Biomedical subjects

Qing Zhang

Publications and source records attributed to Qing Zhang.

At least 181 records · Page 10Linked to original sources

PubMed2003

MGView: an alignment and visualization tool to enhance gap closure of microbial genomes.

Gap closure is a challenging phase in microbial random shotgun genome sequencing projects, particularly since genome assemblies are often complicated by the presence of repeat elements, insertion sequences and other similar factors that contribute to sequence misassemblies. While it is well recognized that the conservation of genetic information between microbial genomes, combined with the exponential increase in available microbial sequences, can be exploited to increase the efficiency of gap closure, we lack the computational tools to aid in this process. We describe here a new tool, MGView, which was developed to create a graphical depiction of the alignment of a set of microbial contigs against a completed microbial genome. The results of our assembly of the Staphylococcus aureus RF122 genome show that MGView enables a considerable reduction in time and economic cost associated with closure. Together, the results also show that the application of MGView not only enables a reduction in fold-coverage requirements of the random shotgun sequence phase, but also provides interesting insights into differences in gene content and organization between finished and unfinished microbial genomes.

Base Sequence↗

PubMed2003

Hermansky-Pudlak syndrome type 7 (HPS-7) results from mutant dysbindin, a member of the biogenesis of lysosome-related organelles complex 1 (BLOC-1).

Hermansky-Pudlak syndrome (HPS; MIM 203300) is a genetically heterogeneous disorder characterized by oculocutaneous albinism, prolonged bleeding and pulmonary fibrosis due to abnormal vesicle trafficking to lysosomes and related organelles, such as melanosomes and platelet dense granules. In mice, at least 16 loci are associated with HPS, including sandy (sdy; ref. 7). Here we show that the sdy mutant mouse expresses no dysbindin protein owing to a deletion in the gene Dtnbp1 (encoding dysbindin) and that mutation of the human ortholog DTNBP1 causes a novel form of HPS called HPS-7. Dysbindin is a ubiquitously expressed protein that binds to alpha- and beta-dystrobrevins, components of the dystrophin-associated protein complex (DPC) in both muscle and nonmuscle cells. We also show that dysbindin is a component of the biogenesis of lysosome-related organelles complex 1 (BLOC-1; refs. 9-11), which regulates trafficking to lysosome-related organelles and includes the proteins pallidin, muted and cappuccino, which are associated with HPS in mice. These findings show that BLOC-1 is important in producing the HPS phenotype in humans, indicate that dysbindin has a role in the biogenesis of lysosome-related organelles and identify unexpected interactions between components of DPC and BLOC-1.

Animals↗

PubMed2003

Src kinases mediate STAT growth pathways in squamous cell carcinoma of the head and neck.

Signal transducer and activator of transcription (STAT) proteins are constitutively activated in many malignancies, including squamous cell carcinoma of the head and neck (SCCHN). Previously, we reported that phosphorylation of the epidermal growth factor receptor (EGFR) is linked to activation of STATs 3 and 5 in SCCHN cells. The present study was undertaken to determine the role of Src family kinases in STAT activation and SCCHN growth. The Src family kinases c-Src, c-Yes, Fyn, and Lyn were expressed and activated by transforming growth factor-alpha stimulation in all four SCCHN cell lines examined but not in corresponding normal epithelial cells. In nine SCCHN cell lines tested, Src phosphotyrosine expression levels were highly correlated with activation levels of STATs 3 and 5. Co-immunoprecipitation analysis demonstrated interaction between c-Src and STATs 3 or 5 and EGFR in SCCHN cells, but no heterodimerization was detected between STAT3 and STAT5. SCCHN cells treated with either of two Src-specific inhibitors or transfected with a dominant-negative c-Src construct demonstrated decreased activation of STATs 3 and 5 and reduced growth rates in vitro. These results demonstrate a role for Src kinases in mediating activation of STATs 3 and 5 in concert with the EGFR in SCCHN cells. Strategies to target Src activation may contribute to the treatment of cancers that demonstrate increased levels of EGFR and STATs, including SCCHN.

Base Sequence↗

PubMed2003

Genomic homogeneity between Mycobacterium avium subsp. avium and Mycobacterium avium subsp. paratuberculosis belies their divergent growth rates.

BACKGROUND: Mycobacterium avium subspecies avium (M. avium) is frequently encountered in the environment, but also causes infections in animals and immunocompromised patients. In contrast, Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) is a slow-growing organism that is the causative agent of Johne's disease in cattle and chronic granulomatous infections in a variety of other ruminant hosts. Yet we show that despite their divergent phenotypes and the diseases they present, the genomes of M. avium and M. paratuberculosis share greater than 97% nucleotide identity over large (25 kb) genomic regions analyzed in this study. RESULTS: To characterize genome similarity between these two subspecies as well as attempt to understand their different growth rates, we designed oligonucleotide primers from M. avium sequence to amplify 15 minimally overlapping fragments of M. paratuberculosis genomic DNA encompassing the chromosomal origin of replication. These strategies resulted in the successful amplification and sequencing of a contiguous 11-kb fragment containing the putative Mycobacterium paratuberculosis origin of replication (oriC). This fragment contained 11 predicted open reading frames that showed a conserved gene order in the oriC locus when compared with several other Gram-positive bacteria. In addition, a GC skew analysis identified the origin of chromosomal replication which lies between the genes dnaA and dnaN. The presence of multiple DnaA boxes and the ATP-binding site in dnaA were also found in M. paratuberculosis. The strong nucleotide identity of M. avium and M. paratuberculosis in the region surrounding the origin of chromosomal replication led us to compare other areas of these genomes. A DNA homology matrix of 2 million nucleotides from each genome revealed strong synteny with only a few sequences present in one genome but absent in the other. Finally, the 16s rRNA gene from these two subspecies is 100% identical. CONCLUSIONS: We present for the first time, a description of the oriC region in M. paratuberculosis. In addition, genomic comparisons between these two mycobacterial subspecies suggest that differences in the oriC region may not be significant enough to account for the diverse bacterial replication rates. Finally, the few genetic differences present outside the origin of chromosomal replication in each genome may be responsible for the diverse growth rates or phenotypes observed between the avium and paratuberculosis subspecies.

Bacterial Proteins↗

PubMed2003

Human chromosome 7: DNA sequence and biology.

DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.

Animals↗

PubMed2003

Deletion of the P2X7 nucleotide receptor reveals its regulatory roles in bone formation and resorption.

The P2X7 nucleotide receptor is an ATP-gated ion channel expressed widely in cells of hematopoietic origin. Our purpose was to explore the involvement of the P2X7 receptor in bone development and remodeling by characterizing the phenotype of mice genetically modified to disrupt the P2X7 receptor [knockout (KO)]. Femoral length did not differ between KO and wild-type (WT) littermates at 2 or 9 months of age, indicating that the P2X7 receptor does not regulate longitudinal bone growth. However, KO mice displayed significant reduction in total and cortical bone content and periosteal circumference in femurs, and reduced periosteal bone formation and increased trabecular bone resorption in tibias. Patch clamp recording confirmed expression of functional P2X7 receptors in osteoclasts from WT but not KO mice. Osteoclasts were present in vivo and formed in cultures of bone marrow from KO mice, indicating that this receptor is not essential for fusion of osteoclast precursors. Functional P2X7 receptors were also found in osteoblasts from WT but not KO mice, suggesting a direct role in bone formation. P2X7 receptor KO mice demonstrate a unique skeletal phenotype that involves deficient periosteal bone formation together with excessive trabecular bone resorption. Thus, the P2X7 receptor represents a novel therapeutic target for the management of skeletal disorders such as osteoporosis.

Animals↗

PubMed2003

Predictors of left ventricular reverse remodeling after cardiac resynchronization therapy for heart failure secondary to idiopathic dilated or ischemic cardiomyopathy.

Biventricular pacing results in left ventricular (LV) reverse remodeling in heart failure patients with wide QRS complexes. This study examines potential predictors of reverse remodeling. Echocardiography with tissue Doppler imaging was performed at baseline and 3 months after biventricular pacing in 30 patients (21 men and 9 women, mean age 62 +/- 14 years). There were 17 responders to reverse remodeling (defined as a reduction in LV end-systolic volume by >15%) and 13 nonresponders. Responders had significant improvement in 6-minute hall-walking distance (p = 0.006), metabolic equivalents (p = 0.02), peak oxygen uptake (p = 0.02), New York Heart Association functional class (p <0.001), and quality of life (p <0.001); an increase in the sphericity index (p = 0.007), ejection fraction (p <0.001), and diastolic filling time (p = 0.03); a decrease in myocardial performance index (p = 0.02), isovolumic relaxation time (p = 0.004), and mitral regurgitation (p = 0.007); and an improvement in systolic dyssynchrony (SD of the time to peak myocardial systolic contraction of the 12 LV segments as dyssynchrony index) (45.0 +/- 8.3 vs 32.5 +/- 14.5 ms, p = 0.003). In contrast, nonresponders only had a small degree of clinical improvement in New York Heart Association class (p = 0.03) and quality-of-life scores (p = 0.03), without any change in cardiac function, and worsening of systolic dyssynchrony (24.8 +/- 4.5 vs 34.1 +/- 13.5 ms, p = 0.02). When all the above factors were put into univariate and multivariate analyses models, systolic dyssynchrony was the only independent predictor of reverse remodeling (r = -0.76, p <0.001) (beta = -1.54, p = 0.007). A preimplant dyssynchrony index of 32.6 ms (+2 SDs from mean of 88 normal controls) was able to totally segregate responders from nonresponders of biventricular pacing. Thus, responders of LV reverse remodeling were associated with improvement in clinical status, cardiac function, and systolic synchronicity. Direct assessment of systolic synchronicity by tissue Doppler imaging is highly accurate in predicting responders to therapy.

Aged↗

PubMed2003

Ru2 and Ru encode mouse orthologs of the genes mutated in human Hermansky-Pudlak syndrome types 5 and 6.

Hermansky-Pudlak syndrome (HPS) is a genetically heterogeneous disease involving abnormalities of melanosomes, platelet dense granules and lysosomes. Here we have used positional candidate and transgenic rescue approaches to identify the genes mutated in ruby-eye 2 and ruby-eye mice (ru2 and ru, respectively), two 'mimic' mouse models of HPS. We also show that these genes are orthologs of the genes mutated in individuals with HPS types 5 and 6, respectively, and that their protein products directly interact. Both genes are previously unknown and are found only in higher eukaryotes, and together represent a new class of genes that have evolved in higher organisms to govern the synthesis of highly specialized lysosome-related organelles.

Adaptor Protein Complex 3↗

PubMed2003

Constructing irregular surfaces to enclose macromolecular complexes for mesoscale modeling using the discrete surface charge optimization (DISCO) algorithm.

Salt-mediated electrostatics interactions play an essential role in biomolecular structures and dynamics. Because macromolecular systems modeled at atomic resolution contain thousands of solute atoms, the electrostatic computations constitute an expensive part of the force and energy calculations. Implicit solvent models are one way to simplify the model and associated calculations, but they are generally used in combination with standard atomic models for the solute. To approximate electrostatics interactions in models on the polymer level (e.g., supercoiled DNA) that are simulated over long times (e.g., milliseconds) using Brownian dynamics, Beard and Schlick have developed the DiSCO (Discrete Surface Charge Optimization) algorithm. DiSCO represents a macromolecular complex by a few hundred discrete charges on a surface enclosing the system modeled by the Debye-Hückel (screened Coulombic) approximation to the Poisson-Boltzmann equation, and treats the salt solution as continuum solvation. DiSCO can represent the nucleosome core particle (>12,000 atoms), for example, by 353 discrete surface charges distributed on the surfaces of a large disk for the nucleosome core particle and a slender cylinder for the histone tail; the charges are optimized with respect to the Poisson-Boltzmann solution for the electric field, yielding a approximately 5.5% residual. Because regular surfaces enclosing macromolecules are not sufficiently general and may be suboptimal for certain systems, we develop a general method to construct irregular models tailored to the geometry of macromolecules. We also compare charge optimization based on both the electric field and electrostatic potential refinement. Results indicate that irregular surfaces can lead to a more accurate approximation (lower residuals), and the refinement in terms of the electric field is more robust. We also show that surface smoothing for irregular models is important, that the charge optimization (by the TNPACK minimizer) is efficient and does not depend on the initial assigned values, and that the residual is acceptable when the distance to the model surface is close to, or larger than, the Debye length. We illustrate applications of DiSCO's model-building procedure to chromatin folding and supercoiled DNA bound to Hin and Fis proteins. DiSCO is generally applicable to other interesting macromolecular systems for which mesoscale models are appropriate, to yield a resolution between the all-atom representative and the polymer level.

Algorithms↗

PubMed2003

Comparison of acute changes in left ventricular volume, systolic and diastolic functions, and intraventricular synchronicity after biventricular and right ventricular pacing for heart failure.

BACKGROUND: Biventricular pacing (BiV) therapy has recently been shown to improve systolic function and cause reverse remodeling in patients with advanced heart failure with electromechanical delay. In these patients, the benefit of right ventricular (RV)-based pacing was controversial. We compared the acute changes in systolic and diastolic function, left ventricular (LV) volume, and intraventricular synchronicity in BiV pacing, RV pacing, and without pacing (No) by means of echocardiography and tissue Doppler imaging (TDI). METHODS: TDI was performed in 33 patients with heart failure after undergoing pacemaker implantation, when the device was randomized to BiV, RV, and no pacing modes. RESULTS: Systolic function was only improved during BiV pacing, but not during RV pacing. This included ejection fraction (No vs RV vs BiV = 24% +/- 12% vs 25% +/- 10% vs 30% +/- 14%, P =.02 vs No), +dp/dt (P =.01), myocardial performance index (P =.01), and isovolumic contraction time (P =.03). Mitral regurgitation was only reduced during BiV pacing (P =.02). LV early diastolic function was depressed in both RV and BiV pacing, as detected by transmitral flow (97 +/- 34 vs 80 +/- 34 vs 82 +/- 32 cm/s, both P < or =.005) and TDI (mean myocardial early diastolic velocity of 6 basal segments, 3.3 +/- 1.7 vs 2.6 +/- 1.0 vs 2.6 +/- 1.0 cm/s, both P =.01). The LV end-diastolic (187 +/- 86 vs 177 +/- 84 vs 166 +/- 79, P =.003) and end-systolic (146 +/- 77 vs 138 +/- 79 vs 122 +/- 69, P =.003) volumes were only decreased during BiV pacing. For systolic synchronicity, a significant delay in peak systolic contraction in the lateral over the septal wall (171 +/- 37 vs 217 +/- 46 ms, P =.004) was revealed by TDI when there was no pacing. This was abolished by BiV pacing, in which septal contraction was delayed (195 +/- 38 vs 201 +/- 53 ms, P = not significant). However, RV pacing restored the lateral wall delay, and systolic asynchrony reappeared (190 +/- 40 vs 227 +/- 56 ms, P =.01). Diastolic asynchrony between the septal and lateral walls was not evident in these patients and was not affected by either pacing mode. CONCLUSION: Only BiV pacing, but not RV pacing, improves systolic function, and reduces mitral regurgitation and LV volumes in patients with heart failure and electromechanical delay. This is attributed to the improvement of systolic synchronicity. Diastolic synchronicity was unaffected, whereas early diastolic function could be jeopardized, by either pacing mode.

Aged↗

PubMed2003

Effect of DNA superhelicity and bound proteins on mechanistic aspects of the Hin-mediated and Fis-enhanced inversion.

Using a recently developed inhomogeneous, macroscopic model for long DNA bound to proteins, we examine topological and geometric aspects of DNA/protein structures and dynamics on various stages of the Hin inversion pathway. This biological reaction involves exchange of DNA in a synaptic complex that brings together several DNA sites bound to Hin dimers as well as Fis enhancers. Brownian dynamics simulations in the millisecond timescale allow us to follow and analyze the DNA/protein dynamics trajectories and to examine the effects of DNA superhelicity and protein binding on various reaction steps. Analysis of the generated kinetic pathways helps explain mechanistic aspects regarding the process by which two or three protein-bound DNA sites come to close spatial proximity and show that how topological selectivity (two trapped supercoils), enhancer binding, and properties of supercoiled DNA play critical roles in regulating the inversion reaction. Specifically, a critical amount of DNA superhelicity (e.g., |sigma| > 0.02) leads to an optimal interplay for the first reaction step-two-site juxtaposition-between large-scale random rearrangements of Hin-bound DNA and local slithering within branches of plectonemes. The three-site juxtaposition, the second step, is significantly accelerated by the presence of an enhancer protein that, due to severe local bending, also alters juxtaposition mechanisms, especially for superhelical density magnitude greater than around 0.04.

Binding Sites↗

PubMed2003

LIGHT-deficiency impairs CD8+ T cell expansion, but not effector function.

LIGHT, a newly identified member of the tumor necrosis factor (TNF) family, is expressed on activated T lymphocytes. To evaluate how LIGHT contributes to T cell functions, we generated LIGHT-deficient (LIGHT(-/-)) mice using gene targeting. Disruption of LIGHT significantly reduced CD8(+) T cell-cycle progression, leading to reduced proliferation to anti-CD3, anti-CD3/anti-CD28 or allogeneic stimulation, whereas proliferation of CD4(+) T cells remained unchanged. In contrast to the observed proliferative defects, isolated CD8(+) T cells from LIGHT(-/-) mice displayed normal cytotoxic effector function development when compared to wild-type CD8(+) T cells. Underlying a potential mechanism of reduced CD8(+) T cell proliferation, LIGHT(-/-) CD8(+) T cells displayed reduced surface levels of CD25 and a diminished ability to proliferate in response to exogenous IL-2. Furthermore, addition of IL-12 to LIGHT(-/-) CD8(+) T cell cultures could not ameliorate this proliferative defect. These results reveal a potential mechanism of action for LIGHT as a positive regulator of CD8(+) T cell expansion, but not lytic effector function development.

Animals↗

PubMed2003

Fractalkine (FRK) levels in amniotic fluid and its production during pregnancy.

Fractalkine is a new CX(3)C chemokine that has chemoattractant activity for T cells, monocytes and natural killer (NK) cells. Western blot analysis revealed that fractalkine protein was detected as a 95 kDa band in both the amniotic fluid and the amnion during the second and third trimesters. Immunohistochemistry using an anti-fractalkine polyclonal antibody revealed positive staining of epithelial cells in amnion and trophoblasts in both the second and third trimesters. Neonatal urine also contained detectable amounts of fractalkine. RT-PCR detected fractalkine mRNA transcripts in the amnion. To determine whether fractalkine receptor (CX(3)CR1)-positive cells were present in amniotic fluid and amnion, we performed RT-PCR using specific primers for CX(3)CR1. CX(3)CR1-positive cells had migrated into the amniotic fluid and the amnion. The present findings suggest that fractalkine found in amniotic fluid may contribute to the immunodefence mechanism during pregnancy.

Amnion↗

PubMed2003

Association of tumor necrosis factor gene polymorphisms and prolonged mechanical ventilation after coronary artery bypass surgery.

OBJECTIVE: Prolonged mechanical ventilation is a common complication after coronary artery bypass graft surgery. Tumor necrosis factor alpha is an important proinflammatory mediator in the post-coronary artery bypass graft inflammatory cascade. We attempted to study the effect of polymorphisms at the -308 site in the promoter region of the tumor necrosis factor gene (TNF-308) and the +250 site within the lymphotoxin-alpha gene (LT alpha+250) on the risk of prolonged mechanical ventilation after coronary artery bypass grafting. DESIGN: Prospective observational study. SETTING: Tertiary care center. PATIENTS: A total of 400 patients undergoing coronary artery bypass grafting were enrolled. MEASUREMENTS: The primary end point was time to extubate. Secondary end points were the percentages of patients extubated at 8, 24, and 48 hrs; the length of intensive care unit and hospital stay; the need for a rehabilitation facility; and 30-day mortality. Precollected blood was used for gene analysis. Genotyping was performed by polymerase chain reaction and restriction enzyme digestion. MAIN RESULTS: Patients with an AA genotype at the LT alpha+250 site and those without the LT alpha+250G/-308TNFG haplotype had a shorter duration of mechanical ventilation (11.5 vs. 27.8 hrs and 11.2 vs. 29.4 hrs; =.039 and.01, respectively). The risk of prolonged mechanical ventilation at 8, 24, and 48 hrs was higher for patients with a GA or GG genotype at the LT alpha+250 site and the LT alpha+250G/TNF-308G haplotype. This association between genotype and duration of mechanical ventilation was more dramatic in patients undergoing conventional coronary artery bypass grafting than in those undergoing off-pump coronary artery bypass grafting. With Bayesian analysis, clinical criteria and genotype can be used sequentially to predict the risk of prolonged mechanical ventilation. CONCLUSIONS: The LT alpha+250 and LT alpha+250G/TNF-308G haplotypes are associated with prolonged mechanical ventilation after coronary artery bypass graft. Preoperative genetic screening may guide intraoperative management to reduce postoperative complications.

Bayes Theorem↗

PubMed2003

Heat shock protein 70-2+1267 AA homozygotes have an increased risk of septic shock in adults with community-acquired pneumonia.

OBJECTIVE: Heat shock protein (HSP)70-2 is an important immunomodulatory protein induced in response to inflammatory stimuli. We assessed whether HSP70-2+1267 genotype influenced the risk of septic shock in a prospective cohort study of community-acquired pneumonia and whether HSP70-2+1267 genotype is a better predictor of septic shock than the genotype at lymphotoxin-alpha +250. DESIGN: Prospective cohort study. SETTING: A large, nonprofit, private hospital system in Memphis, TN. PATIENTS: Adults admitted with community-acquired pneumonia between 1998 and 2001. Septic shock was defined according to consensus criteria (American College of Chest Physicians/Society of Critical Care Medicine, 1992). INTERVENTIONS: Blood sampling. MEASUREMENTS AND MAIN RESULTS: A total of 343 subjects were enrolled; 30 had septic shock. HSP70-2+1267 and lymphotoxin-alpha +250 genotype was determined using polymerase chain reaction and restriction enzyme digestion. HSP70-2+1267 AA genotype was the strongest predictor of septic shock (p =.0005; relative risk, 3.5). Lymphotoxin-alpha +250 AA genotype was also associated with an increased risk of septic shock (p =.002; relative risk, 2.7). Logistic regression analysis found only age (p =.04) and HSP70-2+1267 genotype (p =.006) were predictors of septic shock. The greatest risk of septic shock was associated with carriage of the HSP70-2+1267 A/lymphotoxin-alpha +250 A haplotype (p <.0001). CONCLUSIONS: HSP70-2+1267 genotype is a stronger predictor of septic shock in patients with community-acquired pneumonia than lymphotoxin-alpha +250 genotype.

APACHE↗

PubMed2003

Deglutitive inhibition affects both esophageal peristaltic amplitude and shortening.

Deglutitive inhibition attenuates ongoing esophageal contractions if swallows are separated by short time intervals. This study aimed to determine whether esophageal shortening, mediated by longitudinal muscle, was similarly affected. Eight healthy subjects with two distal esophageal segments demarcated by mucosal clips and manometric recording sites positioned within those segments underwent concurrent manometry and fluoroscopy. Peristaltic amplitude and change in distal segment lengths were quantified during single swallows, paired swallows separated by progressively prolonged intervals, and a series of rapid repetitive swallows. During grouped swallows, deglutitive inhibition with complete attenuation of both the manometric contraction and segment shortening was evident with short-interval swallows and rapid-sequence swallows. No inhibition of either was evident with long-interval pairs. With intermediate interswallow intervals, the occurrence and degree of deglutitive inhibition between peristaltic amplitude and segment shortening were closely correlated. Deglutitive inhibition affects both the longitudinal and circular muscle layers of the esophageal wall, and the occurrence of inhibition evident in one layer is strongly correlated with the other.

Adult↗

PubMed2003

Pharmacokinetic study on the multi-constituents of Huangqin-Tang decoction in rats.

Using a validated high-performance liquid chromatographic (HPLC) method, the pharmacokinetics of multi-constituents in Huangqin-Tang decoction were simultaneously studied both in the compound prescription and in each single herb decoction. At different intervals (0, 1, 2, 4, 8, 12, 24, 36, 48 h) after oral administration of the Huangqin-Tang decoction or a single herb decoction at a dose of 10 g x kg(-1), the concentrations of the constituents and their metabolites: baicalin (BG), wogonoside (WG), oroxylin-A-glucuronide (OG), baicalein (B), wogonin (W), oroxylin-A (O), paeoniflorin (PF), paeonimetabolin-I (PM-I), liquiritin (LG), liquiritigenin (L), glycyrrhizic acid (GL) and glycyrrhetinic acid (GA), were detected in the rat plasma. A new metabolite-3,5,7,2',6'-penta hydroxy flavone (visidulin I, VD-I) was found in rat plasma after oral administration of Huangqin-Tang or a single herb Huangqin decoction, and the quality was identified by HPLC and LC/MS. The pharmacokinetic parameters of the constituents and metabolites in the compound prescription and single herb decoctions were compared. All concentration-time curves corresponded to the one-compartment model. The constituents of BG, WG, OG, VD-I and LG had higher C(max) and AUC(0-lim) in the compound prescription than in the single herb decoction, and WG had significant difference. The constituents of PF, W and O only had a higher AUC(0-lim) in the compound prescription, and O had a significant difference. It was concluded, in brief, that there were obvious differences in the pharmacokinetic parameters of most constituents (especially constituent WG) between the compound prescription and single herb decoction. The constituents in the compound prescription had delayed absorption and elimination, a longer residence time in the body, and higher C(max) and AUC(0-lim), than those in the single herb decoction. Therefore, they were more efficient and durable, making them promising to exerting pharmacological effects in vivo.

Animals↗

PubMed2003

A structure-function analysis of glial cell-line-derived neurotrophic factor receptor alpha1.

The GFRalpha1 cDNA was amplified by RT-PCR from fetal rat hippocampus. The soluble recombinant GFRalpha1 and its mutants were obtained from an Escherichia coli expression system. The biological activity of soluble GFRalpha1 and its mutants were evaluated in PC12 cells. The results suggest that the central domain of GFRalpha1 is a crucial determinant for ligand binding. This established a solid basis for further study to find the key amino acid mediating the binding of GDNF and GFRalpha1.

Amino Acid Sequence↗