A study of muscle spindles in two synergistic avian muscles was undertaken to determine whether morphological or quantitative differences existed between muscle spindles residing in a slow-red (tonic) muscle and a fast-white (twitch) muscle. The avian anterior
(ALD) and posterior (PLD) latissimus dorsi muscles were chosen since they are unique among vertebrates as paradigms of a slow-red and a fast-white muscle respectively.
Serial frozen sections of muscle were stained with Haematoxylin and Eosin or Gomori triehrome and muscle spindles residing in the ALD were assessed and compared with those in the PLD with regard to organization, distribution and density, Contents of muscle spindles were examined for intrafusal fibre size, number and morphology. Attention was also directed to the relationship between muscle spindles and the surrounding extrafusal muscle in which they were located.
Differences were found between muscle spindles residing in the two muscles. In the slow ALD, muscle spindles were relatively evenly distributed, whereas in the fast PLD, they were concentrated around the single nerve entry point into the muscle. The ALD muscle spindle index was the highest yet published for chicken muscle and was 2.3 times higher than that of its fast counterpart. A bimodal trend in intrafusal fibre diameter was noted in the ALD, and a trimodal trend was found in the PLD. The former had 42% fewer intrafusal fibres than the latter.
Muscle spindles were shorter in the ALD, with an average length of 1.9mm compared with 2.3mm in the PLD. An interesting feature of the slow muscle was the monofibril muscle spindle, containing a single intrafusal fibre.
With a few exceptions, ALD muscle spindles were located within the interfascicular perimysium close to a neurovascular trunk. PLD muscle spindles were rarely seen in these areas but were frequently found within a muscle fascicle, surrounded by closely apposed extrafusal fibres. Moreover, neurovascular trunks were less frequently seen in the PLD.
As an adjunct to this study, three ALD-PLD pairs from the Storrs Connecticut strain of muscular dystrophic chickens were also examined to compare muscle spindles in these muscles with those of normal animals. In the PLD, which is known to exhibit early and progressive pathological change, muscle spindles appeared relatively normal until marked extrafusal fibre degeneration had occured. By this time evidence of muscle spindle involvement included capsular hypertrophy and intrafusal fibre splitting. Whereas the slow ALD has been reported to retain apparent normalcy in muscular dystrophy, subtle changes were seen in some of the muscle spindles examined. These included an increase in number of intrafusal fibres per muscle spindle compared with those in the normal. / Land and Food Systems, Faculty of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/22444 |
| Date | January 1981 |
| Creators | Hatfield, Linda Jean |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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