DNA Turnover in Rat Cerebral Cortex

Abstract: After the intracranial injection of [methyl-³H]thymidine the specific activity of rat cortical DNA increases rapidly, reaching a maximum at about 5 h. More than half of the radioactive DNA disappears from the tissue in the following few hours. During the same period of time the concentration of radioactive DNA in liver remains essentially constant. Minor variations occur in both organs after 41 h. An apparent rapid turnover of DNA is also present in a fraction of purified neuronal perikarya prepared from the cerebral cortex.     

Influence of Synchronized Sleep on the Biosynthesis of RNA in Neuronal and Mixed Fractions Isolated from Rabbit Cerebral Cortex

Abstract: Adult male rabbits implanted with dural electrodes were injected intraventricularly with [³H]orotate and killed 1 h later. During the period of incorporation they were left undisturbed while their EEG activity was continuously monitored. In the fraction of neuronal perikarya prepared from cerebral cortex by a method developed by Satake and Abe in 1966, the relative content of radioactive RNA of the nuclear particulate showed a twofold increase in the transition from 0 to 100% synchronization. On the other hand, a slight but significant decline was observed in the corresponding cytoplasmic compartment. A marked increase in the relative content of radioactive RNA was similarly observed in the nuclear particulate prepared from the mixed cellular fraction. The corresponding cytoplasmic compartment showed a nonsignificant increase. These results indicate that during sleep neuronal nuclei accumulate newly synthesized RNA (presumably hnRNA) at a faster rate. Under the same conditions the process of RNA transfer to the cytoplasm (presumably rRNA) may be reduced. These effects may be only partly shared by other cerebral cells.     

Influence of Synchronized Sleep on the Biosynthesis of RNA in Two Nuclear Classes Isolated from Rabbit Cerebral Cortex

The biosynthesis of RNA during sleep has been studied in two purified nuclear fractions, separated from rabbit cerebral cortex after subarachnoidal injection of radioactive orotate. The biochemical parameters have been referred to the percent EEG synchronization recorded during the period of incorporation (1 hr). The content of radioactive RNA per nucleus increases significantly with percent synchronization in the fraction of large nuclei (of neuronal and astroglial origin). While sedimentation and electrophoretic analyses of this RNA are consistent with the hypothesis of an enhanced turnover of rRNA during wakefulness, the accumulation of labelled RNA which is observed during sleep may be due to a modified turnover of nuclear heterogeneous RNA. On the other hand, in the fraction of small nuclei (mostly of oligodendroglial origin) the content of radioactive RNA per nucleus and the pattern of sedimentation of labelled RNA show no dependence on the electrical state of the cortex. These data indicate that in the cerebral cortex the sleep-wakefulness transition is accompanied by a different cellular response in RNA turnover.     

PROTEIN PATTERNS IN DIFFERENT LOBES AND DURING DEVELOPMENT OF OCTOPUS BRAIN

Abstract— Utilizing techniques of continuous and SDS-electrophoresis we have examined the saline-soluble and SDS-soluble (membrane-bound) proteins extracted from the main lobes of adult octopus brain and from the developing optic lobe of the same species. Several additional protein bands are present among the soluble and the membrane-bound proteins of the vertical lobe in comparison with the suboesophageal lobe. Since the former contains an essentially homogeneous population of small neurons, while the suboesophageal lobe is rich in large nerve cells, these protein bands have been attributed to the small neuronal type present in the vertical lobe.
In the course of a 10,000-fold increment in body weight, from 0.4 g to 4 kg, there is a significant increase in the concentration of several soluble proteins extracted from the optic lobe. Three of these proteins increase to a marked degree. Among the membrane-bound proteins some show a moderate increase with age while other protein components of smaller molecular weight undergo a moderate decrease. The overall tissue concentration of the membrane-bound proteins increases between 0.4 g and 50 g body weight, slightly declining in animals of larger size.