Showing papers in "Magnesium Research in 1990"

New experimental and clinical data on the relationship between magnesium and sport.

Abstract: Exercise under certain conditions appears to lead to Mg depletion and may worsen a state of deficiency when Mg intake is inadequate. Whereas hypermagnesaemia occurs following short term high intensity exercise as the consequence of a decrease in plasma volume and a shift of cellular magnesium resulting from acidosis, prolonged submaximal exercise is accompanied by hypomagnesaemia. Discordant findings on the effect of physical exercise on erythrocyte concentrations have been reported. A mechanism for the observed decrease in plasma magnesium concentration after long term physical exercise could be a shift of Mg into the erythrocyte. However, in several studies the decrease in plasma Mg was not accompanied by an increase in RBC Mg, but a decrease in cellular Mg was observed. Urinary Mg losses during an endurance event could play a role in this depletion but are often reduced, reflecting renal compensation. Loss of Mg by sweating takes place only when there is a failure in sweat homeostasis, a situation which arises when exercise is made in conditions of damp atmosphere and high temperature. Stress caused by physical exercise is capable of inducing Mg deficit by various mechanisms. A possible explanation for decreased plasma Mg concentration during long endurance events is the effect of lipolysis. Since fatty acids are mobilized for muscle energy, lipolysis would cause a decrease in plasma Mg. In developed countries Mg intake is often marginal and sport is a factor which is particularly likely to expose athletes to Mg deficit through metabolic depletion linked to exercise itself, which can only aggravate the consequences of a frequent marginal deficiency. Mg depletion and deficiency therefore play a role in the pathophysiology of physical exercise. Experiments on animals have shown that severe Mg deficiency reduces physical performance and in particular the efficiency of energy metabolism. These data, however, do not correspond to those of marginal deficiency most commonly observed in humans. Clinical symptomatology, both in athletes and in other patients, is dominated by the symptomatology of neuromuscular hyperexcitability. Medical authorities in sport have enforced obligatory tests for latent tetany in athletes, with ionic assessment. The effects of the correction of magnesium deficiency are judged from clinical signs, Chvosteck sign, electromyogram and echocardiogram findings and plasma Mg, erythrocyte and urine analysis. These may also be complemented by cardiac and respiratory investigations after exercise. The positive effects (analysis after a minimum period of one month) of a simple oral supplement administered in physiological doses (5 mg/kg body weight/day) provides evidence for the existence of a deficiency.(ABSTRACT TRUNCATED AT 400 WORDS)

Increased need for magnesium with the use of combined oestrogen and calcium for osteoporosis treatment.

Abstract: Prophylactic treatment of postmenopausal osteoporosis with oestrogen and calcium, often in combination, disregards the likelihood that an excess of each agent may increase magnesium requirements and decrease serum Mg levels. Relative or absolute Mg deficiency, which is likely in the Occident where the Mg intake is commonly marginal, can militate against optimal therapeutic bone response, Mg being important for normal bone structure, and can increase the risk of adverse effects. Although oestrogen has cardiovascular protective effects (expressed by the lower incidence of heart disease in premenopausal women than in men, and also in postmenopausal women given low dosage oestrogen replacement treatment), high dosage oestrogen oral contraceptives have caused increased intravascular blood clotting with resultant thromboembolic cardio- and cerebrovascular accidents. This might be contributed to by the oestrogen-mediated shift of circulating Mg to soft and hard tissues, which in persons with marginal Mg intakes may lead to suboptimal serum levels. If the commonly recommended dietary Ca/Mg ratio of 2/1 is exceeded (and it can reach as much as 4/1 in countries with low to marginal Mg intakes), relative or absolute Mg deficiency may result, and this may increase the risk of intravascular coagulation, since blood clotting is enhanced by high Ca/Mg ratios. Mechanisms by which Ca activates the various steps in blood coagulation that are also stimulated by oestrogen are considered here, as are the multifaceted roles of Mg that favourably affect blood coagulation and fibrinolysis, through its activities in lipoprotein and prostanoid metabolism.

Pharmacological and physiological effects of magnesium on experimental traumatic brain injury.

Abstract: It is now generally accepted that in addition to mechanical or primary injury to the central nervous system (CNS) resulting from a traumatic event, much of the irreversible neural injury occurring after CNS trauma is caused by secondary factors. One of the secondary injury factors implicated in the development of irreversible tissue injury, and associated mortality and morbidity after neurotrauma, is magnesium. This review focuses on recent evidence suggesting that magnesium plays a critical role in the injury process, not only by having direct effects on cellular metabolism, but also by regulating other proposed secondary injury factors such as excitatory amino acids, calcium, lipid hydrolysis, opioid peptides, and energy metabolism. Treatments that have a demonstrated neuroprotective effect following neurotrauma are shown to restore brain cellular magnesium homeostasis after injury.

Magnesium depletion and pathogenesis of Alzheimer's disease.

Abstract: Mg depletion, particularly in the hippocampus, appears to represent an important pathogenic factor in Alzheimer's disease. It is associated with high aluminium incorporation into brain neurones. This type of Mg deficit cannot respond to mere Mg supplementation, but requires correction of the dysregulation inducing this Mg depletion. Further research should seek to control the alterations of albumin, which may induce this brain Mg depletion.

Magnesium metabolism in chronic renal failure.

Abstract: Renal excretion is the major route of magnesium elimination from the body and a positive magnesium balance would be expected under conditions of renal insufficiency. However, a compensatory decrease in tubular reabsorption is operating to maintain an adequate urinary magnesium excretion even when glomerular filtration rates are very low. Nevertheless, in end-stage renal disease, the limited ability of the kidney to excrete an increased magnesium load may result in toxic concentrations of the ion in serum. While magnesium intoxication is a real hazard when magnesium-containing drugs are given, magnesium balance may be normal or even decreased in uraemic patients. This is usually due to decreased dietary intake combined with the impaired intestinal magnesium absorption which characterizes chronic renal failure. Impairment of magnesium absorption seems to be related to deficient synthesis of the active metabolite of vitamin D by the non-functioning kidney. Following the institution of chronic haemodialysis or continuous ambulatory peritoneal dialysis (CAPD) treatment, the major determinant of magnesium balance is the concentration of magnesium in the dialysate. Changes in the dialysate magnesium have been used to reduce the incidence of renal osteodystrophy, to alleviate uraemic pruritus, or to retard the development of arterial calcification in chronic renal disease. However, uncertainty about magnesium, calcium and parathyroid hormone relationships in renal failure makes a reasoned approach to such manipulations extremely difficult.

Possible role of water structure in biological magnesium systems.

Abstract: Magnesium chloride-water solutions have been studied by Fourier Transform Infrared Spectroscopy (FT-IR) in the near infrared region, 5000-10,000 cm-1. The effect of the concentration of magnesium chloride and temperature on the solutions has been studied from the spectra and it is concluded that magnesium chloride modifies the structure of the bulk water. The important absorption bands of water at 5200 and 7020 cm-1 may be assigned to combination vibrations and overtones. They are shifted either by increasing the magnesium chloride concentration or the temperature. The hydrated magnesium ions, [Mg(H2O)6]2+, will most probably break important hydrogen bonds in the clusters of water (H2O)n, where n = 2, 3, 4, 5, 6.../forming new hydrogen bonds in the presence of hexa-aquated magnesium cations. FAB mass spectra also suggest the formation of hydrated magnesium cations, Mg (H2O)6(2+).

Correlation between bone magnesium concentration and magnesium retention in the intravenous magnesium load test.

Abstract: It has been suspected that Mg retained in the Mg load test is retained in bone--in both hypomagnesaemic and normomagnesaemic Mg deficiency. Bone Mg concentration was therefore compared to the percentage retention of an intravenously administered load of Mg in normomagnesaemic patients at high risk for Mg deficit. We found that the lower the bone Mg concentration the higher the Mg retention in the Mg load test.

Historical review of the effects of marginal intake of magnesium in chronic experimental magnesium deficiency.

Abstract: After the discovery of magnesium as an essential nutrient in 1926, research focused upon the identification of effects of an acute deficiency state and determination of the requirement for the mineral for normal growth and reproduction. In this early work, marginal intakes of magnesium were reported to result in alterations of tissue composition. Since the 1970s, research has shown that the ability to adapt to a marginal intake of magnesium, which is commonplace in developed countries, is limited. In fact, a low intake of the mineral for an extended period of time may be associated with abnormalities in reproduction, growth, and development and may be a factor in the pathogenesis of disorders of neuromuscular, cardiovascular, renal, and immune function. Problems related to the use of pharmacological agents or to trace metals, such as aluminium, may be worsened in the presence of a low intake of magnesium. Evidence presented illustrates that, although physical signs of magnesium deficiency may be absent, that is to say in cases of latent clinical forms, a marginal dietary inadequacy of the mineral over a long period of time could result in significant problems.

Impact of magnesium supplementation on performance data in young swimmers.

Abstract: We examined whether healthy young swimmers improved performance during emotional and physical stress testing in the laboratory or during competition. Twenty four well trained healthy Caucasian pupils (14 boys and 10 girls, means = 16 years) were randomly treated either with 20 mmol Mg-aspartate-HCl/d or placebo for 3 months. After Mg supplementation serum Mg increased from 0.85 +/- 0.03 to 0.89 +/- 0.06 mmol/litre (P less than 0.05). Mg in red blood cells remained unchanged (4.79 +/- 0.35 mmol/kg dry weight before supplementation and 4.96 +/- 0.27 three months later, P = 0.32) whereas no increase in serum Mg or Mg in red blood cells was found in subjects who received placebo. Student's t test and analyses of variance revealed no significant differences in performance data either in the laboratory or during competition after supplementation with Mg.

Soft tissue calcification treated with local and oral magnesium therapy.

Abstract: Eighty patients with soft tissue calcification were treated: 24 suffered from myositis ossificans traumatica, 23 from calcific bursitis (Duplay's disease), six from osteoarthropathy of elbow joint after severe craniocerebral trauma, nine from calcification around the elbow joint after local trauma, 13 from calcification around the hip joint, and five from calcification in ligaments and tendons. Using a new method of treatment about 75% of patients were cured. Calcifications disappeared or diminished substantially. Very good functional improvement followed in affected joints. The treatment involved local application of MgSO4 under local anaesthesia into calcified areas for 2-20 weeks, together with peroral administration of Mg lactate for 4-6 months. There were no complications or side effects of this treatment.

Angiotensin converting enzyme inhibitors, thiazide diuretics and magnesium balance. A preliminary study.

Abstract: Serum and mononuclear cell magnesium content were determined in a cross-sectional study performed in four groups of hypertensive patients on chronic treatment with atenolol (n = 11), enalapril (n = 10), thiazide diuretics (n = 12), or enalapril + thiazides (n = 11). Our study shows that in patients treated with the thiazides alone, in spite of normal serum potassium and magnesium levels, mononuclear cell magnesium was decreased. To the extent that mononuclear Mg content mirrors the body ion stores, our results indicate that thiazides induce a Mg depletion not detectable by monitoring serum levels.

Magnesium and potassium status in elderly subjects with and without dementia of the Alzheimer type.

Abstract: Magnesium status was evaluated in healthy elderly people, and in patients affected from dementia of the Alzheimer type. Magnesium levels were determined in plasma, erythrocytes (RBC), lymphocytes (MNC), and granulocytes (PMN), and were compared with measurements in young healthy adults. Significantly lower plasma Mg concentrations were found in elderly people compared to controls, with no difference between cognitively normal and demented subjects. Mg levels in healthy elderly people were higher in MNC and lower in PMN, compared to the younger group. No difference was observed between demented patients and young controls in Mg content of white blood cells, but the patients had higher Mg/K ratios. In addition, significant correlations were found between cognitive impairment and the Mg/K ratio in MNC. When we assessed the philothermal response of granulocytes, a significant correlation was observed in demented subjects between the migration rate of PMNs and the PMN Mg/K ratio.

Routine serum magnesium determination: a contemporary clinical imperative.

Abstract: Identification of hypomagnesaemia or hypermagnesaemia is presently the most expeditious method of clinically identifying perturbations in Mg metabolism. Clinicians may overlook as much as 90% of clinical hypomagnesaemia and hypermagnesaemia when serum Mg is determined on order versus on a routine basis. Routine serum Mg determination will facilitate management of digitalis toxicity in patients who are not currently identified as being hypomagnesaemic as well as preventing the occurrence of refractory K repletion. In our opinion routine serum Mg determination represents a clinical need which has not been addressed to date.

Magnesium: a competitive inhibitor of lead and cadmium. Ultrastructural studies of the human amniotic epithelial cell.

Abstract: The measure of the ratio between the volume of intercellular space (R1), the microvilli (R2), and the podocytes (R3) versus the cell volume indicates the effect of lead (Pb) and cadmium (Cd) on the ultrastructure of the human amniotic epithelial cell. Cd decreased R1 significantly, increased R2 and had no effect on R3. Pb had no effect on R1 or R3 but decreased R2 significantly. The addition of Mg chloride to the bathing medium antagonized the effect of Cd on the intercellular spaces and podocytes. The antagonistic effect of Mg on Pb was observed only on microvilli. These results are consistent with the data obtained with electrophysiological studies which show that Mg is a competitive inhibitor of Pb and Cd.

Comparative study of effects of magnesium and taurine on electrical parameters of natural and artificial membranes. VII. Effects on cellular and paracellular ionic transfer through isolated human amnion.

Abstract: The comparative effects of 2 mM magnesium and taurine on various components of the human transamniotic conductance, Gt, were observed. The use of both microelectrodes and metabolic inhibitors enables 10 components of Gt to be distinguished: six cellular components (Na-K ATPase, Na-H antiport, Na-K-2Cl cotransport and Na, K, Cl channels), one coupling component, and three paracellular components (Na, K, Cl). Mg increased all components of Gt while taurine only increased five of them (Na and K channels, coupling, Na and K paracellular conductance). A potentiometric effect of taurine on Mg2+ modified membrane, obtained on paracellular components, was not measured on cellular components. There was only a vicarious effect between Mg and taurine on the non-enzymatic cellular and paracellular transfer of Na and K.

Nephrocalcinosis without functional renal impairment in rats subjected to subacute moderate magnesium deficiency, and intervention studies on the mobilization of calcium deposits.

Abstract: Female Sprague-Dawley rats (100-120 g) were kept for 12 d on diets containing 250, 1500, or 9000 ppm Mg. Then subgroups were loaded with water, frusemide or magnesium and urine was collected over 6 h. Moderately Mg-deficient diet (250 ppm) induced moderate hypomagnesaemia (62.3% of controls), but did not result in hypercalcaemia or the formation of typical erythema. Nevertheless, pronounced nephrocalcinosis developed, as shown by increased renal wet and dry weight and elevated tissue concentrations of Ca, P and Mg, the calculous deposits probably consisting to a large extent of Ca3 (PO4)2. Despite these alterations, renal function remained unimpaired in Mg-deficient rats, as shown by normal urinary creatinine excretion and the unaffected ability of the kidneys to concentrate urine. Loading with water, frusemide or Mg increased urinary excretion of calcium in all three diet groups to a similar extent; hence no significant proof can be given that calculous deposits are mobilized under these conditions. Since comparable conditions may also be present under clinical conditions in man, special care should be given to maintain optimal Mg balance.

Deleterious effects of high magnesium diets and beneficial effects of high potassium diets in hypertensive stroke-prone rats.

Abstract: The effect of varying amounts of dietary magnesium (Mg) in conjunction with potassium (K) on hypertension and stroke mortality in hypertensive stroke-prone (SHRsp) rats was studied. These results show that high K (2.1%) diets strongly protect against stroke mortality and rises of blood pressure, while high Mg (0.26%) diets appeared to increase stroke mortality and accelerate the rise of blood pressure in SHRsp rats. Similarly, medium high (1.3%) levels of K in the diet significantly reduced blood pressure and stroke mortality but not nearly as much as the 2.1% K in the high K diet.

In vitro evidence for a relationship between magnesium and vitamin B-6.

Abstract: Vitamin B-6 and magnesium appear to interact in vivo and it has been suggested that vitamin B-6 may enhance transport or accumulation of magnesium in cells. The purpose of this study was to evaluate the possibility of the formation of B-6 vitamer-Mg complexes in vitro using spectrophotometric analysis of ultraviolet or visible spectra or change in fluorescence intensity of B-6 vitamers. Pyridoxal phosphate but not pyridoxal appears to form a complex with Mg as evidenced by a change in the ultraviolet and visible spectra with an increase in absorption and spectral shift in the visible maxima from 389 to 388 nm and a decrease in the ultraviolet absorption maxima at 296 nm. Addition of Mg to pyridoxal phosphate but not the other B-6 vitamers enhanced the fluorescent intensity of pyridoxal phosphate at least threefold and evoked a spectral shift in both the fluorescence excitation and emission maximum. Electrochemical titration of pyridoxal phosphate in the presence of Mg affects the pKa- of the phenolic hydroxyl and the secondary phosphate ionization. These data collectively indicate that pyridoxal phosphate, but not pyridoxal, appears to form a coordinated complex with Mg and the coordination site is likely to be related to the primary phosphate and aldehyde moiety of pyridoxal phosphate.

Magnesium pidolate in the treatment of seasonal allergic rhinitis. Preliminary data.

Abstract: This paper describes how the authors, after examining the calcium modulating action of the Mg ion and its antihistamine-like action, tested a salt containing Mg (Mg pidolate, MAG2) in the clinical treatment of seasonal allergic rhinitis. A total of 38 hayfever subjects were studied. They were given 1.5 g Mg salt three times a day for one month (oral MAG2 vials); placebo was used as a control in a randomized double-blind study. The efficacy of the product was assessed using the following criteria: intensity of rhinorrhoea, daily consumption of Kleenex tissues, number of sneezes in a day, intensity of lacrimation. The results were analysed using Student's t test and demonstrated the clinical efficacy of the product in the control of seasonal allergic rhinitis symptoms (P less than 0.001).

Effects of acute cisplatin administration on renal ATPase activities and magnesium excretion of rats.

Abstract: Male Wistar rats were killed 1, 2, or 4 days after a single intraperitoneal injection of cisplatin (5 mg/kg). Functional renal indices, enzymatic activities, and morphological variables were studied. One day after the injection, the treated group showed an increase in the magnesium and phosphate fractional urinary excretion (FE) vs the control group (FE Mg = 5.2 +/- SEM 0.5% vs 13.0 +/- 1.7%; P less than 0.01; and FE P = 4.7 +/- 0.7% vs 14.0 +/- 1.9%; P less than 0.01). Two days after cisplatin administration, a decrease in creatinine clearance of treated animals was found, to 0.33 +/- 0.03 vs 0.51 +/- 0.03 ml/min; P less than 0.05. Na-K-ATPase and ouabain-insensitive ATPase activities were studied in the proximal convoluted tubule, the medullary thick ascending limb of the Henle's loop (mTAL), and the distal convoluted tubule. Only in mTAL one day after the cisplatin injection was there a decrease in Na-K-ATPase activity in the treated group vs controls (1103 +/- 145 vs 1734 +/- 189 pmol Pi/mm.h; P less than 0.05). Morphological studies showed a decrease in mTAL diameters on day 1, and an increase in proximal convoluted tuble diameters at day 2 of treated rats vs controls, at 27.8 +/- 0.6 vs 31.4 +/- 0.7 microns; P less than 0.05, and 50.4 +/- 1.2 vs 47.4 +/- 0.2 microns; P less than 0.05 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of potassium and magnesium effluxes by external magnesium in barnacle muscle fibres.

Abstract: Fluxes and flux rate constants for potassium and magnesium were measured as a function of ambient magnesium concentration in giant muscle fibres from the acorn barnacle. Experiments were carried out in the absence of both external Na and Ca (to prevent possible effects of these ions), and fibres were depleted of internal Na and Ca by soaking in Na- and Ca-free solution before each experiment. K efflux was biphasic with respect to increases in external Mg concentration [( Mg+2]0). K efflux approximately doubled (from about 63 to 130 pmol/cm2.s) when [Mg+2]0 was increased from 2 to 5 mM; K efflux remained elevated in Mg up to 60 mM. However, at [Mg+2]0 = 120 mM, the stimulatory effect of external Mg vanished, and at 357 mM it was replaced by an inhibitory effect. Mg efflux was also biphasic with respect to [Mg+2]0, and this efflux was matched at low to moderate [Mg+2]0 by Mg influx of comparable magnitude. This study suggests the possible existence of a Mg transport system that can serve variously as a Na/Mg or a Mg/Mg exchanger that may require the participation of K ions for its operation.

A plasma factor inhibiting erythrocyte magnesium efflux.

Abstract: When incubated at 37 degrees C for 5 h in a magnesium- and calcium-free phosphate buffer solution (PBS), rat and mouse erythrocytes lose 30-40% of their Mg content. However, no Mg loss is observed if these erythrocytes are incubated in their own plasma. In order to investigate this phenomenon, murine erythrocytes were incubated in PBS, in human and murine blood plasmas, and fetal calf serum diluted in PBS (1/4), and in PBS supplemented with MgCl2, CaCl2, and crystallized plasma proteins at concentrations equal to those obtained in plasma/PBS solutions. Erythrocyte Mg efflux was significantly inhibited (P = 10(-8] by diluted human and rat plasmas but the time course of this inhibition was different with these two kinds of plasmas (P = 10(-4]. Mouse plasma and fetal calf serum also entailed a significant inhibition of Mg efflux, while the addition of Mg, Ca, and purified plasma proteins in the incubation medium had little effect. Blood plasma thus contains a factor inhibiting Mg efflux from murine erythrocytes and this effect is not explained by its content of magnesium, calcium, and proteins.

Ultrastructural effects of magnesium on human amniotic epithelial cells.

Abstract: The ultrastructure of the human amniotic epithelial cells from normal pregnancies, at term, was studied using scanning and transmission electron microscopy. The results were analysed by a stereological method which indicates the ratio between the volume of the intercellular space (R1), the microvilli (R2), and the podocytes (R3) versus the cell volume. An increase in this ratio indicates a higher structure and a facilitation of ion transport through the membrane. At low concentration (2 mM), MgSO4 increased R1 and R2 but decreased R3, whereas MgCl2 decreased R1 and R3 and had no significant effect on R2. At high concentration (10 mM), MgCl2 decreased R1 and increased R2 and R3, while MgSO4 had no significant effect on R1, increased R2, and decreased R3. The results are in part consistent with the results obtained after electrophysiological studies.

1,25 Dihydroxycholecalciferol and the genesis of hypocalcaemia in magnesium-deficient chicks.

Abstract: The role of 1,25 dihydroxycholecalciferol (1,25 DHCC) in the genesis of hypocalcaemia of magnesium (Mg) deficiency was studied in chicks fed control or Mg-deficient diets with varying calcium (Ca) content. In one study, Ca and Mg deficiencies were induced simultaneously whereas in a second study, exposure to low dietary Ca followed induction of Mg deficiency. In both studies, Mg-deficient chicks fed adequate dietary Ca were hypocalcaemic yet had normal circulating 1,25 DHCC, whereas Mg-deficient chicks fed low dietary Ca maintained normocalcaemia and had increased 1,25 DHCC. Bone Ca content, which was raised in Mg-deficient chicks fed adequate Ca, decreased in association with increased 1,25 DHCC and normalization of plasma Ca during exposure to low dietary Ca. The results suggest that the inappropriately normal 1,25 DHCC observed in conventional Mg deficiency may contribute to the pathological hypocalcaemia. In addition, these studies indicate that hypomagnesaemia per se does not limit 1,25 DHCC production during Mg deficiency.

Changes in blood magnesium and calcium concentrations in patients with stomach cancer.

Abstract: Blood magnesium (Mg) and calcium (Ca) concentrations were determined in patients with stomach cancer and in normal subjects. The patients were classified into four stages of malignancy and three metastatic categories. High Mg levels were found in plasma and whole blood of patients in the early stages of stomach cancer, while low Ca levels were found in blood plasma in most stages and in all metastatic groups. By contrast, high Ca levels were observed in whole blood in the later malignancy stages and in two of the metastatic categories. The calcium level in blood plasma does not therefore seem to depend on the stage of malignancy and metastasis, while the calcium level in whole blood and the Mg level in blood plasma and whole blood do appear to depend on the stage of malignancy or metastasis.

Severe selective magnesium malabsorption: tests of tolerance of oral magnesium supplements.

Abstract: Since his birth, we have been monitoring a 12-year-old boy suffering from selective severe magnesium malabsorption. Our essential problem is to prepare a form of galena with acceptable taste, tolerated by the digestive tract and well absorbed; also, the carrier compound must not cause short- or long-term side effects. An additional factor is the steadily increasing need for magnesium from 1 mmol/kg.d at 1 year to 14 mmol/kg.d at present age (345 mg/kg.d). The galena forms currently on sale were, with the exception of lactate and pyrollidone carboxylate, immediately rejected since they contain insufficient Mg2+. Following short trials resulting in diarrhoea, the other two preparations were also rejected. We then constituted - and also abandoned - our own galena compounds: aspartate (bitterness), aspartate + glycerophosphate (GLP) (bitterness), glutamate + GLP ('Chinese restaurant syndrome' and fear of the long term toxic effect of the glutamate), gluconate (excessive volume: 11/1 proportion with Mg2+). A recent test featuring GLP of Mg 40 g + cocoa butter 40 g + cocoa 10 g, brought about vomiting and diarrhoea, and was not adequately absorbed. The best tolerated formula is: Mg GLP 21.33 g; saccharose 6 g; aspartam 1 g; gelatin 0.5 g; citric acid, conserving agent, fruity aroma; water: qs 100 g. Such composition yields a caramel cream absorbed in five small portions, at a daily quantity of 375 g (80 g GLP Mg, 10 g Mg2+). Vitamin B6, which promotes intestinal absorption of magnesium, must be given separately in tablet form at a dose of 1 g/d, since it causes nausea if it is included in the Mg preparation.(ABSTRACT TRUNCATED AT 250 WORDS)

The dose rate effects on the in vitro radiolysis products of magnesium-guanosine-5'-monophosphate complexes in aqueous solutions.

Abstract: This study examined the effects on the radiolysis of magnesium-guanosine-5'-monophosphate complexes in deaerated aqueous solutions, investigated by Fourier transform infrared (FT-IR) spectroscopy. It was found that when the system was irradiated with a dose rate of 500 rad/min (low dose rate), the OH radicals, H atoms and hydrated electrons (eaq-) produced from radiolysis of water reacted mainly by addition to the double bonds C4 = C5 and N7 = C8 of guanine. When the dose rate was 23,800 rad/min (high dose rate) the electrons reacted further with the complex by addition to the carbonyl group, C6 = O, of guanine.

Magnesium perchlorate and cis-platinum as radiosensitizers in in vitro radiolysis of nucleotides.

Abstract: The mechanism of the gamma-radiolysis of the nucleotide guanosine-5'-monophosphate (5'-GMP) in the presence of Mg++ ions and cis-platinum was investigated. From high performance liquid chromatography and spectroscopy studies it was found that the OH radicals, produced in irradiated aqueous solutions, reacted with 5'-GMP by addition to the double bonds and that Mg++ as well as cis-Pt sensitized the nucleotide to radiation damage. Furthermore, an important finding was the fact that when the irradiation took place in aerated solutions, the Mg++ ions, contrary to cis-Pt, did not seem to have any effect on the decomposition yield G(-5'-GMP). This result together with the sensitization (100% increase) observed in deaerated solutions led to the conclusion that irradiation in the presence of Mg++ may result in a more effective gamma-radiation therapy for tumours.