Neuronal uptake of plasma proteins in cryogenic brain lesions

A previous light microscopic study on cryogenic brain lesions in rats demonstrated uptake of plasma proteins into damaged neurons within a few minutes after the lesion. The protein concentration was much higher inside the nerve cell bodies than in the surrounding neuropil. This is puzzling since the neuropil to a large extent consists of damaged neuronal processes. The present investigation describes the intracellular localization of albumin in this model using a post-embedding immunoelectron microscopic technique. The distribution of albumin in the lesions was studied after 1, 6 and 12 h survival periods. The intraneuronal albumin was mainly bound to the particulate elements of the cytoplasm and nuclei, while the watery parts of the cells showed no immunoreactivity. The intracellular organelles contained very little albumin, indicating that their membranes may be more resistant to freezing than those of the cells. Most of the neuronal and glial processes in the neuropil were swollen and contained almost no albumin. This explains the contrast between the strong immunoreactivity of the neurons and the vague reactivity of the neuropil in light microscopy.