Morphologic and cytochemical characteristics of amine-containing globule leukocytes in rat tracheal epithelium

Response of rat tracheal epithelium to ozone and oxygen exposure in vitro

Although ozone-induced epithelial injury in vivo has been morphologically characterized, effects of gaseous oxidants on respiratory epithelium in organ culture, where tissue organization is maintained but systemic influences are eliminated, have not been thoroughly investigated. In this study, we exposed tracheal organ cultures from rats to 95% oxygen and 1 ppm ozone, alone and in combination, to determine (1) whether epithelial responses to ozone similar to those observed in vivo occur in airways separated from systemic physiologic, secretory, and inflammatory reactions; (2) whether concentrations of oxygen sufficient to potentially cause oxidant injury result in morphologic epithelial alterations similar to those that occur in ozone toxicity; and (3) if the combined oxidant insult of oxygen and ozone results in more severe damage to the tracheal epithelium than occurs with ozone in air. Tracheal organ cultures were exposed to filtered air and 5% carbon dioxide; filtered air, 5% carbon dioxide, and 1 ppm ozone; 95% oxygen and 5% carbon dioxide; or 95% oxygen, 5% carbon dioxide, and 1 ppm ozone for 96 hr. Light- and quantitative electron-microscopic evaluation showed that epithelia exposed to 1 ppm ozone in air exhibited loss of ciliated cells and ciliated cell damage. The epithelia exposed to 95% oxygen and 5% carbon dioxide were pseudostratified, columnar, ciliated, and hyperplastic. Epithelia exposed to 95% oxygen plus 1 ppm ozone were stratified and nonciliated or very sparsely ciliated. The predominant cell types in epithelia exposed to oxygen plus ozone were serous cells and metaplastic cells, and focal aggregates of adherent necrotic cells were present. We conclude that there was a synergism between oxygen and ozone exposure leading to enhanced epithelial injury and metaplasia.

In vitro evidence of cellular adaptation to ozone toxicity in the rat trachea

Adaptation to prolonged ozone (O3) exposure occurs in the tracheal epithelium of rats and is marked by the presence of ciliated cells with uniform short cilia but is not accompanied by shifts in cell populations, altered characteristics of epithelial secretory cell products, increased cell turnover, or elevated tracheal superoxide dismutase activity. The purpose of this study was to test the hypothesis that adaptation is a result of alterations intrinsic to epithelial cells or to the cells and their matrix, and not due to systemic or neural influences. Rats were preexposed to either filtered air (FA) or 0.96 ppm O3 for 8 hr/night for 60 days, and then their tracheae were removed and exposed to 3 ppm O3 in an explant culture system where behavioral, nasal, exudative, and secretory product influences can be eliminated. After exposure to 3 ppm O3 in vitro, quantitative electron microscopic evaluation demonstrated that the epithelia from the FA preexposure group had significantly more necrotic cells and sloughed cells and fewer ciliated cells than the epithelia from the O3 preexposure group. Thus previous exposure to ozone in vivo induces a change in tracheal epithelium which confers resistance to ozone-induced injury in the explant exposure system.

Globule leukocytes and mast cells in the rat trachea: their number, distribution, and response to compound 48/80 and dexamethasone

Globule leukocytes in the epithelium of the rat trachea may be counterparts of mucosal mast cells that are located in the gastrointestinal tract. If they are indeed similar to mucosal mast cells, globule leukocytes would be expected to decrease in number in rats treated with dexamethasone but not in rats treated with compound 48/80, an agent which causes non-antigenic degranulation of connective tissue mast cells. In this study, we determined the number and compared the distribution of globule leukocytes and connective tissue mast cells in the tracheas of pathogen-free rats. We then determined whether the number of these two types of cells changes in rats treated for 5 days with compound 48/80, dexamethasone, a combination of compound 48/80 and dexamethasone, or saline. We identified globule leukocytes and mast cells in whole mounts and histological sections of rat tracheas by using a histochemical reaction that demonstrates the chymotrypsin-like protease (chloroacetate esterase) present in mast cell granules. Using this method, we found that approximately 225,000 globule leukocytes were present in the epithelium of the trachea. These cells were most abundant in the rostral trachea. Rats treated with dexamethasone had a 91% reduction in the number of globule leukocytes with protease-containing granules, but rats treated with compound 48/80 had a normal number of these cells. We found some 55,000 connective tissue mast cells in the same tracheas. Mast cells were most abundant in the posterior membrane of the caudal trachea and in the lamina propria between cartilaginous rings. Rats treated with compound 48/80 had a 96% reduction in mast cells with protease-containing granules, but rats treated with dexamethasone had a normal complement of mast cells. We conclude that globule leukocytes are abundant in the tracheas of healthy rats, are similar in morphology and pharmacological responses to mucosal mast cells located in other organs of rats, and are more numerous than and have a different distribution than connective tissue mast cells. Globule leukocytes in the tracheal epithelium may have a role in respiratory defenses similar to that of mucosal mast cells in other organs.

Isolation and cytochemical characterization of globule leukocytes from rat tracheal epithelium

Globule leukocytes, dispersed throughout the respiratory epithelium as single cells, were isolated from rat trachea and were enriched by centrifugation on a discontinuous Percoll gradient. The isolation and enrichment procedure yields a cell fraction containing 75% globule leukocytes. The cell viability, as assessed by trypan blue exclusion, was at least 98%. Cells were maintained in short-term culture without apparent loss of viability and enzyme activity. The isolated globule leukocytes seem not to express significant levels of cytotoxicity against 51Cr-labeled YAC-1 target cells. In fixed cytocentrifuge smears, globule leukocytes appear as more or less rounded to oval cells with a low nucleo-cytoplasmic ratio and with a mostly eccentrically located nucleus. Characteristic intracytoplasmic granules are stained with toluidine blue, alcian blue, and May-Grünwald-Giemsa stains. The applied cytochemical methods demonstrate that tracheal globule leukocytes are stained for alpha naphthyl acetate esterase and naphthol-AS-D-chloroacetate esterase, but not for alpha naphthyl butyrate esterase, N-acetyl-DL-phenylalanine-B-naphthyl esterase, and endogenous peroxidase. Isolated rat peritoneal cells were used as positive control cells for the cytochemical reactions. The obtained cytochemical profile of tracheal globule leukocytes is compared to the known cytochemical profile of intestinal globule leukocytes and large granular lymphocytes. The cytochemical dissimilarities between tracheal and intestinal globule leukocytes may suggest that both kinds of globule leukocytes represent a different form of the same cell type or even different cell types. The cytochemical pattern of tracheal globule leukocytes is closely related to that of large granular lymphocytes, which have been postulated as a possible source for globule leukocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Globule leukocytes in the respiratory epithelium of human upper airways: an ultrastructural study

The ultrastructure of globule leukocytes is described in the nasal and tracheal respiratory epithelium of three boys suffering from chronic airway infections. The globule leukocytes lie free in the intercellular spaces and appear to be migratory cells. They are characterized by intracytoplasmic membrane-bound globules, variable in number, size, shape, and internal structure. The globules may apparently release their content between the neighboring epithelial cells. Human globule leukocytes are also characterized by the presence of intracytoplasmic rod-shaped bodies, the significance of which is not known. They usually display an extended juxta-nuclear Golgi apparatus, presumably involved in the formation of the globules. Comparison of the fine structure of the globules in the globule leukocytes with that of the granules found in the subepithelial mast cells does not support a mast cell origin for human globule leukocytes. On morphological grounds, natural killer cells are postulated as a possible source for globule leukocytes. The function of globule leukocytes is briefly discussed. We presume that the globule leukocytes belong to the group of migrating and secreting cells involved in the defense of the organism against foreign material.