Reversal of primary embryonic induction by cold, and the “fixation” of induction in cells activated by lithium chloride

✍ Scribed by Krystyna D. Ansevin

• Publisher: John Wiley and Sons
• Year: 1966
• Tongue: English
• Weight: 688 KB
• Volume: 118
• Category: Article
• ISSN: 0362-2525
• DOI: 10.1002/jmor.1051180102

✦ Synopsis

The effects of low temperature on embryonic induction were investigated. Presumptive epidermis cells of Rana pipiens were either pretreated with cold ( 4 °C ) and then treated with lithium chloride at the same temperature, or activated by lithium chloride at 22"C, then rapidly chilled to 4" and kept at this temperature for a period of time. Cultures were made from the treated cells.

It was found that induction at low temperature could occur, although it did not proceed beyond determining neuralization. When, on the other hand, the cells were first induced with LiCl to the point at which they should have been determined to differentiate into melanophores, but were then rapidly chilled and kept in the cold for some time, the effects of induction were suppressed and the cells differentiated into ciliated epithelium. A 15-60 minute lag in time between induction and chilling (during which the cells were kept in the culture medium at room temperature) allowed neural induction to be gradually "fixed," and a 120-180 minute lag was sufficient for melanphore induction to become insensitive to the subsequent treatment with cold.

It is speculated from these results that induction occurs very slowly at low temperature and that the inductive stimulus activates a sequence of reactions, one or several of which are strongly repressed by the cold. In this case, when no products result from these reactions, the sequence is assumed to stop and possible feed-back mechanisms switch the whole system to its initial condition.