[Fluorine prophylaxis of caries; magnesium fluoride and calcium fluoride as physiological and highly effective caries prophylactics].
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Calcium Fluoride↗
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Oral Mg(2+) supplementation reverses age-related neuroendocrine and sleep EEG changes in humans.
The process of normal aging is accompanied by changes in sleep-related endocrine activity. During aging, an increase in cortisol at its nadir and a decrease in renin and aldosterone concentration occur. In aged subjects, more time is spent awake and slow-wave sleep is reduced: there is a loss of sleep spindles and accordingly a loss of power in the sigma frequency range. Previous studies could show a close association between sleep architecture, especially slow-wave sleep, and activity in the glutamatergic and GABAergic system. Furthermore, recent studies could show that the natural N-methyl-D-aspartate (NMDA) antagonist and GABA(A) agonist Mg(2+) seems to play a key role in the regulation of sleep and endocrine systems such as the HPA system and renin-angiotensin-aldosterone system (RAAS). Therefore, we examined the effect of Mg(2+) in 12 elderly subjects (age range 60-80 years) on the sleep electroencephalogram (EEG) and nocturnal hormone secretion. A placebo-controlled, randomised cross-over design with two treatment intervals of 20 days duration separated by 2 weeks washout was used. Mg(2+) was administered as effervescent tablets in a creeping dose of 10 mmol and 20 mmol each for 3 days followed by 30 mmol for 14 days. At the end of each interval, a sleep EEG was recorded from 11 p.m. to 7 a.m. after one accommodation night. Blood samples were taken every 30 min between 8 p.m. and 10 p.m. and every 20 min between 10 p.m. and 7 a.m. to estimate ACTH, cortisol, renin and aldosterone plasma concentrations, and every hour for arginine-vasopressin (AVP) and angiotensin 11 (ATII) plasma concentrations. Mg(2+) led to a significant increase in slow wave sleep (16.5 +/- 20.4 min vs. 10.1 +/- 15.4 min, < or =0.05), delta power (47128.7 microV(2) +21417.7 microV(2) vs. 37862.1 microV(2) +/- 23241.7 microV(2), p < or =0.05) and sigma power (1923.0 microV(2) + 1111.3 microV(2) vs. 1541.0 microV(2) + 1134.5 microV(2), p< or =0.05 ). Renin increased (3.7 +/- 2.3 ng/ml x min vs. 2.3 +/- 1.0 ng/ml x min, p < 0.05) during the total night and aldosterone (3.6 +/- 4.7 ng/ml x min vs. 1.1 +/- 0.9 ng/ml x min, p < 0.05) in the second half of the night, whereas cortisol (8.3 +/- 2.4 pg/ml x min vs. 11.8 +/- 3.8 pg/ml x min, p < 0.01) decreased significantly and AVP by trend in the first part of the night. ACTH and ATII were not altered. Our results suggest that Mg(2+) partially reverses sleep EEG and nocturnal neuroendocrine changes occurring during aging. The similarities of the effect of Mg(2+) and that of the related electrolyte Li+ furthermore supports the possible efficacy of Mg(2+) as a mood stabilizer.
Administration, Oral↗
[A new method for the evaluation of stone fragmentation after ESWL].
INTRODUCTION: Efficacy of ESWL treatment can be evaluated by determining the number and size of urinary stone fragments. However, the available methods for classification of stone fragments are inaccurate. Therefore, a method for semi-automatic determination of fragment size and number after ESWL was developed. METHODS: Artificial struvite stones (BON[N]-STONES) were disintegrated with a lithotriptor (Siemens, Lithostar plus) by application of 50 and 200 shock waves at 19 kV. The stone fragments were collected and pre-sorted on cascade sieves. Pictures taken of the fractions were digitalized and the images optimized in edge sharpness, contrast, and colour depth using an image processing software. Finally, the pixel number of each fragment was determined and the real area was calculated. Fragment size and volume were then depicted by frequency of occurrence in a histogram. RESULTS: Fragments with a diameter ranging from 0.3 - 5 mm could be determined by the system described. About 2,000 - 3,600 fragments were generated in this size range from the artificial struvite stones. With low shock-wave application, a considerable number of fragments larger than 2 mm could be observed. By increasing the impact to 200, more than 90 % of the stone volume was found in fragments smaller than 2 mm (previously 50 %). CONCLUSION: The system described enables a qualitative and quantitative description of stone fragmentation after ESWL not achieved thus far.
Humans↗
A randomized double-blind study of acetohydroxamic acid in struvite nephrolithiasis.
We studied the effects of the bacterial urease inhibitor acetohydroxamic acid on the growth of struvite stones in the urinary tract. Eighteen patients who received acetohydroxamic acid (15 mg per kilogram of body weight per day, in divided oral doses) for a mean of 15.8 months were compared in a randomized double-blind study with 19 patients who received placebo for a mean of 19.6 months. Seven patients given placebo reached a pre-determined end point: a 100 per cent increase in the two-dimensional surface area of their stones. No patient who received acetohydroxamic acid had a doubling of stone size (P less than 0.01). Nine patients receiving the drug and one patient receiving placebo required a decrease in dosage or cessation of treatment because of adverse effects (P less than 0.01). Episodes of tremulousness (n = 5, P less than 0.05), which reversed with a decrease in drug dose, and phlebothrombosis (n = 3, P not significant) were limited to the group given acetohydroxamic acid. We conclude that acetohydroxamic acid effectively inhibits the growth of struvite stones in the short term in patients infected with urea-splitting bacteria, but the prevalence of adverse reactions appears to be high and the toxicity and effectiveness of long-term therapy for struvite nephrolithiasis remain to be defined.
Adult↗
New treatment for struvite urinary stones.
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Humans↗
Global optimization of ionic Mg(n)F(2n) (n=1-30) clusters.
The global optimization basin-hopping (BH) method has been used to locate the global minima (GM) of Mg(n)F(2n) (n=1-30) clusters using a Born-Mayer-type potential. Some of the GM were particularly difficult to find, requiring more than 1.5 x 10(4) BH steps. We have found that both the binding energy per MgF2 unit and the effective volume of the GM isomers increase almost linearly with n, and that cluster symmetry decreases with cluster size. The data derived from the BH runs reveal a growing density of local minima just above the GM as n increases. Despite this, the attraction basin around each GM is relatively large, since after all their atomic coordinates are randomly displaced by values as high as 2.0 bohrs, the perturbed structures, upon reoptimization, relax back to the GM in more than 50% of the cases (except for n=10 and 11). The relative stabilities derived from energy second differences suggest that n=8,10,13,15, and 20 are probably the magic numbers for these systems. Mass spectrum experiments would be very useful to clarify this issue.
Algorithms↗
Tocolytic treatment for the management of preterm labor: a review of the evidence.
OBJECTIVE: Preterm labor is often a prelude to early births and the significant attendant burden of infant morbidity and mortality. Treatment consists of bedrest, hydration, pharmacologic interventions, and combinations of these. We systematically reviewed the effectiveness of tocolytics to stop uterine contractions (first-line therapy) or maintain quiescence (maintenance therapy). Our objective was to evaluate the evidence on the benefits and harms of five classes of tocolytic therapy for treating uterine contractions related to preterm labor--beta-mimetics, calcium channel blockers, magnesium, nonsteroidal anti-inflammatory agents, and ethanol. STUDY DESIGN: Reports of randomized controlled trials and other study designs in English, French, and German identified from searches of MEDLINE, EMBASE, specialized databases, bibliographies of review articles, unpublished literature, and discussions with investigators in the field were identified. Studies on women with preterm labor between 1966 and February 1999 that met our inclusion criteria were included. Through dual review, we abstracted the following information: study design and masking; definitions of preterm labor and successful tocolysis; patient inclusion/exclusion characteristics; patient demographic characteristics; drug and cointerventions; and numerous birth, maternal, and neonatal outcome measures. RESULTS: Of the 256 articles evaluated, we abstracted data from 60 first-line and 15 maintenance studies. Of these, 16 first-line and 8 maintenance studies met more stringent requirements for meta-analyses. Studies of first-line tocolysis (grade Fair) reveal a mixed outcome pattern with small improvement in pregnancy prolongation and birth at term relative to placebo. Data were insufficient to show directly a beneficial effect on neonatal morbidity or mortality. Ethanol was less beneficial than, and beta-mimetics were not superior to, other tocolytic options. Maintenance tocolytics (grade Poor) showed no improvements in birth or infant outcomes relative to placebo; these results were confirmed through meta-analysis. In contrast to other tocolytic treatments, maternal harms from beta-mimetics were rated High; all tocolytics were rated as Low risk for short-term neonatal harms. CONCLUSIONS: Management of uterine contractions with first-line tocolytic therapy can prolong gestation. Among the tocolytics, however, beta-mimetics appear not to be better than other drugs and pose significant potential harms for mothers; ethanol remains an inappropriate therapy. Continued maintenance tocolytic therapy has little or no value.
Adrenergic beta-Agonists↗
A Trojan horse transition state analogue generated by MgF3- formation in an enzyme active site.
Identifying how enzymes stabilize high-energy species along the reaction pathway is central to explaining their enormous rate acceleration. beta-Phosphoglucomutase catalyses the isomerization of beta-glucose-1-phosphate to beta-glucose-6-phosphate and appeared to be unique in its ability to stabilize a high-energy pentacoordinate phosphorane intermediate sufficiently to be directly observable in the enzyme active site. Using (19)F-NMR and kinetic analysis, we report that the complex that forms is not the postulated high-energy reaction intermediate, but a deceptively similar transition state analogue in which MgF(3)(-) mimics the transferring PO(3)(-) moiety. Here we present a detailed characterization of the metal ion-fluoride complex bound to the enzyme active site in solution, which reveals the molecular mechanism for fluoride inhibition of beta-phosphoglucomutase. This NMR methodology has a general application in identifying specific interactions between fluoride complexes and proteins and resolving structural assignments that are indistinguishable by x-ray crystallography.
Amides↗
Location and properties of pyrophosphate-binding sites in Escherichia coli F1-ATPase.
Binding of pyrophosphate (PPi) to the three catalytic ("C") and three noncatalytic ("NC") nucleotide sites of Escherichia coli F1-ATPase was determined by fluorescence spectroscopy using mutant enzymes with tryptophan inserted specifically in either C sites (beta Y331W) or NC sites (alpha R365W). Fluorescence of the tryptophan is quenched on binding of nucleotide; PPi binding parameters were determined by competition with ATP or adenyl-5'-yl imidodiphosphate. It was found that MgPPi binds to each NC site with Kd = 20 microM. In contrast, even at millimolar concentration, neither MgPPi nor free PPi showed significant binding to C sites. We confirmed that free PPi displaces nucleotide from C sites, but this was shown to be due to complexation of Mg2+ ions rather than to occupancy of the sites. MgPPi bound at NC sites was found not to affect ATP hydrolysis rates. From the data we propose a two-phase model for nucleotide binding at NC sites. In phase one, NC sites recognize the pyrophosphate "end" of the nucleotide, which binds initially with Kd similar to MgPPi; in phase two, a slow conformational change occurs which tightly sequesters adenine nucleotide. Phase two does not occur with guanine nucleotide. This model explains the preference of NC sites for adenine nucleotides. Pi (5 mM) did not bind to either C or NC sites.
Adenine Nucleotides↗
Reciprocal effects of substitutions at the subunit interfaces in hexameric pyrophosphatase of Escherichia coli. Dimeric and monomeric forms of the enzyme.
A homohexameric molecule of Escherichia coli pyrophosphatase is arranged as a dimer of trimers, with an active site present in each of its six monomers. Earlier we reported that substitution of His(136) and His(140) in the intertrimeric subunit interface splits the molecule into active trimers (Velichko, I. S., Mikalahti, K., Kasho, V. N., Dudarenkov, V. Y., Hyytiä, T., Goldman, A., Cooperman, B. S., Lahti, R., and Baykov, A. A. (1998) Biochemistry 37, 734-740). Here we demonstrate that additional substitutions of Tyr(77) and Gln(80) in the intratrimeric interface give rise to moderately active dimers or virtually inactive monomers, depending on pH, temperature, and Mg(2+) concentration. Successive dissociation of the hexamer into trimers, dimers, and monomers progressively decreases the catalytic efficiency (by 10(6)-fold in total), and conversion of a trimer into dimer decreases the affinity of one of the essential Mg(2+)-binding sites/monomer. Disruptive substitutions predominantly in the intratrimeric interface stabilize the intertrimeric interface and vice versa, suggesting that the optimal intratrimeric interaction is not compatible with the optimal intertrimeric interaction. Because of the resulting "conformational strain," hexameric wild-type structure appears to be preformed to bind substrate. A hexameric triple variant substituted at Tyr(77), Gln(80), and His(136) exhibits positive cooperativity in catalysis, consistent with this model.
Amino Acid Substitution↗
Urinary tract stones. Medical management.
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Calcium Oxalate↗
Chemolysis of struvite stones by acidification of artificial urine--an in vitro study.
OBJECTIVE: The aim of the study was to look for strategies that improve the clinical outcome of struvite stones. An in vitro experimental set up with artificial stones made of struvite (BON(N)-STONES) was chosen to perform standardized and reproducible analyses on various artificial urines with pH-values that may be reached by acidification with oral methionine treatment. MATERIALS AND METHODS: Artificial ball-shaped stones made of struvite (BON(N)-STONES) with a diameter of 0.8 cm were used. The investigations on chemolysis were performed using a dissolution device which simulates the physiological conditions in the upper urinary tract with computer-assisted on line measurement of data. For chemolysis of struvite BON(N)-STONES artificial urines according to Griffith at four different pH-values (pH 5.75, pH 6.0, pH 6.25, pH 6.5) were used. Furthermore natural and struvite BON(N)-STONES were treated with Suby G-solution (pH = 4.0). RESULTS: Comparing natural and artificial struvite stones after treatment with Suby G there was no significant difference regarding their dissolution rate. The dissolution rate of struvite stones in artificial urine rose with a decreasing pH-value. The diminution of the pH-value from 6.5 to 5.75 lead to an increase of the dissolution rate of more than 35%. This increase in the dissolution rate decreased with falling pH-value. CONCLUSIONS: The acidification of urine accelerated the dissolution rate of struvite stones in vitro. Considering in vivo conditions the intake of 1,500-3,000 mg L-methionine may lead to a sufficient acidification for a good dissolution of struvite stones.
Humans↗
Crystalline phase differentiation in urinary calcium phosphate and magnesium phosphate calculi.
UNLABELLED: Phosphates are encountered as the main components in about 15% of urinary calculi. Except for struvite, no specific correlations have been found between the crystalline phase of the phosphates and the cause of nephrolithiasis. OBJECTIVE: The relationship between aetiological factors and crystalline phases or carbonate rate in calcium phosphate stones were assessed. MATERIAL AND METHODS: From a series of 1148 phosphate calculi, we investigated the relationship between composition and aetiological factors. RESULTS: Carbapatite was the most frequent crystalline phase (74.0%). It was associated with many possible causes, including hypercalciuria, hypocitraturia, primary hyperparathyroidism, tubular acidosis, medullary sponge kidney and chronic urinary tract infection. The carbonate rate of carbapatite may be of clinical interest because carbonate rates above 15% are frequently related to urinary tract infection with urea-splitting bacteria. Conversely, the carbonate rate was commonly less than 10% in cases of carbapatite induced by metabolic disorders. Among other phosphates, brushite was found in hypercalciuric states and primary hyperparathyroidism and whitlockite in cases of urinary tract infection by non-urease-producing bacteria. CONCLUSION: Identification of crystalline phases and measurement of carbonate rate in calcium phosphate calculi is of clinical interest for identifying stone aetiology.
Acidosis↗
Effects of divalent cations on drug encapsulation efficiency of deacylated gellan gum.
The objective of this research was to evaluate the effects of various divalent cations on the encapsulation efficiency of gellan gum and to probe the underlying mechanisms responsible for drug-loading efficiency. Spherical beads containing azathioprine were prepared from deacetylated gellan gum by ionotropic gelation method. One molar solution of various divalent chlorides (MgCl(2), BaCl(2), CaCl(2), CuCl(2) and ZnCl(2)) and two additional concentrations of CaCl(2) (2.5 M and 5.0 M) were used as ionotropic media. Drug solubility was also determined in these ionotropic media and statistically evaluated using ANOVA. Solubility in various divalent chloride solutions (1.0 M) suggests that azathioprine forms complex with Ca(2+), Zn(2+) and Cu(2+), while there might be a formation of poorly water-soluble chelates with Mg(2+) and Ba(2+) as solubility in these media were less than in deionized water. The encapsulation efficiency of gellan gum was much higher in the presence of transition elements (Cu(2+) and Zn(2+)) when compared to alkaline earth metal ions (Ca(2+), Mg(2+) and Ba(2+)). Higher concentrations of Ca(2+) decreased the encapsulation efficiency of gellan gum in a nearly proportional manner. The correlation between encapsulation efficiency and pH of the ionotropic media was negative and significant (r=-0.9574, p<0.05), although the solubility of azathioprine seems to be independent of the pH of the ionotropic medium. Overall, the results suggest that drug encapsulation efficiency of deacetylated gellan gum is largely affected by the concentration and nature of various divalent cations (e.g. atomic number, valency or electro-positivity, co-ordination property, etc.) and pH of the ionotropic medium.
Antimetabolites↗
Dairy manure treatment, digestion and nutrient recovery as a phosphate fertilizer.
A combined approach of biological treatment, solids digestion and nutrient recovery was tested on dairy manure. A sequencing batch reactor (SBR) was operated in three modes, in order to optimize nutrient (nitrogen and phosphorus) removals. The highest average removal efficiencies of 91% for NH4-N, 59% for PO4-P and 80% for total chemical oxygen demand (COD) were achieved. Staining experiments suggested the coexistence of glycogen and phosphorus accumulating organisms. Anaerobic digestion of wasted bio-solids was able to produce a PO4-P concentration of 70 mgL-1 in the supernatant. A pilot-scale experiment, designed to recover phosphorus in the supernatant as struvite (magnesium ammonium phosphate), was able to remove 82% of soluble PO4-P.
Animals↗
Characterisation of waste solutions to determine optimised P recovery.
A number of waste solutions from processes operating in Western Australia (anaerobic digester supernatants, facultative lagoon treated piggery and abattoir waste effluents) were characterised chemically and by automated titration to determine acid-base characteristics. Titrations were over the pH range 2-12 or less. All waste solutions were excess molar ratios of NH3-N to PO4-P (5:1 up to 20:1). The amounts of acid or base reagent required for each waste solution type were in the sequence anaerobic digestor supernatant>>piggery effluent>abattoir effluent. The most efficient removal of N and P of the field samples considered is from piggery effluent. The results indicate conditions for optmising the removal of N and P by precipitation (predominantly struvite) as well as the way forward in determining the full scope of N and P waste streams for which recycling by precipitation (either magnesium or calcium based salts) may be feasible.
Chemical Precipitation↗
Laboratory studies on recovery of N and P from human urine through struvite crystallisation and zeolite adsorption.
Struvite [Mg (K, NH4)(PO4) x 6H2O] crystallisation and adsorption to zeolite have been proposed as a method for nutrient recovery from human urine collected with urine separating toilets. The aim of the present study was to optimise the use of MgO (to precipitate struvite) and zeolite (to adsorb ammonia) in this process. The experiments were performed with fresh urine, to which various amounts of MgO and zeolite were added. After repeated stirring and settling for 3 days the supernatant was analysed for pH, total-N, total-P and acute toxicity for Daphnia magna (24- and 48-h EC50). The results show that addition of MgO reduced P and addition of zeolite reduced N in the supernatant, as expected. The required concentration of MgO added was less than expected from the stoichiometric Mg-P-ratio for struvite. In combination with zeolite the requirement for MgO was reduced even further. Zeolite was effective in reducing total-N, but because of its interaction with MgO the effect of zeolite on N as well as P reduction was rather complicated. The optimal combination of MgO and zeolite for combined N and P recovery was found to be around 0.5 MgO per litre urine and 15 g zeolite per litre urine. These additions reduced supernatant P from about 1300 mg l(-1) to 10 mg l(-1) and N from 8000 mg l(-1) to 1000 mg l(-1). The 24-h EC50 for D. magna was not significantly affected by these additions. The expected recovery potentials for P and N by addition of MgO and zeolite are, thus, about 99% for P and 90% for N. However, these figures need to be verified, and pilot plant experiments at a science centre with urine separation wastewater treatment (www.universeum.se) are in progress.
Adsorption↗
Optimalisation of magnesium ammonium phosphate precipitation and its applicability to the removal of ammonium.
Among the physico-chemical abatement technologies, mainly acid scrubbers have been used to control NH3-emission. The disadvantage of this technique is that it yields waste water, highly concentrated in ammonia. In this report, the applicability of the magnesium ammonium phosphate (MAP) process to regenerate the liquid phase, produced by scrubbing NH3-loaded waste gases, was investigated. In the MAP process, ammonium is precipitated as magnesium ammonium phosphate, which can be used as a slow release fertilizer. The influence of a number of parameters, e.g. pH, kinetics, molar ratio NH(+)4/Mg2+/PO(3-)4 on the efficiency of the formation of MAP and on the ammonium removal efficiency was investigated. In this way, optimal conditions were determined for the precipitation reaction. Next to this, interference caused by other precipitation reactions was studied. At aqueous NH(+)4-concentrations of about 600 mg l(-1), ammonium removal efficiencies of 97% could be obtained at a molar ratio NH(+)4/Mg2+/PO(3-)4 of 1/1.5/1.5. To obtain this result, the pH was continuously adjusted to a value of 9 during the reaction. According to this study, it is obvious that the MAP-precipitation technology offers opportunities for ammonium removal from scrubbing liquids. The practical applicability of the MAP-process in waste gas treatment systems, however, should be the subject for further investigations.
Chemical Precipitation↗