Large Aggregate Fraction Research Articles

Long-term Influence of Crop Residue Management and Tillage Practices on Distribution of C and N within Aggregate Size Fractions in Alluvial Soils

Aims: The goal of this experiment is to observe the variations in soil aggregate fractions and the change in percentage of carbon and nitrogen stored in the fractions due to the effect of crop residue management and tillage practices in Rice-Wheat cropping system.
 Study Design: An experiment was set up in Randomized Block Design with five treatments, i.e, T0-control, T1- zero-tillage+ no residue application, T2- zero-tillage+ residue application, T3- conventional tillage + no residue application, T4- conventional tillage+ residue application.
 Place and Duration of Study: It was conducted in a long-term experimental plot situated in University Research Farm at Pundibari in Coochbehar district of West Bengal. The data was taken in the 9th and 10th year of the experiment, i.e, 2018 and 2019.
 Methodology: Samples were collected from three different depths, i.e., 0-5 cm, 5-15 cm and 15-30 cm from four cropping seasons, i.e., wheat 2018, rice 2018, wheat 2019 and rice 2019 and were prepared and analyzed for physico-chemical factors. Dry stable aggregates were obtained by the method of sieving and change of carbon, nitrogen and C/N ratios in various fractions were observed.
 Results: Mostly for all the soil depths the total organic carbon content was highest for the treatment with zero-tillage and application of residues (T2). Total nitrogen content also followed the similar trend. Whereas in most of the crop seasons, the C/N ratio was observed to be higher in the treatment where conventional tillage was followed along with residue incorporation (T4). Within the short span of two years positive changes in total organic carbon and total nitrogen content was observed for almost all the treatments, across the depths.
 Conclusion: The optimum percentage of decrease in C/N ratio of the control as well as the treatment with zero-tillage and residue application (T2) in the large aggregate fractions (<2mm) indicates the suitability of the soil for higher productivity.

Does Increasing the Diversity of Small Grain Cropping Systems Improve Aggregate Stability and Soil Hydraulic Properties?

Wheat (Triticum aestivium L.) and barley (Hordeum vulgare L.) are two commonly grown cereal crops in the northern Great Plains. Adding other crops such as field pea (Pisum Sativum L.), canola (Brassica napus L.), or camelina (Camelina sativa L.) to wheat or barley cropping systems may improve soil quality. However, little is known about the effects of including oilseeds in small grain cropping systems on soil physical properties. We sampled an 8-year dryland study with 10 different cropping systems including continuous spring wheat, continuous winter wheat, continuous barley, pea–spring wheat, pea–barley, pea–winter wheat, pea–barley–camelina–spring wheat, pea–barley–canola–spring wheat, pea–winter wheat–camelina–spring wheat and pea–winter wheat–canola–spring wheat. We measured dry aggregate stability, wet aggregate stability, water retention, hydraulic conductivity, bulk density and total carbon. Continuous barley and winter wheat had a higher fraction of large dry soil aggregates, whereas the pea–barley–canola–spring wheat and pea–spring wheat cropping systems had a higher fraction of small aggregates in the 0–15 cm depth. However, wet aggregate stability, water retention, bulk density, hydraulic conductivity and soil carbon concentration were not affected by the cropping system in the 0–15 cm depth. Diversifying small grain cropping systems by adding canola or camelina oil seeds and peas generally did not affect soil physical properties at this location.

Effects of Land Use Change on Constitution, Stability, and C, N, P Stoichiometric Characteristics of Soil Aggregates in Southwest China Karst

Responses of soil aggregate stability and nutrient stoichiometry to land use change are of great significance to the protection and restoration of fragile ecosystems. In order to explore the influence of the law of land use change on soil aggregate stability and C, N, and P nutrient stoichiometric characteristics in the karst ecosystem of Southwest China, a typical region of the Southwest China Karst was selected as the study area. A series of sample plots were established for the seven typical land use types, and the constitution; stability; and C, N, and P contents and stoichiometric ratios of soil aggregates were studied. The results showed that land use change significantly affected the soil aggregate stability. The soil aggregate stability of corn fields and abandoned land was relatively high, whereas that of grassland and bare land was relatively low. The soil aggregate stability generally decreased with the increase in soil layer. There were significant differences in the C, N, and P contents of soil aggregates between different land use types. The C and N contents of soil aggregates of open woodland and abandoned land were higher, the C and N contents of grassland were lower, and the P contents of soil aggregates of bare land and abandoned land were relatively higher. Land use change also significantly affected the stoichiometric ratio of soil aggregate C, N, and P. The C:N of soil aggregates of arbor forest land, open forest land, and abandoned land was relatively high, and that of grassland was the lowest. The C:P of soil aggregates of arbor woodland and open woodland was higher than that in shrub woodland and grassland. The soil aggregate N:P of arbor forest land, open forest land, and shrub forest land was higher and was significantly higher than that of bare land and abandoned land. There were significant or extremely significant correlations between the constitution and stability of soil aggregates and the stoichiometric characteristics of soil aggregate C, N, and P. Soil aggregate stability was positively correlated with the mass fraction of large soil aggregates. The mass fraction of large soil aggregates increased, and the stability of aggregates correspondingly increased, which was conducive to the maintenance and accumulation of soil C, N, and P nutrients. These results are of great significance for vegetation restoration, soil and water conservation, and land use regulation in karst ecosystems of Southwest China.

Numerical Investigation on the Effect of the Oxymethylene Ether-3 (OME3) Blending Ratio in Premixed Sooting Ethylene Flames

Synthetic fuels, especially oxygenated fuels, which can be used as blending components, make it possible to modify the emission properties of conventional fossil fuels. Among oxygenated fuels, one promising candidate is oxymethylene ether-3 (OME3). In this work, the sooting propensity of ethylene (C2H4) blended with OME3 is numerically investigated on a series of laminar burner-stabilized premixed flames with increasing amounts of OME3, from pure ethylene to pure OME3. The numerical analysis is performed using the Conditional Quadrature Method of Moments combined with a detailed physico-chemical soot model. Two different equivalence ratios corresponding to a lightly and a highly sooting flame condition have been investigated. The study examines how different blending ratios of the two fuels affect soot particle formation and a correlation between OME3 blending ratio and corresponding soot reduction is established. The soot precursor species in the gas-phase are analyzed along with the soot volume fraction of small nanoparticles and large aggregates. Furthermore, the influence of the OME3 blending on the particle size distribution is studied applying the entropy maximization concept. The effect of increasing amounts of OME3 is found to be different for soot nanoparticles and larger aggregates. While OME3 blending significantly reduces the amount of larger aggregates, only large amounts of OME3, close to pure OME3, lead to a considerable suppression of nanoparticles formed throughout the flame. A linear correlation is identified between the OME3 content in the fuel and the reduction in the soot volume fraction of larger aggregates, while smaller blending ratios may lead to an increased number of nanoparticles for some positions in the flame for the richer flame condition.

Optimizing granular anammox retention via hydrocycloning during two-stage deammonification of high-solid sludge anaerobic digester supernatant

High-solid sludge anaerobic digestion leads to increased organic matters in digester supernatant, which promotes heterotrophic competition and reduces anaerobic ammonium oxidation (anammox) retention. This research demonstrated effective anammox retention by hydrocycloning during a two-stage deammonification. Anammox retention was evaluated by dividing large (>0.425 mm), medium (0.25 to 0.425 mm), and small (<0.25 mm) aggregate fractions via a sieve, whereby Candidatus Kuenenia abundance in each size aggregate was measured to be 16.8%, 5.0%, and 0.9% respectively. After hydrocyclone separation, large particles took up only 1.7% to 2.7% in the overflow discharge (upper discharge from the reactor), whereas its initial proportion was 19.4%, indicating limited anammox loss. The volume ratio change of large particles to total aggregates was defined for particle breakdown evaluation. Breakdown (23% to 32% large particles) occurred mainly during pumping (influenced by pump frequency and type), while little happened in the hydrocyclone. This research provided methods to use a sieve to evaluate anammox retention by hydrocyclone during high-solid sludge anaerobic digester supernatant deammonification, and information for reducing particle breakdown, pumping selection, and separation optimization.

Three Alveolar Phenotypes Govern Lung Function in Murine Ventilator-Induced Lung Injury.

Mechanical ventilation is an essential lifesaving therapy in acute respiratory distress syndrome (ARDS) that may cause ventilator-induced lung injury (VILI) through a positive feedback between altered alveolar mechanics, edema, surfactant inactivation, and injury. Although the biophysical forces that cause VILI are well documented, a knowledge gap remains in the quantitative link between altered parenchymal structure (namely alveolar derecruitment and flooding), pulmonary function, and VILI. This information is essential to developing diagnostic criteria and ventilation strategies to reduce VILI and improve ARDS survival. To address this unmet need, we mechanically ventilated mice to cause VILI. Lung structure was measured at three air inflation pressures using design-based stereology, and the mechanical function of the pulmonary system was measured with the forced oscillation technique. Assessment of the pulmonary surfactant included total surfactant, distribution of phospholipid aggregates, and surface tension lowering activity. VILI-induced changes in the surfactant included reduced surface tension lowering activity in the typically functional fraction of large phospholipid aggregates and a significant increase in the pool of surface-inactive small phospholipid aggregates. The dominant alterations in lung structure at low airway pressures were alveolar collapse and flooding. At higher airway pressures, alveolar collapse was mitigated and the flooded alveoli remained filled with proteinaceous edema. The loss of ventilated alveoli resulted in decreased alveolar gas volume and gas-exchange surface area. These data characterize three alveolar phenotypes in murine VILI: flooded and non-recruitable alveoli, unstable alveoli that derecruit at airway pressures below 5 cmH2O, and alveoli with relatively normal structure and function. The fraction of alveoli with each phenotype is reflected in the proportional changes in pulmonary system elastance at positive end expiratory pressures of 0, 3, and 6 cmH2O.

Nitrogen addition promotes the transformation of heavy metal speciation from bioavailable to organic bound by increasing the turnover time of organic matter: An analysis on soil aggregate level

Nitrogen (N) addition can change physicochemical properties and biogeochemical processes in soil, but whether or not these changes further affect the transport and transformation of heavy metal speciation is unknown. Here, a long-term (2004–2016) field experiment was conducted to assess the responses of different heavy metal speciation in three soil aggregate fractions to N additions in a temperate agroecosystem of North China. The organic matter turnover time was quantified based on changes in δ13C following the conversion from C3 (wheat) to C4 crop (corn). Averagely, N addition decreases and increases the heavy metal contents in bioavailable and organic bound fractions by 27.5% and 16.6%, respectively, suggesting N addition promotes the transformation of heavy metal speciation from bioavailable to organic bound, and such a promotion in a small aggregate fraction is more remarkable than that in a large aggregate fraction. The transformations of heavy metal speciation from bioavailable to organic bound in all soil aggregate fractions are largely dependent on the increments in the turnover time of organic matter. The increase in organic matter turnover time induced by N addition may inhibit the desorption of heavy metals from organic matter by prolonging the interaction time between heavy metals and organic matter and enhance the capacity of organic matter to adsorb heavy metals by increasing the humification degree and functional group. Our work can provide insights into the accumulation, migration, and transformation of heavy metals in soils in the context of increasing global soil N input from a microenvironmental perspective.

Regulation of Macrophage Foam Cell Formation During Nitrogen Mustard (NM)-Induced Pulmonary Fibrosis by Lung Lipids.

Nitrogen mustard (NM) is a vesicant known to target the lung, causing acute injury which progresses to fibrosis. Evidence suggests that activated macrophages contribute to the pathologic response to NM. In these studies, we analyzed the role of lung lipids generated following NM exposure on macrophage activation and phenotype. Treatment of rats with NM (0.125 mg/kg, i.t.) resulted in a time-related increase in enlarged vacuolated macrophages in the lung. At 28 days postexposure, macrophages stained positively for Oil Red O, a marker of neutral lipids. This was correlated with an accumulation of oxidized phospholipids in lung macrophages and epithelial cells and increases in bronchoalveolar lavage fluid (BAL) phospholipids and cholesterol. RNA-sequencing and immunohistochemical analysis revealed that lipid handling pathways under the control of the transcription factors liver-X receptor (LXR), farnesoid-X receptor (FXR), peroxisome proliferator-activated receptor (PPAR)-ɣ, and sterol regulatory element-binding protein (SREBP) were significantly altered following NM exposure. Whereas at 1-3 days post NM, FXR and the downstream oxidized low-density lipoprotein receptor, Cd36, were increased, Lxr and the lipid efflux transporters, Abca1 and Abcg1, were reduced. Treatment of naïve lung macrophages with phospholipid and cholesterol enriched large aggregate fractions of BAL prepared 3 days after NM exposure resulted in upregulation of Nos2 and Ptgs2, markers of proinflammatory activation, whereas large aggregate fractions prepared 28 days post NM upregulated expression of the anti-inflammatory markers, Il10, Cd163, and Cx3cr1, and induced the formation of lipid-laden foamy macrophages. These data suggest that NM-induced alterations in lipid handling and metabolism drive macrophage foam cell formation, potentially contributing to the development of pulmonary fibrosis.

SELECTION OF THE TECHNOLOGICAL LINE STRUCTURE FOR THE BUILDING AGGREGATES PRODUCTION USING CENTRIFUGAL IMPACT CRUSHERS

The paper considers the problem of the organization of the technological line for the production of building aggregates with a given particle size distribution. The advantage of two-stage crushing schemes is shown, which makes it possible to ensure a change in the ratio of large aggregate fractions within fairly wide limits. The experience of using centrifugal-impact crushers for the operation of the production of CJSC Ural-Omega at the final stage of crushing is summarized. It was demonstrated that the use of two centrifugal impact crushers at the final stage of crushing allows to obtain mixtures of significantly different types. A method for selecting the option of organizing the process line and crushing parameters is proposed.

Micellisation of polystyrene-b-polyglycidol copolymers in water solution

The preparation of a set of amphiphilic polystyrene-b-polyglycidol (PS-b-PGL) diblock copolymers and their characteristics in aqueous media are described. The copolymers were prepared via anionic polymerisation starting from the synthesis of a polystyrene macroinitiator terminated by ethylene oxide, followed by anionic polymerisation of glycidol 1-ethoxyethyl ether to obtain a poly(1-ethoxyethyl glycidyl ether) block. The ethoxyethyl blocking groups of the hydroxyls were subsequently removed by hydrolysis. The copolymers differed in polymerisation degree of the polyglycidol block with DP values equal to 13, 43, 68 and 125, whereas the DP of polystyrene was 29. Two different organic media, N,N-dimethylformamide and dioxane, were used to prepare copolymer solutions dialysed afterward against water. The behaviour of diblock copolymers in water, their self-assembly and the size parameters of their aggregated structures were determined using dynamic light scattering. The critical micelle concentration (CMC) did not depend on the initial solvent and linearly increased with increasing content of hydrophilic glycidol units in the copolymer chain. However, above the CMC, the dispersions obtained from DMF contained a significant fraction of large aggregates. In the case of dioxane after dialysis, only one population of particles of the sizes, which can be related to typical core–shell micelles, was observed. Cryogenic transmission electron microscopy images revealed the presence of spherical objects and confirmed their sizes. PS-b-PGL micelles were highly stable and did not dissociate even after dissolution of their dispersions to concentrations below the CMC.

Physicochemical Investigation on the Pulmonary Surfactant of Some Vertebrates

&lt;p&gt;Large aggregate (LA) fraction of the pulmonary surfactant (PS) isolated from five different animals of the vertebrate group, lungfish, chicken, crocodile, stumpie lizard and guinea pig were isolated and characterized. Active pulmonary surfactant components were obtained by chloroform-methanol extraction of the saline suspended LA fraction. Total phospholipid (PL) and protein content were estimated biochemically by standard enzymatic methods. A systematic progression in the PL and protein content was noticed with the developmental sequence of the animals, except the crocodile, which could be due to the difficulty in the PS isolation procedure. &lt;em&gt;In vitro&lt;/em&gt; functionality of the solvent spread film was carried out in a Langmuir surface balance by way of surface pressure (π)-area (A) measurements. PS from all the species exhibited reversible compression and expansion cycles. A clear correlation between the maximum attainable surface pressure (π&lt;sub&gt;max&lt;/sub&gt;), also known as the collapse pressure (π&lt;sub&gt;c&lt;/sub&gt;) and the developmental sequence, with some exceptions, could have been established. Langmuir-Blodgett deposits, transferred onto freshly cleaved mica, were imaged by atomic force microscopy for the five different species. DPPC enriched domains showed different dimensions for the five different species. The comprehensive set of studies shed light on the composition, film functionality and structure of the pulmonary surfactants of the vertebrates where a correlation with the evolution sequence is observed.&lt;/p&gt;

Effects of long-term grassland management on the carbon and nitrogen pools of different soil aggregate fractions

Common grassland management practices include animal grazing and the repeated addition of lime and nutrient fertilizers to soils. These practices can greatly influence the size and distribution of different soil aggregate fractions, thus altering the cycling and storage of carbon (C) and nitrogen (N) in grassland soils. So far, very few studies have simultaneously addressed the potential long-term effect that multiple management practices might have on soil physical aggregation. Here we specifically ask whether and how grazing, liming and nutrient fertilization might influence C and N content (%) as well as C and N pools of different soil aggregate fractions in a long-term grassland experiment established in 1991 at Silwood Park, Berkshire, UK.We found that repeated liming applications over 23years significantly decreased the C pool (i.e. gCKg−1 soil) of Large Macro Aggregate (LMA>2mm) fractions and increased C pools within three smaller soil aggregate fractions: Small Macro Aggregate (SMA, 250μm–2mm), Micro Aggregate (MiA, 53–250μm), and Silt Clay Aggregate (SCA<53μm). Soil C (and N) accrual in smaller fractions was mainly caused by positive liming effects on aggregate fraction mass rather than on changes in soil C (and N) content (%). Liming effects could be explained by increases in soil pH, as this factor was significantly positively related to greater soil C and N pools of smaller aggregate fractions. Long-term grazing and inorganic nutrient fertilization had much weaker effects on both soil aggregate-fraction mass and on soil C and N concentrations, however, our evidence is that these practices could also contribute to greater C and N pools of smaller soil fractions.Overall our study demonstrates how agricultural liming can contribute to increase C pools of small (more stable) soil fractions with potential significant benefits for the long-term C balance of human-managed grassland soils.

The effect of arm number and solution concentration on phase separation of thermosensitive poly(2-isopropyl-2-oxazoline) stars in aqueous solutions

Four-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx4) with calix[4]arene core was studied by methods of turbidimetry and light scattering in aqueous solutions at concentrations ranging from 0.0002 to 0.0364 g cm−3. The role of arm number in thermosensitive behavior was determined by comparing the experimental data with the results for eight-arm PiPrOx8 star. First of all, it is concerned with the growth of large aggregate fraction in PiPrOx4 solution and the formation of middle mode particles even at low temperature which causes the decrease phase separation temperatures. At relatively high concentrations (c >0.01 g cm−3), the dilution of PiPrOx4 solutions is accompanied by slow growth of phase transition temperatures, and the width ΔT = (1–2) °C of this interval does not depend on the concentration. In the dilute regime, ΔT rises and reaches 9 °C. It is shown that the changes of thermosensitive stars’ behavior with arm number reduction are caused by lower intramolecular density of PiPrOx4 in comparison with that of PiPrOx8.

Altered Lipid Composition of Surfactant and Lung Tissue in Murine Experimental Malaria-Associated Acute Respiratory Distress Syndrome.

Malaria-associated acute lung injury (MA-ALI) and its more severe form malaria-associated acute respiratory distress syndrome (MA-ARDS) are common, often fatal complications of severe malaria infections. However, little is known about their pathogenesis. In this study, biochemical alterations of the lipid composition of the lungs were investigated as possible contributing factors to the severity of murine MA-ALI/ARDS. C57BL/6J mice were infected with Plasmodium berghei NK65 to induce lethal MA-ARDS, or with Plasmodium chabaudi AS, a parasite strain that does not induce lung pathology. The lipid profile of the lung tissue from mice infected with Plasmodium berghei NK65 developing MA-ALI/ARDS, but not that from mice without lung pathology or controls, was characterized by high levels of phospholipids -mainly phosphatidylcholine- and esterified cholesterol. The high levels of polyunsaturated fatty acids and the linoleic/oleic fatty acid ratio of the latter reflect the fatty acid composition of plasma cholesterol esters. In spite of the increased total polyunsaturated fatty acid pool, which augments the relative oxidability of the lung membranes, and the presence of hemozoin, a known pro-oxidant, no excess oxidative stress was detected in the lungs of Plasmodium berghei NK65 infected mice. The bronchoalveolar lavage (BAL) fluid of Plasmodium berghei NK65 infected mice was characterized by high levels of plasma proteins. The phospholipid profile of BAL large and small aggregate fractions was also different from uninfected controls, with a significant increase in the amounts of sphingomyelin and lysophosphatidylcholine and the decrease in phosphatidylglycerol. Both the increase of proteins and lysophosphatidylcholine are known to decrease the intrinsic surface activity of surfactant. Together, these data indicate that an altered lipid composition of lung tissue and BAL fluid, partially ascribed to oedema and lipoprotein infiltration, is a characteristic feature of murine MA-ALI/ARDS and possibly contribute to lung dysfunction.

Self-assembly of star-shaped poly(2-isopropyl-2-oxazoline) in aqueous solutions

Eight-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx) with calix[8]arene core (M ≈ 20,000 g mol−1) was studied by turbidimetry and light scattering in aqueous solutions within concentration c ranging from 0.002 to 0.19 g cm−3. The lower critical solution temperature (LCST) for PiPrOx is about 10 °C lower than for the linear analog. PiPrOx forms two types of particles at room temperature. The specie responsible for the fast mode is single macromolecules or 2–3 ones joined in aggregate with a hydrodynamic radius of 4.9 nm, irrespective of concentration. On heating, at first, growth of a large aggregate fraction was observed without variation of their hydrodynamic radii R h (s). Then, R h (s) increased up to 800 nm at c = 0.002 g cm−3, while the fast mode disappeared. At all concentrations, the third middle mode with a size ranging from 9 to 40 nm was registered. It was observed in a very narrow temperature interval near the cloud point. The hydrodynamic radii of species and their fraction in solution were monitored as a function of time after the change in temperature.

Effect of hydrostatic pressure treatment on the structure–foaming relationships of β-lactoglobulin

The effect of hydrostatic pressure treatment (150 and 250 MPa) on the structure and foaming characteristics of dimeric β-lactoglobulin (β-LG) at pH 7.0 is investigated. Angle- and concentration-dependent dynamic light scattering is used to probe pressure-induced changes in size under ambient conditions. The cumulant method is used to analyze correlation functions of the dynamic light scattering experiments and to estimate hydrodynamic radii and the width of their distribution. Instead of a decrease, hydrodynamic radii slightly increase after pressure treatment and depend on protein concentration. Both native and pressurized samples are almost free of aggregates as indicated by a small polydispersity index, PDI < 0.25. A small fraction of larger aggregates in the native sample is not affected by the pressure treatment and only bias the scattering signal at low scattering angles. Circular dichroism measurements indicate transformation of the secondary structure into a random coil for the pressurized samples. Only slightly unfolded β-LG stabilizes foam best because the largest effect is observed for samples treated with 150 MPa. Pressure-modified β-LG could have the potential to be used as a stabilizer in the food industry because of the low pressure needed during processing.

Surface activity and self-aggregation ability of three cationic quaternized aminocalix[4]arenes

The self-aggregation ability of three amphiphilic cationic calix[4]arenes possessing four quaternary amino groups (aminoCAs) was investigated using a variety of methods. All of the studied compounds possess high aggregation ability. Their critical aggregation concentration (CAC) values in water are in the 0.0009–0.04 % (w/v) concentration range. Several size populations of aggregates were detected by DLS for all three CAs, and restructuring of aggregates was observed to be dependent on concentration. Particles formed above CAC were attributed to formation of vesicular structures (vesicles). The coexistence of other type of aggregates (presumably micelles) with vesicles was observed in the aqueous solution of CAs 2 and 3 from concentrations of 0.5 and 0.8 % (w/v), respectively. The filtration procedure was found to be a significant factor since the obtained data from filtered and unfiltered samples was different. The particle sizes obtained by TEM measurements were somewhat correlated with the DLS data for unfiltered CAs solutions. An analysis of the aggregate composition was undertaken by a size-exclusion method using semi-permeable cellophane membranes with different MWCO. A negative deviation from linearity of permeability flux profile starting from 0.8 % (w/v) concentration of donor phase indicated that the fraction of large aggregates at this point is significant enough that the molecules could not easily permeate through the membranes.

Coping With the Cold: Effect of Hibernation on Pulmonary Surfactant in the Thirteen-Lined Ground Squirrel

Pulmonary surfactant, a mixture of phospholipids, cholesterol, and proteins, stabilizes the lung by reducing surface tension at the air-water interface of the alveoli. We hypothesized that lowering body temperature to approximately 5oC during hibernation would require compositional changes in surfactant lipids and perhaps proteins in order to maintain lung function. Large aggregate (LA) fractions were obtained by centrifuging lung lavage at 40,000 g for 15 min, with small aggregates (SA) remaining in the supernatant. Because hibernating animals have lower body masses, surfactant levels per animal were compared. Hibernation resulted in an increase in total surfactant due to increased LA with little change in SA. Cholesterol at 8 wt% PL was not altered. Hibernation was accompanied by a small (∼15%) decrease in disaturated phosphatidylcholine and phosphatidylglycerol. Decreases were observed in the mRNAs for the surfactant proteins (SP-). Western analysis revealed levels of all SP-s decreased to approximately 10% (SP-A), 50% (SP-B), 90% (SP-C), and 50% (SP-D) of warm active levels. We speculate that the changes in surfactant LA levels might reflect the much lower breathing rate during hibernation. Furthermore, the compositional changes could arise, in part, from a slowing of metabolism. The decrease in disaturated phospholipid levels could lead to enhanced adsorption due to increased fluidity, but this suggestion will have to be confirmed experimentally.

Physicochemical studies on goat pulmonary surfactant

The large aggregate (LA) fraction of goat pulmonary surfactant (GPS) was isolated and characterized. Goat lung surfactant extract (GLSE) was obtained by chloroform–methanol extraction of the saline suspended LA fraction. Total phospholipid (PL), cholesterol (CHOL), and protein were biochemically estimated. It was composed of ~ 83% (w/w) PL, ~ 0.6% (w/w) CHOL and ~ 16% (w/w) protein. CHOL content was found to be lower while the protein content was found to be higher than other mammalian pulmonary surfactants. Electrospray Ionization Mass Spectrometry (ESIMS) of GLSE confirmed dipalmitoylphosphatidylcholine (DPPC) as the major phospholipid species, with significant amounts of palmitoyl-oleoyl phosphatidylcholine (POPC), palmitoyl-myristoyl phosphatidylcholine (PMPC) and dioleoylphosphatidylcholine (DOPC). Functionality of the solvent spread GLSE film was carried out in a Langmuir surface balance by way of surface pressure ( π)–area ( A) measurements. A high value of π (~ 65 mN m − 1 ) could be attained with a lift-off area of ~ 1.2 nm 2 molecule − 1 . A relatively large hysteresis was observed during compression–expansion cycles. Monolayer deposits at different π, transferred onto freshly cleaved mica by Langmuir–Blodgett (LB) technique, were imaged by atomic force microscopy. DPPC-enriched domains (evident from height analyses) showed dimensions of 2.5 μm and underwent changes in shapes after 30 mN m − 1 . Functionality and structure of the surfactant films were proposed to be controlled by the relative abundances of protein and cholesterol.

Lipidomics of cellular and secreted phospholipids from differentiated human fetal type II alveolar epithelial cells

Maturation of fetal alveolar type II epithelial cells in utero is characterized by specific changes to lung surfactant phospholipids. Here, we quantified the effects of hormonal differentiation in vitro on the molecular specificity of cellular and secreted phospholipids from human fetal type II epithelial cells using electrospray ionization mass spectrometry. Differentiation, assessed by morphology and changes in gene expression, was accompanied by restricted and specific modifications to cell phospholipids, principally enrichments of shorter chain species of phosphatidylcholine (PC) and phosphatidylinositol, that were not observed in fetal lung fibroblasts. Treatment of differentiated epithelial cells with secretagogues stimulated the secretion of functional surfactant-containing surfactant proteins B and C (SP-B and SP-C). Secreted material was further enriched in this same set of phospholipid species but was characterized by increased contents of short-chain monounsaturated and disaturated species other than dipalmitoyl PC (PC16:0/16:0), principally palmitoylmyristoyl PC (PC16:0/14:0) and palmitoylpalmitoleoyl PC (PC16:0/16:1). Mixtures of these PC molecular species, phosphatidylglycerol, and SP-B and SP-C were functionally active and rapidly generated low surface tension on compression in a pulsating bubble surfactometer. These results suggest that hormonally differentiated human fetal type II cells do not select the molecular composition of surfactant phospholipid on the basis of saturation but, more likely, on the basis of acyl chain length.