Ultrastructural features of type II alveolar epithelial cells in early embryonic mouse lung

Immunofluorescence studies of type II alveolar epithelial cells indicate that they first appear in the pseudoglandular period of mouse lung development (around day 14.2). They are the only cell type to line the prospective pulmonary acinus at this time. The ultrastructural characteristics of this cell are defined by investigating embryos aged 13-16 days with transmission and scanning electron microscopy. Early embryonic type II cells appear as low-columnar or cuboid cells having large, approximately round nuclei and distinct ultrastructural features, including a well-developed Golgi apparatus with many associated vesicles, multivesicular bodies, dense bodies, and large apical and basal glycogen fields. These fields represent a distinctive property of the cell. Frequently, they show compartmentalization due to the presence of membrane systems, and association with dense bodies of various sizes.     

Specific localization of lysosomal aminopeptidases in type II alveolar epithelial cells of the rat lung

We previously demonstrated that lysosomal cysteine proteinases, cathepsins B, H, and L were localized in lysosomes of alveolar macrophages and bronchial epithelial cells in the rat lung, while cathepsin H, a typical aminopeptidase, was additionally distributed in lamellar bodies containing surfactant in type II alveolar epithelial cells (ISHII et al., 1991). The present immunohistochemical study further examined the localization of lysosomal aminopeptidases, cathepsin C, and tripeptidyl peptidase I (TPP-I) in the rat lung. Western blotting confirmed the presence of cathepsin C and TPP-I as active forms in the pulmonary tissue, showing 25 kD and 47 kD, respectively. Immunohisto/cytochemical observations demonstrated that positive staining for cathepsin C and TPP-I was more intensely localized in alveolar epithelial regions than in bronchial or bronchiolar epithelial cells. By double immunostaining using confocal laser microscopy, immunoreactivity for cathepsin H was found to be co-localized with that for cathepsin C or TPP-I in both type II cells and macrophages. Moreover, when doubly stained with anti-cathepsin C and ED2, single-positive type II cells could be clearly distinguished from double-positive macrophages in the alveolar region. Immunoelectron microscopy revealed the gold labeling of cathepsin C or TPP-I in multivesicular and composite bodies, and lamellar bodies of Type II cells. These results showing that lysosomal aminopeptidases such as cathepsin H, cathepsin C and TPP-I are localized in lamellar bodies of type II alveolar epithelial cells strongly argue for the participation of lysosomal aminopeptidases in the formation process of surfactant containing specific proteins.     

Malignant rhabdoid tumor arising in a mixed epithelial,stromal tumor of kidney: report of a male case,review of the literature

Mixed epithelial and stromal tumor (MEST) of the kidney is a rare biphasic tumor composed of both stromal and epithelial components, the latter showing a variable proportion of solid to cystic areas. These tumors show a marked female predominance, commonly occur in perimenopausal age groups, and often have an ovarian-type stroma with ER and PR positivity, suggesting steroids may play a role in pathogenesis. Although typically benign, rare cases showing malignant transformation have been reported. We present a case of a 42-year-old man with a 10 cm right kidney mass located in the renal pelvis. Histologically, the majority of the tumor was composed of a diffuse, sheet-like growth of malignant cells demonstrating a rhabdoid morphology with large nuclei, prominent nucleoli, and eosinophilic eccentric cytoplasm. Brisk mitotic activity and coagulative type necrosis was also noted. Intimately associated with this malignant rhabdoid component was a much smaller portion of tumor featuring variably sized bland epithelial tubules embedded within a stroma composed of bland spindle cells and areas of hyalinization, diagnostic of MEST. By immunohistochemistry, the malignant rhabdoid tumor portion of the neoplasm showed complete loss of nuclear INI-1, while the MEST component retained nuclear expression of this antigen. With these features taken together, our case represents a malignant rhabdoid tumor arising in a background of MEST. To our knowledge, this case represents the first case of a MEST showing malignant transformation in the form of malignant rhabdoid tumor in a male patient in the English language literature.     

Mixed squamous cell and glandular papilloma of the lung: a case study and literature review

Mixed squamous cell and glandular papilloma (mixed papilloma) of the lung is an extremely rare neoplasm, with only 10 cases reported so far in the English literature. We present a case study of endobronchial mixed papilloma with immunohistochemical and etiological investigations. A 49-year-old male with a smoking history complained of hemoptysis, presented with a lung mass closely adjacent to large vessels in the computed tomography findings, and underwent lobectomy. The 3.0-cm sized polypoid tumor was histologically diagnosed as endobronchial mixed papilloma. Immunohistochemically, intracellular mucin was positive for MUC5AC, which is expressed in tracheobronchial goblet cells. CAM5.2 and CK19 were diffusely positive, indicating that the tumor originated from the columnar epithelium by squamous metaplasia. CEA and CA19-9 were focally positive. A human papillomavirus (HPV) investigation with in situ hybridization using a wide spectrum probe and a newly-developed PCR system did not detect any HPV infection. Including this case with a detailed HPV investigation, all of the reported cases of mixed papilloma were HPV-negative, and a literature review including newly-reported cases indicated a high frequency of smoking in such cases. Endobronchial mixed papillomas might have a smoking-related etiology.     

Primary mixed mullerian tumor of the vagina--a case report with review of the literature

Malignant mixed mullerian tumor (MMMT) is a rare entity. The commonest site of this tumor in the female genital tract is the uterus followed by cervix. Primary MMMT of vagina is extremely rare. We are reporting this rare entity, with a brief review of the literature, in a 48-year-old perimenopausal female who presented with a history of passage of urine per vagina. On pelvic examination, a polypoidal mass arising from the anterior wall of the vagina was identified. Histopathological examination revealed the biphasic nature of the tumor. Immunohistochemistry confirmed the diagnosis of MMMT of vagina. To conclude, although rare, clinicians, oncologists, and pathologists should identify this malignant tumor for appropriate treatment and management.     

Inhibitors of choline transport in alveolar type II epithelial cells.

Isolated alveolar type II epithelial cells (granular pneumocytes) from rat lung accumulate free choline against a concentration gradient by an energy-dependent saturable transport process with apparent Km approximately 18 microM. In order to evaluate the structural requirements for choline transport by these cells, the inhibition of the initial rate of cellular uptake of [3H]choline (5 microM) by its analogue was measured. There was no significant inhibition of substrate uptake by analogues lacking an amino group while the presence of a quaternary nitrogen was most effective. N,N'-dimethylethanolamine (apparent Ki, 7 microM) and n-decylcholine (apparent Ki, 0.5 microM) were potent competitive inhibitors of choline transport. Substitution of the hydroxyl group in choline greatly diminished the inhibitory effect; fluorocholine, thiocholine, betaine, and betaine aldehyde showed little or no inhibition. This requirement for a hydroxyl group raises the possibility of hydrogen bonding of choline with the transport protein. The choline transport system in granular pneumocytes appears to differ from that in synaptosomes by the lower affinity of the carrier for substrate and for hemicholinium-3 and from that in erythrocytes by the role of the hydroxyl in the substrate molecule. The availability of inhibitory analogues for choline transport will facilitate isolation and study of the granular pneumocyte choline transport protein.     

Lecithin biosynthesis in a clonal line of lung adenoma cells with type II alveolar cell properties

The content and synthesis of certain phospholipids associated with lung surfactant has been investigated in a clonal line of epithelial cells derived from mouse lung adenoma. These cells, designated LA-4, possess osmiophilic intracytoplasmic lamellar inclusion bodies similar in appearance to lamellar bodies observed in normal type 2 alveolar epithelial cells (Stoner et al., 1975).Lecithin was the most abundant phospholipid in the LA-4 cells, comprising more than 50% of all phospholipid. LA-4 cells had significantly higher contents of total lecithin than in vivo adenoma and normal lung, but a lower proportion (27–29%) of the total lecithin in disaturated form than normal lung (36%). In addition, LA-4 cells had a significantly higher proportion of total lecithin in disaturated form than a clonal line of mouse lung fibroblasts (14%). The content of phosphatidylglycerol in LA-4 cells was significantly lower than in normal lung.Radiolabeled precursor studies showed that palmitic acid was rapidly incorporated into disaturated lecithin of LA-4 adenoma cells and to a greater extent than glycerol, suggesting that the saturation pathways forming disaturated lecithins are active. Studies with radiolabeled choline and methionine suggest that LA-4 cells synthesize total and disaturated lecithins de novo principally through the choline incorporation pathway, with a minor contribution by the three-step methylation of phosphatidyl-ethanolamine.The present results indicate that the phospholipid metabolism of lung adenoma cells is preserved when cultured in vitro. Urethan-induced transformation of type 2 alveolar cells appears to result in a diminished capacity of the cells to synthesize phosphatidylglycerol and disaturated phosphatidylcholine.     

A morphometric examination of type II alveolar epithelial cells in normal and isolated-perfused dog lungs

The volume densities of type II alveolar cell cytoplasmic organelles and alveolar surface densities were estimated by established stereologic procedures. The morphometric measurements were obtained from normal dog lungs (in situ) and isolated dog lungs perfused for 30-minute, 1-hour, and 2-hour periods. The type II cell lamellar body volume densities and the alveolar surface densities progressively decreased as the times of perfusion were increased. The volume densities of the granular and agranular endoplasmic reticulum progressively increased during the periods of perfusion. These morphometric parameters from lungs in situ and isolated lungs suggest that changes occur in pulmonary surfactant synthesis and activity during perfusion. It is further postulated that progressive increases in the rates of surfactant removal and/or inactivation during perfusion may contribute to spontaneous edema in lungs isolated for periods exceeding two hours. The morphologic and physiologic integrity of isolated perfused lung preparations, widely used as models of lungs in vivo, in situ requires further evaluation.     

Rat alveolar type II cells inhibit lung fibroblast proliferation in vitro

Fibroblasts stimulate alveolar type II epithelial cell differentiation and proliferation in vitro and during lung development. However, little is known about the effects of adult type II cells on fibroblasts. We investigated the effect of adult rat type II cells on proliferation of adult human lung fibroblasts. Fibroblasts were suspended within rat tail collagen which was gelled on a floating polycarbonate filter, and type II cells were cultured on Matrigel. In this coculture system, alveolar type II cells inhibited fibroblast proliferation and indomethacin blocked the inhibitory effect on fibroblast growth. Prostaglandin (PG) E2, the major PG secreted by type II cells, inhibited fibroblast proliferation and was increased during the period of inhibition of fibroblast proliferation. Incubation with arachidonate showed that most of the PGE2 in the coculture system was produced by the fibroblasts. In addition, we found that rat type II cells also inhibited rat fibroblasts and that inhibition of fibroblast growth by type II cells could be stimulated by keratinocyte growth factor. We conclude that in this coculture system, type II cells inhibit fibroblast proliferation by secreting a factor(s) that stimulates PGE2 production by fibroblasts, and that PGE2 directly inhibits fibroblast proliferation.     

The freeze-fracture study of alveolar type II cells and alveolar content in fetal rabbit lung

Freeze-fracture replication technique was utilized to study the morphology of type II alveolar epithelial cells and alveolar contents in the late gestation of rabbit fetuses. It was shown that the lamellar inclusion bodies of type II cells were enveloped by the usual type of unit membrane with membraneassociated particles of 15 nm diameter. The interior of the inclusion bodies was composed of multiple stacks and/or whorls of membranes which were devoid of membrane-associated particles. Small vesicles within the inclusion were found more frequently with this technique than in chemically fixed thin-sectioned preparations. The intra-alveolar contents were comprised of two components; spherical bodies, which were identical to the internal contents of the lamellar bodies of type II cells, and tubular elements. These tubules most often appeared rectangular on cross-fractured faces. Triangular and hexagonal fracture faces were also noted. The tubules were seen to rest on the surfaces of the spherical components. Our observations suggest that the tubular element of the alveolar contents is formed through the interaction between the discharged lamellar body content and the alveolar fluid, and further suggest that at least the major constituent of type II cell lamellar bodies is lipid not bound to protein. Three new observations were made in this study; the absence of membraneassociated particles on the interior of the lamellae of the inclusions, the crossfractured profiles of tubular elements of the alveolar contents, and the occasional multicompartmental nature of type II cell inclusions.