Synergistic Action of Antimicrobial Lung Proteins against Klebsiella pneumoniae.

As key components of innate immunity, lung antimicrobial proteins play a critical role in warding off invading respiratory pathogens. Lung surfactant protein A (SP-A) exerts synergistic antimicrobial activity with the N-terminal segment of the SP-B proprotein (SP-BN) against Klebsiella pneumoniae K2 in vivo. However, the factors that govern SP-A/SP-BN antimicrobial activity are still unclear. The aim of this study was to identify the mechanisms by which SP-A and SP-BN act synergistically against K. pneumoniae, which is resistant to either protein alone. The effect of these proteins on K. pneumoniae was studied by membrane permeabilization and depolarization assays and transmission electron microscopy. Their effects on model membranes of the outer and inner bacterial membranes were analyzed by differential scanning calorimetry and membrane leakage assays. Our results indicate that the SP-A/SP-BN complex alters the ultrastructure of K. pneumoniae by binding to lipopolysaccharide molecules present in the outer membrane, forming packing defects in the membrane that may favor the translocation of both proteins to the periplasmic space. The SP-A/SP-BN complex depolarized and permeabilized the inner membrane, perhaps through the induction of toroidal pores. We conclude that the synergistic antimicrobial activity of SP-A/SP-BN is based on the capability of this complex, but not either protein alone, to alter the integrity of bacterial membranes.

The Anionic Phospholipids of Bovine Pulmonary Surfactant.

The only known compositional change in the phospholipids (PL) of pulmonary surfactant in response to a physiologic stimulus occurs around the time of birth. In most species, the predominant anionic PL changes from phosphatidylinositol (PtdIns) to phosphatidylglycerol (PtdGro). Because prior studies have shown that the change in the headgroup itself is functionally insignificant, we tested the hypothesis that the PtdIns and PtdGro contain different diacyl pairs. Experiments used electrospray-ionization mass spectrometry to determine the molecular species in PtdIns, PtdGro, and phosphatidylcholine (PtdCho) in surfactant from newborn calves and cows. The profiles for the two anionic PL were distinct. The PtdIns contained long, unsaturated fatty acid chains and no disaturated species. The PtdGro more closely resembled the profile from PtdCho. For each headgroup, the molecular species for calf and cow were similar. The differences between the two anionic PL indicate that the switch from PtdIns to PtdGro during maturation involves more than simple substitution of the headgroup, and suggest that the functional significance of the shift may reflect the different pool of diacyl pairs.

Response surface methodological (RSM) approach for optimizing the removal of trihalomethanes (THMs) and its precursor's by surfactant modified magnetic nanoadsorbents (sMNP) - An endeavor to diminish probable cancer risk.

Response surface methodology (RSM) approach was used for optimization of the process parameters and identifying the optimal conditions for the removal of both trihalomethanes (THMs) and natural organic matter (NOM) in drinking water supplies. Co-precipitation process was employed for the synthesis of magnetic nano-adsorbent (sMNP), and were characterized by field emission scanning electron microscopy (SEM), trans-emission electron microscopy (TEM), BET (Brunauer-Emmett-Teller), energy dispersive X-ray (EDX) and zeta potential. Box-Behnken experimental design combined with response surface and optimization was used to predict THM and NOM in drinking water supplies. Variables were concentration of sMNP (0.1 g to 5 g), pH (4-10) and reaction time (5 min to 90 min). Statistical analysis of variance (ANOVA) was carried out to identify the adequacy of the developed model, and revealed good agreement between the experimental data and proposed model. The experimentally derived RSM model was validated using t-test and a range of statistical parameters. The observed R2 value, adj. R2, pred. R2 and "F-values" indicates that the developed THM and NOM models are significant. Risk analysis study revealed that under the RSM optimized conditions, a marked reduction in the cancer risk of THMs was observed for both the groups studied. Therefore, the study observed that the developed process and models can be efficiently applied for the removal of both THM and NOM from drinking water supplies.

Surfactant Dysfunction in ARDS and Bronchiolitis is Repaired with Cyclodextrins.

Objectives: Acute respiratory distress syndrome (ARDS) is caused by many factors including inhalation of toxicants, acute barotrauma, acid aspiration, and burns. Surfactant function is impaired in ARDS and acute airway injury resulting in high surface tension with alveolar and small airway collapse, edema, hypoxemia, and death. In this study, we explore the mechanisms whereby surfactant becomes dysfunctional in ARDS and bronchiolitis and its repair with a cyclodextrin drug that sequesters cholesterol. Methods: We used in vitro model systems, a mouse model of ARDS, and samples from patients with acute bronchiolitis. Surface tension was measured by captive bubble surfactometry. Results: Patient samples showed severe surfactant inhibition even in the absence of elevated cholesterol levels. Surfactant was also impaired in ARDS mice where the cholesterol to phospholipid ratio (W/W%) was increased. Methyl-ß-cyclodextrin (MßCD) restored surfactant function to normal in both human and animal samples. Model studies showed that the inhibition of surfactant was due to both elevated cholesterol and an interaction between cholesterol and oxidized phospholipids. MßCD was also shown to have anti-inflammatory effects. Conclusions: Inhaled cyclodextrins have potential for the treatment of ARDS. They could be delivered in a portable device carried in combat and used following exposure to toxic gases and fumes or shock secondary to hemorrhage and burns.

Feasibility of a prototype newborn resuscitation monitor to study transition at birth, measuring heart rate and ventilator parameters, an animal experimental study.

BACKGROUND: Every year, an estimated 10 million babies are born, non-breathing and in need of resuscitation. Advances in management have been made over the past decades, however, approximately 700.000 yearly deaths result from this global problem. A prototype newborn resuscitation monitor (NRM) (Laerdal Global Health, Stavanger, Norway) has been developed with the purpose of studying newborn resuscitation. The monitor has the ability to continuously display HR using dry electrode ECG technology, to measure tidal volume, pressure and end tidal CO2, and to store the results for later analysis. Such monitor could enhance the care providers performance, and hence survival of neonates, by displaying the quality and response of the given care. The aim of this preclinical study was to describe the abilities of the NRM to measure ventilation and heart rate parameters against pathophysiological responses to different induced conditions in a piglet i.e. increased deadspace, pressure and washout of surfactant. METHODS: Piglets were chosen for the study, as they have tidal volumes of approximately 6 ml/kg, resembling the human neonate. Five piglets were anesthetized and intubated before starting positive pressure ventilation (PPV). The dry electrode ECG sensor of the NRM was placed over the abdomen, and experiments performed: (1) inducing different ventilation scenarios and (2) lavage of surfactant. RESULTS: The NRM was capable of continuously displaying HR and detecting inflicted changes in ventilation and compliance of piglets. It could measure inflated and exhaled volume, the pressure of the ventilations and also the end tidal CO2. CONCLUSIONS: The NRM provides objective feedback in anesthetized animals, and may be used in clinical studies and hopefully generate new knowledge on neonatal transition and resuscitation. The monitor may be further developed for use in both low and high-resource settings.

Interactions between DPPC as a component of lung surfactant and amorphous silica nanoparticles investigated by HILIC-ESI-MS.

This paper reports a rapid HILIC-ESI-MS assay to quantify dipalmitoylphosphatidylcholine (DPPC) as component of lung surfactant for nanosafety studies. The technique was used to investigate the concentration-dependent sorption of DPPC to two-sizes of amorphous SiO2 nanoparticles (SiO2-NPs) in a MeOH:H2O (50/50v/v) mixture and in cell culture medium. In MeOH:H2O (50/50v/v), the sorption of DPPC was positively correlated with the nanoparticles concentration. A substantial affinity of small amorphous SiO2-NPs (25nm) to DPPC standard solution compared to bigger SiO2-NPs (75nm) was not confirmed for biological specimens. After dispersion of SiO2-NPs in DPPC containing cell culture medium, the capacity of the SiO2-NPs to bind DPPC was reduced in comparison to a mixture of MeOH:H2O (50/50v/v) regardless from the nanoparticles size. Furthermore, HILIC-ESI-MS revealed that A549 cells internalized DPPC during growth in serum containing medium complemented with DPPC. This finding was in a good agreement with the potential of alveolar type II cells to recycle surfactant components. Binding of lipids present in the cell culture medium to amorphous SiO2-NPs was supported by means of HILIC-ESI-MS, TEM and ICP-MS independently.

Parental preferences regarding administration of an animal-derived versus a synthetic medication to newborn infants.

AIM: We examined the perceptions of parents with regard to animal-derived versus synthetic medications of comparable efficacy. We hypothesized that this issue is a concern in neonatal care and that the perceptions of parents from one geographical location would be similar to those of another. METHODS: A survey was distributed to parents of neonates admitted to a neonatal intensive care unit of a southeastern hospital. RESULTS: Of 153 parents surveyed, 150 (98%) responded. More mothers than fathers completed the surveys (113 vs. 34). Fifty-six percent of participants indicated a college or higher education; 40% had an income of $51,000/yr or higher. Thirty-four percent of parents had concerns about animal-derived medications, 41% preferred a synthetic medication of equivalent efficacy, and 69% would like to be informed if a medication was animal-derived. CONCLUSION: Parents have concerns about exposing neonates to animal-derived medication and wish to be informed if an animal-derived medication is being considered.

Influence of agglomeration and specific lung lining lipid/protein interaction on short-term inhalation toxicity.

Lung lining fluid is the first biological barrier nanoparticles (NPs) encounter during inhalation. As previous inhalation studies revealed considerable differences between surface functionalized NPs with respect to deposition and toxicity, our aim was to investigate the influence of lipid and/or protein binding on these processes. Thus, we analyzed a set of surface functionalized NPs including different SiO2 and ZrO2 in pure phospholipids, CuroSurf(TM) and purified native porcine pulmonary surfactant (nS). Lipid binding was surprisingly low for pure phospholipids and only few NPs attracted a minimal lipid corona. Additional presence of hydrophobic surfactant protein (SP) B in CuroSurf(TM) promoted lipid binding to NPs functionalized with Amino or PEG residues. The presence of the hydrophilic SP A in nS facilitated lipid binding to all NPs. In line with this the degree of lipid and protein affinities for different surface functionalized SiO2 NPs in nS followed the same order (SiO2 Phosphate ∼ unmodified SiO2 < SiO2 PEG < SiO2 Amino NPs). Agglomeration and biomolecule interaction of NPs in nS was mainly influenced by surface charge and hydrophobicity. Toxicological differences as observed in short-term inhalation studies (STIS) were mainly influenced by the core composition and/or surface reactivity of NPs. However, agglomeration in lipid media and lipid/protein affinity appeared to play a modulatory role on short-term inhalation toxicity. For instance, lipophilic NPs like ZrO2, which are interacting with nS to a higher extent, exhibited a far higher lung burden than their hydrophilic counterparts, which deserves further attention to predict or model effects of respirable NPs.

Biophysical activity of animal-derived exogenous surfactants mixed with rifampicin.

Exogenous pulmonary surfactant is a potential delivery system for topical medications via the conducting airways. Due to the sensitivity to inactivation of surfactant, mutual interaction with the shipped drug should be evaluated. Little is known about the interactions between surfactant and antimicrobial drugs. The aim of the present study was to evaluate whether biophysical properties of animal-derived surfactants are modified by the bactericidal antibiotic rifampicin. An intracellular activity and a broad antimicrobiotic spectrum toward Gram-negative and Gram-positive bacteria make rifampicin an interesting substance against pulmonary infections. Curosurf® (porcine surfactant from minced lungs) and Survanta® (bovine surfactant extract) were diluted to 2.5-5.0 mg/ml of phospholipids in 0.9 % NaCl and rifampicin (RIF) was added at 1, 5, and 10 % (w/w). Minimum (γ(min)) and maximum (γ(max)) surface tension of a cyclically compressed bubble in the mixture was assessed with a pulsating bubble surfactometer. After 5 min, γ(min) of Survanta at a concentration of 3 mg/ml was significantly increased after addition of 5 and 10 % RIF (both p < 0.001). At 1 % RIF, the γ(min) of Survanta was ≈10 mN/m and this value was not significantly different to that of Survanta alone. The γ(min) of Curosurf at 3 mg/ml was increased with 10 % RIF (p < 0.001), but not with 1 and 5 %. At 5 mg/ml Survanta was inhibited by 10 % RIF (p < 0.05), while γ(min) of Curosurf was low (<5 mN/m) in all mixtures. In conclusion, Curosurf and Survanta interfere with RIF in a concentration-dependent manner. At the appropriate phospholipid concentration, especially porcine-derived surfactant is able to retain good surface activity when mixed with antibiotics.

Effectiveness of correction of bleomycin-induced lung injury by early and late administration of surfactant-BL.

Rats were exposed to inhalation of surfactant-BL starting from the first or eighth day after intratracheal administration of bleomycin. At the early stages, the preparation effectively attenuated damage to ultrastructural components of the lung tissue and reduced the severity and extent of subsequent pulmonary pathology.

Atomic force microscopy analysis of rat pulmonary surfactant films.

Pulmonary surfactant facilitates breathing by forming a surface tension reducing film at the air-liquid interface of the alveoli. The objective was to characterize the structure of surfactant films using endogenous rat surfactant. Solid-support surfactant films, at different surface pressures, were obtained using a Langmuir balance and were analyzed using atomic force microscopy. The results showed a lipid film structure with three distinct phases: liquid expanded, liquid ordered and liquid condensed. The area covered by the liquid condensed domains increased as surface pressure increased. The presence of liquid ordered phase within these structures correlated with the cholesterol content. At a surface pressure of 50 mN/m, stacks of bilayers appeared. Several structural details of these films differ from previous observations made with goat and exogenous surfactants. Overall, the data indicate that surfactant films demonstrate phase separation at low surface pressures and multilayer formation at higher pressure, features likely important for normal surfactant function.

Exogenous surfactant protects against endotoxin induced acute respiratory distress syndrome in rodents via vascular endothelial growth factor.

Vascular endothelial growth factor (VEGF) is a potent angiogenic factor which is abundantly expressed in the normal lung and is released by numerous cell types. Using a bacteria-induced lung injury model and surfactant therapy in rats, VEGF expression in lung was investigated. Sprague Dawley male rats were divided into four groups: buffer controls; rats challenged with LPS (055:B5 E. coli); challenged with LPS and treated with porcine surfactant (P-SF); and challenged with LPS and treated with synthetic surfactant (S-SF). The expressions of VEGF, PCNA, and BrdU were studied. VEGF protein expression was decreased in comparison to the control rats, as seen by both Western immunoblot and immunohistochemistry. Protein expression of PCNA and proliferation index as determined by both PCNA and BrdU immunostaining were also seen to be decreased in the LPS-treated animals, and with the surfactant treatment the expression was increased. The downregulation of VEGF in the alveolar space may reflect the recovery from acute lung injury, which leads to the limited endothelial permeability, and may participate in the decrease in capillary number, as observed during acute respiratory distress syndrome with potentially significant clinical consequences.

Phospholipid packing and hydration in pulmonary surfactant membranes and films as sensed by LAURDAN.

The efficiency of pulmonary surfactant to stabilize the respiratory surface depends critically on the ability of surfactant to form highly packed films at the air-liquid interface. In the present study we have compared the packing and hydration properties of lipids in native pulmonary surfactant and in several surfactant models by analyzing the pressure and temperature dependence of the fluorescence emission of the LAURDAN (1-[6-(dimethylamino)-2-naphthyl]dodecan-1-one) probe incorporated into surfactant interfacial films or free-standing membranes. In interfacial films, compression-driven changes in the fluorescence of LAURDAN, evaluated from the generalized polarization function (GPF), correlated with changes in packing monitored by surface pressure. Compression isotherms and GPF profiles of films formed by native surfactant or its organic extract were compared at 25 or 37 °C to those of films made of dipalmitoylphosphatidylcholine (DPPC), palmitoyloleoylphosphatidylcholine (POPC), DPPC/phosphatidylglycerol (PG) (7:3, w/w), or the mixture DPPC/POPC/palmitoyloleoylphosphatidylglycerol (POPG)/cholesterol (Chol) (50:25:15.10), which simulates the lipid composition of surfactant. In general terms, compression of surfactant films at 25 °C leads to LAURDAN GPF values close to those obtained from pure DPPC monolayers, suggesting that compressed surfactant films reach a dehydrated state of the lipid surface, which is similar to that achieved in DPPC monolayers. However, at 37 °C, the highest GPF values were achieved in films made of full surfactant organic extract or the mixture DPPC/POPC/POPG/Chol, suggesting a potentially important role of cholesterol to ensure maximal packing/dehydration under physiological constraints. Native surfactant films reached high pressures at 37 °C while maintaining relatively low GPF, suggesting that the complex three-dimensional structures formed by whole surfactant might withstand the highest pressures without necessarily achieving full dehydration of the lipid environments sensed by LAURDAN. Finally, comparison of the thermotropic profiles of LAURDAN GPF in surfactant model bilayers and monolayers of analogous composition shows that the fluorophore probes an environment that is in average intrinsically more hydrated at the interface than inserted into free-standing bilayers, particularly at 37 °C. This effect suggests that the dependence of membrane and surfactant events on the balance of polar/non-polar interactions could differ in bilayer and monolayer models, and might be affected differently by the access of water molecules to confined or free-standing lipid structures.

Ventilator-associated lung injury superposed to oleic acid infusion or surfactant depletion: histopathological characteristics of two porcine models of acute lung injury.

BACKGROUND: The pathophysiological concept of acute lung injury (ALI) in combination with ventilator-associated lung injury (VALI) is still unclear. We characterized the histopathological features of intravenous injection of oleic acid (OAI) and lung lavage (LAV) combined with VALI. METHODS: Pigs were randomized to the control, LAV or OAI group and ventilated by pressure-controlled ventilation. MEASUREMENTS INCLUDED: haemodynamics, spirometry, blood gas analysis, lung wet-to-dry weight ratio (W/D), total protein content in broncho-alveolar lavage fluid (BALF), and lung pathological description and scoring. RESULTS: Five hours after lung injury induction, gas exchange was significantly impaired in both the OAI and the LAV groups. Compared to controls, we found an increase in W/D and histopathological total injury scores in both the LAV and OAI groups and an increase in BALF total protein content in the OAI group. In contrast to the LAV group, the OAI group showed septal necrosis and alveolar oedema. Both groups exhibited dorsal and caudal atelectasis and interstitial oedema. In addition, the OAI group demonstrated a propensity to dorsal necrosis and congestion whereas the LAV group tended to develop ventral overdistension and barotrauma. CONCLUSIONS: This study presents a comparison of porcine OAI and LAV models combined with VALI, providing information for study design in research on ALI.

Sevoflurane ameliorates gas exchange and attenuates lung damage in experimental lipopolysaccharide-induced lung injury.

BACKGROUND: Acute lung injury is a common complication in critically ill patients. Several studies suggest that volatile anesthetics have immunomodulating effects. The aim of the current study was to assess possible postconditioning with sevoflurane in an in vivo model of endotoxin-induced lung injury. METHODS: Rats were anesthetized, tracheotomized, and mechanically ventilated. Lipopolysaccharide (saline as control) was administered intratracheally. Upon injury after 2 h of propofol anesthesia, general anesthesia was continued with either sevoflurane or propofol for 4 h. Arterial blood gases were measured every 2 h. After 6 h of injury, bronchoalveolar lavage was performed and lungs were collected. Total cell count, albumin content, concentrations of the cytokines cytokine-induced neutrophil chemoattractant-1 and monocyte chemoattractant protein-1, and phospholipids were analyzed in bronchoalveolar lavage fluid. Expression of messenger RNA for the two cytokines and for surfactant protein B was determined in lung tissue. Histopathologic examination of the lung was performed. RESULTS: Significant improvement of the ratio of oxygen tension to inspired oxygen fraction was shown with sevoflurane (mean + or - SD: 243 + or - 94 mmHg [32.4 kPa]) compared with propofol (88 + or - 19 mmHg [11.7 kPa]). Total cell count representing effector cell recruitment as well as albumin content as a measure of lung permeability were significantly decreased in the sevoflurane-lipopolysaccharide group compared with the propofol-lipopolysaccharide group in bronchoalveolar lavage fluid. Expression of the cytokines protein in bronchoalveolar lavage fluid as well as messenger RNA in lung tissue was significantly lower in the sevoflurane-lipopolysaccharide group compared with the propofol-lipopolysaccharide group. CONCLUSIONS: Postconditioning with sevoflurane attenuates lung damage and preserves lung function in an in vivo model of acute lung injury.

Aerosolised surfactant generated by a novel noninvasive apparatus reduced acute lung injury in rats.

INTRODUCTION: Exogenous surfactant has been explored as a potential therapy for acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). In the present study, a nebuliser driven by oxygen lines found in the hospital was developed to deliver aerosolised porcine pulmonary surfactant (PPS). We hypothesised that aerosolised surfactant inhaled through spontaneous breathing may effectively reduce severe lung injury. METHODS: Rats were intravenously injected with oleic acid (OA) to induce ALI and 30 minutes later they were divided into five groups: model (injury only), PPS aerosol (PPS-aer), saline aerosol (saline-aer), PPS instillation (PPS-inst), and saline instillation (Saline-Inst). Blood gases, lung histology, and protein and TNF-alpha concentrations in the bronchoalveolar lavage fluid (BALF) were examined. RESULTS: The PPS aerosol particles were less than 2.0 mum in size as determined by a laser aerosol particle counter. Treatment of animals with a PPS aerosol significantly increased the phospholipid content in the BALF, improved lung function, reduced pulmonary oedema, decreased total protein and TNF-alpha concentrations in BALF, ameliorated lung injury and improved animal survival. These therapeutic effects are similar to those seen in the PPS-inst group. CONCLUSIONS: This new method of PPS aerosolisation combines the therapeutic effects of a surfactant with partial oxygen inhalation under spontaneous breathing. It is an effective, simple and safe method of administering an exogenous surfactant.

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 approximately 83% (w/w) PL, approximately 0.6% (w/w) CHOL and approximately 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 (pi)-area (A) measurements. A high value of pi (approximately 65 mN m(-1)) could be attained with a lift-off area of approximately 1.2 nm(2) molecule(-1). A relatively large hysteresis was observed during compression-expansion cycles. Monolayer deposits at different pi, 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 microm 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.

Probing perturbation of bovine lung surfactant extracts by albumin using DSC and 2H-NMR.

Lung surfactant (LS), a lipid-protein mixture, forms films at the lung air-water interface and prevents alveolar collapse at end expiration. In lung disease and injury, the surface activity of LS is inhibited by leakage of serum proteins such as albumin into the alveolar hypophase. Multilamellar vesicular dispersions of a clinically used replacement, bovine lipid extract surfactant (BLES), to which (2% by weight) chain-perdeuterated dipalmitoylphosphatidycholine (DPPG mixtures-d(62)) had been added, were studied using deuterium-NMR spectroscopy ((2)H-NMR) and differential scanning calorimetry (DSC). DSC scans of BLES showed a broad gel to liquid-crystalline phase transition between 10-35 degrees C, with a temperature of maximum heat flow (T(max)) around 27 degrees C. Incorporation of the DPPC-d(62) into BLES-reconstituted vesicles did not alter the T(max) or the transition range as observed by DSC or the hydrocarbon stretching modes of the lipids observed using infrared spectroscopy. Transition enthalpy change and (2)H-NMR order parameter profiles were not significantly altered by addition of calcium and cholesterol to BLES. (2)H-NMR spectra of the DPPC-d(62) probes in these samples were characteristic of a single average lipid environment at all temperatures. This suggested either continuous ordering of the bilayer through the transition during cooling or averaging of the DPPC-d(62) environment by rapid diffusion between small domains on a short timescale relative to that characteristic of the (2)H-NMR experiment. Addition of 10% by weight of soluble bovine serum albumin (1:0.1, BLES/albumin, dry wt/wt) broadened the transition slightly and resulted in the superposition of (2)H-NMR spectral features characteristic of coexisting fluid and ordered phases. This suggests the persistence of phase-separated domains throughout the transition regime (5-35 degrees C) of BLES with albumin. The study suggests albumin can cause segregation of protein bound-lipid domains in surfactant at NMR timescales (10(-5) s). Persistent phase separation at physiological temperature may provide for a basis for loss of surface activity of surfactant in dysfunction and disease.

Protein inhibition of surfactant during mechanical ventilation of isolated rat lungs.

This study tested the hypothesis that material leaking into the airspace from the vasculature during ventilation interferes with surfactant function and contributes to decreases in lung compliance. Rats were euthanized and the lungs were isolated either with or without flushing of the vasculature, followed by mechanical ventilation and analysis of lung compliance and lung lavage analysis. Flushed lungs had higher lung compliance compared to the non-flushed lungs. This was associated with lower protein concentrations and improved surfactant activity. It is concluded that during mechanical ventilation, leakage of proteins results in surfactant inhibition and thereby contribute to decreased lung compliance.