Biochemical and immunological studies with human optic and olfactory tracts

Area of Science:

• Neuroscience
• Neuropathology
• Biochemistry

Background:

• Multiple sclerosis (MS) frequently impacts optic tracts but rarely olfactory tracts.
• Both optic and olfactory tracts contain central nervous system myelin, prompting investigation into differing vulnerability.
• Understanding myelin composition differences may explain differential tract involvement in MS.

Purpose of the Study:

• To investigate the biochemical differences between optic and olfactory tracts.
• To determine if myelin content or composition explains the varied involvement in multiple sclerosis (MS).
• To compare myelin markers in optic tracts, olfactory tracts, and frontal white matter.

Main Methods:

• Autopsy-obtained optic and olfactory tracts from 7 adult males were analyzed.
• Tissue homogenates were assessed for water, soluble proteins, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) activity, and basic protein (BP) content.
• Disc gel electrophoresis was performed using phenol-formic acid-water and SDS-urea systems.

Main Results:

• Optic tracts showed lower CNP activity but similar BP content compared to frontal white matter.
• Olfactory tracts had higher water content, lower BP, and reduced CNP activity versus frontal white matter.
• Findings suggest olfactory tracts have less myelin, while optic tracts exhibit altered myelin composition.

Conclusions:

• Olfactory tracts appear to possess lower overall myelin content.
• Optic tracts demonstrate a disproportionate amount of basic protein (BP) relative to CNP activity, indicating altered myelin composition.
• These myelin differences may contribute to the distinct patterns of tract involvement observed in multiple sclerosis (MS).