A unique cell type in the lung--the Clara cell (the non-ciliated bronchiolar epithelial cell).

The non-ciliated bronchiolar epithelial cells (the Clara cells) are found most frequently in the distal conducting airways, but they are found throughout the tracheobronchial tree of different mammalian species. According to recent data, the main functions of the Clara cells can summarized as (1), the secretion of certain components of the extracellular bronchiolar lining layer (2), metabolism and detoxification of xenobiotics and other toxic compound (3) and participation in the renewal process of the bronchiolar epithelium. The main goal of this paper is to collect and discuss some of the general features of Clara cells from a functional-morphological point of view, and their possible role in pathological alterations of the lung especially in the pathogenesis of lung tumours originated from Clara cells.

Nucleolar activity after 3-methylcholanthrene treatment of rat liver cells studied by silver staining procedure.

The influence of a single dose of 3-methylcholanthrene (3-MC) was studied in nucleoli of young rat liver cells by means of conventional and ultracytochemical methods. The nucleolar activity was stimulated in our experimental conditions: the appearance of the fibrillar centres in the liver cell nucleoli as well as the silver staining protein content of the fibrillar centres and the dense fibrillar component were increased by 3-MC. The results suggest that the activity of ribosomal genes was increased following 3-MC treatment.

Isolation and characterization of nuclear hnRNP complexes from Drosophila melanogaster tissue culture cells.

Fractionation on sucrose gradients of nuclear described extracts prepared from cultured Drosophila melanogaster cells by sonication of the nuclei in the presence of rat liver cytosol RNAase inhibitor revealed a complex polysome-like pattern of nuclear ribonucleoprotein complexes. The bulk of these heterogeneous ribonucleoprotein (hnRNP) complexes sedimented in the 30S to 80S zone of the sucrose gradient. According to biochemical and morphological data, the monomer particle proved to be the 45S hnRNP and its average diameter was found by electron microscopy to be 24-26 nm.

HnRNP particles from Drosophila melanogaster cells.

The isolation and characterization of HnRNP from cultured Drosophila melanogaster cells is described. HnRNP particles were extracted from the purified nuclei of sonication in the presence of rat liver cytosol RNAse inhibitor. The nuclear extract was centrifuged on a 15-30% sucrose gradient.