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Biomedical subjects

Y Lu

Publications and source records attributed to Y Lu.

At least 127 records · Page 7Linked to original sources
PubMed2001

Apoptosis induction in prostate cancer cells by a novel gene product, pHyde, involves caspase-3.

A novel gene, pHyde, was recently cloned from Dunning rat prostate cancer cells. A recombinant adenovirus containing pHyde cDNA gene (AdpHyde) was generated to investigate the biological function of pHyde protein. AdpHyde inhibited the growth of human prostate cancer cells. Apoptosis was induced in AdpHyde transduced cells as demonstrated by DAPI (4', 6-diamino-2-phenylindole), TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick and labeling) staining, and flow cytometry assays. Apoptosis was also induced in human xenograft prostate cancer tumors growing in nude mice following treatment with AdpHyde. AdpHyde transduction resulted in a dose-dependent stimulation of caspase-3 activity in DU145 cells which was blocked by DEVD (succinyl-Asp-Glu-Val-Asp-aldehyde) and VAD (benzyloxycarbonyl - Val - Ala - Asp -fluoromethylketone), inhibitors specifically against caspase-3. Moreover, cancer cells that lacked expression of endogenous caspase-3 were not or barely inhibited by pHyde. These results taken together suggest that pHyde inhibits cancer growth by inducing apoptosis through a caspase-3 dependent pathway.

Adenoviridae↗
PubMed2001

[2',6'-Dimethyltyrosine]dynorphin A(1-11)-NH2 analogues lacking an N-terminal amino group: potent and selective kappa opioid antagonists.

Recent studies showed that dermorphin and enkephalin analogues containing two methyl groups at the 2',6'-positions of the Tyr(1) aromatic ring and lacking an N-terminal amino group were moderately potent delta and mu opioid antagonists. These results indicate that a positively charged N-terminal amino group may be essential for signal transduction but not for receptor binding and suggested that its deletion in agonist opioid peptides containing an N-terminal 2',6'-dimethyltyrosine (Dmt) residue may represent a general way to convert them into antagonists. In an attempt to develop dynorphin A (Dyn A)-derived kappa opioid antagonists, we prepared analogues of [Dmt(1)]Dyn A(1-11)-NH2 (1), in which the N-terminal amino group was either omitted or replaced with a methyl group. This was achieved by replacement of Tyr(1) with 3-(2,6-dimethyl-4-hydroxyphenyl)propanoic acid (Dhp) or (2S)-2-methyl-3-(2,6-dimethyl-4-hydroxyphenyl)propanoic acid [(2S)-Mdp]. Compounds were tested in the guinea pig ileum and mouse vas deferens bioassays and in rat and guinea pig brain membrane receptor binding assays. All analogues turned out to be potent kappa antagonists against Dyn A(1-13) and the non-peptide agonist U50,488 and showed only weak mu and delta antagonist activity. The most potent and most selective kappa antagonist of the series was [(2S)-Mdp(1)]Dyn A(1-11)-NH2 (5, dynantin), which showed subnanomolar kappa antagonist potency against Dyn A(1-13) and very high kappa selectivity both in terms of its K(e) values determined against kappa, mu, and delta agonists and in terms of its ratios of kappa, mu, and delta receptor binding affinity constants. Dynantin is the first potent and selective Dyn A-derived kappa antagonist known and may complement the non-peptide kappa antagonists norbinaltorphimine and GNTI as a pharmacological tool in opioid research.

Animals↗
PubMed2001

Template-assisted self-assembly: a practical route to complex aggregates of monodispersed colloids with well-defined sizes, shapes, and structures.

This paper describes a strategy that combines physical templating and capillary forces to assemble monodispersed spherical colloids into uniform aggregates with well-controlled sizes, shapes, and structures. When an aqueous dispersion of colloidal particles was allowed to dewet from a solid surface that had been patterned with appropriate relief structures, the particles were trapped by the recessed regions and assembled into aggregates whose structures were determined by the geometric confinement provided by the templates. We have demonstrated the capability and feasibility of this approach by assembling polystyrene beads and silica colloids (> or =150 nm in diameter) into complex aggregates that include polygonal or polyhedral clusters, linear or zigzag chains, and circular rings. We have also been able to generate hybrid aggregates in the shape of HF or H2O molecules that are composed of polymer beads having different diameters, polymer beads labeled with different organic dyes, and a combination of polymeric and inorganic beads. These colloidal aggregates can serve as a useful model system to investigate the hydrodynamic and optical scattering properties of colloidal particles having nonspherical morphologies. They should also find use as the building blocks to generate hierarchically self-assembled systems that may exhibit interesting properties highly valuable to areas ranging from photonics to condensed matter physics.

Journal Article↗
PubMed2001

Immunogene therapy of tumors with vaccine based on Xenopus homologous vascular endothelial growth factor as a model antigen.

Overcoming immune tolerance of the growth factors associated with tumor growth should be a useful approach to cancer therapy by active immunity. We used vascular endothelial growth factor (VEGF) as a model antigen to explore the feasibility of the immunogene tumor therapy with a vaccine based on a single xenogeneic homologous gene, targeting the growth factors associated with angiogenesis. To test this concept, we constructed a plasmid DNA encoding Xenopus homologous VEGF (XVEGF-p) and control vectors. We found that immunogene tumor therapy with a vaccine based on XVEGF was effective at both protective and therapeutic antitumor immunity in several tumor models in mice. VEGF-specific autoantibodies in sera of mice immunized with XVEGF-p could be found in Western blotting analysis and ELISA assay. The purified immunoglobulins were effective at the inhibition of VEGF-mediated endothelial cell proliferation in vitro, and at antitumor activity and the inhibition of angiogenesis by adoptive transfer in vivo. The elevation of VEGF in the sera of the tumor-bearing mice could be abrogated with XVEGF-p immunization. The antitumor activity and production of VEGF-specific autoantibodies, significantly elevated IgG1 and IgG2b, could be abrogated by the depletion of CD4(+) T lymphocytes. The observations may provide a vaccine strategy for cancer therapy through the induction of autoimmunity against the growth factors associated with tumor growth in a cross reaction with single xenogeneic homologous gene and may be of importance in the further exploration of the applications of other xenogeneic homologous genes identified in human and other animal genome sequence projects in cancer therapy.

Animals↗
PubMed2001

Ultraviolet radiation alters the phosphorylation of RNA polymerase II large subunit and accelerates its proteasome-dependent degradation.

It has been shown that ultraviolet (UV) radiation induces the ubiquitination of the large subunit of RNA polymerase II (RNAP II-LS) as well as its proteasomal degradation. Studies in mammalian cells have indicated that highly phosphorylated forms of RNAP II-LS are preferentially ubiquitinated, but studies in Saccharomyces cerevisiae have provided evidence that unphosphorylated RNAP II-LS is an equally suitable substrate. In the present study, an antibody (ARNA-3) that recognizes all forms of RNAP II-LS, regardless of the phosphorylation status of its C-terminal domain (CTD), was utilized to evaluate the degradation of total cellular RNAP II-LS in human fibroblasts under basal conditions or after UV-C (10J/m(2)) irradiation. It was found that UV radiation rapidly shifted the phosphorylation profile of RNAP II-LS from a mixture of dephosphorylated and phosphorylated forms to entirely more phosphorylated forms. This shift in phosphorylation status was not blocked by pharmacologic inhibition of either the ERK or p38 pathways, both of which have been implicated in the cellular UV response. In addition to shifting the phosphorylation profile, UV radiation led to net degradation of total RNAP II-LS. UV-induced degradation of RNAP II-LS was also greatly reduced in the presence of the transcriptional and CTD kinase inhibitor DRB. Using a panel of protease inhibitors, it was shown that the bulk of UV-induced degradation is proteasome-dependent. However, the UV-induced loss of hypophosphorylated RNAP II-LS was proteasome-independent. Lastly, UV radiation induced a similar shift to all hyperphosphorylated RNAP II-LS in Cockayne syndrome (CS) cells of complementation groups A or B (CSA or CSB) when compared to appropriate controls. The UV-induced degradation rates of RNAP II-LS were not significantly altered when comparing CSA or CSB to repair competent control cells. The implications for the cellular UV response are discussed.

Cell Line↗
PubMed2001

Robust HIV type 2 cellular immune response measured by a modified anthrax toxin-based enzyme-linked immunospot assay.

Evaluation of immune mechanisms responsible for control of viral replication is critical to understanding HIV-2 attenuated biological characteristics in pathogenesis and transmission. Evaluation of the cellular immune response is often based on labor-intensive techniques that limit the scope of most studies performed. A simple and rapid anthrax toxin-based ELISPOT method to assess HIV-2 cellular immune response was developed. The modified anthrax toxin-based antigen presentation process performed better than a recombinant vaccinia system and the ELISPOT method significantly enhanced the ease and simplicity of the assay. Using this method, a robust HIV-2 cellular immune response directed toward the p26 core protein was exhibited in 21 of 24 (87.5%) infected women, and all 8 seronegative subjects were negative in both assays. Cellular immune responses were associated with low HIV-2 viral load. This simple and rapid modified anthrax toxin-based ELISPOT method allowed us to demonstrate, strong cellular immune responses that may be critical determinants in the HIV-2 attenuated phenotype.

Antigen Presentation↗
PubMed2001

[MRI-guided transcutaneous aspiration biopsy of liver lesions].

OBJECTIVE: To evaluate the clinical application of MR-guided aspiration biopsy of liver lesions. METHODS: MR-guided aspiration biopsy of liver lesions with 0.5 T Conventional MR system and 19 gauge MRI-compatible aspiration needle was performed in 13 patients. For MR guidance, fast gradient echo sequence or fast spin echo sequence was used. RESULTS: MR-guided aspiration liver biopsy was performed successfully without any complication on all patients. The accurate needle puncture rate was 100%, accurate diagnosis rate 92.3%, and false negative rate 7.7%. CONCLUSION: MR-guided transcutaneous aspiration biopsy of liver lesions is a safe, accurate and effective method for diagnosis and differential diagnosis.

Adult↗
PubMed2001

Correlation between electrophysiology and morphology of three groups of neuron in the dorsal commissural nucleus of lumbosacral spinal cord of mature rats studied in vitro.

The dorsal commissural nucleus (DCN) in the lumbosacral spinal cord receives afferent inputs from the pelvic organs via pudendal and pelvic nerves. Electrophysiological and morphological properties of neurons in the DCN of L6-S1 were examined using whole-cell recordings with biocytin-filled electrodes in transverse slices of mature rat spinal cord. Neurons were categorized into three groups according to their discharge in response to suprathreshold depolarizing pulses; neurons with tonic (19/42) and phasic (13/42) firing patterns, and neurons (10/42) that fired in bursts arising from a Ca(2+)-dependent hump. The predominantly fusiform somata of neurons labeled during recording (n = 31) had on average 3.1 primary dendrites, 7.5 terminating dendritic branches, 3.1 axon collaterals, and 14.2 axon terminations per neuron. The groups were morphologically distinct on the basis of their dendritic branching patterns. Phasic neurons (n = 10) had the most elaborate dendritic branching and the largest numbers of axon collaterals. All tonic neurons (n = 11) had axons/collaterals projecting to the intermediolateral area but none to the funiculi, suggesting that they function as interneurons in local autonomic reflexes. Many axons/collaterals of all phasic neurons lay within the DCN, suggesting that they integrate segmental and descending inputs. Seven of 10 neurons with Ca(2+)-dependent humps had axons/collaterals extending into one of the funiculi, suggesting that they project intersegmentally or to the brain. Ca(2+) hump neurons also had more axons/collaterals within the DCN and fewer in the intermediolateral area than tonic neurons. This correlation between firing pattern and morphology is an important step toward defining the cellular pathways regulating pelvic function.

Action Potentials↗
PubMed2001

Identification of the first trans-(3R,4R)- dimethyl-4-(3-hydroxyphenyl)piperidine derivative to possess highly potent and selective opioid kappa receptor antagonist activity.

A structurally novel opioid kappa receptor selective ligand has been identified. This compound, (3R)-7-hydroxy-N-((1S)-1-[[(3R,4R)-4-(3-hydroxyphenyl)-3,4-dimethyl-1-piperidinyl]methyl]-2-methylpropyl)-1,2,3,4-tetrahydro-3-isoquinolinecarboxamide (JDTic, 10) demonstrated high affinity for the kappa receptor in the binding assay (kappa K(i) = 0.3 nM) and highly potent and selective kappa antagonism in the [(35)S]GTP-gamma-S assay using cloned opioid receptors (kappa K(i) = 0.006 nM, mu/kappa ratio = 570, delta/kappa ratio > 16600).

Animals↗
PubMed2001

Development of a fully integrated analysis system for ions based on ion-selective optodes and centrifugal microfluidics.

A fully integrated, miniaturized analysis system for ions based on a centrifugal microfluidics platform and ion-selective optode membranes is described. The microfluidic architecture is composed of channels, five solution reservoirs, a measuring chamber, and a waste reservoir manufactured onto a disk-shaped substrate of poly(methyl methacrylate). Ion-selective optode membranes, composed of plasticized poly(vinyl chloride) impregnated with an ionophore, a proton chromoionophore, and a lipophilic anionic additive, were cast, with a spin-on device, onto a support layer and then immobilized on the disk. Fluid propulsion is achieved by the centrifugal force that results from spinning the disk, while a system of valves is built onto the disk to control flow. These valves operate based on fluid properties and fluid/substrate interactions and are controlled by the angular frequency of rotation. With this system, we have been able to deliver calibrant solutions, washing buffers, or "test" solutions to the measuring chamber where the optode membrane is located. An analysis system based on a potassium-selective optode has been characterized. Results indicate that optodes immobilized on the platform demonstrate theoretical responses in an absorbance mode of measurement. Samples of unknown concentration can be quantified to within 3% error by fitting the response function for a given optode membrane using an acid (for measuring the signal for a fully protonated chromoionophore), a base (for fully deprotonated chromoionophore), and two standard solutions. Further, the ability to measure ion concentrations by employing one standard solution in conjunction with acid and base and with two standards alone were studied to delineate whether the current architecture could be simplified. Finally, the efficacy of incorporating washing steps into the calibration protocol was investigated.

Calibration↗
PubMed2001

NF-kappaB/RelA transactivation is required for atypical protein kinase C iota-mediated cell survival.

In chronic myelogenous leukemia (CML), the oncogene bcr-abl encodes a dysregulated tyrosine kinase that inhibits apoptosis. We showed previously that human erythroleukemia K562 cells are resistant to antineoplastic drug (taxol)-induced apoptosis through the atypical protein kinase C iota isozyme (PKC iota), a kinase downstream of Bcr-Abl. The mechanism(s) by which PKC iota mediates cell survival to taxol is unknown. Here we demonstrate that PKC iota requires the transcription factor nuclear factor-kappaB (NF-kappaB) to confer cell survival. At apoptosis-inducing concentrations, taxol weakly induces IkappaB(alpha) proteolysis and NF-kappaB translocation in K562 cells, but potently induces its transcriptional activity. Inhibition of NF-kappaB activity (by blocking IkappaB(alpha) degradation) significantly sensitizes cells to taxol-induced apoptosis. Likewise, K562 cells expressing antisense PKC iota mRNA or kinase dead PKC iota (PKC iota-KD) are sensitized to taxol; these cells are rescued from apoptosis by NF-kappaB overexpression. Expression of constitutively active PKC iota (PKC iota-CA) upregulates NF-kappaB transactivation and rescues cells from apoptosis in the absence of Bcr-Abl tyrosine kinase activity. Using a chimeric GAL4-RelA transactivator, we find that taxol potently activates GAL4-RelA-dependent transcription. This activation was further upregulated by expression of PKC iota-CA and inhibited by expression of PKC iota-KD. Our results indicate that RelA transactivation is an important downstream target of the PKC iota-mediated Bcr-Abl signaling pathway and is required for resistance to taxol-induced apoptosis.

Cell Survival↗
PubMed2001

Recombinant vascular endothelial growth factor secreted from tissue-engineered bioartificial muscles promotes localized angiogenesis.

BACKGROUND: Therapeutic angiogenesis by the administration of recombinant vascular endothelial growth factor (rVEGF) is a novel strategy for the treatment of ischemic disorders. rVEGF has been delivered as a protein, by plasmid DNA, and by genetically engineered cells with different pharmacokinetic and physiological properties. In the present study, we examined a new method for delivery of rVEGF using implantable bioartificial muscle (BAM) tissues made from genetically modified primary skeletal myoblasts. Our goal was to determine whether the rVEGF delivered by this technique promoted controlled angiogenesis in nonischemic and/or ischemic adult mouse tissue. METHODS AND RESULTS: Primary adult mouse myoblasts were retrovirally transduced to secrete human or mouse rVEGF and tissue-engineered into implantable 1x10 to 15-mm BAMs containing parallel arrays of postmitotic myofibers. In vitro, they secreted 290 to 511 ng of bioactive mouse or human VEGF/BAM per day. rVEGF BAMs implanted subcutaneously into syngeneic mice caused a 30-fold increase in the number of CD31-positive capillary cells within the BAM by 1 week compared with control BAMs. Implantation of rVEGF-secreting BAMs into ischemic hindlimbs resulted in a 2- to 3-fold increase in capillary density of neighboring host muscle by 1 week and out to 4 weeks with no evidence of hemangioma formation. CONCLUSIONS: Local delivery of rVEGF from BAMs rapidly increases capillary density both within the BAM itself and in adjacent ischemic muscle tissue. Genetically engineered muscle tissue provides a method for therapeutic protein delivery in a dose-regulated fashion.

Animals↗
PubMed2001

A novel mechanical dissociation technique for studying acutely isolated maturing Drosophila central neurons.

A novel mechanical method, for studying acutely isolated maturing Drosophila central neurons, has been developed. Electrophysiological experiments have been carried out to assess the quality of these acutely dissociated neurons. The mechanically dissociated Drosophila central neurons were divided into three categories depending on their size and morphological features. Four types of whole-cell K(+) currents were identified in these neurons, based on their kinetic properties. Moreover, the K(+) currents in the new preparation were found to have similar electrophysiological and pharmacological properties to those reported in the cultured neurons. The new technique, however, was more rapid and convenient. Furthermore, this new system was successfully applied to the isolation of neurons from the adult Drosophila, a process that is extremely difficult by routinely used methods. Thus, this new preparation would be very reliable and applicable to preparing Drosophila central neurons for biophysical and physiological studies.

4-Aminopyridine↗
PubMed2001

Involvement of JNK-mediated pathway in EGF-mediated protection against paclitaxel-induced apoptosis in SiHa human cervical cancer cells.

We investigated the signalling pathways by which epidermal growth factor (EGF) modulates paclitaxel-induced apoptosis in SiHa human cervical cancer cells. SiHa cells exposed to paclitaxel underwent apoptosis, which was strongly inhibited by EGF. This inhibition of apoptosis by EGF was not altered by pharmacological blockade of phosphatidylinositol 3'-OH kinase (PI-3K) with the PI-3K specific inhibitor LY294002 or blockade of the mitogen-activated protein kinase (MAPK) kinase (MEK) with the MEK specific inhibitor PD98059, or by transfection of the cells with PI-3K or MEK dominant-negative expression vectors. EGF did not stimulate PI-3K/Akt, MEK/MAPK, or p38 MAPK activity in SiHa cells but did transiently activate the c-Jun NH2-terminal kinase (JNK). Co-exposure of SiHa cells to SB202190 at concentrations that inhibit JNK abolished the protective effect of EGF on SiHa cells against paclitaxel-induced apoptosis. Our findings indicate that the JNK signaling pathway plays an important role in EGF-mediated protection from paclitaxel-induced apoptosis in SiHa cells.

Antineoplastic Agents, Phytogenic↗
PubMed2001

Lipopolysaccharide-activated B cells down-regulate Th1 immunity and prevent autoimmune diabetes in nonobese diabetic mice.

B cells can serve dual roles in modulating T cell immunity through their potent capacity to present Ag and induce regulatory tolerance. Although B cells are necessary components for the initiation of spontaneous T cell autoimmunity to beta cell Ags in nonobese diabetic (NOD) mice, the role of activated B cells in the autoimmune process is poorly understood. In this study, we show that LPS-activated B cells, but not control B cells, express Fas ligand and secrete TGF-beta. Coincubation of diabetogenic T cells with activated B cells in vitro leads to the apoptosis of both T and B lymphocytes. Transfusion of activated B cells, but not control B cells, into prediabetic NOD mice inhibited spontaneous Th1 autoimmunity, but did not promote Th2 responses to beta cell autoantigens. Furthermore, this treatment induced mononuclear cell apoptosis predominantly in the spleen and temporarily impaired the activity of APCs. Cotransfer of activated B cells with diabetogenic splenic T cells prevented the adoptive transfer of type I diabetes mellitus (T1DM) to NOD/scid mice. Importantly, whereas 90% of NOD mice treated with control B cells developed T1DM within 27 wk, <20% of the NOD mice treated with activated B cells became hyperglycemic up to 1 year of age. Our data suggest that activated B cells can down-regulate pathogenic Th1 immunity through triggering the apoptosis of Th1 cells and/or inhibition of APC activity by the secretion of TGF-beta. These findings provide new insights into T-B cell interactions and may aid in the design of new therapies for human T1DM.

Adoptive Transfer↗