Histochemical studies of the differentiation of microglial cells in the cerebral hemispheres of chick embryos and chicks

Abstract

Using histochemical procedures to reveal the presence of nucleoside diphosphatase (NDPase), thiamine pyrophosphatase (TPPase) and acid phosphatase (AcPase), we investigated the appearance, distribution and ultrastructure of amoeboid and microglial cells in the cerebral hemispheres of chick embryos and young chicks, in order to elucidate the relationship between these two cell populations. On day 6 of incubation, a few round cells exhibiting NDPase, TPPase and AcPase activity were first detected in the thin mantle layer of the cerebral hemisphere. In the corpus striatum, these round cells increased rapidly in abundance until day 13 of incubation, after which their numbers gradually decreased, so that, on day 19 of incubation, they had entirely disappeared. Between day 10 and day 17 or 18 of incubation, round cells were located mainly in the zone of the mantle layer closest to the lumen. On day 10 of incubation, NDPase-, TPPase- and AcPase-positive cells that had a few short cytoplasmic processes (poorly ramified cells) were detected in the intermediate and basal zones of mantle layer. They increased in abundance until day 17 or 18 of incubation and thereafter rapidly decreased in number. Round and poorly ramified cells exhibited NDPase activity on their plasma membranes and in their cytoplasmic vacuoles, with TPPase and AcPase activity being localized within their vacuoles. On day 19 of incubation, NDPase- and TPPase-positive cells with long, well-ramified cytoplasmic processes (well-ramified cells) were observed in the corpus striatum, these being mainly localized in the basal zone. After hatching, these cells increased rapidly in abundance and were distributed throughout the corpus striatum.(ABSTRACT TRUNCATED AT 250 WORDS)

The origin and differentiation of microglial cells during development

“…He remarked that microglial cells invading the brain from the meninges had features similar to these of blood leukocytes (del Rio-Hortega, 1932), and were therefore probably blood-borne cells. Microglial cells and cells of monocytic lineage share several features, such as the presence in monocytes and all or some types of microglia of particular enzymes, as nucleoside diphosphatase, non-speci®c esterase and acid phosphatase (Boya et al, 1979;Ling et al, 1982;Murabe and Sano, 1982a;Fujimoto et al, 1987Fujimoto et al, , 1989Castellano et al, 1991). Microglial and monocytic cells contain large amounts of vault particles (Chugani et al, 1991) and are labeled by several lectins (Streit and Kreutzberg, 1987;Hutchins et al, 1990;Acarin et al, 1994).…”

Distribution of microglial cells in the cerebral hemispheres of embryonic and neonatal chicks

“…Structures in the telencephalon are identified in relatively mature chick brains at 16 days of embryonic development (3), and the histological features observed in the cerebral hemispheres of newly hatched chicks are similar to those seen in 24-dayold and adult chicks (2).…”

“…The walls of the hemispheres enlarge independently, and in 8-day-old embryos the ventrolateral wall is slightly thicker than the dorsolateral wall. Over subsequent days, the hemispheres enlarge in all directions and the principal regions and layers are recognized (2).…”

“…The presence of transiently ameboid cells is a typical feature in the developing CNS (8,11). Del Río-Hortega (12) first referred to these ameboid cells as possible precursors of microglial cells, implying that the rounded ameboid cells were giving rise to more differentiated or ramified forms.…”

“…The distribution and morphology of microglial cells in the brain of mammalian and bird embryos and adults and in the optic nerve, retina and cerebellum have been studied with the aid of markers and histochemical procedures (2,9). Specific labels, such as the lectins, are able to recognize the microglial phenotypes with greater precision (16)(17)(18)(19)(20).…”