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Ion exchanger in the brain: Quantitative analysis of perineuronally fixed anionic binding sites suggests diffusion barriers with ion sorting properties.

Morawski M, Reinert T, Meyer-Klaucke W, Wagner FE, Tröger W, Reinert A, Jäger C, Brückner G, Arendt T - Sci Rep (2015)

Bottom Line: For the first time, we can provide quantitative data on the distribution and net amount of pericellularly fixed charge-densities, which, determined at 0.4-0.5 M, is much higher than previously assumed.PNs, thus, represent an immobilized ion exchanger with ion sorting properties high enough to partition mobile ions in accord with Donnan-equilibrium.We propose that fixed charge-densities in the brain are involved in regulating ion mobility, the volume fraction of extracellular space and the viscosity of matrix components.

View Article: PubMed Central - PubMed

Affiliation: Paul Flechsig Institute for Brain Research, University of Leipzig, Liebigstrasse 19, D04103 Leipzig, Germany.

ABSTRACT
Perineuronal nets (PNs) are a specialized form of brain extracellular matrix, consisting of negatively charged glycosaminoglycans, glycoproteins and proteoglycans in the direct microenvironment of neurons. Still, locally immobilized charges in the tissue have not been accessible so far to direct observations and quantifications. Here, we present a new approach to visualize and quantify fixed charge-densities on brain slices using a focused proton-beam microprobe in combination with ionic metallic probes. For the first time, we can provide quantitative data on the distribution and net amount of pericellularly fixed charge-densities, which, determined at 0.4-0.5 M, is much higher than previously assumed. PNs, thus, represent an immobilized ion exchanger with ion sorting properties high enough to partition mobile ions in accord with Donnan-equilibrium. We propose that fixed charge-densities in the brain are involved in regulating ion mobility, the volume fraction of extracellular space and the viscosity of matrix components.

No MeSH data available.


Prussian blue reaction (PBR) on brain slices loaded with 12.5 mM FeCl3.(A) untreated; (B; CHASE) pre-treated with chondroitinase ABC; and (C; HASE) pre-treated hyaluronidase. PNs are distinct (asterisks) in the untreated section (A), while treatment with either chondroitinase (B) or hyaluronidase (C) prior to Fe3+-loading abolished PN labeling. Scale bar: 20 μm, applies to all.
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f4: Prussian blue reaction (PBR) on brain slices loaded with 12.5 mM FeCl3.(A) untreated; (B; CHASE) pre-treated with chondroitinase ABC; and (C; HASE) pre-treated hyaluronidase. PNs are distinct (asterisks) in the untreated section (A), while treatment with either chondroitinase (B) or hyaluronidase (C) prior to Fe3+-loading abolished PN labeling. Scale bar: 20 μm, applies to all.

Mentions: When sections are treated with either chondroitinase or hyaluronidase, which are known to largely remove charged glycosaminoglycan side chains of the PN, subsequent loading with Fe3+-ions does not lead to perineuronal labeling. Thus, intact PNs are necessary for perineuronal iron-binding (Fig. 4).


Ion exchanger in the brain: Quantitative analysis of perineuronally fixed anionic binding sites suggests diffusion barriers with ion sorting properties.

Morawski M, Reinert T, Meyer-Klaucke W, Wagner FE, Tröger W, Reinert A, Jäger C, Brückner G, Arendt T - Sci Rep (2015)

Prussian blue reaction (PBR) on brain slices loaded with 12.5 mM FeCl3.(A) untreated; (B; CHASE) pre-treated with chondroitinase ABC; and (C; HASE) pre-treated hyaluronidase. PNs are distinct (asterisks) in the untreated section (A), while treatment with either chondroitinase (B) or hyaluronidase (C) prior to Fe3+-loading abolished PN labeling. Scale bar: 20 μm, applies to all.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664884&req=5

f4: Prussian blue reaction (PBR) on brain slices loaded with 12.5 mM FeCl3.(A) untreated; (B; CHASE) pre-treated with chondroitinase ABC; and (C; HASE) pre-treated hyaluronidase. PNs are distinct (asterisks) in the untreated section (A), while treatment with either chondroitinase (B) or hyaluronidase (C) prior to Fe3+-loading abolished PN labeling. Scale bar: 20 μm, applies to all.
Mentions: When sections are treated with either chondroitinase or hyaluronidase, which are known to largely remove charged glycosaminoglycan side chains of the PN, subsequent loading with Fe3+-ions does not lead to perineuronal labeling. Thus, intact PNs are necessary for perineuronal iron-binding (Fig. 4).

Bottom Line: For the first time, we can provide quantitative data on the distribution and net amount of pericellularly fixed charge-densities, which, determined at 0.4-0.5 M, is much higher than previously assumed.PNs, thus, represent an immobilized ion exchanger with ion sorting properties high enough to partition mobile ions in accord with Donnan-equilibrium.We propose that fixed charge-densities in the brain are involved in regulating ion mobility, the volume fraction of extracellular space and the viscosity of matrix components.

View Article: PubMed Central - PubMed

Affiliation: Paul Flechsig Institute for Brain Research, University of Leipzig, Liebigstrasse 19, D04103 Leipzig, Germany.

ABSTRACT
Perineuronal nets (PNs) are a specialized form of brain extracellular matrix, consisting of negatively charged glycosaminoglycans, glycoproteins and proteoglycans in the direct microenvironment of neurons. Still, locally immobilized charges in the tissue have not been accessible so far to direct observations and quantifications. Here, we present a new approach to visualize and quantify fixed charge-densities on brain slices using a focused proton-beam microprobe in combination with ionic metallic probes. For the first time, we can provide quantitative data on the distribution and net amount of pericellularly fixed charge-densities, which, determined at 0.4-0.5 M, is much higher than previously assumed. PNs, thus, represent an immobilized ion exchanger with ion sorting properties high enough to partition mobile ions in accord with Donnan-equilibrium. We propose that fixed charge-densities in the brain are involved in regulating ion mobility, the volume fraction of extracellular space and the viscosity of matrix components.

No MeSH data available.