Astroglial cells derived from lateral and medial midbrain sectors differ in their synthesis and secretion of sulfated glycosaminoglycans

Astroglial cells derived from lateral and medial midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in cocultures. These different properties of the two types of cells may be related to the composition of their extracellular matrix. We have studied the synthesis and secretion of sulfated glycosaminoglycans (GAGs) by the two cell types under control conditions and ß-D-xyloside-stimulated conditions, that stimulate the ability to synthesize and release GAGs. We have confirmed that both cell types synthesize and secrete heparan sulfate and chondroitin sulfate. Only slight differences were observed between the proportions of the two GAGs produced by the two types of cells after a 24-h labeling period. However, a marked difference was observed between the GAGs produced by the astroglial cells derived from lateral and medial midbrain sectors. The medial cells, which contain derivatives of the tectal and tegmental midline radial glia, synthesized and secreted ~2.3 times more chondroitin sulfate than lateral cells. The synthesis of heparan sulfate was only slightly modified by the addition of ß-D-xyloside. Overall, these results indicate that astroglial cells derived from the two midbrain sectors have marked differences in their capacity to synthesize chondroitin sulfate. Under in vivo conditions or a long period of in vitro culture, they may produce extracellular matrix at concentrations which may differentially affect neuritic growth

The pedunculopontine nucleus: its role in the genesis of movement disorders

The pedunculopontine nucleus (PPN) is located in the dorso-lateral part of the ponto-mesencephalic tegmentum. The PPN is composed of two groups of neurons: one containing acetylcholine, and the other containing non-cholinergic neurotransmitters (GABA, glutamate). The PPN is connected reciprocally with the limbic system, the basal ganglia nuclei (globus pallidus, substantia nigra, subthalamic nucleus), and the brainstem reticular formation. The caudally directed corticolimbic-ventral striatal-ventral pallidal-PPN-pontomedullary reticular nuclei-spinal cord pathway seems to be involved in the initiation, acceleration, deceleration, and termination of locomotion. This pathway is under the control of the deep cerebellar and basal ganglia nuclei at the level of the PPN, particularly via potent inputs from the medial globus pallidus, substantia nigra pars reticulata and subthalamic nucleus. The PPN sends profuse ascending cholinergic efferent fibers to almost all the thalamic nuclei, to mediate phasic events in rapid-eye-movement sleep. Experimental evidence suggests that the PPN, along with other brain stem nuclei, is also involved in anti-nociception and startle reactions. In idiopathic Parkinson's disease (IPD) and parkinson plus syndrome, overactive pallidal and nigral inhibitory inputs to the PPN may cause sequential occurrences of PPN hypofunction, decreased excitatory PPN input to the substantia nigra, and aggravation of striatal dopamine deficiency. In addition, neuronal loss in the PPN itself may cause dopamine-r esistant parkinsonian deficits, including gait disorders, postural instability and sleep disturbances. In patients with IPD, such deficits may improve after posteroventral pallidotomy, but not after thalamotomy. One of the possible explanations for such differences is that dopamine-resistant parkinsonian deficits are mediated to the PPN by the descending pallido-PPN inhibitory fibers, which leave the pallido-thalamic pathways before they reach the thalamic targets.

The extracellular matrix of the midline and non-midline midbrain glia: correlations with neurite growth-supporting abilities

The central nervous system (CNS) midline plays an important role in growth and guidance of axons. At the midline, a multiplicity of cell types establish boundaries that control the navigation of crossed and uncrossed axonal fibers. The extracellular matrix (ECM) molecules of the resident neuroepithelial or committed neuronal of glial cells could be involved in the control of axon growth and axon guidance. This review reports the recent advances in the study of the structure and functional role of the ECM at the midline locus of the CNS. In vivo and in vitro approaches are considered to provide new clues in the understanding of processes involved in the cellular decisions of the CNS midline.

Homogenous fetal dopaminergic cell transplantation in rat striatum by cell suspension methods

The transplantation of dopaminergic neurons in the brain has been attempted in experimental animals and humans as the new treatment modality of Parkinson's disease. Before the trial of dopaminergic neuronal transplantation in human, the authors proceeded with the animal experiment of fetal dopaminergic cell transplantation in a rat Parkinson's disease model. The aims of this experiment were to confirm the availability of fetal mesencephalic cells as the donor, to compare the viability of cells according to different cell manipulation methods, and to follow up the functional recovery in the transplanted Parkinson's disease model. As a result, the authors concluded that the simple enzyme digestion method had a better cell survival rate than the multiple enzyme digestion method. Also, the transplanted mesencephalic cells could not only survive in the host animal but also promote functional recovery.