THE ROLE OF NONLYMPHOID ACCESSORY CELLS IN THE IMMUNE RESPONSE TO DIFFERENT ANTIGENS

Tissue culture techniques were combined with cell separation procedures to investigate the cellular requirements for a response to antigen, leading to the production of antibody-forming cells. Mouse spleen was dissociated, and the cells were separated into various groups on the basis of density, size, and active adherence. The ability of fractions to initiate a response in vivo, on transfer to an irradiated recipient, was compared to the response in vitro; and this ability was correlated with the presence or absence of phagocytic cells. Two different antigens were studied, sheep erythrocytes (SRC) and polymerized bacterial flagellin (POL). Density distribution analysis of spleen showed a wide density range of cells responding to both antigens in vivo. The same fractions responded to POL in vitro as in vivo. By contrast, only the light density regions responded in vitro to SRC. Response occurred in regions of overlap between lymphocytes and phagocytic macrophages. Separation by active adherence on columns of large glass beads gave a preparation containing large, medium, and small lymphocytes but no detectable phagocytic macrophages and very low levels of phagocytic polymorphs. This lymphocyte preparation responded to both antigens in vivo. In vitro it gave a full response to POL, but no response to SRC. Addition of a small quantity of the adherent fraction, enriched for phagocytic cells, restored response to SRC. The use of strain-specific antisera in a mixed culture containing a C57 phagocytic fraction and CBA lymphocytes showed that the lymphocyte fraction contributed the precursors of the final antibody-forming cells. The accessory cells from C57 spleen banded in the light regions of the density gradient where phagocytic macrophages were found. Irradiated spleen cells also activated the lymphocyte preparation, suggesting that the irradiated host provided the accessory cells for the in vivo response to SRC. Small lymphocytes were purified from spleen by the small glass bead size filtration technique. This sample of small lymphocytes responded less well to POL than the total lymphocyte population, but it responded as well in vitro as in vivo. The small lymphocyte preparation responded in vivo to SRC but not in vitro. Addition of a small quantity of the phagocyte-rich fraction from adherence columns restored the in vitro response to SRC. The results indicated that phagocytic cells are not required in the initiation of an immune response to POL. By contrast some accessory cell, possibly a phagocytic macrophage, is required for a response to SRC. The basis for this marked difference is discussed

Simple Models of Plant Learning and Memory

Plants are capable of intelligent responses to complex environmental signals. Learning and memory play fundamental roles in such responses. Two simple models of plant memory are proposed based on the calcium-signalling system. The memory states correspond to steady state distributions of calcium ions.Comment: 10 pages,Proceedings of international conference on unconventional application of statistical physics(to be published in Physica Scripta

The Evolution of the Stratopause During the 2006 Major Warming: Satellite Data and Assimilated Meteorological Analyses

Microwave Limb Sounder and Sounding of the Atmosphere with Broadband Emission Radiometry data show the polar stratopause, usually higher than and separated from that at midlatitudes, dropping from <55-60 to near 30 km, and cooling dramatically in January 2006 during a major stratospheric sudden warming (SSW). After a nearly isothermal period, a cool stratopause reforms near 75 km in early February, then drops to <55 km and warms. The stratopause is separated in longitude as well as latitude, with lowest temperatures in the transition regions between higher and lower stratopauses. Operational assimilated meteorological analyses, which are not constrained by data at stratopause altitude, do not capture a secondary temperature maximum that overlies the stratopause or the very high stratopause that reforms after the SSW; they underestimate the stratopause altitude variation during the SSW. High-quality daily satellite temperature measurements are invaluable in improving our understanding of stratopause evolution and its representation in models and assimilation systems

Scattering From a Two Dimensional Array of Flux Tubes: A Study of The Validity of Mean Field Theory

Mean Field Theory has been extensively used in the study of systems of anyons in two spatial dimensions. In this paper we study the physical grounds for the validity of this approximation by considering the Quantum Mechanical scattering of a charged particle from a two dimensional array of magnetic flux tubes. The flux tubes are arranged on a regular lattice which is infinitely long in the ``$y$'' direction but which has a (small) finite number of columns in the ``$x$'' direction. Their physical size is assumed to be infinitesimally small. We develop a method for computing the scattering angle as well as the reflection and transmission coefficients to lowest order in the Aharonov--Bohm interaction. The results of our calculation are compared to the scattering of the same particle from a region of constant magnetic field whose magnitude is equal to the mean field of all the flux tubes. For an incident plane wave, the Mean Field approximation is shown to be valid provided the flux in each tube is much less than a single flux quantum. This is precisely the regime in which Mean Field Theory for anyons is expected to be valid. When the flux per tube becomes of order 1, Mean Field Theory is no longer valid.Comment: 23 pages, University of British Columbia Preprint UBCTP93-01

Created mangrove wetlands store belowground carbon and surface elevation change enables them to adjust to sea-level rise

Mangrove wetlands provide ecosystem services for millions of people, most prominently by providing storm protection, food and fodder. Mangrove wetlands are also valuable ecosystems for promoting carbon (C) sequestration and storage. However, loss of mangrove wetlands and these ecosystem services are a global concern, prompting the restoration and creation of mangrove wetlands as a potential solution. Here, we investigate soil surface elevation change, and its components, in created mangrove wetlands over a 25 year developmental gradient. All created mangrove wetlands were exceeding current relative sea-level rise rates (2.6 mm yr(-1)), with surface elevation change of 4.2-11.0 mm yr(-1) compared with 1.5-7.2 mm yr(-1) for nearby reference mangroves. While mangrove wetlands store C persistently in roots/soils, storage capacity is most valuable if maintained with future sea-level rise. Through empirical modeling, we discovered that properly designed creation projects may not only yield enhanced C storage, but also can facilitate wetland persistence perennially under current rates of sea-level rise and, for most sites, for over a century with projected medium accelerations in sea-level rise (IPCC RCP 6.0). Only the fastest projected accelerations in sea-level rise (IPCC RCP 8.5) led to widespread submergence and potential loss of stored C for created mangrove wetlands before 2100

Identifying a Heart Rate Recovery Criterion After a 6-Minute Walk Test in COPD

Background: Slow heart rate recovery (HRR) after exercise is associated with autonomic dysfunction and increased mortality. What HRR criterion at 1-minute after a 6-minute walk test (6MWT) best defines pulmonary impairment?. Study Design and Methods: A total of 5008 phase 2 COPDGene (NCT00608764) participants with smoking history were included. A total of 2127 had COPD and, of these, 385 were followed-up 5-years later. Lung surgery, transplant, bronchiectasis, atrial fibrillation, heart failure and pacemakers were exclusionary. HR was measured from pulse oximetry at end-walk and after 1-min seated recovery. A receiver operator characteristic (ROC) identified optimal HRR cut-off. Generalized linear regression determined HRR association with spirometry, chest CT, symptoms and exacerbations. Results: HRR after 6MWT (bt/min) was categorized in quintiles: ≤ 5 (23.0% of participants), 6– 10 (20.7%), 11– 15 (18.9%), 16– 22 (18.5%) and ≥ 23 (18.9%). Compared to HRR≤ 5, HRR≥ 11 was associated with (p\u3c 0.001): lower pre-walk HR and 1-min post HR; greater end-walk HR; greater 6MWD; greater FEV1%pred; lower airway wall area and wall thickness. HRR was positively associated with FEV1%pred and negatively associated with airway wall thickness. An optimal HRR ≤ 10 bt/min yielded an area under the ROC curve of 0.62 (95% CI 0.58– 0.66) for identifying FEV1\u3c 30%pred. HRR≥ 11 bt/min was the lowest HRR associated with consistently less impairment in 6MWT, spirometry and CT variables. In COPD, HRR≤ 10 bt/min was associated with (p\u3c 0.001): ≥ 2 exacerbations in the previous year (OR=1.76[1.33– 2.34]); CAT≥ 10 (OR=1.42[1.18– 1.71]); mMRC≥ 2 (OR=1.42[1.19– 1.69]); GOLD 4 (OR=1.98[1.44– 2.73]) and GOLD D (OR=1.51[1.18– 1.95]). HRR≤ 10 bt/min was predicted COPD exacerbations at 5-year follow-up (RR=1.83[1.07– 3.12], P=0.027). Conclusion: HRR≤ 10 bt/min after 6MWT in COPD is associated with more severe expiratory flow limitation, airway wall thickening, worse dyspnoea and quality of life, and future exacerbations, suggesting that an abnormal HRR≤ 10 bt/min after a 6MWT may be used in a comprehensive assessment in COPD for risk of severity, symptoms and future exacerbations

Oxygen isotopes of anhydrous primary minerals show kinship between asteroid Ryugu and comet 81P/Wild2

The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically and mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary minerals in Ryugu and CI chondrites exhibit a bimodal distribution of oxygen isotopic compositions: 16O-rich (associated with refractory inclusions) and 16O-poor (associated with chondrules). Both the 16O-rich and 16O-poor minerals probably formed in the inner solar protoplanetary disk and were subsequently transported outward. The abundance ratios of the 16O-rich to 16O-poor minerals in Ryugu and CI chondrites are higher than in other carbonaceous chondrite groups but are similar to that of comet 81P/Wild2, suggesting that Ryugu and CI chondrites accreted in the outer Solar System closer to the accretion region of comets

Searching for a Stochastic Background of Gravitational Waves with LIGO

The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new limit is $\Omega_{\rm GW} < 6.5 \times 10^{-5}$. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background.Comment: 37 pages, 16 figure