Search PubMed⌕ Search

Biomedical subjects

H Wang

Publications and source records attributed to H Wang.

At least 1,081 records · Page 60Linked to original sources
PubMed1999

Differentiation-promoting effect of 1-O (2 methoxy) hexadecyl glycerol in human colon cancer cells.

Alkylglycerols are naturally occurring bioactive ether lipids found in great abundance in the livers of many marine species. In this study, we evaluated the differentiation-promoting potential of a methoxy substituted alkylglycerol--1-O (2 methoxy) hexadecyl glycerol (MHG)--to promote a more benign or differentiated phenotype in human colon cancer cells. Three cell lines with different biological and phenotypic properties were used. They were the moderately differentiated and growth factor-responsive Moser, the growth factor-unresponsive and malignant HT29, and the poorly differentiated and growth factor-unresponsive HCT116. Treatment of these cell lines with MHG resulted in a downmodulation of cellular proliferation, a reduced propensity for anchorage-independent growth, and a reduced capacity in cellular invasion. Induction of the colon-associated and differentiation-related molecule carcinoembryonic antigen was also observed in the three cell lines. Induction of the transformation-sensitive and differentiation-related glycoprotein fibronectin was observed in the HT29 cells. It is concluded that MHG was biologically active and promoted a more benign or differentiated phenotype in these colon cancer cells. Since differentiation-inducing agents may possess chemoprevention properties, the use of MHG and the alkylglycerols in inducing differentiation or in chemoprevention of malignant diseases warrants further investigation.

Antineoplastic Agents↗
PubMed1999

Efficacy and specificity of antisense laminin chain-specific expression vectors in blocking laminin induction by TGFbeta1: effect of laminin blockade on TGFbeta1-mediated cellular responses.

Transforming growth factorbeta1 (TGFbeta1) elicits a multitude of cellular responses from the epithelial-derived human colon cancer Moser cells. TGFbeta1 induces the expression of laminin and fibronectin, and previous studies show that the induction of fibronectin is functionally associated with the regulation of carcinoembryonic antigen (CEA) expression by TGFbeta1 (Huang and Chakrabarty, 1994, J Biol Chem 269:28764-28768). In this study we constructed antisense laminin chain-specific expression vectors and determined their efficacy in blocking the expression and the induction of the large multichain laminin molecule by TGFbeta1. We also determined the functional role of laminin in several TGFbeta1-mediated responses: growth inhibition, downmodulation of anchorage-independent growth, and cellular invasion. Expression of either antisense laminin chain A, B1, or B2 RNA resulted in a downmodulation of endogenous laminin mRNA expression and blocked the induction of laminin protein by TGFbeta1 without affecting the induction of other adhesion molecules such as fibronectin or CEA. It is concluded that antisense RNA directed to only one of the laminin chains was sufficient to disrupt the induction of the complex laminin molecule in quite a specific manner. Expression of antisense laminin RNA downregulated cellular adhesion to extracellular matrix (ECM) laminin and blocked the ability of TGFbeta1 to upmodulate adhesion to ECM laminin. Expression of antisense laminin RNA, however, did not alter the downregulating effect of TGFbeta1 on cellular proliferation, anchorage-independent growth, or cellular invasion, suggesting that the induction of laminin did not play a significant functional role in these TGFbeta1-mediated cellular responses. It is likely that other adhesion pathways may be involved in mediating the action of TGFbeta1 in this cell line.

Carcinoembryonic Antigen↗
PubMed1999

Differential expression and regulation of chemokines JE, KC, and IP-10 gene in primary cultured murine hepatocytes.

Chemokines are a superfamily of structurally related chemoattractant cytokines. JE (monocyte chemoattractant protein-1) and IP-10 (interferon-inducible protein-10) have been detected in the diseased liver. However the in vitro expression is unclear. In this report, we revealed that JE, KC (melanoma growth-stimulating activity gene), and IP-10 mRNAs are not expressed in the normal liver but spontaneously and time-dependently expressed in the primary hepatocytes. The serum-independent gene expression of both JE and KC lasted over 72 h, but that of IP-10 became undetectable 24 h after isolation with collagenase perfusion method. The induction of the genes' expression was not due to LPS contamination but nevertheless was associated with isolation procedure. Actinomycin D blocked their expression. The increase of their transcripts resulted from greater increase in gene transcription and lower mRNA stability. Consistent with c-jun, their mRNA expressions were simultaneously superinduced by cycloheximide (1 microg/ml), suggesting that de novo protein synthesis is involved their transcriptions. Inhibition by pyrrolidine dithiocarbamate (PDTC), a NF-kappaB/c-rel inhibitor, and EMSA imply that NF-kappaB/c-rel is important in their expressions. Of particular interest is that dexamethasone upregulated the spontaneous expression of KC, but suppressed that of JE and IP-10. LPS upregulated the mRNA levels of JE and KC but did not affect that of IP-10. IFN-gamma induced the expression of IP-10; however unlike in macrophages, it did not selectively inhibit that of JE and KC. Our data demonstrated the existence and differential gene expression of JE, KC, and IP-10 in primary cultured hepatocytes, and these are considered to be a reflex of the alteration of hepatocyte cellular physiology during and after isolation.

Animals↗
PubMed1999

Surgical technique for vascularized thymus transplantation in mice.

Traditionally, mouse nonvascularized thymus implants have been used to investigate various aspects of thymus function. However, these grafts are easily damaged by ischemia and fail to reproduce the normal anatomy of the thymus. In addition, the function of these grafts has not been fully examined. We have recently developed a vascularized thymus transplant model in mice. The donor operation consists of isolating the right lobe of the thymus and creating a single vascular pathway. In the recipient surgery, end-to-side anastomoses between donor brachycephalic artery and recipient right common carotid artery, and between donor superior caval vein and recipient right external jugular vein, were performed. We performed 10 consecutive isografts in BALB/c mice with a success rate of 90%. The thymus grafts had a normal histology and function. This study illustrates that it is technically possible to transplant a mouse vascular thymus graft. This model has several advantages that make it a useful tool to study many aspects of thymus function. We plan to use this model further to study the potential for induction of tolerance by thymus grafts.

Animals↗
PubMed1999

Interleukin-2 receptoralpha gene expression in intestinal allograft rejection.

This study was undertaken to determine whether the interleukin-2 receptor alpha (IL-2Ralpha) coding gene could serve as a genetic marker of intestinal allograft rejection. The small bowel graft from Jinbai mice was heterotopically transplanted to BALB/c mice. Naive BALB/c mice and BALB/c mice with intestinal isografts were used as controls. The mRNA transcription level of the spleen cells harvested from the recipients and controls was measured with quantitative reverse transcription polymerase chain reaction (Q-RT-PCR) on postoperative day (POD) 3 and routine pathology was studied in these grafts. The IL-2Ralpha mRNA transcription level in untreated allografts was significantly higher than that of controls on POD 3, when intestinal allograft rejection was not detected. These data suggest that the IL-2Ralpha mRNA transcription level may reflect the early cellular immune response and this genetic marker may be of value in monitoring intestinal allograft rejection.

Animals↗
PubMed1999

Capillary electrophoresis enantioseparation of drugs using beta-cyclodextrin polymer: intramolecular synergistic effect.

Enantiomers of eight basic compounds of pharmaceutical interest were studied by capillary electrophoresis (CE) using a soluble cyclodextrin (CD) polymer and native CD as chiral selectors. The effects of the polymer concentration and the pH of the buffer solution on resolution were examined. It was found that the beta-CD polymer shows higher stereoselectivity than its parent cyclodextrin. Such improvement is due to the structural difference between beta-CD and beta-CD polymer. These results suggested the existence of an intramolecular synergistic effect in CE.

Buffers↗
PubMed1999

Accurate measurement of H(N)-H(alpha) residual dipolar couplings in proteins.

A method for accurately measuring H(N)-H(alpha) residual dipolar couplings is described. Using this technique, both the sign and magnitude of the coupling can be determined easily. Residual dipolar coupling between H(N)(i)-H(alpha)(i) and H(N)(i)-H(alpha)(i-1) were measured for the FK506 binding protein complexed to FK506. The experimental values were in excellent agreement with predictions based on an X-ray crystal structure of the protein/ligand complex, suggesting that these residual dipolar couplings will provide accurate structural constraints for the refinement of protein structures determined by NMR.

Magnetic Resonance Spectroscopy↗
PubMed1999

Photoassociation of Ultracold Atoms: A New Spectroscopic Technique.

The new spectroscopic technique of photoassociation of ultracold atoms is reviewed, with an emphasis on connecting this area to traditional bound-state molecular spectroscopy. In particular, in contrast to photoassociative spectra at thermal energies, which are broad and of low information content, photoassociative spectra of ultracold atoms are high resolution, permitting observation of small vibrational and rotational spacings of long-range molecular levels near dissociation (typically with outer classical turning points >20 Å). The types of detection and theoretical analysis employed are illustrated, primarily using the example of 39K2. Future directions and applications of this field (e.g., to ultracold molecular formation) are also discussed. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Cloning, sequencing, and characterization of five genes coding for acyl-CoA oxidase isozymes in the yeast Yarrowia lipolytica.

The Acyl-CoA oxidase (AOX) isozymes catalyze the first steps of peroxisomal beta-oxidation, which is important for the degradation of fatty acids. Using conserved blocks in previously identified yeast POX genes encoding AOXs, the authors have shown that five POX genes are present in the yeast Yarrowia lipolytica. These genes show approx 63% identity among themselves, and 42% identity with the POX genes from other yeasts. Mono-disrupted Y. lipolytica strains were constructed using a variation of the sticky-end polymerase chain reaction method. AOX activity in the mono-disrupted strains revealed that a long-chain oxidase is encoded by the POX2 gene and a short-chain oxidase by the POX3 gene.

Acyl-CoA Oxidase↗
PubMed1999

Regulation of autoreactive anti-IgG (rheumatoid factor) B cells in normal and autoimmune mice.

In systemic autoimmune disease, autoantibodies target specific self-components in patterns that depend on the particular underlying disease. Therefore, in order to understand how tolerance to these self-components breaks down, it is important to study B cells with those specificities, rather than artificial autoantigens. We have been investigating the regulation of autoreactive B cells with specificity for self IgG2a (the rheumatoid factor or RF specificity) in order to understand how normal mice regulate RF autoantibodies and how this fails in autoimmune mice. A transgenic (Tgic) mouse based on an RF isolated from a diseased MRL/lpr/lpr mouse was constructed and studied in both normal and autoimmune-prone genetic backgrounds. Normal mice do not appear to regulate the RF clone negatively, nor do they appear to activate it substantially. Thus, a disease-related RF is "clonally indifferent." However, in a, Fas-deficient autoimmune-prone animal, these RF B cells are activated to divide and secrete in an antigen-specific manner. A high-affinity RF Tgic mouse was also constructed to determine whether RFs could be tolerized in normal mice. These B cells were deleted or edited in the presence of the autoantigen, which originated from maternal IgG in young mice. Interestingly, shortly after weaning, many mice began to produce autoreactive RF. Escape from tolerance could last for months and was most likely perpetuated by a positive feedback mechanism. Such a mechanism could exist in autoimmune animals and could have important implications for chronic autoimmune disease, as discussed.

Animals↗
PubMed1999

Effects of serum of Kawasaki disease on PDGF expression in monocytes and on endothelial cell apoptosis.

The effects of serum of patients with Kawasaki disease on the platelet derived growth factor-B (PDGF-B) chain protein expression in monocytes were studied by immunocytochemical method and the effects of the serum on the endothelial cellular (EC) apoptosis were observed by flow cytometric technique. It was found that the serum of patients with Kawasaki disease induced significantly the expression of PDGF-B chain protein. Likewise, EC apoptosis was increased significantly in the experimental group as compared with the control group (P < 0.01). The results suggest that PDGF in monocytes increase and EC apoptosis play an important role in the development of coronary artery complication in Kawasaki disease.

Apoptosis↗
PubMed1999

Microdissection and microcloning of rye (Secale cereale L.) chromosome 1R.

Chromosome 1R was microdissected and collected from mitotic metaphase spreads of rye (Secale cereale L.) by using glass needles. The isolated chromosomes were amplified in vitro by Sau3A linker adaptor-mediated polymerase chain reaction (PCR). After amplification, the presence of rye-specific DNA was verified by Southern hybridization. The second-round PCR products from five 1R chromosomes were cloned into a plasmid vector to create a chromosome-specific library, which produced approximately 220,000 recombinant clones. Characterization of the microclone library showed that the 172 clones evaluated ranged in size from 300-1800 bp with an average size of 950 bp, of which approximately 42% were medium/high copy and 58% were low/unique copy clones. Chromosome in situ hybridization confirmed that the PCR products from microdissected chromosomes originated from chromosome 1R, indicating that many chromosome 1R-specific sequences were present in the library.

Base Sequence↗
PubMed1999

Relationships between muscle mitochondrial DNA content, mitochondrial enzyme activity and oxidative capacity in man: alterations with disease.

Muscle mitochondrial content is tightly regulated, and requires the expression of both nuclear and mitochondrial genes. In addition, muscle mitochondrial content is a major determinant of aerobic exercise capacity in healthy subjects. The current study was designed to test the hypothesis that in healthy humans, muscle mitochondrial DNA (mtDNA) content is correlated with citrate synthase activity (a representative nuclear-encoded mitochondrial enzyme) and aerobic exercise capacity as defined by whole-body peak oxygen consumption (VO2). Furthermore, it was postulated that these relationships might be altered with disease. Twelve healthy and five paraplegic subjects underwent exercise testing and vastus lateralis muscle biopsy sampling. An additional ten healthy subjects and eight patients with unilateral peripheral arterial disease (PAD) underwent exercise testing and gastrocnemius muscle biopsy sampling. Citrate synthase activity and mtDNA content were positively correlated in the vastus lateralis muscles from the healthy subjects. This relationship was similar in muscle from paraplegic subjects. mtDNA content was positively correlated with peak VO2 in the healthy subjects and in the paraplegic subjects in whom peak VO2 had been elicited by functional electrical stimulation of the muscle. In contrast, the PAD subjects demonstrated higher mtDNA contents than would have been predicted based on their claudication-limited peak VO2. Thus, in healthy humans there are strong relationships between muscle mtDNA content and both muscle citrate synthase activity and peak VO2. These relationships are consistent with coordinant nuclear DNA and mtDNA expression, and with mitochondrial content being a determinant of aerobic exercise capacity. The relationships seen in healthy humans are quantitatively similar in paraplegic patients, but not in patients with PAD, a disease which is associated with a metabolic myopathy. The relationships between mtDNA content, mitochondrial enzyme activities and exercise capacity provide insight into the physiologic and pathophysiologic regulation of muscle mitochondrial expression.

Adolescent↗
PubMed1999

The influence of the p53 gene on the in vitro chemosensitivity of colorectal cancer cells.

PURPOSE: The p53 gene is considered one of the most important in the control of apoptosis, and its mutations have a close relationship with chemosensitivity. The aim of this work was to investigate the role of p53 in the apoptosis of colorectal cancer cells in vitro, induced by 5-fluorouracil (5-FU) and hydroxy-camptothecin (HCPT). METHODS: A total of 39 colorectal cancer samples from patients were treated in vitro with 5-FU (10 microg/ml), 5-FU (10 microg/ml) + leucovorin (5 microg/ml), HCPT (0.1 microg/ml) and HCPT (0.1 microg/ml) + Salvia mitorrhiza (6 microl), using an in situ terminal deoxynucleotidyltransferase assay to detect chemosensitivity. p53 gene mutations from tumor DNA were detected, after amplification by the polymerase chain reaction of exons 5-8, by non-radioactive single-strand conformation polymorphism. RESULTS: p53 gene mutations were observed in 43.6% (17/39) of colorectal carcinomas, when the terminal deoxynucleotidyltransferase assay was used to detect the tumor apoptotic rate. Cells with mutated p53 had lower chemosensitivity than those without (p < 0.01). CONCLUSION: Routine assessment of p53 status may be helpful in selecting patients with the wildtype p53 gene, who have a predictably better response to chemotherapy.

Adult↗
PubMed1999

Detection of endogenous biotin in various tissues: novel functions in the hippocampus and implications for its use in avidin-biotin technology.

Significant amounts of endogenous biotin were detected by avidin-peroxidase in fixed rat kidney, liver, and brain. The staining was indistinguishable from the true signals of immunoreactivity and could not be consistently blocked by pretreatment with avidin. The finding that certain neurons in the hippocampus contain more biotin than neurons in other areas of the brain suggests that biotin might have novel functions in the brain other than its well-known role as cofactor of carboxylases. Critical examination of published immunohistochemical localization studies on rat kidney strongly suggests that many false-positive results have been considered as true signals. Interference of endogenous biotin in any study using avidin-biotin technology must be considered if biological tissues are involved. The published data obtained by this method should therefore be reevaluated. Furthermore, appropriate controls, blockers and caution in interpreting results must be exercised, not only in immunohistochemistry but also in any applications of avidin-biotin technology.

Animals↗
PubMed1999

Conformational changes of the in situ nuclear pore complex.

By bridging the double membrane separating the cell nucleus and cytoplasm, nuclear pore complexes (NPCs) are crucial pathways for the exchange of ions, proteins, and RNA between these two cellular compartments. A structure in the central lumen of the NPC, called the nuclear transport protein, central granule, or nuclear plug, appeared to gate diffusion of intermediate-sized molecules (10-40 kDa) across the nuclear membranes. Visualization of the NPC required drying and fixation of the specimen for electron and atomic force microscopy (AFM), a requirement that has raised doubts about the physiological relevance of the observation. Here we present AFM images of the outer nuclear membranes and NPCs of Xenopus laevis oocytes under more physiological conditions. Measured under a variety of Ca2+ depletion conditions, the central granule appeared to occupy and occlude the lumen of the pore in >80% of NPCs compared to <10% in controls. In a few instances images were obtained of the same NPCs as the solution was changed from control saline to store depletion conditions, and finally to store repletion conditions. We conclude that the central lumen of the nuclear pore complex undergoes a conformational change in response to depletion of nuclear cisternal Ca2+ levels.

Adenosine Triphosphate↗