Age-dependent changes in the specificity of tRNA methyltransferases in the cerebellum of the icteric and nonicteric Gunn rat

The activity of tRNA methyltransferases present in the cerebellum of 6- and 21-day-old nonicteric and icteric Gunn rats was compared using purified E. coli tRNAs as substrates. At 6 days the tRNA methyltransferases of the icteric animals were significantly more effective in methylating tRNA Glu 2 and tRNA Phe than were those of their nonicteric counterparts. This relationship reversed itself at 21 days. The action of the tRNA methyltransferases from the 6-day-old icteric animals led to higher proportions of 1-methyladenine in tRNA Glu 2 and tRNA Phe than were obtained using the corresponding enzymes of the nonicteric animals. The proportion of N 2 -methylguanine was also higher, yet only in tRNA fMet and not in tRNA Phe . The study reveals much more extensive fluctuations in the activity and in the substrate recognition specificity among the cerebellar tRNA methyltransferases of the icteric than among those of the nonicteric controls during the crucial 6–21 day period of cerebellar development.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45425/1/11064_2004_Article_BF00964433.pd

Epilepsia experimental en pequeños animales

This work includes the chronic implantation of a nine electrode plug, on the skull of small animals, which had previously been treated as follows: one mi of aluminum oxide placed on the right anterior cerebral cortex. A pollyethylene tube was sometimes placed on each cerebral cortex to permit intracraneal drug administration. E. E.G. recordings were made with unrestrained animals. 1. In the cortical area where the alumina had placed, an initial decrease in voltage was observed during the first four days. Four days later desynchronization of the background electrical activity increased voltage and localization of the primary focus were observed. 2. In the period from eight to twelve days after the alumina application, the animals developed an increased of voltage in the corresponding area of the contra lateral hemisphere. This corresponded to the development of a secondary or mirror" focus which was fully developed in about two days. its discharge at first depended on the primary focus but became independent in 10 to 15 days. 3. Two to three months after the alumina application, the electrical activity in the primary focus began to decrease and had disappeared almost completely after four months. 4. Any studies for the purpose of observing changes in electrical activity of the primary focus, should be done within the first three months after alumina application. On the other hand the secondary focus continues to fire for at least one year