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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 12 (1989), S. 157-168 
    ISSN: 0886-1544
    Keywords: axolotl ; cell differentiation ; cell shape ; cytoskeleton ; nucleated erythrocyte ; microtubule ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The spleen of Ambystoma mexicanum (axolotl) larvae develops as a closed sac containing differentiating nucleated erythrocytes, and is typically isolated from the general circulation for about 10 days post-hatching. Beginning 3-4 days posthatching, it can be removed intact for examination of the morphology and cytoskeletal structure of the erythropoietic cells. In the smallest (earliest) spleens, spheroidal cells predominate, while older ones contain a preponderance of cells exhibiting the flattened elliptical morphology typical of all non-mammalian vertebrate erythrocytes. Most striking in the splenic erythroid population are cells with singly or doubly pointed morphology. Though common in the developing spleen and circulation of young larvae, pointed cells are less frequently encountered in the circulation of older larvae, indicating that they are intermediate stages in the differentiation of spheroids to flattened ellipsoids. This is supported by structural observations on cytoskeletons prepared from the splenic cells. Incomplete singly and doubly pointed marginal bands of microtubules are observed, many of which contain a pair of centrioles within or close to a pointed end, suggestive of organizing center function. The observations are consistent with a sequence of changes in cell morphology from spherical to doubly pointed to singly pointed to flattened ellipse, causally linked to stages of marginal band biogenesis.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 8 (1987), S. 165-173 
    ISSN: 0886-1544
    Keywords: erythrocytes ; brain ; vimentin ; neurofilaments ; desmin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have demonstrated a differential association between two types of spectrin, from erythrocytes and brain, with two types of intermediate filaments, vimentin filaments and neurofilaments. Electron microscopy showed that erythrocyte spectrin promoted the binding of vimentin filaments to red cell inside-out vesicles via lateral associations with the filaments. In vitro binding studies showed that the association of spectrin with vimentin filaments was apparently saturable, increased with temperature, and could be prevented by heat denaturation of the spectrin. Comparisons were made between erythrocyte and brain spectrin binding to both vimentin filaments and neurofilaments. We found that vimentin filaments bound more erythrocyte spectrin than brain spectrin, while neurofilaments bound more brain spectrin than erythrocyte spectrin. Our results show that both erythroid and nonerythroid spectrins are capable of binding to intermediate filaments and that such association may be characterized by differential affinities of the various types of spectrin with the several classes of intermediate filaments present in cells. Our results also suggest a role for both erythroid and nonerythroid spectrins in mediating the association of intermediate filaments with plasma membranes or other cytoskeletal elements.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0886-1544
    Keywords: cytoskeleton ; cell morphogenesis ; immunofluorescence ; antimyosin monoclonal antibody ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A monoclonal antibody, CC212, raised against ciliated cortices of quail oviduct cells and characterized as an antimyosin of smooth muscle and nonmuscle cells, was shown to specifically label a regular cortical network in Paramecium and to recognize two Triton X-100-insoluble polypeptides at 130 and 50 kDa. However, no evidence was obtained that these polypeptides are related to myosin.An immunofluorescence study and ultrastructural immunogold localization allowed us to identify the CC212-decorated material as a component of the outer lattice, a submembrane cytoskeletal network which runs along the top of the ridges visible by scanning electron microscopy and delineates the periphery of each cortical unit. The dynamics of the outer lattice during the cell cycle was studied by immunofluorescence and it was found that the outer lattice growth is achieved without disruption of the preexisting meshes by longitudinal elongation and additon of new transverse partitions. A striking disorganization of the outer lattice was observed in a thermosensitive mutant primarily altered in basal body duplication. These observations suggest possible functions of the outer lattice and demonstrate the interdependence of basal body duplication, surface growth, and outer lattice remodelling.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 124 (1985), S. 275-282 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The biochemistry of human B lymphocyte differentiation to plasma cells is incompletely understood. L-glutamine appears to be required for both lymphoblastic transformation and plasma cell formation in pokeweed-mitogenstimulated human peripheral blood mononuclear cell cultures. Cells cultured with pokeweed mitogen in glutamine-deficient RPMI-1640 with 10% heat-inactivated and dialyzed fetal bovine serum were unable to incorporate 3H-thymidine or undergo morphologic lymphoblastic transformation assessed at 72 hours. However, 3H-thymidine incorporation could be maximally restored with as little as 0.08 mM L-glutamine or by using nondialyzed heat-inactivated fetal bovine serum, containing approximately .1 mM L-glutamine. In subsequent cultures, using glutamine-deficient RPMI-1640 with 10% nondialyzed heat-inactivated fetal bovine serum, lymphoblastic transformation was equivalent with or without additional L-glutamine supplementation. However, only cultures with 2 mM L-glutamine supplementation underwent plasma cell differentiation as assessed by cytoplasmic staining with fluorescein-conjugated anti-immunoglobulin. When the kinetics of cellular immunoglobulin synthesis and secretion were analyzed by 3H- leucine incorporation into immunoglobulin, synthesis was 2-5 fold greater, and secretion 3-10-fold greater in cell cultures with 2 mM L-glutamine supplementation. By electron microscopy, only the glutamine-supplemented cells showed development of rough endoplasmic reticulum consistent with active immunoglobulin production. L-glutamine supplementation had no apparent effect on cell recovery, viability, % B cells, % T cells, % monocytes, or % helper and suppressor T cells. Thus, L-glutamine is essential for both lymphoblastic transformation and plasma cell differentiation. Future investigation of the selective nutritional requirements of cultured cells should yield further insights into the biochemical control of immune cell differentiation and function.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 124 (1985), S. 96-106 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: MDCK cells maintained on extracellular matrix (ECM)-coated dishes and exposed to Dulbecco's modified Eagle's medium (DME) supplemented with transferrin and either high-density lipoproteins (HDLs) or phosphatidyl choline (PC) liposomes have a growth rate and final cell density similar to those of cultures exposed to serum-supplemented DME. When MDCK cells are exposed to a medium consisting of a mixture (1:1) of DME and F12 medium (D/F), the addition of transferrin (10 μg/ml) alone supports cell growth and the presence of HDLs or PC liposomes is no longer required. MDCK cells exposed to D/F medium supplemented with transferrin can be passaged for more than 50 generations in total absence of serum. The F12 components that support growth in the absence of HDLs or PC liposomes are biotin (which is absent in DME) and choline (which is present in insufficient concentration in DME). Supplementation of DME with transferrin, biotin (3.6 ng/ml), and choline (10 μg/ml) allows optimal growth of MDCK cells and permits serial propagation through more than 50 generations. The growth requirement of MDCK cells for HDLs or PC liposomes can therefore be replaced by adequate concentrations of biotin and choline. The widely observed fact that a combination of DME/F12 medium is more effective than DME alone in supporting cell growth may be due in part to the lack of biotin and suboptimal choline concentration in DME.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 133 (1987), S. 75-81 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Efficient expression of the human c-Ha-ras1 gene requires sequences 3′ of those specifying the polyadenylation of its transcripts. These sequences can stimulate the expression of heterologous genes in a manner largely independent of position and orientation, arguing that they possess a transcriptional enhancing activity that regulates the c-Ha-ras1 promoter. As this element is associated with a repetitive domain that is highly polymorphic, it is possible that the activity of this enhancer is variable within the human population.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 122 (1985), S. 98-104 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Glycolytic enzyme activity is significantly (P 〈 0.05) induced between 24 and 48 hours of incubation in phytohemagglutinin-stimulated human lymphocytes. Nonstimulated cultured cells do not show this induction although these cells have an approximate daily doubling of thymidine incorporation. Maximal glycolytic enzyme activity is reached between 96 and 120 hours of culture in stimulated cells (3.5-fold increase) and maintained until at least 168 hours. There is no significant induction of the hexosemonophosphate shunt or the TCA cycle during seven-day transformation. Induction of glucose utilization becomes significantly (P 〈 0.05) greater in stimulated as compared to nonstimulated cultures between 48 and 72 hours of culture and is significantly elevated for at least an additional 96 hours. There is a 17% increase in total protein in the stimulated cells after 24 hours of culture and higher levels of protein content are then maintained over the control. Thymidine incorporation is significantly greater in stimulated cells from 24-144 hours of culture but is not significantly different from the nonstimulated cells at 168 hours (P = 0.98) although glycolytic enzyme activity remains elevated in the stimulated cells. There is a greater enzyme induction of the latter phase of glycolysis during transformation and this phenomenon continues in extended cultures. Increases in glycolytic enzyme activity during mitogenesis appear to be an intrinsic phenomenon independent of cell proliferation and glucose transport. The mitogen-induced increase in the activity of the glycolytic enzymes accompanies blastogenesis and the sustained elevated activity of these enzymes appears to be related to the high metabolic rate of transformed cells.
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  • 8
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The antigen-mediated induction of heparanase, an endoglycosidase capable of degrading heparan sulfate from the subendothelial extracellular matrix (ECM), was investigated in a rat T lymphocyte cell line reactive against the basic protein (BP) of myelin. We found that nonactivated T lymphocytes could be induced to express heparanase activity following exposure to soluble but not to ECM-bound BP. The induction of heparanase was immunologically specific and indpendent of the presence of syngeneic or allogeneic antigen presenting cells (APC). However, anti-IA antibodies inhibited heparanase expression. Soluble BP induced secretion of heparanase into the culture medium within minutes, despite inhibition of protein synthesis. Cell lysates of T lymphocytes contained heparanase activity. Thus, T lymphocytes secrete a preformed heparanase following exposure to specific antigen.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 137 (1988), S. 577-582 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Pentoxifylline is used clinically for the treatment of intermittent claudication. It is believed to exert its effect by altering the rheologic properties of blood. The cytoskeleton plays an important role in the maintenance of cell structure and function. In particular, alterations in the state of actin seem to play an important role in cell motility. Therefore, we examined the effect of pentoxifylline on the actin state in human polymorphonuclear leukocytes (PMN) and mononuclear cells. Pentoxifylline (10 mM final concentration) decreased F-actin content in both PMN and mononuclear cells. Pentoxifylline also inhibited concanavalin A-induced capping in PMN and mononuclear cells. Similarly, surface immunoglobulin capping in B lymphocytes was also inhibited. Pretreatment of cells with pertussis toxin did not inhibit pentoxifylline-induced decrease in F-actin, suggesting pentoxifylline does not act through pertussis toxin-sensitive G-proteins. Dibutyryl cyclic AMP failed to show any significant effect on the F-actin content in PMN. Therefore, the effect of pentoxifylline cannot be attributed to changes in cyclic AMP levels. Chemotactic peptide-induced actin polymerization was unaffected in PMN when expressed as percent change in F-actin. The observations reported here suggest that the rheological effects of pentoxifylline might be due to its effects on the actin state in the cellular elements of the blood. Further studies on the mechanism of action of pentoxifylline on actin state in leukocytes will prove useful in delineating the physiological mechanisms regulating actin state in leukocytes.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 123 (1985), S. 431-434 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A mutant clone (NT-1) of a T-cell lymphoma was selected for its ability to grow in HAT medium (hypoxanthine, aminopterin and thymidine) in the presence of the nucleoside transport inhibitor P-nitrobenzyl-6-mercaptoinosine (NBMI). NT-1 cells contain half the number of NBMI binding sites present on the parental S49 cells and are partially able to transport nucleosides in the presence of the transport inhibitor (NBMI). These observations suggest that the mutant cells are heterozygous for nucleoside transport proteins and contain two types of transport proteins: the first protein can both bind and is inhibited by NBMI similar to the wild type phenotype, and the second is an altered protein. The altered transport protein apparently lost its NBMI binding sites without a parallel loss of nucleoside transport ability suggesting that the nucleoside transported sites are separate from the binding sites of the transport inhibitor.
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