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Joseph M Starobin Christopher P Danford Vivek Varadarajan Andrei J Starobin Vladimir N Polotski 《Nonlinear biomedical physics》2009,3(1):4-7
Background
Duration and speed of propagation of the pulse are essential factors for stability of excitation waves. We explore the propagation of excitation waves resulting from periodic stimulation of an excitable cable to determine the minimal stable pulse duration in a rate-dependent modification of a Chernyak-Starobin-Cohen reaction-diffusion model. 相似文献3.
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Rodrigues PC Aguiar O Serpieri F Lima AP Uetanebaro M Recco-Pimentel SM 《Journal of genetics》2011,90(1):31-37
Dendrobatid frogs have undergone an extensive systematic reorganization based on recent molecular findings. The present work
describes karyotypes of the Brazilian species Adelphobates castaneoticus, A. quinquevittatus, Ameerega picta, A. galactonotus and Dendrobates tinctorius which were compared to each other and with previously described related species. All karyotypes consisted of 2n = 18 chromosomes, except for A. picta which had 2n = 24. The karyotypes of the Adelphobates and D. tinctorius species were highly similar to each other and to the other 2n = 18 previously studied species, revealing conserved karyotypic characteristics in both genera. In recent phylogenetic studies,
all Adelphobates species were grouped in a clade separated from the Dendrobates species. Thus, we hypothesized that their common karyotypic traits may have a distinct origin by chromosome rearrangements
and mutations. In A. picta, with 2n = 24, chromosome features of pairs from 1 to 8 are shared with other previously karyotyped species within this genus. Hence,
the A. picta data reinforced that the C-banding pattern and the NOR location are species-specific traits in the genus Ameerega. Moreover, the Ameerega monophyletism proposed by previous phylogenetic studies indicates that the karyotypic differences among species in this genus
result from a long divergence time. 相似文献
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DIRK KOEDAM E. DAVID MORGAN TÚLIO M. NUNES EDA FLÁVIA L. R. A. PATRICIO VERA L. IMPERATRIZ‐ FONSECA 《Physiological Entomology》2011,36(2):187-193
The specialist digger wasp Trachypus boharti Rubio‐Espina preys exclusively on males of the stingless bee Scaptotrigona postica Latreille 1807, although the hunting attacks involve both male and worker bees of S. postica and members of its own species. To understand the mechanism of prey selection, the cuticular hydrocarbon patterns of workers and males of S. postica are analyzed in detail, and the mandibular secretion of males is examined. The cuticular profiles of males and workers are distinctively different. The major group of cuticular compounds, heptacosene isomers, is twice as abundant in workers as in males. There is no clear distinction between worker and male mandibular secretions. Such a distinct and straightforward caste‐specific difference in cuticular hydrocarbons could function as a recognition cue by which T. boharti distinguishes between workers and males of S. postica. 相似文献
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Measurement of levels of aneuploidy in mammalian cells using a modified hypotonic treatment 总被引:1,自引:0,他引:1
N Danford 《Mutation research》1984,139(3):127-132
The use of a short hypotonic treatment can prevent scattering of chromosomes by retaining them within the cell membrane. This technique allows chromosomes to be counted accurately so that hypodiploidy can be assessed as well as hyperdiploidy. Levels of aneuploidy were measured following treatment of a low passage number Chinese hamster fibroblast cell line derived from liver (CH1-L) with colcemid, resulting in a dose-related increase in both aneuploidy and polyploidy. The system may be a valuable assay to extend the biological profile of environmental agents, particularly those that are carcinogenic but do not induce chromosome breakage. 相似文献
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