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Y Wu

Publications and source records attributed to Y Wu.

At least 937 records · Page 52Linked to original sources
PubMed1995

Induction of nitric oxide synthase and motoneuron death in newborn and early postnatal rats following spinal root avulsion.

It is well established that immature motoneurons are more vulnerable to axonal injury than the adult ones. Many previous studies used distal axonal injury, such as sciatic nerve transection, to examine the response of immature motoneurons to injury. In the present study, a more severe injury, spinal root avulsion, was performed in newborn and early postnatal rats, and the response of immature spinal motoneurons to the injury was observed. In newborn rats, root avulsion causes motoneuron loss which is similar to that of previous studies by distal axonal injury. During the early postnatal development, motoneuron loss in immature rats is greater following root avulsion when compared to cell loss following distal axonal injury at any given age. Following root avulsion, nitric oxide synthase (NOS) is induced in injured immature motoneurons. The induction and accumulation of NOS in injured motoneurons is much more rapid in the immature animals than in the adult, which is coincident with the more rapid motoneuron loss in the immature animals. Results of the present study indicate an involvement of NOS in neuronal degeneration. However, the precise role of NOS in the response of motoneurons to axonal injury is not clear and needs to be further studied.

Animals↗
PubMed1995

Selective coupling of beta 2-adrenergic receptor to hematopoietic-specific G proteins.

The coupling of the beta 2-adrenergic receptor (AR) to the alpha subunits of the Gq class of G proteins was investigated in a cotransfection system. COS-7 cells cotransfected with the beta 2-AR cDNA and the G alpha 15 or G alpha 16 cDNA showed marked norepinephrine-induced increases in accumulation of inositol phosphates in a concentration-dependent manner. However, cells cotransfected with the cDNA encoding G alpha q, G alpha 11, or G alpha 14 instead of G alpha 16 gave no ligand-dependent activation of phospholipase C (PLC). The facts that the beta-AR agonist isoprenaline can also induce activation of PLC in cells coexpressing beta 2-AR and G alpha 16 and that the beta 2-AR-specific antagonist propranolol can block norepinephrine-induced activation of PLC in these cotransfected cells further indicate that it is the beta 2-AR that mediates the activation of phospholipase C in these cotransfected cells. To test the possibility of involvement of G beta gamma, a G beta gamma antagonist, G gamma 3 mutant with substitution of a Ser residue for the C-terminal Cys residue, was used because this protein, when expressed in COS-7 cells, can inhibit only G beta gamma-mediated but not G alpha-mediated activation of PLC. The result that the G gamma 3 mutant could not inhibit beta 2-adrenergic receptor-mediated activation of PLC in cells cotransfected with the G alpha 16 cDNA suggests that G beta gamma is unlikely to be a major mediator of beta 2-adrenergic receptor-induced activation of PLC. Thus, we conclude that the beta 2-adrenergic receptor can specifically couple to G alpha 15 and G alpha 16, but not to G alpha q, G alpha 11, or G alpha 14 to activate PLC.

Animals↗
PubMed1995

Influence of DNA topology on expression of the tdc operon in Escherichia coli K-12.

TdcB activity expressed from the chromosomal gene and LacZ expression from single-copy tdc-lacZ transcriptional and translational fusions were measured in Escherichia coli strains harboring mutations in the genes encoding DNA gyrase, topoisomerase I and the HU protein. The pattern of tdc operon expression in these mutants suggests that relaxation of supercoiled DNA enhances tdc transcription in vivo.

DNA, Bacterial↗
PubMed1995

Rapid down-regulation of [3H]zolpidem binding to rat brain benzodiazepine receptors during flurazepam treatment.

In a previous study, it was found that down-regulation of benzodiazepine (BZ) binding in rats treated 4 weeks with flurazepam was relatively greater and more widespread when measured with [3H]zolpidem, a selective 'BZ1 receptor' ligand, than that measured with the non-selective ligand, [3H]flunitrazepam. In the present study, the time course for down-regulation of [3H]zolpidem binding was studied in rats treated with flurazepam. [3H]Zolpidem binding was also studied in rats given a midazolam treatment shown to cause tolerance. Rats were chronically treated with flurazepam for 1 or 2 weeks, or with midazolam for 3 weeks, then killed immediately after the treatment. Another group of rats was acutely treated with desalkyl-flurazepam and killed 30 min later. After 2 weeks of flurazepam treatment, the Bmax of [3H]zolpidem binding was decreased by 22% in cerebral cortex, 26% in cerebellum and 33% in hippocampus, with no change in the Kd in any region. After 1 week of flurazepam treatment, the Bmax was decreased by 23% in cerebellum and 14% in hippocampus, but not changed in cerebral cortex. The Kd was increased in cerebral cortex, but not in cerebellum or hippocampus. Neither the Bmax nor the Kd of [3H]zolpidem binding was affected by acute desalkyl-flurazepam treatment, or by 3 weeks of midazolam treatment. These results, in combination with previous findings, which showed no change in [3H]flunitrazepam binding after 1 or 2 week flurazepam treatment, and no change in cerebellum even after the 4 week treatment, may indicate a shift in BZ receptor subtypes in flurazepam-tolerant rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Mutational analysis and an alternatively spliced product of B7 defines its CD28/CTLA4-binding site on immunoglobulin C-like domain.

Costimulatory molecules B7 and B7-2 interact with T cell surface receptors CD28/CTLA4 and deliver a costimulatory signal essential for T cell growth. However, the structure basis of this interaction is not known. B7 and B7-2 are members of immunoglobulin (Ig) superfamily and their extracellular portion consists of an IgV- and IgC-like domain. Here we report that a naturally occurring, alternatively spliced form of B7 reveals that exon 3-encoded IgC domain is essential for CD28/CTLA4 binding. Mutational analysis of B7 demonstrates a critical role of several amino acids around loops between strands B and C and D and E, for binding CTLA4/CD28. These amino acids are clustered to form a single binding site centered at 201Y. A comparison of the effects of mutations on the binding of CD28 and CTLA4 reveals that CD28 and CTLA4 binds to the same site on B7. These results have important implications on the role of CTLA4 and CD28 in T cell costimulation. The structure of the CD28/CTLA4-binding site also provides valuable information for immune intervention targeted at the B7/B7-2-CD28/CTLA4 interactions.

Abatacept↗
PubMed1995

GATA-1 transactivates the WT1 hematopoietic specific enhancer.

The Wilms' tumor gene, WT1, is believed to play a role in hematopoiesis as it is expressed in the spleen and in immature leukemias in addition to the developing genitourinary system. WT1 is down-regulated in differentiated leukemia cells both in vivo and in vitro and is up-regulated in fetal spleen and immature leukemia cells. The modulation of WT1 expression was examined in many cell types, and a hematopoietic-specific enhancer element has been identified. Here we describe the transcriptional response of this enhancer to hematopoietic-specific transcription factors. We found co-expression of WT1 and GATA-1 mRNA in K562 cells and in mouse spleen, suggesting potential interactions between these two transcription factors. We find that the activity of the 3' WT1 enhancer is positively correlated with the expression of GATA-1. Gel shift competition experiments and transactivation studies revealed that this functional activity is mediated via binding at a GATA-binding site in the WT1 enhancer. The transactivation of the WT1 enhancer by GATA-1 implies that GATA-1 plays a role in the regulation of WT1 during hematopoiesis.

Base Sequence↗
PubMed1995

MEK-2, a Caenorhabditis elegans MAP kinase kinase, functions in Ras-mediated vulval induction and other developmental events.

Activated Ras initiates a cascade of sequential phosphorylation events, including the protein kinases Raf, MEK, and MAP kinase. The Let-60 Ras-mediated signal transduction pathway controls vulval induction in Caenorhabditis elegans. Both Lin-45 Raf and Sur-1 MAP kinase have been determined to be essential factors during vulval induction; however, the C. elegans mek gene has not been identified. In this paper, we have cloned a C. elegans mek gene, mek-2, and demonstrated that the MEK-2 protein possesses the biochemical properties of MAP kinase kinases: The C. elegans MEK-2 protein can phosphorylate and activate a human MAP kinase (ERK1), and MEK-2 itself can be phosphorylated and activated by immunoprecipitated mammalian Raf. The mek-2 gene plays a key role in the let-60 ras-mediated vulval induction pathway, as loss-of-function mutations in the gene (ku114 and h294) significantly reduce the signal transmitted through Ras. mek-2(ku114) completely suppressed the Multivulva (Muv) phenotype of a hyperactive let-60 ras mutation, and animals homozygous for mek-2(ku114) also displayed a partial larval lethal phenotype. Animals homozygous for mek-2(h294) exhibited a highly penetrant sterile and Vulvaless phenotype. Microinjection of a gain-of-function mek-2 mutation resulted in Muv and other mutant phenotypes, whereas microinjection of a dominant-negative mutation not only suppressed the Muv phenotype of an activated let-60 ras mutation but also caused an egg-laying defective phenotype in otherwise wild type animals. Our results demonstrate that mek-2 acts between lin-45 raf and sur-1/mpk-1 in a signal transduction pathway used in the control of vulval differentiation and other developmental events.

Amino Acid Sequence↗
PubMed1995

Clinical and molecular characterization of a rare syndrome of acute promyelocytic leukemia associated with translocation (11;17).

Analysis of a variant translocation t(11;17) in a case of acute promyelocytic leukemia (APL) led to discovery of a novel zinc finger gene, PLZF, fused to the retinoic acid receptor-alpha (RAR alpha) gene. We reviewed the clinical and molecular features of five additional patients with t(11;17)-associated APL. The clinical course of three patients was characterized by early death and three experienced disseminated intravascular coagulation. Morphologically all of the patients fell in a unusual morphologic spectrum of APL, with features intermediate between M2 and M3 AML. All six patients had PLZF-RAR alpha gene fusion as detected by reverse transcription/polymerase chain reaction assay, Southern blotting, or pulsed-field gel electrophoresis. Five of the six patients failed to achieve complete remission after initial chemotherapy or differentiation therapy with all-trans retinoic acid (ATRA). A sixth patient responded to initial chemotherapy, but on relapse failed to respond to ATRA. When tested in vitro, cultured cells from three of the patients failed to differentiate in response to ATRA. APL associated with t(11;17) and fusion of the PLZF and RAR alpha genes is a discrete clinico-pathologic syndrome with a distinctly worse prognosis than t(15;17) APL.

Adult↗
PubMed1995

Transfection of Plasmodium falciparum within human red blood cells.

Plasmodium falciparum malaria parasites within human red blood cells (RBCs) have been successfully transfected to produce chloramphenicol acetyltransferase (CAT). Electroporation of parasitized RBCs was used to introduce plasmids that have CAT-encoding DNA flanked by 5' and 3' untranslated sequences of the P. falciparum hsp86, hrp3, and hrp2 genes. These flanking sequences were required for expression as their excision abolished CAT activity in transfected parasites. Transfection signals from native CAT-encoding DNA compared well with those from a synthetic DNA sequence adapted to the P. falciparum major codon bias, demonstrating effective expression of the bacterial sequence despite its use of rare P. falciparum codons. Transfected ring-stage parasites produced CAT signals at least as strong as transfected schizont-stage parasites even though ring stages are surrounded by more RBC cytoplasm than schizonts. The transfection of erythrocyte-stage P. falciparum parasites advances our ability to pursue genetic analysis of this major pathogen.

Amino Acid Sequence↗
PubMed1995

Effect of left ventricular hypertrophy and its regression on ventricular electrophysiology and vulnerability to inducible arrhythmia in the feline heart.

BACKGROUND: Left ventricular hypertrophy (LVH) is associated with an increased risk of death, susceptibility to ventricular arrhythmia, and multiple electrophysiological abnormalities. The purpose of the present study was to determine whether the susceptibility to arrhythmia and electrical abnormalities persists after regression of hypertrophy in an animal model of LVH. METHODS AND RESULTS: We placed constricting bands on the ascending aorta of cats (n = 9) or performed sham operations (n = 9). Serial cardiac echocardiography was performed to measure left ventricular wall thickness. After LVH had developed in the banded animals, the constricting bands were removed and serial echocardiograms were used to monitor for regression of hypertrophy. Electrophysiological studies were performed in cats that showed regression of LVH (Regress, n = 5), those that showed no change in LV wall thickness (No Regress, n = 4), and in the sham-operated animals (Sham). Cats with persistent LVH had a higher incidence of inducible polymorphic ventricular tachycardia (4 of 4) compared with Regress (1 of 5) or Sham (1 of 9) cats (P < .05) and had lower ventricular fibrillation thresholds (9 +/- 2 mA) than Regress (17 +/- 4 mA) or Sham (16 +/- 3 mA) cats (P < .05). Persistent LVH in the No Regress group was associated with prolongation of epicardial monophasic action potential duration (MAPD) in the left but not the right ventricle. Dispersion of refractoriness was greater in the No Regress group (P < .05 versus Regress or Sham). Regress cats were identical to Sham cats in having a low incidence of inducible polymorphic ventricular arrhythmia, high fibrillation threshold, and MAPD measurements (P = NS versus Sham). CONCLUSIONS: LVH produces multiple electrophysiological abnormalities and increased vulnerability to inducible polymorphic ventricular arrhythmia in this model of LVH. Cats that show regression of hyperthrophy have normal ventricular electrophysiology and have the same low vulnerability to inducible ventricular arrhythmia as Sham animals.

Action Potentials↗
PubMed1995

Pharmacokinetics of amphotericin B in rats as a function of dose following constant-rate intravenous infusion.

Amphotericin B (AmB) is widely used for the treatment of systemic mycoses. The current therapeutic regimens for this drug are complex and somewhat empirical, in part because of very limited information about the disposition kinetics of this agent. In this study, we examined the disposition kinetics of AmB as a function of dose and estimated clearance values using a steady state study design in an animal model. Groups of male Sprague-Dawley rats were given different two-step infusion regimens to achieve three different steady state concentrations (i.e., three different total infused doses). We observed no significant differences in systemic clearance among the three AmB doses studied. Similarly, only small differences were seen in volumes of distribution as a function of dose. However, renal clearance decreased significantly as the total infused dose was increased (0.76 +/- 0.33, 0.86 +/- 0.24, and 0.37 +/- 0.04 mL min-1 kg-1 for the low-medium and high-dose groups, respectively; p < 0.05). Signs of renal impairment were observed in the high-dose group, as documented by decreased creatinine clearance. Dose-dependent renal clearance may have been due either to nephrotoxicity associated with the high dose of AmB and/or to saturation of an active secretion process. Furthermore, clearance values estimated from steady state conditions were similar to those from time-averaged values (based on the estimation of area under the plasma concentration-time profile). This suggests that clearance calculations from time-averaged concentrations provide reasonable estimates, since steady state plasma concentrations could be reliably determined. However, the possibility that a true tissue steady state condition was not achieved with our study design cannot be ruled out. Further investigation is necessary to identify the renal excretion mechanisms of AmB and to reach steady state tissue concentration to confirm the estimation of systemic clearance.

Amphotericin B↗
PubMed1995

Antigen receptor-triggered apoptosis in immature B cell lines is associated with the binding of a 44-kDa phosphoprotein to the PTP1C tyrosine phosphatase.

While cross-linking of the membrane IgM (mIgM) molecules expressed on WEHI 231 lymphoma cells induces these cells to undergo apoptosis, we have previously observed that ligation of the mIgD expressed on IgD-transfected WEHI 231 (W delta) cells is not associated with induction of cell death. Thus mIgM+IgD+ W delta cells provide a valuable reagent for delineating the molecular events which modulate the physiologic outcome of B cell antigen receptor (BCR) engagement. In view of recent data implicating the cytosolic phosphotyrosine phosphatase PTP1C in the regulation of BCR signaling capacity, we used W delta cells to investigate the potential role for PTP1C in modulating the cell response to BCR activation. The results of this analysis revealed PTP1C to undergo rapid tyrosine phosphorylation following mIgM or mIgD cross-linking and to associate with a number of other phosphoproteins in stimulated W delta cells. Among these latter phosphoproteins, one prominent species of about 44 kDa (pp44) which co-precipitated with PTP1C in mIgM-ligated cells was not detected in PTP1C immunoprecipitates from mIgD-ligated cells. The association of PTP1C with this 44-kDa phosphoprotein following mIgM cross-linking was also observed in two additional B cell lines representing an immature state of differentiation, but was not detected after BCR engagement in two representative mature B cell lines or in splenic B cells. Initial data concerning the identity of pp44 indicate that this molecule does not represent the Shc, MAPK or Ig-beta proteins and may, therefore, constitute a previously unidentified signaling effector. While the structural and biochemical properties of pp44 require further definition, the findings suggest that BCR-triggered interactions of PTP1C with pp44 occur only in the context of an immature state of cellular differentiation and the induction of apoptosis. These data therefore suggest that PTP1C interactions with pp44 may be relevant to the transduction of BCR signals which evoke cell death.

Animals↗
PubMed1995

Onchocerca spp: a "family" of secreted acidic proteins expressed by infective larvae in blackflies.

Biosynthetic labeling of developing larvae of Onchocerca in blackflies has been used to characterize a group of stage-specific, secreted proteins produced by vector-stage parasites. These are highly acidic molecules (pI 4.4-5.1) present in at least three members of the genus (O. volvulus, O. lienalis, O. ochengi) that exhibit minor heterogeneity among species in apparent molecular mass (between 18 and 23 kDa). In O. volvulus, there are two polypeptides that run as a doublet of 18 and 20 kDa. In O. lienalis and O. ochengi, single polypeptides of 23 and 20 kDa were detected. The processes of synthesis and secretion appear to be temperature-sensitive and dissociated events. Experiments with O. volvulus in Simulium damnosum sl revealed that synthesis is initiated in second stage larvae and increases in infective-stage parasites: Secretion occurs when larvae leave the vector and enter the phase of development associated with the vertebrate host. Third-stage larvae of O. lienalis were shown to continue to express and accumulate the 23-kDa protein with age. The primary organ of secretion, as indicated by dissection, was the glandular esophagus. These data point to an important biological role for this group of molecules and suggest that they may belong to a family of related products. Because they have the distinctive characteristics of being secreted larval acidic proteins, we propose the acronym SLAP pending further insights into their functional properties.

Animals↗
PubMed1995

Effects of long-term acclimatization in lowlanders migrating to high altitude: comparison with high altitude residents.

The physiological response to submaximal and maximal exercise was assessed in lowlanders and Tibetans at low (500 m above sea level) and high altitude (HA, 3,680 m). The times spent at HA by the lowland migrators was 8 days (n = 60), 7 months (n = 60, same group), 15 months (n = 29) and 27 months (n = 29). After the 15-month stay at HA, the maximal oxygen uptake (VO2max) and maximal heart rate of the lowland migrators almost reached those of the HA native residents (Tibetans, n = 57), but their total work capacity and the gross efficiency (eta) of mechanical work remained lower than those of the Tibetans. The rate of VO2max achieved at 90 W by the Tibetans was lower than that of the lowland migrators. It was concluded that, at HA, the lowlanders regained much of the aerobic capacity which they had lost initially. However, they did not attain the same gross mechanical efficiency as the Tibetans, who seemed to be at an advantage in respect of work at HA.

Acclimatization↗