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Query: UMLS:C0016382 (flushing)
 6,387 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acid/base titrations of pico- and femtoliter microsamples have been performed previously using a diffusional microburet (DMB) for reagent delivery in a simple droplet-heptane system (Gratzl, M.; Yi, C. Anal. Chem. 1993, 65, 2085-2088). The lowest delivery rate achieved with a DMB was about 6 fmol/s, which would correspond to about a 1 microL/year volumetric flow rate with a hypothetical equivalent mechanical delivery scheme (Yi, C.; Gratzl, M. Anal. Chem. 1994, 66, 1976-1982). In this work, the feasibility of complexometric titrations in microscopic samples is explored. Stability of pH in the microdroplets required for different determinations and the effects of DMB shank geometry on titration characteristics are also studied. Diffusional microtitrations of Fe(III), Zn(II), and Cu(II) have been performed with EDTA. Xylenol orange and Eriochrome Black T provide clear color changes at the end point of the respective titrations, despite the microscopic size of the samples (between 16 and 1570 pL, corresponding to diameters between 30 and 144 microns). Random errors of the determinations relative to full scale were 6.6% for Fe(III), 5.8% for Cu(II), and 7.9% for Zn(II). The pH required for EDTA titrations of the individual metal ions stays stable in the acidic range. This makes the microscopic titration of a number of metal ions, such as Fe(III), Fe(II), Cu(II), and Pb(II), feasible in a simple droplet-heptane system without any modification. With a higher density of strongly alkaline buffer droplets (about 100 droplets/mm2) sprayed on the bottom of the Petri dish, or by flushing N2 above the heptane, the microscopic samples can also be kept alkaline despite ambient CO2 present. In this way, Zn(II) can also be titrated in microdroplets, requiring a pH around 10. This work renders it possible to perform a variety of complexometric titrations and other chemical manipulations in microdroplets even if they need to be kept alkaline. Similar titrations in single biological cells to assess intracellular buffer capacities of different metal ions, such as Ca(II) and Mg(II), are underway.
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PMID:Complexometric determination of metal ions by microscopic diffusional titration. 881 47

The present work examines the mechanism of testicular toxicity of acrylonitrile. In testicular centrifugal fractions from Sprague Dawley rats, the metabolism of VCN to cyanide (CN-) was highest in the microsomal fraction and required NADPH for maximum activity. This biotransformation of VCN to CN- was characterized with respect to time (30 min), microsomal protein concentration (1.5 mg ml(-1)), pH (7.5) and temperature (37 degrees C). The V(max) of the reaction was 65.1 pmol CN- mg protein(-1) min(-1) and K(m) was 88.6 micromol VCN. Flushing the microsomes with carbon monoxide (CO)(4:1, CO/O2 v/v), addition of benzimidazole (1 mM) or addition of SKF 525-A (5x10(-4) M) to incubation mixtures significantly inhibited VCN metabolism by 49%, 54% and 37.4% respectively. Activation of VCN to CN- was markedly increased in microsomes obtained from phenobarbital (PB)-treated rats (128.2%). Addition of glutathione (GSH), L-cysteine, D-penicillamine or 2-mercaptoethanol significantly enhanced the release of CN- from VCN 126%, 247%, 202% and 129% of the control value respectively. These findings indicate that VCN is metabolized in the testis via cytochrome P-450 dependent mixed function oxidase system.
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PMID:In-vitro testicular bioactivation of acrylonitrile. 917 82

The total elimination of air represents a serious hurdle in modified atmosphere packaging of bakery products, due both to the high spin-rates of the packaging lines and, particularly, to the typical texture of bakery products which retain large quantities of air inside their porous structure. Simulating the gas-flushing modified atmosphere packaging with laboratory equipment and measuring the oxygen concentration directly inside bread rolls, by means of a gas analyser connected with the internal portion, it was possible to follow the rate of atmosphere substitution, evaluating the effects of different baking treatments (7, 12 and 23 min at 230 degrees C) and the role played by different gases (nitrogen, argon, helium, nitrous oxide and carbon dioxide). The oxygen content inside the products, plotted versus time, led to typical logistic 'dose-response' curves which made it possible to forecast the time needed to reach established values of residual oxygen concentration and to emphasize the effects of the different conditions used. The gas properties particularly affected the rate of oxygen substitution and the less water-soluble was the gas, the faster was the oxygen reduction; the larger was the gas molecule, the slower was the process. Also baking time was shown to have, to a different extent, some measurable effects on the rate of oxygen substitution and hence, its optimization as well as the choice of gas mixture can contribute to improve modified atmosphere packaging of bakery products.
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PMID:Minimizing the residual oxygen in modified atmosphere packaging of bakery products. 937 39

The feasibility of intratracheal pulmonary ventilation (ITPV) was tested in five ventilated moribund neonatal and pediatric patients with uncontrollable hypercapnia: a 2-year-old child, a 52-day-old infant, and three premature infants (29, 29, and 26 weeks gestation; 1300 g, 1100 g and 890 g birth weight, respectively). ITPV was applied for 9.5, 8, 25, 58.5, and 47.5 hr, respectively. An intratracheal catheter (Cook Critical Care, Inc., Bloomington, IN) with a reversed continuous flow of gas at its tip (away from the lungs) allowed flushing of CO2 from the proximal dead space. Marked reductions in Paco2, ranging from 37% to 71% and improvement in pH were achieved within 4-6 hr of applying ITPV. During ITPV, the mean lowest Paco2 was significantly less than the pre-ITPV Paco2 (p < 0.0017), and the mean best pH was significantly higher than the pre-ITPV pH (p < 0.015). In four patients, despite significant reductions in Paco2, there was no substantial improvement in their baseline condition (shock and severe metabolic acidosis or coma) and they were switched back to conventional ventilation. This led to worsening hypercapnia to pre-ITPV values. These four patients subsequently died. It is possible that these patients were already too ill to derive significant benefit from the technique. One premature infant survived, was successfully weaned to conventional ventilation and was eventually discharged home. ITPV can alleviate uncontrollable hypercapnia in ventilated neonatal and pediatric patients.
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PMID:Intratracheal pulmonary ventilation in premature infants and children with intractable hypercapnia. 946 6

For the operation of manned spacecraft, the removal of CO2 from the cabin atmosphere, produced by its inhabitants, is essential. This is accomplished by chemical absorption in a gas processing unit, a process which requires energy and consumables. Therefore, in terms of resource management, the CO2-level should be kept as high as possible. Otherwise, considering crew health and performance and also the interference with life science experiments, the CO2 load should be as on Earth, close to zero. In order to obtain more information about the permissible CO2 level for future space missions and also to clarify Space Station design criteria, NASA-ESA-DARA have initiated a ground-based simulation study with two different CO2 levels: 0.7% (first campaign) and 1.2% CO2 (second campaign). For this study the deep diving facility of DLR was used to provide atmospheric control and long-term habitation for the test subjects in studying the effect of increased CO2 on physiological and psychological functions. A number of experiments were implemented, which tested selected effects of raised CO2 on humans. Four male subjects stayed in the chamber for 26 d in each campaign, in order to perform the different tests in repeated trials, with the aim of evaluating possible long-term effects. CO2 was controlled by absorption with soda lime, flushing with fresh air and the addition of CO2, if necessary. Essentially, the CO2 produced by the subjects was used to maintain the level at 0.7 and 1.2%, respectively. Basic control of CO2 was carried out in the soda lime container of the Life Support System. In order to maintain the required level, the amount of gas flowing through the soda lime could be adjusted by a remote controlled bypass. With this set-up it was possible to keep CO2 at an average level between 0.67 and 0.73% in the first campaign and between 1.17 and 1.23% in the second campaign. The results of the experiments support the current CO2 limits for space operations, insofar as values around 1% do not impose any severe restrictions to human habitation for at least several weeks, whereas life sciences experiments especially sensitive to CO2 influences have to be carefully evaluated for possible interferences.
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PMID:The influence of CO2 in a space-like environment: study design. 954 66

Procaine has been used to stimulate plant growth and it has been noted that it also promotes growth of microorganisms. The effect of procaine hydrochloride concentration on the growth rates of several species of microalgae and cyanobacteria was studied under both photoautotropic and heterotrophic growth conditions. Procaine hydrochloride was added to cultures at concentrations over the range 0.01-1000 mg L(-1). A stimulating effect of procaine hydrochloride on photoautotrophic growth was observed for the cyanobacteria Anabaena cylindrica and Anabaena variabilis, and for the salt-tolerant green algae Dunaliella primolecta and Dunaliella parva. During active growth in batch culture an increase in growth rate (compared with control culture without procaine hydrochloride) of about 25% was observed at 0.1 mgL(-1) of procaine hydrochloride for A. cylindrica. However, procaine hydrochloride was toxic at concentrations of > 10 mgL(-1). Simultaneous administration of hydrolysis products of procaine, p-aminobenzoic acid and diethyl aminoethanol, in lieu of procaine hydrochloride, was as effective as procaine in stimulating growth of A. cylindrica. Heterotrophic growth of Chlorella ellipsoidea and Prototheca zopfii was not stimulated by procaine hydrochloride over the concentration range studied (0.1-10 mg L(-1)). The combined effects of procaine hydrochloride concentration and four other environmental factors (temperature, light intensity, CO2 concentration in the flushing gas and NaCl concentration) on growth rate of D. primolecta was modelled using both a neural network approach and a response surface method. These results indicate that procaine hydrochloride exerts different effects on the growth of microalgal and cyanobacterial cells as functions of dosage, species and culture conditions.
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PMID:Stimulatory effect of procaine on the growth of several microalgae and cyanobacteria. 1071 57

Fresh cod fillets (Gadus morhua) were sprayed with a 10% acetate buffer (pH 5.6), packed with an industrial gas-flushing packaging machine under modified atmospheres (50% CO2--45% O2--5% N2, 2 cm3/1 g gas/product ratio) and stored at 7 degrees C for 12 days. Control cod fillets were directly packed and stored under the same conditions. A reduction of the aerobic plate counts was observed immediately after the cod fillets had been sprayed. During storage under modified atmospheres, there was complete inhibition of H2S-producing bacteria and Enterobacteriaceae in the treated cod fillets. Production of total volatile bases and trimethylamine (TMA) was inhibited in treated fillets for 10 days' storage under modified atmospheres. Inhibition of TMA production can be attributed to growth inhibition of H2S-producing bacteria, inhibition of the trimethylamine oxide (TMAO)-dependent metabolism of TMAO-reducing bacteria and the stable pH during storage. The shelf-life, at 7 degrees C, of treated cod fillets, based on cooked flavour score, was almost 12 days, ca 8 days more than shelf-life of the control fillets.
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PMID:Shelf-life extension of cod fillets with an acetate buffer spray prior to packaging under modified atmospheres. 1079 51

Sampling is the first and most important step in the bacterial analysis of periodontal or endodontal infections. Sterile paperpoints are the ultimate tool to perform the sampling. Sampling is preferably done under continuous CO2-flushing, to preserve an anaerobic environment for the bacteria. For the dilution and the transport of the bacteria, Reduced Transport Fluid (RTF) is the most reliable fluid, when culturing is indicated. In all other cases, sterile physiologic water is sufficient.
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PMID:[The sampling of plaque specimens in oral microbiology]. 1089 7

The need for aeration of microcosms during mineralization of 14C-labeled compounds in high oxygen demand environments was assessed using active compost-soil mixtures as the model system. Rapid mineralization of 14C-hexadecane occurred in continuously aerated microcosms while no mineralization occurred in unaerated microcosms. Daily flushing with air also yielded no mineralization. Mineralization of 14C-glucose was much less dependent on aeration. The alkaline solution volume and number of CO2 traps required for continuous aeration were calculated and tested experimentally.
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PMID:The design and use of aerated microcosms in mineralization studies. 1106 30

Tracheal gas insufflation (TGI) is an adjunct to mechanical ventilation that allows ventilation with small tidal volumes while carbon dioxide (CO2) is satisfactorily cleared. Pioneering studies in healthy animals and in humans suffering respiratory failure showed that the expiratory flushing of proximal dead space decreased minute ventilation with no change in arterial partial pressure of carbon dioxide (PaCO2). Recent work indicates that conventional mechanical ventilation aided by TGI may represent a novel ventilatory strategy that succeeds in limiting both the distending forces acting on the lungs and the PaCO2 elevation of permissive hypercapnia. Furthermore, some studies suggest that weaning aided by TGI may allow a reduction in minute ventilation, PaCO2, physiologic dead space, and the patient's respiratory demands. Clinical use of TGI requires careful monitoring of delivered volumes and pressures to ensure safe clinical application and to evaluate the effect on lung function. Finally, routine use of TGI in intensive care warrants further investigation to solve some technical problems and randomized clinical trials to confirm the beneficial effects in the absence of complications.
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PMID:Clinical studies of tracheal gas insufflation. 1117 44


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