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At least 1,135 records · Page 63Linked to original sources
PubMed1990

[Monitoring of an acute compartment syndrome of unusual etiology using MRI (magnetic resonance tomography) and MRS (magnetic resonance spectroscopy)].

The authors report on an acute compartment syndrome occurring symmetrically in the extensors of both forearms. The etiology of this unique compartment syndrome, not previously described, could be attributed to the inhalation of a propane-butane gas mixture, low in oxygen, while sleeping, in combination with external compression of both forearms, due to the patient's head lying on both forearms while sleeping. Ischemic damage to muscles was precisely located using non-invasive MRI (Magnetic Resonance Imaging). The extent of cellular damage due to ischemia after fasciotomy and healing by secondary intention was quantitatively assessed using non-invasive 31P-MRS (Phosphorus Magnetic Resonance Spectroscopy). The results correlate with the clinical and histological findings and indicate a bioenergetic regeneration of the ischemic skeletal muscle's cells.

Adult↗
PubMed1989

[Application of isocyanate separating agent for acrylic resin].

The most widely used agents for separating acrylic resin from gypsum molds are the water-soluble alginates, which produce a very thin water- and organic solvent-insoluble calcium alginate film on the gypsum surface. In the present study, a new type of separating agent, an isocyanate type coating agent, was developed and it's properties were investigated. This coating agent is composed mainly of trimethylol-propane-tolylenediisocyanate and ethyl-acetate, with a small amount of bis-tributyl-tin oxide as catalyst. At first, a thin film was formed on the surface by application of the agent, and then alkyl-phosphate was applied to this film to ensure easy separation of the cured resins from the molds. The molds treated with this separating agent had a glossy, hard surface. The surface of the cured resins treated in this way was glossier and smoother than that of resin treated with the water-soluble alginates.

Acrylic Resins↗
PubMed1986

Ventricular tachycardia associated with non-freon aerosol propellants.

A previously well 2-year-old child presented with seizures and ventricular tachycardia shortly after playing with an aerosol can of a well-known proprietary deodorant. She required intensive care and survived without sequelae. The propellants used in this product were isobutane, n-butane, and propane. The propellants have been thought to be safer than the previously used Freons, which were known to be cardiotoxic and neurotoxic. Significant exposure was confirmed by the detection of n-butane and isobutane in the patient's serum. We conclude that unintentional exposure to non-Freon aerosol propellants in a nonconfined space can be hazardous to children. Aerosol cans should be considered to represent toxic hazards and should be kept out of reach of children.

Acetone↗
PubMed1981

Carcinogenicity tests of certain environmental and industrial chemicals.

Fourteen chemicals of varied uses were tested for carcinogenicity by oral administration in male and female Charles River CD rats. Under the conditions of the tests, propane sultone, propylene imine, and ethylenethiourea, in addition to the positive control N-2-fluorenylacetamide, were carcinogenic. Avadex, bis(2-chloroethyl) ether, the potassium salt of bis(2-hydroxyethyl) dithiocarbamic acid, ethylene carbonate, and semicarbazide hydrochloride were not carcinogenic under the test conditions. Dithiooxamide, glycerol alpha-monochlorohydrin, and thiosemicarbazide gave somewhat ambiguous results, though administered at high enough dose levels to be toxic. An inadequate number of animals survived treatments with sodium azide, sodium bisulfide, and vinylene carbonate, or the animals may not have received sufficiently high doses of the test chemicals to provide maximum test sensitivity. However, there were no indications that these three chemicals were carcinogenic under the test conditions.

2-Acetylaminofluorene↗
PubMed1980

[A Cerenkov detector to determine the energy in electron accelerators (author's transl)].

The authors present a Cerenkov threshold value detector consisting of elements originating from the commercial vacuum industry. This detector allows to measure electron energies between 8 MeV and 20 MeV. By the comparison of the signals of two photo-multipliers, a considerable independence of external disturbing factors is achieved. It is demonstrated that the results achieved with normal propane are not worse than those of super-purified gas and, therefore, a cheap and simple method is available in order to control the electron energy of accelerators.

Electrons↗
PubMedDate not supplied

Distributions of long-term household exposure of different population groups to nitrogen dioxide.

Exposure distributions to nitrogen dioxide in living rooms during the summer and winter were calculated for four groups of Zagreb inhabitants (high school students, university students, employed, and retired persons) using Duan's Cartesianization method. Households were classified into three categories according to fuel used for cooking and heating--electricity (or no gas use), propane-butane, and natural gas. The results showed a seasonally dependent contribution to exposure in households from outdoor sources through ventilation, while type of fuel used for heating and cooking, representing indoor pollution sources, had a predominant influence on exposure levels. Exposure distribution functions could be represented by lognormal, or summation by proportion of lognormal and normal distributions. A comparison of the results and the proposed exposure guideline value suggests that either the guideline value is too large, or a nitrogen dioxide exposure problem exists only in a small percentage of homes and is caused by the high rate of air exchange between the kitchen and living room.

Air Pollution, Indoor↗
PubMedDate not supplied

[Mechanism of methane oxidation by intact cells of obligate methylotrophs].

Ethane and propane were found to be competitive inhibitors of methane oxidation. Obligate methylotrophs can oxidize ethane only in the presence of methane, i.e. co-oxidation of ethane takes place. Studies on the kinetics of simultaneous oxidation of ethane and methane have shown that their oxidation is catalysed by one and the same enzyme system, within one and the same enzyme active site; therefore, the absolute substrate specificity is absent. The reactions of methane and ethane oxidation are coupled since ethane can be oxidized only after the reduced coenzyme had been provided by the reaction of methane oxidation.

Ethane↗
PubMed1976

Interactions of short chain aliphatic hydrocarbons with human blood and haemoglobin A solutions.

The solubilities of methane, propane, butane and propylene were measured in human whole blood, human plasma and defatted haemoglobin solutions at 37 degrees C. For these four hydrocarbons the solubility coefficient (alpha = ml of gas STPD dissolved in one mal of the solvent under a pressure of one atmosphere) is higher in plasma than in an isoosmolar aqueous solution and higher in whole blood than in plasma. This is due to the presence of proteins and particularly of haemoglobin as shown by the dependence of alpha upon the concentration of haemoglobin in the medium. O2 capacity of human blood is not altered in the presence of these hydrocarbons and its affinity for O2 is slightly decreased.

Air Pollutants↗
PubMed1998

Characterization of enzymatic pectin digests by matrix-assisted laser desorption/ionization mass spectrometry.

The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for the characterization of partially methyl-esterified enzymatic pectin digests is described. The sensitivities of several matrices, positive and negative ion modes and desalting techniques for these acidic oligosaccharides were compared. The most favorable results were obtained with a thin-layer preparation of a mixture of 2,4,6-trihydroxyacetophenone and nitrocellulose in the negative ion mode. Results are presented demonstrating the sensitive characterization of separated and unseparated high-ester pectin digests obtained after complete digestion using Aspergillus niger pectin lyase and the analysis of digests after chemical modification. In the case of unseparated digests, the analysis of methylation patterns is demonstrated. Oligomers with a degree of polymerization up to 40 were detected after enrichment of large oligomers by propan-2-ol precipitation.

1-Propanol↗
PubMed1997

Spray-freezing freeze substitution (SFFS) of cell suspensions for improved preservation of ultrastructure.

Some unicellular organisms present challenges to chemical fixations that lead to common, yet obvious, artifacts. These can be avoided in entirety by adapting spray-freezing technology to ultrarapidly freeze specimens for freeze substitution. To freeze specimens, concentrated suspensions of cells ranging in diameter from 0.5-30 pm were sprayed with an airbrush at 140-200 kPa (1.05-1.5 torr; 20.3-29.0 psi) into a nylon mesh transfer basket submerged in liquid propane. After freezing, the mesh basket containing the frozen sample was lifted out of the chamber, drained and transferred through several anhydrous acetone rinses at 188 K (-85 degrees C). Freeze substitution was conducted in 1% tannic acid/1% anhydrous glutaraldehyde in acetone at 188 K (-85 degrees C), followed by 1% OsO4/acetone at 277 K (4 degrees C). Freeze substitution was facilitated using a shaking table to provide gentle mixing of the substitution medium on dry ice. High quality freezing was observed in 70% of spray-frozen dinoflagellate cells and in 95% of spray-frozen cyanobacterial cells. These could be infiltrated and observed directly; however, overall ultrastructural appearance and membrane contrast were improved when the freeze-substituted cells were rehydrated and post-fixed in aqueous OSO4, then dehydrated and embedded in either Spurr's or Epon resin. Ultrastructural preservation using this ultrarapid freezing method provided specimens that were consistently superior to those obtainable in even the best comparable chemical fixations.

Animals↗
PubMed1999

Direct determination of bisphenol A and nonylphenol in river water by column-switching semi-microcolumn liquid chromatography/electrospray mass spectrometry

A rapid and sensitive analytical method based on column-switching semi-microcolumn high-performance liquid chromatography (HPLC) with electrospray mass spectrometry was developed for determining trace levels of bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and nonylphenol (4-nonylphenol) in river water. An aliquot of sample solution was directly injected into the precolumn packed with Capcellpak MF-Ph for sample cleanup and enrichment. The compounds of interest were then transferred to a C-18 analytical column for main separation through a change in flow path by a programmed switching valve. Bisphenol A, nonylphenol, and interfering substances were satisfactorily separated with a simple gradient elution complete within 35 min. Detection of their deprotonated molecules was conducted in negative ion mode. A reduced flow rate (100 &mgr;L/min) optimized for the narrow bore column was found advantageous in obtaining a high degree of sensitivity during electrospray detection. The influence of carrier additives on sensitivity was also examined. This method produced detection limits of 0.5 ng/mL for bisphenol A and 10 ng/mL for nonylphenol (signal-to-noise ratio 3). Calibration curves were observed in the range of 2.5-50 ng/mL (r(2) = 0.999) for bisphenol A and 50-500 ng/mL (r(2) = 0.998) for nonylphenol. Recoveries of the compounds from spiked distilled water and river water were 99.7-138.5% with a relative standard deviation (RSD) ranging from 2.2-9.7%. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗
PubMed1997

Secondary structure induction in aqueous vs membrane-like environments.

The conformational propensity of the 20 naturally occurring amino acids was determined in aqueous 3-[N-morpholino]propane-sulfonic acid (MOPS) buffer, protein interior-like [nonmicellar sodium dodecylsulfate (SDS)] and membrane-like environments (micellar SDS and lysophosphatidylglycerol/lysophosphatidylcholine micelles) using a single "guest" position in a polyalanine-based model host peptide (Ac-KYA13K-NH2). This model system allows the intrinsic alpha-helical or beta-sheet propensity of the amino acids to be determined without intra- and interchain side chain interactions. The overall environment dependence observed for the conformational propensity for the amino acids studied confirms the importance of determining propensity in lipidic environments to better elucidate the biological functions of proteins. The hydrophobic interactions between peptide side chains and lipids appeared to be the primary forces driving the conformational induction in lipidic environments of the model peptides studied. Finally, when comparing the results of these studies with those reported in the literature, the local environment was found to highly influence 65% of the 20 naturally occurring amino acids.

Amino Acids↗
PubMed1999

Optimizing lipase activity, enantioselectivity, and stability with medium engineering and immobilization for beta-blocker synthesis.

Lipase from Pseudomonas cepacia showed poor activity and moderate enantioselectivity (E) in pure aqueous systems for hydrolysis of a racemic mixture (+/-)-1-chloro-2-acetoxy-3-(1-naphthyloxy)-propane, which is a potential intermediate for beta-blocker synthesis. However, addition of polar organic solvents to the reaction can change both the activity and the enantioselectivity for this chiral reaction significantly. It was observed, in general, that the activity increases and the enantioselectivity decreases with the increase in the polarity of the organic solvent added to the medium. Among the six solvents chosen (i.e., dimethylsulfoxide [DMSO], 1, 4-dioxane, dimethylformamide [DMF], acetone, 1-propanol, and tetrahydrofuran [THF]), maximum activity and minimum enantioselectivity was obtained with DMSO, whereas minimum activity and maximum enantioselectivity was obtained with THF as the cosolvents. In the subsequent studies, native or polyethylene glycol (PEG)-modified lipase was immobilized by entrapping in Caalginate gel beads. In a fixed-bed continuous reactor containing these catalyst beads, the enzyme was found to be at least three times more enantioselective than the native form in a batch reactor. This fixed-bed reactor with the beads could be operated with high concentration of acetone (33% v/v) for about 1 month without a significant loss of enzyme activity and enantioselectivity.

Adrenergic beta-Antagonists↗
PubMed1997

UV curable bioadhesives: copolymers of N-vinyl pyrrolidone.

A series of UV curable bioadhesives was prepared from copolymers of N-vinyl pyrrolidone with four different comonomers: 2-acrylamido methyl 1-propane sulfonic acid, vinyl succinimide, glycidyl acrylate, and 2-isocyanatoethyl methacrylate. The developed bioadhesives demonstrated a fast UV-induced setting with a set time of about 3 min. Bond strength between the bioadhesive and porcine intestine specimen was determined by the peel test. These bioadhesives can provide improved adhesion values up to 4.6 N/m of 180 degrees peel strength compared to five different commercial bioadhesives (values ranging from 0.52 to 3.04 N/m). In addition, the fully hydrated UV curable bioadhesives have shown a high water uptake ranging from 25 to 350 wt% and equilibrium water content ranging from 20 to 100 wt%. Because N-vinyl pyrrolidone is a monomer all these copolymers are expected to retain good biocompatibility. Obtained promising results of peel strength and water uptake clearly suggest that the developed bioadhesives have a strong potential for many medical applications such as single-layered hydrogel wound dressings and tissue adhesives.

Adhesives↗
PubMed1998

Investigation of dual-staged polymerization and secondary forming of photopultruded, fiber-reinforced, methacrylate-copolymer composites.

To develop a dual-curing monomer system for the photopultrusion of reformable (soft) composites, a microhardness assay showed that in a blend with 2,2-Bis[4-2-hydroxy-3-methacryloxypropoxy)phenyl] propane (Bis-GMA), the substitution of methyl methacrylate (MMA) for triethylene glycol dimethacrylate (TEGDMA) delayed the onset of gelation during photopolymerization. Adding lauroyl peroxide permitted the completion of polymerization thermally. This system was used to form silicate-glass-fiber-reinforced composites, with varying degrees of conversion, by photopultruding over a range of pulling speeds. Sol-gel extractions demonstrated both fully soluble and insoluble matrices. For the soluble material, gel permeation chromatography elucidated a trimodal distribution of molecular weights that corresponded to MMA, Bis-GMA, and polymeric molecules with molecular weights in the tens of thousands. Composites with matrix solubilities above about 10% wt could be swaged after photopultrusion to change the cross section from circular to rectangular before thermal processing. The effect on the final elastic modulus was small (-44GPa, as measured in flexure for 57% vol-reinforced composites); but the final flexure strength was reduced by approximately 25% to a constant of about 1.2 GPa. Morphological characteristics that were seen in the circular-sectioned precursors were observed in the swaged rectangular products as well, including flaws when swaging was conducted at matrix solubilities above about 75%.

Biocompatible Materials↗
PubMed1997

Ultrastructure and synthesis of the extracellular matrix of Pisaster ochraceus embryos preserved by freeze substitution.

When asteroid embryos cryoprotected with propylene glycol are rapidly frozen in liquid propane and freeze substituted with ethanol, preservation of the cells and extracellular matrix (ECM) is excellent. The basal lamina, although thicker and less well defined than in conventionally fixed embryos, demonstrates a region of decreased density just below the cells that corresponds to the lamina lucida and a lamina densa. The former region is often occupied by fibrous material. In addition, as was previously described in conventionally fixed issues, the basal lamina of the ectoderm is generally thicker and more substantial than that of the endoderm, reinforcing an earlier suggestion that the structure of the basal is different in different regions of the embryo. The ECM of the blastocoel consists of thin "twig-like" elements that form a loose meshwork evenly distributed throughout the blastocoel. Bundles of 20 nm fibers, located within the meshwork, are oriented parallel to the base of the cells of the stomodeum. In the long axis of the embryo, similar fibers are present in the dorsal aspect of the animal between the stomach and the ectoderm and radiate out from the esophagus crossing the region between it and the ectoderm. Immunocytochemical work with three different monoclonal antibodies shows that glycoprotein molecules, synthesized in the Golgi apparatus, are also secreted here and form part of the matrix structure. The results suggest that the blastocoel is filled with a gel-like material reinforced with bundles of 20-nm fibers. The manner in which the observed arrangement could contribute to the development and maintainence of the shape of the embryo is discussed.

Animals↗
PubMedDate not supplied

Direct assay of tinidazole in human serum by micellar liquid chromatography.

A liquid chromatographic procedure for the direct determination of tinidazole in human serum is presented. It includes the use of a micellar mobile phase consisting of SDS (5.10(-2) M): propan-1-ol; (94:6, v/v) and a mu Bondapak CN column with UV detection at 320 nm. No solvent extraction or deproteinization are necessary. The linearity (0.1-10 mg L), the precision (3%), the reproducibility (1.3%), the recovery (99%), and the detection limit (0.1 mg L) in the tinidazole determination are comparable and sometimes greater than the corresponding tinidazole parameters when deproteinization and conventional reversed-phase HPLC are used. One hundred injections of serum samples do not affect the column life. The procedure is applied to ascertain the pharmacokinetics of 10 mg/kg of tinidazole.

Acetonitriles↗
PubMedDate not supplied

Chemiluminescent derivatization of adenyl compounds with glyoxal derivatives in the presence of heteropoly acids and its application to the simple and sensitive determination of DNA.

A chemiluminescence (CL) determination of adenyl compounds is described. CL derivatization of adenyl compounds with methylglyoxal dimethyl acetal was performed in the presence of tungstosilicic acid and propan-2-ol. CL from adenyl compounds was produced by hydrogen peroxide and L-cysteine ethyl ester in DMF and water. The proposed method is highly sensitive and specific to compounds containing adenine. Adenine was determined in the range 1.0 x 10(-3)-5.0 x 10(-8) M with the detection limit of 3.0 x 10(-8) M (150 fmol per assay). The method was applied to the determination of DNA and detection limits of a few nanograms of DNA achieved.

Acetone↗