Gas Exchange Analysis Research Articles

Drought Stress Memory in Sugar Beet: Mismatch Between Biochemical and Physiological Parameters

In a greenhouse study, we aimed to determine whether a temporary water deficit induces ‘drought memory’ in sugar beet (Beta vulgaris L.), and whether this effect can be quantified by alterations in the fluorescence signature of the leaves. Plants were subjected to three consecutive water deficit phases, each followed by a recovery period, and in each cycle new, fully developed leaves were analyzed. Changes in the photosynthetic performance and pigment fluorescence were recorded with a hand-held fluorescence sensor, a laser-induced fluorescence spectrometer, and a leaf gas exchange analyzer. Parameters such as osmotic potential, proline, and chlorophyll content were used as indicators for biochemical modifications and quantification of stress intensity. In general, the evaluated cultivars showed a similar response pattern to water deficit, although the intensity of the stress-induced modification was not always on the same level in the distinct parameters. The long-term and repeated drought caused a decrease of net photosynthesis, increase of far-red fluorescence, and a decrease of both the ‘Simple Fluorescence Ratio’ and the fluorescence lifetime (LT mean) in the blue spectral region. In the second drought cycle, changes in osmotic potential and proline content were lower, but alterations in photosynthesis and fluorescence were as strong as in the first and third drought cycles. This indicates that even if a drought stress memory might occur, it was not possible to precisely identify it using gas exchange and pigment fluorescence determinations. Irrespective of that, the photosynthesis and chlorophyll fluorescence-based parameters (RF, SFR) clearly indicated with high temporal resolution the response of sugar beet plants to the stress, and their partial recovery.

0232: Recreational scuba diving in patients with congenital heart disease: proposal for guidelines

The number of people wishing to practice leisure scuba diving is constantly increasing. Currently, Congenital Heart Diseases (CHD) were so far considered contra-indications in the list edited by the Medical and Prevention Commission of the French Underwater Federation. However, due to the progress in their care, the number of living patients with CHD increase. Their quality of life has been also improved, allowing them to practice physical and sports activities the beneficial effect of which has been proven. Thus the question of fitness to dive is put forward. We thought necessary to reconsider the problem in order to define parameters to help in the decision to allow or not diving for these patients. Because of their diversity and of an important heterogeneousness even within a defined group of CHD, we tried to avoid drafting a boring catalog. Thus we propose for every patient a practical and precise evaluation of its capacity from clinical criteria and further common evaluation obtained during usual follow-up of these CHD. The practice of the scuba diving could be authorized according to the clinical and rhythmic status, echocardiographic parameters and physical fitness assessed by exercise testing with gas exchange analysis.

GAS EXCHANGE AND CHLOROPHYLL FLUORESCENCE OF CITRUS ROOTSTOCK VARIETIES UNDER SALT STRESS

ABSTRACT High salt concentration in water are common in Brazilian semirad region, being important to research alternatives for use this waters on crop, like use of tolerant genotypes to salinity. Thus, in order to evaluate the saline stress perception of citrus rootstocks varieties crop from gas exchange and fluorescence analysis, an experiment was realized in greenhouse at the Center for Science and Technology Agrifood, CCTA, of Federal University of Campina Grande, UFCG, Pombal, PB, Brazil. It was studied in a randomized block design with factorial scheme (2x4), two salinity levels (0.3 and 4.0 dSm-1) and four varieties of citrus rootstocks [1 -common Sunki mandarin (TSKC), 2 - Florida Rough lemon (LRF), 3 -Santa Cruz Rangpur lime (LCRSTC) and 4-Volkamer lemon (LVK)], with three replications. The citrus rootstocks varieties grown on hydroponic system and at 90 days after sowing the plants were evaluated by gas exchange and PSII fluorescence at 0, 24 and 48 hours after application of treatments to determine the times for the physiological establishment of salt stress. The first 48h under saline conditions promoted changes in gas exchange and PSII fluorescence in varieties TSKC, LRF and LCRSTC indicating the begin of physiological stress; the common ‘Sunki’ mandarin and the ‘Florida Rough’ lemon are the more sensitive genotypes to saline stress, in order hand the ‘Santa Cruz Rangpur’ lime and ‘Volkamer’ lemon are the genotypes more tolerant.

Abstract 19397: Factors Affecting Exercise Capacity in Diabetic Heart Failure Patients

Background: Exercise intolerance is a key feature of chronic heart failure (CHF). CHF patients with concomitant diabetes (CHF-DM) have heightened exercise intolerance, poorer prognosis and worse symptoms. Causative mechanisms may be impaired ventilatory, cardiac or skeletal muscle function. We prospectively assessed factors affecting exercise capacity in CHF and CHF-DM. Methods: Stable CHF (n=33) and CHF-DM (n=33) patients with left ventricular systolic dysfunction (ejection fraction (EF) <50%; NYHA class I-II; optimal device and medical therapy), were matched for age (mean±SD: 76±7 yr), weight (85±13 kg), height (1.72±0.06 m), systolic function (EF: 38±11%) and diastolic function (EA ratio 0.9±0.2). They underwent peak cardiopulmonary exercise testing with breath-by-breath pulmonary gas exchange analysis. Exertional shortness of breath (S) symptoms were recorded using the standardized Borg 0-10 scale. Continuous variables were reported as means (SD) and analysed using ANCOVA, categorical variables were analysed using the chi-squared test. A p-value of < 0.05 was taken as significant. Results: CHF-DM had reduced exercise capacity (pVO2 13.9±4.3 v 17.5±5.9 ml/kg/min; p=0.01) and lower exercise time (354±209 v 511±250s; p=0.01). Cardiac and ventilatory responses did not differ: Heart rate rise (44±5 v 46±4 bpm; p=0.21), Ve/VCO2 (37.2±9.4 v 39.5±10.5; p=0.35), peak respiratory frequency (31.7± 6.7 v 31.1± 7.6 breaths/min; p=0.76). Symptoms did not differ at baseline, peak or during exercise (Peak Borg S: 4±2 v 4±2; p= 0.73) The lactate threshold (LT) (9.86±0.27 v 11.26 ±0.32 L/min; p=0.48), time to LT (358 ± 92.58 v 393 ± 203.94 s; p=0.22) and the respiratory compensation point (RCP) (12.77±0.37 v 14.37± 0.45 L/min; p=0.64) did not differ. Conclusion: Exercise capacity is reduced in CHF-DM subjects matched for age, BMI and cardiac function. There are no differences in symptoms of breathlessness, Ve/VCO2 slope or respiratory rate. However, LT and time to LT is unchanged, despite lower exercise time overall. Thus, there is an inability to tolerate exercise beyond the LT. This is likely due to altered skeletal mitochondrial function in the context of concomitant diabetes.

Abstract 13099: Study of Right Ventricular to Pulmonary Circulation Uncoupling at Peak Exercise in Heart Failure by gas Exchange Analysis Combined to Echocardiography

Background: Right ventricular (RV) dysfunction and pulmonary hypertension (PH) impact on clinical status and have a prognostic value in heart (HF) patients. There is interest in assessment the RV to pulmonary circulation (PC) uncoupling during exercise even though much needs to be defined on the functional phenotypes. Aim: to define how the degrees of RV-PC uncoupling may engender specific functional phenotypes. Methods: 94 HFrEF patients (mean age 66±11 y, male 70%, ischemic etiology 71%, mean LVEF 34±9%) underwent a maximal CPET (incremental ramp protocol) combined with exercise-echo. Results: Population was divided into 4 groups using the 4 quadrant approach (Figure) based on TAPSE vs systolic PAP (PASP) relationship as a length vs developed force of the RV during exercise (cutoff based on median values of 20 mm and 57 mmHg). At peak exercise patients with more favorable TAPSE vs PASP relationship (group A) showed the better functional CPET response (higher peak VO2; lower VE/VCO2 slope and prevalence of exercise oscillatory ventilation (EOV), p= 0.000, 0.005 and 0.000). Group B and C showed similar peak VO2 and the occurrence of dynamic PH (group C) was related to dynamic mitral regurgitation (MR) and high rate of EOV (B vs C p=0.001 and 0.000). Interestingly, for similar exercise tolerance and LV function parameters, group D patients had more severely impaired ventilatory efficiency associated with very high prevalence of rest severe (MR) and EOV (p=0.005, 0.002). Conclusions: This proposed non-invasive RV functional evaluation approach at peak exercise seems appealing for stageing HF syndrome severity based on the degree of the right heart dysfunction. It appears also useful to unmask different ventilatory phenotypes irrespective of a similar impairment in functional capacity and peak VO2.

Polysomnographic Markers in Children With Cystic Fibrosis Lung Disease.

Children with cystic fibrosis (CF) often report poor sleep, increased daytime sleepiness, and fatigue. The purpose of this study was to identify respiratory patterns over the spectrum of disease severity in children with CF. The overall hypothesis for the current study is that children with CF compared with snoring control subjects demonstrate gas exchange abnormalities and increased respiratory loads during sleep that are not reported or recognized by conventional polysomnography (PSG). Analysis of breathing patterns and gas exchange on PSG was performed in children with CF and healthy controls matched by age and BMI. For all CF and control subjects, the indication for PSG was evaluation for obstructive sleep apnea based on a history of snoring. Children with CF, compared with age- and BMI-matched snoring controls, demonstrated lower oxyhemoglobin saturation (95% ± 1.6% vs 98% ± 0.6%, P = .005), higher respiratory rate (19.5 ± 4.9 vs 16.5 ± 1.2 breaths per minute, P = .03), and a higher proportion of inspiratory flow limitation (44.1% ± 24.7% vs 12.1% ± 13.5%, P = .007) during non-rapid eye movement sleep. The respiratory disturbance index did not differ between CF and snoring control groups (1.5 ± 2.7 vs 0.6 ± 0.6 events per hour, P = .11). Children with CF exhibited abnormalities in gas exchange and increased respiratory load during sleep compared with normal age- and BMI-matched snoring controls. Because these abnormalities were independent of weight and lung function, sleep state may serve as an opportunity for early detection of breathing abnormalities and possibly CF lung disease progression.

DNA microarray revealed and RNAi plants confirmed key genes conferring low Cd accumulation in barley grains.

BackgroundUnderstanding the mechanism of low Cd accumulation in crops is crucial for sustainable safe food production in Cd-contaminated soils.ResultsConfocal microscopy, atomic absorption spectrometry, gas exchange and chlorophyll fluorescence analyses revealed a distinct difference in Cd accumulation and tolerance between the two contrasting barley genotypes: W6nk2 (a low-grain-Cd-accumulating and Cd-sensitive genotype) and Zhenong8 (a high-grain-Cd-accumulating and tolerant genotype). A DNA microarray analysis detected large-scale changes of gene expression in response to Cd stress with a substantial difference between the two genotypes. Cd stress led to higher expression of genes involved in transport, carbohydrate metabolism and signal transduction in the low-grain-Cd-accumulating genotype. Novel transporter genes such as zinc transporter genes were identified as being associated with low Cd accumulation. Quantitative RT-PCR confirmed our microarray data. Furthermore, suppression of the zinc transporter genes HvZIP3 and HvZIP8 by RNAi silencing showed increased Cd accumulation and reduced Zn and Mn concentrations in barley grains. Thus, HvZIP3 and HvZIP8 could be candidate genes related to low-grain-Cd-accumulation.ConclusionNovel transporter genes such as HvZIP3 and HvZIP8 were identified as being associated with low-grain-Cd-accumulation. In addition to advancing academic knowledge, our findings may also result in potential economic benefits for molecular breeding of low Cd accumulating barley and other crops.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0648-5) contains supplementary material, which is available to authorized users.

Effect of thinning on partitioned soil respiration in a young Pinus tabulaeformis plantation during growing season

Understanding soil respiration (Rs) response to thinning is an important component of our understanding of belowground carbon (C) dynamics and evaluating effects of forest management on C cycling. Therefore, we partitioned Rs into heterotrophic respiration (Rh) and autotrophic respiration (Ra) using trenched plots in a 20 year-old Pinus tabulaeformis plantation, subjected to varying thinning intensities, in Shanxi Province, China. Soil respiration was measured using an infrared gas exchange analyzer in untrenched and trenched plots. Rates of soil respiration were measured twice a month from May to October in 2011 and 2012, while soil temperature and moisture were obtained using temperature and moisture probes and data loggers. Rs was measured in untrenched plots and Rh in trenched plots. Mean Rs and Rh values were significantly greater in stands subjected to heavy thinning (HT) (Rs=2.79μmol CO2 m−2s−1, Rh=2.24μmol CO2 m−2s−1) than in the control (CK) (Rs=2.29μmol CO2 m−2s−1, Rh=1.81μmol CO2 m−2s−1) and low thinned stand (LT) (Rs=2.48μmol CO2 m−2s−1, Rh=1.80μmol CO2 m−2s−1). The mean Ra was greater in the thinned stands (Ra=0.69, 0.58, 0.55μmol CO2 m−2s−1 in LT, moderate thinned stand (MT) and HT) than CK (Ra=0.48μmol CO2 m−2s−1), possibly the result of increased productivity and root growth in thinned stands. The relative proportion of Rh to Rs averaged 71.6–79.7% over the four thinned stands. Temperature sensitivity (Q10) values of Rh ranged from 2.16 to 2.75 in the various thinning intensities, with the highest Q10 value in the control stand. Temperature sensitivity of Ra was also affected by thinning ranging from 1.34 to 1.84. The model with the best fitted temperature and moisture factors explained 66.7–77.3% of the variation in Rh and 30.2–46.4% in Ra among the four thinned stands during two growing seasons.

CEREBRAL OXYGENATION-PERFUSION AND CARDIAC HEMODYNAMICS DURING EXERCISE AND RECOVERY IN PATIENTS WITH TYPE 2 DIABETES ACCORDING TO THEIR FITNESS STATUS

CEREBRAL OXYGENATION-PERFUSION AND CARDIAC HEMODYNAMICS DURING EXERCISE AND RECOVERY IN PATIENTS WITH TYPE 2 DIABETES ACCORDING TO THEIR FITNESS STATUS

HIGH-INTENSITY INTERVAL EXERCISE IN CHRONIC HEART FAILURE: COMPARISON OF CARBOHYDRATE AND LIPID OXIDATION

high-intensity interval exercise has been extensively used with athletes and healthy subjects. There are a few evidences that it could improves physiology and functional capacity in heart failure patients, but still some answers about muscle metabolism need to be addressed. substrate oxidation was compared during 4 different high intensity intermittent exercise (HIIE) protocols in patients with heart failure and reduced ejection fraction (HFREF). Eighteen males (56±17 years, LVEF: 28±7%) randomly performed 4 HIIE with measurement of gas exchange. Exercise intensity protocols were set at 100% of peak power output (PPO). Interval duration was 30 seconds (A and B) or 90 seconds (C and D), and recovery was passive (A and C) or active (50% of PPO in B and D). Energy expenditure was calculated using Weir equation and substrate oxidation (glucose: CHO, and lipid) was calculated by the Frayn equation (for quantitative measure) and from a table of non-protein respiratory quotient (qualitative measure) using gas exchange analysis. mean O2peak was 17.8 ± 4.6 ml/min/kg (or 1.54 ± 4.6 L/min) and peak power output was 109 ± 31 Watts. At rest, fat oxidation averaged 0.13 ± 0.04 g/min, representing 68 ± 22 % of total substrate utilisation. CHO oxidation averaged 0.16 ± 0.1 g/min representing 31 ± 22% of total. During exercise, absolute CHO oxidation significantly decreased and absolute lipid oxidation significantly increased in each HIIE protocol (P<0.0001). Protocol B induced higher energy expenditure after 8-10 minutes of exercise compare to passive recovery modes (A and C) (P<0.0001). Short duration intervals with passive recovery (mode A) resulted in significantly lower CHO oxidation in absolute terms compare to modes with active recovery (B and D) (P<0.0001). In relative terms (%), CHO oxidation in mode A was significantly lower than mode C only, after 8-10 minutes of exercise. Lipid oxidation in absolute terms was significantly lower in mode C compare to the other 3 modes of HIIE at time 8-10 min whereas in relative terms it was significantly lower than mode A only (P<0.0001). All together, these 4 HIIE protocols showed increased lipid oxidation over time, and short interval duration with passive recovery showed higher lipid oxidation compared to the others. the choice of an active mode during HIIE may favors glucose oxidation during exercise in patients with HFREF, if the improvement of glucose metabolism is targeted.

How well do you know your growth chambers? Testing for chamber effect using plant traits.

BackgroundPlant growth chambers provide a controlled environment to analyse the effects of environmental parameters (light, temperature, atmospheric gas composition etc.) on plant function. However, it has been shown that a ‘chamber effect’ may exist whereby results observed are not due to an experimental treatment but to inconspicuous differences in supposedly identical chambers. In this study, Vicia faba L. ‘Aquadulce Claudia’ (broad bean) plants were grown in eight walk-in chambers to establish if a chamber effect existed, and if so, what plant traits are best for detecting such an effect. A range of techniques were used to measure differences between chamber plants, including chlorophyll fluorescence measurements, gas exchange analysis, biomass, reproductive yield, anatomical traits and leaf stable carbon isotopes.Results and discussionFour of the eight chambers exhibited a chamber effect. In particular, we identified two types of chamber effect which we term ‘resolvable’ or ‘unresolved’; a resolvable chamber effect is caused by malfunctioning components of a chamber and an unresolved chamber effect is caused by unknown factors that can only be mitigated by appropriate experimental design and sufficient replication. Not all measured plant traits were able to detect a chamber effect and no single trait was capable of detecting all chamber effects. Fresh weight and flower count detected a chamber effect in three chambers, stable carbon isotopes (δ13C) and net rate CO2 assimilation (An) identified a chamber effect in two chambers, stomatal conductance (gs) and total performance index detected an effect only in one chamber.Conclusion(1) Chamber effects can be adequately detected by fresh weight measurements and flower counts on Vicia faba plants. These methods were the most effective in terms of detection and most efficient in terms of time. (2) δ13C, gs and An measurements help distinguish between resolvable and unresolved chamber effects. (3) Unresolved chamber effects require experimental unit replication while resolvable chamber effects require investigation, repair and retesting in advance of initiating further experiments.

Leaf gas exchange and multiple enzymatic and non-enzymatic antioxidant strategies related to drought tolerance in two oil palm hybrids

The drought tolerance in young oil palm plants is related to greater efficiency in preventing oxidative damage by activating enzymatic and non-enzymatic antioxidant strategies simultaneously. Drought is a major environmental constraint limiting growth and yield of oil palm trees. In this study, two oil palm hybrids (BRS Manicore and BRS C 2501) were grown in large containers and subjected to a water deficit during 57 days. Leaf gas exchange analysis was combined with an in-depth assessment of the antioxidant system over the drought imposition. Under drought, leaf water potential at predawn (Ψ pd) decreased similarly in both hybrids. In parallel, there were decreases in the net CO2 assimilation rate (A), chlorophyll concentrations and Rubisco total activity. Overall, these decreases were more pronounced in BRS C 2501 than in BRS Manicore. BRS C 2501 plants triggered more markedly its enzymatic antioxidant system earlier (Ψ pd = −2.1 MPa) than did BRS Manicore, but these responses were accompanied by higher concentrations of H2O2 and malondialdehyde in BRS C 2510 than in BRS Manicore. With the progress of drought stress (Ψ pd = −2.9 MPa and below), BRS Manicore was better able to cope with oxidative stress through a more robust antioxidant system. In addition, significant decreases in drought-induced NAD+-malate dehydrogenase activities were only observed in stressed BRS C 2501 plants. Regardless of watering regimes, the total carotenoid, ascorbate and glutathione concentrations were higher in BRS Manicore than in BRS C 2501. In conclusion, BRS Manicore is better able to tolerate drought than BRS C 2501 by triggering multiple antioxidant strategies involved both in reactive oxygen species scavenging and dissipation of excess energy and/or reducing equivalents particularly under severe drought stress.

Serum testosterone predicts cardiorespiratory fitness impairment in normal-weight women with polycystic ovary syndrome.

Limited literature has shown that maximal oxygen consumption (V'O2max), that is the maximal capacity of an individual to perform aerobic work, may be lowered in overweight/obese women with polycystic ovary syndrome (PCOS). However, it remains unclear whether this impairment is associated with PCOS per se or is entirely due to body fat excess. Our objective was to assess whether cardiorespiratory fitness is altered in normal-weight PCOS women and to investigate which factors are associated with this phenomenon. Fifteen normal-weight PCOS women and 15 age- and BMI-matched healthy controls. Fourteen subjects in each group completed the protocol. V'O2max and ventilatory thresholds (maximal incremental cycle ergometer test with breath-by-breath analysis of gas exchange), insulin sensitivity (hyperinsulinaemic euglycaemic clamp) and androgenaemia (serum total and free testosterone, measured by liquid chromatography mass spectrometry and equilibrium dialysis) were accurately assessed. Maximal V'O2 and power were strikingly impaired in normal-weight PCOS individuals, as compared with healthy controls (29·4 ± 1·5 vs 35·8 ± 1·6 ml O2/kg/min, P = 0·008; 138 ± 6 vs 170 ± 10 W, P = 0·011, respectively). Similarly, oxygen consumption and power at both the first and second ventilatory thresholds were significantly lower in PCOS subjects than in healthy women. In multiple regression analysis, V'O2max was negatively predicted by serum-free testosterone levels, but not by body fat mass and glucose disposal rate (R(2) = 0·45 P = 0·013). Cardiorespiratory fitness is impaired in normal-weight PCOS women. Androgen excess but not insulin sensitivity is associated with this alteration.

Cerebral Hemodynamics During Exercise and Recovery in Heart Transplant Recipients

BackgroundThe aims of this work were (1) to compare cerebral oxygenation-perfusion (COP), central hemodynamics, and peak oxygen uptake (V˙o2peak) in heart transplant recipients (HTRs) vs age-matched healthy controls (AMHCs) during exercise and recovery and (2) to study the relationships between COP, central hemodynamics, and V˙o2peak in HTRs and AMHCs. MethodsTwenty-six HTRs (3 women) and 27 AMHCs (5 women) were recruited. Maximal cardiopulmonary function (gas exchange analysis), cardiac hemodynamics (impedance cardiography), and left frontal COP (near-infrared spectroscopy) were measured continuously during and after a maximal ergocycle (Ergoline 800S, Bitz, Germany) test. ResultsCompared with AMHCs, HTRs had lower V˙o2peak, maximal cardiac index (CImax), and maximal ventilatory variables (P < 0.05). COP was lower during exercise (oxyhemoglobin [ΔO2Hb], 50% and 75% of V˙O2peak, total hemoglobin [ΔtHb], 100% of V˙O2peak; P < 0.05), and recovery in HTRs (ΔO2Hb, minutes 2-5; ΔtHb, minutes 1-5; P < 0.05) compared with AMHCs. End-tidal pressure of CO2 was lower during exercise compared with that in AMHCs (P < 0.0001). In HTRs, CImax was positively correlated with exercise cerebral hemodynamics (R = 0.54-0.60; P < 0.01). ConclusionsIn HTRs, COP was reduced during exercise and recovery compared with that in AMHCs, potentially because of a combination of blunted cerebral vasodilation by CO2, cerebrovascular dysfunction, reduced cardiac function, and medication. The impaired V˙O2peak observed in HTRs was mainly caused by reduced maximal ventilation and CI. In HTRs, COP is impaired and is correlated with cardiac function, potentially impacting cognitive function. Therefore, we need to study which interventions (eg, exercise training) are most effective for improving or normalizing (or both) COP during and after exercise in HTRs.

Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2 - and ABA-induced stomatal closing.

Stomata mediate gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2 ]. [CO2 ] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed. We have generated transgenic Arabidopsis plants that are chlorophyll-deficient in guard cells only, expressing a constitutively active chlorophyllase in a guard cell specific enhancer trap line. Our data show that more than 90% of guard cells were chlorophyll-deficient. Interestingly, approximately 45% of stomata had an unusual, previously not-described, morphology of thin-shaped chlorophyll-less stomata. Nevertheless, stomatal size, stomatal index, plant morphology, and whole-leaf photosynthetic parameters (PSII, qP, qN, FV '/FM' ) were comparable with wild-type plants. Time-resolved intact leaf gas-exchange analyses showed a reduction in stomatal conductance and CO2 -assimilation rates of the transgenic plants. Normalization of CO2 responses showed that stomata of transgenic plants respond to [CO2 ] shifts. Detailed stomatal aperture measurements of normal kidney-shaped stomata, which lack chlorophyll, showed stomatal closing responses to [CO2 ] elevation and abscisic acid (ABA), while thin-shaped stomata were continuously closed. Our present findings show that stomatal movement responses to [CO2 ] and ABA are functional in guard cells that lack chlorophyll. These data suggest that guard cell CO2 and ABA signal transduction are not directly modulated by guard cell photosynthesis/electron transport. Moreover, the finding that chlorophyll-less stomata cause a 'deflated' thin-shaped phenotype, suggests that photosynthesis in guard cells is critical for energization and guard cell turgor production.

A method to identify early-stage transgenic Medicago truncatula with improved physiological response to water deficit

Phenotypic screening after transformation experiments aiming to identify lines with the enhanced/desired trait is still a time consuming process for most agricultural crops, especially when dealing with complex physiological responses such as water deficit. In this study we evaluated the suitability of non-destructive leaf gas-exchange analysis and imaging-PAM chlorophyll a fluorescence to select transgenic lines of Medicago truncatula expressing the Trehalose-6-Phosphate Synthase 1 (AtTPS1) from Arabidopsis thaliana with altered response to water deficit (WD) and WD recovery (WDR) in the early stages of the transformation process (T0). Primary transformants (T0) with different expression levels of a constitutive AtTPS1 construct were used. Additionally, we evaluated if the expression of the transgene could be correlated with the phenotype assessed. Among tested techniques and parameters measured, the net carbon assimilation (A) from gas-exchange analysis was the best parameter to early detect lines with WD and WDR improved performance, at the earliest stages of the transformation process. With this multidisciplinary approach, we selected 3 transgenic lines TPS7, TPS10 and TPS16 for further studies, which have higher or intermediate expression levels of the transgene and improved response to WD and WDR. This work will contribute to speed-up the identification of elite lines with confidence within a large number of individuals, thus reducing time, cost and labor associated with this plant improvement strategy.

Obtaining a formula that improves maximum oxygen consumption estimation in cycle ergometer exercise tests

To evaluate if the estimation of the maximal oxygen consumption (MO2C) in METs (metabolic equivalents) by means of the table proposed in the guidelines of the Spanish Society of Cardiology is a sufficiently reliable method when applied to the bicycle exercise test. The MO2C in METs was obtained by gas-exchange analysis on bicycle ergometer tests in 97 healthy subjects (group i). It was compared with the estimate of METs using the table in which only watts and patient's weight were included. A better-adjusted formula was validated in 289 subjects with normal exercise myocardial perfusion gated-SPECT (group ii) using the introduction of clinical and ergometric variables. In group i individuals a good correlation between METs estimated with the table and those obtained through gas-exchange analysis (CCI: 0.93) was observed. However, the best adjusted formula to estimate METs in group ii subjects included watts, body mass index (BMI), age and gender (METS=11.820-0.054×age-0.189×BMI+1.031×gender+0.020×watts) (women: 0, men: 1). This formula allowed the reclassification of 46.9% of group ii subjects into the category <5METs versus the estimation by table. Estimating the METs with the conventional table is reliable. However, the best adjustment in subjects with normal bicycle exercise SPECT was obtained when, in addition to watts and BMI, age and gender were also considered.

Facemask versus Mouthpiece for Gas Exchange Analysis

Facemask versus Mouthpiece for Gas Exchange Analysis

Obtaining a formula that improves maximum oxygen consumption estimation in cycle ergometer exercise tests

ObjectivesTo evaluate if the estimation of the maximal oxygen consumption (MO2C) in METs (metabolic equivalents) by means of the table proposed in the guidelines of the Spanish Society of Cardiology is a sufficiently reliable method when applied to the bicycle exercise test. Material and methodsThe MO2C in METs was obtained by gas-exchange analysis on bicycle ergometer tests in 97 healthy subjects (group I). It was compared with the estimate of METs using the table in which only watts and patient's weight were included. A better-adjusted formula was validated in 289 subjects with normal exercise myocardial perfusion gated-SPECT (group II) using the introduction of clinical and ergometric variables. ResultsIn group I individuals a good correlation between METs estimated with the table and those obtained through gas-exchange analysis (CCI: 0.93) was observed. However, the best adjusted formula to estimate METs in group II subjects included watts, body mass index (BMI), age and gender (METS=11.820−0.054×age−0.189×BMI+1.031×gender+0.020×watts) (women: 0, men: 1). This formula allowed the reclassification of 46.9% of group ii subjects into the category <5METs versus the estimation by table. ConclusionsEstimating the METs with the conventional table is reliable. However, the best adjustment in subjects with normal bicycle exercise SPECT was obtained when, in addition to watts and BMI, age and gender were also considered.

Reduced fitness and abnormal cardiopulmonary responses to maximal exercise testing in children and young adults with sickle cell anemia.

Physiologic contributors to reduced exercise capacity in individuals with sickle cell anemia (SCA) are not well understood. The objective of this study was to characterize the cardiopulmonary response to maximal cardiopulmonary exercise testing (CPET) and determine factors associated with reduced exercise capacity among children and young adults with SCA. A cross-sectional cohort of 60 children and young adults (mean 15.1 ± 3.4 years) with hemoglobin SS or S/β0 thalassemia and 30 matched controls (mean 14.6 ± 3.5 years) without SCA or sickle cell trait underwent maximal CPET by a graded, symptom-limited cycle ergometry protocol with breath-by-breath, gas exchange analysis. Compared to controls without SCA, subjects with SCA demonstrated significantly lower peak VO2 (26.9 ± 6.9 vs. 37.0 ± 9.2 mL/kg/min, P < 0.001). Subjects demonstrated slower oxygen uptake (ΔVO2/ΔWR, 9 ± 2 vs. 12 ± 2 mL/min/watt, P < 0.001) and lower oxygen pulse (ΔVO2/ΔHR, 12 ± 4 vs. 20 ± 7 mL/beat, P < 0.001) as well as reduced oxygen uptake efficiency (ΔVE/ΔVO2, 42 ± 8 vs. 32 ± 5, P < 0.001) and ventilation efficiency (ΔVE/ΔVCO2, 30.3 ± 3.7 vs. 27.3 ± 2.5, P < 0.001) during CPET. Peak VO2 remained significantly lower in subjects with SCA after adjusting for age, sex, body mass index (BMI), and hemoglobin, which were independent predictors of peak VO2 for subjects with SCA. In the largest study to date using maximal CPET in SCA, we demonstrate that children and young adults with SCA have reduced exercise capacity attributable to factors independent of anemia. Complex derangements in gas exchange and oxygen uptake during maximal exercise are common in this population.