Absorción mineral y retención ósea en ratas normales en crecimiento por el consumo de un yogur experimental reducido en lactosa que contiene galactooligosacáridos (GOS) / Mineral absorption and bone retention in normal growing rats by consumption of an experimental lactose-reduced yogurt containing galactooligosaccharides (GOS)

Introducción: Los GOS son prebióticos naturales presentes en la leche materna que pue-den obtenerse enzimáticamente a partir de la lactosa de leche de vaca durante la fabricación de yogur. El producto lácteo resultante será reducido en lactosa y contendrá prebióticos y bacterias potencialmente probióticas. Sin embargo, mantendrá la baja relación Ca/Pi que aporta la leche de vaca, lo que podría alterar el remodelamiento óseo y la mineralización. Objetivo: comparar si un yogur reducido en lactosa que contiene GOS (YE) ofrece ventajas adicionales respecto de un yogur regular sin GOS (YR) sobre las absorciones (Abs) de Ca y Pi, retención y calidad ósea durante el crecimiento normal. Al destete, ratas machos fueron divididas en 3 grupos alimentados con AIN ́93-G (C), YE o YR durante 28 días. Resultados: YE mostró el mayor aumento de lactobacilos fecales; producción de ácidos grasos de cadena corta especialmente p, profundidad de las criptas colónicas y menor pH cecal. El %AbsCa y %AbsPi aumentó en el siguiente órden: YE> YR> C (p < 0,05). El contenido de Ca y Pi en fémur, la densidad y contenido mineral óseos y los parámetros biomecánicos fueron similares en YE y C, mientras que YR mostró valores significativa-mente menores (p < 0,05). Conclusiones: YE aumentó las Abs y biodisponibilidad de minerales, alcanzando la retención y calidad ósea de C. El aumento en las Abs observado en YR no logró obtener la retención y calidad ósea de C. Conclusión: YE habría contrarrestado el efecto negativo del mayor aporte de Pi de la leche de vaca y sería una buena estrategia para lograr el pico de masa ósea y calidad del hueso adecuados, especialmente en individuos intolerantes a la lactosa. (AU)

Breast milk contains an optimal calcium/phosphate (Ca/Pi) ratio and GOS. These natural prebiotics can be enzymatically produced via cow's milk lactose inyogurt manufacture. This milk product is low in lactose and contains prebiotics and potentially probiotic bacteria but maintains a low Ca/Pi ratio that could alter bone remodeling and mineralization. We evaluated if a lactose-reduced yogurt containing GOS (YE) offers additional advantages over regular yogurt without GOS (YR) on Ca and Pi absorption (Abs), bone retention and quality during normal growth. Weaning male rats were divided into 3 groups fed AIN'93-G (C), YE or YR for 28 days. Results: YE showed the highest increase in fecal lactobacilli; short-chain fatty acids production, especially propionate and butyrate; intestine crypt depth, and the lowest cecal pH. AbsCa% and AbsPi% increased in this order: YE> YR> C (p <0.05). Ca and Pi content in femur, bone density and mineral content, and biomechanical parameters were similar in YE and C, while YR showed the significantly lowest value (p < 0.05). Conclusions: YE increased mineral Abs reaching the retention and bone quality of C. Although YR increased Abs, bone retention and quality did not achieve C values. Seemingly, YE compensated for the negative effect of the higher Pi supply and would be a good strategy to achieve adequate peak bone mass and bone quality, especially in lactose intolerant individuals. (AU)

Potassium affects the phytoextraction potential of Tanzania guinea grass under cadmium stress.

The supply of potassium (K) is a strategy to increase the tolerance of plants exposed to Cd toxicity. The aim of this study was to verify the influence of K on the growth and potential of Tanzania guinea grass (Panicum maximum Jacq. cv. Tanzania (syn. Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs)) for Cd phytoextraction as well as to evaluate nutritional attributes of this grass under conditions of Cd stress. The experiment was conducted in a randomized complete block design, using a 3 × 4 factorial arrangement, with three replications. Three rates of K (0.4, 6.0, and 11.6 mmol L-1) were combined with four rates of Cd (0.0, 0.5, 1.0, and 1.5 mmol L-1) in nutrient solution. Two plant growth periods were evaluated. The increase in K supply to plants exposed to Cd rates of up to 1.0 mmol L-1 caused increase in morphogenic and production attributes, as well as reduction in tiller mortality rate, in the second growth period. K concentrations (in both harvests) increased, while calcium and magnesium concentrations in the second harvest decreased with increasing Cd rates. The high availability of Cd (1.5 mmol L-1) in the nutrient solution caused decrease in relative chlorophyll index (RCI) in both harvests. The high supply of K to plants exposed to Cd resulted in high shoot dry mass production, reducing Cd concentration in the photosynthetic tissues (which means great tolerance of the plant) and increasing the accumulation of this metal in the shoots that can be harvested. Therefore, K increases the Cd phytoextraction capacity of Tanzania guinea grass.

Magnesium in Breast Cancer: What Is Its Influence on the Progression of This Disease?

Breast cancer is a disease of high mortality, characterized by the progressive accumulation of mutations that contribute to the uncontrolled development of breast tissue cells. Literature shows that disturbances in mineral homeostasis, such as magnesium, may interfere with tumor progression. The objective of this study is to provide updated information about magnesium's role in the pathogenesis of breast cancer. A review of literature was carried out from a search for articles in the PubMed and CAPES Periodicals databases published between 1995 and 2016 with the cross-references of the descriptors "magnesium," "breast neoplasms," and "oxidative stress" and the corresponding words in Portuguese. We included studies on the metabolism and bioavailability of magnesium and studies related to breast cancer and excluded articles in which only the abstract was available, dissertations, theses, articles involving adjuvant and/or neoadjuvant therapies, and supplementation of minerals in breast cancer patients. Magnesium is a mineral that participates in the metabolism of various nutrients and nucleic acids. In the presence of breast cancer, neoplastic cells increase the expression of magnesium transport channels, which raises the intracellular concentration of the mineral, contributing to tumor growth through its function of increasing energy demand. The data obtained in this review illustrates the influence of magnesium on the progression of breast cancer. However, the existing data are scarce and inconsistent, which demonstrates a need for further studies on the subject with a goal to have better control of the disease.

Magnesium Status and Its Association with Oxidative Stress in Obese Women.

The aim of this study was to assess the relationship between magnesium status and oxidative stress in obese and nonobese women. This cross-sectional study included 83 women, aged between 20 and 50 years, who were divided into two groups: the obese group (n = 31) and the control group (n = 52). The control group was age-matched with the obese group. Magnesium intake was monitored using 3-day food records and NutWin software version 1.5. The plasma and erythrocyte magnesium concentrations were determined by flame atomic absorption spectrophotometry. Plasma levels of thiobarbituric acid reactive substances (TBARS) were determined as biomarkers for lipid peroxidation and therefore of oxidative stress. The mean values of the magnesium content in the diet were found to be lower than those recommended, though there was no significant difference between groups (p > 0.05). The mean concentrations of plasma and erythrocyte magnesium were within the normal range, with no significant difference between groups (p > 0.05). The mean concentration of plasma TBARS was higher in obese woman, and the difference between the groups was statistically different (p < 0.05). There was a positive correlation between erythrocyte magnesium and plasma TBARS in the obese group (p = 0.021). Obese patients ingest low dietary magnesium content, which does not seem to affect the plasma and erythrocyte concentrations of the mineral. The study showed a negative correlation between erythrocyte magnesium concentrations and plasma TBARS, suggesting the influence of magnesium status on the parameters of oxidative stress in obese women.

Magnesium decreases leaf scald symptoms on rice leaves and preserves their photosynthetic performance.

The aim of this study was to investigate the effect of magnesium (Mg) on the photosynthetic gas exchange parameters ([net CO2 assimilation rate (A), stomatal conductance (gs), and internal CO2 concentration (Ci)], chlorophyll (Chl) fluorescence a parameters {minimal fluorescence (F0), maximum fluorescence (Fm), maximum quantum yield of photosystem II (Fv/Fm), photochemical quenching coefficient (qp), yield of photochemistry [Y(II)], yield of regulated energy dissipation [Y(NPQ)] and yield of non-regulated dissipation losses [Y(NO)]} as well as on the concentrations of chloroplastidic pigments in rice plants grown in a nutrient solution containing 0.5 or 1.5 mM of Mg (-Mg or + Mg plants, respectively) and non-inoculated or inoculated with Monographella albescens. A higher Mg supply decreased the leaf scald symptoms in addition to partially preserving the photosynthetic performance of rice leaves challenged with M. albescens. Photosynthetic impairments were associated with photochemical and biochemical dysfunctions at the chloroplast level. The images of Chl a fluorescence evidenced increases in both the Y(II) and qp coupled with decreases in Y(NPQ) associated with a higher Mg supply regardless of inoculation, suggesting increased electron transport rates and lower energy dissipation as heat. Notably, as the leaf scald developed, the use of light energy through photochemical reactions was continuously lost, especially for the inoculated -Mg plants. Interestingly, the lower values for F0, Fm, and Fv/Fm for -Mg plants were associated with greater photochemical dysfunctions and a progressive loss of photosynthetic pigments during the infection process of M. albescens. The underlying mechanism through which Mg can affect rice resistance against M. albescens remains to be fully elucidated.

Effect of a mixture of GOS/FOS® on calcium absorption and retention during recovery from protein malnutrition: experimental model in growing rats.

INTRODUCTION: During growth, protein deprivation impairs epiphyseal growth plate (EGP) height, bone volume (BV) and endochondral ossification. During catch-up growth, Ca availability becomes essential to ensure the extra amount needed to achieve optimal peak bone mass and strength. GOS and FOS improve mineral absorption in the colon. PURPOSE: The effect of a mixture of GOS/FOS® 9:1 added to a 0.5 %Ca (NCa) and a 0.3 %Ca (LCa) diets on Ca, P and Mg absorptions and bone mineralization, density and structure using an experimental model of growing rats recovering from early protein malnutrition was investigated. METHODS: To induce protein malnutrition, rats were fed a low protein diet: 4 % (LPD) during 1 week and then were randomly assigned to recovery groups (R) until day 50 (T = 50) as follows: R0.5 %: NCa; RP0.5 %: NCa + 5.3 % GOS/FOS®; R0.3 %: LCa and RP0.3 %: LCa + 5.3 % GOS/FOS®. Control groups received the 0.5 %Ca or 0.3 %Ca diet from weaning until day 40 or 50. RESULTS: Body weight and length increased in C groups throughout the study; both were arrested in all R during LPD consumption and increased immediately after re-feeding. Independently of dietary Ca content, LS counts, ß-glucosidase and Ca, P and Mg absorption increased, whereas cecum pH, ß-glucuronidase, urease and tryptophanase decreased in RP0.5 %: and RP0.3 %: as compared to the other studied groups (p < 0.01). Prebiotic consumption decreased CTX levels and increased femur Ca, Mg and P contents, total skeleton bone mineral content, proximal tibia and spine BMD, BV, EGP height and hypertrophic zone thickness, stiffness and elastic modulus as compared to recovery groups fed the prebiotic-free diets. CONCLUSION: Under the present experimental conditions, GOS/FOS® mixture induced colonic positive effects, which increased Ca, P and Mg absorption. Thus, consuming the prebiotic-containing diet resulted in an extra amount of minerals that improved bone development in growing rats recovering from protein malnutrition.

Synthesis and cytotoxicity evaluation of granular magnesium substituted ß-tricalcium phosphate.

OBJECTIVE: The aim of this study was to produce dense granules of tricalcium phosphate (ß-TCP) and magnesium (Mg) substituted ß-TCP, also known as ß-TCMP (Mg/Ca=0.15 mol), in order to evaluate the impact of Mg incorporation on the physicochemical parameters and in vitro biocompatibility of this novel material. MATERIAL AND METHODS: The materials were characterized using X-ray diffraction (XRD), infrared spectroscopy (FTIR), electron microscopy and inductively coupled plasma (ICP). Biocompatibility was assayed according to ISO 10993-12:2007 and 7405:2008, by two different tests of cell survival and integrity (XTT and CVDE). RESULTS: The XRD profile presented the main peaks of ß-TCP (JCPDS 090169) and ß-TCMP (JCPDS 130404). The characteristic absorption bands of TCP were also identified by FTIR. The ICP results of ß-TCMP granules extract showed a precipitation of calcium and release of Mg into the culture medium. Regarding the cytotoxicity assays, ß-TCMP dense granules did not significantly affect the mitochondrial activity and relative cell density in relation to ß-TCP dense granules, despite the release of Mg from granules into the cell culture medium. CONCLUSION: ß-TCMP granules were successfully produced and were able to release Mg into media without cytotoxicity, indicating the suitability of this promising material for further biological studies on its adequacy for bone therapy.

Synthesis and cytotoxicity evaluation of granular magnesium substituted beta-tricalcium phosphate

Objective: The aim of this study was to produce dense granules of tricalcium phosphate (β-TCP) and magnesium (Mg) substituted β-TCP, also known as β-TCMP (Mg/Ca=0.15 mol), in order to evaluate the impact of Mg incorporation on the physicochemical parameters and in vitro biocompatibility of this novel material. Material and Methods: The materials were characterized using X-ray diffraction (XRD), infrared spectroscopy (FTIR), electron microscopy and inductively coupled plasma (ICP). Biocompatibility was assayed according to ISO 10993-12:2007 and 7405:2008, by two different tests of cell survival and integrity (XTT and CVDE). Results: The XRD profile presented the main peaks of β-TCP (JCPDS 090169) and β-TCMP (JCPDS 130404). The characteristic absorption bands of TCP were also identified by FTIR. The ICP results of β-TCMP granules extract showed a precipitation of calcium and release of Mg into the culture medium. Regarding the cytotoxicity assays, β-TCMP dense granules did not significantly affect the mitochondrial activity and relative cell density in relation to β-TCP dense granules, despite the release of Mg from granules into the cell culture medium. Conclusion: β-TCMP granules were successfully produced and were able to release Mg into media without cytotoxicity, indicating the suitability of this promising material for further biological studies on its adequacy for bone therapy.

Magnesium metabolism in health and disease.

Magnesium (Mg) is the main intracellular divalent cation, and under basal conditions the small intestine absorbs 30-50% of its intake. Normal serum Mg ranges between 1.7-2.3 mg/dl (0.75-0.95 mmol/l), at any age. Even though eighty percent of serum Mg is filtered at the glomerulus, only 3% of it is finally excreted in the urine. Altered magnesium balance can be found in diabetes mellitus, chronic renal failure, nephrolithiasis, osteoporosis, aplastic osteopathy, and heart and vascular disease. Three physiopathologic mechanisms can induce Mg deficiency: reduced intestinal absorption, increased urinary losses, or intracellular shift of this cation. Intravenous or oral Mg repletion is the main treatment, and potassium-sparing diuretics may also induce renal Mg saving. Because the kidney has a very large capacity for Mg excretion, hypermagnesemia usually occurs in the setting of renal insufficiency and excessive Mg intake. Body excretion of Mg can be enhanced by use of saline diuresis, furosemide, or dialysis depending on the clinical situation.

Pulque, an alcoholic drink from rural Mexico, contains phytase. Its in vitro effects on corn tortilla.

Pulque is made by fermenting the agave sap or aguamiel of Agave atrovirens with a whole array of microorganisms present in the environment including several lactic acid bacteria and yeasts such as Saccharomyces cerevisiae. Ascorbic acid was determined in pulque and aguamiel, respectively. Phytase activity in lees, liquid and freeze-dried pulque was assayed by measuring the appearance of phosphate from phytate by a colorimetric method likewise phosphate from phytate present in fresh corn tortilla was measured after in vitro incubation with pulque. Iron, zinc, calcium, magnesium and selenium contents were measured in pulque and corn tortilla as well as in nixtamalized corn flour (NCF), the latter is used to make instant tortilla, since corn provides most of the energy as well as most of the phytate in the Mexican rural diet. Pulque showed phytase activity but much less ascorbic acid and iron than previously reported; additionally, phytase in pulque hydrolyzed most of phytate's corn tortilla. Lees, which is mostly made of pulque's microbiota, significantly accumulated iron and zinc but no selenium. NCF was fortified with iron by the manufacturers but poorly blended. There were significant differences on selenium content between tortillas samples, apparently some soils in central Mexico are selenium deficient. Moderate pulque intake appears to increase the bioavailability of iron and zinc bound by phytate in corn.

O magnésio e o sistema biológico / Magnesium and the biological system

Desde que o magnésio foi introduzido na terapia há aproximadamente 30 anos, inúmeros estudos clínicos deveriam ter sido feitos. Embora um grande número de resultados experimentais tem demonstrado a importância do magnésio em eventos biológicos, o interesse pela terapia com magnésio ainda caminha a passos lentos, podendo ser atribuído principalmente às restriçöes dirigidas à prevençäo de doenças, particularmente aquelas associadas ao sistema imune. Entretanto, as aplicaçöes promissoras da terapia com magnésio vêm progredindo à luz da dedicaçäo de grupos de pesquisa de excelência, fazendo que a significância do magnésio näo seja ignorada. O propósito deste trabalho é o de resumir alguns aspectos relevantes da importância biológica deste cátion, com especial atençäo ao seu papel nos mecanismos de resistência e imunocompetência.

Effects of magnesium on blood pressure and intracellular ion levels of Brazilian hypertensive patients.

Fifteen patients with uncomplicated mild to moderate primary hypertension (7 males, 8 females, age range 36-65 years) were submitted to a double blind randomized crossover study, receiving MgO 3 times a day at a daily dose of 1.0 g (600 mg/day of magnesium) and placebo for a period of 6 weeks. This was to test the effects of oral magnesium supplementation on blood pressure and sodium, potassium, calcium and magnesium intraerythrocyte concentrations. Concomitantly, plasma renin activity and serum aldosterone was also measured. Oral magnesium reduced significantly the systolic (delta = -7.6 mmHg, P < 0.05); diastolic (delta = -3.8 mmHg, P < 0.01) and mean blood pressure (delta = -5.9 mmHg, P < 0.01). After magnesium supplementation intraerythrocyte sodium concentration was reduced (delta = -0.55 mEq/l per cell, P < 0.01) and intraerythrocyte magnesium concentration was increased (delta = 1.20 mg/dl per cell, P < 0.01). The diminution of the blood pressure correlated positively with the reduction in intraerythrocyte sodium (r = 0.66, P < 0.01) after magnesium. However, our results have shown that the blood pressure response to oral magnesium was not homogeneous. Forty percent of our patients had their blood pressure effectively controlled (more than 10 mmHg reduction in mean blood pressure), being the hypotensive effect more evident in patients with recent hypertension and in those where the reduction in intraerythrocyte sodium was significantly greater than in the non-responder individuals. Intraerythrocyte potassium and calcium, serum aldosterone, plasma renin activity and urinary sodium excretion were maintained unchanged after magnesium supplementation. These data showed that oral magnesium supplementation may reduce the blood pressure, which can be partially explained by the decrease in intracellular sodium and augment in intracellular magnesium.

[Mechanisms involved in the antiarrhythmic and proarrhythmic effects of magnesium]. / Mecanismos involucrados en el efecto antiarrítmico y proarrítmico del magnesio.

This paper reports an electrophysiological study on the antiarrhythmic and proarrhythmic actions of magnesium chloride and magnesium sulphate intravenous infusions. Magnesium kinetics in control dogs, following a pulse of magnesium chloride or magnesium sulphate, was not affected by the accompanying anion. The experiments were performed with mongrel dogs divided into three groups fed either a normal diet (group I), a low magnesium diet plus chlortalidone treatment and potassium supplementation (group IIA) or a low magnesium diet plus chlortalidone treatment and magnesium sulphate infusion (group II B). In group I, infusion of magnesium sulphate solution decreased plasma sodium, potassium and ventricular fibrillation threshold (VFT), prolonged the ventricular effective refractory period (VERP) and increased the urinary excretion of potassium. The infusion of magnesium chloride solution did not affect VFT, prolonged VERP, QTc, AH and PQ. In this group, sodium chloride or sulphate infusion did not affect the electrophysiological variables but sodium sulphate decreased plasma potassium levels. The group II A was characterized by the decreased levels of potassium and magnesium contents of plasma, lymphocytes and myocardium, decreased VERP and VFT and prolonged QTc. The intravenous infusion of magnesium sulphate solution depressed further VFT and plasma potassium and increased VERP. The acute infusion of potassium chloride solution increased plasma potassium and VFT. In group II B, plasma electrolyte levels and electrophysiological variables were not affected. We conclude that the clinically demonstrable, antiarrhythmic effect of magnesium infusion can be attributed to prolonged VERP. Magnesium sulphate infusion, however, produced potassium depletion and decreased VFT (a pro-arrhythmic effect). These adverse effects can be avoided infusing magnesium chloride solutions.

Mecanismos involucrados en el efecto antiarritmico y proarritmico del magnesio / Mechanisms involved in the antiarrhythmic and proarrhythmic effects of magnesium

El objetivo fue analizar en perros, los efectos del MgCl2, y del MgSO4 sobre los mecanismos electrofisiológicos que pudieran vincularse con las acciones antiarrítmicas y proarrítmicas de estas soluciones. Se estudiaron previamente los parámetros farmacocinéticos del MgCl2 y del MgSO4; ambos mostraron que el Mg plasmático disminuye exponencialmente (constante beta de O,118 ñ O,013 h-l), t 1/2 de eliminación de 6,02 ñ O,68 h y una Vda de O,259 ñ O,02lxkg-l. Posteriormente se estudiaron dos grupos de animales - Grupo I: dieta normal. Grupo II A: dieta sin Mg + clortalidona + K y Grupo II B: dieta sin Mg + clortalidona + KCI + MgSO4. Se midieron los electrolitos y las variables electrofisiológicas por medio de estimulación ventricular programada. El grupo I mostró que la administración de MgSO4 endovenoso disminuye el Na, el K y el umbral de fibrilación ventricular (UFV) y prolonga el período refractaria efectivo ventricular (PREV). El MgCl2 no modifica el UFV, pero prolonga el PREV, el A-H, el QTc y el PQ. El MgSO4 aumenta la excreción de K urinario en forma significativamente mayor que el MgCl2. La administración de NaCl no alteró las variables electrofisiológicas pero el NaSO4 disminuyó el K plasmático, sin modificar el UFV. El Grupo II A presentó descenso del K y Mg plasmático, linfocitario y miocárdico, disminución del PREV y del UFV y aumento del QTc. A este grupo se le administro en forma aguda: 1) MgSO4 que provocó mayor descenso del UFV y del K plasmático y aumento del PREV y 2) KCI que aumento el K piasmático y el UFV. El grupo II B no modificó los electrolitos ni las variables electrofisiológicas. Se concluye que los efectos antiarrítmicos observados en clínica por la administración de sales de Mg se deberían probablemente a la prolongación del PREV. Sin embargo, la depleción de K inducida por el MgSO4 puede provocar un descenso del UFV, efecto proarrítmico que se podría evitar utilizando MgCl2.

Mecanismos involucrados en el efecto antiarritmico y proarritmico del magnesio / Mechanisms involved in the antiarrhythmic and proarrhythmic effects of magnesium

El objetivo fue analizar en perros, los efectos del MgCl2, y del MgSO4 sobre los mecanismos electrofisiológicos que pudieran vincularse con las acciones antiarrítmicas y proarrítmicas de estas soluciones. Se estudiaron previamente los parámetros farmacocinéticos del MgCl2 y del MgSO4; ambos mostraron que el Mg plasmático disminuye exponencialmente (constante beta de O,118 ñ O,013 h-l), t 1/2 de eliminación de 6,02 ñ O,68 h y una Vda de O,259 ñ O,02lxkg-l. Posteriormente se estudiaron dos grupos de animales - Grupo I: dieta normal. Grupo II A: dieta sin Mg + clortalidona + K y Grupo II B: dieta sin Mg + clortalidona + KCI + MgSO4. Se midieron los electrolitos y las variables electrofisiológicas por medio de estimulación ventricular programada. El grupo I mostró que la administración de MgSO4 endovenoso disminuye el Na, el K y el umbral de fibrilación ventricular (UFV) y prolonga el período refractaria efectivo ventricular (PREV). El MgCl2 no modifica el UFV, pero prolonga el PREV, el A-H, el QTc y el PQ. El MgSO4 aumenta la excreción de K urinario en forma significativamente mayor que el MgCl2. La administración de NaCl no alteró las variables electrofisiológicas pero el NaSO4 disminuyó el K plasmático, sin modificar el UFV. El Grupo II A presentó descenso del K y Mg plasmático, linfocitario y miocárdico, disminución del PREV y del UFV y aumento del QTc. A este grupo se le administro en forma aguda: 1) MgSO4 que provocó mayor descenso del UFV y del K plasmático y aumento del PREV y 2) KCI que aumento el K piasmático y el UFV. El grupo II B no modificó los electrolitos ni las variables electrofisiológicas. Se concluye que los efectos antiarrítmicos observados en clínica por la administración de sales de Mg se deberían probablemente a la prolongación del PREV. Sin embargo, la depleción de K inducida por el MgSO4 puede provocar un descenso del UFV, efecto proarrítmico que se podría evitar utilizando MgCl2. (AU)

Plasma mineral concentrations in preterm infants fed a nutrient-enriched formula after hospital discharge.

OBJECTIVE: To determine whether prolonged feeding of preterm infant formula to preterm infants can accelerate recovery to normal plasma zinc levels without affecting plasma mineral homeostasis. DESIGN: Part of concurrent prospective feeding trials in a university hospital-based population. SUBJECTS AND INTERVENTION: Preterm infants (n = 33; birth weight, 1037 +/- 157 gm) were fed a preterm infant formula with higher concentrations of zinc, copper, calcium, magnesium, and potassium until 2 months past expected term, then a term infant formula. Term infants (n = 38; birth weight, 3318 +/- 401 gm) fed this term infant formula from birth were a reference group for comparison with study infants and with published values. Plasma mineral levels were analyzed by inductively coupled plasma atomic emission spectroscopy. RESULTS: Preterm infants fed a preterm infant formula after discharge from the hospital appeared to achieve normal plasma zinc concentrations by at least 2 months past term without adverse effects on mineral homeostasis.

Postnatal attainment of intrauterine macromineral accretion rates in low birth weight infants fed fortified human milk.

HYPOTHESIS: Provision of more bioavailable mineral sources as human milk supplements enables very low birth weight (VLBW) infants to meet the intrauterine accretion rate for calcium and phosphorus. DESIGN: Comparison of currently formulated human milk fortifier with previous formulation. SETTING: Neonatal level II and III nurseries. PATIENTS: Twenty-six healthy, VLBW infants, whose mothers chose to breast-feed. INTERVENTIONS: We tested the effects of two formulations designed for VLBW infants as human milk supplements and differing primarily in their quantity and source of Ca, P, and magnesium. The study interval began with a milk intake of 100 ml.kg-1.day-1 and ended when a body weight reached 2.0 kg. MAIN OUTCOME MEASURES: Net absorption and retention of Ca, P, and Mg during a nutritional balance study conducted once during the study interval, growth during the entire study interval, and bone mineral content of the radius were measured at the beginning and end of the study interval. RESULTS: The newer Ca gluconate-glycerophosphate preparation (given to group CaGP) resulted in greater net absorption and retention of Ca and P (p < 0.01) than in infants given Ca phosphate (group CaTB). Mg retention was greater than (in group CaGP) or equivalent to (in group CaTB) the intrauterine accretion rate. Radius bone mineral content was significantly greater in group CaGP than in group CaTB (p < 0.001). Volumes of the fortified human milk preparation needed to meet the needs for gain in body weight were higher in group CaGP than in group CaTB (p < 0.001). CONCLUSIONS: Intrauterine accretion rates for Ca and P can be achieved when VLBW infants are fed human milk supplemented with Ca gluconate-glycerophosphate. Supplementation of human milk with Mg may not be indicated. In this study, greater intakes of Ca and P, and not improvements in bioavailability, result in improved net retention and bone mineral content of VLBW infants.

Parenteral nutrient needs of very low birth weight infants.

OBJECTIVE: To determine nitrogen and mineral needs in parenterally nourished very low birth weight infants. DESIGN: Prospective observational study. SETTING: Neonatal intensive care unit. PATIENTS: Twenty-four very low birth weight infants (< 1.2 kg) expected to receive parenteral nutrition (PN) exclusively for 3 weeks beginning 3 days after birth. INTERVENTIONS: Infants received PN solutions according to nursery protocol. Serial 24-hour balance studies were conducted twice weekly. Clinical therapies were tabulated. MAIN OUTCOME MEASURES: Intake, urinary excretion, and apparent retention of nitrogen, sodium, potassium, zinc, copper, calcium, phosphorus, and magnesium after initiation of PN. RESULTS: Although urinary K, Zn, Ca, P, and Mg excretion (but not N, Na, and Cu excretion) increased after PN therapy was begun, net nutrient retention increased significantly above baseline for all nutrients. Average weekly nutrient retention was significantly below intrauterine estimates of nutrient accretion for N, Na, Ca, P, and Cu; closely approximated estimates for Zn; and significantly exceeded those for K and Mg. Regression analysis was used to predict parenteral nutrient intakes that would support postnatal nutrient retentions equivalent to the intrauterine estimates. Postnatal therapy with dexamethasone affected N, P, and K excretion and retention. CONCLUSIONS: Soon after PN administration is begun, positive nutrient balance may be achieved early in the neonatal period. The magnitude of this effect remains uniform during PN administration. Adjustments in parenteral nutrient intake are needed to provide nutrient intakes sufficient to support postnatal retention at rates similar to those of intrauterine accretion. These data should be considered in the design of future studies to determine optimal PN needs of very low birth weight infants.

Efeito do íon magnésio no desenvolvimento e produçäo de proteínas extracelulares na linhagem de staphylococcus aureus S-6 / Effect of the ion magnesium on the development and extracellular proteins production of strain Staphylococcus aureus S-6

A remoçäo de íons do hidrolizado de caseína, meio NAKSA. Este tratamento afetou o desenvolvimmento de S.aureus S-6, obtendo-se células com morfologia alterada, diminuiçäo do peso seco e modificaçöes na produçäo das proteínas extracelulares; DNAse, coagulase e as enterotoxinas A(EEA) e B(EEB), assim como a enzima intracelular desidrogenase lática.a adiçäo de 1, 11µg/ml de Mg 2+ ao meio NAKSA teve como efeito a recuperaçäo da peso seco, porém näo houve restabelecimento da morfologia celular. Para este valor de magnésio, o nível de DNAse aumentou 3, 5 vezes em relaçäo ao meio NAK, enquanto que as restantes proteínas extracelulares e intracelulares analisadas, näo atingiram os valores obtidos no meio NAK.a quantidade de EEB produzida foi afetada por variaçöes na concentraçäo de magnésio, enquanto que a de EEA permaneceu constante. Em relaçäo à fraçäo das enzimas extracelulares associadas à célula verificou-se que a DNAse superficial liberada pela açäo de lisostafina foi aproximmadamente 200 vezes inferior à concentraçäo da mesma enzima presente no sobrenadante da cultura. A quantidade de DNAse presente nos protoplastos.