Early changes in experimental hydrocephalus.

In acute obstruction of the cerebral spinal fluid (CSF) absorption pathways, fluid is produced more rapidly than it is absorbed, and the ventricles enlarge proximal to the obstructions. Communicating hydrocephalus results from a difference between the rates of production and absorption of cerebrospinal fluid. In animals with chronic communicating hydrocephalus, the initial pathologic changes appear to involve the periventricular tissue near the angles of the lateral ventricles. The present investigation was designed to identify the various changes associated with the production of communicating hydrocephalus in acutely hydrocephalic preparations and to relate these findings to those found in experimental animals with chronic communicating hydrocephalus. The results of this study seem to confirm that the changes noted in the chronically hydrocephalic animals occur as early as 12 hours after the restriction of the normal flow of CSF.

Chronic ventricular cerebrospinal fluid sampling, drug injections, and pressure monitoring using subcutaneous reservoirs in monkeys.

Animal models enabling reliable access to ventricular cerebrospinal fluid (CSF) are crucial to the study of neuropharmacological and neurotoxicological effects of cytotoxic agents used to treat central nervous system neoplasms. This investigation concludes that 4th ventricular catheterization using subcutaneous CSF reservoirs in rhesus monkeys: (a) provides chronic access to sterile CSF without chronic immobilization, (b) enables mixing of injected drugs with lateral ventricular CSF, (c) permits sensitive monitoring of intraventricular pressure and (d) does not produce tissue damage during cannula implantation or breakdown of the blood-brain barrier.

Evaluation of the central canal of the spinal cord in experimentally induced hydrocephalus.

The central canal of the spinal cord has been proposed as a significant compensatory alternative pathway of cerebrospinal fluid (CSF) flow in hydrocephalus. Ten dogs were made hydrocephalic by a relatively atraumatic experimental model that simulates the human circumstance of chronic communicating hydrocephalus. The central canal was studied by histopathology and compared with 10 normal control dogs. In both groups the central canal of the spinal cord was normal in size, configuration, and histological appearance. In this experimental model dilatation of the canal and increased movement of CSF does not appear to be a compensatory alternative pathway.

Ultrastructural alterations and phagocytic function of cryopreserved platelets.

Fresh human platelets and platelets cryopreserved in 4% dimethylsulfoxide were examined ultrastructurally before and after incubation in a suspension of latex particles. Cryopreserved platelets had fewer discoid forms than fresh platelets. The cryopreserved platelets had many sphered platelets containing an increased number of vacuoles; the sphered platelets were more electron-lucent margination and pallor of organelles. Phagocytosis of latex into vacuoles was markedly impaired in the cryopreserved platelets. The morphologic alterations suggested that the freezing, thawing, and washing procedures reduced the functional activity of platelets.

The central canal of the spinal cord in experimental hydrocephalus: preliminary results.

The central canal of the spinal cord in certain animal species has been shown to be an alternative pathway of cerebrospinal fluid flow in experimentally induced hydrocephalus. Enlargement and increased movement of cerebrospinal fluid in the central canal has been proposed as a compensatory mechanism in hydrocephalus in humans. The central canal of the spinal cord was normal in 5 dogs and 2 primates made hydrocephalic by a relatively atraumatic experimental model which simulates the human disorder to chronic communicating hydrocephalus. Dilatation of the central canal is apparently not an important compensatory alternative pathway.

The ultrastructural basis of periventricular edema: preliminary studies.

The pathophysiology of periventricular lucency (PVL) on CT in primates was evaluated by transmission (TEM) and scanning electron microscopy (SEM). At 100 days after Silastic-induced hydrocephalus, six primate brains showed loss of cilia and ependymal cells over the ventricular surface and abnormal small supraependymal cells. TEM demonstrated communicating pathways between the ventricular lumen and brain parenchyma and the extracellular space was markedly increased. At 1000 days, ependymal changes in two brains were noted at greater distances from the ventricular angle. This study suggests that CT periventricular lucency in patients with hydrocephalus is due to the increased extracellular space. The lack of recognition of PVL by computed tomography in chronic normal pressure hydrocephalus may be due to change in distribution and resolution limits.

Human blood monocytes: characterization of negatively selected human monocytes and their suspension cell culture derivatives.

Normal human monocytes were negatively selected from leucapheresis cell suspensions by countercurrent centrifugation-elutriation in high yield with a mean purity of 93.5%. The combination of the novel methods of negative cell selection and suspension cell culture has provided the opportunity to study serially over several days the morphologic and functional changes of monocytes from a single donor as they matured in culture to typical macrophages. Human monocytes nearly double in size during the first week of culture, experiencing near daily increases in cell volume. This was associated with changes in the ultrastructure of these cells, including the development of numerous small knob-like projections on the cell membrane and the proliferation of microtubules and filamentous structures within the cell cytoplasm during the first 6 days of culture. Peroxidase activity declined during the first 4 days of culture, whereas 5'-nucleotidase activity was acquired during the first 48 h of culture. Lysozyme activity in the cultures increased form day 2 to day 6 of culture. The phagocytic capacity of monocytes for igG-coated erythrocytes increased dramatically during the first week of culture, but the cytotoxic capability of monocytes against similar targets in an antibody-dependent cytotoxicity assay declined to nearly half of base-line levels by day 2 of culture and remained at this diminished level during subsequent days of culture.