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  • 1
    Unknown
    Unknown
    Acacemic
    Call number: ordered ; ordered
    Type of Medium: Unknown
    Edition: 3rd ed.
    ISBN: 9780128203378
    Location: M010
    Location: Library.
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 433 (2005), S. 585-587 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Heart attacks are fatal when they damage more than a quarter of the heart's left ventricle — killing off about 109 heart cells in the process. In patients who survive less severe attacks, dead heart cells are replaced by cells from the connective tissue called fibroblasts, ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1040-452X
    Keywords: ES cells ; Pluripotent ; Bovine embryos ; Nuclear transfer ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Inner cell masses (ICM) from in vitro produced day 8 or 9 bovine blastocysts were isolated by immunosurgery and cultured under different conditions in order to establish which of two feeder cell types and culture media were most efficient in supporting attachment and outgrowth of the bovine ICM cells. The efficiency of attachment and outgrowth of the ICM cells could be markedly improved when STO feeder cells were used instead of bovine uterus epithelial cells, and by using charcoal-stripped serum instead of normal serum to supplement the culture medium. More than 20 stable cell lines were obtained. Some of these lines were examined by immunofluorescence for developmentally regulated markers. From these results we conclude that the cell lines resemble epithelial cells, rather than pluripotent ICM cells. The developmental potential of cells of one of the lines was tested in the nuclear transfer assay. The cell line could support the initial development of enucleated oocytes, but none of the reconstructed embryos passed the eight-cell block. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1040-452X
    Keywords: TEC-03 ; Bovine embryos ; Nuclear transfer ; Nuclear reprogramming ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Bovine embryos, recovered from the uterus in vivo or derived from in vitro matured and in vitro fertilized oocytes, were investigated for the presence of the developmentally regulated mouse antigen TEC-3 by indirect immunofluorescence. During preimplantation embryo development TEC-3 is expressed on bovine morulae and blastocysts. It is absent from unfertilized and fertilized oocytes, and from all stages before the 32-cell stage. The finding that TEC-3 is not expressed before the onset of embryonic transcription, which occurs at the eight-cell stage in the bovine, but only when the embryonic genome is active, makes it a potential marker for studying nuclear reprogramming after nuclear transfer. Nuclear transfer embryos were made by electrical fusion of blastomeres from morulae derived in vivo with enucleated metaphase II oocytes. Indirect immunofluorescence with the TEC-03 antibody showed that the TEC-3 antigen, present on blastomeres of the morula stage embryo, disappeared after fusion and was expressed again when the nuclear transfer embryos developed to the morula and blastocyst stage. These data suggest that the bovine embryonic nucleus may be able to revert to the equivalent of an earlier developmental stage when transferred to ooplasm, and is then capable of following the normal developmental program. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 5
    ISSN: 1058-8388
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The α6β1 integrin is a receptor for laminins and is present from early stages of mouse embryogenesis. In the present study determined the temporal and spatial expression of the two cytoplasmic splice variants of the α6 integrin subunit, α6A and α6B, in the early- and midgestation mouse postimplantation embryo using RT-PCR, in situ hybridization, and immunofluorescence. Our results show that α6B is present in the embryo at all stages studied and is expressed before α6A. α6A expression begins in 8.5 day p.c. embryos and is initially exclusively localized to the developing heart. In 8.5 (and 9.5) day p.c. embryos α6A mRNA and protein are present in a gradient in the myocardium of the heart tube from strongest expression in the sinus venosus and in the common atrial chamber to a weakening expression along the ventricle and bulbus cordis. In 10.5 day p.c. embryos this gradient is less evident and in 12.5 day p.c. embryos α6A mRNA and protein are present in comparable amounts between atria and ventricles. Neither α6A nor α6B is present in endocardial cushion tissue. By day 12.5 p.c. α6A expression is also present in the developing epidermis, dental primordia, lens, gonads, and in a few epithelia such as those of the digestive tract. α6B expression is always much more widespread than α6A expression. For example, only α6B is present in the myotome of the somites of 9.5 day p.c. embryos, in the developing central and peripheral nervous systems, and in the nephrogenic system at all stages studied, except after the differentiation of the gonads when α6A is also present. Furthermore, α6B is the only splice variant present on endothelial cells. We also examined the distribution of the β4 integrin subunit to determine whether the α6β4 integrin was present during these stages of development. β4 protein was absent in early postimplantation stages but was present in the epidermis and digestive tract of 12.5 day p.c. embryos. These results show a differential distribution of α6A and α6B during mouse development and thus strongly suggest a different function of these splice variants during embryogenesis. Our results point to a possible role for the α6Aβ1 integrin in the development of the myocardium of the developing heart, but not in the migration of endocardial cushion cells, while α6Bβ1 could be important in the developing nephrogenic and nervous systems. © 1995 wiley-Liss, Inc.
    Additional Material: 9 Ill.
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Rat pheochromocytoma cells (clone PC12) possess functional surface receptors for both nerve growth factor (NGF) and epidermal growth factor (EGF). PC12 cells respond to NGF as well as to dibutyryl cyclic AMP (dbcAMP) by arrest of cell proliferation and initiation of morphological differentiation, while EGF acts as a mitogen. Exposure of PC12 cells to NGF for several days resulted in a complete loss of rapid EGF responses, such as membrane ruffling and activation of active K+ transport. EGF binding studies revealed that this loss of EGF responses was due to an almost complete reduction of the number of EGF binding sites. In contrast, exposure of PC12 cells to dbcAMP for 2 days did not affect the rapid EGF responses, despite the morphological differentiation. Moreover, EGF binding studies demonstrated a twofold increase in the number of high-affinity binding sites and a small increase in the number of low-affinity sites. In addition, exposure of the cells to dbcAMP caused a twofold increase of EGF-receptor phosphotyrosine kinase activity. These results indicate that neither EGF-binding or the presence of EGF receptors nor the rapid EGF responses are sufficient for persistent proliferation, on one hand, or sufficient to avoid morphological differentiation, on the other.
    Additional Material: 6 Ill.
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  • 7
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Functional and optimal activities of the (Na+-K+)ATPase, as determined by ouabain-sensitive K+ influx in intact cells and ATP hydrolysis in cell homogenates respectively, have been measured during the cell cycle of neuroblastoma (clone Neuro-2A) cells. The cells were synchronized by selective detachment of mitotic cells.The ouabain-sensitive K+ influx decreased more than fourfold from 1.62 ± 0.11 nmoles/min/106 cells to 0.36 ± 0.25 nmoles/min/106 cells on passing from mitosis to early G1 phase. On entry into S phase a transient sixfold increase to 2.07 ± 0.30 nmoles/min/106 cells was observed, followed by a rapid decline, after which the active K+ influx rose again steadily from 1.03 ± 0.25 nmole/min/106 cells in early S phase to 2.10 ± 0.92 nmoles/min/106 cells just prior to the next mitosis. The ouabain-insensitive component rose linearly through the cycle in the same manner as the protein content/cell.Combining total K+ influx values with efflux data obtained previously showed that net loss of K+ occurred with transition from mitosis to G1 phase while net accumulation occurred with entry into S. Throughout mid-S phase net K+ flux was virtually zero, but a large net influx occurred again just before the next mitosis.The (Na+-K+)ATPase activity measured in cell homogenates decreased rapidly from mitosis to G1 phase and increased steadily throughout S phase, but the transient activation on entry into S phase was not observed.Complete inhibition of the (Na+-K+)ATPase mediated K+ influx by ouabain (5 mM) prevents the cells from entering S phase, while partial inhibition by lower concentrations of ouabain (0.2 and 0.5 mM; km = 0.17 mM) causes partial blockage in G1 and, to a lesser extent, a reduced rate of progression through the rest of the cell cycle. We conclude that the transient increase in (Na+-K+)ATPase mediated K+ influx at the G1/S transition is a prerequisite for entry into S phase, while maintenance of adequate levels of K+ influx is necessary for normal rate of progression through the rest of the cell cycle.
    Additional Material: 5 Ill.
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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: Cation transport and membrane potential were studied during the cell cycle of neuroblastoma cells (clone Neuro-2A) to investigate the role of these parameters in growth regulation. The cells were synchronized by selective detachment of mitotic cells. The membrane potential and intracellular K+ activity were measured with conventional and K+-selective microelectrodes respectively. Both the membrane potential and K+ activity were high in mitosis, decreased to half maximal in G1 phase, and rose again during S phase.K+ efflux across the plasma membrane was studied with 42K+ as a radioactive tracer using a washing method for cells grown in monolayer and a continuous efflux method for mitotic cells in suspension. The intracellular K+ content and unidirectional K+ efflux rate obtained from these measurements showed modulations during the cell cycle similar to those of the membrane potential. Using equations of electrodiffusion theory the membrane permeabilities to K+ and Na+ were calculated. These permeabilities were high in mitosis, decreased rapidly in G1 phase and increased during S phase, followed by a transient decrease in G2 phase. A rapid increase was observed between G2 phase and the next mitosis. A similar pattern was obtained for the K+ conductance. K+ resistance changes during the cell cycle were similar to changes in the specific membrane resistance, measured by microelectrodes, except for the early cell cycle phases (mitosis and G1).These studies clearly demonstrate large modulations of the passive membrane permeability properties during the cell cycle. These modulations can be correlated with physicochemical membrane variations during the cell cycle, such as membrane fluidity and lateral mobility of lipids.
    Additional Material: 8 Ill.
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  • 9
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Na+ transport properties of neuroblastoma (clone Neuro-2A) cells have been characterized both in exponentially growing cells and during the cell cycle. In exponentially growing cells, Na+ influx followed the kinetics for a one-compartment system with an influx rate of 9.54 ± 0.96 nmoles/minute/106 cells, equilibrium being reached within 2 minutes. The initial rate of influx in the presence of ouabain (5 mM), a concentration completely inhibiting the (Na+-K+)ATPase and thus backflux of tracer, was 11.33 ± 1.50 nmoles/minute/106 cells and, within error, the same as in the absence of ouabain, provided determinations were made within 3 minutes of ouabain addition.Na+ influx rate was determined at intervals during the cell cycle of synchronized Neuro-2A cells using a 3-minute pulse of 22Na+ in the presence of ouabain. On passing from mitosis to G1-phase Na+ influx decreases from 12.13 ± 1.93 to 7.40 ± 0.90 nmoles/minute/106 cells but increases rapidly and transiently approximately twofold upon entry into S-phase. This transient increase coincides with a transient stimulation of the (Na+-K+) pump activity. It then returns to a steady level of ˜ 12 nmoles/minute/106 cells for most of the remainder S-phase.Intracellular Na+ concentration during the cell cycle was determined from the equilibrium content of 24Na+ and data on the intracellular H2O volume, published previously (Boonstra et al., 1981b). Na+ concentration is maximal in mitosis at 56.96 ± 6.05 mM and decreases rapidly tourfold as cells enter G1-phase. With progression through S-phase a steady increase from 13.80 ± 1.25 mM to 37.35 ± 2.91 mM is observed. Combining the Na+ concentration with the K+ concentration obtained previously (Boonstra et al., 1981b), the K+:Na+ ratio was obtained during the cell cycle. The ratio had a value of between 3 and 5 during most of the cell cycle, but was significantly higher in G1-phase, where the loss of Na+ is considerably greater than the loss of K+. The values for Na+ concentration were combined with membrane potential measurements reported previously (Boonstra et al., 1980b) to obtain the Na+ electrochemical gradient across the cell membrane in the cell cycle. This had a value of 63.2 ± 2.6 mV in mitosis and increased rapidly to reach a maximum value of 84.0 ± 5.5 mV during G1-phase, thereafter maintaining a value of between 73 and 80 mV. The transient increase in Na+ influx and in (Na+-K+)ATPase-mediated K+ influx at the G1/S-phase transition are specifically inhibitable by the diuretic amiloride (0.2 mM) but amiloride has little effect on Na+ or K+ influx in other phases of the cell cycle. This indicated activation of an amiloride-sensitive transport system specically at the G1/S-phase transition and a causal relationship between increased Na+ entry and transient stimulation of the pump at this point in the cell cycle. Further, amiloride (0.1, 0.2 mM) addition was shown to give rise to a significant lengthening of the cell cycle and to cause a partial blockage of the cells specifically in G1-phase, suggesting an important role for the transient ion flux changes in controlling entry into and progression through S-phase.
    Additional Material: 6 Ill.
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  • 10
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Rat pheochromocytoma cells (clone PC12) display cell surface receptors for both nerve growth factor (NGF) and epidermal growth factor (EGF) and therefore provide a useful model system with which to study the role of these receptors in the regulation of proliferation and differentiation. In this paper PC12 cells are demonstrated to possess two classes of EGF receptors, a high-affinity class with 7,600 sites per cell and an apparent dissociation constant (Kd) of 0.05 nM, and a low-affinity class with 62,000 sites per cell and a Kd of 14.1 nM. These findings are contrary to literature data (Huff et al., 1981; Vale and Shooter, 1983) but can be explained in part by differences in experimental conditions. Binding studies at 37°C compared with room temperature demonstrated similar affinities of both classes, but during prolonged incubation at 37°C, the binding capacities of both classes decreased. Furthermore the high-affinity class was sensitive to lectins, such as concanavalin A (Con A), and to the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). Both compounds caused a decrease of the affinity of the high-affinity class without affecting the low-affinity class. At high concentrations of Con A or TPA, a decrease of the apparent number of binding sites of the low-affinity class was also observed. The similarities between the characteristics of EGF binding and NGF binding in PC12 cells are striking and will be discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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