Biomedical subjects

X Jiang

Publications and source records attributed to X Jiang.

At least 91 records · Page 5Linked to original sources

PubMed2001

Reproducibility of the high-performance liquid chromatographic fingerprints obtained from two soybean cultivars and a selected progeny.

Roots from soybean cultivars Williams 82 and Hartwig along with one of their progeny 14a, were extracted with non-polar, moderately polar, and highly polar solvent systems. Extracts were compared by thin-layer chromatography and by HPLC. Methanol extractions conducted at ambient temperature coupled with analysis by reversed-phase HPLC using UV detection provided the most representative sets of reproducible fingerprints. Further optimization of the overall protocol should allow for the profiling of different soybean cultivars when their roots are exposed to various environments and insults during early growth.

Chromatography, High Pressure Liquid↗

PubMed2001

Novel liquid chromatographic-tandem mass spectrometric methods using silica columns and aqueous-organic mobile phases for quantitative analysis of polar ionic analytes in biological fluids.

Use of silica stationary phase and aqueous-organic mobile phases could significantly enhance LC-MS-MS method sensitivity. The LC conditions were compatible with MS detection. Analytes with basic functional groups were eluted with acidic mobile phases and detected by MS in the positive ion mode. Analytes with acid functional groups were eluted with mobile phases at neutral pH and detected by MS in the negative ion mode. Analytes poorly retained on reversed-phase columns showed good retention on silica columns. Compared with reversed-phase LC-MS-MS, 5-8-fold sensitivity increases were observed for basic polar ionic compounds when using silica columns and aqueous-organic mobile phase. Up to a 20-fold sensitivity increase was observed for acidic polar ionic compounds. Silica columns and aqueous-organic mobile phases were used for assaying nicotine, cotinine, and albuterol in biological fluids.

Albuterol↗

PubMed2001

Epidermal transformation leads to increased perlecan synthesis with heparin-binding-growth-factor affinity.

Perlecan, a proteoglycan of basement membrane and extracellular matrices, has important roles in both normal biological and pathological processes. As a result of its ability to store and protect growth factors, perlecan may have crucial roles in tumour-cell growth and invasion. Since the biological functions of different types of glycosaminoglycan vary with cellular origin and structural modifications, we analysed the expression and biological functions of perlecan produced by a normal epidermal cell line (JB6) and its transformed counterpart (RT101). Expression of perlecan in tumorigenic cells was significantly increased in both mRNA and protein levels. JB6 perlecan was exclusively substituted with heparan sulphate, whereas that of RT101 contained some additional chondroitin sulphate. Detailed structural analysis of the heparan sulphate (HS) chains from perlecan of both cell types revealed that their overall sulphation and chain length were similar (approximately 60 kDa), but the HS chains of tumour-cell-derived perlecan were less sulphated. This resulted from reduced 2-O- and 6-O-sulphation, but not N-sulphation, and an increase in the proportion of unsulphated disaccharides. Despite this, the heparan sulphate of RT101- and JB6-derived perlecan bound fibroblast growth factor-1, -2, -4 and -7 and heparin-binding epidermal growth factor with similar affinity. Therefore abundant tumour-derived perlecan may support the angiogenic responses seen in vivo and be a key player in tumorigenesis.

Animals↗

PubMed2001

Search for quadrupole strength in the electroexcitation of the delta+(1232).

High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account.

Journal Article↗

PubMed2001

Polarization measurements in high-energy deuteron photodisintegration.

We present measurements of the recoil proton polarization for the d(gamma-->,p-->)n reaction at straight theta(c.m.) = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization p(y) vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(gamma,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

Journal Article↗

PubMed2001

Primitive quiescent leukemic cells from patients with chronic myeloid leukemia spontaneously initiate factor-independent growth in vitro in association with up-regulation of expression of interleukin-3.

It was previously shown that patients with chronic myeloid leukemia (CML) have a rare but consistently detectable population of quiescent (G0) leukemic (Philadelphia chromosome-positive and BCR-ABL-positive [BCR-ABL+]) CD34+ cells. In the study described here, most such cells expressed a primitive phenotype (CD38-, CD45RA-, CD71-, and HLA-DR(lo)) and cultures of these cells containing growth factors produced ultimately larger, but initially more slowly growing clones than do cultures of initially cycling CD34+ leukemic cells. Initially quiescent leukemic cells expressing BCR-ABL proliferated in single-cell cultures in the absence of added growth factors, thereby demonstrating their ability to spontaneously exit G0 and enter a continuously cycling state. Interestingly, on isolation, few of these quiescent BCR-ABL+ cells contained either interleukin-3 (IL-3) or granulocyte colony-stimulating factor (G-CSF) transcripts, whereas both were present in most cycling BCR-ABL+ CD34+ cells. However, after 4 days of culture in the absence of added growth factors and in association with their entry into the cell cycle (as indicated by up-regulation of Ki-67 and cdc25 transcripts), IL-3 transcripts became detectable. These findings show that entry of leukemic (BCR-ABL-expressing) progenitors into a quiescent (G0) state in vivo is highest among the most primitive leukemic cell populations, associated with a down-regulation of IL-3 and G-CSF gene expression, and spontaneously reversible in association with up-regulation of IL-3 expression. These results highlight the potential physiologic relevance of quiescent CML progenitors, even in treated patients, in whom these cells would be predicted to have a proliferative advantage over their quiescent normal counterparts when cytokine concentrations are low.

ADP-ribosyl Cyclase↗

PubMed2001

Synthesis, conformational analysis and biological activities of lanthionine analogs of a cell adhesion modulator.

Cell adhesion is critical for many biological processes, such as hemostasis, wound healing, tumor metastasis and inflammation. Integrins are important mediators of cell adhesion. The integrin alpha4beta1, also known as VLA-4, is a cell surface receptor involved in inflammation. A cyclic peptide, 1-FCA-Arg-c[Cys-Asp-Thz-Cys]-OH, is a potent antagonist to VLA-4 with an IC50 of 2.4 nM. In the current study, we synthesized the lanthionine analogs of 1-FCA-Arg-c[Cys-Asp-Thz-Cys]-OH and determined the conformations of both the parent compound and its lanthionine analog in solution by NMR and computer simulations. The lanthionine analog retains its selectivity to VLA-4 with high nanomolar potency. Both molecules adopt similar topological arrangements in their conformations, while some important differences remain in the sulfur bridge region, which may cause the difference in potency.

Alanine↗

PubMed2001

A highly automated 96-well solid phase extraction and liquid chromatography/tandem mass spectrometry method for the determination of fentanyl in human plasma.

A high-throughput bioanalytical method based on automated sample transfer, automated solid phase extraction, and fast liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, has been developed for the determination of the analgesic fentanyl in human plasma. Samples were transferred into 96-well plates using an automated sample handling system. Automated solid phase extraction (SPE) was carried out using a 96-channel programmable liquid-handling workstation using a mixed-mode sorbent. The extracted samples were then dried down, reconstituted and injected onto a silica column using an aqueous/organic mobile phase with tandem mass spectrometric detection. The method has been validated over the concentration range 0.05-100 ng/mL fentanyl in human plasma, based on a 0.25-mL sample size. The assay is sensitive, specific and robust. More than 2000 samples have been analyzed using this method. The automation of the sample preparation steps not only increased the analysis throughput, but also facilitated the transfer of the method between different bioanalytical laboratories of the same organization.

Analgesics↗

PubMed2001

Establishment of in vitro cellular model predicting histocompatibility in allograft.

A novel in vitro cellular model producting recipient-donor histocompatibility in allograft was developed to select the donor validity. Fifteen couples of blood samples of donor and recipient in human BMT were examined using the model, and skin allograft in mice was performed to test the model. The results showed that the less the differences of histocompatibility evaluated by the model were, the later GVHR in human BMT occurred and the longer the survival time of skin allografts in mice. It was suggested that the model could be used to predict correctly histocompatibility between donor and recipient.

Animals↗

PubMed2001

Synthesis of (5alpha)-17-azaandrostan-3-ols and (5alpha)-17-aza-D-homoandrostan-3-ols and their N-acylated derivatives.

Two groups of N-acylated D-azasteroids (4 and 5) were synthesized to explore structure-activity relationships for steroid modulation of GABA(A) receptor function. The target compounds were prepared conveniently from (5alpha)-3-hydroxyandrostan-17-ones (6 and 7) via the intermediate (5alpha)-17-aza-D-homoandrostan-3-ols (14 and 15) or (5alpha)-17-azaandrostan-3-ols (18 and 19) precursors in high overall yields. A Beckmann rearrangement and a Hofmann rearrangement were employed as two key steps in the synthetic sequences.

Androstanols↗

PubMed2001

Development and validation of a sensitive and robust LC-tandem MS method for the analysis of warfarin enantiomers in human plasma.

A liquid chromatography-tandem mass spectrometry method (LC-MS-MS) was developed and validated for measuring warfarin (WAR) enantiomers (R-WAR and S-WAR) in human EDTA plasma. Liquid-liquid extraction using ethyl ether was used to extract the analytes from the plasma. Baseline resolution of S- and R-WAR as well as the internal standard enantiomers (S- and R-p-ClWAR, S-IS and R-IS) was achieved on a beta-cyclodextrin column with a mobile phase of acetonitrile-acetic acid-triethylamine (1000:3:2.5, v/v/v). The retention times are 6.9, 8.0, 7.0, and 7.9 min for S-WAR, R-WAR, S-IS and R-IS, respectively. The detection was by monitoring S- and R-WAR at m/z 307-->161 and S- and R-IS at m/z 341-->161 using (-) ESI. The standard curve range was 1-100 ng ml(-1) for both S- and R-WAR. The inter-day precision and accuracy of the quality control (QC) samples were <7.3% relative standard deviation (RSD) and <7.3% bias for S-WAR, and <6.5% RSD and <5.8% bias for R-WAR, respectively. Analyte stability during sample processing and storage were established. Method ruggedness was demonstrated by the reproducible performance from analysis of clinical samples.

Anticoagulants↗

PubMed2001

Importance of injection solution composition for LC-MS-MS methods.

For the first time, the influence of the injection solution composition on the quality of LC-MS-MS methods, in terms of column efficiency and peak shape, was systematically investigated. Various types of compounds, including polar ionic acidic, polar ionic basic and non-polar neutral compounds, were prepared in different solutions ranging from 100% water to 100% acetonitrile. Different volumes of these solutions were injected onto either C18 or silica columns connected to tandem mass spectrometry. The mobile phases consisted of acetonitrile, water, and small amounts of volatile acid or buffer. On silica columns, the influence of injection solution on the peak shape and column efficiency was straightforward. The sharpest peaks and the highest column efficiency were obtained with 100% acetonitrile as the injection solvent. On C18 columns, this type of influence was less clear due to the dual retention mechanism of the bonded phase and of the residual silanol groups. On C18 column, retention due to residual silanol groups was significant even with a mobile phase containing less than 50% acetonitrile. Poor peak shape was observed when the injection solution had a stronger eluting strength than mobile phase, particularly for early eluting peaks.

Acetates↗

PubMed2001

Adolescent smoking in Wuhan, China: baseline data from the Wuhan Smoking Prevention Trial.

BACKGROUND: This study reports the prevalence of adolescent smoking in the urban and rural areas of Wuhan, China, the capital of Hubei Province, on the Yangtze River in central China. METHODS: Smoking behavior was examined by age, gender, and urbanicity as part of the Wuhan Smoking Prevention Trial. Subjects included 6994 seventh- to ninth-grade students attending 22 randomly selected schools in urban and rural districts. Outcome measures included lifetime smoking, past-30-day smoking, established smoking (>100 cigarettes in lifetime), and susceptibility to smoking (absence of a firm commitment not to smoke). RESULTS: Lifetime smoking prevalence was 47% among boys and 18% among girls. Past-30-day smoking prevalence was 16% among boys and 4% among girls. Established smoking prevalence was 2% among boys and 0% among girls. The prevalence of susceptibility to smoking was 31% among boys and 10% among girls. Smoking increased significantly with age (p<.0005). Susceptibility was more prevalent in rural areas than in urban areas (p<.05), but there were no urban-rural differences in lifetime, past 30-day smoking, or established smoking. Trend analyses revealed that smoking increased with age more rapidly among boys than among girls (p<.05). Smoking was more prevalent among rural boys than among urban boys, but it was more prevalent among urban girls than among rural girls (p<.05). CONCLUSIONS: Adolescent smoking is a significant public health problem in China. Boys are at particularly high risk, as are girls living in urban areas. Effective smoking prevention programs for adolescents, as well as restrictions on tobacco industry marketing and youth access to tobacco, are needed to prevent tobacco-related morbidity and mortality in China.

Adolescent↗

PubMed2001

The biomechanical, morphologic, and histochemical properties of the costal cartilages in children with pectus excavatum.

BACKGROUND/PURPOSE: The cause of the pectus excavatum (PE) remains unclear, although some results of research have indicated that the disturbance of the sternum or costal cartilage might be responsible for this deformity. But no decisive evidence has been gained. The authors have analyzed the biomechanical, morphologic, and histochemical properties of the cartilage in PE and intend to support the belief that the disturbance of the cartilage might contribute to the development of PE. METHODS: Thirty-eight specimens of the sixth cartilage were obtained at operation for the PE group (aged from 3 to 6 years; mean, 4.2 years). And 28 specimens of the control group (aged from 3 to 6 years; mean, 4.4 years) were gained from routine postmortem examinations in which the cause of death was unlikely to have affected the cartilage. The biomechanical test was carried out in a material testing machine (Shimadzu AG-10TA, Tokyo, Japan). The relation curve of load-deformation in tensile and compressive tests and the curve of load-time in the flexuous test were recorded automatically. The values of the ultimate strength and strain were calculated from this relation curve. The specimens also underwent H&E staining. The values of the area, circumference, mean diameter, maximal diameter, and morphologic factor of the cell and the nucleus of the cartilage in superficial and deep area were determined with the help of image analysis software (GT-2 model, China). The superficial zone (SZ) and deep zone (DZ) of the cartilage were examinated with electron microscopy (JEM-100SX, Japan). The distribution and intensity of type II collagen was shown by immunohistochemistry staining and analyzed with the image analysis software (GT-2 model, Huakang Co, Chengdu, China). The extent and distribution of proteoglycan were analyzed after Safranin-O and periodic acid shiff (PAS) staining. RESULTS: The mean strength of the costal cartilage in the experimental group was less than that in the control group in terms of tension, compression, and flexure (P <.05). The shape of the stress-strain curve for tension and compression in the experimental group was different from the control group. The fracture load in the experimental group was less than in the control group in tension (1.5 MPa versus 2.8 MPa) and in compression (.2 MPa versus 8.3 MPa). The time of fracture in experimental group was 30 seconds compared with 38 seconds in control group. No denaturation or necrosis could be found in light microscopical examination. There was no manifestation of hyperplasia or hypoplasia in the costal cartilage of the PE group. In SZ and DZ areas, the pattern and the number of mitochondria, endoplasmic reticulum, and Golgi in the experimental group were the same as the control group in transmission electron microscopy. Furthermore, the distribution and the number of proteoglycan in the 2 groups did not show a significant difference both in SZ and DZ areas. Although the distribution of the collagen in SZ areas was normal, this pattern was disturbed in DZ areas in the experiment group. The results of type II collagen immunohistochemistry examination was concordant with that change. No significant difference between control and experimental group could be seen in Safranin-O and PAS staining for proteoglycan. CONCLUSIONS: The biomechanical stability of the cartilage was decreased in the PE group. This might be caused by the disorderly arrangement and distribution of the collagen in the cartilage of PE patients. J Pediatr Surg 36:1770-1776.

Biomechanical Phenomena↗

PubMed2001

TH2 lymphocytes secrete functional VIP upon antigen stimulation.

In addition to the peptidergic innervation, immune cells may also represent a source for VIP in the lymphoid organs. Previous studies reported increased VIP mRNA and protein expression in mitogen-stimulated B and T lymphocytes. To determine whether specific T cell subsets are responsible for VIP production, we derived TH1 and TH2 effector cell lines from T-cell receptor transgenic mice. TH1 and TH2 cells were stimulated with the specific (pigeon cytochrome C peptide) or nonspecific (ovalbumin) antigen presented by MHC class II compatible antigen-presenting cells. Upon stimulation with the specific antigen, TH2, but not TH1 cells express VIP mRNA and intracelllular VIP protein, as determined by Northern blots and FACS analysis. Supernatants harvested from antigen-stimulated TH2 cells contain secreted VIP, as determined by Elisa, and induce cAMP in HEK293 cells transfected with the specific VIP/PACAP receptor VPAC1. These results confirm that TH2, but not TH1 cells, express and secrete functional VIP following specific antigen stimulation. The release of VIP within the lymphoid microenvironment following antigenic stimulation provides a physiological basis for the immunoregulatory effects of VIP on neighboring immune cells, such as downregulation of macrophage activation, effects on lymphocyte migration, on antigen-induced T cell apoptosis, and on T cell differentiation.

Animals↗

PubMed2001

Increasing protein stability using a rational approach combining sequence homology and structural alignment: Stabilizing the WW domain.

This study shows that a combination of sequence homology and structural information can be used to increase the stability of the WW domain by 2.5 kcal mol(-1) and increase the T(m) by 28 degrees C. Previous homology-based protein design efforts typically investigate positions with low sequence identity, whereas this study focuses on semi-conserved core residues and proximal residues, exploring their role(s) in mediating stabilizing interactions on the basis of structural considerations. The A20R and L30Y mutations allow increased hydrophobic interactions because of complimentary surfaces and an electrostatic interaction with a third residue adjacent to the ligand-binding hydrophobic cluster, increasing stability significantly beyond what additivity would predict for the single mutations. The D34T mutation situated in a pi-turn possibly disengages Asn31, allowing it to make up to three hydrogen bonds with the backbone in strand 1 and loop 2. The synergistic mutations A20R/L30Y in combination with the remotely located mutation D34T add together to create a hYap WW domain that is significantly more stable than any of the protein structures on which the design was based (Pin and FBP28 WW domains).

Adaptor Proteins, Signal Transducing↗

PubMed2001

Immune control of Brucella abortus 2308 infections in BALB/c mice.

BALB/c mice infected with Brucella abortus strain 2308 have 10-fold higher levels of bacteria during the plateau phase of infection (the time period when the number of colony-forming units in vivo remains consistent) than the more resistant C57BL/10 mice. This is due to a cessation of interferon-gamma (IFN-gamma) production that begins after the first week of infection and continues until the end of the plateau phase at least 6 weeks post infection. Despite the lack of IFN-gamma production during this time BALB/c mice are able to prevent an increase in bacterial colony-forming units. Here it was shown that both tumor necrosis factor (TNF)-alpha and CD8 T cells were involved in controlling bacterial numbers in BALB/c mice during this time. That is, neutralization of TNF-alpha or depletion of CD8 T cells with monoclonal antibodies resulted in a significant increase in the number of splenic colony-forming units recovered at 3 weeks post infection. In the absence of CD8 T cells there was also a significant increase in splenic macrophages. The role of TNF-alpha may depend upon the presence of interferon-gamma early in the infection since when TNF-alpha was neutralized in interferon-gamma gene knockout mice there was a marked increase in splenic macrophages, NK cells and neutrophils but not a significant increase in colony-forming units.

Animals↗

PubMed2001

Cloning and pharmacological characterization of a fourth histamine receptor (H(4)) expressed in bone marrow.

Histamine is a multifunctional hormone that regulates smooth muscle contraction in the airways, acid secretion in the gut, and neurotransmitter release in the central nervous system through three well characterized receptor subtypes, H(1), H(2), H(3), respectively. As part of a directed effort to discover novel G-protein-coupled receptors through homology searching of genomic databases, we identified a partial clone (GPCR105) that had significant homology to the recently identified histamine H(3) receptor cDNA. Expression of the full-length human GPCR105 in cells confers the ability to bind [(3)H]histamine with high affinity (K(D) = 5 nM). GPCR105 is pharmacologically similar to the histamine H(3) receptor in that it binds many of the known H(3) agonists and antagonists, albeit with a different rank order of affinity/potency. GPCR105 does not bind (i.e., K(D) > 10 microM) all tested H(1) and H(2) receptor antagonists such as diphenhydramine, loratadine, ranitidine, and cimetidine, but has modest affinity for the H(2) receptor agonist, dimaprit (377 nM). Whereas the H(3) receptor is expressed almost exclusively in nervous tissues, GPRC105 is expressed primarily in bone marrow and eosinophils. Together, these data demonstrate that GPCR105 is a novel histamine receptor structurally and pharmacologically related to the H(3) receptor. However, its unique expression profile and physiological role suggest that GPCR105 is a fourth histamine receptor subtype (H(4)) and may be a therapeutic target for the regulation of immune function, particularly with respect to allergy and asthma.

Adenylyl Cyclases↗