577 research outputs found

    A Novel Labeling Approach Identifies Three Stability Levels of Acetylcholine Receptors in the Mouse Neuromuscular Junction In Vivo

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    The turnover of acetylcholine receptors at the neuromuscular junction is regulated in an activity-dependent manner. Upon denervation and under various other pathological conditions, receptor half-life is decreased., in our setup the same animals are used throughout the whole measurement period, thereby permitting a dramatic reduction of animal numbers at increased data quality. We identified three stability levels of acetylcholine receptors depending on the presence or absence of innervation: one pool of receptors with a long half-life of ∼13 days, a second with an intermediate half-life of ∼8 days, and a third with a short half-life of ∼1 day. Data were highly reproducible from animal to animal and followed simple exponential terms. The principal outcomes of these measurements were reproduced by an optical pulse-labeling assay introduced recently.A novel assay to determine kinetics of acetylcholine receptor turnover with small animal numbers is presented. Our data show that nerve activity acts on muscle acetylcholine receptor stability by at least two different means, one shifting receptor lifetime from short to intermediate and another, which further increases receptor stability to a long lifetime. We hypothesize on possible molecular mechanisms

    The moral technical imaginaries of internet convergence in an American television network

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    How emergent technologies are imagined, discussed, and implemented reveals social morality about how society, politics, and economics should be organized. For the television industry in the United States, for instance, the development of internet “convergence” provoked the rise of a new discourse about participatory democracy as well as the hopes for lucrative business opportunities. The simultaneity of technical, moral, and social ordering defines the “moral technical imaginary.” Populating this concept with ethnographic and historical detail, this article expands the theory of the moral technical imaginary with information from six years of participant observation, interviews, and employment with Current TV, an American-based television news network founded by Vice President Al Gore to democratize television production. This chapter explores the limits of political participation and morality when faced with neoliberal capitalism

    Magnetic Catalysis and Quantum Hall Ferromagnetism in Weakly Coupled Graphene

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    We study the realization in a model of graphene of the phenomenon whereby the tendency of gauge-field mediated interactions to break chiral symmetry spontaneously is greatly enhanced in an external magnetic field. We prove that, in the weak coupling limit, and where the electron-electron interaction satisfies certain mild conditions, the ground state of charge neutral graphene in an external magnetic field is a quantum Hall ferromagnet which spontaneously breaks the emergent U(4) symmetry to U(2)XU(2). We argue that, due to a residual CP symmetry, the quantum Hall ferromagnet order parameter is given exactly by the leading order in perturbation theory. On the other hand, the chiral condensate which is the order parameter for chiral symmetry breaking generically obtains contributions at all orders. We compute the leading correction to the chiral condensate. We argue that the ensuing fermion spectrum resembles that of massive fermions with a vanishing U(4)-valued chemical potential. We discuss the realization of parity and charge conjugation symmetries and argue that, in the context of our model, the charge neutral quantum Hall state in graphene is a bulk insulator, with vanishing longitudinal conductivity due to a charge gap and Hall conductivity vanishing due to a residual discrete particle-hole symmetry.Comment: 35 page

    Sources of evidence in HIV/AIDS care: pilot study comparing family physicians and AIDS service organization staff

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    BACKGROUND: The improvement of the quality of the evidence used in treatment decision-making is especially important in the case of patients with complicated disease processes such as HIV/AIDS for which multiple treatment strategies exist with conflicting reports of efficacy. Little is known about the perceptions of distinct groups of health care workers regarding various sources of evidence and how these influence the clinical decision-making process. Our objective was to investigate how two groups of treatment information providers for people living with HIV/AIDS perceive the importance of various sources of treatment information. METHODS: Surveys were distributed to staff at two local AIDS service organizations and to family physicians at three community health centres treating people living with HIV/AIDS. Participants were asked to rate the importance of 10 different sources of evidence for HIV/AIDS treatment information on a 5-point Likert-type scale. Mean rating scores and relative rankings were compared. RESULTS: Findings suggest that a discordance exists between the two health information provider groups in terms of their perceptions of the various sources of evidence. Furthermore, AIDS service organization staff ranked health care professionals as the most important source of information whereas physicians deemed AIDS service organizations to be relatively unimportant. The two groups appear to share a common mistrust for information from pharmaceutical industries. CONCLUSIONS: Discordance exists between medical "experts" from different backgrounds relating to their perceptions of evidence. Further investigation is warranted in order to reveal any effects on the quality of treatment information and implications in the decision-making process. Possible effects on collaboration and working relationships also warrant further exploration

    Weinberg like sum rules revisited

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    The generalized Weinberg sum rules containing the difference of isovector vector and axial-vector spectral functions saturated by both finite and infinite number of narrow resonances are considered. We summarize the status of these sum rules and analyze their overall agreement with phenomenological Lagrangians, low-energy relations, parity doubling, hadron string models, and experimental data.Comment: 31 pages, noticed misprints are corrected, references are added, and other minor corrections are mad

    Whispering to the Deaf: Communication by a Frog without External Vocal Sac or Tympanum in Noisy Environments

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    Atelopus franciscus is a diurnal bufonid frog that lives in South-American tropical rain forests. As in many other frogs, males produce calls to defend their territories and attract females. However, this species is a so-called “earless” frog lacking an external tympanum and is thus anatomically deaf. Moreover, A. franciscus has no external vocal sac and lives in a sound constraining environment along river banks where it competes with other calling frogs. Despite these constraints, male A. franciscus reply acoustically to the calls of conspecifics in the field. To resolve this apparent paradox, we studied the vocal apparatus and middle-ear, analysed signal content of the calls, examined sound and signal content propagation in its natural habitat, and performed playback experiments. We show that A. franciscus males can produce only low intensity calls that propagate a short distance (<8 m) as a result of the lack of an external vocal sac. The species-specific coding of the signal is based on the pulse duration, providing a simple coding that is efficient as it allows discrimination from calls of sympatric frogs. Moreover, the signal is redundant and consequently adapted to noisy environments. As such a coding system can be efficient only at short-range, territory holders established themselves at short distances from each other. Finally, we show that the middle-ear of A. franciscus does not present any particular adaptations to compensate for the lack of an external tympanum, suggesting the existence of extra-tympanic pathways for sound propagation

    Research on health transition in Africa: time for action

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    With rapidly increasing globalization, trends towards unhealthy diets, obesity, sedentary lifestyles and unhealthy habits are resulting in an increased worldwide burden of chronic non-communicable diseases (NCDs). In Africa this means that health systems face the challenge of an increasing burden of NCDs and of continuing high morbidity and mortality from communicable diseases. This health transition represents an enormous challenge to Africa as the region with the least resources for an effective response. Whereas previous epidemics, including HIV, have caught Africa unprepared, the opportunity now arises to take the advancing wave of health transition in Africa seriously. Health research has a key role to play in meeting health and development goals, and must be responsive to changing disease patterns, such as health transition. There is an urgent need for research on health transition in Africa to enable countries to respond effectively to rapidly changing health needs

    Interhemispheric Interactions between the Human Primary Somatosensory Cortices

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    In the somatosensory domain it is still unclear at which processing stage information reaches the opposite hemispheres. Due to dense transcallosal connections, the secondary somatosensory cortex (S2) has been proposed to be the key candidate for interhemispheric information transfer. However, recent animal studies showed that the primary somatosensory cortex (S1) might as well account for interhemispheric information transfer. Using paired median nerve somatosensory evoked potential recordings in humans we tested the hypothesis that interhemispheric inhibitory interactions in the somatosensory system occur already in an early cortical processing stage such as S1. Conditioning right S1 by electrical median nerve (MN) stimulation of the left MN (CS) resulted in a significant reduction of the N20 response in the target (left) S1 relative to a test stimulus (TS) to the right MN alone when the interstimulus interval between CS and TS was between 20 and 25 ms. No such changes were observed for later cortical components such as the N20/P25, N30, P40 and N60 amplitude. Additionally, the subcortically generated P14 response in left S1 was also not affected. These results document the existence of interhemispheric inhibitory interactions between S1 in human subjects in the critical time interval of 20–25 ms after median nerve stimulation
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