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PubMedDate not supplied

Cleaning and heat-treatment effects on unalloyed titanium implant surfaces.

This study tested the following hypotheses: (1) acid-cleaned and passivated unalloyed titanium implants have higher surface energies (which are considered desirable for bone implants) than ethanol-cleaned titanium; (2) higher temperatures of heat treatment of unalloyed titanium result in higher surface energies; and (3) these changes can be related to changes in surface composition and roughness. Thus, unalloyed titanium specimens were either acid-cleaned and passivated (CP) or ethanol-cleaned (Et). Each set was then divided into 3 groups and heat-treated for 1 hour at 316 degrees C (600 degrees F), 427 degrees C (800 degrees F), and 538 degrees C (1,000 degrees F), respectively. Surface roughness values for each of these groups were determined using atomic force microscopy, while surface compositions were determined using Auger electron, x-ray photoelectron, and Raman spectroscopic techniques. Surface energies were estimated using a 2-liquid geometric mean technique and correlated with surface roughness, elemental composition, and elemental thickness. The CP surfaces were slightly rougher than the Et specimens, which had greater oxide thickness and hydrocarbon presence. The surface oxides were composed of TiO2, Ti2O3, and possibly titanium peroxide; those heat-treated at 427 degrees C or above were crystalline. The CP specimens had carbonaceous coverage that was of a different composition from that on Et specimens. The CP specimens had significantly higher surface energies, which showed statistically significant correlations with oxide thickness and carbonaceous presence. In conclusion, ethanol cleaning of unalloyed titanium dental implants may not provide optimal surface properties when compared to cleaning with phosphoric acid followed by nitric acid passivation.

Analysis of Variance↗
PubMed1993

Effect of solvent type on the determination of total iodine in milk powder and human serum by inductively coupled plasma mass spectrometry.

A method for the determination of the total iodine content in milk powder and human serum by inductively coupled plasma mass spectrometry is described. It is shown that the oxidation state of the analyte has a strong impact on the analytical performance. If iodine is present as iodide and nitric acid is used for acidification, the observed ion signal is not stable and samples spiked with iodide yield erroneous recoveries up to 750%. Hence, as the iodine in milk powder is present almost exclusively as iodide, destruction of the sample with nitric acid is not suitable. It was found that such an excessive spike recovery does not occur if ammonia solution instead of nitric acid is used as the diluent. The proposed sample preparation was tested by analysing three reference milk powders, namely Certified Reference Materials 150 and 151 Spiked Skim Milk Powder (from the Community Bureau of Reference) and Standard Reference Material 1549 Non-Fat Milk Powder (from the National Institute of Standards and Technology). Good agreement with the certified values was obtained, indicating that no significant errors are introduced. For human serum, samples treated with nitric acid or with ammonia solution gave results that were not significantly different from each other. Results are given for both a 'second-generation' biological reference material, Freeze-Dried Human Serum (University of Ghent), and for sera from healthy individuals.

Animals↗
PubMed1955

The inactivation of dilute solutions of crystalline trypsin by x-radiation. II. Effects of enzyme concentration, medium, pH, and temperature.

The proteolytic activity of dilute solutions of clystalline trypsin is destroyed by x-rays, the amount of inactivation being an exponential function of the radiation dose. The reaction yield increases steadily with increasing concentration of trypsin, varying, as the concentration of enzyme is increased from 1 to 300 microM, from 0.068 to 0.958 micromole of trypsin per liter inactivated per 1000 r with 0.005 N hydrochloric acid as the solvent, from 0.273 to 0.866 with 0.005 N sulfuric acid as the solvent, and from 0.343 to 0.844 with 0.005 N nitric acid as the solvent. When the reaction yields are plotted as a function of the initial concentration of trypsin, they fall on a curve given by the expression Y alpha X(K), in which Y is the reaction yield, X is the concentration of trypsin, and K is a constant equal to 0.46, 0.20, and 0.16, respectively, with 0.005 N hydrochloric, sulfuric, and nitric acids as solvents. The differences between the reaction yields found with chloride and sulfate ions in I to 10 microM trypsin solutions are significant only in the pH range from 2 to 4. The amount of inactivation obtained with a given dose of x-rays depends on the pH of the solution being irradiated and the nature of the solvent. The reaction yield-pH curve is a symmetrical one, with minimum yields at about pH 7. Buffers such as acetate, citrate, borate and barbiturate, and other organic molecules such as ethanol and glucose, in concentrations as low as 20 microM, inhibit the inactivation of trypsin by x-radiation. Sigmoid inactivation-dose curves instead of exponential ones are obtained in the presence of ethanol. The reaction yields for the inactivation of trypsin solutions by x-rays are approximately 1.5 times greater when the irradiation is done at 26 degrees C. than when it is done at 5 degrees C., when 0.005 N hydrochloric acid is the solvent. The dependence on temperature is less when 0.005 N sulfuric acid is used, and is negligible with 0.005 N nitric acid. The difficulties involved in interpreting radiation effects in aqueous systems, and in comparing the results obtained under different experimental conditions, are discussed.

Buffers↗
PubMed2000

Performance of the annular denuder system with different arrangements for HNO3 and HNO2 measurements in Taiwan.

Experiments on different annular denuder system (ADS) arrangements for sampling nitrous acid (HNO2) and nitric acid (HNO3) gases were conducted in this study to evaluate their sampling artifacts. The evaluation basis is the one that employed one sodium chloride denuder for sampling HNO3 gas and two sodium carbonate (Na2CO3) denuders for sampling HNO2 gas, which is a commonly employed ADS arrangement in many field applications in the United States. A field study was conducted in Hsinchu, Taiwan, and the results indicated that this ADS arrangement may yield over 80% relative errors for HNO3 gas. It also showed that the relative errors for HNO2 gas can be less than 10% as sampled with only one Na2CO3 denuder. This is attributed to the fact that the ambient HNO3 concentration measured in this study was relatively low while the HNO2 concentration was high, as compared to typical concentrations of these two gases measured in the United States. The sampling error of HNO3 gas may be due to high concentrations of N-containing interfering species present in Taiwan's atmosphere. Because the relative sampling errors of HNO3 and HNO2 gases depend mainly on their concentrations in the atmosphere as well as concentrations caused by interfering species, the risk for high error while measuring low HNO2 concentrations by only one Na2CO3 denuder is also possible. As a result, it is suggested that pretests are necessary to evaluate possible sources and degrees of sampling errors before field sampling of HNO2 and HNO3 gases. The sampling errors of these two gases can, therefore, be minimized with a better arrangement of the ADS.

Air Pollutants↗
PubMed1998

Effects of acid-etching on the tensile properties of demineralized dentin matrix.

OBJECTIVES: Little research has been done to evaluate the effects of acids commonly used in adhesive dentistry, on the tensile properties of the demineralized dentin matrix. The purpose of this study was to evaluate the effects of a number of acidic conditioners on the ultimate tensile strength (UTS) and modulus of elasticity (E) of human coronal dentin matrix. METHODS: Small hour-glass shaped (for UTS) or l-beam shaped (for determination of E) were prepared from mid-coronal dentin of extracted human third molars. After protecting the ends with varnish, the middle of the specimens was completely demineralized in 0.5 M EDTA (pH 7). UTS was determined by tensile stressing to failure. Modulus of elasticity was calculated from stress strain curves. The results were analyzed by ANOVA and Student-Neuman-Keuls test at the 95% confidence level. RESULTS: Brief (ca. 1-2 min) exposure of demineralized dentin matrix to acids had no measurable effects on its tensile properties. Ten-minute exposures to 2.5% and 17.5% nitric acid lowered (p < 0.05) the UTS compared to phosphate buffered saline (PBS)-exposed controls. Exposure of the decalcified dentin to 10% citric acid containing 3% ferric chloride, 10% citric acid, 37% phosphoric acid or 17.5% nitric acid containing 3% ferric chloride for 10 min had no effect on UTS. None of these acids consistently lowered stiffness. SIGNIFICANCE: The results indicate that relatively long exposures to acids are required to alter the tensile properties of demineralized dentin. It is unlikely that the brief exposures to acids that are used in adhesive dentistry would acutely weaken the physical properties of demineralized dentin. However, long-term studies should be done to determine if such treatment increases the susceptibility of the matrix to hydrolysis.

Acid Etching, Dental↗
PubMed1994

Fusidic acid suppresses nitric oxide toxicity in pancreatic islet cells.

Earlier preclinical and clinical trials indicate that fusidic acid, a triterpenoid compound originally described as an antimicrobial drug may protect islet beta cells from destruction in type I (insulin-dependent) diabetes mellitus. Since nitric oxide appears to be an important mediator of inflammatory islet cell death we analyzed whether fusidic acid interferes with nitric oxide production or action. We report here that fusidic acid dose-dependently inhibits lysis of isolated islet cells by activated macrophages, a process mediated by nitric oxide. In the presence of 100 microM fusidic acid macrophage-mediated islet cell lysis was reduced from 52.5 to 1.7% (P < 0.001). Fusidic acid only slightly affected macrophage function and did not inhibit the release of nitric oxide. We therefore tested whether fusidic acid suppresses nitric oxide toxicity in target cells. Isolated islet cells were exposed to the nitric oxide donor nitroprusside which led to DNA strand breaks and plasma membrane lysis. DNA strand breaks were reduced from 54.6 to 34.9% (P < 0.001) in the presence of 100 microM fusidic acid and cell lysis was reduced from 60.1 to 27.5% with 100 microM (P < 0.001). In the presence of 500 microM fusidic acid DNA strand breaks and cell lysis were reduced further to 27.1 and 10.7%, respectively (P < 0.001). No protection by fusidic acid was observed when cells were exposed to oxygen radicals or the alkylating beta cell toxin streptozotocin. The suppression of nitric oxide toxicity by fusidic acid was not due to its known inhibitory action on protein biosynthesis and thus represents a hitherto unknown activity of this drug.

Animals↗
PubMedDate not supplied

Atomic absorption spectrophotometric determination of tin in canned foods, using nitric acid-hydrochloric acid digestion and nitrous oxide-acetylene flame: collaborative study.

Twenty-six collaborators participated in a study to evaluate an atomic absorption spectrophotometric (AAS) method for the determination of tin in canned foods. The 5 foods evaluated were meat, pineapple juice, tomato paste, evaporated milk, and green beans, each spiked at 2 levels. The concentration range of tin in the samples was 10-450 micrograms/g, and each level was sent as a blind duplicate. Statistical treatment of results revealed no laboratory outliers and 6 individual or replicate-total outliers, accounting for 3.3% of the data. Repeatability (within-laboratory) coefficient of variation (CVo) ranged from 2.2 to 48%, depending on the tin level and food evaluated. For samples containing greater than or equal to 80 micrograms/g of tin, repeatability CV averaged 5.6% including outliers and 3.7% after their rejection. Overall among-laboratories coefficient of variation (CVx) varied from 3.3 to 58%; at levels greater than or equal to 80 micrograms/g, it averaged 7.3% with outliers and 5.3% after their rejection. Recovery of tin, based on spiking levels, ranged from 100.0 to 112.8% and averaged 105.4%. Detection limit range is 2-10 micrograms/g, and lower quantitation limit is 40 micrograms/g. This method has been adopted official first action.

Acetylene↗
PubMed2002

High frequency and large deposition of acid fog on high elevation forest.

We have collected and analyzed fogwater on the mountainside of Mt. Oyama (1252 m) in the Tanzawa Mountains of Japan and observed the fog event frequency from the base of the mountain with a video camera. The fog event frequency increased with elevation and was observed to be present 46% of the year at the summit. The water deposition via throughfall increased with elevation because of the increase in fogwater interception and was about twice that via rain at the summit, where the air pollutant deposition via throughfall was several times that via rainwater. The dry deposition and the deposition via fogwater were dominant factors in the total ion deposition at high elevation sites. In a fog event, nitric acid, the major acid component on the mountain, is formed during the transport of the air mass from the base of the mountain along the mountainside, where gases including nitric acid deposit and are scavenged by fogwater. Therefore, high acidity caused by nitric acid and relatively low ion strength are observed in the fogwater at high elevation sites.

Acid Rain↗
PubMed1997

Chemical stability of polyether urethanes versus polycarbonate urethanes.

The relative chemical stability of two commercially available polyurethanes-Pellethane, currently used in biomedical devices, and Corethane, considered as a potential biomaterial-was investigated following aging protocols in hydrolytic and oxidative conditions (HOC, water, hydrogen peroxide, and nitric acid) and in physiological media (PHM, phosphate buffer, lipid dispersion, and bile from human donors). The chemical modifications induced on these polymers were characterized using differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR). With the exception of nitric acid, all of the aging media promoted a mild hydrolytic reaction leading to a slight molecular weight loss in both polymers. When aged in water and hydrogen peroxide, Pellethane experienced structural modifications through microdomain phase separation along with an increase of the order within the soft-hard segment domains. The incubation of Pellethane in nitric acid also resulted in an important decrease of the melting temperature of its hard segments with chain scission mechanisms. Moreover, incubation in PHM led to an increase of the order within shorter hard-segment domains. FTIR data revealed the presence of aliphatic amide molecules used as additives on the Pellethane's surface. The incubation of Corethane under the same conditions promoted an almost uniform molecular reorganization through a phase separation between the hard and soft segments as well as an increase of the short-range order within the hard-segment domains. Incubation of this polymer in nitric acid also resulted in a chain scission process that was less pronounced than that measured for the Pellethane samples. Finally, lipid adsorption occurred on the Corethane sample incubated in bile for 120 days. Overall data indicate that polycarbonate urethane presents a greater chemical stability than does polyetherurethane.

Calorimetry, Differential Scanning↗
PubMed1996

Mechanical overload and skeletal muscle fiber hyperplasia: a meta-analysis.

With use of the meta-analytic approach, the purpose of this study was to examine the effects of mechanical overload on skeletal muscle fiber number in animals. A total of 17 studies yielding 37 data points and 360 subjects met the initial criteria: 1) "basic" research studies published in journals, 2) animals (no humans) as subjects, 3) control group included, 4) some type of mechanical overload (stretch, exercise, or compensatory hypertrophy) used to induce changes in muscle fiber number, and 5) sufficient data to accurately calculate percent changes in muscle fiber number. Across all designs and categories, statistically significant increases were found for muscle fiber number [15.00 +/- 19.60% (SD), 95% confidence interval = 8.65-21.53], muscle fiber area (31.60 +/- 44.30%, 95% confidence interval = 16.83-46.37), and muscle mass (90.50 +/- 86.50%, 95% confidence interval = 61.59-119.34). When partitioned according to the fiber-counting technique, larger increases in muscle fiber number were found by using the histological vs. nitric acid digestion method (histological = 20.70%, nitric acid digestion = 11.10%; P = 0.14). Increases in fiber number partitioned according to species were greatest among those groups that used an avian vs. mammalian model (avian = 20.95%, mammalian = 7.97%; P = 0.07). Stretch overload yielded larger increases in muscle fiber number than did exercise and compensatory hypertrophy (stretch = 20.95%, exercise = 11.59%, compensatory hypertrophy = 5.44%; P = 0.06). No significant differences between changes in fiber number were found when data were partitioned according to type of control (intra-animal = 15.20%, between animal = 13.90%; P = 0.82) or fiber arrangement of muscle (parallel = 15.80%, pennate = 11.60%; P = 0.61). The results of this study suggest that in several animal species certain forms of mechanical overload increase muscle fiber number.

Animals↗
PubMed1997

Eicosapentaenoic acid enhances nitric oxide production by cultured human endothelial cells.

It is unclear whether the abnormal relaxation seen in diabetes is due to decreased levels of nitric oxide (NO) and how eicosapentaenoic acid (EPA, C20:5 omega 3) affects the endothelial production of NO. We investigated the effects of EPA ethyl ester (EPA-E) and elevated glucose on NO production by human endothelial cells (HUE). EPA-E (0.3 mM) significantly enhanced [NO2] production and the intracellular concentration of free Ca2+ within 3 min after EPA-E was added to the cultures. High levels of glucose (27.5 mM) significantly increased endothelial glucose, sorbitol and fructose, and inhibited [NO2-] production. However, EPA-E (0.3 mM) prevented the inhibition of [NO2-] production due to the activation of the Ca(2+)-calmodulin system of NO synthase. EPA-E decreased the glucose-mediated inhibition of NO production by HUE. These results suggest this agent might ameliorate endothelial dysfunction associated with diabetes.

Calcium↗
PubMed1994

Isolation and characterization of debris in membranes around total joint prostheses.

Particles of wear debris have been implicated in osteolysis around and aseptic loosening of total joint prostheses, but the number and size distribution of particles present in periprosthetic tissues are unknown. A method of particle assay was developed, consisting of nitric-acid digestion of tissue followed by collection of particles, electronic quantitation, and parallel morphological and chemical characterization. Nitric acid had minimum deleterious effects on control samples of titanium, cobalt-chromium alloy, and polyethylene particles, as determined by atomic absorption spectroscopy, scanning electron microscopy, and electronic measurements of the sizes of the particles. Acid digestion of twelve control samples of tissue, including tissue rich in hemosiderin, resulted in particle counts that were no higher than that in the digestion solution background. Other digestion preparations, including hydrochloric acid and sodium hypophosphate, were not as effective as nitric acid. With the low size limit of detection of approximately 0.58 micrometer, particle analysis of tissue adjacent to twenty retrieved total joint implants indicated a range of concentration of 0.85 to 141.85 x 10(9) particles per gram of tissue (dry weight). Although a few particles of more than 100 micrometers were detected, the mode of particle diameter from each sample ranged from the lower limit of detection (approximately 0.58 micrometer) to 0.79 micrometer. The findings of morphological studies and x-ray spectroscopy of isolated particles corresponded with those of light microscopy of the fibrous membranes. These data indicate that most of the particles in implant membranes are smaller than the resolution of the light microscope and that tissue digestion is necessary for quantitation and characterization.

Adolescent↗
PubMed2003

Changes in brain amino acids and nitric oxide after melatonin administration in rats with pentylenetetrazole-induced seizures.

We examined the effect of melatonin on brain levels of amino acids and nitric oxide (NO) after pentylenetetrazole (PTZ)-induced seizures in rats. Animals were treated with melatonin (10-160 mg/kg, i.p.) 30 min before PTZ administration (100 mg/kg, s.c.), and were killed 3 hr later. At the dose of 80 mg/kg, melatonin significantly increased the latency (5.7-12.7 min) and decreased the duration (31.2-18.4 s) of the first seizure, reducing PTZ induced mortality from 87.5 to 25%. After kill, brains were removed and neurotransmitters and nitrite levels measured in prefrontal cortex (PF), parieto-temporal cortex (PF), striatum (ST), hippocampus (HP) and brain stem (BS) by high performance liquid chromatography. PTZ treatment increased glutamine levels in all brain areas studied, without changes in glutamate, gamma-amino butyric acid (GABA) and glycine. Aspartate and taurine increased in PF and PT and in HS and PT, respectively. Melatonin administration displayed a dose-dependent effect. At doses of 10-40 mg/kg, melatonin counteracted the PTZ-induced glutamine increase and reduced both glutamate and aspartate levels in the studied areas, with minor changes in GABA and glycine content. At doses of 80 and 160 mg/kg, the levels of glutamine, and glutamate, and to a lesser extent aspartate increased, whereas serine levels did not change. These two doses of melatonin also increased taurine, GABA and glycine in most brain areas studied. Treatment with melatonin (40-160 mg/kg) significantly decreased nitrite content in PT cortex, ST and BS areas of epileptic rats, without changes in the other brain regions. The results suggest that the anticonvulsant property of melatonin involves a modulation of both brain amino acids and NO production.

Amino Acids↗
PubMed2006

Removal of heavy metals from kaolin using an upward electrokinetic soil remedial (UESR) technology.

An upward electrokinetic soil remedial (UESR) technology was proposed to remove heavy metals from contaminated kaolin. Unlike conventional electrokinetic treatment that uses boreholes or trenches for horizontal migration of heavy metals, the UESR technology, applying vertical non-uniform electric fields, caused upward transportation of heavy metals to the top surface of the treated soil. The effects of current density, treatment duration, cell diameter, and different cathode chamber influent (distilled water or 0.01 M nitric acid) were studied. The removal efficiencies of heavy metals positively correlated to current density and treatment duration. Higher heavy metals removal efficiency was observed for the reactor cell with smaller diameter. A substantial amount of heavy metals was accumulated in the nearest to cathode 2 cm layer of kaolin when distilled water was continuously supplied to the cathode chamber. Heavy metals accumulated in this layer of kaolin can be easily excavated and disposed off. The main part of the removed heavy metals was dissolved in cathode chamber influent and moved away with cathode chamber effluent when 0.01 M nitric acid was used, instead of distilled water. Energy saving treatment by UESR technology with highest metal removal efficiencies was provided by two regimes: (1) by application of 0.01 M nitric acid as cathode chamber influent, cell diameter of 100 mm, duration of 18 days, and constant voltage of 3.5 V (19.7 k Wh/m(3) of kaolin) and (2) by application of 0.01 M nitric acid as cathode chamber influent, cell diameter of 100 cm, duration of 6 days, and constant current density of 0.191 mA/cm(2) (19.1 k Wh/m(3) of kaolin).

Algorithms↗
PubMed2003

Differential modulation of NMDA-induced calcium transients by arachidonic acid and nitric oxide in cultured hippocampal neurons.

We have examined the effect of arachidonic acid on the transient increases in intracellular Ca2+ evoked by NMDA and AMPA in cultured hippocampal pyramidal cells loaded with Fura-2 AM. Repeated brief pulses of NMDA elicited Ca2+ transients that showed a modest run down. This run down was enhanced if the preparation was shielded from UV light and was reduced by conducting the experiments in the presence of the nitric oxide synthase inhibitor l-nitroarginine (100 micro m). Arachidonic acid (2 micro m) enhanced the Ca2+ transients evoked by NMDA but not those evoked by AMPA. Other C20 unsaturated fatty acids did not alter the time course of the response to NMDA. These experiments suggest that elevated intracellular Ca2+ activates nitric oxide synthase and the resulting synthesis of nitric oxide depresses the Ca2+ response to NMDA while arachidonic acid augments these responses. Therefore two substances implicated in synaptic plasticity (arachidonic acid and nitric oxide) differentially modulate NMDA-mediated Ca2+ entry into hippocampal neurons.

Animals↗
PubMed2000

Eicosapentaenoic acid stimulates nitric oxide production and decreases cardiac noradrenaline in diabetic rats.

1. The aim of the present study was to investigate whether long-term oral administration of eicosapentaenoic acid increases nitric oxide (NO) production and affects cardiac sympathetic activity in rats with diabetes mellitus. 2. We measured changes in urinary excretion of NO3-, a stable NO metabolite, and cardiac noradrenaline (NA) concentrations in non-diabetic rats and streptozotocin-induced diabetic rats treated with either ethyl icosapentate (EPA-E; 100 mg/kg per day; n = 10), a purified ethyl esterification product of eicosapentaenoic acid, or vehicle (distilled water; n = 10) for 6 weeks. The effects of N(G)-nitro-L-arginine (L-NNA), a NO synthase inhibitor, on urinary NO3- excretion and cardiac NA concentrations were also investigated in diabetic rats treated with EPA-E. 3. Urinary NO3- excretion was higher at weeks 5 and 6 in diabetic rats treated with EPA-E than in diabetic rats treated with vehicle (week 5: 120+/-8 vs 51+/-11 micromol/g per day, respectively (P<0.01); week 6: 279+/-83 vs 73+/-9 micromol/g per day, respectively (P<0.01)). Cardiac NA concentrations were higher in diabetic rats than in non-diabetic rats and were decreased in the left atrium and both ventricles in diabetic rats treated with EPA-E compared with control. Systemic administration of L-NNA abolished the increase in urinary excretion of NO3- and the decrease in cardiac NA concentrations in diabetic rats treated with EPA-E. 4. Long-term oral administration of EPA-E may stimulate NO production and increased NO is likely to play a role in inhibiting enhanced cardiac sympathetic activity in diabetic rats.

Animals↗