Ling E A, Penney D, Leblond C P
J Comp Neurol. 1980 Oct 1;193(3):631-57. doi: 10.1002/cne.901930304.
Cells with features suggestive of ameboid motion and phagocytic properties are observed in the rat corpus callosum during the first few days of life. These cells, hereafter referred to as 'ameboid cells', have been investigated in several ways. An electron microscopic study of the corpus callosum in 5- to 7-day-old rats indicated that most 'ameboid cells' were typical macrophages, but some displayed features of monocytes, while others appeared to be transitional between the two types. These observations raised the possibility that blood monocytes were the precursors of 'ameboid cells'. This possibility was tested by injecting a suspension of carbon particles into the circulation of rats of various ages to label and trace monocytes. Within 15 minutes after injection, carbon particles were seen between cells in blood smears as well as in the lumen of capillaries, but not between cells and axons in corpus callosum. By a half hour, a few of the circulationg monocytes, and with time, up to half of them, contained carbon particles. Five days after injection, carbon particles were observed in cells of the corpus callosum identified as 'ameboid cells' of the monocytic and macrophagic type. Such carbon-containing cells were seen in many of the animals injected at the age of 0-1 day, in few of those injected at 3-5 days, and in none of the older animals. Since free carbon had not been observed in corpus callosum spaces, it was concluded that 'ameboid cells' did not pick up carbon locally. The alternative was that blood monocytes, after ingesting carbon particles in the circulation, migrated to the corpus callosum and settled as 'ameboid cells'. In the hope of obtaining a direct confirmation of this conclusion, blood cells obtained from carbon-injected Lewis rats were centrifuged in a Percoll gradient to obtain a fraction which contained 70-80% monocytes, less than 2% granulocytes, and 20-30% lymphocytes. Carbon was present in up to half of the monocytes and 1% of the granulocytes, but not in the lymphocytes; and it was calculated that over 99% of the carbon-labeled cells were monocytes. The cell fraction was then introduced into the blood circulation of 2- to 3-day-old syngeneic Lewis rats, and the animals were sacrificed 5 days later. Occasional carbon-labeled cells appeared not only in liver, spleen and connective tissue, but also in the corpus callosum, where they were identified as 'ameboid cells' of the monocytic and macrophagic type. Even though such cells were infrequent, their presence conclusively demonstrated that at least some 'ameboid cells' of the corpus callosum were derived from circulating blood monocytes.
在出生后的头几天，可在大鼠胼胝体中观察到具有阿米巴样运动和吞噬特性的细胞。这些细胞，以下简称为“阿米巴样细胞”，已经通过多种方式进行了研究。对5至7日龄大鼠的胼胝体进行的电子显微镜研究表明，大多数“阿米巴样细胞”是典型的巨噬细胞，但有些表现出单核细胞的特征，而另一些则似乎是这两种类型之间的过渡细胞。这些观察结果提出了血液单核细胞是“阿米巴样细胞”前体的可能性。通过将碳颗粒悬浮液注入不同年龄大鼠的循环系统以标记和追踪单核细胞来检验这种可能性。注射后15分钟内，在血涂片的细胞之间以及毛细血管腔内可见碳颗粒，但在胼胝体的细胞与轴突之间未见。半小时后，少数循环中的单核细胞，随着时间推移，多达一半的单核细胞含有碳颗粒。注射后五天，在胼胝体中被鉴定为单核细胞和巨噬细胞类型的“阿米巴样细胞”中观察到碳颗粒。在0至1日龄注射的许多动物中都可见到这种含碳细胞，在3至5日龄注射的动物中很少见，而在年龄较大的动物中则未见。由于在胼胝体间隙中未观察到游离碳，因此得出结论，“阿米巴样细胞”不是在局部摄取碳。另一种可能是血液单核细胞在循环中摄取碳颗粒后，迁移到胼胝体并定居为“阿米巴样细胞”。为了直接证实这一结论，将从注射碳的Lewis大鼠获得的血细胞在Percoll梯度中离心，以获得一个含有70 - 80%单核细胞、少于2%粒细胞和20 - 30%淋巴细胞的组分。碳存在于多达一半的单核细胞和1%的粒细胞中，但不存在于淋巴细胞中；据计算，超过99%的碳标记细胞是单核细胞。然后将该细胞组分引入2至3日龄同基因Lewis大鼠的血液循环中，5天后处死动物。偶尔可见碳标记细胞不仅出现在肝脏、脾脏和结缔组织中，也出现在胼胝体中，在那里它们被鉴定为单核细胞和巨噬细胞类型的“阿米巴样细胞”。尽管这种细胞很少见，但它们的存在确凿地证明了胼胝体中至少一些“阿米巴样细胞”来源于循环血液中的单核细胞。
