Clara endoplasmic reticulum

B6C3F1) dilation of endoplasmic reticulum in Clara cells) 1991... 

Smooth endoplasmic reticulum was observed only in M3 (33.8%) and Clara cells (49%). Granular endoplasmic reticulum was most abundant in serous (21%) and least plentiful in M4 (2.2%) cells (Mariassy and Plopper 1984). 

In mice and rats, but not humans, the smooth endoplasmic reticulum of the Clara cell tends to present as a meshwork of branching tubules and/or vesicles. It is believed to be involved in the detoxification of drugs. Evidence demonstrating that the Clara cell is the primary site of cytochrome P-450 monooxygenase activity within the lung derives from four different approaches ... 

The prominent organelle in the cytoplasm of Clara cells from both wild-type strain 129 and Clara cell secretory protein -/- 129 mice is the smooth endoplasmic reticulum, which occupies about 20% of the cell cytoplasm (Strife et al. 2002). Despite the similarities in abundance there were two aspects of the smooth endoplasmic reticulum that differed markedly between both genotypes of mice. First, electron-dense material that was abundant within the lumen of smooth endoplasmic reticulum of Clara cells from wild-type mice was not as evident within the lumen of smooth endoplasmic reticulum of Clara cells from Clara cell secretory protein -/-129 mice. Second, Clara cells from Clara cell secretory protein -/- 129 mice were unique in that they possessed large concentric whorls of endoplasmic reticulum located within the apical portion of the cell. Membrane-bound inclusions, which appeared to he surrounded by at least one layer of endoplasmic reticulum, were found at the centre of these whorls and contained material of varying electron density and compaction. Some of these inclusions had the characteristics of mitochondria based on the presence of crista-like membrane inclusion. 

Fig. 65. Prominent endoplasmic reticulum and ovoid electron-dense secretory granules in the apical cap of a type 4 Clara cell from a bronchiole (block 465) of a male rat (No. 5/104 E) which inhaled 71.5 mg trimethylol melamine (Madurit) dust/1 for a total of 32 h 30 min on 4 consecutive days. Fixed under pentobarbital anaesthesia (30 mg/kg) by intratracheal instillation of 2.5 % glutaraldehyde in 0.1 M sodium cacodylate buffer (pH 7.4) before opening the thorax. Postfixation with 1 % osmium tetroxide in sodium cacodylate buffer. Embedded in Epon 812 and sectioned at 50 nm. Lead citrate and uranyl acetate. Plate 4050...

In the stumptail Macaca arctoides) and bonnet (Macaca radiata) monkeys, the cytoplasm of the Clara cells contained abundant mitochondria, a medium-sized Golgi complex, and a moderate amount of granular endoplasmic reticulum (Cast-LEMAN et al. 1975). In bonnet monkeys, the cells frequently contained round secretory droplets, which were homogeneously electron dense. Secretory droplets were less frequently observed in the non-ciliated bronchiolar cells of the stumptail monkey. The non-ciliated bronchiolar cells of the rhesus monkey (Macaca mulatto) were not observed to contain any secretory droplets. 

In the neonate rat, the apical region of the Clara cell lacks the profusion of smooth endoplasmic reticulum typical of the adult (Smith et al. 1974) also, in all but a few neonatal Clara cells there is less smooth and rough endoplasmic reticulum in the middle zone than occurs in the adult. 

Adrenaline in very large dose (2.5 mg/kg mouse) rapidly dilated the cisternae of the smooth endoplasmic reticulum of the Clara cells with subse-... 

Fig, 72. Smooth endoplasmic reticulum in the apical part of a type 1 Clara cell from a female rat (breeder Winkelmann, Borchen-Kirchborchen) which inhaled 300 jug micronized (mass median diameter 2.45 um) phenylephrine bitartrate/... 

Fig. 74. Smooth endoplasmic reticulum in the apical part of a types Clara cell from a female white rat (breeder Winkel-mann, Borchen-Kirchborchen) 2 h after an inhalation of 200 mg micronized isoprenaline HCl -1- 300 /ig micronized (mass median diameter 2.45 fjm) phenylephrine bitartrate/ uff from a suspension type self-propelled aerosol (Mediha-er). 12 Puffs/min were dispersed into a 164.5 1 box where the animals stayed for 15 min. 30 min later under methitural anaesthesia, the lung was fixed by intratracheal instillation of 2.5 % glutaraldehyde in phosphate buffer (pH 7.4) before opening the thorax. Postfixation with 1 % osmium tetroxide in phosphate buffer (pH 7.4). Contrasted en bloc for 12 h with 0.5 % uranyl acetate in 70 % ethanol. Embedded in a 2 8 mixture of methyl and butyl methacrylate. Sectioned at 50 nm. Lead citrate after Reynolds (1963). Film 374/84...

Cobalt aerosols inhaled by rats at a concentration of 2.1210.55 mg/m for 5 h per day on 4 consecutive days induced Clara cell hypertrophy with abundant rough endoplasmic reticulum and electron lucent glycogen granules which were normally absent in adult rats (Kyono et al. 1992). At 8 days after exposure, the long strands of rough endoplasmic reticulum had disappeared. 

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