We have cultured tissues isolated from the interdigital zones (IDZ) of the mouse footplate in the presence of the digits, ectoderm, and all-trans retinoic acid. The objective was to understand how these various factors influence the developmental fate of the interdigital tissues. Neutral red staining showed that these tissues normally differentiate by dying between day 12.514.5. However, if they were isolated from the footplate between day 12.5-13.5 (when cell death is not overtly obvious in the IDZ) and maintained in organ culture, these tissues would develop into cartilage and soft connective tissues. In culture, chondrogenesis is initiated very rapidly in the interdigital explants as revealed by in situ hybridization with riboprobes specific for type IIA and IIB procollagen mRNAs. The ability of interdigital tissues to form cartilage is not attributed to factors present in the serum of the culture medium as this phenomenon is also observed in serumless cultures. We have found that if all-trans retinoic acid, at concentrations of 10-50 ng/ml culture medium, were added to the explants it could inhibit chondrogenesis and promote cell death. Moreover, in some of the cultures, a single digit was left attached to the interdigital tissue. This also dramatically reduced the incidence of chondrogenesis. We have tried to determine whether the digits and ectoderm can produce a diffusible factor that can prevent cartilage from developing by culturing day 12.5 interdigital tissues in ectoderm and digit conditioned media. The ectoderm conditioned medium had no effects on interdigital growth or chondrogenesis. In contrast, the size of interdigital explants cultured in the presence of digit conditioned medium was shown to be significantly smaller than the control. These explants also produced a smaller quantity of cartilage as revealed by Alcian blue binding assay. In sum, our results showed that the fate of the interdigital tissues are not fully determined until after day 13.5. These tissues have the potentials to form cartilage and soft connective tissues. We tentatively propose that these interdigital tissues do not normally realize their histogenetic potentials because of the antichondrogenic influence of the digits and retinoic acid.

This paper aims to investigate the effectiveness of Halliday’s Sydney School genrebased approach in teaching Chinese written composition to South Asian ethnic minority students in Hong Kong. Chinese language, with its heightened status in Hong Kong, holds a key for South Asians with low socio-economic status to obtain upward mobility (Shum, Gao, Tsung, and Ki, 2011). However, South Asian ethnic minority students, as a disadvantaged group of second language learners, lack sufficient parental and institutional support in Chinese language learning. The genrebased pedagogy derived from Halliday’s Systemic Functional Linguistics (SFL) was applied in this study to improve Chinese language performance of South Asian ethnic minority students for a better chance to participate in mainstream society. The SFL approach is primarily concerned with language choice in social situations and has been widely applied in sociolinguistics (Hyland, 2007, 2012). Its latest model in language teaching methodology, the ’Reading to Learn, Learning to Write’ (R2L) pedagogy, is a genre-based teaching strategy which is designed to guide students to experience different levels of language through extensive classroom reading and writing activities with selected texts. The current study is intended to extend the approach to teaching and learning Chinese as a second language. The employment of genre-based pedagogy aims to support South Asian students with their learning of Chinese written composition in the senior secondary curriculum. The Chinese teachers involved were first provided with appropriate training in the genre-based approach to language teaching focusing on the genres of Narration and Explanation. Research data were collected while the teachers began to use theand Explanation. Research data were collected while the teachers began to use the and Explanation. Research data were collected while the teachers began to use the genre-based teaching approach, by means of pre- and post-tests after and before genre instruction. Text analysis based on SFL was then employed to analyze the students’ written composition in both pre- and post-tests in order to understand the effectiveness of the genre-based pedagogy in teaching Chinese as a second language. The finding shows that the students at the high, medium, and low levels improved both in the construction of schematic structure and the variation of lexicogrammatical choices from the whole-text, sentence and word levels respectively in their writing performance. Hopefully, the findings will help curriculum development and teacher education for teaching Chinese as a second language to non-Chinese speaking students in Hong Kong and beyond.

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