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Showing papers on "Transdifferentiation published in 1981"


Journal ArticleDOI
TL;DR: Embryonic (9-day) chick neuroretinal cells transdifferentiate extensively into lens and pigment cells during prolonged culture in media containing foetal calf serum, and these effects may be due in part to selective survival or growth of particular retinal cell types under the various medium conditions tested.
Abstract: SUMMARY Embryonic (9-day) chick neuroretinal cells transdifferentiate extensively into lens and pigment cells during prolonged culture (4-5 weeks) in media containing foetal calf serum. Medium conditions which promote the attachment and differentiation of neural cells in other culture systems (e.g. horse serum, high glucose levels) both delay the onset and greatly reduce the extent of transdifferentiation in retinal cultures. In the presence of high glucose, horse serum (but not foetal calf serum) also favours cholinergic neuronal differentiation during the early phases of culture, as shown by the levels of choline acetyltransferase activity and accumulation of labelled choline. Substrate conditions have some effect on cholinergic differentiation (promoted by polylysine-coated dishes) but do not affect later transdifferentiation. These effects may be due in part to selective survival or growth of particular retinal cell types under the various medium conditions tested. Cultures stripped of neuronal cells contain negligible choline acetyltransferase activity, but still transdifferentiate into both lens and pigment cells, although more slowly than control cultures. Cell size distributions reveal a significant depletion of the larger cells in high glucose media with foetal calf serum, but not in those with horse serum.

31 citations


Journal ArticleDOI
TL;DR: In this article, the anterior chamber of the eye of guinea pigs was studied electron microscopically and both histo-and biochemically 4, 8 and 12 weeks after transplantation.
Abstract: Autografts of adrenal chromaffin cells from adult guinea pigs to the anterior chamber of the eye were studied electron microscopically and both histo-and biochemically 4, 8 and 12 weeks after transplantation.

29 citations


Book ChapterDOI
TL;DR: The term cell totipotency in the strict sense defines the capability of a single cell to give rise to a whole organism, but this term can also be defined more generally as the ability of a cell to differentiate into any cell type of a multicellular organism.
Abstract: The term cell totipotency in the strict sense defines the capability of a single cell to give rise to a whole organism, but this term can also be defined more generally as the capability of a cell to differentiate into any cell type of a multicellular organism. Cell dedifferentiation refers to the capability of a specialized cell to return to an undifferentiated state and possibly become totipotent again. Cell transdifferentiation is the ability of a cell to first dedifferentiate and then redifferentiate along another line.

24 citations


Journal ArticleDOI
TL;DR: Changes in the capacity of transdifferentiation of retinal pigment cells into lens cells with developmental age were examined by culturing cells obtained from chicks at various developmental stages ranging from 5-day-old embryos to 1-year-old adults, indicating that determination of retina cells alters with age.

19 citations


Journal ArticleDOI
TL;DR: Growth cones formed by adrenal chromaffin cells from young postnatal rats cultured in the presence of nerve growth factor were studied at an electron microscopic level supporting the view that NGF-treated chromAffin cells may undergo neuronal transdifferentiation.

17 citations


Journal Article
TL;DR: Time-lapse photography showed that pigment-cell formation occurs through the intermediate stages of 'undistinguished cells', 'pavement epithelium' and 'potential pigment cells', which lead to a general theory that metaplastic conversion between cell types in eye tissues may require the physical isolation of overtly differentiated, multipotent cells from 'leader' cells which normally hold them in physiological subjugation.
Abstract: SUMMARY Neural retina from 8- to 9-day embryo chickens was grown in long-term cell culture in an experiment to test the hpothesis that one step during the in vitro transdifferentiation of neural retina into pigment cells occurs in response to stimulation of tricarboxylic acid (TCA) cycle activity. Time-lapse photography showed that pigment-cell formation occurs through the intermediate stages of 'undistinguished cells', 'pavement epithelium' and 'potential pigment cells'. Mitosis of undistinguished cells to pavement epithelium was proportional to malonate over most of the tested range of concentrations and was inhibited by succinate, which respectively depress and stimulate the TCA cycle. Conversely mitosis of pavement epithelium to potential pigment cells occurred in proportion to succinate concentration over most of the tested range and was inhibited by malonate, in support of the hypothesis under test. Melanin synthesis begins in a minority of 'pigment leader cells' uniquely stimulated by the lowest concentration of malonate, although higher concentrations blocked pigment synthesis in all cell types. The pigment leader cells appear to act as centres of influence upon neighbouring potential pigment cells, which subsequently also beome pigmented. Lactate inhibited most or all of the steps in formation of pigment epithelium. Between three and five mitoses occur in the production of pigment cells, whereas multilayers and lentoid bodies seem to be formed by expansion of undistinguished cells, probably without mitosis. The observations lead to a general theory that metaplastic conversion between cell types in eye tissues may require the physical isolation of overtly differentiated, multipotent cells from 'leader' cells which normally hold them in physiological subjugation.

16 citations


Journal ArticleDOI
TL;DR: Results were obtained in transfilter experiments, in which a 3‐day period of transfilter interaction between the irises and eye vesicles ensured depigmentation of the iris followed by transdifferentiation into complete NR with visual receptor.
Abstract: The mechanisms of transdifferentiation of iris epithelial cells of Rana temporaria (Anura) in culture depending on influences from different sources were studied. In terminally differentiated iris cells, the process of transdifferentiation is initiated by dedifferentiation. Melanosomes are shed from iris cells due to cell surface activity. After depigmentation, iris epithelial cells become capable of proliferating and competent to react to the influences of various exogenous factors. Under the influence of retinal factors secreted by lentectomized tadpole eyes, both dorsal and ventral irises are converted to neural retina. Under the influence of factors from eye vesicles, the irises are converted to neural retina as well. Similar results were obtained in transfilter experiments, in which a 3-day period of transfilter interaction between the irises and eye vesicles ensured depigmentation of the iris followed by transdifferentiation into complete NR with visual receptor. Lentoid formation occurred under the influence of adult frog lens epithelium. Immunofluorescent analysis confirmed the lens nature of the lentoids. In control experiments under the conditions of the tadpole eye orbit, in which programming influences were absent, iris epithelial cells remained unaffected. The problem of true cell-reprogramming to new differentiation in contrast to expression of inherent properties of the iris epithelial cells is discussed.

13 citations


Journal ArticleDOI
TL;DR: Expiants of adrenal medullary tissue taken from newborn guinea pigs were grown in culture for up to two weeks and revealed the presence of numerous processes within the explants, which extended from chromaffin cells and were characterized by longitudinally oriented cytoskeletal structures, various populations of clear and dense-cored vesicles, varicosities and growth cones.
Abstract: Explants of adrenal medullary tissue taken from newborn guinea pigs were grown in culture for up to two weeks. The explants exhibited sparse outgrowth of neurite-like processes, in contrast to adrenal medullae taken from young postnatal rats or adults guinea pigs that were (i) grown under identical conditions (Unsicker and Chamley 1977) or (ii) transplanted to the anterior chamber of the eye (Unsicker et al. 1981), respectively. Nerve growth factor (10-100 ng/ml, 2.5 S NGF) did not enhance formation of processes. However, electron-microscopic investigations revealed the presence of numerous processes within the explants, which extended from chromaffin cells and were characterized by longitudinally oriented cytoskeletal structures, various population of clear and dense-cored vesicles, varicosities and growth cones. Chromaffin cell bodies largely resembled their in situ-counterparts, but had fewer and smaller storage vesicles than controls. The results are discussed in light of recent findings regarding the potency of NGF and NGF-like growth factors to induce neuronal transdifferentiation of adrenal chromaffin cells.

6 citations