One of the limitations of many bridging
experiments in neural transplantation is that the
CNS tissues cannot be sutured. Fibrin glue is a
two-component system derived from whole
blood which, when mixed, reproduces the final
stage of blood coagulation and solidifies. Many
experimental studies of humans and animals
show that fibrin glue repair of peripheral nerves
is almost equivalent to microsurgical sutures. In
this study, we attempted to extend its use to
CNS tissues and transplants. Two techniques
were tried: (1) Bilateral parietal knife cuts were
performed by stereotaxic technique in six rats.
Fibrin glue was applied in the right-side cortical
lesion. Immunohistochemistry using antisera to
tyrosine hydroxylase (TH), glial fibrillary acidic
protein (GFAP), laminin and neurofilament
(NF) was essentially similar between the control
and treatment groups. The immunoreactivity of
each marker revealed no significant differences
between the two groups on days 1, 7 and 30.
There was no difference in terms of gliosis or
microvascular proliferation. (2) Embryonic day
16 fetal locus coeruleus was grafted together
with E16 cortex to the anterior chamber of sympathectomized
eyes. In the six eyes of the glue
treatment group, the parietal cortical piece and
the locus coeruleus piece were joined together
before grafting by immersing them in the
solution of fibrin glue. In the eight eyes of the
control group, pieces of parietal cortex and locus
coeruleus were introduced individually and approximated
by gently pressing the cornea. The
sizes of double grafts showed no significant
difference between groups during six weeks
postgrafting. The immunohistochemical pictures
using antisera against TH, GFAP and laminin
were similar in both groups. Catecholaminergic
fibers from the grafted locus coeruleus were
found bridging over into the parietal cortical
piece in both the control and treatment groups.
There was no significant difference in TH-positive
nerve fiber density between tissue glue joined
and control double intraocular grafts. In
conclusion, fibrin glue can be used as an adhesive
agent in CNS tissues without hampering
the outgrowth of neurites or causing adverse
tissue reactions in fetal or adult nervous tissues.
Effects of chronic ethanol exposure on the synapse-to-neuron ratio of rat locus ceruleus were investigated. Male Sprague-Dawley rats were given an ethanol-containing liquid diet for 4 months starting at an age of 5 weeks. Littermates, given isocaloric amounts of an ethanol-free diet, served as control. The animals were perfusion fixed using a mixture of glutaraldehyde and paraformaldehyde. Synapse-to-neuron ratio was estimated by the double disector method and calculated from (Ns/A) x (Nsec -1) / (Nn/A) where Ns/A is the number of synapses per unit area estimated in a disector with a height of on section and Nsec -1 is height of the disector, i.e., the number of sections, used for estimating the number of neurons per area (Nn/A). The mean estimated synapse-to-neuron ratio was 2046 +/- 544 (SD) in ethanol-fed rats and 4291 +/- 1171 (SD) in control rats. The difference is statistically significant (p < 0.05). The finding may be of relevance for understanding the development of abuse, tolerance, drug dependence, and abstinence reactions.
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