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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↗
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↗
PubMed1979

The participation of alpha-actinin in the capping of cell membrane components.

By means of double fluorescence staining experiments, intracellular alpha-actinin was found to accumulate under caps and patches induced in several cells by a variety of ligands. This phenomenon was demonstrated in lymphocytes and lymphoma cells treated with anti-H-2 sera; spleen lymphocytes treated with concanavalin A or anti-immunoglobulin antibodies, and VSV-infected mouse fibroblast line MC57 treated with antiserum against viral antigens. It occurred during both rapid and slow capping processes, and could be obtained by either direct or indirect ligand-induced redistribution. These observations were carried out on whole cells. For other cytoskeletal proteins such as filamin, tropomyosin and myosin, a similar accumulation under caps was not readily apparent using whole cell mounts, although earlier experiments with frozen-sectioned cells had shown such an enrichment of myosin (as well as actin). The enrichment of alpha-actinin under the clustered surface molecules was already apparent in early stages (patching) of the capping process, with or without 10 mM sodium azide present. Prolonged incubation of the cells with the different ligands resulted in endocytosis of the ligand-receptor complex. alpha-Actinin was not associated with the inernalized complex, however, suggesting that it may dissociate from the patched or capped surface structures at some stage during endocytosis.

Actinin↗
PubMed1979

Immunocytochemical localization of alpha-actinin in intestinal epithelial cells.

alpha-Actinin was localized in chicken intestinal epithelial cells by immunofluorescence and immunoferritin labeling of thin frozen sections. Most of the label of the brush border was confined to the terminal web area. The label there was concentrated mainly along the "roots" of the microvilli core microfilaments and in the vicinity of the zonula adherens. In the latter structure, the narrow electron-dense zones adjacent to the cell membranes, however, were not significantly labeled. This suggests that alpha-actinin does not mediate directly the association of the transverse terminal web microfilaments to the membrane at the zonula adherens. Sparse ferritin labeling was found near the tight junction, whereas the staining associated with the spot desmosome was negligible. The microvilli were not significantly labeled by either immunofluorescence or immunoferritin staining unless the sections were previously treated with detergent. Moreover, alpha-actinin (or a structurally related protein) was not detected in preparations of purified microvillar vesicles, suggesting the possibility that the alpha-actinin staining in the microvilli may be an artificial due to its translocation by the detergent from the terminal web onto the microvilli. The possible roles of alpha-actinin in the organization and function of the brush border are discussed.

Actinin↗
PubMed1979

Selective and unidirectional membrane redistribution of an H-2 antigen with an antibody-clustered viral antigen: relationship to mechanisms of cytotoxic T-cell interactions.

We have studied the co-redistribution of vesicular stomatitis virus (VSV) antigen and of individual H-2 antigens on the surfaces of mouse cells, and in parallel we have also used these VSV-infected cells as targets in cytotoxic T-cell killing experiments. Antibody-induced patching and capping of the VSV antigen caused an extensive co-patching and co-capping of the H-2Kb antigen but not of the H-2Db antigen. In reciprocal experiments, the antibody-induced patching of the H-2Kb or H-2Db antigen did not result in a co-patching of the VSV antigen. Radioimmunoassays showed that the relative numbers of H-2Kb, H-2Db, and VSV antigens on the surfaces of the cells exhibiting such nonreciprocal co-redistributions were closely similar. Furthermore, the H-2 restricted cytotoxic T-cell lysis of these target cells showed a marked preference for H-2Kb compared to H-2Db compatibility. We propose that the VSV and H-2 antigens are molecularly independent entities in the unpreturbed target cell membrane but that the antibody-induced clustering of the VSV antigen causes a selective and unidirectional co-redistribution (which we designate as syn-capping) of H-2Kb with the VSV antigen clusters. It is suggested that such a T-cell-induced syn-capping process involving an antigen and an H-2 molecule on the target cell may play a critical role in the mechanism of cytotoxic T-cell killing.

Antibodies, Viral↗
PubMed1979

Enzyme replacement in Tay-Sachs disease.

Enzyme replacement therapy was attempted with two Tay-Sachs-diseased individuals--a 14-month-old child and a 7-week-old infant. Treatment consisted of repeated weekly intrathecal injections of pure hexosaminidase A. Injection of this enzyme resulted in almost complete disappearance of GM2 from the serum, but did not bring about dissolution of the GM2 membranous cytoplasmic bodies in the brain, as detected by electronmicroscopy. Both patients tolerated the treatment without apparent clinical complications, but no clear-cut improvement was noted as a result of prolonged injections of hexosaminidase A. Since this treatment was initiated in both an advanced stage and a very early stage of the disease, we conclude that enzyme replacement treatment by this route is not beneficial for patients with Tay-Sachs disease.

Biopsy↗
PubMed1979

The use of antibody-coated liposomes as a target cell model for antibody-dependent cell-mediated cytotoxicity.

A simple model system was developed for antibody-dependent cell-mediated cytotoxicity (ADCC) using antibody-coated synthetic membranes (liposomes) as a target cell model. A synthetic hapten, dinitrophenyl-phosphatidylethanolamine (DNP-PE), was incorporated into fluorophore-quencher-loaded liposomes and the latter were coated with pure anti-DNP antibodies. Normal spleen lymphocytes were capable of binding and subsequently lysing these liposomes. This process is dependent upon the presence of an intact (Fc-containing) IgG molecule and independent of exogenous serum complement. The effector lymphocytes are nylon non-adherent, devoid of Thy-1 antigen and present in nude mice, suggesting an identity with K (Fc receptor positive) lymphocytes. These studies indicate that liposomes may be used as a model to study the requirements for the binding and lysis of target cells in this cell-mediated cytotoxic system.

Animals↗
PubMed1979

Normal adult with absent HEX A: immunoreactive HEX A is present.

Fibroblasts from a normal adult with absent hexosaminidase A (HEX A) activity were demonstrated to possess immunoreactive HEX A as measured by GM2 beta-D-N-acetylgalactosaminidase activity which precipitated with specific anti-HEX A antibodies. Possible explanations for the molecular defect are presented.

Antibodies↗
PubMed1978

Biochemical and immunochemical characterization of hexosaminidase P.

Hexasaminidase P, the main isozyme of hexosaminidase in pregnancy serum, was isolated and purified 600--700-fold by a two-step purification procedure--affinity chromatography on Sepharose-bound epsilon-aminocaproyl-N-acetylglucosylamine, followed by ion-exchange chromatography on DEAE-cellulose. The purified enzyme was subjected to biochemical and immunochemical analysis. Its catalytic property, namely, kinetic behavior, is similar to that of the major isozymes of hexosaminidase, A and B. However, it differs from these isozymes in its electrophoretic mobility and in its apparent molecular weight which is around 150 000 compared with 100 000 of the A and B isozymes. Immunochemical analysis indicates that the P isozymes is antigenically cross-reactive with both A and B isozymes, but it does not contain the A-specific antigenic determinants, and exhibits identical antigenic specificity to hexasaminidase B. Two possible structures are suggested that are compatible with the experimental data: (a) a hexosaminidase B like structure with higher extent of glycosylation; (b) a hexameter of beta chain, possibly arranged as three beta2 subunits.

Chemical Phenomena↗
PubMed1978

Antibodies to ganglioside GM1 induce mitogenic stimulation and cap formation in rat thymocytes.

Antibodies towards the ganglioside GM1 [galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyglucosyl ceramide] stimulated DNA synthesis in rat thymocytes. No mitogenic stimulation was observed with the monomeric Fab fragment of anti-GM1, suggesting that cross-linking of the gangliosides or associated components was required for activation by these antibodies. Incubation of thymocytes with anti-GM1 and fluorescein-labeled anti-rabbit IgG at 0 degree C resulted in uniform ring-like or patchy staining that developed into a pronounced cap upon elevation of temperature. The cap had a characteristic uropod form, enriched with intracellular organelles. Sodium azide and cytochalasin B completely inhibited cap formation, while colchicine was without effect. These results imply a possible direct or indirect association between surface gangliosides and submembraneous cytoskeletal assemblies that control modulation of these surface components and may transmit stimuli to the interior of the cell.

Animals↗