Biomedical subjects

W Xie

Publications and source records attributed to W Xie.

At least 73 records · Page 4Linked to original sources

PubMed2000

Antioxidant property of pramipexole independent of dopamine receptor activation in neuroprotection.

Pramipexole and several other dopamine agonists have been recently demonstrated to have neuroprotective effects in vitro and in vivo. We report here that pramipexole can protect DAergic cell line MES 23.5 against dopamine (DA), 6-hydroxydopamine (6-OHDA), and hydrogen peroxide (H2O2)-induced cytotoxicity in vitro possibly through antioxidant effects, and such neuroprotection could not be blocked by selective D2 or D3 antagonists. Incubation with pramipexole (5-20 microM) in MES 23.5 cell cultures increased cellular levels of glutathione (GSH), and elevated glutathione peroxidase (GSH-Px) and catalase activities, but only marginally enhanced SOD activity. Pretreatment with D2 or D3 antagonists did not block the stimulating effects of pramipexole on the cellular levels of GSH, and on the activities of GSH-Px and catalase in MES 23.5 cells. These results indicate that pramipexole's neuroprotective effects are likely associated with its antioxidant property independent of D2/D3 receptor activation.

Animals↗

PubMed2000

3Beta-hydroxy-6-aza-cholestane and related analogues as phosphatidylinositol specific phospholipase C (PI-PLC) inhibitors with antitumor activity.

6-Aza steroid analogues were synthesized as PI-PLC inhibitors. The most active compound, 3beta-hydroxy-6-aza-cholestane (1) showed potent PI-PLC inhibition (IC50 = 1.8 microM), similar to that of the commercially available steroid analogue U73122 (IC50 = 1-2.1 microM). Compound 1 exhibited significant growth inhibition effects (IC50 = 1.3 microM in each case) against MCF-7 and HT-29 cancer cells in in vitro cell culture. Compound 1 also inhibited the in vitro adhesion and transmigration of HT-1080 fibrosarcoma cells at 2.5 and 5.0 microM, respectively. In vivo, compound 1, at 1 mg/kg/day, reduced the volume of MCF-7 tumors in xenograft models, without weight loss in mice. Structure activity relationships of this series of compounds revealed that a hydrophobic cholesteryl side chain, 3beta-hydroxy group and a C-6 nitrogen containing a hydrogen atom at position-6 are crucial for activity. N-Maleic amidoacid derivative 11 also exhibited weak inhibition (IC50 = 16.2 microM).

Animals↗

PubMed2000

Steroidal derived acids as inhibitors of human Cdc25A protein phosphatase.

A group of steroidal derived acids were synthesized and found to be human Cdc25A inhibitors. Their potency ranged from 1.1 to > 100 microM; the best ones compare very favorably with that of the novel cyano-containing 5,6-seco-cholesteryl acid 1 (IC50=2.2microM) reported by us recently (Peng, H.; Zalkow, L. H.; Abraham, R. T.; Powis, G. J. Med. Chem. 1998, 41, 4677). Structure-activity relationships of these compounds revealed that a hydrophobic cholesteryl side chain and a free carboxyl group are crucial for activity. The distance between these two pharmacophores is also important for the potency of these compounds. Several of the compounds showed selective growth inhibition effects in the NCI in vitro cancer cell line panel.

Acids↗

PubMed2000

Automated in-tube solid phase microextraction coupled with HPLC-ES-MS for the determination of catechins and caffeine in tea.

A polypyrrole (PPY) coated capillary and several commercially available capillaries (capillary GC columns) were used to evaluate their extraction efficiencies for catechins and caffeine. Compared with commercial capillaries that were currently used for in-tube solid phase microextraction (SPME), the PPY coated capillary showed better extraction efficiency for all of the compounds studied. Electrospray mass spectrometric (ES-MS) detection conditions were also investigated. After optimization of the extraction and detection conditions, a method for the sensitive and selective determination of catechins and caffeine was developed by coupling the PPY coated capillary in-tube SPME with HPLC-ES-MS. Catechins could be determined in both positive and negative ion detection modes. The detection limit (S/N = 3) for each of the studied catechins was < 0.5 ng mL-1. Caffeine could only be determined under positive ES-MS detection conditions and its detection limit was 0.01 ng mL-1. Caffeine and the five catechins in several tea samples were determined using the developed method. Small amounts of catechins were also detected in grape juice and wine samples.

Caffeine↗

PubMed2000

Abundant tissue butyrylcholinesterase and its possible function in the acetylcholinesterase knockout mouse.

We have described recently an acetylcholinesterase (AChE) knockout mouse. While comparing the tissue distribution of AChE and butyrylcholinesterase (BChE), we found that extraction buffers containing Triton X-100 strongly inhibited mouse BChE activity. In contrast, buffers with Tween 20 caused no inhibition of BChE. Conventional techniques grossly underestimated BChE activity by up to 15-fold. In Tween 20 buffer, the intestine, serum, lung, liver, and heart had higher BChE than AChE activity. Only brain had higher AChE than BChE activity in AChE +/+ mice. These findings contradict the dogma, based mainly on observations in Triton X-100 extracts, that BChE is a minor cholinesterase in animal tissues. AChE +/- mice had 50% of normal AChE activity and AChE -/- mice had none, but all mice had similar levels of BChE activity. BChE was inhibited by Triton X-100 in all species tested, except rat and chicken. Inhibition was reversible and competitive with substrate binding. The active site of rat BChE was unique, having an arginine in place of leucine at position 286 (human BChE numbering) in the acyl-binding pocket of the active site, thus explaining the lack of inhibition of rat BChE by Triton X-100. The generally high levels of BChE activity in tissues, including the motor endplate, and the observation that mice live without AChE, suggest that BChE has an essential function in nullizygous mice and probably in wild-type mice as well.

Acetylcholinesterase↗

PubMed2000

A previously unrecognized H-2D(b)-restricted peptide prominent in the primary influenza A virus-specific CD8(+) T-cell response is much less apparent following secondary challenge.

Respiratory challenge of H-2(b) mice with an H3N2 influenza A virus causes an acute, transient pneumonitis characterized by the massive infiltration of CD8(+) T lymphocytes. The inflammatory process monitored by quantitative analysis of lymphocyte populations recovered by bronchoalveolar lavage is greatly enhanced by prior exposure to an H1N1 virus, with the recall of cross-reactive CD8(+)-T-cell memory leading to more rapid clearance of the infection from the lungs. The predominant epitope recognized by the influenza virus-specific CD8(+) set has long been thought to be a nucleoprotein (NP(366-374)) presented by H-2D(b) (D(b)NP(366)). This continues to be true for the secondary H3N2-->H1N1 challenge but can no longer be considered the case for the primary response to either virus. Quantitative analysis based on intracellular staining for gamma interferon has shown that the polymerase 2 protein (PA(224-233)) provides a previously undetected epitope (D(b)PA(224)) that is at least as prominent as D(b)NP(366) during the first 10 days following primary exposure to either the H3N2 or H1N1 virus. The response to D(b)NP(366) seems to continue for longer, even when infectious virus can no longer be detected, but there is no obvious difference in the prevalence of memory T cells specific for D(b)NP(366) and D(b)PA(224). The generalization that the magnitude of the functional memory T-cell pool is a direct consequence of the clonal burst size during the primary response may no longer be useful. Previous CD8(+)-T-cell immunodominance heirarchies defined largely by cytotoxic T-lymphocyte assays may need to be revised.

Amino Acid Sequence↗

PubMed2000

Transcriptional activation of thymidylate synthase by 17beta-estradiol in MCF-7 human breast cancer cells.

Thymidylate synthase (TS) catalyzes methylation of deoxyuridine phosphate to give deoxythymidine phosphate, and 17beta-estradiol (E2) induces TS gene expression in MCF-7 human breast cancer cells. Analysis of the TS gene promoter showed that E2-responsiveness required the -229 to -140 promoter region containing a G-rich sequence and CACCC box. Subsequent mutational analysis of this region indicated that only the G-rich motif (-150 to -142) was required for E2 action. Results of gel mobility shift and in vitro DNA footprinting assays showed that both estrogen receptor alpha (ERalpha) and Sp1 proteins were required for hormone-induced trans-activation that involved ERalpha/Sp1 binding to the G-rich site in which only Sp1 protein bound DNA. Both proteins also interacted in Drosophila cells in functional assays, confirming the transcriptional activation of TS-involved ERalpha/Sp1, and this adds to the increasing number of genes that are activated through this pathway in breast cancer cells.

Animals↗

PubMed2000

Toxigenic strains of Fusarium moniliforme and Fusarium proliferatum isolated from dairy cattle feed produce fumonisins, moniliformin and a new C21H38N2O6 metabolite phytotoxic to Lemna minor L.

Corn samples suspected of causing refusal-to-eat syndrome in dairy cattle were examined mycologically. Fusarium moniliforme (14 isolates) and F. proliferatum (12 isolates) were the predominant fungi present. These isolates were tested for mycotoxin production on rice at 25 degrees C. Each strain of F. moniliforme produced fumonisin B1 (FB1: 378-15,600 ppm) and fumonisin B2 (FB2: 2-1050 ppm). Each strain of F. proliferatum produced moniliformin (45-16,000 ppm), FB1 (27-6140 ppm), and FB2 (5-1550 ppm). In addition, a new Fusarium metabolite of molecular composition C21H38N2O6 was produced by 10 of the F. moniliforme isolates and 7 of the F. proliferatum isolates. The metabolite's 1H- and 13C-NMR, HRFAB/MS and IR spectra indicate an alpha amino acid. It is toxic to Lemna minor L. duckweed (LD50 100 micrograms/mL).

Animal Feed↗

PubMed2000

Postnatal developmental delay and supersensitivity to organophosphate in gene-targeted mice lacking acetylcholinesterase.

Acetylcholinesterase (AChE; EC 3.1.1.7) is the primary terminator of nerve impulse transmission at cholinergic synapses and is believed to play an important role in neural development. Targeted deletion of four exons of the ACHE gene reduced AChE activity by half in heterozygous mutant mice and totally eliminated AChE activity in nullizygous animals. Butyrylcholinesterase (EC 3.1.1.8) activity was normal in AChE -/- mice. Although nullizygous mice were born alive and lived up to 21 days, physical development was delayed. The neuromuscular junction of 12-day-old nullizygous animals appeared normal in structure. Nullizygous mice were highly sensitive to the toxic effects of the organophosphate diisopropylfluorophosphate and to the butyrylcholinesterase-specific inhibitor bambuterol. These findings indicate that butyrylcholinesterase and possibly other enzymes are capable of compensating for some functions of AChE and that the inhibition of targets other than AChE by organophosphorus agents results in death.

Acetylcholinesterase↗

PubMed2000

[Fusion expression of cecropin X including the cleavage of FXa in Escherichia coli].

PCR method was used to introduce the code sequence of Factor Xa cleavage site to the 5' end of cecropin CMIV mutant gene X, then the gene was cloned into the expression vector pGEX-KG, and was highly expressed in E. coli BL21 by IPTG induction. The fusion protein was purified by affinity-chromatography and was cleaved by Factor Xa. Cecropin X with antibacterial activity was obtained after purified by ion-exchange chromatography.

Antimicrobial Cationic Peptides↗

PubMed2000

[Clinical application of combined acupuncture-drug anesthesia with isoflurane-induced hypotension in cerebral operation].

OBJECTIVE: To evaluate the feasibility of combined acupuncture-isoflurane anesthesia with deliberated and controlled hypotension induced by isoflurane for the neurosurgical patients. METHODS: Forty-two patients with brain tumor scheduled for selective surgery according to the methods of anesthesia, they were further divided into isoflurane anesthesia (group I, n = 21) and combined acupuncture-isoflurane anesthesia (group II, n = 21). Anesthesia was induced with fentanyl, sodium pentothal and phi avolon intravenously administered. The concentration of isoflurane was elevated to reduce mean arterial pressure (MAP) 30%-40% during dissection and occlusion of the tumor. Compare with the hemodynamic parameters (CO, CI, SV, SI, SVR, LVSWI, RPP) which were measured with Swan-Ganz technique before, during and after isoflurane-induced hypotension. In group II, during tracheal intubation the acupoint of Quanliano (SI 18), Yuyao (EX-HN4), Fengchi (GB 20) and Hegu (LI 4) were stimulated by Han's Acupoint Nerve Stimulator. Meanwhile, the isoflurane was inhalated to maintain anesthesia. RESULTS: As compared with group I, concentration of isoflurane decreased significantly, and isoflurane average dosage per hour reduced by 31%-42% in group II. SVR, PVR, RPP were significantly decreased in the duration of hypotension (P < 0.05). The range change of CO, CI, SV, SI, LVSWI, RPP during controlled hypotension was significantly lower in combined acupuncture-isoflurane anesthesia than that in isoflurane anesthesia (P < 0.05). CONCLUSION: Combined acupuncture-isoflurane anesthesia with isoflurane induced hypotension was used as a selective way for deliberated and controlled hypotension to the neurosurgical patients.

Acupuncture Analgesia↗

PubMed2000

[The role of ozone solution on debridement and sterilization of burn wound].

OBJECTIVE: To observe the role of ozone solution on debridement and sterilization of burn wound. METHODS: In vitro sterilizing effect on common isolated bacteria from burn wound and debridement and sterilization effects on burn wound of ozone disinfectant (ozone solution) were studied. RESULTS: All the bacteria tested were killed in vitro by ozone solution. In addition, when ozone solution was applied on burn wound, its clearance rate of bacteria was 94.5% and the clinical effective rate was 97.1%. CONCLUSION: Ozone is low in cost and high in effect which might be used as an agent for burn wound disinfection.

Adult↗

PubMed2000

[Antigen loading on dendritic cells affects the cell function in stimulating T cells].

OBJECTIVE: To study the effect of antigen loading on dendritic cells (DC). METHODS: DCs collected from peripheral blood monocytes were loaded with a tumor antigen from XG-7 cell line. These DCs were then co-cultured with allogeneic T cells and were compared with those DCs without antigen exposure. RESULTS: Although DCs showed no change in their phenotypes after cultured with the antigen, they secreted more IL-12, and became more powerful in allogenic mixed lymphocyte reaction (MLR). Antigen-loaded DC stimulated more CD(4)(+) cells to proliferate than nonantigen-loaded DCs did. These CD(4)(+) cells did not kill XG-7 cells, but promoted CD(8)(+) cells' ability to inhibit the XG-7 proliferation. CONCLUSION: The proliferation of CD(4)(+) cells after cultured with DC may become an indicator for the function of antigen loaded DC and for the efficiency of DC immunotherapy.

Antigens, Neoplasm↗

PubMed2000

[Preparation of monoclonal antibodies against malaria through immunization of mice with recombinant plasmid DNA].

BALB/c mice were immunized by injection of recombinant plasmid DNA carrying MSP1-31 fragment of Plasmodium falciparum. After antiserum was induced, McAbs were prepared by fusing SP2/0 myeloma cells with spleen cells. Specific McAbs were detected in hybridoma culture supernatant and mouse ascites by ELISA, positive hybridomas were cloned by technique of limiting dilutions. Two McAbs, 9H9 and 8A2, against the malaria protein were produced and characterized. The titers of the two McAbs in acites were 1:10,000 and 1:2500 respectively. The Ig subclass of these McAbs was IgG1. Western blot test showed that the McAb specifically reacted with MSP1-31 antigen. These results proved that monoclonal antibodies could be produced by use of immunization of mice with plasmid DNA or DNA vaccine.

Animals↗

PubMed2000

[Laser-time-resolved fluorescence spectroscopy in immunoassays].

This paper described a laser-excited time-resolved fluoroimmunoassay set. It made lanthanide ion to couple the anhydrde of diethylenetriaminepentaacetic acid (DTPAA) for labeling antibodies. The experiment used polystyrene tap coated with HCV antigen as the solid phase and a chelate of the rare earth metal europium as fluorescent label. A nitrogen laser beam was used to excite the Eu3- chelates and after 60 microseconds delay time, the emission fluorescence was measured. Background fluorescence of short lifetimes caused by serum components and Raman scattering can be eliminated by set the delay time. In the system condition, fluorescent spectra and fluorescent lifetimes of Eu3+ beta-naphthoyltrifluroacetone (NTA) chelates were measured. The fluorescent lifetime value is 650 microseconds. The maximum emission wavelength is 613 nm. The linear range of europium ion concentration is 1 x 10(-7)-1 x 10(-11) g.mL-1 and the detection limit is 1 x 10(-13) g.mL-1. The relative standard deviation of determination (n = 12) for samples at 0.01 ng.mL-1 magnitude is 6.4%. Laser-TRFIA was also found to be suitable for diagnosis of HCV. The sensitivity and specificity were comparable to enzyme immunoassay. The result was obtained with laser-TRFIA for 29 human correlated well with enzyme immunoassay.

Animals↗

PubMed1999

Up-regulation of liver glucose-6-phosphatase in rats fed with a P(i)-deficient diet.

Because P(i) deprivation markedly affects the Na/P(i) co-transporter in kidney and has been related to insulin resistance and glucose intolerance, the effect of a P(i)-deficient diet on the liver microsomal glucose-6-phosphatase (G6Pase) system was investigated. Rats were fed with a control diet (+P(i)) or a diet deficient in phosphate (-P(i)) for 2 days and killed on the morning of the third day, after an overnight fast (fasted) or not (fed). Kinetic parameters of P(i) transport (t((1/2)) and equilibration) into liver microsomes were not changed by the different nutritional conditions. In contrast, it was found that G6Pase activity was significantly increased in the (-P(i)) groups. This was due to an increase in the V(max) of the enzyme, without change in the K(m) for G6P. There was no correlation between liver microsomal glycogen content and G6Pase activity, but both protein abundance and mRNA of liver 36 kDa catalytic subunit of G6Pase (p36) were increased. The mRNA of the putative G6P translocase protein (p46) was changed in parallel with that of the catalytic subunit, but the p46 immunoreactive protein was unchanged. These findings indicate that dietary P(i) deficiency causes increased G6Pase activity by up-regulation of the expression of the 36 kDa-catalytic-subunit gene.

Animals↗

PubMed1999

Regulation of hormone-induced histone hyperacetylation and gene activation via acetylation of an acetylase.

Nuclear receptors have been postulated to regulate gene expression via their association with histone acetylase (HAT) or deacetylase complexes. We report that hormone induces dramatic hyperacetylation at endogenous target genes through the HAT activity of p300/CBP. Unexpectedly, this hyperacetylation is transient and coincides with attenuation of hormone-induced gene activation. In exploring the underlying mechanism, we found that the acetylase ACTR can be acetylated by p300/CBP. The acetylation neutralizes the positive charges of two lysine residues adjacent to the core LXXLL motif and disrupts the association of HAT coactivator complexes with promoter-bound estrogen receptors. These results provide strong in vivo evidence that histone acetylation plays a key role in hormone-induced gene activation and define cofactor acetylation as a novel regulatory mechanism in hormonal signaling.

Acetylation↗

PubMed1999

Genetic alteration of phospholipase C beta3 expression modulates behavioral and cellular responses to mu opioids.

Morphine and other micro opioids regulate a number of intracellular signaling pathways, including the one mediated by phospholipase C (PLC). By studying PLC beta3-deficient mice, we have established a strong link between PLC and mu opioid-mediated responses at both the behavioral and cellular levels. Mice lacking PLC beta3, when compared with the wild type, exhibited up to a 10-fold decrease in the ED(50) value for morphine in producing antinociception. The reduced ED(50) value was unlikely a result of changes in opioid receptor number or affinity because no differences were found in whole-brain B(max) and K(d) values for mu, kappa, and delta opioid receptors between wild-type and PLC beta3-null mice. We also found that opioid regulation of voltage-sensitive Ca(2+) channels in primary sensory neurons (dorsal root ganglion) was different between the two genotypes. Consistent with the behavioral findings, the specific mu agonist [D-Ala(2),(Me)Phe(4),Gly(ol)(5)]enkephalin (DAMGO) induced a greater whole-cell current reduction in a greater proportion of neurons isolated from the PLC beta3-null mice than from the wild type. In addition, reconstitution of recombinant PLC protein back into PLC beta3-deficient dorsal root ganglion neurons reduced DAMGO responses to those of wild-type neurons. In neurons of both genotypes, activation of protein kinase C with phorbol esters markedly reduced DAMGO-mediated Ca(2+) current reduction. These data demonstrate that PLC beta3 constitutes a significant pathway involved in negative modulation of mu opioid responses, perhaps via protein kinase C, and suggests the possibility that differences in opioid sensitivity among individuals could be, in part, because of genetic factors.

Animals↗