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  • 1980-1984  (2)
  • 1975-1979  (4)
  • 1970-1974  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Tumor inhibitors. 124. Structural requirements for antileukemic activity among the naturally occurring and semisynthetic maytansinoids (1978)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 21 (1978), S. 31-37 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00199a006
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  • 2
    Electronic Resource
    Electronic Resource
    REGULATION OF THE IN VIVO MITOTIC APPARATUS BY GLYCOLS AND METABOLIC INHIBITORS (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 253 (1975), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1975.tb19214.x
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  • 3
    Electronic Resource
    Electronic Resource
    Reversible restoration of the birefringence of cold-treated, isolated mitotic apparatus of surf clam eggs with chick brain tubulin (1974)
    [s.l.] : Nature Publishing Group
    Nature 249 (1974), S. 113-115 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Mitotic aparatuses have been isolated which can incorporate heterologous tubulin and can assemble this tubulin into birefringent fibres similar to those of mitotic apparatuses of living ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/249113a0
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Electron microscope studies of glycogen synthase (1973)
    Springer
    Molecular and cellular biochemistry 1 (1973), S. 55-61 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Glycogen synthase from rabbit muscle was examined with the electron microscope. In preparations of the completely converted glucose-6-phosphate dependent form (GSD) and the independent form (GSI) three structures were observed: toroids, hexagons and stacks of four elements which appear to be aggregates of four toroids. Toroids can be formed from hexagons by radial inward movement of subunits which form the vertices of the hexagons. Analysis of the dimensions of these structures and comparison of the known chemistry of the enzyme to the subunits as inferred from electron microscopy suggests a model for the structure of glycogen synthase. The model allows predictions of types of subunits in the enzyme, their relation to phosphorylatable and -SH sites and the possibilities of control by small effector molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01659938
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  • 5
    Electronic Resource
    Electronic Resource
    Concanavalin A-stimulated Ca2+ uptake in rat splenocytes (1980)
    Springer
    Molecular and cellular biochemistry 32 (1980), S. 123-130 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Commercially available concanavalin A binds Ca2+ with high apparent affinity. In order to dissociate concanavalin A stimulated Ca2+ uptake (defined as an increased association of 45Ca2+ with cells) in rat splenocytes and Ca2+ binding to cell-bound concanavalin A, conditions were developed to remove more than 75% of the bound concanavalin A. Under these conditions concanavalin A treated cells showed a considerable increase in 45Ca2+ uptake over control. The concanavalin A stimulated uptake of 45Ca2+ occurred within minutes, and required concentrations of concanavalin A which promoted [3H]thymidine uptake into these cells. Succinyl concanavalin A was less potent in promoting Ca2+ uptake than concanavalin A. Sodium periodate inhibited Ca2+ uptake at concentrations which promoted 3H-thymidine incorporation into splenocytes. It is concluded that con canavalin A promotes Ca2+ uptake which is not due to binding of 45Ca2+ to concanavalin A. Although the concanavalin A-promoted Ca2+ uptake occurs at lectin concentrations that cause lymphocyte proliferation as measured by 3H-thymidine incorporation, the role of Ca2+ in this event remains unclear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227438
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  • 6
    Electronic Resource
    Electronic Resource
    The structural elements responsible for contraction in the ciliateSpirostomum (1971)
    Springer
    Protoplasma 72 (1971), S. 153-178 
    Details
    ISSN: 1615-6102
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The surface of the contractile ciliateSpirostomum contains continuous spiral ciliated grooves traversing its length. Bundles of microtubules run parallel to the base of the grooves and appear to be part of a cohesive, semi-rigid cortex. Beneath this, a network of microfilament bundles occurs which is attached to the peristomal membranelle apparatus, also part of the cortex. The possible roles played by these structures during contraction of the organism were examined. During contraction, the entire cortex twists and the spiral arrangement of the grooves and microtubules decreases in pitch and increases in diameter. Simultaneously, the bundles of microfilaments change in distribution and appearance so as to suggest that they are undergoing an active shortening process. Based on these observations, two models for contraction are presented. In one, shortening of the animal arises from a smooth muscle-like contraction of the microfilament network whose attachment to the basal bodies of the membranellar cilia guarantees shortening and widening of the cortex and consequently the whole animal. In the second, a shortening (or sliding) of external microtubules relative to internal ones in the cortical microtubule bundles would result in an increase in diameter, a decrease in pitch, and a decrease in axial length of the bundles, resulting in contraction of the animal. The observations do not allow a choice between these alternatives to be made, and they may not, in fact, be mutually exclusive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279048
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  • 7
    Electronic Resource
    Electronic Resource
    Cytoplasmic tubulin from the unfertilized sea urchin egg: II. Variation of the intrinsic calcium sensitivity of strongylocentrotus purpuratus egg tubulin as a function of temperature and brain microtubule-associated proteins (1984)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 4 (1984), S. 333-350 
    Details
    ISSN: 0886-1544
    Keywords: microtubule ; tubulin ; MAPs ; calcium ; mitosis ; unfertilized sea urchin egg ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytoplasmic tubulin purified from unfertilized sea urchin eggs self-assembles in the absence of microtubule-associated proteins (MAPs) [Suprenant and Rebhun, 1983; Detrich and Wilson, 1983] with a critical concentration for polymerization of 0.8 mg/ml at 15-18°C, a value well below the 3 mg/ml tubulin present in these eggs [Pfeffer et al, 1976]. Studies of the calcium sensitivity of unfertilized S. purpuratus (sea urchin) egg tubulin were initiated to help understand how this tubulin is maintained unassembled in the unfertilized egg. Egg microtubules, assembled at physiological temperatures (15-18°C) were depolymerized by a 100-fold lower free calcium concentration than egg microtubules assembled at the higher temperatures (25-37°C) generally used to assemble mammalian brain microtubules. The initial rate of egg microtubule assembly was much more sensitive to calcium than was microtubule depolymerization at steady state at 37°C. However, both processes were sensitive to near physiological free calcium of free calcium for depolymerization than microtubules assembled at 18°C from egg tubulin alone. While calcium regulatory MAPs have not yet been found in sea urchin eggs, the fact that brain MAPs interact with egg tubulin and regulate both its critical concentration for polymerization [Suprenant and Rebhun, 1983] and its calcium sensitivty, suggests that such regulatory molecules exist. These results suggest that sea urchin egg tubulin assembly in vivo could be controlled by variations in interacellular calcium levels acting in concert with urchin egg proteins similar in function to brain MAPs.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970040504
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  • 8
    Electronic Resource
    Electronic Resource
    Involvement of glutathione in the inhibition of sea urchin egg mitosis by phenyl glyoxalA preliminary report on this work was presented at the Seventeenth Annual Meeting of the American Society for Cell Biology (Amy and Rebhun, '77). (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 100 (1979), S. 187-198 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cell division in fertilized sea urchin eggs was reversibly inhibited when the ketoaldehyde phenyl glyoxal (PG) at a concentration of 0.1 mM was added to eggs for ten minutes prior to the formation of the mitotic spindle. We investigated whether inhibition of mitosis was due to PG binding to the cell surface (as previously suggested by Stein and Berestecky, '74) or to some intracellular effect. When 14C-PG was added to eggs, label was readily taken up into the egg cytoplasm; very little label was associated with the egg surface. In the cytoplasm PG combined with equimolar amounts of reduced glutathione (GSH), decreasing the levels of cellular GSH to less than 15% of normal and accounting for at least 50% of the PG taken up by eggs. The concentrations of oxidized and protein-bound glutathione were unaffected by PG treatment. We showed that glyoxalase enzymes were present in sea urchin eggs and were capable of metabolizing the PG-GSH complex, thereby restoring GSH to normal levels after PG was removed from the sea water. Though some other effect of PG cannot be ruled out, the major fate of PG in eggs was to combine with GSH, and the transient decrease in GSH which resulted could lead to inhibition of mitosis. While other reports (Nath and Rebhun, '76; Oliver et al., '76) have shown that reagents which oxidize GSH disrupt microtubule-related events, our results showed that such inhibition could be caused by decreased GSH levels alone.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041000119
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  • 9
    Electronic Resource
    Electronic Resource
    Cyclic nucleotides, thioldisulfide status of proteins, and cellular control processes (1976)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 5 (1976), S. 199-219 
    Details
    ISSN: 0091-7419
    Keywords: cyclic nucleotides ; protein sulfhydryls ; tubulin ; glutathione ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: It is shown that cyclic nucleotides can have a variety of effects on cell division, cell shape, cell adhesion, and cell movement, depending on the cells selected and the conditions under which they are used. For example, while CHO cells elongate under the influence of exogenous dibutyryl CAMP, Y-1 adrenal tumor cells round up and polyoma-transformed 3T3 cells show no change in shape. The totality of experience with cyclic nucleotides suggests that where they have been used by cells as control elements involving the four processes listed above, they are superimposed on basic cellular processes that progress in their absence - that is, they must be acting indirectly. In attempting to understand the inhibitory action of methyl xanthines on egg development, we were forced to abandon the idea that they acted through cyclic nucleotides. We found that methyl xanthines inhibited the activation of glutathione reductase and that glutathione oxidizing agents act as mitotic inhibitors. Further, we found that tubulin polymerizability, NAD-kinase activity, and a mitotic apparatus associated Ca+2-ATP-ase were all inhibited by oxidation of some of their sulfhydryls and were activated by reduction of the resulting disulfides. These results are discussed in terms of reported cycles and activations of glutathione reductase (GR) in cells and reports that mixed disulfides of glutathione and proteins can act as substrates for GR. Using the fact that a CAMP-dependent protein kinase has been reported to be activated by glutathione, we have suggested potential sites where sulfhydryl control processes and cyclic nucleotide control processes may interact in certain restricted cases.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400050208
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  • 10
    Electronic Resource
    Electronic Resource
    Regulation of size and birefringence of the in vivo mitotic apparatus (1974)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 2 (1974), S. 466-485 
    Details
    ISSN: 0091-7419
    Keywords: Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Long chain glycols augment in size and birefringence the in vivo mitotic apparatus (MA) of marine eggs. Dinitrophenol and caffeine antagonize the effect but they can be balanced by glycols. Caffeine inhibits the phosphodiesterase for cyclic AMP (CAMP) and CAMP levels increase in its presence. However, added dibutyryl CAMP does not affect MAs or cleavage, but is taken up by eggs. Oxygen uptake studies show that caffeine depresses oxidative metabolism but does not affect ATP levels. Action through the pentosephosphate shunt is suggested.Glycols influence the assembly of tubulin. Optical ultracentrifuge patterns of tubulin polymerized without glycol show a 6S and 30S peak. Similar patterns of tubulin polymerized at pH 6.4 in glycol and depolymerized in its absence show 6S, 8-18S, and 30S, peaks. The 8-18S peak appears in equilibrium with the 6S peak. If glycol is added to cold tubulin polymerized without glycol, only 6S and 30S peaks occur. Preparations with no 30S peak do not show 450 Å rings in the EM. Calcium depolymerizes microtubules. In the absence of glycols 450 Å rings are seen. In the presence of glycol, much higher concentrations of calcium are necessary for depolymerization, and few 450 Å rings occur.We suggest that glycols prevent formation of the stable 30S peak, favor an intermediate structure in equilibrium with the 6S peak, and antagonize calcium depolymerization. Their in vivo effects may arise from these interactions.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400020232
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