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1.
Control of the blastemal cell cycle by the peripheral nervous system during newt limb regeneration; continuous labeling analysis 总被引:1,自引:0,他引:1
B Boilly M Oudkhir B Lassalle 《Biology of the cell / under the auspices of the European Cell Biology Organization》1985,55(1-2):107-111
Forty-eight and 96 hr 3H-thymidine continuous labeling was analyzed on denervated mid-bud limb blastemas of Pleurodeles waltlii M. In innervated blastemas, 92 to 95% of mesenchymal cells are cycling; denervation provokes an early exiting from the cycle in G0-1(+ 15% of non-cycling cells for a 6-day denervation, + 20% for an 8 day denervation) and an elongation of the G1 phase. For epidermis only 25% (48 hr labeling) to 53% (96 hr labeling) of cells are cycling in innervated blastemas; denervation strongly decreases this percentage (+ 40% of non-cycling cells for a 6-day denervation, + 60% for an 8-day denervation). As for mesenchyme, denervation also lengthens the G1 phase of epidermal cells. So our results contradict the conclusion of other authors claiming a G2 blockage. They account for the fall in proliferation indices and the arrest of regeneration after denervation. Finally, they show that the cell cycle of regeneration cells is controlled by the neurotrophic factor. 相似文献
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Myogenic cells were isolated from adult rat skeletal muscles and cultured in vitro. Cell proliferation was analyzed between days 1 and 14. The cell cycle phases were determined by examining Feulgen-stained cultures with a cell image processor. The nuclei were automatically analyzed by calculating 18 parameters relating to the texture and densitometry of chromatin and the shape of each nucleus. Cell cycle phases were characterized (Moustafa and Brugal, 1984). The recognition methods made it possible to analyse the nuclei of the myogenic cell populations which were either involved in each phase of the mitotic cycle, or left out of the cycle after fusion into myotubes.After 3 hr of culture 10% of the cell population was involved in the cell cycle. In the presence of foetal calf serum, this percentage increased until day 3 after plating. At that time, the DNA content of 28.2% of the cell population was higher than 3C, whereas it is 2C in G1 or G0 nuclei; image analysis showed that 42% of these cells were in S or G2 phase. From day 4, the proliferation rate gradually slowed down until day 8. After day 8, when numerous myotubes differentiated, the percentage of S and G2 phase cells had diminished to between 3 and 8%. The percentage of nuclei in G0 increased when the first myotubes differentiated around day 5. Myotube nuclei were largely in G0. When horse serum was added to the culture medium on day 4 to enhance myotube differentiation, significant cell proliferation was observed before cell fusion.These methods of analysis give the first daily pattern of myogenic cell proliferation and fusion in a cell population isolated from adult muscles. 相似文献
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The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from
nucleotide sequence variation across a 765-bp region in the cytochrome
oxidase I and II genes of the mitochondrial genome. Most parsimonious
relationships of 25 haplotypes from 16 Greya species and two outgroup
genera (Tetragma and Prodoxus) showed substantial congruence with the
species relationships indicated by morphological variation. Differences
between mitochondrial and morphological trees were found primarily in the
positions of two species, G. variabilis and G. pectinifera, and in the
branching order of the three major species groups in the genus. Conflicts
between the data sets were examined by comparing levels of homoplasy in
characters supporting alternative hypotheses. The phylogeny of Greya
species suggests that host-plant association at the family level and larval
feeding mode are conservative characters. Transition/transversion ratios
estimated by reconstruction of nucleotide substitutions on the phylogeny
had a range of 2.0-9.3, when different subsets of the phylogeny were used.
The decline of this ratio with the increase in maximum sequence divergence
among taxa indicates that transitions are masked by transversions along
deeper internodes or long branches of the phylogeny. Among transitions,
substitutions of A-->G and T-->C outnumbered their reciprocal
substitutions by 2-6 times, presumably because of the approximately 4:1
(77%) A+T-bias in nucleotide base composition. Of all transversions,
73%-80% were A<-->T substitutions, 85% of which occurred at third
positions of codons; these estimates did not decrease with an increase in
maximum sequence divergence of taxa included in the analysis. The high
frequency of A<-->T substitutions is either a reflection or an
explanation of the 92% A+T bias at third codon positions.
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