Arbuscular mycorrhiza induced ATPases and membrane nutrient transport mechanisms

This paper presents the current understanding of comparative vertebrate intestine basic mechanisms of brush-border membrane transport. Animals control the uptake of monosaccharides and amino acids at three levels: 1) mucosal hyperplasia increases uptake nonselectively, 2) individual enterocytes increase the transport capacity of specific transporter systems, and 3) the transporters themselves are modulated by solute and ion electrochemical gradients. In light of the current literature, This paper summarizes the kinetics, thermodynamics, and the physical arrangement of one mode of transport, the prototype Na(+)-solute cotransporter. The model presented is experimentally consistent with “preferred random” kinetics, with Na+ binding preferentially before solute at the extracellular face. In the case of glucose, the cotransporter system may be physically arranged in the membrane as a tetramer comprising 73,000 Da subunits. All vertebrates may have evolved with a similar mechanism, with particular variations reflecting selected arrangements from a pool of polypeptide sequence blocks. The same fundamental transport mechanisms may be observed in the intestines of animals ranging from lower vertebrates through humans.

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Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-8067-2014 ◽

2014 ◽

Vol 11 (7) ◽

pp. 8067-8123

Author(s):

J. Crossman ◽

M. N. Futter ◽

P. G. Whitehead ◽

E. Stainsby ◽

H. M. Baulch ◽

...

Keyword(s):

Climate Change ◽

Overland Flow ◽

Stream Water ◽

Global Climate Model ◽

Nutrient Transport ◽

Future Climate Change ◽

Catchment Management ◽

Transport Mechanisms ◽

Soil Matrix ◽

Flow Pathways

Abstract. Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which is expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of Global Climate Model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the Integrated Catchment Model of Phosphorus Dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968–1997) to two future periods: 2020–2049 and 2060–2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivity) were highly varied. Sensitivity was governed by soil type (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy-loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

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Investigation of nutrient transport mechanisms in the lacunae-canaliculi system

IOP Conference Series Materials Science and Engineering ◽

10.1088/1757-899x/10/1/012129 ◽

2010 ◽

Vol 10 ◽

pp. 012129

Author(s):

S Scheiner ◽

A Théoval ◽

P Pivonka ◽

D W Smith ◽

L F Bonewald

Keyword(s):

Nutrient Transport ◽

Transport Mechanisms

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Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

Hydrology and Earth System Sciences ◽

10.5194/hess-18-5125-2014 ◽

2014 ◽

Vol 18 (12) ◽

pp. 5125-5148 ◽

Cited By ~ 15

Author(s):

J. Crossman ◽

M. N. Futter ◽

P. G. Whitehead ◽

E. Stainsby ◽

H. M. Baulch ◽

...

Keyword(s):

Climate Change ◽

Overland Flow ◽

Stream Water ◽

Global Climate Model ◽

Nutrient Transport ◽

Future Climate Change ◽

Catchment Management ◽

Transport Mechanisms ◽

Soil Matrix ◽

Flow Pathways

Abstract. Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which are expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as it is to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of global climate model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the INtegrated CAtchment model of Phosphorus dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968–1997) to two future periods: 2020–2049 and 2060–2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivities) were highly varied. Sensitivity was governed by quaternary geology (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

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From Bacteria to Man: Archaic Proton-Dependent Peptide Transporters at Work

Physiology ◽

10.1152/physiol.00054.2005 ◽

2006 ◽

Vol 21 (2) ◽

pp. 93-102 ◽

Cited By ~ 105

Author(s):

Hannelore Daniel ◽

Britta Spanier ◽

Gabor Kottra ◽

Dietmar Weitz

Keyword(s):

Nutrient Transport ◽

Peptide Transport ◽

Transport Mechanisms ◽

Physiological Importance ◽

Peptide Transporters ◽

Sodium Gradient ◽

Lower Vertebrates ◽

Organic Solute ◽

Higher Eukaryotes ◽

Uptake Of Nutrients

Uptake of nutrients into cells is essential to life and occurs in all organisms at the expense of energy. Whereas in most prokaryotic and simple eukaryotic cells electrochemical transmembrane proton gradients provide the central driving force for nutrient uptake, in higher eukaryotes it is more frequently coupled to sodium movement along the transmembrane sodium gradient, occurs via uniport mechanisms driven by the substrate gradient only, or is linked to the countertransport of a similar organic solute. With the cloning of a large number of mammalian nutrient transport proteins, it became obvious that a few “archaic” transporters that utilize a transmembrane proton gradient for nutrient transport into cells can still be found in mammals. The present review focuses on the electrogenic peptide transporters as the best studied examples of proton-dependent nutrient transporters in mammals and summarizes the most recent findings on their physiological importance. Taking peptide transport as a general phenomenon found in nature, we also include peptide transport mechanisms in bacteria, yeast, invertebrates, and lower vertebrates, which are not that often addressed in physiology journals.

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Physical Properties of Isolated Perfused Renal Tubular Basement Membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100065997 ◽

1971 ◽

Vol 29 ◽

pp. 390-391

Author(s):

Jared Grantham ◽

Larry Welling

Keyword(s):

Basement Membrane ◽

Basement Membranes ◽

Transport Mechanisms ◽

Permeability Characteristics ◽

Peritubular Capillaries ◽

Strategic Location ◽

Tubular Lumen ◽

Glomerular Filtrate ◽

Urine Formation ◽

Renal Tubular

In the course of urine formation in mammalian kidneys over 90% of the glomerular filtrate moves from the tubular lumen into the peritubular capillaries by both active and passive transport mechanisms. In all of the morphologically distinct segments of the renal tubule, e.g. proximal tubule, loop of Henle and distal nephron, the tubular absorbate passes through a basement membrane which rests against the basilar surface of the epithelial cells. The basement membrane is in a strategic location to affect the geometry of the tubules and to influence the movement of tubular absorbate into the renal interstitium. In the present studies we have determined directly some of the mechanical and permeability characteristics of tubular basement membranes.

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