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Biomedical subjects

Y Lu

Publications and source records attributed to Y Lu.

At least 109 records · Page 6Linked to original sources
PubMed2002

Delayed delivery of AAV-GDNF prevents nigral neurodegeneration and promotes functional recovery in a rat model of Parkinson's disease.

Glial cell line-derived neurotrophic factor (GDNF) is a strong candidate agent in the neuroprotective treatment of Parkinson's disease (PD). We investigated whether adeno-associated viral (AAV) vector-mediated delivery of a GDNF gene in a delayed manner could prevent progressive degeneration of dopaminergic (DA) neurons, while preserving a functional nigrostriatal pathway. Four weeks after a unilateral intrastriatal injection of 6-hydroxydopamine (6-OHDA), rats received injection of AAV vectors expressing GDNF tagged with FLAG peptide (AAV-GDNFflag) or beta-galactosidase (AAV-LacZ) into the lesioned striatum. Immunostaining for FLAG demonstrated retrograde transport of GDNFflag to the substantia nigra (SN). The density of tyrosine hydroxylase (TH)-positive DA fibers in the striatum and the number of TH-positive or cholera toxin subunit B (CTB, neuronal tracer)-labeled neurons in the SN were significantly greater in the AAV-GDNFflag group than in the AAV-LacZ group. Dopamine levels and those of its metabolites in the striatum were remarkably higher in the AAV-GDNFflag group compared with the control group. Consistent with anatomical and biochemical changes, significant behavioral recovery was observed from 4-20 weeks following AAV-GDNFflag injection. These data indicate that a delayed delivery of GDNF gene using AAV vector is efficacious even 4 weeks after the onset of progressive degeneration in a rat model of PD.

Animals↗
PubMed2002

A gene therapy for cancer based on the angiogenesis inhibitor, vasostatin.

The growth and persistence of solid tumors and their metastasis are angiogenesis-dependent. Vasostatin, the N-terminal domain of calreticulin inclusive of amino acids 1-180, is a potent angiogenesis inhibitor. To investigate whether intramuscular administration of vasostatin gene has the antitumor activity in mouse tumor models, we constructed a plasmid DNA encoding vasostatin and a control vector. Production and secretion of vasostatin protein by COS cells transfected with the plasmid DNA encoding vasostatin (pSecTag2B-vaso) were confirmed by Western blot analysis and ELISA. Conditioned medium from vasostatin-transfected COS cells apparently inhibited human umbilical vein endothelial cell (HUVEC) and mouse endothelial cell (SVEC4-10) proliferation, compared with conditioned medium from the COS cells transfected with control vector or non-transfected cells. Treatment with pSecTag2B-vaso twice weekly for 4 weeks resulted in the inhibition of tumor growth and the prolongation of the survival of tumor-bearing mice. The sustained high level of vasostatin protein in serum could be identified in ELISA. Angiogenesis was apparently inhibited in tumor by immunohistochemical analysis. Angiogenesis was also inhibited in the chicken embryo CAM assay and mouse corneal micropocket assay. The increased apoptotic cells were found within the tumor tissues from the mice treated with plasmid DNA encoding vasostatin. Taken together, the data in the present study indicate that the cancer gene therapy by the intramuscular delivery of plasmid DNA encoding vasostatin, is effective in the inhibition of the systemic angiogenesis and tumor growth in murine models. The present findings also provide further evidence of the anti-tumor effects of the vasostatin, and may be of importance for the further exploration of the application of this molecule in the treatment of cancer.

Angiogenesis Inhibitors↗
PubMed2002

Identification of cis-DNA regions controlling Bmp4 expression during tooth morphogenesis in vivo.

Epithelial-mesenchymal interactions are required for tooth formation. Bone morphogenetic protein 4 (Bmp4) is a crucial signaling molecule during this process. For better understanding of the role of the Bmp4 gene during tooth development, we studied the mechanisms that control its temporal and spatial expression during development. Using a transgenic approach, we determined that the domains which controlled Bmp4 expression in epithelium-derived ameloblasts were located in the region between 0.26 kb and 1.1 kb of the murine Bmp4 promoter. In contrast, the domains controlling Bmp4 expression in mesenchyme-derived odontoblasts and pulp cells existed in other regions of the Bmp4 gene. We have also demonstrated that the domains controlling Bmp4 expression in primordial tooth cells differ from those controlling Bmp4 expression in mature tooth tissues. The determination of unique domains by controlling the expression of the Bmp4 gene suggests that different transcriptional factors regulate the Bmp4 level at different stages during tooth morphogenesis.

Ameloblasts↗
PubMed2001

Insulin-like growth factor-I receptor signaling and resistance to trastuzumab (Herceptin).

BACKGROUND: Trastuzumab (Herceptin), an anti-HER2/neu receptor monoclonal antibody that inhibits growth of ErbB2-overexpressing breast cancer, is used to treat such cancers. Development of resistance to trastuzumab, however, is common. We investigated whether insulin-like growth factor-I (IGF-I), which activates cell survival signals, interferes with the growth-inhibitory action of trastuzumab. METHODS: MCF-7/HER2-18 and SKBR3 human breast cancer models were used to assess cell proliferation, colony formation in soft agar, and cell cycle parameters. Throughout, we used trastuzumab at a dose of 10 microg/mL and IGF-I at a dose of 40 ng/mL. All statistical tests were two-sided. RESULTS: Trastuzumab inhibited the growth of MCF-7/HER2-18 cells, which overexpress HER2/neu receptors and express IGF-I receptors (IGF-IRs), only when IGF-IR signaling was minimized. For example, in 1% fetal bovine serum (FBS), trastuzumab reduced cell proliferation by 42% (P =.002); however, in 10% FBS or IGF-I, trastuzumab had no effect on proliferation. In SKBR3 cells, which overexpress HER2/neu receptor but express few IGF-IRs, trastuzumab reduced proliferation by 42% (P =.008) regardless of IGF-I concentration. When SKBR3 cells were genetically altered to overexpress IGF-IRs and cultured with IGF-I, trastuzumab had no effect on proliferation. However, the addition of IGF-binding protein-3, which decreased IGF-IR signaling, restored trastuzumab-induced growth inhibition. CONCLUSIONS: In breast cancer cell models that overexpress HER2/neu, an increased level of IGF-IR signaling appears to interfere with the action of trastuzumab. Thus, strategies that target IGF-IR signaling may prevent or delay development of resistance to trastuzumab.

Antibodies, Monoclonal↗
PubMed2001

Effects of premature stimulation on HERG K(+) channels.

1. The unusual kinetics of human ether-à-go-go-related gene (HERG) K(+) channels are consistent with a role in the suppression of arrhythmias initiated by premature beats. Action potential clamp protocols were used to investigate the effect of premature stimulation on HERG K(+) channels, transfected in Chinese hamster ovary cells, at 37 degrees C. 2. HERG K(+) channel currents peaked during the terminal repolarization phase of normally paced action potential waveforms. However, the magnitude of the current and the time point at which conductance was maximal depended on the type of action potential waveform used (epicardial, endocardial, Purkinje fibre or atrial). 3. HERG K(+) channel currents recorded during premature action potentials consisted of an early transient outward current followed by a sustained outward current. The magnitude of the transient current component showed a biphasic dependence on the coupling interval between the normally paced and premature action potentials and was maximal at a coupling interval equivalent to 90 % repolarization (APD(90)) for ventricular action potentials. The largest transient current response occurred at shorter coupling intervals for Purkinje fibre (APD(90) - 20 ms) and atrial (APD(90) - 30 ms) action potentials. 4. The magnitude of the sustained current response following premature stimulation was similar to that recorded during the first action potential for ventricular action potential waveforms. However, for Purkinje and atrial action potentials the sustained current response was significantly larger during the premature action potential than during the normally paced action potential. 5. A Markov model that included three closed states, one open and one inactivated state with transitions permitted between the pre-open closed state and the inactivated state, successfully reproduced our results for the effects of premature stimuli, both during square pulse and action potential clamp waveforms. 6. These properties of HERG K(+) channels may help to suppress arrhythmias initiated by early afterdepolarizations and premature beats in the ventricles, Purkinje fibres or atria.

Action Potentials↗
PubMed2001

The role of redox-active amino acids on compound I stability, substrate oxidation, and protein cross-linking in yeast cytochrome C peroxidase.

The role of two tryptophans (Trp51 and Trp191) and six tyrosines (Tyr36, Tyr39, Tyr42, Tyr187, Tyr229, and Tyr236) in yeast cytochrome c peroxidase (CcP) has been probed by site-directed mutagenesis. A series of sequential mutations of these redox-active amino acid residues to the corresponding, less oxidizable residues in lignin peroxidase (LiP) resulted in an increasingly more stable compound I, with rate constants for compound I decay decreasing from 57 s(-1) for CcP(MI, W191F) to 7 s(-1) for CcP(MI, W191F,W51F,Y187F,Y229F,Y236F,Y36F,Y39E,Y42F). These results provide experimental support for the proposal that the stability of compound I depends on the number of endogenous oxidizable amino acids in proteins. The higher stability of compound I in the variant proteins also makes it possible to observe its visible absorption spectroscopic features more clearly. The effects of the mutations on oxidation of ferrocytochrome c and 2,6-dimethoxyphenol were also examined. Since the first mutation in the series involved the change of Trp191, a residue that plays a critical role in the electron transfer pathway between CcP and cyt c, the ability to oxidize cyt c was negligible for all mutant proteins. On the other hand, the W191F mutation had little effect on the proteins' ability to oxidize 2,6-dimethoxyphenol. Instead, the W51F mutation resulted in the largest increase in the k(cat)/K(M), from 2.1 x 10(2) to 5.0 x 10(3) M(-1) s(-1), yielding an efficiency that is comparable to that of manganese peroxidase (MnP). The effect in W51F mutation can be attributed to the residue's influence on the stability and thus reactivity of the ferryl oxygen of compound II, whose substrate oxidation is the rate-determining step in the reaction mechanism. Finally, out of all mutant proteins in this study, only the variant containing the Y36F, Y39E, and Y42F mutations was found to prevent covalent protein cross-links in the presence of excess hydrogen peroxide and in the absence of exogenous reductants. This finding marks the first time a CcP variant is incapable of forming protein cross-links and confirms that one of the three tyrosines must be involved in the protein cross-linking.

Animals↗
PubMed2001

1,3-dichloro-1,1-dimethyl-3,3-diisopropyldistannoxane.

The title compound, [Sn4(CH3)4(C3H7)4Cl4O2] or [Cl[(CH3)2CH]2SnOSn(CH3)2Cl]2, obtained by the reaction of [(CH3)2CH]2SnO and (CH3)2SnCl2, exists as centrosymmetric dimers in the solid state. It contains a central planar four-membered Sn2O2 ring. The coordinate geometry about the Sn atoms is distorted trigonal pyramidal.

Journal Article↗
PubMed2001

Evidence for a novel GTPase priming step in the SRP protein targeting pathway.

Protein targeting by the signal recognition particle (SRP) pathway requires the interaction of two homologous GTPases that reciprocally regulate each other's GTPase activity, the SRP signal peptide- binding subunit (SRP54) and the SRP receptor alpha-subunit (SRalpha). The GTPase domain of both proteins abuts a unique 'N domain' that appears to facilitate external ligand binding. To examine the relationship between the unusual regulation and unique architecture of the SRP pathway GTPases, we mutated an invariant glycine in Escherichia coli SRP54 and SRalpha orthologs ('Ffh' and 'FtsY', respectively) that resides at the N-GTPase domain interface. A G257A mutation in Ffh produced a lethal phenotype. The mutation did not significantly affect Ffh function, but severely reduced interaction with FtsY. Likewise, mutation of FtsY Gly455 produced growth defects and inhibited interaction with Ffh. The data suggest that Ffh and FtsY interact only in a 'primed' conformation which requires interdomain communication. Based on these results, we propose that the distinctive features of the SRP pathway GTPases evolved to ensure that SRP and the SR engage external ligands before interacting with each other.

Alleles↗
PubMed2001

Cutting edge: positive selection induced by a self-peptide with TCR antagonist activity.

Antagonist-like engagement of the TCR has been proposed to induce T cell selection in the thymus. However, no natural TCR ligand with TCR antagonist activity is presently known. Using a combination of bioinformatics and functional testing we identified the first self-peptide that can both deliver antagonist-like signals and promote T cell selection in the thymus. The peptide is presented by appropriate MHC class I molecules in vivo. Thus, endogenous antagonist peptides exist and may be involved in TCR repertoire selection.

Animals↗
PubMed2001

Synergistic neutralizing antibody response to a dengue virus type 2 DNA vaccine by incorporation of lysosome-associated membrane protein sequences and use of plasmid expressing GM-CSF.

We have previously shown that a dengue virus type 1 DNA vaccine expressing premembrane (prM) and envelope (E) genes was immunogenic in mice and monkeys and that rhesus monkeys vaccinated with this construct were completely to partially protected from virus challenge. In order to improve the immunogenicity of dengue DNA vaccines, we have evaluated the effect of lysosome targeting of antigens and coimmunization with a plasmid expressing GM-CSF on antibody responses. A dengue virus type 2 candidate vaccine containing prM and E genes was constructed in which the transmembrane and cytoplasmic regions of E were replaced by those of the lysosome-associated membrane protein (LAMP). The modified vaccine construct expressed antigen that was colocalized with endogenous LAMP in lysosomal vesicles of transfected cells, whereas the antigen expressed from the unmodified construct was not. It was hypothesized that targeting of antigen to the lysosomal compartment will increase antigen presentation by MHC class II, leading to stronger CD4-mediated immune responses. Mice immunized with the modified construct responded with significantly higher levels of virus neutralizing antibodies compared to those immunized with the unmodified construct. Coimmunization of mice with a plasmid expressing murine GM-CSF enhanced the antibody response obtained with either the unmodified or the modified construct alone. The highest antibody responses were noted when the modified construct was coinjected with plasmid expressing the GM-CSF gene. These results could form the basis for an effective tetravalent dengue virus DNA vaccine.

3T3 Cells↗
PubMed2001

[The role of p21 (wafl/cip1) in human colorectal carcinoma cell apoptosis].

OBJECTIVE: To investigate the role of basal expression p21 and stress-stimulated p21 in preventing apoptosis of human colorectal carcinoma cells DLD1 after treatment of adriamycin, roentgenotherapy and gene therapy of p53. METHODS: A human colorectal carcinoma cell line DLD1 whose p21 expression can be controlled by isopropyl-beta-D-thiogalactoside (IPTG) was established. The morphology, DNA fragmentation and survival rates of two kinds of DLD1 cells expressing or not expressing p21 were observed after treatment with adriamycin, X-ray and transient transfection of p53. The cells in S stage were incubated with [3H] thymidine so as to examine the relationship between apoptosis and cell cycle. RESULTS: (1) p21 may be one of the most important stress-stimulated proteins in the cells, which can be induced by the p53-dependent pathway and the p53-independent pathway as well. (2) Basal expression of p21 plays an important antiapoptosis role in carcinoma cells after stress-treatment. In contrast, stress-stimulated p21 plays a minor role in preventing apoptosis. CONCLUSION: Basal expression of p21 plays a more important antiapoptosis role than stress-stimulated p21 in carcinoma cells.

Apoptosis↗
PubMed2001

The vasorelaxant effect of H(2)S as a novel endogenous gaseous K(ATP) channel opener.

Hydrogen sulfide (H(2)S) has been traditionally viewed as a toxic gas. It is also, however, endogenously generated from cysteine metabolism. We attempted to assess the physiological role of H(2)S in the regulation of vascular contractility, the modulation of H(2)S production in vascular tissues, and the underlying mechanisms. Intravenous bolus injection of H(2)S transiently decreased blood pressure of rats by 12- 30 mmHg, which was antagonized by prior blockade of K(ATP) channels. H(2)S relaxed rat aortic tissues in vitro in a K(ATP) channel-dependent manner. In isolated vascular smooth muscle cells (SMCs), H(2)S directly increased K(ATP) channel currents and hyperpolarized membrane. The expression of H(2)S-generating enzyme was identified in vascular SMCs, but not in endothelium. The endogenous production of H(2)S from different vascular tissues was also directly measured with the abundant level in the order of tail artery, aorta and mesenteric artery. Most importantly, H(2)S production from vascular tissues was enhanced by nitric oxide. Our results demonstrate that H(2)S is an important endogenous vasoactive factor and the first identified gaseous opener of K(ATP) channels in vascular SMCs.

Animals↗
PubMed2001

A high coking-resistance catalyst for methane aromatization.

Steaming-dealuminated HZSM-5-supported molybdenum catalysts have been found to be high coking-resistance catalysts for methane aromatization reactions; compared with conventional catalysts, they give a much higher selectivity towards aromatics.

Journal Article↗
PubMed2001

Integrating primary medical care with addiction treatment: a randomized controlled trial.

CONTEXT: The prevalence of medical disorders is high among substance abuse patients, yet medical services are seldom provided in coordination with substance abuse treatment. OBJECTIVE: To examine differences in treatment outcomes and costs between integrated and independent models of medical and substance abuse care as well as the effect of integrated care in a subgroup of patients with substance abuse-related medical conditions (SAMCs). DESIGN: Randomized controlled trial conducted between April 1997 and December 1998. SETTING AND PATIENTS: Adult men and women (n = 592) who were admitted to a large health maintenance organization chemical dependency program in Sacramento, Calif. INTERVENTIONS: Patients were randomly assigned to receive treatment through an integrated model, in which primary health care was included within the addiction treatment program (n = 285), or an independent treatment-as-usual model, in which primary care and substance abuse treatment were provided separately (n = 307). Both programs were group based and lasted 8 weeks, with 10 months of aftercare available. MAIN OUTCOME MEASURES: Abstinence outcomes, treatment utilization, and costs 6 months after randomization. RESULTS: Both groups showed improvement on all drug and alcohol measures. Overall, there were no differences in total abstinence rates between the integrated care and independent care groups (68% vs 63%, P =.18). For patients without SAMCs, there were also no differences in abstinence rates (integrated care, 66% vs independent care, 73%; P =.23) and there was a slight but nonsignificant trend of higher costs for the integrated care group ($367.96 vs $324.09, P =.19). However, patients with SAMCs (n = 341) were more likely to be abstinent in the integrated care group than the independent care group (69% vs 55%, P =.006; odds ratio [OR], 1.90; 95% confidence interval [CI], 1.22-2.97). This was true for both those with medical (OR, 3.38; 95% CI, 1.68-6.80) and psychiatric (OR, 2.10; 95% CI, 1.04-4.25) SAMCs. Patients with SAMCs had a slight but nonsignificant trend of higher costs in the integrated care group ($470.81 vs $427.95, P =.14). The incremental cost-effectiveness ratio per additional abstinent patient with an SAMC in the integrated care group was $1581. CONCLUSIONS: Individuals with SAMCs benefit from integrated medical and substance abuse treatment, and such an approach can be cost-effective. These findings are relevant given the high prevalence and cost of medical conditions among substance abuse patients, new developments in medications for addiction, and recent legislation on parity of substance abuse with other medical benefits.

Adult↗
PubMed2001

Cell cycle-independent upregulation of p27Kip1 by p21Waf1 in K562 cells.

Cellular differentiation frequently involves sequential peaks in the expression of cyclin-dependent kinase inhibitors (cdki's). For example, an increase in levels of the cdki p27Kip1 follows upregulation of p21Waf1 in several cell types induced to differentiate by diverse stimuli. In this study, we have investigated whether p21Waf1 expression itself, rather than the differentiating agent, could be increasing p27Kip1 protein levels. We used an inducible p21Waf1 expression vector in a K562 leukemic cell model which we had previously shown to initiate differentiation following p21Waf1 upregulation. The current study reports that p21Waf1 upregulated p27Kip1 protein without altering p27Kip1 mRNA levels. This effect did not depend on G1-phase arrest-the increase in p27Kip1 occurred at all phases of the cell cycle. p21Waf1-expressing extracts inhibited phosphorylation of p27Kip1 on threonine-187, leading to decreased ubiquitination and decreased proteasomal destruction of p27Kip1. In K562 cells, upregulation of p27Kip1 by p21Waf1 during differentiation facilitated an ordered transition between these two cdki's, each of which may distinctly influence the differentiation process.

CDC2-CDC28 Kinases↗
PubMed2001

Pulsed electrospray for mass spectrometry.

Pulsed electrospray has been developed and been reported for the first time. This new technique is based on the principle of pulsed ion sources, combined with the conventional electrospray. The pulsed ion spray was realized by a homemade pulsed HV circuit and was monitored by a digital microscope and an oscilloscope. Results show that the pulsed ESI device can be operated under proper conditions for a clear on-and-off spray process and that the device was kept in good electric contact for electrospray when pulsed HV was on. A pulsed ion current and pulsed mass spectra can be achieved with this pulsed ESI device. Furthermore, it has been noted that, under the same conditions (i.e., shape and size of sprayer tip, distance from sprayer tip to sampling nozzle, and other parameters for mass spectrometer), stable electrospray could be obtained for lower flow rates with a pulsed spray device. This experimental fact indicates the possible reduction in the total sample consumed could be realized by exploiting this novel design.

Spectrometry, Mass, Electrospray Ionization↗
PubMed2001

Partitioning of copper onto suspended particulate matter in river waters.

Suspended particles and river water from the Susquehanna River, White Clay Creek and the Delaware River were collected to experimentally study the partitioning of copper. The effects of many factors that may influence the partitioning coefficient (Kd) including pH, total suspended solids (TSS), total copper concentration ([Cu]T), dissolved organic matter (DOM), particulate organic matter (POM), hardness, and ionic strength were investigated by performing batch adsorption experiments. The results implied that organic matter binding sites in both the aqueous and solid phases play the most important role in controlling copper partitioning. Other major factors governing the partitioning are pH and TSS. Kd increases with pH in the pH range 3-8. TSS increases caused decreases in Kd values, which may be attributed to the decrease in the quantity of available binding sites caused by interparticle interactions, rather than by the redistribution of organic matter between solid and solution phases with the variation of TSS. Kd decreases slightly when total Cu concentration increases; however, Kd can be considered to be independent of Cu concentration when TSS is high. The effects of calcium competition and ionic strength on partitioning are small.

Binding Sites↗