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W Xu

Publications and source records attributed to W Xu.

At least 487 records · Page 27Linked to original sources
PubMed1994

Spinal serotonin IA and IC/2 receptors mediate supraspinal mu opioid-induced analgesia.

Intracerebroventricular (i.c.v.) injection of highly selective mu opioid receptor agonist ohmefentanyl (OMF) to rats produced dose-dependent antinociception as assessed with the tail flick test. This analgesia could be blocked by intrathecal (i.t.) injection of the 5-HT1A receptor antagonist spiperone or the 5-HT1C/2 receptor antagonist mianserin, but not by the 5-HT2 receptor antagonist 1-NP or the 5-HT3 receptor antagonist ICS 205-930. The results suggest that the descending 5-HT system is involved in mediating spinal mu opioid analgesia via spinal 5-HT1A and 5-HT1C/2 receptors.

Analgesia↗
PubMed1994

Translational control by cytoplasmic polyadenylation of c-mos mRNA is necessary for oocyte maturation in the mouse.

The c-mos proto-oncogene product is a key element in the cascade of events leading to meiotic maturation of vertebrate oocytes. We have investigated the role of cytoplasmic polyadenylation in the translational control of mouse c-mos mRNA and its contribution to meiosis. Using an RNase protection assay we show that optimal cytoplasmic polyadenylation of c-mos mRNA requires three cis elements in the 3' UTR: the polyadenylation hexanucleotide AAUAAA and two U-rich cytoplasmic polyadenylation elements (CPEs) located 4 and 51 nucleotides upstream of the hexanucleotide. When fused to CAT coding sequences, the wild-type 3' UTR of c-mos mRNA, but not a 3' UTR containing mutations in both CPEs, confers translational recruitment during maturation. This recruitment coincides with maximum polyadenylation. To assess whether c-mos mRNA polyadenylation is necessary for maturation of mouse oocytes, we have ablated endogenous c-mos mRNA by injecting an antisense oligonucleotide, which results in a failure to progress to meiosis II after emission of the first polar body. Such antisense oligonucleotide-injected oocytes could be efficiently rescued by co-injection of a c-mos mRNA carrying a wild-type 3' UTR. However, co-injection of a c-mos mRNA lacking functional CPEs substantially lowered the rescue activity. These results demonstrate that translational control of c-mos mRNA by cytoplasmic polyadenylation is necessary for normal development.

Adenosine Monophosphate↗
PubMed1994

Oxygen sensors based on luminescence quenching: interactions of metal complexes with the polymer supports.

Oxygen quenching of [Ru(Ph2phen)3]Cl2 (Ph2phen = 4,7-diphenyl-1,10-phenanthroline) has been studied in a diverse series of polymers, most with a common poly-(dimethylsiloxane) (PDMS) component. Systematic variations in the polymer properties have been made in order to delineate the structural features important for satisfactory use of supports for oxygen sensors. Most measurements were made using homo- or copolymers containing a PDMS region, although some measurements were made on small ring siloxane polymers. In particular, quenching behavior was examined as a function of polymer structure as well as the type of and amount of polar copolymer cross-linkers. Cross-linkers were added to enhance the solubility of oxygen probes in an otherwise nonpolar polymer. In addition, hydrophobic silica was added to alter quenching properties. Domain models are used to explain the variations in oxygen quenching properties as a function of additives and cross-linkers. These considerations have led to the most sensitive ruthenium-based sensor reported to date. The relative affinity of the different domains for the complex and the efficacy of the domains for oxygen quenching control the overall behavior of the sensing response. Guidelines for design of suitable polymer supports for oxygen sensors are proposed.

Acrylates↗
PubMed1994

The cytoplasmic domain of the interleukin-2 receptor beta chain contains both unique and functionally redundant signal transduction elements.

Binding of interleukin-2 (IL-2) to the IL-2 receptor (IL-2R) triggers a series of intracellular events culminating in lymphocyte proliferation and differentiation. A novel transient assay of signal transduction leading to proliferation is now described which allows the rapid functional assessment of wild type and mutant receptors, including the IL-2R and other members of the cytokine receptor superfamily. This assay has been used to define domains and specific residues within the IL-2R beta intracellular region that contribute to growth signal transduction. In these studies, internal deletion of either the conserved "Box 1" or "Box 2" proximal cytokine receptor homology segments significantly impaired receptor function. Similarly, mutation of specific key residues within or between Box 1 and Box 2, or deletion of the C-terminal 94 residues of the IL-2R beta chain, impaired growth signaling. In contrast, either replacement of the transmembrane domain with that of the CD4 molecule or internal deletion of the 119 amino acids immediately downstream of Box 2 had no impact on growth signaling competence. These studies thus further define the functional architecture of the intracellular region of IL-2R beta, and reveal specific receptor domains that are dispensable, unique, or functionally redundant.

Amino Acid Sequence↗
PubMed1994

Mapping of the genes encoding human inducible and endothelial nitric oxide synthase (NOS2 and NOS3) to the pericentric region of chromosome 17 and to chromosome 7, respectively.

Nitric oxide (NO) is an important molecular messenger regulating the functions of a wide variety of cells and tissues. NO is synthesized from L-arginine by a variety of isoforms of the enzyme nitric oxide synthase (NOS). We have used Southern blotting analysis on DNAs obtained from a panel of human-rodent hybrid cell lines to map the gene encoding the inducible NOS (NOS2) to chromosome 17cen-17q11 and the gene encoding the endothelial form of NOS (NOS3) to chromosome 7. Fluorescence in situ hybridization using a NOS2 probe gave several signals in the 17p11-q11 pericentromeric region.

Amino Acid Oxidoreductases↗
PubMed1994

Putative rat sperm lipid-binding protein: isolation and partial characterization.

Previous work has identified a prominent 22-24-kD protein that is present in rat male reproductive tissues, including epididymis and testis (Brooks, 1985; Jones and Brown, 1987; Moore et al., 1987). Using a monoclonal antibody (designated mAb-B109) against this 24-kD antigen (referred to as B109), we have isolated the protein using a combination of chromatofocusing and electroelution from SDS-PAGE gels, and reverse phase HPLC. B109 (pI = 4.8) is amino-terminal blocked. To obtain internal amino acid sequences, the isolated protein was cleaved either with cyanogen bromide in 70% formic acid or with TLCK-treated chymotrypsin. With cyanogen bromide treatment, two peptides, 17.8 kD and 11.9 kD, were isolated and partial amino acid sequences obtained. Chymotryptic peptides were isolated by reverse-phase HPLC and two were chosen for sequence analysis. A computer search for sequence homology through the protein identification resource (PIR) matched B109 to a basic 21-kD cytosolic protein (pI = 7.4) found in bovine brain (> 80% homology). When peptide sequence differences obtained in the present study were substituted into the 21-kD cytosolic protein sequence obtained from the PIR using Intelligenetics software, the calculated pI dropped from 7.4 to 5.8, suggesting that pI differences between the bovine and rat molecules are the result of amino acid substitutions in the testis protein and not tissue-specific posttranslational processing. It has been postulated that the 21-kD bovine brain protein is associated with phospholipid transport, although the function of B109 is unknown.

Amino Acid Sequence↗
PubMed1994

Sodium transport through the amiloride-sensitive Na-Mg pathway of hamster red cells.

Previous work showed that in hamster red cells the amiloride-sensitive (AS) Na+ influx of 0.8 mmol/liter cells/hr is not mediated by Na-H exchange as in other red cells, but depends upon intracellular Mg2+ and can be increased by 40-fold by loading cells with Mg2+ to 10 mM. The purpose of this study was to verify the connection of AS Na+ influx with Na-dependent, amiloride-sensitive Mg2+ efflux and to utilize AS Na+ influx to explore that pathway. Determination of unidirectional influx of Na+ and net loss of Mg2+ in parallel sets of cells showed that activation by extracellular [Na+] follows a simple Michaelis-Menten relationship for both processes with a Km of 105-107 mM and that activation of both processes is sigmoidally dependent upon cytoplasmic [Mg2+] with a [Mg2+]0.5 of 2.1-2.3 mM and a Hill coefficient of 1.8. Comparison of Vmax for both sets of experiments indicated a stoichiometry of 2 Na:1 Mg. Amiloride inhibits Na+ influx and Mg2+ extrusion in parallel (Ki = 0.3 mM). Like Mg2+ extrusion, amiloride-sensitive Na+ influx shows an absolute requirement for cytoplasmic ATP and is increased by cell swelling. Hence, amiloride-sensitive Na+ influx in hamster red cells appears to be through the Na-Mg exchange pathway. There was no amiloride-sensitive Na+ efflux in hamster red cells loaded with Na+ and incubated with high [Mg2+] in the medium with or without external Na+, nor with ATP depletion. Hence, this is not a simple Na-Mg exchange carrier.

Adenosine Triphosphate↗
PubMed1994

Formation of 5 alpha steroids by biotransformation involving the 5 alpha-reductase activity of Penicillium decumbens.

The biotransformation of a series of delta 4-3-ketosteroids by the fungus Penicillium decumbens ATCC 10436 has been investigated. Conversion to the 5 alpha-dihydrosteroid was observed for several substrates of the androstene and pregnene series: the reaction is tolerant of non-polar substituents (Cl and CH3) at C-4 of the substrate, but does not occur in the presence of a 4-hydroxyl group, or with additional unsaturation at the delta 1 or delta 6 positions. A-nor-, B-nor-, 3-deoxy-, and 3,5-cycloandrostanes are not reduced, but 6-methylenetestosterone is converted to a 6-methylene-5 alpha-dihydro derivative. Several biotransformations are reported which involve oxidoreductase activity at C-3 and/or C-17, either concomitant or independent of delta 4 reduction: the substrate specificity of the oxidoreductase processes has been examined and defined by the use of 3 alpha-hydroxy, 3 beta-hydroxy, 3-keto, 17 beta-hydroxy and 17-keto substituted steroids. In this way, the existence in P. decumbens of 3 beta-hydroxy-3-keto and 17 beta-hydroxy-17-keto oxidoreductases has been demonstrated.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1994

Effect of interleukin-1 beta on airway hyperresponsiveness and inflammation in sensitized and nonsensitized Brown-Norway rats.

Airway responsiveness (AR) to inhaled acetylcholine and bradykinin and inflammatory cell recruitment in bronchoalveolar lavage fluid (BALF) were studied in inbred male Brown-Norway rats actively sensitized to ovalbumin and later given 500 U interleukin-1 beta (IL-1 beta) intratracheally. We examined animals 14 to 21 days after initial sensitization at 18 to 24 hours after the intratracheal administration of IL-1 beta. We evaluated AR to acetylcholine as -log PC200, which is -log10 transformation of provocative concentration of acetylcholine producing 200% increase in lung resistance, and to bradykinin as percent increase in lung resistance. BALF was examined as an index of inflammatory changes within the lung. Although there was no significant difference in baseline lung resistance, nonsensitized and sensitized animals that were given IL-1 beta demonstrated a significant increase of AR to bradykinin at 18 to 24 hours and a significant increase of neutrophil counts in BALF, which was already observed by 4 to 6 hours. There was a significant correlation between AR to bradykinin and neutrophil counts in BALF in all animals (r = 0.644; p < 0.0005). We conclude that intratracheal administration of IL-1 beta induces the inflammatory changes, which are characterized by an increase in neutrophil counts in BALF, and increased AR to bradykinin, and that active sensitization per se does not potentiate the effect of IL-1 beta on AR to acetylcholine or bradykinin or on airway inflammation.

Acetylcholine↗
PubMed1994

The molecular cloning and expression of a human synaptic vesicle amine transporter that suppresses MPP+ toxicity.

A synaptic vesicle amine transporter cDNA, termed hSVAT, has been isolated by the reverse transcription and polymerase chain reaction (PCR) technique from human substantia nigra and subsequent screening of a human substantia nigra library. The hSVAT sequence obtained is highly homologous to the rat SVAT sequence (92% homology) and is essentially identical to the human sequence identified recently by Surratt and colleagues [33]. This labelled hSVAT cDNA detected a single band (approximately 5.0 kb) when used as a probe for Northern analysis of human nigral RNA extract. In situ hybridization studies using hSVAT specific antisense oligonucleotides showed a strong hybridization signal concentrated over the cells of the substantia nigra pars compacta. This cDNA sequence when expressed in chinese hamster ovary (CHO) cells conferred resistance to MPP+ the toxic metabolite of MPTP and cells containing it accumulated dopamine.

1-Methyl-4-phenylpyridinium↗
PubMed1994

An antigenic recombinant fusion protein from Trichinella spiralis induces a protective response in BALB/c mice.

A previously reported recombinant lambda Ts39 fusion protein (FP) derived from Trichinella spiralis larvae was purified by affinity chromatography using an anti-beta-galactosidase antibody conjugated column and the effect of FP on induction of a protective response in mice was studied. BALB/c mice were injected three times at weekly intervals with FP emulsified in an equal volume of Freund's complete adjuvant and one week after the last injection mice were each challenged with a lethal dose of 1200 L1 larvae of Trichinella spiralis. As a result, the FP induced significant protection. Mice were also infected orally with 250 L1 larvae each after injection of the FP. On the 35th day of infection, immunized mice with the FP harboured 78% fewer muscle larvae than saline controls. Also, the numbers of adult worms in the small intestine were smaller in FP injected mice than saline controls on day 6 and 9 of the infection. These results suggest that the recombinant lambda Ts39 FP is a potentially valuable antigen for vaccine development.

Animals↗
PubMed1994

The characterization of gene mutations for human glucose phosphate isomerase deficiency associated with chronic hemolytic anemia.

DNA was isolated from four unrelated glucose phosphate isomerase-deficient patients. Seven new mutations in the coding region were found: 247 C-->T, 671 C-->T, 818 G-->A, 833 C-->T, 1039 C-->T, 1459 C-->T, and 1483 G-->A. Three patients were compound heterozygotes, and one patient was a homozygote of 247 C-->T/247 C-->T. Six mutations were found to involve highly conserved amino acids of glucose phosphate isomerase, suggesting that these residues are crucial for the maintenance of biological activity. Two polymorphic sites were also identified, 489 A-->G and 1356 G-->C, which do not produce a change in the amino acid sequence.

Anemia, Hemolytic↗
PubMed1994

[Histopathology of nonacoustic labyrinth following head injury in guinea pigs].

The histopathological changes in nonacoustic labyrinth induced by experimental head injury were studied in 11 guinea pigs. The animals were divided into two groups. The first group were killed after the pain sense recovered and the second group were allowed to survive for 15 days. The temporal bones were serially sectioned and observed under light microscope. The pathological findings of the vestibular organs included arrangement disturbance, lytic, exfoliate and vacuolization of the sensory epithelia, massive spherical bodies in the region of cilium. The otolithic membranes were exfoliated in the utricular and saccular maculae. There was the otolith by the ductus reuniens separated from the saccular maculae in one ear. There were basophilic staining homogenous deposit on the cristae ampullaris. These findings showed that impairments of vestibulae following head injury were obvious. The secondary impairments, cupulolithiasis and obstruction of the ductus reuniens, from the utricular and saccular maculae were one of the pathologic changes in hearing loss and vertigo following head injury.

Animals↗