Metabolic organization of the myelinating Schwann cell

Neural cells from dogfish embryos express the same subtype-specific antigens as mammalian neural cells in vivo and in vitro

Neural cells are classically identified in vivo and in vitro by a combination of morphological and immunocytochemical criteria. Here, we demonstrate that antibodies used to identify mammalian oligodendrocytes, neurons, and astrocytes recognize these cell types in the developing spiny dogfish central nervous system and in cultures prepared from this tissue. Oligodendrocyte-lineage-specific antibodies O1, O4, and R-mAb labeled cells in the 9 cm dogfish brain stem's medial longitudinal fascicle (MLF) and in areas lateral to it. Process-bearing cells, cultured from the dogfish brain stem, were also labeled with these antibodies. An anti-lamprey neurofilament antibody (LCM), which recognized 60 and 150 kDa proteins in dogfish brain stem homogenates, labeled axons and neurons in the brain stem and axons in the cerebellum of the dogfish embryo. It also labeled cell bodies and/or processes of some cultured cerebellar cells. An anti-bovine glial fibrillary acidic protein antibody, which recognized 42-44 kDa protein(s) in dogfish brain stem homogenates, labeled astrocyte-like processes in the brain stem and cerebellum of the dogfish embryo and numerous large and small flat cells in the cerebellar cultures. These results demonstrate that dogfish oligodendrocytes, neurons, and astrocytes express antigens that are conserved in mammalian neural cells. The ability to culture and identify neural cell types from cartilaginous fish sets the stage for studies to determine if proliferation, migration, and differentiation of these cell types are regulated in a similar fashion to mammalian cells.

Differential expression of sodium channels in acutely isolated myelinating and non-myelinating Schwann cells of rabbits

1. Single channel recordings were made of voltage-sensitive sodium channels in outside-out patches excised from the cell body region of Schwann cells. The cells were freshly isolated from sciatic nerves of 10-week-old rabbits and both myelinating and non-myelinating Schwann cells were visually identified for recordings. 2. Sodium channel activities were observed in approximately 75% of patches (n = 41) obtained from cell bodies of non-myelinating Schwann cells. In contrast, sodium channels were not observed in patches (n = 78) obtained from cell bodies of myelinating Schwann cells. 3. Transection of the sciatic nerves and allowing Wallerian degeneration to occur for 5-11 days in vivo prior to recording resulted in the appearance of sodium channel activities in approximately 30% of the patches (n = 33) obtained from the cell body of the myelinating cells. 4. It is interesting that although immunocytochemical and saxitoxin binding experiments indicate the clear presence of sodium channels in the plasmalemma of myelinating Schwann cells (both at the cell body and at the paranodal region), the present study suggests that these channels are absent from the soma region of normal myelinating Schwann cells.