Lung alveolar cell cytosomes: A consideration of their significance

Summary An ultrastructural comparison of mammalian, reptilian, and amphibian lung alveolar cells, and avian lung atrial cells reveals that morphologically similar cytoplasmic bodies (cytosomes) occur in these cells. The cytosomes, which appear generally as osmiophilic, lamellae-containing, membrane-bound, round bodies 0.3 to 0.5 in diameter, are also similar to bodies occurring in epithelial cells of both physoclistous and physostomatous swimbladders of fishes. Because the function of both lung alveolar and swimbladder epithelial cells is gas-handling, the possibility is raised that the morphologically similar lamellae-containing bodies of these vertebrate cells are functionally identical. One function, suggested by other investigators, is that, in mammalian lungs, these bodies supply a surface-tension lowering material (surfactant). Because several assumptions concerning this proposed function remain unproved, an alternative proposal is speculatively explored. The suggestion is offered that cytosomes contain an antioxidant needed to protect alveolar and swimbladder cells against the toxic effects of the relatively high concentration of oxygen to which these cells are exposed.Supported by a research grant from the American Cancer Society, Oregon Division, Inc.     

The alveolar epithelium of the newborn rat,and the significance of the osmiophilic lamellated bodies in cellular autophagy

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.     

Ultrastructural effects of silicic acid on primary lung fibroblasts in tissue culture

Transmission and scanning electron microscopic examination of primary lung fibroblasts exposed in tissue culture to polymeric silicic acid (PSA) revealed profound cellular changes in the cell surface membranes, resulting in rapid endocytosis of affected membranes and formation of multivesicular bodies. Exposure to monomeric silicic acid did not appear to exhibit any immediate adverse effects. Appearance of numerous cytoplasmic vacuoles within 1 h of PSA exposure was easily visible by light microscopy. Electron microscopy revealed that PSA exposure caused formation of an 'osmiophilic' cell surface membrane. Numerous osmiophilic cytoplasmic blebs on the surface and subsequent endocytotic vesicles appeared to collapse and aggregate into multivesicular bodies. This study provides ultrastructural evidence of the direct interaction between lung fibroblasts and polymeric silicic acid, which has a dramatic effect the surface membrane, its subsequent internalization and cytoplasmic processing. This interaction could be one of the key steps in the damaging effects of silica containing dust.     

Ultrastructure of the physostomatous swimbladder of rainbow trout (Salmo gairdneri)

Summary Rainbow trout swimbladder epithelium consists of non-ciliated and ciliated cells in the ratio of greater than 21. Non-ciliated cells contain vesicles filled with a mucus-like material and similar material is found lining the surface of the swimbladder lumen. Morphological evidence for discharge of the vesicle contents was obtained. In addition, nonciliated cells contain osmiophilic lamellar bodies which resemble the cytosomes of lung alveolar cells of air-breathing vertebrates. The non-ciliated cells do not appear to be involved in a process of active gas secretion.Supported by a research grant from the American Cancer Society, Oregon Division, Inc.     

Endocytosis in cultured rat alveolar type II cells: effect of lysosomotropic weak bases on the processes.

We investigated the uptake of Lucifer yellow and surfactant complexed with gold (S-G) by isolated alveolar Type II cells. The fluid phase marker Lucifer yellow did not reach lamellar bodies (LB) even after prolonged incubation time, whereas S-G was internalized and found in LB. Treatment of Type II cells with lysosomotropic weak bases (NH4Cl and chloroquine) resulted in dilation of endosomes, lysosomes, and LB. The effect of these agents on LB resulted in disappearance of their lamellar organization, as detected by polarized light and electron microscopy. After incubation in lysosomotropic agent-free medium, endocytosis of Lucifer yellow and S-G in treated cells was mainly directed towards large vacuoles resembling either multivesicular bodies (MVB) or lysosomes. The possible relationship between LB, MVB, and lysosomes in freshly isolated as well as cultured alveolar Type II cells is discussed.     

Respiratory portion of the lungs of intact BALB strain mice

Four male mice (1-month-old) of BALB strain have been studied. Three types of cells participate in formation of cellular lining of the terminal branchioles: ciliated, Clara cells and villose cells which are included in the neuroepithelial bodies composition. Clara cells are numerous and they are similar in their ultrastructural organization, they contain a great number of polymorphous secretory granules, single mitochondria and a poorly developed endoplasmic reticulum. A comparatively large number of pores of Khone are revealed: there are 4-8 pores per one alveole, and one pore is situated on 197.4 mcm2 of the alveolar surface. Alveolocytes of the second type of make the main actively secreting cell population of the alveolar passages and alveoles. Simultaneously, at the state of secretion there are 76% of the cells. The secretion of alveolar surfactant is realized by means of merocrine exocytosis. Relative volumetric fraction of mitochondria in alveolocytes of the II type comprises 12% and that of "cytophospholiposomes" (osmiophilic laminar bodies)--11%.     

Anatomy of the vegetative organs and secretory structures of Rhaponticum carthamoides (Asteraceae)

Roots, stems, rhizomes and leaves of Rhaponticum carthamoides (Willd.) Iljin (a Siberian adaptogenic plant, originating from the Altai and Saian Mountains) of different ages were investigated by means of light and electron microscopy. Schizogenous secretory reservoirs occurred in every organ, and were located within the secondary xylem (adventitious roots and rhizome of young plants), at the interface of endodermis/cortical parenchyma (roots and hypocotyl), along phloem and primary xylem (older rhizome), around the vascular bundles (inflorescence stem, petiole and leaf midrib veins) and along phloem (cotyledonary and leaf veins). At the interface of endodermis/inner parenchyma, secretion accumulated in the intercellular spaces prior to the formation of proper epithelial cells. The secretion as observed by transmission electron microscopy comprised three components: soluble (i.e. absent from sections; probably phenolic), insoluble and strongly osmiophilic (probably phenolic) and insoluble, moderately osmiophilic (probably lipidic). Numerous osmiophilic oil droplets, similar to the lipidic secretion inside the reservoirs, local proliferation of rough endoplasmic reticulum and numerous multivesicular bodies characterized epithelial cells in all organs. Leucoplasts (in subterranean organs) with osmiophilic inclusions and peroxisomes with crystalloid inclusions were specific for parenchyma cells. Peltate glandular hairs were formed on leaf blades.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 207–233.     

Twenty-four-hour variations in subcellular structures of rat type II alveolar epithelial cells

Summary Subcellular structures of type II alveolar epithelial cells in the rat lung were analyzed at six evenly spaced times over 24 h (light period: 06.00 h–18.00 h), using a morphometric technique. The cell volumes were maximal at 16.00 h and minimal at 08.00 h. The volume and surface densities of rough endoplasmic reticulum and mitochondria were low during the light period, and high during the dark period. Morphometric parameters of multivesicular bodies did not significantly fluctuate over 24 h, but they increased from 04.00 h to 08.00 h. The volume densities of lamellar bodies increased from 16.00 h to 20.00 h, and decreased from 00.00 h to 08.00 h. The change in numerical densities of lamellar bodies was inversely correlated to that in the volume densities. As shown by electron microscopy, small lamellar bodies predominated at 08.00 h, larger lamellar bodies increasing at 16.00h. Composite bodies often appeared at 08.00 h and 12.00 h. Type II cells thus appear to fluctuate, showing three phases over 24 h: formation, accumulation and secretion of lamellar bodies. In particular, it is noteworthy that the accumulation stage occurs during the resting phase of the rat, whereas the secretion stage occurs during its body-active phase.     

Electron microscopic study on the thyroid gland of the salamander Hynobius nebulosus in the breeding season

Summary The thyroid gland of adult salamanders, Hynobius nebulosus, in the breeding season was studied by electron microscopy. The follicular cells are different in cell height and fine structures; the taller cells with many cell organelles and granules and the lower cells with a few cell organelles and granules are both present in the same follicle. In the cytoplasm, three types of membrane-bounded granules, namely, cytosomes, colloid droplets, and vacuolar bodies and circular membrane complexes occur. The vacuolar bodies are subdivided into two types; the ordinary type having loosely distributed particles and the specific type containing tubules and/or closely packed filaments, crystalloid structures, except for the particles. The chromophobe colloids within the Bensley-cells correspond to extremely large, ordinary type vacuolar bodies, while the Langendorff-colloid cells possess increased numbers of granular cisternae of endoplasmic reticulum and a ribosome-rich, dense cytoplasmic matrix but not extremely large colloid. The intracytoplasmic circular membrane complexes appear in the Golgi area of cytosome-rich cells. It is suggested that they originate from the Golgi apparatus which was activated to produce many cytosomes. Intranuclear inclusions consisting of microtubules and filaments and tight junctions between two adjacent lateral plasma membranes are occasionally encountered.     

Polyfunctional role of the alveolar brush cells in the rat lung

By means of scanning and transmission electron microscopy it was demonstrated that the number of vacuoles located in the apical part of cytoplasm in alveolar brush cells of the regenerating rat lung increases, hyperplasia of Golgi-complex takes place and the activation of the protein-synthetising apparatus is evident. The immature surfactant material (osmiophilic lamellar bodies) and secretory dense core vesicles were found in the cytoplasm of alveolar brush cells. Intramuscular injections of colchicin to rats (0.1 mg/100 g body weight) 6 times during 24 hours before decapitation does not influence the number, topography and structure of microfibrilla bundles contained in a sufficient amount by alveolar brush cells. At the same time a part of microvilli of alveolar brush cells undergoes destruction and resorption under the action of colchicin. The data on ultrastructural organization of alveolar brush cells show that they are able to fulfill several functions: absorptive, contractile and secretory.     

Ultrastructure of large granule-containing lymphocytes possessing natural killer activity

By means of light and electron microscopy, ultrastructural cytochemistry and immune cytochemistry methods, contents and ultrastructure of large granule-containing lymphocytes (LGL) have been studied in human blood--this is cell population possessing natural killer and, partly, antibody-depending cytotoxicity. The LGL concentrates are isolated from blood applying successive physical-chemical methods, differential centrifugation in the density gradient of pack-phycoll and percoll included. Separate LGL populations are marked by means of rosette-forming reaction with sheep erythrocytes and monoclonal antibodies OKT4 and OKT8. Relative and absolute amount of the LGL in 1 1 of blood is 5.4 +/- 0.5% and 0.319 +/- 0.28 X 10(9), respectively. The LGL ultrastructure is characterized with a low nuclear-cytoplasmic ratio, with presence of osmiophilic (azurophilic) granules in cytoplasm and specific parallel-tubular structures, with a well developed Golgi complex, an essential number of mitochondria, vesicles with smooth wall and vacuoles, as well as multivesicular bodies and Gallo bodies. The LGL subpopulations, expressing various membrane antigens (E+, E-, OKT8+, OKT8-) differ in their ultrastructure, that is evidently stipulated by the degree of their differentiation and their function.     

Identification of enterochromaffin cells in adjacent Epon-embedded sections at light and electron microscopic levels

Summary Methods for light and electron microscopic comparison of individual argentaffin and argyrophil enterochromaffin cells (EC) in the sheep duodenal mucosa are described. These silver procedures were applied for light microscopy to Epon-embedded sections. The adjacent sections were examined with the electron microscope. The most specific characteristics of the argentaffin and argyrophil EC in electron microscopy are highly osmiophilic cytoplasmic granules. In one cell type these granules are smaller and more roundish than in the another type. These two cell types are stainable both by the argentaffin and argyrophil reactions. No essential difference can be observed in the localization of these elements. It is suggested that both cell types belong to the enterochromaffin system. Both silver methods are also suitable for the light microscopic identification of other intestinal structures in sections adjacent to that sectioned for electron microscopy.This work was supported by a grant from the Yrjö Jahnsson Foundation, Helsinki, Finland.The electron microscopic observations were carried out in the Electron Microscope Laboratory, University of Helsinki.     

Distribution of the wingless gene product in Drosophila embryos: a protein involved in cell-cell communication

wingless, a segment polarity gene required in every segment for the normal development of the Drosophila embryo, encodes a cysteine-rich protein with a signal peptide. A polyclonal antiserum localizes the wingless protein in approximately the same region of the embryo as the wingless mRNA. The pattern of antigen localization changes rapidly during development. In the extended germband stage, stripes of wingless staining are present in the trunk region just anterior to the parasegment boundary; wingless-expressing cells abut engrailed-expressing cells across that boundary. wingless antigen is seen both inside and outside the cell by electron microscopy: inside the cell, in small membrane-bound vesicles and in multivesicular bodies; outside the cell, close to or on the plasma membrane and associated with material in the intercellular space. The multivesicular bodies containing the wingless protein are occasionally found in engrailed-positive cells, suggesting that the wingless protein behaves as a paracrine signal.     

Cytology of Bronchoalveolar Lavage In Some Rare Pulmonary Disorders: Pulmonary Alveolar Proteinosis and Amiodarone Pulmonary Toxicity

Cytological patterns of bronchoalveolar lavage (BAL) in pulmonary alveolar proteinosis (PAP) and amiodarone pulmonary toxicity (APT) are presented together with light and electron microscopy (EM). the differential cell count of BAL in both diseases is similar in that alveolar macrophages predominate. However, the cytology of PAP is characterized by scanty macrophages and alveolar epithelial cells in abundant periodic acid-Schiff (PAS)-positive extracellular material. the gross appearance of the BAL fluid is therefore opaque. In contrast, the cytology of APT is characterized by foamy alveolar macrophages with numerous lamellar bodies in their cytoplasm, and the BAL fluid is clear.     

Ultrastructural Details in Germinating Sporangiospores of Rhizopus stolonifer and Rhizopus arrhizus

Electron microscope examination of sporangiospore sections from Rhizopus stolonifer (Ehrenb. ex Fr.) Lind. and R. arrhizus Fischer revealed details on intracellular organization not previously reported. Aldehyde fixation followed by chromeosmium postfixation permitted clear depiction of ribosomes hitherto unrevealed in these cells. Mitochondria were diversiform. Spore wall structures in the two species were generally similar, but outer contours differed sufficiently to permit easy species identification in examination of sections. The spores of both species abounded in cytosomes, corresponding in size, shape, and heavy-metal "stain" affinities to spherosomes in cells of higher plants. The osmiophilic response of these spherosome-like inclusions was intensified by treatment of sections with thiocarbohydrazide solution and subsequent application of aqueous osmium tetroxide, which strengthens an assumption that they are lipid-rich. The margins of the spherosome-like inclusions in lead citrate-stained sections included dense particles, about 60 A across, whose crystalline-like arrangements suggested that protein as well as lipid was present. Frequent and close associations between the spherosome-like inclusions and various cell membranes suggested that such bodies participate in membrane elaboration during germination.     

Surpellic films, lung surfactant, and their cellular origin in newt, caecilian, and frog

The lung lining and its surfactant have been studied in one species from each of the amphibian sub-classes Anura, Urodela, and Apoda. The surfactant was studied by observation of bubbles derived from the lungs, the morphology by electron microscopy. Other details of the apodan are also given.
The surfactant layers of Rana temporaria and Ichthyophis (species unknown) resemble one another, being somewhat less stable than that of mammals. That of Triturus vulgaris is even less stable, and shows qualitative differences from the other two. Nevertheless, it can reduce the surface tension to 2 mN/m.
The epithelial cells of amphibian lungs cannot be divided into two clearly defined types, as can those of mammals. Microvilli are present on the alveolar surface of all these cells. In the lungs of Rana and Ichthyophis the lining cells contain numerous lamellated osmiophilic bodies (which are intracellular depots of surfactant); in the former their appearance is mainly cross-barred, in the latter mainly concentric. Similar bodies exist in the lung epithelial cells of Triturus but are relatively rare.     

Electron microscopic observations of lung alveolar epithelial cells of normal young mice,with special reference to formation and secretion of osmiophilic lamellar bodies

Summary Using the electron microscopy and electron microscopic histochemistry the authors studied the lung alveolar epithelial cell of normal young mice.Type II cell of the alveolar epithelium has characteristically numerous osmiophilic lamellar bodies. The lamellar boies are formed in the cytoplasmic vesicle, and never originate from the mitochondrion. These bodies have abundant acid phosphatase activity in their limiting membrane therefore it is considered to be lysosomal origin, but the mitochondria have no such enzyme activity.The body which is newly formed in the cytoplasmic vesicle grows up to the large lamellar body as a result of an accumulation of the fibrous dense substance, migrates to the free margin of the type II cell of alveolar epithelium, and then is discharged into the alveolar lumen as a merocrine type secretion.Acknowledgement is given to Professor Dr. Y. Sano and Professor Dr. H. Fujita, Department of Anatomy, and Assistant Professor Dr. S. Fujita, Department of Pathology, for their kind advice and criticism.     

Light- and electron-microscopic observations of the spinal ganglion cells of mice

Under the light microscope, large and small types of spinal ganglion cells can be seen in the mouse. Among those of the small type bipolar cells are observed. By electron microscopy, the cells of the large type have a low electron density and those of the small type a high electron density. Bipolar cells continue to be observed among the latter. The cells of the spinal ganglia contain different cellular apparatus in enormous quantity. There are four kinds of lysosomes in the GERL, i.e. the coated vesicles, dense bodies, multivesicular bodies and autophagic vacuoles.     

An autoradiographic,biochemical, and morphological study of the harderian gland of the mouse

Biochemical and morphological properties of the Harderian gland of the mouse were examined by combining autoradiographic, biochemical, and electron microscopic techniques. Autoradiographs show that the radioactive carbon from [U-¹⁴C]glucose injected into the abdominal cavity is completely incorporated into the acid-insoluble substances within 30 minutes. The results of chemical analysis show that the main components of this gland are glyceryl ether diesters and phospholipids. Scanning electron microscopy shows numerous lipid droplets in the secretory cells and alveolar lumina. Myoepithelial cells lie between the secretory cell base and the basement membrane and have a basket-like distribution of processes as confirmed by hydrochloric acid and collagenase digestions. Myofilaments are demonstrated in the cytoplasm. Two types of secretory cells (A and B) comprise the alveolar epithelium and can be differentiated under the electron microscope. The cytoplasm of both contains numerous vacuoles. The vacuoles are almost empty in A cells, which are a more numerous constituent of the alveolar epithelium than B cells. However, the vacuoles of the B cells contain densely osmiophilic material. In both, cell types show a merocrine mode of secretion. Unmyelinated nerve cell endings occur in the interstices of the connective tissue, and contain clear or cored vesicles.     

Ultrastructure of the respiratory epithelium in the lungs of the tortoise,Testudo graeca

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.