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Numerical simulations of the collisional disruption of large asteroids show that although the parent body is totally shattered, subsequent gravitational reaccumulation leads to the formation of an entire family of large and small objects with dynamical properties similar to those of the parent body. Simulations were performed in two different collisional(More)
The glial reaction is generally considered to be a consequence of neuronal death in neurodegenerative diseases such as Alzheimer's disease, Huntington's disease, and Parkinson's disease. In Parkinson's disease, postmortem examination reveals a loss of dopaminergic neurons in the substantia nigra associated with a massive astrogliosis and the presence of(More)
Dibutyryl cyclic AMP (dbcAMP), a permeant analogue of cyclic AMP (cAMP), prevented, for at least 3 weeks, the death of tyrosine hydroxylase (TH)-immunopositive dopaminergic neurons, which occurred spontaneously by apoptosis in mesencephalic cultures. Treatment with the cyclic nucleotide analogue also led to a significant increase in the uptake of [3H](More)
The death of dopaminergic neurons that occurs spontaneously in mesencephalic cultures was prevented by depolarizing concentrations of K+ (20-50 mM). However, unlike that observed previously in other neuronal populations of the PNS or CNS, promotion of survival required concurrent blockade of either NMDA or(More)
Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive cell loss confined mostly to dopaminergic neurons of the substantia nigra. Several factors, including oxidative stress, and decreased activity of complex I mitochondrial respiratory chain, are involved in the degenerative process. Yet, the underlying mechanisms leading to(More)
The mechanisms leading to degeneration of dopaminergic neurons (DNs) in the substantia nigra of patients with Parkinson's disease (PD) are not completely understood. Here, we show, in the postmortem human tissue, that these neurons aberrantly express mitosis-associated proteins, including the E2F-1 transcription factor, and appear to duplicate their nuclear(More)
Levodopa is the most effective symptomatic agent in the treatment of Parkinson's disease (PD) and the "gold standard" against which new agents must be compared. However, there remain two areas of controversy: (1) whether levodopa is toxic, and (2) whether levodopa directly causes motor complications. Levodopa is toxic to cultured dopamine neurons, and this(More)
In Parkinson's disease, nigral dopaminergic neurones degenerate, whereas post-synaptic striatal target neurones are spared. In some atypical parkinsonian syndromes, both nigral and striatal neurones degenerate. Reduced activity of complex I of the mitochondrial respiratory chain has been implicated in both conditions, but it remains unclear if this affects(More)