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Opportunities for synthetic plant chimeral breeding: Past and future   总被引:6,自引:0,他引:6  
Many plant periclinal chimeras are selected by horticulturalists due to their distinctive, valuable phenotypes, and because they are relatively stable. Most of these have arisen by induced or spontaneous mutation. Interspecific chimeras have been accidentally produced from graft unions of plants from a wide range of families. Early last century Winkler developed a technique to produce interspecific chimeras from graft unions (graft chimeras). More recently in vitro techniques have been developed to synthesize interspecific and intervarietal chimeras. However, these techniques have only been successful for species in the families Solanaceae and Cruciferae, and rarely assessed on plants in other families. Research is required to improve these techniques or develop new approaches so that the efficiency of chimeral shoot production is improved and the techniques are applicable to plants in a wide range of families. The unique characteristics of interspecific or intervarietal chimeras show the potential of chimeral breeding to produce new cultivars. If chimeral breeding techniques were improved, they could become a standard breeding approach for some horticultural crops.  相似文献   

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Two neural mechanisms are described which exhibit recognition of forms. Both are independent of small perturbations at synapses of excitation, threshold, and synchrony, and are referred to partiular appropriate regions of the nervous system, thus suggesting experimental verification. The first mechanism averages an apparition over a group, and in the treatment of this mechanism it is suggested that scansion plays a significant part. The second mechanism reduces an apparition to a standard selected from among its many legitimate presentations. The former mechanism is exemplified by the recognition of chords regardless of pitch and shapes regardless of size. The latter is exemplified here only in the reflexive mechanism translating apparitions to the fovea. Both are extensions to contemporaneous functions of the knowing of universals heretofore treated by the authors only with respect to sequence in time. John Simon Guggenheim Fellow for 1947  相似文献   

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The prevalence of ornithosis and other Chlamydia infections among various groups of the population, some species of birds and mammals was studied in several regions of the Ukrainian SSR. Among the town population having no occupational contact with domestic fowl and farm animals, complement-fixing antibodies to group ornithosis antigen were found in 6.5% of the examined, among the inhabitants of rural localities in 8.4% and among the workers of poultry farms in 19.9%. During the examination of the immunological state of the workers of cattle-breeding farms, antibodies were detected in 15.1%. Pigeons, hens and ducks were investigated as probable sources of infection. The number of positively reacting individuals was 53.7, 13,7 and 24.9%, respectively. This indicates that they play a role in the spread of infection. The obtained data point out a considerable spread of Chlamydia infections among farm animals. Positive results of serological examination were recorded in pigs in 25.7%, in calves in 15.1% and in 8.6% of cases examined.  相似文献   

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Industrial biotechnology promises to revolutionize conventional chemical manufacturing in the years ahead, largely owing to the excellent progress in our ability to re-engineer cellular metabolism. However, most successes of metabolic engineering have been confined to over-producing natively synthesized metabolites in E. coli and S. cerevisiae. A major reason for this development has been the descent of metabolic engineering, particularly secondary metabolic engineering, to a collection of demonstrations rather than a systematic practice with generalizable tools. Synthetic biology, a more recent development, faces similar criticisms. Herein, we attempt to lay down a framework around which bioreaction engineering can systematize itself just like chemical reaction engineering. Central to this undertaking is a new approach to engineering secondary metabolism known as 'multivariate modular metabolic engineering' (MMME), whose novelty lies in its assessment and elimination of regulatory and pathway bottlenecks by re-defining the metabolic network as a collection of distinct modules. After introducing the core principles of MMME, we shall then present a number of recent developments in secondary metabolic engineering that could potentially serve as its facilitators. It is hoped that the ever-declining costs of de novo gene synthesis; the improved use of bioinformatic tools to mine, sort and analyze biological data; and the increasing sensitivity and sophistication of investigational tools will make the maturation of microbial metabolic engineering an autocatalytic process. Encouraged by these advances, research groups across the world would take up the challenge of secondary metabolite production in simple hosts with renewed vigor, thereby adding to the range of products synthesized using metabolic engineering.  相似文献   

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This essay examines the generative effects of claiming moral failure within a Ukrainian liberal movement for media reform in post-Maidan, pre-invasion Ukraine. The reformers wished to reorganize news reporting around the ideals of autonomy, balanced objectivity, impartiality, and corrigibility, which they believed underpinned Western media. They decried most Ukrainian media as failing such standards, highlighting the individual moral failure of journalists bankrolled by oligarchs in return for favourable media representation. In turn, those from whom the reformers tried to distinguish themselves morally mocked them as ‘grant-eaters’ for their dependence on Western democracy promotion grants. This tussle pitted material success against yearnings for moral and professional probity. Developing Selka's idea of moral distinction, I argue that while the reformers’ pursuit of virtuous difference was sincere, their structural vulnerability vis-à-vis the mainstream media also made morality more salient as the basis for agonistic differentiation.  相似文献   

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The electrophoresis of blood serum proteins in polyacrylamide gel has been used to analyze genetic variability of Grey Ukrainian and Hungarian Grey breeds of cattle. The differences in allelic frequency between the breeds and populations of Grey Ukrainian cattle are found. In cattle, post-transferrin-3, new polymorphic protein, controlled by two co-dominant alleles is detected.  相似文献   

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Diachronic patterns of change in the femoral diaphysis are examined in archaeological skeletal samples from the American Southwest. Three cultural periods differing in subsistence-settlement strategies are represented: Early Villages (A.D. 500-1150), Abandonments (A.D. 1150-1300), and Aggregated Villages (A.D. 1300-1540). Relevant properties of cross-sectional geometry and bone density were obtained using computerized tomography. Temporal trends in geometry suggest that activity levels increased between Early Villages and Abandonments, then declined during Aggregated Villages. In both sexes, femoral shape became more circular, and bending stresses were reduced in the a-p plane through time. Compared to the other periods, bone density was the lowest during Abandonments in both sexes. The reduction in bone density may reflect declining nutritional quality through time that was especially poor during the Abandonments period. Patternings in sexual dimorphism suggest that Abandonments males may have been more sensitive to nutritional stress than contemporary females.  相似文献   

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