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PubMed1999

First-principles determination of elastic anisotropy and wave velocities of MgO at lower mantle conditions

The individual elastic constants of magnesium oxide (MgO) have been determined throughout Earth's lower mantle (LM) pressure-temperature regime with density functional perturbation theory. It is shown that temperature effects on seismic observables (density, velocities, and anisotropy) are monotonically suppressed with increasing pressure. Therefore, at realistic LM conditions, the isotropic wave velocities of MgO remain comparable to seismic velocities, as previously noticed in athermal high-pressure calculations. Also, the predicted strong pressure-induced anisotropy is preserved toward the bottom of the LM, so lattice-preferred orientations in MgO may contribute substantially to the observed seismic anisotropy in the D" layer.

Journal Article↗
PubMed2006

Commonly used preparations for colonoscopy: efficacy, tolerability, and safety--a Canadian Association of Gastroenterology position paper.

INTRODUCTION: The increased demand for colonoscopy, coupled with the introduction of new bowel cleansing preparations and recent caution advisories in Canada, has prompted a review of bowel preparations by the Canadian Association of Gastroenterology. METHODS: The present review was conducted by the Clinical Affairs group of committees including the endoscopy, hepatobiliary/transplant, liaison, pediatrics, practice affairs and regional representation committees, along with the assistance of Canadian experts in the field. An effort was made to systematically assess randomized prospective trials evaluating commonly used bowel cleansing preparations in Canada. RESULTS: Polyethylene glycol (PEG)-; sodium phosphate (NaP)-; magnesium citrate (Mg-citrate)-; and sodium picosulphate, citric acid and magnesium oxide (PSMC)-containing preparations were reviewed. Regimens of PEG 2 L with bisacodyl (10 mg to 20 mg) or Mg-citrate (296 mL) are as effective as standard PEG 4 L regimens, but are better tolerated. NaP preparations appear more effective and better tolerated than standard PEG solutions. PSMC has good efficacy and tolerability but head-to-head trials with NaP solutions remain few, and conclusions equivocal. Adequate hydration during preparation and up to the time of colonoscopy is critical in minimizing side effects and improving bowel cleansing in patients receiving NaP and PSMC preparations. All preparations may cause adverse events, including rare, serious outcomes. NaP should not be used in patients with cardiac or renal dysfunction (PEG solution is preferable in these patients), bowel obstruction or ascites, and caution should be exercised when used in patients with pre-existing electrolyte disturbances, those taking medications that may affect electrolyte levels and elderly or debilitated patients. Health Canada's recommended NaP dosing for most patients is two 45 mL doses 24 h apart. However, both safety and efficacy data on this dosing schedule are lacking. Many members of the Canadian Association of Gastroenterology expert panel administer both doses within 24 h, as studied in clinical trials, after careful one-on-one discussion of risks and benefits in carefully selected patients. Safety data on PSMC and combination preparations in North America are limited and clinicians are encouraged to keep abreast of developments in this area. CONCLUSIONS: All four preparations reviewed provided effective bowel cleansing for colonoscopy in the majority of patients, with varying tolerability. Adequate hydration is essential in patients receiving the preparations.

Colonoscopy↗
PubMed1989

Effects of pH and anion substitution on magnesium accumulation in rabbit aortic smooth muscle.

The effects of anion substitution, pH and extracellular Mg2+ concentration on 28Mg accumulation were examined in rabbit aortic smooth muscle. Accumulation of 28Mg (expressed as a 28Mg/Mg2+ ratio) was not changed when the concentration of added, nonradioactive MgCl2 was increased from 1.5 to 15.0 mM. The 28Mg efflux rate was increased by added MgCl2 (0.15, 0.5 or 1.5 mM) in a dose-related manner after a similar delay of 5-10 min. Addition of 1.5 mM MgCl2, MgSO4 or magnesium aspartate hydrochloride enhanced 28Mg efflux and inhibited accumulation of 28Mg to the same extent. An increase or decrease in extracellular pH correspondingly increased or decreased 28Mg accumulation. However, the 28Mg efflux rate was not altered when extracellular pH was decreased. Efflux of 28Mg was increased by added 1.5 mM MgCl2 at pH 7.4 but not at pH 5.8. Thus, the net uptake of Mg2+ appears to be proportional to the concentration of extracellular Mg2+ in rabbit aorta. Low external pH decreases 28Mg retention in rabbit aorta by inhibiting the uptake of 28Mg rather than by increasing 28Mg efflux. Effects of added Mg2+ on transmembrane movements of 28Mg are not altered by changes in the associated anion. Extracellular Mg2+ appears to enter the cell and exchange with an intracellularly located pool of 28Mg in the same manner, regardless of whether the accompanying anion is sulfate, chloride or monoaspartate hydrochloride.

Animals↗
PubMed2005

Ceramic nanoparticle assemblies with tailored shapes and tailored chemistries via biosculpting and shape-preserving inorganic conversion.

A novel biosynthetic paradigm is introduced for fabricating three-dimensional (3-D) ceramic nanoparticle assemblies with tailored shapes and tailored chemistries: biosculpting and shape-preserving inorganic conversion (BaSIC). Biosculpting refers to the use of biomolecules that direct the precipitation of ceramic nanoparticles to form a continuous 3-D structure with a tailored shape. We used a peptide derived from a diatom (a type of unicellular algae) to biosculpt silica nanoparticle based assemblies that, in turn, were converted into a new (nonsilica) composition via a shape-preserving gas/silica displacement reaction. Interwoven, microfilamentary silica structures were prepared by exposing a peptide, derived from the silaffin-1A protein of the diatom Cylindrotheca fusiformis, to a tetramethylorthosilicate solution under a linear shear flow condition. Subsequent exposure of the silica microfilaments to magnesium gas at 900 degrees C resulted in conversion into nanocrystalline magnesium oxide microfilaments with a retention of fine (submicrometer) features. Fluid(gas or liquid)/silica displacement reactions leading to a variety of other oxides have also been identified. This hybrid (biogenic/synthetic) approach opens the door to biosculpted ceramic microcomponents with multifarious tailored shapes and compositions for a wide range of environmental, aerospace, biomedical, chemical, telecommunications, automotive, manufacturing, and defense applications.

Biomimetics↗
PubMed2001

Economic considerations of chromium recovery from tanning wastewater.

The chrome recovery from tanning wastewater was investigated in field conditions using a real-sized pilot plant. The tested wastewaters were from the tanning process both without and with tanning additives, whereas the precipitating chemicals of interest were magnesium oxide (MgO) and sodium carbonate (Na2CO3). The precipitation with MgO followed by 1 hour sedimentation was the best solution. The optimal dosages were 2 and 4 times that of stoichiometric requirements for conditions without and with the additives, respectively. By redissolving the obtained sludge with 1:1 diluted sulfuric acid and maintaining the pH between 2.5 and 2.8, the chromium recovery were 97.6 and 88.6%, respectively. Another alternative of using Na2CO3 as the precipitant was not promising because of its high chemical cost and excessive sludge-settling period (15-20 hours). The MgO precipitation scenario proved to be able to pay back economically within 3 years for the "without-additive" waste stream whereas that of "with-additive" wastewater was not worth the investment. This is because the "with-additive" discharge contains low chromium content whereas it requires high chemical doses.

Chromium↗
PubMed1994

Recombinant thyrotropin receptor and the induction of autoimmune thyroid disease in BALB/c mice: a new animal model.

In a preliminary study, we observed the production of TSH binding-inhibiting (TBII) and thyroid-blocking (TBAb) antibodies accompanied by lymphocytic infiltration of the thyroid in a pool of male BALB/c mice immunized with the extracellular domain (ECD) of the human TSH receptor (TSHR) expressed as a maltose-binding protein (MBP) fusion in bacteria. In the present study we evaluated the humoral response to the same antigenic preparation in a new series of individual male and female BALB/c mice immunized ip on day 0 with 100 micrograms MBP-ECD and days 25, 39, and 53 with 50 micrograms MBP-ECD in an adjuvant composed of aluminum oxide, magnesium hydroxide, and Bordetella pertussis vaccine. Mice immunized with MBP served as control. Individual sera and immunoglobulins were tested for TBII, TBAb, and thyroid-stimulating antibodies (TSAb) on days 0, 32, 46, and 60, and total circulating T4 levels were measured by RIA. Animals were killed on day 120, their thyroids were examined histologically, the infiltrates were characterized using monoclonal antibodies specific for T-cells (total, activated, helper, and suppressor), B-cells, and macrophages. Sera and immunoglobulins G of the MBP-treated control group were all negative for TSAb, TBAb, and TBII activity. The receptor-immunized mice, despite having high titers of antibodies to the immunogen in an enzyme-linked immunosorbent assay, displayed a heterogeneous response in terms of biological activity, with 3 of 7 female and 4 of 8 male mice having TBAb/TBII activities that persisted and whose activity increased throughout the experiment. No significant TSAb antibody activity was observed. Total T4 levels were also heterogeneous even before immunization, but 9 of 15 MBP-ECD-treated mice had levels below the normal range after immunization, and 7 of these also had TBII/TBAb activities. At the end of the experiment, only 4 of the MBP-ECD-treated female mice survived, but all of them had a severe lymphocytic infiltration of their thyroid, composed mostly of activated T-cells, although B-cells and macrophages were also present. A similar infiltrate was seen in 4 of 8 male MBP-ECD-treated mice. No infiltrate was observed in male or female MBP-treated mice. The model described demonstrates the feasibility of using the TSHR as an immunogen to overcome tolerance and mimics some characteristics of human autoimmune disease of the thyroid.

Animals↗
PubMedDate not supplied

[Measurement of the volume of the skin ulcer in cutaneous leishmaniasis].

Skin ulcers by Leishmania (Viannia) braziliensis are often deep and irregular and are difficult to measure by just the skin surface transverse and longitudinal diameters. The proposal is to mould the cavity, after local asepsis with fresh water plus soap, with a gelatinous plastic which contains silence, potassium alginate, calcium sulphate, magnesium oxide commercialized under the name of jeltrate (Dentsply Laboratory), by solving 9.5g of jeltrate in 20ml of fresh water and applying the gel on the ulcer which solidifies in 5 minutes. This mould is then filled with a self polymerising acrylic and its volume measured either by weight (by using an analytical balance)-technique 1-or by water displacement by applying Archimeds'principle-technique 2. We show data in a field trial before and after 20 days treatment in 20 patients using three different schedules as follows: 7 received pentamidine isethionate, 7 patients received aminosidine sulphate and 6 received meglumine antimoniate. The results point out that there was a uniform reduction of ulcer volume occurred during this period in the three groups, in both technique. Regarding the therapeutic schedules we are sure that there was a significant statistical difference between the three schedules using the T Student Test, which showed that aminostdine sulphate produced a better volume reduction of the ulcer than the other drugs. Serial moulds reflect clinical billing and are a permanent record. We conclude that the measure of the volume of the skin ulceration can be useful in the therapeutic evaluation, as a practical and cheap procedure, and may be used in field trials.

Animals↗
PubMed1977

A photometric study of the color of health gingiva.

An apparatus was developed that was found suitable for measuring gingival color in terms of reflectance at 6328 A. A total of 445 readings were taken on 95 Caucasian subjects in order to determine certain properties of healthy gingival color. It was determined that: 1. Healthy adult gingival color ranged in reflectance from 17% to 45% of the magnesium oxide standard, with a mean of 32%. 2. Gingival color of children was lighter than that of adults. The reflectance of children's gingiva ranged from 31% to 43%, with a mean of 35%. 3. Gingival color did not vary with the sex of the individual. 4. Gingival color was lighter in individuals with blonde hair than in individuals with brown hair. 5. Gingival color was darker in individuals with darker eye color. 6. Gingival color was lighter in individuals with geographic origins that are commonly related to lighter complexions. 7. Gingival color did not vary with age, within the adult range covered in this study. 8. Gingival color did not vary with the following physiological and physical factors: menstrual period, use of oral contraceptives, smoking habits, moistness or dryness of the gingiva, which side was measured, time of day, or time after toothbrushing, smoking a cigarette, eating an apple, or drinking a hot beverage.

Adult↗
PubMed1983

Environmental politics and science: the case of PBB contamination in Michigan.

This article examines how politics and science interacted against a background of uncertainty to shape policy in the case of environmental contamination by polybrominated biphenyls (PBB) in Michigan. In 1973, between 500 and 1,000 pounds of the flame retardant PBB were accidentally shipped and used instead of the dairy feed additive magnesium oxide, resulting in the widespread contamination of animal feeds, animals, and human food products. The contamination was initially perceived as the private trouble of a single farmer. The problem next became a public issue as public and private institutions grappled with questions of illness, safety, and disposal. To gain influence over those institutions, dissatisfied individuals and groups then turned the PBB contamination into a political controversy. The final section of the present article analyzes how science and politics interacted in: the ways bureaucratic organizations defined the three problems of contamination; the role political controversy played in redefining problems and influencing policy; and the political roles of scientists in controversies over environmental contamination.

Animals↗
PubMedDate not supplied

Method for determination of xanthene dyes in guava fruits and its application in a field dissipation study.

Xanthene dyes, i.e., phloxine B and uranine or phloxine B alone, are phototoxic to tephritid fruit flies infesting guava fruits. An analytical method was developed for determination of residues of these dyes used in bait solutions for suppression of the tephritid fruit fly population in guava fruits. The procedure involved solvent extraction, anion-exchange cleanup, and determination by liquid chromatography or capillary zone electrophoresis. The dyes were extracted from 50 g guava fruit at 45 degrees degrees with 400 mL methanol-acetonitrile (1 + 1) and 5 g magnesium oxide added as an alkaline and clarifying agent. The guava extract was adjusted to pH 8.5 and subjected to an amino column cleanup. Average recoveries of xanthene dyes added to guava purees ranged from 77 to 99% for phloxine B and from 79 to 102% for uranine at spiking levels of 0.05-1.00 microg/g. The method was applied to the determination of phloxine B residues in guava fruits collected from a dye-sprayed orchard. After phloxine B was applied at a rate of 62.5 g/ha for 14 weekly sprayings, it was found on guava fruits at an average concentration of 111 +/- 18 ng/g 4 h after the llth spraying. The concentration of phloxine B was 426 +/- 94 ng/g in selected fruits with high deposits of the dye 4 h after spraying. Average concentrations of phloxine B 5 days after the 7th and 14th sprayings were 29 +/- 7 and 19 +/- 8 ng/g, respectively.

Coloring Agents↗
PubMed2001

[Irritable colon].

Irritable bowel syndrome is a chronic, relapsing functional bowel disorder of unknown aetiology. Methods of studying intestinal motor function, nociception, and interactions of the central nervous system and enteric nervous system are not applicable for clinical use. The diagnosis is therefore made on the symptoms, but it is necessary to exclude relevant organic disease. Establishment of the diagnosis, information about the disorder, elimination of foods and other factors that provoke the symptoms, and a change in life-style are sufficient in most cases. Treatment is hampered by the lack of effective treatment and the psychological aspects. The therapeutic gain of drug administration is modest and the rate of response to placebo is high. Fibre supplementation, magnesium oxide or cisapride may be tried for constipation, diphenoxylate or loperamide for diarrhoea, and low dose tricyclic antidepressants or serotonin reuptake blockers for severe pain. The introduction of 5-hydroxytryptamine-3 (5-HT3) receptor antagonists seems promising.

Colonic Diseases, Functional↗
PubMed2002

[Study on the determination of iron by silica gel H phase-diffuse reflectance spectrometry].

In this paper a new method for the silica gel H phase-diffuse reflectance spectrophotometric determination of iron(III) with piperonal fluorine (PIF) has been developed. In the presence of cetyltrimethyl ammonium bromide and in a NH4 Cl-NH3.H2O medium at pH 9.6-10.3, iron(III) reacts with PIF to form a stable blue complex which is absorbed by silica gel H with a diffuse reflectance absorption peak at 640 nm. The calibration curve is linear over the concentration range 0-25 ng of iron(III) in 1 mL. The linear regression equation is AR = 0.022 1c-0.005,5(r = 0.999,7), where c is expressed as ng per 1 mL. The method has high analytical speed and sensitivity. The effect of a number of foreign ions has been studied by carrying out determining of 200 ng.(10 mL)-1 of iron (III), 1 mg K+, Na+, F-, Cl-, NO3-, PO(4)3-, 0.6 mg Ca2+, Mg2+, 35 micrograms Sr2+, 20 micrograms Cr(III), 6 micrograms Mn2+, 4 micrograms Pb2+, 3.5 micrograms Cd2+, 2.5 micrograms Cu2+, Ag+, 1.5 micrograms Cr(VI), 1 microgram Ni2+, 0.75 microgram Zn2+, Sn4+ et al don't interfere with the measurement. The method has been applied to the determination of microamount iron in magnesium oxide with satisfactory results.

Iron↗
PubMed2004

Prevention of irinotecan-induced diarrhoea by oral carbonaceous adsorbent (Kremezin) in cancer patients.

Irinotecan (CPT-11) treatments induce severe diarrhoea at a rate of >40%. In clinical trials, we evaluated the preventing effects of oral alkalization, which has been reported previously, and oral carbonaceous adsorbent (Kremezin trade mark ) on diarrhoea possibly induced by CPT-11. Evaluation was made by counting the maximum number of bowel motions in each patient. Five patients out of 7 treated with CPT-11 had bowel motions of >5 times daily, and maximum number of bowel motions reached 20 times in 1 patient. Oral alkalization (2 g sodium bicarbonate, 2 g magnesium oxide and 300 mg ursodeoxycholic acid daily for 4 days) decreased bowel motions from 20 to 8 thereafter in the patient. Maximum number of bowel motions in other 3 patients treated in a combination of CPT-11 and oral alkalization was <3. Oral adsorbent (2 g Kremezin x 3 times, during and after CPT-11 treatment) also decreased maximum number of bowel motions from 7 (without oral adsorbent) to 3 in 1 patient. Also, the maximum number of bowel motions in other 3 patients treated with oral adsorbent was <3 (p<0.05, vs CPT-11 alone). Effect of oral Kremezin on plasma concentrations of CPT-11 and its related compounds after a 1-h CPT-11 infusion, evaluated in a patient, was small. These results suggested that the oral Kremezin is effective in ameliorating CPT-11-induced diarrhoea without decreasing much the plasma clearance of CPT-11.

Adsorption↗
PubMedDate not supplied

Weekly administration of irinotecan (CPT-11) plus cisplatin for non-small cell lung cancer.

BACKGROUND: Weekly administration of irinotecan plus cisplatin was evaluated for untreated patients with non-small cell lung cancer (NSCLC). PATIENTS AND METHODS: Sixty mg/m(2) of irinotecan plus 30 mg/m(2) of cisplatin were administered on days 1, 8 and 15 every 4 weeks. Patients with no evidence of disease progression were treated with at least two cycles (8 weeks). Of the 39 patients, 29 were provided an antidiarrheal program consisting of sodium bicarbonate and magnesium oxide. RESULTS: There were 13 partial responses and an overall response rate of 33.3% [95% CI: 20%-50%]. The median time to progression and survival were 64 days and 12.8 months, respectively. Grade 4 neutropenia occurred in 15.4% of the patients, and Grade 3 and 4 diarrhea was observed in 12.8% and 2.6%, respectively. The incidence of leukopenia of grade 3-4 was significantly lower in patients provided with the antidiarrheal program due to lack of decrease in the lymphocyte count. CONCLUSION: This phase II study indicated that weekly irinotecan plus cisplatin administration was a promising treatment for untreated NSCLC.

Adult↗
PubMed1991

[Effects of air pollution on the etiology of dental caries].

A study has been carried out investigating caries morbidity in children and changes in the macro- and microelement composition of saliva and teeth tissue depending on the degree of ambient air contamination by dust, nitrogen oxides, sulphurous gas, lead and carbon oxide. A positive correlation has been identified between dental caries morbidity and environmental factors (carbon oxide). Magnesium, silicon, iron, aluminum and copper dental content in children living in a relatively clean district was reduced. A conclusion has been made on the necessity to take into account ecological situation in the process of comprehensive prophylaxis of dental caries in children.

Age Factors↗
PubMed1987

Immunotoxicology: environmental contamination by polybrominated biphenyls and immune dysfunction among residents of the State of Michigan.

In 1973, inadvertent contamination occurred in a special farm feed supplement for lactating cows. Polybrominated biphenyls (PBBs) were used in place of magnesium oxide resulting in serious harm to farm animals, including cattle, chickens, geese, ducks. Farm families, accustomed to eating their own products, were most heavily exposed. To study the impact of PBBs, 336 adult Michigan farm residents, 117 general consumers for comparison, 75 dairy farm residents in Wisconsin, who had not eaten PBB-contaminated food, were examined, as were 79 healthy subjects in New York City. Abnormalities in the Michigan groups included hypergammaglobulinemia, exaggerated hypersensitive response to streptococci, significant decrease in absolute numbers and percentage of T and B-lymphocytes, and increased number of lymphocytes with no detectable surface markers ("null cells"). Significant reduction of in vitro immune function was noted in 20-25% of the Michigan farm residents who had eaten food containing PBB. The decreased immune function detected among the PBB-exposed farm residents tended to affect families as a unit and was independent of exposed individuals' age or sex, pointing against the possibility of genetic predisposition.

Agricultural Workers' Diseases↗