Morfometrična analiza sinaptičnih jedrnih skupkov v posamičnih vlaknih hitre in počasne skeletne mišice
A morphometric analysis of synaptic nuclear clusters in isolated fibers of fast and slow skeletal muscle

slovenian

2001

volume 40, issue 2

Muscle, skeletal    Anatomy and histology   Neuromuscular junction    Cell nucleus    Muscle fibers, fast-twitch    Muscle fibers, slow-twitch   Rats, wistar   Microscopy, confocal    molecular biology 

Društvo Medicinski razgledi
(Obvezni izvod spletne publikacije)

Myonuclei of mammalian skeletar muscle fibers are packed at much higher density in the neuromuscular junction region than in the extrajunctional partsof the fiber. Slow muscle fibers are electromechanically active for longer time periods than fast fibers and the frequency patterns of action potentials are different in both fiber types. This difference might reflect inthe distribution of synaptic myonclei and the arrangement of synaptic Schwann cells. Our hypotheses were:1. The number of synaptic myonuclei is significantly higher in slow fibers than in fast fibers. 2. The number of synaptic Schwann cells determined by counting their nuclei is proportional to the neuromuscular junction area. 3. The reach of the influences of neural trophic factors in the skeletal muscle fibers does not differ in regard to thefiber type. Nuclei in single muscle fibers of m. extensor digitorum longus (fast) and m. soleus (slow) were labelled with SYTOX green nuclear acid stain and the endplates with rhodamine-tagged alpha-bungarotoxin. Images obtained byconfocal microscopy were morphometircally analysed. There are 7,15 +- 2,37 (n=20) synaptic myonuclei in slow muscle fiber and 4,60 +- 0,75 (n = 20) synaptic myonuclei in fast muscle fiber. The difference is significantly different (p < 0,05; Student's T-test), The correlation coefficient between the area of the neuromuscular junction and the number of Schwann cell nuclei was higher in fast fibers (KK=0,4) than in slow fibers (KK=0,07), but to our opinion still too low to confirm our second hypothesis; 3. Maximal distance ofthe action of neuronal trophic factors was estimated by measuring the distance between the border of the neuromuscular junction and the first extrasynaptic nucleus. It was found to be 25,5 +- 9,3 microm, (n=20) in fast fiber type and 26,9 +- 7,4 pm (n=20) in slow fiber type and the difference wasnot statistically significant (p > 0,05; Student's T-test).

26.06.2015