Biosynthesis of RNA in two nuclear classes separated from rat cerebral cortex

Transcription and Motoneuron Size

“…On the other hand, biochemical and flow cytometric studies have largely failed to support earlier reports of polyploidy in mammalian neurons (Herman and Lapham, 1969; for review, see Peters et al ., 1976) . Although the possibility of polyploidy has not been eliminated in every type of neuron for which it has been claimed, it now seems certain that many neurons in mammalian brain (Austoker et al, 1972;Giuditta et al ., 1972;Pearson et al, 1984) and spinal cord (McIlwain, 1991 ;McIlwâin and Capps-Covey, 1976) contain diploid or nearly diploid amounts of nuclear DNA . Consequently, a different mechanism has been proposed for the increased transcription observed in the relatively large nuclei of brain neurons vis à vis the smaller nuclei of nonneuronal cells ; namely, a more open chromatin conformation in neuronal nuclei, leading to less steric hindrance of RNA synthesis , which could explain why the transcription rate of neuronal nuclei can exceed that of glial nuclei by two-to sixfold (Kato and Kurokawa, 1970;Lovtrup-Rein, 1970;Austoker et al, 1972;Giuditta et al ., 1972;Thompson, 1973;Albrecht and Hemminki, 1976;Thomas and Thompson, 1977) .…”

“…Until now, this question has not been tested directly, although there is evidence suggesting a positive relationship between nuclear size and total transcription in neurons . For instance, nuclei from neuron-enriched brain fractions are larger and show higher labeling of RNA per unit DNA than do nuclei from glia or hepatocytes (Kato and Kurokawa, 1970;Lovtrup-Rein, 1970;Giuditta et al ., 1972;Thompson, 1973;Mizobe et al, 1974;Pearson et al ., 1984) . Neurons also possess conspicuous amounts of dispersed chromatin Peters et al, 1976) .…”

Cerebral RNA synthesis in experimental hepatogenic encephalopathy

“…The gradients were centrifuged for 75 min at 65,OOOg,, in a SW 6 x 16.5 ml rotor of the MSE-25 centrifuge. Two subfractions of nuclei, the "large" and "small" nuclei, were collected, respectively, from the 2.2-2.4 M sucrose interphase and the pellet [Guiditta et al, 1972;Albrecht 19761. Polyribosomes were spun down from the supernatant after the first homogenate centrifugation in a VAC 602 Janetzki ultracentrifuge for 2 hr at 160,OOOg,, .…”

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

“…The fraction of large and small nuclei were obtained from cortical tissue according to a routine procedure (Giuditta et al, 1972). The nuclear bands separated from the discontinuous sucrose gradient were diluted with 2 vol.…”

“…In a previous paper (Vitale-Neugebauer et al, 1970) we have reported that the relative proportion of different types of RNA synthesized in rabbit cerebral cortex and separated by sedimentation on sucrose gradients depends on the amount of synchronized sleep occurring during the period of incorporation, It has been suggested that preribosomal as well as heterogeneous RNAs contribute to this effect. Before attempting to analyse these changes in more detail, we have considered it necessary to establish the cellular location of the effects and have approached the problem by taking advantage of a procedure of nuclear fractionation which allows separation of large and small nuclei (Giuditta et al, 1972). It is well known that when the period of incorporation is relatively short, i.e.…”