The morphological picture of implanted foetal rat brain tissue.

The authors studied the morphological picture of implanted foetal brain tissue. Macroscopically, they found that the grafts used for morphological study had taken in every case and that the size of the graft had doubled or trebled. The surface of the implant grew above the level of the recipient's cortex and numerous branching blood vessels were observed in the graft-cortex contact area. In the light microscope, organization of the cells in circular clusters or strips was found in the implant. Large numbers of blood vessels of varying calibre were present in the vicinity of large cell concentrations. Distinct differences between the cytoarchitectonics of the normal tissue of the recipient and the graft tissue were seen. Cells with a normal appearance or an apolar form, whose nucleus contained irregularly scattered chromatin and mosaic-like nucleoli, were observed at ultrastructural level. The nuclear membrane was thrown into multiple folds which invaginated deep into the nuclear matter. The Golgi complex covered a large area. Axodendritic synapses indistinguishable from the control were found in the neuropil. No changes were observed in the walls of the capillaries. The pericapillary zone was characterized by the presence of light astrocyte processes.

Ultrastructural changes in the brain capillaries after hypoxia.

The authors describe ultrastructural changes in and around rat brain capillaries after hypoxia. The experimental animals breathed a mixture of 5% oxygen and 95% nitrogen for two or for three hours; a third group, which spent three hours in this atmosphere, was treated 24 h later. Cytoplasm processes and vesicles were observed on the luminal side in the endothelial cells, while the cytoplasm contained vacuoles and altered mitochondria. The basement membrane of the brain capillaries was uneven and longitudinal clear zones were formed in it. Altered mitochondria were present in the pericytes and astrocytes. The most pronounced changes were found in the astrocyte processes, which were light and hydrated and contained destroyed mitochondria and lamellar bodies resembling myelin. After 24 h, morphological changes still persisted, especially in the astrocyte processes.

The ultrastructural picture of cerebral cortex of rat after hypoxia. I. Findings after inhalation of 5% O2 and 95% N2.

The ultrastructure of some elements in the motor region of the cerebral cortex of the rat were studied after hypoxia. The experimental animals, after receiving intraperitoneal chloral hydrate anaesthesia, were placed in a chamber with a controlled supply of a mixture of 95% N2 and 5% O2. After 2- and 3-hour exposure to hypoxic conditions the animals were processed for electron optic study. Edematous mitochondria pith partial or total destruction of the mitochondrial matrix were observed. Some mitochondria were changed into large vacuolar formations. The granular endoplasmic reticulum of neurocytes was dilated and in the broad dilatation structures of lamellar shape were sporadically found. The Golgi complex contained vacuoles of different sizes and long cisterns. Hydrated astrocytes were visualized in the neuropil and perivascular astrocyte processes displayed edematous changes. In the group of animals exposed to hypoxia for 3 hours but processed only 24 hours after termination of hypoxia the same changes were observed yet their extent was considerably diminished. This finding indicates that changes induced by hypoxia tend to return to normal conditions.