Effects of anti-white matter serum on myelin and lipid synthesis in brain prisms

Quantitative chemical analysis of demyelination in cultured mouse spinal cord

These studies were designed to determine whether chemical parameters can be used to quantify the demyelinative potency of anti-CNS sera or other demyelinating factors as revealed by cultured nerve tissue. The activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) and the amount of some major myelin lipids were measured in cultured embryonic mouse spinal cord during different stages of demyelination. Cultures exposed to anti-white matter serum for various times (6-60 h) or various concentrations (2.5-25%) showed a decrease (up to -70%) in CNPase activity. This change paralleled the degree of demyelination as evaluated by light microscopic examination. Cultures exposed to normal rabbit serum under the same conditions did not show changes in the amount of myelin or in the activity of CNPase. Conversely, changes in the lipid content did not correlate with the morphologic evaluation of demyelination. Glycolipids were found to decrease in cultures exposed to anti-white matter as well as in those exposed to normal rabbit sera. The decrease in cerebrosides was higher with anti-white matter serum than with normal serum, but sulfatides were altered in similar amounts in both groups. In contrast, under the same conditions, the amount of total protein or other lipid such as total cholesterol is not altered. Therefore, biochemical analysis of some myelin components could constitute a more sensitive and reliable quantitative method for early evaluation of the time course of demyelination in cultured nerve tissues.

The influence of systemic factors on acrylamide-induced changes in brain, nerve, and other tissues

In order to define the locus of acrylamide neurotoxicity, the effects of chronic intoxication (total dose 500 mg/kg) on cholinergic synthesis and transport, the Schwann cell-myelin complex, lysosomal activity, and several metabolic pathways were determined in rat sciatic nerve, spinal cord, and brain. No changes were found in hematological measures or in the levels of clinically important blood enzymes, indicating no major damage to other organs. The activities of choline acetyltransferase (ChAT), 2',3'-cyclic nucleotide phosphohydrolase, beta-glucuronidase, and lactate dehydrogenase were unaffected in acrylamide paralyzed animals, but creatine kinase (CK) decreased in sciatic nerve, muscle, and brain, particularly in animals dying of the intoxication. CK blood and the CK isoenzyme patterns in blood were unchanged. The synthesis of protein in brain and spinal cord (measured in vivo) were decreased in rats exposed to high-dose acrylamide. However, in brain and cord, CK decreased only after animals became systemically ill and suffered weight loss, with the lowest activities in those animals sick enough to die. The degree of stress to which the animals had been subjected was indicated by enlargement of the adrenal glands and decreased sulfolipid synthesis in the adrenals. Rats exposed to 25 mg/kg/day acrylamide to a total dose of 250 mg/kg developed leg weakness but not paralysis or weight loss and had a 25% decrease in CK only in the distal sciatic nerve. Because of the apparently stress-related or agonal loss of CK, no specific effect of acrylamide on the enzyme could be definitely demonstrated. Neither could the changes in protein synthesis be attributed solely to a direct effect of the toxin. These results illustrate the difficulties encountered in interpreting intoxication studies that produce systemic illness and support the suggestion that CK activity may be a useful marker of the severity and duration of the agonal state in studies of postmortem human brain.

Chemical analysis of organotypic cultures of mouse spinal cord in normal, demyelinative, and nondemyelinative conditions

Several biochemical parameters were analyzed in cultured embryonic mouse spinal cord during various stages of normal myelinogenesis or demyelination. In cultures demyelinated by exposure to anti-whole CNS tissue serum plus complement, the activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase (EC 3.1.4.37) was decreased 70%, whereas in cultures that did not show morphological changes with complement-inactivated anti-CNS serum or anti-myelin basic protein serum, the activity was 30% lower than in control cultures. The lipid composition of these cultures was quantitated by means of high-performance thin-layer chromatography densitometry technique. Cultures with normal nutrient medium alone or with the addition of 5% normal rabbit serum plus 10% guinea pig serum had 30% of the total lipid content of that present in newborn mouse spinal cord of the corresponding age. There were, however, relatively more lysophospholipids, cholesterol esters, triglycerides, and free fatty acids and less phosphatidylethanolamine and galactolipids in cultures as compared with normal spinal cord. Explants demyelinated by exposure to anti-CNS serum plus complement demonstrated principally a 70% decrease in the content of galactolipids with respect to normal cultures. When complement was inactivated, total lipids increased 42% (with increases of 40-70% in individual lipids). Inclusion of anti-myelin basic protein serum plus complement in the medium produced no significant changes in the lipid composition of the cultures.