ABSTRACT
The ependymal layer is in direct contact with the cerebrospinal fluid within the ventricles and aqueducts of the brain. Cilia covering the ependymal cells maintain a constant flow of cerebrospinal fluid (CSF), helping to keep the ventricular and aqueductal surface clear of debris (1). Approximately 40 cilia, 8 |im in length, project from each ependymal cell and beat, continuously, at up to 40 133
beats per second (Hz) (2). We have established a model that allows measurement of ependymal ciliary beat frequency by high-speed video photography during incubation with bacteria or their toxins. We were particularly keen to use our model to study pathogenic modes of action of the pneumococcus. For pneumococcal meningitis, mortality rates of up to 20% remain despite effective antibiotic killing of bacteria (3), and significant problems may occur in survivors, most commonly due to sensorineural deafness (4). The ependymal cells have recently been identified as adult neural stem cells (5). Whether their loss during infection results in a reduced regenerative capacity of certain brain tissues remains speculative. It has been postulated that the rapid release of the pneumococcal toxin, pneumolysin, on antibiotic-induced bacterial lysis may cause local tissue damage and may play a part in the development of sensorineural deafness (6). Indeed, we have shown (2) that pneumolysin causes rapid ependymal ciliary stasis at levels that may be encountered clinically during meningitis. The contribution of pneumolysin to the damage seen in pneumococcal meningitis is still under debate(7). In this chapter we will present evidence to show that pneumolysin in vitro is an important part of the mechanism of damage of ependymal ciliary function by pneumococci. AIMS OF EXPERIMENTS
The aims of the experiments are as follows: 1. To develop a ciliated tissue culture model of the ependyma so that long-term ciliary beat frequency can be measured.2. To test the effects of pneumolysin on ependymal cells from rat brain slices and cultured ependymal cells.3. Examine the effects of pneumolysin-deficient and -sufficient pneumococci on the ependyma.4. Examine the role of pneumococcal hydrogen peroxide as an ependymal toxin.
