PubMed Health⌕ Search

Biomedical subjects

L Nitsch

Publications and source records attributed to L Nitsch.

44 records · Page 3Linked to original sources
PubMed1984

Suspension culture reveals a morphogenetic property of a thyroid epithelial cell line.

It is known that freshly dissociated thyroid cell clusters form follicles in suspension culture. Thyroid epithelial cell lines, grown for many generations in vitro, fail to show colloid-containing lumina when cultured as monolayers. Several thyroid cell lines, some transformed, have been tested with respect to their ability to form extracellular lumina when transferred from monolayer to suspension culture. One cell line in particular, the T78 cell line, showed this property when cultured in suspension. Lumina formed within 3 days even in the absence of added thyrotropin (TSH). The ultrastructure of lumina within cell aggregates resembled that of the thyroid follicle in vivo. The ability to undergo morphogenesis may therefore be an intrinsic property of thyroid epithelial cells which is retained for a large number of generations in vitro and is revealed by proper culture conditions. The shift from monolayer to suspension culture may thus lead to the expression of a thyroid differentiated function such as the formation of follicle-like structures.

Animals↗
PubMed1984

Cytoskeleton and adhesion patterns of cultured chick embryo chondrocytes during cell spreading and Rous sarcoma virus transformation.

The cytoskeleton and the adhesion complex of chick embryo chondrocytes maintained in vitro have been studied by fluorescence and interference reflection microscopy during the process of cell spreading. The pattern of actin-containing microfilaments and the distribution of vinculin speckles on adhesion plaques have been found to change as a function of the culture time. Newly plated chondrocytes adhere to the substratum mostly around a peripheral ring-like region and show a complex tridimensional array of microfilaments. When chondrocytes flatten, they develop stress fibres and show a diffuse system of vinculin-containing adhesion plaques scattered over the entire ventral side of the cells. Upon infection with Rous sarcoma virus (RSV) chondrocytes display one or more actin-containing ruffles located on the dorsal side similar to the 'actin flowers' earlier described in other cell types. These structures have been found to accumulate vinculin too. In chondrocytes infected with two td-ts mutants of RSV, 'actin flowers' have been found to persist at the restrictive temperature. At this temperature, however, in the majority of cells, stress fibres and adhesion plaques reappear.

Actinin↗
PubMed1984

Embedding in a collagen gel stabilizes the polarity of epithelial cells in thyroid follicles in suspension culture.

Separated thyroid follicles are stable in suspension culture in Coon's modified Ham's F12 medium containing 0.5% calf serum. They resemble follicles in vivo except for the absence of a basal lamina. However, the epithelial cells reverse polarity and the follicles invert when the serum concentration is raised to 5%. A number of substances, especially components of extracellular matrix, were added to the medium to ascertain if they could stabilize the follicles against inversion in 5% serum. Cellular and plasma fibronectin, gelatin, heat-denatured collagen, methylcellulose and laminin did not stabilize. The addition to the medium of as little as 50 micrograms/ml of acid-soluble collagen prepared from calf skin or rat tail tendons resulted in the formation of small clouds of gel. Follicles embedded within the gel were stabilized. Follicles in the same dish but not embedded in the gel inverted. Stabilization was not specific for collagen, since follicles embedded in a plasma clot were also stabilized. A gel was not sufficient for stabilization, since embedding in an agarose gel did not stabilize. Ultrastructural studies indicate that adherence to a limited number of gelled fibers of collagen covering only a small fraction of the basal plasma membrane may be sufficient to stabilize and that a basal lamina formed in the presence of laminin but without added collagen does not stabilize.

Animals↗
PubMed1982

The culture of chick embryo chondrocytes and the control of their differentiated functions in vitro. I. Characterization of the chondrocyte-specific phenotypes.

We have maintained chick embryo chondrocytes in culture for more than 2 months, passaging the floating cells in the absence of ascorbic acid. Throughout the culture period some of the cells attached to the dish, assuming an epithelial-like morphology and subsequently giving rise to new floating cells. The interconversion of the two cell populations was highest in primaries and decreased with the aging of the culture. Cartilage cells synthesized pro-alpha 1 (II) collagen and sulphated proteoglycans in vitro; compared with floaters, the epithelial-like cells secreted relatively large amounts of fibronectin. When ascorbic acid was added to the medium, all cells attached, maintaining their rounded shape; in this condition the pro-alpha, (II) collagen was matured and collagen fibres were detectable outside the cells. Other specific proteins synthesized by the chondrocytes in culture were also identified. One of these, a 64 K collagenase-sensitive protein, was not related to the type II collagen and may represent a new collagen type.

Animals↗
PubMed1980

Suspension culture of separated follicles consisting of differentiated thyroid epithelial cells.

We have prepared thyroid follicles in suspension culture to use as a model system in vitro for investigation of some properties of the thyroid gland. The follicles were free of endothelial cells, fibroblasts, and other nonepithelial cells. They were prepared by collagenase treatment of minced rat thyroid glands followed by differential filtration of the suspension through nylon meshes. Small clusters of principal thyroid epithelial cells were separated from large fragments and single cells. They were cultured in dilute suspension in Coon's modified F-12 medium in dishes coated with agarose to avoid having the cells attach to the dishes. By culture day 3, most of the clusters formed closed follicles containing a periodic acid-Schiff-positive colloid but without a basal lamina. Follicle walls contained an occasional C cell. The epithelium resembled that in the thyroid of a recently hypophysectomized rat, with normal polarity and organelle complement normal with respect to position and abundance, with basally located lysosomes, no pseudopods, and no colloid droplets. The cells were responsive to thyroid-stimulating hormone (thyrotropin) and to dibutyryl cyclic AMP. Thyroid-stimulating hormone at 10 munits/ml resulted in apical migration of lysosomes and formation of pseudopods and colloid droplets within 30 min; longer exposure resulted in depletion of luminal colloid. The results indicate that the suspended follicles resemble follicles in vivo with respect to morphology and responsiveness to thyroid-stimulating hormone in the absence of other cell types.

Animals↗
PubMed1980

Thyrotropin preparations are mitogenic for thyroid epithelial cells in follicles in suspension culture.

We have been investigating the extent to which separated thyroid follicles in suspension culture, free of endothelium and fibroblasts, have the properties of follicles in vivo. To test whether thyrotropin (TSH) can cause thyroid epithelial cells to undergo mitosis, preparations of follicles suspended in Coon's modified F-12 medium with 0.5% calf serum were incubated with 10 milliunits of impure or pure TSH per ml. Three results were obtained: (i) TSH preparations stimulated the incorporation of [3H]thymidine into cell nuclei; (ii) mitotic figures were induced and they had the same characteristic ultrastructural features as those observed in vivo; and (iii) the cell number doubled in the course of 3 days of exposure to TSH. The results suggest that TSH is a mitogen for the principal thyroid epithelial celland that other substances found in the usual impure TSH preparations are not necessary for the mitogenic activity. It can act in the absence of nonfollicular cells. The initial multiplication rates are similar to those in vivo. The cells do not have to spread to divide in contrast to the requirement for spreading in the case of fibroblasts.

Animals↗
PubMed1980

Ultrastructure of intermediate stages in polarity reversal of thyroid epithelium in follicles in suspension culture.

Separated thyroid follicles can be maintained in suspension culture in Coon's modified F-12 medium in 0.5% calf serum. If the serum concentration is raised to 5%, the follicles undergo inversion in 3-5 d. During the process of inversion, epithelial cells can be observed in intermediate stages of polarity reversal. The earliest ultrastructural changes recognized are surface changes in which tight junctions and microvilli appear at the lateral margins of the cell near the medium. Later, changes in the distribution of intracellular organelles occur. The Golgi apparatus shifts towards the end of the cell facing the medium, and lysosomes shift toward the luminal end of the cell. The right junctions and microvilli at the luminal end of the cell disappear sometime after the cytoplasmic organelles rearrange. The luminal colloid disappears only after the surface changes (loss of tight junctions and microvilli) occur at the luminal end of the cell. There appears to be some regulation of the order in which changes occur during polarity reversal of the thyroid epithelial cell.

Animals↗