Hydrogen peroxide activates cell death and defense gene expression in birch.
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The function of hydrogen peroxide (H(2)O(2)) as a signal molecule regulating gene expression and cell death induced by external stresses was studied in birch (Betula pendula). Ozone (O(3)), Pseudomonas syringae pv syringae (Pss), and wounding all induced cell death of various extents in birch leaves. This was temporally preceded and closely accompanied by H(2)O(2) accumulation at, and especially surrounding, the lesion sites. O(3) and Pss, along with an artificial H(2)O(2) producing system glucose (Glc)/Glc oxidase, elicited elevated mRNA levels corresponding to genes encoding reactive oxygen species detoxifying enzymes, Pal, Ypr10, and mitochondrial phosphate translocator 1. In addition to the regulation of gene expression, Glc/Glc oxidase also induced endogenous H(2)O(2) production in birch leaves, accompanied by cell death that resembled O(3) and Pss damage. Wound-induced gene expression differed from that induced by O(3) and Pss. Thus, it appears that at least two separate defense pathways can be activated in birch leaves by stress factors, even though the early H(2)O(2) accumulation response is common among them all. (+info)
Evaluation of effects of magnesium sulphate in reducing intraoperative anaesthetic requirements.
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BACKGROUND: The present randomized, placebo-controlled, double-blind study was designed to assess the effect of peroperatively administered i.v. magnesium sulphate on anaesthetic and analgesic requirements during total i.v. anaesthesia. METHODS: Eighty-one patients (36 women, 45 men) undergoing elective spinal surgery were included in one of two parallel groups. The magnesium group received magnesium sulphate 30 mg kg(-1) as a bolus before induction of anaesthesia and 10 mg kg(-1) h(-1) by continuous i.v. infusion during the operation period. The same volume of isotonic solution was administered to the control group. Anaesthesia was maintained with propofol (administered according to the bispectral index) and remifentanil (adjusted according to heart rate and arterial blood pressure) infusions. RESULTS: A significant reduction in hourly propofol consumption was observed with magnesium administration. For example, the mean infusion rate of propofol in the second hour of the operation was 7.09 mg kg(-1) h(-1) in the control group vs 4.35 mg kg(-1) h(-1) in the magnesium group (P<0.001). The magnesium group required significantly less remifentanil (P<0.001) and vecuronium (P<0.001). No side-effects were observed with magnesium administration. CONCLUSION: The administration of magnesium led to a significant reduction in the requirements for anaesthetic drugs during total i.v. anaesthesia with propofol, remifentanil and vecuronium. (+info)
Efficacy of intravenous magnesium in neuropathic pain.
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BACKGROUND: Postherpetic neuralgia is a complication of acute herpes zoster characterized by severe pain and paraesthesia in the skin area affected by the initial infection. There is evidence that the N-methyl-D-aspartate receptor is involved in the development of hypersensitivity states and it is known that magnesium blocks the N-methyl-D-aspartate receptor. METHOD: A double-blind, placebo-controlled, cross-over study was conducted in which magnesium sulphate was administered as an i.v. infusion. Spontaneous pain was recorded and qualitative sensory testing with cotton wool was performed in seven patients with postherpetic neuralgia before and after the i.v. administration of either magnesium sulphate 30 mg kg(-1) or saline. RESULTS: During the administration, pain scores were significantly lower for magnesium compared with placebo at 20 and 30 min (P=0.016) but not at 10 min. I.V. magnesium sulphate was safe, well-tolerated and effective in patients with postherpetic neuralgia. CONCLUSION: The present study supports the concept that the N-methyl-D-aspartate receptor is involved in the control of postherpetic neuralgia. (+info)
Intravenous magnesium sulfate administration reduces propofol infusion requirements during maintenance of propofol-N2O anesthesia: part I: comparing propofol requirements according to hemodynamic responses: part II: comparing bispectral index in control and magnesium groups.
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BACKGROUND: The authors investigated whether an intravenous administration of magnesium sulfate reduces propofol infusion requirements during maintenance of propofol-N2O anesthesia. METHODS: Part I study: 54 patients undergoing total abdominal hysterectomy were randomly divided into two groups (n = 27 per group). The patients in the control group received 0.9% sodium chloride solution, whereas the patients in the magnesium group received magnesium (50 mg/kg as a bolus, then 8 mg x kg(-1) x h(-1)). To maintain mean arterial blood pressure (MAP) and heart rate (HR) at baseline value, the propofol infusion rate was changed when the MAP or the HR changed. The amount of propofol infused excluding the bolus dosage was divided by patient's body weight and total infusion time. Part II study: Another 20 patients were randomly divided into two groups (n = 10 per group). When the MAP and HR had been maintained at baseline value and the propofol infusion rate had been maintained at 80 microg x kg(-1) x min(-1) (magnesium group) and 160 microg x kg(-1) x min(-1) (control group), bispectral index (BIS) values were measured. RESULTS: Part I: The mean propofol infusion rate in the magnesium group (81.81 +/- 13.09 microg x kg(-1) x min(-1)) was significantly less than in the control group (167.57 +/- 47.27). Part II: BIS values in the control group (40.70 +/- 3.89) were significantly less than those in the magnesium group (57.80 +/- 7.32). CONCLUSION: Intravenous administration of magnesium sulfate reduces propofol infusion requirements. These results suggest that magnesium administration may have an effect on anesthesia or analgesia and may be a useful adjunct to propofol anesthesia. (+info)
A comparison of magnesium sulfate and nimodipine for the prevention of eclampsia.
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OBJECTIVE: Magnesium sulfate may prevent eclampsia by reducing cerebral vasoconstriction and ischemia. Nimodipine is a calcium-channel blocker with specific cerebral vasodilator activity. Our objective was to determine whether nimodipine is more effective than magnesium sulfate for seizure prophylaxis in women with severe preeclampsia. METHODS: We conducted an unblinded, multicenter trial in which 1650 women with severe preeclampsia were randomly assigned to receive either nimodipine (60 mg orally every 4 hours) or intravenous magnesium sulfate (given according to the institutional protocol) from enrollment until 24 hours post partum. High blood pressure was controlled with intravenous hydralazine as needed. The primary outcome measure was the development of eclampsia, as defined by a witnessed tonic-clonic seizure. RESULTS: Demographic and clinical characteristics were similar in the two groups. The women who received nimodipine were more likely to have a seizure than those who received magnesium sulfate (21 of 819 [2.6 percent] vs. 7 of 831 [0.8 percent], P=0.01). The adjusted risk ratio for eclampsia associated with nimodipine, as compared with magnesium sulfate, was 3.2 (95 percent confidence interval, 1.1 to 9.1). The antepartum seizure rates did not differ significantly between groups, but the nimodipine group had a higher rate of postpartum seizures (9 of 819 [1.1 percent] vs. 0 of 831, P=0.01). There were no significant differences in neonatal outcome between the two groups. More women in the magnesium sulfate group than in the nimodipine group needed hydralazine to control blood pressure (54.3 percent vs. 45.7 percent, P<0.001). CONCLUSIONS: Magnesium sulfate is more effective than nimodipine for prophylaxis against seizures in women with severe preeclampsia. (+info)
Urinary sulfur excretion and the nitrogen/sulfur balance ratio reveal nonprotein sulfur amino acid retention in piglets.
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We evaluated the use of urinary sulfur (S) excretion as a measure of sulfur amino acid (SAA) catabolism and the nitrogen/sulfur (N/S) molar balance ratio as an indicator of nonprotein SAA storage in growing piglets. After confirming that an intravenous dose of sulfate is fully recovered in urinary sulfate, we measured urinary S recovery after an intravenous dose of methionine in 6 piglets fed an adequate protein (AP) diet and 6 piglets fed a low protein (LP) diet with normal energy provision. As measured over 48 h, recoveries of the methionine load as urinary total S was 106% in the AP group but only 69% in the LP group (P < 0.05). On the baseline diets the N/S balance ratio in the AP group was 36, whereas that in the LP group was 30 (P < 0.05); immediately after the methionine load, this ratio remained constant in the AP group but decreased further, to 26 (P < 0.05) in the LP group. These results indicate that protein-deficient piglets accumulate relatively more S than N from their diet, and under these conditions a significant portion of the S derived from a methionine load is retained in nonprotein compounds. Urinary S excretion, a simple nontracer measurement, can provide an accurate measure of SAA catabolism, and the N/S balance ratio is a potentially useful indicator of changes in nonprotein SAA stores of growing piglets. (+info)
Na+/H+ exchange activity in the plasma membrane of Arabidopsis.
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In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt. (+info)
Effects of magnesium sulphate on cerebral haemodynamics in healthy volunteers: a transcranial Doppler study.
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BACKGROUND: Magnesium is increasingly being considered as a neuroprotective agent. We aimed to study its effects on middle cerebral artery blood flow velocity (V(mca)), cerebral autoregulation and cerebral vascular reactivity to carbon dioxide (CRCO(2)) in healthy volunteers. METHODS: Fifteen healthy volunteers were recruited. Using transcranial Doppler ultrasonography, V(mca) was recorded continuously. The strength of autoregulation was assessed by the transient hyperaemic response test, and the CRCO(2) was measured by assessing changes in V(mca) to the induced changes in end-tidal carbon dioxide. I.V. infusion of magnesium sulphate was then started (loading dose of 16 mmol followed by an infusion at the rate of 2.7 mmol h(-1)) for 45 min. The cerebral haemodynamic variables were measured again near the end of the infusion of magnesium sulphate. RESULTS: Total serum magnesium levels were doubled by the infusion regimen. However, there were no significant changes in V(mca), strength of autoregulation, or CRCO(2). Five of the volunteers reported marked nausea and two developed significant hypotension during the loading dose. CONCLUSIONS: Infusion of magnesium sulphate, in a dose that doubles its concentration in plasma, does not affect V(mca), strength of autoregulation or CRCO(2) in healthy volunteers. However, it can be associated with nausea and hypotension. (+info)