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Degeneration-regeneration as a mechanism contributing to the fast to slow conversion of chronically stimulated fast-twitch rabbit muscle (1986)

Maier, Alfred ; Gambke, Brigitte ; Pette, Dirk

Springer

Cell & tissue research 244 (1986), S. 635-643

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ISSN: 1432-0878

Keywords: Muscle, striated, skeletal ; Stimulation, chronic ; Degeneration ; Regeneration ; Myosin, embryonic ; Rabbit

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary Extensor digitorum longus muscles of male adult White New Zealand rabbits were indirectly stimulated at 10 Hz for 12 h daily for periods ranging up to 28 days. After four weeks the stimulated muscles showed a nearly uniform profile of high succinate dehydrogenase activity and, when incubated after acid preincubation for myofibrillar adenosine triphosphatase, displayed more dark- and intermediate-staining fibers than their contralateral counterparts. Muscles stimulated from between 6 to 21 days revealed degenerative foci and phagocytosis of degenerated fibers. These fibers were mostly of the fast-twitch, glycolytic type. Small myofibers, which often contained central nuclei, and structures identified as myoblasts or myotubes, reacted with a monoclonal antibody prepared against embryonic myosin heavy chains. The data suggest that under the employed conditions the fast to slow conversion of chronically stimulated fast-twitch rabbit muscle is not exclusively caused by adult fiber transformation, but results in part from the substitution of fast-twitch glycolytic fibers with newly formed fibers that have a high oxidative profile.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00212544

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Stereoisomerisierungen von Keteniminen (1981)

Lambrecht, Johanna ; Gambke, Brigitte ; von Seyerl, Joachim ; [et al.]

Weinheim : Wiley-Blackwell

Berichte der deutschen chemischen Gesellschaft 114 (1981), S. 3751-3771

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ISSN: 0009-2940

Keywords: Chemistry ; Inorganic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Description / Table of Contents: Stereoisomerization of Ketene IminesBarriers to racemization in solution of the ketene imines 1a-y and X-ray structures of the ketene imines 1s and z are described. Similar to allenes all ketene imines have dihedral angles of 90° between the C-and N-substituents. The barriers to racemization range from 30 to 63 kJmol-1 and are lowered by electron attracting substituents on C and N. The barriers of m-and p-substituted N-arylketene imines give a linear Hammett correlation with σ- constants. N-Arylketene imines racemize through inversion at nitrogen and simultaneous rotation of the aryl group around the N- aryl bond.

Notes: Es werden Racemisierungsbarrieren der Ketenimine 1a-y in Lösung und Röntgenstrukturanalysen der Ketenimine 1s und z beschrieben. Alle Ketenimine haben ein allenartig gewinkeltes Molekülgerüst mit Torsionswinkeln von 90° zwischen den C- und N-Substituenten. Die Racemisierungsbarrieren (ΔG≠) liegen zwischen 30 und 63 KJmol -1 und werden durch elektronenziehende Substituenten am C- und N-Ende erniedrigt. Die Racemisierungsbarrieren m-und p-substituierter N-Arylketenimine korrelieren nach Hammett linear mit σ- - Werten. N-Arylketenimine racemisieren durch inversion am Stickstoff und synchrone Rotation des Arylrestes um die N-Arylbindung.

Additional Material: 3 Ill.