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Biomedical subjects

X Fang

Publications and source records attributed to X Fang.

At least 37 records · Page 2Linked to original sources
PubMed2002

Novel role for CFTR in fluid absorption from the distal airspaces of the lung.

The active absorption of fluid from the airspaces of the lung is important for the resolution of clinical pulmonary edema. Although ENaC channels provide a major route for Na(+) absorption, the route of Cl(-) transport has been unclear. We applied a series of complementary approaches to define the role of Cl(-) transport in fluid clearance in the distal airspaces of the intact mouse lung, using wild-type and cystic fibrosis Delta F508 mice. Initial studies in wild-type mice showed marked inhibition of fluid clearance by Cl(-) channel inhibitors and Cl(-) ion substitution, providing evidence for a transcellular route for Cl(-) transport. In response to cAMP stimulation by isoproterenol, clearance was inhibited by the CFTR inhibitor glibenclamide in both wild-type mice and the normal human lung. Although isoproterenol markedly increased fluid absorption in wild-type mice, there was no effect in Delta F508 mice. Radioisotopic clearance studies done at 23 degrees C (to block active fluid absorption) showed approximately 20% clearance of (22)Na in 30 min both without and with isoproterenol. However, the clearance of (36)Cl was increased by 47% by isoproterenol in wild-type mice but was not changed in Delta F508 mice, providing independent evidence for involvement of CFTR in cAMP-stimulated Cl(-) transport. Further, CFTR played a major role in fluid clearance in a mouse model of acute volume-overload pulmonary edema. After infusion of saline (40% body weight), the lung wet-to-dry weight ratio increased by 28% in wild-type versus 64% in Delta F508 mice. These results provide direct evidence for a functionally important role for CFTR in the distal airspaces of the lung.

Absorption↗
PubMed2002

Selected contribution: long-term effects of beta(2)-adrenergic receptor stimulation on alveolar fluid clearance in mice.

Stimulation of active fluid transport with beta-adrenergic receptor (betaAR) agonists can accelerate the resolution of alveolar edema. However, chronic betaAR-agonist administration may cause betaAR desensitization and downregulation that may impair physiological responsiveness to betaAR-agonist stimulation. Therefore, we measured baseline and terbutaline- (10(-3) M) stimulated alveolar fluid clearance in mice that received subcutaneously (miniosmotic pumps) either saline or albuterol (2 mg. kg(-1). day(-1)) for 1, 3, or 6 days. Continuous albuterol administration increased plasma albuterol levels (10(-5) M), an effect that was associated with 1) a significant decrease in betaAR density and 2) attenuation, but not ablation, of maximal terbutaline-induced cAMP production. Forskolin-mediated cAMP-release was unaffected. Continuous albuterol infusion stimulated alveolar fluid clearance on day 1 but did not increase alveolar fluid clearance on days 3 and 6. However, terbutaline-stimulated alveolar fluid clearance in albuterol-treated mice was not reduced compared with saline-treated mice. Despite significant reductions in betaAR density and agonist-mediated cAMP production by long-term betaAR-agonist exposure, maximal betaAR-agonist-mediated increase in alveolar fluid clearance is not diminished in mice.

Adrenergic beta-Agonists↗
PubMed2001

Roles of phytanoyl-CoA alpha-hydroxylase in mediating the expression of human coagulation factor VIII.

The coagulation factor VIII (FVIII) is the coagulation factor deficient in the X-chromosome-linked bleeding disorder hemophilia A. Previous transfection studies demonstrated that factor VIII was 10-100-fold less efficiently expressed than the homologous coagulation factor, factor V. To investigate the regulatory mechanisms of FVIII synthesis and secretion, we used the yeast two-hybrid system as an approach to search for proteins that associated with FVIII. The A2 domain (337-740 amino acids) of factor VIII (FVIII-A2) was used as a bait and phytanoyl-CoA alpha-hydroxylase (PAHX) was identified as a binding protein of FVIII-A2. PAHX had potential to interact with the residues 373-508 within the A2 domain, but not with A1 and A3 (the homologous domains of A2). The interaction between the A2 domain and PAHX was independent of the type 2 peroxisomal targeting signal (PTS2) of PAHX. Overexpression of PAHX in FVIII-produced cells decreased the expression of FVIII by about 70%. The elevated expression of von Willebrand factor had no effect on the suppression of FVIII secretion by PAHX. Expression of the green fluorescent PAHX fusion protein in SMMC-7721 cells affected the intracellular trafficking of FVIII-A2. These results suggested that the interaction between PAHX and FVIII-A2 was in part responsible for the low-level expression of factor VIII.

Animals↗
PubMed2001

Molecular aptamer for real-time oncoprotein platelet-derived growth factor monitoring by fluorescence anisotropy.

Monitoring proteins in real time and in homogeneous solution has always been a difficult task. We have applied a fluorophore-labeled molecular probe based on a high-affinity platelet-derived growth factor (PDGF) aptamer for the ultrasensitive detection of PDGF in homogeneous solutions. The aptamer is labeled with fluorescein to specifically bind with the PDGF protein. Fluorescence anisotropy is used for the real-time monitoring of the binding between the aptamer and the protein. When the labeled aptamer is bound with its target protein, the rotational motion of the fluorophore attached to the complex becomes much slower because of an increased molecular weight after binding, resulting in a significant fluorescence anisotropy change. Using the anisotropy change, we are able to detect the binding events between the aptamer and the protein in real time and in homogeneous solutions (detection without separation). This assay is highly selective and ultrasensitive. It can detect PDGF in the subnanomolar range. The new method for protein detection is simple and inherits all of the advantages of molecular aptamers. Efficient oncoprotein detection using aptamer-based fluorescence anisotropy measurement will find wide applications in protein monitoring, in cancer diagnosis as well as other studies in which protein analysis is important.

Anisotropy↗
PubMed2001

[An epidemiologic study of bowel habit in adult non-patient population in Beijing area].

OBJECTIVE: To determine the bowel habit and its influencing factors in the adult non-patient population in Beijing area. METHODS: A questionnaire survey was conducted among 2486 adult permanent residents in Beijing area by randomized stratified sampling. The bowel habit (defecation frequency, characters of feces, time of defecation, and abnormal defecation) of the 1 952 non-patients among them were further investigated. The non-patient subject should fulfil the following criteria: (1) without gastrointestinal and hepatic organic diseases; (2) without metabolic disease affecting the motility of the gastrointestinal tract, such as diabetes mellitus and thyroid hyperfunction; (3) without irritable bowel syndrome which fits in the Manning criteria; and (4) considering oneself as having normal bowel habits. RESULTS: 84.17% of the non-patient interviewees defecated once per day with the mean defecation frequency of 7.09 times per week. 89.86% of the interviewees had formed or soft stool. 93.08% of the non-patients defecated formed or soft stool 3 to 21 times per week. No evidence showed that the frequency of defecation and character of feces were related to age and sex. 77% of them defecated in the morning. The prevalence rates of constipation, diarrhea, and abdominal pain associated with defecation were 3.74%, 1.08%, and 7.38% respectively. CONCLUSION: The defecation frequency of adult nonpatient population in Beijing area is almost identical to that reported in the west. 93.08% of the non-patient subjects have normal defecation patterns. It is necessary to define the judgement criteria for constipation and diarrhea for Chinese based on their defecation patterns.

Adult↗
PubMed2001

Chemical modifications of the (1-->3)-alpha-D-glucan from spores of Ganoderma lucidum and investigation of their physicochemical properties and immunological activity.

A linear (1-->3)-alpha-D-glucan was isolated from the spores of Ganoderma lucidum (Fr.) Karst. Six different functionalized derivatives of the (1-->3)-alpha-D-glucan-aminopropylated, hydroxyethylated, sulfated, carboxymethylated, carboxymethylated and sulfated, and benzylamidated-carboxymethylated-with varying degrees of substitution were synthesized. The structural features and physicochemical properties of all derivatives were investigated by means of chemical and spectral analyses, and their effects on lymphocyte proliferation and antibody production were tested in vitro and in vivo. In general, the structural and physicochemical properties, and lymphocyte proliferation activity of all samples varied with the functionalized groups and the degree of substitution. The results of immunological assays indicated that some modified derivatives had potent stimulating effects on lymphocyte proliferation and antibody production and the introduction of carboxymethyl group with low degree of substitution (DS<0.28) was the best choice on the improvement of the immunostimulating activity.

Adjuvants, Immunologic↗
PubMed2001

First examples of oxidizing secondary alcohols to ketones in the presence of the disulfide functional group: synthesis of novel diketone disulfides.

The disulfide functionality is present in a number of organic compounds of interest in the fields of both chemistry and biology. Because the disulfide group is known to be highly susceptible to further oxidation by a wide range of agents, performing a chemoselective oxidation without further oxidizing the disulfide moiety poses a synthetic challenge. Reported herein are the first examples of such a chemoselective oxidation in which a series of novel secondary alcohol disulfides 2a-f have been converted to the corresponding symmetrical diketones 3a-f utilizing a modified Swern oxidation.

Alcohols↗
PubMed2001

Kappa-opioid receptor agonist suppression of HIV-1 expression in CD4+ lymphocytes.

Synthetic kappa-opioid receptor (KOR) agonists have been shown to suppress HIV-1 expression in acutely infected macrophages. In the present study, we examined the effects of the KOR ligand trans-3,4-dichloro-N-methyl-N[2-(1-pyrolidinyl)cyclohexyl]benzeneaceamide methanesulfonate (U50,488) on HIV-1 expression in CD4+ lymphocytes, the main target cell of this virus. When U50,488 was added to activated CD4+ lymphocytes, HIV-1 expression was inhibited in a concentration- and time-dependent manner with maximal suppression (approximately 60%) at 10(-7) M U50,488. The KOR selective antagonist nor-binaltorphimine (nor-BNI) had no effect by itself on viral expression but blocked the antiviral property of U50,488, suggesting that U50,488 was acting via a KOR-related mechanism. Support for the involvement of KOR was provided by the findings that 34% of activated CD4+ lymphocytes were positive for KOR, using an immunofluorescence technique, and that seven additional synthetic KOR ligands also inhibited HIV-1 expression. The results of this study broaden understanding of the antiviral properties of KOR ligands to include cells outside of the nervous system and suggest a potential role for these agents in the treatment of HIV-1 infection.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed2001

The interaction of the calcium- and integrin-binding protein (CIBP) with the coagulation factor VIII.

The gene encoding the C-terminal part of A1-domain of human blood coagulation factor VIII (FVIII), a 110-amino acid fragment from Ala(227) to Arg(336), namely A1(Delta1-226), was cloned and used as a 'bait' to screen a protein, which might interact with this region by using the yeast two-hybrid system. A gene coding for a related protein of FVIII named calcium- and integrin-binding protein (CIBP) was isolated from the normal human liver cDNA library. The results were confirmed by using the mammalian two-hybrid system and coimmunoprecipitation. The gene coding for CIBP was constructed by polymerase chain reaction (PCR) and then cotransfected with the B-domain-deleted FVIII gene into mammalian cell lines using the expression vector of FVIII for transient or stable expression. The culture supernatant was collected and analyzed both by enzyme-linked immunosorbent assay (ELISA) for FVIII antigen level and by one-stage method for procoagulant activity. Coexpressed with CIBP, the antigen level of FVIII in the mammalian cell line baby hamster kidney (BHK) cells increased up to about 170% and its bioactivity rose accordingly.

Animals↗
PubMed2001

Pathways of epoxyeicosatrienoic acid metabolism in endothelial cells. Implications for the vascular effects of soluble epoxide hydrolase inhibition.

Epoxyeicosatrienoic acids (EETs) are products of cytochrome P-450 epoxygenase that possess important vasodilating and anti-inflammatory properties. EETs are converted to the corresponding dihydroxyeicosatrienoic acid (DHET) by soluble epoxide hydrolase (sEH) in mammalian tissues, and inhibition of sEH has been proposed as a novel approach for the treatment of hypertension. We observed that sEH is present in porcine coronary endothelial cells (PCEC), and we found that low concentrations of N,N'-dicyclohexylurea (DCU), a selective sEH inhibitor, have profound effects on EET metabolism in PCEC cultures. Treatment with 3 microM DCU reduced cellular conversion of 14,15-EET to 14,15-DHET by 3-fold after 4 h of incubation, with a concomitant increase in the formation of the novel beta-oxidation products 10,11-epoxy-16:2 and 8,9-epoxy-14:1. DCU also markedly enhanced the incorporation of 14,15-EET and its metabolites into PCEC lipids. The most abundant product in DCU-treated cells was 16,17-epoxy-22:3, the elongation product of 14,15-EET. Another novel metabolite, 14,15-epoxy-20:2, was present in DCU-treated cells. DCU also caused a 4-fold increase in release of 14,15-EET when the cells were stimulated with a calcium ionophore. Furthermore, DCU decreased the conversion of [3H]11,12-EET to 11,12-DHET, increased 11,12-EET retention in PCEC lipids, and produced an accumulation of the partial beta-oxidation product 7,8-epoxy-16:2 in the medium. These findings suggest that in addition to being metabolized by sEH, EETs are substrates for beta-oxidation and chain elongation in endothelial cells and that there is considerable interaction among the three pathways. The modulation of EET metabolism by DCU provides novel insight into the mechanisms by which pharmacological or molecular inhibition of sEH effectively treats hypertension.

8,11,14-Eicosatrienoic Acid↗
PubMed2001

Purification and identification of an impurity in bulk hydrochlorothiazide.

Hydrochlorothiazide (6-chloro-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide 1,1-dioxide) (HCTZ) 1 is a widely used diuretic and anti-hypertensive. Recently, the Pharmeuropa recognized a new impurity initially thought to be an HCTZ dimer 6, which consists of the active drug (HCTZ) linked via the former beta-ring methylene to a known degradate, 5-chloro-2,4-disulfamylaniline 2. In an effort to meet a new requirement, an analytical high-pressure liquid chromatography method was developed that was selective and sensitive to the subject impurity. The impurity was concentrated and purified using a combination of solid phase extraction and reverse-phase high-pressure liquid chromatography. Subsequently, the impurity has been identified as a specific HCTZ-CH2-HCTZ isomer utilizing a variety of analytical techniques, including hydrolysis, ultraviolet spectroscopy, liquid chromatography/mass spectrometry, and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The data resulting from the application of these analytical techniques confirm the identity of the impurity as a methylene bridged pair of HCTZ molecules; however, a total of six possible isomers 7a-f exist because of the presence of three reactive amines/sulfonamides on each HCTZ molecule. One unique molecular structure (4-[[6-chloro-3,4,-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide-1,1-dioxide]-methyl]-chloro-3-hydro-H-1,2,4-benzothiadiazine-7-sulfonamide-1,1-dioxide) 7f was identified using two-dimensional COSY, NOESY, and TOCSY 1H NMR experiments.

Antihypertensive Agents↗
PubMed2001

NMR studies of molecular structure in fruit cuticle polyesters.

The cuticle of higher plants functions primarily as a protective barrier for the leaves and fruits, controlling microbial attack as well as the diffusion of water and chemicals from the outside environment. Its major chemical constituents are waxes (for waterproofing) and cutin (a structural support polymer). However, the insolubility of cutin has hampered investigations of its covalent structure and domain architecture, which are viewed as essential for the design of crop protection strategies and the development of improved synthetic waterproofing materials. Recently developed strategies designed to meet these investigative challenges include partial depolymerization using enzymatic or chemical reagents and spectroscopic examination of the intact polyesters in a solvent-swelled form. The soluble oligomers from degradative treatments of lime fruit cutin are composed primarily of the expected 10,16-dihydroxyhexadecanoic and 16-hydroxy-10-oxo-hexadecanoic acids; low-temperature HF treatments also reveal sugar units that are covalently attached to the hydroxyfatty acids. Parallel investigations of solvent-swollen cutin using 2D NMR spectroscopy assisted by magic-angle spinning yield well-resolved spectra that permit detailed comparisons to be made among chemical moieties present in the intact biopolymer, the soluble degradation products, and the unreacted solid residue.

Citrus↗
PubMed2001

The role of genetic abnormalities of PTEN and the phosphatidylinositol 3-kinase pathway in breast and ovarian tumorigenesis, prognosis, and therapy.

Breast and ovarian cancers exhibit similar epidemiologic, genotypic, and phenotypic characteristics. Phosphatidylinositol 3-kinase (PI3K) and the PTEN tumor suppressor gene product phosphorylate and dephosphorylate the same 3' site in the inositol ring of membrane phosphatidylinositols. Germ-line mutations in the PTEN tumor suppressor gene are causative of Cowden's breast cancer predisposition syndrome, and PTEN is frequently mutated in sporadic breast cancers. In contrast, amplification of multiple components of the PI3K pathway is a hallmark of serous epithelial ovarian cancers. The resultant activation of the PI3K pathway in both breast and ovarian cancers contributes to cell-cycle progression, decreased apoptosis, and increased metastatic capabilities. Strikingly, both ovarian and breast cancer cells are selectively sensitive to pharmacologic and genetic manipulation of the PI3K pathway, making molecular therapeutics targeting this pathway particularly attractive approaches for these cancers.

Animals↗
PubMed2001

Novel nuclear signaling pathway mediates activation of fibroblast growth factor-2 gene by type 1 and type 2 angiotensin II receptors.

In bovine adrenal medullary cells synergistically acting type 1 and type 2 angiotensin II (AII) receptors activate the fibroblast growth factor-2 (FGF-2) gene through a unique AII-responsive promoter element. Both the type 1 and type 2 AII receptors and the downstream cyclic adenosine 1',3'-monophosphate- and protein kinase C-dependent signaling pathways activate the FGF-2 promoter through a novel signal-transducing mechanism. This mechanism, which we have named integrative nuclear FGF receptor-1 signaling, involves the nuclear translocation of FGF receptor-1 and its subsequent transactivation of the AII-responsive element in the FGF-2 promoter.

Adrenal Medulla↗
PubMed2001

Biomarker identification by feature wrappers.

Gene expression studies bridge the gap between DNA information and trait information by dissecting biochemical pathways into intermediate components between genotype and phenotype. These studies open new avenues for identifying complex disease genes and biomarkers for disease diagnosis and for assessing drug efficacy and toxicity. However, the majority of analytical methods applied to gene expression data are not efficient for biomarker identification and disease diagnosis. In this paper, we propose a general framework to incorporate feature (gene) selection into pattern recognition in the process to identify biomarkers. Using this framework, we develop three feature wrappers that search through the space of feature subsets using the classification error as measure of goodness for a particular feature subset being "wrapped around": linear discriminant analysis, logistic regression, and support vector machines. To effectively carry out this computationally intensive search process, we employ sequential forward search and sequential forward floating search algorithms. To evaluate the performance of feature selection for biomarker identification we have applied the proposed methods to three data sets. The preliminary results demonstrate that very high classification accuracy can be attained by identified composite classifiers with several biomarkers.

Algorithms↗
PubMed2001

Cutaneous neuroendocrine (Merkel cell) carcinoma occurred after resection of malignant melanoma.

An elderly man presented with a brown border nodule of the left upper lip that appeared to be clinically consistent with metastatic melanoma; he had previously undergone two surgical removals of melanoma in the right temporal region. Routine histologic examination was not sufficient for diagnosis, but Merkel cell carcinoma was diagnosed by immunohistochemical studies Neuroendocrine carcinoma of viscera was excluded. Because this case could not be differentiated from amelanotic melanoma and malignant lymphoma based on histologic appearances, immunohistochemical staining was helpful for diagnosis and differentiation.

Aged↗
PubMed2001

Developmental regulation of the heat shock response by nuclear transport factor karyopherin-alpha3.

During early stages of Drosophila development the heat-shock response cannot be induced. It is reasoned that the adverse effects on cell cycle and cell growth brought about by Hsp70 induction must outweigh the beneficial aspects of Hsp70 induction in the early embryo. Although the Drosophila heat shock transcription factor (dHSF) is abundant in the early embryo it does not enter the nucleus in response to heat shock. In older embryos and in cultured cells the factor is localized within the nucleus in an apparent trimeric structure that binds DNA with high affinity. The domain responsible for nuclear localization upon stress resides between residues 390 and 420 of the dHSF. Using that domain as bait in a yeast two-hybrid system we now report the identification and cloning of a Drosophila nuclear transport protein karyopherin-alpha3 (dKap-alpha3). Biochemical methods demonstrate that the dKap-alpha3 protein binds specifically to the dHSF's nuclear localization sequence (NLS). Furthermore, the dKap-alpha3 protein does not associate with NLSs that contain point mutations, which are not transported in vivo. Nuclear docking studies also demonstrate specific nuclear targeting of the NLS substrate by dKap-alpha3. Consistant with previous studies demonstrating that early Drosophila embryos are refractory to heat shock as a result of dHSF nuclear exclusion, we demonstrate that the early embryo is deficient in dKap-alpha3 protein through cycle 12. From cycle 13 onward the transport factor is present and the dHSF is localized within the nucleus thus allowing the embryo to respond to heat shock.

Active Transport, Cell Nucleus↗