Endometrial squamous metaplasia. An unusual response to progestin therapy of hyperplasia

OBJECTIVE

To report the finding of squamous metaplasia within endometrial glands occurring as a result of progestin therapy of hyperplasia.

DESIGN

Case series. Retrospective analysis of two cases from 9235 accessioned endometrial biopsies.

SETTING

Hospital-based pathology laboratory processing inpatient and outpatient specimens.

PATIENTS

Two women, ages 49 and 34 years, with endometrial hyperplasia without squamous metaplasia who were treated with progestin.

RESULTS

Extensive squamous metaplasia was found in endometrial glands following progestin therapy. The post-therapy biopsies also showed progestin-related alterations but no evidence of active hyperplasia.

CONCLUSION

Squamous metaplasia in these cases appears to be a consequence of progestin therapy. The absence of hyperplasia in the progestin-treated endometrium suggests that the squamous metaplasia does not represent persistence or progression of the original hyperplastic lesion.

Retinoic acid provokes metaplasia of epithelium formed in vitro by adult human epidermal keratinocytes

A striking effect of retinoids is their ability to alter cell fate during development. The mucous metaplasia produced by treating chick embryo skin in organ culture with retinoic acid is a classical example of this property. It has been impossible so far to demonstrate that retinoids are able to provoke metaplasia of adult keratinocytes grown in vitro, although these agents have been shown to block terminal epidermal differentiation, to induce increased synthesis of mucopolysaccharides, and to induce the ectopic expression of K19 and K13 keratins. Our previous work showed that adult human epidermal keratinocytes grown on dermal equivalents at the surface of a culture medium containing physiological amounts of retinoids form a normal keratinized epidermis, while when excess retinoic acid is added to the culture medium, keratinization is prevented but stratification is not. Here we show that the distribution of tissue- and differentiation-stage-specific markers in retinoic acid-treated epithelium is similar to that of the oral mucosa. Moreover, when the excess retinoic acid is removed, a new epithelium is formed beneath the "old" one and this epithelium displays an epidermal orthokeratinized phenotype, whereas the "old" epithelium remains unchanged. This phenomenon of "partial reversibility", as well as the mutually exclusive distribution of the markers of the two alternative routes of differentiation, demonstrate that retinoic acid is indeed able to provoke metaplasia of adult epidermal keratinocytes.

Two-year inhalation exposure of female and male B6C3F1 mice and F344 rats to chlorine gas induces lesions confined to the nose

Chlorine gas is a respiratory irritant in both animals and humans that produces concentration-dependent responses ranging from minor irritation to death. Female and male B6C3F1 mice and F344 rats were exposed to chlorine gas for up to 2 years to determine chronic toxicity and carcinogenicity. Groups of approximately 70 each of female and male mice and rats were exposed to 0, 0.4, 1.0, or 2.5 ppm chlorine gas for 6 hr/day, 5 days/week (mice and male rats), or 3 alternate days/week (female rats) for 2 years, with an interim necropsy of rats at 12 months (10 rats/sex/concentration group). A complete necropsy was performed on all animals. Histological examination was performed on all organs from high-concentration and control animals and selected target organs from mid- and low-concentration groups. Exposure-dependent lesions were confined to the nasal passages in all sex and species groups. Chlorine-induced lesions, which were most severe in the anterior nasal cavity, included respiratory and olfactory epithelial degeneration, septal fenestration, mucosal inflammation, respiratory epithelial hyperplasia, squamous metaplasia and goblet cell hypertrophy and hyperplasia, and secretory metaplasia of the transitional epithelium of the lateral meatus. Intracellular accumulation of eosinophilic proteinaceous material was also a prominent response involving the respiratory, transitional, and olfactory epithelia, and in some cases the squamous epithelium of the nasal vestibule. Many of these nasal lesions exhibited an increase in incidence and/or severity that was related to chlorine exposure concentration and were statistically significantly increased at all chlorine concentrations studied. Male mice and female rats appeared more sensitive to chlorine than female mice and male rats, respectively. The reasons for the sex differences within a species were not determined. Interspecies differences in regional dosimetry and site-specific tissue susceptibility to chlorine exposure should be taken into account when using these data for accurate assessment of potential human health risks. The incidence of neoplasia was not increased by exposure, indicating that inhaled chlorine in rats and mice is an upper respiratory tract toxicant but not a carcinogen.

Temporal and spatial factors in diethylstilbestrol-induced squamous metaplasia in the developing human prostate. II. Persistent changes after removal of diethylstilbestrol

To determine if the metaplastic effects of diethylstilbestrol (DES) on prostatic development are reversible, human fetal prostates (obtained from abortus specimens 6-22 weeks old) were bisected mid-sagittally; one half was grafted under the renal capsule of untreated, athymic, male nude mice and the contralateral half was similarly grafted into DES-treated hosts. Severe squamous metaplasia seen in the prostatic ducts after 1 month of continuous DES exposure either disappeared entirely or became reduced in extent and degree after retransplantation of the DES-treated specimens to untreated, intact male hosts and 2 additional months of growth. However, 14 of 21 DES-treated prostates harvested after a 2-month recovery period without DES revealed ductal dilatation (ectasia) and persistent distortion of ductal architecture. Ectasia was most severe in the proximal ducts near the urethra and in prostates 17 weeks or older at the end of 1 month of DES treatment. The clinical consequences of early alteration of prostatic ductal architecture and development are potentially deleterious, as men who were prenatally exposed to DES may be at increased risk for the development of prostatic disease.

Carcinogens show comedogenic activity: a potential animal screen for tumorigenic substances

Formation of a comedo, an impaction of horny cells in sebaceous follicles, entails a metaplastic change in the differentiation patterns of the follicular epithelium. Since metaplasia is a requisite early stage in carcinogenesis, we postulated that carcinogens might be comedogenic. The rabbit ear was used to assay the comedogenic potentialities of an array of known tumorigens. Complete carcinogens and some tumor promotors were invariably strongly comedogenic at concentrations of 1.0% and below. Comedogenic chemicals commonly found in skin care products usually required concentrations of 40% and greater to induce comedones which were small in comparison to carcinogen induced comedones. We suggest that the rabbit ear model might be an easy and reliable way to screen for carcinogenicity.

DNA-protein cross-links and cell replication at specific sites in the nose of F344 rats exposed subchronically to formaldehyde

Chronic exposures to high concentrations (> or = 6 ppm) of formaldehyde (HCHO) induce cell proliferation, squamous metaplasia, and squamous cell carcinomas in F344 rats. To assess the cancer risk associated with HCHO exposure, DNA-protein cross-links (DPX) formed in a single exposure of naive (previously unexposed) rats and monkeys have been used as a surrogate for the internal dose. Since the quantity of DPX may differ in subchronically exposed animals, the effects of preexposure to HCHO on the acute DPX yield (concentration of DPX following a single exposure) and the cumulative DPX yield (concentration of DPX following repeated exposures) were determined. Male F344 rats were preexposed (PE) to 0.7, 2, 6, or 15 ppm of HCHO (6 hr/day, 5 days/week, 11 weeks + 4 days). Naive (N) rats were exposed to room air. On the 5th day of the 12th week, PE and N rats were simultaneously exposed (3 hr) to H14CHO at the same concentrations used for preexposure. Acute DPX yields and cell replication (incorporation of 14C into DNA) were determined in the mucosal lining of the nasal lateral meatus (LM) (high tumor site in HCHO bioassay) and the medial and posterior meatuses (M:PM) (low tumor site in bioassay). DPX yields in the LM were approximately sixfold higher than in the M:PM. At 0.7 and 2 ppm, no differences between PE and N rats were detected in either tissue. At 6 and 15 ppm, acute DPX yields in the LM of PE rats were approximately half those of N rats, but no differences were detected in the M:PM. Cell proliferation was induced in PE rats at 6 ppm (LM only) and especially at 15 ppm (LM and M:PM). Cumulative DPX yields were measured indirectly by determining the decrease in extractability of DNA from proteins. PE rats were preexposed to 6 or 10 ppm as above, while N rats were exposed to room air. Both groups (PE and N) were then exposed (3 hr) to the same concentration of unlabeled HCHO. DPX yields increased in a concentration-dependent manner in both groups, but the yields were smaller in PE than N rats, suggesting that no accumulation of DPX occurred in PE rats. The results demonstrate that at concentrations < or = 2 ppm, N and PE rats are equivalent with respect to the formation of DPX.(ABSTRACT TRUNCATED AT 400 WORDS)

Consequences of prolonged inhalation of ozone on F344/N rats: collaborative studies. Part VII: Effects on the nasal mucociliary apparatus

Besides the centriacinar region of the lung, the nose is a principal target for ozone toxicity. Acute exposures to concentrations of ozone in ambient air induce secretory cell metaplasia in the nasal transitional epithelium of rats. This study examined the effects of chronic ozone exposure on the structure and function of the nasal mucociliary apparatus of the rat. Male and female F344/N rats were exposed to ozone concentrations of 0.0 (controls), 0.12, 0.5, or 1.0 parts per million (ppm), six hours per day, five days per week, for 20 months. All rats were killed seven or eight days after the end of the exposure. Immediately after death, mucous flow rates throughout the nasal passages were determined using in vitro video motion analysis. Following assessment of mucociliary function, the nasal tissues were processed for light microscopy and stained with Alcian blue (pH 2.5)/periodic acid-Schiff to detect intraepithelial mucus. Image analysis was used to quantitate the amount of mucus within the nasal transitional epithelium. In rats exposed to 0.5 or 1.0 ppm ozone, mucous flow rates were markedly slower over the lateral wall and turbinates of the proximal third of the nasal airways than they were in rats exposed to 0.0 or 0.12 ppm ozone. These intranasal regions in the rats exposed to 0.5 or 1.0 ppm ozone contained marked mucous cell metaplasia and 25 to 300 times more mucus in nasal transitional epithelium than was found in control rats. In addition, male and female rats exposed to 0.5 or 1.0 ppm ozone had marked epithelial hyperplasia in nasal transitional epithelium, increases in eosinophilic globules in the surface epithelium lining the distal nasal airways, and a mild to moderate inflammatory cell influx in the nasal mucosa in the proximal and middle nasal passages. Male rats also had conspicuous bony atrophy in maxilloturbinates and nasoturbinates. There were no significant decreases between the mucous flow rates of rats exposed to 0.12 ppm ozone and those of control rats. There were, however, mild increases in various flow rates in some areas of the nasal airways in rats exposed to 0.12 ppm ozone compared with control rats. No significant morphologic alterations were evident in the rats exposed to 0.0 or 0.12 ppm ozone. The results of this study indicate that rats chronically exposed to 0.5 or 1.0 ppm ozone have significant alterations in the function and structure of the nasal mucociliary apparatus. Though there was a mild increase in mucous flow rates in a few nasal regions of some rats exposed to 0.12 ppm ozone, this functional change was interpreted as a physiologic, rather than a pathologic, response to ozone at this relatively low concentration.

Effect of S-carboxymethylcysteine lysine salt on mucociliary clearance in rabbits with secretory cell metaplasia

A single intratracheal instillation of porcine pancreatic elastase (PPE, 100 U/Kg) induces in rabbits bronchial secretory cell metaplasia as well as emphysematous changes. The mucus hypersecretion and the marked reduction of ciliated cells matched by a high percentage of atypical cilia are responsible for the delayed mucociliary clearance in this model. S-Carboxymethylcysteine lysine salt (SCMC-LYS, 0.35 g/Kg b.w.), given per os daily for 10 days starting 2 days before elastase administration, significantly ameliorated the mucociliary clearance. The pharmacological treatment did not modify the degree of secretory cell metaplasia and the percentage of atypical cilia, or prevent the alveolar wall destruction. At TEM examination, the morphological aspects of secretion occurring in bronchial tree of PPE-treated animals were rarely visible in the PPE + SCMC-LYS treated group. The beneficial effect of SCMC-LYS on mucociliary clearance may be ascribed to an antisecretagogue effect of this drug through elastase inhibition and to a reduction of mucus viscosity.

Dissimilar frequency of hepatoblastomas and hepatic cystadenomas and adenocarcinomas arising in hepatocellular neoplasms of D2B6F1 mice initiated with N-nitrosodiethylamine and subsequently given Aroclor-1254, dichlorodiphenyltrichloroethane, or phenobarbital

Aroclor-1254 (Ar-1254) and dichlorodiphenyltrichloroethane (DDT) were compared to phenobarbital (PB) for their ability to promote hepatocellular proliferative lesions to hepatocellular adenomas and carcinomas and to hepatoblastomas in D2B6F1 male mice initiated with N-nitrosodiethylamine (NDEA). Hepatocellular neoplasms developed in all mice given NDEA and were more numerous in mice fed promoters. Multiplicities decreased in the order Ar-1254 > PB > DDT, indicating that Ar-1254 was more potent than either PB or DDT at the dosage levels used. PB was the most effective of the 3 agents in stimulating the evolution of hepatocellular neoplasms to hepatoblastoma. The incidence of hepatoblastomas in the NDEA.PB group was 72% but was only 27% in NDEA-initiated, DDT-promoted mice and 33% in low-dose and only 9% in high-dose Ar-1254-promoted mice. In contrast, lesions resembling benign and malignant cholangiocellular neoplasms were frequently found within hepatocellular tumors in Ar-1254-promoted mice but not in mice fed PB or DDT, either alone or after NDEA. Some cystic glandular structures in Ar-1254-promoted mice contained mucous cells, argentaffin cells, and Paneth cells and thus constituted intestinal metaplasia. Hepatoblastoma and intestinal metaplasia/cholangiocellular tumor morphology appear to constitute different patterns of genetic programming induced by certain promoters in expanding clones of initiated hepatocytes, on favorable genetic backgrounds such as that of D2B6F1 male mice.

High survival rate of hamsters given intratracheal instillations of benzo[a]pyrene and ferric oxide and kept on a high beta-carotene diet

The study described in this paper was primarily conducted to identify the cell types involved in the formation, progression and regression of metaplastic changes in the respiratory tract epithelium of hamsters after intratracheal intubations with benzo[a]pyrene. Furthermore, the role of vitamin A and beta-carotene in these processes was studied. In the course of the study a remarkable effect of dietary beta-carotene on survival of hamsters became a subject of investigation. Hamsters were fed diets with various levels of vitamin A or beta-carotene and were treated intratracheally with a suspension of benzo[a]pyrene with ferric oxide in saline. The tumour response of the respiratory tract was very low (2.8%) and hyper- and metaplasia of respiratory epithelium were virtually absent. However, an interesting observation was an exceptionally low mortality of only 2% after 69 weeks in the group of hamsters fed a high beta-carotene diet (1% w/w), whereas in the other groups mortality after 69 weeks amounted to 25%. Although the exact cause of death of most of the hamsters could not be established, a 40% reduction of lipid peroxidation in the livers was found in the high beta-carotene group. Moreover, in this group the degree and incidence of nephrosis and of focal mineralization of kidneys and heart were lower than in the other groups. These favourable effects of the high beta-carotene diet may have contributed to the unusually high survival rate in hamsters fed this diet. Further studies are planned to verify and study this observation.

Influence of gastric pH modifiers on development of intestinal metaplasia induced by X-irradiation in rats

The influence of gastric pH on intestinal metaplasia was examined in male Crj:CD(SD) rats. At the age of 5 weeks, animals were irradiated with two 10 Gy doses of X-rays to the gastric region at a 3-day interval (total 20 Gy), and 6 months after irradiation, received either secretin or histamine in silicon tubes for 2 months or had their bilateral submandibular salivary glands removed. The incidence of intestinal metaplasia in the fundus of animals after administration of secretin or histamine, or removal of the salivary glands were reduced, along with the pH values, as compared with values for rats given X-rays alone. In both the pyloric and the fundic gland mucosae, the numbers of alkaline phosphatase (ALP)-positive foci and type B metaplasias (intestinal crypts without Paneth cells) were also significantly decreased (P < 0.01). In a second experiment, started six months after irradiation, rats were kept on 1% sodium chloride (NaCl) diet for 6 months. Subsequent removal of salivary glands along with histamine treatment brought about a marked drop in pH and in numbers of ALP-positive foci after three and five days. The present results thus indicated that development and maintenance of intestinal metaplasia can be influenced by a decrease of pH value.

Effect of mineral particles containing iron on primary cultures of rabbit tracheal epithelial cells: possible implication of oxidative stress

Environmental mineral particles such as asbestos are responsible for numerous respiratory diseases. In addition to effects related to their geometry, particles are now assumed to act by triggering an oxidative stress process. Iron-containing particles, in particular, can produce oxygen-activated species by oxidizing their iron. To evaluate the involvement of iron-containing particles in respiratory diseases, three mineral particles (chrysotile, nemalite, and hematite) were tested in primary cultures of tracheal epithelium. Because of the ciliary beat, the three mineral particles were quickly concentrated at the periphery of the mucociliary epithelium, reconstituted in vitro where they induced cellular lesions. Endocytosis of the three types of particles was observed. Cytotoxicity studies have indicated that among the tested particles, the most cytostatic after 24 hr of treatment was the one that contained more Fe2+ available on the surface, nemalite. Moreover, the effect of nemalite was reduced by pretreatment with desferrioxamine. As mineral particles, especially asbestos, are suspected to induce squamous metaplasia, we chose to study two specific transformations of the epithelium: the expression of cytokeratin-13 and the formation of cross-linked envelopes. Under our culture conditions, nemalite and chrysotile increased the expression of the cytokeratin-13, a specific marker of squamous metaplasia, whereas nemalite was the only particle able to strongly induce the formation of cross-linked envelopes. Nemalite was the most cytostatic particle and the most efficient at inducing squamous metaplasia. Measures of oxidizing power by electron-spin resonance revealed that nemalite produced the most oxygen-activated species.(ABSTRACT TRUNCATED AT 250 WORDS)

Ozone- and endotoxin-induced mucous cell metaplasias in rat airway epithelium: novel animal models to study toxicant-induced epithelial transformation in airways

Mucous (goblet) cell proliferation and hypersecretion of airway mucus are important characteristics of human respiratory disorders, especially chronic bronchitis and cystic fibrosis. These changes in secretory patterns also occur in animals experimentally exposed to chemical irritants such as ozone (O3), sulfur dioxide (SO2), and cigarette smoke. The cellular and molecular mechanisms involved in irritant-induced mucous cell metaplasia (MCM; transformation of airway epithelium, normally devoid of mucous cells, to a secretory epithelium containing numerous mucous cells) are still unclear. We used two experimental models of toxicant-induced MCM in rat airways to study the cellular and molecular changes that occur during the development of this respiratory tract lesion. MCM can be induced in the nasal transitional epithelium of rats by repeated exposure to ambient levels of ozone. In addition, MCM can be induced in the tracheobronchial airways of rats repeatedly exposed to endotoxin, a lipopolysaccharide-protein molecule found in the outer walls of Gram-negative bacteria. The pathogenesis of ozone- or endotoxin-induced MCM has been partially characterized using a variety of morphometric and histochemical techniques. Toxicant-induced changes in the numbers and types of airway epithelial cells have been estimated using morphometric methods designed for estimating the abundance of cell populations. Nasal pulmonary airway tissues are also processed for light microscopy and stained with Alcian Blue (pH 2.5)/Periodic Acid Schiff (AB/PAS) for detection of acidic and neutral mucosubstances (the specific glycoprotein product of mucous cells), respectively, within the tissue. Computerized image analysis is used to quantitate the amount of the stained mucous product within the airway epithelium. To better characterize the molecular and cellular events in the pathogenesis of ozone- or endotoxin-induced MCM in the rat airway epithelium, we are conducting studies to determine when, and in which epithelial cells, the mucin gene is expressed after exposure to the toxicant. In these studies, rats undergo single or repeated exposures to ozone or endotoxin and are then sacrificed immediately or a few days after the end of the exposures. Airway tissues are microdissected from specific regions of the exposed respiratory tract, and changes in mucin core polypeptide mRNA are evaluated by Northern analysis using human and rat mucin cDNA. In future studies using in situ hybridization, we will establish when, and in which epithelial cells, the expression of high molecular weight airway mucin is initiated in response to ozone or endotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Morphology and histogenesis of squamous cell metaplasia of the rat lung after chronic exposure to a pyrolized pitch condensate and/or carbon black, or to combinations of pyrolized pitch condensate, carbon black and irritant gases

Female Wistar rats were exposed to different concentrations of a pyrolized pitch condensate and/or carbon black particles and/or a combination of irritant gases for 18 hours/day, 5 days/week for 10 months, followed by a clean air period of up to 20 months. Bronchiolo-alveolar hyperplasia and squamous metaplasia were important components of the resulting lesions. Squamous metaplasia and associated hyperplasia was investigated by routine histology, scanning and transmission electron microscopy, and by immunohistochemical detection of various cytokeratins (CKs). Intensely CK positive squamous metaplasia lacking a distinct stratum spinosum was distinguishable from squamous metaplasia with a distinct stratum spinosum that reacted weakly CK positive or CK negative. The CK positive type was histologically characterized by narrow intercellular spaces, the weakly CK positive or CK negative type had markedly enlarged intercellular spaces. Differentiated hyperplastic epithelium and the normal lung parenchyma reacted CK negative. In poorly differentiated hyperplasia of the alveolar type associated with squamous metaplasia scattered cells with characteristics of squamous differentiation were detected. Ultrastructurally these cells showed increased amounts of filament bundles and immunohistochemically a positive reaction with the CK antibody. These cells were regarded as precursor stages of squamous metaplasia of the lung periphery in rats.

Effects of nitroso compounds and aromatic amines on fetal tracheal explants

Tracheas were excised from fetal Syrian golden hamsters on the 15th day of gestation. Tracheal explants were cultured in vitro and exposed to different dose-levels of well known carcinogens. We chose two nitroso compounds, N-Methyl-N-nitro-N-nitrosoguanidine (MNNG) and Diethylnitrosamine (DEN) and two aromatic amines, Aminofluorene (AF) and Acetylaminofluorene (AAF). The tracheal explants were treated for 24 h in vitro, then the carcinogens were washed off and the tracheas were kept for 21, 28 or 35 days in culture. After fixation tracheal explants were transversely cut with serial section techniques and scored for morphological changes of the epithelium by light microscopy. Most of the control explants completed differentiation and had a normal morphology at the end of the in vitro culture period. Occasionally we found a decrease of the number of ciliated cells and some areas with squamous metaplasia in the respiratory epithelium. Carcinogen treatment with nitroso compounds led to a significant increase of the morphologic changes of the epithelium. These effects were especially obvious after DEN treatment. Morphologic changes of the epithelium such as metaplasia and hyperplasia were discussed as carcinogen-related events. In vitro exposure with aromatic amines did not induce marked metaplastic or hyperplastic changes in the respiratory epithelium of tracheal explants.

Experimental study of the therapeutic effects of folate, vitamin A, and vitamin B12 on squamous metaplasia of the bronchial epithelium

BACKGROUND

Vitamin deficiency may be related to carcinogenesis. Cytologic examinations of sputum have already found that the administration of folate and vitamin B12 suppressed the development of squamous metaplasia and atypia in smokers' airways. The authors investigated the effect of folic acid, vitamin B12, and vitamin A on the formation of metaplasia and hyperplasia in methylcholanthrene (MCA)-treated rats.

METHODS

The SD strain of rats received 10 mg of MCA intratracheally and was divided into six groups as follows: (1) vitamin A; (2) folic acid; (3) vitamin B12; (4) vitamin B12 with folic acid; (5) a combination of vitamin A, folic acid, and vitamin B12; and (6) no vitamins. The Lower respiratory tract epithelia of the rats were examined histologically 20, 32, and 36 weeks after MCA administration and at the end of the experiment.

RESULTS

A clear difference was detected between the group receiving folic acid and that receiving vitamin A. In the former group, metaplasia was found in only one rat, atypia was not found, and hyperplasia with marked changes was present in less than 50% of other groups. In the latter group, atypia was found in all of the metaplastic foci.

CONCLUSIONS

It was suggested that the epithelial hyperplasia and metaplasia of respiratory tract induced by MCA can be suppressed by the administration of folic acid.

Elastase causes secretory discharge in bronchi of hamsters with elastase-induced secretory cell metaplasia

A single intratracheal instillation of human neutrophil elastase (HNE) into hamsters causes granule discharge from bronchial secretory cells followed by marked accumulation of granules, visible by light microscopy at 21 days and persisting through 18 months. To determine whether persistence of this secretory cell metaplasia (SCM) is due to inability of the metaplastic secretory cells to secrete their granules, hamsters having HNE-induced SCM were challenged with the potent secretagogue HNE. Four groups of 10 hamsters each received 300 micrograms HNE intratracheally. Twenty-one days later, hamsters were intratracheally treated with HNE or saline; the groups were designated HNE-HNE and HNE-SAL, respectively. Hamsters were killed 2 h or 21 days following the second treatment. Using light microscopy, nucleated epithelial cells were counted in plastic sections of the left main intrapulmonary bronchus. Cells were classified as ciliated (C), basal (B), indeterminate (IN), or secretory. Secretory cells were subcategorized as S0 (0 granules), S1 (1-4 granules), S2 (> or = 5 granules with intervening cytoplasm), and S3 (abundant granules completely filling the cytoplasm). At 2 h, S3 cell frequency in the HNE-HNE group was 13.0 +/- 2.2 (% mean +/- SE), significantly lower than in the 2 h HNE-SAL group (31.1 +/- 4.5). Concomitantly, higher cell frequencies were seen in the other secretory categories of the HNE-HNE group compared to the HNE-SAL group; S2 17.1 +/- 1.9 compared to 9.4 +/- 1.9, S1 2.4 +/- 0.4 compared to 1.1 +/- 0.5, and S0 2.4 +/- 0.5 compared to 1.1 +/- 0.5, respectively. The S3 cell frequency of the 21-day HNE-HNE group was 25.4 +/- 4.7, increased significantly compared to the 2 h HNE-HNE group; this change was concomitant with significant decrease in the frequency of the S0 secretory cells. Cell frequencies of C, B, and IN were not affected by treatment or time. It is concluded that metaplastic secretory cells discharge their granules in response to HNE; SCM returns to its original state after HNE rechallenge; persistent SCM is not due to the inability of metaplastic secretory cells to discharge their granules.

[Benzo(a)pyrene induces planocellular metaplasia of the respiratory epithelium in explants of embryonic mouse lung]

The direct effect of benz(a)pyrene (BP) induces squamous epithelial metaplasia (SEM) in organ cultures from embryonic lungs of C57BL and A. The incidence of SEM depend on the doses of BP (3-6-12 mkg/ml), duration of treatment and on the mice line.

Morphology of nasal lesions induced in Osborne-Mendel rats and B6C3F1 mice by chronic inhalation of allyl glycidyl ether

Chronic (24-month) inhalation exposure to 5 or 10 ppm allyl glycidyl ether (AGE) induced nasal lesions in Osborne-Mendel rats and B6C3F1 mice. Inflammation, degeneration, regeneration, metaplasia, hyperplasia, and neoplasia were observed in the nasal mucosa. Squamous metaplasia and hyperplasia of the respiratory epithelium and degeneration and regeneration with subsequent squamous and/or respiratory metaplasia of the olfactory epithelium were observed in many AGE-exposed animals. Three primary nasal neoplasms (1 papillary adenoma, 1 squamous cell carcinoma, and 1 olfactory epithelial carcinoma) were observed in rats exposed to 10 ppm AGE, and 1 nasal papillary adenoma was observed in a rat exposed to 5 ppm. Four papillary adenomas and 2 hemangiomas were observed in the noses of mice exposed to 10 ppm AGE. Although the incidence of primary nasal tumors in AGE-exposed rats or mice was not statistically significant compared to the incidence in concurrent controls, the relative rarity of primary nasal tumors in historical controls and the concurrent presence of metaplastic and hyperplastic nasal lesions similar to those reported to be associated with induced tumors of nasal epithelia by other chemicals suggest that the nasal tumors observed may be related to AGE exposure. It was concluded that, in addition to lesions indicating a toxic effect on the nasal mucosa, inhalation exposure to AGE for 24 months resulted in some evidence of carcinogenicity of AGE for male mice, equivocal evidence of carcinogenicity for female mice and male rats, and no evidence of carcinogenicity for female rats.

Squamous metaplasia in the penile urethra due to oestrogen therapy

Histological examination was performed on the anterior penile urethra from 21 asymptomatic trans-sexual patients taking oestrogens prior to surgery. Squamous metaplasia was present in 15 of these patients and in 1 man taking progesterones. Immunohistochemical staining for oestrogen receptors in the urethra was negative. Severe squamous metaplasia was associated with patchy chronic inflammatory cell infiltration but this was also present in normal controls. The lack of recognised complications of squamous metaplasia at this site suggests that it is an incidental observation in men taking oestrogens.

[A nephrogenic adenoma during treatment with intravesical BCG]

Two patients who had undergone resection of a transitional cell bladder tumor presented with nephrogenic adenoma of the bladder during treatment with BCG. Nephrogenic adenoma presenting in the course of intravesical chemotherapy has been previously reported in 5 cases and can mimic tumor recurrence. Thus, we consider the present case to be of special interest.

Phenotypic characterization of metaplastic intestinal glands and ductular hepatocytes in cholangiofibrotic lesions rapidly induced in the caudate liver lobe of rats treated with furan

In order to investigate the early cellular changes in liver associated with furan cholangiocarcinogenesis, young adult male Fischer 344 rats were administered furan by gavage once a day, 5 days a wk for 2 to 3 wk at doses ranging from 15 to 60 mg/kg of body weight per day. The most conspicuous feature observed in the liver of animals receiving the higher doses of furan was a rapidly developed cholangiofibrosis characterized by the presence of bile ductular hyperplasia, intestinal metaplasia, and fibrosis. Moreover, this lesion was found to be almost exclusively localized to the caudate liver lobe, which by morphometric analysis was further determined to be largely replaced by cholangiofibrotic tissue. Both the hyperplastic bile ductular epithelial cells and the intestinal-like epithelial cells in these areas selectively exhibited a strongly positive immunohistochemical staining for cytokeratin 19 and were supported by well-developed basement membranes enriched in both laminin and type IV collagen. However, in contrast to the hyperplastic bile ductules, electron microscopy of the metaplastic intestinal glands revealed them to be composed mostly of columnar epithelial cells with well-developed striated borders, less numerous mucin-secreting goblet cells, and occasional neuroendocrine-like cells, thus closely resembling in their cellular composition that of intestinal mucosa. These metaplastic glands also showed a more heterogeneous pattern of staining for both gamma-glutamyl transpeptidase and the placental form of glutathione S-transferase than did the hyperplastic bile ductules. At the 60-mg/kg/day furan dose, cholangiolar-like structures composed of biliary epithelial cells and ductular hepatocytic cells at different stages of morphological differentiation were also observed. Phenotypically, the biliary epithelial and "ductular hepatocytes" of these cholangioles shared a common basement membrane containing laminin and type IV collagen, as well as a luminal plasma membrane gamma-glutamyl transpeptidase. On the other hand, only the biliary epithelial cells of the newly appearing mixed cell cholangioles stained positive for cytokeratin 19. Interestingly, unlike hepatocarcinogen-induced oval cells, alpha-fetoprotein expression was not detected in any of the cell types comprising the furan-induced cholangiofibrotic tissue. These results support a novel in vivo model for investigating cell lineages in the development in liver of intestinal metaplasia, "ductular hepatocytes," and cholangiofibrosis in relation to intrahepatic cholangiocarcinogenesis.

Cell-specific alterations in glycoconjugates in the development of squamous metaplasia induced by benzo[a]pyrene in hamster tracheal explants

Squamous metaplasia of tracheal mucosa, putative preneoplastic lesions, involves replacement of normal mucociliary epithelium with epidermoid lesions. Alterations in cell differentiation and neoplasia accompany changes in glycoconjugates at the plasma membrane. Lectins which bind to specific cell surface glycoconjugates are used to elucidate such alterations. We have used peanut agglutinin (PNA) and concanavalin A (Con A) as specific molecular probes to elucidate cell specific alterations in the development and progression of squamous metaplasia in the hamster tracheal explants induced by benzo[a]pyrene (BP), a component of cigarette smoke. The tracheal explants were cultured in serum-free chemically defined medium and treated with BP (7.5 micrograms/ml) for up to 15 days. At this time, 80-90% of the carcinogen treated explants exhibited epidermoid lesions at various stages of development. The untreated control explants maintained normal pseudostratified epithelium. In these explants, PNA and Con A exhibited moderate reaction in the cytoplasm of luminal mucociliary cells; the basal cells showed no reaction. In early metaplastic lesions PNA and Con A stained only the cytoplasm of luminal cells; the metaplastic cells along the basal lamina were negative. In well-developed lesions, in which the luminal mucociliary layer was still intact overlying the lesions, the metaplastic epithelium remained unreactive with the lectins. In highly advanced lesions exhibiting cornification, and in which the mucociliary layer was sloughed, the metaplastic lesions showed strong reaction with both the lectins. The reaction was limited mainly to the plasma membrane of the metaplastic cells. These results show that induction and progression of the BP induced lesions accompany dynamic cell specific alterations in glycoconjugates. The epidermoid lesions acquire glycoconjugates rich in beta-D-galactose and D-mannose. These results are also consistent with the basal cell origin of the metaplastic lesions.

Histologic characterization of mouse bronchiolar cell hyperplasia, metaplasia, and neoplasia induced intratracheally by 3-methylcholanthrene

Female B6C3F1 mice were treated intratracheally with 3-methylcholanthrene (MCA) at intervals of once every 2 weeks for a total of six doses each of 222 micrograms or 457 micrograms/mouse per dose. Animals were necropsied when found dead, moribund, or at the end of the study 43 weeks after the first treatment. Controls were treated with the vehicle (0.2% gelatin saline) only. Lungs were fixed in neutral buffered formalin and processed for light microscopic evaluation. Proliferative and metaplastic bronchiolar cell alterations were seen both within bronchioles and in the alveolar parenchyma. In both locations, changes included hyperplasia of nonciliated cells, squamous cell metaplasia, presence of ciliated cells, and mucous cell metaplasia. Mucous cells were either positive for alcian blue or the periodic-acid Schiff's reaction (PAS), or appeared eosinophilic with hematoxylin and eosin (H&E) but colorless with PAS. Tumors seemed to develop from both extra- and intrabronchiolar areas of cellular proliferation and invaded pulmonary structures. The majority were squamous cell carcinomas and adenosquamous carcinomas, accompanied by a few mucinous cell tumors and some rare tumors that were largely composed of ciliated cells. Combinations of the different metaplastic changes were frequently present in these neoplasms. In summary, it appears that tumors originating from bronchiolar cells in mice show the same morphologic variability that is observed in hyperplastic and metaplastic bronchiolar cells within airways.