Gas Exchange Area Research Articles

Lipopolysaccharide-induced injury is more pronounced in fetal transgenic ErbB4-deleted lungs

Pulmonary ErbB4 deletion leads to a delay in fetal lung development, alveolar simplification, and lung function disturbances in adult mice. We generated a model of intrauterine infection in ErbB4 transgenic mice to study the additive effects of antenatal LPS administration and ErbB4 deletion during fetal lung development. Pregnant mice were treated intra-amniotically with an LPS dose of 4 μg at E17 of gestation. Lungs were analyzed 24 h later. A significant influx of inflammatory cells was seen in all LPS-treated lungs. In heterozygote control lungs, LPS treatment resulted in a delay of lung morphogenesis characterized by a significant increase in the fraction of mesenchyme, a decrease in gas exchange area, and disorganization of elastic fibers. Surfactant protein (Sftp)b and Sftpc were upregulated, but mRNA of Sftpb and Sftpc was downregulated compared with non-LPS-treated controls. The mRNA of Sftpa1 and Sftpd was upregulated. In ErbB4-deleted lungs, the LPS effects were more pronounced, resulting in a further delay in morphological development, a more pronounced inflammation in the parenchyma, and a significant higher increase in all Sftp. The effect on Sftpb and Sftpc mRNA was somewhat different, resulting in a significant increase. These results imply a major role of ErbB4 in LPS-induced signaling in structural and functional lung development.

Elimination of hydrophobic volatile organic compounds in fungal biofilters: Reducing start‐up time using different carbon sources

Fungal biofilters have been recently studied as an alternative to the bacterial systems for the elimination of hydrophobic volatile organic compounds (VOC). Fungi foster reduced transport limitation of hydrophobic VOCs due to their hydrophobic surface and extended gas exchange area associated to the hyphal growth. Nevertheless, one of their principal drawbacks is their slow growth, which is critical in the start-up of fungal biofilters. This work compares the use of different carbon sources (glycerol, 1-hexanol, wheat bran, and n-hexane) to reduce the start-up period and sustain high n-hexane elimination capacities (EC) in biofilters inoculated with Fusarium solani. Four parallel experiments were performed with the different media and the EC, the n-hexane partition coefficient, the biomass production and the specific consumption rate were evaluated. Biofilters were operated with a residence time of 1.3 min and an inlet n-hexane load of 325 g m(-3) (reactor) h(-1). The time to attain maximum EC once gaseous n-hexane was fed was reduced in the three experiments with alternate substrates, as compared to the 36 days needed with the control where only n-hexane was added. The shortest adaptation period was 7 days when wheat bran was initially used obtaining a maximum EC of 160 g m(-3) (reactor) h(-1) and a critical load of 55 g m(-3) (reactor) h(-1). The results were also consistent with the pressure drop, the amount of biomass produced and its affinity for the gaseous n-hexane, as represented by its partition coefficient.

Retinoid treatment of Emphysema in Patients on the Alpha-1 International Registry. The REPAIR study: study design, methodology and quality control of study assessments

Emphysema is characterized by the destruction of alveolar wall and enlargement of alveolar airspaces, resulting in a reduction of the total lung gas exchange area, loss of lung elastic recoil and hyperinflation. The REPAIR study (Retinoid treatment of Emphysema in Patients on the Alpha-1 International Registry) is the first proof-of-concept study of a new potential disease-modifying drug, Palovarotene©, an orally active, gamma selective retinoid agonist in patients with emphysema secondary to alpha-1-antitrypsin deficiency (AATD) as a model population for the general smoke-induced emphysema population. This article describes the study design as well as the effectiveness of the quality control that was implemented on the key efficacy endpoints, based on data derived from the placebo-treated subjects. In this multicentre, multinational study the implementation of standardized procedures included: careful site selection, use of trained staff, regular monitoring and machine calibration, use of biological controls and regular feedback to sites by an independent quality control centre. All of these procedures resulted in high-quality measurements of lung density, spirometry, static lung volumes and gas transfer. It was also confirmed that CT lung density was the most sensitive endpoint followed by TLco, FEV(1) and RV measured by body box.

Lung Recruitment and Positive End-Expiratory Pressure Have Different Effects on CO2 Elimination in Healthy and Sick Lungs

We studied the effects that the lung recruitment maneuver (RM) and positive end-expiratory pressure (PEEP) have on the elimination of CO(2) per breath (Vtco(2,br)). In 7 healthy and 7 lung-lavaged pigs at constant ventilation, PEEP was increased from 0 to 18 cm H(2)O and then decreased to 0 in steps of 6 cm H(2)O every 10 minutes. Cycling RMs with plateau pressure/PEEP of 40/20 (healthy) and 50/25 (lavaged) cm H(2)O were applied for 2 minutes between 18-PEEP steps. Volumetric capnography, respiratory mechanics, blood gas, and hemodynamic data were recorded. In healthy lungs before the RM, Vtco(2,br) was inversely proportional to PEEP decreasing from 4.0 (3.6-4.4) mL (median and interquartile range) at 0-PEEP to 3.1 (2.8-3.4) mL at 18-PEEP (P < 0.05). After the RM, Vtco(2,br) increased from 3.3 (3-3.6) mL at 18-PEEP to 4.0 (3.5-4.5) mL at 0-PEEP (P < 0.05). In lavaged lungs before the RM, Vtco(2,br) increased initially from 2.0 (1.7-2.3) mL at 0-PEEP to 2.6 (2.2-3) mL at 12-PEEP (P < 0.05) but then decreased to 2.4 (2-2.8) mL when PEEP was increased further to 18 cm H(2)O (P < 0.05). After the RM, the highest Vtco(2,br) of 2.9 (2.1-3.7) mL was observed at 12-PEEP and then decreased to 2.5 (1.9-3.1) mL at 0-PEEP (P < 0.05). Vtco(2,br) was directly related to changes in lung perfusion, the area of gas exchange, and alveolar ventilation but inversely related to changes in dead space. CO(2) elimination by the lungs was dependent on PEEP and recruitment and showed major differences between healthy and lavaged lungs.

A vacuum-vortex technique for preparation of anoxic solutions or liquid culture media in small volumes for cultivating methanogens or other strict anaerobes

A highly efficient method is described for producing at room temperature anoxic solutions of 50 ml or less in test tubes or serum vials by combining negative pressure with strong vortexing so that the liquid-surface, gas exchange area is increased by orders of magnitude. Liquid media suitable for the cultivation of methanogens may be rendered anoxic after three short vacuum-vortex steps.

Anatomy, pathology, and physiology of the tracheobronchial tree: Emphasis on the distal airways

This article covers the airway tree with respect to anatomy, pathology, and physiology. The anatomic portion discusses various primate groups so as to help investigators understand similarities and differences between animal models. An emphasis is on distal airway findings. The pathology section focuses on the inflammatory responses that occur in proximal and distal airways. The physiologic review brings together the anatomic and pathologic components to the functional state and proposes ways to evaluate the small airways in patients with asthma.

Automated Analysis of Intratidal Dynamics of Alveolar Geometry From Microscopic Endoscopy

Alveolar parenchyma, the gas exchange area of the respiratory system, is prone to mechanical damage during mechanical ventilation. Development of lung protective ventilation strategies therefore requires a better understanding of alveolar dynamics during mechanical ventilation. In this paper, we propose a novel method for automated analysis of the intratidal geometry of subpleural alveoli based on the evaluation of video frames recorded from alveolar microscopy in an experimental setting. Our method includes the recording with a microscopic endoscope, feature extraction from image data, the analysis of a single frame, the tracking and analysis of single alveoli in a video sequence, and the evaluation of the obtained sequence of alveolar geometry data. Our method enables automated analysis of 2-D alveolar geometry with sufficient temporal resolution to follow intratidal dynamics. The developed method and the reproducibility of the results were successfully validated with manually segmented video frames.

Integumentary Histology of the Amphibious Blenny, Isteblennius edentulus (Forester and Schneider, 1801)

The skin of the amphibious blenny, Istiblennius edentulus, was studied using both light and scanning electron microscopy. Rich vascularisation was found immediately below the epidermis and the dermis. Surface epithelial cells displayed microridges in a fingerprint-like pattern. It was speculated that this increased surface area may aid in the adhesion of mucous secretions as well as to increase the surface area for gas exchange. The number of pores on the dorsal side (6.3x103 per mm2) was significantly higher than that on the ventral side (4.3x103 per mm2). The thickness of the skin on the dorsal side was measured at 31.6±10.0µm and that on the ventral side was 32.9 ± 7.8µm.

Interactive effect of elevated temperature and O3 on antioxidant capacity and gas exchange in Betula pendula saplings

We studied the effects of slightly elevated temperature (T), O(3) concentration (O(3)) and their combination (T + O(3)) on the antioxidant defense, gas exchange and total leaf area of Betula pendula saplings in field conditions. During the second year of the experiment, T enhanced the total leaf area, net photosynthesis (P (n)) and maximum capacity of carboxylation, redox state of ascorbate and total antioxidant capacity in the apoplast. O(3) did not affect the total leaf area, but P (n) was slightly and g (s) significantly reduced. The saplings responded to elevated O(3) level by closing the stomata and by developing leaves with a lower leaf area per mass, rather than by accumulating ascorbate in the apoplast. The effects of T and O(3) on total leaf area and P (n) were counteractive. Elevated O(3) reduced the saplings' ability to utilize the warmer growth environment by increasing the stomatal limitation for photosynthesis and by reducing the redox state of ascorbate in the apoplast in the combination treatment as compared to T alone.

Impact of Pregnancy at High Altitude on Placental Morphology in Non-native Women With and Without Preeclampsia

Previous data indicate that placentas from normotensive pregnancies in non-native women at 3100m (Leadville, CO) are not hypoxic at term, despite lower uterine artery blood flow, than in the same population at sea-level. We hypothesized that placental vascular development is greater at 3100m in compensation. Further, because the incidence of preeclampsia (PE), which has been linked to placental hypoxia, is 3–4 fold higher in this population, we investigated if preeclamptic placentas have altered vascularity compared to normotensive controls at 3100m. Placentas from normotensive (NT) pregnancies at sea-level, 1600 and 3100m, and late-onset preeclamptic placentas were collected at 3100m. Placental and birth weights were determined, and stereology performed on paraffin- and resin-embedded tissue. Both normal and preeclamptic placentas at high altitude were smaller than those at sea-level, and birth weights trended down with no change in the placental index. Volume fractions of the placental and villous compartments were similar between all conditions, but the absolute volume of each compartment was reduced at 3100m compared to sea-level. Villous volume was equivalent between sea-level and 1600m. There were no differences between PE and NT placentas at 3100m. Placental vascularity was similar at all altitudes, and the gas-exchange area was preserved at 1600m but not 3100m. Late-onset preeclampsia was not associated with placental changes at 3100m.

Seasonal variation in the maximum rate of leaf gas exchange of canopy and understory tree species in an Amazonian semi-deciduous forest

Leaf gas exchange, water potential, and specific leaf area of two tropical semi-deciduous tree species, Brosimum lactescens S. Moore and Tovomita schomburgkii Planch & Triana, were quantified to establish how these properties were affected by seasonal variations in rainfall and leaf canopy position. The study was conducted at a site near Sinop Mato Grosso, Brazil, which is located within the ecotone of savanna and tropical rain forest. Both species exhibited significant declines in leaf water potential (ΨL), specific leaf area, area- and mass-based light saturated photosynthesis and dark respiration, and maximum stomatal conductance during the dry-season, suggesting that leaf structural properties and gas exchange are significantly altered by drought that develops during the 4-month dry season. Internal leaf CO2 concentrations (Ci) were consistently lower during the dry season suggesting that the decline in maximum photosynthesis was due in part to a decline in stomatal conductance. However, seasonal variations in leaf gas exchange were larger for upper-canopy leaves, indicating an important interaction between drought stress and canopy position. The seasonal variation in leaf gas exchange and morphology was presumably due to a combination of drought stress and leaf lifespan. The results of this study suggest that drought has important implications for the leaf physiology and morphology of semi-deciduous Amazonian forest trees.

Linking population density and habitat structure to ecophysiological responses in semiarid Spanish steppes

We have studied the underlying factors responsible for the heterogeneous ecophysiological status of a semiarid Stipa tenacissima L. steppe in a subcatchment of SE Spain by assessing population composition and habitat structure of S. tenacissima stands. To do this, we measured and estimated 18 variables (11 biotic and seven abiotic) in 15 plots randomly distributed in the subcatchment, and then zoned this area by plot affinity using PCA. This analysis produced three sectors determined mainly by S. tenacissima cover and soil depth variables. The linear relationship fitted between S. tenacissima tussock biomass and tussock density in monospecific stands (both logarithmic) indicated a curve close to −1, suggesting that the system is close to the maximum constant yield state. Ecophysiological measurements (gas exchange, fluorescence and individual leaf area index) were taken in two periods with different water availability in a representative plot in each sector. The intraspecific competition (inferred from the density dependence of green biomass) and rock outcrops were the main factors influencing the ecophysiological status in the study area. While, in the wet season, intraspecific competition regulated water consumption in zones where S. tenacissima tussocks (monospecific stands) are dominant, during the dry season, stands in zones with extensive rock outcrops and stone cover (tussocks in “soil pockets”) had no access to non-rainfall water gains because of the adjacent bare soil, and so in these stands, gas exchange was lower and photoinhibition higher. This article stresses the importance of considering the connection between tussocks and bare-ground interspace in the functional and structural analysis of semiarid steppes.

Annexin A2 Interactions with Rab14 in Alveolar Type II Cells

Annexin A2, a calcium-dependent phospholipid-binding protein, is abundantly expressed in alveolar type II cells where it plays a role in lung surfactant secretion. Nevertheless, little is known about the details of its cellular pathways. To identify annexin A2-regulated or associated proteins, we silenced endogenous annexin A2 expression in rat alveolar type II cells by RNA interference and assessed the change of the cellular transcriptome by DNA microarray analysis. The loss of annexin A2 resulted in the change of 61 genes. Thirteen of the selected genes (11 down-regulated and 2 up-regulated genes) were validated by real time quantitative PCR. When the loss of rat annexin A2 was rescued by overexpressing EGFP-tagged human annexin A2, six of seven selected targets returned to their normal expression level, indicating that these genes are indeed annexin A2-associated targets. One of the targets, Rab14, co-immunoprecipitated with annexin A2. Rab14 also co-localized in part with annexin A2 and lamellar bodies in alveolar type II cells. The silencing of Rab14 resulted in a decrease in surfactant secretion, suggesting that Rab14 may play a role in surfactant secretion.

Further evidence for the involvement of anatomical parameters of the cardiopulmonary system in the development of ascites syndrome in broiler chickens

Eggs from a broiler line were incubated at two different altitudes and hatched. Relative heart and lung weights, volumes of the heart, lung and thoracic cavity, incidence of right ventricular hypertrophy and ascites, and related physiological parameters were followed in the day-old chickens hatched from the above eggs. Lung and heart weights as a percentage of body weight, lung and heart volumes relative to the volume of the thoracic cavity after removing the heart and lungs were higher in chickens hatched at high altitude. Additionally, embryonic triiodothyronine (T3) and thyroxine (T4) levels relative to cardiopulmonary parameters were higher in day-old chickens that hatched at high altitude as compared with chickens hatched at low altitude. This was associated with a lower incidence of right ventricular hypertrophy and ascites in chickens hatched at high altitude. Our data indicate that chronic hypoxia interacting with the endogenous functions of embryos during embryonic development at high altitude, as adaptation mechanisms, changed the developmental trajectories of cardiopulmonary parameters in postnatal chickens. This important development facilitates an increase in the gas exchange area in broiler chickens, thus lowering their susceptibility to pulmonary hypertension and ascites.

Neoalveolarisation contributes to compensatory lung growth following pneumonectomy in mice

Regeneration of the gas exchange area by induction of neoalveolarisation would greatly improve therapeutic options in destructive pulmonary diseases. Unilateral pneumonectomy is an established model to remove defined portions of gas exchange area and study mechanisms of compensatory lung growth. The question of whether new alveoli are added to the residual lung after pneumonectomy in mice was addressed. Left-sided pneumonectomy was performed in 11 adult C57BL/6 mice. Alveolar numbers were analysed in lungs fixed at days 6 and 20 after pneumonectomy and in 10 age-matched controls using design-based stereology based on a physical fractionator. Post-fixation lung volume was determined by fluid displacement. Complete restoration of lung volume was observed 20 days after pneumonectomy. Alveolar numbers were significantly increased by 33% in residual right lungs at day 20 in comparison with control right lungs. In control left lungs, an average of 471+/-162 x 10(3) alveoli was estimated, 49% of which were regenerated by residual lungs at day 20. Of the newly formed alveoli seen at day 20, 74% were already present at day 6. The present data demonstrate that, in addition to growth in size of existing alveoli, neoalveolarisation contributes to restoration of the gas exchange area in adult mice and is induced early after pneumonectomy.

Review Series: Lung function made easy: Assessing gas exchange

In clinical practice there are two sorts of measurements, a) arterial oxygen and carbon dioxide partial pressure (PaO2, PaCO2) or arterial oxygen saturation (SaO2), and b) the transfer capacity for carbon monoxide (TLCO). The former measures the output or performance of the lung as a gas exchanger, and the latter estimates the available surface area or potential for gas exchange. As gas exchange deteriorates (PaO2 falls and PaCO2 rises), the body compensates by increasing ventilation and lowering PaCO2). Therefore, a high PaCO2 represents chronic respiratory or "compensation" failure, either chemo-insensitivity ("won't breathe") or neuromuscular weakness/increased work of breathing ("cannot breathe"). Chronic respiratory failure may progress to acute failure in which PaCO2 falls and PaCO2 rises progressively, assisted ventilation is usually required. The TLCO is a laboratory test which measures the integrity of the blood-gas barrier, it is particularly useful in the assessment of emphysema, interstitial disease and pulmonary vascular disease.

Inhaled Nitric Oxide for Modulation of Ischemia–Reperfusion Injury in Lung Transplantation

The prophylactic administration of inhaled nitric oxide (NO) during reperfusion after lung transplantation has been shown to reduce neutrophil-induced injury in animal models. There remain questions regarding efficacy in the clinical setting and concerns regarding increased free radical injury. We sought to assess the efficacy of NO in reducing neutrophil infiltration and associated injury if administered from the very onset of reperfusion in clinical lung transplantation. Twenty bilateral sequential lung transplant recipients were randomized to receive 20-ppm inhaled NO (NO group) or a standard anesthetic gas mixture (control group) from the onset of ventilation. Bronchoalveolar lavage was performed immediately prior to implantation and after 30 minutes of reperfusion and analyzed for inflammatory cytokine levels and free radical surrogates. Primary graft dysfunction (PGD) scoring was performed prospectively for 72 hours post-transplant. The prophylactic administration of NO during the first 30 minutes of reperfusion had no statistically significant effect on the development of Grade II to III PGD (5 of 10 in NO group and 7 of 10 in control group, p = 0.36) or gas exchange (area under the curve: 429 +/- 296 vs 336 +/- 306; p = 0.64) in the NO and control groups, respectively. Pulmonary neutrophil sequestration, as measured by the transpulmonary arteriovenous neutrophil difference, was not influenced by the administration of NO. Prophylactic NO did not significantly alter the concentration of interleukin-8, myeloperoxidase or nitrotyrosine during transplantation. This study could not demonstrate a significant effect of inhaled NO during the first 30 minutes of reperfusion in the prevention of neutrophil injury and primary graft dysfunction after lung transplantation.

Mechanics of airway and alveolar collapse in human breath-hold diving

A computational model of the human respiratory tract was developed to study airway and alveolar compression and re-expansion during deep breath-hold dives. The model incorporates the chest wall, supraglottic airway, trachea, branched airway tree, and elastic alveoli assigned time-dependent surfactant properties. Total lung collapse with degassing of all alveoli is predicted to occur around 235 m, much deeper than estimates for aquatic mammals. Hysteresis of the pressure-volume loop increases with maximum diving depth due to progressive alveolar collapse. Reopening of alveoli occurs stochastically as airway pressure overcomes adhesive and compressive forces on ascent. Surface area for gas exchange vanishes at collapse depth, implying that the risk of decompression sickness should reach a plateau beyond this depth. Pulmonary capillary transmural stresses cannot increase after local alveolar collapse. Consolidation of lung parenchyma might provide protection from capillary injury or leakage caused by vascular engorgement due to outward chest wall recoil at extreme depths.

High-resolution gas volume change measurements bring new insights in pressure regulation of the middle ear

in this issue, the paper by Kania et al. ([7][1]) presents measurements and modeling results on the role of nitrogen in the gas exchange processes in the middle ear. The middle ear is a semirigid biological gas pocket that is closed most of the time. External influences, such as changing weather

TRANSPLANTING AND ORGANIC MULCH AFFECT GAS EXCHANGE AND GROWTH OF FIELD GROWN RED OAK (QUERCUS SHUMARDII BUCKLI.)

Balled in burlaped is a common method for moving large trees into landscapes and affects of transplanting on tree gas exchange and growth has been documented. Organic mulch provides many benefits and is often recommended for landscapes. Because little research has been conducted on affects organic mulch has on gas exchange and growth of transplanted and non-transplanted trees, this research investigated the effects transplanting and organic mulch have on gas exchange and growth of field grown red oak (Quercus shumardii) trees. In March 2003, 12 multi-trunked trees were selected from a tree farm near Lubbock, Texas, and six trees were dug using a tree spade and placed in their original location. Mulch at a depth of 10 cm was placed around the rootball of 3 transplanted and 3 nontransplanted trees and maintained at this depth the remainder of the experiment. Over the next three growing seasons predawn leaf water potential and midday stomatal conductance were measured on each tree every 1 to 3 weeks. At the end of every growing season shoot elongation, stem caliper and subsample leaf area were recorded. Our data indicates transplanting has a negative affect on gas exchange and growth of red oak. Each growing season gas exchange, shoot growth, and subsample leaf area were less for transplanted trees when compared to nontransplanted trees. Mulch also influenced gas exchange and growth of these trees. For nontransplanted trees with mulch, gas exchange and growth were reduced when compared to nonmulched, nontransplanted trees. For transplanted trees with mulch, predawn leaf water potential was less negative and subsample leaf area was greater when compared to transplanted trees with out mulch.