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Post mortem breakdown of the myotendinous junction in fish

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Bremner, H Allan (1993) Post mortem breakdown of the myotendinous junction in fish. PhD thesis, University of Tasmania.

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Abstract

The myotendinous junction of fish muscle was investigated in detail using
both scanning and transmission electron microscopy (SEM, TEM
respectively). The properties of the main connective tissue structure, type I
collagen, were characterised and the purified collagen was used to prepare
antibodies to examine structural aspects by immunogold procedures.
The SEM studies showed that a network of fibrous connective tissue
surrounds each muscle fibre, linking it into a socket-like indentation in the
myocomma. These connective tissue fibres were degraded in chill storage,
leading to the detachment of muscle fibres from the myocommata and
subsequent loss of tissue integrity. Detailed study by TEM demonstrated
grooves and invaginations in the terminal ends of the muscle fibres that
were filled with fine collagen fibres from the myocomma. These collagen
fibres were linked by fine connections to the basal lamina which in turn
was linked to the sarcolemma.
During chill storage, the basal lamina, the fine connections and the fine
collagen fibres progressively degraded and significant deterioration
occurred in the myotendinous junction. This deterioration preceded any
obvious changes within the muscle fibre structure.
The major structural collagen of the skin and muscle and other organs in
the fish blue grenadier is an heterotrimer of type I collagen. This collagen
was highly soluble in dilute acid and the proportion of insoluble collagen increased with the age of the fish. The collagen possessed three alpha
chains in its molecular structure and the amino acid composition of the a-3
chain indicated its derivation from the a-1 chain. The melting and
shrinkage temperatures obtained for this collagen were consistent with the
imino acid levels and the environment of the fish.
Immunogold labelling procedures were developed which confirmed the
presence of type I collagen fibres in the myocomma adjacent to the muscle
fibre cell but which were inadequate to define individual collagen fibre
types.
These studies illustrate the complex and intricate nature of the
myotendinous junction in commercial fish species. They show that post
mortem degradation occurs external to the muscle fibre cell in the
extracellular matrix and, in particular, in the fine collagen fibres that form
the muscle cell envelope and fill the interstitial muscle space. The study has
thus shown that the initial problems of post mortem softening and gaping
have their origin in the myotendinous junction not within the muscle fibre
itself. The TEM work confirms the SEM work that the breakdown occurs
at the interface between the muscle fibres and the connective tissue of the
myocomma. It has highlighted the need for further work on the nature and
properties of the interstinal collagens and on the nature, activity, specificity
and location of the enzymes responsible for the degradation. It has also
pointed out the need to establish whether the marine equivalents of minor components of mammalian muscle and its extracellular matrix occur in
fish.

Item Type: Thesis (PhD)
Keywords: Fishes, Collagen, Connective tissues
Copyright Holders: The Author
Copyright Information:

Copyright 1993 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Includes bibliographical references. Thesis (Ph.D.)--University of Tasmania, 1994

Date Deposited: 25 Nov 2014 00:44
Last Modified: 21 Jun 2016 01:29
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