Round and ramified microglia in mixed glial cultures. Bright field image of a murine primary cortical mixed glial culture stained with the microglial marker Tomato lectin (brown) and counterstained with hematoxylin (blue). In this field the proportion of microglial cells is 13%. Three of them, identified with arrows, are round microglial cells with a strong lectin staining. These cells are easily identified by phase contrast by virtue of their refringency. In contrast, there are several microglial cells with ramified morphology and less intense lectin staining. These cells are non-refringent by phase contrast microscopy. Because of their weaker staining with various microglial markers and their non-refringency, the proportion of ramified microglial cells in astroglial-enriched/mixed glial cultures is often underestimated. Microglial cells were identified with biotin-labelled Tomato lectin (1:500, Sigma). Bar, 100 μm.