Ultrastructural Changes in the Air-Blood Barrier of Rats in Acute Intoxication with Furoplast Pyrolysis Products.

Rats were exposed to fluoroplast-4 pyrolysis products (sample weight 2.6 g, pyrolysis temperature 440-750°C, pyrolysis duration 4 min) containing perfluoroisobutylene over 15 min. Lung tissue samples for histological and electron microscopic examination were isolated in 3 and 30 min after intoxication and processed routinely. Histological examination revealed no structural changes in the lungs. In ultrathin sections of rat lungs, some changes in the structure of type I pneumocytes were detected in 3 min after the exposure: detachment of cytoplasmic processes and the appearance of transcytosis pores. These changes attested to impaired cell-cell interactions and their adhesion to the basement membrane, where structural disorganization and edema of the collagen matrix were observed. In 30 min following exposure, the signs of damage to type I pneumocytes became more pronounced. The increase in the equivalents of transcellular and paracellular permeability in the alveolar lining profile was observed. No changes in the pulmonary capillary endotheliocytes were detected, which suggest that type I pneumocytes are the primary target of the toxic effect of perfluoroisobutylene. The vulnerability of a particular cell population, in view of specific metabolism of these cells, can be the key to deciphering of the mechanisms of the toxic effect of pyrolysis products of fluorinated polymer materials.

The length and width of diatoms in drowning cases as the evidence of diatoms penetrating the alveoli-capillary barrier.

Forensic diatom test has been considered as a significant tool for diagnosis of drowning. Most of the studies in this field discussed the methodology of extracting, enriching and detecting diatoms from different tissues and drowning media. There are few studies on the basic principle of diatom test which was based on the theory developed by forensic scientists many years ago. This study was designed to analyze the length and width of diatoms in different organs and drowning medium samples of drowning cases. This study is designed to find evidence of diatoms penetrating the alveoli-capillary barrier. Samples from 100 drowning cases were analyzed using the methodology we developed: the Microwave Digestion-Vacuum Filtration-Automated Scanning Electron Microscopy method (MD-VF-Auto SEM method). The results showed that the length and width of diatoms in the liver and kidney tissues are smaller than that of the lung tissues and water samples. Our studies also found that the pennate diatoms are easier to penetrate through the alveoli-capillary barrier, travel in the blood stream and finally deposit in the distant tissues including liver and kidney. These findings provided evidences to support the process of diatoms penetrating the alveoli-capillary barrier.

Autophagy maintains the integrity of endothelial barrier in LPS-induced lung injury.

Understanding the role and underlying regulation mechanism of autophagy in lipopolysaccharide-induced lung injury (LPS-LI) may provide potentially new pharmacological targets for treatment of acute lung injury. The aim of this study was to investigate the functional significance of autophagy in LPS-LI. The autophagy of human pulmonary microvascular endothelial cells (HPMVECs) and mice was inhibited before they were challenged with LPS. In vitro, permeability, vitality, and the LDH release rate of the cells were detected, the zonula occluden-1 (ZO-1) expression and the stress fiber formation were determined. In vivo, the lung injury was assessed. We found LPS caused high permeability and increased lactate dehydrogenase (LDH) release rate, lowered viability of the cells, inhibited the ZO-1 expression and induced stress fiber formation, these effects were further aggravated by prohibiting the level of autophagy. Consistently, in in vivo experiments, LPS-induced serious lung injury, which was reflected as edema, leukocyte infiltration and hemorrhage in lung tissue, and the high concentration of pro-inflammation cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-1ß in bronchoalveolar lavage fluid (BALF). Inhibiting autophagy further exacerbated LPS-LI. It appears that autophagy played a protective role in LPS-LI in part through restricting the injury of lung microvascular barrier.

Biodistribution of single and aggregated gold nanoparticles exposed to the human lung epithelial tissue barrier at the air-liquid interface.

BACKGROUND: The lung represents the primary entry route for airborne particles into the human body. Most studies addressed possible adverse effects using single (nano)particles, but aerosolic nanoparticles (NPs) tend to aggregate and form structures of several hundreds nm in diameter, changing the physico-chemical properties and interaction with cells. Our aim was to investigate how aggregation might affect the biodistribution; cellular uptake and translocation over time of aerosolized NPs at the air-blood barrier interface using a multicellular lung system. RESULTS: Model gold nanoparticles (AuNPs) were engineered and well characterized to compare single NPs with aggregated NPs with hydrodynamic diameter of 32 and 106 nm, respectively. Exposures were performed by aerosolization of the particles onto the air-liquid interface of a three dimensional (3D) lung model. Particle deposition, cellular uptake and translocation kinetics of single and aggregated AuNPs were determined for various concentrations, (30, 60, 150 and 300 ng/cm2) and time points (4, 24 and 48 h) using transmission electron microscopy and inductively coupled plasma optical emission spectroscopy. No apparent harmful effect for single and aggregated AuNPs was observed by lactate dehydrogenase assay, nor pro-inflammation response by tumor necrosis factor α assessment. The cell layer integrity was also not impaired. The bio-distribution revealed that majority of the AuNPs, single or aggregated, were inside the cells, and only a minor fraction, less than 5%, was found on the basolateral side. No significant difference was observed in the translocation rate. However, aggregated AuNPs showed a significantly faster cellular uptake than single AuNPs at the first time point, i.e. 4 h. CONCLUSIONS: Our studies revealed that aggregated AuNPs showed significantly faster cellular uptake than single AuNPs at the first time point, i.e. 4 h, but the uptake rate was similar at later time points. In addition, aggregation did not affect translocation rate across the lung barrier model since similar translocation rates were observed for single as well as aggregated AuNPs.

Electron Microscopy Observation of Human Pulmonary Ultrastructure in Two Patients with High-Altitude Pulmonary Edema.

We examined the pulmonary ultrastructure in tissue from two patients with high-altitude pulmonary edema (HAPE) by electron microscopy. In one case, we found that neutrophils were trapped in pulmonary capillary lumen of alveolar-capillary wall and part of the cytoplasm of a neutrophil protruded and adhered to the capillary endothelium. There were several degranulated vacuoles in the cytoplasm of the neutrophil. The pulmonary capillary wall was deformed, thickened, and swollen and there was evidence of degeneration. In another case, infiltration of neutrophils and macrophages, proliferation of type II pneumocytes, and numerous red blood cells were also observed in alveolar air space. These electron microscopic ultrastructural observations illustrate for the first time damage to the pulmonary alveolar-capillary barrier in lung tissue of humans with advanced HAPE.

Aging exacerbates acute lung injury-induced changes of the air-blood barrier, lung function, and inflammation in the mouse.

Acute lung injury (ALI) is characterized by hypoxemia, enhanced permeability of the air-blood barrier, and pulmonary edema. Particularly in the elderly, ALI is associated with increased morbidity and mortality. The reasons for this, however, are poorly understood. We hypothesized that age-related changes in pulmonary structure, function, and inflammation lead to a worse prognosis in ALI. ALI was induced in young (10 wk old) and old (18 mo old) male C57BL/6 mice by intranasal application of 2.5 mg lipopolysaccharide (LPS)/kg body wt or saline (control mice). After 24 h, lung function was assessed, and lungs were either processed for stereological or inflammatory analysis, such as bronchoalveolar lavage fluid (BALF) cytometry and qPCR. Both young and old mice developed severe signs of ALI, including alveolar and septal edema and enhanced inflammatory BALF cells. However, the pathology of ALI was more pronounced in old compared with young mice with nearly sixfold higher BALF protein concentration, twice the number of neutrophils, and significantly higher expression of neutrophil chemokine Cxcl1, adhesion molecule Icam-1, and metalloprotease-9, whereas the expression of tight junction protein occludin significantly decreased. The old LPS mice had thicker alveolar septa attributable to higher volumes of interstitial cells and extracellular matrix. Tissue resistance and elastance reflected observed changes at the ultrastructural level in the lung parenchyma in ALI of young and old mice. In summary, the pathology of ALI with advanced age in mice is characterized by a greater neutrophilic inflammation, leakier air-blood barrier, and altered lung function, which is in line with findings in elderly patients.

[EFFECT OF FLIXOTIDE ON ELECTRON-MICROSCOPIC CHANGES IN LUNG TISSUE OF GUINEA PIGS WITH BRONCHIAL ASTHMA MODEL.]

Chronic experiments on nonlinear short-hair guinea pigs with bronchial asthma model caused by administration of ovalbumin without treatment showed the ap- pearance of electron-microscopic changes of the lungs tissue in the form of chronic allergic inflammation. Significant changes in air - blood barrier with a loo- sening of intercellular contacts, degenerative changes in alveolocytes, and circulatory disorders with symptoms of vascular dilatation and stasis of blood cor- puscles were revealed. Treatment with inhaled fluticasone propionate in the form of flixotide preparation (GlaxoSmithKline, UK) for 3 months (2 times a day for 30 - 45 sec) partially reduced disorders of circulation and transcapillary exchange, decreased edema and degenerative changes in the cells, and restored in- tercellular contacts and pinocytic activity of the air - blood barrier. The obtained results show the expediency of further studies for determining the optimal du- ration of basic treatment during remission of bronchial asthma.

Frank Low and the first images of the ultrastructure of the pulmonary blood-gas barrier.

Frank N. Low (1911-1998) has the distinction of publishing the first electron micrographs showing the ultrastructure of the pulmonary capillary and particularly the blood-gas barrier. This work in 1952 and 1953 was enabled by the progress in fixation and staining of tissue made by George Palade and was part of the very rapid advance in electron microscopy during the previous 25 years. Low's micrographs clearly showed the three layers of the blood-gas barrier: capillary endothelium, extracellular matrix, and alveolar epithelium. The images immediately resolved the debate about the composition of the blood-gas barrier that had been raging for 100 years. The first published micrographs were rather poor, but the quality rapidly improved and a major event was the first electron micrograph of the human blood-gas barrier published in 1953. These images had an enormous influence on the development of pulmonary physiology and biology. For example, for the first time it became clear that the barrier separating the blood from the alveolar gas was vanishingly thin. The discovery of the extracellular matrix layer ultimately clarified how this barrier, despite its extraordinary thinness, was sufficiently strong to avoid mechanical failure. Despite the major advances made by Low, his name is almost unknown in pulmonary physiology and biology, and perhaps this tribute will help to give him his due.

Hyperbaric oxygen treatment reduced the lung injury of type II decompression sickness.

OBJECTIVE: To detect the ultrastructural changes in rabbits with type II decompression sickness (DCS), and study the therapeutic effects of hyperbaric oxygen (HBO). METHODS: Twenty-seven male New Zealand rabbits were randomly divided equally into the DCS group, HBO treatment group and control group. Experimental models of each group were prepared. Lung apex tissues were harvested to prepare paraffin- and EPON812-embedded tissues. RESULTS: In the DCS group, macroscopic and histological examination revealed severe and rapid damage to lung tissue. Ultrastructural examination revealed exudation of red blood cells in the alveolar space. Type I alveolar epithelial cells exhibited retracted cell processes and swollen mitochondria, and type II cells showed highly swollen mitochondria and decrease in cytoplasmic lamellar bodies. Dilatation and congestion of capillary vessels were accompanied by swelling of endothelial cells and incomplete basement membrane. In the HBO treatment group, the findings were somewhat similar to those in the DCS group, but the extent of damage was lesser. Only a small amount of tiny bubbles could be seen in the blood vessels. Type I alveolar epithelia cells and endothelial cells of the capillaries illustrated slight shortening of cells, swollen cytoplasm and decreased cell processes. Type II alveolar epithelial cells showed slight swelling of the mitochondria, decreased vacuolar degeneration of lamellar bodies, and increase in the number of free ribosomes. CONCLUSIONS: Our microscopic and ultrastructural findings confirm that the lung is an important organ affected by DCS. We also confirmed that HBO can alleviate DCS-induced pulmonary damage.

Ultrastructural changes in the air-blood barrier in mice after intratracheal instillations of Asian sand dust and gold nanoparticles.

The purpose of this study was to investigate a possible translocation pathway of intratracheally instilled gold nanoparticles after the induction of acute pulmonary injury by Asian sand dust. ICR mice were intratracheally instilled with 800µg Asian sand particles (CJ-2 particles) 24h before instillation of 50-nm gold nanoparticles. Lungs from mice treated with Asian sand particles and gold nanoparticles showed an acute focal inflammation with an increased expression of proinflammatory cytokines (IL-6 and TNF-α) and oxidative stress markers (Cu/Zn SOD and iNOS) in alveolar macrophages, type I alveolar epithelial cells, and endothelial cells at the alveolar walls. Electron microscopy revealed a destruction of the alveolar walls with an increased number of endocytic vesicles in the cytoplasm of both type I epithelial cells and endothelial cells; gold nanoparticles were demonstrated in these endocytic vesicles. These findings suggest that translocation of the exposed nanoparticles may be enhanced in the lung tissues with acute inflammatory changes.

Immuno-localization of type-IV collagen in the blood-gas barrier and the epithelial-epithelial cell connections of the avian lung.

The terminal respiratory units of the gas exchange tissue of the avian lung, the air capillaries (ACs) and the blood capillaries (BCs), are small and rigid: the basis of this mechanical feature has been highly contentious. Because the strength of the blood-gas barrier (BGB) of the mammalian lung has been attributed to the presence of type-IV collagen (T-IVc), localization of T-IVc in the basement membranes (BM) of the BGB and the epithelial-epithelial cell connections (E-ECCs) of the exchange tissue of the lung of the avian (chicken) lung was performed in order to determine whether it may likewise contribute to the strength of the BGB. T-IVc was localized in both the BM and the E-ECCs. As part of an integrated fibroskeletal scaffold on the lung, T-IVc may directly contribute to the strengths of the ACs and the BCs.

Structure-function studies of blood and air capillaries in chicken lung using 3D electron microscopy.

Avian pulmonary capillaries differ from those of mammals in three important ways. The blood-gas barrier is much thinner, it is more uniform in thickness, and the capillaries are far more rigid when their transmural pressure is altered. The thinness of the barrier is surprising because it predisposes the capillaries to stress failure. A possible mechanism for these differences is that avian pulmonary capillaries, unlike mammalian, are supported from the outside by air capillaries, but the details of the support are poorly understood. To clarify this we studied the blood and air capillaries in chicken lung using transmission electron microscopy (EM) and two relatively new techniques that allow 3D visualization: electron tomography and serial block-face scanning EM. These studies show that the pulmonary capillaries are flanked by epithelial bridges composed of two extremely thin epithelial cells with large surface areas. The junctions of the bridges with the capillary walls show thickening of the epithelial cells and an accumulation of extracellular matrix. Collapse of the pulmonary capillaries when the pressure outside them is increased is apparently prevented by the guy wire-like action of the epithelial bridges. The enlarged junctions between the bridges and the walls could provide a mechanism that limits the hoop stress in the capillary walls when the pressure inside them is increased. The support of the pulmonary capillaries may also be explained by an interdependence mechanism whereby the capillaries are linked to a rigid assemblage of air capillaries. These EM studies show the supporting structures in greater detail than has previously been possible, particularly in 3D, and they allow a more complete analysis of the mechanical forces affecting avian pulmonary capillaries.

Cell injuries of the blood-air barrier in acute lung injury caused by perfluoroisobutylene exposure.

OBJECTIVES: To investigate the complete process of cell injuries in the blood-air barrier after perfluoroisobutylene (PFIB) exposure. METHODS: Rats were exposed to PFIB (140 mg/m(3)) for 5 min. The pathological changes were evaluated by lung wet-to-dry weight ratio, total protein concentration of bronchoalveolar lavage fluid and HE stain. Ultrastructural changes were observed by transmission electron microscope. Apoptosis was detected by in situ apoptosis detection. Changes of actin in the lung tissue were evaluated by western blot assay. RESULTS: No significant pulmonary edema or increased permeability was observed within the first 4 h, post PFIB exposure. However, inflammatory cell infiltration and alveolar wall thickening were observed from 2 h. Destruction of the alveoli constitution integrity, edema and protein leakage were observed at 8 h. The injuries culminated at 24 h and then recovered gradually. The ultrastructural injuries of alveolar type I epithelial cells, alveolar type II epithelial cells and pulmonary microvascular endothelial cells were observed at 30 min post PFIB exposure. Some injuries were similar to apoptosis. Compared with control, more serious injuries were observed in PFIB-exposed rats after 30 min. At 8 h, some signs of cell necrosis were observed. The injuries culminated at 24 h and then ameliorated. The number of apoptotic cells abnormally increased at 30 min post PFIB exposure, the maximum appeared at 24 h, and then ameliorated gradually. Western blot analysis revealed that the level of actin in the lung showed no significant changes within the first 4 h post PFIB exposure. However, it decreased at 8 h, reached a nadir at 24 h, and then recovered gradually. CONCLUSIONS: The pathological processes were in progress persistently post PFIB exposure. The early injuries probably were the result of the direct attack of PFIB and the advanced injuries probably arose from the inflammatory reaction induced by PFIB.

Pulmonary tissue engineering using dual-compartment polymer scaffolds with integrated vascular tree.

OBJECTIVES: The persistent shortage of donor organs for lung transplantation illustrates the need for new strategies in organ replacement therapy. Pulmonary tissue engineering aims at developing viable hybrid tissue for patients with chronic respiratory failure. METHODS: Dual-chamber polymer constructs that mimic the characteristics of the pulmonary air-blood interface were fabricated by microfabrication techniques using the biocompatible polymer polydimethylsiloxane. One compartment ("vascular chamber") was designed as a capillary network to mimic the pulmonary microvasculature. The other compartment ("parenchymal chamber") was designed to permit gas exchange. Immortalized mouse lung epithelium cells (MLE-12) were cultured on the surface of polystyrene microcarrier beads. These beads were subsequently injected into the parenchymal chamber of the dual-chamber microsystems. The vascular compartment was perfused with cell culture medium in a bioreactor and the construct was maintained in culture for 1 week. RESULTS: The microcarriers evenly distributed MLE-12 cells on the parenchymal compartment surface. Confluent cell layers were confirmed by fluorescent and electron microscopy. Adequate proliferation of MLE-12 cells within the construct was monitored via the DNA content. Viability of the cells was maintained over 1 week. Finally, cellular specificity and functional capacity in situ were demonstrated by immunostaining for proSP-B and proSP-C (alveolar epithelium), and by using MLE-12 cells transfected to overexpress green fluorescent protein. CONCLUSION: We conclude that functional hybrid microsystems mimicking the basic building plan of alveolar tissue can be engineered in vitro.

Translocation pathway of the intratracheally instilled C60 fullerene from the lung into the blood circulation in the mouse: possible association of diffusion and caveolae-mediated pinocytosis.

Ultrafine particles are ubiquitous in ambient urban and indoor air from multiple sources and may contribute to adverse respiratory and cardiovascular diseases. Recently, it has been demonstrated that ultrafine particles (UFPs) are translocated from the lung into the systemic circulation. The exact pathway, however, for the translocation in the lung remains unclear. In this study, we examined the translocation pathway of intratracheally instilled C60 fullerene particles from the lung into the blood circulation in the mouse. Using light microscopy, aggregated particles of fullerene were observed in the capillary lumen in the lung and the pulmonary lymph nodes immediately after instillation. Electron microscopic analysis demonstrated an increased number of pinocytotic vesicles (caveolae) of various sizes in the type 1 alveolar epithelial cells (AEC) and endothelial cells; occasional caveolae containing some particulate substances were observed. In addition, particles of various sizes were observed throughout the structure of the air-blood barrier (ABB). These findings suggest that fullerene particles may pass the ABB by both diffusion and caveolae-mediated pinocytosis, resulting in immediate translocation into the systemic circulation.

Ultrastructural changes of the air-blood barrier in mice after intratracheal instillation of lipopolysaccharide and ultrafine carbon black particles.

Epidemiological studies have indicated associations between exposure to increased concentrations of ambient ultrafine particles and adverse health effects especially in susceptible individuals. To ellucidate the mechanisms underlying the findings from epidemiological studies, mice pretreated with lipopolysaccharide (LPS) (acute lung injury model) were intratracheally instilled with ultrafine carbon black particles (UFCB), and the air-blood barrier was observed to examine the translocation pathway of UFCB from the lung into the systemic circulation. In addition, lung toxicity induced by the intratracheal instillation of LPS and UFCB was studied with the use of electron microscope. LPS treatment induced acute inflammatory changes with increased number of activated macrophages and neutrophils in the degenerated alveolar walls. UFCB were demonstrated on or in the denuded basement membrane in the air-blood barrier; these findings were associated with edematous changes and fragmentation of the cytoplasms of alveolar epithelial cell type 1, and the damages of alveolar epithelial cell type 1 were frequently observed in the close vicinity of the clumps of UFCB. These findings suggest that translocation of the exposed ultrafine particles may be enhanced in the lung tissues with acute inflammatory changes.

Thrombin enhances the barrier function of rat microvascular endothelium in a PAR-1-dependent manner.

Thrombin is a multifunctional coagulation protease with pro- and anti-inflammatory vascular effects. We questioned whether thrombin may have segmentally differentiated effects on pulmonary endothelium. In cultured rat endothelial cells, rat thrombin (10 U/ml) recapitulated the previously reported decrease in transmonolayer electrical resistance (TER), F-actin stress fiber formation, paracellular gap formation, and increased permeability. In contrast, in rat pulmonary microvascular endothelial cells (PMVEC), isolated on the basis of Griffonia simplicifolia lectin recognition, thrombin increased TER, induced fewer stress fibers, and decreased permeability. To assess for differential proteinase-activated receptor (PAR) expression as a basis for the different responses, PAR family expression was analyzed. Both pulmonary artery endothelial cells and PMVEC expressed PAR-1 and PAR-2; however, only PMVEC expressed PAR-3, as shown by both RT-PCR and Western analysis. PAR-1 activating peptides (PAR-APs: SFLLRN-NH(2) and TFLLRN-NH(2)) were used to confirm a role for the PAR-1 receptor. PAR-APs (25-250 muM) also increased TER, formed fewer stress fibers, and did not induce paracellular gaps in PMVEC in contrast to that shown in pulmonary artery endothelial cells. These results were confirmed in isolated perfused rat lung preparations. PAR-APs (100 mug/ml) induced a 60% increase in the filtration coefficient over baseline. However, by transmission electron microscopy, perivascular fluid cuffs were seen only along conduit veins and arteries without evidence of intra-alveolar edema. We conclude that thrombin exerts a segmentally differentiated effect on endothelial barrier function in vitro, which corresponds to a pattern of predominant perivascular fluid cuff formation in situ. This may indicate a distinct role for thrombin in the microcirculation.

Functional respiratory morphology in the newborn quokka wallaby (Setonix brachyurus).

A morphological and morphometric study of the lung of the newborn quokka wallaby (Setonix brachyurus) was undertaken to assess its morphofunctional status at birth. Additionally, skin structure and morphometry were investigated to assess the possibility of cutaneous gas exchange. The lung was at canalicular stage and comprised a few conducting airways and a parenchyma of thick-walled tubules lined by stretches of cuboidal pneumocytes alternating with squamous epithelium, with occasional portions of thin blood-gas barrier. The tubules were separated by abundant intertubular mesenchyme, aggregations of developing capillaries and mesenchymal cells. Conversion of the cuboidal pneumocytes to type I cells occurred through cell broadening and lamellar body extrusion. Superfluous cuboidal cells were lost through apoptosis and subsequent clearance by alveolar macrophages. The establishment of the thin blood-gas barrier was established through apposition of the incipient capillaries to the formative thin squamous epithelium. The absolute volume of the lung was 0.02 +/- 0.001 cm(3) with an air space surface area of 4.85 +/- 0.43 cm(2). Differentiated type I pneumocytes covered 78% of the tubular surface, the rest 22% going to long stretches of type II cells, their precursors or low cuboidal transitory cells with sparse lamellar bodies. The body weight-related diffusion capacity was 2.52 +/- 0.56 mL O(2) min(-1) kg(-1). The epidermis was poorly developed, and measured 29.97 +/- 4.88 microm in thickness, 13% of which was taken by a thin layer of stratum corneum, measuring 4.87 +/- 0.98 microm thick. Superficial capillaries were closely associated with the epidermis, showing the possibility that the skin also participated in some gaseous exchange. Qualitatively, the neonate quokka lung had the basic constituents for gas exchange but was quantitatively inadequate, implying the significance of percutaneous gas exchange.

Impact of preservation solution on the extent of blood-air barrier damage and edema formation in experimental lung transplantation.

A major aim in lung transplantation is to prevent the loss of structural integrity due to ischemia and reperfusion (I/R) injury. Preservation solutions protect the lung against I/R injury to a variable extent. We compared the influence of two extracellular-type preservation solutions (Perfadex, or PX, and Celsior, or CE) on the morphological alterations induced by I/R. Pigs were randomly assigned to sham (n = 4), PX (n = 5), or CE (n = 2) group. After flush perfusion with PX or CE, donor lungs were excised and stored for 27 hr at 4 degrees C. The left donor lung was implanted into the recipient, reperfused for 6 hr, and, afterward, prepared for light and electron microscopy. Intra-alveolar, septal, and peribronchovascular edema as well as the integrity of the blood-air barrier were determined stereologically. Intra-alveolar edema was more pronounced in CE (219.80 +/- 207.55 ml) than in PX (31.46 +/- 15.75 ml). Peribronchovascular (sham: 13.20 +/- 4.99 ml; PX: 15.57 +/- 5.53 ml; CE: 31.56 +/- 5.78 ml) and septal edema (thickness of alveolar septal interstitium, sham: 98 +/- 33 nm; PX: 84 +/- 8 nm; CE: 249 +/- 85 nm) were only found in CE. The blood-air barrier was similarly well preserved in sham and PX but showed larger areas of swollen and fragmented epithelium or endothelium in CE. The present study shows that Perfadex effectively prevents intra-alveolar, septal, and peribronchovascular edema formation as well as injury of the blood-air barrier during I/R. Celsior was not effective in preserving the lung from morphological I/R injury.