Labelling Of Cytoplasmic RNA Research Articles

Maternal dietary deficiency in rats and the in vivo synthesis of cytoplasmic, nucleolar and chromosomal RNA in the liver of their 21-day-old progeny

The metabolism of cytoplasmic, nucleolar and chromosomal RNA was studied at various time intervals ranging from 6 to 120 minutes in the liver of the 21-day-old progeny of well-fed and dietary restricted rats. The dietary-restricted group's progeny demonstrated significant increases in the kinetics of labelling of cytoplasmic RNA (p<0.001) at 120 minutes, of nucleolar RNA (p<0.001) at 30, 60 and 120 minutes, and of chromosomal RNA (p<0.001) at 60 and 120 minutes. At 60 minutes, there was a pronounced 10-fold increase in incorporation in the 18S region (mRNA) of the gradient of nucleolar RNA of the dietary-restricted group's progeny, which became 3-fold higher at 120 minutes. Radioactivity was lower in chromosomal RNA at 6 and 30 minutes but was considerably higher at 60 and 120 minutes in the dietary-restricted group's offspring compared to the well-fed pups. These data clearly demonstrate that maternal dietary restriction in rats leads to cellular events which increase the synthesis of RNA in the liver of their 21-day-old progeny.

The effect of convulsions induced by flurothyl on ribonucleic acid synthesis in rat cerebral cortex during the recovery phase.

The effect of convulsions, induced by flurothyl, on RNA synthesis in purified unfractionated nuclei and the cytoplasm of rat cerebral cortex was studied by using a double-label technique involving injection of [3H]- and [14C]-orotate intracisternally. 2. Intact RNA was extracted in 80% yield by an enzymic method by using a proteinase in the presence of sodium dodecyl sulphate followed by deoxyribonuclease. Electrophoresis on 1.5% polyacrylamide-0.5% agarose gels revealed the presence of giant nuclear RNA of size up to approx. 300X 10(6) daltons and mRNA of maximal mol.wt. 9 X 10(6)-16 X 10(6). 3. Nuclear RNA synthesis was decreased to 27% in the first 15 min after convulsions but rapidly increased, so that at 1 1/2 h it was 124% of the control, and at 6 h 147%. 4. Labelling of cytoplasmic RNA was decreased to 15% at 15 min after convulsions but had not recovered to control values by 6 h. 5. Analysis of radioactive gel patterns and the 3H/14C ratio at six time-points (15 min-6h) showed that the major effect was inhibition of the processing of heterogeneous nuclear RNA resulting in a sharp decline in the export of newly synthesized RNA from the nucleus. 6. Cytoplasmic RNA patterns indicated that specific messengers were synthesized at different times during the recovery of the cell after convulsions.

The relationship of rapidly labeled adrenal RNA synthesis to steroidogenesis in a superfusion system: effect of ACTH.

A system of superfusion of rat adrenal glands with continuous collection of the incubation medium has been found to be useful for studies of the effect of ACTH on labelling of cytoplasmic RNA as well as upon corticosterone secretion. A continuous infusion of ACTH (24 mU/ml medium) maintained steroid output at a higher level than controls. The kinetics of incorporation of radioactive uridine into total cytoplasmic RNA indicated that at different time intervals the rate of synthesis of RNA was constant for 60 min of incubation. ACTH produced a rapid increase in the incorporation of radioactive precursor into total cytoplasmic RNA. A change in labeling patterns of cytoplasmic RNA species separated by polyacrylamide gel electrophoresis provided evidence for stimulation by ACTH of incorporation of radioactive precursor into rapidly labelled cytoplasmic RNA within 30 min. These results suggest that the continuous superfusion of adrenal glands provides a suitable method for studying the relationship between ster...

The Rapid Acceleration of Hepatic Nuclear Ribonucleic Acid Breakdown by Actinomycin But Not by Ethionine

Abstract The effects of two different inhibitors of rat liver RNA synthesis, actinomycin D and ethionine, upon liver RNA metabolism have been studied and compared. Whereas ethionine administration leads to a relatively slow loss of about 30% of total nuclear RNA over a period of 12 to 16 hours involving the molecular species representative of the total pool, the administration of actinomycin D is followed by a rapid loss of recently labeled moieties of nuclear RNA. The pretreatment of animals with ethionine had no significant effect upon the loss of nuclear RNA induced by actinomycin D. The labeling of cytoplasmic RNA with orotic acid-6-14C was inhibited by each agent. It is considered probable that the different patterns of response of hepatic nuclear RNA to these two agents are a reflection of the different mechanisms whereby they inhibit RNA synthesis. It is concluded that compounds which bind to DNA, such as actinomycin D, have effects on nuclear RNA metabolism in addition to those resulting from the inhibition of RNA synthesis.

Studies on RNA in goldfish brain. I. Isolation and in vivo labeling

Methods are presented for the isolation of high molecular weight RNA from nuclear and cytoplasmic fractions of goldfish brain following intracranial injection of [5- 3 H]uridine. Nuclear RNA is labeled first and is followed by labeling of cytoplasmic RNA. The pattern of labeling in the nuclear fraction reflects the formation of broadly distributed RNA species some of which sediment more rapidly than 28S RNA. Radioactivity appears later in the cytoplasm and sediments heterogeneously from 4S to > 50S. Evidence is presented for the presence of a 45S ribosomal RNA precursor and for messenger RNA in the goldfish brain.