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Biomedical subjects

Y Yue

Publications and source records attributed to Y Yue.

At least 37 records · Page 2Linked to original sources
PubMed2000

The p38 MAPK inhibitor, SB203580, abrogates ischaemic preconditioning in rat heart but timing of administration is critical.

There is debate concerning the involvement of p38 mitogen activated protein kinase (MAPK) in the mediation of ischaemic preconditioning. Pharmacological inhibition of p38 MAPK with SB203580 has been reported to block preconditioning in some studies but not in others. We hypothesised that this divergence could be due to differences in the timing of inhibitor administration. Isolated rat hearts were perfused in the Langendorff mode and subjected to 35 min regional ischaemia followed by 120 min reperfusion. Hearts were then double stained with Evans' blue and triphenyltetrazolium chloride to determine risk (R) and infarct zones (I), expressed as I/R% ratios. Preconditioned hearts were subjected to 2 times 5 min global ischaemia with 10 min intervening reperfusion. SB203580 10 microM was perfused either during the preconditioning protocol (PC+/-SB-early),just prior to and during the first 15 min of the lethal ischaemia (PC+/-SB-late) or prior to regional ischaemia in the absence of preconditioning. Ischaemic preconditioning significantly limited infarct size (I/R 38.9 +/- 3.0% in control vs 13.4 +/- 2.4%, P < 0.01). In the PC+/-SB-early group, preconditioning was still fully protective (I/R% 14.6 +/- 1.0). However, in the PC+/-SB-late group, SB203580 completely blocked the protection afforded by preconditioning (I/R% 33.6 +/- 4.4%, P < 0.01 vs 13.4 +/- 2.4% in preconditioned hearts, p < 0.05). SB203580 alone did not affect infarct size when given prior to and during regional ischaemia (I/R 36.2 +/- 2.7%). These histological data are corroborated by a significant increase in p38 MAPK activation in the preconditioned hearts during sustained ischaemia in comparison with the controls. In conclusion the activation of p38 MAPK during lethal ischaemia, but not during the ischaemic preconditioning protocol, is essential for the mediation of protection and may resolve some of the earlier controversy surrounding the use of SB203580 in preconditioning studies.

Animals↗
PubMed2000

Single-channel properties in endoplasmic reticulum membrane of recombinant type 3 inositol trisphosphate receptor.

The inositol 1,4,5-trisphosphate receptor (InsP(3)R) is an intracellular Ca(2+)-release channel localized in endoplasmic reticulum (ER) with a central role in complex Ca(2+) signaling in most cell types. A family of InsP(3)Rs encoded by several genes has been identified with different primary sequences, subcellular locations, variable ratios of expression, and heteromultimer formation. This diversity suggests that cells require distinct InsP(3)Rs, but the functional correlates of this diversity are largely unknown. Lacking are single-channel recordings of the recombinant type 3 receptor (InsP(3)R-3), a widely expressed isoform also implicated in plasma membrane Ca(2+) influx and apoptosis. Here, we describe functional expression and single-channel recording of recombinant rat InsP(3)R-3 in its native membrane environment. The approach we describe suggests a novel strategy for expression and recording of recombinant ER-localized ion channels in the ER membrane. Ion permeation and channel gating properties of the rat InsP(3)R-3 are strikingly similar to those of Xenopus type 1 InsP(3)R in the same membrane. Using two different two-electrode voltage clamp protocols to examine calcium store-operated calcium influx, no difference in the magnitude of calcium influx was observed in oocytes injected with rat InsP(3)R-3 cRNA compared with control oocytes. Our results suggest that if cellular expression of multiple InsP(3)R isoforms is a mechanism to modify the temporal and spatial features of [Ca(2+)](i) signals, then it must be achieved by isoform-specific regulation or localization of various types of InsP(3)Rs that have relatively similar Ca(2+) permeation properties.

Animals↗
PubMed2000

Analysis of the mechanism by which glucose inhibits maltose induction of MAL gene expression in Saccharomyces.

Expression of the MAL genes required for maltose fermentation in Saccharomyces cerevisiae is induced by maltose and repressed by glucose. Maltose-inducible regulation requires maltose permease and the MAL-activator protein, a DNA-binding transcription factor encoded by MAL63 and its homologues at the other MAL loci. Previously, we showed that the Mig1 repressor mediates glucose repression of MAL gene expression. Glucose also blocks MAL-activator-mediated maltose induction through a Mig1p-independent mechanism that we refer to as glucose inhibition. Here we report the characterization of this process. Our results indicate that glucose inhibition is also Mig2p independent. Moreover, we show that neither overexpression of the MAL-activator nor elimination of inducer exclusion is sufficient to relieve glucose inhibition, suggesting that glucose acts to inhibit induction by affecting maltose sensing and/or signaling. The glucose inhibition pathway requires HXK2, REG1, and GSF1 and appears to overlap upstream with the glucose repression pathway. The likely target of glucose inhibition is Snf1 protein kinase. Evidence is presented indicating that, in addition to its role in the inactivation of Mig1p, Snf1p is required post-transcriptionally for the synthesis of maltose permease whose function is essential for maltose induction.

Base Sequence↗
PubMed2000

Endosomal processing limits gene transfer to polarized airway epithelia by adeno-associated virus.

The restriction of viral receptors and coreceptors to the basolateral surface of airway epithelial cells has been blamed for the inefficient transfer of viral vectors to the apical surface of this tissue. We now report, however, that differentiated human airway epithelia internalize rAAV type-2 virus efficiently from their apical surfaces, despite the absence of known adeno-associated virus-2 (AAV-2) receptors or coreceptors at these sites. The dramatically lower transduction efficiency of rAAV infection from the apical surface of airway cells appears to result instead from differences in endosomal processing and nuclear trafficking of apically or basolaterally internalized virions. AAV capsid proteins are ubiquitinated after endocytosis, and gene transfer can be significantly enhanced by proteasome or ubiquitin ligase inhibitors. Tripeptide proteasome inhibitors increased persistent rAAV gene delivery from the apical surface >200-fold, to a level nearly equivalent to that achieved with basolateral infection. In vivo application of proteasome inhibitor in mouse lung augmented rAAV gene transfer from undetectable levels to a mean of 10.4 +/- 1.6% of the epithelial cells in large bronchioles. Proteasome inhibitors also increased rAAV-2-mediated gene transfer to the liver tenfold, but they did not affect transduction of skeletal or cardiac muscle. These findings suggest that tissue-specific ubiquitination of viral capsid proteins interferes with rAAV-2 transduction and provides new approaches to circumvent this barrier for gene therapy of diseases such as cystic fibrosis.

Animals↗
PubMed2000

[Modification of surface of Dacron materials by UV irradiation for prevention of microbial adhesion].

UV irradiation grafting method was used to modify the surface of Prosthetic Valve materials (Dacron) for prevention of bacteria-adhesion, and PEG was introduced to the surface of Dacron by this method. The result showed that the chemical magnifying effect of PEG improved the grafting of heparin on the material surface. This method can obviously reduce the number of adherent bacteria.

Bacterial Adhesion↗
PubMed2000

[Researches on surface modification for prevention of bacterial adhesion to implanting biomaterials].

The failure of operation caused by biomaterials centered infections (BCI) has seriously restricted the clinical application of biomaterials. Two mechanisms of bacterial adhesion and the relationship between surface free energy of bimaterials and bacterial adhesion are introduced and discussed in this paper. Increasing the surface free energy can improve (decrease) the adhesion of some kinds of bacteria. At last, some methods of the surface modification are reviewed.

Bacterial Adhesion↗
PubMed2000

[In vitro study of C3a des Arg produced by plasma incubation with blood purification materials].

This study was performed to evaluate the degree of complement C3 activation of five biomedical polymers (cellulose acetate (CA), polymethylmethacrylate (PMMA), polysulphone (PS), polyethersulphone (PES), sulphonated polyethersulphone(PES-SO3) which are used to make hemofilters. The concentration of the activation derivative C3a des Arg was measured by radioimmunoassay (RIA) in human plasma after incubation with these five polymers for 30, 60, 90 and 120 minutes. The experimental results indicated that the presence of polymers caused an increase in C3a des Arg. The potential to activate complement C3 decreased in sequence of CA, PMMA, PES, PS and PES-SO3. CA activated the most complement C3. PES-SO3 activated the least complement C3, and the concentration of C3a des Arg decreased with the increase in sulphonation degree. The investigation demonstrates that with good biocompatibility PES is a promising material to make biocompatible hemofilters. Furthermore, it indicates that PES containing sulphonate groups can achieve a marked reduction in complement activation and supports the sulphonation as a means of improving the biocompatibility of PES for blood purification application. RIA is a reliable and precise quantitative determination of human C3a des Arg and is suitable for testing the activation of complement of various synthetic materials that are utilized or to be utilized in the medical field.

Complement Activation↗
PubMed2000

[Evaluation of performance and blood compatibility of polyethersulfone hollow fiber plasma separator].

In this study, we evaluated the performance and blood compatibility of polyethersulfone hollow fiber membrane plasma separator by animal experiment. Hemolysis did not occur under the usual conditions of plasma separation. The sieving coefficients of total protein, albumin and globulin were over 95%, and about 60% of total plasma were extracted from the whole blood. White blood cells, platelets, fibrinogen, and coagulation factors were decreased during the early stage of plasma separation and appeared to be within acceptable ranges for clinical use.

Animals↗
PubMed2000

[Photochemical immobilization--a new approach to surface modification of medical polymer materials].

The present paper reviews the approach of surface modification of medical polymer materials-photochemical immobilization. The approach is dramatically different from any other surface modification process available for medical materials. The topics include the principle of photochemical immobilization, the fundamental classification photoreactive groups and the typical applications of photochemical surface modification.

Biocompatible Materials↗
PubMed1999

Selective inhibition of spinal cord neurite outgrowth and cell survival by the Eph family ligand ephrin-A5.

The Eph family tyrosine kinase receptors and their ligands, the ephrins, have been shown to play critical roles in cell migration, tissue morphogenesis, and axonal guidance in many different systems. However, their function in the spinal cord has not been examined carefully. We showed in this study that several Eph receptors, including EphA3, Eph A4, and Eph A5, are expressed in the ventral spinal cord in partially overlapping patterns, with EphA5 exhibiting the most widespread transcription in the entire ventral spinal cord during early development. Complementary to the receptor expression, a ligand of these receptors, ephrin-A5, is transcribed in the dorsal half of the spinal cord. Consistent with the spatial location of receptor expression, the ligand selectively inhibits neurite outgrowth and induces cell death of the ventral, but not the dorsal, spinal cord neurons. These observations suggest that interactions between the Eph family receptors and ligands exerts negative influences on ventral spinal cord neurons and thus may play important roles in regulating morphogenesis and axon guidance in the spinal cord.

Animals↗
PubMed1999

Structural analysis of adeno-associated virus transduction circular intermediates.

Recombinant adeno-associated virus (rAAV) has recently been demonstrated to form circular intermediates following transduction in muscle tissue and cell lines. Although restriction enzyme and Southern blot analysis has revealed a consistent monomer and multimer head-to-tail conformation, detailed structural sequence analysis has been lacking due to the high secondary structure of the ITR arrays. To gain further insight into potential mechanisms by which AAV circular genomes are formed from linear single-stranded viral DNA, we have performed chemical sequencing of ITR arrays within seven circular intermediates independently isolated from primary fibroblasts and Hela cells. Results from these studies demonstrated several types of circular intermediates with mosaic ITR elements flanked by two D sequences. The most predominant form consisted of a structure similar to that of previously generated AAV double-D plasmids, with one complete ITR flanked by two D-region elements. However, intermediately deleted ITR arrays with more than one complete ITR were also seen. Based on this structural information, we have proposed a model for formation of AAV circular intermediates by recombination/ligation between ITR ends of panhandle single-stranded AAV genomes.

Base Sequence↗
PubMed1999

Ephrin-dependent growth and pruning of hippocampal axons.

Neuronal connections are arranged topographically such that the spatial organization of neurons is preserved by their termini in the targets. During the development of topographic projections, axons initially explore areas much wider than the final targets, and mistargeted axons are pruned later. The molecules regulating these processes are not known. We report here that the ligands of the Eph family tyrosine kinase receptors may regulate both the initial outgrowth and the subsequent pruning of axons. In the presence of ephrins, the outgrowth and branching of the receptor-positive hippocampal axons are enhanced. However, these axons are induced later to degenerate. These observations suggest that the ephrins and their receptors may regulate topographic map formation by stimulating axonal arborization and by pruning mistargeted axons.

3T3 Cells↗
PubMed1999

Specification of distinct dopaminergic neural pathways: roles of the Eph family receptor EphB1 and ligand ephrin-B2.

Dopaminergic neurons in the substantia nigra and ventral tegmental area project to the caudate putamen and nucleus accumbens/olfactory tubercle, respectively, constituting mesostriatal and mesolimbic pathways. The molecular signals that confer target specificity of different dopaminergic neurons are not known. We now report that EphB1 and ephrin-B2, a receptor and ligand of the Eph family, are candidate guidance molecules for the development of these distinct pathways. EphB1 and ephrin-B2 are expressed in complementary patterns in the midbrain dopaminergic neurons and their targets, and the ligand specifically inhibits the growth of neurites and induces the cell loss of substantia nigra, but not ventral tegmental, dopaminergic neurons. These studies suggest that the ligand-receptor pair may contribute to the establishment of distinct neural pathways by selectively inhibiting the neurite outgrowth and cell survival of mistargeted neurons. In addition, we show that ephrin-B2 expression is upregulated by cocaine and amphetamine in adult mice, suggesting that ephrin-B2/EphB1 interaction may play a role in drug-induced plasticity in adults as well.

Animals↗
PubMed1999

Maskless fabrication of light-directed oligonucleotide microarrays using a digital micromirror array.

Oligonucleotide microarrays, also called "DNA chips," are currently made by a light-directed chemistry that requires a large number of photolithographic masks for each chip. Here we describe a maskless array synthesizer (MAS) that replaces the chrome masks with virtual masks generated on a computer, which are relayed to a digital micromirror array. A 1:1 reflective imaging system forms an ultraviolet image of the virtual mask on the active surface of the glass substrate, which is mounted in a flow cell reaction chamber connected to a DNA synthesizer. Programmed chemical coupling cycles follow light exposure, and these steps are repeated with different virtual masks to grow desired oligonucleotides in a selected pattern. This instrument has been used to synthesize oligonucleotide microarrays containing more than 76,000 features measuring 16 microm 2. The oligonucleotides were synthesized at high repetitive yield and, after hybridization, could readily discriminate single-base pair mismatches. The MAS is adaptable to the fabrication of DNA chips containing probes for thousands of genes, as well as any other solid-phase combinatorial chemistry to be performed in high-density microarrays.

Base Sequence↗
PubMed1999

Formation of adeno-associated virus circular genomes is differentially regulated by adenovirus E4 ORF6 and E2a gene expression.

A central feature of the adeno-associated virus (AAV) latent life cycle is persistence in the form of both integrated and episomal genomes. However, the molecular processes associated with episomal long-term persistence of AAV genomes are only poorly understood. To investigate these mechanisms, we have utilized a recombinant AAV (rAAV) shuttle vector to identify circular AAV intermediates from transduced HeLa cells and primary fibroblasts. The unique structural features exhibited by these transduction intermediates included circularized monomer and dimer virus genomes in a head-to-tail array, with associated specific base pair alterations in the 5' viral D sequence. In HeLa cells, the abundance and stability of AAV circular intermediates were augmented by adenovirus expressing the E2a gene product. In the absence of E2a, adenovirus expressing the E4 open reading frame 6 gene product decreased the abundance of AAV circular intermediates, favoring instead the linear replication form monomer (Rfm) and dimer (Rfd) structures. In summary, the formation of AAV circular intermediates appears to represent a new pathway for AAV genome conversion, which is consistent with the head-to-tail concatemerization associated with latent-phase persistence of rAAV. A better understanding of this pathway may increase the utility of rAAV vectors for gene therapy.

Adenovirus E2 Proteins↗
PubMed1999

Pathogenesis of experimental rhesus cytomegalovirus infection.

Human cytomegalovirus (HCMV) establishes and maintains a lifelong persistence following infection in an immunocompetent host. The determinants of a stable virus-host relationship are poorly defined. A nonhuman primate model for HCMV was used to investigate virological and host parameters of infection in a healthy host. Juvenile rhesus macaques (Macaca mulatta) were inoculated with rhesus cytomegalovirus (RhCMV), either orally or intravenously (i.v. ), and longitudinally necropsied. None of the animals displayed clinical signs of disease, although hematologic abnormalities were observed intermittently in i.v. inoculated animals. RhCMV DNA was detected transiently in the plasma of all animals at 1 to 2 weeks postinfection (wpi) and in multiple tissues beginning at 2 to 4 wpi. Splenic tissue was the only organ positive for RhCMV DNA in all animals. The location of splenic cells expressing RhCMV immediate-early protein 1 (IE1) in i.v. inoculated animals changed following inoculation. At 4 to 5 wpi, most IE1-positive cells were perifollicular, and at 25 wpi, the majority were located within the red pulp. All animals developed anti-RhCMV immunoglobulin M (IgM) antibodies within 1 to 2 wpi and IgG antibodies within 2 to 4 wpi against a limited number of viral proteins. Host reactivity to RhCMV proteins increased in titer (total and neutralizing) and avidity with time. These results demonstrate that while antiviral immune responses were able to protect from disease, they were insufficient to eliminate reservoirs of persistent viral gene expression.

Animals↗