Long-term survival followed by degradation of neurofilament proteins in severed mauthner axons of goldfish.
The morphology and protein composition of intact and severed Mauthner axons (M-axons) from goldfish were examined on electron micrographs, sodium dodecyl sulfate gels, and immunoblots. Neurofilaments were the most common cytoskeletal element on electron micrographs, and neurofilament proteins (NFPs) were the most intensely silver-stained bands in M-axoplasm microdissected from control M-axons. NFPs at about 235, 145, 123, 105, 80, and 60 kD in M-axoplasm were identified with four monoclonal and three polyclonal antibodies. Similar immunoblots of samples of the M-axon myelin sheath (M-sheath) showed no reactivity to antibodies against NFPs. For up to 62 days following spinal cord severance in goldfish maintained at 15 degrees C, the ultrastructure, protein banding pattern, and anti-NFP immunoreactivity of several distal segments of M-axons did not change compared with control M-axons. At 62 to 81 days after severance, novel bands appeared in many silver-stained gels and anti-NFP immunoblots of distal M-axons. NFP bands completely disappeared from distal M-axon segments of some M-axons as early as 72 days after severance. However, NFP bands persisted in some distal segments for up to 81 days after severance. The degradation of NFPs occurred equally along the entire length of a distal M-axon segment, that is, there was no indication of a proximal-to-distal or distal-to-proximal sequence of NFP degradation in distal segments of severed M-axons. These biochemical data were consistent with morphological data that showed little change in the diameter or ultrastructure of severed M-axons held at 15 degrees C for about 2 months followed by a rapid collapse of the entire distal segment at 72 to 85 days postseverance.
Moehlenbruck
J W
JW
Department of Zoology, University of Texas at Austin 78712-1064.
Cummings
J A
JA
Bittner
G D
GD
D000818:Animals; D001369:Axons / Q000502:physiology* / Q000648:ultrastructure; D002470:Cell Survival; D006054:Goldfish; D016900:Neurofilament Proteins / Q000378:metabolism*; D012183:Retrograde Degeneration; D013116:Spinal Cord
D016900:Neurofilament Proteins