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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.


Concentration of iron bound to perineuronal nets in rat cortex, subiculum, substantia nigra and red nucleus as a function of the iron concentration applied.The relation can be described by a Langmuir adsorption equation. The stated errors are 20% of the average values from three PNs per applied iron concentration.
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f5: Concentration of iron bound to perineuronal nets in rat cortex, subiculum, substantia nigra and red nucleus as a function of the iron concentration applied.The relation can be described by a Langmuir adsorption equation. The stated errors are 20% of the average values from three PNs per applied iron concentration.

Mentions: The dynamic binding characteristic of Fe3+ to the perineuronal anionic binding sites was determined using quantitative elemental imaging of tissue sections loaded with increasing concentrations of the Fe3+-probe. PNs accumulate more Fe than any other ECM component, which amounts to two- to three times that of ECM structures outside PNs. The affinity of the Fe3+-probe binding to PNs was extracted from concentration values of Fe accumulated at PNs. The relationship between the concentration of the bound Fe-probe to the applied load can be described by a Langmuir adsorption equation (Fig. 5). The relationship is given by B(c) = Bmax (c + cph)/(KD + c + cph), with B being the concentration of PN bound iron and c is the iron load applied. cph accounts for the low physiological free Fe concentration. The parameter KD represents the load concentration at which the concentration of bound iron is half of its maximum value. KD is the inverse of the affinity or Langmuir constant. The KD and saturation values were extracted for the four rat brain regions cerebral cortex, subiculum, substantia nigra and red nucleus (Fig. 5).


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)

Concentration of iron bound to perineuronal nets in rat cortex, subiculum, substantia nigra and red nucleus as a function of the iron concentration applied.The relation can be described by a Langmuir adsorption equation. The stated errors are 20% of the average values from three PNs per applied iron concentration.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5: Concentration of iron bound to perineuronal nets in rat cortex, subiculum, substantia nigra and red nucleus as a function of the iron concentration applied.The relation can be described by a Langmuir adsorption equation. The stated errors are 20% of the average values from three PNs per applied iron concentration.
Mentions: The dynamic binding characteristic of Fe3+ to the perineuronal anionic binding sites was determined using quantitative elemental imaging of tissue sections loaded with increasing concentrations of the Fe3+-probe. PNs accumulate more Fe than any other ECM component, which amounts to two- to three times that of ECM structures outside PNs. The affinity of the Fe3+-probe binding to PNs was extracted from concentration values of Fe accumulated at PNs. The relationship between the concentration of the bound Fe-probe to the applied load can be described by a Langmuir adsorption equation (Fig. 5). The relationship is given by B(c) = Bmax (c + cph)/(KD + c + cph), with B being the concentration of PN bound iron and c is the iron load applied. cph accounts for the low physiological free Fe concentration. The parameter KD represents the load concentration at which the concentration of bound iron is half of its maximum value. KD is the inverse of the affinity or Langmuir constant. The KD and saturation values were extracted for the four rat brain regions cerebral cortex, subiculum, substantia nigra and red nucleus (Fig. 5).

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.