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Biomedical subjects

X J Huang

Publications and source records attributed to X J Huang.

12 recordsLinked to original sources
PubMed2001

A miniaturized liquid core waveguide-capillary electrophoresis system with flow injection sample introduction and fluorometric detection using light-emitting diodes.

A novel miniaturized capillary electrophoresis (CE) system is described where a Teflon AF-coated silica capillary serves both as the separation channel and as a transversely illuminated liquid core waveguide. This device uniquely uses flow injection (FI)-based split-flow sample introduction through a falling-drop interface. An H-channel structure fixed on a microscope glass slide utilizes a horizontal separation capillary with tubular sidearms on each end that serve as inlet and outlet flow-through electrode reservoirs. The inlet reservoir also functions as a falling-drop interface for coupling to the FI system. A blue LED is used as excitation source. A large-core optical fiber takes the emitted fluorescence to an inexpensive PMT with two layers of green plastic used for optical filtering. No focusing arrangement is needed. Continuous FI introduction of a series of 30-microL samples containing a mixture of of fluorescein isothiocyanate (FITC)-labeled amino acids allowed a throughput rate up to 144 samples/ h, with approximately 2% carryover and good precision (3.2% RSD). Baseline separation was achieved for FITC-labeled arginine, phenylalanine, glycine, and FITC in sodium tetraborate buffer (pH 9.5) with plate heights of 5.4-5.5 microm and plate numbers of 2.34 x 10(4)-2.37 x 10(4) under electrical field strengths of 214 V/cm for injection and 500 V/cm for separation (14-cm capillary, 48-microm i.d.). Detection limits (S/N = 3) were 1.3 microM for arginine and 1.9 microM for phenylalanine and glycine.

Amino Acids↗
PubMed2001

Serum TNFalpha levels in patients with acute graft-versus-host disease after bone marrow transplantation.

Tumor necrosis factor alpha (TNFalpha) has been implicated in the pathogenesis of graft-versus-host disease (GVHD). In this study, serum levels of TNFalpha were assessed by ELISA in 243 sera samples from 40 patients who had undergone allogeneic bone marrow transplantation (BMT). Serum TNFalpha levels were measured before BMT and at different time points after BMT. The results were correlated with acute GVHD (aGVHD), infection and conditioning regimen. Serum TNFalpha levels were significantly higher in patients with grades II-IV aGVHD than in those with grade 0 or I aGVHD, but there was no clear correlation between serum TNFalpha and severity of aGVHD. Serum TNFalpha levels in infected patients were not statistically different from those in patients without infection. The conditioning regimen did not cause a significant rise in TNFalpha levels. These results indicate that TNFalpha may be useful for the diagnosis of aGVHD and for differentiating between aGVHD and other BMT-related complications, such as infection.

Acute Disease↗
PubMed2001

Capillary electrophoresis system with flow injection sample introduction and chemiluminescence detection on a chip platform.

A capillary electrophoresis (CE) system with chemiluminescence (CL) detection was combined with flow injection (FI) sample introduction on a chip platform. A falling-drop interface was applied to perform FI split-flow sample introduction while achieving electrical isolation from the CE high voltage. A tubular reservoir at the capillary outlet served as both the CL reaction and detection cell for the luminol-peroxide-metallic ion chemiluminescent reaction, with the luminol included in the separation buffer and CL reagent H2O2 continuously introduced into the outlet reservoir. An optical fiber was positioned within the outlet reservoir directly opposite, and 300 microns away from, the capillary outlet for collecting and transferring the generated CL to the PMT. The peak height signals and the separation efficiency were almost independent of the reagent flow-rate, making the system a robust one. The performance of the system was illustrated by the separation of Co(II) and Cu(II), achieving baseline separation in 60 s. Detection limits (3 sigma) were 1.25 x 10(-8) and 2.3 x 10(-6) mol dm-3 for Co(II) and Cu(II), respectively. Peak height precision was 1.9% RSD (n = 9) at the 10(-7) mol dm-3 Co level.

Journal Article↗
PubMed2001

[Preparation and evaluation of alkyl ether-bonded phase for reversed-phase high performance liquid chromatography].

A new silane coupling agent, beta-(3,4-epoxycyclohexyl)ethyltrimethoxy silane, was for the firsty time used to react with octanol, then the intermediate product was coupled onto porous silica to obtain a novel bonded phase for reversed-phase high performance liquid chromatography (RP-HPLC). Characterization of prepared packing was carried out with elemental analysis, solid-state 13C nuclear magnetic resonance spectrometry (NMR), Fourier transform infrared(FT-IR) spectroscopy. Chromatographic evaluations were carried out by using a mixture of organic compounds and methanol-water as the binary mobile phase. The results showed that the stationary phase has excellent chromatographic properties and resist to hydrolysis at a pH value between 2.5 and 7.5. The silanophilic activity of the OEBP was weakened because of the existence of the cyclohexyl group in the packing. It can be efficiently used for the separation of basic compounds.

Aminophylline↗
PubMed2001

[Preparation and evaluation of amide-octyl-bonded phase for the separation of basic substances in reversed-phase liquid chromatography].

A new bonded-phase, amide-octyl-bonded phase (AOBP), with an internal polar functional group-amide was firstly prepared in domestic by two-step reaction process. The amino phase was formed in the first step and further modified in the second step by attaching an alkyl chain via reaction of an acid chloride with the amino ligand. Characterization of prepared packing was carried out with elemental analysis and Fourier transform infrared (FTIR) spectrometry. Hydrophobicity, selectivity and silanophilic activity of AOBP were evaluated by using organic components including acidic, bascic and neutral analytes and methanol-water as binary mobile phase. The applicable ranges of pH and stability of AOBP were also evaluated. The results showed that AOBP has excellent chromatographic properties and resistance to hydrolysis between pH = 2.5-7.5, It can be used for the separation of basic solutes efficiently.

1-Octanol↗
PubMed1999

Arsenic trioxide induces apoptosis of myeloid leukemia cells by activation of caspases.

The primary objective of this study was to determine whether caspases are involved in arsenic trioxide(ATO)-induced apoptosis of human myeloid leukemia cells. A secondary objective was to determine whether apoptosis induced by ATO compared with VP-16 is differentially affected by an activator of protein kinase C (PKC), phorbol 12-myristate 13-acetate (PMA), which has been reported to inhibit apoptosis induced by some chemotherapeutic agents. NB4 and HL60 cells were incubated with ATO in the presence and absence of the caspase protease inhibitors Z-VAD.fmk or Y-VAD.cho. Apoptosis was assessed by morphology, DNA laddering and flow cytometry. Poly (ADP-ribose) polymerase (PARP) cleavage was used as a marker for the activation of caspases. PARP cleavage occurred during ATO-induced apoptosis in both NB4 and HL60 cells. Z-VAD.fmk, a broad-spectrum inhibitor, could block ATO-induced apoptosis and PARP cleavage, whilst Y-VAD.cho, a selective inhibitor of caspase 1, had no such effect. PMA pre-incubation for up to 8 hours under conditions known to activate PKC had no effect on either ATO- or VP-16-induced apoptosis. We conclude that in cultured myeloid leukemia cells ATO-induced apoptosis is executed by caspases from the distal, PARP-cleaving part of the activation cascade and that PKC activation has no effect on apoptosis induced by either ATO or VP-16 in these cells.

Amino Acid Chloromethyl Ketones↗
PubMed1995

[Hepatitis virus infection and bone marrow transplantation].

Hepatitis virus infection is a special problem in China and the role of Hepatitis virus infection in allogeneic bone marrow transplantation (BMT) is not well-defined. In this study, 106 BMT patients were included for analysis of the role of virus infection in allo-BMT. Seven and 65 of 106 patients were found to have HBV infection and HCV infection, respectively. Neither HBV infection and HCV infection interfered with the engraftment of bone marrow cells nor increased the rate of AGVHD, CGVHD, VOID. Neither HBV infection nor HCV infection prohibited allo-BMT. But Hepatitis virus infection can cause mild to moderate liver dysfunction, even death because of acute liver function failure, active prevention and treatment of hepatitis virus infection remains necessary. In this respect, rh-interferon is useful.

Adolescent↗
PubMed1994

Transgenic mice expressing IFN-gamma in the retina develop inflammation of the eye and photoreceptor loss.

PURPOSE: Inflammatory mediators such as interferon-gamma (IFN-gamma) are thought to play a role in ocular disease. Although IFN-gamma was found in the vitreous of mice with experimentally induced autoimmune uveitis, intracameral injection of this cytokine did not induce intraocular inflammation in mice. Therefore, the authors created a transgenic mouse line using the rhodopsin promoter to direct the expression of IFN-gamma in the photoreceptor cells of the retina. These mice, designated rho gamma, enabled them to model intraocular inflammatory disease. METHODS: The authors fused a 2.1 kb 5' Hind III fragment from the murine rhodopsin gene to the IFN-gamma gene and introduced the DNA construct into fertilized zygotes. These were implanted into pseudopregnant C57BL/6 mice, and the resulting progeny were crossed back to balb/c mice. The transgene was identified by Southern blot hybridization. Eyes from the rho gamma mice were either fixed in zinc formalin and stained with hematoxylin and eosin or were frozen in OCT compound and processed for immunostaining using the indirect immunoperoxidase method with DAB as a chromogen. RESULTS: The rho gamma transgenic mice developed intraocular disease, manifested as intraocular cellular infiltration, loss of photoreceptors, corneal clouding, cataract formation, and epithelial and microglial proliferation. Additionally, rho gamma mice exhibited antigenic changes, comprising GFAP expression on Müller cells, accumulation of neurofilament on photoreceptors, and expression of MHC class I and class II molecules on retinal cells. CONCLUSIONS: IFN-gamma alters the antigenic properties of intraocular tissue and induces intraocular inflammation in mice. The results suggest a key position of IFN-gamma in the development of pathologic conditions related to intraocular inflammation and provide a useful animal model for the further study of inflammatory disorders, including autoimmune diseases.

Animals↗
PubMed1991

Minimal Rev-response element for type 1 human immunodeficiency virus.

Rev protein regulates nuclear export of viral mRNAs that contain a 240-base RNA sequence termed the Rev-response element (RRE). We demonstrate that an 88-base truncated RRE encompassing a known Rev binding site can mediate Rev responsiveness in vivo. Two tandem copies of this mutant function as efficiently as the full-length RRE.

Base Sequence↗
PubMed1990

Steroid-receptor fusion of the human immunodeficiency virus type 1 Rev transactivator: mapping cryptic functions of the arginine-rich motif.

The human immunodeficiency virus type 1 (HIV-1) transactivator Rev is a nuclear protein that regulates expression of certain HIV-1 transcripts by binding to an RNA target element (the RRE) present in these transcripts. A short arginine-rich sequence in Rev contains the signals required to direct this protein into nuclei, where it associates preferentially with nucleoli. We created a steroid-inducible transactivator by fusing Rev with the steroid-binding domain of the glucocorticoid receptor (GR). This Rev/GR protein remains inactive in the cytoplasm when steroids are absent, but it enters the nucleus and initiates transactivation within minutes after exposure to dexamethasone. Although the GR moiety is sufficient to transport Rev/GR into nuclei, mutation of certain residues in the arginine-rich region blocks nucleolar localization and also inhibits transactivation. We find that other mutations in this region, however, can abolish the function of Rev/GR without affecting its localization; the latter phenotype may reflect a specific defect in binding of the RRE.

Amino Acid Sequence↗
PubMed1990

Mutational analysis of the human immunodeficiency virus type 1 Rev transactivator: essential residues near the amino terminus.

The expression of certain mRNAs from human immunodeficiency virus type 1 (HIV-1) is controlled by the viral transactivator Rev, a nucleolar protein that binds a cis-acting element in these mRNAs. Rev is encoded by two viral exons that specify amino acids 1 to 26 and 27 to 116, respectively. Earlier studies have mapped essential regions of the protein that are encoded in the second exon. By further mutational analysis of Rev, we have now identified a novel locus encoded by the first exon that also is essential for transactivation in vivo. Defined by mutations at residues 14 to 20, this locus coincides with a cluster of positively charged and nonpolar amino acids that is conserved in Rev proteins of all known primate immunodeficiency viruses. Rev proteins that contained mutations at this site were defective in both nuclear localization and transactivation and did not function as trans-dominant inhibitors of wild-type Rev. Fusion of these mutants to a heterologous nuclear protein complemented the defect in localization but did not restore biological activity. Our findings suggest that this N-terminal locus may play a direct role in transactivation, perhaps contributing to essential protein-protein interactions or forming part of the RNA-binding domain of Rev.

Amino Acid Sequence↗