Biomedical subjects

Z Lu

Publications and source records attributed to Z Lu.

At least 199 records · Page 11Linked to original sources

PubMed1999

DANCE, a novel secreted RGD protein expressed in developing, atherosclerotic, and balloon-injured arteries.

We have identified and characterized mouse, rat, and human cDNAs that encode a novel secreted protein of 448 amino acids named DANCE (developmental arteries and neural crest epidermal growth factor (EGF)-like). DANCE contains six calcium-binding EGF-like domains, one of which includes an RGD motif. Overexpression studies of recombinant DANCE protein document that DANCE is a secreted 66-kDa protein. DANCE and recently described protein S1-5 comprise a new EGF-like protein family. The human DANCE gene was mapped at chromosome 14q32.1. DANCE mRNA is mainly expressed in heart, ovary, and colon in adult human tissues. Expression profile analysis by in situ hybridization revealed prominent DANCE expression in developing arteries. DANCE is also expressed in neural crest cell derivatives, endocardial cushion tissue, and several other mesenchymal tissues. In adult vessels, DANCE expression is largely diminished but is reinduced in balloon-injured vessels and atherosclerotic lesions, notably in intimal vascular smooth muscle cells and endothelial cells that lose their ability to proliferate in late stage of injury. DANCE protein was shown to promote adhesion of endothelial cells through interaction of integrins and the RGD motif of DANCE. DANCE is thus a novel vascular ligand for integrin receptors and may play a role in vascular development and remodeling.

Amino Acid Sequence↗

PubMed1999

Differential mechanisms of recognition and activation of interleukin-8 receptor subtypes.

We have probed an epitope sequence (His18-Pro19-Lys20-Phe21) in interleukin-8 (IL-8) by site-directed mutagenesis. This work shows that single and double Ala substitutions of His18 and Phe21 in IL-8 reduced up to 77-fold the binding affinity to IL-8 receptor subtypes A (CXCR1) and B (CXCR2) and to the Duffy antigen. These Ala mutants triggered neutrophil degranulation and induced calcium responses mediated by CXCR1 and CXCR2. Single Asp or Ser substitutions, H18D, F21D, F21S, and double substitutions, H18A/F21D, H18A/F21S, and H18D/F21D, reduced up to 431-fold the binding affinity to CXCR1, CXCR2, and the Duffy antigen. Interestingly, double mutants with charged residue substitutions failed to trigger degranulation or to induce wild-type calcium responses mediated by CXCR1. Except for the H18A and F21A mutants, all other IL-8 mutants failed to induce superoxide production in neutrophils. This study demonstrates that IL-8 recognizes and activates CXCR1, CXCR2, and the Duffy antigen by distinct mechanisms.

Antigens, CD↗

PubMed1999

The Hdj-2/Hsc70 chaperone pair facilitates early steps in CFTR biogenesis.

The cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride ion channel constructed from two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBD) and a regulatory (R) domain. The NBDs and R-domain are cytosolic and how they are assembled with the MSDs to achieve the native CFTR structure is not clear. Human DnaJ 2 (Hdj-2) is a co-chaperone of heat shock cognate 70 (Hsc70) which is localized to the cytosolic face of the ER. Whether Hdj-2 directs Hsc70 to facilitate the assembly of cytosolic regions on CFTR was investigated. We report that immature ER forms of CFTR and DeltaF508 CFTR can be isolated in complexes with Hdj-2 and Hsc70. The DeltaF508 mutation is localized in NBD1 and causes the CFTR to misfold. Levels of complex formation between DeltaF508 CFTR and Hdj-2/Hsp70 were approximately 2-fold higher than those with CFTR. The earliest stage at which Hdj-2/Hsc70 could bind CFTR translation intermediates coincided with the expression of NBD1 in the cytosol. Interestingly, complex formation between Hdj-2 and nascent CFTR was greatly reduced after expression of the R-domain. In experiments with purified components, Hdj-2 and Hsc70 acted synergistically to suppress NBD1 aggregation. Collectively, these data suggest that Hdj-2 and Hsc70 facilitate early steps in CFTR assembly. A putative step in the CFTR folding pathway catalyzed by Hdj-2/Hsc70 is the formation of an intramolecular NBD1-R-domain complex. Whether this step is defective in the biogenesis of DeltaF508 CFTR will be discussed.

Carrier Proteins↗

PubMed1999

Solution structure of potassium channel-inhibiting scorpion toxin Lq2.

Lq2 is a unique scorpion toxin. Acting from the extracellular side, Lq2 blocks the ion conduction pore in not only the voltage- and Ca2+ -activated channels, but also the inward-rectifier K+ channels. This finding argues that the three-dimensional structures of the pores in these K+ channels are similar. However, the amino acid sequences that form the external part of the pore are minimally conserved among the various classes of K+ channels. Because Lq2 can bind to all the three classes of K+ channels, we can use Lq2 as a structural probe to examine how the non-conserved pore-forming sequences are arranged in space to form similar pore structures. In the present study, we determined the three-dimensional structure of Lq2 using nuclear magnetic resonance (NMR) techniques. Lq2 consists of an alpha-helix (residues S10 to L20) and a beta-sheet, connected by an alphabeta3 loop (residues N22 to N24). The beta-sheet has two well-defined anti-parallel strands (residues G26 to M29 and residues K32 to C35), which are connected by a type I' beta-turn centered between residues N30 and K31. The N-terminal segment (residues Z1 to T8) appears to form a quasi-third strand of the beta-sheet.

Amino Acids↗

PubMed1999

Dynamics study on the anti-human immunodeficiency virus chemokine viral macrophage-inflammatory protein-II (VMIP-II) reveals a fully monomeric protein.

Encoded by Kaposi's sarcoma-associated herpesvirus, viral macrophage-inflammatory protein-II (VMIP-II) is unique among CC chemokines in that it has been shown to bind to the CXC chemokine receptor CXCR4 as well as to a variety of CC chemokine receptors. This unique binding ability allows vMIP-II to block infection by a wide range of human immunodeficiency virus type I (HIV-1) strains, but the structural and dynamic basis for this broad range of binding is not known. 15N T1, T2 and 15N[-HN] nuclear Overhauser effect (NOE) values of vMIP-II, determined through a series of heteronuclear multidimensional nuclear magnetic resonance (NMR) experiments, were used to obtain information about the backbone dynamics of the protein. Whereas almost all chemokine structures reveal a dimer or multimer, vMIP-II has a rotational correlation time (tauc) of 4.7 +/- 0.3 ns, which is consistent with a monomeric chemokine. The rotational diffusion anisotropy, D parallel/D perpendicular, is approximately 1.5 +/- 0.1. The conformation of vMIP-II is quite similar to other known chemokines, containing an unstructured N-terminus followed by an ordered turn, three beta-strands arranged in an antiparallel fashion, and one C-terminal alpha-helix that lies across the beta-strands. Most of the protein is well-ordered on a picosecond time scale, with an average order parameter S2 (excluding the N-terminal 13 amino acids) of 0.83 +/- 0. 09, and with even greater order in regions of secondary structure. The NMR data reveal that the N-terminus, which in other chemokines has been implicated in receptor binding, extends like a flexible tail in solution and possesses no secondary structure. The region of the ordered turn, including residues 25-28, experiences conformational exchange dynamics. The implications of these NMR data to the broad receptor binding capability of vMIP-II are discussed.

Amino Acid Sequence↗

PubMed1999

Potential thermal artifacts in hip joint wear simulators.

Frictional heat was monitored during wear tests of ultrahigh molecular weight polyethylene acetabular cups bearing against femoral balls of metal or ceramic in a hip simulator, using bovine serum as a lubricant. About 1 to 2 h of continuous cycling were required for the temperature in the zone of contact between the cup and ball to rise to its maximum steady value, and this equilibrium temperature was markedly higher with increased load and/or cycling rate. Frictional heating caused substantial precipitation of the proteins from the serum and, in some of the tests running at 1.5 or 2 Hz, an adherent proteinaceous layer was observed attached to the surface of the balls. The maximum temperature was also substantially higher in tests run with the cup mounted above the ball rather than below. Surprisingly, the tests running at higher frictional torque and temperature (i.e., those with the most protein precipitation and/or adherent layers) produced the least wear of the polyethylene. This might have been due to the solid proteins that formed a protective layer between the ball and cup. Because patients with hip prostheses typically do not walk for hours without rest, the maximum temperatures in vivo are likely to be much lower than those reached in the hip simulator. Therefore, the affects of protein precipitation on the resultant wear properties of the materials should be considered potential artifacts of the hip simulator tests. Increasing the volume of the lubricant bath reduced the maximum temperatures for tests running at 1.5 Hz but had little affect at 2 Hz. Reducing the cycling rate is an effective way to avoid overheating of the specimens, but this necessarily extends the time required to complete a test.

Animals↗

PubMed1999

Dielectrophoresis of human red cells in microchips.

The dielectric properties of human red cells are strongly affected by the applied electric field, especially the frequency. Under the high frequency, the cells are acted on by positive dielectrophoresis (DEP) force and move to the tip region of the interdigitated electrode where the electric field is strongest. The cells are acted on by negative DEP force and aggregated in the "bay" zone between the neighboring electrode castellation tips and the surface of the electrodes. The patterns formed by DEP force are identical with the distribution of the electric field.

Electrodes↗

PubMed1999

Effect of terazosin on blood pressure and serum lipids.

In an open multicenter prospective study, the effects of short-term (4 weeks, n = 101) and long-term (6 months, n = 38) terazosin treatment on blood pressure, serum lipids and safety in the patients with mild to moderate essential hypertension were observed. Mean systolic and diastolic blood pressure in sitting position were significantly reduced by 16.4% and 14.0% respectively (P < 0.01) after 4 weeks of terazosin therapy, with the total efficacy rate being 87.1%. During a 6 month therapy, antihypertensive effect of terazosin could be maintained. Total cholesterol (TC) and low density lipoprotein (LDL) cholesterol in serum were significantly decreased P < 0.05-0.01) in patients with hypercholesterolemia (TC > or = 6 mmol/ml) after 4 week terazosin treatment; the levels of TC, LDL and triglyceride were significantly improved in hypertensive patients after 3-6 month terazosin treatment. The improvement of lipid metabolism was related to the dosage of terazosin but not to antihypertensive effects of terazosin. The results suggested that terazosin is effective in decreasing blood pressure and improving lipid metabolism. It may serve as a good antihypertensive agent for hypertensive patients with hypercholesterolemia.

Antihypertensive Agents↗

PubMed1999

Effect of Salvia Miltiorrhiza on coronary collateral circulation in dogs with experimental acute myocardial infarction.

To evaluate the effect of Salvia Miltiorrhiza on coronary collateral circulation in dogs with experimental acute myocardial infarction, 12 dogs were randomly divided into Salvia Miltiorrhiza group (group D) and control group (group C). Acute myocardial infarction model was established in all dogs, Salvia Miltiorrhiza or saline was administered to the 2 groups respectively for 21 days. Coronary angiography was performed before and after ligation of coronary artery. The capillaries and distribution vessel density in tissue sections of myocardia were assessed. Angiography 2 h and 22 days after ligation of coronary artery revealed significant augmentation of collateral vessels, and capillaries and distribution vessel density in ischemic zone on day 22 showed statistically significant augmentation in group D as compared with that of controls (P < 0.05 and P < 0.01). It is concluded that Salvia Miltiorrhiza might improve the opening and formation of coronary collateral circulation of ischemic myocardia in dogs and thereby protecting myocardia from ischemia.

Animals↗

PubMed1999

Permanence and global attractivity for Lotka-Volterra difference systems.

The permanence and global attractivity for two-species difference systems of Lotka-Volterra type are considered. It is proved that a cooperative system cannot be permanent. For a permanent competitive system, the explicit expression of the permanent set E is obtained and sufficient conditions are given to guarantee the global attractivity of the positive equilibrium of the system.

Animals↗

PubMed1999

Fast reversible electron transfer for photosynthetic reaction center from wild type Rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film.

Direct reversible electron transfer for photosynthetic reaction center from wild type Rhodobacter sphaeroides re-constituted in polycation sandwiched monolayer film was observed in this work. The redox potential E0' = 0.46 V vs. NHE for first primary donor redox couple P/P+ was accurately measured from reversible CV or SWV peaks, which were quite close to those obtained from optic redox titration method. Reaction center (RC) in film was found re-constituted in such an ordered way that the orientation of RC favored the electron transfer in film. Thus, the protein electroactivity seems to be turned on in this artificial biomimic thin film. Furthermore, RC in the film features a photo-induced redox-peak fluctuation, suggesting an intact and functional state for RC in such film. Redox peaks were also found dependent of pH, implying a proton-coupled electron transfer occurring in film. Charge recombination was observed accompanied with change of electrochemical driving force. Electrochemical model assuming several classes of electroactive sites in the films on the electrode with a dispersion of standard potentials successfully fits SWV experimental data at different pulse height and frequency.

Electrochemistry↗

PubMed1999

Conversion of tumor-specific CD4+ T-cell tolerance to T-cell priming through in vivo ligation of CD40.

Tumor antigen-specific T-cell tolerance limits the efficacy of therapeutic cancer vaccines. Antigen-presenting cells mediate the induction of T-cell tolerance to self-antigens. We therefore assessed the fate of tumor-specific CD4+ T cells in tumor-bearing recipients after in vivo activation of antigen-presenting cells with antibodies against CD40. Such treatment not only preserved the responsiveness of this population, but resulted in their endogenous activation. Established tumors regressed in vaccinated mice treated with antibody against CD40 at a time when no response was achieved with vaccination alone. These results indicate that modulation of antigen-presenting cells may be a useful strategy for enhancing responsiveness to immunization.

Adoptive Transfer↗

PubMed1999

Blockade of a retinal cGMP-gated channel by polyamines.

The cyclic nucleotide-gated (CNG) channel in retinal rods converts the light-regulated intracellular cGMP concentration to various levels of membrane potential. Blockade of the channel by cations such as Ca2+ and Mg2+ lowers its effective conductance. Consequently, the membrane potential has very low noise, which enables rods to detect light with extremely high sensitivity. Here, we report that three polyamines (putrescine, spermidine, and spermine), which exist in both the intracellular and extracellular media, also effectively block the CNG channel from both sides of the membrane. Among them, spermine has the greatest potency. Extracellular spermine blocks the channel as a permeant blocker, whereas intracellular spermine appears to block the channel in two conformations-one permeant, and the other non- (or much less) permeant. The membrane potential in rods is typically depolarized to approximately -40 mV in the dark. At this voltage, K1/2 of the CNG channel for extracellular spermine is 3 microM, which is 100-1,000-fold higher affinity than that of the NMDA receptor-channel for extracellular spermine. Blockade of the CNG channel by polyamines may play an important role in suppressing noise in the signal transduction system in rods.

Animals↗

PubMed1999

Tuning the voltage dependence of tetraethylammonium block with permeant ions in an inward-rectifier K+ channel.

To understand the role of permeating ions in determining blocking ion-induced rectification, we examined block of the ROMK1 inward-rectifier K+ channel by intracellular tetraethylammonium in the presence of various alkali metal ions in both the extra- and intracellular solutions. We found that the channel exhibits different degrees of rectification when different alkali metal ions (all at 100 mM) are present in the extra- and intracellular solution. A quantitative analysis shows that an external ion site in the ROMK1 pore binds various alkali metal ions (Na+, K+, Rb+, and Cs+) with different affinities, which can in turn be altered by the binding of different permeating ions at an internal site through a nonelectrostatic mechanism. Consequently, the external site is saturated to a different level under the various ionic conditions. Since rectification is determined by the movement of all energetically coupled ions in the transmembrane electrical field along the pore, different degrees of rectification are observed in various combinations of extra- and intracellular permeant ions. Furthermore, the external and internal ion-binding sites in the ROMK1 pore appear to have different ion selectivity: the external site selects strongly against the smaller Na+, but only modestly among the three larger ions, whereas the internal site interacts quite differently with the larger K+ and Rb+ ions.

Animals↗

PubMed1999

An African swine fever virus ORF with similarity to C-type lectins is non-essential for growth in swine macrophages in vitro and for virus virulence in domestic swine.

An African swine fever virus (ASFV) ORF, 8CR, with similarity to the C-type lectin family of adhesion proteins has been described in the pathogenic isolate Malawi Lil-20/1. The similarity of 8CR to cellular and poxvirus genes associated with cell adhesion, cell recognition and virus infectivity suggested that 8CR may be of significance to ASFV-host cell interactions. Sequence analysis of the 8CR ORF from additional pathogenic ASFV isolates demonstrated conservation among isolates from both pig and tick sources. Northern blot analysis demonstrated 8CR mRNA transcription late in the virus replication cycle. A Malawi Lil-20/1 8CR deletion mutant (delta8CR) was constructed to analyse 8CR function further. The growth characteristics in vitro of delta8CR in porcine macrophage cell cultures were identical to those observed for parental virus. In domestic swine, delta8CR exhibited an unaltered parental Malawi Lil-20/1 disease and virulence phenotype. Thus, although well conserved among pathogenic ASFV field isolates, 8CR is non-essential for growth in porcine macrophages in vitro and for virus virulence in domestic swine.

African Swine Fever↗

PubMed1999

North American and European porcine reproductive and respiratory syndrome viruses differ in non-structural protein coding regions.

Although North American and European serotypes of porcine reproductive and respiratory syndrome virus (PRRSV) are recognized, only the genome of the European Lelystad strain (LV) has been sequenced completely. Here, the genome of the pathogenic North American PRRSV isolate 16244B has been sequenced and compared with LV. The genomic organization of 16244B was the same as LV but with only 63.4% nucleotide identity. The 189 nucleotide 5' non-coding region (NCR) of 16244B was distinct from the LV NCR, with good conservation (83%) only over a 43 base region immediately upstream of open reading frame (ORF) 1a. Major differences were found in the region encoding the non-structural part of the ORF1a polyprotein, which shared only 47% amino acid identity over 2503 residues of the six non-structural proteins (Nsps) encoded. Nsp2, thought to have a species-specific function, showed the greatest divergence, sharing only 32% amino acid identity with LV and containing 120 additional amino acids in the central region. Nsps encoded by the 5'-proximal and central regions of ORF1b had from 66 to 75% amino acid identity; however, the carboxy-terminal protein CP4 was distinct (42% identity). The ORF 1a-1b frameshift region of 16244B had 98% nucleotide identity with LV. Consistent with previous reports for North American isolates, the six structural proteins encoded were 58 to 79% identical to LV proteins. The 3' NCR (150 nucleotides) was 76% identical between isolates. These genomic differences confirm the presence of distinct North American and European PRRSV genotypes.

5' Untranslated Regions↗

PubMed1999

Water stress inhibits hydraulic conductance and leaf growth in rice seedlings but not the transport of water via mercury-sensitive water channels in the root

The mechanisms by which moderate water stress (adding polyethylene glycol 6000 to the root medium) induces a sustained inhibition of growth in emerging first leaves of intact rice (Oryza sativa) seedlings was investigated under growth-chamber conditions. Early (24 h) inhibition of leaf growth was not related to changes in root size or in osmotic potential gradients and cell wall-yielding characteristics in the leaf-expansion zone of stressed seedlings. However, reductions in root-to-leaf hydraulic conductance (L) were measured in two rice cultivars after 4 or 24 h at various levels of water stress, and these reductions correlated well with the inhibition of leaf growth. We assayed L by a psychrometric method and, in intact seedlings, by a novel osmotic-jump method. The addition of 0.5 mM HgCl2 to the root medium to inhibit water transport through Hg-sensitive water channels in the roots did not inhibit leaf growth in unstressed seedlings. However, both leaf growth and L were additionally reduced (by 49% and 43%, respectively) within minutes of adding HgCl2 to roots of water-stressed seedlings. Water stress therefore appeared to increase the transport of water via Hg-sensitive water channels. Other mechanisms were apparently involved in inhibiting overall L and leaf growth.

Journal Article↗

PubMed1999

The genome of Melanoplus sanguinipes entomopoxvirus.

The family Poxviridae contains two subfamilies: the Entomopoxvirinae (poxviruses of insects) and the Chordopoxvirinae (poxviruses of vertebrates). Here we present the first characterization of the genome of an entomopoxvirus (EPV) which infects the North American migratory grasshopper Melanoplus sanguinipes and other important orthopteran pests. The 236-kbp M. sanguinipes EPV (MsEPV) genome consists of a central coding region bounded by 7-kbp inverted terminal repeats and contains 267 open reading frames (ORFs), of which 107 exhibit similarity to previously described genes. The presence of genes not previously described in poxviruses, and in some cases in any other known virus, suggests significant viral adaptation to the arthropod host and the external environment. Genes predicting interactions with host cellular mechanisms include homologues of the inhibitor of apoptosis protein, stress response protein phosphatase 2C, extracellular matrixin metalloproteases, ubiquitin, calcium binding EF-hand protein, glycosyltransferase, and a triacylglyceride lipase. MsEPV genes with putative functions in prevention and repair of DNA damage include a complete base excision repair pathway (uracil DNA glycosylase, AP endonuclease, DNA polymerase beta, and an NAD+-dependent DNA ligase), a photoreactivation repair pathway (cyclobutane pyrimidine dimer photolyase), a LINE-type reverse transcriptase, and a mutT homologue. The presence of these specific repair pathways may represent viral adaptation for repair of environmentally induced DNA damage. The absence of previously described poxvirus enzymes involved in nucleotide metabolism and the presence of a novel thymidylate synthase homologue suggest that MsEPV is heavily reliant on host cell nucleotide pools and the de novo nucleotide biosynthesis pathway. MsEPV and lepidopteran genus B EPVs lack genome colinearity and exhibit a low level of amino acid identity among homologous genes (20 to 59%), perhaps reflecting a significant evolutionary distance between lepidopteran and orthopteran viruses. Divergence between MsEPV and the Chordopoxvirinae is indicated by the presence of only 49 identifiable chordopoxvirus homologues, low-level amino acid identity among these genes (20 to 48%), and the presence in MsEPV of 43 novel ORFs in five gene families. Genes common to both poxvirus subfamilies, which include those encoding enzymes involved in RNA transcription and modification, DNA replication, protein processing, virion assembly, and virion structural proteins, define the genetic core of the Poxviridae.

Amino Acid Sequence↗