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Biomedical subjects

B Geiger

Publications and source records attributed to B Geiger.

At least 109 records · Page 6Linked to original sources
PubMed1982

The interaction of cultured thyroid cells of early bovine embryos with thyrotropin and thyroglobulin.

We have prepared primary thyroid cell cultures of early bovine embryos from the first trimester of pregnancy in order to study the ontogeny of their interaction with TSH and thyroglobulin (Tg). The ability of these cells to synthesize and secrete Tg, as well as the trophic effect of TSH on the organization of the thyroid cells, were also investigated. To determine the maturation of these functions we prepared fluorescent conjugates of TSH, Tg, and anti-Tg antibodies, and visualized their interaction with the thyroid epithelial cells. Our study shows that the ability to bind TSH and Tg exists as early as the gestational age of 3 cm crown-rump length (CRL; 40 days) but does not develop linearly with embryonic age. Thus, there is a significant increase in the percentage of Tg-binding cells at 12 cm CRL, when colloid is first noticed in vivo, and a considerable elevation in TSH-binding cells around 15 cm CRL, when thyrotropic cells and TSH secretion from the fetal pituitary are first evident. Tg-containing cells and the ability to secrete Tg are observed at about 20 intrauterine days. The three thyroidal properties probably develop independently since only part of the Tg-containing cells bind Tg or TSH, and a significant proportion of the cells that exhibit Tg-binding do not bind TSH. The results support the notion that TSH is essential for the formation of follicle-like structures and effects the organization of thyroid cells into a functional structure in vitro from the late precolloidal stage.

Animals↗
PubMed1982

Altered organization of cell-substrate contacts and membrane-associated cytoskeleton in tumor cell variants exhibiting different metastatic capabilities.

The pattern of cell-substrate attachment and the organization of actin-containing microfilament bundles were analyzed in tumor cell variants of the K-1735 melanoma and UV-2237 fibrosarcoma series exhibiting distinct metastatic phenotypes. In both tumors, the low-metastatic cells were relatively flat, with well-developed focal contacts. Visualization of the cellular organization of actin and vinculin by fluorescence microscopy indicated that the low-metastatic cells contained prominent stress fibers which terminated in large vinculin-containing focal contacts. The high-metastatic cells were characterized by poor organization of vinculin and adhesion plaques as well as by low number and disarray of actin bundles. These results are compatible with the notion that cytoskeletal organization may be involved in cytodynamic processes related to tumor cell dissemination and implantation.

Animals↗
PubMed1981

Dynamics of antibody- and lectin-mediated endocytosis of hapten-containing liposomes by murine macrophages.

The uptake by murine macrophages of liposomes, exhibiting one of a variety of haptenic groups on their surfaces, was greatly enhanced by the addition of an intact antibody or a lectin specific for the incorporated hapten. The uptake of untreated liposomes was slow and linear over long periods, whereas upon addition of the antibody or lectin, over 30-fold increase in the maximal rate of uptake was observed. The process reached a plateau after 90-120 min. The interaction of the antibody- or lectin-treated liposome with the macrophages apparently resulted in an active endocytosis of soluble fluorescent, intraliposomal marker had a granular intracellular pattern in treated cells. The uptake was sensitive to azide and the liposome constituents could not be detected at the cell surface. The size of the liposomes as well as the state of stimulation of the macrophages (thioglycollate stimulated vs. normal) did not seem to have a major effect on the phagocytic process. The time required to reach the plateau in uptake was independent of liposome composition or antibody concentration and is, apparently, an intrinsic property of the cells. The implication of this phenomenon on the dynamics of the relevant macrophage receptors is discussed.

Adsorption↗
PubMed1981

The association of rhodamine - labelled alpha-actinin with actin bundles in demembranated cells.

Rhodamine-labelled alpha-actinin was specifically bound to actin containing filament bundles of demembranated fibroblasts, and was particularly associated with their termini. Optimal binding of rhodamine-alpha-actinin occurred at pH 6.0 - 6.2 and could be abolished by the addition of unlabeled alpha-actinin or myosin subfragment 1. The spatial relationships between the decorating alpha-actinin and several actin associated proteins was determined by double fluorescence microscopy.

Actinin↗
PubMed1981

Ultrastructure of chicken cardiac muscle as studied by double immunolabeling in electron microscopy.

The ultrastructural localization of alpha-actinin and vinculin in chicken cardiac muscle was studied by double indirect immunoelectron microscopy, using ferritin and iron-dextran (Imposil) as the electron-dense markers conjugated to the secondary antibodies, on ultrathin frozen sections of fixed tissue. Fixation and immunolabeling procedures were developed that permitted maximal retention of the two proteins at their natural sites as well as their adequate labeling. alpha-Actinin was found both on the Z-bands, as expected, and near the fascia adherens of the intercalated discs, whereas vinculin was confined to the latter sites. At the fascia adherens, the double labeling results clearly showed that vinculin was situated closer to the membrane than was alpha-actinin. These results, coupled with earlier observations, suggest that vinculin may participate in the linkage of actin-containing microfilament bundles to membranes in a variety of cell types.

Actinin↗
PubMed1981

Immunoelectron microscope studies of membrane-microfilament interactions: distributions of alpha-actinin, tropomyosin, and vinculin in intestinal epithelial brush border and chicken gizzard smooth muscle cells.

The ultrastructural localization of three cytoskeletal proteins, alpha-actinin, tropomyosin, and vinculin, in the brush border of epithelial cells of chicken small intestine and the smooth muscle cells of chicken gizzard was studied by immunofluorescence and immunonelectron microscope labeling of frozen sections of lightly fixed, intact tissues. In the immunoelectron microscope studies, a recently described new type of electron-dense antibody conjugate, imposil-antibody, has been successfully used, along with ferritin-antibody conjugates, in single and double immunolabeling experiments. In the intestinal brush border shows that vinvulin is sharply confined to the junctional complex close to the membrane region of the zonula adherens, in distinct contrast to the more diffuse distributions of the other two proteins. In the smooth muscle cells, the labeling patterns show that vinculin is sharply confined to the membrane-associated dense plaques, closer to the membrane than the alpha-Actinin is also present in the cytoplastic dense bodies, from which vinculin is absent. Tropomyosin is present diffusely distributed in the cytoplasm, but absent from both dense plaques and dense bodies. These findings with the muscle cells demonstrate, therefore, that the dense plaques and dense bodies are chemically and structurally distinct entities. The results with both tissues, along with those in previous papers (Geiger, 1979, Cell. 18:193-205.; Geiger et al., 1980, Proc. Natl. Acad. Sci. U. S. A. 77:4127-4131), suggest that vinculin may play an important and widespread role in the linkage of actin-containing microfilament bundles to membranes.

Actinin↗
PubMed1980

The localization of acetylcholine receptor clusters in areas of cell-substrate contact in cultures of rat myotubes.

We have used interference reflection and fluorescence microscopy to investigate the relationship between cell-substrate contact and the location of clusters of acetylcholine receptors (AChRs) in cultures of rat myotubes. We have found that AChR clusters on the ventral myotubes surfaces are always located within broad regions of close cell-substrate contact. Detailed analysis of the fine structure of the AChR cluster and its associated contact region showed that AChRs within a cluster are concentrated between the points of closest cell-substrate apposition. Vinculin, a recently discovered intracellular smooth muscle protein, is also concentrated in broad regions of close contact, interdigitating with AChRs within the clusters.

Animals↗
PubMed1980

Vinculin, an intracellular protein localized at specialized sites where microfilament bundles terminate at cell membranes.

As intracellular protein of 130,000 molecular weight was recently isolated in this laboratory from chicken gizzard smooth muscle. By immunofluorescence observations of cultured chicken fibroblasts, it was shown to be concentrated on the ventral surfaces of the cells where they formed focal adhesions to the substratum [Geiger, B. (1979) Cell 18, 193-205]. Focal adhesions are sites where, inside the fibroblast, microfilament bundles are known to terminate at the cell membrane. The suggestion was made that this new protein (herein named "vinculin") might be involved in the linkage of the termini of microfilament bundles to membranes in various cell types. To explore this possibility, in the present study we examined several chicken tissues, including intestinal epithelium, gizzard smooth muscle, and cardiac striated muscle, by immunoelectron microscopic labeling for vinculin on ultrathin frozen sections of the specimens. In each case, the immunolabeling for vinculin was concentrated close to membrane sites where microfilament bundles terminate: at the zonula adherens in the junctional complex of the brush border of epithelial cells; at the membrane-associated sense plaques of smooth cells; and at the fascia adherens of the intercalated disk membranes of cardiac muscle cells. These results suggest therefore that vinculin may participate in the anchoring of microfilament bundles to specific membrane sites in various cells.

Animals↗
PubMed1980

Association of microtubules and intermediate filaments in chicken gizzard cells as detected by double immunofluorescence.

By double indirect immunofluorescence, using guinea pig and rabbit antibodies to tubulin and to desmin, we have simultaneously labeled microtubules and intermediate filaments in cultured chicken embryo gizzard cells. At the resolution of the light microscope there was extensive but not complete superposition of the labeling patterns for the two filamentous structures within cells in interphase and an essentially complete dissociation of the two labeling patterns in cells in mitosis. These results indicate that there is an extensive association of microtubules and intermediate filaments in these interphase muscle cells and suggest that this association is regulated metabolically.

Animals↗
PubMed1979

Carbohydrate composition of human placental N-acetylhexosaminidase A and B.

The carbohydrate composition of N-acetyl-beta-D-hexosaminidases (EC 3.2.1.52) A, B and heat-converted B was determined by g.l.c. Similar quantities of mannose, N-acetyl-glucosamine and galactose are present in the A and B isoenzymes, whereas N-acetyl-neuraminic acid is found in significant amount in only the A isoenzyme. The heat-converted hexosaminidase B also contains only trace amounts of N-acetylneuraminic acid, but is about 1.5-fold richer in mannose and N-acetylglucosamine and nearly 2-fold richer in galactose than native hexosaminidase B. Since native and converted hexosaminidase B are thought to be composed of four identical protein chains, our results suggest that there may be variable glycosylation of these chains.

Carbohydrates↗