Surfactant protein D increases phagocytosis and aggregation of pollen-allergen starch granules

Recent studies have shown that surfactant components, in particular the collectins surfactant protein (SP)-A and -D, modulate the phagocytosis of various pathogens by alveolar macrophages. This interaction might be important not only for the elimination of pathogens but also for the elimination of inhaled allergens and might explain anti-inflammatory effects of SP-A and SP-D in allergic airway inflammation. We investigated the effect of surfactant components on the phagocytosis of allergen-containing pollen starch granules (PSG) by alveolar macrophages. PSG were isolated from Dactylis glomerata or Phleum pratense, two common grass pollen allergens, and incubated with either rat or human alveolar macrophages in the presence of recombinant human SP-A, SP-A purified from patients suffering from alveolar proteinosis, a recombinant fragment of human SP-D, dodecameric recombinant rat SP-D, or the commercially available surfactant preparations Curosurf and Alveofact. Dodecameric rat recombinant SP-D enhanced binding and phagocytosis of the PSG by alveolar macrophages, whereas the recombinant fragment of human SP-D, SP-A, or the surfactant lipid preparations had no effect. In addition, recombinant rat SP-D bound to the surface of the PSG and induced aggregation. Binding, aggregation, and enhancement of phagocytosis by recombinant rat SP-D was completely blocked by EDTA and inhibited by d-maltose and to a lesser extent by d-galactose, indicating the involvement of the carbohydrate recognition domain of SP-D in these functions. The modulation of allergen phagocytosis by SP-D might play an important role in allergen clearance from the lung and thereby modulate the allergic inflammation of asthma.     

The Bacterial Community of the Lithistid Sponge Discodermia spp. as Determined by Cultivation and Culture-Independent Methods

The marine lithistid sponge Discodermia spp. (Family Theonellidae) contains many types of associated bacteria visible in the mesohyl while biofilms cover the pinacoderm. This study determined the identity of bacteria associated with members of the genus Discodermia using microbial culture, 16S rRNA gene clone libraries and fluorescence in situ hybridization. Four samples of Discodermia spp. were collected at depths between 24–161?m near Grand Bahama Island and Cay Sal Bank, Bahamas. A total of 80 unique isolates and 94 different clone sequences from at least eight bacterial classes were obtained. It appeared that Discodermia spp. may have a core community of bacteria that is common to all sponges of this genus. Species of at least six different classes of bacteria were regularly found in most of the sponge specimens collected, irrespective of collection depth or location. This indicates that a diverse spectrum of bacteria is associated with lithistid sponges irrespective of the transient seawater community that enters the sponge.     

Crustacea subterranea aus Argentinien

En el curso de las investigaciones sobre la fauna de las aguas subterráneas límnicas de la Argentina, se encontraron en pocas muestras una sorprendente cantidad de especies de crustáceos.

Una de las especies (Leptobathynella richerti) fué descubierta poco antes en Paraguay y 3 especies (Parastygocaris goerssi, P. andina e Ingolfiella uspallatae) ya han sido publicadas por el autor. Aqui se describen, se ilustran y se discuten 2 especies del género Parabathynella, 1 Nitocrella y 12 Parastenocaris como nuevas para la ciencia. Se completa la descripción de Leptobathynella richerti. Por falta de material, otras 5 especies aún no se han podido determinar.

Por consiguiente, la fauna de las aguas subterráneas neotropicales prueba ser abun‐dante y representada por mudias especies también en la Argentina. Un análisis biogeo‐gráfico del material aparecerá en otra oportunidad con relaciones más ámplias.

Las investigaciones serán continuadas.     

A three-species model explaining cyclic dominance of Pacific salmon

The four-year oscillations of the number of spawning sockeye salmon (Oncorhynchus nerka) that return to their native stream within the Fraser River basin in Canada are a striking example of population oscillations. The period of the oscillation corresponds to the dominant generation time of these fish. Various—not fully convincing—explanations for these oscillations have been proposed, including stochastic influences, depensatory fishing, or genetic effects. Here, we show that the oscillations can be explained as an attractor of the population dynamics, resulting from a strong resonance near a Neimark Sacker bifurcation. This explains not only the long-term persistence of these oscillations, but also reproduces correctly the empirical sequence of salmon abundance within one period of the oscillations. Furthermore, it explains the observation that these oscillations occur only in sockeye stocks originating from large oligotrophic lakes, and that they are usually not observed in salmon species that have a longer generation time.     

Abscisic acid in the xylem: where does it come from, where does it go to?

Abscisic acid is a hormonal stress signal that moves in the xylem from the root to the different parts of the shoot where it regulates transpirational water loss and leaf growth. The factors that modify the intensity of the ABA signal in the xylem are of particular interest because target cells recognize concentrations. ABA(xyl), will be decreased as radial water flow through the roots is increased, assuming that radial ABA transport occurs in the symplast only. Such dilutions of the plant hormone concentration can be compensated in different ways, which help to keep the ABA-concentrations in the xylem constant: (i) apoplastic bypass flows of ABA, (ii) ABA flows between the stem parenchyma and the xylem during transport and (iii) the action of beta-D-glucosidases that release free ABA from its conjugates to the root cortex and the leaf apoplast. The significance of reflection coefficients (sigma(ABA)), permeability coefficients of membranes (P(S)(ABA)) and apoplastic barriers for ABA is discussed.