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  • 1
    ISSN: 0886-1544
    Keywords: video microscopy ; axonal transport ; computer motion analysis ; giant axon ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Moving intra-axonal organelles demonstrate frequent variations in speed when viewed over several seconds. To evaluate these and other motion variations, a long-term analysis of organelle motion in isolated axoplasm of Myxicola infundibulum was carried out using differential interference contrast optics and analog and digital image enhancement techniques. Motion characteristics of individual organelles were analyzed for periods of up to 58 minutes. Three principle observations on organelle motion were made: (1) Classes of organelles of the same size demonstrated a 5- to 25-fold variation of speed, with the slowest speeds occurring most frequently; (2) organelle speeds over individual translocations (motion without stopping) are inversely proportional to their size, but the speeds calculated for the long-term analysis of organelle motion (total distance travelled/total observation time, including pauses) did not reflect this observation; and (3) organelles displayed variable trip lengths, durations, mean speeds, and pause durations, and the relationships between these variations showed no repetitive patterns. In contrast to reported observations of uniform velocities of organelles moving on isolated microtubule preparations, these observations suggest that a variety of factors must play a role in organelle translocation in Myxicola axoplasm.
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  • 2
    ISSN: 0886-1544
    Keywords: axoplasmic transport ; motility ; microtubules ; MAPs ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Vesikin, a protein that can associate with squid axoplasmic vesicles or optic lobe microtubuies, has been implicated as a force-generating molecule involved in microtubule-dependent vesicle transport [Gilbert and Sloboda, 1986, 1988]. Because vesikin crossreacts with an antibody to porcine brain microtubule associated protein 2 (MAP 2), studies were conducted to compare squid vesikin and brain MAPs. When taxol stabilized microtubules containing vesikin as a microtubule associated protein were incubated in the presence of ATP, vesikin dissociated from the microtubule subunit lattice. This behavior would be expected for an ATP-dependent, force generating molecule that serves as a crossbridge between vesicles and microtubules. When chick brain microtubules were treated under the same conditions, MAP 2 remained bound to the microtubules while MAP 1 dissociated in a manner similar to vesikin. One dimensional peptide mapping procedures revealed that, although digestion of vesikin and MAP 2 generated several peptides common to both proteins, vesikin and MAP 2 are clearly not identical. Furthermore, the addition of vesikin or MAPS 1 and 2 to purified tubulin stimulated microtubule assembly in a manner dependent on the concentration of added protein. These findings demonstrate that brain MAPs share characteristics common to squid vesikin and support the suggestion that brain MAPs 1 and 2 might act as a force generating complex for vesicle transport in higher organisms.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 22 (1992), S. 99-116 
    ISSN: 0886-1544
    Keywords: microinjection ; second messengers ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have directly evaluated the effects of various intracellular second messengers including cyclic nucleotides, calcium ion, and inositol polyphosphates on shape and motility of differentiating mouse neuroblastoma cells. The messengers were microinjected into cells and the responses of the soma, neurite, and growth cone were monitored using time-lapse video microscopy. Each messenger altered cell shape and motility in a characteristic manner. Cyclic AMP promoted lamellipodial expansion, neurite outgrowth, and motility. The other injected messengers opposed motility. Cyclic GMP caused motile structures to freeze and to retract permanently, while the inhibitory effects of calcium injection were concentrationdependent. Small calcium injections affected specifically actincontaining motile structures which froze and retracted temporarily. Intermediate calcium injections caused a strong contraction at the site of injection in all cells. With large injections, cells retracted long neurites, rounded up, and frequently began vigorous blebbing that continued to cell death. Injections of the inositol polyphosphates 1P3(1,4,5) and IP4(1,4,5,6) mimicked the effects of small calcium injections, as did electrical stimulation that elicited action potentials. The results suggest that in mouse neuroblastoma cells, intracellular CAMP elevation increases cytoskeletal organization and promotes neurite extension perhaps through an enhancement of cell-substratum adhesion. On the other hand, a rise of intracellular cGMP or intracellular calcium interferes directly with the function and organization of the actin-microfilament system. The integrated action of these second messenger systems may, therefore, operate in vivo to allow substances released from neighboring cells to regulate neuronal architecture. © 1992 Wiley-Liss, Inc.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 25-33 
    ISSN: 0886-1544
    Keywords: actin structures ; vinculin ; focal contacts ; spontaneous metastasis ; extracellular pH ; cell motility ; malignancy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have studied the organisation of the actin cytoskeleton in three related rat sarcoma cell populations of differing malignancy. They were derived by neoplastic progression from a population which had transformed spontaneously in vitro, and were distinguished by their ability to give rise to reproducibly different numbers of metastases, ranging from 10% to 80% of the animals inoculated. We found characteristic differences in the arrangement of the actin cytoskeleton. Confocal three-dimensional microscopy showed that nearly all of the least malignant population contained conspicuous actin stress fibres lying in the lower part of the cell parallel to the substratum and no other actin structures. Actin in the intermediate population was typically situated in a diffuse layer underlying the whole plasma membrane, in which no fibres could be seen. Two thirds of the most malignant population consisted of more rounded cells filled with a three-dimensional network of fine oblique actin fibres. There were focal contacts in all these cells; their area showed a regular decrease from 1.3 μm2 to 0.4 μm2. The differences in actin distribution were accompanied by differences in motility, which increased as malignancy increased. When individual cells were fixed after they had been tracked by time-lapse, their cytoskeleton type correlated with the speed at which they had moved. All these differences were enhanced at low pH. These findings point to the possibility that the three-dimensional network of fine actin fibres in acid culture could be a measure of the malignant potential of transformed cells in vitro. © 1994 Wiley-Liss, Inc.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 4 (1984), S. 351-370 
    ISSN: 0886-1544
    Keywords: axon ; rate ; nervous system ; tissue culture ; cell growth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A new formula calculates rates of directed axonal growth (elongation or retraction) using measurements of growth cone movements. By explicitly separating changes in axonal length from other nonelongational growth cone movements, the calculated rates reflect the detailed cellular growth mechanisms more directly than previous growth measures. In addition, the formula produces three distinct parameters of axonal elongation: n, a growth step rate; s, a growth step size; and P, a probability that a growth step leads to axonal elongation. For normal and regenerating individual chick and frog axons in culture, the formula has quantitated the following differences: the axon itself can elongate more rapidly in the chick, and the axon elongates in smaller steps in the chick. The underlying dynamics of growth of regenerating axons are quite similar to normal axons, but, in the short term, regenerating axons elongate in larger steps and at a slower rate. The distribution of these new rate measurements suggests that the elongation of axons can be usefully modelled as a one-dimensional stochastic walk.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 11 (1988), S. 260-274 
    ISSN: 0886-1544
    Keywords: cytoskeleton ; atheromatosis ; wound healing ; fibromatosis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The distribution of smooth muscle (SM) and non muscle myosins was compared with that of α-SM actin in various normal and pathological tissues and in cultured cells by means of indirect immunofluorescence using a monoclonal antibody specific for α-SM actin [anti-αsm-1, Skalli et al., 1986b] and two polyclonal antibodies raised against bovine aortic myosin (ABAM) and human platelet myosin (AHPM), respectively.In normal tissues ABAM stained vascular and parenchymal smooth muscle cells (SMC), myoepithelial cells and myoid cells of the testis in a pattern similar to that reported by other authors with antisera raised against non vascular SM myosin. Cells stained with ABAM were always positive for anti-αsm-1. In human and experimental atheromatous plaques, most cells were positive for AHPM; a variable proportion was also stained for ABAM plus anti-αsm-1. Myofibroblasts from rat granulation tissue, Dupuytren's nodule and stroma from breast carcinoma were constantly positive for AHPM and negative for ABAM; however, myofibroblasts from Dupuytren's nodule and breast carcinoma were anti-αsm-1 positive. Early primary cultures of rat aortic SMC were positive for ABAM and anti-αsm-1 and became negative for ABAM and positive for AHPM after a few days in culture. They remained positive for AHPM and anti-αsm-1 after passages; the staining of AHPM and anti-αsm-1 appeared to be colocalized along the same stress fibers.These results may be relevant for the understanding of SMC function and adaptation, and show that in non malignant SMC proliferation, α-SM actin represents a more general marker of SM origin than SM myosin.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 157 (1993), S. 128-132 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Both nitric oxide and prostaglandins are potent paracrine mediators of intercellular communication. An endotoxin-lipopolysaccharide (LPS) inducible form of nitric oxide synthase (mac-NOS) has recently been cloned from murine macrophages. An inducible prostaglandin synthase (TIS1O/PGS-2), cloned from 3T3 cells, is also induced in LPS-activated macrophage. Because of the wide range of ligands that induce primary response genes in 3T3 cells, the ease of studying chimeric promoter constructs in 3T3 cells, and the importance of both nitric oxide and prostaglandins as paracrine mediators, we examined expression of mac-NOS in 3T3 cells. Tetradecanoyl phorbol-13 acetate (TPA), forskolin, platelet-derived growth factor, fibroblast growth factor, and serum all induce mac-NOS expression in Swiss 3T3 cells. Thus the mac-NOS gene can respond to a far wider range of inducers than previously suspected. mac-NOS is a primary response gene; cycloheximide does not block induction. TPA-induced mac-NOS and TIS10/PGS-2 mRNA accumulation patterns are similar. LPS is a potent inducer of mac-NOS in Swiss 3T3 cells but cannot induce TIS10/PGS-2. In contrast, v-src expression induces TIS10/PGS-2 message, but not iNOS message in a BALB/c 3T3 cell line containing a temperature-sensitive v-src gene. Dexamethasone (DEX) prevents induction of TIS10/PGS-2, but not most other primary response genes. DEX also blocks mac-NOS induction in Swiss 3T3 cells. The inducible TIS10/PGS-2 and mac-NOS genes, responsible for the production of two distinct paracrine agents, appear to share many regulatory features in 3T3 cells. © 1993 Wiley-Liss, Inc.
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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: Transforming growth factor-beta (TGF-beta), a potent cytokine, modulates a wide variety of biological responses. Among its actions, TGF-beta can augment prostaglandin synthesis in several cell types. Although TGF-beta alone has no effect on prostaglandin production in Swiss 3T3 cells, we find that TGF-beta augments the ability of tetradecanoyl phorbol acetate (TPA) or serum to stimulate PGE2 production. The TIS10 gene is a primary response gene encoding a second form of prostaglandin synthase (PGS), the rate-limiting enzyme in the biosynthesis of prostaglandins, thrornboxanes, and prostacyclins from arachidonic acid. TIS10/PGS-2 expression is induced by mitogens in Swiss 3T3 cells. TGF-beta also augments mitogen-induced synthesis and accumulation of TIS10/PGS-2 protein and induction of TIS10/PGS-2 message in Swiss 3T3 cells. In contrast, TGF-beta has little or no effect on the level of PGS-1 (EC1.14.99.1) message, either alone or in concert with TPA or serum. TGF-beta concentrations in the range of 0.01-0.10 ng/ml (0.4-4.0 pM) maximally enhance mitogen induction of TIS10/PGS-2 message. TPA-induced accumulation of unspliced TIS10/PGS-2 transcript is augmented by TGF-beta, suggesting that this cytokine exerts its effect on expression of the TIS10/PGS-2 gene by transcriptional regulation. TGF-beta also augments TPA-induced prostaglandin production, TIS10/PGS-2 antigen accumulation, and TIS10/PGS-2 message induction in primary cultures of mouse embryo fibroblasts. Dexamethasone attenuates TGF-beta enhancement of all these mitogen-induced responses: PGE2 accumulation, appearance of TIS10/PGS-2 protein and message, and accumulation of TIS10/PGS-2 unprocessed transcript. © 1994 wiley-Liss, Inc.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 10 (1984), S. 45-56 
    ISSN: 0148-7280
    Keywords: blastocyst ; messenger RNA ; heat shock ; recombinant DNA ; actin ; transcription ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have utilized the rabbit 6-day blastocyst as a model system in which to examine the effect of environmental stress on embryonic gene expression. Elevation of the incubation temperature from 37 to 43 °C, exposure to 50 μM sodium arsenite or mechanical injury (resulting in the structural collapse of the 6-day rabbit blastocyst) was found to depress total protein synthesis as well as enhance the synthesis of a 70,000-dalton stress-induced protein. The molecular mass of this stress protein is similar to a heat shock protein (HSP) found in other eukaryotic systems. A recombinant DNA probe consisting of the 5′ end of a mouse gene for a 70,000-dalton HSP hybridized to RNA isolated from heat shocked, sodium arsenite-treated, and mechanically injured blastocysts but not to RNA isolated from control embryos. These results as well as in vitro translation data suggest that the expression of the 70 K HSP is controlled at the transcriptional level. The levels of actin mRNA, as detected by means of a recombinant DNA probe encoding a Drosophila actin gene, did not undergo a major alteration following these different stresses. The relevance of these observations to embryonic cellular homeostatis is discussed.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 25-34 
    ISSN: 0148-7280
    Keywords: fertilization ; pronuclei ; chromatin decondensation ; protamine ; kinase ; glutathione reductase ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In order to derive information about possible mechanisms by which the sperm head is converted into the male pronucleus during fertilization in the rabbit, unfertilized egg homogenate was assayed for two enzyme activities. Protamine was extracted from rabbit sperm, purified, and labelled with [14C] in an in vitro reaction and used as a probe to assay for a protein kinase which could transfer [32P]PO4 from [γ-32P]ATP onto the substrate. A kinase with a pH optimum of approximately 8.0 to 8.5 is described. Assays for the enzyme glutathione reductase were performed using homogenates from eggs or embryos at three early stages of development. Results suggest that oocytes can oxidize 2.58 × 10-6 μmol NADPH per minute per oocyte, unfertilized eggs 5.16 × 10-7 μmol NADPH per minute per ovum, and 20- to 24-hour postcoitus fertilized eggs 2.30 × 10-6 μmol NADPH per minute per ovum. The relevance of these observations to male pronuclear formation is discussed.
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