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Biomedical subjects

L Prichard

Publications and source records attributed to L Prichard.

9 recordsLinked to original sources
PubMed2001

Expression of suppressors of cytokine signaling during liver regeneration.

The cytokines TNF and IL-6 play a critical role early in liver regeneration following partial hepatectomy (PH). Since IL-6 activates signal transducers and activators of transcription (STATs), we examined whether the suppressors of cytokine signaling (SOCS) may be involved in terminating IL-6 signaling. We show here that SOCS-3 mRNA is induced 40-fold 2 hours after surgery. SOCS-2 and CIS mRNA are only weakly induced, and SOCS-1 is not detectable. SOCS-3 induction after PH is transient and correlates with a decrease in STAT-3 DNA binding and a loss of tyrosine 705 phosphorylation. This response is markedly reduced in IL-6 knockout (KO) mice. TNF injection induces SOCS-3 mRNA in wild-type mice (albeit weakly compared with the increase observed after PH) but not in TNF receptor 1 or IL-6 KO mice. In contrast, IL-6 injection induces SOCS-3 in these animals, demonstrating a requirement for IL-6 in SOCS-3 induction. IL-6 injection into wild-type mice also induces SOCS-1, -2, and CIS mRNA, in addition to SOCS-3. Together, these results suggest that SOCS-3 may be a key component in downregulating STAT-3 signaling after PH and that SOCS-3 mRNA levels in the regenerating liver are regulated by IL-6.

Animals↗
PubMed2000

Prevention of hepatic apoptosis and embryonic lethality in RelA/TNFR-1 double knockout mice.

Mice deficient in the nuclear factor kappaB (NF-kappaB)-transactivating gene RelA (p65) die at embryonic days 14-15 with massive liver apoptosis. In the adult liver, activation of the NF-kappaB heterodimer RelA/p50 can cause hepatocyte proliferation, apoptosis, or the induction of acute-phase response genes. We examined, during wild-type fetal liver development, the expression of the Rel family member proteins, as well as other proteins known to be important for NF-kappaB activation. We found these proteins and active NF-kappaB complexes in the developing liver from at least 2 days before the onset of lethality observed in RelA knockouts. This suggests that the timing of NF-kappaB activation is not related to the timing of lethality. We therefore hypothesized that, in the absence of RelA, embryos were sensitized to tumor necrosis factor (TNF) receptor 1 (TNFR-1)-mediated apoptosis. Thus, we generated mice that were deficient in both RelA and TNFR-1 to determine whether apoptotic signaling through TNFR-1 was responsible for the lethal phenotype. RelA/TNFR-1 double knockout mice survived embryonic development and were born with normal livers without evidence of increased hepatocyte apoptosis. These animals became runted shortly after birth and survived an average of 10 days, dying from acute hepatitis with an extensive hepatic infiltration of immature neutrophils. We conclude that neither RelA nor TNFR-1 is required for liver development and that RelA protects the embryonic liver from TNFR-1-mediated apoptotic signals. However, the absence of both TNFR-1 signaling and RelA activity in newborn mice makes these animals susceptible to endogenous hepatic infection.

Animals↗
PubMed1999

Interactions between neurogranin and calmodulin in vivo.

Neurogranin is a neural-specific, calmodulin (CaM)-binding protein that is phosphorylated by protein kinase C (PKC) within its IQ domain at serine 36. Since CaM binds to neurogranin through the IQ domain, PKC phosphorylation and CaM binding are mutually exclusive. Consequently, we hypothesize that neurogranin may function to concentrate CaM at specific sites in neurons and release free CaM in response to increased Ca2+ and PKC activation. However, it has not been established that neurogranin interacts with CaM in vivo. In this study, we examined this question using yeast two-hybrid methodology. We also searched for additional proteins that might interact with neurogranin by screening brain cDNA libraries. Our data illustrate that CaM binds to neurogranin in vivo and that CaM is the only neurogranin-interacting protein isolated from brain cDNA libraries. Single amino acid mutagenesis indicated that residues within the IQ domain are important for CaM binding to neurogranin in vivo. The Ile-33 --> Gln point mutant completely inhibited and Arg-38 --> Gln and Ser-36 --> Asp point mutants reduced neurogranin/CaM interactions. These data demonstrate that CaM is the major protein that interacts with neurogranin in vivo and support the hypothesis that phosphorylation of neurogranin at Ser-36 regulates its binding to CaM.

Adenylyl Cyclase Inhibitors↗
PubMed1997

The prooncoprotein EWS binds calmodulin and is phosphorylated by protein kinase C through an IQ domain.

A growing family of proteins is regulated by protein kinase C and calmodulin through IQ domains, a regulatory motif originally identified in neuromodulin (Alexander, K. A., Wakim, B. T., Doyle, G. S., Walsh, K. A., and Storm, D. R. (1988) J. Biol. Chem. 263, 7544-7549). Here we report that EWS, a nuclear RNA-binding prooncoprotein, contains an IQ domain, is phosphorylated by protein kinase C, and interacts with calmodulin. Interestingly, PKC phosphorylation of EWS inhibits its binding to RNA homopolymers, and conversely, RNA binding to EWS interferes with PKC phosphorylation. Several other RNA-binding proteins, including TLS/FUS and PSF, co-purify with EWS. PKC phosphorylation of these proteins also inhibits their binding to RNA in vitro. These data suggest that PKC may regulate interactions of EWS and other RNA-binding proteins with their RNA targets and that IQ domains may provide a regulatory link between Ca2+ signal transduction pathways and RNA processing.

3T3 Cells↗
PubMed1994

Synergistic activation of the type I adenylyl cyclase by Ca2+ and Gs-coupled receptors in vivo.

The type I adenylyl cyclase is directly stimulated by Ca2+ and calmodulin in vivo (Choi, E. J., Wong, S. T., Hinds, T. R. and Storm, D. R. (1992) J. Biol. Chem. 267, 12440-12442; Wu, Z., Wong, S. T., and Storm, D. R. (1993) J. Biol. Chem. 268, 23766-23768). In this study, we examined the sensitivity of the type I adenylyl cyclase expressed in HEK-293 cells to beta-adrenergic agonists or glucagon when intracellular Ca2+ was elevated by Ca2+ ionophore or carbachol. Although previous studies have shown that this enzyme can be directly stimulated by activated Gs in vitro, we demonstrate that it is not stimulated by Gs-coupled receptors in vivo. However, the enzyme was stimulated by Gs-coupled receptors in vivo when it was activated by intracellular Ca2+. For example, the Ca2+ ionophore A23187 stimulated the enzyme 3 +/- 0.5-fold (n = 9) and isoproterenol alone did not stimulate the enzyme, but the combination of the two stimulated type I adenylyl cyclase 13 +/- 2-fold (n = 9) in vivo. Similarly, 500 nM glucagon alone did not stimulate the enzyme but the combination of A23187 and glucagon activated the enzyme 90 +/- 8-fold (n = 4). Synergistic stimulation of type I adenylyl cyclase activity was also obtained with combinations of carbachol and isoproterenol or glucagon. This phenomenon was not observed with a mutant enzyme that is insensitive to Ca2+ and calmodulin, suggesting that conformational changes caused by binding of calmodulin to the type I adenylyl cyclase enhance binding or coupling to activated Gs. These data illustrate that this adenylyl cyclase can couple Ca2+ and neurotransmitter signals to generate optimal cAMP levels, a property of the enzyme that may be important for its role in learning and memory in mammals.

Adenylyl Cyclases↗
PubMed1992

Bedside nursing research. A new category of research?

A new category of clinical nursing research, labeled "bedside nursing research," is proposed and described in this article. Justification for this research category is based on its particular characteristics, such as its narrow focus on direct care procedures that have well-defined parameters and the patient outcomes of those procedures. Findings from this type of research have high clinical relevance and can directly influence nursing practice at the study site.

Clinical Nursing Research↗
PubMed1974

Birth control, sterilization and abortion. Attitudes of catholic and protestant clergymen in San Diego toward use in families with genetic illness.

A questionnaire comprising case histories was administered to 27 Protestant and 27 Catholic clergymen in the San Diego area to test their attitudes toward the use of birth control, sterilization and abortion in families with specific genetic problems. The responses indicated:* Catholic and Protestant clergymen do not always follow the official positions of their churches in these matters, although the majority of them do.* Protestant clergymen were more likely to approve of birth control, sterilization, and abortion than Catholic clergymen.* The approval responses of Protestant and Catholic clergymen were not greatly influenced by whether the illness variables involved high Mendelian risk, high psychological cost, high social cost, or poor prognosis.* The approval responses of Protestant and Catholic clergymen were not significantly influenced by the socio-ethnic background of the families.

Abortion, Induced↗