ABSTRACT
Protein aggregation is a hallmark of several severe neurodegenerative disorders such as Huntington's, Parkinson's, or Alzheimer's disease. Metal ions play a profound role in protein aggregation and altered metal-ion homeostasis is associated with disease progression. Here we utilize µ-X-ray fluorescence imaging in combination with rapid freezing to resolve the elemental distribution of phosphorus, sulfur, potassium, and zinc in huntingtin exon-1-mYFP expressing HeLa cells. Using quantitative XRF analysis, we find a threefold increase in zinc and a 10-fold enrichment of potassium that can be attributed to cellular stress response. While the averaged intracellular ion areal masses are significantly different in aggregate-containing cells, a local intracellular analysis shows no different ion content at the location of intracellular inclusion bodies. The results are compared to corresponding experiments on HeLa cells forming pseudoisocyanine chloride aggregates. As those show similar results, changes in ion concentrations are not exclusively linked to huntingtin exon-1 amyloid formation.
Subject(s)
Neurodegenerative Diseases , Protein Aggregates , Exons , HeLa Cells , Humans , IonsABSTRACT
Lateral exchange of water and nutrients between xylem and surrounding tissues helps to de-couple uptake from utilization in all parts of a plant. We studied the dynamics of these exchanges, using stable isotope tracers for water (H(2)(18)O), magnesium ((26)Mg), potassium ((41)K) and calcium ((44)Ca) delivered via a cut stem for various periods to the transpiration stream of bean shoots (Phaseolus vulgaris cv. Fardenlosa Shiny). Tracers were subsequently mapped in stem cross-sections with cryo-secondary ion mass spectrometry. The water tracer equilibrated within minutes across the entire cross-section. In contrast, the nutrient tracers showed a very heterogeneous exchange between xylem vessels and the different stem tissues, even after 4 h. Dynamics of nutrients in the tissues revealed a fast and extensive exchange of nutrients in the xylem parenchyma, with, for example, calcium being completely replaced by tracer in less than 5 min. Dilution of potassium tracer during its 30 s transit in xylem sap through the stem showed that potassium concentration was up-regulated over many hours, to the extent that some of it was probably supplied by phloem recirculation from the shoot.
Subject(s)
Phaseolus/metabolism , Plant Transpiration , Water/metabolism , Xylem/metabolism , Isotopes/analysis , Phaseolus/physiology , Plant Stems/metabolism , Plant Stems/physiology , Xylem/physiologyABSTRACT
Yellow cypress (Chamaecyparis obtusa (Siebold & Zucc.) Endl. var. formosana (Hayata) Rehder) is the predominant tree species of Taiwan's nutrient-poor, mountain fog forests. Little is known about the potential contribution of solute uptake from fog to the overall nutrition of these trees. Shoots of yellow cypress seedlings were misted with artificial fog containing the tracer rubidium (Rb) in laboratory and field experiments to determine if there is solute uptake from the fog. After misting shoots for six weeks, substantial amounts of tracer were detected in unexposed roots by inductively coupled plasma mass spectroscopy bulk analysis. Possible routes of entry were examined by element imaging with energy dispersive X-ray analysis. Direct uptake of the tracer into leaves across the cuticle and epidermis was small, excluding this as the major uptake path. Accumulations of Rb were found on leaf surfaces along the edges of the leaves. The almost daily changes in fog coverage and air humidity may enhance the accumulation of fog solutes at leaf edges. Accumulation of Rb was also found in narrow clefts between opposite leaves and between the outermost and underlying alternating stacked leaves. The clefts provide a direct passage from the leaf surface to the space beneath the imbricate leaves and the underlying alternate leaves, possibly facilitating solute uptake from fog, which in turn may contribute to the nutrition of yellow cypress.
