da Costa Calaza K, Hokoç J N, Gardino P F
Programa de Neurobiologia, Instituto de Biofísicas Carlos Chagas Filho, Centro de Ciências da Saúde, Universidade Federal do Rio de Janeiro, Brazil.
Int J Dev Neurosci. 2000 Dec;18(8):721-6. doi: 10.1016/s0736-5748(00)00055-1.
Two classes of retinal neurons in the chick retina, the horizontal and the amacrine cells, are GABAergic. This study evaluates the neurogenesis of glutamic acid decarboxylase immunoreactive cells in the chick retina. Twenty-five microCi [3H]thymidine was injected into eggs of 2-10 days and the embryos were sacrificed at embryonic day 18 (E18). Glutamic acid decarboxylase immunohistochemistry was revealed by avidin-biotin complex method followed by autoradiography of thymidine. We used the cumulative method for counting autoradiographic grains. At E3, 10% of the amacrine cells were thymidine negative/glutamic acid decarboxylase positive and this rate remained constant until E6. From E6 to E8 about 80% of the amacrine cells were thymidine negative/glutamic acid decarboxylase positive. At E9, 100% of these neurons had been generated. On the other hand, at E3 only 1.5% of the horizontal cells had been generated (thymidine negative/glutamic acid decarboxylase positive) while at E6 this number increased to 10%. From E6 to E9 the neurogenesis pattern was similar to that found for amacrine cells. Our data show that the great majority (80%) of glutamic acid decarboxylase positive amacrine and horizontal cells proliferate between E6 and E9, i.e. the last 3 days of the neurogenesis period. From E3 to E6 only 20% of the glutamic acid decarboxylase positive amacrine and horizontal cells are generated, which suggests that glutamic acid decarboxylase positive cells may require a specific signal at about E6, which triggers their withdrawal from the cell cycle.
鸡视网膜中的两类神经元，即水平细胞和无长突细胞，是γ-氨基丁酸能的。本研究评估了鸡视网膜中谷氨酸脱羧酶免疫反应性细胞的神经发生。将25微居里的[3H]胸腺嘧啶核苷注射到孵化2至10天的鸡蛋中，胚胎在胚胎第18天（E18）处死。采用抗生物素蛋白-生物素复合物法进行谷氨酸脱羧酶免疫组织化学染色，随后对胸腺嘧啶核苷进行放射自显影。我们使用累积法计数放射自显影颗粒。在E3时，10%的无长突细胞为胸腺嘧啶核苷阴性/谷氨酸脱羧酶阳性，这一比例在E6之前保持恒定。从E6到E8，约80%的无长突细胞为胸腺嘧啶核苷阴性/谷氨酸脱羧酶阳性。在E9时，这些神经元全部生成。另一方面，在E3时，仅1.5%的水平细胞已生成（胸腺嘧啶核苷阴性/谷氨酸脱羧酶阳性），而在E6时这一比例增加到10%。从E6到E9，神经发生模式与无长突细胞相似。我们的数据表明，绝大多数（80%）谷氨酸脱羧酶阳性的无长突细胞和水平细胞在E6至E9之间增殖，即神经发生期的最后3天。从E3到E6，仅20%的谷氨酸脱羧酶阳性无长突细胞和水平细胞生成，这表明谷氨酸脱羧酶阳性细胞可能在约E6时需要特定信号，从而触发它们退出细胞周期。
