76
JERALD J. BERNSTEIN
from dedifferentiated and subsequently redifferentiated ependymal cells.
Large numbers of these specialized neurons and glial elements were
developed and reconstituted the caudal neurosecretory system with
almost its original orientation. The reconstitution of the caudal neurosecretory system (Fridberg et al., 1966) demonstrated that the spinal
cord of teleost fish can reorganize cytologically and organogenically and
thus reconstitute an extirpated area.
Imai (1965) has studied the caudal neurosecretory system of the
Japanese eel and has found malformations of this sysem which he considers to be regenerative responses to wounding of the tail area. The
new Dahlgren cells took their origin from ependyma. The regenerated
neurosecretory area of the spinal cord developed rather rapidly and
was fully reconstituted by the end of 5 months, but the urophysis did
not regenerate into its original form. The urophysis was found incorporated into the area of the regenerated caudal neurosecretory cells which
demonstrated the return of function by the presence of neuroscretory
elementary granules. In addition, axons of other nerve fibers which have
their cell bodies in the upper portion of the spinal cord were located
in the urophysis. Thus, the dual system of innervation was reconstructed (Fridberg et al., 1966).
IX. MYOTYPIC RESPECIFICATION OF REGENERATED NERVES
Studies on myotypic respecification following the heterotrophic regeneration of cranial or peripheral nerves asks the question: Can the
specificity of a given muscle alter nerve function in such a manner as to
result in return of normal function following regeneration of a foreign
innervation? Experimentally this was accomplished by surgical section
and cross-union of branches of nerves thus forcing foreign innervation to
muscles. This was followed by an assessment of functional recovery. In
the Oscar, Astronotus ocellatus, the trigeminal nerve ( Cr.N.V. ) supplies
two motor mandibular branches to the muscles of mastication (Arora
and Sperry, 1957). Opening the jaw was controlled by the intermandibular muscle and hyoid muscles. The jaw was closed by the abductor or
levator mandibulae muscles. Both of these antagonistic muscle
complexes were innervated by separate rami of the mandibularis trigemini
(motor root Cr.N.V). Transection of the entire motor root of the trigeminal nerve resulted in complete paralysis of the jaw. However, within
16 days, mandibular movement had returned to normal.
The two separate nerve roots (derived from the trigeminal nerve)
JERALD J. BERNSTEIN
from dedifferentiated and subsequently redifferentiated ependymal cells.
Large numbers of these specialized neurons and glial elements were
developed and reconstituted the caudal neurosecretory system with
almost its original orientation. The reconstitution of the caudal neurosecretory system (Fridberg et al., 1966) demonstrated that the spinal
cord of teleost fish can reorganize cytologically and organogenically and
thus reconstitute an extirpated area.
Imai (1965) has studied the caudal neurosecretory system of the
Japanese eel and has found malformations of this sysem which he considers to be regenerative responses to wounding of the tail area. The
new Dahlgren cells took their origin from ependyma. The regenerated
neurosecretory area of the spinal cord developed rather rapidly and
was fully reconstituted by the end of 5 months, but the urophysis did
not regenerate into its original form. The urophysis was found incorporated into the area of the regenerated caudal neurosecretory cells which
demonstrated the return of function by the presence of neuroscretory
elementary granules. In addition, axons of other nerve fibers which have
their cell bodies in the upper portion of the spinal cord were located
in the urophysis. Thus, the dual system of innervation was reconstructed (Fridberg et al., 1966).
IX. MYOTYPIC RESPECIFICATION OF REGENERATED NERVES
Studies on myotypic respecification following the heterotrophic regeneration of cranial or peripheral nerves asks the question: Can the
specificity of a given muscle alter nerve function in such a manner as to
result in return of normal function following regeneration of a foreign
innervation? Experimentally this was accomplished by surgical section
and cross-union of branches of nerves thus forcing foreign innervation to
muscles. This was followed by an assessment of functional recovery. In
the Oscar, Astronotus ocellatus, the trigeminal nerve ( Cr.N.V. ) supplies
two motor mandibular branches to the muscles of mastication (Arora
and Sperry, 1957). Opening the jaw was controlled by the intermandibular muscle and hyoid muscles. The jaw was closed by the abductor or
levator mandibulae muscles. Both of these antagonistic muscle
complexes were innervated by separate rami of the mandibularis trigemini
(motor root Cr.N.V). Transection of the entire motor root of the trigeminal nerve resulted in complete paralysis of the jaw. However, within
16 days, mandibular movement had returned to normal.
The two separate nerve roots (derived from the trigeminal nerve)