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  • 1
    Online Resource
    Online Resource
    Enhancement of toxicity of antitransferrin receptor antibody-Pseudomonas exotoxin conjugates by adenovirus.
    Proceedings of the National Academy of Sciences ; 1983
    In:  Proceedings of the National Academy of Sciences Vol. 80, No. 13 ( 1983-07), p. 4134-4138
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 80, No. 13 ( 1983-07), p. 4134-4138
    Abstract: Cytotoxic conjugates were constructed by chemically coupling Pseudomonas exotoxin to antitransferrin receptor antibodies. Toxicity of these conjugates, due to entry via the transferrin receptor, was enhanced 100- to 300-fold in the presence of adenovirus. By electron microscopy and immunofluorescence it was determined that antitransferrin receptor antibodies and the conjugates derived from them entered cells from coated pits into receptosomes. We believe that the enhanced toxicity resulted when adenovirus and the toxin conjugates were internalized into the same receptosomes. In the process of infection, adenovirus enters cells and brings about a virus-mediated disruption of receptosomes; and this disruption can liberate many more toxin molecules into the cytosol than is possible in the absence of virus.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.80.13.4134
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1983
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 2
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    Online Resource
    Immunohistochemical localization in normal tissues of different epitopes in the multidrug transport protein P170: evidence for localization in brain capillaries and crossreactivity of one antibody with a muscle protein.
    SAGE Publications ; 1989
    In:  Journal of Histochemistry & Cytochemistry Vol. 37, No. 2 ( 1989-02), p. 159-164
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 37, No. 2 ( 1989-02), p. 159-164
    Abstract: Using peroxidase immunohistochemistry, we examined the distribution of P170, a multidrug transport protein, in normal tissues by use of two different monoclonal antibodies (MAb). MAb MRK16 is a MAb that has been shown to react with an epitope in P170 located on the external face of the plasma membrane of multidrug-resistant human cells. MAb C219 has been shown to react with P170 in many mammalian species, and detects an epitope located on the cytoplasmic face of the plasma membrane. Using MRK16, we have previously described the localization of P170 on the bile canalicular face of hepatocytes, the apical surface of proximal tubular cells in kidney, and the surface epithelium in the lower GI tract in normal human tissues. In this work, we report that MRK16 also detects P170 in the capillaries of some human brain samples. A similar pattern was found using MAb C219 in rat tissues. in addition, MAb C219 showed intense localization in selected skeletal muscle fibers and all cardiac muscle fibers in rat and human tissues. ATPase cytochemistry showed that these reactive skeletal muscle fibers were of the type I (slow-twitch) class. Other additional sites of C219 reactivity in rat tissues were found in pancreatic acini, seminal vesicle, and testis. Electrophoretic gel immunoblotting showed two protein bands reactive with MAb C219. In liver, MAb C219 reacted with a approximately 170 KD band. In skeletal and cardiac muscle, MAb C219 reacted with a approximately 200 KD band which migrated in the same position as myosin. This band also reacted with an antibody to skeletal muscle myosin. This result suggests that C219 may crossreact with the heavy chain of muscle myosin in cardiac and skeletal muscle. Because MAb C219 reacts with proteins other than P170, it should be used with caution in studies of multidrug resistance.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/37.2.2463300
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1989
    detail.hit.zdb_id: 1421306-0
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  • 3
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    Online Resource
    Pre-lysosomal divergence of alpha 2-macroglobulin and transferrin: a kinetic study using a monoclonal antibody against a lysosomal membrane glycoprotein (LAMP-1).
    SAGE Publications ; 1988
    In:  Journal of Histochemistry & Cytochemistry Vol. 36, No. 4 ( 1988-04), p. 391-400
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 36, No. 4 ( 1988-04), p. 391-400
    Abstract: We have used electron microscopic immunocytochemistry to compare the distribution of LAMP-1, a marker for lysosomal membranes, with the intracellular localization of alpha 2-macroglobulin (alpha 2-M) and transferrin at various time points after their endocytosis into cultured NIH 3T3 cells. The purposes of this study were (a) to determine how soon endocytic ligands reach lysosomal organelles, (b) to examine whether the intermediate endocytic vesicles gained lysosomal markers gradually or in a precipitous, discrete event, and (c) to examine the relationship, if any, between the pathway of recycling ligands and lysosomes. At early time points (0-5 min) after initiation of endocytosis, most structures containing alpha 2-M labeled with colloidal gold (receptosomes) were not labeled by anti-LAMP-1 detected using ferritin bridge or peroxidase immunocytochemistry. At late time points (greater than or equal to 15 min), the structures containing alpha 2-M (lysosomes) were strongly labeled by anti-LAMP-1. In contrast, transferrin that was directly labeled with ferritin was mostly located in LAMP-1-negative structures at all time points studied. The proportion of alpha 2-M-gold containing vesicles strongly labeled for LAMP-1 roughly paralleled the proportion of alpha 2-M-gold-containing structures positive for cytochemically detectable acid phosphatase. Our data indicate that ligands such as transferrin that are internalized through coated pits and receptosomes, but not delivered to lysosomes, do not traverse a lysosomal organelle compartment as marked by LAMP-1 content. Ligands such as alpha 2-M that are destined for lysosomal delivery reach a LAMP-1-positive organelle compartment only after they traverse LAMP-1-negative, non-lysosomal vesicles previously described as receptosomes.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/36.4.2450119
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1988
    detail.hit.zdb_id: 1421306-0
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  • 4
    Online Resource
    Online Resource
    Ultrastructural localization of tubulin in cultured fibroblasts.
    SAGE Publications ; 1980
    In:  Journal of Histochemistry & Cytochemistry Vol. 28, No. 5 ( 1980-05), p. 453-461
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 28, No. 5 ( 1980-05), p. 453-461
    Abstract: Antibodies to barin tubulin were created in rabbits and used to localize tubulin in cultured fibroblasts. Cells were fixed and permeabilized using the EGS procedure (Willingham et al: J Cell Biol 79:256a, 1978). Tubulin was localized and quantified using a ferritin-bridge labeling method. Antibody localization was generally confined to morphologically identifiable microtubules, with a smaller concentration in a diffuse cytoplasmic distribution. Following treatment with colchicine, morphologically identifiable microtubules disappeared and the amount of diffuse localization in the cytosol increased. However, a significant concentration of tubulin was found associated with the microfilament mat under the plasma membrane after colchicine treatment, whereas in untreated cells, very little tubulin was found in the microfilament mat. These results demonstrate that tubulin is a component of microtubules and that colchicine treatment results in an association of this tubulin with microfilaments.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/28.5.6991592
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1980
    detail.hit.zdb_id: 1421306-0
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  • 5
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    Online Resource
    The multidrug transporter: rapid modulation of efflux activity monitored in single cells by the morphologic effects of vinblastine and daunomycin.
    SAGE Publications ; 1989
    In:  Journal of Histochemistry & Cytochemistry Vol. 37, No. 7 ( 1989-07), p. 1141-1145
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 37, No. 7 ( 1989-07), p. 1141-1145
    Abstract: Double-label fluorescence microscopy was used to demonstrate the efflux activity of the multidrug transporter in single cultured cells. NIH3T3 cells expressing a transfected MDR1 gene (NIH3T3-MDR) were treated with vinblastine or daunomycin. The accumulation of vinblastine was monitored by examining the morphology of tubulin in cells, using immunofluorescence. Overnight treatment of drug-sensitive cells caused disassembly of microtubules and formation of paracrystals; the absence of vinblastine effects was evident by the presence of intact microtubules. Daunomycin accumulation was detected in nuclei using the inherent fluorescence of the drug with rhodamine epifluorescence microscopy. Drug efflux in multidrug-resistant cells was inhibited with verapamil. When multidrug-resistant cells were treated overnight in vinblastine, an effect of 0.5 microM vinblastine on microtubules was seen only in the presence of verapamil. Similarly, when cells were treated with daunomycin, this drug accumulated in nuclei only when verapamil was present. When cells incubated with vinblastine and verapamil were washed free of drugs, they did not accumulate daunomycin in a subsequent incubation, indicating that the multidrug transporter was still active; this occurred even though the morphologic effects of vinblastine persisted. Cells incubated with vinblastine alone showed an immediate inhibition of efflux activity when verapamil was subsequently added with daunomycin. These results show that the efflux activity of the multidrug transporter can be rapidly manipulated by agents such as verapamil, despite a prior history of drug treatment, and that the effects of inhibition of the transporter are rapidly reversible.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/37.7.2567301
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1989
    detail.hit.zdb_id: 1421306-0
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  • 6
    Online Resource
    Online Resource
    Ultrastructural immunocytochemical localization of the phosphomannosyl receptor in Chinese hamster ovary (CHO) cells.
    SAGE Publications ; 1983
    In:  Journal of Histochemistry & Cytochemistry Vol. 31, No. 1 ( 1983-01), p. 1-11
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 31, No. 1 ( 1983-01), p. 1-11
    Abstract: Using ultrastructural immunocytochemistry and antibodies directed against bovine liver phosphomannosyl (PM) receptor, we have localized the receptor in Chinese hamster ovary (CHO) cells. The majority of the receptor was found within the cell. Only a small fraction of the receptor was found on the surface and most of it was clustered in coated pits. Because these cells contain endogenous ligands for the receptor, it was not possible to determine if this clustered state was dependent on occupancy of the receptor. The bulk of the cell's receptor was found in the endoplasmic reticulum, nuclear envelope, and in the Golgi system. Most of the Golgi localization was associated with peripheral Golgi elements, suggesting a possible concentration of receptor in GERL. Very little receptor was found associated with mature lysosomes. PM receptor was also localized in structures that were identified as receptosomes by the presence of alpha 2-macroglobulin (alpha 2M)-gold, a ligand previously shown to enter CHO cells by the coated pit-receptosome pathway. This finding is consistent with the notion that during receptor-mediated endocytosis, receptors accompany ligand from the coated pit into the receptosome. The observation that the majority of the receptor was found in the endoplasmic reticulum and structures similar to GERL raises the possibility that the PM receptor plays an important role in compartmentalization of lysosomal enzymes in the GERL system.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/31.1.6300218
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1983
    detail.hit.zdb_id: 1421306-0
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  • 7
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    Online Resource
    Activity of the multidrug transporter results in alkalinization of the cytosol: measurement of cytosolic pH by microinjection of a pH-sensitive dye.
    SAGE Publications ; 1990
    In:  Journal of Histochemistry & Cytochemistry Vol. 38, No. 5 ( 1990-05), p. 685-690
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 38, No. 5 ( 1990-05), p. 685-690
    Abstract: Multidrug-resistant cells contain a plasma membrane efflux pump, the multidrug transporter, which actively expels certain hydrophobic drugs from the cytosol to the cell exterior. These drugs are usually positively charged at physiological pH. Because one might predict that this efflux of positively charged molecules might deplete the cytosol of protons, raising the cytosolic pH, we examined the cytosolic pH of multidrug-resistant cells directly using a pH-sensitive dye coupled to a membrane-impermeable molecule. The dye (SNARF), covalently coupled to 10,000 MW dextran, was mechanically microinjected into the cytosol of cultured multidrug-resistant mouse NIH3T3 cells which express the human multidrug transporter. The fluorescence emission of the dye in living cells was measured using epifluorescence microscopy at different wavelengths to provide a measure of the pH of the cytosolic environment. Multidrug-resistant cells had a higher cytosolic pH than drug-sensitive normal parental cells. As the pH of the culture medium was increased, normal cells maintained their cytosolic pH below 7.0, whereas the cytosolic pH of multidrug resistant cells rose. The difference in cytosolic pH between the two cell types was more than 0.2 pH units at an external culture medium pH of 8.2. Treatment with agents that inhibit multidrug transporter-mediated efflux, such as verapamil and vinblastine, essentially eliminated the elevation of cytosolic pH, presumably because they are good substrates for the pump which overwhelm its capacity to pump other materials. These results suggest that the multidrug transporter is indirectly a proton pump, and that cells may contain an endogenous substrate or substrates for this transporter in the absence of added drugs.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/38.5.1692055
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1990
    detail.hit.zdb_id: 1421306-0
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  • 8
    Online Resource
    Online Resource
    Role of a low-pH environment in adenovirus enhancement of the toxicity of a Pseudomonas exotoxin-epidermal growth factor conjugate
    American Society for Microbiology ; 1984
    In:  Journal of Virology Vol. 51, No. 3 ( 1984-09), p. 650-655
    Details
    In: Journal of Virology, American Society for Microbiology, Vol. 51, No. 3 ( 1984-09), p. 650-655
    Abstract: A conjugate of Pseudomonas exotoxin and epidermal growth factor (PE-EGF) inhibits proteins synthesis in KB cells, and this inhibition is increased by adenovirus. Protein synthesis inhibition is dependent on the amount of adenovirus and PE-EGF used and the time of incubation of cells with these agents. With 1 microgram of adenovirus and 0.5 micrograms of PE-EGF per ml, protein synthesis is inhibited about 80% in a 60-min experiment. Under these conditions neither adenovirus nor PE-EGF alone has any effect. In the presence of several weak bases or monensin, the enhancement of toxicity was substantially inhibited; half-maximal inhibition was achieved with 40 microM chloroquine, 10 mM ammonium chloride, 5 mM methylamine, 0.1 mM N-hexylamine and 1 microM monensin. At the concentrations employed, none of the inhibitors affected the amount of virus taken up or bound to the cell surface, and chloroquine had no effect on the amount of EGF taken up in 60 min. Chloroquine did not prevent the toxicity of the PE-EGF (5 micrograms/ml) alone. Because these compounds are known to elevate the pH in receptosomes, it seems likely that the acidification of the receptosome either enhances the lysis of the membrane by adenovirus or enhances some other step in the release of PE-EGF.
    Type of Medium: Online Resource
    ISSN: 0022-538X , 1098-5514
    URL: Article
    DOI: 10.1128/jvi.51.3.650-655.1984
    Language: English
    Publisher: American Society for Microbiology
    Publication Date: 1984
    detail.hit.zdb_id: 1495529-5
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  • 9
    Online Resource
    Online Resource
    Ultrastructural immunocytochemical localization of myosin in cultured fibroblastic cells.
    SAGE Publications ; 1981
    In:  Journal of Histochemistry & Cytochemistry Vol. 29, No. 11 ( 1981-11), p. 1289-1301
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 29, No. 11 ( 1981-11), p. 1289-1301
    Abstract: Nonmuscle myosin in the cytoplasm of cultured fibroblastic cells has been localized using light and electron microscopic immunocytochemistry. Antibodies to purified fibroblast myosin were produced in goat and rabbit and purified by affinity chromatography. Light microscopic immunofluorescence localization showed patterns similar to those previously published. Electron microscopic localization using the ethyldimethyl aminopropyl carbodiimide-glutaraldehyde-saponin (EGS) fixation-permeabilization procedure and the ferritin bridge localization method produced quantifiable localization in intracellular sites with well-preserved ultrastructural morphology. Myosin was found to be a major component of the cytosol. It was distributed diffusely with no preferential localization on membranous organelles. Myosin was found to be slightly concentrated on the surface of microfilament-containing structures, including the subplasmalemmal microfilament mat and stress fibers, occasionally with an interrupted periodicity. However, no myosin was found in surface ruffles or microvilli. Morphometric quantitation showed that the majority of the cell's myosin was in the cytosol. This location is compatible with myosin being a component of the microtrabecular lattice of the cytoplasmic ground substance. The concentration of myosin in association with microfilaments was only twice that of the cytosol. This interpretation must be somewhat tempered by the possibility that some myosin bound to tightly packed actin may be inaccessible. The significance of this distribution of myosin in cell function is discussed.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/29.11.7033361
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1981
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  • 10
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    Receptor-mediated endocytosis in cultured fibroblasts: cryptic coated pits and the formation of receptosomes.
    SAGE Publications ; 1981
    In:  Journal of Histochemistry & Cytochemistry Vol. 29, No. 9 ( 1981-09), p. 1003-1013
    Details
    In: Journal of Histochemistry & Cytochemistry, SAGE Publications, Vol. 29, No. 9 ( 1981-09), p. 1003-1013
    Abstract: Concentrative receptor-mediated endocytosis of many specific ligands by cultured fibroblasts occurs through the coated pit-receptosome pathway. The formation of receptosomes was studied using two impermeant electron-dense labels for the cell surface, ruthenium red and concanavalin A-horseradish peroxidase. These studies show that at 4 degrees C, virtually all coated structures near the plasma membrane are in communication with the cell surface, and are not isolated coated vesicles. On warming cells to 37 degrees C for only 1 minute, a major portion of these structures become cryptic, that is, not labeled by these surface markers. However, on cooling cells immediately back to 4 degrees C, virtually all of these structures are again in communication with the surface. Many images showed that membrane of these cryptic pits to be continuous with the cell surface when caught in the appropriate plane of section; often there was a very narrow entrance that excluded extracellular label. At 37 degrees C, receptosomes could be occasionally seen forming as an invagination of membrane adjacent to the coated region. Mechanisms by which receptosomes may form and other evidence demonstrating the failure of coated pits to pinch off to form isolated coated vesicles during endocytosis are discussed.
    Type of Medium: Online Resource
    ISSN: 0022-1554 , 1551-5044
    URL: Article
    DOI: 10.1177/29.9.6169759
    Language: English
    Publisher: SAGE Publications
    Publication Date: 1981
    detail.hit.zdb_id: 1421306-0
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