Biomedical subjects

Dan Wang

Publications and source records attributed to Dan Wang.

88 records · Page 5Linked to original sources

PubMed2003

Role of oxidative stress in endothelial dysfunction and enhanced responses to angiotensin II of afferent arterioles from rabbits infused with angiotensin II.

The hypothesis that O(2)(.-) enhances angiotensin II (AngII)-induced vasoconstriction and impairs acetylcholine-induced vasodilation of afferent arterioles (Aff) in AngII-induced hypertension was investigated. Rabbits (n = 6 per group) received 12 to 14 d of 0.154 M NaCl (Sham), subpressor AngII (60 ng/kg per min; AngII 60) or slow pressor AngII (200 ng/kg per min; AngII 200). Individual Aff were perfused in vitro at 60 mmHg. AngII 200 increased mean arterial pressure (mean +/- SD; 103 +/- 9 versus 73 +/- 6 mmHg; P < 0.01), plasma lipid peroxides (2.6 +/- 0.3 versus 2.0 +/- 0.3 nM; P < 0.05), renal cortical NADPH- and NADH-dependent O(2)(.-) generation, and Aff mRNA for p22(phox) 5-fold (P < 0.001) but decreased that for AT(1)-receptor 2.4-fold (P < 0.01). AngII 60 increased only NADH-dependent O(2)(.-) generation by renal cortex. Aff from AngII 200 rabbits had diminished acetylcholine relaxations (+50 +/- 4 versus +85 +/- 6%; P < 0.001), but these became similar in the presence of nitro-L-arginine (10(-4) M). Aff from AngII 60 and AngII 200 rabbits had unchanged norepinephrine contractions (10(-7) M) but significantly (P < 0.05) enhanced AngII contractions (10(-8) M: Sham -52 +/- 5 versus AngII 60 to 77 +/- 5 versus AngII 200 to 110 +/- 10%). The superoxide dismutase mimetic tempol (10(-4) M) moderated the AngII responses of Aff from AngII 200 rabbits to levels of AngII 60 rabbits (-64 +/- 7%). The AngII slow pressor response enhances renal cortical O(2)(.-) and p22(phox) expression. Increased O(2)(.-) generation in Aff mediates an impaired nitric oxide synthase-dependent endothelium-derived relaxing factor response and paradoxically enhances contractions to AngII despite downregulation of the mRNA for AT(1) receptors. A subpressor dose of AngII enhances Aff responses to AngII independent of O(2)(.-).

Afferent Pathways↗

PubMed2003

Syntaxin 1A inhibits GABA flux, efflux, and exchange mediated by the rat brain GABA transporter GAT1.

GABA transporters control extracellular GABA levels by coupling transmitter uptake to the sodium and chloride cotransport. The rat brain GABA transporter GAT1 and other members of this family are regulated by direct interactions with syntaxin 1A, a protein involved in vesicle docking and in the regulation of several ion channels and transporters. We have shown previously that syntaxin 1A exerts its effects on GAT1 by decreasing the net uptake of GABA and its associated ions through interactions with aspartic acid residues in the N-terminal tail of GAT1. This reduction in net uptake could be caused by many steps in the transport cycle, including substrate binding, substrate flux, substrate efflux, or reorientation of the unliganded transporter. To address this question, we performed GABA flux assays, measured flux- and efflux-associated ion currents, and assessed GABA exchange in multiple experimental systems expressing syntaxin 1A and wild-type GAT1 or GAT1 mutants. Syntaxin 1A caused similar reductions in forward and reverse transport that did not involve changes in apparent transport affinities for sodium, chloride, or GABA. The syntaxin 1A-mediated reduction in GABA flux and efflux was mimicked by mutations in GAT1 at the syntaxin 1A binding site. The binding site GAT1 mutant also caused a reduction in exchange. These data suggest that syntaxin 1A exerts its effects, directly or indirectly, on GAT1 function through interactions with GAT1's N-terminal tail and that the inhibition occurs at a step in the translocation process after substrate binding but which involves both unidirectional transport and transmitter exchange.

Animals↗

PubMed2003

The mouse RACK1 gene is regulated by nuclear factor-kappa B and contributes to cell survival.

Receptor for activated C kinase 1 (RACK1) is a multifunctional, WD motif-containing protein important in regulating several cell surface receptors and intracellular protein kinases. To better understand its function, we cloned the mouse RACK1 gene and found it contains eight exons and seven introns, and maps to mouse chromosome 11B1.2-1.3. Promoter analysis identified NF-kappaB as an important transcription factor for promoter activity. In PC-12 cells, nerve growth factor (NGF), which activates nuclear factor-kappaB (NF-kappaB), maintained RACK1 levels and promoted cell survival in serum-free medium. Inhibitors of NF-kappaB activation blocked NGF-stimulated survival and RACK1 expression, whereas transgenic expression of RACK1 promoted survival in cells deprived of serum and NGF. Thus, RACK1 gene expression is induced by NF-kappaB and RACK1 contributes to NF-kappaB-mediated cell survival.

Animals↗

PubMed2003

[Inhibitory effect of egg white lysozyme on ceftazidime-induced release of endotoxin from Pseudomonas aeruginosa].

AIM: To investigate the inhibitory effect of egg white lysozyme (LZM) on ceftazidime (CFT)-induced release of endotoxin from Pseudomonas aeruginosa. METHODS: P. aeruginosa PAO1 was inoculated in nutrition broth or diluted rabbit blood free of antibiotics in the presence or absence of LZM and incubated at 37 degrees C on a water bath shaker. beta-Lactam antibiotic, CFT, was added to cultures at 3.5 h (nutrition broth culture) or 5 h (diluted rabbit blood culture) after inoculation. After 3 h of CFT treatment, the supernatants from different bacterial cultures were prepared by centrifuge and the concentrations of endotoxin in the supernatants were measured. The bacterial supernatants were also added to a murine macrophage cell line RAW 264.7 or intravenously injected into carrageenin-sensitized mice. Tumor necrosis factor-alpha (TNF alpha) and nitric oxide (NO) concentrations in RAW 264.7 supernatants or in mouse sera were tested. RESULTS: CFT treatment alone obviously inhibited the growth of P. aeruginosa PAO1 accompanied by strong and rapid bacteriolysis and released relatively high concentration of endotoxin from bacteria both in nutrition broth and in diluted rabbit blood cultures. The bacterial supernatant from CFT treatment alone yielded high concentrations of TNF alpha both in RAW 264.7 cells and in mice and high level of NO in RAW 264.7 cells. Treatment with the combination of LZM and CFT evidently blocked the lysis of bacteria and reduced the release of endotoxin without decreasing bactericidal activity of CFT. TNF alpha and NO productivity of the supernatants prepared from the LZM/CFT combinative treated bacterial cultures were significantly decreased both in RAW 264.7 cells and in mice indicating that the inflammatory activity was reduced. CONCLUSION: LZM can effectively prevent CFT-induced bacteriolysis, endotoxin release and subsequent proinflammatory factor production but without decreasing bactericidal activity of CFT, resulting in the disassociation of bactericidal activity and bacteriolysis. Thus, LZM might be important for preventing endotoxemia in Gram-negative sepsis with the treatment of antibiotics.

Animals↗

PubMed2003

[Study on xylose fermentation by Neurospora crassa].

The influence of oxygen limitation and medium initial pH on xylose fermentation by Neurospora crassa AS 3.1602 was investigated. N. crassa AS 3.1602 has high ability of xylose fermentation producing ethanol and xylitol. Oxygen limitation has big influence on ethanol and xylitol production. The maximum conversion rate of ethanol was 63.2% obtained under semi-aerobic conditions. The maximum conversion rate of xylitol was 31.8% obtained under micro-aerobic conditions. Xylitol accumulation is behind the accumulation of ethanol. The optimal pH is 5.0 for ethanol fermentation, and 4.0 for xylitol fermentation, respectively. Xylose fermentation is greatly inhibited at high pH. The yields of ethanol and xylitol are greatly influenced by the initial concentration of xylose. The addition of glucose inhibits both the xylose utilization and the ethanol and xylitol production.

Culture Media↗

PubMed2002

Number, density, and surface/cytoplasmic distribution of GABA transporters at presynaptic structures of knock-in mice carrying GABA transporter subtype 1-green fluorescent protein fusions.

GABA transporter subtype 1 (GAT1) molecules were counted near GABAergic synapses, to a resolution of approximately 0.5 microm. Fusions between GAT1 and green fluorescent protein (GFP) were tested in heterologous expression systems, and a construct was selected that shows function, expression level, and trafficking similar to that of wild-type (WT) GAT1. A strain of knock-in mice was constructed that expresses this mGAT1-GFP fusion in place of the WT GAT1 gene. The pattern of fluorescence in brain slices agreed with previous immunocytochemical observations. [3H]GABA uptake, synaptic electrophysiology, and subcellular localization of the mGAT1-GFP construct were also compared with WT mice. Quantitative fluorescence microscopy was used to measure the density of mGAT1-GFP at presynaptic structures in CNS preparations from the knock-in mice. Fluorescence measurements were calibrated with transparent beads and gels that have known GFP densities. Surface biotinylation defined the fraction of transporters on the surface versus those in the nearby cytoplasm. The data show that the presynaptic boutons of GABAergic interneurons in cerebellum and hippocampus have a membrane density of 800-1300 GAT1 molecules per square micrometer, and the axons that connect boutons have a linear density of 640 GAT1 molecules per micrometer. A cerebellar basket cell bouton, a pinceau surrounding a Purkinje cell axon, and a cortical chandelier cell cartridge carry 9000, 7.8 million, and 430,000 GAT1 molecules, respectively; 61-63% of these molecules are on the surface membrane. In cultures from hippocampus, the set of fluorescent cells equals the set of GABAergic interneurons. Knock-in mice carrying GFP fusions of membrane proteins provide quantitative data required for understanding the details of synaptic transmission in living neurons.

Animals↗

PubMed2002

Conditional rescue of protein kinase C epsilon regulates ethanol preference and hypnotic sensitivity in adult mice.

Conventional gene targeting is a powerful tool to study the influence of specific genes on behavior. However, conclusions relevant for adult animals are limited by consequences of gene loss during development. Mice lacking protein kinase C epsilon (PKCepsilon) consume less alcohol and show greater acute sensitivity to alcohol than do wild-type mice. There are no selective inhibitors of PKCepsilon that can be administered systemically and cross the blood-brain barrier to test whether these phenotypes result from loss of PKCepsilon during development or in adulthood. Here we used conditional expression of PKCepsilon in the basal forebrain, amygdala, and cerebellum to rescue wild-type responses to alcohol in adult PKCepsilon(-/-) mice. Subsequent suppression of transgenic PKCepsilon restored PKCepsilon(-/-) behaviors. These findings establish that PKCepsilon signaling in the adult brain regulates alcohol consumption and sensitivity. If this extends to humans, then PKCepsilon inhibitors might prove useful as novel therapeutics for alcoholism.

Age Factors↗

PubMed2002

Simultaneous determination of fluoxetine and its metabolite p-trifluoromethylphenol in human liver microsomes using a gas chromatographic-electron-capture detection procedure.

An gas chromatography-electron-capture detection method has been developed for simultaneous determination of fluoxetine and p-trifluoromethylphenol (TFMP), an O-dealkylated metabolite of fluoxetine in human liver microsomes. Prior to the analysis, aliquots of alkalinized microsomal mixture were extracted with ethyl acetate solvent containing acetonitrile (10%, v/v) and the derivatizing reagent, pentafluorobenzenesulfonyl chloride (0.1%, v/v). The organ phase was retained and taken to dryness, the residue was reconstituted in methanol, and the aliquot of extracts was injected directly into a gas chromatograph equipped with an electron-capture detector. 2,4-Dichlorophenol was added to the initial incubation mixture and carried through the procedure as the internal standard. The method provided the mean recoveries of up to 103% for fluoxetine and 104% for TFMP. Acceptable relative standard deviations were found for both within-run and day-to-day assays. The practical limit of detection (signal-to-noise ratio=3) was 1.62 ng/ml for TFMP and 6.92 ng/ml for fluoxetine in human liver microsomes, and the limit of quantitation was 8.1 pg for TFMP and 34.6 pg for fluoxetine. The assay is rapid and sensitive and has been applied successfully to simultaneous quantification of fluoxetine and TFMP in human liver microsomes with different CYP2C19 genotypes.

Chromatography, Gas↗

PubMed2002

Analysis of the C314T and A595G mutations in histamine N-methyltransferase gene in a Chinese population.

BACKGROUND: Histamine N-methyltransferase (HNMT) plays an important role in the metabolism of histamine, a biogenic amine that has many physiologic and pathological roles in human tissues. A missense mutation C314T (Thr105Ile) in the HNMT gene has been identified to represent a common functional polymorphism in Caucasians, whereas an A595G (Ile199Val) variant has been reported in one HNMT cDNA from a Japanese subject. METHODS: By using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay, the point mutations C314T and A595G within HNMT were both detected in 352 unrelated Chinese Han subjects. RESULTS: None of the 352 subjects contained the A595G mutation, whereas 40 (11.6%) heterozygotes and 1 (0.3%) homozygote for the variant T314 allele were detected. The frequency of the variant T314 allele in this Chinese population was 0.060 (95% CI: 0.042-0.078), not different from Japanese but significantly lower than American Caucasians. CONCLUSIONS: The C314T mutation represents a common functional genetic polymorphism in the Chinese Han population with a variant T314 allele frequency similar to Japanese but lower than American Caucasians, whereas the A595G mutation does not appear to exist in this population.

Adult↗

PubMed2002

Development of human lymphohematopoiesis defined by CD34 and CD81 expression.

Human blood cells, except for erythrocytes and platelets, express CD81, a member of the transmembrane 4 superfamily (TM4SF). CD81 is also expressed on most of human immature hematopoietic cells, CD34+ cells, which are divided into three populations according to the expression of CD34 and CD81; CD34+CD81+, CD34+CD81(High) and CD34(Low)CD81+. Myeloid and lymphoid progenitors exist in the CD34+CD81+ population, and megakaryocytic progenitors are only in CD34(Low)CD81+ population. Erythroid and multipotential progenitors are shared by CD34+CD81+ and CD34(Low)CD81+ populations, but multipotential progenitors in the CD34+CD81+ population have already lost most of their myeloid potential. NK cells and mast cells can be generated from all three populations. Long-term repopulating (LTR) lymphohematopoietic stem cells are present in the CD34+CD81+ population. Based on these findings, we propose a model for the development of CD34+CD81+ lymphohematopoietic stem cells. Along the differentiation cascade from CD34+CD81+ lymphohematopoietic stem cells, there appear to be pathways to CD34(Low)CD81 + or CD34+CD81(High) cells, even if they are indirect. CD34(Low)CD81+ pathways define the loss of LTR ability, and lymphoid and myeloid potentials, whereas CD34+CD81(High) pathways represent the exclusive commitment to NK cells and mast cells.

Animals↗

PubMed2002

[Identification and tissue-specific expression of a full length cDNA encoding ZIP protein in Arabidopsis].

A full-length cDNA encoding a putative ZIP proteins, has been isolated from Arabidopsis cDNA library using a heterologous DNA probe. Sequence analysis showed that the deduced protein contained a leucine zipper and a possible nuclear localization signal domain. There was no identical proteins in the database we searched, but it shared high sequence homology with PNZIP from Pharbitis nil and two other open reading frames (ORF) of unknown function from Synechocystis spp and Porphyra purpurea. These together defined a new family of evolutionarily conserved leucine zipper proteins, which might play a role as a transcription factor in the regulation of gene expression. Southern and Northern blot analysis indicated that AT103 was a single copy gene and the accumulation of mRNA was obviously different in leaves, stems and roots in Arabidopsis.

Amino Acid Sequence↗

PubMed2002

Genotype of CYP3AP1 associated with CYP3A activity in Chinese Han population.

AIM: To investigate the distribution of genotype of CYP3AP1 in Chinese Han population and the correlation with CYP3A activity. METHODS: Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was employed in CYP3AP1 genotype analysis; using midazolam as probe drug, CYP3A activity of 191 Chinese healthy subjects was measured by plasma 1'-hydroxymidazolam/midazolam (1'-OH-MDZ/MDZ) ratio at 1 h after oral administration of 7.5 mg midazolam. RESULTS: There was significant difference of CYP3A activity in different genotypes of CYP3AP1 in vivo (P <0.05). The activity of CYP3A in homozygous A(-44) (CYP3AP1*3/CYP3AP1*3) is lower than heterozygous A(-44)G (CYP3AP1*1/CYP3AP1*3), and the CYP3A activity in homozygous G(-44) (CYP3AP1*1/CYP3AP1*1) is t he highest. CONCLUSION: There was association between the genotype of CYP3AP1 and increased activity of CYP3A in vivo.

Adolescent↗

PubMed2002

[Nitrification of high concentration NH4(+)-N in membrane bioreactor].

Nitrification performance of a membrane bioreactor was investigated under high concentration of NH4(+)-N. The removal rate of NH4(+)-N was over 99% under the condition of influent NH4(+)-N of 2000 mg/L and volumetric loading rate of NH4(+)-N 2.0 kg/(m3.d). The specific nitrification rate was kept to be 0.36/d in a period of half year.

Ammonia↗

PubMed2002

[Major, minor and trace-elemental contents analysis in northeast soybeans by ICP-AES].

Major, minor and trace elemental contents in northeast China soybeans were determined by using inductively coupled plasma atomic emission spectrometry (ICP-AES). Three different sample digestion methods including two wet digestions, HNO3-HClO4 and HNO3-H2SO4 and a dry ash method were compared. Owing to the high oil content in soybeans, long time is needed and access acid should be added with mixed acid digestion methods, which may result in higher sample blank. Therefore, the dry ask method would be more proper for the pre-treatment of soybean samples. Potassium and phosphorus are major elements in soybeans, so the effect of potassium and phosphorus on the other elements was investigated. Results showed that the potassium and phosphorus did not affect the determination of other trace elements. There are not significant differences in trace elemental contents for the eleven northeast China soybeans.

Copper↗

PubMed2000

Endothelium-dependent relaxation of small resistance vessels is impaired in patients with autosomal dominant polycystic kidney disease.

Impaired endothelium-dependent relaxation has been demonstrated previously in resistance vessels of Han:SPRD polycystic kidney disease rats. The aim of the present study was to investigate whether endothelium-dependent relaxation is reduced also in patients with autosomal dominant polycystic kidney disease (ADPKD) and whether this is influenced by the nitric oxide (NO) system. Small subcutaneous resistance vessels from normotensive ADPKD patients with normal or near-normal renal function (n = 9) and from healthy control subjects (n = 10) were mounted in a Mulvany-Halpern myograph. The morphology of the vessels and acetylcholine (ACh)-induced endothelium-dependent relaxation, as well as 3-morpholino-sydnonimine (SIN-1, NO donor)-induced endothelium-independent relaxation were investigated. The results showed that: (1) there were no significant differences in morphologic parameters of resistance vessels between the two groups; (2) the maximal ACh-induced relaxation rate was decreased in ADPKD patients compared with control subjects (71.5 +/- 12.1 versus 85.2 +/- 8.7%, P < 0.01); (3) in the presence of L-arginine (a substrate of NO synthase), a left shift of the ACh dose-response curves was found in control subjects, but not in ADPKD patients; (4) in the presence of the N(G)-nitro-L-arginine methyl ester (an inhibitor of NO synthase), a right shift of the ACh dose-response curve was found in control subjects, but not in ADPKD patients; and (5) endothelium-independent relaxation rate induced with SIN-1 was similar in patients and control subjects. In conclusion, endothelium-dependent relaxation was impaired in resistance vessels from patients with ADPKD. The reduced response of the vessels to both the substrate and inhibitor of NO synthase in ADPKD suggests that an impairment of NO synthase may be involved in the mechanism of endothelial dysfunction in ADPKD.

Acetylcholine↗

PubMed1999

Preparation and assessment of heterotopic osteoinduction of beta-TCP/rhBMP-2 composite.

OBJECTIVE: To search for ideal bone graft substitute. METHODS: The beta TCP/rhBMP-2 composite was constructed by combining beta-Tricalcium phosphat (beta-TCP) that was prepared by the authors with recombinant human morphogenetic protein-2 (rhBMP-2) and was implanted into the muscle pouches in the thigh of mice. beta-TCP alone was implanted on the opposite side as controls. At intervals of 1,3,7,14 and 28 days after the implantation, the specimens were obtained, and histologic study and alkaline phosphatase assay (7,14,28 days) were performed. RESULTS: There was a large amount of cartilage and bone formation within the composite, increasing with time; whereas there was no new bone formation where beta-TCP alone was implanted. Besides, the levels of alkaline phosphatase in the beta-TCP/rhBMP-2 implants also were increasing with time and were higher than those in controls. CONCLUSIONS: The results indicate that beta-TCP/rhBMP-2 composite possesses heterotopic osteoinductive potential.

Journal Article↗