Biomedical subjects

H Xu

Publications and source records attributed to H Xu.

At least 163 records · Page 9Linked to original sources

PubMed2001

Genetic mapping and allelic loss analysis in mouse thymic lymphomas of Helios and Aiolos belonging to the Ikaros gene family.

The Ikaros gene undergoes bi-allelic changes at a high frequency in gamma-ray-induced mouse thymic lymphomas, suggesting the relevance of Ikaros to the lymphoma development. Here we test whether Helios and Aiolos, two other members of the Ikaros gene family, are also involved in lymphomagenesis. Genetic mapping showed that Helios is located between D1Mit531 and D1Mit19 on chromosome 1 and Aiolos is between D11Mit222 and D11Mit332 on chromosome 11. Analysis using polymorphic markers around the two regions revealed that neither locus exhibited allelic loss in the 78 lymphomas that were induced in p53 wild-type mice, whereas in 102 p53(KO / + ) mouse-derived lymphomas Helios and Aiolos loci showed allelic loss in 8% (8 / 102) and 33% (34 / 102), respectively. However, 33 of the 34 lymphomas showing allelic loss at Aiolos were p53(KO / - ) and were accompanied by loss of the p53 wild-type allele on the same chromosome. Homozygous deletion and mutation analyses failed to detect bi-allelic alterations. These results do not suggest any obvious contribution of Helios or Aiolos to oncogenesis of the mouse thymic lymphomas.

Animals↗

PubMed2001

Yaba-like disease virus: an alternative replicating poxvirus vector for cancer gene therapy.

Vaccinia virus is being investigated as a replicating vector for tumor-directed gene therapy. However, the majority of cancer patients have preformed immunologic reactivity against vaccinia virus, as a result of smallpox vaccination, which may limit its use as a vector. The Yaba-like disease (YLD) virus was investigated here as an alternative, replicating poxvirus for cancer gene therapy. We have demonstrated that the YLD virus does not cross-react with vaccinia virus antibodies, and it replicates efficiently in human tumor cells. YLD virus can be expanded and purified to high titer in CV-1 cells under conditions utilized for vaccinia virus. The YLD virus RNA polymerase was able to express genes regulated by a synthetic promoter designed for use in orthopoxviruses. We sequenced the YLD virus TK gene and created a shuttle plasmid, which allowed the recombination of the green fluorescent protein (GFP) gene into the YLD virus. In a murine model of ovarian cancer, up to 38% of cells in the tumor expressed the GFP transgene 12 days after intraperitoneal virus delivery. YLD virus has favorable characteristics as a vector for cancer gene therapy, and this potential should be explored further.

Animals↗

PubMed2001

RNA trafficking signals in human immunodeficiency virus type 1.

Intracellular trafficking of retroviral RNAs is a potential mechanism to target viral gene expression to specific regions of infected cells. Here we show that the human immunodeficiency virus type 1 (HIV-1) genome contains two sequences similar to the hnRNP A2 response element (A2RE), a cis-acting RNA trafficking sequence that binds to the trans-acting trafficking factor, hnRNP A2, and mediates a specific RNA trafficking pathway characterized extensively in oligodendrocytes. The two HIV-1 sequences, designated A2RE-1, within the major homology region of the gag gene, and A2RE-2, in a region of overlap between the vpr and tat genes, both bind to hnRNP A2 in vitro and are necessary and sufficient for RNA transport in oligodendrocytes in vivo. A single base change (A8G) in either sequence reduces hnRNP A2 binding and, in the case of A2RE-2, inhibits RNA transport. A2RE-mediated RNA transport is microtubule and hnRNP A2 dependent. Differentially labelled gag and vpr RNAs, containing A2RE-1 and A2RE-2, respectively, coassemble into the same RNA trafficking granules and are cotransported to the periphery of the cell. tat RNA, although it contains A2RE-2, is not transported as efficiently as vpr RNA. An A2RE/hnRNP A2-mediated trafficking pathway for HIV RNA is proposed, and the role of RNA trafficking in targeting HIV gene expression is discussed.

Animals↗

PubMed2001

Regulation of the human sodium-phosphate cotransporter NaP(i)-IIb gene promoter by epidermal growth factor.

The intestinal sodium-phosphate cotransporter (NaP(i)-IIb) plays a major role in intestinal P(i) absorption. Epidermal growth factor (EGF) is involved in the regulation of P(i) homeostasis. However, the role of EGF in intestinal NaP(i)-IIb regulation is not clear. The current studies showed that EGF decreased NaP(i)-IIb mRNA abundance by 40-50% in both rat intestine and Caco-2 cells. To understand the mechanism of this regulation, we cloned the human NaP(i)-IIb gene and promoter region and studied the effect of EGF on NaP(i)-IIb gene transcription. The human NaP(i)-IIb gene has 12 exons and 11 introns. Two transcription initiation sites were identified by primer extension. Additionally, 2.8 kb of the 5'-flanking region of the gene was characterized as a functional promoter in human intestinal (Caco-2) and human lung (A549) cells. Additional studies showed that EGF inhibited promoter activity by 40-50% in Caco-2 cells and that actinomycin D treatment abolished this inhibition. EGF had no effect on promoter activity in lung (A549) cells. We conclude that the human NaP(i)-IIb gene promoter is functional in Caco-2 and A549 cells and that the gene is responsive to EGF by a transcriptionally mediated mechanism in intestinal cells.

Animals↗

PubMed2001

Transcriptional regulation of rat Na(+)/H(+) exchanger isoform-2 (NHE-2) gene by Sp1 transcription factor.

The rat Na(+)/H(+) exchanger isoform-2 (NHE-2) gene promoter lacks a TATA box and is very GC rich. A minimal promoter extending from bp -36 to +116 directs high-level expression of NHE-2 in mouse inner medullary collecting duct (mIMCD-3) cells. Four Sp1 consensus elements were found in this region. The introduction of mutations within these Sp1 consensus elements and DNA footprinting revealed that only two of them were utilized and are critical for basal transcriptional activation in mIMCD-3 cells. The use of Sp1, Sp3, and Sp4 antisera in electrophoretic mobility shift assays demonstrated that Sp1, Sp3, and Sp4 bound to this minimal promoter. We further analyzed the transcriptional regulation of NHE-2 by members of the Sp1 multigene family. In Drosophila SL2 cells, which lack endogenous Sp1, the minimal promoter cannot drive transcription. Introduction of Sp1 activated transcription over 100-fold, suggesting that Sp1 is critical for transcriptional regulation. However, neither Sp3 nor Sp4 was able to activate transcription in these cells. Furthermore, in mIMCD-3 cells, Sp1-mediated transcriptional activation was repressed by expression of Sp3 and Sp4. These data suggest that Sp1 is critical for the basal promoter function of rat NHE-2 and that Sp3 and Sp4 may repress transcriptional activation by competing with Sp1 for binding to core cis-elements.

Animals↗

PubMed2001

Epidermal growth factor regulation of rat NHE2 gene expression.

Epidermal growth factor (EGF) is involved in acute regulation of Na(+)/H(+) exchangers (NHEs), but the effect of chronic EGF administration on NHE gene expression is unknown. The present studies showed that EGF treatment increased NHE2-mediated intestinal brush-border membrane vesicle Na(+) absorption and NHE2 mRNA abundance by nearly twofold in 19-day-old rats. However, no changes were observed in renal NHE2 mRNA or intestinal and renal NHE3 mRNA abundance. To understand the mechanism of this regulation, we developed the rat intestinal epithelial (RIE) cell as an in vitro model to study the effect of EGF on NHE2 gene expression. EGF increased functional NHE2 activity and mRNA abundance in cultured RIE cells, and this stimulation could be blocked by actinomycin D (a transcriptional inhibitor). Additionally, NHE2 promoter reporter gene assays in transiently transfected RIE cells showed an almost twofold increase in promoter activity after EGF treatment. We conclude that rat NHE2 activity can be stimulated by chronic EGF treatment and that this response is at least partially mediated by gene transcription.

Animals↗

PubMed2001

Nitric oxide-independent effects of tempol on sympathetic nerve activity and blood pressure in normotensive rats.

The role of the sympathetic nervous system in 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol)-induced cardiovascular responses in urethane-anesthetized, normotensive rats was evaluated. Tempol caused dose-dependent (30-300 micromol/kg iv) decreases in renal sympathetic nerve activity (RSNA), mean arterial blood pressure (MAP), and heart rate (HR). Similar responses were obtained after sinoaortic denervation and cervical vagotomy. These responses were not blocked following treatment with the nitric oxide synthase inhibitor NG-nitro-L-arginine (2.6 mg x kg(-1) x min(-1) iv for 5 min) or the alpha2-adrenergic receptor antagonist idazoxan (0.3 mg/kg iv bolus). Idazoxan blocked the effects of clonidine (10 miccrog/kg iv) on HR, MAP, and RSNA. Hexamethonium (30 mg/kg iv) inhibited RSNA, and tempol did not decrease RSNA after hexamethonium. The effects of tempol on HR and MAP were reduced by hexamethonium. In conclusion, depressor responses caused by tempol are mediated, partly, by sympathoinhibition in urethane-anesthetized, normotensive rats. Nitric oxide does not contribute to this response, and the sympathoinhibitory effect of tempol is not mediated via alpha2-adrenergic receptors. Finally, tempol directly decreases HR, which may contribute to the MAP decrease.

Animals↗

PubMed2001

Functional expression of a GFP-tagged Kv1.5 alpha-subunit in mouse ventricle.

The experiments here were undertaken to determine the feasibility of increasing the cell surface expression of voltage-gated ion channels in cardiac cells in vivo and to explore the functional consequences of ectopic channel expression. Transgenic mice expressing a green fluorescent protein (GFP)-tagged, voltage-gated K+ (Kv) channel alpha-subunit, Kv1.5-GFP, driven by the cardiac-specific alpha-MHC promoter, were generated. In recent studies, Kv1.5 has been shown to encode the micromolar 4-aminopyridine (4-AP)-sensitive delayed rectifier K+ current (I(K,slow)) in mouse myocardium. Unexpectedly, Kv1.5-GFP expression is heterogeneous in the ventricles of these animals. Although no electrocardiographic abnormalities were evident, expression of Kv1.5-GFP results in marked decreases in action potential durations in GFP-positive ventricular myocytes. In voltage-clamp recordings from GFP-positive ventricular myocytes, peak outward K+ currents are significantly higher, and their waveforms are distinct from those recorded from wild-type cells. Pharmacological experiments revealed a selective increase in a micromolar 4-AP-sensitive current, similar to the 4-AP-sensitive component of I(K,slow) in wild-type cells. The inactivation rate of the "overexpressed" current, however, is significantly slower than the Kv1.5-encoded component of I(K,slow) in wild-type cells, suggesting differences in association with accessory subunits and/or posttranslational processing.

Action Potentials↗

PubMed2001

Amplification effect and mechanism of action of ET-1 in U-46619-induced vasoconstriction in pig skin.

The aim of this study was to investigate if a low concentration of endothelin-1 (ET-1; 8 x 10(-10) M) may amplify the skin vasoconstrictor effect of other vasoactive substances in the pathogenesis of skin vasospasm. Pig skin flaps (6 x 16 cm) were perfused with Krebs buffer equilibrated with 95% O(2) and 5% CO(2) at 37 degrees C and pH 7.4. Skin perfusion pressure measured by a pressure transducer and skin perfusion assessed by the dermofluorometry technique were used for assessment of skin vasoconstriction. We observed that ET-1 (8 x 10(-10) M) significantly amplified the concentration-dependent (10(-7)-10(-5) M) skin vasoconstrictor effect of norepinephrine. More importantly, we observed for the first time that this low concentration of ET-1 also amplified the concentration-dependent (10(-8)-10(-6) M) skin vasoconstrictor effect of the thromboxane A(2) mimetic U-46619, and this amplification effect of ET-1 was completely blocked by the protein kinase C (PKC) inhibitor chelerythrine (5 x 10(-6) M). Conversely, the PKC activator phorbol 12,13-dibutyrate (10(-7) M) amplified the vasoconstrictor effect of U-46619. Furthermore, the sensitivity of the skin vasculature to the vasoconstrictor effect of extracellular Ca(2+) in U-46619-induced skin vasoconstriction was significantly enhanced in the presence of 8 x 10(-10) M ET-1. Finally, the cyclooxygenase inhibitor indomethacin (5 x 10(-6) M) did not affect the amplification effect of ET-1 on U-46619-induced skin vasoconstriction. We conclude that a low concentration of ET-1 can amplify the skin vasoconstrictor effect of U-46619 independent of endogenous cyclooxygenase products, and the mechanism may involve activation of PKC and increase in sensitivity of the contractile apparatus to Ca(2+) in smooth muscle cells.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

PubMed2001

Mechanisms of interleukin 1beta-induced human airway smooth muscle hyporesponsiveness to histamine. Involvement of p38 MAPK NF-kappaB.

We have investigated the effect of IL-1beta on histamine H(1)-receptor (H(1)R)-mediated inositol phosphate (IP) accumulation in human airway smooth muscle cells (HASMC) and on histamine-induced contraction of human bronchial rings. Stimulation of HASMC for 24 h with IL-1beta resulted in significant loss of histamine-induced IP formation, which was associated with a reduction of histamine- induced contraction of IL-1beta-treated human bronchial rings. An inhibitor of NF-kappaB activation, pyrrolidine dithiocarbamate, and a p38 MAPK inhibitor, blocked the IL-1beta-induced H(1)R desensitization, whereas anisomycin, an SAPK/JNK and p38 MAPK activator, mimicked the effect of IL-1beta. IL-1beta has been demonstrated to induce cox-2 expression and PGE(2) synthesis. In our study, indomethacin a cox antagonist, completely inhibited the effect of IL-1beta on H(1)R, whereas exogenously added PGE(2) was able to desensitize H(1)R. Furthermore, H-89, a selective PKA inhibitor, antagonized the effect of IL-1beta. Here, we have demonstrated that IL-1beta desensitizes H(1)R, which involves the activation of p38 MAPK and NF-kappaB, leading to the expression of cox-2 and the synthesis of PGE(2). PGE(2) increases intracellular cAMP resulting in PKA activation, which phosphorylates and functionally uncouples H(1)R. Our results suggest that IL-1beta protects airway smooth muscle against histamine-induced contractile responses and that bronchial hyperreactivity to histamine is not associated with proinflammatory cytokine-induced enhancement in H(1)R signaling.

Blotting, Western↗

PubMed2001

Skin reflectance in the Han Chinese and Tibetan populations.

Genetic and environmental factors are involved in the determination of skin pigmentation in humans. With the recent development of statistical and genetic tools in mapping complex traits in humans, it is becoming feasible to utilize such methods in identifying genes involved in skin pigmentation. Furthermore, the use of new portable reflectance spectroscopy instruments such as the Photovolt ColorWalk colorimeter allows researchers to measure skin reflectance of a large number of subjects with ease and accuracy. We used a new portable instrument (Photovolt ColorWalk) to study the skin reflectance of 372 Han Chinese and 274 Tibetan individuals to establish background reflectance measurements of unexposed skin of the inner upper arm in these two populations. In addition, we explored the effect of various factors such as age and gender on skin reflectance.

Adolescent↗

PubMed2001

Germinating barley selenium-containing peroxidase is one of the peroxidase isoenzymes.

A selenium-containing peroxidase from the germinating barley grown on a selenium-containing artificial medium was isolated and purified by means of cold acetone precipitation, Sephadex-G150 filtration, followed by DEAE-Sepharose chromatography and sodium dodecyl sulfate--polyacrylamid gel electrophoresis. The form of selenium existing in the peptide assayed with paper chromatography was selenomethionine. The amino acid composition of this enzyme was similar to those peroxidases from other sources except amino acids Glu, Val Phe, Lys, and Arg. Electron-spin resonance (ESR) spectra recorded at -136 degrees C showed that both the selenium-containing peroxidase from germinating barley and horseradish peroxidase had same the ESR signals as iron protoporphyine. Those results suggested that the germinating barley selenium-containing peroxidase is one of the peroxidase isoenzymes.

Amino Acids↗

PubMed2001

End-labeling of long DNA fragments with biotin and detection of DNA immobilized on magnetic beads.

To immobilize DNA fragments onto magnetic beads coated with streptavidin for isolation purpose, it is important to label one biotin molecule at one terminus of DNA fragment. After failure to label long DNA with biotin by PCR and filling-in reaction, a 9.2 kb DNA was labeled with biotin by a modified ligation strategy. A simple method is also reported to detect the quantity and integrity of DNA immobilized on the magnetic beads.

Base Sequence↗

PubMed2001

Tissue-specific expression and splicing of the rat polycystic kidney disease 1 gene.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic potentially lethal human disorder and the polycystic kidney disease 1 (Pkd1) gene is accounted for 85-90% of these cases. We have obtained rat Pkdl cDNA sequence and characterized splicing of Pkdl RNA transcripts in normal rat tissues. Our sequence data revealed a high conservation of the Pkdl gene between rat and other species and mapped rat Pkdl to chromosome 10 in "tail-to-tail" orientation to the tuberous sclerosis 2 (Tsc2) gene. Pkdl was found ubiquitously expressed in the normal rat tissues and the brain had a complex pattern of exon 12 splicing. A novel splicing variant lacking entire exon 31, which occurs in rat and mouse but not in humans, was also identified. As the rat appears to be a valuable model for investigating polycystic kidney disease, the characterization of the rat Pkdl gene will help facilitate future studies to elucidate the molecular mechanisms of cystogenesis in this animal model.

3' Untranslated Regions↗

PubMed2001

[Single nucleotide polymorphism in beta2-adrenoceptor gene and the distribution in Chinese Han ethnic group].

OBJECTIVE: The study was conducted to investigate single nucleotide polymorphism(SNP) in beta2-adrenoceptor(beta2-AR) gene and the distribution of these identified SNPs in Chinese Han ethnic group. METHODS: beta2-AR gene was sequenced to detect SNPs by fluorescent labeling automatic sequencing method in 80 unrelated samples from territory of Dabie Mountain in Anhui province. RESULTS: A total of 8 SNPs were identified in length of 3.8 kb, including 5 SNPs in code region, 3 SNPs in regulatory region. Although the variations, -468C to G, -367T to C, -47C to T,-20T to C, +79C to G, +100G to A, +491C to T, +1098T to C have been identified in other ethnic groups, they have not been found in our study. The allele distribution of SNPs is in good unity with the Hardy-Weinberg equilibrium. CONCLUSION: The distribution of SNPs in beta2-AR gene is not equable and the SNPs in different ethnic groups differ greatly. The allele distribution of SNPs conforms well to the Hardy-Weinberg equilibrium.

Alleles↗

PubMed2001

Determination of nucleic acids with crystal violet by a resonance light-scattering technique.

For the first time, Crystal Violet (CV) was used to determine nucleic acid concentrations using the resonance light-scattering (RLS) technique. Based on the enhancement of the RLS of CV by nucleic acids, a new quantitative determination method for nucleic acids in aqueous solutions has been developed. At pH 5.03 and ionic strength 0.005 mol kg-1, the interaction of CV with nucleic acids results in three characteristic RLS peaks at 344.0, 483.0 and 666.0 nm. With 4.0 x 10(-5) mol l-1 of CV, linear relationships were found between the enhanced intensity of RLS at 666.0 nm and the concentration of nucleic acids in the range 0-2.5 micrograms ml-1 for herring sperm DNA, 0-4.0 micrograms ml-1 for calf thymus DNA and 0-4.5 micrograms ml-1 for yeast RNA. The limits of determination were 13.8 ng ml-1 for herring sperm DNA, 36.8 ng ml-1 for calf thymus DNA and 69.0 ng ml-1 for yeast RNA. The assay is convenient, rapid, inexpensive and simple.

Animals↗

PubMed2001

[A resource investigation and commodity identification of Fructus Amomi].

Resource investigation and commodity identification were carried out for 28 samples of Fructus Amomi collected from 7 provinces. The results showed that Fructus Amomi used currently were mainly from the dried ripe-fruit of Amomum villosum, A. villosum var. xanthioides or A. longiligulare. Fructus Amomi in market is nainly A. villosum which comes from Yunnan and Guangdong province.

China↗

PubMed2001

[Isolation, purification and determination of polysaccharides X-C-3-III and X-C-3-IV from Angelica sinensis (Oliv) Diels].

Polysaccharides X-C-3-III and X-C-3-IV had been obtained from Angelica sinensis (Oliv) Diels. Their average MW were determined to be 85,000 and 65,765 by gel chromatography after the hydrolysates of X-C-3-III and X-C-3-IV, the compositions of them were identified by silanization method and capillary gas chromatography. X-C-3-III and X-C-3-IV are composed of galacose, arabinose, rhamnose, glucuronic acid and galacturonic acid. The molar ratio of those sugars were determined as 24.3:15.8:4.2:3.1:52.6 and 12.6:10.7:7.2:8.3:61.2, respectively.

Angelica sinensis↗