Glial repair in an insect central nervous system: effects of selective glial disruption

In vivo application of ethidium bromide to cockroach central nervous connectives caused extensive disruption of the neuroglia within 24 hr. Axonal conduction persisted following treatment with the glial toxin. A consistent feature of glial damage and repair was the prominent involvement of granule-containing cells. These cells (which were never seen in control cords) shared a number of cytological features with hemocytes that were seen adhering to and penetrating the neural lamella, in the early stages of glial damage. The granule-containing cells appear to serve dual functions: phagocytosis and structural repair. After 48 hr, granule-containing cells, or their processes, formed layers at the periphery of the connectives. By 4 to 6 days after treatment, the peripheral cells had assumed the morphological characteristics of normal perineurial cells and by 28 days were indistinguishable, ultrastructurally, from those of the perineurium of normal, untreated animals. These structural changes paralleled the re-establishment of the normal permeability properties of the blood-brain interface revealed by the exclusion of an extracellular tracer, ionic lanthanum, and electrophysiological observations

Mechanisms of glial regeneration in an insect central nervous system

As in other repairing systems, glial regeneration in insect central nervous connectives, following selective chemical lesioning, involves both exogenous and endogenous elements. Our current evidence, including that obtained with monoclonal antibodies, indicates that the reactive, granule-containing cells are derived from a sub-population of circulating haemocytes which, within 24 h, invade, and are restricted to, the lesion zone. The granule-containing cells are involved in the initial repair of the perineurial region. They also contribute to the first stage in the restoration of the blood-brain barrier and are responsible for recruiting reactive endogenous glia, apparently from the vicinity of the anterior abdominal ganglion. The granule-containing cells transform into or are replaced by functional glia between 3 and 5 days after selective glial disruption, coincident with the appearance in the lesion zone of dividing reactive cells

Cell proliferation in the repairing adult insect central nervous system: incorporation of the thymidine analogue 5-bromo-2-deoxyuridine in vivo

Uptake of the thymidine analogue 5-bromo-2-deoxyuridine into non-neuronal cells of the insect central nervous system has been examined following a controlled lesioning of the glial elements. The pattern of BUdR labelling along the penultimate abdominal connective was examined over a period of 17 days. Cell proliferation occurred in and immediately around the site of damage in both perineurial and subperineurial glial cells but at different times post-lesion for the two regions. Proliferation in the perineurial zone was maximal at 6-8 days post-lesion but continued for at least 17 days. Subperineurial proliferation was less dramatic and peaked between days 8-11 post-lesion. In both areas division appears to be confined to the reactive glial cells. These results are discussed in the context of past research on this system, particularly with regard to the restoration of the blood-brain barrier