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Q Yang

Publications and source records attributed to Q Yang.

At least 397 records · Page 22Linked to original sources
PubMed1996

[Changes in the calcium channels in rat cardiac cells during sepsis].

Changes in the number of calcium channels in two subcellular fractions, the sarcolemma and the light vesicle, of rat cardic cells were studied during sepsis. Sepsis was induced by cecal ligation and puncture (CLP). The results showed that some of the calcium channels in the light vesicle translocated to the sarcolemma during the early sepsis (9 h after CLP) while during the late sepsis (18 h after CLP), some of these in the sarcolemma translocated to the light vesicle. The mechanisms of redistribution of the calcium channels in the sarcolemma and the light vesicle during sepsis was not associated to the phosphorylation of the calcium channels by cAMP dependent protein kinase (PKA), Ca2+/calmodulin dependent protein kinase (PKM) and protein kinase C (PKC). Since beta-adrenergic receptors, muscarinic cholinergic receptors and Na+/K(+)-ATPase were also redistributed during sepsis, it is suggested that the redistribution might be non-specific.

Animals↗
PubMed1996

[Pharmacological comparative study on baiqian and baiwei].

The decoction of Cynanchum glaucescens and the ethanol extract of C. stauntonii show significant antitussive and expectorant actions. The decoctions of C. stauntonii or C. glaucescens have antiasthmatic and anti-inflammatory effects. The decoction of C. atratum has some expectorant effect but no antitussive or antiasthmatic actions. On the other hand, the decoction of C. versicolor cannot relieve cough nor sputum. The results indicate that both C. atratum and C. versicolor cannot be used as C. glaucescens or C. stauntonii.

Adolescent↗
PubMed1995

Acanthamoeba castellanii contains a ribosomal RNA enhancer binding protein which stimulates TIF-IB binding and transcription under stringent conditions.

The intergenic spacer (IGS) of Acanthamoeba castellanii rRNA genes contains repeated elements which are weak enhancers for transcription by RNA polymerase I. A protein, EBF, was identified and partially purified which binds to the enhancers and to several other sequences within the IGS, but not to other DNA fragments, including the rRNA core promoter. No consensus binding sequence could be discerned in these fragments and bound factor is in rapid equilibrium with unbound. EBF has functional characteristics similar to vertebrate upstream binding factors (UBF). Not only does it bind to the enhancer and other IGS elements, but it also stimulates binding of TIF-IB, the fundamental transcription initiation factor, to the core promoter and stimulates transcription from the promoter. Attempts to identify polypeptides with epitopes similar to rat or Xenopus laevis UBF suggest that structurally the protein from A.castellanii is not closely related to vertebrate UBF.

Acanthamoeba↗
PubMed1995

S-100 beta has a neuronal localisation in the rat hindbrain revealed by an antigen retrieval method.

The localisation of S-100 in mammalian CNS neurons has been under debate for more than two decades. We address the question with two polyclonal and two new monoclonal antibodies. The specificity and the distribution in rat brain is based on an antigen retrieval method. We present evidence that aldehyde fixatives mask S-100 beta in neurons, and that the immunoreactivity is retrieved after trypsinisation. Neuronal S-100 beta is also detected in unfixed and ethanol fixed sections. The neuronal immunoreactivity is partly solubilised from unfixed tissue sections with 2.5 mM EDTA and is completely extracted with 2.5 mM EDTA and 1% Triton X-100. Most of the glial S-100 beta is washed out from unfixed tissue sections with saline. S-100 beta has distinct distribution in neurons of the hindbrain, i.e., the brainstem and cerebellum, but is not observed in the forebrain. One of the monoclonal antibodies immunostained neither neurons nor glia when it had been absorbed with S-100 crosslinked to nitrocellulose membranes. The distribution of neuronal S-100 beta differed from that of other neuronal calcium binding proteins, such as calbindin and parvalbumin. It was confined mainly to cholinergic neurons of the hindbrain. The presence of S-100 beta in distinct neuronal populations may indicate neurotrophic effects of S-100 beta. The notion is supported by the capability of S-100 to cause neurite outgrowth in vitro.

Animals↗
PubMed1995

S-100 beta immunoreactivity in neurones of the rat peripheral sensory ganglia.

S-100 beta, which is capable of exerting neurotrophic effects on cultured neurones and promoting the survival of motor neurones in vivo, has recently been found in distinct neurones of the rat hindbrain. Here we report that S-100 beta, as well as being present in satellite and Schwann cells, is also present in neurones of sensory ganglia (dorsal root ganglion, trigeminal, petrosal, jugular and nodose ganglia) but absent from neurones of the superior cervical ganglion. In the sensory ganglia, many neurones were immunoreactive, while the staining intensity varied among the neurones. Neuronal S-100 beta appeared in developing rats as early as postnatal day 1. No immunoreactive neurones were observed in the superior cervical ganglion during development. The results are suggestive of selective neurotrophic effects of S-100 beta.

Animals↗
PubMed1995

Biochemical characterization of a human band 4.1-related protein-tyrosine phosphatase, PTPH1.

PTPH1 is a human protein-tyrosine phosphatase with homology to the band 4.1 superfamily of cytoskeleton-associated proteins. Here, we report the purification and biochemical characterization of this enzyme from baculovirus-infected insect cells. The purified protein exhibited an apparent M(r) of 120,000 on SDS gels. The native enzyme dephosphorylated both myelin basic protein (MBP) and reduced, carboxamidomethylated, and maleylated lysozyme (RCML) but was over 5-fold more active on MBP. The Km values for the two substrates were similar (1.45 microM for MBP and 1.6 microM for RCML). Phosphorylation of PTPH1 by protein kinase C in vitro resulted in a decrease in Km but had no effect on Vmax. Removal of the NH2-terminal band 4.1 homology domain of PTPH1 by limited trypsin cleavage stimulated dephosphorylation of RCML but inhibited its activity toward MBP. The dephosphorylation of RCML by full-length PTPH1 was enhanced up to 6-fold by unphosphorylated MBP and increasing ionic strength up to 0.2 M NaCl, whereas trypsinized preparations of PTPH1 containing the isolated catalytic domain were unaffected. These results suggest that in addition to a potential role in controlling subcellular localization, the NH2-terminal band 4.1 homology domain of PTPH1 may exert a direct effect on catalytic function.

Amino Acid Sequence↗
PubMed1995

Immobilized liposome chromatography for analysis of interactions between lipid bilayers and peptides.

Liposomes were sterically immobilized in gel beads to be used for isocratic chromatographic analysis of interactions between lipid bilayers, amino acids, and water-soluble peptides. Tryptophan was more retarded on the immobilized liposomes than were other amino acids, and peptides with C-terminal cysteine were much more retarded than were peptides with serine or aminobutyric acid instead of the cysteine. Peptide sequences could affect the peptide-liposome interactions. For peptides corresponding to polypeptide segments of a membrane protein, the human red cell glucose transporter (Glut1), the retention volumes increased with decreasing water-to-oil transfer free energy of the peptides and were related to the transfer free energy distribution within the peptides as shown by hydropathy plots and to the presence of cysteine. Among these peptides, the partially hydrophobic peptides 125GRFIIGVYCG134 and 201CIVLPFCPES210 and the hydrophilic peptide 421CFQYVEQLC429 were most strongly retarded on immobilized phosphatidylcholine liposomes. The results indicated that the peptide-liposome interactions were mainly of hydrophobic nature and that the structure of the interfacial head-group region of the lipid bilayers was important.

Amino Acid Sequence↗
PubMed1995

Immobilized-liposome chromatographic analysis of drug partitioning into lipid bilayers.

The chromatographic retardation of drugs on a gel bed with immobilized liposomes was shown to correlate with the absorption of the drugs through epithelial cell layers, which is related to drug partitioning into the lipid bilayers of cell membranes. The capacity factors were divided by the lipid concentration (mM) in the gel bed to obtain specific capacity factors, Ks. The logarithm of the octanol-water distribution ratios showed a linear correlation with log Ks, whereas the logarithm of the apparent permeability coefficients in epithelial cell monolayers and the absorption of drugs orally administered in humans (data from other laboratories) increased over the interval 0 < log Ks < 1 and attained a saturation level in the interval 1 < log Ks < 3. Immobilized-liposome chromatography may be applicable for prediction of drug uptake through epithelial cell membranes.

Cell Membrane Permeability↗
PubMed1995

Immobilized proteoliposome affinity chromatography for quantitative analysis of specific interactions between solutes and membrane proteins. Interaction of cytochalasin B and D-glucose with the glucose transporter Glut1.

An affinity gel bed was prepared by reconstitution of a transmembrane protein, the human red cell glucose transporter (Glut1), followed by steric immobilization of the proteoliposomes in small and rigid gel beads by freeze-thawing. The specific interactions between the reconstituted Glut1, the transport inhibitor cytochalasin B (CB), and the transported solute D-glucose were analyzed by isocratic chromatography of CB on the Glut1-proteoliposome gel bed. Specific retardation of CB which decreased upon inclusion of the competitor D-glucose in the eluent was observed on-line. The equilibrium constants for CB and D-glucose interaction with Glut1 (Kd 1.5 x 10(-7) M and 67 mM, respectively) obtained by use of equations derived for the affinity chromatographic analysis were consistent with values obtained by others by conventional methods. Effects of liposome composition, pH, and time on the CB binding activity of Glut1 were studied. Reconstitution of a membrane protein into a lipid environment and steric immobilization of the proteoliposomes favor retention of the protein activity. Immobilized proteoliposome affinity chromatography (IPAC) is a novel, powerful method for analysis of interactions between membrane proteins and solutes.

Chromatography, Affinity↗
PubMed1995

Isolation of a high affinity inhibitor of urokinase-type plasminogen activator by phage display of ecotin.

Ecotin, a serine protease inhibitor found in the periplasm of Escherichia coli, is unique in its ability and mechanism of inhibiting serine proteases of a broad range of substrate specificity. However, although the catalytic domain of human urokinase-type plasminogen activator (uPA) has 40% identity to bovine trypsin and the substrate specificities of these two proteases are virtually identical, ecotin inhibits uPA almost 10,000-fold less efficiently than trypsin. Ecotin was expressed on the surface of filamentous bacteriophage (ecotin phage) to allow the isolation of more potent inhibitors of uPA from a library of ecotin variants. The 142-amino acid inhibitor was fused to the C-terminal domain of the M13 minor coat protein, pIII, through a Gly-Gly-Gly linker and assembled into phage particles. The ecotin phage were shown to react with anti-ecotin antibodies, revealing a stoichiometry of approximately one ecotin per bacteriophage. The ecotin displayed on the surface of phage inhibited trypsin with an equilibrium dissociation constant of 6.7 nM, in close approximation to that of free ecotin, indicating that phage-associated ecotin is correctly folded and functionally active. Reactive-site amino acids 84 and 85 of ecotin were then randomized and a library of 400 unique ecotin phage was created. Three hundred thousand members of the library were screened with immobilized uPA and subjected to three rounds of binding and in vitro selection. DNA sequence analysis of the selected ecotin phage showed that ecotin M84R/M85R predominated while ecotin M84R, M84K, and M84R/M85K were present at a lower frequency. The four ecotin variants were overexpressed and purified and their affinities toward uPA were determined. Each of the selected ecotin variants exhibited increased affinity for uPA when compared to wild-type ecotin with ecotin M84R/M85R showing a 2800-fold increase in binding affinity.

Amino Acid Sequence↗
PubMed1995

Inhibition of cellular and SV40 DNA replication by the adeno-associated virus Rep proteins.

In order to define the mechanism used by the adeno-associated virus replication (rep) gene to mediate inhibition of cell proliferation, we have studied its effects on SV40 and cellular DNA replication. SV40 DNA replication was inhibited by the presence of the rep gene in human 293 cells, and the inhibition was not linked to suppression of SV40 early gene expression. Using double-immunofluorescence assays that measured both rep gene expression and bromodeoxyuridine incorporation, we found that the presence of the Rep78 and Rep68 proteins correlated with inhibition of cellular DNA synthesis in NIH3T3 cells. This links the rep gene's anti-proliferative effects to either: (i) a direct inhibition of DNA synthesis or (ii) a possible cell cycle block.

3T3 Cells↗
PubMed1995

Planned relaparotomy vs relaparotomy on demand in the treatment of intra-abdominal infections. The Peritonitis Study Group of the Surgical Infection Society-Europe.

OBJECTIVE: To define the role of planned relaparotomy (PR) in the treatment of intraperitoneal infection, compared with that of relaparotomy on demand (RD). DESIGN: Case-control study on the basis of a prospective multicenter cohort analytic study. Statistical evaluation was done by the McNemar test for qualitative data and the Wilcoxon matched-pairs signed rank test for qualitative data. SETTING: Eighteen hospitals of different care levels in Austria, Germany, and Switzerland. PATIENTS: Thirty-eight of 42 patients with intra-abdominal infections who underwent PR were matched for APACHE II (Acute Physiology and Chronic Health Evaluation II) score, age, cause of infection, site of origin of peritonitis, and the ability of the surgeon to securely eliminate the source of infection with 38 patients taken from a cohort of 278 undergoing RD. INTERVENTIONS: Planned relaparotomy was defined as at least one relaparotomy decided on at the time of the first surgical intervention; RD, relaparotomy indicated by clinical findings. MAIN OUTCOME MEASURES: Mortality and incidence of postoperative multiple organ failure and infectious complications. RESULTS: There was no significant difference in mortality between patients treated with PR (21%) or RD (13%). Postoperative multiple organ failure as defined by a Goris score of more than 5 was more frequent in the group of patients undergoing PR (50%), compared with the group undergoing RD (24%) (P = .01), as were infectious complications (68% vs 39% [P = .01]). Infectious complications were due to more frequent suture leaks (16% vs 0% [P = .05]), recurrent intra-abdominal sepsis (16% vs 0% [P = .05]), and septecemia (45% vs 18% [P = .05]) in the PR vs the RD groups. The incidence of other complications was not different in the two groups. CONCLUSIONS: Until larger prospective studies are available, the indication for PR should be evaluated with caution.

Abdomen↗
PubMed1995

Conformation of parathyroid hormone antagonists by CD, NMR, and molecular dynamics simulations.

The conformation of two highly potent parathyroid hormone (PTH) antagonists was investigated in water/2,2,2-trifluoroethanol mixtures. The two peptides are derived from the sequence (7-34) of PTH and of PTH-related protein (PTHrP) and have a D-Trp replacing Gly in position 12. In the analogue derived from PTHrP, Lys11 was replaced by Leu to remove the residual agonist activity. The study was conducted by CD and two-dimensional proton magnetic resonance spectroscopy, and the nuclear Overhauser effects found were utilized in restrained distance geometry and molecular dynamics simulations. Both peptides adopt a helical C-terminal conformation, which seems more stable in the case of the PTHrP analogue. A type II' beta-turn centered around D-Trp12 and Lys13 is present in both structures.

Amino Acid Sequence↗