Changes of Exponential Growth Rates in Relation to Differentiation of Geotrichum candidum in Submerged Culture

Growth and differentiation of the imperfect fungus Geotrichum candidum were followed in submerged cultures containing a simple synthetic glucose salt medium. Uptake of glucose, ammonium and oxygen from the medium were measured during the entire growth perod. In 0.1% glucose the fungus grows with one exponential growth phase until all the glucose has been consumed. The arthrospores are formed in the stationary phase. In 0.5% glucose the growth curve has two exponential growth phases, one with a doubling time of 1.8 h and a second one with a doubling time of 4.9 h. The second exponential growth phase, which starts when less than 15% of the glucose and less than 30% of the ammonium have been consumed, is shown to be the sporulation phase. During this growth phase the oxygen saturation in the culture remained constant at about 50%.     

二氧化碳安乐死在实验动物中的应用与最新进展

本文概述了二氧化碳（CO2）安乐死法的作用机制、CO2使用浓度、应用范围和操作注意事项,并讨论了该方法的动物福利、设备改进等问题。     

Growth of Geotrichum candidum and Penicillium camemberti Cultivated on Liquid Media Correlated with Ammonia and Methanethiol Emission

The growth of Geotrichum candidum and Penicillium camemberti plays an important role in the ripening of Camembert‐type cheeses, but the monitoring of the corresponding kinetics for fungal cocultures on solid media appears difficult. Continuous and non‐intrusive methods to characterize the growth of both species (like the monitoring of the emissions of ammonia and volatile sulphur compounds) may be highly relevant, under the condition that such emissions could be correlated with growth. This would be easier to investigate in submerged culture, since total biomass concentration is known to vary in proportion to broth turbidity. For this reason, growth kinetics, ammonia and flavour gas emission of both Geotrichum candidum and Penicillium camemberti grown separately in submerged cultures under the conditions of low aeration rate and uncontrolled pH were continuously recorded.In the basal medium (peptone+lactate supplemented with both glutamic acid and methionine [1 g/l]each), no significant gas emission was observed during the growth of both fungi. Ammonia and sulphur gas emissions by G. candidum were a little stimulated by supplementing the basal medium with trace elements, and, at a larger extent, by the addition of inorganic phosphate: Such a gaseous emission took place at the end of the growth phase of G. candidum. Irrespective of the basal medium supplementation, no significant emission ofammonia and sulphur gas was observed during the growth of P. camemberti. For the media and strains used, ammonia and volatile sulphur compounds emissions unequivocally showed the growth of Geotrichum candidum.     

Model-Based Analysis of Mechanisms Responsible for Sleep-Induced Carbon Dioxide Differences

This work describes a comprehensive mathematical model of the human respiratory control system which incorporates the central mechanisms for predicting sleep-induced changes in chemical regulation of ventilation. The model integrates four individual compartments for gas storage and exchange, namely alveolar air, pulmonary blood, tissue capillary blood, body tissues, and gas transport between them. An essential mechanism in the carbon dioxide transport is its dissociation into bicarbonate and acid, where a buffering mechanism through hemoglobin is used to prevent harmfully low pH levels. In the current model, we assume high oxygen levels and consider intracellular hydrogen ion concentration as the principal respiratory control variable. The resulting system of delayed differential equations is solved numerically. With an appropriate choice of key parameters, such as velocity of blood flow and gain of a non-linear controller function, the model provides steady-state results consistent with our experimental observations measured in subjects across sleep onset. Dynamic predictions from the model give new insights into the behaviour of the system in subjects with different buffering capacities and suggest novel hypotheses for future experimental and clinical studies.     

Potential of pure and mixed cultures of Cladosporium cladosporioides and Geotrichum candidum for application in bioremediation and detergent industry

The effect of ethoxylated oleyl–cetyl alcohol (Henkel, “Merima”, Serbia) on the growth and metabolic activity of Cladosporium cladosporioides, Geotrichum candidum and their mixed culture was in the focus of this paper. The cultures were grown in Czapek-Dox liquid nutrient medium with the addition of 0.5% pollutant and without it. The physico-chemical and biochemical changes of pH, the total biomass dry weight, the quantity of free and total organic acids, proteolytic activity and the quality of carbohydrates were evaluated from 4th to 19th day of fungal growth. The pollutant caused an inhibitory effect on biomass dry weight of C. cladosporioides and G. candidum for 10.36% and 4.65% respectively, and stimulatory effect on biomass of mixed culture for 3.80%. The pollutant had influence on the decrease in pH value of the media in the phase of culture growth, and pH changes were correlated with the amount of excreted total organic acids. The highest quantity of free and total organic acids was noted in media with pollutant of mixed culture and C. cladosporioides, respectively. The alkaline protease activities of C. cladosporioides, G. candidum and mixed culture were enhanced by addition of pollutant for 56.88%, 55.84% and 30.94% respectively. The obtained results indicate the potential of both pure and mixed cultures in mycoremediation environment contaminated by alcohol ethoxylated and detergent industry.     

慢性间断性缺氧伴二氧化碳潴留小鼠模型的建立

目的建立慢性间断性缺氧伴二氧化碳潴留（chronic intermittent hypoxia with carbon dioxide retention,CIH-CR）小鼠模型。方法选取雄性昆明小鼠22只,随机分为常氧组（normal control group,NC）和CIH-CR组,每组11只。CIH-CR组小鼠每天CIH-CR处理8 h,共4周,实验期间监测箱内O2和CO2浓度及小鼠尾部末端血氧饱和度（SO2）。实验终点测定右室肥厚指数并观察心、肺、肾、脑组织病理改变。结果 CIH-CR组箱内O2浓度、CO2浓度和小鼠尾部末端SO2随实验仓的关闭和开启出现周期性的变化;与NC组相比CIH-CR组右心室明显肥大（P〈0.01）;小鼠心、肺、肾和脑组织均出现明显缺氧改变。结论成功建立了CIH-CR小鼠模型。     

常用功率密度CO2激光治疗尖锐湿疣时烟尘中HPV DNA的检测

目的 :了解临床常用功率密度的 CO2 激光治疗尖锐湿疣术中烟尘是否含有 HPVDNA。方法 :选择皮损较多的尖锐湿疣 ,病程在 6个月以内的患者作为研究对象 ,分别用 5 W、1 0 W、1 5 W对应功率密度下的 CO2 激光汽化在体疣体组织 ,离光斑 5 cm或 5 0 cm处用吸尘器抽吸烟尘于 PBS中 ,经固定后观察烟尘的细胞形态学 ,并用 HPV通用型引物作 PCR检测烟尘是否含有 HPV-DNA。结果 :三种功率密度的烟尘主要由炭化颗粒组成 ,其中含有少量破碎的上皮细胞及形态完整和不完整的单个表皮细胞或细胞团 ;PCR检测 CO2 激光在 5 W、1 0 W、1 5 W对应功率密度下治疗时的烟尘 ,HPV DNA阳性数分别为 :1 /1 3、3 /9、3 /1 5例。结论 :CO2激光常用功率密度治疗尖锐湿疣时 ,烟尘中有 HPV DNA存在 ,为防其对人体造成的危害 ,需要及时抽排烟尘。     

Carbon Dioxide Exchange of Spring-wheat in Relation to Age and Photon-flux Density at Different Growth Temperatures

CO₂-exchange rates (CER) of the sixth and the flag leaves oftwo spring-wheat varieties, Kolibri and Famos, were comparedusing an open-circuit infrared gas analysing system. Measurementswere repeated every two weeks starting when leaf blades werefully expanded. Single plants were grown in a controlled environmenthaving a photopuiod of 15 h and a day/night temperature of 24/19°C(H), 18/13 °C (M), and 12/7 °C (L) respectively untilapprox. 2 weeks after anthesis and at 18/13 °C until maturity.The photosynthetic photon-flux density (PPFD) at the top ofthe plants was 500 µE m^–2 sec^–1. During themeasurements PPFD was gradually reduced from 2000 to 0 µEm^–2 sec^–1 whereas the temperature was maintainedat the respctive growth-temperatures during the light period.The CER of the sixth leaf declined fairly similarly for bothvarieties, except for Kolibri where a faster decline was observedduring the first two weeks after full leaf expansion. The CERof the flag leaf declined more slowly than that of the sixthleaf. With the flag leaf of Famos, the decline was nearly linear,whereas with Kolibri it was very slow during the first few weeksbut rapid as the leaves further senesced. This pattern becamemore pronounced as the growth temperature decreased. The declinein relation to leaf age was much smaller at low PPFD than athigh PPFD during the same period. At full leaf expansion Kolibrireached higher maximum CER than Famos except at H. As the PPFDwas reduced the difference became smaller and at very low PPFDsuch as 50 µE m^–2 sec^–1 was reversed for thesixth leaf. Under optimum growth conditions maximum values ofCER were greater than 50mg CO₂ dm^–2h^–1 and PPFDfor light saturation was close to 2000 µE m^–2 sec^–1.A comparison between the actual CER and a fitted curve widelyused, PN=(a+b/l)^–1–DR, showed that the goodnessof fit strongly depends on cultivar, treatment and leaf ageas well as on the number and the level of PPFD from which datafor calculations are taken. Triticum aestivum, L., wheat, photosynthesis, photon-flux density, light response, carbon, dioxide exchange     

The Analysis of Correlative Growth in the Etiolated Oat Seedling in Relation to Carbon Dioxide and Nutrient Supply

To overcome the reduced extension growth of the coleoptile whichoccurs when oats are grown in air enriched with 5 per cent.CO¹, plants have been provided with nutrients via the roots.2 per cent, sucrose, glucose or mannitol so applied furtherpromoted the mesocotyl and further depressed the coleoptile.Root growth was also depressed. To induce promotion of coleoptile growth by externally appliedsucrose, seedlings were heated in darkness at 40° C. for3 hours so restricting selectively the growth of the mesocotyl.Promotion of the coleoptile, however, was not observed. Application of mixed Na and K nitrates occasioned an immediategrowth promotion of doleoptile and leaves in both the presenceand absence of CO², and also a.much less pronounced promotionof the mesocotyl in CO²; there was no effect in air. This enhancedgrowth of the coleoptile and leaves was coupled with a correspondinglygreater dry weight and also with an increased outflow of reservesfrom the endosperm into the plumule. Thus, while externally applied sugars seemed not to reach thecoleoptile, those made available from the endosperm as a resultof improved nitrogen supply were rapidly translocated to it.Simultaneous provision to the roots of nitrate and sucrose didnot improve the absorption and translocation of sugar. An analysis of covariance has been computed using the mesocotyland coleoptile length data together with the outflow from theendosperm and the conclusions so derived are discussed in relationto the problem of growth integration in etiolated oat seedlings.     

Temporal accumulation of mannitol and arabitol in Geotrichum candidum

The temporal depletion and accumulation of polyols were investigated in the fungus Geotrichum candidum. The major intracellular polyols were tentatively identified by paper chromatography as mannitol and arabitol. Inositol was also present in small quantities, and trehalose was also detected in appreciable concentrations.Germination and vegetative growth depended on the type and concentration of the sole exogenous carbon source. Mannitol occurred in arthrospores at 9.4% of the dry weight after several days growth in 2% (w/v) glucose solid medium, and became depleted during germination and vegetative growth in liquid medium containing 2% (w/v) glucose, 2% (w/v) sodium acetate or 25% (w/v) glucose as sole carbon source. This hexitol latter accumulated during arthrosporulation. The depletion and accumulation of ethanol-soluble carbohydrate believed to be primarily trehalose was temporally similar to that of mannitol. Arabitol accumulated intracellularly during germination and vegetative growth in sodium acetate medium and 25% glucose medium. This pentitol was not detected intracellularly at any culture age during growth in 2% glucose medium.Prolonged incubation of the culture in 25% glucose medium after stationary phase was reached resulted in the gradual disappearance of arabitol from the arthrospores simultaneously with an increase in intracellular mannitol. In comparison, ethanol-soluble carbohydrate did not change with prolonged incubation in this medium.     

Direct Observation of Spin-Trapped Carbon Dioxide Radicals in Hepatocytes Exposed to Carbon Tetrachloride

Carbon dioxide radical adducts of the spin trapping agent, α-phenyl N-t-butyl nitrone (PBN), have been observed to occur in the urine and bile of rats exposed to carbon tetrachloride as well as in perfusates of liver in which the perfusion medium contained carbon tetrachloride (Connor er al., J. Biol. Chem., 261, 4542, (1986)). The carbon dioxide adduct was proven to be derived from CCI, by use of 13-C-labelled compound. These adducts were not observed in the liver itself suggesting that they might be rapidly secreted from the liver. However, using isolated hepatocytes, we have demonstrated that the carbon dioxide radical adduct can be observed directly in the liver cells as it is formed. Since this water-soluble adduct cannot be extracted by non-aqueous solvents such as chloroform or toluene, its formation in liver in vivo or in perfused livers was not detected. Lowering the oxygen tension in the system diminished the intensity of production of the carbon dioxide adduct, consistent with the adduct being produced as a result of ·OOCCl₃ generation. It is not clear the extent to which this adduct is formed as a result of the ·CO₂ radical or is produced by metabolic oxidation of the trichloromethyl radical adduct of PBN per se to the carbon dioxide radical adduct. The intensity of the signal of the carbon dioxide radical adduct suggests that adduct conversion may be the route of formation since it seems unlikely that a sufficient amount of the halocarbon could be metabolized to ·COCl or ·CO₂ radicals to generate a signal of the magnitude involved. The ·CO₂ adduct is readily observed in intact hepatocytes, but the ·CCl₃ adduct is not (although we know the ·CCl₃ adduct has been produced in these cells), indicating that the ·CO₂ adduct is present in considerable abundance compared to the ·CCl₃ adduct.     

Altered Circadian Relationship Between Serum Nitric Oxide, Carbon Dioxide, and Uric Acid in Multiple Sclerosis

The free radical nitric oxide (NO^·) is involved in a variety of diverse biological processes from acting as a vasodilator in the cardiovascular system to being the rate-limiting component in the production of peroxynitrite (ONOO^-), a contributor to neurodegenerative disorders such as multiple sclerosis (MS). Uric acid (UA), the end product of purine metabolism in humans and a selective inhibitor of toxic reactions attributed to radicals formed by the interaction of ONOO^- and CO₂, is generally low in MS patients. We investigated the relationship between serum ONOO^-, CO₂, and UA in MS patients and normal controls by comparing the circadian characteristics of the NO^· metabolites nitrite/nitrate (NO), CO₂, and UA. In this preliminary study, we found the functional relationship ascribed to the circadian timing of the peak and trough levels of NO, CO₂, and UA in healthy subjects to be clearly altered in MS patients. These findings suggest that alterations in the temporal relationship between the 24 h pattern in serum ONOO^- formation and UA may either contribute to or reflect the disease processes in MS.     

Altered Circadian Relationship Between Serum Nitric Oxide,Carbon Dioxide,and Uric Acid in Multiple Sclerosis

The free radical nitric oxide (NO^·) is involved in a variety of diverse biological processes from acting as a vasodilator in the cardiovascular system to being the rate-limiting component in the production of peroxynitrite (ONOO^?), a contributor to neurodegenerative disorders such as multiple sclerosis (MS). Uric acid (UA), the end product of purine metabolism in humans and a selective inhibitor of toxic reactions attributed to radicals formed by the interaction of ONOO^? and CO₂, is generally low in MS patients. We investigated the relationship between serum ONOO^?, CO₂, and UA in MS patients and normal controls by comparing the circadian characteristics of the NO^· metabolites nitrite/nitrate (NO), CO₂, and UA. In this preliminary study, we found the functional relationship ascribed to the circadian timing of the peak and trough levels of NO, CO₂, and UA in healthy subjects to be clearly altered in MS patients. These findings suggest that alterations in the temporal relationship between the 24 h pattern in serum ONOO^? formation and UA may either contribute to or reflect the disease processes in MS.     

The Effect of Atmospheric Carbon Dioxide Elevation on Plant Growth in Freshwater Ecosystems

We developed a dynamic model to investigate the effect of atmospheric carbon dioxide (CO₂) increase on plant growth in freshwater ecosystems. Steady-state simulations were performed to analyze the response of phytoplankton and submerged macrophytes to atmospheric CO₂ elevation from 350 to 700 ppm. We studied various conditions that may affect this response, such as alkalinity, the air–water exchange rate of CO₂, the community respiration rate, and the phosphorus (P) supply rate. The increase in atmospheric CO₂ could affect submerged plant growth only under relatively eutrophic conditions and at a low community respiration rate. Alkalinity had little effect on the response of the different species. When the air–water exchange was low, the proportional effect of the CO₂ increase on plant growth was higher. Under eutrophic conditions, algae and macrophytes using CO₂ and HCO₃^– may double their growth rate due to atmospheric CO₂ elevation, while the growth of macrophytes restricted to CO₂ assimilation may be threefold. The differences in response of the species under various conditions indicate that the elevation of atmospheric CO₂ may induce drastic changes in the productivity and species dominance in freshwater systems.     

中国热带天然林变迁对大气CO2的影响及经济损益评估

我国目前保存较好的热带天然林（包括热带原始林、结构良好的天然更新林,而不包括疏林、残次林、灌木林等）面积约１１８７万ｈｍ２,其中云南南部约有６０万ｈｍ２,海南中南部山区约有５８７万ｈｍ２。在过去的４５年中,我国的热带原始林面积减少了５０％（约１１０ｈｍ２）。在海南岛尖峰岭的实例结果表明,热带原始林的生态系统的Ｃ素库为３４２ｔ／ｈｍ２（其中,森林群落Ｃ素库为２３４ｔ／ｈｍ２,土壤为１０５ｔ／ｈｍ２,凋落物层为３ｔ／ｈｍ２）,系统每年净固定ＣＯ２量为１３３６ｔ／ｈｍ２,折合Ｃ量为０３７３ｔ／ｈｍ２;热带天然更新林生态系统每年净固定ＣＯ２量为７２１３ｔ／ｈｍ２,折合成Ｃ量为１９７ｔ／ｈｍ２。在我国现有的热带天然林生态系统中,森林植被层的Ｃ素库为１４４８亿ｔ,土壤中的Ｃ素库为１４２２亿ｔ,与植被层Ｃ库相当。在减少的热带森林中,Ｃ素库减少了约２２３１亿ｔ、ＣＯ２净同化量减少了０１８３亿ｔ,其经济损益高达２２００亿元。最后从森林与ＣＯ２的关系方面探讨了热带林可持续经营的问题。     

Carbon Dioxide and pH in Relation to Salt Uptake by Beetroot Tissue

The enhancement of cation uptake in beetroot disks with increasingpH is confirmed. In disks taken from growing beet, the presenceof 2 per cent carbon dioxide in air results in a further promotionof cation uptake at pH 7.4, but not at lower pH levels. Theability to respond to added carbon dioxide is often absent indisks cut from dormant roots in winter storage, but may be partlyrestored by pre-washing the disks for a suitable period. Theinfluence of various washing pre-treatrnents indicates thatthe carbon dioxide effect is most pronounced when excess cationuptake is at a maximum. The additional cation uptake at highpH with or without 2 per cent carbon dioxide, and part of thecation uptake at pH 5.6, is balanced by an equivalent synthesisof organic acids. It is concluded that cation uptake is notprimarily determined by the external bicarbonate concentration,and that the pH effect is a genuine one. An electrochemicalapproach shows that the observed effects of high pH and of carbondioxide can be largely accounted for in terms of passive diffusionof ions across the cell membrane, whilst cation accumulationat low pH may involve a hydrogen ion excretion pump.     

Growth Response to Salinity at High Levels of Carbon Dioxide

Plants of the C₃ species Phaseolus vulgaris and Xanthium strumariumand of the C₄ salt-sensitive Zea mays and the C₄ halophyte Atriplexhalimus were grown with and without NaCl salt-stress at normal(340 µl I^–1) and at high (2500 µl I^–1)ambient CO₂. In all four species growth (dry weight increment)was enhanced by CO₂ supplementation. The relative response wasgreater in the salinized than in the control plants. Plant topsresponded more to CO, than the roots. CO₂ supplementation appearsto increase plant tolerance of low levels of salinity. Key words: Salinity, CO₂, Growth     

Carbon dioxide supersaturation in Florida lakes

We examined data on CO₂ and related limnological and geographic information from a sample of 948 Florida freshwater lakes. The objectives for this study were (1) to determine the partial pressures of carbon dioxide (ρCO₂) in the surface waters of a large sample of Florida lakes, (2) to determine if several limnological or geographic factors are related to levels of ρCO₂ in Florida lakes, and (3) to estimate the net annual rate of loss of CO₂ to the atmosphere from the freshwater lakes of Florida. The calculated ρCO₂ for the lakes in our sample range from 0 to 81,000 μatm, with a mean of 3,550 μatm, a median of 1,030 μatm, and a geometric mean of 1,270 μatm. About 87% of the Florida lakes were supersaturated with CO₂. There were statistically significant correlations between values for ρCO₂ and several water chemistry variables; however, the R ² values were small and accounted for only a small portion of the variance. In general the ρCO₂ values were higher in the lakes with low alkalinities and low contents of dissolved salts. The best predictor of ρCO₂ is pH, with an R ² of 0.82 for a polynomial relationship. The ρCO₂ values tend to decrease from northwest to southeast across the state of Florida, which corresponds to the gradients we found for pH, alkalinity, and specific conductance. The average areal rate of carbon emission from the Florida lakes was 328 g C m⁻² y⁻¹, and the total carbon loss for the lakes and ponds of Florida was 2.0 Tg y⁻¹. This amounts to about 2% of the total carbon emissions from all the lakes of the world as estimated by previous studies. Handling editors: Darren Bade     

美国俄亥俄州南部两种不同间伐强度对森林可燃物载量和碳的影响(英文)

本研究的目的是测定两种不同间伐强度下(70%和50%),美国俄亥俄州南部橡树混交林森林可燃物(包括枯落物、木本、草本和倒木)碳储量和其燃烧后可能释放的碳量。研究结果表明枯落物和木本碳含量显著高于草本部分。在50%、70%间伐和对照中,森林枯落物分别占了总的橡树混交林可燃物碳储量的36.6%,50.9%和66.0%。粗木质残体分别占了58.4%,48.0%和32.6%。小的木本和草本在总的森林可燃物中占据很小比例。在50%、70%间伐和对照三种情况下,总的森林可燃物分别是54.07t/ha、41.98t/ha和20.73t/ha。如果对这些森林可燃物进行燃烧,50%、70%间伐和对照中,其森林可燃物将释放碳量分别为90.39t/ha、70.19t/ha和34.66t/ha。虽然它们之间没有产生显著的差异,但和对照进行比较,间伐后仍产生了较多的一、二级森林可燃物。在50%、70%间伐和对照中,分别产生了25.08t/ha、23.47t/ha和14.38t/ha一、二级的可燃物。计划用火在燃烧这些可燃物成分时,在50%、70%间伐和对照中,可能会分别释放41.93t/ha、39.24t/ha和23.55t/ha碳。此研究对使用计划用火来减少引起森林火灾的森林可燃物具有一定的意义。