咽喉部高频喷射通气调节各参数对狗肺通气效率的影响

用相关和回归处理方法,研究了8条正常狗咽喉部高频喷射通气时,调节驱动压、呼吸比和频率对喷气量、吸入气氧浓度、动脉血气及气道内压的作用。结果显示,驱动压和呼吸此对各观察指标几乎有同等重要的作用,频率的影响很小,喷气量与吸入气氧浓度、动脉血气、气道内压间存在显著的正相关关系。说明调节参数的意义主要在于改变了喷气量。     

Characterization of a thermo-osmotic gas transport mechanism in Alnus glutinosa (L.) Gaertn.

Summary A gas transport system based upon the physico-chemical effect of thermo-osmosis of gases in described for the black alder, Alnus glutinosa (L.) Gaertn. Air is transported through the alder's stem to the roots, thus improving O₂ supply to respiring tissues of the root system. The gas transport system is investigated by means of a tracer gas technique (11% ethane in air, v/v). Gas transport depends on any source of radiant heat generating a temperature difference between the tree's stems and the atmosphere. The amount of gas transported in leafless trees is four times higher than the amount of gas reaching the roots by gas diffusion. Two-thirds of the gas is transported in the wood, only one-third in the bark. Intercellular spaces inside the porous lenticels of the bark are responsible for this kind of gas transport. Their diameters are estimated by the effusion rates of different tracer gases to be in the range of 1 m.     

Gas exchange and blood gases of Puna teal (Anas versicolor puna) embryos in the Peruvian Andes

Oxygen consumption, air cell gases, hematology, blood gases and pH of Puna teal (Anas versicolor puna) embryos were measured at the altitude at which the eggs were laid (4150 m) in the Peruvian Andes. In contrast to the metabolic depression described by other studies on avian embryos incubated above 3700 m, O₂ consumption of Puna teal embryos was higher than even that of some lowland avian embryos at equivalent body masses. Air cell O₂ tensions dropped from about 80 toor in eggs with small embryos to about 45 toor in eggs containing a 14-g embryo; simultaneously air cell CO₂ tension rose from virtually negligible amounts to around 26 torr. Arterial and venous O₂ tensions (32–38 and 10–12 toor, respectively, in 12- to 14-g embryos) were lower than described previously in similarly-sized lowland wild avian embryos or chicken embryos incubated in shells with restricted gas exchange. The difference between air cell and arterial O₂ tensions dropped significantly during incubation to a minimum of 11 torr, the lowest value recorded in any avian egg. Blood pH (mean 7.49) did not vary significantly during incubation. Hemoglobin concentration and hematocrits rose steadily throughout incubation to 11.5 g · 100 ml^-1 and 39.9%, respectively, in 14-g embryos.Abbreviations PO₂ partial pressure gradient of O₂ - BM body mass - D diffusion coefficient - G gas conductance (cm³·s^-1·torr^-1) - conductance to water vapor - IP internal pipping of embryos - P _ACO₂ partial pressure of carbon dioxide in air cell - P _AO₂ partial pressure of oxygen in air cell - P _aCO₂ partial pressure of carbon dioxide in arterial blood - P _aCO₂ partial pressure of oxygen in arteries - P _H barometric pressure (torr) - PCO₂ partial pressure of carbon dioxide - P _IO₂ partial pressure in ambiant air - PO₂ partial pressure of oxygen - P _VCO₂ venous carbon dioxide partial pressure - P _VO₂ mixed venous oxygen partial pressure - SE standard error - VO ₂ oxygen consumption     

Some rumen ciliates have endosymbiotic methanogens

Abstract Most of the small ciliate protozoa, including Dasytricha ruminantium and Entodinium spp. living in the rumen of sheep, were found to have intracellular bacteria. These bacteria were not present in digestive vacuoles. They showed characteristic coenzyme F₄₂₀ autofluorescence and they were detected with a rhodamine-labelled Archaea-specific oligonucleotide probe. The measured volume percent of autofluorescing bacteria (1%) was close to the total volume of intracellular bacteria estimated from TEM stereology. Thus it is likely that all of the bacteria living in the cytoplasm of these ciliates were endosymbiotic methanogens, using H₂ evolved by the host ciliate to form methane. Intracellular methanogens appear to be much more numerous than those attached to the external cell surface of ciliates.     

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.     

Integrated membrane systems for gas separation in biotechnology: potential and prospects

Integrated non-porous membrane systems were applied for microbial combustible gas separation processes. Methane/CO₂ mixtures of various concentrations from methane fermentation processes (biogas) were separated using a membrane-separation complex of permabsorber type into individual components of technical grade (more than 95% purity). In experiments with three-component mixtures, using a selective membrane valve with various liquid carriers, all the gases of interest (H₂, CH₄ and CO₂) were obtained at greater than 90% purity in one separation step. The perspectives for the further application of non-porous membrane separating devices for various gaseous mixtures from different microbial processes are discussed.V. Teplyakov and E. Sostina are with the A.V. Topchiev institute of Petrochemical Synthesis, Russian Academy of Sciences, Membrane Research Center, Moscow 117912, Russia. E. Sostina is also, and A. Netrusov is with the Microbiology Department, Moscow University, Moscow 119899, Russia. I. Beckman is with the Chemistry Department, Moscow University, Moscow 119899, Russia.     

Influence of soil gas contamination on tree root growth

Summary Rooted-cuttings and saplings of green ash (Fraxinus lanceolata) and hybrid poplar (Populus spp) were planted on a former municipal refuse landfill and on a nearby nonlandfill control plot. The root systems of four trees of each species and size were excavated on the landfill plot-two growing in an area where the concentrations of anaerobic landfill gases were relatively high and two in a relatively low-gas area. Two trees of each species and size were also excavated on the control. The root systems of both species were significantly shallower on the landfill plot than on the control. Green ash appeared to avoid the adverse gas environment of the deeper soil layers on the landfill by producing adventitious roots. Hybrid poplar became adapted in a different manner, by redirecting root growth from the deepter soil layers to the soil surface.     

Nodulation and growth ofLablab purpureus (Dolichos lablab) in relation to rhizobium strain,liming and phosphorus

Summary Greenhouse experiments were done with two purposes: (1) to identify strains of rhizobia effective and acid-tolerant in symbiosis withLablab purpureus, and (2) to determine whether soil acidity or the symbiotic condition increased the phosphate requirement for growth.Five rhizobial strains were tested in one neutral soil, two acid soils, and the two acid soils limed to pH 6.6. In the neutral and limed soils, three of the strains were effective (CB1024, CB756, TAL169), but only two strains (CB756, TAL169) remained effective in acid soil.Strain CB756 and plus-N treatments were further compared in a factorial trial involving combinations of five levels of P with lime, no lime and CaCl₂ treatments, applied to an acid soil. Some of the treatments were also applied to plants inoculated with CB1024. Between the N-fertilized and CB756 treatments there was no clear difference in growth response to applied P, and the critical internal concentration of P for 95% of maximal growth was the same (0.22% shoot dry weight). Increasing P beyond levels needed for maximal growth increased nodulation and N concentration in plants inoculated with CB756. It lowered N concentration in N-fertilized plants. There was evidence suggesting that the P requirement of symbiotic plants increased if the soil was acid, or if CB756 were replaced by CB1024 as microsymbiont; but the critical statistical interactions were not significant.     

Inoculation of millet with azospirillum

Summary Millet plants (Pennisetum glaucum) were grown at three levels of nitrogen fertilization with and without an inoculum of live nitrogen-fixing Azospirillum cells. The highest average rate of nitrogen fixation as estimated from acetylene reduction by excised preincubated roots was only 23g N₂ fixed per ha per day and occurred after treatment with low levels of nitrogen amendment. The average rates of acetylene reduction for intact plants at all treatments were also low. The lack of significant nitrogen fixation due to an Azospirillum-millet association in this study was substantiated by plant dry weight analysis, and determination of the nitrogen content of plants, pot leachate, and soil. There was significant correlation between the total nitrogen content of the plants per pot at the termination of the experiment and the amount of nitrogen fertilizer added initially, but there was no effect of inoculum on final total nitrogen content.     

Nodulation,nitrogen fixation,leaf area,and sugars content inLablab purpureus as affected by sulfur nutrition

Summary In order to explore interrelations between S nutrition, soluble sugars, leaf area, nodulation and N₂ fixation, greenhouse experiments were done with several levels of S added to perlite-sand cultures or to a moderately S-deficient soil. Sulfur had indirect effects on nodulation and N₂ fixation, possibly by improving sugars supply and N metabolism.In perlite-sand culture, leaf area increased with concentrations of supplied S up to 50 and 200 M for symbiotic and N-treated plants respectively, then decreased at higher concentrations. Plant yield and total sugars content (mg per plant) for the N-treated plants behaved similar to leaf area in response to added S but in the symbiotic plants maximum values were obtained at 100 M S. In soil, Mo had no effect on growth but interacted significantly with S in affecting total sugars content. High levels of S depressed sugars content at low Mo but raised it at high Mo.Sulfur increased the N content of soil-grown plants. It increased the N content of plants grown in perlite-sand culture except at very high levels of S. There was little effect on concentration of N in the shoots. Nitrogen content correlated significantly with leaf area and sugar content, and highly significantly with S concentration in the shoots.