The proto-oncogenes c-fos and c-jun have been shown in numerous model systems to be induced within minutes of growth factor stimulation, during the G0/G1 transition. In this report we use the mitotic ...shake-off procedure to generate a population of highly synchronized Swiss 3T3 cells. We show that both of these immediate-early, competence genes are also induced during the M/G1 transition, immediately after completion of mitosis. While c-fos mRNA levels drop to undetectable levels within 2 hr after division, c-jun mRNA levels are maintained at a basal level which is approximately 30% maximum throughout the remainder of G1. In order to access the functional significance of these patterns of c-fos and c-jun expression, antisense oligodeoxynucleotides specific to c-fos or c-jun were added to either actively growing Swiss 3T3 cells or mitotically synchronized cells, and their ability to inhibit DNA synthesis and cell division determined. Our results show that treatment of Swiss 3T3 cells with either c-fos or c-jun antisense oligodeoxynucleotides, while actively growing, during mitosis, or in early G1, results in a reduction in ability to enter S and subsequently divide. This was also true if Swiss 3T3 cells were treated during mid-G1 with c-jun antisense oligodeoxynucleotides. These results demonstrate that the regulation of G1 progression following mitosis is dependent upon the expression and function of the immediate-early, competence proto-oncogenes c-fos and c-jun.
Three-year-olds and 4-year-olds have severe difficulties solving standard mental rotation tasks. Only 5-year-olds solve such tasks above chance reliably. In contrast studies relying on simplified ...mental rotation tasks indicate that infants discriminate between an object and its mirror image. Furthermore in another simplified mental rotation task with 3-year-olds, a linear relation between angular disparity and reaction time typical for mental rotation was revealed. Therefore it was assumed that 3-year-olds' capabilities are underestimated. In the current study, 3-year-olds were trained in two isolated sessions to solve standard mental rotation tasks and were tested in a third session. Three-year-olds solved this test above chance as a group - a substantial number of them doing so on an individual level. However, a linear relation between angular disparity and reaction time, that would indicate an analog mental transformation, was not discernable. Nevertheless, these findings are in accordance with a continuous line describing mental rotation in infants and older children. And, these also indicate that children's mental rotation capabilities might be underestimated.
Previous studies measuring looking-time suggested that already infants possess intuitive knowledge about physical support. The aim of the present study was to investigate whether children were able ...to apply this knowledge in an active search task. Two- to five-year-olds (N = 105) were presented with pairs of identical blocks positioned on the left- and right-hand side of an elevated platform with only one of the blocks sufficiently supported. At test, one of the blocks fell into one of two chutes adjacent to the platform out of children's view. Children's task was to retrieve the block they thought had fallen. Results revealed that while children aged 3 years or older searched reliably in the correct chute with symmetrically-shaped blocks, only 4- and 5-year-olds did so with asymmetrical blocks. Thus, intuitions about support do not appear to become accessible in action before children can use them to make verbal predictions.
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Based on violation-of-expectation (VoE) paradigms, amazing cognitive competencies have been demonstrated in young infants, which could not be shown in toddlers or even preschoolers. This divergence ...might as much be caused by different research methods as by discontinuities in development. As looking-time measures are not readily applicable to older children, we suggest a new method that is suitable for children from two years of age onwards. In an empirical examination of this method, 26 children aged 2-7 years learned by trial and error to always find a target picture among a pair of pictures. Each target picture was an impossible version of the non-target picture. After reaching a learning criterion, children had to generalize the learned concept to pictures belonging to a different category. Results showed that even the youngest participants reached the learning criterion and were able to apply what they had learned to another category.
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