Biomedical subjects

X Xu

Publications and source records attributed to X Xu.

At least 271 records · Page 15Linked to original sources

PubMed2001

[Effects of selenium on the damage of learning-memory ability of mice induced by fluoride].

Sodium fluoride added with or without sodium selenite in deionized water was administered to male mice for 8 weeks. The influences of fluoride on learning-memory behavior were tested on Y-maze, and the ultrastructure of Gray I synaptic interface in the CA3 area hippocampus was quantitatively analyzed by electron microscopy and computer image processing appliance. The main results showed that the learning capability of mice drinking higher concentration of fluoride presented remarkable deterioration. The thickness of post-synaptic density (PSD) was decreased. The width of the synaptic cleft was remarkably increased. It was found that combined administration of fluoride and proper concentration of selenium could decrease the toxic effect of fluoride. There were synergetic toxicities if the concentration of selenium was too high. The results suggested that selenium might antagonize the neurotoxicity of fluoride on behavior and morphology.

Animals↗

PubMed2001

[Study on HIV DNA of epidemic HIV-1 strains].

OBJECTIVE: To study the characteristics of variation of HIV DNA in prevalent HIV-1 strains. METHODS: HIV DNA, extracted from peripheral blood mononuclear cell(PBMC) in 63 patients infected with HIV, was investigated by reverse-transcript PCR (RT-PCR), Long-Distance PCR(LD-PCR), molecular cloning hybridization and sequencing, respectively. RESULTS: The subtypes were identified in 57 samples. Subtype B was identified in 43 cases, subtype C in 5 and subtype E in 9. It was found that both full-length and defective HIV DNA in 31 out of 57 cases, defective HIV DNA in 19 cases and full-length HIV DNA in 7 cases. The deleted regions of genome were from 71 to 7,759 nucleotides. CONCLUSION: The variation of gene segments of HIV DNA plays an important role in the infection and epidemic of HIV.

Adult↗

PubMed2001

[Inhibitory effect of antisense c-myb cDNA on the growth of asynchronous glioma cells in vivo].

OBJECTIVE: To examine the therapeutic effect of oncogene c-myb antisense oligodeoxynucleotide (AON) on rat C6 glioma in vivo. METHODS: C6 glioma cells were implanted into the subcutis of nude mice, the animals were randomly divided into three groups (12 mice respectively) when the tumor grew about 10 mm in size, and the mice with subcutaneous tumor foci were treated with sense oligodeoxynucleotide (SON), AON and normal saline. Three animals of each group were killed after treatment at 4, 8, 12 and 16 days respectively. The dynamic growth manifestations, features, histopathological changes and apoptosis of the glioma in each group were observed. RESULTS: AON suppressed the growth of C6 glioma cells, the suppression rates being 66.7%, 71.4%, 72% and 73% at 4, 8, 12, 16 days respectively (P < 0.05). The changes in weight were concurrent with the variations of tumor volume, the tumor weight of AON groups was significantly decreased (P < 0.05). The immunohistochemical assay showed the expression of c-myb proto-oncogenes was significantly decreased in AON groups (P < 0.05). The flow cytometry analysis found the apoptosis cell percentage of AON groups to be 13.4%, 27.1%, 46.1% and 48.4% at 4, 8, 12 and 16 days respectively, and this percentage of AON groups was about 3.5 times the apoptosis cell percentage of SON and control groups at the corresponding time. In addition, noticeable inflammatory infiltration and calcification were observed after the treatment with AON. CONCLUSION: The above findings indicate that c-myb gene might be associated with the suppression of carcinogenesis in brain glioma, and oncogene c-myb might be chosen as a target for antisense gene therapy of gliomas.

Animals↗

PubMed2001

[A study of the acting mechanism of aspirin for resistance to oxidative damage].

OBJECTIVE: To explore the mechanism of aspirin for resistance to oxidative damage in endothelial cells. METHODS: Using cultured endothelial cells, we measured the levels of aspirin induced ferritin expression on resistance to hydrogen peroxide toxicity toward cells in the presence of the iron chelator desferrioxamine added to FeCl3. RESULTS: Aspirin at low concentration (0.1 mmol/L) induced significant increase of ferritin expression in a time- and concentration-dependent fashion up to 25% over basal levels(P < 0.05). Preincubating the cells for 8 h with aspirin (0.1 mmol/L) reduced lactate dehydrogenase(LDH) release rate by 50%, toxicity reduction by 40%, and significant decrease of malondialdehyde (MDA) production. Aspirin induced cytoprotection from H2O2 damage was also in a concentration- and time-dependent fashion. However, in the presence of the iron chelator desferrioxamine, aspirin enhanced ferritin synthesis was abrogated, in contrast, FeCl3 increased aspirin induced ferritin synthesis in cells. CONCLUSION: The study suggested that the antioxidation of aspirin was brought into action by affecting the cellular iron metabolism pathway to induce ferritin synthesis.

Antioxidants↗

PubMed2001

[Cloning and DNA sequencing of Bacillus pumilus endo-1,4-beta-glucanase gene].

Bacillus pumilus S-27 screened from marine environment produces an extracellular endo-1,4-beta-glucanase. The enzyme has its optimal activity at pH 5.0-7.0 and 55 degrees C and still retained 79.0% of it at pH 9.0. The gene encoded this endo-1,4-beta-glucanase was cloned and sequenced. The structural gene contained an open reading frame of 1980 bp, corresponding to 660 amino acids, the amino acid sequence of this enzyme is very close to that of an EG of C. cellulovorans and an EG of Bacillus sp. KSM-522, all belong to the cellulase family E2.

Amino Acid Sequence↗

PubMed2001

[Assessment on effect of treatment of chronic plaque type psoriasis by combination therapy of composite shendi decoction and diyin tablet].

OBJECTIVE: To seek for a better therapy for chronic plaque type psoriasis. METHODS: The effect of 35 patients in the tested group treated with combination therapy of composite Shendi Decoction (CSDD) and Diyin Tablet (DYT) was observed and compared with the effect of those treated by CSDD alone (25 cases) or by DYT alone (18 cases) as the control groups. RESULTS: The total effective rate in the treated group was 94.29%, and that in the two control groups was 88.00% and 83.33% respectively. The markedly effective rate in the treated group was 62.86%, and that for the control group was 36.00% and 27.78% respectively. Ridit test showed significant difference among the effectiveness in the three groups, while chi 2 showed the difference of the total effective rate in the three groups was insignificant, but that of the markedly effective rate was significant. Serum IL-8 and plasma endothelin levels of 11 cases in the treated group were examined before and after treatment, the results showed that both the two parameters were reduced after the combination therapy. CONCLUSION: The effect of combination therapy of CSDD and DYT was better than that of CSDD or DYT alone, therefore, it is worth further studying and spreading.

Adolescent↗

PubMed2001

[Loss of heterozygosity on chromosome 9p13-23 in microdissected laryngeal squamous cell carcinoma by microsatellite analysis].

OBJECTIVE: Loss of heterozygosity (LOH) studies indicate that allelic loss associated with the development of head and neck of squamous cell carcinoma occurs most frequently at 9p21-22. However, the target of chromosome 9p21-22 loss has been the source of significant debate. A putative tumor suppressor gene, p16, has been identified at the 9p21 location, but genetic alterations of p16 located in this region are unusual. To refine the hot spots of LOH on chromosome 9p13-23 will be helpful to find other putative tumor suppressor genes in laryngeal squamous cell carcinoma. METHODS: The sections of paraffin-embedded tumor tissues were microdissected to enrich for neoplastic cells. LOH on 9p13-23 was analyzed in a set of 42 paired blood and tumor samples using polymerase chain reaction (PCR) with 13 highly polymorphic microsatellite markers. RESULTS: Of the 42 total tumors, 41(97.6%) showed LOH in at least one of the microsatellite markers tested at the chromosome 9p13-23 region. The most frequently deleted marker was D9S162 with in 17 of 19 (89.5%) informative samples. The marker D9S171, which is located in 9p21, had LOH detected in 12 of 15 informative cases (80.0%). LOH at the D9S1748 marker (closest to the p16 gene locus) was detected in 18 of 36 informative cases (50.0%). Fine deletion mapping also revealed two minimal regions of LOH encompassing markers D9S161-D9S171 at 9p21 and IFNA-D9S162 at 9p22-23. CONCLUSION: These findings imply the high frequency of LOH at 9p13-23 in laryngeal squamous cell carcinoma and the presence of at least two as yet unidentified tumor suppressor genes in 9p13-23 region. Those putative tumor suppressor genes may become inactivated during the progression of the laryngeal squamous cell carcinoma.

Adult↗

PubMed2001

[Green electroluminescence generated from a new rare earth complex: Tb(asprin)3phen].

Pure Green and narrow bandwidth emission from organic electroluminescent device was presented by using a new rare earth complex Tb(asprin)3phen as emissive layer. The structure of the device was ITO/PVK:Tb(asprin)3phen/Al, where PVK was used to improve the film-forming ability and conductivity of Tb(asprin)3phen. The electroluminescent property of the device was studied. It proved that this new kind of rare earth complex has excellent optoluminescent and electroluminescent properties. The electroluminescent mechanism of the device was proposed by measuring and analyzing the emission and excitation spectra of the emissive layer. The excitation spectrum of Tb(asprin)3phen-dispersed PVK film was very similar to that of the PVK. We proposed that the excited carriers of PVK and Tb(asprin)3phen were captured by Tb3+ and light was emitted when the electrons and holes recombined at Tb3+.

Chelating Agents↗

PubMed2001

[The effect of air abrasion on enamel composite resin adhesive strength].

OBJECTIVE: In this study we observed the effect of air abrasion on enamel-composite resin adhesive strength in vitro. METHODS: Thirty teeth were prepared and divided into three groups. One group was air abraded and was acid-etched, another one was air abraded, and the other one was acid-etched. Next the bond and resin were used. Then we observed and compared the shear bond strength. The data were analysed by Chi square(chi(2)) test. RESULTS: Enamel-composite resin adhesive strength were not affected by acid etching and air abrading, but can be affected by air abrading alone. CONCLUSION: In clinic the traditional acidetch technique that used in composite resin restoration can be replaced with air abrasion surface preparation technique.

English Abstract↗

PubMed2001

[Experimental study on bioglass application in extending alveolar bone crest in rabbit].

OBJECTIVE: To observe the effect of Bioglass guiding bone regeneration and forming normal new bone in extending alveolar bone crest by surgery. METHODS: Thirty-six rabbits were randomly divided into three groups. The first group was treated with Bioglass and the second with hudroxyapectite (HA). The third group was control group. At 4 8 12 weeks after surgery, the condition of bone regeneration was observed with radiological and pathological methods. RESULTS: Statistical analysis showed that there was a significant difference between the third group and the other two groups (P<0.05). In addition, Bioglass can guide bone regeneration faster than hydroxyapatite, and it can be substituted by new bone to form completely normal bone. CONCLUSION: Since Bioglass is more effective than HA in guiding bone regeneration, it is an ideal bone graft substitute.

English Abstract↗

PubMed2001

[Study on the expression of human acute myeloid leukemia retrovirus gene].

OBJECTIVE: To explore the potentiality of retroviral etiology in human acute myeloid leukemia (AML). METHODS: The expression of retrovirus clone 6 # 11 in leukemic cells from 19 AML patients and peripheral blood mononuclear cells (PBMNCs) from 20 controls was studied by Northern blot and reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Northern blot revealed the positive bands of 9.4 kb and 4.5 kb in 18 of 19 AML patients, and RT-PCR a 790 bp product in 11 of 14 AML patients. CONCLUSION: There was a specific expression of acute myeloid leukemia associated retrovirus in AML patients.

Adolescent↗

PubMed2001

[Effects of glutamine on the intestinal failure in rats model of acute necrotizing pancreatitis].

OBJECTIVE: To determine the effects of glutamine (Gln) on the intestinal failure in rats with acute necrotizing pancreatitis (ANP) and its possible mechanisms. METHODS: Fifty-four Sprague-Dawley rats were randomly divided into 3 groups: sham operation (SO, n = 18), ANP (n = 18), and ANP treated with Gln (ANP + Gln, n = 18). ANP model was induced by injection of 5% sodium taurocholate solution into bilo-pancreatic duct. The therapy was continuously given with amino acid solution by a mini-pump via a central intravenous line. In addition, the ANP + Gin group was received 3% Gln dipeptide solution (equal to 2% Gln) with a dosage of 0.5g x kg(-1) x d(-1). These groups were isocaloric and isonitrogenous. Bacterial cultures from pancreas, mesenteric lymph node (MLN), liver, spleen and ascites were done at 24, 48, 72 h after operation. Endotoxin level in portal vein was determined. Pathologic changes of intestinal mucosa were also studied. Apoptosis of intestinal mucosa was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method. Expressions of insulin-like growth factor 1 (IGF-1), Gln synthetase (GSase) and glutaminase (Glnase) mRNA were assayed by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: At 24, 48, 72h, the positive rate of bacterial culture and the endotoxin concentration were increased significantly in ANP group compared to the SO group (P < 0.05), while Gln could decrease them significantly. Pathologic study showed that the height of mucosal villous in ANP group was lower than that in SO group, indicating the intestinal mucosa became more atrophy. However, the height of mucosal villous in ANP + Gln group was no significantly difference compared to that in SO group, indicated Gln could preserve the mucosa well. Apoptotic index was increased in ANP group and decreased in Gln treated rats. Expressions of IGF-1, GSase, Glnase mRNA were down-regulated in ANP group, but were up-regulated in ANP + Gln group. CONCLUSIONS: The intestinal barrier function was impaired in ANP. Gln could protect intestinal barrier function. This action was probably related to its enhancement of IGF-1, GSase and Glnase mRNA expressions and its inhibition of intestinal mucosal apoptosis.

Animals↗

PubMed2000

Differential targeting of beta -adrenergic receptor subtypes and adenylyl cyclase to cardiomyocyte caveolae. A mechanism to functionally regulate the cAMP signaling pathway.

Differential modes for beta(1)- and beta(2)-adrenergic receptor (AR) regulation of adenylyl cyclase in cardiomyocytes is most consistent with spatial regulation in microdomains of the plasma membrane. This study examines whether caveolae represent specialized subdomains that concentrate and organize these moieties in cardiomyocytes. Caveolae from quiescent rat ventricular cardiomyocytes are highly enriched in beta(2)-ARs, Galpha(i), protein kinase A RIIalpha subunits, caveolin-3, and flotillins (caveolin functional homologues); beta(1)-ARs, m(2)-muscarinic cholinergic receptors, Galpha(s), and cardiac types V/VI adenylyl cyclase distribute between caveolae and other cell fractions, whereas protein kinase A RIalpha subunits, G protein-coupled receptor kinase-2, and clathrin are largely excluded from caveolae. Cell surface beta(2)-ARs localize to caveolae in cardiomyocytes and cardiac fibroblasts (with markedly different beta(2)-AR expression levels), indicating that the fidelity of beta(2)-AR targeting to caveolae is maintained over a physiologic range of beta(2)-AR expression. In cardiomyocytes, agonist stimulation leads to a marked decline in the abundance of beta(2)-ARs (but not beta(1)-ARs) in caveolae. Other studies show co-immunoprecipitation of cardiomyocytes adenylyl cyclase V/VI and caveolin-3, suggesting their in vivo association. However, caveolin is not required for adenylyl cyclase targeting to low density membranes, since adenylyl cyclase targets to low buoyant density membrane fractions of HEK cells that lack prototypical caveolins. Nevertheless, cholesterol depletion with cyclodextrin augments agonist-stimulated cAMP accumulation, indicating that caveolae function as negative regulators of cAMP accumulation. The inhibitory interaction between caveolae and the cAMP signaling pathway as well as domain-specific differences in the stoichiometry of individual elements in the beta-AR signaling cascade represent important modifiers of cAMP-dependent signaling in the heart.

Adenylyl Cyclases↗

PubMed2000

Methane emission from a simulated rice field ecosystem as influenced by hydroquinone and dicyandiamide.

A simple apparatus for collecting methane emission from a simulated rice field ecosystem was formed. With no wheat straw powder amended all treatments with inhibitor(s) had so much lower methane emission during rice growth than the treatment with urea alone (control), which was contrary to methane emission from the cut rice-soil system. Especially for treatments with dicyandiamide (DCD) and with DCD plus hydroquinone (HQ), the total amount of methane emission from the soil system and intact rice-soil system was 68.25-46.64% and 46.89-41.78% of the control, respectively. Hence, DCD, especially in combination with HQ, not only increased methane oxidation in the floodwater-soil interface following application of urea, but also significantly enhanced methane oxidation in rice root rhizosphere, particularly from its tillering to booting stage. Wheat straw powder incorporated into flooded surface layer soil significantly weakened the above-mentioned simulating effects. Regression analysis indicated that methane emission from the rice field ecosystem was related to the turnover of ammonium-N in flooded surface layer soil. Diminishing methane emissions from the rice field ecosystem was significantly beneficial to the growth of rice.

Agriculture↗

PubMed2000

Transglutaminase-3, an esophageal cancer-related gene.

Transglutaminase-3 (TGase-3) is an enzyme with the ability to catalyze the irreversible cross-linking of peptide-bound glutamine residues either with peptide-bound lysines or with primary amines. It has been implicated in the formation and assembly of the cornified cell envelope of the epidermis, hair follicle and perhaps other stratified squamous epithelia. We show here the involvement of TGase-3 in human esophageal cancer. In an initial study, mRNA differential display was performed with 3 pairs of esophageal cancer tissues and matched normal adjacent mucosa by a 10-mer arbitrary primer and mixed anchored primers (GT15N, N = A, C and G). Four differentially expressed cDNA bands were consistently observed in all 3 normal tissues but barely detected in their tumor counterparts. One of them was identified to be the 3; end of TGase-3. Northern blot and dot blot analyses of 14 samples confirmed the down-regulation of TGase-3 in malignant tissues compared with normal epithelia. RT-PCR revealed that TGase-3 expression was lost in 3 esophageal carcinoma cell lines and decreased in 35/38 tumors compared with adjacent normal mucosa. Taken together, 49/52 (94.2%) esophageal tumors presented down-regulation of the gene. Our data suggest that alteration of TGase-3 expression is a common event in the development of human esophageal cancer.

Adenocarcinoma↗

PubMed2000

Re(V) complexes with an open-chain quadridentate ligand containing two amine and two amido donors. Synthesis, characterization, and solution equilibria of Re2O3(dioxo-tetH4)2 and [ReO(H2O)(dioxo-tetH4)]Cl (dioxo-tetH6 = 1,4,8,11-tetraazaundecane-5,7-dione).

We are interested in identifying mononuclear cationic [M(V)=O]3+ (M = Tc, Re) complexes for radiopharmaceutical applications. The open-chain ligand, 1,4,8,11-tetraazaundecane-5,7-dione-(dioxo-tetH6) with two amine and two amide donors, was selected for investigation since the literature led us to expect that a five-coordinate [Re(V)=O(dioxo-tetH4)]+ cation would dominate. Instead, the neutral mu-oxo bridged dinuclear complex, Re2O3(dioxo-tetH4)2 (1), and a salt of the six-coordinate mononuclear cation, [ReO(H2O)(dioxo-tetH4)]+ (2), were isolated; the structure of each was determined by X-ray crystallography. The cation (2) is unusual because it has a trans-oxo/aqua core. Such aqua compounds are rarely isolated, and the Re-OH2 distance is relatively short (2.185 A). The cation has two pKa values, 4.1 and 8.7, determined with visible spectroscopy. Since the Re-OH2 bond is short, the coordinated water is likely to be acidic. Thus the two pKa's are assigned to the stepwise deprotonation of the water ligand to give a trans-oxo/hydroxo neutral form and a trans-dioxo anion. Although 1 was the first product isolated following ligand exchange of ReOCl3(Me2S)(OPPh3) with dioxo-tetH6 under neutral conditions, it probably formed from the hydroxo mononuclear complex. Under concentrated conditions (approximately 300 mM) the dinuclear complex deposited from solution, but the 1H NMR spectra of 2 (approximately 20 mM) were consistent with the presence of only monomeric forms in D2O, pH 3-12. 1H NMR experiments demonstrated that in DMSO-d6 2 converts to 1 upon addition of base, consistent with the proposal that two units of the hydroxo monomer condense to give the dinuclear form. In addition, all spectra of pure 1 dissolved in DMSO-d6 included extra low intensity signals that were characteristic of the monomer. Thus, although 1 is favored over the neutral monomer in DMSO-d6, the two complexes exist as a mixture of equilibrating forms. Our results do not support the previous findings for the Re(V) complex with a macrocyclic diamine-diamide ligand related to dioxo-tetH6. The data indicate that the ability of an amido group to donate electron density to a Re(V) center is moderately greater than the donating ability of a neutral amine group.

Amides↗

PubMed2000

Nature of cysteine-based Re(V)=O(N2S2) radiopharmaceuticals at physiological pH ascertained by investigation of a new complex with a meso N2S2 ligand having carboxyl groups anti to the oxo group.

X-ray structural characterization of a new isomer of ReO(TMECH3) revealed that it is anti-ReO(DL-TMECH3) (1). (DL-TMECH6 is meso-tetramethyl-ethylene-dicysteine prepared from racemic penicillamine (penH4), the subscript on H indicating the number of dissociable protons; anti denotes the geometric isomer having both carboxyl groups anti to the oxo ligand.) In 1, one carboxyl is deprotonated and coordinated trans to the oxo ligand, and the other is protonated and dangling. The 1H NMR spectrum (assigned by 2D methods) of 1 at pH 4 in aqueous solution revealed that the structure of 1 is the same as in the solid state except for deprotonation of the dangling carboxyl group, affording the monoanion. All chelate ring protons and methyl groups are inequivalent and give sharp signals. As the pH was raised above 7, the 1D 1H NMR signals of the monoanion broadened. Broadening was severe for the methyl and ethylene signals of the tridentate half of the monoanion, and these signals were replaced by new signals for the dianion. The changes suggested a rate process that was intermediate on the NMR time scale, such as CO2- ligation/deligation. With increasing pH the dianion signals sharpened up to pH approximately 8 and then broadened up to pH approximately 10. Finally, the spectrum at pH 10.8 showed only half the number of signals. Each signal was at the midpoint shift between two corresponding signals observed at lower pH, indicating a time averaging between the halves of the DL-TMEC ligand, but no change in protonation state. Two Re=O stretching bands (923 and 933 cm-1) with a constant intensity ratio of approximately 1 were observed for the dianion. These results can be explained if the dianion exists detectably only as a NH-deprotonated/carboxyl-deligated form having two conformers. The conformers differ in the N lone pair (NLp) orientation (either endo or exo with respect to the oxo ligand) and thus have slightly different Re=O stretching frequencies. Although they can be detected by resonance Raman spectroscopy, the conformers are indistinguishable by NMR spectroscopy because NLp inversion (and hence conformer interconversion) is very fast. Interchange of the NH and NLp sites affects the NMR spectra. At pH 8.3 the signals of the dianion are sharpest because interchange is slowest. Below and above pH 8.3, the signals are broader because acid and base catalysis, respectively, increase the rate of interchange between the NH and NLp sites.

Crystallography, X-Ray↗

PubMed2000

The smallest known non-avian theropod dinosaur.

Non-avian dinosaurs are mostly medium to large-sized animals, and to date all known mature specimens are larger than the most primitive bird, Archaeopteryx. Here we report on a new dromaeosaurid dinosaur, Microraptor zhaoianus gen. et sp. nov., from the Early Cretaceous Jiufotang Formation of Liaoning, China. This is the first mature non-avian dinosaur to be found that is smaller than Archaeopteryx, and it eliminates the size disparity between the earliest birds and their closest non-avian theropod relatives. The more bird-like teeth, the Rahonavis-like ischium and the small number of caudal vertebrae of Microraptor are unique among dromaeosaurids and improve our understanding of the morphological transition to birds. The nearly completely articulated foot shows features, such as distally positioned digit I, slender and recurved pedal claws, and elongated penultimate phalanges, that are comparable to those of arboreal birds. The discovery of these in non-avian theropods provides new insights for studying the palaeoecology of some bird-like theropod dinosaurs.

Animals↗