Pulmonary MRI with hyperpolarized xenon-129 demonstrates novel alterations in gas transfer across the air-blood barrier in asthma

BACKGROUND

Individuals with asthma can vary widely in clinical presentation, severity, and pathobiology. Hyperpolarized xenon-129 (Xe129) MRI is a novel imaging method to provide 3-D mapping of both ventilation and gas exchange in the human lung.

PURPOSE

To evaluate the functional changes in adults with asthma as compared to healthy controls using Xe129 MRI.

METHODS

All subjects (20 controls and 20 asthmatics) underwent lung function measurements and Xe129 MRI on the same day. Outcome measures included the pulmonary ventilation defect and transfer of inspired Xe129 into two soluble compartments: tissue and blood. Ten asthmatics underwent Xe129 MRI before and after bronchodilator to test whether gas transfer measures change with bronchodilator effects.

RESULTS

Initial analysis of the results revealed striking differences in gas transfer measures based on age, hence we compared outcomes in younger (n = 24, ≤ 35 years) versus older (n = 16, > 45 years) asthmatics and controls. The younger asthmatics exhibited significantly lower Xe129 gas uptake by lung tissue (Asthmatic: 0.98% ± 0.24%, Control: 1.17% ± 0.12%, P = 0.035), and higher Xe129 gas transfer from tissue to the blood (Asthmatic: 0.40 ± 0.10, Control: 0.31% ± 0.03%, P = 0.035) than the younger controls. No significant difference in Xe129 gas transfer was observed in the older group between asthmatics and controls (P > 0.05). No significant change in Xe129 transfer was observed before and after bronchodilator treatment.

CONCLUSIONS

By using Xe129 MRI, we discovered heterogeneous alterations of gas transfer that have associations with age. This finding suggests a heretofore unrecognized physiological derangement in the gas/tissue/blood interface in young adults with asthma that deserves further study.

Dynamic tissue model in vitro and its application for assessment of microplastics-induced toxicity to air-blood barrier (ABB)

The replication of the hominine physiological environment was identified as an effectual strategy to develop the physiological model in vitro to perform the intuitionistic assessment of toxicity of contaminations. Herein, we proposed a dynamic interface strategy that accurately mimicked the blood flow and shear stress in human capillaries to subtly evaluate the physiological damages. To proof the concept, the dynamic air-blood barrier (ABB) model in vitro was developed by the dynamic interface strategy and was utilized to assess the toxicity of polyethylene terephthalate microplastics (PET-MPs). The developed dynamic ABB model was compared with the static ABB model developed by the conventional Transwell® system and the animal model, then the performance of the dynamic ABB model in evaluation of the PET-MPs induced pulmonary damage via replicating the hominine ABB. The experimental data revealed that the developed dynamic ABB model in vitro effectively mimicked the physiological structure and barrier functions of human ABB, in which more sophisticated physiological microenvironment enabled the distinguishment of the toxicities of PET-MPs in different sizes and different concentrations comparing with the static ABB model constructed on Transwell® systems. Furthermore, the consistent physiological and biochemical characters adopted dynamic ABB model could be achieved in a quick manner referring with that of the mouse model in the evaluation of the microplastics-induced pulmonary damage. The proposed dynamic interface strategy supplied a general approach to develop the hominine physiological environment in vitro and exhibited a potential to develop the ABB model in vitro to evaluate the hazards of inhaled airborne pollutants.

Advances in In Vitro Blood-Air Barrier Models and the Use of Nanoparticles in COVID-19 Research

Respiratory infections caused by coronaviruses (CoVs) have become a major public health concern in the past two decades as revealed by the emergence of SARS-CoV in 2002, MERS-CoV in 2012, and SARS-CoV-2 in 2019. The most severe clinical phenotypes commonly arise from exacerbation of immune response following the infection of alveolar epithelial cells localized at the pulmonary blood-air barrier. Preclinical rodent models do not adequately represent the essential genetic properties of the barrier, thus necessitating the use of humanized transgenic models. However, existing monolayer cell culture models have so far been unable to mimic the complex lung microenvironment. In this respect, air-liquid interface models, tissue engineered models, and organ-on-a-chip systems, which aim to better imitate the infection site microenvironment and microphysiology, are being developed to replace the commonly used monolayer cell culture models, and their use is becoming more widespread every day. On the contrary, studies on the development of nanoparticles (NPs) that mimic respiratory viruses, and those NPs used in therapy are progressing rapidly. The first part of this review describes in vitro models that mimic the blood-air barrier, the tissue interface that plays a central role in COVID-19 progression. In the second part of the review, NPs mimicking the virus and/or designed to carry therapeutic agents are explained and exemplified.

The pathogenesis of influenza in intact alveoli: virion endocytosis and its effects on the lung's air-blood barrier

Lung infection by influenza A virus (IAV) is a major cause of global mortality from lung injury, a disease defined by widespread dysfunction of the lung's air-blood barrier. Endocytosis of IAV virions by the alveolar epithelium - the cells that determine barrier function - is central to barrier loss mechanisms. Here, we address the current understanding of the mechanistic steps that lead to endocytosis in the alveolar epithelium, with an eye to how the unique structure of lung alveoli shapes endocytic mechanisms. We highlight where future studies of alveolar interactions with IAV virions may lead to new therapeutic approaches for IAV-induced lung injury.

A century of exercise physiology: lung fluid balance during and following exercise

PURPOSE

This review recalls the principles developed over a century to describe trans-capillary fluid exchanges concerning in particular the lung during exercise, a specific condition where dyspnea is a leading symptom, the question being whether this symptom simply relates to fatigue or also implies some degree of lung edema.

METHOD

Data from experimental models of lung edema are recalled aiming to: (1) describe how extravascular lung water is strictly controlled by "safety factors" in physiological conditions, (2) consider how waning of "safety factors" inevitably leads to development of lung edema, (3) correlate data from experimental models with data from exercising humans.

RESULTS

Exercise is a strong edemagenic condition as the increase in cardiac output leads to lung capillary recruitment, increase in capillary surface for fluid exchange and potential increase in capillary pressure. The physiological low microvascular permeability may be impaired by conditions causing damage to the interstitial matrix macromolecular assembly leading to alveolar edema and haemorrhage. These conditions include hypoxia, cyclic alveolar unfolding/folding during hyperventilation putting a tensile stress on septa, intensity and duration of exercise as well as inter-individual proneness to develop lung edema.

CONCLUSION

Data from exercising humans showed inter-individual differences in the dispersion of the lung ventilation/perfusion ratio and increase in oxygen alveolar-capillary gradient. More recent data in humans support the hypothesis that greater vasoconstriction, pulmonary hypertension and slower kinetics of alveolar-capillary O2 equilibration relate with greater proneness to develop lung edema due higher inborn microvascular permeability possibly reflecting the morpho-functional features of the air-blood barrier.

Bioengineering the Blood-gas Barrier

The pulmonary blood-gas barrier represents a remarkable feat of engineering. It achieves the exquisite thinness needed for gas exchange by diffusion, the strength to withstand the stresses and strains of repetitive and changing ventilation, and the ability to actively maintain itself under varied demands. Understanding the design principles of this barrier is essential to understanding a variety of lung diseases, and to successfully regenerating or artificially recapitulating the barrier ex vivo. Many classical studies helped to elucidate the unique structure and morphology of the mammalian blood-gas barrier, and ongoing investigations have helped to refine these descriptions and to understand the biological aspects of blood-gas barrier function and regulation. This article reviews the key features of the blood-gas barrier that enable achievement of the necessary design criteria and describes the mechanical environment to which the barrier is exposed. It then focuses on the biological and mechanical components of the barrier that preserve integrity during homeostasis, but which may be compromised in certain pathophysiological states, leading to disease. Finally, this article summarizes recent key advances in efforts to engineer the blood-gas barrier ex vivo, using the platforms of lung-on-a-chip and tissue-engineered whole lungs. © 2020 American Physiological Society. Compr Physiol 10:415-452, 2020.

Therapeutic delivery of RNA effectors: diseases affecting the respiratory system

Although there are several hurdles to overcome on the way to the lung, this target organ provides several advantages for successful drug absorption. Recent findings in this field of research give reason to assume that the pulmonary delivery of RNA effector molecules holds a promising potential for the treatment of numerous severe respiratory diseases.

Air-blood barrier translocation of tracheally instilled gold nanoparticles inversely depends on particle size

Gold nanoparticles (AuNP) provide many opportunities in imaging, diagnostics, and therapy in nanomedicine. For the assessment of AuNP biokinetics, we intratracheally instilled into rats a suite of (198)Au-radio-labeled monodisperse, well-characterized, negatively charged AuNP of five different sizes (1.4, 2.8, 5, 18, 80, 200 nm) and 2.8 nm AuNP with positive surface charges. At 1, 3, and 24 h, the biodistribution of the AuNP was quantitatively measured by gamma-spectrometry to be used for comprehensive risk assessment. Our study shows that as AuNP get smaller, they are more likely to cross the air-blood barrier (ABB) depending strongly on the inverse diameter d(-1) of their gold core, i.e., their specific surface area (SSA). So, 1.4 nm AuNP (highest SSA) translocated most, while 80 nm AuNP (lowest SSA) translocated least, but 200 nm particles did not follow the d(-1) relation translocating significantly higher than 80 nm AuNP. However, relative to the AuNP that had crossed the ABB, their retention in most of the secondary organs and tissues was SSA-independent. Only renal filtration, retention in blood, and excretion via urine further declined with d(-1) of AuNP core. Translocation of 5, 18, and 80 nm AuNP is virtually complete after 1 h, while 1.4 nm AuNP continue to translocate until 3 h. Translocation of negatively charged 2.8 nm AuNP was significantly higher than for positively charged 2.8 nm AuNP. Our study shows that translocation across the ABB and accumulation and retention in secondary organs and tissues are two distinct processes, both depending specifically on particle characteristics such as SSA and surface charge.

Systematic influence induced by 3 nm titanium dioxide following intratracheal instillation of mice

This work reported the systematic influence of titanium dioxide nanoparticles (TiO2 NPs) with a diameter of 3 nm on mice. Mice were repeated intratracheally instilled with TiO2 NPs, once per-week for 4 consecutive weeks, at total dose of 13.2 mg/kg. At 28 days post-instillation, the biochemical parameters in broncboalveolar lavage fluid (BALF) and brain homogenate as well as histopathologic changes of tissues were examined to describe the subacute toxicity of instilled TiO2 NPs. The results showed that instilled TiO2 NPs could induce lung damage, and change the permeability of alveolar-capillary barrier. The TiO2 NPs were able to get access to blood circulation and reach extrapulmonary tissues, then lead to injury at the different level, such as liver and kidney. Our results also indicated that TiO2 NPs might pass through the blood-brain barrier (BBB), and induce the brain injury through oxidative stress response.

Reconstituting organ-level lung functions on a chip

Here, we describe a biomimetic microsystem that reconstitutes the critical functional alveolar-capillary interface of the human lung. This bioinspired microdevice reproduces complex integrated organ-level responses to bacteria and inflammatory cytokines introduced into the alveolar space. In nanotoxicology studies, this lung mimic revealed that cyclic mechanical strain accentuates toxic and inflammatory responses of the lung to silica nanoparticles. Mechanical strain also enhances epithelial and endothelial uptake of nanoparticulates and stimulates their transport into the underlying microvascular channel. Similar effects of physiological breathing on nanoparticle absorption are observed in whole mouse lung. Mechanically active "organ-on-a-chip" microdevices that reconstitute tissue-tissue interfaces critical to organ function may therefore expand the capabilities of cell culture models and provide low-cost alternatives to animal and clinical studies for drug screening and toxicology applications.

Development of a Physiologically Based Pharmacokinetic Model for Decane, a Constituent of Jet Propellent-8

Decane, a 10-carbon n-alkane and one of the highest vapor phase constituents of jet propellent-8 (JP-8), was selected to represent the semivolatile fraction for the initial development of a physiologically based pharmacokinetic (PBPK) model for JP-8. Rats were exposed to decane vapors at time-weighted average concentrations of 1200, 781, or 273 ppm in a 32-L Leach chamber for 4 h. Time-course samples for 1200 ppm and end-of-exposure samples for 781 and 273 ppm decane exposures were collected from blood, brain, liver, fat, bone marrow, lung, skin, and spleen. The pharmacokinetics of decane could not be described by flow-limited assumptions and measured in vitro tissue/air partition coefficients. A refined PBPK model for decane was then developed using flow-limited (liver and lung) and diffusion-limited (brain, bone marrow, fat, skin, and spleen) equations to describe the uptake and clearance of decane in the blood and tissues. Partition coefficient values for blood/air and tissue/blood were estimated by fitting end-of-exposure pharmacokinetic data and assumed to reflect the available decane for rapid exchange with blood. A portion of decane is speculated to be sequestered in "deep" pools in the body, unavailable for rapid exchange with blood. PBPK model predictions were adequate in describing the tissues and blood kinetics. For model validation, the refined PBPK model for decane had mixed successes at predicting tissue and blood concentrations for lower concentrations of decane vapor, suggesting that further improvements in the model may be necessary to extrapolate to lower concentrations.

Morphometry of the extremely thin pulmonary blood-gas barrier in the chicken lung

The gas exchanging region in the avian lung, although proportionally smaller than that of the mammalian lung, efficiently manages respiration to meet the high energetic requirements of flapping flight. Gas exchange in the bird lung is enhanced, in part, by an extremely thin blood-gas barrier (BGB). We measured the arithmetic mean thickness of the different components (endothelium, interstitium, and epithelium) of the BGB in the domestic chicken lung and compared the results with three mammals. Morphometric analysis showed that the total BGB of the chicken lung was significantly thinner than that of the rabbit, dog, and horse (54, 66, and 70% thinner, respectively) and that all layers of the BGB were significantly thinner in the chicken compared with the mammals. The interstitial layer was strikingly thin in the chicken lung ( approximately 86% thinner than the dog and horse, and 75% thinner than rabbit) which is a paradox because the strength of the BGB is believed to come from the interstitium. In addition, the thickness of the interstitium was remarkably uniform, unlike the mammalian interstitium. The uniformity of the interstitial layer in the chicken is attributable to a lack of the supportive type I collagen cable that is found in mammalian alveolar lungs. We propose that the surrounding air capillaries provide additional structural support for the pulmonary capillaries in the bird lung, thus allowing the barrier to be both very thin and extremely uniform. The net result is to improve gas exchanging efficiency.

Development, structure, and function of a novel respiratory organ, the lung-air sac system of birds: to go where no other vertebrate has gone

Among the air-breathing vertebrates, the avian respiratory apparatus, the lung-air sac system, is the most structurally complex and functionally efficient. After intricate morphogenesis, elaborate pulmonary vascular and airway (bronchial) architectures are formed. The crosscurrent, countercurrent, and multicapillary serial arterialization systems represent outstanding operational designs. The arrangement between the conduits of air and blood allows the respiratory media to be transported optimally in adequate measures and rates and to be exposed to each other over an extensive respiratory surface while separated by an extremely thin blood-gas barrier. As a consequence, the diffusing capacity (conductance) of the avian lung for oxygen is remarkably efficient. The foremost adaptive refinements are: (1) rigidity of the lung which allows intense subdivision of the exchange tissue (parenchyma) leading to formation of very small terminal respiratory units and consequently a vast respiratory surface; (2) a thin blood-gas barrier enabled by confinement of the pneumocytes (especially the type II cells) and the connective tissue elements to the atria and infundibulae, i.e. away from the respiratory surface of the air capillaries; (3) physical separation (uncoupling) of the lung (the gas exchanger) from the air sacs (the mechanical ventilators), permitting continuous and unidirectional ventilation of the lung. Among others, these features have created an incredibly efficient gas exchanger that supports the highly aerobic lifestyles and great metabolic capacities characteristic of birds. Interestingly, despite remarkable morphological heterogeneity in the gas exchangers of extant vertebrates at maturity, the processes involved in their formation and development are very similar. Transformation of one lung type to another is clearly conceivable, especially at lower levels of specialization. The crocodilian (reptilian) multicameral lung type represents a Bauplan from which the respiratory organs of nonavian theropod dinosaurs and the lung-air sac system of birds appear to have evolved. However, many fundamental aspects of the evolution, development, and even the structure and function of the avian respiratory system still remain uncertain.

An allometric study of lung morphology during development in the Australian pelican, Pelicanus conspicillatus, from embryo to adult

Pelicans produce altricial chicks that develop into some of the largest birds capable of sustained flight. We traced pulmonary morphological development in the Australian pelican, Pelicanus conspicillatus, from third trimester embryos to adults. We described growth and development with allometric relationships between lung components and body mass or lung volume, according to the equation y = ax(b). Pelican lung volume increased faster than body mass (b = 1.07). Relative to lung volume, the airways and vascular spaces increased allometrically (b > 1) in embryos, but isometrically (b approximately 1) after hatching. Parabronchial mantle volume decreased (b < 1) prior to hatching and increased isometrically thereafter. Surface area of air capillaries, blood capillaries and the blood-gas barrier increased relative to lung volume (b > 0.67) before and after hatching. Barrier thickness decreased before hatching, remained constant in juveniles and decreased by adulthood. The anatomical diffusing capacity significantly increased before hatching (b = 4.44) and after hatching (b = 1.26). Although altricial pelicans developed pulmonary complexity later than precocial turkeys, the volume-specific characteristics were similar. However, lungs of volant adult pelicans became significantly larger, with a greater capacity for gas exchange, than lungs of terrestrial turkeys. Exchange characteristics of growing pelican lungs were inferior to those of adult birds of 26 other species, but converged with them at maturity.

Coexpression of RTI40 with alveolar epithelial type II cell proteins in lungs following injury: identification of alveolar intermediate cell types

Injured alveolar epithelial type (AT) I cells are replaced following the proliferation and transformation of ATII cells to new ATI cells. RTI(40) is an ATI cell-specific protein required for normal lung development. We hypothesized that intermediate cell types in the ATII-to-ATI cell transformation would coexpress RTI(40) and ATII cell-selective proteins. To test this hypothesis, we used a rat model of Staphylococcus aureus-induced acute lung injury and a panel of ATI and ATII cell-specific and -selective antibodies. S. aureus induced an acute inflammatory reaction that was resolving by day 3 postinoculation. At day 3 postinoculation, the alveolar wall was thickened secondary to ATII cell hyperplasia. With the use of confocal microscopy, there was a fivefold increase in the fractional surface area of alveolar walls stained with ATII cell membrane proteins (RTII(70) and MMC4) and a decrease in the fractional surface area associated with RTI(40)-expressing cells. S. aureus-treated lungs also contained unique cell types that coexpressed the RTI(40) and ATII markers RTI(40)/MMC4/RTII(70)- and RTI(40)/MMC4-positive cells. These cells were not observed in control lungs. RTI(40)/MMC4-positive cells were also found in cultured ATII cells before they transformed to an ATI-like phenotype. Our data suggest that RTI(40)/MMC4/RTII(70)- and RTI(40)/MMC4-positive cells are intermediates in the ATII-to-ATI cell transformation. These data also suggest that the coexpression of RTI(40) with ATII cell proteins may be used to identify and investigate ATII cell transdifferentiation to ATI cells following injury.

[Protective effects of bactericidal/permeability increasing protein simulated peptide on murine acute lung injury induced by lipopolysaccharide]

OBJECTIVE

To investigate the protective effects of bactericidal/permeability increasing protein simulated peptide (bactericidal neutralizing endotoxin protein, BNEP) on murine acute lung injury (ALI) induced by lipopolysaccharide (LPS).

METHODS

A murine model of ALI was reproduced by lipopolysaccharide via intranasal instillation. The Balb/c mice were randomly divided into control (n = 20, with nasal instillation of isotonic saline), LPS instillation (n = 20, with nasal instillation of isotonic saline and LPS) and BNEP treatment (n = 20, with nasal instillation of isotonic saline plus LPS and BNEP) groups. The ratio of lung wet weight to dry weight, the permeability of pulmonary capillary vessels and the histopathology of pulmonary tissue were determined in all groups. The change in the expression of Toll-like receptor 2 and 4 (TLR2/4) in the pulmonary tissue was detected by immunohistochemistry.

RESULTS

Compared with LPS instillation group, the ratio of lung wet weight to dry weight and the permeability of pulmonary capillary vessel was decreased significantly in the BNEP group, and the inflammatory infiltration in the pulmonary tissue induced by neutrophil influx was alleviated markedly with BNEP treatment. The expression of TLR2 and TLR4 in pulmonary vascular endothelial cells, macrophages and alveolar type II epithelial cells in BNEP group were lower than those in LPS group (TLR2: 128 +/- 10 vs 214 +/- 12, P < 0.01).

CONCLUSION

BNEP, as a simulated peptide of BPI, exerted a remarkable protective effect on ALI induced by LPS.

Tacrolimus reduces staphylococcal colonization on the skin in Korean atopic dermatitis patients

It is well known that topical tacrolimus is safe and effective in the treatment of atopic dermatitis (AD) patients. Tacrolimus is primarily an immunosuppressive agent without any antistaphylococcal effects. Thus colonization of Staphylococcus aureus on the skin of patients treated with this agent might be increased. The purpose of this study was to determine the effect of tacrolimus on S. aureus colonization in patients with AD and to compare the results with clinical severity and skin barrier function. We enrolled 65 patients with moderate to severe AD. They were treated with 0.03% tacrolimus ointment twice daily for 4 weeks. Clinical severity was assessed by the eczema area and severity index (EASI). S. aureus colonization was measured by the tape method. Skin barrier function was checked by measuring transepidermal water loss (TEWL). Evaluations were performed at weeks 0 (baseline), 1, 2 and 4. The results were compared and statistical analysis was performed. S. aureus colonization was significantly decreased with tacrolimus treatment at week 1 compared with baseline. However, there were no differences among weeks 1, 2 and 4. EASI and TEWL showed a decreasing tendency in a time-dependent fashion. The correlations between data were variable.

Emerging technologies that overcome biological barriers for therapeutic protein delivery

In the past decade, genomic research and the nascent field of proteomics have exponentially increased the number of potential protein therapeutic molecules for treating medical needs that were previously unmet. To realise the full clinical potential of many of the novel protein drug entities arising from these intense research efforts, emerging protein delivery technologies may be required. Advanced delivery technologies may offer the ability to overcome biochemical and anatomical barriers to protein drug transport, without incurring adverse events, to deliver the agent(s) at a certain desired rate and duration, to protect therapeutic macromolecules from in situ or systemic degradation, as well as increase their therapeutic index by targeting the drug action to a specific site. This review will cover a myriad of novel and emerging technologies that are directed at bypassing biological barriers and that have shown promise in advancing the therapeutic potential of protein drugs.

Vulnerability of Pulmonary Capillaries During Exercise

Pulmonary capillaries have a dilemma. Their walls must be extremely thin for efficient gas exchange, but be immensely strong to resist the mechanical stresses that develop during heavy exercise. Elite human athletes at maximal exercise develop changes in the structure of the capillary wall as evidenced by red blood cells in their alveoli. Racehorses routinely break their pulmonary capillaries while galloping.

Morphology of the air-breathing stomach of the catfish Hypostomus plecostomus

Histological and ultrastructural investigations of the stomach of the catfish Hypostomus plecostomus show that its structure is different from that typical of the stomachs of other teleostean fishes: the wall is thin and transparent, while the mucosal layer is smooth and devoid of folds. The epithelium lining the whole internal surface of the stomach consists of several types of cells, the most prominent being flattened respiratory epithelial cells. There are also two types of gastric gland cells, three types of endocrine cells (EC), and basal cells. The epithelial layer is underlain by capillaries of a diameter ranging from 6.1-13.1 microm. Capillaries are more numerous in the anterior part of the stomach, where the mean number of capillary sections per 100 microm of epithelium length is 4, compared with 3 in the posterior part. The cytoplasm of the epithelial cells, apart from its typical organelles, contains electron-dense and lamellar bodies at different stages of maturation, which form the sites of accumulation of surfactant. Small, electron-dense vesicles containing acidic mucopolysaccharides are found in the apical parts of some respiratory epithelial cells. Numerous gastric glands (2 glands per 100 microm of epithelium length), composed of two types of pyramidal cells, extend from the surface epithelium into the subjacent lamina propria. The gland outlets, as well as the apical cytoplasm of the cells are Alcian blue-positive, indicating the presence of acidic mucopolysaccharides. Zymogen granules have not been found, but the apical parts of cells contain vesicles of variable electron density. The cytoplasm of the gastric gland cells also contains numerous electron-dense and lamellar bodies. Gastric gland cells with electron-dense cytoplasm and tubulovesicular system are probably involved in the production of hydrochloric acid. Fixation with tannic acid as well as with ruthenium red revealed a thin layer of phospholipids and glycosaminoglycans covering the entire inner surface of the stomach. In regions of the epithelium where the capillaries are covered by the thin cytoplasmic sheets of the respiratory epithelial cells, a thin air-blood barrier (0.25-2.02 microm) is formed, thus enabling gaseous exchange. Relatively numerous pores closed by diaphragms are seen in the endothelium lining the apical and lateral parts of the capillaries. Between gastric gland cells, solitary, noninnervated endocrine cells (EC) of three types were found. EC are characterized by lighter cytoplasm than the surrounding cells and they contain dense core vesicles (DCV) with a halo between the electron-dense core and the limiting membrane. EC of type I are the most abundant. They are of an open type, reaching the stomach lumen. The round DCV of this type, with a diameter from 92-194 nm, have a centrally located core surrounded by a narrow halo. EC of type II are rarely observed and are of a closed type. They possess two kinds of DCV with a very narrow halo. The majority of them are round, with a diameter ranging from 88-177 nm, while elongated ones, 159-389 nm long, are rare. EC of type III are numerous and also closed. The whole cytoplasm is filled with large DCV: round, with a diameter from 123-283 nm, and oval, 230-371 nm long, both with a core of irregular shape and a wide, irregular halo. EC are involved in the regulation of digestion and probably local gas exchange. In conclusion, the thin-walled stomach of Hypostomus plecostomus, with its rich network of capillaries, has a morphology suggesting it is an efficient organ for air breathing.

[Alveolar epithelial barrier in patients with acute respiratory distress syndrome (ARDS)]

The clearance of alveolar fluid depends on the anatomic and physiologic integrity of alveolar epithelial barrier. The vectorial transport of sodium begins at the apical surface in the type II cell through amiloride-sensitive sodium channel. Sodium is pumping by Na, K-ATPasa from the basolateral surface of type II cell to the interstice. Water passes through specialized channels in the type I cell membrane by the osmotic gradient created by sodium. The activity of the sodium transporters is regulated actively by genetics and depends on molecular processes that involve the hormonal stimulation. The damage to the epithelial membrane produces an increased of the permeability of great molecules, which favors generation of edema in the alveolar space, delay in the resolution and incapacity to regenerate epithelium. More clinic trials are required to demonstrate the paper of the transport of chloride and to clarify the true function of the specialized water channels in the regulation of the alveolar fluid clearance.

Liquid-ordered microdomains in lipid rafts and plasma membrane of U-87 MG cells: a time-resolved fluorescence study

Lipid rafts, the functional microdomains in the cell membrane, are believed to exist as liquid-ordered (Lo) phase domains along with the liquid-disordered (Ld) phase of the bulk of the cell membranes. We have examined the lipid order in model and natural membranes by time-resolved fluorescence of trimethylammonium-1,6-diphenylhexatriene incorporated into the membranes. The lipid phases were discerned by the limiting anisotropy, rotational diffusion rate and distribution of the fluorescence lifetime. In dipalmitoylphosphatidylcholine (DPPC)-cholesterol mixtures the gel phase exhibited higher anisotropy and a two-fold slower rotational diffusion rate of the probe as compared to the Ld phase. On the other hand, the Lo phase exhibited higher limiting anisotropy but a rotational diffusion rate comparable to the Ld phase. The Ld and Lo phases elicited unimodal distribution of lifetimes with distinct mean values and their co-existence in phospholipid-cholesterol mixtures was reflected as a biphasic change in the width of the lifetime distribution. Global analysis of the lifetimes yielded a best fit with two lifetimes which were identical to those observed in single Lo or Ld phases, but their fractional contribution varied with cholesterol concentration. Attributing the shorter and longer lifetime components to the Ld and Lo phases, respectively, the extent of the Lo/Ld phase domains in the membranes was estimated by their fractional contribution to the fluorescence decay. In ternary mixtures of egg PC-gangliosides-cholesterol, the gangliosides induced heterogeneity in the membrane but the Ld phase prevailed. The Lo phase properties were observed only in the presence of cholesterol. Results obtained in the plasma membrane and detergent-resistant membrane fractions (DRMs) isolated from U-87 MG cells revealed that DRMs mainly possess the Lo phase; however, a substantially large proportion of plasma membrane also exists in the Lo phase. Our data show that, besides cholesterol, the membrane proteins play a significant role in the organization of lipid rafts and, furthermore, a considerable amount of heterogeneity is present among the lipid rafts.

T1alpha, a lung type I cell differentiation gene, is required for normal lung cell proliferation and alveolus formation at birth

T1alpha, a differentiation gene of lung alveolar epithelial type I cells, is developmentally regulated and encodes an apical membrane protein of unknown function. Morphological differentiation of type I cells to form the air-blood barrier starts in the last few days of gestation and continues postnatally. Although T1alpha is expressed in the foregut endoderm before the lung buds, T1alpha mRNA and protein levels increase substantially in late fetuses when expression is restricted to alveolar type I cells. We generated T1alpha null mutant mice to study the role of T1alpha in lung development and differentiation and to gain insight into its potential function. Homozygous null mice die at birth of respiratory failure, and their lungs cannot be inflated to normal volumes. Distal lung morphology is altered. In the absence of T1alpha protein, type I cell differentiation is blocked, as indicated by smaller airspaces, many fewer attenuated type I cells, and reduced levels of aquaporin-5 mRNA and protein, a type I cell water channel. Abundant secreted surfactant in the narrowed airspaces, normal levels of surfactant protein mRNAs, and normal patterns and numbers of cells expressing surfactant protein-B suggest that differentiation of type II cells, also alveolar epithelial cells, is normal. Anomalous proliferation of the mesenchyme and epithelium at birth with unchanged numbers of apoptotic cells suggests that loss of T1alpha and/or abnormal morphogenesis of type I cells alter the proliferation rate of distal lung cells, probably by disruption of epithelial-mesenchymal signaling.

[Structural manifestations of changes in lipid metabolism at the blood-gas barrier developed following prior ventricular fibrillation in patients in the acute period of myocardial infarction]

On the material of necropsies, structural changes were studied in the blood-air barrier in patients in the acute period of myocardial infarction developed in the wake of prior ventricular fibrillation. It has been ascertained that in the lungs, there develop significant alterative changes that are characterized by adipose degeneration and destruction of components of the surfactant system.

Chronic bronchial allergic inflammation increases alveolar liquid clearance by TNF-alpha -dependent mechanism

Bronchial inflammation in allergic asthma is associated with active exudation from the bronchial tree into the interstitial space of both mucosa and submucosa. The aim of this study was to evaluate epithelial and endothelial permeability as well as alveolar fluid movement in a model of chronic allergic inflammation in Brown-Norway rats sensitized and challenged with ovalbumin (OA). Control groups were challenged with saline solution (C), and rats were immunized by OA but not challenged (Se). Lung sections showed a marked inflammatory infiltrate associated with perivascular and peribronchiolar edema in OA. To measure alveolar liquid clearance, a 5% bovine albumin solution with 1 microCi of (125)I-labeled human albumin was instilled into the air spaces. Alveolar-capillary barrier permeability was evaluated by intravascular injection of 1 microCi of (131)I-labeled albumin. Endothelial permeability was significantly increased in OA, from 0.08 +/- 0.01 in the C group to 0.19 +/- 0.03 in OA group (P < 0.05). Final-to-initial protein ratio was also statistically higher in OA (1.6 +/- 0.05) compared with C (1.38 +/- 0.03, P = 0.01) and Se groups (1.42 +/- 0.03, P = 0.04). Administration of anti-tumor necrosis factor-alpha antibodies within the instillate significantly decreased this ratio (1.32 +/- 0.08, P = 0.003 vs. OA). To conclude, we demonstrated a tumor necrosis factor-alpha-dependent increase in alveolar fluid movement in a model of severe bronchial allergic inflammation associated with endothelial and epithelial leakage.

Drug absorption by the respiratory mucosa: cell culture models and particulate drug carriers

The inhalation route is of increasing interest for both local and systemic drug delivery, including macromolecular biopharmaceuticals, such as peptides, proteins, and gene therapeutics. In addition to appropriate aerosolization for deposition in relevant areas of the respiratory tract, therapeutic molecules may require an advanced carrier system for safe and efficient delivery to their target. Two approaches to obtain novel carrier systems for pulmonary drug delivery are large porous microparticles with a low aerodynamic diameter and lectin-functionalized liposomes. Epithelial cells of alveolar or bronchial origin, obtained either from patient material or from established cell lines, can be grown on permeable filter supports, resulting in polarized monolayers with functional intercellular junctions. With such in vitro models, transport of drugs into pulmonary epithelial cells and/or across the air-blood barrier, as well as the effect and efficacy of novel drug carrier systems can be systematically studied.

Immunity, inflammation, and remodeling in the airway epithelial barrier: epithelial-viral-allergic paradigm

The concept that airway inflammation leads to airway disease has led to a widening search for the types of cellular and molecular interactions responsible for linking the initial stimulus to the final abnormality in airway function. It has not yet been possible to integrate all of this information into a single model for the development of airway inflammation and remodeling, but a useful framework has been based on the behavior of the adaptive immune system. In that paradigm, an exaggeration of T-helper type 2 (Th2) over Th1 responses to allergic and nonallergic stimuli leads to airway inflammatory disease, especially asthma. In this review, we summarize alternative evidence that the innate immune system, typified by actions of airway epithelial cells and macrophages, may also be specially programmed for antiviral defense and abnormally programmed in inflammatory disease. Furthermore, this abnormality may be inducible by paramyxoviral infection and, in the proper genetic background, may persist indefinitely. Taken together, we propose a new model that highlights specific interactions between epithelial, viral, and allergic components and so better explains the basis for airway immunity, inflammation, and remodeling in response to viral infection and the development of long-term disease phenotypes typical of asthma and other hypersecretory airway diseases.

Differences in corneocyte surface area in pre- and post-menopausal women. Assessment with the noninvasive videomicroscopic imaging of corneocytes method (VIC) under basal conditions

The differences between pre- and postmenopausal women and men on corneocyte surface area were investigated by a noninvasive exfoliation method. Surface corneocytes were collected with a modified detergent scrub technique. Separated corneocytes were analyzed by videomicroscopy and image analyses (NIH Image 1.59). Additionally transepidermal water loss (TEWL) and stratum corneum hydration, water-holding capacity and moisture accumulation velocity were measured. 21 postmenopausal females without hormonal substitution (age 50.6 years), 33 premenopausal women (age 41.0 years) and 25 men matched for age (age 44.0 years) were included in this study. The smallest corneocyte surface area was seen in premenopausal women (368.0 pixels). For postmenopausal women and the male control population almost equal values could be detected (postmenopausal women 401.1 pixels; men 401.8 pixels). Significant differences were calculated with the ANOVA test (p = 0.0050) and post-hoc analyses (Dunn test); premenopausal vs. postmenopausal women (p < 0.05) and premenopausal women vs. men (p < 0.05), but not postmenopausal women vs. men (p > 0.05). No statistically significant differences could be detected for TEWL, stratum corneum hydration parameters. No correlation could be found between the corneocyte surface area and barrier or hydration parameters. The detected differences support the hypothesis that sexual hormones have an impact on corneocyte surface area, because sex hormone levels are higher in premenopausal women than in non-hormone-substituted postmenopausal women or men.

Iontophoretic transport across the skin

There have been many attempts to define the key relationships between passive drug diffusion across the skin and the molecular and physicochemical properties of the permeant. At the present time, the importance of lipophilicity (or hydrogen bond donor and acceptor properties) and of molecular volume are well established, and useful predictive relationships for passive percutaneous permeability exist. With respect to iontophoresis, on the other hand, the situation is far less clear and the mechanisms involved have not been completely defined. The roles of electromigration and electroosmosis (current-induced convective solvent flow) are now beginning to be understood and experimentally separated. In turn, this allows the manner in which certain physicochemical parameters influence the efficiency of drug electrotransport to be deduced. An initial examination of a database drawn from the literature and from our own work (for which the experimental conditions employed were reasonably constant) suggests a rather sharp dependence of cationic drug delivery via electromigration upon molecular size. We suggest that the analysis reveals useful paths for further investigation.

New aspects of the skin barrier organization

In the superficial layer of the skin, the stratum corneum (SC), the lipids form two crystalline lamellar phases with periodicities of 6.4 and 13.4 nm (long-periodicity phase). The main lipid classes in SC are ceramides, free fatty acids and cholesterol. Studies with mixtures prepared with isolated ceramides revealed that cholesterol and ceramides are very important for the formation of the lamellar phases, and the presence of ceramide 1 is crucial for the formation of the long-periodicity phase. This observation and the broad-narrow-broad sequence of lipid layers in the 13.4-nm phase led us to propose a molecular model for this phase. This consists of one narrow central lipid layer with fluid domains on both sides of a broad layer with a crystalline structure. This model is referred to as 'the sandwich model'. While the presence of free fatty acids does not substantially affect the lipid lamellar organization, it is crucial for the formation of the orthorhombic sublattice, since the addition of free fatty acids to cholesterol/ceramide mixtures results in transition from a hexagonal to a crystalline lipid phase. Studies examining lipid organization in SC derived from dry or lamellar X-linked ichthyosis skin revealed that in native tissue the role of ceramide 1 and free fatty acids is similar to that observed with mixtures prepared with isolated SC lipids. From this we conclude that the results obtained with lipid mixtures can be used to predict the SC lipid organization in native tissue.

Serum Clara cell protein (CC16), a marker of the integrity of the air-blood barrier in sarcoidosis

To test the hypothesis that sarcoidosis is associated with an intravascular leakage of lung epithelium secretory proteins, the occurrence and determinants in serum of sarcoid patients of CC16, a small size and readily diffusible lung-specific protein of 16 kDa secreted by bronchiolar Clara cells, was investigated. CC16 was measured by a sensitive latex immunoassay in the serum of 117 patients with established sarcoidosis and of 117 healthy subjects matched for age, sex and smoking status. Stepwise regression analysis was used to identify extrapulmonary variables of CC16 changes in serum. These changes were then compared with biochemical and cellular parameters in bronchoalveolar lavage fluid (BALF) as well as with the number of CC16 immunostaining cells on bronchial or pulmonary biopsy samples. CC16 concentration in serum of sarcoid patients was significantly increased, compared to their matched controls (25.9 +/- 16.2 versus 13.9 +/- 5.2 microg x L(-1)). In nonsmoking patients without significant renal impairment, CC16 in serum increased with the severity of the chest radiograph and computed tomography changes, and was on average 50-100% higher when parenchymal involvement was present. Sarcoid patients had, however, normal levels of CC16 in BALF and an unchanged number of CC16-immunopositive cells in lung biopsy samples, suggesting that an increased secretion of CC16 in the sarcoid lung is very unlikely, and that the elevation of CC16 in sarcoidosis results from an increased intravascular leakage of the protein across the air-blood barrier. The present study suggests that CC16 in serum might provide a useful tool to noninvasively evaluate the damage and increased permeability to proteins of the air-blood barrier associated with sarcoidosis.

Effect of prior high-intensity exercise on exercise-induced arterial hypoxemia in Thoroughbred horses

Strenuously exercising horses exhibit arterial hypoxemia and exercise-induced pulmonary hemorrhage (EIPH), the latter resulting from stress failure of pulmonary capillaries. The present study was carried out to examine whether the structural changes in the blood-gas barrier caused by a prior bout of high-intensity short-term exercise capable of inducing EIPH would affect the arterial hypoxemia induced during a successive bout of exercise performed at the same workload. Two sets of experiments, double- and single-exercise-bout experiments, were carried out on seven healthy, sound Thoroughbred horses. Experiments were carried out in random order, 7 days apart. In the double-exercise experiments, horses performed two successive bouts (each lasting 120 s) of galloping at 14 m/s on a 3.5% uphill grade, separated by an interval of 6 min. Exertion at this workload induced arterial hypoxemia within 30 s of the onset of galloping as well as desaturation of Hb, a progressive rise in arterial PCO2, and acidosis as exercise duration increased from 30 to 120 s. In the single-exercise-bout experiments, blood-gas/pH data resembled those from the first run of the double-exercise experiments, and all horses experienced EIPH. Thus, in the double-exercise experiments, before the horses performed the second bout of galloping at 14 m/s on a 3.5% uphill grade, stress failure of pulmonary capillaries had occurred. Although arterial hypoxemia developed during the second run, arterial PO2 values were significantly (P < 0.01) higher than in the first run. Thus prior exercise not only failed to accentuate the severity of arterial hypoxemia, it actually diminished the magnitude of exercise-induced arterial hypoxemia. The decreased severity of exercise-induced arterial hypoxemia in the second run was due to an associated increase in alveolar PO2, as arterial PCO2 was significantly lower than in the first run. Thus our data do not support a role for structural changes in the blood-gas barrier related to the stress failure of pulmonary capillaries in causing the exercise-induced arterial hypoxemia in horses.

The presence of v-abl-transformed V3 mast cells in the lungs augments pulmonary vascular permeability to acid aspiration

Acid aspiration causes pulmonary vascular permeability and PMN sequestration. By increasing pulmonary mast cells through adoptive transfer of v-abl-transformed mast cells (V3MCs) into BALB/c mice, we now show that the greater mast cell number in the lung is associated with increased pulmonary injury.

Thickness of the air-blood tissue barrier in infants

The harmonic mean barrier thickness of the alveolar air-blood tissue barrier was measured in nine SIDS cases, six cases of unnatural death (three with asphyxiation, three without asphyxiation) and six cases showing interstitial pneumonia (IP, three cases with lymphomonocyte infiltration of alveolar walls, three cases with peribronchiolar infiltration). Approximately 550-600 measurements were carried out in each case using micrographs with a final magnification of 11,000. The Th values ranged between 0.37 micron and 0.39 micron in the SIDS group, in deaths due to asphyxiation and IP with a peribronchiolar type of infiltration, were lowest in the unnatural deaths without asphyxiation (0.32 micron) and highest in cases showing IP with alveoloseptal infiltration (0.44 micron). The differences between the groups were significant (H-test, Hcor = 5.927). Compared to "normal" unnatural deaths (Th = 0.32 micron), cases with interstitial cell infiltration of the alveolar septa showed a nearly 40% increase of the barrier thickness which indicates a corresponding decrease of the diffusion capacity. A decreased diffusion capacity can cause hypoxemia which could be an additional trigger mechanism in the death process.

EEMCO guidance for the assessment of transepidermal water loss in cosmetic sciences

Measurement of transepidermal water loss (TEWL), based on the estimation of the water vapour gradient in an open chamber, is being used to support claims of cosmetics including product mildness, reduction in irritative skin reactions, skin hydration, skin repair, protective effect against UV damage and others. TEWL measurement can also screen ingredients that have a beneficial effect on the barrier function and offer the possibility to monitor in vivo, on human skin, the effect of topical treatment in an objective and non-invasive way. A high number of variables affecting TEWL measurements have been identified. These should be rigorously taken into consideration. To work under standardised conditions is of the utmost importance to obtain reliable and reproducible results.

Effect of high transcapillary pressures on capillary ultrastructure and permeability coefficients in dog lung

To determine the correlation between ultrastructural and physiological changes in blood-gas barrier function in lungs transiently exposed to very high vascular pressures, we increased capillary transmural pressure (Ptm) of 6 canine isolated perfused left lower lung lobe preparations (high-pressure group) to 80.3 Torr for 3.8 min and then determined the capillary filtration (K(fc)) and osmotic reflection (sigma(d)) coefficients at a Ptm of 19.1 Torr in the ventilated lung lobes. This was followed by perfusion fixation of the lobes at a Ptm of 20.5 Torr for ultrastructural analysis. These data were compared with those obtained in six lobes in which Ptm was not transiently elevated before K(fc), sigma(d), and ultrastructural evaluation. K(fc) was higher [0.249 +/- 0.042 (SE) vs. 0.054 +/- 0.009 g. min(-1). Torr(-1). 100 g(-1); P < 0.01] and sigma(d) was lower (0.52 +/- 0.07 vs. 0.85 +/- 0.08; P < 0.01) in the high-pressure group. In contrast, although endothelial and epithelial breaks were occasionally observed in some experiments, their incidence was not increased in the high-pressure group. These data suggest that the increased transvascular water and protein flux occurred through pathways of a size not resolvable by electron microscopy after vascular perfusion-fixation at a Ptm of 20.5 Torr.

[The ultrastructural changes in the air-blood barrier in the acute period of a myocardial infarct with the development of pneumonia (data from autopsy materials)]

In this paper, the author highlights the ultrastructural changes in the lung respiratory zone during the acute period of myocardial infarction in origination and development of pneumonia. The development of inflammatory process was found out to be preceded by microcirculation disorders, focal damage to the gas-blood barrier, and lung tissue bacterial contamination at day 2 to 4 of the course of myocardial infarction. The exudate was seen to contain much fibrin, alveolar macrophages, and erythrocytes. The lung tissue develops albuminous and fatty degeneration with the alveolar septa and lumina storing fibrin and fatty drops.

[The structural changes in the lungs in the acute period of a myocardial infarct in the wake of ventricular fibrillation]

Time-related course was studied of structural changes in the lung tissue in acute myocardial infarction having developed in the wake of secondary ventricular fibrillation, using investigational methods common in biology, histochemistry, and electron-microscopy. It has been found out that development in patients with acute myocardial infarction of ventricular fibrillation greatly aggravates the course of the illness inducing origination of profound and even irreversible alternative changes in all constituents of the aerohematic barrier. The above patients developed structural as well as functional pulmonary insufficiency which is at its greatest within 2 to 4 days of the onset of ventricular fibrillation.

Differentiated and functional human airway epithelium regeneration in tracheal xenografts

To investigate the regeneration process of a well-differentiated and functional human airway epithelium, we adapted an in vivo xenograft model in which adult human nasal epithelial cells adhere and progressively repopulate denuded rat tracheae grafted in nude mice. The proliferating activity, the degree of differentiation, and the barrier integrity of the repopulated epithelium were studied during the regeneration process at optical and ultrastructural levels with immunocytochemistry and a permeability tracer. Three days after implantation in nude mice, tracheal xenografts were partially repopulated with a flattened nonciliated and poorly differentiated leaky epithelium. By the end of the first week after the graft, cell proliferation produced on the entire surface of the rat trachea an epithelium that was stratified into multiple layers and tightly sealed. During successive weeks, cell proliferation dramatically decreased. Moreover, the epithelium became progressively columnar, secretory, ciliated, and transiently leaky. At 4-5 wk, a fully differentiated pseudostratified functional epithelial barrier impermeable to a low-molecular-weight tracer was reconstituted. The regeneration of a well-differentiated and functional human airway epithelium in rat tracheae grafted in nude mice includes several steps that mimic the regeneration dynamics of airway epithelium after injury.

Vascular recruitment increases evidence of lung injury

OBJECTIVE

Changes in pulmonary blood flow rate can alter the size of the perfused pulmonary capillary surface area. We tested the hypothesis that full recruitment of the pulmonary vascular bed may decrease evidence of lung injury by recruiting less injured capillaries. We also tested the hypothesis that endothelial ectoenzyme activity is an earlier indicator of lung injury than are permeability measures.

DESIGN

Isolated canine lung lobes were perfused with autologous blood at constant blood flows of either 2.05+/-0.04 L/min (SEM) (high flow, full recruitment, n = 12) or 0.600 +/- 0.004 L/min (low flow, 33% full recruitment, n = 12) after lung injury to determine the effect of vascular recruitment on measures of injury.

SETTING

Research laboratory at a medical university.

SUBJECTS

Lung lobes were obtained from 36 mongrel dogs of either gender.

INTERVENTIONS

Lung injury was induced by adding phorbol myristate acetate (PMA) to the blood perfusing the isolated lung.

MEASUREMENTS AND MAIN RESULTS

Indicator dilution methods were used to measure single pass hydrolysis of 3[H]-benzoyl-Phe-Ala-Pro, a synthetic substrate for angiotensin converting enzyme, and calculate the modified first order kinetic parameter corresponding to the ratio of a normalized maximal enzymatic conversion rate (A(max)) to the Michaelis-Menten constant (K(m)), i.e., A(max)/K(m), before and after PMA. At a given flow rate, the decrease in A(max)/K(m)serves as an index of vascular injury. PMA decreased A(max)/K(m), percent metabolism, and fractional substrate utilization, and increased permeability, vascular resistance, and vascular pressures regardless of flow rate. The decrease in enzyme activity was detected earlier than the increase in permeability.

CONCLUSION

The greater percentage decrease in percent metabolism and fractional substrate utilization and the earlier appearance of increased permeability during high flow indicates that increasing blood flow three-fold recruited injured vessels and/or increased vascular injury by increasing vascular perfusion pressures.

Scanning and transmission electron microscopical evidence of the capacity of diatoms to penetrate the alveolo-capillary barrier in drowning

The diagnostic value of diatom analysis for drowning is considered to be one of the most controversial arguments in forensic medicine. However, the theoretical assumption of the method, i.e. the capacity of diatoms to penetrate the alveolo-capillary barrier during drowning, has never been addressed. Using scanning (SEM) and transmission electron microscopy (TEM), we have investigated the interaction of a natural population of diatoms and an unialgal culture of Phaeodactylum tricornutum (PT) with the alveolo-capillary barrier in an experimental model of drowning. The SEM analysis allowed the identification of several diatom species along the whole airways and their close interaction with the alveolar wall, but was poorly informative about the effective penetration of diatoms into pulmonary vessels. The TEM analysis was more informative and allowed a precise identification of the PT cells in alveolar spaces and to detect their phagocytosis by alveolar macrophages. PT penetrated into the pulmonary vessels through the thinnest portions of the alveolo-capillary barrier and through the interstitial spaces and were identified in pulmonary capillaries and venules. The morphological demonstration of the capacity of diatoms to penetrate the alveolo-capillary barrier is a step forward in assessing the potentiality, reliability and limitations of diatom analysis on a new basis as a tool for the diagnosis of drowning.

The pattern of early lung parenchymal and air space injury following acute blood loss

Acute lung injury is a frequent clinical occurrence following blood loss and trauma. The nature of this injury remains poorly understood.

OBJECTIVE

To examine the relative parenchymal and intra-alveolar distribution of inflammation in a rat model of hemorrhage and resuscitation.

METHODS

Rats were anesthetized and subjected to hemorrhage followed by resuscitation with shed blood and saline. Myeloperoxidase activity of lung homogenates and cytology of bronchoalveolar lavage fluid were used to measure total lung and intra-alveolar neutrophil invasion. Extravasation of i.v.-administered [125I]-albumin was used to determine total lung and alveolar permeability. Permeability results were analyzed using their base-10 logarithmic transformations.

RESULTS

86 animals were studied. Whole-lung myeloperoxidase activity was increased (control = 0.34 +/- 0.16 units, injured = 0.84 +/- 0.43 units, p < 0.01), while there was no difference in intra-alveolar leukocyte counts (injured = 1.85 +/- 1.30 x 10(5)/mL, control = 2.44 +/- 1.75 x 10(5)/mL, p = 0.40), suggesting that the cellular component of the injury was more severe in the intravascular and interstitial spaces. There was a strong trend toward increased permeability in the interstitial compartment, and a significant increase in permeability in the intra-alveolar compartment (whole-lung permeability: control = -0.27 +/- 0.19 units, injured = 0.10 +/- 0.55 units, p = 0.06; alveolar permeability: control = -2.00 +/- 0.47 units, injured = -1.32 +/- 0.49 units, p < 0.01), suggesting that the loss of integrity to macromolecules was not limited to the interstitium.

CONCLUSION

Hemorrhage and resuscitation resulted in an acute lung injury characterized by extravasation of intravascular protein into both the interstitium and the intra-alveolar space. Neutrophil invasion of the lung was demonstrable only in the interstitial compartment.

Alveolo-capillary protein permeability and lung function in patients with late pulmonary complications after allogeneic bone marrow transplantation

A prospective study was performed to identify markers predictive for the development of pulmonary complications in the early (<50 days) and late (>50 days) phase after bone marrow transplantation (BMT). The characterization of BMT patients with early or late pulmonary complications revealed clear-cut differences. Early and long term increase of alveolo-capillary protein permeability was associated with smoking and was found in 20 patients developing pulmonary complications within 50 days after BMT (group 1). The 22 patients who developed such complications thereafter (group 2) had more acute graft vs host disease than 66 patients who remained free of these complications for a minimum of 1 year. Concentrations of bronchoalveolar lavage (BAL) fluid albumin (alb) and serum beta2-microglobulin (S-beta2m) were determined 10 days before BMT, on days 1, 30, and 40 after BMT, whereas lung function tests were performed before BMT, after discharge from the hospital, and 6 months as well 1 year after BMT. Using cut-off values for BAL fluid alb (>2.3 mg/dl) and S-beta2m (>0.8 mg/liter) we could significantly discriminate 12 patients out of 19 group 1 patients (early pulmonary complications) as well as 9 out of 21 group 2 patients (late pulmonary complications) from 12 out of 64 group 3 patients (without such complications) 1 day after BMT. Our results demonstrate that early increased alveolo-capillary protein permeability defines a patient population at risk to develop pulmonary complications later than 50 days after BMT with up to 1 year significantly decreased lung volumes (FEV1, 73% predicted, VC, 85% predicted).