ANATOMICAL AND IMMUNOHISTOCHEMICAL STUDIES OF THE SPINAL CORD OF THE GRASSCUTTER (Thryonomysswinderianus)
ANATOMICAL AND IMMUNOHISTOCHEMICAL STUDIES OF THE SPINAL CORD OF THE GRASSCUTTER (Thryonomysswinderianus)
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Date
2019-12
Authors
FELIX, Udawinojo Enemali
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Abstract
Grasscutters are currently being explored as laboratory models for scientific, medical and
behavioural researches. In the present study, the anatomical, histological, histochemical and
immunohistochemical studies of the spinal cord of the grasscutter was evaluated. Twelve
adult Grasscutters comprising six males and six females were utilized for the study. The
studies on the spinal cord of Grasscutter were done by gross observations and light
microscopical methods. The animals were weighed and sacrificed by dissected. The spinal
cords were removed by splitting open the vertebrae to expose the spinal cords which were
then cleaned by removing the meninges surrounding them. The gross morphology of the
spinal cord was studied while the segments were fixed, processed, sectioned and were taken
for histological, histochemical and immunohistochemical studies using H and E, Cresyl fast
violet, Golgi-Cox and Alpha-1 antityrosine hydroxylase methods respectively for detailed
studies of the spinal cord segments of the Grasscutter. Histometrical evaluation wasdone for
detailed studies on the areas and perimeters of the various neurons in the spinal cord
segments of Grasscutter. The results showed that the mean weight of the males was
significantly higher than the females (P<0.05) while the mean weight of the spinal cord did
not show sexual dimorphism. The mean weight of the Grasscutter was 4700.27±0.05 g and
3633.40±0.80 g for males and females respectively. The spinal cord of the Grasscutter was
observed to be made up of 28 segments which are regionally divided into 7 cervical, 13
thoracic, 6 lumbar and 2 sacral spinal segments. Two enlarged regions were observed in the
spinal cord of Grasscutters namely, the cervical enlargement which was observed between C2
and C7 and lumbosacral enlargement observed between L1 and S2 spinal cord segments. The
result showed that the histological features of the spinal cord of the Grasscutter with H & E
method, has inner gray matter core surrounded by an outer white matter. No histological
difference was observed between male and female Grasscutter. The basic structural pattern was the same throughout the length of the spinal cord of the Grasscutter. The present study
using Cresyl fast violet method showed that the gray matter was stained dark purple due to
the abundant presence of Nissl bodies in the neuronal cell bodies while the outer zone of
white matter stained relatively lighter due to the presence of nerve fibers in the region. The
neurons in the anterior gray horns of cervical, thoracic, lumbar and sacral segments of the
spinal cord are multipolar motor neurons with prominent vesicular nucleus while cells in the
posterior gray horns of cervical, thoracic, lumbar and sacral segments are sensory neurons.
The spinal cord of the Grasscutter when stained with Golgi-Cox method revealed neurons
which are of various shapes in the gray matter of the spinal cord of the Grasscutter. The gray
matters of the spinal cord which had posterior and anterior horns were seen to contain
neurons which were composed of several dendrites and one axon. Neurons found mainly in
the posterior horns of the spinal cord of Grasscutter especially in the cervical and lumbar
spinal segments were unipolar neurons while neurons of the anterior horns of the spinal cord
of cervical, thoracic, lumbar and sacral spinal segments of Grasscutter were multipolar
neurons. The result of immunohistochemical studies of the spinal cord of the Grasscutter
treated with alpha-1 antityrosine hydroxylase, showed that dopaminergic neurons are present
in the spinal cord of Grasscutters. The dopaminergic neurons were deeply stained in the
lumbosacral segments than in other spinal cord segments of Grasscutters. The result of the
histometrical studies of cell areas and cell sizes of the spinal cord of Grasscutters showed
that the greatest value for mean for cell perimeter and cell area was observed in the lumbar
spinal cord segment to be 9.30± 0.67 and 3.28± 0.59 respectively while the least values
cell perimeters and cell areas were calculated to be 3.86± 0.24 and 0.83± 0.09 respectively
were observed in the cervical spinal cord segment. Using t- test analysis the cell area in
cervical ventral horn wassignificantly higher than cell area in the sacral ventral horn (P<0.05)
and cell area in the dorsal horn of cervical spinal cord was significantly higher than the cell area in the dorsal horn of the thoracic spinal cord segment of Grasscutter. The cell perimeter
of the cells of the ventral horn of lumbar spinal cord segment was significant larger than cell
perimeter of the cells of the ventral horn of the cervical spinal cord segment (P<0.05) and the
cell sizes of the dorsal horns of lumbar spinal cord segment was significantly higher of the
dorsal horn cell of the cervical spinal cord segment (P<0.05). The anatomical, histological,
Histochemical, immunohistochemical and histometrical studies on the spinal cord of
Grasscutter (thryonomysswinderianus) showed unique features which include cervical and
lumbosacal enlargements, presence of Nissl bodies in the cell bodies of neurons and
abundance of dopamergic neurons in the cervical and lumbosacral regions. These features
could be helpful in understanding the biology and behaviour of this rodent.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES AHMADU
BELLO UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR
THE AWARD OF DOCTOR OF PHILOSOPHY (Ph.D) DEGREE IN HUMAN
ANATOMY
DEPARTMENT OF HUMAN ANATOMY,
FACULTY OF BASIC MEDICAL SCIENCES,
COLLEGE OF MEDICAL SCIENCES,
AHMADU BELLO UNIVERSITY,
ZARIA, NIGERIA
Keywords
ANATOMICAL,, IMMUNOHISTOCHEMICAL STUDIES,, SPINAL CORD,, GRASSCUTTER,, (Thryonomysswinderianus).