呼吸末二氧化碳监测在临床中的应用

呼吸末二氧化碳监测是评估患者通气状态的重要指标,也是确保病人安全的重要参数之一。呼吸末二氧化碳分压与动脉血二氧化碳分压之间存在良好的相关关系,可以通过持续监测其动态观察动脉血二氧化碳分压,近年来呼吸末二氧化碳监测已经成为了临床工作中一项常规监测技术手段。在临床的实际工作中呼吸末二氧化碳监测不仅能够确定气管插管的位置,评估心肺复苏的预后,而且能够监测患者的通气功能状态,更好地指导工作中呼吸模式和呼吸机的参数的调整,为撤机提供准确的时机,并能及时发现机械故障和减少不必要的操作。本文重点对呼吸末二氧化碳监测的原理以及其在临床中的应用展开综述。     

Does soil nitrogen influence growth,water transport and survival of snow gum (Eucalyptus pauciflora Sieber ex Sprengel.) under CO2 enrichment?

Eucalyptus pauciflora Sieber ex Sprengel. (snow gum) was grown under ambient (370  µ L L⁻¹) and elevated (700  µ L L⁻¹) atmospheric [CO₂] in open-top chambers (OTCs) in the field and temperature-controlled glasshouses. Nitrogen applications to the soil ranged from 0.1 to 2.75 g N per plant. Trees in the field at high N levels grew rapidly during summer, particularly in CO₂-enriched atmosphere, but suffered high mortality during summer heatwaves. Generally, wider and more numerous secondary xylem vessels at the root–shoot junction in CO₂-enriched trees conferred fourfold higher below-ground hydraulic conductance. Enhanced hydraulic capacity was typical of plants at elevated [CO₂] (in which root and shoot growth was accelerated), but did not result from high N supply. However, because high rates of N application consistently made trees prone to dehydration during heatwaves, glasshouse studies were required to identify the effect of N nutrition on root development and hydraulics. While the effects of elevated [CO₂] were again predominantly on hydraulic conductivity, N nutrition acted specifically by constraining deep root penetration into soil. Specifically, 15–40% shallower root systems supported marginally larger shoot canopies. Independent changes to hydraulics and root penetration have implications for survival of fertilized trees under elevated atmospheric [CO₂], particularly during water stress.     

Effect of carbon dioxide concentration on the bioleaching of a pyrite-arsenopyrite ore concentrate

The effect of carbon dioxide concentration on the bacterial leaching of a pyrite-arsenopyrite ore concentrate was studied in continuous-flow reactors. Steady-state operation with two feed slurry densities, 6 wt% and 16 wt% solids, were tested for the effect of carbon dioxide concentration. Bacterial growth rates were estimated via the measurement of carbon dioxide consumption rates. Aqueous-phase carbon dioxide concentrations in excess of 10 mg/L were found to be inhibitory to bacterial growth. (c) 1993 John Wiley & Sons, Inc.     

Isoelectric precipitation of soybean protein using carbon dioxide as a volatile acid

A novel process is presented for the isoelectric precipitation of soy protein, using carbon dioxide as a volatile acid. By contacting a soy meal extract with pressurized carbon dioxide, the solution pH was decreased to the isoelectric region of the soy proteins. Complete precipitation of the precipitable soy proteins could be achieved for protein concentrations up to 40 g/l at pressures less than 50 bar. Isoelectric precipitation with a volatile acid enabled accurate control of the solution pH by pressure and eliminated the local pH overshoot, usual in conventional precipitation techniques. The advantage of the improved precipitation control was reflected by the morphology of the precipitate particles. Protein aggregates formed by CO₂ were perfectly spherical whereas protein precipitated by sulfuric acid had an irregular morphology. The influence of process variables to control particle size is discussed.     

DIVERSITY IN THE MECHANISM OF CARBON DIOXIDE FIXATION IN DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE)1

The mechanism of photosynthetic carbon dioxide fixation in the green flagellate Dunaliella tertiolecta Butcher varies during growth in batch culture. Evidence for this change comes from three sources: i) algae from the stationary phase incorporated a greater proportion of the fixed carbon into amino arids and protein than did cells from the mid-exponential phase; ii) the activity of phosphoenolpyruvate carboxylase relative to that of ribulose-1, 5-di-phosphate carboxylase increased with age in batch culture; and, iii) cells from the stationary phase appeared to utilize the bicarbonate ion as the substrate for photosynthesis, whereas those from mid-exponential phase appeared to utilize fire carbon dioxide. These data suggest that a change of photosynthetic mechanism can occur within a single species of alga, depending on its physiological state.     

Induction of Ascorbate Peroxidase and Glutathione Reductase Activities by Interactions of Mixtures of Air Pollutants

The response of ascorbate peroxidase and glutathione reductase activities in peas (Pisum sativum var. Waverex) was investigated after three weeks of exposure to mixed fumigations with S0₂, NO, and O, (0.050 parts per million each) and increasing concentrations of O, (0-0.150 parts per million). The results show that plants respond similarly to a high concentration (0.150 parts per million) of a single air pollutant (ozone) and to mixtures of air pollutants (S0₂, NO: and O,) when individual concentrations are low (0.050 parts per million each). In both cases, levels of ascorbate peroxidase and glutathione reductase activites were approximately twice those to be found in plants grown in charcoal-filtered air (p 0.01).     

Inactivation of Pseudomonas aeruginosa biofilm by dense phase carbon dioxide

Dense phase carbon dioxide (DPCD) is one of the most promising techniques available to control microorganisms as a non-thermal disinfection method. However, no study on the efficiency of biofilm disinfection using DPCD has been reported. The efficiency of DPCD in inactivating Pseudomonas aeruginosa biofilm, which is known to have high antimicrobial resistance, was thus investigated. P. aeruginosa biofilm, which was not immersed in water but was completely wet, was found to be more effectively inactivated by DPCD treatment, achieving a 6-log reduction within 7 min. The inactivation efficiency increased modestly with increasing pressure and temperature. This study also reports that the water-unimmersed condition is one of the most important operating parameters in achieving efficient biofilm control by DPCD treatment. In addition, observations by confocal laser scanning microscopy revealed that DPCD treatment not only inactivated biofilm cells on the glass coupons but also caused detachment of the biofilm following weakening of its structure as a result of the DPCD treatment; this is an added benefit of DPCD treatment.     

Platelet activating factor (PAF) production by mouse embryos in vitro and its effect on embryonic metabolism

Factors affecting the production of platelet activating factor (PAF) by mouse embryos during culture in vitro were investigated. Detectable levels of embryo-derived PAF were produced within 1-4 hr with maximum PAF activity being observed after 6 hr of culture in vitro. The amount of PAF detected in media after 24 hr of culture of two-cell embryos was equivalent to 12.8 ng PAF/embryo. However, differences in activity were apparent with increased time in culture. Reduced synthesis of PAF during culture in vitro was supported by the observation that morulae stage embryos collected fresh from the reproductive tract displayed more PAF activity than morulae resulting from the 48 hr culture of two-cell embryos. In addition to determining production characteristics of PAF by embryos, we also show that the production of CO2 from carbon-1 position of lactate is positively correlated with the ability of embryos to develop during subsequent culture in vitro and therefore could be used as a measure of embryo viability. Furthermore, culture of embryos in media supplemented with PAF resulted in an increase in lactate utilization demonstrating a direct effect of PAF on the embryo. As PAF is produced by preimplantation embryos, an autocoid role of PAF in regulating embryo development is implicated. Therefore, the reduced production of PAF by embryos in vitro may explain the decreased viability of embryos commonly observed following their culture in vitro.     

CO2 concentrations in perennially ice-covered lakes of Taylor Valley, Antarctica

Lakes in Taylor Valley, southern Victoria Land,Antarctica, are unusual in that they areperennially covered by a 3–5 m thick ice layer.Previous work on gas concentrations in theselakes has shown that the surface waters aresupersaturated with respect to O₂,N₂O, as well as the noble gases. Our datashow that the dissolved CO₂ (CO_2(aq))concentrations, calculated from pH andCO₂, can be highly undersaturatedat shallow depths of the lakes. CO₂partial pressure values (pCO₂) are as lowas 10^–4.3 atm and 10^–4.2 atm in theeast and west lobes of Lake Bonney,respectively, and 10^–3.8 atm in LakeHoare. CO_2(aq) depletion occurred only inthe uppermost part of the water column, inassociation with elevated primary productivity(PPR). The upward diffusion of CO_2(aq)from the aphotic zone, and the annual input ofCO₂ via glacial meltwater can notreplenish the amount of CO_2(aq) annuallylost to primary productivity in the uppermostmeters of the water column. Calcification is alimited source of CO_2(aq), since the lakesare undersaturated with respect to calcitethrough portions of the austral summer.Preliminary respiration rates have been used toobtain an annual inorganic carbon balance.Further down in the water column, at the sitesof the deep-water maximum in primary production(PPR_max), which in Lakes Bonney andFryxell is associated with nutrient gradients,CO_2(aq) is not undersaturated. A largeupward flux from CO₂-supersaturatedaphotic waters provides a surplus ofCO_2(aq) at the PPR_max. Lake Fryxell,unlike the other lakes, is supersaturated withCO_2(aq) throughout the entire water column.     

Effects of daytime carbon dioxide concentration on dark respiration in rice

Rising atmospheric carbon dioxide concentration ([CO₂]) has generated considerable interest in the response of agricultural crops to [CO₂]. The objectives of this study were to determine the effects of a wide range of daytime [CO₂] on dark respiration of rice (Oryza sativa L. cv. IR-30). Rice plants were grown season-long in naturally sunlit plant growth chambers in subambient (160 and 250), ambient (330), or super-ambient (500, 660 and 900 μmol CO₂ mol^?1 air) [CO₂] treatments. Canopy dark respiration, expressed on a ground area basis (R_d) increased with increasing [CO₂] treatment from 160 to 500 μmol mol^?1 treatments and was very similar among the superambient treatments. The trends in R_d over time and in response to increasing daytime [CO₂] treatment were associated with and similar to trends previously described for photosynthesis. Specific respiration rate (R_dw) decreased with time during the growing season and was higher in the subambient than the ambient and superambient [CO₂] treatments. This greater R_dw in the subambient [CO₂] treatments was attributed to a higher specific maintenance respiration rate and was associated with higher plant tissue nitrogen concentration.     

沈阳市区大气SO2污染程度的叶绿素含量监测分析

沈阳市区大气ＳＯ２污染程度的叶绿素含量监测分析周兴文（沈阳大学师范学院生物系,沈阳１１００１５）ＴｈｅｃｈｌｏｒｏｐｈｙｌｃｏｎｔｅｎｔｍｏｎｉｔｏｒｉｎｇａｎａｌｙｓｉｓｏｆｔｒｅｌｅａｖｅｓｆｏｒＳＯ２ｐｏｌｕｔｉｏｎｉｎＳｈｅｎｙａｎｇＣｉｔｙ...     

啤酒花的萃取

本文综述了使用啤酒花萃取物的优点以及啤酒花的超临界二氧化碳萃取和液态二氧化碳萃取的特点。     

Studies on the anesthetic mechanism of carbon dioxide by using Bombyx mori larvae.

The study of heartbeat variations of Bombyx mori larvae submitted to CO2 narcosis has provided new information on carbon dioxide anesthesia. Purely anoxiant action must be dismissed. Action at a nerve level is possible since CO2 produces the same effect as ether, which is a classical anesthetic.     

Enzymatic HCO 3 − fixation: A common mechanism for all enzymes involved?

Conclusion Present evidence is highly suggestive of a stepwise mechanism with a common initial step of HCO ₃ ^– activation, for all enzymes that use HCO ₃ ^– rather than CO₂ as the substrate. This activated form of HCO ₃ ^– appears to be the carbonic-phosphoric anhydride, although this has only been proved rigorously with carbamoyl phosphate synthetase. Further studies using isotope scrambling and other techniques will be necessary to establish conclusively that this is the case with the other enzymes.For brevity an extensive bibliographical coverage has not been attempted, and only references directly relevant to the points discussed have been included.     

Crop responses to CO2 enrichment

Carbon dioxide is rising in the global atmosphere, and this increase can be expected to continue into the foreseeable future. This compound is an essential input to plant life. Crop function is affected across all scales from biochemical to agro-ecosystem. An array of methods (leaf cuvettes, field chambers, free-air release systems) are available for experimental studies of CO₂ effects. Carbon dioxide enrichment of the air in which crops grow usually stimulates their growth and yield. Plant structure and physiology are markedly altered. Interactions between CO₂ and environmental factors that influence plants are known to occur. Implications for crop growth and yield are enormous. Strategies designed to assure future global food security must include a consideration of crop responses to elevated atmospheric CO₂. Future research should include these targets: search for new insights, development of new techniques, construction of better simulation models, investigation of belowground processes, study of interactions, and the elimination of major discrepancies in the scientific knowledge base.