Stem cells have great potential for clinical application because of their self-renewal property and ability to differentiate into many types of cells, but because there are ethical and biological limitations with current sources of stem cells, the search continues for more suitable sources of multipotent cells. We have reported previously on a population of multipotent cells isolated from the human term placenta, an ethically unproblematic and easily available source of tissue. These placenta-derived multipotent cells (PDMCs) can differentiate into lineages of mesenchymal tissues, including osteoblasts and adipocytes, as well as non-mesenchymal tissue of neuron-like cells. We further examined the ability of PDMCs to differentiate into all 3 types of neural cells--neurons, astrocytes, and oligodendrocytes--under various induction conditions, including retinoic acid (RA), 1-methyl-3-isobutylxanthine (IBMX), and co-culture with neonatal rat brain cells. PDMCs exhibited outgrowth of processes and the expression of neuron-specific molecules such as neuron-specific enolase upon induction. Co-culture with neonatal rat brain cells also induced neural differentiation. Our results indicate that PDMCs can be differentiated into neural cell types of the human nervous system upon exposure to RA, IBMX, or primary rat brain cells.

Transcranial magnetic stimulation (TMS) of the motor cortex can interrupt voluntary contralateral rhythmic limb movements. Using the method of "resetting index" (RI), our study investigated the TMS effect on different types of bimanual movements. Six normal subjects participated. For unimanual movement, each subject tapped either the right or left index finger at a comfortable rate. For bimanual movement, index fingers of both hands tapped in the same (in-phase) direction or in the opposite (antiphase) direction. TMS was applied to each hemisphere separately at various intensities from 0.5 to 1.5 times motor threshold (MT). TMS interruption of rhythm was quantified by RI. For the unimanual movements, TMS disrupted both contralateral and ipsilateral rhythmic hand movements, although the effect was much less in the ipsilateral hand. For the bimanual in-phase task, TMS could simultaneously reset the rhythmic movements of both hands, but the effect on the contralateral hand was less and the effect on the ipsilateral hand was more compared with the unimanual tasks. Similar effects were seen from right and left hemisphere stimulation. TMS had little effect on the bimanual antiphase task. The equal effect of right and left hemisphere stimulation indicates that neither motor cortex is dominant for simple bimanual in-phase movement. The smaller influence of contralateral stimulation and the greater effect of ipsilateral stimulation during bimanual in-phase movement compared with unimanual movement suggest hemispheric coupling. The antiphase movements were resistant to TMS disruption, and this suggests that control of rhythm differs in the 2 tasks. TMS produced a transient asynchrony of movements on the 2 sides, indicating that both motor cortices might be downstream of the clocking command or that the clocking is a consequence of the 2 hemispheres communicating equally with each other.

No abstract

No abstract