Effect of surgical trauma on the endogeneous heme iron in the brain

Paucity of electron-microscopic studies on the fate of endogenous heme iron, released as a result of planned surgery, in the central nervous system warranted the present work. During investigations of neuronal plasticity in the cat, an experimental model, in which the proximal cut end of the vagosympathetic trunk was rerouted into the diencephalon, presented an ideal substrate for studying this problem. At 3 months, the brain tissue containing the implant was processed for light and electron microscopy and histochemistry. Under light microscopy, Prussian-blue-positive, dense cytoplasmic aggregates were visible within the macrophages. The cells were mostly clustered around the junctional area between the central and peripheral nerve elements. Electorn-microscopic findings were highly characteristic and distinguished the macrophages from the surrounding neural elements by their rich content of electron-dense granules. While the latter were mostly scattered as free cytoplasmic particles, large aggregates of the same were also observed inside the lysosomes. Besides, a few inclusions were seen within astrocytic processes, close to the plasma membranes. At higher magnifications, the particles revealed the characteristic internal subunit structure of ferritin micelles. The uptake of hemoglobin and its subsequent conversion of ferritin within the macrophages and astrocytic processes are discussed at subcellular level in the light of other available studies.