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Biomedical subjects

B Wang

Publications and source records attributed to B Wang.

At least 577 records · Page 32Linked to original sources
PubMed1997

Structure and expression of the gene encoding secretor-type galactoside 2-alpha-L-fucosyltransferase (FUT2).

The expression and secretion of ABO antigens in epithelial cells of glands are controlled by secretor-type alpha (1,2)fucosyltransferase activity. We have examined the expression of the secretor-type alpha(1,2)fucosyltransferase gene (FUT2) and a pseudogene of FUT2 (Sec1) in several tumor cell lines by northern blot and/or reverse-transcription-PCR (RT-PCR) analyses. Transcripts of FUT2 were found in total RNA from ovarian, gastric and colonic cancer cell lines but not from six leukemic cell lines, including erythroleukemic HEL cells, by RT-PCR. On the other hand, RT-PCR indicated that Sec1 was expressed in all these tumor cells, including all hematopoietic cells studied. Northern blot analysis indicated that FUT2 transcripts with a similar size (3.3 kb) were expressed in cancer cell lines. Rapid amplification of cDNA ends suggested that the entire FUT2 cDNA is 3.1-kb long and has two Alu repetitive elements in its 3' untranslated region, including an inverted repeat. The mRNA, therefore, may form a large stem-and-loop structure (1.2 kb). Each stem contains about 300 bases, the loop contains 640 bases, and the percentage of complementary nucleotide sequences in the stem region is 85%. The presence of a large stem-and-loop structure in the 3' untranslated region may regulate the level of the FUT2 transcript by affecting the stability of the mRNA.

Animals↗
PubMed1997

CD16-expressing CD8alpha alpha+ T lymphocytes in the intestinal epithelium: possible precursors of Fc gammaR-CD8alpha alpha+ T cells.

T lymphocytes normally express their Ag receptors in association with the CD3 proteins, which include CD3zeta. In CD3zeta eta(null) mice thymic and peripheral T lymphocytes do not express the TCR/CD3 complex on their surface due to retention in the endoplasmic reticulum of the remaining polypeptide chains. However, intestinal intraepithelial lymphocytes (iIEL) of CD3zeta eta(null) mice do express surface TCR, because the Fc epsilonRI gamma chain replaced the CD3zeta chain in the TCR/CD3 complex. Here we report that in a subset of CD8alpha alpha+ iIEL the presence of the Fc epsilonRI gamma chain could be accounted for by the surface expression of the Fc gammaRIII(CD16) complex. Because in wild-type (wt) mice only CD16+ iIEL coexpressed Fc epsilonRI gamma and CD3zeta, we concluded that the presence of Fc epsilonRI gamma was dictated by its required participation of CD16 complex. CD8alpha alpha+ iIEL bearing CD16 and B220 were also detected in the intestinal mucosa of RAG-2(null) mice from 12 days after birth onward. Two independent experimental settings were used in an attempt to demonstrate that CD16+ iIEL matured into CD16- T cells. First, in the RAG-2(null) mice, iIEL responded to in vivo administration of an anti-CD3epsilon mAb by progression to a more mature stage of development, characterized by a loss of CD16 and B220. Secondly, a conversion to CD16- iIEL occurred upon transfer of wt CD16+ iIEL into RAG-2(null) mice. We conclude from these experiments that in both RAG-2(null) and wt mice, a precursor/progeny relationship may exists between CD16+ B220+ CD8alpha alpha+ and CD16- B220- CD8alpha alpha+ iIEL.

Animals↗
PubMed1997

Local intramural delivery of L-arginine enhances nitric oxide generation and inhibits lesion formation after balloon angioplasty.

BACKGROUND: Long-term oral administration of L-arginine has been shown to enhance production of nitric oxide (NO) and to reduce lesion formation. The goal of this study was to determine whether local intramural administration of L-arginine could enhance NO generation and reduce intimal thickening. METHODS AND RESULTS: New Zealand White rabbits (n = 27) received a 1% cholesterol diet. For the short-term study, after 1 week of diet, both iliac arteries were balloon injured. Four weeks later, vasoreactivity was assessed angiographically during infusion of acetylcholine (Ach) before and after delivery of L-arginine or saline into the right or left iliac artery (800 mg/5 mL; 0.2 mL/min, 15 minutes) by use of a local drug-delivery balloon. Vessels were then harvested for measurements of NO. For the long-term study, after balloon injury, drugs were delivered as above into the iliac arteries. Two and 4 weeks after L-arginine delivery, vasoreactivity was determined. Subsequently, the iliac arteries were harvested for histomorphometric analysis and measurements of NO. In the short-term study, local delivery of L-arginine restored endothelium-dependent vasodilatation (Ach 10(-5) mol/L; L-arginine +35 +/- 10%; saline -14 +/- 5%; P < .001) and enhanced local production of nitrogen oxides (L-arginine 152 +/- 28; saline 78 +/- 12 nmol/L per milligram of tissue per hour; P < .04). In the long-term study, local administration of L-arginine enhanced vascular NO production as long as 1 week after the injury (L-arginine 394.4 +/- 141.6; saline 86.3 +/- 34.3 nmol/L per milligram of tissue per hour; P < .01) and reduced intimal thickening 4 weeks later (intima/ media ratio: L-arginine 0.56 +/- 0.1; saline 1.40 +/- 0.2; P < .001), largely due to suppression of macrophage accumulation. CONCLUSIONS: A single intramural administration of L-arginine enhances vascular NO generation and inhibits lesion formation. Local augmentation of NO production at the site of balloon angioplasty may be a novel strategy to prevent restenosis.

Acetylcholine↗
PubMed1997

Molecular cloning and characterization of a novel human receptor protein tyrosine phosphatase gene, hPTP-J: down-regulation of gene expression by PMA and calcium ionophore in Jurkat T lymphoma cells.

A novel cDNA encoding a 1436 aa protein was cloned using a PCR system with degenerate primers. This new gene, hPTP-J, was found to encode a PTP protein consisting of an extracellular region containing an MAM (meprin, A5, mu)-like domain, an immunoglobulin-like domain, four fibronectin type-III repeats, a transmembrane region, and a cytoplasmic region containing two tandemly repeated PTP domains hPTP-J is thus considered to be a new member of the type II receptor PTP (RPTP) subfamily, like RPTP mu and RPTP kappa. hPTP-J gene expression was strongly detected in skeletal muscle and moderately detected in the prostate, pancreas, placenta, and heart, but was only weakly detected in the peripheral blood lymphocytes, thymus, and spleen even though gene expression was relatively high in the Jurkat T lymphoma cell line. Moreover, hPTP-J gene expression was down-regulated after Jurkat cells were stimulated by either PMA or calcium ionophore. Based on these findings, it is suggested that some signaling pathways mediated by PMA and/or intracellular calcium are involved in the regulation of hPTP-J gene expression in Jurkat cells.

Amino Acid Sequence↗
PubMed1997

In vivo engineering of a cellular immune response by coadministration of IL-12 expression vector with a DNA immunogen.

Recent studies support the importance of investigating a DNA vaccination approach for the immunologic control of HIV-1. In this regard, it may be important to specifically engineer immune responses in order to improve on first generation vaccine attempts. Especially for HIV, induction of cell-mediated immunity may be an important feature for any candidate vaccine. In an attempt to engineer in vivo the enhancement of cellular immune response and to direct Ag-dependent immune response from Th2 to Th1 type, we investigated the role of codelivery of genes for IL-12 and granulocyte-macrophage-CSF along with DNA vaccine formulations for HIV-1 Ag. We found that codelivery of IL-12 expression cassettes with DNA vaccines for HIV-1 in mice resulted in splenomegaly as well as a shift in the specific immune responses induced. The codelivery of IL-12 genes resulted in the reduction of specific Ab response, while the coinjection of granulocyte-macrophage-CSF genes resulted in the enhancement of specific Ab response. In addition, we observed a significant Ag-specific stimulation of T cells with codelivery of both cytokines. Most importantly, we observed a dramatic increase in specific CTL response from the group coimmunized with the HIV-1 DNA vaccine and IL-12 genes. This work demonstrates the power of DNA delivery in vivo for both the production of a new generation of more effective and targeted vaccines or immunotherapies as well as an analytic tool for the molecular dissection of the mechanisms of immune function.

Animals↗
PubMed1997

Expression of pro-inflammatory cytokines by TCR alpha beta+ and TCR gamma delta+ T cells in an experimental model of colitis.

An inflammatory bowel disease (IBD) comparable to human ulcerative colitis is induced upon transfer of T cell-depleted wild-type (F1) bone marrow into syngeneic T cell-deficient (tg epsilon26) mice (F1 --> tg epsilon26). Previously we have shown that activated CD4+ T cells predominate in transplanted tg epsilon26 mice, and adoptive transfer experiments verified the potential of these cells to cause disease in immunodeficient recipient mice. Using flow cytometry for the detection of intracellular cytokine expression, we demonstrate in the present study that large numbers of CD4+ and CD8+ TCR alphabeta+ T cells from the intraepithelial region and lamina propria of the colon of diseased, but not from disease-free mice, produced interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). Large numbers of T cells from peripheral lymphoid tissues of these animals also expressed IFN-gamma and TNF-alpha, but few expressed interleukin-4, demonstrating a strong bias towards Th1-type T cell responses in these animals. TCR gammadelta+ T cells, typically minor constituents of the inflammatory infiltrate of the colon in F1 --> tg epsilon26 mice, also expressed IFN-gamma at a high frequency upon CD3 stimulation. In light of these findings we examined the potential involvement of TCR gammadelta+ T cells by testing their ability to induce colitis in tg epsilon26 mice. We report here that tg epsilon26 mice transplanted with T cell-depleted bone marrow from TCR alpha(null) and TCR beta(null) animals developed IBD. Furthermore, disease in these mice correlated with the development of peripheral and colonic TCR gammadelta+ T cells capable of IFN-gamma production. These results suggest that IFN-gamma may be a common mediator of IBD utilized by pathogenic T cells of distinct phenotype.

Animals↗
PubMed1997

HIV infection of macrophages and pathogenesis of AIDS dementia complex: interaction of the host cell and viral genotype.

AIDS dementia complex (ADC) develops in only a third of HIV-infected patients who progress to AIDS. Macrophages and microglial cells are the major cellular sites of productive HIV replication in brain. Using 11 blood isolates of HIV from asymptomatic patients there was marked variation in tropism and the level of productive infection in recently adherent monocytes and monocyte-derived macrophages cultured in vitro. However, less variation was seen with 19 blood isolates from advanced HIV infection and 11 postmortem tissue isolates from brain, cerebrospinal fluid, spleen, and lung. Newly adherent monocytes expressed CCR5 in all seven patients tested, consistent with their susceptibility to infection but not explaining the above variability. There is, also marked regional variability in neuropathology in the brain of patients with ADC. We have demonstrated that there was marked variation in the V3 sequences of HIV clones from different regions of the cortex of a patient with ADC, suggesting independent evolution of HIV replication in brain. Furthermore, production of the neurotoxin quinolinic acid from HIV-infected macrophages varied, depending on the host and source of HIV isolate. Hence variations in viral genotype, production by infected macrophages, and subsequent toxin production may contribute to the variability in neuropathology between individuals and between different regions of the brain in the same individual.

AIDS Dementia Complex↗
PubMed1997

Soluble expression in Escherichia coli, one-step purification, and characterization of Chinese hamster dihydrofolate reductase.

Chinese hamster dihydrofolate reductase (ch-DHFR) was overexpressed in Escherichia coli DH5 alpha under the transcriptional control of PRPL promoters regulated by temperature-sensitive repressors. The desired recombinant product is soluble and constitutes about 30% of the total soluble proteins of the bacterial cell. With repeated cycles of freezing and thawing as a first step, the purification of the recombinant ch-DHFR to homogeneity requires only one further step, gel filtration on a Sephadex G-75 column with 85-90% enzyme recovery, two to three times higher than that obtained with the commonly used affinity chromatography on a methotrexate-Sepharose column. The purified enzyme migrates as a single protein band on SDS-polyacrylamide gel electrophoresis with approximate mass of 23 kDa, in accord with that calculated from the DNA sequence. The initiation methionine residue at the N-terminus of the enzyme is completely removed by E. coli methionine aminopeptidase as judged by amino-terminal analysis. The steady-state kinetic parameters, dissociation constants for binary complexes of dihydrofolate, NADPH, and methotrexate with ch-DHFR, and the inhibitor constant of methotrexate have also been determined. The enzyme is activated about 4-fold in 3 M urea and about 2.5-fold in 0.5 M guanidine hydrochloride.

Animals↗
PubMed1997

Novel embryonic regulation of Ca(2+)-activated K+ channel expression in Drosophila.

The slowpoke gene of Drosophila melanogaster encodes a Ca(2+)-activated K+ channel that is expressed in neurons, muscles, tracheal cells and the middle midgut. The entire transcriptional control region of slowpoke is contained in 11 kb of genomic DNA. Previous work has identified four different tissue-specific promoters (Promoters C1, C1b, C1c and C2) and sequences that regulate their activity. Here we describe and contrast the regulation of neuronal and muscle expression during embryogenesis with its regulation during larval and adult stages. Embryonic regulation is fundamentally different. The embryo uses Promoter C1 and a previously undescribed promoter, called Promoter Ce, to drive neuronal expression. The expression patterns of these promoters are distinct. Muscle expression arises from Promoter C2 as in other developmental stages. A downstream intronic region has been shown to contain control elements that modulate promoter activity differently in embryos, larvae and adults. Embryonic CNS expression is not dependent on the intron, however; its deletion has substantial effects on neuronal expression in larvae and adults. In embryonic muscle, removal of the intron eliminates muscle expression even though this deletion does not reduce larval muscle expression.

Animals↗
PubMed1997

Effect of concurrent use of rh-IL-3 and rh-GM-CSF on apoptosis of HL-60 cells induced by Ara-C.

The myeloid leukemic cell line HL-60 was studied by using DNA gel electrophoresis, flow cytomery, McAb C-myc, McAb Bcl-2 and CFU-L. From zero to 36 h, the apoptosis rates of 8 different phases and other indexes were observed. The results showed that with the prolonged time of drug incubation, apoptosis of HL-60 cells increased progressively. This effect can be enhanced obviously by rh-IL-3 and rh-GM-CSF. At the same time, the killed rate of leukemic cells by Ara-C induction was increased. C-myc expression was decreased and Bcl-2 expression did not display apparent change. Interestingly, the normal hemopoietic cells were not affected by these two kinds of cytokine. The theoretical basis was provided for concurrent use of rh-IL-3, rh-GM-CSF and cytotoxic drugs whose purpose is to elevate remission rate during the phase of induced remission of leukemia.

Apoptosis↗
PubMed1997

The molecular epidemiological study on enteric adenovirus in stool specimens collected from Wuhan area by using digoxigenin labeled DNA probes.

A summer-autumn (1994) molecular epidemiological study of enteric adenoviruses (EAds) in stool specimens collected in Wuhan area was conducted by using Digoxigenin-labelled DNA probes specific to EAd40 and EAd41 respectively. 44 of 602 specimens were positive, among which 23 cases were identified as EAd40, 14 were EAd41 infection and 7 were dual infection. The ratio of males to females for the positive specimens was 1. 44. The infection rate of EAd40 and EAd41 each displayed no marked difference in seasons (summer and autumn) and similar age distribution was found between them. All of the two types of EAds infections predominated in patients with diarrhea under 3 years old. The results indicated that the Digoxigenin probe could detect DNA quantities as low as 1 pg with satisfactory specificity and the technique can be used for both clinical and experimental purposes.

Adenovirus Infections, Human↗
PubMed1997

Rearranged patterns of IgH and TcR gamma genes in patients with acute lymphoblastic leukemia.

The rearrangement of immunoglobulin heavy chain gene (IgH) and T cell receptor gamma gene (TcR gamma) was studied in 30 patients with acute lymphoblastic leukemia (ALL) by the polymerase chain reaction (PCR). 19 cases was found to have rearrangement of IgH gene, 12 of TcR gamma. Most of IgH rearrangement was characterized by one or two specific bands while some had more than two. Rearrangement of TcR gamma gene appeared as one specific band. A slight difference in number, size and lightness of bands was found among the patients. 4 different kinds of rearrangement were observed in the detection of IgH rearrangement in combination with TcR gamma gene. The rearranged patterns of IgH and TcR gamma gene as well as the clinical significance were discussed.

Adult↗
PubMed1997

Biotransformation for L-ephedrine production.

L-ephedrine is widely used in pharmaceutical preparations as a decongestant and anti-asthmatic compound. One of the key intermediates in its production is L-phenylacetylcarbinol (L-PAC) which can be obtained either from plants (Ephedra sp.), chemical synthesis involving resolution of a racemic mixture, or by biotransformation of benzaldehyde using various yeasts. In the present review, recent significant improvements in the microbial biotransformation are assessed for both fed-batch and continuous processes using free and immobilised yeasts. From previous fed-batch culture data, maximal levels of L-PAC of 10-12 gl-1 were reported with yields of 55-60% theoretical based on benzaldehyde. However, recently concentrations of more than 22 gl-1 have been obtained using a wild-type strain of Candida utilis. This has been achieved through optimal control of yeast metabolism (via microprocessor control of the respiratory quotient, RQ) in order to enhance substrate pyruvate production and induce pyruvate decarboxylase (PDC) activity. Processes involving purified PDC have also been evaluated and it has been demonstrated that L-PAC levels up to 28 gl-1 can be obtained with yields of 90-95% theoretical based on the benzaldehyde added. In the review the advantages and disadvantages of the various strategies for the microbial and enzymatic production of L-PAC are compared. In view of the increasing interest in microbial biotransformations, L-PAC production provides an interesting example of enhancement through on-line control of a process involving both toxic substrate (benzaldehyde) and end-product (L-PAC, benzyl alcohol) inhibition.

Acetone↗
PubMed1997

Nucleic acid immunization of chimpanzees as a prophylactic/immunotherapeutic vaccination model for HIV-1: prelude to a clinical trial.

Vaccine development strategies have often utilized recombinant envelope glycoproteins which usually generate strong humoral immune responses but which do not generate strong cytotoxic T lymphocytes (CTL). A recent novel experimental vaccination approach involves the technology known as nucleic acid immunization in which DNA plasmids expressing a gene of interest is injected intramuscularly in experimental animals. These expressed proteins then are presented to the immune system with the subsequent development of strong antibody and cellular (particularly CTL) immune responses. These types of immune responses have been elicited in rodents as well as nonhuman primates including chimpanzees. Results from studies on nucleic acid immunization of HIV-1 infected chimpanzees with envelope glycoprotein expressing constructs indicated that this method was able to decrease substantially HIV-1 viral load in these chimpanzees. These data are useful for the development and implementation of human phase I clinical trials with HIV constructs expressing various genes from the HIV-1 genome.

AIDS Vaccines↗