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)

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.

Effects of different dose regimens of magnesium on pharmacodynamics and anesthetic requirements of balanced general anesthesia

The present double- blind, randomized, placebo- controlled study was designed to assess the effect of two different dose regimens of magnesium sulphate [MgSO[4] administration on intraoperative propofol and vecuronium requirements and postoperative fentanyl consumption in patients undergoing hernioraphy. Sixty patients were allocated to three equal groups; two magnesium groups and control group. Magnesium groups received 50 mg kg[-1] of magnesium preoperatively followed by intravenous infusion of magnesium 8 mg kg[-1] h[-1] [Mgl G] or 16 mg kg[-1]h[-1] [Mg2 G]. Patients in control group received the same volume of isotonic solution. Anesthesia was induced and maintained with propofol, fentanyl, and vecuronium. Magnesium Gs required significantly lower propofol [121.0 +/- 4.5, 117.4 +/- 6.3 micro g kg[-1] min.[-1] in Mgl and Mg2 Gs respectively vs. 153.8 +/- 8.4 micro g kg[-1] min.[-1] in control G], and vecuronium requirements [0.097 +/- 0.008, 0.092 +/- 0.006 mg kg[-1] h[-1] in Mgl and Mg2 Gs respectively vs. 0.124 +/- 0.01 mg kg[-1] h in control G]. Magnesium significantly shortened the onset time of vecuronium [154.0 +/- 25.9, 162.0 +/- 22.4 sec. in Mgl and Mg2 Gs respectively vs. 227.4 +/- 10.9 sec. in control], prolonged its clinical duration [44.7 +/- 3.2, 46.4 +/- 5.1 min. in Mgl and Mg2 Gs respectively vs. 26.0 +/- 3.9 min. in control] and prolonged its recovery index which was significantly longest in Mg2 G [25.4 +/- 1.9 min.] compared to Mgl G [20.1 +/- 2.1 min.] and control [15.3 +/- 1.4 min.] Fentanyl consumption on the first postoperative day was significantly higher in control [1.52 +/- 0.08 micro g kg[-1] than in magnesium Gs [0.96 +/- 0.07, 0.91 +/- 0.08 micro g kg[-1] in Mgl and Mg2 Gs respectively]. Postoperative sedation score showed significantly the highest value in Mg2 G compared to Mgl and control Gs. Mean arterial blood pressure and heart rate were lower in magnesium groups with lowest value in Mg2 G. It is concluded that magnesium 50 mg kg[-1] bolus followed by 8 mg kg[-1] h[-1] leads to significant reductions in intraoperative propofol and vecuronium and postoperative fentanyl consumption. Doubling magnesium infusion rate added minimal benefits on the expense of haemodynamic consequences and delayed recovery

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.

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.

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.