PubMed Health⌕ Search

Biomedical subjects

Yan Sun

Publications and source records attributed to Yan Sun.

At least 73 records · Page 4Linked to original sources
PubMed2005

Oscillatory transverse electric field enhances mass transfer and protein capacity in ion-exchange electrochromatography.

Ion-exchange electrochromatography with an oscillatory electric field perpendicular to mobile-phase flow driven by pressure (pIEEC) was developed with a column design of rectangle cross-section. The effect of electric field strength on the dynamic binding capacity (DBC) was examined by frontal analysis of bovine serum albumin (BSA) adsorption to the packed beds of DEAE Sepharose FF in Tris-glycine buffer (pH 8.2). It was shown that the DBC at 10% breakthrough (Q(10)) in the pIEEC increased linearly with increasing the electric field strength. For example, with a packed-bed height of 15mm and electric potential gradient of 38V/cm, Q(10) increased four times over that in normal ion-exchange chromatography. So, the transverse electric field has created significant electro-kinetic mass transports (electroosmosis and electrophoresis) that intensified exterior liquid-film and intraparticle mass transfers, leading to the increased protein binding capacity. Due to the increased capacity in the pIEEC, partial resolution of BSA and IgG under an overload condition was realized without any process optimization. The results have revealed that an electric potential gradient of 20V/cm was enough to greatly enhance the DBC in the pIEEC, and when necessary, high electric field strength can be realized with a low applied voltage because the side distance of the column is usually an order of magnitude smaller than its height. The use of low voltage to carry out electrochromatography is a significant advantage of the pIEEC over conventional electrochromatography with axial electric field.

Adsorption↗
PubMed2005

Energy and structural analysis of double nucleic acid triplets.

In order to investigate the energy and structural character of RNA-RNA triplets and RNA-DNA duplex base triplets, 64 sets of three-dimensional models of RNA-DNA duplex base triplets and mRNA-tRNA triplex base triplets were constructed and optimized by homologous modeling method using the software InsightII. The comparative statistical method and cluster analysis were adopted to study these features. The result showed: (i) all energy parameters of monomer RNA-DNA hybrid triplets and ternary complexes appeared significantly different; and some parameters related with overall molecules such as overall energy, bond energy and coulomb energy have statistically significant correlations between the structures in vacuum and aquatic solutions while other parameters, including theta energy, phi energy, hydrogen bond energy and non-bond energy, changed significantly, but not continuously. (ii) However, the case of mRNA-tRNA triplets was much more complicated in that only the bond energy's correlation coefficient is -0.8. Typically, the main contribution of GC pairs and G/A/U bases were interesting. The models of RNA-DNA hybrid triplets and mRNA-tRNA triplet should be helpful for the study of base pairing in codons and the biological effectiveness of antisense nucleic acids.

Animals↗
PubMed2005

Evaluation of the true precocious puberty rats induced by neonatal administration of Danazol: therapeutic effects of nourishing "Yin"-Removing "Fire" Chinese herb mixture.

BACKGROUND: Nourishing "Yin"-Removing "Fire" Chinese Herb Mixture, a traditional herb-based formulation, has been successfully used for the management of idiopathic true precocious puberty (IPP) for more than thirty years. Precocious puberty rat model by neonatal administration of Danazol was used to investigate the effects of the herb mixture on the advanced sexual development of the rats, and the expression of hypothalamic gonadotropin-releasing hormone (GnRH), which is the important regulator for the hypothalamus-pituitary-gonadal axis, particularly at puberty. METHODS: Female Sprague-Dawley rats were divided into five groups: intact normal (N), IPP model (M), vehicle with no IPP (V), IPP model exposed to herb mixture (HM) and IPP model exposed to saline (S). Rats at 5 days of age were given a single subcutaneous injection of 300 microgram of Danazol dissolved in 25 microliter vehicle of propylene glycol-ethanol (1:1, v/v), to establish the precocious puberty model. From the day 15, rats in HM and S groups were continuously fed with either Nourishing "Yin"-Removing "Fire" Chinese Herb Mixture 2 ml or saline 2 ml, until 3 consecutive regular estrous cycles were established. The day of vaginal opening and the day of setup regular estrous cycle of the rats were observed. Blood concentration of estrogen was determined by radioimmunoassay. Immunohistochemistry and RT-PCR analysis were used to explore the expression of GnRH. RESULTS: The day of vaginal opening and first estrous showed significant advancement in M compared with N and V (p < 0.05, respectively). The blood estrogen level increased significantly in M compared with those in other groups (about 28 days of age, at the time of vaginal opening in M rats) (p < 0.05, respectively). GnRH cells in rostral medial septum (MS), Broca diagonal band nucleus (DBB) and the medial preoptic area (MPOA), were calculated. The number in M was less than those in N and V (p < 0.05, respectively). The number was significantly higher in HM than that in M (p < 0.05). The GnRH mRNA expression increased significantly in M compared with that in N and V (p < 0.05). CONCLUSION: The true precocious puberty model by neonatal administration of Danazol in female rats showed augmented expression of hypothalamic GnRH; the Nourishing "Yin"-Removing "Fire" Chinese Herb Mixture down-regulated the increased GnRH expression, and significantly delayed the sexual development of the precocious puberty rat.

Animals↗
PubMed2005

Augmented extracellular ATP signaling in bladder urothelial cells from patients with interstitial cystitis.

Interstitial cystitis (IC) is an idiopathic hypersensory condition of the bladder associated with increased urinary ATP and increased stretch-activated ATP release by bladder urothelial cells (BUCs), suggesting augmented purinergic signaling in the bladder. To test this theory further, monolayers of cultured BUCs derived from bladder biopsies obtained from patients with IC and control patients were stimulated with 10-30 microM ATP with subsequent measurement of extracellular ATP levels using the luciferin-luciferase assay. Stimulation with 30 microM ATP resulted in IC supernatant containing several-fold more ATP than control BUCs initially, followed by a slower decrease in ATP levels. This difference in ATP levels was not completely due to activity of cellular ecto-ATPase, because blockade with ARL67156 did not normalize the difference. Exposure to hypotonic solutions resulted in similar extracellular ATP concentrations in IC and control BUCs, but there was a slower decrease in ATP levels in IC supernatants. Treatment of IC BUCs with 10-40 microM suramin, a nonspecific P2 receptor antagonist, significantly attenuated the IC BUC response to extracellular ATP, restoring IC BUCs to a control phenotype. Pretreatment of IC BUCs with 20 ng/ml of heparin-binding EGF-like growth factor (HB-EGF), which previously has been shown to be decreased in IC urine specimens, also restored IC BUCs to a control phenotype with respect to response to ATP stimulation. In conclusion, IC BUCs have augmented extracellular ATP signaling that could be blocked by suramin and HB-EGF. These findings suggest the possible development of future novel therapeutic techniques.

Adenosine Triphosphatases↗
PubMed2005

Functional analysis of the BIN 2 genes of cotton.

Brassinosteroids (BR) promote the elongation of cotton fibers and may be a factor in determining their final length. To begin to understand the role of BR-mediated responses in the development of cotton fibers we have characterized the BIN 2 genes of cotton. BIN 2 is a member of the shaggy-like protein kinase family that has been identified as a negative regulator of BR signaling in Arabidopsis. Sequence analyses indicate that the tetraploid cotton genome includes four genes with strong sequence similarity to BIN 2. These genes fall into two distinct subclasses based on sequence and expression patterns. Sequence comparisons with corresponding genes from cotton species that have the diploid A and D genomes, respectively, shows that each pair of genes comprises homeologs derived from the A and D sub-genomes. Transgenic Arabidopsis plants that express these cotton BIN 2 cDNAs show reduced growth and similar phenotypes to the semi-dominant bin 2 mutant plants. These results indicate that the cotton BIN 2 genes encode functional BIN 2 isoforms that can inhibit BR signaling. Further analyses of the function of BIN 2 genes and their possible roles in determining fiber yield and quality are underway.

Amino Acid Sequence↗
PubMed2005

Brassinosteroid regulates fiber development on cultured cotton ovules.

Our current understanding of the role of phytohormones in the development of cotton fibers is derived largely from an amenable culture system in which cotton ovules, collected on the day of anthesis, are floated on liquid media. Under these conditions, supplemental auxin and gibberellin were found to promote fiber initiation and elongation. More recently, addition of low concentrations of the brassinosteroid brassinolide (BL) were also found to promote fiber elongation while a brassinosteroid biosynthesis inhibitor brassinazole2001 (Brz) inhibited fiber development. In order to elucidate the role of brassinosteroid in cotton fiber development further, we have performed a more detailed analysis of the effects of these chemicals on cultured cotton ovules. Our results confirm that exogenous BL promotes fiber elongation while treatment with Brz inhibits it. Furthermore, treatment of cotton floral buds with Brz results in the complete absence of fiber differentiation, indicating that BR is required for fiber initiation as well as elongation. Expression of fiber genes associated with cell elongation increased in ovules treated with BL and was suppressed by Brz treatment, establishing a correlation between brassinosteroid-regulated gene expression and fiber elongation. These results establish a clear connection between brassinosteroid and fiber development and open the door for genetic analysis of cotton development through direct modification of the brassinosteroid signal transduction pathway.

Base Sequence↗
PubMed2005

Variations of particle size and bed voidage distributions in expanded bed during transient operation processes.

Changes in bed expansion are frequently encountered during an expanded bed adsorption, such as during the initial bed expansion, feed loading and washing processes. We have here studied the changes of local particle size distribution and bed voidage of an expanded bed in the initial bed expansion process as well as those during the changes in mobile phase viscosity, which imitated feed loading and column washing processes. Using a glass column modified with three side sampling ports and Streamline AC as the solid phase, experimental measurements on a series of operation moments during the transient processes were carried out by sampling the particles from within the column at different axial positions. In the initial bed expansion process, the gradual formation of an axial classification from a settled bed to a stable expanded bed was first displayed. By changing the mobile phase from water to 10% (w/w) glycerol solution or vice versa, the variations in both the particle size distribution and bed voidage corresponding to the increase or decrease of the bed height caused by the changes of the mobile phase viscosity were examined as well. The transient changes of the local particle size distribution and bed voidage first occurred in the bed bottom and then progressed from bottom to top along the axial direction. However, the changes of bed voidage at different axial positions were not unidirectional. That is, by changing the mobile phase to the high-viscosity glycerol solution, a constant increase of the bed voidage was observed in the bed bottom, while a distinct decrease of the bed voidage before its increase was involved at the middle and top positions. This is ascribed to the compression effect caused by the upward movement of the lower part particles.

Chromatography↗
PubMed2005

[Thirteen to fourteen years' follow-up of patients with hepatitis C].

OBJECTIVE: To investigate the clinical outcomes and hepatic histology of patients with hepatitis C. METHODS: Nine patients with hepatitis, 4 males and 5 females, aged 44 +/- 7, who were infected during transfusion or blood donation underwent follow-up for 13 approximately 14 years: liver histological examination by biopsy, ultrasonography, biochemical examination of alanine transaminase (ALT), apartate aminotransferase (AST), and total bilirubin (TBIL), serum anti-HCV by ELISA, and HCV RNA quantification by PCR. RESULTS: ALT were higher than the normal value at every time point and HCV RNA remained positive (3.57 x 10(8) approximately 7.21 x 10(9) copies/L) in all patients. Ultrasonography showed mild and moderate hepatitis (3 and 6 cases respectively). The modified histological activity indices (HAI) were 5.0 approximately 8.5 and the fibrosis scores were 1 approximately 4. The ALT value was higher in the moderate cases than in the mild cases, and higher in those with higher HAI. The viral load was higher in the patients infected by the virus of the genotype 1b than in the patients infected by the virus of the genotype 2. CONCLUSION: The clinical outcomes and hepatic histology of patients with hepatitis C seem not very severe.

Adult↗
PubMed2005

[Polymorphisms in nucleotide excision repair genes XPC and XPD and clinical responses to platinum-based chemotherapy in advanced non-small cell lung cancer].

OBJECTIVE: Nucleotide excision repair has been shown to have great impact on the sensitivity of tumors to platinum-based chemotherapy. This study was to examine the association between genetic polymorphisms in XPC and XPD, two important components in nucleotide excision repair system, and clinical response to platinum-based chemotherapy in advanced non-small cell lung cancer. METHODS: Patients (n = 151) treated with platinum-based chemotherapy were genotyped for the AT dinucleotide insertion or deletion in intron 9 of XPC or Lys751Gln polymorphism in XPD. Clinical response to chemotherapy was obtained after 2 to 3 cycles. The adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using unconditional logistic regression model and adjusted for sex, age, clinical stage, and regime of chemotherapy. RESULTS: The overall response rate to the chemotherapy (CR + PR) was 35.1%, with 1 CR, 52 PR, 75 SD, and 23 PD. It was found that patients with the XPC LL genotype had significantly higher response rate than patients with the XPC SS genotype (adjusted OR = 3.19, 95% CI = 1.11 - 9.17; P = 0.031). However, no association was found between the XPD Lys751Gln polymorphism and response to the chemotherapy. In addition, these two polymorphisms seemed to have synergic effect, with the OR being 2.90 (95% CI = 1.07 - 7.86) for patients carrying the XPC LL and XPD Lys/Lys genotypes compared with those carrying the XPC SS or SL and XPD Lys/Lys genotypes. CONCLUSION: These results suggest that genetic polymorphisms in nucleotide excision repair might be associated with clinical response to platinum-based chemotherapy.

Adult↗
PubMed2005

Serine proteinase over-expression in relation to deltamethrin resistance in Culex pipiens pallens.

Two serine proteinase genes were isolated from Culex pipiens pallens as significantly up-regulated genes in a deltamethrin-resistant strain through a combination of suppression substractive hybridization and gene expression profiling by macroarrays. These two genes were found to be expressed at least threefold higher in the resistant strain than in the susceptible one. By using rapid amplification of cDNA ends to screen the constructed cDNA library, we cloned these two sequences. There were 909 bp with an open reading frame of 786 bp in the sequence of trypsin cDNA (GenBank/NCBI AF468495), the deduced protein had 261 amino acids, which was most similar to the trypsin gene of Anopheles gambiae. There were 992 bp with an open reading frame of 816 bp in the chymotrypsin cDNA (GenBank/NCBI AY034060), and its deduced amino acid sequence had 271 amino acids, which was most similar to the chymotrypsin-like protein from Aedes aegypti. The two genes were stably expressed in mosquito C6/36 cells, and the expected 29 and 30 kDa bands were shown with Western blot, respectively. In these cells, after deltamethrin treatment, they had protective effects on the viability. The results indicate that trypsin and chymotrypsin were more highly expressed in the deltamethrin-resistant strain, and was related to insecticide resistance in mosquitoes, Cx. pipiens pallens.

Amino Acid Sequence↗
PubMed2005

Rheological characterization and dissolution kinetics of fibrin gels crosslinked by a microbial transglutaminase.

Various fibrin gels were prepared with a microbial transglutaminase under miscellaneous conditions. The gels were characterized through their rheological properties. The influence of fibronectin addition and that of covalent bonding on the viscoelastic characteristics were evaluated. Gel elasticity is proportional to fibrinogen concentration but shows a nonlinear dependence on transglutaminase concentration. Additional crosslink of fibronectin in fibrin gels has no effect on the rheological character of the matrix. Dissolution kinetics in concentrated urea solutions evidences the role of covalent bonds on gel stability. The rheological properties and gel stability are discussed in relation with the enzyme-catalyzed covalent bonding. The microbial enzyme reactions are compared to those of FXIII and tissue transglutaminases.

Cross-Linking Reagents↗
PubMed2005

The APOC3 SstI polymorphism is weakly associated with sporadic Alzheimer's disease in a Chinese population.

In order to clarify the relationship of apolipoprotein CIII (APOC3) polymorphism and sporadic Alzheimer's disease (AD) in Chinese, 165 sporadic AD patients and 174 age-matched elderly individuals were genotyped for the APOC3 SstI and apolipoprotein E (APOE) HhaI polymorphisms. As the result, the APOC3 3017G allele was found to be associated with AD in APOE epsilon4 allele noncarriers (chi2=4.433, P=0.035), and the risk estimate of allele C versus G resulted in an OR of 1.56 (95% CI: 1.03-2.37), although in total no significant differences of allelic or genotypic frequencies between patients and controls were found. Assessment of interaction between APOE epsilon4 and APOC3 3017G status presented an adjusted odds ratio of 0.62 (95% CI: 0.37-1.03) with a borderline significant P-value (P=0.066). Therefore, we conclude that the rare APOC3 G allele may offer some protection against the development of sporadic AD in APOE epsilon4 noncarriers in Chinese.

Aged↗
PubMed2005

Life-threatening ventricular arrhythmia recognition by nonlinear descriptor.

BACKGROUND: Ventricular tachycardia (VT) and ventricular fibrillation (VF) are ventricular cardiac arrhythmia that could be catastrophic and life threatening. Correct and timely detection of VT or VF can save lives. METHODS: In this paper, a multiscale-based non-linear descriptor, the Hurst index, is proposed to characterize the ECG episode, so that VT and VF can be recognized as different from normal sinus rhythm (NSR) in the descriptor domain. RESULTS: This newly proposed technique was tested using MIT-BIH malignant ventricular arrhythmia database. The relationship between the ECG episode length and the corresponding recognition performance was studied. The experiments demonstrated good performance of the proposed descriptor. An accuracy rate as high as 100% was obtained for VT/VF to be recognized from NSR; for VT and VF to be recognized from each other, the recognition accuracy varies from 84.24% to 100%. In addition, the results were compared favorably against those obtained using Complexity measure. CONCLUSIONS: There is strong potential for using the Hurst index for malignant ventricular arrhythmia recognition in clinical applications.

Algorithms↗
PubMed2005

Retention behavior of proteins in size-exclusion electrochromatography with a low-voltage electric field perpendicular to the liquid phase streamline.

A novel preparative size-exclusion electrochromatography with an oscillatory low-voltage electric field perpendicular to the liquid phase streamline (pSEEC) was proposed with a column design of rectangular cross-section. The column of 12 cm length was packed with Sephadex G-75, and the retention behavior of bovine serum albumin (BSA) and myoglobin (Myo) was extensively investigated under various conditions. The results indicated that the partition coefficient of a charged protein increased significantly on increasing the current strength as well as the difference between its pI and pH. The partition coefficient also increased on decreasing the mobile phase conductivity. For the gel-excluded protein like BSA, the concentration polarization (CP) on the gel surface induced by the protein electromigration was the main reason for the increased retention. For a gel-permeable protein like Myo, both the CP and electrophoretic migration in the solid phase contributed to its increased retention. Further results exhibited that the polarization would be offset by diffusion, because the accumulated protein would flux back to the bulk liquid phase. Therefore, when the electrically induced mass flux was equal to the diffusion flux, the partition coefficient did not change with a further increase of the oscillatory current cycle. Finally, pSEEC was compared with SEC in the separation of protein mixtures of BSA/Myo as well as BSA/Myo/lysozyme. The results showed much better resolutions of the protein mixtures in pSEEC with the column as short as 12 cm. The potential of pSEEC for preparative protein separation was therefore demonstrated.

Buffers↗
PubMed2005

Mutation screening and association study of the neprilysin gene in sporadic Alzheimer's disease in Chinese persons.

Neprilysin has been reported to be a major beta-amyloid peptide (Abeta)-degrading enzyme. The decreased expression and activity of it may contribute to the development of Alzheimer's disease by promoting the accumulation of Abeta. We used denaturing high-performance liquid chromatography to screen the neprilysin gene (NEP) for single nucleotide polymorphisms (SNPs) in 257 Chinese sporadic Alzheimer's disease patients and 242 cognitive normal controls. As a result, eight novel and one known SNP were identified. Three of them, -204G-->C in the promoter region, IVS17-294C-->T, and IVS22+36C-->A showed a significant association with Alzheimer's disease (p = .006,.017, and.003, respectively). Subsequent haplotype analysis provided further evidence of the association (global p < .0001 for the three SNPs mentioned above, and global p < .01 for the eight SNPs with rare allele frequency > 1%). These findings indicate that genetic variations within or extremely close to NEP might influence the susceptibility to Alzheimer's disease in Chinese persons.

Aged↗
PubMed2005

Cellular automata with object-oriented features for parallel molecular network modeling.

Cellular automata are an important modeling paradigm for studying the dynamics of large, parallel systems composed of multiple, interacting components. However, to model biological systems, cellular automata need to be extended beyond the large-scale parallelism and intensive communication in order to capture two fundamental properties characteristic of complex biological systems: hierarchy and heterogeneity. This paper proposes extensions to a cellular automata language, Cellang, to meet this purpose. The extended language, with object-oriented features, can be used to describe the structure and activity of parallel molecular networks within cells. Capabilities of this new programming language include object structure to define molecular programs within a cell, floating-point data type and mathematical functions to perform quantitative computation, message passing capability to describe molecular interactions, as well as new operators, statements, and built-in functions. We discuss relevant programming issues of these features, including the object-oriented description of molecular interactions with molecule encapsulation, message passing, and the description of heterogeneity and anisotropy at the cell and molecule levels. By enabling the integration of modeling at the molecular level with system behavior at cell, tissue, organ, or even organism levels, the program will help improve our understanding of how complex and dynamic biological activities are generated and controlled by parallel functioning of molecular networks. Index Terms-Cellular automata, modeling, molecular network, object-oriented.

Algorithms↗
PubMed2005

Functional diversity of AT2 receptor orthologues in closely related species.

BACKGROUND: The most striking feature of life is biodiversity. However, mechanisms of biodiversity remain poorly understood, as most protein orthologues of different species are highly homologous in sequence and identical in function. Interestingly, recent evidence has demonstrated heterogeneity for a G protein-coupled angiotensin II (Ang II) type 2 (AT(2)) receptor in both ligand binding and induction of arachidonic acid (AA) release. The present study investigated the properties of AT(2) receptors in closely related species. METHODS: AT(2) receptors cloned from human, rabbit, rat, and mouse were expressed in Chinese hamster ovary cells (CHO-K1), African green monkey kidney cells (COS-1), and human embryonic kidney (HEK)-293 cells and characterized in ligand binding and signal transductions. Critical residues in rabbit AT(2) receptor attributable to heterogeneity were examined using both gain-of-function and loss-of-function approaches with mutagenesis. RESULTS: The newly cloned rabbit AT(2) receptor exhibits distinct biochemical and biologic properties compared to its highly homologous orthologues (91% in overall amino acid sequence) of rat, mouse, and human. All these orthologues activate SH2 domain-containing phosphatase-1 (SHP-1) and show similar binding affinities for Ang II and AT(2)-specific ligands CGP42112A and PD123319. However, reducing agent dithiothreitol (DTT) inactivates the rabbit orthologue but potentiates the others in ligand binding, a hallmark of AT(2) versus AT(1) receptor subtypes. Most interestingly, rabbit AT(2) receptor, but not the other orthologues, induces AA release in various cell systems when stimulated by both Ang II and CGP42112A, the peptide antagonist. Mutagenesis studies and sequence analyses further indicate that residues His(106), Asp(188), and Thr(293) are responsible for the DTT inactivation and residues Val(209) and Val(249) are partially responsible for AA release. CONCLUSION: These results deny the coexistence of an additional AT(2) subtype in rabbit proximal tubule cells and demonstrate for the first time the presence of functional diversity for closely related Eutherian orthologues of a G protein-coupled receptor (GPCR) that are more than 90% homologous in the amino acid sequence.

Amino Acid Sequence↗