The influence of the cytoplasm on the nucleus during cell differentiation, with special reference to
            <i>RNA</i>
            synthesis during amphibian cleavage

Gurdon, J. B.; Woodland, Hugh R.

doi:10.1098/rspb.1969.0042

Cited by 43 publications

(2 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From Figure 3 (9-24, 12-24) it is clear that 5S°°c RNA is not synthesized at a detectable rate after gastrulation in either NT or F egg embryos. These results were quantified by densitometry of gel autoradiographs and are summarised in Our observation that NT embryos show exactly the same pattern of RNA synthesis as normal embryos reared from fertilized eggs is consistent with previous nuclear transplantation experiments (Gurdon and Woodland, 1969; reviewed by Gurdon and Melton, 1981). Earlier results have demonstrated the ability of embryo cytoplasm to activate non-expressed genes, but have not directly tested the repression of genes already active in donor nuclei.…”

Section: _ Ssupporting

confidence: 69%

Cytoplasmic regulation of 5S RNA genes in nuclear-transplant embryos.

Wakefield

Gurdon

1983

The EMBO Journal

View full text Add to dashboard Cite

In the normal development of Xenopus laevis, genes for oocyte-type and somatic-type 5S RNAs are both expressed in late blastulae. Estimates of rates of synthesis indicate that the oocyte-type genes (5S°O9 undergo at least a 100-fold reduction in transcriptional activity between the end of oogenesis and the late blastula stage, and at least a further 20-fold reduction during gastrulation. When neurula nuclei, with inactive 5SO°genes, were transplanted to enucleated eggs, the resulting nuclear-transplant embryos showed a reactivation of 550c genes in blastulae and a subsequent inactivation after this stage. This effect is not explicable by a differential stability of the two types of 5S RNA. We conclude that egg or early embryo cytoplasm must contain components which can continuously regulate 5S gene expression, and that the mechanism by which 5S°0c genes are developmentally inactivated does not persist through mitosis in early embryos. These results have been obtained by a new procedure in which oocyte-and somatic-type 5S RNAs are separated in a 4 M urea-1507o acrylamide gel.

show abstract

Section: _ Ssupporting

confidence: 69%

Cytoplasmic regulation of 5S RNA genes in nuclear-transplant embryos.

Wakefield

Gurdon

1983

The EMBO Journal

View full text Add to dashboard Cite

show abstract

“…Eggs are clearly well supplied with ribonucleotides, even though they do not make a significant amount of RNA in their nuclei (Gurdon & Woodland, 1969). The ribonucleoside triphosphates are 20-100 times more abundant than the corresponding deoxyribonucleotides.…”

Section: Determination Of Non-phosphorylated Deoxyribose Derivativesmentioning

confidence: 94%

Determination of the nucleoside triphosphate contents of eggs and oocytes of Xenopus laevis

Woodland

Pestell

1972

Biochemical Journal

106

View full text Add to dashboard Cite

The ribonucleotide and deoxyribonucleotide contents of eggs and oocytes of Xenopus laevis were measured. Eggs contained most deoxyribonucleotide in the form of triphosphates. dCTP, dTTP, dATP and dGTP were present in similar amounts. The egg contained sufficient deoxynucleotide triphosphate to make approximately 2500 nuclei. Oocytes contained less pyrimidine deoxyribonucleoside triphosphates than did eggs, and purine deoxyribonucleoside triphosphates were not detected. These differences may be correlated with the ability of eggs to induce nuclear DNA synthesis, a property not shown by oocytes. Both oocytes and eggs seem to contain non-phosphorylated, aunsubstituted aldehydes, which may be deoxyribose derivatives. Eggs and oocytes contain similar amounts of ribonucleoside triphosphates. The low rate of RNA synthesis found in eggs, but not in oocytes, is therefore not caused by simple precursor control.In Amphibia the conversion of an ovarian oocyte into an egg involves a total change in nucleic acid metabolism, for the oocyte makes only RNA and the zygote only DNA. Since in these cells the activity of the nucleus has been shown to be under cytoplasmic control [see review articles by Gurdon (1968) and Gurdon & Woodland (1968)] the comparison of oocytes and eggs is likely to be especially helpful in analysing the control of DNA and RNA synthesis. One possible way in which a gross change in nucleic acid synthesis might be mediated is through the cellular content of DNA and RNA precursors. The amount of DNA and its precursors in the eggs and embryos offrogs has been a matter of controversy for many years (see review by Grant, 1965). The confusion about DNA content has been clarified by Dawid (1965Dawid ( , 1966 and by Baltus et al. (1968), who showed that most of the high-molecular-weight DNA of the egg was mitochondrial, or else associated with the yolk platelets. The nature and content of lowmolecular-weight deoxyribose derivatives is still uncertain. In the present paper we report the determination of the amounts of nucleoside triphosphates in the eggs and oocytes of the toad Xenopus laevis. We have determined these molecules because they are generally believed to be the precursors of DNA and RNA. Experimental MaterialsChemicals. These were all obtained from the sources indicated by Pestell & Woodland (1972).Biological material. Female X. laevis were kept and induced to lay eggs as described by Gurdon (1967a Oocytes and eggs were handled in standard saline modified from that of Barth & Barth (1959), and containing 88mM-NaCl, 1 mM-KCI, 2.4mM-NaHCO3, 15mM-tris-HCl buffer, pH7.6, and 0.01g each of sodium benzylpenicillin and streptomycin sulphate/l. Unfertilized eggs were de-jellied immediately after laying by using a solution of 1 % papain and 2% cysteine hydrochloride in the standard saline, which was adjusted to pH 8.0 with NaOH (Brown, 1967). They were frozen and stored at -70°C.Ovaries were removed from females killed by decapitation. The lobes of the ovary were dissected open and the oocytes released by agitati...

show abstract

Experimental demonstration of holokinetic chromosomes, and of differential “radiosensitivity” during oogenesis, in the grass mite, Siteroptes graminum (Reuter)

Cooper

1972

J. Exp. Zool.

View full text Add to dashboard Cite

Ex pe r i men t a I Demon st ration of Ho I o k i net ic C h ro m oso m es, and of Differentia I " Rad iosens i t ivi ty" d u ri ng Oog enesis, in the Grass Mite, Siteroptes graminum (Reuter) RUTH ABSTRACTEarly cleavage stages, mature eggs and developing oocytes of the grass mite Siteroptes graminum (Reuter), formerly Pediculopsis graminum (Reuter), (2n = 6; males haploid), were irradiated to: (a) test the hypothesis that the chromosomes are not monokinetic, (b) determine whether the chromosomes respond differently to irradiation during oogenesis and cleavage, and (c) find out whether a special region on the chromosome is required for elaboration of its chromosomoid (Feulgen-negative body otherwise resembling the chromosome) which is left on the equator during both the meiotic and early cleavage mitoses. Fixation occurred 1-27 hours after irradiation.Chromosomal complements of more than 160 embryos (egg through 128 cell), and a few meiotic figures, were analyzed. Clusters of cells with decipherable chromosomal complements of 8-16 elements occurred frequently, and in especially favorable embryos karyotypes of all or nearly all the blastomeres could be analyzed. Many chromosomal fragments passed through at least three to five cleavage divisions in normal or nearly normal manner. Fragments which had come through one or both meiotic divisions behaved i n blastomeres in a manner similar to those induced in cleavage stages. The chromosomes, therefore, are holo-or polykinetic in the classical sense. The tiniest fragments and very large translocations, however, tended to missegregate or to be eliminated.Some fragments were observed en route to or at the poles in both meiotic divisions. However, aberrancies in chromosomal behavior were more frequent during the maturation divisions, especially anaphase and telophase I, than during cleavage mitoses.Differential radiosensitivity was detected during the course of oogenesis, and between oogenesis and cleavage stages, the first known case in the class Arachnida. As earlier stages were irradiated, there was a trend in blastomeres toward fewer fragments, and far more normal and nearly normal karyotypes. Irradiation of cleavage stages yielded most fragments. Probable causes of this differential radiosensitivity are discussed.In the few cases with well-preserved, discrete chromosomoids the relative size of the chromosomoid and its associated chromosomal elements (including very small fragments) were correlated, and in several cases more than the diploid number of each was present. This suggests, but does not prove, that any part of the chromosome can elaborate chromosomoidal material.Possible causes, other than restriction of the kinetochore, for aberrancies in chromosomal behavior during both somatic and meiotic mitoses are discussed. The more recent literature on holokinetic chromosomes is analyzed, and new speculations about differences between mono-and holokinetic chromosomes are made. Factors of importance in design of experiments to determine the location of kinetochores are ...

show abstract

The influence of the cytoplasm on the nucleus during cell differentiation, with special reference to RNA synthesis during amphibian cleavage

Cited by 43 publications

References 2 publications

Cytoplasmic regulation of 5S RNA genes in nuclear-transplant embryos.

Cytoplasmic regulation of 5S RNA genes in nuclear-transplant embryos.

Determination of the nucleoside triphosphate contents of eggs and oocytes of Xenopus laevis

Experimental demonstration of holokinetic chromosomes, and of differential “radiosensitivity” during oogenesis, in the grass mite, Siteroptes graminum (Reuter)

Contact Info

Product

Resources

About