Neural stem/progenitor cells (NSPCs) capable of generating new neurons and glia reside in the adult mammalian spinal cord. Transplantation of NSPCs has therapeutic potential for spinal cord injury, although there is limited information on the ability of these cells to survive and differentiate in vivo. Neurospheres cultured from the periventricular region of the adult spinal cord contain NSPCs that are self-renewing and multipotent. We examined the survival, proliferation, migration, and differentiation of adult spinal cord NSPCs generated from green fluorescent protein (GFP) transgenic rats and transplanted into the intact spinal cord. The grafted GFP-expressing cells survived for at least 6 weeks in vivo and migrated from the injection site along the rostro-caudal axis of the spinal cord. Transplanted cells transiently proliferated following transplantation and approximately 17% of the GFP-positive cells were apoptotic at 1 day. Also, better survival was seen with NSPCs transplanted as neurospheres in comparison to NSPCs transplanted as dissociated cells. By 1 week posttransplantation, grafted cells primarily expressed an oligodendrocytic phenotype and only 2% differentiated into astrocytes. Approximately 75% versus 38% of the grafted cells differentiated into oligodendrocytes after transplantation into spinal white versus gray matter, respectively. This is the first report to examine the time course of cell survival, proliferation, apoptosis, and phenotypic differentiation of transplanted NSPSs in the spinal cord. This is also the first report to examine the differences between transplanted NSPCs grafted as neurospheres or dissociated cells, and to compare the differentiation potential after transplantation into spinal cord white versus gray matter.

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The effects of alkyltriphenylphosphonium bromides (C n TPB, n ¼ 10, 12, 14, 16) on the rates of S N 2 reactions of methyl 4-nitrobenzenesulfonate and bromide ion have been studied. Observed first-order rate constants are significantly higher than those found for other cationic surfactants for the same reaction. The results have been analyzed by the pseudophase model of micellar kinetics and show true micellar catalysis in the sense that second-order micellar rate constants are higher than the second-order rate constants in water. An attempt has also been made to investigate mixed cationic-cationic surfactant systems with respect to observed rates and pseudophase regression parameters. In addition, modeling of some cationic head groups has illustrated possible differences in head group charges and counterion interactions that may prove kinetically relevant.

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