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Studies on neurotrophic factors in chick muscle.

Mundy, Nicholas Ian; (1990) Studies on neurotrophic factors in chick muscle. Doctoral thesis (Ph.D.), University College London. Green open access

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Abstract

Experiments have been performed in order to try to elucidate the biological function of intramuscular protein (IMP), a novel substance antigenically related to vasoactive intestinal polypeptide (VIP). IMP was previously shown to be present in chick skeletal muscle during a restricted phase of development and to be secreted by cultured myotubes. This evidence and other findings suggested that IMP might be a trophic factor for motoneurons, and it is this hypothesis which the thesis sets out to test. Immunocytochemistry showed that IMP is present in ciliary muscle over a time course related to that of naturally occurring cell death in the ciliary ganglion (CG) and raised the possibility that IMP may be a trophic factor for CG neurons in addition to spinal cord motoneurons. IMP for use in bioassays was partially purified from embryonic muscle extract and myotube conditioned medium (MCM) by column chromatography, using a modified VIP radioimmunoassay to assay for IMP concentration. The molecular weight of IMP in muscle extracted in a neutral buffer is ca. 120kD, but when extracted in acid the major form has a molecular weight of ca. 35kD. The major form of IMP in MCM also has a molecular weight of ca. 35kD. Fractions containing IMP were tested in in vitro bioassays on CG neurons and motoneurons. Many IMP-containing fractions had survival activity for CG neurons; activities in IMP-containing fractions were also identified which (i) increased ChAT activity of CG neurons, (ii) had a synergistic effect on survival of CG neurons in the presence of ciliary neurotrophic factor, and (iii) had survival activity for spinal cord motoneurons. The role of IMP in these bioactivities was assessed by using fractions that had been depleted of IMP by antibody affinity chromatography, and in no case was activity clearly attributable to IMP. Thus several, possibly novel, trophic activities were identified. In conclusion, the strong circumstantial evidence for IMP being a neurotrophic factor has not been supported thus far by experiments designed to test this idea in vitro.

Type: Thesis (Doctoral)
Qualification: Ph.D.
Title: Studies on neurotrophic factors in chick muscle.
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis Digitised by Proquest.
URI: https://discovery.ucl.ac.uk/id/eprint/10124853
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