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PubMed1982

Microbial Oxidation of Hydrocarbons: Properties of a Soluble Methane Monooxygenase from a Facultative Methane-Utilizing Organism, Methylobacterium sp. Strain CRL-26.

Methylobacterium sp. strain CRL-26 grown in a fermentor contained methane monooxygenase activity in soluble fractions. Soluble methane monooxygenase catalyzed the epoxidation/hydroxylation of a variety of hydrocarbons, including terminal alkenes, internal alkenes, substituted alkenes, branched-chain alkenes, alkanes (C(1) to C(8)), substituted alkanes, branched-chain alkanes, carbon monoxide, ethers, and cyclic and aromatic compounds. The optimum pH and temperature for the epoxidation of propylene by soluble methane monooxygenase were found to be 7.0 and 40 degrees C, respectively. Among various compounds tested, only NADH(2) or NADPH(2) could act as an electron donor. Formate and NAD (in the presence of formate dehydrogenase contained in the soluble fraction) or 2-butanol in the presence of NAD and secondary alcohol dehydrogenase generated the NADH(2) required for the methane monooxygenase. Epoxidation of propylene catalyzed by methane monooxygenase was not inhibited by a range of potential inhibitors, including metal-chelating compounds and potassium cyanide. Sulfhydryl agents and acriflavin inhibited monooxygenase activity. Soluble methane monooxygenase was resolved into three components by ion-exchange chromatography. All three compounds are required for the epoxidation and hydroxylation reactions.

Journal Article↗
PubMed2005

Temperatures in soda lime during degradation of desflurane, isoflurane, and sevoflurane by desiccated soda lime.

Rarely, fire and patient injury result from the degradation of sevoflurane by desiccated Baralyme. The present investigation sought to determine whether high temperatures also arose with sevoflurane use in the presence of desiccated soda lime. We desiccated soda lime by directing a 10 L/min flow of oxygen through fresh absorbent. Using 1140 +/- 30 g (mean +/- sd) of this desiccated absorbent, we filled a single standard absorber canister placed in a standard anesthetic circuit to which we directed a 6 L/min flow of oxygen containing 1.5 minimum alveolar concentration (MAC) desflurane or sevoflurane, or 3.0 MAC desflurane, isoflurane, or sevoflurane (with and without concurrent delivery of 200 mL/min carbon dioxide). In an additional test, 2 canisters (rather than a single canister) containing desiccated absorbent were used and 3.0 MAC sevoflurane was applied. A 3-L reservoir bag served as a surrogate lung, and we ventilated this lung with a minute ventilation of 10 L/min. With desflurane at 1.5 MAC or 3.0 MAC or isoflurane at 3.0 MAC temperatures increased in 20 to 40 min to a peak of 30 degrees C to 45 degrees C and then declined. With 1.5 or 3.0 MAC sevoflurane, temperatures increased to approximately 90 degrees C, after which temperatures declined. Concurrent delivery of carbon dioxide and sevoflurane did not increase the peak temperatures reached. The use of 2 canisters increased the duration but not the peak of increased temperature reached with 3.0 MAC sevoflurane. No fires resulted from degradation of any anesthetic.

Anesthetics, Inhalation↗
PubMed1994

Effect of leucite crystals on the strength of glassy porcelain.

Porcelains with leucite crystals dispersed into various glass matrices were prepared for investigating the effects of the leucite crystals on the mechanical strength of glassy porcelain. The strength of glassy porcelains containing leucite crystals was affected by the differences of thermal expansion coefficients, compositions and deformation temperatures of the glass matrices. In the case of a large mismatch of thermal expansion between the leucite crystals and boro-silicate glass, the strength decreased with increasing amount of leucite. In leucite porcelains using a feldspar glass matrix, there was little or no effect of leucite on the strength. However, the strength of porcelains consisting of leucite crystals and a soda-lime glass matrix was enhanced with increasing leucite content, compared with that of the glassy matrix alone. Such an increase in strength is considered to be because the interface between the glassy matrix and leucite particles occurred in continuous phases, with an effect due to fusion occurring during the transition from leucite particles to the glass phase.

Aluminum Silicates↗
PubMed1998

Degradation of hemicellulosic and cellulosic polysaccharides in pickled green olives.

Changes that take place in the hemicellulosic and cellulosic polysaccharide fractions of the cell wall of olives (Olea europaea pomiformis, Manzanilla variety) during "Spanish style" processing have been studied. A comparative study of the extraction of hemicellulosic polysaccharides with and without prior delignification showed that these compounds could be extracted without previous delignification of the cell wall material. The depectinated material was sequentially extracted with 1 M and 4 M potassium hydroxide. In the unprocessed fruit, the neutral polysaccharides of the 1 M potassium hydroxide-soluble fraction contained mainly xyloglucans with significant amounts of arabinans. In the 4 M potassium hydroxide-soluble fraction, xyloglucans were the most important polysaccharide. The apparent molecular weight of these polysaccharides was 40 to 250 kDa. In addition, hemicelluloses (xylans and xyloglucans), which it was not possible to isolate in the previous stages of fractionation, were also found to be closely linked to the cellulose fraction. The most important changes during processing were the decrease in the molecular weight of xyloglucans in the 4 M potassium hydroxide-soluble fraction and the substantial decrease in the cellulose fraction, which in quantitative terms was one of the largest decreases that took place in the components of the total cell wall polysaccharides.

Cellulose↗
PubMed1997

[Potassium as an indicator of anthropogenic contamination of swimming pool water].

Swimming pool water is processed, filtered and disinfected repeatedly in order to maintain hygienic conditions. Additionally, fresh water is added. However, it cannot be avoided, that the concentrations of certain components of swimming pool water will increase in the course of time. DIN 19,643 regulates that fresh water supply can be measured by nitrate concentration. Nitrate is mainly formed by oxidation of nitrogen containing organic compounds. Oxidation reactions are complex and the amount of nitrate formed by this process depends on specific factors which may vary in swimming pools with different technical equipment. Therefore nitrate is only of limited reliability to estimate fresh water addition in public swimming pools. Main sources for nitrogen containing compounds in pool water are sweat and urine which contain inorganic compounds like potassium. Potassium is a direct indicator of contamination. Its concentration is not influenced by chemical reactions because it is an inert compound. The urine release into the water of indoor pools was estimated by this parameter to be 77.5 ml/person, in outdoor pools about 60 ml. Potassium concentration in swimming pools will reach an equilibrium concentration, depending on the size of the pool, the number of bathers and the amount of fresh water added. This equilibrium concentration is mathematically calculated in a general approach. In none of 36 swimming pools where potassium concentration was measured, this calculated value was exceeded. The results indicate that the potassium concentration is a new valuable parameter to assess the quality of swimming pool water under hygienic aspects.

Fresh Water↗
PubMed1980

Membrane potentials in cell-free preparations from guinea pig cerebral cortex: effect of depolarizing agents and cyclic nucleotides.

The distribution of [3H]triphenylmethylphosphonium ion between the medium and vesicular entities was examined in a cell-free, particulate preparation from guinea pig cerebral cortex. This distribution followed the Nernst relationship with regard to the external potassium ion concentration and, in physiological media, indicated the maintenance of a mean trans-membrane potential ranging from -58 to -78 mV. The neurotoxins batrachotoxin, veratridine, and grayanotoxin I, partially depolarized the preparation. Tetrodotoxin blocked the depolarization by batrachotoxin, veratridine, and gray-anotoxin I. The depolarization by these neurotoxins was potentiated by the presence of anemone toxin II and presumably reflected the response of vesicular components of neuronal origin. An additional potassium-sensitive depolarization probably represented the response of vesicular components of glial origin with an apparent transmembrane potential of -8 to -35 mV. No correlation could be demonstrated between changes in transmembrane potential and stimulation of cyclic AMP generation by a variety of agents in this preparation.

Animals↗
PubMed1989

A quantitative assessment of the use of 36Cl- distribution to measure plasma membrane potential in isolated hepatocytes.

The plasma membrane potential of isolated rat hepatocytes was clamped at different values between 0 and -68 mV by addition of valinomycin in the presence of different extracellular concentrations of K+, and measured by the distribution of 86Rb+ between cells and medium. 36Cl- distribution came to steady state in 10-15 min. This steady-state distribution was compared to the plasma membrane potential over a range of values. 36Cl- distribution provided an accurate measurement of plasma membrane potential between -4 and -40 mV. At higher potentials intracellular chloride concentration is less than 20% of the extracellular concentration and errors due to uncertainties in the measurement of intracellular volume and of the contamination of cell pellets by extracellular medium precluded accurate determination of membrane potential: thus in our experiments 36Cl- underestimated the plasma membrane potential at -68 mV by 8 mV.

Adenosine Triphosphate↗
PubMed1996

Factors affecting production of compound A from the interaction of sevoflurane with Baralyme and soda lime.

Various alkali (e.g., soda lime) convert sevoflurane to CF2=C(CF3)OCH2F, a vinyl ether called "Compound A, " whose toxicity raises concerns regarding the safe administration of sevoflurane via rebreathing circuits. In the present investigation, we measured the sevoflurane degradation and output of Compound A caused by standard (13% water) Baralyme brand absorbent and standard (15% water) soda lime, and Baralyme and soda lime having various water contents (including no water). We used a flow-through system, applying a gas flow rate relative to absorbent volume that roughly equaled the rate/volume found in clinical practice. Both absorbents, at similar water contents, temperatures, and sevoflurane concentrations, produced roughly equal concentrations of Compound A. Dry and nearly dry absorbents produced less Compound A early in exposure to sevoflurane, and more later, than standard absorbents. Increases in temperature and sevoflurane concentration increased output of Compound A. Both absorbents, especially when dry, also destroyed Compound A, the concentration exiting from absorbent resulting from a complex sum of production and destruction. We conclude that the variability of concentrations of Compound A found in clinical practice may be largely explained by the inflow rate used (i.e., by rebreathing), sevoflurane concentration, and absorbent temperature and dryness. The effect of dryness is complex, with fresh dry absorbent destroying Compound A as it is made, and with dry absorbent that has been exposed to sevoflurane for a period of time providing a sometimes unusually high output of Compound A.

Absorption↗
PubMed1991

Absorption and degradation of sevoflurane and isoflurane in a conventional anesthetic circuit.

Soda lime and Baralyme degrade sevoflurane, the rate of degradation being a direct function of temperature. We tested whether this degradation would impede the development of an anesthetizing concentration of sevoflurane (compared with isoflurane, a compound that is not degraded) in a circle-absorption system having an increased temperature consequent to (a) carbon dioxide production (200 mL/min) and absorption; and (b) a low inflow rate (70 mL/min). We also measured the temperatures reached in various parts of the absorption system when used in clinical practice, finding that peak temperatures usually reached 37 degrees - 46 degrees C when low inflow rates (500 mL/min) were applied. The tests in the model system demonstrated that soda lime and Baralyme absorbed both sevoflurane and isoflurane, and that both absorbants degraded sevoflurane but not isoflurane. Baralyme produced a fourfold greater degradation of sevoflurane vapor than did soda lime (0.66 mL/min compared with 0.17 mL/min). However, except for a slight delay at the start of anesthesia, neither absorption nor degradation should noticeably affect the requirement for anesthetic delivery in clinical practice, even in low-flow systems.

Absorption↗
PubMed2004

Quality evaluation of sugar beet (Beta vulgaris) by near-infrared spectroscopy.

The legal method (polarimetric measurement) for the determination of sucrose content and the wet chemical analysis for the quality control of sugar beet uses lead acetate. Because heavy metals are pollutants, the law could forbid their use in the future. Therefore, near-infrared spectroscopy (NIRS) was evaluated as a procedure to replace these methods. However, there are alternatives to lead clarification, such as the use of aluminum salts, which have been applied at many sugar companies. The real advantage of NIRS is in speed and ease of analysis. The aim of this study was to determine simultaneously the concentration of several components which define the industrial quality of beets. The first objective was the determination of sucrose content, which determines the sugar beet price. The standard error of prediction (SEP) was low: 0.11 g of sucrose/100 g of fresh beet. NIRS was also able to determine other beet quality parameters: brix, marc, glucose, nitrogen, sodium, potassium, sugar in molasses (i.e. sucrose in molasses), and juice purity. The results concerning brix, marc, sugar in molasses, and juice purity were satisfactory. NIRS accuracy was lower for the other parameters. Nevertheless, RPD (ratio standard deviation of concentration/SEP) and RER (ratio concentration range/SEP ratio) show that NIRS might be used for the sample screening on nitrogen, potassium, sodium, and glucose content.

Beta vulgaris↗
PubMed2001

Clinical dentin hypersensitivity: understanding the causes and prescribing a treatment.

Dentin hypersensitivity is a common condition of transient tooth pain associated with a variety of exogenous stimuli. There is substantial variation in the response to such stimuli from one person to another. Except for sensitivity associated with tooth bleaching or other tooth pathology, the clinical cause of dentin hypersensitivity is exposed dentinal tubules as a result of gingival recession and subsequent loss of cementum on root surfaces. The most widely accepted theory of how the pain occurs is Brännström's hydrodynamic theory of dentin hypersensitivity. Dentinal hypersensitivity must be differentiated from other conditions that may cause sensitive teeth prior to treatment. Three principal treatment strategies are used. Dentinal tubules can be covered by gingival grafts or dental restorations. The tubules can be plugged using compounds that can precipitate together into a large enough mass to occlude the tubules. The third strategy is to desensitize the nerve tissue within the tubules using potassium nitrate. Several over-the-counter products are available to patients to treat this condition.

Dental Cementum↗
PubMed1988

Membrane potential in liposomes measured by the transmembrane distribution of 86Rb+, tetraphenylphosphonium or triphenylmethylphosphonium: effect of cholesterol in the lipid bilayer.

Valinomycin-induced potassium diffusion potential (delta psi, inside negative) in the liposomes made of phosphatidylcholine and various amounts of cholesterol was measured by uptake of 86Rb+, tetraphenylphosphonium (TPP+) or triphenylmethylphosphonium (TPMP+). In any liposome, the values of membrane potential obtained by 86Rb+ uptake (delta psi Rb) agreed well with those calculated from the imposed potassium concentration gradient using the Nernst equation, and were not affected by the presence of cholesterol. However, both delta psi TPP and delta psi TPMP showed smaller values than delta psi Rb when the cholesterol content in liposomes increased. delta psi TPMP at a stationary state was much smaller than delta psi TPP. The orientational order parameter of the lipids' bilayer with various cholesterol content was estimated from fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. The results indicated that the permeation of TPP+ or TPMP+ into liposomes containing a large amount of cholesterol is strongly restricted by the high ordering of phosphatidylcholine acyl chains.

Algorithms↗