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Biomedical subjects

W Guo

Publications and source records attributed to W Guo.

At least 19 recordsLinked to original sources
PubMed2004

Micro-X-ray diffraction observation of nickel-titanium orthodontic wires in simulated oral environment.

A micro-X-ray diffraction (micro-XRD) technique has been employed to determine the phases in two superelastic nickel-titanium orthodontic wires that exhibit shape memory in the oral environment and one superelastic nickel-titanium wire that does not exhibit shape memory in vivo. The micro-XRD analyses were performed over the clinically relevant temperature range of 0-55 degrees C, which corresponds to the ingestion of cold and hot liquids, and both straight and bent (135 degrees ) test samples were analyzed. The results showed that for straight (as-received) test samples, the rhombohedral phase (R-phase) was definitely present in one shape memory wire product and perhaps in the other shape memory wire product, but was apparently absent in the superelastic wire product that did not display shape memory. Martensite was observed in all three wire products after bending. Phase transformations occurred with temperature changes simulating the oral environment for straight test samples of the two shape memory wires, but the micro-XRD pattern changed minimally with temperature for straight test samples of the superelastic wire and for bent test samples of all three wire products. The phase transformations revealed by micro-XRD were consistent with results recently found by temperature-modulated differential scanning calorimetry.

Body Temperature↗
PubMed2003

Determination by liquid chromatography with fluorescence detection of total 7-ethyl-10-hydroxy-camptothecin (SN-38) in beagle dog plasma after intravenous administration of liposome-based SN-38 (LE-SN38).

An HPLC- fluorescence method to quantitate total 7-ethyl-10-hydroxy-camptothecin (SN-38) in beagle dog plasma spiked with liposome based formulation of SN-38 (LE-SN38) and using camptothecin (CPT) as the internal standard (I.S.) was developed and validated to support pharmacokinetics/toxicokinetics studies. Sample preparation was done by protein precipitation using acetonitrile with 0.5% acetic acid. The supernatant was evaporated, and reconstituted in acetonitrile-20 mM ammonium acetate, pH 3.5 (20:80, v/v). When injected onto a Zorbax SB-C(18) HPLC column SN-38 as well as I.S. were detected by fluorescence using an excitation at 368 nm and emission at 515 nm. The SN-38 concentrations in samples were calculated from a standard curve of peak area ratios of SN-38 to the I.S. using weighted linear regression. The sensitivity limit for SN-38 was 1.00 ng/ml in beagle dog plasma with a precision (expressed as relative standard deviation) of 12.4% and an accuracy (expressed as analytical recovery) of 104%. The assay was linear within the standard curve range of 1-750 ng/ml. Acceptable precision and accuracy were also obtained for concentrations over the balance of the standard curve range from between-run and within-run calculations.

Animals↗
PubMed2003

Glial cell line-derived neurotrophic factor normalizes neurochemical changes in injured dorsal root ganglion neurons and prevents the expression of experimental neuropathic pain.

Glial cell line-derived neurotrophic factor (GDNF) is necessary for the development of sensory neurons, and appears to be critical for the survival of dorsal root ganglion (DRG) cells that bind the lectin IB4. Intrathecal infusion of GDNF has been shown to prevent and reverse the behavioral expression of experimental neuropathic pain arising from injury to spinal nerves. This effect of GDNF has been attributed to a blockade of the expression of the voltage gated, tetrodotoxin-sensitive sodium channel subtype, Na(V)1.3, in the injured DRG. Here we report that GDNF given intrathecally via osmotic-pump to nerve-injured rats (L5/L6 spinal nerve ligation) prevented the changes in a variety of neurochemical markers in the DRG upon injury. They include a loss of binding of IB4, downregulation of the purinergic receptor P2X(3), upregulation of galanin and neuropeptide Y immunoreactivity in large diameter DRG cells, and expression of the transcription factor ATF3. GDNF infusion concomitantly prevented the development of spinal nerve ligation-induced tactile hypersensitivity and thermal hyperalgesia. These observations suggest that high dose, exogenous GDNF has a broad neuroprotective role in injured primary afferent. The receptor(s) that mediates these effects of GDNF is not known. GDNF's ability to block neuropathic pain states is not likely to be specific to Na(V)1.3 expression.

Activating Transcription Factors↗
PubMed2002

Inheritance and fine mapping of fertility restoration for cytoplasmic male sterility in Gossypium hirsutum L.

Genetics of CMS fertility restoration was presented through the analysis of classic genetics and molecular markers. Based on F(2) segregation of the crosses between CMS and the restoring lines, the testcrosses and F(1) x F(1) populations, together with RAPD and SSR mapping, one dominant gene was identified to control the CMS fertility restoration in cotton. The strategy of genotype representation analysis (GRA) was put forward to screen the markers linked with the Rf(1) locus. Using 1,025 random decamer primers and 282 pairs of SSR primers, two RAPD and three SSR markers were identified to be closely linked to the Rf(1) gene. Among the five markers, three were co-dominantly inherited. Additionally, based on the analysis of monosomic and telesomic lines with one SSR maker, the Rf(1) locus could be located on the long arm of chromosome 4. The molecular markers available here are helpful in the development of the elite restoring lines in cotton by marker-assisted selection.

Chromosome Mapping↗
PubMed2002

Changes in gene expression and neuronal phenotype in brain stem pain modulatory circuitry after inflammation.

Recent studies indicate that descending pain modulatory pathways undergo time-dependent changes in excitability following inflammation involving both facilitation and inhibition. The cellular and molecular mechanisms of these phenomena are unclear. In the present study, we examined N-methyl-D-aspartate (NMDA) receptor gene expression and neuronal activity in the rostral ventromedial medulla (RVM), a pivotal structure in pain modulatory circuitry, after complete Freund's adjuvant (CFA)-induced hindpaw inflammation. The reverse transcription polymerase chain reaction analysis indicated that there was an upregulation of mRNAs encoding NMDA receptor subunits in the RVM after inflammation. The increase in the NR1, NR2A, and NR2B receptor mRNAs started at 5 h, maintained for 1-7 days (P < 0.05-0.001) and returned to the control level at 14 days after inflammation. Western blot analysis indicated that the protein translation products of the NR2A subunit were also increased (P < 0.01). In single-unit extracellular recordings, we correlated RVM neuronal activity with the paw withdrawal response in rats with inflammation. We describe these RVM cells as on-, off-, and neutral-like cells because of their similarity to previous studies in which neuronal responses were correlated with tail-flick nocifensive behavior in the absence of inflammation. In contrast to previous studies in the absence of inflammation, using tail flick as a behavioral correlate, fewer off-like cells in naïve animals exhibited a complete pause before the paw withdrawal to a noxious thermal stimulus. The percentage of cells showing a pause of activity after noxious stimulation was further reduced after inflammation (chi(2) P < 0.0001 vs. naïve rats). Continuous neuronal recordings (3-6.5 h) revealed a phenotypic switch of RVM neurons during the development of inflammation: 11/15 neutral-like cells initially unresponsive to noxious stimuli exhibited and maintained response profiles characteristic of pain modulatory neurons (became off-like: n = 5; became on-like: n = 6). Neutral-like cells recorded in noninflamed animals did not show response profile changes during continuous recordings (5-5.5 h, n = 7). A population study (n = 165) confirmed an increase in on- and off-like cells and a decrease in neutral-like cells at 24 h after inflammation as compared with naïve rats (P < 0.001). These results suggest that enhanced NMDA receptor activation mediates time-dependent changes in excitability of RVM pain modulatory circuitry. The functional phenotypic switch of RVM neurons provides a novel mechanism underlying activity-dependent plasticity and enhanced net descending inhibition after inflammation.

Action Potentials↗
PubMed2002

Acipimox stimulates leptin production from isolated rat adipocytes.

Acipimox is a nicotinic acid-derived antilipolytic drug devoid of major side effects, and has been used in a number of human trials. This work reports the effects of Acipimox on leptin production from isolated rat adipocytes, in comparison with nicotinic acid and insulin. For cells isolated from normal animals, all these three reagents stimulated leptin release to a similar extent. Acipimox and nicotinic acid were more potent than insulin in stimulating leptin release from cells isolated from diabetic animals, probably because of impaired insulin sensitivity in cells from these diseased animals. Co-incubation of Acipimox with norepinephrine or dibutyryl cAMP diminished its stimulatory effects on leptin release, in parallel with increased lipolysis, suggesting that intracellular free fatty acids play an important role in mediating leptin production in adipocytes.

Adipocytes↗
PubMed2001

Efficient gene delivery via non-covalent complexes of folic acid and polyethylenimine.

Polyethylenimine (PEI) is a cationic polymer capable of delivering DNA molecules into cultured mammalian cells as charge complexes. The application of PEI polyplexes in gene therapy, however, is hampered by the sensitivity of its transfection activity to the presence of serum. We found that folic acid, in a variety of cell lines, significantly enhanced PEI-mediated transfection activity in the presence of serum, whether the folic acid was added during or after PEI/DNA polyplex formation. The increase in activity could not be produced with other anionic compounds such as cholic acid, citric acid, EDTA, or glutamic acid. This novel formulation provides a reliable, low-cost, and highly efficient method for delivery of genes and may have applications in gene therapy.

DNA↗
PubMed2001

Cdc42 interacts with the exocyst and regulates polarized secretion.

Polarized delivery and incorporation of proteins and lipids to specific domains of the plasma membrane is fundamental to a wide range of biological processes such as neuronal synaptogenesis and epithelial cell polarization. The exocyst complex is specifically localized to sites of active exocytosis and plays essential roles in secretory vesicle targeting and docking at the plasma membrane. Sec3p, a component of the exocyst, is thought to be a spatial landmark for polarized exocytosis. In a search for proteins that regulate the localization of the exocyst in the budding yeast Saccharomyces cerevisiae, we found that certain cdc42 mutants affect the polarized localization of the exocyst proteins. In addition, we found that these mutant cells have a randomized protein secretion pattern on the cell surface. Biochemical experiments indicated that Sec3p directly interacts with Cdc42 in its GTP-bound form. Genetic studies demonstrated synthetically lethal interactions between cdc42 and several exocyst mutants. These results have revealed a role for Cdc42 in exocytosis. We propose that Cdc42 coordinates the vesicle docking machinery and the actin cytoskeleton for polarized secretion.

Actins↗
PubMed2001

[In vitro inhibitive effects of Tripterygium wilforii on NO production, iNOS activity, and iNOS-mRNA expression in chondrocyrtes of patients with rheumatoid arthritis].

OBJECTIVE: To study the mechanism of treatment of rheumatoid arthritis with Tripterygium wilfordii Hook. f. (TWHF). METHODS: Chondrocytes from the resected knee joint cartilage of patients with rheumatoid and TWHF, dexamethasone, or (arthritis were isolated and cultured. IL-1 indomethacin of different concentrations were added into the culture solution overnight. Griess reagent was added to the supernatant to detect the content of NO. Chondrocytes were collected to examine the iNOS activity by detecting the conversion of L-14C-arginine into L-14C-citruline. The total RNA of chondrocyte was extracted and the iNOS-mRNA was examined by Northern blotting. RESULTS: The inhibitory rates of NO production by TWHF of concentrations of 2 mg/L, 4 mg/L, 8 mg/L, and 16 mg/L were 10.8%, 25.48%, 55.17%, and 80.45% respectively. The inhibitory rates of iNOS activity by TWHF of concentrations of 2 mg/L, 4 mg/L, 8 mg/L, and 16 mg/L were 12.29%, 27.67%, 59.04%, and 85.06% respectively. Such inhibitory effects were dosage-dependent. TWHF ffectively inhibited the expression of iNOS-mRNA induced by IL-1 in chondrocyte (r = 0.976 and 0.974). Dexamethasone inhibited NO production, iNOS activity, and expression of iNOS-mRNA significantly but not dosage-dependently. Indomethcin only had weak inhibitory effect. CONCLUSION: TWHF inhibits NO production in chondrocytes by limiting the transcription of iNOS gene, which may be one of the mechanisms of treatment of RA with TWHF.

Arthritis, Rheumatoid↗
PubMed2001

A protein interaction map for cell polarity development.

Many genes required for cell polarity development in budding yeast have been identified and arranged into a functional hierarchy. Core elements of the hierarchy are widely conserved, underlying cell polarity development in diverse eukaryotes. To enumerate more fully the protein-protein interactions that mediate cell polarity development, and to uncover novel mechanisms that coordinate the numerous events involved, we carried out a large-scale two-hybrid experiment. 68 Gal4 DNA binding domain fusions of yeast proteins associated with the actin cytoskeleton, septins, the secretory apparatus, and Rho-type GTPases were used to screen an array of yeast transformants that express approximately 90% of the predicted Saccharomyces cerevisiae open reading frames as Gal4 activation domain fusions. 191 protein-protein interactions were detected, of which 128 had not been described previously. 44 interactions implicated 20 previously uncharacterized proteins in cell polarity development. Further insights into possible roles of 13 of these proteins were revealed by their multiple two-hybrid interactions and by subcellular localization. Included in the interaction network were associations of Cdc42 and Rho1 pathways with proteins involved in exocytosis, septin organization, actin assembly, microtubule organization, autophagy, cytokinesis, and cell wall synthesis. Other interactions suggested direct connections between Rho1- and Cdc42-regulated pathways; the secretory apparatus and regulators of polarity establishment; actin assembly and the morphogenesis checkpoint; and the exocytic and endocytic machinery. In total, a network of interactions that provide an integrated response of signaling proteins, the cytoskeleton, and organelles to the spatial cues that direct polarity development was revealed.

Actins↗
PubMed2001

Targeted replacement of KV1.5 in the mouse leads to loss of the 4-aminopyridine-sensitive component of I(K,slow) and resistance to drug-induced qt prolongation.

The K(+) channel mKv1.5 is thought to encode a 4-aminopyridine (4-AP)-sensitive component of the current I(K,slow) in the mouse heart. We used gene targeting to replace mKv1.5 with the 4-AP-insensitive channel rKv1.1 (SWAP mice) and directly test the role of Kv1.5 in the mouse ventricle. Kv1.5 RNA and protein were undetectable, rKv1.1 was expressed, and Kv2.1 protein was upregulated in homozygous SWAP hearts. The density of the K(+) current I(K,slow) (depolarizations to +40 mV, pA/pF) was similar in left ventricular myocytes isolated from SWAP homozygotes (17+/-1, n=27) and littermate controls (16+/-2, n=19). The densities and properties of I(peak), I(to,f), I(to,s), and I(ss) were also unchanged. In homozygous SWAP myocytes, the 50-micromol/L 4-AP-sensitive component of IK,slowwas absent (n=6), the density of the 20-mmol/L tetraethylammonium-sensitive component of I(K,slow) was increased (9+/-1 versus 5+/-1, P<0.05), and no 100- to 200-nmol/L alpha-dendrotoxin-sensitive current was found (n=8). APD(90) in SWAP myocytes was similar to controls at baseline but did not prolong in response to 30 micromol/L 4-AP. Similarly, QTc (ms) was not prolonged in anesthetized SWAP mice (64+/-2, homozygotes, n=9; 62+/-2, controls, n=9), and injection with 4-AP prolonged QTc only in controls (63+/-1, homozygotes; 72+/-2, controls; P<0.05). SWAP mice had no increase in arrhythmias during ambulatory telemetry monitoring. Thus, Kv1.5 encodes the 4-AP-sensitive component of I(K,slow) in the mouse ventricle and confers sensitivity to 4-AP-induced prolongation of APD and QTC: Compensatory upregulation of Kv2.1 may explain the phenotypic differences between SWAP mice and the previously described transgenic mice expressing a truncated dominant-negative Kv1.1 construct.

4-Aminopyridine↗
PubMed2001

Effects of all-trans-retinoic acid and arsenic trioxide on the hemostatic disturbance associated with acute promyelocytic leukemia.

To study the in vivo effect of all-trans-retinoic acid (ATRA) and arsenic trioxide (As(2)O(3)) on the expression of tissue factor (TF) and the other hemostatic disturbance, a series of parameters were measured either in bone marrow blasts or plasma from acute promyelocytic leukemia (APL) patients. The plasma parameters were measured by ELISA or chromogenic studies. The TF transcription was assessed using reverse transcription-polymerase chain reaction (RT-PCR) technique. The results indicated that the blast cell procoagulant activity (PCA), TF antigen of APL cell lysate, as well as the transcription of APL TF mRNA elevated at diagnosis, were reduced after ATRA or As(2)O(3) therapy. The plasma level of P-selectin, TF, thrombin-antithrombin complex (TAT), soluble fibrinmonomer complex, thrombomodulin (TM), tissue factor pathway inhibitor (TFPI), plasmin-antiplasmin complex, tissue plasminogen activator (t-PA) activity, urokinase plasminogen activator (u-PA) and its receptor (u-PAR), and D-dimer (D-D) significantly increased. Fibrinogen (Fg), antigen level of protein C (PC), plasminogen (PLG) activity, alpha(2)-plasminogen inhibitor activity (alpha(2)-PI), and plasminogen activator inhibitor (PAI) activity were decreased at diagnosis. The protein C activity (PC:A) and protein S (PS) remained unchanged. All the parameters were restored to normal ranges after complete remission (CR) except elevation of TF and TAT in both groups, as well as PC:A, PS, and t-PA in the ATRA group. In conclusion, there existed activation of platelets and consumption of anticoagulants as well as activation of coagulation and fibrinolytic system before treatment. Both ATRA and As(2)O(3) therapy downregulated the expression of TF mRNA, decreased the PCA and TF level in APL cells, significantly inhibited coagulation activation, corrected secondary hyperfibrinolysis and the other hemostatic abnormalities, and thus greatly improved the bleeding symptom in early stage of the treatment.

Adolescent↗
PubMed2001

Regulation of interferon and retinoic acid-induced cell death activation through thioredoxin reductase.

Interferons (IFNs) and retinoids are potent biological response modifiers. The IFN-beta and all-trans-retinoic acid combination, but not these single agents individually, induces death in several tumor cell lines. To elucidate the molecular basis for these actions, we have employed an antisense knockout approach to identify the gene products that mediate cell death and isolated several genes associated with retinoid-IFN-induced mortality (GRIMs). One of the GRIM cDNAs, GRIM-12, was identical to human thioredoxin reductase (TR). To define the functional relevance of TR to cell death and to define its mechanism of death-modulating functions, we generated mutants of TR and studied their influence on the IFN/RA-induced death regulatory functions of caspases. Wild-type TR activates cell death that was inhibited in the presence of caspase inhibitors or catalytically inactive caspases. A mutant TR, lacking the active site cysteines, inhibits the cell death induced by caspase 8. IFN/all-trans-retinoic acid-induced cytochrome c release from the mitochondrion was promoted in the presence of wild type and was inhibited in the presence of mutant TR. We find that TR modulates the activity of caspase 8 to promote death. This effect is in part caused by the stimulation of death receptor gene expression. These studies identify a new mechanism of cell death regulation by the IFN/all-trans-retinoic acid combination involving redox enzymes.

Animals↗
PubMed2001

Enhanced activity of cloned hamster TERT gene promoter in transformed cells.

In 7,12-dimethylbenz[a]anthracene-treated hamster pouch epithelial cells, telomerase activity increased within 1 week of treatment and reached a 6-7-fold increase within 3 weeks. To investigate this phenomenon, we have cloned and sequenced the hamster telomerase catalytic subunit (hamTERT) promoter. Transient transfection with different genomic segments upstream of the ATG translation initiation codon linked to the luciferase reporter gene mapped the core promoter within a 250 bp region. Three major transcription initiation sites and several minor sites were found between -42 and -140 bp relative to the ATG site. Like the human and murine TERT promoters, the hamTERT promoter lacks TATA and CAT boxes and all three promoters share similar regulatory factor binding sites. DNase I footprint analysis revealed six protected regions which contain sequences homologous with known transcription factor binding sites. Three protein binding regions (I, II, and III) were essential for the promoter activity. Regions I and III bound to Sp1 and Sp3 transcriptional factors, whereas region II bound to an unknown factor. Transient transfection of a promoter-luciferase plasmid into Drosophila SL2 cells showed that Sp1 and Sp3 regulated the hamster TERT promoter in a concentration-dependent and synergistic manner. Telomerase activity showed a 2-4-fold and 8-10-fold increase in immortalized cells and tumor cells, respectively, but hamTERT expression was only increased 1.7-fold and 2.4-fold, respectively, in the same cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Simultaneous quantitative UV spectrophotometric determination of multicomponents of amino acids using linear neural network.

Simultaneous determination of multicomponents of six amino acids with a novel chemometric technique-a linear neural network (LNN) algorithm is reported in this study. Based on the data correlation coefficient and standard deviation method, 17 representative wavelength points are selected from the original UV spectral data (343 points) as the original input patterns for LNN to build a neural network model. The results obtained only by iterating 15 times is satisfying, with a correlation coefficient of 0.999 and a relative small standard deviation.

Algorithms↗