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Biomedical subjects

X Fu

Publications and source records attributed to X Fu.

At least 19 recordsLinked to original sources
PubMed2000

Alternative silencing effects involve distinct types of non-spreading cytosine methylation at a three-gene, single-copy transgenic locus in rice.

We investigated transgene silencing in a line of rice plants that carries a single-copy 6.6-kb transgenic locus comprising three heterologous transgenes: bar, hpt and gusA. We identified at least three distinct types of silencing effects associated with different methylation patterns, including a novel form of transcriptional silencing involving methylation of cytosine residues only at non-conventional acceptor sites in the coding region. Silencing arose de novo in individual R1, R2 and R3 plants despite the stability of the transgenic locus, although the basic structure of the locus, transgene dosage and position effects remained constant within the line. We found that different silencing effects could occur concurrently in adjacent heterologous transgenes in the same plant, with no evidence for spreading of silenced states or methylation patterns from one transgene to another.

Base Sequence↗
PubMed2000

Prostaglandin F2alpha-induced Ca++ oscillations in human myometrial cells and the role of RU 486.

OBJECTIVE: We sought to examine the change of cytosolic calcium concentration caused by prostaglandin F(2)(alpha) and RU 486 in cultured human myometrial cells. STUDY DESIGN: Human myometrial cells obtained from 16 nonpregnant women were loaded with fura 2, and the intracellular cytosolic calcium concentrations were measured by the use of wavelength spectrophotofluorometry. RESULTS: Application of prostaglandin F(2)(alpha) (2.8 micromol/L) caused an initial rapid rise in cytosolic calcium concentration followed by sustained cytosolic calcium oscillations at an average frequency of 0.43 +/- 0.04 min(-1) and an amplitude in the range of 296.82 +/- 27. 16 nmol/L. The oscillatory activity was not affected by increasing the concentration of prostaglandin F(2)(alpha) but varied by changing the concentration of extracellular cytosolic calcium concentration. The cytosolic calcium oscillations were suppressed by caffeine, 2,5-di-tert-butylhydroquinone, and lanthanum but not affected by ryanodine. Verapamil decreased the amplitude but not the frequency of oscillations. The progesterone antagonist RU 486 at a concentration of 10(-8) to 10(-5) mol/L had no significant effect on the basal intracellular cytosolic calcium. However, RU 486 (10(-5) mol/L) significantly increased the frequency but not the amplitude of intracellular cytosolic calcium oscillations induced by prostaglandin F(2)(alpha). CONCLUSION: The results indicate that prostaglandin F(2)(alpha)-stimulated cytosolic calcium oscillations are mediated by an increase in both cytosolic calcium release from inositol 1,4,5-trisphosphate-sensitive cytosolic calcium stores and a cytosolic calcium influx from the extracellular space. Moreover, RU 486 seems to directly regulate prostaglandin F(2)(alpha)-induced intracellular cytosolic calcium in human myometrial cells.

Adult↗
PubMed2000

Membrane redistribution of the Escherichia coli MinD protein induced by MinE.

Escherichia coli cells contain potential division sites at midcell and adjacent to the cell poles. Selection of the correct division site at midcell is controlled by three proteins: MinC, MinD, and MinE. It has previously been shown (D. Raskin and P. de Boer, Cell 91:685-694, 1997) that MinE-Gfp localizes to the midcell site in an MinD-dependent manner. We use here Gfp-MinD to show that MinD associates with the membrane around the entire periphery of the cell in the absence of the other Min proteins and that MinE is capable of altering the membrane distribution pattern of Gfp-MinD. Studies with the isolated N-terminal and C-terminal MinE domains indicated different roles for the two MinE domains in the redistribution of membrane-associated MinD.

Adenosine Triphosphatases↗
PubMed2000

Oxytocin-induced oscillations of cytoplasmic Ca2+ in human myometrial cells.

BACKGROUND: To investigate the mechanisms of oxytocin (OT) induced oscillations of the cytoplasmic Ca2+ concentration ([Ca2+]i) in cultured human myometrial cells. METHODS: [Ca2+]i was measured in individual myometrial cells by dual wavelength spectrophotofluorometry using the fluorescent indicator fura-2. Myometrium was obtained at abdominal hysterectomy (n=8) and during cesarean section (n=7). RESULTS: OT (10-300 nM) typically induced [Ca2+]i oscillations with frequencies in the 0.6-0.8/min range. There were no obvious differences in the responses of cells taken from non-pregnant and term pregnant women. The frequency and amplitude of the oscillations were not significantly affected by OT concentrations up to 300 nM. The amplitude of the oscillations decreased in the presence of the voltage-dependent Ca2+ channel antagonist verapamil and gradually disappeared in Ca2+-free medium. The oscillations were further blocked by the inorganic Ca2+ antagonist La3+ and by the intracellular Ca2+-ATPase inhibitor 2.5-di-tert-butylhydroquinone (DTBHQ). Caffeine inhibited the OT-induced oscillations in a concentration-dependent manner. DTBHQ and high concentrations of OT made [Ca2+]i remarkably sensitive to changes in the external Ca2+ concentration. CONCLUSIONS: The results indicate that OT-induced [Ca2+]i oscillations in human myometrial cells are due to inositol 1,4,5-trisphosphate-mediated release of intracellular Ca2+ combined with capacitative as well as voltage-dependent influx of the ion.

Calcium Signaling↗
PubMed1999

Fibroblast growth factor protects the kidney against ischemia-reperfusion injury.

Ischemia-reperfusion injury, a common source of renal dysfunction in adults, is associated with tubular epithelial cell damage. Since fibroblast growth factors (FGF) attenuated tissue injury after transient myocardial ischemia, we hypothesized that acidic fibroblast growth factor (aFGF; FGF-1) would attenuate renal ischemia-reperfusion injury. We studied the effects of FGF-1 in a rat model of acute renal failure induced by bilateral renal ischemia (60 min) and 1, 2 or 7 days reperfusion. After FGF-1 administration at the onset of renal reperfusion, there was less functional impairment of the kidneys. The histological changes were not as severe as in controls. Increases in serum creatinine and blood urea nitrogen 24 h after reperfusion were attenuated by 35% (p< 0.01) and by 53% (p< 0.001), respectively, in FGF-1-treated animals compared to vehicle-treated rats. The ischemia/reperfusion-induced increase in tissue myeloperoxidase, a marker of neutrophil infiltration, was mitigated (67% reduction, p< 0.05) with FGF-1 treatment. As shown by histology, neutrophil infiltration and tubular cell necrosis in medulla were less pronounced (p< 0.0001 and p< 0.05, respectively) in animals receiving FGF-1. Furthermore, ischemia-induced apoptosis, prevalent in tubular cells of the cortex, was also attenuated by FGF-1-treatment (83% reduction, p< 0.0001). Pretreatment of animals with Nw-nitro-L-arginine (L-NNA), an inhibitor of nitric oxide synthase, abolished the attenuating effects of FGF-1 on neutrophil infiltration, suggesting that nitric oxide might participate in the anti-inflammatory effects of FGF-1 in this experimental design. Our data support a role for FGF-1 in attenuation of renal damage or failure after ischemia-reperfusion injury of the kidney, in part at least by inhibition of neutrophil infiltration.

Animals↗
PubMed1999

EB-1, a tyrosine kinase signal transduction gene, is transcriptionally activated in the t(1;19) subset of pre-B ALL, which express oncoprotein E2a-Pbx1.

The t(1;19) translocation of pre-B cell acute lymphocytic leukemia (ALL) produces E2a-Pbx1, a chimeric oncoprotein containing the transactivation domains of E2a joined to the homeodomain protein, Pbx1. E2a-Pbx1 causes T cell and myeloid leukemia in mice, blocks differentiation of cultured myeloid progenitors, and transforms fibroblasts through a mechanism accompanied by aberrant expression of tissue-specific and developmentally-regulated genes. Here we investigate whether aberrant gene expression also occurs specifically in the t(1;19)-containing subset of pre-B cell ALL in man. Two new genes, EB-1 and EB-2, as well as Caldesmon were transcriptionally activated in each of seven t(1;19) cell lines. EB-1 expression was extremely low in marrow from patients having pre-B ALL not associated with the t(1;19), and elevated more than 100-fold in marrow from patients with pre-B ALL associated with the t(1;19). Normal EB-1 expression was strong in brain and testis, the same tissues exhibiting the highest levels of PBX1 expression. EB-1 encodes a signaling protein containing a phosphotyrosine binding domain homologous to that of dNumb developmental regulators and two SAM domains homologous to those in the C-terminal tail of Eph receptor tyrosine kinases. We conclude that aberrant expression of tissue-specific genes is a characteristic of t(1;19) pre-B ALL, as was previously found in fibroblasts transformed by E2a-Pbx1. Potentially, EB-1 overexpression could interfere with normal signaling controlling proliferation or differentiation.

Adenomatous Polyposis Coli Protein↗
PubMed1999

A pathway for conformational diversity in proteins mediated by intramolecular chaperones.

Conformational diversity within unique amino acid sequences is observed in diseases like scrapie and Alzheimer's disease. The molecular basis of such diversity is unknown. Similar phenomena occur in subtilisin, a serine protease homologous with eukaryotic pro-hormone convertases. The subtilisin propeptide functions as an intramolecular chaperone (IMC) that imparts steric information during folding but is not required for enzymatic activity. Point mutations within IMCs alter folding, resulting in structural conformers that specifically interact with their cognate IMCs in a process termed "protein memory." Here, we show a mechanism that mediates conformational diversity in subtilisin. During maturation, while the IMC is autocleaved and subsequently degraded by the active site of subtilisin, enzymatic properties of this site differ significantly before and after cleavage. Although subtilisin folded by Ile-48 --> Thr IMC (IMCI-48T) acquires an "altered" enzymatically active conformation (SubI-48T) significantly different from wild-type subtilisin (SubWT), both precursors undergo autocleavage at similar rates. IMC cleavage initiates conformational changes during which the IMC continues its chaperoning function subsequent to its cleavage from subtilisin. Structural imprinting resulting in conformational diversity originates during this reorganization stage and is a late folding event catalyzed by autocleavage of the IMC.

Amino Acid Sequence↗
PubMed1999

Abuse of guaifenesin-containing medications generates an excess of a carboxylate salt of beta-(2-methoxyphenoxy)-lactic acid, a guaifenesin metabolite, and results in urolithiasis.

OBJECTIVES: Several urinary calculi were submitted to our institution for compositional analysis. The typical techniques of analysis, polarized light microscopy, electron microprobe analysis, and infrared spectroscopy proved inadequate for a definitive identification. As a result, a more detailed organic analysis was conducted to determine the exact chemical structure of the material. METHODS: Infrared spectroscopy and mass spectrometric analysis were carried out on the solid material, providing information concerning the functional groups and the molecular mass of the organic constituent and its components. The stone was solubilized in deuterated solvents and analyzed by nuclear magnetic resonance spectroscopy, which resulted in a definitive chemical structure. RESULTS: The spectroscopic analysis indicated that the stones were composed of a calcium salt of beta-(2-methoxyphenoxy)-lactic acid, a metabolite of the pharmaceutical guaifenesin, which is used as an expectorant. CONCLUSIONS: Guaifenesin, an expectorant common in over-the-counter cold and allergy remedies, can cause urolithiasis if taken in excess. Discussions with physicians and their patients confirmed that most patients admitted to taking large doses of guaifenesin-containing medications.

Adolescent↗
PubMed1999

Malayenolides A-D, novel diterpenes from the indonesian sea pen veretillum malayense

Malayenolides A-D (1-4), four new briarane diterpenes, were isolated from the sea pen Veretillum malayense collected in Indonesia. The new diterpenes possess benzoate and senecioate substitutents, both of which are rare among marine natural products. The structures of the new compounds were determined from spectral data. Compounds 1-4 are toxic to brine shrimp.

Journal Article↗
PubMed1999

Longithorols A and B, novel prenylated paracyclophane- and metacyclophane-type hydroquinones from the tunicate Aplidium longithorax.

The tunicate Aplidium longithorax collected from Palau contained two novel prenylated paracyclophane- and metacyclophane-type hydroquinones, longithorols A (1) and B (2), in addition to longithorones A-I. Longithorols A and B were very unstable and were therefore isolated as their more stable pentaacetate forms, 3 and 4, respectively. The structures of 3 and 4 were determined by spectral data, especially 2D NMR data.

Animals↗
PubMed1999

mAngiogenin-3, a target gene of oncoprotein E2a-Pbx1, encodes a new angiogenic member of the angiogenin family.

Angiogenins are proteins in the pancreatic ribonuclease superfamily that utilize their ribonuclease activity to induce formation of new blood vessels. Recently we identified a new member of the angiogenin gene family, mouse angiogenin-3, by virtue of its transcriptional activation in NIH3T3 fibroblasts coincident with transformation by the chimeric leukemia oncogene, E2a-Pbx1. Here we have isolated the cDNA encoding mouse angiogenin-3 and used it to produce the protein in E. coli. We demonstrate that mouse angiogenin-3 is a ribonuclease whose activity and specificity towards tRNA and dinucleotide substrates differ from those of mouse angiogenin or of mouse angiogenin-related protein, a non-angiogenic factor. Mouse angiogenin-3 induced angiogenesis in both the chicken embryo chorioallantoic membrane assay and the rat cremaster muscle. Electron microscopy revealed that endothelial cells within vessels induced by both mouse angiogenin-3 and mouse angiogenin contain fenestrations similar to those observed in endothelial cells from neovasculature induced by vascular endothelial growth factor and basic fibroblast growth factor. Mouse angiogenin-3 also induced other molecular events typical of rapidly proliferating endothelial cells, such as increases in rough endoplasmic reticulum, polysomes, and mitochondria.

3T3 Cells↗
PubMed1998

The effects of the Rho-kinase inhibitor Y-27632 on arachidonic acid-, GTPgammaS-, and phorbol ester-induced Ca2+-sensitization of smooth muscle.

The effects of the Rho-kinase inhibitor, Y-27632 [1] on Ca2+-sensitization of force induced by arachidonic acid (AA), phorbol 12,13-dibutyrate (PDBu), GTPgammaS, and by the stable thromboxane analog, 9,11-dideoxy-9alpha,11alpha-methanoepoxy-PGF2alpha (U-46619), were determined in alpha-toxin-permeabilized smooth muscles. Y-27632 relaxed (up to 99%) Ca2+-sensitization by GTPgammaS (10 microM) and U46619 (1 microM), but not by PDBu (20 microM), and reduced GTPgammaS-induced myosin light chain (MLC20) phosphorylation from 28% to 17% (P=0.002). GTPgammaS-induced force sensitization was inhibited by Y-27632 more potently when the inhibitor was added during the plateau of force than prior to stimulation. In alpha-toxin-permeabilized smooth muscle, Y-27632 inhibited AA (50 microM)-induced Ca2+-sensitization of force (by 66 +/- 1.3%) and reduced MLC20 phosphorylation. In contrast, Y-27632 did not relax force Ca2+-sensitized by AA in smooth muscle permeabilized with Triton X-100. We conclude that (i) AA induces Ca2+-sensitization through dual mechanisms, one mediated by Rho-kinase (or a related kinase), and (ii) Rho-kinase is not required for phorbol ester-induced Ca2+-sensitization.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1998

Randomised placebo-controlled trial of use of topical recombinant bovine basic fibroblast growth factor for second-degree burns.

BACKGROUND: Wound healing is a dynamic process that could be accelerated by growth factors. We investigated the effect of recombinant bovine basic fibroblast growth factor (rbFGF) on burn healing in a randomised placebo-controlled trial. METHODS: We recruited 600 patients with superficial or deep second-degree burns. Patients received 150 AU/cm2 daily topical rbFGF (n=300) or placebo (n=300) plus vehicle. We assessed healing by photography, punch-biopsy, and clinical examination. FINDINGS: All patients treated with rbFGF had faster granulation tissue formation and epidermal regeneration than those in the placebo group. Superficial and deep second-degree burns treated with rbFGF healed in a mean of 9.9 (SD 2.5) days and 17.0 (4.6) days, respectively, compared with 12.4 (2.7) and 21.2 (4.9) days (p=0.0008 and p=0.0003, respectively). No adverse effects were seen locally or systemically with rbFGF. INTERPRETATION: rbFGF effectively decreased healing time and improved healing quality. Clinical benefits would be shorter hospital stays and the patient's skin quickly becoming available for harvesting and grafting.

Administration, Cutaneous↗
PubMed1998

[DNA sequencing of human ciliary neurotropic factor gene by silver staining method].

OBJECTIVE: To introduce a non-radioactive protocol for DNA sequence analysis which employs a silver staining procedure METHODS: DNA template is amplified by Taq DNA polymerase to generate sequence ladder, No labeled nucleotide or primer is involved in the thermal-cycling sequencing reaction. A sensitive silver staining procedure is employed to visualize bands in sequencing gel. RESULTS: This silver staining method is used for DNA sequence analysis of human cilliary neurotrophic factor (hCNTF) gene. The resulted band resolution is comparable to radioactive sequencing method, and data can be obtain within less than 2 hours after sequencing reaction. CONCLUSION: Silver staining is a rapid, inexpensive and reliable method for DNA sequence analysis.

Ciliary Neurotrophic Factor↗