Showing papers on "Transdifferentiation published in 1982"

Effects of Thioureas, Inhibitors of Melanogenesis, on Lens Transdifferentiation of Cultured Chicken Embryonic Retinal Pigment Cells. (retinal pigment cells/thioureas/transdifferentiation/cell culture)

Abstract: The effects of phenylthiourea (PTU) and its analogues on chick embryonic pigmented epithelial cells (PECs) in culture were studied to elucidate the correlation between inhibition of melanogenesis of PECs and enhancement of their transdifferentiation into lens cells. Both 0.25–0.5 mM PTU and 0.1 mM alpha-naphthylthiourea (ANTU) effectively inhibited melanogenesis of PECs and stimulated their transdifferentiation into lens cells at the same time. Thiourea (TU) also inhibited melanogenesis at a much higher concentration (4 mM), but did not stimulate the lens transdifferentiation at all. Methylthiourea (MTU), on the other hand, did not inhibit melanogenesis, but stimulated the lens transdifferentiation. Testicular hyaluronidase effectively amplified the above-mentioned stimulating effects of thioureas without their altering optimum concentrations, although this enzyme itself never enhanced the lens transdifferentiation of PECs but suppressed their melanogenesis at a concentration of 100 U/ml medium, onward. These results suggest that the suppression of melanogenesis of PECs by PTU or its analogues does not directly correlate with their transdifferentiation into lens cells. The possible mode of thiourea actions on the lens transdifferentiation of PECs cultured in vitro is discussed.

Regeneration of the lens as a phenomenon of cellular transdifferentiation: regulability of the differentiated state of the vertebrate pigment epithelial cell.

Abstract: The transdifferentiation of pigment epithelial cells in vitro was reviewed on the basis of results in the classic studies of lens regeneration in the newt. It is now known that pigment epithelial cells of avian embryos and human foetuses as well as of the newt can readily transdifferentiate into lens cells, when dissociated and cultured in vitro. The evidence now permits us to postulate that the potential of the pigment epithelial cell population for transdifferentiation is strongly conserved in vertebrates in general. Several environmental conditions controlling the processes have been suggested, and we can now provide an in vitro experimental system which is particularly useful for analysis of the molecular basis of transdifferentiation of the pigment epithelial cell, and its role as the cellular basis of lens regeneration.

Microenvironments controlling the transdifferentiation of vertebrate pigmented epithelial cells in in vitro culture.

Abstract: The transdifferentiation of pigmented epithelial cells in vitro is briefly introduced. Several environmental conditions regulating the process have been demonstrated experimentally. On the basis of these data we have suggested regulatory factors in relation to the mechanisms for the initiation of the transdifferentiation of pigmented epithelial cells, focussing particularly on cell surface functions. Finally, we have presented data which contributes to the establishment of a useful and powerful cell culture system which makes it possible for us to analyse the molecular basis of transdifferentiation.

Transdetermination and transdifferentiation of neural retinal cells into lens in cell culture.

Abstract: Two aspects of transdifferentiation of avian neural retina (NR) cells into lens in cell culture were discussed. First, by means of the transfer experiments of NR cells pre-cultivated in spreading cultures (SpC) longer than 10 days into aggregation cultures (AgC), it was shown that NR cells are "transdetermined" into lens direction, before the phenotypic expression of lens in cells at such earlier stages of SpC. In the second part of this article, we showed that NR-cells which have already expressed some neuronal phenotypes can transdifferentiate into lens. This statement is based upon the results of chimeric cultures consisting of neuronal cell fraction separated from 10-day SpC of quail NR and of the epithelial cell fraction of SpC of chick NR. Lens cells formed in such chimeric cultures were mainly of quail origin.

Can Once Neuronally Differentiated Cells of Neural Retina Be Lentoidogenic in Cell Culture?*. (neural retina/transdifferentiation/lens differentiation/merocyanine)

Abstract: Cells dissociated from neural retina of 3.5-day-old chick embryos transdifferentiated extensively into lens cells under the conditions of a cell culture for 3 to 4 weeks. In early satges of cell culture by about 10 days, cultures consisted of small round cells often with cytoplasmic processes(N-cells) and flattened epithelial cells (E-cells). Only N-cells were stained with a fluorescent dye Merocyanine 540. When cells harvested from early cultures were separated into two fractions by centrifugation in Percoll gradient, the specific activity of choline acetyltransferase was much higher in the fraction consisting mainly of N-cells than in other fraction mainly of E-cells. Continuous daily observations as well as cinematographic observations of living cultures indicate that lentoid bodies were often formed in the locations where clusters of N-cells had been found in early stages of culturing. The possibility of transdifferentiation of N-cell clusters into lentoid bodies is discussed.

Serum factors affecting transdifferentiation in chick embryo neuro-retinal cultures.

Abstract: Adult sera (horse, chicken and newborn bovine serum) do not support extensive transdifferentiation of lens cells in cultures of 9-day chick embryo neural retina. Conversely, both chick embryo extract and foetal calf serum promote the accumulation of delta-crystallin (a marker for lens cells) in such cultures. Dialysed foetal calf serum does not allow transdifferentiation into lens, whereas the dialysis medium is able to do so in the absence of macromolecular serum components, suggesting one or more active factors of low molecular weight. Choline acetyltransferase activity (cholinergic neuronal marker) is generally maintained for longer under conditions which do not permit extensive transdifferentiation. Glutamine synthetase activity (a glial marker) is inducible by hydrocortisone in dense neuro-retinal cultures, and this hormone also reduces the extent of later lens development.