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Using ethnographic data collected in a second grade classroom over the course of a school year, this paper describes the ways in which one school's discourse of liberalism is deleteriously deployed. We view the school's discipline creed as emblematic of the school's liberal curriculum, and interrogate the effects on four African American boys in the classroom when the school enacts this creed. Despite the agency that these boys obviously had, they were unable to control the ways in which they were placed at a structural disadvantage and manipulated by a system far more powerful than they were. The results were that these four boys suffered. Not only did the intended liberal curriculum fail to be translated fully into the enacted curriculum, the liberal underpinnings of this curriculum precluded teachers and students from taking any critical stance. 相似文献
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Excised cotyledons of Pinus radiata D. Don cultured under shoot-forming(plus benzyladenine) and non shoot-forming (minus benzyladenine)conditions for 10 and 21 days were fed U-[14C]-glucose for 3h in the light followed by a 3 h chase period. The labellingof individual metabolites as well as 14C incorporation intoprotein was assessed. It was found that the general metabolicpatterns were qualitatively the same in shoot-forming and nonshoot-forming conditions, however, metabolism leading to respirationas well as to the synthesis of some amino acids and proteinsynthesis was enhanced in the shoot-forming cultures. (Received February 16, 1987; Accepted July 8, 1987) 相似文献
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A new approach to selection of lines of spontaneously transformed cells from the rat embryo "precrisis" cultures is described and their phenotypes at the initial and advanced stages during a long-term cultivation are characterized. The new selective system, referred to as 2T7, differs from the well known 3T3, 2T6 and 3T12 systems (Todaro, Green, 1963; Aaronson, Todaro, 1968). It is based on the maintenance of cultures under maximum cell densities. Such an approach facilitated and accelerated the start of the "crisis" stage (up to 3-8 passages) with the following gradual death of almost the whole normal senescent cell population, the colony formation resulting from the proliferation of single clonogenic cells. The frequency of clonogenic cells was about 6 x 10(-6). Six lines of spontaneously transformed cells from embryos of noninbred white rats (LRec-1--LRec-6) and one line from the Wistar embryos (LRec-7) were established. All the lines are characterized as diploid or near-tetraploid, with 1-4 different marker chromosomes formed from chromosome 7, as was reported elsewhere (Artsybasheva et al., 1988). The values of saturation densities and the time of population doubling for all the 7 lines differed from those for the rat embryo primary cultures cells. LRec-1--LRec-6 cells were unable to form the colonies in soft agar, while LRec-7 cells were able to grow in agar. The lines LRec became oncogenic for 1-2 day old rats after different periods of cultivation in vitro--from 3 to 7 months. The line LRec-7 Wistar appeared to be highly oncogenic from the very beginning after its selection. The histological analysis revealed that the LRec-1 tumors could be classified as polymorphocellular sarcoma. Up to 20 passages the LRec-1 line had numerous clonogenic cells (50-60%) in sparse cultures independently on the serum content in the media. By a 3-step selection of LRec-1 cells, on cultivation in media with lower serum contents (1-0.1-0%), a semisuspension of LRec-1sf subline (serum free) was established. This line was highly oncogenic for 1-2 day old rats, was easily cryopreserved and proliferated in the serum-free media for unlimited time, forming small colonies in agar. Thus, the new approach allows to establish with high effectiveness spontaneous lines of rat embryo cells with differently transformed phenotypes, i.e. preneoplastic and oncogenic ones.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
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Richard W. Joy IV Kamlesh R. Patel Trevor A. Thorpe 《Plant Cell, Tissue and Organ Culture》1988,13(3):219-228
The effect of ascorbic acid on growth and shoot formation in callus cultures of tobacco (Nicotiana tabacum L.) was investigated, using young (4–12 subcultures) and old (more than 30 subcultures) tissue. It was found that ascorbate, at levels of 4–8×10-4M, enhanced shoot formation in both young and old callus. Treatment with ascorbate also speeded up the shoot-forming process. In addition, ascorbate completely reversed the inhibition of shoot formation by gibberellic acid in young callus, but was less effective in old callus. 相似文献
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TRANSFORMATION of allogenic lymphocytes in mixed cultures depends chiefly on an incompatibility between the lymphocyte donors at the major histocompatibility locus in man (HL-A), mouse (H-2) and rat (H-l)1. Although the mouse H-2 locus can be divided into several regions each of which controls one or more antigenic specificities2 and two or more subloci control HL-A antigens in man3, it is not known whether all parts of the major histocompatibility locus are equally important in eliciting transformation in mixed lymphocyte cultures. We now show that capacity to elicit lymphocyte transformation is different for different parts of the mouse H-2 locus. 相似文献
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