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Biomedical subjects

H Turner

Publications and source records attributed to H Turner.

At least 37 records · Page 2Linked to original sources
PubMed1998

Rac-1 regulates nuclear factor of activated T cells (NFAT) C1 nuclear translocation in response to Fcepsilon receptor type 1 stimulation of mast cells.

Transcription factors of the nuclear factor of activated T cells (NFAT) family play a key role in antigen receptor-mediated responses in lymphocytes by controlling induction of a wide variety of cytokine genes. The GTPases Ras and Rac-1 have essential functions in regulation of NFAT transcriptional activity in the mast cell system, where Fcepsilon receptor type 1 (FcepsilonR1) ligation results in induction of multiple NFAT target genes. This report examines the precise biochemical basis for the Rac-1 dependency of FcepsilonR1 activation of NFAT in mast cells. We are able to place Rac-1 in two positions in the signaling network that regulates the assembly and activation of NFAT transcriptional complexes in lymphocytes. First, we show that activity of Rac-1 is required for FcepsilonR1-mediated NFATC1 dephosphorylation and nuclear import. Regulation of NFAT localization by the FcepsilonR1 is a Rac-dependent but Ras-independent process. This novel signaling role for Rac-1 is distinct from its established regulation of the actin cytoskeleton. Our data also reveal a second GTPase signaling pathway regulating NFAT transcriptional activity, in which Rac-1 mediates a Ras signal. These data illustrate that the GTPase Rac-1 should now be considered as a component of the therapeutically important pathways controlling NFATC1 subcellular localization. They also reveal that GTPases may serve multiple functions in cellular responses to antigen receptor ligation.

Actins↗
PubMed1997

Distinct Ras effector pathways are involved in Fc epsilon R1 regulation of the transcriptional activity of Elk-1 and NFAT in mast cells.

Activation of Ras GTPases is a conserved feature of antigen receptor signaling, including Fc epsilon R1 activation of mast cells. Antigenic cross-linking of the Fc epsilon R1 on mast cells results in secretion of allergic mediators and induction of immediate early and cytokine genes. Here we examine the role of Ras in coupling the Fc epsilon R1 to transcriptional regulation. The transcription factors Elk-1, an immediate early gene regulator and the nuclear factor of activated T cells (NFAT), in the context of the IL-4 gene, are identified as Ras targets in mast cells. Ras mediates diverse effects via its diverse effector pathways, which may include other members of the Ras GTPase family such as RhoA and Rac-1. We observe that Elk-1 and NFAT are targeted by distinct Ras effector pathways in mast cells. Activation of the "classical" Ras/Raf-1/MEK/ ERK cascade is necessary and sufficient for Fc epsilon R1 induction of Elk-1. Ras function is required, but not sufficient for Fc epsilon R1 induction of NFAT. However, activation or inhibition of Ras markedly shifts the antigen dose-response for Fc epsilon R1 induction of NFAT. The effector pathway for Ras activation of NFAT is not Raf-1/MEK. We identify that the Rac-1 GTPase is critical in Fc epsilon R1 regulation of NFAT, acting either in parallel with or as an effector of Ras. These data place Ras in a crucial position in mast cells, regulating disparate nuclear targets. Moreover, we identify that two GTPases, Ras and Rac-1, are important regulators of NFAT, and therefore of cytokine expression in mast cells.

Animals↗
PubMed1997

Incorporating the named nurse concept into care.

The named nurse concept stresses the importance of individualised care for patients. The concept is compatible with methods of nursing that put emphasis on the individual relationship with patients, such as primary nursing and team nursing. With sufficient resources, the named nurse is a suitable concept to apply in the organisation of care delivery in mental health nursing.

Continuity of Patient Care↗
PubMed1996

Informed choice for users of health services: views on ultrasonography leaflets of women in early pregnancy, midwives, and ultrasonographers.

With the aim of promoting the informed choice of pregnant women, staff and pregnant women at two urban hospitals were offered leaflets summarising the best available evidence about the effectiveness of routine ultrasonography in early pregnancy. Ultrasonographers doubted the credibility of the evidence and were concerned that the leaflets would raise women's anxiety, reduce uptake of scans, disrupt hospital organisation, and reinforce media messages about the poor safety record of ultrasonography. Midwives thought that the leaflets would inform women, help them to talk about their care with health professionals, and help them to get better care. Women were shocked at some of the contents but thought that it was appropriate to include both advantages and disadvantages of routine scanning in the leaflet. This case study highlights the resistance of some health professionals to evidence based health care; underlying conflicts with the principle of professional autonomy; concern that informed choice may create anxiety; and professional and organisational barriers to allowing informed choice.

Attitude of Health Personnel↗
PubMed1996

Altered hexamerin regulation in prepupal Trichoplusia ni pseudoparasitized by Chelonus sp. near curvimaculatus.

Adult female wasps of species in the subfamily Cheloninae inject an egg, venom, polydnavirus and other materials into the host egg during oviposition. Hosts then exhibit precocious expression of the metamorphic developmental program, but then further development by the precocious prepupa is suppressed. These effects occur in truly parasitized hosts (those that contain a live endoparasite larva) as well as in pseudoparasitized hosts (that do not contain a live endoparasite). We report here that during the precocious prepupal stage, the hexamerins BJHSP1 and BJHSP2 persist in the hemolymph of pseudoparasitized hosts, whereas in normal larvae these proteins are cleared from the hemolymph in response to the normal surge in prepupal ecdysteroids. Northern blot analysis of poly(A) RNA showed that the basis for this persistence is not an abnormally high abundance of the transcripts on the day following wandering in pseudoparasitized larvae. Nor is the source of the hexamerins the parasite larva, for it is missing from the pseudoparasitized hosts. The hypothesis that the persistence is due to a suppressed titer of ecdysteroids in pseudoparasitized hosts (reported earlier: [jones et al., Arch Insect Biochem Physiol 21:155 (1992)] was tested by use of a large size variant of pseudoparasitized hosts in which the prepupal ecdysteroid titer is partially restored by endogenous ecdysteroid production. In such pseudoparasitized prepupae, the two hexamerins were cleared from the hemolymph on the day following host wandering behavior, as in normal larvae. Thus, the regulatory basis of the persistence of the hexamerins BJHSP1 and BJHSP2 in the hemolymph of pseudoparasitized hosts appears to be at the posttranslational level, with suppression of the prepupal ecdysteroid titer causing omission of the normal trigger for fat body uptake of the hexamerins.

Animals↗
PubMed1996

The protein interactions of the immunoglobulin receptor family tyrosine-based activation motifs present in the T cell receptor zeta subunits and the CD3 gamma, delta and epsilon chains.

Immunoglobulin family tyrosine-based activation motifs (ITAM), which define the conserved signaling sequence EX2YX2L/IX7YX2L/I, couple the T cell antigen receptor (TCR) to cellular proteins including protein tyrosine kinases (PTK) and adapter molecules. The TCR is a multichain complex with four invariant chains CD3 gamma, delta and epsilon that each contain a single ITAM and the TCR zeta chain that contains three ITAM. The present study explores the protein interactions of the doubly phosphorylated CD3 gamma, delta, epsilon ITAM to determine whether they have common or unique biochemical properties. The data show that the doubly phosphorylated ITAM all bind the PTK ZAP-70, but the ITAM also variably bind the PTK p59fyn and the adapters Shc, Grb-2 and the p85 regulatory subunit of phosphoinositol 3' kinase. The CD3 and zeta ITAM display a hierarchy of ZAP-70 binding: zeta 1 = gamma = delta > zeta 3 > zeta 2 = epsilon. Shc, Grb-2 and p85 could bind the zeta ITAM and the CD3 gamma and delta ITAM, but not the CD3 epsilon ITAM. There were also subtle differences in the hierarchy of reactivity of these adapters for the CD3 gamma, delta and zeta ITAM that show that the zeta, CD3 gamma, delta and epsilon ITAM have different binding properties. The present study thus shows that the different ITAM of the TCR/CD3 complex can interact with different cytosolic effectors, indicating that differential ITAM phosphorylation during T cell activation could be a mechanism to generate signaling diversity by the TCR complex.

Amino Acid Sequence↗
PubMed1995

A comparison of the interaction of Shc and the tyrosine kinase ZAP-70 with the T cell antigen receptor zeta chain tyrosine-based activation motif.

Tyrosine-based activation motifs (TAMs) define a conserved signaling sequence, EX2YX2L/IX7YX2L/I, that couples the T cell antigen receptor to protein tyrosine kinases and adapter molecules. The present study shows that phosphorylation of both tyrosines within the motif is required for high affinity binding of the tyrosine kinase ZAP-70 whereas phosphorylation of the single COOH-terminal tyrosine within the motif is optimal for the binding of the adapter Shc. There were also quantitative differences in the ZAP-70 and Shc association with the zeta 1-TAM since nM concentrations of the doubly phosphorylated zeta 1-TAM are sufficient for ZAP-70 recruitment whereas micromolar levels of singly phosphorylated TAMs are necessary for Shc binding. Shc is tyrosine phosphorylated in antigen receptor-activated T cells and can potentially form a complex with the adapter molecule Grb2 and could thus recruit the Ras guanine nucleotide exchange protein Sos into the antigen receptor complex. The present data show that Grb2 can bind to the phosphorylated TAM, but this binding is independent of Shc and there is no formation of zeta 1-TAM.Shc.Grb2.Sos complexes in antigen receptor-activated cells. Accordingly, Shc function should not be considered in the context of Grb2/Sos recruitment to the T cell antigen receptor complex.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Regulation of the adapter molecule Grb2 by the Fc epsilon R1 in the mast cell line RBL2H3.

Antigenic cross-linking of the high affinity IgE receptor (Fc epsilon R1) on mast cells results in protein tyrosine kinase activation. The object of the present study was to explore the regulation of the SH2 and SH3 domain containing adapter molecule Grb2 by Fc epsilon R1-stimulated PTK signal transduction pathways. Affinity purification of in vivo Grb2 complexes together with in vitro experiments with Grb2 glutathione S-transferase fusion proteins were used to analyze Grb2 complexes in the mast cell line RBL2H3. The data show that in RBL2H3 cells several different proteins are complexed to the SH3 domains of Grb2. These include the p21ras guanine nucleotide exchange factor Sos, two basally tyrosine-phosphorylated 110- and 120-kDa molecules, and a 75-kDa protein that is a substrate for Fc epsilon R1-activated PTKs. By analogy with Sos, p75, p110 and p120 are candidates for Grb2 effector proteins which suggests that Grb2 may be a pleiotropic adapter. Two Grb2 SH2-binding proteins were also characterized in RBL2H3 cells; the adapter Shc and a 33-kDa molecule. Shc is constitutively tyrosine phosphorylated in unstimulated cells and Fc epsilon R1 ligation induces no changes in its phosphorylation or binding to Grb2. In contrast, p33 is a substrate for Fc epsilon R1-activated PTKs and binds to Grb2 SH2 domains in Fc epsilon R1 activated but not quiescent cells. The beta subunit of the Fc epsilon R1 is a 33-kDa tyrosine phosphoprotein, but the p33 Grb2-binding protein described in the present report is not the Fc epsilon R1 beta chain and its identity is unknown. The present report thus demonstrates that there are multiple Grb2 containing protein complexes in mast cells of which a subset are Fc epsilon R1-regulated. Two other of the Grb2-binding proteins described herein are tyrosine phosphorylated in response to Fc epsilon R1 ligation: the 75-kDa protein which binds to Grb2 SH3 domains and the 33-kDa protein that associates with the Grb2 SH2 domain. We propose that protein complex formation by Grb2 is an important consequence of Fc epsilon R1 cross-linking and that this may be a signal transduction pathway which acts synergistically with calcium/PKC signals to bring about optimal mast cell end function.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Supporting vulnerable families: an evaluation of Newpin.

Newpin (the New Parent Infant Network) was set up in 1980 to provide support for vulnerable families. But according to a new study, while nearly half the women referred to four Newpin centres went on to make use of its services, a larger proportion did not: either the support package offered was felt to be inappropriate, or the referral was inappropriate, or the women were simply lost to the system. Ann Oakley et al argue that voluntary sector initiatives should be subjected to the same rigorous scrutiny for cost-effectiveness as the statutory sector.

Adult↗
PubMed1994

Identification of a 40- to 42-kDa attachment polypeptide for canine parvovirus in A72 cells.

The attachment of canine parvovirus (CPV) to different cell lines was quantitated by a fluorescence-activated cell sorter assay. The viral attachment was observed to both permissive A72 and nonpermissive ST cells but not to nonpermissive MDBK cells. The binding of and infectivity for CPV to A72 cells was reduced upon prior treatment of cells with Vibrio cholerae neuraminidase or lectins, specific for sialic acid. Similarly, treatment of cells with any of several proteases reduced virus binding; however, phospholipase treatment had no effect indicating that one or more membrane glycoproteins were involved in virus binding. These proteins were characterized with a virus overlay protein blot assay. Virus bound to a protein with a molecular mass of 40 to 42 kDa in membranes prepared from A72 and ST cells and not from MDBK cells. The binding to this polypeptide was specific since increasing amounts of unlabeled virions competitively inhibited binding of radiolabeled virions in a dose-dependent manner. A polypeptide of similar molecular mass was immunoprecipitated from radiolabeled octyl glucoside (OG) extract of A72 cells using purified virions, virion-specific antiserum, and protein A. The binding to this polypeptide was decreased but not abolished upon prior treatment of the membrane with V. cholerae neuraminidase. CPV preferentially recognized a polypeptide of similar molecular size in the OG extract prepared from the biotinylated basolateral surface of polarized MDCK monolayer. Hence, we propose that the 40- to 42-kDa glycoprotein represents a specific attachment molecule for CPV in A72 cells.

Animals↗
PubMed1994

Structure, expression and gene sequence of a juvenile hormone esterase-related protein from metamorphosing larvae of Trichoplusia ni.

A carboxylesterase with an encoded molecular size of 61 kDa and a high sequence similarity to juvenile hormone esterase (JHE) has been cloned from cDNA prepared from final instar larvae of Trichoplusia ni. The absence of a recognizable encoded signal peptide suggests that the enzyme, JHER (for JHE-related) may not be secreted, in contrast to JHE. When the amino acid sequence of JHE, JHER and other esterases were mapped onto the secondary and tertiary structure determined crystallographically for acetylcholinesterase, certain structural features for the substrate binding/catalytic site were identified as common only to JHE and JHER. However, several differences between JHE and JHER were identified in residues at the binding/catalytic site, suggesting that although the two enzymes prefer similar natural substrates, these substrates are not identical. JHER is present as a single-copy gene, transcribed during the feeding stage of the final stage of the final larval stadium, but not after metamorphic commitment to the pupal developmental programme. The gene transcribes a single-size message of 2.0 kb. The genes for JHER and JHE appear to be physically juxtaposed in the T. ni genome. The 5' flanking sequence to the JHER gene possesses some sequences in common with the JHE gene, but is also missing some regulatory elements previously identified in the JHE gene. Sequences conserved between the promoters for the two genes were identified that were different from previously reported regulatory elements of eukaryotic transcription factors.

Acetylcholinesterase↗
PubMed1993

HIV antibody testing among those at risk for infection. The National AIDS Behavioral Surveys.

OBJECTIVE: To determine the prevalence of testing for human immunodeficiency virus (HIV) antibody among adults with various risk factors for infection, particularly those residing in large metropolitan areas where the bulk of cases of acquired immunodeficiency syndrome (AIDS) have occurred. DESIGN: A nationwide, population-based telephone survey eliciting testing, sexual, and injection drug use histories. PARTICIPANTS: A total of 2673 randomly chosen US residents and 8263 randomly chosen residents of 23 metropolitan areas containing 64% of reported cases of AIDS. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Testing for HIV antibody. MAIN RESULTS: Overall, rates of individuals ever tested were only slightly higher in the urban areas (23%) than in the nation as a whole (21%). Testing frequencies were low among all risk groups (less than 40%), except men engaging in same-sex sexual activity (60%) and male and female injection drug users (46% and 73%, respectively). The low rate of testing (35%) among the largest risk group, heterosexual men and women engaging in unprotected sexual intercourse with multiple partners, was particularly worrisome. CONCLUSIONS: To encourage antibody testing among the many at risk for infection who have not yet been tested, promotional campaigns should explain the universal susceptibility to infection among those at risk, and the availability of prophylactic medical therapies and social support services to persons who are HIV-seropositive. As there were comparable levels of risk-taking behavior among subjects in both samples, these campaigns must be designed to reach all segments of the population.

AIDS Serodiagnosis↗
PubMed1992

Prevalence of AIDS-related risk factors and condom use in the United States.

A national probability survey of human immunodeficiency virus (HIV)-related risk factors among the general heterosexual population, the National AIDS (acquired immunodeficiency syndrome) Behavioral Surveys, has obtained data from 10,630 respondents. Data are presented on the prevalence of HIV-related risks in the general heterosexual population, on the distribution of the three largest risk groups across social strata, and on the prevalence and distribution of condom use among heterosexuals reporting a risk factor. Between 15 and 31 percent of heterosexuals nationally and 20 and 41 percent in cities with a high prevalence of AIDS reported an HIV risk factor. Condom use was relatively low. Only 17 percent of those with multiple sexual partners, 12.6 percent of those with risky sexual partners, and 10.8 percent of untested transfusion recipients used condoms all the time. Overall, the results suggest that current HIV prevention programs have, to a very limited extent, reached those heterosexuals with multiple sexual partners but have failed to reach many other groups of the heterosexual population at risk for HIV. New public health strategies may be needed for these specific risk groups.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Infectious entry pathway for canine parvovirus.

We have investigated whether canine parvovirus (CPV) infection involves a low pH-dependent entry pathway. The effects of two lysosomotropic bases, NH4Cl and chloroquine, on CPV entry were studied by immunofluorescence and ultrastructural and biochemical methods. In the presence of these reagents, input virions appear to accumulate in large vacuoles. Ultrastructural studies indicated that uptake of virions takes place predominantly in small uncoated vesicles that appear to fuse with larger vesicles. In the presence of NH4Cl, virions accumulate in the latter structures and their uncoating appears to be prevented. Viral DNA as well as antigen synthesis were found to be significantly inhibited in the presence of these reagents. In addition, inhibition of viral DNA and antigen synthesis appeared to be most extensive when NH4Cl was present from 30 min preinfection, whereas no significant inhibition was observed when the cells were treated after 2 hr postinfection. Thus, the results indicate that CPV requires exposure to low pH in an endosomal compartment to initiate a productive infection.

Ammonium Chloride↗
PubMed1992

Expression of SV40 receptors on apical surfaces of polarized epithelial cells.

We have investigated the interaction of SV40 virions with polarized monkey kidney epithelial cells. Virions were tagged with biotin to facilitate their detection and were found to retain full infectivity. When polarized Vero C1008 cells were incubated with biotinylated virions followed by a strepavidin-rhodamine conjugate, distinct cell populations were identified which expressed very different levels of SV40 receptors. The parental Vero C1008 cells yielded three types of cell clones which exhibited low, moderate, or predominantly high levels of SV40 binding. Virus-binding assays to each of these clones as well as to parental Vero C1008 cells indicated that the level of SV40 receptor expression is cell-cycle-dependent. The cellular receptors for influenza A virus (WSN strain) were also found to be distributed heterogeneously on polarized epithelial cells. In contrast, in several types of nonpolarized cells, SV40 receptors were found to be uniformly distributed over the monolayer. SV40 binding was not found to correlate with HLA expression on Vero C1008 cells or other cell types. Also in contrast to SV40 receptor expression, which is restricted to the apical domain, HLA was found to be distributed on both apical and basolateral domains of Vero C1008 cells.

Animals↗
PubMed1992

Development of the sensory innervation of muscle spindles in the kitten.

This is a report of the changes observed in the pattern of sensory innervation of muscle spindles in hindlimb muscles of kittens during the first four weeks of life. The structural analysis, made on teased, silver-stained preparations, was complemented by a series of recordings of afferent responses of kitten spindles during ramp-and-hold stretches of the muscle. The primary endings of spindles from newborn animals showed a large degree of variability in their branching pattern and branches formed a network across the intrafusal fibres. In older animals there was less variability and lateral branches of stem axons began to encircle the intrafusal fibres. The process of maturation was characterized by a more uniform shape of the endings and more complete, evenly spaced, annulospiral terminals. Recordings of the responses of primary endings of spindles during muscle stretch showed that several features of the adult response were already present in the newborn, although the overall rate of discharge was very much lower. It was concluded that the changes observed in the structure of the sensory endings of kitten spindles did not have clearly identifiable physiological correlates. It appears that an annulospiral shape of the sensory terminals is not a necessary prerequisite for the generation of stretch responses. The predominant factor which appears to determine the responses of spindles to stretch is the maturity of the intrafusal fibres, in particular, the bag2 fibre.

Aging↗