The hedgehog-patched (hh-ptc) intercellular signaling pathway has recently been shown to control the proliferation of epithelial stem cells in both Drosophila and vertebrates. Mutant and ectopic expression analyses in...The hedgehog-patched (hh-ptc) intercellular signaling pathway has recently been shown to control the proliferation of epithelial stem cells in both Drosophila and vertebrates. Mutant and ectopic expression analyses in Drosophila suggest that the HH protein diffuses from the signaling cells to promote the proliferation of nearby ovarian somatic stem cells by antagonizing the suppression of its receptor PTC towards the CI transcription factor in the stem cells. Consequently, the transcription of CIdependent genes leads to stem cell proliferation. This regulatory pathway appears to function also in vertebrates,where defects in ptc cause basal cell carcinoma, tumors of epidermal stem cell origin. Basal cell carcinoma can also be induced by ectopic expression of Sonic hedgehog (shh) or Glil, the vertebrate homolog of ci. These studies suggest the conservation of the hh signaling pathway in controlling epithelial stem cell divisions among different organisms.展开更多
The present paper reviews 25 studies conducted in the domain of L2 （second/foreign language） dynamic assessment （DA） in recent years. It begins with a survey of relevant research, then discusses some of the major ...The present paper reviews 25 studies conducted in the domain of L2 （second/foreign language） dynamic assessment （DA） in recent years. It begins with a survey of relevant research, then discusses some of the major findings and problems, and finishes with some suggestions for further research. The main findings of the review are as follows： （a） DA has the potential to promote L2 competence development; （b） both the interactionist approach and interventionist approach have attracted the interest of L2 researchers; （c） most studies have focused on small samples; （d） reading and grammatical knowledge have drawn the most attention; （e） group DA may be a potential method to advance L2 competence development in both the focused individual and the other members of the group; （f） computers might play a complementary role to humans acting as mediators; and （g） case study methodology has been the overwhelming choice for experimental design. Based on the available research, we suggest that additional studies are called for on the following issues： （a） L2 DA as an approach to measurement, （b） potential mediators, （c） validity issues of L2 DA, （d） the interface between DA and second language acquisition, and （e） the development of L2 classroom teachers.展开更多
文摘The hedgehog-patched (hh-ptc) intercellular signaling pathway has recently been shown to control the proliferation of epithelial stem cells in both Drosophila and vertebrates. Mutant and ectopic expression analyses in Drosophila suggest that the HH protein diffuses from the signaling cells to promote the proliferation of nearby ovarian somatic stem cells by antagonizing the suppression of its receptor PTC towards the CI transcription factor in the stem cells. Consequently, the transcription of CIdependent genes leads to stem cell proliferation. This regulatory pathway appears to function also in vertebrates,where defects in ptc cause basal cell carcinoma, tumors of epidermal stem cell origin. Basal cell carcinoma can also be induced by ectopic expression of Sonic hedgehog (shh) or Glil, the vertebrate homolog of ci. These studies suggest the conservation of the hh signaling pathway in controlling epithelial stem cell divisions among different organisms.
基金part of the achievements of the project "Reform of Reading-to-Writing Courses of English Major,"supported by Guangdong Province Higher Educational Reform Essential Project(2013)the education reform project of Southern Medical University
文摘The present paper reviews 25 studies conducted in the domain of L2 （second/foreign language） dynamic assessment （DA） in recent years. It begins with a survey of relevant research, then discusses some of the major findings and problems, and finishes with some suggestions for further research. The main findings of the review are as follows： （a） DA has the potential to promote L2 competence development; （b） both the interactionist approach and interventionist approach have attracted the interest of L2 researchers; （c） most studies have focused on small samples; （d） reading and grammatical knowledge have drawn the most attention; （e） group DA may be a potential method to advance L2 competence development in both the focused individual and the other members of the group; （f） computers might play a complementary role to humans acting as mediators; and （g） case study methodology has been the overwhelming choice for experimental design. Based on the available research, we suggest that additional studies are called for on the following issues： （a） L2 DA as an approach to measurement, （b） potential mediators, （c） validity issues of L2 DA, （d） the interface between DA and second language acquisition, and （e） the development of L2 classroom teachers.
