How Widespread Are the “Young” Neurons of the Mammalian Brain?

After the discovery of adult neurogenesis (stem cell-driven production of new neuronal elements), it is conceivable to find young, undifferentiated neurons mixed with mature neurons in the neural networks of the adult mammalian brain. This “canonical” neurogenesis is restricted to small stem cell niches persisting from embryonic germinal layers, yet, the genesis of new neurons has also been reported in various parenchymal brain regions. Whichever the process involved, several populations of “young” neurons can be found at different locations of the brain. Across the years, further complexity emerged: (i) molecules of immaturity can also be expressed by non-dividing cells born during embryogenesis, then maintaining immature features later on; (ii) remarkable interspecies differences exist concerning the types, location, amount of undifferentiated neurons; (iii) re-expression of immaturity can occur in aging (dematuration). These twists are introducing a somewhat different definition of neurogenesis than normally assumed, in which our knowledge of the “young” neurons is less sharp. In this emerging complexity, there is a need for complete mapping of the different “types” of young neurons, considering their role in postnatal development, plasticity, functioning, and interspecies differences. Several important aspects are at stake: the possible role(s) that the young neurons may play in maintaining brain efficiency and in prevention/repair of neurological disorders; nonetheless, the correct translation of results obtained from laboratory rodents. Hence, the open question is: how many types of undifferentiated neurons do exist in the brain, and how widespread are they

Pyrolysis of phenyl acetate: a concerted reaction

A kinetic study reveals that the unimolecular decomposition of phenyl acetate into phenol and ketone occurs concertedly, probably via a four-cyclic transition state

Movimentos sociais, periferia e formas de dominação: dois estudos de caso sobre economia política e território em Buenos Aires

Discutir as mudanças e permanências na ação coletiva de dominados em termos de processos de territorialização e de luta de classes na periferia de Buenos Aires na década de 2000, questionando conceitos como exclusão social e de segregação territorial.This article discusses the changes and continuities in collective action to overcome in terms of processes of territorialization and class struggle in the periphery of Buenos Aires in the 2000s, questioning concepts such as social exclusion and spatial segregation.En ce qui concerne aux processus de territorialisation et de la lutte de classes à l'intérieur de la restructuration productive intervenue à Buenos Aires pendant les années 2000, cet article veut discuter les changements et les permanences dans l’action collective des groups dominés. Sous le point du vue conceptuel, on profite de l'occasion pour interroger les notions d’exclusion sociale et de ségrégation territoriale afin de comprendre les nouvelles dynamiques de l'espace et de la société à Buenos Aires