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  • 1990-1994  (10,908)
  • Life and Medical Sciences  (10,278)
  • Industrial Chemistry and Chemical Engineering  (629)
  • Nuclear reactions
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  • 1
    Electronic Resource
    Electronic Resource
    Primary health care as a guideline for preclinical anatomy teaching (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 297-299 
    Details
    ISSN: 0897-3806
    Keywords: education ; anatomy ; family practices ; primary health care ; Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This article, based upon a survey distributed to general practitioners in Switzerland, is part of a comprehensive work directed toward the development of a medical curriculum based on the specific requirements of primary health care. Analysis shows that it is possible to make a reduction in the amount of anatomy taught without endangering the basic knowledge necessary for clinical practice. © 1994 Wiley-Liss, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070510
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  • 2
    Electronic Resource
    Electronic Resource
    Meetings (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 303-304 
    Details
    ISSN: 0897-3806
    Keywords: Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070512
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  • 3
    Electronic Resource
    Electronic Resource
    Meetings (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 380-381 
    Details
    ISSN: 0897-3806
    Keywords: Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070615
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  • 4
    Electronic Resource
    Electronic Resource
    Gross anatomy in the practice of medicine, by Frank J. Slaby, Susan K. McCune, and Rbert W. Summers. 669 pp., 490 illus. Baltimore: Williams and Wilkins, 1994. $49.50 (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 375-376 
    Details
    ISSN: 0897-3806
    Keywords: Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070613
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  • 5
    Electronic Resource
    Electronic Resource
    Positions available (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 382-382 
    Details
    ISSN: 0897-3806
    Keywords: Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070616
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  • 6
    Electronic Resource
    Electronic Resource
    New concepts for the design of mass polymerization reactors (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 127-130 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel reactor arrangement for the anionic polymerization of styrene described in this paper comprises alternating adiabatically operated plug-flow reactors and heat exchangers. A novel tube-bundle recycle reactor is presented for the bulk polymerization of styrene and acrylonitrile.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170210
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics and mechanisms of reaction between carbon disulphide and morpholine in aqueous solutions (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 138-140 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The reaction in aqueous solutions between carbon disulphide and morpholine has been studied experimentally at 303 K using a conductimetric stopped-flow technique. The observed pseudo-first order rate constant does not vary linearly with amine concentration but follows the equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{obs} = k_{Am} [R_2 NH]^2 + k_w [R_2 NH][H_2 O] $$\end{document} .This equation is compatible both with (i) zwitterion intermediate and (ii) single-step termolecular reaction mechanisms which were previously proposed for the corresponding reactions of CO2 and COS. Values of rate constants kAm and kw at 303 K are also reported.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170212
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  • 8
    Electronic Resource
    Electronic Resource
    Continuous fermentation with product recovery by in-situ extraction (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 365-373 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The productivity of fermentations is often limited by end product inhibition. This can be avoided by continuous removal of the inhibiting product from the broth. Such in-situ separation can be conveniently accomplished by liquid-liquid extraction. As an example, the continuous fermentation of ethanol by the thermophilic, anaerobic bacterium Clostridium thermohydrosulfuricum is investigated in a 20-1 fermenter with simultaneous in-situ extraction by oleyl alcohol as organic solvent. Continuous fermentations with and without in-situextraction were carried out with systematic variation of the independent operating conditions, viz. feed glucose concentration, broth flow rate and solvent flow rate. The experimental results of 18 steady states are reported. They show that in-situ extractions doubles the yield, selectivity and space-time yield of ethanol in comparison to fermentations without in-situ extraction. A biomodel elucidates the influence of feed glucose concentration, broth flow rate and solvent flow rate on the productivity of the fermentation process. Finally, a cost model was developed for the investigated fermentation which allows economic evaluation of the results of experiments and simulation. A sensitivity study elucidates the economic limits and advantages of fermentation with in-situ extraction compared to a common fermentation without product separation.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170602
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  • 9
    Electronic Resource
    Electronic Resource
    Hydrogen consuming anodes for energy saving in sodium sulphate electrolysisDedicated to Professor Dr. Hartmut Wendt on the occassion of his 60th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 382-389 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas diffusion electrodes, made of PTFE-bonded carbon with precious metal catalysts, were investigated as hydrogen consuming anodes in sodium sulphate electrolysis. The catalysts used were platinum and palladium and mixtures of both metals, prepared by two different methods. Various metal meshes were used as current collector. The electrodes performed well in pure sulphuric acid (5-15 wt-%) and in mixtures with sodium sulphate (10 wt-%) at temperatures of 30 to 70°C and current densities up to 5 kA/m2. In long-term experiments, at a current density of 2.6 kA/m2, the electrodes were stable over three months. The electrodes were characterised by stationary current density/potential curves and by galvanostatic current interruption measurements.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170604
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  • 10
    Electronic Resource
    Electronic Resource
    Swelling phenomena of emulsion liquid membranes with dithio-DEHPA as carrier (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 242-248 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The purpose of this paper is to investigate the swelling of emulsion liquid membranes using dithio-DEHPA as carrier. The application of interest was the removal of zinc from a synthetic aqueous solution which simulates a zinc plant effluent. The effect of several variables such as the concentration of carrier in the membrane, stirring speed and permeation time on the swelling of the emulsion is reported. Experimental results show that occlusion depends mainly on the amount of carrier in the membrane and can be significant when the concentration of carrier is lower than 6.0%. The interfacial tension analysis confirms that the size of globules is influenced by the concentration of carrier in the membrane. Stirring speed and permeation time are related to the water transport and must be kept at low values.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170405
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  • 11
    Electronic Resource
    Electronic Resource
    The use of small group case-based exercises in human gross anatomy: A method for introducing active learning in a traditional course format (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 357-366 
    Details
    ISSN: 0897-3806
    Keywords: small groups ; case studies ; gross anatomy ; active learning ; Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: As part of the curricular change at the University of Rochester School of Medicine and Dentistry, we focused on active learning and greater integration of basic and clinical sciences. With these objectives in mind, this report describes the use of small-group, case-based exercises in our gross anatomy course and provides one example of integrating such activities into a traditional course. In addition to formal lectures and laboratory dissection, students meet approximately every fourth class period in small groups to discuss a clinical case which focuses on the relevant anatomy taught at that time. Two first-year students lead each small group; one fourth-year student facilitator also attends to provide clinical correlations, answer questions, and reinforce the anatomy. Formative feedback suggests students enthusiastically endorse the self-directed active learning; they feel these exercises offer both a valuable approach to learning and an opportunity to practice presentation and leadership skills. First-year students enjoy the interaction with fourth-year facilitators and the fourth-year students appreciate the opportunity to review basic science material. Our data suggest that students learn to “think” about the anatomy, and we hope learn to use their understanding and knowledge base in a practical fashion. Moreover, these case-based exercises can fit nicely into a variety of curricular formats, especially where problem-based tutorials may not be feasible or desirable. © 1994 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070608
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  • 12
    Electronic Resource
    Electronic Resource
    Myenteric plexus of the upper part of the human esophagus: A quantitative study (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 331-334 
    Details
    ISSN: 0897-3806
    Keywords: upper human esophagus ; myenteric plexus ; neuron density ; Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The myenteric plexus of the upper 12 cm of the human esophagus was studied quantitatively in five necropsy esophagi using whole-mount preparations in which the neurons were stained by a modified Giemsa method. The numerical densities of ganglia and neurons that first appear just below the caudal edge of the cricopharyngeus muscle increase progressively along the oral aboral axis of the esophagus. In the proximal third of the upper esophagus, the plexus contains 10-34 ganglia/cm and 223-1,306 neurons/cm2. The ganglia in this segment are relatively small, containing 17-55 neurons. In the middle third there are 7-35 ganglia/cm2 and 298-1,991 neurons/cm2. The ganglia contain 30-64 neurons. In the distal third of the upper esophagus, the plexus contains 11-46 ganglia/cm2 and 468-1,955 neurons/cm2. The ganglia contain 33-65 neurons. The total number of neurons in this upper part of the esophagus was calculated to be approximately 225-250,000. © 1994 Wiley-Liss, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070605
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  • 13
    Electronic Resource
    Electronic Resource
    Review questions for gross anatomy and embryology, by T.R. Gest, W.E. Burkel, and N.A. Waanders. 401 pp. New York: Parthenon Publishing Group Inc., 1993. $21.95 (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 7 (1994), S. 374-374 
    Details
    ISSN: 0897-3806
    Keywords: Life and Medical Sciences ; Miscellaneous Medical
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ca.980070612
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  • 14
    Electronic Resource
    Electronic Resource
    Hybrid modelling of yeast production processes - combination of a priori knowledge on different levels of sophisticationDedicated to Professor Dr. Dr. h. c. Hanns Hofmann on the Occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 10-20 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Process models are used to formulate knowledge about process behaviour. They are applied, e.g., to predict the process' future behaviour and for state estimation when reliable on-line measuring techniques to monitor the key variables of the process are not available. There are different sources of information available for modelling, which provide process knowledge in different representations. Some elements or aspects may be described by physically based mathematical models and others by heuristically obtained rules of thumb, while some information may still be hidden in the process data recorded during previous runs of the process. Heuristic rules are conveniently processed with fuzzy expert systems, while artificial neural networks present themselves as a powerful tool for uncovering the information within the process data without the need to transform the information into one of the other representations. Artificial neural networks and fuzzy technology are increasingly being employed for modelling biotechnological processes, thus extending the traditional way of process modelling by mathematical equations. However, a sufficiently comprehensive combination of all these techniques has not yet been put forward. Here, we present a simple way of combining all the available knowledge relating to a given process. In a case study, we demonstrate the development of a hybrid model for state estimation and prediction on the example of a yeast production process. The model was validated during a cultivation performed in a standard pilot-scale fermenter.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170103
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  • 15
    Electronic Resource
    Electronic Resource
    HCl formation via pyrolytic degradation of polyvinyl chloride (PVC): An empirical approach to kinetic modelling (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 67-72 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The pyrolysis of polyvinyl chloride (PVC) has been described in terms of a relatively simple kinetic model, based on a large number of laboratory tests. The model predictions are in a good agreement with experimental data, regarding hydrochloric acid and non-condensable combustible gases. Therefore, the proposed model can be used to predict with good approximation the distributions of the above classes of compounds, in the whole range of applied experimental conditions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170111
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  • 16
    Electronic Resource
    Electronic Resource
    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170101
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  • 17
    Electronic Resource
    Electronic Resource
    Design of a packed column for ethanol extraction. Equilibrium and kinetics studies (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 414-421 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computer-aided design of a packed column to remove ethanol from aqueous solution with dibutyl butylphosphonate (DBBP) was accomplished with a programme based on the Pratt method and on the slip velocity equation. Reliable data for successful computation were obtained from literature correlations (drop size, hold-up and axial mixing coefficients for different types of packing) and from experimental work (equilibria and kinetics). Equilibrium studies on the H2O-ethanol-dibutyl butylphosphonate system were performed at different temperatures. A decrease in temperature increased the selectivity of the extractant while the distribution coefficient of ethanol, KD ≈ 1.0, remained constant. The behaviour of the system kinetics towards temperature is assessed in order to determine the initial mass transfer flux (892 × 10-3 kg m-2s-1, 30°C) and the activation energy, 22.9 kJ/kmol. The process is governed by the diffusion of the species involved. The influence of the type of packing of the column on its design is analyzed from the inventory volume of the solvent, the total volume of the column and the axial dispersion coefficients under normalised inlet and outlet conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170609
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  • 18
    Electronic Resource
    Electronic Resource
    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170501
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  • 19
    Electronic Resource
    Electronic Resource
    Determination of overall mass transfer coefficients in fixed bed sorption columns (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 285-289 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this study, a simple and effective technique for determining overall mass transfer coefficients in fixed bed sorption columns with recycle is presented. This new technique is free of the assumption of negligible time rate of solute concentration change in the fluid, i.e. (∂c/∂t) = 0, which has been widely used in former fixed bed sorption column analyses.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170411
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  • 20
    Electronic Resource
    Electronic Resource
    Comparison of the dynamic behaviour of packed and plate distillation columnsExpanded version of a paper presented by G. Fieg at the “Jahrestreffen der Verfahrensingenieure”, Nürnberg, September 29-October 1, 1993. (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 301-306 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The results of experimental investigations on distillation columns operating on a lab and on a production scale are presented and compared with the results obtained by simulation. There is good agreement between experiment and simulation. On the basis of these results a dynamic analysis was carried out. It compares the dynamic behaviour of packed and plate distillation columns of the same diameter and same number of theoretical plates. This reflects the influence of the different hold-ups of the two columns.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170503
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  • 21
    Electronic Resource
    Electronic Resource
    Modelling of coadsorption of different-sized molecules by using methods of statistical thermodynamicsDedicated to Professor Dr. Dr. h.c. Hanns Hofmann on the occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 119-126 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using methods of statistical thermodynamics, adsorption isotherms for the description of multicomponent chemisorption of different-sized molecular species are derived by assuming the adsorbing surface to be energetically homogeneous and by neglecting lateral interactions between the adsorbed particles. In the first part of this contribution, the adsorption equilibria for a mixture of different-sized chain molecules adsorbed on a lattice of coordination number z are discussed supposing each unit of a given chain to bind to one adsorption site only. In the second part, the coadsorption of molecular species consisting of a different number of segments on a continuous surface is treated. A comparison of the predicted to the measured isotherms for the coadsorption of two freon species on activated carbon shows that the proposed equations describe the results of the coadsorption measurements sufficiently well, provided the adsorption data for the pure components have been determined experimentally.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170209
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  • 22
    Electronic Resource
    Electronic Resource
    Single and multicomponent adsorption equilibria of carbon dioxide, nitrogen, carbon monoxide and methane in hydrogen purification processes (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 325-337 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Single, binary, ternary and quaternary adsorption equilibria of CO2, CO, CH4 and N2 on molecular sieve 5A and activated carbon were experimentally determined over a pressure range from 10-4 to 101 MPa, a temperature range from 303 to 363 K and at various compositions. The adsorption equilibria of steam reformer gases as needed for the hydrogen purification in pressure swing adsorption units were measured by using a circulating volumetric method. For the temperature-dependent correlation of pure gas isotherm fields the Toth equation, which is a favorable model for heterogeneous adsorbents, was extended by two parameters accounting for the temperature-dependencies of the saturation loading and the heterogeneity parameter. Multicomponent equilibria were successfully predicted from single component isotherms by the Ideal Adsorbed Solution Theory based on the accurate representation of the pure component data by this temperature dependent Toth equation. Other thermodynamic models like the HIAS, the MIAS, the SPD or the VS theory and the Statistical Thermodynamics Model were also applied to the prediction of the adsorption equilibrium and the temperature and pressure dependence of the selectivity, with comparable success, which is due to the quasi-ideal adsorption behavior even at a high pressure.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170507
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  • 23
    Electronic Resource
    Electronic Resource
    Basic characteristics of spinel type manganese mixed oxide/titanium composite anodes for electroorganic redox catalysisDedicated to Professor Dr. Hartmut Wendt on the occasion of his 60th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 338-347 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Manganese mixed oxide composite layers of about 1 μm thickness on titanium sheet as substrate were fabricated by firing of the corresponding nitrates at a typical temperature of 400°C in air. The activity of these anodes was evaluated by cyclic voltammetry (10 mV/s) and the stability was determined by chronopotentiometry (2.5 mA/cm2) in 1M H2SO4. The oxidation of 2-propanol was examined as a simple electroorganic model reaction. The quality of a first category of mixed oxides with general composition MnMe2O4 decresed in the order Me = Co, Ni, Fe. In a second group with the general formula MeMn2O4 a decrease in the order Me = Co, Cu, Fe, Ni, Ti, Zn, Cd, Ca, Mg, (Zn, Ge), Li was observed. The corresponding candidates of the second group were superior to those of the first. The anode service life τ of the optimum spinel anode CoMn2O4/Ti is dependent on the current density, according to jλ τ = const. (λ = 1.7). Thus high current densities are precluded. The mechanism has been discussed in terms of a heterogeneous redox catalysis: surface Mn(VII) states are formed in a slow electrochemical step. In a subsequent fast chemical oxidation of the organic molecule the original reduced state is regenerated. This also explains the comparatively good service life of these anodes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170508
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  • 24
    Electronic Resource
    Electronic Resource
    Process for production of pure 4-methyl-1-pentene (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 354-357 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A process for the manufacture of pure 4-methyl-1-pentene by catalytic dimerization of propylene has been developed in three stages. The first stage involves preparation of a new process catalyst, which contains metallic sodium and potassium deposited on a Bulgarian natural zeolite, the support having been passivated previously by potassium carbonate. The experimental results demonstrate the advantages of the resulting catalyst over exisisting technology, namely 36% conversion and 92% selectivity relevant to liquid isomers. The second development stage concerns the technological regime of chemical reaction for production of 4-methyl-1-pentene. In the third stage, the regime conditions and equipment ensuring desired quality of the product and utilization of the unreacted propylene returned to the reactor are determined. Based on the studies of all stages, a flowsheet is proposed for synthesis and separation of the reaction mixture of isomeric hexenes to give pure 4-methyl-1-pentene.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170510
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    On the para/ortho product ratio of phenol and anisole hydroxylation over titanium silicalite-1Dedicated to Professor Dr. Manfred Baerns on occasion of his 60th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 348-353 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Titanium silicalite-1 samples of different particle size are synthesised and characterised by X-ray diffraction (XRD), photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), Raman and infrared spectroscopy. Size histograms are taken from transmission electron micrographs. Temporal changes of activity and selectivity for the hydroxylation of phenol and anisole are monitored. It is postulated that the p/o product ratios are due to the greater chemisorption of the ortho molecule.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170509
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  • 26
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    Reduction of diesel particulate emissions by catalytic filtrationDedicated to Professor Dr. Dr. h. c. Hanns Hofmann on the occasion of his 70th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 149-160 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several kinds of diesel soot filters and filter materials of high melting points with eleven different catalytic coatings were prepared. They were calcined at a maximum temperature of 1000°C. The reaction rate and the kinetic parameters of the combustion of diesel soot were determined in a closed loop laboratory reactor. A packed bed of alumina particulates was the most active filter in soot combustion. Catalytic coatings with oxides of vanadium, copper or cerium accelerated the reaction. In each case the effect of the coating was dependent on specific interactions between the catalyst and the filter material. The manner of filtration and the nature of the soot filter are found to be more important for the overall result than the nature of the catalytic coating.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170303
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  • 27
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    Investigations on precious metal/alumina interactions on three-way automotive emission control catalysts, BMA catalysts and model samplesDedicated to Professor Dr. Dr. h. c. Hanns Hofmann on the occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 161-168 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Combined XPS and SIMS measurements, partly supplemented by XRD investigations, were utilized to detect precious metal/support interactions on catalysts containing various precious metals. The Klemm-Bronger reaction between Pt and α-Al2O3 on methane/ammonia catalysts was used as a standard reference. Evidence was found for different stages of Pt/Al interactions and changing electronic properties of Pt on the surfaces of these Pt/α-Al2O3 catalysts by means of XPS and SIMS, and in the bulk material by XRD. The SIMS investigations on Pt and Rh on γ-Al2O3 showed that, even at temperatures around 500 °C, Rh/Al interactions can appear to a small extent in the topmost atomic layers, whereas the Pt/γ-Al2O3 specimens did not show any measurable effects. After on-road operation, enhanced SIMS cluster-ion signals as well as anomalous XPS signal contributions were measured on the surfaces of used three-way automotive emission control catalysts. These signals did not appear for the fresh catalysts. By analogy with the related results reported on the methane/ammonia catalysts, the ion signals were used as qualitative surface probes indicating the presence of precious metal/support interactions, especially between Rh and Al.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170304
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  • 28
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    Reaction engineering simulations of a fluidized-bed reactor for selective oxidation of fluorene to 9-fluorenonePaper presented at the DECHEMA Annual Meeting, May 26-28, 1993 in Nürnberg.Dedicated to Professor Dr. Dr. h. c. Hanns Hofmann on the occasion of his 70th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 169-178 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The catalytic oxidation of fluorene to 9-fluorenone in a fluidized-bed reactor was investigated by modeling of the reactor and simulation of its performance. The “Bubble Assemblage Model” of Kato and Wen, the “Bubbling Bed Model” of Kunii and Levenspiel and the “Countercurrent Backmixing Model” of Potter were applied. From a comparison of simulation results obtained by the various fluidized-bed models and a fixed-bed model conclusions were drawn about the influence of interphase mass transfer and gas backmixing on the conversion of fluorene and slectivity of 9-fluorenone formation. Furthermore, the dependence of conversion and selectivity on temperature and hydrodynamic conditions was investigated. In particular, the implications of a change of hydrodynamic conditions for scale-up were analysed. The highest yield of 9-fluorenone predicted for a bench-scale fluidized bed amounted to 88% (XF = 97%, SNON = 91%). This yield was lower than in a fixed-bed reactor (YNON = 92%, XF = 99%, SNON = 93%). A further drop of the yield was predicted when scaling-up from a bench-scale reactor to a commercial size unit (YNON = 54%, XF = 86%, SNON = 63%).
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170305
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  • 29
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    Conversion of ethanol over zeolite H-ZSM-5 (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 179-186 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The conversion of ethanol over H-ZSM-5 was studied as a function of ethanol partial pressure, reaction temperature, weight hourly space velocity and Si/Al ratio. The results obtained were in qualitative agreement with most of those in the literature. Combination with all published results to give a significant regression model was not possible due to the large scatter of the data from various scientific groups. In mechanistic investigations, temperature programmed reaction measurements of ethanol, diethyl ether and ethene were performed. The formation of ethene from ethanol via direct elimination or from diethyl ether as intermediate could be confirmed. In the conversion of ethanol/water mixtures, the product distribution did not change significantly up to a water content of 60 wt%. Then, a pronounced increase of ethene formation and a considerable decrease of the yields of aromatics was observed. When several reaction mixtures from syngas conversion to ethanol were converted over H-ZSM-5, the coking rate depended on the product distribution in the feed. Product mixtures from processes with higher amounts of compounds having an unfavourable C/H ratio led to rapid deactivation of the zeolite.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170306
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  • 30
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    Liquid phase oxidation of α-pinene initiated by ozone. 2: Formation of verbenol, verbenone and acid products (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 187-194 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The formation of verbenol, verbenone and acids during liquid phase ozone-initiated oxidation of α-pinene has been investigated; temperature, ozone partial pressure and ozone initiation time were the variables studied. While increasing temperature promotes the formation of secondary products, the other two variables affect mainly the selectivity. Thus, an ozone partial pressure and ozone initiation time of 1014 Pa and 10 min, respectively, lead to the highest selectivities. Kinetic expressions for the formation of verbenol and verbenone, which are consistent with experimental data, have also been developed from a free radical mechanism.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170307
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  • 31
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    Controlled precipitationPaper presented by A. Mersmann at the Meeting of German Chemical Engineers, Vienna, 30. Sept.-2. Oct. 1992. (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 1-9 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a process of precipitation, two or more reactants form a product. In many cases, the solubility of this product is very low and high supersaturation is generated which leads to nucleation and crystal growth. The number of the formed nuclei and their growth govern the particle size distribution of the precipitate. As a rule, the precipitate is separated from the mother liquor in a centrifuge or on a filter. This separation and the subsequent drying process of very fine particles can be very expensive with respect to investment and energy costs. Therefore, it is desirable to produce as coarse a precipitate as possible with a narrow crystal size distribution.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170102
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  • 32
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    Kinetic studies on high temperature desulphurization of synthesis gas with zinc ferrite (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 21-29 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The desulphurization of synthesis gas with zinc ferrite was studied in a laboratory-scale fixed-bed reactor. Desulphurization efficiency of 97-99% was obtained. The inlet hydrogen sulphide concentration was about 2600 ppm. A flat breakthrough curve showed that diffusion through the sulphide layer controlled the rate of sulphidization. The degrees of utilization varied between 5 and 11%. Experimental data formed the basis of a kinetic evaluation with the fixed bed model and the unreacted core model. Rate constants, reaction orders, and effective diffusion constants were calculated. When chemical reaction controlled the rate, the order of reaction was between zero and unity. The rate of reaction increased with temperature. Effective diffusivities were of the order of 10-5 m2 s-1, increasing slightly in the temperature range between 500 and 600°C. The activation energy was determined as 54 kJ mol-1, which corresponds to an unexpectedly strong temperature dependence of the diffusion-controlled reaction. The low degrees of utilization, and also the strong temperature dependence, are explained by sintering of the sulphidized zinc ferrite.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170104
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  • 33
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    Supported nickel catalyst from hydroxycarbonate of nickel and aluminium (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 41-46 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hydroxycarbonate of nickel and aluminium (Ni/ Al = 3) with a hydrotalcite-like structure is an outstanding precursor of the active component of supported nickel catalysts. Good mechanical strength and suitable nickel content of these catalysts, which are necessary for practical applications, can be achieved by mechanical mixing of this compound with an additional support. The catalyst prepared from a mixture of 56.5 wt-% of nickel-aluminium hydroxycarbonate and 43.5 wt-% of γ-alumina was proven to have a stable catalytic activity in the methanation reaction at 2 MPa and 800 K.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170107
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  • 34
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    Catalytic dehydrogenation of methanol to water-free formaldehydeDedicated to Professor Horst Langemann on the Occasion of his 65th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 34-40 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Catalytic dehydrogenation of methanol is a promising process of producing water-free formaldehyde. The present paper reviews research in this field. As effective catalysts mainly transition metal compounds as well as oxides and salts containing sodium have been reported. Several catalysts exhibit high activity and high selectivity, for formaldehyde at low conversions while further efforts have to be made to improve catalyst stability and selectivity at high conversions. Catalytic dehydrogenation of methanol to formaldehyde is compared with methanol oxidation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170106
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  • 35
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    Removal of ethoxylated aliphatic amines from zinc containing effluents by adsorption on macroporous resinspaper presented at the sci conference iex '92 - ion exchange advances, cambridge, uk, 12-17 july, 1992. (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 30-33 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The separation of ethoxylated aliphatic amines from zinc containing effluents with macroporous polymeric adsorbents Wofatit EP 61, EP 62, Y 59, Y 77 and active carbons has been examined. The adsorption behaviour has been investigated as a function of temperature, time and concentration of Na2SO4, ZnSO4 and H2SO4. The macroporous polymers EP 61, Y 77 and Y 59 are capable of separating ethoxylated aliphatic amines from effluents of viscose fibre industry at higher temperatures and under weakly acidic conditions. In contrast to active carbon, inorganic components are not adsorbed on the investigated macroporous resins. Data obtained in a concentration range of 0 to 10 g of adsorbate per litre produced a Langmuir profile for adsorption of ethoxylated aliphatic amines by polymeric adsorbents.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170105
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  • 36
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    Non-Darcian non-isothermal compressible flow and heat transfer in cylindrical packed beds (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 50-60 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Knowledge of transport processes is of considerable practical importance in the design and performance evaluation of packed bed reactor systems. Acquisition of the required information necessitates a realistic mathematical description of the system. In this study, numerical analysis is performed for forced convective non-Darcian, non-isothermal compressible flow and heat transfer in cylindrical packed beds. Local structural and transport properties are considered. The influence of compressional work as well as viscous dissipation on the thermal field is evaluated and a general criterion provided for assessing the effect of expansion.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170109
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  • 37
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    Further remarks on the linear relationship between stoichiometry and dimensional analysisDedicated to Professor Dr. Horst Langemann on the Occasion of his 65th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 47-49 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The phrase “further remarks” in the title of this short paper is meant to imply that reactions and dimensionless groups are not only purely algebraic concepts, but definite numerical values can also be associated with them; in stoichiometry this evaluation may relate, for example, to the heat of reaction and, in dimensional analysis, to what is called a dimensionless number. On the basis of the evaluation concept, it will be shown that a counterpart of Hess' law in thermochemistry is valid in dimensional analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170108
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  • 38
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    Inertial impaction of aerosol particles on single and multiple spherical targets (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 88-94 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Inertial deposition of aerosol droplets (diameter: 1-14 μm) on steel spheres (diameter: 3-9 mm) was investigated. Air velocity was varied between 7 and 28 m/s (corresponding sphere Reynolds numbers: 1400-17000). The impaction on single spheres as well as that on linear arrays of eight spheres was measured. Theoretical results, based on potential flow investigations were verified by single sphere experiments. Of special interest was the range of lower Stokes numbers, where the theoretically predicted limit of deposition cannot be verified. The experiments on sphere arrays were for the first time performed in the low Stokes number range. Deposition on the leading sphere, relative to that on the shielded spheres, exhibits a maximum in the high Stokes number range, but this changes drastically in the low Stokes number range. Here, maximum deposition can be found on the shielded spheres while the leading sphere shows a markedly lower deposition.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170204
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  • 39
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    Electronic Resource
    The cyclone scrubber - a high efficiency wet separator (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 73-80 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Due to induced turbulent interactions between particles to be separated and the scrubbing liquid present as droplets, very good collection efficiency down to submicron particle size can be achieved as shown by detailed studies [1]. Assumed are suitable flow conditions, a long residence time and a certain droplet size distribution or a special liquid dispersion system. As the name implies, the cyclone scrubber basically consists of a cyclone. This cyclone serves as a contact space in which the interaction between dust particles and scrubbing liquid droplets takes place, and as a droplet separator. Thus, under normal conditions, a water saturated but dust- and droplet-free gas stream leaves the cyclone. The droplets are generated by a pneumatic atomization nozzle, arranged at the cyclone inlet in the direction of flow. A complete theoretical description of the three-dimensional, three-phase, non-steady turbulent flow in the cyclone scrubber has not been possible up to now. The detailed experimental investigations presented in this work, and covering multiple parameters, led to physically based conclusions about the dominant interactions and separation mechanisms involved. Grade efficiencies which did not fall below 0.75, down to a particle size of 0.5 μm, could be measured by an optical particle counter. Collection efficiency of 99.2% was determined by gravimetric analysis of the dust load, according to VDI-guideline 2066, in the raw and clean gas sections of the dust load, according to VDI-guideline 2066, in the raw and clean gas sections of the cyclone scrubber.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170202
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  • 40
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    A rotating two-phase gas/liquid flow regime for pressure reduction in underwater plasma arc welding (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 81-87 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plasma arc welding processes are used in the off-shore industry for construction and maintenance of underwater structures and pipelines in a wet environment. At greater water depths the density of the plasma gas increases because of the greater hydrostatic pressure. This causes conductive heat losses to the wet environment to increase. To maintain the energy flux to the workpiece to be welded, the plasma arc has to burn in a local dry area with an inside pressure of 1 bar. This requirement can be fulfilled by a rotating cylinder with a liquid film flowing down the inner wall. The flow around the rotating cylinder is experimentally investigated. The rotating cylinder is placed above the work surface which is simulated by a flat plate. Because of the centrifugal forces of the rotating flow inside the gap between the lower end of the cylinder and the flat plate the water is forced out of the cylinder. The velocity distribution in the flow is measured by laser Doppler anemometry. The phase distribution in the two-phase flow in the gap is measured by local electrical probes. The static pressure inside the gaseous atmosphere is reduced in comparison to the hydrostatic pressure of the surrounding water. The pressure reduction is given by the void fraction, the phase distribution and the volume flow rates of both phases in the gap as well as by the speed of revolution and the design of the cylinder and the work surface. The influence of these parameters on heat transfer from the workpiece to the two-phase flow regime is also investigated.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170203
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  • 41
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    Homogenization of liquids in tanks stirred by multiple impellers (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 95-101 
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    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The process of homogenization of liquids in a tall vessel equipped with a multiple impeller was studied. Up to four standard Rushton turbines and/or six pitched-blade turbines were used. The mixing time in the system was measured by the conductivity method. A continuous time history of the tracer concentration at several points in the system was recorded. The data were interpreted by means of an adapted cell model of the flow within the stirred vessel with several impellers based on the assumption of well mixed cells and intercellular flow of liquid. The liquid transfer flow rate between the cells, as a parameter of the model, was calculated from experimental data. A good agreement between the time dependence of concentration obtained experimentally and that calculated from theory was obtained. A direct relationship between the flow numbers between cells and those of impellers was established.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170205
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  • 42
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    Heterogeneous catalytic methylation of catecholDedicated to Professor Dr. Dr. h. c. Hanns Hofmann on the occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 108-111 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been shown that, after a partial deactivation, γ-alumina (γ-Al2O3) is a good catalyst for selective methylation of 1,2-benzenediol in the temperature range of 260-310°C. The main products are the desired 3-methyl-1,2-benzenediol and 2-methoxyphenol, which may be converted in another step into 3-methyl-1,2-benzenediol, giving an overall selectivity for the desired products of 80 to 90%. The catechol forms a strongly chemisorbed surface species on γ-alumina and its steric adsorption model correlates with the kinetic data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170207
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  • 43
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    Deactivation of a vinyl acetate catalystDedicated to Professor Dr. Dr. h. c. Hanns Hofmann on the occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 112-118 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetic studies as well as morphological and physico-chemical surface studies have been carried out on the deactivation of a palladium carrier catalyst for vinyl acetate synthesis in the ethylene gas phase process. The experiments cover concentration and temperature ranges of technical interest at a total pressure of 900 kPa. The deactivation rate depends on the temperature and the oxygen and acetic acid concentrations. The decline in activity is best described by a rate law of second order relative to the activity number. This behaviour is attributed to the observed aggregation of finely dispersed palladium. It can be concluded that palladium(II) acetate acts as a transport species in a chemically assisted sintering mechanism. At temperatures T ≤ 438 K the more advantageous final texture of the catalyst will only be formed on reaction.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170208
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  • 44
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    Continuous computer controlled production of formate dehydrogenase (FDH) and isolation on a pilot scaleDedicated to Professor Dr. Dr. h.c. Hanns Hofmann on the occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 131-137 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A continuous production process has been developed up to pilot scale (300 l) for FDH production with the methylotrophic yeast Candida boidinii. A high cell mass specific FDH activity (50 U/g) is achieved by process computer controlled supply of pure methanol to operate the reactor at an optimum methanol concentration of 10 g/l. The maximum FDH spacetime yield achievable with this process control involves a residence time of 7 h. The FDH space-time yield (STY) and FDH concentration are a function of the oxygen transfer rate (OTR) of the fermenter (maximum STY = 255 U/(l h) at kLa = 870 l/h). For a reasonable compromise between high FDH space-time yield and high FDH concentration, an optimum residence time is adjustable by regulating the supply of nutrient salt solution in relation to the OTR of the fermenter. On a pilot scale (200 l continuously stirred tank reactor) roughly 4 million U of FDH were produced within 10 days at a residence time of 14.3 h. Isolation of intracellular FDH enzyme was performed using extraction with an aqueous two-phase system (PEG/K2HPO4). A technical product quality of 1.2 U/mg FDH was achieved without any chromatographic purification step.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170211
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    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170301
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  • 46
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    A mathematical model describing the ARI “autocirculation reactor” for low temperature conversion of H2S into sulphur (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 141-143 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A prototype “autocirculation”-type reactor has been designed and constructed at the N.I.O.C. Research Institute, Tehran and a mathematical model describing the concentration versus time profile subsequently developed. The model encompasses mass transfer considerations and kinetic studies of the regeneration reaction. For this purpose, the rate equation for iron complex oxidation, proposed by Japanese researchers, was modified and a new rate equation presented. This rate equation has been widely used in the above mentioned mathematical model. With this model, the vessel volume for a time-dependent H2S feed has been calculated for a “ZDDP” production unit.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170213
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    Applications of computational fluid dynamics in the chemical industryDedicated to Professor Dr. Dr. h. c. Hanns Hofmann on the occasion of his 70th Birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 145-148 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to illustrate the use of CFD in providing an understanding of mixing processes, three examples, mixing in a pipe, homogenization with a static mixer and flow in a mixing vessel with a Rushton turbine, are discussed and compared with experimental results. Special attention is focussed on the resultant concentration distribution, which is closely linked to turbulent properties. A semi-empirical model is presented for a quantitative prediction of the initial turbulent conditions. Using special numerical techniques a mixing vessel with wall-separated baffles, which represents a problem generally regarded as beyond the capabilities of numerical analysis, can be simulated.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170302
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  • 48
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    Dynamic response and safety assessment of a batch process on cooling breakdown (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 358-363 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cooling breakdown in highly exothermic reaction processes may lead to runaway. The sensitivity and the safety assessment of a batch process on cooling breakdown are studied. The dependence of the minimum cooling time and the maximum allowable time of cooling breakdown for safe operation on the process parameters is investigated.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170511
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  • 49
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    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170601
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  • 50
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    Concept of a sterile concentration process for milk by multistage flash evaporationDedicated to Professor Dr. Dr. h. c. Hansjörg Sinn on occasion of his 65th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 374-381 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the proposed combined sterilisation and concentration method, the original milk is first sterilised under conditions of continuous flow and after reaching the desired sterilisation temperature the product is concentrated by means of flash evaporation during subsequent cooling. Addition of stabilisers to maintain the thermal stability of the concentrate during sterilisation is not necessary in this process. The method presupposes that cooling with concentration is carried out under sterile conditions. This is technically quite feasible on use of multistage flash evaporation.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170603
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  • 51
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    Pyrolysis of propane at reflected shock-wave temperatures from 1300 to 2700 K (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 195-200 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Shock tube pyrolysis of propane at temperatures between 1300 K and 2700 K at reflected shock pressures of 500 to 1500 kN/m2 has been investigated. The reaction is of 1st order with a rate constant K = 1.79 × 108 exp (-176.2 kJ/RT) s-1. The major reaction products were acetylene, ethylene and methane, while traces of propylene and ethane were only detected at temperatures below 1500 K. At higher temperatures, propane conversion to acetylene increased at the expense of the other products. Optimum conversions to ethylene and methane, in contrast to that to acetylene, were more sensitive to changes in temperature than to variations in reaction time. However, at reaction pressures above 550 kN/m2, extension of reaction time beyond 0.5 ms did not favour the formation of acetylene. A simple kinetic model which confirmed the experimental optimum product selectivity conditions is put forward.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170308
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    Mass transfer and reaction behaviour of a circulating fluidized bed reactorPaper presented at the DECHEMA annual meeting, May 26-28, 1993, Nürnberg, GermanyDedicated to Prof. Dr. Dr. h. c. Hanns Hofmann on the occasion of his 70th birthday (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 201-209 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution presents a chemical reactor model of a circulating fluidized bed (CFB) which takes into account adsorption effects and provides a description of the vertical profiles of gas concentration in the riser. The oxidation of NO is used as an example of a heterogeneous catalytic reaction. Mass transfer between the gas phase and solid particles in the CFB was investigated at various temperatures and solids mass flow rates. The measurements show that the mass transfer coefficient decreases with increasing solids mass flux and that the CFB resembles a bubbling fluidized bed as regards gas-solid contacting.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170309
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  • 53
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    Masthead (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994) 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ceat.270170401
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  • 54
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    Kinetic study of the synthesis of n-octyl octanoate using cobalt chloride as catalyst (1994)
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 210-215 
    Details
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the pseudohomogeneous liquid phase synthesis of a high molecular weight ester in a stirred tank reactor using cobalt chloride as catalyst has been studied at various temperatures, catalyst concentrations, and acid/alcohol molar ratios. A kinetic model has been determined that predicts the experimental results quite well.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ceat.270170310
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  • 55
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    Three-dimensional dynamics of pseudopod formation and the regulation of turning during the motility cycle of Dictyostelium (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 1-12 
    Details
    ISSN: 0886-1544
    Keywords: pseudopod extension ; amoebae ; uropod retraction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Employing a newly developed computer-assisted system for visualizing and quantitating cell motility in three dimensions, we have examined the 3-dimensional changes in cell shape and the dynamics of pseuodopod extension during translocation of Dictyostelium amoebae. Amoebae exhibit a 3-dimensional behavior cycle with an average period of 1.5 min. The cycle includes a transient pseudopod extension phase in the x, y axis followed by a z-axis expansion phase. Anterior pseudopod extension in the x, y axis is accompanied by a decrease in height, not by uropod retraction. The increase in height is accompanied by uropod retraction. In the pseudopod extension phase in the x, y axes, pseudopods form either anteriorly or laterally, and either on or above the substratum. Pseudopods which initially form on the substratum in almost all cases continue to expand as the anterior end of the cell. In the case of lateral pseuodopods, anteriorization leads to a turn. Approximately half of anterior pseudopod and two-thirds of lateral pseudopods which initially form above the substratum are retracted. These results suggest that pseudopod-substratum interaction plays a fundamental role in the regulation of directionality and turning in the translocation phase of the 3-dimensional behavior cycle. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270102
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  • 56
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    Microtubule converging centers and reorganization of the interphase cytoskeleton and the mitotic spindle in higher plant Haemanthus (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 219-233 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; mitosis ; cytoskeleton reorganization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We analyzed the distribution and orientation of transitory microtubule structures, microtubule converging centers, during interphase and mitosis in endosperm of the higher plant Haemanthus. In interphase the pointed tips of microtubule converging centers are associated with the nuclear envelope. Their orientation gradually reverses during prophase, and the tips tend to point away from the nucleus. From prometaphase through early telophase, microtubule converging centers are present predominantly in the cytoplasm at the polar region. They are either “free” or associated with chromosomes or microtubule bundles. In late telophase, pointed tips of microtubule converging centers are again associated with the reconstructed nuclear envelope and, additionally, they often appear in the phragmoplast area. The orientation of microtubule converging centers seems to be directly correlated to the previously determined microtubule polarity, with the converging tip being minus and the diverging one, plus.Elevated temperature (35°-37°) enhances the number of microtubule converging centers in the cytoplasm and at the nuclear envelope. This is especially pronounced during the telophase-interphase transition and in some interphase cells, indicating temperature and stage dependence.Our data imply that microtubule converging centers bind together MT minus ends and, thus, control the predominant direction of elongation and shortening of microtubule arrays. We argue that these configurations are instrumental during the reorganization of interphase cytoskeleton and mitotic spindle in Haemanthus endosperm. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270304
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  • 57
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    ATP-induced sliding of microtubules on tracks of 22S dynein molecules aligned with the same polarity (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 180-191 
    Details
    ISSN: 0886-1544
    Keywords: sliding movement ; 22S dynein ; Tetrahymena cilia ; dynein-track ; singlet microtubule ; ATP ; polarity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chlamydomonas and Tetrahymena axonemal dyneins have previously been found to bind to porcine brain microtubules to produce a microtubule-dynein complex. At appropriate microtubule:dynein concentration, microtubules in the complex became covered to saturation by dynein arms of the same polarity and at a spacing of 24 nm [Haimo et al., 1979; Haimo and Fenton, 1988; Haimo, 1989; Porter and Johnson, 1983a].In the present study, two different types of microtubule-dynein complexes (α-and β-complexes) were prepared from Tetrahymena ciliary 22S dynein and porcine brain tubulin. The characteristics of the adenosine triphosphate (ATP)-induced extrusion of microtubules from these complexes were analyzed, as a simple and direct in vitro assay for the ATP-induced extrusion of single microtubules. The α-complex prepared by adding dynein to microtubules showed an interrupted sliding movement, which would stop and start several times following the addition of ATP. In the β-complex, prepared by adding dynein bound to DEAE-tubulin to pre-assembled microtubules, microtubules became covered with dynein molecules whose orientation and binding were uniform with respect to microtubule polarity. The microtubules in the β-complex extruded at 12 μm/second following the addition of ATP. Dark-field and electron microscopy indicated that the extruded microtubules had undergone sliding on a dynein-track that had become detached from the complexes and had been absorbed onto the surface of the glass slide. At higher light intensity under a dark-field microscope, the dynein-track was seen to be composed of rows of dynein molecules arranged densely. The orientation of dynein molecules in rows appeared to be uniform considering the images of bound dynein in the β-complex under electron microscope. The higher sliding velocity of the microtubules on these dynein-tracks compared to that seen on slides coated at random with dynein [Vale and Toyoshima, 1988, 1989], may be due to more efficient force generation by this dense arrangement of dynein molecules with the same polarity on the tracks. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270209
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    Role of cAMP in the reactivation of demembranated ram spermatozoa (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 206-218 
    Details
    ISSN: 0886-1544
    Keywords: sperm motility ; sperm maturation ; flagella ; protein kinases ; protein kinase inhibitor ; cGMP ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Ejaculated ram sperm were demembranated with Triton X-100, separated from the detergent-soluble matrix, and reactivated [San Agustin and Witman (1993): Cell Motil. Cytoskeleton 24:264-273]. The percent motility of models prepared from freshly washed sperm was comparable to that of the washed sample before demembranation, regardless of whether cAMP was included in the reactivation medium. However, demembranated models derived from aging or metabolically inhibited sperm exhibited a lower percent reactivation and required cAMP to attain the level of motility of freshly washed sperm. Cyclic AMP was ∼100 times more effective than cGMP. The requirement for cAMP could be bypassed by addition of porcine heart cAMP-dependent protein kinase (PKA) catalytic subunit to the reactivation medium, demonstrating that cAMP was acting via PKA. The cAMP stimulation of reactivation was not affected by inclusion of the PKA inhibitor PKI(5-24) in the reactivation medium, but was decreased when the models were preincubated with PKI(5-24) prior to reactivation. The cytosol-free models retained 〉90% of the sperm PKA activity; therefore, the PKA appears to be anchored to internal sperm structures. This PKA could not be extracted by cAMP or Triton X-100 alone, but only by cAMP and Triton X-100 in combination. We conclude that cAMP-dependent protein phosphorylation is critical for sperm motility, but that the essential protein phosphate sites turn over slowly under our reactivation conditions, so that the cAMP requirement is apparent only in models prepared from sperm having a low internal ATP or cAMP content. Interestingly, reactivation was rapidly blocked by the peptide arg-lys-arg-ala-arg-lys-glu, which has been reported to be a selective inhibitor of cGMP-dependent protein kinase. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970270303
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  • 59
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    Coordinated expression of five tropomyosin isoforms and β-actin in astrocytes treated with dibutyryl cAMP and cytochalasin D (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 303-316 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; cell culture ; gene expression ; Northern blot ; serum-induction ; rat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cytochalasin D and dBcAMP cause cultured astrocytes to change from flat cells to retrated process-bearing cells. F-actin was present throughout cells stimulated with dBcAMP for 16 h, whereas cytochalasin D caused F-actin to form massive aggregates at the tips of the cell processes. The two drugs differently regulated the expression of both β-actin and tropomyosin genes in astrocytes cultured in the presence or absence of serum: dBcAMP caused down-regulation and cytochalasin D caused up-regulation. Northern blot analyses indicated that: (1) serum deprivation halved the concentration of all tropomyosin transcripts (TM-1, TM-2, TM-4, TMBr-1, TMBr-2). Serum induced TM-4 via transcriptional activation, independent of protein synthesis, (2) dBcAMP induced down-regulation of β-actin (-50%) and tropomyosin transcripts (-35 to 52%) even in the presence of serum. The concentration of profilin mRNA decreased in dBcAMP-reactive astrocytes (-46%). The decrease in β-actin mRNA concentration was not blocked by cycloheximide, whereas down-regulation of tropomyosin transcripts was completely reversed when protein synthesis was inhibited, and (3) cytochalasin D induced an increase in the concentration of tropomyosin transcripts (+ 69 to 185%) which was cumulative with serum stimulation. Cytochalasin D induction of both β-actin and TM-4 operated through transcriptional activation, independent of protein synthesis.The production of all tropomyosin transcripts examined here were strictly coordinated with β-actin expression in serum-, dBcAMP- and cytochalasin D-treated astrocytes. This indicates that the differential expression of tropomyosin isoforms occurring during astrocyte maturation is due to more complex regulation than that involved in serum- or cAMP-stimulated astrocytes. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970280404
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    Announcement (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 360-360 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970280410
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  • 61
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    Regulation of the Ascaris major sperm protein (MSP) cytoskeleton by intracellular pH (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 193-205 
    Details
    ISSN: 0886-1544
    Keywords: amoeboid motility ; fluorescence ratio imaging ; BCECF ; nematodes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development and locomotion of the amoeboid sperm of the nematode, Ascaris suum, depend on precise control of the assembly of their unique major sperm protein (MSP) filament system. We used fluorescence ratio imaging of cells loaded with BCECF to show that intracellular pH (pHi) is involved in controlling MSP polymerization in vivo. Spermatogenesis is marked by a cycle of MSP assembly-disassembly-reassembly that coincides with changes in pHi. In spermatocytes, which contain MSP in paracrystalline fibrous bodies, pHi was 6.8, 0.6 units higher than in spermatids, which disassemble the fibrous bodies and contain no assemblies of MSP filaments. Activation of spermatids to complete development resulted in rapid increase in pHi to 6.4 and reappearance of filaments. Treatment of spermatocytes with weak acids caused the fibrous bodies to disassemble whereas incubation of spermatids in weak bases induced MSP assembly. The MSP filaments in spermatozoa are organized into fiber complexes that flow continuously rearward from the leading edge of the pseudopod. These cells established a pseudopodial pH gradient with pHi 0.15 units higher at the leading edge, where fiber complexes assemble, than at the base of the pseudopod, where disassembly occurs. Acidification of these cells caused the MSP cytoskeleton to disassemble and abolished the pH gradient. Acid removal resulted in reassembly of the cytoskeleton, re-establishment of the pH gradient, and re-initiation of motility. MSP assembly in sperm undergoing normal development and motility and in cells responding to chemical manipulation of pHi occurs preferentially at membranes. Thus, we propose that filament assembly in sperm is controlled by pH-sensitive MSP-membrane interaction. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970270302
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    Antisense MAP-2 oligonucleotides induce changes in microtubule assembly and neuritic elongation in pre-existing neurites of rat cortical neurons (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 234-247 
    Details
    ISSN: 0886-1544
    Keywords: microtubule-associated protein 2 ; neurons ; microtubule-associated proteins ; cytoskeleton ; dendrites ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubule-associated protein 2 (MAP-2) is an abundant component of the cytoskeleton present in dendrites and cell bodies of neurons of the CNS. To examine the biological function of MAP-2, two MAP-2 antisense (AS) oligonucleotides complementary to the 5′ region of the rat MAP-2 cDNA were added to rat primary embryonic day 17-18 (E17-18) cultured cortical neurons 24 h after plating and neurite outgrowth and morphology studied. The treatment of primary cortical cultures with either of the two MAP-2 AS oligonucleotides resulted in decreased MAP-2 and reduction in the number of neuritic processes relative to the control or MAP-2 sense-treated cultures. By immunostaining and light microscopy the AS-treated neurons appeared smaller, more rounded, and less intensely stained for MAP-2 than the untreated or the MAP-2 sense-treated cultures. By electron microscopy disorganized microtubules and a reduction in the number of microtubules within neurites of the AS-treated cultures were observed. We conclude that MAP-2 continues to be required for microtubule spacing and stability within neurites once they have formed. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270305
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    Cellular infrared detector appears to be contained in the centrosome (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 262-271 
    Details
    ISSN: 0886-1544
    Keywords: 3T3 cells ; cell motility ; infrared ; phototaxis ; centrosome ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous experiments have suggested that 3T3 cells were able to extend pseudopodia toward latex particles up to 60 μm away from the cell body if the particles were irradiated by an infrared beam in the range of 700-900 nm [Albrecht-Buehler, 1991: J. Cell Biol. 114:493-502]. The present article reports that this response of cells to infrared light can be inhibited if the cell center is simultaneously irradiated with a beam of the same light. In marked contrast, the cells responded normally to the presence of infrared light scattering particles if the second beam irradiated other parts of the cell body. The results imply that the cellular mechanism of infrared detection is located at the cell center. The infrared sensing mechanism remains intact in enucleated cells and in cells which were incubated in monensin to vesiculate their Golgi apparatus and inhibit their Golgi functions. Accordingly, it is proposed that the centrosome which contains the centrioles is the only remaining candidate in the cell center for a cellular detection device for the direction of infrared signal sources. The results support an earlier suggestion that centrioles may be such detection devices [Albrecht-Buehler, 1981: Cell Motil. Cytoskeleton 1:237-245]. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270307
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    Regulation and evolution of the single alpha-tubulin gene of the ciliate Tetrahymena thermophila (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 272-283 
    Details
    ISSN: 0886-1544
    Keywords: cell cycle ; transcription ; mRNA decay ; autoregulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The single alpha-tubulin gene of Tetrahymena thermophila was isolated from a genomic library and shown to encode a single protein. Comparisons of the rates of evolution of this gene with other alpha-tubulin sequences revealed that it belongs to a group of more evolutionarily constrained alpha-tubulin proteins in animals, plants, and protozoans versus the group of more rapidly evolving fungal and variant animal alpha-tubulins. The single alpha-tubulin of Tetrahymena must be used in a variety of microtubule structures, and we suggest that equivalently conserved alpha-tubulins in other organisms are evolutionarily constrained because they, too, are multifunctional. Reduced constraints on fungal tubulins are consistent with their simpler microtubule systems. The animal variant alpha-tubulins may also have diverged because of fewer functional requirements or they could be examples of specialized tubulins. To analyze the role of tubulin gene expression in regulation of the complex microtubule system of Tetrahymena, alpha-tubulin mRNA amounts were examined in a number of cell states. Message levels increased in growing versus starved cells and also during early stages of conjugation. These changes were correlated with increases in transcription rates. Additionally, alpha-tubulin mRNA levels oscillate in a cell cycle dependent fashion caused by changes in both transcription and decay rates. Therefore, as in other organisms, Tetrahymena adjusts alpha-tubulin message amounts via message decay. However the complex control of alpha-tubulin mRNA during the Tetrahymena life cycle involves regulation of both decay and transcription rates. © 1994 Wiley-Liss, Inc.
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    Physical model of axonemal splitting (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 287-298 
    Details
    ISSN: 0886-1544
    Keywords: cilium ; flagellum ; motility ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A physical model developed to explain microtubule sliding patterns in the trypsintreated ciliary axoneme has been extended to investigate the generation of bending moments by microtubules sliding in an axoneme in which the dublets are anchored at one end. With sliding restricted, a bending moment is developed by the polarized shearing interaction between neighbouring doublets, effected by the activity of dynein arms on doublet N pushing N + 1 in a tipward ( + ) direction. In arrested axonemes in which arms on several contiguous doublets are active, the bending moment causes splitting of the 9 + 2 microtubule array into two or more sets of doublets. In the absence of special constraints, splitting depends only on breaking the circumferential interdoublet links most distorted by the bending moment. The analysis, which permits assignment of arm activity to specific microtubules in each of the observed patterns of splitting, indicates that the axoneme will split between doublet N and N + 1 if arms on doublet N are inactive and arms on either N + 1 or N-1 are active. To produce the observed major splits, dynein arms on the microtubules of roughly one-half of the axoneme are predicted to be active, in a manner consistent with the switch-point hypothesis of ciliary motion. Electron microscopic examination indicates that virtually every set of doublets in the split axonemes retains its cylindrical form. Maintenance of cylindrical symmetry can be ascribed to the mechanical properties of the unbroken links, which may resist both tensile and compressive stress, and to active dynein arms. © 1994 Wiley-Liss, Inc.
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    Functional analysis of a cardiac myosin rod in Dictyostelium discoideum (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 313-326 
    Details
    ISSN: 0886-1544
    Keywords: myosin II ; cardiac ; sarcomeric ; cytoplasmic myosin ; LMM ; Dd ; heterologous expression ; ConA ; receptor capping ; aggregation ; filament assembly region ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Manipulation of the single conventional myosin heavy chain (mhc) gene in Dictyostelium discoideum (Dd) has delineated an essential role for the filament-forming, or light meromyosin (LMM) domain of the myosin molecule in cyto-kinesis, development, and in the capping of cell surface receptors (see Spudich: Cell Regulation 1:1-11, 1989; Egelhoff et al.: Journal of Cell Biology, 112:677-688, 1991a). In order to assess the functional relationship between sarcomeric and cytoplasmic myosins, a chimeric gene encoding the Dd myosin head and subfragment 2 fused to rat β cardiac LMM was transfected into both wild-type and Dd mhc null cells. Chimeric myosin was organized into dense cortical patches in the cytoplasm of both wild-type and Dd mhc null cells. Although null cells expressing chimeric mhc at ∼10% of Dd mhc levels were unable to grow in shaking suspension or to complete development, chimeric myosin was able to rescue capping of cell surface receptors, to associate with filamentous actin, and to localize to the correct subcellular position during aggregation. Deletion of 29 amino acids in the rod corresponding to a previously defined filament assembly competent region eliminated the cortical patches and the posterior localization during chemotaxis. Taken together, these observations suggest that sarcomeric and cytoplasmic myosin rods are functionally interchangeable in several aspects of nonmuscle motility. © 1994 Wiley-Liss, Inc.
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    Cell motility and the cytoskeleton video supplement 4 (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 361-372 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270408
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970280101
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    Effects of 6-dimethylaminopurine on the length of the cell cycle and on the state of phosphorylation of putative intermediate filament proteins in sea urchin embryos (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 131-140 
    Details
    ISSN: 0886-1544
    Keywords: intermediate filaments ; phosphorylation ; sea urchin embryos ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of 6-dimethylaminopurine (6-DMAP) on the length of the cell cycle and on the state of phosphorylation of a putative intermediate filament protein, p117, have been studied in sea urchin embryos. Embryos were transferred into sea water containing 600 μM 6-DMAP at 0.5, 2 or 5 min after insemination, and incubated for 30 or 90 min. The effects of 6-DMAP on cell cycle length were studied by determining the time required for completion of mitosis upon return of the embryos in normal sea water. In all instances, except for the embryos transferred 0.5 min after insemination (AI) and incubated for 30 min, the duration of the M phase was shortened compared to controls, being faster in the embryos incubated for 90 minutes compared to the 30 min incubation period. However, embryos transferred 0.5 min AI have a longer M-phase than those transferred 2 minutes or later after fertilization, suggesting that between 0.5 and 2 min after fertilization, critical phosphorylating events occur which affect the commitment of the cells to enter M-phase.To study the pattern of p117 phosphorylation during the cell cycle, the eggs were transferred 2 minutes after fertilization in presence of 600 μM 6-DMAP and with 200 μCi/ml of 32P-orthophosphate. Analyses of 32P-labelled proteins after exposure of SDS-PAGE gels and their corresponding blots suggested that phosphorylation of p117 greatly increases at the time of pronuclear fusion, and then declines slightly at prophase-metaphase. This decrease is markedly enhanced when the cells are treated with 6-DMAP during metaphase in order to induce a premature breakdown of the mitotic apparatus. A causal link is suggested between the level of phosphorylation of p117 and its state of assembly. © 1994 Wiley-Liss, Inc.
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    Kinesin-related polypeptide is associated with vesicles from Corylus avellana pollen (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 155-166 
    Details
    ISSN: 0886-1544
    Keywords: Golgi vesicles ; pollen ; pollen tube ; microtubules ; kinesin-related protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A 100-kDa polypeptide with microtubule-interacting properties was identified in a Golgi vesicle-enriched fraction from Corylus avellana pollen. The k71s23 antibody (directed to the kinesin heavy chain from bovine brain) [Tiezzi et al., 1992: Cell Motil. Cytoskeleton 21:132-137] localized the polypeptide on the external surface of membrane-bounded organelles. Some 100-kDa-containing vesicles co-pelleted with microtubules (polymerized from purified bovine brain tubulin) either in presence or absence of 5 mM AMPPNP, but they could be released by 10 mM ATP or 0.5 M KCl. The pollen microtubule-interacting protein, salt-extracted from membranes and partially purified by gel filtration, exhibited an ATPase activity (16.2 nmolPi/mg/min) which could be stimulated about 2-fold (32.5 nmolPi/mg/min) by addition of bovine brain microtubules. We suppose that the 100-kDa polypeptide is part of a molecular complex showing properties of the kinesin class. © 1994 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970290207
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    Assembly and bundling of marginal band microtubule protein: Role of tau (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 57-71 
    Details
    ISSN: 0886-1544
    Keywords: microtubule bundling ; cytoskeleton ; tau ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubule protein extracted from dogfish erythrocyte cytoskeletons by disassembly of marginal bands at low temperature formed linear microtubule (MT) bundles upon reassembly at 22°C. The bundles, which were readily visible by video-enhanced phase contrast or DIC microscopy, increased in length and thickness with time. At steady state after 1 hour, most bundles were 6-11 μm in length and 2-5 MTs in thickness. No inter-MT cross-bridges were visible by negative staining. The bundles exhibited mechanical stability in flow as well as flexibility, in this respect resembling native marginal bands. As analyzed by SDS-PAGE and immunoblotting, our standard extraction conditions yielded MT protein preparations and bundles containing tau protein but not high molecular weight MAPs such as MAP-2 or syncolin. In addition, late fractions of MT protein obtained by gel filtration were devoid of high molecular weight proteins but still produced MT bundles. The marginal band tau was salt-extractable and heat-stable, bound antibodies to mammalian brain tau, and formed aggregates upon desalting. Antibodies to tau blocked MT assembly, but both assembly and bundling occurred in the presence of antibodies to actin or syncolin. The MTs were “unbundled” by subtilisin or by high salt (0.5-1 M KCl or NaCl), consistent with tau involvement in bundling. High salt extracts retained bundling activity, and salt-induced unbundling was reversible with desalting. However, reversibility was observed only after salt-induced MT disassembly had occurred. Reconstitution experiments showed that addition of marginal band tau to preassembled MTs did not produce bundles, whereas tau presence during MT reassembly did yield bundles. Thus, in this system, tau appears to play a role in both MT assembly and bundling, serving in the latter function as a coassembly factor. © 1994 Wiley-Liss, Inc.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970290106
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    Fluorescence studies of spectrin and its subunits (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 72-81 
    Details
    ISSN: 0886-1544
    Keywords: spectrin ; intrinsic fluorescence ; spectrin elasticity ; fluorescence quenching ; spectrin α chain ; spectrin β chain ; membrane skeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To better understand the solution structure of spectrin, the environments of its tryptophan residues have been examined by fluorescence spectroscopy. The spectra and the extent of quenching by several quenching agents have been determined for intact spectrin and its α and β subunits. The arsenal of quenchers used in the study represented both hydrophilic and hydrophobic species including anionic, cationic and neutral compounds. Effects on spectrin fluorescence of ethanol and ionic strength, which extend and/or rigidify spectrin, and of glycerol, which is commonly used in electron microscopy of the protein, have also been assessed in the presence and absence of quenchers. Most of the tryptophans of spectrin are either internally quenched or are sequestered, hindering the approach of hydrophilic quenching agents. Both the spectral shape and the extent of quenching by acrylamide indicate that some tryptophans of the β subunit are slightly more exposed in the isolated chain than in the dimer. Similar effects on spectra and on quenching of the intact dimer and of the isolated β chain are seen when the ionic strength is reduced. Ethanol and glycerol reduce spectrin tryptophan accessibility to 2-p-toluidinyl napthalene-6-sulfonic acid (TNS). It therefore appears that low ionic strength, α-β association and neutral solute (or lowered dielectric constant) all induce a similar, but modest conformational change in the domain structure. The extent of TNS binding is not increased by lowering the ionic strength, suggesting that the expansion and/or stiffening of the molecule in low electrolyte solutions does not involve exposure of significant numbers of hydrophobic sites. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970290107
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970290201
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    Nanometer scale vibration in mutant axonemes of Chlamydomonas (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 177-185 
    Details
    ISSN: 0886-1544
    Keywords: flagella ; Chalamydomonas ; mutant ; high-frequency vibration ; nanometer scale measurement ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Flagellar axonemes of sea urchin sperm display high frequency (200-400 Hz) vibration with nanometer scale amplitudes in the presence of ATP [Kamimura and Kamiya, 1992: J. Cell Biol. 116:1443-1454]. To investigate how various axonemal components affect the vibration, we examined vibration in wild-type and mutant axonemes of Chlamydomonas. At 1 mM ATP, wild-type axonemes underwent vibration at 100-650 Hz with amplitudes of 4-40 nm. This vibration was similar to, but less regular than, that in sea urchin sperm. Axonemes of the mutants ida1 and ida4 lacking part of the inner arm dynein underwent vibrations indistinguishable from that of wild-type. The mutant oda1 lacking the entire outer arm underwent vibration at about half the wild-type frequency. Unexpectedly, the paralyzed mutants pf18 lacking the central pair and pf14 lacking the radial spokes displayed vibration with significantly higher frequencies and smaller amplitudes than those in the wild-type vibration. These results indicate that the high-frequency vibration is common to many kinds of mutant axonemes that lack various axonemal substructures, but that its manner is sensitive to the presence of outer arm dynein and the central pair/radial spoke system. Simultaneous measurements of amplitude and frequency in wild-type and mutant axonemes suggest that the velocity of microtubule sliding in vibrating axonemes is lower than the velocity of sliding under load-free conditions. The velocity is particularly low in pf18. A possible mechanism is proposed to explain the lower sliding velocity and vibration amplitude in the pf18 axoneme, based on an assumption that central pair/radial spoke system may work to regulate the switching of two antagonizing forces within the axoneme. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970290209
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    Microtubules restrict plastid sedimentation in protonemata of the moss Ceratodon (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 366-374 
    Details
    ISSN: 0886-1544
    Keywords: cytoskeleton ; microfilaments ; cytochalasin ; gravity ; amiprophos-methyl ; tip-growth ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Apical cells of protonemata of the moss Ceratodon purpureus are unusual among plant cells with sedimentation in that only some amyloplasts sediment and these do not fall completely to the bottom of vertical cells. To determine whether the cytoskeleton restricts plastid sedimentation, the effects of amiprophos-methyl (APM) and cytochalasin D (CD) on plastid position were quantified. APM treatments of 30-60 min increased the plastid sedimentation that is normally seen along the length of untreated or control cells. Longer APM treatments often resulted in more dramatic plastid sedimentation, and in some cases almost all plastids sedimented to the lowermost point in the cell. In contrast, the microfilament inhibitor CD did not affect longitudinal plastid sedimentation compared to untreated cells, although it did disturb or eliminate plastid zonation in the tip. These data suggest that microtubules restrict the sedimentation of plastids along the length of the cell and that microtubules are load-bearing for all the plastids in the apical cell. This demonstrates the importance of the cytoskeleton in maintaining organelle position and cell organization against the force of gravity. © 1994 Wiley-Liss, Inc.
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    Regulation of motility and cytoskeletal organization of rat bladder carcinoma cells by cyclic AMP (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 375-382 
    Details
    ISSN: 0886-1544
    Keywords: collagen ; actin ; α-actinin ; cAMP-dependent protein kinase ; NBT-II cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cyclic AMP (cAMP) has been implicated in the regulation of movement of certain cultured cell types. We have studied the effects of cAMP on epithelial cell motility using serum-free NBT-II cells, derived from a rat bladder carcinoma. The random movement of these cells on type I collagen was reduced upon elevation of intracellular cAMP by several means and this effect was reversible. Alterations in the organization of the cytoskeletal proteins F-actin and α-actinin occurred concurrently with the reduction in motility, and the arrangement of these proteins resembled that seen in non-motile cells on glass. In addition, pretreatment of cells with KT5720, a cAMP-dependent protein kinase (PKA)-specific inhibitor, prevented the dibutyryl cAMP-induced reduction in cell movement as well as the associated cytoskeletal changes. These results suggest that elevation of PKA is responsible for the observed effects on cell motility and cytoskeletal reorganization and demonstrate a role for PKA in the regulation of cell motility in this system. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970290410
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    Substructure of cytoplasmic dense bodies and changes in distribution of desmin and α-actinin in developing smooth muscle cells (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 204-214 
    Details
    ISSN: 0886-1544
    Keywords: intermediate filaments ; cytoskeleton ; filament attachment sites ; immunogold labeling ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The substructure of assembling cytoplasmic dense bodies (CDBs) and changes in the distribution of desmin and α-actinin during development of smooth muscle were studied in gizzard samples from 10- and 16-day embryos and from 1- and 7-day post-hatch chickens. CDBs in these cells lack the density of CDBs in mature or adult smooth muscle cells and, thus, allow observations of the changes inside CDBs. The random filament orientation seen in younger embryonic cells is first modified to include relatively small patches of IFs that are somewhat straighter and are approaching a side-by-side arrangement. As development proceeds, the IFs in these arrays become straighter, are parallel over longer lengths of the IFs and later acquire the density characteristic of mature CDBs. Anti-desmin labeling in embryonic 10- and 16-day cells showed that desmin intermediate filaments (IFs) were located in the myofilament compartment but were concentrated in or near assembling CDBs. Anti-desmin labeling shifted to the perimeter of CDBs after hatching. Cross sections, longitudinal sections, and stereo pairs all show that IF profiles are present inside unlabeled assembling CDBs. Anti-α-actinin labeling was directly on CDBs and was often associated with the cross-connecting filaments (CCFs) (average diameter of 2-3nm) inside CDBs. We propose, based on these data, that desmin IFs, α-actinin-containing CCFs, and actin filaments are the principal components of the substructure of assembling CDBs. We also present a proposed model for CDB assembly. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970290303
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    Antibodies that can discriminate between dynein heavy chains and their HUV1 photoproducts (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 271-279 
    Details
    ISSN: 0886-1544
    Keywords: peptide antibodies ; protein processing ; axonemes ; microtubule associated proteins ; UV photocleavage ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Dyneins are multi-subunit enzymes that transduce chemical energy into the mechanical energy that makes cilia and flagella beat and moves organelles towards the minus end of microtubules. The ATPase activity is borne by heavy chains, and recent molecular analysis indicates that dynein heavy chain genes form an ancient multigene family: the similarity between the same isoform of two distantly related species is greater than that between different isoforms of the same species. We have exploited sequence identities between a Paramecium axonemal dynein heavy chain gene cloned in our laboratory and sequences of dynein heavy chains from other species to prepare antibodies against active-site peptides capable of recognizing dynein heavy chains regardless of species or isoform. One of the antibodies is perfectly specific for the larger product of V1 photolysis (HUV1) and thus incorporates a unique property of the hydrolytic ATP binding site of all known dynein heavy chains, the capacity for photocleavage in the presence of micromolar vanadate. Our characterization of these reagents suggests that they will be useful for biochemical and in situ studies of known dyneins as well as identification of potential new members of the family. © 1994 Wiley-Liss, Inc.
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970290401
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    Interactions among endoplasmic reticulum, microtubules, and retrograde movements of the cell surface (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 291-300 
    Details
    ISSN: 0886-1544
    Keywords: endoplasmic reticulum ; DiOC6(3) ; microtubules ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Relationships among the endoplasmic reticulum (ER), microtubules, and bead movements on the cell surface were investigated in the thin peripheral region of A6 cells, a frog kidney cell line. ER tubules were often aligned with microtubules, as shown by double-labeling with DiOC6(3) and anti-tubulin in fixed cells. In living cells stained with DiOC6(3) and observed in time lapse, there were frequent extensions, but few retractions, of ER tubules. In addition, there was a steady retrograde (towards the cell center) movement of all of the ER at ∼0.3 μm/min. Since microtubules are often aligned with the ER, microtubules must also be moving retrogradely. By simultaneous imaging, it was found that the ER moves retrogradely at the same rate as aminated latex beads on the cell surface. This indicates that the mechanisms for ER and bead movement are closely related. Cytochalasin B stopped bead and ER movement in most of the cells, providing evidence that actin is involved in both retrograde movements. The ER retracted towards the cell center in nocodazole while both ER and microtubules retracted in taxol. Time lapse observations showed that for both drugs, the retraction of the ER is the result of retrograde movement in the absence of new ER extensions. Presumably, ER extensions do not occur in nocodazole because of the absence of microtubules, and do not occur in taxol because taxol-stabilized microtubules move retrogradely and there is no polymerization of new microtubule tracks for ER elongation. © 1994 Wiley-Liss, Inc.This Article is a US Government work and, as such, is in the public domain in the United States of America.
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    Characteristics of pronuclear migration in Beroe ovata (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 301-311 
    Details
    ISSN: 0886-1544
    Keywords: ctenophore ; egg ; nucleus ; microtubule ; endoplasmic reticulum (ER) ; sperm aster ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the large eggs (∼1 mm) of the ctenophore Beroe ovata, female pronuclei migrate long distances to join stationary male pronuclei in the peripheral cytoplasm that surrounds the yolky interior. We have investigated the mechanism of nuclear migration using time lapse video recording, automated image analysis, visualization of microtubules by immunofluorescence and rhodamine-tubulin injection, and electron microscopy. Female pronuclei migrated at average speeds of 0.2 μm/sec, and were found to show periodic oscillations in velocity. Alternating phases of acceleration and deceleration occurred with an average periodicity of 235 seconds covering distances of 47 μm (about 3 times the nuclear diameter). Migration velocities and velocity oscillations were similar in fertilized and unfertilized eggs; however, changes in migration direction were much more frequent in unfertilized eggs. Characteristic deformations of the pronuclear membrane and occasional rotation of the nuclear contents were observed during migration. Inhibitor studies indicated that microtubules are required for nuclear migration. In fertilized eggs the top of the nucleus was found to move through the dense layer of aligned sperm aster microtubules. The frequent changes in direction of pronuclear migration in unfertilized eggs reflect the random organization of the microtubule layer in the absence of sperm derived centrosomes. Densely packed endoplasmic reticulum was found intermeshed with sperm aster microtubules and connected extensively with the nuclear membrane during migration. Most nuclear pores were grouped in an infolding of the nuclear membrane. We suggest that in fertilized eggs the female pronucleus is transported to the minus ends of sperm aster microtubules using motor molecules attached either to the outer nuclear membrane and/or to the network of connecting ER. © 1994 Wiley-Liss, Inc.
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    Myosin I localizes to the midbody region during mammalian cytokinesis (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 312-320 
    Details
    ISSN: 0886-1544
    Keywords: contractile ring ; cleavage furrow ; mitosis ; unconventional myosin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: During cytokinesis, daughter cells are cleaved in two by the constriction of an actin-rich contractile ring which encircles the equator of the dividing cell. Filamentous myosin II is present in the contractile ring and necessary for constriction of the furrow, as shown in several cell types [Satterwhite and Pollard, 1992: Curr. Opin. Cell Biol. 4:43-52]. However, no functional role nor distinctive localization has been previously identified for non-filamentous “unconventional” myosins, such as myosin I, during cytokinesis. Using antibodies to adrenal medullary myosin I, we report that myosin I is localized in 3T3 fibroblasts to the mid-equatorial plane during late-cytokinesis, as well as to the polar edges as previously described in ameboid cells [Fukui et al., 1989: Nature 341:328-331]. Confocal microscopy revealed that myosin I is concentrated at the midbody region in a nearly continuous transverse disk, extending from the cortical region of the furrow through the midbody itself. These findings suggest that, in addition to the accepted role of filamentous myosin II in constriction of the contractile ring, non-filamentous myosin I might contribute to motile events occurring late in cytokinesis. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270101
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    Microtubule centers and the interphase microtubule cytoskeleton in amoebae of the cellular slime molds (mycetozoans) Acytostelium leptosomum and Protostelium mycophaga (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 45-58 
    Details
    ISSN: 0886-1544
    Keywords: MTOC ; cytoplasmic microtubule complex ; antitubulin ; Immunofluorescence ; ultrastructure ; immunogold ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We investigated the microtubule (MT) cytoskeleton and microtubule centers (MTC) in undifferentiated amoebae by indirect immunofluorescence with six monoclonal antitubulin antibodies, and by transmission electron microscopy and immunogold ultracytochemistry. Interphase amoebae of both species contain a distinct cytoplasmic complex of MTs, which is more elaborate in Protostelium mycophaga. In Acytostelium leptosomum amoebae a single MTC is attached to each interphase nucleus at its pointed end, as in the other dictyostelid cellular slime molds Dictyostelium discoideum and Polysphondylium violaceum. Ultrastructurally, MTCs of A. leptosomum also resemble those of these two species: They consist of an electron-opaque core shaped like a stout rod, which is embedded, together with nodules, in a fuzzy matrix. The nodules are the points of origin of the MTs. In most amoebae of P. mycophaga there are two MTCs on opposite sides of and close to the nucleus, but many amoebae also contain a variable number of MTCs that are remote from the nucleus. Nucleus-associated and “remote” MTCs are structurally identical. They consist of a ring-shaped core with inner and outer diameters of ca. 130 nm and 340 nm. A plug sits in the ring, and satellites are connected to the core by fine fibrils. The satellites are the points of origin of MTs. New MTCs are apparently formed during mitosis, the parent MTC probably serving as a template for the genesis of a new ring. The results support the notion that phylogenetically related organisms have similarly constructed MTCs and that these are dissimilar in less closely related organisms. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970280105
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    Microtubules with altered assembly kinetics have a decreased rate of kinesin-based transport (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 79-87 
    Details
    ISSN: 0886-1544
    Keywords: microtubule transport ; microtubules ; 2,5-hexanedione ; glutaraldehyde ; kinesin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubules treated with the γ-diketone 2,5-hexanedione (2,5-HD) have altered assembly behavior characterized by precocious nucleation and rapid elongation. By measuring the rate of microtubule transport, we have examined the potential functional significance of this 2,5-HD-induced microtubule modification. 2,5-HD-treated microtubules were transported at only 70% of the rate of control microtubules in a simple kinesin-based motility assay on glass coverslips using video and computer enhanced differential interference contrast microscopy. Since 2,5-HD is capable of forming both pyrrole adducts and crosslinks with tubulin, the contributions of pyrrole formation and crosslinking to slowed microtubule transport were determined. 3-Acetyl-2,5-hexanedione (AcHD), a pyrrole forming, non-crosslinking congener of 2,5-HD which does not alter microtubule assembly, did not produce slowed microtubule transport as occurs with 2,5-HD. However, glutaraldehyde, a pyrrole-independent crosslinking agent which alters microtubule assembly in the same way as 2,5-HD, slowed microtubule transport. These results indicate that a 2,5-HD-induced microtubule modification, possibly a crosslink-related conformational change, produces both an alteration in the kinetics of assembly and an alteration in the microtubule-motor interaction. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970270109
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    β-actin specific monoclonal antibody (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 108-116 
    Details
    ISSN: 0886-1544
    Keywords: smooth muscle ; fibroblasts ; lamellipodia ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using a synthetic peptide mimicking the NH2-terminus of β-actin we have raised a monoclonal antibody specific for this cytoplasmic actin isoform. Specificity of the antibody was demonstrated by its labelling of the actin polypeptide only in tissues containing the β isoform, by its exclusive recognition of the synthetic β-actin peptide amongst those mimicking all six vertebrate isoactins, and by its selective recognition of the β-actin spot in two-dimensional electrophoresis gels of smooth muscle extracts. The antibody bound to actin filaments in both living and fixed fibroblasts where it labelled the stress fiber bundles and, more predominantly, the peripheral actin rich lamellipodia. The characteristics of the antibody indicate that it should serve as a useful tool for studying isoactin distribution and function. © 1994 Wiley-Liss, Inc.
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    Cellular microtubules heterogeneous in their content of microtubule-associated protein 4 (MAP4) (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 133-149 
    Details
    ISSN: 0886-1544
    Keywords: MAP4 depletion ; antibody blocking ; detyrosination ; midbody ; asymmetric cell processes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous immunolocalization studies using many primate cultured cell lines demonstrated that a microtubule-associated protein of Mr ∼210,000 which is now called MAP4, is present along the length of microtubules in interphase and mitotic cells [Bulinski and Borisy (1980) J. Cell Biol. 87:802-808; DeBrabander et al. (1981) J. Cell Biol. 91:438-455]. Since MAP4 has been implicated as a microtubule stabilizer, we asked whether all classes of microtubules possess an equal complement of MAP4. We have reexamined the cellular distribution of MAP4, using both conventional double-label immunofluorescence and an antibody blocking technique [Schulze and Kirschner (1987) J. Cell Biol. 104:277-288] to highlight microtubules lacking, or depleted in, MAP4. These techniques have revealed that thin processes extending from monkey kidney cells (TC-7), and those made by human neuroblastoma cells (IMR-32) in response to retinoic acid, are often deficient in MAP4 immunoreactivity. Since both types of cellular processes contain stable microtubules, which are enriched in detyrosinated (Glu) tubulin, we tested the ability of MAP4 to bind to microtubules made from pure Glu and pure tyrosinated (Tyr) tubulin in vitro. MAP4 bound to both types of microtubules, and the similar saturation level of MAP4 binding to Glu and Tyr microtubules suggested that differential binding to these forms of tubulin does not contribute directly to a mechanism for segregation of MAP4 on microtubules in vivo. In TC-7 cells, we also observed MAP4-depletion on single microtubules, distal regions of broad cytoplasmic extensions, and midbodies of dividing cells. MAP4 depletion may reflect recent, rapid growth of microtubules to which MAP4 has not yet bound, or the presence of other MAPs that may compete with MAP4 for binding sites on the MT. We suggest that different levels of MAP4 on microtubules may directly modulate microtubule dynamics within single cells, as well as other microtubule functions such as those involving microtubule motor activity. © 1994 Wiley-Liss, Inc.
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270301
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  • 89
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    Novel 130-kDa rat liver myosin-1 will translocate actin filaments (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 41-48 
    Details
    ISSN: 0886-1544
    Keywords: myosin-1 ; motility ; F-actin ; liver ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have recently purified and characterized from rat liver, polypeptides of 110-kDa and 130-kDa which possess several characteristics of myosin-1 [Coluccio and Conaty: Cell Motil. Cytoskeleton 24:189-199, 1993]. What roles these myosin-1 molecules play in hepatocytes is not yet defined. One hypothesis is that they are involved in either intracellular transport or locomotion. As a first step in establishing their function, we have investigated whether these molecules are capable of supporting motility in vitro. Our results clearly demonstrate that the isolated 130-kDa-calmodulin complex will translocate filaments at a rate of 0.03-0.05 μ/sec; motility is inhibited in free calcium ion concentrations above 0.1 μM. This inhibition is reversed with the addition of exogenous calmodulin. These results provide supporting evidence of a motile role for the 130-kDa-calmodulin complex in vivo. This is the first demonstration that in higher eukaryotes, myosin-1 from a tissue other than intestine will support motility. Partial peptide sequence analysis indicates that the 130-kDa polypeptide resembles the recently described myr 1 [Ruppert et al.: J. Cell Biol. 120:1393-1403, 1993] or MM1α [Sherr et al.: J. Cell Biol. 1405-1416, 1993] gene product. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 90
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    Effects of thymosin β4 and thymosin β10 on actin structures in living cells (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 13-25 
    Details
    ISSN: 0886-1544
    Keywords: Tβ4 ; Tβ10 ; β-thymosins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The β-thymosins are a family of small proteins originally isolated from the thymus. Recently, two of the major mammalian isoforms, thymosin β4 (Tβ4) and thymosin β10 (Tβ10), are identified as significant actin monomer sequestering proteins which may be involved in regulating actin filament assembly. To study the cellular function of β-thymosins, we have used isoform-specific antibodies to determine their concentration and intracellular distribution, and examined the effects of inducing overexpression of Tβ4 and Tβ10 on actin filament structures. Immunofluorescence labeling of peritoneal macrophages showed that both β-thymosins are uniformly distributed within the cytoplasm. cDNA-mediated overexpression of β-thymosins in CV1 fibroblasts induced extensive loss of phalloidinstained actin stress fibers. Stress fibers in the cell center were more susceptible than those at the periphery. There was a decrease in the number of focal adhesions, as evidenced by a decrease in discrete vinculin staining and an increase in diffuse vinculin fluorescence. The majority of the transfected cells had normal shape in spite of extensive loss of actin filaments. Occasionally, cells overexpressing β-thymosin were observed to divide. In these cells, β-thymosin was excluded from the midbody which contains an actin filament-rich contractile ring. Our results indicate that Tβ4 and Tβ10 are functionally very similar and both are effective regulators of a large subset of actin filaments in living cells. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/cm.970270103
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  • 91
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    Announcements (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 97-97 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270111
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  • 92
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270201
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  • 93
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    Regulation of dynein-driven motility in cilia and flagella (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 101-107 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270202
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  • 94
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970270401
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  • 95
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    Structural and geometrical constraints on the outer dynein arm in situ (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 299-312 
    Details
    ISSN: 0886-1544
    Keywords: microtubule motors ; dynein ; cilia ; axoneme ; computer modeling ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study considers the relationship between two structural forms of the 22S dynein arm of Tetrahymena thermophila: the bouquet and the compact arm. The compact arm differs from the bouquet and from other proposed forms (e.g., the “toadstool”) in that the globular domains are situated transversely across the interdoublet gap with one globular subunit, the head, proximal to the adjacent doublet microtubule. The other models place all three globular domains proximal to the neighboring doublet microtubule. When sliding of an isolated axoneme is induced, at least 57% of total attached arms on exposed doublets are in the compact form within dimensions of 24 × 24 × 12 nm, and only about 2% of the arms are bouquets. Toadstools are incompatible with the images seen. Bouquets are not found in regions of the doublet protected by a neighboring doublet. When axonemes with exposed doublets are treated with 0.5 M KCl for 30 min, the compct arms and the dynein heavy (H)-chains disappear, while isolated bouquets and dynein H-chains appear in the medium, suggesting that the compact arms give rise to the bouquets as they are solubilized. The bouquet is the predominant form of isolated 22S dynein molecules, which are found in two apparently enantiomorphic forms, within dimensions 45 × 39 × 13 nm; bouquets attached to doublets have dimensions similar to those of isolated bouquets. Computer modeling indicates that in an intact standard-diameter axoneme, these dimensions are incompatible with the interdoublet volume available for an arm; the bouquet therefore represents an unfolded compact arm. A plausible sequence of changes can be modeled to illustrate the conversion of an attached compact arm to an attached and then free bouquet. The toadstool is probably an artifact that arises after unfolding. Consistent with the conformational difference, H-chains of attached compact arms differ from those of isolated bouquets in their susceptibility to limited proteolysis. These results suggest that the compact arm, rather than the unfolded bouquet or the toadstool, is the functional form of the outer arm in the intact axoneme. © 1994 Wiley-Liss, Inc.
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    Two-step mechanism for actin polymerization in human erythroleukemia cells induced by phorbol ester (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 327-336 
    Details
    ISSN: 0886-1544
    Keywords: HEL cells ; cell spreading ; fibronectin ; diacyl glycerol ; phorbol myristate acetate ; protein kinase C ; staurosporine ; thymosin beta four ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human erythroleukemia (HEL) cells grow in suspension, but after treatment with nM PMA the cells adhere and spread on glass or fibronectin [Jarvinen et al., 1987: Eur. J. Cell Biol. 44:238-246]. We observed an early (20-30 min) stage of spreading in which F-actin was organized into peripheral arcs near the spreading margin and vinculin was localised to the cell's periphery at the ends of these arcs. By 1 h the cells were well spread with straight actin bundles many of which ended at more central sites terminating on patches containing vinculin and talin; thus the cells assemble typical stress fibers but do not appear to polarize. The cells also spread on RGD polymer. DiC8 (1,2-dioctanoyl-sn-glycerol, C8:0, Sigma Chemical Co., St. Louis, MO) induced spreading but only if DAG kinase inhibitor and A-23187 were also present; in their absence cells adhered but did not spread. Spreading was ∼85% inhibited by 100 nM staurosporine. PKC-β was shown to be present in the cells by immunoblotting. In cells spread for 1 h with PMA, F-actin increased to 180% of control levels as measured by RP binding and the actin sequestering complex of G-actin-thymosin β4 decreased significantly.To determine whether the F-actin increase required adhesion, we inhibited cell attachment to the substratum by adding RGDS, by coating glass surfaces with hemoglobin, or by a combined treatment. Under these conditions PMA-treated suspended cells still increased their F-actin to 126-137% of controls, a significant increase over control levels. Staurosporine inhibited F-actin increases under all the conditions studied.Permeabilized cell suspensions, incubated with rhodamine labelled G-actin, incorporated the labelled actin along cell membranes at a low level. A few minutes preincubation with either diC8 plus DAG kinase inhibitor or with PMA strongly increased the incorporation. This increased incorporation was reduced to below control levels by either staurosporine (100 nM) or cytochalasin D (1 μM).We conclude that both suspended and spreading HEL cells can be stimulated to polymerize actin by a mechanism dependent on PKC or a PKC-like molecule. In suspended cells, the polymerization occurs along the membrane. When cells spread, F-actin increased to a significantly greater extent. This second step could involve additional polymerization, perhaps at the observed adhesion sites, decreased turnover of the actin bundles, or a combined effect of both mechanisms. © 1994 Wiley-Liss, Inc.
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  • 97
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    Glutamylated tubulin probed in ciliates with the monoclonal antibody GT335 (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 337-349 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; glutamylation ; Paramecium ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Microtubular networks are extensively developped in many ciliate species. In several of them, we investigate the occurrence of the post-translational glutamylation of tubulin [Eddé et al., 1990: Science 247:82-85; Eddé et al., 1991: J. Cell. Biochem. 46:134-142] using as a probe for such modified tubulin, the monoclonal antibody GT335 [Wolff et al., 1992: Eur. J. Cell Biol. 59:425-432]. Results obtained in Paramecium strongly suggest that both axonemal and cytoplasmic tubulin are glutamylated. As in the vertebrate brain tubulin so far tested, the GT335 epitope is located at the carboxy-terminal fragment of cytoplasmic tubulin removed by subtilisin treatment. Immunoblotting and immunofluorescence experiments reveal that, unlike tubulin acetylation, glutamylation is not restricted to cold-resistant microtubules. In addition, immunofluorescence studies performed on dividing cells show that glutamylation takes place soon after the polymerization of microtubules.Finally, glutamylated tubulin is also detected in the ciliate species Euplotes, Tetrahymena, and Paraurostyla. Together with results obtained on flagellate species, this suggests that tubulin glutamylation came out early in the course of eukaryotic evolution and has been widely exploited in various cellular strategies. © 1994 Wiley-Liss, Inc.
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    URL: http://dx.doi.org/10.1002/cm.970270406
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    Localization of tau and other proteins of isolated marginal bands (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 27 (1994), S. 350-360 
    Details
    ISSN: 0886-1544
    Keywords: microtubules ; MAPs ; cytoskeleton ; tau ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To determine which proteins were associated with and intrinsic to the marginal band (MB) of microtubules (MTs), we studied protein components of MBs isolated from nucleated erythrocytes by differential detergent solubilization of the membrane skeleton (MS). MBs isolated from dogfish erythrocytes contained major proteins in the tubulin Mr range. A high molecular weight protein of ∼290 kD that bound antibody to syncolin and to heat-stable brain MAPs was present in the whole cytoskeleton. However, most of it was solubilized by the MB isolation medium, together with the MS. Dogfish erythrocyte cytoskeletons and isolated MBs were examined with polyclonal and monoclonal antibodies against mammalian brain tau and chicken erythrocyte tau. As shown by immunofluorescence and immunoblotting, these antibodies bound to proteins in the 50 to 67 kD range, located along the length of isolated MBs. Two-dimensional SDS-PAGE revealed isolated MB proteins of pI ∼6.8 in the same molecular weight range, as well as α- and β-tubulin with pI ∼5.4. Subtilisin or high-salt treatment of isolated MBs resulted in unbundling of MTs, indicating involvement of MAPs. MBs isolated from chicken erythrocyte cytoskeletons also contained tau as shown by antimammalian brain tau immunofluorescence. Both chicken and dogfish isolated MBs also bound phalloidin, but the binding was usually discontinuous and, for any given MB, matched the pattern of anti-syncolin binding. Both syncolin and F-actin were part of the MS remnant remaining after MT disassembly, supporting their assignment to a specialized MS region at the MB/MS interface. In contrast, tau protein appears to be intrinsic to the MB, where it may have an MT stabilizing and bundling function. © 1994 Wiley-Liss, Inc.
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  • 99
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994) 
    Details
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970280301
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    Clustered acetylcholine receptors have two levels of organization in Xenopus muscle cells (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 179-193 
    Details
    ISSN: 0886-1544
    Keywords: acetylcholine receptor ; deep-etch replication ; sarcolemma ; cytoskeleton ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We studied the organization of acetylcholine receptor (AChR) clusters by shearing cultured Xenopus muscle cells with a stream of buffer, and preparing rotary replicas of the exposed cytoplasmic surface of the sarcolemma. AChR clusters contained numerous particles that protruded from the sarcolemma and formed an irregular array composed of discrete aggregates. AChR were located within these particle aggregates, as shown by comparison of the replicas to labeling by fluorescent α-bungarotoxin, and by immunogold cytochemistry with antibodies specific for the receptor. The aggregates were cross-linked by a dense network of 7 nm filaments that replicated with the banded pattern characteristic of actin microfilaments. The organization of receptors into the small aggregates was independent of the organization of these aggregates into clusters, as alkaline extraction removed the microfilament network and disrupted the irregular array of particle aggregates, but did not disperse individual receptors from the aggregates. We conclude that two levels of interactions organize AChR clusters in Xenopus muscle cells: short-range interactions that assemble individual AChR into small aggregates, and long-range interactions, perhaps mediated by actin microfilaments, that anchor the aggregates into larger clusters. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970280209
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