High Levels Of Mg Research Articles

Highly purified sarcoplasmic reticulum vesicles are devoid of Ca 2+-independent (‘basal’) ATPase activity

On solubilization with Triton X-100 of sarcoplasmic reticulum vesicles isolated by differential centrifugation, the Ca 2+-ATPase is selectively extracted while approximately half of the initial Mg 2+-, or ‘basal’, ATPase remains in the Triton X-100 insoluble residue. The insoluble fraction, which does not contain the 100 000 dalton polypeptide of the Ca 2+-ATPase, contains high levels of cytochrome c oxidase. Furthermore, its Mg 2+-ATPase activity is inhibited by specific inhibitors of mitochondrial ATPase, indicating that the ‘basal’ ATPase separated from the Ca 2+-ATPase by detergent extraction originates from mitochondrial contaminants. To minimize mitochondrial contamination, sarcoplasmic reticulum vesicles were fractionated by sedimentation in discontinuous sucrose density gradients into four fractions: heavy, intermediate and light, comprising among them 90–95% of the initial sarcoplasmic reticulum protein, and a very light fraction, which contains high levels of Mg 2+-ATPase. Only the heavy, intermediate and light fractions originate from sarcoplasmic reticulum; the very light fraction is of surface membrane origin. Each fraction of sarcoplasmic reticulum origin was incubated with calcium phosphate in the presence of ATP and the loaded fractions were separated from the unloaded fractions by sedimentation in discontinuous sucrose density gradients. It was found that vesicles from the intermediate fraction had, after loading, minimal amounts of mitochondrial and surface membrane contamination, and displayed little or no Ca 2+-independent basal ATPase activity. This shows conclusively that the basal ATPase is not an intrinsic enzymatic activity of the sarcoplasmic reticulum membrane, but probably originates from variable amounts of mitochondrial and surface membrane contamination in sarcoplasmic reticulum preparations isolated by conventional procedures.

Trace metal interactions in corn inbreds differing in efficiency of Mg uptake

Abstract The Mg‐efficient corn (Zea mays L.) inbred B57 and the Mg‐inefficient inbred Oh40B were grown in solution culture with moderate levels of some trace metals to test their relative interactions since previous studies had indicated that excess trace metals may be part of the Mg‐inefficient syndrome. At the levels used only Co depressed yields and that for the Mg‐inefficient inbred only. Distribution of minerals in the plants was mostly as reported in the literature. At both a high and low level of Mg, Mg concentration was lower in the shoots of the Mg‐inefficient inbred than in the efficient one. In roots the reverse held especially at the low Mg level. The P concentration was higher in both roots and shoots of the inefficient inbred. The Zn was always higher in the inefficient inbred and this was more pronounced for roots than for shoots. Such effects with Mn were even more pronounced. Where extra Cu was supplied less was associated with roots of the inefficient inbred than with the efficient. When...

Relative Requirements for Magnesium of Protein and Chlorophyll Synthesis in Euglena gracilis

The relationships among Mg, growth, chlorophyll synthesis, and cytoplasmic polysome content were studied in Euglena gracilis grown in different levels of the metal. At all levels of magnesium from 20 to 1,600 mumolar, both protein and chlorophyll are formed with exponential kinetics. The apparent rates of synthesis and final yields of both components are greater at higher levels of Mg, but the rate of chlorophyll synthesis always exceeds the rate of protein formation; i.e. the most severely deficient cells contain proportionally more chlorophyll than the sufficient cells. Cytoplasmic polysomes isolated from Mg-deficient Euglena are indistinguishable from those isolated from control cells. We conclude that decreased rates of protein synthesis occur prior to and possibly are causal to decreased rates of chlorophyll synthesis, but that the mechanism of this inhibition remains unclear.

Magnesium-phenethylbiguanide competition in Mg 2+-depleted hepatic mitochondria

Guinea pig liver mitochondria 40–70 per cent depleted of magnesium are three times more sensitive to phenethylbiguanide inhibition of state 3 respiration than are comparable controls. Similar results are obtained whether the depletion is accomplished by the divalent cation ionophore A23187 or by incubation with inorganic phosphate. In contrast to controls, inhibition in Mg-depleted mitochondria is competitively reversed by Mg 2+. These phenomena are observed with NAD + -linked substrates, stimulated by either ADP or Ca 2+, but not with succinate. The Mg-depleted mitochondria can be restored to the normal degree of phenethylbiguanide sensitivity by incubation with high levels of Mg 2+ followed by washing. As in controls, phenethylbiguanide inhibition in Mg-repleted mitochondria is not reversed by Mg 2+. These results suggest a dual action of Mg 2+: (1) a structural role of bound magnesium which regulates the activity of cation transporters, and (2) competition between Mg 2+ in solution and guanidinium derivatives for a cation carrier.

Cyclic nucleotide-dependent protein kinase activity of adult female locust fat body

Locust fat body protein kinase is dependent on, and maximally stimulated by 5 × 10 −6 M cyclic GMP and to a lesser extent by cyclic AMP. It exhibits a pH optimum of 6.9, an unusual requirement for high Mg 2+ (maximum at 100 mM) or an alternative requirement for Mn 2+ (maximum at 5 mM). Maximal stimulation by Mg 2+ is twice that by Mn 2+. Rabbit muscle protein kinase inhibitor uncharacteristically inhibits both cyclic AMP and cyclic GMP stimulated protein kinase activity of locust fat body, the former 5-fold more than the latter, with histone IIA as acceptor. The degree of phosphorylation differs for different acceptor proteins: histone IIA > locust vitellin > arginine-rich histone. Casein is barely phosphorylated and bovine serum albumin (fraction V) not at all. The high threshold for Mg 2+ activation may be related to the high levels of Mg 2+ in locust haemolymph, to the preferential phosphorylation of vitellin, and to the fact that the fat body is the site of vitellogenin synthesis.

キャベツ栄養におけるマグネシウムとカルシウムの相互作用について

Cabbage plants were water-cultured under a combination of 4 levels of magnesium (0, 5, 25, 125ppm) and calcium (4, 20, 100, 500ppm), and the effect of the elements supplied on the growth and nutrient status of the plants was studied.The dry weight of a whole plant (plant-top+roots) and inner leaves increased with increasing levels of Mg from 0 to 125ppm when the concentration of Ca in the culture solution was high, whereas it decreased at higher levels of Mg when the concentration of Ca was low. The contents of Mg and Ca in the plants increased with increasing levels of each element, and an increase in the content of one element caused a decrease in the content of the other element. The plants high in Mg or Ca were liable to suffer from deficiency injury involving Ca or Mg. The critical contents of Mg and Ca in outer leaves resulting in deficiency injury were about 0.1 and 1.3% on a dry matter basis, respectively.A suitable range of the Ca/Mg content ratio as well as adequate contents of Mg and Ca in each organ is considered to be favorable for the growth of cabbage plants.

Isolation and characterization of cytoplasmic and chloroplastic ribosomes and their ribosomal RNAs from the diatom Cylindrotheca fusiformis.

The cytoplasmic and chloroplast ribosomes from the marine diatom Cylindrotheca fusiformis were isolated and characterized. The cytoplasmic ribosomes sedimented in sucrose at 84S and dissociated into subunits of 64S and 42S in the absence of Mg2+. It contained ribosomal RNAs with molecular weights of 1.31 X 10(6) and 0.70 X 10(6). The chloroplast ribosomes sedimented at 70S only in the presence of high Mg2+ concentrations (25-100 mM). No stable subunits were routinely observed and at very high levels of Mg2+ (greater than 100 mM) the 70S species was converted to a form sedimenting at 55S. At 4 degrees C ribosomal RNAs with molecular weights of 1.1 X 10(6) and 0.40 X 10(6) were detected on polyacrylamide gel electrophoresis. When the RNAs were resolved at room temperature the large molecular weight component disappeared while RNA with molecular weights of 0.65 X 10(6) and 0.53 X 10(6) were observed. Apparently the large chloroplast RNAs dissociated into two pieces of unequal molecular weight. These properties of the diatom's chloroplast ribosomes are very similar to those of the counterparts in unicellular green algae, which suggests that both types of algae have a common phylogenetic ancestor.

The Response of Serpentine and Non-Serpentine Agrostis Stolonifera to Magnesium and Calcium

Serpentine soils often support a sparse and unusual vegetation, the cause of which has been variously attributed to low nutrient levels, high concentrations of heavy metals and an unusually low Ca/Mg ratio. Proctor & Woodell (1975) have provided a recent review of the literature on the ecology of these soils. The present paper is concerned with the adaptations of two races of Agrostis stolonifera L. to a low Ca/Mg ratio in two European serpentine soils. American workers, most recently Madhok & Walker (1969) and Main (1970, 1974), have observed the growth of plants in culture media in which the levels of Ca and Mg have been varied. Madhok & Walker showed that a species endemic to serpentine sites, Helianthus bolanderi Gray ssp. exilis Heiser, could tolerate higher levels of Mg in the culture solutions than a non-serpentine species Helianthus annuus L. The non-serpentine species tended to absorb much more Mg than the serpentine species and they postulated that this 'luxury consumption' of Mg was toxic to the plant. They also showed that the serpentine species contained more Ca in the shoots than the non-serpentine species. Main (1970, 1974) obtained similar results and demonstrated 'luxury consumption' of Mg in a non-serpentine race of Agropyron spicatum (Pursh) Scribn. and a tolerance to high Mg levels in a serpentine race of the same species and also in Poa curtifolia Scribn., a species endemic to serpentine sites. The serpentine race and endemic species also showed a higher Ca uptake. Both Madhok & Walker and Main showed that the serpentine plants required a higher level of Mg in the culture solutions to obtain maximum growth than non-serpentine control plants. For example Madhok & Walker found that the nonserpentine species, H. annuus, reached maximum growth when a 2 mM Mg solution was supplied compared to the serpentine endemic species H. bolanderi ssp. exilis which required a 10 mM solution of Mg. Moreover the serpentine species had a higher Mg concentration in its tissues at the point of maximum growth (17-0-27-0 m-equiv./100 g) compared to that of the non-serpentine species (9-0-15-0 m-equiv./100 g). There is a shortage of similar work on European serpentine plants. Recent analyses of plants and soils from European serpentine sites by Johnston (1974) and Shewry & Peterson (1975) have shown that species differ in the amounts of Mg and Ca taken up from the soil. This may indicate that different tolerance or exclusion mechanisms occur in different species, although the authors attempted no experimental work on the species which they analysed. We have investigated the Ca and Mg nutrition of races of Agrostis stolonifera from two serpentine soils, at Kittelfjall, Sweden (Latitude c. 65?N, Longitude 15?45'E) and the Keen of Hamar, Unst, Shetland (Latitude c. 60?50'N,

Magnesium in New Zealand Soils

Abstract A cation exchange resin method, that had previously been developed for the determination uf non-exchangeable K (resin K), was applied to the determination of non-exchangeable Mg (resin Mg). An analysis of variance on the reproducibility of the method showed it to be somewhat variable, with a CV of 11%. A regression line, comparing the results given by an acid-extraction method for non-exchangeable Mg (reserve Mg) with those from the resin method, was curved, the resin method giving lower values for higher reserve Mg levels. Regression lines for reserve Mg on total Mg and resin Mg on total Mg were both linear. The resin method was shown to underestimate non-exchangeable Mg levels when these exceeded approximately 40 me./100 g, and this produced the curvature in the reserve Mg : resin Mg regression line. High levels of non-exchangeable Mg were also found to affect the adsorption of K by the resin, leading to anomalous resin K values. The method offers a rapid and easy means of analysing a large number of samples for non-exchangeable Mg. It should not, however, be used for precise determinations or where non-exchangeable Mg levels could exceed 40 me./100 g.

Magnesium or calcium activated ATPase in mammalian nerve

Sciatic nerves from cat contain a relatively high level of Mg 2+ Ca 2+ activated ATPase (MgCa ATPase). The enzyme was found by subcellular fractionation to be present for the most part in the particulate fraction (61.5%) and to a lesser extent in the mitochondrial fraction (21.4%). The high speed supernatant fraction contains the least amount (7.6%). In decreasing order of effectiveness MgCa ATPase hydrolyzes ATP, GTP, UTP, ITP and CTP with ADP, UDP, IDP and CDP hydrolyzed to a small extent and neither AMP or cyclic AMP effective as substrates. The enzyme was activated either by Mg 2+ or Ca 2+ at an optimum concentration of3.0m M. It had a K m of 4.8 × 10 −4 with an optimum pH of 7.4. It was inhibited by mersalyl, PCMP, iodoacetate and dinitrophenol. Oligomycin did not block its action, nor did the mitotic blocking agents colchicine and vinblastine to any great extent. Approximately 54% of the enzyme present in the particulate fraction could be solubilized by Triton X-100, and a molecular weight of 150,000 was tentatively assigned to it on the basis of Sephadex G-200 gel filtration. The enzyme is carried down within nerve fibers by slow axoplasmic transport as shown by its accumulation over a period of 5–30 days above ligations made in cat sciatic nerves.

Diet and mineral nutrition of sheep on undeveloped and developed tussock grassland

Abstract Na, K, Ca, Mg, P, Fe, Mn, Zn, and Cu levels in the plasma of sheep set stocked on undeveloped and developed tussock grassland are given for 5 sampling dates during one season together with those for 10 plant species common on these blocks. The mean plasma Cu levels were significantly lower on the developed than on the undeveloped block, but were still within the normal range. Seasonally the plasma K and Ca levels were lowest at the November 1970 and February 1971 samplings, and P and Zn were lowest at the September 1970 sampling. The dicotyledonous plants contained higher levels of Na, Ca, Mg, and Cu than the grasses. The two native tussocks had the lowest levels. The P levels of Hieracium praealtum were lower, and the K, Mg, P, Fe, and Zn levels of Notodanthonia clavata and the Mn levels of Anthoxanthum odoratum were higher, on the developed block than on the undeveloped block. This was reversed for Mn levels in Agrostis tenuis and Fe content of A. odoratum. There were differences between sites ...

Direct potentiometric determination of fluorine in water after 8-hydroxyquinoline extraction

A rapid method for fluoride determination in natural and waste water with a fluoride ion-specific electrode is described. This method involves a preliminary extraction of the interfering polyvalent cations, as their 8-hydroxyquinoline complexes, into a butyl cellosolve-chloroform mixture. The procedure is directly usable for water samples containing fluoride in the 0.2–6.0 p.p.m. range, with an overall error of less than 0.5%. The method can be successfully employed for fluoride determination in most polluted water samples which contain a high level of Ca, Mg, Fe and Al ions.

The effect of magnesium and fluoride on bone pyrophosphatase activity.

SummaryThe addition of Mg ions to bone homogenates stimulated pyrophosphatase activity in the absence of F ions, but inhibited pyrophosphatase activity in the presence of F ions. However, femur pyrophosphatase levels were increased in chicks fed diets containing high levels of both Mg and F for 3 or 6 days as compared with chicks fed diets containing identical levels of either element alone.

Adenosine Triphosphate: Uridine Monophosphate-Cytidine Monophosphate Phosphotransferase from Tetrahymena pyriformis

Abstract An enzyme that synthesizes uridine diphosphate from uridine monophosphate and adenosine triphosphate has been purified 300-fold from Tetrahymena pyriformis. The enzyme also converts cytidine monophosphate to cytidine diphosphate and deoxycytidine monophosphate to deoxycytidine diphosphate. The S0.5 was estimated to be 1.5 x 10-3 m for UMP and 0.74 x 10-3 m for CMP. The purified enzyme preparation is stable for at least 2 weeks at 4° when stored at a concentration of 0.2 mg of protein per ml; 3-fold dilution results in rapid inactivation. The enzyme is inhibited by CDP, UDP, and ADP, and by high levels of ATP or Mg++. Kinetic studies suggest that ADP inhibition is competitive with ATP, and that CDP and UDP compete with the analogous monophosphate substrates. It appears that there may be two binding sites for UMP, but that CMP may bind at only one of them.

Magnesium Nutrition of Two Species of Sunflower

Helianthus annuus L., the common cultivated sunflower, and Helianthus bolanderi Gray subspecies exilis Heiser, a form endemic on serpentine soils, were grown in culture solutions with widely varying Mg levels. For comparable development, H. bolanderi exilis required higher levels of Mg in the solution than H. annuus, both in the range of visual deficiency symptoms and in higher ranges.With 0.5 mm Ca in the solutions, H. annuus reached a plateau in yield in the range of 0.25 to 2.0 mm Mg in the solution, then declined in weight markedly as Mg was increased further. This decline was probably caused by the marked "luxury" consumption of Mg. Conversely, H. bolanderi exilis increased steadily in yield as Mg was raised up to 10 mm and tolerated up to 50 mm Mg in the solution with only about 30% decline in yield. The increasing yield of H. bolanderi exilis in solutions of increasing Mg level is attributable to the steadily rising Mg content of the plants. A high level of external Mg is apparently needed to bring internal Mg to the sufficiency range. This characteristic of the species also serves to obviate luxury consumption of Mg, thus contributing to its tolerance of very high external levels of this ion.

Magnesium‐Phosphorus Interrelationships in Tomatoes

AbstractTomato (Lycopersicon esculentum) plants were grown in nutrient solution with Mg levels which varied from 0.96 ppm to 96 ppm and with P levels of 5 and 31 ppm. At low levels of Mg better growth was obtained when the P level was low. At high levels of Mg better growth was obtained when the P level was high. A nutrient solution containing 96 ppm of Mg promoted plant growth when the P concentration was 31 ppm but reduced growth when the P concentration was 5 ppm. Phosphorus fertilization of tomatoes grown on clay soils reduced the Mg content of the leaves from 1.2 to 0.65%. Analysis of leaves of commercial tomato fields during the late bloom stage showed a negative relationship between Mg and P (r = —0.896).

Plaque Enhancement of Newcastle Disease Virus (Lentogenic Strains) by Magnesium and Diethylaminoethyl Dextran

This report describes a reproducible plaque assay for lentogenic strains of Newcastle disease in primary cultures of chick embryo fibroblasts (CEF). The conditions required for this test are: 1) a suitable agar overlay medium; 2) high levels of Mg++; 3) use of solidifying agents with low-sulfated polysaccharides; and 4) high concentration of diethylaminoethyl (DEAE) dextran. The importance of divalent cations in the attachment of phages to the bacterial host cell was established by Puck and co-workers (5,6,10). More recently, a number of investigators (4,15,16,17,18) have reported the enhancement of rhinovirus and enterovirus plaque formation by increased Mg+ . DEAE dextran has been found to prevent or reverse the inhibitory effects of sulfated polysaccharides from agar (2,4,8,14) and to facilitate the uptake of viral ribonucleic acid (11) or complete virus particles (7) by cells in tissue culture.

73 The In Vitro Control of Calcification in Osteogenesis Imperfecta

Previous work has implicated bone collagen obtained from patients with osteogenesis imperfecta as a potent inhibitor of the in vitro formation of bone mineral. The present investigation further examines the mechanism of inhibition and suggests a possibility for therapy. It was observed that the citrate-soluble fraction of bone collagen from two patients with the disease had a pyrophosphate content of 1.4 μm/mg collagen which is four times the normal value. Urinary excretion of pyrophosphate was also elevated. As pyrophosphates are thought to be inhibitors of calcification both in vitro and in vivo (FLEISCH, H. et al. Nature 212: 903-3 [1966].), the abnormal collagen was treated with the enzyme pyrophosphatase in the presence of Mg as cofactor during the in vitro mineralization procedure. It was found that Mg alone significantly increased the catalytic properties of osteogenesis imperfecta collagen and this effect was doubled when pyrophosphatase was present. These results suggest that collagen-bound pyrophosphate is partly responsible for the failure of bone matrix to calcify. The possibility that these patients need a high level of Mg as cofactor for their pyrophosphatase activity is being investigated. (Supported by U.S.P.H.S. AM 08757–03) (SPR).

Effect of Nitrogen, Potassium, Calcium, and Magnesium on Mineral Composition of Lakeland Fine Sand in Relation to Mineral Content of Tung Leaves

AbstractEight‐year‐old tung trees growing on Lakeland fine sand were treated from 1949 to 1955 with factorial combinations of 3 sources of N and 2 levels each of N, K, Ca, and Mg. Soil samples collected in October 1954 showed that exchangeable K was increased to a depth of 36 inches (lowest depth sampled) by the high level of applied K, but was reduced by the high level of Mg. Exchangeable Ca was increased by the high level of Ca, but was reduced by the high level of K or Mg. Exchangeable Mg was increased by the high level of Mg in the 0‐ to 6‐inch depth only. Below 6 inches, it was reduced by the high level of K or Mg.The chemical analyses of leaves collected in 1955 show the same general trends as those found in the soil. The polynomial equations of degrees n = 1, 2, 3, and 4 were calculated for the regression of the concentration of K, Ca, and Mg in the leaves on saturation percentage of these elements in the soil. The linear equation for K was significant for each soil depth and the equations of higher degree show no significant improvement. The linear equations for Ca were significant at all depths, but the second‐degree equations were an improvement on the linear in the top 18 inches of soil. The linear equations for Mg were significant in the top 18 inches of soil. The second‐degree equations were an improvement on the linear in the 6‐ to 12‐ and 12‐ to 18‐inch depths.