Impact of micronutrients supplementation on bone repair around implants: microCT and counter-torque analysis in rats

ABSTRACT The use of natural substances and micronutritional approaches has been suggested as a therapeutic alternative to benefit the bone healing associated with no side effects. Nevertheless, the influence of micronutritional interventions with therapeutic proprieties on the bone repair has yet to be intensely evaluated, and no evidence is available exploring the impact of micronutrient supplementation on the peri-implant bone healing. Objective This study investigated the effect of micronutrients supplementation on the bone repair around implants. Material and Methods One screw-shaped titanium implant was inserted in each tibia of each rat, which were assigned to: daily administration, for 30 d, of the placebo solution (Placebo group-n:18) or micronutrients supplementation (Micronutrients group-n:18), based on calcium, magnesium, zinc, and vitamin D3 intake. After, the animals were sacrificed. One of the implants was removed by applying a counter-torque force to evaluate the force to rupture the bone-implant interface. The other implant was evaluated by microcomputed tomography (CT) examination to determine the bone-to-implant contact (BIC) and the bone volume (BV/TV). Results No statistically significant differences were observed between the groups for both counter-torque values and microCT parameters (p>0.05). Conclusion Within the limits of this study, micronutrients supplementation did not provide additional benefits to the bone healing around dental implants.

Effect of magnesium ion on human osteoblast activity

Magnesium, a promising biodegradable metal, has been reported in several studies to increase bone formation. Although there is some information regarding the concentrations of magnesium ions that affect bone remodeling at a cellular level, little is known about the effect of magnesium ions on cell gap junctions. Therefore, this study aimed to systematically investigate the effects of different concentrations of magnesium on bone cells, and further evaluate its effect on gap junctions of osteoblasts. Cultures of normal human osteoblasts were treated with magnesium ions at concentrations of 1, 2 and 3 mM, for 24, 48 and 72 h. The effects of magnesium ions on viability and function of normal human osteoblasts and on gap junction intercellular communication (GJIC) in osteoblasts were investigated. Magnesium ions induced significant (P<0.05) increases in cell viability, alkaline phosphate activity and osteocalcin levels of human osteoblasts. These stimulatory actions were positively associated with the concentration of magnesium and the time of exposure. Furthermore, the GJIC of osteoblasts was significantly promoted by magnesium ions. In conclusion, this study demonstrated that magnesium ions induced the activity of osteoblasts by enhancing GJIC between cells, and influenced bone formation. These findings may contribute to a better understanding of the influence of magnesium on bone remodeling and to the advance of its application in clinical practice.

Inhibitory and stimulating effect of magnesium on vanadate-induced lipid peroxidation under in vitro conditions.

The behaviour of Mg related to vanadium(V)-induced lipid peroxidation (LPO) under in vitro conditions was examined. The studies performed on the liver supernatants (LS) obtained from control, sodium metavanadate-intoxicated, and sodium metavanadate-magnesium sulphate-administered male Wistar rats revealed and confirmed the pro-oxidative potential of V. Simultaneously, they indicated that the improved Mg status may be one of the mechanisms by which the treatment with this element may contribute to reduction of oxidative stress under the conditions of vanadate exposure. On the other hand, the results confirmed that Mg may also stimulate LPO and demonstrated that the incubation conditions and the experimental treatment of the rats from which the liver supernatants were obtained affect the intensity of the examined free radical process.

Efeito da deficiência dietética de magnésio na resistência insulínica e no status inflamatório e oxidativo em ratos alimentados com dieta hiperlipídica / Effect of dietary magnesium deficiency on insulin resistance and on inflammatory and oxidative status in rats fed with high-fat diet

O objetivo deste trabalho foi avaliar, em ratos, os efeitos do consumo, em curto prazo, de dieta hiperlipídica e deficiente em magnésio (Mg) na adiposidade, no status de Mg, na sensibilidade à insulina, e no status inflamatório e oxidativo. Foi inicialmente realizado um ensaio piloto (n = 12), de 24 dias, que permitiu avaliar o padrão alimentar dos animais. A dieta hiperlipídica testada teve sua composição em micronutrientes aumentada proporcionalmente à redução esperada de consumo. A partir desses resultados, delineou-se o ensaio principal, de 32 dias, com os animais alimentados com rações controle (ad libitum [CT; n = 8] e pair-feeding [PF; n = 16]), e hiperlipídica (adequada [HF; n = 12] e deficiente em Mg [HFMg-; n = 12]). Foram avaliados a adiposidade, o perfil lipídico, o status de Mg, a resistência insulínica (glicemia e insulinemia de jejum, teste de tolerância à insulina - TTI, fosforilação do receptor de insulina [IR-ß], do substrato 1 do IR [IRS-1] e da proteína quinase B [Akt]), e marcadores de inflamação e de estresse oxidativo. O consumo de dieta HFMg- e HF resultou em maior ganho de peso e adiposidade em relação ao PF. Da mesma forma os grupos HF e HFMg- apresentaram concentrações séricas de colesterol total, VLDL-c e de triacilgliceróis mais elevadas em relação ao grupo PF. Como esperado, os animais HFMg- apresentaram alterações no status de Mg, evidenciadas pela redução de suas concentrações no osso e na urina. Apesar de não terem sido observadas diferenças na glicemia e na insulinemia entre os grupos, a menor fosforilação das proteínas da via de sinalização de insulina comprovam que a deficiência de Mg agrava os efeitos da dieta hiperlipídica nesta via. Não foram observadas diferenças nos parâmetros de inflamação e de estresse oxidativo. No entanto, observou-se associação inversa do malondialdeído e do inibidor do ativador de plasminogênio-1 com o status de Mg. Os resultados do presente estudo reforçam a importância da análise de micronutrientes em dietas experimentais, a fim de se obter dados reprodutíveis. A utilização do grupo PF permitiu verificar que o consumo de dietas hiperlipídicas predispõem a maior adiposidade, resistência insulínica e dislipidemia, e que a deficiência de Mg pode piorar a resistência insulínica

The aim of this study was to assess, in rats, the effects of high-fat and magnesium (Mg) deficient diet, in short-time, on adiposity, magnesium status, insulin sensitivity, and oxidative and inflammatory status. Firstly, it was realized a pilot study (n = 12), 24 days, which allowed to assess the dietary patterns of the animals. The high-fat diet tested had its micronutrient composition increased proportionally to the expected reduction in consumption. Based in these results, it was outlined the principal study, 32 days, with the animals fed with control diet (ad libitum [CT; n = 8] and pair-feeding [PF; n = 16]), and high-fat diet (adequate [HF; n = 12] and magnesium deficient [HFMg-; n = 12]). It was assessed the adiposity, serum lipid profile, Mg status, insulin resistance (fasting glucose and insulin, insulin tolerance test - ITT, phosphorylation of insulin receptor [IR-ß], insulin receptor substrate 1 [IRS-1] and protein kinase B [Akt]), and markers of inflammation and oxidative stress. The consumption of HFMg- and HF results in greater weight gain and adiposity compared to PF. Likewise, the high-fat groups showed serum total cholesterol, VLDL-c, and triglycerides higher than PF group. As expected, the animals showed changes in magnesium status, as evidenced by lower bone and urine levels. Although no differences were observed in blood glucose and serum insulin levels among the groups, the lowest phosphorylation of the insulin signaling pathway show that Mg deficiency intensifies the effects of high-fat diet in this pathway. No differences were observed in the inflammatory and oxidative stress parameters. However, it was observed an inverse association of malondialdehyde and plasminogen activator inhibitor-1 with Mg status. The results of this study support the importance of micronutrients analyzes in the experimental diets, in order to obtain reproducible data. With the PF group it was showed that high-fat diets predisposes to greater adiposity, dyslipidemia, insulin resistance, and that Mg deficiency can worse the effects on insulin resistance

Comparative experimental study of myocardial protection with crystalloid solutions for heart transplantation / Estudo comparativo experimental da proteção miocárdica com soluções cristalóides para transplante cardíaco

BACKGROUND: There is a growing need to improve myocardial protection, which will lead to better performance of cardiac operations and reduce morbidity and mortality. Therefore, the objective of this study was to compare the efficacy of myocardial protection solution using both intracellular and extracellular crystalloid type regarding the performance of the electrical conduction system, left ventricular contractility and edema, after being subjected to ischemic arrest and reperfusion. METHODS: Hearts isolated from male Wistar (n=32) rats were prepared using Langendorff method and randomly divided equally into four groups according the cardioprotective solutions used Krebs-Henseleit-Buffer (KHB), Bretschneider-HTK (HTK), St. Thomas-1 (STH-1) and Celsior (CEL). After stabilization with KHB at 37ºC, baseline values (control) were collected for heart rate (HR), left ventricle systolic pressure (LVSP), maximum first derivate of rise left ventricular pressure (+dP/dt), maximum first derivate of fall left ventricular pressure (-dP/dt) and coronary flow (CF). The hearts were then perfused at 10ºC for 5 min and kept for 2 h in static ischemia at 20ºC in each cardioprotective solution. Data evaluation was done using analysis of variance in completely randomized One-Way ANOVA and Tukey's test for multiple comparisons. The level of statistical significance chosen was P<0.05. RESULTS: HR was restored with all the solutions used. The evaluation of left ventricular contractility (LVSP, +dP/ dt and -dP/dt) showed that treatment with CEL solution was better compared to other solutions. When analyzing the CF, the HTK solution showed better protection against edema. CONCLUSION: Despite the cardioprotective crystalloid solutions studied are not fully able to suppress the deleterious effects of ischemia and reperfusion in the rat heart, the CEL solution had significantly higher results followed by HTK>KHB>STH-1.

INTRODUÇÃO: Existe crescente necessidade de aprimorar a proteção miocárdica, para melhor desempenho das operações cardíacas e diminuição da morbimortalidade. Portanto, o objetivo deste estudo foi comparar a eficácia da proteção miocárdica usando tanto solução cristaloide tipo intracelular como extracelular quanto ao desempenho do sistema de condução elétrica, contratilidade do ventrículo esquerdo e edema, após parada isquêmica e posterior reperfusão. MÉTODOS: Corações isolados de ratos Wistar foram montados em Langendorff e aleatoriamente divididos em quatro grupos. de acordo com as soluções cardioprotetoras utilizadas Krebs-Henseleit-Buffer (KHB), Bretschneider-HTK (HTK), St. Thomas-1(STH-1) e Celsior (CEL). Após a estabilização com KHB a 37ºC, valores basais (controle) foram coletados para frequência cardíaca (FC), pressão sistólica do ventrículo esquerdo (PSVE), derivada máxima de aumento da pressão ventricular esquerda (+dP/dt), derivada máxima de queda da pressão ventricular esquerda (-dP/dt) e fluxo coronariano (FCo). Os corações foram então perfundidos a 10ºC por 5 min e mantidos por 2 h em isquemia estática a 20ºC em cada solução cardioprotetora. Avaliação dos dados foi por análise de variância inteiramente casualizados em One-Way ANOVA e teste de Tukey para comparações múltiplas. O nível de significância estatística escolhido foi P<0,05. RESULTADOS: Houve recuperação da FC com todas as soluções utilizadas. A avaliação da contratilidade ventricular esquerda (PSVE, +dP/dt e -dP/dt) demonstrou que o tratamento com a solução CEL foi melhor em comparação às outras soluções. Ao analisar o CF, a solução HTK indicou melhor proteção contra edema. CONCLUSÃO: Apesar das soluções cristaloides cardioprotetoras estudadas não serem capazes de suprimir os efeitos deletérios da isquemia e reperfusão no coração de ratos, a solução CEL apresentou resultado superior seguido por HTK>KHB>STH-1.

[ effects of dietary supplementation with zinc, magnesium and zinc plus magnesium on muscle strength in active women]

The purpose of this study was to determine the effect of dietary supplementation with zinc, magnesium and zinc plus magnesium on muscle strength in active women. Forty active women selected randomly were randomly divided into 4 groups of 10 each, all undergonig resistance training and receiving, daily, a supplement of either zinc [50 mg zinc sulfate], magnesium [250 mg magnesium oxide], or zinc plus magnesium [50 mg zinc sulfate plus 250 mg magnesium oxide], or no supplement [control group]. All the subjects had a history of sports activity. Blood samples were collected and 1-RM was measured at the beginning and after 8weeks. Independent and paired-sample t-test showed that zinc, magnesium and zinc plus magnesium supplements had no statistically significant effects on the strength of lower body muscles. However, the magnesium supplement had a significant positive effect on the strength of upper body muscles [chest, back, as well as back and hand bending muscles]. In addition, the zinc and zinc plus magnesium supplements affected significantly the strength of the back and hand bending muscles. Further analysis of the data showed that the zinc plus magnesium supplement had no significant effect on the serum zinc and magnesium concentrations. Dietary supplementation with zinc, magnesium and zinc plus magnesium can effect desirably the upper body muscles strength in active women

Differences in intracellular localization of corn stunt spiroplasmas in magnesium treated maize

Maize plants infected with Spiroplasma kunkelii show symptoms similar to that of plants in a magnesium-deficient soil, and it has been shown that the spiroplasma alters the plants' magnesium absorption. In the current study we compared changes associated to either spiroplasma infection, two soil magnesium levels and their combinations. Plant symptoms were recorded and correlated with transmission electron microscopy observations. Plants grown on a high magnesium treatment showed no macroscopical alterations nor organelle ultrastructural alterations, while plants on a low magnesium treatment showed macroscopical vein yellowing and, ultrastructurally, they had most chloroplasts and mitochondrial membranes altered. Infected plants on a low magnesium treatment had an ageing aspect, ultrastructurally showed chloroplast s and mitochondrial alterations similar to those non-infected and grown on a low magnesium treatment, and spiroplasma cells were found in phloem cells, but outside their cytoplasm. Infected plants on a high magnesium treatment showed similar symptoms and ultrastructural alterations as either non-infected plants on the low magnesium treatment or in infected plants on the low magnesium treatment, but differ from them in that the spiroplasma cells were located inside the cytoplasm. Results suggest that magnesium is involved in the plant-pathogen interaction.

Trimetazidina como aditivo em solução cardioplégica sem pré-tratamento não traz proteção adicional ao miocárdio isquêmico: estudo em modelo suíno de coração isolado / Trimetazidine as cardioplegia addictive without pre-treatment does not improve myocardial protection: study in a swine working heart model

OBJETIVO: Verificar, em modelo experimental de coração isolado de suínos, se a associação da trimetazidina à solução cardioplégica promove melhora no desempenho do coração. MÉTODOS: O modelo experimental utilizou suínos Large-White, com coração isolado perfundido por suporte de outro animal em modo de execução de trabalho ("working heart state"). Foram divididos em três grupos (n = 6), submetidos a isquemia regional seguida de isquemia global, que recebiam um dos três tratamentos: solução St Thomas (ST), solução St Thomas acrescida de trimetazidina (TMZ) e grupo controle (Co). Durante período de reperfusão, aos 30, 60 e 90 minutos, foram medidos parâmetros hemodinâmicos de contratilidade e metabólicos, obtendo-se assim a elastância máxima (Emáx), o índice de trabalho sistólico pré-recrutável (PRSW), "dureza" do ventrículo (EDPRV), fluxo coronariano, consumo de oxigênio e dosagens de lactato e glicose. Os resultados foram analisados estatisticamente. RESULTADOS: Em relação aos parâmetros hemodinâmicos de contratilidade, não houve diferença estatística significante entre os três grupos. Houve produção crescente de lactato nos três grupos de forma uniforme quanto maior o tempo de reperfusão. O fluxo coronariano, o consumo de oxigênio e o consumo de glicose tiveram grande variação entre os diferentes tempos medidos, mas sem diferença entre os três tratamentos. O peso final do ventrículo esquerdo foi significativamente menor no grupo trimetazidina (TMZ) do que nos demais. CONCLUSÃO: A administração da trimetazidina associada como adjuvante à solução cardioplégica, sem pré-tratamento, não demonstrou benefício hemodinâmico ou metabólico em modelo experimental "working heart" de coração isolado em porcos.

OBJECTIVE: The aim of this study is to verify in an isolated working heart swine model if the acute administration of trimetazidine to cardioplegia, without pre=treatment improves heart performance. METHODS: Eighteen pairs of swines were used in this working heart model, divided into three groups (n = 6) that underwent regional and global ischemia. Each group was selected to a different treatment: St Thomas cardioplegia (ST), St Thomas enriched with trimetazidine (TMZ) and control group (Co). Data was collected during reperfusion period at 30, 60 and 90 minutes. Hemodinamic parameters such as elastance contractility index (Emax), preload recruitable stroke work relationship (PRSW) and heart "stiffness" (EDPVR) were measured. Other data included coronary flow, lactate, oxygen and glucose consumption. Results were statistically analyzed. RESULTS: All contractility data were not significantly different among three groups. Lactate became constantly higher according to time uniformly in all three groups. Coronary flow, glucose consumption and oxygen consumption presented large variations during time periods but according to treatments showed no statistical differences in all three groups. Left ventricle final weight was significantly lower in trimetazidine group compared to both other groups. CONCLUSION: Administration of trimetazidine enhanced cardioplegia, without pre-treatment, showed no hemodinamic or metabolic improvement in swine isolated working heart model.

Effect of monothiol along with antioxidant against mercury-induced oxidative stress in rat.

Efficacy of thiol chelators viz. N-acetyl cysteine and D-penicillamine (NAC and DPA) along with nutritional supplements viz. zinc acetate, sodium selenite and magnesium sulphate (Zn, Se and Mg) in the treatment of mercury intoxication was investigated in rats. This is of particular interest since high bonding affinity between mercuric ion and the thiol group exits. The mutual antagonism of mercury and selenium is one of the strongest examples of the interaction in the trace element field. Adult rats of Sprague-Dawley strain were administered a bolus dose of dimethyl mercury (10 mg/kg) orally. A significant rise in the aspartate aminotransferase, alanine aminotransferase, serum alkaline phosphatase, lactate dehydrogenase, gamma glutamyltranspeptidase, bilirubin and creatinine were observed. Single mercury exposure also resulted in a significant increase in lipid peroxides with a concomitant decrease in reduced glutathione level in liver, kidney and brain. A decrease in the enzymatic activities of acetyl cholinesterase in different regions of the brain was observed. These parameters were restored considerably with chelating agents along with nutritional supplementation, but NAC+Se and DPA+Mg offered significant protection in comparison with other combinations.

[ effects of orally administrated magnesium on denuded aorta contractility in streptozotocin induced diabetic rats]

Some studies suggest that magnesium deficiency contributes to the cardiovascular complications associated with diabetes mellitus; hence the present study investigated the effects of long term orally administrated magnesium on isolated denuded aorta contractility in response to KCl and Phenylephrine [Phe]. Sixty male Wister rats [180-250 g] were divided into two diabetic and two control groups. One group of each received magnesium sulfate in their drinking water, while the two other groups, had only tap water. After 8 weeks, thoracic aorta was isolated, cut into 2-3 mm rings, endothelium removed and transferred to an organ bath. The tissue was then exposed to cumulative doses of KCl [10, 20, 40, 60 and 80 mM] and Phe [10-9, 10-8, 10-7, 10-6 and 10-5 M] and contractions were measured by an isometric transducer. During the study period, fasting blood samples were obtained every 2 weeks to measure Plasma Glucose level. Vasoconstrictive responses to KCl and Phe were significantly [p<0.05] higher in the control group as compared to the diabetic groups [p<0.05] and there were no significant differences between Mg-treated and non Mg-treated rats. Maximal contractions to KCl were 2.32 +/- 0.23, 2.76 +/- 0.19, 1.96 +/- 0.11 and 1.84 +/- 0.21 and the maximal responses to Phe were 2.94 +/- 0.24, 3.38 +/- 0.20, 2.24 +/- 0.27and 2.61 +/- .27 in the control, Mg-treated control, diabetics and Mg-treated diabetic groups, respectively. No significant differences were found in plasma glucose concentrations between the Mg-treated and non Mg-treated groups. Oral administration of magnesium for 8 weeks has no effect on isolated denuded aorta contractility in diabetic rats

Effects of N-acetyl cysteine and magnesium on oxidative stress in streptozotocin induced - diabetic nephropathy in rats

Increased production of reactive oxygen species [ROS] in diabetes may be a common pathway linking diverse pathogenic mechanisms of diabetic vascular complications, including nephropathy. Assessment of the oxidative stress production pathway is therefore important for the prediction and prevention of diabetic complications. this study was designed to evaluate the effects of N-acetyl cysteine [NAC] supplementation alone or combined with magnesium [Mg], on oxidative stress in streptozotocin-induced diabetic nephropathy in rats, Sprague Dawley rats [n=40] were rendered diabetic with streptozotocin [STZ] and followed consecutively for 12-weeks with non-diabetic controls [n=10]. Diabetic rats were subdivided into equal three subgroups DM4 NAC group treated with NAC [440 mg/kg/day], DM+Mg group treated with Mg [0.6%], or NAC+Mg diabetic group treated with a combination of both drugs. The following parameters were measured at week 12 in similar rats chosen randomly from each group: body weight [BW], kidney weight [KW], 24-hour urinary albumin excretion [UAE], biochemical indexes including blood glucose, serum creatinine [SCr], antioxidant enzymes including superoxide dismutase. [SOD], catalase [CAT], reduced glutathione, lipid peroxidation product as malondialdehyde in plasma [MDAp]. At weeks 12, blood glucose and kidney weight to body weight ratio were notably increased in the diabetic groups compared with those in the control group with significant decrease in DM+Mg and NAC+ Mg treated groups in comparison to the diabetic untreated group. There were no significant differences of SCr among all groups. Plasma MDA were significantly increased in the diabetic groups, while SOD, CAT and reduced glutathione were significantly decreased compared with those in the control group. Also, UAE was also increased in the diabetic groups. Pre-treatment with NAC, Mg or both produced significant decrease of lipid peroxidation production and increase of antioxidant enzymes. Correlation analysis and regression analysis shown that plasma MDA was increased while SOD, CAT and reduced glutathione in plasma were decreased with elevation of UAE. Increased lipid peroxidation and decreased antioxidant enzymes in plasma may play a role in the progression of diabetic nephropathy. NAC and Mg may ameliorate these changes to protect kidney from oxidative lesion in diabetes

role of K-ATP channel in the preconditioning effect of magnesium in the rat isolated heart

There is growing interest for beneficial effect of Mg in the cardiovascular disorders. A number of cardiovascular disorders including myocardial infarction, arrhythmias and congestive heart failure have been associated with low extracellular or intracellular concentrations of Mg. The aim of present study was to investigate the preconditioning effects of magnesium [Mg] on cardiac function and infarct size in the globally ischemic-reperfusion in isolated rat heart. Rat hearts were Langendorff-perfused, subjected to 30 minutes of global ischemia and 90 minutes of reperfusion, and assigned to one of the following treatment groups with 7 hearts in each group: [1] control, [2] ischemic- reperfusion, [IR], [3] ischemic preconditioning, [IPC] of 5 minutes of global ischemia - reperfusion before lethal ischemia; or pretreatment with [4] 30 Mu mol/L of Diazoxide [Dia], [5] 8 mmol/L magnesium, [6] 10 Mu mol/L glibenclamid [Gli], [7] magnesium and Dia and [8] magnesium and Gli. Infarct size was measured by the triphenyltetrazolium chloride method. Left ventricular function was assessed by left ventricular developed pressure [LVDP], heart rate and coronary flow [CF]. Mg limited infarct size [9.76% vs 44.47% in IR, P< 0.001] as did Dia [10.2% vs 44.4% in IR P< 0.001] and IPC [8.69% vs 44.47% in IR, P< 0.001]. The protective effect of magnesium was abolished by Gli. Administration of Mg had an anti-infarct effect in ischemic-reperfusion isolated rat hearts and improved cardiac function. Blockade of K-ATP channel abolished the protective effects of magnesium and suggest that K-ATP channel has an important role in this effects

Amplifying the manganese scavenging potential of Streptococcus zooepidemicus to reactive oxygen species during production of hyaluronic acid

Streptococcus zooepidemicus (SZ) is an aerotolerant bacteria and its ability to survive under reactive oxidant challenge raises the question of the existence of a defense system. Thus growth, hyaluronic acid (HA) and hydrogen peroxide (H2O2) production by SZ in the presence of increasing concentration of Mn2+ were studied. The results suggested that the tested strain supported growth and HA production in cultures treated with 1 and 10 mM of Mn2+ regardless of H2O2 presence in the medium. This showed that SZ have acquired elaborate defense mechanisms to scavenge oxygen toxicity and thus protect cells from direct and indirect effect of this radical. In contrast, cells treated with 25 mM Mn2+ were sensitive, in which, the HA production was reduced considerably. Thus showing that the oxygen scavenger systems of the cells may be fully saturated at this concentration.

Comparative effect of ion calcium and magnesium in the activation and infection of the murine macrophage by Leishmania major

Amastigotes of Leishmania major have a great ability to evade destruction in host cells. This study investigated the activation in resident, inflammatory macrophages and J774 cells in vitro treated with lipopolysaccharide (LPS), soluble Leishmania antigen (SLA), calcium ionophore (CaI) and magnesium (Mg2+) alone or combined. An increase in nitric oxide (NO) production was observed in J774 or inflammatory macrophages treated with LPS alone or in combination with SLA and CaI. The same treatments did not affect the NO release by resident macrophages. There was no interference in uptake of L. major but CaI decreased intracellular proliferation of the parasite. This study demonstrated the importance of CaI in decreasing L. major proliferation inside murine macrophages while Mg2+ seemed to increase parasite proliferation. These finding may help to understand the events involved in host cells' clearance of this pathogen..

Limited proteolysis by trypsin influences activity of maize phosphoenolpyruvate carboxylase.

Maize phosphoenolpyruvate carboxylase (PEPC) was rapidly and completely inactivated by very low concentrations of trypsin at 37 degrees C. PEP+Mg2+ and several other effectors of PEP carboxylase offered substantial protection against trypsin inactivation. Inactivation resulted from a fairly specific cleavage of 20 kDa peptide from the enzyme subunit. Limited proteolysis under catalytic condition (in presence of PEP, Mg2+ and HCO3) although yielded a truncated subunit of 90 kDa, did not affect the catalytic function appreciably but desensitized the enzyme to the effectors like glucose-6-phosphate glycine and malate. However, under non-catalytic condition, only malate sensitivity was appreciably affected. Significant protection of the enzyme activity against trypsin during catalytic phase could be either due to a conformational change induced on substrate binding. Several lines of evidence indicate that the inactivation caused by a cleavage at a highly conserved C-terminal end of the subunit.

Hipomagnesemia - grau de conhecimentos médicos / Magnesium deficiency - medical knowledge degree

Avaliar conhecimentos sobre a hipomagnesemia dos preceptores da Residência da Clínica Médica do Hospital Regional de Säo José, Säo José, SC. Aplicaçäo de questionário por escrito, durante uma reuniäo preparatória da Residência, para 18 clínicos do serviço. Todos os questionários foram recolhidos ao final da reuniäo. Doze (66,67 por cento) dos 18 participantes responderam, sendo sete mulheres (58,33 por cento). Anos de formado: 4 a 25 anos (média e mediana de 11,25). Eram de nove especialidades distintas, 10 (83,33 por cento) completaram residência médica e dois (16,67 por cento) mestrado. cinco (41,67 por cento) trabalhavam na emergência e cinco na UTI. A freqüência estimada da hipomagnesemia era <25 por cento para nove (75 por cento) respondentes. Das causas, o diurético foi citado por sete (58,33 por cento) e o álcool três (25 por cento). Os sintomas mais lembrados foram arritmia - sete (58,33 por cento), convulsäo e alteraçäo de consciência - quatro (33,33 por cento) cada. Sete (58,33 por cento) consideravam a hipomagnesemia uma emergência. Sete (58,33 por cento) solicitavam rotineiramente a dosagem. Outros exames laboratoriais necessários para avaliaçäo inicial: creatinina citada por oito (66,67 por cento), glicemia sete (58,33 por cento), hemograma e potássio: cinco (41,67 por cento), sódio e parcial de urina: três (25 por cento). Nenhum respondente sabia o valor correto da dosagem de Mg. Os respondentes possuíam os conhecimentos adequados e refletiam as diferenças existentes na literatura médica. Isso permitiu as variaçöes clínicas em diagnóstico e terapêutica. Assim, mais que a metade considerava hipomagnesemia como emergência e a mesma quantidade solicitava rotineiramente a dosagem do Mg independente da sintomatologia. E nenhum sabia o custo real do exame.

Interactions of chromomycin A3 and mithramycin with the sequence d(TAGCTAGCTA)2.

Anti-cancer antibiotics, chromomycin A3 (CHR) and mithramycin (MTR) inhibit DNA directed RNA synthesis in vivo by binding reversibly to template DNA in the minor groove with GC base specificity, in the presence of divalent cations like Mg2+. Under physiological conditions, (drug)2Mg2+ complexes formed by the antibiotics are the potential DNA binding ligands. Structures of CHR and MTR differ in their saccharide residues. Scrutiny of the DNA binding properties reveal significant differences in their sequence selectivity, orientation and stoichiometry of binding. Here, we have analyzed binding and thermodynamic parameters for the interaction of the antibiotics with a model oligonucleotide sequence, d(TAGCTAGCTA)2 to understand the role of sugars. The oligomer contains two potential binding sites (GpC) for the ligands. The study illustrates that the drugs bind differently to the sequence. (MTR)2Mg2+ binds to both sites whereas (CHR)2Mg2+ binds to a single site. UV melting profiles for the decanucleotide saturated with the ligands show that MTR bound oligomer is highly stabilized and melts symmetrically. In contrast, with CHR, loss of symmetry in the oligomer following its association with a single (CHR)2Mg2+ complex molecule leads to a biphasic melting curve. Results have been interpreted in the light of saccharide dependent differences in ligand flexibility between the two antibiotics.

O íon magnésio no tratamento de acidentes causados pelos escorpiöes Tityus serrulatus, T. bahiensis e Centruroides sculpturatus: estudo experimental / Magnesium in the treatment of accidents caused by the scorpions Tityus serrulatus, T. bahiensis and Centruroides sculpturatus: an experimental study

Os efeitos produzidos pelas peçonhas escorpiônicas säo consequentes, em sua maioria, à liberaçäo de acetilcolina (ACh) e catecolaminas. A verificaçäo de que o magnésio (Mg2+) inibe a liberaçäo de ACh em razäo de bloquear o influxo de cálcio nas terminaçöes nervosas, levou-nos a investigar a açäo deste cátion sobre os distúrbios produzidos pelas peçonhas escorpiônicas. Relatamos na presente comunicaçäo a açäo do Mg2+ sobre os efeitos induzidos pelas peçonhas dos escorpiöes Tityus serrulatus, T. bahiensis e Centruroides sculpturatus nas preparaçöes isoladas nervo frênico-diafragma, íleo, canal deferente e átrios de rato e in vivo, em ratos anestesiados com registro da pressäo arterial e do eletrocardiograma. Os efeitos da peçonha dos escorpiöes nas preparaçöes isoladas foram abolidos ou muito atenuados pelo Mg2+. O Mg2+, no entanto, somente antagonizou os efeitos da peçonha de C. sculpturatus no íleo de rato. Em ratos anestesiados, a hipertensäo e arritmias provocadas pela peçonha de T. serrulatus foram revertidas com exclusäo de bradicardia pela injeçäo do Mg2+. A peçonha de C. sculpturatus na maioria das experiências causou hipotensäo e arritmias de pequena gravidade. O Mg2+ reverteu as arritmias, mas causou quedas acentuadas da pressäo arterial. Os resultados da pesquisa sugerem o emprego do Mg2+ em acidentes graves na ausência de hipotensäo e bradicardia, produzidos por T. serrulatus e T. bahiensis. Parece contra-indicado nos acidentes causados por C. sculpturatus em vista de seu efeito acima referido na pressäo arterial.

Modification of maize NADP-malic enzyme by Woodward's reagent 'K'.

Maize leaf NADP-malic enzyme was rapidly inactivated by micromolar concentrations of Woodward's reagent K (WRK). The inactivation followed pseudo-first order reaction kinetics. The order of reaction with respect to WRK was 1, suggesting that inactivation was a consequence of the modification of a single residue per active site. The modified enzyme showed a characteristic absorbance at 346 nm due to carboxyl group modification and also exhibited altered surface charge as seen from the elution profile on "Mono Q" anion exchange column and the mobility on native polyacrylamide gel electrophoresis. Substrate NADP and NADP + Mg2+ strongly protected the enzyme against WRK inactivation indicating that the modified residue may be located at or near the active site. Binding affinity of NADPH to the malic enzyme was studied by the fluorescence technique. The native enzyme binds NADPH strongly resulting in enhancement of the fluorescence emission and also causes a blue shift in the emission maximum of NADPH from 465 nm to 450 nm, however, the modified enzyme neither exhibited the enhancement of fluorescence emission nor the blue shift, indicating loss of NADPH binding site on modification. The essential carboxyl group may be involved in NADPH binding during catalysis by the enzyme.

Magnésio no infarto agudo do miocárdio: reposiçäo e efeitos na mortalidade / Magnesium in acute myocardial infarction (AMI): replacment and effects in mortality

Apesar dos recentes avanços terapêuticos, o IAM constitui-se em importante causa de morte, acometendo indistintamente a populaçäo, o que justifica a busca por terapêuticas eficazes e de baixo custo. Existem evidências, clínicas e experimentais de que o uso do magnésio poderia reduzir mortalidade em pacientes infartados. Objetivo: Verificar a mortalidade em pacientes na fase aguda do IAM com o uso do magnésio nas doses de 40 e 80 mmol por 24 horas. Desenho do estudo: Ensaio clínico randomizado, prospectivo, duplo-cego, placebo controlado. Material e métodos: Estudados 66 pacientes nas primeiras 24 horas de evoluçäo do IAM, randomizados em grupo I (placebo) com 22 pacientes, grupo II (40 mmol de magnésio) com 25 pacientes e grupo III (80 mmol de magnésio) com 19 pacientes. Resultados: Verificados três (13,6 por cento) óbitos no grupo I, um (4,0 por cento) no grupo II e seis (31,6 por cento) nogrupo III, com diferença significante na comparaçäo entre os grupos II e III. A reduçÝo de mortalidade foi de 70 por cento no grupo II (40 mmol de magnésio) comparando com o I (placebo), observado aumento da mortalidade de 57 por cento no grupo III (80 mmol de magnésio) comparando com o grupo I, porém sem significância estatística. Conclusöes: A reduçäo de mortalidade observada no grupo de pacientes que recebeu magnésio na dose de 40 mmol é superponível àquela observada na literatura, entretanto o número reduzido de pacientes provavelmente näo permitiu significância estatística. A elevada mortalidade verificada no grupo que recebeu 80 mmol de magnésio provavelmente foi acentuada pelo perfil de maior gravidade desses pacientes, entretanto a literatura indica tendência a pior prognóstico em pacientes que utilizaram doses semelhantes.