scholarly journals Nucleolar necklaces in chick embryo fibroblast cells. II. Microscope observations of the effect of adenosine analogues on nucleolar necklace formation.

1975 ◽  
Vol 65 (2) ◽  
pp. 418-427 ◽  
Author(s):  
D Granick
Keyword(s):  
Chick Embryo ◽  
Ribosomal Rna ◽  
Messenger Rna ◽  
Rna Synthesis ◽  
Rrna Synthesis ◽  
Fibroblast Cells ◽  
Chick Embryo Fibroblast ◽  
Adenosine Analogues ◽  
Nucleolar Apparatus ◽  
Extensive Degradation

The round nucleoli of chick embryo fibroblast cells, when exposed to adenosine (2 mM)or to a number of adenosine analogues, lose material and unravel over a period of several hours to become beaded strands, 20 mu M in length, termed nucleolar necklaces (NN). Light microscope observations on this process are described. Biochemical experiments have revealed that most of these analogues interfere with both messenger RNA synthesis and ribosome synthesis, causing extensive degradation of the preribosome species containing 32S RNA although most of the preribosomes containing 18S RNA survive. We suggest that it is the depletion from the nucleolus of the adhesive 32S and 28S RNA preribosomes which allows the remaining nucleolar apparatus to spread apart into the NN configuration. Also required for the maintenance of the NN structure is the synthesis of some ribosomal RNA (rRNA) possibly present as rRNA "feathers" on the DNA. The addition of inhibitors of rRNA synthesis such as actinomycin D to the NN-containing cells causes loss of rRNA. Then a contraction and collapse of the NN structure into small dense spheres is observed.

scholarly journals Nucleolar necklaces in chick embryo fibroblast cells. I. Formation of necklaces by dichlororibobenzimidazole and other adenosine analogues that decrease RNA synthesis and degrade preribosomes.

1975 ◽  
Vol 65 (2) ◽  
pp. 398-417 ◽  
Author(s):  
D Granick
Keyword(s):  
Chick Embryo ◽  
Messenger Rna ◽  
Rna Synthesis ◽  
28S Rrna ◽  
Chick Embryo Fibroblast ◽  
Adenosine Analogues ◽  
Biochemical Alterations ◽  
High Concentrations ◽  
Precursor Rna ◽  
Extensive Degradation

A number of chemicals, mostly adenosine analogues, cause the nucleolus of the chick embryo fibroblast to lose material and unravel over a period of several hours into beaded strands termed nucleolar necklaces (NN). The results of analyses of the fibroblasts, treated with the NN-forming chemical dichlororibobenzimidazole (DRB), suggests that the following biochemical alterations occur: DRB almost completely prevents the increase in both messenger RNA (mRNA) and heterogeneous nuclear RNA. It interferes with ribosome synthesis by decreasing the rate of 45S ribosomal RNA (rRNA) accumulation by 50%, slowing the rate of 18S rRNA appearance by 50%, and causing an extensive degradation (80%) of the 32S and 28S rRNA-containing preribisomes. Most of this preribosome degration probably occurs at or before the 32S rRNA preribosome stage. The degradation of these preribosomes appears to be due to the formation of defective 45S rRNA preribosomes rather than to a direct DRB interference with preribosome processing enzyme action. DRB inhibits total cellular RNA synthesis in less than 15 min, suggesting a direct interference with RNA synthesis. DRB also inhibits the uptake of nucleosides into the cell. DRB in the concentrations used does not appear to directly interfere with the translation of mRNA (i.e., protein synthesis). Other NN-forming adenoside analogues and high concentrations of adenosine (2 mM) cause biochemical alterations similar to those produced by DRB. To explain the preribosome degradation, we propose the hypothesis that DRB inhibits the synthesis of mRNA; as a consequence, some of the preribosomal proteins that normally coat the 32S rRNA portion of the 45S precursor RNA become limiting, and this defective portion is then subject to degradation by nucleases.

Analyse des Vermehrungsmechanismus des Newcastle disease Virus (NDV) mit Hilfe verschiedener Inhibitoren

1967 ◽  
Vol 22 (12) ◽  
pp. 1319-1330 ◽  
Author(s):  
Werner Schäfer ◽  
Liselotte Pister ◽  
Rita Schneider
Keyword(s):  
Chick Embryo ◽  
Viral Antigen ◽  
Rna Synthesis ◽  
Protein S ◽  
Viral Rna ◽  
Chick Embryo Fibroblast ◽  
Sensitive Material ◽  
Sensitive Phase ◽  
Antigenic Material ◽  
Structural Antigen

The reproduction of NDV in chick-embryo-fibroblast cultures was studied with 6-Azauridine, 8-Azaguanine, Parafluorophenylalanine (FPA) and Puromycine as inhibitors. The results suggest that no virus initiated FPA-sensitive material is needed for the uncoating of the infecting particles, and that viral parental RNA is able to induce the formation of protein (s) needed for viral RNA-synthesis (“RNA-protein“) as well as the production of viral structural antigen (s). Further antigenic material appears after the beginning of new viral RNA-synthesis. The “RNA-protein (s)“become (s) detectable between 2 and 3 hours after infection and is (are) stable in its function over several hours. According to the formation of viral antigenic material parental viral RNA can act as a messenger longer than 9 hours. The capacity for the production of hemagglutinating units appears after the viral antigen producing capacity, when viral RNA can already be synthesized. This capacity is separated from that to produce plaque forming particles by a FPA-sensitive phase. The character of the corresponding FPA-sensititve material is unknown.

The appearance and quantitation of cytoplasmic ribonucleic acid in the early chick embryo

Development ◽  
1972 ◽  
Vol 28 (2) ◽  
pp. 367-384
Author(s):  
C. C. Wylie
Keyword(s):  
Chick Embryo ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Specific Activity ◽  
Cell Number ◽  
Present Knowledge ◽  
Precursor Pool ◽  
Cytoplasmic Rna ◽  
Labelling Experiment ◽  
Neurula Stage

This paper seeks to extend our knowledge about RNA synthesis in early embryogenesis to the domestic fowl, Gallus domesticus. Using this species for research, apart from increasing our knowledge of higher vertebrate embryology, has certain advantages such as rapid uptake of isotopic precursors and ease of microdissection in culture. The following results are presented: (1) The cell number in the whole chick embryos is shown to be increasing logarithmically between the time of laying and the early neurula stage; with a doubling time of 7·4 h. (2) The onset of ribosomal RNA synthesis has been shown to be during mid-cleavage of the chick embryo, while development is taking place in the oviduct and uterus of the mother. (3) In a cumulative labelling experiment, embryos were labelled at the unincubated-egg stage, allowed to develop to various morphological stages up to neurulation, and their cytoplasmic RNA prepared and analysed by gel electrophoresis. (4) The specific activity of the precursor pool for RNA synthesis was measured at several stages, using the same labelling conditions, and the results were used to quantitate the RNA synthesis from the incorporated radioactivity. (5) Using these techniques, it was found that newly synthesized cytoplasmic RNA accumulates steadily in the whole chick embryo, reaching a level of 104 μg by the early neurula stage. On a per cell basis, however, the amount of newly synthesized cytoplasmic RNA seems to decrease slightly. These findings are discussed in the light of present knowledge about embryos of other vertebrates and certain invertebrates.

Interferon Action:Effect on the Formation of Poxvirus Specific Polysomes and Viral RNA

1970 ◽  
Vol 25 (10) ◽  
pp. 1164-1170 ◽  
Author(s):  
I. Horak ◽  
J. Hilfenhaus ◽  
W. Siegert ◽  
C. Jungwirth ◽  
G. Bodo ◽  
...  
Keyword(s):  
Chick Embryo ◽  
Viral Rna ◽  
Fibroblast Cells ◽  
Cowpox Virus ◽  
Chick Embryo Fibroblast ◽  
L Cells ◽  
Chicken Fibroblast

Treatment of chick embryo fibroblast cells or mouse L-cells with homologous interferon resulted in a reduced formation of poxvirus specific polysomes and of viral RNA. In chick cells infected with cowpox virus the reduced formation of viral polysomes and virus-specific RNA after pretreatment of cells with interferon was observed at all timepoints studied (1 - 6 hours p. i.). Exposure of cells to poly I: poly C caused a similar effect. In mouse L-cells infected with vaccinia WR virus pretreatment with interferon did not result in a reduced formation of viral polysomes or virus-specific RNA up to 1 hour p. i. At about 45 min even a slight increase of the formation of viral polysomes and RNA was observed. At later stages of infection (2 -4 hours p. i.) a reduced synthesis of viral polysomes and RNA was seen, similar to that found in the chicken fibroblast system.

scholarly journals REGULATION OF RIBOSOMAL RNA AND 5s RNA SYNTHESIS IN DROSOPHILA MELANOGASTER: I. BOBBED MUTANTS

Genetics ◽  
1972 ◽  
Vol 72 (2) ◽  
pp. 267-276
Author(s):  
Roberto Weinmann
Keyword(s):  
Drosophila Melanogaster ◽  
Developmental Delay ◽  
Ribosomal Rna ◽  
Gel Electrophoresis ◽  
Rna Synthesis ◽  
Rrna Synthesis ◽  
Wild Type ◽  
5S Rna ◽  
Wild Type Level

ABSTRACT Analysis of the rates and amounts of rRNA and 5s RNA synthesized in Drosophila melanogaster bobbed mutants was done by using acrylamide-gel electrophoresis. The results show that the amounts of rRNA synthesized are constant, although the rates of rRNA synthesis in bb's are reduced to 30% of the wild-type level. The rates of synthesis of 5s RNA were constant. The rate of synthesis of the two kinds of molecules that enter in equimolar amounts into the mature ribosome is non-coordinated.—The rates of rRNA synthesis were shown to be proportional to the length of the scutellar bristles, supporting the notion that in trichogen cells there is no developmental delay, but the size of the bristle depends directly on the rate of rRNA synthesis.

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