2,862 research outputs found
Chloride channels in stellate cells are essential for uniquely high secretion rates in neuropeptide-stimulated Drosophila diuresis
Epithelia frequently segregate transport processes to specific cell types, presumably for improved efficiency and control. The molecular players underlying this functional specialization are of particular interest. In Drosophila, the renal (Malpighian) tubule displays the highest per-cell transport rates known and has two main secretory cell types, principal and stellate. Electrogenic cation transport is known to reside in the principal cells, whereas stellate cells control the anion conductance, but by an as-yet-undefined route. Here, we resolve this issue by showing that a plasma membrane chloride channel, encoded by ClC-a, is exclusively expressed in the stellate cell and is required for Drosophila kinin-mediated induction of diuresis and chloride shunt conductance, evidenced by chloride ion movement through the stellate cells, leading to depolarization of the transepithelial potential. By contrast, ClC-a knockdown had no impact on resting secretion levels. Knockdown of a second CLC gene showing highly abundant expression in adult Malpighian tubules, ClC-c, did not impact depolarization of transepithelial potential after kinin stimulation. Therefore, the diuretic action of kinin in Drosophila can be explained by an increase in ClC-a–mediated chloride conductance, over and above a resting fluid transport level that relies on other (ClC-a–independent) mechanisms or routes. This key segregation of cation and anion transport could explain the extraordinary fluid transport rates displayed by some epithelia
Correlations, spectral gap, and entanglement in harmonic quantum systems on generic lattices
We investigate the relationship between the gap between the energy of the
ground state and the first excited state and the decay of correlation functions
in harmonic lattice systems. We prove that in gapped systems, the exponential
decay of correlations follows for both the ground state and thermal states.
Considering the converse direction, we show that an energy gap can follow from
algebraic decay and always does for exponential decay. The underlying lattices
are described as general graphs of not necessarily integer dimension, including
translationally invariant instances of cubic lattices as special cases. Any
local quadratic couplings in position and momentum coordinates are allowed for,
leading to quasi-free (Gaussian) ground states. We make use of methods of
deriving bounds to matrix functions of banded matrices corresponding to local
interactions on general graphs. Finally, we give an explicit entanglement-area
relationship in terms of the energy gap for arbitrary, not necessarily
contiguous regions on lattices characterized by general graphs.Comment: 26 pages, LaTeX, published version (figure added
Recommended from our members
Precision engineering center. 1988 Annual report, Volume VI
To reverse the downward trend in the balance of trade, American companies must concentrate on increasing research into new products, boosting productivity, and improving manufacturing processes. The Precision Engineering Center at North Carolina State University is a multidisciplinary research and graduate education program dedicated to providing the new technology necessary to respond to this challenge. One extremely demanding manufacturing area is the fabrication and assembly of optical systems. These systems are at the heart of such consumer products as cameras, lenses, copy machines, laser bar-code scanners, VCRs, and compact audio discs - products that the Japanese and other East Asian countries are building dominance. A second critical area is the fabrication of VLSI and ULSI circuits. The tolerances required to produce the next generation of components for such systems have created the need for new approaches - approaches that could either make or break America`s competitive position. This report contains individual reports on research projects grouped into three broad areas: measurement and actuation; real-time control; precision fabrication. Separate abstracts for these articles have been indexed into the energy database
Altered drug susceptibility during host adaptation of a <i>Plasmodium falciparum</i> strain in a non-human primate model
Infections with Plasmodium falciparum, the most pathogenic of the Plasmodium species affecting man, have been reduced in part due to artemisinin-based combination therapies. However, artemisinin resistant parasites have recently emerged in South-East Asia. Novel intervention strategies are therefore urgently needed to maintain the current momentum for control and elimination of this disease. In the present study we characterize the phenotypic and genetic properties of the multi drug resistant (MDR) P. falciparum Thai C2A parasite strain in the non-human Aotus primate model, and across multiple passages. Aotus infections with C2A failed to clear upon oral artesunate and mefloquine treatment alone or in combination, and ex vivo drug assays demonstrated reduction in drug susceptibility profiles in later Aotus passages. Further analysis revealed mutations in the pfcrt and pfdhfr loci and increased parasite multiplication rate (PMR) across passages, despite elevated pfmdr1 copy number. Altogether our experiments suggest alterations in parasite population structure and increased fitness during Aotus adaptation. We also present data of early treatment failures with an oral artemisinin combination therapy in a pre-artemisinin resistant P. falciparum Thai isolate in this animal model
Theory of High-Tc Superconductivity: Accurate Predictions of Tc
The superconducting transition temperatures of high-Tc compounds based on
copper, iron, ruthenium and certain organic molecules are discovered to be
dependent on bond lengths, ionic valences, and Coulomb coupling between
electronic bands in adjacent, spatially separated layers [1]. Optimal
transition temperature, denoted as T_c0, is given by the universal expression
; is the spacing between interacting
charges within the layers, \zeta is the distance between interacting layers and
\Lambda is a universal constant, equal to about twice the reduced electron
Compton wavelength (suggesting that Compton scattering plays a role in
pairing). Non-optimum compounds in which sample degradation is evident
typically exhibit Tc < T_c0. For the 31+ optimum compounds tested, the
theoretical and experimental T_c0 agree statistically to within +/- 1.4 K. The
elemental high Tc building block comprises two adjacent and spatially separated
charge layers; the factor e^2/\zeta arises from Coulomb forces between them.
The theoretical charge structure representing a room-temperature superconductor
is also presented.Comment: 7 pages 5 references, 6 figures 1 tabl
Conditional Reverse Tet-Transactivator Mouse Strains for the Efficient Induction of TRE-Regulated Transgenes in Mice
Tetracycline or doxycycline (dox)-regulated control of genetic elements allows inducible, reversible and tissue specific regulation of gene expression in mice. This approach provides a means to investigate protein function in specific cell lineages and at defined periods of development and disease. Efficient and stable regulation of cDNAs or non-coding elements (e.g. shRNAs) downstream of the tetracycline-regulated element (TRE) requires the robust expression of a tet-transactivator protein, commonly the reverse tet-transactivator, rtTA. Most rtTA strains rely on tissue specific promoters that often do not provide sufficient rtTA levels for optimal inducible expression. Here we describe the generation of two mouse strains that enable Cre-dependent, robust expression of rtTA3, providing tissue-restricted and consistent induction of TRE-controlled transgenes. We show that these transgenic strains can be effectively combined with established mouse models of disease, including both Cre/LoxP-based approaches and non Cre-dependent disease models. The integration of these new tools with established mouse models promises the development of more flexible genetic systems to uncover the mechanisms of development and disease pathogenesis
A Qualitative Exploration of the Mental Health and Psychosocial Contexts of HIV-Positive Adolescents in Tanzania
Although 85% of HIV-positive adolescents reside in sub-Saharan Africa, little is known about the psychosocial and mental health factors affecting their daily well-being. Identifying these contextual variables is key to development of culturally appropriate and effective interventions for this understudied and high-risk population. The purpose of this study was to identify salient psychosocial and mental health challenges confronted by HIV-positive youth in a resource-poor Tanzanian setting. A total of 24 qualitative interviews were conducted with a convenience sample of adolescents aged 12–24 receiving outpatient HIV care at a medical center in Moshi, Tanzania. All interviews were audio-recorded, transcribed, and coded using thematic analysis. Psychosocial challenges identified included loss of one or more parents, chronic domestic abuse, financial stressors restricting access to medical care and education, and high levels of internalized and community stigma among peers and other social contacts. Over half of youth (56%) reported difficulties coming to terms with their HIV diagnosis and espoused related feelings of self-blame. These findings highlight the urgent need to develop culturally proficient programs aimed at helping adolescents cope with these manifold challenges. Results from this study guided the development of Sauti ya Vijana (The Voice of Youth), a 10-session group mental health intervention designed to address the psychosocial and mental health needs of HIV-positive Tanzanian youth
The Charge Form Factor of the Neutron at Low Momentum Transfer from the Reaction
We report new measurements of the neutron charge form factor at low momentum
transfer using quasielastic electrodisintegration of the deuteron.
Longitudinally polarized electrons at an energy of 850 MeV were scattered from
an isotopically pure, highly polarized deuterium gas target. The scattered
electrons and coincident neutrons were measured by the Bates Large Acceptance
Spectrometer Toroid (BLAST) detector. The neutron form factor ratio
was extracted from the beam-target vector asymmetry
at four-momentum transfers , 0.20, 0.29 and 0.42
(GeV/c).Comment: 5 pages, 3 figures, submitted to Phys. Rev. Let
- …