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Biomedical subjects

Y X Wang

Publications and source records attributed to Y X Wang.

At least 19 recordsLinked to original sources
PubMed2005

Rapid non-genomic inhibitory effects of glucocorticoids on human neutrophil degranulation.

BACKGROUND: Glucocorticoids acting as anti-inflammatory or immunosuppressive drugs have been shown to exert most of their effects genomically. Recent findings suggest that non-genomic activity might be relatively more important in mediating the therapeutic effects of high-dose pulsed glucocorticoid. However, few non-genomic anti-inflammatory effects were reported, much less non-genomic mechanisms. OBJECTIVE: This study was performed to investigate the nongenomic effects of glucocorticoids on human neutrophil degranulation. METHODS: Purified human neutrophils were pretreated with 6 alpha-methylprednisolone or hydrocortisone for 5 min, and then primed with N-formyl-methionyl-leucyl-phenylalanine (fMLP) (10(-6) M) or phorbol myristate acetate (PMA) (50 ng/ml) in the presence of cytochalasin B. The release of two markers of neutrophil granules, lactoferrin and myeloperoxidase, was measured by ELISA and enzymology methods respectively. RESULTS: Both 6 alpha-methylprednisolone (10(-5)-10(-4) M) and hydrocortisone (10(-4) M) showed significant inhibitory effects on neutrophil degranulation within 5 min after fMLP administration. For PMA stimulated degranulation, 6 alpha-methylprednisolone (10(-4) M) showed significant inhibitory effects (p < 0.01), while hydrocortisone (10(-4) M) only showed an inhibitory tendency (P > 0.05). Neither RU486 (10(-5) M) nor cycloheximide (10(-4) M) could alter the inhibitory effects of glucocorticoids. CONCLUSION: Our results demonstrate that megadoses of glucocorticoids exert rapid inhibitory effects on human neutrophil degranulation at the cellular level via a new mechanism that is independent of corticosteroid type II receptor occupation or protein synthesis. We infer that these effects may be very important when glucocorticoids act as anti-inflammatory drugs during pulse therapy.

Cell Degranulation↗
PubMed2003

Anti-beta2-glycoprotein I autoantibodies require an antigen density threshold, consistent with divalent binding.

Autoantibodies binding beta2-glycoprotein I (B2GPI) are an important finding in the antiphospholipid syndrome. While antibodies from mice or rabbits immunized with B2GPI readily bind B2GPI coated on a polystyrene microwell plate, anti-B2GPI autoantibodies only do so when using a modified microwell plate with a negatively charged surface. This study demonstrates that, for the detection of anti-B2GPI autoantibodies in an ELISA using modified plates, an antigen coating concentration threshold exists, such that minimal or no binding occurs below a certain coating concentration of antigen, even though antigen is easily demonstrable on the plate. This is consistent with the hypothesis that autoantibodies require divalent binding to B2GPI for detection, as sufficient antigen density for two protein molecules to be sufficiently close to enable divalent binding would only be expected to occur at higher coating concentrations. Several mutant forms of B2GPI developed for epitope determination experiments are shown to have decreased binding to microtitre plates compared to wild-type. If wild-type and mutants are assayed for antibody binding near the threshold a significant diminution in binding to mutants occurs that is the result of inadequate binding to the plate, but could be misinterpreted as the result of interruption of an epitope by the mutation.

Animals↗
PubMed2002

[Molecular cloning, expression and characterization of the clones encoding soluble TF mutants].

Tissue factor (TF) plays an important role in the pathogenesis of atherosclerotic, sepsis and disseminated intravascular coagulation (DIC). TF pathway is therefore an attractive therapeutic target in a number of disease states. Here two TF mutants were developed and named MCsTF and MFsTF, in which the amino acids of active sites were mutated. Both of them were expressed in E.coli and used to inhibit TF pathway through competitive FVII/VIIa binding with TF. The results indicated that rMCsTF almost lost all activities of FX activation and procoagulation, and rMFsTF lost 90% activity. The specific catalytic constant ( k ( cat )/ K (m)) of FX activation by the complex formed by FVIIa with rMCsTF or rMFsTF were 2.0% and 3.7%, respectively, compared to that of rsTF. The inhibition effects of the mutants were studied in vitro, and it appeared that the prothrombin time were prolonged in a dose-dependent manner. Therefore, these mutants of TF may become new kind of specific inhibitors of TF pathway, as a promising drug for the treatment of patients with over-expression of TF.

Arteriosclerosis↗
PubMed2001

Synapse-associated protein 97 selectively associates with a subset of AMPA receptors early in their biosynthetic pathway.

The regulation of AMPA receptors at the postsynaptic membrane is a fundamental component of synaptic plasticity. In the hippocampus, the induction of long-term potentiation increases the delivery of GluR1, a major AMPA receptor subunit in hippocampal pyramidal neurons, to the synaptic plasma membrane through a mechanism that requires the PDZ binding domain of GluR1. Synapse-associated protein 97 (SAP97), a member of the membrane-associated guanylate kinase family, is believed to associate with AMPA receptors (AMPARs) containing the GluR1 subunit, but the functional significance of these interactions is unclear. We investigated the interaction of GluR1 with SAP97, the only PDZ protein known to interact with GluR1. We find that interactions involving SAP97 and GluR1 occur early in the secretory pathway, while the receptors are in the endoplasmic reticulum or cis-Golgi. In contrast, few synaptic receptors associate with SAP97, suggesting that SAP97 dissociates from the receptor complex at the plasma membrane. We also show that internalization of GluR1, as triggered by NMDAR activation, does not require SAP97. These results implicate GluR1-SAP97 interactions in mechanisms underlying AMPA receptor targeting.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Nitric oxide synthase inhibition increases aortic stiffness measured by pulse wave velocity in rats.

OBJECTIVE: The present study was to examine whether endogenous nitric oxide (NO) plays a role in the regulation of vascular stiffness. METHODS: Pulse wave velocity (PWV) was determined as the time delay between the foot of pressure waves recorded simultaneously at the aortic arch and abdominal aorta (just above the bifurcation) in anesthetized Sprague-Dawley rats. A decrease in vascular compliance results in an increase in PWV. RESULTS: A bolus injection of a NO synthase inhibitor, L-NAME (30 mg/kg), significantly increased PWV, accompanied by an increase in blood pressure. Since changes in blood pressure are known to affect PWV, phenylephrine (PE) was administered to mimic the blood pressure changes induced by L-NAME, thus compensating for the pressure-dependent component of the PWV changes. At each given level of mean arterial pressure (MAP), PWV was significantly higher with L-NAME than with PE treatment, suggesting that acute withdrawal of endogenous NO reduces aortic compliance independent of changes in MAP. In rats chronically treated with L-NAME (0.5 g/l in drinking water) for 3 weeks, PWV was even higher than those acutely treated with L-NAME (at MAP=150 mmHg). This additional increase in vascular stiffness may be due to the remodeling of the vascular wall as a result of chronic NOS inhibition and hypertension. CONCLUSION: These data demonstrate that NO modulates vascular compliance independent of blood pressure changes and that an intact endogenous NO system is required to maintain normal vascular compliance.

Analysis of Variance↗
PubMed2001

Effects of doxorubicinol on excitation--contraction coupling in guinea pig ventricular myocytes.

The cardiotoxicity of the anticancer drug doxorubicin may be related to its main metabolite doxorubicinol. In this study, the acute effects of doxorubicinol on excitation-contraction coupling in isolated guinea pig ventricular myocytes were investigated and compared with doxorubicin using the whole-cell patch-clamp-, fura-2 fluorescence- and cell-edge tracking techniques. Both drugs were applied intracellularly by diffusion from the patch electrode for 15--20 min. Doxorubicin (100 microM) prolonged the action potential duration (APD) by 31% and enhanced cell shortening by 26%. Contrary to doxorubicin, doxorubicinol (10 microM) shortened APD by 25% and decreased cell shortening by 31%. APD shortening by doxorubicinol was due to an increase of the delayed rectifier K(+) current. Neither the inward rectifier K(+) current nor the L-type Ca(2+) current was influenced by doxorubicinol. The decline in cell shortening induced by doxorubicinol was not exclusively due to APD shortening because doxorubicinol reduced the peak Ca(2+) transient by 23% in cells clamped with an action potential of constant duration. Despite opposite effects on APD and contractility, both doxorubicin and doxorubicinol produced a considerable delay in the activation and inactivation of contraction and Ca(2+) transient, compatible with an impaired function of the sarcoplasmic reticulum. It is suggested that doxorubicinol-induced APD shortening may amplify the detrimental effects of both doxorubicin and doxorubicinol on sarcoplasmic reticulum Ca(2+) load and hence on contractile function. The accumulation of doxorubicinol in the cardiac myocytes may play an important role in the time-dependent development of doxorubicin-induced ventricular dysfunction.

Action Potentials↗
PubMed2001

Fusion of docked membranes requires the armadillo repeat protein Vac8p.

The discovery of molecules required for membrane fusion has revealed a remarkably conserved mechanism that centers upon the formation of a complex of SNARE proteins. However, whether the SNARE proteins or other components catalyze the final steps of membrane fusion in vivo remains unclear. Understanding this last step depends on the identification of molecules that act late in the fusion process. Here we demonstrate that in Saccharomyces cerevisiae, Vac8p, a myristoylated and palmitoylated armadillo repeat protein, is required for homotypic vacuole fusion. Vac8p is palmitoylated during the fusion reaction, and the ability of Vac8p to be palmitoylated appears to be necessary for its function in fusion. Both in vivo and in vitro analyses show that Vac8p functions after both Rab-dependent vacuole docking and the formation of trans-SNARE pairs. We propose that Vac8p may bind the fusion machinery through its armadillo repeats and that palmitoylation brings this machinery to a specialized lipid domain that facilitates bilayer mixing.

Fungal Proteins↗
PubMed2001

Syntheses of hydrated molybdenum bronzes by reduction of MoO3 with NaBH4.

Hydrated molybdenum bronzes have been prepared by reduction reaction of MoO3 with NaBH4 in ethanol and DMSO. The reduction reactions in both solvents occur smoothly; thus, the layered structure of MoO3 is maintained in the product. Divalent cation Ca2+ has been intercalated between the MoO3 layers, which leads to highly reduced molybdenum bronze (Mo5.26+). Solvated molybdenum bronze catalyzes the reduction reaction of DMSO by NaBH4, producing CH3SCH3. The structure model of hydrated sodium molybdenum bronze has also been reinvestigated by using the Rietveld analysis. The hydrated molybdenum bronze crystallizes in an orthorhombic structure, in which the structure of Mo octahedron layers is closely related to that in MoO3. However, the structure refinement reveals that the Mo octahedron in the MoO3 layers is axially distorted, which is different from that in MoO3 but similar to an isoelectron compound H0.33MoO3.

Journal Article↗
PubMed2001

Analgesic domains of interferon-alpha.

Interferon-alpha (IFNalpha) is not only an immunoregulatory factor, but is also an analgesic molecule. We ever reported that there exist distinct domains in IFNalpha molecule that mediate immune and analgesic effects respectively and inferred that the analgesic domain locates around the 122nd Tyr residue of IFNalpha molecule in the tertiary structure. After the 36th Phe residue, which was located closely to the 122nd Tyr residue in the tertiary structure, was mutated to Ser using site-directed mutagenesis, the analgesic activity of this mutant lost completely, but the antiviral activity of IFNalpha still maintained 40.5% of wild type IFNalpha. The results suggest that the 36th Phe residue is one of the constituent for the analgesic domain of IFNalpha and inferred that the analgesic domain of IFNalpha consists of the 122nd Tyr and the residues around the 122nd in the tertiary structure, which include the 36th Phe.

Analgesics↗
PubMed2001

Impaired thrombin generation in beta 2-glycoprotein I null mice.

Autoimmune antibodies to beta(2)-glycoprotein I (beta2GPI) have been proposed to be clinically relevant because of their strong association with thrombosis, miscarriage, and thrombocytopenia. By using a homologous recombination approach, beta2GPI-null mice were generated to begin to understand the physiologic and pathologic role of this prominent plasma protein in mammals. When beta2GPI heterozygotes on a 129/Sv/C57BL/6 mixed genetic background were intercrossed, only 8.9% of the resulting 336 offspring possessed both disrupted alleles. These data suggest that beta2GPI plays a beneficial role in implantation and/or fetal development in at least some mouse strains. Although those beta2GPI-null mice that were born appeared to be relatively normal anatomically and histologically, subsequent analysis revealed that they possessed an impaired in vitro ability to generate thrombin relative to wild type mice. Thus, beta2GPI also appears to play an important role in thrombin-mediated coagulation.

Alleles↗
PubMed2001

Superparamagnetic iron oxide contrast agents: physicochemical characteristics and applications in MR imaging.

Superparamagnetic iron oxide MR imaging contrast agents have been the subjects of extensive research over the past decade. The iron oxide particle size of these contrast agents varies widely, and influences their physicochemical and pharmacokinetic properties, and thus clinical application. Superparamagnetic agents enhance both T1 and T2/T2* relaxation. In most situations it is their significant capacity to reduce the T2/T2* relaxation time to be utilized. The T1 relaxivity can be improved (and the T2/T2* effect can be reduced) using small particles and T1-weighted imaging sequences. Large iron oxide particles are used for bowel contrast [AMI-121 (i.e. Lumirem and Gastromark) and OMP (i.e. Abdoscan), mean diameter no less than 300 nm] and liver/spleen imaging [AMI-25 (i.e. Endorem and Feridex IV, diameter 80-150 nm); SHU 555A (i.e. Resovist, mean diameter 60 nm)]. Smaller iron oxide particles are selected for lymph node imaging [AMI-227 (i.e. Sinerem and Combidex, diameter 20-40 nm)], bone marrow imaging (AMI-227), perfusion imaging [NC100150 (i.e. Clariscan, mean diameter 20 nm)] and MR angiography (NC100150). Even smaller monocrystalline iron oxide nanoparticles are under research for receptor-directed MR imaging and magnetically labeled cell probe MR imaging. Iron oxide particles for bowel contrast are coated with insoluble material, and all iron oxide particles for intravenous injection are biodegradable. Superparamagnetic agents open up an important field for research in MR imaging.

Contrast Media↗
PubMed2001

Angiotensin II increases urokinase-type plasminogen activator expression and induces aneurysm in the abdominal aorta of apolipoprotein E-deficient mice.

Urokinase-type plasminogen activator (uPA) is increased in human abdominal aortic aneurysm (AAA). Chronic infusion of angiotensin II (Ang II) results in AAA in apolipoprotein E-deficient mice. We tested the hypothesis that Ang II infusion results in an elevation of uPA expression contributing to aneurysm formation. Ang II or vehicle was infused by osmotic pumps into apoE-KO mice. All mice treated with Ang II developed a localized expansion of the suprarenal aorta (75% increase in outer diameter), accompanied by an elevation of blood pressure (22 mmHg), compared to the vehicle-treated group. Histological examination of the dilated aortic segment revealed similarities to human AAA including focal elastin fragmentation, macrophage infiltration, and intravascular hemorrhage. Ang II treatment resulted in a 13-fold increase in the expression of uPA mRNA in the AAA segment in contrast to a twofold increase in the atherosclerotic aortic arch. Increased uPA protein was detected in the abdominal aorta as early as 10 days after Ang II infusion before significant aorta expansion. Thus, Ang II infusion results in macrophage infiltration, increased uPA activity, and aneurysm formation in the abdominal aorta of apoE-KO mice. These data are consistent with a causal role for uPA in the pathogenesis of AAA.

Angiotensin II↗
PubMed2001

Glutamate receptor targeting in the postsynaptic spine involves mechanisms that are independent of myosin Va.

Targeting of glutamate receptors (GluRs) to synapses involves rapid movement of intracellular receptors. This occurs in forms of synaptic upregulation of receptors, such as long-term potentiation. Thus, many GluRs are retained in a cytoplasmic pool in dendrites, and are transported to synapses for upregulation, presumably via motor proteins such as myosins travelling along cytoskeletal elements that extend up into the spine. In this ultrastructural immunogold study of the cerebellar cortex, we compared synapses between normal rats/mice and dilute lethal mutant mice. These mutant mice lack myosin Va, which has been implicated in protein trafficking at synapses. The postsynaptic spine in the cerebellum lacks the inositol trisphosphate receptor (IP3R) -laden reticular tubules that are found in normal mice and rats (Takagishi et al., Neurosci. Lett., 1996, 215, 169). Thus, we tested the hypothesis that myosin Va is necessary for transport of GluRs and associated proteins to spine synapses. We found that these spines retain a normal distribution of (i) GluRs (delta 1/2, GluR2/3 and mGluR1alpha), (ii) at least one associated MAGUK (membrane-associated guanylate kinase) protein, (iii) Homer (which interacts with mGluR1alpha and IP3Rs), (iv) the actin cytoskeleton, (v) the reticulum-associated protein BiP, and (vi) the motor-associated protein, dynein light chain. Thus, while myosin Va may maintain the IP3R-laden reticulum in the spine for proper calcium regulation, other mechanisms must be involved in the delivery of GluRs and associated proteins to synapses. Other possible mechanisms include diffusion along the extrasynaptic membrane and delivery via other motors running along the spine's actin cytoskeleton.

Actins↗
PubMed2001

Atypical magnetic resonance imaging findings of craniopharyngioma.

Three cases of craniopharyngiomas with atypical MRI findings are reported. The first patient had a nasopharyngeal craniopharyngioma. Its unusual location made diagnosis difficult. The second patient had a massive craniopharyngioma with extensive cystic expansion, involving the anterior, middle and posterior cranial fossae, and extending into the foramen magnum. The tumour of the third patient involved the suprasellar region with a large extension into the third ventricle, and demonstrated a predominantly high signal intensity on all T1-weighted, proton-weighted and T2-weighted images. These patients further stressed the complexity of MRI findings in craniopharyngiomas.

Child↗
PubMed2001

Increased nitric oxide accounts for decreased basal vascular tone and responsiveness in the resistance vessels of high-cholesterol-fed rabbits.

The objective of this study was to determine the effects of hypercholesterolemia on basal vascular tone and vascular responses to pharmacologic agents in hindquarter resistance vessels. Blood pressure and hindquarter blood flow were measured in conscious rabbits fed a high cholesterol diet (1%) for 17 weeks (HC) compared to age-matched rabbits fed a normal diet (control). Basal hindquarter blood flow and vascular conductance were significantly higher in HC than in control rabbits. Administration of a non-selective nitric oxide synthase (NOS) inhibitor, L-NAME (100 mg/kg) decreased basal hindquarter blood flow and vascular conductance in a greater magnitude in HC than in control rabbits, thus, abolished the differences in both the flow and conductance between 2 groups, indicating that increased NO was responsible for reduced basal vascular tone in the HC rabbits. L-NIL (30 mg/kg), a selective inducible NOS (iNOS) inhibitor had no effects on either flow or conductance. This result does not support the involvement of iNOS. In separate experiments, animals were anesthetized and instrumented with an extracorporeal circuit to measure perfusion pressure under constant blood flow to the hindquarter vascular bed. In the HC group, vascular responses to acetylcholine, S-nitroso-N-acetyl-penicillamine and phenylephrine were all attenuated when compared to the responses in the control rabbits. These results indicate that local overproduction of NO due to hypercholesteremia could desensitize smooth muscle reactivity, thus causing general vascular hyporesponsiveness to vasoactive agents.

Acetylcholine↗
PubMed2001

Radiographic contrast media induced nephropathy: experimental observations and the protective effect of calcium channel blockers.

Combined acute inhibition of the synthesis of nitric oxide with L-nitroarginine methyl ester (L-NAME) and of prostacycline synthesis with indomethacin predisposes rats to severe renal injury from radiographic contrast media. The reliability of this pharmacological manipulation in the study of radiographic contrast medium induced nephropathy (RCMN) was investigated. Adult male Sprague-Dawley rats were injected with iv L-NAME (10 mg kg(-1)) and iv indomethacin (10 mg kg(-1)) 15 min apart and prior to injection of RCM or normal saline (control group). A dose-dependent reduction in renal function was observed after intravascular injection of the high osmolar RCM diatrizoate (Angiografin, 306 mgI ml(-1)). A significant (p<0.01) increase in serum creatinine (Cr) (from 54.66+/-8.39 micromol l(-1) to 171.96+/-24.49 micromol l(-1) and from 80.95+/-6.73 micromol l(-1) to 204.76+/-16.73 micromol (-1), n=5 per group) was observed 24 h after injection of 6 ml and 8 ml of diatrizoate, respectively. The increase in serum Cr after injection of 8 ml of diatrizoate recovered spontaneously to 80.87+/-8.70 micromol l(-1) 7 days after injection. No significant change in renal function was observed in the control group (n=5) receiving 8 ml kg(-1) of normal saline or after injection of 4 ml of diatrizoate (serum Cr 69.84+/-5.5 micromol l(-1) pre contrast injection and 66.67+/-13.47 micromol l(-1) 24 h post contrast injection, n=5). The increase in serum Cr observed with 6 ml of diatrizoate was significantly higher (p<0.01) than the rise induced by equivolume of the low osmolar non-ionic monomer iopromide (Ultravist, 300 mgI ml(-1)) (serum CR 68.47+/-8.39 micromol l(-1) pre contrast injection and 143.59+/-32.03 micromol l(-1) 24 h post contrast injection, n=5). The calcium channel blocker diltiazem (10 mg kg(-1) injected intraperitoneally 30 min prior to RCM injection) prevented the rise in serum Cr observed with 6 ml of diatrizoate (serum Cr pre contrast injection 70.31+/-7.28 micromol(-1) and 78.21+/-17.81 micromol(-1) 24 h post contrast injection in animals pre-treated with diltiazem, n=5). The protective effect against RCM-induced reduction in renal function was less with lower doses of diltiazem. In conclusion, the animal model used is reliable and reproduced previously established observations in the field of RCMN. The protective effect of a calcium channel blocker at the appropriate dose against RCMN has also been shown. The clinical effectiveness of this class of drugs in preventing RCMN requires further evaluation.

Animals↗
PubMed2001

[Molecular cloning and expression of the cDNA encoding angiogenesis inhibitor K4K5 with Pichia pastoris].

Kringles of human plasminogen except kringle 4 can inhibit the endothelial cell growth. To determine whether recombinant plasminogen kringle 4-5 (r-K4K5) can inhibit the growth of bovine capillary endothelial (BCE) cell and the angiogenesis of chick embryo chorioallantoic membrane (CAM), we cloned and constructed the modified cDNA region encoding kringles 4 and 5 (K4K5) of human plasmin (ogen) and expressed it with pichia multi-copy expression system. One clone, with the most productive expression was selected from hundreds of transformants. Our data showed that the expression product r-K4K5 (MW 21.5 kD) amounted to 150-250 mg/liter, over 80% of the total secreted protein. It could, dose-dependently, inhibit BCE cell proliferation and inhibit chick embryo CAM angiogenesis.

Angiogenesis Inhibitors↗