A comparison of freeze‐substitution with other methods for preservation of the pulmonary alveolar lining layer

Kuhn, Charles

doi:10.1002/aja.1001330410

Cited by 26 publications

(4 citation statements)

References 20 publications

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“…Although abundant physiologic evidence suggests that mammalian lung surfaces are covered by an extracellular layer of lipid, or lipid-protein complexes (32), which facilitates a decrease in surface tension when the lungs deflate, the morphology of this layer is uncertain (26,30,35,56,57). Surface layers of mono-or bimolecular dimensions have been demonstrated with such poor reproducibility that it is uncertain that they represent complete layers adsorbed onto all alveolar surfaces.…”

Section: Discussionmentioning

confidence: 99%

Conversion of lamellar body membranes into tubular myelin in alveoli of fetal rat lungs.

Williams¹

1977

The Journal of Cell Biology

283

112

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Fluid-filled lumina of fetal rat lungs contain lamellar bodies (LBs) as well as tubular myelin (TM), both of which are thought to be stores of phospholipid-rich pulmonary surfactant. The alveolar epithelium is believed to secrete LBs, but neither the origin nor the mechanism of TM formation is entirely certain. The main objective of this study was to determine the relationship between secreted LBs and TM and to define membrane phenomena which occur during TM formation. I examined lung tissues of 20-21 day-old fetuses (day 22 = term) using transmission and high voltage transmission electron microscopy and cytochemistry. My findings indicate that secreted LBs, identified by the presence of an acid-phosphatase reactive core, are the precursor of TM. Secreted LBs are highly organized structures which contain structurally specialized areas, one of which is a "mini-lattice" structure similar to TM. During TM formation, fuzzes or 8.0-nm diameter particles appear on transition membranes, although LB membranes appear to lack both structures. Similar particles are present on TM membranes and are generally associated with membrane intersections. My results provide evidence that TM is formed from LBs within the alveolar lumen by mechanisms which may be complex.Abundant evidence suggests that pulmonary surfactant (surface-active material), a phospholipidrich material (5, 32, 33), forms an extracellular layer covering the alveolar epithelium. Numerous studies support the hypothesis that the surfactant prevents alveolar collapse at low lung volumes by decreasing alveolar surface tension; thus, the presence of surfactant is important in maintaining ~or-mal respiratory functions (10, 40). After their synthesis by type II epithelial cells (7,9,29,31), lamellar bodies, the intracellular form of surfactant (2, 6, 18), are secreted into the alveolar lumen as layers of membranes arranged in a spherical granule (43). To perform its proposed function, however, the lamellar body material must be arranged upon lung surfaces to form a phospholipid monolayer which is probably a continuous sheet-like film.Although the sequence of events which takes place in the rearrangement from lamellar form to monolayer has not been directly visualized, morphological, chemical, and physical observations (18,43,52,53) suggest that a second form of surfactant, tubular myelin, is generated within the alveolar lumen. Tubular myelin formation may therefore be an intermediate step in monolayer formation.As described by Weibel et al. (55), tubular myelin is composed of numerous tightly packed tubules whose walls have a trilaminate structure 260

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Section: Discussionmentioning

confidence: 99%

Conversion of lamellar body membranes into tubular myelin in alveoli of fetal rat lungs.

Williams¹

1977

The Journal of Cell Biology

283

112

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“…F IV contained tubular myelin figures . It is known that this structure is a frequent constituent of the lining layer of mammalian and amphibian lungs (27,29) fixed by a method that preserves the integrity of the air-liquid interface . It was surface active (see Table I) .…”

Section: Fatty Acid Compositions Of the Lecithinsmentioning

confidence: 99%

“…These structures have been repeatedly observed in the alveoli of normal and diseased lungs by other authors (22)(23)(24)(25) . By using methods of fixation that permit the preservation of an intact airliquid interface, it was shown that tubular myelin figures are a constant element of the extracellular lining layer of mammalian alveoli (26)(27)(28)(29)(30) . They also appear on the bronchiolar surfaces (31), in pictures of freeze-etched alveoli (32), and their presence in lung washings has been reported (33,34) .…”

Section: Introductionmentioning

confidence: 99%

Isolation and Characterization of Lamellar Bodies and Tubular Myelin From Rat Lung Homogenates

Gil

Reiss

1973

The Journal of Cell Biology

251

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Three surface-active fractions which differ in their morphology have been isolated from rat lung homogenates by ultracentrifugation in a discontinuous sucrose density gradient . In order of increasing density, the fractions consisted, as shown by electron microscopy, primarily of common myelin figures, lamellar bodies, and tubular myelin figures . The lipid of all three fractions contained approximately 94% polar lipids and 2 % cholesterol . In the case of the common myelin figures and the lamellar bodies, the polar lipids consisted of 73% phosphatidylcholines, 9 % phosphatidylserines and inositols, and 8 % phosphatidylethanolamines. In the case of the tubular myelin figures, the respective percentages were 58, 19, and 5 . Over 90% of the fatty acids of the lecithins of all three fractions were saturated . Electrophoresis of the proteins of the fractions in sodium dodecyl sulfate or Triton X-100 revealed that the lamellar bodies and the tubular myelin figures differed in the mobilities of their proteins . The common myelin figures, however, contained proteins from both of the other fractions. These data indicate that, whereas the lipids of the extracellular, alveolar surfactant(s) originate in the lamellar bodies, the proteins arise from another source . It is further postulated that the tubular myelin figures represent a liquid crystalline state of the alveolar surface-active lipoproteins.

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“…Pulmonary surfactant forms a layer which covers not only the alveoli but also alveolar ducts, and is contiguous with secretions present a t the level of the respiratory and terminal bronchiolar regions. At the alveolar level, transmission electron microscopic studies have shown that the surfactant system of the lung has two phases-a superficial, osmiophilic layer a t the air-liquid interface, and a homogeneous, less dense basel layer (136,193,216,372). It has been proposed that the superficial, interfacial layer (epiphase) represents the more potent surface-active phospholipid molecules; the subjacent aqueous phase (hypophase) contains ions, protein, phospholipid, and carbohydrate, a possible reservoir of components necessary for the synthesis a n d or stabilization of the surface-active interfa-cial layer (30, 246,314).…”

Section: Compositionmentioning

confidence: 99%

Lung development and the pulmonary surfactant system: Hormonal influences

Hitchcock

1980

Anat. Rec.

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The effect of hormones on developmental events is not a new area of scientific investigation. However, in the last decade, the developing lung has been the focus of an increasing amount of basic and applied research. Inadequate development of the newborn's respiratory system precludes extra-uterine existence; indeed, such respiratory inadequacy has been a leading cause of death in premature infants. Tremendous strides have been made in understanding the basic cell biology of the developing lung. Much has been learned about the source, composition, and function of pulmonary surfactant, a surface-active material produced by the lung and essential to alveolar stability. Deficient stores of this material is a major etiologic factor in the respiratory distress syndrome of the newborn (RDS). This fact, coupled with observations that certain hormones can accelerate lung development and the consequent availability of adequate stores of pulmonary surfactant, has led to a large body of literaturae dealing with the effects of hormones (and other agents) on lung development. It is the purpose of this literature review (1) to discuss the various kinds of investigations which have linked surfactant synthesis to the type II pulmonary epithelial cell; and (2) to review the current status of research dealing with the effects of glucocorticoids and thyroid hormones on lung maturation.

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A comparison of freeze‐substitution with other methods for preservation of the pulmonary alveolar lining layer

Cited by 26 publications

References 20 publications

Conversion of lamellar body membranes into tubular myelin in alveoli of fetal rat lungs.

Conversion of lamellar body membranes into tubular myelin in alveoli of fetal rat lungs.

Isolation and Characterization of Lamellar Bodies and Tubular Myelin From Rat Lung Homogenates

Lung development and the pulmonary surfactant system: Hormonal influences

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