Problemas jurídicos de un tratado de desnuclearización para América Latina.

Fue el 6 de agosto del ana 1945 cuando la humanidad entr6 en la era nuclear al ser lanzada sobre la indefensa ciudad de Hiroshima la primera bomba atomica y despues la segunda sobre la ciudad de Nagasaki. Se iniciaba asi, el despertar de una nueva era, la mas importante de su larga historia, con un acto que en pocos segundos pulverizaba una ciudad entera, y causaba decenas de miles de muertos hombres, mujeres y niños- indefensos y dejaba otros tantos millares lacerados y mutilados por el resto de sus vidas. Tragico y amargo despertar fue ese. Lo que debio ser motivo de regocijo mundial, por la trascendencia que significaba el dominio del hombre sobre el átomo, se convirtio en una pesadilia. Con el correr de los anos y conforme otras naciones fueron logrando la fabricacion y el perfeccionamiento de las armas nucleares y la proliferacion de las mismas tiende hoy a generalizarse; la pesadilla del 45 se ha canvertidoahora en la mas formidable espada de Damocles que jamas haya pendido sobre la existencia misma de la humanidad. Hoy, 20 anos despues de aguella fecha fatldica, el peligro de un holocausto nuclear ha crecidoen tales proporciones, que dificilmente existe tema de mas importancia y urgencia, que este del desarme nuclear

A Sweet Talk: The Molecular Systems of Perineuronal Nets in Controlling Neuronal Communication

Perineuronal nets (PNNs) are mesh-like structures, composed of a hierarchical assembly of extracellular matrix molecules in the central nervous system (CNS), ensheathing neurons and regulating plasticity. The mechanism of interactions between PNNs and neurons remain uncharacterized. In this review, we pose the question: how do PNNs regulate communication to and from neurons? We provide an overview of the current knowledge on PNNs with a focus on the cellular interactions. PNNs ensheath a subset of the neuronal population with distinct molecular aspects in different areas of the CNS. PNNs control neuronal communication through molecular interactions involving specific components of the PNNs. This review proposes that the PNNs are an integral part of neurons, crucial for the regulation of plasticity in the CNS

Experience-Dependent Plasticity and Modulation of Growth Regulatory Molecules at Central Synapses

Structural remodeling or repair of neural circuits depends on the balance between intrinsic neuronal properties and regulatory cues present in the surrounding microenvironment. These processes are also influenced by experience, but it is still unclear how external stimuli modulate growth-regulatory mechanisms in the central nervous system. We asked whether environmental stimulation promotes neuronal plasticity by modifying the expression of growth-inhibitory molecules, specifically those of the extracellular matrix. We examined the effects of an enriched environment on neuritic remodeling and modulation of perineuronal nets in the deep cerebellar nuclei of adult mice. Perineuronal nets are meshworks of extracellular matrix that enwrap the neuronal perikaryon and restrict plasticity in the adult CNS. We found that exposure to an enriched environment induces significant morphological changes of Purkinje and precerebellar axon terminals in the cerebellar nuclei, accompanied by a conspicuous reduction of perineuronal nets. In the animals reared in an enriched environment, cerebellar nuclear neurons show decreased expression of mRNAs coding for key matrix components (as shown by real time PCR experiments), and enhanced activity of matrix degrading enzymes (matrix metalloproteinases 2 and 9), which was assessed by in situ zymography. Accordingly, we found that in mutant mice lacking a crucial perineuronal net component, cartilage link protein 1, perineuronal nets around cerebellar neurons are disrupted and plasticity of Purkinje cell terminal is enhanced. Moreover, all the effects of environmental stimulation are amplified if the afferent Purkinje axons are endowed with enhanced intrinsic growth capabilities, induced by overexpression of GAP-43. Our observations show that the maintenance and growth-inhibitory function of perineuronal nets are regulated by a dynamic interplay between pre- and postsynaptic neurons. External stimuli act on this interaction and shift the balance between synthesis and removal of matrix components in order to facilitate neuritic growth by locally dampening the activity of inhibitory cues