RESUMEN
In a previous study we showed that Cistus albidus (L.) experiences an age-dependent decay in flower vigour correlated with a decline in trans-zeatin (tZ) levels. In the present study we aimed to establish a causal relationship between these two phenomena. Exogenous tZ applied to plants grown under semi-controlled conditions did not rescue flower vigour; however, it accelerated flower development, but only in younger individuals. Older plants showed lower tocopherol levels in flower buds, which were restored by exogenous tZ, suggesting that a loss of antioxidant defences may underlie the age-dependent decay in flower vigour. We conclude that declining tZ levels may not be directly responsible for the age-associated loss of floral vigour; that tZ modulates the speed of flower development as plants age; and that flower buds alter their sensitivity to tZ as plants age.
Asunto(s)
Antioxidantes/metabolismo , Cistus/fisiología , Reguladores del Crecimiento de las Plantas/farmacología , Tocoferoles/metabolismo , Zeatina/farmacología , Antioxidantes/análisis , Cistus/efectos de los fármacos , Cistus/genética , Cistus/crecimiento & desarrollo , Flores/efectos de los fármacos , Flores/genética , Flores/crecimiento & desarrollo , Flores/fisiología , Perfilación de la Expresión Génica , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/genética , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/fisiología , Factores de Tiempo , Tocoferoles/análisisRESUMEN
Functional imaging techniques have demonstrated a relationship between the intensity of tinnitus and the degree of reorganization of the primary auditory cortex. Studies in experimental animals and humans have revealed that tinnitus is associated with a synchronized hyperactivity in the auditory cortex and proposed that the underlying pathophysiological mechanism is thalamocortical dysrhythmia; hence, decreased auditory stimulation results in decreased firing rate, and decreased lateral inhibition. Consequently, the surrounding brain area becomes hyperactive, firing at gamma band rates; this is considered a necessary precondition of auditory consciousness, and also tinnitus. Synchronization of the gamma band activity could possibly induce a topographical reorganization based on Hebbian mechanisms. Therefore, it seems logical to try to suppress tinnitus by modifying the tinnitus-related auditory cortex reorganization and hyperactivity. This can be achieved using neuronavigation-guided transcranial magnetic stimulation (TMS), which is capable of modulating cortical activity. If TMS is capable of suppressing tinnitus, the effect should be maintained by implanting electrodes over the area of electrophysiological signal abnormality on the auditory cortex. The results in the first patients treated by auditory cortex stimulation demonstrate a statistically significant tinnitus suppression in cases of unilateral pure tone tinnitus without suppression of white or narrow band noise. Hence, auditory cortex stimulation could become a physiologically guided treatment for a selected category of patients with severe tinnitus.