Evidence of a square two-dimensional solid of methane physisorbed on the (100) surface of magnesium oxide.
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Journal Article↗
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Highly mobile oxygen holes in magnesium oxide.
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Journal Article↗
Equation of state and shear strength at multimegabar pressures: Magnesium oxide to 227 GPa.
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Journal Article↗
Diffusion of palladium clusters on magnesium oxide.
The diffusion of small palladium clusters on MgO(100) is theoretically investigated. It is found that small clusters can diffuse even faster than isolated adatoms by a variety of mechanisms (some of which are novel), such as dimer rotation, trimer walking, tetramer rolling, and sliding. The consequences of the diffusion of small clusters on the growth of Pd aggregates on MgO(100) are investigated, and it is shown that fast mobility of clusters larger than a single atom is essential to bring the theoretical results into agreement with the outcome of molecular beam epitaxy experiments.
Journal Article↗
In vitro availability of gliclazide in presence of antacids.
Gliclazide is the most commonly used sulfonylurea derivative for NIDDM therapy. Due to its prolonged therapy, there is always a likelihood of its use with other drugs. On the other hand antacids are commonly prescribed to encounter gastric acidity etc. Present paper deals with the in vitro availability studies of gliclazide in presence of antacids. These studies were carried out in simulated gastric juice and in buffer of pH 7.4 at body and accelerated temperature. The antacids used in these studies were aluminum hydroxide, aluminum trisilicate, magnesium oxide, magnesium trisilicate, sodium bicarbonate, calcium carbonate, magaldrate and simethicone (2,4-dimethoxypoly-siloxane). It has been found that in case of magnesium oxide, magnesium trisilicate and sodium bicarbonate, availability of gliclazide was enhanced while in rest of the antacids retarded the availability of gliclazide.
Journal Article↗
In vitro availability of glibenclamide in presence of antacids.
The in vitro availability studies of glibenclamide in presence of commonly used antacids are present in this paper. Glibenclamide is used for the treatment of Non-Insulin dependent diabetes mellitus. It is a sulfonylurea derivative. Antacids are prescribed to encounter gastric acidity etc. These studies were carried out in simulated gastric juice and in buffer of pH 7.4 at 37 and 48 degrees C. Aluminum hydroxide, aluminum trisilicate, magnesium oxide, magnesium trisilicate, sodium bicarbonate, calcium carbonate, magaldrate and simethicone (2,4-dimethoxypolysiloxane) antacids were used in these studies. It has been observed that in case of magnesium oxide, magnesium trisilicate and sodium bicarbonate, availability of glibenclamide was enhanced while in rest of the antacids retarded the availability of glibenclamide.
Journal Article↗
[Fluorimetric determination of some alkaloids after thin-layer chromatographic separation on magnesium oxide].
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Alkaloids↗
Effects of magnesium salts in preventing experimental oxalate urolithiasis in rats.
Magnesium oxide, magnesium hydroxide, magnesium sulfate, magnesium trisilicate, and magnesium citrate were added to a calcium-oxalate lithogenic diet in order to determine their effects in preventing lithogenesis. Male Wistar-strain rats which had been fed the glycolic-acid diet developed marked urinary calculi within four weeks. Rats in the magnesium-hydroxide, magnesium-citrate, and magnesium-trisilicate groups, however, had almost no stones in the urinary system. Rats in the magnesium-oxide and magnesium-sulfate groups showed significantly less effect than those in the former three groups. During the experimental period, the 24-hour urinary oxalate excretion and concentration were higher in the glycolic-acid group than in the other groups. The urinary citrate excretion and concentration were the highest in the magnesium-hydroxide and magnesium-citrate groups and higher in the magnesium-trisilicate and magnesium-oxide groups than in the magnesium-sulfate and glycolic-acid groups. Similar trends were observed in the urinary magnesium excretion and in its concentration. The urinary calcium excretion and concentration were higher in the experimental groups than in the glycolic-acid group. The urinary calcium/magnesium ratio remained mostly unchanged. Therefore, it can be concluded that alkaline magnesium salts increase the urinary calcium and magnesium concentrations, without changing the calcium/magnesium ratio, and inhibit urinary calculi formation, most likely by increasing the urinary citrate concentration.
Animals↗
Polymer implant materials with improved X-ray opacity and biocompatibility.
Poly(methyl methacrylate) samples containing 28 wt% inorganic fillers such as zirconium oxide, barium sulphate, zinc oxide, magnesium oxide and tricalcium phosphate were prepared and studied for their suitability as implant materials by physical property tests, X-ray opacity measurement, cell culture, and animal implantations. Addition of inorganic fillers to poly(methyl methacrylate) increased the compressive strength but decreased the transverse strength. Zirconium oxide was found to be most suitable as an X-ray opaque filler, and tricalcium phosphate showed superior biocompatibility when added to poly(methyl methacrylate) in cell culture experiments. The zirconium oxide and tricalcium phosphate composites evoked no greater unfavourable tissue reaction in rats than pure poly(methyl methacrylate). From the physical and biological standpoints zirconium oxide is the radiopaque filler of choice to be incorporated in poly(methyl methacrylate) implant material and addition of tricalcium phosphate could improve it's biocompatibility.
Animals↗
In vitro adsorption of some corticosteroids on antacids.
The adsorption of prednisone, prednisolone, fluprednisolone, betamethasone, triamcinolone, beta-methylprednisone acetate and hydrocortisone acetate on various antacids or adsorbents was studied at 37 degrees C. The antacids or adsorbents used were magnesium trisilicate, aluminum hydroxide, bismuth oxycarbonate, magnesium oxide, magnesium carbonate, calcium carbonate, talc, kaolin and charcoal. Magnesium trisilicate and charcoal had the highest adsorption capacity for the corticosteroids tested. Bismuth oxycarbonate and talc had intermediate adsorption properties while kaolin and aluminium hydroxide had lower effects. Other antacids were without any adsorption character. Results of the elution study confirmed the higher affinity of magnesium trisilicate over that of bismuth oxycarbonate and talc for the steroids tested. Further in vivo testings are still needed to assess the effect of antacids on the bioavailability of coadministered corticosteroids.
Adrenal Cortex Hormones↗
Erythromycin-antacid interaction.
The in vitro release of erythromycin stearate in the presence of aluminium hydroxide, aluminium trisilicate, magnesium oxide, magnesium trisilicate, sodium hydrogen carbonate and a combination of aluminium hydroxide gel, magnesium hydroxide and dimethyl polysiloxane has been studied by the USP XX dissolution method. The dissolution of erythromycin was found to be markedly retarded in the presence of all the antacids studied except sodium hydrogen carbonate. An attempt was made to elucidate the mechanism of this effect.
Antacids↗
Simple metallic compounds as pulp-capping agents. A pilot study.
A pilot study is described in which the exposed pulps of molar teeth of normal laboratory rats were capped with various metallic compounds in general medical usage. There appeared to be no relationship between the response obtained and the pH of the compounds studied. Aluminum powder, aluminum hydroxide, Aludrox, aluminum oxide, light magnesium oxide, magnesium hydroxide, and titanium dioxide gave poor results. Barium sulfate, calcium carbonate, cupric oxide, ferric oxide, heavy magnesium oxide, and stannic oxide merited more detailed study.
Animals↗
Magnesium deficiency in rats induces a rise in plasma nitric oxide.
Magnesium deficiency in rats leads to an oxidative stress involving an increased production of radical oxygen species. The present study was designed to examine the effect of experimental magnesium deficiency on plasma nitric oxide (NO) level and nitric oxide synthases (NOS) activities in rats. The data show that the concentration of NO is markedly increased in plasma of magnesium-deficient rats. This rise in plasma NO results from activation of inducible nitric oxide synthase (iNOS) rather than of the constitutive form (cNOS) of the enzyme. These data are in agreement with previous observations indicating that inflammation occurs during magnesium-deficiency and provide an additional cause of oxidative lesions through formation of peroxynitrite from nitric oxide and superoxide anion.
Animals↗
Alterations in magnesium and oxidative status during chronic emotional stress.
Magnesium and oxidative status were investigated in young volunteers exposed to chronic stress (political intolerance, awareness of potential military attacks, permanent stand-by duty and reduced holidays more than 10 years) or subchronic stress consisting of everyday mortal danger in military actions lasting more than 3 months. Significant decreases in plasma ionized Mg2+, total Mg and ionized Ca2+ concentrations were found in both groups. Similarly, both study groups exhibited oxidative stress as assessed by increased plasma superoxide anions and malondialdehyde and modified antioxidant defense. There were no significant differences between the two stress groups. A negative correlation between magnesium balance and oxidative stress was observed suggesting that the same etiological factor (chronic stress) initiate decreases in both free and total magnesium concentrations and simultaneously increase oxidative stress intensity. These findings support the need for magnesium supplementation with antioxidant vitamins for people living in conditions of chronic stress.
Adolescent↗
Formation and stability of polychlorinated biphenyl Pickering emulsions.
An emulsion stabilized by colloidal suspensions of finely divided solids is known as a Pickering emulsion. The potential for polychlorinated biphenyls (PCBs) to form Pickering emulsions ex situ when in contact with powdered solids, such as clays and metal oxides, is investigated here. Bentonite, iron oxide and magnesium oxide dispersions proved to be robust Pickering emulsion stabilizers, whereas manganese oxide dispersions were not. Batch experiments revealed that emulsions can be formed using a moderately low energy input and can be stabilized with solid concentrations as low as 0.5 wt.%. For the base conditions (volumetric oil fraction (phi(oil))=30 vol.%; solid concentration (chi)=2 wt.%), the formed emulsions were indefinitely stable and the initial average droplet diameters varied from 80 to 258 mum, depending on the solid used in the colloidal dispersion. The average droplet size varied at early time, but for most conditions stabilized to a steady-state value 1 week after preparation. The effect of Ostwald ripening was limited. At greater than 0.5 wt.% concentration, the efficiency of the solid dispersion as a stabilizer was dependant on the volumetric oil fraction but not on the solid concentration. Generally, systems with volumetric oil fractions outside of the 20-70 vol.% range were unstable. The emulsions' droplet stability, average droplet size and size distribution were observed to vary as a function of the amount of energy provided to the system, the volumetric oil fraction, and the concentration of the solid in the aqueous dispersion. It is hypothesized that drilling through fractured rock in the immediate vicinity of dense, non-aqueous phase liquid (DNAPL) PCBs may provide both the energy and solid material necessary to form Pickering emulsions.
Bentonite↗
Comparison of the effects of ranitidine effervescent tablets and magnesium hydroxide-aluminium oxide on intragastric acidity. A single-centre, randomised, open cross-over study.
In previous studies measuring intragastric pH in healthy volunteers it was shown that there was a faster onset of action with ranitidine (CAS 66357-35-5) 300 mg effervescent tablets (Zantac) compared to standard tablets. In a single-centre, randomised, open cross-over study the pH-values obtained over 6 h following the administration of one ranitidine 150 mg effervescent tablet were compared with those after aluminium oxide-magnesium hydroxide (algeldrate, CAS 1330-44-5, Al-Mg-hydroxide) 10 ml and placebo in healthy volunteers. 24 healthy male subjects between 19 and 32 years of age entered the study, 19 subjects were available for all three measurements. After an overnight fast, intragastric pH was monitored for 7 h using a glass electrode and a digital data recorder. The time in % during which the pH was > or = 3.5 and the area under the curve of the obtained pH-curves were compared. There was a highly statistically significant difference between ranitidine effervescent tablets versus Al-Mg-hydroxide and placebo whereas there was no such difference between Al-Mg-hydroxide and placebo. The onset of action of ranitidine effervescent tablets was almost immediate. It is concluded that there was a clear superiority of ranitidine effervescent tablets in healthy volunteers and it is suggested that pH-metry in patients with acidity-related diseases should be investigated for a better understanding of the function of effervescent tablets.
Adult↗
Effect of antacids on activity of oral hypoglycemics.
The effect of some antacids on the dissolution and hypoglycemic activity of acetohexamide, tolazamide, and tolbutamide tablets was investigated, as was the adsorption of the three drugs onto the antacids. The dissolution rates of the three drugs in the presence of magnesium oxide, aluminum hydroxide, magnesium carbonate, and calcium carbonate increased (0.5-1 hr) and then plateaued or decreased (1-3 hr). Magnesium trisilicate directly suppressed the dissolution of the three drugs. The antacids reduced the hypoglycemic activity of tolbutamide in the following order:magnesium trisilicate greater than magnesium oxide greater than aluminum hydroxide greater than magnesium carbonate greater than calcium carbonate. The same order occurred for the first three antacids with acetohexamide and tolazamide. Decreased hypoglycemic activity of the drugs may have been due to their adsorption to the coadministered antacids.
Adsorption↗
The in-vitro adsorption of some antirheumatics on antacids.
The adsorption of sodium salicylate, salicylamide, acetylsalicylic acid, paracetamol, mefenamic acid, flufenamic acid, phenylbutazone, oxyphenbutazone, phenazone, aminophenazone, indometacin and methiazinic acid on some antacids was studied. The antacids used were magnesium trisilicate, magnesium oxide, aluminium hydroxide, bismuth oxycarbonate, calcium carbonate and kaolin. Magnesium oxide, followed by aluminium hydroxide and bismuth oxycarbonate showed a fairly high adsorptive capacity for salicylates, mefenamic acid, flufenamic acid, methiazinic acid, indometacin and to a lesser extent for phenylbutazone and oxyphenbutazone. On the other hand, magnesium trisilicate exhibited a tendency to adsorb phenazone, aminophenazone, indometacin and methiazinic acid. Kaolin was found to be a good adsorbent for anthranilic acid derivatives, indometacin and methiazinic acid. Calcium carbonate showed a weak adsorptive capacity for all drugs tested. The adsorption of phenylbutazone and salicylates on magnesium oxide, aluminium hydroxide and/or bismuth oxycarbonate obeyed the Freundlich adsorption isotherm. Elution study showed that salicylates and anthranilic acid derivatives were tenaciously held by magnesium oxide while magnesium trisilicate showed an intermediate retention power for phenazone and aminophenazone. Sodium hydrogen carbonate solution gave, in general, a higher eluting power than hydrochloric acid solution. A marked reduction in the apparent partition coefficients of all drugs tested was observed in the presence of magnesium trisilicate or aluminium hydroxide. Careful in vitro and in vivo testing of drug availability is advisable prior to the concomitant administration of antirheumatics with antacids or other adsorbents.
Adsorption↗