scholarly journals Axoplasmic free magnesium levels and magnesium extrusion from squid giant axons.

1976 ◽  
Vol 68 (2) ◽  
pp. 159-178 ◽  
Author(s):  
P De Weer
Keyword(s):  
Sodium Pump ◽  
Giant Axon ◽  
Magnesium Content ◽  
Magnesium Concentration ◽  
Citrate Buffer ◽  
Sodium Efflux ◽  
Loligo Pealei ◽  
Free Magnesium ◽  
Total Magnesium ◽  
Very High

The free magnesium concentration in the axoplasm of the giant axon of the squid, Loligo pealei, was estimated by exploting the known sensitivity of the sodium pump to intracellular Mg2+ levels. The Mg-citrate buffer which, when injected into the axon, resulted in no change in sodium efflux was in equilibrium with a Mg2+ level of about 3--4 mM. Optimal [Mg2+] for the sodium pump is somewhat higher. Total magnesium content of axoplasm was 6.7 mmol/kg, and that of hemolymph was 44 mM. The rate coefficient for 28Mg efflux was about 2 X 10(-3) min-u for a 500-mum axon at 22-25degreesC, with a very high temperature coefficient (Q10=4-5). This efflux is inhibited 95% by injection of apyrase and 75% by removal of external sodium, and seems unaffected by membrane potential or potassium ions. Increased intracellular ADP levels do not affect Mg efflux nor its requirement for Na+/o, but extracellularl magnesium ions do. Activation of 28Mg efflux by Na+/o follows hyperbolic kinetics, with Mg2+/o reducing the affinity of the system for Na+/o. Lanthanum and D600 reversibly inhibit Mg efflux. In the absence of both Na+ and Mg2+, but not in their presence, removal of Ca2+ from the seawater vastly increased 28Mg efflux; this efflux was also strongly inhibited by lanthanum. A small (10(-14) mol cm-2) extra Mg efflux accompanies the conduction of an action potential.

Electric current generated by squid giant axon sodium pump: external K and internal ADP effects

1978 ◽  
Vol 235 (1) ◽  
pp. C63-C68 ◽  
Author(s):  
R. F. Abercrombie ◽  
P. de Weer
Keyword(s):  
Sodium Pump ◽  
Giant Axon ◽  
Pump Current ◽  
Membrane Resistance ◽  
Extracellular Potassium ◽  
Sodium Efflux ◽  
Steroid Sensitive ◽  
External Potassium ◽  
Loligo Pealei ◽  
External K

The operation of the sodium pump of giant axons of the squid, Loligo pealei, has been studied simultaneously in two independent ways: 1) by measuring sodium efflux with 22Na, and 2) by calculating the transmembrane current generated by the pump from measurements of membrane resistance and digitalis-sensitive membrane potential. In normal, untreated axons, the effect of increasing the external potassium concentration on both sodium efflux and pump current is similar, which suggests that Na:K pump stoichiometry remains relatively constant in the range of 0-20 mM external K. The data are compatible with a 3:2 Na:K ratio. In axons whose intracellular ADP level has been elevated by injection of L-arginine, a large, electrically silent, cardiotonic steroid-sensitive sodium efflux takes place in the absence of external potassium; this suggests that pump-mediated Na:Na exchange is 1:1 or electroneutral. Finally, elevation of external potassium levels causes the appearance, in high-ADP axons, of electrogenic pumping, with little effect on sodium efflux; hence, in contrast to what is seen in normal (low-ADP) axons, the charge translocated, per sodium ion extruded, increases sharply with increasing extracellular potassium levels.

Effects of pH changes on sodium pump fluxes in squid giant axon

1987 ◽  
Vol 253 (4) ◽  
pp. C547-C554 ◽  
Author(s):  
G. E. Breitwieser ◽  
A. A. Altamirano ◽  
J. M. Russell
Keyword(s):  
Sodium Pump ◽  
Maximum Velocity ◽  
Activation Parameters ◽  
Giant Axon ◽  
Inhibitory Effect ◽  
Squid Giant Axon ◽  
Extracellular Ph ◽  
Sodium Efflux ◽  
Effects Of Ph ◽  
Ph Range

The effects of independently varying intracellular and extracellular pH on sodium pump fluxes were studied in the squid giant axon. By means of intracellular dialysis, we found that changes of intracellular pH (pHi), but not of extracellular pH, affected ouabain-sensitive Na+ efflux and K+ influx over the pH range of 6.0-8.6. Both fluxes were maximum at a pHi of 7.2-7.4. Variations away from this optimal pHi in either the acidic or alkaline direction resulted in a graded inhibition of both ouabain-sensitive fluxes. The kinetic basis for the inhibitory effect of acidic pHi was examined by comparing the kinetic parameters of activation of ouabain-sensitive sodium efflux by intracellular Na+ (Na+i) and extracellular K+ (K+o) at normal pHi with those at acidic pHi. We found that the inhibitory effect of intracellular acidity results from a reversible decrease in maximum velocity (Vmax), without an effect on the activation parameters for Na+i (K1/2 Na+i) or K+o (K1/2 K+o).

scholarly journals Circulating Ionized Magnesium as a Measure of Supplement Bioavailability: Results from a Pilot Study for Randomized Clinical Trial

Nutrients ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1245 ◽  
Author(s):  
Jiada Zhan ◽  
Taylor C. Wallace ◽  
Sarah J. Butts ◽  
Sisi Cao ◽  
Velarie Ansu ◽  
...  
Keyword(s):  
Pilot Study ◽  
Whole Blood ◽  
Area Under The Curve ◽  
Oral Intake ◽  
Magnesium Content ◽  
Magnesium Concentration ◽  
Rank Test ◽  
Ionized Magnesium ◽  
Signed Rank Test ◽  
Total Magnesium

Oral supplementation may improve the dietary intake of magnesium, which has been identified as a shortfall nutrient. We conducted a pilot study to evaluate appropriate methods for assessing responses to the ingestion of oral magnesium supplements, including ionized magnesium in whole blood (iMg2+) concentration, serum total magnesium concentration, and total urinary magnesium content. In a single-blinded crossover study, 17 healthy adults were randomly assigned to consume 300 mg of magnesium from MgCl2 (ReMag®, a picosized magnesium formulation) or placebo, while having a low-magnesium breakfast. Blood and urine samples were obtained for the measurement of iMg2+, serum total magnesium, and total urine magnesium, during 24 h following the magnesium supplement or placebo dosing. Bioavailability was assessed using area-under-the-curve (AUC) as well as maximum (Cmax) and time-to-maximum (Tmax) concentration. Depending on normality, data were expressed as the mean ± standard deviation or median (range), and differences between responses to MgCl2 or placebo were measured using the paired t-test or Wilcoxon signed-rank test. Following MgCl2 administration versus placebo administration, we observed significantly greater increases in iMg2+ concentrations (AUC = 1.51 ± 0.96 vs. 0.84 ± 0.82 mg/dL•24h; Cmax = 1.38 ± 0.13 vs. 1.32 ± 0.07 mg/dL, respectively; both p < 0.05) but not in serum total magnesium (AUC = 27.00 [0, 172.93] vs. 14.55 [0, 91.18] mg/dL•24h; Cmax = 2.38 [1.97, 4.01] vs. 2.24 [1.98, 4.31] mg/dL) or in urinary magnesium (AUC = 201.74 ± 161.63 vs. 139.30 ± 92.84 mg•24h; Cmax = 26.12 [12.91, 88.63] vs. 24.38 [13.51, 81.51] mg/dL; p > 0.05). Whole blood iMg2+ may be a more sensitive measure of acute oral intake of magnesium compared to serum and urinary magnesium and may be preferred for assessing supplement bioavailability.

scholarly journals Genetic specificity of magnesium nutrition in sunflower

2008 ◽  
pp. 27-34 ◽  
Author(s):  
Rudolf Kastori ◽  
Radovan Marinkovic ◽  
Petar Sekulic ◽  
Ivana Maksimovic ◽  
Mira Pucarevic
Keyword(s):  
Wild Species ◽  
Magnesium Content ◽  
Magnesium Concentration ◽  
Helianthus Tuberosus ◽  
Breeding Programs ◽  
Wild Sunflower ◽  
Different Populations ◽  
Helianthus Petiolaris ◽  
Very High ◽  
Genetic Specificity

Magnesium content was analyzed in five of the most grown sunflower hybrids in Serbia, as well as in different populations of wild sunflower species: Helianthus agrophyllus (5), Helianthus annuus (4), Helianthus neglectus (3), Helianthus petiolaris (5), Helianthus tuberosus (5). Magnesium content in the populations of wild sunflower species ranged from 317 to 824 mg/100 g DW. The highest magnesium content was found in Helianthus petiolaris and the lowest in Helianthus tuberosus. Different populations within each species differed significantly in magnesium content. The highest variation coefficient was found in Helianthus tuberosus and the lowest in Helianthus petiolaris. Magnesium concentration in hybrids was significantly different as well, and in two years it was in average between 575 and 813 mg/g DW. The results suggest that genetic variability between magnesium concentrations in wild species and hybrids of sunflower is very high. This should be taken into consideration when requirements for mineral nutrition are analyzed, as well as when wild species are included in breeding programs.

scholarly journals CONTENTS OF MAGNESIUM IN THE ENVIRONMENT AND POPULATION MORBIDITY RATE OF ARTERIAL HYPERTENSION

2019 ◽  
Vol 98 (5) ◽  
pp. 494-497 ◽  
Author(s):  
M. A. Yahyaev ◽  
Shamil K. Salikhov ◽  
S. O. Abdulkadyrova ◽  
A. Sh. Aselderova ◽  
Z. Z. Surkhayeva ◽  
...  
Keyword(s):  
Arterial Hypertension ◽  
Natural Waters ◽  
Medical Information ◽  
Magnesium Deficiency ◽  
Magnesium Content ◽  
Magnesium Concentration ◽  
Morbidity Rate ◽  
Photometric Method ◽  
Number Of Patients ◽  
Water Plants

Introduction. Study of the interrelation between magnesium content in biosphere objects (soil, natural water, plants) with arterial hypertension (AH) incidence among the population living in the territory of the plain Dagestan (Babayurtovsky, Kizlyar, Tarumovsky and Nogai districts of the Republic). material and Methods. To assess the development of hypertension, the data were obtained from the medical information center of the Ministry of Health of Dagestan. Samples of soil, water, plants with the determination of the magnesium content in them were processed by the photometric method in the biogeochemical laboratory of the Prikaspiyskiy Institute of Biology Resources of Daghestan Scientific Centre of the Russian Academy of Sciences. For analyzes, the material was selected in the summer months. The correlation coefficients are calculated by Pearson. Results. When comparing the incidence rates of AH for 2005-2007 with the magnesium content in soils, natural waters, plants, a negative average correlation of magnesium concentration in the study sites with the incidence of AH population was established in the study area. A number of patients in the studied years was also noted to be changing, but the dependence of the incidence of AH of the population on the magnesium content in the biosphere objects is preserved. Conclusions. One of the factors of occurrence and course of hypertension is the magnesium status of the population, which depends on the geochemical features of the territory. As a result of the study, it was found that the higher the magnesium content in biosphere objects, the lower the incidence of AH population. In order to reduce the AH values among the population, it is necessary to correct the lack of magnesium in the human body with magnesium additives, which contribute to the regulation of blood pressure and reduce the risk of cardiovascular diseases. In connection with the possible subclinical magnesium deficiency, an important factor in informing about the possible morbidity of hypertension is information on the magnesium content in environmental objects.

scholarly journals Magnesium Metabolism of Human and Rabbit Erythrocytes

Blood ◽  
1962 ◽  
Vol 20 (6) ◽  
pp. 722-729 ◽  
Author(s):  
STANLEY GINSBURG ◽  
JAMES G. SMITH ◽  
FREEMAN M. GINSBURG ◽  
JACQUELINE Z. REARDON ◽  
JERRY K. AIKAWA
Keyword(s):  
Bone Marrow ◽  
Serum Magnesium ◽  
Ammonium Phosphate ◽  
Magnesium Content ◽  
Peripheral Circulation ◽  
Precipitation Method ◽  
Magnesium Concentration ◽  
Experimental Production ◽  
Magnesium Ammonium Phosphate

Abstract A modification of the magnesium ammonium phosphate precipitation method for the determination of serum magnesium was devised to determine the magnesium content of erythrocytes. The concentration of magnesium in the red cells of healthy hospital personnel was 4.67 ± 0.92 mEq./L. An increase in erythrocyte magnesium concentration was observed in patients with reticulocytosis. Experimental production of reticulocytosis by the administration of phenylhydrazine to rabbits confirmed these clinical observations. No significant in vitro uptake of Mg28 from the suspending medium occurred in mature human erythrocytes or in mature or immature erythrocytes from rabbits. The relative tissue uptake of Mg28 in the bone marrow was significantly increased in animals in whom anemia and marked reticulocytosis were produced by phenylhydrazine. Relative activity was decreased in the hearts, spleens, and kidneys of these animals. Since there is no evidence for significant exchange of magnesium in immature or mature erythrocytes in the peripheral circulation, it is concluded that the magnesium content of erythrocytes is increased in the bone marrow prior to their release into the peripheral circulation.

Free magnesium concentration in isolated rabbit hearts subjected to high dose isoproterenol infusion: a 31P NMR study

1997 ◽  
Vol 75 (8) ◽  
pp. 1015-1021 ◽  
Author(s):  
I. Mottet ◽  
J.-F. Goudemant ◽  
M. Francaux ◽  
R. Demeure ◽  
X. Sturbois
Keyword(s):  
Magnesium Concentration ◽  
High Dose ◽  
Nmr Study ◽  
Free Magnesium ◽  
Isoproterenol Infusion

scholarly journals Strophanthidin-sensitive sodium fluxes in metabolically poisoned frog skeletal muscle.

1976 ◽  
Vol 68 (4) ◽  
pp. 405-420 ◽  
Author(s):  
B G Kennedy ◽  
P De Weer
Keyword(s):  
Skeletal Muscle ◽  
Membrane Potential ◽  
Human Erythrocyte ◽  
Sodium Pump ◽  
Giant Axon ◽  
Squid Giant Axon ◽  
Frog Skeletal Muscle ◽  
Na Efflux ◽  
Unidirectional Fluxes ◽  
External K

Strophanthidin-sensitive and insensitive unidirectional fluxes of Na were measured in fog sartorius muscles whose internal Na levels were elevated by overnight storage in the cold. ATP levels were lowered, and ADP levels raised, by metabolic poisoning with either 2,4-dinitrofluorobenzene or iodoacetamide. Strophanthidin-sensitive Na efflux and influx both increased after poisoning, while strophanthidin-insensitives fluxes did not. The increase in efflux did not require the presence of external K but was greatly attenuated when Li replaced Na as the major external cation. Membrane potential was not markedly altered by 2,4-dinitrofluorobenzene. These observations indicate that the sodium pump of frog skeletal muscle resembles that of squid giant axon and human erythrocyte in its ability to catalyze Na-Na exchange to an extent determined by intracellular ATP/ADP levels.

Sign in / Sign up

Export Citation Format

Share Document