Receptor-Coupled Phosphoinositide Hydrolysis in Human Retinal Pigment Epithelium

Carbachol and histamine stimulated phosphoinositide (PPI) hydrolysis in cultured human retinal pigment epithelium (RPE), as reflected by an accumulation of 3 H-inositol phosphates in the presence of 10 m M Li + . Carbachol increased PPI hydrolysis to greater than 600% of basal with an EC 50 of 60 Μ M ; stimulation was linear up to 60 min. This activation likely occurred via the M 3 muscarinic cholinergic receptor based on the IC 50 values for 4-diphenylacetoxy- N -methylpiperidine methiodide (0.47 n M ), pirenzepine (280 n M ), and 11-[[2-[(diethylamino)methyl]-1-piperidinyl]-acetyl]-5,11-dihydro-6 H -pyrido[2,3- b ][1,4]benzodiazepin-6-one (1.4 Μ M ). Carbachol-mediated PPI hydrolysis was decreased by 80% in the absence of extracellular Ca 2+ . Histamine stimulated PPI turnover in a linear manner by 180% with an EC 50 of 20 Μ M by the H 1 histaminergic receptor. Serotonin, glutamate, norepinephrine, and dopamine were inactive. In human RPE, the resting cytoplasmic Ca 2+ concentration, as determined by fura-2 fluorescence, was 138 ± 24 n M . On the addition of carbachol, there was a 180% increase in peak intracellular Ca 2+ ; addition of histamine increased intracellular Ca 2+ by 187%. These results suggest receptor-mediated, inositol lipid hydrolysis is coupled to intracellular Ca 2+ flux in human RPE.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66430/1/j.1471-4159.1991.tb03471.x.pd

Search for radio pulsations in LS I +61 303

Context. LS I +61 303 is a member of the select group of gamma-ray binaries: galactic binary systems that contain a massive star and a compact object, show a changing milliarcsecond morphology and a similar broad spectral energy distribution (SED) that peaks at MeV-TeV energies and is modulated by the orbital motion. The nature of the compact object is unclear in LS I +61 303, LS 5039 and HESS J0632+057, whereas PSR B1259-63 harbours a 47.74 ms radio pulsar. Aims. A scenario in which a young pulsar wind interacts with the stellar wind has been proposed to explain the very high energy (VHE, E > 100 GeV) gamma-ray emission detected from LS I +61 303, although no pulses have been reported from this system at any wavelength. We aim to find evidence of the pulsar nature of the compact object. Methods. We performed phased array observations with the Giant Metrewave Radio Telescope (GMRT) at 1280 MHz centred at phase 0.54. Simultaneous data from the multi-bit phased array (PA) back-end with a sampling time of tsamp = 128 microsec and from the polarimeter (PMT) back-end with tsamp = 256 microsec where taken. Results. No pulses have been found in the data set, with a minimum detectable mean flux density of \sim 0.38 mJy at 8-sigma level for the pulsed emission from a putative pulsar with period P >2 ms and duty cycle D = 10% in the direction of LS I +61 303. Conclusions. The detection of posible radio pulsations will require deep and sensitive observations at frequencies \sim0.5-5 GHz and orbital phases 0.6-0.7. However, it may be unfeasible to detect pulses if the putative pulsar is not beamed at the Earth or if there is a strong absorption within the binary system.Comment: 8 pages. 5 figures. Accepted for publication in Astronomy and Astrophysic

AE9, AP9 and SPM: New Models for Specifying the Trapped Energetic Particle and Space Plasma Environment

The radiation belts and plasma in the Earth’s magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper.United States. Air Force (e contracts FA8718-05-C-0036, FA8718-10-C-001, FA8721-05-C-0002 and FA8802-09-C-0001)United States. National Aeronautics and Space Administration (grant NNG05GM22G

Use of sonic tomography to detect and quantify wood decay in living trees.

Premise of the studyField methodology and image analysis protocols using acoustic tomography were developed and evaluated as a tool to estimate the amount of internal decay and damage of living trees, with special attention to tropical rainforest trees with irregular trunk shapes.Methods and resultsLiving trunks of a diversity of tree species in tropical rainforests in the Republic of Panama were scanned using an Argus Electronic PiCUS 3 Sonic Tomograph and evaluated for the amount and patterns of internal decay. A protocol using ImageJ analysis software was used to quantify the proportions of intact and compromised wood. The protocols provide replicable estimates of internal decay and cavities for trees of varying shapes, wood density, and bark thickness.ConclusionsSonic tomography, coupled with image analysis, provides an efficient, noninvasive approach to evaluate decay patterns and structural integrity of even irregularly shaped living trees

Entangled-State Cycles of Atomic Collective-Spin States

We study quantum trajectories of collective atomic spin states of $N$ effective two-level atoms driven with laser and cavity fields. We show that interesting ``entangled-state cycles'' arise probabilistically when the (Raman) transition rates between the two atomic levels are set equal. For odd (even) $N$, there are $(N+1)/2$ ($N/2$) possible cycles. During each cycle the $N$-qubit state switches, with each cavity photon emission, between the states $(|N/2,m>\pm |N/2,-m>)/\sqrt{2}$, where $|N/2,m>$ is a Dicke state in a rotated collective basis. The quantum number $m$ ($>0$), which distinguishes the particular cycle, is determined by the photon counting record and varies randomly from one trajectory to the next. For even $N$ it is also possible, under the same conditions, to prepare probabilistically (but in steady state) the Dicke state $|N/2,0>$, i.e., an $N$-qubit state with $N/2$ excitations, which is of particular interest in the context of multipartite entanglement.Comment: 10 pages, 9 figure

The secreted triose phosphate isomerase of Brugia malayi is required to sustain microfilaria production in vivo

Human lymphatic filariasis is a major tropical disease transmitted through mosquito vectors which take up microfilarial larvae from the blood of infected subjects. Microfilariae are produced by long-lived adult parasites, which also release a suite of excretory-secretory products that have recently been subject to in-depth proteomic analysis. Surprisingly, the most abundant secreted protein of adult Brugia malayi is triose phosphate isomerase (TPI), a glycolytic enzyme usually associated with the cytosol. We now show that while TPI is a prominent target of the antibody response to infection, there is little antibody-mediated inhibition of catalytic activity by polyclonal sera. We generated a panel of twenty-three anti-TPI monoclonal antibodies and found only two were able to block TPI enzymatic activity. Immunisation of jirds with B. malayi TPI, or mice with the homologous protein from the rodent filaria Litomosoides sigmodontis, failed to induce neutralising antibodies or protective immunity. In contrast, passive transfer of neutralising monoclonal antibody to mice prior to implantation with adult B. malayi resulted in 60–70% reductions in microfilarial levels in vivo and both oocyte and microfilarial production by individual adult females. The loss of fecundity was accompanied by reduced IFNγ expression by CD4+ T cells and a higher proportion of macrophages at the site of infection. Thus, enzymatically active TPI plays an important role in the transmission cycle of B. malayi filarial parasites and is identified as a potential target for immunological and pharmacological intervention against filarial infections

3-D Ultrastructure of O. tauri: Electron Cryotomography of an Entire Eukaryotic Cell

The hallmark of eukaryotic cells is their segregation of key biological functions into discrete, membrane-bound organelles. Creating accurate models of their ultrastructural complexity has been difficult in part because of the limited resolution of light microscopy and the artifact-prone nature of conventional electron microscopy. Here we explored the potential of the emerging technology electron cryotomography to produce three-dimensional images of an entire eukaryotic cell in a near-native state. Ostreococcus tauri was chosen as the specimen because as a unicellular picoplankton with just one copy of each organelle, it is the smallest known eukaryote and was therefore likely to yield the highest resolution images. Whole cells were imaged at various stages of the cell cycle, yielding 3-D reconstructions of complete chloroplasts, mitochondria, endoplasmic reticula, Golgi bodies, peroxisomes, microtubules, and putative ribosome distributions in-situ. Surprisingly, the nucleus was seen to open long before mitosis, and while one microtubule (or two in some predivisional cells) was consistently present, no mitotic spindle was ever observed, prompting speculation that a single microtubule might be sufficient to segregate multiple chromosomes

Construction and application of a protein and genetic interaction network (yeast interactome)

Cytoscape is a bioinformatic data analysis and visualization platform that is well-suited to the analysis of gene expression data. To facilitate the analysis of yeast microarray data using Cytoscape, we constructed an interaction network (interactome) using the curated interaction data available from the Saccharomyces Genome Database (www.yeastgenome.org) and the database of yeast transcription factors at YEASTRACT (www.yeastract.com). These data were formatted and imported into Cytoscape using semi-automated methods, including Linux-based scripts, that simplified the process while minimizing the introduction of processing errors. The methods described for the construction of this yeast interactome are generally applicable to the construction of any interactome. Using Cytoscape, we illustrate the use of this interactome through the analysis of expression data from a recent yeast diauxic shift experiment. We also report and briefly describe the complex associations among transcription factors that result in the regulation of thousands of genes through coordinated changes in expression of dozens of transcription factors. These cells are thus able to sensitively regulate cellular metabolism in response to changes in genetic or environmental conditions through relatively small changes in the expression of large numbers of genes, affecting the entire yeast metabolome