Rudiuk T.Y., Khrapai O.V., Raskaley V.B., Kovalchuk O.I., Demydchuk A.S.
MORPHOLOGICAL TRAITS OF DAMAGED SCIATIC NERVE UNDER
HYPOTHERIOSIS
Chairof Histologyand Embryology (Headof Chair–Prof. Chaikovsky Y.B., a
corresponding member of the National Academy of Medical Sciences of Ukraine)
of Bogomolets National Medical University (Kyiv)
t_darmogray@ukr.net
The thesis is devoted to studyin gof ultrastructural changes in the sciatic nerve in
hypothyroid rats after 6 and 12 weeks of its standard section.
Frequency of diagnosed hypotheriosis cases has significantly escalated among
Ukrainian population for the last decades. Hypotheriosis manifestations include
signs of nervous system impairments that are manifested as neurotic disorders and
trigger malfunctions in other organs and systems. Damage to the nerve fiber
myelin sheath is known to be a reason of the vast majority of those affections.
Structural basis of myelin sheath is a Schwann cell plasmolemma sensitive to
external and internal factors. Myelin sheath formation occurs with the participation
of thyroid hormones. Taking into account a swift growth of the accident rate
among the population in the context of concentration of a great quantity of
buildings and equipment in living communities, the damaged nerve regeneration
process under hypotheriosis is a topical subject of study.
Experimental observations were carried out in 15 white rats weighing 150-200 g
each. The experimental animals were divided into 3 groups. The first group (І)
were “pseudo-operated” animals (5 rats), which anatomy features were used to
evaluate the repair of damaged nerves. Group ІІ and ІІІ animalshad a
thyroidectomy. The II and III group animals underwent a simulation of an
experimental model of a sciatic nerve standard injury, 100 days after the
thyroidectomy. Distal segments (more distal from the post-operation neuroma) of
the damaged sciatic nerve after 6 and 12 weeks of having simulated the peripheral
nerve damage model were materials for the study.
It has been establish hed that the distal segment of the sciatic nerve displays
regeneration after having underwent standard damage under hypotheriosis
conditions 6 weeksago. It is manifestedina new growth of non-myelinated and
myelinic fibers. However, some signs of a sudden activity of degeneration
processes in the form of phagocytic activity in Schwann cells with subsequent
formation of a significant quantity of degeneration ovules for utilizing newly
formed large-diameter aberrant myelin fibers are identified simultaneously. As the
objective of a damaged nerve regeneration isrecanalization and a new growth of
non-myelinated and myelinic fibers of various diameters, including large diameter
fibers, the findings of our studies reveal a significant impediment in termination of
degeneration and launch of regeneration because of nerve fiber myelination
malfunction. The myelination malfunction persists under hypotheriosis even 12
weeks after the experimental damage of the sciatic nerve.
Conclusions.
The animal swith asimulated standard injury of sciatic nerve under hypotheriosis
displayed signs of degeneration inits distal segment which were much more
decelerated inits developmentas compared withnon-hypothyroid animals.Six weeks
after the nerve damage, the nerve distal segment in hypothyroid animals showed
active processes of recurrent degeneration in newlyformed, but aberrant tmyelin
fibers. The large-diameter newly-formed myelin fibers in hypothyroid animals
were inadequate because of myelination malfunction. Reinitiation of regeneration
was observed within 12 weeks after the hypothyroid nerve section. Deceleration of
degeneration processes great lyprolongs the time of regeneration.