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PubMedDate not supplied

[The anticoagulant action of the nitric acid ester of oxidized starch].

The effect of oxidized starch (OS) which contained 15% of COOH groups and its nitroether (NOS) with 4% of nitrogen on coagulation properties of rat blood was studied in vitro and in vivo. The results of the study in vitro showed that OS did not affect the function of the coagulation system. In contrast to OS, a dose-dependent increase in prothrombin-, thrombin time, and activated partial thromboplastin time was observed for NOS. The activity of the components of the internal coagulation pathway changed when the NOS concentration reached 0.1 mg/ml. At a concentration of 0.6 mg/ml and higher this compound affect the external pathway and final stage of coagulation. According to the efficiency (in vitro) of the influence on the thrombine time I mg/ml NOS corresponded to 0.2 U/ml of heparine. The anticoagulant effect of NOS was also observed in vivo along with reliable changes in thromboplastin and thrombin time. Antithrombin activity of plasma remained the same. Standard test was negative and indicated to the absence of fibrin monomers. The pronounced anticoagulant effect of NOS in the experiments in vitro and quick response in the experiments in vivo make it possible to consider this compound as anticoagulant of direct action.

Animals↗
PubMed2006

Batch salicylic acid nitration by nitric acid/acetic acid mixture under isothermal, isoperibolic and adiabatic conditions.

Runaway phenomena and thermal explosions can originate during the nitration of salicylic acid by means of a nitric acid/acetic acid mixture when the thermal control is lost, mainly as a result of the formation and thermal decomposition of picric acid. The prediction of the behaviour of this system is thus of great importance in view of possible industrial applications and the need to avoid the occurrence of unwanted dangerous events. During a previous investigation a model was developed to simulate its behaviour when the starting concentration of the substrate is too low, thus, preventing the precipitation of poor soluble intermediates. In this work this model is extended to deal with more concentrated systems even in case of a solid phase separating during the process. To this purpose the previously assessed dependence of the solubility of 3-nitro and 5-nitrosalicylic acids upon temperature and nitric acid concentration is included in the model. It is assumed that when 3-nitro and 5-nitrosalicylic acids are partially suspended in the reacting medium a kinetic regime of "dissolution with reaction" is established; that is, the redissolution of these species is a fast process compared to the successive nitration to give dinitroderivatives. Good results are obtained in the comparison of the experimental data with those calculated both in isoperibolic and adiabatic conditions when the revised model is used.

Acetic Acid↗
PubMed1983

Compounds in urban air compete with 2,3,7,8-tetrachlorodibenzo-p-dioxin for binding to the receptor protein.

Acetone extracts of filter-collected urban airborne particulate matter contain compounds which can competitively inhibit 2,3,7,8-[1,6-3H]tetrachlorodibenzo-p-dioxin (TCDD) binding to the rat liver TCDD-receptor protein. The concentration of conventional polycyclic aromatic hydrocarbons (PAHs) or chlorinated dioxins and dibenzofurans cannot account for more than 1-30% of the observed competition for [3H]TCDD binding to the receptor protein. The difference in potency between samples collected in urban areas during different periods of the year and a background sample is 25-400-fold. Collecting samples in the presence of increased concentrations of nitrogen dioxide, nitrous acid, nitric acid or ozone did not increase the amount of compounds with receptor affinity. However, with nitrogen dioxide and especially with nitric acid, a substantial increase of the mutagenic effects in the Ames Salmonella assay in the absence of mammalian activation as well as a degradation of several PAHs were noted. Affinity for the TCDD-receptor protein, mutagenicity in the absence of mammalian metabolic activation in the Ames Salmonella assay and PAH-content are characteristics of urban particulate matter showing the presence of compounds, that represent potential health risks. The compounds with affinity for the receptor may constitute a group of substances different from both conventional PAHs and direct-acting mutagens.

Air Pollution↗
PubMed2005

Kinetic and safety assessment for salicylic acid nitration by nitric acid/acetic acid system.

The nitration process of salicylic acid for the production of the important intermediate 5-nitrosalicylic acid is studied from thermokinetic and safety points of view. Investigations carried out by considering, as process deviations, the loss of the thermal control point out the possibility of runaway phenomena due to the occurrence of polynitration reactions. Isothermal experiments are carried out in various conditions to assess the involved reaction network and reaction kinetics.

Acetic Acid↗
PubMed1999

Gas chromatographic study of complexing in the system hydrazoic acid-tributyl phosphate-nitric acid-uranyl nitrate.

Elution gas chromatography has been used to study complexing of hydrazoic acid with tributyl phosphate (TBP) in hexadecane solution in the presence of nitric acid and/or uranyl nitrate. The study covered the temperature range 298-338 K, with concentrations of either additive up to 0.41 mol dm(-3). The results for hydrazoic acid elution at infinite dilution establish (a) that stoichiometry of the TBP-HNO3 complex is 1:1 and (b) that both 2:1 and 1:1 TBP-UO2(NO3)2 complexes co-exist in the system, the latter increasing in amount as the temperature is raised. Both HNO3 and UO2(NO3)2 act simply to reduce the amount of TBP free to form the 1:1 TBP-HN3 complex. Stability constants for the equilibrium UO2(NO3)2 TBP+TBP4<-->UO2(NO3)2 x 2TBP are presented.

Azides↗
PubMed1997

Different routes of Ca2+ influx in NMDA-mediated generation of nitric oxide and arachidonic acid.

Nitric oxide and arachidonic acid act as inter- and intracellular messengers in the central nervous system. It is well known that the NMDA-mediated generation of nitric oxide and arachidonic acid is dependent on extracellular Ca2+. However, the role of voltage-dependent calcium channels (VDCCs) in this regard is poorly understood. We report here that NMDA-mediated nitric oxide production in striatal neuron cultures is blocked (80%) by the L-type VDCC antagonist nifedipine, but not by omega-conotoxin or omega-agatoxin IVA, antagonists of the N- and P-type VDCCs respectively. By contrast, none of the VDCC antagonists inhibited the NMDA-mediated release of arachidonic acid. These data indicate that permeation through different Ca2+ channels is responsible for the production of arachidonic acid and nitric oxide in striatal neurons.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed2003

A study of air pollutants and acute asthma exacerbations in urban areas: status report.

A study to try to better understand the interactions between various air contaminants and acute asthma exacerbations is described. The study evaluates temporal associations between a panel of air contaminants and acute asthmatic exacerbations as measured by emergency room visits for asthma in communities in the Bronx and Manhattan in New York City (NYC). In addition, ambient levels of various air pollutants in two NYC communities are being compared. Almost 2 years of daily data have been collected for most of the air contaminants to be investigated. The air contaminants measured include gaseous compounds (ozone, sulfur dioxide, nitrogen oxides, aldehydes, nitrous acid, nitric acid, hydrochloric acid and ammonia), particulate matter components (metals, elemental and organic carbon, sulfate, hydrogen ion, pollen, mold spores and particle mass and number).

Acute Disease↗
PubMedDate not supplied

An in vitro shear bond strength study of enamel/dentin bonding systems on enamel.

The purpose of this study was to compare the enamel shear bond strengths achieved with four acid conditioners employed by current enamel/dentin bonding systems (maleic acid, citric acid, nitric acid, oxalic acid) with a 37% phosphoric acid etching technique. The study also compared enamel shear bond strengths between the manufacturers' enamel/dentin conditioner used with an unfilled enamel bonding resin. The facial surfaces of 135 bovine incisors were ground flat and divided into nine test groups of n=15. Conditioning and bonding procedures were carried out following manufacturers' instructions. The phosphoric acid groups were etched for 15 seconds, rinsed for 30 seconds, and dried for 20 seconds with compressed air. All bonding was accomplished at a constant temperature of 21 degrees C and a relative humidity of 60%. A single composite restorative resin (Z-100) was used with all specimens to eliminate variables between composite materials. All specimens were thermocycled 2500 times (5 to 45 degrees C) and had a total storage time of 21 days prior to shear testing on an Instron at a crosshead speed of 1.0 mm/minute. Shear strengths were calculated by dividing load at failure by specimen area. A light microscope was used to determine failure mode. The data were subjected to Bartlett's test for homogeneity of variance and were found not to be homogeneous. The Welch Test was applied and indicated that the treatments used had influence on bond strength at P<0.05. There was no significant difference in bond strength values between traditional phosphoric acid/enamel bonding resin and Mirage Bond Dentin and Enamel Adhesive, Clearfil Liner Bond System, and Scotchbond Multi-Purpose Dental Adhesive System.

Acid Etching, Dental↗
PubMed2000

A habitat for psychrophiles in deep Antarctic ice.

Microbes, some of which may be viable, have been found in ice cores drilled at Vostok Station at depths down to approximately 3,600 m, close to the surface of the huge subglacial Lake Vostok. Two types of ice have been found. The upper 3,500 m comprises glacial ice containing traces of nutrients of aeolian origin including sulfuric acid, nitric acid, methanosulfonic acid (MSA), formic acid, sea salts, and mineral grains. Ice below approximately 3,500 m comprises refrozen water from Lake Vostok, accreted to the bottom of the glacial ice. Nutrients in the accretion ice include salts and dissolved organic carbon. There is great interest in searching for living microbes and especially for new species in deepest Antarctic ice. I propose a habitat consisting of interconnected liquid veins along three-grain boundaries in ice in which psychrophilic bacteria can move and obtain energy and carbon from ions in solution. In the accretion ice, with an age of a few 10(4) years and a temperature a few degrees below freezing, the carbon and energy sources in the veins can maintain significant numbers of cells per cubic centimeter that are metabolizing but not multiplying. In the 4 x 10(5)-year-old colder glacial ice, at least 1 cell per cm(3) in acid veins can be maintained. With fluorescence microscopy tuned to detect NADH in live organisms, motile bacteria could be detected by direct scanning of the veins in ice samples.

Antarctic Regions↗
PubMed1996

Surface roughness modulates the local production of growth factors and cytokines by osteoblast-like MG-63 cells.

Titanium (Ti) surface roughness affects proliferation, differentiation, and matrix production of MG-63 osteoblast-like cells. Cytokines and growth factors produced in the milieu surrounding an implant may also be influenced by its surface, thereby modulating the healing process. This study examined the effect of surface roughness on the production of two factors known to have potent effects on bone, prostaglandin E2 (PGE2) and transforming growth factor beta 1 (TGF-beta 1). MG-63 cells were cultured on Ti disks of varying roughness. The surfaces were ranked from smoothest to roughest: electropolished (EP), pretreated with hydrofluoric acid-nitric acid (PT), fine sand-blasted, etched with HCl and H2SO4, and washed (EA), coarse sand-blasted, etched with HCl and H2SO4, and washed (CA), and Ti plasma-sprayed (TPS). Cells were cultured in 24-well polystyrene (plastic) dishes as controls and to determine when confluence was achieved. Media were collected and cell number determined 24 h postconfluence. PGE2 and TGF-beta 1 levels in the conditioned media were determined using commercial radioimmunoassay and enzyme-linked immunosorbent assay kits, respectively. There was an inverse relationship between cell number and Ti surface roughness. Total PGE2 content in the media of cultures grown on the three roughest surfaces (FA, CA, and TPS) was significantly increased 1.5-4.0 times over that found in media of cultures grown on plastic or smooth surfaces. When PGE2 production was expressed per cell number, CA and TPS cultures exhibited six- to eightfold increases compared to cultures on plastic and smooth surfaces. There was a direct relationship between TGF-beta 1 production and surface roughness, both in terms of total TGF-beta 1 per culture and when normalized for cell number. TGF-beta 1 production on rough surfaces (CA and TPS) was three to five times higher than on plastic. These studies indicate that substrate surface roughness affects cytokine and growth factor production by MG-63 cells, suggesting that surface roughness may modulate the activity of cells interacting with an implant, and thereby affect tissue healing and implant success.

Biocompatible Materials↗