L1 and GAD65 are expressed on dorsal commissural axons in embryonic rat spinal cord.

Using immunocytochemical methods, the cell adhesion molecule L1 was detected on axons crossing in the dorsal commissure of developing rat spinal cord. Immunoreactive axons were found in locations similar to fiber bundles illustrated by Ramón y Cajal and designated the anterior, middle and posterior bundles of the dorsal commissure. L1-immunoreactive dorsal commissural axons were first observed on embryonic day 17 (E17), appeared more numerous by E19, and remained detectable in early postnatal ages. The massive middle axon bundles extended bilaterally from the dorsolateral funiculi towards the midline and crossed in the central part of the commissure. In horizontal sections, bundles of L1-labeled middle axons were observed to traverse the dorsal commissure in a periodic pattern along the entire rostrocaudal extent of the spinal cord. Bundles of glutamic acid decarboxylase (GAD65)-positive axons were detected crossing in the middle and posterior regions of the dorsal commissure between E17 and E20. Results from double-labeling experiments demonstrated that GAD65-positive fibers were embedded in larger bundles of L1-labeled axons and that some dorsal commissural axons were double-labeled. To determine if there were axons crossing in the dorsal commissure that did not express L1, double-labeling experiments were conducted using neurofilament and L1 antibodies. Results indicated that bundles of axons identified with anti-neurofilament antibodies were also L1-positive, whereas individually coursing axons within the commissure were L1-negative. The predominance of L1 on fiber bundles traversing the dorsal commissure adds to the growing evidence that this molecule may play a role in axon outgrowth and fasciculation.

An enzyme immunoassay for neuron-specific enolase in cerebrospinal fluid.

A direct (as opposed to competitive) enzyme immunoassay (EIA) was developed to detect neuron-specific enolase (NSE) in cerebrospinal fluid (CSF). Most common methods of evaluating NSE levels have utilized radioimmunoassay. These are highly sensitive, but cannot be employed in laboratories not equipped or licensed for the use of radioisotopes. The EIA developed here shows sensitivity within the physiological range of values for CSF-NSE (> I ng/ml) and can be used in laboratories with appropriate densitometric scanning capabilities. The assay was applied to CSF samples obtained from patients with a variety of diagnoses at the time of surgical intervention for their respective disorders. While there were no diagnostically significant differences between the level of NSE in CSF from patients with different neurological disorders utilized in the development of this procedure, we were able to differentiate between marginally different levels of NSE. We conclude that we have developed a safe, fast, reliable, and sensitive assay for NSE in the CSF that can be used to study NSE levels in a variety of neurological cases.

Neuroamine related compounds in the CSF of hydrocephalic rabbits.

The effects of neonatal hydrocephalus on the levels of tyrosine, tryptophan, 5-hydroxyindoleacetic acid (5-HIAA), and homovanillic acid (HVA) in CSF were determined by high-performance liquid chromatography (HPLC) with fluorometric detection in normal and chronically hydrocephalic rabbits. The hydrocephalic rabbits showed a highly significant increase in both the serotonin metabolite 5-HIAA and the dopamine metabolite HVA. There were no significant effects of the hydrocephalus on either tyrosine or tryptophan levels. There was a significant positive correlation between the intracranial pressure (ICP) and the increase in 5-HIAA and HVA, but not with the two precursor amino acids. There was a significant decrease in these amino acid precursors with age in both groups. A trend towards higher levels of 5-HIAA and HVA in older rabbits was also evident, however this change was not to the degree found in the hydrocephalics. These data indicate that increased ICP affects the mechanism of removal of 5-HIAA and HVA from the cerebrospinal fluid.