Differences In Concentrations Of Cations Research Articles

Na+ and K+ ion imbalances in Alzheimer's disease

Alzheimer's disease (AD) is associated with impaired glutamate clearance and depressed Na+/K+ ATPase levels in AD brain that might lead to a cellular ion imbalance. To test this hypothesis, [Na+] and [K+] were analyzed in postmortem brain samples of 12 normal and 16 AD individuals, and in cerebrospinal fluid (CSF) from AD patients and matched controls. Statistically significant increases in [Na+] in frontal (25%) and parietal cortex (20%) and in cerebellar [K+] (15%) were observed in AD samples compared to controls. CSF from AD patients and matched controls exhibited no differences, suggesting that tissue ion imbalances reflected changes in the intracellular compartment. Differences in cation concentrations between normal and AD brain samples were modeled by a 2-fold increase in intracellular [Na+] and an 8–15% increase in intracellular [K+]. Since amyloid beta peptide (Aβ) is an important contributor to AD brain pathology, we assessed how Aβ affects ion homeostasis in primary murine astrocytes, the most abundant cells in brain tissue. We demonstrate that treatment of astrocytes with the Aβ 25–35 peptide increases intracellular levels of Na+ (~2–3-fold) and K+ (~1.5-fold), which were associated with reduced levels of Na+/K+ ATPase and the Na+-dependent glutamate transporters, GLAST and GLT-1. Similar increases in astrocytic Na+ and K+ levels were also caused by Aβ 1–40, but not by Aβ 1–42 treatment. Our study suggests a previously unrecognized impairment in AD brain cell ion homeostasis that might be triggered by Aβ and could significantly affect electrophysiological activity of brain cells, contributing to the pathophysiology of AD.

Growth Behavior, Nitrogen-Form Effects on Phosphorus Acquisition, and Phosphorus–Zinc Interactions in Brassica Cultivars under Phosphorus-Stress Environment

Phosphorus (P) and zinc (Zn) interact both in plants and soils and hence may affect the availability and utilization of each other. To investigate P and Zn nutritional status and P–Zn interactions, two genetically diverse Brassica cultivars classified as P tolerant (Brown Raya) and P sensitive (Sultan Raya) were grown in a sand-based pot culture. Jordan rock phosphate (RP) and monocalcium phosphate [Ca(H2PO4)2] were used as P sources, and ammonium nitrate (NH4NO3) or nitrate (NO3 --) only were used as nitrogen (N) sources. Two Zn levels [0.25 (low Zn) and 2.5 (high Zn) mg zinc sulfate (ZnSO4·5H2O) kg−1 sand, respectively] were applied along with recommended doses of other essential nutrients in the culture media. Cultivars differed significantly for their response to added P for biomass accumulation, but Zn supply had little effect. Cultivar Brown Raya had greater P uptake and P-utilization efficiency (PUE) than Sultan Raya under a P-stress environment, irrespective of Zn and N supply. Zinc supply had little effect on tissue P concentration and P uptake per unit of root dry matter (RDM) in either cultivar, irrespective of N supply. An increase in P supply caused a significant reduction in specific Zn uptake (Zn uptake per unit of RDM; SZnU) and tissue Zn concentration of both cultivars. The reduction in tissue Zn concentration cannot be ascribed entirely to a dilution effect. Zinc concentrations and uptake by P-efficient cultivar Brown Raya were significantly lower and more sensitive to P uptake than those of P-sensitive Sultan Raya cultivar. It is suggested that high PUE may depress plant Zn uptake and therefore cause a reduction in Zn concentration of Brassica grown in low-P and possibly low-Zn soils. In NH4NO3 nutrition, plants had significantly lower cation concentrations compared to NO3 -- nutrition only. Brown Raya consistently had lower cation concentrations than Sultan Raya under P stress. The differences in cation concentrations decreased with increased P availability, but Zn supply had no significant effect. In Brown Raya, the ratio of potassium in roots to shoots was always greater than in Sultan Raya. This suggested that lower cation concentrations in Brown Raya were due to root carboxylate exudations, which in turn were related to better P acquisition and PUE under insufficiently buffered P-stress environment.

Acid soil indicators in forest soils of the Cherry River Watershed, West Virginia

Declining forest health has been observed during the past several decades in several areas of the eastern USA, and some of this decline is attributed to acid deposition. Decreases in soil pH and increases in soil acidity are indicators of potential impacts on tree growth due to acid inputs and Al toxicity. The Cherry River watershed, which lies within the Monongahela National Forest in West Virginia, has some of the highest rates of acid deposition in Appalachia. East and West areas within the watershed, which showed differences in precipitation, stream chemistry, and vegetation composition, were compared to evaluate soil acidity conditions and to assess their degree of risk on tree growth. Thirty-one soil pits in the West area and 36 pits in the East area were dug and described, and soil samples from each horizon were analyzed for chemical parameters. In A horizons, East area soils averaged 3.7 pH with 9.4 cmol(c) kg(-1) of acidity compared to pH 4.0 and 6.2 cmol(c) kg(-1) of acidity in West area soils. Extractable cations (Ca, Mg, and Al) were significantly higher in the A, transition, and upper B horizons of East versus West soils. However, even with differences in cation concentrations, Ca/Al molar ratios were similar for East and West soils. For both sites using the Ca/Al ratio, a 50% risk of impaired tree growth was found for A horizons, while a 75% risk was found for deeper horizons. Low concentrations of base cations and high extractable Al in these soils translate into a high degree of risk for forest regeneration and tree growth after conventional tree harvesting.

Plant growth and cation composition of two cultivars of spring wheat (Triticum aestivum L.) differing in P uptake efficiency

Phosphorus (P)-zinc (Zn) interactions were investigated in two wheat cultivars (Brookton versus Krichauff) differing in P uptake efficiency. The experiment was done in a growth chamber. Rock phosphate (RP) or CaHPO4 (CaP) were used as P sources, and ammonium nitrate (AN) or nitrate only (NO) were used as nitrogen sources. Two Zn levels were used, 0.22 mg x kg(-1) (LZ) and 2.2 mg ZnSO4.7H2O x kg(-1) (HZ), respectively. P availability significantly affected plant biomass production, but Zn supply had little effect. Plants fed ammonium nitrate had significantly lower concentrations of cations than those fed nitrate only. Cultivar Brookton (with higher P uptake efficiency) consistently had lower concentrations of cations than cv. Krichauff (with low P uptake efficiency) under limited P supply. The differences in concentrations of cations increased with the decrease in P availability, but were not affected by Zn supply. The ratio of potassium in roots to shoots of cultivar Brookton was always higher than in cultivar Krichauff. Based on these findings, it is postulated that the lower concentrations of cations in cultivar Brookton are related to root exudation of organic anions, and a conceptual model is established to describe the regulation of root exudation of organic anions and concentrations of cations.

Groundwater cation concentrations in the riparian zone of a forested headwater stream

AbstractGroundwater cation concentrations in relation to hydrologic flow paths were studied in the riparian forest zone of a small headwater catchment near Toronto, Ontario. Groundwater entering the riparian zone from uplands showed significant differences in cation concentrations between slope‐foot and near‐stream locations. Mean Ca, Mg, K, and Na concentrations in shallow groundwater at the upland perimeter of the riparian forest were 65‐0, 11‐2, 0‐7, and 1‐8 mg L−1 respectively. Mean Ca, Mg, K, and Na concentrations in deep groundwater flowing upwards through glacial sands beneath the riparian zone were 52‐1, 15‐1, 1‐3, and 2‐6 mg L−1 respectively. Shallow groundwater emerged as slope‐foot springs producing surface rivulets which crossed the riparian zone to the streams. Deep groundwater flowed upward through organic soils into the rivulets and also discharged directly to the streams as bed and bank seepage. Springs had higher Ca concentrations and lower Mg, K, and Na values than rivulets entering the streams. Conversely, Mg, K, and Na concentrations were higher and Ca concentrations were lower in bank seeps in comparison to rivulets. These results suggest that differences in cation concentrations in groundwater entering the streams result from initial contrast in the chemistry of shallow and deep groundwater rather than from the effects of riparian soils and vegetation.