A case of papillary adenoma of type 2 pneumocytes is reported. A 57-year-old man had an unusual c... more A case of papillary adenoma of type 2 pneumocytes is reported. A 57-year-old man had an unusual coin lesion in the periphery of the right lung without any symptoms. When detected in a mass survey examination, it was approximately 1.5 cm in diameter, well circumscribed, and located in S4, involving the sixth-order bronchus of B4. Light-microscopic examination revealed cuboidal tumor cells arranged in a papillary pattern. Ultrastructurally, the cells had characteristic osmiophilic lamellar bodies. By immunoperoxidase staining, the tumor cells were shown to have intracytoplasmic surfactant apoproteins. The postoperative course was uneventful, and there is no evidence of disease 8 years later.
An antibody to a protein produced by Clara cells in adult Syrian golden hamsters has been used to... more An antibody to a protein produced by Clara cells in adult Syrian golden hamsters has been used to monitor the development and functional differentiation of secretory cells in the conducting airway epithelium of this species. Lungs from fetal and neonatal hamsters at gestational day 11 and at intervals up to and including 3.5 weeks of age (as well as adults) were studied. The earliest time this Clara cell protein could be identified by immunoperoxidase labeling in the fetal conducting airways was at gestational day 15. On this day, labeling was observed in a few secretory cells lining the trachea, in many lining the lobar bronchi, and in virtually all secretory cells lining the bronchioles. Ciliated cells and endocrine cells were not labeled. Granules first appeared within the apical cytoplasm of the secretory cells on gestational day 15 at all airway levels. To identify the exact subcellular location of this protein, an ultrastructural labeling procedure using protein A gold was employed. The gold particles labeled only electron-dense granules within the secretory cells, indicating that they represent the specific site of this protein. Since secretory cells in the most distal conducting airways began to produce this protein on the same day in development as cells in the larger airways, including the trachea, this expression of functional maturation occurs simultaneously throughout the conducting respiratory tree rather than proceeding sequentially in a cranial to caudal direction. Consequently, secretory cells lining the smaller conducting airways mature more rapidly than those lining the larger airways.
We have reported that dexamethasone (DEX) treatment of early embryonic rat lungs in culture induc... more We have reported that dexamethasone (DEX) treatment of early embryonic rat lungs in culture induced features of both distorted and accelerated maturation. In this report, we investigated the effects of retinoids on normal and DEX-induced lung development in vitro. Lung maturation was assessed by examining the morphology and the expression of genes related to epithelial differentiation (surfactant proteins, SP-A, SP-B and SP-C and Clara cell protein, CC10) and growth [keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF)]. We cultured d 14 and 15 fetal rat lungs in the presence of DEX (1-1000 nM) and/or all-trans-retinoic acid (RA) (10(-7)-10(-5) M) for 4 d. RA at 10(-6) and 10(-5) M inhibited branching and dilated the distal tubules, and at 10(-5) M caused dilatation of the proximal tubules destined to form the trachea and the main bronchi. The adverse effects of DEX, such as distorted branching, tubular dilatation, and suppression of both lung growth and epithelial cell proliferation, were all prevented by RA. In addition, RA inhibited several features of DEX-induced accelerated maturation, such as: 1) the increased levels of SP-A, SP-B, and CC10 mRNAs; 2) the attenuation of mesenchymal tissue; and 3) the mature distribution of cells expressing SP-C mRNA. In contrast, RA potentiated the increase of KGF and decrease of HGF transcripts induced by DEX. In conclusion, the study shows antagonism by RA of DEX-induced effects on lung morphology and gene expression. We postulate that normal lung development requires a balanced action of endogenous retinoids and glucocorticoids.
In this study, we examined the effects of dexamethasone (DEX) on airway branching and subsequent ... more In this study, we examined the effects of dexamethasone (DEX) on airway branching and subsequent lung maturation. DEX treatment of fetal rat lung explants was initiated during the early pseudoglandular stage of development. Day 14 fetal lung explants were cultured with and without DEX for 4 d. Explants treated with 10 nM or higher concentrations of DEX showed features of both distorted and accelerated maturation. DEX-treated lungs had growth retardation, distorted branching, dilated proximal tubules, and suppressed proliferation of epithelial cells of the distal tubules. Several biochemical and morphologic features of accelerated maturation were also observed: 1) the epithelial cells lining the distal tubules (prospective respiratory airways) were generally cuboidal or flattened; 2) the cuboidal cells often contained lamellar bodies and abundant glycogen; 3) rudimentary septa and large airspace were present; 4) mesenchymal tissue was attenuated and compressed between adjacent epithelial tubules; 5) the distribution of SP-C mRNA in distal tubules was more mature, with individual and clusters of cells expressing SP-C transcripts; and 6) the transcript levels of several genes related to epithelial growth [keratinocyte growth factor (KGF), KGF receptor, and hepatocyte growth factor receptor] and differentiation [surfactant proteins, SP-A, SP-B and SP-C and the Clara cell secretory protein, CC10] were precociously increased. These results show that DEX treatment of the lung during the early pseudoglandular stage accelerates the acquisition of several features of advanced maturation that normally accompany late stages of fetal development. We postulate that KGF mediates at least some effects of DEX on lung maturation and gene expression.
Abstract: Clara cells are nonciliated, nonmucous, secretory cells of the pulmonary airways. These... more Abstract: Clara cells are nonciliated, nonmucous, secretory cells of the pulmonary airways. These cells are known to secrete a variety of proteins, including Clara cell 10-kDa protein/uteroglobin. This protein consists of a homodimer of 70–77 amino acid polypeptides arranged in antiparallel fashion. In vitro testing suggests that the protein suppresses inflammation. The physiologic role of the protein remains to be determined.
A protein similar to the rat Clara cell 10-kDa protein (CC10) was isolated from mouse lung homoge... more A protein similar to the rat Clara cell 10-kDa protein (CC10) was isolated from mouse lung homogenate by conventional chromatography. cDNA for the mouse CC10 protein was identified in the mouse lung cDNA library by using radiolabeled rat CC10 cDNA as the probe. The isolated cDNA was sequenced and the deduced primary amino acid sequence was compared to the known sequences of rabbit and hare uteroglobins and human and rat CC10 proteins. The cDNA sequence was confirmed by N-terminal amino acid sequencing of the purified protein. The purified mouse CC10 was tested for its ability to bind progesterone, and the binding was found to be 27% lower than rat CC10 and 48% lower than rabbit uteroglobin. The relative binding of mouse, rat, and human CC10 may reflect subtle structural perturbations. The only notable difference between mouse and rat CC10 is in the beta bend between helices 1 and 2, at residue 16. This difference also exists between rat and human CC10. The mouse CC10 sequence compares favorably with human CC10, which does not bind progesterone; however, the mouse CC10 does not contain M60, which has been proposed to block the binding of progesterone with human CC10. The wide variation in progesterone binding among this family of proteins casts doubt on the importance of such binding as a physiologic function.
Rat lung lavage contains a 10 kDa protein that has been shown by immunocytochemistry to be specif... more Rat lung lavage contains a 10 kDa protein that has been shown by immunocytochemistry to be specific for Clara cells. An inhibition enzyme-linked immunosorbent assay was established for this protein using rabbit antibody to the 10 kDa Clara cell protein. The assay has a sensitivity of about 3.0 ng/ml and a working range of about 5 to 50 ng/ml. Quantitation of the 10 kDa protein in amniotic fluid revealed an increase of about 4-fold at day 20 of gestation. The 10 kDa protein content of lung homogenate increased steadily from day 18 of gestation to 1 wk after birth, after which a decline was observed. Nearly 60-fold increase in the concentration of the 10 kDa Clara cell protein in lungs was noted from day 18 of gestation to birth and a further about 7-fold increase was noted from the day of birth to 1 wk of age. A progressive increase in the 10 kDa protein, with increasing age, was also noted on immunoblot analysis of lung homogenates. As judged from the immunoblots of lung homogenates, stained with rabbit antirat 10 kDa protein antiserum, the content of an antigenically similar 200 kDa Clara cell protein was negligible. The quantitative results for 10 kDa Clara cell protein parallel the results of immunocytochemistry and quantitation of the volume density of Clara cell granules indicating that quantitation for the 10 kDa protein could be used to monitor the development of Clara cells and that of the pulmonary airways.
A protein of molecular weight about 10,000 (Clara cell protein C) present in lung lavage fluid an... more A protein of molecular weight about 10,000 (Clara cell protein C) present in lung lavage fluid and specific to Clara cells has been shown to have three isotypes. The isotypes have been individually isolated and purified by a combination of molecular sieving, ion exchange chromatography, column chromatofocusing, and reverse phase chromatography. The protein was monitored by immunoblotting and its purity tested by silver staining of the gel following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. About 33.7% of the 10-kDa protein present in starting rat lavage was recovered in final pure preparation. The 10-kDa Clara cell protein amounted to 0.38% of the total protein in rat lung lavage fluid. The three isotypes were present in a ratio of 1.0:2.8:8.8, the amounts increasing with decreasing pI. None of the isotypes bound to concanavalin A. The amino acid compositions of the three isotypes were similar and were remarkable in that the contents of leucine, glutamic acid, aspartic acid, serine, and proline were high, tyrosine was present in low amounts, and methionine and histidine were absent.
A case of papillary adenoma of type 2 pneumocytes is reported. A 57-year-old man had an unusual c... more A case of papillary adenoma of type 2 pneumocytes is reported. A 57-year-old man had an unusual coin lesion in the periphery of the right lung without any symptoms. When detected in a mass survey examination, it was approximately 1.5 cm in diameter, well circumscribed, and located in S4, involving the sixth-order bronchus of B4. Light-microscopic examination revealed cuboidal tumor cells arranged in a papillary pattern. Ultrastructurally, the cells had characteristic osmiophilic lamellar bodies. By immunoperoxidase staining, the tumor cells were shown to have intracytoplasmic surfactant apoproteins. The postoperative course was uneventful, and there is no evidence of disease 8 years later.
An antibody to a protein produced by Clara cells in adult Syrian golden hamsters has been used to... more An antibody to a protein produced by Clara cells in adult Syrian golden hamsters has been used to monitor the development and functional differentiation of secretory cells in the conducting airway epithelium of this species. Lungs from fetal and neonatal hamsters at gestational day 11 and at intervals up to and including 3.5 weeks of age (as well as adults) were studied. The earliest time this Clara cell protein could be identified by immunoperoxidase labeling in the fetal conducting airways was at gestational day 15. On this day, labeling was observed in a few secretory cells lining the trachea, in many lining the lobar bronchi, and in virtually all secretory cells lining the bronchioles. Ciliated cells and endocrine cells were not labeled. Granules first appeared within the apical cytoplasm of the secretory cells on gestational day 15 at all airway levels. To identify the exact subcellular location of this protein, an ultrastructural labeling procedure using protein A gold was employed. The gold particles labeled only electron-dense granules within the secretory cells, indicating that they represent the specific site of this protein. Since secretory cells in the most distal conducting airways began to produce this protein on the same day in development as cells in the larger airways, including the trachea, this expression of functional maturation occurs simultaneously throughout the conducting respiratory tree rather than proceeding sequentially in a cranial to caudal direction. Consequently, secretory cells lining the smaller conducting airways mature more rapidly than those lining the larger airways.
We have reported that dexamethasone (DEX) treatment of early embryonic rat lungs in culture induc... more We have reported that dexamethasone (DEX) treatment of early embryonic rat lungs in culture induced features of both distorted and accelerated maturation. In this report, we investigated the effects of retinoids on normal and DEX-induced lung development in vitro. Lung maturation was assessed by examining the morphology and the expression of genes related to epithelial differentiation (surfactant proteins, SP-A, SP-B and SP-C and Clara cell protein, CC10) and growth [keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF)]. We cultured d 14 and 15 fetal rat lungs in the presence of DEX (1-1000 nM) and/or all-trans-retinoic acid (RA) (10(-7)-10(-5) M) for 4 d. RA at 10(-6) and 10(-5) M inhibited branching and dilated the distal tubules, and at 10(-5) M caused dilatation of the proximal tubules destined to form the trachea and the main bronchi. The adverse effects of DEX, such as distorted branching, tubular dilatation, and suppression of both lung growth and epithelial cell proliferation, were all prevented by RA. In addition, RA inhibited several features of DEX-induced accelerated maturation, such as: 1) the increased levels of SP-A, SP-B, and CC10 mRNAs; 2) the attenuation of mesenchymal tissue; and 3) the mature distribution of cells expressing SP-C mRNA. In contrast, RA potentiated the increase of KGF and decrease of HGF transcripts induced by DEX. In conclusion, the study shows antagonism by RA of DEX-induced effects on lung morphology and gene expression. We postulate that normal lung development requires a balanced action of endogenous retinoids and glucocorticoids.
In this study, we examined the effects of dexamethasone (DEX) on airway branching and subsequent ... more In this study, we examined the effects of dexamethasone (DEX) on airway branching and subsequent lung maturation. DEX treatment of fetal rat lung explants was initiated during the early pseudoglandular stage of development. Day 14 fetal lung explants were cultured with and without DEX for 4 d. Explants treated with 10 nM or higher concentrations of DEX showed features of both distorted and accelerated maturation. DEX-treated lungs had growth retardation, distorted branching, dilated proximal tubules, and suppressed proliferation of epithelial cells of the distal tubules. Several biochemical and morphologic features of accelerated maturation were also observed: 1) the epithelial cells lining the distal tubules (prospective respiratory airways) were generally cuboidal or flattened; 2) the cuboidal cells often contained lamellar bodies and abundant glycogen; 3) rudimentary septa and large airspace were present; 4) mesenchymal tissue was attenuated and compressed between adjacent epithelial tubules; 5) the distribution of SP-C mRNA in distal tubules was more mature, with individual and clusters of cells expressing SP-C transcripts; and 6) the transcript levels of several genes related to epithelial growth [keratinocyte growth factor (KGF), KGF receptor, and hepatocyte growth factor receptor] and differentiation [surfactant proteins, SP-A, SP-B and SP-C and the Clara cell secretory protein, CC10] were precociously increased. These results show that DEX treatment of the lung during the early pseudoglandular stage accelerates the acquisition of several features of advanced maturation that normally accompany late stages of fetal development. We postulate that KGF mediates at least some effects of DEX on lung maturation and gene expression.
Abstract: Clara cells are nonciliated, nonmucous, secretory cells of the pulmonary airways. These... more Abstract: Clara cells are nonciliated, nonmucous, secretory cells of the pulmonary airways. These cells are known to secrete a variety of proteins, including Clara cell 10-kDa protein/uteroglobin. This protein consists of a homodimer of 70–77 amino acid polypeptides arranged in antiparallel fashion. In vitro testing suggests that the protein suppresses inflammation. The physiologic role of the protein remains to be determined.
A protein similar to the rat Clara cell 10-kDa protein (CC10) was isolated from mouse lung homoge... more A protein similar to the rat Clara cell 10-kDa protein (CC10) was isolated from mouse lung homogenate by conventional chromatography. cDNA for the mouse CC10 protein was identified in the mouse lung cDNA library by using radiolabeled rat CC10 cDNA as the probe. The isolated cDNA was sequenced and the deduced primary amino acid sequence was compared to the known sequences of rabbit and hare uteroglobins and human and rat CC10 proteins. The cDNA sequence was confirmed by N-terminal amino acid sequencing of the purified protein. The purified mouse CC10 was tested for its ability to bind progesterone, and the binding was found to be 27% lower than rat CC10 and 48% lower than rabbit uteroglobin. The relative binding of mouse, rat, and human CC10 may reflect subtle structural perturbations. The only notable difference between mouse and rat CC10 is in the beta bend between helices 1 and 2, at residue 16. This difference also exists between rat and human CC10. The mouse CC10 sequence compares favorably with human CC10, which does not bind progesterone; however, the mouse CC10 does not contain M60, which has been proposed to block the binding of progesterone with human CC10. The wide variation in progesterone binding among this family of proteins casts doubt on the importance of such binding as a physiologic function.
Rat lung lavage contains a 10 kDa protein that has been shown by immunocytochemistry to be specif... more Rat lung lavage contains a 10 kDa protein that has been shown by immunocytochemistry to be specific for Clara cells. An inhibition enzyme-linked immunosorbent assay was established for this protein using rabbit antibody to the 10 kDa Clara cell protein. The assay has a sensitivity of about 3.0 ng/ml and a working range of about 5 to 50 ng/ml. Quantitation of the 10 kDa protein in amniotic fluid revealed an increase of about 4-fold at day 20 of gestation. The 10 kDa protein content of lung homogenate increased steadily from day 18 of gestation to 1 wk after birth, after which a decline was observed. Nearly 60-fold increase in the concentration of the 10 kDa Clara cell protein in lungs was noted from day 18 of gestation to birth and a further about 7-fold increase was noted from the day of birth to 1 wk of age. A progressive increase in the 10 kDa protein, with increasing age, was also noted on immunoblot analysis of lung homogenates. As judged from the immunoblots of lung homogenates, stained with rabbit antirat 10 kDa protein antiserum, the content of an antigenically similar 200 kDa Clara cell protein was negligible. The quantitative results for 10 kDa Clara cell protein parallel the results of immunocytochemistry and quantitation of the volume density of Clara cell granules indicating that quantitation for the 10 kDa protein could be used to monitor the development of Clara cells and that of the pulmonary airways.
A protein of molecular weight about 10,000 (Clara cell protein C) present in lung lavage fluid an... more A protein of molecular weight about 10,000 (Clara cell protein C) present in lung lavage fluid and specific to Clara cells has been shown to have three isotypes. The isotypes have been individually isolated and purified by a combination of molecular sieving, ion exchange chromatography, column chromatofocusing, and reverse phase chromatography. The protein was monitored by immunoblotting and its purity tested by silver staining of the gel following sodium dodecyl sulfate-polyacrylamide gel electrophoresis. About 33.7% of the 10-kDa protein present in starting rat lavage was recovered in final pure preparation. The 10-kDa Clara cell protein amounted to 0.38% of the total protein in rat lung lavage fluid. The three isotypes were present in a ratio of 1.0:2.8:8.8, the amounts increasing with decreasing pI. None of the isotypes bound to concanavalin A. The amino acid compositions of the three isotypes were similar and were remarkable in that the contents of leucine, glutamic acid, aspartic acid, serine, and proline were high, tyrosine was present in low amounts, and methionine and histidine were absent.
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