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Protein synthesis and Golgi-mediated vesicle traffic is not required to maintain a polarised membrane voltage in the presence of auxin (1997)

Thiel, G. ; Brüdern, A. ; Moroni, A.

Springer

Protoplasma 197 (1997), S. 182-187

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ISSN: 1615-6102

Keywords: Auxin ; Maize coleoptiles ; Membrane potential ; Cycloheximide ; Protein synthesis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The contribution of protein synthesis and secretion to indol acetic acid (IAA) induced polarisation of the plasma membrane voltage (V M) was investigated. TheV M of coleoptiles fromZea mays was measured in the presence of known inhibitors of protein- and RNA synthesis, as well as those of Golgi-mediated vesicle secretion. Inhibitors were applied under conditions at which they are known to abolish IAA stimulated H+ secretion and cell elongation effectively. Cycloheximide (CHI), an inhibitor of protein synthesis, caused depolarisation ofV M with a half maximal concentration of approximately 20 μM. At 100 μM CHI,V M depolarised to a new stable voltage with a half time of 9.8 ± 0.6 min. The temporal similarity of CHI-induced depolarisation and cessation of coleoptile elongation suggests that the induced change inV M underlies inhibition of elongation. CHI evoked membrane depolarisation to a final voltage of about −100 mV irrespective of the presence or absence of auxin in the external medium. Thus, CHI probably affected constitutive membrane transport properties independently of IAA-induced modulation of transport proteins. Cordycepin (COR), an inhibitor of RNA synthesis, had no significant effect at 400 μM onV M of IAA-treated cells, suggesting that gene transcription for transport- or regulatory protein synthesis was not essential for IAA-generated polarisation ofV M. Brefeldin-A (BFA), an inhibitor of Golgi-mediated vesicle secretion in maize coleoptiles, had no perceivable effect at 20 mg/1 onV M of IAA-treated coleoptile cells, demonstrating that constitutive or IAA-stimulated protein secretion was not essential for the mechanism underlying IAA-evokedV M polarisation. Hence, IAA-stimulated and COR/BFA-depressed H+ extrusion in elongating coleoptiles may not be entirely mediated by auxin-enhanced ATPase activity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01288027

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An approach for the processing engineer: Rheotechnics (1974)

Casale, A. ; Moroni, A. ; Ronzoni, I.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 14 (1974), S. 651-655

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ISSN: 0032-3888

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Processing involves complex polymer flow problems, either in the melt or in solution. Rheologists have developed many studies with the aim of correlating polymer structure with flow properties and polymer processing. Most of these studies, however, have had relatively little impact on practical processing because of the difficulty in solving the mathematical equations involved. Recently, a relatively few papers have been published with the aim of bridging the gap between theoretical rheology and technology. The first part of the paper presents an account of works which have dealt with the process of filling a mold cavity. The second part discusses briefly some experimental results which provide a correlation between moldability and rheological properties. By analogy with the terms “electrology” and “electrotechnics,” the term “rheotechnics” is suggested for this new area of study.

Additional Material: 6 Ill.