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Biomedical subjects

N Wu

Publications and source records attributed to N Wu.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Effects of intracerebroventricular administration of endomorphin-1 on blood pressure in anesthetized rats].

AIM: To observe the effects of intracerebroventricular administration of endomorphin-1 on blood pressure in anesthetized rats and to assess its mechanism. METHODS: Variations of mean arterial pressure (MAP) were observed after icv injection of endomorphine-1 in rats. The effects of i.v. or icv of various blockers, naloxone, phentolamine, propranolol, atropine and N omega-nitro-L-arginine, on the variation of MAP caused by endomorphin-1 were observed. RESULTS: Endomorphin-1 was shown to decrease MAP. The decrease in MAP was blocked by naloxone. Pretreatments with icv phentolamine and propranolol showed no effect on the vasodepression induced by icv endomorphin-1. However, pretreatment with icv atropine (25 micrograms.kg-1) attenuated the vasodepression. Pretreatments with i.v. phentolamine, propranolol and N omega-nitro-L-arginine showed no effect on the vasodepression induced by icv endomorphin-1. But, pretreatment with i.v. atropine (50 micrograms.kg-1) and bilateral vagotomy attenuated the vasodepression. CONCLUSION: Intracerebroventricular administration of endomorphin-1 produces vasodepressor response in anesthetized rats, which is mediated by opioid receptor. The vasodepression is associated with the central M cholinoceptor and the excitation of the vagus.

Anesthesia↗
PubMed2001

[Effects of endomorphins and their analogs on cardiovascular system].

AIM: To analyze the effects of endomorphins (EMs) and their analogs ([D-Pro2]EM-1, [D-Ala2]EM-1, [D-Pro2]EM-2 and [D-Ala2]EM-2) on the cardiovascular system of anestetized rats and to study its mechanism. METHODS: Responses to EMs and their analogs were investigated in the systemic vascular bed of rats and the mesenteric microarteria of Bufo gargarizans. Responses to EMs were investigated on the hindquarters of the rat vascular bed under constant-flow conditions and on the isolated rabbit thoracic aorta strips. RESULTS: The EMs and their analogs showed dose-related (10(-9)-10(-6) mol.L-1, i.v.) and naloxone-sensitive (2 mg.kg-1, i.v.) hypotension in mean arterial pressure of rats with similar duration and vasodilatation in mesenteric microarteria of Bufa gargarizans. The sequence of potencies was EMs > [D-Pro2] EM-2 > [D-Ala2]EM-2 > [D-Ala2]EM-1 > [D-Pro2]EM-1. EMs were shown not to relax the isolated rabbit thoracic aorta strips without endothelium. EMs, however, relaxed them with endothelium significantly. This action was blocked by Nx (10(-5) mol.L-1) and L-NNA (10(-4) mol.L-1). CONCLUSION: The significant hypotensive activity of EMs and their analogs is mainly associated with their vasodilatation, which is related to the release of NO from vascular endothelium, and their potency is not completely related to their affinity for mu-opiate receptor.

Animals↗
PubMed2000

Fast gas chromatography: packed column solvating gas chromatography versus open tubular column gas chromatography.

Packed capillary column solvating gas chromatography (SGC) and open tubular column gas chromatography (GC) were compared with respect to their potentials for fast separations. A recently introduced "universal" peak capacity equation was used to compare the performance of these two methods. The effects of various factors on peak capacity were investigated. Results demonstrate that retention factor and column efficiency are the main factors affecting peak capacity for fast separations. Packed columns produce both high retention factors and high selectivities. While high efficiencies and high peak capacities can be demonstrated by both techniques, open tubular column GC can surpass packed capillary column SGC in both measurements, except for the case of the analysis of simple mixtures in short analysis times, where retention factor and selectivity become important. Practical aspects such as pressure drop and sample capacity are compared for SGC and open tubular column GC. It was found that packed column SGC demonstrates higher sample capacities, but requires much higher column inlet pressures than open tubular column GC. A variety of mobile phases can be used for packed column SGC, which can provide high solvating power for large and polar compounds.

Chromatography, Gas↗
PubMed2000

Electrostatic stress in catalysis: structure and mechanism of the enzyme orotidine monophosphate decarboxylase.

Orotidine 5'-monophosphate decarboxylase catalyzes the conversion of orotidine 5'-monophosphate to uridine 5'-monophosphate, the last step in biosynthesis of pyrimidine nucleotides. As part of a Structural Genomics Initiative, the crystal structures of the ligand-free and the6-azauridine 5'-monophosphate-complexed forms have been determined at 1.8 and 1.5 A, respectively. The protein assumes a TIM-barrel fold with one side of the barrel closed off and the other side binding the inhibitor. A unique array of alternating charges (Lys-Asp-Lys-Asp) in the active site prompted us to apply quantum mechanical and molecular dynamics calculations to analyze the relative contributions of ground state destabilization and transition state stabilization to catalysis. The remarkable catalytic power of orotidine 5'-monophosphate decarboxylase is almost exclusively achieved via destabilization of the reactive part of the substrate, which is compensated for by strong binding of the phosphate and ribose groups. The computational results are consistent with a catalytic mechanism that is characterized by Jencks's Circe effect.

Amino Acid Sequence↗
PubMed2000

Production of viral vectors for gene therapy applications.

Advances in cell culture engineering, cell metabolism, bioreactor design and operation, and downstream processing will all positively impact the bioprocessing of viral vectors. Design of appropriate vectors and tailoring of packaging cells to support more productive infections will be of paramount importance for production of high-titer and high-quality vectors. Furthermore, quantitative analysis of the infection parameters during virus propagation, such as time of infection, multiplicity of infection, the length of replication cycle, virus half-life, and burst size, will also be important to the process optimization. Finally, procedures for separation, purification and formulation of vector preparations have to be further developed.

Adenoviridae↗
PubMed2000

Structural proteomics of an archaeon.

A set of 424 nonmembrane proteins from Methanobacterium thermoautotrophicum were cloned, expressed and purified for structural studies. Of these, approximately 20% were found to be suitable candidates for X-ray crystallographic or NMR spectroscopic analysis without further optimization of conditions, providing an estimate of the number of the most accessible structural targets in the proteome. A retrospective analysis of the experimental behavior of these proteins suggested some simple relations between sequence and solubility, implying that data bases of protein properties will be useful in optimizing high throughput strategies. Of the first 10 structures determined, several provided clues to biochemical functions that were not detectable from sequence analysis, and in many cases these putative functions could be readily confirmed by biochemical methods. This demonstrates that structural proteomics is feasible and can play a central role in functional genomics.

Cloning, Molecular↗
PubMed2000

Purification, crystallization and preliminary X-ray study of orotidine 5'-monophosphate decarboxylase.

Orotidine-5'-monophosphate decarboxylase (ODCase) from Methanobacterium thermoautotrophicum has been crystallized with and without the inhibitor 6-azaUMP by the vapour-diffusion method. In the absence of the inhibitor, the protein crystallizes in space group P4(1)2(1)2 (unit-cell parameters a = b = 56.9, c = 124.5 A) with one molecule per asymmetric unit; the crystals diffract to 1.8 A resolution. In the presence of the inhibitor, the protein crystals are monoclinic, space group P2(1) (unit-cell parameters a = 73.0, b = 98.6, c = 73.3 A, gamma = 104.0 degrees ), with four molecules in the asymmetric unit; the crystals diffract to 1.5 A resolution.

Base Sequence↗
PubMed2000

[The serologic study on the blood transmission origin of HIV].

OBJECTIVE: To study the origin of HIV blood spread in China. METHODS: Markers of HBV and HCV in 62 HIV - infections sera (27 blood donors and 35 i.v. drug users) were detected by EIA. RESULTS: The results show that the total HBV infection was 53.2% (33/62) and anti - HCV positive 95.2% (59/62). Super - infection of HIV, HBV, HCV was 51.6% (32/60) and super - infection of HIV, HCV and HIV, HBV were 27.4% (17/62) and 1.6% (1/62). Comparing the markers of HBV and anti - HCV between blood donors and i.v. drug users, there was no statistical significant difference (P > 0.05). The super - infection of HIV, HBV, HCV and HIV, HCV and HIV, HBV were also no statistical differences (P > 0.05) between two groups. CONCLUSION: Results indicated that a common infection mechanism might exist between Chinese HIV - infection blood donors and i.v. drug users.

Blood Donors↗
PubMed2000

[The regulation of vitamin D3 and 9-cis-retinoic acid and their receptors on human hsp90 beta gene].

OBJECTIVE: To study the effects of vitamin D3(VD3), 9-cis-retinoic acid (9-cis-RA) and their receptors on the regulation of human hsp90 beta gene. METHODS: We first transfected Jurkat cells with "full length" (-1,039 bp/+1,531 bp) hsp90 beta reporter plasmid beta 1.11, then the transfected cells were treated with VD3 or/and 9-cis-RA; or beta 1.11 was cotransfected with wild type vitamin D3 receptor (VDR) or/and retinoid X receptor (RXR) expression construction and the reporter activities were assayed. Western blot was carried out to detect the protein level of hsp90 beta in the Jurkat cells that were transfected by VDR cDNA or treated with VD3 or/and 9-cis-RA. By electrophoresis mobility shift assay (EMSA), we evaluated the DNA binding activity of VDR and RXR in Jurkat cell nuclear extracts. RESULTS: With VD3 or/and 9-cis-RA treatment, the expression of hsp90 beta gene was slightly increased. The induction became prominent when both of the ligands were present. The unliganded VDR or RXR alpha all slightly repressed the constitutive expression of hsp90 beta gene, while overexpression of VDR and RXR alpha further inhibited the gene. In addition, EMSA results showed that unliganded VDR and RXR simultaneously bound to the vitamin D3 response element (VDRE) of hsp90 beta gene. CONCLUSIONS: These results suggest that VD3/VDR and 9-cis-RA/RXR co-participate in the regulation of hsp90 beta gene in Jurkat cells.

Cholecalciferol↗
PubMed2000

[The role of MAPK pathways in hsp90 genes expression].

OBJECTIVE: To study the effect of mitogen-activated protein kinase (MAPK) pathways on hsp90 genes expression in Jurkat cells. METHODS: Firstly, the phosphorylation of extracellular signal-regulated protein kinase (ERK), p38 kinase and c-Jun in Jurkat cells were detected by using Western blotting-enhanced chemically lightening (ECL) system. Secondly, Jurkat cells were transfected transiently with c-Jun N-terminal kinase (JNK) dominant negative plasmid, DN-JNK1, p38 cDNA antisense plasmid, anti-p38, respectively or incubated in the present of PD98059, specific inhibitor of ERK kinase. Then the constitutive and heat-induced mRNA levels of hsp90 alpha and hsp90 beta in these cells were determined quantitatively by competitive RT-PCR. The relative mRNA level of hsp90 was compared with those in the cells transfected with mock vector (pCDNA3) or untreated cells respectively. RESULTS: In the Jurkat cells treated at 45 degrees C for 15 min, the phosphorylation of c-Jun and p38 kinase enhanced obviously, whereas the phosphorylation of ERK increased at certain degree as compared with control. Both constitutive and heat-induced expression of hsp90 genes decreased in the Jurkat cells transfected with DN-JNK1, especially for the heat-induced expression of hsp90 alpha gene which reduced to 68% of that of control. After transfected with anti-p38, the constitutive expression of hsp90 alpha gene and the heat-induced expression of hsp90 beta gene increased by 26% and 22% over the control. The constitutive expression of hsp90 alpha and hsp90 beta genes in the Jurkat cells treated with PD98059, increased to 46% and 16% of the control respectively, whereas the heat-induced expression of hsp90 genes did not change. CONCLUSIONS: Evidences showed that ERK signal pathway inhibited the constitutive expression of hsp90 genes in Jurkat cell. JNK pathway promoted both constitutive and heat-induced expression of hsp90 genes, whereas p38 pathway may not play an important role in the hsp90 genes expression.

Gene Expression↗
PubMed2000

[Studies on the stable integration and expression of IL-2R alpha gene in CHO cells and it's applications].

OBJECTIVES: To establish a novel bioassay method for quantitative analysis of human IL-2 based on the specific binding of Interleukin-2 receptor alpha subunit (IL-2R alpha) with IL-2. METHODS: Southern blot hybridization was first used to detect the stability of integration of recombinant secretive IL-2R alpha (rsIL-2R alpha) gene into the genome of highly expressed cell line reported elsewhere; the apparent Mr of the rsIL-2R alpha was then determined by using Western blotting; finally, a receptor-antibody sandwich ELISA method has been established for quantitative analysis of IL-2. RESULTS: (1) Stable integration of rsIL-2R alpha gene into the genome of #17 CHO cell line has been identified; (2) the apparent Mr of rsIL-2R alpha was approximately 40,000; (3) linear range of the standard curve obtained from the receptor-based ELISA fell between 31.25-500 U of IL-2 (r = 0.9995). The slop of the standard curve decreased significantly when IL-2 was pre-incubated with goat anti-IL-2 antibody IgG (P < 0.01). CONCLUSIONS: An IL-2R alpha-based IL-2 ELISA has been established for laboratory and clinical use with advantages of accuracy, specificity and simplicity over other conventional bioassays for IL-2 detection.

Animals↗
PubMed1999

T (Brachyury) is a direct target of Wnt3a during paraxial mesoderm specification.

Wnt3a encodes a signal that is expressed in the primitive streak of the gastrulating mouse embryo and is required for paraxial mesoderm development. In its absence cells adopt ectopic neural fates. Embryos lacking the T-box-containing transcription factors, Brachyury or Tbx6, also lack paraxial mesoderm. Here we show that Brachyury is specifically down-regulated in Wnt3a mutants in cells fated to form paraxial mesoderm. Transgenic analysis of the T promoter identifies T (Brachyury) as a direct transcriptional target of the Wnt signaling pathway. Our results suggest that Wnt3a, signaling via Brachyury, modulates a balance between mesodermal and neural cell fates during gastrulation.

Animals↗
PubMed1999

Dynamic Surface Tension Measurement with a Dynamic Wilhelmy Plate Technique.

An experimental method called dynamic Wilhelmy plate technique (DWPT) for studying dynamic surface tension was designed in this study. A diffusion-controlled model corresponding to the initial and boundary conditions of this method was proposed. Dynamic surface tension of Triton X-100 and SDS was measured with this technique and analyzed with the proposed model. The calculated diffusion coefficients for the short- and long-time approximations are 3.7 x 10(-6) and 0.97 x 10(-6) cm(2)/s for Triton X-100 and 4.6 x 10(-6) and 0.79 x 10(-6) cm(2)/s for SDS, respectively. The predicted dynamic surface tension with these diffusion coefficients for the simultaneously generated aqueous/air interfaces is in good agreement with the drop mass technique. Another diffusion controlled model that considers the energy barrier at the aqueous/air interface was also proposed in this study. The calculated energy barriers are in the range of 4.1-5.7 RT for Triton X-100 and 6.5-8.0 RT for SDS. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Vector engineering anomalies: impact on fusion protein purification performance.

Recombinant protein purification using IMAC is often carried out by protein fusion to affinity tags. We have identified several tags useful for protein purification on Zn(II)-IDA columns. These tags were fused to the green fluorescent protein (rGFPuv) using the vector pGFPuv distributed by Clontech Lab (Palo Alto, CA) and analyzed for purification on Zn(II)-IDA. Each fusion protein exhibited elution heterogeneity (elution in two distinct pHs) from Zn(II)-IDA columns This led us to believe that two populations of fluorescent proteins were being expressed: one without the tag coeluting with Escherichia coli proteins at pH 7.5 and one bearing the tag eluting at a pH lower than pH 7.5. Assessment of the constructs revealed the possibility of a ribosomal binding site and start codon between the fusion tag and the rGFPuv sequence which might be used as a secondary translation start site. This hypothesis was confirmed by changing the second ATG (methionine) codon to an ACG (threonine) codon. The protein produced from this new construct eluted in a single fraction from a Zn(II)-IDA column. Thus, vector irregularities (along with other possibilities) should be examined when searching for the cause of elution heterogeneity of a target protein.

Chromatography, Affinity↗
PubMed1999

Comparison between micellar electrokinetic chromatography and HPLC for the determination of Betamethasone Dipropionate, Clotrimazole and their related substances.

The complete separation of a composite mixture that consisted of Betamethasone Dipropionate (BMD), Clotrimazole and their derivatives in a pharmaceutical dosage form was achieved within 15 min using sodium dodecyl sulfate (SDS) micellar electrokinetic chromatography (MEKC). For the MEKC separations, electrophoretic media consisting of SDS-phosphate buffer and various concentrations of alcohols or acetonitrile were used. The optimal condition for separating BMD, Clotrimazole and their analogues was found to be 50 mM SDS-15% acetonitrile-5% butanol at pH 7.2. The results demonstrated that the method was valid for the quantitation of BMD, Clotrimazole and analogues with selectivity and precision comparable to that of High-Performance Liquid Chromatography (HPLC).

Administration, Topical↗
PubMed1999

Is ethanol an important antioxidant in alcoholic beverages associated with risk reduction of cataract and atherosclerosis?

It has been reported in the epidemiological literature that cataract, stroke, and atherosclerosis risk is reduced by 50% in people consuming one alcoholic drink per day. Peroxide has been implicated as a causative agent in cataractogenesis, and LDL oxidation appears to play a role in atherosclerosis. The antioxidant activity of alcohol was measured by: (i) use of a luminescent assay developed in our laboratory, confirmed as appropriate; (ii) electron spin resonance (ESR) spin-trapping; and (iii) copper-catalysed oxidation of LDL and VLDL from hamsters fed 6% ethanol in their drinking water. Ethanol reduced the luminescent counts/min from peroxide and superoxide. It significantly reduced the spin-trapped signal of hydroxyl radical, but not the superoxide signal. Other alcohols also showed large reductions in counts from hydrogen peroxide. Plasma from hamsters fed 6% ethanol had lower lipid peroxides and the oxidizability of LDL and VLDL was significantly reduced compared to controls. These data provide a possible explanation for the effect of beverages containing ethanol in the reduction of cataract and atherosclerosis risk observed in human population studies.

Alcohol Drinking↗