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1.
Woody plant encroachment of grasslands: a comparison of terrestrial and wetland settings.
Saintilan, N, Rogers, K
The New phytologist. 2015;(3):1062-70
Abstract
A global trend of woody plant encroachment of terrestrial grasslands is co-incident with woody plant encroachment of wetland in freshwater and saline intertidal settings. There are several arguments for considering tree encroachment of wetlands in the context of woody shrub encroachment of grassland biomes. In both cases, delimitation of woody shrubs at regional scales is set by temperature thresholds for poleward extent, and by aridity within temperature limits. Latitudinal expansion has been observed for terrestrial woody shrubs and mangroves, following recent warming, but most expansion and thickening has been due to the occupation of previously water-limited grassland/saltmarsh environments. Increases in atmospheric CO₂, may facilitate the recruitment of trees in terrestrial and wetland settings. Improved water relations, a mechanism that would predict higher soil moisture in grasslands and saltmarshes, and also an enhanced capacity to survive arid conditions, reinforces local mechanisms of change. The expansion of woody shrubs and mangroves provides a negative feedback on elevated atmospheric CO₂ by increasing carbon sequestration in grassland and saltmarsh, and is a significant carbon sink globally. These broad-scale vegetation shifts may represent a new stable state, reinforced by positive feedbacks between global change drivers and endogenic mechanisms of persistence in the landscape.
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2.
Comparison of three indirect calorimetry devices and three methods of gas collection: a prospective observational study.
Graf, S, Karsegard, VL, Viatte, V, Maisonneuve, N, Pichard, C, Genton, L
Clinical nutrition (Edinburgh, Scotland). 2013;(6):1067-72
Abstract
BACKGROUND & AIMS Indirect calorimetry was performed for a long time with the DeltatracII(®) device (Datex, Finland), considered as a reference but no longer produced. This study aims at comparing the energy expenditure (EE), the volume of oxygen (VO2) and carbon dioxide (VCO2) measured by two new available indirect calorimeters, the QuarkRMR(®) (Cosmed, Italy) and the CCMexpress(®) (MedGraphic,USA), using three different methods of gas collection, with the DeltatracII(®) in healthy subjects. METHODS Twenty-four healthy subjects (15 women and 9 men, age 53 ± 15 yrs, mean BMI 25.5 ± 7.1 kg/m(2)) underwent measurements of EE with DeltatracII(®) using canopy, QuarkRMR(®) using canopy and CCMexpress(®) using canopy, face tent and facemask. All measurements were performed for 10 min in random order. Results are presented as mean ± SD and compared by linear regression, repeated measure one-way ANOVA with Bonferroni's post hoc test and Bland & Altman test. RESULTS EE was 1630 ± 340 kcal for DeltatracII(®) and 1607 ± 307 kcal, 1741 ± 360 kcal, 1666 ± 315 and 1626 ± 336 kcal for QuarkRMR(®) and CCMexpress(®) with canopy, face tent and facemask, respectively (p = 0.001). Compared to DeltatracII(®), Bland & Altman test showed a mean EE difference (2SD) of 24(220)kcal for QuarkRMR(®), and -111(260) kcal, -36(304) kcal, 5(402) kcal for CCMexpress(®) with canopy, face tent and facemask, respectively. There was no systematic over- or underestimation with any device or gas collection method. CONCLUSION Mean EE was similar between QuarkRMR(®) and DeltatracII(®) but not between CCMexpress(®), in any mode of gas collection, and DeltatracII(®). Bland & Altman test shows a large variability in EE differences with both devices compared to DeltatracII(®), highlighting the need for refining their accuracy.
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3.
Determination of calcium salt solubility with changes in pH and P(CO(2)), simulating varying gastrointestinal environments.
Goss, SL, Lemons, KA, Kerstetter, JE, Bogner, RH
The Journal of pharmacy and pharmacology. 2007;(11):1485-92
Abstract
The amount of calcium available for absorption is dependent, in part, on its sustained solubility in the gastrointestinal (GI) tract. Many calcium salts, which are the calcium sources in supplements and food, have pH-dependent solubility and may have limited availability in the small intestine, the major site of absorption. The equilibrium solubility of four calcium salts (calcium oxalate hydrate, calcium citrate tetrahydrate, calcium phosphate, calcium glycerophosphate) were determined at controlled pH values (7.5, 6.0, 4.5 and < or = 3.0) and in distilled water. The solubility of calcium carbonate was also measured at pH 7.5, 6.0 and 4.5 with two CO(2) environments (0.3 and 152 mmHg) above the solution. The precipitation profile of CaCO(3) was calculated using in-vivo data for bicarbonate and pH from literature and equilibrium calculations. As pH increased, the solubility of each calcium salt increased. However, in distilled water each salt produced a different pH, affecting its solubility value. Although calcium citrate does have a higher solubility than CaCO(3) in water, there is little difference when the pH is controlled at pH 7.5. The partial pressure of CO(2) also played a role in calcium carbonate solubility, depressing the solubility at pH 7.5. The calculations of soluble calcium resulted in profiles of available calcium, which agreed with previously published in-vivo data on absorbed calcium. The experimental data illustrate the impact of pH and CO(2) on the solubility of many calcium salts in the presence of bicarbonate secretions in the intestine. Calculated profiles using in-vivo calcium and bicarbonate concentrations demonstrate that large calcium doses may not further increase intestinal calcium absorption once the calcium carbonate solubility product has been reached.
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4.
Survival strategies of plants during secondary growth: barrier properties of phellems and lenticels towards water, oxygen, and carbon dioxide.
Lendzian, KJ
Journal of experimental botany. 2006;(11):2535-46
Abstract
Ever since plants began to conquer the terrestrial environment, a simple but effective evolutionary strategy has been employed to cope with the combined necessities of preventing an excessive loss of water via the aerial surface while also supporting the vital exchange of CO(2) and O(2) for photosynthesis and respiration. Large areas of the primary above-ground surface of plants are covered by a hydrophobic, non-cellular cuticle which effectively minimizes evaporation and very strongly reduces exchange of CO(2) and O(2). Hence, gas exchange is controlled by regulating stomatal apertures. Upon wounding or entering into secondary growth, however, the epidermis, cuticle, and stomata are replaced by a phellem (cork), which is produced by a lateral cambium, the phellogen. Former stomata are replaced by lenticels, which are multicellular structures and functionally analogous to stomata. In the secondary plant body, phellems effectively prevent the loss of water from the cortex of the stem while lenticels support the exchange of vital gases such as CO(2), O(2), and water vapour. The permeance of these gases via the lenticels reaches a maximum during July and is minimal during autumn and winter. In contrast to stomatal control, gas exchange through phellems is regulated by long-term structural changes. The permeances of cuticles, phellems, and lenticels are compared and discussed.
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5.
Transcutaneous carbon dioxide monitoring during diabetic ketoacidosis in children and adolescents.
McBride, ME, Berkenbosch, JW, Tobias, JD
Paediatric anaesthesia. 2004;(2):167-71
Abstract
OBJECTIVE Our aim was to evaluate the utility of transcutaneous CO2 (TC-CO2) monitoring in following the response to therapy in children and adolescents in diabetic ketoacidosis (DKA) requiring ICU admission. METHODS During therapy for DKA, TC-CO2 was monitored and compared with the serum bicarbonate values (HCO3-). As clinically indicated, serum electrolytes including serum HCO3- were drawn and at the same time, the TC-CO2 value was recorded. Using the TC-CO2 value and the equation (PaCO2=1.5xHCO3-+8), a calculated HCO3- value was determined. The measured serum HCO3- value was subtracted from the calculated HCO3- value and the absolute difference was recorded. The difference between the measured serum HCO3- and the calculated HCO3- was analysed using analysis of variance after stratification for serum HCO3- values and patient age ranges. Calculated to serum HCO3- values were compared using linear regression analysis. In addition, serum HCO3- values were plotted against TC-CO2 values to derive an equation from these data which would relate the TC-CO2 values to the measured serum HCO3-. RESULTS The cohort included 28 patients ranging in age from 1.6 to 21 years (9.4 +/- 4.7 years) and in weight from 13 to 96 kg (35.6 +/- 18.2 kg). Two additional patients were not included as the initial TC-CO2 values were inaccurate because of tissue hypoperfusion. In the remaining 28 patients, the absolute difference between the calculated bicarbonate and serum bicarbonate values was 1.5 +/- 1.2 mmol.l-1. The difference was < or =2 mol.l in 74.4% of samples and < or=5 mmol.l(-1) in 99.2%. No difference in the value between the calculated and measured serum HCO3- was present according to serum HCO3- value or patient's age. Linear regression analysis of calculated HCO3- against serum HCO3- revealed a slope of 0.95 and an r2 value of 0.88. Linear regression analysis using serum HCO3- against TC-CO2 resulted in the following equations: TC-CO2=(1.64xHCO3-)+3.9 or HCO3-=0.61x(TC-CO2-3.9). CONCLUSIONS TC-CO2 correlates with serum HCO3- and can be used to follow therapy in children and adolescents in DKA.
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6.
The difference between intramural and arterial partial pressure of carbon dioxide increases significantly during laparoscopic cholecystectomy: the effect of thoracic epidural anesthesia.
Nandate, K, Ogata, M, Nishimura, M, Katsuki, T, Kusuda, S, Okamoto, K, Nagata, N, Shigematsu, A
Anesthesia and analgesia. 2003;(6):1818-1823
Abstract
UNLABELLED We studied the effects of pneumoperitoneum on gastric submucosal perfusion metabolism during elective laparoscopic cholecystectomy (LASC) by measuring the PCO(2) gap, defined as the difference between intramucosal PCO(2) and arterial PCO(2), using gas tonometry in 20 patients. Furthermore, we examined whether thoracic epidural anesthesia (TEA) affects gastric submucosal perfusion metabolism during LASC. Patients were randomly allocated to receive general anesthesia (group G, n = 10) or general anesthesia combined with TEA (group E, n = 10). In both groups, the PCO(2) gap increased significantly during pneumoperitoneum and remained at this level until the end of surgery compared with the baseline value. There were no significant differences in PCO(2) gap values between the two groups at any time sampled. These results suggested that pneumoperitoneum significantly impaired gastric submucosal perfusion and metabolism and that TEA did not attenuate the impairment of gastric submucosal perfusion during or after pneumoperitoneum. IMPLICATIONS We investigated the effect of pneumoperitoneum on gastric submucosal perfusion by measuring PCO(2) gap with the use of gas tonometry. PCO(2) gap significantly increased during and after the pneumoperitoneum compared with the control level. Thoracic epidural anesthesia did not attenuate this inhibition.
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7.
CO2 concentrating mechanisms in cyanobacteria: molecular components, their diversity and evolution.
Badger, MR, Price, GD
Journal of experimental botany. 2003;(383):609-22
Abstract
Cyanobacteria have evolved an extremely effective single-cell CO(2) concentrating mechanism (CCM). Recent molecular, biochemical and physiological studies have significantly extended current knowledge about the genes and protein components of this system and how they operate to elevate CO(2) around Rubisco during photosynthesis. The CCM components include at least four modes of active inorganic carbon uptake, including two bicarbonate transporters and two CO(2) uptake systems associated with the operation of specialized NDH-1 complexes. All these uptake systems serve to accumulate HCO(3)(-) in the cytosol of the cell, which is subsequently used by the Rubisco-containing carboxysome protein micro-compartment within the cell to elevate CO(2) around Rubisco. A specialized carbonic anhydrase is also generally present in this compartment. The recent availability of at least nine cyanobacterial genomes has made it possible to begin to undertake comparative genomics of the CCM in cyanobacteria. Analyses have revealed a number of surprising findings. Firstly, cyanobacteria have evolved two types of carboxysomes, correlated with the form of Rubisco present (Form 1A and 1B). Secondly, the two HCO(3)(-) and CO(2) transport systems are distributed variably, with some cyanobacteria (Prochlorococcus marinus species) appearing to lack CO(2) uptake systems entirely. Finally, there are multiple carbonic anhydrases in many cyanobacteria, but, surprisingly, several cyanobacterial genomes appear to lack any identifiable CA genes. A pathway for the evolution of CCM components is suggested.
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8.
Inactivation of bacteria and spores by pulse electric field and high pressure CO2 at low temperature.
Spilimbergo, S, Dehghani, F, Bertucco, A, Foster, NR
Biotechnology and bioengineering. 2003;(1):118-25
Abstract
The common methods for inactivation of bacteria involve heating or exposure to toxic chemicals. These methods are not suitable for heat-sensitive materials, food, and pharmaceutical products. Recently, a complete inactivation of many microorganisms was achieved with high-pressure carbon dioxide at ambient temperature and in the absence of organic solvent and irradiation. The inactivation of spores with CO(2) required long residence time and high temperatures, such as 60 degrees C. In this study the synergistic effect of pulsed electric field (PEF) in combination with high-pressure CO(2) for inactivation was investigated. The bacteria Escherichia coli, Staphylococcus aureus, and Bacillus cereus were suspended in glycerol solution and treated in the first step with PEF (up to 25 KV/cm) and then with high-pressure CO(2) not higher than 40 degrees C and 200 bar. The inactivation efficiency was determined by counting the colony formation units of control and sample. Samples of the cells subjected to PEF treatment alone and in combination with CO(2) treatment were examined by scanning electron microscopy to determine the effect of the processes on the cell wall. Experimental results indicate that the viability decreased with increasing electrical field strength and number of pulses. A further batch treatment with supercritical CO(2) lead to complete inactivation of bacterial species and decreased the count of the spores by at least three orders of magnitude, the inactivation being enhanced by an increase of contact time between CO(2) and the sample. A synergistic effect between the pulsed electric field and the high-pressure CO(2) was evident in all the species treated. The new low temperature process is an alternative for pasteurization of thermally labile compounds such as protein and plasma and minimizes denaturation of important nutrient compounds in the liquid media.
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9.
Effect of atorvastatin on chylomicron remnant metabolism in visceral obesity: a study employing a new stable isotope breath test.
Chan, DC, Watts, GF, Barrett, PH, Martins, IJ, James, AP, Mamo, JC, Mori, TA, Redgrave, TG
Journal of lipid research. 2002;(5):706-12
Abstract
Elevated plasma concentration of chylomicron remnants may be causally related to atherosclerosis in obesity. We examined the effect of atorvastatin on chylomicron remnant metabolism in 25 obese men with dyslipidaemia. A remnant-like emulsion labeled with cholesteryl [(13)C]oleate was injected intravenously into patients; the fractional catabolic rate (FCR) of the remnant-like emulsion was determined by measurement of (13)CO(2) in the breath and analyzed using compartmental modelling. Compared with placebo, atorvastatin significantly decreased the plasma concentrations of total cholesterol, triglycerides, LDL cholesterol, apolipoprotein B (apoB), and lathosterol (P < 0.001). ApoB-48 and remnant-like particle-cholesterol (RLP-C) both decreased significantly by 23% (P = 0.002) and 33% (P = 0.045), respectively. The FCR of the remnant-like emulsion increased significantly from 0.054 +/- 0.008 to 0.090 +/- 0.010 pools/h (P = 0.002). The decrease in RLP-C was associated with the decrease in plasma triglycerides (r = 0.750, P = 0.003). Furthermore, the change in FCR of remnant-like emulsions was inversely associated with the change in LDL-C (r = -0.575, P = 0.040), suggesting removal of LDL and chylomicron remnants by similar hepatic receptor pathways. We conclude that in obese subjects, inhibition of cholesterol synthesis with atorvastatin decreases the plasma concentrations of both LDL-C and triglyceride-rich remnants and that this may be partially due to an enhancement in hepatic clearance of these lipoproteins.
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10.
Changes in serum S100beta protein and Mini-Mental State Examination after cold (28 degrees C) and warm (34 degrees C) cardiopulmonary bypass using different blood gas strategies (alpha-stat and pH-stat).
Shaaban-Ali, M, Harmer, M, Vaughan, RS, Dunne, JA, Latto, IP, Haaverstad, R, Kulatilake, EN, Butchart, EG
Acta anaesthesiologica Scandinavica. 2002;(1):10-6
Abstract
BACKGROUND The effect of cardiopulmonary bypass temperature and blood gas management on the brain is still controversial. This study was designed to compare the changes in S100beta protein concentration and Mini-Mental State Examination in patients undergoing cold (28 degrees C) vs. warm (34 degrees C) cardiopulmonary bypass using different blood gas strategies (alpha-stat and pH-stat). METHODS Sixty patients were randomly allocated to one of four equal groups (cold alpha-stat, cold pH-stat, warm alpha-stat, warm pH-stat). Serum S100beta concentrations were measured before CPB, directly after CPB, at 4.5 h and at 24 h after CPB. Mini-Mental State Examination was performed one day before surgery and on day five after the operation. Antegrade warm blood cardioplegia (37 degrees C) was used in all patients. RESULTS There was no significant difference in postoperative S100beta protein levels between the four groups. Also, there was no interaction between bypass temperature and type of blood gas strategy on S100beta levels after bypass (directly after bypass, 4.5 h and 24 h after bypass). Mini-Mental State Examination score was not affected by blood gas strategy but it was significantly lower in patients undergoing cold cardiopulmonary bypass surgery: median (range), 26 (12-29) vs. 27 (23-30) in warm patients, P = 0.014. There was no significant correlation between Mini-Mental State Examination score 5 days after CPB and S100beta levels at any of the studied time-points after CPB. CONCLUSION These results support the use of warm CPB (34 degrees C) in patients undergoing coronary artery bypass surgery regardless of the type of blood gas strategy.