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PubMed2000

polyhomeotic controls engrailed expression and the hedgehog signaling pathway in imaginal discs.

Polycomb group (PcG) genes maintain cell identities during development in insects and mammals and their products are required in many developmental pathways. These include limb morphogenesis in Drosophila melanogaster, since PcG genes interact with identity and pattern specifying genes in imaginal discs and clones of polyhomeotic (ph) null cells induce abnormal limb patterning. Such clones are associated with ectopic expression of engrailed, hedgehog, patched, cubitus interruptus and decapentaplegic, in a compartment specific manner. Our results also reveal negative engrailed regulation by ph in both disc compartments: ph silences engrailed in anterior cells and maintains the level of engrailed expression in posterior ones. We suggest that PcG targets are not exclusively regulated by an on/off mechanism, but that the PcG also exerts negative transcriptional control on active genes.

Animals↗
PubMed2003

Imagined movements that leak out.

In a case study that fundamentally alters our understanding of motor imagery, Schwoebel et al. report a patient who unintentionally carries out imagined movements. Furthermore, his 'imagery' movements are more accurate than his intended movements, which suggests that the inhibitory signal that normally prevents us from acting out our motor imagery can be selectively blocked. Removing this inhibition allows us to observe motor imagery 'in action', and reveals that motor imagery and motor planning for execution are not identical.

Journal Article↗
PubMed2001

The sex determination gene doublesex regulates the A/P organizer to direct sex-specific patterns of growth in the Drosophila genital imaginal disc.

Each Drosophila genital imaginal disc contains primordia for both male and female genitalia and analia. The sexually dimorphic development of this disc is governed by the sex-specific expression of doublesex (dsx). We present data that substantially revises our understanding of how dsx controls growth and differentiation in the genital disc. The classical view of genital disc development is that in each sex, dsx autonomously "represses" the development of the inappropriate genital primordium while allowing the development of the appropriate primordium. Instead, we show that dsx regulates the A/P organizer to control growth of each genital primordium, and then directs each genital primordium to differentiate defined adult structures in both sexes.

Animals↗
PubMed2000

Shamanism, psychosis and autonomous imagination.

This paper focuses on traditional healers (balian) in Bali, Indonesia, to raise new arguments concerning the nature of the initiatory sufferings reportedly experienced by shamans in many cultures. Our evidence suggests that a) contrary to our expectations, an initiatory madness or illness is experienced by a minority rather than the majority of balian, and b) whether or not a balian undergoes initiatory sufferings seems to be linked to gender and to the methods of healing employed - thus women healers who employ trance possession are those most likely to report an initiatory madness or illness. This leads to the central argument of the paper: c) the nature of the initiatory sufferings, where they do occur, can be clearly distinguished on several grounds from the onset of mental illness among Balinese, both emically in terms of cultural understandings, and ethically in terms of objective criteria. Finally we discuss the concept of "autonomous imagination," suggesting that the key to becoming a balian is not overcoming an initiatory madness but gaining control over this special mode of imagery thought. We further suggest that Western ideas concerning the self and self healing, the superficial resemblance of the initiatory sufferings to schizophrenia, and the dramatic nature of the initiatory sufferings when they occur, have combined to give a misleading prominence to the role of an initiatory madness in shamanism.

Adult↗
PubMed1999

(Re)imagining aging lives: ethnographic narratives of Muslim women in diaspora.

This article explores the potential of the narrative genre in (re)imagining aging lives of women in diaspora, spanning cultures as well as generations. Minimal attention given to combined constituencies of gender, age and minority status in feminist ethnography and the literature on aging may be redressed by the realization that minority aging women negotiate culturally based and innovative strategies to overcome patriarchal, age-based and colonizing and postcolonizing constraints. Ethnographic narratives of two Ismaili Muslim Canadian women, as part of a cohort of immigrants from East Africa, provide insights into the complex process of reimagining lives in-between spaces of home work and waged work as well as in-between action and repose (silence, and stillness that complement mundane action-oriented activities) modes of the Ismaili tradition. The narratives are a living metaphor of lives engaged in recapturing meaning. As such, the creative endeavors of aging women in diaspora has implications for a feminist ethnography of aging -- an area that to date remains substantively unexplored.

Journal Article↗
PubMed2001

Ultrastructural changes in the muscles, midgut, hemopoietic organ, imaginal discs and Malpighian tubules of the mosquito Aedes aegypti larvae infected by the fungus Coelomomyces stegomyiae.

Fungi belonging to the genus Coelomomyces can infect mosquito larvae and develop within the larval hemocoel. To examine fungal development, Aedes aegypti larvae infected with Coelomomyces stegomyiae Keilin were fixed, embedded and sectioned for both light and electron microscopy. While fungal hyphae of C. stegomyiae did not invade cells other than the cuticular epithelial cells, they did penetrate a number of tissues including muscles, midgut, hemopoietic organ, imaginal discs, and Malpighian tubules.

Aedes↗
PubMed2004

Patterns of autonomic arousal in imaginal situations of winning and losing in problem gambling.

AIMS: To examine changes in skin conductance level (SCL), for problem gamblers in response to personally relevant imaginal tasks, representing winning or losing. SETTING, DESIGN, PARTICIPANTS AND MEASUREMENTS: SCL and subjective arousal were compared for problem poker machine gamblers (n = 13) and a control group (n = 20). Participants were asked to describe a situation in which they had (a) won and (b) lost during a period of gambling. Before and during the task, recordings of SCL were taken. FINDINGS: There were significant differences between responses of problem and social gamblers. A significant interaction indicated that social gamblers became more aroused in reaction to winning than losing, whereas problem gamblers became equally aroused in response to both tasks. CONCLUSIONS: The results suggest that it may be responses to losing, rather than winning that are paramount to the development and maintenance of problem gambling.

Adult↗
PubMed1999

A randomized trial of cognitive therapy and imaginal exposure in the treatment of chronic posttraumatic stress disorder.

A randomized trial was performed in which imaginal exposure (IE) and cognitive therapy (CT) were compared in the treatment of chronic posttraumatic stress disorder (PTSD). Patients who continued to meet PTSD caseness at the end of a 4-week symptom-monitoring baseline period (n = 72) were randomly allocated to either IE or CT. There was a significant improvement in all measures over treatment and at follow-up, although there were no significant differences between the 2 treatments at any assessment. A significantly greater number of patients who showed worsening over treatment received IE, although this effect was not found at follow-up. Patients who worsened showed a greater tendency to miss treatment sessions, rated therapy as less credible, and were rated as less motivated by the therapist. It was concluded that either exposure or a challenge to cognition can result in symptom reduction, although neither resulted in complete improvement.

Adult↗
PubMedDate not supplied

Posterior-to-anterior transformation in engrailed wing imaginal disks of Drosophila.

Segments in the Drosophila adult are divided into clonally distinct anterior and posterior compartments. Mutations at the engrailed locus can affect the pattern of cuticular structures in the posterior compartments of segments, but have no obvious effect on anterior structures; for example, bristles that are normally seen only on the anterior wing margin in wild-type flies can be found on the posterior margin of engrailed wings. These and clonal analysis data led to the hypothesis that engrailed causes a transformation of posterior to anterior identity in the wing cells. Despite some striking examples of this transformation, a common engrailed phenotype is the disruption or elimination of posterior pattern elements, without a clear replacement by anterior structures; this, together with indications that localized cell death can mimic some of the observed posterior-to-anterior transformations, has led some investigators to question the original engrailed hypothesis. Recently, monoclonal antibodies displaying region-specific binding patterns on the wing imaginal disk have been described, and one of these antibodies in particular provides a novel probe for the engrailed phenotype in the larval precursors of the adult wing. Here I compare the antibody binding patterns on engrailed and wild-type wing disks. The results strongly support the notion that engrailed mutations cause a posterior-to-anterior transformation in these cells.

Animals↗
PubMed1994

Biological activity of soluble wingless protein in cultured Drosophila imaginal disc cells.

The phenotypes caused by mutations in Wnt genes suggest that their gene products are involved in cell-to-cell communication. Wnt genes indeed encode secreted molecules, but soluble active Wnt protein has not been found. We have developed a novel cell culture assay for the Drosophila Wnt gene wingless, using a Drosophila imaginal disc cell line (cl-8; ref. 13), and measured effects on the adherens junction protein armadillo, a known genetic target of wingless. Transfection of a temperature-sensitive wingless complementary DNA into cl-8 cells increases the levels of the armadillo protein. The wingless protein does not affect the rate of synthesis of armadillo, but leads to increased stability of an otherwise rapidly decaying armadillo protein. The wingless protein in the extracellular matrix and soluble medium from donor cells also increases the levels of armadillo protein. The protein in the medium acts fast and is inhibited by an antibody to wingless protein, demonstrating that Wnt products can act as soluble extracellular signalling molecules.

Animals↗
PubMed2005

Dependence of Drosophila wing imaginal disc cytonemes on Decapentaplegic.

The anterior/posterior (A/P) and dorsal/ventral (D/V) compartment borders that subdivide the wing imaginal discs of Drosophila third instar larvae are each associated with a developmental organizer. Decapentaplegic (Dpp), a member of the transforming growth factor-beta (TGF-beta) superfamily, embodies the activity of the A/P organizer. It is produced at the A/P organizer and distributes in a gradient of decreasing concentration to regulate target genes, functioning non-autonomously to regulate growth and patterning of both the anterior and posterior compartments. Wingless (Wg) is produced at the D/V organizer and embodies its activity. The mechanisms that distribute Dpp and Wg are not known, but proposed mechanisms include extracellular diffusion, successive transfers between neighbouring cells, vesicle-mediated movement, and direct transfer via cytonemes. Cytonemes are actin-based filopodial extensions that have been found to orient towards the A/P organizer from outlying cells. Here we show that in the wing disc, cytonemes orient towards both the A/P and D/V organizers, and that their presence and orientation correlates with Dpp signalling. We also show that the Dpp receptor, Thickveins (Tkv), is present in punctae that move along cytonemes. These observations are consistent with a role for cytonemes in signal transduction.

Actins↗
PubMed2005

Suppression of Polycomb group proteins by JNK signalling induces transdetermination in Drosophila imaginal discs.

During the regeneration of Drosophila imaginal discs, cellular identities can switch fate in a process known as transdetermination. For leg-to-wing transdetermination, the underlying mechanism involves morphogens such as Wingless that, when activated outside their normal context, induce ectopic expression of the wing-specific selector gene vestigial. Polycomb group (PcG) proteins maintain cellular fates by controlling the expression patterns of homeotic genes and other developmental regulators. Here we report that transdetermination events are coupled to PcG regulation. We show that the frequency of transdetermination is enhanced in PcG mutant flies. Downregulation of PcG function, as monitored by the reactivation of a silent PcG-regulated reporter gene, is observed in transdetermined cells. This downregulation is directly controlled by the Jun amino-terminal kinase (JNK) signalling pathway, which is activated in cells undergoing regeneration. Accordingly, transdetermination frequency is reduced in a JNK mutant background. This regulatory interaction also occurs in mammalian cells, indicating that the role of this signalling cascade in remodelling cellular fates may be conserved.

Animals↗
PubMed2006

Imagining the brain cell: the neuron in visual culture.

Images of the exquisitely formed apparatus of the nervous system have great potential to capture the imagination. However, the fascinating complexity and diversity of neuronal form has only rarely been celebrated in broader visual culture. We discuss how scientific and cultural practices at the time of the neuron's discovery generated a legacy of schematic and simplified popular neuronal imagery, which is only now being revised in the light of technological advances and a changing artistic climate.

Animals↗
PubMed2004

The Drosophila wing differentiation factor vestigial-scalloped is required for cell proliferation and cell survival at the dorso-ventral boundary of the wing imaginal disc.

Links between genes involved in development, proliferation and apoptosis have been difficult to establish. In the Drosophila wing disc, the vestigial (vg) and the scalloped (sd) gene products dimerize to form a functional transcription factor. Ectopic expression of vg in other imaginal discs induces outgrowth and wing tissue specification. We investigated the role of the VG-SD dimer in proliferation and showed that vg antagonizes the effect of dacapo, the cyclin-cdk inhibitor. Moreover, ectopic vg drives cell cycle progression and in HeLa cultured cells, the VG-SD dimer induces cell proliferation per se. In Drosophila, ectopic vg induces expression of dE2F1 and its targets dRNR2 and string. In addition vg, but not dE2F1, interacts with and induces expression of dihydrofolate reductase (DHFR). Moreover, a decrease in VG or addition of aminopterin, a specific DHFR inhibitor, shift the dorso-ventral boundary cells of the disc to a cell death sensitive state that is correlated with reaper induction and DIAP1 downregulation. This indicates that vg in interaction with dE2F1 and DHFR is a critical player for both cell proliferation and cell survival in the presumptive wing margin area.

Animals↗
PubMed2004

Analysis of cell proliferation in Drosophila wing imaginal discs using mosaic clones.

Experimental data on spatial and temporal distributions of mosaic clones in Drosophila wing imaginal disc were analyzed. Long-lived proliferation centers (PR1, PR2, and PR3) and areas with decreased proliferation activity were found in the notum region of the disc. Simulation of the growth kinetics of mosaic patches demonstrated that the cell cycle in proliferation centers PR2 and PR3 was shorter than the average cycle in the disc and in the center PR1. A nonrandom clustering of rapidly dividing cells was observed in the PR2, but not in the other cases. The reason why the cell-cycle duration and the clustering of dividing cells may not coincide is discussed in terms of the recruitment of nondividing cells into the cell cycle. The simulation of the time course of the first and second moments of the size distribution of mosaic clones allowed the variance of cell-cycle progression rates to be determined and demonstrated that a model with a continuous cell-cycle rates gave a better fit to the data than the transition probability model of Smith and Martin.

Animals↗
PubMed2003

TID1, a mammalian homologue of the drosophila tumor suppressor lethal(2) tumorous imaginal discs, regulates activation-induced cell death in Th2 cells.

We previously described two human DnaJ proteins, hTid-1L and hTid-1S, which are derived from alternative splicing of the TID1 gene, the human homologue of the Drosophila tumor suppressor lethal(2) tumorous imaginal discs, and showed that hTid-1L promoted while hTid-1S antagonized apoptosis. There are two subsets of helper T cells, Th1 and Th2, of which Th2 cells are significantly less prone to apoptosis induced by stimulation through the T-cell receptor. This apoptotic process is known as activation-induced cell death (AICD). The molecular basis for the differential susceptibility of Th1 and Th2 cells to AICD is not known. Here we show that the antiapoptotic variant, Tid-1S, is selectively induced in murine Th2 cells following activation. Expression of a dominant-negative mutant of hTid-1S in a Th2 cell line strikingly enhanced activation of caspase 3 in response to CD3 stimulation, and caused the cells to become sensitive to AICD. Hence, the accumulation of Tid-1S in Th2 cells following activation represents a novel mechanism that may contribute to the induction of apoptosis resistance during the activation of Th2 cells.

Amino Acid Sequence↗
PubMed1997

The professional imagination: narrative and the symbolic boundaries between medicine and nursing.

The sociology of nursing, despite decisive interventions by recent commentators, continues to take as its main focus the subordination of nursing to biomedicine. This view reflects analytic stability, as well as institutional inertia. Far less attention has been paid by sociologists to the ways in which nursing is constructing its difference from medicine, and the exercise of the professional imagination that this involves. This paper suggests a strategy by which this might be remedied, which would focus on professional narratives.

Delivery of Health Care↗
PubMed1998

Hope: future imagined reality. The meaning of hope as described by a group of healthy Pentecostalists.

A holistic health care approach involves body, mind and spirit. Religiosity, spirituality and hope, as a part of the spiritual dimension, are often linked to various health-related outcomes such as physical health, spiritual well-being and experienced meaning in life. A person's outlook on life and the experience of hope are essential issues in all health care. The purpose of this paper is to describe the meaning of hope as expressed by a group of healthy adult Pentecostalists (n = 15). Using narratives, the ultimate hope was described as life after death, the future imagined reality, promised by God. Hope was strengthened by reading the Bible and saying prayers, through experienced meetings with God and shared values. Hope was quite stable but sometimes God was experienced as being at a distance, which resulted in a sense of alienation. Hope unconnected to Christian belief was of no significant importance to the interviewees.

Adult↗