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821.
822.
823.
Ammonium uptake in Lemna gibba G 1, related membrane potential changes, and inhibition of anion uptake 总被引:6,自引:0,他引:6
Wolfram R. Ullrich Marie Larsson Carl-Magnus Larsson Sigrid Lesch Anton Novacky 《Physiologia plantarum》1984,61(3):369-376
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 (Em) 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 Em remained at the level of the K+ diffusion potential (ED) 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. 相似文献
824.
Jan Bauer Sigrid R. Ruuls Ingeborg Huitinga Christine D. Dijkstra 《The Histochemical journal》1996,28(2):83-97
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. 相似文献
825.
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. 相似文献
826.
Sigrid E. M. Heinsbroek Philip R. Taylor Fernando O. Martinez Luisa Martinez-Pomares Gordon D. Brown Siamon Gordon 《PLoS pathogens》2008,4(11)
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. 相似文献