Occurence of lipid bodies in canine type II pneumocytes during hypothermic lung ischemia

Type II pneumocytes defend the pulmonary alveolus by synthesis and secretion of surfactant and by contributing to alveolar epithelial regeneration. Lipid bodies are regarded as intracellular domains for the synthesis of eicosanoid mediators that can be induced by inflammatory stimuli. The aim of the present study was to establish whether hypothermic ischemic lung storage without further preservation measures leads to an induction of lipid body formation in canine type II pneumocytes. The lungs of 18 dogs were fixed for transmission electron microscopy (TEM) immediately after cardiac arrest (six double lungs) and after ischemic storage in Tutofusin solution at 4 degrees C for 20 min, 4 hr, 8 hr, and 12 hr (six single lungs, respectively). Type II pneumocytes were analyzed qualitatively by conventional TEM (CTEM) and quantitatively by stereology. The relative phosphorus content of surfactant containing lamellar bodies, lipid bodies, and intermediate forms was investigated by energy-filtering TEM (EFTEM). By CTEM, lipid bodies as well as forms intermediate between lipid bodies and lamellar bodies were already noted in the control group but were more pronounced in the ischemia groups. Beginning at 20 min of ischemic storage, a significant increase in the volume density of lipid bodies was noted in the ischemic groups as compared to the control group. By EFTEM, the highest intracellular phosphorus signals were recorded over lamellar bodies and lamellar areas of intermediate forms in all experimental groups, while lipid bodies and homogeneous areas of intermediate forms did not show a clear phosphorus signal. These results indicate that the formation of lipid bodies in canine type II pneumocytes is induced early during ischemic lung storage.     

High-voltage electron microscopy and conventional transmission electron microscopy of the interface zone between bone and endosteal dental implants.

The interface between mandibular bone and endosteal dental implants was examined with an in vivo dog model. Undecalcified mandibular implant samples were observed with both conventional transmission electron microscopy and high-voltage transmission electron microscopy (HVEM). Results demonstrated the variable nature of the interfacial support tissues. Mineralized bone was often found within 50 nm of the implant surface, separated from that surface only by an electron dense deposit. Osteocytes were observed close to the interface encased within lacunae extending numerous cellular processes through canaliculi. An osteoblast was also observed directly at the interface within a developing lacuna. Other interfacial areas exhibited a finely fibrillar and more electron lucent morphology. Furthermore, other areas were shown to be composed of wider zones of extracellular products containing collagen fibrils, ground substance, and calcified inclusions. Because bone is an actively growing and remodeling tissue, these different morphological zones around the entire area of the implants would appear to confirm the dynamic tissue response to endosteal dental implants. Further, HVEM stereology was shown to be an exciting research tool to investigate this tissue response.     

The molecular mass of adenovirus type 5 as determined by means of scanning transmission electron microscopy (STEM)

The mass of adenovirus type 5 was determined by means of computer-assisted scanning transmission electron microscopy (STEM). Arithmetic mean of 157 +/- 10(SD) X 10(6) daltons and mode between 160 and 170 X 10(6) daltons compare favourably with previously reported data. The advantages of the STEM-procedure over the physical and chemical techniques are: low amounts of purified virus particles are needed; visual control of the physical state of virus particles; no need to know the chemical composition or protein concentration of the virus sample.     

Atrioventricular valves of the mouse: II. Light and transmission electron microscopy

Background: Mouse atrioventricular(AV) valves present a number of conspicuous morphologic differences with human AV valves. Given the existence of these differences, it is important to know the structural oranization of mouse AV valves. Since the mouse is often considered to be good animal model for developmental and anatomical studies, the presence of significant difference in structure may render comparative studies difficult. In addition, we wished to learn about the existence of structural changes in the mouse AV valves with age. Methods:The structural organization of mouse AV valves from 21 days to 1 year of age was studied by polarizing microscopy and by conventional light and transmission electron microscopy. Results:Polarizing microscopy reveals the presence of a system of birefringent fibers that consist of collagen bundles that organize like tendons. The spatial organization of these fibers is different in the two AV valves, reflecting differences in the anatomy of the entire valvular complex. Interstitial cells (IC) are of two different phenotypes: some are typical fibroblast, while some others share smooth muscle cell characteristics. In addition, small areas of fibrocartilage are also observed. The compactness and thickness of the collagen bundles increase with age. Also with age, the basement membranes become thickened or multilayered, and matrix vesicles and deposits of amyloid P can be observed. Conclusions:The collagenous birefringent fibers from an internal skeleton that should transmit the cycling stress evenly over the entire leaflets. IC should help to maintain the structure and deformability of the valve tissue and appear actively involved in the synthesis and renewal of extracellular material. The cartilagionous foci appear to be a normal component of the valve tissue. The Structural changes observed in old animals appear to be related to the degenerative processes which take place in normal valvular tissues with age. Despite the structural differeces, age changes appear to be similar in the AV valves of mouse and man. © 1995 Wiley-Liss, Inc.     

Scanning and transmission electron microscopy of venous sphincters in the rat lung

The rat pulmonary microvasculature was studied using scanning and transmission electron microscopy of vascular corrosion casts and tissue sections. Special emphasis was placed on small pulmonary venous vessels. The shape of vascular casts was analyzed and interpreted concerning the wall composition of corresponding vessels studied in tissue sections. On the casts of pulmonary venules and small pulmonary veins, narrow or wider annular constrictions were regularly observed. Within these constrictions, marks of circularly running grooves were seen as an additional structural detail, which obviously mimic impressions of single or grouped smooth muscle cells. The depth of the constrictions varies; it may be more or less pronounced, occasionally narrowing down the luminal diameter to approximately 50%. These constrictions are caused by muscular sphincters. In tissue sections of small pulmonary veins, sphincter regions were identified as abruptly appearing single or grouped true smooth muscle cells. Smooth muscle cells may be arranged side by side in a group or bundle or even staked in two or three layers. Between the sphincter regions, the venous wall consists merely of endothelium and an accompanying connective tissue layer. The smooth muscle cells of a sphincter are regularly positioned between endothelial layer and elastic lamina. The smooth muscle cells next to the endothelium form myoendothelial junctions. Autonomic nerves near the sphincters were never seen. The venous sphincters described are suggested to be effective devices involved in blood flow regulation. Blood-borne substances or local tissue hormones might govern sphincter function. © 1992 Wiley-Liss, Inc.     

Hürthle-cell lesions of the thyroid: a combined study using transmission electron microscopy, scanning electron microscopy, and immunocytochemistry

Hürthle cell transformation found in 2 nodular goiters, 2 cases of Hashimoto's thyroiditis, 4 follicular adenomas, 3 follicular carcinomas, 2 papillary carcinomas and 1 anaplastic carcinoma were studied by transmission electron microscopy, scanning electron microscopy and immunocytochemistry. Ultrastructural features of Hürthle cells were identical in non-neoplastic and neoplastic lesions. Cells crammed with mitochondria, showing abnormalities in size, shape and content were prominent in most cases. The presence of distinct smooth-surfaced cells interspersed with cells with many microvilli is almost a pathognomonic scanning electron microscopic feature of benign and malignant Hürthle cell lesions. Most Hürthle cells stained positively for thyroglobulin in all cases, but no immunoreactivity for CEA and calcitonin was found.     

Adenocarcinoma of the lung: a comparative diagnostic study using light and electron microscopy

Several techniques for diagnosing adenocarcinoma of the lung are commonly available, but the frequency of their use and diagnostic sensitivity may vary. Twenty cases of primary lung adenocarcinoma obtained at surgery were studied by the following four routine techniques: light microscopy (LM) using hematoxylin-eosin (H&E) stain, mucicarmine stain, and PAS-diastase stain, and electron microscopy (EM). Three observers independently determined the positivity (0 [none], +/- [equivocal], 1 + [slight], 2 + [moderate], 3 + [marked]) of each of these cases for lumen formation in H&E-stained sections (LM lumens), intracytoplasmic (cytoplasmic mucicarmine) or intraluminal (luminal mucicarmine) mucicarmine, intracytoplasmic (cytoplasmic PAS) or intraluminal (luminal PAS) PAS-diastase, and lumen formation (EM lumens) or microvilli (EM microvilli) on electron microscopy. Comparative matching of these seven microscopic determinants (using Wilcoxon signed-rank test) demonstrated significant (P less than .01) sensitivity of EM microvilli over EM lumens, EM microvilli over luminal mucicarmine, cytoplasmic PAS over luminal mucicarmine, EM microvilli over cytoplasmic mucicarmine, cytoplasmic PAS over cytoplasmic mucicarmine, and EM microvilli over LM lumens, and a significant (P less than .05) sensitivity of cytoplasmic PAS over LM lumens, EM microvilli over luminal PAS, luminal PAS over luminal mucicarmine, and cytoplasmic PAS over EM lumens. Friedman's nonparametric test (P less than .05) indicated a significant difference among the microscopic determinants. The most sensitive was EM microvilli (mean rank score, 5.17) followed by cytoplasmic PAS (4.77), luminal PAS (4.02), cytoplasmic mucicarmine (3.62), LM lumens (3.52), EM lumens (3.47), and luminal mucicarmine (3.40). However, each of the diagnostic techniques had case examples positive for one, but not for the others, indicating that maximum yield of adenocarcinoma diagnoses will be obtained by performing all four techniques (H&E, mucicarmine, PAS-diastase, and electron microscopy.     

Papillary adenocarcinoma of lung with psammoma bodies: report of a case derived from type II pneumocytes

A 52-year-old woman underwent thoracotomy for the removal of a mass in the middle lobe of the right lung. Light microscopy showed a tumour with the morphology of a papillary adenocarcinoma with numerous psammoma bodies. Electron microscopy revealed the tumour cells to possess the lamellated intracytoplasmic inclusions characteristic of normal and neoplastic type II pneumocytes. Psammoma bodies have not previously been reported in type II cell carcinoma of the lung. Alveolar cell carcinoma should be considered in the differential diagnosis of a papillary adenocarcinoma with psammoma bodies occurring in the lung.     

Dendritic cell/lymphocyte clustering: Morphologic analysis by transmission electron microscopy and distribution of gold-labeled MHC class II antigens by high-resolution scanning electron microscopy

Dendritic cells (DCs) are potent antigen-presenting cells for a variety of immune responses; however, their mechanism of action has not been established. It is known that DCs can cluster with one another and with other cell types during in vitro immune responses, and clustering may be essential for the activation of resting lymphocytes. In this study, ultrastructural examination of clusters that form during extended culture of enriched rat splenic DCs (approximately 70% DCs) is reported. DCs were readily distinguished from other cell types, which inclued lymphocytes and macrophages. DCs displayed characteristic veils and/or dendritic processes that intertwined with processes of other cells within the cluster, or extended from the cluster periphery. Occasional DCs contained large vacuoles lined with small vesicles. A paramount feature of DCs is their constitutive expression of high levels of surface major histocompatibility complex class II antigens. The surface distribution of class II antigens on clustering DCs was examined using 10 nm immunogold labeling techniques and high-resolution scanning electon microscopy. DCs were readily distinguished by morphologic criteria, and examination of various surface membrane regions revealed a differential distribution of class II antigens. Gold label was frequently distributed in linear arrays and clusters, suggesting a cytoskeletal role in the recycling/redistribution of Class II antigens. These morphologic findings further an understanding of basic DC biology and their mechanism of action as antigen presenting cells. © 1993 Wiley-Liss, Inc.     

Chronic myelomonocytic leukemia: an ultrastructural study by transmission and scanning electron microscopy.

The hematologic findings in three cases of chronic myelomonocytic leukemia are presented, with results of ultrastructural studies by transmission and scanning electron microscopy on two of the cases. In the peripheral blood there was a dual, non-lymphocytic, markedly increased population of granulocytes and monocytes. The granulocytes showed marked nuclear abnormality and nuclear cytoplasmic organelle asynchrony. In the marrow the majority of the cells appeared granulocytic but atypical forms and intermediate difficult to distinguish from monocyte precursors were evident by electron microscopy. The ultrastructural findings lend some support to the concept that the neoplastic granulocytes and monocytes having a common precursor.     

Energy filtering transmission electron microscopy of polymers – Benefit and limitations of the method

Energy filtering transmission electron microscopy (EFTEM) of polymers can often be successful where conventional methods fail due to insufficient contrast. A necessary prerequisite is that heteroatoms are contained in one of the phases to be discriminated. After an introduction of the method and a consideration of contrast in polymer systems, it is shown how and under what conditions EFTEM can contribute to the solution of typical problems in polymer research. The examples given cover representative areas from the fields of polymer blends, block copolymer morphology, structure of interpenetrating networks, film formation of water borne coatings, and organic-inorganic composites. All examples have in common that conventional TEM fails to yield the desired information on structure and composition, while EFTEM proves to be successful. Problems encountered upon interpretation of results are discussed, and ways to avoid artifacts are shown.     

Scanning and transmission electron microscopy of venous sphincters in the rat lung.

The rat pulmonary microvasculature was studied using scanning and transmission electron microscopy of vascular corrosion casts and tissue sections. Special emphasis was placed on small pulmonary venous vessels. The shape of vascular casts was analyzed and interpreted concerning the wall composition of corresponding vessels studied in tissue sections. On the casts of pulmonary venules and small pulmonary veins, narrow or wider annular constrictions were regularly observed. Within these constrictions, marks of circularly running grooves were seen as an additional structural detail, which obviously mimic impressions of single or grouped smooth muscle cells. The depth of the constrictions varies; it may be more or less pronounced, occasionally narrowing down the luminal diameter to approximately 50%. These constrictions are caused by muscular sphincters. In tissue sections of small pulmonary veins, sphincter regions were identified as abruptly appearing single or grouped true smooth muscle cells. Smooth muscle cells may be arranged side by side in a group or bundle or even staked in two or three layers. Between the sphincter regions, the venous wall consists merely of endothelium and an accompanying connective tissue layer. The smooth muscle cells of a sphincter are regularly positioned between endothelial layer and elastic lamina. The smooth muscle cells next to the endothelium form myoendothelial junctions. Autonomic nerves near the sphincters were never seen. The venous sphincters described are suggested to be effective devices involved in blood flow regulation. Blood-borne substances or local tissue hormones might govern sphincter function.     

The epithelium of the rabbit vagina: a microtopographical study by light, transmission and scanning electron microscopy.

In order to obtain a more precise microtopographical surface map of the epithelium of the rabbit vaginal mucosa, investigations by light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) have been systematically correlated. The epithelium was examined from the "portio vaginalis cervicis uteri" down to the "vestibulum". This study shows that the upper 2/3 of the vagina--which, in this species, is very long, measuring 13-14 cm--is lined by a single epithelial layer of tall ciliated and microvillous cells closely resembling the endocervical epithelium with which it is continuous. Moreover, these ciliated and microvillous cells also cover mucosal infoldings in the upper part of the vagina, especially those on the ectocervix and in the fornices, and scattered vaginal crypts. In particular, the ciliated elements decrease in number below the fornices, so that in large areas of the middle part of the vagina only microvillous cells are recognizable. Prior to the squamo-columnar junction, however, the ciliated cells increase again. This study also reveals that in the rabbit the squamo-columnar junction is located at the level of the pubic symphysis and that a squamous pluristratified epithelium covers only the lower 1/3 of the inner surface of the vaginal wall. In the estrous, i.e., precoital rabbit, the microvillous cells show little sign of secretion, whereas after mating they exhibit remarkable secretory features. These seem to increase progressively with postcoital stages (5 h, 24 h and 10 days) in the form of extensive mucification. These secretions often come in contact with spermatozoa retained in the mucosal infoldings and crypts, and are similar to those occurring in the endometrium, where they clearly depend upon progesterone activity. These epithelial features, different from those of other mammals, including humans, suggest that the greater part of the rabbit vagina accomplishes functions other than serving for copulation and as a fetal passageway. The present findings support the view that the rabbit vagina also plays a role as a reservoir of spermatozoa and in maintaining their viability, like the endometrium and endocervix.     

Apoptosis is a major pathway responsible for the resolution of type II pneumocytes in acute lung injury.

Proliferation of type II pneumocytes has been linked to a repair process during the early phase of acute lung injury, and it persists for a variable period. The mechanisms responsible for their dissolution and/or disappearance are not known, but we speculate that it may be partly due to apoptosis. Sections of lung tissue from patients with acute lung injury (n = 7) and chronic interstitial pneumonia (n = 14) were stained for detection of apoptotic cells via specific labeling of nuclear DNA fragmentation. Results were correlated with those of proliferating cell nuclear antigen (PCNA) staining for cell proliferation. Marked apoptosis of CD68-negative type II pneumocytes (30 to 80%) was detected in four of the seven (57%) cases of acute lung injury. In these cases, representing the resolution phase of acute lung injury, PCNA positivity in pneumocytes was extremely rare. In the 3 other cases in the acute/proliferative phase, apoptotic type II pneumocytes were rare whereas PCNA expression was quite evident in these cells. In chronic interstitial pneumonia, only rare type II pneumocytes (< 5%) exhibited apoptosis, and they showed variable staining for PCNA (up to 70%). We conclude that proliferation of type II pneumocytes occurs during the early phase of acute lung injury and is of variable extent and duration. In the resolution phase of acute lung injury, extensive apoptosis of type II pneumocytes is largely responsible for the disappearance of these cells. The time frame within which the apoptotic response occurs is variable and is likely to be dependent upon the specific etiology and extent of the injury. In chronic interstitial pneumonia, type II pneumocytes proliferate continuously, although to a much lesser degree than in the early phase of acute lung injury, and are minimally apoptotic.     

Correlative microscopy of Purkinje dendritic spines: a field emission scanning and transmission electron microscopic study

Purkinje dendritic spines (Pds) of mouse cerebellar cortex were examined by field emission scanning electron microscopy (FESEM) and by transmission electron microscopy (TEM) using ultrathin sections and freeze-etching replicas, to study their three-dimensional features and intramembrane morphology. FESEM showed unattached mushroom-type, elongated and lanceolate Pds separated by 100-500 nm on the dendritic shaft surface. High resolution FESEM showed 25-50 nm globular subunits at the spine postsynaptic density corresponding to the localization of postsynaptic proteins and/or postsynaptic receptors. TEM images of ultrathin sections showed gem-like, mushroom-shaped, lanceolate and neckless or stubby spines. Freeze etching replicas exposed postsynaptic intramembrane particles that can be correlated with the globular subunits observed at high resolution FESEM. Parallel and climbing fiber endings were observed making asymmetric synaptic contacts with the Pds heads. Simultaneous contacts with the necks and heads were also found. The variety of Pds shapes were interpreted as spine conformational changes related with spine dynamic, and spine plasticity.     

The formaldehyde-fixed and paraffin-embedded tissues for diagnostic transmission electron microscopy: a retrospective and prospective study

The fine structures of tissues processed routinely for light microscopy were studied retrospectively in 44 tissues and tumors and prospectively in 13 tissues and tumors. In the prospective study, we fixed tissues in an ample amount of fixatives, carefully avoiding crushed and air-dried portions, and processed them by five methods. The fine structures of the retrospective cases were mostly poor or passable, whereas those of the prospective cases were generally good. All formaldehyde-fixed tissues showed varied degrees of tissue extraction, notably of lipids, membranous structures, ribosomes, glycogen, and other loose cellular and intercellular matrix materials, that was related to the status and type of tissue as well as the kind and duration of fixation, dehydration, and tissue clearance. Paraffin embedding per se appeared to cause little alteration of the fine structure. Transmission electron microscopy of the paraffin-embedded tissue appeared most useful to identify infective agents, foreign particles, and densely packed organelles or structures, usually in the differential diagnosis of neoplasms. Although many factors are difficult to control, initial careful thin slicing, judicious selection, and fixation of the tissue (even by regular phosphate-buffered formaldehyde solution) can improve the fine structure of paraffin-embedded tissues and be useful in the direct correlation of light and electron microscopic findings.     

Ultrastructural changes during stimulation of amphibian oxyntic cells viewed by scanning and transmission electron microscopy

Amphibian oxyntic cells exposed by cryofracture were examined by field emission scanning electron microscopy. Comparisons were made between the structure thus revealed and those seen in thin-sectioned material from the same mucosas examined by transmission electron microscopy. Resting oxyntic cells had apical surfaces which were relatively smooth with some short microvilli. Apical cytoplasm was filled with smooth membrane tubules (so-called vesicotubules). Stimulation with a combination of histamine, dibutyryl cyclic AMP, and isobutylmethylxanthine (a phosphodiesterase inhibitor) led to a dramatic elaboration (i.e., increased membrane surface area) and a decrease in number of vesicotubules in the apical cytoplasm. The surface morphology of the stimulated oxyntic cell was much different from that reported for the mammalian parietal cell. Two types of surface elaboration were observed. Most commonly the surface was formed of flattened microplicae or lingulae. An irregular surface formed by the swelling of enlarged spaces near the apical surface was also observed. These new data have been used to evaluate the models which have been proposed to explain the nature of the transition from resting to stimulated morphology. A new model, which incorporates fusion of intracellular vesicotubules with each other and also with apical membrane, is proposed. The proposed fusion process may cause an increase in membrane area open to the extracellular (luminal) solution within the cell (rather than the eversion of membranes into the gastric lumen). Expansion of spaces between the microplicae may be caused by hydroosmotic pressures developed during active HCl secretion.