Changes in pCO<Subscript>2</Subscript>, Symptoms,and Lung Function of Asthma Patients During Capnometry-assisted Breathing Training

In a recent pilot study with asthma patients we demonstrated beneficial outcomes of a breathing training using capnometry biofeedback and paced breathing assistance to increase pCO₂ levels and reduce hyperventilation. Here we explored the time course changes in pCO₂, respiration rate, symptoms and lung function across treatment weeks, in order to determine how long training needs to continue. We analyzed in eight asthma patients whether gains in pCO₂ and reductions in respiration rate achieved in home exercises with paced breathing tapes followed a linear trend across the 4-week treatment period. We also explored the extent to which gains at home were manifest in weekly training sessions in the clinic, in terms of improvement in symptoms and spirometric lung function. The increases in pCO₂ and respiration rate were linear across treatment weeks for home exercises. Similar increases were seen for in-session measurements, together with gradual decreases in symptoms from week to week. Basal lung function remained stable throughout treatment. With our current protocol of paced breathing and capnometry-assisted biofeedback at least 4 weeks are needed to achieve a normalization of pCO₂ levels and reduction in symptoms in asthma patients.     

Effect of elevated atmospheric CO2 concentration on soil and root respiration in winter wheat by using a respiration partitioning chamber

Soil respiration in a cropland is the sum of heterotrophic (mainly microorganisms) and autotrophic (root) respiration. The contribution of both these types to soil respiration needs to be understood to evaluate the effects of environmental change on soil carbon cycling and sequestration. In this paper, the effects of free-air CO₂ enrichment (FACE) on hetero- and autotrophic respiration in a wheat field were differentiated and evaluated by a novel split-root growth and gas collection system. Elevated atmospheric pCO₂ of approximately 200 μmol mol⁻¹ above the ambient pCO₂ significantly increased soil respiration by 15.1 and 14.8% at high nitrogen (HN) and low nitrogen (LN) application rates, respectively. The effect of elevated atmospheric pCO₂ on root respiration was not consistent across the wheat growth stages. Elevated pCO₂ significantly increased and decreased root respiration at the booting-heading stage (middle stage) and the late-filling stage (late stage), respectively, in HN and LN treatments; however, no significant effect was found at the jointing stage (early stage). Thus, the effect of increased pCO₂ on cumulative root respiration for the entire wheat growing season was not significant. Cumulative root respiration accounted for approximately 25–30% of cumulative soil respiration in the entire wheat growing season. Consequently, cumulative microbial respiration (soil respiration minus root respiration) increased by 22.5 and 21.1% due to elevated pCO₂ in HN and LN, respectively. High nitrogen application significantly increased root respiration at the late stage under both elevated pCO₂ and ambient pCO₂; however, no significant effects were found on cumulative soil respiration, root respiration, and microbial respiration. These findings suggest that heterotrophic respiration, which is influenced by increased substrate supplies from the plant to the soil, is the key process to determine C emission from agro-ecosystems with regard to future scenarios of enriched pCO₂.     

哮喘患儿呼出气一氧化氮、1,25-二羟维生素D3及儿童哮喘控制测试评分与肺功能的相关性

目的:探讨哮喘患儿呼出气一氧化氮(FeNO)、1,25-二羟维生素D_3[1,25(OH)_2D_3]及儿童哮喘控制测试(C-ACT)评分与肺功能的相关性。方法:选取2017年6月～2018年6月在我院就诊的86例哮喘患儿作为观察组,另选取同期于我院进行健康检查的86例健康儿童作为对照组。比较两组受试儿童1,25(OH)_2D_3浓度、FeNO、一秒用力呼气容积(FEV1)、呼气流量峰值(PEF)水平,比较不同病情哮喘患儿1,25(OH)_2D_3浓度、FeNO、C-ACT、FEV1、PEF水平,并分析哮喘患儿1,25(OH)_2D_3、FeNO、C-ACT与肺功能的相关性。结果:观察组1,25(OH)_2D_3浓度、FEV1、PEF水平低于对照组(P0.05),FeNO水平高于对照组(P0.05);随着病情加重,1,25(OH)_2D_3浓度、PEF、FEV1水平、C-ACT评分均逐渐下降,FeNO水平逐渐升高,不同病情患儿间比较差异均有统计学意义(P0.05)。哮喘患儿1,25(OH)_2D_3与FEV1、PEF呈正相关(r=0.912、0.873,P=0.006、0.008);C-ACT与FEV1、PEF呈正相关(r=0.472、0.366,P=0.036、0.032);FeNO与FEV1、PEF无相关(r=-0.035、-0.124,P=0.075、0.064)。结论:哮喘患儿1,25(OH)_2D_3浓度、C-ACT评分明显降低,FeNO水平明显升高,1,25(OH)_2D_3、C-ACT评分与肺功能呈正相关,但FeNO与肺功能无相关,C-ACT可用于哮喘患儿病情的预测,同时,通过提高患儿体内1,25(OH)_2D_3浓度可以改善其肺功能。     

Hypoventilation Training for Asthma: A Case Illustration

Hyperventilation-induced hypocapnia is common among asthma patients. This case study illustrates both methodology and results from a patient undergoing training in capnometry-assisted respiratory training (CART). CART is a 4-week training aimed at normalizing basal and acute levels of end-tidal carbon dioxide (PCO₂) using a portable capnometer. In the presented case, basal levels of PCO₂ increased from hypocapnic to normocapnic range over the course of treatment. Improvements were accompanied by improvements in lung function and reductions in diurnal lung function variability. Improvements remained stable throughout follow-up.     

Atlantic cod actively avoid CO<Subscript>2</Subscript> and predator odour,even after long-term CO<Subscript>2</Subscript> exposure

Introduction

The rising atmospheric CO₂ level is continuously driving the dissolution of more CO₂ into the oceans, and some emission scenarios project that the surface waters may reach 1000 μatm by the end of the century. It is not known if fish can detect moderately elevated CO₂ levels, and if they avoid areas with high CO₂. If so, avoidance behaviour to water with high CO₂ could affect movement patterns and migrations of fish in the future. It is also being increasingly recognized that fish behaviour can be altered by exposure to CO₂. Therefore this study investigated how long-term exposure to elevated pCO₂ affects predator avoidance and CO₂ avoidance in juvenile Atlantic cod (Gadus morhua). The fish were exposed to control water or CO₂-enriched water (1000 μatm) for six weeks before being subjected to tests of behaviour.

Results

Despite long term exposure to elevated pCO₂ the cod still strongly avoided the smell of a predator. These data are surprising because several coral reef fish have demonstrated reversal of olfactory responses after CO₂ exposure, turning avoidance of predator cues into preference for predator cues. Fish from both treatment groups also demonstrated strong avoidance of CO₂ when presented with the choice of control or CO₂-acidified water, indicating that habituation to the CO₂ sensory stimuli is negligible.

Conclusions

As Atlantic cod maintained normal behavioural responses to olfactory cues, they may be tolerant to CO₂-induced behavioural changes. The results also suggest that despite the long-term exposure to CO₂-acidified water, the fish still preferred the control water over CO₂-acidified water. Therefore, in the future, fish may alter their movements and migrations in search of waters with a lower CO₂ content.

     

Alteration of the Circadian Rhythm in Peak Expiratory Flow of Nocturnal Asthma Following Nighttime Transdermal β2‐adrenoceptor Agonist Tulobuterol Chronotherapy

We investigated the efficacy of nighttime transdermal tulobuterol (β₂‐adrenoceptor agonist) chronotherapy for nocturnal asthma by assessing changes both in the frequency of symptoms and features of the circadian rhythm in peak expiratory flow (PEF), a measure of airway caliber. Thirteen patients with nocturnal asthma were evaluated before and during tulobuterol patch chronotherapy, applied once daily in the evening for 6 consecutive days. Patients were asked to record their PEF every 4 h between 03:00 and 23:00 h for one day. Circadian rhythms in PEF were examined by group‐mean cosinor analysis. The group average PEF at 03:00 h, the time during the 24 h when PEF is generally the poorest, before the application of the chronotherapy, when asthma was unstable and nocturnal symptoms frequent, was 276±45 L/min. Application of the tulobuterol patch at nighttime significantly increased (p<0.001) the 03:00 h group average PEF to 363±67 L/min. Significant circadian rhythms in PEF were observed during the span of study when nocturnal symptoms were frequent as well as with the use of the tulobuterol patch. Before the initiation of tulobuterol chronotherapy, the bathyphase (trough time of the circadian rhythm) in PEF narrowed to around 04:00 h, and the group circadian amplitude was 28.8 L/min. In contrast, the group circadian amplitude significantly (p<0.01) decreased to 10.4 L/min, and the 24 h mean PEF increased significantly with tulobuterol patch chronotherapy. These changes indicate that tulobuterol chronotherapy significantly increased both the level and stability of airway function over the 24 h. The circadian rhythm in PEF varied with the severity and frequency of asthmatic symptoms with and without the nighttime application of the tulobuterol patch medication. We conclude that the parameters of the circadian rhythm of PEF proved useful both in determining the need for and effectiveness of tulobuterol chronotherapy for nocturnal asthma.     

Soil pCO2, soil respiration,and root activity in CO2-fumigated and nitrogen-fertilized ponderosa pine

The purpose of this paper is to describe the effects of CO₂ and N treatments on soil pCO₂, calculated CO₂ efflux, root biomass and soil carbon in open-top chambers planted with Pinus ponderosa seedlings. Based upon the literature, it was hypothesized that both elevated CO₂ and N would cause increased root biomass which would in turn cause increases in both total soil CO₂ efflux and microbial respiration. This hypothesis was only supported in part: both CO₂ and N treatments caused significant increases in root biomass, soil pCO₂, and calculated CO₂ efflux, but there were no differences in soil microbial respiration measured in the laboratory. Both correlative and quantitative comparisons of CO₂ efflux rates indicated that microbial respiration contributes little to total soil CO₂ efflux in the field. Measurements of soil pCO₂ and calculated CO₂ efflux provided inexpensive, non-invasive, and relatively sensitive indices of belowground response to CO₂ and N treatments.     

Freshwater biota and rising pCO2?

Rising atmospheric carbon dioxide (CO₂) has caused a suite of environmental issues, however, little is known about how the partial pressure of CO₂ (pCO₂) in freshwater will be affected by climate change. Freshwater pCO₂ varies across systems and is controlled by a diverse array of factors, making it difficult to make predictions about future levels of pCO₂. Recent evidence suggests that increasing levels of atmospheric CO₂ may directly increase freshwater pCO₂ levels in lakes, but rising atmospheric CO₂ may also indirectly impact freshwater pCO₂ levels in a variety of systems by affecting other contributing factors such as soil respiration, terrestrial productivity and climate regimes. Although future freshwater pCO₂ levels remain uncertain, studies have considered the potential impacts of changes to pCO₂ levels on freshwater biota. Studies to date have focused on impacts of elevated pCO₂ on plankton and macrophytes, and have shown that phytoplankton nutritional quality is reduced, plankton community structure is altered, photosynthesis rates increase and macrophyte distribution shifts with increasing pCO₂. However, a number of key knowledge gaps remain and gaining a better understanding of how freshwater pCO₂ levels are regulated and how these levels may impact biota, will be important for predicting future responses to climate change.     

hCG treatment raises H<Subscript>2</Subscript>O<Subscript>2</Subscript> levels and induces germ cell apoptosis in rat testis

The clinical significance of exogenous hCG treatment is to stimulate steroidogenesis and spermatogenesis in the testis. However, the pathogenesis of detrimental effects on the testis arising out of chronic hCG treatment is yet to be clearly ascertained. In the present study we have shown that hCG treatment (100 IU/day) to rats for 30 days raises testicular oxidative stress leading to germ cell apoptosis and impairment of spermatogenesis. The treatment raises testicular H₂O₂ levels along with increase in lipid peroxidation and concomitant decrease in the enzymatic antioxidant activities like superoxide dismutase, catalase and glutathione-s-transferase. The rise in the number of apoptotic germ cells was associated with up regulation of Fas protein expression and caspase-3 activity in the testis. However, serum testosterone which was elevated by 15 days of hCG treatment declined to pretreatment levels by 30 days. No significant alteration in serum gonadotropins was observed. The above findings indicate that the pathogenesis of deleterious effects following chronic hCG treatment is due to increase in testicular oxidative stress with high H₂O₂ availability leading to apoptosis among germ cells.     

Photosynthetic CO<Subscript>2</Subscript> uptake in seedlings of two tropical tree species exposed to oscillating elevated concentrations of CO<Subscript>2</Subscript>

Do short-term fluctuations in CO₂ concentrations at elevated CO₂ levels affect net CO₂ uptake rates of plants? When exposed to 600 μl CO₂ l^?1, net CO₂ uptake rates in shoots or leaves of seedlings of two tropical C₃ tree species, teak (Tectona grandis L. f.) and barrigon [Pseudobombax septenatum (Jacq.) Dug.], increased by 28 and 52% respectively. In the presence of oscillations with half-cycles of 20 s, amplitude of ca. 170 μl CO₂ l^?1 and mean of 600 μl CO₂ l^?1, the stimulation in net CO₂ uptake by the two species was reduced to 19 and 36%, respectively, i.e. the CO₂ stimulation in photosynthesis associated with a change in exposure from 370 to 600 μl CO₂ l^?1 was reduced by a third in both species. Similar reductions in CO₂-stimulated net CO₂ uptake were observed in T. grandis exposed to 40-s oscillations. Rates of CO₂ efflux in the dark by whole shoots of T. grandis decreased by 4.8% upon exposure of plants grown at 370 μl CO₂ l^?1 to 600 μl CO₂ l^?1. The potential implications of the observations on CO₂ oscillations and dark respiration are discussed in the context of free-air CO₂ enrichment (FACE) systems in which short-term fluctuations of CO₂ concentration are a common feature.     

Productivity gains do not compensate for reduced calcification under near‐future ocean acidification in the photosynthetic benthic foraminifer species Marginopora vertebralis

Changes in the seawater carbonate chemistry (ocean acidification) from increasing atmospheric carbon dioxide (CO₂) concentrations negatively affect many marine calcifying organisms, but may benefit primary producers under dissolved inorganic carbon (DIC) limitation. To improve predictions of the ecological effects of ocean acidification, the net gains and losses between the processes of photosynthesis and calcification need to be studied jointly on physiological and population levels. We studied productivity, respiration, and abundances of the symbiont‐bearing foraminifer species Marginopora vertebralis on natural CO₂ seeps in Papua New Guinea and conducted additional studies on production and calcification on the Great Barrier Reef (GBR) using artificially enhanced pCO₂. Net oxygen production increased up to 90% with increasing pCO₂; temperature, light, and pH together explaining 61% of the variance in production. Production increased with increasing light and increasing pCO₂ and declined at higher temperatures. Respiration was also significantly elevated (~25%), whereas calcification was reduced (16–39%) at low pH/high pCO₂ compared to present‐day conditions. In the field, M. vertebralis was absent at three CO₂ seep sites at pH_Total levels below ~7.9 (pCO₂ ~700 μatm), but it was found in densities of over 1000 m^?2 at all three control sites. The study showed that endosymbiotic algae in foraminifera benefit from increased DIC availability and may be naturally carbon limited. The observed reduction in calcification may have been caused either by increased energy demands for proton pumping (measured as elevated rates of respiration) or by stronger competition for DIC from the more productive symbionts. The net outcome of these two competing processes is that M. vertebralis cannot maintain populations under pCO₂ exceeding 700 μatm, thus are likely to be extinct in the next century.     

Changes in urinary dinor dihydro F2-isoprostane metabolite concentrations,a marker of oxidative stress,during and following asthma exacerbations

To investigate changes in oxidant stress during and following acute asthma exacerbations, this stidy measured 2,3-dinor-5,6-dihydro-15-F_2t-IsoP (F₂-IsoP-M), the major urinary metabolite of 15-F_2t-IsoP, in eight asthmatic adults, during and following an asthma hospitalization. F₂-IsoP-M concentrations at admission and follow-up were significantly higher than discharge (admission median: 4.12 ng/Cr mg, range 1.89–7.8; follow-up: 2.47 ng/Cr mg (1.56–6.86); discharge: 1.42 ng/Cr mg (0.7–4.44); both p<0.01), but not significantly different between admission and follow-up. F₂-IsoP-M concentrations at follow-up were higher than a control group with stable asthma (0.68 ng/Cr mg (0.31–1.5), p=0.0008). In conclusion, asthma exacerbations requiring hospitalization are associated with 6-fold higher urinary F₂-IsoP-M concentrations compared to stable asthmatics. F₂-IsoP-M concentrations decreased significantly during hospitalization, but significant elevations 3 months following hospitalization suggest ongoing oxidative stress despite clinical improvement. Urinary F₂-IsoP-M may be a clinically useful, simple non-invasive systemic measure of oxidative stress in asthmatics, providing information not captured by spirometry or symptoms.     

Effect of clear-cutting on soil CO<Subscript>2</Subscript> emission

An experimental study to estimate the effect of clear-cutting on CO₂ emission from the soil surface was performed using the chamber method. For field measurements, several experimental plots within the clear-cut with different degrees of damage of the upper organic soil layer and different amounts of litter and logging residue on the surface were selected. Soil CO₂ fluxes were simultaneously measured both on the clear-cutting plots and on two plots within the spruce forest stand located close to the clear-cut area. The results show a significant seasonal and diurnal variability of soil CO₂ emission. It was found that the soil respiration rate varies significantly among plots and depends on the damage to the upper soil layer and the availability of litter and logging residue on the soil surface. It was found that the rate of CO₂ emission from soil surface is strongly dependent on the air and soil temperature and moisture of the upper soil layer. Different rates of soil respiration are also revealed on the plots located at different distances from tree trunks within the control forest stand.     

Phase 1B study to improve immune responses in head and neck cancer patients using escalating doses of 25-hydroxyvitamin D<Subscript>3</Subscript>

Patients with head and neck squamous cell carcinoma (HNSCC) have profound immune defects. These defects are associated with a poor prognosis and are mediated, in part, by immune inhibitory CD34⁺ progenitor cells, whose numbers are increased in the peripheral blood of HNSCC patients. Immune inhibitory CD34⁺ cells are also present within HNSCC tumors. A phase IB clinical trial was conducted with HNSCC patients to determine if treatment with the differentiation-inducer 25-hydroxyvitamin D₃ could diminish CD34⁺ cell levels and improve a panel of immune parameters. Here we present the results of treatment with orally administered escalating doses (20, 40, 60 g) of 25-hydroxyvitamin D₃, with an emphasis on the six patients who received the maximum dosage of 60 g per day. Peripheral blood was collected at 0, 1, 2, 4, and 6 weeks, and assessed for markers of immune activity. Although no clinical responses were observed, results of this pilot study demonstrated that treatment of HNSCC patients with 25-hydroxyvitamin D₃ reduces the number of immune suppressive CD34⁺ cells, increases HLA-DR expression, increases plasma IL-12 and IFN- levels, and improves T-cell blastogenesis. In contrast, 25-hydroxyvitamin D₃ treatment did not modulate plasma IL-1, IL-2, IL-4, IL-6, IL-10, GM-CSF, or TGF- levels.Abbreviations GM-CSF granulocyte-macrophage colony-stimulating factor - high CD34⁺ patients patients with greater than 1% baseline CD34⁺ cell levels - HLA human leukocyte antigen - IFN interferon - IL interleukin - low CD34⁺ patients patients with less than 1% baseline CD34⁺ cell levels - OD optical density - TGF transforming growth factor     

Modeling soil CO<Subscript>2</Subscript> emissions from ecosystems

We present a new soil respiration model, describe a formal model testing procedure, and compare our model with five alternative models using an extensive data set of observed soil respiration. Gas flux data from rangeland soils that included a large number of measurements at low temperatures were used to model soil CO₂ emissions as a function of soil temperature and water content. Our arctangent temperature function predicts that Q₁₀ values vary inversely with temperature and that CO₂ fluxes are significant below 0 °C. Independent data representing a broad range of ecosystems and temperature values were used for model testing. The effects of plant phenology, differences in substrate availability among sites, and water limitation were accounted for so that the temperature equations could be fairly evaluated. Four of the six tested models did equally well at simulating the observed soil CO₂ respiration rates. However, the arctangent variable Q₁₀ model agreed closely with observed Q₁₀ values over a wide range of temperatures (r² = 0.94) and was superior to published variable Q₁₀ equations using the Akaike information criterion (AIC). The arctangent temperature equation explained 16–85% of the observed intra-site variability in CO₂ flux rates. Including a water stress factor yielded a stronger correlation than temperature alone only in the dryland soils. The observed change in Q₁₀ with increasing temperature was the same for data sets that included only heterotrophic respiration and data sets that included both heterotrophic and autotrophic respiration.     

Long-term effects of elevated atmospheric CO<Subscript>2</Subscript> on species composition and productivity of a southern African C<Subscript>4</Subscript> dominated grassland in the vicinity of a CO<Subscript>2</Subscript> exhalation

We describe the long-term effects of a CO₂ exhalation, created more than 70 years ago, on a natural C₄ dominated sub-tropical grassland in terms of ecosystem structure and functioning. We tested whether long-term CO₂ enrichment changes the competitive balance between plants with C₃ and C₄ photosynthetic pathways and how CO₂ enrichment has affected species composition, plant growth responses, leaf properties and soil nutrient, carbon and water dynamics. Long-term effects of elevated CO₂ on plant community composition and system processes in this sub-tropical grassland indicate very subtle changes in ecosystem functioning and no changes in species composition and dominance which could be ascribed to elevated CO₂ alone. Species compositional data and soil δ¹³C isotopic evidence suggest no detectable effect of CO₂ enrichment on C₃:C₄ plant mixtures and individual species dominance. Contrary to many general predictions C₃ grasses did not become more abundant and C₃ shrubs and trees did not invade the site. No season length stimulation of plant growth was found even after 5 years of exposure to CO₂ concentrations averaging 610 μmol mol⁻¹. Leaf properties such as total N decreased in the C₃ but not C₄ grass under elevated CO₂ while total non-structural carbohydrate accumulation was not affected. Elevated CO₂ possibly lead to increased end-of-season soil water contents and this result agrees with earlier studies despite the topographic water gradient being a confounding problem at our research site. Long-term CO₂ enrichment also had little effect on soil carbon storage with no detectable changes in soil organic matter found. There were indications that potential soil respiration and N mineralization rates could be higher in soils close to the CO₂ source. The conservative response of this grassland suggests that many of the reported effects of elevated CO₂ on similar ecosystems could be short duration experimental artefacts that disappear under long-term elevated CO₂ conditions.     

The Improvement of Spinach Growth by Nano-anatase TiO<Subscript>2</Subscript> Treatment Is Related to Nitrogen Photoreduction

The improvement of spinach growth is proved to relate to N₂ fixation by nano-anatase TiO₂ in this study. The results show that all spinach leaves kept green by nano-anatase TiO₂ treatment and all old leaves of control turned yellow white under culture with N-deficient solution. And the fresh weight, dry weight, and contents of total nitrogen, , chlorophyll, and protein of spinach by nano-anatase TiO₂ treatment presented obvious enhancement compared with control. Whereas the improvements of yield of spinach were not as good as nano-anatase TiO₂ treatment under N-deficient condition, confirming that nano-anatase TiO₂ on exposure to sunlight could chemisorb N₂ directly or reduce N₂ to NH₃ in the spinach leaves, transforming into organic nitrogen and improving the growth of spinach. Bulk TiO₂ effect, however, was not as significant as nano-anatase TiO₂. A possible metabolism of the function of nano-anatase TiO₂ reducing N₂ to NH₃ was discussed.     

The impact of invasion and subsequent removal of an exotic thistle, <Emphasis Type="Italic">Cynara cardunculus</Emphasis>, on CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O vapor exchange in a coastal California grassland

Changes in vegetation structure and composition, particularly due to the invasion of exotic species, are predicted to influence biosphere-atmosphere exchanges of mass and energy. Invasion of Cynara cardunculus (cardoon or artichoke thistle), a perennial, non-native thistle in coastal California grasslands presently dominated by non-native annual grasses, may alter rates of ecosystem CO₂ exchange and evapotranspiration (ET). During spring and summer 2006, we compared midday maximum net ecosystem CO₂ exchange (NEE) and ET among adjacent grassland plots where Cynara was present and where it was absent. Measurements of NEE supported the prediction that deeply-rooted Cynara increase midday ecosystem C-assimilation. Cynara-mediated shifts in NEE were associated with increases in ecosystem photosynthesis rather than changes in ecosystem respiration. Furthermore, the presence of Cynara was associated with increased ET during the growing season. An increase in aboveground live biomass (a proxy for leaf area) associated with Cynara invasion may underlie shifts in ecosystem CO₂ and water vapor exchange. Following mid-growing season sampling during April, we removed Cynara from half of the Cynara-containing plots with spot applications of herbicide. Three weeks later, midday fluxes in removal plots were indistinguishable from those in plots where Cynara was never present suggesting a lack of biogeochemical legacy effects. Similar to woody-encroachment in some semi-arid ecosystems, Cynara invasion increases midday ecosystem CO₂ assimilation and evapotranspiration rates and has the potential to increase C-storage in California coastal grasslands.     

Effects of Breathing Training on Voluntary Hypo- and Hyperventilation in Patients with Panic Disorder and Episodic Anxiety

Anxiety disorders are associated with respiratory abnormalities. Breathing training (BT) aimed at reversing these abnormalities may also alter the anxiogenic effects of biological challenges. Forty-five Panic Disorder (PD) patients, 39 Episodic Anxiety patients, and 20 non-anxious controls underwent voluntary hypoventilation and hyperventilation tests twice while psychophysiological measures were recorded. Patients were randomized to one of two BT therapies (Lowering vs. Raising pCO₂) or to a waitlist. Before treatment panic patients had higher respiration rates and more tidal volume instability and sighing at rest than did non-anxious controls. After the Lowering therapy, patients had lower pCO₂ during testing. However, neither reactivity nor recovery to either test differed between patients and controls, or were affected by treatment. Although the two treatments had their intended opposite effects on baseline pCO₂, other physiological measures were not affected. We conclude that baseline respiratory abnormalities are somewhat specific to PD, but that previously reported greater reactivity and slower recovery to respiratory challenges may be absent.     

Influence of drainage basin topography and elevation on carbon dioxide and methane supersaturation of stream water

The partial pressures of CO₂ (pCO₂) andCH₄ (pCH₄) in streams are not only governed byinstream processes, but also by transformations occurring in soil andgroundwater ecosystems. As such, stream water pCO₂ andpCH₄ can provide a tool to assess ecosystem respiration andanaerobic metabolism throughout drainage basins. We conducted three surveyssampling the gas content of streams in eastern Tennessee and western NorthCarolina to assess factors regulating ecosystem metabolism in catchmentswith contrasting geomorphologies, elevations and soil organic matterstorage. In our first survey, the influence of drainage basin geomorphologyon ecosystem respiration was examined by sampling streams drainingcatchments underlain by either shale or dolomite. Geomorphology isinfluenced by geology with shale catchments having shallower soils, broader,unconstrained valley floors compared with dolomite catchments.pCO₂ varied little between catchment types but increased froman average of 3340 ppmv in spring to 9927 ppmv in summer or 9.3 and 28 timesatmospheric equilibrium (pCO_2(equilib)), respectively. Incontrast, pCH₄ was over twice as high in streams drainingshale catchments (306 ppmv; pCH_4(equilib) = 116) compared withmore steeply incised dolomite basins (130 ppmv; pCH_4(equilib)= 51). Using the ratio of pCH₄:pCO₂ as an indexof anaerobic metabolism, shale catchments had nearly twice as muchanaerobiosis (pCH₄:pCO₂ = 0.046) than dolomitedrainages (pCH₄:pCO₂ = 0.024). In our secondsurvey, streams were sampled along an elevational gradient (525 to 1700 m)in the Great Smoky Mountains National Park, USA where soil organic matterstorage increases with elevation. pCO₂ did not vary betweenstreams but increased from 5340 ppmv (pCO_2(equilib) = 15) to8565 ppmv (pCO_2(equilib) = 24) from spring to summer,respectively. During spring pCH₄ was low and constant acrossstreams, but during summer increased with elevation ranging from 17 to 2068ppmv (pCH_4(equilib) = 10 to 1216). The contribution ofanaerobiosis to total respiration was constant during spring(pCH₄:pCO₂ = 0.017) but during summer increasedwith elevation from 0.002 at 524 m to 0.289 at 1286 m. In our last survey,we examined how pCO₂ and pCH₄ changed withcatchment size along two rivers (ca. 60 km stretches in both riverscorresponding to increases in basin size from 1.7–477km² and 2.5–275 km²). pCO₂and pCH₄ showed opposite trends, with pCO₂decreasing ca. 50% along the rivers, whereas pCH₄roughly doubled in concentration downstream. These opposing shifts resultedin a nearly five-fold increase of pCH₄:pCO₂along the rivers from a low of 0.012 in headwaters to a high of 0.266 65-kmdownstream. pCO₂ likely declines moving downstream asgroundwater influences on stream chemistry decreases, whereaspCH₄ may increase as the prevalence of anoxia in riversexpands due to finer-grained sediments and reduced hydrologic exchange withoxygenated surface water.