Bioleaching of gold, copper and nickel from waste cellular phone PCBs and computer goldfinger motherboards by two Aspergillus nigerstrains

In an effort to develop alternate techniques to recover metals from waste electrical and electronic equipment (WEEE), this research evaluated the bioleaching efficiency of gold (Au), copper (Cu) and nickel (Ni) by two strains of Aspergillus niger in the presence of gold-plated finger integrated circuits found in computer motherboards (GFICMs) and cellular phone printed circuit boards (PCBs). These three metals were analyzed for their commercial value and their diverse applications in the industry. Au-bioleaching ranged from 42 to 1% for Aspergillus niger strain MXPE6; with the combination of Aspergillus niger MXPE6 + Aspergillus niger MX7, the Au-bioleaching was 87 and 28% for PCBs and GFICMs, respectively. In contrast, the bioleaching of Cu by Aspergillus niger MXPE6 was 24 and 5%; using the combination of both strains, the values were 0.2 and 29% for PCBs and GFICMs, respectively. Fungal Ni-leaching was only found for PCBs, but with no significant differences among treatments. Improvement of the metal recovery efficiency by means of fungal metabolism is also discussed.

Participación de los canales de calcio dependientes de voltaje en el desarrollo de la epilepsia / Participation of voltage-dependent calcium channels in the development of epilepsy

La epilepsia es una afección crónica producida por diferentes etiologías, caracterizada por la repetición de crisis debidas a una descarga excesiva de las neuronas cerebrales asociadas a síntomas clínicos o paraclínicos. Se debe a una despolarización rápida, en la membrana, de iones en una población de neuronas susceptibles, es decir, un cambio repentino en la carga intracelular negativa a positiva. Las causas más conocidas son: alteraciones genéticas, anoxia perinatal, traumatismos, tumores, malformaciones congénitas, alteraciones metabólicas, intoxicaciones farmacológicas, infecciones del sistema nervioso. Una crisis epiléptica es la aparición transitoria de signos y síntomas anormales causados por la actividad neuronal excesiva, mientras que la epilepsia se caracteriza por una permanente predisposición a generar crisis. En la despolarización de la membrana neuronal, los iones calcio desempeñan un papel importante debido a que son mensajeros intracelulares que regulan funciones como: liberación de neurotransmisores, neurosecreción, excitación neuronal, supervivencia de neuronas y regulación de expresión de genes. El ingreso de calcio a través de la membrana plasmática representa una forma para controlar el nivel intracelular de calcio. Se conoce poco sobre el mecanismo de entrada del calcio a la neurona pero un progreso notable representa la comprensión de la estructura, función y regulación de los canales de calcio dependientes de voltaje.

Epilepsy is defined as a chronic condition produced by different etiologies, characterized by the repetition of crises due to an excessive discharge of the cerebral neurons assoclated wlth cllnlcal symptoms. It responds to a fast ion depolarization in a population of abnormal neurons. Causes of epilepsy are: genetíc alteratíons, perínatal anoxía, traumatísms, tumors, congenital malformations, metabolic alterations, drug poisonings, and infections of the nervous system. Epileptic selzure Is the transitory occurrence of signs and abnormal symptoms caused by excessive or synchronous neurona! activity whereas, epilepsy Is characterized by a permaneni predisposition to genérate seizures. During depolarization of neurona! membrane, calcium ions play an important role because they are intracellular messengers that regúlate functions llke: neurotransmltter reléase, neurosecretlon, neuronal excltatlon, neuron survlval and gene expresslon regulatlon . The Influx of calcium through the plasmatlc membrane represents a way to control Intracellular calcium level. The mechanlsm of the entrance of calcium to the neuron Is llttle known, but understandlng the structure, functlon and regulatlon of voltage-gated calcium channels Is of remarkable progress.