A semithin light microscopic, transmission electron microscopic and scanning electron microscopic study of macrophages in the lateral ventricle of mice from embryonic to adult life.

A developmental study of intraventricular macrophages was carried out from 11 days post-conception up to 90 days post-natum, using semithin sections, transmission electron microscopy and scanning electron microscopy. In semithin sections and in the TEM three main morphological types (and some transitional forms) were identified and are described as circular, irregular and flattened, respectively. In the SEM three corresponding types were identified, a relatively smooth spherical type, a highly ruffled type and a fairly smooth flattened type. A fourth, multi-blebbed type, was occasionally seen in late prenatal and early postnatal mice. It seemed most likely that these cells were mitotic. The likely sequence of development is that the spherical or circular type is the most primitive, although capable of phagocytosis; and that this differentiates into the ruffled or irregular variety, which in turn differentiates into the flattened type, which is by far the most common type found after birth.