Biomedical subjects

B Geiger

Publications and source records attributed to B Geiger.

At least 73 records · Page 4Linked to original sources

PubMed1985

Embryonal rhabdomyosarcoma: immunohistochemical characterization.

A 15-year-old boy was referred to the ear, nose, and throat clinic because of a swelling in the upper premolar region. The initial diagnosis of a poorly differentiated soft-tissue sarcoma was made. Further immunohistochemical studies established a definitive diagnosis of embryonal rhabdomyosarcoma. The tumor cells coexpressed both desmin, the component of muscle type intermediate filaments, and vimentin, which is typically found in mesenchymal tissues. Such coexpression is found in the early stages of myogenic differentiation. Another cytoskeletal protein, actin, was also found in relatively high concentrations. These results suggested the possible use of antibodies to these cytoskeletal proteins as histogenetic markers for the diagnosis of poorly differentiated rhabdomyosarcoma.

Actins↗

PubMed1985

Molecular heterogeneity of adherens junctions.

We describe here the subcellular distributions of three junctional proteins in different adherens-type contacts. The proteins examined include vinculin, talin, and a recently described 135-kD protein (Volk, T., and B. Geiger, 1984, EMBO (Eur. Mol. Biol. Organ.) J., 10:2249-2260). Immunofluorescent localization of the three proteins indicated that while vinculin was ubiquitously present in all adherens junctions, the other two showed selective and mutually exclusive association with either cell-substrate or cell-cell adhesions. Talin was abundant in focal contacts and in dense plaques of smooth muscle, but was essentially absent from intercellular junctions such as intercalated disks or adherens junctions of lens fibers. The 135-kD protein, on the other hand, was present in the latter two loci and was apparently absent from membrane-bound plaques of gizzard or from focal contacts. Radioimmunoassay of tissue extracts and immunolabeling of cultured chick lens cells indicated that the selective presence of talin and of the 135-kD protein in different cell contacts is spatially regulated within individual cells. On the basis of these findings it was concluded that adherens junctions are molecularly heterogeneous and consist of at least two major subgroups. Contacts with noncellular substrates contain talin and vinculin but not the 135-kD protein, whereas their intercellular counterparts contain the latter two proteins and are devoid of talin. The significance of these results and their possible relationships to contact-induced regulation of cell behavior are discussed.

Animals↗

PubMed1985

Immunofluorescent localization of intermediate filament subunits for the differential diagnosis of malignant melanoma.

Intermediate filament subunits in normal cells and in their malignant derivatives can be used as specific markers for their histogenetic origins. We have studied five neoplasms of the skin in which positive identification of vimentin containing intermediate filaments by indirect immunofluorescence microscopy helped to establish the diagnosis of malignant melanoma. All of the neoplasms included in this study posed problems in differential diagnosis by conventional light microscopy and yielded equivocal results by conventional histochemistry. Thus, definitive distinction between poorly differentiated carcinoma and poorly differentiated melanoma could not be made by conventional microscopy. In all of the neoplasms described here, immunolabeling with antibodies against different intermediate filaments demonstrated positive staining for vimentin only. This intermediate filament subunit is present in melanocytes (as well as in many mesenchymal cells) but not in epithelial cells. Our study indicates that this technique may be valuable in differential diagnosis of malignant melanoma, particularly in instances where cells lack melanin or show other atypical morphologic features.

Aged↗

PubMed1985

Coexpression of neuroendocrine markers and epithelial cytoskeletal proteins in bronchopulmonary neuroendocrine neoplasms.

Neuroendocrine (NE) neoplasms of the human bronchopulmonary tract were examined by electron microscopy, immunocytochemistry, and gel electrophoresis of cytoskeletal proteins from microdissected tissue samples. All samples (carcinoids, well-differentiated NE carcinoma, NE carcinomas of intermediate type, NE carcinomas of the small cell type) contained significant numbers of cells that immunostained for one or more of the following neuroendocrine markers tested: bombesin, calcitonin, ACTH, leu-enkephalin, gastrin, serotonin, somatostatin, alpha-melanocyte-stimulating hormone, vasoactive intestinal peptide, glucagon, insulin, substance P, and neuron-specific enolase. Electron microscopy revealed typical NE cell features, including variable abundant and frequently heterogeneous neurosecretory granules. Tumor cells contained filaments specifically stained with different conventional and monoclonal antibodies to cytokeratins and displayed punctate plasma membrane staining with antibodies to desmoplakins, in agreement with the electron microscopic demonstration of tonofilament bundles and desmosomes. Immunocytochemistry for NE markers and cytoskeletal proteins on consecutive sections revealed both cytokeratins and neuroendocrine substances in single cells. Using gel electrophoresis of cytoskeletal proteins of tissue regions extracted with high salt buffer and detergent, we could detect, in the tumors tested, appreciable amounts of cytokeratin polypeptides 8, 18, and 19, i.e., major cytokeratins also found in certain other lung carcinomas such as adenocarcinomas. Tumor cells were not significantly stained with antibodies to other intermediate filament proteins such as vimentin, desmin, glial filament protein, and neurofilament protein. The results show that NE substances can be synthesized in cells containing a typical epithelial cytoskeleton, i.e., cytokeratin filaments and desmosomes. These findings support the notion of an epithelial character of these tumors and appear in contrast with recent reports that neurofilaments are the only type of intermediate filaments present in carcinoids and other pulmonary NE tumors. These observations may have important implications for the histogenesis of NE carcinomas and for diagnostic pathology.

Adrenocorticotropic Hormone↗

PubMed1984

Distinctive immunofluorescent labeling of epithelial and mesenchymal elements of carcinosarcoma with antibodies specific for different intermediate filaments.

A carcinosarcoma of the lung, as well as the paratracheal lymph nodes from the same patient, were subjected to immunofluorescent labeling with antibodies to tissue-specific intermediate-filament subunits, including desmin, vimentin, and prekeratin. Within the tumor mass two distinct populations of malignant cells were found: prekeratin-positive cells, corresponding to the carcinomatous component of the tumor, and vimentin-positive cells, corresponding to the sarcomatous elements. Tumor cells were also detected in lymph node metastases in which only the prekeratin-containing carcinoma cells were found. In view of the strict specificity of antivimentin and anti-prekeratin for cells of mesenchymal or epithelial origin, respectively, it is proposed that the two components of the carcinosarcoma are derived from distinct cell types and are not morphologic variants of the same tumor.

Carcinosarcoma↗

PubMed1984

IgE induces secretion of prostaglandin E2 by human monocytes.

IgE was isolated from a patient with the hyper IgE, recurrent infection syndrome by immunoadsorption on sepharose bound goat anti-human IgE. Addition of this IgE to a monolayer culture of human monocytes resulted in a dose-dependent increase in PGE2 secretion. The addition of F(ab')2 fraction of goat anti-human IgE in the presence of sub-stimulating doses of IgE markedly increased PGE2 secretion; whereas addition of F(ab')2 fragment of irrelevant goat IgG had no effect. Similar activation of monocytes which could be enhanced by anti IgE was observed in the presence of the patient's serum. No such effect was seen in the presence of normal human serum. These results indicate that IgE may activate human monocytes and induce PGE secretion.

Adolescent↗

PubMed1983

On spatial periodicity in the formation of cell adhesions to a substrate.

Interference reflection microscopy reveals a fairly regular array of marginal focal contacts in early states of cell spreading. A theoretical explanation of the onset of patchiness is given, based on the positively cooperative binding to the substrate of laterally diffusing receptor molecules.

Animals↗

PubMed1983

De novo synthesis and specific assembly of keratin filaments in nonepithelial cells after microinjection of mRNA for epidermal keratin.

Poly(A)+ RNA isolated from bovine muzzle epidermis was microinjected into nonepithelial cells containing only intermediate-sized filaments of the vimentin type. In recipient cells keratin polypeptides are synthesized and assemble into intermediate-sized filaments at multiple dispersed sites. We describe the time course and the pattern of de novo assembly of keratin filaments within living cells. These filaments were indistinguishable, by immunofluorescence and immunoelectron microscopic criteria, from keratin filament arrays present in true epithelial cells. The presence of extended keratin fibril meshworks in these injected cells is compatible with cell growth and mitosis. Double immunolabeling revealed that newly assembled keratin was not codistributed with microfilament bundles, microtubules or vimentin filaments. We suggest that assembly mechanisms exist which in vivo sort out newly synthesized cytokeratin polypeptides from vimentin.

Animals↗

PubMed1983

Use of antibodies to intermediate filaments in the diagnosis of metastatic amelanotic malignant melanoma.

Immunofluorescent staining of tissue from a lung tumor detected 12 years after excision of a primary malignant melanoma of the skin was negative for prekeratin and positive for vimentin, indicating that the tumor was not epithelial in origin and excluding carcinoma from the differential diagnosis. Complementary conventional staining with hematoxylin-eosin confirmed the melanocytic origin of the tumor, indicating that it was probably an amelanotic metastasis of the original malignant melanoma. The findings in this case demonstrate the potential usefulness of immunohistochemical microscopic characterization of specific intermediate filament proteins in the diagnosis of otherwise ambiguous cases of amelanotic melanoma.

Antibodies↗

PubMed1983

Change of cytokeratin filament organization during the cell cycle: selective masking of an immunologic determinant in interphase PtK2 cells.

The organization of intermediate-sized filaments (IF) of the cytokeratin type was studied in cultures of PtK2 cells in which typical IF structures are maintained during mitosis, using a monoclonal antibody (KG 8.13). This antibody reacts, in immunoblotting experiments, with the larger of the two major cytokeratin polypeptides present in these cells but, using standard immunofluorescence microscopy procedures, does not react with the cytokeratin filaments abundant in interphase cells, in striking contrast to various antisera and other monoclonal cytokeratin antibodies. In the same cell cultures, however, the antibody does react with cytokeratin filaments of mitotic and early postmitotic cells. The specific reaction with cytokeratin filaments of mitotic cells only is due to the exposure of the specific immunologic determinant in mitosis and its masking in interphase cells. Treatment of interphase cells with both Triton X-100 as well as with methanol and acetone alters the cytokeratin filaments and allows them to react with this monoclonal antibody. A similar unmasking was noted after treatment with buffer containing 2 M urea or low concentrations of trypsin. We conclude that the organization of cytokeratin, albeit still arranged in typical IF, is altered during mitosis of PtK2 cells.

Animals↗

PubMed1983

Spatial distribution of proteins specific for desmosomes and adhaerens junctions in epithelial cells demonstrated by double immunofluorescence microscopy.

The spatial relationships between the protein constituents to two junctional structures, adhaerens junctions and desmosomes, were determined by double immunofluorescence microscopy using marker proteins specific for these structures. Adhaerens junctions were visualized by immunofluorescent labeling for the membrane-associated protein vinculin and by their association with actin filaments. Desmosomal components were identified by labeling with antibodies to a group of minor desmosomal plaque proteins (DP1 antigens) and their association with filaments stained by cytokeratin antibodies. Double immunofluorescence microscopy of these components was performed in several tissues and cultured cells, including intact intestine, dissociated intestinal cells, and two morphologically different types of epithelial cells, cultured bovine kidney (MDBK), and mammary gland (BMGE) epithelial cells. This allowed the direct demonstration that each filament system is associated exclusively with its specific membrane-bound junctional protein. Vinculin and DP1-protein were found in distinct sites in the subapical intercellular junctional complex of intestinal epithelium and MDBK cells. Cell-substrate focal contacts contained vinculin and actin and showed no apparent relationships to the tonofilament system whereas intercellular contacts of BMGE cells were characterized by positive staining for DP1-protein and associated cytokeratin filaments. Immunolabeling of the cultured cells at different intervals after plating for the cytoskeletal elements and their membrane anchorage proteins was used to determine the temporal sequence of their organization. We propose that this approach may be used for the molecular definition and identification of cellular contacts and junctions as well as for studies of junction topology, dynamics and junction-cytoskeleton interactions, and junction biogenesis.

Actins↗

PubMed1982

Mapping of distinct structural domains on microtubule-associated protein 2 by monoclonal antibodies.

Monoclonal antibodies against microtubule-associated protein 2 (MAP2) were prepared and their specificity was verified by visualization of the antigens using the antibody overlay technique and by radioimmunoassay. MAP2 was cleaved by alpha-chymotrypsin to generate a series of high-molecular-mass fragments ranging between 270 and 140 kDa. The precursor-product relationship of these fragments was suggested from the rate of their appearance and from the analysis of the tryptic peptide map of each fragment. A group of monoclonal antibodies was found to react predominantly with the intact 270-kDa MAP2 molecule and a fragment having a mass of 240 kDa and to some extent with a 215-kDa fragment. Another group of monoclonal antibodies reacted with an antigenic determinant which was located on the 270-kDa molecule as well as on fragments as small as 140 kDa. None of the two groups of monoclonal antibodies reacted with the microtubule-binding domain of MAP2. These results suggest that one group of antibodies reacts with sites located at or dependent upon a terminal 60-kDa domain(s) distal to the microtubule-binding site of MAP2. The second group of antibodies, which can still bind to smaller proteolytic products, appear to be associated with the central region of the MAP2 molecule. Indirect immunofluorescence experiments with the antibody preparations indicated that at least some of the antigenic determinants are exposed when MAP2 is associated with microtubules in the cell body and neurite outgrowths of differentiated rat brain neuroblastoma B104 cells.

Animals↗

PubMed1982

A subfamily of relatively large and basic cytokeratin polypeptides as defined by peptide mapping is represented by one or several polypeptides in epithelial cells.

Epithelial cells contain a class of intermediate-sized filaments formed by proteins related to epidermal alpha-keratins ('cytokeratins'). Different epithelia can express different combinations of cytokeratin polypeptides widely varying in apparent mol. wt. (40 000-68 000) and isoelectric pH (5.0-8.5). We have separated, by two-dimensional gel electrophoresis, cytokeratin polypeptides from various tissues and cultured cells of man, cow, and rodents and examined their relatedness by tryptic peptide mapping. By this method, a subfamily of closely related cytokeratin polypeptides has been identified which comprises the relatively large (greater than or equal to mol. wt. 52 500 in human cells) and basic (pH greater than or equal to 6.0) polypeptides but not the smaller and acidic cytokeratins. In all species examined, the smallest polypeptide of this subfamily is cytokeratin A, which is widespread in many simple epithelia and is the first cytokeratin expressed during embryogenesis. This cytokeratin polypeptide subfamily is represented by at least one member in all epithelial and carcinoma cells examined, indicating that polypeptides of this subfamily serve an important role as tonofilament constitutents . Diverse stratified epithelia and tumours derived therefrom contain two or more polypeptides of this subfamily, and the patterns of expression in different cell types suggest that some polypeptides of this subfamily are specific for certain routes of epithelial differentiation.

Animals↗

PubMed1982

Detection of a cytokeratin determinant common to diverse epithelial cells by a broadly cross-reacting monoclonal antibody.

A monoclonal antibody derived from a mouse immunized with bovine epidermal prekeratin has been characterized by its binding to cytoskeletal polypeptides separated by one- or two-dimensional gel electrophoresis and by immunofluorescence microscopy. This antibody (KG 8.13) binds to a determinant present in a large number of human cytokeratin polypeptides, notably some polypeptides (Nos. 1, 5, 6, 7, and 8) of the 'basic cytokeratin subfamily' defined by peptide mapping, as well as a few acidic cytokeratins such as the epidermis-specific cytokeratins Nos. 10 and 11 and the more widespread cytokeratin No. 18. This antibody reacts specifically with a wide variety of epithelial tissues and cultured epithelial cells, in agreement with previous findings that at least one polypeptide of the basic cytokeratin subfamily is present in all normal and neoplastic epithelial cells so far examined. The antibody also reacts with corresponding cytokeratin polypeptides in a broad range of species including man, cow, chick, and amphibia but shows only limited reactivity with only a few rodent cytokeratins. The value of this broad-range monoclonal antibody, which apparently recognizes a stable cytokeratin determinant ubiquitous in human epithelia, for the immunohistochemical identification of epithelia and carcinomas is discussed.

Animals↗

PubMed1982