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Extremely low birth weight (ELBW) infants are at risk for hypotension. Abnormal adrenal function may play a role in the pathogenesis of hypotension, and therefore, the administration of hydrocortisone (HC) may be an effective treatment for hypotension in some infants. However, the efficacy of prophylactic HC to prevent the use of vasopressors for a defined hypotensive state has not been studied. We conducted a randomized-controlled trial to determine the potential role on adrenal insufficiency in early neonatal hypotension and to determine the effectiveness of prophylactic HC in reducing treatment of hypotension in ELBW infants. STUDY DESIGN:Infants were assigned to receive either HC or placebo within the first 3 hours of life. Therapy was continued for 5 days. The presence of hypotension was based on an operational definition and treatment with vasopressors (VP) was standardized based on an a priori protocol. RESULTS:A total of 34 patients were enrolled. Baseline characteristics were similar between groups. Of the HC group 25% received VP at 24 hours of age compared to 44% of the placebo group. On day of life 2, only 7% of the HC group received VP compared to 39% of the placebo group (p<0.05). CONCLUSION:Prophylactic treatment with HC reduces the incidence of hypotension, defined by treatment with VP, among ELBW infants during the first 2 days of life. However, the mounting evidence that prophylactic administration of glucocorticoids in the first days of life is harmful to ELBW infants makes HC prophylaxis unwise until the efficacy of treatment relative to safety can be clearly established.

The process by which oligodendrocyte progenitors differentiate into mature oligodendrocytes is complex and incompletely understood in part because of the paucity of oligodendrocyte precursors cell lines that can be studied in culture. We have developed a non-immortalized rat oligodendrocyte precursor line, called OL-1, which behaves in a fashion consistent with developing oligodendrocytes in vivo. This OL-1 line provides a model for the study of oligodendrocyte development and offers an alternative to the CG-4 cell line. When OL-1 cells are propagated in conditioned growth media, they have morphology consistent with immature oligodendrocytes and exhibit A2B5 antigen positive and myelin basic protein-negative immunoreactivity. Withdrawal of conditioned growth media and culture in serum-free medium results in OL-1 cell maturation, manifested by a shift to myelin basic protein-positive immunoreactivity, A2B5 antigen-negative immunoreactivity, decreased NG2 mRNA expression, increased expression of proteolipid protein mRNA, and increased expression of CNP protein. In addition, the expression of proteolipid protein and its splicing variant DM-20 exhibit a pattern that is similar to brain proteolipid protein expression during development. When OL-1 cells are exposed to Insulin-like growth factor-I, there are significant increases in proteolipid protein mRNA expression (p<0.05), the number of cell processes (p<0.05), and cell number (p<0.05). Treatment with the caspase inhibitors Z-DEVD-FMK and Z-VAD-FMK (inhibitors of caspases 3, 6, 7, 8, 10 and 1, 3, 4, respectively), Insulin-like growth factor-I, or both, results in a similar increase in cell number. Because Insulin-like growth factor-I does not substantially increase the BrdU labeling of OL-1 cells, these data collectively indicate that Insulin-like growth factor-I increases OL-1 cell number predominately by promoting survival, rather than stimulating proliferation. This non-immortalized oligodendrocyte precursor cell line, therefore, exhibits behavior consistent with the in vivo development of oligodendrocytes and provides an excellent model for the study of developing oligodendrocytes.

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