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  • 1
    ISSN: 1432-0568
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The submucosal glands are thought to be the primary source of the mucus overlying the primate trachea and conducting airways. This study characterizes the development of submucosal glands in the trachea of the rhesus monkey. Tracheas from 46 age-dated fetal, 8 postnatal and 3 adult rhesus were fixed in glutaraldehyde/paraformaldehyde and slices processed for electron microscopy. The earliest (70 days gestational age (DGA)) indication of gland development was the projection of a group of closely packed electron lucent cells with few organelles and small pockets of glycogen into the submucosa. This configuration was observed up to 110 DGA. In fetuses younger than 87 DGA it was present almost exclusively over cartilaginous areas. Between 80 and 140 DGA, a cylinder of electron lucent cells projected into the submucosal connective tissue perpendicular to the surface. In fetuses younger than 100 DGA, it was restricted to cartilaginous areas. By 90 DGA, some glycogen containing cells in proximal regions contained apical cored granules. By 106 DGA, cells in proximal areas contained apical electron lucent granules. More distal cells had abundant GER and electron dense granules. The most distal cells resembled the undifferentiated cells at younger ages. Ciliated cells were present in the most proximal portions of glands at 120 DGA. This glandular organization was found in older animals, including adults, with the following changes: (1) abundance of proximal cells with electron lucent granules increased; (2) abundance of distal cells with electron dense granules increased; and (3) abundance of distal cells with abundant glycogen and few organelles decreased. We conclude that submucosal gland development in the rhesus monkey: (1) is primarily a prenatal process; (2) occurs first over cartilage; (3) continues into the postnatal period; and (4) involves secretory cell maturation in a proximal to distal sequence with mucous cells differentiating before serous cells.
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  • 2
    ISSN: 1432-0568
    Keywords: Perinatal ; Neonatal ; Adult ; Type II cell ; Sheep lung development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The quantitative morphologic changes in alveolar type II cells during the perinatal period were characterized morphometrically in the lungs of fetal lambs at 132, 138, and 147 days gestational age (DGA) and in newborns at 2 days postnatal age (2 DPN). Ultrastructural features were compared with those of type II cells of ewes 365 days old. Lamellar body profile number per type II cell profile was highest at term (147 DGA) and 2 DPN. In adults, the number of lamellar body profiles and volume density of lamellar bodies were equal to those of the 132 DGA fetus. Multivesicular bodies were most common at 138 DGA and in adults. The volume density of cytoplasmic glycogen fell dramatically during the latter part of gestation. The volume density of many cellular organelles increased to the level observed in adults by term (147 DGA). Subcellular composition of type II cells of adult sheep differs from that reported for adult rats chiefly by the volume density of lamellar material within the cytoplasm. Plate-like or globe-like inclusions were present only in the type II cells of adults. Cytoplasmic extensions of the type II cell crossing the basal lamina were most abundant in the 132 and 138 DGA fetal sheep. Cytoplasmic extensions were rare in adults. We conclude that morphologic changes of the alveolar type II cell associated with gestational age follow a species-specific time course. In the sheep, this occurs during the later part of gestation and extends into the neonatal period. Morphologic and morphometric changes appear to correspond with cellular interactions between alveolar type II cells and mesenchymal cells of the interstitium.
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  • 3
    ISSN: 1059-910X
    Keywords: Particle deposition ; Nebulization ; Albumin-coated microspheres ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Aerosolized fluorescent microspheres were used to study particle deposition in site-specific regions of the lung with confocal laser scanning microscopy. A nebulizer was used to aerosolize microspheres followed by passage through a heated discharging column to reduce static charge and to remove water surrounding each microsphere. Precoating of microspheres with albumin helped to minimize displacement during vascular fixation of the lungs. Confocal laser microscopy facilitated visualization of microspheres throughout the bronchial tree, ducts, and alveoli of the lungs. The use of fluorescent microspheres and confocal laser imaging provided distinct advantages compared with other methods to study lung particle deposition due to (1) the generation of single microspheres of uniform size by nebulization, (2) easy detection of microspheres in large slabs of microdissected lung tissues, (3) excellent resolution of tissue surfaces and microspheres for an infinite number of orientations and planes of section, and (4) the ability to visualize microspheres below fluid lining layers and on surfaces that could not easily be done by other methods of microscopy.© 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 26 (1993), S. 355-356 
    ISSN: 1059-910X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
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  • 5
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The nonciliated bronchiolar epithelial (Clara) cell of adult lung is commonly defined by two cellular components: abundant agranular endoplasmic reticulum (AER) and electron-dense ovoid secretory granules. These reflect the Clara cell's proposed functions as the source of bronchiolar surface secretions and the site of xenobiotic metabolism via the cytochrome P-450 monooxygenase system. Since previous studies have indicated that Clara cells may not attain a fully functional state until some weeks after birth, the present study was undertaken to characterize systematically the differentiation of this cell type during lung maturation. Lungs were fixed by airway infusion with glutaraldehyde/paraformaldehyde (550 mOsm, pH 7.4) from at least three male rabbits at each of the following ages: 24, 27, and 30 days fetal, and 0-1 day, 3-4 days, 1, 2, 3, 4, 5, 8, 12, 15, 17, and 25 weeks postnatal; and pieces were processed for transmission electron microscopy by a selective embedding procedure. Quantitation was performed on electron micrographs (at 15,750 x) of cell profiles, which included the base, apex, and nucleus. Volume fractions of constituents of a minumum of 30 cells per animal (8 weeks and younger) and 10 per animal in older groups, were estimated by point counting with a Weibel 168-point test grid. Cell and nuclear size were estimated with a computerized digitizer (Zeiss Videoplan). Nonciliated cells of prenatal animals had large amounts of cytoplasmic glycogen (over 60% of the cell cytoplasm), few mitochondria (less than 15%), little granular endoplasmic reticulum (GER) (20%), minimal AER (less than 5%), and no granules. Postnatal animals 2 weeks of age and younger were similar, except for the presence of secretory granules and slightly more abundant AER (5 to 20%). By 4 weeks postnatal age, nonciliated cells resembled that of older animals with abundant apical AER (over 40%), secretory granules, little glycogen (11%), and GER (10%). We concluded that (1) the Clara cell is immature at birth; (2) differentiation occurs primarily during weeks 3 and 4 of postnatal life; (3) vast amounts of cytoplasmic glycogen are characteristic of the undifferentiated cell; and (4) four cellular constituents, AER, glycogen, mitochondria, and GER, undergo significant shifts in abundance during differentiation. These shifts appear to be in the sequence expected of a cell type undergoing the initiation of biosynthesis of secretory products and biogenesis of agranular endoplasmic reticulum.
    Additional Material: 21 Ill.
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  • 6
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: To estimate the numbers and volumes of bronchiolar epithelial cells during lung maturation, we examined rabbits at three time points, 30 days gestation and 4 and 17 weeks postnatal age. Morphometric measures (mean caliper diameter, surface area, and volume) of nonciliated and ciliated bronchiolar cell nuclei, using computer modeling from serial sections, showed a significant decrease in nuclear size for both cell types and a significant increase in cell volume for the nonciliated bronchiolar cell during lung maturation. A shape coefficient (β) proved to be the most efficient estimator of the number of cells per unit volume when it was used with estimates of the number of nuclei per unit area and the volumetric density of nuclei. Two-dimensional estimates of bronchiolar epithelial cell abundance (the number of nuclei per unit length or area) significantly underestimated the percentage of nonciliated bronchiolar cells as compared to three-dimensional estimates for rabbits 17 weeks of age. We have shown an inverse relationship between nonciliated and ciliated bronchiolar cell abundance during lung maturation. Nonciliated cells decreased while ciliated cells increased.We have confirmed that cytodifferentiation of the nonciliated bronchiolar cell occurs within the first 4 weeks of postnatal development. The volume of the nonciliated bronchiolar cell increased about twofold during development. Because of the concomitant decrease in nuclear volume, the cytoplasm of the cell showed an even greater increase in volume. Within the cytoplasm of the nonciliated bronchiolar cell, glycogen significantly decreased, and agranular endoplasmic reticulum (AER) and mitochondria significantly increased in volume during development. The biosynthesis of AER closely correlated with pharmacological studies of xenobiotic metabolism during rabbit lung maturation.
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  • 7
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Since there are major differences between the airway epithelium of man and that of common laboratory species, the tracheobronchial epithelium of the bonnet macaque was characterized to evaluate its usefulness as a model for study of human conducting airways. This study compared the light microscopic, scanning electron microscopic, and ultrastructural appearance of epithelium from the posterior membranous and anterior cartilaginous trachea and mainstem bronchus. Population densities, epithelial volumetric densities, and frequency distributions of cross-sectional areas of nuclei were determined for cell types present on electron micrographs. Four epithelial cell types were distinguished by ultrastructural criteria. Basal cells were 31% of the population and were similar to those described in other species. Ciliated cells were also similar to those of other species and composed 41% of the population; their nuclei were larger than those of other cell types. Mucous goblet cells had large numbers of secretory granules with electron-dense cores and a lucent periphery. They were only 8% of the population by nuclear count but composed 20% of the epithelial volume. The fourth cell type had multiple small vesicles containing small amounts of granular material and was termed a “small mucous granule cell.” Small mucous granule cells (16% of the population) were present in greater numbers than mucous goblet cells but were a smaller proportion of the epithelial volume (8%). While population densities of cell types determined from transmission electron micrographs did not vary between sample sites, scanning electron microscopy demonstrated longitudinal streaks of secretory cells in the posterior trachea suggesting that regional differences in epithelial organization exist. We conclude that the macaque extrapulmonary airway epithelium differs from published descriptions of laboratory rodents in both cell types present and relative abundance of those cell types. Although detailed quantitative studies of human extrapulmonary airways are not available, the primate airways resemble those of man in both the types of cells present and the complexity of pseudostratification.
    Additional Material: 20 Ill.
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  • 8
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We examined histochemically (light microscopy-LM) and cytochemically (electron microscopy-EM) the secretory epithelial cells in the tracheobronchial mucosa of sheep. Six morphologically distinct, granule-containing cells have been described, on the basis of their morphology and airway distribution: four mucous (M1-M4), serous (SC), and Clara (CC). Stereological and morphometric data indicated that M3, M4, SC, and CC were distinctly different from each other and from M1 and M2 cells. Mucous cells M1 and M2 differed in granule morphology. Samples of tracheas, sixth-generation bronchi, distal bronchi, and terminal bronchioles of 18 adult sheep were examined. At the LM level, methacrylate sections were reacted with an alcian blue (pH 2.5), periodic acid Schiff (PAS) sequence to differentiate neutral from acidic glycoconjugates (GC), and a high-iron diamine (HID), alcian blue sequence to differentiate sulfated from nonsulfated (sialated) GC. At the EM level the periodic acid-thiocarbohydrazide localized hexose-rich, neutral GC. Dialyzed iron (DI) and high-iron diamine localized carboxylated and sulfated GC, respectively. Granules of all but Clara cells were PAS-positive. All mucous cells contained acidic groups, but only M1 and M4 cells had LM-detectable sulfated GC. At the ultrastructural level, minimal but discernible HID and LID reaction product was observed on granule profiles of M2, M3, and SC, indicating acidic and sulfated GC not detected at the LM level. Histochemically, the sheep tracheobronchial epithelium was more similar to that of humans than some other examined mammalian species.
    Additional Material: 40 Ill.
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  • 9
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Conventional histochemical characterization of the mucus secretory apparatus is often difficult to reconcile with the biochemical analysis of respiratory secretions. This study was designed to examine the secretory glycoconjugates in airways using lectins with biochemically defined affinities for main sugar residues of mucus. We used five biotinylated lectins - DBA (Dolichos biflorus) and SBA (Glycine max) for N-acetyl galactosamine (gaINAc), BSAI (Bandeiraea simplicifolia) and PNA (Arachis hypogea) for galactose (gal), UEA I (Ulex europeus) - for detection of fucose (fuc) in HgCl2 -fixed, paraffin-embedded, serially sectioned trachea, lobar and segmental bronchi and bronchioles of nine sheep. Lectins selectively localized the carbohydrate residues in lumminal secretions, on epithelial cell surfaces, and in secretory cells. Inp proximal airways, the major carbohydrate residues in luminal secretions, cell surfaces, goblet cells, and glands were fuc and gal-NAc. PNA reacted mainly with apical granules of 〈 10% of goblet cells, and gal residues were only detected in some of the mucous cells and on basolateral cell surfaces. Distal airways contained sparse secretion in the lumen, mucous cells containde weakly reactive fuc and gal-NAc, and the epithelial surfaces of Clara cells contained gal. Sugars abundant in the airway secretions were also the major component of cells in glands. We conclude that there is a correlation between specific sugar residues in secretory cells, glycocalyx, and luminal secretions in proximal and distal airways. This suggests that lectins may be used to obtain information about airway secretory cell composition from respiratory secretions.
    Additional Material: 24 Ill.
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  • 10
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The epithelium of the respiratory bronchiole in the adult rhesus monkey consists of two populations: a pseudostratified epithelium with basal, mucous goblet, and ciliated cells located near the pulmonary artery (PA); and a simple cuboidal epithelium composed only of nonciliated bronchiolar epithelial (or Clara) cells in areas away from the PA. This study describes the pattern of differentiation of these two epithelial populations, and their relationship to the PA and to the time of appearance of alveoli. in the respiratory bronchiole of the rhesus monkey during the period of 90-125 days gestational age (DGA). These events were related to changes in the adjacent parenchyma. Dissected airways of infusion-fixed, critical-point-dried lungs were evaluated by scanning microscopy followed by light microscopy of the same airways. At 54% of gestation (90 DGA), the distal airway was lined by a mixture of ciliated and nonciliated cells. By 67% of gestation (110 DGA), the ciliated cells were confined to the epithelium over the PA. The underlying connective tissue initially was cellular containing few fibers but was fibrous by 76% of gestation (125 DGA). Alveolarization began near the most distal cartilage at 57% of gestation (95 DGA), the same period at which secondary septation occurred in the distal acinus. Thus, alveolarization occurred simultaneously in two centers: (1) the proximal centriacinar region in the vicinity of the most distal cartilage and (2) the distal lung parenchyma. The duration of centriacinar alvcolarization was short, approximately 5 days.
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