Regenerative process of the facial nerve: rate of regeneration of fibers and their bifurcations
NEUROSCIENCE RESEARCH
Authors: Kamijo, Y; Koyama, J; Oikawa, S; Koizumi, Y; Yokouchi, K; Fukushima, N; Moriizumi, T
Abstract
After the main trunk of the mouse facial nerve was injured by crushing, a fiber tracing method was used to quantify the facial motor neurons that extended regenerating nerve fibers to the specific site of the facial nerve branch. The total number of motor neurons retrogradely labeled with a fluorescent tracer, Fluoro-Gold (FG), were 0 on postsurgical days (PSDs) 1 and 2, 75 +/- 25 on PSD3, 264 +/- 21 on PSD4, 378 +/- 9 on PSD6, 428 +/- 19 on PSD8, 491 +/- 13 on PSD12 and 532 +/- 15 on PSD16. Assuming that the FG-positive neurons (535 +/- 11) of the control mice represent 100%, the FG-labeled neurons accounted for 0, 14, 49, 71, 80, 92 and 99% on the corresponding days. Two different fluorescent tracers were applied to the different facial nerve branches 16 days after facial nerve injuries. Double-labeled neurons were consistently found in the nerve-crushed facial nucleus (3.2%), and their number increased in the nerve-transected facial nucleus (12.2%). The present study indicates that the regenerating facial nerve consists of heterogeneous nerve fibers with varying growth rates and that excessive axonal branching occurs more frequently in the nervetransected than in the nerve-crushed injuries. (C) 2003 Elsevier Science Ireland Ltd and the Japan Neuroscience Society. All rights reserved.
CHARACTERIZATION OF 2 GENE TRANSCRIPTS MODULATED BY CYTOKININS IN MICROPROPAGATED APPLE (MALUS-DOMESTICA [L] BORKH) PLANTLETS
PLANT PHYSIOLOGY
Authors: WATILLON, B; KETTMANN, R; BOXUS, P; BURNY, A
Abstract
The micropropagation of apple (Malus domestica [L.] Borkh) cultivars is usually achieved by axillary bud stimulation and requires an exogenous cytokinin supply. Two cDNA libraries were constructed from mRNA isolated from plantlets grown in vitro on medium with or without benzyladenine. One cDNA clone (pSD3), corresponding to transcripts more abundant in plantlets grown on medium containing cytokinin than on medium lacking the hormone, was isolated. It corresponds to a mRNA of about 1,800 nucleotides which codes for a proline-rich protein with a predicted mass of 31,000 daltons. Its accumulation is restricted to roots and stems of in vivo grown apple plantlets and to stems of microcuttings cultivated on medium without cytokinin. Furthermore, it accumulates to comparable levels in leaves and stems when plantlets are grown on medium containing benzyladenine. A second cDNA clone (pSD4), corresponding to transcripts down-regulated in the presence of cytokinin in the culture medium, was also characterized. Its corresponding mRNA is about 700 nucleotides in length and encodes a protein highly homologous to the precursor of the 10-kilodalton polypeptide of the photosystem II from spinach. This mRNA accumulates specifically in leaves of apple plantlets and is more abundant in leaves of plantlets grown in the absence of cytokinin compared with plantlets grown in the presence of benzyladenine.