Poly(adenylate) polymerase activity of rat brain

Methods using tissue preparations and isolated biomolecules

The possibility to use organs, organelle preparations and biologically active chemicals in toxicity tests and in toxicology will be reviewed. Examples are perfused liver preparations, tissue slices and homogenates, isolated nerve preparations, nerve-muscle preparations, membrane preparations, microsomes, mitochondria, synaptosomes, antibodies and isolated chemical compounds (receptors, enzymes).

Nuclear polyadenylate polymerase activity in the brain of seizure-prone EL mice

Nuclear polyadenylate polymerase from I activity in the brains of seizure-prone EL mice was significantly higher than in seizure-non-susceptible progenitor ddY mice. This finding may be essential in acquiring susceptibility to seizures, since there was no significant difference between EL(S) mice and those that did not receive stimulation, EL(NS) mice. Lower form II enzymatic activity was observed in both groups of EL mice but not in ddY mice. Moreover, significantly lower activities of form II 7 days after seizures were found in EL(S) mice compared with EL(NS) mice, suggesting that this is a consequence of repeated seizures. The activity of form I enzyme decreased immediately and at 30 and 60 min after seizures, then returned to control levels at 100 min. Form II enzymatic activity was significantly decreased only at 30 min after seizures, implying that seizures exerted a later effect on form II enzyme. These changes may cause a decrease in the rate of polyadenylation in the brain; thus, alteration of post-transcriptional events, including messenger RNA processing and transport, may occur during epileptic seizures.

Thyroid hormone regulation of poly(adenylate) polymerase activities in neuronal nuclei of developing rat brain cortex

Neuronal and glial cell-enriched nuclei were prepared from developing rat brain cortex to study the effect of thyroxine on nuclear poly(A) polymerase. Long-term thyroxine treatment stimulated the activity of the chromatin-associated enzyme of neuronal nuclei without significantly affecting that of glial nuclei. The nuclear content of poly(A)-containing RNA in neuronal nuclei was also increased by thyroxine administrations. A single dose of thyroxine enhanced both the chromatin-bound and the free, nucleoplasmic form of neuronal poly(A) polymerase in hypothyroid rats aged 12 days. The results suggest that thyroid hormones may regulate both transcriptional and post-transcriptional events in target cell nuclei.