Ammonium uptake in Lemna gibba G 1, related membrane potential changes, and inhibition of anion uptake

In N-starved (?N) fronds of Lemna gibba L. G 1, NH₄⁺ uptake rates were several-fold those of NO₃^?-supplied (+N) fronds. NO₃^?, uptake in +N-plants was slow and not inhibited by addition of NH₄⁺. However, in ?N-plants with higher NO₃^? and still higher NH₄⁺ uptake rates, addition of NH₄⁺ immediately reduced the NO₃^? uptake rates to about one third until the NH₄⁺ was consumed. The membrane potential (E_m) decreased immediately upon addition of NH₄⁺ in all fronds, but whereas depolarisation was moderate and transient in +N-plants, it was strong, up to 150 mV, in N-starved plants, where E_m remained at the level of the K⁺ diffusion potential (E_D) until NH₄⁺ was removed. In N-starved plants NH₄⁺ uptake and membrane depolarisation showed the same concentration dependence, except for an apparent linear component for uptake. Phosphate uptake was inhibited by NH₄⁺ similarly to NO₃^? uptake, but only in P- and N-starved plants, not after mere P starvation. Influx of NO₃^? and H₂PO ₄^? into the negatively charged cells of Lemna is mediated by anion/H⁺ cotransport, but NH₄⁺ influx can follow the electrochemical gradient. Its saturating component may reflect a carrier-mediated NH₄⁺ uniport, the linear component diffusion of NH₄⁺ or NH₃. Inhibition of anion/H⁺ cotransport by high NH₄⁺ influx rates may be due to loss of the proton-driving force, Δμ?H⁺, across the plasmalemma. Reversible inhibition by NH₄⁺ of the H⁺ extrusion pump may contribute to the finding that Δμ?H⁺ cannot be reconstituted in the presence of higher NH₄⁺ concentrations.     

The role of macrophage subpopulations in autoimmune disease of the central nervous system

Summary In this review the role of various subpopulations of macrophages in the pathogenesis of experimental autoimmune encephalomyetitis is discussed. Immunohistochemistry with macrophage markers shows that in this disease different populations of macrophages (i.e. perivascular cells, microglia and infiltrating blood-borne macrophages) are present in the central nervous system. These subpopulations partially overlap in some functional activity while other activities seem to be restricted to a distinct subpopulation, indicating that these subpopulations have different roles in the pathogenesis of encephalomyelitis. The studies discussed in this review reveal that immunocytochemical and morphological studies, combined with new techniques such asin situ nick translation and experimental approaches like the use of bone marrow chimeras and macrophage depletion techniques, give valuable information about the types and functions of cells involved in central nervous system inflammation. The review is divided in three parts. In the first part the experimental autoimmune encephalomyelitis model is introduced. The second part gives an overview of the origin, morphology and functions of the various subpopulations. In the third part the role of these subpopulations is discussed in relation to the various stages (i.e. preclinical, clinical and recovery) of the experimental disease.     

High-performance liquid chromatographic analysis of porphyrins and their isomers with radial compression columns

Porphyrin methyl esters and the isomers of uroporphyrin and heptacarboxylic porphyrin were separated by high-performance liquid chromatography. Isocoproporphyrin was also separated from coproporphyrin. By slight modifications to the solvent mixture, the separation of all biological polycarboxylic porphyrins was achieved. These separations were made possible through the high efficiency of 10- or 5-μm particle-size Radial-PAK cartridges, which have been used in the separation of porphyrins in various excreta and tissues in a number of porphyrias.     

The use of a replanted riparian habitat by the Lumholtz's Tree‐kangaroo (Dendrolagus lumholtzi)

This study describes the use of a section of a replanted riparian wildlife corridor by Lumholtz's Tree‐kangaroo (Dendrolagus lumholtzi) (referred to here as LTK) on the Atherton Tablelands in north‐east Queensland, Australia. Selection of plants for replanting had been adjusted to the seasonally inundated clay‐rich and acid soils of the site, and, in some cases, with the aim to establish wind breaks which resulted in a plant composition of this section that differs from known LTK habitats. Through semi‐regular daily observations of individual LTKs over eight years, it was found that LTKs were most commonly recorded on Tallowwood (Eucalyptus microcorys), Rose Gum (E. grandis), Caribbean Pine (Pinus caribaea) and Bunya Pine (Araucaria bidwillii) which were planted as wind breaks in the 1950s and 1980s. On a section planted in 1998, it was found that LTKs used certain tree species more frequently than would have been expected from the relative number in which these species had been planted. This may be associated with certain structural features of the used tree species. The presence of these structural habitat features may allow LTKs to establish home ranges within the restored habitat. Home ranges were calculated for four females, and it was found that they did not differ in size from those reported from other LTK habitats. However, home ranges showed extensive overlaps. The study reveals that LTK will colonise replanted habitat and may be adaptable in its spatial requirements in a restored landscape.     

Stage-Specific Sampling by Pattern Recognition Receptors during Candida albicans Phagocytosis

Candida albicans is a medically important pathogen, and recognition by innate immune cells is critical for its clearance. Although a number of pattern recognition receptors have been shown to be involved in recognition and phagocytosis of this fungus, the relative role of these receptors has not been formally examined. In this paper, we have investigated the contribution of the mannose receptor, Dectin-1, and complement receptor 3; and we have demonstrated that Dectin-1 is the main non-opsonic receptor involved in fungal uptake. However, both Dectin-1 and complement receptor 3 were found to accumulate at the site of uptake, while mannose receptor accumulated on C. albicans phagosomes at later stages. These results suggest a potential role for MR in phagosome sampling; and, accordingly, MR deficiency led to a reduction in TNF-α and MCP-1 production in response to C. albicans uptake. Our data suggest that pattern recognition receptors sample the fungal phagosome in a sequential fashion.