RESUMO
Adolescence is a period of heightened susceptibility to psychiatric disorders of medial prefrontal cortex (mPFC) dysfunction and cognitive impairment. mPFC dopamine (DA) projections reach maturity only in early adulthood, when their control over cognition becomes fully functional. The mechanisms governing this protracted and unique development are unknown. Here we identify dcc as the first DA neuron gene to regulate mPFC connectivity during adolescence and dissect the mechanisms involved. Reduction or loss of dcc from DA neurons by Cre-lox recombination increased mPFC DA innervation. Underlying this was the presence of ectopic DA fibers that normally innervate non-cortical targets. Altered DA input changed the anatomy and electrophysiology of mPFC circuits, leading to enhanced cognitive flexibility. All phenotypes only emerged in adulthood. Using viral Cre, we demonstrated that dcc organizes mPFC wiring specifically during adolescence. Variations in DCC may determine differential predisposition to mPFC disorders in humans. Indeed, DCC expression is elevated in brains of antidepressant-free subjects who committed suicide.
Assuntos
Neurônios Dopaminérgicos/metabolismo , Genes DCC/fisiologia , Transtornos Mentais/genética , Córtex Pré-Frontal/crescimento & desenvolvimento , Adolescente , Desenvolvimento do Adolescente/fisiologia , Animais , Estudos de Casos e Controles , Predisposição Genética para Doença , Haploinsuficiência , Humanos , Masculino , Camundongos , Vias Neurais/crescimento & desenvolvimento , Vias Neurais/metabolismo , Córtex Pré-Frontal/citologia , Córtex Pré-Frontal/metabolismo , Comportamento Autodestrutivo/genética , SuicídioRESUMO
Laboratory experiments showed that under certain conditions of vorticity the electrical heatinig produced by a high-voltage discharge at atmospheric pressure can cause the formation of a miniature tornado-like vortex. Once it forms, this vortex stabilizes the electrical discharge along its axis and changes its character from that of a spark to high-pressure variety of a glow discharge. Electrical and dynamic parameters were measured. By relating observations and measurements made in these experiments to previous work and to analogous situations in nature, it is concluded that the heating produced by electrical discharges in a large storm may play a significant role in forming and maintaining natural tornadoes.
RESUMO
The design and performance characteristics of a prototype cloud physics laser nephelometer are described. The instrument measures radiation scattered from individual cloud droplets, determining droplet concentrations from scattered light-pulse count rates and size distributions from pulse amplitudes.