ALTERATIONS IN MYELIN FORMATION IN FETAL BRAINS OF TWINS

Insufficient nutrition is known to lead to disturbances in postnatal m yelin formation. This study aims to demonstrate that early myelination is altered in human twin pregnancies. Five brains of twins with a sym metric blood supply and three brains of twins with chronic fetal-fetal transfusion syndrome tone hypervolemic acceptor and two hypoxemic don ors) were investigated and compared with six brains of singletons. The globus pallidus, where myelination normally starts within the prosenc ephalon, was studied immunohistochemically using antibodies against my elin basic protein (MBP) and with the aid of electron microscopy, In t wins and donors, MBP-immunostained somata of myelin-forming oligodendr ocytes were packed densely within the globus pallidus, whereas in sing letons and accepters an intense fibrous immunoreactivity was observed. Electron micrographs revealed noncompacted myelin in twins, whereas i n singletons the multilaminar structure of compact myelin was observed . The results demonstrate a distinct qualitative alteration in myelina tion because of nutritional insufficiency during pregnancy. The lack o f MBP-positive fibers (i,e., compact myelin sheaths) may be correlated to impaired maturation of oligodendroglia, The alterations described here may reflect a delayed incorporation of MBP into the processes so that the formation of compact myelin is retarded, (C) 1998 by Elsevier Science Inc. All rights reserved.