Differential ultrastructural distribution of synapsin and synaptophysin proximal to a ligation in bovine splenic nerve

Extremely low frequency electromagnetic field exposure promotes differentiation of pituitary corticotrope-derived AtT20 D16V cells

The pituitary corticotrope-derived AtT20 D16V cell line responds to nerve growth factor (NGF) by extending neurite-like processes and differentiating into neurosecretory-like cells. The aim of this work is the study of the effect of extremely low frequency electromagnetic fields (ELF-EMF) at a frequency of 50 Hz on these differentiation activities. To establish whether exposure to the field could influence the molecular biology of the cells, they were exposed to a magnetic flux density of 2 milli-Tesla (mT). Intracellular calcium ([Ca2+]i) and intracellular pH (pHi) were monitored in single exposed AtT20 D16V cells using fluorophores Indo-1 and SNARF for [Ca2+]i and pHi, respectively. Single-cell fluorescence microscopy showed a statistically significant increase in [Ca2+]i followed by a drop in pHi in exposed cells. Both scanning electron microscopy (SEM) and transmission microscopy of exposed AtT20 D16V cells show morphological changes in plasma membrane compared to non-exposed cells; this modification was accompanied by a rearrangement in actin filament distribution and the emergence of properties typical of peptidergic neuronal cells-the appearance of secretory-like granules in the cytosol and the increase of synaptophysin in synaptic vesicles, changes typical of neurosecretory-like cells. Using a monoclonal antibody toward the neurofilament protein NF-200 gave additional evidence that exposed cells were in an early stage of differentiation compared to control. Pre-treatment with 0.3 microM nifedipine, which specifically blocks L-type Ca2+ channels, prevented NF-200 expression in AtT20 D16V exposed cells. The above findings demonstrate that exposure to 50 Hz ELF-EMF is responsible for the premature differentiation in AtT20 D 16 V cells.

Developmental changes in the neuronal protein composition: A study by high resolution 2D-gel electrophoresis

Cerebellar granular neurons were grown in culture up to 21 days and the protein compositions of undifferentiated (day 1), partially differentiated (day 7) and fully differentiated (day 21) neurons were analyzed by high-resolution 2D-gel electrophoresis. During neuronal differentiation there were not only increase in the amount of several known proteins, viz. actin, tubulin (both alpha and beta subunits), myosin (heavy and light chains), but very interesting changes were also observed in the expressions of different subunits and isoforms of those proteins. Furthermore, both in the acidic (pI 4.0-4.5) and alkaline (pI 7.0-8.5) regions interesting up and down regulations of several unidentified proteins were observed during the neuronal differentiation. These results indicated that there were several unidentified proteins that might be very valuable targets for studying regulation of neuronal differentiation. Research is going on for further characterization of those proteins using recently developed proteomics technology.