PubMed Health⌕ Search

Biomedical subjects

X Y Zhu

Publications and source records attributed to X Y Zhu.

At least 19 recordsLinked to original sources
PubMed2001

Intestinal serotonin acts as a paracrine substance to mediate vagal signal transmission evoked by luminal factors in the rat.

The vagus nerve conveys primary afferent information produced by a meal to the brainstem. Serotonin (5-HT), which abounds in intestinal enterochromaffin cells, is released in response to various stimuli. We have recently demonstrated that 5-HT released from intestinal enterochromaffin cells activates 5-HT3 receptors on vagal afferent fibres to mediate luminal non-cholecystokinin-stimulated pancreatic secretion. The present study was designed to evaluate the responses of vagal sensory neurons to intraluminal osmotic stimulation and luminal infusion of maltose, glucose or 5-HT. We investigated the role of endogenous 5-HT in signal transmission evoked by luminal stimuli to activate vagal sensory neurons. The discharges of vagal primary afferent neurons innervating the intestine were recorded from rat nodose ganglia. Luminal factors such as intestinal osmotic stimuli and perfusion of carbohydrates elicited powerful vagal nodose responses. Electrical subdiaphragmatic vagal stimulation activated 364 single units; 40 of these responded to intestinal mucosal stimuli. Of these 40, 30 responded to intraduodenal perfusion of hyperosmolar NaCl (500 mosmol l(-1)), 27 responded to tap water (5 mosmol l(-1)) and 20 and 19 responded to maltose (300 mM) and glucose (277.5 mM), respectively. The 5-HT3/4 antagonist tropisetron (ICS 205-930) or 5-HT3 antagonist granisetron abolished luminal stimuli-evoked nodose neuronal responses. Intraluminal infusion of 10(-5) and 10(-4) M 5-HT elicited increases in vagal afferent discharge in 25 and 31 units, respectively, by activating the 5-HT3 receptors. Acute subdiaphragmatic vagotomy, intestinal mucosal application of the local anaesthetic lidocaine (lignocaine) or administration of 5-HT3 antagonist each abolished the luminal 5-HT-induced nodose neuronal responses. In contrast, distension-sensitive neurons did not respond to duodenal infusion of 5-HT. Pharmacological depletion of 5-HT stores using p-chlorophenylalanine (PCPA), a 5-HT-synthesis inhibitor, abolished luminal factor-stimulated nodose neuronal responses. In contrast, pretreatment with 5,7-dihydroxytryptamine (5,7-DHT), a specific 5-HT neurotoxin that destroys 5-HT-containing neurons without affecting 5-HT-containing mucosal cells, had no effect on these responses. These results suggested that the nodose neuronal responses to luminal osmolarity and to the digestion products of carbohydrates are dependent on the release of endogenous 5-HT from the mucosal enterochromaffin cells, which acts on the 5-HT3 receptors on vagal afferent fibres to stimulate vagal sensory neurons.

Action Potentials↗
PubMed2001

Effect of p58GTA on beta-1,4-galactosyltransferase 1 activity and cell-cycle in human hepatocarcinoma cells.

Beta-1,4-galactosyltransferase 1 (beta1,4-GT 1) is the key enzyme transferring galactose to the terminal N-acetylglucosamine (GlcNAc) forming Galbeta3-->4GlcNAc structure in the Golgi apparatus. In addition, it also serves as a cell adhesion molecule by recognizing and binding to terminal GlcNAc of glycoconjugates on the adjacent cell surface and matrix through a subpopulation of the enzyme distributed on the cell surface. Transient expression of the p58GTA protein kinase, which belongs to the p34cdc2-related supergene family, could enhance beta1,4-GT 1 total activity in COS cells. In this study, the p58GTA interaction with beta1,4-GT 1 was confirmed using an in vitro assay with the TNT Coupled Reticulocyte Lysate System. An expression vector containing p58GTA was stably transfected into 7721 cells, a human hepatocarcinoma cell line, expression was confirmed by Northern and Western blot analyses. The cells transfected with p58GTA (p58GTA/7721) contained 1.9 times higher total beta1,4-GT 1 activity and 2.6 times higher cell-surface beta1,4-GT 1 activity than the mock transfected cells (pcDNA3/7721). However, Ricinus communis agglutinin-I lectin blot analysis revealed that the enhanced beta1,4-GT1 activity did not increase the Galbetal-->4GlcNAc groups on most of the membrane proteins in p58GTA/7721 cells. By flow cytometry analysis, it was found that the p58GTA/7721 cells were G2/M phase arrested, compared with the pcDNA3/7721 cells. These results suggest that the p58GTA stable transfection into human hepatocarcinoma cells could enhance the two beta1,4-GT1 subcellular pool activities independently and change its cell-cycle without modifying the beta-1,4-linked galactose residues on most membrane proteins.

Animals↗
PubMed2001

Systemic distribution of Staphylococcus aureus following intradermal footpad challenge of broilers.

We conducted an experiment with broilers to determine if prior exposure to Staphylococcus aureus would facilitate the systemic infiltration of this pathogen following intradermal footpad challenge with live S. aureus. Litter-raised broilers were sensitized at 3 and 4 wk of age with s.c. injections in the neck with heat-killed S. aureus diluted in polyethylene glycol (PEG). Equal numbers of control birds were injected at the same times with PEG. At 7 wk of age, chicks previously sensitized to killed S. aureus or injected with PEG were injected intradermally in the right footpad with PBS or live S. aureus. The left footpads of all birds were injected with PBS. The difference in thickness between the right and left footpads was determined at 0, 24, and 48 h postchallenge. Blood, liver, spleen, lung, and synovial fluid were collected six times between 1 and 48 h postchallenge to determine the recovery of S. aureus. Sensitized and non-sensitized birds showed footpad swelling following challenge with live S. aureus in the right footpad (P < 0.001). Injection of PBS did not induce footpad swelling. Birds injected in the footpads with live S. aureus as compared to PBS had significantly higher isolation rates of S. aureus in the spleen, liver, and blood; however, recovery of S. aureus from S. aureus-sensitized and PEG-injected birds was not significantly different. Time postchallenge (1, 3, 7, 11, 24, and 48 h) had no significant effect on the recovery of S. aureus. It was concluded that the intradermal challenge of the footpad with S. aureus resulted in systemic infiltration of S. aureus into the spleen, liver, and blood. Prior exposures to killed S. aureus as compared to PEG controls did not affect the systemic distribution of S.

Analysis of Variance↗
PubMed2001

[Effects of musk glucoprotein on the function of rat polymorphonuclear leukocytes activated by IL-8 in vitro].

OBJECTIVE: To investigate the effects of musk-1, a glucoprotein component isolated from the water extract of musk, on some functions of rat polymorphonuclear leukocytes activated by IL-8 in vitro. METHOD: An in vitro incubation system was used. Superoxide anion production was determined by cytochrome C reduction. beta-glucuronidase and lysozyme release was quantitated by enzyme reactions in which phenolph-thaleinglucuronic acid and Micrococcus Lysodeikticus were as the substrates, respectively. RESULTS: In comparison with control, musk-1 at concentration 1-100 micrograms.ml-1 can increase superoxide anion production by 91.7%-291%, and decrease beta-glucuronidase and lysozyme release by 2.2%-58.1% and 3.9%-39.8%, respectively. CONCLUSION: Inhibition of lysosomel enzyme release might be considered as one of mechanisms of antiinflammatory action of musk.

Animals↗
PubMed2001

[Direct optical resolution of the enantiomers of biphenyl compounds by high performance liquid chromatography on amylose tris-(3,5-dimethylphenylcarbamate) stationary phase].

A chiral stationary phase(CSP) was prepared by coating amylose tris-(3,5-dimethylphenylcarbamate) onto aminopropylated spherical silica gel. The enantioselective chromatographic separation of a series of biphenyl compounds with antihepatitis activity was performed for the first time on CSP. The effect of alcohol modifiers in mobile phase was investigated. The mobile phases used in the study were hexane modified by ethanol, 1-propanol, 1-butanol or 2-propanol. It was found that the retention times and the separation of the enantiomers of biphenyl compounds on the CSP were dramatically influenced by the nature of alcohols in the mobile phase, and the best alcohol modifier for some compounds was ethanol. The interaction between the stationary phase and samples was also discussed.

Amylose↗
PubMed2001

[Effect of stilbene polymer (Gn-3) on experimental liver injuries in mice].

AIM: To study the protective effect of Gn-3 (a stilbene polymer isolated from Gnetum parvifolium) against liver injury induced by CCl4, N-acetyl-p-aminophenol (APAP) and Bacillus Calmette-Guerin (BCG) plus bacterial lipopolysaccharide (LPS) in mice. METHODS: The experimental model of liver injury were induced by 0.1% CCl4 i.p. (10 mL.kg-1.d-1 for 3d), APAP i.p. (150 mg.kg-1) or BCG (5 mg) plus LPS (7.5 micrograms) in mice. The levels of ALT in serum, MDA and GSH in liver tissues were detected. The histopathologic changes were observed by light microscope. RESULTS: Gn-3 was shown to markedly reduce the elevated serum ALT levels, liver tissue MDA and improve the histopathological changes in all the three experimental liver injury models. No effect of Gn-3 was observed on the liver GSH level in liver injury mice. CONCLUSION: Gn-3 was found to inhibit the development of liver injury caused by CCl4, APAP, or BCG plus LPS. This means that Gn-3 has liver protective effects.

Acetaminophen↗
PubMed2000

Characterization, crystallization and preliminary X--ray diffraction analysis of acutohaemolysin, a haemolytic toxin from Agkistrodon acutus venom.

Acutohaemolysin, a phospholipase A(2) (PLA(2)) from the venom of the snake Agkistrodon acutus, has been isolated and purified to homogeneity by anion-exchange chromatography on a DEAE-Sepharose column followed by cation-exchange chromatography on a CM-Sepharose column. It is an alkaline protein with an isoelectric point of 10.5 and is comprised of a single polypeptide chain of 13 938 Da. Its N-terminal amino-acid sequence shows very high similarity to Lys49-type PLA(2) proteins from other snake venoms. Although its PLA(2) enzymatic activity is very low, acutohaemolysin has a strong indirect haemolytic activity and anticoagulant activity. Acutohaemolysin crystals with a diffraction limit of 1.60 A were obtained by the hanging-drop vapour-diffusion method. The crystals belong to the space group C2, with unit-cell parameters a = 45.30, b = 59.55, c = 46.13 A, beta = 117.69 degrees. The asymmetric unit contains one molecule.

Agkistrodon↗
PubMed2000

[Mutations of Q20L and G247D improved the specific-activity and optimum pH of glucose isomerase].

The mutants of Q20L and G247D of glucose isomerase (GI) were constructed by in vitro site-directed mutagenesis of GI gene with double-primersmethod. The recombinant plasmids pTKD-GIQ20L and pTKD-GIG247D were expressed in E. coli K38 strain. The comparison experiments of mutant enzymes with wild-type GI showed that: (1) the optimum temperature of GIQ20L was decreased by 5 degrees C. Its thermostability was only 78% half-time of the wild type. But its substrate affinity was enhanced. (2) The specific-activity of GIG247D was increased by 33%, and the optimum pH was lowered by 0.6 unit. However, the thermostability of GIG247D was decreased. We supposed, based on the above facts and 0.19 nm resolution crystal structure of SM33GI, that Gln20 locates between alpha 0-helix and alpha 1-helix, the substitution of hydrophobic side chain of Leu for hydrophilic side chain of Gln may enhance the hydrophobic interaction of the molecular surface, leading to the decrease of the stability and thermostability of GIQ20L. Gly247 which is the last amino acid of a beta-sheet from 242 to 247 residues locates in the active core of GI. After replacement, Asp247 which has strong negative electricity may change the electrostatic distribution and influence the charge transfer processes of the active core. So the specific-activity of GIG247D was increased. The introduced charge could alter the pKa of dissociable groups and make the optimum pH lower. In addition, the side chain of Asp247 seems to be very crowded in the surrounding space conformation and is easy to exclude with the other side chains, therefore influences the stability of beta-sheet. Furthermore, Asp247 is in the vicinity of the interface of subunits, so it could interfere with the stability of the interaction between subunits. Thus, the GIG247D decreased the thermostability of SM33GI. The higher enzyme activity and the lower optimum pH will be very useful for industrial production of GI.

Aldose-Ketose Isomerases↗
PubMed2000

[Effects of musk glucoprotein on PAF production and cytosolic Ca2+ level in rat polymorphonuclear leukocytes in vitro].

OBJECTIVE: To investigate the effects of Musk glucoprotein on platelet activating factor (PAF) production and the concentration of cytosolic free Ca2+ in polymorphonuclear leukocytes of rat. METHODS: An in vitro incubation system was used, production of PAF and activity of acetyl transferase were measured by isotope incorporation, the concentration of cytosolic free Ca2+ was quantitated using the fluorescent Ca2+ indicator Fura-2. RESULTS: Musk-1 at concentration of 1-100 micrograms.ml-1 can significantly inhibit production of PAF, activity of acetyl transferase and the increase of cytosolic Ca2+ concentration in polymorphonuclear leukocytes of rat. CONCLUSION: Part of mechanisms underlying antiinflammatory action of Musk-1 is through inhibiting the synthesis of PAF and the increase of cytosolic Ca2+ level.

Acetyltransferases↗
PubMed2000

[Effects of baicalin on liver microsomal cytochrome P450 system].

AIM: To investigate the effect of baicalin on liver microsomal cytochrome P450 system and the mechanism of liver protective action of baicalin. METHODS: Liver microsomal cytochrome P450, b5, aminopyrin N-demethylase (ADM), 7-ethoxycoumarin O-deethylase (ECD) and benzopyrene hydroxylase (AHH) activity were quantitated by UV chromatography. Activities of six cytochrome P450 isoforms were assayed with Western Blotting. RESULTS: Baicalin increased liver microsomal cytochrome. P450 level and ADM, ECD and AHH activity significantly. The three P450 isoforms, 1A1, 2B1 and 2C11, were also induced selectively by baicalin, but the b5 level, 3A2, 2D1 and 2E1 were not induced. CONCLUSION: Baicalin increases liver microsomal cytochrome P450 level and induces selectively 1A1, 2B1 and 2C11 of P450 isoforms in mice.

Animals↗
PubMed1999

Inhibitory effect of resveratrol on interleukin 6 release by stimulated peritoneal macrophages of mice.

In the present investigation, interleukin 6 (IL-6) activity in the supernatant of cultured mouse peritoneal macrophages was monitored using a sensitive bioassay involving the IL-6-dependent murine hybridoma B9 cell line. The effects of resveratrol on Il-6 release by mouse peritoneal macrophages stimulated with calcium ionophore A23187 and fMLP were explored. Resveratrol, at a concentration range from 5 x 10(-6) to 4 x 10(-5) mol.l-1, was found to dose-dependently inhibit IL-6 release by cultured macrophages induced by A23187 and fMLP, and showed no direct cytotoxic effect, but induced proliferation of cultured mouse thymus cells. Resveratrol, at a concentration range from 10(-8) to 10(-5) mol.l-1, was shown to dose-dependently inhibit calcium ion influx into the cells with the stimulation of fMLP (10(-6) mol.l-1). These results suggest that the blocking of calcium ion influx into cells by reveratrol is one of the possible mechanisms of the IL-6 biosynthesis inhibitory action of resveratrol.

Animals↗
PubMed1999

Increasing the thermostability of D-xylose isomerase by introduction of a proline into the turn of a random coil.

Thermostability can be increased by introducing prolines at suitable sites in target proteins. Two single (G138P, G247D) mutants and one double (G138P/G247D) mutant of xylose isomerase from Streptomyces diastaticus No.7, strain M1033 have been constructed by site-directed mutagenesis. With respect to the wild-type enzyme, G138P showed about a 100% increase in thermostability, and G247D showed an increased catalytic activity. Significantly, the double mutant, G138P/G247D displayed even higher activity than G247D and better heat stability than G138P. Its half life was about 2.5-fold greater than the wild-type enzyme, using xylose as a substrate. Molecular modelling suggested that the introduction of a proline residue in the turn of a random coil may cause the surrounding conformation to be tightened by reducing the backbone flexibility. The change in thermostability can, therefore, be explained based on changes in the molecular rigidity. Furthermore, the improvements in the properties of the double mutant indicated that the advantages of two single mutants can be combined effectively.

Aldose-Ketose Isomerases↗
PubMed1999

Delayed-type hypersensitivity reaction induced in broilers by killed Staphylococcus aureus.

A trial was conducted to determine whether the delayed footpad reaction (DFR) induced by killed Staphylococcus aureus in chickens is a delayed-type hypersensitivity (DTH) reaction. Five criteria were used to assess DTH: 1) DFR with a peak response at 24 to 48 h postchallenge, 2) inhibition of monocyte/macrophage migration, 3) lymphocyte blastogenic response, 4) mononuclear cell infiltration at the challenge site, and 5) passive transfer of DFR by splenic lymphocytes. Broilers were sensitized twice with a s.c. injection in the neck of S. aureus antigen (150 microg/bird) diluted in polyethylene glycol at 3 and 4 wk of age. Controls were s.c. injected with polyethylene glycol. At 6 wk of age, a migration inhibition test was conducted before the birds were challenged intradermally with S. aureus antigen (75 microg/bird) in PBS in the right footpad. The left footpad was injected with PBS. The thickness of the footpad was measured at 0, 4, 24, and 48 h postchallenge to evaluate the DFR. After challenge, blood was collected for the lymphocyte blastogenesis assay. Birds were euthanatized, and both footpads were removed for histology. The spleens were collected aseptically; splenic lymphocytes were injected i.v. into recipient birds. Sensitized birds showed an increase in the DFR (P < 0.02) and blastogenic response (P < 0.01) compared with nonsensitized birds. Delayed footpad reaction reached a maximum response at 24 h postchallenge. The in vitro migration of monocytes/macrophages from sensitized birds was significantly inhibited (P < 0.01). The histological appearance of S. aureus-injected footpads was characterized by dermal edema and perivascular infiltrates of small lymphocytes and macrophages. Birds that received sensitized splenic lymphocytes had a significantly pronounced DFR following challenge with S. aureus when compared with birds that received nonsensitized lymphocytes (P < 0.0001). These results indicated that the DFR can be used as a standard in vivo test for cell-mediated DTH reaction induced by killed S. aureus antigen in chickens.

Animals↗
PubMed1999

Delayed-type hypersensitivity reaction induced in broilers via trachea inoculation of killed Staphylococcus aureus.

A study was conducted to determine whether the delayed-type hypersensitivity (DTH) reaction to killed Staphylococcus aureus antigen in chickens could be induced through multiple intratracheal inoculations. Three criteria were used to assess DTH: 1) delayed footpad reaction (DFR) with a peak response at 24 to 48 h postchallenge, 2) inhibition of monocyte/macrophage migration, and 3) mononuclear cell infiltration at the challenge site. Broilers were sensitized three times with a s.c. injection in the neck or intratracheal inoculation of killed S. aureus in polyethylene glycol at 2, 3, and 4 wk of age. Controls were given polyethylene glycol with a s.c. injection in the neck or intratracheal inoculation. Migration inhibition tests were conducted at 6 wk of age. At 7 wk of age, all birds were challenged intradermally with S. aureus antigen in PBS in the right footpad. The left footpad was injected with PBS. The thickness of the footpad was measured at 0, 4, 24, and 48 h postchallenge to evaluate the DFR. Birds were euthanatized, and both footpads were removed for histopathological examination. Subcutaneously or intratracheally sensitized birds showed significant DFR compared with nonsensitized birds (P < 0.0001), which reached maximum response at 24 h postchallenge. The s.c. sensitization resulted in an inhibition of the in vitro migration of monocytes/macrophages (P < 0.0001), whereas intratracheally sensitized birds did not show migration inhibition of monocytes/macrophages. Histological examination showed typical perivascular infiltration of small lymphocytes in S. aureus-injected footpads from s.c. and intratracheally sensitized birds. These results indicate that multiple intratracheal inoculation, as well as s.c. injection of killed S. aureus antigen, can be used to induce a cell-mediated DTH reaction in chickens.

Animals↗
PubMed1999

Induction of the delayed footpad and wattle reaction to killed Staphylococcus aureus in chickens.

Two experiments were conducted to induce the delayed footpad reaction (DFR) to killed Staphylococcus aureus antigen. In Experiment 1, tracheal, cloacal, and choanal swabs were collected from chickens prior to sensitization with S. aureus to determine the carrier status of S. aureus. The second experiment compared the DFR to the delayed wattle reaction (DWR). Chickens were subjected to single or multiple sensitizations in the neck with S. aureus antigen between 4 and 6 wk of age. One week later, birds were challenged with S. aureus either in the right footpad or wattle. The left footpad or wattle was injected with PBS. The thicknesses of the footpad or the wattle were measured up to 96 h postchallenge. The recoveries of S. aureus from the choanal slit and trachea were significantly higher than that of the cloaca (P < 0.001). Birds of Experiment 1 showed a significant DFR (P < 0.0001) following intradermal challenge with killed S. aureus that was sustained through 48 h postchallenge with no difference in the DFR between carrier and noncarrier birds. In Experiment 2, the thicknesses of the footpad and wattle were significantly increased following challenge with S. aureus (P < 0.0001), with the footpad showing a greater response than the wattle (P < 0.001). Three sensitizing dosages, as compared to two dosages, resulted in a less pronounced DFR and DWR (P < 0.02). These results indicate that the DFR can be used as a delayed reaction model in the study of staphylococcosis in poultry.

Animals↗
PubMed1999

Purification, characterization, crystallization and preliminary X-ray diffraction of acuthrombin-B, a thrombin-like enzyme from Agkistrodon acutus venom.

Acuthrombin-B, a thrombin-like enzyme from Agkistrodon acutus venom, has been isolated and purified to homogeneity by ion-exchange chromatography on DEAE-Sepharose, gel filtration on Sephacryl S-100 and fast performance liquid chromatography on DEAE-8HR. The protease is an acid protein (pI 6.0) consisting of two non-identical polypeptide chains (14.4 and 16 kDa) and there is no disulfide bond between the subunits. Its molecular weight is 27 kDa as estimated by gel filtration on Sephacryl S-100. The protease has arginine-esterase activity and hydrolyzes synthetic substrates such as p-toluenesulfonyl arginine methyl ester and alpha-N-benzoyl-L-arginine amide ethyl ester, and shows clotting activity with human fibrinogen, rabbit citrated plasma and human citrated plasma in vitro. The specific activity with human fibrinogen was estimated to be 230 NIH units mg-1. The protease is considered as a serine-type protease and contains metal ion(s) to some extent, as indicated by the fact that its clotting and arginine-esterase activities could be completely inhibited by PMSF and partially inhibited by the chelating agent EDTA, while the thrombin inhibitor heparin had no effect on its clotting activity towards rabbit citrated plasma. Acuthrombin-B crystals with a resolution limit of 2.06 A were obtained by conventional hanging-drop vapour diffusion. The crystals belong to space group P21 with unit-cell parameters a = 34.97, b = 53.58, c = 67.88 A, beta = 98.89 degrees and contain one molecule per asymmetric unit.

Agkistrodon↗
PubMed1999

The induction of liver microsomal cytochrome P450 by Glycyrrhiza uralensis and glycyrrhetinic acid in mice.

The effect of Glycyrrhiza uralensis Fisch (GRZ) aqueous extract and one of its active principles Glycyrrhetinic acid (GRT) on hepatic cytochrome P450 in mice were investigated. Oral administration of GRZ at 10 g/kg/d or GRT at 50 mg/kg/d for 7 days was found to increase the P450 contents up to 4.6 fold compared with the controls. The activities of aryl hydrocarbon hydroxylase (AHH, 3.1 and 3.3 fold), aminopyrine N-demethylase (ADM, 4.2 and 3.2 folds), and 7-ethoxycumarin O-deethylase (ECOD, 2.8 and 2.5 fold) were also shown to be increased. Western blot analysis showed that the subtypes of P450 isoforms induced selectively by GRZ and GRT included CYP1A1 (1.8 and 1.5 fold over that of the control, respectively), CYP2B1 (both 1.3 fold), and CYP2C11 (3.2 and 3.0 fold). Moreover, significant positive correlation between the P450 content or the isoforms and the corresponding enzyme activities mentioned above was observed.

Animals↗