Study of the self‐diffusion coefficients of cations in the presence of an acidic polysaccharide

Magdelénat, H.; Turq, Pierre; Chemla, M.

doi:10.1002/bip.1974.360130803

Cited by 33 publications

(21 citation statements)

References 29 publications

(2 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Di/D^f [l-p A (?c, ξ-1χ)] (4) where Dj/D^ are the tracer diffusion coefficients of the i th ion in the condensation term f = Uc ξ" 1 * + D/(X + D (5) where X = Np/Ns, the equivalent concentration of polyelectrolyte to that of simple salt. The value of f is unity for coions and for counterions if ξ < ξ α .…”

Section: Resultsmentioning

confidence: 99%

Sodium-Ion Interactions with Polyions in Aqueous Salt-Free Solutions by Diffusion

Ander

1991

ACS Symposium Series

View full text Add to dashboard Cite

An unambiguous way to study the interactions of counterions with polyelectrolytes in solution is by determining the counterion and coion radioactive tracer diffusion coefficients inthe presence of a polyelectrolyte with a common counterion. This has been done principally by FernandezPrini, et al. 1,2 , Magdelenat, et al. 3,4 and Ander, et al. 5-13 . A capillary diffusion technique was employed. Aqueous solutions have been used in almost all studies. This brief review will focus on the experimental findings of the author. Equations have been developed by Manning for counterion and coion diffusion coefficients in polyelectrolyte solutions in the absence and presence of simple salts for a line charge model for the polyelectrolyte. 14-20 DIFFUSION MEASUREMENTS To determine the self-diffusion coefficients of ions, the open-end capillary method originally introduced by Anderson and Saddington 21 was employed without stirring. Due to the high viscosity of polyelectrolyte solutions, a non-stirring technique was found to be more reliable than one employing stirring because of the considerable change of viscosity of the solution as concentration varies. Fawcett and Caton 22 analyzed the source of error in the capillary method of measuring diffusion coefficients. They concluded that the serious source of systematic error results from convective loss of diffusant from the mouth of the capillary, and that accurate results require the use of fine bore capillaries from which convective loss is minimal.In our laboratory all diffusion measurements were carried out in a constant temperature bath at 25.00 + 0.01°C. Precision bore capillaries of 1.00 + 0.005 mm diameter and 2.82 + 0.005 cm length were filled with the desired polyelectrolyte solution containing tracer amount of radioactively labeled ion under investigation. The outside of the filled capillaries were then wiped dry and each capillary was placed into an individual test tube (100 mm χ 13 mm), which was subsequently filled with a radioactively inert solution of identical composition to the solution inside the capillary. Since the solutions inside and outside the capillary were the same polyelectrolyte concentration and the same simple salt concentration, no concentration

show abstract

Section: Resultsmentioning

confidence: 99%

Sodium-Ion Interactions with Polyions in Aqueous Salt-Free Solutions by Diffusion

Ander

1991

ACS Symposium Series

View full text Add to dashboard Cite

show abstract

“…Prior modeling of CS’s interaction with cations in the ECM suggested that the high concentrations of Na + in the extracellular space of normal brain tissue might shield larger, divalent cations from the negative charges on CS (Magdelenat et al, 1974). The potential for a robust electrostatic interaction between CS and Ca 2+ was further supported by Hrabetova and with co-investigators' finding that cleavage of CS from the ECM of brain tissue increased the rate of diffusion of Ca 2+ through the extracellular space (Hrabetova et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Under this model, decreases in [Ca 2+ ] e represent an increase in [Ca 2+ ] i exclusively. However, it has been suggested that Na + might screen larger divalent cations like Ca 2+ from binding to the matrix (Magdelenat et al, 1974). Based on these studies, it is possible that when [Na + ] e is decreased, additional binding sites for Ca 2+ become available on the ECM of brain.…”

Section: Introductionmentioning

confidence: 99%

T-type calcium channels contribute to calcium disturbances in brain during hyponatremia

Odackal

Sherpa

Patel

et al. 2015

Experimental Neurology

View full text Add to dashboard Cite

Disturbance of calcium homeostasis is implicated in the normal process of aging and brain pathology prevalent in the elderly such as Alzheimer’s, Parkinson’s, and amyotrophic lateral sclerosis. Previous studies demonstrated that applying a hyponatremic iso-osmotic (low-NaCl) artificial cerebrospinal fluid (ACSF) to rodent hippocampus causes extracellular calcium to rapidly decrease. Restoring normonatremia after low-NaCl treatment causes a rapid increase in extracellular calcium that overshoots baseline. This study examined the amplitude, timing, and mechanism of these surprising calcium changes. We also tested whether hyponatremia increased calcium entry into brain cells or calcium binding to chondroitin sulfate (CS), a negatively charged constituent of the extracellular matrix (ECM) that may be occupied by sodium during normonatremia. We report three major findings. First we show that CS does not contribute to extracellular calcium changes during low-NaCl treatments. Second, we show that the time to minimum extracellular calcium during low-NaCl treatment is significantly shorter than the time to maximum extracellular calcium in recovery from low-NaCl treatment. Third, we show that the decrease in extracellular calcium observed during hyponatremia is attenuated by ML 218, a highly selective T-type calcium channel blocker. Together these data suggest that calcium rapidly enters cells at the onset of low-NaCl treatment and is extruded from cells when normonatremia is restored. Calcium binding to CS does not significantly contribute to calcium changes in brain during hyponatremia. Differences in timing suggest that extracellular calcium changes during and in recovery from hyponatremia occur by distinct mechanisms or by a multistep process. Finally, partial block of extracellular calcium influx by ML 218 suggests that T-type channels are involved in calcium entering cells during hyponatremia. Given the high prevalence of hyponatremia among elderly patients and the growing understanding of calcium’s role in multiple neurologic pathologies, this study promotes a novel approach for studying and potentially preventing the effects of hyponatremia on calcium dysregulation in brain tissue.

show abstract

“…It is further stated that the diffusion of neutral molecules is impeded about 50% (D in gel/D in water -~ 0.5), whereas cations and anions are even more impeded, 55 to 75%, in passing through a fixed but hydrated matrix. On the basis of these generalizations and the data on self-diffusion [6][7][8][9], one can calculate the expected diffusion rates in bone relative to water, of several substances studied. These predictions assume that the matrix does not have a high net charge density and that the partition coefficient medium/bone is near unity.…”

Section: Discussionmentioning

confidence: 99%

Studies of diffusion in calvaria

Neuman

1981

Calcif Tissue Int

View full text Add to dashboard Cite

The rates of diffusion of small ions and neutral molecules through isolated calvaria have been determined. Compared with data published on self-diffusion and diffusion through cartilage, H2O, 3-O-methylglucose, lactate, sulfate, and methylamine diffuse at approximately 2/3 the expected rate. Diffusion of H2O and sulfate was unaffected by the administration of the diphosphonate 1-hydroxyethane-1,1-diphosphonate (EHDP), although phosphate fluxes are markedly diminished. Diffusion of water was nearly doubled by vitamin D deficiency. A 1-week treatment with 1,25(OH)2D3 had no effect on H2O diffusion while returning calcium influx to normal. It is concluded that bone matrix permits a flow of small neutral and ionized molecules nearly comparable to that in cartilage. When changes in calcium and phosphate influx are observed, they can be ascribed to the exchange properties of bone mineral and not to changes in matrix permeability.

show abstract

Study of the self‐diffusion coefficients of cations in the presence of an acidic polysaccharide

Cited by 33 publications

References 29 publications

Sodium-Ion Interactions with Polyions in Aqueous Salt-Free Solutions by Diffusion

Sodium-Ion Interactions with Polyions in Aqueous Salt-Free Solutions by Diffusion

T-type calcium channels contribute to calcium disturbances in brain during hyponatremia

Studies of diffusion in calvaria

Contact Info

Product

Resources

About