Transcription of Repeated and Unique Dna Sequences in Brain Nuclei

Abstract

—Transcription of repeated and unique DNA in rat brain nuclei was examined using a RNA‐DNA hybridization technique. Saturation hybridization experiments with a membrane filter showed that there were differences in the base sequence complements between labelled brain and labelled liver nuclear RNA. In competition hybridization experiments using a membrane filter, brain nuclear labelled RNA was in competition most effectively with unlabelled brain nuclear RNA, but less effectively with kidney or liver nuclear RNA. Experiments using a membrane filter loaded with isolated unique or repeated DNA fragments gave similar results. Furthermore, competition hybridization with a DNA excess also showed similar results at Cot 10,000. These results indicate the existence of tissue‐specificity in the transcription of unique and repeated DNA sequences in brain nuclei. Subsequently, rat brain nuclei were separated into neuronal and glial nuclear fractions for the purpose of detecting the cell‐specificity of RNA. The results of these experiments give evidence of significant differences in the transcription of unique DNA sequences, but indicate no differences in that of repeated DNA sequences between the two nuclear classes.

Changes in plasma phenylalanine, isoleucine, leucine, and valine are associated with significant changes in intracranial pressure and jugular venous oxygen saturation in patients with severe traumatic brain injury

“…This, in turn, favors an amino acid-driven influence. Sustained cerebral oxygen consumption and Leu-driven increased cerebral CO 2 production (Chaplin et al, 1976) could result in increased cerebral vasodilation which, in turn, might explain the increased ICP at higher Ile and Leu levels. The present data does not allow to determine a possible Ile-, Leu-and Val-mediated edema-aggravating effect.…”

Glial Metabolism of Valine

“…These are transported through the blood-brain barrier into the brain parenchyma [1][2][3][4]. Although in brain BCAAs appear to be predominantly metabolized [5,6], they also fulfill other distinct tasks [7][8][9]. The most prominent among them are the roles as vehicle molecules for nitrogen import into the brain parenchyma and as shuttle molecules for the exchange of nitrogen in the glutamate/glutamine cycle [10,11].…”

“…The cells of the brain parenchyma readily metabolize leucine [6]. The capacity of brain tissue to metabolize also valine can be deduced from experiments with brain slices, which showed that brain cells oxidize the cognate 2-oxo acid of valine, 2-oxoisovaleric acid ( Fig.…”

“…Starting from propionyl-CoA with a uniformly labelled propionyl residue [1,2,3-13 C]succinyl-CoA is formed, which gives rise to the equally populated isotopomers [1,2,3-13 C]succinate and [2,3,4-13 C]succinate. From the subsequent TCA cycle members further TCA cycle derivatives are formed, i.e.,[1,2,[3][4][5][6][7][8][9][10][11][12][13] C]malate/[2,3,4-13 C]malate is transformed into pyruvate via malic enzyme and sub--13 C]glutamine. The signal intensities of the triple labelled isotopomers of glutamine were too low for quantification.…”

Transport of Neutral Amino Acids at the Blood-Brain Barrier

“…In essence, any model o f transport would have to include as a condition that net transport of NAA as a group could not occur. While this condition would be consistent with maintaining constant the brain's environment in the face of wide fluctuations in the blood content of NAA, it seems incon sistent with what is known about the brain's capacity to metabolize to a considerable extent the branched chain amino acids (5,26) and, to a lesser extent, the aromatic amino acids. To satisfy the conditions of equal exchange, then, the brain must produce some nonessential system L substrates to excltange for those amino acids of which it is a net consumer.…”