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1.
Abstract

An attempt was made to determine the nature, origin, and fate of the membrane material of osmiophilic lamellated bodies, using lung tissue from neonate rats. The cytoplasm of the type II alveolar pneumonocyte contains centrioles, multivesicular bodies, and minute free vesicles similar to those in the multivesicular bodies. Autolysosomes, comprising membrane-bounded cytoplasmic regions and osmiophilic lamellated material, also occur in the type II pneumonocytes. The mitochondria often contain concentric membrane accumulations and membranous whorls. The type II alveolar cells are characterised by an intensive autophagy; this is apparently correlated with glycogenolysis, and with a radical cytodifferentiation by which the cells transform to the type I pneumonocyte. The osmiophilic lamellae of the autolysosomes are probably emptied isolation membranes. The mitochondria possibly serve as repositories for the massive membrane accumulations remaining after cytoplasmic lysis, which may invaginate into the organelles. The osmiophilic lamellated bodies typical of type II alveolar pneumonocytes may be mitochondrial membranes packed with the residual membranous material. Myeloid matter in the alveolar spaces (derived from the osmiophilic lamellated bodies) is best interpreted, not as an organised secretory product, but rather as a residue of cellular autophagy.  相似文献   

2.
Cytochemistry of the gas-exchange area in vertebrate lungs   总被引:2,自引:0,他引:2  
Considerable progress has been made in the localization of chemical substances within the gas-exchange zones of vertebrate lungs since cytochemical techniques suitable for use with the electron microscope have been developed. The light microscope, an instrument with an effective resolution limit of about 0.2 micron, is ill-suited for studying regions such as these where small tissue elements are arranged in a complex manner. A wide range of acid hydrolases have been detected in the vacuoles and dense bodies of alveolar macrophages by means of cytochemical techniques. The enzymes demonstrated in this way include acid phosphatase, aryl sulphatase, cathepsin D, beta-glucuronidase, acetyl glucosaminidase, nonspecific esterase, dipeptidyl peptidase II and dipeptidyl peptidase IV. Such enzymes are, of course, to be expected in the lysosomes of cells which have a primary phagocytic role. Nevertheless, it must be confessed that very little is yet known about the actual mechanism of phagocytosis or of the fate of the digested material. It is fortunate, however, that some of the tools which are likely to be of value in research on these aspects of macrophage function are currently being developed. Of particular interest in this connection are the immunocytochemical techniques which permit the localization of surface-associated antigens and intracellular contractile proteins. It must be emphasized that phagocytosis is not the only function of macrophages in the gas-exchange zone of the lung. These cells are thought to be involved in the presentation of exogenous antigenic material to the reactive cells of the lymphoid system. Recent research has also indicated that mammalian alveolar macrophages synthesize a diverse range of substances. Furthermore, the elastases associated with pulmonary macrophages are now thought to be involved in the pathogenesis of emphysema. All of the above-mentioned activities are of great biological and clinical significance and, consequently, merit the cytochemists' attention in future. The epithelial lining of the greater part of the pulmonary gas-exchange area is composed of type I pneumonocytes. In terms of ultrastructure, these are very specialized cells; their extensive and highly-attenuated cytoplasmic processes form the outer layer of the air-blood barrier. No special carrier systems have been identified within type I pneumonocytes and this is in keeping with the claims that oxygen is transferred across the alveolar tissue barrier by a process of simple diffusion. Type II pneumonocytes, in contrast, have considerable metabolic activity.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

3.
C Meban 《Histochemistry》1975,43(4):367-372
The fine structural localization of nonspecific alkaline phosphatase was studied in the granular pneumonocytes (type II alveolar epithelial cells) of hamster lung by incubating sections of glutaraldehyde-fixed tissues in a medium containing lead ions and sodium beta-glycerophosphate or alpha-naphthyl acid phosphate. The specificity of the reaction was tested by exposing the sections to inhibitors of alkaline phosphatase. The results showed that alkaline phosphatase activity was present in the inclusion bodies of granular pneumonocytes. The enzyme reaction was strong in the membrane lining the inclusion bodies and a weaker reaction was generally detectable in the inclusion contents. Although only a proportion of the inclusion bodies showed enzyme activity, there was no obvious correlation between the reactivity of the inclusions and their intracellular position or size. The other organelles were unreactive. The finding of alkaline phosphatase activity within the inclusion bodies of granular pneumonocytes is an enigma as these organelles are generally considered to be lyosomes.  相似文献   

4.
The respiratory epithelium in the lungs of the tortoise (Testudo graeca) has been studied by electron microscopy. The epithelium consists of a mosaic of two different cell types (here called "pneumonocytes"). Type I pneumonocytes are roughly squamous and possess attenuated flanges of cytoplasm which extend over the septal capillaries. Localized cytoplasmic expansions are often present near the periphery of these flanges. Most of the organelles are concentrated in the perinuclear region; the most prominent of these are the mitochondria and osmiophilic inclusions. In contrast, type II pneumonocytes are cuboidal and are richly endowed with organelles including large Golgi complexes, extensive endoplasmic reticulum and numerous inclusion bodies. The morphological evidence suggests that type I pneumonocytes are involved in the secretion of osmiophilic material (presumed to be pulmonary surfactant) and in maintaining the integrity of the air-blood barrier. Type II pneumonocytes appear to be concerned solely with the production of surfactant.  相似文献   

5.
Enzymatically dissociated lungs from rat fetuses at 19-days gestation yield single cells which reaggregate to form alveolar-like structures when cultured on gelatin sponge discs. These structures form within 2 days and have been maintained in vitro for as long as 6 weeks. They are composed primarily of type II pneumonocytes as characterized by large, lightly stained nuclei and cytoplasmic inclusion bodies. The lamellar structure of these inclusion bodies has been confirmed by electron microscopy. The dynamic formation of inclusion bodies is suggested by the presence of lamellar bodies in the extra-cellular space and the appearance of new inclusions in the cytoplasm of the type II pneumonocytes. The formation and long-term maintenance of histotypic lung structures in vitro provides a model system for the study of lung development and synthesis of surfactant by type II alveolar pneumonocytes.  相似文献   

6.
Using electron microscopy we have examined the lining layer of the rat pulmonary alveolus. This layer appears as a morphological entity 1-3 days after birth: it is composed at first of a filamentous Ruthenium Red-negative material derived from lamellar bodies, and subsequently (4 days after birth) of a homogeneous Ruthenium Red-positive material. This latter material, which corresponds to the epithelia lining of the alveolus typical of adult rats, is presumably derived from a mixture of the filamentous material produced by the lamellar bodies, and a material produced by the alveolar cells 4 days after birth which contains acidic groups which bind Ruthenium Red.  相似文献   

7.
Scanning and transmission electron microscopic observations were made on the rattlesnake lung, which has the form of a cigar-shaped bag enclosing a large axial air chamber. The lungs were fixed by tracheal instillation of fixative to preserve the structural features of inflated lungs. An open tracheal groove along the ventral aspect of the lung is the only structural “airway” present. The wall of the lung has two histologically distinct regions: anteriorly, a respiratory portion, where up to three generations of septa subdivide the wall into cup-shaped gas-exchange chambers, termed faveoli; and posteriorly, a simple, thin-walled saccular portion. The epithelium lining the internal surface of the lung is composed of several cell types: (1) ciliated cells; (2) type I pneumonocytes; (3) type II pneumonocytes, secretory cells characterized by the presence of lamellar bodies; and (4) serous epithelial cells, secretory cells characterized by the presence of homogeneous, densely staining secretory granules. However, the distinctiveness of the secretory cell types in the snake lung is blurred because intermediate-appearing cells have both the lamellar body and homogenous type of secretory granule. The nonepithelial components of the pulmonary wall and septa consist of blood vessels and lymphatics, smooth muscle cells and fibroblasts, embedded in a matrix of extracellular connective tissue fibers. Tubular myelin figures were observed in the faveolar lining layer.  相似文献   

8.
Summary Enzymatically dissociated lungs from rat fetuses at 19-days gestation yield single cells which reaggregate to form alveolar-like structures when cultured on gelatin sponge discs. These structures form within 2 days and have been maintained in vitro for as long as 6 weeks. They are composed primarily of type II pneumonocytes as characterized by large, lightly stained nuclei and cytoplasmic inclusion bodies. The lamellar structure of these inclusion bodies has been confirmed by electron microscopy. The dynamic formation of inclusion bodies is suggested by the presence of lamellar bodies in the extra-cellular space and the appearance of new inclusions in the cytoplasm of the type II pneumonocytes. The formation and long-term maintenance of histotypic lung structures in vitro provides a model system for the study of lung development and synthesis of surfactant by type II alveolar pneumonocytes. This work was supported by funds from the American Lung Association, National Heart and Lung Institute (grant HL-17110-01) and the W. Alton Jones Foundation.  相似文献   

9.
In experiments on 150 guinea pigs, processes of lung wound healing were followed and the more active cellular sources of regeneration were identified. Measurements of cyclic adenosine monophosphate components in the course of lung healing indicated that histologic and electron-microscopic studies would be more informative if done at days 1, 3, 4, 7, and 14 after lung damage. Both cellular and intracellular mechanisms of regeneration were involved in the healing processes. The type II pneumonocyte be designated as a cambial cell of pulmonary parenchyma, for this cell displays the highest proliferative potency and is responsible for the epithelial lining of newly formed alveoli. The formation of these is shown to be assured through functional activity of all cellular alveolar elements (involving intracellular hyperplasia and hypertrophy of ultrastructures and especially dynamic morphological and functional alterations in osmiophilic bodies of type II pneumonocytes) and capillary neoformation.  相似文献   

10.
The layer of mucosubstance that is associated with the free surface membranes of the pneumonocytes in the lungs of the toad Xenopus laevis and the lizard Lacerta viridis was demonstrated by electron microscopy using iron oxide stain. The form and staining reactions of the mucosubstance layer were similar in both animals. In electron micrographs the mucosubstance was represented by a band of densely stained material (25-50 nm thick) which coated the entire free surface of the pneumonocytes. It appeared to be firmly attached to the outer leaflet of the superficial plasma membrane. Short lengths of osmiophilic membranes, presumed to be fragments of pulmonary surfactant, were often observed lying free in the air spaces but they did not show any affinity for iron stain. Incubation of lung sections in a solution of neuraminidase produced a marked decrease in the intensity of the surface staining; no change was detected after incubation in trypsin, papain, hyaluronidase, N-acetyl cysteine, or phosphate buffer. It is, therefore, concluded that the pneumonocyte surface coat consists mainly of a sialomucin.  相似文献   

11.
Synopsis Electron microscope techniques were used to study the intercellular distribution of aryl sulphatase and acid phosphatase in the pneumonocytes which line the air spaces in the lung ofXenopus laevis. Strong reactions for aryl sulphatase and acid phosphatase were present in the limiting membranes of the cytoplasmic inclusion bodies; no significant activity was found in the inclusion contents or in the membranous material present in the air spaces. Both enzymes were present in the multivesicular bodies but other organelles were unreactive. These results suggest that hydrolytic enzymes are involved in the secretion of surface-active materials in amphibian lung.  相似文献   

12.
The study concerns the action of dehumidified or humidified gas on the pulmonary lining layer. The results of our research suggest that water vapor used in artificial ventilation may be an important determining factor of the respiratory problems reported by clinicians in man. Important modifications of the lining layer of the alveolar epithelium occur, accompanied by more important alterations, including those of the content of the alveolus, all of which contribute to the pulmonary edema observed.  相似文献   

13.
Lung alveoli are coated by a thin layer of extracellular material rich in anionic charges. The nature of this acid layer and its relationship to the phospholipid surfactant are not known. We investigated the possible presence of sialic acid groups by light and electron microscopy in tissues from normal fetal and adult lungs, using neuraminidase treatment followed by staining with the galactose-binding lectin from peanut, labeled with peroxidase. Our results showed that adult lung does not bear peanut lectin-reactive sites but that a very thin and distinct reactive layer becomes evident after neuraminidase treatment, especially on type II pneumocytes. In fetal lung, the entire surface of the developing respiratory tree is outlined by a strongly peanut lectin-reactive layer even if neuraminidase digestion is not performed. We conclude that the acid coat of the alveolar lining is in part composed of sialic acid residues and that sialic acid is added to the fetal lung as the alveoli mature.  相似文献   

14.
Clonal isolation of differentiated rat lung cells   总被引:4,自引:0,他引:4  
Summary A number of diploid clones have been isolated from an enzymatic dispersion of normal rat lung. Four of these clones are epithelial in morphology, the remainder fibroblastic. On the basis of electron microscopic observations, two of the epithelial clones appear to have originated from type II alveolar pneumonocytes. Supported by funds from the W. Alton Jones Foundation and the American Lung Association.  相似文献   

15.
Comarisons have been made of the structure of layers lining the lungs of lungfish, frog and rat using material fixed by perfusion of the pulmonary circulation of physiological pressures and at normal air pressures within the lung. The lining consists of a thin densely osmiophilic surface layer which covers a much thicker hypophase of generally floccular appearance. Tubular myelin, present in the frog and rat lung lining, was not observed in the layers lining the lung of Lepidosiren.  相似文献   

16.
The female reproductive system of viviparous monogeneans (Gyrodactylus and Macrogyrodactylus) has been examined using fluorescence microscopy and transmission electron microscopy. The female system is tubular, made up of a thin-walled proximal seminal receptacle/ootype and a distal uterus, separated by a complex cellular region. Both parts have a continuous syncytial cytoplasmic lining. Maturing oocytes in the seminal receptacle/ootype are in intimate contact with the receptacle lining. The uterus cytoplasmic lining completely surrounds the developing embryo, and is continuous with anterior and posterior cell bodies which fluoresce strongly when stained with bisBenzimide. This lining is most extensive around small embryos, when it contains specialised organelles including star-shaped configurations of electron-dense membranes and multilamellate bodies. Pits in the uterus wall bridged by membranous structures connect the cytoplasmic lining to parenchyma or digestive cells. The cytoplasmic lining regresses as the embryo develops, but remains continuous and in intimate contact with the embryonic tegument (at least until the near-term embryo begins independent movement). Numerous ribosomes, membranes and mitochondria in the uterine cytoplasmic layer indicate a high metabolic rate, and exo/endocytotic vesicles in the F1 tegument suggest transfer of materials occurs between parent and embryo. Putative vitelline cells in the posterior of the body contain abundant RNA, ribosomes and membrane-bound secretory bodies, and are filled with an electron-lucent secretion. However, there are no ducts associated with these cells, and their function remains unknown. The cytoplasmic lining of both the seminal receptacle/ootype and the uterus appears to regulate oocyte/embryo nutrition. Similar syncytial layers occur in rotifers, but are unlike the nutritive epithelia of most other viviparous organisms.  相似文献   

17.
Summary Four heavy metal staining methods have been applied to frog lung surfactant. Among them, the iodoplatinate method is the only one that almost exclusively visualizes the phospholipid moiety being produced in the lamellated bodies of the pulmonary epithelial cells and forming the backbone of organized structures within the extracellular lining layer. The other three techniques — ruthenium red-osmium tetroxide, osmium tetroxideferrocyanide, acidic phosphotungstic acid in chromate (Rambourg technique) — more or less give electron contrast to glycoproteins and to a lesser extent to the hydrophilic parts of phospholipids. They all show the extracellular lining layer to be a two component system: the content of the lamellar bodies from — when released — membranous configurations, similar to those observed in mammalian lungs; they unfold in an amorphous hypophase, which is apparently secreted by goblet cells of the pulmonary epithelium.  相似文献   

18.
The location of autologous serum albumin within the alveolar-capillary membrane was studied in the rat under physiological conditions using antialbumin antibodies labeled with peroxidase. Albumin was detected in the lung interstitium, and in numerous pinocytic vesicles within endothelial cells and type I alveolar epithelial cells. The immunoreaction was also positive at the level of plasmalemmal membranes of both cell types and in the alveolar lining material.  相似文献   

19.
A procedure is described for the isolation of a surface-active fraction from dog lung. This material meets the established criteria for pulmonary surfactant. The fraction was shown to contain lipid, protein, and carbohydrate. The predominant lipid present was dipalmitoyl phosphatidylcholine. Surface chemistry studies indicated the surface properties of the fraction could not be explained solely from a consideration of the properties of dipalmitoyl phosphatidylcholine. Electron microscopic studies demonstrated the presence of intact osmiophilic bodies as well as other myelin forms in the surface-active fraction. It is speculated that, in situ, the alveolar lining layer is similar to a structured gel.  相似文献   

20.
The entire alveolar surface is lined by a thin fluid continuum. As a consequence, surface forces at the air-liquid interface are operative, which in part are transmitted to the delicate lung tissue. Morphologic and morphometric analyses of lungs show that the alveolar surface forces exert a moulding effect on alveolar tissue elements. In particular, in lungs at low degrees of inflation, equivalent to the volume range of normal breathing, there is a derecruitment of alveolar surface area with increasing surface tensions which reflects equilibrium configurations of peripheral air spaces where the sum of tissue energy and surface energy is minimum. Thus, changes in surface tension alter the recoil pressure of the lung directly and indirectly by deforming lung tissue and hence changing tissue tensions. However, the interplay between tissue and surface forces is rather complex, and there is a marked volume dependence of the shaping influence of surface forces. With increasing lung volumes the tissue forces transmitted by the fiber scaffold of the lung become the predominant factor of alveolar micromechanics: at lung volumes of 80% total lung capacity or more, the alveolar surface area-volume relation is largely independent of surface tension. Most important, within the range of normal breathing, the surface tension, its variations and the associated variations in surface area are small. The moulding power of surface forces also affects the configuration of capillaries, and hence the microcirculation, of free cellular elements such as the alveolar macrophages beneath the surface lining layer, and of the surfaces of the peripheral airways. Still enigmatic is the coupling mechanism between the fluid continua of alveoli and airways which might also be of importance for alveolar clearance. As to the surface active lining layer of peripheral air spaces, which determines alveolar surface tension, its structure and structure-function relationship are still ill-defined owing to persisting problems of film preservation and fixation. Electron micrographs of alveolar tissue, of lining layers of captive bubbles, and scanning force micrographs of surfactant films transferred on mica plates reveal a complex structural pattern which precludes so far the formulation of an unequivocal hypothesis.  相似文献   

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