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P J Murray

Publications and source records attributed to P J Murray.

At least 19 recordsLinked to original sources
PubMed2006

Suppressor of cytokine signaling-1 is an IL-4-inducible gene in macrophages and feedback inhibits IL-4 signaling.

Interferon-gamma and interleukin-4 (IL-4) induce distinct gene expression profiles in macrophages by differentially activating signal transducers and activators of transcription (STAT)1 and STAT6, respectively. The role of suppressor of cytokine signaling (SOCS)-1 as a negative regulator of IFN-gamma signaling is well established. However, its potential role as a negative regulator of IL-4 signaling has not been explored. We found that IL-4, like IFN-gamma, induces rapid de novo expression of SOCS-1 in primary macrophages. Induction of SOCS-1 gene expression by IL-4 is STAT6-dependent, whereas induction of SOCS-1 by IFN-gamma is STAT1-dependent. Unlike their common ability to induce expression of SOCS-1, IL-4 also induced expression of SOCS-2 but not SOCS-3 in macrophages, whereas IFN-gamma induced expression of SOCS-3 but not SOCS-2. Forced expression of SOCS-1 or SOCS-3, but not SOCS-2, inhibited activation of STAT6 by IL-4. Moreover, SOCS-1 appears to serve as an endogenous regulator of IL-4 signaling in macrophages because the magnitude and duration of STAT6 activation as well as IL-4-mediated gene expression were much greater in SOCS-1-deficient (SOCS-1(-/-)) macrophages than in wild-type macrophages. Our findings demonstrate that, like IFN-gamma, IL-4 also induces expression of SOCS-1 in macrophages, and SOCS-1 feedback inhibits expression of STAT6-responsive genes.

Animals↗
PubMed2006

STAT3-mediated anti-inflammatory signalling.

IL-1O (interleukin-10) negatively regulates inflammation through a mechanism that blocks the expression of pro-inflammatory genes encoding cytokines, chemokines, cell-surface molecules and other molecules required for the full activation of the innate and adaptive immune responses. The signalling pathway used by the IL-10 receptor to generate the anti-inflammatory response requires STAT3 (signal transducer and activator of transcription 3) and is indirect. Thus STAT3 activates other genes whose task is to selectively control transcription of inflammatory targets. Here, I summarize current knowledge of the key features of IL-10 signalling and make predictions concerning the mechanism of IL-10 at the level of inflammatory genes. Understanding IL-10 signalling should be a gateway to the development of broadly acting anti-inflammatory agents.

Gene Expression Regulation↗
PubMed2006

Effects of carbon dioxide on the searching behaviour of the root-feeding clover weevil Sitona lepidus (Coleoptera: Curculionidae).

The respiratory emission of CO2 from roots is frequently proposed as an attractant that allows soil-dwelling insects to locate host plant roots, but this role has recently become less certain. CO2 is emitted from many sources other than roots, so does not necessarily indicate the presence of host plants, and because of the high density of roots in the upper soil layers, spatial gradients may not always be perceptible by soil-dwelling insects. The role of CO2 in host location was investigated using the clover root weevil Sitona lepidus Gyllenhall and its host plant white clover (Trifolium repens L.) as a model system. Rhizochamber experiments showed that CO2 concentrations were approximately 1000 ppm around the roots of white clover, but significantly decreased with increasing distance from roots. In behavioural experiments, no evidence was found for any attraction by S. lepidus larvae to point emissions of CO2, regardless of emission rates. Fewer than 15% of larvae were attracted to point emissions of CO2, compared with a control response of 17%. However, fractal analysis of movement paths in constant CO2 concentrations demonstrated that searching by S. lepidus larvae significantly intensified when they experienced CO2 concentrations similar to those found around the roots of white clover (i.e. 1000 ppm). It is suggested that respiratory emissions of CO2 may act as a 'search trigger' for S. lepidus, whereby it induces larvae to search a smaller area more intensively, in order to detect location cues that are more specific to their host plant.

Animals↗
PubMed2004

Host plant recognition by the root feeding clover weevil, Sitona lepidus (Coleoptera: Curculionidae).

This study investigated the ability of neonatal larvae of the root-feeding weevil, Sitona lepidus Gyllenhal, to locate white clover Trifolium repens L. (Fabaceae) roots growing in soil and to distinguish them from the roots of other species of clover and a co-occurring grass species. Choice experiments used a combination of invasive techniques and the novel technique of high resolution X-ray microtomography to non-invasively track larval movement in the soil towards plant roots. Burrowing distances towards roots of different plant species were also examined. Newly hatched S. lepidus recognized T. repens roots and moved preferentially towards them when given a choice of roots of subterranean clover, Trifolium subterraneum L. (Fabaceae), strawberry clover Trifolium fragiferum L. (Fabaceae), or perennial ryegrass Lolium perenneL. (Poaceae). Larvae recognized T. repens roots, whether released in groups of five or singly, when released 25 mm (meso-scale recognition) or 60 mm (macro-scale recognition) away from plant roots. There was no statistically significant difference in movement rates of larvae.

Animals↗
PubMed2003

Fluconazole toxicity is independent of oxidative stress and apoptotic effector mechanisms in Saccharomyces cerevisiae.

Fluconazole toxicity was previously shown to require intact mitochondria in Saccharomyces cerevisiae, however, the mechanism of mitochondrial-dependent azole toxicity is unclear. Here we show that fluconazole toxicity is not attenuated by the overexpression of the mitochondrially-acting human antiapoptotic protein Bcl-2 nor is it increased by the presence of the oxidating agents in S. cerevisiae. Our data further support the notion that mitochondrial toxicity in the presence of azoles is modulated by the conversion of ergosterol precursors to toxic sterols.

Apoptosis↗
PubMed2002

Self-collected vaginal swabs for the detection of multiple sexually transmitted infections in adolescent girls.

OBJECTIVE: To evaluate the use of self-collected vaginal swabs to test for Neisseria gonorrhoeae, Chlamydia trachomatis, and Trichomonas vaginalis, and to describe the acceptability of this technique to adolescents. DESIGN: Comparison of a new protocol for sexually transmitted infection (STI) testing with the current standard of care, using the same subjects. Survey of attitudes regarding the self-collection technique. SETTING: A juvenile correctional facility in western Pennsylvania. PARTICIPANTS: Convenience sample of 133 detainees, 12-17 years of age. INTERVENTION: Girls were invited to undergo STI screening using a self-collected vaginal swab. Polymerase chain reaction was used to test this specimen for each of the above three infections. Pelvic exams and endocervical testing were performed at the discretion of the physician performing the intake physical, independent of the study. MAIN OUTCOME MEASURES: The number of infections diagnosed using the self-testing protocol, compared to the number diagnosed using standard practices; acceptability of the self-collection technique. RESULTS: Twenty-four percent of sexually active subjects had one or more infections diagnosed by self-testing: 11.3% had C. trachomatis, 8.5% had N. gonorrhoeae, and 11.7% had T. vaginalis. Only 30% of subjects with infections had pelvic exams while detained; therefore 70% of girls with infections would have been missed in the absence of the self-testing option. The self-collection technique was acceptable to 95% of subjects. CONCLUSIONS: STI testing using self-collected vaginal specimens is highly acceptable to adolescent girls, and can dramatically increase the detection rate for these three treatable infections when pelvic exams are not performed.

Adolescent↗
PubMed2001

Apoptosis-inducing factor mediates microglial and neuronal apoptosis caused by pneumococcus.

Streptococcus pneumoniae is the major cause of bacterial meningitis and it damages the hippocampus by inducing neuronal apoptosis. The blocking of caspases provides only partial protection in experimental meningitis, which suggests that there is an additional apoptotic pathway. A trigger of this pathway is the bacterium itself, as exposure of microglia or neurons to live pneumococci induces rapid apoptosis. In this study, apoptosis was not associated with the activation of caspases-1-10 and was not inhibited by z-VAD-fmk, a broad-spectrum caspase inhibitor. Rather, apoptosis was attributed to damage to mitochondria, which was followed by the release of apoptosis-inducing factor (AIF) from the mitochondria, large-scale DNA fragmentation, and hypodiploidy. Furthermore, intracytoplasmatic microinjection of AIF-specific antiserum markedly impaired pneumococcus-induced apoptosis. These findings indicate that AIF may play a central role in brain cell apoptosis and bacterial pathogenesis.

Animals↗
PubMed2001

Yeast artificial chromosome targeting technology: an approach for the deletion of genes in the C57BL/6 mouse.

An approach is described to modify yeast artificial chromosomes (YACs) with cassettes that can be easily excised for embryonic stem (ES) cell gene targeting experiments. YAC targeting technology (YTT) uses the WIBR/MIT-820 C57BL/6-mapped YAC library derived from the C57BL/6 mouse as the starting point for Internet- or PCR-based clone isolation, although in principle any YAC system can be used. Homologous recombination is initially performed in yeast using cassettes that function in Saccharomyces cerevisiae, Escherichia coli, and ES cells, followed by cloning or conversion of the targeted locus into a plasmid. The completed targeting vector can be transfected into C57BL/6 ES cells and clones selected with G418 followed by injection into Balb/c blastocysts. YTT increases the speed of targeting vector construction and obviates the need for extensive backcrossing to the C57BL/6 background.

Animals↗
PubMed2001

TNF-alpha controls intracellular mycobacterial growth by both inducible nitric oxide synthase-dependent and inducible nitric oxide synthase-independent pathways.

The role of TNF-alpha in the control of mycobacterial growth in murine macrophages was studied in vitro. Infection of macrophages from TNF-alpha gene disrupted (TNF-knockout (KO)) mice with recombinant Mycobacterium bovis bacillus Calmette Guérin (BCG) expressing the vector only (BCG-vector) resulted in logarithmic growth of the intracellular bacilli. Infection with BCG-secreting murine TNF-alpha (BCG-TNF) led to bacillary killing. Killing of BCG-TNF was associated with rapid accumulation of inducible NO synthase (iNOS) protein and the production of nitrite. The uncontrolled growth of BCG-vector was associated with low iNOS expression but no nitrite production. Thus, iNOS expression appears to be TNF-alpha independent but iNOS generation of NO requires TNF-alpha. In cultures of TNF-KO macrophages infected with BCG-TNF, inhibition of iNOS by aminoguanidine (AMG) abolished the killing of the bacilli. However, the growth of the organisms was still inhibited, suggesting an iNOS-independent TNF-alpha-mediated growth inhibition. To confirm this, macrophages from iNOS-KO mice were infected with either BCG-vector or BCG-TNF. As expected, no nitrite was detected in the culture medium. TNF-alpha was detected only when the cells were infected with BCG-TNF. In the iNOS-KO macrophages, the growth of BCG was inhibited only in the BCG-TNF infection. These results suggest that in the absence of iNOS activity, TNF-alpha stimulates macrophages to control the growth of intracellular BCG. Thus, there appears to be both a TNF-alpha-dependent-iNOS-dependent killing pathway as well as a TNF-alpha-dependent-iNOS-independent growth inhibitory pathway for the control of intracellular mycobacteria in murine macrophages.

Animals↗
PubMed2001

Cutting edge: Stat6-dependent substrate depletion regulates nitric oxide production.

The cytokines IL-4 and IL-13 inhibit the production of NO from activated macrophages through an unresolved molecular mechanism. We show here that IL-4 and IL-13 regulate NO production through depletion of arginine, the substrate of inducible NO synthase (iNOS). Inhibition of NO production from murine macrophages stimulated with LPS and IFN-gamma by IL-4 or IL-13 was dependent on Stat6, cell density in the cultures, and pretreatment for at least 6 h. IL-4/IL-13 did not interfere with the expression or activity of iNOS but up-regulated arginase I (the liver isoform of arginase) in a Stat6-dependent manner. Addition of exogenous arginine completely restored NO production in IL-4-treated macrophages. Furthermore, impaired killing of the intracellular pathogen Toxoplasma gondii in IL-4-treated macrophages was overcome by supplementing L-arginine. The simple system of regulated substrate competition between arginase and iNOS has implications for understanding the physiological regulation of NO production.

Animals↗
PubMed2001

Screening for chronic hepatitis B and C virus infections in an urban sexually transmitted disease clinic: rationale for integrating services.

BACKGROUND AND OBJECTIVES: Clients attending sexually transmitted disease (STD) clinics are at risk for multiple infections (e.g., STDs, HIV, and infectious viral hepatitis). Risk assessment and serosurveys can document the need for hepatitis screening and vaccination services. GOAL: To determine hepatitis C and B virus seroprevalence, identify predictive risk factors, and provide a rationale for integrating hepatitis services in an STD clinic. METHODS: During various periods in 1998, consecutive clients completed a self-administered risk assessment and were offered screening for markers of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection (HBV core antibody and anti-HCV [enzyme-linked immunosorbent assay 3.0, confirmed by recombinant immunoblot assay 2.0]). RESULTS: Sixteen percent of 300 clients tested for an anti-HBV core were positive, with injecting-drug users (IDUs) and men who have sex with men (MSM) having higher prevalences (50% and 37%, respectively). Of 615 clients tested for anti-HCV, 21 (3.4%) were positive. Injecting-drug users (n = 34) had a 38% anti-HCV prevalence compared with 1.1% for non-IDUs. Of 66 non-IDU MSM tested, none was HCV infected. IDUs had a high prevalence of past STDs (> 50%) and unsafe sexual behavior. CONCLUSIONS: Injecting drug users and MSM are at high risk for STDs, HIV, and hepatitis infections and could benefit from a "one-stop" STD clinic that included hepatitis prevention services.

Adult↗
PubMed2000

Aerosol infection of mice with recombinant BCG secreting murine IFN-gamma partially reconstitutes local protective immunity.

To better understand the contribution of interferon-gamma (IFN-gamma) to the immune response during the first 60 days of mycobacterial infection in the lungs, IFN-gamma gene disrupted (IFN-gamma-/-) mice were infected via aerosol with recombinant Mycobacterium bovis Bacillus Calmette-Guerin (BCG) secreting murine IFN-gamma (BCG-IFN-gamma) and compared to mice infected with recombinant BCG containing the vector only (BCG-vector). When IFN-gamma-/- mice were infected with BCG-vector, increasing bacillary loads and large undifferentiated granulomas that did not express inducible nitric oxide synthase (iNOS) were observed in the lungs. In contrast, infection with BCG-IFN-gamma resulted in reduced bacillary load and better differentiated granulomas containing epithelioid macrophages expressing iNOS as well as reduced levels of interleukin 10 (IL-10) mRNA. However, local production of IFN-gamma by the recombinant BCG did not protect IFN-gamma-/- mice from subsequent challenge with M. tuberculosis. Infection of IFN-gamma-/- peritoneal macrophages in vitro with BCG-IFN-gamma led to induction of iNOS expression and lower IL-10 mRNA levels. Nevertheless, the growth of the intracellular BCG was unaffected. Since IFN-gamma induced-iNOS protein and reduced IL-10 production were insufficient to control mycobacterial growth in vitro, the results suggest that additional mediator(s) present in vivo are required for control of mycobacterial growth.

Aerosols↗
PubMed2000

Phospholipase Cgamma2 is essential in the functions of B cell and several Fc receptors.

Many receptors activate phospholipase Cgamma1 or -gamma2. To assess the role of PLCgamma2, we derived enzyme-deficient mice. The mice are viable but have decreased mature B cells, a block in pro-B cell differentiation, and B1 B cell deficiency. IgM receptor-induced Ca2+ flux and proliferation to B cell mitogens are absent. IgM, IgG2a, and IgG3 levels are reduced, and T cell-independent antibody production is absent. The similarity to Btk- or Blnk-deficient mice demonstrates that PLCgamma2 is downstream in Btk/Blnk signaling. FcRgamma signaling is also defective, resulting in a loss of collagen-induced platelet aggregation, mast cell FcepsilonR function, and NK cell FcgammaRIII and 2B4 function. The results define a signal transduction pathway broadly utilized by immunoglobulin superfamily receptors.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Ubiquitous expression and embryonic requirement for RNA polymerase II coactivator subunit Srb7 in mice.

Mammalian RNA polymerase II complexes and coactivators containing homologs of yeast Srb/Med proteins have been isolated recently from tissue culture cells. The yeast Srb/Med complex is involved in global gene expression and is essential, but it is not yet known if its mammalian counterparts are broadly expressed in tissues or if they are essential. We have isolated the murine gene encoding Srb7, an Srb/Med complex protein whose sequence and function is highly conserved between yeast and humans. The mouse Srb7 gene is single copy, and Northern analysis showed that it is expressed in all tissues examined. Disruption of the gene in embryonic stem cells revealed that it is essential for cell viability and murine embryonic development. These results, together with evidence that murine Srb7 is associated exclusively with high molecular weight forms of RNA polymerase II in extracts, suggest that Srb7-containing polymerase complexes occur in most tissues and have essential roles in expression of protein coding genes.

Amino Acid Sequence↗
PubMed1999

Defining the requirements for immunological control of mycobacterial infections.

Tuberculosis remains a major public health problem throughout the world. Research into the immunological basis of the host-pathogen relationship has recently benefited from the fascinating convergence of genetic data from mouse models and from humans. Latency - the seemingly quiescent phase of bacterial persistence - is the central problem in controlling tuberculosis and will be the next frontier of research.

Animals↗