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Reactive microglia in the developing brain
Abstract:
Reactive microglia in the developing brain after stab wound was studied by morphological, cytochemical, and autoradiographic methods. Morphologically, early reactive cells are of the "M" cell type (Matthews 1974). They show an activated nucleus, cytoplasm rich in ribosomes with wide Golgi complex and variable numbers of lipid inclusions. Big clear vacuoles are found in many of these cells. Microtubules not associated with centrioles and filaments may or may not be present. Junctional complexes of the zonula or puncta adherentia types are occasionally found. Strong NADPH dehydrogenase, weak NADH dehydrogenase, strong ATPase, and strong acid phosphatase, in addition to nonspecific esterase activities were demonstrated in many reactive cells. Intravenous infusion of labelled bone marrow cells from a donor showed labelled macrophages and labelled perivascular cells at the site of injury. Intracerebral injection of a small dose of tritiated thymidine at the time of injury resulted in the appearance of labelled macrophages in the following days. These data suggest that many of the reactive cells have an exogenous, more probably monocytic, origin; but a certain amount of endogenous cells also act as macrophages in brain injuries.
Insights
Reactive microglia in developing brains originate from monocytes, with some endogenous cells also contributing to brain injury repair. This study investigated their origin and characteristics after stab wounds.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are the primary immune cells of the central nervous system.
- Understanding reactive microglia is crucial for studying brain injury and development.
- The origin of reactive microglia following injury remains a key research question.
Purpose of the Study:
- To investigate the origin and characteristics of reactive microglia in the developing brain after stab wound injury.
- To differentiate between endogenous and exogenous sources of reactive cells.
Main Methods:
- Morphological, cytochemical, and autoradiographic techniques were employed.
- Analysis of cellular morphology, enzyme activities, and cell labeling (tritiated thymidine, bone marrow cells) was performed.
- Observation of reactive cells at the site of stab wound injury in the developing brain.
Main Results:
- Early reactive cells exhibited characteristics of the 'M' cell type with specific organelle features and enzyme activities.
- Labeled macrophages and perivascular cells were identified at the injury site following bone marrow cell infusion.
- Intracerebral thymidine labeling confirmed the proliferation of endogenous cells contributing to the macrophage population.
Conclusions:
- Many reactive microglia in brain injuries originate from exogenous sources, likely monocytes.
- A portion of reactive cells also arise from endogenous sources within the brain.
- These findings elucidate the cellular origins of immune responses in the developing brain following injury.