Using NMR chemical shift imaging to monitor swelling and molecular transport in drug-loaded tablets of hydrophobically modified poly(acrylic acid): methodology and effects of polymer (in)solubility.
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Elimination of permeability mutants from selections for drug resistance in mammalian cells.
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Chinese hamster ovary (CHO) cells exhibit increased sensitivity to a wide variety of microtubule inhibitory drugs when verapamil is present in the growth medium. The extent of this increased sensitivity is drug specific: some drugs such as taxol and vinblastine respond greatly to the presence of verapamil, whereas other drugs such as griseofulvin respond very poorly. For the majority of drugs examined, however, a 2- to 10-fold increase in drug sensitivity is observed in the presence of verapamil at 5 micrograms/ml. The effects of verapamil are even more dramatic when drug-resistant mutant cells with a presumed alteration in membrane permeability are examined. In the presence of appropriate levels of verapamil, these mutants demonstrate a level of drug sensitivity comparable to that of the wild-type parental cells. Drug-resistant cells from similar selections but with well-defined alterations in alpha- or beta-tubulin and no evidence of alterations in membrane permeability, however, continue to exhibit increased resistance to the selecting drug even in the presence of verapamil. These studies support the conclusion that verapamil affects the membrane permeability to or transport of a wide variety of hydrophobic drugs. In addition, we have used this information to devise selections that virtually eliminate the isolation of drug-resistant permeability mutants. This methodology should be generally applicable to genetic studies of drug action that are complicated by the isolation of large numbers of mutants with permeability alterations. (+info)
Succinyl concanavalin A stimulates and antimicrotubular drugs inhibit the synthesis of a brain-specific protein in rat glial cells.
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The relative synthesis of the brain-specific s100 protein increased as clonal rat glial cells, C6, progressed from logarithmic to stationary growth in monolayer culture. Drugs that disrupt microtubules, such as colchicine, vinblastine, Colcemid, and podophyllotoxin, inhibited the relative synthesis of S100 protein in stationary cultures. Colchicine (0.1 muM) caused a 50% inhibition of the relative synthesis of S100 protein whereas lumicolchicine,an isomer of colchicine that does not disrupt the microtubular system, had no effect. Succinylated concanavalin A (500 mug/ml) increased relative synthesis in logarithmic but not stationary cultures. These results suggest that signals inducing an increase in the relative synthesis of S100 protein in stationary cultures are transmitted intracellularly from the cell membrane by the microtubular network. (+info)
Action of anticytoskeletal compounds on in vitro cytopathic effect, phagocytosis, and adhesiveness of Trichomonas vaginalis.
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The cytopathic effects of Trichomonas vaginalis treated with inhibitory concentrations of anticytoskeletal compounds (mebendazole, griseofulvin, colchicine, taxol, and cytochalasin B) were studied in mouse CLID fibroblast cultures. The evaluation, at different times, of cell numbers and morphological alterations showed that cytopathic effect was considerably reduced when protozoa were pretreated with mebendazole and griseofulvin, whereas colchicine, taxol, and cytochalasin B had less effect. Furthermore, treatment with mebendazole, griseofulvin, and colchicine decreased adhesiveness of the protozoan, whereas treatment with cytochalasin B and colchicine completely inhibited its phagocytic activity. From these results it may be concluded that alterations induced in the trichomonal cytoskeleton may affect its adhesiveness and its in vitro cytopathic effect, but there is no direct correlation between protozoan phagocytosis and its in vitro pathogenic effect. (+info)
Interaction of 7-acetyltaxol with different tubulin assemblies.
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Equilibrium microdialysis of [3H]acetyltaxol against different tubulin assemblies showed that: (i) the binding capacity of tubulin does not depend on the temperature; (ii) two classes of 'polymers' exist, with respect to Ac-taxol binding. Some of them (plaques, complex cylinders induced with some polycations and spirals made with rhazinilam) bound Ac-taxol, as do normal microtubules. In contrast, spirals formed with vinblastine and griseofulvin, rings made with polycations and complex cylinders induced with spermine do not bind Ac-taxol as is the case with free tubulin. (+info)
Formation and involution of Mallory bodies ("alcoholic hyalin") in murine and human liver revealed by immunofluorescence microscopy with antibodies to prekeratin.
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Antibodies raised against prekeratin intensely and specifically stain, in immunofluorescence microscopy, Mallory bodies ("alcoholic hyalin") present in livers of human alcoholics and griseofulyin-treated mice. The high sensitivity of this method allows the identification of small distinct cytoplasmic structures that are observed during early stages of Mallory body formation, especially frequent in the perinuclear cytoplasm, as well as during stages of Mallory body disintegration and disappearance, such as after withdrawal of the drug. In the latter situation, the prekeratin-containing small particles exhibit a characteristic pattern of arrangement in the hepatocyte periphery. Electron microscopy illustrates that such small bodies are heap-like aggregates of typical Mallory body filaments. Immunofluorescence studies with antibodies to isolated prekeratin polypeptides from bovine hoof or muzzle epidermis show that Mallory body filaments, in particular those in human liver, are immunologically more closely related to prekeratin of tonofilaments from living epidermal cells (stratum spinosum). The data indicate that Mallory bodies contain a pathologic form of prekeratin-like material. They also suggest that disorders of cytoskeletal structures of the intermediate-sized filament class are associated with specific diseases and can be visualized and characterized by immunofluorescence microscopy by using antibodies to constitutive proteins of such filaments. (+info)
Microtubule configurations during fertilization, mitosis, and early development in the mouse and the requirement for egg microtubule-mediated motility during mammalian fertilization.
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Microtubules forming within the mouse egg during fertilization are required for the movements leading to the union of the sperm and egg nuclei (male and female pronuclei, respectively). In the unfertilized oocyte, microtubules are predominantly found in the arrested meiotic spindle. At the time for sperm incorporation, a dozen cytoplasmic asters assemble, often associated with the pronuclei. As the pronuclei move to the egg center, these asters enlarge into a dense array. At the end of first interphase, the dense array disassembles and is replaced by sheaths of microtubules surrounding the adjacent pronuclei. Syngamy (pronuclear fusion) is not observed; rather the adjacent paternal and maternal chromosome sets first meet at metaphase. The mitotic apparatus emerges from these perinuclear microtubules and is barrel-shaped and anastral, reminiscent of plant cell spindles; the sperm centriole does not nucleate mitotic microtubules. After cleavage, monasters extend from each blastomere nucleus. The second division mitotic spindles also have broad poles, though by third and later divisions the spindles are typical for higher animals, with narrow mitotic poles and fusiform shapes. Colcemid, griseofulvin, and nocodazole inhibit the microtubule formation and prevent the movements leading to pronuclear union; the meiotic spindle is disassembled, and the maternal chromosomes are scattered throughout the oocyte cortex. These results indicate that microtubules forming within fertilized mouse oocytes are required for the union of the sperm and egg nuclei and raise questions about the paternal inheritance of centrioles in mammals. (+info)