CYTOPLASMIC DNA SYNTHESIS IN AMOEBA PROTEUS

The incorporation of tritiated thymidine in Amoeba proteus was reinvestigated in order to see if it could be associated with microscopically detectable structures. Staining experiments with basic dyes, including the fluorochrome acridine orange, revealed the presence of large numbers of 0.3 to 0.5 µ particles in the cytoplasm of all cells studied. The effect of nuclease digestion on the dye affinity of the particles suggests that they contain DNA as well as RNA. Centrifugation of living cells at 10,000 g leads to the sedimentation of the particles in the centrifugal third of the ameba near the nucleus. Analysis of centrifuged cells which had been incubated with H3-thymidine showed a very high degree of correlation between the location of the nucleic acid-containing granules and that of acid-insoluble, deoxyribonuclease-sensitive labeled molecules and leads to the conclusion that cytoplasmic DNA synthesis in Amoeba proteus occurs in association with these particles.

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CYTOPLASMIC DNA SYNTHESIS IN AMOEBA PROTEUS

The Journal of Cell Biology ◽

10.1083/jcb.22.3.505 ◽

1964 ◽

Vol 22 (3) ◽

pp. 505-513 ◽

Cited By ~ 24

Author(s):

D. R. Wolstenholme ◽

W. Plaut

Keyword(s):

Electron Microscope ◽

Dna Synthesis ◽

Light Microscope ◽

Tritiated Thymidine ◽

Amoeba Proteus ◽

Electron Microscope Autoradiography ◽

Cytoplasmic Dna ◽

Microscope Autoradiography ◽

Normal Particle ◽

Labeling Pattern

The application of electron microscope autoradiography to Amoeba proteus cells labeled with tritiated thymidine has permitted the identification of morphologically distinct particles in the cytoplasm as the sites of incorporated DNA precursor. The particles correspond to those previously described from light microscope studies, with respect to both H3Tdr incorporation and distribution in centrifugally stratified amoebae. Ingested bacteria differ from the particles, in morphology as well as in the absence of associated label. Attempts to introduce a normal particle labeling pattern by incubating amoebae with labeled sediment derived from used amoeba medium failed. The resultant conclusion, that the particles are maintained in the amoeba by self-duplication, is supported by the presence of particles in configurations suggestive of division.

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CYTOPLASMIC DNA SYNTHESIS IN AMOEBA PROTEUS

The Journal of Cell Biology ◽

10.1083/jcb.15.3.535 ◽

1962 ◽

Vol 15 (3) ◽

pp. 535-540 ◽

Cited By ~ 23

Author(s):

M. Rabinovitch ◽

W. Plaut

Keyword(s):

Nucleic Acid ◽

Dna Synthesis ◽

Acridine Orange ◽

Particle Number ◽

Amoeba Proteus ◽

Acridine Orange Staining ◽

Particle Population ◽

Cell Age ◽

Cytoplasmic Dna ◽

Number Of Particles

Nucleic acid-containing particles in the cytoplasm of Amoeba proteus (cf. reference 1) were counted after acridine orange staining. The number of particles per ameba was found to be correlated with cell age and size. Fresh daughters had a mean particle number of 5400, whereas predivision amebae contained around 11,000 particles. Amebae from two other strains contained similar particles. The particles were found to be clustered in fasted cells and redispersed after feeding. A marked increase in the particle population was noted in anucleate fragments. These results, together with those previously presented, suggest that the particles multiply intracellularly. Their nature and their relationship to previous work on nucleic acid labeling in Amoeba are discussed.

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Continuous DNA replication in the nucleus of the dinoflagellate Prorocentrum micans (Ehrenberg)

Journal of Cell Science ◽

10.1242/jcs.27.1.81 ◽

1977 ◽

Vol 27 (1) ◽

pp. 81-90

Author(s):

S.A. Filfilan ◽

D.C. Sigee

Keyword(s):

Electron Microscope ◽

Dna Synthesis ◽

Nuclear Dna ◽

Continuous Process ◽

Prorocentrum Micans ◽

Interphase Nuclei ◽

Electron Microscope Autoradiography ◽

Dividing Cells ◽

High Degree ◽

Very High

The uptake of tritiated thymine into cells of a heterogeneous population of Prorocentrum micans was investigated using light-microscope and electron-microscope autoradiography. Specificity of thymine uptake into DNA was demonstrated by the specific removal of label from wax-embedded material using DNase and by the high degree of localization of nuclear label to chromosomes in the electron-microscope autoradiographs. All nuclei, including both dividing and non-dividing cells, showed a substantial uptake of label, indicating that nuclear DNA synthesis in Prorocentrum micans is a continuous process. The level of DNA synthesis does show considerable variation, however, with very high levels in some interphase nuclei. The continuous replication of nuclear DNA provides further evidence of dinoflagellate affinity to the prokaryotes, and indicates that Prorocentrum micans is a very primitive eukaryote cell.

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Timing of nucleolar DNA replication in Amoeba proteus

Journal of Cell Science ◽

10.1242/jcs.22.3.521 ◽

1976 ◽

Vol 22 (3) ◽

pp. 521-530

Author(s):

I. Minassian ◽

L.G. Bell

Keyword(s):

Electron Microscope ◽

Dna Replication ◽

Dna Synthesis ◽

Central Region ◽

Thymidine Incorporation ◽

Tritiated Thymidine ◽

Amoeba Proteus ◽

Electron Microscope Autoradiography ◽

Microscope Autoradiography ◽

G2 Phase

Light- and electron-microscope autoradiography have been used to follow the incorporation of [3H]thymidine at different stages during the interphase of synchronously growing populations of Amoeba proteus. Two main patterns were found for tritiated thymidine incorporation, i.e. DNA synthesis. The major incorporation was in the central region of the nucleus, but a lesser degree of incorporation occurred in the nucleolar region. The bulk of this nucleolar DNA was found to be late replicating, i.e. it replicated during the G2 phase.

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Acquired tolerance of foreign cells in newborn animals

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1956.0073 ◽

1956 ◽

Vol 146 (922) ◽

pp. 78-90 ◽

Cited By ~ 43

Keyword(s):

Direct Injection ◽

Chorioallantoic Membrane ◽

Later Life ◽

High Rate ◽

Direct Result ◽

In Ovo ◽

Large Numbers ◽

High Degree ◽

Experimental Interference ◽

Very High

Acquired tolerance of skin homografts may be brought about experimentally by the introduction of the antigenic stimulus, in the form of living homologous tissue cells, into the embryo before its immunological defence mechanism has become functionally mature (Billingham, Brent & Medawar 1953, 1956). In practice, this may be accomplished in one or other of the following ways, depending on the species concerned: ( a ) in mice, rats and rabbits, by direct injection of cells into the foetus; ( b ) in birds, by the injection of blood into the chorioallantoic circulation, or ( c ) by the parabiosis of embryos, an ingenious technique devised by Hašek (I953) which leads to an exchange of blood cells, or ( d ) by the transplantation of tissues to the chorioallantoic membrane. Although any one of these techniques is capable of inducing a very high degree of tolerance in respect of skin homografts transplanted in later life each, unfortunately, has its own technical shortcomings. In particular, these techniques are all severely restricted by a very high rate of mortality which is a direct result of experimental interference in utero or in ovo . For this and other reasons they do not easily lend themselves to the analysis of problems which require the use of relatively large numbers of tolerant animals.

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CHROMOSOMAL DNA SYNTHESIS IN DROSOPHILA MELANOGASTER

The Journal of Cell Biology ◽

10.1083/jcb.39.2.415 ◽

1968 ◽

Vol 39 (2) ◽

pp. 415-429 ◽

Cited By ~ 29

Author(s):

E. F. Howard ◽

W. Plaut

Keyword(s):

Drosophila Melanogaster ◽

Dna Synthesis ◽

Chromosome Region ◽

Chromosomal Dna ◽

Ordered Arrays ◽

Intermediate Time ◽

High Degree ◽

Chromosome Segments ◽

Very High ◽

Chromosome Regions

Analysis of labeling patterns in three chromosome segments of Drosophila melanogaster has shown that the replicative activity within chromosomes is temporally ordered. Moreover, specific labeling patterns on one chromosome occur with specific patterns on another chromosome with a very high degree of correlation. This circumstance leads to the conclusion that DNA synthesis among all the regions in the three chromosome segments studied is coordinated. The various labeling patterns observed in any one chromosome and the combinations of labeling patterns observed in all three chromosome segments can be arranged in ordered arrays, if one assumes that the DNA synthesis in each chromosome region will go to completion without stopping once it has started. Such arrays can serve as models for the temporal order of DNA synthesis among chromosome regions. They predict that in any one chromosome DNA replication begins and ends at very few loci and that synthesis at a larger number of points occurs at an intermediate time.

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Electron Microscopy in Molecular Biology

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060027 ◽

1967 ◽

Vol 25 ◽

pp. 2-3

Author(s):

Cecil E. Hall

Keyword(s):

Electron Microscopy ◽

Molecular Biology ◽

Noise Level ◽

Molecular Structures ◽

Material Structure ◽

The Arts ◽

Shadow Casting ◽

Electron Image ◽

High Degree ◽

Very High

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.

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A Low-Noise, High-Gain Quasi-Millimeter-Wave Receiver MMIC with a Very High Degree of Integration Using 3D-MMIC Technology

IEICE Transactions on Electronics ◽

10.1587/transele.e94.c.1548 ◽

2011 ◽

Vol E94-C (10) ◽

pp. 1548-1556 ◽

Cited By ~ 1

Author(s):

Takana KAHO ◽

Yo YAMAGUCHI ◽

Kazuhiro UEHARA ◽

Kiyomichi ARAKI

Keyword(s):

Millimeter Wave ◽

High Gain ◽

Low Noise ◽

High Degree ◽

Very High ◽

Millimeter Wave Receiver

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Multi-Locus Selection and the Structure of Variation at the white Gene of Drosophila melanogaster

Genetics ◽

10.1093/genetics/144.2.635 ◽

1996 ◽

Vol 144 (2) ◽

pp. 635-645 ◽

Cited By ~ 3

Author(s):

David A Kirby ◽

Wolfgang Stephan

Keyword(s):

Drosophila Melanogaster ◽

White Gene ◽

Transcriptional Unit ◽

North American Population ◽

Evolutionary Mechanisms ◽

Locus Selection ◽

Neutral Equilibrium ◽

History Of ◽

High Degree ◽

Very High

Abstract We surveyed sequence variation and divergence for the entire 5972-bp transcriptional unit of the white gene in 15 lines of Drosophila melanogaster and one line of D. simulans. We found a very high degree of haplotypic structuring for the polymorphisms in the 3′ half of the gene, as opposed to the polymorphisms in the 5′ half. To determine the evolutionary mechanisms responsible for this pattern, we sequenced a 1612-bp segment of the white gene from an additional 33 lines of D. melanogaster from a European and a North American population. This 1612-bp segment encompasses an 834bp region of the white gene in which the polymorphisms form high frequency haplotypes that cannot be explained by a neutral equilibrium model of molecular evolution. The small number of recombinants in the 834bp region suggests epistatic selection as the cause of the haplotypic structuring, while an investigation of nucleotide diversity supports a directional selection hypothesis. A multi-locus selection model that combines features from both-hypotheses and takes the recent history of D. melanogaster into account may be the best explanation for these data.

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