The cerebral ventricles of the dog. I. Ultrastructural features of supraependymal cells during the inflammatory response

History of research concerning the ependyma: a view from inside the human brain

The history of research concerning ependymal cells is reviewed. Cilia were identified along the surface of the cerebral ventricles c1835. Numerous anatomical and histopathological studies in the late 1800's showed irregularities in the ependymal surface that were thought to be indicative of specific pathologies such as syphilis; this was subsequently disproven. The evolution of thoughts about functions of cilia, the possible role of ependyma in the brain-cerebrospinal fluid barrier, and the relationship of ependyma to the subventricular zone germinal cells is discussed. How advances in light and electron microscopy and cell culture contributed to our understanding of the ependyma is described. Discoveries of the supraependymal serotoninergic axon network and supraependymal macrophages are recounted. Finally, the consequences of loss of ependymal cells from different regions of the central nervous system are considered.

Scanning electron microscopy of central nervous system cerebrospinal-fluid-contacting surfaces: a bibliography (1963-1995)

This bibliography is compiled to assist in locating papers related to the application of scanning electron microscopy (SEM) to cerebrospinal-fluid-contacting surfaces in vertebrates. The use of SEM by neuroscientists has continued apace since the publication of the first bibliography in 1980. SEM studies now include more than 50 species of vertebrates and range from cyclostomes to humans; they encompass development from embryo to senescence and concern both normal and pathologic morphology. Although remarkable strides have been made toward a greater understanding of many aspects of the structure and function of cerebrospinal-fluid-contacting surfaces, many significant problems await the judicious application of scanning electron microscopy.

Acute infusion of chemotactic or enkephalin-analog peptides into rat cerebral ventricles: scanning and transmission electron microscopy of leukocyte immigration in vivo

Acute infusions of the formylated chemotactic peptide formyl-methionyl-leucyl-phenylalanine-lysine (FMLPL) or enkephalin analogue (Sandoz peptide) were made to the lateral cerebral ventricle of adult male rats to examine potential cellular responses within the central nervous system (CNS). Ependymal regions lining the third ventricle atop the hypothalamus were examined using scanning and transmission electron microscopy. The formylated peptide induced a significant, primarily neutrophilic cellular response in animals sacrificed 1 h after infusion. Cells were observed within and external to neuropil blood capillaries, suggestive of emigration from vasculature in response to the peptide. In contrast, the enkephalin analogue did not induce any leukocyte cellular response within the same time frame. Earlier studies have shown a monocyte/macrophage response in the same setting to the opioid peptides beta-endorphin, and to a lesser extent, methionine enkephalin. The present findings suggest that a formylated peptide is a potent stimulus for neutrophil migration within a CNS site, while opioid peptides may be variable with respect to effectiveness on cells of the immune system within the CNS, depending upon chemical configuration.

Scanning electron microscopy of the subarachnoid space in the dog: inflammatory response after injection of defibrinated chicken erythrocytes

The leptomeningeal reaction and the cerebrospinal fluid reaction of the canine inflammatory response were investigated concurrently. One-half milliliter cerebrospinal fluid (CSF) was withdrawn from the cisterna magna of 17 anesthetized mongrel dogs and analyzed. Using this same spinal tap, control and experimental animals were injected with 0.5 ml sterile saline and 0.5 ml defibrinated chicken erythrocytes, respectively. A second spinal tap was performed 2 to 168 hr later. The CSF from the first spinal tap contained less than 1 WBC/mm3. The cell population was unchanged in the second spinal tap of control animals. In experimental animals, the WBC population increased more than 100-fold by 24 hr. Polymorphonuclear cells (PMNs) appeared in the CSF first, followed by lymphocytes and monocytes. Injected erythrocytes seemed trapped in the subarachnoid space (SAS), especially in the inner sheet of the arachnoid mater. The leptomeninges had a substantial increase in free cells without fibrosis. Pial and leptomeningeal cells of the arachnoid trabeculae appeared swollen. Two hours after injection, chicken erythrocytes were phagocytosed by pial cells, macrophages, and free cells adherent to the leptomeninges. The epiplexus cell populations for saline-control and erythrocyte-experimental animals were similar, suggesting that the choroid plexuses were not a gateway for PMN, lymphocyte, or monocyte infusion into the SAS.

Chronic infusion of opiate peptides to rat cerebrospinal fluid with osmotic minipumps

Beta-endorphin-related opiate peptides or the opiate antagonist naloxone were chronically infused for periods of 24 to 48 hours to the lateral cerebral ventricle of adult male rats using Alza osmotic minipumps. Previous studies have suggested a "chemotactic"-like effect of opiate peptides for supraependymal macrophages in the region of the third ventricle of the brain. The present study demonstrates a stimulatory effect of beta-endorphin infusion on the appearance of lymphocyte and neutrophil-like cells, in addition to macrophages, in the region of the third ventricle, suggestive of an intracerebral inflammatory response. None of the other molecules, including alpha-endorphin, methionine-enkephalin, naloxone, or sterile saline produced similar cellular responses after infusion, although some of the latter substances may have induced the appearance of supraependymal neuron-like cells in the area. Observations suggest that the chronic presence of beta-endorphin, a biologically active opiate peptide, will interact with cells of the immune system, which have the ability to gain access to the cerebrospinal fluid.

Acute injections of opiate peptides into the rat cerebral ventricle: a macrophage-like cellular response

Opiate peptides (beta-endorphin, alpha-endorphin or met-enkephalin) were administered to the lateral cerebral ventricle of adult male rats via single injection into implanted cannulas. Scanning EM of the third ventricle above the median eminence of animals sacrificed approximately one hour after peptide injection revealed numerous free cells above the ependyma. Beta-endorphin induced a significantly greater cellular response than other peptides or control injections. Transmission EM demonstrated that the cells had morphologic characteristics of macrophages. Opiate peptides in cerebrospinal fluid may act as "chemotactic" factors to induce the migration of macrophage-like supraependymal cells.

The cerebral ventricles of the dog. II. Evidence of a hematogenous origin of supraependymal cells during the inflammatory response

The present investigation examined the ependymal linings of the choroid plexus and cerebral ventricles of the dog following a single intracisternal injection of viable, bacillus Calmette-Guerin (BCG). One or 3 days following the injection of BCG, animals were perfused with buffered aldehydes. The choroid plexus of each cerebral ventricle as well as samples of the ependyma from the caudate nucleus, interthalamic adhesion, and median sulcus were removed and prepared for transmission electron microscopy. Following injection of BCG, leukocytic cells are found in association with the following structures and areas of the subependyma and choroid plexus: the endothelium of small blood vessels and capillaries; the walls of small blood vessels; the subependymal neuropil; the choroid plexus stroma; the single layer of ependyma bordering the luminal surfaces of the choroid plexi and ventricles; and the free, luminal surfaces of the choroid plexus and ventricular ependyma. The population of leukocytic cells included monocytes, macrophages, neutrophils, lymphoblasts, and plasma cells. The results of the present study suggest that the supraependymal leukocyte population of infected animals reaches the cerebral ventricular linings by migrating from the choroidal and subependymal vasculature.