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At least 397 records · Page 22Linked to original sources
PubMed1994

Altered tissue contribution to interfacial bond strength with acid conditioned dentin.

PURPOSE: To measure the shear bond strength of resin composite to dentin using three fourth generation bonding agents in combination with three different acid treatments. One such treatment was followed by sodium hypochlorite. The purpose was to determine the contribution which the collagen rich, demineralized zone made to bond strength. MATERIALS AND METHODS: Three groups, representing (1) All Bond 2/BisFil, (2) Optibond Dual Cure/XRV and (3) Scotchbond Multi-Purpose/Z100, contained four sub-groups each comprised of 10 caries-free molar teeth whose dentin was exposed in a transverse mid-coronal plane. Dressed with 320 grit, wet silicon carbide paper, the dentin surface in each sub-group was conditioned with 10% maleic acid (15 seconds), 10% phosphoric acid (20 seconds), 2.5% nitric acid (60 seconds) and 10% phosphoric acid (20 seconds) followed by 5% sodium hypochlorite (120 seconds). The bonded resin composite assemblies were stored in water at 37 degrees C for 24 hours and then subjected to shear force at a crosshead speed of 5 mm/minute until failure. RESULTS: The mean and standard deviation values derived for the groups were not statistically different from each other (P < 0.05). It was concluded that the type of conditioning agent was not a factor in achieving optimal bond strength for the system tested. Furthermore, it was tentatively concluded that the collagen-rich zone offered no direct, quantitative contribution to the interfacial bond strength which is probably derived from complete resin diffusion into the porous, partially demineralized dentin below.

Acid Etching, Dental↗
PubMed1957

Local treatment of wounds to prevent rabies.

This article reports experiments with guinea-pigs on methods of producing wounds and infecting them with street virus, and on the use of nitric acid, detergent solution and antirabies serum in the local treatment of these wounds for the prevention of rabies. Despite certain limitations in the experimental arrangement, the authors consider that these findings are valuable in verifying some of the similar experiments performed by other workers.The addition of hyaluronidase to the virus challenge suspension did not increase the infectivity of the suspension when applied to wounds, but there was a trend towards increased pathogenicity of the hyaluronidase-virus mixture over virus suspension alone when inoculated intramuscularly.In the local treatment of wounds the protective action which resulted when nitric acid was applied within 4 hours, but not after a 24-hour interval, after infection, confirmed the results of other workers.Antirabies serum also proved effective both when infiltrated under the wound and when inoculated systemically up to 24 hours after infection, this being the longest interval tested. The results suggested that the serum exerted a specific local action.While some protective action was apparently achieved with the detergent Terjolate when applied by gentle swabbing, or by infiltration of saline solution under the wound, up to 3 hours after infection, this protection was distinctly inferior to that obtained with nitric acid or serum. The authors point out the excellent results reported by other workers with a different detergent, Zephiran chloride, and recommend further studies on this and other similar substances less corrosive than nitric acid.These experiments, considered together with those reported by other workers, indicate the value of simple washing, flushing or irrigation of wounds as a means of reducing virus levels below the infective dose.The authors cite the need for further research on local treatment of wounds in order to clarify mechanisms of action of various procedures and agents now used, and to improve the methods for handling the worrisome situation presented by a bite wound from an animal suspected of having rabies.

Animals↗
PubMedDate not supplied

Determination of disodium clodronate in bulk material and pharmaceuticals by ion chromatography with post-column derivatization.

A validated ion chromatographic method for the determination of disodium clodronate in bulk material and pharmaceuticals is described. Separations are performed on a poly(styrene-divinylbenzene) copolymer column using 40 mM nitric acid as mobile phase at a flow rate of 0.5 ml min-1. The analyte is detected by UV absorption at 300 nm after post-column derivatization with acidic iron(III) solution (0.25 ml min-1). The proposed ion chromatographic method is validated in terms of selectivity, precision, linearity, accuracy and ruggedness.

Chromatography, Ion Exchange↗
PubMed2001

A comparison of techniques for preparing fish fillet for ICP-AES multielemental analysis and the microwave digestion of whole fish.

Four catfish fillet homogenate treatments before multielemental metal analysis by simultaneous inductively coupled plasma/atomic emission spectroscopy were compared in triplicate. These treatments were: nitric acid wet-ashing by Parr bomb digestion; nitric acid wet-ashing by microwave digestion; tetramethylammonium hydroxide/nitric acid wet digestion; and dry-ashing. The tetramethylammonium hydroxide/nitric acid method was imprecise (coefficients of variation > 20%). The dry-ashing method was fast and sensitive but had low recoveries of 50% for spiked Pb and Al and was not as precise as the Parr bomb or microwave treatments. The Parr bomb method was the most precise method but was less sensitive than the microwave method which had nearly the same precision. The microwave method was then adapted to homogenates of small whole fish < or = 3 cm in length. The whole fish homogenate required more vigorous digestion conditions, and addition of more acid after the evaporative step because of the presence of less oxidizable and acid-soluble components than fillet. The whole fish homogenate was also more heterogeneous than catfish fillet. A quality assurance protocol to demonstrate homogenate uniformity is essential. The use of a non-specialized microwave oven system allowed precise results for fillet and whole fish homogenates.

Animals↗
PubMed2001

[Determination of cobalt in solidified resin promoter by successive extraction and FAAS].

A new method had been investigated for the analysis of micro-amount of cobalt in solidified resin promoter. Methyl isobutyl ketone (MIBK) was used in 1 mol.L-1 NH4SCN medium followed by 4 mol.L-1 nitric acid back extraction step, then analysis by flame atomic absorption spectrometry. The results indicated that the method was accurate and the interference with concomitant in solidified resin promoter was negligible. The method had a recovery of 96.2%-104.6%.

Carboxylic Acids↗
PubMed2003

Direct determination of phosphate esters in concentrated nitrate media by capillary zone electrophoresis.

The potential of capillary zone electrophoresis (CZE) for the determination of dibutyl phosphate (DBP) and monobutyl phosphate (MBP), two degradation products of the tributyl phosphate extractant used in the nuclear fuel reprocessing industry, was evaluated. Analysis conditions were optimised, taking particularly into account that many determinations had to be performed in concentrated aqueous nitrate or nitric acid solutions. Separations were therefore carried out using the counter-electroosmotic mode with cathodic detection in a pH 8.3 electrolyte containing a suitably selected chromophore, salicylate, to ensure the indirect UV detection of the analytes. Various aspects of the method, including its sensitivity, working range, repeatability, and rapidity, were examined. Quantification of both phosphate esters was achieved in less than 3 min at concentrations ranging from 2 x 10(-6) to 10(-3) mol l(-1) in samples containing no macro-component. The lower end of this range increased to 5 x 10(-6) mol l(-1) for MBP and 1.5 x 10(-5) mol l(-1) for DBP in samples containing 5 x 10(-2) mol l(-1) of sodium nitrate, thus enabling their determination in solutions containing nitrate or nitric acid at concentrations up to, respectively, 10,000 and 3000 times higher than the target analyte concentration. This simple, fast and reliable method is routinely applicable to aqueous samples with no other preliminary treatment than a proper dilution; analysis was also performed in organic matrices after a prior extraction. The method was validated by an excellent correlation with the standard DBP analysis technique, gas chromatography (GC). In order to develop appropriate chemical treatments to destroy these compounds, the method was applied to the monitoring of DBP and MBP degradation by hydrogen peroxide in 1 mol l(-1) nitric acid solutions.

Electrophoresis, Capillary↗
PubMed1996

Health effects of acid aerosols on North American children: air pollution exposures.

Air pollution measurements were conducted over a 1-year period in 24 North American communities participating in a respiratory health study. Ozone, particle strong acidity, sulfate, and mass (PM10 and PM2.1) were measured in all communities. In 20 of the communities, sulfur dioxide, ammonia, nitric acid, nitrous acid, and particulate nitrate were measured. The sampler was located centrally in the community whenever possible and samples were collected every other day. Concentrations of particle strong acidity, mass, sulfate, and ozone were highly correlated both in the region of the country defined as a high-sulfur source area and in the downwind transport regions. These regions of the eastern United States and southern Canada experienced the greatest particle strong acidity, sulfate, and particle mass concentrations during the spring and summer months (May-September). The particle strong acidity concentrations were highest in regions close to the high sulfur emission areas of the United States; that is, in the area immediately to the west of the Appalachian Plateau and west of the Allegheny Mountains (western Pennsylvania, eastern Ohio, and West Virginia) up through southern Ontario. The frequency of particle strong acidity events decreased with transport distance from the region of highest sulfur emissions. Low particle strong acidity and sulfates were found at the western and midwestern sites of both the United States and Canada. Substantial concentrations of nitric acid were found in two of the California sites as well as many sites in the northeastern portion of the United States. Sites selected for the epidemiologic study provide a range of annual mean particle strong acidity exposures from below the limit of detection to more than 50 nmol/m3.

Aerosols↗
PubMed2001

Effects of excitatory amino acids and nitric oxide on flight behavior elicited from the dorsolateral periaqueductal gray.

Microinjection of excitatory amino acids (EAA) into the dorsolateral periaqueductal gray (dlPAG) induces flight reactions while EAA antagonists show anxiolytic effects. Part of the effects mediated by NMDA receptors may involve an increase in nitric oxide (NO) production. We showed that nitric oxide synthase (NOS) inhibitors injected into the dlPAG induced anxiolytic effects. Conversely, SIN-1, a NO donor, produced orientated flight reactions that resemble stimulation of the medial hypothalamus. This compound also produced extensive Fos-like immunoreactivity in this region and in other areas related to defensive reactions such as the medial amygdala and cingulate cortex. Since part of the effects of NO involves increases in guanylate cyclase levels, we found that intra-dlPAG injection of 8-Br-cGMP induced a brief flight reaction followed by increased locomotion. In another experiment, we showed that single or repeated restraint stress produced an increased expression of neuronal NOS in the dlPAG and other areas related to defense, as measured by in situ hybridization, diaphorase histochemistry and immunocytochemistry. Together, these data suggest that NO may participate in the modulation of defensive responses in the dlPAG.

Animals↗
PubMed2003

Anti-inflammatory compounds of plant origin. Part I. Action on arachidonic acid pathway, nitric oxide and nuclear factor kappa B (NF-kappaB).

Over the last 10 years, a significant body of evidence has emerged indicating that chemically diverse classes of naturally-occurring substances derived from higher plants are of potential interest for therapeutic interventions in several inflammatory diseases. Part I of this review article focuses on our current knowledge of the mechanisms by which a large range of plant-derived constituents interfere with three relevant targets involved in the inflammatory process, namely arachidonic acid metabolite pathways, nitric oxide and NF-kappaB, and discusses their potential therapeutic use in the management of relevant inflammatory diseases.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

Ion chromatographic analysis of the purity and synthesis of sulfonium and selenonium ions.

The use of single-column ion chromatography with conductometric detection was shown to be useful for the analysis of sulfonium and selenonium ions. A Hamilton PRP X-200 cation column was eluted with either solvent A (5 mM nitric acid in 30% methanol) or solvent B (4 mM nitric acid). With solvent B, trimethylsulfonium ion was separated from trimethylselenonium ion. With solvent A, amounts of trimethylsulfonium ion from 2 to 250 nmol were detected with a linear response. The retention times and response factors for a series of sulfonium ions with various organic groups were determined. In general the ions with more hydrophobic groups eluted later, but all had similar response factors. The method was shown to be useful for optimizing conditions for the synthesis of methylsulfonium ions, specifically the reaction of methyl iodide with diallyl sulfide.

Allyl Compounds↗
PubMed1982

Tissue distribution of lead in rat pups nourished by lead-poisoned mothers.

Lead accumulation was studied in rats treated with Pb through the dam's milk from birth to weaning. Dams of experimental litters received lead acetate in drinking water, while dams of control litters received a sodium solution. Fluid consumption by dams and pup weight were monitored daily. No differences were seen in the dams' fluid consumption or in mortality or growth rate of pups. Rats were sacrificed after 5, 10, 16, or 21 d of Pb treatment, or 3 and 3.5 mo after weaning. Samples of heart, brain, liver, kidney, intestine, and bone were solubilized in concentration nitric acid and analyzed for Pb by atomic absorption spectrophotometry. Nitric acid digests of blood samples from pups 10 and 21 d old and from animals allowed a Pb-free period of 3-3.5 mo after treatment were also analyzed for Pb concentration. Levels of Pb in all tissues analyzed progressively increased during the first 10 d of treatment. After the Pb-free period only bone Pb concentration remained elevated. The results indicate that treatment of lactating dams is an efficient method of producing chronic Pb exposure of rat pups. The results also provide a means of comparing studies of Pb toxicity in which different treatment paradigms are used.

Animal Population Groups↗
PubMed2003

Isotope dilution analysis of selenite and selenate in natural water using microwave-induced nitrogen plasma mass spectrometry.

Isotope dilution analysis of the sub-microg l(-1) levels of selenite and selenate in natural water samples by microwave-induced nitrogen plasma mass spectrometry (MIP-MS) was performed. An appropriate amount of a spike solution containing 78Se-selenite and 78Se-selenate was added to the natural water sample to be analyzed. Both analytes in the water were then concentrated simultaneously by passing the sample through a column that was filled with an anionic exchange resin. After the concentration process, all of the selenite and some of the selenate on the resin were eluted by 0.03 M nitric acid. The residual selenate was eluted by 0.13 M nitric acid. The eluted sample solutions were injected into MIP-MS, and isotope dilution analyses were carried out. Selenite and selenate concentrations as low as 0.01 microg l(-1) in the natural water sample were successfully determined by the proposed method.

Fresh Water↗
PubMed1991

Application of biological samples treated by wet-digested mineralization to cation-exchange high-performance liquid chromatography with post-column reaction by 4-(2-pyridylazo)-resorcinol.

To quantify metals in biological samples, we tried to find good conditions for wet-digested mineralization of the samples and for separation of metal ions in chromatography. A 500 microliters volume of aliquot was transferred to a glass tube, and was evapolated at 100 degrees C for 2 hours. A 5.5 ml volume of a mixture of concentrated nitric acid-70% perchloric acid (10: 1, v/v) was added and heated, consecutively, at 80 degrees C for 12 hours, at 140 degrees C for 2 hours, at 180 degrees C for 2 hours, and finally at 190 degrees C for 1 hour to evapolate the residual acids. After addition of 500 microliters of 10 mM nitric acid, the metals were extracted by a suspension mixer (32 r.p.m., 1 hour). One hundred microliters of the extracted solution was applied to the chromatographic system: cation-exchange column, TSKgel IC-Cation SW (Tosoh Co.); eluent, 0.35 M lactic acid-0.35 M sodium lactate (pH 3.0); flow rate, 0.7 ml/minute; column temperature, 30 degrees C. After adding a color-forming reagent (100 mg/l 4-(2-pyridylazo)-resorcinol in 40 g/l Na2CO3; flow rate, 0.7 ml/minute) to the effluent, five different metal ions of Cd2+, Co2+, Cu2+, Ni2+ and Zn2+ were detected at 520 nm. The peaks were separated in approximately 25 minutes, and were quantified even at the 1-10 ppb levels. The present procedures were considered to provide simultaneous detection and accurate quantitation of the above five metals in the biological samples.

Animals↗
PubMed2004

[A comparative study of cadmium, lead, mercury, arsenic, selenium, manganese, copper and zinc in brown rice and fish by inductively coupled plasma-mass spectrometry (ICP-MS) and atomic absorption spectrometry].

A study was conducted to evaluate the applicability of ICP-MS techniques for determination of metals in brown rice and fish. Cadmium, lead, mercury, arsenic, selenium, manganese, copper and zinc were determined by this method. An open digestion with nitric acid (Method A) and a rapid open digestion with nitric acid and hydrochloric acid (Method B) were used to solubilize analytes in samples, and these procedures were followed by ICP-MS analysis. Recovery of certified elements from standard reference materials by Method A and Method B ranged from 92 to 110% except for mercury (70 to 100%). Analytical results of brown rice and fish samples obtained by this ICP-MS agreed with those obtained by atomic absorption spectrometry (AAS). The results of this study demonstrate that quadrupole ICP-MS provides precise and accurate measurements of the elements tested in brown rice and fish samples.

Animals↗
PubMed1985

[Determination of polyethylene during the process of measuring feed passage rate in sheep].

In a trial with rams, application of polyethylene powder (PE) as a marker for determination of feed passage rate through the digestive tract and three methods of its determination in feed and feces were tested. PE with particle size 0.4 mm and specific weight 0.924 was administered to animals in feed and its excretion was studied during the period of 10 days in two experimental diets based on secondary sources of wood, and in one control diet. PE formed 3.9% (D-2), 3.5% (D-1) and 4% (control) of the diet dry matter and was determined by gravimetric method; for mineralizing organic matter in the sample, nitric acid (Chandler et al., 1964), mixture of sulphuric and nitric acid (Kemmink and Dijkstra, 1968) and sodium hydroxide (Boling et al., 1967) were used. The most suitable was the method using sodium hydroxide, by which 81.23% (D-2), 84.78% (D-1) and 86.6% (control) of PE recovery was determined in feces samples.

Animal Feed↗
PubMed1999

Effects of mild hypothermia on the cortical release of excitatory amino acids and nitric oxide synthesis following hypoxia.

Studies concerning neurotransmitter release following cerebral hypoxia are scarce, and the effects of mild hypothermia on hypoxia-induced neurotransmitter release are unknown. The purpose of this study was to investigate changes in excitatory amino acid (EAA) concentrations and nitric oxide (NO) synthesis following cerebral hypoxia in rats, and the effects of mild hypothermia on both. Cerebral hypoxia (PaO2, 30-40 mm Hg) was induced in each rat for 60 min. Cerebral blood flow (CBF) was measured by laser-Doppler flowmetry, and the extracellular concentrations of EAAs and NO end-products (nitrite and nitrate) were measured by in vivo microdialysis in normothermic (37 degrees C) and hypothermic (32 degrees C) rats. In both groups, CBF showed modest increases during hypoxia and returned to baseline during reoxygenation. The EAA levels of the normothermic rats increased markedly after hypoxia induction and returned to baseline levels during reoxygenation. Hypothermia abolished these increases completely. The NO end-product levels under normothermic conditions declined slightly during hypoxia, and then increased transiently during reoxygenation. Hypothermia appeared to attenuate the NO end-product level and to delay the peak. When the relationship between glutamate and the NO end-products was examined on an individual-animal basis, glutamate release did not parallel NO synthesis. The results indicate that hypothermic neuroprotection during cerebral hypoxia may be attributable to the amelioration of damage by reduction of presynaptic EAA release. Although it is unclear from the present results alone whether endothelial NO synthase, neuronal NO synthase or both caused the elevation of the NO end-products during reoxygenation, it is possible that the attenuation and delay of the peak of the NO end-product level plays a role in protection from NO-induced neuronal damage.

Animals↗
PubMedDate not supplied

A comparison of six enamel treatment procedures for sealant bonding.

This in-vitro study evaluated the effectiveness of six different enamel treatment procedures for bonding a dental sealant. Sixty extracted human molar teeth were separated into the following enamel treatment groups (10 teeth each): group 1 (control)-etched with 37% phosphoric acid; group 2-air polished (air abraded) with 45 microns particles of sodium bicarbonate; group 3-air abraded with 50 microns aluminum oxide particles; group 4-etched with 2.5% nitric acid; group 5-air abraded with sodium bicarbonate particles and etched with 37% phosphoric acid; and group 6-air abraded with 50-microns aluminum oxide particles and etched with 37% phosphoric acid. The enamel treatment procedures were accomplished on intact mesial or distal surfaces. Following the enamel treatment, a sealant was bonded to the surfaces using a plastic matrix technique. After 24 hr of water storage at 37 degrees C, the specimens were debonded using an Instron machine. The mean shear bond strengths (MPa) were as follows: group 1-9.19 +/- 1.34 MPa; group 2-2.03 +/- 1.67 MPa; group 3-1.50 +/- 0.93 MPa; group 4-4.99 +/- 1.26 MPa; group 5-11.61 +/- 4.51; and group 6-11.14 +/- 1.70 MPa. Statistical analysis using a one-way ANOVA and Scheffe F-test revealed no significant difference (P > 0.05) among groups 1,5, and 6. However, there was a significant difference (P < 0.05) between groups 1,5, and 6 and the other three groups (2,3, and 4). In conclusion, 37% phosphoric acid treatment of intact enamel, or a combination of air abrasion with sodium bicarbonate or aluminum oxide followed by phosphoric acid, provides significantly higher bond strengths of a sealant material than enamel conditioning with 2.5% nitric acid or air abrasion with sodium bicarbonate or aluminum oxide.

Acid Etching, Dental↗