Transformation of amoeboid microglial cells into microglia in the corpus callosum of the postnatal rat brain. An electron microscopical study.

Kaur, Charanjit; Ling, Eng‐Ang; Wong, Weng-Fai

doi:10.1679/aohc.48.17

Cited by 45 publications

(15 citation statements)

References 19 publications

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“…1A,C), which also occur in the perinatal brain but preponderate and contribute to most, if not all, of the microglia in the adult (Ling, 1981). Our studies (Kaur et al, 1985(Kaur et al, , 1986Ling 1977Ling , 1981Ling and Wong, 1993) in the past two decades in the developing brain have provided morphological evidence with respect to the functional roles of amoeboid microglial cells and have also added the fact that they transform into ramified microglia with age. It is evident that the two morphological forms of microglia are ontogenetically related and they probably subserve specific functions at different developmental stages.…”

Section: Introductionmentioning

confidence: 61%

Origin of microglia

Kaur

Hao

et al. 2001

Microscopy Res & Technique

152

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This paper reviews the various proposed hypotheses on the origin of microglia. The seminal study of del Rio-Hortega first stated that the cells were derived from the mesodermal pial cells that invaded the brain during embryonic development. Along with this was the description of precursor cells in the yolk sac in early development. Our results in the embryonic mouse brain have shown the occurrence of lectin-labelled precursor cells at the yolk sac that later appeared in the mesenchymal tissue associated with the neuroepithelium where they penetrated the nervous tissue to become the microglia. A second major view has held that microglia are of neuroectodermal origin; the cells either originate from glioblasts or the germinal matrix. Another school of thought is that microglia are derived from blood monocytes. In this connection, circulating monocytes enter the developing brain to assume the form as amoeboid microglia that subsequently evolve to become the ramified microglia. In traumatic brain lesions following an intravenous injection of colloidal carbon as a cytoplasmic marker for monocytes, it was found that carbon-labelled monocytes were the main source of brain macrophages, some of which transformed into microglia during the healing process. In conclusion, our results derived from the normal and altered brain development as well as from experimental lesions tend to favour the view of the monocytic nature of microglia. Recent studies by us also point to the possibility that some microglial cells may arise from the pial mesenchymal macrophages that appear to originate from the yolk sac precursors.

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Section: Introductionmentioning

confidence: 61%

Origin of microglia

Kaur

Hao

et al. 2001

Microscopy Res & Technique

152

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“…Ultrastructurally, the round, amoeboid microglia are characterized by the presence of numerous large clear vacuoles and lysosomes in their abundant cytoplasm (Ling, 1976;Kaur et al, 1985), a feature in common with the stimulated (thioglycollated-elicited) tissue (peritoneal) macrophages (Thyberg, 1980). In the present lectin-labelling study, the round cells displayed an intense GSA I-B4 staining at their entire surface membrane.…”

Section: Internalization and Synthesis And/or Modification Of Galactomentioning

confidence: 99%

Down-regulation of membrane glycoprotein in amoeboid microglia transforming into ramified microglia in postnatal rat brain

Wen

Shieh

et al. 1994

J Neurocytol

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The present study describes the ultrastructural localization and labelling pattern of lectin in different microglial cell phenotypes in the postnatal rat brain using the isolectin, GSA I-B4. The nascent round and amoeboid microglial cells (round cells and cells displaying short processes) were labelled at their cytoplasmic membrane and the membrane of the subplasmalemmal vacuoles. In the course of their transformation into ramified forms with age, dense lectin labelling was observed successively at different sites in the differentiating cells. The most striking feature was the staining of the Golgi saccules on the trans face, the trans tubular network and associated vesicles and vacuoles in the 'intermediate' ramified microglia (ramified cells bearing thick and long processes and those with thin and long processes). The vacuoles with accumulated reaction products were closely associated with many microtubules extending into the cytoplasmic processes. At the surface, the lectin-labelled vacuoles and vesicles appeared to fuse with the membrane and their contents communicated with the exterior. In the advanced or most differentiated ramified microglial cells (cells bearing attenuated processes), the lectin staining at all the above mentioned sites became diminished. In conclusion, in the transformation of the round microglia into their ramified derivatives, the glycoconjugates at the cytoplasmic membrane are progressively reduced. It is postulated from this study that the down-regulation of the glycoconjugates of the microglial plasma membrane is due primarily to their internalization during endocytosis. This process would trigger a de novo galactosyl protein synthesis and/or modification at the trans Golgi saccules and trans tubular network probably in an attempt to degrade the internalized membrane glycoproteins or to replenish the consumption of the membrane glycoconjugates.

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“…Upon invasion of the CNS as amoeboid cells, they progressively transform into the ramified microglia characteristic of the mature brain (for a review see Ling and Wong 1993). The ramified phenotype represents fully differentiated microglia (Ling 1981, Kaur et al 1985, which can be activated to become reactive microglia after various pathological stimuli (Stagaard et al 1987;Akiyama et al 1988; Streit and Kreutzberg 1988).…”

Section: Introductionmentioning

confidence: 99%

Ramification of microglia, monocytes and macrophages in vitro: influences of various epithelial and mesenchymal cells and their conditioned media *

Wilms

Hartmann

Sievers

1997

Cell and Tissue Research

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Microglial cells are able to switch between an "active" amoeboid and a ramified "resting" morphology during development and after experiencing lesions. We have previously shown that in vitro microglial morphology is controlled by their cellular environment, i. e. cells become ramified in astrocyte coculture but amoeboid on monolayers of fibroblasts. In the present study we have extended the analysis of the control of macrophage morphology by maintaining macrophages of different origins in coculture with different epithelial or mesenchymal cells and their conditioned media. Microglia, monocytes and spleen macrophages seeded onto monolayers of astrocytes, kidney epithelia or hepatoma cells developed the ramified morphology but remained amoeboid in fibroblast coculture. Ramification was also induced by media conditioned by these cells as well as by phorbolic esters, i.e. activators of protein kinase C. In double coculture assays, even small numbers of fibroblasts were able to override the "epithelial" influence. Likewise, microglia remained amoeboid, when incubated on several constituents of the extracellular matrix. These results indicate that macrophage ramification is an active process initiated by diffusible factors secreted by various epithelial cells, possibly acting upon a protein-kinase-C-related receptor. We interprete the modification of macrophage morphology as a functional adaptation to the surrounding type of tissue that is enforced by its constituent cells. Thus, the specific morphologies of microglia, hepatic von Kupffer's cells or peritubular kidney macrophages could be explained by similar epithelium-macrophage interaction.

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Transformation of amoeboid microglial cells into microglia in the corpus callosum of the postnatal rat brain. An electron microscopical study.

Cited by 45 publications

References 19 publications

Origin of microglia

Origin of microglia

Down-regulation of membrane glycoprotein in amoeboid microglia transforming into ramified microglia in postnatal rat brain

Ramification of microglia, monocytes and macrophages in vitro: influences of various epithelial and mesenchymal cells and their conditioned media *

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