Keeping an enzyme in its native form with high catalytic activity is of great significance. In the present study, thermal stabilizers of horseradish peroxidase (HRP) were screened. The results indicated that thermal stability of HRP was enhanced by magnesium sulphate and gelatin. A synergic effect of magnesium sulphate and gelatin was observed. In the presence of the stabilizer, the enzymatic activity of HRP remained 89% after kept for 80 h at 50 degrees C and 57% for 90 days at room temperature. Thermal alterations of HRP structure in the absence and presence of the stabilizers were explored by using UV absorption spectra at 402 nm (Soret band), intrinsic fluorescence and 8-anilinonaphthalene-1-sulfonic acid (ANS) fluorescence. The results suggested that magnesium sulphate and gelatin attenuated the extent of unfolding of HRP and therefore the native enzyme structure was stabilized.
Drug Synergism ; Enzyme Stability ; drug effects ; Gelatin ; pharmacology ; Horseradish Peroxidase ; metabolism ; Hot Temperature ; Magnesium Sulfate ; pharmacology

Culture medium and fermentation conditions for lipid production by Rhodosporidium toruloides were optimized with single factor and uniform design experiment. The best medium recipe was found with 70 g/L glucose, 0.1 g/L (NH4)2SO4, 0.75 g/L yeast extract, 1.5 g/L MgSO4. 7H2O, 0.4g/L KH2PO4, sterilized at 121 degrees C for 15 min, and then supplemented with ZnSO4 1.91 x 10(-6) mmol/L, CaCl2 1.50 mmol/L, MnCl2 1.22 x 10(-4) mmol/L and CuSO4 1.00 x 10(-4) mmol/L. The optimal fermentation conditions were as follows: 50 mL of medium (pH 6.0) in 250 mL Erlenmeyer flask with 10% inoculum (28h) under orbital shaking at 200 r/min for 120h at 30 degrees C. Under these conditions, yeast biomass accumulated lipids up to 76.1%.
Basidiomycota ; growth & development ; metabolism ; Copper ; pharmacology ; Culture Media ; Fermentation ; Hydrogen-Ion Concentration ; Lipids ; biosynthesis ; Magnesium Sulfate ; pharmacology ; Zinc ; pharmacology

Different neutralizing agents were used as pH controller to investigate their effects on the growth and succinic acid production of Actinobacillus succinogenes NJ113. The fermentation results showed that Ca(OH)2, CaCO3 and NH4OH were not suitable for succinic acid production by A. succinogenes NJ113 because of their negative effects on cell growth. When Na-base was used, cells would flocculate and lump, and due to the sodium ion concentration reaching to a high level, OD660 dropped sharply after 12 h of fermentation. Mg-base was better because there was no significant inhibition by magnesium ion. Two combined neutralizing agents were used to maintain pH level, one with NaOH and Mg(OH)2 while the other with Na2CO3 and Mg(OH)2. The optimum ratios of the combined neutralizing agents were both 1:1 (g:g) when using 100 g/L glucose. When NaOH and Mg(OH)2 were chosen with the ratio of 1:1(g:g), 69.8 g/L of the succinic acid and 74.5% of the yield was obtained.
Actinobacillus ; genetics ; metabolism ; Fermentation ; Hydrogen-Ion Concentration ; Industrial Microbiology ; Magnesium Hydroxide ; pharmacology ; Sodium Hydroxide ; pharmacology ; Succinic Acid ; metabolism

OBJECTIVETo investigate the influencing factors of polyethylenimine (PEI) in gene transfer in vitro.

METHODSCytotoxic effects of PEI on in vitro cultured NIH 3T3 cells were quantified by MTT assay. The interaction between PEI and DNA at different charge ratios was analyzed by agarose gel electrophoresis retardation assay. The expression of gene transfer was monitored in Cos-7 cells using pEGFP and pSV beta plasmids as the reporter gene systems. Influences of chloroquine, albumin, serum, salt ion strength, and Mg(2+) ion and other factors on PEI/DNA transfer efficiency were evaluated.

RESULTThe survival rate of NIH3T3 cells at 6 mg/L of PEI was 64.2% and at 7 mg/L of PEI was 54.4%. Gel electrophoresis retardation assays showed that PEI completely retarded DNA migration at 3.0 PEI nitrogen per DNA phosphate. Chloroquine enhanced the transfection efficiency of PEI. Albumin and serum in the culture medium decreased the transfection efficiency. HBS(HEPES buffered solution) or 150 mmol/L NaCl as the dilution solution of PEI/DNA was superior over 278 mmol/L glucose solution in the transfection efficiency. Mg(2+) in the dilution solution decreased the transfer efficiency of PEI/DNA.

CONCLUSIONPEI is efficient gene transfer agent of eukaryotes in vitro, and can be possibly used in vivo.

Animals ; COS Cells ; Cell Survival ; Chloroquine ; pharmacology ; Culture Media ; Gene Transfer Techniques ; Magnesium ; pharmacology ; Mice ; NIH 3T3 Cells ; Osmolar Concentration ; Polyethyleneimine ; pharmacology

OBJECTIVETo determine the effect of neostigmine on antagonizing atracurium-induced neuromuscular blockage with sulfate magnesium pretreatment.

METHODSForty patients who undertook elective gynecologic laparoscopic examinations and treatments under general anesthesia were randomized into four groups (group A, B, C, and D, group A paired with group C, and group B paired with group D). Before induction of general anesthesia, patients in group A and group C received MgSO4 30 mg/kg in saline intravenously within 5 min, while patients in group B and group D received the same volume of saline. Anesthesia was induced with fentanyl and propofol; subsequently tracheal intubation was performed with 0.5 mg/kg atracurium after stabilization of the electromyography recording, and neostigmine (0.02 mg/kg) and atropine (0.01 mg/kg) were infused in group C and group D when neuromuscular recovery (T1/T(C)) reached 10%. T1/T(C) changes after neostigmine infusion as well as haemodynamic changes and other responses during induction and neostigmine and atropine infusion were recorded.

RESULTSThe neuromuscular recovery speed had no significant difference between group A and group B after the neuromuscular recovery reached 10%, but it was lower in group C than in group D (P < 0.05). Significant difference existed between group AC and group BD (P < 0.05). No haemodynamic changes and other responses were found during induction and neostigmine and atropine infusion.

CONCLUSIONNeostigmine-induced neuromuscular recovery can be attenuated in patients pretreated with magnesium sulfate.

Adolescent ; Adult ; Anesthesia, General ; Atracurium ; antagonists & inhibitors ; Cholinesterase Inhibitors ; pharmacology ; Female ; Humans ; Laparoscopy ; Magnesium Sulfate ; pharmacology ; Middle Aged ; Neostigmine ; pharmacology ; Neuromuscular Blockade ; Neuromuscular Nondepolarizing Agents ; antagonists & inhibitors

OBJECTIVES: To investigate the effect of taurine magnesium coordination compound (TMCC) on torsades de pointes (TdP) in isolated guinea pig hearts. METHODS: Healthy male guinea pigs weighting 250~300 g were randomly divided into 4 groups:①TdP model group (=7):Isolated hearts were perfused by normal K-H solution 20 minutes, then perfused by slowly activated delayed rectifier potassium current(IKs) blocker 10mol/L Chromanol 293B under hypokalemic solution(1.8 mmol/L) to establish TdP model;②~④ TdP model + TMCC group (=6):Isolated hearts were perfused by normal K-H solution for 20 minutes, then perfused by IKs blocker 10mol/L Chromanol 293B under hypokalemic solution(1.8 mmol/L) for 60 minutes, at the same time TMCC which concentration was 1, 2, 4 mmol/L was administered respectively by Langendorff retrograde aortic perfusion method. Cardiac surface electrocardiogram of guinea pigs was collected and recorded by Biopac electrophysiological recorder. Incidence of TdP, transmural dispersion of repolarization (TDR), instability of QT interval were acquired from Lead Ⅱ electrocardiograph (ECG) wave forms to describe the effect of TMCC on TdP model. Datas were acquired at the time of 20 min and pre-TdP, in case there was no TdP observed, a value of 60 min was entered for calculation purpose. RESULTS: Incidence of TdP in TdP model group was 6/7. TdP incidence could be decreased significantly by 1, 2, 4 mmol/L TMCC, and was 5/6, 1/6, 0/6 respectively. Compared with the pre-drug, Chromanol 293B under hypokalemic solution in TdP model group increased TDR(corrected) evidently(<0.01). Compared with the pre-drug, 1, 2, 4 mmol/L TMCC in TdP model + TMCC group could decrease the increased TDR(corrected) induced by Chromanol 293B under hypokalemic solution(>0.05). Compared with the TdP model group, 2, 4 mmol/L TMCC could evidently decrease the instability of QT interval induced by Chromanol 293B under hypokalemic solution(<0.05). During the establishment of TdP model, P waves in more than one cardiac cycle continuously were disappeared in ECG. However, P wave could always be seen independent in ECG acquired from TdP model + TMCC group. CONCLUSIONS TMCC can play the role against TdP through decreasing TDR and instability of QT interval, and inhibiting early after depolarization(EAD).
Animals ; Anti-Arrhythmia Agents ; pharmacology ; Electrocardiography ; Guinea Pigs ; In Vitro Techniques ; Long QT Syndrome ; Magnesium ; pharmacology ; Male ; Random Allocation ; Taurine ; pharmacology ; Torsades de Pointes ; drug therapy

AIMTo study the effects of sodium magnesium fructose diphosphate (SMFD) on free calcium concentration and nitric oxide synthase activity of ischemic synaptosome, so as to explore the protective mechanisms of SMFD on cerebral ischemia.

METHODSThe synaptosomes from normal rat brain were prepared by phase partition and cultured with oxygen-glucose deprivation to establish ischemic synaptosome model. The intrasynaptosomal free calcium concentration and nitric oxide synthase activity were detected separately after the synaptosomes were co-incubated with SMFD (1.3 mmol.L-1) or fructose-1, 6-diphosphate (FDP, 4.0 mmol.L-1) for 60 min.

RESULTSSMFD decreased the free calcium concentration and reduced the activity of nitric oxide synthase (NOS) of ischemic synaptosomes. Its effects were more powerful than those of FDP.

CONCLUSIONSMFD may protect neurons from ischemic injury by preventing intracellular Ca2+ overload and inhibiting the activity of nitric oxide synthase.

Animals ; Brain Ischemia ; enzymology ; metabolism ; Calcium ; metabolism ; Chelating Agents ; pharmacology ; Fructosediphosphates ; pharmacology ; Magnesium ; chemistry ; Male ; Nitric Oxide Synthase ; drug effects ; metabolism ; Rats ; Rats, Wistar ; Sodium ; chemistry ; Synaptosomes ; metabolism

The activity of Mg++-dependent, Ca++-activated adenosine triphosphatase (Ca-ATPase) of rat liver mitochondria was studied at varying medium compositions, pH and temperatures. The enzyme system was characteristically sensitive to Ca++ concentration with a KmCa of approximately 0.06 mM. The optimal concentration of Mg was about l mM, above which the enzyme activity was progressively inhibited. The inhibitory effect of high Mg++ concentrations appeared to be due to the alteration of the Mg++/ATP ratio. Variations in the Mg++/ATP ratio affected Vmax but not the KmATP. The pH optimum for enzyme activity increased as the incubation temperature decreased, but the optimal OH-/H+ ratio of the medium was constant at around 0.1, regardless of temperature. The activity of the enzyme was not affected by La# (0.01-1 mM) and Ruthenium red (2.5-10.0 microM). These results indicate that 1) the enzymatic characteristics of the Ca-ATPase system in the rat liver mitochondria is typical of those from other tissue preparations, 2) the enzyme system maintains the most effective catalytic conformation at a fixed level of OH-/H+ ratio of 0.1 when the temperature changes, and 3) the enzyme system may not play a role in the physiological transport of Ca++ in mitochondria.
Animal ; Ca(2+)-Transporting ATPase/metabolism* ; Calcium/pharmacology ; Enzyme Activation/drug effects ; Female ; Hydrogen-Ion Concentration ; Magnesium/pharmacology ; Male ; Mitochondria, Liver/enzymology* ; Rats ; Temperature

OBJECTIVETo study cortical neuron injury following recurrent epileptiform discharges induced by magnesium-free treatment in vitro.

METHODSCultured embryo cortical neurons were exposed to magnesium-free media for 3 h, then they were returned to regular media containing normal level magnesium. At different time after Mg(2+)-free treatment, trypan blue staining and determination of LDH activity were used to determine the cell viability, flow cytometry was applied to measure neuronal apoptosis, and MTT assay to study metabolic rate.

RESULTS(1) Neuronal morphology on light microscopy following Mg(2+)-free treatment showed that there were no prominent alterations. (2) At different time (6, 12, 72 h) after Mg(2+)-free treatment, neuronal viability by trypan blue staining and LDH activity showed modest changes compared with time-matched control in different culture days (6, 12, 17 d) (P > 0.05). (3) Cell apoptosis increased mildly at different time after Mg(2+)-free treatment in neurons cultured for different days, but the increase was not significant (P > 0.05). (4) Metabolic rate decreased at 6 h after Mg(2+)-free treatment (P < 0.05) in neurons cultured for 6 d, and was 86.4% of that of the control; while the rate at 24 h in neurons cultured for 12 d and 17 d also decreased (P < 0.05), being 78.7% and 70.9%, respectively, of that of the control.

CONCLUSIONSThese findings demonstrated that the injury occurred on cultured cortical neurons caused by magnesium-free-treatment-induced recurrent epileptiform discharges was mainly functional and relatively mature neurons displayed more severe and much later mitochondrial function impairment than immature neurons.

Animals ; Cerebral Cortex ; embryology ; Culture Media ; chemistry ; pharmacology ; Culture Techniques ; Magnesium ; pharmacology ; Neurons ; drug effects ; pathology ; Rats ; Rats, Wistar ; Seizures ; physiopathology

To investigate the modulation of Mg(2+) on rat P2X4 receptors and its underlying mechanism, we transcribed cDNA coding for wild-type and mutant P2X4 receptors to cRNA in vitro, injected the cRNA to oocytes of Xenopus laevis using the microinjection technique and revealed the effect of Mg(2+) on ATP-activated currents (I(ATP)) mediated by P2X4 receptors using the two-electrode whole-cell voltage clamp technique. The effects of extracellular Mg(2+) on I(ATP) were as follows: (1) In oocytes expressing P2X4 receptors, Mg(2+) with concentration ranging from 0.5-10 mmol/L inhibited the amplitude of I(ATP) in a concentration-dependent and reversible manner, with a 50% inhibitory concentration value (IC(50)) of (1.24 ± 0.07) mmol/L for current activated by 100 μmol/L ATP. (2) Mg(2+) (1 mmol/L) shifted the dose-response curve for I(ATP) right-downward without changing the EC(50), but reduced the maximal current (E(max)) by (42.0 ± 2.1)%. (3) After being preincubated with Mg(2+) for 80 s, the inhibitory effect of the Mg(2+) on I(ATP) reached the maximum. (4) The inhibition of Mg(2+) on I(ATP) was independent of membrane potential from -120 mV to +60 mV. (5) Compared with the current activated by 100 μmol/L ATP in the wild-type P2X4 receptors, mutant P2X4 D280Q responded to the application of 100 μmol/L ATP with a smaller current. The peak current was only (4.12 ± 0.15)% of that seen in wild-type receptors. Mutant P2X4 D280E responded to ATP stimulation with a current similar to that observed in cells expressing wild-type receptors. (6) When Asp280 was removed from P2X4, the current amplitude of I(ATP) was increased almost one-fold, and Mg(2+) with concentration ranging from 0.5-10 mmol/L did not affect the I(ATP) significantly. The results suggest that Mg(2+) inhibits I(ATP) mediated by P2X4 receptors non-competitively, reversibly, concentration-dependently, time-dependently and voltage-independently. The inhibitory effect of Mg(2+) might be realized by acting on the site Asp280 of the P2X4 receptors.
Adenosine Triphosphate ; antagonists & inhibitors ; pharmacology ; Animals ; Female ; Magnesium ; pharmacology ; Membrane Potentials ; drug effects ; Oocytes ; metabolism ; physiology ; Patch-Clamp Techniques ; Rats ; Receptors, Purinergic P2X4 ; genetics ; physiology ; Xenopus laevis