Atypical cilia in the tracheobronchial epithelium of the hamster during respiratory carcinogenesis

Alcohol, vitamin A, and beta-carotene: adverse interactions, including hepatotoxicity and carcinogenicity

Isozymes of alcohol and other dehydrogenases convert ethanol and retinol to their corresponding aldehydes in vitro. In addition, new pathways of retinol metabolism have been described in hepatic microsomes that involve, in part, cytochrome P450s, which can also metabolize various drugs. In view of these overlapping metabolic pathways, it is not surprising that multiple interactions between retinol, ethanol, and other drugs occur. Accordingly, prolonged use of alcohol, drugs, or both, results not only in decreased dietary intake of retinoids and carotenoids, but also accelerates the breakdown of retinol through cross-induction of degradative enzymes. There is also competition between ethanol and retinoic acid precursors. Depletion ensues, with associated hepatic and extrahepatic pathology, including carcinogenesis and contribution to fetal defects. Correction of deficiency through vitamin A supplementation has been advocated. It is, however, complicated by the intrinsic hepatotoxicity of retinol, which is potentiated by concomitant alcohol consumption. By contrast, beta-carotene, a precursor of vitamin A, was considered innocuous until recently, when it was found to also interact with ethanol, which interferes with its conversion to retinol. Furthermore, the combination of beta-carotene with ethanol results in hepatotoxicity. Moreover, in smokers who also consume alcohol, beta-carotene supplementation promotes pulmonary cancer and, possibly, cardiovascular complications. Experimentally, beta-carotene toxicity was exacerbated when administered as part of beadlets. Thus ethanol, while promoting a deficiency of vitamin A also enhances its toxicity as well as that of beta-carotene. This narrowing of the therapeutic window for retinol and beta-carotene must be taken into account when formulating treatments aimed at correcting vitamin A deficiency, especially in drinking populations.

Light and electron microscopic observations on ciliated vacuoles and cysts in the oviductal and endocervical epithelia of the rabbit

Ciliated vacuoles and intraepithelial cysts have been observed in oviductal and endocervical epithelia of rabbits. In this study, rabbits under various hormonal conditions were studied by light and transmission electron microscopy and tissue culture in an attempt to determine their distribution and origin. Ciliated vacuoles most frequently lay in the basal cytoplasm, below or beside the nucleus, and very close to the basal lamina. A few were apically located. Their average diameter was 8.8 by 5.1 microns. Cilia and microvilli projected into the vacuolar lumen. These vacuoles were located intracellularly as evidenced first by the degeneration of both their cilia and microvilli and the moderately dense matrix that often filled the vacuolar lumen, as observed by electron microscopy. Secondly, phase microscopy of the living endocervical epithelium allowed us to observe the beating of the cilia within the vacuoles, not on the surface of such cells. Thirdly, ruthenium red stained the surface glycocalyx of ciliated and secretory cells, but not that of the cilia and microvilli within the vacuoles. The intraepithelial cysts were not observed in all tissue blocks. The largest numbers were found in ovariectomized animals treated for 3 and 5 days with estradiol. More were seen in the isthmus and cervix than in the fimbria and ampulla. The cysts were located most often within the epithelium along the sides of, and at the bases of, the mucosal folds. They were lined by flattened epithelium of various combinations of secretory and ciliated cells. An unusual cell type was associated with some of the cysts and ciliated vacuoles. Its cytoplasm contained aggregates of mitochondria and vesicles whose contents varied in density. Although the genesis of the ciliated vacuoles is not certain, our results indicate that they may arise from aberrant positioning of proliferating procentrioles or from a defect in targeting or transporting the centrioles to the apical plasma membrane to serve as basal bodies. Fusion of adjacent ciliated vacuoles with lumina lined by secretory cells having deep apical invaginations appeared to contribute to the formation of cysts.

Nonolfactory surface epithelium of the nasal cavity of the bonnet monkey: a morphologic and morphometric study of the transitional and respiratory epithelium

The purpose of the present study was to characterize ultrastructurally the nonolfactory nasal epithelium of a nonhuman primate, the bonnet monkey. Nasal cavities from eight subadult bonnet monkeys were processed for light microscopy, and scanning and transmission electron microscopy. Nonolfactory epithelium covered the majority of the nasal cavity and consisted of squamous (SE), transitional (TE), and respiratory epithelium (RE). Stratified SE covered septal and lateral walls of the nasal vestibule, while ciliated pseudostratified RE covered most of the remaining nasal cavity. Stratified, nonciliated TE was present between SE and RE in the anterior nasal cavity. This epithelium was distinct from the other epithelial populations in abundance and types of cells present. TE was composed of lumenal nonciliated cuboidal cells, goblet cells, small mucous granule (SMG) cells, and basal cells, while RE contained ciliated cells, goblet cells, SMG cells, basal cells, and cells with intracytoplasmic lumina lined by cilia and microvilli. TE and RE contained similar numbers of total epithelial cells and basal cells per millimeter of basal lamina. TE was composed of more SMG cells but fewer goblet cells compared to RE. We conclude that nonolfactory nasal epithelium in the bonnet monkey is complex with distinct regional epithelial populations which must be recognized before pathologic changes within this tissue can be assessed adequately.

Abnormal cilia in a fourth ventricular ependymoma

Although the luminal surface of the ependymal cells of the human ventricular system is characterized by the presence of cilia with a typical 9 + 2 arrangement of microtubules, cilia are usually described as sparse or absent in ependymal cells of ependymomas. The incidence of aberrant cilia and structurally abnormal cilia in normal ependymal cells and ependymomal cells has not been documented. This report describes detailed ultrastructural and quantitative studies of cilia of the ependymal cells of a fourth ventricular ependymoma in a 5-year-old boy. Of a total of 267 cilia studied, 50% were located in the extracellular microrosettes, 30% in the intracytoplasmic lumina and 20% in the cytoplasm. Thirty precent of all cilia studied showed structural abnormalities. Those present in the aberrant locations, e.g., intracytoplasmic lumina and in the cytoplasm, had a higher incidence of abnormality. Ciliary abnormalities fell into four majors categories: (1) cilia with abnormal axial microtubules, (2) compound cilia, (3) swollen cilia, and (4) cilia with dynein arm defect. Of these, addition, deletion and disorganization of axonemal microtubules were most common. The present study suggested that ciliary abnormality is common in ependymoma and may represent another example of oncogenetic effect on the ciliogenesis of ciliated epithelium.

Abnormal cilia in a malignant ependymoma

Abnormal cilia were frequently exposed in a malignant ependymoma of the cerebellar vermis by an electron microscope study. Among these erratic cilia, compound cilia, huge axoneme with bizarre shapes, were repeatedly observed. These giant cilia commonly had random orientation of many microtubular doublets as well as complicated cavities in their granular ciliary matrix. Additionally, abnormal cilia of normal-sized axoneme showed diversified arrangement of peripheral doublets and central singlets. The formation process of these abnormal cilia is discussed.

Morphology of tracheal and bronchial epithelium and type II cells of the peripheral lung of the guinea pig after inhalation of toluene diisocyanate vapors

Toluene diisocyanate (TDI), a polymerizing agent used in production of plastics, can cause airways disease in some exposed individuals. Using guinea pigs as a model, the response of the airways and the type II cells of the peripheral lung was monitored morphologically and morphometrically after exposure to TDI vapors at 30 ppb, 260 ppb, and 3100 ppb. The two low doses of TDI caused little change in airways epithelium. There was no gross inflammatory cell infiltrate, however, surface infoldings and intracellular ciliated cysts increased in numbers. Animals exposed to 3100 ppb TDI 4 h/day for 5 days, sustained considerable damage to the epithelium, and stratified nonkeratinizing cells lined the airways until one week after exposure. Polymorphonuclear leukocytes were present in the early period after exposure. Increased numbers of eosinophils were present between one and two weeks following exposure. Mitoses in the epithelium were common during recovery. In the peripheral lung, though a modest subjective increase in the number of type II cells was seen after 3100 ppb TDI, the volume density of type II cells, and organellar components (lamellar bodies, mitochondria, cisternal bodies) did not change significantly after any exposure level of TDI.

Abnormal cilia in the small airways of mice induced by bleomycin

The frequency and types of abnormal cilia in the small airways before and after parenteral administration of bleomycin were examined by transmission electron microscopy. Bleomycin was injected subcutaneously at a dose of 40 mg/kg twice weekly for 6 weeks. Bronchioles less than 0.1 mm in diameter from animals sacrificed 1 day after a single dose, 1 day after three doses, 3 days after 8 doses, and 13 days after 12 doses were selected for evaluation. Although ciliated cells proper did not show pronounced alterations, abnormal cilia such as swollen cilia, compound cilia, and cilia with abnormal axonemes frequently occurred. Repeated injections did not necessarily induce much more abnormal cilia than one dose. The results suggested that ciliated cells remain undamaged and that normal cilia can be restored. The specific type of abnormal cilia induced by bleomycin was not identified.

Regeneration of hamster tracheal epithelium after mechanical injury. IV. Histochemical, immunocytochemical and ultrastructural studies

All stages of regeneration in hamster tracheal epithelium were studied following a denuding mechanical injury. At 1 h all the cells had sloughed from the wound site leaving a bare and sometimes disrupted basal lamina. Viable cells at the wound margins rapidly changed shape, flattened and migrated to cover the denuded lesion by 12 h. In addition, epithelial cells that remained viable demonstrated sublethal changes that included the rapid discharge of mucous granules from secretory cells, internalization of cilia by ciliated cells and evidence of heterophagy in both cell types. By 24 h a wave of epithelial cell divisions occurred, primarily by secretory cells. This produced a multilayered epidermoid metaplasia that was best developed at 48 h. The metaplastic epithelium was largely composed of cells with both secretory (mucous granules) and epidermoid (tonofilament bundles and numerous desmosomes) characteristics. The peroxidase-antiperoxidase (PAP) method demonstrated a few keratin-positive cells in the wound as early as 12 h post-wounding and keratin was demonstrated in more cells by 24 h. All cells in the metaplastic wound epithelium were keratin-positive by 48 h. Following 48 h some of the most superficial keratinized cells sloughed from the epithelium and the keratin content of the remaining cells began to decline. At 72 h pre-ciliated and pre-secretory cells were seen in the wound. Pre-ciliated cells were characterized by an abundant electron-lucent cytoplasm, large pale nucleus, filiform apical microvilli and evidence of ciliogenesis, similar to that seen during fetal development. Pre-ciliated cells often contained apical mucous granules, apparently carried over from the parent secretory cells. With the appearance of these columnar cells the normal mucociliary morphology was restored in small wounds by 120 h, but some persistent epidermoid metaplasia remained in the large wounds through 168 h post-wounding. These data provide further evidence for the important role of secretory cells in the histogenesis of epidermoid metaplasia and the regeneration of normal morphology following injury. The implications of these findings in understanding the histogenesis of other lesions in the tracheo-bronchial epithelium are discussed.

Surface architecture of the mucosal epithelium of the cat trachea: I. Cartilaginous portion

The mucosal covering of the cartilaginous portion of the cat trachea was studied by correlated light, transmission-electron, and scanning-electron microscopy. While in some areas the ciliated pseudostratified epithelial lining is fairly smooth in contour, in other areas it contains longitudinally oriented, cilia-lined clefts. Ducts from submucosal glands sometimes open into the base of these clefts, or into funnel-shaped stomata that are lined by either ciliated or microvillus-rich cells. Specialized epithelial cells are occasionally associated with the clefts or with other regions of surface epithelium. In single sections, these cells appear to contain a cilium-lined vacuole, but serial sectioning has demonstrated that these apparent vacuoles actually are long intracellular invaginations in enormously elongated cells that extend longitudinally in the plane of the epithelium. The function of these cells is undetermined. Basal cells are attached to the lamina densa by means of hemidesmosomes that consistently lack peripheral densities; in contrast, the tall columnar cells have no hemidesmosomes.

An ultrastructural study of primary cilia, abnormal cilia and ciliary knobs from the ciliated cells of the guinea-pig trachea

Single primary cilia are found in developing as well as mature ciliated cells of guinea-pig tracheal epithelium. A few biciliated cells were observed, and in a rare case one cell had developed four such processes. Primary cilia are characterized by a 9 + 0 microtubular arrangement near the base, while a transition to an 8 + 1 pattern occurs at a slightly more distal position. Spokes are lacking, and dynein arms are absent or incompletely developed. The function, if any, of primary cilia remains unknown. In the population of the motile 9 + 2 cilia atypical forms are very rare, i.e. less than 0.1%. Of the various abnormalities cilia with supernumary microtubules are most common. Only one atypical basal body was observed. Although some of the aberrant forms undoubtedly are non-motile, their very low number suggests that they have no practical influence on the muco-ciliary clearance. Local extrusions of the ciliary membrane, here named ciliary knobs, are believed to be fixation artefacts. It is suggested that they represent circumscribed regions of the ciliary membrane which are sensitive to changes in the environmental osmotic pressure.

Recurrent chest infections, ciliary abnormalities and partial complement deficiency in a Jordanian family

Four girls born to second cousin parents developed chronic chest infection and bronchiectasis in infancy. Three were studied in detail: they all had the same HLA haplotype, all showed random orientation of cilia or compound cilia in the respiratory tract, and all had low levels of the C1 and C2 components of the complement system. Although the cause of the respiratory disease in this family remains unclear, it is suggested that the low C1 levels may have contributed to the disease in two of the children while the low C2 levels were artefacts and the ciliary abnormalities were secondary to chronic chest infection.

Identification and definition of chemical carcinogens: review of criteria and research needs

Advances in carcinogenesis research have greatly improved the methods for detection, investigation, and definition of occupational carcinogens. A basis of scientific criteria has been developed for carcinogen identification and evaluation. Research, legislative, and regulatory initiatives in the United States are reviewed. The 1979 Report of the Working Group on Occupational Carcinogenesis, Occupational Cancer Task Force, National Cancer Institute, is added as an appendix. A detailed discussion is given of the 1979 report of the Interagency Regulatory Liaison Group entitled "Scientific bases for identification of potential carcinogens and estimation of risks." Two separate approaches are considered, i.e., the qualitative determination that a substance poses a carcinogenic hazard and the quantitative estimation of risk. The qualitative criteria are reviewed in the present paper. The need for critical data evaluation and the judgmental nature of the process are emphasized. Research needs arising from the analysis of these criteria are discussed. Laboratory research contributions to the identification and characterization of carcinogens are summarized, including development and study of organ target models for carcinogenesis in animals; studies of human target tissues and cells in culture; studies of transformation, initiation, and promotion of epidermal cells in culture; studies of transplacental carcinogenesis; and studies of molecular mechanisms.

Atypical cilia in rabbit bronchial epithelial cells induced by elastase: an ultrastructural study

Ultrastructural study of the bronchial epithelium of elastase-treated rabbits revealed the presence of luminal atypical cilia resembling the pathological cilia seen in the tracheobronchial epithelium in animal models of human lung cancer. It is suggested that the results may contribute to knowledge of the mechanisms whereby compound cilia are produced.

Atypical cilia of the human nasal mucosa

Typical and atypical ultrastructural features of the cilia in the human nasal mucosa are reported in this paper. The specimens were taken from patients with the diagnosis of allergic rhinitis or chronic sinusitis. Most of the cilia showed a typical 9 + 2 arrangement of the axial filament complexes, but atypical axonemes such as 9 + 4, 8 + 2 and 10 + 2 patterns were found in six cilia of three patients. The supernumerary central fibrils were observed in one cilium only, whereas atypical patterns of the peripheral fibrils were found in five cilia. Cilia which contained a multiple axial filament complex, so-called compound clia, were also found in the mucosa of the chronic sinusitis cases. On the basis of their ultrastructural appearance, we classified these cilia into two groups, an "adhesive type" and a "bulging type." The former had a columnar shape of variable diameter, whereas the latter had a balloon-like form. The former contained closely packed multiple axial filament complexes whereas the latter possessed only sparse and irregularly oriented complexes. Electron-lucent lumina which were formed by the remnants of the ciliary membrane were frequently found in the former's transitional portion, but never in the latter.

Effects of cigarette smoke residue on rabbit tracheal epithelium in organ culture

The effects of tobacco cigarette smoke residues on rings of rabbit tracheal epithelium in organ culture were examined. Residue from cigarette smoke was collected through continuous suction and the residue from one cigarette was used for each two tracheal rings. Epithelium exposed to residue showed cellular desquamation, initially of only scattered columnar cells. As exposure time increased the entire columnar cell layer was lost, resulting in exposure of basal cells to residue. Columnar cell loss occurred through breakdown of intercellular junctions. Alteration was also observed in columnar cell mitochondria, cilia, and microvilli. Loss of columnar cells and subsequent exposure of basal cells to tobacco smoke residue may account for the hyperplasia and metaplasia observed by other investigators after long-term in vivo exposure of tracheal epithelium to cigarette smoke.

Ultrastructure of airways in children with asthma

This study describes the histopathology and ultrastructure of bronchial mucosa in lung biopsies from two children with bronchial asthma in remission, and compares them with lung samples from two children who died in status asthmaticus. Light microscopy of all samples showed changes typical of bronchial asthma, e.g. mucus plugging, goblet cell hyperplasia, 'thickening of bronchial basement membrane', peribronchial smooth muscle hypertrophy and eosinophilic infiltration. Electron microscopy revealed that the mucus plugs consisted of moderately electron-dense floccular material containing degenerate epithelial cells, macrophages and cell fragments. The luminal surfaces of ciliated cells showed cytoplasmic blebs and abnormal cilia. Mast cells in various stages of degranulation were scattered between bronchial epithelial cells. The subepithelial hyaline layer, commonly referred to as "thickened basement membrane", consisted of collagen fibrils in plexiform arrangement. The basement membrane proper appeared intact. These electron microscopic changes, particularly the presence of mast cells and subepithelial collagen deposits, were also found in autopsy samples. This combined light and electron microscopic study shows that marked, possibly irreversible changes may be present in the lungs of patients with severe bronchial asthma, even when they are asymptomatic. These pulmonary changes could be the direct consequence of mast cell activation and the release of various mediators. No evidence of immune complex deposition was found.

Abnormal cilia in the bronchial mucosa. Case reports of non-smoking women with bronchogenic carcinomas and an experimental model in guinea-pigs

Atypical cilia in the bronchial mucosa of non-smoking women and in guinea-pig lungs were studied by the electron microscope. In human cases, numerous compound cilia were observed in the main bronchi. The largest one contained about 40 axial filament complexes in a ciliary shaft. Occasionally, atypical basal bodies were also seen. In the experimental model in guniea-pigs, 50% oxygen at one atmospheric pressure damaged the bronchial surface and resulted in degeneration and reduction of cilia and pellicular structures. The injury was not sufficiently severe to initiate adaptation and reparative mechanisms in the bronchial mucosa, and rapid renewal of the surface structures was found. The human cases were associated with bronchogenic carcinoma but the experimental model suggested that atypical cilia were not always related to pulmonary carcinogenesis.

Ciliary alterations in hamster respiratory tract epithelium after exposure to carcinogens and cigarette smoke

Alterations in the ultrastructure of cilia were found to be one of the initial stages in the development of benzo(a)pyrene induced cancers in the trachea and bronchi of Syrian golden hamsters, as well as in the bronchi from which pulmonary adenocarcinomata originated after European hamsters were treated with N-dibutylnitrosamine. Similar abnormalities of cilia occurred in the respiratory epithelia of Syrian golden hamsters after one year of daily exposure to cigarette smoke.