Siegel G, Grunz H, Grundmann U, Tiedemann H, Tiedemann H
Cell Differ. 1985 Nov;17(4):209-19. doi: 10.1016/0045-6039(85)90495-6.
Explanted ectoderm from early gastrulae of Triturus alpestris was treated with the Na-K ionophore gramicidin (10(-9) to 10(-5) M) and the Ca-ionophore A 23187 (10(-7) to 10(-5) M). The ectoderm developed almost exclusively to atypical epidermis as in the control explants. When the ectoderm was treated with ouabain (10(-4) M), intracellular Na+ increased about 4.4-fold and K+ was reduced by half. Mesenchyme cells in small number differentiated in about 40% of the ouabain-treated explants. The time course of total Na+ and K+ ion concentrations was measured over a period of 72 h in ectoderm of T. alpestris after induction with vegetalizing factor and in control explants. In the first 15 h after explantation, no significant differences between control and induced explants were found. Thereafter, the steady state concentration of K+ decreased in the induced explants, whereas the steady-state concentration of Na+ slightly increased. The membrane resting potential recorded intracellularly of ectoderm sandwiches from early gastrula stages was found to be -41.3 mV in control and -59.3 mV in induced explants. From the specific conductances and permeabilities of non-induced and induced cells it is concluded that the induction process leads to a differentiation of the cell membrane, which acquires the characteristics of ionic selectivity. Ectoderm from Ambystoma mexicanum forms neural or neuroid tissue, mesenchyme and melanophores after explantation in salt solution in up to 50% of the explants without any additions. Isolated Ambystoma ectoderm is therefore not suitable for test experiments.
用钠钾离子载体短杆菌肽（10⁻⁹至10⁻⁵M）和钙离子载体A 23187（10⁻⁷至10⁻⁵M）处理高山蝾螈早期原肠胚的外植体外胚层。外胚层几乎完全发育为非典型表皮，如同对照外植体一样。当外胚层用哇巴因（10⁻⁴M）处理时，细胞内钠离子增加约4.4倍，钾离子减少一半。在约40%用哇巴因处理的外植体中，有少量间充质细胞分化。在用植物化因子诱导后，在72小时内测量了高山蝾螈外胚层中总钠和钾离子浓度的时间进程，并与对照外植体进行比较。在植入后的最初12小时内，对照外植体和诱导外植体之间未发现显著差异。此后，诱导外植体中钾离子的稳态浓度下降，而钠离子的稳态浓度略有增加。在早期原肠胚阶段的外胚层三明治中，细胞内记录的膜静息电位在对照中为-41.3 mV，在诱导外植体中为-59.3 mV。根据未诱导和诱导细胞的比电导率和渗透率得出结论，诱导过程导致细胞膜分化，使其获得离子选择性特征。墨西哥钝口螈的外胚层在盐溶液中培养后，高达50%的外植体可形成神经或类神经组织、间充质和黑素细胞，且无需任何添加物。因此，分离的墨西哥钝口螈外胚层不适用于测试实验。
