scholarly journals NUCLEAR ENVELOPE-ASSOCIATED RESUMPTION OF RNA SYNTHESIS IN LATE MITOSIS OF HELA CELLS

1973 ◽  
Vol 59 (1) ◽  
pp. 150-164 ◽  
Author(s):  
T. Simmons ◽  
P. Heywood ◽  
L. Hodge
Keyword(s):  
Protein Synthesis ◽  
Nuclear Envelope ◽  
Rna Synthesis ◽  
Electron Microscope Autoradiography ◽  
Molecular Synthesis ◽  
Hela S3 ◽  
Precursor Rna ◽  
Ribosomal Precursor ◽  
Hela S3 Cells ◽  
Silver Grains

The restitution of RNA synthesis in cultures progressing from metaphase into interphase (G1) has been investigated in synchronized HeLa S3 cells by using inhibitors of macro-molecular synthesis and the technique of electron microscope autoradiography. The rate of incorporation of radioactive uridine into RNA approached interphase levels in the absence of renewed protein synthesis. In contrast, maintenance of this rate in G1 was dependent upon renewed protein synthesis. Restoration of synthesis of heterogeneous nuclear RNA occurred under conditions that inhibited production of ribosomal precursor RNA. In autoradiographs of individual cells exposed to radioactive uridine, silver grains were first detected after nuclear envelope reformation at the periphery of the chromosome mass but before chromosomal decondensation. These data are consistent with the following interpretation. Multiple RNA polymerase activities persist through mitosis and are involved in the initiation of RNA synthesis in early telophase at sites on the nuclear envelope.

scholarly journals Carcinogenesis and Cellular Injury. The effect of ethionine on ribonucleic acid synthesis in rat liver

1975 ◽  
Vol 150 (3) ◽  
pp. 335-344 ◽  
Author(s):  
P F Swann ◽  
A C Peacock ◽  
S Bunting
Keyword(s):  
Protein Synthesis ◽  
Rna Synthesis ◽  
Acid Synthesis ◽  
Female Rat ◽  
Concurrent Administration ◽  
Polyamine Synthesis ◽  
Rrna Maturation ◽  
Precursor Rna ◽  
Inhibitor Of Protein Synthesis ◽  
Ribosomal Precursor

1. By 1h after administration of ethionine to the female rat the appearance of newly synthesized 18SrRNA in the cytoplasm is completely inhibited. This is not caused by inhibition of RNA synthesis, for the synthesis of the large ribosomal precursor RNA (45S) and of tRNA continues. Cleavage of 45S RNA to 32S RNA also occurs, but there was no evidence for the accumulation of mature or immature rRNA in the nucleus. 2. The effect of ethionine on the maturation of rRNA was not mimicked by an inhibitor of protein synthesis (cycloheximide) or an inhibitor of polyamine synthesis [methylglyoxal bis(guanylhydrazone)]. 3. Unlike the ethionine-induced inhibition of protein synthesis, this effect was not prevented by concurrent administration of inosine. A similar effect could be induced in HeLa cells by incubation for 1h in a medium lacking methionine. The ATP concentration in these cells was normal. From these two observations it was concluded that the effect of etionine on rRNA maturation is not caused by an ethionine-induced lack of ATP. It is suggested that ethionine, by lowering the hepatic concentration of S-adenosylmethionine, prevents methylation of the ribosomal precursor. The methylation is essential for the correct maturation of the molecule; without methylation complete degradation occurs.

scholarly journals Ribonucleic acid labelling and nucleotide pools during compensatory renal hypertrophy

1974 ◽  
Vol 144 (3) ◽  
pp. 447-453 ◽  
Author(s):  
J M Hill ◽  
G Ab ◽  
R A Malt
Keyword(s):  
Rna Synthesis ◽  
Single Injection ◽  
Specific Radioactivity ◽  
Compensatory Hypertrophy ◽  
Rrna Synthesis ◽  
Renal Hypertrophy ◽  
Rna Content ◽  
Compensatory Renal Hypertrophy ◽  
Precursor Rna ◽  
Ribosomal Precursor

During the first 48h of compensatory renal hypertrophy induced by unilateral nephrectomy, RNA content per cell increased by 20–40%. During this period, rates of RNA synthesis derived from the rates of labelling of UTP and RNA after a single injection of [5-3H]uridine showed no change in the rate of RNA synthesis (3.1nmol of UTP incorporated into RNA/min per mg of RNA). ATP and ADP pools were not changed. The rate of RNA synthesis was considerably in excess of the increment of total RNA appearing in the kidneys. With [5-3H]uridine as label, only continuous infusion for 24h could produce an increase (60%) in the specific radioactivity of renal rRNA in mice with contralateral nephrectomies. With a single injection of [methyl-3H]methionine used to identify methyl groups inserted into newly synthesized rRNA, the specific radioactivity of this rRNA was unchanged 5h after contralateral nephrectomy, increased by 60% at 9–48h, and returned to normal values at 120h. Most RNA synthesized in both nephrectomized and sham-nephrectomized mice has a short half-life. Since total cellular RNA content increases in compensatory hypertrophy despite unchanged rates of rRNA synthesis, the accretion of RNA might involve conservation of ribosomal precursor RNA or a change in rate of degradation of mature rRNA.

The effects of mating on the fine structure of neurosecretory caudodorsal cells in Helisoma duryi (Mollusca)

1990 ◽  
Vol 68 (6) ◽  
pp. 1233-1240 ◽  
Author(s):  
Hamid R. Khan ◽  
Mary Lou Ashton ◽  
Spencer T. Mukai ◽  
A. S. M. Saleuddin
Keyword(s):  
Electron Microscopy ◽  
Protein Synthesis ◽  
Fine Structure ◽  
Tannic Acid ◽  
Egg Laying ◽  
Electron Microscope Autoradiography ◽  
Large Numbers ◽  
Helisoma Duryi ◽  
Microscope Autoradiography ◽  
Silver Grains

The hermaphroditic snail Helisoma duryi does not lay eggs if raised as a virgin in isolation or when castrated. The fine structure of its neurosecretory caudodorsal cells (CDC), which produce the putative egg-laying hormone, was studied in reproductively inactive virgin and castrated snails and compared with that of the reproductively active mated snails, using electron microscopy, tannic acid incubation technique, and electron microscope autoradiography after injection of [3H]leucine. The CDC of virgin and castrated snails accumulate large numbers of elementary granules and appear synthetically inactive, whereas the CDC of mated snails contain fewer elementary granules and possess features characteristic of increased protein synthesis. The flattened cisternae of the rough endoplasmic reticulum of the CDC of the virgins become swollen 3 h after first mating. In tannic acid incubated tissues, more released granules were seen in CDC from snails 12 h after first mating than in CDC from virgin and castrated snails. Autoradiography showed more silver grains on the CDC from snails 12–48 h after first mating than on those from snails 3–6 h after first mating. It is suggested that, in Helisoma, mating provides a stimulus to the CDC for increased protein synthesis and release of the putative egg-laying hormone.

scholarly journals Action of dichlorobenzimidazole riboside on RNA synthesis in L-929 and HeLa cells.

1976 ◽  
Vol 69 (2) ◽  
pp. 229-240 ◽  
Author(s):  
I Tamm ◽  
R Hand ◽  
L A Caliguiri
Keyword(s):  
Hela Cells ◽  
Rna Synthesis ◽  
Dose Range ◽  
Inhibitory Effect ◽  
Mouse Fibroblast ◽  
L Cells ◽  
Uridine Uptake ◽  
High Concentrations ◽  
Precursor Rna ◽  
Ribosomal Precursor

5,6-Dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) inhibits RNA synthesis in L-929 cells (mouse fibroblast line) and HeLa cells (human epitheloid carcinoma line) within 2 min of addition of the compound to the medium. By removing DRB from the medium, the inhibition is promptly and completely reversed after treatment of cells for as long as 1 h or even longer. The inhibitory effect of DRB on the overall rate of RNA synthesis is similar in L and HeLa cells and is markedly concentration-dependent in the low dose range (5-20 muM or 1.6-6.4 mug/ml), but not as higher concentrations of DRB. At a concentration of 12 muM, DRB has a highly selective inhibitory effect on the synthesis of nuclear heterogenous RNA in L cells. At higher concentrations, there is also inhibition of 45 S ribosomal precursor RNA synthesis, but at all concentrations the effect on heterogeneous RNA synthesis in L cells in considerably greater than that on preribosomal RNA synthesis. In HeLa cells, too, DRB has a selective effect on heterogeneous RNA synthesis, but quantitatively the selectivity of action is somewhat less pronounced. In both L and HeLa cells, the inhibition of synthesis of nuclear heterogeneous RNA is incomplete even at very high concentrations of DRB (150 muM). Thus, while DRB is a selective inhibitor of nuclear heterogeneous RNA synthesis, not all such RNA synthesis is sensitive to inhibition. It is proposed that messenger precursor RNA synthesis may largely be sensitive to inhibition by DRB. In short-term experiments, DRB has no effect on protein synthesis in L or HeLa cells. DRB has a slight to moderate inhibitory effect on uridine uptake into L cells and a moderate to marked effect on uptake of uridine into HeLa cells.

Microsurgical Studies on the Formation of the Golgi Apparatus and Nuclear Envelope in Amebae

1974 ◽  
Vol 32 ◽  
pp. 310-311
Author(s):  
C. J. Flickinger
Keyword(s):  
Protein Synthesis ◽  
Golgi Apparatus ◽  
Nuclear Envelope ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Amoeba Proteus ◽  
Cytoplasmic Protein ◽  
Golgi Bodies ◽  
Nuclear Rna Synthesis ◽  
Nuclear Rna

The means of formation of the Golgi apparatus is uncertain. In beginning these studies, it seemed that an important first step was to determine the degree of dependence of the Golgi apparatus on the nucleus. This was investigated in Amoeba proteus because these cells are readily enucleated microsurgically. Normal amebae contained multiple Golgi bodies, which declined in size and number in the absence of the nucleus, indicating that the Golgi apparatus in amebae depends upon the nucleus. The influence of the nucleus on the Golgi apparatus may be mediated through nuclear RNA synthesis and cytoplasmic protein synthesis, since the ultrastructural effects of enucleation were mimicked by treating amebae with actinomycin D to inhibit RNA synthesis and, in part, by treating cells with emetine, which inhibits protein synthesis in amebae.

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