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51.
Addition of the arginine analogue, canavanine, to cultures of nitrogen-fixing Anabaena cylindrica at the onset of akinete formation, resulted in the development of akinetes randomly distributed within the filament, in addition to those adjacent to heterocysts. The total frequency of akinetes increased up to five-fold. A feature of akinetes is their increased content of cyanophycin granules (an arginine-aspartic acid polymer) and addition of canavanine to cultures at an earlier stage resulted in entire filaments becoming agranular and containing agranular akinetes. The effects on akinete pattern appeared to be specific for canavanine since other amino acid analogues, although increasing the frequency of akinetes (approximately two-fold), had no effect on their position relative to heterocysts. In ammonia-grown, stationary phase cultures of A. cylindrica, akinetes were observed adjacent to proheterocysts and in positions more than 20 cells from any heterocyst. These observations indicate that nitrogen fixation and heterocysts are not essential for akinete formation in A. cylindrica, although the availability of a source of fixed nitrogen does appear to be a requirement.These results suggest that during exponential growth some aspect of the physiology of vegetative cells suppresses their development into akinetes and that the role of the heterocyst may not be one of direct stimulation of adjacent vegetative cells to form akinetes, but the removal or negation of the inhibition within them. A model for akinete formation and the involvement of canavanine is given. 相似文献
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Asclepias welshii, restricted to the Coral Pink Sand Dunes of southern Utah, is described and illustrated. Its relationship to other species of seriesRoseae is discussed. 相似文献
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J. Edson Pontes James M. Pierce Jr. Byung-Kil Choe Noel R. Rose 《In vitro cellular & developmental biology. Plant》1979,15(7):469-472
Summary Studies of acid phosphates produced by cell lines MA 160 and EB 33 demonstrated immunochemically their prostatic origin. MA
160 and EB 33, rather than being HeLa contaminants, may be hybrids of prostatic epithelial and HeLa cells or true prostatic
cell lines with chromosomal changes common to all long-term cultivated cell lines.
This research was supported by NIH (Cancer) Research Grants Nos. 18748 and 16426; and Detroit General Hospital Research Corporation. 相似文献
55.
Noel H. Holmgren 《Brittonia》1978,30(2):182-194
The mountains of Costa Rica and western Panama constitute a natural floristic region that is inhabited by six species ofCastilleja.Castilleja talamancensis, C. lentii andC. tayloriorum are described as new. The remaining three areC. arvensis,C. irasuensis andC. quirosii. All butC. arvensis are endemic to the area. The six species are keyed, described, illustrated, mapped and documented with literature and specimen citations. 相似文献
56.
Galactokinase Mutants of Chinese Hamster Somatic Cells Resistant to 2-Deoxygalactose 总被引:6,自引:0,他引:6
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The growth of Chinese hamster somatic cells was inhibited by 0.2 mg/cc of 2-deoxygalactose. Mutants partially or fully resistant to 2-deoxygalactose were isolated in a single-step or two-step selection. Some of them did not grow as well as the wild type; one of them which lacked galactokinase(EC.2.7.1.6) activity did not grow at all in galactose medium. The galactokinase kinetic properties (Vmax & kmax of the other mutants and of the wild type were different. Therefore resistance resulted either from the possible absence of galactokinase synthesis or from a structural mutation, possible a missence mutation, in the galactokinase gene.- A simple diagnostic test for juvenile cataract is proposed. 相似文献
57.
Noel W. Preston 《BMJ (Clinical research ed.)》1965,2(5452):11-13
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Julianne M. O��Reilly-Wapstra Jules S. Freeman Noel W. Davies Ren�� E. Vaillancourt Hugh Fitzgerald Brad M. Potts 《Tree Genetics & Genomes》2011,7(3):485-498
Terpenes are a diverse group of plant secondary metabolites that mediate a plethora of ecological interactions in many plant species. Despite increasing research into the genetic control of important adaptive traits in some plant species, the genetic control of terpenes in forest tree species is still relatively poorly studied. In this study, we use quantitative genetic and quantitative trait loci (QTL) analysis to investigate the genetic control of foliar terpenes in an ecologically and commercially important eucalypt species, Eucalyptus globulus. We show a moderate to high within-family broad-sense heritability and significant genetic basis to the variation in 14 of the 16 terpenes assayed. This is the first report of QTL for terpenes in this species. Eleven QTL influenced the terpenes overall. One QTL on linkage group 6 affected six of the seven different sesquiterpenes assayed (plus one monoterpene), which, in combination with highly significant correlations between these compounds, argues that their variation is influenced by a QTL with pleiotropic effect early in the biosynthetic pathway. We examine the homology of these QTL to those found in a closely related eucalypt, Eucalyptus nitens, and provide evidence that both common and unique QTL influence terpene levels. 相似文献