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Xenopus temporal retinal neurites collapse on contact with glial cells from caudal tectum in vitro.
Johnston AR
,
Gooday DJ
.
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Nasal and temporal retinal neurites were confronted in culture with glial cells from the rostral and caudal parts of the optic tectum and with glial cells from the diencephalon. Twenty of each of the six classes of encounter between individual growth cones and isolated glial cells were analysed by time-lapse videorecording. The results show that growth cones from the temporal retina collapse when they contact glial cells from the caudal tectum, but do not collapse when they contact glia from other areas. Growth cones of nasal retinal fibres do not collapse on contact with any of the glial types examined. This suggests that the inhibitory phenomena described by others are in part due to the cell surface characteristics of glial cells, and that there are differences between glia from the front and back of the optic tectum.
Figs 1 and 2. Sequences of photographs of temporal retinal growth cones contacting caudal tectal glial cells. The numbers at the top right of each photograph refer to the time in minutes since the sequence started. Fig. 1A-D. Temporal growth cone (A) advancing, (B) contacting, (C) collapsing and (D) retracting from an elongated caudal tectal glial cell. Scale bar represents 50/im. Fig. 2A-D. Temporal growth cone contacting and retracting from a highly flattened glial cell. Scale bar represents 50um.
Fig. 3. A-D. Two temporal retinal growth cones retracting
from two caudal tectal glial cells. (A) Fibre 1 has already
contacted and retracted from cell a and a fine stretched
process can be seen linking the two (arrowed), fibre 2 has
just contacted cell b. (B) Twenty-four minutes later fibre 1
has again contacted cell a, and fibre 2 has retracted from
cell b. (C) The growth cone of fibre 1 has collapsed 8min
after contacting cell a, and has begun to withdraw from the
cell. Fibre 2 has developed a new growth cone. (D) Fibre 1
has completely retracted from cell a, and fibre 2 has begun
to advance towards cell b again. Scale bar represents 50 um.
Fig. 4. A-D. Temporal retinal growth cone contacting a
diencephalic glial cell. (A) The growth cone advances
towards the cell, (B) makes extensive contact with the cell
and (C) continues to grow over the cell (the micrographs
were taken using an inverted microscope with the cellsubstratum
interface as the focal plane). (D) The growth
cone progresses in contact with an extended process of the
glial cell. Scale bar represents 50um.
Fig. 5. A-D. Nasal growth cone encountering a rostral
tectal glial cell. (A) The growth cone advances towards the
stretched process of a glial cell. (B) Contact is made with
the cell and (C) the growth cone grows over the cell
process. Scale bar represents 50um.
Figs 6 and 7. Temporal growth cones collapsing and retracting from caudal tectal glial cells. After retraction, the cultures
were fixed and stained with anti-GFAP. Scale bars represent 50um.
Fig. 8. (A) Anti-GFAP staining of frozen section of tadpoletectum. This antibody (clone G-A-5) only stains radial glial
cells which span the width of the brain. Scale bar represents 100/zm. (B,C) Higher power views of the areas outlined in A
to show the glial endfeet at the pial margin. Scale bar represents 100um.
