplitudes in control cells in response to depolarizing pulses. The peak current was observed at +20mV and the average amplitude was approximately 50pA in the calbindin expressing cells compared to approximately 250pA in control cells. In calbindin-D(28k) expressing cells, the channels had enhanced sensitivity to Ca(2+) dependent inactivation and currents decayed much more rapidly than in control cells. The Ca(2+) channels affected by calbindin were found to have biophysical properties consistent with dihydropyridine-sensitive L-type calcium channels. In response to depolarizing concentrations of K(+), calbindin expression caused a five-fold decrease in the rate of rise of [Ca(2+)](i) and decay was slower in the calbindin expressing cells. Application of verapamil resulted in a drop in the [Ca(2+)](i) signal to pre-stimulation levels indicating that the Ca(2+) channel responsible for the depolarization evoked Ca(2+) entry, modulated by calbindin, is the L-type. Co-immunoprecipitation and GST pull-down assays indicate that calbindin-D(28k) can interact with the alpha(1) subunit of Ca(v)1.2. We thus conclude that calbindin-D(28k) can regulate calcium influx via L-type calcium channels. Our findings suggest a role for calbindin-D(28k) in the beta cell in modulating Ca(2+) influx via L-type voltage-dependent calcium channels.

Animals↗
PubMed2006

Recognition imaging with a DNA aptamer.

We have used a DNA-aptamer tethered to an atomic force microscope probe to carry out recognition imaging of IgE molecules attached to a mica substrate. The recognition was efficient (approximately 90%) and specific, being blocked by injection of IgE molecules in solution, and not being interfered with by high concentrations of a second protein. The signal/noise ratio of the recognition signal was better than that obtained with antibodies, despite the fact that the average force required to break the aptamer-protein bonds was somewhat smaller.

Aluminum Silicates↗
PubMed2006

Analysis of chain and blood group type and branching pattern of sialylated oligosaccharides by negative ion electrospray tandem mass spectrometry.

We previously reported sequence determination of neutral oligosaccharides by negative ion electrospray tandem mass spectrometry on a quadrupole-orthogonal time-of-flight instrument with high sensitivity and without the need of derivatization. In the present report, we extend our strategies to sialylated oligosaccharides for analysis of chain and blood group types together with branching patterns. A main feature in the negative ion mass spectrometry approach is the unique double glycosidic cleavage induced by 3-glycosidic substitution, producing characteristic D-type fragments which can be used to distinguish the type 1 and type 2 chains, the blood group related Lewis determinants, 3,6-disubstituted core branching patterns, and to assign the structural details of each of the branches. Twenty mono- and disialylated linear and branched oligosaccharides were used for the investigation, and the sensitivity achieved is in the femtomole range. To demonstrate the efficacy of the strategy, we have determined a novel complex disialylated and monofucosylated tridecasaccharide that is based on the lacto-N-decaose core. The structure and sequence assignment was corroborated by methylation analysis and 1H NMR spectroscopy.

Blood Group Antigens↗
PubMed2006

Electrochemical detection of hepatitis B surface antigen using colloidal gold nanoparticles modified by a sol-gel network interface.

BACKGROUND: A novel potentiometric immunosensor for the detection of hepatitis B surface antigen has been developed by self-assembling gold nanoparticles to a thiol-containing sol-gel network. METHODS: A cleaned gold electrode was first immersed in a hydrolyzed (3-mercaptopropyl) trimethoxysilane sol-gel solution to assemble a three-dimensional silica gel, and then gold nanoparticles were absorbed onto the thiol groups of the sol-gel network. Finally, hepatitis B surface antibody was assembled onto the surface of the gold nanoparticles. The self-assembling procedure was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Detection is based on the change in potentiometric response before and after the antigen-antibody reaction. RESULTS: Tests relating to the detection of hepatitis B surface antigen demonstrate that the potentiometric immunosensor exhibited a rapid potentiometric response (<4 min), with high sensitivity, good reproducibility, and long-term stability. The linear range was from 4 to 960 ng.mL(-1) with a detection limit of 1.9 ng.mL(-1) (S/N = 3) and the lifetime was 1 month. CONCLUSION: Analytical results of several specimens using the developed technique showed satisfactory agreement with those from an ELISA method. This method shows promise for detecting HBsAg in clinical specimens.

Calibration↗
PubMed2006

[The anatomic relationship of the umbilicus to retroperitoneal major vessels].

OBJECTIVE: To study the anatomic relationship of the umbilicus to the retroperitoneal major vessels and the characteristics of such relationships among the Chinese with different body weights so as to provide a clear reference to the operator of laparoscopy. METHODS: Eighty-nine patients without pelvic disease, 57 males and 32 females who accepted digital subtraction angiography (DSA) of aorta were randomly selected and divided into 3 groups: non-obese group, overweight group, and obese group according to body mass index (BMI). All the patients lied supine with a round block of lead 1 cm in diameter located on the umbilicus. Seldinger technique was used to puncture the right femoral artery so as to conduct DSA. Using the bifurcation of the abdominal aorta as reference point the vertical projection relationships of the umbilicus to the retroperitoneal major vessels, abdominal aorta, right common iliac artery, and left common iliac artery were evaluated and the distance from the umbilicus to the aortic bifurcation was measured. The distance was regarded as positive if the umbilicus was cephalic to the aortic bifurcation and as negative if the umbilicus was caudal to the aortic bifurcation RESULTS: There were 32 patients in the normal body weight group, 35 in the overweight group, and 22 in the obese group with the mean distances from the umbilicus to the aortic bifurcation of (14.8 +/- 19.7) mm, (0.04 +/- 2.5) mm, and (-12.6 +/- 15.4) mm respectively. In 50 of the 89 patients (63.9%) the location of umbilicus corresponded to the retroperitoneal major vessels, among which the umbilicus of 47 patients (94%) projected vertically to the abdominal aorta or the right common iliac, and the umbilicus of 3 patients (6%) projected vertically to the left common iliac artery. Compared to the above-mentioned 50 patients, in the other 39 patients (36.1%) the location of umbilicus did not corresponded to the retroperitoneal major vessels (P < 0.05), among which the umbilicus of 32 patients (82.1%) projected vertically to the right side of the aorta or of the right common iliac artery, and the umbilicus of 7 patients (17.9%) projected vertically to the internal side of the right iliac common artery. Along with the increase of body weight the projection of umbilicus gradually moved downward to the inferior side of the bifurcation of the abdominal artery. For example, among the male subjects, the distance were (10.4 +/- 4.0) mm, (-0.51 +/- 5.5) mm, and (-13.1 +/- 2.2) mm respectively in the normal body weight group, overweight group, and obese group (all P < 0.05), and in the females, the distance were (13.7 +/- 2.8) mm, (-0.14 +/- 4.4) mm, and (-11.5 +/- 3.2) mm respectively in the normal body weight group, overweight group, and obese group (all P < 0.05). CONCLUSION: The location of umbilicus was more caudal with the increase of BMI. So once the retroperitoneal major vessels are injured, the incidence of aorta or the right common iliac artery is higher than that of other vessels.

Aorta, Abdominal↗