Ultrastructural localization of thiamine pyrophosphatase in plasma membranes of brain phagocytes long time after cardiac arrest.

Brain phagocytes are members of a heterogeneous family of microglial cells. In this study we investigated the membrane activity of the enzyme, thiamine pyrophosphatase (TPP-ase), in brain phagocytes. Studies were performed on rats subjected to a transient ischemia because ischemic incident precipitates proliferation of microglial cells in the brain. Brain tissue was sampled from animals that survived 12 months after experimentally evoked cardiac arrest. The product characteristic for TPP-ase activity was present in the Golgi cisterns of neurons, basement membranes of endothelia and capillary pericytes. TPP-ase activity was present on plasma membranes of brain phagocytes. The phagocyte TPP-ase activity did not depend on the anatomical localization of the cell in the brain (cortex, hippocampus, hypothalamus). Thus, TPP-ase activity can be considered as a marker of brain phagocytes.

The perivascular fibrotic reaction in rat brain in the late period after experimental clinical death. I. Capillary vessels.

In this paper we studied the pericapillary zone of the hypothalamic neurosecretory nuclei and temporal cerebral cortex of rats 6-12 months after experimentally evoked cardiac arrest of 10 minutes duration. The most significant ultrastructural findings were presence of single collagen fibrils and collagen bundles in the compartment between endothelia and pericytes, pericytes and basement membrane and also inside the phagocytic cells. In the animals that survived at least 10 months after resuscitation the capillaries filled with thrombocytes were encountered. Moreover, in the vicinity of these capillaries the dead cells and collagen bundles were observed. We interpret these findings as the evidence of the reparatory process in the border between capillaries and the surrounding brain cells. We discuss the hypothesis that the non-fibroblastic cells present in rat brain are able to synthesize collagen that leads to a process comparable with the fibrosis of parenchymal organs.

Studies on the hypothalamus and secretory nuclei of rat in the remote period following clinical death.

Ultrastructural studies of hypothalamic secretory nuclei were carried out on rats which survived 16 weeks after 5- or 10-min-long clinical death. Active neurosecretory cells were noted without any signs of injury. In perikaryonic area numerous polymorphic lysosomes and "nucleolus-like bodies" were observed. Attention was called to significant changes in the structure of cytoskeleton and observations were discussed in relation to biochemical data. In both groups of the studied animals neurosecretory cells with features of apoptosis were found. Apoptotic cells appeared more often in animals which survived 10-min-long clinical death. Characteristic morphological features of the process of apoptosis are shown in illustrations.

Ultrastructure of phagocytizing cells of the rat hypothalamic neurosurgery nuclei in a remote period after the sustained clinical death.

Ultrastructural studies were carried out on neurosecretory nuclei taken from brains of rats which have survived for 16 weeks following clinical death of 5 or 10 min duration. The reported observations indicate that brain lesions were caused by changes due to ischemia and superimposed secondary changes resulting from the maturation of pathological processes. In animals subjected to clinical death for 5 min the observed cells in the perivascular area were integrated in the capillary wall and wrapped by the basement membrane. Sometimes they were accompanied by cells engaged in the process of phagocytosis. Phagocytizing cells were more frequently noted in the animals subjected to clinical death for 10 min and then their cytoplasmic processes were connected with the adjacent capillaries. We assume that these cells, which may represent cerebral macrophages occur by transformation of pericytes or blood derived monocytes.