Carbon Dioxide-enriched Atmosphere Research Articles

Generation of long-chain fatty acids by hydrogen-driven bicarbonate reduction in ancient alkaline hydrothermal vents

The origin of life required membrane-bound compartments to allow the separation and concentration of internal biochemistry from the external environment and establish energy-harnessing ion gradients. Long-chain amphiphilic molecules, such as fatty acids, appear strong candidates to have formed the first cell membranes although how they were first generated remains unclear. Here we show that the reaction of dissolved hydrogen and bicarbonate with the iron-rich mineral magnetite under conditions of continuous flow, alkaline pH and relatively low temperatures (90 °C) generate a range of functionalised long-chain aliphatic compounds, including mixed fatty acids up to 18 carbon atoms in length. Readily generated membrane-forming amphiphilic organic molecules in the first cellular life may have been driven by similar chemistry generated from the mixing of bicarbonate-rich water (equilibrated with a carbon dioxide-enriched atmosphere) with alkaline hydrogen-rich fluids fed by the serpentinisation of the Earth’s iron-rich early crust.

Pharmacokinetics of tildipirosin in porcine plasma, lung tissue, and bronchial fluid and effects of test conditions on in vitro activity against reference strains and field isolates of Actinobacillus pleuropneumoniae

The pharmacokinetics of tildipirosin (Zuprevo(®) 40 mg/mL solution for injection for pigs), a novel 16-membered-ring macrolide for the treatment for swine respiratory disease (SRD), was investigated in studies collecting blood plasma and postmortem samples of lung tissue and bronchial fluid (BF) from swine. In view of factors influencing the in vitro activity of macrolides, and for the interpretation of tildipirosin pharmacokinetics in relation to minimum inhibitory concentrations (MIC), additional experiments were conducted to study the effects of pH, carbon dioxide-enriched atmosphere, buffers, and serum on tildipirosin MICs for various reference strains and Actinobacillus (A.) pleuropneumoniae field isolates. After single intramuscular (i.m.) injection at 4 mg/kg body weight, maximum plasma concentration (Cmax) was 0.9 μg/mL observed within 23 min (Tmax ). Mean residence time from the time of dosing to the time of last measurable concentration (MRTlast) and terminal half-life (T1/2) both were about 4 days. A dose-response relationship with no significant sex effect is observed for area under the plasma concentration-time curve from time 0 to the last sampling time with a quantifiable drug concentration (AUClast) over the range of doses up to 6 mg/kg. However, linear dose proportionality could not be proven with statistical methods. The time-concentration profile of tildipirosin in BF and lung far exceeded that in blood plasma. In lung, tildipirosin concentrations reached 3.1 μg/g at 2 h, peaked at 4.3 μg/g at day 1, and slowly declined to 0.8 μg/g at day 17. In BF, tildipirosin levels were 14.3, 7.0, and 6.5 μg/g at days 5, 10, and 14. T1/2 in lung was ∼7 days. Tildipirosin is rapidly and extensively distributed to the respiratory tract followed by slow elimination. Culture media pH and carbon dioxide-enriched atmosphere (CO2 -EA) had a marked impact on in vitro activity of tildipirosin in reference strains of various rapidly growing aerobic and fastidious bacteria including Histophilus (H.) somni ATCC 700025 and A. pleuropneumoniae ATCC 27090. For A. pleuropneumoniae ATCC 27090 testing conditions without CO2 -EA resulted in reduced acidification of culture media pH and a reduction in the minimum inhibitory concentrations compared to standard in vitro test conditions by 2 log2 dilution steps (4-fold) from 8 to 2 μg/mL. Supplementary buffering of standard culture media resulted in a reduction in the A. pleuropneumoniae (n = 8) MIC range by 4 log2 dilution steps (16-fold) from 8-16 to 0.5-1 μg/mL. Incremental supplementation of culture media with 50% serum resulted in noticeable shifts to lower minimum or maximum MICs by at least 2 log2 dilution steps (≥4-fold) in all aerobic and fastidious reference strains tested except for Pasteurella (P.) multocida. The MIC of A. pleuropneumoniae ATCC 27090 decreased by 2-4 log2 dilution steps (4 to 16-fold) from 8 to 0.5-2 μg/mL when 50% serum was added to the standard assay. Considering a higher presence of serum and the rather neutral pH conditions maintained in vivo, it is suggested to take the influence of these factors on in vitro activity into account when interpreting tildipirosin MICs for A. pleuropneumoniae in relation to pharmacokinetics.

Effect of Carbon Dioxide-Enriched Atmosphere during Cold Storage on Limiting Antioxidant Losses and Maintaining Quality of ‘Barhy’ Date Fruits

Mature ‘Barhy’ date fruits (Phoenix dactylifera L.) were stored under different storage temperatures (0, 2, 4, 6°C) under modified atmosphere (MA) conditions with 0.03, 5, 10, or 20% carbon dioxide concentrations (balance air). Fruit total phenolic content (TPC), flavonoids content, carotenoids content, total sugar %, SSC %, and fruit skin color (L*a*b*c* and h*) were determined. Total phenolic content (TPC) was determined by the Folin-Ciocalteu method, and antioxidant capacity was determined using ferric reducing antioxidant power (FRAP). A clear integration was observed between modified atmosphere and cold storage treatments regarding maintaining fruit quality during the storage period. Fruits stored under low temperature conditions (0°C) or relatively high CO2 concentration (20% CO2) did not show any chilling or CO2 injury symptoms. Fruits kept under MA conditions with 20% CO2 at cold storage (0°C) showed brightest yellow color, and highest storage ability among all stored fruits. All MA conditions investigated extended date storability by maintaining fruit quality. The effect of MA conditions on maintaining fruit quality was magnified when fruits were stored under cold temperature. Fruit quality was maintained for 173 days when stored in 20% CO2 at 0°C, whereas it did not exceed 60 days when stored under common air composition (containing 0.03% CO2) at 0°C. Treatments with high CO2 concentrations (20% CO2) under cold storage conditions (0°C) maintained fruit total phenolic content, SSC%, total sugar content, and total tannins.

The Behaviour of Paper Treated in a Carbon Dioxide Modified Atmosphere

The treatment of museum exhibits, including books and archival documents, in an atmoshpere containing a high concentration of carbon dioxide is one of the techniques using a modified atmosphere for the fumigation of objects. The efficiency of this method for pest infestation is confirmed by its commercial application. Some companies (for example, RENTOKIL) have developed stationary and portable extermination equipment. The concentration of the carbon dioxide in a gas mixture is between 58-75 per cent, the temperature during the disinfecting procedure is kept within 19-30 degrees C, and the relative humidity is kept to 70 per cent. The efficiency of this prodecure as an effective technique against microorgnisms has not been studied fully. There is evidence of both positive and negative results. Specific data on the influence of a carbon dioxide enriched atmosphere on the physical and chemical properties is limited. In theory this treatment could be dangerous for paper because of the formation of carbonic acid from carbon dioxide and water. In order to decrease the possible destructive influence of this treatment used on textile museum objects, humidity in a chamber has been kept at no more than 50 per cent. According to the data of the German conservator Binker the fumigation of a wooden altarpiece in an atmosphere of carbon dioxide did not have any adverse affect on the material or colouring of the wooden sculpture. The purpose of our research was to investigate the influence of a modified, carbon dioxide-enriched atmosphere on the properties of paper.

Microbial flora of root canal–treated teeth associated with asymptomatic periapical radiolucent lesions

This study aimed to investigate the composition of microflora in endodontically treated teeth associated with asymptomatic periapical lesions in southern Chinese patients. Twenty-four teeth which had received nonsurgical root canal treatment more than 4 years previously, and which presents an acceptable coronal restoration with a periapical radiolucent area, were re-treated nonsurgically. Bacteriological samples were obtained after removal of the old root canal filling. The samples were inoculated on enriched trypticase soy agar and four selective media for incubation at 37 degrees C in both a carbon dioxide-enriched atmosphere and anaerobically. Eighteen teeth that had received gutta-percha root canal fillings were grouped for analysis, 12 (66.7%) of which contained cultivable microorganisms. The total colony forming units per ml of transport medium ranged from 0 to 2.3 x 10(5). The number of bacterial genera recovered ranged between 0 and 6, with facultative gram-positive cocci being the most prevalent group of bacteria isolated. Facultative anaerobic bacteria were present in all, whereas strict anaerobic bacteria were found in 3 out of the 12 teeth with positive growth. The size of the periapical rarefaction did not show any relationship with the quantity of microorganisms recovered. Coagulase-negative staphylococci, streptococci and Pseudomonas aeruginosa were most frequently isolated in this group of patients. The possible origin of these organisms is discussed.

Effect of carbon dioxide on testing of susceptibilities of respiratory tract pathogens to macrolide and azalide antimicrobial agents.

The in vitro activities of erythromycin, azithromycin, and clarithromycin against 178 clinical isolates from the lower respiratory tract of patients with chronic obstructive pulmonary disease were determined by an agar dilution method. The plates were incubated in air alone or in 5% carbon dioxide. The MICs measured in air alone were lower for most isolates than those measured in 5% carbon dioxide, illustrating the "pH effect" of incubation in carbon dioxide. Testing of isolates in 5% carbon dioxide on pH-adjusted medium (pH 8.4) resulted in MICs of one or two doubling dilutions lower than those obtained on agar with a neutral pH. A bioassay of the three agents incubated in air and in 5% carbon dioxide resulted in a significant loss of activity of all three agents in the carbon dioxide-enriched atmosphere. However, this loss-of-activity effect was significantly reduced when the bioassay medium was adjusted to pH 8.4 prior to incubation in 5% carbon dioxide.

高濃度炭酸ガスがモモおよびトマト果実のエチレン生合成に及ぼす影響

Ethylene production, oxygen uptake, the activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase in vivo and the contents of ACC and 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC) were determined in peach and tomato fruits held in carbon dioxide-enriched atmosphere. Ethylene production in peaches decreased to a trace level with 60% carbon dioxide and in tomatoes to 50% of the initial level. The ethylene production rates in both fruits reverted to the initial level when the fruits were transferred back to air. Oxygen uptake in both fruits was markedly inhibited during carbon dioxide exposure. In vivo activities of ACC oxidase and ACC synthase in both fruits were also inhibited during carbon dioxide exposure. ACC content in peaches held in carbon dioxide-enriched atmosphere decreased but it increased in tomatoes. The level of MACC in peaches was constant during carbon dioxide treatment, whereas that in tomatoes slightly increased. These results indicate that inhibition in ethylene production by carbon dioxide may be mediated mainly by reduced conversion of ACC to ethylene in tomatoes, whereas in peaches, the inhibition is attributed to both reduced conversion of S-adenosylmethionine to ACC and ACC to ethylene.

Growth of Listeria monocytogenes in meat juice under a modified atmosphere at 4°C with or without members of a microbial association from chilled lamb under a modified atmosphere

Listeria monocytogenes together with Gram-positive and Gram-negative bacteria was grown in axenic cultures in meat juice under an atmosphere enriched with carbon dioxide at 4 o C. The size of the final population of listeriae was determined by that of the initial inoculum. Growth of L. monocytogenes ceased with glucose depletion. Glucose-6-phosphate was not catabolized by listeriae. In aerobic axenic cultures generation times of L. monocytogenes were shorter and glucose depletion was faster than with a carbon dioxide-enriched atmosphere. Oxidation of L- and D-lactic to acetic acid was probably associated with the subsequent die-off of L. monocytogenes

CHANGES IN SUGAR CONTENT IN CUT ONION DURING STORAGE

Our purpose was to study the impact of controlled atmosphere (CA) on respiration of and changes in sugar content of diced onions. The onions were peeled, diced, washed, disinfected, and centrifuged before storage for 12 days under gas mixtures of 21% O2 and 0% CO2 (air), 2% O2 and 0% CO2, and 2% O2 and 10% CO2. Every 4 days, respiration rate and sugar content (total, sucrose, fructose, and glucose) were determined. Carbon dioxide-enriched atmosphere limited respiration rate and sucrose depletion, whereas the mere reduction of O2 had no effect. Reducing sugar contents remained constant during storage regardless of the treatment.

Laboratory selection of resistance by the Red Flour Beetle,Tribolium castaneum (Herbst), To a carbon dioxide-enriched atmosphere

Adult populations of the red flour beetle,Tribolium castaneum (Herbst), were exposed for 40 generations to an atmosphere containing 65% CO2, 20% O2 and 15% N2 at 95% RH, in order to select a strain resistant to a high carbon dioxide content (HCC) atmosphere. Selection pressure was maintained at between 50% and 70% mortality. At the 40th generation, comparison of sensitivity between the selected strain and the original non-selected strain indicated a resistance factor at the 50% mortality level (LT50) of x 9.2. Throughout the selection process, log-time against probit-mortality lines remained roughly parallel and the slope remained low and similar to that of the non-selected strain until the last generation. Implications are that at a high level of selection, multiple genetic factors continued to act together even at the 40th generation to select for adaptation to survival at high CO2 concentrations. Removal of selection pressure from a sub-population of the selected strain from the 13th to 21st generation revealed that resistance was partially retained with a decrease of 17% in the resistance factor. The modified atmosphere chosen in this study does not represent real-life situations where O2 concentrations are reduced by flushing with CO2, and intergranular relative humidities are generally not above 70%.

Influence of carbon dioxide on growth and antibiotic susceptibility of coagulase-negative staphylococci cultured in human peritoneal dialysate

Used peritoneal dialysis fluid was collected from patients undergoing continuous ambulatory peritoneal dialysis, and its pH and composition were assessed after incubation in either air or air with 5% CO2. Precipitation of calcium, magnesium, phosphate, and proteins occurred in the dialysis fluid incubated in air at 37 degrees C and was associated with a mean pH increase of 1.23 U. Incubation of dialysis fluid in air with 5% CO2 prevented precipitation and maintained pCO2 and pH levels at those found physiologically. Coagulase-negative staphylococcal strains isolated from patients with peritonitis tended to grow less well in dialysis fluid incubated in air than in dialysis fluid incubated in the carbon dioxide-enriched atmosphere. MICs of cefuroxime, ciprofloxacin, and vancomycin for seven strains of coagulase-negative staphylococci in dialysis fluid were markedly affected by atmosphere type (16 of 21 MICs). Of these 16 atmosphere-dependent MICs, 14 were at least fourfold higher in air than in air with 5% CO2.

Increases in the Diffusion Resistances of Leaves in a Carbon Dioxide-Enriched Atmosphere

The stomatal closing reaction to C02, which has been observed in laboratory studies by many workers, was investigated in plant-growth cabinets under conditions similar to those in glass houses with C02-enriched atmospheres. Lettuce and Xanthium plants grown in a normal atmosphere showed the expected stomatal closure in response to increasing 0O2 concentrations, and lettuce plants grown in 1000 ppm C02 showed the same response, even after 4 weeks. Thus there was no evidence of acclimatization of the stomata and it is concluded that they must remain partially closed during C02-enrichment. Estimates of diffusion resistances to COa intake in lettuce leaves showed that in light of 14-4 J m-2 s_1, 880 ppm C02 in the atmosphere resulted in a concentration of 367 ppm near the mesophyll cell walls. If the stomata remained open this same internal concentration could be achieved with an external concentration of only 640 ppm. There could, therefore, be some economic advantage if stomatal closure were prevented during C02-enrichment.

EFFECTS OF GIBBERELLIC ACID ON GROWTH OF ANTIRRHINUM MAJUS ’UTAH WHITE’ IN A CARBON DIOXIDE-ENRICHED ENVIRONMENT

Snapdragon seedlings (Antirrhinum majus ’Utah White’) were benched in two adjoining greenhouse compartments. A randomized-block design including three concentrations of gibberellic acid (GA3) and a distilled water control was employed in each compartment. Treatments were replicated three times. Treatment of snapdragon seedlings with GA3 significantly increased the length of inflorescences, the overall height of the plants at maturity and the fresh weight of the tops when the plants were grown in a carbon dioxide-enriched atmosphere. Treatment hindered root development and reduced chlorophyll content of leaves in relation to dry weight. Plants grown in an atmosphere containing 0.09% CO2 had longer inflorescences, were taller, had greater fresh weight and more chlorophyll at each level of treatment with GA3 than such plants grown in an atmosphere containing 0.03% CO2. However, these comparisons were considered significant only for total height (control) and fresh weight of tops (0, 10 and 50 μg/ml GA3). Whereas GA3 at 10 μg/ml reduced length of roots proportionally in both levels of CO2, higher concentrations of GA3 continued to give significant reduction only under the higher level of CO2.