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Digitale Medien

Possible involvement of membrane fluidity in helicoidal microfibrillar orientation in the coenocytic green alga,Boergesenia forbesii (1994)

Mizuta, S. ; Watanabe, A. ; Kimura, S. ; [weitere]

Springer

Protoplasma 180 (1994), S. 82-91

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ISSN: 1615-6102

Schlagwort(e): Boergesenia forbesii ; Cellulose synthesizing complex ; Cytoskeleton ; Helicoidal wall ; Membrane fluidity ; Microfibril orientation ; Plasma membrane

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Microfibrillar textures and orientation of cellulose microfibrils (MFs) in the coenocytic green alga,Boergesenia forbesii, were investigated by fluorescence and electron microscopy. Newly formed aplanosporic spherical cells inBoergesenia start to form cellulose MFs on their surfaces after 2 h of culture at 25°C. Microfibrillar orientation becomes random, fountain-shaped, and helicoidal after 2, 4, and 5 h, respectively. The fountain orientation of MFs is usually apparent prior to helicoidal MF orientation and thus may be considered to initiate helicoid formation. Microfibrils continue to take on the helicoidal arrangement during the growth ofBoergesenia thallus. The helicoidal orientation of MFs occurs through gradual counterclockwise change in MF deposition by terminal complexes (TCs) viewed from inside the cell. On the dorsal side of curving TC impressions in helicoidal texture formation on a freeze-fractured plasma membrane, the aggregation of intramembranous particles (IMPs) occurs. Membrane flow may thus possibly affect the regulation of helicoidal orientation inBoergesenia. Following treatment with 3 μM amiprophos-methyl (APM) or 1 mM colchicine, cortical microtubules (MTs) completely disappear within 24 h but helicoidal textures formation is not affected. With 15 μM cytochalasin B or 30 μM phalloidin, however, the helicoidal orientation of MFs becomes random. Treatment with CaCl2 (10 mM) causes the helicoidal MF orientation of cells to become random, but co-treatment with N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7) (100 mM) prevents this effect, though W-7 has no effect on the helicoidal MF formation. It thus follows that MF orientation inBoergesenia possibly involves actin whose action may be regulated by calmodulin.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01379226

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Digitale Medien

Development of a new advanced process for manufacturing polyacetal resins. Part III. End-capping during polymerization for manufacturing acetal homopolymer and copolymer (1993)

Masamoto, J. ; Matsuzaki, K. ; Iwaisako, T. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 50 (1993), S. 1317-1329

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Conventionally, acetal homopolymer or copolymer is obtained by the polymerization of formaldehyde or trioxane, following the end-capping using acetic anhydride or unzipping of the unstable polymer end fraction. First, Asahi Chemical developed a new process to obtain an end-capped polymer during polymerization of highly purified formaldehyde using acetic anhydride as the chain-transfer agent. Use of highly purified formaldehyde and endcapping during polymerization using acetic anhydride as a chain-transfer agent or an endcapping agent will provide a simple process for manufacturing acetal homopolymer. The polymerization mechanism was confirmed by infrared spectroscopy analysis and proton NMR analysis of the polymer obtained. Second, for the acetal copolymer, purified trioxane was copolymerized with ethylene oxide in the presence of methylal, which gave an endcapped polymer with high thermal stability. Two new intermediates from the initiation reaction of the copolymerization, 1,3,5,7-tetraoxacyclononane (TOCN) and 1,3,5,7,10-pentaoxacyclododecane (POCD), were isolated and a new initiation mechanism was proposed. © 1993 John Wiley & Sons, Inc.

Zusätzliches Material: 16 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1993.070500803

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Digitale Medien

Identification of rat faecal metabolites of ebastine by B/E linked scanning liquid secondary ion mass spectrometry (1994)

Yoshida, K. ; Hatoyama, T. ; Fujii, T. ; [weitere]

Chichester : Wiley-Blackwell

Biological Mass Spectrometry 23 (1994), S. 385-390

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ISSN: 1052-9306

Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The identification of rat faecal metabolites of a new antihistaminic agent, ebastine, 4′-tert-butyl-4-[4-(diphenylmethoxy)piperidino]butyrophenone, is presented. After oral administration of (14C)ebastine (20 mg kg-1) to rats, 84% of the radioactive dose was excreted in the 24 h faeces. Unchanged drug and five metabolites were isolated from the faeces by thin-layer chromatography and solid-phase extraction, and their structures were identified by liquid secondary ion mass spectrometry using the B/E linked scanning technique. The main metabolic pathways were oxidation of a terminal methyl group to give the hydroxymethyl and carboxyl derivatives, and hydroxylation of a phenyl ring in the diphenylmethoxy moiety. In addition to the oxidative mechanism, metabolism of ebastine involved sulphate conjugation. It is noteworthy that M-4, having both phenolic and alcoholic hydroxyl groups, was sulphated selectively in the latter position.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bms.1200230702

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Digitale Medien

Effects of the addition of a liquid crystalline copolyester to polystyrenes on blending torque and mechanical properties of blends (1993)

Ogata, N. ; Tanaka, T. ; Ogihara, T. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 48 (1993), S. 383-391

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Blending of polystyrenes (PS) with a thermotropic liquid crystalline polymer (LCP) was performed by using a continuous corotating twin screw extruder. The influence of LCP content on the blending process was studied by changing the barrel heater temperature and the screw speed. The torque of screw shafts, generated during the blending process, was influenced by LCP content and its influence was not simple. The torque generated during the blending process was not directly related to the apparent melt viscosity of blends. Further, the effects of the matrix viscosity on the morphology and mechanical properties of the PS/LCP blends were studied using three grades of PS as matrix resins. It was found that the size of the LCP dispersed phase decreased with increasing matrix viscosity. Consequently, the mechanical properties of the PS/LCP blend were improved. © 1993 John Wiley & Sons, Inc.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1993.070480302

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