Fibronectin and serum amyloid P component stimulate C3b- and C3bi-mediated phagocytosis in cultured human monocytes

Fibronectin (FN) and serum amyloid P component (SAP) markedly enhance phagocytosis mediated by the C3b and C3bi receptors of cultured human monocytes but not of granulocytes. (The C3b and C3bi receptors of granulocytes can be activated by treatment of these phagocytes with PMA.) Activation of monocyte C3 receptors by FN is developmentally regulated: Freshly explanted monocytes respond to FN with a small increase in C3 receptor-mediated phagocytosis while monocytes matured in culture exhibit a much greater response. The mechanism of action of FN on C3 receptors of cultured monocytes is unique in two respects. First, while substrate-bound FN or SAP activate monocyte C3 receptors, soluble FN does not. Second, stimulation of the basal surface of monocyte plasma membranes by substrate-bound FN activates C3b and C3bi receptors on the apical surface of the plasma membrane, i.e., at sites remote from the segments of membrane in contact with the FN or SAP

Study of resonance light scattering for remote optical probing

Enhanced scattering and fluorescence processes in the visible and UV were investigated which will enable improved remote measurements of gas properties. The theoretical relationship between scattering and fluorescence from an isolated molecule in the approach to resonance is examined through analysis of the time dependence of re-emitted light following excitation of pulsed incident light. Quantitative estimates are developed for the relative and absolute intensities of fluorescence and resonance scattering. New results are obtained for depolarization of scattering excited by light at wavelengths within a dissociative continuum. The experimental work was performed in two separate facilities. One of these utilizes argon and krypton lasers, single moded by a tilted etalon, and a 3/4 meter double monochromator. This facility was used to determine properties of the re-emission from NO2, I2 and O3 excited by visible light. The second facility involves a narrow-line dye laser, and a 3/4 meter single monochromator. The dye laser produces pulsed light with 5 nsec pulse duration and 0.005 nm spectral width

A New Handle on de Sitter Compactifications

We construct a large new class of de Sitter (and anti de Sitter) vacua of critical string theory from flux compactifications on products of Riemann surfaces. In the construction, the leading effects stabilizing the moduli are perturbative. We show that these effects self-consistently dominate over standard estimates for further $\alpha^\prime$ and quantum corrections, via tuning available from large flux and brane quantum numbers.Comment: 26 pages, harvmac big. v2: Correction generalizing specific ingredients required for tunable negative term; conclusions and structure of potential unchange

Communication between receptors for different ligands on a single cell...

Receptors for the third component of complement (C3) on cultured human monocytes (MO) bind ligand-coated particles but do not initiate phagocytosis. The function of these receptors, however, is altered dramatically after MO attach to surfaces coated with fibronectin (FN) or after MO are exposed to phorbol esters. FN and phorbol esters "activate" C3 receptors such that they promote vigorous phagocytosis. Here we show that activation of C3 receptors requires the continuous presence of FN or phorbol esters and is rapidly reversible when these stimuli are removed. Activation does not change the number or distribution of C3 receptors on the surface of MO. We conclude that the function of C3 receptors is regulated by reversible reactions that are initiated by ligation of a different class of receptors on the surface of the same cell

Macrophages possess probenecid-inhibitable organic anion transporters that remove fluorescent dyes from the cytoplasmic matrix

We introduced several membrane-impermeant fluorescent dyes, including Lucifer Yellow, carboxyfluorescein, and fura-2, into the cytoplasmic matrix of J774 cells and thioglycollate-elicited mouse peritoneal macrophages by ATP permeabilization of the plasma membrane and observed the subsequent fate of these dyes. The dyes did not remain within the cytoplasmic matrix; instead they were sequestered within phase-lucent cytoplasmic vacuoles and released into the extracellular medium. We used Lucifer Yellow to study these processes further. In cells incubated at 37 degrees C, 87% of Lucifer Yellow was released from the cells within 30 min after dye loading. The dye that remained within the cells at this time was predominantly within cytoplasmic vacuoles. Lucifer yellow transport was temperature dependent and occurred against a concentration gradient; therefore it appeared to be an energy-requiring process. The fluorescent dyes used in these studies are all organic anions. We therefore examined the ability of probenecid (p-[dipropylsulfamoyl]benzoic acid), which blocks organic anion transport across many epithelia, to inhibit efflux of Lucifer Yellow, and found that this drug inhibited this process in a dose-dependent and reversible manner. Efflux of Lucifer Yellow from the cells did not require Na+ co-transport or Cl- antiport; however, it was inhibited by lowering of the extracellular pH. These experiments indicate that macrophages possess probenecid-inhibitable transporters which are similar in their functional properties to organic anion transporters of epithelial cells. Such organic anion transporters have not been described previously in macrophages; they may mediate the release of naturally occurring organic anions such as prostaglandins, leukotrienes, glutathione, bilirubin, or lactate from macrophages

The HIBEAM/NNBAR Calorimeter Prototype

The HIBEAM/NNBAR experiment is a free-neutron search for $n \rightarrow$ sterile $n$ and $n \rightarrow \bar{n}$ oscillations planned to be installed at the European Spallation Source under construction in Lund, Sweden. A key component in the experiment is the detector to identify $n-\bar{n}$ annihilation events, which will produce on average four pions with a final state invariant mass of two nucleons, around $1.9\,$GeV. The beamline and experiment are shielded from magnetic fields which would suppress $n \rightarrow \bar{n}$ transitions, thus no momentum measurement will be possible. Additionally, calorimetry for particles with kinetic energies below $600\,$MeV is challenging, as traditional sampling calorimeters used in HEP would suffer from poor shower statistics. A design study is underway to use a novel approach of a hadronic range measurement in multiple plastic scintillator layers, followed by EM calorimetery with lead glass. A prototype calorimeter system is being built, and will eventually be installed at an ESS test beam line for \textit{in situ} neutron background studies.Comment: Contribution to the International Conference on Technology and Instrumentation in Particle Physics (TIPP2021

Inaccessible Singularities in Toral Cosmology

The familiar Bang/Crunch singularities of classical cosmology have recently been augmented by new varieties: rips, sudden singularities, and so on. These tend to be associated with final states. Here we consider an alternative possibility for the initial state: a singularity which has the novel property of being inaccessible to physically well-defined probes. These singularities arise naturally in cosmologies with toral spatial sections.Comment: 10 pages, version to appear in Classical and Quantum Gravit